methylnitronitrosoguanidine and Stomach-Neoplasms

Helicobacter pylori infection is well accepted to be a very important factor for the development of gastric carcinogenesis in the human stomach. In Mongolian gerbils treated with chemical carcinogens, H. pylori infection enhances glandular stomach carcinogenesis, and eradication of infection and results in curtailment of enhancing effects, particularly at early stages of associated inflammation. A high-salt diet exacerbates the effects of H. pylori infection on gastric carcinogenesis, and these two factors act synergistically to promote the development of gastric cancers in this animal model. However, the bacterium exerts the greater effects. Early acquisition significantly increases gastric chemical carcinogenesis in Mongolian gerbils, as compared to later infection. While heterotopic proliferative glands, hyperplastic and dilated glands localized beneath the muscularis mucosae, frequently develop with H. pylori infection alone in this animal model, they obviously regress on eradication, suggesting a relation to severe gastritis, rather than a malignant character. Furthermore, endocrine cells, positive for chromogranin A, are observed in the heterotopic proliferative glands, in contrast to cancerous lesions which lack endocrine elements. In conclusion, H. pylori is not an initiator, but rather a strong promoter of gastric carcinogenesis, whose eradication, together with reduction in salt intake, might effectively prevent gastric cancer development.

Topics: Adenocarcinoma; Animals; Cocarcinogenesis; Disease Models, Animal; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Humans; Methylnitronitrosoguanidine; Methylnitrosourea; Precancerous Conditions; Sodium Chloride, Dietary; Stem Cells; Stomach Neoplasms

Helicobacter pylori (Hp) was concluded to be 'a definite carcinogen' by WHO/IARC in 1994. We have demonstrated that Hp infection enhances chemical carcinogen-induced stomach carcinogenesis in Mongolian gerbils (MGs) using N-methyl-N'-nitro-N-nitrosoguanidine or N-methyl-N-nitrosourea. Not only well-differentiated but also poorly differentiated and signet ring cell types of cancers are observed, mimicking the human case. Eradication of Hp was found to be effective of preventing enhancing effects. Hp infection alone, without chemical carcinogens, caused submucosal proliferating lesions, but not gastric carcinomas, in contrast to reports that Hp infection alone may act on a complete carcinogen. Precise pathological assessment is required to solve this controversy. Here we demonstrate alleviation of Hp induced gastric lesions with eradication in MGs.

Topics: Animals; Disease Models, Animal; Gastric Mucosa; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Humans; Metaplasia; Methylnitronitrosoguanidine; Methylnitrosourea; Stomach Neoplasms

To explore the 'causal link' between Helicobacter pylori(Hp) infection and stomach carcinogenesis, we have established experimental models of stomach carcinogenesis in Mongolian Gerbils(MGs) using the chemical carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine(MNNG) and N-methyl-N-nitrosourea(MNU). The incidence of adenocarcinoma was significantly higher in animals treated with Hp than in the controls. Eradication of Hp was effective in reducing the incidence of adenocarcinoma. No gastric carcinoma was found without any chemical carcinogen. Hp infection enhances glandular stomach carcinogenesis not only of well-differentiated type but also poorly differentiated type and signet ring cell type. Eradication of Hp, apparently a gastric promoter rather than gastric carcinogen, may be useful as a measure for prevention of stomach cancer.

Topics: Adenocarcinoma; Animals; Carcinogens; Disease Models, Animal; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Humans; Methylnitronitrosoguanidine; Methylnitrosourea; Stomach Neoplasms

Experimental chemical carcinogenesis in the digestive tract is reviewed, mainly on the basis of information obtained in the laboratories of the National Cancer Center Research Institute. It is generally accepted that cancer is the outcome of DNA damage, resulting in mutation, loss, amplification and recombination of genes. Gastric cancer is no exception. It was shown very early that cancer of the glandular stomach can be produced in rats by administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a widely used mutagen. However, this depends on the genotype. Whereas the ACI rat is susceptible to MNNG, the Buffalo rat is resistant and this is a dominantly inherited trait. Genes responsible for the sensitivity to gastric cancer induction are at present under investigation by linkage analysis of rat genome markers. With regard to cancer in humans, our finding that cooked proteinaceous foods can give rise to a series of heterocyclic amines (HCAs) is of major significance. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), one of the most abundant, causes colon cancers in male rats, whereas in females it induces breast cancers. The colon cancers induced by PhIP feature a deletion of G as represented by 5-GGGA-3-->5-GGA-3 in the Apc gene, resulting in a truncated Apc molecule. Microsatellite mutations have also been found in PhIP-induced colon tumors, as in human hereditary non-polyposis colorectal cancer cases. Similarly to the case of gastric cancer production by MNNG, there is a genetic component and F344 rats are more susceptible to PhIP colon carcinogenesis than the ACI/N strain and the gene responsible is being sought. Since carcinogenesis proceeds with accumulation of genetic alteration, often involving genomic instability, exposure to any kind of carcinogenic substances, either xeno- or autobiotics, needs to be reduced as far as possible, taking account of inconvenience at the individual and socio-economical levels.

Topics: Adenomatous Polyposis Coli; Animals; Carrier Proteins; Colonic Neoplasms; DNA, Neoplasm; Gene Deletion; Genes, APC; Humans; Male; Methylnitronitrosoguanidine; Molecular Chaperones; Nerve Tissue Proteins; Rats; Rats, Inbred ACI; Rats, Inbred BUF; Rats, Inbred F344; Rats, Wistar; Receptors, Aryl Hydrocarbon; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Cricetinae; Methylnitronitrosoguanidine; Neoplasms, Glandular and Epithelial; Soft Tissue Neoplasms; Species Specificity; Stomach; Stomach Neoplasms

Topics: Animals; Carcinogens; Epithelium; Gastric Acid; Gastric Mucosa; Gastritis, Atrophic; Humans; Methylnitronitrosoguanidine; Mucus; Rats; Regional Blood Flow; Risk Factors; Stomach Neoplasms; Sulfhydryl Compounds

Animal models are being used to study the mechanisms by which Helicobacter spp. induce gastric disease. To assess the effects of a natural gastric pathogen, Helicobacter mustelae, in the development of chronic gastritis, premalignancy and cancer, the ferret model was studied under natural and experimental conditions.. H. mustelae-infected ferrets were used to study the metabolism of nitrates/nitrites, which are dietary and endogenously formed substances that have been linked to gastric cancer. The ferret was also manipulated by performing gastric reconstructive surgery to study the processing of nitrite and nitrate and to assess the effect of surgery on gastric pathology. In addition, the ferret was tested for its suitability as an animal model for the induction of gastric cancer by oral dosing with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The influence of these variables on gastric pathology and/or metabolic outcomes was examined, and the results in ferrets were compared to findings in humans.. The ferret appears to be an ideal model for studying various gastric parameters and how these factors influence the development of H. mustelae-associated gastric disease. Gastric reconstructive surgery did not effect nitrite processing or overall severity of gastritis in ferrets. However, a single dose of MNNG (50 mg/kg) produced an unprecedented 90% gastric carcinoma in H. mustelae-infected ferrets. This implies that chronic inflammation induced by the bacterium is a cofactor in gastric carcinogenesis.

Topics: Adenocarcinoma; Animals; Disease Models, Animal; Ferrets; Gastric Mucosa; Gastritis; Helicobacter; Helicobacter Infections; Methylnitronitrosoguanidine; Nitrosamines; Proliferating Cell Nuclear Antigen; Stomach; Stomach Neoplasms

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Gastric Mucosa; Methylcholanthrene; Methylnitronitrosoguanidine; Methylnitrosourea; Mice; Rats; Sarcoma, Experimental; Stomach; Stomach Neoplasms

Gastric cancer is a very typical cancer related to life styles, including nutrition and dietary conditions. Cigarette smoking has also been pointed out as an enhancing factor in gastric cancer development. Improvement of dietary conditions, regular dietary habits including lower salt, nitrite and nitrite intake and balanced nutritious food may be factors suppressing the incidence of gastric cancer. At the same time, advances in technology for early diagnosis and early surgical treatment have elevated the cure rate of gastric cancers. From both primary and secondary cancer prevention aspects, gastric cancer is now a conquerable disease.

Topics: Animals; Diet; Humans; Male; Metaplasia; Methylnitronitrosoguanidine; Mutagens; Rats; Rats, Inbred Strains; Risk Factors; Stomach; Stomach Neoplasms

The historical background of studies in Japan on chemical carcinogenesis from environmental sources is described from personal experience.

Topics: 4-Nitroquinoline-1-oxide; Animals; Biotransformation; Carcinogens; Cyanobacteria; Environmental Pollution; Food Additives; Food Handling; Furylfuramide; Health Policy; Humans; Indoles; Japan; Lyngbya Toxins; Methods; Methylnitronitrosoguanidine; Mutagenicity Tests; Oncogenes; Primary Prevention; Rats; Risk; Stereoisomerism; Stomach Neoplasms; Streptomyces; Structure-Activity Relationship; Urinary Bladder Neoplasms

Topics: Animals; Antioxidants; Ascorbic Acid; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Carcinogens; Colonic Neoplasms; Ethoxyquin; Glutathione Transferase; Mammary Neoplasms, Experimental; Methylnitronitrosoguanidine; Neoplasms, Experimental; Phenobarbital; Propyl Gallate; Rats; Rats, Inbred F344; Saccharin; Stomach Neoplasms; Substrate Specificity; Urinary Bladder Neoplasms

Topics: Animals; Carcinogens; Cell Transformation, Neoplastic; Disease Models, Animal; Epithelium; Gastric Mucosa; Humans; Methylnitronitrosoguanidine; Mice; Mucus; Precancerous Conditions; Rats; Stomach; Stomach Neoplasms

Relatively short-term treatment (8 weeks) of rats with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water (100 mg/l) was shown to adequately initiate gastric carcinogenesis when 10% NaCl was simultaneously administered in the diet. Utilizing this MNNG plus high salt diet as the initiation stage of a two-step protocol, it was also established that subsequent dietary administration of NaCl (10% of the diet) for 32 weeks tended to enhance tumor development in the glandular stomach. Similar tumor promoting activity was demonstrated for other mucosal damaging agents, such as potassium metabisulfite and formaldehyde. Biological changes of the gastric mucosa were examined after chronic administration or a single oral intubation of NaCl. Morphological lesions observed included diffuse mild erosions, atrophy of the glands, and hyperplasia of the foveolar epithelium when given 10% NaCl diet chronically. After a single oral intubation of NaCl, increased tritiated thymidine labeling index and ornithine decarboxylase (ODC) activity were observed in both pyloric and fundic mucosa. No remarkable effects of NaCl were observed on the forestomach or duodenal mucosa. These results suggest that NaCl exerts an enhancing effect at both initiation and promotion steps within the two stage model system of the gastric carcinogenesis, and that these effects of NaCl are possibly related to its mucosal damaging activity.

Topics: Animals; DNA; Gastric Mucosa; Histocytochemistry; Hyperplasia; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Ornithine Decarboxylase; Rats; Sodium Chloride; Stomach Neoplasms

Intestinal metaplasia of the stomach is classified into two types, complete and incomplete, by enzymatical, mucin histochemical and histological differences. Complete type resembles the small intestine while incomplete type does not. But, even complete type differs from the small intestine from the point of cytological observations. Vascular structures of the metaplastic mucosa are different from those in the mucosae of stomach, small and large intestines. Focal intestinal metaplasia can be induced in rats by a gastric carcinogen, N-propyl-N'-nitro-N-nitrosoguanidine or regeneration after ulceration with 0.5 NaOH. There is no solid evidence that intestinal metaplasia is a precancerous change of the stomach. However, the patients with extensive intestinal metaplasia of the stomach belong to the high risk group for the gastric cancer. Therefore, careful follow-up studies are needed for these patients using endoscopy by dye-staining method.

Topics: Animals; Epithelium; Gastric Mucosa; Humans; Metaplasia; Methylnitronitrosoguanidine; Middle Aged; Precancerous Conditions; Rats; Stomach Neoplasms

The early sequential development of gastric cancer was studied with experimental animals and examined with respect to what conclusions can be drawn for understanding carcinogenesis in man. After limited oral administration of N-methyl-N'nitro-N-nitrosoguanidine to 174 rats carcinomas developed in most cases directly from the otherwise unchanged mucosa through various successive stages of transformation, without passing through a benign-appearing proliferative or neoplastic epithelial lesion. Focal dysplasia grade I was the first recognizable change observed by light microscopy, followed by dysplasia grade II, and subsequently dysplasia grade III. In spite of very similar morphological characteristics, the experimentally induced dysplasias cannot be simply equated in their etiology and biological behavior with the dysplasias of the human stomach. Dysplasias of grade I and II commonly found in man are usually associated with a chronic gastritis; they are located in the upper third of the mucosa and are for the most part reversible. The experimental dysplasias occuring in the proliferative zone of an otherwise undisturbed mucosa must be considered potentially premalignant, as they are irreversible and develop progressively. This finding points out that in man dysplasias grade III within the regenerative zone of non-inflammatory mucosa should be considered particularly as possible precursors of gastric carcinomas.

Topics: Adenoma; Animals; Female; Gastric Mucosa; Hyperplasia; Methylnitronitrosoguanidine; Neoplasms, Experimental; Precancerous Conditions; Rats; Stomach Neoplasms; Time Factors

Topics: 9,10-Dimethyl-1,2-benzanthracene; Adenocarcinoma; Animals; Cricetinae; Disease Models, Animal; Dogs; Drug Interactions; Guinea Pigs; Haplorhini; Kidney Neoplasms; Liver Neoplasms; Liver Neoplasms, Experimental; Lung Neoplasms; Methylcholanthrene; Methylnitronitrosoguanidine; Mice; Neoplasms, Experimental; Rabbits; Rats; Stomach Neoplasms; Urinary Bladder Neoplasms

The present survey deals with requirements the experimental-oncological models used in morphogenetic investigations should meet. Data on ways of inducing tumours of various organs the most suited for such investigations are presented. The available at present literature comprises data on different variants of morphogenesis of tumours; in a number of cases malignant neoplasms can develop against the background of an unchanged structure without previous alterations. Because of a contradictory character of the literature reports on morphogenesis of tumours, further investigations into the morphodynamics of the process of cancerogenesis are needed; at present, this may be successfully implemented if adequate models of the majority of tumour diseases in man are available. These studies are of importance for better understanding of pathogenesis or tumour growth and for ascertaining the concept of precancer changes.

Topics: 2-Acetylaminofluorene; 9,10-Dimethyl-1,2-benzanthracene; Aflatoxins; Animals; Azoxymethane; Benzopyrenes; Brain Neoplasms; Carcinogens; Cricetinae; Dimethylhydrazines; Dogs; Esophageal Neoplasms; Ethionine; Ethylnitrosourea; Female; Hematopoietic System; Intestinal Neoplasms; Liver Neoplasms; Lung Neoplasms; Male; Mammary Neoplasms, Experimental; Methylnitronitrosoguanidine; Methylnitrosourea; Mice; Neoplasms, Experimental; Nitrosamines; Nitroso Compounds; Nitrosoguanidines; o-Aminoazotoluene; p-Dimethylaminoazobenzene; Precancerous Conditions; Rats; Skin Neoplasms; Stomach Neoplasms; Urinary Bladder Neoplasms

To observe the curative effect of Weiansan (WAS) on gastric precancerous lesions (GPL) and H pylori elimination.. Seventy-six patients with GPL were randomly divided into two groups: WAS group (n = 42) and Weifuchun (WFC) group (n = 34). The patients in the WAS group were administered 5 g WAS 3 times a day, and the patients in the WFC group took WFC (4 tablets) 3 times a day. To monitor inflammation of gastric mucosa, degree of glandular atrophy (GA), intestinal metaplasia (IM) and dysplasia, and H pylori infection, all patients underwent gastroscopy and biopsy with pathological examination before and after treatment. Fifty male Sprague-Dawley (SD) rats were used in animal experiments. Of these, 10 served as the control group (n = 10), 40 were given ranitidine combined with N-methyl-N(1)-nitro-N-nitrosoguanidine (MNNG) for 12 wk and divided into 4 groups randomly: model group (n = 10), high-dose WAS group (n = 10), low-dose WAS group (n = 10) and WFC group (n = 10). Twelve weeks later, all rats were killed and a 2 cm multiply 1 cm tissue was taken from the lesser curvature of the gastric antrum. H pylori infection was determined by the fast urease method.. The curative effect in WAS groups was similar to that in WFC groups. There was no statistical difference in degree of GA, IM and dysplasia between WAS and WFC groups. The rate of H pylori infection in the model group (positive/negative: 9/1) was significantly higher than that in the control group (positive/negative: 1/9) (P < 0.01). H pylori elimination in the high-dose WAS group (positive/negative: 4/6) and low-dose WAS group (positive/negative: 6/4) was similar to that in the WFC group (positive/negative: 4/6) (P > 0.05).. WAS improves clinical symptoms by suppressing GA, IM and dysplasia and eliminating H pylori.

Topics: Adult; Aged; Animals; Female; Helicobacter Infections; Helicobacter pylori; Humans; Male; Medicine, Chinese Traditional; Methylnitronitrosoguanidine; Middle Aged; Precancerous Conditions; Rats; Rats, Sprague-Dawley; Stomach Diseases; Stomach Neoplasms; Time Factors; Treatment Outcome

Chi006Eese herbal medicine Weifuchun Tablets (WFC) approved by the State Food and Drug Administration in 1982 has been widely used in treating a variety of chronic stomach disorders including Chronic atrophic gastritis (CAG) and Gastric precancerous lesions in China clinically. This study aimed to investigate the efficacy and potential mechanism of WFC in treating Gastric intestinal metaplasia (GIM) and Gastric dysplasia (GDys).. Rat GIM and GDys established by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) combined with hot paste, ethanol injury, and intermittent fasting were intervened by WFC. Body weight, histopathology, pH of gastric acid, pepsin activity, intestinal metaplasia index and inflammation were detected. Rat bone marrow derived macrophages (BMDMs) pretreated with WFC were stimulated by LPS. Inflammatory factors and the nuclear factor-kappa B (NF-κB) pathway were assessed. GES-1 cells pretreated by WFC were stimulated by MNNG and TNF-α, intestinal metaplasia index, the NF-κB pathway and interaction between P65 and CDX2 were detected.. WFC improved rat body weight, histopathology, pH value of gastric acid, activity of gastric pepsin, intestinal metaplasia (CDX2), inflammation (IL-1β, IL-6 and TNF-α), macrophage aggregation (CD68) in gastric mucosa in rat GIM and GDys. WFC inhibited inflammation (IL-1β and TNF-α) by inactivating the NF-κB pathway. WFC reduced the expression of CDX2 by inhibiting the binding of CDX2 promoter TSS upstream region with p65.. WFC blocked GIM and GDys associated with inflammation by regulating the NF-κB pathway.

Topics: Animals; Gastric Mucosa; Hyperplasia; Inflammation; Metaplasia; Methylnitronitrosoguanidine; NF-kappa B; Pepsin A; Precancerous Conditions; Rats; Stomach Neoplasms; Tumor Necrosis Factor-alpha

Gallic acid (GA) is a natural polyphenolic compound derived from Rhus chinensis Mill. with a variety of biological activities such as astringent sweat, cough, dysentery, hemostasis, and detoxification, and is widely used in China as a treatment for cough, bleeding, and gastrointestinal disorders. In recent years, the anticancer activity of GA has been demonstrated in a variety of cancers, affecting multiple cellular pathways associated with cancer onset, development and progression.. To investigate the role and potential mechanism of GA on gastric precancerous lesions (GPL), the key turning point of gastritis to gastric cancer, with the aim of delaying, blocking or reversing the dynamic overall process of "inflammation-cancer transformation" and thus blocking GPL to prevent the development of gastric cancer.. In this study, we established N-Nitroso-N-methylurea (MNU)-induced GPL mice model and induced precancerous lesions of gastric cancer cells (MC), i.e. epithelial mesenchymal transition (EMT), in human gastric mucosal epithelial cells (GES-1) with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). We used conventional pathology, immunohistochemistry, RNA sequencing, Western blot and other techniques to study the therapeutic effect of GA on GPL and its possiblemechanism in vitro and in vivo.. The results showed that compared with normal GES-1 cells, MC cells had the characteristics of malignant cells such as abnormal proliferation, invasion and metastasis, accompanied by decreased expression of EMT-related protein E-cadherin and increased expression of N-cadherin and Vimentin. GA can inhibit the malignant behavior of MC cell proliferation and induce its G0/G1 phase arrest, which is achieved by downregulating the Wnt/β-catenin signaling pathway and thereby inhibiting the EMT process. However, when we incubated with the Wnt pathway activator (Wnt agonist 1), the effect of GA was reversed. Furthermore, analysis of human gastric specimens showed that activation of the Wnt/β-catenin pathway was significantly associated with GPL pathological changes. Meanwhile, GA reversed MNU-induced intestinal metaplasia and partial dysplasia in GPL mice.. Taken together, these results indicate that GA prevents the occurrence and development of GPL by inhibiting the Wnt/β-catenin signaling pathway and then inhibiting the EMT process, which may become potential candidates for the treatment of GPL.

Topics: Animals; beta Catenin; Cadherins; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cough; Epithelial-Mesenchymal Transition; Gallic Acid; Humans; Methylnitronitrosoguanidine; Mice; Precancerous Conditions; Stomach Neoplasms; Wnt Signaling Pathway

Dendrobium huoshanense C. Z. Tang et S. J. Cheng is an important edible medicinal plant that thickens the stomach and intestines, and its active ingredient, polysaccharide, can have anti-inflammatory, immunoregulatory, and antitumor effects. However, the gastroprotective effects and potential mechanisms of Dendrobium huoshanense polysaccharides (DHP) remain unclear.. An N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induced human gastric mucosal epithelial cells (GES-1) damage model was used in this research, aiming to investigate whether DHP has a protective effect on MNNG-induced GES-1 cell injury and its underlying mechanism based on the combination of multiple methods.. DHP was extracted using water extraction and alcohol precipitation methods, and the proteins were removed using the Sevag method. The morphology was observed using scanning electron microscopy. A MNNG-induced GES-1 cell damage model was developed. Cell viability and proliferation of the experimental cells were investigated using a cell counting kit-8 (CCK-8). Cell nuclear morphology was detected using the fluorescent dye Hoechst 33342. Cell scratch wounds and migration were detected using a Transwell chamber. The expression levels of apoptosis proteins (Bcl-2, Bax, Caspase-3) in the experimental cells were detected by Western blotting. Ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) was performed to investigate the potential mechanism of action of DHP.. The CCK-8 kit analysis showed that DHP increased GES-1 cell viability and ameliorated GES-1 cell injury by MNNG. In addition, scratch assay and Transwell chambers results suggested that DHP improved the MNNG-induced motility and migration ability of GES-1 cells. Likewise, the results of the apoptotic protein assay indicated that DHP had a protective effect against gastric mucosal epithelial cell injury. To further investigate the potential mechanism of action of DHP, we analyzed the metabolite differences between GES-1 cells, GES-1 cells with MNNG-induced injury, and DHP + MMNG-treated cells using UHPLC-HRMS. The results indicated that DHP upregulated 1-methylnicotinamide, famotidine, N4-acetylsulfamethoxazole, acetyl-L-carnitine, choline and cer (d18:1/19:0) metabolites and significantly down-regulated 6-O-desmethyldonepezil, valet hamate, L-cystine, propoxur, and oleic acid.. DHP may protect against gastric mucosal cell injury through nicotinamide and energy metabolism-related pathways. This research may provide a useful reference for further in-depth studies on the treatment of gastric cancer, precancerous lesions, and other gastric diseases.

Topics: Dendrobium; Humans; Mass Spectrometry; Methylnitronitrosoguanidine; Polysaccharides; Stomach Neoplasms

Biological organisms are exposed to low-dose arsenic or N-nitro compounds (NOCs) alone or in combination worldwide, especially in areas with high cancer prevalence through drinking water or food exposure; however, information on their combined exposure effects is limited. Here, we conducted an in-depth study of the effects on the gut microbiota, metabolomics, and signaling pathways using rat models exposed to arsenic or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), one of the most active carcinogenic NOCs, separately or in combination with metabolomics and high-throughput sequencing. Compared to exposure alone, combined exposure to arsenic and MNNG exacerbated damage to gastric tissue morphology, interfered with intestinal microflora and substance metabolism, and exerted a stronger carcinogenic effect. This may be related to intestinal microbiota disorders, including Dyella, Oscillibacter, Myroides, and metabolic pathways such as glycine, serine, and threonine metabolism, arginine biosynthesis, central carbon metabolism in cancer, and purine and pyrimidine metabolism, thereby enhancing the cancer-causing effects of gonadotrophin-releasing hormone (GnRH), P53, and Wnt signaling pathways.

Topics: Animals; Arsenic; Gastrointestinal Microbiome; Metabolome; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

Chronic atrophic gastritis (CAG) is an important stage in the transformation of the normal gastric mucosa into gastric cancer. Granule Dendrobii (GD), a proprietary Chinese medicine, has proven clinical efficacy in treating CAG. GD might promote the reversal of precancerous lesions by improving them in CAG patients. However, the mechanism of GD in CAG treatment is relatively less understood. Here, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced CAG rats were treated with GD and its efficacy was evaluated by observing the changes in the rats' weight and the pathology of gastric tissues. The potential effect of GD on the bacteria was predicted and verified in the large and small intestines and stomachs of CAG rats using amplicon sequencing and RT-qPCR. The results showed that GD could ameliorate the symptoms of body weight loss in CAG rats. Hematoxylin-Eosin (HE) and Alcian Blue (AB) staining showed that GD significantly improved the pathological state of the gastric mucosa in CAG rats. The relative abundance (RA) of Lactobacillus and Turicibacter significantly decreased after GD intervention compared with that of the model group (P < 0.05), indicating that GD might improve CAG by regulating the RA of Lactobacillus and Turicibacter. These findings revealed that Lactobacillus and Turicibacter as bacteria agents associated with gastritis, have the potential to inhibit gastric cancer, especially Turicibacter maybe another pathogen of CAG besides Helicobacter pylori (HP), which is worthy of further study. Meanwhile, the findings provided new ideas and materials for the research and development of new CAG drugs.

Topics: Animals; Gastritis; Gastritis, Atrophic; Lactobacillus; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

Elian Granules have been applied in the treatment of precancerous lesions of gastric cancer (PLGC) and achieved good results. However, its exact mechanism remains unclear.. To explore the mechanism of Elian granules in treating PLGC through the mitogen-activated protein kinase (MAPK) signalling pathway based on network pharmacology.. 394 and 4,395 targets were identified in Elian granules and PLGC, respectively. The 190 common targets were mainly enriched in MAPK signalling pathways. The gastric mucosal epithelium was still intact, the glands were arranged regularly, and no goblet cells or apparent inflammatory cell infiltration were observed in the Elian granule group. The expression of p-JNK and p-p38 protein of the Elian granule group (0.83 ± 0.08; 1.18 ± 0.40) was significantly higher than the model group (0.27 ± 0.14; 0.63 ± 0.14) (. Elian granules may play a critical role in the treatment of rat PLGC by up-regulating the expression of p-JNK and p-p38 proteins in the MAPK signalling pathway, thus providing a scientific basis for clinical application.

Topics: Animals; Disease Models, Animal; Drugs, Chinese Herbal; JNK Mitogen-Activated Protein Kinases; Male; MAP Kinase Signaling System; Methylnitronitrosoguanidine; Network Pharmacology; p38 Mitogen-Activated Protein Kinases; Precancerous Conditions; Rats; Rats, Sprague-Dawley; Stomach Neoplasms; Up-Regulation

Gastric cancer, invasive cancer of the gastrointestinal tract, found in developing countries. Chemotherapy to patients with advanced gastric cancer, exhibits greater drug resistance to standard chemotherapy drugs. Therefore, important to establish anti-cancer drugs that are successful for cancer therapy. Corilagin is a natural ellagitannin (ET) with profound pharmacological properties has been used for the study to assess its anticancer effects against N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) stimulated gastric cancer rats. Biochemical studies showed Thiobarbituric acid reactive substances (TBARS) and enzymatic and non-enzymatic antioxidants increased in corilagin treated animals compared with controls. Histopathologic evaluation revealed corilagin treated rats showed cell morphology similar that control showing its ameliorating effects. In corillagen treament mRNA protein expression levels of HIF-1α, AKT, PI3K, CT4, CD147 and HMGB1 were drastically lowered transcription factors triggering gastric cancer. In Western blot analysis showed released higher apoptotic marker of caspase-3, -9, Bax while Bcl-2 levels were significantly reduced confirming that corilagin triggers apoptosis in gastric cancer.

Topics: Animals; Apoptosis; Carcinogenesis; Glucosides; Humans; Hydrolyzable Tannins; Methylnitronitrosoguanidine; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Rats; Rats, Wistar; Signal Transduction; Stomach Neoplasms

Xiaopi granules have been shown to ameliorate gastric epithelial dysplasia in patients. However, the therapeutic mechanism is unclear. Herein, the proteomics method was applied to identify the differentially expressed proteins and related pathways. Sixty male Sprague-Dawley rats were randomly divided into four groups: control (C group, n = 10), model (M group), Xiaopi granules (X group), and vitacoenzyme (V group). The rat gastric epithelial dysplasia model was established by intragastrically administering N-methyl-N'-nitro-N-nitrosoguanidine and ranitidine and by orally administering 0.05% ammonia solution. After 12 weeks, the stomach tissue was analyzed by hematoxylin and eosin staining and proteomics analyses. Western-blot analysis was applied to further validate the proteomics results. Compared to the M group, levels of 326 and 350 proteins were altered significantly in the X and V groups (1.5-fold, p < 0.05), which were significantly enriched in digestion, metabolism, coagulation, and cell apoptosis. CELA2A, GHRL, NDUFB9, and PGC were significantly upregulated (p < 0.0001), whereas CLCA1, PLG, and DAC2 were downregulated (p < 0.001 or 0.0001) in the M group vs. the C group. The change in these proteins could be reversed after the treatment of Xiaopi granules or vitacoenzyme tablets. Xiaopi granules ameliorated gastric epithelial dysplasia by intervening in digestion, metabolism, blood coagulation, cell apoptosis, and other related pathways.

Topics: Animals; Chromatography, Liquid; Male; Methylnitronitrosoguanidine; Proteomics; Rats; Rats, Sprague-Dawley; Stomach Neoplasms; Tandem Mass Spectrometry

This study evaluated the chemoprotective effect of scutellarin (SC) in vitro and in vivo against gastric carcinogenesis in rats and celllines and examined the underlying mechanism. Gastric cancer celllines (AGS) was used for the in vitro study and lactate dehydrogenase (LDH) profile, histone deacetylase (HDAC) assay, cell cycle & apoptosis ratio and antioxidant parameters were measured. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was used to induce gastric carcinogenesis in rats and the rats received the different doses of SC (10, 20 and 30 mg/kg). The body weight and tumor incidence were measured at regular time intervals. The antioxidant and pro-inflammatory cytokines were estimated. The finding of data showed that the drug was effective against AGS cell line. Supplementation of scutellarin revealed an upregulation in body weight compared with the MNNG group rats. Moreover, it also reduced the incidence of tumor. It also altered the significant DNA density, LDH content, mucus content and acidity. Scutellarin treated rats showed improved activity in enzymatic and non-enzymatic antioxidant profile and reversed the content of cytokines compared with MNNG induced gastric cancer group rats. This research reveals the chemoprotective property of the scutellarin and highlights the promising role of drug by alteration of inflammatory pathway by minimizing its adverse effect.

Topics: Animals; Antioxidants; Apigenin; Body Weight; Carcinogenesis; Cytokines; Glucuronates; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

Topics: Animals; Autophagy; Cell Proliferation; Epithelial-Mesenchymal Transition; Hesperidin; Methylnitronitrosoguanidine; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Rats; Stomach Neoplasms

Gastric cancer(GC), one of the most common malignancies worldwide, seriously threatens human health due to its high morbidity and mortality. Precancerous lesion of gastric cancer(PLGC) is a critical stage for preventing the occurrence of gastric cancer, and PLGC therapy has frequently been investigated in clinical research. Exploring the proper animal modeling methods is necessary since animal experiment acts as the main avenue of the research on GC treatment. At present, N-methyl-N'-nitro-N-nitroso-guanidine(MNNG) serves as a common chemical inducer for the rat model of GC and PLGC. In this study, MNNG-based methods for modeling PLGC rats in related papers were summarized, and the applications and effects of these methods were demonstrated by examples. Additionally, the advantages, disadvantages, and precautions of various modeling methods were briefly reviewed, and the experience of this research group in exploring modeling methods was shared. This study is expected to provide a reference for the establishment of MNNG-induced PLGC animal model, and a model support for the following studies on PLGC.

Topics: Animals; Gastric Mucosa; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Stomach Neoplasms

We examined the development of gastric cancer risk screening, from rat pepsinogen studies in an experimental rat gastric carcinogenesis model induced with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and human pepsinogen studies in the 1970s and 1980s to the recent "ABC method" for human gastric cancer risk screening. First, decreased expression or absence of a major pepsinogen isozyme, PG1, was observed in the rat gastric mucosa from the early stages of gastric carcinogenesis to adenocarcinomas following treatment with MNNG. In the 1980s, decreases in PGI in the human gastric mucosa and serum were identified as markers of atrophic gastritis. In the 1990s, other researchers revealed that chronic infection with Helicobacter pylori (Hp) causes atrophic gastritis and later gastric cancer. In the 2000s, a gastric cancer risk screening method combining assays to detect serum anti-Hp IgG antibody and serum PGI and PGII levels, the "ABC method", was established. Eradication of Hp and endoscopic follow-up examination after the ABC method are recommended to prevent gastric cancer.

Topics: Animals; Carcinogenesis; Early Detection of Cancer; Gastritis, Atrophic; Helicobacter Infections; Helicobacter pylori; Humans; Methylnitronitrosoguanidine; Pepsinogen A; Persistent Infection; Rats; Stomach Neoplasms

Protective effect of Tagetes erecta flowers essential oils was investigated on oxidative stress, immune response, inflammation, and apoptosis against N-methyl-N'nitro-N-nitroguanidine (MNNG) induced gastric cancer in rats. Essential oil were extracted from Tagetes erecta flowers and analyzed using gas chromatography-mass spectrometry (GC-MS). For observing a protective effect against MNNG induced gastric cancer, we divided rats into 4 groups (group A to D) having 10 rats in each group. Performed various experiments and measured a different parameters to investigate antioxidant activity, immune response, anti-inflammatory and anti-apoptotic activity. The levels of malondialdehyde were markedly increased in the presence of N-methyl-N'nitro-N-nitroguanidine, whereas, the antioxidant activities of superoxide dismutase, and catalase were lowered in the treated rats in contrast with the control. Intervention with TEEO to gastric cancer-induced rats upregulated the redox status and the activity of the immune system to decrease cancer risk. The proinflammatory cytokines (IL-6 and TNF-α) secretions that were induced by MNNG were markedly inhibited by TEEO. Administration of TEEO also significantly reduced terminal deoxynucleotidyl transferase dUTP nick end labeling positive gastric cancer cells, expression of mRNA of caspase-3, and Bax. Whereas, the expression of Bcl-2 was increased. Additionally, downregulation of nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) and IκBα degradation and the nuclear factor-κB (NF-κB) p65 expression in tissues of the stomach of MNNG-induced-rats were markedly elevated due to TEEO. This suggested possession of TEEO with a protective shield against MNNG induced gastric cancer by the exertion of antioxidative stress, anti-apoptotic response, the anti-inflammatory response through Nrf2/HO-1, and NF-κB signaling pathways.

Topics: Animals; Antioxidants; Apoptosis; Catalase; Cell Line, Tumor; Flowers; Gas Chromatography-Mass Spectrometry; Guanidines; Heme Oxygenase (Decyclizing); Immunoglobulin A; Immunoglobulin G; Immunoglobulin M; Inflammation; Male; Methylnitronitrosoguanidine; Mice; Neoplasm Proteins; NF-E2-Related Factor 2; NF-KappaB Inhibitor alpha; Nucleocytoplasmic Transport Proteins; Oils, Volatile; Oxidative Stress; Plant Extracts; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Wistar; Signal Transduction; Stomach Neoplasms; Tagetes

Although many studies have examined changes in gut microbiota composition in gastric carcinogenesis to clarify the mechanism of action of anticancer drugs, it is unclear whether animal models of gastric carcinogenesis adequately reflect the disease in humans.. To address this issue, the present study investigated changes in the gut microbiome profile of a rat model of gastric carcinogenesis established using a combination of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), sodium salicylate, irregular fasting, and ranitidine. The rats were divided into control (Normal), chronic non-atrophic gastritis (CNAG), chronic atrophic gastritis (CAG), precancerous lesion of gastric cancer (PLGC), and gastric cancer (GC) groups according to histopathological features. Gut microbiome in gastric carcinogenesis profiling was performed by 16S rRNA gene sequencing of rat feces samples.. We found that gut bacterial species richness increased whereas species diversity decreased during gastric carcinogenesis, with the most significant changes detected in the PLGC group. Gut microbiota community composition differed across groups, with the greatest similarities observed between CNAG and CAG groups and between PLGC and GC groups. There were significant differences in taxonomic representation at the phylum level: the PLGC group had the highest ratio of Firmicutes/Bacteroidetes whereas the GC group had the highest abundance of Proteobacteria and Actinobacteria.. These results indicate that changes in the gut microbiome in a rat model of MNNG-induced gastric carcinogenesis are similar to those observed in humans, thus providing a useful tool for evaluating the efficacy and mechanism of action of novel monotherapies or drug combinations for the treatment of gastric carcinogenesis.

Topics: Animals; Bacteria; Carcinogenesis; Dysbiosis; Feces; Food Deprivation; Gastritis; Gastrointestinal Microbiome; Male; Methylnitronitrosoguanidine; Ranitidine; Rats; RNA, Bacterial; RNA, Ribosomal, 16S; Sodium Salicylate; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Carcinogenesis; Cell Proliferation; Gastric Mucosa; Hyperplasia; Leptin; Male; Methylnitronitrosoguanidine; Rats; Rats, Sprague-Dawley; Stomach; Stomach Neoplasms

Gastric cancer is recognized as one of the most common cancer. In-depth research of gastric precancerous lesions (GPL) plays an important role in preventing the occurrence of gastric cancer. Meanwhile, traditional treatment provides a novel sight in the prevention of occurrence and development of gastric cancer. The current study was designed to assess the effects of therapy with Weipixiao (WPX) decoction on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced GPL rats and the underlying molecular mechanisms. After 10-weeks treatment, all rats were sacrificed. Histopathological changes of gastric tissue were assessed via hematoxylin-eosin (HE) and High-iron diamine-Alcian blue-Periodic acid-Schiff (HID-AB-PAS) staining. To be fully evidenced, RT-qPCR, Western blot and immunohistochemistry were used to detect the expressions of LDHA, CD147, HIF-1α, MCT4, PI3K, AKT, mTOR and miRNA-34a, which were crucial factors for evaluating GPL in the aspect of glycolysis pathogenesis. According to the results of HE and HID-AB-PAS staining, it could be confirmed that MNNG-induced GPL rats were obviously reversed by WPX decoction. Additionally, the increased gene levels of LDHA, CD147, MCT4, PI3K, AKT, mTOR and HIF-1α in model group were down-regulated by WPX decoction, while miRNA-34a expression was decreased and up-regulated by WPX decoction. The significantly increased protein levels of LDHA, CD147, MCT4, PI3K, AKT, mTOR and HIF-1α induced by MNNG were attenuated in rats treated with WPX decoction. In brief, the findings of this study imply that abnormal glycolysis in MNNG-induced GPL rats was relieved by WPX decoction via regulation of the expressions of LDHA, CD147, HIF-1α, MCT4, PI3K, AKT, mTOR and miRNA-34a.

Topics: Animals; Anticarcinogenic Agents; Cytoprotection; Disease Models, Animal; Drugs, Chinese Herbal; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Glycolysis; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Rats, Sprague-Dawley; Signal Transduction; Stomach; Stomach Neoplasms

To investigate the protective effect and molecular mechanisms of Weining granule on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer in rats.. A total of sixty healthy male wistar rats were randomly divided into five groups, including control group (CG), gastric cancer model group (MG), low-dose Weining granule treated group (LWT), medium-dose Weining granule treated group (MWT), and high-dose Weining granule treated group (HWT). Except the control group, the other groups were treated with MNNG to establish a rat model of gastric cancer. Low-dose Weining granule treated group, medium-dose Weining granule treated group, and high-dose Weining granule treated group were fed 9.0, 18.0 and 36.0 g/kg Weining granule, respectively. Histopathologic and molecular biologic technology were adopted to determine the protective effect of Weining granule on MNNG-induced gastric cancer in rats. The pathological changes of gastrointestinal tissue were observed. Meanwhile, the differential expression of proliferation, apoptosis and angiogenesis markers were determined, including proliferating cell nuclear antigen (PCNA), pokemon, cyclin D1, B-cell lymphoma-2 (Bcl-2), caspase-3, phosphatase and tensin homolog (PTEN) and vascular endothelial growth factor (VEGF).. After the MNNG treated, the pathological changes of stomach tissue were improved noticeably, including the intestinal metaplasia and atypic hyperplasia. The experiment was completed in 58 rats (96.67%). As compared with gastric cancer model group, the general states of rats were improved significantly after treated with different dose Weining granule. Moreover, treatment with different doses of Weining granule could inhibit the protein and mRNA expression of PCNA, pokemon, cyclin D1, Bcl-2, and VEGF, while increase caspase-3 and PTEN (P < 0.01).. Weining granule could improve gastric cancer by suppressing cell proliferation, promoting tumor cell apoptosis, and inhibiting angiogenesis.

Topics: Animals; Apoptosis; Blotting, Western; Cell Proliferation; Drugs, Chinese Herbal; Male; Methylnitronitrosoguanidine; Random Allocation; Rats; Rats, Wistar; Stomach Neoplasms

To explore the changes of Sonic Hedgehog (Shh) signaling pathway in the stomach mucosa during the formation of gastric precancerous lesions.. A total of 72 suckling rats in half genders were randomly and equally divided into the normal group and model group. The rats in the model group were administered with 0.1 ml 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) at the dosage of 800 mg/L for 10 days, whereas the rats in the normal group were similarly administered with normal saline. A total of 12 rats in each group were killed at the end of 10th, 22nd, and 34th weeks in half gender, respectively. Histopathological changes of the gastric mucosa were observed by hematoxylin and eosin (HE) staining; the levels of Shh, Ptch1, Smo, Gli1, Gli2, Gli3, SuFu, Cyclin D1, Cyclin E1, c-Myc, and β-actin mRNAs in the gastric mucosa were determined by real-time polymerase chain reaction; while the protein expression of Shh, Ptch1, Smo, Gli1, SuFu, Cyclin D1, Cyclin E1, c-Myc, and p-c-Myc was detected by western blot analysis.. With the development of atrophy and dysplasia of gastric mucosa, the levels of Shh, Smo, Gli1, Cyclin D1, Cyclin E1, and c-Myc mRNAs increased, while those of Ptch1 and SuFu decreased. The expression of Shh, Smo, Gli1, Cyclin D1, Cyclin E1, and p-c-Myc proteins were elevated, while the expression of Ptch1 and SuFu proteins were decreased, however, without statistical difference.. Shh signaling is activated during the formation of gastric precancerous lesions, which indicates that the Shh signaling pathway participates in the development and progression of gastric precancerous lesions.

Topics: Animals; Atrophy; Disease Models, Animal; Female; Gastric Mucosa; Gene Expression Regulation, Neoplastic; Hedgehog Proteins; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Rats, Sprague-Dawley; RNA, Messenger; Signal Transduction; Stomach Neoplasms; Time Factors

Topics: Animals; Antineoplastic Agents, Phytogenic; beta Catenin; Betaine; Cyclin D1; Dendrobium; Gene Expression Regulation, Neoplastic; Glycogen Synthase Kinase 3 beta; Male; Metabolome; Methylnitronitrosoguanidine; Plant Extracts; Polysaccharides; Precancerous Conditions; Proliferating Cell Nuclear Antigen; Rats; Rats, Sprague-Dawley; Signal Transduction; Stomach Neoplasms; Wnt Proteins

Evidence shows that aberrant expression of long non-coding RNA (lncRNA) is closely associated with tumor development and progression. However, the role of lncRNA in environmental carcinogen induced gastric tumorigenesis remains largely unknown. This study aimed at investigating the function role of lncRNA in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induce malignantly transformed human gastric epithelial cells.. In this study, high-throughput sequencing and qRT-PCR assay revealed marked downregulation of lncRNA LOC101927497 in the malignant transformed gastric epithelial cells induced by MNNG (GES-1-T cells), gain-of-function and loss-of-function assays showed that LOC101927497 can suppress the proliferation and migration of GES-1-T cells in vitro. RNA antisense purification experiment showed that LOC101927497 interacted with miR-574-5p in GES-1-T cells the most obvious. Further studies suggested that LOC101927497 may function as a tumor suppressor by interacting with miR-574-5p.. LncRNA LOC101927497 functions as a suppressor by interacting with miR-574-5p, thus inhibiting the malignant phenotype of GES-1-T cells.. To the best of our knowledge, this is the first study to demonstrate the role of lncRNA in MNNG-induced gastric tumorigenesis, and it will provide new insights into the role of lncRNA in environmental carcinogen-induced gastric cancer.

Topics: Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Epithelial Cells; Gastric Mucosa; Humans; Methylnitronitrosoguanidine; RNA, Long Noncoding; Stomach Neoplasms

Gastric Cancer is one of the most common types of cancer. And the occurrence of gastric carcinoma is an evolutionary histopathological stage. As a result, further research of GPL, which is a borderline of gastric cancer, is indispensable for preventing the formation and development of gastric carcinoma. Several studies have demonstrated a correlation between the expression of autophagy, apoptosis and Gastric cancer (GC). However, the effects of autophagy and apoptosis on human gastric cancer progression, particularly on gastric precancerous lesions (GPL), have not totally been investigated. At present, Astragaloside IV(AS-IV) is a saponin purified from Astragalus membranaceous Bge, a traditional Chinese herb that has been widely used for more than 2000 y in the treatment of cancer, cardiovascular and immune disorders. This study was designed to investigate the mechanism of AS-IV protecting gastric mucosa in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced GPL rats. The lesions of GIM and GED were significantly ameliorated compared with the model rats, especially crowded tubular glandular and back-to-back tubular structure, which were the dangerous borderline between GPL and GC. Western Blot analysis showed that the ratio of Bcl-2/Bax and the protein expression of Bcl-XL, p53, Beclin1, p62, ATG5 and ATG12 were decreased and the level of Caspase3 was increased in the group of AS-IV compared with the model group; RT-PCR analysis showed that the gene expression Ambra1, Beclin1, ATG5, LC3 and p62 were decreased in the group of AS-IV compared with the model group. This research manifested that the occurrence of gastric cancer was preceded by a prolonged precancerous stage, which could be ameliorated by the AS-IV. Meanwhile, the mild and moderate stage of precancerous lesions is similar with gastric adenocarcinoma in critical biological processes, including inflammation, cell proliferation, differentiation. But this lesion is very different from cancer, because it does not appear obvious invasion and malignant lesions in this pathologic stag. Further, AS-IV could regulate p53 expression to activate the Ambra1/Beclin1 complex in GPL, and it will protect the gastric mucosal injury, prevent and cure gastric mucosal atrophy, intestinal metaplasia and atypical hyperplastic lesions. It provided a potential therapeutic strategy in reversing intestinal metaplasia and dysplasia of gastric precancerous lesions and protecting the gastric mucosa in GPL rats.

Topics: Adenocarcinoma; Animals; Apoptosis; Cell Differentiation; Cell Proliferation; Gastric Mucosa; Hyperplasia; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Protective Agents; Rats; Rats, Sprague-Dawley; Saponins; Stomach; Stomach Neoplasms; Triterpenes

In recent years, Chinese medicine has played an important role in the prognosis of gastric cancer. Precancerous lesions of gastric carcinoma (PLGC) is a class of gastric cancer which is closely related to the gastric mucosal pathology changes in the role of carcinogenic incentives, and plays key role in the progression of normal gastric mucosal cells into gastric cancerous cells. In current experiment, we explore the relationship between Chinese traditional medicine (Xiao Tan He Wei Decoction) and gastric cancer in the PLGC rat animal models and epithelial-mesenchymal transitioned GES-1 cells which were induced useing 1- Methyl-3-nitro-1-nitrosoguanidine (MNNG). PLGC rat model showed significant deterioration in the gastric mucosa with terrible growth rate in body weight and more atypical hyperplasia in gastric mucosa. MC cells, MNNG induced GES-1 cells which epithelial- mesenchymal-transition (EMT)-related proteins have a great change compare with normal GES-1 cells. The cells had characteristics of malignant cells including proliferation, invasion and metastasis ability. Our research founds that Xiao Tan He Wei Decoction could inhibit cell proliferation and increased apoptosis by increase the level of pro-apoptotic proteins like Bax and caspase-3 and decreased the level of anti-apoptotic protein Bcl-2, block the cells in G0/G1 phase simultaneously. Furthermore, Xiao Tan He Wei Decoction could inhibit nuclear factor kappa-light-chain-enhancer (NF-kB) activity and inhibit its transfer from the cytoplasm to the nucleus. However, when we incubated with NF-κB activator PMA, the effect of Xiao Tan He Wei Decoction was reversed. These results suggested that Xiao Tan He Wei Decoction could be used as a method for the treatment of gastric precancerous lesions, and possibly provide a theoretical basis for the clinical treatment of gastric cancer and gastric precancerous lesions.

Topics: Animals; Apoptosis; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cell Transformation, Neoplastic; Disease Models, Animal; Drugs, Chinese Herbal; Epithelial-Mesenchymal Transition; Humans; Hyperplasia; Methylnitronitrosoguanidine; NF-kappa B; Precancerous Conditions; Rats, Wistar; Stomach Neoplasms; Tetradecanoylphorbol Acetate

Mesenchymal stem cells (MSCs) are a critical component of the tumor microenvironment. Upon distinct pathological stimulus, MSCs show phenotypic and functional changes. Gastric cancer is one of the leading causes of cancer‑related deaths worldwide. The roles and mechanisms of MSCs in gastric cancer have not been well characterized. In the present study, we investigated the roles of MSCs in the malignant transformation from gastritis to gastric cancer using an N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer model. We isolated MSCs from the gastric tissues of normal (RGN-MSCs) and MNNG-exposed rats (RGI-MSCs), and compared the biological properties of RGI-MSCs with RGN-MSCs. We found that RGI-MSCs had increased proliferative and migratory capabilities than these capacities noted in the RGN-MSCs. In addition, RGI-MSCs produced higher levels of IL-6, CXCL10 and MCP-1 than RGN-MSCs. Moreover, RGI-MSCs promoted the migration of normal gastric mucosa epithelial cells by inducing epithelial-mesenchymal transition (EMT). The upregulation of miR-374 in RGI-MSCs was partially responsible for their increased proliferative and migratory capabilities. Collectively, our findings provide new evidence for the roles of MSCs in gastric carcinogenesis, suggesting that targeting gastric cancer-associated MSCs may represent a novel avenue for gastric cancer therapy.

Topics: Animals; Cell Movement; Cell Proliferation; Cell Transformation, Neoplastic; Chemokine CXCL10; Epithelial-Mesenchymal Transition; Gastritis; Humans; Interleukin-6; Mesenchymal Stem Cells; Methylnitronitrosoguanidine; MicroRNAs; Neoplastic Stem Cells; Rats; Stomach Neoplasms; Tumor Microenvironment

The effects of miR-148a in regulating the expression of TGFβ2 and SMAD2 in MNNG-initiated gastric cancer rats and the mechanism of action in GC cells were determined. Effects of miR-148a on the proliferation, migration, and invasion of GC cell lines were demonstrated. We used Wistar rats, Balb/c nude mice, and GC cell lines. Rats were treated with MNNG to establish a GC rat model. Levels of miR-148a, TGFα, TGFβ2, SMAD2, SMAD3, and SMAD4 were tested in gastric tissues from different groups. In GC cell lines, we constructed and transfected a primary miR-148a plasmid to determine the expression patterns of TGFβ2, SMAD2, and SMAD4. A luciferase activity assay was used to monitor the effects of miR-148a on the TGFβ2- and SMAD2-3'UTRs. We identified nude mouse models bearing BGC-823-miR-148a or BGC-823-vector cells. Tumor volumes were detected, and TGFβ2, SMAD2 expression levels were determined in tumor tissues. The in vivo study demonstrated an increase in the mRNA and protein levels of TGFβ2, SMAD2, and SMAD4 in the MNNG-treated group compared with the control group. However, there were no differences in the mRNA and protein levels in either TGFα or SMAD3. The in vitro study demonstrated that overexpression of miR-148a reduced TGFβ2 and SMAD2 significantly in GC cells. The results of the luciferase activity assay showed that miR-148a could bind to the 3'UTRs of TGFβ2 and SMAD2 and inhibited their activity. Overexpression of miR-148a inhibited proliferation, migration, and invasion significantly in GC cell lines. In vivo, tumor volume of BGC-823-miR-148a was smaller than that of BGC-823-vector. Overall, miR-148a inhibited the proliferation, migration, invasion, and expression of TGFβ2 and SMAD2 in GC cells. It was concluded that miR-148a might play an important role in gastric cancer, and is a potential candidate for GC treatment.

Topics: 3' Untranslated Regions; Animals; Cell Line, Tumor; Cell Movement; Cell Proliferation; Down-Regulation; Gene Expression Regulation, Neoplastic; Humans; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Mice, Nude; MicroRNAs; Neoplasms, Experimental; Rats; Rats, Wistar; Smad2 Protein; Stomach Neoplasms; Transforming Growth Factor beta2

The objective of the present study was to evaluate the effect of combination of telmisartan with 5-flourouracil (5-FU) in gastric cancer cachexia induced by administering N-methyl-N'-methyl-N-nitrosoguanidine (MNNG).. MNND was administered once daily by oral gavage for two weeks, and saturated NaCl (1ml per rat) was then given once every 3days for 4weeks. 5-FU (75mg/kg, i.v.) was administered once three weeks from 7th to 22nd week. From 7th to 22nd week, telmisartan (5mg/kg, p.o.) was also administered along with 5-FU.. MNNG produced significant decrease in food intake, body weight, caused hyperglycemia, dyslipidemia, hypertension worsened hemodyanamics, increased cachexia markers and increased tumor markers like lactate dehydrogenase and γ-glutamyltransferase. MNNG also produced oxidative stress in the stomach tissue. Treatment with combination of telmisartan with 5-FU produced significant increase in food intake and body weight, controlled hyperglycemia and dyslipidemia, preserved hemodynamic function, and decreased the cachexia markers while 5-FU alone did not produce any such effects. Further, the combination of telmisartan with 5-FU significantly reduced tumor marker levels, oxidative stress and also significantly decreased the cell proliferation, apoptosis, hyperkeratosis, keratohyaline granules and invasive carcinoma of forestomach and reduced muscle atrophy in tibilias anterior skeletal muscle.. Our data suggests that combination of telmisartan with 5-FU treatment is beneficial in controlling cancer cachexia. Telmisartan can be used as an add-on therapy with 5-FU or other traditional chemotherapeutic agents.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Benzimidazoles; Benzoates; Cachexia; Fluorouracil; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Telmisartan

In the current study, we investigated the chemopreventive activity of arabinoxylan rice bran, MGN-3/Biobran, against chemical induction of glandular stomach carcinogenesis in rats. Gastric cancer was induced by carcinogen methylnitronitrosoguanidine (MNNG), and rats received MNNG alone or MNNG plus Biobran (40 mg/kg body weight) for a total of 8 months. Averaged results from 2 separate readings showed that exposure to MNNG plus Biobran caused gastric dysplasia and cancer (adenocarcinoma) in 4.5/12 rats (9/24 readings, 37.5%), with 3.5/12 rats (7/24 readings, 29.2%) showing dysplasia and 1/12 rats (8.3%) developing adenocarcinoma. In contrast, in rats treated with MNNG alone, 8/10 (80%) developed dysplasia and adenocarcinoma, with 6/10 rats (60%) showing dysplasia and 2/10 rats (20%) developing adenocarcinoma. The effect of combining both agents was also associated with significant suppression of the expression of the tumor marker Ki-67 and remarkable induction in the apoptotic gastric cancer cells via mitochondrial-dependent pathway as indicated by the upregulation in p53 expression, Bax expression, downregulation in Bcl-2 expression, an increase in Bax/Bcl-2 ratio, and an activation of caspase-3. In addition, Biobran treatment induced cell-cycle arrest in the subG1 phase, where the hypodiploid cell population was markedly increased. Moreover, Biobran treatment protected rats against MNNG-induced significant decrease in lymphocyte levels. We conclude that Biobran provides protection against chemical induction of glandular stomach carcinogenesis in rats and may be useful for the treatment of human patients with gastric cancer.

Topics: Adenocarcinoma; Animals; Apoptosis; bcl-2-Associated X Protein; Carcinogenesis; Caspase 3; Cell Cycle Checkpoints; Cell Line, Tumor; Down-Regulation; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Wistar; Stomach; Stomach Neoplasms; Xylans

Iranian propolis is a natural product of honeybees that has significant and varied anti-cancer benefits. The present study was designed to investigate the protective effects of Iranian propolis on gastric tissue carcinogenesis in an animal model. . Propolis samples were collected from Hamadan and Taleghan districts of Iran, followed by ultra performance liquid chromatography mass spectrometry analysis. Fifty-five rats were divided into three groups; control, Taleghan propolis and Hamadan propolis. All the animals received N-methyl-N-nitro-N-nitrosoguanidine (MNNG, 100 μg/ml) in drinking water ad libitum for 34 weeks. In the treated groups, nutrition with propolis was started two weeks before MNNG administration. At the end of the study, the entire gastrointestinal tract was scrutinized for tumors, and the rest of the body was assessed for metastatic deposits. . Results indicated that the incidence and number of tumors were significantly decreased by propolis in comparison with the control group (P < 0.05). The nuclear/cytoplasmic ratio, epithelial stratification, nuclear dispolarity, structural abnormality, and Beta-catenin and Bcl-2 proteins expression were significantly reduced in the propolis group compared to the control group (P < 0.05). In addition, Bax protein expression was significantly increased in the propolis group in comparison with the control group (P < 0.05). . The present study demonstrated the potential chemoprotective effects of the Iranian propolis against gastric cancer in a typical animal model. The results provide evidence for the hypothesis that Iranian propolis may exert a chemoprotective effect on MNNG-initiated gastric cancer through inhibition of cell proliferation and apoptosis induction.

Topics: Adenocarcinoma; Animals; Anticarcinogenic Agents; Apoptosis; bcl-2-Associated X Protein; beta Catenin; Cell Proliferation; Gastric Mucosa; Iran; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Propolis; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Wistar; Stomach Neoplasms

Chemoprevention strategies against gastric cancer (GC) need to be explored in light of the fact that stomach cancer still occurs in the absence of Helicobacter pylori (HP) infection and following HP eradication. We evaluated the effect of rebamipide on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis in SD rats. Thirty-nine male rats were divided into four groups based on whether or not they were treated with rebamipide and/or MNNG: Control, Rebamipide, Control-M, and Rebamipide-M groups. From 8 weeks of age, rats in the Control-M and Rebamipide-M groups received MNNG in drinking water for 30 weeks. The Rebamipide and Rebamipide-M groups were administered 5mg/kg/day of rebamipide. At 50 weeks, cancerous lesions were not observed in either the Control or Rebamipide groups. Nine rats in the Control-M group had developed GC, while four rats in the Rebamipide-M group had developed GC. The incidence of cancer in the Rebamipide-M group was significantly less than in the Control-M group (p<0.05), with a trend toward a lower incidence of invasive carcinoma in the Rebamipide-M group. Carcinomatous invasion into the muscularis propria was not observed in the Rebamipide-M group. In conclusion, the present study demonstrates that rebamipide suppresses. MNNG-induced carcinogenesis and may also inhibit progression of cancer in rats.

Topics: Adenocarcinoma; Alanine; Animals; Antioxidants; Carcinogenesis; Carcinogens; Disease Models, Animal; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Quinolones; Rats; Rats, Sprague-Dawley; Stomach Neoplasms

Peritoneal dissemination is a major clinical obstacle in gastrointestinal cancer therapy, and it accounts for the majority of cancer-related mortality. Calreticulin (CRT) is over-expressed in gastric tumors and has been linked to poor prognosis. In this study, immunohistochemistry studies revealed that the up-regulation of CRT was associated with lymph node and distant metastasis in patients with gastric cancer specimens. CRT was significantly down-regulated in highly metastatic gastric cancer cell lines and metastatic animal by Honokiol-treated. Small RNA interference blocking CRT by siRNA-CRT was translocated to the cells in the early immunogenic response to Honokiol. Honokiol activated endoplasmic reticulum (ER) stress and down-regulated peroxisome proliferator-activated receptor-γ (PPARγ) activity resulting in PPARγ and CRT degradation through calpain-II activity, which could be reversed by siRNA-calpain-II. The Calpain-II/PPARγ/CRT axis and interaction evoked by Honokiol could be blocked by gene silencing or pharmacological agents. Both transforming growth factor (TGF)-β1 and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induced cell migration, invasion and reciprocal down-regulation of epithelial marker E-cadherin, which could be abrogated by siRNA-CRT. Moreover, Honokiol significantly suppressed MNNG-induced gastrointestinal tumor growth and over-expression of CRT in mice. Knockdown CRT in gastric cancer cells was found to effectively reduce growth ability and metastasis in vivo. The present study provides insight into the specific biological behavior of CRT in epithelial-to-mesenchymal transition (EMT) and metastasis. Taken together, our results suggest that the therapeutic inhibition of CRT by Honokiol suppresses both gastric tumor growth and peritoneal dissemination by dictating early translocation of CRT in immunogenic cell death, activating ER stress, and blocking EMT.

Topics: Adult; Animals; Biomarkers, Tumor; Biphenyl Compounds; Calpain; Calreticulin; Cell Death; Cell Line, Tumor; Down-Regulation; Endoplasmic Reticulum Stress; Epithelial-Mesenchymal Transition; Female; Gene Knockdown Techniques; Humans; Lignans; Macrophages; Male; Methylnitronitrosoguanidine; Mice, Inbred BALB C; Mice, Inbred C57BL; Middle Aged; Neoplasm Invasiveness; Phagocytosis; PPAR gamma; Promoter Regions, Genetic; Protein Binding; Stomach Neoplasms; Up-Regulation

In the current study, we examined the protective effect of hydroferrate fluid MRN-100 against the carcinogen methylnitronitrosoguanidine (MNNG)-induced gastric and esophageal cancer in rats. MRN-100 is an iron-based compound composed of bivalent and trivalent ferrates. At 33 weeks post treatment with MNNG, rats were killed and examined for the histopathology of esophagus and stomach; liver, spleen, and total body weight; and antioxidant levels in the blood and stomach tissues. Results showed that 17/20 (85%) gastroesophageal tissues from carcinogen MNNG-treated rats developed dysplasia and cancer, as compared to 8/20 (40%) rats treated with MNNG plus MRN-100. In addition, MRN-100 exerted an antioxidant effect in both the blood and stomach tissues by increasing levels of GSH, antioxidant enzymes SOD, CAT, and GPx, and total antioxidant capacity (TAC) level. This was accompanied by a reduction in the total free-radical and malondialdehyde levels. Furthermore, MRN-100 protected against body and organ weight loss. Thus, MRN-100 exhibited significant cancer chemopreventive activity by protecting tissues against oxidative damage in rats, which may suggest its effectiveness as an adjuvant for the treatment of gastric/esophageal carcinoma.

Topics: Animals; Esophageal Neoplasms; Free Radicals; Iron; Methylnitronitrosoguanidine; Organ Size; Oxidation-Reduction; Oxidative Stress; Protective Agents; Rats, Wistar; Stomach Neoplasms

MicroRNAs (miRNAs) are recently discovered regulators of gene expression and are important in the regulation of many cellular events. Evidence collected to date shows that miRNAs are altered after exposure to environmental toxicants. However, the role that miR-21 plays in the gastric tumorigenesis induced by environmental carcinogens remains largely unknown. The aim of this study was to characterize the regulatory role of miR-21 in the carcinogenic processes following exposure to the N-nitroso carcinogen N-methyl-N-nitro-N'-nitrosoguanidine (MNNG). We found a progressive dose- and time-dependent increase in miR-21 expression following treatment with MNNG. Dysregulated miR-21 affected both cell growth in GES-1 cells and the gastric tumorigenesis induced with MNNG. These data demonstrate the involvement of miR-21 in the malignant transformation and tumorigenesis activated by MNNG. We also established that the Fas ligand (FASLG) and B-cell translocation gene 2 (BTG2), regulated by miR-21, contribute to the transformation induced by MNNG in GES-1 cells. This is the first study to show that miR-21 is involved in chemical carcinogenesis in vivo and in vitro. The regulation by miR-21 of the gastric carcinogenesis induced by MNNG highlights the functional roles of miRNAs in chemical carcinogenesis, and offers a new explanation of the mechanisms underlying chemical carcinogenesis.

Topics: 3' Untranslated Regions; Animals; Apoptosis; Binding Sites; Carcinogens; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Dose-Response Relationship, Drug; Fas Ligand Protein; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Humans; Immediate-Early Proteins; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Mice, Nude; MicroRNAs; RNA Interference; Stomach Neoplasms; Time Factors; Transfection; Tumor Suppressor Proteins

The aim of the study was to determine the phosphorylated c-Jun content and reduced and oxidized glutathione (GSH/GSSG) ratio in gastric mucosa cells during the process of gastric cancer development in rats.. Gastric carcinoge-nesis was initiated in 80 white male rats by 10-week replacement of drinking water with 0.01% solution of N-methyl-N´-nitro-N-nitrosoguanidine, at the same time they were redefined on diet containing 5% NaCl. Then the animals were fed with standard vivarium diet till the end of 24(th) week. The gastric mucosa cells were examined at the end of 4(th), 6(th), 8(th), 10(th), 12(th), 18(th), and 24(th) weeks. Sandwich ELISA method was used to determine the content of phospho-c-Jun. The contents of GSH and GSSG were analyzed by spectrofluorymetric method with the use of orthophthalic aldehyde.. At the end of 6(th), 8(th), 10(th) weeks of MNNG and NaCl treatment the gastric mucosa cells were characterized by 4-, 6.3-, 1.9-fold higher content of phospho-c-Jun compared to the control, respectively, and 12, 18 and 24 weeks there was registered a stable increase of phospho-c-Jun content on the average at 3.6-fold compared to control values. Starting from 6(th) week of gastric cancer development an average decrease of GSH/GSSG was 3.4-fold compared with the control.. During gastric carcinogenesis there was registered the decrease of GSH/GSSG ratio and increased level of phosphorylated c-Jun what points on MAP-kinase cascade activation in prooxidant conditions.

Topics: Animals; Cells, Cultured; Gastric Mucosa; Glutathione; Glutathione Disulfide; Immunoenzyme Techniques; JNK Mitogen-Activated Protein Kinases; Male; Methylnitronitrosoguanidine; Phosphorylation; Rats; Stomach Neoplasms

This study investigated the therapeutic effect of crocetin, a carotenoid derived from saffron, on gastric adenocarcinoma (AGS) cells and 1-methyl-3-nitro-1-nitrosoguanidine (MNNG)-induced gastric cancer in rats. An MTT assay showed a significant dose- and time-dependent inhibition of AGS cell proliferation as a result of crocetin administration. Flow cytometry and caspases activity assays revealed apoptosis had been induced in these cells; RT-PCR and Western blot analyses revealed the suppression of Bcl-2 and up-regulation of Bax expression in AGS cells treated with crocetin. These changes were not observed in normal human fibroblast (HFSF-PI3) cells. Pathological study of the tumor tissue in MNNG-induced gastric cancer in rats indicated the dose-dependent inhibition of tumor progression. In addition, crocetin reversed some changed biochemical parameters, including serum antioxidant activity and lactate dehydrogenase in rat serum. The present study demonstrates the antioxidant, anti-proliferative, and apoptotic activities of crocetin against gastric cancer that may benefit human stomach cancer treatment.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents, Phytogenic; Antioxidants; Apoptosis; bcl-2 Homologous Antagonist-Killer Protein; bcl-2-Associated X Protein; Carotenoids; Caspases; Cell Line, Tumor; Cell Proliferation; Crocus; Dose-Response Relationship, Drug; Fibroblasts; Gene Expression Regulation, Neoplastic; Humans; L-Lactate Dehydrogenase; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Signal Transduction; Stomach Neoplasms; Vitamin A

Tea polysaccharides were fractionated by Sephadex G-100 gel permeation chromatography. The results showed that tea polysaccharides were mainly composed of TF-1, TF-2 and TF-3. The average molecular weights of TF-1, TF-2 and TF-3 determined by high-performance gel permeation chromatography (HPGPC) and high performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD) were 231,568 Da, 46,278 Da and 7251 Da, respectively. The monosaccharide composition of Renshen polysaccharides was evaluated by GC. TF-1 was composed of glucose, mannose, xylose with molar ratio of 1:3.2:1.4. TF-2 and TF-3 consisted of glucose, xylose and glucose, xylose, arabinose with molar ratios of 1:1.7 and 1:2.5:0.9, respectively. TF-1 contained mannose as main sugar component and TF-2 was rich in xylose, whereas TF-3 was rich in xylose. In addition, tea polysaccharides could decrease stomach malondialdehyde (MDA) level, serum interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels, increased serum immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-10 (IL-10) levels, and stomach antioxidant enzymes activities in gastric cancer mice.

Topics: Animals; Antioxidants; Carcinoma; Glutathione; Malondialdehyde; Methylnitronitrosoguanidine; Mice; Neoplasms, Experimental; Polysaccharides; Stomach Neoplasms; Superoxide Dismutase; Tea

High temperature- and pressure-treated garlic (HTPG) has been shown to have enhanced antioxidative activity and polyphenol contents. Previously, we reported that HTPG inhibited 1,2-dimethylhydrazine-induced mucin depleted foci (premalignant lesions) and O6-methylguanine DNA adduct formation in the rat colorectum. In the present study, we investigated the modifying effects of HTPG on N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG)- induced pyloric stomach and small intestinal carcinogenesis in mice. Male C57BL/6 mice were given ENNG (100 mg/l) in drinking water for the first 4 weeks, then a basal diet or diet containing 2% or 5% HTPG for 30 weeks. The incidence and multiplicity of pyloric stomach and small intestinal (duodenal and jejunal) tumors in the 2% HTPG group (but not in the 5% HTPG group) were significantly lower than those in the control group. Cell proliferation of normal-appearing duodenal mucosa was assessed by MIB-5 immunohistochemistry and shown to be significantly lower with 2% HTPG (but again not 5% HTPG) than in controls. These results in dicate that HTPG, at 2% in the diet, inhibited ENNG-induced pyloric stomach and small intestinal (especially duodenal) tumorigenesis in mice, associated with suppression of cell proliferation.

Topics: Animals; Carcinogens; Cell Proliferation; Garlic; Hot Temperature; Immunoenzyme Techniques; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Mice; Mice, Inbred C57BL; Pressure; Stomach Neoplasms

The human pathogen Helicobacter pylori causes inflammation in the stomach of infected hosts, leading in some cases to the development of gastric cancer. Several mouse models have been developed to study Helicobacter-induced carcinogenesis with similarities to gastric adenocarcinoma and mucosa-associated lymphoid tissue lymphoma (MALToma) in humans. These models require chronic infection of animals with mouse-colonizing isolates of H. pylori or with related gastric Helicobacter spp., such as the canine/feline species Helicobacter felis. Furthermore, consistent with the known influence of host and environmental factors in human gastric cancer, it is possible to manipulate the type and severity of gastric lesions in mouse Helicobacter infection models through the use of different mouse genetic backgrounds and/or by the administration of known cocarcinogens, such as alkylating agents (e.g., N-nitroso-N-methylurea), or even elevated quantities of dietary salt. Here, we describe protocols for the inoculation of mice with gastric Helicobacter spp. and the administration of these cocarcinogens. Furthermore, we will describe the various methodologies used to study gastric inflammation and carcinogenesis in Helicobacter-infected animals.

Topics: Animals; Carcinogens; Cell Proliferation; Culture Media; Culture Techniques; Cytokines; Disease Models, Animal; Drug Interactions; Epithelial Cells; Female; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Methylnitrosourea; Mice; Microbial Viability; Polymerase Chain Reaction; Specimen Handling; Stomach Neoplasms; Urease

In this study, anticancer effects of mirtazapine on rats were investigated in an adenocarcinoma model induced by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and compared with those of cisplatin.. For this purpose, 10 mg/kg doses of mirtazapine were administered orally to one group of rats, while 1 mg/kg doses of cisplatin were administered intraperitoneally to another group. At 1 hour after administration, 200 mg/kg doses of MNNG were given orally to both groups. MNNG administration was repeated once every 10 days through 3 months, after which period, gastric tissue was taken and pathologically evaluated.. Mirtazapine prevented adenocarcinoma induction by MNNG in rats to a greater extent than cisplatin. Some of the rats receiving cisplatin demonstrated severe dysplasia in gastric samples and others exhibited mild dysplasia. Rats given mirtazapine were not observed to suffer severe dysplasia, only mild dysplasia being observed.. For adenocarcinoma induced by MNNG on rats, mirtazapine was determined more effective than cisplatin. In order to make statement about mechanism of anticancer activity of mirtazapine, wider studies are required.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Cisplatin; Histamine H1 Antagonists; Immunoenzyme Techniques; Male; Methylnitronitrosoguanidine; Mianserin; Mirtazapine; Rats; Rats, Wistar; Stomach Neoplasms

The modulation of intracellular nuclear factor-kappaB (NF-κB) signaling pathway involved in the deregulated expression of cell proliferation and cell cycle regulatory molecules is a pragmatic approach for chemoprevention. Eugenol (4-allyl-1-hydroxy-2-methoxybenzene), a natural phenolic constituent of oils of cloves is known to possess attractive remedial features. In the present study, we investigated the modulatory effects of eugenol on NF-κB signaling in a rat model of gastric carcinogenesis induced by N-methyl-N(')-nitro-N-nitrosoguanidine (MNNG) by analysing the expression of nuclear factor-kappaB (NF-κB) family members ((NF-κB (p50 and p65), inhibitor of kappaB alpha (IκBα), phosphorylated IκBα (p-IκBα), IκB kinase β (IKKβ)) and the NF-κB target genes that promote (e.g., cyclin D1, cyclin B and PCNA) or inhibit (e.g., p53, p21, and Gadd45) cell proliferation and cell survival. MNNG-induced gastric tumours were characterized by NF-κB activation that correlated with upregulation of IKKβ, and phosphorylation and degradation of IκBα. Furthermore, upregulation of cyclins and PCNA with downregulation of p21, p53, and Gadd45 suggested that the proliferative advantage in gastric carcinomas is dependent on elevated constitutive NF-κB activity. Administration of eugenol significantly reduced the incidence of MNNG-induced gastric tumours by suppressing NF-κB activation and modulating the expression of NF-κB target genes that regulate cell proliferation and cell survival. The targeting of NF-κB signaling pathway by eugenol may have a significant impact on chemopreventive and therapeutic approaches for cancer.

Topics: Animals; Body Weight; Cell Proliferation; Disease Models, Animal; Drug Screening Assays, Antitumor; Eugenol; Gene Expression Regulation, Neoplastic; Immunohistochemistry; Male; Methylnitronitrosoguanidine; NF-kappa B; Rats; Rats, Wistar; RNA, Messenger; Signal Transduction; Stomach; Stomach Neoplasms

This study evaluated the galectin-1 and -3 expression during N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in denervated rat stomachs using benzalkonium chloride.. Four experimental situations were evaluated: nondenervated and denervated stomachs without lesions and nondenervated and denervated stomachs with lesions. Sections of the pyloric region were stained with toluidine blue and incubated with mouse monoclonal anti-Gal-1 and rabbit polyclonal anti-Gal-3 for histopathological and immunohistochemical analysis, respectively.. MNNG caused the development of benign and malignant epithelial lesions, which were more pronounced in nondenervated stomachs with lesions and accompanied by inflammatory cell-enriched stroma. By immunostaining, the epithelial cells, blood vessels, muscle layer, and myenteric plexus were Gal-1 and -3 positive. Gal-3 was also detected in the gastric crypts, mucus secretion, and fibroblasts of pyloric fragments. Development of lesions in denervated stomachs was associated with a significant decrease in Gal-1 and -3 expression in epithelial cells, mast cells, and neutrophil cytoplasm, compared with that of nondenervated stomach lesions (P < 0.01; P < 0.001; P < 0.001, respectively).. These results demonstrate that myenteric denervation downregulates endogenous Gal-1 and -3 expression, which might inhibit tumor development in this experimental model.

Topics: Adenocarcinoma; Animals; Denervation; Down-Regulation; Enteric Nervous System; Galectin 1; Galectin 3; Gene Expression Regulation, Neoplastic; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Wistar; Stomach Neoplasms

Gastric cancer is often diagnosed at advanced stages and there is no accurate method for its screening and diagnosis, especially in small animals. Here, we explain the application of B-mode ultrasound imaging (BMUI) for screening of gastric changes in the rat. Thus, male Albino Wistar rats, weighing 100-120 grams were randomly divided into two groups. The control group rats (n=10) were given water as routine; the remaining (n=90), were given N-methyl-N-nitro-N-nitrosoguanidine (MNNG, 100 μg/mL) in drinking water ad libitum for 40 weeks. Fifteen rats were killed at different time intervals and the others were sacrificed after 55 weeks. The BMUI of the stomach of animals after MNNG administration show some changes compared with the normal groups. Pathologic investigations of the stomach indicate cancer induction at different levels. The sensitivity and specificity of BMUI is 96.6% and 78.78%, respectively. Thus, it is a useful method of diagnosis of gastric cancer in rats.

Topics: Animals; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sensitivity and Specificity; Stomach Neoplasms; Ultrasonography

Hyperproliferative cell growth due to cyclin D1/cdk4, marker of cellular proliferation, is considered to be regulated by the expression of estrogen receptors (ERs). We investigated the immunohistochemical expression of cyclin D1/cdk4 and ERs in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced rat gastric carcinogenesis. The gastric cancer incidence and expression of cyclin D1/ckd4 in gastric carcinogenesis were significantly higher in males than females. Although the ERα expression index was similar in both sexes, the ERβ expression in preneoplastic hyperplastic lesions as well as gastric cancers was significantly higher in females than in males. The present study revealed a gender difference in MNNG-induced rat gastric carcinogenesis that seemed to involve the sex difference in cyclin D1/cdk4 expression, and ERβ expression became evident at the preneoplastic promotion stage in gastric carcinogenesis.

Topics: Adenocarcinoma; Animals; Biomarkers, Tumor; Carcinogens; Cyclin D1; Cyclin-Dependent Kinase 4; Estrogen Receptor alpha; Estrogen Receptor beta; Female; Gastric Mucosa; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sex Factors; Stomach Neoplasms

To investigate anticancer effect of lycopene, we examined the effects of lycopene on the oxidative injury and immunity activities of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer rats. The animals were divided into five groups. Group I served as the normal control and was given corn oil orally for 20 weeks. Group II were induced with MNNG 200 mg/kg body weight by oral gavage at days 0 and 14, and saturated NaCl (1 mL per rats) was given once every three days for four weeks until the end of the experimental period. Group III, IV and V were posttreated with lycopene (50, 100 and 150 mg/kg body weight, dissolved in corn oil) from the sixth week of MNNG (as in group II) induction up to the end of the experimental period. In the presence of MNNG, MDA and immunity levels were significantly increased, whereas enzymatic (SOD, CAT, and GPx) antioxidant activities were decreased in the treated rats compared with normal control rats. Administration of lycopene to gastric carcinoma-induced rats largely up-regulated the redox status and immunity activities to decrease the risk of cancer compared to group II. We conclude that up-regulation of antioxidants and immunity by lycopene treatment might be responsible for the anticancer effect in gastric carcinoma.

Topics: Animals; Antioxidants; Carotenoids; Catalase; Enzyme-Linked Immunosorbent Assay; Glutathione Peroxidase; Interleukins; Lycopene; Male; Methylnitronitrosoguanidine; Rats, Wistar; Stomach; Stomach Neoplasms; Superoxide Dismutase

Epidemiologic studies indicate that the incidence of gastric cancer is higher in males than in females. Although the mechanisms mediating this difference are unclear, a role for estrogens has been proposed. We used Western blotting to evaluate the role of estrogen receptor (ER) subtypes ERα and ERβ and proliferating cell nuclear antigen (PCNA) in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats; ERα and ERβ mRNA levels also were analyzed by quantitative real-time RT-PCR analysis. The incidence of gastric cancer was significantly higher in male than female rats. In both sexes, ERα expression was similar in MNNG-treated cancerous and noncancerous tissues and normal gastric tissue. However, ERβ expression in MNNG-treated cancerous and noncancerous tissues was significantly lower in male rats and higher in female rats than that in normal gastric tissue; MNNG-induced cancerous tissue showed the highest ERβ expression. PCNA expression in MNNG-treated cancerous tissues was higher than that in noncancerous tissues, and was higher in male rats than female rats. Western blotting results were consistent with the mRNA changes determined by quantitative real-time RT-PCR. The present study provides evidence of a sex-associated difference in ERβ and PCNA expression in MNNG-induced gastric cancers in Wistar rats.

Topics: Animals; Blotting, Western; Estrogen Receptor beta; Female; Male; Methylnitronitrosoguanidine; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; Sex Factors; Stomach Neoplasms

In this study, the anticancer effect of prednisolone was investigated using rats with normal endogen adrenaline levels (intact), reduced adrenaline levels (metyrosine-induced) and adrenaline deficiency (adrenalectomized) via gastric adenocarcinoma model. Gastric adenocarcinoma was induced with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). According to our experimental results, prednisolone could not prevent MNNG-induced adenocarcinoma when used alone in intact rats. There were neither macroscopic nor microscopic signs of cancer in the rat groups that received metyrosine and prednisolone. However, dysplasia occurred in the stomachs of 2 of 10 rats that received metyrosine and prednisolone. There was no adenocarcinoma genesis in the stomachs of adrenalectomized rats that received prednisolone alone. However, yohimbine (a selective blocker of alpha2-adrenoreceptors) pretreatment in adrenalectomized rats negated the anticancer effect of prednisolone. In conclusion, prednisolone was shown not to be an anticancer agent in intact rats when used alone; however, it has anticancer effects in rats whose adrenaline levels were reduced via adrenalectomy or metyrosine, which is a catecholamine synthesis inhibitor.

Topics: Adenocarcinoma; Adrenalectomy; Animals; Anti-Inflammatory Agents; Antineoplastic Agents; Catecholamines; Epinephrine; Male; Methylnitronitrosoguanidine; Prednisolone; Rats; Rats, Wistar; Stomach Neoplasms

To study the effects of an extract solution from radix curcumae on the expressions of VEGF, COX-2 and PCNA in gastric mucosa of rats during carcinogenesis induced MNNG.. Eighty male Wistar rats were randomly divided into 5 groups: group A, water and normal saline; group B, MNNG and normal saline; group C, MNNG and celecoxib; group D, MNNG and low-dose (1 g/ml) radix curcumae steam distillation extract solution; group E, MNNG and high-dose (2g/ml) radix curcumae wet distillation extract solution. In the end of the 40(th) week, all rats alive were sacrificed and the expressions of VEGF, COX-2 and PCNA in gastric mucosa were determined by immunohistochemistry.. The expression levels of VEGF and COX-2 and the optical density levels of PCNA in group C, D and E were remarkably lower than that of group B (P<0.05), while the optical density levels of PCNA in group E were higher than that of group C and D (P<0.05).. The distilled extract of curcumae can down-regulate the expressions of VEGF, COX-2 and PCNA in the gastric mucosa of rats during carcinogenesis induced MNNG and can reduce the incidence of gastric caner, suggesting it maybe as a potential chemopreventive agent for gastric cancer.

Topics: Administration, Oral; Animals; Antineoplastic Agents, Phytogenic; Carcinogens; Curcuma; Cyclooxygenase 2; Gene Expression; Male; Methylnitronitrosoguanidine; Plant Extracts; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Stomach Neoplasms; Treatment Outcome; Vascular Endothelial Growth Factor A

Combining apoptosis induction with anti-invasive and anti-angiogenic treatment is gaining increasing attention as a promising strategy for cancer chemoprevention. In the present study, eugenol (4-allyl-2-methoxyphenol) was evaluated for its chemopreventive effects on N-methyl-N(')-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats by analyzing markers of apoptosis, invasion and angiogenesis.. The expressions of markers of apoptosis (Bcl-2, Bcl-xL, Bax, Apaf-1, cytochrome C, caspase-9, caspase-3 and poly(ADP-ribose)polymerase; PARP), invasion (matrix metalloproteinase-2; MMP-2, matrix metalloproteinase-9; MMP-9, reversion-inducing cysteine rich protein with Kazal motifs; RECK and tissue inhibitors of metalloproteinase-2; TIMP-2) and angiogenesis (vascular endothelial growth factor; VEGF and VEGF receptor1; VEGFR1) in stomach tissue of experimental and control animals were measured by gelatin zymogram, immunohistochemical, Western blot and RT-PCR analysis.. Rats administered MNNG developed gastric carcinomas that displayed apoptosis avoidance coupled to upregulation of pro-invasive and angiogenic factors. Administration of eugenol induced apoptosis via the mitochondrial pathway by modulating the Bcl-2 family proteins, Apaf-1, cytochrome C, and caspases and inhibiting invasion, and angiogenesis as evidenced by changes in the activities of MMPs and the expression of MMP-2 and -9, VEGF, VEGFR1, TIMP-2 and RECK.. Phytochemicals such as eugenol that are capable of manipulating the equilibrium between pro- and anti-apoptotic proteins as well as the delicate balance between stimulators and inhibitors of invasion and angiogenesis are attractive candidates for preventing tumour progression.

Topics: Animals; Apoptosis; Blotting, Western; Densitometry; Disease Models, Animal; Eugenol; Gene Expression Regulation, Neoplastic; Immunohistochemistry; Male; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Methylnitronitrosoguanidine; Neoplasm Invasiveness; Neoplasm Proteins; Neovascularization, Pathologic; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; Stomach Neoplasms

Hyperinsulinemia and hyperglycemia in prediabetic and diabetic patients are thought to increase the risk of developing neoplasms because insulin is a growth factor with pre-eminent metabolic but also mitogenic effects. To determine the effect of hypoinsulinemic diabetic conditions on carcinogenesis, we examined N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced forestomach carcinogenesis in hypoinsulinemic diabetic WBN/Kob rats aged about 45 weeks (DM) compared with non-diabetic younger WBN/Kob rats (C1), non-diabetic Wistar rats age-matched to DM (C2), and non-diabetic Wistar rats age-matched to C1 (C3). All rats were treated with MNNG by gavage and were killed at 40 weeks after dosing. Various-sized tumors were disseminated throughout the forestomach of all rats, and the ratio of the area of tumors to the whole forestomach area was 23.3% in the DM group and was higher than in the C1-3 (4.2-14.3%) groups. The incidence of carcinoma was much higher in the DM group (36.8%) than in the C1-3 (7.1-16.7%) groups, and the incidence of papilloma was also significantly higher in the DM group (84.2%) than in the C1-3 (28.5-50.0%) groups. The average thickness of the squamous epithelium in the non-neoplastic mucosa was significantly greater in the DM group (50.8 mum) than in the C1-3 (29.6-37.9 microm) groups. Immunohistochemically, the Ki-67-positive index in the non-tumorous mucosa of the DM group (42.0%) was significantly higher than that of the C1-3 groups (18.8-33.3%). These results suggest that prolonged hyperglycemic conditions without hyperinsulinemia enhance tumorigenesis of MNNG-induced tumors by enhanced proliferative activity of the squamous epithelium in the rat forestomach.

Topics: Adipose Tissue; Animals; Carcinogens; Carcinoma; Diabetes Mellitus, Experimental; Epithelial Cells; Gastric Mucosa; Insulin; Ki-67 Antigen; Male; Methylnitronitrosoguanidine; Pancreatitis; Papilloma; Rats; Rats, Inbred Strains; Rats, Wistar; Stomach; Stomach Neoplasms

Gastric cancer results from a combination of Helicobacter pylori (H pylori) infection, exposure to dietary carcinogens, and predisposing genetic make-up. Because the role of these factors in gastric carcinogenesis cannot be determined readily in human beings, the present study examined the role of an oral carcinogen and H pylori infection in rhesus monkeys.. Gastroscopies were performed in 23 monkeys assigned to 4 groups: controls; nitrosating carcinogen ethyl-nitro-nitrosoguanidine administration alone; inoculation of a virulent H pylori strain alone (H); and ethyl-nitro-nitrosoguanidine in combination with H pylori (EH). Follow-up gastroscopies and biopsies were performed at 3-month intervals for 5 years for pathologic and molecular studies.. Postinoculation, H and EH groups showed persistent infection and antral gastritis. Starting at 2 and 5 years, respectively, gastric intestinal metaplasia and intraepithelial neoplasia developed in 3 EH monkeys but in no other groups. Transcriptional analysis of biopsy specimens at 5 years revealed group-specific expression profiles, with striking changes in EH monkeys, plus a neoplasia-specific expression profile characterized by changes in multiple cancer-associated genes. Importantly, this neoplastic profile was evident in nonneoplastic mucosa, suggesting that the identified genes may represent markers preceding cancer.. Gastric intraglandular neoplasia is induced in primates when H pylori infection is associated with consumption of a carcinogen similar to the nitrosamines found in pickled vegetables, suggesting that H pylori and the carcinogen synergistically induce gastric neoplasia in primates.

Topics: Animals; Biopsy; Carcinogens; Carcinoma in Situ; Cell Transformation, Neoplastic; Cluster Analysis; Diet; Disease Models, Animal; Disease Progression; DNA Repair; Female; Gastritis; Gastroscopy; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Helicobacter Infections; Helicobacter pylori; Macaca mulatta; Male; Metaplasia; Methylnitronitrosoguanidine; Oligonucleotide Array Sequence Analysis; Precancerous Conditions; Stomach Neoplasms; Time Factors

To evaluate the optimal intervention point of a selective cyclooxygenase-2 (COX-2) inhibitor, celecoxib, for inhibiting Helicobacter pylori (H. pylori)-associated gastric carcinogenesis in Mongolian gerbils (MGs).. One hundred and twelve MGs were divided into six groups (A-F). One hundred gerbils were inoculated with H. pylori (groups A-E). Twelve gerbils were inoculated with vehicle broth only (group F). After 4 wk, they were given N'-methyl-N'-nitro-N-nitroso-guanidine (MNNG) (50 microg/mL) in the drinking water for 20 wk. In groups B-E, the animals were given the stock celecoxib (10 mg/kg per day) diet from the 21st, 31st, 21st and 41st week respectively. The periods of administering celecoxib were 30, 20, 20, and 15 wk respectively. On the 51st week, the animals were sacrificed for histological examination. Local PCNA expression was examined by the immunohistochemistry method. The expression of COX-2 protein was assessed by western blot. Analysis used the chi(2) test. The difference was regarded as significant when P value was less than 0.05.. Seventeen percent (17/100) of H. pylori-infected MGs developed gastric cancer. All of these lesions were well-differentiated adenocarcinoma. The incidence rates of adenocarcinoma in groups A-F were 40%, 0%, 0%, 20%, 25%, and 0% respectively. The inflammatory scores were higher in group B than in other groups. There was no inflammatory response noted in group F. Celecoxib treatment resulted in a significant reduction in the proliferation of H. pylori-infected mucosal cells (groups B, C and D) (P < 0.01). The expression of COX-2 protein was significantly attenuated in the groups which were celecoxib-treated for more than 20 wk (groups B, C, D). The groups treated with celecoxib had a significantly lower rate of advanced gastric cancer (34% vs 75%, P < 0.001) There were no sudden deaths in any of the groups.. Short-term treatment with celecoxib has an anti-carcinogenic effect, and resulted in less severe inflammation and inhibited the invasive degree of gastric cancer.

Topics: Adenocarcinoma; Animals; Anticarcinogenic Agents; Celecoxib; Cell Proliferation; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Disease Models, Animal; Drug Administration Schedule; Gastric Mucosa; Gerbillinae; Helicobacter pylori; Methylnitronitrosoguanidine; Neoplasm Invasiveness; Proliferating Cell Nuclear Antigen; Pyrazoles; Stomach Neoplasms; Sulfonamides; Time Factors

To investigate the effect of Ginkgo biloba extract on gastric precancerous lesions in rats.. 80 4-week-old Wistar rats were randomly divided into four groups: a control group, a model group, a low and a high dose Ginkgo biloba extract intervention group; 20 in each group. Gastric precancerous lesions were induced by giving them 100 mg/L N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) solution to drink ad libitum for 20 weeks. In addition to the MNNG, the intervention groups were lavaged with Ginkgo biloba extract (0.5 mg/kg/d in the low dose group, 1.5 mg/kg/d in the high dose group) for 20 weeks. Starting from week 21 all the rats were fed with normal rat chow and tap water. At the end of week 30 the rats were killed. The histopathological changes of their gastric mucosa, ISA, NGI, the serum and gastric mucosal SOD/MDA and the expressions of oncogenes were studied.. The incidence of mild to severe intestinal metaplasia and dysplasia were significantly lower in the intervention groups than those in the model group (P < 0.01). The ISA and NGI in the intervention groups were significantly lower than those in the model group (P < 0.01). In the intervention groups the activity of SOD was increased and the concentration of MDA was decreased (P < 0.01). Expressions of Bcl-2, c-myc and FasL decreased in the intervention groups, whereas the expression of Fas increased. When compared with the model group, the differences were statistically significant (P < 0.01, P < 0.05, respectively).. Ginkgo biloba extract can increase anti-oxidative activity and inhibit the progression of gastric precancerous lesions via the regulation of cell proliferation and apoptosis.

Topics: Animals; Antioxidants; Apoptosis; Body Weight; Cell Division; Disease Progression; Dose-Response Relationship, Drug; Fas Ligand Protein; fas Receptor; Gastric Mucosa; Gastritis; Gene Expression; Ginkgo biloba; Malondialdehyde; Methylnitronitrosoguanidine; Plant Extracts; Precancerous Conditions; Proto-Oncogene Proteins c-bcl-2; Proto-Oncogene Proteins c-myc; Rats; Rats, Wistar; Serum Albumin; Stomach Neoplasms; Superoxide Dismutase

Endoscopy can be used for sequential observation of gastric carcinogenesis in animal models. In the present study, we applied endoscopic examination and biopsy technique on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced stomach cancer in rats using a newly-developed flexible 2.5 mm endoscope. A total of 36 rats were divided into MNNG-treated and non-treated groups, observed on gastric endoscopy every 5 weeks, and sacrificed at week 10, 25, 35, and 50. The sequential growth process of MNNG-induced gastric tumor was clearly found by the endoscopic examination. Endoscopic appearances including incidence and size of tumor were well consistent with histological findings. In addition, biopsy specimens could be extracted from gastric mucosa in living rats using a biopsy forceps. These results indicate that the endoscopic technique can be a useful tool for investigating gastric carcinogenesis by sequential observation and collection of biopsy specimens.

Topics: Animals; Endoscopy, Digestive System; Male; Methylnitronitrosoguanidine; Prognosis; Rats; Rats, Sprague-Dawley; Stomach Neoplasms

Naringenin is a flavanone that is believed to have many biological actions, including as an anti-oxidant, free radical scavenger and an antiproliferative agent. The global incidence of gastric carcinoma is increasing rapidly, more than for any other cancer. Therefore, in the present study, we tested the effects of naringenin on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and saturated sodium chloride (S-NaCl) in rats. Male Wistar rats were divided into five groups and treated over a period of 20 weeks as follows: (i) a control group given corn oil (1 mL/rat, p.o.) daily 20 weeks; (ii) 200 mg/kg, p.o., MNNG on Days 0 and 14 with S-NaCl (1 mL/rat) administered twice a week for the first 3 weeks; (iii) 200 mg/kg, p.o., MNNG on Days 0 and 14, with naringenin (200 mg/kg, p.o., daily) treatment for the entire 20 weeks; (iv) 200 mg/kg, p.o., MNNG on Days 0 and 14, with naringenin treatment (200 mg/kg, p.o., daily) initiated from 6 to 20 weeks; (v) 200 mg/kg, p.o., naringenin alone daily for 20 weeks. In Group II rats in which gastric cancer was inducted with MNNG and S-NaCl, there was a significant increase in hydrogen peroxide and lipid peroxidation levels, with decreases in reduced glutathione, oxidized glutathione, glutathione peroxidase, glutathione reductase and glucose 6-phosphate dehydrogenase. In addition, in Group II rats with gastric cancer, there were significant increases in the activity of cytochrome P450, cytochrome b(5) and NADPH cytochrome c reductase, with concomitant decreases in the activity of the phase II enzymes glutathione S-transferase and UDP-glucuronosyl transferase. Naringenin treatment (Groups III and IV) restored enzyme activity to near control levels. These results indicate that naringenin has a chemopreventive action against MNNG-induced gastric carcinoma in experimental rats.

Topics: Animals; Antineoplastic Agents, Phytogenic; Enzyme Activation; Flavanones; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Microsomes, Liver; Plants, Medicinal; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

To investigate the effects of Radix notoginseng extracts drug-containing serum on the expressions of apoptosis-regulating proteins including Bax, bcl-2 and p21WAF1 in precancerous gastric cells.. The N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) transformed eternalized human gastric mucosa epithelium GES-1 cell line (MC cell) was used in vitro as a model of gastric precancerous lesion. The medicated canine serum was prepared by feeding to the adult Beagle dog with Radix notoginseng extracts and obtaining the serum after 2-hour medication. MC cells were cultured with medicated canine serum (medicated serum group) or non-medicated canine serum (normal control group) for 72 hours. Expressions of Bax, bcl-2 and p21WAF1 proteins were detected by immunocytochemical assay and the average optical density of the cells was determined by an image analysis system.. Compared with those of the normal control group, Bax and p21WAF1 expressions in medicated serum group were significantly enhanced (P<0.01), while the expression of bcl-2 was significantly reduced (P<0.01).. Radix notoginseng extracts may inhibit the proliferation and promote the apoptosis of precancerous gastric cells through altering expressions of the bcl-2, Bax and p21WAF1 genes.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Cyclin-Dependent Kinase Inhibitor p21; Dogs; Drugs, Chinese Herbal; Gastric Mucosa; Humans; Methylnitronitrosoguanidine; Panax notoginseng; Plant Roots; Precancerous Conditions; Proto-Oncogene Proteins c-bcl-2; Serum; Stomach Neoplasms

We have studied the chemopreventive role of naringenin against experimental gastric carcinogenesis in male Wistar rats. The animals were divided into five groups and six animals were included in each group. Stomach, liver, sera and kidney specimens were collected in the 20th week and the level of glycoproteins namely, hexose, hexosamine, sialic acid and fucose, were measured in the control, gastric cancer-induced, cancer naringenin pretreated, cancer naringenin posttreated and naringenin alone animals. The glycoprotein levels were increased in the gastric cancer-induced rats when compared with the control rats. The levels of glycoprotein were decreased significantly in cancer-bearing rats supplemented with naringenin as compared with the gastric cancer-induced rats. The result shows the gastroprotective effect of naringenin and describes the likelihood of naringenin in maintaining the integrity of cell membranes and gastric mucosa against oxidative damage. Moreover, we hypothesize that regulation of glycoprotein levels by naringenin could be associated with the regression of N-methyl-N'-nitro-N-nitrosoguanidine-induced gastric carcinoma.

Topics: Animals; Anticarcinogenic Agents; Flavanones; Glycoproteins; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms

To investigate the accumulation and distribution of blood and tissue Se in rats with long-term and high-dose of Se supplementation by four Se-enriched plants (Se-enriched garlic, Se-enriched broccoli, Se-enriched green kale and Se-enriched red kale) in the N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced stomach cancer model.. Ninety rats were fed by basal diet for a week, divided equally into the control, MNNG and seven Se supplementation groups. Rats were daily given 15 mg/kg bw of MNNG for ten days except those in the control group, and rats in five Se-enriched plant treatment groups were daily given 150 or 300 microg Se/kg of bw of the plant suspension by gavage for 17 weeks. Rats were sacrificed at the end of 18th week, the Se contents of blood, red blood cell, plasma, liver, kidney, spleen, heart, brain and testicle were determined.. The Se contents of liver and kidney in rats supplemented by Se-enriched garlic were significantly lower than those in rats supplemented by Se-enriched broccoli and two Se-enriched kales, and the Se contents of red blood cell and spleen higher than those in rats supplemented by Se-enriched broccoli and two Se-enriched kales.. The data primarily shows that the differences of the accumulation and distribution of blood and tissue Se in rats are related to the supplemented plant Se components, and that lower Se accumulation of the liver and kidney in rats supplemented by Se-enriched garlic than by other plants may be one of Se safety indices of Se-enriched garlic.

Topics: Animals; Brassica; Garlic; Kidney; Liver; Methylnitronitrosoguanidine; Rats; Selenium; Stomach Neoplasms; Tissue Distribution

We investigated the combinatorial chemopreventive efficacy of Azadirachta indica (AI) and Ocimum sanctum (OS) against N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis, based on changes in oxidant-antioxidant status, cell proliferation, apoptosis and angiogenesis.. Male Wistar rats were assigned to four groups. Rats in groups 1 and 2 received MNNG (150 mg/kg body weight i.g.) three times with a gap of two weeks in between the treatment. Group 2 rats additionally received ethanolic AI (100 mg/kg body weight i.g.) and OS (150 mg/kg body weight i.g.) leaf extract three times per week for 26 weeks. Group 3 animals were given AI and OS leaf extract alone, whereas group 4 served as the control.. Lipid and protein oxidation and status of the antioxidants, superoxide dismutases, catalase, reduced glutathione (GSH) and GSH-dependent enzymes together with markers of proliferation (proliferating cell nuclear antigen [PCNA], glutathione S-transferase-Pi [GST-P]), invasion (cytokeratin [CK]), angiogenesis (vascular endothelial growth factor [VEGF]) and apoptosis (Bcl-2, Bax, cytochrome C and caspase-3) were used to biomonitor chemoprevention. Rats administered MNNG developed forestomach carcinomas that displayed low lipid and protein oxidation coupled to enhanced antioxidant activities, and overexpression of PCNA, GST-P, CK, VEGF and Bcl-2 with downregulation of Bax, cytochrome C and caspase-3. Coadministration of AI and OS extract suppressed MNNG-induced gastric carcinomas accompanied by modulation of the oxidant-antioxidant status, inhibition of cell proliferation and angiogenesis, and induction of apoptosis.. The results of the present study suggest that chemoprevention by AI and OS combination may be mediated by their antioxidant, antiangiogenic, antiproliferative and apoptosis inducing properties.

Topics: Animals; Antioxidants; Apoptosis; Azadirachta; Disease Models, Animal; Male; Methylnitronitrosoguanidine; Neovascularization, Pathologic; Ocimum; Oxidants; Phytotherapy; Plant Extracts; Rats; Rats, Wistar; Stomach Neoplasms

Our previous study demonstrated that PPARgamma ligand rosiglitazone prevents gastric carcinogenesis in rats induced by chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In this study, we attempted to identify novel anti-cancer mechanisms of rosiglitazone. By examining the gene expression profiles of MNNG-induced and rosiglitazone-treated gastric cancer with Uniset Rat I Bioarray microarray, we identified a gene that showed prominent responses in the rosiglitazone-treated group. The hypertension-related, calcium-regulated gene (HCaRG) was significantly up-regulated in rat gastric carcinoma of the rosiglitazone-treated group when compared with the MNNG group. We further examined HCaRG expression in human gastric cancer and found that the expression of HCaRG was down-regulated in human gastric cancerous tissue. Rosiglitazone markedly induced the expression of HCaRG in the AGS cell line. The up-regulation of HCaRG may be one of the mechanisms underlying the chemopreventive effect of rosiglitazone in gastric cancer.

Topics: Animals; Antineoplastic Agents; Cell Cycle Proteins; Cell Line, Tumor; Down-Regulation; Gene Expression; Humans; Immunohistochemistry; Methylnitronitrosoguanidine; Nuclear Proteins; Oligonucleotide Array Sequence Analysis; Rats; Reverse Transcriptase Polymerase Chain Reaction; Rosiglitazone; Stomach Neoplasms; Thiazolidinediones; Up-Regulation

Carcinoma of the stomach is reportedly the second most common cancerous condition affecting the general population. Administration of antioxidants is reported to effectively alleviate the risk of gastric carcinoma. Therefore, we assessed the protective role of naringenin, an antioxidant and naturally occurring citrus flavanone, on gastric carcinogenesis induced by MNNG (200 mg/kg body weight) and S-NaCl (1 mL per rat) in Wistar rats (obtained from the Central Animal House Facility, University of Madras, Taramani Campus, Chennai, India). The animals were divided into 5 groups, and the effects of naringenin on simultaneous and posttreated stages of MNNG were tested. Cancer risk was analyzed along with their antioxidant status. The LPO levels in the experimental groups were assessed as an index of oxidative milieu. Altered redox status was subsequently investigated by assaying the superoxide and hydroxyl radicals, the enzymatic antioxidants (SOD, CAT, GPx), and the nonenzymatic antioxidants viz reduced GSH, vitamin C, and vitamin E. In the presence of MNNG, cancer incidence and LPO levels were significantly increased, whereas enzymatic (SOD, CAT, and GPx) and nonenzymatic antioxidant activities (GSH, Vitamins C, and E) were decreased in the treated rats compared with control rats. Administration of naringenin to gastric carcinoma-induced rats largely up-regulated the redox status to decrease the risk of cancer. We conclude that up-regulation of antioxidants by naringenin treatment might be responsible for the anticancer effect in gastric carcinoma.

Topics: Animals; Antineoplastic Agents; Antioxidants; Carcinoma; Cysteine; Disease Models, Animal; Flavanones; Gastric Mucosa; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Oxidation-Reduction; Random Allocation; Rats; Rats, Wistar; Reactive Oxygen Species; Stomach Neoplasms; Superoxide Dismutase; Thiobarbituric Acid Reactive Substances; Weight Loss

A number of possible preventive agents for cancers in different organs have been reported, however, little information is available regarding the effective agents for the development of gastric cancers. The rice components are known to be effective for the prevention of the development of cancers. Our group has demonstrated that fermented brown rice by Aspergillus Orzae (FBRA) has chemopreventive potentials in several organs. In this study, we investigated the modifying effects of FBRA exposed during the initiation or post-initiation phase of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in rats. Five-week-old male ACI rats were divided into 7 groups. Groups 1-5 were given oral administration of MNNG (100 mg/l in distilled water) for 24 weeks starting at 6 weeks of age. Groups 2 and 3 were fed a diet containing 5 and 10% FBRA during the initiation phase, respectively, whereas groups 4 and 5 were fed these diets during the post-initiation phase. Group 6 was given a diet containing 10% FBRA throughout the experiment. Group 7 was kept on the basal diet alone and served as an untreated control. Rats were sacrificed at 52 weeks after the start, and the epithelium of the stomach was investigated in detail. Incidence and multiplicity of gastric proliferative lesions of group 1 (MNNG alone) were 61% and 1.67+/-1.57/rat, respectively. Those of group 5 (25%, 0.35+/-0.67) which were given FBRA at a dose of 10% during the post-initiation phase were significantly less than those of group 1. Furthermore, the same group expressed a significantly decreased Ki67-labeling index in the non-lesional gastric epithelium when compared to that of group 1. These results indicate that FBRA inhibits MNNG-induced development of gastric tumors by administration during the post-initiation phase in rats. FBRA is regarded as a promising dietary agent for the prevention of human gastric cancer.

Topics: Adenocarcinoma; Animals; Anticarcinogenic Agents; Apoptosis; Carcinogens; Cell Proliferation; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Oryza; Phytotherapy; Rats; Stomach Neoplasms

To guide the application of selenium (Se) in the prevention of human chronic diseases, the safety of different Se resources (selenite, Se-enriched garlic, Se-enriched broccoli, Se-enriched green kale and Se-enriched red kale) was investigated.. Ninety rats were fed the basal diet for a week, divided equally into the control, N-methyl- N'-nitro-N-nitrosoguanidine (MNNG) and seven Se treatment groups. Rats were daily given 15 mg/kg bw of MNNG for ten days except those in the control group, and rats in seven Se supplementation groups were daily given 75 microg/kg bw or 150 microg/kg bw sodium selenite solution, 150 or 300 microg/kg bw Se as of Se-enriched plant suspension by gavage for 17 weeks. Rats were sacrificed at the end of 18th week, the liver glutathione S-transferase (GST), serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were detected. Rats were given with the basal diet and water freely during the experiment. The data was statistically analyzed by SPSS 12.0 software.. All rats in Se 75 microg/kg bw of Se as sodium selenite group died within 6 weeks, the body weights of rats in 75 microg/kg bw of Se as sodium selenite group were significantly lower than those of rats in other groups, the serum AST and ALT activities of rats in 75 microg/kg bw of Se as sodium selenite group were significantly higher than those of rats in other groups, and only the Se supplementation of 75 microg/kg bw of Se as selenite led to rat liver pathological change.. Selenite is at least 4 times as toxic as Se-enriched higher plants selected in this experiment.

Topics: Animals; Antineoplastic Agents; Brassica; Dose-Response Relationship, Drug; Garlic; Liver; Methylnitronitrosoguanidine; Rats; Safety; Selenium; Stomach Neoplasms

Combination treatment with sodium nitrite (NaNO(2)) and ascorbic acid (AsA) is well known to promote forestomach carcinogenesis in rats and weakly enhance esophageal carcinogenesis under acid reflux conditions. Nitric oxide generation and oxidative DNA damage are considered to be related to the enhancement of carcinogenesis. The purpose of the present study was to investigate whether oxidative DNA damage-associated genotoxicity and tumor initiating potential are involved in the carcinogenesis. In the bacterial reverse mutation assay using Escherichia coli deficient in the mutM gene encoding 8-hydroxydeoxyguanosine (8-OHdG) DNA glycosylase, the combination with NaNO(2) and AsA increased the mutation frequency dramatically, slight increase being evident in the parental strain. In vivo, a significant increase in 8-OHdG levels in the rat forestomach epithelium occurred at 24 h after combined treatment. Six-week-old F344 male rats were given drinking water containing 0.2% NaNO(2) and a diet supplemented with 1% AsA in combination, or the chemicals individually or basal diet alone for 12 weeks. After an interval of 2 weeks, they received 1% butylated hydroxyanisole in the diet for promotion until the end of weeks 52 and 78. Although one squamous cell carcinoma was observed in the combined group, there was no significant variation in tumor development among the groups. The study indicated that the combination of NaNO(2) with AsA induces genotoxicity due to oxidative DNA damage in vitro, and elevates 8-OHdG levels in the forestomach epithelium, but lacks initiating activity in the rat two-stage carcinogenesis model.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Antioxidants; Ascorbic Acid; Butylated Hydroxyanisole; Carcinogens; Cocarcinogenesis; Deoxyguanosine; Disease Models, Animal; DNA Damage; DNA, Bacterial; Drug Therapy, Combination; Escherichia coli; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Mutagens; Organisms, Genetically Modified; Oxidation-Reduction; Oxidative Stress; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms

Combined treatment with several phenolic antioxidants and sodium nitrite (NaNO(2)) has already shown to enhance rat forestomach carcinogenesis. In the present experiment, effects of green tea catechins (GTC) alone or in combination with NaNO(2) on gastric carcinogenesis were investigated in a rat two-stage carcinogenesis model. Groups of eight, 6-week-old F344 male rats were given 0.01%N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in their drinking water and 5% NaCl in the diet for 10 weeks for glandular stomach initiation and a single intragastric administration of 100 mg/kg/bodyweight of MNNG at week 9 for forestomach initiation. From week 11, they received either drinking water containing 0.2% NaNO(2) and a diet supplemented with 1% GTC in combination, each individual chemical alone or a basal diet until the end of week 42. In the forestomach, incidences and multiplicities of neoplastic lesions were clearly increased by the combined treatment, in spite of GTC alone suppressing the occurrence of papillomas. In a short-term experiment with similar protocol without MNNG pretreatment, a significant increase of 8-hydroxydeoxyguanosine (8-OHdG) levels in forestomach DNA occurred 24 h after the combined treatment, concomitant with erosion and inflammatory cell infiltration. In an in vitro study, electron spin resonance demonstrated hydroxyl radical formation after incubation of epigallocatechin gallate or epicatechin gallate with the NO generator, NOC-7. Thus, GTC alone showed a weak chemopreventive effect on forestomach carcinogenesis, but in the presence of NaNO(2) it exerted a promotive effect which might involve hydroxyl-radical-associated oxidative DNA damage. However, no influence was exerted in the glandular stomach.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Catechin; Deoxyguanosine; Disease Models, Animal; Epithelial Cells; Hyperplasia; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms; Tea

This study was designed to evaluate the chemopreventive effects of ethanolic Ocimum sanctum (OS) leaf extract on cell proliferation, apoptosis and angiogenesis during N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis.. The rats were divided into four groups of ten each. Rats in group one were given MNNG (150 mg/kg body weight) by intragastric intubation three times, with a two-week interval between treatments. Rats in group two were administered MNNG as in group one, and in addition, they received intragastric intubation of ethanolic OS extract (300 mg/kg body weight) three times per week, starting on the day following the first exposure to MNNG. The intubation of ethanolic OS extract continued until the end of the experimental period. Rats in group three were given ethanolic OS leaf extract only. Group four served as controls. All the rats were killed after an experimental period of 26 weeks.. Intragastric administration of MNNG-induced well-differentiated squamous cell carcinomas that showed increased cell proliferation, and angiogenesis with evasion of apoptosis, as revealed by the upregulation of proliferating cell nuclear antigen (PCNA), glutathione S-transferase-pi (GST-pi), Bcl-2, cytokeratin (CK) and vascular endothelial growth factor (VEGF) and with downregulation of Bax, cytochrome C and caspase 3 protein expression. Administration of ethanolic OS leaf extract reduced the incidence of MNNG-induced gastric carcinomas. This was accompanied by decreased expression of PCNA, GST-pi, Bcl-2, CK and VEGF, and overexpression of Bax, cytochrome C, and caspase 3.. This study provides evidence that, in MNNG-induced gastric carcinogenesis, the key proteins involved in the proliferation, invasion, angiogenesis and apoptosis, are viable molecular targets for chemoprevention using ethanolic OS leaf extract.

Topics: Animals; Anticarcinogenic Agents; Apoptosis; Carcinoma, Squamous Cell; Cell Proliferation; Chemoprevention; Disease Models, Animal; Male; Methylnitronitrosoguanidine; Neovascularization, Pathologic; Ocimum; Phytotherapy; Plant Extracts; Plant Leaves; Random Allocation; Rats; Rats, Wistar; Stomach Neoplasms; Vascular Endothelial Growth Factor A

Changes in cell cycle regulation are involved in many human cancers, including gastric cancer. In the present study, cyclin D1 expression and localization were immunohistochemically analyzed in 23 N-methyl-N'-nitro-N-nitrosoguanidine-induced rat gastric adenocarcinomas and compared with findings for beta-catenin. Cyclin D1 nuclear overexpression was more frequently observed in tumors displaying nuclear (4/4=100%) and cytoplasmic (3/4=75%) beta-catenin accumulation than those with membranous (3/15=20%) localization (nuclear vs. membranous, P<0.02). In the former cases it was considered that cyclin D1 was induced with beta-catenin activation; in the latter, a direct or indirect pathway for cyclin D1 accumulation bypassing Wnt pathway might be involved. Cyclin D1 was also found to be accumulated in gastric glands within normal-looking mucosa, these perhaps representing preneoplastic lesions for cancers with membranous beta-catenin accumulation.

Topics: Adenocarcinoma; Animals; beta Catenin; Carcinogens; Cell Membrane; Cell Nucleus; Cyclin D; Cyclins; Cytoplasm; Gastric Mucosa; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred ACI; Stomach Neoplasms

To obtain new Se resources with high healthy value (both high activity and low toxicity), the preventive efficacies of three Se-enriched higher plants on stomach cancer were compared with selenite and Se-enriched garlic.. Ninety weanling male Wistar rats were fed the basal diet for a week, divided equally into nine groups, control, MNNG,Se 75 and 150 microg/kg bw of selenite, Se 150 and 300 microg/kg bw of Se-enriched garlic, Se 150 microg/kg bw of Se-enriched broccoli, Se 300 microg/kg bw of Se-enriched red kales and green kales group. Rats in MNNG and Se supplementation groups were daily given 15 mg/kg bw of MNNG (solved in 1 ml distilled water) and the rats of control group were given 1 ml distilled water by gavage for ten days. Meanwhile, the rats of the control and MNNG group were daily given 1 ml distilled water and the rats of other groups were given 1 ml water suspension of Se-enriched garlic, red kavas, green kavas, broccoli or 1 ml solution of sodium selenite by gavage for seventeen weeks. All rats were freely fed the basal diet and water during the period of the experiment. At the end of 18th week, the rats were sacrificed, the incidence of aneuploid cells (IAC) in mucosal epithelium of the gastric antrum was detected, and the IAC data were analyzed by SPSS 12.0.. The results showed that the IACs were 25% and 30%, respectively, in the Se 150 microg/kg bw of Se-enriched garlic and -broccoli group, and were in turn 22%, 50% and 30% in the 300 microg/kg bw of Se-enriched garlic, -red kale and -green kale. No significant differences of IACs were found in the same level of Se supplementation groups by Se-enriched plants.. The data showed that Se-enriched broccoli, red kale and green kale had high activities similar to Se-enriched garlic in stomach cancer prevention and lower toxicity than selenite.

Topics: Aneuploidy; Animals; Brassica; Cell Transformation, Neoplastic; Cells, Cultured; Epithelial Cells; Garlic; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Pyloric Antrum; Rats; Rats, Wistar; Selenium; Stomach Neoplasms

Dose-dependent promotion effects of combined treatment with sodium nitrite (NaNO2) and ascorbic acid (AsA) on gastric carcinogenesis were examined in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Groups of 15 6-week-old F344 male rats were given 0.01% MNNG in their drinking water for 10 weeks to initiate carcinogenesis in the glandular stomach and a single intragastric administration of 100 mg/kg/bodyweight of MNNG by stomach tube at week 9 to initiate carcinogenesis in the forestomach. From week 11, they received either drinking water containing 0.05, 0.1 or 0.2% NaNO2 and a diet supplemented with 0.1 or 0.2% AsA in combination, each individual chemical alone or a basal diet until the end of week 42. In the forestomach, the incidence of hyperplasia was increased dose dependently by the treatment with NaNO2 alone. Incidences of neoplastic lesions were dramatically increased by the combined treatment with NaNO2 and AsA in a dose-dependent manner, but AsA itself had no effect. In the glandular stomach, only toxicity and regenerative changes were increased by the high-dose combination. In a second short-term experiment conducted for sequential observation, necrosis and strong inflammation were found in the forestomach epithelium shortly after commencing combined treatment with 1.0% AsA and 0.2% NaNO2, followed by hyperplasia, whereas there were no obvious effects in the glandular stomach. In addition, after a 4 h treatment with 1.0% AsA and 0.2% NaNO2, a slight increase in the 8-hydroxy-deoxyguanosine levels in the forestomach epithelium was observed by high-performance liquid chromatography and an electrochemical detection system, albeit without statistical significance. In vitro, electron spin resonance demonstrated nitric oxide formation during incubation with NaNO2 and AsA under acidic conditions. Thus, NaNO2 was demonstrated to exert promoter action in the forestomach, with AsA acting as a strong copromoter through cytotoxicity and regenerative cell proliferation, possibly mediated by oxidative DNA damage, but the combined treatment with NaNO2 and AsA had little influence on glandular stomach carcinogenesis.

Topics: Animals; Ascorbic Acid; DNA Damage; Dose-Response Relationship, Drug; Male; Methylnitronitrosoguanidine; Nitric Oxide; Oxidative Stress; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms

Epidemiological and experimental studies indicate that non-steroidal anti-inflammatory drugs (NSAIDs) are chemopreventive agents of gastrointestinal cancers, but few studies on gastric cancer have been carried out. A decrease in folic acid supplement and subsequent DNA hypomethylation are related to gastrointestinal cancers, and it has been shown that high-dose folic acid may interfere with gastric carcinogenesis in dogs. The objective of this study was to investigate the effects of rofecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, and folic acid on the chemoprevention of gastric cancer induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Wistar rats, and to evaluate the cell proliferation of gastric mucosa in different experimental groups.. Eighty male Wistar rats were randomly divided into five groups (16 rats in each group). In the control group, the rats were given pure water and basal diet. In the MNNG group, the rats received MNNG in drinking water (100 mg/L) and basal diet. In the MNNG + low-dose rofecoxib group, the rats were given MNNG and rofecoxib 5 mg/kg per day with basal diet. In the MNNG + high-dose rofecoxib group, the rats were given MNNG and rofecoxib 15 mg/kg per day with basal diet. In the MNNG + folic acid group, the rats were given MNNG and folic acid 5 mg/kg per day with basal diet. The experiment was terminated at 50 weeks, and all rats were killed. Blood samples of 3 mL were obtained for measurement of serum folic acid concentrations in the control group, the MNNG group and the MNNG + folic acid group by using chemiluminescent method. The stomach was removed from all rats for histopathological examination and immunohistochemical study. Proliferating cell nuclear antigen (PCNA) expression in gastric epithelial cells was also determined.. In the MNNG group, five of 11 rats (45.5%) developed gastric cancer, while in all other four groups no gastric cancer was found (P < 0.05). The positivity rate of PCNA expression in the cancerous tissues was significantly higher than that in the non-cancerous tissues (80.0%vs 14.1%, P < 0.05). The positivity rate of PCNA expression in the gastric mucosal cells of the MNNG group was significantly higher than that in the other four groups. The mean serum folic acid concentration of rats was significantly higher in the MNNG + folic acid group (193.70 +/- 60.73 ng/mL) than those in the control group (84.21 +/- 25.26 ng/mL) and the MNNG group (72.27 +/- 16.70 ng/mL, P < 0.05). It was shown that both low- and high-dose rofecoxib as well as folic acid interfered with the development of gastric cancer induced by MNNG in Wistar rats.. The results indicate that rofecoxib as well as folic acid interferes with gastric carcinogenesis induced by MNNG in Wistar rats, and the suppression of gastric cell proliferation may play a crucial role in the chemoprevention of gastric cancer by rofecoxib and folic acid. The higher serum folic acid concentration of rats may play an important role in the prevention of gastric cancer.

Topics: Adenocarcinoma; Animals; Anticarcinogenic Agents; Body Weight; Cell Proliferation; Folic Acid; Gastric Mucosa; Lactones; Male; Methylnitronitrosoguanidine; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Stomach Neoplasms; Sulfones

Although we have previously showed that a selective cyclooxygenase-2(COX-2) inhibitor celecoxib prevents gastric cancer development in a rat model of gastric carcinogenesis, the role of celecoxib on gastric premalignant lesions remains unknown. This study was to explore whether celecoxib was effective for the prevention of premalignancy, and further to clarify its mechanism.. Ninety-four male Wistar rats were divided into 5 groups. Group A (n=12) was fed with water only; group B (n=16) with daily 10 mg/kg celecoxib; group C (n=22) with 100 microg/ml N-methyl-No-nitro-N-nitrosoguanidine (MNNG); group D (n=22) with 100 microg/ml MNNG and daily 10 mg/kg celecoxib; group E (n=22) with 100 microg/ml MNNG and daily 3 mg/kg indomethacin. The rats in groups B to E were given 10% sodium chloride in the initial 6 weeks, and the rats in groups C to E were given 100 microg/ml MNNG in drinking water to induce premalignant lesions in the stomach. Six rats in group A, 8 in group B, 10 in group C, 10 in group D, and 10 in group E were killed at week 16, and others were killed at week 24. The occurrence rates of gastric premalignant lesions in the groups were compared. The mRNA and protein levels of COX-1 and COX-2 in gastric mucosa were determined by real-time polymerase chain reaction (PCR) and immunohistochemistry; prostaglandin E2 (PGE2) level was measured by an ELISA-based assay.. Ninety-three rats were studied. In week 16 and week 24, the occurrence rates of glandular atrophy in groups C, D, and E had no significant difference (P>0.05). In week 16, gastric mucosal dysplasia was not detected in groups C, D, and E; at week 24, the occurrence rates of dysplasia were 75% (9/12) on group C, 25% (3/12) in group D, and 46% (5/11) in group E. The occurrence rate of gastric mucosal dysplasia was significantly lower in group D than in group C (25% vs. 75%, P=0.039); there was no significant difference between group E and group C (46% vs. 75%, P=0.214). At week 16 and week 24, there was no significant difference in COX-1 expression between treatment groups and control group. The mRNA and protein levels of COX-2 in group C (3.29+/-1.50 and 3.41+/-0.94) were significantly higher than those in other groups (P<0.001). There was no significant difference in PGE2 level between groups C, D, and E (P>0.05).. Celecoxib effectively inhibits the development of gastric mucosal dysplasia in rats induced by MNNG, but has no effect on the PGE2 level in the gastric mucosa, indicating that the anti-neoplastic activities of celecoxib may be independent of COX-2.

Topics: Animals; Atrophy; Celecoxib; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Dinoprostone; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Pyrazoles; Random Allocation; Rats; Rats, Wistar; RNA, Messenger; Stomach; Stomach Neoplasms; Sulfonamides

The chemopreventive effect of tea polyphenol (TP) on precancerous gastric lesion was examined. A rat model was established by gavage of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and different concentrations of TP were given to Wistar rats in drinking water during the 16 weeks of the experiment. The histopathological data showed an effect of TP to lighten the lesions induced by MNNG. By flow cytometry, we demonstrated that TP treatment decreased the proliferation and apoptosis index (AI) induced by MNNG. The arrest in the G0-G1 phase of the cell cycle was also obtained. The results suggested that TP had preventive effect against gastric carcinogenesis at the preinitiation stage and such prevention may be related to the modulation of the balance of cell death and cell proliferation.

Topics: Animals; Calcium; Cell Cycle; Cell Division; Drinking; Flavonoids; Flow Cytometry; L-Lactate Dehydrogenase; Male; Methylnitronitrosoguanidine; Phenols; Polyphenols; Precancerous Conditions; Rats; Rats, Wistar; Stomach Neoplasms; Tea

To study the apoptosis-promoting effect of the serum from Panax notoginseng extracts-fed dog on precancerous gastric cells by means of flow cytometry.. In the experiment, we adopted eternalized human gastric mucosa epithelium GES-1 cells transformed by N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) (MC cells) as the model of precancerous lesions for study in vitro. We took the serum of a dog before and at two different points of time (2 and 6 hours) after feeding the dog with Panax notoginseng extracts for experiment. The MC cells were cultured in mediums with different concentrations of the medicated serum at 2- or 6-hour point of time for 72 hours. By means of flow cytometry, we examined the apoptosis-promoting effects of the serums on the MC cells.. The medicated serums at these 2 points of time had significant effects in promoting MC cell apoptosis. The proportions of apoptotic cells in culture mediums with medicated serums had a significant increase as compared with those in culture mediums with non-medicated serums (serum obtained before administration of extracts to the dog) under the same conditions (P<0.05). The number of MC cells in G(0)/G(1)phase was decreased (P<0.05) and that in G(2)/M phase increased (P<0.05), while no consistent changes were observed in S phase.. The medicated serums obtained at the two different points of time have significant apoptosis-promoting effects on MC cells. They decrease the number of MC cells in G(0)/G(1) phase and increase the number of MC cells in G(2)/M phase. This is probably responsible for the effects of Panax notoginseng extracts in inhibiting the proliferation of MC cells and promoting its apoptosis.

Topics: Animals; Apoptosis; Cell Line, Tumor; Cells, Cultured; Dogs; Drugs, Chinese Herbal; Gastric Mucosa; Methylnitronitrosoguanidine; Panax; Precancerous Conditions; Serum; Stomach Neoplasms

Combination chemoprevention by diet-derived agents that induce apoptosis is a promising strategy to control gastric cancer, the second most common malignancy worldwide. The present study was undertaken to investigate the apoptosis-inducing potential of a combination of S-allylcysteine (SAC), an organosulphur constituent of garlic and lycopene, a tomato carotenoid during N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) and saturated sodium chloride (S-NaCl)-induced gastric carcinogenesis in Wistar rats using the apoptosis-associated proteins Bcl-2, Bax, Bim, caspase 8 and caspase 3 as markers. Animals administered MNNG followed by S-NaCl developed squamous cell carcinomas of the stomach associated with increased Bcl-2 expression and decreased expression of Bax, Bim, caspase 8 and caspase 3. Although SAC and lycopene alone significantly suppressed the development of gastric cancer, administration of SAC and lycopene in combination was more effective in inhibiting MNNG-induced stomach tumours and modulating the expression of apoptosis-associated proteins. Our results suggest that induction of apoptosis by SAC and lycopene combination represents one of the possible mechanisms that could account for their synergistic chemopreventive activity against gastric cancer.

Topics: Analysis of Variance; Animals; Apoptosis; bcl-2-Associated X Protein; Biomarkers, Tumor; Blotting, Western; Carotenoids; Caspase 3; Caspases; Chemoprevention; Cysteine; Disease Models, Animal; Drug Therapy, Combination; Lycopene; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Probability; Proto-Oncogene Proteins c-bcl-2; Random Allocation; Rats; Rats, Wistar; Sensitivity and Specificity; Stomach Neoplasms

N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced rat stomach carcinomas are considered to be a good model for differentiated-type human stomach carcinomas. However, as for their molecular basis, only infrequent mutations of Catnb (beta-catenin) and Trp53 (p53) have been observed. Here, we carried out a whole-genome analysis of loss of heterozygosity (LOH) using 21 stomach carcinomas induced by MNNG in F(1) hybrids of ACI and BUF rats, and also analyzed promoter methylation of four tumor-suppressor genes. LOH analysis was performed using 130 polymorphic markers covering rat chromosomes 1-20 with an average interval of 20 Mbp. Despite adapting conditions so that LOH could be detected with up to a 50% contamination of stromal cells, no LOH was detected at any loci. CpG islands in putative promoter regions of four tumor-suppressor genes, Cdh1 (E-cadherin), Cdkn2a (p16), Mlh1, and Rassf1a, were analyzed by methylation-specific polymerase chain reaction (PCR). However, no methylation was detected. In contrast, the promoter region of Pgc (pepsinogen C), which lacks a CpG island, was methylated in all 21-cancer samples. These results indicated that LOH spanning a chromosomal region larger than 30-40 Mbp or silencing of Cdh1, Cdkn2a, Mlh1, and Rassf1a, was not involved in MNNG-induced rat stomach carcinomas. The search for other genes involved in these carcinomas needs to be continued.

Topics: Adaptor Proteins, Signal Transducing; Animals; Cadherins; Carrier Proteins; CpG Islands; Cyclin-Dependent Kinase Inhibitor p16; DNA Methylation; Genes, Tumor Suppressor; Genome; Loss of Heterozygosity; Methylnitronitrosoguanidine; MutL Protein Homolog 1; Neoplasm Proteins; Nuclear Proteins; Polymerase Chain Reaction; Rats; Rats, Inbred ACI; Rats, Inbred BUF; Stomach Neoplasms; Tumor Suppressor Proteins

To study the effect drug contained canine serum, prepared by gastric perfusion with Sanchi extract (SE), in inhibiting proliferation and promoting apoptosis of cultured precancerous gastric cells by cell culture.. The precancerous model cells (MC) used in the experiment were prepared through transforming eternalized human gastric mucosa epithelial cells GES-1 by N-methyl-N'-nitro-N-nitroso-guanidine (MNNG). After once gastric perfusion of SE extract to dogs, the canine serum gotten before and at different time points after medication was used for test. The inhibitory effect of the drug serum obtained at different time points on MC after acting for 72 hrs was detected by 3-(4,5)-dimethy thioazol-2-yl-2,5-diphenyl-tetrazoliumbromide (MTT) method to find the optimal time point for drug serum preparation, that were 2 hrs and 6 hrs after medication. Then the cell apoptosis promoting effect after acting for 72 hrs of the drug serum obtained at the optimal time points was determined by flow cytometry.. The drug serum obtained at 2-hr and 6-hr after medication showed the highest inhibitive effect on MC cells, reaching 45.3% and 42.4% respectively, as compared with the effect of blank serum, the difference was significant (P<0.01). They could evidently promote the MC cell apoptosis, the apoptosis rate also showed significant difference to that of the blank serum (P < 0.05). Under their action, the proportion of MC cells in G0/G1 phase was obviously decreased (P < 0.05) while that in the G2/M phase significantly increased (P <0.05). However, the change of cells in S phase was not uniform.. The drug contained canine serum gotten 2 hr and 6 hr after SE feeding shows the optimal MC proliferation inhibitive effect and significant apoptosis promoting effect. Besides, it could significantly decrease the proportion of MC cells in G0/G1 phase and significantly increase that in G2/M phase, this effect might be one of the mechanisms of ES in inhibiting MC cell proliferation and promoting its apoptosis.

Topics: Animals; Antineoplastic Agents, Phytogenic; Apoptosis; Araliaceae; Cell Proliferation; Cell Transformation, Neoplastic; Cells, Cultured; Dogs; Drugs, Chinese Herbal; Embryo, Mammalian; Gastric Mucosa; Ginsenosides; Humans; Methylnitronitrosoguanidine; Precancerous Conditions; Stomach Neoplasms

Combination chemoprevention by diet-derived agents is a promising strategy for protection against gastric cancer. We therefore evaluated the combined chemopreventive effect of S-allylcysteine (SAC), an organosulfur constituent of garlic, and lycopene, a major carotenoid present in tomatoes, against N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and saturated sodium chloride (S-NaCl)-induced gastric carcinogenesis in Wistar rats. The animals were divided into eight groups of six animals each. Rats in group 1 were given MNNG by intragastric intubation on days 0 and 14 as well as S-NaCl every 3 days during weeks 0-3. Animals in groups 2-4, administered MNNG and S-NaCl as in group 1, received in addition SAC and lycopene alone and in combination, respectively, three times per week starting on the day following the first exposure to MNNG. Groups 5-7 were given the chemopreventive agents alone, whereas group 8 served as controls. The animals were sacrificed after an experimental period of 21 weeks. Measurement of lipid peroxidation and antioxidants of the glutathione redox cycle in the stomach, liver, and erythrocytes was used to monitor the chemopreventive potential of SAC and lycopene. In the tumor tissue, diminished lipid peroxidation was accompanied by an increase in reduced glutathione (GSH) and GSH-dependent enzymes, whereas in the liver and erythrocytes, enhanced lipid peroxidation was associated with antioxidant depletion. Although SAC and lycopene alone significantly suppressed the development of gastric cancer, administration of SAC and lycopene in combination was more effective in inhibiting MNNG-induced stomach tumors and modulating the redox status in the tumor and host tissues. The results of the present study validate the hypothesis that diet-derived chemopreventive agents such as SAC and lycopene in combination may interact synergistically with high efficacy and lessened toxicity against gastric cancer.

Topics: Animals; Antioxidants; Carotenoids; Cysteine; Diet; Erythrocytes; Garlic; Gastric Mucosa; Glutathione; Lipid Peroxidation; Liver; Lycopene; Male; Methylnitronitrosoguanidine; Oxidation-Reduction; Rats; Rats, Wistar; Sodium Chloride; Solanum lycopersicum; Stomach; Stomach Neoplasms

Overexpression of cyclooxygenase 2 (COX-2) is frequently detected in gastric cancer and is believed to play a crucial role in gastric carcinogenesis.. We examined the chemopreventive effect of a COX-2 inhibitor in an animal model of stomach carcinogenesis.. Eighty six male Wistar rats were divided into six different treatment groups: group A, water alone (n = 5); group B, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG 100 micro g/ml) (n = 16); group C, indomethacin (3 mg/kg/day) (n = 16); group D, celecoxib (5 mg/kg/day) (n = 17); group E, celecoxib (10 mg/kg/day) (n = 16); and group F, celecoxib (20 mg/kg/day) (n = 16). Group B-F animals were treated with 10% sodium chloride (in the initial six weeks) and MNNG in drinking water to induce adenocarcinoma in the stomach. All animals received treatment for 40 weeks, and were sacrificed after death or at 48 weeks. Gastric neoplasm was evaluated by histology.. The incidences of gastric cancer were 0% in group A, 75% in group B, 68.8% in group C, 70.6% in group D, 18.8% in group E, and 31.3% in group F (p = 0.002, ANOVA). Compared with MNNG controls, treatment with celecoxib 10 mg/kg/day also showed lower tumour multiplicity (0.19 (0.40) v 1.00 (0.73); p = 0.004) and lower mean tumour volume (2.4 v 2805 mm(3); p = 0.02). Although tumours had significantly higher COX-2 expression than their adjacent normal tissues (p<0.02), there was no significant difference in COX-2 levels among tumours in the different treatment groups. The lowest tumour prostaglandin E(2) level was found in the indomethacin treated group, suggesting that the chemopreventive effect of celecoxib may be mediated by a COX independent pathway.. While treatment with indomethacin had no significant effect on tumour development, treatment with celecoxib reduced gastric cancer incidence and growth in rats.

Topics: Analysis of Variance; Animals; Celecoxib; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Dinoprostone; Drug Administration Schedule; Indomethacin; Isoenzymes; Male; Methylnitronitrosoguanidine; Models, Animal; Prostaglandin-Endoperoxide Synthases; Pyrazoles; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms; Sulfonamides

Exposure to N-nitroso compounds is thought to play a key role in the development of gastric cancer in humans. The alkylating agent N-methyl-N'-nitrosoguanidine (MNNG) is carcinogenic in a number of animal models and its preferential target tissue is the gastrointestinal (GI) tract. The genetic synteny among rats and humans makes the rat a useful model for induced tumorigenesis. However, because of the limited availability of genetic information, cytogenetic and molecular studies are rarely performed in the rat. We report an investigation of eight MNNG-induced rat gastric tumors by comparative genomic hybridization (CGH). The tumors were from forestomach (induced by a single dose of MNNG) and from pylorus (induced by chronic exposure). CGH identified a genetic fingerprint of chromosomal imbalances common to the two types of the tumors. Frequent gains were observed at 9q11-q12, 15q22-25, and Xq11-q12. Forestomach carcinomas were also characterized by gains in 7q11-q12, 20q13, and Yq12. Homology studies between the rat and human genomes indicate the presence of genes within these regions with potential relevance to tumorigenesis in the GI tract. Our findings provide new insights into the location of genes involved in MNNG-induced gastric cancer initiation and/or progression in the rat.

Topics: Animals; Chromosome Aberrations; DNA Fingerprinting; DNA, Neoplasm; In Situ Hybridization, Fluorescence; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms

Both Helicobacter pylori (Hp) and bile acids are gastric carcinogens. An experimental model of duodenogastric reflux in Mongolian gerbils was developed and was used to study the effects of Hp infection and duodenogastric reflux on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced glandular stomach tumorigenesis independently and synergistically. Male Mongolian gerbils underwent both inoculation with Hp, and had duodenogastric reflux (DR) induced, or neither, followed by MNNG administration. Animals were sacrificed at week 40, and histopathological examination of their excised stomachs and serological investigation were performed. Glandular stomach adenocarcinomas were observed in animals that underwent Hp inoculation and/or induction of DR after MNNG administration, and glandular stomach adenomas were found in animals inoculated with Hp after MNNG administration. The incidence of glandular stomach tumors was significantly higher in animals inoculated with Hp after MNNG administration and in animals undergoing combined Hp inoculation, DR induction and MNNG administration than in animals only administered MNNG. These findings indicate that Hp infection has a stronger tumorigenic effect than the exposure to duodenal contents, and duodenal contents may attenuate the effect of Hp on glandular stomach tumorigenesis.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Deoxyguanosine; Duodenogastric Reflux; Gastrointestinal Contents; Gerbillinae; Helicobacter Infections; Inflammation; Male; Methylnitronitrosoguanidine; Mongolia; Neoplasms, Glandular and Epithelial; Stomach Neoplasms

Cancers induced by different carcinogens show distinct expression profiles. In addition to the specific alterations of tumor-related genes induced by specific carcinogens, it is possible that some initial responses induced by a carcinogen could persist for long periods and are consistently present in the cancers induced. We have analyzed the initial responses in the rat pyloric mucosae after treatment for 2 weeks with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Gene expression was monitored 1 day, 2 weeks and 4 weeks after MNNG treatment by oligonucleotide microarray analysis. Of the differentially expressed genes showing greater than three-fold difference 1 day after MNNG treatment, 143 and 26 genes were up- and down-regulated, respectively, in MNNG-induced stomach cancers. Among these genes, 25 and 6 genes were up- and down-regulated, respectively, in the histologically normal pyloric mucosae, even 4 weeks after cessation of MNNG treatment. Among the up-regulated genes, many genes involved in tissue remodeling (Spi15, Serpine1 and Fst) and cellular growth (Bdnf, Ros1 and Fgf10) were present. The six down-regulated genes included TGF-beta-inducible early growth response gene. These findings demonstrate that some expression changes induced by MNNG persist for a prolonged period and are present in cancers. Persistent expression changes are considered to be important for prediction of past carcinogen exposure, and could provide a molecular environment favorable for malignant transformation.

Topics: Animals; Base Sequence; DNA Primers; Gastric Mucosa; Gene Expression Regulation; Methylnitronitrosoguanidine; Mutagens; Oligonucleotide Array Sequence Analysis; Rats; Rats, Inbred F344; Reverse Transcriptase Polymerase Chain Reaction; Stomach Neoplasms

It has been recently shown that the catecholamine neurotransmitter dopamine (DA) strongly and selectively inhibits vascular permeability factor/vascular endothelial growth factor (VPF/VEGF)-induced angiogenesis. Gastric cancer is highly angiogenic and is dependent on VEGF for its growth and progression. Because substantial amounts of DA present in normal stomach tissues has been implicated in several gastric functions, we therefore investigated the role, if any, of this neurotransmitter in the growth and progression of gastric cancer.. Initially, the status of DA and tyrosine hydroxylase, the rate-limiting enzyme required for DA synthesis, were determined in human gastric cancer tissues and in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer tissues of rats. On the basis of our observation of inverse correlation between stomach DA and gastric cancer growth, we determined the effect of pharmacological dose of DA on the angiogenesis and growth of MNNG induced gastric cancer in rats and Hs746T human gastric cancer in nude mice.. DA and tyrosine hydroxylase were absent in both human and rat gastric cancer tissues. On the contrary, a low nontoxic pharmacological dose of DA significantly retarded tumor angiogenesis by inhibiting VEGFR-2 phosphorylation in tumor endothelial cells, which expressed DA D(2) receptors. This action of DA was associated with the growth inhibition of both MNNG-induced rat malignant gastric tumors and xenotransplanted human gastric cancer in nude mice.. Our study demonstrates that there is an inverse correlation between endogenous stomach DA and gastric cancer and indicates that DA already in clinical use for other purposes might have a role as an antiangiogenic agent in the treatment of gastric cancer.

Topics: Adenocarcinoma; Adult; Animals; Apoptosis; Blotting, Western; Cardiotonic Agents; Cell Line, Tumor; Cell Proliferation; Chromatography, High Pressure Liquid; Disease Progression; Dopamine; Female; Flow Cytometry; Humans; Immunoblotting; Immunohistochemistry; Immunoprecipitation; Male; Methylnitronitrosoguanidine; Mice; Mice, Nude; Middle Aged; Neoplasm Transplantation; Neovascularization, Pathologic; Neurotransmitter Agents; Phosphorylation; Rats; Rats, Sprague-Dawley; Stomach Neoplasms; Tyrosine 3-Monooxygenase; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

Electron paramagnetic resonance imaging (EPRI) enables noninvasive spatial mapping of free radical metabolism and has recently been shown to provide in vivo physiologic information regarding alterations in the redox state of tumors and neoplastic tissues. With the use of nitroxide spin probes, it has been shown that certain tumors possess a highly reduced state. To determine whether EPRI can be used for early detection and visualization of gastric carcinoma based on its altered redox metabolism, studies were performed in a rat gastric cancer model induced by 1-methyl-3-nitro-1-nitrosoguanidine. Using a specialized 750 MHz resonator and EPRI instrument, a technique was developed for imaging nitroxide radicals in the whole stomach. In vivo three-dimensional EPRI of the stomach of rats with continuous intravenous administration of nitroxide 3-carboxamido-2,2,5,5-tetramethylpyrrolidine-N-oxyl (3-carbamoyl-proxyl) [3-CP] was performed. Whereas electron paramagnetic resonance images from untreated controls provide a uniform visualization of the stomach mucosa and wall, in the treated rats with gastric cancer, holes were present in the image at the locations of tumors. With localized spectroscopy, it was confirmed that the tumor regions were devoid of signal, and this was largely due to the presence of a more reduced state with rapid reduction of nitroxide. Pharmacokinetic studies indicated that 3-CP in tumors was rapidly reduced to an undetectable level, whereas the 3-CP levels in normal stomach tissue persisted. Near-infrared reflectance measurements of indocyanine green dye uptake indicated that there were no significant differences in tumor versus normal mucosal perfusion. From these results, we concluded that gastric cancer tumors could be distinguished from normal tissue based primarily on the marked difference in their rate of radical metabolism. Because alterations in cellular redox state and radical metabolism are of critical importance in tumor biology and treatment, this methodology should provide an important new tool for the study and visualization of gastric carcinoma and may also be of use in other cancer models.

Topics: Animals; Carcinogens; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Indocyanine Green; Methylnitronitrosoguanidine; Nitrogen Oxides; Oxidation-Reduction; Pyrrolidines; Rats; Rats, Wistar; Spectroscopy, Near-Infrared; Stomach; Stomach Neoplasms

The modifying effects of aqueous extracts of garlic and neem leaf during the pre-initiation and post-initiation phases of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in male Wistar rats. The extent of lipid peroxidation and the status of phase II biotransformation enzymes such as glutathione peroxidase and glutathione-S-transferase that use reduced glutathione (GSH) as substrate were used to biomonitor the chemopreventive potential of these extracts. Enhanced lipid peroxidation in the liver and blood of tumor-bearing animals was accompanied by significant decreases in the activities of GSH-dependent antioxidants in the pre-initiation as well as in the post-initiation phases. Our results suggest that the modulatory effects of garlic and neem leaf on hepatic and blood oxidant-antioxidant status may play a key role in preventing cancer development at extrahepatic sites.

Topics: Animals; Antioxidants; Azadirachta; Garlic; Glutathione Peroxidase; Glutathione Transferase; Lipid Peroxidation; Liver; Male; Methylnitronitrosoguanidine; Oxidation-Reduction; Plant Extracts; Plant Leaves; Random Allocation; Rats; Rats, Wistar; Stomach Neoplasms

Through cell cultivation, we studied the inhibiting effects of the serum of the dog fed with Panax notoginseng extracts on precancerous gastric cells, trying to find the best time points or periods when the extracts' function was the strongest after administration of the extracts to the dog.. The experiments adopted eternalized human gastric mucosa epithelium GES-1 cells and MC cells gained from GES-1 cells transformed by N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) as the model of precancerous lesions for study in vitro. We took the serum of a dog before and at different points of time after feeding the dog with Panax notoginseng extracts for experiment. By means of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay, we examined the inhibiting effects of the serum after culturing the GES-1 and MC cells for 72 hours with different concentration (8%, 4%, 2%) of medicated serum obtained from the dog at different points of time, so as to find that, at which points of time the medicated serum obtained, it would be the most effective.. The results showed that the GES-1 and MC cells inhibition rates of medicated serum from the points of 2-hour and 6-hour were the highest, and the culture medium containing 8% of medicated serum from these two points had prominent inhibiting effects on both kinds of cells. The GES-1 cells inhibition rate in culture medium containing 8% of medicated serum from the point of 2-hour was 70.8% (P<0.01) and that of the MC cells was 45.3% (P<0.01). The GES-1 cells inhibition rate in culture medium containing 8% of medicated serum from the point of 6-hour was 88.5%(P<0.01) and that of the MC cells was 42.4% (P<0.01).. The points of time with the strongest inhibiting effects are 2 hours and 6 hours after being fed with Panax notoginseng extracts. At these two points, the serum is most effective in inhibiting the proliferation of GES-1 and MC cells.

Topics: Animals; Cell Line, Tumor; Cell Proliferation; Cell Transformation, Neoplastic; Dogs; Dose-Response Relationship, Drug; Drugs, Chinese Herbal; Immune Sera; Male; Methylnitronitrosoguanidine; Panax; Plant Extracts; Stomach Neoplasms; Time Factors

The influence of myenteric denervation on the development of gastric tumors induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied after chemical denervation of the rat stomach with benzalkonium chloride (BAC). Three groups were evaluated: control, denervated and denervated with pyloroplasty. Random bred male Wistar rats were given MNNG in drinking water (100 mg/l) for 28 weeks. After the sacrifice of animals, the stomachs were removed for morphological study. BAC reduced myenteric neurons number, increased the gastric mucosa area and decreased the adenocarcinomas number and size. This decrease was more evident when denervation was associated with pyloroplasty. These results indicate that myenteric denervation reduces the incidence of experimentally induced gastric tumors.

Topics: Animals; Benzalkonium Compounds; Carcinogens; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Wistar; Stomach; Stomach Neoplasms; Sympathectomy, Chemical

Inactivation of the tumor suppressor gene, p16 by CpG hypermethylation is a common event in various tumors including gastric carcinoma. The aim of this study is to investigate if p16 hypermethylation is an early and frequent event in gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The frequency and timing of p16 hypermethylation during the multistep gastric carcinogenesis in Wistar rats were analyzed in various microdissected gastric lesions. The p16 methylation status and the presence of p16 protein were analyzed by methylation-specific PCR and immunohistochemistry, respectively. Results showed that p16 methylation frequency was correlated with the severity of gastric pathologic lesions, positively. For instance, p16 methylation was found in 2.7% of normal gastric epithelium (n = 36), 16.7% of chronic atrophy gastritis (n = 24), 37.5% of dysplasia (n = 24), 67.4% of gastric adenoma (n = 43), and 85.2% of gastric carcinoma (n = 27). The p16 methylation in the distal stomach epithelium was higher than that in the proximal stomach. p16 protein was expressed in all of 15 p16 unmethylated gastric epithelial samples, but not expressed in all of 12 p16 methylated samples. These results suggest that CpG island hypermethylation may account for the silencing of p16 in rat stomach and is an early event whose accumulation will finally lead to gastric carcinogenesis.

Topics: Animals; Base Sequence; Carcinogens; CpG Islands; Cyclin-Dependent Kinase Inhibitor p16; DNA Methylation; DNA, Neoplasm; Gene Expression; Gene Silencing; Genes, p16; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms

The effect of prolonged administration of iron chelator phenanthroline on sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and the labeling and apoptotic indices in the gastric cancers was investigated in Wistar rats. After 25 weeks of carcinogen treatment, the rats were given chow pellets containing 10% sodium chloride and intraperitoneal injections of phenanthroline at doses of 15 or 30 mg/kg body weight every other day. At week 52, feeding of sodium chloride significantly increased the incidence of gastric cancers, as compared with the control group. Prolonged injections of phenanthroline at both doses significantly reduced the incidence of gastric cancers, which was enhanced by oral supplementation with sodium chloride. Phenanthroline at both doses significantly decreased the labeling index of gastric cancers, which was enhanced by sodium chloride, and significantly increased the apoptotic index of gastric cancers, which was lowered by sodium chloride. In vitro examination using electron spin resonance revealed that sodium chloride promotes the production of hydroxyl radical during Fe(2+) oxidation by Fenton's reaction. These findings suggest that enhancement by sodium chloride of gastric carcinogenesis may be mediated by hydroxyl radicals.

Topics: Adenocarcinoma; Animals; Antigens, Neoplasm; Apoptosis; Cell Division; Cocarcinogenesis; Drug Synergism; Electron Spin Resonance Spectroscopy; Hydroxyl Radical; Iron Chelating Agents; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Oxidation-Reduction; Phenanthrolines; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Sodium Chloride, Dietary; Stomach Neoplasms

To understand the response of human REV3 gene to gastric cancer inducing carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and its role in human mutagenesis.. The response of the human REV3 gene to MNNG was measured in human 293 cells and FL cells by RT-PCR. By using antisense technology, mutation analysis at HPRT locus (on which lesion-targeted mutation usually occurs) was conducted in human transgenic cell line FL-REV3(-) by 8-azaguanine screening, and mutation occurred on undamaged DNA template was detected by using a shuttle plasmid pZ189 as the probe in human transgenic cell lines 293-REV3(-) and FL-REV3(-). The blockage effect of REV3 was measured by combination of reverse transcription-polymerase chain reaction to detect the expression of antisense REV3 RNA and Western blotting to detect the REV3 protein level.. The human REV3 gene was significantly activated by MNNG treatment, as indicated by the upregulation of REV3 gene expression at the transcriptional level in MNNG-treated human cells, with significant increase of REV3 expression level by 0.38 fold, 0.33 fold and 0.27 fold respectively at 6 h, 12 h and 24 h in MNNG-treated 293 cells (P<0.05); and to 0.77 fold and 0.65 fold at 12 h and 24 h respectively in MNNG-treated FL cells (P<0.05). In transgenic cell line (in which REV3 was blocked by antisense REV3 RNA), high level of antisense REV3 RNA was detected, with a decreased level of REV3 protein. MNNG treatment significantly increased the mutation frequencies on undamaged DNA template (untargeted mutation), and also at HPRT locus (lesion-targeted mutation). However, when REV3 gene was blocked by antisense REV3 RNA, the MNNG-induced mutation frequency on undamaged DNA templates was significantly decreased by 3.8 fold (P<0.05) and 5.8 fold (P<0.01) respectively both in MNNG-pretreated transgenic 293 cells and FL cells in which REV3 was blocked by antisense RNA, and almost recovered to their spontaneous mutation levels. The spontaneous HPRT mutation was disappeared in REV3-disrupted cells, and induced mutation frequency at HPRT locus significantly decreased from 8.66 x 10(-6) in FL cells to 0.14 x 10(-6) in transgenic cells as well (P<0.01).. The expression of the human REV3 can be upregulated at the transcriptional level in response to MNNG. The human REV3 gene plays a role not only in lesion-targeted DNA mutagenesis, but also in mutagenesis on undamaged DNA templates that is called untargeted mutation.

Topics: Base Sequence; Carcinogens; Cell Line; DNA-Binding Proteins; DNA-Directed DNA Polymerase; DNA, Antisense; Humans; Hypoxanthine Phosphoribosyltransferase; Methylnitronitrosoguanidine; Mutagenesis; Plasmids; Stomach Neoplasms; Transfection

Rat stomach carcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) are widely used as a model for differentiated-type human stomach carcinomas. Here, we analyzed expression profiles in five MNNG-induced rat stomach carcinomas by the high-density oligonucleotide microarray containing approximately 8000 probe sets. 244 and 208 genes were up- and down-regulated, respectively, by 3-fold and over in four or five carcinomas. Up-regulated genes included those involved in the extracellular matrix remodeling (i.e. Collagen types I, III, V, MMP3), immune response (i.e. lysozyme, complements) and in ossification (i.e. Osteoblast-specific factor). Genes down-regulated included those related to hydrocarbon metabolism (i.e. aldose A, aldehyde dehydrogenase), gastric juice (ion transporter genes) and mucous production (Mucin 5) and gastric hormones (gastrin and somatostatin). The expression profile of the MNNG-induced rat stomach carcinomas shared many features with human stomach carcinomas while cyclin D1 was down-regulated in rat stomach carcinomas but up-regulated in human stomach carcinomas. When the expression profile of the MNNG-induced rat stomach carcinomas was compared with those of two kinds of rat mammary carcinomas, only 13 genes were commonly altered. These results showed that MNNG-induced stomach carcinomas possessed infiltrating capacity and had lost differentiated phenotypes of the stomach, in the same way as human stomach carcinomas, and could be used as a good model for them from the viewpoint of molecular expression profile.

Topics: Animals; Biomarkers, Tumor; DNA Primers; DNA, Neoplasm; Expressed Sequence Tags; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Humans; Male; Mammary Neoplasms, Experimental; Methylnitronitrosoguanidine; Neoplasm Proteins; Oligonucleotide Array Sequence Analysis; Rats; Rats, Inbred ACI; Reverse Transcriptase Polymerase Chain Reaction; Stomach Neoplasms

The effect of prolonged administration of the cytokine interleukin (IL)-1beta on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was examined in Wistar rats. In addition, we examined the effects on the proliferating cell nuclear antigen (PCNA) labeling index and the hepatocyte growth factor (HGF) immunoreactivity of the gastric mucosa. The rats received intraperitoneal injections of 0.1 or 0.3 microg/kg body weight of IL-1beta every other day after oral treatment with MNNG for 25 weeks. Long-term administration of IL-1beta at high dose, but not at low dose, significantly increased the incidence of gastric cancer in week 52. Administration of IL-1beta at high dose also significantly increased the labeling index and the HGF immunoreactivity of the gastric antral mucosa, and induced inflammatory cell infiltration and glandular atrophy of the gastric mucosa. Because IL-1beta production in the gastric mucosa is increased in patients with Helicobacter pylori-associated gastritis and eradiation of the organism significantly decreases the IL-1beta production, these findings suggest that Helicobacter pylori-associated gastric carcinogenesis may be in part mediated through IL-1beta.

Topics: Adenocarcinoma; Animals; Cell Division; Drug Synergism; Gastric Mucosa; Gastritis; Helicobacter Infections; Helicobacter pylori; Interleukin-1; Male; Methylnitronitrosoguanidine; Neoplasm Invasiveness; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Stomach; Stomach Neoplasms

Aberrant Wnt/beta-catenin signaling caused by mutations in exon 3 of the beta-catenin gene has been identified in a number of human malignancies, including stomach cancer. However, studies of mutation frequency have yielded conflicting results, and timing during progression remains largely unknown. In this study, we utilized an animal model to address this question. A total of 20 ACI male rats were treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water and 22 induced differentiated adenocarcinomas were histopathologically and immunohistochemically evaluated for beta-catenin localization. Fourteen tumors (63.6%) that showed homogeneous low-grade morphology, preserving cell polarity, were found to harbor beta-catenin protein on the cell membranes (M). Eight tumors exhibited regions of high-grade morphology among areas with low-grade morphology, and they were characterized by denser cell growth and loss of cell polarity. Among these 8 tumors, 4 (18.2%) showed cytoplasmic localization (C) of beta-catenin in small regions. The remaining 4 tumors (18.2%) contained more dysplastic regions that displayed nuclear (N) beta-catenin staining. Analysis of DNA obtained by microdissection demonstrated that all of 4 regions with C staining and 20 with M staining, as well as 17 samples of surrounding normal mucosa (S) had wild-type beta-catenin. In contrast, all of 3 regions with N staining featured mutations (3 of 3 = 100%; N vs. C, P < 0.05; N vs. M and N vs. S, P < 0.001, Fisher's exact test) in exon 3, at glycine 34, threonine 41, and serine 45, which affected phosphorylation sites. In conclusion, beta-catenin mutations appear to be associated with the late progression stage of adenocarcinoma development in rat stomach carcinogenesis, in contrast to the case of colorectal cancers, in which mutations appear to occur in the early stages.

Topics: Adenocarcinoma; Animals; Base Sequence; beta Catenin; Carcinogens; Cell Nucleus; Disease Progression; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Mutation; Polymerase Chain Reaction; Polymorphism, Single-Stranded Conformational; Rats; Stomach Neoplasms

We investigated the chemopreventive effect of S-allylcysteine (SAC), a water-soluble garlic constituent against gastric carcinogenesis induced in male Wistar rats by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and saturated sodium chloride (S-NaCl). The animals were divided into four groups of six animals. Rats in groups 1 and 2 were administered MNNG (200 mg/kg body weight) on days 0 and 14 as well as S-NaCl (1 mL/rat) three days during weeks 0 to 3, and thereafter placed on basal diet until the end of the experiment. Rats in group 2 in addition received SAC (200 mg/kg body weight) three times per week starting on the day following the first exposure to MNNG and continued until the end of the experimental period. Group 3 animals were given SAC alone as in group 2. Group 4 animals received basal diet and tap water throughout the experiment and served as the untreated control. The animals were sacrificed after an experimental period of 21 weeks. Measurement of lipid peroxidation and antioxidants of the glutathione redox cycle in the stomach tissue, liver and venous blood was used to monitor the chemopreventive potential of SAC. All animals that received MNNG and S-NaCl alone, developed tumours, identified histologically as squamous cell carcinomas. In the tumour tissue, diminished lipid peroxidation was accompanied by increase in reduced glutathione (GSH) and GSH-dependent enzymes, whereas in the liver and circulation, enhanced lipid peroxidation was associated with antioxidant depletion. Administration of SAC suppressed the incidence of MNNG+S-NaCl-induced gastric tumours as revealed by the absence of carcinomas. SAC ameliorated MNNG-induced decreased susceptibility of the gastric mucosa to lipid peroxidation, whilst simultaneously increasing the antioxidant status. In the liver and blood, SAC reduced the extent of lipid peroxidation and significantly enhanced antioxidant activities. We suggest that SAC exerts its chemopreventive effects by modulating lipid peroxidation and enhancing GSH-dependent antioxidants in the target organ as well as in the liver and blood.

Topics: Animals; Antineoplastic Agents; Antioxidants; Biomarkers, Tumor; Carcinoma, Squamous Cell; Cysteine; Disease Models, Animal; Gastric Mucosa; Glutathione; Lipid Peroxidation; Liver; Male; Methylnitronitrosoguanidine; Oxidants; Oxidation-Reduction; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

We have examined the mechanism of 1-methyl-3-nitro-1-nitrosoguanidine (MNNG)-induced gastric cancer with respect to the production of hydroxyl free radical (OH). Nucleophilic attack by H2O2 on the nitroso group of MNNG produces 1-methyl-3-nitroguanidine (MNG) and the intermediate peroxynitric acid (ONOOH), which splits into hydroxyl free radical (OH) and nitrogen dioxide leading to the formation of nitric and nitrate ions in water. Xanthine oxidase (XO) induces the production of O2.- or H2O2 from molecular oxygen, depending on the overall level of enzyme reduction. In this study, we examined OH production by the reaction of MNNG with H2O2 derived from the XO-HX system containing XO and the purine substrate hypoxanthine by ESR using the spin trapping reagent 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO). OH was produced in the XO-HX-DMPO system with addition of MNNG (the MNNG-XO-HX-DMPO system) under aerobic conditions, but was not in the XO-HX-DMPO system, and production of OH was inhibited by catalase but not by superoxide dismutase, suggesting that OH was produced by the reaction of MNNG with H2O2 derived from the XO-HX system. The production of OH was significantly increased with increase in the reducing activity of XO, though that of O2.- was not, also suggesting the O2(.-)-independent .OH production. The productions of nitrite ion and MNG in the MNNG-XO-HX system were determined by the colorimetric method and HPLC, respectively. Based on these findings, we conclude that .OH was produced by homolytic split of the intermediate ONOOH formed by nucleophilic attack of H2O2 derived from the XO-HX system on MNNG.

Topics: Cell-Free System; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Humans; Hydrogen Peroxide; Hydroxyl Radical; Methylnitronitrosoguanidine; Spin Labels; Stomach Neoplasms; Xanthine Oxidase

The present study was designed to define molecular alterations in the initiation stage of rat stomach carcinogenesis. Groups of male Lewis rats, 6 weeks old, were given drinking water with or without N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; 100 mg/liter). Total RNA was isolated from the stomach pyloric mucosa, and fluorescent differential display analysis was performed. A cDNA fragment of 125 bp encoding an extracellular matrix-associated matricellular glycoprotein, osteonectin, was identified after 14 days of MNNG exposure. A severalfold increase in expression was observed after 14 and 27 days of MNNG exposure, as determined by northern blot and RT-PCR. Immunohistochemistry revealed that osteonectin-mAb-stained fibroblastic cells appeared in interstitial tissue of pyloric mucosa. Additionally the gene expression of other extracellular matrix proteins, viz., collagen type III, fibronectin, osteopontin, proteoglycan NG2, laminin gamma1 and S-laminin, was also markedly increased, as determined by competitive RT-PCR after 14 days of MNNG exposure. The gene expression of osteonectin and the six other extracellular matrix proteins was elevated in twelve stomach adenocarcinomas and adenomas induced by MNNG in Lewis and WKY rats. Osteonectin-mAb-stained fibroblastic cells were evident in interstitial tissue of stomach tumor. These results suggest that osteonectin-expressing fibroblastic cells appear in the interstitial tissue of pyloric mucosa from the early initiation stage of rat stomach chemical carcinogenesis, and that this phenomenon probably plays a role in cancer development.

Topics: Animals; Cell Division; Fibroblasts; Gastric Mucosa; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Osteonectin; Rats; Rats, Inbred Lew; Rats, Inbred WKY; Reverse Transcriptase Polymerase Chain Reaction; Stomach Neoplasms

Human beings are exposed to a multitude of carcinogens in their environment, and most cancers are considered to be chemically induced. Here we examined differences in genetic alterations in rat forestomach tumors induced by repeated exposure to a genotoxic carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or N-methylnitrosourethane (MNUR), and chronic treatment with a non-genotoxic carcinogen, butylated hydroxyanisole (BHA) or caffeic acid (CA). A total of 132, 6-week-old male F344 rats were employed. Forty rats were treated with MNNG by intragastric administration at a dose of 20 mg/kg body wt once a week for 32 weeks, and 20 rats received 20 p.p.m. MNUR in their drinking water for 48 weeks. Further groups of 20 animals were administered 2% BHA or 2% CA in the diet for 104 weeks. The remaining rats were maintained without any supplement as controls. Multiple forestomach tumors were observed in all rats of the MNNG-, MNUR-, BHA- and CA-treated groups. Histopathologically, MNUR- and CA-treated groups showed almost the same pattern. On polymerase chain reaction-single strand conformation polymorphism analysis, H-ras and p53 gene mutations were observed at high and relatively low frequencies, respectively, in forestomach tumors induced by MNNG and MNUR. Most H-ras gene mutations were G-->A transitions in codons 7 and 12 of exon 1. On the other hand, forestomach tumors due to the non-genotoxic carcinogens, BHA and CA, had almost no mutations of the H-ras and p53 genes. Moreover, relative overexpression of cyclin D1 and p53 was detected in forestomach tumors induced by the genotoxic carcinogens, while their non-genotoxic counterparts had a tendency to show low expression of those molecules. Mutations of the beta-catenin gene were not detected in any group. The present study demonstrates that rat forestomach tumors induced by genotoxic and non-genotoxic carcinogens have different underlying genetic alterations, even if their pathological features are similar.

Topics: Animals; Base Sequence; Butylated Hydroxyanisole; Carcinogens; Disease Models, Animal; DNA Primers; Gene Expression Regulation, Neoplastic; Humans; Male; Methylnitronitrosoguanidine; Mutagens; Nitrosomethylurethane; Polymerase Chain Reaction; Polymorphism, Single-Stranded Conformational; Rats; Rats, Inbred F344; Stomach Neoplasms

The mucosal changes by which duodenogastric reflux may predispose to gastric cancer have not been fully clarified. In this study in rats, duodenal fluid was directed into the stomach through a gastroenterostomy (jejunal reflux, N = 29) or through the pylorus (pyloric reflux, N = 30) and compared with 30 controls. Twenty-four weeks later the stomach was exposed to N-[3H]methyl-N-nitro-N-nitrosoguanidine ([3H]MNNG). The corpus mucosa was examined for proliferating cells (bromodeoxyuridine labeled) and cells at risk of methyl-N-nitro-N-nitrosoguanidine-induced carcinogenesis (cells labeled with bromodeoxyuridine and [3H]MNNG). The number of double-labeled cells increased from 0.8 +/- 0.1/mm mucosa in the control group to 5.2 +/- 0.9 in the jejunal reflux group (P < 0.05) and 2.7 +/- 0.5 in the pyloric reflux group (P < 0.05). An erosion or ulcer appeared at the gastroenterostomy in 52% of animals with jejunal reflux and 17% of those with pyloric reflux (P < 0.006). Within erosions the mean number of double-labeled cells was 9.6 +/- 2.2 in the jejunal reflux group and 7.7 +/- 4.8 in the pyloric reflux group, and significantly higher than in the nonlesion area of the mucosa (0.6 +/- 0.2 and 0.8 +/- 0.3). In erosions the distance between the gastric lumen and the proliferating cells was significantly shorter and the cell proliferation significantly higher than in the nonlesion area of the mucosa. We conclude that duodenogastric reflux increases the penetration of [3H]MNNG into the corpus mucosa of rats and also induces mucosa lesions, which further increase the penetration of [3H]MNNG into the corpus mucosa.

Topics: Animals; Cell Transformation, Neoplastic; Duodenogastric Reflux; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Tritium

The effects of lycopene on blood oxidant-antioxidant balance during N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in the presence of saturated sodium chloride (S-NaCl) as promoting agent were investigated. Enhanced lipid peroxidation in the blood of tumour-bearing animals was accompanied by significant decreases in the levels of reduced glutathione (GSH), ascorbic acid and vitamin E and the activities of glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR). Administration of lycopene significantly lowered the concentrations of lipid peroxides and enhanced antioxidant levels. We suggest that the modulatory effects of lycopene on the blood oxidant-antioxidant balance may be responsible for its chemopreventive potential.

Topics: Animals; Ascorbic Acid; Body Weight; Carotenoids; Erythrocytes; Glutathione; Glutathione Peroxidase; Glutathione Reductase; Glutathione Transferase; Lipid Peroxidation; Lycopene; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms; Thiobarbituric Acid Reactive Substances; Vitamin E

Dendritic cell appearance and differentiation during early and late stages of rat stomach carcinogenesis were studied in the pyloric mucosa. Young male rats were given drinking water with or without N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; 100 mg/liter) for 14 days. Use of competitive RT-PCR and northern blotting showed that MNNG exposure induced 3- to 4-fold greater expression of the genes for integrin beta7 and integrin alphaE2 (identical with antigen OX-62, a dendritic cell marker), as well as three cytokines, IL-4, GM-CSF and TNFalpha, in the stomach pyloric mucosa of resistant Buffalo rats compared to sensitive ACI rats. These genes were minimally expressed in control animals. The results confirm the appearance of dendritic cells in the target pyloric mucosa and suggest the possibility that dendritic cell differentiation and maturation are induced by various cytokines, at least in Buffalo rats. Competitive RT-PCR showed expression of integrin alphaE2 and beta7, MHC class II-associated invariant chain (Ii), MHC class II, B7-1, CD28, GM-CSF and TNFalpha genes in all 12 examined stomach adenocarcinomas and adenomas induced in male Lewis and WKY rats with 30 weeks' MNNG exposure, suggesting the presence of dendritic cells in tumors. OX-62 staining and western blotting for OX-62 also confirmed the presence of dendritic cells in tumors. However, the population of dendritic cells in tumors was less than that in the pyloric mucosa after 14 days' MNNG exposure. The present results suggest that immune defense involving dendritic cells is marshaled from the very early initiation stage during rat stomach cancer development, but is downgraded in developed tumors.

Topics: Animals; Antigens, CD; Binding, Competitive; Blotting, Northern; Blotting, Western; Cadherins; Carcinogens; Cell Differentiation; Dendritic Cells; Gastric Mucosa; Granulocyte-Macrophage Colony-Stimulating Factor; Immunohistochemistry; Integrin alpha Chains; Integrin beta Chains; Interleukin-4; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Lew; Rats, Inbred WKY; Reverse Transcriptase Polymerase Chain Reaction; RNA; Stomach Neoplasms; Tumor Necrosis Factor-alpha

A decrease in folic acid and subsequent DNA hypomethylation may be involved in gastric carcinogenesis. Epidemiological and nutritional studies have indicated that folate status modulates the risk of developing cancers.. To investigate whether folic acid plays an important role in the chemoprevention of gastric carcinogenesis induced by N-ethyl-N-nitrosoguanidine (ENNG) in beagles.. Sixteen male beagles were randomly divided into two groups: folic acid treated group and control group. In both groups beagles were fed ENNG 75 mg per day for eight months and in the treated group 20 mg folic acid was given to beagles for 15 months. Gastroscopy and biopsies were performed before and every 2-3 months after administration of ENNG until the end of the experiment. Histopathological lesions were diagnosed with regard to the criteria for human gastric mucosal biopsies. Serum and gastric mucosal tissue folic acid concentrations were measured.. In the control group, all beagles developed gastric cancer (8/8) compared with only 3/8 in the folic acid treated group (p<0.05). Moreover, serum and gastric mucosal tissue folic acid concentrations were markedly elevated 15 months after folic acid administration. The difference was statistically significant between the two groups (p<0.05).. Our results indicate that high dose folic acid plays an important role in the chemoprevention of gastric carcinogenesis induced by a chemical carcinogen ENNG in beagles.

Topics: Animals; Carcinogens; Dogs; Folic Acid; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Radioimmunoassay; Reagent Kits, Diagnostic; Spectrophotometry; Stomach Neoplasms; Treatment Outcome

The effects of sodium nitrite (NaNO2), in combination with one of three antioxidants, tert-butylhydroquinone (TBHQ), alpha-tocopherol (alpha-Toc) and propyl gallate (PG), on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) stomach carcinogenesis were investigated in F344 rats. Groups of 15 male rats were treated with an intragastric dose of 150 mg/kg body weight of MNNG, and starting 1 week later, were treated with 0.5% TBHQ, 1% alpha-Toc, 1% PG or basal diet with or without 0.2% NaNO2 in their drinking water until they were killed at the end of week 36. Macroscopically, in MNNG-treated animals, combined administration of alpha-Toc or PG with NaNO2 significantly increased the areas and numbers of forestomach nodules as compared with the respective antioxidant alone values. Microscopically, in MNNG-treated animals, treatment with TBHQ significantly increased the incidence and multiplicity of forestomach papillomas as compared with basal diet alone value. Combined administration of alpha-Toc with NaNO2 significantly raised the multiplicity of forestomach papillomas, with a tendency to elevation in the incidence as compared with the group given alpha-Toc alone. Incidences of forestomach moderate and/or severe hyperplasias were significantly higher in the TBHQ or PG plus NaNO2 groups than in the single compound groups. In rats without MNNG treatment, combined treatment of antioxidants with NaNO2 significantly increased the incidences of mild or moderate hyperplasia. In the glandular stomach, although the incidence of atypical hyperplasia showed a non-significant tendency for decrease with TBHQ treatment, additional administration of NaNO2 caused significant increase. These results indicate that co-administration of NaNO2 with alpha-Toc, TBHQ or PG and particularly the first, promotes forestomach carcinogenesis. Concurrent alpha-Toc, TBHQ or PG treatment with NaNO2 is likely to induce forestomach tumors in the long term.

Topics: alpha-Tocopherol; Animals; Antioxidants; Body Weight; Carcinoma, Squamous Cell; Drug Combinations; Drug Interactions; Food Preservatives; Hydroquinones; Hyperplasia; Male; Methylnitronitrosoguanidine; Papilloma; Propyl Gallate; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms

Strain differences in susceptibility regarding stomach carcinogenesis due to N-methyl-N-nitrosourea were examined in males of six strains of mice: BALB/cA (BALB), C57BL/6N (C57BL6), CBA/JN (CBA), C3H/HeN (C3H), DBA/2N (DBA/2), and CD-1 (ICR). The frequency of pepsinogen-altered pyloric glands (PAPGs), putative precancerous lesions, was highest (19.6+/-9.9%) in the BALB and lowest in the ICR (12.3+/-5.7%) mice (P<0.05). Incidences of adenocarcinomas at week 52 were 59.3% (16 of 27) and 18.5% (5 of 27), respectively (P<0.005). Invasion also tended to be deepest in BALB compared with the other strains. Intestinal alkaline phosphatase-positive intestinal type cells were observed heterogeneously in some hyperplasias, adenomas and adenocarcinomas consisting of gastric type cells. Thus, intestinalization appeared to occur at random in both non-neoplastic and monoclonal neoplastic lesions, making it unlikely that IAP-positive cells could be precursors of gastric tumors. In contrast, the data suggest a direct histogenetic role for the PAPG, a useful preneoplastic marker lesion in mouse strains.

Topics: Adenocarcinoma; Adenoma; Alkaline Phosphatase; Animals; Disease Susceptibility; Immunohistochemistry; Intestinal Mucosa; Male; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Inbred CBA; Mice, Inbred DBA; Mice, Inbred ICR; Pepsinogen A; Precancerous Conditions; Pylorus; Species Specificity; Stomach; Stomach Neoplasms; Survival Rate

We investigated "the "chemopreventive potential of lycopene against gastric carcinogenesis induced in male Wistar rats by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and saturated sodium chloride (S-NaCl). Administration of lycopene inhibited MNNG+S-NaCl-induced gastric carcinogenesis as revealed by the absence of carcinomas. Lipid peroxidation, reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were used to monitor the chemopreventive potential of lycopene. The extent of lipid peroxidation was significantly lower, whereas GSH, GPx, GST and GR were markedly enhanced in the gastric mucosa of tumour-bearing animals. Our data suggest that lycopene may exert its inhibitory effects by modulating the oxidant and antioxidant status in the gastric mucosa.

Topics: Animals; Anticarcinogenic Agents; Antioxidants; Carcinogens; Carcinoma, Squamous Cell; Carotenoids; Glutathione; Glutathione Peroxidase; Lipid Peroxidation; Lycopene; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Saline Solution, Hypertonic; Stomach Neoplasms

Duodenogastric reflux is a risk factor for gastric carcinogenesis, but the pathogenesis is not fully understood. We studied the risk of N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis in the antrum of rats with duodenogastric reflux. Duodenal fluid was directed into the stomach through the pylorus (pyloric reflux group) or through a gastrojejunostomy (jejunal reflux group). After twenty-four weeks, 5-bromo-2-deoxyuridine (BrdU) was injected intravenously and the stomach was exposed to N-(3)H-methyl-N-nitro-N-nitrosoguanidine ((3)H-MNNG). The antral mucosa was examined with immunohistochemistry and autoradiography for identification of proliferating cells (BrdU labelled) and cells at risk of MNNG-induced carcinogenesis ((3)H-MNNG and BrdU-labelled cells). Duodenogastric reflux increased the number of double-labelled cells in the antral mucosa from 4.8 +/- 0.6 per mm in the control group to 11.3 +/- 1.9 in the jejunal reflux group (P < 0.05) and 12.7 +/- 0.9 in the pyloric reflux group (P < 0.05). Mucosal erosions were observed in 15 of 28 animals with pyloric reflux and the number of double-labelled cells in the erosion area (4.3 +/- 0.7) was higher than in the same area of animals without erosion (1.4 +/- 0.5) (P < 0.05). Duodeno-gastric reflux increased the cell proliferation and significantly changed the distance between the surface epithelial lining and the proliferating cells when compared to the controls. These results indicate that duodenogastric reflux increases the penetration of (3)H-MNNG into the antrum mucosa of rats. Increased cell proliferation and erosions increase the number of cells at risk of an initiation process from a penetrating gastric carcinogen.

Topics: Animals; Bile Ducts; Bromodeoxyuridine; Carcinogens; Cell Division; Duodenogastric Reflux; Gastric Mucosa; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Pancreatic Ducts; Rats; Stomach Neoplasms; Time Factors

Laboratory studies have described the carcinogenicity of fumonisin B1 (FB1) in rodents and epidemiological evidence suggests an association between FB1 (a mycotoxin produced by Fusarium moniliforme) and cancer in humans. This study was designed to reveal in rainbow trout, a species with very low spontaneous tumor incidence, if FB1 was (i) a complete carcinogen, in the absence of an initiator; (ii) a promoter of liver tumors in fish initiated as fry with aflatoxin B1 (AFB1); and (iii) a promoter of liver, kidney, stomach, or swim bladder tumors in fish initiated as fry with N-methyl-N'-nitro-nitrosoguanidine (MNNG). FB1 was not a complete carcinogen in trout. No tumors were observed in any tissue of fish fed diets containing 0, 3.2, 23, or 104 ppm FB1 for a total of 34 weeks (4 weeks FB1 exposure, 2 weeks outgrowth on control diet, followed by 30 weeks FB1 diet) in the absence of a known initiator. FB1 promoted AFB1 initiated liver tumors in fish fed > or = 23 ppm FB1 for 42 weeks. A 1-week pretreatment of FB1 did not alter the amount of liver [3H]AFB1 DNA adducts, which suggests that short-term exposure to FB1 will not alter phase I or phase II metabolism of AFB1. In MNNG-initiated fish, liver tumors were promoted in the 104 ppm FB1 treatment (42 weeks), but FB1 did not promote tumors in any other tissue. Tumor incidence decreased in kidney and stomach in the 104 ppm FB1 treatment of MNNG-initiated trout. The FB1 promotional activity in AFB1-initiated fish was correlated with disruption of sphingolipid metabolism, suggesting that alterations in associated sphingolipid signaling pathways are potentially responsible for the promotional activity of FB1 in AFB1-initiated fish.

Topics: Aflatoxin B1; Air Sacs; Animals; Carboxylic Acids; Carcinogenicity Tests; Carcinogens; Diet; Drug Synergism; Fumonisins; Kidney Neoplasms; Liver; Liver Neoplasms, Experimental; Methylnitronitrosoguanidine; Mycotoxins; Oncorhynchus mykiss; Sphingosine; Stomach Neoplasms

The effects of combined administration of a reactive oxidant, monochloramine, and a mucoregulatory agent, ambroxol, on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in inbred Wistar rats. After receiving oral MNNG and regular chow pellets for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without subcutaneous injection of ambroxol at high or low doses, until the end of the experiment at week 52. Treatment with both ammonium acetate and sodium hypochlorite, which produce monochloramine, significantly increased the incidence of gastric cancers at week 52, whereas concomitant administration of ambroxol with ammonium acetate and sodium hypochlorite significantly attenuated this enhanced gastric carcinogenesis. Results also revealed that ambroxol scavenged monochloramine. Because monochloramine is closely related to Helicobacter pylori-associated gastric carcinogenesis, these findings suggest that ambroxol may prevent H. pylori-associated gastric carcinogenesis.

Topics: Ambroxol; Animals; Anticarcinogenic Agents; Apoptosis; Carcinogens; Chloramines; Drug Interactions; Free Radical Scavengers; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms

Gastrointestinal cancer is the most important clinical target of gene therapy. Suicide gene therapy, such as with the herpes simplex virus type 1 thymidine kinase (HSV-TK) gene, has been shown to exert antitumor efficacy in various cancer models in vitro. We previously reported in situ gene transfer and gene therapy for gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) in dogs. Here, we describe the sequential histopathological changes after suicide gene therapy of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer in rats. Gastric tumors were induced by MNNG in 38 / 73 (52%) of Wistar strain rats. The suicide gene therapy group (14 rats) was subjected to in situ gene transfer with a recombinant adenovirus vector carrying the HSV-TK gene driven by CAG promoter (Ad.CAGHSV-TK) in gastric tumor, followed by the antiviral drug ganciclovir (GCV). To observe the histopathological changes at various times after HSV-TK / GCV gene therapy, groups of animals were sacrificed at 3, 8, and 30 days after gene transfer. Apoptosis in the gastric tumors was detected by the TUNEL method to assess the efficacy of HSV-TK / GCV gene therapy, and it was marked in the 8- and 30-day treatment groups compared to the sham operation controls (P < 0.001). Various histopathological changes, degeneration of cancer tissue and fibrosis after necrosis and apoptosis were significantly greater in the 30-day treatment group. The HSV-TK gene was detectable in peripheral blood by PCR until 30 days after gene transfer. These results may be useful in devising a method of suicide gene therapy for humans.

Topics: Adenoviridae; Animals; Antiviral Agents; Apoptosis; Carcinogens; Cell Nucleus; Cytoplasm; Fibrosis; Ganciclovir; Gene Transfer Techniques; Genetic Therapy; Herpesvirus 1, Human; In Situ Nick-End Labeling; Male; Methylnitronitrosoguanidine; Necrosis; Polymerase Chain Reaction; Promoter Regions, Genetic; Rats; Rats, Wistar; Stomach Neoplasms; Thymidine Kinase; Time Factors

The modifying effect of irsogladine maleate (IRG) on N-methyl-N-nitro-N-nitrosoguanidine (MNNG)-initiated and glyoxal-promoted gastric carcinogenesis was examined in male Wistar rats. Six-week-old rats were divided into ten groups. Groups 1 through 6 were given MNNG (100 mg/l in drinking water) for 25 weeks from the start of the experiment, whereas groups 7 through 10 received distilled water in the initiation phase as the vehicle treatment. Groups 1 and 8 were kept on the basal diet and distilled water throughout the experiment (55 weeks). Groups 2-8 were given 0.5% glyoxal in the drinking water for 30 weeks from 26th week of the experiment. Group 3 was fed the diet mixed with 100 ppm IRG for 25 weeks from the start of experiment. Groups 4 and 8 were fed the diet mixed with 100 ppm IRG for 30 weeks from 26th week of experiment. Groups 5 and 9 or 6 were given 100 or 25 ppm IRG containing diet, respectively throughout the experiment. Group 10 was given the basal diet and distilled water as the vehicle treated control. Tumors of upper digestive tracts (stomach and duodenum) were developed in groups: 1 (12/17 rats, 71%), 2 (11/12 rats, 92%), 3 (9/16 rats, 56%), 4 (5/12 rats, 42%), 5 (6/15 rats, 40%) and 6 (7/12 rats, 58%). High dose of IRG in initiation and/or promotion phase significantly reduced the incidence of tumors of the upper digestive tracts. The average numbers of the digestive tracts neoplasms in groups 3,5 and 6 given glyoxal and IRG were less than those in group 2 which received only glyoxal. These results suggest that IRG could be a preventive agent against the occurrence of neoplasms of the upper digestive tract.

Topics: Animals; Anticarcinogenic Agents; Body Weight; Drug Interactions; Glyoxal; Liver Neoplasms; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Triazines

We investigated the effect of the gastrointestinal regulatory peptide, bombesin, on the development of peritoneal metastasis from gastric cancers induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and on Rho activity in the gastric cancers.. Rats were allocated to three groups. All groups received MNNG (100 micrograms/ml) solution for 25 weeks from the start of the experiment. Group 1 (controls) received olive oil injections from the start of MNNG treatment; group 2 animals received alternate-day s.c. injections of bombesin (40 micrograms/kg body weight) in olive oil from the start of the experiment until the end of the experiment at week 52; and group 3 received the s.c. bombesin injection on alternate days from week 26 until week 52. The effect of bombesin on Rho activity in gastric cancer was examined by Western blotting.. Bombesin given from the start of the experiment (group 2) and after the MNNG treatment (group 3) both significantly increased the incidence of gastric cancer metastasis, compared with controls, at week 52: The incidence of metastasis was significantly higher in group 2 than in group 3. Bombesin from the start of the experiment (group 2) significantly increased the incidence of tumors with deeper invasion or more infiltrative growth pattern, or lymphatic vessel tumor invasion, while bombesin after MNNG treatment (group 3) significantly increased the incidence of lymphatic vessel invasion. Bombesin also increased the activity of Rho protein in the tumors.. Bombesin significantly increased the incidence of peritoneal metastasis from gastric cancers through the activation of Rho protein.

Topics: Animals; Bombesin; Carcinogens; Male; Methylnitronitrosoguanidine; Peritoneal Neoplasms; Rats; Rats, Wistar; rho GTP-Binding Proteins; Stomach Neoplasms

The modulatory effects of garlic extract on the in vivo clastogenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a carcinogenic nitrosamine, were evaluated by quantification of micronuclei and chromosomal aberrations in metaphase cells from the bone marrow of male Wistar rats. A single intraperitoneal injection of MNNG (40 mg/kg bodyweight) was found to be clastogenic as revealed by the increased frequency of micronucleated polychromatic erythrocytes and chromosomal aberrations. Pretreatment with aqueous garlic extract (250 mg/kg bodyweight) for 5 days significantly reduced the frequencies of MNNG-induced micronuclei and chromosomal aberrations. The results demonstrate that administration of garlic extract protects against the clastogenic effects of MNNG.

Topics: Animals; Cell Transformation, Neoplastic; Chromosome Aberrations; Garlic; Male; Metaphase; Methylnitronitrosoguanidine; Micronucleus Tests; Mutagenesis; Mutagens; Plant Extracts; Random Allocation; Rats; Rats, Wistar; Stomach Neoplasms

Helicobacter pylori infection is a risk factor for gastric cancer. How the bacterium contributes to this process is still unclear. We present a new Wistar rat model that was used to evaluate the effect of H. pylori on early preneoplastic events as judged from epithelial cell turnover and histopathological changes. One hundred and four rats were colonized with H. pylori and exposed MNNG (N-methyl-N'-nitro-N'-nitrosoguanidine) and/or taurocholic acid. Inflammation, goblet cell-like metaplasia, atrophy, dysplasia, and adenocarcinoma were scored in a blinded manner. Apoptotic cells were counted after staining with terminal uridine deoxynucleotidyl nick end labeling, and epithelial cell proliferation was determined by means of the Ki-67 labeling index. No early tumor enhancement with H. pylori could be found in ordinary histology. However, H. pylori significantly enhanced the epithelial cell proliferation compared with the control group, and the combination with taurocholic acid appeared to have a synergistic effect. MNNG significantly increased the normal gastric epithelial apoptosis. This increase was reduced in antral mucosa with H. pylori infection. The findings suggest that H. pylori, especially when combined with bile. has an influence on cell kinetics, contributing to the development of gastric cancer. The reduced apoptosis of MNNG also observed in infected animals indicates a dual function of H. pylori.

Topics: Adenocarcinoma; Animals; Apoptosis; Carcinogens; Disease Models, Animal; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Immunohistochemistry; In Situ Nick-End Labeling; Ki-67 Antigen; Kinetics; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Taurocholic Acid

The aim of this study was to evaluate the early influence of Helicobacter pylori infection on cell kinetics in the antral mucosa of mice exposed to N-methyl-N'-nitro-N'-nitrosoguanidine (MNNG) and bile alone or in combinations. Four hundred and one C57BL/6 male and female mice were assigned into seven treatment groups and one non-treated control group. The gastric antrums were assessed by histology and immunohistochemistry for studies of cell proliferation and apoptosis at 32 and 44 weeks. One female and one male mouse had developed dysplastic adenomas in the pylorus mucosa and one male animal had dysplastic proliferation in the antrum. Only one of these lesions occurred in a H. pylori colonized animal. H. pylori infection significantly increased the cell proliferation at 32 weeks and promoted the cell proliferation in the MNNG and bile group at 44 weeks. Female mice showed less increase in cell proliferation than did the males. No change in apoptosis was seen in any of the groups. Bile had no promotional effect on cell proliferation. These results indicate that H. pylori infection has the potential to alter epithelial cell kinetics as well as antrum mucosa of an animal species that is regarded as resistant to MNNG. However, this change is not sufficient to promote the early development of neoplastic lesions.

Topics: Adenoma; Animals; Apoptosis; Carcinogens; Disease Models, Animal; Epithelium; Female; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Immunohistochemistry; In Situ Nick-End Labeling; Ki-67 Antigen; Kinetics; Male; Methylnitronitrosoguanidine; Mice; Mice, Inbred C57BL; Pyloric Antrum; Stomach Neoplasms; Taurocholic Acid

Ivermectin is widely used against parasitic infections in veterinary and human medicine and was found to promote the growth of lesions leading to neoplasia when given continuously in the diet to Wistar rats receiving a single low dose of N-methyl-N1-nitro-N-nitrosoguanidine (MNNG). No tumors or pathological lesions were observed in the forestomach of the control animals or those given ivermectin alone. However, compared to animals receiving MNNG alone, rats maintained on a diet containing ivermectin (2 ppm) and given MNNG (12.5 mg/kg) by gavage showed an increased number of neoplasms (9/26 vs 3/18; p = 0.30) and a statistically significant fourfold increase in the number of pathological lesions (18/26 vs 3/18; p = 0.002), which include preneoplasia in the forestomach. In all cases, the pathological lesions were more severe in the animals receiving ivermectin and MNNG, compared to those receiving MNNG alone.

Topics: Administration, Oral; Animals; Diet; Drug Interactions; Insecticides; Ivermectin; Male; Methylnitronitrosoguanidine; Mutagens; Precancerous Conditions; Rats; Rats, Wistar; Severity of Illness Index; Stomach Neoplasms

The protective effect of garlic (Allium sativum L.) and neem leaf (Azadirachta indica A. Juss.) was investigated on hepatic lipid peroxidation and antioxidant status during N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in male Wistar rats. Enhanced lipid peroxidation in the liver of tumour-bearing animals was accompanied by significant decreases in the activities of glutathione peroxidase (GPx), glutathione-S-transferase (GST), gamma-glutamyl transpeptidase (GGT) and reduced glutathione (GSH) levels. Administration of garlic and neem leaf extracts significantly lowered lipid peroxidation and enhanced the hepatic levels of glutathione and glutathione dependent enzymes. We speculate that garlic and neem leaf significantly alter cancer development at extrahepatic sites by influencing hepatic biotransformation enzymes and antioxidants.

Topics: Animals; Carcinogens; gamma-Glutamyltransferase; Garlic; Glutathione; Glutathione Peroxidase; Glutathione Transferase; Lipid Peroxidation; Liver; Male; Methylnitronitrosoguanidine; Plant Extracts; Plant Leaves; Plants; Plants, Medicinal; Rats; Rats, Wistar; Stomach Neoplasms

To observe the development and progression of intestinal metaplasia (IM) in dog's stomach and expression of tumor-related proteins in gastric mucosa lesions.. IM animal model was induced in stomach of Beagle dog by combining treatment of oral administration of N-methyl-N'-nito-N-nitrosoguanidine (MNNG) and ranitidine (R) with X-ray irradiation to the target organ. Expression of APC, p53, K-ras and bcl-2 gene proteins in animal gastric mucosa lesions were determined with immunohistochemical method.. IM animal model was successfully induced and the dynamic pathological changes were observed by means of this model. It was confirmed that the progression from normal epithelial cells to IM cells may require several stages, including superficial gastritis, chronic atrophic gastritis, slight focal IM and moderate or severe IM. Aberrant bcl-2 protein can be detected in the atrophic mucosa epithelium and the abnormal expression of APC, K-ras and bcl-2 can be found in IM of mucosa.. IM model in stomach of Beagle dog can be successfully induced by our method (MNNG + R + X-ray). The progression from normal to IM in dog resembles that of human being and the expression of tumor-related proteins (APC, bcl-2, K-ras) may play a role in the malignant transformation of IM.

Topics: Adenomatous Polyposis Coli Protein; Animals; Dogs; Gastric Mucosa; Immunohistochemistry; Male; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Proto-Oncogene Proteins c-bcl-2; Stomach Neoplasms; Tumor Suppressor Protein p53

The effects of prolonged administration of genistein, a tyrosine-kinase inhibitor, on sodium-chloride-enhanced induction of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and the labeling and apoptotic indices and vessel counts in the gastric mucosa and gastric cancers, were investigated in Wistar rats. After 25 weeks of the carcinogen treatment, rats were fed chow pellets containing 10% sodium chloride and were given s.c. injections of genistein at dosages of 15 mg/kg or 30 mg/kg body weight every other day. In week 52, the incidence of gastric cancers was significantly greater in rats fed sodium chloride than in untreated control rats. Prolonged administration of genistein at a dosage of 30 mg/kg, but not 15 mg/kg, body weight significantly reduced the incidence of gastric cancers, which was increased by oral treatment with sodium chloride. Genistein at the higher dose significantly decreased the labeling index and vessel counts of the antral mucosa and the gastric cancers (which were increased by treatment with sodium chloride) and significantly increased the apoptotic index of the antral mucosa and the cancers (which was lowered by the treatment with sodium chloride). These findings suggest that genistein attenuates gastric carcinogenesis promoted by sodium chloride, by inducing increased apoptosis and lower cell proliferation and angiogenesis of antral mucosa and gastric cancers.

Topics: Animals; Anticarcinogenic Agents; Carcinogens; Drug Synergism; Genistein; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

The effect of prolonged administration of all-trans-retinoic acid (RA) on sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and the labelling and apoptotic indices and immunoreactivity of transforming growth factor (TGF) alpha in the gastric cancers was investigated in Wistar rats. After 25 weeks of carcinogen treatment, the rats were given chow pellets containing 10% sodium chloride and subcutaneous injections of RA at doses of 0.75 or 1.5 mg kg(-1) body weight every other day. In week 52, oral supplementation with sodium chloride significantly increased the incidence of gastric cancers compared with the untreated controls. Long-term administration of RA at both doses significantly reduced the incidence of gastric cancers, which was enhanced by oral administration of sodium chloride. RA at both doses significantly decreased the labelling index and TGF-alpha immunoreactivity of gastric cancers, which were enhanced by administration of sodium chloride, and significantly increased the apoptotic index of cancers, which was lowered by administration of sodium chloride. These findings suggest that RA attenuates gastric carcinogenesis, enhanced by sodium chloride, by increasing apoptosis, decreasing DNA synthesis, and reducing TGF-alpha expression in gastric cancers.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Apoptosis; Carcinogens; Dietary Supplements; Drug Synergism; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Mitotic Index; Rats; Rats, Wistar; Sodium, Dietary; Stomach Neoplasms; Transforming Growth Factor alpha; Tretinoin

Helicobacter pylori (Hp) is thought to be a stomach carcinogen from epidemiological findings. To determine the effects of infection with the bacteria on experimental carcinogenesis, a study of the glandular stomach of Mongolian gerbils (MGs) was performed. Male MGs were treated with N-methyl-N'-nitro-N-nitrosoguanidine followed by inoculation with Hp or infected with Hp followed by N-methyl-N'-nitro-N-nitrosoguanidine administration. Animals were killed at week 50, and their excised stomachs underwent microbiological and histopathological examinations. In addition, a serological investigation was performed. The incidences of adenocarcinomas were significantly higher in animals treated with 60 or 300 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine for 10 weeks followed by Hp inoculation or Hp followed by 20 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine for 30 weeks than in the respective controls. Moreover, tumour-bearing animals had higher titres of anti-Hp antibodies than tumour-free animals. Of interest was the finding that a dose of 100 p.p.m. N-methyl-N'-nitro-N-nitrosoguanidine given to infected gerbils eradicated the Hp in about half the animals, with a concomitant reduction in the promoting effect. No tumours were found in animals infected with Hp without N-methyl-N'-nitro-N-nitrosoguanidine or non-treated gerbils. Hp infection enhances glandular stomach carcinogenesis in MGs treated with N-methyl-N'-nitro-N-nitrosoguanidine. Animals with high titres of anti-Hp antibodies are at greatest risk of developing neoplasms.

Topics: Adenocarcinoma; Animals; Antibodies, Bacterial; Carcinogens; Cell Differentiation; Cocarcinogenesis; Drug Administration Schedule; Edema; Gastric Mucosa; Gastritis; Gastrointestinal Hemorrhage; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Hyperplasia; Male; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Specific Pathogen-Free Organisms; Stomach Neoplasms; Stomach Ulcer; Time Factors

The modifying effects of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a mutagenic by-product in chlorinated water, on the development of glandular stomach cancers were investigated in Wistar rats. A total of 120 males, 6 weeks of age, were divided into six groups. After initiation with 100 ppm N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) solution and 5% NaCl diet for 8 weeks, 30 rats each in groups 1-3 were given MX in the drinking water at concentrations of 30, 10, or 0 ppm for the following 57 weeks. Ten animals each in groups 4-6 were administered the MX without prior carcinogen exposure. There were no statistical significant differences in final body weights between the groups. The incidences and multiplicities of adenocarcinomas in the glandular stomachs were significantly higher (P < 0.05) in the initiated 30 ppm MX group than those in the MNNG/NaCl group. The incidences of atypical hyperplasias in the glandular stomachs were also significantly increased (P < 0.05 or 0.01) by the MX treatments. With their multiplicity, the effects were clearly dose dependent. Interestingly, the 30 ppm MX alone itself induced atypical hyperplasias in the pylorus, although the incidences and severity were low. Moreover, MX showed a tendency to enhance the development of intrahepatic cholangiocellular tumors and thyroid follicular cell tumors in the MNNG-treated animals. The results of the present study thus indicate that MX exerts promoting effects when given during the postinitiation phase of two-stage glandular stomach carcinogenesis in rats.

Topics: Adenocarcinoma; Adenocarcinoma, Follicular; Adenoma, Bile Duct; Animals; Bile Duct Neoplasms; Bile Ducts, Intrahepatic; Body Weight; Carcinogens; Cholangiocarcinoma; Cocarcinogenesis; Fibrosis; Furans; Hyperplasia; Male; Methylnitronitrosoguanidine; Mutagens; Organ Size; Precancerous Conditions; Pylorus; Rats; Rats, Wistar; Stomach; Stomach Diseases; Stomach Neoplasms; Thyroid Neoplasms; Water Pollutants, Chemical

Rat stomach cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) have been widely used as a model for human stomach cancers of the differentiated type. However, there has been little information regarding their molecular basis. In this study, we examined the genetic alterations reported in human stomach cancers in 10 rat stomach cancers that had been induced in male ACI/N rats by administering MNNG in the drinking water. One of the 10 cancers had a mutation of the p53 gene at the second position of codon 171 (Val --> Glu). However, none of the 10 cancers had mutations in codons 12, 13, or 61 of Ki-ras or in the N-terminal phosphorylation sites of the beta-catenin gene. Southern blot analysis showed no amplification of K-sam or c-erbB-2 in the seven cancers examined. Finally, we searched for microsatellite alterations in 12 loci in nine cancers, but no alterations were observed. As these genetic alterations are observed in only a minor fraction of human stomach cancers, further analysis of genetic and epigenetic alterations in MNNG-induced rat stomach cancers is needed to disclose the major mechanisms of stomach carcinogenesis.

Topics: Animals; beta Catenin; Blotting, Southern; Codon; Cytoskeletal Proteins; Disease Models, Animal; DNA Mutational Analysis; Exons; Gene Amplification; Genes, erbB-2; Genes, p53; Genes, ras; Male; Methylnitronitrosoguanidine; Microsatellite Repeats; Mutation; Phosphorylation; Polymorphism, Single-Stranded Conformational; Rats; Rats, Inbred ACI; Receptor Protein-Tyrosine Kinases; Receptor, Fibroblast Growth Factor, Type 2; Receptors, Fibroblast Growth Factor; Stomach Neoplasms; Trans-Activators

The effect of prolonged oral administration of D-limonene on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on the labeling and apoptotic indices of gastric cancers were investigated in Wistar rats. After 25 weeks of the carcinogen treatment, rats were given chow pellets containing 1% or 2% limonene. In week 52, long-term oral administration of 2%, but not 1%, limonene significantly decreased the incidence of gastric cancers. Limonene also significantly decreased the labeling index and significantly increased the apoptotic index of gastric cancers. No K-ras mutations were detected in gastric cancers induced by MNNG in either group. These findings indicate that limonene inhibits the development of gastric cancers through increased apoptosis and decreased DNA synthesis of gastric cancers, but not through ras oncoprotein plasma membrane association.

Topics: Adenocarcinoma; Animals; Anticarcinogenic Agents; Apoptosis; Carcinogenicity Tests; Cyclohexenes; Dose-Response Relationship, Drug; Genes, ras; Limonene; Male; Methylnitronitrosoguanidine; Point Mutation; Rats; Rats, Wistar; Stomach Neoplasms; Terpenes

The modifying effect of diethyl maleate (DEM) on gastric tumor development was studied in rats initially given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and hypertonic sodium chloride (H-NaCl 10% or 5%). Groups of animals were maintained with or without a 0.2% DEM dietary supplement after treatment with MNNG and H-NaCl and sacrificed at week 20. Forestomachs and livers cytosolic NAD(P)H:quinone-acceptor oxidoreductase (QR) activity was also analyzed. The incidences of forestomach severe hyperplasias in the MNNG + H-NaCl --> DEM groups were also significantly higher than in the MNNG + H-NaCl alone group (P < 0.01 and P < 0.05 for 5% and 10% groups, respectively). Similarly, in the glandular stomach, the numbers of preneoplastic pepsinogen 1 altered pyloric glands (PAPGs) in the MNNG + H-NaCl --> DEM groups were significantly increased (P < 0.01 for both concentrations). The QR activities in the groups treated with DEM showed 2- to 3-fold increases as compared with the control level. The results indicate that treatment with 0.2% DEM after MNNG initiation exerts enhancing effects on both forestomach and glandular stomach carcinogenesis. Induction of QR, a Phase II enzyme, activity in the rat stomach by DEM may be associated with promotion of stomach carcinogenesis rather than inhibition.

Topics: Animals; Body Weight; Carcinogenicity Tests; Carcinogens; Carcinoma, Squamous Cell; Gastric Mucosa; Male; Maleates; Methylnitronitrosoguanidine; NAD(P)H Dehydrogenase (Quinone); Papilloma; Pepsinogen A; Rats; Rats, Wistar; Saline Solution, Hypertonic; Stomach; Stomach Neoplasms

Two-month-old female LIO rats were given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) with tap water in a concentration of 100 mg/l for 12 months (groups 1 and 2) or were kept without the carcinogen treatment (groups 3 and 4). From the first day of exposure to MNNG rats from groups 2 and 3 were given activated carbon fiber adsorbent Aqualen in their diet five times per week together with lab chow in a daily dose of 100 mg/kg of body weight. The experiment was finalized 16 months after first exposure to the carcinogen. The total stomach adenocarcinoma incidence was 43% in group 1 and 39% in group 2, whereas invasive stomach adenocarcinomas occurred in 36% and 8% of rats from groups 1 and 2, respectively (P < 0.05). Tumors other then stomach sites (duodenum and liver) only developed in rats from group 1 (29%). No lesions were observed in rats exposed to Aqualen without MNNG. Thus, our results demonstrate the inhibitory effect of the activated carbon fiber adsorbent Aqualen on stomach carcinogenesis in rats.

Topics: Adsorption; Animals; Carbon; Carcinogens; Dietary Fiber; Female; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

The effect of Helicobacter pylori infection on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer was studied using a Mongolian gerbil model. Five-week-old male Mongolian gerbils were divided into four groups of 25-30 animals each and challenged for 20 weeks with H.pylori, MNNG, a combination of H.pylori and MNNG, or neither of them. Four to 20 animals from each group were killed at 16, 24 and 52 weeks after H.pylori inoculation, and histopathological changes in their stomachs were examined. A well-differentiated adenocarcinoma was first observed 24 weeks after inoculation in the combination group. At 52 weeks, only six of 15 animals were colonized with H.pylori persistently, and four of them showed well-differentiated adenocarcinomas; on the other hand, neither of the animals with disappearance of H.pylori from the combination group showed adenocarcinoma. At the same observation time, three of 17 animals from MNNG group showed poorly differentiated adenocarcinomas. The incidence of gastric carcinoma in the combination group was significantly higher than that in the MNNG group (P < 0.05). However, no tumors were seen in the control and H.pylori groups. The present findings demonstrate that H.pylori infection enhances the carcinogenic action of MNNG.

Topics: Adenocarcinoma; Animals; Carcinogenicity Tests; Gastric Mucosa; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Stomach Neoplasms; Time Factors

The effects of prolonged administration of d-limonene, a monocyclic monoterpene, on sodium chloride-enhanced induction of gastric carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine, the labeling and apoptotic indices, and ornithine decarboxylase (ODC) activity of gastric cancers were investigated in Wistar rats. After 25 weeks of carcinogen treatment, rats were given chow pellets containing 10% sodium chloride and 1% limonene ad libitum. In week 52, the incidence of gastric cancers, the labeling index and ODC activity were significantly higher and the apoptotic index was significantly lower in rats given sodium chlolide than in untreated control rats. However, in rats given both sodium chloride and d-limonene, the incidence of gastric cancers, the labeling index and ODC activity were significantly lower and the apoptotic index was significantly higher than in rats given sodium chloride alone. Our findings suggest that limonene attenuates the gastric carcinogenesis enhanced by sodium chloride via increased apoptosis and decreased ODC activity in gastric cancers.

Topics: Animals; Antineoplastic Agents, Phytogenic; Apoptosis; Cyclohexenes; Incidence; Limonene; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms; Terpenes

Sodium chloride (NaCl) initiates and promotes experimental carcinogenesis in rats. We recently found that a high-protein diet attenuates NaCl-enhanced gastric carcinogenesis in Wistar rats. To investigate the effect of a purified low-protein diet on NaCl-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Wistar rats, rats were fed a purified diet with an equalized caloric content containing 1% or 2% NaCl and 25% casein (normal-protein diet) or 10% casein (low-protein diet) after oral treatment with MNNG for 25 weeks. In week 52, neither 1% nor 2% NaCl had a significant effect on gastric carcinogenesis in rats fed a normal-protein diet. However, oral administration of 2%, but not 1%, NaCl significantly increased the incidence of gastric cancers in rats fed a low-protein diet. Oral administration of 2% NaCl also significantly increased the bromodeoxyuridine (BrdU)-labeling index and the ornithine decarboxylase (ODC) activity and decreased apoptosis of gastric cancers in rats fed a low-protein diet. However, 2% NaCl had no significant effect on these three parameters in rats fed a normal-protein diet. These findings indicate that a low-protein diet enhances the effect of NaCl in gastric carcinogenesis and that this enhancement may be mediated by increased cell proliferation and reduced apoptosis of gastric cancers.

Topics: Adenocarcinoma; Animals; Apoptosis; Carcinogenicity Tests; Diet, Protein-Restricted; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Mitotic Index; Ornithine Decarboxylase; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

Gastric cancers are a significant cause of morbidity worldwide. Epidemiological studies and animal models show that males have higher incidences of gastric cancers compared with females, suggesting that sex hormones may modulate gastric cancer risk. An animal model of the initiation phase of gastric cancer was used to determine the effects of systemic estrogen administration on morphological progression of preneoplastic lesions and to define cell populations at which estrogens may act. Preneoplastic progression in antral and duodenal mucosa was examined in male rats that received the chemical carcinogen, N-methyl-N'-nitro-nitrosoguanidine (MNNG), during treatment with implants containing 17beta-estradiol or oil vehicle. Histopathological changes in antral and duodenal gland morphology, numbers of proliferating cells and apoptotic bodies, and antral gastrin cell numbers and protein storage levels were determined 4 weeks later. With MNNG treatment, duodenal villous heights were significantly decreased, and epithelial cells displayed histological features of hyperplasia and dysplasia. Antral glands showed epithelial hyperplasia and dysplasia, increased mucosal height, and decreased mucin levels. Antral gastrin storage protein levels were decreased by MNNG. Systemic treatment with 17beta-estradiol significantly reversed MNNG-induced alterations in duodenal gland heights while increasing mucin and gastrin levels in antral glands. Cell proliferation and apoptosis rates were not significantly different between groups. The present results indicate that systemic 17beta-estradiol treatment influences antral and duodenal gland differentiation during the initiation phase of chemical gastroduodenal carcinogenesis in male rats. These results explain, in part, a potential pathway through which protective effects of estrogens on chemical carcinogenesis are mediated in the upper gastrointestinal tract.

Topics: Animals; Apoptosis; Carcinogens; Cell Division; Duodenal Neoplasms; Duodenum; Estradiol; Gastrins; Health Status; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Pyloric Antrum; Rats; Rats, Sprague-Dawley; Stomach Neoplasms

The effect of prolonged administration of a rat C-erbB-2/neu (C-erbB-2) antisense oligonucleotide on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on the labeling and apoptotic indices of gastric cancer was examined in Wistar rats After oral treatment with MNNG for 25 weeks, the rats received intraperitoneal injections of a C-erbB-2 antisense-liposome complex or a sense-liposome complex at a dose of 50 microgram oligonucleotide/kg body weight every other day until the end of the experiment in week 52. In week 52, the incidence of gastric cancers was significantly lover in rats treated with the C-erbB-2 antisense oligonucleotide than in rats treated with the sense oligonucleotide. Administration of the C-erbB-2 antisense oligonucleotide also significantly decreased the bromodeoxyuridine-labeling index and significantly increased the apoptotic index of gastric cancers. The mean cellular fluorescence of gastric antral cells in MNNG-treated rats was positively correlated with the dose of FITC-labeled C-erbB-2 antisense oligonucleotide. Our findings indicate that the antisense oligonucleotide inhibits gastric carcinogenesis through decreased cell proliferation and increased apoptosis induction and suggest that antisense strategies may provide new treatment for gastric cancer.

Topics: Animals; Antimetabolites; Apoptosis; Bromodeoxyuridine; Carcinogens; Cell Division; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Oligonucleotides, Antisense; Rats; Rats, Wistar; Receptor, ErbB-2; Stomach Neoplasms

The morphology and evolution of epithelial lesions that developed at a gastrojejunal stoma due to reflux of duodenal contents were compared with MNNG-induced carcinomas in the pyloric mucosa of rats in a long term experiment. Random bred male Wistar rats were given MNNG in drinking water (100 mg/l) for 12 weeks and then one group was submitted to a gastrojejunal anastomosis at the greater curvature in the oxyntic mucosa. Untreated rats underwent either gastrojejunostomy or gastrotomy. The animals were killed at the 24th and 66th weeks of the experiment. The lesions obtained in the pyloric mucosa and in the mucosa of the gastrojejunal stoma were analyzed histologically using hematoxylin and eosin staining and immunohistochemistry for pepsinogen isoenzyme 1. Duodenal reflux induced proliferative lesions at the gastrojejunal junction that increased in incidence and size with time. Histologically they consisted of benign epithelial proliferation of gastric type. No evidence of malignant transformation within the gastric components of the proliferative lesions at the gastrojejunal stoma was observed even at the 66th week. Adenocarcinomas induced by MNNG in the pyloric mucosa increased in size during the experiment and were morphologically and histochemically distinct from the proliferative lesions at the gastrojejunal junction. In conclusion, proliferative lesions at the gastrojejunal stoma stimulated by duodenal reflux are biologically distinct from adenocarcinomas induced by MNNG in the pyloric mucosa. They do not seem to be precursor lesions of gastric carcinogenesis, as they do not undergo malignant transformation even after long-term, up to 66 weeks, follow-up.

Topics: Adenocarcinoma; Animals; Carcinogens; Cell Division; Duodenogastric Reflux; Gastric Mucosa; Hyperplasia; Male; Methylnitronitrosoguanidine; Pyloric Antrum; Rats; Rats, Wistar; Stomach Neoplasms; Surgical Stomas

Gene therapy could potentially revolutionize the treatment of gastrointestinal (GI) tract cancer. The aim of this study was to establish a practical method of gene transfer which would be applicable to human gastric cancer. Retrovirus or/and adenovirus vectors carrying the lacZ marker gene were transferred in situ by needle through an endoscopic biopsy channel into primary gastric cancer in six male beagle dogs that had been treated with N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). In addition, an adenovirus vector carrying the herpes simplex virus thymidine kinase (Ad.CAGHSV-TK) gene was introduced in situ into cancer tissues in the stomach of three dogs, and the animals were treated with intravenous ganciclovir (GCV). Retrovirus-producing cells which expressed the lacZ gene were specifically localized to the injection site in the stomach. The lacZ gene was more widely transferred into the tumor by the adenovirus vector than by retrovirus-producing cells. Improvement of the needle used for gene transfer and the use of multiple injections per tumor led to more diffuse transfer of the vector into the tumor. The Ad.CAGlacZ gene was also transferred into regional lymph nodes of the stomach. Moderate to diffuse degeneration of the primary cancer tissues of the stomach was found after Ad.CAGHSV-TK/GCV gene therapy. Moreover, almost complete tissue degeneration was observed in the regional lymph nodes of the stomach. An adverse effect of HSV-TK/GCV gene therapy was acute hepatotoxicity, which was not found after Ad.CAGlacZ gene transfer, but was found after high-titer Ad.CAGHSV-TK gene transfer followed by GCV. These findings suggest that in situ gene transfer of a suicide gene followed by prodrug treatment may be applicable not only to primary tumors, but also to lymph node metastases of gastric cancer, though further study of both beneficial and adverse effects is required before clinical usage.

Topics: Adenoviridae; Animals; Dogs; Gastric Mucosa; Gene Transfer Techniques; Genetic Therapy; Genetic Vectors; Lac Operon; Lymph Nodes; Methylnitronitrosoguanidine; Retroviridae; Stomach; Stomach Neoplasms; Thymidine Kinase; Viral Proteins

In 1994 WHO/IARC concluded that "Helicobacter pylori is a definite carcinogen" based on epidemiological studies, but there have been few reports demonstrating a relation between H. pylori and stomach cancer in animal models. We have succeeded in producing adenocarcinomas in the glandular stomachs of Mongolian gerbils with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or N-methyl-N-nitrosourea as carcinogens and hope to establish an experimental stomach carcinogenesis model using H. pylori. Male Mongolian gerbils, 7 weeks old, were infected with H. pylori followed by MNNG administration at a concentration of 100ppm administration or treated with MNNG at a concentration of 300ppm in their drinking water followed by inoculation with H. pylori. They were then killed sequentially, and their excised stomachs underwent microbiological and histopathological examinations. H. pylori were detected in all infected gerbils. Hyperplastic change of pyloric mucosa was observed with high 5-bromo-2'-deoxyuridine incorporation in affected animals. H. pylori infection persists on administration of MMNG and enhances glandular stomach proliferation in Mongolian gerbils. Whether long-term colonization promotes carcinogenesis in the glandular stomach of Mongolian gerbils is a matter of great interest.

Topics: Adenocarcinoma; Animals; Carcinogens; Colony Count, Microbial; Disease Models, Animal; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Specific Pathogen-Free Organisms; Stomach Neoplasms

The effects of prolonged administration of the alpha-adrenoceptor agonist phenylephrine and the beta-adrenoceptor agonist isoproterenol on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine and on the labeling index of gastric mucosa were compared in Wistar rats. Rats received subcutaneous injections of 3 or 6 mg/kg body weight of phenylephrine or 0.1 or 0.2 mg/kg body weight of isoproterenol every other day after 25 weeks of oral treatment with the carcinogen. Long-term administration of phenylephrine at a high dose, but not at a low dose, significantly increased the incidence of gastric cancers and the labeling index of antral epithelial cells at the end of the experiment in week 52. However, administration of isoproterenol at either dosage had no significant effect on the incidence of gastric cancers and the labeling index of antral epithelial cells. These findings indicate that increased activity of the sympathetic nervous system enhances gastric carcinogenesis through alpha-adrenoceptors.

Topics: Adrenergic alpha-Agonists; Adrenergic beta-Agonists; Animals; Gastric Mucosa; Isoproterenol; Male; Methylnitronitrosoguanidine; Phenylephrine; Rats; Rats, Wistar; Receptors, Adrenergic, alpha; Stomach Neoplasms

Combined effects of catechol, sodium chloride (NaCl) and ethanol on the post-initiation stage of gastric carcinogenesis were examined in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). F344 male rats were given a single intragastric dose of 150 mg/kg b.w. MNNG at 6 weeks of age. Starting 1 week thereafter, groups of 15 rats were administered 0.8% catechol, 5% NaCl and 10% ethanol either individually or in combination, or basal diet alone for 51 weeks. Further groups of animals were similarly treated with these chemicals without the MNNG pretreatment. All rats were killed at the end of week 52 for histopathological examination. In the forestomach, treatment with catechol alone after MNNG initiation caused a 100% incidence of papillomas (versus 67% in the controls) as well as carcinomas (versus 0% in the controls). On the other hand, the treatment with ethanol alone significantly lowered the incidence of papillomas (13 versus 67% in the controls). The combined treatment with catechol, NaCl and ethanol significantly lowered the incidence of squamous cell carcinomas (57%) as compared to the catechol alone group value (100%). In the glandular stomach, catechol enhanced the development of adenocarcinomas (73 versus 0% in the controls), but this was decreased to 29% by the combined treatment with ethanol and NaCl. NaCl without MNNG pretreatment slightly enhanced epithelial cell proliferation in the forestomach. These results indicate that combined treatment with NaCl and ethanol exerts protective effects against catechol-induced forestomach and glandular stomach carcinogenesis, this apparently being largely due to the ethanol.

Topics: Animals; Body Weight; Carcinogenicity Tests; Catechols; Eating; Ethanol; Liver; Male; Methylnitronitrosoguanidine; Organ Size; Rats; Rats, Inbred F344; Sodium Chloride; Stomach Neoplasms

The modifying effects of oltipraz on induction of glandular stomach carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in a total of 120 male 6-week-old Wistar rats, divided into six groups. Groups 1-3 (30 animals each) were given 100 p.p.m. MNNG in their drinking water for 10 weeks as an initiation treatment for gastric cancer induction and respectively fed diets supplemented with 0.04%, 0.02% and 0% oltipraz for 12 weeks, starting 1 week before and finishing 1 week after the carcinogen exposure. Groups 4-6 (10 animals each) were similarly treated without the application of MNNG. At the end of the 80th experimental week, all surviving animals were autopsied and examined histopathologically for the existence of gastric proliferative lesions. The incidence and multiplicity of adenocarcinomas were significantly (P < 0.01) lower in group 1 than in group 3. In addition, the multiplicity of atypical hyperplasias in the pyloric region was significantly (P < 0.05) decreased in group 1 as compared with the group 3 value. No gastric proliferative lesions were found in groups 4-6. In an additional short-term experiment, oltipraz significantly reduced cell proliferative activity (P < 0.01) and elevated glutathione levels (P < 0.05) in the glandular stomach mucosa of rats treated with MNNG. Thus our results clearly indicate that oltipraz can inhibit induction of proliferative glandular stomach lesions by MNNG in the rat.

Topics: Adenocarcinoma; Animals; Anticarcinogenic Agents; Hyperplasia; Male; Methylnitronitrosoguanidine; Pylorus; Pyrazines; Rats; Rats, Wistar; Stomach Neoplasms; Thiones; Thiophenes

Helicobacter pylori appears to play a major role in the development of gastric cancer in humans. The mechanism behind the carcinogenic or co-carcinogenic effects of H. pylori has not been established. Ammonia, generated by urea from H. pylori, has been studied as a possible cause. However, the ammonia-monochloramine system has been shown to play a more important role in H. pylori-associated mucosal injury. Therefore, the effects of combined administration of monochloramine and methionine, singly or together, on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in inbred Wistar rats. After receiving oral MNNG and regular chow pellet for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without a subcutaneous injection of methionine, until the end of the experiment (week 52). Treatment with both ammonium acetate and sodium hypochlorite, which produce monochloramine, significantly increased the incidence of gastric cancers in week 52, whereas the concomitant administration of methionine with ammonium acetate and sodium hypochlorite significantly attenuated such enhanced gastric carcinogenesis. Spectrophotometric examination revealed that methionine scavenged monochloramine. Our findings suggest that H. pylori-associated gastric carcinogenesis may be mediated by monochloramine.

Topics: Animals; Apoptosis; Carcinogens; Cell Division; Chloramines; Male; Methionine; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

We previously suggested that hydroxyl free radical (-OH) production may play a role in carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). MNNG-induced gastric cancer in rats and human gastric carcinoma occur most often in the antral mucosa and rarely in the normal fundic mucosa. We hypothesized that regional differences in anti-oxidant activity may be responsible. In the present study, we examined anti-oxidant activity by comparing the relative rates of reduction of a nitroxide free radical, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (Tempol), in the antral and fundic mucosa of male Wistar rats using ESR. The relative rate of Tempol reduction was significantly slower in the antral portion of the wall than in the fundic portion when Tempol [4 x 10(-6) mole/mg wet weight of gastric wall] in HEPES buffer (pH 7.4) was spread over the mucosal surface of a section of the gastric wall. Addition of a sulfhydryl group modulator, N-ethylmaleimide, to the mucosal surface before treatment with Tempol removed the significant difference observed in the rates of reduction in the antral and fundic portions of the gastric wall. No signals were detected in the muscle layer. Our results indicate that the relative rate of free radical reduction by sulfhydryl groups was significantly slower in the antral mucosa than in the fundic mucosa. We therefore conclude that a regional difference in the rates of reduction of free radicals by sulfhydryl groups may result in the site susceptible to development of MNNG-induced gastric cancer.

Topics: Animals; Antioxidants; Carcinogens; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Free Radical Scavengers; Gastric Fundus; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Oxidation-Reduction; Pyloric Antrum; Rats; Rats, Wistar; Spin Labels; Stomach Neoplasms; Sulfhydryl Compounds

An animal model of stomach carcinogenesis was established using Mongolian gerbils with N-methyl-N-nitrosourea (MNU) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) as the carcinogens. In addition, the sensitivity of these gerbils to Helicobacter pylori (H. pylori) was confirmed. One hundred and sixty specific pathogen-free male MGS/Sea animals, 7 weeks old, were treated with MNU in the drinking water (30 ppm for alternate weeks to give 10 weeks exposure, or 10 ppm or 3 ppm for 20 weeks continuous exposure), or given MNNG in the drinking water at 400 ppm or 200 ppm for 20 weeks, or orally inoculated with ATCC43504 H. pylori (1.7 x 10(8) CFUs/animal). Adenocarcinomas in the glandular stomach were found in 2 out of 12 effective animals (2/ 12) treated with 30 ppm MNU at week 20, although all were dead or moribund by week 30 due to MNU toxicity. At week 50, the incidences of gastric adenocarcinomas in groups treated with 10 ppm MNU, 3 ppm MNU, 400 ppm MNNG, and 200 ppm MNNG were 2/21 (9.5%), 1/23 (4.3%), 7/ 11 (63.6%), and 1/10 (10.0%). The lesions were generally well differentiated, although poorly differentiated adenocarcinoma was also found in a single gerbil in each of the 10 ppm MNU and 400 ppm MNNG groups. In control animals no tumors were found. In the infection study, the animals were killed at week 20, and H. pylori was detected in all cases, causing multiple erosions with marked inflammatory cell infiltration in the lamina propria and submucosa, and frequent formation of lymphoid follicles. Thus, MNU and MNNG in the drinking water induced neoplastic lesions in the glandular stomach epithelium of H. pylori-sensitive gerbils.

Topics: Adenocarcinoma; Administration, Oral; Animals; Carcinogens; Cocarcinogenesis; Disease Models, Animal; Disease Susceptibility; Drinking; Gerbillinae; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Methylnitrosourea; Stomach Neoplasms; Water

MAPK (Mitogen-Activated Protein Kinase) is one of the elements of kinase cascades (MAPK, MEK-MAP kinase, kinase, Raf-1, Ras) regulating cellular proliferation and differentiation processes. It seems that the changes in its number and activity may be the factor having influence on carcinogenesis. In some human carcinomas a significant increase of its activity is observed, in others a decrease of its activity is described. Our research aimed at the evaluation of the dynamics of precancerous and cancerous changes in the stomach stump in rats after the experimental, partial stomach resection. Apart from histological and ultrastructural examination we also determined the activity of the sub-unit p42 MAP kinase. The material comprised segments of gastric mucosa of the stomach stump of 15 rats after subtotal gastrectomy. Part of the rats after the procedure were administered carcinogen orally (MNNG). On the histological and ultrastructural examination we used routine methods, the activity of MAP kinase was determined by western-blotting method with the use of IgG against MAPK p42, Santa Cruz #154). In 8 examined rats we observed the increase of MAP kinase activity. We established probable correlation (without statistical analysis, regarding miserly material) between the increase of MAPK activity and histological and ultrastructural changes. Among three cases diagnosed as adenoma tubulare in two we observed the increase of MAPK activity. A clear increase of this kinase was also present in the stomach stump of a rat, which was diagnosed as adenocarcinoma. On the basis of our research carried so far we think that the increase of the MAPK activity may be one of the causes of the neoplasm development. It seems important to obtain the confirmation of our results and to establish a possible usefulness of MAPK activity determination as a prognostic indicator in case of the neoplasm of stomach stump.

Topics: Animals; Calcium-Calmodulin-Dependent Protein Kinases; Carcinogens; Cell Transformation, Neoplastic; Gastrectomy; Gastric Mucosa; Gastric Stump; Humans; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Risk Factors; Stomach Neoplasms

The effect of prolonged administration of the norepinephrine-mimicking agent metaraminol, the alpha1-adrenergic agonist phenylephrine and the alpha2-adrenergic agonist clonidine on the incidence of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), the ornithine decarboxylase activity of the gastric cancer and the labeling index of the gastric mucosa were investigated in Wistar rats. Rats received s.c. injections of metaraminol, phenylephrine or clonidine every other day after 20 weeks of oral treatment with MNNG. At week 52, administration of metaraminol and phenylephrine at the higher dose significantly increased the incidence of gastric cancers, the ornithine decarboxylase activity of the gastric cancers and the labeling index of the antral epithelial cells. Administration of phenylephrine at the lower dose and clonidine at both doses had no significant effect on the incidence of gastric cancers, the ornithine decarboxylase activity of the gastric cancers or the labeling index of the gastric mucosa. Our results suggest that adrenoreceptor stimulation enhances gastric carcinogenesis and that such enhancement is mediated through alpha1-adrenoceptors without alpha2-adrenoceptor involvement.

Topics: Adrenergic alpha-Agonists; Animals; Carcinogens; Clonidine; Gastric Mucosa; Incidence; Male; Metaraminol; Methylnitronitrosoguanidine; Mitotic Index; Ornithine Decarboxylase; Phenylephrine; Rats; Rats, Wistar; Receptors, Adrenergic, alpha-1; Receptors, Adrenergic, alpha-2; Stomach Neoplasms

The effects of prolonged administration of sodium nitroprusside (SNP), a generator of nitric oxide (NO), on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and the labelling index of the gastric mucosa were investigated in male Wistar rats. The rats received intra-peritoneal injections of 2 or 4 mg/kg body weight of SNP every other day after 25 weeks' oral treatment with the carcinogen. Prolonged administration of SNP at 4 mg/kg body weight, but not at 2 mg/kg body weight, significantly decreased the incidence of gastric cancers in experimental week 52. However, it did not affect the histological types or depths of involvement of gastric cancers. SNP at 4 mg/kg body weight, but not at 2 mg/kg body weight, also significantly decreased the bromodeoxyuridine labelling index of the antral epithelial cells. These findings indicate that SNP inhibits gastric carcinogenesis and suggest that this effect may be related to the suppression of proliferation of the antral epithelial cells.

Topics: Animals; Carcinogens; Drug Screening Assays, Antitumor; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitroprusside; Rats; Rats, Wistar; Stomach Neoplasms

Defective hMLH1 function has been increasingly associated with acquired cellular resistance to DNA alkylation damage in human colorectal and endometrial cancer cells. To investigate the relationship between the DNA alkylation tolerance and the hMLH1 status in human gastric carcinoma cells, we determined the cellular response to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), the mutational changes, and the expression of hMLH1 in 11 human gastric carcinoma cell lines. Of 11 cell lines, 4 (SNU-5, -16, -620, and -719) were sensitive, whereas 7 (SNU-1, -216, -484, -520, -601, -638, and -668) were resistant to the cytotoxic effect of MNNG. As determined by Western analysis, it was evident that all the MNNG-resistant cell lines except one (SNU-601) produced very low or undetectable levels of hMLH1 protein compared to the MNNG-sensitive cell lines. A homozygous non-sense mutation that resulted in truncated protein was found in one MNNG-resistant cell line (SNU-1). Therefore, to determine whether the sensitivity of cells to MNNG can be restored by exogenous expression of hMLH1 protein, wild-type hMLH1 cDNA was introduced into the MNNG-resistant cells (SNU-1). The cytotoxicity test showed that expression of exogenous wild-type hMLH1 protein caused an increase in sensitivity to the cytotoxic effect of MNNG. This restoration was confirmed by an increase in the cell population containing less than the G1 amount of DNA (cell death) in the wild-type hMLH1-transfected cells, as determined by flow cytometry analysis. Together our results suggest that (1) the absence or decreased level of wild-type hMLH1 protein may be a frequent event in the human gastric carcinoma cell lines, (2) such alterations in the hMLH1 protein are closely associated with the MNNG tolerance in the human gastric carcinoma cell lines, and (3) the hMLH1 protein participates not only in the repair of DNA mismatches but also in the mechanism of escape from the cytotoxic effects of DNA alkylation damage.

Topics: Adaptor Proteins, Signal Transducing; Alkylation; Carcinogens; Carcinoma; Carrier Proteins; DNA Primers; DNA Repair; Flow Cytometry; Humans; Methylnitronitrosoguanidine; MutL Protein Homolog 1; Neoplasm Proteins; Nuclear Proteins; Polymerase Chain Reaction; Stomach Neoplasms; Tumor Cells, Cultured

The involvement of immune response in the resistance of chemically induced stomach cancer was studied in a resistant rat strain (Buffalo) and a sensitive rat strain (ACI). Groups of 10 male Buffalo and ACI rats, 6 weeks of age, were given drinking water with or without N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; 100 mg/l) for 14 days. Total RNA was isolated from the stomach pyloric mucosa from five rats, and cDNA was prepared with reverse transcriptase. Tissue sections of the stomach pyloric mucosa from five rats were stained with antibodies recognizing molecules expressed by various immune cells. Reverse transcription-PCR (RT-PCR), competitive RT-PCR, and Northern blot demonstrated that the expression of MHC class II group genes [MHC class II, MHC class II-associated invariant chain (Ii), CD4 and IgM (B cell marker)], MHC class I group genes (MHC class I and CD8), B7-1 (costimulator on dendritic cells), and CD28 (receptor to B7 on T cells) in the pyloric mucosa was elevated by MNNG in both rat strains but was elevated to a 4-7-fold greater extent in Buffalo rats than in ACI rats. These genes were scarcely expressed in control rats. Histochemical antibody staining after MNNG exposure showed a greater number of cells stained with monoclonal antibody to Ii, OX-62 (dendritic cell marker), and ED-1 (dendritic cell and macrophage common marker) in the interstitial tissue of the pyloric mucosa of Buffalo rats compared with ACI rats. Cell proliferation, as measured by 5-bromo-2-deoxyuridine (BrdUrd)-labeling indices, revealed the presence of BrdUrd-labeled cells only among epithelial cells in the proliferative zone; cells in the interstitial tissue were not labeled with BrdUrd. The results suggest the involvement of dendritic cell response in the resistance to the MNNG induction of stomach carcinogenesis in rats.

Topics: Animals; Antigens, CD; B7-1 Antigen; B7-2 Antigen; Blotting, Northern; Carcinogens; CD28 Antigens; Cell Division; Dendritic Cells; Gastric Mucosa; Histocompatibility Antigens Class I; Histocompatibility Antigens Class II; Immunity, Cellular; Male; Membrane Glycoproteins; Methylnitronitrosoguanidine; Polymerase Chain Reaction; Pylorus; Rats; Rats, Inbred ACI; Rats, Inbred BUF; RNA, Messenger; Species Specificity; Stomach Neoplasms

The effect of prolonged administration of transforming growth factor (34-43)-alpha, an antagonist of TGF-alpha, on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on the labelling and apoptotic indices and TGF-alpha immunoreactivity of gastric mucosa and gastric cancers was examined in Wistar rats. The rats received intraperitoneal injections of 10 or 20 microg kg(-1) body weight of TGF(34-43)-alpha every other day after oral treatment with MNNG for 25 weeks. Long-term administration of TGF(34-43)-alpha at both doses significantly reduced the incidence of gastric cancers at the end of the experiment in week 52. However, TGF(34-43)-alpha had no significant effect on the number, histological type or depth of involvement of gastric cancers. Administration of TGF(34-43)-alpha also significantly decreased the bromodeoxyuridine labelling index and TGF-alpha immunoreactivity, and significantly increased the apoptotic index of antral mucosa and gastric cancers. These findings indicate that TGF(34-43)-alpha inhibits gastric carcinogenesis, and that its effects are mediated through decreased cell proliferation and TGF-alpha immunoreactivity and increased apoptosis induction in the gastric cancers.

Topics: Adenocarcinoma; Animals; Apoptosis; Carcinogens; Male; Methylnitronitrosoguanidine; Neoplasm Proteins; Neoplasms, Experimental; Rats; Rats, Wistar; Stomach Neoplasms; Transforming Growth Factor alpha

The aim of this study was to determine whether gastric epithelial proliferation due to gastric Helicobacter infection in mice represents a preneoplastic lesion.. Helicobacter heilmannii infected and uninfected mice were treated with 150 microg/ml N-methyl-N'-nitro-N-nitrosoguanidine in drinking water for either 20 or 38 weeks. Mice were killed 12 or 18 months after bacterial inoculation.. All infected mice developed lymphoplasmocytic gastritis and epithelial hyperplasia. Proliferative gastric lesions were characterised by nodular hypertrophy of the glandular mucosa, multifocal epithelial hyperplasia, and elevated BrdU labeling index. Intestinal metaplasia and true atrophy were not present but proliferative glands were poorly differentiated, lined by mucus-type epithelial cells with no parietal, chief or other specialized cell types. Neoplasms developed only in MNNG-treated mice. of the 180 treated mice the following neoplasms developed: 14 squamous cell carcinomas of mouth and forestomach; 37 hemangiosarcomas of the intestinal serosa; and 15 splenic lymphomas. No tumors were present in the glandular gastric mucosa, and infection did not affect tumor incidence. p53 overexpression occurred in 79% of hemangiosarcomas and 71% of squamous cell carcinomas but not in normal or proliferative gastric glandular mucosa.. Gastric proliferative lesions in Helicobacter-infected mice are not preneoplastic, and the combination of an alkylating agent and non-neoplastic proliferation does not result in gastric carcinogenesis in mice.

Topics: Animals; Bromodeoxyuridine; Carcinogens; Disease Models, Animal; Female; Gastric Mucosa; Gastritis; Gene Expression Regulation, Neoplastic; Genes, p53; Helicobacter; Helicobacter Infections; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Neoplasms, Experimental; Stomach Neoplasms

To investigate the effect of p53 and H-ras genes in the carcinogenesis of and development of gastric cancer induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Wistar rats.. The expression of p53 and H-ras genes in normal mucosa, precancerous lesions and induced-cancers were studied immunohistochemically. DNA isolated from the precancerous lesion and tumors were analysed by PCR-SSCP for exon 5-8 of p53 gene and exon 1 and 2 of H-ras gene.. p53 protein were detected in 50% (20/40) of the gastric cancers studied, but not in the precancerous lesion, while p21 ras protein seen in 23% (9/40) of the gastric cancers and 44% (23/52) of the precancerous lesions. p53 gene mutations were detected in 45% (18/40) of the cancers and none in the precancerous lesions by PCR-SSCP. H-ras gene mutation was not found in either the cancers or the precancerous lesions.. The activation of ras gene is an early event and may be involved in the carcinogenesis of gastric cancer induced by MNNG. Inactivation of p53 gene may influence the development of the cancer.

Topics: Adenocarcinoma; Animals; Gene Expression; Genes, p53; Genes, ras; Male; Methylnitronitrosoguanidine; Mutation; Proto-Oncogene Proteins p21(ras); Rats; Rats, Wistar; Stomach Neoplasms; Tumor Suppressor Protein p53

The modifying effects of Chelidonium majis L. (Papaveraceae) herb extract (CH), an analgesic traditionally prescribed for gastric and duodenal ulcer patients, on gastric tumor development were studied in rats given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Sixty-four male 6-week-old Wistar rats were used. Group 1 rats were initially given MNNG (200 mg/kg b.w.) by gavage at days 0 and 14 as well as saturated sodium chloride solution (S-NaCl, 1 ml per rat) every 3 days during weeks 0-3 (six times), and then placed on basal diet containing 0.1 or 0.2% CH for 16 weeks from week 4. Rats of Group 2 and 3 were treated with MNNG together with S-NaCl or saline (0.9% NaCl, 1 ml per rat), respectively, timed as in Group 1 but without further treatment. All surviving animals were killed at week 20 and histopathologically investigated. In the glandular stomach, the number of preneoplastic pepsinogen 1 altered pyloric glands (PAPGs) in the MNNG + S-NaCl-->CH (0.1%) group (Group 1) was significantly smaller than in the MNNG + S-NaCl group (Group 2) (P < 0.02). The incidences of forestomach neoplastic lesions (papillomas and squamous cell carcinomas) also showed a tendency to decrease with the CH treatment. The results thus indicate that CH exerts inhibitory effects on glandular stomach carcinogenesis in the rat, so that it may have potential as a chemopreventive agent for stomach cancer in man.

Topics: Animals; Anticarcinogenic Agents; Body Weight; Carcinogens; Cocarcinogenesis; Hyperplasia; Male; Methylnitronitrosoguanidine; Organ Size; Pepsinogens; Plant Extracts; Plants, Medicinal; Precancerous Conditions; Pyloric Antrum; Rats; Rats, Wistar; Saline Solution, Hypertonic; Stomach; Stomach Neoplasms

Epithelial dysplasia in the gastric remnant is generally considered to have a positive predictive value for malignancy. Whether dysplasia progresses to carcinoma or whether both just have a common origin, is still a matter of controversy. The aim of the present study in rats was to investigate the natural history of epithelial lesions in the gastric remnant. A gastric resection was carried out in 50 male Wistar rats. Postoperatively the animals received N-methyl-N'-nitro-N-nitrosoguanidine orally. Gastroscopy was carried out monthly and biopsies were taken for histologic evaluation. The rats were killed after 12 months or if gastric cancer was found on gastroscopy. Twenty-four rats died postoperatively and were excluded from the study. A total of 228 gastroscopies was performed in the remaining 26 animals; 24 animals developed dysplastic lesions during the follow-up period. The rate of development of gastric cancer within one month increased with the stage of dysplasia at the previous examination (3% for mild, 48% for moderate, 100% for severe dysplasia). There was a strong correlation between the time period following gastric resection and grade of dysplasia and between the grade of dysplasia and development of cancer. Our study demonstrates that gastric stump cancer in rats develops from dysplastic lesions. A dysplasia-carcinoma sequence can therefore be assumed.

Topics: Animals; Carcinogens; Carcinoma; Epithelium; Gastrectomy; Gastric Mucosa; Gastric Stump; Gastroscopy; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Suture Techniques; Time Factors

Administration of N-methyl-N'-nitro-N-nitrosoguanidine, a glandular stomach carcinogen, at the concentration of 100 microg/ml in drinking water for 8 days induced the appearance of a MHC class II-associated invariant chain in the target organ of stomach pyloric mucosa of male Lewis rats. The up-regulation of the MHC class II-associated invariant chain was revealed by fluorescent differential display analysis, reverse transcription-PCR, Northern blot, and histochemical staining. The appearance of MHC class II and MHC class I was also demonstrated by reverse transcription-PCR and Northern blot. The results suggest the involvement of MHC-controlled immune reactions in chemically-induced stomach carcinogenesis.

Topics: Animals; Blotting, Northern; Carcinogens; Cloning, Molecular; Gastric Mucosa; Histocompatibility Antigens Class II; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Polymerase Chain Reaction; Pylorus; Rats; Stomach Neoplasms

The effect of a purified, high protein diet on enhanced gastric carcinogenesis induced by oral administration of NaCl was investigated in Wistar rats. Rats were fed on a purified diet with an equalized caloric content, containing 8% NaCl and 25% casein (normal protein diet), or 50% casein (high protein diet) after oral treatment with N-methyl-N'-nitro-N-nitrosoguanidine for 25 weeks. In week 52, oral administration of NaCl had significantly increased the incidence and size of gastric cancer in rats fed a normal protein diet. However, NaCl had no significant effect on gastric carcinogenesis in rats fed a high protein diet. Oral administration of NaCl also caused a significant increase in tissue norepinephrine concentrations in the antral portion of the gastric wall, and increased the labeling indices of the antral epithelial cells of rats fed on a normal protein diet. However, in rats fed a high protein diet, administration of NaCl had no significant influence on these two parameters. These findings indicate that a high protein diet attenuates enhanced gastric carcinogenesis induced by the administration of NaCl, and that this effect may be related to its ability to decrease norepinephrine concentrations in the gastric wall, which subsequently decreases the proliferation of antral epithelial cells.

Topics: Animals; Dietary Proteins; Male; Methylnitronitrosoguanidine; Norepinephrine; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

The effects of cytotoxic monochloramine on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in Wistar rats. After oral administration of drinking water containing the carcinogen and regular chow pellets for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without s.c. injection of taurine, until the end of the experiment in week 52. Treatment with both ammonium acetate and sodium hypochlorite significantly increased the incidence of gastric cancers in week 52, while the concomitant use of taurine with ammonium acetate and sodium hypochlorite significantly attenuated the enhanced gastric carcinogenesis. Spectrophotometric examinations revealed that taurine scavenged monochloramine. These findings suggest that Helicobacter pylori-associated gastric carcinogenesis may be mediated by monochloramine.

Topics: Animals; Body Weight; Chloramines; Cocarcinogenesis; Gastric Mucosa; Helicobacter Infections; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sodium Acetate; Sodium Hypochlorite; Stomach Neoplasms; Taurine

The effects of combined administration of a catecholamine precursor, tyrosine methyl ester (TME), and an ornithine decarboxylase (ODC) inhibitor, 1,3-diaminopropane (DAP), on the incidence of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), the norepinephrine (NE) concentration and ODC activity of the gastric wall, and the labeling index of the gastric mucosa were investigated in inbred Wistar rats. Rats received s.c. injections of TME, 512 mg/kg body weight, every other day and drinking water with or without 2.5 g/l of DAP after 25 weeks of oral administration of MNNG. At week 52, administration of TME resulted in significant increases in the incidence of gastric cancers, in the NE concentration and the ODC activity of the antral portion of the gastric wall, and in the labeling index of antral epithelial cells. Administration of both TME and DAP significantly reduced the enhancements by TME of gastric carcinogenesis, NE concentration and ODC activity of the antral wall, and the labeling index of the antral mucosa. Our results suggest that ODC inhibition lessens enhancement by TME of gastric carcinogenesis and that the enhancement by TME of gastric carcinogenesis is mediated in part by polyamine biosynthesis.

Topics: Animals; Diamines; Enzyme Inhibitors; Male; Methylnitronitrosoguanidine; Norepinephrine; Ornithine Decarboxylase; Ornithine Decarboxylase Inhibitors; Rats; Rats, Wistar; Stomach Neoplasms; Tyrosine

Innervation of the gastric mucosa plays an important role in its defense mechanism. In a previous study, gastrectomy with denervation promoted tumorigenesis in the gastric body in rats after administration of a carcinogenic agent. In this study we investigated the induced gastric mucosal changes from the viewpoint of mucin histochemistry. Gastrectomy with denervation promoted the development of intestinal metaplasia, dysplasia, and carcinoma in the gastric body. Proliferating cell nuclear antigen labeling indexes as a marker for cell kinetics were significantly elevated in the denervated group. Analysis of mucin histochemistry by staining with paradoxical concanavalin A (PCA) and galactose oxidase-Schiff (GOS), which are markers for expression of the gastric phenotype, revealed that these mucins were positive in submucosal adenocystic proliferation and carcinoma at the anastomotic site. Conversely, in the gastric body these mucins disappeared with progression of dysplasia, and carcinoma cells contained neither PCA- nor GOS-positive mucins. These results suggest that there are two different processes of carcinogenesis in the gastric remnant, depending on the location, and that denervation of the remnant gastric mucosa promotes the development of cancer-related lesions in the gastric body.

Topics: Animals; Carcinogens; Denervation; Gastrectomy; Gastric Mucosa; Gastric Stump; Male; Methylnitronitrosoguanidine; Mucins; Proliferating Cell Nuclear Antigen; Rats; Rats, Wistar; Stomach Neoplasms

In many cases of stomach disease, specific epithelial changes of the mucous membrane have already been detected and staged in the past. An attempt has been made in this study to assess with a more up-to-date approach the data concerning the possible molecular biological mechanisms of tumor proliferation in stomach epithelial cells.

Topics: Adenocarcinoma; Administration, Oral; Animals; Drinking; Gastric Mucosa; Methylnitronitrosoguanidine; Pepsinogens; Rats; Rats, Wistar; Stomach Neoplasms

The modifying effects of alpha-difluoromethylomithine (DFMO) on glandular stomach carcinogenesis after initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and sodium chloride were investigated in male outbred Wistar rats. Animals were simultaneously given MNNG solution (100 ppm) as their drinking water and diet supplemented with 10% sodium chloride for 8 weeks, and administered DFMO (dietary levels of 2000 ppm or 500 ppm) and tap water for the following 70 weeks. The DFMO treatment did not show any tendency to inhibit the development of gastric adenocarcinomas. The incidences and multiplicities of atypical hyperplasias in the glandular stomachs were also comparable in all groups of rats given MNNG/sodium chloride. Neither gastric carcinomas nor atypical hyperplasias were observed without the carcinogen treatment. Thus, DFMO did not exert any inhibitory effects when given during the post-initiation phase of two-stage glandular stomach carcinogenesis in rats initiated with MNNG and sodium chloride for 8 weeks.

Topics: Adenocarcinoma; Animals; Cell Division; Chemoprevention; Eflornithine; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

The incidence of gastric remnant cancer after surgery for gastric malignancies has been increasing. The interval between previous operations and the diagnosis of gastric remnant cancer, location of cancer development, and histologic type were different from those after surgery for benign diseases. However, very little is known about the reasons for these differences. Patients with gastric cancer already have cancer-related gastric mucosal changes at gastrectomy, and they undergo a wide range of dissection of nerve distribution to the stomach due to lymph node dissection. Therefore, the effects of preliminary administration of a carcinogenic agent and denervation of the gastric mucosa on tumorigenesis in the gastric remnant were investigated.. Using male Wistar rats, N-methyl-N'-nitro-N-nitroguanidine (MNNG; 50 mg/L) was given in drinking water for 10 weeks. The animals were then assigned into four groups of those undergoing Billroth I (B-I) gastrectomy or Billroth II (B-II) gastrectomy, with and without denervation. Subdiaphragmatic truncal vagotomy was performed in the denervated group. Thirty weeks after gastrectomy, the following investigations were performed: histologic examination and periodic acid-Schiff-Alcian blue (PAS-AB) staining of the gastric mucosa by immunohistochemistry of proliferating cell nuclear antigen (PCNA).. In macroscopic findings, the groups undergoing nitrosoguanide (NG) gastrectomy with denervation showed a significant increase in the development of whitish, nodular changes in the gastric body. These changes mainly consisted of intestinal metaplasia in microscopic findings. In the NG gastrectomy group, the cancer developed at a lower rate of incidence at the anastomotic site and in the gastric body (1 of 11 rats and 1 of 11 rats, respectively). Conversely, a higher incidence of cancer development (5 of 13 rats) in the gastric body was observed in the group that underwent NG gastrectomy with denervation. Furthermore, the denervation group showed a significant increase in the PCNA labeling index and a distinct increase in the staining of Alcian blue positive mucin in the mucosa of the gastric body. The cancers that developed in the gastric body showed horizontal growth and were accompanied by intestinal metaplasia. In contrast, the cancers that developed in the gastric stumps showed downward growth, and were always accompanied by adenocystic proliferation, but not intestinal metaplasia.. Different processes of carcinogenesis in the gastric remnant are postulated after the surgery for gastric malignancies. The developed cancer is defined by its location and the gastric mucosal changes that developed at the time of gastrectomy.

Topics: Animals; Carcinogens; Cell Cycle; Cocarcinogenesis; Dose-Response Relationship, Drug; Female; Gastrectomy; Gastric Stump; Humans; Male; Methylnitronitrosoguanidine; Nitrosourea Compounds; Rats; Rats, Wistar; Stomach Neoplasms

The effects of baclofen, a gamma-amino-n-butyric acid receptor B agonist, on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine and how its effects are influenced by selective (M1) and non-selective (M1 and M2) pharmacological blockade of muscarinic receptors were investigated in inbred Wistar rats. Rats were given s.c. injections of 8 mg/kg body wt baclofen with and without 0.5 mg/kg body wt atropine (non-selective M1 and M2 muscarinic receptor antagonist) or 1.0 mg/kg body wt pirenzepine (selective M1 muscarinic receptor antagonist) every other day after a 25 week carcinogen treatment. At week 52 baclofen significantly decreased the incidence of gastric cancers. Concomitant treatment with atropine significantly attenuated the inhibition by baclofen of gastric carcinogenesis, but combined use with pirenzepine had no significant effect on the inhibition by baclofen of gastric carcinogenesis. Baclofen also significantly decreased the labeling index of the antral mucosa. Baclofen plus atropine attenuated the decrease in the labeling index of the antral mucosa due to baclofen, but baclofen plus pirenzepine had no significant effect on the labeling index. These results suggest that the inhibition of gastric carcinogenesis by baclofen is mediated through muscarinic receptors and M2 receptors, but not M1 receptors, are involved in this response.

Topics: Adenocarcinoma; Animals; Atropine; Baclofen; Bromodeoxyuridine; Carcinogens; GABA Agonists; Male; Methylnitronitrosoguanidine; Muscarinic Antagonists; Neoplasms, Experimental; Pirenzepine; Rats; Rats, Wistar; Stomach Neoplasms

The modifying effects of 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3], a vitamin D3 derivative, on glandular stomach carcinogenesis were investigated in male Wistar rats by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and sodium chloride exposure during the postinitiation phase. A total of 130 male 6-week-old rats was divided into five groups. Groups 1-3 (consisting of 30 rats/group) were given MNNG in drinking water at a concentration of 100 ppm and were simultaneously fed a diet supplemented with 10% NaCl for 8 weeks. They were fed a diet containing either 5.0 ppm (group 1) or 2.5 ppm (group 2) 24R,25(OH)2D3 or were kept on the basal diet alone (group 3) for the following 57 weeks. Rats in groups 4 and 5 were given 24R,25(OH)2D3, as were animals in groups 1 and 3, but did not receive the MNNG + NaCl treatment. The total incidence of combined atypical hyperplasias and adenocarcinomas in the glandular stomachs was significantly lower in group 1 (24%) than in group 3 (70%; P < 0.01). The mean numbers of atypical hyperplasias or adenocarcinomas of the glandular stomachs in groups 1 (0.31) and 2 (0.66) were also significantly decreased (P < 0.01 and P < 0.05, respectively) as compared to the group 3 value (1.21). Thus, the development of cancerous and precancerous lesions in the glandular stomach was decreased by exposure to 24R,25(OH)2D3 in a dose-dependent manner. Urinary calcium levels were increased by this vitamin D3 derivative (in line with the applied dose) when assayed at 10, 30, and 62 weeks, regardless of the MNNG + NaCl treatment The present results clearly indicate that 24,25(OH)2D3 exerts chemopreventive effects, possibly by influencing calcium pharmacodynamics, when given during the postinitiation phase of glandular stomach carcinogenesis in rats.

Topics: 24,25-Dihydroxyvitamin D 3; Adenocarcinoma; Animals; Calcium; Carcinogens; Drug Screening Assays, Antitumor; Hyperplasia; Male; Methylnitronitrosoguanidine; Phosphorus; Precancerous Conditions; Rats; Rats, Wistar; Sodium Chloride; Stomach; Stomach Neoplasms

The effects of oral calcium chloride (CaCl2) on sodium chloride (NaCl)-enhanced induction of gastric carcinogenesis by the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine, and the norepinephrine (NE) concentration in the gastric wall, were investigated in Wistar rats. Animals were given the carcinogen for 25 weeks and then chow pellets containing 10% NaCl with or without 8% or 4% CaCl2. In week 52, the incidence of gastric cancers, the NE concentration in the antral portion of gastric wall and the labelling index of antral epithelial cells were significantly greater in rats fed NaCl alone than in untreated control rats. Concomitant oral treatment with CaCl2 at 8%, but not 4%, significantly reduced the incidence of gastric cancers, the NE concentration in the antral portion of gastric wall and the labelling index of the antral epithelial cells in week 52 compared with those in rats fed NaCl alone. Because NE concentration reflects sympathetic nervous system activity, our findings suggest that the sympathetic nervous system could play a role in NaCl-enhanced gastric carcinogenesis. Our findings also suggest that NE depletion by CaCl2 may be related to its inhibition of NaCl-enhanced carcinogenesis.

Topics: Animals; Calcium Chloride; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Norepinephrine; Ornithine Decarboxylase; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

This study was conducted to examine the possible relationship among connexin 32 (Cx32) expression, cell proliferation and differentiation in the normal stomach, N-methyl-N'-nitro-nitrosoguanidine (MNNG)-induced atrophic gastritis, and carcinoma in rats. Atrophic gastritis and adenocarcinoma were induced by the administration of MNNG for 8 and 30 weeks, respectively. Cell proliferation was detected by staining with 5-bromo-2'-deoxyuridine (BrdU). The proliferative zone (BrdU-positive zone), located in the lower third of the gastric gland in controls, was elongated in atrophic gastritis. In adenocarcinoma, BrdU-positive cells were distributed diffusely. Cx32 expression was investigated by an indirect immunofluorescence method. In both control and atrophic gastritis specimens, Cx32 fluorescence was abundant in the surface epithelium, but was rarely detected in the glandular portion or the proliferative zone. The length of the Cx32-positive mucosa was significantly less than the control value in atrophic gastritis and no such positive mucosa was visible in adenocarcinoma. The results of this study indicate that the loss of cell-cell communication through the gap junction, associated with elongation of the proliferative cell zone, may be manifested much earlier than carcinoma. We regard this model as useful for investigating the development of atrophic gastritis into gastric carcinoma.

Topics: Adenocarcinoma; Animals; Carcinogens; Cell Communication; Cell Differentiation; Cell Division; Connexins; Female; Fluorescent Antibody Technique, Indirect; Gap Junction beta-1 Protein; Gastric Mucosa; Gastritis, Atrophic; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms

There are divergent opinions on the effect of ethanol in the carcinogenesis of gastroduodenal tumors. The effect of the synchronous application of 11% ethanol or wine (11% ethanol) and N-methyl-N'-nitro-N-nitrosoguanidine (100 micrograms/ml, MNNG) in a drinking solution on the incidence of gastroduodenal tumors was evaluated. Sixty outbred male Wistar rats were distributed among three groups. The animals drank MNNG and ethanol or wine for six months and consumed the same quantity of MNNG. Then they consumed a normal diet until the 13th month, when the experiment was terminated. The stomach and duodenum were examined histologically. In the stomach, 15 tumors (2 squamous paillomas, 4 squamous carcinomas, 1 sarcoma, and 8 adenocarcinomas) and 4 cases of dysplasia were found; in the duodenum, there were four cases of adenocarcinoma. There were 6 cases of multiple tumors. Incidence of forestomach tumors did not differ among the groups, whereas the incidence of glandular stomach carcinoma and duodenal carcinoma was significantly lower in the groups treated with 11% ethanol or wine than in the control group. MNNG was not inactivated by ethanol in the drinking solutions. We concluded that the inhibitory effect on gastroduodenal carcinogenesis is the result of 11% ethanol ingestion and its protective action on the mucosa and not of the wine's nonethanol components.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Drinking; Duodenal Neoplasms; Ethanol; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sarcoma, Experimental; Stomach Neoplasms; Wine

Dehydroepiandrosterone (DHEA) and its sulfate conjugate are the major circulating steroids in human plasma. Low levels of these adrenal steroids are associated with a number of human diseases including certain cancers. In animal studies, DHEA is chemopreventive toward both spontaneous and chemically induced cancers. A potential concern for long-term usage of DHEA in humans is the finding that DHEA is hepatocarcinogenic in rats. The human health risk has been thought to be minimal, however, as the mechanism of DHEA hepatocarcinogenesis is assumed to be due to its properties as a peroxisome proliferator, a class of compounds to which humans are relatively insensitive. Recently, we have found DHEA to be a potent promoter of aflatoxin B1-initiation as well as a complete hepatocarcinogen in the rainbow trout, a species which is also insensitive to peroxisome proliferators. In order to determine the initiator- and tissue-specificity of DHEA promotion, we examined the effects of DHEA on N-methyl-N'-nitro-nitrosoguanidine (MNNG)-initiated carcinogenesis. Trout fry were initiated by a bath exposure (30 min at 35 ppm) to MNNG and then fed DHEA at levels of 0, 55, 111, 222, 444, or 888 ppm for 7 months. DHEA increased liver tumor incidence, multiplicity, and size in a dose-dependent manner. The liver tumor incidence ranged from 0 in the MNNG-initiated controls to 99% in initiated trout fed 888 ppm DHEA. The latter represents a potential synergistic interaction in liver between MNNG and DHEA, as tumor incidence in sham-initiated trout fed this level of DHEA was 41%. The kidney tumor incidence was also enhanced two- and threefold over initiated controls by 111 and 888 ppm DHEA, respectively. In contrast, the total number of stomach and swim bladder tumors was reduced by DHEA treatment. This study demonstrates differential effects of DHEA on MNNG-initiated carcinogenesis in liver, kidney, stomach, and swim bladder.

Topics: Animals; Carcinogens; Dehydroepiandrosterone; Kidney Neoplasms; Liver Neoplasms, Experimental; Methylnitronitrosoguanidine; Neoplasms, Experimental; Oncorhynchus mykiss; Stomach Neoplasms; Urinary Bladder Neoplasms

N-Methyl-N'-nitrosoguanidine (MNNG) was administered (100 mg/L) in drinking water in 100 Wistar rats for 24 weeks to induce the precancerous lesion in glandular stomach. 77 rats with the precancerous lesion in glandular stomach were divided into 3 groups randomly at the 25 thweek. Yeast selenium (Yse, 4 mg/L) and carboxyethyl germanium sesquioxide (Ge-132, 600 mg/L) in drinking water were administered respectively in the corresponding treatment groups: 100 ml/MNNG in drinking water was administered in the treatment group, and 100 ml/MNN in drinking water was administered in the treatment group and control group for another 5 weeks. The experiment ended at the end of the 37th week. The results showed that the incidence of glandular stomach cancer in the Yse group was significantly lower than that in the control group; the infiltrating depth of glandular stomach cancer in the Yse group and the Ge-132 group was remarkably shallower than that in the control group. These findings suggest that Yse and Ge-132 have some preventive effect on the precancerous lesion in rat glandular stomach induced by MNNG.

Topics: Animals; Antidotes; Antineoplastic Agents; Germanium; Male; Methylnitronitrosoguanidine; Organometallic Compounds; Precancerous Conditions; Propionates; Rats; Rats, Wistar; Selenium; Stomach Neoplasms; Yeast, Dried

The effects of chronic progesterone treatment on gastric tumorigenesis were examined in 6-week-old male SD rats. The rats were castrated, progesterone or testosterone pellets were implanted, and, starting one week after the operation, 100 mg/liter of N-methyl-N'-nitro- N-nitrosoguanidine (MNNG) was administered in the drinking water for 16 weeks. Every 2 months the pellets were changed. Group 1 animals received castration plus MNNG while Groups 2 and 3 also received progesterone and testosterone, respectively. In the Group 4 case, progesterone and testosterone were administered alternately for 2-month periods and in Group 5 MNNG was given to intact animals. All survivors were killed one year after the start of MNNG treatment. In Group 1 the incidence of gastric tumors was significantly decreased as compared with the Group 5 value. The Group 2 incidence, in contrast, was similar to that in Group 5, and the size of the observed gastric tumors was massively increased. The area of the pyloric gland mucosa was also greater than in other groups. Testosterone treatment was associated with a less pronounced increase in tumor size and a recovery in incidence. The results indicate that progesterone may exert a promoting influence on gastric tumor development.

Topics: Animals; Body Weight; Drug Synergism; Intestinal Diseases; Male; Methylnitronitrosoguanidine; Orchiectomy; Precancerous Conditions; Progesterone; Rats; Rats, Sprague-Dawley; Stomach Neoplasms; Testosterone

The effects of prolonged administration of neuropeptide substance P (SP) on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on the labeling index of gastric mucosa were investigated in Wistar rats. Rats received subcutaneous injections of 12 micrograms/kg body weight of SP every other day after 25 weeks of oral treatment with MNNG. Long-term administration of SP significantly increased the incidence of gastric cancers in week 52. However, it did not affect the histological type and depth of involvement of gastric cancers. SP also caused a significant increase in the labeling index of the antral and fundic epithelial cells in week 52. These findings indicate that SP promotes gastric carcinogenesis and suggest that this effect may be related to its stimulation of antral epithelial cell proliferation.

Topics: Animals; Carcinogens; Cell Division; Gastric Mucosa; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Substance P

The effects of combined administration of NaCl and the ornithine decarboxylase (ODC) inhibitor 1,3-diaminopropane (DAP) on the incidence and number of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on the ODC activity of the gastric wall and the labeling index of the gastric mucosa were investigated in inbred Wistar rats. Rats were given drinking water with or without 2.5 g/l DAP and chow pellets with and without 10% NaCl ad libitum after 25 weeks of oral administration of MNNG. At week 52 feeding 10% NaCl resulted in significant increases in the incidence of gastric cancers, in the ODC activity of the antral portion of the gastric wall and in the labeling index of antral epithelial cells. Administration of both NaCl and DAP significantly reduced the enhancements by NaCl of gastric carcinogenesis, ODC activity of the antral wall and the labeling index of antral epithelial cells. These results suggest that inhibition of ODC attenuates NaCl enhancement of gastric carcinogenesis and that enhancement by NaCl of gastric carcinogenesis is mediated by polyamine biosynthesis.

Topics: Animals; Carcinogens; Cocarcinogenesis; Diamines; Drug Interactions; Enzyme Inhibitors; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase; Ornithine Decarboxylase Inhibitors; Rats; Rats, Wistar; Sodium Chloride; Stomach; Stomach Neoplasms

Humans show heterogeneous susceptibility to cancer development, suggesting the involvement of various genetic backgrounds in control of the production of endogenous carcinogens, the metabolism of carcinogens, the repair of DNA damage, cell proliferation and defence mechanisms including immune reactions. Gastric cancer is the major cancer in Japan. However, little is known about the genes linked with its development. In 1967, we found that N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induced gastric cancers in Wistar rats. Subsequently the Buffalo strain of rats was reported to be resistant to MNNG stomach carcinogenesis, while ACI rats were very sensitive. In a carcinogenesis study using F1 and F2 rats, we suggested that this trait of MNNG stomach carcinogenesis-resistance was regulated by a single autosomal dominant allele. The O6-methylguanine adduct levels in gastric mucosa induced by MNNG were the same in Buffalo and ACI rats, but cell proliferation induced by MNNG was much higher in ACI than Buffalo animals. Chromosome mapping of the gene responsible for susceptibility to MNNG-induced carcinogenesis is now in progress and its identification will hopefully give us clues to the involvement of genetic traits in susceptibility to gastric cancer in humans. In addition, the genetic background of susceptibility to breast cancer is also being studied. In Japan, about 5% of all cases of breast cancer are familial. We have studied BRCA1, the breast cancer susceptibility gene, as a determinant of susceptibility to breast cancer by linkage analyses in 11 families, but our results indicate that BRCA1 may not be important for development of familial breast cancer in Japanese.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; BRCA1 Protein; Breast Neoplasms; Female; Gastric Mucosa; Genetic Predisposition to Disease; Humans; Japan; Lod Score; Methylnitronitrosoguanidine; Middle Aged; Neoplasm Proteins; Neoplasms; Ovarian Neoplasms; Polymorphism, Genetic; Rats; Rats, Inbred ACI; Rats, Inbred BUF; Rats, Wistar; Species Specificity; Stomach Neoplasms; Transcription Factors

The susceptibility of pepsinogen-altered pyloric glands (PAPG) and neoplastic glandular stomach lesions induced by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and catechol or sodium cholate in Nagase analbuminemic rats (NAR) was compared to Sprague-Dawley rats (SD). Male NAR and SD rats were given a single dose of 80 mg/kg body weight of MNNG by gastric intubation and, 2 weeks later, fed basal diet containing 0.8% catechol or 0.3% sodium cholate for 18 weeks. The animals were killed at the end of week 20 or after maintenance on basal diet at week 60. The number of pepsinogen-altered pyloric glands at week 20 was significantly (P < 0.001) higher in NAR fed either catechol or sodium cholate compared with SD rats. At week 60, adenomatous hyperplasias and adenocarcinomas were observed in 7 (88%; P < 0.01) and 3 (38%; P < 0.01) of 8 NAR fed catechol and in 4 (22%) and 0 of 18 SD rats, respectively. The results show that the frequency of PAPG in NAR and SD rats is related to the susceptibility to glandular stomach carcinoma. PAPG is a useful endpoint lesion for evaluation of gastric carcinogenicity in a 20-week carcinogenicity test, and NAR are sensitive for glandular stomach carcinogenesis.

Topics: Adenocarcinoma; Animals; Carcinogens; Catechols; Cholic Acid; Cholic Acids; Gastric Mucosa; Hyperplasia; Male; Methylnitronitrosoguanidine; Pepsinogens; Pyloric Antrum; Rats; Rats, Mutant Strains; Rats, Sprague-Dawley; Serum Albumin; Species Specificity; Stomach Neoplasms

The modifying effects of potassium chloride (KCl) ingestion on glandular stomach carcinogenesis were investigated in male Wistar rats induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and were compared with those of sodium chloride (NaCl). A total of 120 male 6-week-old Wistar rats were divided into six groups, each consisting of 20 animals. After initiation of treatment with a MNNG solution (100 parts/million) as their drinking water for 10 weeks, rats were fed a diet supplemented with 5% NaCl, 2.5% NaCl, 2.5% NaCl plus 2.5% KCl, 5% KCl, 2.5% KCl, or a basal diet alone for the following 62 weeks. Under this experimental condition, there were no statistical differences in the final body weights between groups. The incidences of adenocarcinomas in the glandular stomachs were significantly higher in the 5% NaCl and combined 2.5% NaCl-plus-2.5% KCl groups (P < 0.05 and 0.01) than in the MNNG alone (control) group. The incidences of atypical or precancerous hyperplasias in the glandular stomachs were increased significantly by the 5% NaCl, 2.5% NaCl-plus-2.5% KCl, and 5% KCl treatments (P < 0.05 or 0.01). The multiplicities of adenocarcinomas were significantly greater in the 5% NaCl, 2.5% NaCl, and combined NaCl-plus-KCl groups (P < 0.05 or 0.01) compared with the control value. The multiplicity data for atypical hyperplasias were most striking; namely, their multiplicities were increased significantly by the treatments of NaCl or KCl (P , 0.01) in a clear dose-dependent manner and enhanced synergistically by the combined treatment of NaCl and KCl. Because the concentrations of KCl used in this study were about 1.3 times lower than those of NaCl on a molar basis, although the doses of each chemical were exactly the same on a weight-percent basis, it is suggested that the enhancing effects of KCl might not be much different from those of NaCl. The results in the present study thus indicate that, similarly to NaCl, KCl ingestion exerts dose-dependent promoting effects and a synergistic influence with NaCl when given during the postinitiation phase of two-stage glandular stomach carcinogenesis in rats.

Topics: Animals; Carcinogens; Dose-Response Relationship, Drug; Drug Synergism; Male; Methylnitronitrosoguanidine; Potassium Chloride; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

The pathogenetic effect of duodenogastric reflux of the development of gastric stump carcinoma was studied experimentally. In this animal model, 95 male Wistar rats were subjected to a specially designed gastrojejunostomy to divert the duodenal contents into the resected stomach through the afferent and efferent loop. The rats were fed normally without any carcinogen administration. The incidence of adenocarcinomas around the anastomosis of afferent loop was 0% at 10 weeks, 18.8% at 20 weeks and 34.4% at 40 weeks, so the incidence was apt to rise in parallel with passing of the weeks. At 40 weeks, the rats had a significantly higher incidence of adenocarcinoma in the gastric mucosa around the afferent loop than around the efferent loop (P < 0.05). Of particular interest is that invasive growth of the cancerous tissue into the liver was observed in one animal. Polypoid lesions called 'atypical hyperplasia' in the present study were similar to gastritis cystica polyposa of humans. The development of adenocarcinoma was found to be intimately connected with atypical hyperplasia, which might be promoted by repeated destruction and regeneration by duodenogastric reflux. These results suggest that the direct contact of the duodenal juice with the gastric mucosa induces carcinoma in the anastomotic lesion. From the clinical perspective, our findings suggest that a surgical technique that minimizes the duodenogastric reflux should be chosen.

Topics: Adenocarcinoma; Animals; Duodenogastric Reflux; Gastrectomy; Gastric Stump; Jejunostomy; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms

In this study we tested the influence of blood flow and the mucoid cap on the penetration of carcinogens to the proliferative cells in the injures rat gastric mucosa. Ten minutes after mucosal exposure to 4.5 mol/liter NaCl, N-[3H]methyl-N'-nitro-N-nitrosoguanidine was instilled intragastrically. Hypertonic saline caused superficial mucosal damage, formation of a mucoid cap, high gastric mucosal blood flow, and a large flux of fluid into the gastric lumen. The mean percentage of S-phase cells labeled with carcinogen (the cell population at risk for N-methyl-N'nitro-N-nitrosoguanidine-induced carcinogenesis) in the antrum and corpus was 0.2 and 0.2, respectively, in the injury control group, 10.1 and 2.0 after removal of the mucoid cap, 1.5 and 9.8 after celiac artery ligation, and 28.2 and 21.9 after removal of the mucoid cap and celiac artery ligation. These results show that both the mucoid cap and gastric mucosal blood flow protect against penetration of carcinogens into the superficially injured gastric mucosa.

Topics: Animals; Celiac Artery; Gastric Mucosa; Ligation; Male; Methylnitronitrosoguanidine; Mucus; Rats; Rats, Wistar; Regional Blood Flow; Stomach Neoplasms

The frequency of nuclear anomalies (micronuclei, pyknosis, and karyorrhexis) in the forestomach mucosa was examined in Sprague-Dawley male rats given a single oral dose of 50 or 150 mg/kg of the gastric carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) 17 h after the administration of 2 ml of a 3 M NaCl solution. Rats pretreated with NaCl displayed an incidence of nuclear anomalies approximately 3-fold greater than the one observed in rats given MNNG alone, and micronucleated cells accounted to a significant extent for this increase. These findings confirm that NaCl presumably acts as co-carcinogen in the initial phase of gastric carcinogenesis, and suggest that its administration before the carcinogen might increase the sensitivity of short-term tests for the preliminary screening of potential gastric carcinogens.

Topics: Animals; Carcinogens; Cell Nucleus; Drug Synergism; Male; Methylnitronitrosoguanidine; Micronucleus Tests; Rats; Rats, Sprague-Dawley; Sodium Chloride; Stomach; Stomach Neoplasms

Although an association is suggested between gastric cancer and prior infection with Helicobacter pylori (HP), the role of HP in gastric carcinogenesis remains obscure. HP has potent urease activity and produces ammonia, a factor causing HP-related gastroduodenal mucosal lesions. In this study, rats were examined in an effort to determine effects of ammonia on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). After pretreatment with MNNG (83 mg/l) for 24 weeks, a solution of either 0.01% ammonia or plain tap water was administered to the animals as drinking water for an additional 24 weeks. The administration of the 0.01% ammonia solution significantly increased the incidence and number of cancers in the glandular stomach. The numbers of cases in which these cancers penetrated the muscle layer or deeper and of low-grade differentiated adenocarcinomas were significantly higher in rats receiving the ammonia solution. Continuing administration of ammonia accelerated cell proliferation in the gastric mucosa, but had no effect on the serum gastrin level. Therefore, gastric ammonia, which stimulates mucosal cell proliferation, appears to be an important promoter in carcinogenesis in rats and possibly in the HP-related gastric carcinogenesis in humans.

Topics: Ammonia; Animals; Carcinogens; Cell Division; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Rats; Rats, Sprague-Dawley; Stomach Neoplasms

Recently, an epidemiological study showed a lower risk of gastric cancer among people who consume a large amount of green tea. (-)-Epigallocatechin gallate (EGCG), one of the main constituents of green tea, inhibited tumor promotion by teleocidin in a two-stage carcinogenesis experiment with the use of mouse skin. The inhibitory effect of EGCG on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced carcinogenesis of the glandular stomach in rats was examined. The percentage of tumor-bearing rats in the group treated with MNNG plus EGCG was 31%, compared to 62% in the MNNG group. The difference was statistically significant (P < 0.05). To assess the effect of p.o. administration of EGCG, the gastric mucosal cellular kinetics was examined with the use of the bromodeoxyuridine labeling index, ornithine decarboxylase activity, and tissue polyamine levels. The labeling index of the EGCG treatment group decreased significantly (P < 0.05) compared to the EGCG plus MNNG treatment group. The ornithine decarboxylase activity and tissue spermidine levels were also decreased. On the other hand, the tissue putrescine and spermine levels were partly increased. These findings suggest that EGCG inhibits the cellular kinetics of the gastric mucosa during the promotion stage of MNNG-induced gastric carcinogenesis. EGCG may be useful in preventing gastric carcinogenesis. Moreover, EGCG may be applied clinically without any harmful effects and at a low cost.

Topics: Adenocarcinoma; Adenoma; Animals; Antineoplastic Agents; Carcinoma, Papillary; Catechin; Drug Screening Assays, Antitumor; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase; Papilloma; Rats; Rats, Wistar; Stomach Neoplasms

The modifying effects of caffeine ingestion on glandular stomach carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and sodium chloride (NaCl) were investigated in male Wistar rats. Animals were given a MNNG solution (100 ppm) as their drinking water and simultaneously fed a diet supplemented with 5% NaCl for 8 wk. They then received 0.25% caffeine solution (groups 1 and 3) or tap water (groups 2 and 4) as the drinking water, and were fed the NaCl diet (groups 1 and 2) or basal diet (groups 3 and 4) for the following 32 wk. Both caffeine and NaCl treatments exerted growth retardation effects, the suppression being stronger with caffeine than NaCl, and animals in group 1 (NaCl plus caffeine) showing the lowest body weight. The incidence of adenocarcinomas in the pylorus was significantly decreased in group 1 compared with the group 2 (NaCl) value (P < 0.05). The incidence of atypical hyperplasias in the fundus was also lower in group 1 than in group 2, although in both cases significantly higher (P < 0.05 and P < 0.01) than in group 4 (no treatment). These results were in good agreement with short-term assay findings whereby lipid peroxidation in the glandular stomach mucosa induced by 4% NaCl ingestion was inhibited by caffeine treatment. In group 3 (caffeine), caffeine intake by itself did not modulate glandular stomach tumour development. The results thus suggest that caffeine inhibits the gastric tumour promotion activity of NaCl in rats.

Topics: Adenocarcinoma; Animals; Biological Assay; Body Weight; Caffeine; Cell Division; Drug Interactions; Gastric Mucosa; Hyperplasia; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

The effects of intragastric capsaicin and gastric artery ligation on the penetration of the gastric carcinogen N[methyl-3H]-N'-nitro-N-nitrosoguanidine ([3H]MNNG) to proliferative cells were studied in normal and healing rat gastric mucosa. The percentage of S-phase cells labeled with [3H]MNNG in normal corpus mucosa was higher (7.0 +/- 2.0%) after gastric artery ligation than in controls with intact blood flow (2.7 +/- 1.0%) and in animals treated with capsaicin (1.8 +/- 0.5%). Corpus mucosal blood flow was correlated with the percentage of S-phase cells labeled with [3H] MNNG in normal controls and in capsaicin-treated animals. In healing corpus mucosa and in the antrum, capsaicin or gastric artery ligation did not affect carcinogen penetration. We conclude that blood flow protects against penetration of carcinogens to proliferative cells in normal corpus mucosa but not in the antrum. Low mucosal blood flow in the corpus could be a risk factor for initiation of gastric carcinogenesis.

Topics: Animals; Arteries; Capsaicin; Carcinogens; Cell Division; Gastric Mucosa; Ligation; Male; Methylnitronitrosoguanidine; Pyloric Antrum; Rats; Rats, Wistar; Regional Blood Flow; Risk Factors; S Phase; Stomach; Stomach Neoplasms; Tritium

The effects of prolonged administration of the neuropeptide galanin on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, the norepinephrine concentration in the gastric wall, and the labeling index of the gastric mucosa were investigated in Wistar rats. The rats received 2 or 4 micrograms/kg body weight of galanin s.c. every other day after 25 weeks oral treatment with the carcinogen. Prolonged administration of galanin at 4 micrograms/kg body weight, but not at 2 micrograms/kg body weight, significantly decreased the incidence of gastric cancers in experimental week 52. However, it did not influence the histological types of cancers. Galanin at 4 micrograms/kg body weight also significantly decreased the labeling index of the antral epithelial cells but not the norepinephrine concentration in the gastric wall. These findings indicate that galanin inhibits gastric carcinogenesis and suggest that its effect may be related to the suppression of proliferation of the antral epithelial cells.

Topics: Animals; Anticarcinogenic Agents; Drug Interactions; Galanin; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Norepinephrine; Peptides; Rats; Rats, Wistar; Stomach Neoplasms

The aim of the present investigation was to evaluate abnormal changes in trace element concentrations during carcinogenesis. First, Al, Zn and Cu in the liver tissues of rats were measured by atomic absorption analysis over a half year of hepatocarcinogenesis. Male Wistar rats were given carcinogenic food containing 600 mg/kg of 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB) in a basal diet for several months. After 4 to 6 months of feeding, hepatocarcinomas developed in the rats. Zn and Cu concentrations in the hepatocarcinomas of the 3'-MeDAB group significantly decreased as compared with normal liver tissues of the control groups. On the other hand, the aluminum concentration in the hepatocarcinomas was more than three times that in the normal liver tissues. The Al and Se contents of developed gastric and mammary cancers were measured in Experiment II. Male and female rats were given 1-methyl-3-nitrothoguanidine(MNNG) and 2,7-dimehtylbenz(a)anthracene(DMBA), respectively. After several months, carcinomas developed in over half of the rats. The Al and Se concentrations in cancers, livers and the blood were determined by atomic absorption analysis. It was shown that both gastric and mammary carcinomas contained a high level of aluminum and very little selenium in comparison with normal liver tissues. The present study demonstrated that aluminum accumulated in experimentally induced carcinomas in rats, i.e., cancers of the liver, stomach, duodenum and mammary glands.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Aluminum; Animals; Carcinoma, Hepatocellular; Copper; Disease Models, Animal; Duodenal Neoplasms; Female; Liver Neoplasms; Male; Mammary Neoplasms, Experimental; Methyldimethylaminoazobenzene; Methylnitronitrosoguanidine; Rats; Rats, Sprague-Dawley; Rats, Wistar; Reference Standards; Spectrophotometry, Atomic; Stomach Neoplasms; Zinc

Adenocarcinoma, adenoma and dysplasia of the stomach of adult Wistar rats were induced following administration of MNNG for 10 days by gavage when they were new-born. The incidence of the three types of pathological lesions at the dose of 0.4 mg MNNG per rat being 39%, 50% and 100% respectively. Induction of gastric adenocarcinoma is dose-dependent. The incidence of adenocarcinoma in male rats being significantly higher then that of female rats (P < 0.02). 23 of 33 (70%) induced cancers were found in the gastric antrum. By the use of DNA cotransfection technique and the assay of carcinogenicity in the Balb/c nude mice, it was also found that the DNA of 4 of the 6 induced gastric carcinomas could transform NIH/3T3 cells into malignant cells, an indication that the induced cancer DNA contains transforming gene.

Topics: 3T3 Cells; Adenocarcinoma; Animals; Animals, Newborn; Cell Transformation, Neoplastic; Disease Models, Animal; DNA, Neoplasm; Female; Male; Methylnitronitrosoguanidine; Mice; Mice, Inbred BALB C; Mice, Nude; Rats; Rats, Wistar; Stomach Neoplasms; Transfection

Curcumin (diferuloylmethane), a yellow pigment that is obtained from the rhizomes of Curcuma longa Linn., is a major component of turmeric and is commonly used as a spice and food-coloring agent. The inhibitory effects of feeding commercial grade curcumin (77% curcumin, 17% demethoxycurcumin, and 3% bisdemethoxycurcumin) in AIN 76A diet on carcinogen-induced tumorigenesis in the forestomach, duodenum, and colon of mice were evaluated. Administration p.o. of commercial grade curcumin in the diet inhibited benzo(a)pyrene-induced forestomach tumorigenesis in A/J mice, N-ethyl-N'-nitro-N-nitrosoguanidine-induced duodenal tumorigenesis in C57BL/6 mice, and azoxymethane (AOM)-induced colon tumorigenesis in CF-1 mice. Dietary commercial grade curcumin was given to mice at: (a) 2 weeks before, during, and for 1 week after carcinogen administration (during the initiation period); (b) 1 week after carcinogen treatment until the end of the experiment (during the postinitiation period); or (c) during both the initiation and postinitiation periods. Feeding 0.5-2.0% commercial grade curcumin in the diet decreased the number of benzo(a)pyrene-induced forestomach tumors per mouse by 51-53% when administered during the initiation period and 47-67% when administered during the postinitiation period. Feeding 0.5-2.0% commercial grade curcumin in the diet decreased the number of N-ethyl-N'-nitro-N-nitrosoguanidine-induced duodenal tumors per mouse by 47-77% when administered during the postinitiation period. Administration of 0.5-4.0% commercial grade curcumin in the diet both during the initiation and postinitation periods decreased the number of AOM-induced colon tumors per mouse by 51-62%. Administration of 2% commercial grade curcumin in the diet inhibited the number of AOM-induced colon tumors per mouse by 66% when fed during the initiation period and 25% when fed during the postinitiation period. The ability of commercial grade curcumin to inhibit AOM-induced colon tumorigenesis is comparable to that of pure curcumin (purity greater than 98%). Administration of pure or commercial grade curcumin in the diet to AOM-treated mice resulted in development of colon tumors which were generally smaller in number and size as compared to the control group of AOM-treated mice. These results indicate that not only did curcumin inhibit the number of tumors per mouse and the percentage of mice with tumors but it also reduced tumor size. Histopathological examination of the tumors sho

Topics: Adenocarcinoma; Adenoma; Adenoma, Villous; Animals; Azoxymethane; Benzo(a)pyrene; Carcinogens; Colonic Neoplasms; Curcumin; Duodenal Neoplasms; Female; Male; Methylnitronitrosoguanidine; Mice; Stomach Neoplasms

A polyclonal antibody against rat intestinal-type alkaline phosphatase (I-ALP) was generated and proven to be applicable immunohistochemically to paraffin-embedded sections. Expression of I-ALP in normal tissues, intestinal metaplasia and stomach tumors induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was then investigated in five different strains of rats. Male SD (Crj:CD), Lewis (LEW/Crj), WKY (WKY/NCrj), Wistar (Crj:Wistar) and F344 (F344/DuCrj) animals were given drinking water containing 100 micrograms/ml of MNNG for 30 weeks and were killed at week 50. Among the 5 strains, stomach adenocarcinomas were found most frequently in the SD case. The susceptibility of rats to induction of stomach carcinoma did not correlate with the development of intestinal metaplasias in each strain. Histochemical staining for mucin demonstrated all stomach tumors (adenomatous hyperplasias and well-differentiated adenocarcinomas) to consist mainly of gastric type cells (pyloric gland cell and surface mucous cell types), with intestinal-type tumor cells (goblet cell and intestinal absorptive cell types) being only occasional findings. Immunohistochemically, I-ALP was strongly positive on the striated cell borders of small intestinal absorptive cells of the villus and on brush borders of epithelial cells of kidney proximal tubules. I-ALP was also detected in the normal stomach, limited to the striated cell borders of absorptive cells of the upper one-fourth of intestinal metaplastic glands. I-ALP may thus be a useful marker for stomach tumor cells of intestinal absorptive cell type, indicative of maturation and differentiation. No stomach tumors consisting mainly of intestinal-type cells were found, and therefore there was no suggestion of any derivation from intestinal metaplasias.

Topics: Adenocarcinoma; Adenoma; Alkaline Phosphatase; Animals; Immunoenzyme Techniques; Intestines; Male; Metaplasia; Methylnitronitrosoguanidine; Mucins; Rats; Rats, Inbred Strains; Rats, Sprague-Dawley; Rats, Wistar; Stomach Neoplasms

The influence of different doses of sodium chloride (NaCl) on glandular stomach carcinogenesis was examined in male outbred Wistar rats after initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Rats were given 100 p.p.m. MNNG in their drinking water for 8 weeks and then fed a diet supplemented with NaCl at doses of 10, 5, 2.5 or 0% for the next 82 weeks. The administration of 10% and 5% NaCl significantly enhanced the development of gastric adenocarcinomas and adenomas in a dose-dependent manner. Similar but non-significant tendencies for increase were also seen in the group given 2.5% NaCl compared to the MNNG-alone group values. Clear linear correlations between incidences of adenocarcinomas and/or adenomas and the concentration of supplemented NaCl were found. Mesenchymal tumors were also induced in the stomach of rats given MNNG, although the incidence was not statistically different between groups. Independent of the MNNG treatment, urinary lipid peroxidation levels were significantly increased in the NaCl-treated groups as compared to the control values. Thus, the results in the present study indicate that NaCl exerts dose-dependent tumor promoting activity on gastric carcinogenesis in rats, even at doses as low as 2.5%, when given after MNNG initiation.

Topics: Adenocarcinoma; Adenoma; Animals; Cocarcinogenesis; Dose-Response Relationship, Drug; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sodium Chloride; Stomach Neoplasms

We evaluated killer cell activity and suppressor cell activity as the indicators of immunological function of spleen cells in rats implanted with N-methyl-N'-nitro-N-nitrosoguanidine-induced cancer. The effect of splenectomy on tumor growth was also investigated. Splenectomy was performed 2 (early stage of tumor growth), 5 (intermediate stage), or 8 weeks (late stage) after tumor implantation. The mean survival time of rats splenectomized at the early or intermediate stage of tumor growth was shorter than that of sham-operated rats, while that of rats splenectomized at the late stage was longer than controls. Natural killer (NK) and Cytotoxic T lymphocyte (CTL) activity of spleen lymphocytes of tumor-bearing rats were increased during the intermediate stage of tumor growth and then were declined during the late stage, while suppressor cell activity showed progressive increase after tumor implantation. The results of Winn assay showed that most of the splenic effector cells during the intermediate stage were T-lymphocytes, and some were NK cells. Furthermore suppressor macrophages and suppressor T-lymphocytes were increased in spleen lymphocytes of rats in the late stage of tumor growth. These results suggest that preservation of the spleen may be beneficial in the treatment of gastric cancer at the early and intermediate stage but that splenectomy is necessary for the advanced stage of cancer.

Topics: Animals; Cytotoxicity, Immunologic; Killer Cells, Natural; Male; Methylnitronitrosoguanidine; Neoplasm Transplantation; Rats; Rats, Wistar; Spleen; Splenectomy; Stomach Neoplasms; T-Lymphocytes, Cytotoxic; T-Lymphocytes, Regulatory

The effects of combined treatment with NaNO2 and phenolic compounds on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) stomach carcinogenesis were investigated in F344 rats. In the first experiment, groups of 15-20 male rats were treated with an intragastric dose of 150 mg/kg body weight of MNNG, and starting 1 wk later, were given 2.0% butylated hydroxyanisole, 0.8% catechol, 2.0% 3-methoxycatechol or basal diet either alone or in combination with 0.2% NaNO2 in the drinking water until they were killed at week 52. All three antioxidants significantly enhanced forestomach carcinogenesis without any effect of additional NaNO2 treatment. However, in the absence of MNNG pretreatment, the grade of forestomach hyperplasia in the catechol and 3-methoxycatechol groups was significantly increased by the combined treatment with NaNO2. In a second experiment, the combined effects of various phenolic compounds and NaNO2 on cell proliferation in the upper digestive tract were examined. Groups of 5 rats were given one of 24 phenolic compounds or basal diet either alone or in combination with 0.3% NaNO2 for 4 weeks and then killed. Particularly strong enhancing effects in terms of thickness of the forestomach mucosa were seen with t-butylhydroquinone (TBHQ), catechol, gallic acid, 1,2,4-benzenetriol, dl-3-(3,4-dihydroxyphenyl)-alanine and hydroquinone in combination with NaNO2. In the glandular stomach, similar enhancing effects were evident in 11 cases, and in the esophagus with phenol, TBHQ and gallic acid. These results demonstrate that NaNO2 can augment cell proliferation induced in the stomach epithelium by various phenolic compounds.

Topics: Animals; Butylated Hydroxyanisole; Carcinoma, Squamous Cell; Catechols; Cell Division; Hyperplasia; Male; Methylnitronitrosoguanidine; Phenols; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach; Stomach Neoplasms

Complex and conflicting relationships between epidermal growth factor (EGF), estrogens (E), androgens (A), and related receptors (EGF-R, E-R, A-R) have been reported in different biological situations associated with cell proliferation. There is also evidence that EGF and sex hormone receptors may be involved in normal and neoplastic growth of the gastrointestinal mucosa. In this study, we investigated the behavior of EGF receptors and sex hormone and related receptors, during N-methyl-N'-nitro-N-nitrosoguanidine (NG)-induced gastric carcinogenesis in Sprague-Dawley male rats. Four groups of 15 rats each (10 NG-treated and five controls) were sacrificed after 1, 20, 30, and 40 weeks of treatment. Gastric tissue from each rat was processed for receptor status (number and affinity) and proliferative activity. A significant and progressive decrease of A-R and EGF-R was observed starting from the 20th week, while no change of E-R occurred throughout the experiment. Cell proliferation in the gastric mucosa of NG-treated rats increased after 30 weeks of treatment. These data indicate that NG treatment is able to modify the receptor status of gastric mucosa in rats.

Topics: Adenocarcinoma; Androgens; Animals; ErbB Receptors; Estrogens; Male; Methylnitronitrosoguanidine; Rats; Rats, Sprague-Dawley; Receptors, Androgen; Receptors, Estrogen; Stomach Neoplasms

The antioxidant food preservative butylated hydroxyanisole (BHA) was tested in an initiation-promotion protocol in which male F344 rats (6 wk old), 27 per group, were gavaged with a single dose of 200 mg N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)/kg. After 3 wk on control diet, test diets containing 0, 60, 300, 1000, 3000, 6000 or 12,000 ppm BHA were fed until termination of the experiment at approximately 110 wk, at which time most animals had died with stomach tumours. MNNG caused a high incidence of tumours in the glandular stomach and forestomach of all groups. Administration of 12,000 and 6000 ppm BHA, but not 3000 ppm or lower doses, caused statistically significant increases in the time-related incidence of MNNG-induced forestomach tumours as analyzed by life table analysis. BHA had no effect on the incidence of tumours in the glandular stomach or oesophagus. Tumour incidences in other organs were not related to BHA dose. No increase in hyperplasia in the oesophagus was evident in the high-dose BHA-treated animals compared with the MNNG-only group. This study provides corroboration that BHA affects only forestomach tumorigenesis and that the dose for enhancement of tumorigenesis is at least 1500-fold greater than human exposure.

Topics: Animals; Butylated Hydroxyanisole; Carcinogenicity Tests; Carcinogens; Dose-Response Relationship, Drug; Life Tables; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

The induction of adenocarcinomas in the glandular stomach of the adult male Wistar rat by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was used as a model to study the expression of the growth promoting peptide, transforming growth factor alpha (TGF alpha), during experimental gastric carcinogenesis. TGF alpha was identified using the monoclonal antibody Ab-2 and standard immunohistochemistry, together with a semiquantitative assessment of the intensity of expression. Immunoreactivity was confined to the differentiated compartment of the mucosa while the carcinogen MNNG caused a significant increase in the intensity of TGF alpha expression (p < 0.01), after as little as 16 weeks' exposure. In experimental adenocarcinomas, a change to a previously undescribed pattern of perinuclear TGF alpha expression was found, which may represent the site of intense TGF alpha production in the Golgi apparatus after malignant transformation.

Topics: Adenocarcinoma; Animals; Immunohistochemistry; Intestinal Mucosa; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Wistar; Stomach Neoplasms; Transforming Growth Factor alpha

We have studied the effect of intragastric instillation of 4.5 M NaCl on cell proliferation and carcinogen penetration into the forestomach of Wistar rats at different time intervals after salt exposure. Cells in the S-phase were labelled by incorporation of bromodeoxyuridine and located after immunohistochemistry. N-[3H]Methyl-N'-nitro-N-nitrosoguanidine ([3H]MNNG) was used as the carcinogen and penetration of [3H]MNNG to proliferative cells was determined by autoradiography. The number of cells in S-phase per millimetre epithelium length 12 h and 24 h after salt exposure (32.2 +/- 11.9 and 20.6 +/- 7.4) was significantly higher than in the control animals (9.4 +/- 3.6). No increase in cell proliferation occurred during the first 2 h after salt exposure. Microscopy also revealed oedema in the lamina propia. The forestomach blood flow was not influenced by the application of hypertonic saline. [3H]MNNG at a concentration of 40 micrograms/ml did not penetrate to the proliferative cells in the forestomach and no effect of salt pretreatment on carcinogen penetration was seen. The low penetration of [3H]MNNG to proliferative cells in the forestomach epithelium may explain why this concentration of MNNG given in drinking water over several weeks usually does not induce squamous cell carcinomas in the forestomach. The previously observed cocarcinogenic effect of salt on squamous cell cercinogenesis in the upper gastrointestinal tract could be due to the observed increase in cell proliferation after salt exposure.

Topics: Animals; Autoradiography; Body Water; Cell Division; Cocarcinogenesis; Gastric Mucosa; Hypertonic Solutions; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; S Phase; Sodium Chloride; Stomach; Stomach Neoplasms

In experiment I, short-term effects of combined treatment with anti-oxidants, sodium ascorbate (NaAsA) and sodium nitrite (NaNO2) on forestomach cell proliferation were examined in F344 male rats. Groups of 5 animals aged 6 weeks were treated for 4 weeks with 0.8% catechol, 0.8% hydroquinone, 1% tert-butyl-hydroquinone (TBHQ), 2% gallic acid or 2% pyrogallor alone or in combination with 0.3% NaNO2 in the drinking water and/or 1% NaAsA in the diet. The thicknesses of forestomach mucosa in rats treated with anti-oxidants and NaNO2 in combination were greater than those with antioxidant alone and additional NaAsA treatment further enhanced the thickening of mucosa. It was noteworthy that values for mucosae of animals treated with NaNO2 and NaAsA without anti-oxidant were similar to those for anti-oxidants. In experiment 2, effects of combined treatment with NaAsA or ascorbic acid (AsA) and NaNO2 on carcinogenesis were examined in F344 male rats with or without N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) pre-treatment. Groups of 20 or 15 rats, respectively, aged 6 weeks, were given a single intra-gastric administration of 150 mg/kg body weight of MNNG in DMSO:water = 1:1 or the vehicle alone by stomach tube. Starting 1 week later, they received supplements of 1% NaAsA or 1% AsA in the diet and 0.3% NaNO2 in drinking water in combination, each of the individual chemicals alone, or basal diet until the end of week 52. In MNNG-treated animals, incidences of forestomach papillomas and carcinomas were significantly enhanced in the NaNO2 alone group (84 and 47%, respectively) as compared with the basal diet group (30 and 10%), with further significant increase in carcinomas occurring with additional NaAsA (79%, p < 0.05) or AsA (85%, p < 0.05) treatment. In animals without MNNG, all animals in the NaNO2 group demonstrated mild hyperplasia, additional administration of NaAsA or AsA remarkably enhancing the grade of hyperplasia, and resulting in 53% and 20% incidences, respectively, of papillomas. Thus NaNO2 was demonstrated to exert promoter action for forestomach carcinogenesis, with NaAsA and AsA acting as co-promoters. The results strongly indicate that combined treatment with NaAsA or AsA and NaNO2 may induce forestomach carcinomas in the long term.

Topics: Animals; Ascorbic Acid; Body Weight; Carcinoma, Squamous Cell; Drug Interactions; Kidney; Liver; Male; Methylnitronitrosoguanidine; Organ Size; Papilloma; Rats; Rats, Inbred F344; Sodium Nitrite; Stomach Neoplasms

A 1-ml dose of 4.5 M NaCl was given intragastrically to male Wistar rats at 10 min, 1 h, 4 h, 12 h, 24 h or 48 h before a single intragastric dose of 250 mg/kg N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). After 52 weeks the incidence of forestomach squamous cell carcinoma was 21% in control animals receiving MNNG alone. The cancer incidence in the forestomach varied with the time elapsed between application of NaCl and MNNG, and was significantly increased in animals pretreated with NaCl 4 h (43%), 12 h (54%) and 24 h (41%) before MNNG. These results show that salt has a cocarcinogenic effect on initiation of forestomach carcinogenesis in rats, and that this effect depends on the time interval between pretreatment with NaCl and application of MNNG. Gastric adenocarcinomas occurred more frequently in the antrum (78%) than in the corpus (22%). The incidence of gastric adenocarcinoma in animals pretreated with salt before application of MNNG (11%-22%) was not significantly influenced by the time elapsed between pretreatment with salt and application of MNNG, and did not differ from animals receiving MNNG alone (18%). The lack of a cocarcinogenic effect of NaCl on glandular gastric carcinogenesis might be due to the use of dimethyl/sulfoxide as solvent for MNNG.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Drug Administration Schedule; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Rats, Wistar; Saline Solution, Hypertonic; Stomach; Stomach Neoplasms

Green tea extract (GTE) inhibits obviously gastrointestinal malignant tumors in rats induced by N-methyl-N'-nitro-n-nitrosoguanidine (MNNG). The incidence of tumor was 93.3% in the MNNG positive control group, whereas 53.3% in the MNNG plus GTE group (P < 0.01). The percentage of inhibiting tumor growth was 88% (P < 0.001). N-nitrosoproline blockage test in 3 groups of 45 cases of patients from the highly prone to (gastric cancer people), examined with gastroscope and classified pathologically, revealed that GTE can block N-nitroso-proline synthesis in vivo, with blockage rate of 91% in superficial chronic gastritis (P < 0.001), 94% in intestinal metaplasia (P < 0.001) and 93% in atypical hyperplasia and gastric cancer (P < 0.001). Chemical analysis demonstrated that the main ingredients in GTE are catechols (with the content of 50%), vitamins and trace elements. The mechanism of GTE's cancer-inhibiting and cancer-preventing function might be that catechols combine with N-nitroso-compounds or resolve them, and reduce their carcinogenic activity. These results will be of great significance in preventing gastrointestinal cancer.

Topics: Animals; Gastric Mucosa; Humans; Male; Methylnitronitrosoguanidine; Nitrosamines; Plant Extracts; Rats; Rats, Sprague-Dawley; Stomach Neoplasms; Tea

The activity of a DNA repair enzyme, O6-alkylguanine-DNA alkyltransferase (AGT), was studied in gastric mucosa of 15 Macaca fascicularis monkeys before and during chronic oral exposure to the ethylating carcinogen N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) in order to investigate possible causes of inter-individual differences in susceptibility to its gastrocarcinogenic effect. A wide range of AGT activity (307-1903 fmol/mg protein, mean 695) was found before treatment and it decreased during the first year of exposure (means 627, 479 and 452 fmol/mg protein respectively at 6, 12 and 18 months after the beginning of the experiment). The carcinogenesis study is under way and to date four monkeys with low initial AGT level in gastric mucosa died of gastric cancer. The relevance of AGT level measurement for prediction of individual susceptibility to ENNG is discussed.

Topics: Administration, Oral; Animals; Carcinogens; Female; Gastric Mucosa; Macaca fascicularis; Male; Methylnitronitrosoguanidine; Methyltransferases; O(6)-Methylguanine-DNA Methyltransferase; Stomach Neoplasms

Topics: Animals; Anticarcinogenic Agents; Antioxidants; Benzodioxoles; Butylated Hydroxyanisole; Caffeic Acids; Carcinogens; Carcinoma; Catechols; Cell Division; Hydroquinones; Kidney Neoplasms; Male; Maleates; Methylnitronitrosoguanidine; Organ Specificity; Papilloma; Phenols; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

The methylation patterns of the rat pepsinogen 1 (Pg1) gene in preneoplastic and neoplastic stomach lesions induced by genotoxic N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or the non-genotoxic carcinogen catechol were investigated. Male WKY/Ncrj rats were given MNNG in their drinking water (50 mg/l) for 30 weeks or 0.8% catechol throughout the experiment (60 weeks). MNNG induced Pg1 altered pyloric glands (PAPG), adenomatous hyperplasias and well-differentiated adenocarcinomas. Catechol also induced PAPG and adenomatous hyperplasias although cancers did not develop. Adenomatous hyperplasias and adenocarcinomas all consisted of gastric type cells resembling surface mucous cells or pyloric gland cells with little or no Pg1 expression. In MNNG-induced stomach cancers generally lacking Pg1, altered Pg1 gene methylation was observed with both CCGG and GCGC sites being methylated more than normal pyloric mucosa. MNNG or catechol-induced adenomatous hyperplasias also demonstrated essentially the same methylation changes in the CCGG, but not in the GCGC sites. In the mucosa containing PAPG in groups treated with MNNG or catechol the methylation patterns of the Pg1 gene were quite similar to those of normal pyloric mucosa, although the CCGG sites tended to demonstrate slightly increased methylation. The results suggest that the altered methylation of the Pg1 gene observed in stomach cancers is acquired early in the carcinogenic process and progressive methylation changes occur with tumor development.

Topics: Adenocarcinoma; Animals; Catechols; DNA; Gastric Mucosa; Hyperplasia; Male; Methylation; Methylnitronitrosoguanidine; Pepsinogens; Precancerous Conditions; Rats; Rats, Inbred WKY; Stomach; Stomach Neoplasms

Male Wistar rats were treated concurrently with a combination of the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; CAS 70-25-7) and the polyamine-synthesis inhibitor alpha-difluoromethylornithine (DFMO) at two different doses of 0.5% and 1.0% (w/v). Experimental groups were treated with (I) MNNG alone (n = 25), (II) MNNG plus 0.5% (w/v) DFMO (n = 25), (III) MNNG plus 1.0% (w/v) DFMO (n = 25), (IV) 1.0% (w/v) DFMO alone (n = 25). Group V represented untreated controls (n = 20). Both the carcinogen and DFMO were administered in drinking water. The treatment time with the carcinogen and DFMO was 35 weeks. After treatment was completed animals were followed for an additional 50 weeks to cover a total observation time of 85 weeks. Significantly fewer animals developed gastric adenocarcinoma in the two groups of animals that received a combined treatment of MNNG plus DFMO compared to animals treated with the carcinogen alone (P < 0.05 and 0.005). No benign or malignant neoplastic lesions were observed in the stomach or duodenum of animals treated with DFMO alone or in untreated controls. It is concluded that concurrent treatment with DFMO prevents the development of malignant gastric epithelial tumors induced by MNNG in rats.

Topics: Adenocarcinoma; Adenoma; Animals; Cell Transformation, Neoplastic; Duodenal Neoplasms; Eflornithine; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Sarcoma, Experimental; Stomach Neoplasms

The affects of L-thyroxine (T4) on the incidence and histology of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and on the labelling index of gastric mucosal epithelial cells were investigated in Wistar rats. After oral treatment with MNNG for 25 weeks, the rats received s.c. injections of T4 (0.2 microgram kg-1) in depot form every other day until the end of the experiment in Week 52. This long-term treatment with T4 significantly increased the incidence of gastric cancers in Week 52. However, it did not influence the histological type of the gastric cancers. It also caused significant increases in the labelling indices of the fundic and antral epithelial cells. These findings indicate that T4 enhances the development of gastric cancers, and that its effect may be related to its effect in increasing proliferation of gastric epithelial cells.

Topics: Administration, Oral; Animals; Cell Division; Drug Synergism; Epithelial Cells; Injections, Subcutaneous; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Thyroxine; Time Factors; Triiodothyronine

Male Wistar rats were treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) either as a single dose of 50, 125 or 250 mg/kg given by gavage or via drinking water for 28 weeks at a concentration of 40, 80 or 160 micrograms/ml, in the case of the higher concentration reverting to 80 micrograms/ml after the first 8 weeks. The single dose regimen had no effect on water intake or body weight, but the chronic exposure led to a dose-dependent reduction in water intake that was paralleled by a slower weight gain, with the final body weights at approximately 90, 84 and 79% of the control weight values. The combined yield of benign and malignant tumours (79-100% of the animals treated) occurred in the forestomach in the case of the single doses, whereas the chronic exposure resulted in a maximum yield of tumours located in the pyloric region of the glandular stomach (64-100% of animals treated). The principal histological types of tumours induced were squamous cell papilloma and carcinoma in the forestomach and adenocarcinoma in the pylorus. There was a persistent, but low yield (25-30% of animals treated) of tumours in the jejunum, mainly adenocarcinoma, after administration via drinking water, whereas after single doses, multiple solitary cysts and cholangioma (30% and 25-70% respectively of the animals treated) were found in the liver. This report differs from earlier reports in that marked effects were noted on water consumption and body weight gain and that tumour induction can be achieved after much shorter periods of exposure than previously reported in the literature. These data confirm the tissue specificity of MNNG when given either as a single or chronic dose regimen and provide a suitable model for the investigation of the target cell specificity of tumour induction.

Topics: Adenocarcinoma; Adenoma; Administration, Oral; Animals; Body Weight; Dose-Response Relationship, Drug; Drinking; Drug Administration Schedule; Duodenal Neoplasms; Gastrointestinal Neoplasms; Jejunal Neoplasms; Liver Neoplasms, Experimental; Male; Methylnitronitrosoguanidine; Pylorus; Rats; Rats, Wistar; Stomach Neoplasms

N-Methyl-N-nitro-N'-nitrosoguanidine (MNNG) is a gastric carcinogen in several animal species and has been used in a number of systems to dissect the co-carcinogenic potential of various compounds in the induction of gastric adenocarcinoma. Recent epidemiological evidence suggests that Helicobacter pylori may play a role as a co-carcinogen in the etiology of this tumor in humans and we have been interested in developing an animal model to study this possibility. A related organism, H. mustelae, naturally colonizes the ferret stomach and causes persistent chronic gastritis. The pathology elicited by H. mustelae in ferrets has many similarities with the human disease including different stages of multifocal atrophic gastritis which underlie the gastric ulcer and gastric carcinoma syndrome. There is little evidence, however, demonstrating the susceptibility of ferrets toward chemical carcinogenesis. We have consequently undertaken a study to ascertain whether 10 6-month-old female ferrets given a single oral dose of MNNG (50-100 mg/kg) would develop adenocarcinoma of the stomach. Five age-matched unmanipulated control animals were included for comparative purposes. All 15 ferrets were infected with H. mustelae. Nine of 10 ferrets dosed with MNNG developed gastric adenocarcinoma (29-55 months after dosing), while none of the five historical control ferrets examined an average of 63 months after the initiation of the study developed gastric tumors. By comparison, we have not observed gastric adenocarcinoma, nor has it been reported, in > 10 years of observation of untreated ferrets naturally infected with H. mustelae. The H. mustelae-infected ferret, with demonstrated susceptibility to a gastric carcinogen, plus the recent availability of specific pathogen-free ferrets, should now allow longitudinal studies in vivo to probe the role of Helicobacter in the development of gastric cancer.

Topics: Adenocarcinoma; Animals; Biopsy; Cocarcinogenesis; Disease Models, Animal; Female; Ferrets; Gastritis; Helicobacter Infections; Longitudinal Studies; Methylnitronitrosoguanidine; Pyloric Antrum; Stomach; Stomach Neoplasms

The effects of ad libitum feeding of calcium-deficient diet on the incidence, number and histological types of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in male Wistar rats. Rats were fed standard pellet diet containing 0.5% (normal-calcium diet) or 0.01% calcium (calcium-deficient diet) after oral treatment with MNNG for 25 weeks. Oral administration of the calcium-deficient diet resulted in a significant increase in the incidence, but not the number, of gastric cancers in experimental Week 52. However, it did not affect the histological types of cancer. The calcium-deficient diet also caused a significant increase in tissue norepinephrine concentration of the antral portion of the gastric wall and in the labeling index of the antral epithelial cells. These findings indicate that the calcium-deficient diet enhanced gastric carcinogenesis and suggest that its effect may be related to increase in norepinephrine in the gastric wall and consequent stimulation of proliferation of antral epithelial cells.

Topics: Adenocarcinoma; Administration, Oral; Animals; Body Weight; Calcium, Dietary; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Norepinephrine; Rats; Rats, Wistar; Stomach Neoplasms

Short-term assays in vivo have suggested that hickory smoke condensate (HSC), a food flavouring, might have tumour-initiating and/or promoting activities in the glandular stomach of the rat. In the present study, the modifying effects of HSC on glandular stomach carcinogenesis after initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and sodium chloride (MNNG salt) were investigated in male Wistar rats. Animals were given MNNG solution (100 ppm) as drinking water and simultaneously fed the diet supplemented with 5% sodium chloride for 8 wk. Matched negative controls received neither MNNG nor sodium chloride. Rats were then fed a basal diet and given HSC solution (1 or 3%) or tap water for the following 32 wk. During the experimental period, treatment with MNNG salt and administration of HSC both brought about growth retardation although the final body weight of rats was comparable between groups. Only two rats treated with MNNG salt followed by 1% HSC developed adenocarcinoma of the stomach. HSC treatment appeared to increase the number of rats with preneoplastic hyperplasias and/or adenocarcinomas in both the fundic and pyloric mucosa, although not to a statistically significant extent. HSC administration significantly increased malondialdehyde levels in the urine and gastric mucosa, the former in a dose-dependent manner. The results suggest that HSC has little, if any, promoting effect on two-stage glandular stomach carcinogenesis in rats when given during the post-initiation phase. However, the tumour co-initiating effects of HSC require further clarification.

Topics: Adenocarcinoma; Animals; Diet; Drinking; Flavoring Agents; Gastric Mucosa; Hyperplasia; Male; Malondialdehyde; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Wistar; Smoke; Sodium Chloride; Stomach Neoplasms; Weight Gain; Wood

The effects of amiloride on the incidence and histological types of gastric cancers in Wistar rats induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and on the labelling index and proliferative fraction of gastric mucosa were investigated. After oral treatment with MNNG for 25 weeks, rats received s.c. injections of amiloride (0.25 mg kg-1 or 5.0 mg kg-1 body weight) in depot form every other day until the end of the experiment. Prolonged administration of 5.0 mg kg-1, but not 2.5 mg kg-1 of amiloride significantly decreased the incidence of gastric cancers in Week 52. However, it did not influence the histological features of the gastric cancers. It also significantly decreased the labelling index and proliferative fraction of the antral mucosa. These findings indicate that amiloride inhibits the development of gastric cancers, and that its effect may be related to its effect in decreasing cell proliferation of the antral mucosa.

Topics: Adenocarcinoma; Amiloride; Animals; Cell Division; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms

Variations in the activity of a DNA repair enzyme 0(6)-alkylgianine-DNA alkyltransferase (AGT) were studied in gastric mucosa samples obtained from 15 M. fascicularis monkeys chronically exposed to a gastrocarcinogen N-ethyl-N'-nitro-N-nitrosoguanidine. Marked interindividual difference in the enzyme activity before and in the course of the exposure was observed. The value of AGT activity assay to predict individual susceptibility to alkylating carcinogens is discussed.

Topics: Animals; Biopsy; Carcinogens; DNA Repair; Female; Gastric Mucosa; Leukocytes; Macaca fascicularis; Male; Methylnitronitrosoguanidine; Methyltransferases; O(6)-Methylguanine-DNA Methyltransferase; Stomach Neoplasms; Time Factors

To challenge the theory of tissue specificity of tumor promoters, the biochemical and tumor promoting effects of okadaic acid (OA), a potent tumor promoter on mouse skin, were studied in the mucosa of rat glandular stomach. OA strongly inhibited protein phosphatases 1 and 2A, and increased 4-fold the phosphorylation of elongation factor 2 in vitro in the mucosa. Intubation of 10 micrograms (12.4 nmol) OA induced ornithine decarboxylase in the mucosa. Tumor promotion of OA was studied in the glandular stomach initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in a two-stage carcinogenesis experiment. OA in drinking water, 10 micrograms (12.4 nmol) per rat per day from weeks 9-55 of the experiment, and 20 micrograms (24.8 nmol) from weeks 56-72, significantly enhanced development of the neoplastic changes in the glandular stomach (P < 0.05). The neoplastic changes included adenomatous hyperplasias and adenocarcinomas, both of which correspond to papillomas and carcinomas in a two-stage mouse skin carcinogenesis experiment. The percentages of neoplastic change-bearing rats of the groups treated with MNNG plus OA, MNNG alone or OA alone were 75.0, 46.4 and 0% respectively. OA enhanced tumorigenesis in the MNNG-initiated glandular stomach of rats through the same mechanisms of action as in mouse skin. The OA pathway mediated through inhibition of protein phosphatases 1 and 2A is applicable to various organs as a general mechanism of tumor promotion.

Topics: Animals; Body Weight; Carcinogens; Enzyme Induction; Ethers, Cyclic; Female; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Okadaic Acid; Organ Specificity; Ornithine Decarboxylase; Phosphoprotein Phosphatases; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Stomach; Stomach Neoplasms

Pathohistological studies of resected human stomachs and of experimental gastric cancers induced by ENNG have revealed that undifferentiated carcinomas arise at the neck region of glandular tubules both in the fundic and the pyloric mucosa, and tumor cells disclose the earliest invasion in the lamina propria by dripping from the glandular tubule. At earlier stages, the carcinoma cells tend to be confined to the middle level of the mucosa, and they extend to the horizontal direction of the mucosa. Most carcinomas at earlier stages comprise the diploid cell line. When tumors grow beyond a size of 2 cm in diameter in the mucosal layer, they begin to invade into the submucosal layer. As tumors grow, aneuploid and polyploid cancer cells arise in the diploid cell population. This is a kind of tumor progression. Aneuploid cancer cells disclose a more invasiveness, and they are ready to invade into the deep layer of the gastric wall. Scirrhous cancers are mostly composed of aneuploid cells, and it is suggested that small mucosal cancers which exclusively consist of aneuploid cells may become scirrhous cancers in a relatively short period.

Topics: Adenocarcinoma, Mucinous; Animals; Cell Division; DNA, Neoplasm; Dogs; Humans; Methylnitronitrosoguanidine; Ploidies; Stomach Neoplasms

Effects of dietary bile acids and their sodium salts on the development of pepsinogen-altered pyloric glands (PAPG) were examined in male WKY/N Crj rats initially given a single dose of 160 mg/kg body weight of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) by gastric intubation. From week 3 the animals were administered basal diet containing 0.5% supplements of cholic acid (CA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA) or their sodium salts (Na-C, Na-DC and Na-CDC), or 5% ascorbic acid (ASA) or its salt (Na-AS) for 18 weeks. The concentration of DCA and Na-DC was reduced to 0.3% from week 12. At week 20, animals were killed and the numbers of immunohistochemically-demonstrated PAPG were determined. Values were significantly higher with Na-C and Na-CDC than with the corresponding parent acids, and in the Na-C case PAPG development was greater than with MNNG alone. In addition, Na-CDC itself induced the numbers of PAPG significantly. These results suggest that bile salts are possible intrinsic promoters of gastric carcinogenesis. They were without effect, however, on forestomach lesions.

Topics: Animals; Bile Acids and Salts; Carcinoma; Drug Synergism; Male; Methylnitronitrosoguanidine; Pylorus; Rats; Rats, Inbred WKY; Stomach Neoplasms

Glyrrhiza Uralensis (GU) and Chelidonium Majus (CM) are two kinds of Chinese herbal medicine. GU and CM not only exert much stronger effects in blocking mutagenesis due to strains of Salmonella typhimurium (TA 97, TA 98, TA 100, TA 102), but also have different degrees of obstructing mutagenesis induced by Furapromidum (F30066), Zhengdingmycin Hydrochloride (DM), N-methyl-N1-nitro-N-nitrosoguanidine (MNNG) and Methyl-methanesulfonate (MMS). The blockage effect of GU and CM obviously depends on the doses used. GU and CM could also impede the occurrence of stomach cancer induced by MNNG, and the impeding rate is about sixty percent.

Topics: Aflatoxin B1; Animals; Antineoplastic Agents, Phytogenic; DNA Damage; Drugs, Chinese Herbal; Female; Glycyrrhiza; Male; Methylnitronitrosoguanidine; Mutagenesis; Plants, Medicinal; Rats; Rats, Inbred Strains; Salmonella typhimurium; Stomach Neoplasms

Promotion effects of the o-dihydroxybenzene derivatives, protocatechuic acid (PCA), dopamine hydrochloride (DAH), dl-dopa and caffeic acid on forestomach and glandular stomach carcinogenesis were investigated in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Groups of 20 male F344 rats were given a single intragastric administration of 150 mg/kg body wt MNNG and starting 1 week later than received diet containing 1.5% PCA, 1.5% DAH, 1.5% dl-dopa or 1% caffeic acid or basal diet alone for 51 weeks and then killed. Other groups of 10-15 rats were given PCA, DAH, dl-dopa or basal diet alone without the MNNG pretreatment. On histological assessment, the incidences of forestomach papillomas and squamous cell carcinomas were significantly enhanced in the group treated with caffeic acid (95 and 100%) as compared with the control values (35 and 10%). Although the incidence was not different, the number of papillomas per rat in the group given DAH (0.79 +/- 0.79) was also significantly increased (0.35 +/- 0.49). PCA and dl-dopa treatments did not modify the development of neoplastic lesions in the forestomach epithelium to any significant extent. None of the four chemicals enhanced glandular stomach carcinogenesis. The results thus demonstrated that whereas caffeic acid and DAH respectively, exert strong and weak promotion activity for rat forestomach carcinogenesis this promotion potential is not shared by all dihydroxybenzene derivatives. An influence of substituents in the para position in addition to the o-dihydroxy moiety is indicated.

Topics: Adenocarcinoma; Animals; Body Weight; Caffeic Acids; Carcinogens; Carcinoma, Squamous Cell; Dihydroxyphenylalanine; Dopamine; Drug Synergism; Epithelium; Hydroxybenzoates; Hyperplasia; Leiomyosarcoma; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

Hickory-smoke condensate (HSC) is a popular food flavouring in the USA. Available data have suggested that this food additive has tumour-initiating/promoting potential. Accordingly, a commercial HSC has been investigated for its capacity to promote tumours in the rat glandular stomach using pepsinogen 1 (Pg 1)-altered pyloric glands (PAPG) as the marker of preneoplastic lesions. The development of PAPG initiated by a single intragastric administration of N-methyl-N'-nitroso-N-nitrosoguanidine was significantly increased by feeding rats a diet containing 5% HSC; no effect was observed with lower doses (1.25 or 2.5%) of HSC. The results suggest that HSC has weak tumour-promoting potential in the rat glandular stomach.

Topics: Animals; Atrophy; Food Additives; Gastric Mucosa; Hyperplasia; Immunoenzyme Techniques; Male; Methylnitronitrosoguanidine; Pepsinogens; Pyloric Antrum; Rats; Rats, Inbred WKY; Smoke; Stomach Neoplasms; Wood

The effects of chemical sympathectomy induced by 6-hydroxydopamine (6-OHDA) on the enhanced induction of gastric carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in spontaneously hypertensive rats (SHR), and the norepinephrine (NE) concentrations in their gastric wall and the labeling index of gastric epithelial cells were investigated. SHR rats and normotensive Wistar Kyoto rats (WKY) as controls were given MNNG (25 micrograms/ml) in their drinking water for 25 weeks and then i.p. injections of 6-OHDA (42 mg/kg twice within 24 hr, and then 105 mg/kg every 2 weeks from 1 week later). In control group (WKY rat + NaCl), gastric cancers were found in 2 (11%) of 18 rats examined in week 52. In SHR rats treated with NaCl solution only, the incidence of gastric cancers significantly increased, to 53% compared with that in control WKY rats. Treatment of SHR rats with 6-OHDA significantly decreased its incidence to 12% compared with the value in SHR rats treated with NaCl solution only. Prolonged administration of 6-OHDA to SHR rats significantly reduced the NE concentration in the antral portion of the gastric wall and the labeling index of antral epithelial cells. These findings indicate that prolonged i.p. treatment with 6-OHDA attenuated the normally higher incidence of MNNG-induced gastric cancer in SHR rats.

Topics: Animals; DNA; Gastric Mucosa; Hydrogen-Ion Concentration; Hypertension; Methylnitronitrosoguanidine; Norepinephrine; Oxidopamine; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Stomach Neoplasms

Four carotenoids, canthaxanthin, beta-carotene, 8H-apo-beta-carotenal, and 8'-apo-beta-carotene methylester were tested for their ability to suppress the mutagenicity of 1-methyl-3-nitro-1-nitrosoguanidine and benzo[a]pyrene (BP) in Salmonella typhimurium tester strain TA 100. The anticarcinogenic efficacy of the four carotenoids was further assessed in the BP-induced forestomach tumor model in female Swiss mice. The effect of dietary palm oil was also examined in BP-induced neoplasia in the female Haffkine Swiss mouse strain. Canthaxanthin, beta-carotene, 8'-apo-beta-carotenal, and 8'-apo-beta-carotene methylester showed a dose-dependent decrease in the mutagenicity compared with 1-methyl-3-nitro-1-nitrosoguanidine and BP in strain TA 100. In the BP-induced forestomach tumor model, all four carotenoids showed a similar significant anticarcinogenic effect. Dietary administration of palm oil showed a dose-dependent antitumor activity in the animals. Our results show that the intrinsic antimutagenic and anticarcinogenic properties of the carotenoids are not significantly influenced by their conversion to vitamin A.

Topics: Animals; Anticarcinogenic Agents; Antimutagenic Agents; Benzo(a)pyrene; Carotenoids; Dietary Fats, Unsaturated; Female; Methylnitronitrosoguanidine; Mice; Mutagenicity Tests; Palm Oil; Plant Oils; Salmonella typhimurium; Stomach Neoplasms; Time Factors

The effects of prolonged administration of the gamma-aminobutyric acid receptor agonist muscimol on enhanced induction of gastric carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in spontaneously hypertensive rats (SHR), and on the norepinephrine concentration in the gastric wall and the labeling index of gastric mucosa were investigated. SHR and normotensive Wistar Kyoto (WKY) rats as controls were given a solution of MNNG (25 micrograms/ml) for 25 weeks and then i.p. injections of 0.5 mg/kg body weight of muscimol every other day. In control WKY rats, gastric cancers were found in 1 (7%) of 14 rats examined at week 52. In SHR treated with NaCl solution only, the incidence of gastric cancers was significantly increased to 50% compared with that in control WKY rats. However, treatment of SHR with muscimol significantly increased its incidence to 12% compared with the value in SHR treated with NaCl solution only. The norepinephrine concentration in the gastric wall and the labeling index of the gastric mucosa were significantly greater in SHR than in WKY rats. Prolonged administration of muscimol to SHR significantly reduced the norepinephrine concentration in the antral portion of the gastric wall or the labeling index of the antral epithelial cells. These findings indicate that long-term treatment of SHR with muscimol attenuated the enhancement of gastric carcinogenesis in SHR.

Topics: Analysis of Variance; Animals; Chi-Square Distribution; Gastric Fundus; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Muscimol; Norepinephrine; Pyloric Antrum; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Stomach Neoplasms

Helicobacter pylori (HP) has been shown to possibly be a pathogen of gastric carcinoma. HP has urease activity and produces ammonia in the stomach. In this study, the role of ammonia on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in rats. After 24 weeks pretreatment with MNNG (83 mg/l), 0.01% ammonia or tap water as a drinking water was administered for 24 weeks. The ammonia-treated rats showed a significantly higher incidence of gastric cancer (percent of animals with tumors and number of tumors per rat). Ammonia would thus appear to have an important role in HP-related human gastric carcinogenesis.

Topics: Adenocarcinoma; Administration, Oral; Ammonia; Animals; Cell Transformation, Neoplastic; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The mechanisms of reversibility of basal cell hyperplasia in the rat forestomach were investigated. Male F344 rats were given an initial single gastric intubation of N-methyl-N'-nitro-N-nitorosoguanidine and then received 2% butylated hydroxyanisole in the diet from the third week to the 26th week. Rats were killed at weeks 26 and 46 after return to basal diet and their forestomachs were removed. Bromouracil deoxyriboside (BUdR) was administered as a single i.p. injection 1 h before death or by osmotic minipump (120 micrograms/h) continuously for 7 days before death. Additional animals were maintained for 2 or 4 weeks after removal of osmotic minipumps to allow assessment of the fate of proliferating populations. In each case BUdR-labeled cells were demonstrated by immunohistochemistry by immunohistochemistry. At week 26, hyperplastic changes were more pronounced than at week 46. Squamous cells above basal cell hyperplasias were strongly labeled even 4 weeks after cessation of continuous BUdR Three-dimensional reconstruction of persisting basal cell hyperplasias showed almost all basal cells limited to a thin sheet in direct contact with the squamous cell layer, occasional separate islands demonstrating differentiation to squamous cells and formation of epidermal cysts. The results thus showed that the mechanism of reversibility of basal cell hyperplasia involves differentiation of basal cells to squamous cells.

Topics: Animals; Bromodeoxyuridine; Butylated Hydroxyanisole; Carcinoma, Basal Cell; Carcinoma, Squamous Cell; Cell Differentiation; Cell Transformation, Neoplastic; Gastric Mucosa; Hyperplasia; Image Processing, Computer-Assisted; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

The effects of the opioid receptor agonists methionine-enkephalin (Met-ENK) and leucine-enkephalin (Leu-ENK) on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in Wistar rats. After 25 weeks of oral treatment with the carcinogen, the rats received subcutaneous injections of Met-ENK (20 micrograms/kg) or Leu-ENK (20 micrograms/kg) once every 2 days. The prolonged administrations of Met-ENK and Leu-ENK significantly increased the incidence of gastric cancers in week 52. Treatments with these opioid receptor agonists significantly increased the labeling index of the antral mucosa. These findings indicate that opioids enhance gastric carcinogenesis and suggest that their effects may be related to their influence on increasing proliferation of the antral epithelial cells.

Topics: Animals; Carcinoma; Cell Division; Drug Synergism; Enkephalin, Leucine; Enkephalin, Methionine; Gastric Mucosa; Gastrins; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effects of vaso-active intestinal peptide (VIP) on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in Wistar rats given VIP every other day for 27 weeks after oral administration of MNNG for 25 weeks. In week 52, administration of VIP caused a significant increase in the incidence of gastric cancers, but did not influence their histological appearance. VIP significantly increased the labeling indices of the antral mucosa. Our findings indicate that VIP enhances gastric carcinogenesis, and that this effect may be related to its effect in increasing cell proliferation of the antral epithelial cells.

Topics: Animals; Drug Synergism; Gastric Juice; Gastrins; Hyperplasia; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms; Vasoactive Intestinal Peptide

The effects of the dopamine agonist 2-bromo-alpha-ergocryptine methanesulfonate (bromocriptine) on the incidence, number and histology of gastric cancer induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in Wistar rats. Rats were given 1 or 2 mg kg-1 body weight of bromocriptine subcutaneously every other day in depot form after 25 weeks of oral treatment with MNNG. Prolonged administration of bromocriptine at both dosages every other day resulted in a significant increase in the incidence and number of gastric cancers of the glandular stomach by week 52. Bromocriptine treatment did not influence the histological type of gastric cancer, but caused a significant increase in the labelling index of epithelial cells of the antrum. These findings indicate that the dopamine agonist bromocriptine promotes gastric carcinogenesis, and that this effect may be related to its effect in increasing proliferation of epithelial cells in the antral mucosa.

Topics: Adenocarcinoma; Animals; Bromocriptine; Dopamine; Epinephrine; Gastric Mucosa; Gastrins; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Norepinephrine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of gamma-butyrolactone (GBL) on inhibition by baclofen of gastric carcinogenesis was investigated in Wistar rats. In week 52, baclofen significantly decreased the incidence of gastric cancers. Concomitant treatment with GBL significantly increased gastric acid secretion but had no influence on the inhibition by baclofen of gastric carcinogenesis. This finding suggest that GBL significantly increased the sensitivity of gamma-aminobutyric acid (GABA) receptor to GABA mimetics in gastric acid secretion but not in the inhibitory effect of gastric carcinogenesis.

Topics: 4-Butyrolactone; Animals; Baclofen; DNA; Gastric Juice; Gastrins; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Secretory Rate; Stomach Neoplasms

The effects of chemical sympathectomy induced by 6-hydroxydopamine (6-OHDA) and administration of the acetylcholinesterase inhibitor neostigmine, singly or together, on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and on the tissue catecholamine concentration of the gastric wall and the labeling index of the gastric mucosa, were investigated in inbred Wistar rats. Rats received s.c. injections of neostigmine (0.075 mg/kg), and/or i.p. injections of 6-OHDA (42 mg/kg twice within 24 hr, and then 105 mg/kg every 2 weeks from 1 week later) 25 weeks after oral treatment with MNNG. Prolonged administration of 6-OHDA or neostigmine significantly reduced the incidence of gastric cancers by week 52, and in combination they had a significantly greater inhibitory effect. 6-OHDA and/or neostigmine had no influence on the histology of gastric cancers. Administration of 6-OHDA, but not neostigmine, significantly decreased the norepinephrine concentration in the antral portion of the gastric wall. The labeling index of the antral mucosa was decreased significantly by treatment with 6-OHDA or neostigmine, and decreased even more significantly by 6-OHDA plus neostigmine. Our findings indicate that 6-OHDA and neostigmine have protective effects against gastric carcinogenesis and that in combination their effects are additive. These results imply that the activities of the sympathetic and parasympathetic autonomic systems together influence gastric carcinogenesis.

Topics: Animals; Drug Interactions; Gastric Fundus; Gastric Mucosa; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Neostigmine; Norepinephrine; Oxidopamine; Pyloric Antrum; Rats; Rats, Inbred Strains; Stomach Neoplasms

The purpose of this study was to investigate the effect of long-term misoprostol administration, at non-antisecretory doses, on N-methyl-N'-nitro-N-nitrosoguanidine(MNNG)-induced gastric carcinogenesis. The incidence of gastric carcinomas and precancerous lesions was evaluated in 50 male 250-g Sprague-Dawley rats after 52 weeks of continuous oral administration of MNNG (120 mg/l; n = 20), MNNG plus misoprostol (2 mg kg-1 day-1; n = 20) or tap water (n = 10) (experiment 1), and in 30 rats treated with MNNG for 30 weeks followed by tap water (n = 15) or by misoprostol (n = 15) for 22 weeks; a third group (n = 10) received tap water only for 52 weeks (experiment 2). After sacrifice, gastric mucosal lesions were macroscopically evaluated and their histology obtained. MNNG consumption was comparable in all groups (6.5 +/- 1.1 mg rat-1 day-1). Misoprostol consumption was 180 +/- 0.25 mg kg-1 day-1 rat-1. In experiment 1 the incidence of gastric carcinomas was 60% in the MNNG group and 25% in the group treated with MNNG plus misoprostol (P less than 0.05). Cytotoxic and hyperplastic gastric mucosal lesions were also significantly reduced by misoprostol. In experiment 2 the incidence of carcinomas was 31% and 38.6% respectively. Misoprostol significantly decreased the incidence of gastric cancer formation when given from the beginning of the experiment. By contrast, when administered after 30 weeks of MNNG treatment it did not interfere with experimental gastric cancer formation. Exogenous prostaglandins are able to prevent the early MNNG-induced gastric mucosal lesions, thus interfering with gastric carcinogenesis.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Cell Nucleus; Cystadenocarcinoma; Male; Methylnitronitrosoguanidine; Misoprostol; Rats; Rats, Inbred Strains; Stomach Neoplasms; Time Factors

The development of carcinoma was examined in male Wistar rats (n = 120) exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water (83 micrograms/ml) for 16 weeks. After MNNG administration, rats were investigated by endoscopic observation, visualization of microvascular structure, and estimation of lectin binding sites. Changes of bile reflux to the stomach was observed endoscopically at 24 weeks as well as the development of gastric mucosal erosions. Protruding and expansive ulcerating carcinomas developed at 36 weeks and had a microvascular pattern similar to that of human adenocarcinoma. Estimation of lectin binding site and pattern was useful to evaluate the malignant potential of cell proliferation. We postulate that endoscopic observation is valuable in investigating the development of gastric carcinoma, and microvascular structure and lectin binding pattern may be useful to demonstrate the mechanism of growth of gastric carcinoma.

Topics: Animals; Binding Sites; Cell Transformation, Neoplastic; Disease Models, Animal; Gastric Mucosa; Lectins; Male; Methylnitronitrosoguanidine; Protein Binding; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effects of calcium chloride on glandular stomach carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and sodium chloride were investigated in male outbred Wistar rats. Animals were given MNNG solution (100 p.p.m.) as drinking water and simultaneously fed a diet supplemented with 5% sodium chloride for 8 weeks. Matched negative controls received neither MNNG nor sodium chloride. Rats were then fed basal diet and given calcium chloride solution (1 or 0.2%) or tap water for the following 52 weeks. The incidences and multiplicities of preneoplastic hyperplasias in the glandular stomachs of rats given MNNG/sodium chloride followed by 1 and 0.2% calcium chloride were significantly lower than those in rats given MNNG/sodium chloride alone. The inhibitory effects of calcium were exerted in a dose-dependent manner. Calcium treatment also showed a tendency to inhibit the development of gastric adenocarcinomas although this was not statistically significant. Rats without carcinogen treatment had neither carcinomas nor preneoplastic hyperplasias in the glandular stomach. Calcium intake also significantly reduced the levels of malondialdehyde, a measure of lipid peroxidation, in the gastric mucosa and urine, the former in a dose-dependent manner. Thus, calcium chloride exerted inhibitory effects when given during the post-initiation phase of two-stage glandular stomach carcinogenesis in rats.

Topics: Animals; Antineoplastic Agents; Calcium Chloride; Carcinogens; Gastric Mucosa; Hyperplasia; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Inbred Strains; Sodium Chloride; Stomach Neoplasms

Effects of sodium chloride (NaCl) and ethanol on gastric tumor development in rats after treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were studied. MNNG, dissolved in distilled water (5 g/liter), was administered orally once by gastric tube at a dose of 0.25 ml/10 g body weight to 4-week-old ACI rats. After this carcinogen initiation, animals were fed on a diet containing 10% NaCl (Group 2) or normal diet with 10% ethanol in the drinking water (Group 4). MNNG alone (Group 1), NaCl alone (Group 3), ethanol alone (Group 5), and control (Group 6) animals were also maintained. All survivors were killed one year after the MNNG application. Incidences of tumors in the forestomach and glandular stomach were significantly increased in Group 2 as compared to Group 1 (P less than 0.05). The height of the pyloric mucosa was significantly greater in Group 2 than in Groups 4, 5 or 6 (P less than 0.05). In the fundic area, the mucosal height was significantly decreased in Group 4 as compared to Group 6 (P less than 0.05). The present results demonstrate that whereas tumors in the glandular stomach and forestomach are both promoted by NaCl, ethanol is without influence. Furthermore, NaCl, a promoter of glandular stomach tumorigenesis also increases cell proliferation.

Topics: Animals; Body Weight; Carcinogens; Carcinoma, Squamous Cell; Ethanol; Gastric Mucosa; Intestinal Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Organ Size; Rats; Rats, Inbred Strains; Sodium Chloride; Stomach Neoplasms

The effects of combined administration of bombesin and the ornithine decarboxylase (ODC) inhibitor 1,3-diaminopropane (DAP) on the incidence and number of gastric tumors induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), the ODC activity of the gastric wall and the labelling index of the gastric mucosa were investigated in inbred Wistar rats. Rats were given drinking water containing MNNG (50 micrograms/ml) for 25 weeks and then drinking water containing DAP (2.5 g/l) and/or injections of 40 micrograms/kg body weight of bombesin in depot form every other day. Administration of bombesin alone resulted in significant increases in the incidence of gastric cancers, the ODC activity of the antral portion of the gastric wall and the labelling index of the antral mucosa. Administration of DAP with bombesin significantly reduced enhancement by the latter of gastric carcinogenesis, ODC activity of the antral portion of the gastric wall and the labelling index of the antral mucosa. Our results suggest that ODC inhibition attenuated the enhancement of gastric carcinogenesis by bombesin, and that this enhancement by bombesin was mediated by polyamine biosynthesis.

Topics: Adenocarcinoma; Animals; Bombesin; Diamines; Drug Interactions; Drug Synergism; Gastric Mucosa; Gastrins; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase Inhibitors; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms

Cell kinetics of reversible and persistent forestomach lesions induced by the genotoxic agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and/or the nongenotoxic antioxidant butylated hydroxyanisole (BHA) was investigated. A total of 184 male F344 rats were divided into four groups: Group 1 given an initial single gastric intubation of MNNG received 2% BHA diet from the third wk to the 26th wk and then basal diet; Group 2 receiving 2% BHA without MNNG initiation; Group 3 given MNNG alone; and Group 4 serving as a nontreated control. Rats were sequentially sacrificed at 6, 16, 26, 30, and 46 wk. Bromodeoxyuridine was administered either as a single i.p. injection (100 mg/kg of body weight) 1 h before killing or continuously via an osmotic minipump (120 micrograms/h) for 1, 3, or 7 days prior to sacrifice, in each case labeled cells being detected by immunohistochemistry. Squamous cell hyperplasia (SCH) and basal cell hyperplasia (BCH), each characterized by different phenotypic keratin expression, were induced in Groups 1 to 3. After withdrawal of BHA, rapid regression of SCH and extremely slow regression of BCH were observed. Papillomas and squamous cell carcinomas developed irreversibly in Group 1 and 3, BHA significantly (P less than 0.01) enhancing the incidence of SCC in Group 1. Flash and continuous bromodeoxyuridine labeling revealed SCH to consist of cells of high mitotic activity and short life span, whereas BCH consisted of cells with low mitotic activity and long life span. In addition, highly labeled areas were observed in SCH after cessation of BHA feeding in Group 1 without regression, and similar lesions were also evident in Group 3. The results suggest that rapid regression of SCH and slow regression of BCH reflect different cell kinetic patterns and that highly labeled areas after release from stimulating agents might be preneoplastic changes related to cancer development.

Topics: Animals; Butylated Hydroxyanisole; DNA; Epithelium; Hyperplasia; Immunoenzyme Techniques; Keratins; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms; Time Factors

Eighty rats out of 233 developed malignant tumors in the stomach and small intestine by administration of 100 micrograms/ml N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water for 28 weeks. Fifteen lesions (30%) among the 50 small intestinal carcinomas showed ossification in the tumor, while none in the sarcomas (12 lesions) or gastric adenocarcinomas (59 lesions) showed ossification. Multifocal heterotopic bone formation was found within stroma in close approximation to the neoplastic glands. The islands of bone trabeculae were covered by osteoblast-like cells, and abundant fibroblasts in loose stroma gathered around the bony islands which enclosed osteocytes in lacunae. Neither osteoclast nor cartilage was identified. In 5 cases, ossification was extensive, which comprised the major portion of the stroma. In contrast, intraluminal calcification without ossified foci were occasionally seen in the gastric carcinoma. Ossification of the intestinal tumors correlated to the degree of mucin content (p < 0.05, chi square with Yates' correction), degree of neutrophilic infiltration (p < 0.05), and size of the tumor (p < 0.1). (The average size of the ossified tumor was 21.5 +/- 4.0 mm, while that of nonossified tumors was 12.5 +/- 1.9 mm). The degree of tumoral necrosis, desmoplasia or depth of invasion did not seem to be related to the ossification of the tumor. The ossification rate of this experimental model was much higher than in human cases. Various histologic alterations, such as mucin leakage, inflammatory cell infiltration, necrosis and/or fibrosis, which might be caused by continuous stimulation of the strong carcinogen, may play some role in the ossification of experimental tumors.

Topics: Adenocarcinoma; Animals; Intestinal Neoplasms; Intestine, Small; Methylnitronitrosoguanidine; Ossification, Heterotopic; Rats; Rats, Sprague-Dawley; Staining and Labeling; Stomach Neoplasms

Helicobacter pylori was implicated in gastric carcinogenesis through the induction of metaplasia of the gastric mucosa. In this experiment a co-carcinogenic effect of H. pylori on chemically induced gastric carcinogenesis was examined. Wistar WKY male rats received drinking water containing 50 mg/l of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and intragastric administration of 10(6) to 10(8) colony forming unit of H. pylori thrice a week for 40 weeks. Thus, 3 groups were assigned as Group I; MNNG alone, Group II; MNNG + vehicle, and Group III; MNNG + H. pylori (n = 30, each). At autopsy, 9 rats (30%) had 7 glandular stomach and 3 duodenal tumors in Group I, and 10 rats (33%) had 8 glandular stomach and 2 duodenal tumors in Group II, whereas in Group III 4 rats (13%) had 2 glandular stomach and 2 duodenal tumors (chi 2 = 4.257, P < 0.15 for the incidences of glandular stomach tumors among 3 groups). The finding seems to suggest that H. pylori has an ambitendency in the gastritis-metaplasia-carcinogenesis sequence as a promoter for the induction of the predisposing mucosa and as an inhibitor against certain carcinogens.

Topics: Animals; Cocarcinogenesis; Duodenal Neoplasms; Helicobacter pylori; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred WKY; Stomach Neoplasms

Signet-ring-cell carcinomas were induced in the stomach of 12 beagle dogs by p.o. administration of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG), and the morphology and modes of cell proliferation in an incipient stage of cancer growth were studied with bromodeoxyuridine (BrdUrd) incorporation. From 5 to 27 months after the completion of 8 months' carcinogen treatment, minute carcinomas were found in the stomachs of 9 dogs. Before sacrifice, the dogs were given a single or repeated i.v. injections of BrdUrd for 1-3 days. Minute signet-ring-cell carcinomas were found to form a layered structure, in which the cancer cells proliferated in the lamina propria at the gland-neck level and differentiated to postmitotic signet-ring cells at the upper and lower levels of the mucosa. From repeated injections of BrdUrd, the time required for all the proliferative cells to be labelled with BrdUrd (reflecting the maximum cell-cycle time) was estimated to be 1.7 days for the normal glands, and 2.7 days for minute signet-ring-cell carcinomas. From the labelling index with BrdUrd as well as from the morphology, earliest carcinomas were identified in the single gland. There remained atrophic normal epithelium commonly in the single-gland lesions. Proliferative atypical cells appeared to be shed into the stroma passively through the atrophy and subsequent collapse of the gland rather than through active invasion. This may be a reason why cancer cells in minute signet-ring cell carcinomas preserved the normal pattern of cell renewal movement to form the layered structure.

Topics: Adenocarcinoma, Mucinous; Alcian Blue; Animals; Bromodeoxyuridine; Cell Division; Dogs; Gastric Mucosa; Immunoenzyme Techniques; Methylnitronitrosoguanidine; Precancerous Conditions; Stomach Neoplasms

Experimental studies were performed to investigate the role, if any, of bile reflux in cancer development in the stomach. A 20% solution of human bile juice and 50 micrograms/ml of the known carcinogenic MNNG were given perorally and heterochronically to male Wistar rat, and the incidence of carcinoma in the gastric gland of the rat was studied. The animals were divided into 4 groups: Group I, to which only MNNG was given. Group II, to which human bile juice and then MNNG were administered. Group III, to which MNNG and then human bile juice were administered. And Group IV, to which only human bile juice was given. The incidence of cancer was 37.5% (3/8) in Group II, 25% (2/8) in Group III, and 0% in Group I (0/12) and IV (0/12). The gastric gland mucosa was histologically examined at various times and also by microautoradiography using 3H-TdR. The results suggested that a reverse flow of bile juice to the human remnant stomach may induce an increase in proliferative cells in the lacunar epithelia of the stomach mucosa and that a predisposed site would then be available for cancer development.

Topics: Animals; Bile; Bile Reflux; Gastrectomy; Gastric Mucosa; Humans; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The susceptibility to cancer in the vagotomized stomach which was assigned either to selective vagotomy (SV) or selective proximal vagotomy (SPV) was studied by gastric carcinoma model of male Wistar rat on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) administration. Predilection for cancer of the remnant stomach was also studied. Four groups of the rats submitted to either one of the SV, SPV, antrectomy (Billroth-I reconstruction) or control (simple laparotomy) group, were prepared. The techniques of SV and SPV in rat was originally developed. MNNG in drinking water was given as carcinogen. Gastric acid output, gastric stasis, serum gastrin levels together with the number and the invasiveness of the atypical glands those were recognized in the glandular stomach of rats were examined. The results were as follows: (1) the reduction rate of gastric acid output was the most conspicuous at antrectomy group followed by SV and SPV groups, (2) gastric stasis was observed in almost the same degree in SV and SPV groups, (3) serum gastrin level was the highest in SV group followed by SPV, control and antrectomy groups in this order and (4) the susceptibility to malignancy was significantly high at SV group but not high at SPV and antrectomy group as compared with control group.

Topics: Animals; Gastrectomy; Gastric Acid; Gastric Emptying; Gastrins; Male; Methylnitronitrosoguanidine; Pyloric Antrum; Rats; Stomach; Stomach Neoplasms; Vagotomy; Vagotomy, Proximal Gastric

The effects of oral potassium supplementation on the enhanced induction of gastric carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in spontaneously hypertensive rats (SHR), and the norepinephrine concentration in their gastric wall were investigated. The SHR and normotensive Wistar Kyoto rats (WKY) as controls were given a solution of the carcinogen for 25 weeks and then 1% KCl solution or tap water to drink. In Week 52, the incidence of gastric cancers and their number per rat and the norepinephrine concentration in the gastric wall were significantly greater in SHR than in WKY. Prolonged oral treatment of SHR with potassium significantly reduced the incidence of gastric cancers and their number per rat, as well as the blood pressure and the norepinephrine concentration in the antral portion of the gastric wall. These findings indicate that prolonged treatment with KCl attenuated the enhancement of gastric carcinogenesis by MNNG in SHR.

Topics: Animals; Antineoplastic Agents; Blood Pressure; Body Weight; Epinephrine; Intestinal Mucosa; Methylnitronitrosoguanidine; Muscle, Smooth; Norepinephrine; Potassium Chloride; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Stomach; Stomach Neoplasms

Dietary habits have been causally implicated in gastric carcinogenesis, whereas minor dietary items may also play a part. Wasabi is a popular pungent spice in Japanese meals. In this study the effect of wasabi on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis was studied in rats. Wistar WKY male rats received drinking water containing 50 micrograms/ml of MNNG or tap water alone and a basal diet (PCE-2) or PCE-2 containing 10% (wt/wt) of wasabi powder for 40 weeks. Thus, three groups were completed as MNNG + PCE-2 (n = 30), MNNG + wasabi (n = 30), and tap water + wasabi (n = 30). At autopsy, nine rats (30%) had seven glandular stomach tumors (2 adenocarcinomas, 2 adenomatous polyps, and 3 adenomatous glandular hyperplasias) and three duodenal adenocarcinomas in the MNNG + PCE-2 group, whereas in the MNNG + wasabi group, two rats (7%) had one forestomach epidermoid cyst and one duodenal carcinosarcoma (corrected chi 2 = 4.63, p less than 0.05 for incidences of glandular stomach tumors between 2 groups). In addition, two rats had microscopic atypical glands in the MNNG + PCE-2 group. There was no tumor in the tap water + wasabi group. These results indicated that glandular stomach carcinogenesis induced by MNNG was suppressed by the administration of wasabi.

Topics: Adenocarcinoma; Animals; Condiments; Diet; Duodenal Neoplasms; Gastric Mucosa; Hyperplasia; Japan; Male; Methylnitronitrosoguanidine; Plants, Edible; Polyps; Rats; Rats, Inbred WKY; Stomach Neoplasms; Water

The effects of butylated hydroxyanisole (BHA) pretreatment on subsequent low dose N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or N,N-dibutylnitrosamine (DBN) treatment on forestomach or esophageal carcinogenesis were investigated in male F344 rats. Groups of animals were pretreated with 2% BHA or basal diet alone for 24 weeks and then were given 20 mg/kg body wt MNNG once every 2 weeks, 0.025% DBN in drinking water continuously or basal diet alone for the subsequent 24 weeks. Further groups of rats were similarly treated with BHA or basal diet alone for 24 weeks, placed on basal diet for the next 24 weeks and then treated with MNNG, DBN or basal diet alone for the subsequent 24 weeks. Animals were killed 48 or 72 weeks after the beginning of the experiment. Histopathological examination showed that the incidence of forestomach tumors was not significantly affected by the BHA pretreatment in the MNNG-treated groups. On the other hand, the incidence of esophageal squamous cell carcinomas was lower in the group pretreated with BHA followed by DBN than in that treated with basal diet followed by DBN (48 week experiment). There was no significant difference in esophageal tumor incidence in the 72 week experiment. The results thus indicate that continuous treatment with 2% BHA for 24 weeks does not exert initiating activity on forestomach and esophageal epithelia.

Topics: Animals; Body Weight; Butylated Hydroxyanisole; Carcinogens; Carcinoma, Squamous Cell; Esophageal Neoplasms; Esophagus; Hyperplasia; Male; Methylnitronitrosoguanidine; Nitrosamines; Organ Size; Papilloma; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

Topics: Adenoma; Animals; Antioxidants; Butylated Hydroxyanisole; Carcinoma; Cell Division; Epithelium; Female; Hyperplasia; Lipid Peroxidation; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

The effects of sulpiride on cysteamine inhibition of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on the BUdR labelling index of gastric mucosa were investigated in inbred Wistar rats. After 25 weeks of oral treatment with MNNG, rats received one of the following alternate-day injections: cysteamine (2 doses), cysteamine (2 doses) plus sulpiride or sulpiride. At week 52, prolonged administration of cysteamine significantly reduced the incidence of adenocarcinomas of the glandular stomach. Cysteamine at low dose had no effect on the incidence of gastric cancers, but a combination of low-dose cysteamine and sulpiride caused a significantly greater reduction in the incidence of gastric cancers. Administration of sulpiride alone had no influence on gastric carcinogenesis. The labelling index of the antral mucosa was significantly lower in rats treated with high but not low doses of cysteamine. However, a combination of low-dose cysteamine and sulpiride significantly decreased the labelling index of the antral mucosa. Our findings indicate that cysteamine suppressed gastric carcinogenesis and that sulpiride enhanced this inhibition. Because sulpiride is a dopamine antagonist, these findings also indicate that dopamine may play an important role in cysteamine inhibition of gastric carcinogenesis.

Topics: Animals; Cysteamine; Dose-Response Relationship, Drug; Drug Synergism; Gastric Acid; Gastric Mucosa; Gastrins; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Sulpiride

The combined effects of low doses of promoters or carcinogens on two-stage forestomach carcinogenesis were examined in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine. Groups of 15 rats were given a single 150 mg/kg body weight intragastric dose of N-methyl-N'-nitro-N-nitrosoguanidine. Starting 1 week later they were fed a diet containing low doses of known forestomach promoters/carcinogens (0.5% caffeic acid, 0.2% catechol, 0.5% butylated hydroxyanisole, or 0.25% 2-tert-butyl-4-methylphenol), alone or in combination, or basal diet without antioxidant supplement for 35 weeks. Histopathological examination revealed the incidences of forestomach squamous cell carcinomas in animals treated with N-methyl-N'-nitro-N-nitrosoguanidine followed by caffeic acid, catechol, butylated hydroxyanisole, 2-tert-butyl-4-methylphenol, and basal diet to be 27, 20, 13, 13, and 7%, respectively, whereas the incidence increased to 80% by the combined treatment with these four chemicals. The present results thus show that although the low doses of individual promoters/carcinogens did not have significant promoting activity, their combination exerted a strong enhancing influence on rat forestomach carcinogenesis. The findings indicate the importance of summation and synergism at a low dose for agents present in the human environment.

Topics: Animals; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Hyperplasia; Male; Methylnitronitrosoguanidine; Premedication; Rats; Stomach; Stomach Neoplasms

The effect of s.c. administration of deoxycorticosterone acetate (DOCA) plus p.o. treatment with NaCl solution on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine and the effect of p.o. potassium supplementation on the enhanced induction of gastric carcinogenesis in DOCA-NaCl rats were investigated in Wistar rats. After 25 weeks of p.o. treatment with the carcinogen, rats received s.c. injections of DOCA (50 mg/kg) twice a week and were given 1% NaCl solution with and without 1% KCl as drinking water. In Week 52, the blood pressure, the incidence of gastric cancer, and the number of cancers per rat were significantly greater in DOCA-NaCl rats than in the untreated group. Prolonged p.o. treatment of DOCA-NaCl hypertensive rats with potassium significantly reduced their blood pressure, the incidence of gastric cancers, and their number per rat. All gastric tumors were in the glandular portions of the stomach. The norepinephrine concentration in the gastric wall and the labeling indices of gastric mucosa were significantly greater in DOCA-NaCl hypertensive rats than in the untreated group, but p.o. potassium supplementation significantly reduced the norepinephrine concentration in the gastric wall and the labeling indices of the gastric mucosa in DOCA-NaCl rats. Thus, administration of DOCA and NaCl increased the norepinephrine concentration in the gastric wall and promoted gastric carcinogenesis, and p.o. potassium supplementation decreased the norepinephrine concentration in the gastric rats. Inasmuch as the norepinephrine concentration has been used as a marker of sympathetic nervous activity, these findings suggest that the sympathetic nervous system plays an important role in gastric carcinogenesis, probably associated with cell proliferation of antral epithelial cells.

Topics: Adenocarcinoma; Animals; Desoxycorticosterone; Drug Interactions; Gastric Mucosa; Hypertension; Male; Methylnitronitrosoguanidine; Norepinephrine; Potassium Chloride; Rats; Rats, Inbred Strains; Sodium Chloride; Stomach Neoplasms

The effect of furazolidone on inhibition by cysteamine of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated in inbred Wistar rats. After oral treatment with MNNG for 25 weeks, rats received cysteamine, furazolidone, or both compounds. In week 52, rats treated with cysteamine had a significantly decreased incidence of gastric cancers. Concomitant treatment with furazolidone significantly attenuated the inhibitory effect of cysteamine on gastric carcinogenesis. Administration of furazolidone alone significantly increased the number, but not the incidence, of gastric cancers. The norepinephrine concentration of the antral portion of the gastric wall and the labelling index of the antral mucosa were significantly reduced in rats treated with cysteamine, and significantly higher in rats treated with both compounds than in those treated with cysteamine alone. These findings indicate that the cysteamine-induced inhibition of gastric carcinogenesis is mediated by catecholamines.

Topics: Adenocarcinoma; Animals; Cysteamine; Epinephrine; Furazolidone; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Monoamine Oxidase Inhibitors; Muscle, Smooth; Norepinephrine; Rats; Rats, Inbred Strains; Reference Values; Stomach; Stomach Neoplasms

The effects of ad libitum feeding of synthetic, low-protein diets on the incidence and number of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in Wistar rats. Rats were fed synthetic diets of equal calorie content containing 25% casein (normal protein diet), 10% casein (low-protein diet), or 5% casein (very-low-protein diet) after treatment with N-methyl-N'-nitro-N-nitrosoguanidine p.o. for 25 weeks. Administration p.o. of a very-low-protein diet containing 5% casein resulted in a significant increase in the incidence and number of gastric cancers in experimental Week 52. However, it did not affect the histology of the cancers. The very-low-protein diet also caused a significant increase in tissue norepinephrine concentration of the antral portion of the gastric wall and in the labeling index of the antral epithelial cells. These findings indicate that a very-low-protein diet enhances gastric carcinogenesis and that this effect may be related to its effect in increasing norepinephrine in the gastric wall and stimulating proliferation of antral epithelial cells.

Topics: Animals; Cell Division; Dietary Proteins; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Norepinephrine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Sympathetic Nervous System

The effect of tyrosine methyl ester (TME) on the incidence, number, and histological types of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated in male Wistar rats. Rats were subcutaneously given TME, 512 mg/kg body weight, every other day after 20 weeks of oral treatment with MNNG. Prolonged alternate-day administration of TME caused a significant increase in the incidence and number of gastric cancers of the glandular stomach by week 52. However, it did not affect the histology of the cancers. TME also caused a significant increase in tissue norepinephrine concentrations in the antral portion of the gastric wall and in the labelling indices of the antral epithelial cells. However, TME had no influence on the serum gastrin level and antral pH. These findings indicate that TME enhances gastric carcinogenesis, and this may be related to its effects on increasing norepinephrine levels in the gastric wall and stimulating proliferation of the antral epithelial cells.

Topics: Adenocarcinoma; Animals; Catecholamines; Drug Synergism; Epinephrine; Gastric Acidity Determination; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Muscle, Smooth; Norepinephrine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms; Tyrosine

In order to predict the chemopreventive activity of garlic on gastric cancer, the effect of diallyl sulfide (DAS), a natural extract of the garlic, on MNNG-induced nuclear aberration (NA) and ornithine decarboxylase (ODC) activity in Wistar rat glandular stomach mucosa was studied. The results showed that NA and ODC activity were positively correlated to MNNG dose given 24 and 6 hr after oral intubation with MNNG. Oral or parenteral pretreatment with DAS significantly and dose-dependently inhibited MNNG-induced NA and ODC. These data suggest that DAS has the potential to inhibit MNNG-induced gastric cancer, supporting the epidemiological evidence of the chemopreventive effect of garlic on gastric cancer.

Topics: Allyl Compounds; Animals; Cell Nucleus; Dose-Response Relationship, Drug; Garlic; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase; Plants, Medicinal; Rats; Rats, Inbred Strains; Stomach Neoplasms; Sulfides

The effects of combined administration of tetragastrin and the ornithine decarboxylase inhibitor 1,3-diaminopropane (DAP) on the incidence and number of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and the BUdR labelling indices of the fundic and antral mucosae, were investigated in inbred Wistar rats. Rats were given drinking water containing 2.5 g/l of DAP ad libitum and received alternate-day injections of 1 mg/kg body weight of tetragastrin in depot form after 25 weeks of oral treatment with MNNG. At week 52, prolonged administration of tetragastrin alone resulted in a significant reduction in the incidence and number of gastric cancers and a significant increase or decrease in the labelling indices of the fundic and antral mucosae, respectively. Concomitant administration of tetragastrin and DAP had no effect on the inhibition by tetragastrin of gastric carcinogenesis. With this treatment, the labelling index was significantly reduced in the fundic mucosa but not in the antral mucosa. These results suggest that ODC inhibitor does not attenuate tetragastrin inhibition of gastric carcinogenesis, and that anti-trophic action of tetragastrin on antral mucosa may be related to tetragastrin inhibition of gastric carcinogenesis.

Topics: Animals; Diamines; DNA; Eflornithine; Gastrins; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase Inhibitors; Rats; Rats, Inbred Strains; Stomach Neoplasms; Tetragastrin

DNA content and nuclear area were measured by microspectrophotometry in gastric carcinogenesis of three adult wolfdogs induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). The mean values and standard deviations of DNA content and nuclear area in normal gastric mucosa were 10.03 +/- 2.30 AU and 28.76 +/- 5.85/microns2; those in atrophic gastritis were 12.04 +/- 3.34 AU and 28.69 +/- 8.02/microns2; in mild dysplasia 13.52 +/- 3.73 AU and 28.23 +/- 8.12/microns2; in moderate dysplasia 20.88 +/- 4.57 AU and 47.58 +/- 10.74/microns2; in severe dysplasia 24.01 +/- 4.48 AU and 56.64 +/- 12.53/microns2; in well-differentiated adenocarcinoma 33.07 +/- 9.38 AU and 72.99 +/- 15.57/microns. These figures were different (P less than 0.01). The nuclear area of gastric carcinoma increased with DNA content (r = 0.73, P less than 0.01). The distribution patterns of DNA content in the histogram showed that diploidy was decreased and polyploidy increased in cancer cells. These findings indicate that DNA ploidy patterns and nuclear area can be useful indices for differentiating carcinoma from precancerous lesions.

Topics: Animals; DNA, Neoplasm; Dogs; Methylnitronitrosoguanidine; Microspectrophotometry; Ploidies; Precancerous Conditions; Prospective Studies; Stomach Neoplasms

A signet ring cell carcinoma in the gastric antrum of a Cynomolgus monkey induced by N-ethyl-N'-nitro-N-nitrosoguanidine was sequentially studied by endoscopy, biopsy, and autopsy. The carcinoma was first detected on the angulus of the stomach at the 38th month as a slightly elevated lesion. Sixty-one months later this tumor was found to be still in the "early" (intramucosal) stage. Another, independent, initial gastric cancer was also discovered. This is the first example of an induced gastric carcinoma remaining in the "early" stage during a six-year follow-up period after the initial histologic diagnosis.

Topics: Adenocarcinoma, Mucinous; Animals; Biopsy; Carcinogens; Gastroscopy; Macaca; Methylnitronitrosoguanidine; Stomach Neoplasms; Time Factors

The modifying effects of para-methoxyphenol (PMP) second stage treatment on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-initiated rat forestomach carcinogenesis were investigated. Groups of 15 6 week old male F344 rats were given a single intragastric administration of 150 mg/kg body wt MNNG and starting 1 week later were administered powdered diet containing 2.0, 1.0, 0.5, 0.25 or 0% PMP until they were killed at week 52. PMP caused epithelial damage and hyperplasia in a dose-dependent manner in the forestomach epithelium, but nevertheless was not associated with any increase in the incidence of either papillomas or squamous cell carcinomas. The results thus clearly indicated that stimulation of cell proliferation does not necessarily correlate with promotion in the second stage of two-stage forestomach carcinogenesis.

Topics: Animals; Anisoles; Carcinogenicity Tests; Carcinoma; Cell Division; Hyperplasia; Male; Methylnitronitrosoguanidine; Muscle, Smooth; Organ Size; Papilloma; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

In prostaglandin E2 (PGE2)-, pirenzepine-, and indomethacin-administered rats, the incorporation of N-[methyl-3H]-N'-nitro-N-nitrosoguanidine ([methyl-3H]MNNG) into gastric mucosal DNA was measured quantitatively by liquid scintillation counting after intragastric instillation of [methyl-3H]MNNG. The amount of incorporation was 25.4 +/- 5.9 pmol/mg DNA in control rats, 11.7 +/- 3.8 pmol/mg DNA in PGE2-administered rats, 6.2 +/- 5.6 pmol/mg DNA in pirenzepine-administered rats, and 42.9 +/- 14.4 pmol/mg DNA in indomethacin-administered rats. PGE2 and pirenzepine significantly decreased the incorporation as compared with the control group. In contrast, indomethacin increased the incorporation. In addition, gastric mucosa of these drug-treated rats was studied histochemically. PGE2 and pirenzepine increased secretion of gastric mucus whereas indomethacin decreased it. It is possible that gastric mucus has a protective effect not only against ulcerogenic agents but also against carcinogens. It is considered that gastric mucus plays an important role in the defense mechanism against carcinogenesis.

Topics: Animals; Dinoprostone; DNA; Gastric Mucosa; Indomethacin; Male; Methylnitronitrosoguanidine; Mucus; Pirenzepine; Rats; Rats, Inbred Strains; Stomach Neoplasms

To assess the possibility of establishing an in vivo, medium-term bioassay system for gastric carcinogens and promoters, a total of 220 male WKY rats were divided into two groups. Group 1 animals were treated first with a single dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (160 mg/kg body wt) and starting 2 weeks later administrated one of five gastric carcinogens, a gastric promoter, one of five non-gastric carcinogens or no treatment, as a control, for 14 weeks. Saturated sodium chloride solution (1 ml) treatments were given by gastric intubation at weeks 4, 6, 8 and 10. Group 2 rats received 1 ml of DMSO instead of MNNG and were then treated in the same way as group 1. Analysis of pyloric mucosa sections for pepsinogen altered pyloric glands (PAPG) detected immunohistochemically after the animals were killed at week 16 revealed increased lesion numbers in group 1, with all gastric carcinogens and promoters examined. However, none of the five non-gastric carcinogens exerted any significant modification of PAPG development. The results strongly suggest that the experimental protocol consisting of the following four components: (i) adoption of PAPG as the end-point marker lesion; (ii) single dose of MNNG as initiator; (iii) test chemical administration for 14 weeks; and (iv) administration of saturated sodium chloride solution during the test chemical exposure, could be used effectively for the detection of gastric carcinogens as well as promoters of gastric carcinogenesis in a relatively short time period.

Topics: Animals; Carcinogenicity Tests; Dimethyl Sulfoxide; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Pepsinogens; Precancerous Conditions; Pylorus; Rats; Rats, Inbred WKY; Stomach Neoplasms; Time Factors

The effects of dietary bile acids on the development of pepsinogenaltered pyloric glands (PAPG) were examined. Male WKY/NCrj rats were given a single dose of 160 mg/kg body wt. of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) by gastric intubation and fed basal diet containing 0.3% sodium taurocholate (Na-TC), 0.3% sodium cholate (Na-C), 0.3% sodium glycocholate (Na-GC), 0.3% sodium tauroglycocholate, 0.3% sodium deoxycholate, 0.1% chenodeoxycholic acid or 0.5% lithocholic acid for 14 weeks. All rats also received 1 ml of saturated NaCl solution 4 times by i.g. intubation. At the end of week 16, the animals were killed, and the number of PAPG per cm of mucosal length was determined immunohistochemically. Na-TC, Na-C and Na-GC significantly increased the number of PAPG over the control value, suggesting that they may have activity to promote gastric carcinogenesis.

Topics: Animals; Bile Acids and Salts; Body Weight; Gastric Mucosa; Immunohistochemistry; Male; Methylnitronitrosoguanidine; Pepsinogens; Pylorus; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms

The effect of an exogenous synthetic prostaglandin analogue, 16,16-dimethyl prostaglandin E2 (16,16-dm-PGE2), as well as the effect of endogenous prostaglandin synthesis inhibition by a cyclooxygenase inhibitor, flurbiprofen, on chemically induced gastric carcinogenesis has been investigated in rats. Carcinogenesis was induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; CAS:70-25-7). Animals were divided into six groups: Group I, treatment with MNNG alone; Group II, treatment with 16,16-dm-PGE2 plus MNNG; Group III, treatment with flurbiprofen plus MNNG; Group IV, treatment with 16,16-dm-PGE2 alone; Group V, treatment with flurbiprofen alone; and Group VI, controls. Treatment with high doses of MNNG resulted in rapid development of malignant tumors originating from the glandular epithelium of the stomach and duodenum in animals of all groups receiving the carcinogen. The first gastric adenocarcinoma infiltrating the muscularis proper was detected after 139 days in an animal treated with a combination of MNNG and flurbiprofen. The incidence of infiltrating adenocarcinoma and the incidence of all neoplastic lesions of the glandular stomach were both significantly higher in animals treated with a combination of MNNG and flurbiprofen compared with treatment by MNNG alone or in combination with 16,16-dm-PGE2 (P less than 0.05 and P less than 0.001). The difference in tumor incidence between the last two groups was not significant. The first duodenal adenocarcinoma was detected on Day 114 in another animal of the group treated with MNNG plus flurbiprofen. When compared with the group treated with MNNG plus 16,16-dm-PGE2, significantly more animals developed duodenal adenocarcinoma when treated with MNNG plus flurbiprofen (P less than 0.005) or with MNNG alone (P less than 0.05). Results of this study indicate that inhibition of endogenous prostaglandin synthesis favors development of adenocarcinoma in the glandular stomach of rats. Vice versa, the addition of an exogenous prostaglandin analogue inhibits the development of duodenal adenocarcinoma. This protective effect of prostaglandins may be due to an increase of the thickness of the mucus gel covering the glandular epithelium, thereby preventing access of carcinogen to the mucosa.

Topics: 16,16-Dimethylprostaglandin E2; Adenocarcinoma; Animals; Body Weight; Duodenal Neoplasms; Female; Flurbiprofen; Gastric Mucosa; Methylnitronitrosoguanidine; Prostaglandins; Prostaglandins E, Synthetic; Rats; Rats, Inbred Strains; Stomach Neoplasms

The study was initiated to evaluate the sequential changes of gastric intraluminal prostaglandin E2 (PGE2), gastric acid secretion and of the DNA-flowcytometric patterns during gastric carcinogenesis induced by 45-week N-methyl-N-nitro-N-nitrosoguanidine (NG) administration in the rat. Twenty male chronic gastric fistula Sprague-Dawley rats received NG solution (120 mg/l) for 45 weeks and 20 were used as controls. Samples of gastric juice (1 h) were obtained from all animals under basal conditions and every 5 weeks until the end of the experiment. Aliquots of gastric juice were titrated with 0.1 N NaOH. Other aliquots were extracted with ethylacetate and processed for specific PGE2 RIA. On the day following gastric juice collection a gastric lavage and gastric biopsies (n = 4) were obtained through the fistula and processed for flowcytometry. All surviving animals were killed after 45 weeks and histology was obtained. The incidence of cancer in NG treated chronic gastric fistula rats was 66%. Flowcytometry segregated at an early stage (30-35 weeks) those animals which were to develop gastric carcinoma from those which were not. Administration of NG decreased gastric secretion volume, acid and intraluminal PGE2 concentration both in animals developing and not developing cancer. During the last 10 weeks a sharp rise in gastric intraluminal PGE2 concentration was observed in tumor-bearing animals only probably due to production by tumor cells. Prostaglandin deficiency may contribute to the NG-induced mucosal damage and may be involved in gastric carcinogenesis.

Topics: Animals; Dinoprostone; DNA; Flow Cytometry; Gastric Acid; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The reversibility of butylated hydroxyanisole (BHA)-induced hamster forestomach hyperplasia was examined histopathologically. Groups of 10-15 male Syrian golden hamsters were treated with 2% BHA, for 12, 24 or 48 weeks and in each case then placed on basal diet until termination of the experiment at week 72, or treated with 2% BHA continuously for 72 weeks. Although sequential sampling revealed that BHA-induced hyperplasia reverted after cessation of antioxidant treatment, dysplastic lesions such as squamous cell dysplasia and basal cell dysplasia persisted and tended to increase with time on BHA. Basal cell dysplasia was observed in some hamsters later than squamous cell dysplasia, i.e. those treated with BHA for 24 weeks or more and killed up to 48 weeks later. Whereas the increase in labeling index evident in areas of hyperplasia during treatment returned to control level after cessation, this was not the case for the dysplastic lesions which continued to demonstrate elevated proliferation. The results thus suggest that basal cell dysplasia, including regions of squamous cell dysplasia, may be of particular importance as a precursor pre-neoplastic lesion.

Topics: Animals; Butylated Hydroxyanisole; Cricetinae; Hyperplasia; Male; Mesocricetus; Methylnitronitrosoguanidine; Precancerous Conditions; Stomach; Stomach Neoplasms; Uracil; Urinary Bladder

The effects of the organic calcium channel blocker verapamil and the inorganic calcium channel blocker MgCl2 on gastric carcinogenesis, on caerulein enhancement of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and on the labeling index of gastric mucosa were investigated in inbred Wistar rats. After 25 weeks of treatment with N-methyl-N'-nitro-N-nitrosoguanidine (50 micrograms/ml p.o.), rats received one of the following alternate-day injections: caerulein (2 micrograms/kg body weight, s.c.), MgCl2 (150 mg/kg, s.c.), verapamil (20 mg/kg body weight, i.p.), caerulein (2 micrograms/kg body weight, s.c.) plus MgCl2 (150 mg/kg body weight, s.c.), or caerulein (2 micrograms/kg body weight, s.c.) plus verapamil (20 mg/kg body weight, i.p.). At Week 52, prolonged administration of caerulein had significantly increased the incidence and number of adenocarcinomas in the glandular stomach and the incidence of gastric cancers that penetrated through or beyond the muscle layer. Concomitant administration of MgCl2 significantly attenuated the enhancing effect of caerulein on gastric carcinogenesis. Combined administration of caerulein and verapamil did not affect the incidence and number of gastric cancers but significantly reduced the incidence of cancers penetrating through or beyond the muscle layer. Administration of MgCl2 or verapamil alone had no influence on gastric carcinogenesis. Rats treated with caerulein had a significantly elevated labeling index of the antral mucosa which was significantly decreased by concomitant administration of MgCl2 and/or of verapamil, as compared with the labeling index observed after treatment with caerulein alone. Either MgCl2 or verapamil alone had no influence on the labeling index of the antral mucosa. These findings indicate that caerulein enhances gastric carcinogenesis and that MgCl2 and verapamil attenuate this enhancement. These findings also indicate that calcium may play an important role in caerulein enhancement of gastric carcinogenesis.

Topics: Adenocarcinoma; Animals; Calcium Channel Blockers; Ceruletide; DNA; Gastric Juice; Gastrins; Hydrogen-Ion Concentration; Magnesium Chloride; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Verapamil

Peculiarities of carcinogenic effect of N-methyl-N'-nitro-N-nitrosoguanidine administered through a stomach tube on rats were studied in 30 rats given 1-2 ml MNNG dissolved in distilled water (5 mg/ml) through a gastric tube for 2-3 days. The procedure is repeated every 4-10 days. This intermittent carcinogen administration continued until week 20; the animals were killed on week 25. All effective 26 (100%) rats had multiple papillomas and squamous cell carcinomas of the forestomach, 5 (19.2%) had adenomatous hyperplasias and adenocarcinomas of the glandular stomach, 7 (26.9%) had adenocarcinomas and sarcomas of the small intestine.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Papilloma; Rats; Sarcoma, Experimental; Stomach Neoplasms; Time Factors

The effect of epidermal growth factor (EGF) on rat stomach carcinogenesis induced by N-methyl-N'-nitro-N-nitro-soguanidine (MNNG) was studied. Male Wistar rats given MNNG for 30 weeks in drinking water (80 micrograms/ml) were treated with s.c. injections of human EGF (10 micrograms/kg, once daily) at various stages of the carcinogenesis. Four (30.8%) out of 13 rats treated with EGF immediately after cessation of the MNNG treatment had stomach tumors including one adenocarcinoma, one adenoma and two carcinoids. No stomach tumor was found in rats treated with MNNG alone or in those treated with MNNG and EGF for different periods such as synchronously for 10 weeks, for 30 weeks or throughout the experiment. These findings suggest a possible enhancing effect of EGF on stomach carcinogenesis in rats.

Topics: Animals; Drug Interactions; Epidermal Growth Factor; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of gamma-amino-n-butyric acid (GABA), the GABA(A) receptor agonist muscimol (5-aminomethyl-3-hydroxyisoxazole), and the GABA(B) receptor agonist baclofen [4-amino-3-(4-chlorophenyl)butanoic acid] on the incidence and number of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine was investigated in Wistar rats. Rats received alternate-day i.p. injections of 500 or 1000 mg/kg of body weight GABA, 0.25 or 0.5 mg/kg of body weight muscimol, or 4 or 8 mg/kg of body weight baclofen after 25 wk of p.o. treatment with the carcinogen. Prolonged administration of GABA at 1000 mg/kg of body weight, but not at 500 mg/kg of body weight, and of baclofen at 4 and 8 mg/kg of body weight significantly decreased the incidence and number of gastric cancers of the glandular stomach in Wk 52, but long-term muscimol administration had no influence. Histologically, GABA at the high dosage and baclofen at both dosages significantly decreased the labeling index of the antral mucosa and significantly increased the serum gastrin level. Furthermore, baclofen at both dosages significantly decreased antral pH and significantly increased gastric acid secretion. These findings indicate that GABA inhibits gastric carcinogenesis via the GABAB receptor and that this effect may be related to its effect in decreasing the proliferation of antral mucosa.

Topics: Animals; Baclofen; gamma-Aminobutyric Acid; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Reference Values; Stomach Neoplasms

MNNG-induced experimental gastric cancer developed in the pyloric glandular region. Many of the tumors produced were well or moderately differentiated adenocarcinomas of elevated type. According to the degree of depth invasion, a majority of the tumors were classified as early-stage lesions invading within submucosal layer. There were two poorly differentiated lesions, which were both recognized as serosal neoplastic involvements. The tumors were positively stained by toluidine blue (pH 4.1) to indicate the presence of stroma. The Brdu-LI determined for gastric mucosal epithelial cells was significantly higher in the MNNG-treated group than in the untreated control group. However, the LI for cancer tissue in the MNNG-treated group did not significantly differ from that for gastric mucosa in the same group.

Topics: Animals; Bromodeoxyuridine; DNA; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of oral administration of L-phenylalanine on the incidence and histology of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine was investigated in inbred Wistar rats. Oral administration of 6% phenylalanine after 25 weeks of treatment with the carcinogen significantly reduced the incidence and number of adenocarcinomas of the glandular stomach at experimental week 52. Oral administration of high dose phenylalanine significantly increased the basal serum gastrin level and significantly decreased the norepinephrine concentration in the antral portion of the gastric wall, as well as the labelling indices of antral mucosa. These findings indicate that orally administered phenylalanine inhibits the development of gastric cancers.

Topics: Adenocarcinoma; Administration, Oral; Animals; Gastric Mucosa; Gastrins; Hydrogen-Ion Concentration; Incidence; Male; Methylnitronitrosoguanidine; Norepinephrine; Phenylalanine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of bromocriptine on inhibition by cysteamine of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine was investigated in inbred Wistar rats. After 25 weeks of p.o. treatment with N-methyl-N'-nitro-N-nitrosoguanidine, rats were given injections every other day: cysteamine (50 mg/kg body weight); cysteamine (50 mg/kg body weight) plus bromocriptine (0.5 or 0.25 mg/kg body weight); or bromocriptine (0.5 or 0.25 mg/kg body weight). In week 52, the group treated with cysteamine showed a significantly decreased incidence of gastric cancers. Concomitant treatment with bromocriptine at 0.5 but not at 0.25 mg/kg body weight significantly attenuated the inhibitory effect of cysteamine on gastric carcinogenesis. Administration of bromocriptine alone at either dosage had no influence on gastric carcinogenesis. The labeling index of the antral mucosa was significantly reduced in rats treated with cysteamine and significantly higher in those treated concomitantly with bromocriptine at 0.5 mg/kg body weight than in those treated with cysteamine alone. These findings indicate that cysteamine suppressed gastric carcinogenesis and that bromocriptine at high dosage attenuated this inhibition. These findings also suggest that dopamine is involved in the mechanism of inhibition of gastric carcinogenesis by cysteamine.

Topics: Animals; Bromocriptine; Cysteamine; Drug Interactions; Gastric Acid; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Mitotic Index; Norepinephrine; Rats; Rats, Inbred Strains; Reference Values; Stomach Neoplasms

Mucin histochemistry of experimental gastric cancers induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine or 4-nitroquinoline 1-oxide was analysed by labelled lectin staining for concanavalin A (Con A) after prior periodate oxidation (paradoxical Con A staining) or Arachis hypogarea agglutinin (peanut lectin, PNA) with or without prior periodate oxidation. In the digestive tracts of control-group rats the mucins were classified into class II or III by paradoxical Con A staining. Class II mucins were found in surface mucous cells, goblet cells and the surface coat of intestinal absorptive cells, while class III mucins were present in mucous neck cells, pyloric gland cells and Brunner's gland cells. Although class III mucins showed PNA reactivity, those in pyloric gland cells selectively lost positive staining after 1-4 h oxidation with periodate. Thus phenotypic expression of class III mucin-positive cells in the gastric mucosa could be further classified into mucous-neck-cell type and pyloric-gland-cell type on the basis of this sensitivity to periodate oxidation. Metaplastic cells in fundic mucosa and almost all class III mucin-positive cells in adenomatous hyperplasias, well-differentiated adenocarcinomas and signet-ring cell carcinomas, which developed in both fundic and pyloric mucosae, showed pyloric gland phenotypic expression.

Topics: 4-Nitroquinoline-1-oxide; Adenocarcinoma; Animals; Intestinal Mucosa; Male; Methylnitronitrosoguanidine; Mucins; Phenotype; Pyloric Antrum; Pylorus; Rats; Rats, Inbred Lew; Rats, Inbred Strains; Rats, Inbred WKY; Reference Values; Species Specificity; Stomach Neoplasms

The effects of 6-hydroxydopamine (6-OHDA) on gastric carcinogenesis, on inhibition by tetragastrin of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and on the tissue catecholamine concentrations of the gastric wall and the labeling index of the gastric mucosa were investigated in inbred Wistar rats. Rats received s.c. injections of tetragastrin (1 mg/kg of body weight every other day) in depot form, i.p. injections of 6-OHDA (42 mg/kg twice within 24 h and 105 mg/kg every 2 wk), or injections of both compounds after 25 wk of p.o. treatment with N-methyl-N'-nitro-N-nitrosoguanidine (100 micrograms/ml). At Wk 52, prolonged administration of tetragastrin or 6-OHDA had significantly reduced the incidence and the number of adenocarcinomas. Combined administration of tetragastrin and 6-OHDA significantly enhanced the inhibitory effects of tetragastrin or 6-OHDA on gastric carcinogenesis. Administration of 6-OHDA but not tetragastrin, caused a significant decrease in norepinephrine concentrations in the antral portion of the gastric wall. Rats treated with tetragastrin or 6-OHDA had a significantly lower labelling index of the antral mucosa, and this index was significantly decreased by combined administration of tetragastrin and 6-OHDA, as compared with labeling indices observed after treatment with tetragastrin or 6-OHDA alone. These findings indicate that 6-OHDA exerts a protective effect against gastric carcinogenesis and enhances the inhibitory effect of tetragastrin on gastric carcinogenesis. This effect of 6-OHDA may be related to its ability to inhibit cell proliferation of the antral mucosa.

Topics: Animals; Catecholamines; Cell Division; Ganglia, Sympathetic; Gastrins; Hydroxydopamines; Male; Methylnitronitrosoguanidine; Organ Size; Oxidopamine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Sympathetic Nervous System; Tetragastrin

The effects of nialamide, a monoamine oxidase inhibitor, on the incidence, number, and histology of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in male Wistar rats. Rats were given subcutaneously 50 mg/kg body weight of nialamide in depot form every other day after 25 weeks of oral treatment with MNNG. Prolonged alternate-day administration of nialamide caused a significant increase in the incidence and number of gastric cancers of the glandular stomach in week 52. However, it did not affect the histology of the cancers. Nialamide also caused a significant increase in tissue norepinephrine concentrations in the gastric wall and in the labeling indices of the gastric mucosae. However, nialamide had no influence on serum gastrin levels in the fasting state and after re-feeding. These findings indicate that nialamide promotes gastric carcinogenesis and that this may be related to its effects in increasing norepinephrine in the gastric wall and stimulating proliferation of gastric epithelial cells.

Topics: Adenocarcinoma; Animals; Gastric Fundus; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Nialamide; Norepinephrine; Pyloric Antrum; Rats; Rats, Inbred Strains; Stomach Neoplasms

In an approach to early detection of gastric carcinogens and promoters in an in vivo test system, promotion by sodium chloride (NaCl) and the synergistic effects of NaCl and sodium taurocholate (Na-TC) on development of pepsinogen-altered pyloric glands (PAPG) in rat glandular stomach after initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated. A total of 205 male WKY/NCrj rats were divided into 8 groups. Group 1 was given a single dose of MNNG of 160 mg/kg body weight by gastric intubation, and starting 2 weeks later basal diet containing Na-TC for 18 weeks. In addition, 1 ml doses of saturated NaCl solution were given by gastric intubation at weeks 4, 6, 8 and 10. Similarly, group 2 was treated with MNNG and Na-TC, while group 3 animals received MNNG and NaCl. Group 4 was given MNNG alone. Groups 5-8 served as equivalent controls without MNNG initiation. The results revealed significantly enhanced induction of immunohistochemically defined PAPG in the Na-TC + NaCl (P less than 0.001), Na-TC (P less than 0.01) and NaCl (P less than 0.01) treated animals initiated with MNNG. Sodium chloride demonstrated a clear synergistic effect with Na-TC in promoting the development of PAPG, suggesting possible advantage for its use in medium-term in vivo assays for detection of gastric carcinogens and promoters.

Topics: Animals; Biological Assay; Carcinogens; Drug Synergism; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Pepsinogens; Rats; Rats, Inbred WKY; Sodium Chloride; Stomach Neoplasms; Taurocholic Acid

The effects of somatostatin on the incidence, number, and histological type of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in Wistar rats. Rats received alternate-day s.c. injections of 100 or 200 micrograms/kg body weight of somatostatin in depot form after 25 weeks of p.o. treatment with the carcinogen. Prolonged administration of somatostatin at both dosages significantly increased the incidence and number of gastric cancers of the glandular stomach in Week 52. Furthermore, somatostatin at 200 micrograms/kg caused a significant increase in the incidence of gastric cancers penetrating the muscle layer or deeper layers. However, somatostatin at both dosages did not influence their histological appearance. Histologically, somatostatin at both dosages significantly elevated the labeling index of gastric cancers but not of the antral mucosa and significantly reduced the gastrin levels. These findings indicate that somatostatin enhances gastric carcinogenesis after N-methyl-N'-nitro-N-nitrosoguanidine treatment and that this effect may be related to its effect in increasing proliferation of gastric cancers and decreasing serum gastrin level.

Topics: Animals; Carcinoma; Cell Division; Gastric Mucosa; Gastrins; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Somatostatin; Stomach Neoplasms

Six-week old non-castrated and castrated Wistar rats of both sexes, 20 in each group, received a continuous dose of 83 micrograms/ml MNNG in drinking water for 32 weeks. All animals were autopsied at the 52nd week for pathological examination. The incidence of the gastric adenocarcinoma was 31.6-50.0%, and no significant differences were obtained statistically between different MNNG-treated groups. No tumor was found in the control group. Quantitative and qualitative studies of the intramucosal cyst (IC) showed that the ICs might be classified into simple and dysplastic. The former was subdivided into 5 groups and the commonest type was fundic cyst (81%). In MNNG-treated groups, the number of fundic cysts was decreased; nevertheless, the neck cell cysts were increased in number markedly. The number of dysplastic cysts in the MNNG-treated groups was significantly increased and this important precancerous lesion was closely related with the genesis of gastric adenocarcinoma.

Topics: Adenocarcinoma; Animals; Castration; Female; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The dependence of gastrocarcinogenesis on biochemical and morphological disorders of the stomach mucous membrane, i.e. epimolecular alteration of chromatin structure, inhibition of pepsinogen synthesis, alteration of ontogenetic heritage of glandular epithelium was studied in 450 random-bred white rats with the aid of a model of gastrocarcinogenesis induced with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). This agent weakened the DNA-protein linkage in the chromatin. The irreversibility of this phenomenon coincided with the crucial point of the MNNG gastrocarcinogenesis (precancer sign appearance). The consequences of MNNG-induced specific alteration of epithelial stem cells became inherited (stomach adenocarcinoma development). In parallel with gastrocarcinogenesis, concomitant deficiency of pepsinogen-pepsin in the mucous membrane also developed. The data suggest that deficiency of the enzyme was in some degree obliged to alteration of pepsinogen mRNA synthesis.

Topics: Adenocarcinoma; Animals; Chromatin; Female; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Pepsinogens; Rats; RNA, Messenger; Stomach Neoplasms

The effects of diethylmaleate (DEM), previously demonstrated to inhibit butylated hydroxyanisole (BHA)-induced forestomach hyperplasia, on BHA promotion of forestomach carcinogenesis in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined. Groups of male 6-week-old F344 animals were given a single i.g. administration of 150 mg/kg body weight MNNG and starting 1 week later administered powdered diet containing 1% BHA plus 0.2% DEM, 1% BHA, 0.2% DEM or basal diet alone for 51 weeks. Further groups of rats were treated with 1% BHA plus 0.2% DEM, 1% BHA, 0.2% DEM or basal diet alone without MNNG pretreatment. Histopathological assessment of lesions at week 52 revealed enhancement of MNNG-initiated papilloma (100 versus 50%) and squamous cell carcinoma (100 versus 0%) development by BHA as compared to controls. Additional treatment with DEM, however, significantly reduced the relative incidences of carcinoma in situ (0 versus 35.7%) and squamous cell carcinoma (35.7 versus 100%), as well as BHA-induced forestomach hyperplasia with or without prior MNNG treatment. The results thus clearly demonstrate that DEM acts as a potent antagonist to BHA-promotion of rat forestomach carcinogenesis.

Topics: Animals; Butylated Hydroxyanisole; Cocarcinogenesis; Male; Maleates; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms

The effects of tea extracts and their ingredients, catechins and L-ascorbic acid (AsA), on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined in vitro and in the stomachs of rats using E. coli WP2 and S. typhimurium TA100. The extracts of green tea and black tea leaves decreased the mutagenic activity of MNNG to E. coli WP2 in vitro in a desmutagenic manner. Catechins such as (-)-epigallocatechin from green tea leaves and the low-molecular-weight tannin fraction isolated from black tea extract with HP-20 resin also exhibited inhibitory effects against the mutagenic activity of MNNG. A desmutagenic effect of AsA on MNNG-induced mutagenicity was observed depending on the dose, though it was complicated. The effects were also demonstrated in the stomachs of rats by assaying the bacterial mutagenic in vitro; the tea extracts previously given orally to rats reduced the mutagenic activity of MNNG remarkably, though simultaneous administration showed less effect. The effectiveness of tea extracts for the decrease of MNNG-induced mutagenesis in vitro and in vivo suggests that the habitual drinking of tea may reduce the tumor-initiating potency of MNNG-type nitrosoureido compounds if they are formed in the stomach.

Topics: Animals; Ascorbic Acid; Catechin; Escherichia coli; Methylnitronitrosoguanidine; Mutagenicity Tests; Mutation; Plant Extracts; Rats; Salmonella typhimurium; Stomach Neoplasms; Tea

The promoting effect of bile acids on the development of gastric carcinoma was examined in rats treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). At the first experiment, two hundred and fifteen male Wistar rats were divided into 5 groups; after oral administration MNNG (120 micrograms/ml) for 24 weeks, group 1 received tap water, group 2 administered of chenodeoxycholic acid (CDCA) solution, group 3 had deoxycholic acid (DCA) solution for the next 12 weeks. Group 4 received CDCA solution and group 5 received DCA solution for 36 weeks without MNNG. At the second experiment, fifty one rats were divided into 3 groups; for the first 12 weeks, group 1 received tap water, group 2 CDCA and group 3 DCA. These 3 groups received MNNG for the next 24 weeks followed by tap water for 12 weeks. The incidence of gastric adenocarcinoma in MNNG-treated rats was significantly higher in group 3 (63.6%) as compared with that in group 1 (36.7%) in the first experiment. No carcinoma lesions was found in groups 4 and 5. In the second experiment, no significant changes was observed among 3 groups. Undifferentiated adenocarcinomas were identified in groups 2 and 3, especially treated with MNNG plus bile acids. The result suggested a promoting effect of bile acids, especially DCA, in stomach carcinogenesis.

Topics: Adenocarcinoma; Animals; Bile Acids and Salts; Chenodeoxycholic Acid; Deoxycholic Acid; Drug Synergism; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

N-methyl-N-nitro-N-nitrosoguanidine (MNNG) was administered to 9 Macaca fascicularis monkeys (7 males and 2 females) through a tube at a dose of 40 mg/kg body weight 3 times a month. Tumors of the pyloric part of the stomach were observed in 2 male monkeys after MNNG doses of 800 and 848 mg/kg body weight, with a latent period of tumor development of 49 and 50 weeks, respectively. Histologically, in one case the tumor was a solid carcinoma, and in the other it had a mixed structure showing alternating solid and signet ring cell carcinoma areas.

Topics: Animals; Female; Macaca fascicularis; Male; Methylnitronitrosoguanidine; Stomach; Stomach Neoplasms

The effects of ethanol (EtOH) on the incidence and histology of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in Wistar rats. The animals received alternate-day i.p. injections of 2.5 ml kg-1 body weight of 20% EtOH in 0.9% NaCl solution after 20 weeks of oral treatment with MNNG. Prolonged administration of EtOH resulted in a significant increase in the incidence and number of gastric cancers of the glandular stomach in week 52. However, it had no influence on the histological types of the gastric cancers. Furthermore, it caused a significant increase in the labelling index of the epithelial cells of the antrum in week 52. These findings indicate that EtOH promotes gastric carcinogenesis, and that this effect may be related to its effect in increasing proliferation of the antral epithelial cells.

Topics: Adenocarcinoma; Animals; Ethanol; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Animals; Atropine; Isoproterenol; Male; Methylnitronitrosoguanidine; Neostigmine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The study was initiated to evaluate the effect of N-methyl-N-nitro-N-nitrosoguanidine (NG) on gastric intraluminal prostaglandin release during a 30-day treatment period and to investigate the effect of a stable prostaglandin E1 analogue (misoprostol) on NG-induced gastric mucosal damage during the same time period. Samples of gastric juice (1 h) were obtained from 40 male Sprague-Dawley rats with chronic gastric fistulas, in basal conditions and after 5, 15 and 30 days of continuous oral administration of NG (120 mg/l) or tap water. Aliquots of gastric juice were titrated with 0.1 M NaOH. Other aliquots were extracted with ethyl acetate and subjected to specific radioimmunoassay for prostaglandin E2. The severity of gastric mucosal lesions was evaluated in 60 rats after 5 days and 30 days of continuous oral administration of NG (120 mg/l) or NG plus misoprostol (200 micrograms/kg-1/day-1) or tap water, and a histological study was carried out. Administration of NG induced a significant decrease of gastric intraluminal prostaglandin E2 concentration at 15 and 30 days. Oral administration of misoprostol, at non-antisecretory doses, protected the rats against NG-induced gastric mucosal damage. Prostaglandins may be involved in the early phases of experimental gastric carcinogenesis.

Topics: Animals; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Prostaglandins; Rats; Rats, Inbred Strains; Stomach Neoplasms

Modifying effects of resorcinol, hydroquinone, p-tert-butylcatechol (PTBC), p-methylcatechol (PMC), and o-methylcatechol on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced forestomach and glandular stomach carcinogenesis were investigated in F344 rats. Groups of 15 to 16 male 6-wk-old animals were given a single intragastric administration of 150 mg/kg of body weight of MNNG and starting 1 wk later were administered powdered diet containing 0.8% resorcinol, 0.8% hydroquinone, 1.5% PTBC, 1.5% o-methylcatechol, 1.5% PMC, or basal diet alone for 51 wk. Additional groups of 10 to 15 rats each were treated with the phenolic compounds or received basal diet without prior carcinogen exposure. Histological examination after sacrifice at Wk 52 revealed that squamous cell carcinoma development in the forestomachs of rats treated with MNNG followed by PTBC (75%, P less than 0.001) or MNNG followed by PMC (100%, P less than 0.001) was significantly greater than in animals receiving MNNG alone (20%). Treatment with PMC alone also resulted in a 40% yield of papilloma. In the glandular stomach, incidences of adenomatous hyperplasias in rats treated with MNNG followed by PTBC (31.3%, P less than 0.05) or PMC (100%, P less than 0.001) and the incidence of adenocarcinomas in rats treated with MNNG followed by PMC (100%, P less than 0.001) were significantly higher than in controls. In addition, PMC alone induced a 100% yield of adenomatous hyperplasias and 6.7% of adenocarcinomas. Thus, the results demonstrated that PTBC and PMC treatment significantly enhances forestomach and glandular stomach carcinogenesis and that PMC itself may possess weak carcinogenic potential in these organs. The ortho-position appears to be important for this dihydroxybenzene activity.

Topics: Adenocarcinoma; Adenoma; Animals; Hyperplasia; Male; Methylnitronitrosoguanidine; Phenols; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms; Structure-Activity Relationship

The effects of bombesin on the incidence, number, histological type, and depth of involvement of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in male Wistar rats. Rats received alternate-day s.c. administration of 20 or 40 micrograms/kg body weight of bombesin in depot form after p.o. treatment with the carcinogen for 25 weeks. Prolonged administration of bombesin at 40 micrograms/kg led to a significant increase in the incidence and number per rat of gastric cancers of the glandular stomach at Week 52. In rats that had received alternate-day injections of 20 micrograms/kg of bombesin, the number of gastric cancers per rat, but not the incidence of cancer, was significantly more than in untreated rats. However, bombesin at both dosages did not affect the histological appearance of the lesions or their depth of involvement. At Weeks 30 and 52, norepinephrine concentrations in the fundic and antral portion of the gastric walls and labeling indices in the antral and fundic mucosae were significantly higher in rats treated with bombesin at both dosages than in untreated rats. These findings indicate that bombesin enhances gastric carcinogenesis after administration of N-methyl-N'-nitro-N-nitrosoguanidine is stopped and that this effect may be related to its effects in increasing tissue norepinephrine concentrations in the stomach wall and increasing cell proliferation in the gastric mucosa.

Topics: Animals; Bombesin; Cocarcinogenesis; Drug Administration Schedule; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Norepinephrine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Glyoxal and methylglyoxal were tested for tumor-promoting potential in a two-stage stomach carcinogenesis model. Male outbred Wistar rats were initially given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water (100 mg/l) along with a 10% sodium chloride dietary supplement for 8 weeks. Thereafter, they were returned to basal diet and maintained on drinking water containing no addition or either 0.5% glyoxal or 0.25% methylglyoxal for 32 weeks and then killed for necropsy and histological examination at week 40. Glyoxal treatment significantly increased the incidence of adenocarcinomas in the pylorus of the glandular stomach of rats pretreated with MNNG and sodium chloride. Furthermore, although methylglyoxal did not enhance the development of adenocarcinomas, the incidence of hyperplasias in the pylorus was significantly increased. The results indicate that glyoxal exerts tumor promoting activity on rat glandular stomach carcinogenesis and that methylglyoxal might also have promoting potential.

Topics: Aldehydes; Animals; Body Weight; Glyoxal; Hyperplasia; Male; Methylnitronitrosoguanidine; Pyruvaldehyde; Rats; Rats, Inbred Strains; Reference Values; Stomach; Stomach Neoplasms

We examined the tumor-promoting activity of sodium taurocholate in the remnant stomach of rats. Ninety male Wistar rats, 8 weeks of age, were separated into four groups. In group I, the rats were given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at a concentration of 83 mg/l in drinking water for 15 weeks, and distal partial gastrectomy was performed by Roux-en-Y procedure to prevent duodenal reflux into the remnant stomach. Thereafter, a diet containing 0.25% sodium taurocholate was given for 43 weeks. The group II rats were given MNNG and gastrectomy and were then given the usual commercial diet. The rats in group III were given gastrectomy and sodium taurocholate and no previous administration of MNNG. Only MNNG was given to the rats in group IV. The incidence of malignant tumors in the remnant stomach was 40.9% (9/22), 27.3% (6/22), and 0% (0/22) in groups I, II, and III, respectively, while the incidence in the area corresponding to the remnant stomach (control) was 8.3% (2/24) in group IV. The difference in tumor incidence was statistically significant (P less than 0.05) between groups I and IV but not between groups II and IV, and not between groups I and II. Six of nine tumors in group I and all six tumors in group II were located in the anastomotic area. These results suggest that sodium taurocholate promotes tumor production in the remnant stomach, and that the surgical procedure may well be associated with this enhanced tumor occurrence.

Topics: Animals; Cocarcinogenesis; Gastrectomy; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms; Taurocholic Acid

In order to establish an effective method to induce selectively experimental dog esophageal carcinoma, we compared the restricted oral administration of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) with projecting spout with the ad libitum oral administration of it. Five dogs were given a solution of ENNG at a concentration of 50mg/l with restricted oral administration with projecting spout for 52 weeks. In all of them, elevated type of esophageal lesions were endoscopically observed soon after the cessation of the ENNG administration. Histological examination revealed that besides the multiple squamous cell carcinomas of the esophagus, various degrees of dysplasias were seen. Two dogs had metastasizes to the regional lymph nodes and one dog had metastatic lesions in the lung. Gastric carcinomas were also seen in four dogs. Another five dogs were given ad libitum the same concentration of ENNG solution. Gastric carcinomas were induced in four dogs, but esophageal carcinomas were seen in small lesions in two dogs. The restricted oral administration of ENNG with projecting spout is a reliable method for the selective induction of esophageal carcinoma in dog.

Topics: Administration, Oral; Animals; Carcinogens; Carcinoma, Squamous Cell; Dogs; Esophageal Neoplasms; Female; Male; Methylnitronitrosoguanidine; Papilloma; Stomach Neoplasms

The influence of bile acids on the development of remnant gastric carcinoma was examined by investigating the incidence of carcinogenesis in noninbred male Wistar rats treated orally with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; CAS 70-25-7; 1-methyl-3-nitro-1-nitrosoguanidine) and fed a diet containing 1% cholesterol. The high-cholesterol diet did not influence the incidence of carcinoma in the nongastrectomized, MNNG-treated groups of rats. However, in the gastrectomized groups, the incidence of carcinoma was significantly higher in the group given the high-cholesterol diet (60.6%) than in the group given a normal diet (35.5%). Histologically undifferentiated adenocarcinoma was recognized more frequently in the high-cholesterol-diet group. Three gastrectomized rats not treated with MNNG but fed the high-cholesterol diet developed remnant gastric carcinoma (13%), whereas none of the rats given the normal diet did. Because the fecal excretion of bile acids increased significantly in the rats fed the high-cholesterol diet and the gastroduodenal reflux of bile acids was probably accelerated, the increase in the incidence of carcinogenesis in the remnant stomach was considered to be the result of the increase in the reflux of bile acids evoked by a high-cholesterol diet.

Topics: Animals; Bile Acids and Salts; Cholesterol, Dietary; Cocarcinogenesis; Female; Gastrectomy; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

The incidence, number, and histological types of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine and the tissue norepinephrine concentration of the gastric wall were investigated in spontaneously hypertensive rats and in control Wistar Kyoto rats and Wistar rats. All rats were given drinking water containing 25 micrograms/ml of N-methyl-N'-nitro-N-nitrosoguanidine for 25 weeks. During Week 52, the incidence and number per rat of gastric cancers were significantly greater in spontaneously hypertensive rats than in Wistar Kyoto and Wistar rats. All tumors induced in the glandular stomach were adenocarcinomas, but no significant difference was found in the histological types of adenocarcinoma in the three strains of rats. At Weeks 15, 30, and 52, norepinephrine concentrations in the fundic and antral portion of the gastric walls and labeling indices in the antral and fundic mucosa were significantly higher in spontaneously hypertensive rats than in Wistar Kyoto and/or Wistar rats. These findings indicate that increased sympathetic nervous system activity enhances the development of gastric cancers, but immunological dysfunction in spontaneously hypertensive rats may contribute to the increased susceptibility to gastric cancer.

Topics: Adenocarcinoma; Animals; Blood Pressure; Body Weight; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Mitotic Index; Norepinephrine; Rats; Rats, Inbred SHR; Rats, Inbred Strains; Rats, Inbred WKY; Species Specificity; Stomach Neoplasms

The effects of neurotensin on the incidence and histology of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in Wistar rats. Rats were given 100 or 200 micrograms per kg of body weight of neurotensin s.c. every other day in depot form after 25 wk of p.o. treatment with the carcinogen. Prolonged alternate-day administration of neurotensin at 200 micrograms per kg of body weight resulted in a significant increase in the incidence of gastric cancers of the glandular stomach by Wk 52. However, it did not influence the histological appearance of the gastric cancers. Furthermore, it caused a significant increase in the labeling indices of the epithelial cells of the antrum and of gastric cancers. In contrast, the administration of neurotensin at 100 micrograms per kg of body weight had a slight, but not significant, influence on the development of gastric cancers. These findings indicate that neurotensin promotes gastric carcinogenesis, and that this effect may be related to its effect in increasing proliferation of epithelial cells in the antral mucosa and in gastric cancers.

Topics: Animals; Carcinogens; Drug Synergism; Male; Methylnitronitrosoguanidine; Neurotensin; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of oral administration of cysteamine (2-aminoethanethiol hydrochloride) on the incidence and histology of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated in inbred Wistar rats. Oral administration of 0.4% cysteamine in food after treatment with MNNG for 25 weeks significantly reduced the incidence and number of adenocarcinomas of the glandular stomach in experimental Week 52. Histological examination showed that adenocarcinomas that did develop in rats fed on cysteamine had high mucin-producing activity. Furthermore, oral administration of cysteamine caused a significant increase in serum gastrin level and significant decreases in the antral mucosal pH and the labeling indices of the antral mucosa. These findings indicate that cysteamine inhibits the development of gastric adenocarcinomas when given orally. This effect may be related to its ability to decrease proliferation of antral mucosal cells.

Topics: Adenocarcinoma; Animals; Cysteamine; Gastric Mucosa; Gastrins; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Mitosis; Rats; Rats, Inbred Strains; Stomach Neoplasms

The expression of c-Ha-ras-1, Ki-ras, N-ras, abl, src, fos and myc protooncogenes was analyzed in 13 cases of human gastric carcinomas. The transcriptional activity of both fos and myc protooncogenes was found to be disturbed in 47% and 42% of cases, respectively. An overexpression of fos protooncogenes as well as an appearance in some cases of atypical foc-mRNA transcripts were established. Only an elevation of the number of myc mRNA copies was observed. In one patient with gastric carcinoma a c-Ha-ras-1 overexpression was detected due to its amplification both in tumour tissues and in regional metastasis. The expression of other protooncogenes under investigation was similar to those found in normal gastric mucose. In addition, no differences in expression in protooncogenes mentioned above plus sis protooncogene were established in unchanged, premalignant and malignant stomach tissues in the course of N-methyl-N'-nitro-N-nitrosoguanidin-induced carcinogenesis.

Topics: Animals; Carcinoma; DNA, Neoplasm; Gastric Mucosa; Gene Expression Regulation; Humans; Lymphatic Metastasis; Male; Methylnitronitrosoguanidine; Nucleic Acid Hybridization; Proto-Oncogene Mas; Proto-Oncogenes; Rats; RNA, Neoplasm; Stomach Neoplasms; Time Factors; Transcription, Genetic

The effects of propranolol and cimetidine on inhibition by cysteamine (2-aminoethanethiol hydrochloride) of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and on gastric acid secretion, serum gastrin level, and labelling index of the gastric mucosa were investigated in inbred Wistar rats. Rats received alternate-day injections of cysteamine (25 mg/kg body weight) with or without propranolol (dl-propranolol hydrochloride) (2 mg/kg bw) or cimetidine (50 mg/kg bw) in depot form after 25 weeks of oral treatment with MNNG. Prolonged administration of cysteamine significantly reduced the incidence of adenocarcinoma of the glandular stomach. A combination of cysteamine and propranolol significantly accelerated the inhibitory effect of cysteamine on gastric carcinogenesis. However, with concomitant administration of cysteamine and cimetidine, the incidence of adenocarcinoma was slightly but not significantly increased as compared to that after treatment with cysteamine alone. Administration of cysteamine caused a significant increase in gastric acid secretion and serum gastrin level, and a significant decrease in the labelling index of the antral mucosa. A combination of cysteamine and propranolol significantly increased gastric acid secretion by cysteamine alone and significantly decreased the labelling index of the antral mucosa. With this treatment, the serum gastrin level was significantly higher than the basal level, but the stimulated serum gastrin level was significantly lower than observed that after administration of cysteamine alone. In contrast, concomitant administration of cysteamine and cimetidine caused a significant decrease in gastric acid secretion and significant increase in the serum gastrin level as compared to the levels seen after treatment with cysteamine alone, but had no influence on the labelling index of the antral mucosa. These findings indicate that hypersecretion of acid, but not hypergastrinemia associated with hyposecretion of acid or achlorhydria, exerts a protective effect against gastric carcinogenesis, and that this effect may be related to its activity in decreasing proliferation of the antral mucosa.

Topics: Adenocarcinoma; Animals; Cimetidine; Cysteamine; Gastric Acid; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Propranolol; Rats; Rats, Inbred Strains; Stomach Neoplasms

The experiments carried on 107 rats have shown that the sensitivity of the epithelium of experimental adenomatous diverticuli of the stomach to the action of N-methyl-N'-nitro-N-nitrosoguanidine is lower than that of the gland epithelium of the organ.

Topics: Adenocarcinoma; Animals; Diverticulum, Stomach; Epithelium; Female; Foreign Bodies; Gastric Mucosa; Hyperplasia; Methylnitronitrosoguanidine; Microscopy, Electron; Rats; Stomach; Stomach Neoplasms

Topics: Animals; Diverticulum, Stomach; Epithelium; Female; Foreign-Body Reaction; Gastric Mucosa; Methylnitronitrosoguanidine; Microscopy, Electron; Rats; Stomach Neoplasms

The comparative sensibility of the stomach gland epithelium and the epithelium of experimental gastric adenomatous diverticuli to carcinogenic action of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was examined in experiments carried out in 107 rats; pathohistological techniques and electron-microscopic methods were applied. The epithelium of adenomatous diverticuli showed no signs of atypia or neoplasia in the course of MNNG-induced gastrocarcinogenesis. On the contrary, the epithelium of the gland cambial zone developed precancerous changes and adenocarcinomas. The formation of experimental diverticuli did not stimulate the development of rat stomach cancer.

Topics: Adenoma; Animals; Diverticulitis; Diverticulum, Stomach; Female; Foreign Bodies; Gastric Mucosa; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

The genetically-controlled, distinct sensitivity of different rat strains to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced cancer of the glandular stomach and duodenum was investigated. MNNG is activated through thiols, and the thiol content of the glandular stomach, duodenum, and liver of the BN rat tended to be slightly, but not significantly higher than that of the Wistar, Sprague-Dawley, Lewis, and Buffalo rats. The levels of the DNA repair system, O6-alkylguanine transferase (AGT), in sensitive Wistar strain rats had values similar to those in resistant Buffalo strain rats. Administration of 80 mg/liter of MNNG in the drinking water for six weeks up to the time of tissue collection yielded the same AGT levels. Of all the parameters examined to account for genetically-mediated sensitivity to gastrointestinal cancer induction, namely, N-denitrosation, thiol activation, AGT-related DNA repair, and cell duplication rates, the latter yielded the best association, although these factors acting together may be involved.

Topics: Animals; DNA Repair; Gastric Mucosa; Glutathione; Male; Methylnitronitrosoguanidine; Methyltransferases; O(6)-Methylguanine-DNA Methyltransferase; Rats; Rats, Inbred Strains; Species Specificity; Stomach Neoplasms; Sulfhydryl Compounds

This paper describes factorial experiments designed to determine whether two carcinogens that act on different organ systems act synergistically to produce cancers in Fischer 344 rats. Four carcinogens, N-methyl-N'-nitrosoguanidine (MNNG), N-butanol-N-butylnitrosamine (NBBN), nitilotriacetic acid (NTA), and dipentylnitrosamine (DPN) were studied in pairwise combinations. Each of the six possible pairs was studied by means of a 4 X 4 factorial experiment, each agent being fed at zero and at three non-zero doses. Methods of analysis designed explicitly for this study were derived to study interaction. These methods were supplemented by standard statistical methods appropriate for single agent studies. Antagonism was demonstrated in some chemical mixtures containing NTA. Other chemical mixtures did not interact. Findings for male and female animals were generally, but not always, in agreement.

Topics: Animals; Butylhydroxybutylnitrosamine; Carcinogens; Cocarcinogenesis; Data Interpretation, Statistical; Drug Interactions; Female; Kidney Neoplasms; Liver Neoplasms, Experimental; Male; Methylnitronitrosoguanidine; Nitrilotriacetic Acid; Nitrosamines; Rats; Rats, Inbred F344; Sex Factors; Stomach Neoplasms; Urinary Bladder Neoplasms

The effect of caerulein on the incidence and histology of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine was investigated in inbred Wistar rats. Prolonged alternate-day administration of caerulein at 10 micrograms/kg body weight after treatment with the carcinogen for 20 weeks significantly increased the incidence and number of adenocarcinomas of the glandular stomach. Histological examination showed that treatment with caerulein had no influence on the histology of induced adenocarcinomas. Furthermore, administration of caerulein resulted in a significant increase in the bromodeoxyuridine-labeling indices of the antral mucosa but did not influence the bromodeoxyuridine-labeling indices of the fundic mucosa and the carcinomas. These findings indicate that caerulein enhances gastric carcinogenesis and that the effect may be related to the promoting effect of caerulein on cell proliferation in the antral mucosa.

Topics: Animals; Bromodeoxyuridine; Cell Division; Ceruletide; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) induces a high incidence of carcinomas in the glandular stomach of rats following chronic administration in the drinking water. We determined the level of 7-methylguanine and O6-methylguanine in gastric and duodenal DNA during chronic exposure to MNNG (80 p.p.m.). After considerable fluctuations during the initial 3 weeks, levels of methylpurines reached a steady state which was approximately three times higher in the pylorus (i.e. the preferential site of tumor induction) than in the fundus and duodenum, with 7-methylguanine and O6-methylguanine values in the range of 520 and 110 mumol/mol guanine, respectively. When rats were given MNNG in the drinking water at concentrations ranging from 10 to 80 p.p.m. for 3 weeks, levels of methylpurines reached maximum values already at 10-20 p.p.m. At higher MNNG concentrations, there was no further increase in DNA alkylation. The reason for this lack of dose response remained unclear. Immunohistochemical analyses showed that DNA methylation by MNNG is restricted to epithelial cells bordering the luminal surface. The possibility exists that in this target cell population the content of free thiols is a limiting factor for the decomposition of MNNG and its reaction with macromolecules in the gastric mucosa. Addition to the diet of sodium taurocholate, a bile acid previously shown to enhance MNNG-induced stomach carcinogenesis, did not influence the extent of DNA methylation, indicating that it acts as a promoter.

Topics: Animals; Diet; DNA; Duodenum; Gastric Mucosa; Male; Methylation; Methylnitronitrosoguanidine; Organ Specificity; Rats; Rats, Inbred Strains; Stomach Neoplasms; Taurocholic Acid

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Prostaglandins E; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Duodenogastric Reflux; Female; Gastrectomy; Gastroenterostomy; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effects of combined administration of cimetidine and tetragastrin on gastric acid secretion, the labeling index of the gastric mucosa, and the incidence of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in inbred Wistar rats. Prolonged administration of tetragastrin in depot form after treatment with N-methyl-N'-nitro-N-nitrosoguanidine resulted in a significant increase in gastric acid secretion, a significant decrease in the labeling index of the antral mucosa, and a significant decrease in the incidence of adenocarcinomas of the glandular stomach. Administration of cimetidine at 20 mg, but not 10 mg, per kg body weight with tetragastrin significantly reduced the gastric acid secretion induced by tetragastrin alone but did not influence the labeling index of the antral mucosa or the inhibitory effect of tetragastrin on gastric carcinogenesis. These findings indicate that gastric acid secretion has no influence on the development of gastric adenocarcinomas and that the inhibitory effect of tetragastrin on gastric carcinogenesis may be related to its effect in decreasing proliferation of cells in the antral mucosa.

Topics: Adenocarcinoma; Animals; Cimetidine; DNA; Gastric Acid; Gastric Mucosa; Gastrins; Hyperplasia; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Tetragastrin

Sequential changes of numbers of pepsinogen 1 (Pg 1)-decreased pyloric glands (PDPG) detected by immunohistochemistry and of the incidence of gastric carcinomas were examined in five different strains of rats treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG;CAS:70-25-7). Male SD (Crj:CD), WKY (WKY/NCrj), Lewis (LEW/Crj), Wistar (Crj:Wistar) and F344 (F344/DuCrj) rats (40 per strain), were given drinking water containing 100 micrograms/ml MNNG for 30 weeks and then normal tap water, and were killed at week 10, 30 and 50 of the experiment. Adenocarcinomas of the glandular stomach were found in nine of 15 SD rats (60%), in eight of 12 WKY rats (67%), in eight of 15 Lewis rats (53%), in three of 13 Wistar rats (23%) and in one of 18 F344 rats (6%) at week 50. These incidences of carcinomas in SD, WKY and Lewis were significantly higher (P less than 0.01) than that in F344 rats. From week 10, the numbers of PDPG in SD, WKY and Lewis rats were significantly greater (P less than 0.01) than that in F344 rats. From week 30, the numbers of PDPG in Wistar rats were also significantly greater (P less than 0.05-0.01) than that of F344. The susceptibility of rats to induction of gastric carcinoma by MNNG correlated with the susceptibility to induction of PDPG by MNNG in each strain, suggesting that induction of PDPG is a preneoplastic change in chemical gastric carcinogenesis.

Topics: Animals; Gastric Mucosa; Hyperplasia; Immunohistochemistry; Intestinal Neoplasms; Male; Methylnitronitrosoguanidine; Pepsinogens; Precancerous Conditions; Pylorus; Rats; Rats, Inbred Strains; Species Specificity; Stomach Neoplasms

The effect of cysteamine (2-aminoethanethiol hydrochloride) on the incidence and histology of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated in inbred Wistar rats. Prolonged administration of 25 or 50 mg per kg body weight of cysteamine after treatment with MNNG for 25 weeks significantly reduced the incidence and number of adenocarcinomas of the glandular stomach. Histological examination showed that the adenocarcinomas that did develop in rats treated with these 2 doses of cysteamine had high mucin-producing activity. Furthermore, treatment with cysteamine caused significant increases in serum gastrin level and gastric acid secretion, together with significant decreases in the antral mucosal pH and the labelling indices of pyloric and oxyntic gland mucosae and gastric cancer. These findings indicate that cysteamine inhibits the development of gastric adenocarcinomas and that its effect may be related to decreasing proliferation of cells in the gastric mucosae.

Topics: Adenocarcinoma; Animals; Cysteamine; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Time Factors

The pathologic characteristics of gastric tumors induced by single injections of N-methyl-N'-nitro-N-nitrosoguanidine (15 mg) solution and N-methyl-N-nitrosourea (10 mg) solution in 0.1 ml dimethylformamide were studied in 23 noninbred rats. The chemicals were injected into the antropyloric segment of the stomach. By months 11-15, specific changes in the glandular epithelium had developed at that site in 20 rats: dysplasia--in 6, precancer--7, and adenocarcinoma in 7 animals. Also, there were papillomas (6), squamous cell carcinoma (3), precancer and sarcoma (4) in various segments of the organ.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Methylnitrosourea; Papilloma; Precancerous Conditions; Rats; Sarcoma, Experimental; Stomach Neoplasms

Studies have been initiated to find compounds that can trap direct-acting carcinogens within the lumen of the gastrointestinal tract and thus prevent these carcinogens from attacking tissues of the host. Sodium 4-mercaptobenzene sulfonate (4-MBSNa) is a potent nucleophile and was found to react rapidly in vitro with the direct-acting carcinogen beta-propiolactone (BPL). In further investigations 4-MBSNa was shown to inhibit mutagenesis resulting from exposure of Salmonella typhimurium strain TA-100 to BPL and a second direct-acting carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine. Subsequent experiments were performed to determine if 4-MBSNa would inhibit BPL-induced carcinogenesis in vivo. In the first of these, 4-MBSNa was administered by p.o. intubation to female A/J mice 5 min before p.o. administration of BPL. Under these conditions inhibition of carcinogenesis of the forestomach occurred. In a second experiment, 4-MBSNa was given by rectal intubation 5 min before BPL also administered intrarectally. Administration of BPL intrarectally produced adenomatous polyps of the large intestine. The occurrence of these neoplasms was inhibited by the prior administration of 4-MBSNa. The data presented show that 4-MBSNa has the capacity to trap direct-acting carcinogens and to inhibit the occurrence of BPL-induced neoplasia.

Topics: Animals; Benzenesulfonates; Colonic Neoplasms; Female; Lactones; Male; Methylnitronitrosoguanidine; Mice; Propiolactone; Rats; Rats, Inbred F344; Stomach Neoplasms

The effect of ad libitum feeding of a defined diet in liquid form on the incidence of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated in Wistar rats. Fresh defined diet was supplied once every 24 h from 2 weeks before oral administration of MNNG to the end of the experiment in week 52. Oral administration of the defined diet resulted in significant decrease in the incidence of gastric cancers in experimental week 52. It also caused a significant increase in the incidence of atypical glandular hyperplasia, which is a precursor of gastric cancer. Furthermore, administration of the defined diet for 30 and 52 weeks also resulted in significant decrease in the serum gastrin level and the marked gastric mucosal hypoplasia. These findings indicate that the defined diet in liquid form inhibited the development of gastric cancers and that this effect may have been related to its effect in decreasing proliferation of cells in the antral mucosa.

Topics: Animals; Food, Formulated; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Reflux of duodenal contents into the stomach occurs in patients with pyloric incompetence and after gastric resection when bile-diverting procedures are omitted. In such settings duodenal contents have been considered to favor the development of gastric cancer. We have studied the effect of chronic duodenogastric reflux on gastric tumor promotion in rats treated with N-methyl-N'-nitrosoguanidine (MNNG) in an experimental design that avoids physical trauma to the glandular stomach. Thus the effect of trauma-induced tissue repair on carcinogenesis is eliminated, and duodenogastric reflux is isolated as an experimental parameter. To achieve such reflux the first jejunal loop was anastomosed to the forestomach in rats. Animals were exposed to MNNG in drinking water (83 mg/L) for 12 weeks before induction of reflux. Experimental groups were as follow: I, reflux plus MNNG (n = 32); II, MNNG alone (n = 27); III, reflux alone (n = 28); IV, control (n = 25). The experiment was terminated after 56 weeks. Only animals that had survived for 90 days were included in the effective number of animals, which allowed for equal chances of tumor development. In no animal that died earlier had tumors developed. Animals with reflux plus MNNG treatment had significantly more glandular neoplasms (12/32) than did animals with MNNG treatment alone (4/27; p less than 0.05). Similarly, more animals with squamous cell neoplasms were recorded in group I (9/32) than in group II (2/27; p less than 0.05). In consideration of all tumors of epithelial and mesenchymal origin, more gastric malignant tumors were observed in group I (9/32) than in group II (2/27; p less than 0.05). It is concluded that chronic exposure to duodenal contents promotes the development of gastric neoplasia.

Topics: Adenocarcinoma; Adenoma; Animals; Carcinoma, Squamous Cell; Cocarcinogenesis; Duodenogastric Reflux; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) dissolved in distilled water (5 g/l) was administered orally once by gastric tube at a dose of 0.25 ml/10 g body weight to 5-day-old or 28-day-old Wistar Furth (W/Fu) or ACI rats. Gastric tumors in the glandular stomach were found in 58% of 5-day-old ACI rats, but none were found in the rest of the groups. Forestomach tumors were found in both strains of rats at both age groups with incidences of 68-100%. Lung tumors were induced in 64% of 5-day-old and 6% of 28-day-old W/Fu rats, but not in ACI rats. Besides the tumors, a high frequency of hepatic cysts was also noted in ACI rats. Intestinal metaplastic foci with alkaline phosphatase activity were found in the group of 5-day-old ACI rats and none in the rest of the groups. The results showed that the incidences and the locations of tumors in rats induced by MNNG are greatly influenced by both strain and age.

Topics: Age Factors; Animals; Intestinal Neoplasms; Liver Neoplasms; Lung Neoplasms; Methylnitronitrosoguanidine; Mitotic Index; Neoplasms, Experimental; Rats; Rats, Inbred ACI; Rats, Inbred WF; Stomach Neoplasms

The effect of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) on the proliferative characteristics of the pyloric epithelium was investigated in ACI and Buffalo rats and their F1 rats, which are susceptible, resistant, and resistant, respectively, to gastric carcinogenesis by this chemical. After injection of bromodeoxyuridine (BrdUrd), DNA synthesizing cells in the pyloric epithelium were stained immunohistochemically with anti-BrdUrd antibody. The average number and range of distribution of cells labeled with BrdUrd in the pyloric glands were significantly larger in ACI rats than in Buffalo or F1 rats after administration of MNNG (83 micrograms/ml in the drinking water) for 2 or 16 weeks. In control rats given tap water for 2 weeks, there was no significant difference in these values in the three groups (Experiment 1). The distribution of cells that were labeled with [methyl-3H]MNNG in the pyloric epithelium was measured by histoautoradiography, and the distribution of cells double labeled with both [methyl-3H]MNNG and BrdUrd was also analyzed. Rats were given 83 micrograms/ml of MNNG in their drinking water for 2 weeks and then received [methyl-3H]MNNG by gavage and an injection of BrdUrd 2 and 1 h, respectively, before sacrifice. The average number of double labeled cells (i.e., replicating cells exposed to MNNG) was significantly larger in ACI rats than in Buffalo or F1 rats. In control rats given tap water without MNNG for 2 weeks, there was no significant difference in these values in the three groups (Experiment 2). Cells double labeled with [methyl-3H]MNNG and BrdUrd are considered to be cells with the potential to establish mutations (cell population at risk of MNNG-induced carcinogenesis). Our results show that, after MNNG treatment, the size of this cell population is larger in susceptible ACI rats than in resistant Buffalo and F1 rats. Thus, differential responses of the gastric mucosa to MNNG may be a key factor in the difference of susceptibility to gastric carcinogenesis between ACI and Buffalo rats.

Topics: Animals; Antibodies, Monoclonal; Cell Division; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Pyloric Antrum; Rats; Rats, Inbred BUF; Stomach Neoplasms

The modifying effects of five phenolic antioxidants on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-initiated forestomach and glandular stomach carcinogenesis were investigated in male F344 rats. Groups of 20 rats were given an intragastric dose of 150 mg/kg body weight MNNG, and starting from 1 week later received diet supplemented with 0.8% catechol (CC), 1.0% 2-tert-butyl-4-methylphenol, 1.5% p-tert-butyl-phenol, 1.5% methylhydroquinone, 1.5% 4-methoxyphenol (4MP), or basal diet alone for 51 weeks. Further groups of 10-15 rats were maintained as controls without prior treatment with MNNG. The incidences of squamous cell carcinoma of the forestomach in MNNG-treated animals were significantly elevated by the diets containing CC (P less than 0.001), 2-tert-butyl-4-methylphenol (P less than 0.001), or p-tert-butylphenol (P less than 0.01), while the development of carcinoma in situ was inhibited by 4MP (P less than 0.01). Treatment with CC, 2-tert-butyl-4-methylphenol, p-tert-butylphenol, or 4MP alone induced forestomach hyperplasia at incidences of 86.7, 40, 93.3, and 100%, respectively. In the pyloric region of the glandular stomach, the development of adenomatous hyperplasia and adenocarcinoma after MNNG treatment was significantly enhanced by diet containing CC (P less than 0.001). Moreover, treatment with CC alone induced 100% adenomatous hyperplasia and induced adenocarcinoma in 20% of animals. These results clearly demonstrated that while antioxidants causing proliferation in forestomach epithelium can markedly enhance carcinogenesis in this tissue, others displaying the same or greater potential for generating a hyperplastic response, like 4MP, can exert an inhibitory effect. In addition, it was shown that CC, which is widely present in our environment, is an unequivocal glandular stomach carcinogen also possessing strong enhancing activity for MNNG-induced lesion development.

Topics: Animals; Anisoles; Antioxidants; Butylated Hydroxytoluene; Carcinoma in Situ; Carcinoma, Squamous Cell; Catechols; Male; Methylnitronitrosoguanidine; Phenols; Rats; Rats, Inbred F344; Stomach Neoplasms

After administration of N-methyl-N'-nitro-N-nitrosoguanidine for 15 weeks, the effects of bilateral, anterior and posterior vagotomy on the incidence, number and location of gastric adenocarcinomas, gastric acid secretion and cell proliferation of the gastric mucosa were investigated in inbred Wistar rats. Bilateral or anterior vagotomy, but not posterior vagotomy, significantly increased the incidence and number of adenocarcinomas at experimental week 52. In sham-operated control rats and rats subjected to bilateral vagotomy, there was no significant difference between the incidence or number of gastric tumors in the anterior and posterior walls. After anterior and posterior vagal denervation, however, there were significantly more gastric cancers on the denervated side than on the other. Bilateral and unilateral vagotomy resulted in significantly reduced gastric acid secretion by experimental weeks 25 and 52. Bilateral vagotomy significantly increased the labelling indices of both the fundic and antral mucosa at both times, but did not cause any significant difference between those of the anterior and posterior wall. Anterior or posterior vagotomy resulted in a significant increase in the labelling indices of both the fundic and antral mucosa on the denervated side. These findings indicate that the vagal nerve exerts a trophic action on the gastric mucosa, and that the promoting effect of vagotomy on gastric carcinogenesis may be related to its effect in increasing proliferation of cells in the antral mucosa.

Topics: Animals; Gastric Acid; Gastric Mucosa; Gastrins; Hyperplasia; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Vagotomy

The cell kinetic alteration in the background mucosa of canine gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) was evaluated by cytofluorometry in which the rate of S and G2 + M phase cell in gastric mucosal cells could be calculated, and a triphasic alteration was demonstrated; an initial reduction phase, an increase phase and a plateau phase with a high value. The initial reduction phase was caused by non-specific toxicity of ENNG as observed in drug induced gastric mucosal lesions, and subsequent increase and plateau phases originated from the action of ENNG itself to activate the mucosal turn-over and from histological changes in the background mucosa such as regenerative hyperplastic change after mucosal erosion and atrophic changes, sometimes including intestinal metaplastic change. Further, in comparison to carcinogenesis in chemically induced gastric cancer with and without a surfactant (Tween 60), it was suggested that one of the promotion effects of Tween 60 was closely related with activation of the mucosal turn-over.

Topics: Adenocarcinoma, Mucinous; Animals; Cell Cycle; Cell Transformation, Neoplastic; DNA, Neoplasm; Dogs; Flow Cytometry; Gastric Mucosa; Gastroscopy; Male; Methylnitronitrosoguanidine; Polysorbates; RNA, Neoplasm; Stomach Neoplasms

Intestinal metaplasia (IM) in the glandular stomach of male Wistar rats induced by oral administration of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) and/or intubation of 0.1N sodium hydroxide (NaOH) was studied as follows. Experiment I, sequential study: Rats in group I were given 100 micrograms/ml ENNG in drinking water for 12 weeks. Rats in group II were given 5 ml of 0.1N NaOH by gastric intubation once a week for 12 weeks. Group III control rats were given tap water. Rats were killed from week 1 until week 69 sequentially. IM was first found at week 26 in group I and at week 58 in groups II and III, its incidence being significantly higher in group I than in the other two groups (P less than 0.01), but without any difference between group II and group III. Experiment II, two-stage carcinogenesis: Rats in groups I and II were treated in the same way as in experiment I, while rats in group III were given 100 micrograms/ml ENNG for 12 weeks, followed by 0.1N NaOH once a week for 12 weeks intragastrically. All rats were killed at week 56. The numbers of metaplastic glands in groups I and III were higher than in group II. Gastric carcinomas were induced in all groups of rats treated with ENNG. The results of these two experiments show that IM is effectively induced by a carcinogen but is not enhanced by regeneration induced by alkaline treatment.

Topics: Aging; Animals; Carcinogens; Carcinoma; Gastric Mucosa; Male; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Inbred Strains; Regeneration; Sodium Hydroxide; Stomach Neoplasms

Therapeutic effects and dynamics of UFT were studied using beagles with ENNG-induced gastric cancers. Nine canine subjects confirmed to have gastric cancers by punch biopsy under gastrofiberscopy were divided into 3 group given 5 mg/kg/day of UFT for 101 days, 7.5 mg/kg/day for 67 days and 12 mg/kg/day for 45 days, respectively. Although the extent of macroscopic change revealed by gastrofiberscopy was minor, one of the dogs in the third group did show a Grade II b effect according to the criteria of Histopathological Effects on Cancer Tissues by Chemotherapy proposed by Oboshi and Shimozato. Animals were sacrificed by bleeding 4 hours after the last administration of anticancer agent and concentration of 5-FU and tegafur in the serum and each organ were determined. It was recognized that the concentration of anticancer agent in gastric cancer tissue was higher than that in neighboring normal gastric tissue.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Body Weight; Dogs; Male; Methylnitronitrosoguanidine; Stomach Neoplasms; Tegafur; Tissue Distribution; Uracil

Sequential quantitative analyses were made of pepsinogen 1 (Pg 1) decreased pyloric glands after treating male WKY rats first with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and then with N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) as a second gastric carcinogen or sodium taurocholate (Na-TC) as a gastric promoter. Animals received a single dose of MNNG (160 mg/kg body weight) by gastric intubation followed two weeks later by either ENNG in drinking water (100 micrograms/ml) (group 1), basal diet containing 0.25% Na-TC (group 2), or basal diet and tap water (group 3), from weeks 3 to 24. Animals were sacrificed at weeks 8, 12, 16, 20 and 24. Sections of the pyloric mucosa were investigated for Pg 1 immunostaining. In comparison with group 3, induction of Pg 1 decreased pyloric glands was significantly enhanced by ENNG from week 8 and by Na-TC from week 16. The former exerted a significantly stronger effect at each time point. The results suggest that Pg 1 decreased pyloric glands represent a good marker for early detection of gastric carcinogens and promoters in in vivo test systems.

Topics: Animals; Carcinogens; Gastric Mucosa; Immunologic Techniques; Isoenzymes; Male; Methylnitronitrosoguanidine; Pepsinogens; Precancerous Conditions; Rats; Stomach Neoplasms; Taurocholic Acid

The effect of the duodenal ulceration induced by cysteamine hydrochloride on the development of gastroduodenal tumors initiated by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in F344 rats of both sexes. Cysteamine (200 mg/kg body wt.) was administered by gastric intubation at various times, before, during or after a 16 week period of MNNG (100 mg/liter in drinking water) treatment. In the preliminary experiment, while the ulcers induced were confined to the proximal duodenum, the pyloric region of the stomach also showed slight erosion. Five of 25 male rats given cysteamine 2 weeks before the start of MNNG treatment developed adenocarcinoma in the duodenum as compared to 1 case in the MNNG alone group. In addition, animals of both sexes which received cysteamine during MNNG treatment yielded significantly increased incidences of adenocarcinoma in the pyloric area of the stomach. In line with earlier reports, the present findings suggest that mucosal damage and subsequent regeneration or proliferation of mucosa are important co-factors for MNNG-induced gastroduodenal carcinogenesis in rats.

Topics: Adenocarcinoma; Animals; Cysteamine; Duodenal Neoplasms; Duodenal Ulcer; Female; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms

In a series of extensive studies on gastric carcinogenesis, we have used Sprague-Dawley rats to examine the morphologic, histochemical, and biochemical effects of risk and protective factors on N-methyl-N'-nitro-N-nitroso guanidine (MNNG)-induced tumors in an attempt to link early observations with the end-point lesion, gastric cancer. We have observed that the putative risk factors sodium chloride (NaCl); a mixture of bile acids; aspirin; alcohol; and nitrite enhance MNNG-induced neoplasia of the gastric mucosa. On the other hand butylated hydroxyanisol (BHA), Se and difluromethylornithine (DFMO) were protective and inhibited the induction of gastric mucosal neoplasia. In most cases, early changes detected by a number of criteria correlated with the end-point, gastric neoplasia. This model appears to be useful in screening and evaluating chemicals for risk for or protection against gastric cancer.

Topics: Animals; Bile Acids and Salts; Disease Models, Animal; Eflornithine; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Risk Factors; Sodium Chloride; Stomach Neoplasms; Sulfhydryl Compounds

Catechol (CAS: 120-80-9) is present in the environment, being a major industrial chemical as well as a major phenolic component of cigarette smoke. Continuous oral treatment of rats with 0.8% catechol for 51 weeks after a single intragastric dose of 150 mg/kg of N-methyl-N'-nitro-N-nitrosoguanidine strongly enhanced both forestomach and glandular stomach carcinogenesis. In addition, and more importantly, catechol alone induced adenocarcinoma and adenomatous hyperplasia in the pyloric region of the glandular stomach. These results clearly indicate that this environmental contaminant merits classification as an enhancer of forestomach and glandular stomach carcinogenesis with complete carcinogenic potential for the glandular stomach. Its significance for gastric tumor development in man requires elucidation.

Topics: Adenocarcinoma; Adenoma; Animals; Carcinogens, Environmental; Catechols; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms

The inductions of ornithine decarboxylase (ODC) and DNA synthesis in the pyloric mucosa of the stomach of male F344 rats after oral administrations of chemicals were studied. The glandular stomach carcinogens N-methyl-N'-nitro-N-nitrosoguanidine, N-ethyl-N'-nitro-N-nitrosoguanidine, N-propyl-N'-nitro-N-nitrosoguanidine, 4-nitroquinoline 1-oxide and N-nitroso-N-methylurethane induced up to 100-fold increase in ODC activity in the pyloric mucosa of the stomach; the activity was maximal 24 hr after administration and returned to the control level after 48 to 72 hr. These compounds also induced 14- to 30-fold increase in DNA synthesis in the pyloric mucosa of the stomach; synthesis was maximal 16 to 24 hr after administration and returned to the control level after 144 hr. The non-gastric carcinogens 2-acetylaminofluorene, dimethylnitrosamine and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) did not induce ODC or DNA synthesis in the pyloric mucosa of the stomach. Ethyl alcohol also did not induce ODC or DNA synthesis in the pyloric mucosa of the stomach. These results and previous findings that stomach-tumor promoters such as NaCl, taurocholate, glyoxal, K2S2O5 and formaldehyde induced ODC and DNA synthesis in the pyloric mucosa of the stomach of F344 rats suggest that the inductions of ODC and DNA synthesis in the glandular stomach mucosa are markers of promotive activities of complete carcinogens and tumor promoters in the glandular stomach.

Topics: Animals; Carcinogens; DNA; Enzyme Induction; Ethanol; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Ornithine Decarboxylase; Pylorus; Rats; Rats, Inbred F344; Stomach Neoplasms; Time Factors

In the experiments carried out on white male rats the effect of vinblastine on the development of malignant stomach tumours induced with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) has been studied. The combined administration of MNNG and vinblastine inhibits the experimental carcinogenesis at the stage of "intestinalization" and decreases the indicence of stomach adenocarcinomas by 3-fold. Pharmacological analysis using the application of apomorphine stereotypy showed the antagonism of MNNG and vinblastine at the level of central parts of the autonomic nervous system due to the inhibition of axoplasmic transport of catecholamines. These results confirm the earlier data on the essential role of catecholamines in the mechanisms of carcinogenic action of nitrosamines.

Topics: Animals; Autonomic Nervous System; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Vinblastine

The appearance of pyloric gland-type cells with a low pepsinogen isozyme 1 (Pg 1) content in the stomach mucosa of F344/Du rats during stomach carcinogenesis was examined by a combination of paradoxical concanavalin A (Con A) staining and immunohistochemical staining for Pg 1. Male F344 rats were given drinking water containing 100 micrograms N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7]/ml for 30 weeks and then normal tap water and were killed in week 10, 20, 30, 40, 50, or 70. Untreated rats were killed in week 30 or 70. Serial sections of pyloric mucosa were stained by paradoxical Con A staining and Pg 1 immunostaining. After MNNG treatment, tissues showing changes were classified into normal-looking pyloric mucosa with a low Pg 1 content, mucosa showing atrophic or hyperplastic changes, adenomatous hyperplasia, and adenocarcinoma. From the results of paradoxical Con A staining and Pg 1 immunostaining, the cells in lesions were classified into gastric types (surface mucous cell type and pyloric gland cell type) and intestinal types (intestinal-absorptive cell type and goblet cell type). In this experiment, the cells in lesions were mainly of the gastric cell types. All pyloric glands of control rats in weeks 30 and 70 contained class III mucins and had a high Pg 1 content demonstrated immunohistochemically. After MNNG treatment, class III mucin-positive pyloric glands with a low Pg 1 content in normal-looking pyloric mucosa were found from week 10; subsequently, their number increased with time. Changed mucosa was found from week 20, and the area of cells of the pyloric gland cell type with little or no Pg 1 in changed mucosa was about 30% of the area of cells of the pyloric gland cell type. Adenomatous hyperplasias were found from week 30; adenocarcinomas were found from week 50. Almost all cells of the pyloric gland cell type (greater than 95%) in areas of adenomatous hyperplasia and adenocarcinomas had little or no Pg 1 content. The present results suggested that the appearance of pyloric glands with a low Pg 1 content in normal-looking mucosa might be an immunohistochemically detectable preneoplastic change preceding morphologically detectable preneoplastic changes in stomach carcinogenesis.

Topics: Animals; Histocytochemistry; Isoenzymes; Male; Methylnitronitrosoguanidine; Mucins; Pepsinogens; Precancerous Conditions; Pylorus; Rats; Rats, Inbred F344; Stomach; Stomach Neoplasms

The effect of exogenous synthetic prostaglandins and the inhibition of endogenous prostaglandin synthesis on gastrointestinal tumorigenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7] was studied in female Wistar rats (100 g). Animals were divided into 6 groups: Group I was treated with MNNG alone (No. = 43); group II was treated with MNNG after application of the cyclo-oxygenase inhibitor flurbiprofen (No. = 44); group III was treated with MNNG after oral administration of 16,16-dimethyl-prostaglandin E2 (16,16-dm-PGE2; No. = 43); group IV received flurbiprofen alone (No. = 15); group V was treated with 16,16-dm-PGE2 alone (No. = 11). Animals in group VI served as controls (No. = 15). All drugs were administered orally. Hyperkeratosis and hyperplasia of the forestomach developed by 10 days after the first treatment with the carcinogen. Later, benign papillomas and dysplastic lesions were noted. Progressive ingrowth of squamous epithelium from the forestomach ridge into the glandular stomach started as early as day 13 and was more frequent in animals treated with a combination of MNNG plus flurbiprofen (P less than .001). The first squamous cell carcinomas of the forestomach were detected on day 51. Their incidence was 38, 60, and 42% in groups I, II, and III, respectively. This difference was not statistically significant. The incidence of mesenchymal tumors (leiomyosarcoma) in the stomach and duodenum was higher following treatment with MNNG plus flurbiprofen as compared to the incidence following treatment with MNNG alone or in combination with 16,16-dm-PGE2 (P less than .005). No malignant tumors developed in the gastrointestinal tracts of animals treated with flurbiprofen or 16,16-dm-PGE2 alone or in controls. The higher incidence of gastric and duodenal leiomyosarcomas after treatment with flurbiprofen suggests that reduction of prostaglandin synthesis favored the development of MNNG-induced cancer in mesenchymal tissues of the upper gastrointestinal tract.

Topics: Animals; Body Weight; Carcinoma, Squamous Cell; Female; Flurbiprofen; Gastric Acid; Gastrointestinal Neoplasms; Leiomyosarcoma; Methylnitronitrosoguanidine; Papilloma; Propionates; Prostaglandins E, Synthetic; Rats; Rats, Inbred Strains; Stomach Neoplasms

The expression of Ha-ras oncogene product in rat gastrointestinal carcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or 1, 2-dimethylhydrazine (DMH) was studied by Western blotting and immunohistochemistry using anti-Ha-ras p 21 oncoprotein antibody. In Western blotting, high levels of c-Ha-ras p 21 were found in serially transplantable rat duodenal carcinomas induced by MNNG and rat colon carcinomas induced by DMH. Immunohistochemically, c-Ha-ras p 21 immunoreactivity was detected in 3 (16.7%) of 17 MNNG-induced stomach carcinomas and in 21 (63.6%) of 33 DMH-induced colon carcinomas, respectively. In the colon carcinomas, c-Ha-ras p 21 immunoreactivity in deeply invasive tumors was stronger than that in superficially invasive tumors and was expressed in all subserosal tumors. Moreover, all of the metastatic colon carcinomas had c-Ha-ras p 21 immunoreactive tumor cells. These findings suggest that c-Ha-ras p 21 expression plays an important role in tumor proliferation, invasion and metastasis of DMH-induced colon carcinoma.

Topics: Adenocarcinoma; Animals; Colonic Neoplasms; Dimethylhydrazines; Methylnitronitrosoguanidine; Oncogene Protein p21(ras); Oncogene Proteins, Viral; Proto-Oncogenes; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Adenocarcinoma; Administration, Oral; Animals; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The influence of allogeneic blood transfusions (BT) on experimental tumor growth was investigated in three syngeneic, one allogeneic and one autochthonous tumor model in the rat. Con A induced T-cell response, relative distribution of lymphocyte subsets using flow cytometry and cytotoxic antibodies were determined. No differences in take rate, induction time, incidence and growth rate of tumors were observed in the different models. A significant decrease of cell-mediated immunity and a significant increase of peripheral Ia-positive cells could be observed. The relative distribution of T-cell subsets showed no differences between BT-groups and controls.

Topics: Adenocarcinoma; Adjuvants, Immunologic; Animals; Benzo(a)pyrene; Blood Transfusion; Ethylnitrosourea; Fibrosarcoma; Methylnitronitrosoguanidine; Neoplasm Transplantation; Neoplasms, Experimental; Neuroma; Rats; Rats, Inbred Strains; Stomach Neoplasms; Transplantation Immunology

The data obtained did not prove the stimulating effect of experimental chronic ulcer on the induced carcinogenesis of the stomach in the rat. It is shown that some surgical procedures followed by a gastroduodenal reflux enhance the gastric carcinogenesis while the procedures without such a reflux do not reveal any modifying effect on stomach cancer. The results of this study together with data from literature may have some relevance to the treatment procedures of patients with gastric ulcers.

Topics: Animals; Carcinoma; Chronic Disease; Duodenogastric Reflux; Male; Methylnitronitrosoguanidine; Postgastrectomy Syndromes; Rats; Stomach Neoplasms; Stomach Ulcer; Time Factors

We undertook a case-control study regarding the excretions of 14 urinary steroids in gastric cancer (GC) patients. The results are as follows: the levels of androgens, progestins, and two corticosteroids were, relative to tetrahydrocortisol, significantly depressed in GC patients of both sexes compared with the corresponding normal controls. The deviation profile of urinary steroids was not affected by radical gastrectomy. Evidence indicated that observed changes of GC urines were the steroidal expression of a decrease of endogenous testosterone combined with an increase of endogenous hydrocortisone; there was also evidence that the hormonal environment of our GC patients was endocrinologically homologous to that of rice-fed or salty rice-fed mice. Epidemiological inquiry revealed that GC patients having more access to rice-rich or salt-rich diets were taller and less obese than were rural healthy controls. In agreement with the anthropometric data of those cancer patients is the finding that the specific death rate of GC (as calculated for each of 15 prefectures of northern Japan) was positively correlated for each sex with the mean heights, but not with the mean weights, of 14-year-old youths of those areas. This paper discusses the possible relevancy of the hormonal and epidemiological aspects of GC patients to gastrocarcinogenesis in light of steroid physiology.

Topics: Adult; Aged; Aged, 80 and over; Androgens; Body Height; Body Weight; Female; Gastrectomy; Gastric Acid; Humans; Male; Methylnitronitrosoguanidine; Middle Aged; Oryza; Risk; Sex Factors; Sodium Chloride; Steroids; Stomach Neoplasms

N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was given to 3 groups of rats with the drinking water for 32 weeks in different doses: 25, 50 and 100 micrograms/ml. After 50 weeks the induced tumours of the stomach and the upper small intestine were investigated. Most tumours were well differentiated adenocarcinomas or adenomatous-hyperplastic lesions with focal adenocarcinoma. After low MNNG-concentration (25 micrograms/ml) only adenomatous hyperplastic lesions with focal adenocarcinoma were found. A tumour development in connection with intestinal metaplasia was detectable exclusively in two rats of the group receiving 50 micrograms MNNG/ml. The frequency of gastric tumours shows a relatively low peak (3.3 tumours/10 animals) after administering a medium MNNG-concentration (50 micrograms/ml) and a little decrease of the frequency after higher MNNG-concentration, as opposed to the approximately linear dose-related increase of the tumour frequency in the upper small intestine. The highest tumour induction rate was found in the upper small intestine after 100 micrograms MNNG/ml (5.6 tumours/10 rats). It can be concluded that the mucosa of the upper small intestine possesses a greater susceptibility to the carcinogenic effect of MNNG than the glandular stomach of the rat.

Topics: Adenocarcinoma; Administration, Oral; Animals; Cell Transformation, Neoplastic; Dose-Response Relationship, Drug; Hyperplasia; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasm Invasiveness; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms

Topics: Animals; Carcinoma, Squamous Cell; Intubation, Gastrointestinal; Methylnitronitrosoguanidine; Mice; Papilloma; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Dogs; Dose-Response Relationship, Drug; Esophageal Neoplasms; Male; Methylnitronitrosoguanidine; Stomach Neoplasms

The effects of combined administration of propranolol and tetragastrin on gastric acid secretion and the incidence and histological types of gastric adenocarcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in inbred Wistar rats. Prolonged administration of tetragastrin, 1 but not 0.2 mg/kg body weight in depot form after treatment with N-methyl-N'-nitro-N-nitrosoguanidine significantly reduced the incidence of adenocarcinoma of the glandular stomach. The adenocarcinomas that did develop in rats treated with the higher dose of tetragastrin had high mucin-producing activity and showed little or no typical glandular structure. A combination of propranolol (2 mg/kg) and tetragastrin (1 mg/kg) did not influence the inhibitory effect of gastrin on gastric carcinogenesis. However, concomitant administration of propranolol (2 mg/kg) and tetragastrin (0.2 mg/kg) caused a significant increase in gastric acid secretion and a reduction in the incidence of gastric carcinomas. With this treatment, the incidence of adenocarcinoma was similar to that of treatment with tetragastrin (1 mg/kg). Histological examinations showed that like the cancers in control rats, the adenocarcinomas induced in these rats were all highly differentiated.

Topics: Adenocarcinoma; Animals; Drug Synergism; Gastric Acid; Gastric Mucosa; Gastrins; Hyperplasia; Male; Methylnitronitrosoguanidine; Propranolol; Rats; Rats, Inbred Strains; Stomach Neoplasms; Tetragastrin

The study of the influence of long-term injection of whole bile into rat's stomach on N-methyl-N-nitro-N-nitrosoguanidine-induced tumors revealed an increased frequency of stomach malignancies matched by a lower frequency of those in the small intestine as well as slower rates of growth of gastrointestinal tumors.

Topics: Animals; Bile; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Time Factors

N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and N-propyl-N'-nitro-N-nitrosoguanidine (PNNG) were administered to male F344 rats at a single dose of 200 mg/kg by gavage and the animals were observed for 110 weeks. The results revealed that PNNG was a weaker carcinogen for the stomach than MNNG under these conditions. After MNNG, the mortality of animals was higher and their average survival time was shorter than after PNNG. Neoplasms were induced in both the forestomach and glandular stomach by both agents. The incidence of forestomach tumors was high: 85% with MNNG, 64% with PNNG, but with PNNG a greater proportion of the forestomach neoplasms were benign. The incidence of neoplasms of the glandular stomach was 18% with PNNG as compared to 65% with MNNG. Intestinal metaplasia appeared in the glandular stomach after exposure to either MNNG or PNNG. There was also a high incidence in untreated control rats. Most glandular stomach neoplasms were composed of both gastric-type and intestinal-type epithelial elements. Only 3 cases of adenocarcinomas were composed solely of intestinal-type cells. These findings suggest that intestinal metaplasia may not necessarily be a preneoplastic stage.

Topics: Animals; Gastric Mucosa; Hyperplasia; Male; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Inbred F344; Stomach Neoplasms

An experimental study was performed using an organ culture method to evaluate the effect of a duodenal juice reflux on the development of cancer in the residual stomach. The following results were as follows. An intracellular DNA levels to combine with carcinogenic agents was significantly increased in the mucosa of the residual stomach compared to the parietal mucosa in the whole stomach (control group). In the human gastric mucosa exposed to the bile acid, the intracellular DNA level to combined with carcinogenic agents was increased, and thus the effect of the bile acid as a surfactant on the experimental development of gastric cancer was suggested. An atrophic change was main feature of the residual stomach. Autoradiographic findings revealed that the proliferative zone was extended and a number of immature cells appeared which became to be target cells. Therefore, the residual stomach might provide a situation where the cancer would easily develop.

Topics: Bile Acids and Salts; Bile Reflux; Biliary Tract Diseases; Cocarcinogenesis; DNA; Duodenum; Gastric Mucosa; Humans; Intestinal Secretions; Methylnitronitrosoguanidine; Organ Culture Techniques; Stomach Neoplasms

The experiments on inbred male rats have been carried out to estimate the effect of parenteral vinblastine, an inhibitor of catecholamine axoplasmatic transport, on gastric tumour growth induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) added to drinking water. The maximum tolerance dose of vinblastine was determined in subchronic experiments on 30 rats (0.25 mg/kg subcutaneously, once per week). Chronic experiments with combined introductions of MNNG and vinblastine were performed on 70 rats. Vinblastine was shown to inhibit carcinogenesis on "intestinization" stake and to decrease three-fold the incidence of gastric adenocarcinomas. Vinblastine-induced changes in the behaviour of animals reflect the decreased activity of central adrenergic processes. The role of catecholamines in the mechanisms of specific action of chemical carcinogens is discussed.

Topics: Adenocarcinoma; Animals; Axonal Transport; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Time Factors; Vinblastine

Pepsinogen mRNA is shown to be the major fraction of rat poly (A)+RNA. It codes polypeptide with molecular weight of about 45 kD. Changes in the pepsinogen mRNA content at the early stage of carcinogenesis are nonspecific and are due to the toxic effect of MNNG. Steady shifts in the quantity of pepsinogen mRNA are found between the 1st and 3d months. Pepsinogen mRNA content decreases down to the half of the normal one between the 3d and 6th months. A quantity of RNA capable to be a template for pepsinogen synthesis is reduced by more than 90% in the MNNG induced tumour. The pepsinogen production defect in gastric mucosa neoplasia is mainly due to pepsinogen mRNA synthesis damage.

Topics: Animals; Cell Transformation, Neoplastic; Gastric Mucosa; Methylnitronitrosoguanidine; Pepsinogens; Poly A; Protein Biosynthesis; Rats; RNA; RNA, Messenger; Stomach Neoplasms; Time Factors

Gut endocrine cells in a total of 18 gastric adenocarcinomas in inbred Wistar rats induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and gastrin or serotonin, were examined histologically, ultrastructurally, and immunohistochemically for gastrin, somatostatin, calcitonin, glicentin, and serotonin. A large number of argyrophil cells were observed in 17 tumors (94.4%) and 14 tumors (77.8%) had argentaffin cells. Immunohistochemically, C-terminal fragment of gastrin (G17) immunoreactivity was observed in 15 (82.2%) out of the 18 tumors, but 3 G17-positive tumors had no G 34 immunoreactive cells in rats treated with MNNG plus gastrin. Serotonin immunoreactivity was detected in 14 tumors (77.8%). Somatostatin immunoreactivity was detected in 7 of the 11 tumors (63.6%) in rats treated with MNNG plus gastrin whereas no tumor in rats treated with MNNG plus serotonin had somatostatin, the difference of the incidence being significant (P less than 0.05). One endocrine cell carcinoma which consisted mainly of serotonin-producing cells was observed in a rat treated with MNNG plus serotonin. Calcitonin and glicentin immunoreactivity was not demonstrated in any tumors. Ultrastructurally, three types of endocrine granule were found in the tumor cells. These data suggest that hormonal environment in stomach carcinogenesis may influence the expression of endocrine cells within the tumors.

Topics: Adenocarcinoma; Animals; Calcitonin; Chromaffin System; Enterochromaffin Cells; Female; Gastrins; Glucagon; Histocytochemistry; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Proglucagon; Protein Precursors; Rats; Serotonin; Somatostatin; Stomach Neoplasms; Time Factors

Topics: Adenocarcinoma; Aflatoxins; Animals; Chronic Disease; Female; Gastritis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Animals; Carcinoma, Squamous Cell; Digestive System Neoplasms; Female; Male; Methylnitronitrosoguanidine; Polysorbates; Rats; Stomach Neoplasms; Surface-Active Agents

N-Ethyl-N'-nitro-N-nitrosoguanidine [(ENNG) CAS: 63885-23-4] was administered to 5 Macaca monkeys (Macaca mulatta and M. irus) at a concentration of 200 or 300 micrograms/ml for 11-26 months in their drinking water. Gastric carcinomas in the pyloric region were observed in all 5 monkeys between experimental months 11 and 38. Histologically, these carcinomas were mainly poorly differentiated adenocarcinomas and signet-ring cell carcinomas, and a few moderately and well-differentiated adenocarcinomas were also found. The macroscopic and histologic appearances of these carcinomas were similar to those in humans.

Topics: Adenocarcinoma; Adenocarcinoma, Mucinous; Animals; Female; Femoral Neoplasms; Macaca fascicularis; Macaca mulatta; Male; Methylnitronitrosoguanidine; Osteosarcoma; Stomach Neoplasms; Tracheal Neoplasms

Topics: Adenocarcinoma, Mucinous; Animals; Disease Models, Animal; Dogs; Female; Gastric Mucosa; Male; Metaplasia; Methylnitronitrosoguanidine; Stomach Neoplasms

Ethanol, potassium metabisulfite, formaldehyde and hydrogen peroxide were tested for tumor-promoting activity in a two-stage stomach carcinogenesis experiment. Male outbred Wistar rats were given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water (100 mg/liter) and a diet supplemented with 10% sodium chloride for 8 weeks. Thereafter, they were maintained on drinking water containing either 10% ethanol, 1% potassium metabisulfite, 0.5% formalin (formaldehyde) or 1% hydrogen peroxide for 32 weeks and then sacrificed for necropsy and histological examination. In the pylorus of the glandular stomach, potassium metabisulfite and formaldehyde significantly increased the incidence of adenocarcinoma after initiation with MNNG and sodium chloride. Hydrogen peroxide did not enhance the tumor yield, and ethanol showed a tendency to decrease neoplastic development. In the forestomach the incidence of squamous cell papilloma was significantly increased in the groups given hydrogen peroxide or formaldehyde, irrespective of prior initiation. Duodenal adenocarcinoma was induced by the initiation alone (10%) and the incidence was not affected by the subsequent treatments. The results indicate that potassium metabisulfite and formaldehyde both exert tumor-promoting activity in the rat glandular stomach.

Topics: Adenocarcinoma; Animals; Body Weight; Cocarcinogenesis; Duodenal Neoplasms; Ethanol; Formaldehyde; Gastric Mucosa; Hydrogen Peroxide; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Rats, Inbred Strains; Stomach Neoplasms; Sulfites

Analbuminemic rats were found to be highly susceptible to induction of gastric tumors by N-methyl-N'-nitro-N-nitrosoguanidine (67-83 micrograms/ml) given to the rats in drinking water for 32 weeks. The rats were sacrificed at experimental week 44. Gastric tumors were found in 12 of 17 analbuminemic rats (70%) and in 8 of 21 normal rats (38%). Intestinal tumors developed in 7 of 17 (41%) analbuminemic rats and in 9 of 21 (42%) normal rats.

Topics: Animals; Intestinal Neoplasms; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Serum Albumin; Stomach Neoplasms

Three groups of male Fischer rats were given single doses of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at 160 mg (group 1), 80 mg (group 2) and 40 mg (group 3)/kg body weight by gastric intubation. A fourth group was given drinking water containing 100 micrograms/ml of MNNG for 2 weeks, and a fifth group served as a control. Rats were killed in weeks 5, 8 and 12. Serial sections of the pyloric mucosa were examined by paradoxical concanavalin A (Con A) staining and pepsinogen isozyme 1 (Pg 1) immunostaining. All pyloric glands contained class III mucin as detected by paradoxical Con A staining. Most pyloric glands had a high Pg 1 content, but a few stained only weakly if at all. The percentage and number (No./500 normal-looking pyloric glands) of pyloric glands with a low Pg 1 content were 50.0 and 0.2 +/- 0.4 (week 5), 87.5 and 0.5 +/- 0.4 (week 8) and 100.0 and 1.2 +/- 1.0 (week 12) in group 1, 50.0 and 0.2 +/- 0.3 (week 8) and 87.5 and 0.5 +/- 0.4 (week 12) in group 2, and 30.0 and 0.2 +/- 0.4 (week 12) in group 4. No pyloric glands with a low Pg 1 content were found in groups 3 and 5. Thus the results showed significant dose-dependent induction (P less than 0.05-0.01) of altered pyloric glands demonstrating reduced Pg 1 content and their earlier appearance in groups given higher doses of MNNG. The results suggest that the appearance of pyloric glands with a low Pg 1 content may be a preneoplastic change in gastric carcinogenesis.

Topics: Animals; Dose-Response Relationship, Drug; Gastric Mucosa; Histocytochemistry; Isoenzymes; Male; Methylnitronitrosoguanidine; Mucins; Pepsinogens; Precancerous Conditions; Rats; Rats, Inbred F344; Stomach Neoplasms

Tumours of the glandular stomach and upper small intestine were induced in rats by oral administration of MNNG. In most cases the lesions were identified histologically as adenocarcinomas and their prestages, such as polypeous and downward growing adenomatous hyperplasias. Out of 48 adenomatous hyperplasias and adenocarcinomas of the stomach and 24 well differentiated adenocarcinomas of the small intestine, we observed argyrophilic cells in nearly the half of the cases. Endocrine cells were also identified by electron microscopy. The frequency of endocrine cells was reduced with decreasing degree of tissue differentiation. In poorly differentiated carcinomas, including signet ring cell carcinomas, no argyrophilic cells were found. Out of 10 adenomatous hyperplasias and tumours of the stomach investigated immunohistochemically, 5 cases showed gastrin producing cells. Most of these animals were radioimmunologically characterized by strongly elevated serum gastrin levels. Derivation and potential relevance of the endocrine cells in tumours are discussed.

Topics: Adenocarcinoma; Administration, Oral; Animals; Duodenal Neoplasms; Endocrine Glands; Fluorescent Antibody Technique; Gastrins; Histocytochemistry; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Precancerous Conditions; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms

The effects of tetragastrin and histamine on the incidence and histology of tumors induced in the small intestine by N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7] were investigated in male W rats. Animals were given MNNG at 150 micrograms/ml in their drinking water for 25 weeks and then 300 micrograms tetragastrin or 4 mg histamine dihydrochloride sc per day in depot form. Administration of tetragastrin or histamine after MNNG treatment resulted in a significant increase in gastric acid secretion and a significant reduction in the incidence of tumors in the duodenum; however, only histamine decreased the incidence of tumors in the jejunum. Histologically, the tumors induced in the small intestine were mostly adenocarcinomas, and their histologic type was not affected by either tetragastrin or histamine.

Topics: Adenocarcinoma; Animals; Drug Antagonism; Duodenum; Gastric Acidity Determination; Gastrins; Histamine; Intestinal Neoplasms; Jejunum; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Tetragastrin

The influence of x-radiation and N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7] on intestinal metaplasia and gastric tumorigenesis was examined in 5-week-old male Crj:CD(SD) rats. The animals were treated either with two 10-Gy fractions of x-rays separated by 3 days for a total of 20 Gy to the gastric region and/or with MNNG orally for 4 months. Simultaneous treatment with x-rays and MNNG (group II) and MNNG only (group IV) induced gastric tumors in the majority of the animals. Sequential treatment with x-radiation and MNNG, either x-ray 2 months prior to MNNG (group I) or MNNG 2 months prior to x-ray (group III), resulted in a lower incidence of gastric tumors as compared with the incidence after treatment with MNNG alone. The frequencies of intestinal metaplasia in the x-irradiated groups (groups I and V) were significantly higher than those in group II, III, or IV. The incidence of intestinal metaplasia and of gastric tumor was inversely proportional. These results indicate that intestinal metaplasia does not play a role in the induction of gastric tumors by MNNG.

Topics: Animals; Cocarcinogenesis; Gastric Mucosa; Male; Metaplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Inbred Strains; Regression Analysis; Stomach Neoplasms

Sequential histologic changes of the stomach during carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; CAS: 70-25-7) were studied in susceptible ACI and resistant BUF strain rats. Rats were given MNNG at a concentration of 83 micrograms/ml in their drinking water for 32 weeks and then tap water and were sacrificed sequentially between weeks 1 and 57. In ACI rats, erosions, regenerative changes, focal and slightly atypical changes, and diffuse and severe atypical changes were observed sequentially in the pyloric region during the period of MNNG administration, where adenocarcinomas were observed after the cessation of MNNG treatment. In BUF rats, the main histologic changes induced by MNNG were erosions and hyperplasia of the glandular portion of pyloric glands at the margin of erosions. After the cessation of MNNG treatment, the hyperplasia of the pyloric glands subsided and was followed by atrophy of these glands. The results suggested that the responses of the gastric mucosa to MNNG in ACI and BUF rats were qualitatively different.

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Hyperplasia; Male; Methylnitronitrosoguanidine; Pylorus; Rats; Rats, Inbred ACI; Rats, Inbred BUF; Regeneration; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Duodenal Neoplasms; Female; Intubation, Gastrointestinal; Jejunal Neoplasms; Male; Methylnitronitrosoguanidine; Mice; Papilloma; Stomach Neoplasms

The influence of dietary selenium on the incidence of stomach carcinoma induced by N-methyl-N'-nitro-N-nitrosoguanidine was studied in 108 rats that survived for over 10 wk. The incidence of glandular stomach cancer in the high-selenium (4.0 ppm) diet group (20 carcinomas in 54 rats) was lower than in the low-selenium (0.1 ppm) diet group (33 carcinomas in 54 rats). The selenium level and glutathione peroxidase activity in the blood, liver, and stomach mucosa were significantly higher in the high-selenium diet group than in the low-selenium diet group. Glutathione peroxidase activity as well as the concentration of selenium in the glandular stomach was increased significantly in the high-selenium diet group.

Topics: Adenocarcinoma; Adenoma; Animals; Body Weight; Carcinoma; Diet; Gastric Mucosa; Glutathione Peroxidase; Liver; Methylnitronitrosoguanidine; Rats; Sarcoma, Experimental; Selenium; Stomach Neoplasms

In an attempt to elucidate histogenesis of stomach cancer, quantitative analysis and measurement of DNA contents of various atypical lesions were sequentially made in the process of gastric carcinogenesis of Wistar strain of rats. Along with this, the effect of vagotomy on the development of atypical or neoplastic lesions were studied. A variety of focal lesions in the glandular stomach were seen in the middle or 4 and 12 weeks after the oral administration of N-methyl-N'-nitrosoguanidine (MNNG, 83 mg/l in drinking water) for 25 weeks. Both upward and downward growth was found in the intramucosal atypical lesions as well as frank carcinoma; the former lesions were histologically classified into 3 (Type I--Type III). On the basis of DNA distribution pattern, Type III lesions were considered to be intramucosal carcinoma and Type II to include precancerous state in some instances. In a group of rats vagotomized 1 week prior to the start of MNNG administration, there were significantly more lesions than in a group of MNNG alone. In contrast to the latter group which developed lesions in an uniform distribution pattern along the lesser curvature in the pyloric region, lesions in the former were characterized by random distribution pattern.

Topics: Adenocarcinoma; Animals; Body Weight; DNA, Neoplasm; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Vagotomy

The purpose of this experiment was to determine whether chronic gastric ulcers in the rat are predisposed to tumor formation when exposed to a usually noncarcinogenic dose of the carcinogen, N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG). Two groups of rats were prepared; one subjected to a standard ulcer-producing operation, the other as control. Both groups were given oral MNNG (100 mg/liter as drinking water) for 12 weeks, the carcinogen was then stopped and replaced with tap water, and the experiment terminated at 52 weeks. Results showed that a low dose of carcinogen (200 mg) did not induce tumor formation in any of the normal rats. In the presence of a chronic gastric ulcer, only intestinal metaplasia and hyperplastic glandular nodules were observed, but there were no gastric tumors. It is concluded that the presence of a chronic gastric ulcer did not increase the likelihood of gastric tumor formation in rats treated with a noncarcinogenic dose of the carcinogen MNNG.

Topics: Animals; Carcinogens; Female; Gastric Acid; Gastrins; Liver; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms; Stomach Ulcer

The effect of ubenimex on the progression of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced stomach tumor in rats was studied. Tumor induction was performed by giving MNNG via drinking water for 34 weeks. Ubenimex was ip administered twice a week at 0.5 mg/kg for 84 weeks in one group and 49 weeks in another starting from the first and 36th weeks after initiation of MNNG administration, respectively. The stomachs were endoscopically examined 2 times. At the 64th week after initiation of MNNG administration tumorous lesions were observed with about 70% of the rats in both ubenimex administration groups. In the ubenimex non-administration group nearly 90% of the rats had the lesions. After completion of ubenimex administration almost all the rats had the lesions in the three groups but the sizes were much smaller with the two ubenimex administration groups. Almost all of these lesions were histopathologically identified as tumorous. The tumor volume per rat in the two ubenimex administration groups from the 1 and 36th weeks was 21.0 and 19.2% of the volume in the control group, respectively. Tumor number per rat was similar among the three groups. The natural killer activity of rats was also examined after completion of the above experiment. The activity markedly increased when ubenimex was administered from the 36th week after initiation of MNNG administration. When ubenimex was administered from the first week, the activity did not increase demonstratively. From all the results described above we conclude that ubenimex exerts an inhibitory action against the progression of MNNG-induced stomach tumor in rats. Contribution of the increase of natural killer activity to ubenimex antitumor action may be dependent on schedule of ubenimex administration.

Topics: Animals; Antibiotics, Antineoplastic; Killer Cells, Natural; Leucine; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of vitamins A, C and E, butylated hydroxytoluene (BHT) and glutathione (GSH) on gastric carcinogenesis induced by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) was investigated. Male and female BD-VI rats 2-3 months old received a single oral application of MNNG dissolved in corn oil. The male rats were divided into four groups: Group-I: MNNG 250 mg/kg by intubation; Group-II: MNNG + vitamin C daily in the drinking water (400 mg/l); Group-III: MNNG + vitamin C (400 mg/l) + 100 g of milk broth (for each of 10 rats) containing vitamin A (40,000 IU), vitamin E (0.5 g) and BHT (0.1 g) three times a week. The treatment with antioxidants started 7 days before the MNNG administration and continued until the end of experiment. Group-IV rats received MNNG + oxyferriscorbone, i.p. as a single dose of 1.0 mg/kg, daily during the week before and the week after MNNG exposure and than 3 times a week till the end of the experiment. Female rats were divided into two groups: Group-I: MNNG 333 mg/kg by intubation; Group-II: MNNG + GSH orally at a dose of 100 mg/rat 1 h before and 5, 24, 48, and 72 h after MNNG intubation. The incidence of gastric tumors after 15 months of treatment was as follows: male rats, 82.4% in Group-I, 40.0% in Group-II, 40.7% in Group-III, and 50.0% in Group-IV; female rats; 72.7% in Group-I, and 36.0% in Group-II.

Topics: Animals; Antioxidants; Ascorbic Acid; Butylated Hydroxytoluene; Drug Interactions; Female; Glutathione; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Vitamin A; Vitamin E

A model of gastric tumour induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in rats made it possible to detect essential alterations of chromatin-DNA-protein complexes, that is a weakening of the DNA-protein linkage. The changes appear at early stages of carcinogenesis and persist in induced adenocarcinomas of the stomach. Simultaneously an inhibition was established in pepsinogen synthesis during MNNG carcinogenesis, which reflects a damage in expression of functionally important genetic information. This fact shows a molecular-genetic connection between the process of the gastric mucosa malignization and a disturbance of physiologically important tissue-specific gene functions.

Topics: Adenocarcinoma; Animals; Chromatin; DNA, Neoplasm; Drug Interactions; Female; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Neoplasm Proteins; Pepsinogens; Protein Conformation; Rats; Stomach Neoplasms; Time Factors

The effects of antioxidant administration during the post initiation phase of gastric tumor development were investigated in male Wistar rats treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Animals (20/group) were given MNNG in the drinking water (100 mg/l) for 8 weeks, and for the duration of this treatment were also fed on diet supplemented with 10% sodium chloride. Thereafter, they were divided into 6 groups and were maintained on diet containing either 2% butylated hydroxyanisole (BHA), 1% BHA, 1% butylated hydroxytoluene (BHT), 1% ethoxyquin (EQ) or 1% DL-alpha-tocopherol (alpha-TP) for 32 weeks. A carcinogen control group was fed the basal diet without antioxidant supplementation. The experiment was terminated 40 weeks after the beginning of administration of MNNG and development of gastroduodenal tumors was determined histopathologically. EQ significantly increased the incidence of tumors in the glandular stomach. No modification of tumor development in this region of the organ were observed with 2% BHA, 1% BHA, 1% BHT or 1% alpha-TP, although both 2% BHA and 1% BHA induced and/or promoted tumor development in the forestomach. In addition, nephrocalcinosis was identified only in the kidneys of rats given EQ after MNNG treatment.

Topics: Animals; Antioxidants; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Cocarcinogenesis; Duodenal Neoplasms; Ethoxyquin; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Time Factors; Vitamin E

The effect of hydrochlorhydria caused by vagotomy on carcinogenesis in the glandular stomach of male rats was studied. Group A (35 rats): After N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) 80 mg/l solution was orally administered during the first 15 weeks of life, vagotomy was performed. Group B (35 rats): After the oral administration of MNNG 80 mg/l solution during the first 15 weeks of life, laparotomy was done. Group C (10 rats): As the control, vagotomy was undertaken at the 15th week of life. Group D (10 rats): As the control, laparotomy was done at the same time. At the 52nd week, all surviving rats were autopsied, and gastrin cell counts and body weight were ascertained. The incidence of adenocarcinoma was 62% in Group A, 32% in Group B (p less than 0.05) and nil in Group C and D. These results strongly support the view that the hypochlorhydria plays the role of a promoting factor in producing gastric carcinoma.

Topics: Adenocarcinoma; Animals; Gastric Acidity Determination; Gastrins; Histamine H2 Antagonists; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Vagotomy

Topics: Animals; Blood Protein Electrophoresis; Blood Proteins; Dogs; Glycosaminoglycans; Methylnitronitrosoguanidine; Sizofiran; Stomach Neoplasms

Changes in the activity of protein kinases in the glandular stomach mucosa of rat were studied in the case of carcinogenesis induced by N-methyl-N'-nitro-N'-nitrosoguanidine. No essential changes in the activity of cAMP-dependent protein kinase (histone kinase) were found in the mucosa as well as in tissues of the developed tumours of the rat glandular stomach. The activity of cAMP-independent protein kinase (casein kinase) increased significantly 3 months after the beginning of the carcinogen administration and at the late stages (after 12-15 months) it was decreased considerably both in the glandular stomach tumours and in the stomach mucosa without the characters of the malignant growth. It is supposed that changes in the activity of casein kinase in the stomach mucosa at the late carcinogenesis stages are associated with the neoplastic transformation and precede the appearance of morphological characters of the malignization.

Topics: Animals; Casein Kinases; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Protamine Kinase; Protein Kinases; Rats; Stomach Neoplasms

Signet ring cell carcinoma was induced in canine stomachs by N-ethyl-N'-nitro-N-nitrosoguanidine, and modes of cell proliferation and turnover in the carcinoma were studied by 3H-thymidine autoradiography in conjunction with morphometric analysis. From 2 to 15 months after the cessation of 8 months carcinogen treatment, carcinomas in an early stage were obtained. Most of the cancer tissues confined to the lamina propria showed a layered structure. This comprised three layers; the superficial and the deep layer were composed of signet ring cells, and the middle layer was composed of small round cells. The dogs were labeled with 3H-thymidine by s.c. injection and by local infusion of the celiac artery. Flash-labeled autoradiographs revealed that most 3H-thymidine incorporating cancer cells were located around the middle layer, with a small amount of mucin. Using a pulse labeling experiment, those labeled carcinoma cells were shown to migrate from the middle layer towards the surface. Morphometric analysis of the autoradiographs showed that the small cells in the middle layer migrated upwards and produced mucin to become full-blown signet ring cells by 5.5 days. In 15 days, most labeled cancer cells in the superficial layer had disappeared. This mode of cellular turnover appeared to mimic a cell renewal system of the normal gastric mucosa. If the cancer cells turn over in this way, the tumor must grow slowly, remaining as an intramucosal cancer for a relatively long period.

Topics: Adenocarcinoma, Mucinous; Animals; Autoradiography; Carcinogens; Cell Division; Cell Survival; Dogs; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Stomach Neoplasms

An experimental trial in the induction of canine gastric cancers was conducted to study the relationship between the histological differentiation of adenocarcinoma and the duration of administration of the carcinogen, N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). Twenty-three adult Beagle dogs were divided into three groups according to the duration of administration. Over 3 months administration, the total dose of ENNG per animal was 5.85 g, and only signet ring cell carcinomas and poorly differentiated adenocarcinomas were induced in the antral mucosa of the stomach in 5 of 10 recipients. During 6 and 9 months administration, the total doses per animal were 11.70 g and 17.55 g, well differentiated adenocarcinomas were observed in 12 of 13 animals and they coexisted with poorly differentiated adenocarcinomas and/or signet ring cell carcinomas. Atrophic hyperplastic gastritis and hyperplastic polyps were seen in the same stomach. The results of this study suggest that a greater amount of carcinogen, i.e., a higher total dose, is required for the development of well differentiated adenocarcinoma than for inducing poorly differentiated adenocarcinoma and signet ring cell carcinoma.

Topics: Adenocarcinoma; Adenocarcinoma, Mucinous; Animals; Dogs; Drug Administration Schedule; Female; Male; Methylnitronitrosoguanidine; Stomach Neoplasms

In study I, 48 ACI and Fisher inbred rats were given MNNG 100 micrograms/ml, with or without 1 per cent or 3 per cent red pepper diet; in study II, 164 Sprague-Dawley rats given MNNG 100 micrograms/ml, with or without 5 per cent or 10 per cent NaCl; in study III, 181 Wistar rats given MNNG 83 micrograms/ml with or without maejoo 10 gm per cent/diet; in study IV, 78 Wistar rats given MNNG 83 micrograms/ml with or without ginseng extract 150 micrograms/ml; in study V, 120 Wistar rats given MNNG 83 micrograms/ml with or without retinyl palmitate 150,000 IU/kg. Except for study II (28 weeks), all rats were fed the diets for 37 weeks and were examined at 38 weeks or 40 weeks. In study I, tumor incidence in rats fed a red pepper diet and MNNG solution were 57 per cent (ACI rats, 1 per cent red pepper) and 63 per cent (Fisher rats, 1 per cent or 3 per cent red pepper) which were higher than control group (44 per cent, 43 per cent); in study II, gastric cancer, 61.9 per cent (10 per cent NaCl-MNNG), 27.3 per cent (control); in study III, gastric cancer, 14.8 per cent (maejoo-MNNG), 24 per cent (control); in study IV, malignant tumor of gastroduodenum, 3.4 per cent (ginseng-MNNG), 32.1 per cent (control); in study V, forestomach papilloma, 10.7 per cent (retinoid-MNNG), 29.4 per cent (control), and cancer in duodenum and small intestine, 50.0 per cent (retinoid-MNNG), 17.6 per cent (control). Thus, gastric carcinogenesis was enhanced by red pepper and a high salt diet, was inhibited by a maejoo and ginseng diet and was not effected by vitamin A.

Topics: Animals; Cocarcinogenesis; Condiments; Diterpenes; Duodenal Neoplasms; Feeding Behavior; Glycine max; Korea; Methylnitronitrosoguanidine; Panax; Plants, Medicinal; Rats; Rats, Inbred ACI; Rats, Inbred F344; Rats, Inbred Strains; Retinyl Esters; Sodium Chloride; Stomach Neoplasms; Vitamin A

The effect of gastrectomy and duodenal reflux on gastric carcinogenesis was studied because gastrectomized patients may be considered at "high risk" for the development of gastric stump cancer. Wistar rats received N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (83 mg/liter) ad libitum in the drinking water for either four, eight, or twelve weeks. A control group received tap water. After MNNG administration animals were antrectomized. Antrectomy was not performed in a control group. Bowel continuity was restored either with a Billroth II (BIL) or with a ROUX en Y (ROUX) procedure. Duodenogastric reflux is possible after the BIL but not after the ROUX procedure. Eight months after the beginning of the experiment the stomachs of the animals were studied. In both operated and unoperated animals, the number of cancers observed was significantly related to the duration of MNNG administration. Animals receiving MNNG plus the BIL procedure had a significantly higher number of anastomotic cancers than the ROUX animals, indicating that duodenogastric reflux played a promotional role in gastric carcinogenesis. Three BIL gastrectomized rats not receiving the carcinogen had an adenocarcinoma on the anastomotic line further emphasizing the risk attached to the duodeno-gastric reflux.

Topics: Animals; Cocarcinogenesis; Duodenogastric Reflux; Gastrectomy; Male; Methylnitronitrosoguanidine; Pyloric Antrum; Rats; Rats, Inbred Strains; Stomach Neoplasms

The paper discusses changes occurring in the enzymatic activity of pepsin in rat's gastric mucosa at early stages of carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine treatment with drinking water. All doses (5, 15, 45, 75 and 150 mg/l) proved to be effective and inhibited pepsinogen biosynthesis considerably. Particularly sharp drops in the enzyme activity were observed with the concentrations of 45, 75 and 150 mg/l. The effect was reversible at early stages, particularly, at low concentrations of the agent. It is suggested that the critical point reached by pepsinogen synthesis in gastric mucosa carcinogenesis, which is manifested by the enzyme synthesis resumption on treatment being suspended, may be regarded as the check point in the course of neoplastic development.

Topics: Animals; Dose-Response Relationship, Drug; Female; Gastric Mucosa; Guanidines; Male; Methylnitronitrosoguanidine; Pepsin A; Polyribosomes; Rats; Stomach Neoplasms; Time Factors

The effects of truncal vagotomy after administration of N-methyl-N'-nitro-N-nitrosoguanidine on the incidence and number of gastric carcinomas and gastric acid secretion, gastrin secretion, antral pH, and duodenal reflux were investigated in inbred Wistar rats. Rats were subjected to truncal vagotomy after N-methyl-N'-nitro-N-nitrosoguanidine treatment. Vagotomy significantly increased the incidence and number of adenocarcinomas of the glandular stomach. It also resulted in significantly more atypical glandular hyperplasias, which are precursors of gastric cancer. Furthermore, it caused a decrease in gastric secretion and an increase in mucosal pH in the antrum but did not increase duodenal reflux. These findings indicate that vagotomy has a promoting effect on the development of gastric cancers. The reduced gastric acid secretion, but not duodenal reflux, may be related to this increased incidence of gastric cancer.

Topics: Animals; Body Weight; Duodenogastric Reflux; Gastric Acid; Gastric Juice; Gastrins; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Time Factors; Vagotomy

Microspectrophotometric measurement of the DNA content of cell nuclei was performed on the lesions (including atypical glands) in gastric carcinogenesis of 15 male beagle dogs, which had been induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The distribution patterns of DNA content were classified into three types: normal, subnormal, and abnormal. The histograms of the distribution in normal and regenerative glands were a normal type and subnormal type, respectively, while adenocarcinoma showed an abnormal distribution type. In atypical glands, the distribution patterns in autopsy cases were subnormal and abnormal types. When sequential endoscopic observation of the angulus of the stomach in dog No. 3 was carried out, atypical glands were found in an ulcer in the early stage of MNNG administration and a precancerous lesion in the late stage after termination of MNNG. The atypical glands in the early stage were of the subnormal type, while the atypical glands in the late stage were of the abnormal type. According to the results, these two types-subnormal and abnormal - of distribution of DNA content on the atypical glands may be related to regeneration and subsequent development of cancer, respectively.

Topics: Adenocarcinoma; Animals; Biopsy; DNA, Neoplasm; Dogs; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Regeneration; Stomach Neoplasms; Stomach Ulcer

In order to obtain a reliable experimental model simulating human esophageal cancer, endoscopic and histopathological studies were undertaken in the esophageal cancer produced in the beagle dog. Thirty-seven dogs had been given a solution of N-Ethyl-N'-nitro-N-nitrosoguanidine (ENNG) at a concentration of 150 micrograms/ml for 3-9 months. Follow-up studies included serial endoscopy and biopsy, and almost all animals were eventually sacrificed for histological examination. The results were as follows: Squamous cell carcinoma was observed in 5 out of 22 female dogs, while none in male dogs at all. For the induction of squamous cell carcinoma in the esophagus, administration in the condition of 150 micrograms/ml (75mg/day) for 6-9 months was most suitable. Almost all of esophageal lesions were protruding and well-differentiated squamous cell carcinoma with invasion of the submucosa. The stages of hyperplasia, dysplasia and squamous cell carcinoma in the esophagus were chronologically followed. Carcinoma had been observed in the stomach about 4 months prior to the appearance of esophageal carcinoma. This experimental model was proved to be useful for studies on histogenesis of human esophageal cancer both light and electron microscopically.

Topics: Animals; Carcinoma, Squamous Cell; Dogs; Esophageal Neoplasms; Female; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Sex Factors; Stomach Neoplasms

The aim of this report is to prove that cancer tissue is to be eradicated by Nd:YAG laser irradiation and to show the process of its eradication using MNNG induced gastric cancers in rats as a material. Material and Method; in male rats of Wister strain, gastric cancers were induced by 30 weeks administration of 80 mg/1 MNNG solution. Then tumor bearing rats underwent laparotomy and gastrotomy, and tumors were irradiated by the Nd:YAG laser with 30W at the distance of 1cm, total energy ranging 120-1800 joules. These 20 stomachs were examined histologically; 10 of them within 14 days, the rest more than 4 weeks after the irradiation.

Topics: Adenocarcinoma; Animals; Disease Models, Animal; Gastroscopy; Laser Therapy; Male; Methods; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Electron microscopic examination of the MNNG-induced gastric cancer revealed cytodifferentiation processes in it. Transformation of gastric epithelium under the effect of MNNG at the submicroscopic and cell levels is investigated. The model is shown to be adequate to human gastric cancer.

Topics: Adenocarcinoma; Animals; Cell Transformation, Neoplastic; Methylnitronitrosoguanidine; Microscopy, Electron; Rats; Stomach Neoplasms

Topics: Animals; DNA; Gastric Juice; Gastric Mucosa; Humans; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

This was a study of the effects of gastrin on gastric mucosal cyclic-adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase activity and DNA synthesis in rat stomach carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in order to clarify the mechanism of the enhanced effect of gastrin on the early stage of stomach carcinogenesis. Inbred Basel-Wistar rats received MNNG in drinking water (50 micrograms/ml for 32 weeks) and were treated with s.c. injections of pentagastrin (300 micrograms/kg twice daily for 4 weeks) beginning with the fourth and eighth weeks after the initiation of MNNG treatment. The incidence of gastric adenocarcinoma in fourth-week gastrin-treated rats and of gastric carcinoid in eighth-week gastrin-treated rats was higher than that in rats treated with MNNG alone. The former tumors developed in the antrum and most of the latter tumors in the fundus. In the early stage of carcinogenesis the labeling index [( 3H]thymidine-labeled nuclei/one gland) in both the antrum and fundus was the same in MNNG-plus-gastrin-treated groups and in the MNNG-only-treated group. With regard to the distribution of cAMP-dependent protein kinase isoenzyme in fourth-week gastrin-treated rats, the proportion of type I cAMP-dependent protein kinase significantly increased in the antrum during the eighth week after the initiation of MNNG treatment (P less than 0.01). The increased type I activity in the antrum of the gastrin-treated rats agreed with the high incidence of gastric adenocarcinoma in the antrum. Type I isoenzyme clearly increased in gastric adenocarcinoma. These results suggest that type I cAMP-dependent protein kinase can play an important role in the enhanced effect of gastrin on rat stomach carcinogenesis induced by MNNG.

Topics: Adenocarcinoma; Animals; DNA; Drug Synergism; Gastric Mucosa; Gastrins; Isoenzymes; Methylnitronitrosoguanidine; Protein Kinases; Rats; Rats, Inbred Strains; Stomach Neoplasms

A histological and ultrastructural survey on the histogenesis of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric sarcomas in hamsters was attempted. Within 3 months after the beginning of oral administration of MNNG, simple spindle cell proliferation in the submucosal zone of the pyloric region of the glandular stomach was evident. By 5-6 months, the cells had acquired a sarcomatous appearance. Ultrastructurally, the spindle cells in the early stage, were divided into 3 types, i.e., angiogenic cells, fibroblastic cells, and primitive mesenchymal cells. Similarly, those in the late-appearing sarcomatous tumors were also classified into different types of angiogenic, fibroblastic, histiocytic and miscellaneous cells. Among the cell population of the 2 major groups, angiogenic cells were the most predominant cell type. Some morphological transition appeared to occur between the corresponding cell types at the early and late stages. DNA content of cell nuclei of the representative forms of the nitrosamide-induced sarcomas was higher than that of early appearing spindle cells. Thus, the evidence suggests that the early appearing spindle cells are precursors for the gastric sarcomas.

Topics: Animals; Cell Division; Cricetinae; Female; Mesocricetus; Methylnitronitrosoguanidine; Microscopy, Electron; Sarcoma; Stomach Neoplasms; Time Factors

Dietary sodium chloride has been identified, both experimentally and epidemiologically, as a risk factor for gastric cancer. In order to elucidate the manner in which salt increases gastric tumor incidence in N-methyl-N'-nitro-N-nitrosoguanidine-treated animals, flow cytometric cell cycle analyses were performed on rats which had been treated with 1 ml of a solution of saturated NaCl by gavage and sacrificed 0, 1, 6, 12, 24, or 48 h after treatment. The gastric antra were excised, disaggregated, and stained with propidium iodide for cell cycle analysis. Results showed that there is a reduction in cell yield at early time points due to the toxicity of NaCl, followed by a net increase in the number of cells in the S phase of the cell cycle at 24 h. Treatment of rats with NaCl 24 h prior to a dose of 10 micrograms of 3H-labeled N-methyl-N'-nitro-N-nitrosoguanidine did not lead to an increase in alkylation of DNA isolated from mucosal cells. Therefore, the hypothesis that salt enhances gastric cancer risk from N-methyl-N'-nitro-N-nitrosoguanidine by disruption of the "mucosal barrier" leading to an increased effective dose to target cells is not supported by the results of these experiments. Several studies have shown that cells in S phase are the most susceptible to mutagenesis and that increasing the number of cycling cells in a target organ will increase tumor incidence (e.g., partial hepatectomy). Thus it is possible that NaCl increases gastric cancer risk through the mitogenesis which results from the damage caused to the mucosa by this agent.

Topics: Animals; Autoradiography; Cell Cycle; DNA; Flow Cytometry; Gastric Mucosa; Male; Methylation; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Risk; Sodium Chloride; Stomach Neoplasms; Urinary Bladder Neoplasms

Detection of gastric carcinoma in the experimental rat can be difficult. We investigated whether or not serological testing for carcinoembryonic antigen might aid in the diagnostic process. Twenty-five young adult male Wistar rats were studied; 15 were treated with the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and 10 received no treatment. A complete autopsy was done on the 22 animals (12 in MNNG group, 10 in control group) that completed the 37-week study. Serum obtained at autopsy was evaluated by radioimmunoassay for the presence of CEA-like immunoreactivity. Grossly normal stomach, as well as gastric and small bowel cancers, were also stained for CEA. Of the 12 autopsied animals in the MNNG group, eight had a total of 12 cancers (seven gastric and five proximal small bowel); in no animal was an elevated serum CEA level detected. Immunoreactive tissue CEA was demonstrable in normal stomach and in gastrointestinal cancers; the tumors usually stained less intensely than adjacent normal stomach and did not exhibit normal intracellular CEA distribution.

Topics: Animals; Carcinoembryonic Antigen; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The modifying effects of 3 antioxidants, sodium L-ascorbate (SA), ascorbic acid (AA) and sodium erythorbate (SE) on two-stage gastric carcinogenesis in F344 rats initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated. Administration of 5% SE in the diet significantly decreased the incidence of dysplasia of the pylorus and, more marginally the incidence of papilloma of the forestomach, whereas administration of 5% and 1% SA and 5% AA in the diet was not associated with effect. These results suggest that SE exerts a weak inhibitory effect on gastric carcinogenesis.

Topics: Animals; Ascorbic Acid; Body Weight; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms; Urinary Bladder Neoplasms

It is well known that the nuclear DNA content closely correlates with the histologic grade of malignancy. In this study, eight beagle dogs with gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) received weekly administration of 7-N-(p-hydroxyphenyl)-mitomycin C (M-83), a variant of mitomycin C. Endoscopic observations were carried out biweekly, and a biopsy specimen was taken from the same tumor site on each occasion. The nuclear DNA content of these biopsy specimens was measured by Feulgen-DNA-cytofluorometry and was sequentially observed in comparison with histologic findings. In conclusion, 1) the appearance rate of cells over 4C decreased from 25.6% to 14.7% on an average (p less than 0.02); 2) the maximum value of distribution decreased from 9.55C to 7.64C on an average (p less than 0.001); 3) the stem line reduced from 2.63C to 2.20C on an average (p less than 0.05) at the early stage of administration of the oncostatic agent prior to the appearance of histologic changes; 4) in the chemotherapy-effective group, the histogram approached a normal pattern; 5) this procedure will be useful for objective evaluation of oncostatic effects at the cytomorphologic level.

Topics: Animals; Cell Cycle; DNA, Neoplasm; Dogs; Endoscopy; Female; Male; Methylnitronitrosoguanidine; Mitomycin; Mitomycins; Ploidies; Stomach Neoplasms

150 micrograms/day of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) was administered to a total of 8 dogs, (4 mongrels at age of 4 months and 4 beagles at age of 6 months) over a period of 8 months by Kurihara 's method. As a result of the administration, we found development of minute cancer as follows: In 3 animals, male beagle killed at 575th day, male mongrel at 1, 105th days and male mongrel at 1, 245th days, a total of 20 neoplasms of the stomach was found (18 early cancers and 2 advanced cancers). 13 of which being the minute cancer measuring less than 0.5 cm. There were 11 mucosal cancers and 2 submucosal cancers. When classified by the macroscopic pathological type, none was classified as the elevated type (I, IIa types), 5 lesions as the flat type (IIb type), and 8 lesions as the depression type (IIc type). Two lesions of submucosal cancer belonged to IIc type. When classified by the histological type, 2 were classified as papillary adenocarcinoma, 2 as well differentiated tubular adenocarcinoma, 1 as moderately differentiated tubular adenocarcinoma, 5 as poorly differentiated adenocarcinoma and 3 as signet-ring cell carcinoma.

Topics: Adenocarcinoma; Adenocarcinoma, Mucinous; Adenocarcinoma, Papillary; Animals; Dogs; Male; Methylnitronitrosoguanidine; Neoplasm Staging; Stomach Neoplasms

The effect of one single dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) on the antigenic structures of gastric juice glycoproteins, was studied in dogs. Antisera to glycoproteins of the fetal alimentary canal were raised. Histologic mucosal specimens and glycoprotein fractions of gastric juice which were taken from four dogs during a 15.5-month period after MNNG administration, were examined immunohistologically and by immunodiffusion for the appearance of fetal-like antigens. Fetal-like structures appeared in a stepwise manner in both the acid and neutral glycoprotein fractions of the gastric juice, and showed gradual crossreactivity between macromolecules obtained from gastric juice samples obtained during the observation period. Eight immunizations carried out using physicochemically different glycoprotein fractions of fetal canine alimentary canal mucosa, produced a similar response, thus indicating that the same antigenic structures are incorporated into all mucus glycoproteins, even though they do differ physicochemically. It is suggested that this "omnipotential" incorporation picture could also be found after exposure to MNNG and is, by its nature, typically fetal.

Topics: Animals; Cross Reactions; Dogs; Fetal Proteins; Fluorescent Antibody Technique; Gastric Juice; Gastric Mucosa; Glycoproteins; Histocytochemistry; Immunodiffusion; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Stomach Neoplasms

Lesions of the rat glandular stomach induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were classified into 4 categories: intramucosal lesions; polypous lesion; downward-growth lesions, and unequivocal adenocarcinomas. Each lesion was examined by three-dimensional reconstruction from serial sections to study the spacial arrangement of the glandular tubules. In the intramucosal lesions, the tubules showed tree-like branchings. In the polypous lesions and downward-growth lesions, the tubules were interconnected to form a three-dimensional network. In unequivocal adenocarcinomas, the tubules appeared separated and were dispersed into nests. These findings indicate that interruption of continuity of the epithelium in proliferated tubules is a possible sign of malignant transformation. Erosions were always observed in the intramucosal, the polypous and the downward-growth lesions. There were locations in the tubular system where the tubules became so attenuated as to resemble cord like structures. Inflammatory reactions were always demonstrable in the intertubular spaces in such lesions. These findings indicate that MNNG-induced anatomical changes may participate in the formation of erosions by causing local obstruction of the ductules.

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Models, Biological; Precancerous Conditions; Rats; Stomach; Stomach Diseases; Stomach Neoplasms

Sodium chloride, saccharin sodium, phenobarbital sodium and aspirin were tested for tumor-promoting activity in the glandular stomach of rats after initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) coupled with administration of a high salt diet. Male outbred Wistar rats were given MNNG in the drinking water (100 mg/liter) for 8 weeks, and during this period they were fed on diet supplemented with 10% sodium chloride. Thereafter, they were divided into 5 groups and fed on the basal diet or one of various diets supplemented with 10% sodium chloride, 5% saccharin, 0.05% phenobarbital or 1% aspirin until the end of the experiment. All animals were killed at the 40th experimental week for necropsy and histological examination. The incidence of adenocarcinoma was increased in the group given sodium chloride following initiation by MNNG and sodium chloride as compared with the group given MNNG and sodium chloride initiation only, but not significantly. However, the incidence of preneoplastic hyperplasia was significantly increased in this group. Saccharin also enhanced the development of adenocarcinomas of the glandular stomach. The results indicated that dietary administration of sodium chloride or saccharin after MNNG tends to promote tumor development. Phenobarbital or aspirin did not enhance tumor development, aspirin in fact rather showing a tendency to decrease the tumor incidence.

Topics: Adenocarcinoma; Animals; Aspirin; Carcinogens; Male; Methylnitronitrosoguanidine; Phenobarbital; Rats; Saccharin; Sodium Chloride; Stomach Neoplasms

Gastric carcinoma was induced in inbred Wistar rats by p.o. administration of N-methyl-N'-nitro-N-nitrosoguanidine for 25 weeks, and cell proliferation and growth of the gastric carcinoma in an incipient stage were studied. A microscopic cancer was found by 24 weeks, and macroscopic cancers were found after 27 weeks. All the cancers were a single lesion located at the midpoint of the lesser curvature of the stomach. Histologically, they were tubular adenocarcinomas. The mucosal changes predisposing to the development of carcinomas were focal erosions and dysplasias confined to the midpoint of the lesser curvature. The malignant transformation appeared to occur in the dysplastic cells of the eroded mucosa by 17 to 18 weeks after N-methyl-N'-nitro-N-nitrosoguanidine treatment. Following the malignant change, the labeling indices of the tissues with [3H]thymidine decreased, suggesting an elongation of cell cycle time. By repeated injections of [3H]thymidine, a time required for all the cancer cells to enter S phase (reflecting the maximum cell cycle time) was estimated to be about 3.5 days. This gave a theoretical doubling time for the gastric cancers. On the other hand, from the temporal observations of tumor volumes, it was shown that the gastric cancers in an incipient stage underwent exponential growth with a doubling time of 14 days. The difference between the theoretical and actual doubling time might reflect a cell loss rate in the cancer tissue.

Topics: Animals; Autoradiography; Cell Division; DNA Replication; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Thymidine; Tritium

Male Wistar rats that had received a low dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and sodium taurocholate showed a significantly higher incidence of hyperplastic and neoplastic lesions in the stomach mucosa than did the MNNG-treated controls. The result suggested an enhancing effect of taurocholate in stomach tumorigenesis.

Topics: Animals; Drug Synergism; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Taurocholic Acid

The susceptibility of healed, experimental gastric ulcers to chemical carcinogenesis was investigated. Slowly healing gastric ulcers were induced by the acetic acid method in the fundic and pyloric gastric mucosae of inbred male Wistar rats. N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) was administered in drinking water at a concentration of 50 mg/liter for 360 days after ulcer induction. Twenty-eight adenomatous hyperplasias and six-adenocarcinomas developed in the pyloric mucosae of rats, including five cases of adenomatous hyperplasia which developed in the periphery of the healed ulcer. In contrast, only one adenomatous lesion was found in the regenerated mucosa of the healed pyloric ulcer. No neoplasm was observed in the healed fundic ulcer area. The results demonstrated an increased incidence of neoplasms in the peripheral area of the healed pyloric ulcer and a decreased incidence of neoplasms in the regenerated mucosa within the healed pyloric ulcer scar, although these differences were not statistically significant in comparison with the intact pyloric mucosae of the MNNG-treated rats. Histoautoradiographs of the gastric mucosae demonstrated increased labeling indices in the healed ulcer periphery of the pyloric mucosa and decreased labeling indices in the regenerated mucosa within the healed pyloric ulcer scar of MNNG-treated rats, which might be related to the differential susceptibility of the two regions to gastric carcinogenesis. Intestinal metaplasia preferentially developed near the pyloroduodenal junction in MNNG-treated rats but was not localized in control rats. In the fundic ulcer scar area, an unusual squamous cell metaplasia was observed in one rat.

Topics: Animals; Cell Division; Disease Susceptibility; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Pyloric Antrum; Rats; Rats, Inbred Strains; Stomach Neoplasms; Stomach Ulcer; Wound Healing

On the basis of paradoxical concanavalin A (Con A) staining, the tendency of tumor cells of gastric phenotype to shift to intestinal phenotype and the stability of the latter phenotype in stomach tumors of different sizes were examined quantitatively with an image processor. Phenotypic expression of tumors of the small intestine was also studied. One hundred male Wistar rats were given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at 50 micrograms/ml in their drinking water for 20 weeks (group 1). Twenty male F344 rats were given methylnitrosourea (MNU) at a dose of 50 mg/kg ip twice a week for 2 weeks (group 2). Rats in group 1 were killed in week 50 of the experiment and rats in group 2 were killed in week 25. In group 1, the percentage areas of intestinal-type cells in small, medium and large adenocarcinoma of the stomach were 0.5, 2.7 and 6.6%, the differences between these values being significant (P less than 0.05-0.01). Intestinal phenotypic expression of tumor cells of the stomach is stable and the proportion of intestinal-type cells in adenocarcinomas of the stomach is higher in the larger tumors. Adenomatous hyperplasias and adenocarcinomas of the small intestine in groups 1 and 2 were all composed entirely of cells of the intestinal type. These results suggested that intestinal-type cells in adenocarcinoma of the stomach did not originate from intestinal metaplasias but from gastric-type cells in stomach adenocarcinomas.

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Hyperplasia; Intestinal Neoplasms; Intestines; Male; Metaplasia; Methylnitronitrosoguanidine; Methylnitrosourea; Nitrosourea Compounds; Phenotype; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of sodium chloride on the promotion stage of gastric carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in male inbred Wistar rats. Rats in group I were given MNNG at a concentration of 50 micrograms/ml in their drinking water for 12 weeks and then 1 ml of saturated NaCl solution intragastrically once a week until experimental week 65. Rats in group II were given MNNG for 12 weeks and then 1 ml of distilled water intragastrically once a week until week 65. Rats in group III were not treated for the first 12 weeks and were then given 1 ml of saturated NaCl solution intragastrically once a week until week 65. The incidence of adenomatous hyperplasias in the glandular stomach was significantly higher in group I than in group II, but the incidences of gastric adenocarcinomas and adenomas in groups I and II were not significantly different. No neoplastic or preneoplastic changes were observed in the stomach in group III.

Topics: Adenocarcinoma; Adenoma; Animals; Carcinogens; Cocarcinogenesis; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Sodium Chloride; Stomach Neoplasms

It is known that the nuclear DNA contents correlate with the grade of malignancy. In this study, nuclear DNA contents of biopsy specimens taken from N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG)-induced canine gastric cancer were measured by Feulgen-DNA-cytofluorometry. The DNA content and histological findings were sequentially observed after weekly administration of 7-N-(p-hydroxyphenyl)-mitomycin C (0.8 mg/kg), a kind of mitomycin C derivative. The appearance rate of cells over 4C decreased remarkably from 18.8% to 9.86% on average (p less than 0.02) and the maximum value of distribution also went down from 9.18C to 7.33C (p less than 0.01) at the early stage of administration of the oncostatic agent when no histological change was yet observable. It might be expected that this procedure will enable the future evaluation of oncostatic effects at the cellular level more objectively.

Topics: Adenocarcinoma; Animals; Carcinogens; Cell Nucleus; DNA, Neoplasm; Dogs; Flow Cytometry; Methylnitronitrosoguanidine; Mitomycin; Mitomycins; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Cell Transformation, Neoplastic; Gastric Fundus; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Stomach Ulcer

Topics: Adenocarcinoma; Animals; Dogs; Female; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Dogs; Male; Methylnitronitrosoguanidine; Stomach Neoplasms

Chronic administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water causes a high incidence of carcinomas of the glandular stomach in rats (Sugimura & Fujimura, 1967). Following a single oral dose of [14C-methyl]-MNNG (80 mg/L; 2.5 mg/kg b.w.), the extent of DNA methylation in the glandular stomach was 9 and 21 times higher than in forestomach and oesophagus, respectively. These differences were found to correlate with regional variations in the concentration of cellular thiols, which are known to accelerate the heterolytic decomposition of MNNG. When [14C-methyl]-MNNG was given intragastrically together with the thiol-blocking agent, N-ethylmaleimide, covalent binding of 14C-radioactivity to forestomach, glandular stomach and duodenum was almost completely abolished.

Topics: Animals; Autoradiography; DNA, Neoplasm; Ethylmaleimide; Female; Methylation; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Sulfhydryl Compounds

Bile reflux is generally accepted as a causative factor of gastric cancer after partial gastrectomy. The present study was designed to evaluate the promotion, by the per oral administration of taurocholic acid, of methyl-N-nitro-N'-nitrosoguanidine (MNNG)-induced gastric carcinogenesis. MNNG (83 mg/l) was given in the drinking water to half the male Wistar rats during 12 weeks while the other half served as controls. After this treatment half of the MNNG-treated animals and half of the controls were placed under a diet containing 0.2% of taurocholic acid while the other animals received the standard diet. At the 40th week after initiation of MNNG, surviving animals were killed. Their stomachs and their duodenums were observed for macro and microscopic examination. Macroscopically there were 7 animals bearing gastric tumors in the MNNG group and 15 in the MNNG + bile group (P less than 0.05). Microscopically there were 7 animals with severe antral dysplasia in the MNNG group, 7 rats with fundic dysplasia and 18 with severe antral dysplasia in the MNNG + bile group. Both groups developed an identical number of duodenal tumors which were invasive adenocarcinomas or angiosarcomas. In this experiment taurocholic acid significantly promoted gastric carcinogenesis. It is postulated that surgical techniques inducing duodenal reflux in the stomach may produced a 'high risk' group of patients in which a long and careful follow-up is required.

Topics: Adenocarcinoma; Administration, Oral; Animals; Body Weight; Cocarcinogenesis; Duodenal Neoplasms; Gastrointestinal Neoplasms; Hemangiosarcoma; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Taurocholic Acid

Promoting activities of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and NaCl and of combinations of these antioxidants with NaCl on gastric carcinogenesis initiated by N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) (CAS: 70-25-7; 1-methyl-3-nitro-1-nitrosoguanidine] were investigated in male inbred F344 rats. Animals, 6-week old, were given an intragastric administration of MNNG at 150 mg/kg body weight by gastric tube and 1 week later were placed on a diet containing BHA (0.5%), BHT (1.0%), NaCl (5.0%), BHA (0.5%) plus NaCl (5%), or BHT (1.0%) plus NaCl (5.0%) for 51 weeks. Control rats received no further treatment after MNNG administration. A single intragastric application of MNNG to rats induced multiple epithelial tumors of the forestomach and a few epithelial tumors of the glandular stomach after 52 weeks. Squamous cell carcinomas of the forestomach were seen in 2 of 18 effective rats (11.1%) in the control groups, and the incidences in the groups receiving the subsequent treatment were 45.0% with BHA, 15.8% with BHT, 30% with NaCl, 70% with BHA plus NaCl, and 52.9% with BHT plus NaCl. Differences in the incidences of squamous cell carcinoma between the controls and groups given BHA, BHA plus NaCl, and BHT plus NaCl were statistically significant. NaCl given alone after MNNG administration also significantly increased the incidence of papillomas in the forestomach. Incidences of glandular stomach tumors, adenomas and carcinomas were not affected by any of the subsequent treatments. No tumors of the stomach developed in the groups given BHA, BHT, and NaCl without MNNG pretreatment. Thus the present experiment revealed that BHA and NaCl but not BHT exert promoting activity on MNNG-induced forestomach carcinogenesis in rats and that, when BHA and BHT were given with NaCl, promotion was more marked, suggesting a synergistic effect on tumor promotion.

Topics: Animals; Anisoles; Body Weight; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Male; Metaplasia; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Sodium Chloride; Stomach; Stomach Neoplasms

The relationship between operative procedures and the incidence of remnant stomach carcinoma was investigated in male Wistar rats orally treated with N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7; 1-methyl-3-nitro-1-nitrosoguanidine]. A total of 178 rats was divided into 5 groups: After gastrectomy in which half of the glandular stomach was removed, group 1 received Billroth II reconstruction; group 2 was given short Roux-en-Y reconstruction; group 3 had long Roux-en-Y reconstruction; group 4 received gastrotomy alone; and group 5 consisted of nonoperated control rats. The incidence of gastric adenocarcinoma in MNNG-treated rats was significantly higher in group 1 (38.9%) as compared with that in group 3 (7.1%) and that in group 5 (9.5%). All tumors developed in the gastroenteric anastomotic area. Histologic examination of the gastric mucosa revealed atrophic gastritis and erosion in the gastroenteric anastomotic area, especially in rats with carcinoma. These findings seem to implicate the duodenogastric reflux, especially the reflux of bile acids, in the development of remnant stomach carcinoma in rats.

Topics: Animals; Carcinoma; Duodenogastric Reflux; Gastrectomy; Gastric Mucosa; Gastritis, Atrophic; Gastrostomy; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Time Factors

Whereas there is no longer any significant controversy regarding whether the resected stomach is subject to an increased risk of cancer, this question remains of great importance in terms of the cancer risk of nonresecting procedures performed on the stomach. Attention was given in particular to investigating with respect to carcinogenic potential the influence of gastrotomy. Heineke-Mikulicz pyloroplasty, gastrotomy plus pyloroplasty, vagotomy plus pyloroplasty, and gastroenterostomy without resection. As with resecting procedures, the carcinomas were also first observed in larger numbers following the nonresecting procedures without application of carcinogen. Of the 227 animals surviving the prescribed period 16 developed carcinomas of the stomach following application of carcinogen. 20 developed gastric carcinomas without carcinogen. Which individual factors in this multifactorial process might be the main contributors to carcinogenesis cannot be ascertained from our study.

Topics: Animals; Carcinoma; Female; Gastroenterostomy; Methylnitronitrosoguanidine; Postoperative Complications; Pylorus; Rats; Risk; Stomach; Stomach Neoplasms; Time Factors; Vagotomy

The carcinogenic or cocarcinogenic effects of bile or bile acid on stomach carcinogenesis were investigated in inbred W rats. Bile or bile acid was introduced into the stomach by choledochogastrostomy or with food after the administration of N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS: 70-25-7; 1-methyl-3-nitro-1-nitrosoguanidine] in drinking water. The animals that received MNNG and bile or sodium taurocholate (CAS: 145-42-6; N-choloyltaurine sodium salt) had a significantly higher incidence of hyperplastic and neoplastic lesions in the stomach mucosa than did the relevant MNNG-treated controls. The result suggested an enhancing effect of bile and sodium taurocholate in stomach tumorigenesis.

Topics: Animals; Bile; Carcinogens; Drug Synergism; Hyperplasia; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms; Taurocholic Acid

A series of experiments was devised to determine possible modifying effects of stress, aspirin, and sodium taurocholate on the activity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the Buffalo rat stomach. MNNG is a well known, direct-reacting carcinogen, and has been a reliable agent for the experimental production of gastric adenocarcinoma. The authors were able to produce adenocarcinomas in rats, but found a great number of gastric leiomyosarcomas. These occurred only in the groups given MNNG in combination with stress, aspirin, or sodium taurocholate, and did not occur in experimental groups given either MNNG, stress, aspirin, or sodium taurocholate alone, and did not occur in the control group.

Topics: Adenocarcinoma; Animals; Aspirin; Cocarcinogenesis; Diet; Disease Models, Animal; Leiomyosarcoma; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred BUF; Stomach Neoplasms; Stress, Physiological; Taurocholic Acid

N-Nitrosocimetidine, a nitroso derivative of the drug cimetidine, was given to groups of 20 male and 20 female rats in drinking water at a concentration of 0.5 mM for more than 2 years. The life span of the rats was not decreased compared with untreated control animals, and there was no significant increase in incidence of any tumor that could be attributed to the treatment. In comparison, 45% or more of 20 male rats treated with the analogous nitrosoguanidine, N-nitroso-N-methyl-N'-nitroguanidine, at an equimolar concentration in drinking water developed neoplasms of the glandular stomach. There was some shortening of life span in these animals. An additional group of 20 male rats was given an identical treatment with N-nitroso-N-methyl-N'-nitroguanidine in water, but prepared fresh on alternate days, rather than once a week, to minimize decomposition. These animals died more rapidly than did the previous group and had a higher incidence of neoplasms of the glandular stomach. The neoplasms seen in this organ were usually adenomas or adenocarcinomas, but there were a few hemangiosarcomas and neurosarcomas. There is a possibility that nitrosocimetidine could be formed by interaction of cimetidine with nitrite in the stomach, but the carcinogenic risk arising would be very small based on the negative result of this study.

Topics: Animals; Cimetidine; Drinking; Female; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms

Following chronic oral administration of hot water and N-methyl-N'-Nitro-N-nitrosoguanidine (MNNG), 4 of 30 Wistar rats developed sarcoma of the esophagus. 6 animals had tumors of the stomach, the liver and in the jejunum. One malignant tumor of the mediastinum was observed. The relatively short tumor induction time may be caused by the combined action of thermal injury and subsequently administered carcinogen. Organotropy of MNNG is changed and malignancies not only developed in the glandular stomach but also at the site of thermal injury to the esophagus.

Topics: Adenocarcinoma; Administration, Oral; Animals; Burns; Colonic Neoplasms; Esophageal Neoplasms; Female; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Sarcoma; Stomach Neoplasms

The promoting effect of partial gastrectomy in the development of cancer in the remnant stomach was examined in rats after oral administration of N-methyl-N'-nitro-N-nitrosoguanidine, using various surgical approaches. The incidence with which cancer developed in the remnant stomach following gastrectomy was lower than the incidence of gastric cancer in the entire glandular stomach. The incidence of cancer in the remnant stomach following Billroth II procedure according to Mayo's method, was higher than the incidence of cancer with other reconstructive methods as well as the corresponding area in the nonresected groups. There was a correlation between the incidence of cancer and the total bile acid concentration in the remnant stomach.

Topics: Administration, Oral; Animals; Bile Acids and Salts; Body Weight; Cocarcinogenesis; Gastrectomy; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms

Topics: Administration, Oral; Animals; Duodenal Neoplasms; Guanine; Jejunal Neoplasms; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of reflux of the duodenal contents on the development of gastric stump carcinoma induced in male rats was studied. Two gastro-jejunal anastomoses were made in the resected stomach of 28 rats and about half of the rats were also given a single dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Well-differentiated adenocarcinomas developed in the resected stomachs with and without MNNG administration at incidences of 40% in the former and 23% in the latter. All the carcinomas were localized in the vicinity of the gastro-jejunal anastomosis, at which the proximal jejunal segment was drained. Several mucosal changes were found predominantly in the fundic mucosa surrounding the anastomosis, i.e., ulcer, foveolar hyperplasia, intestinal metaplasia and atypical hyperplasia. On the other hand, there was little mucosal change surrounding the gastro-jejunal anastomosis of the distal jejunal segment. These findings suggest a direct correlation between the exposure of mucosa of the anastomotic region to the duodenal contents and the development of adenocarcinoma.

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Hyperplasia; Jejunum; Male; Metaplasia; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms; Stomach Ulcer

The biochemical denitrosation of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in tissues from four strains of rat, inbred Buffalo, Lewis, B-N, and the random-bred Sprague-Dawley, with different sensitivities to MNNG-induced gastric carcinomas was investigated as a possible explanation for the species/strain differences in MNNG-induced carcinogenesis. An analytical HPLC method was developed to assay denitrosation of MNNG to N-methyl-N'-nitroguanidine (MNG) by cytosolic, microsomal, mitochondrial, and nuclear cell fractions. All the activity was contained in the microsomal and cytosolic fractions, with the major portion occurring in the cytosol. The activity in both fractions was NADPH-dependent, but denitrosation was not reduced by inhibitors of the cytochrome P-450 system. Denitrosation of MNNG post-mitochondrial supernatant (S9) fractions from liver, glandular stomach mucosa, and duodenal mucosa of the four rat strains was determined. In all strains, denitrosation activities were highest in liver. Comparisons between the three strains most sensitive to MNNG-induced gastric carcinogenesis indicated no large differences for any tissue. However, Buffalo, the most resistant strain, did have a higher level of denitrosating activity in all three tissues, which is consistent with the hypothesis that higher levels of detoxifying enzymes may lead to a decreased incidence of tumors. On the other hand, denitrosation accounts for less than 3% of the MNNG that disappears during the incubation period so that the relevance of denitrosation as a mechanism in strain-specific sensitivity to MNNG-induced gastric carcinoma requires additional studies.

Topics: Analysis of Variance; Animals; Cytochrome P-450 Enzyme System; Inactivation, Metabolic; Methylnitronitrosoguanidine; NADP; Rats; Rats, Inbred Strains; Species Specificity; Stomach Neoplasms

Topics: Animals; Gastric Acid; Gastric Juice; Gastric Mucosa; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Cyclosporine administration has been associated with the development of lymphomas in human transplant patients as well as animals. Its effect on the genesis of common epithelial carcinomas is unknown. To investigate this N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was administered in drinking water to Wistar rats. Seventy-five young healthy male animals were divided into six groups and received cyclosporine alone, cyclosporine followed by MNNG, MNNG alone, cyclosporine during MNNG administration, MNNG followed by cyclosporine, and no treatment. Cyclosporine seemed to have minimal overall health effects and no cancers were encountered in the group receiving this agent alone. Animals in all carcinogen-treated groups developed gastric and upper intestinal carcinomas by Week 39. No statistically significant differences among carcinogen-treated groups were evident with respect to tumor incidence, histology, or distribution. There appeared to be trends (not statistically significant) toward a greater incidence of small bowel carcinomas in animals receiving cyclosporine plus MNNG as compared to those receiving MNNG alone; greater multiplicity of small intestinal carcinomas in animals receiving cyclosporine after MNNG as compared to all other groups; and greater incidence of small bowel tumors greater than 1 cm3 in animals receiving cyclosporine after MNNG as compared to all other groups. The median total tumor volume in the animals receiving cyclosporine following carcinogen was significantly greater than in any other group. This study does not support a policy of aggressive surveillance for gastrointestinal carcinoma in the human population receiving cyclosporine.

Topics: Animals; Cyclosporins; Drug Synergism; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Adenocarcinoma; Adenocarcinoma, Mucinous; Adenocarcinoma, Papillary; Adenoma; Animals; Dogs; Male; Methylnitronitrosoguanidine; Stomach Neoplasms

The effect of Pseudomonas aeruginosa colonizing in the gut on the development of gastrointestinal tumors was studied in rats treated orally with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The animals were inoculated with or accidentally colonized by P. aeruginosa after MNNG treatment. In 3 serial experiments, P. aeruginosa-positive, MNNG-treated rats consistently showed a significantly higher incidence of gastric tumors than P. aeruginosa-negative, MNNG-treated animals. The total incidence of gastric tumors was 40% (34/86) in the former, and only 11% (7/61) in the latter. The development of tumors in the small intestine was not likely to be influenced by P. aeruginosa colonization. It is concluded that P. aeruginosa in the gut plays a promoting role in gastric tumorigenesis in rats orally administered with MNNG.

Topics: Animals; Intestinal Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Pseudomonas aeruginosa; Rats; Rats, Inbred Strains; Stomach Neoplasms

Serial autoradiographic studies were made in wistar-rats during oral administration of N-methyl-N'-nitroso-guanidine (MNNG). Between the 4th and the 40th week 16 rats were killed at intervals. During the first period of the experiment we observed a foveolar hyperplasia of the mucosa of the glandular stomach. Later we found adenomatous hyperplasia but finally severe mucosal dysplasiae, which were looked upon as precursors of cancer. In the course of the 40th weeks investigation period no cancer was induced. In the antral mucosa the labelling index was higher than in the other parts of the glandular stomach. On the lesser curvature the proliferation rate was higher than on the greater curvature, or in comparison with the anterior and the posterior wall of the stomach. Furthermore the severe mucosal dysplasiae showed a higher labelling index than the adjacent area or the corresponding part of the lesser curvature.

Topics: Animals; Gastric Mucosa; Hyperplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms; Time Factors

Many gastrointestinal hormones have a stimulating action on the proliferation and growth of stomach and intestinal mucosa and on pancreas. This so-called trophic action was investigated most intensive on gastrin. We reproduced this effect autoradiographically by 3H-thymidine incorporation on the stomach corpus mucosa of rats. The animals had increased serum gastrin levels by partial stomach corpus resection that increased the endogenous serum gastrin level. The proliferation stimulating action of gastrin is also detectable at chronic oral application of N-Methyl-N'-nitroso-N-nitroguanidine for induction of stomach and intestinal tumors simultaneously to pentagastrin administration or partial stomach resection in the intact, tumor free oxyntic mucosa of stomach.

Topics: Animals; Cell Division; Gastrectomy; Gastric Fundus; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Pentagastrin; Radioimmunoassay; Rats; Rats, Inbred Strains; Stomach Neoplasms

A study was made of the distribution of pepsinogen-synthesizing polyribosomes in the rat's stomach mucous membrane, in the process of chemical carcinogenesis induced by N-methyl-N'-nitro-N-nitrozoguanidine. A sharp decrease in the content and proteolytic activity of pepsin is shown in cytosol and membrane-bound polyribosomes of the mucous membrane of the rat stomach due to the inducing substance. The appearance of this enzymatic activity is noted in free polyribosomes isolated from the rat stomach tumours.

Topics: Animals; Free Radicals; Gastric Mucosa; Methylnitronitrosoguanidine; Pepsin A; Pepsinogens; Polyribosomes; Protein Binding; Rats; Stomach Neoplasms; Time Factors

Albino rats (noninbred) were divided into 4 groups: 1) 56 control rats, 2) 40 rats fed 1 ml aspirin suspension (40 mg/ml) twice a week, 3) 20 rats given N-nitroso-N-methylnitroguanidine (MNNG) solution (250 micrograms/ml) to drink ad libitum, and 4) 40 rats given both aspirin and MNNG. In 18 months, there were no gastrointestinal tumors in groups 1 and 2, 8 cases of gastric tumors in group 3, and 37 cases of gastric tumors in group 4. Adenocarcinomas of the glandular stomach were found in 21 of 40 rats in group 4 but in only 4 of the 20 rats in group 3; the difference in incidence was significant. Histologic and electron microscopic examination of the epidermoid carcinomas and adenocarcinomas in group 4 showed no difference from such tumors induced by MNNG only. Hyperplasia of the forestomach mucosa and hyperplasia of the pyloric gland region of the glandular stomach in group 4 were more severe.

Topics: Adenocarcinoma; Animals; Aspirin; Carcinoma, Squamous Cell; Cocarcinogenesis; Female; Humans; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Papilloma; Probability; Rats; Stomach Neoplasms

The effect of histamine on induction of tumors in the forestomach and the glandular stomach after N-nitroso-N-methylnitroguanidine (MNNG) administration was studied in male inbred W rats. Animals were given 50 micrograms MNNG solution/ml orally for 25 weeks and then 4 mg histamine dihydrochloride sc per day in depot form. Administration of histamine in depot form after MNNG significantly increased the incidence of tumors in the forestomach, but it significantly decreased the incidence of adenocarcinomas in the glandular stomach. All of the tumors induced in the forestomach were of the squamous cell type, and 50% of them were squamous cell carcinomas. Histamine alone had no apparent carcinogenicity in rats.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Histamine; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms

A periodical and histological study on the histogenesis of experimental stomach carcinoma induced by N-methyl-N'-nitro-N-nitrosoguanidine in rats suggested that cancer progression occurred from the submucosal focus under the condition of existing adenomatous hyperplasia. This carcinoma manifested particular atypia, combined hyperplasia of the smooth muscle, indistinct borderline from the surrounding normal mucosa. These were considered to be specific histological findings in experimental carcinoma. In 3 of 273 gastrectomized patients with gastric carcinoma the same histological findings were obtained as in experimental gastric carcinoma; 35 patients had submucosal heterotopic glands similar to the experimentally induced rat foci or adenomatous hyperplasias seen in the experimental carcinoma. These results suggest the same histogenesis for human stomach cancer and the experimental carcinoma.

Topics: Aged; Animals; Female; Gastric Mucosa; Humans; Hyperplasia; Male; Methylnitronitrosoguanidine; Middle Aged; Neoplasm Invasiveness; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Animals; Castration; Estradiol; Female; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Sex Factors; Stomach Neoplasms

No relationship was found between general sensitivity of rats to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) as identified by tumor incidence and mean latent period of tumorigenesis and the age of experimental animals at the beginning of treatment.

Topics: Adenocarcinoma; Adenoma; Age Factors; Animals; Ileal Neoplasms; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

Glandular stomachs of fetal and newborn Wistar rats were transplanted s.c. after treatment in vitro with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at concentrations of 10, 5 and 1 microgram/ml for 2 h. Eleven adenocarcinomas developed from 118 MNNG-treated transplants, whereas no adenocarcinomas developed from 28 untreated transplants. The incidence of adenocarcinomas in fetal glandular stomach (9/46) was significantly different (p less than 0.01) from that in glandular stomach of newborn rats (2/67). Various types of mesenchymal tumors also developed from untreated (9/28) and MNNG-treated (20/118) transplants.

Topics: Adenocarcinoma; Animals; Embryo, Mammalian; Male; Methylnitronitrosoguanidine; Neoplasm Transplantation; Organ Culture Techniques; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Animals; Cell Nucleus; DNA, Neoplasm; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: Adenocarcinoma; Adenoma; Animals; Diet; Female; Jejunal Neoplasms; Male; Methylnitronitrosoguanidine; Mice; Mice, Inbred C57BL; Mice, Inbred Strains; Rats; Rats, Inbred Strains; Sodium Chloride; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Antioxidants; Ascorbic Acid; Carcinoma, Squamous Cell; Male; Methylnitronitrosoguanidine; Neoplasms; Rats; Rats, Inbred F344; Sarcoma; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Intestines; Isoenzymes; Male; Metaplasia; Methylnitronitrosoguanidine; Models, Biological; Pepsinogens; Pylorus; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effect of vaccinia virus on MNNG-induced gastric cancer in rats was studied. Subcutaneous inoculation of the highly attenuated vaccinia virus AS strain at intervals of 3 days from the beginning of the experiment showed prominent antitumor activity not only against adenocarcinoma induced by MNNG in the glandular stomach but also against squamous cell carcinoma in the forestomach. Both UV-inactivated vaccinia virus and the DI strain of mammalian pathogenic vaccinia virus, from which the AS strain originated, showed no antitumor effect.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms; Vaccines, Attenuated; Vaccinia virus; Viral Vaccines

After 12 oral applications of 80 mg/kg MNNG as a suspension in 30% aqueous ethanol at weekly intervals, 98 Sprague-Dawley rats died with multiple tumors of the forestomach after a medium latency period of 226 days. Histological examination showed generalized papillomatosis developing into keratinizing squamous cell carcinomas with infiltrative growth in 88/98 (89%) animals. Tumorigenic lesions in the glandular stomach ware only observed in 3/98 rats. In two of these animals, mucosal adenocarcinomas were found and in the third a leiomyosarcoma. In about 30% of the animals treated with MNNG, degenerative liver changes were found, especially single cell and focal necroses, cystic alterations, and bile-duct proliferations.

Topics: Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Leiomyosarcoma; Liver; Methylnitronitrosoguanidine; Neoplasms, Experimental; Papilloma; Rats; Rats, Inbred Strains; Stomach Neoplasms

The influence of sodium chloride on chemical carcinogenesis of the gastroduodenal tract was examined in male outbred Wistar rats exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water (100 mg/liter) for 20 weeks. Sodium chloride given concomitantly with MNNG during the first 20 weeks of the experiment increased both the incidence and the size of tumors at 40 weeks. However, sodium chloride given after MNNG during the second 20 weeks of the experiment did not enhance tumor development. This study indicates that, although sodium chloride given with MNNG enhances tumor development, sodium chloride does not promote gastric carcinogenesis.

Topics: Animals; Body Weight; Diet; Drinking; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Sodium Chloride; Stomach Neoplasms

Topics: Alkaline Phosphatase; Animals; Isoenzymes; Methylnitronitrosoguanidine; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms

Genetic control of the induction of gastric tumors by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in susceptible ACI rats, resistant Buffalo rats, and their F1 and F2 offspring. Both sexes of all strains, initially 7 to 9 weeks old, were given MNNG at a concentration of 83 micrograms/ml in their drinking water for 32 weeks and were sacrificed at experimental Week 72. The incidence of gastric adenocarcinoma in ACI rats was 80% in males and 47% in females; in Buffalo rats, the incidence was 18% in males and 0% in females. F1 hybrids showed the same resistance to MNNG as did Buffalo rats; the incidence of gastric adenocarcinoma was 17% in males and 8% in females. These results suggest that resistance to induction of gastric adenocarcinoma by MNNG is a dominant characteristic. The incidence of gastric adenocarcinoma in the F2 generation was 36% in males and 14% in females, which is close to the 3:1 ratio expected from the segregation of a single resistant gene. In ACI and Buffalo strains and their hybrids, males were more susceptible than females to induction of gastric carcinoma by MNNG. Intestinal tumors were observed mainly in the duodenum and jejunum in both strains and their hybrids, and the incidences were as follows: ACI: males, 67% and females 42%; Buffalo: males, 12% and females, 18%; F1: males, 18% and females, 15%; and F2: males, 15% and females, 19%. Thus, there seems to be a common genetic basis for both gastric and intestinal carcinogenesis by MNNG.

Topics: Animals; Disease Susceptibility; Female; Intestinal Neoplasms; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred BUF; Rats, Inbred Strains; Stomach Neoplasms

Chronic administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water causes a high incidence of carcinomas of the glandular stomach in rats. Following a single oral dose of [14C-methyl]MNNG (80 p.p.m.; 2.5 mg/kg), the extent of DNA methylation in the glandular stomach was 9 and 20 times higher than that in the forestomach and oesophagus, respectively. The autoradiographic distribution of tissue-bound radioactivity within the glandular stomach of BONN/WIST rats coincides with strain-specific tumor location at the small curvature. Following intragastric administration of [14C-methyl]MNNG, alkylation levels in forestomach and glandular stomach were twice as high as those observed after oral exposure via the drinking water, whereas duodenal DNA showed a much lower extent of methylation. The regional differences in DNA alkylation correlated with tissue-specific variations in the concentration of cellular thiols which are known to accelerate the heterolytic decomposition of MNNG. When [14C-methyl]MNNG was given intragastrically together with the thiol-blocking agent, N-ethylmaleimide, covalent binding of the 14C-radioactivity to forestomach, glandular stomach and duodenum was almost completely abolished. This indicates that the preferential induction of glandular stomach tumors by MNNG relies on high concentrations of cellular thiols in the target tissue.

Topics: Animals; Carbon Radioisotopes; Duodenal Neoplasms; Esophageal Neoplasms; Ethylmaleimide; Female; Gastrointestinal Neoplasms; Jejunal Neoplasms; Liver Neoplasms; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effects of butylated hydroxytoluene (BHT) on the incidence and histology of gastric cancers induced by oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in Wistar rats. Oral administration of 1.0% BHT in regular chow pellets during treatment with MNNG for 25 weeks significantly reduced the incidence of gastric cancers in experimental week 40. BHT had no influence on the histological type of adenocarcinomas induced in MNNG-treated rats. BHT alone induced slight glandular hyperplasia, but not moderate glandular hyperplasia or gastric cancer.

Topics: Animals; Butylated Hydroxytoluene; Drug Evaluation, Preclinical; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms; Time Factors

Modifiers of gastric carcinogenesis are reviewed with evidence of experimental results using rats. 1) Physical modifiers: Route of administration, medium (vehicle) of carcinogens, detergents, dosage (concentration), period (frequency) of administration, exposure time, and condition of mucus. Effects of surfactants and presence of a foreign body in the stomach lumen are also samples of physical enhancing factors. 2) Biological modifiers: Species, genetics, sex, hormonal factors, nutrition, and age. Moreover, effect of preexisting ulceration is important. 3) Chemical modifiers: Chemical substances administered prior to, simultaneously with, or following exposure of experimental animals to chemical carcinogens, or promoters of carcinogenesis. Chemical modifiers are: co-initiators, tumor promoters and inhibitors. NaCl having both co-initiator and tumor promoter action on MNNG gastric carcinogenesis is clearly shown in our investigations.

Topics: Age Factors; Animals; Cricetinae; Diet; Dogs; Male; Methylnitronitrosoguanidine; Mice; Neoplasms, Experimental; Rabbits; Rats; Saccharin; Sodium Chloride; Solvents; Stomach Neoplasms; Surface-Active Agents

Genetic control of susceptibility of rats to gastro-carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in susceptible ACI strain rats, resistant Buffalo strain rats, and their F1 and F2 offsprings. Rats were given MNNG at a concentration of 83 micrograms/ml in drinking water for 32 weeks and sacrificed on week 72. The incidence of gastric adenocarcinomas in F1 was as low as that in Buffalo rats. The results showed that susceptibility to MNNG was controlled genetically and that the resistance of Buffalo strain rats was autosomal dominant. To clarify the mechanisms which determine susceptibility to MNNG, some biochemical parameters such as pH of gastric juice, glutathione content in the gastric mucosa and the binding of MNNG to DNA, were analysed. No difference was observed between ACI and Buffalo strains in regard to the events leading to the binding of MNNG to DNA.

Topics: Animals; DNA; Drug Resistance; Female; Gastric Juice; Gastric Mucosa; Glutathione; Hydrogen-Ion Concentration; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Species Specificity; Stomach Neoplasms

Influences of sex-hormones on gastric cancer development induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Wistar rats were studied. Well-differentiated adenocarcinoma developed in glandular stomach of 81% of male rats given 50 micrograms/ml of MNNG in drinking water for 4 months and sacrificed on the 12th month of the experiment. No gastric cancer was found in female rats given MNNG. In the additional estradiol-treated or castrated male rats, and the additional testosterone-treated or oophorectomized female rats, the incidence of carcinoma was 68% and 29%, and 33% and 5%, respectively. In the latter 3 groups, gastric erosion of the early stage was also low incidence. Histologically, poorly-differentiated adenocarcinoma was observed more frequently in these groups than in the alone MNNG-treated male group. These results have sagg-suggested that female-sex-hormone may inhibit and male-sex-hormone may accelerate the gastric carcinogenesis.

Topics: Adenocarcinoma; Animals; Castration; Estradiol; Female; Humans; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms; Testosterone; Time Factors

Fine structure of poorly differentiated adenocarcinoma selectively induced in the canine stomach by a low concentration of N-ethyl-N'-nitro-N-nitrosoguanidine was studied with special reference to the so-called signet ring cells. These cells were electron microscopically classified into two groups: 1) mucin-containing cells and 2) intracellular microcyst cells. The cytoplasm of mucin-containing cells was packed with fused large and low electrondense secretory granules. In another type of signet ring cells, there were intracellular microcysts with microvilli on the internal surface. A comparison of canine and human signet ring cells revealed a close resemblance in the fine structure. Canine gastric carcinoma should be a good model for human gastric carcinoma therapeutics.

Topics: Adenocarcinoma; Animals; Carcinogens; Cell Nucleus; Cytoplasmic Granules; Dogs; Female; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Stomach Neoplasms

The effects of gastrin on the histopathology of the glandular stomach and on the incidence of gastric carcinoma induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in inbred Wistar (W) rats. Prolonged administration of gastrin after treatment with MNNG significantly reduced the incidence of adenocarcinomas of the glandular stomach. In addition, atypical glandular proliferations were significantly less frequent and were smaller, and the incidence of marked mucosal atrophy was significantly reduced in both the antral and oxyntic gland mucosae. Both atypical glandular hyperplasia and mucosal atrophy are precursors of gastric cancers; prolonged administration of gastrin to rats after treatment with MNNG suppressed development of precursors of gastric cancer and so prevented development of gastric cancers.

Topics: Adenocarcinoma; Animals; Atrophy; Delayed-Action Preparations; Drug Interactions; Gastric Mucosa; Gastrins; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms

This study deals with the effects of gastrin on the incidence of gastric tumors in rats induced by N-methyl-N'-nitro-N-nitrosoguanidine. Inbred Basel-Wistar rats received N-methyl-N'-nitro-N-nitrosoguanidine in drinking water (50 micrograms/ml for 32 weeks) in order to produce gastric carcinoids. A treatment with s.c. injection of pentagastrin (300 micrograms/kg, once daily for 4 weeks) was started at the beginning of N-methyl-N'-nitro-N-nitrosoguanidine treatment simultaneously, on the 4th, 8th, 16th, and 32nd week after start of N-methyl-N'-nitro-N-nitrosoguanidine treatment, respectively. At autopsy, from the 55th to 60th week after start of the experiment, only in the eighth-week group of gastrin-treated rats was the incidence of gastric carcinoid significantly higher than in the gastrin-untreated group of rats receiving N-methyl-N'-nitro-N-nitrosoguanidine alone. The incidence of adenocarcinoma in the glandular stomach also was high only in the fourth-week group of gastrin-treated rats. However, these effects could not be seen in other gastrin-treated or untreated groups of rats. The data suggest that gastrin treatment in the early stage of rat stomach carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine is effective in increasing the development of gastric tumors.

Topics: Adenocarcinoma; Animals; Carcinoid Tumor; Diet; Drug Synergism; Female; Intestinal Neoplasms; Male; Methylnitronitrosoguanidine; Pentagastrin; Rats; Rats, Inbred Strains; Stomach Neoplasms; Time Factors

Nineteen male Wistar rats received N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water (83 mg/L) to initiate glandular adenocarcinoma of the stomach; eight control rats received tap water. After 12 weeks a pyloroplasty was performed on nine rats receiving MNNG and three control rats. Ten MNNG-treated rats and five control rats had no operation. All were observed for 38 weeks before being killed. No difference in the incidence of antral adenocarcinomas was found between the MNNG-treated groups; however, those without operation showed in situ changes in the duodenum and those treated with pyloroplasty showed five invasive adenocarcinomas. In this model pyloroplasty alone did not increase the risk of gastric cancer but increased the risk of duodenal tumors. Pyloroplasty apparently accelerated the gastric evacuation rate, resulting in greater insult to the duodenal mucosa. Such a condition may require a higher proliferative rate in the duodenum and may increase subsequent formation of malignant tumors.

Topics: Adenocarcinoma; Animals; Disease Models, Animal; Duodenal Neoplasms; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Pyloric Antrum; Pylorus; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effects of sex hormones on the induction of gastric carcinoma by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in Wistar rats. Well-differentiated adenocarcinomas developed with high frequency (88%) on the glandular stomach of male rats given MNNG in drinking water (50 micrograms/ml) for 4 months and sacrificed on the 12th month of the experiment. In female rats given MNNG, no gastric cancer was observed. In the castrated or estradiol-treated male rats, the incidence of carcinoma was lower (29 and 68%, respectively) than in the nontreated male rats. Histologically, poorly differentiated adenocarcinomas were observed more frequently in these groups than in the nontreated male group. In MNNG carcinogenesis, female, castrated male and estrogen-treated male rats had a lower incidence of gastric cancer with lower histological differentiation than did nontreated male rats.

Topics: Adenocarcinoma; Animals; Castration; Estradiol; Female; Gonadal Steroid Hormones; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms; Testis

The study of nicotine action upon N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) stomach cancer development was carried out in rats. As compared with control it was established that combined MNNG and nicotine long-term administration led to the occurrences: 1) stomach pretumorous changes of the whole mucous membrane; 2) earlier development of stomach cancer tumors and its frequency was doubled; 3) progressive decrease of acetylcholinesterase activity, especially expressed in homogenates of cerebrum hemispheres, hypothalamic region and medulla oblongata (where this activity is practically failed to be expressed). The obtained data are the witness of the nicotine ability to enhance the MNNG-stomach carcinogenesis in rats. The possible action of the autonomic nervous system in such nicotine effects is under discussion.

Topics: Acetylcholinesterase; Animals; Brain; Drug Interactions; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nicotine; Rats; Stomach Neoplasms

We have been investigating possible effects of sex hormones on the carcinogenesis of stomach cancer in Wistar rats that were given N-methyl-N'-nitro-N-nitrosoguanidine in drinking water (50 micrograms/ml) for 4 months. The incidences of stomach cancer in intact male, intact female, castrated male, and castrated female rats at Month 4 of the experiment were 5, 0, 0, and 0% respectively; and those at Month 8 were 40, 10, 0, and 0% respectively; indicating that the incidence in intact males was much higher than in the other groups. The difference in the incidence became more evident when the animals were sacrificed at Month 12 of the experiment (81, 0, 29, and 5%, respectively). Hypertrophy and dissociation of the lamina muscularis mucosae which are considered to occur in the carcinogenic process were observed only in the male rats at the earlier months, but not in female nor in castrated rats. In N-methyl-N'-nitro-N-nitrosoguanidine carcinogenesis, female and castrated rats had a lower incidence of gastric cancers with less change in the lamina muscularis mucosae than did the nontreated male rats. These findings, therefore, suggest that, in addition to the suppressive action of female hormones, male hormones facilitate carcinogenesis.

Topics: Animals; Castration; Female; Male; Methylnitronitrosoguanidine; Ovary; Rats; Rats, Inbred Strains; Sex Factors; Stomach Neoplasms; Testis

The administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water induces tumours, mainly adenocarcinomas in the glandular stomach of rats. The sensitivities of different strains of rats to gastrocarcinogenesis induced by MNNG vary: Wistar and ACI strains are sensitive, whereas the Buffalo strain is resistant. Genetic analyses were made on the induction of gastric tumous by MNNG in the ACI and Buffalo strains and their F1 and F2 hybrids. Rats of both sexes, 7-9 weeks old, were given 83 micrograms of MNNG/ml of drinking water for 32 weeks and sacrificed in experimental week 72. The incidences of gastric tumours were as follows: ACI strain, male 80%, female 63%; Buffalo strain, male 29%, female 6%; F1 hybrid, male 35%, female 9%; F2 hybrid, male 65%, female 29%. There were no significant differences in the sensitivities of Buffalo X ACI F1 and ACI X Buffalo F1, or of Buffalo X ACI F2 and ACI X Buffalo F2. These results show that the gene(s) controlling resistance to MNNG is autosomal in the Buffalo strain and is inherited dominantly by F1 and F2 hybrids. In both strains and their hybrids, the incidence of gastric tumours was higher in males than in females.

Topics: Adenocarcinoma; Animals; Disease Susceptibility; Female; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Sex Factors; Species Specificity; Stomach Neoplasms

Effects of NaCl, Tween 60 and N-ethyl-N'-nitro-N-nitroso-guanidine (ENNG) on gastric carcinogenesis were investigated in male Wistar rats. Animals received a single dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at 250 mg/kg body weight by gastric tube followed one week later by either 10% NaCl in their diet, twice-weekly applications of 1 ml of saturated NaCl solution by gastric tube, 1.0% Tween 60 in their drinking water or 0.0005% ENNG in their drinking water. One group of rats were given MNNG 24 h after a single application of 1 ml of saturated NaCl solution to investigate the effect of NaCl on initiation. A single dose of MNNG to rats resulted in development of multiple epithelial tumors in the forestomach and no epithelial tumors in the glandular stomach after 52 weeks. There were no differences in tumor incidences of the forestomach and glandular stomach between experimental groups which were given a subsequent treatment with NaCl or Tween 60 and the control group with MNNG alone. ENNG significantly enhanced the tumor induction in the glandular stomach, while ENNG alone did not induce any tumors in the stomach. The NaCl treatment prior to MNNG administration also increased tumor development in the glandular stomach but not in the forestomach.

Topics: Animals; Body Weight; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Polysorbates; Rats; Rats, Inbred Strains; Sodium Chloride; Stomach Neoplasms

Cimetidine is a histamine H2-antagonist. Since in vitro formed N-nitrosocimetidine (NC) has been shown to be genotoxic, we investigated it for carcinogenicity. Two groups of 40 Sprague-Dawley rats each received 500 and 50 mg/kg NC, respectively, by gavage twice weekly for one year with subsequent lifetime follow-up. An additional 40 rats were given the structurally related carcinogen methylnitro-nitrosoguanidine (MNNG) orally at weekly doses of 80 mg/kg for 3 months. 100 animals served as untreated controls. MNNG-treated rats died with carcinomas of the forestomach (median induction time: 226 days). No evidently treatment-related tumors were seen in animals receiving NC. The median survival time in both NC-treated groups was reduced (400 and 393 vs. 630 days in the control). No evidence of carcinogenicity of NC was seen in this bioassay. It is concluded that NC is not carcinogenic, or at least significantly less so than MNNG.

Topics: Animals; Cimetidine; Female; Follow-Up Studies; Guanidines; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms

The effects of genetic factors on gastrocarcinogenesis in rats were studied by giving 83 micrograms/ml of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking-water to ACI strain rats, Buffalo strain rats, and their F1 hybrid rats for eight months. Animals were sacrificed on the 505th experimental day and examined histologically. The incidences of gastric carcinoma were as follows (no. of carcinoma-bearing rats/no. of effective animals): ACI rats, 86% (12/14) of males and 53% (9/17) of females; Buffalo rats, 19% (3/16) of males and 0% (0/13) of females; F1 hybrids between ACI and Buffalo rats, 23% (7/30) of males and 3% (1/32) of females. The incidence of gastric carcinoma in F1 hybrids was significantly lower than that in ACI rats but not significantly different from that in Buffalo rats. These results suggest that resistance to gastrocarcinogenesis by MNNG is an autosomally dominant trait.

Topics: Animals; Female; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Female; Male; Methylnitronitrosoguanidine; Mice; Neoplasms, Experimental; Stomach; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Lymphatic Metastasis; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms

The morphological and biochemical characteristics of a transplantable tumor line of rat gastric carcinoma (SG2B), that developed in a Wistar strain rat after treatment with N-methyl-N'-nitro-N-nitrosoguanidine and then 4-nitro-quinoline 1-oxide were examined at the 60th passage. The tumor was serially transplanted into newborn rats by subcutaneous and intraperitoneal routes and has been passed through 60 transplant generations over a 4-year period. The tumors appeared to be well-differentiated tubular adenocarcinomas throughout successive passages, and at each generation transplants were almost identical to the original gastric adenocarcinoma as judged by light and electron microscopic observation. Ultrastructurally, the neoplastic cell contained abundant free ribosomes and exhibited few mucin granules. The microville on the apical cell surface were short and irregularly spaced. Electrophoresis showed that pepsinogens (Pg) 3 and 4 were present but no Pg 1 was detectable at the 60th passage, as was the case in the tissue at the 2nd and 5th passages. The pepsinogen content of the tissue at the 60th passage was similar to that at the 5th passage. The tumor tissue has thus retained the morphological and biochemical character of a pyloric gland type tumor for a long time (over 4 years) during serial transplantation.

Topics: 4-Nitroquinoline-1-oxide; Adenocarcinoma; Animals; Animals, Newborn; Female; gamma-Glutamyltransferase; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Neoplasm Transplantation; Neoplasms, Experimental; Pepsinogens; Rats; Stomach Neoplasms

Gastric tumours were induced in rats by orally administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The received adenomas and adenocarcinomas were investigated electron microscopically. In this paper we give a short description of main ultrastructural specialities of tumour cells, which can be derived from mucoid surface cells and mucous cells of antropyloric glands.

Topics: Adenocarcinoma; Adenocarcinoma, Mucinous; Adenoma; Animals; Methylnitronitrosoguanidine; Microscopy, Electron; Neoplasms, Experimental; Rats; Stomach; Stomach Neoplasms

Biochemical changes in the stomach mucous membrane of rats treated with N-methyl-N-nitro-N-nitrosoguanidine (MNNG) were studied. Carcinogenesis was shown to involve considerable changes in gastric mucous membrane, e. g. disorders in biosynthesis of isoforms of pepsinogen-pepsin. Their level and proteolytic activity are gradually declined. This effect can be reversed at an early stage of treatment and is persistent in advanced tumors of glandular part of rat stomach.

Topics: Animals; Female; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Pepsin A; Pepsinogens; Polyribosomes; Rats; Stomach Neoplasms; Time Factors

A gastroenterostomy without entero-anastomosis in rats favours the development of adenomatous epithelial lesions at the gastroenteral borderline in dependence of exposition to MNNG. The extent of such changes in the mucosa could be modified by vagotomy, pyloroplasty, or the prevention of duodenogastric reflux (Roux-en-Y method), whereby vagotomy has an enhancing effect on proliferation. A comparison of the mucosal changes at the gastroenteral anastomosis indicates that a multitude of factors causes environmental changes at the gastroenteral borderline, stimulating epithelial proliferation to the point of cancer formation. Thus, it is not possible to accuse any single factor such as intestinal reflux, carcinogens or different surgical techniques as the sole culprit in carcinogenesis.

Topics: Animals; Bile Reflux; Epithelium; Methylnitronitrosoguanidine; Neoplasms, Experimental; Postoperative Complications; Precancerous Conditions; Rats; Stomach; Stomach Neoplasms; Vagotomy

The effect of ulcers on the development of gastric tumors by N-methyl-N'-nitro-N-nitrosoguanidine in (MNNG) was studied in male Wistar rats. Ulcers were produced by the application of a steel rod, 5 mm in diameter and frozen at -78 degrees C, to the serosal surface of the forestomach, fundus, pylorus, or proximal duodenum. The existence of the ulcers at these areas was confirmed 1 week later in a preliminary experiment. Experimental groups were given MNNG in their drinking water at a concentration of 100 micrograms/ml for 16 weeks beginning 7 days after the ulcers developed. Administration of MNNG after ulceration resulted in a relative increase in the tumor incidences at each ulcer site, especially the proximal duodenum, which suggested that regenerating cells in the duodenum were the most susceptible cells among the cells of the four sites. The increase in tumor incidence following ulceration may be due to exposure of MNNG to a greater number of regenerating cells during the renewal process that seem to be more responsive to carcinogenic influences that normal cells.

Topics: Adenocarcinoma; Animals; Duodenal Neoplasms; Duodenal Ulcer; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Papilloma; Rats; Stomach Neoplasms; Stomach Ulcer

Methyl linoleate hydroperoxide (MLHP) and native methyl linoleate (ML) were tested for carcinogenicity toward the gastrointestinal (GI) tract in male specific-pathogen-free outbred Wistar rats. N-Methyl-N-nitro-N-nitrosoguanidine (MNNG) was given in the drinking water in a dose of 20 mg/liter when cocarcinogenic properties of the test substances were to be tested. MLHP and ML were fed by stomach tube and had no effect as complete carcinogens. Given concomitantly with MNNG, ML did not enhance carcinogenesis. MLHP in conjunction with MNNG was the only treatment which, as treatment with MNNG in a dose of 83 mg/liter, led to an increase of GI cancers in animals that died before day 354. Cumulative results after a maximum of 612 days showed a distribution of GI cancers in favor of the glandular stomach only after MLHP was given with MNNG.

Topics: Animals; Body Weight; Cocarcinogenesis; Gastrointestinal Neoplasms; Intubation, Gastrointestinal; Linoleic Acids; Lipid Peroxides; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Time Factors

A total of 30 inbred Wistar rats were orally administered 70 microgram/ml solution of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) for 35 weeks and then tap water for the following 20 to 30 weeks. Four of the 20 females and two of ten males developed carcinoids in the glandular stomach, but no metastasis could be found. Carcinoids developed most frequently in the fundic portion along the greater curvature. Histologically, these tumors were medullary anaplastic carcinomas containing two different endocrine cell populations. The first cell type was argentaffin having the electron-dense, somewhat pleomorphic secretory granules (437-810 nm) and the second type was argyrophil having round granules with a dense core and a pale halo (550 nm). None of these tumors showed endocrine immunoactivity for gastrin, somatostatin, insulin, glucagon, and enkephalin. One of these gastric tumors developed into scirrhous carcinoma, but differentiated adenocarcinoma could not be seen in the glandular stomach.

Topics: Animals; Carcinoid Tumor; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach; Stomach Neoplasms

Rats of non-pure strain were allowed to drink N-Methyl-N-Nitro-N-Nitroso-guanidine (MNNG) solution (200-250 micrograms per milliliter) ad libitum. After 14 months, in addition to MNNG, each of them was fed with 1 ml of saturated NaCl solution once a week. During a period of 18 months, there were 5 cases of gastric adenocarcinoma and 2 cases of adenocarcinoma of the duodenum among 18 experimental rats. Besides, there were a few cases of papilloma of the fore-stomach and carcinoma of the lung. In 17 control rats, no tumors of the gastro-intestinal tract were seen. Microscopic examination of the mucosa of the pyloric gland region of the stomach in the experimental rats showed that the deep epithelial cells of the gastric pit exhibited a marked degree of proliferation and a malignant change had started in these cells. Electron microscopic observation of these epithelial cells revealed that the the proliferating cells showed only increased nucleocytoplasmic ratio, while those with atypical hyperplasia showed that the form of the nucleus and the changes in the basement membrane and intercellular junctions were somewhat similar to those of malignant cells. It is believed that increase in concentration of the carcinogens and prolongation of the time of contact with them may induce malignant tumors in the insensitive animal.

Topics: Adenocarcinoma; Animals; Epithelium; Gastric Mucosa; Hyperplasia; Methylnitronitrosoguanidine; Microscopy, Electron; Neoplasms, Experimental; Pylorus; Rats; Stomach Neoplasms

Experimental colonic carcinoma in a dog was induced by anal insertion of an N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) suppository (each cone containing 50 mg of ENNG) for 17 months. The dog was autopsied 20 months after the initiation insertion of the suppository. Grossly, the colonic wall from the anus of the 10-cm oral side of the colon was thickened, and there was an infiltrating tumor with shallow depressions in the rough mucosa. The lymph node around this portion were enlarged, and white spots were found in the liver and redness in the lungs. Histological examination of the colon revealed a variety of pathologic features, e.g., undifferentiated carcinoma, squamous cell carcinoma and malignant melanoma in the region adjacent to the anus. Well and moderately differentiated adenocarcinomas involving the proper muscle layer were found in a region oral to these tumors and were accompanied by marked invasion of the blood vessels and lymphatic permeation. There were metastases to the liver, lungs and lymph nodes which corresponded to the gross findings, and also metastases to renal glomeruli. A well differentiated adenocarcinoma and signet ring cell carcinoma were evident in the gastric mucosa. This experimental model should be useful for studies related to colonic carcinoma in humans.

Topics: Adenocarcinoma; Animals; Carcinogens; Carcinoma; Carcinoma, Squamous Cell; Colon; Colonic Neoplasms; Dogs; Female; Melanoma; Methylnitronitrosoguanidine; Neoplasms, Experimental; Stomach; Stomach Neoplasms; Suppositories

Topics: Animals; Ligation; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach; Stomach Neoplasms

Topics: Animals; Female; Gastrectomy; Gastroenterostomy; Methylnitronitrosoguanidine; Postgastrectomy Syndromes; Postoperative Complications; Rats; Rats, Inbred Strains; Stomach Neoplasms; Vagotomy

The present work was undertaken to investigate the possible role of microflora in gastric tumorigenesis by the comparison of tumor production between germ-free and conventional male Wistar rats given the same amount of N-methyl-N'-nitro-N-nitrosoguanidine into the stomach by catheter during the newborn period. Only 29% of germ-free rats treated with 450 microgram/animal that were killed 300 days after the first intubation had tumors in the stomach, whereas 93% of conventional similarly treated rats had such tumors at the same period, suggesting that the microflora might exert a promoting influence upon stomach tumor production.

Topics: Adenocarcinoma; Animals; Germ-Free Life; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Stomach Neoplasms

Topics: 4-Nitroquinoline-1-oxide; Adenocarcinoma; Animals; Concanavalin A; Gastric Mucosa; Intestinal Mucosa; Male; Methylnitronitrosoguanidine; Mucins; Rats; Staining and Labeling; Stomach Neoplasms

Polyploid carcinoma in the gastric antrum of a Beagle dog induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was sequentially studied by endoscopy and biopsy. Ulcer appeared on the angulus of the stomach at the 28th week and resulted in ulcer scar at the 42nd week. A new depression with atypical glands arose on the ulcer scar at the 69th week, developed elevated border at the 77th week, and progressed to a polyploid lesion at the 90th week. Well-differentiated adenocarcinoma in situ was found in the polyploid lesion at the 97th week. It gradually grew with nodular change of its surface. However, the carcinoma was ulcerated at the 126th week, became an elevated lesion with central depression at the 138th week, and finally regressed at the 154th week. At necropsy on the 202nd week, no carcinoma was found in the stomach.

Topics: Adenocarcinoma; Animals; Carcinoma in Situ; Dogs; Male; Methylnitronitrosoguanidine; Neoplasm Regression, Spontaneous; Neoplasms, Experimental; Polyps; Stomach Neoplasms

Sequential studies were made on the histopathologic changes in the glandular stomach of rats induced by a weak carcinogen. N-propyl-N'-nitro-N-nitrosoguanidine (PNNG). Fiftyfour rats were given 100 micrograms/ml of PNNG in their drinking water for 44 weeks, and then normal tap water until the end of the experiment. Rats were killed at intervals between week 1 and week 88. No marked atrophy or ulceration of the mucosa was found between week 1 and the end of the experiment. Focal intestinal metaplasia was found in week 19 and its incidence increased during the experiment. Adenocarcinoma in situ with extreme cellular atypia was found in mucosa with a normal appearance in week 67. An adenocarcinoma invading the submucosa was found in week 69, and one invading the serosa in week 88. All these pathological lesions were found on the anal side of the pyloric region. No pathologic changes were found in the fundic region. The sequential changes of the mucosa of the glandular stomach induced by this weak gastric carcinogen, PNNG, were very different from those induced by the potent gastric carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Gastric carcinoma induced by PNNG seems to be more similar to human gastric cancer than that induced by MNNG.

Topics: Adenocarcinoma; Animals; Carcinogens; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Time Factors

Malignant transformation of rat stomach was studied after oral administration of MNNG. The lesions were investigated with cytomorphological and histochemical methods, while the alkaline phosphatase (ALP) isoenzyme pattern was investigated by means of gel electrophoresis. Hyperdiploid-aneuploid DNA values were observed in dysplasias, as well as in carcinomas. The liver type ALP isoenzyme could be detected in intact and regenerative gastric mucosa. It also occurred in atypical hyperplasia and carcinoma. Placental type ALP isoenzyme was absent in all intact or regenerating gastric mucosa, but present in atypical hyperplasias and carcinomas. It can be concluded that DNA aneuploidy and the presence of placental type ALP are indicative of malignant transformations. The MNNG-induced adenomatous hyperplasia associated with atypia behaved like cancer and can thus be regarded as an obligatory preneoplastic lesion.

Topics: Adenoma; Animals; Carcinoma; Hyperplasia; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Stomach; Stomach Neoplasms; Time Factors

CD/CRJ rats were subjected to localized X-irradiation of the stomach and given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water. Rats given MNNG alone and non-treated rats were used as controls. Upon sacrifice at 15 months after the initial MNNG administration, intestinal metaplasia was observed; the histology was of complete type and the incidence was 100% in rats treated with X-rays and MNNG, whereas in rats treated with MNNG alone the intestinal metaplasia was of incomplete type and its incidence was 80%. However, the incidence of gastric cancer in rats treated with MNNG alone was 25%.

Topics: Adenocarcinoma; Administration, Oral; Animals; Metaplasia; Methylnitronitrosoguanidine; Neoplasms, Radiation-Induced; Rats; Stomach; Stomach Neoplasms; Thymidine

Intestinal metaplasia and carcinoma of the stomach were produced in Wistar strain rats by oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Alkaline phosphatase (AlP) isoenzymes of tissues from intestinal metaplastic mucosa and carcinoma of the stomach were studied. The ALP activity from all carcinoma tissues was several times higher than that of the surrounding gastric mucosa, and two of the tissues has over 100 times higher activity. An AlP zymogram from carcinoma tissues of the stomach showed one broad active band on 5% polyacrylamide-gel disc electrophoresis. This band was separated into 2 sharp active bands after treatment with neuraminidase: A-band (Rf = 19%) and B-band (Rf = 32%). From the enzymological and immunological study, B-band had properties similar to those of AlP isoenzyme from the intestinal metaplastic mucosa of the stomach, as well as intestinal AlP isoenzyme, while A-band had different ones. Anm AlP zymogram from glandular mucosa of the stomach showed 2 types of active band (A and B band) after treatment with neuraminidase, which were identical with those appearing in carcinoma tissues. The properties of AlP isoenzyme from the intestinal metaplastic mucosa of rat stomach induced by MNNG were similar to those of humans, and the carcinoma tissues of rat stomach were suspected of producing high amounts of AlP, especially the intestinal-type AlP isoenzyme.

Topics: Alkaline Phosphatase; Animals; Female; Gastric Mucosa; Intestines; Isoenzymes; Metaplasia; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Gastrectomy; Gastric Juice; Gastrins; Intestinal Polyps; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms; Stomach Ulcer

Topics: Adenocarcinoma; Animals; Gastrins; Histamine; Male; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

Serial studies by endoscopy and biopsy were made in a Beagle dog during and after oral administration of N-methyl-N'-nitro-N-nitroguanidine (MNNG). Between the 23rd and the 45th week of observation erosions and ulcers appeared at the angulus of the stomach and turned into ulcer scar. A depression with atypical glands was seen in the ulcer scar of the posterior wall of the angulus at the 94th week. It developed elevated margins at the 102nd week, when a well differentiated adenocarcinoma was found histopathologically. Ulceration and reepithelialization were observed in the early carcinoma. The carcinoma progressed into a larger one of Borrmann's type 2 at the 115th week and further into its type 3 at the 181st week. A second carcinoma with signet ring cell carcinoma developed in the anterior wall of the angulus. The two carcinomas fused and formed a single lesion. At autopsy in the 216th week the carcinoma invaded the serosa, and metastasis to regional lymph nodes was observed.

Topics: Adenocarcinoma; Animals; Biopsy; Carcinoma; Dogs; Gastroscopy; Jejunal Neoplasms; Methylnitronitrosoguanidine; Neoplasms, Experimental; Sarcoma, Experimental; Stomach; Stomach Neoplasms; Stomach Ulcer

Topics: Alkaline Phosphatase; Animals; Electrophoresis, Disc; Isoenzymes; Male; Methylnitronitrosoguanidine; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Stomach Neoplasms; Transplantation, Homologous

The modifying influence of atropine and reserpine on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induction of stomach tumors was studied in experiments on 120 random-bred male white rats. At the same time, pharmacological analysis of the mechanism of the carcinogenic action of MNNG was carried out. Atropine stimulated and reserpine markedly inhibited the carcinogenic effect of MNNG. MNNG interference altered the specific effects of amphetamine and phenobarbital. These alterations are due to the MNNG damage of the permeability of the presynaptic membrane of the central adrenergic structures. The leading role of adrenergic influences on the presence of carcinogenic transformation of stomach cell processes is discussed.

Topics: Amphetamine; Animals; Atropine; Male; Methylnitronitrosoguanidine; Nervous System; Phenobarbital; Rats; Reserpine; Stomach; Stomach Neoplasms; Synaptic Membranes

Studies were made on the chemotherapy of gastric cancer in dogs induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). Four male Beagle dogs were given a solution of ENNG at 100 approximately 150 microgram/ml with or without 0.4% Tween 60 to drink for 5 approximately 8 months. They all developed gastric adenocarcinomas, which were confirmed by histological examination of biopsy specimens taken in months 13 approximately 32 of the experiment. After confirming the presence of gastric cancer, 1-n-hexylcarbamoyl-5-fluorouracil (HCFU), a derivative of 5-fluorouracil, was given to the dogs orally as capsules at a daily dose of 5 or 10 mg/kg body weight. One dog died from adverse effects of HCFU 12 days after the beginning of chemotherapy. The other 3 dogs were treated with CHFU for 82 approximately 424 days. In these dogs, the tumor size, measured by X-ray examination, increased during chemotherapy. On autopsy, the tumors in the stomach were found to be restricted to the antrum, and metastases of the gastric adenocarcinomas to the regional lymph nodes and/or liver were found in 2 dogs. No degenerative changes of tumor cells were found in the stomach or metastasized organs, except for necrosis of cells in a perigastric regional lymph node of the dog. The value of using canine gastric cancer in studies on chemotherapy is discussed.

Topics: Adenocarcinoma; Animals; Dogs; Fluorouracil; Humans; Male; Methylnitronitrosoguanidine; Stomach Neoplasms

Topics: Animals; Chronic Disease; Female; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms; Stomach Ulcer

Topics: Achlorhydria; Animals; Carcinogens; Cimetidine; Guanidines; Humans; In Vitro Techniques; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

Eight beagle dogs of four-month-old received both oral administration of N-Ethyl-N'-Nitro-N-Nitrosoguanidine (ENNG) and subcutaneous injection of gastrin, and one of them was found to have an annularly infiltrating advanced carcinoma with marked fibrous thickening of the antral wall resulting in stenosis of the antrum (carcinoma scirrhosum) which resembled "Linitis plastica" (Borrmann's type IV carcinoma) in human stomach.

Topics: Adenocarcinoma, Scirrhous; Animals; Carcinogens; Dogs; Gastric Acidity Determination; Gastrins; Methylnitronitrosoguanidine; Neoplasms, Experimental; Stomach Neoplasms

The effect of administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at a dose level of 83 mg/liter in the drinking water was followed in the pyloric mucosae of male noninbred Wistar rats. Autoradiographic studies were done on animals killed after 10, 15, 26, and 36 weeks of treatment. In the normal-appearing mucosae of the rats treated with MNNG for 10 weeks, the number of epithelial cells per pit column was significantly increased over that in control rats. Simultaneously, a shift in the major zone of epithelial cell proliferation was noted in the treated rats. Along with the formation of a longer pit in MNNG-treated rats, the greatest number of DNA-synthesizing cells was displaced from the middle third of the pit in a downward direction toward the muscularis mucosa. In addition, at this early experimental time period, pits lined with more immature, cuboidal, mucus-depleted cells were recognizable. These pits not only had higher labeling indices than normal-appearing pits of the same animals but also expressed a dual nature with increased proliferative activity extending either upward to the luminal surface or further in a downward direction. Focal areas of cellular atypism were present by week 10 of treatment with a threefold to sevenfold greater DNA synthesis activity than that found in the normal-appearing mucosa of the same animal. A wide range of values in proliferative activity was found not only among invasive pyloric tumors within the same animal but also within different areas of the same tumor. The mechanism for the formation of adenomas and invasive adenocarcinomas is believed to be related to the dual character of the hyperplastic pits described.

Topics: Animals; Autoradiography; DNA; DNA, Neoplasm; Epithelium; Gastric Mucosa; Hyperplasia; Kinetics; Male; Methylnitronitrosoguanidine; Neoplasm Invasiveness; Pyloric Antrum; Rats; Stomach Neoplasms; Time Factors

Topics: Adenocarcinoma; Animals; Intestines; Male; Metaplasia; Methylnitronitrosoguanidine; Neoplasms, Experimental; Precancerous Conditions; Rats; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Dogs; Female; Gastric Juice; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Neoplasms, Experimental; Sarcoma, Experimental; Stomach Neoplasms; Vagotomy; Vagus Nerve

Five gastric carcinomas, induced in inbred Wistar rats by oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) dissolved in drinking water, were successfully transplanted to isologous rats. The transplants grew to a size of 10 to 35 mm in diameter within 8 to 25 weeks of implantation. In one case, serial transplantation were maintained up to the 11th generation, with occurrence of distant metastasis in the 3rd generation. Histological histochemical, and electron microscopical comparison of the original and transplanted tumors revealed that (1) the original tumors were quite well differentiated, forming either papillary or tubular structures, whereas the transplants were more anaplastic and pleomorphic showing often solid nests; and (2) tumor cells with gastrointestinal differentiation and cells with neuroendocrine differentiation were present and evenly distributed in both the original and the serially transplanted tumors. As it is unlikely that the normal and neoplastic neuroendocrine cells are growing side-by-side with and independently of the epithelial neoplastic components in the present series of transplants, the findings strongly suggest (1) the multidirectional potency of the inbred rat stomach carcinoma cells and (2) the common neoplastic origin of the epithelial and neuroendocrine components.

Topics: Animals; Carcinoma; Histocytochemistry; Lung Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Stomach; Stomach Neoplasms; Transplantation, Isogeneic

Topics: Animals; Atrophy; Autoradiography; Gastrectomy; Gastric Mucosa; Histocytochemistry; Hyperplasia; Male; Methylnitronitrosoguanidine; Postoperative Complications; Rats; Stomach Neoplasms; Time Factors

Topics: Adenocarcinoma; Animals; Dogs; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Stomach Neoplasms

It was possible to produce gastric adenocarcinoma in five of 69, healthy, young albino mice of both sexes given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in their drinking water at a concentration of 100 microgram/ml. The tumoral lesions were most clearly defined in the group that received MNNG for the longest period of time, that is, 68 weeks. On the other hand, in the rest of the groups, which received MNNG for fewer weeks, there were lesions found in a total of nine animals which consisted in foci of typical and atypical hyperplasia, erosion of the mucosa, and, in one animal, an adenomatous polyp. Contrary to findings in humans, intestinal metaplasia preceding or accompanying the neoplasia was found to be an inconsistent alteration and a not very frequent one.

Topics: Adenocarcinoma; Animals; Autoradiography; Female; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Mice; Neoplasms, Experimental; Stomach Neoplasms; Time Factors

The promoting effect of croton oil on gastrocarcinogenesis by MNNG was examined in male Wistar rats. Gastric carcinomas were found in five of 10 rats given 83 micrograms/ml MNNG for three months and then 0.02% croton oil with 0.5% Tween 60 as solvent for nine months. No gastric carcinomas were found in rats given MNNG for three months and then Tween 60 only for nine months. The incidence of gastric carcinomas in these two groups was significantly different (p less than 0.05). No tumors were found in rats given only croton oil with Tween 60.

Topics: Adenocarcinoma; Adenoma; Animals; Croton Oil; Dose-Response Relationship, Drug; Drug Synergism; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Polysorbates; Rats; Stomach Neoplasms

PNNG, the propyl derivative of MNNG, was administered to Wistar rats by a concentration of 59.5 micrograms/ml in the drinking water for 4, 8, and 12 months and the rats were killed in the 15th month. Intestinal metaplasia was induced in the glandular stomachs of 25%, 75%, and 83% of the rats treated with PNNG for 4, 8, and 12 months, respectively. Metaplastic glands were found in the pyloric region, especially near the pyloric ring. These glands contained goblet cells and columnar cells with striated borders. No tumors were found in the stomach of rats after 4-months treatment, but adenomas were found after 8-months treatment, and both adenomas and adenocarcinomas after 12-months treatment.

Topics: Adenocarcinoma; Animals; Intestinal Mucosa; Male; Metaplasia; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

Topics: Animals; Male; Metaplasia; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrosoguanidines; Rats; Stomach; Stomach Neoplasms

Morphological and biochemical changes reflecting the process of genesis of experimental stomach cancer were studied and compared in experiments carried out on 170 rats to whom N-methyl-N'-nitro-N-nitrosoguanidine had been given in drinking water. The concentration of the compound in drinking water was 167 mg/l. Malignization mostly developed during the ingrowth of the epithelial complexes involved in the process of carcinogenesis into the submucous membrane, in rare cases, into the mucous membrane itself. The results of experiments showed that biochemical changes preceded morphological alterations. The signs of inhibition of the synthesis of the isoenzyme spectrum of pepsinogen-pepsin revealed the qualitative changes of biochemical processes of the epithelium. A possible dependence of morphological features of the process of carcinogenesis on the evolutionally-established functional peculiarities of rat stomach epithelium is discussed.

Topics: Animals; Female; Gastric Mucosa; Isoenzymes; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Pepsinogens; Precancerous Conditions; Rats; Stomach Neoplasms; Time Factors

Tumors of the gastrointestinal tract were induced in white non-inbred rats exposed to MNNG in various doses. Gastric tumors appeared in the dosage of 153 mg, with its 2 and 3.3 times increase no change in the frequency of gastric tumors was noted. The frequency of jejunal tumors was higher with increased MNNG dosage.

Topics: Animals; Dose-Response Relationship, Drug; Gastrointestinal Neoplasms; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms; Time Factors

A cell line designated as BV9 was established in culture from a transplantable rat stomach cancer, which was originally induced in the glandular stomach of a Wistar rat by p.o. administration of N-methyl-N'-nitro-N-nitrosoguanidine. The monolayer cells, which have been subcultured for more than 35 passages, revealed pleomorphic features. Chromosomal analysis showed hypertetraploidy (mode, 95), and marker chromosomes were present. Cultured cells were injected s.c. into cyclophosphamide-conditioned syngeneic rats and produced tubular adenocarcinomas resembling the original tumor.

Topics: Animals; Cell Line; Chromosome Aberrations; Male; Methylnitronitrosoguanidine; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Stomach Neoplasms; Transplantation, Homologous

This experiment was carried out to see the effect of aging on the induction of gastric carcinoma in rats by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Three groups of rats of 3 different ages, 6, 20, and 40 weeks old, were used. Comparison of incidence of gastric carcinoma in these groups revealed a significant difference. Tumor incidence of the gastrointestinal tract of rats were 94.7, 73.8, and 48.8%, resepctively, at 6, 20, and 40 weeks of age. The incidence of adenocarcinomas of glandular stomach was also significantly decreased with the advance in age. However, there was a significant difference in the intake rate of MNNG per gram body weight between the young (6 weeks of age) and old rats for the first 25 weeks during the experiment which may account for the difference in tumor incidence between young and old rats. However, even when the young rats were administered a decreased amount of MNNG, same as that in old rats, they also showed higher incidence. From these results, it was concluded that the amount of MNNG ingested was not responsible for the decreased incidence of gastric adenocarcinoma in older rats. Aging might be the primarily the cause of low incidence.

Topics: Adenocarcinoma; Aging; Animals; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Cell Line; Methylnitronitrosoguanidine; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Stomach Neoplasms; Transplantation

Topics: Alkaline Phosphatase; Animals; Electrophoresis, Polyacrylamide Gel; Female; Gastric Mucosa; Isoenzymes; Male; Metaplasia; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Estrogens; Female; Humans; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms

The oral acute LD50 of N-Methyl-N'-Nitro-N-Nitrosoguanidine (MNNG) in a 10% aqueous solution of dimethylsulfoxide (DMSO) amounted to approximately 90 mg/kg. After single oral application of 50 mg/kg (group I), 75 mg/kg (group II) and 100 mg/kg (group III) of MNNG in a 10% aqueous solution of DMSO, generalized papillomatoses of the forestomach were found in all BD-VI rats after a test period of 500 days. Squamous cell carcinomas could be detected in 7/24 (21%) rats in group I, in 12/26 (46%) in group II and in 7/23 (30%) in group III). Benign adenomatous dysplasia of the glandular stomach was diagnosed in 2 rats (8%) of group I, in 1 animal (4%) of group II and in 12 rats (52%) of group III. Adenocarcinomas of the glandular stomach were induced in 1 animal (4%) of both group I and II and in 8 rats (35%) of group III. 20--30% of the animals treated with MNNG also showed degenerative cystic alterations in the liver with bile-duct proliferation.

Topics: Animals; Dimethyl Sulfoxide; Methylnitronitrosoguanidine; Rats; Rats, Inbred Strains; Stomach Neoplasms

N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) was administered orally to male Wistar rats at a concentration of 83 microgram/ml in the drinking water for 2, 4, 5, and 7 months; the rats were killed at about month 15. Intestinal metaplasia was found in the stomachs of 80-100% of the rats treated with MNNG for 4 or more months, of 37.5% treated with MNNG for 2 months, and of 10% of the controls. Metaplastic glands, composed of goblet cells and columnar cells with striated borders, were found in the pyloric region. Paneth's cells were found at the bottom of metaplastic glands in a rat treated with MNNG for 4 months. The incidence of well-differentiated adenocarcinomas of the stomach was 63-90% in rats treated with MNNG for 4 or more months and 25% in those treated with MNNG for 2 months.

Topics: Adenocarcinoma; Animals; Intestines; Male; Metaplasia; Methylnitronitrosoguanidine; Neoplasms, Experimental; Precancerous Conditions; Pylorus; Rats; Stomach Neoplasms; Time Factors

180 male Wistar-rats were daily exposed to 30 and 100 mg MNNG/1000 ccm tapwater. After 7 weeks exposure a truncal vagotomy with pyloroplasty or a Billroth-II-resection was performed in 25 animals of each dosage-group. 80 rats were not operated. The incidence of carcinomas in the Billroth-II-rats of both dosage-groups was evidently higher than in the exposed controls. In the vagotomized rats an increased occurrence of carcinomas could not be observed.

Topics: Animals; Gastrectomy; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Pylorus; Rats; Stomach Neoplasms; Time Factors; Vagotomy

Laboratory-bred European hamsters received intragastric administrations of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) once weekly for 20 weeks. The animals showed mainly squamous cell papillomas and carcinomas of the fore-stomach. The tumour incidence was higher in males (80%) than in females (30%). The average tumour latency was comparatively short (25 weeks).

Topics: Animals; Carcinogens; Carcinoma, Squamous Cell; Cricetinae; Female; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Papilloma; Species Specificity; Stomach Neoplasms

Differences in susceptibility to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) of fundic mucosa in various states of regeneration after induction of ulcer with iodoacetamide were examined histologically in male Wistar rats. Iodoacetamide was given to rats in their drinking water, before (Group 1), with (Group 2), or after (Group 3) MNNG. Atypical hyperplasia in the renewed mucosa and pyloric gland metaplasia were observed on the ulcers in Group 1 in higher incidence than in Groups 2 and 3. In addition, adenocarcinoma developed in the ulcer of 2 of 17 effective animals in Group 1. These observations suggest that the mucosa showing pyloric gland metaplasia is more susceptible to MNNG than the young rapidly regenerating mucosa at the margin of ulcers.

Topics: Adenocarcinoma; Adenoma; Animals; Gastric Mucosa; Hyperplasia; Iodoacetamide; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Precancerous Conditions; Rats; Regeneration; Stomach Neoplasms; Stomach Ulcer

Fifteen male Beagle dogs received N-methyl-N-nitro-N-nitrosoguanidine (MNNG), 50 or 83 microgram/ml, in drinking water for 35 to 63 weeks. Broad superficial erosion and ulceration were observed in the angulus of the antrum and the anterior or posterior wall of the fundus during MNNG administration. After the discontinuation of MNNG administration, the erosions and ulcers healed rapidly, resulting in mucosal atrophy and scarring of the ulcer. In two dogs new depressions with atypical glands were observed by endoscopy and biopsy of the ulcer scars of the angulus, which became carcinomatous lesions at about the 100th week. Necropsy revealed 5 other carcinomas in the fundus of 5 additional dogs. One lesion was located in the ulcer scar and the other 4 in the areas of the mucosal atrophy. The possible relationship between carcinoma and the associated lesions was discussed.

Topics: Animals; Biopsy; Dogs; Endoscopy; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Precancerous Conditions; Stomach Neoplasms; Stomach Ulcer; Time Factors

Topics: Animals; Disease Models, Animal; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms; Stomach Ulcer

Topics: Animals; Humans; Methylnitronitrosoguanidine; Neoplasms, Experimental; Precancerous Conditions; Rats; Stomach Neoplasms

When N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was orally intubated to conventional newborn rats by the catheter technique, the rats were found with tumors almost exclusively developed in the glandular stomach, mostly until 280 days after the first intubation. Tumor incidence was about 50% in both sexs of rats that survived the intubation of a single dose of MNNG in rats of less than 24 hr after birth and almost 100% in both sexes of rats that survived the intubation of three consecutive daily doses of MNNG on 5th day after birth. Out of 52 rats treated with MNNG, 40.4% developed carcinomas (20 adenocarcinomas and 1 squamous cell carcinoma), three of them having metastatic lesions. The predilective localization of tumors in the glandular, especially fundic, portion of the stomach, might be attributed to the use of newborns and to the catheter technique devised here.

Topics: Adenocarcinoma; Administration, Oral; Animals; Animals, Newborn; Carcinoma, Squamous Cell; Female; Leiomyosarcoma; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach; Stomach Neoplasms

Adenomatous changes, and early and invasive carcinomas of the glandular stomach in Wistar rats ingesting N-methyl-N'-nitro-N-nitrosoguanidine were studied. Almost all adenomatous changes and carcinomata were located near the midpoint of the lesser curvature. In electron microscopic and histochemical studies, both changes showed great cytological similarity. Electron microscopically, they were found to consist of predominantly undifferentiated cells with poorly developed cytoplasmic organelles, with some highly differentiated cells present. Histochemically, both showed strongly positive reactions for lysosomal enzymes. For tumor transplantation, five lesions were used and in all cases, the transplants were successful.

Topics: Adenocarcinoma; Adenoma; Animals; Cell Differentiation; Histocytochemistry; Lysosomes; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Neoplasm Transplantation; Neoplasms, Experimental; Precancerous Conditions; Rats; Rats, Inbred Strains; Stomach Neoplasms; Time Factors; Transplantation, Isogeneic

Examinations were made on the carcinogenic effects of a chemical compound, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and a physical carcinogen, whole-body irradiation with fission neutrons, on the gastrointestinal tract of male albino Sprague-Dawley rats. The carcinogens were used singly and together in order to investigate their possible synergistic effects on the induction of adenocarcinomas of the stomach and small intestine. Of the 13 animals treated with the chemical, MNNG, and living more than 9 months, 9 showed gross tumors (5 gastric and 4 duodenal), confirming the high incidence of gastrointestinal carcinomas induced by MNNG in the rat. There were no gastrointestinal tumors found after neutron exposure. When the 2 carcinogens were combined, no additivity or synergism occurred. After neutron irradiation, a dental syndrome with loss of incisor teeth was observed. The effect of neutron irradiation on subgingival pathology of the teeth is being investigated.

Topics: Adenocarcinoma; Animals; Carcinogens; Cocarcinogenesis; Fast Neutrons; Gastrointestinal Neoplasms; Incisor; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Neoplasms, Radiation-Induced; Rats; Stomach Neoplasms

This study was undertaken to determine the effect of ulcer induced by iodoacetamide on the development of gastric carcinoma by N-methyl-N'-nitro-N-nitrosoguanidine in male Wistar rats. Fifty-six of the 62 ulcers induced by IAM were located in the fundic gland area along the limiting ridge. The incidence of fundic carcinoma was 16% in the groups treated with IAM and MNNG, while no fundic carcinoma was found in the group treated with MNNG alone. This difference was statistically significant. All the carcinomas in the fundic gland area were confined within the ulcer itself or its scar tissue, produced by IAM. These findings indicate that if an ulcer is present, carcinoma develops even in the fundic mucosa which is, if intact, resistant to the carcinogenic stimulation of MNNG. It was concluded that gastric ulcer predisposes the development of gastric carcinoma.

Topics: Adenocarcinoma; Adenoma; Animals; Cell Transformation, Neoplastic; Drug Synergism; Iodoacetamide; Iodoacetates; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach; Stomach Neoplasms; Stomach Ulcer

180 Wistar-rats were daily exposed to 30 and 100 mg MNNG/1000 ccm tapwater. After an exposure of 7 weeks a truncal vagotomy with pyloroplasty or a Billroth II-resection was performed in 25 animals of each dosage-group. 80 rats were not operated. The incidence of carcinomas in the Billroth II-rats of both dosage-groups was evidently higher than in the exposed controls. In the vagotomized rats an increased occurrence of carcinomas could not be observed.

Topics: Animals; Gastrectomy; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Risk; Stomach Neoplasms; Vagotomy

The effects of gastrin on gastric acid secretion and on the incidence of gastric carcinoma induced by N-methyl-N'-nitro-N-nitrosoquanidine were investigated in rats. At Week 50 after the start of the experiment, it was found that prolonged administration of gastrin after treatment with N-methyl-N'-nitro-N-nitrosoquanidine resulted in a significant increase in gastric acid secretion and a significant reduction in the incidence of adenocarcinomas of the glandular stomach. The administration of gastrin did not influence the histological appearance of the few gastric adenocarcinomas that did develop.

Topics: Adenocarcinoma; Animals; Drug Administration Schedule; Gastric Juice; Gastrins; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms

Topics: Adenocarcinoma; Adenoma; Animals; Isoenzymes; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Pepsinogens; Precancerous Conditions; Pylorus; Rats; Stomach Neoplasms

Three 6-month-old male beagle dogs were given a solution of 150 microng N-ethyl-N'-nitrosoguanidine (ENNG)/ml to drink ad libitum for 9 months. They all developed esophageal squamous cell carcinomas and gastric adenocarcinomas. The stomach adenocarcinomas were mostly in the antrum along the lesser curvature and were either well differentiated or poorly differentiated, with or without signet ring cells. The well-differentiated adenocarcinomas metastasized to the liver, and the poorly differentiated ones metastasized to the lymph nodes. The gastric mucosa in the antrum was atrophic, and the muscularis mucosae was fibrotic. Esophageal lesions were multicentric moderately differentiated squamous cell carcinomas, and they developed without diffuse hyperplastic changes of the epithelium. One dog with a large ulcerated carcinoma of the esophagus had metastases in the lung, liver, peritoneum, and abdominal lymph nodes. One dog also had a hemangiosarcoma with hepatic metastasis and spindle cell sarcoma in the stomach and duodenum, respectively.

Topics: Adenocarcinoma; Administration, Oral; Animals; Carcinoma, Squamous Cell; Dogs; Esophageal Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Neoplasms, Experimental; Neoplasms, Multiple Primary; Stomach Neoplasms

The electrophysiological effects of the chemical gastric carcinogen N-methyl-N'-nitro-N-nitrosoquanidine (MNNG) were determined in an in vivo chambered canine stomach and in an in vitro canine gastric mucosal preparation. In the in vivo stomach, the topical application of 2.5 mg MNNG/ml decreased the transmural electrical potential difference, and the systemic blood pressure was essentially unchanged. In the in vitro preparation, exposure of the mucosal side of the isolated canine gastric mucosa to 0.25 and 2.5 mg MNNG/ml for 1 hour sequentially or exposure of the serosal side to 2.5 mg MNNG/ml for 2 hours inhibited net Na+ and Cl- fluxes. With longer duration, the undirectional fluxes of Na+ and Cl- increased, indicating an increase in permeability. These findings suggested that inhibition of active transport in the gastric mucosa may have an important function in the gastric carcinogenicity of MNNG.

Topics: Animals; Biological Transport, Active; Cell Membrane Permeability; Chlorides; Dogs; Female; Gastric Mucosa; In Vitro Techniques; Male; Membrane Potentials; Methylnitronitrosoguanidine; Neoplasms, Experimental; Sodium; Stomach Neoplasms

N-methyl-N'-nitroguanidine and sodium nitrite were administered as drinking water to non-inbred male rats at the level of Img/ml for over two years. Gastric adenocarcinomas were produced in 43.7% of rats surviving for 15.5 months when the first tumor was noticed. Gastric mucous membrane of other rats had morphological changes analogous to those induced by N-methyl-N-nitoroso-N'-nitroguanidine (MNNG). The results obtained indicate endogenous synthesis of MNNG from precursors in the stomach of rats.

Topics: Adenocarcinoma; Administration, Oral; Animals; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrites; Rats; Sodium; Stomach Neoplasms; Time Factors

The purpose of this study was to find whether gastric resection enhances the incidence of carcinoma in the remaining part of the stomach. 66 male Wistar rats were subjected to stomach resection according to the Billroth I or the Billroth II method. These rats, as well as control animals with intact stomachs, were fed the carcinogen N-Methyl-N'-nitro-N-nitrosoguanidine (NG). -- 25 of 66 animals developed carcinomas in the gastric remnant. Precancerous lesions were seen in 18 rats. The tumours were characterized histologically as adenocarcinomas. They were almost exclusively localized in the region of the gastroenteral anastomosis. The process of tumour formation in the resected stomach was completed within 17-31 weeks on continuous administration of NG in a concentration of 120 mg/l in the drinking water. In contrast to these findings, the development of cancer in the intact stomach required on average 41 weeks under the same conditions of NG administration. However, with regard to the incidence of malignant changes, no significant difference was observed between animals undergoing the Billroth I method and those undergoing the Billroth II method.--The results suggest that the resected stomach of the rat is more susceptible to induction of cancer than the intac one. Exposure of the resected stomach to an oral carcinogen induces carcinogenesis predominantly in the anastomotic region.

Topics: Adenocarcinoma; Animals; Gastrectomy; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Postgastrectomy Syndromes; Rats; Stomach Neoplasms

In rats with Nitrosoguanidine induced carcinomas of the gastric stump, heterotopic ossifications are found freqently. The following stages of differentiation during the desmal ossification in the stump carcinomas are demonstrated: 1. Osteoblasts, 2. Osteoid, 3. Woven bone, 4. Lamellar bone. --The islands of metaplastic bone cells are predominantly located in the invasive marginal zone of the carcinoma of the gastric stump. The histology of the heterotopic ossification in the gastric stump of the rat is similar to that one seen in stomach cancer of men. The model here described seems to be suitable for further study of metaplastic bone formation in the gastrointestinal tract.

Topics: Adenoma; Animals; Carcinoma; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Ossification, Heterotopic; Osteogenesis; Precancerous Conditions; Rats; Stomach Neoplasms

Early mucosal changes of the glandular stomach in Wistar rats ingesting N-methyl-N'-nitro-N-nitrosoguanidine were studied. Special attention was paid to clarifying the localization and chronological relationship between the expected regenerative changes and the succeeding carcinoma. For this purpose, drinking water of MNNG at a low concentration was given to the inbred Wistar rats which were sacrificed every second week during the first 35 weeks. In the 5th week, localized erosions appeared, which were constantly observed through about the 20th week. These changes were always located near the midpoint of the lesser curvature. Epithelial cells, which were found there, were studied with light and electron microscope, and with enzyme histochemistry. It has been observed that these cells corresponded with the so-called immature cells in the normal gastric epithelium and also with the regenerating epithelial cells, which were obtained from the vicinity of mechanically induced ulcer of the stomach. From about the 20th week 2 cases showing ectopic gland, 4 adenomatous changes, 2 early carcinomas, and 5 invasive carcinomas were found. All these lesions were located on the lesser curvature, near its midpoint, i.e. exactly the same area where regularly the erosions were observed.

Topics: Animals; Epithelial Cells; Gastric Mucosa; Histocytochemistry; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Neoplasms, Experimental; Precancerous Conditions; Rats; Rats, Inbred Strains; Regeneration; Stomach Neoplasms; Time Factors

Experimental carcinomas in the glandular stomach of rats were induced by oral administration of MNNG (M-methyl-N'-nitro-N-nitrosoguanidin) for 35 weeks or ENNG (N-ethyl-N'-nitro-N-nitrosoguanidin) for 20 weeks. Rats were killed at different times after beginning of carcinogen treatment and tissue specimens were prepared for histologic investigation. Particular interest was placed on the development of tumors and on pathological findings possibly contributing to early diagnosis of stomach cancer. During the development of tumors, several dysplastic reactions were observed in the antral mucosa. They could be classified into 4 groups: One was regenerative hyperplasia (1) that meant irregular glandular proliferations without cell atypism at the margin of erosions and ulcers. This lesion was mainly found 1-9 weeks after administration of MNNG. In glandular hyperplasia (2) either crypts or glands were extended and mucosal layers were thickened. No signs of cell atypism were observed. This lesion was mainly found 12-17 weeks after administration of MNNG. Dysplasia (3) was combined with considerable structural modifications and cellular atypism. However, this lesion was limited to the mucosal layer. Neoplastic changes (4) were characterized by marked cellular atypism and extension to tunica submucosa and tunica serosa. Some tumors showed the histological patterns of benign tumors, but most of them were adenocarcinomas. In some cases metastases into pancreas, liver and lymph nodes and in one case into the 12th rib were observed. No particular enzyme patterns were found by histochemistry.

Topics: Animals; Gastric Mucosa; Hyperplasia; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Neoplasms, Experimental; Nitrosoguanidines; Precancerous Conditions; Rats; Stomach Neoplasms

Seven of 35 male Wistar rats developed well-differentiated adenocarcinoma of the glandular stomach on combined treatment with N-methyl-N'-nitro-N-nitro soguanidine and 4-nitroquinolin 1-oxide. One of the tumors was successfully transplanted into newborn Wistar rats by subcutaneous inoculation. The latent period after inoculation was less than one month and the growth of the transplanted tumor was slow throughout 10 transplant generations. The tumor appeared nodular or cystic in subcutaneous tissues of rats and often caused ulceration of the skin. The histology of transplanted tumors was very similar to that of the primary tumor. Metastasis to both lungs was observed in one rat of the first transplant generation.

Topics: 4-Nitroquinoline-1-oxide; Adenocarcinoma; Animals; Animals, Newborn; Lung Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Stomach Neoplasms; Time Factors; Transplantation, Homologous

Experiments were made on induction of cancer of the glandular stomach of rats by a combination of oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and insertion of a plastic bead into the gastric lumen. The incidence of cancer with this combination of treatments was greater than by administration of MNNG alone. Fluoroscopic examination showed that barium sulfate remained in the stomach longer when a bead had been inserted into the gastric lumen. This indicates that after insertion of a bead, MNNG must have remained in the stomach longer, and so the period of exposure of the gastric mucosa to the carcinogen must have increased.

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Microscopy, Electron; Neoplasms, Experimental; Nitrosoguanidines; Physical Stimulation; Plastics; Rats; Sarcoma, Experimental; Stomach Neoplasms

Studies were made on the effect of mucin on the induction of gastric carcinomas by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), with or without sodium chloride, in male Wistar rats. Seven groups of rats were treated as follows: Group 4 was given continuously 50 mg MNNG/liter solution to drink and 1 ml of saturated sodium chloride once a week and fed on stock diet supplemented with 4% mucin. Group 2 was given 50 mg MNNG/liter solution and fed on stock diet supplemented with 4% mucin. Group 3 received 1 ml of saturated sodium chloride once a week and 50 mg MNNG/liter solution to drink. Group 1 was treated with MNNG only. Group 5 was fed on stock diet supplemented with 4% mucin. Group 6 was given sodium chloride only. Group 7 was untreated. The incidence of gastric cancer in Group 3 was significantly higher than that in Group 4 (P less than 0.05) or in Group 1 (P less than 0.05). The difference in the incidence of gastric cancer in Groups 2 and 4, and of intestinal tumors in Groups 1 to 4 were not statistically significant. No malignant tumors were seen in Groups 5, 6, and 7. Thus mucin reduced the high incidence of gastric cancer induced by MNNG and sodium chloride to the level induced by MNNG alone, but it had no effect on the incidence of intestinal tumors. The effect of mucin in preventing destruction of the gastric mucosal barrier by sodium chloride and so reducing the induction of gastric cancer is discussed.

Topics: Adenocarcinoma; Animals; Body Weight; Carcinoma; Drug Synergism; Gastric Mucosa; Intestinal Neoplasms; Male; Methylnitronitrosoguanidine; Mucins; Neoplasms, Experimental; Nitrosoguanidines; Rats; Sarcoma, Experimental; Sodium Chloride; Stomach Neoplasms

Leiomyosarcomas of the small intestine were found in dogs during experimental induction of gastric carcinoma by oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Leiomyosarcomas were found most frequenly in the duodenum and jejunum, and occasionally in the stomach but never in the ileum, colon, or rectum. The leiomyosarcomas developed in all the dogs given 50 mug/ml of MNNG in deionized water to drink but not in dogs fed on porridge food made from standard pellet diet mashed with MNNG at the same concentration in tap water. Intestinal sarcomas developed in 3 months to 5 years after the end of MNNG administration, and frequently metastasized to the liver and/or the peritoneum.

Topics: Administration, Oral; Animals; Dogs; Female; Intestinal Neoplasms; Intestine, Small; Leiomyosarcoma; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Nitrosoguanidines; Sarcoma, Experimental; Stomach Neoplasms; Time Factors

Methods have been established to produce gastric cancer in rats and dogs by administration of N-methyl-N'-nitro-N-nitrosoguanidine or of the ethyl derivate. The agent is administered in drinking water or by a pellet diet soaked in the carcinogen. Histologically well differentiated and poorly differentiated types of adenocarcinoma and signet-ring cell tumors are induced in several months with greath reliability. Metastases were observed in both rats and dogs with gastric carcinoma. The carcinogenic effect could be enhanced by surface active agents, sodium chloride, iodoacetamide, insertion of plastic beads into the stomach and gastroenteroanastomosis. Follow-up studies by radiologic, endoscopic and bioptic examinations are possible in the dog. There are similarities in these experimental tumors to those in man and thus they provide means for the investigation of histogenesis, prevention, and chemotherapy of gastric cancer. An adenocarcinoma of the glandular stomach of a Wistar rat was successively transplanted to new born rats of the same strain.

Topics: Adenocarcinoma; Animals; Dogs; Female; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Stomach Neoplasms; Surface-Active Agents

Topics: Animals; Azoxymethane; Benz(a)Anthracenes; Colonic Neoplasms; Cricetinae; Dogs; Duodenal Neoplasms; Esophageal Neoplasms; Gastrointestinal Neoplasms; Guinea Pigs; Methylnitronitrosoguanidine; Mice; Neoplasms, Experimental; Nitrites; Nitrosamines; Nitrosoguanidines; Pancreatic Neoplasms; Rabbits; Rats; Stomach Neoplasms

Subcutaneous injections of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at the dose of 50 mg/kg body weight for 10 days showed depressed production of hemolysin against sheep red blood cells (SRNC) in Wistar rats. On the other hand, oral administration at the dose of approximately 35 mg/kg body weight for 30 weeks scarcely suppressed antibody preduction to heterologous RBC and cell-mediated immune response to Walker-256 carcinosarcoma in Wistar rats during the experimental period of 55 weeks. The daily administration by way of oral route proved to be efficient for the induction of stomach cancer. The difference in immunosuppressive effect of MNNG by these two routes will be discussed in relation to the susceptibility of in vivo degradation of the carcinogen.

Topics: Administration, Oral; Animals; Antibody Formation; Immunity, Cellular; Immunosuppressive Agents; Injections, Subcutaneous; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Rats; Stomach Neoplasms

Topics: Animals; Iodoacetamide; Male; Methylnitronitrosoguanidine; Precancerous Conditions; Rats; Stomach Neoplasms; Stomach Ulcer

An improved method of assay of urinary polyamines (putrescine, spermidine, and spermine) was applied to the study of cancer patients and an experimental gastric tumor of rats. Although total polyamines (putrescine, spermidine, and spermine) in urine of patients with blood and solid cancers were significantly high, putrescine concentrations also increased significantly and were shown to be of diagnostic aid even in solid cancers. A significant increase in putrescine was also noted in the urine of rats with experimental stomach tumors induced by N-methyl-N-nitro-N'-nitrosoguanidine.

Topics: Animals; Female; Humans; Leukemia; Lymphoma; Methylnitronitrosoguanidine; Neoplasms; Neoplasms, Experimental; Polyamines; Pregnancy; Putrescine; Rats; Spermidine; Spermine; Stomach Neoplasms

The effect of ulcers induced by iodoacetamine on the development of gastric tumors by N-methyl-N'-nitro-N-nitrosoguanidine was studied in male Wistar rats. The ulcerative lesions induced by iodoacetamide were confined symmetrically to the fundic region along the limiting ridge in the stomach and the pyloric region was unaffected. Animals treated with iodoacetamide and N-methyl-N'-nitro-N-nitrosoguanidine produced a high incidence of tumors including adenocarcinoma in the fundic region. The incidence of tumors in the pyloric region in the control group was 80% but there were no tumors in the fundic region. The tumors in the fundic region were most frequently found in the same areas that ulcers had previously been induced. These findings suggest that ulceration and regeneration of the mucosa are important factors in gastric carcinogenesis induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine.

Topics: Adenocarcinoma; Adenoma; Animals; Gastric Mucosa; Iodoacetamide; Iodoacetates; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrosoguanidines; Pylorus; Rats; Sarcoma; Stomach Neoplasms; Stomach Ulcer

Electron microscopic study was made on precancerous and cancerous lesions in glandular stomach of rats induced by MNNG. Three types of lesions, were found: regenerative glandular hyperplasia, adenomatous hyperplasia and adenocarcinoma. These were compared with the fine structure of similar lesions produced by X-irradiation in the glandular stomach of mice. The precancerous lesion in the present study demonstrated formation of adenomatous hyperplasia by epithelial cells which included mucoid cells characterized by sparce surface microvilli, a few erratic terminal webs, small number of mucous granules, many small mitochondria, and a bizarre nucleus. The development of these mucoid cells seems to be related with the growth of gastric carcinoma. The ultrastructure of adenocarcinomas revealed many structural variations or abnormalities of cellular differentiation. They were classified into 1) surface and pit mucous cell type, 2) pyloric gland cell type, 3) goblet cell type, 4) paneth cell type, 5) intestinal epithelial cell type, 6) endocrine cell type, 7) oncocyte type, 8) filament-rich cell type, and 9) anaplastic cell type involving intracellular microcyst cells. Filament-rich cells were found in poorly differentiated adenocarcinoma or scirrhous carcinoma and may be derived from metaplasia of tumor cell.

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrosoguanidines; Precancerous Conditions; Rats; Stomach Neoplasms

Using advanced gastric adenocarcinoma and carcinoid as human material and gastric adenocarcinoma in rats induced by MNNG and in mice by localized X-irradiation of the stomach as experimental material, a pathological study was made on the relationship of gastric endocrine cells to gastric cancer. The results of the present study suggest that most of the endocrine cells in the cancer tissue are derived from the differentiation of cancer cells. Therefore, the following three may be given as the aformentioned relationship, that is, 1) carcinoid of endocrine cell origin, 2) endocrine cell carcinoma showing undifferentiated adenocarcinoma, and 3) endocrine cell cloning developed from the differentiation of cancer cell of adenocarcinoma. There is the possibility that most of 2) are of 3) origin and thus 2) and 3) should be discriminated from 1), having a functioning tumor in rare cases. The significance of reactive hyperplasia of endocrine cells in the non-metaplastic mucosa of the stomach around cancer and atypical epithelium is not yet determined, but that of EC cell seems at least to be related with the development of intestinal metaplasia in the gastric mucosa.

Topics: Adenocarcinoma; Adenocarcinoma, Mucinous; Adult; Aged; Animals; Carcinoid Tumor; Chromaffin System; Enterochromaffin Cells; Female; Gastric Mucosa; Humans; Male; Methylnitronitrosoguanidine; Mice; Middle Aged; Neoplasms, Experimental; Neoplasms, Radiation-Induced; Rats; Stomach Neoplasms

One of five gastro-entero-pancreatic hormones, gastrin, serotonin, histamine, glucagon, and insulin, was intraperitoneally administered for a long period to the rats that received N-methy-N'-nitro-N-nitrosoguanidine. A frequent development of scirrhous carcinoma was demonstrated in the group treated with gastrin.

Topics: Adenocarcinoma, Mucinous; Adenocarcinoma, Scirrhous; Animals; Gastrins; Glucagon; Histamine; Insulin; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrosoguanidines; Pancreatic Hormones; Rats; Serotonin; Stomach; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Carcinoid Tumor; Carcinoma, Hepatocellular; Carcinoma, Squamous Cell; Duodenal Neoplasms; Female; Hyperplasia; Liver Neoplasms; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrosoguanidines; Papilloma; Rats; Rodent Diseases; Stomach Neoplasms

The effects were studied of NaCl on the production of gastric carcinomas by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and by 4-nitroquinoline-1-oxide (NQO) in male Wistar rats. Nine groups of rats were treated as follows: Group 1 was given 50 mg MNNG/liter and 6 g NaCl solution/liter to drink and was fed a stock diet supplemented with 10% NaCl. Group 2 received 1 ml saturated NaCl once a week and 50 mg MNNG/liter to drink. Group 3 was treated with MNNG alone. Group 4 was given a solution of 1 mg NQO once a week and fed a stock diet supplemented with 10% NaCl. Group 5 received a solution of 1 mg NQO saturated with NaCl. Group 6 was given NQO alone. Groups 7 and 8 were given NaCl alone. Group 9 was untreated. Adenocarcinomas developed in the glandular stomach in group 2 at a significantly higher incidence than in group 3. Poorly differentiated adenocarcinomas of the glandular stomach were detected in only groups 1 and 2. One poorly differentiated adenocarcinoma metastasized to the lymph nodes. A high incidence of squamous cell carcinomas of the forestomach was found in groups 4 and 5. No malignant tumors were seen in groups 6-9. NaCl given alone had no apparent carcinogenicity in rats but, when administered with MNNG or NQO, it enhanced the carcinogenic effects of MNNG and NQO in the stomach.

Topics: 4-Nitroquinoline-1-oxide; Adenocarcinoma; Animals; Carcinoma, Squamous Cell; Drug Synergism; Gastric Mucosa; Intestinal Neoplasms; Intestine, Small; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitroquinolines; Nitrosoguanidines; Papilloma; Rats; Sarcoma; Sodium Chloride; Stomach; Stomach Neoplasms

Immunohistological studies, using the fluorescein isothiocyanate-labeled antibody against gastric mucosal glycoprotein, were made during the development of gastric cancer, induced in dogs and rats by oral administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In an early stage, the regenerative glands were lined by fluorescent mucus cells. Carcinoma cells of orderly glandular structure, produced in dogs, were devoid of fluorescence. Carcinoma cells of less differentiation, produced in rats during further advanced stage, were well fluorescent. The immunofluorescent profiles of such experimentally induced gastric carcinoma were found to be the same as those of human gastric adenocarcinoma.

Topics: Adenocarcinoma; Animals; Dogs; Fluorescent Antibody Technique; Gastric Mucosa; Glycoproteins; Histocytochemistry; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Nitrosoguanidines; Rats; Species Specificity; Stomach Neoplasms

Topics: Adenocarcinoma; Animals; Dogs; Female; Lung Neoplasms; Lymphatic Metastasis; Male; Methylnitronitrosoguanidine; Neoplasm Metastasis; Neoplasms, Experimental; Nitrosoguanidines; Stomach Neoplasms

Male Wistar rats were divided into three groups for studying the chronic effect of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), in continuous dose of 50 mg/L in drinking water, or 50 mg/L MNNG and 0.4% Tween 60 in drinking water. From the 2nd to 50th week after the administration of MNNG, every 3 or 5 rats were sacrificed and autopsied after the intraperitoneal injection of 1 muCi 3-H-thymidine/g body weight at 2- or 3-week intervals. The resected stomachs were studied morphologically and autoradiographically. Six cases of experimental gastric cancer were produced that fulfilled Stewart's criteria. Autoradiographically, there was no significant different in the flash labeling index in the normal antral mucosa, in the non-pathologic antral mucosa, and in the cancerous lesion, but generation time and DNA synthesizing time of the cancerous lesion were 2 or 3 times longer than those of the glandular stomach of normal rats reported by Galjaard. They were also longer than those of the non-pathologic antral mucosa of rats treated with MNNG. These experiments results were discussed, comparing with cell kinetics of the gastrointestinal tracts in man.

Topics: Administration, Oral; Animals; DNA; DNA, Neoplasm; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Nitrosoguanidines; Polyethylene Glycols; Polysorbates; Pyloric Antrum; Rats; Stomach; Stomach Neoplasms; Thymidine; Time Factors; Tritium

Changes in the isozymes of pepsinogen (Pg) separated from the glandular stomachs of rats were studied by polyacrylamide gel electrophoresis during carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), from the beginning of MNNG administration to 3 months after the end of its 7-month regimen. In 13 of 25 rats killed successively, one (Pg 1) of the three pepsinogen isozymes (Pg 1, 3, 4) normally present in the pyloric mucosa had decreased or disappeared. It decreas was observed from 1 week after the beginning of MNNG treatment to at least 3 months after the end of the 7-month MNNG administration. Remarkable histopathologic changes were found from 8 months after MNNG was given, and rats showing such unusual histopathologic alterations also had changes in their pepsinogen isozyme pattern. In 4 of 27 rats, two (Pg 1, 2) of the four isozymes of pepsinogen (Pg 1-4) in the fundic mucosa decreased or disappeared from 3 months after the beginning of MNNG treatment to at least 2 months after the end of its 7-month administration. Histopathologic changes induced by MNNG were not as remarkable in the fundic mucosa as in the pyloric mucosa.

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Neoplasms, Experimental; Pepsinogens; Pylorus; Rats; Stomach Neoplasms

N-methyl-N-nitroso-N'-nitroguanidine was administered as drinking water to Wistar strain and non-inbred male rats in the dosage of 100 mKg/ml for 7 months, Adenocarcinomas of the stomach were produced in about 70% of rats. The first tumors in the glandular stomach were noticed in 10-12.5 months. Studies of the kinetics of morphological changes indicated that MNNG induced a damage to the mucous membrane, subsequent regenerative hyperplasia, adenomatous hyperplasia with cellular and structural atypism, atrophy, pylorization of the mucosa and development of gastric adenocarcinomas.

Topics: Adenocarcinoma; Animals; Gastric Mucosa; Male; Methylnitronitrosoguanidine; Nitrosoguanidines; Rats; Stomach Neoplasms

Topics: Animals; Carcinogens; Gastric Mucosa; Methylnitronitrosoguanidine; Rats; Stomach Neoplasms

Topics: Adenocarcinoma; Administration, Oral; Animals; Carcinogens; Disease Progression; Hyperplasia; Male; Methylnitronitrosoguanidine; Rats; Rats, Wistar; Stomach Neoplasms; Time Factors; Water