cyclic-gmp and Cholera

Misregulation of gut function and homeostasis impinges on the overall well-being of the entire organism. Diarrheal disease is the second leading cause of death in children under 5 years of age, and globally, 1.7 billion cases of childhood diarrhea are reported every year. Accompanying diarrheal episodes are a number of secondary effects in gut physiology and structure, such as erosion of the mucosal barrier that lines the gut, facilitating further inflammation of the gut in response to the normal microbiome. Here, we focus on pathogenic bacteria-mediated diarrhea, emphasizing the role of cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate in driving signaling outputs that result in the secretion of water and ions from the epithelial cells of the gut. We also speculate on how this aberrant efflux and influx of ions could modulate inflammasome signaling, and therefore cell survival and maintenance of gut architecture and function.

Topics: Animals; Cholera; Cyclic AMP; Cyclic GMP; Diarrhea; Escherichia coli Infections; Gastrointestinal Microbiome; Humans; Inflammasomes; Inflammation; NLR Family, Pyrin Domain-Containing 3 Protein; Pyroptosis; Salmonella Infections

Topics: Adenylyl Cyclases; Animals; Cholera; Cyclic AMP; Cyclic GMP; Diarrhea; Enterotoxins; Escherichia coli; Escherichia coli Infections; Guanylate Cyclase; Humans; Mice; Vibrio cholerae

Enteric infections cause more than a billion episodes of diarrhoeal disease in humans each year killing many millions of people, especially young children, in developing countries. Recent progress, reviewed in this article, has enabled that a specific pathogen now can be isolated in the majority of patients with acute diarrhoea, and has also elucidated fundamental pathogenic mechanisms and their pathophysiological effects for several of these agents. Based on this understanding it now seems possible to devise new techniques for the treatment and prevention of diarrhoeal disease to complement those based on fluid replacement therapy and sanitation; prospects for the development of new or improved vaccines, receptor-prophylactic binding agents, and antisecretory drugs are discussed.. Enteric infections cause more than 1 billion episodes of diarrheal disease in humans each year killing many millions of people, especially young children, in developing countries. Recent progress, reviewed here, has enabled that a specific pathogen can now be isolated in the majority of patients with acute diarrhea, and has also elucidated fundamental pathogenic mechanisms and their pathophysiological effects for several of these agents. Based on this understanding, it now seems possible to devise new techniques for the treatment and prevention of diarrheal disease to complement those based on fluid replacement therapy and sanitation. Prospects for the development of new or improved vaccines, receptor-prophylactic binding agents, and antisecretory drugs are discussed.

Topics: Antidiarrheals; Bacterial Vaccines; Calcium; Cholera; Cyclic AMP; Cyclic GMP; Diarrhea; Dysentery, Amebic; Escherichia coli Infections; G(M1) Ganglioside; Humans; Reoviridae Infections; Rotavirus; Viral Vaccines

Topics: Adenylyl Cyclases; Angiotensin II; Animals; Calcitonin; Catecholamines; Cell Division; Cell Membrane; Cholera; Cyclic AMP; Cyclic GMP; Humans; Pancreatic Hormones; Parathyroid Hormone; Pituitary Hormone-Releasing Hormones; Pituitary Hormones; Pituitary Hormones, Anterior; Pituitary Hormones, Posterior; Prostaglandins; Receptors, Cell Surface; Toxins, Biological

Topics: Adenylyl Cyclases; Animals; Calcium; Catecholamines; Cholera; Colon; Cyclic AMP; Cyclic GMP; Digestive System; Enterotoxins; Enzyme Activation; Escherichia coli; Gastric Juice; Guanylate Cyclase; Intestinal Mucosa; Intestine, Small; Models, Biological; Nucleotides, Cyclic; Pancreas; Phosphoric Diester Hydrolases; Prostaglandins; Protein Kinases; Salivary Glands; Toxins, Biological

The bacterial secondary messenger bis-(3',5')-cyclic-dimeric-guanosine monophosphate (c-di-GMP) has been implicated in the pathogenesis of Vibrio cholerae, due to its significant role in regulating the virulence, biofilm formation and motility of the host organism. The VC0395_0300 protein from V. cholerae, possessing a GGEEF sequence has been established as a diguanylate cyclase (DGC) capable of catalyzing the conversion of two GTP molecules to form cyclic-di-GMP. This in turn, plays a crucial role in allowing the organism to adopt a dual lifestyle, thriving both in human and aquatic systems. The difficulty in procuring sufficient amounts of homogenous soluble protein for structural assessment of the GGDEF domain in VC0395_0300 and the lack of soluble protein yield, prompted the truncation into smaller constructs (Sebox31 and Sebox32) carrying the GGDEF domain. The truncates retained their diguanylate cyclase activity comparable to the wild type, and were able to form biofilms as well. Fluorescence and circular dichroism spectroscopy measurements revealed that the basic structural elements do not show significant changes in the truncated proteins as compared to the full-length. This has also been confirmed using homology modeling and molecular docking of the wild type and truncates. This led us to conclude that the truncated constructs retain their activity in spite of the deletions in the N terminal region. This is supportive of the fact that DGC activity in GGDEF proteins is predominantly dependent on the presence of the conserved GGD(/E)EF domain and its interaction with GTP.

Topics: Amino Acid Sequence; Bacterial Proteins; Cholera; Cyclic GMP; Escherichia coli Proteins; Guanosine Triphosphate; Humans; Models, Molecular; Phosphorus-Oxygen Lyases; Vibrio cholerae

The LonA (or Lon) protease is a central post-translational regulator in diverse bacterial species. In Vibrio cholerae, LonA regulates a broad range of behaviors including cell division, biofilm formation, flagellar motility, c-di-GMP levels, the type VI secretion system (T6SS), virulence gene expression, and host colonization. Despite LonA's role in cellular processes critical for V. cholerae's aquatic and infectious life cycles, relatively few LonA substrates have been identified. LonA protease substrates were therefore identified through comparison of the proteomes of wild-type and ΔlonA strains following translational inhibition. The most significantly enriched LonA-dependent protein was TfoY, a known regulator of motility and the T6SS in V. cholerae. Experiments showed that TfoY was required for LonA-mediated repression of motility and T6SS-dependent killing. In addition, TfoY was stabilized under high c-di-GMP conditions and biochemical analysis determined direct binding of c-di-GMP to LonA results in inhibition of its protease activity. The work presented here adds to the list of LonA substrates, identifies LonA as a c-di-GMP receptor, demonstrates that c-di-GMP regulates LonA activity and TfoY protein stability, and helps elucidate the mechanisms by which LonA controls important V. cholerae behaviors.

Topics: Animals; Bacterial Proteins; Biofilms; Cholera; Cyclic GMP; Disease Models, Animal; Humans; Mice; Mutation; Protease La; Protein Processing, Post-Translational; Protein Stability; Proteolysis; Proteomics; Recombinant Proteins; Type VI Secretion Systems; Vibrio cholerae; Virulence

The bacterial enhancer-binding protein (bEBP) FlrC, controls motility and colonization of

Topics: Adenosine Triphosphatases; Bacterial Proteins; Cholera; Crystallography, X-Ray; Cyclic GMP; DNA-Binding Proteins; Flagella; Gene Expression Regulation, Bacterial; Phylogeny; Protein Structure, Tertiary; Vibrio cholerae

Vibrio cholerae of serogroups O1 and O139, the causative agent of Asiatic cholera, continues to be a major global health threat. This pathogen utilizes substratum-specific pili to attach to distinct surfaces in the aquatic environment and the human small intestine and detaches when conditions become unfavorable. Both attachment and detachment are critical to bacterial environmental survival, pathogenesis and disease transmission. However, the factors that promote detachment are less understood. In this study, we examine the role of flagellar motility and hemagglutinin/protease (HapA) in vibrio detachment from a non-degradable abiotic surface and from the suckling mouse intestine. Flagellar motility facilitated V. cholerae detachment from abiotic surfaces. HapA had no effect on the stability of biofilms formed on abiotic surfaces despite representing >50% of the proteolytic activity present in the extracellular matrix. We developed a balanced lethal plasmid system to increase the bacterial cyclic diguanylate (c-di-GMP) pool late in infection, a condition that represses motility and HapA expression. Increasing the c-di-GMP pool enhanced V. cholerae colonization of the suckling mouse intestine. The c-di-GMP effect was fully abolished in hapA isogenic mutants. These results suggest that motility facilitates detachment in a substratum-independent manner. Instead, HapA appears to function as a substratum-specific detachment factor.

Topics: Animals; Bacterial Adhesion; Biofilms; Cholera; Cyclic GMP; Fimbriae, Bacterial; Flagella; Gene Expression Regulation, Bacterial; Intestinal Mucosa; Intestine, Small; Metalloendopeptidases; Mice; Movement; Polystyrenes; Vibrio cholerae

Biofilm formation is crucial to the environmental survival and transmission of Vibrio cholerae, the facultative human pathogen responsible for the disease cholera. During its infectious cycle, V. cholerae experiences fluctuations in temperature within the aquatic environment and during the transition between human host and aquatic reservoirs. In this study, we report that biofilm formation is induced at low temperatures through increased levels of the signalling molecule, cyclic diguanylate (c-di-GMP). Strains harbouring in frame deletions of all V. cholerae genes that are predicted to encode diguanylate cyclases (DGCs) or phosphodiesterases (PDEs) were screened for their involvement in low-temperature-induced biofilm formation and Vibrio polysaccharide gene expression. Of the 52 mutants tested, deletions of six DGCs and three PDEs were found to affect these phenotypes at low temperatures. Unlike wild type, a strain lacking all six DGCs did not exhibit a low-temperature-dependent increase in c-di-GMP, indicating that these DGCs are required for temperature modulation of c-di-GMP levels. We also show that temperature modulates c-di-GMP levels in a similar fashion in the Gram-negative pathogen Pseudomonas aeruginosa but not in the Gram-positive pathogen Listeria monocytogenes. This study uncovers the role of temperature in environmental regulation of biofilm formation and c-di-GMP signalling.

Topics: Biofilms; Cholera; Cyclic GMP; Escherichia coli Proteins; Humans; Listeria monocytogenes; Phosphoric Diester Hydrolases; Phosphorus-Oxygen Lyases; Pseudomonas aeruginosa; Sequence Deletion; Signal Transduction; Temperature; Vibrio cholerae

The second messenger cyclic diguanylate (c-di-GMP) plays a central role in bacterial adaptation to extracellular stimuli, controlling processes such as motility, biofilm development, cell development and, in some pathogens, virulence. The intracellular level of c-di-GMP is controlled by the complementary activities of diguanylate cyclases containing a GGDEF domain and two classes of c-di-GMP phosphodiesterases containing an EAL or HD-GYP hydrolytic domain. Compared to the GGDEF and EAL domains, the functions of HD-GYP domain family proteins are poorly characterized. The human diarrheal pathogen Vibrio cholerae encodes nine putative HD-GYP domain proteins. To determine the contributions of HD-GYP domain proteins to c-di-GMP signaling in V. cholerae, we systematically analyzed the enzymatic functionality of each protein and their involvement in processes known to be regulated by c-di-GMP: motility, biofilm development and virulence.. Complementary in vitro and in vivo experiments showed that four HD-GYP domain proteins are active c-di-GMP phosphodiesterases: VC1295, VC1348, VCA0210 and VCA0681. Mutation of individual HD-GYP domain genes, as well as combinatorial mutations of multiple HD-GYP domain genes, had no effect on motility or biofilm formation of V. cholerae under the conditions tested. Furthermore, no single HD-GYP domain gene affected intestinal colonization by V. cholerae in an infant mouse model. However, inactivation of multiple HD-GYP domain genes, including the four encoding functional phosphodiesterases, significantly attenuated colonization.. These results indicate that the HD-GYP family of c-di-GMP phosphodiesterases impacts signaling by this second messenger during infection. Altogether, this work greatly furthers the understanding of this important family of c-di-GMP metabolic enzymes and demonstrates a role for HD-GYP domain proteins in the virulence of V. cholerae.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Biofilms; Cholera; Cyclic GMP; Disease Models, Animal; Locomotion; Mice; Mutation; Signal Transduction; Vibrio cholerae; Virulence

Signaling through the second messenger cyclic di-GMP (c-di-GMP) is central to the life cycle of Vibrio cholerae. However, relatively little is known about the signaling mechanism, including the specific external stimuli that regulate c-di-GMP concentration. Here, we show that the phosphate responsive regulator PhoB regulates an operon, acgAB, which encodes c-di-GMP metabolic enzymes. We show that induction of acgAB by PhoB positively regulates V. cholerae motility in vitro and that PhoB regulates expression of acgAB at late stages during V. cholerae infection in the infant mouse small intestine. These data support a model whereby PhoB becomes activated at a late stage of infection in preparation for dissemination of V. cholerae to the aquatic environment and suggest that the concentration of exogenous phosphate may become limited at late stages of infection.

Topics: Animals; Bacterial Proteins; Biofilms; Cholera; Cyclic GMP; Gene Expression Regulation, Bacterial; Mice; Vibrio cholerae

In Vibrio cholerae, the second messenger cyclic di-GMP (c-di-GMP) positively regulates biofilm formation and negatively regulates virulence and is proposed to play an important role in the transition from persistence in the environment to survival in the host. Herein we describe a characterization of the infection-induced gene cdpA, which encodes both GGDEF and EAL domains, which are known to mediate diguanylate cyclase and c-di-GMP phosphodiesterase (PDE) activities, respectively. CdpA is shown to possess PDE activity, and this activity is regulated by its inactive degenerate GGDEF domain. CdpA inhibits biofilm formation but has no effect on colonization of the infant mouse small intestine. Consistent with these observations, cdpA is expressed during in vitro growth in a biofilm but is not expressed in vivo until the late stage of infection, after colonization has occurred. To test for a role of c-di-GMP in the early stages of infection, we artificially increased c-di-GMP and observed reduced colonization. This was attributed to a significant reduction in toxT transcription during infection. Cumulatively, these results support a model of the V. cholerae life cycle in which c-di-GMP must be down-regulated early after entering the small intestine and maintained at a low level to allow virulence gene expression, colonization, and motility at appropriate stages of infection.

Topics: Animals; Bacterial Proteins; Bacterial Typing Techniques; Biofilms; Cholera; Cyclic GMP; Gene Expression Regulation, Bacterial; Mice; Phosphoric Diester Hydrolases; Protein Structure, Tertiary; Vibrio cholerae

The facultative pathogen Vibrio cholerae can exist in both the human small bowel and in aquatic environments. While investigation of the infection process has revealed many factors important for pathogenesis, little is known regarding transmission of this or other water-borne pathogens. Using a temporally controlled reporter of transcription, we focus on bacterial gene expression during the late stage of infection and identify a unique class of V. cholerae genes specific to this stage. Mutational analysis revealed limited roles for these genes in infection. However, using a host-to-environment transition assay, we detected roles for six of ten genes examined for the ability of V. cholerae to persist within cholera stool and/or aquatic environments. Furthermore, passage through the intestinal tract was necessary to observe this phenotype. Thus, V. cholerae genes expressed prior to exiting the host intestinal tract are advantageous for subsequent life in aquatic environments.

Topics: Animals; Animals, Suckling; Cholera; Cyclic GMP; Diarrhea; Gene Expression Regulation, Bacterial; Genes, Bacterial; Humans; Mice; Osmolar Concentration; Reverse Transcriptase Polymerase Chain Reaction; Vibrio cholerae; Water Microbiology

Topics: Adenylyl Cyclases; Animals; Cholera; Cholera Toxin; Cyclic AMP; Cyclic GMP; Diarrhea; Drug Stability; Electrolytes; Enterotoxins; Enzyme Activation; Escherichia coli; Ileum; Intestinal Mucosa; Rabbits

Topics: Adenylyl Cyclases; Animals; Cholera; Cholera Toxin; Cyclic AMP; Cyclic GMP; Cystic Fibrosis; Humans; Intestinal Mucosa; Rabbits

Topics: Adolescent; Adult; Cholera; Colitis, Ulcerative; Cyclic AMP; Cyclic GMP; Diarrhea; Female; Humans; Male; Middle Aged

Topics: Adult; Cholera; Cyclic AMP; Cyclic GMP; Duodenum; Endoscopy; Female; Histamine; Humans; Male; Serotonin

The effect of aspirin on normal and cholera toxin-stimulated electrolyte transport has been investigated in vitro, because this drug appears to inhibit cholera toxin-induced intestinal secretion in in vivo animal models. In the Ussing chamber, 10 mM aspirin decreased the control rabbit ileal potential difference and short-circuit current by 50% and increased conductance by 28%. Bidirectional electrolyte flux determinations showed that aspirin significantly increased both Na and Cl absorption and reduced flux (which probably represents HCO3 secretion) to zero. This effect of aspirin appears to be identical to that reported to others with catecholamines as determined with similar techniques. However, alpha-adrenergic blockers did not prevent the electrical effects of aspirin, suggesting that aspirin does not have its effect through release of tissue stores of catecholamines. In the presence of aspirin, cholera toxin increased the potential difference and short-circuit current, and decreased the conductance of rabbit ileum in a fashion qualitatively similar to control tissues. However, aspirin reversed cholera toxin-stimulated Na transport from secretion to absorption, inhibited cholera toxin, induced Cl secretion by 58% and partially, but not significantly, inhibited HCO3 secretion. Thus, the inhibitory effect of aspirin on cholera toxin-induced electrolyte secretion appears to be due to aspirin-stimulated Na and Cl absorption. Although aspirin reduced tissue cyclic AMP concentrations in normal and cholera toxin-stimulated ileum, it also inhibited the electrolyte secretion induced by exogenous cyclic AMP. Thus, if aspirin's stimulatory effect on sodium and anion absorption in normal tissue and its inhibitory effect on cholera toxin-stimulated sodium and anion secretion involves a cyclic AMP-mediated system, the effect must be a step distal to cyclic AMP production or degradation. The exact mechanism of aspirin's effect on normal and cholera toxin-induced electrolyte transport, and its possible usefulness in the treatment of cholera diarrhea, remains to be determined.

Topics: Animals; Aspirin; Biological Transport; Cholera; Cyclic AMP; Cyclic GMP; Electrolytes; Electrophysiology; Epinephrine; Ileum; Intestinal Absorption; Intestinal Mucosa; Ions; Male; Norepinephrine; Phenoxybenzamine; Phentolamine; Rabbits; Stimulation, Chemical; Toxins, Biological

Insulin action is discussed with emphasis on events that occur at the plasma membrane. A summary is presented of previous studies which indicate that the insulin receptor of fat and liver cells is a large glycoprotein, partially buried in the outer surface of the plasma membrane, with a high (K-D approximately 10-10 M) and specific affinity for insulin. The participation of membrane phospholipids in the binding of insulin and the role of sialic acid residues in the transmission of the insulin binding signal are discussed. The relation of insulin action to its effects on cyclic nucleotide levels is explored. On the one hand, insulin action (glucose transport) is inhibited by compounds (cholera toxin, ACTH, glucagon and L-norepinephrine) that stimulate adenylate cyclase; conversely, insulin both inhibits the lipolytic action of these compounds, and raises cellular levels of cyclic GMP. An hypothesis is presented whereby a single cyclase species may be responsible for the formation of either cyclic AMP or cyclic GMP, depending on the nature of the hormone stimulus. The role of membrane phosphorylation in the action of insulin is discussed in the context of experiments demonstrating a specific inhibition by ATP of insulin-mediated glucose transport, in association with the phosphorylation of two specific membrane proteins. The ability of insulin to modulate cyclic nucleotide levels in cultured cells and to act as a growth factor is discussed. Insulin stimulates DNA synthesis and the uptake of alpha-aminoisobutyric acid in human fibroblasts, which effects are also mediated by epidermal growth factor. Insulin acts at concentrations much higher than those obtained in vivo, whereas epidermal growth factor acts at concentrations thought to be physiological. The insulin binding sites (K-D is approximately equal to 10-9 M) related to growth, and observed both in human fibroblasts and in lectin-stimulated and leukemic human lymphocytes would not be appreciably occupied at physiological insulin concentrations. The implications of such 'low affinity' binding sites for insulin are discussed in relation to the action of other growth factors.

Topics: Adipose Tissue; Adrenocorticotropic Hormone; Animals; Atropine; Cell Division; Cell Membrane; Cholera; Cyclic AMP; Cyclic GMP; Female; Fibroblasts; Glucagon; Humans; Infant, Newborn; Insulin; Liver; Lymphocytes; Male; Norepinephrine; Rats; Receptors, Cell Surface; Toxins, Biological

Topics: Adenosine Triphosphate; Adenylyl Cyclases; Adult; Animals; Cholera; Cyclic AMP; Cyclic GMP; Diarrhea; Diarrhea, Infantile; Enterotoxins; Epithelial Cells; Epithelium; Escherichia coli Infections; Fluorides; Guanosine Triphosphate; Guanylate Cyclase; Humans; Infant; Intestinal Mucosa; Phosphoric Diester Hydrolases; Phosphorus Radioisotopes; Prostaglandins; Temperature; Tritium

Selective release of inflammatory materials from leukocyte lysosomes is reduced by compounds which increase cyclic 3',5'-adenosine monophosphate (cAMP) levels in suspensions of human leukocytes and is augmented by agents which increase cyclic 3',5'-guanosine monophosphate (cGMP) levels in these cell suspensions. Lysosomal enzymes are released in the absence of phagocytosis when cytochalasin B (5 mug/ml) converts polymorphonuclear leukocytes (PMN) to secretory cells: lysosomes merge directly with the plasma membrane upon encounter of PMN with zymosan, and cells selectively extrude substantial proportions of lysosomal, but not cytoplasmic enzymes. beta-Adrenergic stimulation of human leukocytes produced a dose-related reduction in beta-glucuronidase release (blocked by 10(-6) M propranolol) whereas alpha-adrenergic stimulation (phenylephrine plus propranolol) was ineffective. In contrast, the cholinergic agonist carbamylcholine chloride enhanced enzyme secretion, an effect blocked by 10(-6) M atropine. Incubation of cells with exogenous cAMP or with agents that increase endogenous cAMP levels (prostaglandin E1, histamine, isoproterenol, and cholera enterotoxin) reduced extrusion of lysosomal enzymes; in contrast, exogenous cGMP and carbamylcholine chloride (which increases endogenous cGMP levels), increased beta-glucuronidase release. Whereas colchicine (5 x 10(-4) M), a drug which impairs microtubule integrity, reduced selective enzyme release, deuterium oxide, which favors microtubule assembly, enhanced selective release of lyosomal enzymes. The data suggest that granule movement and acid hydrolase release from leukocyte lysosomes requires intact microtubules and may be modulated by adrenergic and cholinergic agents which appear to provoke changes in concentrations of cyclic nucleotides.

Topics: Atropine; Carbachol; Cholera; Colchicine; Cyclic AMP; Cyclic GMP; Cytochalasin B; Deuterium; Enterotoxins; Glucuronidase; Histamine; Humans; Isoproterenol; Leukocytes; Lysosomes; Phagocytosis; Phenylephrine; Propranolol; Prostaglandins; Zymosan

Topics: Acetylcholine; Aminophylline; Animals; Antibodies; Carbachol; Cholera; Colchicine; Cyclic AMP; Cyclic GMP; Cytotoxicity Tests, Immunologic; Edetic Acid; Epinephrine; Humans; Imidazoles; Immune Adherence Reaction; Immune Sera; Isoproterenol; Leukemia, Experimental; Neutrophils; Propranolol; Rabbits; Toxins, Biological

The capacity of allosensitized thymus-derived lymphocytes to destroy target cells bearing donor alloantigens is modulated by the cellular levels of cyclic AMP and cyclic GMP. Increases in the cyclic AMP levels of attacking lymphocytes by stimulation with prostaglandin E(1), isoproterenol, and cholera toxin inhibit lymphocyte-mediated cytotoxicity; whereas, depletion of cyclic AMP with imidazole enhances cytotoxicity. The augmentation of cytotoxicity produced by cholinergic stimulation with carbamylcholine is not associated with alterations in cyclic AMP levels and is duplicated by 8-bromo-cyclic GMP. The effects of activators of adenylate cyclase, cholinomimetic agents, and 8-bromocyclic GMP are upon the attacking and not the target cells and occur at the time of initial interaction of attacking and target cells. Indeed, the level of cyclic nucleotide (cyclic AMP and cyclic GMP) at the time of initial cell-to-cell interaction determines the extent of cytotoxicity.

Topics: Animals; Carbachol; Cholera; Cyclic AMP; Cyclic GMP; Cytotoxicity Tests, Immunologic; Graft Rejection; Imidazoles; Isoproterenol; Lymphocyte Depletion; Prostaglandins; Rats; T-Lymphocytes; Toxins, Biological

Topics: Amino Acids; Animals; Biological Transport, Active; Bucladesine; Carbon Radioisotopes; Cholera; Cyclic AMP; Cyclic GMP; Female; Hydrogen-Ion Concentration; Ileum; Intestinal Mucosa; Jejunum; Leucine; Lysine; Rats; Structure-Activity Relationship; Theophylline; Toxins, Biological; Tritium

Topics: Animals; Chick Embryo; Cholera; Cyclic AMP; Cyclic GMP; Dogs; Enterotoxins; Fetal Heart; In Vitro Techniques; Insulin; Intestinal Mucosa; Intestinal Secretions; Jejunum; Muscle Contraction; Stimulation, Chemical; Theophylline