demecolcine and Brain-Neoplasms

About 9% of human cancers are brain tumors, of which 90% are gliomas. gamma-Radiation has been identified as a risk factor for brain tumors. In a previous pilot study, we found that lymphocytes from patients with glioma were more sensitive to gamma-radiation than were lymphocytes from matched control subjects. In this larger case-control study, we compared the gamma-radiation sensitivity of lymphocytes from glioma patients with those from control subjects and investigated the association between mutagen sensitivity and the risk for developing glioma.. We used a mutagen sensitivity assay (an indirect measure of DNA repair activity) to assess chromosomal damage. We gamma-irradiated (1.5 Gy) short-term lymphocyte cultures from 219 case patients with glioma and from 238 healthy control subjects frequency matched by age and sex. After irradiation, cells were cultured for 4 hours, and then Colcemid was added for 1 hour to arrest cells in mitosis. Fifty metaphases were randomly selected for each sample and scored for chromatid breaks. All statistical tests were two-sided.. We observed a statistically significantly higher frequency of chromatid breaks per cell from case patients with glioma (mean = 0.55; 95% confidence interval [CI] = 0.50 to 0.59) than from control subjects (mean = 0.44; 95% CI = 0.41 to 0.48) (P<.001). Using 0.40 (the median number of chromatid breaks per cell in control subjects) as the cut point for defining mutagen sensitivity and adjusting for age, sex, and smoking status, we found that mutagen sensitivity was statistically significantly associated with an increased risk for glioma (odds ratio = 2.09; 95% CI = 1.43 to 3.06). When the data were divided into tertiles, the relative risk for glioma increased from the lowest tertile to the highest tertile (trend test, P<.001).. gamma-Radiation-induced mutagen sensitivity of lymphocytes may be associated with an increased risk for glioma, a result that supports our earlier preliminary findings.

Topics: Adult; Animals; Brain Neoplasms; Case-Control Studies; Chromatids; Chromosome Breakage; Demecolcine; DNA; DNA Damage; DNA Repair; DNA, Single-Stranded; Female; Gamma Rays; Genetic Predisposition to Disease; Glioma; Humans; Lymphocytes; Male; Middle Aged; Neoplasms, Radiation-Induced; Odds Ratio; Radiation Tolerance; Risk; Smoking

The localization of high molecular weight (HMW) tau proteins in neuroblastoma N115 cells and of their transcripts was compared to that of non-tyrosinated and tyrosinated tubulin before and after treatment with depolymerizing drugs. Microtubules stained by tau antibodies were present both in a limited region of the cell center and in the cell processes, whereas tau transcripts were detected only in the cell body. The microtubules localized in the cell center and labeled by tau antibodies resisted colcemid treatment, whereas those in the neurites were completely depolymerized by the drug. Microtubules containing stable and unstable microtubule tracts were identified in the neurites after colcemid treatment. These composite microtubules were not labeled by tau antibodies. It is concluded that stable and unstable polymers--localized in the cell center and in the neurites, respectively--contain HMW tau proteins, whereas composite microtubules displayed in the cell processes do not. Microtubule stability in this cell line does not therefore seem to be related to the association of tau proteins to the polymers but, rather, to posttranslational modifications of the tubulin subunits.

Topics: Animals; Brain Neoplasms; Cell Differentiation; Demecolcine; DNA, Complementary; Fluorescent Antibody Technique; Immunohistochemistry; In Situ Hybridization; Mice; Microtubules; Molecular Weight; Neuroblastoma; Nocodazole; tau Proteins; Tubulin; Tumor Cells, Cultured

As part of our research on the anti-tumour effects of calmodulin antagonists, we examined the localization of Ca(2+)-calmodulin in mitotic C6 glioma cells. Monoclonal anticalmodulin antibodies which require Ca2+ for binding and CREST serum which recognizes kinetochores were used to stain ultrathin frozen sections. By indirect immunofluorescence and immunoelectron microscopy of colcemid-treated cells, Ca(2+)-calmodulin was present in the kinetochore region of the cell. By double label indirect immunofluorescence using anticalmodulin antibodies and CREST serum to stain untreated cells, calmodulin was found to colocalize with kinetochores. On the basis of these results, we hypothesize that Ca(2+)-calmodulin in the kinetochore depolymerizes the microtubules which are transported by dynein in the kinetochore during metaphase oscillating and anaphase poleward chromosomal movements. This hypothesis, which is currently under further investigation, may help explain a mechanism for the antitumour effects of calmodulin antagonists in the treatment of brain tumours.

Topics: Animals; Antineoplastic Agents; Brain Neoplasms; Calcium; Calmodulin; Demecolcine; Fluorescent Antibody Technique; Glioma; Microscopy, Immunoelectron; Rats; Spindle Apparatus

Topics: Animals; Brain Neoplasms; Cell Division; Cells, Cultured; Demecolcine; Glioma; Neoplasms, Experimental; Rats

Cellular synchronization using Colcemid as pretreatment for combined chemoradiotherapy was investigated. C6 rat brain tumour was cultured in RPMI medium containing 10(-5)-10(-7) Mol. of Colcemid for 24 hours. The basic cell kinetics were analysed with a Pulse Cytophotometer, which facilitated the analysis of tumour cell cycle phase distribution according to the DNA content. The effect of Colcemid depended on the concentration, and the minimal concentration showing continuous blocking during 48 hours after removal of the drug was 10(-6) Mol. G1 fraction of 2 C DNA content was reduced from 74% to 36%. G2-M phase of 4 C DNA content increased from 9% to 28%. S phase cells increased from 17% to 31%. Polyploid cells in the Tetraploid cell cycle could be recognized. The remaining 36% of cells within the GO + G1 peak of 2 C DNA content were considered to be diploid GO cells.

Topics: Brain Neoplasms; Cell Division; Cells, Cultured; Demecolcine; Glioma; Humans; Neoplasms, Experimental; Premedication; Time Factors