Induction of sister chromatid exchanges in vivo in bone marrow cells of AKR mice]

Induction of sister chromatid exchanges (SCEs) in bone-marrow cells of AKR Mice receiving in vivo four drugs well-known for their mutagenesis activity has been tested. A decreasing activity in SCE was shown by the drugs tested in the order cyclophosphamide, procarbazine, methylmethane sulfonate and diethylnitrosamine. This technique presents an encouraging method for testing the effect of chemical agents in vivo.     

Occurrence of sister chromatid exchanges at euchromatin-C band junctions inAllium cepa chromosomes

Summary Distribution of SCE in C band and non-C band regions ofAllium cepa chromosomes.     

Mitotic response and sister chromatid exchanges in lymphocytes cultured in sera from different sources

Summary The numbers of sister chromatid exchanges in lymphocytes grown in varying concentrations of serum from different sources indicated that some sera contain a factor, probably introduced as a contaminant, which induces SCEs. Sera from 6 animals showed no evidence of a difference in baseline SCE levels due to the donor of the serum.Research sponsored by U.S. Department of Energy contract number DE-ACO5-760R00242 with The University of Tennessee.     

Distribution of sister chromatid exchanges in different types of chromatin in the X chromosome ofMicrotus cabrerae

We used the X chromosomes ofMicrotus cabrerae as a model to analyze the distribution of sister chromatid exchanges (SCEs) on different types of chromatin, because of the marked heterogeneity of the heterochromatin in the entire short arm and a portion of the long arm of this chromosome. Computer-simulated distributions, according to an algorithm that makes it possible to modify the distribution on the basis of any possible hypothesis, were compared with real distributions by log-linear models. We found that the frequency of SCEs in different types of heterochromatin was higher than that expected for a random distribution, and located an SCE hot-spot at the junction between euchromatin and heterochromatin. The possible relationship between the distribution of SCEs and base composition or chromatin accessibility are discussed.     

Genotype-specific reduction in methyl nitrosourea (MNU) induced sister chromatid exchanges (SCE) in vivo during aging

Summary We studied mice from five strains (BALB/c, C3H/HeSnJ, C57BL/6J, Cs^b and 129/ReJ) at two ages (young, 10±1 weeks; and old, 67±3 weeks) for the induction of sister chromatid exchanges (SCEs) in vivo by methyl nitrosourea (MNU). The SCE frequency is genotype-specific. The F₁ phenotype resembles the low responding parent. SCE induction is significantly lower in the older animals of each strain than their younger counterparts, and the reduction of SCE/cell with old age is strain-specific. A general explanation for these results must include strain differences in relative mutagenic sensitivity, genotype-specific pattern of reduction in DNA repair and other such factors affecting SCE formation, with old age.     

Genotype-specific reduction in methyl nitrosourea (MNU) induced sister chromatid exchanges (SCE) in vivo during aging

We studied mice from five strains (BALB/c, C3H/HeSnJ, C57BL/6J, Csb and 129/ReJ) at two ages (young, 10 +/- 1 weeks; and old, 67 +/- 3 weeks) for the induction of sister chromatid exchanges (SCEs) in vivo by methyl nitrosourea (MNU). The SCE frequency is genotype-specific. The F1 phenotype resembles the 'low' responding parent. SCE induction is significantly lower in the older animals of each strain than their younger counterparts, and the reduction of SCE/cell with old age is strain-specific. A general explanation for these results must include strain differences in relative mutagenic sensitivity, genotype-specific pattern of reduction in DNA repair and other such factors affecting SCE formation, with old age.     

Effect of the gas phase of cigarette smoke on the rate of sister chromatid exchanges in human lymphocytes in vitro]

A technique of differential staining of chromatids after BudR treatment enabled us to study the influence of the gas phase of cigarette smoke on human lymphocytes. We ascertained that the number of exchanges increased in proportion to the concentration of gas phase extant in the medium. Moreover, the base-line exchange rate was a little higher in smokers than in nonsmokers.     

The dose-dependence of sister chromatid exchanges induced by 3 hydrocarbons,in the in vivo bone marrow test with Chinese Hamsters

Summary In accordance with their carcinogenic effects, 7, 12-dimethylbenzanthracene and 3,4-benzo(a)pyrene induce sister chromatid exchanges in the bone marrow of Chinese Hamsters in vivo. Phenanthrene is inactive. A dose dependence of induced sister-chromatid exchanges can be shown.Work carried out under Contract No. 022-74-1-ENVD of the E. G. Environmental Research Programme and the Bundesministerium für Forschung und Technologie (Nr. MT 420).     

Sister chromatid exchanges in lymphocytes of normal and alcoholic subjects

The effects of alcohol consumption, cigarette smoking and age on sister chromatid exchangen (SCE) frequency in human lymphocytes were assessed by means of multiple linear regression. An increase in SCE rates was associated with alcohol consumption (p=0.0001), smoking (p=0.0231), and, to a small extent (p=0.057), age. These three confounding factors explain 48% of the inter-personal variation in SCE rates among subjects studied.We are grateful to Dr D. Krapavickaité for performing, the statistical analysis, and to Mrs V. Navickiené for technical assistance. We also wish to thank Dr B. Lambert (Stockholm, Sweden) for his valuable suggestions.     

Sister chromatid exchanges in lymphocytes of normal and alcoholic subjects.

The effects of alcohol consumption, cigarette smoking and age on sister chromatid exchange (SCE) frequency in human lymphocytes were assessed by means of multiple linear regression. An increase in SCE rates was associated with alcohol consumption (p = 0.0001), smoking (p = 0.0231), and, to a small extent (p = 0.057), age. These three confounding factors explain 48% of the inter-personal variation in SCE rates among subjects studied.     

5-Bromodeoxyuridine induced sister chromatid exchange frequencies in primate lymphocytes

Summary Comparisons of SCE frequencies at various BrdUrd concentrations showed significant interspecies differences with human lymphocytes being the most sensitive. I wish to thank S. Noble. A Kirkilionis and D. Lang for their assistance, Dr S.L. Cleland of Connaught Laboratories, Toronto, who provided most of the monkey blood samples and the Metro Toronto Zoo for providing the gorilla blood samples.     

A combination of sister chromatid differential staining and giemsa banding

Summary We report a procedure for combining sister chromatid differential staining and G banding in the same metaphase plate. Mammalian cells in culture are grown in medium containing 5-bromodeoxyuridine for two cell cycles, and conventional air-dried preparations are made. The slides are treated with a trypsin or a urea solution the same way as for regular G banding. This method is simple and fast and provides additional information for cytogeneticists.     

Influence of pulsing electromagnetic field on the frequency of sister-chromatid exchanges in cultured mammalian cells

Exposures of Chinese hamster cells to pulsing electromagnetic field (PEMF) with 0.18-2.5 mT did not influence the baseline frequency of sister-chromatid exchanges (SCE). The results suggest that PEMF with the magnetic intensity examined does not interfere with DNA replication nor produce DNA lesions, thereby leading to an increased frequency of SCE.     

Influence of pulsing electromagnetic field on the frequency of sister-chromatid exchanges in cultured mammalian cells

Summary Exposure of Chinese hamster cells to pulsing electromagnetic field (PEMF) with 0.18–2.5 mT did not influence the baseline frequency of sister-chromatid exchanges (SCE). The results suggest that PEMF with the magnetic intensity examined does not interfere with DNA replication nor produce DNA lesions, thereby leading to an increased frequency of SCE.     

A combination of sister chromatid differential staining and giemsa banding.

We report a procedure for combining sister chromatid differential staining and G banding in the same metaphase plate. Mammalian cells in culture are grown in medium containing 5-bromodeoxyuridine for two cell cycles, and conventional air-dried preparations are made. The slides are treated with a trypsin or a urea solution the same way as for regular G banding. This method is simple and fast and provides additional information for cytogeneticists.     

Sister chromatid exchanges induced by methylxanthines contained in coffee,tea and cocoa

Summary Methylxanthines consumed daily by most humans were investigated for induction of sister chromatid exchanges (SCE). Effects observed in this highly sensitive in vivo system decreased in the order theophylline/theobromine>caffeine >paraxathine>monomethylxanthines.     

Increases in frequency of sister chromatid exchange following tumor grafts in different immunocompetent hosts]

Measurement of sister chromatid exchanges (SCEs) frequency of inbred Rat or nu/nu Mice bone marrow cells, following tumour grafts, have been developed. Increase of SCEs was observed in hosts which present or not metases and with reduced survival rates after malignant tumour grafts. These results suggest a remote control of tumoral tissue by a diffused matter effect.     

The equilibrium of ubiquitination and deubiquitination at PLK1 regulates sister chromatid separation

PLK1 regulates almost every aspect of mitotic events, including mitotic entry, spindle assembly, chromosome alignment, sister chromatid segregation, metaphase-anaphase transition, cytokinesis, etc. In regulating the chromosome alignment and sister chromatid segregation, PLK1 has to be localized to and removed from kinetochores at the right times, and the underlying mechanism that regulates PLK1 both spatially and temporally only became clearer recently. It has been found that deubiquitination and ubiquitination of PLK1 are responsible for its localization to and dissociation from the kinetochores, respectively. The equilibrium of this ubiquitination and deubiquitination plays an important role in regulating proper chromosome alignment and timely sister chromatid segregation. Here, we summarize and discuss the recent findings in investigating the spatial and temporal regulation of PLK1 during chromosome alignment and sister chromatid segregation.