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.     

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.     

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).     

Bone marrow genotoxicity of N-methyl, N-nitrosourea (NMU): n-alkanols as sister chromatid exchange (SCE) anti-inducers

The in vivo SCE test was used to demonstrate significant inhibition of NMU bone marrow genotoxicity by pretreatment of Chinese hamsters with n-alkanols. Our findings exclude a loss of intracellular DNA alkylation potential through a competitive direct reaction of NMU with the weakly nucleophilic polar end of the n-alkanols, but not through methylations of nucleophilic membrane sites possibly liberated by structural modifications which the membrane-active amphiphilics induce.     

Rate of sister chromatid exchanges in mammalian cells differing in diploid numbers

Summary The rate of sister chromatid exchanges (SCE) under identical experimental conditions is the same in various mammalian species irrespective of their diploid chromosome numbers.Supported in part by Research grants VC-21 from American Cancer Society and DEB-76-10580 from National Science Foundation.     

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.     

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.     

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.     

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.     

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.     

Effect of fluoride on in vivo nitrate reduction in rice leaves (Oryza sativa L.)

Summary Fluoride had no effect on in vitro nitrate reductase activity in rice leaves, but in vivo activity was strongly inhibited. It is suggested that fluoride brings about this inhibition by adversely affecting the physiological NADH generating system required for in vivo nitrate reduction.Acknowledgments. We thank Dr M.S. Naik for useful suggestions and discussion. C.S.R. is grateful to Indian Council of Agricultural Research for a Senior Research Fellowship.     

Genetic basis of susceptibility for development of neoplasms following treatment with N-methyl-N-nitrosourea (MNU) or X-rays in the platyfish/swordtail system

Summary Specific genotypes of the xiphophorine fish develop neoplasms following treatment with N-methyl-N-nitrosourea or X-rays. Several of these neoplasms can be related to the presence of specific chromosomes. The implications of these findings are discussed.Supported by Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 103 Zellenergetik und Zelldifferenzierung, Marburg (projects C 9 and C 10), and by Justus-Liebig-Universität Giessen. We are indebted to Prof. K. Frese, Veterinär-Pathologisches Institut, Giessen and Dr H. D. Mennel, Pathologisches Institut, Freiburg, for their help in the classification of neoplasms. We furthermore thank K. Klinke for breeding the fish. Dedicated to Prof. C. Kosswig on the occasion of his 75^th birthday.The paper contains parts of the dissertations of S. Abdo, J. Haas and G. Kollinger.supported by the Egypt ministry of education.     

Comparison of the time courses of luteinizing hormone (LH) secretion rates during continuous stimulation by LH-releasing hormone (LH-RH) in vivo and in vitro

Summary The patterns of LH secretion during constant stimulation of the pituitary glands of estradiol-treated ovariectomized rats with a maximally stimulating amount of LH-RH in vivo and in vitro correspond with each other qualitatively and quantitatively. In vitro the changes with time of the LH secretion rate are somewhat retarded, especially the occurrence of desensitization.     

Comparison of the time courses of luteinizing hormone (LH) secretion rates during continuous stimulation by LH-releasing hormone (LH-RH) in vivo and in vitro

The patterns of LH secretion during constant stimulation of the pituitary glands of estradiol-treated ovariectomized rats with a maximally stimulating amount of LH-RH in vivo and in vitro correspond with each other qualitatively and quantitatively. In vitro the changes with time of the LH secretion rate are somewhat retarded, especially the occurrence of desensitization.     

Purification of pig kidney diamine oxidase (histaminase) and in vivo effects on passive cutaneous anaphylaxis and histamine induced bronchoconstriction of guinea-pigs

Summary Histaminase (diamine oxidase) was purified from pig kidney using cadaverine-Sepharose affinity chromatography. Pretreatment of guinea-pigs with histaminase caused marked inhibition of the passive cutaneous anaphylaxis. The effect of histaminase on histamine induced bronchoconstriction in vivo was studied. Histaminase significantly reduced the response in guinea-pigs. Histaminase is effective as a potent antihistaminic agent in vivo.     

Appearance of growth-inhibiting activity (G1 chalone) during ontogenetic development of rat and chick epidermis in vivo and in vitro

Summary A comparative study was carried out between the stage of embryonic development of epidermis and its content of growth-inhibitory activity (G₁ chalone). Injections of aqueous extracts from keratinized fetal rat or chick embryo epidermis led to a depression of DNA-synthesis in adult mouse epidermis, whereas extracts from undifferentiated epidermis did not contain such an activity.This investigation was supported by the Deutsche Forschungsgemeinschaft.     

Appearance of growth-inhibiting activity (G1 chalone) during ontogenetic development of rat and chick epidermis in vivo and in vitro.

A comparative study was carried out between the stage of embryonic development of epidermis and its content of growth-inhibitory activity (G1 chalone). Injections of aqueous extracts from keratinized fetal rat or chick embryo epidermis led to a depression of DNA-synthesis in adult mouse epidermis, whereas extracts from undifferentiated epidermis did not contain such an activity.