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.     

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.     

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.     

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.     

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.     

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.     

Models as products of interdisciplinary exchange: Evidence from evolutionary game theory

The development of evolutionary game theory (EGT) is closely linked with two interdisciplinary exchanges: the import of game theory into biology, and the import of biologists’ version of game theory into economics. This paper traces the history of these two import episodes. In each case the investigation covers what exactly was imported, what the motives for the import were, how the imported elements were put to use, and how they related to existing practices in the respective disciplines. Two conclusions emerged from this study. First, concepts derived from the unity of science discussion or the unification accounts of explanation are too strong and too narrow to be useful for analysing these interdisciplinary exchanges. Secondly, biology and economics—at least in relation to EGT—show significant differences in modelling practices: biologists seek to link EGT models to concrete empirical situations, whereas economists pursue conceptual exploration and possible explanation.     

La respiration tissulaire chez les poissons: Etude des conditions optimales pour obtenir et mesurer une «respiration potentielle» sur broyats tissulaires

Summary Research was undertaken to find the formula of a physiological serum (saccharose, Na succinate and CaCl₂) permitting intense gaseous exchanges, a potential respiration, to be obtained from tissue homogenates of fish.     

Subcellular steroid distribution in the rat adrenal cortex

Summary The subcellular distribution of main steroids (pregnenolone, progesterone, corticosterone) and of cholesterol — this last after correction according to exchanges occuring during differential centrifugation — is presented in the rat adrenal cortex. The distribution patterns are not necessarly the same as established according to the localization of hydroxylating enzymes.This work was carried out under contract of the Ministère de la Politique Scientifique within the framework of the Association: Euratom, University of Brussels, University of Pise and also thanks to a grant of the Caisse Générale d'Epargne et de Retraite.     

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.     

Chromosome aberrations,micronuclei, and activity of superoxide dismutases in human lymphocytes after irradiation in vitro

The goal of this study was to provide data on the dose-dependent production of dicentrics and micronuclei in human lymphocytes irradiated with 22.6 MeV protons and to estimate the possible contribution of intracellular superoxide dismutases (SOD) to the relative biological effectiveness (RBE) of protons. For the dose-response study, heparinized whole blood of a healthy volunteer was irradiated with protons and X-rays employing radiation doses of 0.5-4 Gy. Three biological endpoints were analyzed: chromosomal aberrations, micronuclei, and specific activity of cytosolic (CuZnSOD) and mitochondrial (MnSOD) superoxide dismutases in harvested human blood cells. Dicentric dose-response curves fit a linear-quadratic form (alpha = 0.094 +/- 0.006, beta = 0.032 +/- 0.001) induced with X-rays and (alpha = 0.119 +/- 0.057, beta = 0.029 +/- 0.014) for 22.6 MeV protons. Protons were more effective than X-rays in producing exchanges, particularly at 0.5 and 1 Gy. In contrast to X-ray irradiated samples where a significant increase in the specific activity of MnSOD was recorded (up to a radiation dose of 1 Gy), irradiation with protons markedly reduced its activity. As a consequence of the reduced activity of MnSOD, the chromosomal dose-response curve became quadratic. The RBE for dicentrics varies with dose (from 2.2 to 1.01) and reduced activity of MnSOD is an important contributor to the RBE of protons. SODs, particularly MnSOD, play an important role in defending DNA from reactive oxygen species. A reduced activity of SOD, particularly MnSOD, is an important contributor to the RBE of protons.     

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.     

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.     

Release of synthesized lipids by isolated Wistar rat liver perfused by labelled oleic acid and glycerol]

After perfusions with oleic acid (9, 10-3H) and glycerol (1-14C) of isolated livers from wistar Rats, previously subjected to fasting, the study of the TG and PL synthesized by the liver and released in the circulation gives of evidence similar ways of metabolising TG and PL. Two liver pools are present: -- a storage pool, built with slow exchanges of AG of endogenous glycerolipids. In our experiments, the TG: 16 : 0 18 : 1 18: 2 and 16 : 0 18 : 1 18 : 1 and the PL: PE and PC are the glycerolipids of liver constitution: -- a pool of liver secretion. TG and PL are formed according to a rapid de novo synthesis using preferentially the exogenous substrates. They are released in the circulation. In our experiments, the TG secreted are the TG 18 : 1 18 : 1 18 : 1 and 16 : 0 18 : 1 18 : 2, the PL are the PE, AP and LPC.     

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.     

Estimating daily seasonality in foreign exchange rate changes

Combining time- and frequency-domain analysis demonstrates considerable improvement in modelling seasonal patterns in daily exchange rate changes. A high-pass filter in the frequency domain is used, followed by the usual time-domain analysis with GARCH models, to estimate day-of-the-week effects in the spot returns on five exchanges against US dollars and the results are seen to compare favourably with those from a pure time-domain GARCH approach.     

Sister chromatid exchanges in human lymphocytes exposed to 8-methoxypsoralen and long wave UV radiation prior to incorporation of bromodeoxyuridine

Summary Human lymphocytes exposed to the effects of long wave UV radiation in the presence of 8-methoxypsoralen prior to stimulation by PHA show dose related sister chromatid exchanges after 2 replication cycles in vitro. This has implications for interpreting the repair processes involved and for monitoring DNA damaging agents in vivo.     

Suppression of ‘dot-like’ echanges in C-bands and late replicating DNA-rich regions of chromosomes

Summary An apparent suppression of dot-like exchanges in C-bands and late replicating DNA-rich regions of chromosomes has been observed inAllium cepa. This result suggests that the occurrence of SCE very near each other could be avoided in these chromosomal regions.