Enhancement by caffeine of sister-chromatid exchange frequency induced by antineoplastic agents in human lymphocytes

Summary The SCE frequency induced by Thiotepa and the effect of this antineoplastic drug in combination with caffeine have been studied in cultures of human peripheral blood. Caffeine was found to enhance SCE and breakage frequencies induced by Thiotepa in human lymphocytes.Acknowledgment. I am deeply grateful to Dr M.J.W. Faed, for stimulating discussions, guidance and constructive criticism. This paper is a part of my Ph.D. thesis submitted to Dundee University.     

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.     

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 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.     

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.     

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.     

In vitro enhancement of human platelet aggregation by somatostatin

Summary Very low concentrations of somatostatin (S-14) strongly potentiate the in vitro aggregation induced by collagen, ristocetin and arachidonic acid, but not that induced by ADP or epinephrine, in both human platelet rich plasmas and gel-filtered platelet preparations. Desensitization phenomena may be induced either by repeated addition of S-14 or long lasting contact between S-14 and platelets.     

In vitro enhancement of human platelet aggregation by somatostatin

Very low concentrations of somatostatin (S-14) strongly potentiate the in vitro aggregation induced by collagen, ristocetin and arachidonic acid, but not that induced by ADP or epinephrine, in both human platelet rich plasmas and gel-filtered platelet preparations. Desensitization phenomena may be induced either by repeated addition of S-14 or long lasting contact between S-14 and platelets.     

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.     

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.     

Steroid hormones enhanced sister-chromatid exchange in cultured CHO cells

The influence of steroid hormones on the induction of sister-chromatid exchange (SCE) in cultured CHO cells was studied. It was observed that estradiol-17 beta, estriol, estrone and ethynyl estradiol treatments enhanced SCE rates compared to the controls. Overall, these compounds produced a dose response effect. The importance of a detailed study on the long-term genetic effects of steroids on mammalian cells is emphasized.     

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.     

Steroid hormones enhanced sister-chromatid exchange in cultured CHO cells

Summary The influence of steroid hormones on the induction of sister-chromatid exchange (SCE) in cultured CHO cells was studied. It was observed that estradiol-17 , estriol, estrone and ethynyl estradiol treatments enhanced SCE rates compared to the controls. Overall, these compounds produced a dose response effect. The importance of a detailed study on the long-term genetic effects of steroids on mammalian cells is emphasized.This work was supported by NIH-Minority Biomedical Research Support Program (MBRS), Grant No. RR 08124-11. The author is thankful for the technical assistance provided by NIH-MBRS student, Hoang Duong.     

Platelet aggregation and stimulation of leucocyte procoagulant activity by rickettsial lipopolysaccharides in rabbits and in man

Summary The effects in vitro of 4 purified lipopolysaccharide (LPS) preparations from Rickettsiae on platelets and leucocytes were studied in rabbits and in man. All LPS induced aggregation in rabbit platelet-rich plasma but to differing degrees. This activity was abolished by inactivation of complement. None of the preparations induced aggregation of human platelets. Both rabbit and human leucocytes, when incubated with each of the rickettsial LPS preparations, generated a potent procoagulant activity (tissue factor). These findings add further support to the concept that rickettsial LPS behave as typical LPS from gram-negative bacteria and may be relevant to the understanding of the mechanism(s) responsible for triggering intravascular coagulation in rickettsial diseases.     

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.     

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.     

Inhibition of new blood vessel formation in mice by systemic administration of human rib cartilage extract

1 M HCl-guanidine extract of human funnel chest rib cartilage administered i.v. to mice decreased specifically vasoproliferation induced by intradermal injection of allogeneic murine lymphocytes.     

The alcohol syndromes: the intrarecombigenic effect of acetaldehyde

Sister chromatid exchange was studied in lymphocyte and fibroblast cultures. Alcohol caused no disturbance under normal conditions but an acetaldehyde level above 40 muM inhibited cell multiplication and elevated SCE considerably. A high acetaldehyde level is thought to elicit the fetal alcohol syndrome, a view supported by clinical and experimental observations.     

Possible mutagenic activity of saccharin

Summary A mutagenic effect of saccharin in Chinese hamsters, using the in vivo SCE test, was observed when massive overdoses were administered; cyclamate was not mutagenic.     

Possible mutagenic activity of saccharin.

A mutagenic effect of saccharin in Chinese hamsters, using the in vivo SCE test, was observed when massive overdoses were administered; cyclamate was not mutagenic.