Spontaneous sister-chromatid exchange frequencies in human B and T lymphocytes at BrdU borderline concentrations for sister-chromatid differentiation

Human peripheral blood B and T lymphocytes, highly purified by immunologic methods, were supplemented with gamma-irradiated unseparated autologous mononuclear cells to restore helper functions and stimulated with pokeweed mitogen and phytohemagglutinin, respectively. Spontaneous sister-chromatid exchange (SCE) frequencies were investigated in proliferating B and T lymphocyte cultures labeled with the cell-type-specific borderline concentrations of 5-bromodeoxyuridine (BrdU) for sister-chromatid differentiation (SCD). B lymphocytes from 6 different donors showed mean values of 3.28-3.72 SCE events/cell. In T lymphocytes, mean values of 6.30-7.28 SCEs/cell were observed. The differences between the SCE distributions of the cell populations are highly significant. The results show that the differences in the spontaneous SCE frequencies between human B and T lymphocytes were not due to a difference in the uptake of BrdU.     

In vitro genotoxic effects of the anticancer drug gemcitabine in human lymphocytes

This research was carried out to investigate in vitro genotoxic effects of the anticancer agent gemcitabine on the induction of chromosomal aberrations and sister-chromatid exchange in human lymphocytes. Three doses of gemcitabine (0.001, 0.002 and 0.004 microg/ml) were applied to lymphocyte cultures from 15 donors. There was a significant increase in the induction of chromosome aberrations and in the occurrence of sister-chromatid exchange in these cells. In addition, gemcitabine significantly decreased the mitotic index and replicative index for all doses. Dose-response regression lines were used to compare the individual susceptibilities to gemcitabine with respect to the chromosome aberration and sister-chromatid exchange frequencies. Our results indicate that gemcitabine is able to induce both cytotoxic and genotoxic effects in human lymphocyte cultures in vitro in a dose-dependent manner.     

Baseline and mutagen-induced sister-chromatid exchanges in cultures of human whole blood and purified fresh or frozen lymphocytes

Baseline and mutagen-induced levels of sister-chromatid exchanges were evaluated in 10 normal individuals. Cultures with whole blood or purified lymphocytes, either freshly isolated or after 1 or 6 months of cryopreservation, were analyzed to determine whether frozen lymphocytes are suitable for SCE studies. Whole blood and freshly isolated lymphocytes were cultured from samples taken at the beginning of the study (Time 0) and 6 months later (Time 6). Cryopreserved lymphocytes were recovered after 1 month (Time 1) and 6 months (Time 6) of cryopreservation and then challenged with mutagens in culture. The mutagens used were mitomycin C, 4-nitroquinoline-1-oxide, and N-methyl-N'-nitro-N-nitrosoguanidine. Purified lymphocytes had consistently and significantly higher baseline SCE frequencies than cells from whole blood cultures and were more sensitive to N-methyl-N'-nitro-N-nitrosoguanidine and 4-nitroquinoline-1-oxide. The response to mitomycin C was similar in all culture types. There was, overall, no consistent effect of freezing on baseline or induced sister-chromatid exchange frequencies in the purified lymphocytes. This suggests that purification and cryopreservation of human lymphocytes does not alter the baseline or mutagen-induced sister-chromatid exchange response and in certain epidemiological, occupational and monitoring situations may have logistical and technical advantages over the use of fresh whole blood.     

No increase in sister-chromatid exchange frequency in lymphocytes of chromium platers

To detect mutagenic effects of hexavalent chromium (Cr) in vivo, sister-chromatid exchange (SCE) frequency was analyzed in lymphocytes of 24 Cr platers occupationally exposed to hexavalent Cr and 24 matched controls. There were no significant differences in SCE frequency between the two groups. Smokers, both Cr platers and controls, had a significantly higher SCE frequency than non-smokers.     

Frequencies of sister-chromatid exchanges in relation to cell kinetics in lymphocyte cultures

The frequency of sister-chromatid exchanges (SCE) was determined on second-division metaphase of lymphocytes stimulated by phytohaemagglutinin (PHA) during 9 days of culture.

By using either a continuous or a pulsed bromodeoxyuridine (BUdR) treatment, cells were selected that had divided only twice, or at least twice, after different culture periods. No significant differences were observed in the SCE frequencies among the various samples. The incidence of SCE appears to be independent of the proliferation properties of cultured lymphocytes, such as length of cell cycle, fast or delayed response to PHA and number of divisions performed in vitro.     

The effect of fluoride on chromosome aberration and sister-chromatid exchange frequencies in cultured human lymphocytes

Sodium fluoride, at concentrations of up to 60 times the level normally used in drinking water for the prevention of dental decay, was compared with 2 other inorganic salts for its ability to induce chromosome aberrations and sister-chromatid exchanges (SCE) in cultured human lymphocytes. No significant increases in the frequencies of aberrations of SCEs were found.     

Mitomycin C and ethyl methanesulphonate-induced sister-chromatid exchanges in lymphocytes from individuals with Alzheimer's pre-senile dementia

Baseline and mutagen-induced sister-chromatid exchange frequencies were compared in peripheral blood lymphocytes from patients with Alzheimer's pre-senile dementia and control individuals. No significant differences were found between the two groups.     

Cytogenetic monitoring of petrochemical workers

The frequencies of chromosomal aberrations and sister-chromatid exchanges (SCEs) in the peripheral blood lymphocytes of 360 persons, 180 workers in a petrochemical corporation and 180 appropriate controls, were studied. A significant increase in chromosomal aberrations and SCEs, compared to the control group, was observed in two sewage-treatment workshop workers; however, there were no significant differences between petrochemical workers from four workshops and a control group.     

Sister-chromatid exchanges in lymphocytes of workers exposed to trichloroethylene

To detect mutagenic effects of trichloroethylene (TCE) on humans, sister-chromatid exchanges (SCEs) were analyzed in lymphocytes of 22 workers occupationally exposed to TCE and 22 matched controls. Although urinalysis in the workers revealed their obvious exposure to TCE, no increase in SCE frequencies was found in lymphocytes of the workers. SCE analysis in lymphocytes could not detect mutagenic effects by occupational exposure to TCE on humans.     

A genetic study of human interferon-alpha-induced repair of DNA damage in hepatitis B patients

In vitro treatment with human interferon-alpha (HuIFN-alpha) of hepatitis B virus-infected peripheral lymphocytes from 17 hepatitis B patients induced a decrease in the frequency of sister-chromatid exchanges (SCE). There was a significant difference in mean SCE frequencies between the HuIFN-alpha-treated patients and the control group, but not between acute and chronic hepatitis B patients treated with HuIFN-alpha.     

In vitro induction of chromosome damage by sulphasalazine in human lymphocytes

Two different endpoints, sister-chromatid exchange and micronucleus induction, were measured in human peripheral blood lymphocytes stimulated to divide in short-term in vitro cultures. The cultures were exposed to sulphasalazine and 6 of its metabolites for 72 h in the absence of any exogenous metabolic activation system. Analysis of the sister-chromatid exchange and micronuclei frequencies clearly indicates that sulphasalazine itself is capable of inducing both sister-chromatid exchange and micronuclei while sulphapyridine and its acetylated metabolites only induce sister-chromatid exchange. 5-Aminosalicylic acid, the therapeutic moiety of sulphasalazine, and its acetylated metabolite did not induce either sister-chromatid exchange or micronuclei at the concentrations tested. The data from these in vitro experiments are discussed in relation to the previously reported elevations in sister-chromatid exchange and micronucleus frequencies in inflammatory bowel disease patients receiving sulphasalazine therapy.     

The mutagenic effect of benzene, toluene and xylene studied by the SCE technique.

In experiments in vitro, neither benzene, toluene nor xylene changed the number of sister-chromatid exchanges (SCEs) or the number of chromosomal aberrations in human lymphocytes. Toluene and xylene caused a significant cell growth inhibition which was not observed with benzene in the same concentrations.     

Hypotonic treatment leads to chromosomal aberrations but not to sister-chromatid exchanges in human lymphocytes

Human peripheral lymphocytes were isolated from whole blood and exposed to culture medium of reduced osmolality. This hypotonic treatment led to a significant increase in the frequencies of chromosomal aberrations when the osmolality was reduced to 60 mOsm/kg H2O and below. Maximum damage occurred when the hypotonic treatment was done 27 or 30 h after starting the cultures. We also looked for the induction of sister-chromatid exchanges (SCE) by hypotonic culture conditions, but the SCE frequencies were not influenced.     

Alterations in the baseline sister-chromatid exchange frequency in human lymphocyte culture following a number of cell divisions

A significant decrease in the baseline of sister-chromatid exchanges (SCEs) was observed in cultured human lymphocytes, if 5-bromodeoxyuridine (BrdU) was added after 60 h of culture, and the cells were harvested at least 24–30 h after BrdU exposure. This decrease is supposed to occur if at least one cell division takes place before the addition of BrdU. For cytogenetic monitoring of mutagenic environmental factors, using human lymphocyte cultures, it is assumed that two time periods are sufficient for comparison.     

Repair of sister-chromatid exchange-inducing lesions in mutagen-treated cultures of human whole blood and purified fresh or frozen lymphocytes

Repair of mutagen-induced lesions that result in sister-chromatid exchanges was evaluated in 10 normal individuals. The mutagens used were mitomycin C (MMC), 4-nitroquinoline 1-oxide (4NQO), and N-methyl-N'nitro-N-nitrosoguanidine (MNNG). Cultures of whole blood, freshly purified lymphocytes, or purified lymphocytes cryopreserved for 6 months were analyzed after the mutagen treatments. All 3 mutagens induced reparable damage as evaluated by comparison of sister-chromatid exchanges between cultures that were given time to repair induced damage before 5-bromo-2'-deoxyuridine (BrdUrd) was added to the culture medium with those where BrdUrd was added immediately after the administration of the mutagens (MMC or 4NQO) or at culture initiation (MNNG). Repair of mutagen-induced DNA damage was detected in all 3 culture types; thus cryopreservation did not appear to alter the capacity of lymphocytes to repair mutagen-induced lesions. Quantitative differences in apparent repair capabilities were observed among individuals. Variability also existed among the different culture types within an individual, suggesting that caution should be exercised in interpreting these apparent differences.     

Analysis of chromosome aberrations and sister-chromatid exchanges in peripheral blood lymphocytes of workers with occupational exposure to the mancozeb-containing fungicide Novozir Mn80

Chromosome aberrations and sister-chromatid exchanges (SCEs) were analyzed in short-term cultures of peripheral lymphocytes of 44 workers occupationally exposed to mancozeb during the production of the pesticide Novozir Mn80 and 30 control persons. The results suggest that mancozeb exposure was associated with a significant increase in the frequencies of cells with structural chromosome aberrations (2.07% vs. 1.10% in the controls), and the number of SCEs per cell (9.19 +/- 1.81 vs. 7.82 +/- 1.04 in the controls).     

Effects of theophylline on chromosomal breakage and sister-chromatid exchange

Frequencies of both sister-chromatid exchange (SCE) and chromosomal breakage (CB) were studied in the lymphocytes of normal individuals (10 and 7 individuals respectively). The cells were exposed in vitro to 3 different concentrations of theophylline (1, 10 and 100 micrograms/ml). A significant concentration effect of the drug was demonstrated for both SCEs and CB. Utilizing a Dunnett's test for individual comparisons, the 10 and 100 micrograms/ml concentrations both demonstrated a significant elevation of SCEs and CB compared to the untreated control cultures. This study suggests that in vitro concentrations of theophylline equal to or greater than 10 micrograms/ml, corresponding to serum levels attained during therapy, increase the frequency of SCEs and chromosome breakage in human lymphocytes.     

Influence of dietary carrot on cytostatic drug activity of cyclophosphamide and its main directly acting metabolite: induction of sister-chromatid exchanges in normal human lymphocytes, Chinese hamster ovary cells, and their DNA repair-deficient cell lines

We have utilized an in vivo drug metabolism technique (i.e. injecting the chemical into rat and isolating plasma with metabolites from blood) for detecting the genotoxicity of indirectly acting cyclophosphamide and its directly acting metabolite phosphoramide mustard in cultures of human peripheral blood lymphocytes of normal individuals, Fanconi's anaemia (FA) and aplastic anaemia (AA) patients, wild-type Chinese hamster ovary cells (CHO) and its DNA repair-deficient mutant 43-3B cells. In addition, the influence of dietary carrot on the clastogenic activity of these 2 chemicals in all the different cell types was studied. The genotoxicity was assessed by the ability of the metabolites of these agents to induce sister-chromatid exchanges in the treated cells. A dose-dependent increase in the frequencies of sister-chromatid exchanges was observed in all cell strains following treatment with activated metabolites of cyclophosphamide or phosphoramide mustard. The sensitivity of lymphocytes from normal donors, FA and AA patients to these 2 chemicals was similar. In CHO cell lines the induced frequency of sister-chromatid exchanges was slightly higher after treatment with the metabolites of cyclophosphamide than with phosphoramide mustard. The mutant 43-3B cells responded with higher frequencies of SCEs when compared to the wild-type CHO cells, about 1.5-2-fold, at low doses. Pretreating of rats with fresh carrot juice effectively inhibited the increase in the frequencies of sister-chromatid exchanges induced by cyclophosphamide in wild-type and mutant CHO cells (P less than 0.01), and to a lesser extent in human lymphocytes (p less than 0.05). In contrast, no inhibitory effect was observed in any of these cell types in combination of dietary carrot for direct acting phosphoramide mustard on the frequency of induced sister-chromatid exchanges. The possibility that dietary carrot exerts its antimutagenic effect by affecting the processes of enzymatic activation of cyclophosphamide is discussed.     

A genetic study of human interferon-α-induced repair of DNA damage in hepatitis B patients

In vitro treatment with human interferon-α (HuIFN-α) of hepatitis B virus-infected peripheral lymphocytes from 17 hepatitis B patients induced a decrease in the frequency of sister-chromatid exchanges (SCE). There was a significant difference in mean SCE frequencies between the HuIFN-α-treated patients and the control group, but not between acute and chronic hepatitis B patients treated with HuIFN-α     

Cytogenetic monitoring of chemical workers in production of the drug 1-propoxy-2-acetamino-4-nitrobenzol with reference to their smoking habits

The induction of chromosome aberrations (CAs) and sister-chromatid exchanges (SCEs) was examined in cultured lymphocytes from 23 individuals employed in the production of the drug 1-propoxy-2-acetamino-4-nitrobenzol. Lymphocytes of workers were cultured before and 13 weeks after starting professional activity. The latter showed a significant increase in both CAs and SCEs. Smokers (11 individuals) and non-smokers (12 individuals) were indistinguishable with respect to the frequencies of CAs or SCEs before starting professional activity, 13 weeks later smokers exhibited significantly more SCEs than non-smokers. This strongly suggests a comutagenic interaction of cigarette smoke and exposure to chemicals during drug production. On the basis of the technology applied the compound inducing CAs and SCEs in lymphocytes of smoking workers seems to be 2-acetamino-4-nitrophenol.