Nitroso-aldicarb induces sister-chromatid exchanges in human lymphocytes in vitro

Nitroso-aldicarb was tested for its ability to induce sister-chromatid exchanges (SCE) and cell-cycle delay in human peripheral blood lymphocytes in vitro. This derivative of aldicarb induced a dose-dependent increase in SCE values per cell. In addition, a slight decrease in the successive mitotic progression of cells in culture was observed.     

Variation of superoxide dismutase levels in fetal calf serum

The results of cytogenetic studies and of other experiments based on tissue-culture systems may be influenced by various components of tissue-culture medium and by variations among batches of fetal calf serum used for supplementation of the media. Negative results may be obtained in breakage studies as a consequence of medium components with a protective effect [6]. Attention has been drawn to differences in growth pattern [8] and mitotic indices [11] in lymphocyte cultures set up with different culture media. Variations in the incidence of sister-chromatid exchanges according to differences in media [7] and sera [5] have also been observed. It has been suggested [9] that the failure of some laboratories to detect increases in sister-chromatid exchanges after treatment with the tumor promoter phorbol-myristate-acetate (PMA) may be due to high concentrations of the free-radical-scavenging enzyme superoxide dismutase (SOD) in the sera used and that heat inactivation of the sera may be responsible for these differences. In the following, we report that considerable variation in the SOD content exists between batches of fetal calf serum, up to levels with anticlastogenic effect.     

Chromosomal aberrations and sister-chromatid exchanges in Chinese hamster cells treated in vitro with hexavalent chromium compounds.

Chinese hamster cells (CHO line) were treated in vitro for 30--39 h with hexavalent chromium compounds (K2Cr2O7 and Na2CrO7), at concentrations ranging from 0.1 to 1.0 microgram of Cr6+ per ml, in medium containing BUdr. Chromosomal aberrations and sister-chromatid exchanges were scored on BUdr-labelled 2nd division metaphases, collected at the end of treatment and stained with Giemsa. Treatment with mitomycin C 0.009--0.030 microgram/ml) was carried out as a control for the responsiveness of the cell system to chromosomal damage. Both chromium compounds induced marked mitotic delays. Chromosomal aberrations were increased about 10-fold by exposure to Cr6+ (1.0 microgram/ml). The principal aberrations observed were single chromatid gaps, breaks and interchanges, whose frequencies increased proportionally to the concentration of chromium. Dicentric chromosomes, isochromatid breaks, chromosome and chromatid rings were also induced. The frequenyc of sister-chromatid exchanges was hardly doubled 30 h after exposure to Cr6+ at 0.3 microgram/ml, whereas it was trebled 39 h after treatment, in the cells whose division cycle had been slowed down by chromium.     

Cytogenetic damage induced in human lymphocytes by sodium bisulfite.

The frequencies of chromosomal aberrations (CA), sister-chromatid exchanges (SCE), and micronuclei (MN) in human blood lymphocytes exposed to sodium bisulfite (sulfur dioxide) at various concentrations ranging from 5 x 10(-5) M to 2 x 10(-3) M in vitro were studied. It was shown that sodium bisulfite (NaHSO3 and Na2SO3, 1:3 M/M) caused an increase in SCE and MN in human blood lymphocytes in a dose-dependent manner, and also induced mitotic delays and decreased mitotic index. For CA, our results indicated that sodium bisulfite induced an increase of chromatid-type aberrations in lymphocytes from three of four donors in a dose-dependent manner. The chemical at low concentrations induced chromatid-type aberrations, but not chromosome-type aberrations; high concentrations induced both chromatid- and chromosome-type aberrations. No cytogenetic damage in human lymphocytes was induced by sodium sulfate. The results have confirmed that sulfur dioxide is a clastogenic and genotoxic agent.     

Analysis of sister-chromatid exchanges, cell kinetics and mitotic index in lymphocytes of smoking pesticide sprayers

Whole blood of 50 smokers who were exposed to pesticides was set up in RPMI 1640 medium, and observed for sister-chromatid exchanges (SCEs), cell kinetics (CK) and mitotic index (MI). As controls, blood samples were collected from 20 non-smokers (control I) and 27 smokers (control II) who were not exposed to pesticides. A significant increase in SCEs was observed as the duration of exposure increased. The frequency of M1 metaphases increased significantly whereas M2 and M3+ metaphases decreased in the exposed group. The mitotic index increased in control II and in the exposed population while it showed a decrease at 11-25 years' exposure.     

Mouse bone marrow cytogenetic damage produced by residues of tequila

Five concentrations (50-860 mg/kg) of residues obtained after distillation and lyophilization of commercial tequila were injected into mice for evaluation of chromosome aberrations, sister-chromatid exchanges, and proliferation kinetics in mouse bone marrow cells. Appropriate positive and negative controls were included. Our results showed significant dose-related increases of chromosomal aberrations starting at 50 mg/kg and for sister-chromatid exchanges at 430 mg/kg. Cellular proliferation kinetics showed no alterations. With these data we demonstrated that the residues of tequila are genotoxic in vivo.     

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.     

Sister-chromatid exchange (SCE) among individuals chronically exposed to arsenic in drinking water

A study was carried out on human subjects of various ages and backgrounds who had been drinking water containing more than 0.13 mg/l (0.13 ppm) arsenic for a period of at least 20 years. The main aim was not only to correlate the frequency of sister-chromatid exchanges in the lymphocytes with the amount of arsenic in water and urine but also to correlate the frequency of SCE with sex and age. In addition, family background regarding skin alterations or other arsenic-related symptoms was explored, so that individual health conditions could be assessed. External factors such as exposure to other chemical or contaminating agents (pesticides, battery manufacturing plants, foundries) were also taken into consideration. The data on sister-chromatid exchanges (282 exposed and 155 control individuals) showed that arsenic at concentrations used by our population (0.13 mg/l) induced a significantly elevated response. Other health effects of arsenic at these concentrations were found, e.g., hyperkeratosis, melanosis, actinic keratosis, basal cell carcinoma.     

Induction of chromosome damage and sister-chromatid exchanges in human lymphocyte cultures by the antitumour antibiotic Neocarzinostatin

Neocarzinostatin (NCS), a chemotherapeutic antibiotic, was investigated for the ability to induce chromosomal aberrations and sister-chromatid exchanges (SCEs) in human lymphocyte cultures. It was observed that the antibiotic causes a cell-cycle delay and reduces the mitotic index. Analysis of the induced chromosomal abnormalities showed that they are mainly chromosome and chromatid breaks; while the frequency of SCEs was increased, the magnitude indicates that NCS cannot be considered a potent inducer of SCEs.     

Cytological effects of 60 Hz magnetic fields on human lymphocytes in vitro: sister-chromatid exchanges, cell kinetics and mitotic rate

Incubation for 72 h of human peripheral blood cultures in the presence of 60 Hz sinusoidal magnetic fields (MF) at magnetic flux densities of 1.0, 1.5, and 2.0 mT led to stimulation of lymphocyte proliferation but had no influence on the frequency of sister-chromatid exchanges (SCE). The cytotoxic potential of MF combined with the mutagen Mitomycin-C also was analyzed. An opposite effect between MF exposure and Mitomycin-C treatment in terms of cell kinetics and mitotic rate was found, whereas no variation in SCE frequency was observed for this coexposure condition.     

Indirect mechanism of lead-induced genotoxicity in cultured mammalian cells

The data concerning the mutagenic, clastogenic and carcinogenic properties of inorganic lead compounds have been conflicting. To investigate whether the genotoxicity of lead is due to indirect effects such as interference with DNA-repair processes, the induction of mutations, sister-chromatid exchanges and strand breaks by lead ions alone as well as in combination with UV light as a standard mutagen were determined. Lead acetate alone does not induce DNA-strand breaks in HeLa cells or mutations at the HPRT locus and sister-chromatid exchanges in V79 Chinese hamster cells. However, at all endpoints tested, lead ions interfere with the processing of UV-induced DNA damage. They inhibit the closing of DNA-strand breaks after UV irradiation and enhance the number of UV-induced mutations and sister-chromatid exchanges, indicating an inhibition of DNA repair. These data point out the necessity to consider such indirect effects when assessing the genotoxicity of metal compounds. As possible mechanisms of repair inhibition we suggest either the interaction with repair enzymes such as polymerase or ligase or else the interaction with calcium-regulated processes, for example with calmodulin.     

cis-diamminedichloroplatinum(II)-induced sister-chromatid exchanges and chromosome aberration formation in cultured human lymphocytes and their inhibition by sodium thiosulfate

cis-Diamminedichloroplatinum(II) (cis-DDP)-induced sister-chromatid exchanges (SCEs) and chromosome aberration formation were studied in human lymphocytes. The mitotic index decreased abruptly at 2 X 10(-6) M cis-DDP and the frequency of SCEs was dose-related; a marked increase was recorded at 10(-6) M cis-DDP. A dose-dependent effect was also found for chromosome aberration formation at concentrations between 10(-11) and 4 X 10(-6) M. The aberrations observed were primarily chromatid breaks and gaps. We also examined the inhibition of these genotoxicities by treating the cells with sodium thiosulfate (STS). Simultaneous treatment with 10(-4)-10(-3) M STS (100-1000-fold molar ratio to cis-DDP) significantly reduced the frequency of SCEs induced by 10(-6) M cis-DDP. Furthermore, a 3-h delay in treating with STS significantly reduced cis-DDP-induced SCEs, but not chromosome aberration formation.     

Cytogenetic effects of airborne particulate matter in human lymphocytes in vitro

City smog was collected in a heavily industrialized area and investigated for its ability to induce cytogenetic effects in human lymphocytes in vitro. Total extract of city smog was found to produce sister-chromatid exchanges and chromosomal aberrations in a dose-dependent manner. In addition cell-cycle delay was observed at higher concentrations of city smog extract. Results of cytogenetic testing are discussed with respect to cell-cycle kinetics.     

Chromosomal aberration and sister-chromatid exchange frequencies in peripheral blood lymphocytes of a large human population sample

In order to assess the potential of cytogenetic determinations on peripheral blood lymphocytes as a means of monitoring human populations subject to low level occupational and environmental exposures to chemical mutagens and carcinogens, accurate baseline data are required. Accordingly, we have determined mean frequencies of chromosomal aberrations and of sister-chromatid exchanges, their variances, and the sources of this variance in a cohort of 353 healthy employees of the Brookhaven National Laboratory. A detailed protocol was adopted for blood sampling, lymphocyte culture, cytogenetic preparation and scoring in order to minimize variation from these potential sources. Scoring was divided between the Oak Ridge and the Brookhaven groups with duplicate scoring sufficient to evaluate and minimize the effect of any differences between laboratories or between individual scorers. In all, the data include 71,950 cells scored for chromosomal aberrations and 16,898 cells scored for sister-chromatid exchanges. The mean unadjusted frequency of sister-chromatid exchanges was 8.29 +/- 0.08/cell. As reported in other studies, cigarette smoking very significantly influenced sister-chromatid exchange frequencies; in our study the mean for smokers was 9.0 +/- 0.2, while that for non-smokers was 8.1 +/- 0.1/cell. The mean frequency was statistically higher in females than in males, regardless of smoking status. On the other hand, age of the subject did not significantly influence sister-chromatid exchange frequencies. Curiously, the subject's total white cell count did influence sister-chromatid exchange frequency. No other source of variation was found. The frequencies of chromosomal aberrations of all types were determined. The frequency of the most common unequivocal chromatid type, the chromatid deletion, was 0.81 +/- 0.05%, that of the most common unequivocal chromosome type, the dicentric, was 0.16 +/- 0.02%. No statistically significant influence was found of age or sex, nor of any other parameter tested, on the frequency of any chromosomal aberration type, with the single exception of long acentric fragments, often "supernumerary", believed to represent X chromosomes precociously separated at the centromere. Such fragments were significantly more frequent in samples from females than those from males, and showed a significant positive regression on age.     

Induction of sister-chromatid exchanges in Chinese hamster ovary cells by the biotic ketoaldehyde methylglyoxal

The number of sister-chromatid exchanges (SCEs) per metaphase was determined in Chinese hamster ovary cells after 16 h exposure to methylglyoxal (MG) concentrations ranging from 0.1 to 0.75 mM. MG produced an increase of SCE frequency that proved to be dose-dependent, and to reach a maximum of 2 X baseline at the highest nontoxic concentration (0.5 mM).     

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.     

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.     

Effects of a tumor promoter and an anti-promoter on spontaneous and UV-induced 6-thioguanine-resistant mutations and sister-chromatid exchanges in V79 Chinese hamster cells

The effects of a tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and/or an anti-promotor antipain (protease inhibitor) on spontaneous and ultraviolet-induced sister-chromatid exchanges (SCEs) and 6-thioguanine- resistant (6TG^r) recessive mutations were examined in V79 Chinese hamster cells in culture. TPA and/or antipain neither significantly altered base-line and UV-induced immediate SCE frequencies, nor decreased the level of delayed SCEs which persisted 6–7 days after irradiation. TPA and/or antipain appeared to enhance the recovery of UV-induced 6TG^r colonies at the plateau expression phase despite non-mutagenicity by themselves and unaltered metabolic co- operation. Thus, the results conceivably imply that the 6TG^r-recessive mutation expression, but not fixation, can be modulated at the cell level by the TPA and/or antipain. Our results, together with the recent results of Loveday and Latt, may argue against the notion that TPA enhances the antipain-suppressible SCEs as an index of mitotic recombination in relevance with a tumor-promotion mechanism.     

Acrylonitrile-induced sister-chromatid exchanges and DNA single-strand breaks in adult human bronchial epithelial cells

The ability of acrylonitrile to induce cytotoxicity, sister-chromatid exchanges and DNA single-strand breaks was studied in cultured human bronchial epithelial cells. The toxic effect as determined by cloning efficiency was observed at a dose of 600 micrograms/ml but not at doses of both 150 and 300 micrograms/ml. The frequency of sister-chromatid exchange in untreated cells was 3.7 +/- 1.3 per cell. In contrast, cells treated with acrylonitrile at 150 and 300 micrograms/ml exhibited 6.6 +/- 1.3 and 10.7 +/- 1.7 sister-chromatid exchanges per metaphase, respectively. DNA single-strand breaks were induced by acrylonitrile at dose levels of 200 and 500 micrograms/ml. The genotoxic effects on human bronchial epithelial cells that were directly exposed to acrylonitrile are of interest in relation to evidence for the higher lung cancer incidence of acrylonitrile workers in epidemiological studies.     

Abnormal sister-chromatid exchange induction by 3-aminobenzamide in an SV40-transformed Indian muntjac cell line: relationships with DNA maturation and DNA-strand breakage.

In SVM cells, an SV40-transformed line of Indian muntjac fibroblasts, levels of sister-chromatid exchanges are known to be abnormally high after UV-irradiation or alkylation. The SVM line is also known to have a defect in the processing of DNA-strand breaks. Sister-chromatid exchange in other cells is known to be stimulated by the poly(ADP-ribose) transferase inhibitor, 3-aminobenzamide, which also retards DNA-break sealing. Sister-chromatid exchanges in SVM cells are found to be hypersensitive to 3-aminobenzamide, or to nicotinamide deprivation which similarly inhibits poly(ADP-ribosyl)ation; DNA-strand breaks are likewise induced by 3-aminobenzamide. Bromodeoxyuridine, needed to detect sister-chromatid exchanges, is more toxic to SVM cells and itself induces sister-chromatid exchanges to a greater extent than it does in normal muntjac cells. However, in contrast to the situation reported for other cell types prone to sister-chromatid exchange (the Chinese hamster ovary mutant EM9 and human Bloom's Syndrome cells), SVM cells do not show an abnormal delay in DNA maturation when, under the influence of bromodeoxyuridine and 3-aminobenzamide, they show a high level of sister-chromatid exchange. The mechanism by which BrdU exerts its effects can largely be explained in terms of familiar effects on deoxyribonucleotide pools and DNA integrity. 3-Aminobenzamide, however, induces sister-chromatid exchanges in SVM cells by another mechanism.