Chemical induction of sister-chromatid exchanges in human lymphocytes treated in G0 prior to stimulation by different mitogens and revealed 72 h later in second division cells

A search for possible cytogenetic effects of low frequency vibrations in cultured human lymphocytes

1. Acute cytogenetic effects expressed as sister-chromatid exchanges (SCE) in peripheral blood lymphocytes were investigated after in vitro exposure to low vibration regimes (5-30 Hz. at 0.1 cm amplitude) for 20 min intervals and compared to non-vibrated control cultures. 2. There was no significant (P < 0.05) increase in the range of SCE incidence at any vibration frequency compared to the mean value of control; 6.88 +/- 0.11 to 7.97 +/- 0.22 versus 6.83 +/- 0.86, respectively. 3. When cultures were incubated for 1 h in the presence of 0.5 microgram ml-1 mitomycin C (MMC; the positive control) significant elevations in the SCE frequency were observed (19.81 +/- 0.67), indicating the sensitivity of the system to in vitro SCE induction. 4. Other cell parameters, such as mitotic index and cell proliferation index were statistically similar in the experimental cultures and the negative control. 5. The observed differences in the investigated end-points are considered within those typically found in vitro. This suggests no relation between low frequency vibrations and cytogenetic effects.

Sister-chromatid exchanges after exposure to metal-containing emissions

The effect of in vivo feeding of metal-containing emissions from an aluminum refining plant upon the induction of sister-chromatid exchanges (SCEs) and mitotic delay was investigated in cultured sheep lymphocytes. The experimental animals were given a daily dose of industrial emissions (mostly aluminum and fluoride) of either 0.75 g or 1.5 g/animal, for 1 year. The experiments were aimed at induction of chronic fluorosis under clinical conditions. A significant increase in mean serum fluoride, aluminum, arsenic and cadmium levels between both experimental groups and control was observed from 5 and 7 months on, respectively. The occurrence of SCEs in the experimental groups was higher (reaching statistical significance at a dose of 1.5 g/animal) than that seen in the controls. The emission was found to reduce the proliferation index. A significant heterogeneity of the first, second and third metaphases as compared to the controls was also observed.

Sister-chromatid exchanges induced by chloramphenicol on bovine lymphocytes

The induction of sister-chromatid exchanges (SCE) was studied in bovine lymphocyte cultures treated with chloramphenicol (CAP), an antibiotic agent in wide use in human and animal therapy. A total of six individuals, matched for sex, race, age and environmental conditions, were used for the analysis. Chloramphenicol was tested at four different concentrations (5, 10, 20 and 40 micrograms/ml) and acted for the last 24 h of the culture. Each experiment included two animals, each of which was exposed to all chloramphenicol doses, for a total of three repetitions. The results of the corresponding analysis of variance showed that this chemical had a small but statistically significant effect on the SCE frequency. In addition, the lymphocyte cultures responded strangely to this chemical: the highest SCE induction was produced by the lowest dose. However, the study of high frequency cells did not show the presence of this kind of cell which could explain this chloramphenicol response. In addition, chloramphenicol induced a high delay in the cell cycle.

Stable chromosome aberrations 25 years after severe accidental radiation exposure

A thorough cytogenetic analysis using G-banding was performed on 100 peripheral blood lymphocytes from an individual who had been accidentally exposed to radiation more than 25 years previously. More than 60% of the analysed cells were found to possess one or more stable chromosome aberrations (e.g. reciprocal translocations). Chromosomes 1 and 11 were more involved in these aberrations than would be expected from the relative chromosome lengths. No identical stable aberrations were found, suggesting that, 25 years after near-lethal exposure, haemopoietic stem cells display substantial diversity.

Sister-chromatid exchanges in human lymphocytes induced by dimethoate, omethoate, deltamethrin, benomyl and their mixture

Dimethoate and omethoate, two common organophosphorus insecticides, induced a dose-related increase in the frequency of sister-chromatid exchanges (SCEs) in human lymphocytes in vitro (P of the regression lines less than 0.01). Two other common pesticides, the pyrethroid insecticide deltamethrin and the systemic fungicide benomyl, induced a modest increase in SCEs which bordered on statistical significance (P = 0.053 and 0.055, respectively). Mixtures of the four pesticides at total concentrations of 41.5 and 83 micrograms/ml (composed of 43% dimethoate, 43% omethoate, 12% deltamethrin and 1.2% benomyl) induced a dose-dependent increase in SCEs (P less than 0.01). The effects of these mixtures of pesticides were variable using lymphocytes from different individuals, although these differences did not attain statistical significance. Moreover, low concentrations of the four pesticides that did not increase SCEs significantly when tested alone, were positive for SCE induction when tested as a mixture. The experiments show that sub-threshold doses of pesticides may increase SCEs when present in a mixture.

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.