[Show abstract][Hide abstract] ABSTRACT: The spontaneous level of sister chromatid exchanges (SCEs) in the sheep, estimated by exposing peripheral blood lymphocytes in 0.1 microgram/ml of 5'-bromodeoxyuridine (BrdU), was 4.08 +/- 2.47 SCE/cell, 2.04 SCE/cell cycle, 0.038 SCE/chromosome. The dose-response relationships, observed by exposing the cells to 0.1, 0.25, 0.5, 1.0, 2.5, and 5.0 micrograms/ml of BrdU, rose rapidly from 0.1 to 0.25 microgram/ml, and less rapidly at higher concentrations, thus reaching a saturation level. The analysis of variance, performed on the square root transformed data at 0.1 and 5 micrograms/ml of BrdU, indicated significant differences (P < 0.001) among the four donors tested. The distribution of the SCE/cell frequencies in the cell population of the four donors followed the Poisson 'mixture' probability function, thus confirming previous findings. The spontaneous rate of SCE/cell of sheep is compared with those previously reported for cattle, goat and river buffalo. The theoretical and practical implications of the spontaneous sister chromatid exchanges are discussed in relation to their possible use in animal production for (a) better genetic evaluation of the breeding animals under selection, (b) more precise monitoring of the genotoxic effects of environmental pollutants.
[Show abstract][Hide abstract] ABSTRACT: A differential sister chromatid exchange (SCE)/cell response was observed between phytohemagglutinin (PHA) and pokeweed (PKW) stimulated blood lymphocytes of goat (Capra hircus L) exposed to final concentrations of 0.1, 0.25, 0.5, 1, 2.5 and 5 μg/mL of BUdR. At 0.1 μg/mL of BUdR, the two mitogens gave very similar SCE/cell responses: the SCE mean values were 3.17 ± 1.93 for PHA and 3.28 ± 1.76 for PKW, and the frequency distributions fit very well the Poisson probability function with both mitogens. For 0.25 μg/mL and increasing BUdR concentrations, SCE/cell rates for pokeweed mitogen were significantly higher than those of PHA. At 5 μg/mL of BUdR, the SCE/cell response was 8.68 ± 3.24 for PKW and 6.96 ± 3.45 for PHA, and the difference was statistically significant (P = 0.0001); for both mitogens the SCE/cell frequency distributions fit the Poisson probability function only by adopting a Poisson 'mixture' model, which takes into account the presence of two different subpopulations of cells.
[Show abstract][Hide abstract] ABSTRACT: The spontaneous level of sister chromatid exchange (SCEs) in the goat, estimated by exposing peripheral blood lymphocytes to 0.1 microgram/ml of 5-bromodeoxyuridine (BrdU), was 3.28 +/- 1.71 SCE/cell, 1.64 SCE/cell generation and 0.027 SCE/chromosome. The dose-response curve of SCE/cell, observed by exposing the cells to 0.1, 0.25, 0.5, 1.0, 2.5, and 5.0 micrograms/ml of BrdU, rose rapidly from 0.1 to 0.5 microgram/ml, remained fairly stable from 0.5 to 1.0 microgram/ml and rose less rapidly from 1.0 to 5.0 micrograms/ml of BrdU. The frequency distribution of sister chromatid exchanges/cell and that of chromosomes showing various number of exchanges followed the Poisson probability at all BrdU levels; only at 5.0 micrograms/ml of BrdU was the fit found on the border of the 5% probability level. The usefulness of determining the spontaneous level of SCE/cell in domestic animals is discussed in relation to its possible application for a more precise evaluation of the genotoxic effects of environmental pollutants.
[Show abstract][Hide abstract] ABSTRACT: Peripheral blood lymphocytes from 4 cattle donors were grown for 2 cell cycles in the presence of 0.1, 0.25, 0.5, 1.0, 2.5 and 5.0 mu g/ml of 5-bromodeoxyuridine in order to detect the spontaneous level of sister chromatid exchanges and the dose-response relationships at low bromodeoxyuridine levels. Sister chromatid exchanges were counted on 50 s cycle metaphase spreads, randomly scored, for each donor at each dose. The mean rate of sister chromatid exchanges/cell at 0.1 mu g/ml of BUdR was 2.48 +/- 1.75, which can be considered as spontaneous. The dose-response curve increased more rapidly from 0.1 to 0.5 mu g/ml of bromodeoxyuridine and less rapidly at higher concentrations. The frequency distribution of sister chromatid exchanges/cell and that of chromosomes showing various numbers of exchanges followed the Poisson probability function only within the range of 0.1 to 1.0 mu g/ml of bromodeoxyuridine. The usefulness of determining the spontaneous level of sister chromatid exchanges in domestic animals is discussed in relation to its possible application for selection programs.