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Analysis of sister chromatid exchanges (SCE) in human population studies

Fernando N. Dulout^I; Jorge S. López Camelo^II; Huberto N. von Guradze^I

^ICIGEBA, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, 1900 La Plata, Argentina. Send correspondence to F.N.D.
^IIFundação Oswaldo Cruz, Av. Brasil, 4365, 21040 Rio de Janeiro, RJ, Brasil

ABSTRACT

The analysis of sister chromatid exchange frequencies in human population studies is discussed, taking into account: 1) the SCE frequencies in a population of floriculturists exposed to pesticides; 2) the distribution of SCE frequencies; 3) the number of cells scored per individual and 4) the proportion of cells with high SCE frequencies (HFC). SCE data were obtained from a sample of 14 floriculturists with chronic intoxication symptoms and 13 floriculturists without chronic intoxication symptoms. These results were compared with those obtained from a sample of nonexposed donors.
For the analysis of SCE frequencies in symptomatic and asymptomatic floriculturists, the use of parametric and nonparametric statistical tests, as well as the comparison of the distribution curves of SCE frequencies is discussed. As no dramatic increases of SCE frequencies would be expected in population studies, the usefulness of different methods combined with the comparison of distribution curves is demonstrated for the detection of small significant differences.
In the floriculturists and nonexposed donors, the SCE frequencies followed a negative binomial distribution, having a poor fit with the Poisson distribution. This confirms the utility of nonparametric statistical tests for the analysis of the data obtained.
The SCE frequencies of 20 individuals after 20, 25, 30 and 50 cell counts were analysed to determine if the number of cells to be scored per individual depends on the population sample size.
Finally, the detection of cells with high SCE frequencies can be used with large sample size and a great number of cells scored per individual.

Keywords: Sister chromatid; Human population.

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