Comparative investigations on cytogenetic effects of X-irradiation on the germinal epithelium of male mice and Chinese hamsters.

In one short-term-experiment and one long-term-experiment spermatogonia of mice and Chinese hamsters were compared for their sensitivity of X-ray induced chromosome aberrations. Short-term-experiment: Six hours after varying doses of X-rays the spermatogonia of both species were analysed and the number of induced chromatid breaks determined. At the dose range from 25-125 R the number of induced chromatid breaks per cell per roentgen is 0.01 in mice. In Chinese hamsters this value is 0.0072. The frequencies of chromatid breaks were studied in both species after a single dose of 100 R until 48 h p.i. The frequency in mice decreased more slowly than in hamster spermatogonia. After 12 h p.i. the ratio breaks in mice cells: breaks in hamster cells was 3.5:1, after 24 h this ratio was 5.2:1 after 48 h both frequencies were on the same level. Long-term-experiment: Analysis of spermatogonia and primary spermatocytes has been done 5 weeks after irradiation of the mice and 2, and 4 months after irradiation of the Chinese hamsters. The number of observed reciprocal translocations turned out to be higher in spermatogonial mitoses than in diakinesis-metaphases I in each animal. The conclusion is drawn for mice that a selection against abnormal cells is taking place already during pre-meiosis. In hamster pre-meiosis, the results are only indicative for a similar effect.