title: Chromosomal radiosensitivity in meiotic oocytes of Chinese hamsters.
abstract: The X-ray sensitivity of unfertilized Chinese hamster oocytes was investigated. Female Chinese hamsters were exposed to a single X-ray dose of 200R at various preovulatory phases classified into 4 stages. These stages ranged from 12 hours to 5 estrous cycles before the time of collecting the oocytes. Chromosome analysis of the irradiated oocytes in metaphase-II was performed. The frequency of oocytes with abnormal chromosomes was compared with the non-irradiated control. The frequency of the oocytes with chromosome aberrations was 42.1% in the group in which females were irradiated at metaphase-I, 9.8% in the group irradiated at 2-4 days before the time of collecting the oocytes and 10.8% in that irradiated 1 estrous cycle before the time of collecting the oocytes. In the group irradiated at the 5th estrous cycle prior to the time of collecting the oocytes, the number of oocytes with chromosome aberrations could not be distinguished from that of the control. Comparing the frequency of oocytes carrying numerical chromosome aberrations with those carrying structural chromosome aberrations, there were more obvious differences in structural aberrations than in numerical ones among the irradiated stages. It was suggested that X-ray exposures of gonads, not only at postovulatory, but also preovulatory phases, may be hazardous and should be considered more carefully in the case of humans.
mesh_terms: D000818:Animals; D002869:Chromosome Aberrations; D006224:Cricetinae; D003412:Cricetulus; D004171:Diploidy; D005260:Female; D008540:Meiosis / Q000528:radiation effects; D008677:Metaphase; D009865:Oocytes / Q000166:cytology / Q000528:radiation effects*; D010060:Ovulation; D010063:Ovum / Q000528:radiation effects*