Synaptonemal complex damage in fetal mouse oocytes induced by ionizing irradiation.

Fetal female mice were exposed to ionizing irradiation of 2 Gy in a single dose at days 14, 16, and 17 of gestation. Synaptonemal complexes of primary oocytes were analyzed on day 17. It has been demonstrated that electron beam irradiation of early oocytes on day 14 with 2 Gy is accompanied by a duplication of atretic cells. A significant increase in fragmentations of the synaptonemal complexes over the base level became evident when mice were exposed to irradiation on days 16 and 17 of gestation. Frequencies of multivalent formation and univalents were not increased over the levels in the control group. Reduction of fertility and malsegregation of chromosomes may be a reflection of the consequences of the observed nuclear lesions.