Effects on embryonic development of X-irradiation of rabbit spermatozoain vitro

Abstract

Rabbits in which ovulation was induced artificially were inseminated with spermatozoa exposedin vitroto doses of X -rays varying from 50 to 100,000 r. Exposure of the spermatozoa to 50 and 100 r. did not interfere with fertilization, segmentation of the ovum or embryonic and foetal development, and apparently normal young were born at term. With doses of 250, 500 and 1000 r., an increasing proportion of the tubal ova obtained about 40 hr. after ovulation showed arrest of segmentation. With 500 r. the incidence of established pregnancy and litter size were reduced, but some, not obviously abnormal, young were obtained. Most of theseF1animals reared were found to be fertile. No implanted embryos, foetuses or living young were obtained when the spermatozoa were exposed to 1000 r. or over. With doses of 2500 r. and over, all the tubal ova obtained showed lack or arrest of development. The stage to which segmentation had proceeded showed a general relationship with dosage. Histological examination of the tubal ova showed that spermatozoa had penetrated the ova at all dose levels, but the process was often delayed. Polyspermy was not uncommon. With the higher doses, the male pronucleus was abnormal, syngamy was delayed and irregular, and many activated ova failed to divide. The arrest of segmentation was associated with the occurrence of irregular nuclei and anucleate or multinucleate cells. There was some evidence of slight activation without syngamy, but none of continued gynogenetic development, i. e. of the Hertwig phenomenon.