Prenatal X-Irradiation and Postnatal Mortality

Abstract

A total of 1265 pregnant mice were X-rayed at various stages of gestation to determine the pre-natal exposure required to kill 50% of those coming to term within the first 30 days after birth. The value of the LD/50/30 could not determined for those embryos exposed during the first 5 days after conception, due to the high intra-uterine mortality, but values are determinedfor mouse (CF1) embryos from 5 to 17 days gestation. The exposure at 8 days which killed 50% in utero also killed half of those surviving to birth, hence reducing the the original implantation number to 25% surviving mice. Ahigher dose was required to kill in utero, after 8 days than the dose required to kill after oirth. X-irradiation did not alter the usual sex ratio of 52% males to 48% females.