Effects of X-Irradiation on the Implanting Canine Embryo

Abstract

The response of beagle embryos to an exposure of 100 R x-rays on day 13, 16, 19, 22, or 25 of gestation has been measured in terms of pre- and postnatal mortality, birth weight and the incidence of developmental anomalies. Following irradiation on day 19, corresponding approximately to the primitive streak stage, few bitches produced litters than at any other exposure time. Postnatal mortality was markedly increased after exposure on day 16, 19, or 22. Irradiation at times from 16 through 25 days produced a significant reduction in birth weight, the greatest deficit occurring at 22 days. A rather high incidence of developmental anomalies was observed following irradiation on days 19 and 22, during the period of early organogenesis. From this it appears that the time of greatest radiosensitivity as measured by pre- and postnatal mortality occurred at about the primitive streak stage and immediately thereafter during early neurogenesis. In the dog this time shortly follows implantation. The overall pattern ...