The early and long-term effects of X-irradiation on skeletal growth were investigated with respect to the age at exposure. Rats exposed at a juvenile age (37 days) to a sublethal dose (430 rad) exhibited a retardation in femur, tibia, and tail growth within 14 days after exposure. The maximal deficit was attained within 30 days after exposure and remained approximately constant for the next 300 days. In animals which were exposed to X-rays as young adults (101 days of age), femur and tibia length did not differ from those of controls for the first 2 months after exposure. However, there was a deficit in femur and tibia length in these animals at the end of life span. The magnitude of the bone length reduction at the end of life span was dose dependent. The two major differences in response between the two age groups were the time course of the radiation effect on growth and the magnitude of the deficit. The reduction in bone length occurred faster and was greater in the younger irradiated group.
LONG TERM EFFECTS OF PRENATAL X-IRRADIATION ON CEREBRAL CORTEX. Technical Progress Report, December 1, 1966--December 1, 1967.