Brain Damage in 90 Day-old Rats Exposed During the Entire Gestation to Co-90 Gamma Rays or Cf-252 Neutrons At Different Dose Rates

Purpose: To determine the effect of dose rate and relative biological efficiency of neutron vs gamma irradiation for protracted, in utero exposure Status: 1989 - 1992, terminated Treatment: Protracted Co-60 gamma irradiation and Cf-252 neutrons plus gamma (ratio 2/1) irradiation at different dose rates delivered over the entire gestation Dosimetry: Gamma: ionization chamber; neutrons: ionization chamber filled with circulating tissue-equivalent gas Endpoints: Early and late effects on brain weight and late effects on brain histology Animal: Sprague-Dawley SPF rats offspring Results: Ninety day old rats exposed during the entire gestation to C0-60 gamma rays or Cf-252 neutrons at various dose rates showed a marked decrease in brain weight (RBE = 4) but no gross malformations of the brain when examined by histological methods.