Effects of different doses of gamma-radiation on the developing brain of mice.

Morphogenetic changes in the developing brain induced by doses of 60Co gamma-irradiation ranging from 0 to 1.5 Gy on day 13 of pregnancy (E13) were studied in 6-week-old mice. Dose-related reductions in brain weight and cortical thickness (field 3 of Caviness) were significant for all irradiated groups, but abnormal cortical architecture was evident only in mice exposed to 1.0 and 1.5 Gy. Ectopic gray matter, enlarged lateral ventricles, and the absence of trunks from the corpus callosum were observed respectively in 23%, 30% and 10% of the mice exposed to 1.0 Gy, but these anomalies rose to 90%, 82% and 35% of the mice, respectively, when 1.5 Gy irradiation was applied. Brain malformations identical to the small heads and ectopic gray matter typically observed among atomic bomb survivors were reproduced in mice exposed to 1.5 Gy irradiation on E13.