The cellular composition of the cerebral cortex of rat fetuses after fractionated low-dose irradiation.

Histological and morphometric studies were performed to address the characteristics of the morphogenesis of the sensorimotor cortex of the brain in rat fetuses subjected to fractionated gamma irradiation during the period from day 6 to day 18 of antenatal development at doses of 5, 25, 30, and 75 cGy. The results showed that fractionated irradiation at doses of 5-75 cGy had adverse effects on the processes of stem cell proliferation in the tissues of the developing cortex and also increased the intensity of cell destruction proportionally to the radiation dose. All cellular zones of the developing cortex showed increases in the absolute number of macroglial cells, which may be associated on the one hand with reactive increases in their production due to functional deficiencies and, on the other, with accelerated transformation of radial gliocytes into macroglial cells. Irradiation at doses of 5-75 cGy decreased the rate of migration of neuroblasts into the primary cortex, as shown by decreases in the numbers of cells in the neural differon in the neocortical rudiment and increases in their levels in the deep layers of the developing cortex.