Early effects of gamma radiation on the developing rat cerebellum. Induction of cell pyknosis.

Radiation induced cell pyknosis was analysed in the cerebellar cortex of developing rats. Rats of 1, 5 or 10 days of age were irradiated with 60Co and pyknotic cells were evaluated with respect to time after irradiation with 0.1 Gy and with respect to dose in the range 0.05 to 1.0 Gy. In all ages pyknotic cells began to appear about 2 hours after irradiation, a maximum was reached at about 8 hours. With a dose of 0.1 Gy, control values were obtained after 24 hours. The effects varied linearly with dose up to 1 Gy and no threshold seemed to exist at low doses.