Late ultrastructural changes in neuronal mitochondria after lonizing radiation of the brain.

Brain tissue was examined for morphological changes at 12 and 16 months after focal irradiation of the brain in female mice. Irradiation was performed with deuteron beams derived from the 60-inch Brookhaven cyclotron at a rate of 1925 rad second -minus 1 though an anti-Bragg device which produced uniform exposure. Experimental animals received a dose of 10,000 rad, covering a 9 by 5 mm area over the skull and extending into the brain from a depth of about 2 mm. An additional group of animals served as sham-irradiated controls. Histological studies revealed extensive cell loss, vacuolation, and prominent vascular changes in irradiated regions of the brain at 16 months post-irradiation. Ultrastructural examination of brain tissue at 12 and 16 months after irradiation revealed the presence of unusual elongated mitochondria with parallel arrays of cristae. Altered mitochondria were more prevalent at the longer post-irradiation interval.