EXPERIMENTAL STUDY OF THE RADIATION HAZARD IN WHITE RATS CAUSED BY EXTERNAL SERIAL EXPOSURE TO Zn$sup 6$$sup 5$

Twenty-four Wistar strain rats were exposed to gamma -ray irradiation emitted from Zn/sup 65/ for 182 days 24 hours daily. These rats were divided into 4 groups of 3 males and 3 females according to the time of irradiation: 15, 30, 60, and 182 days, respectively. There hematopoietic organs and reprcductive organs were examined histopathologically. Peripheral blood drawn from the tall vein was examined in those exposed for 182 days. The red blocd cell count showed a slight decrease from the l2th week until 172 days. The white blood cell count was 10,650/cu mm after 6 weeks and became under 10,000/cu mm at 14 weeks, a significant change chiefly due to decrease in the lymphocyte count. The spleen weighed 505 mg on the l5th day and 377 mg on the 172nd day after exposure. The testicle showed no atrophy but an increase in connective tissues. The spleen showed an atrophy of the lymph follicles and a fibrosis which were parallel to the duration of exposure. The bone marrow showed slight infiltration of fat cells. The ovary showed a decrease in primitive follicles and mature follicles. The liver showed fatty degeneration, vacuolar degeneration of liver cells and small round cell infiltrationmore » in the liver lobules and Glisson's capsule. (Absts. Japan. Med., 1: No. 6, 1961)« less