Ionizing irradiation effect on the thymus development

The study was performed on mice irradiated with the dose of 650 rd on the 16th and 20th day of pregnancy, and 3 days after birth. The fetal thymus and newborn thymus were collected 24 hrs after the irradiation. On the basis of observation of semithin and ultrathin sections of the irradiated fetal thymus, the thymocyte atrophy of the cortical part and the appearance of reticular cells, making the cortex looking similar to the medullary part, were stated. On the other hand, medullary thymocytes still occurred in the thymus with the simultaneous nuclear hyperchromatosis. In reticular cells, damaged structures of the nuclei and the cytoplasm were found many times. (author)