Ultrastructural changes in mouse testes after X-irradiation

Sexually mature male BALB/c mice, divided in three groups, received single X-irradiation with 2.5, 5.0 and 7.0 Gy accordingly. The ultrastructural changes in the testicular cells were studied on the 2-nd, 5-th and 9-th postirradiation day. The earliest changes in the spermatogonia and the spermatocytes were characterized by dilatation of the smooth endoplasmic reticulum, swelling of mitochondria, expansion of the perinuclear space and chromatin condenstation. The changes in the spermatogonia (the most radiosensitive sex cells) affected equally the nucleus and the cytoplasm; in the spermatocytes and spermatids the degree of cytoplasm injury was more advanced. The enchanced radioresistance of pachytene spermatocytes, spermatides and spermatozoa seems to be due to the strong chromatin condenstation, which is a distinctive feature of sex cells in these stages of spermatogenesis. (authors)