Radiation-induced formation of apoptotic bodies in rat thymus.

The process of interphase death of thymocytes in whole-body X-irradiated rats were studied. Cell size distribution analysis indicates that cell fragments (= apoptotic bodies) appeared in the thymus and increased in number depending on dose (200-1000 R) and time (2-6 hr) after irradiation with corresponding decrease in normal-size thymocytes. Occurrence of nuclear fragmentation in association with the cellular fragmentation was proved with cytofluorometric determination of DNA content in individual cells. Scanning electron microscopic observations also revealed extensive fragmentation of cells in the irradiated rat thymus. The results show clearly that cells as well as nuclei fragment rapidly into smaller pieces of various sizes in the irradiated rat thymus as commonly observed with apoptosis.