ULTRASTRUCTURAL PATTERNS OF CELL-DAMAGE AND DEATH FOLLOWING GAMMA-RADIATION EXPOSURE OF MURINE ERYTHROLEUKEMIA-CELLS

Radiation causes damage to cell surface membranes, cytoplasmic organel les, and the nuclear process of DNA synthesis and repair, and this eve ntually results in different modes of cell death. In this study we exa mined murine erythroleukemia (MEL) cells, exposed to 15 and 60 Gy of 1 0 MeV photonic energy, and left in culture for up to 96 hours. Electro n microscopical analysis was performed on conventionally embedded samp les and freeze-fracture replicas, in order to detect ultrastructural p atterns of cell damage and death. Of interest was the observation of c hromatin condensates,nuclear membrane associations and nuclear pore re distribution during early apoptosis. Pronounced rearrangements of tran smembrane particles during late stages of cellular necrosis were also found. The morphological damage induced by both doses of radiation as a function of time after exposure was only quantitatively but not qual itatively different.