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Characterization of Programmed Cell Death of Bone Marrow Cells in Sublethally ~60Co γ Irradiated Mice

It has been confirmed that immune organ atrophy and immunosupression caused by irradiation are associated with thymocyte programmed celi death (PCD). Bone marrovv tissue is sensitive to radiation too. But little is known how hematopoietic cells are injuried by it. By trans-mission electron microscopy (TEM), flow cytometry and electrophoretic analysis of DNA, we determined the changes of hematopoietic celis in bone marrow of SPF BALB / c mice irradiated sublethally (2.0-6.0 Gy 60Co γ rays). TEM showed that there appeared nuclear condensation and cytoplasmic blebs. Percentage of DNA fragmentation measured by diphenylamine reaction increased in experimental mice. Agarose gel electrophoresis of DNA in the 27 000 x g supernatant from lysates obtained from bone marrow nucleated cells of irradiated mice showed ladder pattern, which suggest that the chromatin cleavage is at internucleosome sites. Our re-sults indicate that pragrammed celi death (or apoptosis) occurs in hematopoietic celis of mice with sublethal irradiation. However, hematopoietic stem cells are difficult to identified in morphology, it is necessary to do further work to confirm pragrammed cell death of stem cells induced by irradiation.