Blood stem cells and radiation injuries

''In what way a general idea of stem cells came into existence'' was described from a viewpoint of a study on effect of radiation on hematopoietic system, and ''how radiation injuries were explained'' was also described from the viewpoint of stem cell disorders. First, effects of radiation on living body were given an outline, and effects of radiation on pooling of functional cells (peripheral blood cells), proliferated mature cells (hematopoietic cells in hematopoietic organs) and stem cells were described. Hematopoietic disorders by local irradiation, and bone-marrow transplantation for the treatment of hematopoietic disorders were described. The examination of stem cells by in vitro cultivation, and the estimation of exposed dose by analysis of chromosomes were described. Delayed effects of irradiation were described, and the study theme still remained to elucidate the mechanism of leukemogenesis was mentioned. (Serizawa, K.)