| Abstract: | The effects of sublethal radiation and the mitotic inhibitor, vinblastine sulphate, on the number of cells in mouse bone marrow capable upon transplantation of forming macroscopic colonies on the surface of the spleens of irradiated recipient mice (CFU) and on the number of cells capable of forming colonies in soft agar after cell culture (ACFU) were studied as a function of time after injury. The results show that ACFU are radiosensitive and vinblastine-sensitive cells, comparable in sensitivity to erythropoietin-sensitive cells. The temporal pattern of recovery following radiation of ACFU, different from that for CFU, is compatible with the concept that these are two distinct but closely related stem cell populations. The relevance of these findings to models of hematopoiesis and to studies on the precursors of macrophages and monocytes in inflammatory exudates is discussed. |
