STRUCTURAL AND CYTOLOGICAL STUDIES ON INJURY AND REGENERATION OF THE RAT BONE MARROW FOLLOWING TOTAL BODY IRRADIATION

Male Wister rats were exposed to a single dosis of X-ray, 500 r, 700 r and 1000 r respectively, and the processes of injury and regeneration of their bone marrow were studied hematologically, histologically, electron microscopically, histochemically, and histoautoradiographically. Structural and cytological alterations of the bone marrow tissue, especially of the hematopoietic cells as well as of the reticuloendothelial cells at the injured phase were described. Distribution of the regenerative foci of myeloid and erythroid cells in the bone marrow was examined by serial sectioning. Prior to the recovery of the peripheral leucocyte count, regeneration of the immature myeloid cells in the bone marrow appeared, of which feature was demonstrated with the myelograms and electron micrographs. Stress was given on the movement of blastic cells and non-phagocytic reticular cells which were found particularly dominant in the subsinusoidal region in the control and in this experimental animals. At the regenerative phase, those blastic cells labeled with 3H-thymidine increased in number, especially significantly in the subsinusoidal layer. Non-phagocytic reticular cells were also found proliferated in this area. It was evidenced that the bone marrow fat cells could be derived from those subsinusoidal non-phagocytic reticular cells. However, it was still obscure in this study whether or not such subsinusoidal reticular cells had a potency to differentiate into other kinds of bone marrow cells related to actual hematopoiesis