Variations in the Cellularity of the Bone Marrow following Local X-Irradiation and Administration of Cysteamine

Abstract

The cellularity of bone marrow of rats exposed to local X-irradiation with doses of 3000 R, 1500 R, and 400 R decreased rapidly and remained at a low level for about 3 days. From the third to the fifth day there was a marked rise in the cellularity. During the ensuing 3 weeks the cell number of the marrow gradually increased towards normal values. In non-irradiated marrow a certain reduction of the cell ularity was observed (abscopal effect). Following exposure to doses of 100 R and 50 R the reduction in cell numbers was less pronounced, and complete regeneration was obtained in the course of a week. When the protective substance cysteamine was administered to the animals prior to irradiation, the initial cell reduction was not modified. The subsequent repopulation was accelerated, and the abscopal effect was reduced.