Qnantitation of Femoral Bone Marrow Cellularity of Rats with Acute Chloroleukemia

Procedures of bone marrow quantitation have been applied to the study of the pathogenesis of a leukemia in rats. Mature Long-Evans rats developed an acute form of the Shay Chloroleukemia after intravenous administration of leukemic cells. Assessment of total nucleated cell numbers (normal and leukemic) per mg. of femoral bone marrow was made during the course of the pathogenesis (20 days). Reductions in the numbers of normal marrow elements were observed prior to significant increases in chloroleukemic cells. A progressive decrease in total marrow cellularity was noted in all subsequent stages. In animals surviving 17-20 days, the total number of hemic cells in the femoral marrow was found to be approximately 40 per cent of that seen in normal animals. The leukemia developed more rapidly in young than in adult animals. Using total and differential bone marrow cellularity as a criterion for the stage of pathogenesis, standardized leukemic rats can be prepared for experimentation.