Mitotic Indices of Human Bone Marrow Cells. III. Duration of Some Phases of Erythrocytic and Granulocytic Proliferation Computed from Mitotic Indices

1. Weighted average mitotic time of human bone marrow cells is estimated. Mitotic time is about 0.75 hours in red cell precursors and about 0.58 hours in neutrophil precursors.

2. Estimated weighted average DNA-synthesis time is about 9 hours in red cell precursors and about 24 hours in neutrophil precursors.

3. Upper and lower limits for compartment transit times of proerythroblasts, basophilic normoblasts, polychromatic normoblasts, myeloblasts, promyelocytes and myelocytes are presented (table 2).

4. Total mass of nucleated red cell precursors is estimated at 3.5 x 10⁹/kg. and total mass of neutrophils and their precursors in the marrow at 8.8 x 10⁹/kg.