The Chronology of the Mitotic Cycle of Human Granulocytopoietic Cells Phase Contrast Studies on Living Cells in Vitro

Data on the mitotic index of human granulocytopoietic cells are presented. From these and from the duration of mitosis directly measured in living cells by phase contrast microscope, the weighted average generation time and the mean compartment transit time are computed. Maturation in granulocytopoietic cells appears to induce a reduction of mitotic indices and mitotic rate and an increase in mitotic time and in mean compartment transit time. Part of the increment in mitotic duration may be due to the acquisition by a part of the granulocytopoietic cells of cytoplasmic peripheral motility or other specialized activities, thus distracting part of the energies destined to mitosis.