Generation time (GT) of human bone marrow cells cultured in the CFC-gm assay

Generation time (GT) of normal human bone marrow cells cultured in the CFC-gm assay was measured by using bromodeoxyuridine (BrdU) incorporation and sister chromatid differential staining. Cells were cultured in methylcellulose for 72 hr prior to the addition of BrdU and then harvested at 6-12 hr intervals for up to 72 hr. The time interval between the appearance of second and third division metaphases at the 50% level gave mean GTs which ranged from 32 to 43 hr. These values are longer than those reported for myeloblasts and promyelocytes but shorter than those previously reported for myelocytes.