Changes with time in stem cell functional abilities in mouse models of umbilical cord blood — experiment 1. Pooled erythroid and lymphoid repopulating units per 106 nucleated cells are shown. Repopulating units are not measures of single cells but of repopulating ability relative to standard BM. Each unit is equivalent to repopulating abilities of 100,000 standard BM cells. Thus, relative functional abilities per million cells of late fetal and newborn blood are several times less than found in adult BM, while values for late fetal or newborn liver are several times more. Fetal and newborn values tended to increase, and adult BM values to decrease, from 62 to 306 days (details in Table 1). (○), Newborn liver (1); (•), fetal liver; (▵), newborn liver (2); (▴), adult marrow; (□), fetal blood; (▪), newborn blood.
