Changes in the proliferative status and total number of hematopoietic stem cells in B6 and DBA mice during aging. (A) The percentage of CAFC day-7 in S-phase was measured at different timepoints during development in the fetal liver (FL) and adult bone marrow (BM) in B6 and DBA mice. (B) The total number of CAFC day-35 per B6 (▪) and DBA (▴) mouse was calculated in the fetal liver (first three datapoints) or adult bone marrow (other datapoints). Differences between B6 and DBA values are significant (nonoverlapping 95% confidence intervals) at all timepoints, except at 1 year.