Frequency analysis of hematopoietic stem cells. (a) Live, lineage negative-to-low cells (gated cells in upper panels) were analyzed for the expression of c-Kit and Sca-1 (lower panels) at different microenvironments and stages of development. Gate shows the Lineage-/lowSca-1+c-Kit+ (LSK) population, containing hematopoietic stem cells (HSC). (b) Analysis of LSK population for the expression of CD150 versus CD41 and CD48 in different microenvironments and stages of development. Gate shows LSK CD150+CD41-CD48- LT-HSC. Data shown in 5% of contour plots, using Bi-Exponential scaling. (c) Representation of the absolute number of LSK and LT-HSC in the different microenvironment and stages of development studied. Note: * = P < 0.05, obtained by Tukey analysis, indicating that values are significant when compared to the adult bone marrow.