Reconstituting activity of cells in the PHK67-low versus PHK67-high region. PKH67-labeled cells were either directly injected into lethally irradiated animals or incubated for 7 days on DAS 104-4, sorted for PKH-67-low versus -high fluorescence, and then injected into lethally irradiated animals. As can be seen, all of the reconstituting activity is found in the PKH67-high fraction with a mean fluorescence of 8.45 versus a starting fluorescence of 279.4, consistent with self-renewal and maintenance of stem cell phenotype of hematopoietic cells proliferating on DAS 104-4.