The Estrous Cycle and the Hernopoietic Steni Cell

A large variability in the stem cell by colony development in sublethally content of the spleens of female mice irradiated female mice. It is shown by comparison with that of the bone that, for mice in pre-estrus, the spleens marrow, or with that of the spleen contain up to three times as many and bone marrow of male mice, is hemopoietic stem cells (CFU) as durdemonstrated. This variability is shown ing the estrus and post-estrus stages to be associated with the estrous of the cycle. Although the association cycle. Stem cells are assayed by the may be indirect, it is suggested that spleen colony-forming test, either the changes in splenic stem cell numexogenously by transplantation to irrabers may be related to the hormonal diated recipient mice, or endogenously milieu at the time of observation.