[The action of the cells of hemopoietic organs in chick embryos on mouse CFUdc and CLFUdc].

The humoral influence of cells of hemopoietic organs of chicken embryos of different terms on the development of the colony and cluster formation of mononuclears of the bone marrow of mice was studied in joint cultivation in two-compartment cylindrical diffuse microchambers. The process of formation of colonies and clusters is inhibited by cells of the yolk sac on the 2nd-4th day of the development, by cells of the liver on the 8th-12th day, of the spleen on the 13th-18th day and of the bone marrow--on the 15th day. The yolk sac cells were found to have most considerable inhibiting influence on proliferation and differentiation of cells on the 2nd day of the development of chicken embryo. The yolk sac cells on the 6th day stimulate the formation of colonies and clusters. The yolk sac, beginning from the 4th day of the development, and the liver release humoral factors promoting the formation of erythroid colonies. The erythroid colonies are formed but when cultivated on the vascular membrane of the chicken embryo; the erythroid colonies are not formed when cultivated in the abdominal cavity of mice. Local erythropoietinoid factors are not synthetized by the spleen and bone marrow cells. A supposition is put forward that a combination of the local inhibiting and erythropoietic effects promotes the erythroid differentiation of cells.