Cell proliferation stimulating factors in the supernatant of embryos and adult muscles of chickens of the same strain.

Stimulating factors of cell proliferation were extracted from the supernatant of embryos and adult muscles of chickens of the same strain. The stimulating activity and physicochemical properties of these factors were altered after embryological development. The embryonic factors were about 3.5 times more effective than the muscular factors. These factors might be useful in analysis of the regulatory mechanisms of cell proliferation.