The Effects of Fractions of Chick Embryo Extract on the Fusion of Cultured Chick Embryonic Myoblasts

In order to find factors which are essential for the differentiation of chick embryonic myoblasts in culture, chick embryo extract was fractionated by ammonium sulfate or/and Sephadex G-75, and the effects of each fraction on the proliferation and fusion of the myoblasts were examined. The results obtained were as follows: (1) High concentration of embryo extract in the culture medium enhanced the cell proliferation and delayed the fusion of myoblasts. (2) The Sephadex G-75 fractions of embryo extract having proteins of molecular weight between 40,000 and 22,000 enhanced the proliferation and fusion of myoblasts when added to culture media. (3) The fraction of embryo extract precipitated in $60\\sim95%$ saturated ammonium sulfate solution enhanced evidently both the proliferation and fusion of myoblasts. Elution of this effective fraction by Sephadex G-75 showed similar elution profile and effects on the myoblast differentiation as those observed by Sephadex G-75 chromatography of the whole embryo extract, suggesting that the Sephadex fractions and ammonium sulfate fractions contain the same factors that enhance the proliferation and fusion of myoblasts.