[Reversible suppression of muscle differentiation expression in a monolayer culture]

The phenotype of skeletal-muscle cells of a chick embryo in the primary monolayer culture maintained in the full medium (80% of the Eagle medium, 15% of serum, 5% of embryonic extract) and in the poor one (85% of the Eagle medium, 15% of serum) has been studied using both light and electron microscopy. In the full medium culture, which served as a control, the fusion of myoblasts (the index of fusion 51%) with the consequent formation of muscles fibers was observed. These fibres were able to contract and their ultrastructure was typical for differentiated skeletal-muscle cells. In the medium without an embryonic extract, the fusion of myoblasts was suppressed (the index of fusion 6%). The monolayer fibroblast-like cells lacking characters of differentiated muscle cells and, unlike, having those of typical fibroblasts were most numerous. The transference of myogene cells into fibroblast-like ones is reversal : after the substitution of the poor medium by the full one, both cell fusion (the index of fusion 45-47%) and differentiation of cell fibres are observed.