Muscle proteins in the chick myotome examined by the immunofluorescent method

In previous studies on the development of the somite (Langman & Nelson, 1968), the majority of the cells of the myotome appeared to arise from the dermatome and not, as previously suggested, from the cells of the so-called dorso-medial somite lip (Williams, 1910; Hamilton, 1952; Boyd, 1960). Once the myotome cells, characterized by a pale, round to irregular, nucleus and darkly stained nucleolus, are formed, they fail to synthesize DNA. During subsequent development, the myotome appears to extend in ventro-lateral direction by the addition of new cells originating primarily from the dermatome. After the dermatome has lost its epithelial structure, the myotome, in transverse section, consists of a tissue band with an abundance of cytoplasm and a large number of round to spindle-shaped nuclei. Though DNA synthesis was rarely observed among the cells of the extended myotome, considerable proliferative activity was observed in the adjacent tissues.