[The appearance and changes of gap junctions during myogenesis of Cynops embryos].

The appearance and changes of gap junctions during the development of striated muscle cells of Cynops orientalis have been studied by paraffin section, ultrathin-section and freeze-etching techniques. Gap junctions first appear between the somitic mesoderm cells in the late gastrula. A marked increase of the number of gap junctions occurs at the end of gastrulation. The number of gap junctions remains at a high level from neural plate stage up to nasal pit stage. After the stage of muscle contraction, the number of gap junctions decreases. Gap junctions do not disappear until muscle cells have attained their final differentiation and neuromuscular junctions have fully developed. The changes of size of gap junctions parallel with the changes in number. In addition, the number and size of gap junctions are both at the high level before cell fusion. Therefore, it is possible to conclude that cell communication is closely correlated with the development of striated muscle cells. The role of communications in cell determination and differentiation and in cell fusion of muscle cells are discussed.