ABSTRACT
Gap junctions are present between a large variety of cell types in the developing embryo, a result that has led many investigators to speculate that the gap junctions play a role in the process of normal embryonic development. In the embryo of the clawed frog Xenopus laevis, groups of cells become coupled and later uncoupled during development, and blockage of the junctions has been reported to result in abnormal development. The experiments of I. Chow and M. M. Poo on the formation of coupling in cultured Xenopus muscle cells provided both a useful technique and several interesting pieces of information about the formation of coupling in the muscle cells. The Xenopus nerve and muscle cultures have been used to study the formation of the neuromuscular junction. Of particular technical interest is the fact that single, selected muscle cells may be placed into contact with nerve cells.
