PROPAGATION OF ACTION POTENTIALS AND THE STRUCTURE OF THE NEXUS IN CARDIAC MUSCLE.

The hypothesis that the nexus is a specialized structure allowing current flow between cell interiors is corroborated by concomitant structural changes of the nexus and changes of electrical coupling between cells due to soaking in solutions of abnormal tonicity. Fusiform frog atrial fibers are interconnected by nexuses. The nexuses, desmosomes, and regions of myofibrillar attachment of this muscle are not associated in a manner similar to intercalated discs of guinea pig cardiac muscle.

A STUDY OF THE STRUCTURE AND DISTRIBUTION OF THE NEXUS.

Nexuses, that is, fusions of plasma membranes of adjacent cells, are described in mammalian smooth and cardiac muscle, median giant axon of earthworm, frog skin, and rat submandibular gland. In smooth muscle they usually occur where a process from one cell either meets a process of, or projects into a neighboring cell. On the other hand, in mammalian heart muscle and in earthworm giant axon the nexuses occur along the intercalated disc and intercellular segmental septa, respectively.

Intercellular Connection between Smooth Muscle Cells: the Nexus.

High-resolution electron microscopy has revealed that the regions of contact between smooth muscle cells from dog intestine are areas of fusion of adjacent cell membranes. For morphological and functional reasons this type of contact between excitable cells has been termed a nexus.