The study demonstrates that junctional processes (pillars) connect the sarcolemma with the junctional sarcoplasmic reticulum across skeletal, cardiac, and smooth muscle cells.
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No immediate clinical implications for cardiac disease; leaves open the functional role of pillars in human striated muscle.
Junctional processes are found in the junctional gap of couplings in skeletal, cardiac, and vascular smooth muscle cells. Visualization of the structure of junctional processes is greatly facilitated by the use of a tilting specimen stage and stereoscopic analysis. Relatively small changes of tilt angle create a spectrum of images for the same junctional process which can range from that of an amorphous electron‐opaque body to a distinct linear structure (“pillar”). In both striated and smooth muscles, pillars connect the sarcolemma with the limiting membrane of junctional sarcoplasmic reticulum (J‐SR). In addition, in vascular smooth muscle cells, pillars join the J‐SR with surface‐connected caveolae.
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Forbes et al. (1982) studied this question.
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