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The fine structure of skeletal muscle triad junctions

1969; Academic Press; Volume: 29; Issue: 1-2 Linguagem: Inglês

10.1016/s0022-5320(69)80054-7

1878-2345

Douglas E. Kelly,

Cellular transport and secretion

Triad junctions in skeletal muscle of young newts and adult frogs have been examined after a wide variety of fixation procedures. When collidine-osmium is employed, the T-tubules of younger larval newt muscle appear as dilated channels which retain normal junctional relations with adjacent terminal cisterns. In older muscle, or after other fixation techniques, the T-tubule is narrow. This latter condition is less useful for analysis of junctional morphology, particularly when sections parallel to and including the junction are utilized. The images (including stereo electron micrographs) suggest that a given triad junction contains a gap distance of about 150 Å bridged by an array of cementing materials. “Dimples” in the terminal cistern membrane bring it into tight or close junctional proximity to the T-tubule membrane. The overall appearance resembles an intermediate junction within which small foci of tight or close junctional contact exist. Evidence of direct pore-like membrane continuities between T-tubules and terminal cisterns was not observed.