Glycogen-membrane complexes in denervated human skeletal muscle.
We describe an unusual intracellular complex of glycogen with smooth, cisternal, cytoplasmic membranes (glycogen-membrane complexes, GMC) in denervated human skeletal muscle. Glycogen particles were always intimately associated with these structures, although the staining intensity varied markedly with different fixation conditions. This may account for previous investigations of similar structures in which an association with glycogen was not recognized. Electron micrographs of tannic acid-enhanced specimens, and of freeze-fracture replicas, showed similarities between the GMCs and the terminal cisternae of the sarcoplasmic reticulum: (i) GMCs resembled the terminal cisternae of the sarcoplasmic reticulum in the size and asymmetric distribution of intramembranous particles seen in freeze-fracture replicas; (ii) tannic acid-enhanced thin sections of GMCs showed intense staining of the cisternal contents and irregular staining of the cytoplasmic leaflet, similar to the appearance of the sarcoplasmic reticulum terminal cisternae; and (iii) triad-like junctions were seen between the glycogen-membrane complexes and elements of the transverse tubule system.
D002462:Cell Membrane / Q000648:ultrastructure; D005614:Freeze Fracturing; D006003:Glycogen / Q000502:physiology*; D006801:Humans; D008297:Male; D008566:Membranes / Q000648:ultrastructure; D008854:Microscopy, Electron; D008875:Middle Aged; D009121:Muscle Denervation; D009132:Muscles / Q000648:ultrastructure*
D006003:Glycogen