XXXX in subsarcolemmal densities in @entity1573 skeletal muscle: localization and relationship to intracellular and extracellular structures.

@entity1573 @entity53568 @entity8019
Using immunocytochemical methods we have studied the distribution of @entity53568 in the anterior and posterior latissimus dorsi skeletal ( @entity8019 and PLD, respectively) muscles of the adult @entity1573 . The @entity8019 muscle is made up of both tonic (85%) and twitch (15%) myofibers, and the PLD muscle is made up entirely of twitch myofibers. In indirect immunofluorescence, antivinculin antibodies stained specific regions adjacent to the sarcolemma of the @entity8019 and PLD muscles. In the central and myotendinous regions of the @entity8019 , staining of the tonic fibers was intense all around the fiber periphery. Staining of the twitch fibers of both @entity8019 and PLD muscles was intense only at neuromuscular junctions and myotendinous regions. Electron microscopy revealed subsarcolemmal, electron-dense plaques associated with the membrane only in those regions where @entity53568 was localized by immunofluorescence. Using antivinculin antibody and protein A conjugated to colloidal gold, we found that the electron-dense subsarcolemmal densities in the tonic fibers of the @entity8019 contain @entity53568 ; no other structures were labeled. The basal lamina overlying the densities appeared to be connected to the sarcolemma by fine, filamentous structures, more enriched at these sites than elsewhere along the muscle fiber. Increased amounts of endomysial connective tissue were often found just outside the basal lamina near the densities. In @entity8019 muscle fibers, the subsarcolemmal densities were present preferentially over the I-bands. In partially contracted @entity8019 muscle, subsarcolemmal densities adjacent to the Z-disk appeared to be connected to that structure by short filaments. We propose that in the @entity8019 muscle, through their association with the extracellular matrix, the densities stabilize the muscle membrane and perhaps assist in force transmission.
