The membrane morphology of the neuromuscular junction, sarcolemma, sarcoplasmic reticulum and transverse tubule system in murine muscular dystrophy studied by freeze-fracture electron microscopy.
'Dystrophic' mice of the 129/ReJ-dy strain have a genetic defect in Schwann cell proliferation and neuromuscular junction formation. The presynaptic membrane specializations associated with vesicle fusion and acetylcholine release, as well as the postsynaptic membrane specializations associated with acetylcholine receptivity, appear normal in these animals when visualized with freeze-fracture techniques. However, there is a reduction in the infolding of the postsynaptic membrane, which forms the secondary synaptic cleft at the motor endplate and is the site of acetylcholinesterase activity. The orthogonal arrays of the non-junctional sarcolemma are found on dystrophic muscles, but at lower than normal densities. These observations are made on muscle fibers in which the membrane molecular organization of the sarcoplasmic reticulum and transverse tubule systems appear normal. Several possible linkages between the deficit in myelination and the altered synaptic morphology are discussed in the context of neuromuscular interaction.
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D005614:Freeze Fracturing; D051379:Mice; D008818:Mice, Neurologic Mutants; D008854:Microscopy, Electron; D008870:Microtubules / Q000648:ultrastructure; D009137:Muscular Dystrophy, Animal / Q000473:pathology*; D009469:Neuromuscular Junction / Q000473:pathology*; D011950:Receptors, Cholinergic / Q000378:metabolism; D012508:Sarcolemma / Q000648:ultrastructure*; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure*; D013570:Synaptic Membranes / Q000648:ultrastructure*; D013572:Synaptic Vesicles / Q000648:ultrastructure
D011950:Receptors, Cholinergic; D000109:Acetylcholine