title: 'Square arrays' in the sarcolemma of human skeletal muscle fibres.
abstract: Fast twitch fibres of rat and rabbit show rectangular patterns of intramembrane particles in freeze-fracture preparations of the sarcolemma. These 'square arrays' are almost totally absent in the slow twitch coleus muscle of rat. I report here differences in the incidence of square arrays in human fetal and adult muscle and in different fibres within a human muscle. Square arrays probably classify fast and slow twitch fibres in freeze-fracture preparations of mixed muscles.
mesh_terms: D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins; D009119:Muscle Contraction; D009132:Muscles / Q000196:embryology; D012508:Sarcolemma / Q000648:ultrastructure*
chemical_list: D008565:Membrane Proteins