Summary
An electron-microscopic study of the myotendinous portion of the diaphragm in the Wistar rat has shown that at the ends of muscle fibers, longitudinally oriented invaginations and peripheral furrows of the sarcolemma establish specialized contacts with individual sacs of the sarcoplasmic reticulum. The construction of these terminal contacts is similar to that of contacts between sarcolemmic T-tubules and terminal cisternae of the sarcoplasmic reticulum, characterized by formation of triads. The contact zones of the sac membrane are undulated and bound to the adjoining sarcolemma via electron-dense profiles of varying forms. Frequently, the terminal contacts and triads are located at the same level within the muscle fiber, at the borderline between A- and I-bands of the sarcomeres. At the ends of muscle fibers combined contacts between peripheral furrows of the sarcolemma, terminal cisternae of the sarcoplasmic reticulum, and T-tubules of the triads are also disclosed. The implications of the terminal contacts for muscle contraction are discussed.
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References
Campbell KP, Shamoo AE (1980) Phosphorylation of heavy sarcoplasmic reticulum vesicles: identification and characterization of three phosphorylated proteins. J Membr Biol 56:241–248
Chandler WK, Rakowski RF, Schneider MF (1976) Effects of glycerol treatment and maintained depolarization on charge movement in skeletal muscle. J Physiol (Lond) 254:285–316
Ebashi S (1960) Calcium binding and relaxation in the actomyosin system. J Biochem 48:150–151
Eisenberg BR, Eisenberg RS (1982) The T-SR junction in contracting single skeletal muscle fibers. J Gen Physiol 79:1–19
Forbes MS, Sperelakis N (1982) Bridging junctional processes in couplings of skeletal, cardiac, and smooth muscle. Muscle Nerve 5:674–681
Franzini-Armstrong C (1970) Studies of the triad. I. Structure of the junction in frog twitch fibers. J Cell Biol 47:488–499
Ishikawa H (1965) The fine structure of myo-tendon junction in some mammalian skeletal muscles. Arch Histol Jpn 25:275–296
Jorgensen AO, Kalnins V, MacLennan DH (1979) Localization of sarcoplasmic reticulum proteins in rat skeletal muscle by immunofluorescence. J Cell Biol 80:372–384
Korneliussen H (1973) Ultrastructure of myotendinous junctions in Myxine and rat. Specializations between the plasma membrane and the lamina densa. Z Anat Entwickl-Gesch 142:91–101
Mackay B, Harrop TJ, Muir AR (1969) The fine structure of the muscle tendon junction in the rat. Acta Anat 73:588–604
Meissner G (1975) Isolation and characterization of two types of sarcoplasmic reticulum vesicles. Biochim Biophys Acta 389:51–68
Meissner G, Conner GE, Fleischer S (1973) Isolation of sarcoplasmic reticulum by zonal centrifugation and purification of Ca2+ pump and Ca2+ binding proteins. Biochim Biophys Acta 298:246–269
Nakao T (1975) Fine structure of the myotendinous junction and “terminal coupling” in the skeletal muscle of the lamprey, Lampetra japonica. Anat Rec 182:321–338
Nakao T (1976) Some observations on the fine structure of the myotendinous junction in myotomal muscles of the tadpole tail. Cell Tissue Res 166:241–254
Nakao T (1977) Electron microscopic studies on the myotomes of larval lamprey, Lampetra japonica. Anat Rec 187:383–403
Oba T, Yamamoto M, Acki T, Hotta K (1983) Mechanical, electrical, and morphological characteristics of skeletal muscle fibers from Xenopus and other species of frogs. Jpn J Physiol 33:521–534
Somlyo AV (1979) Bridging structures spanning the junctional gap at the triad of skeletal muscle. J Cell Biol 80:743–750
Sommer JR, Johnson EA (1970) Comparative ultrastructure of cardiac cell membrane specializations. A review. Am J Cardiol 25:184–194
Spray TL, Waugh RA, Sommer JR (1974) Peripheral couplings in adult vertebrate skeletal muscle. Anatomical observations and functional implications. J Cell Biol 62:223–227
Taylor SR, Lopez JR, Griffiths PJ, Trube G, Cecchi G (1982) Calcium in excitation-contraction coupling of frog skeletal muscle. Can J Physiol Pharmacol 60:489–502
Tidball JG (1983) The geometry of actin filament-membrane associations can modify adhesive strength of the myotendinous junction. Cell Motil 3:439–447
Trotter JA, Eberhard S, Samora A (1983) Structural domains of the muscle-tendon junction. 1. The internal lamina and the connecting domain. Anat Rec 207:573–591
Wassilev W, Andreev D (1983) Über die Feinstruktur der MuskelSehnenverbindung. Verh Anat Ges 77:617–619
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Andreev, D.P., Wassilev, W.A. Specialized contacts between sarcolemma and sarcoplasmic reticulum at the ends of muscle fibers in the diaphragm of the rat. Cell Tissue Res. 243, 415–420 (1986). https://doi.org/10.1007/BF00251058
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DOI: https://doi.org/10.1007/BF00251058