Correlated morphological and physiological studies on isolated single muscle fibers. I. Fine structure of the crayfish muscle fiber.
Single fibers isolated from walking leg muscles of crayfish have 8- to 10-micro sarcomeres which are divided into A, I, and Z bands. The H zone is poorly defined and no M band is distinguishable. Changes in the width of the I band, accompanied by change in the overlap between thick and thin myofilaments, occur when the length of the sarcomere is changed by stretching or by shortening the fiber. The thick myofilaments (ca. 200 A in diameter) are confined to the A band. The thin myofilaments (ca. 50 A in diameter) are difficult to resolve except in swollen fibers, when they clearly lie between the thick filaments and run to the Z disc. The sarcolemma invaginates at 50 to 200 sites in each sarcomere. The sarcolemmal invaginations (SI) form tubes about 0.2 micro in diameter which run radially into the fiber and have longitudinal side branches. Tubules about 150 A in diameter arise from the SI and from the sarcolemma. The invaginations and tubules are all derived from and are continuous with the plasma membrane, forming the transverse tubular system (TTS), which is analogous with the T system of vertebrate muscle. In the A band region each myofibril is enveloped by a fenestrated membranous covering of sarcoplasmic reticulum (SR). Sacculations of the SR extend over the A-I junctions of the myofibrils, where they make specialized contacts (diads) with the TTS. At the diads the opposing membranes of the TTS and SR are spaced 150 A apart, with a 35-A plate centrally located in the gap. It appears likely that the anion-permselective membrane of the TTS which was described previously is located at the diads, and that this property of the diadic structures therefore may function in excitation-contraction coupling.
D000818:Animals; D003445:Crustacea; D004721:Endoplasmic Reticulum; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D009132:Muscles / Q000166:cytology*
J Gen Physiol. 1963 Sep;47:189-214
14060445
Nature. 1964 Jun 13;202:1067-71
14207194
Am J Anat. 1961 Nov;109:277-97
14485812
J Biophys Biochem Cytol. 1961 Dec;11:729-32
14454024
J Biophys Biochem Cytol. 1961 Aug;10(4)Suppl:177-85
13768449
J Cell Biol. 1963 Feb;16:297-313
13938025
Nature. 1964 Apr 25;202:355-7
14152819
Nature. 1953 Sep 19;172(4377):530-2
13099257
J Cell Biol. 1962 May;13:323-35
14457201
J Physiol. 1962 Aug;163(1):61-103
16992124
J Cell Biol. 1963 Dec;19:637-41
14086142
J Cell Biol. 1963 Jul;18:213-8
13942794
J Gen Physiol. 1964 Jul;47:1141-74
14192551
J Cell Biol. 1963 Jan;16:143-57
13990905
J Cell Biol. 1963 Nov;19:369-90
14086763
Nature. 1954 May 22;173(4412):973-6
13165698
Nature. 1964 Jun 13;202:1115-6
14207209
Helv Physiol Pharmacol Acta. 1964;22:C72-3
14221010
J Cell Biol. 1962 Jan;12:91-100
13913207
Nature. 1954 May 22;173(4412):971-3
13165697
Biochem J. 1958 Jan;68(1):5-12
13522566
Ann N Y Acad Sci. 1959 Aug 28;81:446-52
14405665