Sarcomere Length Changes in Single Frog Muscle Fibres during Tetani at Long Sarcomere Lengths
Laser diffraction and photomicrography have been used to monitor sarcomere length changes in single muscle fibres of the frog, at long sarcomere lengths, during fixed end tetani.
In the central 90% of all fibres, changes in sarcomere length were consistently less than 0.25 μm. Sarcomere length showed an initial rapid change, followed by a progressively slower increase, which persisted throughout a 4s tetanus. Sarcomere length in the terminal 200–400 μm segment at each end of a fibre decreased rapidly by up to 1 μm in the first second of a tetanus. This shortening was accompanied by a marked increase in disorder of the striation pattern.
Maximum isometric tensions in fixed end tetani were much greater than those predicted by crossbridge theory over the entire range of sarcomere lengths studied. An analysis of the intersarcomere dynamics suggests that this extra tension may be explained by known phenomena on the basis of a progressive increase in sarcomere length dispersion along the fibre.
KeywordsDepression Assure Acetylcholine Photography Tetanus
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- Edman, K.A.P. (1980) Depression of mechanical performance by active shortening during twitch and tetanus of vertebrate muscle fibres. Acta Physiol. Scand. 109: 15–26.Google Scholar
- Edman, K.A.P., Elzinga, G. and Noble, M.I.M. (1981) Critical sarcomere extension required to recruit a decaying component of extra force during stretch in tetanic contractions of frog skeletal muscle fibres. J. Gen. Physiol. 78: 365–382.Google Scholar
- Edman, K.A.P., Elzinga, G. and Noble, M.I.M. (1983) Stretch of contracting muscle fibres. Evidence for regularly spaced active sites along the filaments and enhanced mechanical performance. This volume.Google Scholar
- Edman, K.A.P., Mulieri, L.A. and Scupon-Mulieri, H.C. (1976) Non-hyperbolic force-velocity relationship in single muscle fibres. Acta Physiol. Scand. 98: 143–156.Google Scholar
- Huxley, A.F. (1957) Muscle structure and theories of contraction. Prog. Biophys. Biophys. Chem. 7: 255–318.Google Scholar
- Huxley, A.F. (1980) Reflections on muscle. Publ. Liverpool University Press.Google Scholar
- Julian, F.J. Sc Morgan, D.C. (1979) Intersarcomere dynamics during fixed end tetanie contractions of frog muscle fibres. J. Physiol. 293: 365–378.Google Scholar
- Julian, F.J., Sollins, M.R. and Moss, R.L. (1978) Sarcomere length non-uniformity in relation to tetanic responses of stretched skeletal muscle fibres. Proc. Roy. Soc. Lond. B. 200: 109116.Google Scholar
- Locker, R.H. and Leet, N.G. (1976) Histology of highly stretched beef muscle. IV. Evidence for movement of Gap filaments through the Z-line, using the Ne-line and M-line as markers. J. Ultrastruct. Res. 56: 31–38.Google Scholar
- Magid, A. (1981) Interfilamentary forces in relaxed detergent-skinned frog skeletal muscle. Biophys. J. 33: 226a.Google Scholar
- Myers, J., Tirosh, R., Jacobson, R.C. and Pollack, G.H. (1982) Phase locked loop measurement of sarcomere length with high time resolution. IEEE Trans. B.M.E. 29: 463–466Google Scholar
- Ramsey, R.W. Sc Street, S.F. (1940) The isometric length-tension diagram of isolated skeletal muscle fibres of the frog. J. Cell. Comp. Physiol. 15: 11–34.Google Scholar
- Tameyasu, T., Ishide, N. and Pollack, G.H. (1982) Discrete sarcomere length distribution in skeletal muscle. Biophys. J. 37: 469–492.Google Scholar
- ter Keurs, H.E.D.J., Iwazumi, T. and Pollack, G.H. (1978) The sarcomere length-tension relation in skeletal muscle. J. Gen. Physiol. 72: 565–592.Google Scholar
- Wang, K. and Williamson C L. (1980) Identification of an N2-line protein of striated muscle. Proc. Natl. Acad. Sci. U.S.A. 77: 3254–3258.Google Scholar