Cross bridge slippage in skinned frog muscle fibres |
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Authors: | P J Griffiths K Güth H J Kuhn J C Rüegg |
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Institution: | (1) Department of Physiology II, University of Heidelberg, Im Neuenheimer Feld 326, D-6900 Heidelberg, Germany;(2) Present address: c/o Dr. S. R. Taylor's Laboratory, Department of Pharmacology, Mayo Foundation, 55901 Rochester, Minnesota, USA |
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Abstract: | Mechanically skinned single fibres of the semitendinosus muscles of Rana esculenta were investigated at ca. 4 C. The fibres were activated by a Ca2+ jump technique, which allowed the development of a steady isometric tension within several seconds of entering a calcium rich solution at 4 C. Sequences of length changes of different duration and amplitude were applied to the fibre. It could be demonstrated that the fibre behaved as a Hookean spring in the case of small amplitude length changes (up to 0.5% L0, ramp duration 0.5 ms) and that a sequence of length changes induced reversible changes in fibre state. In contrast, large stretches (> 1% L0) induced a muscle give if the stretch were not immediately preceded by a release. The data was interpreted on the basis of a strain induced detachment of cross bridges in combination with a rapid reattachment of presumably the same cross bridges in a discharged position. The rates of strain induced detachment and reattachment depended on the stretch amplitude. At amplitudes exceeding 2% L0 the rates were estimated to be at least several thousands per second. |
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Keywords: | Actomyosin interaction Muscle mechanics Cross bridge slippage Contraction mechanism |
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