Dataset Information

Reversal of the myosin power stroke induced by fast stretching of intact skeletal muscle fibers.

ABSTRACT: Force generation and movement in skeletal muscle result from a cyclical interaction of overlapping myosin and actin filaments that permits the free energy of ATP hydrolysis to be converted into mechanical work. The rapid force recovery that occurs after a step release imposed on a muscle is thought to result from a synchronized tilting of myosin lever arms toward a position of lower free energy (the power stroke). We investigated the power stroke mechanism in intact muscle fibers of Rana esculenta using a fast stretch to detach forcibly cross-bridges. Stretches were applied either with or without a conditioning step release. Cross-bridge rupture tension was not significantly influenced by the release, whereas sarcomere elongation at the rupture point increased immediately after the release and returned to the prerelease condition within 15-20 ms, following a slower time course compared to the recovery of tension. These observations suggest that the rupture force of a bridge is unaltered by a conditioning release, but rupture must first be preceded by a power stroke reversal, which restores the prepower stroke state. The sarcomere extension at the rupture point indicates both the extent of this power stroke reversal and the time course of strained bridge replenishment.

SUBMITTER: Colombini B

PROVIDER: S-EPMC2784556 | biostudies-other | 2009 Dec

REPOSITORIES: biostudies-other

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Reversal of the myosin power stroke induced by fast stretching of intact skeletal muscle fibers.

Colombini Barbara B Nocella Marta M Benelli Giulia G Cecchi Giovanni G Griffiths Peter J PJ Bagni M Angela MA

Biophysical journal 20091201 11

Force generation and movement in skeletal muscle result from a cyclical interaction of overlapping myosin and actin filaments that permits the free energy of ATP hydrolysis to be converted into mechanical work. The rapid force recovery that occurs after a step release imposed on a muscle is thought to result from a synchronized tilting of myosin lever arms toward a position of lower free energy (the power stroke). We investigated the power stroke mechanism in intact muscle fibers of Rana esculen ...[more]

PMID: 19948121

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Project description:Nuclear Ca(2+) is important for the regulation of several nuclear processes such as gene expression. Localized Ca(2+) signals (LCSs) in skeletal muscle fibers of mice have been mainly studied as Ca(2+) release events from the sarcoplasmic reticulum. Their location with regard to cell nuclei has not been investigated. Our study is based on the hypothesis that LCSs associated with nuclei are present in skeletal muscle fibers of adult mice. Therefore, we carried out experiments addressing this question and we found novel Ca(2+) signals associated with nuclei of skeletal muscle fibers (with possibly attached satellite cells). We measured localized nuclear and perinuclear Ca(2+) signals (NLCSs and PLCSs) alongside cytosolic localized Ca(2+) signals (CLCSs) during a hypertonic treatment. We also observed NLCSs under isotonic conditions. The NLCSs and PLCSs are Ca(2+) signals in the range of micrometer [FWHM (full width at half maximum): 2.75 ± 0.27 μm (NLCSs) and 2.55 ± 0.17 μm (PLCSs), S.E.M.]. Additionally, global nuclear Ca(2+) signals (NGCSs) were observed. To investigate which type of Ca(2+) channels contribute to the Ca(2+) signals associated with nuclei in skeletal muscle fibers, we performed measurements with the RyR blocker dantrolene, the DHPR blocker nifedipine or the IP3R blocker Xestospongin C. We observed Ca(2+) signals associated with nuclei in the presence of each blocker. Nifedipine and dantrolene had an inhibitory effect on the fraction of fibers with PLCSs. The situation for the fraction of fibers with NLCSs is more complex indicating that RyR is less important for the generation of NLCSs compared to the generation of PLCSs. The fraction of fibers with NLCSs and PLCSs is not reduced in the presence of Xestospongin C. The localized perinuclear and intranuclear Ca(2+) signals may be a powerful tool for the cell to regulate adaptive processes as gene expression. The intranuclear Ca(2+) signals may be particularly interesting in this respect.

Dataset Information

Reversal of the myosin power stroke induced by fast stretching of intact skeletal muscle fibers.

Publications

Reversal of the myosin power stroke induced by fast stretching of intact skeletal muscle fibers.

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