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  • Mechano-chemistry of muscle  (2)
  • Rigor state of muscle  (1)
  • 1975-1979  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 4 (1978), S. 209-222 
    ISSN: 1432-1017
    Keywords: ATP analogue ; Insect fibrillar muscle ; Stiffness per cross bridge ; Quick release-recovery ; Mechano-chemistry of muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The recovery in tension after release of a fibrillar muscle preparation as well as the fall in tension after restretch was found to be greater in presence of AMP-PNP than in its absence (rigor). The effect of AMP-PNP was concentration-dependent with an optimum at 0.1 mM corresponding to the dissociation constant of AMP-PNP from the myosin heads. This evidence supports the validity of the teinochemical principle which predicts a stretch-dependent AMP-PNP binding. The stiffness calculated per cross bridge was similar to that found by Huxley and Simmons (1971). It was further calculated that only 15% of the cross bridges are in a force-maintaining state in rigor.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European biophysics journal 4 (1978), S. 223-236 
    ISSN: 1432-1017
    Keywords: Actin-myosin interactions ; Muscle mechanics ; ATP hydrolysis in skeletal muscle ; Rigor state of muscle ; Cross-bridge slippage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract A sudden stretch (within 0.3 ms) of glycerol-extracted rabbit psoas fibre bundle suspended in ATP-salt solution caused an immediate tension increase followed by a rapid tension decay (quick phase) which was nearly completed within 3 ms. The quick phase was missing or much reduced in the absence of ATP when the fibres were in rigor. Since the immediate stiffness of the fibres was nearly the same at the onset and at the end of the quick phase, the latter cannot be due to cross-bridges detachment per se. However, it may be ascribed to a conformational change (e.g. rotation) of attached bridges as suggested by Huxley and Simmons. Alternatively it might be explained by a slippage of attached cross-bridges. This mechanism would presuppose fast detachment and reattachment of strongly strained cross-bridges during the quick phase. Evidence for such a process was obtained by analysing the tension transients obtained when fibre bundles subjected to a large stretch were subsequently (within 10 ms) released to the initial length, as well as from stiffness measurements during the sudden length change: The stiffness was not found to be constant either during stretch or during the release. This may be taken to mean that the number of attached cross-bridges does not remain constant even during a rapid length change. In view of these results, the model proposed by Huxley and Simmons might be extended to take account of rapid attachment and detachment of crossbridges.
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  • 3
    ISSN: 1432-1017
    Keywords: Myofibrillar ATPase ; Mechano-chemistry of muscle ; Insect fibrillar muscle ; Muscular energetics ; Kinetics of actin-myosin interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract 1) A study is presented on the effect of temperature on the mechanochemical states involved in the cross bridge cycle of single glycerinated dorsal longitudinal fibres from Lethocerus. Contraction was induced by immersing the fibre in a MgATP-salt solution at Ca2+∼10 ΜM (pH 6.7). 2) Rising the temperature increases the rates of isometric tension generation following an increase in the [Ca2+] from 0.01 to 10 ΜM as well as the steady state levels of isometric tension and the rates of ATP splitting. 3) Tension transients following stretches of rise times 250 Μs and amplitudes up to 0.4% L i comprise at least four phases: an elastic phase the amplitude of which decreases by raising the temperature; a biphasic quick phase of tension decay with a mean Q 10=2; a delayed tension rise (Q 10∼5). 4) Tension transients following releases of fall time 250 Μs and amplitudes up to 0.3% L i also comprise four phases: an elastic phase comparable to that observed following stretches; a deactivation phase composed of a single exponential and a slow recovery phase. 5) The number of cross bridges attached to the actin at any moment is not changed during the elastic and quick recovery phase following a release as well as during the elastic and fast quick phase following a stretch. However, the number of attached cross bridges decreases during the deactivation phase. 6) The early phases of tension adjustment (T curves) which were recorded during the releases showed a marked dependence on temperature. The T curves fitted with high accuracy the Huxley and Simmons (1971) predictions of cross bridge rotation. 7) Analysis of the T curves in terms of the Huxley and Simmons (1971) model shows that a) the stiffness of a single cross bridge (D=1.2 104− N/m) obeys Hook's law; b) the number of myosin heads attached to actin (24% of the total number) is not altered during releases; c) rotation of myosin heads from a perpendicular to an acute angled position extends the elastic element of a cross bridge by 11 nm; d) at 25
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