Calcium and strontium activation characteristics of skeletal muscle fibres from the small marsupialSminthopsis macroura

Wilson, Gregory S.; Stephenson, D. George

doi:10.1007/bf01833322

Cited by 31 publications

(41 citation statements)

References 46 publications

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“…4A. The curve fitted through the data points from the fresh fibre was similar to a classical sigmoidal Hill curve Fink et al 1986;Wilson & Stephenson, 1990) generated using an n value of 8-0 and showed that the mid-point for force activation (pCa50) was 5-84. After DTNB treatment for 10 s Pr fell to 14% of P0.…”

Section: Fibre Stiffnessmentioning

confidence: 61%

“…Fast-twitch and slow-twitch fibres were classified according to their Ca2+-activation characteristics at different pCa (pCa = -loglo[Ca2"]) levels and according to whether they possessed low-frequency force oscillations of myofibrillar origin when submaximally Ca2"-activated (Stephenson & Williams, 1981;Fink et al 1986;Wilson & Stephenson. 1990).…”

Section: Skinned Fibresmentioning

confidence: 99%

“…The solutions used for the Ca2" activation of skinned fibres were prepared from a set G. J. WVILSON AND OTHERS of pre-activating, Ca2+-activating and relaxing solutions. The preparation and composition of these solutions were previously described in detail (Stephenson & Williams, 1981;Fink et al 1986;Wilson & Stephenson, 1990). In pre-activating solutions the predominant anion was hexamethylenediamine-N,V,N',N'-tetraacetic acid (HDTA2-).…”

Section: Skinned Fibresmentioning

confidence: 99%

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Effects of sulphydryl modification on skinned rat skeletal muscle fibres using 5,5'‐dithiobis(2‐nitrobenzoic acid).

Wilson

Remedios

Stephenson

et al. 1991

The Journal of Physiology

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SUMMARY1. The sulphydryl groups of skinned skeletal muscle fibres have been reacted with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) in order to determine whether the effects of modifications to the contractile proteins are reflected in changes in the physiological properties of the contractile apparatus and Ca2+-regulatory system. 2. Results obtained from fast-twitch and slow-twitch rat fibres which were treated with DTNB (10 mm, pH 8-6, 5 C) for various periods of time under relaxing conditions showed that a major effect of the modification was to reduce the level of maximally Ca2+-activated force and fibre stiffness. Force and fibre stiffness were found to decline in proportion. Treatment with DTNB under these conditions did not cause a rise in force or fibre stiffness in relaxed fibres of either type.3. The effects induced by DTNB under relaxing conditions were substantially reversed by exposure to the reducing agent dithiothreitol (DTT) (10 mM, pH 741, 23°C). Force abolished by 30-35 s treatment with DTNB recovered after subsequent DTT treatment to 67+3 % (mean + S.E.M., n = 4) in fast-twitch fibres and to 91 + 2 % (n = 7) in slow-twitch fibres. These results were significantly different (t test, P < 0f001) indicating that the level of force recovery depended upon the fibre type.4. DTNB was found to affect not only the maximal Ca2+-activated force, but also the force-pCa (pCa = -logl0[Ca2+]) relationships of the fibres in a complex, fibretype specific way. DTT treatment partially reversed these DTNB effects. 5. The skinned fibre preparations reacted differently with DTNB under rigor conditions than under relaxing conditions, indicating that rigor modifies the reactivity of the functional sulphydryl groups to the thiol-targeted agents.6. When superprecipitation assays (an in vitro analogue of fibre contraction) were

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Section: Fibre Stiffnessmentioning

confidence: 61%

Section: Skinned Fibresmentioning

confidence: 99%

Section: Skinned Fibresmentioning

confidence: 99%

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Effects of sulphydryl modification on skinned rat skeletal muscle fibres using 5,5'‐dithiobis(2‐nitrobenzoic acid).

Wilson

Remedios

Stephenson

et al. 1991

The Journal of Physiology

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show abstract

“…Assessment of the effects of Ca2+ and Sr2+ activation was achieved by construction of force-pCa and force-pSr curves for the contractile responses of each individual skinned fibre as previously described in detail (Fink et al 1990;Wilson & Stephenson, 1990;Lynch et al 1991 The procedure for classifying fibres into respective types. on the basis of' their contractile characteristics has been described in detail previously (Wilson & Stephenson 1990.…”

Section: Discussionmentioning

confidence: 99%

“…on the basis of' their contractile characteristics has been described in detail previously (Wilson & Stephenson 1990. Individual fibres were only allocated to one of the two major fibre-type groups.…”

Section: Discussionmentioning

confidence: 99%

Contractile properties of skinned muscle fibres from young and adult normal and dystrophic (mdx) mice.

Williams¹,

Head²,

Lynch³

et al. 1993

The Journal of Physiology

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SUMMARY1. Single muscle fibres were enzymatically isolated from the soleus and extensor digitorum longus (EDL) muscles of genetically dystrophic mdx and normal (C57BL/10) mice aged 3-6 or 17-23 weeks.2. Fibres of both muscles were chemically skinned with the non-ionic detergent Triton X-100 (2 % v/v). Ca2+-and Sr21-activated contractile responses were recorded and comparisons were made between several contractile parameters of various fibre types of normal and dystrophic mice of similar age.3. There were no significant differences in the following contractile parameters of skinned fibres of normal and mdx mice of the same age: sensitivity to activating Ca21 (pCa50) or Sr2" (pSr50) and differential sensitivity to the activating ions (pCa50-pSr50).However the maximum isometric tension (P.) and the frequenev of myofibrillar force oscillations in EDL fast-twitch fibres of young mdx mice were significantly lower than those of soleus fast-twitch fibres of the same animals, or fast-twitch fibres (EDL or soleus) of normal mice.4. Age-related differences were apparent in some contractile parameters of both normal and mdx mice. In particular the steepness of force-pCa anid force-pSr curves increased with age in normal mice. yet decreased with age in fibres of mdx mice. 5. A fluorescent probe, ethidium bromide, which interchelates with DNA, was used with laser-scanning confocal microscopy to determine the distribution of myonuclei in fibres. Fibres isolated from either muscle type of normal animnals displayed a characteristic peripheral spiral of myonuclei. Fibres from muscles of m1dx mice displayed three major patterns of nuclear distribution: the normal peripheral spiral, long central strands of nuclei, and a mixture of these two patterns.6. The contractile characteristics of mdx fibres were not markedly influenced by the nuclear distribution pattern in that there were no discernible differences in the major contractile parameters (the Hill coefficients nCa and nSr, which are associated with the steepness of the Ca2' and Sr2+ activation curves, pCa50, pSr50, pCa50-pSr50) of skinned fibres possessing peripheral or central nuclei. However, except for nSr, these values were all lower in individual fibres which displayed similar proportions of central and peripheral nuclei. The presence of mixed nucleation and absence of MS 9920

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Theory and observation of spontaneous oscillatory contractions in skeletal myofibrils

Smith

Stephenson

1994

J Muscle Res Cell Motil

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At low levels of activation, an isometrically-held myofibrillar preparation on the descending limb may exhibit persistent oscillations of period 1-6 s in tension and sarcomere lengths. We propose a sarcomeric theory of spontaneous oscillatory contraction, based on the phenomena of force creep and delayed length activation. The time delay leads to oscillations and controls their period. A computer model using these ideas simulates spontaneous oscillatory contraction for fixed-end fibres only if isometric tension capacity varies slightly along the fibre. The form of this inhomogeneity controls a diversity of spontaneous oscillatory contraction behaviour: the tension waveform can vary from large and sinusoidal to small-amplitude pulses or chaotic behaviour, and these variations are observed in slow-twitch soleus fibres from the same animal (rat). The model predicts that oscillatory and quiescent regions coexist in the fibre, with large-amplitude sawtooth waveforms in sarcomere length in the former as observed. It can also generate travelling-wave structures, similar to those found by the Tokyo group, in oscillating regions when there is a spatial gradient in isometric tension capacity. Phase discontinuities in sarcomere length occur near the oscillatory-quiescent boundary. Predictions for the Ca2+ concentrations and sarcomere lengths in which spontaneous oscillatory contraction occurs and for differences in the spontaneous oscillatory contraction frequencies of fast- and slow-twitch fibres compare well with experiment. Spontaneous oscillatory contraction is also predicted under isotonic conditions.

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Calcium and strontium activation characteristics of skeletal muscle fibres from the small marsupialSminthopsis macroura

Cited by 31 publications

References 46 publications

Effects of sulphydryl modification on skinned rat skeletal muscle fibres using 5,5'‐dithiobis(2‐nitrobenzoic acid).

Effects of sulphydryl modification on skinned rat skeletal muscle fibres using 5,5'‐dithiobis(2‐nitrobenzoic acid).

Contractile properties of skinned muscle fibres from young and adult normal and dystrophic (mdx) mice.

Theory and observation of spontaneous oscillatory contractions in skeletal myofibrils

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