Lateral filamentary spacing in chemically skinned murine muscles during contraction.

Matsubara, Ichiro; Umazume, Yoshiki; Yagi, Naoto

doi:10.1113/jphysiol.1985.sp015608

Cited by 76 publications

(77 citation statements)

References 24 publications

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“…Interfilament spacing is a sensitive function of SL (11,12,19). Furthermore, significant changes in interfilament spacing have been reported to occur during activation in skeletal muscle (3,27). There may be a direct effect of interfilament spacing on myofilament Ca 2ϩ responsiveness (11,12,15,28,36).…”

Section: Discussionmentioning

confidence: 99%

Cooperative activation in cardiac muscle: impact of sarcomere length

Dobesh

Konhilas

Tombe

2002

American Journal of Physiology-Heart and Circulatory Physiology

107

132

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This study was undertaken to determine the impact of sarcomere length (SL) on the level of cooperative activation of the cardiac myofilament at physiological [Mg2+]. Active force development was measured in skinned rat cardiac trabeculae as a function of free [Ca2+] at five SLs (1.85–2.25 μm; 1 mM free [Mg2+]; 15°C). Only muscle preparations with minimal force rundown during the entire protocol were included in the analysis (average 7.2 ± 1.7%). Median SL was measured by on-line computer video micrometry and controlled within 0.01 μm. Care was taken to ensure a sufficient number of data points in the steep portion of the [Ca2+]-force relationship at every SL to allow for accurate fit of the data to a modified Hill equation. Multiple linear regression analysis of the fit parameters revealed that both maximum, Ca2+-saturated force and Ca2+sensitivity were a significant function of SL ( P < 0.001), whereas the level of cooperativity did not depend on SL ( P = 0.2). Further analysis of the [Ca2+]-force relationships revealed a marked asymmetry that, also, was not affected by SL ( P = 0.2–0.6). Finally, we found that the level of cooperativity in isolated skinned myocardium was comparable to that reported for intact, nonskinned myocardium. Our results suggest that an increase in SL induces an increase in the Ca2+ responsiveness of the cardiac sarcomere without affecting the level of cooperativity.

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Section: Discussionmentioning

confidence: 99%

Cooperative activation in cardiac muscle: impact of sarcomere length

Dobesh

Konhilas

Tombe

2002

American Journal of Physiology-Heart and Circulatory Physiology

107

132

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“…Our results are qualitatively similar to those reported by Bagni et al (1995) from single frog fibres, which showed large reductions in the passive tension components following mechanical skinning. Skinning of frog muscle fibres is known to result in expansion of the filament lattice (Matsubura & Elliot, 1972;Goldman & Simmons, 1986) and, in skinned mouse muscle fibres, addition of •3% dextran to the relaxing solution is thought to restore the filament lattice spacing to intact fibre dimensions (see Matsubara, Umazume & Yagi, 1985). In a few experiments, the effects of adding 4% dextran on the tension response to a ramp stretch was examined after a preparation was skinned.…”

Section: The Effects Of Chemical Skinning (At 10°c)mentioning

confidence: 99%

Temperature‐dependent changes in the viscoelasticity of intact resting mammalian (rat) fast‐ and slow‐twitch muscle fibres

Mutungi

Ranatunga

1998

The Journal of Physiology

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The tension and sarcomere length responses induced by ramp stretches (at amplitudes of 1‐3 % fibre length (Lo) and speeds of 0.01‐12 Lo s−1) were examined at different temperatures (range, 10‐35 °C) in resting intact muscle fibre bundles isolated from the soleus (a slow‐twitch muscle) and extensor digitorum longus (a fast‐twitch muscle) of the rat. Some observations are also presented on the effects of chemical skinning on passive viscoelasticity at 10 °C. As previously reported, the tension response to a ramp stretch, in different preparations and under various conditions, could be resolved into a viscous (P1), a viscoelastic (P2) and an elastic (P3) component and showed characteristic differences between slow and fast muscle fibres. Chemical skinning of the muscle fibres led to a decrease in the amplitude of all three tension components. However, the fast‐slow fibre differences remained after skinning. For example, the viscosity coefficient derived from P1 tension data decreased from 0.84 ± 0.06 before skinning to 0.44 ± 0.06 kN s m−2 after skinning in fast fibres; the corresponding values in slow fibres were 2.1 ± 0.08 and 0.87 ± 0.09 kN s m−2, respectively. Increasing the experimental temperature from 10 to 35 °C led to a decrease in all the tension components in both fast and slow muscle fibre bundles. The decrease of P1 (viscous) tension was such that the viscosity coefficient calculated using P1 data was reduced from 0.84 ± 0.1 to 0.43 ± 0.05 kN s m−2 in fast fibres and from 2.0 ± 0.1 to 1.0 ± 0.1 kN s m−2 in slow fibres (Q10 of ≈1.3 in both). In both fast and slow muscle fibre preparations, the plateau tension of the viscoelastic component (P2) decreased by 60‐80 % as the temperature was increased from 10 to 35 °C giving P2 tension a Q10 of ≈1.4 in slow fibres and ≈1.7 in the fast fibres. Additionally, the relaxation time of the viscoelasticity decreased from 11.9 ± 1 ms (fast) and 43.1 ± 1 ms (slow) at 10 °C to 3 ± 0.5 ms (fast) at 25 °C and 8.7 ± 0.6 ms (slow) at 35 °C (Q10 of ≈2.0 in slow and ≈2.5 in fast fibres). The fast‐slow fibre differences in passive viscoelasticity remained at the high physiological temperatures. The physiological significance of such fibre‐type differences and their possible underlying mechanisms are discussed.

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“…It was shown that the radial force generated by attached cross-bridges in activated and rigor states varied as a function of filament separation (Matsubara et al 1984(Matsubara et al , 1985Brenner & Yu, 1985, 1991. At large separations, the direction of the force is toward the centre of the fibre; its magnitude decreases monotonically with decreasing d1o until it reaches zero at the equilibrium spacing.…”

Section: Introductionmentioning

confidence: 99%

“…In skinned striated muscle fibres, where the surface membrane is made permeable or removed, the spacing between the contractile filaments decreases in transition from the relaxed state to isometric contraction (Shapiro, Tawada & Podolsky, 1979;Matsubara, Umazume & Yagi, 1985;Brenner & Yu, 1985, 1991, or to the rigor state (Maughan & Godt, 1981;Matsubara, Goldman & Simmons, 1984;Brenner, Yu & Podolsky, 1984;Umazume & Kasuga, 1984), suggesting that force is generated in the radial direction. Experimental evidence supports the idea that the radial force is generated by attached cross-bridges.…”

Section: Introductionmentioning

confidence: 99%

State‐dependent radial elasticity of attached cross‐bridges in single skinned fibres of rabbit psoas muscle

Brenner

1993

The Journal of Physiology

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SUMMARY1. In a single skinned fibre of rabbit psoas muscle, upon attachment of crossbridges to actin in the presence of ADP or pvrophosphate (PPi), the separation between the contractile filaments, as determined by equatorial X-ray diffraction, is found to decrease, suggesting that force is generated in the radial direction.2. The single muscle fibres were subjected to compression by 0-8 % of dextran T500. The changes in lattice spacings by dextran compression were compared with changes induced by cross-bridge attachment to actin. Based on this comparison, the magnitude and the direction of the radial force generated by the attached crossbridges were estimated. The radial cross-bridge force varied with filament separation, and the magnitude of the radial cross-bridge force reached as high as the maximal axial force produced during isometric contraction. 3. One key parameter of the radial elasticity, i.e. the equilibrium spacing where the radial force is zero, was found to depend on the ligand bound to the myosin head. In the presence of ADP, the equilibrium spacing was 36 nm. In the presence of MgPPi the equilibrium spacing shifted to 35 nm and Ca2" had little effect on the equilibrium spacing.4. The equilibrium spacing was independent of the fraction of cross-bridges attached to actin. The fraction of cross-bridges attached in rigor was modulated from 100 % to close to 0 % by adding up to 10 mm of ATPyS in the rigor solution. The lattice spacing remained at 38 nm. the equilibrium spacing for nucleotide-free crossbridges at ,u = 170 mm.5. Radial force generated by cross-bridges in rigor at large lattice spacings (38 nm < d0o < 46 nm) appeared to vary linearly with lattice spacing.6. The titration of ATPyS to fibres in rigor provided a correlation between the radial stiffness of the nucleotide-free cross-bridges and the equatorial intensities. The relation between the equatorial intensity ratio I1,/I1o and radial stiffness appeared to be approximately linear.7. The fibres under different conditions showed a wide range of radial stiffness, which was not proportional to the apparent axial stiffness of the fibre. If the apparent axial stiffness is a measure of the fraction of cross-bridges bound to actin, it follows that the radial elastic constant is state dependent; or vice versa.t To whom correspondence should be addressed. MS 9894S. XL, B. BRENNE-R AND L. C YUT 8. Differences in equilibrium lattice spacing and in radial elastic constant, most probably reflect differences in the molecular structure of the acto-myosin complex and there is more than one single conformation of the various strongly bound crossbridge states.9. Determining equilibrium spacings of the radial elasticity appears to be an effective new approach in detecting structural differences among the attached crossbridges, since this approach is independent of the fraction of cross-bridges attached, a factor that frequently encumbers the interpretation of structural studies of attached cross-bridge states.

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Lateral filamentary spacing in chemically skinned murine muscles during contraction.

Cited by 76 publications

References 24 publications

Cooperative activation in cardiac muscle: impact of sarcomere length

Cooperative activation in cardiac muscle: impact of sarcomere length

Temperature‐dependent changes in the viscoelasticity of intact resting mammalian (rat) fast‐ and slow‐twitch muscle fibres

State‐dependent radial elasticity of attached cross‐bridges in single skinned fibres of rabbit psoas muscle

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