X-ray evidence for radial cross-bridge movement and for the sliding filament model in actively contracting skeletal muscle

Haselgrove, John C.; Huxley, H. E.

doi:10.1016/0022-2836(73)90222-2

Cited by 279 publications

(226 citation statements)

References 14 publications

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“…This has been shown in the case of changes in the number of force-generating crossbridges as a result of changes in the calcium concentration in activated fibres or as a result of changes in the sarcomere length of rigor and activated fibres. Similar observations have been made by Matsubara et al (1984) in the case of mechanically skinned muscle fibres of the frog (incubated in rigor solution at various sarcomere lengths), Matsubara, Umazume & Yagi (1985) in the case of chemically skinned toe muscle of the mouse (incubated in Ca-activating solutions) and Haselgrove & Huxley (1973) in the case of living frog muscle (activated at various sarcomere lengths). Changes in the repulsive forces between the filaments, or in the attractive forces produced by interfilamentary connections, also caused changes in the spacing of the lattice of myosin and actin filaments either in the case of changes in the ionic strength of the relaxing solution or in the case of changes in sarcomere length.…”

Section: Discussionsupporting

confidence: 78%

Changes in the filament lattice of skeletal muscle fibres induced by changes in osmotic pressure, sarcomere length and the number of crossbridges

Jung¹,

Blangé²,

Treijtel³

1991

J Appl Cryst

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Equatorial small-angle X-ray diffraction patterns offer the possibility of obtaining detailed knowledge about interfilament distance and mass distribution of the myofilament lattice of skeletal muscle. These patterns of skinned frog-muscle fibres have been studied as a function of changes in the incubation solution using the Synchrotron Radiation Source in Daresbury (England). The results of these X-ray diffraction measurements and the results of measurements of the elastic properties of single muscle fibres, with microsecond time resolution, enabled an insight to be gained into the mechanism of muscle contraction. Interfilament distance decreased with increasing osmotic pressure in the absence of free calcium, whereas the mass distribution within the filament lattice did not change. Similar changes in the interfilament distance could be obtained either by decreasing the ionic strength in the absence of free calcium or by increasing the concentration of free calcium of the incubation solution. In both cases, however, mass distribution within the filament lattice also changed, which indicates that under these conditions the number of operating actomyosin complexes in the muscle fibre (crossbridges) tends to increase. The changes in interfilament distance and mass distribution that occur which depend on the free calcium concentration can be explained by a changed number of force-generating crossbridges. In the case of changes induced by ionic strength two effects interfere. Only part of the change in lattice spacing can be explained by an increased number of weakly attached crossbridges; the remaining part is caused by a process similar to that in the case of osmotic pressure. The effect of weakly attached crossbridges in the absence of free calcium under normal ionicstrength conditions is small. Therefore, the large decrement in interfilament distance due to an increased sarcomere length, in the absence of free calcium, is not caused by weakly attached crossbridges. Changes in sacromere length, in the presence of free calcium, resulted in changes in the number of force-generating crossbridges. However, the observed effect on interfilament distance cannot be explained solely by the variation of the number of forcegenerating crossbridges. The results of X-ray diffraction patterns and stiffness measurements of fibres in rigor solutions [absence of ATP (adenosine triphosphate) and calcium] and fibres in calcium solutions indicated that the (force-generating) crossbridges in the latter differ from crossbridges in rigor fibres.

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Section: Discussionsupporting

confidence: 78%

Changes in the filament lattice of skeletal muscle fibres induced by changes in osmotic pressure, sarcomere length and the number of crossbridges

Jung¹,

Blangé²,

Treijtel³

1991

J Appl Cryst

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“…Haselgrove & Huxley, 1973). In contrast with the stiffness, the intensity ratio during isotonic shortening under moderate loads does not differ significantly from that during isometric contraction (Podolsky, St. Onge, Yu & Lymn, 1976;H.…”

Section: Discussionmentioning

confidence: 87%

“…Haselgrove & Huxley, 1973;H. E. Huxley, 1979), does not change significantly after stretching, indicating that the high tension attained after stretch may be due to an increase in force exerted by each cross-bridge but not to an increase in the number of attached cross-bridges (Sugi, Amemiya & Hashizume, 1977;Amemiya, Sugi & Hashizume, 1979).…”

Section: Discussionmentioning

confidence: 99%

Enhancement of mechanical performance in frog muscle fibres after quick increases in load.

Sugi¹,

Tsuchiya²

1981

The Journal of Physiology

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SUMMARY1. The change in the ability of frog skeletal muscle fibres to sustain a load was studied during the course of oscillatory length changes or continuous isotonic lengthening following quick increases in load, by applying 'test' load steps and measuring the initial velocity of resulting isotonic motion.2. When quick decreases in load were applied during oscillatory length changes or continuous isotonic lengthening, the fibres were found to shorten against a load above the maximum tension (P0), indicating an increase in load-sustaining ability after quick increases in load.3. If quick increases in load were applied at various times after preceding quick increase in load, the initial velocity of resulting isotonic lengthening decreased with time, also indicating an increase in load-sustaining ability.4. An increase in load-sustaining ability was also observed during the course of rapid isotonic lengthening under a load of 1-6-1-7 P0, in which the fibres lengthened with increasing velocity.5. The increase in load-sustaining ability after quick increases in load was associated with a shift of the force-velocity curve towards higher force values, while no significant change was observed in the maximum shortening velocity at zero load.6. The stiffness of muscle fibres was estimated by measuring quick length changes coincident with load steps. It decreased with decreasing isotonic load below P0, approaching a certain finite value as the load tended to zero. For isotonic loads above P0, the stiffness increased with increasing isotonic load up to 1-6-1'7 P0, when step decreases in load were used for stiffness measurements.7. The mechanism of enhancement of mechanical performance of the fibres after quick increases in load is discussed in relation to the sliding filament/cross bridge hypotheses of muscle contraction.

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“…Correlation between the intensity ratio I,111,o and radial stiffness Changes in the intensity ratio 111/110 has been widely used as an indication of crossbridge formation between the thick and the thin filaments (Huxley, 1968;Haselgrove & Huxley, 1973). An increase in the ratio has been correlated with increasing isometric force level (Yu, Hartt & Podolskv.…”

Section: Radial Elasticity Of Cross-bridges In Musclementioning

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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X-ray evidence for radial cross-bridge movement and for the sliding filament model in actively contracting skeletal muscle

Cited by 279 publications

References 14 publications

Changes in the filament lattice of skeletal muscle fibres induced by changes in osmotic pressure, sarcomere length and the number of crossbridges

Changes in the filament lattice of skeletal muscle fibres induced by changes in osmotic pressure, sarcomere length and the number of crossbridges

Enhancement of mechanical performance in frog muscle fibres after quick increases in load.

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

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