Return of Myosin Heads to Thick Filaments After Muscle Contraction

Yagi, Naoto; Ito, M; Nakajima, Hideo; Izumi, Takao; Matsubara, Ichiro

doi:10.1126/science.301660

Cited by 35 publications

(22 citation statements)

References 7 publications

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“…Since almost all myosin projections are supposed to attach to actin in skeletal muscle on going into rigor (62), this result was interpreted to suggest that 45-58% of the myosin projections are attached to actin (or in the vicinity of the thin filaments) at any particular moment during contrac tion. More recent stroboscopic experiments, which required a smaller number of contractions and therefore caused less fatigue to muscle, showed a greater change in the equatorial intensity ratio (54,63,65). In an experiment in which the equatorial pattern was obtained from a single isometric tetanus of lO-sec duration, the intensity ratio was 0.51, very close to the rigor value (49).…”

Section: Patterns From Skeletal Muscle During Contractionmentioning

confidence: 67%

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X-Ray Diffraction Studies of the Heart

Matsubara¹

1980

Annu. Rev. Biophys. Bioeng.

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The contractile apparatus of vertebrate heart muscle is similar to that of vertebrate skeletal muscle when viewed in the electron microscope (52, 61). The sarcomeres contain regular, overlapping arrays of thick and thin filaments as in skeletal muscle, and the length of these filaments are about the same as those of skeletal myofilaments. The amounts of the major myofibrillar proteins (myosin, actin, tropomyosin, and troponin) are comparable to those found in skeletal muscle (34). Based on such structural and biochemical similarities, the contractile mechanism of heart muscle is believed to be essentially the same as that of skeletal muscle. According to currently accepted models of skeletal muscle contraction. (14,20,21,25), the myosin heads that project from the backbone of the thick filament react with actin molecules aligned on the thin filament. A relative sliding force between the two types of filaments is produced in the course of the reaction, leading to contraction of muscle. These models have also been applied to heart muscle to explain the molecular basis of its mechanical properties.However, heart muscle has important mechanical properties that are not shared by skeletal muscle. A typical example is the staircase phenomenon in which the contractile tension of heart muscle increases with the frequency of contraction (4). The twitch tension of skeletal muscle, in contrast, is relatively independent of the frequency. Many such differences between the two types of muscle have been ascribed to differences in the events responsible for excitation-contraction coupling.

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Section: Patterns From Skeletal Muscle During Contractionmentioning

confidence: 67%

“…The initial rapid return occurs almost simultaneously with the fall of tension. The slow return continues after the tension has fallen to zero (63).…”

Section: Musclementioning

confidence: 98%

X-Ray Diffraction Studies of the Heart

Matsubara¹

1980

Annu. Rev. Biophys. Bioeng.

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“…4 and table 1. Yagi et al [14] have found, in whole frog muscles, that -80% of the heads attached during contraction return rapidly to the thick filaments (< 500ms) after cessation of a tetanus. The rest return slowly ( > 5 s).…”

Section: !7mentioning

confidence: 99%

“…Thus, the A-heads can produce large distortions in the close-packing of the tails and, in a more general way, in the overall arrangement of the thick filaments. During contraction, most of the B-heads are attached to actin or in the vicinity of the thin filaments [14,171 and the distortions in the myosin filaments are certainly considerable. This conclusion agrees with the findings of Huxley et al [ 18,191, who have observed the disappearance of some layer-lines arising from the thick filaments and a more blurred structure of these latter, during contraction.…”

Section: !7mentioning

confidence: 99%

The possible roles of the myosin heads

Morel

Garrigos

1982

FEBS Letters

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It is suggested that, in the conditions which exist in vivo, one head of a myosin molecule interacts with another head of the opposite molecule, inside the backbone of the thick filament. The other head lies outside and can interact with actin. This model is based on the fact that a dimer of the myosin heads exists and that there is a close correlation between the properties of the dimer and those of the thick filament diameter. In natural filaments, there are myosin molecules in excess and it is suggested that these molecules have their two heads outside the backbone.

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“…Hill (1968), Schoenberg, Brenner, Chalovich, Greene & Eisenberg (1984) and Schoenberg (1988) have provided evidence from intact and skinned fibres that is consistent with attachment of cross-bridges to thin filaments during periods of rest. Yagi, Ito, Nakajima, Izumi & Matsubara (1977) interpreted X-ray diffraction patterns of sartorius muscle following isometric tetanus as indicating that 80 % of the myosin heads returned rapidly to the thick filaments simultaneously with the fall of tension. The remaining 20% of the cross-bridges returned slowly to the thick filaments; complete return required as much as 7 s following a tetanus, which is consistent with the decline in additional force which we observed.…”

Section: Discussionmentioning

confidence: 99%

Additional force during stretch of single frog muscle fibres following tetanus

Kilgore

Mobley²

1991

Experimental Physiology

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SUMMARYSingle fibres from the anterior tibialis muscles of frogs were used in paired difference experiments to investigate the long-term effect (up to 3 8 s) of tetanic stimulation on fibre stiffness during relaxation. The fibres were stretched from sarcomere lengths of 25 ,um to 3 0 ,tm at constant velocities for periods ranging from 0 5 to 1 75 s. The first stretch of each pair took place when the fibres had not experienced a tetanus for at least 5 min. The second stretch took place 20-30 s after the first, but it was preceded by a tetanus (100 Hz stimulation applied for 190 ms; temperature, 23°C). The force produced by the first stretch was subtracted from the force produced by the second to produce a paired difference. The fibres were held at the sarcomere length of 3 0 ,um except for a brief period of time immediately prior to the stretches (1200 or 1450 ms). During those periods the fibres were shortened to 2 5 ,um (250 ms) and then held at 2-5 ,um, regardless of whether a tetanus was elicited, for either 950 or 1200 ms. The second stretch of each pair began either at the end of, or 250 ms after, the last stimulating pulse of the tetanus. At every velocity of stretch, the force produced by the fibres during the stretches was greater when the stretches were preceded by a tetanus than when they were not, and the additional force peaked at the conclusion of the stretches. The additional force, which was produced during the stretches following the tetani, declined for the remainder of the data acquisition period (up to 3 s) following the completion of stretches; it extrapolated to zero at 7-8 s after the completion of the stretches. The magnitude of the additional force was a nonlinear direct function of the rate of stretch. Thixotropy or an increased stiffness to stretch was observed in all of the fibres following periods of quiescence.

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Return of Myosin Heads to Thick Filaments After Muscle Contraction

Cited by 35 publications

References 7 publications

X-Ray Diffraction Studies of the Heart

X-Ray Diffraction Studies of the Heart

The possible roles of the myosin heads

Additional force during stretch of single frog muscle fibres following tetanus

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