1990 Fiscal Year Final Research Report Summary
Physiological Significance of Delay in the Early Phase of Muscle Contraction.
| Project/Area Number |
63440019
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Neurophysiology and muscle physiology
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| Research Institution | Tohoku University |
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Principal Investigator |
YAGI Naoto Tohoku Univ. Sch. Med., Lecturer, 医学部, 講師 (80133940)
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| Co-Investigator(Kenkyū-buntansha) |
USUKURA Jiro Nagoya Univ. Sch. Med., Assoc. Prof., 医学部, 助教授 (30143415)
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| Project Period (FY) |
1988 – 1990
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| Keywords | Muscle contraction / Cross-bridges / X-ray diffraction |
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| Research Abstract |
1. Fast (posterior latissimus dorsi, PLD) and slow (anterior latissimus dorsi, ALD) muscles of the chick were studied by time-resolved X-ray diffraction using a synchrotron radiation source.
2. In both muscles and at both 20 and 30^ﾟC, intensities of the X-ray equatorial reflections changed fester than tension at the beginning of tetanus. When the intensity change was converted into the mass transfer from the thick to the thin filament, the difference between the half-rise times of the transfer and tension development at 20^ﾟC was 140 msec in ALD and 37 msec in PLD. At 30^ﾟC, it was 110 msec and 10-20 msec, respectively.
3. Measurement of the spacing of the myofilament hexagonal lattice showed that the change in the sarcomere length takes place much faster than tension development, suggesting that the delay in tension development is not caused by the internal shortening of sarcomeres.
4. These results indicate that in the early stage of contraction, some of the myosin heads in the vicinity of the thin filament are developing little or no tension. A detailed calculation based on a simplified model suggests that the fast and slow muscles differ in the transition rate of myosin heads from the state of attachment with low tension (weak binding) to that with high tension (strong binding). Changes in the temperature affects both the rate of formation of the weak binding and that of transition from the weak to the strong binding.
5. Electron miscoscopy of ALD and PLD, rapidly frozen during contraction using liquid-helium, showed fine structures such as myosin cross-bridges. This method is considered potentially powerful in the structural investigation of weakly and strongly bound cross-bridges.
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Research Products
(10 results)
