1997 Fiscal Year Final Research Report Summary
Oscillatory length changes in skeletal muscle fibers initiated by step tension changes
| Project/Area Number |
08670062
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General physiology
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| Research Institution | School of Medicine, Teikyo University |
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Principal Investigator |
SUGI H. Teikyo Univ.Sch.Med.Professor, 医学部, 教授 (20082076)
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| Co-Investigator(Kenkyū-buntansha) |
SHIRAKAWA I. Teikyo Univ.Sch.Med.Instructor, 医学部, 助手 (80236190)
KOBAYASHI T. Teikyo Univ.Sch.Med.Assistant Professor, 医学部, 講師 (00112756)
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| Project Period (FY) |
1995 – 1997
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| Keywords | skeletal muscle fiber / muscle contraction / stretch velocity change / tension response |
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| Research Abstract |
1. When tetanized frog skeletal muscle fibers were subjected to moderate-velocity stretches (<1L_0/s), the tension developed above the level of isometric tension started to decay after a sudden reduction of stretch velocity by more than 40-50%, though the fibers were still being stretched.
2. We analyzed the decay of tension response caused by the sudden reduction of stretch velocity, by applying three different types of stretch to a tetanized fiber, i.e.a 1.5% stretch with velocity V_1 (stretch 1), a 1.5% stretch with velocity V_2<V_1 (stretch 2) and a 3% stretch consisting of stretch 1 and stretch 2 applied in succession (stretch 3), and comparing the corresponding tension responses, TR 1, TR 2 and TR 3.
3. It was found that TR 3 to stretch 3 resulted from algebraical summation of TR 1 to the preceding stretch 1 and TR 2 to the subsequent stretch 2. In other words, TR 2 started on the falling tension baseline equal to the decay of TR 1 after the completion of stretch 1.
4. These results can be explained by assuming two distinct cross-bridge populations mechanically acting in parallel with each other ; one population consists of ordinary cycling cross-bridges generating steady level of isometric tension in tetanized fibers, while the other consists of locked-on cross-bridges producing the tension response to stretch above the level of isometric tension.
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