| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1996: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Maintrnance of differentiated, fiber-type specific structural and functional properties of muscle fibers is dependent on innervation, pattern of activity, hormonal influences, and aging. The membrane systems responsible for Ca^<2+> movements during excitation-contraction (E-C) coupling and relaxation are also affected by the same factors. However, it is not entirely clear but there is no general agreement on what there response is. For example, both an increase in the volume gractions of transverse (T-) tubules and sacoplasmic reticulum (SR) and reduced Ca^<2+>-pump density following aging have been reported. The specific aim of thes tudy is to determine the effect of ageing on the membrane systems directly concerned with the E-C coupling in skeletal muscle fibers to clarify the relationship between the ultrastructural changes of membrane systems and the E-C coupling deficiency in aged muscle fibers. The arrangement of the membrane systems was disordered with aging. Increases in transverse tubules network were apparent ; there were clearly more triads than in younger fibers, and pentadic and heptadic structures (i.e., a close approximation of two or three T-tubule elements with three or four elements of terminal cisternae of SR) were frewuently appeared following aging. It is not clear why pentads and heptads appear promptly with aging. On the other hand, the running exercise traning tends to inhibit ultrastructural changes of these membrane systems depend on aging. It is possible that decline is due to the spontaneous activity of the aged skeletal muscle fibers, indicating the pentads and heptads are more sensitive than myofibrils to a small amount of activity. Thus in these former muscle fibers there is a quantitative unbalance between the components of the membrane systems involved in E-C coupling and the rest of the system in old skeletal muscle fibers.
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