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Effect of spaceflight on skeletal muscle: Mechanical properties and myosin isoform content of a slow muscleThis study examined changes in contractile, biochemical, and histochemical properties of slow antigravity skeletal muscle after a 6-day spaceflight mission. Twelve male Sprague-Dawley rats were randomly divided into two groups: flight and ground-based control. Approximately 3 h after the landing, in situ contractile measurements were made on the soleus muscles of the flight animals. The control animals were studied 24 h later. The contractile measurements included force-velocity relationship, force-frequency relationship, and fatigability. Biochemical measurements focused on the myosin heavy chain (MHC) and myosin light chain profiles. Adenosinetriphosphatase histochemistry was performed to identify cross-sectional area of slow and fast muscle fibers and to determine the percent fiber type distribution. The force-velocity relationships of the flight muscles were altered such that maximal isometric tension P(sub o) was decreased by 24% and maximal shortening velocity was increased by 14% (P less than 0.05). The force-frequency relationship of the flight muscles was shifted to the right of the control muscles. At the end of the 2-min fatigue test, the flight muscles generated only 34% of P(sub o), whereas the control muscles generated 64% of P(sub o). The flight muscles exhibited de novo expression of the type IIx MHC isoform as well as a slight decrease in the slow type I and fast type IIa MHC isoforms. Histochemical analyses of flight muscles demonstrated a small increase in the percentage of fast type II fibers and a greater atrophy of the slow type I fibers. The results demonstrate that contractile properties of slow antigravity skeletal muscle are sensitive to the microgravity environment and that changes begin to occur within the 1st wk. These changes were at least, in part, associated with changes in the amount and type of contractile protein expressed.
Document ID
19950030336
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Caiozzo, Vincent J.
(Univ. of California, Irvine, CA United States)
Baker, Michael J.
(Univ. of California, Irvine, CA United States)
Herrick, Robert E.
(Univ. of California, Irvine, CA United States)
Tao, Ming
(Univ. of California, Irvine, CA United States)
Baldwin, Kenneth M.
(Univ. of California, Irvine, CA United States)
Date Acquired
August 16, 2013
Publication Date
April 1, 1994
Publication Information
Publication: Journal of Applied Physiology
Volume: 76
Issue: 4
ISSN: 8750-7587
Subject Category
Aerospace Medicine
Accession Number
95A61935
Funding Number(s)
CONTRACT_GRANT: NAG2-555
Distribution Limits
Public
Copyright
Other

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