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Review of spaceflight and hindlimb suspension unloading induced sarcomere damage and repairHindlimb suspension unloading (HSU) and spaceflight microgravity induce atrophy of the slow adductor longus muscle fibers which, following reloading, exhibit eccentric contraction (EC)-like lesions (abnormal widening of sarcomeres with A band disruption and excessively wavy, extracted Z lines). These lesions are similar morphologically to those produced in normal muscles after strenuous eccentric exercise. It appears that atrophic muscles exhibit increased susceptibility to eccentric damage because lesions are produced during nonstressful voluntary movements upon return to weightbearing. The EC-like lesions are absent in the unweighted conditions, but appear in HSU rats 15-60 minutes after reloading and in space-flown rates about 4 hrs after landing. By 12 hours, many EC-like lesioned sarcomeres are fully covered by longitudinal patches of Z line-like material which increases in density by 48 hours, producing the so-called "Z line streaming" morphology. In this case, Z line streaming is indicative of rapid repair of damaged sarcomeres rather than the onset of sarcomere breakdown. Immunoelectron microscopy is necessary to determine the composition of this dense material. By 9 days of reloading at 1 gravity, sarcomeres have regained normal structure, except for very rare persistence of faint Z patches. The morphological data indicate that Z patches serve at least two functions: 1) to permit contractile force to be transmitted across the damaged sarcomeres and 2) to provide a scaffold upon which sarcomeres are reconstructed in an active functional muscle.
Document ID
20040089769
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Riley, D. A.
(Medical College of Wisconsin Milwaukee, United States)
Thompson, J. L.
Krippendorf, B. B.
Slocum, G. R.
Date Acquired
August 21, 2013
Publication Date
January 1, 1995
Publication Information
Publication: Basic and applied myology : BAM
Volume: 5
Issue: 2
ISSN: 1120-9992
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: NAG2-633
CONTRACT_GRANT: NAGW-70
CONTRACT_GRANT: NAG2-522
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Number 00-00
Cosmos 2044 Project
Flight Experiment
NASA Program Flight
NASA Program Space Biology Research Associates
Cosmos 1887 Project
STS-40 Shuttle Project
Non-NASA Center
NASA Discipline Musculoskeletal
NASA Discipline Number 40-99
STS-58 Shuttle Project
STS-51B Shuttle Project
manned
unmanned
short duration

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