Decreased Thin Filament Density and Length in Human Atrophic Soleus Muscle Fibers After Spaceflight
Document Type
Article
Language
eng
Format of Original
6 p.
Publication Date
2-2000
Publisher
American Physiological Society
Source Publication
Journal of Applied Physiology
Source ISSN
0021-8987
Original Item ID
DOI: 10.1152/jappl.2000.88.2.567
Abstract
Soleus muscle fibers were examined electron microscopically from pre- and postflight biopsies of four astronauts orbited for 17 days during the Life and Microgravity Sciences Spacelab Mission (June 1996). Myofilament density and spacing were normalized to a 2.4-μm sarcomere length. Thick filament density (~1,062 filaments/μm2) and spacing (~32.5 nm) were unchanged by spaceflight. Preflight thin filament density (2,976/μm2) decreased significantly (P < 0.01) to 2,215/μm2 in the overlap A band region as a result of a 17% filament loss and a 9% increase in short filaments. Normal fibers had 13% short thin filaments. The 26% decrease in thin filaments is consistent with preliminary findings of a 14% increase in the myosin-to-actin ratio. Lower thin filament density was calculated to increase thick-to-thin filament spacing in vivo from 17 to 23 nm. Decreased density is postulated to promote earlier cross-bridge detachment and faster contraction velocity. Atrophic fibers may be more susceptible to sarcomere reloading damage, because force per thin filament is estimated to increase by 23%.
Recommended Citation
Riley, Danny A.; Bain, James L. W.; Thompson, Joyce L.; Fitts, Robert; Widrick, Jeffrey J.; Trappe, Scott W.; Trappe, Todd A.; and Costill, David L., "Decreased Thin Filament Density and Length in Human Atrophic Soleus Muscle Fibers After Spaceflight" (2000). Biological Sciences Faculty Research and Publications. 15.
https://epublications.marquette.edu/bio_fac/15
Comments
Journal of Applied Physiology, Volume 88, No. 2 (February 2000): 567-572. DOI.