Faculty Collaboration Database

Decreased thin filament density and length in human atrophic soleus muscle fibers after spaceflight. J Appl Physiol (1985) 2000 Feb;88(2):567-72

Date

02/05/2000

Pubmed ID

10658024

DOI

10.1152/jappl.2000.88.2.567

Scopus ID

2-s2.0-0033974488 (requires institutional sign-in at Scopus site)   103 Citations

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-microm sarcomere length. Thick filament density ( approximately 1, 062 filaments/microm(2)) and spacing ( approximately 32.5 nm) were unchanged by spaceflight. Preflight thin filament density (2, 976/microm(2)) decreased significantly (P < 0.01) to 2,215/microm(2) 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%.

Author List

Riley DA, Bain JL, Thompson JL, Fitts RH, Widrick JJ, Trappe SW, Trappe TA, Costill DL

Author

Robert Fitts PhD Professor in the Biological Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Actin Cytoskeleton
Astronauts
Humans
Male
Microscopy, Electron
Muscle Fibers, Skeletal
Muscle, Skeletal
Muscular Atrophy
Myofibrils
Sarcomeres
Space Flight
Weightlessness