Faculty Collaboration Database

Disproportionate loss of thin filaments in human soleus muscle after 17-day bed rest. Muscle Nerve 1998 Oct;21(10):1280-9

Date

09/15/1998

Pubmed ID

9736056

DOI

10.1002/(sici)1097-4598(199810)21:10<1280::aid-mus6>3.0.co;2-7

Scopus ID

2-s2.0-0031784365 (requires institutional sign-in at Scopus site)   82 Citations

Abstract

Previously we reported that, after 17-day bed rest unloading of 8 humans, soleus slow fibers atrophied and exhibited increased velocity of shortening without fast myosin expression. The present ultrastructural study examined fibers from the same muscle biopsies to determine whether decreased myofilament packing density accounted for the observed speeding. Quantitation was by computer-assisted morphometry of electron micrographs. Filament densities were normalized for sarcomere length, because density depends directly on length. Thick filament density was unchanged by bed rest. Thin filaments/microm2 decreased 16-23%. Glycogen filled the I band sites vacated by filaments. The percentage decrease in thin filaments (Y) correlated significantly (P < 0.05) with the percentage increase in velocity (X), (Y = 0.1X + 20%, R2 = 0.62). An interpretation is that fewer filaments increases thick to thin filament spacing and causes earlier cross-bridge detachment and faster cycling. Increased velocity helps maintain power (force x velocity) as atrophy lowers force. Atrophic muscles may be prone to sarcomere reloading damage because force/microm2 was near normal, and force per thin filament increased an estimated 30%.

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
Adult
Atrophy
Bed Rest
Biopsy
Humans
Male
Middle Aged
Muscle Fibers, Skeletal
Muscle, Skeletal
Time Factors