Thin filament diversity and physiological properties of fast and slow fiber types in astronaut leg muscles. J Appl Physiol (1985) 2002 Feb;92(2):817-25
Date
01/18/2002Pubmed ID
11796697DOI
10.1152/japplphysiol.00717.2001Scopus ID
2-s2.0-0036089917 (requires institutional sign-in at Scopus site) 39 CitationsAbstract
Slow type I fibers in soleus and fast white (IIa/IIx, IIx), fast red (IIa), and slow red (I) fibers in gastrocnemius were examined electron microscopically and physiologically from pre- and postflight biopsies of four astronauts from the 17-day, Life and Microgravity Sciences Spacelab Shuttle Transport System-78 mission. At 2.5-microm sarcomere length, thick filament density is approximately 1,012 filaments/microm(2) in all fiber types and unchanged by spaceflight. In preflight aldehyde-fixed biopsies, gastrocnemius fibers possess higher percentages (approximately 23%) of short thin filaments than soleus (9%). In type I fibers, spaceflight increases short, thin filament content from 9 to 24% in soleus and from 26 to 31% in gastrocnemius. Thick and thin filament spacing is wider at short sarcomere lengths. The Z-band lattice is also expanded, except for soleus type I fibers with presumably stiffer Z bands. Thin filament packing density correlates directly with specific tension for gastrocnemius fibers but not soleus. Thin filament density is inversely related to shortening velocity in all fibers. Thin filament structural variation contributes to the functional diversity of normal and spaceflight-unloaded muscles.
Author List
Riley DA, Bain JL, Thompson JL, Fitts RH, Widrick JJ, Trappe SW, Trappe TA, Costill DLAuthor
Robert Fitts PhD Professor in the Biological Sciences department at Marquette UniversityMESH terms used to index this publication - Major topics in bold
AdultAstronauts
Humans
Male
Microscopy, Electron
Middle Aged
Muscle Contraction
Muscle Fibers, Fast-Twitch
Muscle Fibers, Skeletal
Muscle Fibers, Slow-Twitch
Muscle, Skeletal
Space Flight
Time Factors
Ultrasonography
