期刊
JOURNAL OF APPLIED PHYSIOLOGY
卷 92, 期 2, 页码 817-825出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/japplphysiol.00717.2001
关键词
human; skeletal muscle; electron microscopy; myofilaments; actin
资金
- NINDS NIH HHS [U01 NS-33472] Funding Source: Medline
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-mum sarcomere length, thick filament density is similar to1,012 filaments/mum(2) in all fiber types and unchanged by space-flight. In preflight aldehyde-fixed biopsies, gastrocnemius fibers possess higher percentages (similar to23%) 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.
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