Decreased thin filament density and length in human atrophic soleus muscle fibers after spaceflight. |
| |
Authors: | D A Riley J L Bain J L Thompson R H Fitts J J Widrick S W Trappe T A Trappe D L Costill |
| |
Institution: | Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee 53226, USA. dariley@mcw.edu |
| |
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%. |
| |
Keywords: | |
|
| 点击此处可从《Journal of applied physiology (Bethesda, Md. : 1985)》浏览原始摘要信息 |
| 点击此处可从《Journal of applied physiology (Bethesda, Md. : 1985)》下载免费的PDF全文 |
|