| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Vol. 273, Issue 5, C1690-C1699, November 1997
1 Department of Biology,
The purpose of this study was to examine the effect of prolonged bed rest (BR) on the peak isometric force (Po) and unloaded shortening velocity (Vo) of single Ca2+-activated muscle fibers. Soleus muscle biopsies were obtained from eight adult males before and after 17 days of 6° head-down BR. Chemically permeabilized single fiber segments were mounted between a force transducer and position motor, activated with saturating levels of Ca2+, and subjected to slack length steps. Vo was determined by plotting the time for force redevelopment vs. the slack step distance. Gel electrophoresis revealed that 96% of the pre- and 87% of the post-BR fibers studied expressed only the slow type I myosin heavy chain isoform. Fibers with diameter >100 µm made up only 14% of this post-BR type I population compared with 33% of the pre-BR type I population. Consequently, the post-BR type I fibers (n = 147) were, on average, 5% smaller in diameter than the pre-BR type I fibers (n = 218) and produced 13% less absolute Po. BR had no overall effect on Po per fiber cross-sectional area (Po/CSA), even though half of the subjects displayed a decline of 9-12% in Po/CSA after BR. Type I fiber Vo increased by an average of 34% with BR. Although the ratio of myosin light chain 3 to myosin light chain 2 also rose with BR, there was no correlation between this ratio and Vo for either the pre- or post-BR fibers. In separate fibers obtained from the original biopsies, quantitative electron microscopy revealed a 20-24% decrease in thin filament density, with no change in thick filament density. These results raise the possibility that alterations in the geometric relationships between thin and thick filaments may be at least partially responsible for the elevated Vo of the post-BR type I fibers.
contractile properties; non-weight bearing; skeletal muscle atrophy; muscle disuse; spaceflight
This article has been cited by other articles:
|
|
 |
|
  D. Slivka, U. Raue, C. Hollon, K. Minchev, and S. Trappe Single muscle fiber adaptations to resistance training in old (>80 yr) men: evidence for limited skeletal muscle plasticity Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2008; 295(1): R273 - R280. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. D. de Boer, C. N. Maganaris, O. R. Seynnes, M. J. Rennie, and M. V. Narici Time course of muscular, neural and tendinous adaptations to 23 day unilateral lower-limb suspension in young men J. Physiol., September 15, 2007; 583(3): 1079 - 1091. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. H. Fitts, J. G. Romatowski, J. R. Peters, D. Paddon-Jones, R. R. Wolfe, and A. A. Ferrando The deleterious effects of bed rest on human skeletal muscle fibers are exacerbated by hypercortisolemia and ameliorated by dietary supplementation Am J Physiol Cell Physiol, July 1, 2007; 293(1): C313 - C320. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Malisoux, C. Jamart, K. Delplace, H. Nielens, M. Francaux, and D. Theisen Effect of long-term muscle paralysis on human single fiber mechanics J Appl Physiol, January 1, 2007; 102(1): 340 - 349. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. P. Debold, J. Romatowski, and R. H. Fitts The depressive effect of Pi on the force-pCa relationship in skinned single muscle fibers is temperature dependent Am J Physiol Cell Physiol, April 1, 2006; 290(4): C1041 - C1050. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Caruso, J. Hamill, M. Yamauchi, D. Mercado, T. Cook, B. Higginson, S. O'Meara, J. Elias, and S. Siconolfi Albuterol aids resistance exercise in reducing unloading-induced ankle extensor strength losses J Appl Physiol, May 1, 2005; 98(5): 1705 - 1711. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. A. Riley, J. L. W. Bain, J. G. Romatowski, and R. H. Fitts Skeletal muscle fiber atrophy: altered thin filament density changes slow fiber force and shortening velocity Am J Physiol Cell Physiol, February 1, 2005; 288(2): C360 - C365. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. A. Tesch, J. T. Trieschmann, and A. Ekberg Hypertrophy of chronically unloaded muscle subjected to resistance exercise J Appl Physiol, April 1, 2004; 96(4): 1451 - 1458. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. R. Adams, V. J. Caiozzo, and K. M. Baldwin Skeletal muscle unweighting: spaceflight and ground-based models J Appl Physiol, December 1, 2003; 95(6): 2185 - 2201. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E. Stelzer and J. J. Widrick Effect of hindlimb suspension on the functional properties of slow and fast soleus fibers from three strains of mice J Appl Physiol, December 1, 2003; 95(6): 2425 - 2433. [Abstract] [Full Text]
|
|
|
|
|
|
D. A. Riley, J. L. W. Bain, J. L. Thompson, R. H. Fitts, J. J. Widrick, S. W. Trappe, T. A. Trappe, and D. L. Costill Decreased thin filament density and length in human atrophic soleus muscle fibers after spaceflight J Appl Physiol, February 1, 2000; 88(2): 567 - 572. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Williamson, M. P. Godard, D. A. Porter, D. L. Costill, and S. W. Trappe Progressive resistance training reduces myosin heavy chain coexpression in single muscle fibers from older men J Appl Physiol, February 1, 2000; 88(2): 627 - 633. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
