Spaceflight Effects on Single Skeletal Muscle Fiber Function in the Rhesus Monkey

Authors

Robert Fitts, Marquette UniversityFollow
Dominique Desplanches, Faculté de Medecine
Janell Romatowski, Marquette UniversityFollow
Jeffrey J. Widrick, Marquette University

Document Type

Article

Language

eng

Format of Original

12 p.

Publication Date

11-2000

Publisher

American Physiological Society

Source Publication

American Journal of Physiology - Regulatory, Integrative, and Comparative Physiology

Source ISSN

0363-6119

Original Item ID

DOI: 10.1152/ajpregu.2000.279.5.R1546

Abstract

The purpose of this investigation was to understand how 14 days of weightlessness alters the cellular properties of individual slow- and fast-twitch muscle fibers in the rhesus monkey. The diameter of the soleus (Sol) type I, medial gastrocnemius (MG) type I, and MG type II fibers from the vivarium controls averaged 60 ± 1, 46 ± 2, and 59 ± 2 µm, respectively. Both a control 1-G capsule sit (CS) and spaceflight (SF) significantly reduced the Sol type I fiber diameter (20 and 13%, respectively) and peak force, with the latter declining from 0.48 ± 0.01 to 0.31 ± 0.02 (CS group) and 0.32 ± 0.01 mN (SF group). When the peak force was expressed as kiloNewtons per square meter (kN/m²), only the SF group showed a significant decline. This group also showed a significant 15% drop in peak fiber stiffness that suggests that fewer cross bridges were contracting in parallel. In the MG, SF but not CS depressed the type I fiber diameter and force. Additionally, SF significantly depressed absolute (mN) and relative (kN/m²) force in the fast-twitch MG fibers by 30% and 28%, respectively. The Ca²⁺ sensitivity of the type I fiber (Sol and MG) was significantly reduced by growth but unaltered by SF. Flight had no significant effect on the mean maximal fiber shortening velocity in any fiber type or muscle. The post-SF Sol type I fibers showed a reduced peak power and, at peak power, an elevated velocity and decreased force. In conclusion, CS and SF caused atrophy and a reduced force and power in the Sol type I fiber. However, only SF elicited atrophy and reduced force (mN) in the MG type I fiber and a decline in relative force (kN/m²) in the Sol type I and MG type II fibers.

Comments

American Journal of Physiology - Regulatory, Integrative, and Comparative Physiology, Vol. 279, No. 5 (November 2000): R1546-R1557. DOI.

Recommended Citation

Fitts, Robert; Desplanches, Dominique; Romatowski, Janell; and Widrick, Jeffrey J., "Spaceflight Effects on Single Skeletal Muscle Fiber Function in the Rhesus Monkey" (2000). Biological Sciences Faculty Research and Publications. 51.
https://epublications.marquette.edu/bio_fac/51