Journal of Applied Physiology, Vol 60, Issue 4 1284-1292, Copyright © 1986 by American Physiological Society

ARTICLES

SDH activity and cross-sectional area of muscle fibers in cat diaphragm

G. C. Sieck, R. D. Sacks, C. E. Blanco and V. R. Edgerton

The succinate dehydrogenase (SDH) activity and cross-sectional area of individual muscle fibers in the cat diaphragm were quantified using a computerized image-processing system. The population distributions of fiber-SDH activities and cross-sectional areas showed considerable range within each diaphragm. Despite an overlap in the distribution of SDH activities between fast-twitch (i.e., those staining darkly for myosin ATPase) and slow-twitch (i.e., those staining lightly for myosin ATPase) fibers, differences between the two populations of fibers were observed. Fast-twitch fibers generally had lower SDH activities and greater cross-sectional areas than slow-twitch fibers. However, the range of SDH activities and cross-sectional areas of fast-twitch fibers was much greater than in slow-twitch fibers. The population distributions of SDH activities and cross-sectional areas of both fast- and slow-twitch fibers were unimodal. The unimodal distribution of SDH activities in fast-twitch fibers suggested that these fibers could not be clearly subdivided into two groups based on differences in their oxidative capacity (i.e., high- and low-oxidative fibers). These results were discussed in the context of the classification of fast-twitch glycolytic and fast-twitch oxidative-glycolytic fibers using qualitative histochemistry. In addition, the functional significance of the unimodal distribution of oxidative capacities in fast-twitch fibers was discussed in relation to the distribution of fatigue properties in fast-twitch motor units. A significant negative correlation between cross-sectional area and SDH activity in both fast- and slow-twitch fibers was also observed. The importance of this negative correlation in relationship to the diffusion of energy substrates for oxidative metabolism was discussed.

This article has been cited by other articles:

				C. S. H. Sassoon, V. J. Caiozzo, A. Manka, and G. C. Sieck Altered diaphragm contractile properties with controlled mechanical ventilation J Appl Physiol, June 1, 2002; 92(6): 2585 - 2595. [Abstract] [Full Text] [PDF]

				Y. S. Prakash, C. B. Mantilla, W.-Z. Zhan, K. G. Smithson, and G. C. Sieck Phrenic motoneuron morphology during rapid diaphragm muscle growth J Appl Physiol, August 1, 2000; 89(2): 563 - 572. [Abstract] [Full Text] [PDF]

				W. Z. Zhan, J. G. Swallow, T. Garland Jr., D. N. Proctor, P. A. Carter, and G. C. Sieck Effects of genetic selection and voluntary activity on the medial gastrocnemius muscle in house mice J Appl Physiol, December 1, 1999; 87(6): 2326 - 2333. [Abstract] [Full Text] [PDF]

				M. I. Lewis, A. T. Feinberg, and M. Fournier IGF-I and/or growth hormone preserve diaphragm fiber size with moderate malnutrition J Appl Physiol, July 1, 1998; 85(1): 189 - 197. [Abstract] [Full Text] [PDF]

				M. I. Lewis, T. J. Lorusso, and M. Fournier Anabolic influences of insulin-like growth factor I and/or growth hormone on the diaphragm of young rats J Appl Physiol, June 1, 1997; 82(6): 1972 - 1978. [Abstract] [Full Text] [PDF]

				W.-Z. Zhan, H. Miyata, Y. S. Prakash, and G. C. Sieck Metabolic and phenotypic adaptations of diaphragm muscle fibers with inactivation J Appl Physiol, April 1, 1997; 82(4): 1145 - 1153. [Abstract] [Full Text] [PDF]