Muscle fiber necrosis and regeneration induced by prolonged weight‐lifting exercise in the cat

Abstract

For periods ranging from 26 to 87 weeks, the morphological characteristics of the flexor carpi radialis (FCR) muscle were examined in four cats trained to perform weight-lifting exercise. Four untrained, sex and weight-matched cats served as controls. The right FCR from each cat was surgically isolated, attached to a tension transducer, and set at its optimal length. The forelimb was perfused with 2% glutaraldehyde in 0.1 M cacodylate buffer. Small bundles of fibers were teased from their origin and insertion tendons and embedded in Epon. Spaced serial sections were used to examine the morphological features of the fibers for trained and control animals. Ultrastructural examination revealed muscle fiber degenerative changes, such as pyknotic nuclei, disruption of the sarcolemma, vacuolation, and disorganization of myofilaments. Such changes were observed at a higher frequency in trained muscle than in control muscle. Spaced serial sections of fiber bundles showed that the degree of degeneration varied along the length of the fiber. Fiber area measurements showed that trained muscle had both larger and smaller fibers than control samples. The very small fibers observed in the trained muscle were considered to be regenerating or "new" fibers since they had not undergone degenerative changes. "Satellite-like" cells were observed in trained muscle. Such cells resembled satellite cells but also contained developing myofilaments. Since evidence of degeneration-regeneration was observed in control samples, but at a lower frequency, it was postulated that weight-lifting exercise accelerates muscle fiber turnover in the cat FCR.

Role of satellite cells in altering myosin expression during avian skeletal muscle hypertrophy

“…ALD muscles from birds in the BASE group exhibited a low, but measurable level of fiber damage (less than 1%, Fig, 3). This low level of damage in baseline muscle may reflect a n ongoing process of fiber turnover in which fibers degenerate and are repaired or replaced (Giddings et al, 1985). Sham-weighted ALD muscle exhibited significantly more damage than baseline muscle.…”

Effect of radiation on satellite cell activity and protein expression in overloaded mammalian skeletal muscle

“…Since activated satellite cells fuse to each other to form new fibers during regeneration (Snow, 1977), they might also form new fibers during hypertrophy. The appearance of small muscle fibers has been observed in weight-trained human (MacDougall et al, 1982;Alway et al, 1989aAlway et al, , 1992Staron et al, 1991Staron et al, , 1992Staron et al, , 1994, cat (Giddings et al, 1985;Giddings and Gonyea, 1992), and rat muscle (Tamaki et al, 1992); in rodent and cat muscle undergoing compensatory hypertrophy following removal of synergists (James, 1973;Salleo et al, 1980;Atherton et al, 1981;Yamada et al, 1989;Chalmers et al, 1992); and in stretch-overloaded avian muscle (Kennedy et al, 1988;Alway et al, 1989b;McCormick and Schultz, 1992). Researchers in these studies have suggested that small fibers may arise by atrophy of mature fibers, by fiber splitting, or by fusion of satellite cells.…”

Quantitative Morphometric Analyses of the Exercised Extensor Digitorum Longus Muscle of the Mouse

“…For example, some investigators use either 2% glutaraldehyde [Campion et al. 1981: Giddings et al. 1985 or 3 f glutaraldehyde .…”