On the Differential Response of Sarcoplasm and Myoplasm to Denervation in Frog Muscle

Abstract

Electron microscopic evidence is presented that the early response to denervation ("simple atrophy") of the semitendinosus m. of the frog is characterized by a greater prominence of the sarcoplasmic reticulum and by the presence, in the interfibrillar spaces, of mitochondria which are more numerous and smaller than in normal muscle. In contrast with the dynamic changes of the sarcoplasmic structural components, the myofibrils showed a progressive decrease in diameter after denervation and throughout the period studied. By carrying out tissue fractionation experiments, the yield of microsome-protein was found significantly greater in the denervated muscles, as compared with the contralateral controls, in this initial stage. Under the conditions attending the overdevelopment of the sarcoplasmic reticulum (SR), denervated semitendinosus m. incorporated valine-C14 into proteins more actively than the control pairs. The denervated muscles also showed an increase in the number of freely scattered and membrane-bound ribosomes and of polyribosomes, suggesting a more active synthesis of the SR membranes. Pronounced atrophy of the myofibrils, disorganization of the SR, and an increased number of ribonucleoprotein particles lying in the enlarged interfibrillar spaces were the main ultrastructural features of "degenerative atrophy" in frog muscle in the late periods after denervation. The probably adaptive character of the early changes occurring on denervation of frog muscle is discussed.

Effects of prolonged mechanical ventilation on respiratory muscle ultrastructure and mitochondrial respiration in rabbits

“…In accordance with these previous studies, we found disruption of myofibrils, with preserved areas adjacent to disintegrated sarcomers [15,30,31,33] and increased amounts of lipid vacuoles, glycogen granules, and connective tissue [14,15,31,33]. As in the denervation studies, we observed changes in triads and sarcoplasmic reticulum [33,35]. Concerning mitochondria, we did not observe swelling or alterations in cristae and matrix [14,15,32] but only smaller rounded mitochondria, which were irregularly located near the Z-bands.…”

The influence of immobilization and stretch on protein turnover of rat skeletal muscle.

“…1973;Go ldspink, 1976) and dystrophic muscles (Williams & Goldspink, 1976) as well as normal innervated ones, are known to grow and add on new sarcomeres in series when held in a lengthened state. These findings suggest that although denervated, or dystrophic, muscles undergo atrophy mainly by decreases in fibre diameters (Muscatello, Margreth & Aloisi, 1965;Rowe & Goldspink, 1969) longitudinal growth can be induced in such muscles by stretching. In the absence of the stretch reflex denervated muscle appears to grow ) and add on new sarcomeres (Goldspink, Tabary, Tabary, Tardieu & Tardieu, 1974) under the influence of passive stretch.…”

Effects of strain on contractile force and number of sarcomeres in series of Xenopus laevis single muscle fibres during long-term culture

“…Although temperature and the low degree of activity may have inhibited the breakdown of proteins, some atrophy was expected at least after more than 3 months of culture at negative strain. In vivo, dry weight of denervated frog muscle was shown to be reduced by 20% within 2 months (Muscatello et al, 1965). Therefore, it can be excluded that the lack of atrophy is due to the culture temperature of 20°C.…”