Gillespie Ca

Motor unit recruitment as reflected by muscle fibre glycogen loss in a prosimian (bushbaby) after running and jumping

A qualitative histochemical assessment of glycogen loss in biopsies was made in bush-babies after running and jumping. Glycogen loss was related to the specific type of exercise. After running, glycogen loss was greatest in the slow-twitch oxidative fibre and depletion in the fast-twitch oxidative glycolytic fibres was similarly greater than in the fast-twitch glycolytic fibres. After jumping, the opposite pattern of glycogen utilization occurred (FG>FOG>SO).

Overloaded skeletal muscles of a nonhuman primate (Galago senegalensis)

Abstract Selected morphological, biochemical, and physiological properties of skeletal muscles from five control and six trained adult nonhuman primates, Galago senegalensis , were studied. After a 6-month treadmill endurance-training program, fewer glycogen-depleted fibers were found in the plantaris of trained than in controls after 15 min of electrical stimulation. There was an increase in the proportion of fast-twitch oxidative-glycolytic fibers at the expense of fast-twitch glycolytic fibers, enhanced cytochrome a and c concentrations, and elevated SDH activity. No changes in glycolytic enzymes or contraction time of the normally fast-twitch plantaris muscle were found. Maximal twitch and tetanic muscle tension and overall fiber size were not significantly different in the controls and trained Galagos. However, fast-twitch oxidative-glycolytic fibers in the plantaris were significantly larger in the trained Galagos. These adaptations were muscle specific, demonstrating that muscles vary in response to treadmill exercise depending on anatomical location or action (or both) in the exercise as well as fiber-type composition.

Lactate dehydrogenase isoenzymes: Distribution in fast-twitch red, fast-twitch white, and slow-twitch intermediate fibers of guinea pig skeletal muscle

Abstract Lactate dehydrogenase activity and LDH isoenzyme distribution were determined in supernatants of skeletal muscles consisting predominately of fast-twitch red, fast-twitch white, or slow-twitch intermediate fibers. The LDH activity was highest in the fast-twitch white. The activity in the fast-twitch red was significantly lower than in the fast-twitch white but significantly greater than in slow-twitch intermediate muscle or the heart. LDH5 was found to be the predominant isoenzyme in both the fast-twitch white and fast-twitch red fibers whereas LDH1 predominated in both the slow-twitch intermediate fibers and the heart.

Response of muscle glycogen and phosphorylase to electrical stimulation in trained and nontrained guinea pigs

Abstract Total phosphorylase activity determined histochemically was selectively depleted in white fibers of the medial gastrocnemius of adult guinea pigs after 1 hour of electrical stimulation at a frequency of 5/sec. Histochemical depletion of phosphorylase was paralleled by glycogen depletion measured spectrophotometrically in homogenates and histochemically in frozen sections. Every phosphorylase-negative fiber was negative for glycogen as determined by the PAS stain. The number of PAS-negative fibers slightly exceeded the number of phosphorylase-negative fibers. No PAS- and 11 phosphorylase-negative fibers were found in nonstimulated muscles. The histochemical depletion of glycogen and of phosphorylase was more pronounced in the nontrained than in the trained animals.