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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fatigue of isolated gastrocnemius muscles from R. pipiens leads to a marked increase in the proportion of phosphofructokinase bound to the particulate fraction and a decrease in the binding of lactate dehydrogenase, pyruvate kinase, creatine phosphokinase and glyceraldehyde-3-phosphate dehydrogenase. Only the proportion of aldolase bound to the particulate fraction was unaffected by fatigue. This pattern was unchanged when fatigued muscles were extracted at pH 6.5 rather than 7.5. Thus, muscle fatigue leads to opposite changes in the binding of the glycolytic enzymes.
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PMID:The effect of fatigue on the binding of glycolytic enzymes in the isolated gastrocnemius of Rana pipiens. 280 95

In the process of defining the recruitment of fuel and pathway selection in rainbow trout fast-twitch white skeletal muscle, it was clear that the near-maximal myosin adenosinetriphosphatase activity during a 10-s sprint was supported solely by phosphocreatine hydrolysis. A conservative estimate of the ATP turnover was 188 mumol X g wet wt-1 X min-1. It was not until the rate and force of contraction decreased that the relative contribution of anaerobic glycogenolysis became increasingly important. Over a 10-min period of burst swimming at approximately 120% of maximum aerobic steady-state swimming velocity of trout determined in a Brett-type swim tunnel, fatigue was associated with the near-depletion of glycogen in white muscle. The ATP turnover supported by anaerobic glycogenolysis was 78 mumol X g wet wt-1 X min-1. The glycolytic pathway appeared functional at this time with control sites being identified at hexokinase and phosphofructokinase (PFK-1). PFK-1 did not appear to be inhibited by low muscle pH (pH 6.66). In another exercise protocol lasting 30 min, complete exhaustion was related to glycogen depletion. The sum of all glycolytic intermediates from glucose 6-phosphate to pyruvate at exhaustion decreased by a dramatic 80% compared with the 25% decrease for the 10-min fatigue swimming protocol. This large depletion of glycolytic intermediates was accompanied by an 80% fall in ATP, a 70-80% reduction in the ATP/ADP and phosphorylation potential, and a 2.5-fold increase in the NAD/NADH. Associated with these changes was a marked displacement of the phosphoglycerate kinase (PGK), and the combined glyceraldehyde-3-phosphate dehydrogenase-PGK reactions from thermodynamic equilibrium. As a general conclusion, fatigue and exhaustion should be viewed as a multicomponent biochemical process in response to low glycogen and not leveled at one particular step of the glycolytic pathway.
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PMID:Regulation of anaerobic ATP-generating pathways in trout fast-twitch skeletal muscle. 360 83

Since the male oyster toadfish (Opsanus tau) is more active in sound production than the female, we hypothesized that sonic muscles of the male are biochemically specialized to perform more work. In order to categorize the muscle biochemically and test for sexual differences, we measured the activity of two anaerobic enzymes, 3-phosphoglyceraldehyde dehydrogenase (3PG) and lactic dehydrogenase (LDH), and two aerobic enzymes, malate dehydrogenase (MDH) and glutamic oxaloacetic transaminase (GOT). Males exhibited greater 3PG and GOT activity than females (p less than 0.05). Both MDH and LDH showed little activity in either sex. High 3PG and low LDH levels indicate a sustained level of glycolysis, with pyruvate shuttled into aerobic metabolism, and high GOT activity indicates a high level of aerobic metabolism. From this and other data, we conclude that toadfish sonic muscle can be classified as fast-twitch oxidative glycolytic or fast-twitch fatigue resistant. The endocrine basis for these sexual differences was examined by implanting steroid pellets into ovariectomized females. Testosterone induced a doubling of 3PG activity (p less than 0.02), and dihydrotestosterone induced an eight-fold increase (p less than 0.0005) in GOT concentration over controls. The steroids had no effect on LDH and MDH activities. Hormones, therefore, trigger one of the fundamental sexual differences underlying toadfish communication, namely a difference in metabolism, providing the male with the capacity for increased sound production.
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PMID:Sexual differences and steroid-induced changes in metabolic activity in toadfish sonic muscle. 408 85

In rats, chronic sacral spinal isolation eliminates both descending and afferent inputs to motoneurons supplying the segmental tail muscles, eliminating daily tail muscle EMG activity. In contrast, chronic sacral spinal cord transection preserves afferent inputs, causing tail muscle spasticity that generates quantitatively normal daily EMG. Compared with normal rats, rats with spinal isolation and transection/spasticity provide a chronic model of progressive neuromuscular injury. Using normal, spinal isolated and spastic rats, we characterized the activity dependence of calcium-handling protein expression for parvalbumin, fast sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA1) and slow SERCA2. As these proteins may influence fatigue resistance, we also assayed the activities of oxidative (citrate synthase; CS) and glycolytic enzymes (glyceraldehyde phosphate dehydrogenase; GAPDH). We hypothesized that, compared with normal rats, chronic isolation would cause decreased parvalbumin, SERCA1 and SERCA2 expression and CS and GAPDH activities. We further hypothesized that chronic spasticity would promote recovery of parvalbumin, SERCA1 and SERCA2 expression and of CS and GAPDH activities. Parvalbumin, SERCA1 and SERCA2 were quantified with Western blotting. Citrate synthase and GAPDH activities were quantified photometrically. Compared with normal rats, spinal isolation caused large decreases in parvalbumin (95%), SERCA1 (70%) and SERCA2 (68%). Compared with spinal isolation, spasticity promoted parvalbumin recovery (ninefold increase) and a SERCA2-to-SERCA1 transformation (84% increase in the ratio of SERCA1 to SERCA2). Compared with normal values, CS and GAPDH activities decreased in isolated and spastic muscles. In conclusion, with complete paralysis due to spinal isolation, parvalbumin expression is nearly eliminated, but with muscle spasticity after spinal cord transection, parvalbumin expression partly recovers. Additionally, spasticity after transection causes a slow-to-fast SERCA isoform transformation that may be compensatory for decreased parvalbumin content.
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PMID:Tail muscle parvalbumin content is decreased in chronic sacral spinal cord injured rats with spasticity. 2193 Jun 74