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

The histochemical profiles of myofibrillar adenosine triphosphatase (ATPase), nicotinamide adenine dinucleotide diaphorase (NADDase), and phosphorylase (Pase) activities were studied in the respiratory muscles of the chicken. Most respiratory muscles contained fibers exhibiting 18 possible combinations of staining reactions (dark or light ATPase; dark, intermediate, or light NADDase; dark, intermediate, or light Pase). Fibers that stained light for ATPase constituted as little as 10% of the total population in rectus abdominis, but as much as 32% of the total in costosternalis pars major. Those fibers did not tend to be smaller than fibers that stained dark for ATPase in the respiratory muscles as a group. Assuming these staining characteristics are correlated with functional properties of the fibers, as they are in mammals, the majority of the fibers should contract rapidly (dark ATPase) and be fatigue resistant (dark and intermediate NADDase).
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PMID:Histochemical studies of respiratory muscles of chicken. 14 96

On the basis of the histochemical activity of succinic dehydrogenase, only two fibre-types are distinguished in pigeon pectoralis major muscle. These are narrow "Red" and broad "White". The histochemical activity of myofibrillar ATPase was studied in these two distinct fibre-types. Both fibre-types showed high activity for the ATPase. "Red" fibres of pigeon pectoralis were not alkali-labile, at incubation pH 9.4, as were the "Type I" fibres of both avian and mammalian muscles. Again unlike "Type I" fibres, the "Red" fibres of pigeon pectoralis lacked the characteristic activation of acid-preincubated ATPase reaction. Pigeon pectoralis "Red" fibres are known to possess some characteristics of fast-twitch fibres (e.g. high fat, considerable phosphorylase, fibrillenstruktur myofibrillar arrangement, focal "en plaque" pattern of nerve endings). It is emphasized, therefore, that the pigeon pectoralis "Red" fibres are not equivalent to "Type I or slow-twitch", muscle fibres, but they are possibly "fast-twitch fatigue resistent or Type II Red" muscle fibres.
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PMID:"Red" fibres of pigeon pectoralis major muscle are "type II red". 14 61

During studies of the regulation of phosphorylase activity and glycogenolysis in contracting muscle, it was found that conversion of phosphorlyase beta to alpha is transient. Reversal of phosphorylase activation during both continuous and intermittent stimulation in the plantaris might, in part, have been due to development of fatigue. However, a complete reversal of phosphorylase activation was also evident within 5 min in the absence of fatigue in soleus muscles stimulated tetanically with 100-ms-long trains at a rate of 60/min. These muscles showed no significant decline in contractile force. Glycogen breakdown stopped in the soleus when phosphorylase reverted to the beta form, providing evidence that phosphorylase beta was not active. This lack of activity is probably explained by the finding that ATP and AMP concentrations changed little, while glucose 6-phosphate increased. Reversal of phosphorlyase activation soon after the onset of steady-state work may be a mechanism for conserving glycogen when the supply of other substrates is adequate to meet the muscles' energy needs.
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PMID:Reversal of phosphorylase activation in muscle despite continued contractile activity. 49 77

For the first time in Germany cases of a "centronuclear myopathy" are described in a 14-year-old boy and his 18-year-old sister. First symptoms in both patients appeared at 4 to 5 years of age with a "sleepy facial expression", clumsy gait and rapid fatigue. Within few years the disease progressed to generalized muscle weakness and atrophy, ptosis, ophthalmoplegia externa and areflexia. Weakness and atrophy were most pronounced in the distal muscles of the lower extremities. Both patients were free of epilepsy and the EEG recordings were normal. Motor and sensory nerve conduction velocities were normal. Repetitive stimulation of nerves revealed a normal transmission from nerve to muscle. Muscle biopsy showed a type I muscle fiber hypotrophy and a type II muscle fibre hypertrophy in addition to a predominance of type I fibres. Both fibre types showed central nuclei, sometimes appearing as chains in longitudinal sections. In most cells with central nuclei there persists a very small pericentral zone free of myofibrils but with increased activity of oxidative enzymes and phosphorylase. 2--3% of muscle fibres in cross sections showed a decreased of absent enzyme activity in the most peripheral fibre zone. Electron microscopy showed evidence of a centrally distinct myofibrillar disintegration. The father of both children had a ptosis at least from the 20th year of age. 5 years later generalized progressive muscle atrophy was recorded. Aged 51 years he died of pneumonia. Though not proved most probably the father suffered from the same disease as the children, pointing to an autosomal dominant inheritance in this family. The disease, according to the literature, seems to be genetically heterogeneous. The clinical picture seems to be independent of the mode of inheritance. Our patients showed a relatively rapid progression of symptoms. Pathogenetically the "centronuclear myopathy" may result from a disturbance of correlated nerve-muscle structures starting during early fetal life.
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PMID:[Centronuclear myopathy with autosomal dominant inheritance(author's transl)]. 115 Feb 40

Experimental therapies for McArdle's disease have been directed toward increasing substrate availability to exercising muscle. Such therapies to date have proven largely unsuccessful. These include administration of isoproterenol to increase blood flow, glucagon treatment to elevate serum glucose and increased dietary fat intake. Each of these therapies also results in greater levels of unesterified fatty acids in blood. More recently, a high protein diet is suggested to provide increased amounts of amino acids which would be available as fuel sources. We hypothesize that the absence of myophosphorylase in McArdle's disease creates an imbalance between the enzymes of the redox systems that control the generation, propagation and inactivation of free radicals. This occurs because muscle cells are forced to rely more heavily on fatty acid oxidation. The resulting free radical damage to cellular components disrupts metabolic control and increases the permeability of membranes. Elevated levels of Ca2+ in the sarcoplasm activate proteases, phospholipases and other catabolic enzymes initiating muscle fatigue and cramping. Lipid peroxidation is a consequence of normal muscle activity and may occur unchecked in individuals with McArdle's disease. Continued muscle activity in the absence of a favorable nutritional environment may promote the progression of the disease by increasing susceptibility to oxidative stress.
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PMID:The role of lipid peroxidation in McArdle's disease: applications for treatment of other myopathies. 146 Nov 77

A 25-year-old female with McArdle's disease was reported. She had no characteristic symptoms for McArdle's disease such as muscle cramp and brown urine, but had general fatiguability from childhood. On examination, she showed no neurological abnormalities including muscle atrophy and weakness. On laboratory examination, serum creatinine kinase (CK) level was elevated, though serum lactic acid level remained unchanged after the ischemic forearm exercise test. Muscle biopsy from the biceps brachii showed almost completely absent phosphorylase activity both histochemically and biochemically. Thus, she was diagnosed as having McArdle's disease. The skinned fiber test of the muscle showed no enhanced Ca induced Ca release (CICR), and serum VLDL level was normal. Her 27-year-old elder brother had similar clinical symptoms and serological abnormalities and may also have McArdle's disease, although muscle biopsy was not performed. A possibility of McArdle's disease should be considered when we encounter a patient who has only general fatigue and high serum CK level.
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PMID:[McArdle's disease without typical symptoms]. 208 31

Skeletal muscle has an inherent biochemical phenotypic plasticity that provides the possibility for it to be remodeled into a "heart-like" muscle for use in cardiac-assist devices. The purpose of this study was to chronically stimulate skeletal muscle electrically to transform the biochemical capacities of the three major subcellular systems (i.e., metabolic, calcium regulating, and contractile) to resemble those of heart muscle. The latissimus dorsi muscle (LDM) of mongrel dogs weighing 22-27 kg was stimulated via the thoracodorsal nerve at 2 Hz for 6-8 wk. This stimulation protocol reduced the phosphorylase (glycogenolytic) and phosphofructokinase (glycolytic) activities by 70%. The aerobic (citrate synthase activity) and fatty acid oxidative (3-hydroxyacyl-CoA dehydrogenase activity) capacities were not significantly increased by chronic stimulation and remained at about one-fourth those in the canine heart. The calcium-dependent sarcoplasmic reticulum adenosinetriphosphatase (ATPase) activity in the microsomal fraction, which was sixfold greater in the nonstimulated LDM than in the heart, was reduced by electrical stimulation to a level similar to that of the dog heart. The contractile capacity was evaluated by determining the percentage of types I and II fibers, the myofibrillar ATPase activity, and the proportion of myosin isoforms. The transformed muscle was comprised of 93 +/- 2% type I fibers, a myofibrillar ATPase activity similar to that in heart with primarily a slow-twitch muscle myosin isoform. In conclusion, electrical stimulation of canine LDM at 2 Hz for 6-8 wk resulted in two of the three biochemical systems, which confer physiological expression and fatigue resistance to muscle being transformed to resemble those of the myocardium.
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PMID:Biochemical transformation of canine skeletal muscle for use in cardiac-assist devices. 214 Aug 28

Experimental myotonia was induced in rats by 2,4-dichloro-phenoxyacetic acid (2,4-D). After 4 to 24 h of treatment, the anterior tibialis muscles exhibited increased fatigue at low frequency (30 Hz) nerve stimulation, but they developed normal tension at high-frequency (100 Hz) stimulation. Glycogen content and the activities of glycogen phosphorylase, lactate dehydrogenase and malate dehydrogenase remained normal. The absence of correlation between fatigability and energetic metabolism in this experimental model of myotonia suggests a dysfunction in excitation-contraction coupling.
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PMID:Energetic metabolism and fatigability in experimental myotonia. 215 93

Recent studies in patients with long-term heart failure have suggested that intrinsic abnormalities in skeletal muscle can contribute to the development of early lactic acidosis and fatigue during exercise. The present study provides an analysis of substrate and enzyme content, fiber typing, and capillarization in skeletal muscle biopsy samples obtained at rest from the vastus lateralis in 11 patients with long-term heart failure (left ventricular ejection fraction, 21 +/- 8%) and nine normal subjects. Patients demonstrated a reduced peak exercise oxygen consumption (13.0 +/- 3.3 ml/kg/min) when compared with normals (30.2 +/- 8.6 ml/kg/min, p less than 0.001) and had an accelerated rise in blood lactate levels during exercise. In mixed fiber skeletal muscle, total phosphorylase and glycolytic enzyme activities were not different in the two groups, whereas mitochondrial enzymes involved in terminal oxidation were decreased in patients as compared with normal subjects as indicated by reductions in succinate dehydrogenase (51 +/- 15 vs. 81 +/- 17 microM/g protein/min, p less than 0.001) and citrate synthetase (26 +/- 7 vs. 43 +/- 20 microM/g protein/min, p less than 0.05). 3-Hydroxyacyl-CoA-dehydrogenase, an important enzyme mediating beta-oxidation of fatty acids, was also reduced in patients as compared with normals (18 +/- 7 vs. 27 +/- 10 microM/g protein/min, p less than 0.05). There was no difference in high-energy phosphagens or lactate concentration of mixed muscle in the two groups, whereas glycogen content was decreased in patients (262 +/- 29 vs. 298 +/- 35 microM glucosyl units/kg dry wt, p = 0.01). Patients demonstrated a reduced percentage of slow twitch type I fibers (36 +/- 7% vs. 52 +/- 22%, p less than 0.05) and had a higher percentage of type IIb fast twitch fibers (24 +/- 9% vs. 11 +/- 12%, p = 0.02), which were smaller than the type IIb fibers seen in normal subjects (p less than 0.05). In patients, the number of capillaries per fiber was decreased for type I and type IIa fibers (both, p less than 0.03), but the ratio of capillaries to cross-sectional fiber area was not different for the two groups. These data demonstrate major alterations in skeletal muscle histology and biochemistry in patients with long-term heart failure, including fiber atrophy, a decrease in percentage of composition of type I fibers, and an increase in type IIb fibers accompanied by a decrease in oxidative enzyme capacity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Skeletal muscle biochemistry and histology in ambulatory patients with long-term heart failure. 229 59

The study of skeletal muscle disorders is providing potentially important insights into regulatory mechanisms in human exercise and fatigue and information useful for diagnostic and treatment purposes. This review primarily concerned the general metabolic and physiological factors which set upper limits to performance of various types of exercise in patients with a variety of muscle disorders. From the standpoint of exercise performance, skeletal muscle diseases can be classified into three major groups. One group consists of primary disorders of muscle energy metabolism, including defects in muscle carbohydrate and lipid metabolism, disorders of mitochondrial electron transport, and abnormalities of purine nucleotide metabolism. Exercise performance largely reflects the capacity for ATP resynthesis. Oxidative phosphorylation is the dominant quantitative source of energy for ATP resynthesis under most exercise conditions. Consequently, patients with disordered oxidative metabolism (i.e., patients with defects in the availability or utilization of oxidizable substrate, such as those with phosphorylase or PFK deficiency or those with defects in mitochondrial electron transport) typically demonstrate severely impaired exercise performance. Intolerance to sustained exercise and premature fatigability are salient features of muscle oxidative disorders. Maximal oxygen uptake and maximal a-v O2 difference are markedly subnormal related to an attenuated muscle oxygen extraction. Muscle weakness and atrophy are less common. Anaerobic muscle performance is dramatically limited in patients with virtually complete defects of glycogenolysis/glycolysis but appears relatively normal in those with electron transport defects. A second major group of disorders includes patients with decreased muscle mass due to muscle necrosis, atrophy, and replacement of muscle by fat and connective tissue. These disorders are exemplified by the various muscular dystrophies (Duchenne's dystrophy, Becker's dystrophy, LG dystrophy, FSH dystrophy, and myotonic dystrophy) in which exercise performance is severely impaired due to muscle wasting and weakness in spite of largely normal pathways for muscle ATP resynthesis. In muscular dystrophy patients, the degree to which maximal oxygen uptake and anaerobic muscle performance are impaired appears to be a function of the severity of muscle weakness and atrophy. A third group of disorders includes patients with impaired activation of muscle contraction or relaxation. These disorders may be considered in two subcategories. In the first, impaired activation or relaxation of contractile activity is due to intrinsic muscle dysfunction (e.g., diseases associated with myotonia or periodic paralysis). In the second subcategory, there is impaired muscle activation due to a primary abnormality in the central nervous system, motor nerves, or neuromuscular junction.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Skeletal muscle disorders and associated factors that limit exercise performance. 267 57


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