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

1. Quadriceps strength, relaxation rate, fibre-type composition and energy-turnover rate during a submaximal contraction have been measured in hypo- and hyper-thyroid patients and compared with findings in normal subjects. 2. Six out of eight hypothyroid patients had normal strength whereas four out of five hyperthyroid patients were weak. 3. Relaxation rate was decreased in all the hypothyroid patients but increased in only three out of five hyperthyroid patients. 4. In hypothyroidism there was a marked reduction in the percentage contributed by type II fibres to muscle cross-section, partly due to type II atrophy but also due to a decrease in the relative frequency of type II fibres. In hyperthyroidism both fibre types tended to atrophy. 5. The rate of ATP turnover during submaximal contraction held to fatigue was reduced in hypothyroidism. This was probably due to decreased ATP utilization rather than an impaired supply of energy-supplying substrates. In hyperthyroidism the rate of ATP turnover was increased. 6. Altered relaxation rate and ATP-turnover rate may be explained on the basis of changes in myosin ATPase activity with thyroid status. Changes in muscle-fibre-type composition, as determined histochemically, could not per se account for the functional abnormalities.
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PMID:Muscle relaxation rate, fibre-type composition and energy turnover in hyper- and hypo-thyroid patients. 50 76

The effect of 1.5 to 2.5 h tourniquet ischemia on energy metabolism of the quadriceps muscle was studied using percutaneous needle biopsy technique in sixteen patients operated on for an inveterated knee injury. During occlusion there was a moderate decrease in ATP with an increase in ADP and AMP. This change resulted in a decreased energy charge potential. At the same time phosphorylcreatine (PC) decreased markedly while creatine (Cr) increased giving a constant total creatine (TCr). An accumulation of lactate during occlusion with values up to 80 mmol/kg d.m. (dry muscle) was seen. A 15% reduction in glycogen was calculated. After release of the tourniquet the active phosphate concentration and the energy charge potential returned to basal levels within 5 min and most of the metabolites in the glycolytic sequence were also normalized. Muscle lactate content was normal after 30 min of intact circulation. The results suggest that longterm tourniquet ischemia induces marked changes in energy metabolism in skeletal muscle, but that the changes are rapidly and completely reversible with restoration of blood flow.
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PMID:The effect of long-term arterial occlusion on energy metabolism of the human quadriceps muscle. 52 75

1. Adaptive mechanisms of oxygen transport by blood have been studied in severely anaemic young patients on maintenance haemodialysis, in conditions of hyperphosphataemia (Pi greater than or equal to 2.2 mmol/l) or normophosphataemia. 2. In hyperphosphataemia whole-blood affinity for oxygen was slightly decreased, as measured by an increase in P50 (the partial pressure of oxygen necessary to half saturate haemoglobin). 2,3-Diphosphoglycerate was increased by 10% (P less than 0.10) whereas Pi, total erythrocyte phosphate and ATP were increased by 100%, 47% and 36% respectively, compared with control values. 3. After correction of hyperphosphataemia a small but significant decrease in P50 and 2,3-diphosphoglycerate, to normal values, was observed whereas the other variables, although significantly lowered, remained above control values. 4. In these severely anaemic and hyperphosphataemic patients P50 and 2,3-diphosphoglycerate are only slightly increased. ATP synthesis appears to be favoured over that of 2,3-diphosphoglycerate. This is possibly due to alterations in the erythrocyte membrane elicited by bi-weekly extracorporeal circulation. Adequate oxygen transport can be achieved only through a drastic increase in blood flow. Correction of hyperphosphataemia adds further to the abnormality. It is concluded that this condition could induce a long-term myocardial fatigue, which might be prevented with occasional small blood transfusions.
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PMID:Oxygen transport in children on maintenance haemodialysis. 62 Apr 97

In rats with third-degree burns, the blood glucose level increased remarkably, with a concomitant suppression of insulin secretion from the pancreas after an oral glucose load. The energy charge (ATP + 1/2 ADP/ATP + ADP + AMP) levels of the kidney decreased to 0.659 as compared with 0.858 of controls at 8 hr after the burn (p less than 0.001). The phosphorylative activity of the kidney mitochondria fell to one third of controls at 8 hr after the burn (p less than 0.001), and that of heart mitochondria decreased to approximately 70% (p less than 0.005); the fall in liver and brain was less remarkable. The decrease in mitochondrial phosphorylative activity was accompanied by a reduction in the respiratory control ratio, P/O ratio, and state 3 respiration. The concentrations of cytochrome a(+a3) in the kidney mitochondria decreased to 69.9% of controls at 8 hr after the burn (p less than 0.001), those of cytochrome b to 82.6%, and those of cytochrome c + c1 to 75.3% (p less than 0.001). The decreased energy charge and oxidative phosphorylation of the kidney in burned rats were remarkably restored by subcutaneous administration of insulin. It is suggested that a reduction in insulin secretion from the pancreas may play an important role in initiating an impairment of adenine nucleotide and mitochondrial metabolism of the kidney.
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PMID:Changes in adenine nucleotide and mitochondrial metabolism of the kidney of burned rats and their relation to insulin. 89 1

Studies have been made of the effect of controlled muscle work (swimming against water stream at a rate 1.2 m/sec) and fatigue on the content of adenylic nucleotides (ATP, ADP, AMP), phosphocreatine and inorganic phosphorus in red lateral muscles of the Black sea saurel T. mediterraneus under various thermal conditions (15-16 degrees and 11-12 degrees). It was shown that the content of the phosphates studied is lower in red muscles than in white ones. At water temperature 15-16 degrees, prolonged swimming results in significant changes of the content of the phosphates investigated in the red muscles. These changes correspond to three periods of biochemical adaptation to prolonged muscle work, which were earlier described for white muscles. At water temperature 11-12 degrees, the level of energy rich phosphates in the red muscles is affected insignificantly which is taken as an indication of the secondary role of these muscles in swimming of fish under these conditions.
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PMID:[Phosphorus metabolism in the red lateral muscles of Trachurus mediterraneus during muscle loading]. 94 67

Rat hepatocytes were isolated by liver perfusion in the presence of collagenase and hyaluronidase and incubated in the absence or presence of oxygen. As a result of anoxia, there was a gradual increase in plasma membrane permeability, noted as an increase in succinate-stimulated oxygen uptake, a decrease in trypan blue exclusion frequency, a leakage of cytosolic lactate dehydrogenase activity and an increased proportion of swollen and disrupted cells. After anaerobic incubation for 30 minutes--but not for 60 minutes--there were signs of recovery from anoxic cell injury upon re-oxygenation. The changes in plasma membrane permeability properties in anoxia seemed to be preceded by a marked decrease in cellular ATP level; aerobic incubation of hepatocytes in the presence of an uncoupler of phosphorylation from respiration led to a similar decrease in cellular ATP concentration followed by similar disturbances in plasma membrane permeability properties. It is suggested that a distrubed plasma membrane function caused by a decreased energy level is of primary importance for the initiation of cell death in anoxia.
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PMID:Isolated rat hepatocytes as an experimental tool in the study of cell injury. Effect of anoxia. 100 75

The relationship between lactic acid concentration and twitch tension was reevaluated in electrically stimulated frog sartorius muscle. In muscles stimulated under anaerobic conditions at a rate of 30 stimuli/MIN CONTRACTILE FORCE DECREASED TO 36% OF THE INITIAL VALUE IN 15 MIN, Concomitantly lactate increased from 3.3 to 18.7 mumol/g of muscle. The correlaiton between the increase in lactate and the decrease in contractile force was significant (r = -0.99, P less than 0.000001). Recovery occurred in two phases. A rapid increase in contractile force, which represented 20% of the total recovery, took place during the first 15 s and occurred concomitantly with an increase in ATP from 3.9 to 4.6 mumol/g. Lactate concentration did not change significantly during this period. The second phase of recovery of contractile force was complete in 50 min. Lactate concentration and contractile force were significatly correlated during recovery (r = -0;92, P less than 0.00001). However, recovery of contractile force lagged behind the decrease in lactate; a given concentration of muscle lactate was associated with a higher contractile force early during development of fatigue than late during recovery.
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PMID:Lactate and contractile force in frog muscle during development of fatigue and recovery. 108 70

1. The biochemical basis of the slowing of relaxation seen in fatigue has been examined using an isolated mouse soleus preparation. 2. Slowing of relaxation occurred during prolonged tetani under anaerobic conditions when ATP and PC fell and lactate accumulated. 3. Slowing of relaxation was also demonstrated with muscles poisoned with cyanide and iodoacetic acid when there was a fall in ATP and PC but no accumulation of lactate. During a period of anaerobic recovery following a fatiguing tetanus, relaxation became faster at a time when lactate was accumulating in the muscle. 4. It is concluded that the slowing of relaxation in fatigue is not a consequence of lactate accumulation, and a relationship is demonstrated between the ATP content of the muscle and the rate of relaxation in muscles fatigued by prolonged stimulation, 5. Rates of ATP turn-over in fresh muscle, and at intervals throughout a tetanus are consistent with the suggestion that the rate limiting step for myofibrillar ATPase may be directly related to the rate limiting step for the decay of tension during relaxation.
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PMID:Metabolic changes associated with the slowing of relaxation in fatigued mouse muscle. 118 65

Narcine brasiliensis electric organ was stimulated to fatigue in vivo. Electrical display of organ output and biochemical assay of bound acetylcholine (ACh) and ATP in isolated vesicles were used to assess the state of fatigue relative to denervated control organs of the same fish. A morphometric analysis of the fate of the synaptic vesicle populations in the nerve terminals was carried out. Statistically significant morphological changes in vesicle populations and plasma membranes were observed between control and fatigued electroplaque stacks from individual fish. Pooled data from several fish were used to evaluate the possible role of the different vesicle types in neurotransmission. Fatigue resulted in the loss of 49% of the total vesicle population and a 76% loss of vesicles with bound calcium (Ca). An approximately equivalent increase in the nerve-terminal plasma membrane area was measured. This was predominantly in the form of fingerlike protrusions and/or invaginations of the terminals which were present in the control organs but which were significantly increased by stimulation. Vesicle attachments to the nerve terminal membrane were reduced by 90%. This suggests that the failure in transmission may be due to reduction in the number of vesicles which are loaded with transmitter and can attach to the terminal membrane. The Ca-binding capacity of the lost vesicles was not transferred to the plasma membranes. This result was interpreted as support for the hypothesis that vesicle-bound ATP provides the Ca-binding site.
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PMID:Changes in cholinergic synaptic vesicle populations and the ultrastructure of the nerve terminal membranes of Narcine brasiliensis electron organ stimulated to fatigue in vivo. 120 24

Fatigue during the 400-m sprint was studied by measuring muscle ATP, creatine phosphate (CP), lactate (M-La), and blood lactate (B-La) in six male runners before and after four experimental sprints (100, 200, 300, and 400 m). During the first 100 m, muscle CP decreased from 15.8 +/- 1.7 to 8.3 +/- 0.3 mmol/kg while M-La increased to 3.6 +/- 0.4 mmol/kg. After 200 m the CP had decreased to 6.5 +/- 0.5 mmol/kg and M-La had increased to 8.3 +/- 1.1 mmol/kg. At the end of the 400 meters, ATP and CP concentrations had decreased by 27% and 89%, respectively, and M-La had increased to 17.3 +/- 0.9 mmol/kg. It was concluded that after 200 m the speed of running decreased, although CP was not depleted and lactate concentration was not at maximum level. Complete fatigue occurred when CP stores were depleted and B-La and M-La attained an individual maximum.
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PMID:Fatigue and changes of ATP, creatine phosphate, and lactate during the 400-m sprint. 132 8


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