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

Phosphorus nuclear magnetic resonance (31P NMR) spectroscopy is a non-destructive analytical laboratory technique that, due to recent technical advances, has become applicable to the study of high-energy phosphate metabolism in both animal and human extremity muscles (in vivo). 31P NMR can assay cellular phosphocreatine, ATP, inorganic phosphate, the phosphorylated glycolytic intermediates, and intra-cellular pH in either resting or exercising muscle, in a non-invasive manner. NMR uses non-perturbing levels of radio-frequency energy as its biophysical probe and can therefore safely study intact muscle in a repeated fashion while exerting no artifactual influence on ongoing metabolic processes. Compared with standard tissue biopsy and biochemical assay techniques, NMR possesses the advantages of being non-invasive, allowing serial in situ studies of the same tissue sample, and providing measurements of only active (unbound) metabolites. NMR studies of exercising muscle have yielded information regarding fatigue mechanisms at the cellular level and are helping resolve long-standing questions regarding the metabolic control of glycolysis, oxidative phosphorylation, and post-exercise phosphocreatine re-synthesis. NMR is also being utilized to measure enzymatic reaction rates in vivo. In the near future, other forms of NMR spectroscopy may also permit the non-invasive measurement of tissue glycogen and lactate content.
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PMID:Phosphorus nuclear magnetic resonance: a non-invasive technique for the study of muscle bioenergetics during exercise. 330 42

Chronic stimulation converts skeletal muscle of mixed fiber type to a uniform muscle made up of type I, fatigue-resistant fibers. Here, the bioenergetic correlates of fatigue resistance in conditioned canine latissimus dorsi are assessed with in vivo phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy. After chronic electrical stimulation, five dogs underwent 31P-NMR spectroscopic and isometric tension measurements on conditioned and contralateral control muscle during stimulation for 200, 300, 500, and 800 ms of an 1,100-ms duty cycle. With stimulation, phosphocreatine (PCr) fell proportional to the degree of stimulation in both conditioned and control muscle but fell significantly less in conditioned muscle at all but the least intense stimulation period (200 ms). Isometric tension, expressed as a tension time index per gram muscle, was significantly greater in the conditioned muscle at the two longest stimulation periods. The overall small change in PCr and the lack of a plateau in tension observed in the conditioned muscle are similar to that seen in cardiac muscle during increased energy demand. This study indicates that the conditioned muscle's markedly enhanced resistance to fatigue is in part the result of its increased capacity for oxidative phosphorylation.
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PMID:In vivo 31P-NMR spectroscopy of chronically stimulated canine skeletal muscle. 334 65

Computed tomographic (CT) findings of cerebral and cerebellar calcification are described in three American adults with raised serum lead levels and known exposure to lead for 30 or more years. Calcification patterns were punctiform, curvilinear, speck-like, and diffuse and were found in the subcortical area, basal ganglia, vermis, and cerebellum. Admission serum lead levels ranged from 54 to 72 micrograms/dl (normal, 0-30 micrograms/dl). Nonspecific neurologic manifestations consisted of dementia, diminished visual acuity, peripheral neuropathy, syncope, dizziness, nystagmus, easy fatigue, and back pain. Two patients developed chronic renal disease and hypertension; in both cases, serum parathormone was elevated. Blood, calcium, and phosphorus were normal in all three. No other structural abnormalities were observed with CT. Although the pathophysiologic mechanism of these findings remains poorly understood, it is suggested that chronic lead exposure should be included in the differential diagnosis of unexplained intracranial calcifications in adults.
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PMID:Intracranial calcification in adults with chronic lead exposure. 348 74

In muscle phosphorylase deficiency (McArdle's disease) there is an abnormally rapid fatigue during strenuous exercise. Increasing substrate availability to working muscle can improve exercise tolerance but the effect on muscle energy metabolism has not been studied. Using phosphorus-31 nuclear magnetic resonance (31P-NMR) we examined forearm muscle ATP, phosphocreatine (PCr), inorganic phosphate (Pi) and pH in a McArdle patient (MP) and two healthy subjects (HS) at rest and during intermittent maximal effort handgrip contractions under control conditions (CC) and during intravenous glucose infusion (GI). Under CC, MP gripped to impending forearm muscle contracture in 130 s with a marked decline in muscle PCr and a dramatic elevation in Pi. During GI, MP exercised easily for greater than 420 s at higher tensions and with attenuated PCr depletion and Pi accumulation. In HS, muscle PCr and Pi changed more modestly and were not affected by GI. In MP and HS, ATP changed little or not at all with exercise. The results suggest that alterations in the levels of muscle PCr and Pi but not ATP are involved in the muscle fatigue in McArdle's disease and the improved exercise performance during glucose infusion.
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PMID:Muscle fatigue in McArdle's disease studied by 31P-NMR: effect of glucose infusion. 386 26

The objective was to determine the effect of daily s.c. injection of bovine growth hormone (bGH) on nitrogen and energy balance in six Hereford heifers. In addition, effects on urinary excretion of 3-methylhistidine and hydroxyproline and on serum mineral concentrations were monitored. A single reversal design was used with two 14-d injection periods of placebo or bGH (29.2 IU/d). Measurements were made on d 8-14 of each period. Injection of bGH did not alter apparent digestibility of dry matter, energy or nitrogen, nor urinary excretion of 3-methylhistidine or hydroxyproline. Serum concentrations of calcium, phosphorus and magnesium were normal with bGH treatment. Nitrogen retention was higher and urinary nitrogen excretion was lower when the heifers were injected with bGH than with the placebo demonstrating an effect of bGH on postabsorptive metabolism of nitrogen. Total energy balance was not altered by treatment. Energy retained as protein was higher after bGH treatment than after the placebo, implying decreased energy retained as fat and demonstrating a role for GH in altering energy partition in growing animals. Total heat production was not altered by treatment indicating no change in the gross efficiency of metabolizable energy use with bGH treatment.
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PMID:Effect of bovine growth hormone administration on metabolism of growing Hereford heifers: dietary digestibility, energy and nitrogen balance. 394 54

The diseases which are commonly complicated by hypercapnic respiratory failure also compromise the respiratory muscles in several ways. Increased work of breathing, mechanical disadvantage, neuromuscular disease, impaired nutritional status, shock, hypoxemia, acidosis, and deficiency of potassium, magnesium, and inorganic phosphorus are the major non-neurologic factors which contribute to respiratory muscle fatigue and failure. Respiratory muscle fatigue has two components. High frequency fatigue occurs rapidly with intense contractile efforts but is usually not severe. It also recovers rapidly with rest. Low frequency fatigue develops more slowly but is severe and requires hours for recovery. Since the spontaneous rate of neural stimulation is predominantly in the low frequency range, this component of fatigue is of particular clinical importance. Fatigue of the inspiratory muscles leads to acute respiratory acidosis, but before carbon dioxide retention occurs, it can be recognized from characteristic symptoms and signs. These include dyspnea which responds to mechanical ventilation, rapid shallow breathing, and asynchronous movements of the chest and abdomen. Inspiratory muscle fatigue must be treated by putting these muscles to rest, by mechanically supporting ventilation. In addition, underlying metabolic nutritional and circulatory abnormalities must be corrected and infection treated. Aminophylline and isoproterenol can restore inspiratory muscle contractility, but controlled clinical trials remain to be done regarding their application in acute and chronic respiratory failure. Inspiratory muscle training improves strength and endurance in patients with obstructive lung disease, cystic fibrosis, and spinal cord injury, but does not always improve physical exercise performance. Again, more work is needed to develop the indications for inspiratory muscle training and to determine the optimum type and duration of the training regimen.
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PMID:Respiratory muscle failure. 634 27

1. We have used phosphorus nuclear magnetic resonance (31P NMR) to study muscular fatigue in anaerobic amphibian muscle. In this paper the biochemical and energetic changes that result from a series of tetani are related to the decrease in rate constant (1/tau) for the final, exponential, phase of relaxation. 2. Using 31P NMR we have measured the concentrations of phosphocreatine (PCr), inorganic phosphate (Pi) and ATP as well as the internal pH. From our measurements we have calculated [creatine], [free ADP], the free-energy change (more precisely, the affinity A = -dG/d xi) for ATP hydrolysis and the rates of lactic acid production and of ATP hydrolysis. 3. We have found that 1/tau, the rate constant of relaxation, is correlated with each of the following, independently of the pattern of stimulation: isometric force production, all of the measured or calculated metabolite levels, pH and dG/d xi. 4. There is a clear dependence upon the pattern of stimulation of the relation between 1/tau and each of the following: total duration of the experiment, number of contractions, rate of lactic acid production and rate of ATP hydrolysis. 5. The rate of relaxation is linearly related to [PCr], [creatine], [Pi] and dG/d xi. It is nonlinearly related to isometric force, [ATP], [H+] and rate of ATP hydrolysis. 6. We conclude that the change in 1/tau, like that of isometric force, depends upon metabolic factors, and not upon any independent changes in the activation or deactivation of contraction. We suggest that 1/tau may depend upon the free-energy change for ATP hydrolysis which in turn may be related to the rate of Ca2+ uptake into the sarcoplasmic reticulum.
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PMID:Mechanical relaxation rate and metabolism studied in fatiguing muscle by phosphorus nuclear magnetic resonance. 696 88

137 patients on maintenance dialysis were studied. All but 2 patients were ambulatory, and all patients demonstrated good to normal strength on manual motor tests. With the exception of systemic lupus erythematosus, no correlation was found between primary diagnosis and patients' fatigue ratings. Laboratory studies of hematocrit, BUN, creatinine, calcium, and phosphorus did not correlate with fatigue ratings for the majority of patients. Fatigue appeared more problematic for patients who had been dialyzing for less than 4 years. Depression was pronounced among patients who reported feeling fatigued upon arising.
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PMID:The problem of fatigue in dialysis patients. 711 Apr 64

Seven patients with advanced cancer underwent whole-body hyperthermia using a nylon and vinyl mesh, water-perfused suit. Treatments were given at 41.8 degrees C for 4 hours. Five patients received concomitant cyclophosphamide with hyperthermia. Compared to baseline (37 degrees C) conditions, there was a significant rise in pulse rate (P less than 0.001), a fall in diastolic pressure (P less than 0.02), and an increase in respiratory rate (P less than 0.001). Toxic effects included fatigue, extremity edema, diarrhea, nausea and vomiting, and respiratory depression in a patient with cerebral metastases. Compared to baseline values, there was a significant increase in serum glucose (P less than 0.02) and decreases in serum calcium (P less than 0.01) and phosphorus (P less than 0.01). Significant elevations in serum LDH and SGOT values occurred 24 hours following hyperthermia, suggesting hepatic sensitivity to heat. The methods used to induce whole-body hyperthermia, as described in this paper, are feasible, permit relatively easy access to the patient, and are potentially applicable in diverse hospital settings such as intensive care units, radiation therapy areas, and conventional rooms. The physiologic alterations that were observed and the toxic effects that were documented indicate that careful monitoring of patients is necessary.
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PMID:Physiologic response and toxicity in patients undergoing whole-body hyperthermia for the treatment of cancer. 723 54

The interaction of phosphorus nutrition and fasting on the tolerance of young chickens acutely exposed to high temperature was studied. We also investigated a possible relationship between plasma phosphate (Pi) and body temperature (Tr) of chicks during heat exposure. Survival time (ST) of 24-hour fasted (F-24) chicks previously fed a low-phosphorus diet (LP) was markedly lower than ST of F-24 chicks fed an adequate phosphorus diet (AP). Diet, however, had no effect on ST of chicks fasted 12 hours (F-12). The apparent metabolic responses of F-24 chicks were qualitatively different than those of F-12 chicks suggesting that the effect of previous phosphorus nutrition was dependent on metabolic status of chicks before heat exposure. The concentration of Pi during heat exposure of F-24 chicks fed the experimental diets was highly (P less than 0.001) correlated with Tr. At heat-induced exhaustion, Tr of chicks fed either diet was not different. Pi of these groups at this point was nearly identical despite marked differences in the time at which this event occurred. An investigation concerning a possible relationship between Pi and the respiratory failure known to occur in hyperthermic chickens, revealed that respiratory muscular fatigue is not the primal cause of respiratory failure. Our results demonstrated that phosphorus nutrition, Pi and metabolic status are dependent factors related to the tolerance of young chickens exposed to high temperature.
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PMID:Phosphorus nutrition and fasting: interrelated factors which affect the survival of young chickens exposed to high ambient temperature. 736 46


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