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

The development of fatigue was investigated by electrical stimulation in 15 domestic pigs (1 yr old, 70-90 kg body weight) and seven adult dogs (3 yr old, 45 kg body weight). After anaesthesia, silver electrodes were implanted in the anterior and posterior parts of the right masseter muscles. The contralateral muscle was used as control. The bite force was measured. Muscle biopsies were obtained from the anterior, central and posterior parts, and were immediately frozen in liquid nitrogen. A fluorometrical analysis by enzymatic methods for glycogen, glucose, creatine phosphate, NAD, NADH, lactate and pyruvate was made. Blood flow was measured by 133Xe wash-out; oxygen consumption was monitored with an oxygen electrode. The porcine masseter was continuously stimulated for 60 min (100 V, 4 Hz and 2 ms). The canine masseter was intermittently stimulated (100 V, 20 Hz and 2 ms). The contraction was repeated four times, with a 10-min rest between. The porcine masseter could sustain longer endurance times than the canine masseter, which was easily fatigued. A marked substrate depletion was evident. The precontractional contents of glycogen, glucose and creatine phosphate were reduced. Lactate accumulation was evident (2-4 times more in the porcine and 4-8 times more in the canine masseter). The NADH concentration increased and the NAD content decreased. Blood-flow impairment (80% reduction in the dog, 60% in the pig) was observed. After the contraction phase, there was a hyperaemia (58% elevation of blood flow in the pig masseter, 45% in the canine). The oxygen tension followed in magnitude and time the blood-flow changes. These circulatory variables returned to normal after recovery. The high degree of substrate depletion, blood-flow impairment and a simultaneous decrease in oxygen transport to the contracted muscle, in combination with a prominent lactate accumulation, may induce a decrease in bite-force production.
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PMID:Bite-force development, metabolic and circulatory response to electrical stimulation in the canine and porcine masseter muscles. 147 60

The combined effects of inspiratory resistive loaded breathing (IRL) and hypoxemia on transdiaphragmatic pressure (Pdi) in nine 1-mo-old Yorkshire piglets were studied. IRL was adjusted to increase spontaneously generated Pdi five to six times above baseline but maintain arterial PCO2 < 70 Torr to prevent hypercapnic depression of diaphragmatic contractility. Measurements of ventilation, blood gases and pH, Pdi, diaphragmatic electromyogram, Pdi during phrenic nerve stimulation, diaphragmatic blood flow, and end-expiratory lung volume were obtained at baseline, after 2 h of IRL, and then after 1 h of hypoxemia (arterial PO2 approximately 40 Torr) combined with IRL. Diaphragmatic muscle samples were obtained after study completion and immediately frozen in liquid nitrogen for determination of tissue ATP, phosphocreatine, lactate, and glycogen levels. Ten 1-mo-old piglets were subjected to IRL alone and served as controls. IRL alone resulted in significant impairment of Pdi generation. The addition of hypoxemia for 1 h did not further compromise Pdi in comparison to control animals who were subjected to IRL alone. Blood flow to both the costal and crural segments of the diaphragm increased significantly during IRL; the addition of the hypoxemic stress resulted in further significant augmentation of blood flow to both segments of the diaphragm. No differences were noted in diaphragmatic muscle tissue ATP, phosphocreatine, or glycogen between control and IRL animals or between control and IRL plus hypoxemia animals. Muscle lactate levels increased significantly in the IRL plus hypoxemia animals only. The data from this study suggest that moderate hypoxemia during resistive-loaded breathing in the piglet does not accentuate diaphragmatic fatigue.
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PMID:Effect of inspiratory resistive loaded breathing and hypoxemia on diaphragmatic function in the piglet. 147 65

One of the most important nutritional goals amongst athletes is to maintain adequate energy and fluid balance, since these are subject to relatively rapid changes and are directly related to performance and health. This may especially be the case when exercise intensity is high. Furthermore, when due to exercise and environmental stress food and fluid intake become depressed. In such conditions there may be a dramatic increase in the utilization of carbohydrate (CHO), fluid, and in some instances protein. These increased requirements may then not be covered. Insufficient replacement of CHO may lead to hypoglycemia, altered protein metabolism, central fatigue and exhaustion. Large sweat losses may pose a risk to health by inducing severe dehydration, impaired blood circulation and heat transfer, leading to heat exhaustion and collapse. Inadequate CHO and protein intake leads to a negative nitrogen balance, which over the long term will lead to a loss of muscle mass. In the scope of this presentation we will refer to the most important nutritional factors which are known to affect performance over a short term, at sea level and altitude.
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PMID:Nutritional aspects of health and performance at lowland and altitude. 148 43

A total of 930 patients have been evaluated for safety in a programme of clinical trials for lisinopril-hydrochlorothiazide combination treatment. Combination therapy with these two agents is generally well tolerated. In clinical trials, adverse experiences in patients treated with a lisinopril-hydrochlorothiazide combination were dizziness (7.5%), headache (5.2%), cough (3.9%), fatigue (3.7%), orthostatic effects (3.2%), diarrhoea (2.5%), nausea (2.2%) and upper respiratory tract infection (2.2%). Withdrawals from treatment have been relatively infrequent comprising dizziness (0.8%), headache (0.3%), cough (0.6%), fatigue (0.4%), diarrhoea (0.2%), orthostatic effects and nausea (0.1% each). The most common laboratory adverse experiences in patients on therapy with the lisinopril-hydrochlorothiazide combination are: increases in serum glucose, triglycerides, uric acid, serum creatinine, blood urea nitrogen and blood urea; and decreases in serum potassium. However, in individual controlled studies, the addition of lisinopril to treatment with hydrochlorothiazide results in attenuation of some of the potentially adverse metabolic affects of the diuretic. Adverse experiences in the patients treated for periods of 50 weeks or more, the elderly and the renally impaired are similar to those seen in the total population. Overall the available data indicate that a fixed dose combination of lisinopril-hydrochlorothiazide is a well-tolerated therapeutic option in patients with mild-to-moderate hypertension.
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PMID:Review of international safety data for lisinopril-hydrochlorothiazide combination treatment. 166 80

The relationship between elevated plasma ammonia (NH3) levels, fatigue development and muscle metabolism were examined in horses during a submaximal fatigue test. Eight Quarter Horse mares were intravenously infused prior to exercise with either sodium acetate (control) or ammonium acetate (AMINF), and exercised to fatigue on an 11% grade treadmill, carrying 27 kg of lead. Time to fatigue was not different (P greater than 0.05) between groups. Intramuscular NH3 and lactate increased (P less than 0.001) during exercise; however, the treatment did not (P greater than 0.05) affect either. A treatment by exercise interaction (P less than 0.01) occurred for plasma NH3. The reciprocal relationship between changes in plasma and intramuscular alanine (ala) and glutamate (glu) indicated activation of the glucose-alanine cycle. Plasma glutamine (gln) increased (P less than 0.001) during exercise; however intramuscular gln was not (P greater than 0.05) altered. The excretion of urea-N was depressed as a result of exercise while the orotic acid/creatinine ratio did not (P greater than 0.05) change. The amino acids and urinary metabolites were not (P greater than 0.05) affected by treatment. These results did not show any metabolic evidence for a role of increased plasma NH3 levels in fatigue development. However this study did provide insight into other aspects of nitrogen metabolism during exercise in the horse.
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PMID:Metabolic responses to ammonium acetate infusion in exercising horses. 168 73

Fifteen patients with advanced, measurable renal cell carcinoma entered a Phase II clinical trial of interleukin-2 (IL-2) (Teceleukin, Hoffmann-La Roche Inc., Nutley, NJ) and interferon (IFN) (Roferon A, Hoffmann-La Roche Inc.). IL-2 was administered by continuous infusion daily for 4 days and IFN was administered by intramuscular injection daily for 4 days; therapy continued for 4 weeks. Eight men and seven women were treated in this trial (median age, 61 years). Toxicity was moderate to severe with fatigue, nausea, vomiting, hypotension, and elevated blood urea nitrogen bunion and creatinine levels seen in all patients. Two patients achieved a complete remission and two patients achieved a partial remission. The median duration of response was 18 months. IL-2 and IFN is an active combination in the treatment of renal cell carcinoma and warrants further investigation.
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PMID:A phase II trial of interleukin-2 by continuous infusion and interferon by intramuscular injection in patients with renal cell carcinoma. 171 25

We attempted to define the site of muscle action accounting for the apparent muscle weakness occurring with postoperative fatigue. A model of the normal pathway of muscle contraction is presented. A series of studies, designed to separate the elements of the pathway, was performed on 38 patients undergoing major abdominal surgery. Central fatigue was measured with Christensen's analogue, voluntary strength by grip strength, perceived effort by grading the difficulty of a set work load, involuntary muscle function by ulnar nerve stimulation, and muscle bulk represented by total body nitrogen, measured by in vivo neuron activation analysis. Fatigue increased for the first 2 weeks after operation, was back to pre-operative levels within 1 month, and improved further at 3 months. Grip strength fell after operation and returned to pre-operative levels within 3 months. Perceived effort rose after operation and returned to pre-operative levels by 3 months. Involuntary muscle function was unaffected by operation. Similarly, total body nitrogen fell in the first 2 weeks after operation but was improved on baseline levels at 3 months. However, there was no consistent correlation between the movement patterns of any of the muscle parameters and fatigue. The results suggest that fatigue after surgery is not accompanied by any muscular defect, and that the apparent muscular weakness is probably a secondary phenomenon to the central fatigue.
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PMID:Postoperative fatigue: a prospective physiological study of patients undergoing major abdominal surgery. 192 79

Contractile activity is an important determinant of the size, rate of protein turnover and phenotypic properties of muscle. Animal models that decrease muscle activity invariably accelerate the rate of protein degradation, usually complementing decreases in the rate of protein synthesis. The net effect is muscle atrophy. By contrast, increased activity and/or passive stretch enhance the synthesis of new proteins, whilst protein catabolism may be either decreased or increased. Muscle hypertrophy results. Endurance activities in man and animals usually induce cardiac hypertrophy, and increased fatigue resistance in skeletal muscle. During exercise the whole body and its skeletal musculature exhibit a negative nitrogen balance, and there is general agreement that rates of protein synthesis are decreased. Changes in protein degradation are, however, much less clearly defined. Resistance exercises induce the opposite changes, with the size of the heart remaining unchanged whilst the bulk and strength of skeletal muscle increase. No real consensus currently exists about the nature of the changes in protein turnover with this type of exercise. More carefully designed and executed experiments are required.
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PMID:Exercise-related changes in protein turnover in mammalian striated muscle. 196 May 11

The clinical, metabolic and anthropometric effects and wound healing metabolism of two regimens of total parenteral nutrition with different amount of nitrogen low, 0.1 g, and high, 0.3 g/body weight kg/day were examined in this prospective double-blind study in two groups of ten patients subjected to abdominoperineal rectum resection for carcinoma for seven postoperative days. The results showed that the high nitrogen infusion associated with metabolic stress indicated by high excretion of urea, high level of serum urea and by a higher frequency of complications. Five patients of the high and one of the low nitrogen group showed complications (p less than 0.05). Further, the metabolic load, complications and high nitrogen infusion associated with higher body temperature, degree of fatigue, levels of C-reactive proteins, leukocytosis and lower of hand pressure force than found in those with low nitrogen infusion. The patient with low or high nitrogen infusion had similar parameters in wound healing metabolism of incision and stoma. The patients with complications showed a reduced stomal hydroxyproline concentration on the third postoperative day (p less than 0.05) and an increase of stomal and wound hydroxyproline and DNA on the seventh postoperative day (p less than 0.05). It is concluded that nitrogen amount of 0.1 g body weight kg/day is a better and a good alternative as compared to 0.3 g in total parenteral nutrition after major abdominal surgery for carcinoma.
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PMID:Clinical and metabolic effects and wound healing metabolism in controlled total parenteral nutrition with high vs. low nitrogen content for seven days after abdominoperineal rectum resection for carcinoma. 213 29

The present paper reviews evidence for the role of specific amino acids in the etiology of fatigue and the overtraining syndrome in athletes. An increase in the plasma concentration ratio of free tryptophan: branched-chain amino acids may mediate an increase in 5-HT synthesis in the brain and thus induce fatigue during exercise. Glutamine is essential for the proper functioning of cells of the immune system and a decrease in plasma glutamine concentration post-exercise and in overtraining may induce an impairment in immune function. Branched-chain amino acids may play a central role in both these processes. Thus, they compete with free tryptophan for entry into the brain. Branched-chain amino acids may also be important precursors of nitrogen for the synthesis of glutamine in skeletal muscle or important in the control of glutamine release from muscle. Consequently, the metabolism of glutamine, tryptophan, and branched-chain amino acids may be the key to understanding some aspects of central fatigue and some aspects of immunosuppression that are very relevant to athletic endeavor. They may be also relevant to other physiological and pathological conditions.
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PMID:A communicational link between skeletal muscle, brain, and cells of the immune system. 219 90


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