Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0392674 (exhaustion)
 13,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of menstrual cycle phase and carbohydrate (CHO) supplementation were investigated during prolonged exercise. Nine healthy, moderately trained women cycled at 70% peak O(2) consumption until exhaustion. Two trials were completed during the follicular (Fol) and luteal (Lut) phases of the menstrual cycle. Subjects consumed 0.6 g CHO. kg body wt(-1). h(-1) (5 ml/kg of a 6% CHO solution every 30 min beginning at min 30 of exercise) or a placebo drink (Pl) during exercise. Time to exhaustion during CHO increased from Pl values (P < 0.05) by 14.4 +/- 8.5 (Fol) and 11.4 +/- 7.1% (Lut); no differences were observed between menstrual cycle phases. CHO attenuated (P < 0.05) the decrease in plasma glucose and insulin and the increase in plasma free fatty acids, tryptophan, epinephrine, and cortisol observed during Pl for both phases. Plasma alanine, glutamine, proline, and isoleucine were lower (P < 0.05) in Lut than in Fol phase. CHO resulted in lower (P < 0.05) plasma tyrosine, valine, leucine, isoleucine, and phenylalanine. These results indicate that the menstrual cycle phase does not alter the effects of CHO supplementation on performance and plasma levels of related substrates during prolonged exercise.
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PMID:Effect of menstrual cycle phase on carbohydrate supplementation during prolonged exercise to fatigue. 1065 39

Nagase genetically analbuminemic rats (NAR) were run to fatigue. Administration of branched chain amino acids (BCAA) before exhaustive exercise, resulted in a post-fatigue decreased tryptophan uptake (-22%, p < 0.05) and 5-hydroxytryptophan (5-HTP) uptake (-29%, p < 0.01) into the synaptosomes isolated from the striatum when compared with saline administration. At the same time, NAR who received either BCAA or 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH, a specific inhibitor for the L-system transporter) had a considerably prolonged run time to exhaustion (by twofold), compared to those who received either saline or albumin treatments. When classified by run time, it was of interest that, when the data for BCAA and BCH treatments for the longer run time NAR (Group B) was combined, it gave rise to a significant decrease in synaptosomal tryptophan and 5-HTP of a similar magnitude to that observed with BCAA alone. These levels were lower than those observed in NAR in the shorter run time group (Group A) for all treatments. These results support the view that an activated serotonergic function may be involved in central fatigue, which can be diminished by inhibition of the L-system transporter.
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PMID:Diminished central fatigue by inhibition of the L-system transporter for the uptake of tryptophan. 1077

The purpose of the present investigation was to determine the independent effects of hypoxia and physical exercise on peripheral cholecystokinin (CCK) metabolism in humans. Thirty-two physically active men were randomly assigned in a double-blind manner to either a normoxic (N; n = 14) or hypoxic (H; n = 18) group. During the acute study, subjects in the H group only participated in two tests, separated by 48 h, which involved a cycling test to exhaustion in normobaric normoxia and normobaric hypoxia (inspired O(2) fraction = 0.21 and 0.16, respectively). In the intermittent study, N and H groups cycle-trained for 4 wk at the same relative exercise intensity in both normoxia and hypoxia. Acute normoxic exercise consistently raised plasma CCK during both studies by 290-723%, which correlated with increases in the plasma ratio of free tryptophan to branched chain amino acids (r = 0.58-0.71, P < 0.05). In contrast, acute hypoxic exercise decreased CCK by 7.0 +/- 5.5 pmol/l, which correlated with the decrease in arterial oxygen saturation (r = 0.56, P < 0.05). In the intermittent study, plasma CCK response at rest and after normoxic exercise was not altered after physical training, despite a slight decrease in adiposity. We conclude that peripheral CCK metabolism 1) is more sensitive to acute changes than chronic changes in energy expenditure and 2) is potentially associated with acute changes in tissue PO(2) and metabolic precursors of cerebral serotoninergic activity.
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PMID:Physical exercise and normobaric hypoxia: independent modulators of peripheral cholecystokinin metabolism in man. 1113 99

We previously reported that the blood NAD levels are decreased by severe exercise, and administration of nicotinamide, a precursor of NAD, improves the endurance capacity of mice. In the present study, we determined whether moderate exercise changes the blood NAD levels in humans and mice. College female students exercised moderately with bike-ergometers. The blood NAD levels elevated after moderate exercise. Mice were forced to swim in a running water pool for 5 min as a moderate exercise, 15 min as a strong exercise, and until exhaustion as a severe exercise (average swimming time was 28.7 min). A 5 min swim gave a result similar to that of moderate exercise by human subjects. However, the blood NAD levels decreased after all-out exercise. The changes in whole blood tryptophan (a precursor of pyridine nucleotides) levels were similar to that in NAD. The glucose levels in whole blood and the non-esterified fatty acid levels in serum decreased according to exercising time. These data are the first demonstration of moderate exercise raising the blood NAD levels in human and mice. Elevation of the blood NAD levels may reflect changes in niacin metabolism that occur in response to exercise.
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PMID:Elevation of blood NAD level after moderate exercise in young women and mice. 1150 11

Several lines of evidence suggest that central serotoninergic neurons may mediate fatigue signals during prolonged exercise. In this study we examined the effects of diet and ambient temperature on peripheral modulators and indices of serotoninergic function and their relationship to exercise performance. Six well-trained cyclists participated, in randomised order, in two diet and exercise regimens each lasting 8 days and comprising four cycle tests to exhaustion at 70 % of maximum oxygen uptake. On days 1 and 5, subjects exercised to exhaustion to deplete muscle glycogen. For 3 days after the first depletion trial a diet providing 10 % of energy in the form of carbohydrate (CHO) was consumed (low CHO), and for 3 days after the second depletion trial a diet providing 80 % (high CHO) of energy as CHO was consumed, and each diet was followed by a performance trial at the same ambient temperature, either 10 degrees C or 30 degrees C (days 4 and 8). This schedule was repeated after 1 week, but performance trials were carried out at the other ambient temperature. In the cold, cycling time increased (P < 0.01) from 89.2 (78.0-129.5) min (median (range)) in the low CHO trial to 158.2 (116.9-165.6) min in the high CHO trial. In the heat, cycling time increased from 44.0 (31.8-51.4) min in the low CHO trial to 53.2 (50.2-82.2) min on the high CHO trial (P = 0.02). The serum prolactin (Prl) concentration was higher at exhaustion during the two trials in the heat than in the two trials in the cold. Serum Prl levels were unrelated to the purported peripheral modulators of serotoninergic function (plasma concentrations of total tryptophan (Trp), free Trp, branched-chain amino acids (BCAAs), free Trp/BCAA ratio and total Trp/BCAA ratio) but were significantly related to the rectal temperatures measured during the two trials in the heat. This finding provides indirect evidence that the serotoninergic system may be involved in fatigue during exercise under conditions of heat stress.
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PMID:Hyperprolactinaemia during prolonged exercise in the heat: evidence for a centrally mediated component of fatigue in trained cyclists. 1185 66

It has been reported that exercise increases brain tryptophan (TRP), which is related to exhaustive fatigue. To study this further, the effect of increased TRP availability on the central nervous system (CNS) with regard to mechanical efficiency, oxygen consumption (VO(2)) and run-time to exhaustion was studied in normal untrained rats. Each rat was anesthetized with thiopental (30 mg/kg ip b. wt.) and fitted with a chronic guiding cannula attached to the right lateral cerebral ventricle 1 week prior to the experiments. Immediately before exercise, the rats were randomly injected through these cannulae with 2.0 microl of 0.15 M NaCl (n=6) or 20.3 microM L-TRP solution (n=6). Exercise consisted of running on a treadmill at 18 m min(-1) and 5% inclination until exhaustion. TRP-treated rats presented a decrease in their mechanical efficiency (21.25+/-0.84%, TRP group vs. 24.31+/-0.98%, saline-treated group; P< or =.05), and increased VO(2) at exhaustion (40.3+/-1.6 ml kg(-1) min(-1), TRP group vs. 36.0+/-0.8 ml kg(-1) min(-1), saline group; P< or =.05), indicating that the metabolic cost of exercise was higher in the former group. In addition, a highly significant reduction was also observed in run-time to exhaustion of TRP animals compared to those of the saline-treated group (15.2+/-1.52 min, TRP group vs. 50.6+/-5.4 min, saline group; P< or =.0001). It can be deduced from the data that intracerebroventricular TRP injection in rats increases O(2) consumption and reduces mechanical efficiency during exercise, diminishing running performance.
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PMID:Evidence that tryptophan reduces mechanical efficiency and running performance in rats. 1247 55

Considerable evidence points towards a prominent role for central nervous system (CNS) mechanisms in the pathogenesis of chronic fatigue syndrome (CFS), a disorder characterized chiefly by persistent, often debilitating, fatigue. We wished to characterize circulating profiles of putative amino acid modulators of CNS 5-hydroxytryptamine (5-HT; serotoninergic) and dopaminergic function in CFS patients at rest, as well as during symptom-limited exercise and subsequent recovery. Groups of 12 CFS patients and 11 age- and sex-matched sedentary controls, with similar physical activity histories, underwent ramp-incremental exercise to the limit of tolerance. Plasma amino acid concentrations, oxygen uptake and ratings of perceived exertion were measured at rest, and during exercise and recovery. Peak oxygen uptake was significantly lower in the CFS patients compared with controls. Rating of perceived exertion in the patients was higher at all time points measured, including at rest, relative to controls. Levels of free tryptophan (free Trp), the rate-limiting 5-HT precursor, were significantly higher in CFS patients at exhaustion and during recovery, whereas concentrations of branched-chain amino acids (BCAA) and large neutral amino acids (LNAA) were lower in CFS patients at exhaustion, and for LNAA also during recovery. Consequently, the [free Trp]/[BCAA] and [free Trp]/[LNAA] ratios were significantly higher in CFS patients, except at rest. On the other hand, levels of tyrosine, the rate-limiting dopaminergic precursor, were significantly lower at all time points in the CFS patients. The significant differences observed in a number of key putative CNS 5-HT and dopaminergic modulators, coupled with the exacerbated perception of effort, provide further evidence for a potentially significant role for CNS mechanisms in the pathogenesis of CFS.
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PMID:Chronic fatigue syndrome: new evidence for a central fatigue disorder. 1270 66

Beggs, William H. (University of Cincinnati, Cincinnati, Ohio), and Herman C. Lichstein. Repression of tryptophanase synthesis in Escherichia coli. J. Bacteriol. 89:996-1004. 1965.-The nature of the glucose effect on tryptophanase in Escherichia coli (Crookes) was investigated to test the catabolite-repression hypothesis. Under static conditions of growth in the presence of 0.005 m glucose, tryptophanase was repressed and remained so upon continued static incubation subsequent to glucose exhaustion. Aeration following glucose exhaustion under static cultural conditions resulted in rapid enzyme synthesis. In the absence of glucose, certain amino acids repressed tryptophanase synthesis early in the growth cycle under aerated conditions. An inverse relationship was observed between the concentration of acid-hydrolyzed casein and the level of tryptophanase. At 3 hr, enzyme activity in cells grown in media containing 0.05% acid-hydrolyzed casein was at least five times that of cells grown in the presence of 1% casein. Addition of 0.005 m d- or l-serine to a 0.05% acid-hydrolyzed casein medium rendered the medium capable of strongly repressing tryptophanase. Glucose-expended medium was prepared by allowing cells to grow and exhaust glucose in static culture. When this expended medium was recovered and inoculated with fresh cells not previously exposed to glucose, tryptophanase synthesis was repressed for a short period in shake culture, but in static culture enzyme synthesis was only slightly affected. When the expended medium was prepared from shake cultures, fresh cells were not repressed strongly when subsequent incubation was carried out aerobically. The tryptophan pool in glucose-repressed cells grown in shake culture was appreciably less than in cells grown in the absence of glucose or in cells undergoing synthesis of tryptophanase after exhaustion of the sugar.
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PMID:REPRESSION OF TRYPTOPHANASE SYNTHESIS IN ESCHERICHIA COLI. 1427 27

Eight males were recruited to examine the effect of branched-chain amino acid (BCAA) supplementation on exercise capacity in a glycogen-depleted state in a warm environment. Following a exercise and dietary regimen designed to reduce glycogen availability, subjects returned to the laboratory the following morning and remained seated for 2 h, before cycling to volitional exhaustion at 50% VO2 peak in a warm environment [30.0 (0.2) degrees C; mean (SD)]. Four 250 ml aliquots of a 12 g l(-1) BCAA solution or placebo were ingested at 30 min intervals prior to exercise, with an additional 150 ml consumed every 15 min throughout exercise. BCAA ingestion had no effect on exercise capacity [placebo 103.9 (26.9) min; BCAA 111.0 (29.2) min; P = 0.129). No difference in heart rate (P = 0.345), core temperature (P = 0.628), or weighted mean skin temperature (P = 0.114) was apparent between trials. Ingestion of the BCAA solution produced a marked increase in plasma BCAA immediately prior to exercise [+ 1126 (158) micromol l(-1); P < 0.001) with this difference maintained throughout. Consequently, a significant reduction in the plasma concentration ratio of free tryptophan to BCAA was observed during the BCAA trial when compared to the placebo (P < 0.001). Plasma ammonia concentration was significantly elevated during exercise throughout the BCAA trial (P < 0.001), with no change from rest apparent during the placebo trial (P = 0.608). Blood glucose (P = 0.114) and lactate (P = 0.836) concentrations were not different between trials. Ingestion of a BCAA solution prior to, and during, prolonged exercise in glycogen-depleted subjects did not influence exercise capacity in a warm environment.
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PMID:The effect of acute branched-chain amino acid supplementation on prolonged exercise capacity in a warm environment. 1534 84

Branched chain amino acids (BCAA), particularly leucine, have been suggested to be ergogenic for both endurance and strength/power performance. This study investigated the effects of dietary leucine supplementation on the exercise performance of outrigger canoeists. Thirteen (ten female, three male) competitive outrigger canoeists [aged 31.6 (2.2) year, VO(2max) 47.1 (2.0) ml kg(-1) min(-1)] underwent testing before and after 6-week supplementation with either capsulated L: -leucine (45 mg kg(-1) d(-1); n = 6) or placebo (cornflour; n = 7). Testing included anthropometry, 10 s upper body power and work and a row to exhaustion at 70-75% maximal aerobic power where perceived exertion (RPE), heart rate (HR) and plasma BCAA and tryptophan concentrations were assessed. Leucine supplementation resulted in significant increases in plasma leucine and total BCAA concentrations. Upper body power and work significantly increased in both groups after supplementation but power was significantly greater after leucine supplementation compared to the placebo [6.7 (0.7) v. 6.0 (0.7) W kg(-1)]. Rowing time significantly increased [77.6 (6.3)-88.3 (7.3) min] and average RPE significantly decreased [14.5 (1.5)-12.9 (1.4)] with leucine supplementation while these variables were unchanged with the placebo. Leucine supplementation had no effect on the plasma tryptophan to BCAA ratio, HR or anthropometric variables. Six weeks' dietary leucine supplementation significantly improved endurance performance and upper body power in outrigger canoeists without significant change in the plasma ratio of tryptophan to BCAA.
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PMID:Effects of dietary leucine supplementation on exercise performance. 1626


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