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

Six commercial wine yeast strains and three nonindustrial strains (two laboratory strains and one haploid strain derived from a wine yeast strain) were engineered to produce large amounts of glycerol with a lower ethanol yield. Overexpression of the GPD1 gene, encoding a glycerol-3-phosphate dehydrogenase, resulted in a 1.5- to 2.5-fold increase in glycerol production and a slight decrease in ethanol formation under conditions simulating wine fermentation. All the strains overexpressing GPD1 produced a larger amount of succinate and acetate, with marked differences in the level of these compounds between industrial and nonindustrial engineered strains. Acetoin and 2,3-butanediol formation was enhanced with significant variation between strains and in relation to the level of glycerol produced. Wine strains overproducing glycerol at moderate levels (12 to 18 g/liter) reduced acetoin almost completely to 2,3-butanediol. A lower biomass concentration was attained by GPD1-overexpressing strains, probably due to high acetaldehyde production during the growth phase. Despite the reduction in cell numbers, complete sugar exhaustion was achieved during fermentation in a sugar-rich medium. Surprisingly, the engineered wine yeast strains exhibited a significant increase in the fermentation rate in the stationary phase, which reduced the time of fermentation.
 ...
PMID:Glycerol overproduction by engineered saccharomyces cerevisiae wine yeast strains leads to substantial changes in By-product formation and to a stimulation of fermentation rate in stationary phase 987 72

The participation of hepatic glycogenolysis and gluconeogenesis to the glycemic changes promoted by exercise was investigated. For this purpose, we employed swimming rats (2.5% body weight extra load attached to the tail, at 24 degrees C) using a favorable condition to measure hepatic glycogenolysis (fed rats) and a favorable condition to measure hepatic gluconeogenesis (fasted rats). This experimental approach permits us to compare the contribution of hepatic glycogenolysis and gluconeogenesis to glucose changes for a specific schedule of exercise. The animals were investigated at rest, after 5 minutes of swimming and after swimming to exhaustion. Our results show that hepatic glycogen has a crucial role to determine hyperglycemia during exercise. In contrast, hypoglycemia developed during exercise when glycogen was depleted. However, the ability of the liver to produce glucose from L-lactate, glycerol and L-glutamine was increased during exercise. Taken together, these findings suggest that the hepatic capacity to produce glucose from gluconeogenic substrates (except for L-alanine) was increased when hepatic glycogen stores were depleted. Thus, the increased capacity to produce glucose shown by livers from exercising rats must to be an important metabolic adaptation to protect against severe hypoglycemia.
 ...
PMID:Changes in glycemia induced by exercise in rats: contribution of hepatic glycogenolysis and gluconeogenesis. 1010 May 3

1. The present study examined whether reductions in muscle blood flow with exercise-induced dehydration would reduce substrate delivery and metabolite and heat removal to and from active skeletal muscles during prolonged exercise in the heat. A second aim was to examine the effects of dehydration on fuel utilisation across the exercising leg and identify factors related to fatigue. 2. Seven cyclists performed two cycle ergometer exercise trials in the heat (35 C; 61 +/- 2 % of maximal oxygen consumption rate, VO2,max), separated by 1 week. During the first trial (dehydration, DE), they cycled until volitional exhaustion (135 +/- 4 min, mean +/- s.e.m.), while developing progressive DE and hyperthermia (3.9 +/- 0.3 % body weight loss and 39.7 +/- 0.2 C oesophageal temperature, Toes). On the second trial (control), they cycled for the same period of time maintaining euhydration by ingesting fluids and stabilising Toes at 38.2 +/- 0.1 degrees C. 3. After 20 min of exercise in both trials, leg blood flow (LBF) and leg exchange of lactate, glucose, free fatty acids (FFA) and glycerol were similar. During the 20 to 135 +/- 4 min period of exercise, LBF declined significantly in DE but tended to increase in control. Therefore, after 120 and 135 +/- 4 min of DE, LBF was 0.6 +/- 0.2 and 1.0 +/- 0.3 l min-1 lower (P < 0.05), respectively, compared with control. 4. The lower LBF after 2 h in DE did not alter glucose or FFA delivery compared with control. However, DE resulted in lower (P < 0.05) net FFA uptake and higher (P < 0.05) muscle glycogen utilisation (45 %), muscle lactate accumulation (4.6-fold) and net lactate release (52 %), without altering net glycerol release or net glucose uptake. 5. In both trials, the mean convective heat transfer from the exercising legs to the body core ranged from 6.3 +/- 1.7 to 7.2 +/- 1.3 kJ min-1, thereby accounting for 35-40 % of the estimated rate of heat production ( approximately 18 kJ min-1). 6. At exhaustion in DE, blood lactate values were low whereas blood glucose and muscle glycogen levels were still high. Exhaustion coincided with high body temperature ( approximately 40 C). 7. In conclusion, the present results demonstrate that reductions in exercising muscle blood flow with dehydration do not impair either the delivery of glucose and FFA or the removal of lactate during moderately intense prolonged exercise in the heat. However, dehydration during exercise in the heat elevates carbohydrate oxidation and lactate production. A major finding is that more than one-half of the metabolic heat liberated in the contracting leg muscles is dissipated directly to the surrounding environment. The present results indicate that hyperthermia, rather than altered metabolism, is the main factor underlying the early fatigue with dehydration during prolonged exercise in the heat.
 ...
PMID:Metabolic and thermodynamic responses to dehydration-induced reductions in muscle blood flow in exercising humans. 1052 24

The aim of the current study was to examine the effect of a moderate alteration in pre-exercise diet composition on the performance of, and metabolic response to, intermittent treadmill exercise in a group of normally menstruating females. Eight recreationally active women performed two intermittent, incremental exercise trials, one preceded by 2 days of a high [61 (1)%] carbohydrate (CHO) diet and the other by 2 days of a low [31 (1)%] CHO diet. Oxygen uptake (VO2) was measured during, and blood samples were obtained immediately after, each bout for the determination of blood lactate, glucose, glycerol, plasma free fatty acids and plasma ammonia. Performance, as assessed by time to exhaustion in the final bout, was found to be similar whether preceded by a high- or low-CHO diet [median (range): 28.0 (18-54) s, 29 (18-54) s, respectively]. No significant between trial differences were found in VO2, heart rate, or any of the blood metabolites. The results of the current, study indicate that moderate alterations of pre-exercise diet do not affect intermittent, high-intensity exercise performance in women, despite some evidence of an alteration in the pattern of the metabolic response to exercise.
 ...
PMID:Effects of moderate dietary manipulation on intermittent exercise performance and metabolism in women. 1063 77

The purposes of the present studies were to test the hypotheses that lower dosages of oral pyruvate ingestion would increase blood pyruvate concentration and that the ingestion of a commonly recommended dosage of pyruvate (7 g) for 7 days would enhance performance during intense aerobic exercise in well-trained individuals. Nine recreationally active subjects (8 women, 1 man) consumed 7, 15, and 25 g of pyruvate and were monitored for a 4-h period to determine whether blood metabolites were altered. Pyruvate consumption failed to significantly elevate blood pyruvate, and it had no effect on indexes of carbohydrate (blood glucose, lactate) or lipid metabolism (blood glycerol, plasma free fatty acids). As a follow-up, we administered 7 g/day of either placebo or pyruvate, for a 1-wk period to seven, well-trained male cyclists (maximal oxygen consumption, 62.3 +/- 3.0 ml. kg(-1). min(-1)) in a randomized, double-blind, crossover trial. Subjects cycled at 74-80% of their maximal oxygen consumption until exhaustion. There was no difference in performance times between the two trials (placebo, 91 +/- 9 min; pyruvate, 88 +/- 8 min). Measured blood parameters (insulin, peptide C, glucose, lactate, glycerol, free fatty acids) were also unaffected. Our results indicate that oral pyruvate supplementation does not increase blood pyruvate content and does not enhance performance during intense exercise in well-trained cyclists.
 ...
PMID:Pyruvate ingestion for 7 days does not improve aerobic performance in well-trained individuals. 1092 37

This two-part investigation compared the ergogenic and metabolic effects of theophylline and caffeine. Initially (part A), the ergogenic potential of theophylline on endurance exercise was investigated. Eight men cycled at 80% maximum O(2) consumption to exhaustion 90 min after ingesting either placebo (dextrose), caffeine (6 mg/kg; Caff), or theophylline (4.5 mg/kg Theolair; Theo). There was a significant increase in time to exhaustion in both the Caff (41.2+/-4.8 min) and Theo (37.4+/-5.0 min) trials compared with placebo (32.6+/-3.4 min) (P<0.05). In part B, the effects of Theo on muscle metabolism were investigated and compared with Caff. Seven men cycled for 45 min at 70% maximum O(2) consumption (identical treatment protocol as in part A). Neither methylxanthines (MX) affected muscle glycogen utilization (P>0.05). Only Caff increased plasma epinephrine (P<0.05), but both MX increased blood glycerol levels (P<0.05). Muscle cAMP was increased (P<0.05) by both MX at 15 min and remained elevated at 45 min with Theo. This demonstrates that both MX are ergogenic and that this can be independent of muscle glycogen.
 ...
PMID:Comparison of caffeine and theophylline ingestion: exercise metabolism and endurance. 1105 34

On two occasions, 8 male subjects completed a dehydration protocol, immediately followed by a 180-min rehydration protocol, then a subsequent exercise bout. During each dehydration session, subjects lost 3.1 +/- 0.4% body weight (BW) following discontinuous exercise in the heat (40 degreesC, 33% rh). During the first 30 min of rehydration, subjects ingested either 1.0-g glycerol x kg body weight(-1) + 30% of the total rehydration water volume (GLY), or 30% of the total rehydration water volume without glycerol (CON). The five remaining ingestions (every 30 min) were equal to 14% of the remaining fluid volume and were identical in nature. Fluid volume ingested equaled fluid volume lost during dehydration. Following the 180 min rehydration period, subjects cycled (appoximately 50% VO2 peak) in the heat (40 degrees C, 33% rh) until volitional exhaustion. Three observations were made: (a) Following glycerol-induced rehydration, time to volitional exhaustion was greater during the subsequent exercise bout in the heat (CON: 38.0 +/- 2.0, GLY 42.8 +/- 1.0 min, p <.05); (b) glycerol-induced rehydration significantly increased plasma volume restoration within 60 min and at the end of the 180-min rehydration period; and (c) total urine volume was lower and percent rehydration was greater following GLY, but neither was significantly different.
 ...
PMID:Effectiveness of glycerol as a rehydrating agent. 1125 37

When stimulated, the ammocoetes (larvae) of Geotria australis swim continuously at a moderate rate for only approximately 20 min, whereas the downstream migrants (young adults) of this species did not become exhausted following similar swimming activity over the same period. Mean concentrations of muscle glycogen in ammocoetes declined during exercise, but returned to resting levels within 30 min of recovery, whereas those in young adults changed little during the corresponding periods. Moreover, muscle lactate concentrations of ammocoetes rose markedly during exercise and the first 30 min of recovery, before declining significantly, while those of young adults remained similar during and immediately after exercise. Calculations, using the glycogen and lactate concentrations immediately after exercise, suggest that during exercise glycogen is, to some extent, utilised anaerobically (approx. 24%) by ammocoetes, but only aerobically by young adults. Furthermore, since young adults used only a small amount of glycogen, they presumably metabolised triacylglycerol aerobically to produce energy. Muscle glycerol-3-phosphate levels were far higher prior to and immediately after exercise in downstream migrants than in ammocoetes and then declined precipitously. The above trends in muscle glycogen and lactate of larval G. australis parallels, to some degree, those recorded by other workers for upstream migrant Petromyzon marinus that had been exercised to exhaustion.
 ...
PMID:Muscle glycogen, lactate and glycerol-3-phosphate concentrations of larval and young adult lampreys in response to exercise. 1143 30

The purpose of this study was to determine whether pre-exercise ingestion of meals with moderate and high glycemic indexes (GI) affects glucose availability during exercise and exercise performance time. Six male volunteers (22 +/- 1 years; 80.4 +/- 3.7 kg; VO(2peak), 54.3 +/- 1.2 ml. kg(-1). min(-1)) ingested 75 g of carbohydrate in the form of 2 different breakfast cereals, rolled oats (moderate GI, approximately 61; MOD-GI) or puffed rice (high GI, approximately 82; HI-GI), combined with 300 mL of water; or water alone (control). The trials were randomized, and the meals were ingested 45 minutes before the subjects performed cycling exercise (60% VO(2peak)) to exhaustion. Venous blood samples were drawn to measure glucose, free fatty acids (FFAs), glycerol, insulin (INS), epinephrine (EPI) and norepinephrine (NE) concentrations. A muscle biopsy specimen was obtained from the vastus lateralis before the meal and immediately after exercise for glycogen determination. Before exercise, both test meals elicited significant (P <.05) hyperglycemia and hyperinsulinemia compared with control. The glycemic response was higher (P <.05) at the start of exercise after the HI-GI meal than after the control. During exercise, plasma glucose levels were higher (P <.05) at 60 (5.2 +/- 0.1, 4.2 +/- 0.2, and 4.6 +/- 0.1 mmol. L(-1)) and 90 (4.8 +/- 0.1, 4.1 +/- 0.1, and 4.3 +/- 0.1 mmol. L(-1)) minutes after the MOD-GI meal than after either the HI-GI or control. Total carbohydrate oxidation was greater (P <.05) during the MOD-GI trial than in control and was directly correlated with exercise performance time (r =.95, P <.0001). Pre-exercise plasma FFA levels were suppressed (P <.05) 30 and 45 minutes after ingestion of the HI-GI meal and 45 minutes after the MOD-GI meal compared with control. At 30, 60, and 120 minutes of exercise, FFAs remained suppressed (P <.05) for both test meals compared with control. At exhaustion, plasma glucose, INS, FFA, glycerol, EPI, and NE levels and muscle glycogen use were not different for all trials. Exercise time was prolonged (P <.05) after the MOD-GI meal compared with control, but the HI-GI trial was not different from control (MOD-GI, 165 +/- 11; HI-GI, 141 +/- 8; control, 134 +/- 13 minutes). Thus, in contrast to the HI-GI meal or control, the MOD-GI breakfast cereal ingested 45 minutes before exercise enhanced performance time, maintained euglycemia for a longer period during exercise, and resulted in greater total carbohydrate oxidation during the exercise bout. We conclude that a MOD-GI meal provides a significant performance and metabolic advantage when consumed 45 minutes before exercise.
 ...
PMID:Effects of moderate and high glycemic index meals on metabolism and exercise performance. 1143 93

The effect of periodic aeration on the physiological activity of a strain of Saccharomyces cerevisiae yeast during development of velum (flor) and biological aging of Sherry wine of the Fino type was investigated. L-Proline amino acid was the main nitrogen source for yeasts cells during the biological aging, and its exhaustion may be the cause of the production and consumption of other compounds that are involved in the aroma of wines. Aeration was found to increase adenylate energy charge, growth, and viability of the yeast cells. Also, it affected the intracellular redox equilibrium and the consumption and production of compounds including acetoin, acetaldehyde, higher alcohols, ethanol, glycerol, and acetic acid. Acetaldehyde reached its highest level after the second aeration, which coincided with the exhaustion of the nitrogen source in the medium. The enzyme activity of alcohol dehydrogenases I and II decreased immediately after each aeration, subsequently increasing once all of the dissolved oxygen in the wine had been consumed by yeast cells. Aldehyde dehydrogenase activity was detected only after the first aeration, and it may be related to the production and consumption of acetic acid in the wine.
 ...
PMID:Influence of aeration on the physiological activity of flor yeasts. 1145 78


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>