Muscle glycogen and glucose have been suggested to be carbon-chain precursors for glutamine synthesis in skeletal muscle. Therefore, the aim of the present study is to investigate whether carbohydrate supplementation affects plasma glutamine and other amino acids during exercise and 7 h of recovery. Eight well-trained subjects cycled at an ...

The effect of chronic voluntary exercise on the plasma level of nitrate, a major stable metabolite of nitric oxide (NO) was studied in spontaneously hypertensive rats (SHR). Exercise consisted of spontaneous running in wheels for 3-35 days. Blood samples were collected after 3, 7, 14, 21 and 35 days of ...

The cardiovascular and humoral responses to sustained muscle metaboreflex activation were examined in eight male volunteers while they performed two 24-min exercise protocols. Each of these consisted of six 1-min bouts of isometric handgrip exercise (the left and right hands being used alternately) at 50% of maximal voluntary contraction; after ...

Cardiovascular and neuroendocrine responses to exercise in a physically fit and an untrained group of young healthy subjects were compared to study the significance of physical fitness for performance in a discipline for which the athletes were not trained. Ten wrestlers of national rank prepared for an international competition (age ...

The administration of 41 of an isotonic, plasma-like oral rehydration solution (ORS) with an osmotic skeleton and 41 of water (water; no osmotic skeleton), were evaluated in five thoroughbred horses. Solutions were administered by nasogastric tube 4 h after feeding. Uptake of deuterium, concentrations of plasma sodium, potassium, chloride, glucose, ...

We evaluated the hypothesis that impaired sarcolemmal function associated with exaggerated potassium release, impaired potassium uptake, or both may contribute to exertional fatigue and abnormal circulatory responses to exercise in McArdle disease (MD). The cellular mechanism of exertional fatigue and muscle injury in MD is unknown but likely involves impaired ...

To investigate the effects of chronic exercise and deconditioning on platelet function in women, 16 healthy sedentary women were divided into control and exercise groups. The exercise group cycled on an ergometer at 50% maximal oxygen consumption for 30 min/day, 5 days/wk, for two consecutive menstrual cycles and then were ...

BACKGROUND: Exercise increases plasma arginine-vasopressin (PAVP), plasma atrial natriuretic peptide (PANP), plasma renin activity (PRA), and plasma aldosterone (PALDO) in an intensity-dependent manner. With acute exercise, urine osmolality (UOSM) is often decreased despite increased PAVP. The hyperbaric environment lowers PAVP and UOSM, and increases urine flow. HYPOTHESIS: If work produced ...

To identify whether muscular exercise increases the plasma concentration of uridine and of purine bases, the effect of rigorous muscular exercise was determined in five healthy men with a bicycle ergometer. Twenty-five-minute muscular exercise at 65% maximum O2 consumption increased the concentration of uridine, purine bases, and inorganicphosphate in plasma ...

BACKGROUND: A laboratory-based model which links regional and central fatigue during physical exercise has not yet developed. Today we can assay the oxypurines, a specific and sensible marker of muscle cell-energy exhaustion during strenuous physical exercise, thus allowing us to insight in peripheral fatigue mechanisms. Prolonged physical exercise modifies plasma ...

This study employed Stewart's physicochemical approach to quantify the effects of pregnancy and strenuous exercise on the independent determinants of plasma H+ concentration ([H+]). Subjects were nine physically active pregnant women [mean gestational age = 33 +/- 1 (SE) wk] and 14 age-matched nonpregnant controls. Venous blood samples and respiratory ...

Although transdermal nicotine patches have been studied extensively under recommended conditions, the present studies were designed to assess the nicotine plasma levels and the safety of transdermal nicotine patches in smokers undergoing situations suspected to result in increased nicotine plasma levels. The first study examined the effects of increasing nicotine ...

Loperamide, a peripherally acting opiate receptor agonist with antidiarrheal action, inhibits ileal and colonic motor function. It was determined whether loperamide also affects gallbladder emptying and pancreatic enzyme secretion in humans. Plasma cholecystokinin (radioimmunoassay), gallbladder volume (ultrasonography), and intraduodenal bilirubin and amylase output (spot sampling) were measured at regular intervals ...

OBJECTIVE: To assess the effects that exercise-induced plasma volume changes (PVCs) have on the interpretation of biochemical and hormonal parameters in the blood of athletes after high-intensity exercise. It was hypothesized that two unrelated high-intensity exercise protocols, performed by two separate subject groups each using different exercise modes, would result ...

1. This study investigated the effects of 7 weeks of sprint training on changes in electrolyte concentrations and acid-base status in arterial and femoral venous blood, during and following maximal exercise for 30 s on an isokinetic cycle ergometer. 2. Six healthy males performed maximal exercise, before and after training. ...

The effect of different rates of fluid ingestion on heart rate, rectal temperature, plasma electrolytes, hormones and performance was examined during prolonged strenuous exercise conducted at 21 degrees C. Seven well-trained males (24 +/- 1 yr; 68.6 +/- 2.9 kg; VO2 peak = 4.69 +/- 0.17 L min-1; mean +/- ...

The potential of exercise-induced changes in peripheral amino acids to alter blood prolactin levels through a serotonergic system modification was investigated in 8 male athletes. In two trials, subjects (N = 8) exercised on a cycle ergometer for 5 hr. The intensity of exercise corresponded to 55% VO2max (T55) or ...

Aging is associated with elevations in plasma norepinephrine concentrations. The purpose of this investigation was to examine total body and regional norepinephrine spillover as an indicator of sympathetic nerve activity. Eight young (26 +/- 3 yr) and seven old (69 +/- 5 yr) male subjects were studied at rest and ...

Sodium is the major cation of the extracellular fluid and has a potent influence on fluid movement. Sodium has been likened to a sponge that draws fluids into the extracellular space, including the plasma volume, to equalize gradients in concentration. Conventional wisdom suggests limiting dietary intake of Na+ to decrease ...

Our object was to evaluate the effects of regular mild exercise on blood pressure and on circulating level of ouabainlike factors (OLF) and of nitrate anion, an endproduct of nitric oxide (NO) in humans. We measured plasma ouabainlike immunoreactivity (OLI) and nitrate ions (NO3.) before and after mild exercise for ...

Prolonged exercise can elicit a reduction in the plasma glutamine concentration and an increase in the plasma concentration ratio of free tryptophan (FTrp) to branched-chain amino acids (BCAA). The purpose of this investigation was to study the effects of a 60-min bout of vigorous treadmill running with dietary manipulation on ...

To determine the effect of acute plasma volume (PV) expansion on substrate utilization, blood metabolites and catecholamines to prolonged, moderate intensity cycle exercise, eight untrained men mean maximal oxygen uptake VO2max 4.10 (SEM 0.32) 1.min-1 were infused (10 ml.kg-1) with a 6% dextran (DEX) solution. These responses were also compared ...

The effects of hydromineral hormones and catecholamines on renal concentrating ability at different hydration states were examined in five male volunteers while they performed three trials. Each of these trials comprised a 60-min exercise bout on a treadmill (at 50% of maximal oxygen uptake) in a warm environment (dry bulb ...

The objective of our study was to examine the effects of beverage content on hormone responses involved in fuel substrate metabolism (catecholamines, insulin and glucagon) in previously dehydrated subjects exercising at a moderate intensity in the heat. Six healthy men walked for 60-min on five occasions at 50% maximal oxygen ...

The intracellular pH (pHi) and the concentrations of lactate and selected modulators of phosphofructokinase (PFK; EC 2.7.1.11) were measured in white epaxial muscle of 15 °C-acclimated rainbow trout (Oncorhynchus mykiss) maintained at 8, 15 or 22 °C for 48 h and sampled at rest and after 10 min of exhaustive ...

Several studies have indicated that endothelin-1 (ET-1) and endothelin-3 (ET-3) are produced by different cells. Although ET-1 is produced by vascular endothelial cells, these cells do not produce ET-3. The presence of ET-3 in the brain of several species suggests that ET-3 is a novel neuropeptide. It is unclear whether ...

The present study was undertaken to determine the haematological and cardiovascular status, at rest and during prolonged (1h) submaximal exercise (approximately 70% of peak oxygen uptake) in a group (n = 12) of chronic coca users after chewing approximately 50 g of coca leaves. The results were compared to those ...

The purpose of this study was to compare accumulated oxygen deficits and markers of anaerobic metabolism [plasma ammonia (NH3) and lactate (La-) concentrations] in anaerobically trained male [n = 8, age 14.8 (0.5) years; maximal oxygen consumption VO2max 61.74 (2.23) ml x kg(-1) x min(-1)] and female [n = 8, ...

The neurohumoral, peptidergic and biochemical responses to supine leg exercise were studied in two groups with primary autonomic failure: Shy-Drager syndrome (SDS, n = 15) and pure autonomic failure (PAF, n = 15), to determine if these accounted for exercise-induced hypotension and the greater blood pressure (BP) fall in PAF. ...

In experimental animals, stress and catecholamines stimulate endogenous interleukin-6 (IL-6) secretion, whereas glucocorticoids inhibit it. To examine whether physical stress alters the secretion of IL-6 in humans, and to what extent this is correlated with catecholamines and modified by glucocorticoids, we performed high-intensity treadmill exercise test runs on 15 male ...

The objective of this investigation was to determine fluid electrolyte changes after water-loading tests and during hypokinesia (decreased number of km taken per day) and daily intake of fluid and salt supplementation (FSS). The studies during hypokinesia (HK) were performed for 364 d on 30 endurance-trained male volunteers in the ...

Serum potassium levels rise substantially during vigorous exercise as a result of the release of potassium from contracting muscle cells. Widespread use of erythropoietin has allowed for increased exercise capacity in patients with ESRD, raising the concern for severe exertional hyperkalemia. The aim of this study was to determine whether ...

In this study, 4 Standardbred geldings were exercised at 20 and 35 degrees C. The exercise test (ET) consisted of 2 exercise bouts separated by 2 h of rest in their boxes. Blood samples were taken before, during and after the second exercise bout and muscle (m. gluteus medius) biopsies ...

To avoid dehydration and a decrease in performance capacity in horses, fluid and electrolyte losses need to be compensated for during long distance rides as well as on other occasions when sweat losses are high during exercise. Thirteen endurance-trained horses, age 5-14 years, were used to compare 3 strategies of ...

The influence of a 56-km endurance exercise on cortisol kinetics and production rate was evaluated in six horses administered [3H]cortisol. Exercise resulted in an immediate two- to threefold increase in plasma cortisol, with values returning very rapidly to preexercise levels. During exercise, clearance and steady-state volume of distribution of total ...

Skeletal muscle catabolism, low plasma glutamine, and high venous glutamate levels are common among patients with cancer or human immunodeficiency virus infection. In addition, a high glycolytic activity is commonly found in muscle tissue of cachectic cancer patients, suggesting insufficient mitochondrial energy metabolism. We therefore investigated (a) whether an "an-aerobic ...

The serpins C1 esterase inhibitor (C1Inh), antithrombin (AT), alpha 1-antitrypsin (alpha 1AT) and alpha 2-antiplasmin (alpha 2AP) are known inhibitors of coagulation factor XIa (FXIa). Although initial studies suggested alpha 1AT to be the main inhibitor of FXIa, we recently demonstrated C1Inh to be a predominant inhibitor of FXIa in ...

Haemostatic disturbances associated with elevated plasma fibrinogen levels have been implicated in coronary heart disease. Changes involving plasma fibrinogen levels have been reported after acute exercise. However, the results reported have sometimes been controversial, due to differences in the populations studied, exercise protocols and testing procedures, and the analytical methods ...

Plasma concentration of uric acid, total peroxyl radical-trapping antioxidative parameter (TRAP), blood lactate concentration and plasma activity of xanthine oxidase (XO) were measured in six Standardbreed trotters after six bouts of exercise with increasing intensity on two separate days three days apart. Blood samples were taken immediately, 5, 10, 15, ...

Maximal oxygen uptake (VO2 max) and lactate threshold (LT) were measured during graded, incremental exercise in 8 healthy, untrained volunteers (aged 22 +/- 0.9 yrs) following 3 days on a control, mixed diet, or a ketogenic (50% fat, 45% protein and 5% carbohydrates) diet of equal energy content. Before and ...

Tryptophan is converted to 5-hydroxytryptamine (5-HT) in the brain and evidence is presented that an increase in the concentration of 5-HT can result in physical and mental fatigue during prolonged exercise. The entry of tryptophan in the brain is influenced by the plasma level of free tryptophan (that not bound ...

This study was designed to determine metabolic and physical performance responses to ingestion of pre-exercise meals with different macronutrient and fiber profiles. Twelve physically active subjects (6 males and 6 females) were used to investigate the metabolic and physical performance consequences of consuming pre-exercise meals consisting of oat, corn, or ...

Norepinephrine and its metabolites were studied in various body fluids (plasma, urine and cerebrospinal fluid) of patients with anorexia nervosa, bulimia nervosa and healthy young women. The reaction of plasma norepinephrine to different stimuli like orthostatic challenge, test meals, standardized exercise, mental challenge tests etc. were studied. All results indicate ...

OBJECTIVE: To evaluate the effects of simultaneous pharmacologic inhibition of catechol-O-methyltransferase (COMT) and monoamine oxidase type A (MAO-A) on hemodynamics and catecholamine metabolism in healthy volunteers at rest and during exercise. BACKGROUND: Entacapone, a COMT inhibitor, is studied as an adjunct to levodopa treatment in patients with Parkinson's disease. Moclobemide, ...

The present study was designed to test the hypothesis that changes in plasma concentrations of hormones may be responsible for the exercise-induced macrophage phagocytic stimulation. The effect of 30-min incubation of macrophages with plasma from mice previously exposed to swimming until exhaustion (with or without previous training) was studied, and ...

1. We manipulated plasma catecholamines (combined adrenaline and noradrenaline concentrations) to three levels during prolonged exercise to determine their effect on cutaneous and forearm vascular conductance (CVC and FVC), oesophageal temperature (T(oes)) and cardiovascular responses. 2. On three occasions, seven endurance-trained men cycled at 65% VO2, max in the heat ...

BACKGROUND: Xylitol exerts a nitrogen-sparing effect in stress catabolic states with hyperglucagonemia, but the mechanism(s) is unknown. We examined the effects of xylitol on urea synthesis during physiologic glucagon concentrations and during hyperglucagonemia. METHODS: Urea synthesis was measured independently of blood amino acid concentration by means of functional hepatic nitrogen ...

We have investigated the effects of chronic physical training and acute intensive exercise on plasma fibrinogen levels and the relationship of these responses to beta-fibrinogen G-453-A polymorphism genotype. One hundred fifty-six male British Army recruits were studied at the start of their 10-week basic training, which emphasizes physical fitness. Cohorts ...

To determine the combined sympathoadrenal effects of cocaine and exercise in awake animals, rats were assigned to one of four treatment groups: saline-rest (SR), saline-exercise (SE), cocaine-rest (CR), and cocaine-exercise (CE). Venous blood samples from jugular catheters were obtained at -40, 0-4, 7, 10, 13, 16, 19, 26, and 36 ...

The purpose of our study was to clarify the role of capsaicin-sensitive nerves in the control of plasma catecholamine and glucose concentrations during exercise. In vehicle-treated rats, plasma epinephrine (E) and norepinephrine (NE) levels were significantly higher in animals exercised to exhaustion than in the group sacrificed at rest. However, ...