In an attempt to identify a possible defect of mitochondrial metabolism in Rett syndrome we studied 9 girls with typical Rett syndrome using a clinical protocol designed to identify disorders of oxidative metabolism. One girl, (RO) had marked lactic acidemia. Biochemical studies on samples from these patients included leukocyte pyruvate ...

Nine male healthy and physically active volunteers performed four different exercise tests: an incremental load exercise test to exhaustion and a constant load exercise test of 15 min at 65% VO2max, both on the bicycle ergometer and on the treadmill. During the incremental exercise test, blood ammonia levels were significantly ...

PURPOSE: Oxygen-enriched gases enable patients and healthy individuals to exercise submaximally with reduced lactate concentration, lower minute ventilation (VE), and less subjective stress compared to normoxia. These findings suggest that hyperoxia may raise the lactate accumulation threshold, also known as the anaerobic threshold (AT). METHODS: This study measured the anaerobic ...

We used a new stable isotope tracer approach incorporating muscle intracellular lactate enrichment to determine the flux of glucose/glucosyl toward lactate [i.e., nonoxidized pyruvate (Pyr) production (Pyrno)] in moderately trained cyclists exercising at approximately 80% (259 +/- 16 W; n = 6) and approximately 100% (341 +/- 9 W; n ...

Vascular smooth muscle metabolism is characterized by substantial production of lactic acid even under fully oxygenated conditions. The role the aerobic production of lactate plays in the energetics of smooth muscle is obscure and was investigated in this study. Helical strips of porcine carotid arteries were incubated in medium containing ...

BACKGROUND: The objective of this study was to investigate whether luminal perfusion with glutamine or with oxygenated glutamine solutions prevents endotoxin-induced changes in mucosal permeability. METHODS: Three 15-cm segments of distal ileum were isolated in anesthetized 21-day-old piglets (n = 4) and perfused (50 mL/h) with Ringer's lactate solution, Ringer's ...

Data from a survey performed from 1986 to 1990 were analyzed to assess the effects of diseases on length of productive life of 3589 Holstein cows from 47 herds, using a proportional hazard model. The probability of a cow being culled, or hazard function, was supposed to be the product ...

Tracers have been used extensively to study lactate metabolism in humans during rest and exercise. Nevertheless, quantification of in vivo lactate kinetics as measured by lactate tracers remains controversial and new data are necessary to clarify the issue. The present study has developed a simple kinetic model which does not ...

Blood concentrations of lactate normally increase during and after intense exercise as does the ratio of concentrations of lactate to pyruvate (L:P). Since there appear to be differences in blood lactate concentrations on exercise, in muscle metabolic enzyme activities, and in anaerobic capacity between children and adults, we speculated that ...

Relationships between the postexercise values of blood lactate concentration, pH, oxygen uptake, heart rate, power output on the one hand, and the pre- and postexercise blood cortisol concentrations on the other, were studied in 74 male and 40 female athletes (wrestlers and senior and junior rowers), performing graded exercise of ...

The correlation between the behaviour of the heart rate/work performance (fc/W) curve and blood lactate ([la]b) and plasma adrenaline/noradrenaline concentrations ([A]/[NA]) during incremental cycle ergometer exercise was investigated. A group of 21 male sports students was divided into two groups: group I, with a clear deflection of the fc/W curve; ...

Metabolic and cardiorespiratory reactions were investigated during a sport-specific incremental field test (FT) for tennis and compared with a treadmill step test (TT) in a group of 13 trained male tennis players. In both the FT and the TT lactate acid (La), heart rate and oxygen uptake (VO2) were measured. ...

In a cyclist, competing at national and international level, submaximal lactate concentrations were initially interpreted as improved endurance capacity. However, 2 weeks later, a test in which maximal lactate was measured showed that maximal lactate was decreased as well. Together with the complaints of deteriorating performance and subjective complaints of ...

The brain usually depends almost exclusively on glucose for its energy requirements. During hypoglycemia associated with prolonged fasting or strenuous exercise, circulating ketone-body and lactate levels increase several-fold; in both situations, certain signs and symptoms of hypoglycemia are diminished. Therefore, to test the hypothesis that hyperketonemia or hyperlacticacidemia of the ...

During severe oxygen shortage, the fetal brain resorts to anaerobic metabolism and ATP becomes catabolized. High levels of nucleosides, hypoxanthine, and xanthine (ATP catabolites) in cerebrospinal fluid (CSF) may therefore be associated with increased neonatal neurologic morbidity. In 22 fetal lambs (3 to 5 d after surgery, gestational age 123.5 ...

The influence of training on blood lactate concentrations during treadmill exercise and a 40-minute inactive recovery period was examined in seven trained and seven detrained thoroughbred horses. Lactate concentrations were measured in venous blood collected at the end of each exercise state, and at intervals for 40 minutes afterwards. Measurements ...

OBJECTIVE: We postulated a 'kinin-tensin system' in which angiotensin II (Ang II) is cleaved by one or more serine protease independent of renin or angiotensin converting enzyme (ACE). The aim was to determine whether this alternative Ang II-forming pathway by serine proteases participates in the rise in plasma levels of ...

Ten endurance athletes performed two exhaustive intensive endurance exercises (Ex1: 21 +/- 7 min; Ex2: 18 +/- 6 min) on a cycle ergometer at 110% of their individual anaerobic threshold (maximal lactate concentration at Ex1: 9.7 +/- 2.3 mmol.1-1, Ex2: 9.5 +/- 2.2 mmol.l-1). Ex1 was performed two weeks before, ...

Skeletal muscle lactate transport was investigated in vitro in isolated fast-twitch (EDL) and slow-twitch soleus (Sol) skeletal muscles from control and exercised mice. Exercise (23 m/min, 8% grade) reduced muscle glycogen by 37% in EDL (p < 0.05) and by 35% in Sol muscles (p < 0.05). Lactate transport measurements ...

Twenty middle aged endurance runners underwent physiological testing to determine their maximal oxygen uptake (VO2max), lactate threshold, ventilatory threshold, the slope variation point (SVP) of the linear relationship between running speed (RS) and heart rate (HR) both on the treadmill and during a field test, and the onset of blood ...

The effect of pranayama a controlled breathing practice, on exercise tests was studied in athletes in two phases; sub-maximal and maximal exercise tests. At the end of phase I (one year) both the groups (control and experimental) achieved significantly higher work rate and reduction in oxygen consumption per unit work. ...

The purpose of this study was to cross-validate the method of Conconi et al. (5) that purports to determine "anaerobic threshold" based on a deflection point between heart rate (HR) vs power output. Eight males (22.6 +/- 1.6 y) were tested with maximal progressive cycle ergometry under normal (NG) and ...

Treadmill exercise activates the hypothalamic-pituitary-adrenal axis and evokes metabolic responses proportional to exercise intensity and duration. To determine whether glucocorticoid administration would alter humoral and metabolic regulation during exercise, we administered 4 mg dexamethasone (DEX) or placebo to 11 normal, moderately trained men (19-42 yr old) in a double blinded ...

Our goal was to design a stimulation-contraction paradigm using an isolated in situ dog gastrocnemius muscle preparation that would provide an experimental model for brief intense intermittent (IC) exercise in humans. Second, acid-base and ion exchanges across the muscle were investigated using four 30-s bouts of isotonic tetanic contractions (2 ...

A perfused rat hindlimb preparation was used to assess the effects of perfusate flow and electrical stimulation to mimic exercise on the rates of lactate influx (measured by a dual tracer technique with [3H]mannitol as the extracellular marker) and net lactate production. The same perfused muscle system was also used ...

Three transgenic females from a first generation transgenic male were induced to lactate between 11 and 12 months of age using a series of estrogen and progesterone injections. The milk contained human longer acting tissue plasminogen activator (LAtPA) at comparable concentrations (1-3 mg/ml) as occurred in the original founder female. ...

The effect of clinical, spontaneous-onset seizures on extracellular fluid lactate was investigated by the method of lactography, the in vivo on-line measurement of lactate levels using microdialysis. Studies of experimental animals have suggested that generation of extracellular lactate as measured by microdialysis is an index of local glucose utilization and ...

The different mechanisms of acidosis buffering were investigated in 15 RDT patients dialyzed in cross-over with four depurative techniques: acetate dialysis (AD), bicarbonate dialysis (BD), lactate hemofiltration (LHF) and hemodiafiltration (HDF) with acetate bath and lactate reinfusion fluid. Blood pH, bicarbonate, blood gases, intraerythrocytic pH - on red cell hemolisates ...

OBJECTIVES: The aim of this study was to determine the relation between femoral vein oxygen partial pressure (PO2) and lactate increase during exercise in patients with cardiovascular disease. BACKGROUND: Considerable controversy surrounds the relation between the increase in lactate during exercise and the oxygen supply to the exercising muscles. We ...

In the amphibian Bufo marinus, progressive hypoxia below a critical PO2 elicits a transient 50% increase in O2 consumption that coincides with the onset of lactate formation. The present study was designed to test the hypothesis that lactate causes the observed rise in metabolic rate. Arterial bolus infusions of pH-neutral ...

Whether lambs were used to evaluate the influence of treadmill exercise (TME) on physiological responses and meat quality. Lambs were exercised at either 5.6, 7.2, or 8.8 km/h on a 9 degrees incline for 10 min, followed by a 10-min walk at 4.0 km/h and 0 degrees incline, or were ...

The purpose of this investigation was to determine the effect of physostigmine (Phy) and/or concurrent exercise on lactate, pyruvate, and L/P ratio in plasma, skeletal muscle, and brain tissue in male Sprague-Dawley rats. The Phy-dosed (Phy-D) and Phy-dosed + concurrent acute exercise (Phy-D + CAE) groups elicited significantly higher L/P ...

The slow rise in O2 uptake (VO2), which has been shown to be linearly correlated with the increase in lactate concentration during heavy constant work rate exercise, led us to investigate the role of H+ from lactic acid in facilitating oxyhemoglobin (O2Hb) dissociation. We measured femoral venous PO2, O2Hb saturation, ...

The respiratory and circulatory physiology of exercising Christmas Island red crabs Gecarcoidea natalis were investigated with respect to their annual breeding migration. Red crabs were allowed to walk for up to 45 min. During this exercise period, the functioning of the circulatory system in gas transport and the energy status ...

Patients with fibromyalgia often complain of fatigue and pain during exercise and of worsening of pain days after exercise. The aim of the study described here was to determine if abnormal changes in potassium or lactate could be observed during an exercise test in fibromyalgia. Whether an abnormal incline in ...

Constant-load exercise that engenders a sustained lactic acidosis (i.e., above the lactate threshold) is accompanied by a slow component of O2 uptake (VO2) kinetics that increases VO2 above rather than toward the predicted value. This response arises predominantly from within the exercising limbs and is temporally correlated with that of ...

OBJECTIVE: To characterize changes associated with lactate-induced panic, proton magnetic resonance spectroscopy (MRS) was used to measure brain lactate during intravenous infusion of 0.5-M sodium lactate in panic disorder patients and comparison subjects. METHOD: Eight panic disorder subjects, five medicated and three unmedicated, and eight healthy comparison subjects were studied ...

The study investigated the concentrations of free plasma catecholamines (CAT), adrenaline and noradrenaline, in comparison to heart rate and lactic acid concentrations during endurance exercises (EE) of different intensities related to the individual anaerobic threshold (IAT). A group of 14 endurance trained male athletes took part in the tests on ...

Eight highly trained male kayakers were studied to determine the relationship between critical power (CP) and the onset of blood lactate accumulation (OBLA). Four exercise sessions of 90 s, 240 s, 600 s, and 1200 s were used to identify the CP of each kayaker. Each individual CP was obtained ...

A number of studies have identified the existence of two ventilation thresholds during ramp or incremental exercise to exhaustion on the cycle ergometer. This study was undertaken to investigate whether two threshold turnpoints could be identified in blood lactate concentration data collected at such times. Five trained athletes provided serial ...

The aim of this study was to estimate the characteristic exercise intensity (WCL) which produces the maximal steady state of blood lactate concentration (MLSS) from submaximal intensities of 20 min carried out on the same day and separated by 40 min. Ten fit male adults [maximal oxygen uptake (VO2max) 62 ...

To elucidate the mechanisms of lactate formation during submaximal exercise, eight men were studied during one- (1-LE) and two-leg (2-LE) exercise (approximately 11-min cycling) using the catheterization technique and muscle biopsies (quadriceps femoris muscle). The absolute exercise intensity and thus the energy demand for the exercising limb was the same ...

We investigated the effects of the angiotensin-converting enzyme (ACE) inhibitor trandolapril (2 mg/o.d.) on the physical work capacity (PWC), the received perception of exertion (RPE), as well as parameters determining physical performance (i.e., energy metabolism, lactate production, and oxygen uptake) in well-trained, healthy subjects. Twenty male sports students underwent a ...

The effects of menstrual cycle phase on the blood lactate response to exercise were examined in eumenorrheic women (n = 9). Exercise tests were performed at the mid-follicular and mid-luteal points in the menstrual cycle (confirmed by basal body temperature records and hormone levels). Blood lactates were measured at rest ...

The addition of Na-lactate (50-150 mmol/l) to media with glucose had only marginal effect on the growth of rumen lactate-producing bacteria at pH between 6.5 and 5.8. Butyrivibrio fibrisolvens was somewhat more sensitive to external lactate than Streptococcus bovis, Lactobacillus fermentum and Selenomonas ruminantium. It can be concluded that rumen ...

This study investigated the frequency and severity of symptoms during naturally occurring panic attacks recollected as "usual" and during sodium lactate-induced attacks. Seventy-six male and 126 female patients with panic disorder or agoraphobics with panic attack (DSM-III criteria) underwent lactate infusion studies and were serially administered the Acute Panic Inventory ...

This study analysed the changes in electromyographic (EMG) activity of the vastus lateralis, biceps femoris and gastrocnemius muscles during incremental treadmill running. The changes in EMG were related to the lactate and ventilatory thresholds. Ten trained subjects participated in the study. Minute ventilation, oxygen consumption, carbon dioxide expired and the ...

We investigated the effects of a stimulation of pyruvate dehydrogenase (PDH) activity induced by 2-chloropropionate (2-CP) on venous plasma lactate concentration and peak anaerobic power (W an, peak) during periods (6 s) of incremental intense exercise, i.e. a force-velocity (F-v) test known to induce a marked accumulation of lactate in ...

The present study was undertaken to examine the relationship between maximal pulmonary ventilation (VEmax) and potassium concentration ([K+]) or lactate concentration ([La]) of venous blood in man. Nine healthy men performed exercise on a bicycle ergometer at a constant rate of 60 rpm until volitional fatigue. VEmax ranged from 100.4 ...

The purpose of the present study was to determine the anaerobic threshold by analysis of changes in saliva composition during an incremental exercise test on a cycle ergometer. Thirteen healthy males underwent a submaximal test with an initial load of 50 W and load increases of 50 W per 3 ...