Hypothermic perfusion of rat livers was investigated by 31phosphorus nuclear magnetic resonance (31P NMR) spectroscopy using a temperature-controlled module that allowed data acquisition at various time points during a 48-h period. The livers were perfused with an oxygenated lactobionate/raffinose-based solution containing adenosine and inorganic phosphate, and changes in tissue oedema ...

The BioStat 1000 is a new device which employs dialysate-based urea kinetics to calculate the dose of dialysis (Kt/V) based on a two-pool model and protein catabolic rate (PCR). Previous methods relying on blood sampling techniques were subject to error and difficult to implement. This paper describes the features of ...

Masseter muscle metabolism is poorly understood. 31P Magnetic Resonance Spectroscopy (MRS) provides an opportunity for non-invasive study of muscle metabolism during rest, exercise, and recovery. The aim of this study was to investigate the changes in high-energy phosphates and pH in human masseter muscle associated with exertional pain. Phosphates and ...

We report here a glycogen storage myopathy type V associated with multifocal encephalopathy. The patient, a 43-year-old male with increased serum CK, a heavy drinker and smoker, had been affected by generalized epilepsy since age 24, after a cranial injury. He had had a right hemiparesis 2 years before coming ...

31Phosphorus nuclear magnetic resonance spectroscopy was used to examine skeletal muscle in 29 patients with mitochondrial myopathy, 9 male and 20 female. Gastrocnemius was investigated in 15 patients and 30 normal subjects and finger flexor muscle (flexor digitorum superficialis, fds) in 24 patients and 35 normal controls. Both muscles were ...

To examine the effect of heat stress on muscle energy metabolism during submaximal exercise, 12 endurance-trained men cycled on two occasions for approximately 40 min at 70% maximal O2 uptake in an environmental chamber at either 20 degrees C and 20% relative humidity (T20) or 40 degrees C and 20% ...

Metabolic myopathies are disorders of muscle energy production that result in skeletal muscle dysfunction. Cardiac and systemic metabolic dysfunction may coexist. Symptoms are often intermittent and provoked by exercise or changes in supply of lipid and carbohydrate fuels. Specific disorders of lipid and carbohydrate metabolism in muscle are reviewed. Evaluation ...

Maximal rates, coupling, and control of oxidative phosphorylation were studied in isolated skeletal muscle mitochondria from rat and rabbit. Mitochondria were incubated under various conditions of temperature, pH, and substrate availability. A 20% decrease in coupling (ADP/O) was observed at 43 degrees C as compared to 37 degrees C in ...

The present study was designed to compare evaluation of skeletal muscle metabolism (vastus lateralis) evaluated by 31P-magnetic resonance spectroscopy (MRS) and biochemical analysis. During identical isometric knee extensor exercise protocols to fatigue in eight men, biopsy samples were taken at rest, peak exercise, and 32 s postexercise and 31P-MRS data ...

The purpose of this study was to evaluate the consequences of non-linear changes in phosphocreatine (PCr) and pH during incremental calf exercise on estimates of ADP and cytosolic free energy of ATP hydrolysis (delta GATP). Six subjects performed incremental plantar flexion exercise on a treadle ergometer while muscle P(i) metabolism ...

The present study tested whether, during moderate exercise, 1) the dynamic responses of ADP and changes in free energy of ATP hydrolysis (delta GATP) were similar to those of phosphocreatine [PCr; as would be expected for a simple controller of muscle respiration (QO2)] and 2) the rise in pulmonary O2 ...

Several studies of phosphorus 31 (31P) magnetic resonance spectroscopy (MRS) have demonstrated the presence of skeletal muscle metabolic abnormalities during exercise in patients with chronic heart failure (CHF). We studied the contribution of these abnormalities to the limitation of exercise capacity in CHF. In 25 patients (age 57 +/- 2 ...

We employed magnetic stimulation to study the masseter silent period (SP) in 16 healthy volunteers. Cutaneous perception threshold (CPT or 1 T) was determined. SP threshold was 30% M (maximal output) in each subject, equivalent to 1.5-3 T, and as intensity increased, SP durations prolonged. The correlation was higher with ...

The purpose of this study was to 1) evaluate the baroreflex (BR) modulation of the sinus node during isometric exercise in humans by analyzing the variations in pulse interval (PI) in response to beat-by-beat spontaneous changes in systolic arterial pressure (SAP), thus avoiding external intervention to alter arterial pressure (AP); ...

Intense exercise can double arterial K+ concentration, decrease pH by 0.4 units, and increase catecholamines 15-fold. Any one of these changes may be cardiotoxic in a subject at rest, yet these changes are well tolerated in exercise. We tested the interactive effects of extracellular K+ concentration ([K+]o), metabolic acidosis (pH ...

This study examined the effects of 14 days of L-carnitine supplementation on muscle and blood carnitine fractions, and muscle and blood lactate concentrations, during high-intensity sprint cycling exercise. Eight subjects performed three experimental trials: control I (CON I, Day 0), control II (CON II, Day 14), and L-carnitine (L-CN, Day ...

Carnitine plays a central role in lipid metabolism by transporting long-chain fatty acids into the mitochondria for beta-oxidation. Reduction of carnitine concentration does not automatically imply that functional carnitine deficiency exists with direct consequences on energy metabolism. In our experimental model, we reduced tissue concentrations of carnitine to levels that ...

To determine how diet modulates short-term exercise capacity, skeletal muscle pH and bioenergetic state were examined by 31P-magnetic resonance spectroscopy in nine healthy volunteers. Subjects performed incremental quadriceps exercise to exhaustion after 5 days of high-carbohydrate (HCHO) or high-fat (HFAT) diet randomly assigned in crossover fashion and separated by a ...

A point mutation in the mtDNA-encoded ATP6 gene (T-->G at nt 8993) associated with Leigh syndrome in two pedigrees was found to decrease ADP-stimulated (state III) respiration and the ratio of ADP molecules phosphorylated to oxygen atoms reduced (ADP/O ratio) but did not affect 2,4-dinitrophenol (DNP)-uncoupled respiration, suggesting a defective ...

The activity of complex I of the respiratory chain is decreased in the substantia nigra of patients with Parkinson's disease (PD) but the presence of this defect in skeletal muscle is controversial. Therefore, the mitochondrial function of skeletal muscle in patients with PD was investigated in vivo using 31P magnetic ...

To determine whether skeletal muscle oxidative metabolism is impaired in multiple sclerosis (MS), phosphorus magnetic resonance spectroscopy was used to measure the rate of intramuscular phosphocreatine (PCr) resynthesis following exercise in MS and controls. Thirteen MS patients underwent intermittent isometric tetanic contractions of the dorsiflexor muscles elicited by stimulation of ...

Many disease states decrease intracellular adenosine triphosphate (ATP) levels and elevate body fluid purine levels. The use of specific metabolic substrates may reverse this process. This study was designed to test the hypothesis that beta-hydroxybutyrate, a substrate for ATP synthesis, decreases body fluid purine levels during interventions that induce ATP ...

Simultaneous measurements of phosphocreatine (PCr) and oxyhemoglobin (HbO2) saturation were made during recovery from exercise in calf muscles of five male subjects. PCr was measured using magnetic resonance spectroscopy in a 2.0-T 78-cm-bore magnet with a 9-cm-diam surface coil. Relative HbO2 saturation was measured as the difference in absorption of ...

PURPOSE: To evaluate the sensitivity of standardized exercise phosphorus-31 magnetic resonance (MR) spectroscopy in screening for subclinical muscle involvement in mitochondrial encephalomyopathy and to estimate if changes seen at biopsy have functional consequences. MATERIALS AND METHODS: Exercise MR spectroscopy was performed in 52 examinations of 18 healthy volunteers and 14 ...

BACKGROUND: Zidovudine (AZT) as used in the treatment of AIDS, causes a mitochondrial myopathy characterized by depletion of mitochondrial DNA, enzymatic defects in the respiratory chain system, and accumulation of lipid droplets. Most of these changes are also seen in normal human myotubes treated with AZT. Because L-carnitine plays a ...

BACKGROUND: Skeletal muscle metabolic abnormalities have been described in patients with heart failure that are independent of total limb perfusion, histochemical changes, and muscle mass. However, these skeletal muscle metabolic abnormalities may result from tissue hypoxia caused by maldistribution of flow. Myoglobin is an O2 binding protein that can indirectly ...

This study was undertaken to challenge the hypothesis that short-term administration of carnitine during exercise can modify skeletal muscle carnitine homeostasis and fuel metabolism in normal humans. With a randomized, blinded, crossover design, subjects received carnitine or placebo at the start of a bicycle ergometer exercise session. During the 2 ...

OBJECTIVE: To determine if patients with fibromyalgia syndrome (FMS) are more susceptible to activity-induced muscle damage than are healthy subjects. METHODS: Eleven FMS patients and 10 healthy subjects performed concentric and eccentric exercise with their dominant and nondominant forearms, respectively. 31P magnetic resonance spectroscopy (to assess inorganic phosphate [P(i)] and ...

Studies of fluid percussion-induced traumatic brain injury have shown that moderate trauma results in ionic imbalances, with resultant increases in energy demand to restore these ion gradients. Because there are also increased rates of glucose metabolism during periods of focal decline in blood flow, it has been suggested that the ...

Using 31P nuclear magnetic resonance spectroscopy of the calf muscle, the authors studied patients with peripheral arterial occlusive disease. They studied PCr depletion and intracellular pH during aerobic exercise in patients and controls. The phosphocreatine (PCr) index ([PCr]/([PCr] + [Pi])) at rest was correlated with blood flow measured by plethysmography. ...

Echo-planar magnetic resonance imaging was used to study the effect of exercise rate and duration on magnetic resonance imaging signal intensity (SI) of anterior tibialis muscle in normal human subjects (mean age 35 yr, n = 6). Axial midcalf echo-planar images (repetition time/echo time = 6,000/45, acquisition time = 80 ...

Carnitine palmitoyl transferase deficiency is one of the mitochondrial myopathies characterized by weakness, exercise intolerance, and myoglobinuria after prolonged exercise. This is the first case report concerning a pregnant woman with carnitine palmitoyl transferase deficiency that was also proved by the decrease of carnitine palmitoyl transferase activity in uterine myometrium ...

Changes of intracellular pH (pHi) after alpha-1-adrenoceptor stimulation (5 x 10(-5) mol/l phenylephrine in the presence of 10(-6) mol/l timolol) were studied in isolated perfused rat hearts by 31P-NMR spectroscopy in order to use the whole organ without disruption. The contractility was monitored simultaneously in all hearts. Alpha-1-adrenoceptor stimulation gave ...

The cells of Corynebacterium (Brevibacterium) ammonia-genes cultivated in a medium supplemented with diquat or benzylviologen accumulate 2-methylbutane-1,2,3,4-tetraol-2,4- cyclopyrophosphate as revealed by 31P-NMR spectroscopy. On heating at 120 degrees C for 30 min the cells still maintain a substantial portion of this compound and acquire new cyclic phosphates characterized by 31P-NMR ...

Unidirectional myocardial ATP synthesis, P(i)-->ATP flux, was studied in vivo using 31P magnetization transfer techniques in intact sheep hearts (n = 5) which were functioning aerobically. Myocardial oxygen consumption (MVO) expressed as mu moles of oxygen atoms/gm/min was estimated using linear regression analysis of data derived from sheep (n = ...

Although it has been hypothesized that exogenously administered bicarbonate can exacerbate intramyocardial acidosis and compromise contractile function, this phenomenon has not been demonstrated in an intact model in which intramyocardial pH (pH(int)), regional venous pCO2, and regional contractile function have been simultaneously monitored. In 20 anesthetized dogs, we studied the ...

BACKGROUND: The metabolic changes of myocardial ischemia in patients with coronary artery disease assessed by 31P magnetic resonance spectroscopy (MRS) have been reported previously. A significant decrease in the ratio of phosphocreatine (PCr) to ATP during handgrip exercise in a group of patients with severe coronary artery disease has been ...

BACKGROUND: Patients with advanced heart failure have bioenergetic abnormalities of skeletal muscle metabolism during exercise. Using 31P magnetic resonance spectroscopy, we sought to determine whether skeletal metabolic responses to exercise are normalized by orthotopic cardiac transplantation. METHODS AND RESULTS: Four groups were studied: healthy normal volunteers (n = 9), subjects ...

Using 31P-magnetic resonance spectroscopy during and after exercise, we studied whether forearm metabolic responses to exercise were improved by 1 mo of training in 10 males with heart failure. In the control (untrained) arm, there were no changes in any of the measured variables. In the trained arm, maximal voluntary ...

Inorganic phosphate (Pi) supplementation has been reported to provide ergogenic benefits, though the research findings are inconsistent. Several confounding influences may explain these results, including mode of exercise, exercise intensity, dietary intake, daily biological fluctuations, type of supplement, administered dose of the supplement, washout period, length of loading period, fitness ...

1. The effects of changes in extracellular and intracellular pH on spontaneous contractile activity in isolated rat portal vein have been investigated. 2. Small strips of portal vein were loaded with the pH-sensitive fluorophore carboxy-SNARF and intracellular pH (pHi) and contraction were measured simultaneously at 37 degrees C. The tissue ...

To investigate human muscle bioenergetics quantitatively in vivo, we used 31P magnetic resonance spectroscopy to study the flexor digitorum superficialis of four adult males during dynamic ischemic and aerobic exercise at 0.50-1.00 W and during recovery from aerobic exercise. During exercise, changes in pH and [PCr] were larger at higher ...

The transport of Pi between the cytosol and the mitochondria was investigated in perfused rat liver stimulated with phenylephrine and metabolic precursors of glucose and urea: pyruvate, lactate, NH4+ and ornithine. The relative concentrations of phosphorus metabolites in the liver were measured by 31P-n.m.r. spectroscopy. When added simultaneously, phenylephrine and ...

The metabolic response to graded rhythmic forearm exercise determined by phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy was evaluated with respect to recruitment pattern of muscles and to fiber type composition of the nondominant arm in 14 untrained subjects. Rectified smoothed surface electromyography (rsEMG) over finger and wrist flexor muscles increased ...

Previous experiments showed that acute hyperosmolality results in an extracellular acidosis that does not stimulate respiratory compensation (C.E. Kasserra, D. R. Jones, and M. R. Hughes. Respir. Physiol. 85: 383-393, 1991). The data suggested that development of the extracellular dilution acidosis would also result in a concomitant intracellular contraction alkalosis. ...

We used 31P magnetic resonance spectroscopy to compare the response of rat skeletal muscle to three kinds of proton load. During exercise (tetanic sciatic nerve stimulation), protons from lactic acid were buffered passively and consumed by net hydrolysis of phosphocreatine (PCr). During recovery from exercise, the pH-dependent efflux of protons ...

Biologists have long known that rates of adenosine triphosphate utilization and production need to be extremely closely balanced in all cells at all work rates. To put it in molecular rather than molar terms, in human muscle engaged in a 15-min work protocol, some 3.3 x 10(20) ATP molecules g-1 ...

Carnitine is an important cofactor for normal cellular metabolism. Optimal utilization of fuel substrates for ATP generation by skeletal muscle during exercise is dependent on adequate carnitine stores. During short periods of exercise the skeletal muscle carnitine pool is largely segregated from extracellular carnitine. In normal human subjects, only minimal ...

An 11-year-old girl with exercise intolerance, fatiguability from early childhood, had high blood lactate levels. Histochemistry showed increased activity of succinate dehydrogenase at the periphery of the muscle fibres, whereas aggregates of mitochondria were seen by electron microscopy. Biochemical investigation of isolated mitochondria and homogenate from muscle showed evidence of ...

To investigate the splitting of the inorganic phosphate (Pi) peak during exercise and recovery, a time-resolved 31phosphorus nuclear magnetic resonance spectroscopy (31P-MRS) technique was used. Seven healthy young sedentary male subjects performed knee flexion exercise in the prone position inside a 2.1-T magnet, with the surface coil for 31P-MRS being ...