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Biomedical subjects

E Hultman

Publications and source records attributed to E Hultman.

At least 163 records · Page 9Linked to original sources
PubMed1981

Glycolytic intermediates in human muscle after isometric contraction.

Isometric contraction of the quadriceps muscle sustained to fatigue with a force of 66% of the maximum voluntary contraction force resulted in a mean glycogen utilization of 80.4 (S.D. 58.4) mmol glucosyl units/kg dry muscle (d.m.) and an accumulation of glycolytic intermediates and glucose corresponding to 82.9 (S.D. 17.5) mmol glucosyl units/kg d.m. Accumulation of hexose phosphates (principally glucose 6-phosphate) accounted for 35.4% (S.D. 4.1) of the total increase and lactate for 59.3% (S.D. 2.8). During a 4 min recovery period glucose 6-phosphate content showed a linear decrease with a half time of 2.0 min and lactate decreased exponentially with a half time of 2.5 min. The rate of lactate disappearance from the muscle was approximately 4 times as fast as that observed previously after maximal bicycle exercise. This was probably due to a lower lactate concentration in blood after isometric contraction resulting in a larger muscle-blood gradient for lactate. Muscle content of free glucose was increased after contraction and increased further during recovery. It is concluded that the glucose increase is confined to the intracellular pool and is an effect of hexokinase inhibition by accumulated glucose 6-phosphate. Occlusion of the local circulation after the contraction inhibited the recovery processes for lactate and glucose 6-phosphate.

Energy Metabolism↗
PubMed1981

Effect of short-term CO2-breathing on the CO2 content and intracellular pH in skeletal muscle of man.

Subjects inhaled air with 8% CO2 for 10 min. Carbon dioxide tension in arterial blood increased rapidly from about 5 kPa to 7 kPa, whereas venous CO2 tension increased more slowly, reaching the arterial value at the end of the CO2-breathing period. Muscle content of total CO2 (HCO-3, H2CO3, solubilized CO2) did not change during CO2-breathing or the following 15 min of recovery. However, when CO2-breathing was combined with light bicycle exercise, total CO2 increased by 30%. This could be an effect of both increased local circulation and increased endogenous CO2 production in the muscle. It is concluded that 10 min CO2-breathing alone is insufficient to affect CO2 content and intracellular pH in resting skeletal muscle.

Acid-Base Equilibrium↗
PubMed1981

Effects of lactic acid accumulation and ATP decrease on muscle tension and relaxation.

The present study was undertaken to evaluate the effect of lactic acid accumulation on peak tension and relaxation rate of the isometric twitch. Isolated extensor digitorum longus muscle from rat was stimulated electrically at a frequency of 2/s under anaerobic conditions. Comparison was made with muscles in which glycolysis was blocked with iodoacetic acid (IAA). Stimulation of unpoisoned muscles for 3 min decreased tension to 50% and increased relaxation time to 250% of the initial value. Lactate increased 15-fold, and muscle pH decreased from 7.10 to 6.76. Stimulation of IAA-poisoned muscles for 1 min decreased tension to 50% but did not increase the relaxation time. Stimulation of IAA-poisoned muscle resulted in a pronounced decrease (about 50%) of the ATP and total adenine nucleotide content in muscle, whereas only a small decrease (10-15%) occurred in unpoisoned muscle. The main findings in the present study were that tension decline in unpoisoned muscle is closely related to decrease in muscle pH and increase in ADP but not to ATP content per se and that slowing of relaxation rate is closely related to decrease in muscle pH but not to muscle content of ATP or creatine phosphate.

Adenosine Diphosphate↗
PubMed1981

Glycolytic and oxidative energy metabolism and contraction characteristics of intact human muscle.

It is proposed that glycolytic rate may be measured as lactate accumulation after electrical stimulation of the quadriceps femoris muscle under anaerobic conditions. The ratio of glucose 6-phosphate to lactate is an internal monitor of the glycolytic pathway. The phosphocreatine/lactate ratio links glycolysis and the creatine kinase reaction and could be used to distinguish abnormalities in energy metabolism. The rate of resynthesis of phosphocreatine after stimulation when the circulation is restored should be measure of oxidative phosphorylation. The relaxation rate seems to be a mechanical index of the metabolic state of the muscle.

Adenosine Triphosphate↗
PubMed1979

The effect of long-term arterial occlusion on energy metabolism of the human quadriceps muscle.

The effect of 1.5 to 2.5 h tourniquet ischemia on energy metabolism of the quadriceps muscle was studied using percutaneous needle biopsy technique in sixteen patients operated on for an inveterated knee injury. During occlusion there was a moderate decrease in ATP with an increase in ADP and AMP. This change resulted in a decreased energy charge potential. At the same time phosphorylcreatine (PC) decreased markedly while creatine (Cr) increased giving a constant total creatine (TCr). An accumulation of lactate during occlusion with values up to 80 mmol/kg d.m. (dry muscle) was seen. A 15% reduction in glycogen was calculated. After release of the tourniquet the active phosphate concentration and the energy charge potential returned to basal levels within 5 min and most of the metabolites in the glycolytic sequence were also normalized. Muscle lactate content was normal after 30 min of intact circulation. The results suggest that longterm tourniquet ischemia induces marked changes in energy metabolism in skeletal muscle, but that the changes are rapidly and completely reversible with restoration of blood flow.

Adenosine Diphosphate↗
PubMed1979

Resynthesis of creatine phosphate in human muscle after exercise in relation to intramuscular pH and availability of oxygen.

After exhaustive exercise the muscular store of creatine phosphate (CP) is almost completely depleted. The resynthesis of CP during recovery normally occurs rapidly, but is totally inhibited if the local circulation to the muscle is occluded. The limiting factor for CP resynthesis which could be a low intramuscular pH or availability of oxygen has been investigated in the present study. Biopsies from musculis quadriceps femoris of man were analyzed for pH, ATP, ADP, CP, creatine, lactate and pyruvate. It was shown that resynthesis of CP only occurs when the blood supply to the muscle is intact. From this it was concluded that the creatine kinase reaction is at a steady state or at equilibrium during the period of recovery. The influence of oxygen on the resynthesis of CP was investigated by incubating muscle samples taken after a fatiguing isometric contraction in atmospheres of oxygen and nitrogen, respectively. During 15 min incubation in oxygen CP was resynthesized from a starting value of 4% to 68% of the normal value at rest. No resynthesis was observed when parallel muscle samples were incubated for the same time in nitrogen. It is suggested that the initial fast phase of CP resynthesis is limited by the availability of oxygen whereas the subsequent slow phase is limited by the hydrogen ion transport out from the muscle.

Adenosine Diphosphate↗
PubMed1978

Intracellular pH and bicarbonate concentration in human muscle during recovery from exercise.

Eight subjects exercised on an ergometer until exhaustion. Femoral venous blood was analyzed for lactate, pyruvate, protein, electrolytes, and acid-base parameters. Muscle samples taken during the recovery period from m. quadriceps femoris were analyzed for water, electrolytes, lactate, and acid-labile CO2. Water content in the muscle biopsy sample was increased after exercise to 78.7 +/- 0.5% compared with the normal 76.7 +/- 0.8% at rest. The distribution of water between the extra- and intracellular space was calculated by the chloride method. In spite of elevated PCO2 in femoral venous blood the content of acid-labile CO2 was decreased in muscle after exercise. One minute after termination of exercise muscle CO2 was about half of the normal content at rest. During the recovery period muscle CO2 increased but was 20 min after termination of exercise still significantly below the value at rest. Intracellular pH (pHi) and bicarbonate concentration ([HCO3-]i) in muscle have been calculated. The validity of the assumptions underlying the calculations are thoroughly discussed. pHi decreased from the normal value at rest, 7.00 +/- 0.06 (mean +/- SD), to about 6.4 after exercise. [HCO3-] decreased from 10.2 +/- 1.2 mmol/l at rest to about 3 mmol/l after exercise. The changes are the greatest so far reported for an in vivo situation. After 20 min recovery pHi was almost the same as at rest, whereas bicarbonate was still well below.

Acid-Base Equilibrium↗
PubMed1977

Quantitative determination of 5-hydroxyindole-3-acetic acid in body fluids by high-performance liquid chromatography.

A method for the quantitative determination of 5-hydroxyindole-3-acetic acid in urine and cerebrospinal fluid is described. The method is based on reversed phase high-performance liquid chromatography and fluorometric detection. The experimental error was below 5% in urine and 8% in cerebrospinal fluid. Urine and cerebrospinal fluid samples were analysed both by the described method and by a mass fragmentographic method. The correlation coefficients for the two methods were 0.986 in the urine samples and 0.965 in the cerebrospinal fluid samples. Analysis of 100 samples can be achieved within 3 days. The described method offers a possibility to determine 5-hydroxyindole-3-acetic acid in urine and cerebrospinal fluid with the same precision and capacity as do mass fragmentography but with the use of a less sophisticated equipment.

Chromatography, High Pressure Liquid↗
PubMed1977

Intracellular pH and bicarbonate concentration as determined in biopsy samples from the quadriceps muscle of man at rest.

1. A method for measuring intracellular pH and bicarbonate concentration of human muscle is described. 2. Muscle biopsies from the quadriceps muscle of 13 healthy subjects at rest were analysed for acid-labile carbon dioxide and volume of extra- and intra-cellular water. Extracellular water volume was estimated from the chloride content and intracellular water volume from the potassium content, or alternatively derived from the sample weight. 3. The measured total carbon dioxide content in muscle was 9-84+/-1-39 mmol/kg. 4. Assuming a normal membrane potential (88 mV) and PCO2 of muscle equal to venous blood, calculated intracellular pH was 7-00+/-0-06 and intracellular bicarbonate concentration was 10-2+/-1-2 mmol/l of water.

Adult↗