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Biomedical subjects

E Hultman

Publications and source records attributed to E Hultman.

At least 145 records · Page 8Linked to original sources
PubMed1983

Quantitative estimation of anaerobic and oxidative energy metabolism and contraction characteristics in intact human skeletal muscle in response to electrical stimulation.

A set up for electrical stimulation of the human quadriceps femoris muscle and registration of tension is described. Normal values for the frequency-tension relations and relaxation time are presented. There was no relationship between contraction characteristics and fibre type distribution. Muscle tissue was sampled after electrical stimulation by percutaneous biopsy technique. Phosphocreatine (PCr) decreased during a 75 s isometric contraction from 76 mmol per kg dry muscle down to a mean value of 9 mmol. Lactate increased during the same time period from 5 mmol per kg dry muscle to 100 mmol. At end of contraction there was a rapid resynthesis of PCr with a half time of about 20 s while the lactate content decreased slowly. The relaxation time of the muscle was prolonged from 38 ms, in non-fatigued muscle, to 128 ms after 75 s of isometric contraction. The relaxation time was normalized after the contraction at the same rate as the resynthesis of PCr. It is proposed that the relationship between PCr and lactate of contracting muscle can be used as an index of glycolytic capacity and that the rate of resynthesis of PCr after contraction is a measure of oxidative capacity. Relaxation time measurements alone may be used as a non-invasive estimation of the oxidative capacity.

Adenosine Diphosphate↗
PubMed1983

The cyclic-AMP concentration in plasma and in muscle in response to exercise and beta-blockade in man.

At rest the cAMP concentration in (muscle samples of) the quadriceps femoris ranged from 1.55 to 3.00 mumol per kg dry muscle and in plasma from 15.3 to 32.3 nmol per 1. Blockade of the beta adrenoreceptors with propranolol resulted in a significant decrease in the concentration in muscle at rest, the magnitude of the fall being related to the initial level. Similarly in plasma there was a trend towards lower levels of cAMP in those with the highest pretreatment levels, but the overall change was not statistically significant. There was no relation between the concentrations in muscle and plasma, before or after beta-blockade. Maximum dynamic exercise for 4-8 min resulted in an approximate doubling in the cAMP concentration in both muscle and blood. The increase in plasma was closely related to that in muscle. Beta-blockade inhibited totally the rise in cAMP in muscle during exercise but was marginally less effective in preventing the increase in blood. No increase in plasma or muscle cAMP levels during 40-70 s isometric contraction were observed.

Adolescent↗
PubMed1983

Acidotic depression of cyclic AMP accumulation and phosphorylase b to a transformation in skeletal muscle of man.

Intravenous infusion of adrenaline was performed in three healthy subjects on two occasions. In one case subjects performed a maximal isometric contraction before infusion. Biopsies were taken from the quadriceps femoris muscle before and after infusion for 0.5 and 2 min, and analysed for muscle pH, cyclic AMP, metabolites and activities of glycogen phosphorylase and synthetase. Isometric contraction resulted in a decrease of muscle pH to 6.60 (normal value at rest 7.0-7.1). By this experimental procedure the effect of adrenaline infusion could be studied on a muscle with normal pH and one with low pH. Cyclic AMP increased from 3 to about 9.5 mumol per kg dry weight after 0.5 min of adrenaline infusion. When isometric contraction preceded the infusion, cyclic AMP increased more slowly and was about 5.5 mumol per kg dry weight after the same time of infusion. Phosphorylase a constituted about 22% of total phosphorylase in resting muscle but increased rapidly to 80% after 0.5 min infusion. When exercise preceded infusion phosphorylase a decreased and was still lower after 2 min infusion. The results can be explained by inhibition of adenylcyclase and phosphorylase b kinase at low muscle pH.

Acid-Base Equilibrium↗
PubMed1983

Electromyogram, force and relaxation time during and after continuous electrical stimulation of human skeletal muscle in situ.

A technique for recording the surface electromyogram (e.m.g.) simultaneously with electrical stimulation of human skeletal muscle is described. During a fatiguing electrical stimulation the e.m.g. amplitude and force decreased in the same proportion. During recovery the e.m.g. was quickly normalized whereas force remained at a reduced level. Relaxation time increased during the stimulation and helps substantially in keeping up tension during a fatiguing contraction. In the recovery phase the rapid normalization of relaxation time counteracts recovery of tension. It is concluded that e.m.g. measurements alone can be misleading as an index of contraction force and that muscular fatigue during electrical stimulation can be attributed to excitation failure only to a lesser extent.

Adult↗
PubMed1983

The effect of circulatory occlusion on the glycogen phosphorylase-synthetase system in human skeletal muscle.

The effect of circulatory occlusion upon the glycogen phosphorylase-synthetase system in intact human muscle at rest has been investigated using the needle biopsy technique. The fraction of phosphorylase in the a form was 26% before occlusion and decreased to 9% after 40 min of occlusion. Synthetase I activity was unchanged during occlusion. After 40 min of occlusion the content of phosphocreatine was decreased by 40%, with a corresponding increase in creatine and inorganic phosphate (Pi). The observed glycogenolytic rate increased during occlusion up to 0.8 mmol glycosyl units kg-1 dry muscle min-1. An intracellular Pi concentration at rest of 2.0 mmol l-1 was calculated from the activities of phosphorylase a and synthetase I assuming that under these conditions they are equal. It is concluded that the glycogenolytic rate during occlusion is a function of both the fraction of phosphorylase in the a form and the availability of Pi at the active site of the enzyme.

Adult↗
PubMed1983

Energy metabolism and contraction force of human skeletal muscle in situ during electrical stimulation.

The quadriceps femoris muscles of nine volunteers were stimulated with intramuscular electrodes for 50 s. The stimulation frequency was 20 Hz and the voltage adjusted to produce an initial tension of 50-75% of the maximum voluntary contraction force. The force decreased after 25-30 s of contraction to reach a mean of 78% of the initial value after 50 s. During the stimulation up to four muscle biopsy samples were taken from each leg. The ATP turnover rate was initially 5.6 mmol kg-1 dry wt. s-1 and decreased during the later stages of contraction to 4.0 mmol kg-1 dry wt. s-1. The force declined at approximately the same rate as the ATP turnover during the contraction. The phosphocreatine (PCr) store decreased exponentially during contraction and was practically depleted at 50 s. Glycolysis began within 5 s after initiation of contraction. The rate of glycolysis measured as lactate accumulation increased with time throughout the entire contraction period.

Adenosine Triphosphate↗
PubMed1983

Effects of beta-blockade on glycogen metabolism in human subjects during exercise.

The effect of beta-blockade on glycogen metabolism during isometric and dynamic exercise in humans has been investigated. Isometric exercise increased the glycogenolytic rate in muscle but had no effect on the cAMP content. Neither the metabolic pattern nor the time of contraction was affected by beta-blockade. Dynamic exercise increased the cAMP content in muscle by about 100%. The cAMP content at rest was significantly reduced after propranolol infusion and did not increase during exercise. Total hexosemonophosphates increased sixfold during exercise but little or no increase occurred after administration of propranolol. The accumulation of lactate in muscle was slightly reduced during exercise following beta-blockade. The fraction of phosphorylase in the alpha form was 22.5% of the total at rest but decreased to 16% at exhaustion. Synthetase I was similarly decreased. During exercise with propranolol phosphorylase alpha decreased further to 3%, whereas synthetase I was unchanged. It is concluded that beta-blockade has no effect on muscle glycogenolysis during isometric contraction but decreases the rate of glycogen degradation during dynamic exercise at high work loads due to changes in the phosphorylase-synthetase system.

Adolescent↗
PubMed1983

Regulation of glycogenolysis in human muscle in response to epinephrine infusion.

The regulation of glycogenolysis in human muscle during epinephrine infusion has been investigated. The content of cAMP in resting muscle was 2.7 +/- 0.7 (SD) mumol . kg dry muscle-1 and increased threefold during the first 5 min of infusion. Total glycogen phosphorylase and glycogen synthase activities were unchanged during the infusion. The proportion of phosphorylase in the a form in the basal state was estimated to be at least 22.5% and during infusion 80-90%. During infusion, synthase I activity decreased. The muscle glycogen content was 340 mmol . kg dry wt-1 and decreased during the first 2 min of infusion at a rate of 11.0 mmol glycosyl units . kg dry wt-1 . min-1. Prolonged infusion resulted in a much lower glycogenolytic rate, even though most of the phosphorylase was still in the a form. Accumulation of hexose monophosphates and lactate followed the changes in glycogen. It was concluded that despite the almost total transformation of phosphorylase to the a form, the in vivo activity was maintained at a low level. It is suggested that this may be due to a low concentration of inorganic phosphate at the active site of the enzyme.

Adolescent↗
PubMed1983

Muscle intracellular electrolytes in patients with chronic uremia.

We performed 182 percutaneous muscle biopsies in 161 nondialyzed or dialyzed patients with chronic renal failure. Muscle sodium (NaM), potassium (KM), magnesium (MgM) and phosphorus (PM) were determined by neutron activation analysis and atomic absorption spectrophotometry. Intracellular water (H2OI) in muscle was increased in all groups of uremic patients but was not correlated with total muscle water (H2OM) which varied with the content of extracellular water (H2OE). In the nondialyzed patients KM, MgM, and PM were normal in relation to fat free solids (FFS). KM/MgM and KM/PM were also normal. Alkali soluble muscle protein (ASP) was low, and KM/ASP was significantly increased. In hemodialyzed patients and in predialysis peritoneal dialysis patients, KM/FFS and KM/MgM were high. For 22 to 24 hours after peritoneal dialysis, H2OM, H2OE, ClM, NaM, KM, and PM fell significantly, but H2OI was unchanged. The calculated intracellular potassium concentration (KI/H2OI) was significantly reduced in all groups of patients, even though KM was normal or increased. This decrease became more marked when calculating H2OE, H2OI, and KI/H2OI with the chloride method, assuming a reduced muscle transmembrane potential. There was a covariation between KM and PM, KM and H2OI, and KM and plasma potassium, but not between MgM and plasma magnesium or PM and plasma inorganic phosphate. Thus, typical features of chronically uremic muscle are an increase in intracellular water and normal or increased content of potassium in relation to various reference bases representing cell mass. However, the concentration of potassium in intracellular fluid is reduced, presumably because of inhibition of the sodium pump, which reduces transmembrane potential and interferes with the volume regulation of the muscle cells.

Adolescent↗
PubMed1983

Kinetic methods that are independent of the rate of reaction.

Kinetic methods for the quantification of substrates offer a number of advantages over equilibrium methods, such as speed and economy. However, in their most commonly practiced form they are liable to error from various sources in addition to those ordinarily encountered in equilibrium methods, owing to variations in enzymic activity between test and standard assays. In certain circumstances the differences in enzymic activity may be such as to completely invalidate the method. Such difficulties may, however, be avoided if three or more measurements are made during the reaction of the sample and are evaluated by one of five means. In each case data from the early course of the reaction are used to predict the total change in sensor signal at infinite time, from which the concentration of the substrate may be calculated as for an equilibrium method.

Acid-Base Equilibrium↗
PubMed1982

Intracellular potassium in man. A comparison of in vivo and in vitro measurement techniques.

In order to evaluate different methods of estimating intracellular content of potassium, determinations of potassium were made in erythrocytes, in muscle biopsy specimens and in the total body. The total body potassium (TBK) was related to body weight (Bwt), lean body mass (LBM), dry LBM, soft fat-free solids (SFFS), total body water (TBW) and calculated intracellular fluid (ICF). Sixty-two healthy subjects and 80 patients with various diseases and therapy known to influence the potassium metabolism were studied. Statistically significant correlations were found between potassium content in muscle biopsies related to fat-free solids and TBK/Bwt (r = +0.56, P less than 0.05), TBK/LBM (r = + 0.58, P less than 0.01), dry LBM (r = + 0.54, P less than 0.05) and TBK/SFFS (r = + 0.68, P less than 0.01). A correlation was found between muscle potassium related to intramuscular water and TBK/TBW (r = + 0.47, P less than 0.05). No correlations were found between EK and TBK/LBM, TBK/dry LBM or TBK/ICF. Between EK and serum potassium a negative correlation (r = -0.31, P less than 0.05) was found in a group of untreated hypertensives. It is concluded that the quotients of TBK (TBK/LBM, TBK/TBW and TBK/SFFS) might be used in the study of intracellular potassium--at least in the study of patient groups.

Adipose Tissue↗
PubMed1982

Magnesium deficiency following jejunoileal bypass operations for obesity.

Skeletal muscle biopsies, blood samples, and 24-hour urines, before and after magnesium infusions, were obtained from 12 patients who had undergone jejuno-ileal bypass surgery several years earlier, selected for probable magnesium deficiency on the basis of repeated hypomagnesemia. The patients retained significant amounts of the infused magnesium, and exhibited elevation of low skeletal muscle magnesium and potassium, with concomitant decreases of muscle sodium and chloride. These changes were accompanied by increased urinary calcium and sodium and decreased urinary phosphorus excretion.

Adult↗
PubMed1982

Blood pressure and heart rate response to voluntary and nonvoluntary static exercise in man.

6 healthy men produced static knee extension with one leg for 5 min. In one series of experiments the force was held constant at 20% of the isometric maximum voluntary contraction force. In another series of experiments the same subjects performed the same work non-voluntarily by direct percutaneous electrical stimulation. Heart rate and blood pressure was continuously recorded. Heart rate increased by 40% and systolic and diastolic blood pressure by 30% and 50% in both kind of experiments. It is concluded that receptors within the muscle has the full capacity to adjust central circulation to the muscle work performed.

Adult↗
PubMed1982

The contents of high-energy phosphates in different fibre types in skeletal muscles from rat, guinea-pig and man.

1. The contents of high-energy phosphates at rest have been measured in skeletal muscles with different fibre-type composition from rat, guinea-pig and man. All muscles studied biochemically have been characterized histochemically. 2. Fast-twitch muscles had a higher ATP/ADP ratio than slow-twitch muscles and, with the exception of the tongue in the rat, higher contents of ATP and phosphocreatine. 3. There was an inverse relationship between the content of phosphocreatine and the stainability for succinyl dehydrogenase, which is a marker enzyme for oxidative capacity. 4. The biochemical and histochemical data are discussed in relation to known morphological and functional properties of the different muscle-fibre types. It is concluded that fast-twitch fibres have a high ATP/ADP ratio favouring a fast acceleration of energy production. The content of phosphocreatine seems to be related to the glycolytic capacity but not to the contraction time. In addition to being an immediate energy source, phosphocreatine functions as a buffer against lactic acidosis.

Adenine Nucleotides↗
PubMed1982

Shrinking pleuritis with atelectasis.

During a 10-year period 28 patients with shrinking pleuritis with atelectasis (SPA) were observed and operated upon. This lesion has been given different names in the literature, for instance rounded atelectasis, pleuroma, pulmonary pseudotumour, and lung folding. All patients except two were operated upon because of a diagnosis of pulmonary tumour. However, at operation no tumour was found. The aetiology and pathogenesis of SPA are discussed on the basis of X-ray, operative, and histopathological findings.

Diagnosis, Differential↗
PubMed1982

Regulation of glycogenolysis in human muscle at rest and during exercise.

The regulation of glycogenolysis in human muscle during isometric and dynamic exercise has been investigated. Total glycogen phosphorylase and synthase activities were unchanged during exercise. The fraction of phosphorylase in the alpha form at rest was estimated to be 20%, but the data indicate that the in vivo activity was low and critically dependent on the concentration of inorganic phosphate (Pi) in the muscle. Phosphorylase alpha increased initially 2.4-fold during isometric contraction and 1.6-fold during maximal bicycle exercise but reverted to or below the resting value at fatigue/exhaustion. At rest synthase I was 17-48% of the total activity but decreased during exercise to about half of this value. The reciprocal changes in phosphorylase and synthase correlate with the enhanced rate of glycogenolysis during exercise. Michaelis constant (Km) for Pi was 27 mmol . l-1 for phosphorylase alpha and 7 mmol . l-1 for alpha + b. From consideration of the changes in Pi during exercise (to 20-30 mmol . l-1) it was concluded that Pi is one of the main factors determining phosphorylase activity and provides a link between phosphocreatine breakdown and glycogen utilization in muscle.

Adult↗