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Biomedical subjects

E Hultman

Publications and source records attributed to E Hultman.

At least 127 records · Page 7Linked to original sources
PubMed1986

Skeletal muscle metabolism, contraction force and glycogen utilization during prolonged electrical stimulation in humans.

Muscle metabolism and contraction force were examined in the quadriceps femoris muscles of seven volunteers during 45 min of electrical stimulation. Intermittent stimulation was used, with tetanic trains at 20 Hz lasting 1.6 s, separated by pauses of 1.6 s. Muscle biopsies were taken at rest and during stimulation (80 s, 15, 30 and 45 min). During the initial 80 s of stimulation contraction force decreased to 72% of initial force. The glycogenolytic rate was 40.9 mmol glucosyl units kg-1 dry muscle min-1 and glycolytic intermediate levels increased several fold. Muscle phosphocreatine decreased to 26% of resting concentration and the ATP turnover rate from anaerobic sources was 4.99 mmol kg-1 dry muscle s-1. With continued stimulation from 80 s to 15 min, force decreased to 43% of the initial value at 5 min and 31% at 15 min. Glycogenolysis fell to 5.4 mmol kg-1 dry muscle min-1 and glycolytic intermediate levels decreased suggesting that anaerobic glycolysis contributed progressively less ATP for force production. The final 30 min of stimulation was characterized by a low rate of glycogenolysis (1.35-1.67 mmol kg-1 dry muscle min-1) and a constant force production (25.5% of initial). The ATP turnover rate, assuming glycogen was metabolized aerobically, was 1.86 mmol kg-1 dry muscle s-1. Phosphocreatine, ATP and glycolytic intermediates returned to near resting levels, indicating that anaerobic energy pathways were not reactivated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1986

Disposal of lactate during and after strenuous exercise in humans.

Heavy dynamic exercise using both arm and leg muscles was performed to exhaustion by seven well-trained subjects. The aerobic and anaerobic energy utilization was determined and/or calculated. O2 uptake during exercise and during 1 h of recovery was measured as well as splanchnic and muscle metabolite exchange. Glycogen and lactate content in the quadriceps femoris was determined before exercise, immediately after exercise, and after a recovery period. In four male subjects the estimated mean lactate production during exercise was 830 mmol. The splanchnic uptake of lactate during recovery was 80 mmol, and the calculated maximum amount oxidized during the recovery period was 330 mmol. About 60 mmol were accounted for in the body water at the end of the rest period. The remaining 360 mmol of lactate were apparently resynthesized into glycogen in muscle via gluconeogenesis. It is concluded that approximately 50% of the lactate formed during heavy exercise is transformed to glycogen via glyconeogenesis in muscle during recovery and that lactate uptake by the liver is only 10%.

Adult↗
PubMed1986

Effects of delayed freezing on content of phosphagens in human skeletal muscle biopsy samples.

The concentrations of ATP, phosphocreatine (PCr), creatine, and lactate were determined in muscle biopsy samples frozen immediately or after a delay of 1-6 min. During the delay the samples were exposed to normal air or a gas mixture of 6.5% CO2-93.5% O2. The ATP content was unchanged, but PCr increased significantly from 72 mmol after rapid freezing to 85 mmol X kg dry muscle-1 during the 1st min in air. The lactate concentration increased (2.8 to 5.2 mmol X kg-1). If muscles were made anoxic by circulatory occlusion for 4-6 min before sampling, no increase in PCr was observed. Direct homogenization of fresh tissue in perchloric acid gave the same ATP, PCr, and lactate contents as frozen samples. It is concluded that the ATP and PCr contents in muscle are unaffected by freezing but that the biopsy procedure activates the energy utilization processes resulting in PCr decrease. It is suggested that the muscle PCr content after a 1-min delay in tissue freezing corresponds to the level in resting fresh muscle.

Adenosine Triphosphate↗
PubMed1986

pH measurement in human skeletal muscle samples: effect of phosphagen hydrolysis.

Measurements of muscle pH (pHm) with the homogenate technique are routinely made when extensive phosphagen hydrolysis has occurred. Upon exposure of the homogenate to 37 degrees C in the pH meter, phosphocreatine and ATP were rapidly degraded to 35 and 60% of control concentrations after 30 s. Attempts at chemically arresting this hydrolysis were unsuccessful. Therefore we examined the significance of phosphagen hydrolysis on pHm measurement in human biopsies taken at rest and following intense electrical stimulation. To accomplish this, pHm was measured at 0 degree C, where extensive hydrolysis did not occur. On the same homogenate, pHm was measured at 0 degree C with phosphagens and at 0 and 37 degrees C after phosphagen hydrolysis. The effect of phosphagen hydrolysis on pHm at 0 degrees C was used to estimate this effect at 37 degrees C. In resting samples, phosphagen hydrolysis produced a nonsignificant acidification of 0.008 pH units and, in electrically stimulated samples, a nonsignificant alkalinization of 0.033 units. Measurements of homogenate PCO2 suggested that most of the CO2 remained in the sample during pHm measurement at 37 degrees C. The present work substantiates the use of the homogenate technique as an accurate and practical method for the estimation of intracellular pH in resting and exercise human muscle samples.

Adenosine Triphosphate↗
PubMed1986

Surface morphology of unused and used Hydromer-coated intravenous catheters.

Hydromer-coated polyurethane (Erythroflex) catheters, unused, or intravenously inserted for 2-20 days, were studied by scanning electron microscopy (SEM). Both unfixed and fixed (2% glutaraldehyde in phosphate buffer), and air-or critical-point dried (CPD) specimens were investigated. The catheter segments were sputter-coated with approx. 20 nm gold and studied at an accelerating voltage of 20 kV. The specimens were examined for surface depositions, thickness and structure of the Hydromer layers, and occurrence of adhering and embedded bacteria. The outer Hydromer layer showed, in the unused specimens, scratches and fissures, as well as adhering foreign bodies. In used specimens, the layer was swollen, with cracks (like "dried earth"), and, occasionally, amorphous substances and coccoid bacteria were seen adhering. Damage to the layer, or even its total disappearance was also noted in some specimens. The inner (luminal) Hydromer layer was, in unused specimens, clean and slightly wavy. In used catheters, it was thicker, possibly swollen, with small, isolated or agglomerated protrusions, like a "lunar landscape". Adhering platelets and amorphous substances were also occasionally seen. The results suggest that the Hydromer is a fragile material in both its dry and wet forms. Thus, the Hydromer-coated catheters should neither be stored in flexible packs, nor inserted by the Seldinger technique. The findings do not support the belief that the Hydromer-coating can prevent either thrombus formation, or intraluminal occlusion of the in-situ catheters.

Catheters, Indwelling↗
PubMed1986

Biochemistry of muscle fatigue.

Fatigue--or decrease in force generation--is a reduction of simultaneously attached cross-bridges in the force generating state. Two processes are necessary for the force generation: Firstly Ca++ release from the sarcoplasmic reticulum to the sarcoplasm and the binding of Ca++ by the troponin molecule and secondly the turnover of myosin-actin cross-bridges. These processes require energy in at least three different ATPase reactions and can consequently be inhibited when ATP hydrolysis is decreased, i.e. when ATP content is to low or when the reaction products (ADP, Pi and H+) reach inhibiting levels or when muscle pH has decreased to values inhibiting actomyosin ATPase activity (22). Low pH will also decrease Ca++ release and Ca++ affinity by troponin (23). In isometric contraction the force is well preserved as long as ADP phosphorylation can be provided by both PCr degradation and anaerobic glycolysis. When the PCr store is exhausted the force starts to decline and if muscle activation is maintained the force will continue to decrease along with falling glycolytic rate. ADP phosphorylation rate decreases successively and ATP content falls with an at least transient increase in ADP. The ATP decrease, apart from the minor increase in ADP, is balanced by an equimolar increase in IMP. Lactate accumulation produces an increasing acidity with muscle pH values down to 6.25. Early changes in free ADP content cannot be excluded as reason for the initial decrease in force production followed by more pronounced inhibition of ATPase activity during continued contraction due to both substrate lack and product inhibition together with pH effect on the excitation--contraction mechanism. In dynamic exercise with supramaximum work intensity the relation between fatigue development and metabolism is similar. In prolonged dynamic exercise relying on oxidative metabolism without lactate formation the point of fatigue is reached when the glycogen store is exhausted. Again ADP phosphorylation rate is decreased when the energy substrate is changed from carbohydrate to fat with lower maximum rate of ATP resynthesis.

Adenosine Triphosphate↗
PubMed1985

Effect of induced metabolic acidosis on intracellular pH, buffer capacity and contraction force of human skeletal muscle.

Five volunteers were studied before and after oral administration of NH4Cl (0.3 g/kg body wt.) given in order to create a moderate acidosis. The quadriceps femoris muscles were stimulated electrically for 75 s and muscle biopsies for determination of pH and metabolite content were taken before, at the end of contraction and after 10 min in the recovery period. Muscle pH at rest (mean 7.04) was not significantly decreased after acidification despite an extracellular pH decrease of 0.15 unit. After contraction muscle pH was significantly lower after NH4Cl. Mean values before and after acidification were 6.70 and 6.54 respectively. The buffer capacity calculated as the total capacity of the muscle to buffer H+ produced during the isometric contraction before and after NH4Cl ingestion was reduced from 68.6 sl to 54.5 sl. The force produced by contracting muscle was significantly lower at the end of the contraction period after NH4Cl ingestion, 44.6% of initial compared with 55.4% without NH4Cl.

Acidosis↗
PubMed1985

Free amino acids in muscle tissue and plasma during exercise in man.

Blood and muscle samples (percutaneous biopsy of m. quadriceps femoris) were taken before exercise and after 10 and 20 min of exercise in four healthy subjects working on a bicycle ergometer with a load of 70% of Vo2 max. Free amino acids were determined in plasma and muscle and the intracellular concentration of each amino acid was calculated by the chloride method. The plasma concentration of alanine, arginine and glutamine increased during exercise. In muscle there was an increase in glutamine and alanine concentration and a decrease in glutamate concentration at 10 min of exercise; after 20 min of exercise the increase in alanine and glutamine concentrations was less marked, but the decrease in glutamate concentration was of a similar magnitude. The results demonstrate that glutamate is a quantitatively important ammonia acceptor during heavy exercise.

Adult↗
PubMed1985

The effect of adrenaline infusion on the regulation of glycogenolysis in human muscle during isometric contraction.

The regulation of glycogenolysis in human muscle during isometric contraction without and with adrenaline infusion has been investigated. The content of cAMP in muscle increased three-fold during the infusion. Total glycogen phosphorylase and synthetase activities were unchanged during contraction without and with adrenaline infusion. The fraction of phosphorylase in the a form was in resting muscle 26% and at the end of contraction 24%. During adrenaline infusion phosphorylase a increased to 80%. Contraction during continued infusion resulted in a decrease of phosphorylase a to 42%, despite persistently increased cAMP content in muscle. The activity of synthetase I decreased to about half of the initial value during adrenaline infusion and contraction both without and with the infusion. The rate of glycogenolysis in muscle during contraction was not significantly changed by the infusion. Phosphocreatine (PCr) decreased during the contraction and the decrease was similar without and with adrenaline infusion. The amount of inorganic phosphate (Pi) accumulated in muscle during contraction was lower when adrenaline was given due to a greater accumulation of hexose-monophosphates. It is concluded that the rate of glycogenolysis in muscle during contraction without and with adrenaline infusion is a function both of phosphorylase in the form a form and the availability of Pi at the active site of the enzyme.

Adult↗
PubMed1985

"Half-way" venous catheters. II. Anatomoradiological basis.

In order to develop a "half-way" venous catheter for clinical use, anthropometric (n = 200), radiographic (n = 101), and phlebographic (n = 44) investigations were undertaken to determine the lengths, diameters, and morphology of the basilic and cephalic veins from fossa cubiti to the lateral edge of the first rib. The lengths of basilic and cephalic veins varied from 25 to 45 cm, exceeding 40 cm in approximately 5% of cases. Catheter lengths to be inserted were correlated ("r" = 0.6-0.7) with body heights, accurately estimated by 1/5 of the body height (cm) plus 2 cm for the basilic vein, and 4 cm for the cephalic vein. The cephalic veins have small proximal end diameters (mean = 6 mm), and present terminal arches of 2-3 cm. These are connected by a rich anastomotic network to the superficial cervical veins. The basilico-axillary courses are regular with gradually increasing diameters (mean = 16 mm), but in some observations, with the arms maximally abducted, the axillary veins presented accentuated folds. With these considerations, we recommend the insertion of the "half-way" catheters by basilic approach with the patient's arm in 90 degree abduction. The axillosubclavian length (mean = 18.5 cm) ensures wide limits for accurate placement of the "half-way" catheter tips when a basilic approach is used. Further, their large diameters (16-19 mm) make flotation of the soft catheters probable.

Adolescent↗
PubMed1985

"Half-way" venous catheters. IV. Clinical experience and thrombogenicity.

"Half-way", Secalon-Seldy, soft venous catheters, 40 cm long, were inserted by basilic (n = 90) and cephalic (n = 31) veins at the fossa cubiti in 121 patients (71 men and 50 women) aged between 19 and 88 years whose heights varied from 152-197 cm. The inserted catheter lengths approximated 1/5 of the patient's height. Sixty-five per cent of 106 radiologically investigated catheter tips were located proximally in the axillary veins, and 34% distally in the subclavian veins. The duration of catheterization varied from 1 to 44 (mean 9 +/- 7) days (means +/- 1 s.d.). Perfect function was recorded in 93 of 121 catheters. No serious, but some minor complications were registered such as temporary interruption of infusion flow with movements of the arm (n = 12), partial or total catheter occlusion (n = 16), leakage of the infusate at the insertion site (n = 1), and pain along the vein during infusion (n = 2). Five patients (4%) developed thrombophlebitis 2-.10 days after insertion. Pull out phlebographies at catheter withdrawal (4-35 days after insertion) were performed in 36 patients. Radiological thrombi were small and similar to those recorded in another 53 phlebographies of "long-way" brachial catheters of similar stiffness. Neither local infection nor episodes of sepsis were registered over a period of 1,081 catheter days. "Half-way" catheters proved able to take over all the functions of both peripheral and central venous catheters, lacking the frequent complications (phlebitis and infection) of the former, and the serious mechanical complications (pneumothorax, vein perforations, and injuries of the ductus thoracicus, nerves, arteries, and heart) of the latter.

Adult↗
PubMed1984

Material thrombogenicity in central venous catheterization III. A comparison between soft polyvinylchloride and soft polyurethane elastomer, long, antebrachial catheters.

Soft venous catheters, 36 made of polyurethane (PU) and 37 made of polyvinylchloride (PVC), were inserted in 73 patients via basilic and cephalic veins punctured at the cubital fossa, and compared regarding their thrombogenicity. The mean duration of catheterization was 12.5 days. Two patients with PU- and six patients with PVC-catheters developed clinical thrombophlebitis 4-36 days after insertion. The radiological thrombi were rather small with both PU- and PVC-catheters in both peripheral and central veins with no significant difference between the catheters. Also, the incidence of thrombosis and the rate of catheter occlusions were similar. The surface topography of the PVC-catheters was relatively smoother, but less uniform than that of the PU-catheters. Platelet adhesion in vitro to the catheter surfaces, expressed as ATP-concentration in relation to catheter area after contact with human blood, was relatively low with both catheters. The results suggest that soft PU- and PVC-catheters have a similar thrombogenicity.

Adolescent↗
PubMed1984

A single step polarographic assay of glycogen in muscle tissue and a note on the action of amyloglucosidase.

A rapid, single step polarographic assay of glycogen in KOH digests of muscle is presented. Amyloglucosidase is used to hydrolyse the glycogen to glucose, which is then immediately reacted with glucose oxidase. The method has a good reproducibility, is rapid, and requires as little as 0.7 mg freeze-dried muscle powder. From comparison of the rate of reaction of glycogen in the complete assay mixture with those of alpha- and beta-D-glucose, it was concluded that in the hydrolysis of glycogen--a polymer of alpha-D-glucose--by amyloglucosidase, the immediate and only product is beta-D-glucose. This suggests that during hydrolysis, the pyranose ring is opened at carbon 1, and that carbon 1 is rotated to the beta-configuration before closure.

Glucan 1,4-alpha-Glucosidase↗
PubMed1984

Dynamics of thrombophlebitis in central venous catheterization via basilic and cephalic veins.

The incidence distribution of thrombophlebitis after central catheterization via basilic and cephalic veins was investigated, using 227 catheters made of various plain or heparin-coated materials and with differing stiffness and surface structures. The platelet-adhesion stimulating properties were measured in vitro. Thrombophlebitis showed similar incidence patterns with all catheter types. The maximum incidence of venous reaction was found one to ten days after catheter insertion (central tendency 3-8 days with a peak at 5 days). After ten days the risk of thrombophlebitis fell significantly. The results supported the view that central venous catheters inserted via basilic or cephalic veins should not be withdrawn or exchanged as prophylaxis against thrombophlebitis, at any rate when long-term catheterization is intended. For conclusive comparisons between catheter materials regarding induction of clinically apparent thrombophlebitis, all the patients in the trial should be catheterized for ten days or more, unless symptoms of venous reaction arise earlier.

Adolescent↗
PubMed1983

Evaluation of methods for electrical stimulation of human skeletal muscle in situ.

A comparison was made between three different techniques for electrical stimulation of human skeletal muscle: percutaneous stimulation via large aluminum foil electrodes or via ordinary ECG-electrodes and intramuscular stimulation via platinum-coated wires.--The relationship between voltage and duration of the stimulating pulses and the evoked force of contraction is described.--A series of experiments on surgical patients who were curarized showed that these electrical stimulation techniques selectively activate nerve-endings within the muscle, and not the muscle fibres directly.--In a group of male volunteers there were linear relationships between body weight and maximum voluntary contraction force (MVC) of the knee extensors and between body weight and the stimulating voltage needed to produce 50% of MVC.

Adult↗
PubMed1983

The diagnostic accuracy of CSF analyses in stroke.

The ability of routine analyses of cerebrospinal fluid (CSF) to differentiate between haemorrhage and infarction was evaluated in 231 stroke patients, whose diagnoses were based on computed tomography or autopsy. In all diagnostic groups the mean protein level was above normal, the highest values being associated with haemorrhage. Taking a protein level greater than 1 g/l to be characteristic of bleeding, sensitivity was 89% and specificity 92%. Spectrophotometric CSF absorbance was measured at wave lengths of 410, 415, 455 and 630 nm. Validity was equal for the first three. Taking absorbance greater than or equal to 0.040 at 415 nm to be diagnostic for haemorrhage, sensitivity was 72% and specificity 94%. The human eye was almost as sensitive as spectrophotometry in this context. Thus, among 100 patients with stroke, 7-9 out of 10 plausible cases of haemorrhage would be identified by means of routine CSF analyses. At the same time, 5-9 patients with ischaemic lesions would be diagnosed incorrectly as bleedings.

Blood Cell Count↗