bluuebunny/crossref_metadata_2025 huggingface dataset:
External work and arterial load in canine left ventricular ischaemic failure: evidence of ventricle‐load mismatch
Authors: Myhre Eivind S. P. , Piene Hroar
Published: April 2008

Summary. It has been proposed that a normal ventricle and its arterial load constitute a matched system, and that such matching is not present during ventricular failure, i.e., failure represents a state of mismatch between ventricle and arterial load. To investigate this assumption we studied the relationship between external work and load in an equatorial segment of left ventricle (LV) in an intact canine preparation under the hypothesis that the LV works at the peak of the work versus load relationship during control conditions, but is shifted from this peak during LV failure. LV systolic wall force (F) and circumferential segment work (W) were calculated in eight pentobarbital anaesthetized, open‐chest dogs from LV pressure (P) and anterior‐posterior diameter (D) before and after induction of LV ischaemic failure (50 um microspheres were injected into the left coronary vascular bed). Variations of arterial load were created by acute partial occlusions of the aorta, raising aortic pressure by 45 mm Hg before and 15 mm Hg during failure. Before failure W was unaffected by the variations of arterial load, but W decreased significantly during failure. From the relation between end‐systolic F and D, theoretically optimal F (Fopt) corresponding to maximum W was estimated. Before failure the observed F did not differ significantly from Fopt, but the observed F was significantly greater than Foptduring failure. These findings support the notion that ventricular failure represents a state of mismatch between the ventricle and its systolic load.
Skin capillary blood cell velocity in patients with arterial obliterative disease and polycythaemia: a disturbed reactive hyperaemia response
Authors: Östergren Jan , Fagrell Bengt
Published: April 2008

Summary. . Nailfold skin capillary blood cell velocity (CBV) was studied at rest and during post‐occlusive reactive hyperaemia after a 1 min arterial occlusion (PRH1) in: (i) both hands of patients with arterial obliterative disease (AOD) of one arm, (ii) patients with polycythaemia, before and after a moderate haemodilution and (iii) healthy controls. CBV was analysed by videophotometric cross‐correlation utilizing the different optical densities produced by the passage of erythrocytes, leucocytes and plasma gaps through the monitored capillary. Resting CBV in the patients with unilateral AOD was similar in equivalent fingers of both hands. However, the time to peak (p)CBV during PRH was significantly prolonged in the low‐pressure arm as compared to the contralateral arm. pCBV was also delayed in the patients with polycythaemia as compared to the healthy controls. This delay was not affected by the replacement of 500–750 ml of blood with the same amount of a 6% Dextran 70 solution. The mean capillary blood cell velocity during rest (rCBV) did not differ between controls and patients before or after the haemodilution. The prolonged time to pCBV in the polycythaemic patients may be attributed to increased blood viscosity that is presumably not significantly influenced by a moderate haemodilution using Dextran 70. The marked delay to pCBV observed distal to the arterial obstruction in patients with AOD probably is an effect of the lower arterial pressure, presumably involving an alteration of vascular smooth muscle function.
Haemodynamic effects of low and high doses of insulin during beta receptor blockade in dogs
Authors: Reikerås Olav , Gunnes Pål , Sørlie Dag , Ekroth Rolf , Jorde Rolf , Mjøs Ole Danbolt
Published: April 2008

Summary. Haemodynamic effects of small and high doses of insulin during beta receptor blockade were studied in nine dogs. Beta receptor blockade was induced by 0.5 mg/kg propranolol and caused depression of cardiac performance with a significant increase in left ventricular end‐diastolic pressure (LVEDP) and a significant decrease in heart rate; maximum rate of left ventricular (LV) pressure rise (LVdP/dtmax), stroke volume and cardiac output. At 15 min, after beta receptor blockade, a bolus injection of 0.5 IU/kg of insulin, free of glucagon and calcium, was given followed by a continuous infusion of 0.5 IU/kg/h. After 30 min another bolus dose of 300 IU insulin was injected.

Glucose and potassium were given to maintain physiological levels of these factors. Five minutes after a low dose of insulin there was a significant decrease in LVEDP (P<0.01), and a significant increase in LVdP/dtmax (P<0.01), in stroke volume (P<0.01) and in cardiac output (P<0.01). The other haemodynamic variables were not significantly changed. Administration of a high dose of insulin further, significantly, improved performance of the beta receptor blocked heart and caused a significant reduction in total peripheral resistance. In conclusion, insulin exerts inotropic and vasodilator effects which are dose‐dependent and not related to adrenergic mechanisms.
Relationship between pulse amplitude and thermal exchange in the finger: the effect of smoking
Authors: Saumet J. L. , Leftheriotis G. , Dittmar A. , Delhomme G.
Published: April 2008

Summary. In 24 healthy volunteers finger pulse amplitude and heart rate (HR) were monitored by pulse plethysmography and thermal exchange from the finger and were compared before and after the smoking of a single cigarette. Thermal exchange was measured using a direct calorimeter consisting of a recording bath and a reference bath, both of which were filled with water at 18°C. The subject immersed the two distal phalanx of a finger into the recording bath. The water thermal gradient between both baths after 4 min of finger immersion and the maximal value of heat loss from the finger to the water were recorded. Decreases in the water thermal gradient (from 6·06 to 5·33°C, P < 0·05) in maximal value of heat loss (from 22·5 to 18·75 w.m‐2, P < 0·01) and in plethysmographic wave amplitude (from 25·8 to 14·6 mm, P < 0·01) and increased HR (from 72 to 83 beats min‐1) were observed in smokers. These changes were not statistically significant in non‐smokers. Water thermal gradient and maximal value of heat loss correlated with plethysmographic wave amplitude before and after smoking but not with HR in the 24 subjects studied. The present study shows a good relationship between vascular phenomena and thermal exchange in the fingers. The variations of finger pulse amplitude provide an adequate and sensitive adjustment of thermal exchange since the effects of smoking a single cigarette can be detected by both PWA and calorimetric measurements in the finger.
Effect of β1‐selective and non‐selective β‐blockade on work capacity and muscle metabolism
Authors: Kaiser P. , Tesch P. A. , Frisk‐Holmberg M. , Juhlin‐Dannfelt A. , Kaijser L.
Published: April 2008

Summary. Six well‐trained men were studied while performing a maximal bicycle exercise. The seven experiments included in this study were randomized in a double‐blind cross‐over fashion. On each occasion the subjects were given either placebo or 40, 80, or 160 mg propranolol (non‐selective blockade) or 25,50, or 100 mg atenolol (β1‐selective blockade). After completion of the study each subject had performed once under each of the seven treatments. Heart rate, maximal oxygen uptake (V̇o2max), blood lactate and performance time to exhaustion were measured. A muscle biopsy from vastus lateralis was taken at exhaustion after placebo, 80 mg propranolol and 50 mg atenolol trials, for analysis of ATP, creatine phosphate (CP), glucose‐6‐phosphate (G‐6‐P), glucose and lactate. The performance time was reduced (P<0·05—0·001) with both blockers compared to placebo. At an equal heart rate reduction, V̇o2max was equally reduced by both blockers. Performance time, on the other hand, was reduced to a greater extent (P<0·05) with propranolol. ATP and CP levels were decreased (P<0·05) by both drugs. G‐6‐P, however, was lower (P<0·05) with propranolol than with either placebo or atenolol. No difference was observed between placebo and atenolol. In conclusion, both pVselective and non‐selective blockade reduced short‐term maximal exercise capacity. The major limiting factor seems to be the reduction in oxygen transport. The finding that at an equivalent reduction in V̇o2max propranolol reduced performance time to a greater extent than atenolol suggests that β2‐blockade may reduce performance by mechanisms additional to those that affect oxygen transport. One possible mechanism is a retardation of glycolysis.
Effect of adrenaline on exchange of glucose in leg tissues and splanchnic area. A comparison with the metabolic response to surgical stress
Authors: HåRkanson E. , Rutberg H. , Jorfeldt L.
Published: April 2008

Summary. Surgical trauma is accompanied by increased energy expenditure and raised arterial concentrations of adrenaline and glucose. In order to study the acute effects of an adrenaline infusion on glucose metabolism and oxygen uptake in the leg and splanchnic bed, adrenaline was administered at a rate giving plasma concentrations of adrenaline similar to those in connection with abdominal surgery.

Seven healthy males participated in the study. Adrenaline 40 ng/(min×kg body weight) (0·22 nmol/(min×kg body weight)) was infused producing a plasma concentration of 2–77±0·42 nmol/1 (mean±SEM). Leg and splanchnic blood flows and the femoral and hepatic arterio‐venous differences for oxygen, glucose, lactate and other metabolites were determined. Measurements were made before and between 30 and 40 min after the start of the adrenaline infusion.

Following the infusion of adrenaline the leg blood flow increased by 140% and hepatic blood flow by 25%. The leg oxygen uptake increased by 30%, but no significant increase in splanchnic oxygen uptake was observed. The arterial glucose concentration rose by 35%. Splanchnic glucose output increased × 2·5, but no significant increase in leg glucose uptake was observed. Leg release of gluconeogenic substrates increased but only lactate and glycerol uptake increased in the splanchnic bed. Leg blood flow increased more than that usually seen after surgery, whereas leg oxygen uptake and splanchnic oxygen uptake was higher in the immediate postoperative period. Splanchnic glucose release increased more during the infusion than in connection with surgery.

It is concluded that adrenaline at a plasma concentration similar to that during and immediately after surgery can induce changes in glucose metabolism which are of the same order or more pronounced than those seen in connection with abdominal surgery.
Effects of dipyridamole and theophylline on reactive hyperaemia in subcutaneous adipose tissue in humans
Authors: Linde B. , Sollevi A.
Published: April 2008

Summary. The importance of adenosine for reactive hyperaemia in subcutaneous adipose tissue was studied in healthy volunteers, using the adenosine uptake inhibitor dipyridamole (bolus 0·1 mg/kg i.v. followed by infusion of 0·7 μg/kg/min) and the adenosine receptor antagonist theophylline (4 or 6 mg/kg i.v.). Basal blood flow, total blood flow and hyperaemia (total minus basal flow) after a 20‐min arterial occlusion were measured in the distal femoral region by the 133Xe washout technique with and without drug treatment. Basal blood flow (mean±SEM) was 2·4 ± 0·3 ml/min/100 g, while total post‐occlusive flow and total reactive hyperaemia were 97·3 ±8·4 and 61·8 ± 6·5 ml/100 g, respectively, without drug treatment. Basal blood flow was unaffected by dipyridamole but the total flow and hyperaemia were enhanced by 49 ± 24 and 60 ± 31%, respectively (P<·005 for both). This enhancement was due to increases in both amplitude and duration of the hyperaemia. Neither basal blood flow, total post‐occlusive flow nor hyperaemia were significantly altered by theophylline. The amplitude of the enhanced hyperaemia during dipyridamole was not significantly counteracted by simultaneous theophylline treatment (6 mg/kg) but the duration of hyperaemia was reduced from 13 ± 1 to 8 ± 1 min (P<0·01). The results suggest that endogenous adenosine does not regulate basal blood flow or reactive hyperaemia of limited duration in human adipose tissue. However, reactive hyperaemia may be enhanced by pharmacological elevation of endogenous adenosine levels.
Digitized echocardiographic measurements of left ventricular function: reproducibility and physiological factors influencing the method
Authors: Danielsen R. , Nordrehaug J. E. , Vik‐Mo H.
Published: April 2008

Summary. The variability of digitized M‐mode echocardiographic measurements and the potential influence of physiological factors on these was studied in 28 relatively young (<50 years) healthy subjects. All had heart rates within the normal range. Echocardiographic recordings were standarized in the end‐expiratory phase. The coefficients of variation for direct echocardiographic measurements were <6% and for most digitized time derived variables <15%. They were generally greater for inter‐ than for intracycle comparisons. In systole, the peak shortening rate and the time period from the start of systole to the point of peak shortening rate showed the best reproducibility, while in diastole the peak filling rate, the rapid filling period and the percentage filling during the same period. In multivariate analysis, age and heart rate were found to influence the digitized derived systolic but not the diastolic variables. Their influence, however, on digitized echocardiographic measurements may vary with study subjects selection and should be considered when interpreting results.
Indocyanine green plasma clearance as a measure of changes in hepatic blood flow
Authors: Kanstrup I.‐L. , Winkler K.
Published: April 2008

Summary. The results from simultaneous measurements of indocyanine green (ICG) plasma clearance and hepatic blood flow (HBF) in subjects without hepatic dysfunction duringchanges in HBF induced pharmacologically or by food stimulation, are reported.

A linear relation is established between the relative changes in HBF and that of ICG clearance (r= 0·94), but the changes are not identical, and therefore the changes in HBF cannot be accurately predicted from that of ICG plasma clearance. The reason behind the lack of identity of the changes lies in the complicated kinetics of dye removal by the liver. The hepatic venous catheterization technique is the only method when physiologically correct values for hepatic blood flow or changes therein are wanted.
Venous circulation after fasciotomy of the lower leg in man
Authors: Rosfors S. , Bygdeman S. , Wallensten R.
Published: April 2008

Summary. The study was performed in order to evaluate the effect of fasciotomy of the lower leg on venous circulation and venous muscle pump function. Twenty patients with unilateral fasciotomy were investigated with photoplethysmography (PPG), strain‐gauge plethysmography, foot volumetry and Doppler ultrasound. In the operated legs shorter venous refilling times were registered both with PPG (P<0·1) and foot volumetry (P<0·05). PPG recordings from different parts of the leg showed regional changes in venous circulation with shorter refilling times only with the transducer placed over the affected muscular compartment. With foot volumetry a reduced expelled volume was found in patients earlier treated with extensive fasciotomies. The results of the study indicate that an intact muscle fascia is of importance for venous return and venous pump function.
Physical training plasma lipoproteins and faecal steroid excretion in sedentary men
Authors: Sutherland W. H. F. , Nye E. R. , Boulter C. P. , Shelling A.
Published: April 2008

Summary. Thirty sedentary men aged 25–52 participated in a 4‐month randomized and controlled study of the effects of exercise on plasma lipoproteins and faecal steroid excretion. After 4 months the aerobic training group showed a significant (P= 0·047) increase in physical work capacity (+38 watts) and a significant (P= 0·025) decrease in faecal total steroid excretion (‐257 mg/day) compared to corresponding changes in the control group. The drop in faecal total steroid excretion in the men who trained was mainly due to a significant (P<0·05) fall in faecal neutral sterol excretion (‐240 mg/day). Plasma lipoprotein lipid concentrations did not change significantly during the study although plasma levels of very low density lipoprotein (VLDL) cholesterol and low density lipoprotein (LDL) cholesterol tended to fall in the men who trained. In the aerobic training group individual changes in plasma LDL cholesterol levels were significantly correlated with decreases in faecal total steroid excretion (p = 0·615, P<0·05) and faecal neutral sterol excretion (p = 0·627, P<0·05). The results of this study show that regular exercise is associated with a drop in faecal neutral sterol excretion which, if sufficiently large, may be associated with a decrease in plasma LDL cholesterol concentration.
Improved working capacity following theophylline infusion in patients with ischaemic heart disease
Authors: Edlund A. , Söderberg R. , Henriksson P.
Published: April 2008

Summary. The effect of theophylline on the working capacity of patients with ischaemic heart disease was evaluated in a double‐blind, randomized cross‐over study. Eight patients, receiving no medication, with stable effort‐provoked angina pectoris and typical exercise‐induced ST depressions were studied. Following intravenous administration of theophylline or placebo, the patients did a supine leg exercise limited by intolerable chest pain. The workload was continuously increased by 10 W/min. Following theophylline treatment the workload at the onset of chest pain increased from 71 ± 9 to 114 ± 14 W (P< 0·002). The ST depression was less pronounced following theophylline at submaximal exercise (‐0·01 ± 0·00 vs. ‐0·09 ± 0·02 mV, P< 0·005, at 70 W). The maximum tolerable workload increased from 129 ± 15 after placebo infusion to 153 ± 12 W after theophylline infusion P<0·01).

It is speculated that this beneficial effect of the adenosine receptor antagonist theophylline may possibly be due to inhibition of a pathophysiological coronary steal induced by elevated levels of adenosine during ischaemia.
Left ventricular performance during exercise in long‐term type 1 diabetic men: an echocardiography study
Authors: Danielsen R. , Nordrehaug J. E. , Vik‐Mo H.
Published: April 2008

Summary.M‐mode echocardiograms were recorded and digitized during semisupine bicycle exercise in 10 young (<40 years) long‐term (≥12 years) type 1 diabetic men, without heart symptoms, and 10 controls. Recordings were done at rest, during workloads of 50 and 100 W and 1, 3 and 5 min post‐exercise. The groups were comparable at rest. Exercise intervention caused a higher heart rate and systolic blood pressure response in the diabetics. Overall, diabetics had a smaller left ventricular (LV) end‐diastolic dimension, but it did not change during exercise within either group; LV end‐systolic dimensions (ESD), however, decreased in both. The fractional shortening, normalized peak shortening rate and systolic blood pressure/ESD ratio increased in both groups. However, fractional shortening was lower in the diabetics during peak exercise, while the two latter variables of LV systolic function were similar to the controls. Furthermore, fractional shortening during peak exercise remained lower in the diabetics even when adjusted for systolic blood pressure by covariance analysis. Therefore, the decreased LV performance during exercise in the diabetic subjects is most likely secondary to reduced LV diastolic filling, as indicated by their smaller end‐diastolic dimension, rather than due to decreased contractility or a higher afterload.
Calf muscle adaptation in intermittent claudication. Side‐differences in muscle metabolic characteristics in patients with unilateral arterial disease
Authors: Jansson E. , Johansson J. , Sylvén C. , Kaijser L.
Published: April 2008

Summary. The adaptation of enzyme activities, notably in the oxidative metabolism, and of prerequisites for tissue transport of oxygen in the claudication leg was evaluated by comparing muscle biopsies from the gastrocnemius muscle of the claudication and the symptom‐free leg of seven patients with unilateral claudication. The claudication leg had higher activities of a marker enzyme for mitochondrial oxidative capacity, citrate synthase (CS), as well as of the MB and the mitochondrial isoenzyme of creatine kinase (CK), which are considered to be involved in the transfer of high energy phosphate from the mitochondria to the resynthesis of ATP in the cytoplasm. The difference between claudication and healthy leg in activities of these CK isoenzymes were well correlated with the corresponding side difference in CS activity. No significant differences between claudication and healthy leg were found in distribution of muscle fibre types or fibre dimension, capillary density or myoglobin content, nor was there any side difference in phosphofructokinase or lactate dehydrogenase. Side differences tended to be greater in those patients with the most advanced obstructive arterial disease as estimated from non‐invasive pressure measurements. It is concluded that in reasonably physically‐active patients, the mode of ischaemia to which the claudication leg is subjected leads to a metabolic adaptation characterized by increased activities of enzymes involved in the oxidative metabolism, but no significant adaptation of either the conditions for local oxygen transport, as estimated by myoglobin content, and capillary density, or capacity for anaerobic metabolism.
Excretion of thromboxane A2 and prostacyclin metabolites during treadmill exercise in patients with intermittent claudication
Authors: Wennmalm Å. , Edlund A. , Sevastik B. , FitzGerald G. A.
Published: April 2008

Platelet activation, with subsequent formation of thromboxane A2 (TxA2), is thought to play a role in the development of arterial occlusion. In patients with severe atherosclerosis of the lower limbs, characterized by leg ulcers and rest pain, the basal formation of TxA2 and prostacyclin (PGI2) is increased. Corresponding data in patients with more moderate atherosclerosis of the lower limbs have not been reported. Since the capacity to physical exercise is not blunted in such patients proper evaluation of their TxA2‐PGI2 synthesis should comprise not only assessment of the basal formation, but also TxA2/PGI2 biosynthesis during conditions of elevated cardiovascular activity. To address this, we analysed these eicosanoids in patients with a history of intermittent claudication. Urinary dinormetabolites of TxB2 and PGI2 (Tx‐M and PGI‐M, respectively) were estimated by gas chromatography/negative ion‐chemical ionization mass spectrometry in samples collected prior to, during and immediately after 20 min of severe treadmill exertion. The basal excretion of Tx‐M was 105 ± 26 pg/mg creatinine. It was not changed during exercise, but increased to 176 ± 48 pg/mg creatinine (P<0·05) during the recovery. The basal excretion of PGI‐M was 142 ± 25 pg/mg creatinine. The PGI‐M response to exercise varied from no change at all to a 30‐fold increase, without any obvious correlation to experienced leg pain, walking distance or other recorded variables. During the recovery period the outflow of PGI‐M was significantly higher than at rest (482 ± 145 pg/mg creatinine; P<0·01).

We conclude that in patients with intermittent claudication due to atherosclerosis (1) platelet activation does not occur during the course of the exercise, and (2) vascular prostacyclin formation can be dissociated from of TxA2 synthesis. The observed increase in PGI‐M in some of the patients is suggested to reflect tissue ischaemia induced by the lack of adequate hyperaemia during exercise.
Muscular venous blood metabolites during rhythmic forearm exercise while breathing air or normoxic helium and argon gas mixtures
Authors: Douguet D. , Raynaud J. , Capderou A. , Pánnier C. , Reiss G. , Durand J.
Published: April 2008

Summary. The effects of breathing normoxic helium or argon gas mixture on the local muscular metabolism during exercise were compared to those of room air in four healthy subjects. For this purpose, Po2, Pco2, pH, the concentrations of lactate (LA), glucose (Gl) haemoglobin (Hb) and K+ and osmolarity were repeatedly measured in efferent muscular venous blood during 12 min of rhythmic forearm exercise and 16 min of recovery.

The time courses and magnitude of the changes in Pco2, pH, [Gl], [Hb], [K+] and osmolarity during exercise and recovery were similar for breathing both the helium and argon gas mixtures.

The main finding was that during exercise, the [LA] curve reached a peak value significantly higher by 25% under normoxic helium than under room air or normoxic argon breathing. This rise in [LA] was accompanied by a slight reduction in muscular venous Po2, too small to signify muscular hypoxia. The possibility that this decline in Po2 might be due to a shift in muscular metabolism towards lipid oxidation was confirmed by the lower muscular respiratory quotient observed during helium breathing. However, such a shift did not explain why [LA] rose during this breathing. The probable explanation is that helium facilitates LA diffusion out of the myocytes.
Inosine causing insulin release and increased myocardial uptake of carbohydrates relative to free fatty acids in dogs
Authors: Smiseth O. A. , Gunnes P. , Sand T. , Mjøs O. D.
Published: April 2008

Summary. The aim of the present study was to determine the effect of i.v. inosine on myocardial substrate uptake and function in the in situ dog heart. Inosine was infused i.v. at a rate of 5 mg kg min‐1 in eight closed‐chest pentobarbital anaesthetized dogs. Inosine caused a 46% decrease (P<0.01) in plasma free fatty acids (FFA), a 15% decrease (P<0.05) in plasma glycerol, an 18% decrease (P<0.05) in plasma glucose and a 46% increase (P<0.01) in blood lactate. This was associated with a 55% decrease (P<0.01) in myocardial FFA uptake and a 72% increase in lactate uptake, while glucose uptake remained unchanged. These metabolic changes were associated with a five‐fold increase (P<0.05) in arterial insulin. Inosine caused an 18% increase (P<0.01) in myocardial blood flow without changing MVO2. There was a 33% increase (P<0.01) in LV dP/dtmax, a decrease in LVEDP from 4.9 ± 0.9 (mean ± SEM) to 0.9 ± 0.3 mmHg (P<0.05) and a 24% decrease (P<0.01) in systemic vascular resistance. Inosine caused a transient 38% increase (P<0.05) in pulmonary vascular resistance. In conclusion, in addition to a positive inotropic effect and vascular effects inosine was found to cause release of insulin and to shift myocardial metabolism towards increased uptake of carbohydrates relative to FFA.
Diagnostic value of longterm ambulatory ECG in patients with syncope, dizziness or palpitations
Authors: Ringqvist I. , Jonason T. , Nilsson G. , Khan A. R.
Published: April 2008

Summary.The diagnostic value of longterm ambulatory ECG recording (LTER) was determined in 63 patients referred for investigation of syncope, in 32 with dizziness and in 89 with palpitations.

Among patients referred for syncope, dizziness or palpitations 8, 13 and 54%, respectively, had typical symptoms during the recording with concomitant arrhythmia explaining the symptom, and 6, 50 and 11% had a typical symptom without concomitant arrhythmia. In 12 and 3% of the patients referred for syncope or dizziness, respectively, arrhythmia was observed and probably explained their previous complaint, but no symptoms occurred during LTER.

LTER was found to be of diagnostic value in 24% of the patients with syncope, in 66% of those with dizziness and in 65% of those with palpitations. In the latter two groups the presence of symptoms the week before the start of these recordings predicted the occurrence of symptoms during LTER. Only occasionally was there a higher yield of typical symptoms beyond 48 h of recording.
Variability in muscle fibre areas in whole human quadriceps muscle: how to reduce sampling errors in biopsy techniques
Authors: Lexell J. , Taylor C. C.
Published: April 2008

Summary. A single biopsy is a poor estimator of the muscle fibre cross‐sectional area (CSA) for a whole human muscle because of the large variability in the fibre area within a muscle. To determine how the sampling errors in biopsy techniques can be reduced, data on the CSA of type 1 and type 2 fibres obtained from cross‐sections of whole vastus lateralis muscle of young men, have been analysed statistically. To obtain a good estimate of the mean fibre CSA in a biopsy, measuring all fibres in that biopsy gives the best result. To obtain a good estimate of the mean fibre CSA for a whole muscle, the number of biopsies has a much greater influence on the sampling error than the number of fibres measured in each biopsy, but the number of biopsies needed to obtain a given sampling error can vary by a factor of two. If the fibre CSA in three or more biopsies is measured, it is sufficient to measure only 25 fibres in each biopsy. If less than three biopsies are taken, there is no worthwhile reduction in sampling error when more than 100 fibres are measured. To determine the mean fibre CSA for a whole group of individuals, our preference is to maximize the number of individuals, and only take single biopsies. In conclusion, to determine the mean fibre CSA for this particular muscle with a certain precision, we suggest analysis of three biopsies, taken from different depths of the muscle, and measurement of 25 fibres in each biopsy.
Cardiac repolarization properties during standardized exercise test as studied by QT, QT peak and terminated T‐wave intervals
Authors: Sundqvist K. , Sylvén C.
Published: April 2008

Summary. Changes in QT, QT peak (QTp) and terminal T‐wave, Tp–Te (QT–QTp) were studied in 11 apparently healthy subjects during and after a standardized exercise test. ECG was recorded at scalar lead positions. Averaged complexes were later analysed by computer for the different time intervals. QT and QTp decreased in parallel with increasing heart rate with a ratio QTp/QT of 0·80 ± 0.02 at rest and 0·74 ± 0·02 at maximal heart rate around 170. After exercise QT and QTp prolonged disproportionately slower than heart rate, reaching the relation observed during exercise only 9·5 min post exercise. Tp–Te was 75 ± 10 ms at rest and 65 ± 8 ms at maximal heart rate. The decrease was significant (P<0·001). The main part of the rate‐associated shortening of the QT interval occurred in the QTp interval where it was about six to seven times larger than in the Tp–Te interval. In conclusion, QT and QTp decreased similarly with heart rate during exercise. Post exercise there was an initial slower return of these intervals to the resting state than for heart rate. Tp–Te changes were minimal.
Limitation of finger systolic pressure measurement as a diagnostic test for primary Raynaud's phenomenon in a female population
Authors: Leppert J.
Published: April 2008

Summary. The diagnostic value of measurement of the finger systolic pressure (FSP) was assessed during combined local and whole body cooling in a population‐based sample of women with a medical history of primary Raynaud's phenomenon. Forty women had mild Raynaud's phenomenon and 40 had pronounced Raynaud's phenomenon. The results were compared with subjective assessments of complaints from Raynaud's phenomenon as indicated on a visual analogue scale (VAS) in the same group of women.

The mean FSP at 10°C was significantly lower in the patients than in 24 age‐ and sex‐matched controls, but there was a large overlap in individual responses. The sensitivity of the FSP method was only 51% for the whole group with primary Raynaud's phenomenon. There was no significant difference in FSP at 10°C between subjects with mild and those with pronounced Raynaud's phenomenon. The subjective severity of the symptoms as indicated on VAS was significantly higher in these two combined groups than in the controls. The mean VAS value was significantly higher in the group with pronounced Raynaud's phenomenon (P<0·01) than in that with the mild type.

The low sensitivity of FSP measurement implies that this method is of limited value as a diagnostic test in subjects with primary Raynaud's phenomenon. Furthermore, there was no significant correlation between FSP and the VAS values (r= 0·23).
Meal‐induced thermogenesis in obese patients before and after weight reduction
Authors: Thörne A. , Hallberg D. , Wahren J.
Published: April 2008

Summary. The purpose of this study was to find out whether human obesity is associated with a diminished meal‐induced thermogenesis and, if so, to what extent this response is influenced by weight reduction. Ten obese subjects (body mass index 42 ± 2) and 10 age‐ and sex‐matched non‐obese volunteers were studied with continuous indirect calorimetry in the basal state and after the ingestion of a standardized test meal. Six obese subjects (body mass index 44 ± 2) were examined on two occasions, once before and once after gastric banding and an average weight reduction of 18 ± 3 kg. Basal oxygen uptake and energy expenditure were 30% (P<0·001) greater in the obese subjects compared to non‐obese controls. After the meal, pulmonary oxygen uptake and energy expenditure increased rapidly and reached a relatively constant level after 60 min; for pulmonary oxygen uptake the average rise above basal was less in the obese (17·7 ± 1·6%) than the non‐obese (27·8 ± 1·9%, P<0·001); the increase in energy expenditure was 18·5 ± 1·7% in obese and 30·8 ± 2·1% in non‐obese subjects (P<0·001). After weight reduction, oxygen uptake and energy expenditure in the basal state were 20% lower (P<0·05) than before weight reduction. The average postprandial increase in oxygen uptake was greater after weight reduction (24·8 ± 2·0%) than before (16·7 ± 1·6%, P<0·001). Corresponding values for energy expenditure were 27·2 ± 2·2 and 18·2 ± 2·2% (P<0·001).

It is concluded that:

(1) the thermogenic response to a mixed meal is lower in obese compared to non‐obese individuals; and,

(2) this impaired response is partly normalized after weight reduction.

These findings suggest that a diminished meal‐induced thermogenesis is a secondary phenomenon rather than a primary pathogenic factor in human obesity.
Does post‐tetanic potentiation compensate for low frequency fatigue?
Authors: Green H. J. , Jones S. R.
Published: April 2008

Summary. The purpose of this study was to examine the effect of post‐tetanic potentiation on low frequency fatigue in adult human quadriceps muscle. Sixteen subjects (10 male and six female) performed three 60 s sets of knee extension exercise in order to induce low frequency fatigue (reduction in torque output at 10 and 20 Hz). The potentiating stimulus (a 10 s maximal voluntary contraction) induced a 58% increase in twitch tension (Pt) during the pre‐fatigue state. Immediately following the fatiguing exercise, torque (X± SE, Nm) at 10 and 20 Hz (submaximal transcutaneous stimulation, 50 μs pulses) decreased (P<0·05) from 54·8 ± 5·8 and 94·9 ± 9·6 to 40·3 ± 6·1 and 77·0 ± 11, respectively. Although potentiation at this time increased P, from 40·9 ± 4·0 to 54·8 ± 3·7 (P<0·05), torque at 10 and 20 Hz was unaffected. At 60, 120 and 240 min post‐contraction, torque at 10 and 20 Hz remained depressed. Following potentiation, which increased twitch tensions to between 64 and 75%, torque at 10 Hz was increased (P<0·05) at 60 min (36·3 ± 4·1 vs. 50·7 ± 6·2), 120 min (40·8 ± 6·3 vs. 56·5 ± 8·9) and 240 min (42·0 ± 4·7 vs. 57·5 ± 8·3) of recovery. Similar effects were also noted at 20 Hz. These findings indicate that post‐tetanic potentiation can overcome the low frequency fatigue during the post‐contraction period and restore torque to pre‐exercise levels.
Evaluation of a dynamometer measuring torque of uni‐ and bilateral concentric and eccentric muscle action
Authors: Tesch P. A. , Lindborg B. P. O. , Colliander E. B.
Published: April 2008

Summary. A dynamometer designed for torque measurements of uni‐ and bilateral concentric and eccentric muscle actions of the quadriceps and hamstring muscle groups is described.

Torque reproducibility and control of lever‐arm position were studied using known standards. In vivo measurements assessed angular velocity, lever‐arm acceleration, variability of torque between limbs and reproducibility of torque.

Torque obtained from left and right leg attachments was equal when using weights and during dynamic in vivo conditions. Static torque recorded at different lever‐arm positions and known torque were equal. Likewise, lever‐arm position output equated with known angles. In vivo test‐retest of peak torque was found to be reliable. Acceleration of the lever arm was greater for concentric bilateral than for unilateral muscle actions but equal during eccentric muscle actions.

The dynamometer is suggested to provide valid and reproducible torque measurements up to at least 700 Nm at constant angular velocities up to 2·62 rad s‐1. Besides being a research tool the dynamometer is useful in clinical settings for rehabilitation and evaluation of skeletal muscle function.
Vectorcardiogram more sensitive than 12‐lead ECG in the detection of inferior myocardial infarction
Authors: Edenbrand L. , Pahlm O. , Lyttkens K. , Albrechtsson U.
Published: April 2008

Summary. The vectorcardiogram (VCG) is commonly stated to be more sensitive than the 12‐lead electrocardiogram (ECG) for the diagnosis of inferior myocardial infarction. However, a recent study indicated that VCG is not superior to ECG for this diagnosis. The purpose of this study was to compare the performance of VCG and ECG criteria and to indicate possible explanations for the disagreement between earlier studies. Accordingly, we studied 65 patients with inferior myocardial infarction verified by left ventriculography or 201‐TI myocardial scintigraphy and 351 normal subjects. Sensitivity was 69% (45/65) and 43% (28/65) for the VCG and ECG criteria, respectively. This difference was highly significant (P<0·001). Among the normal subjects there were only three with false positive VCG and none with false positive ECG. We conclude that both VCG and ECG criteria for the diagnosis of inferior myocardial infarction are highly specific and that VCG criteria have greater sensitivity than ECG criteria.
Plasma lipolytic activity and substrate oxidation after intravenous administration of heparin and a low molecular weight heparin fragment
Authors: Persson E. , Nordenström J. , Nilsson‐Ehle P. , Hagenfeldt L. , Wahren J.
Published: April 2008

Summary. This study examines the effects of heparin and a low molecular weight heparin (LMWH) fragment on plasma lipolytic activity and substrate oxidation. Indirect calorimetry was performed continuously in healthy male subjects receiving a constant infusion of fat emulsion (0·2 g min‐1) and glucose (0·8 g min‐1) during a period of 4 h. After 2 h an infusion of heparin (n= 6) or LMWH (n= 6) (100 antifactor Xa units kg‐1) or saline (n= 6) was given over 1 h.

Plasma concentration of the fat emulsion decreased by 76 ± 5% with heparin and by 12 ± 7% with LMWH (P<0·01). In the case of LMWH the initial fall was followed by a consistent rise in fat emulsion concentration for the entire remaining study period. Compared to the control experiments, plasma FFA increased five times with heparin and three times with LMWH (P<0·05). The average respiratory quotient (RQ) and energy expenditure (EE) increased constantly during the study period and did not differ significantly between the groups. In all groups the average increase in glucose oxidation was 40–50%, while fat oxidation decreased to a comparable extent. Infusions of heparin and LMWH had no effect on RQ or EE. A microcalorimetric study on isolated rat adipocytes in buffer solutions containing glucose, fat emulsion, heparin or LMWH was also made. The heat output from the adipocytes was not influenced by the presence of heparin or LMWH.

In conclusion, infusion of heparin resulted in a pronounced increase in FFA availability, whereas LMWH exerted a less marked lipolytic effect. However, the heparin‐induced elevations in plasma FFA were not accompanied by measurable rises in lipid oxidation rate.
Endothelin does not affect aggregation of human platelets
Authors: Edlund A. , Wennmalm Å.
Published: April 2008

Summary. Endothelin (ET‐1) is a recently discovered endothelial‐derived peptide with pronounced vasoconstrictor activity. The present study addressed whether ET‐1, in analogy with several other vasoactive agents, can induce or modulate aggregation of human platelets in vitro. Venous blood from healthy donors was collected in citrate or heparin and platelet‐rich plasma (PRP) was prepared. Portions of the PRP were added to drugs, and platelet aggregation was recorded according to Born & Cross (1963). ET‐1 added to the PRP (final concentrations 1–100 nM) did not induce aggregation of platelets, either in citrate‐ or heparin‐containing plasma. Adenosine‐diphosphate (0·5‐2 μM) or thrombin (0·1‐0·4 NIH units ml‐1) induced dose‐dependent aggregation of platelets in citrate‐ or heparin‐containing PRP; such aggregation was, however, not affected by ET‐1 (1–100 μM) either. We conclude that ET‐1, in contrast to other endothelial‐derived vasoactive agents, lacks direct effect on platelet aggregation in vitro.
Decrease in myoglobin and enzyme contents with haemodilution in non‐hypoxaemic polycythaemic patients
Authors: Hildebrand I. L. , Sylvén C. , Hellström K. , Jansson E.
Published: April 2008

Summary. Quadriceps muscle biopsies from five patients with primary polycythaemia and four patients with non‐primary polycythaemia, all with normal respiratory functions, were studied before and after normalization of haemoglobin and erythrocyte volume fraction by haemodilution or venaesectio. Since similar results were obtained from both groups of patients data were pooled. After normalization of the erythrocyte volume fraction myoglobin decreased by 19 ± 16%, P<0·01, the activity of creatine kinase and citrate synthase by 12 ± 8 and 14 ± 18%, P<0·05, respectively. The decrease in myoglobin content was related to the decrease in haemoglobin concentration (r= 0·77, P<0·01). In conclusion, these data suggest that in non‐hypoxaemic polycythaemia skeletal muscle shows adaptations indicative of an impaired oxygenation and a metabolic stress, adaptations that are reversed by haemodilution.
Gas‐exchange impairment: its correlation to lung mechanics in acute airway obstruction (studies on a rabbit asthma model)
Authors: Lagerstrand L. , Hedenstierna G.
Published: April 2008

Summary. A rabbit model was developed for the studies of ventilation/perfusion relationships (V̇/Q̇) and thorax mechanics during bronchial provocation tests. Baseline data from 14 anaesthetized rabbits show a V̇A/Q̇ distribution that is broader (less efficientV̇A/Q̇match) than that of lung‐healthy humans, dogs and horses.

Airway provocation was created by inhalation of ammonia, prostaglandin (PGE1) and methacholine bromide. Methacholine bromide was the only substance that triggered measurable V̇A/Q̇ changes. Measurements 5 min after methacholine provocation showed markedly increased thorax resistance, widened V̇A/Q̇ distribution and in some rabbits an increased shunt. Fifteen minutes after provocation that was still a broad V̇A/Q̇ distribution and in several rabbits a further increase of shunt. Both thorax resistance and perfusion of regions with low V̇A/Q̇ were reduced. Our results suggest a correlation between thorax resistance and perfusion of regions with low V̇A/Q̇. However, the slower normalization in V̇A/Q̇ disturbance and the remaining or increased shunt suggests that factors other than airway resistance contribute to the gas‐exchange impairment. These factors might be alveolar oedema, or mucus and oedema in the smallest airways.
Short‐term variability of systolic blood pressure and heart rate in normotensive subjects
Authors: Turjanmaa V. , Kalli S. , Sydänmaa M. , Uusitalo A.
Published: April 2008

Abstract. Short‐term fluctuations in systolic blood pressure (SBP) and heart rate (HR) and their inter‐relationship were analysed in a group of normotensive middle‐aged men (n= 16) using a multivariate autoregressive modelling technique. This study is the first to evaluate the beat‐to‐beat variability of SBP and HR in a group of real normotensive subjects. Direct intra‐arterial blood pressure was registered together with ECG using an ambulatory tape recording technique (the Oxford method). Power spectrum density estimates (PSD) were used as a measure of the variability. PSDs were calculated over 3‐min periods for four basic physiological conditions: during sleep and in the supine, sitting and standing positions. The inter‐relationship between the blood pressure and heart rate variabilities was analysed using a closed‐loop model. In agreement with results presented earlier in the literature, the beat‐to‐beat variation in SBP and HR was concentrated in three typical power spectrum regions: the high‐frequency (HF = 0·15‐0·35 Hz) region (respiration), the mid‐frequency (MF = 0·075‐0·15 Hz) region (vasomotor oscillation) and the low‐frequency (LF = 0·02‐0·075 Hz) region (thermoregulation). The variability changes considerably between different situations, especially that of the MF region. The variability was most prominent in the MF region and in the standing position. The variability was generally smallest in the HF region and in sleep. The results also demonstrate that the beat‐to‐beat variability in SBP and HR can considerably affect one another.
Deep venous valvular function assessed with intramuscular pressure recording
Authors: Rosfors S. , Styf J.
Published: April 2008

Summary. Intramuscular pressures were measured in the anterior tibial muscle with the microcapillary infusion method in 10 patients (11 limbs) with deep venous valvular insufficiency. The results were compared with pressure measurements in healthy controls (n= 8) and in patients with only superficial venous insufficiency n= 7). The technique could differentiate patients with deep venous reflux from patients with superficial venous reflux and healthy controls. In contrast to the other two groups studied, patients with deep venous reflux were characterized by a small decrease of muscle relaxation pressure during exercise followed by a short recovery time. The method described provides a potential for evaluating regional deep venous valvular function. However, besides deep venous reflux other factors such as rate of arterial inflow, venous capacity and muscle pump function also might influence the results obtained with intramuscular pressure recordings.
Estimation of pulmonary vascular resistance in patients with ventricular septal defects by echo‐Doppler cardiography
Authors: Teien D.
Published: April 2008

Summary. The pulmonary vascular resistance is one of the parameters considered in the evaluation of patients with ventricular septal defects. We describe a new method to estimate resistance. The method estimates the systolic resistance in the pulmonary circulation and we assume that there is a linear relation between this resistance and the traditional resistance in which a continuous flow in systole and diastole is assumed.

The systolic resistance was compared to the traditional resistance index in a group of patients whose invasive data were evaluated retrospectively. A close correlation between the two estimates of resistance was found and when the results were applied to another group of patients examined non‐invasively and invasively there was no significant difference between the invasive resistance index and the non‐invasive estimate arrived at by the new method.