bluuebunny/crossref_metadata_2025 huggingface dataset:
Ammonia metabolism during exercise in man
Authors: Eriksson Ljusk Siw , Broberg Sylvia , Björkman Ola , Wahren John
Published: April 2008

Summary. Physical exercise is accompanied by increased plasma levels of ammonia but it is not known whether this rise primarily reflects accelerated formation in muscle or decreased removal by the liver. Consequently, leg and splanchnic exchange of ammonia was examined, using the catheter technique, in 11 healthy subjects at rest, during three consecutive 15 min periods of bicycle exercise at gradually increasing work loads (35%, 55% and 80% of maximum oxygen uptake) and for 60 min during post‐exercise recovery. The basal arterial ammonia level was 22±2 umol/1, the concentration rose curvilinearly in response to increasing work loads (peak value 84±12 umol/1), and fell rapidly after exercise, reaching basal levels after 30–60 min. A linear regression was found for ammonia levels in relation to lactate concentrations at rest and during exercise (r=0–85, P<0001). A significant relationship was also observed between arterial ammonia and alanine levels (r=0–75, P<0001). Leg tissues showed a net uptake of ammonia in the basal state (2–4±0–5 umol/min). During exercise this changed to a net production, which increased curvilinearly with rising work intensity (peak value 46±15 umol/min) but reverted to a net ammonia uptake at 30–60 min after exercise. Splanchnic ammonia uptake (basal 12±2 umol/min) did not change in response to exercise but increased transiently during the early post‐exercise period.

From the above observations we conclude that the hyperammonaemia of exercise comes primarily from muscle release, while the splanchnic removal of ammonia is essentially unaltered. Part of the ammonia formed in contracting muscle is most likely used in the synthesis of amino acids, mainly glutamine and probably alanine.
Reproducibility of coronary haemodynamics and cardiac metabolism during pacing‐induced angina pectoris
Authors: Bagger Jens Peder , Nielsen Torsten Toftegaard , Thomassen Anne
Published: April 2008

Summary. The reproducibility of coronary sinus blood flow (CSBF) (thermodilution technique) and myocardial metabolism (exchange of oxygen, lactate, free fatty acids, glucose, citrate, glutamate and alanine) during two identical pacing periods separated by 45 min were studied in eight patients with chronic coronary artery disease. The mean of the individual difference (Δ‐values) between values during the first (T1) and second (T2) test, at corresponding times (rest, pacing and after 3–5 min of recovery), were calculated and expressed as a percentage of the resting level of each parameter in order to assess their reproducibility. All patients experienced angina pectoris during both pacing sessions, and pacetime to onset of symptoms did not differ between the tests. Group values for haemodynamics and exchange of metabolites were acceptably reproducible throughout the period under study. Mean Δ‐values of CSBF ranged from 10% to 16% and myocardial oxygen uptake from 14% to 22% in relation to the resting levels. In contrast, mean A‐values of metabolites ranged from 5% to 136% in relation to the respective A‐V differences during the study. The greatest variation occurred during pacing and of all the metabolites lactate exchange varied most. A spontaneous variation in the degree of ischaemia during repeat stress tests might be the major reason for the metabolite variability. Changes in CSBF, however, tended to correlate inversely to the Δ‐aortocoronary sinus differences of substrates during pacing. Precision of chemical analysis and blood sampling technique were of minor importance for the variability. Since lactate exchange varied most, the study suggests that additional measurements should be made of more metabolites when assessing the efficacy of therapy by means of myocardial metabolism.
Transport of sodium fluorescein between the mucosal and muscular layers in man, possibly indicating functional serially‐coupled exchange vessels
Authors: Perbeck Leif , Nyberg Björn , Thulin Lars , Tydén Gunnar
Published: April 2008

Summary. In sixteen patients subjected to intestinal surgery, the transport of sodium fluorescein (Na‐F) was measured between the mucosal and serosal‐muscular layers. Experiments were carried out in intestinal anastomosis by fluorescein flowmetry (FF). The blood‐flow index of the mucosal layer was about twice the serosal‐muscularis, per unit tissue volume. The temporal changes in fluorescence pattern from the two layers showed that more than 90% of Na‐F, eliminated from the mucosal layer, was transported to the serosal‐muscular layers. In six patients, in whom Na‐F was instilled intraluminarily, fluorescence was seen on the outside of the intestine after 3 min. However, when the circulation was stopped before Na‐F was instilled, no fluorescence was seen, this suggests that the transport was not only due to diffusion but also to convection. The results suggest that functional serially‐coupled exchange vessels may exist within the intestinal wall, and that Na‐F is transported both by convection and diffusion.
Do substance P and vasoactive intestinal polypeptide (VIP) play a role in the acute occlusive or chronic ischaemic vasodilation in man?
Authors: Henriksen J. H. , Bülow J. B. , de Muckadell O. Schaffalitzky , Fahrenkrug J.
Published: April 2008

Summary. The concentrations of substance P (SP) and vasoactive intestinal polypeptide (VIP) were determined in plasma in normal volunteers during acute occlusive ischaemia (n= 5) and in patients with chronic ischaemia (n= 5) due to obliterative arterial disease in the lower limbs. Venous SP, but not VIP, increased significantly in the early post‐occlusive period in normal volunteers (P < 0·02). In the patients no significant veno‐arterial difference in plasma concentration of SP or VIP could be detected across normal or chronic ischaemic areas.

The results may suggest a role for SP in the acute post‐occlusive vasodilatation and/or in the post‐occlusive heat‐pain sensation. A role for SP in chronic ischaemia could not be defined. Plasma VIP was unchanged in both acute and chronic ischaemia.
Activities of key enzymes in the energy metabolism of human myocardial and skeletal muscle
Authors: Jansson Eva , Sylvén Christer
Published: April 2008

Summary. Activities of total creatine kinase (CK), its isoenzyme MB (CK‐MB), total lactate dehydrogenase (LD) and its isoenzyme LD1, phosphofructokinase (PFK), asparate aminotransferase (ASAT) and citrate synthase (CS) were determined in skeletal muscle biopsies obtained from physically trained and untrained men and in myocardial biopsies from patients subjected to open heart surgery because of valve disease. The LD1, ASAT and CS activities were higher in trained than in untrained skeletal muscle and still higher in heart muscle than in either trained or untrained skeletal muscle. The CK‐MB activity was higher in trained than untrained skeletal muscle and the myocardial CK‐MB activity was similar to that in trained skeletal muscle. Total CK activity was slightly lower in trained than in untrained skeletal muscle and the myocardial CK activity was approximately one third of the skeletal muscle CK. Both the PFK and the total LD activity was of similar magnitude in the different muscle types. In conclusion, as estimated by enzyme activities, the oxidative capacity is 2–3 times larger in myocardial than in skeletal muscle, while the glycolytic capacity as estimated by PFK appears to be the same.
Effect of local warming on forearm reactive hyperaemia
Authors: Johnson J. M. , O‘Leary D. S. , Taylor W. F. , Kosiba W.
Published: April 2008

Summary. Measurement of minimal vascular resistance has proved useful in quantifying structural changes in regional circulations. Accurate measurement of minimal vascular resistance requires full relaxation of all resistance vessels within the region under examination. The usual procedure in humans involves the measurement of maximal forearm blood‐flow following 6–10 min of forearm ischaemia. We conducted this study to find whether forearm skin was fully vasodilated by this procedure. Peak forearm blood‐flow was measured by plethysmography in six healthy subjects following 10 min of ischaemia while the arm was at a neutral temperature (33°C) and while the arm was locally warmed to 42°C. Peak reactive hyperaemia blood‐flow was significantly elevated by local heating (P<0·001) to 79·6 ml100ml‐1min‐1 from a value of 50·2 ml100ml‐1min‐1 during normothermia. Peak reactive hyperaemia blood‐flow in the contralateral unheated forearm showed no significant change between the two periods of ischaemia (P>0·05). These findings were confirmed in four subjects by laser Doppler velocimetry, which gives a linear index of skin blood‐flow. In normothermic conditions, this index rose to 0·89 V following 10 min of ischaemia and to 1·26 V with local warming to 42°C (P<0·001). Ischaemia plus local warming did not cause a further significant rise in this index of skin blood‐flow (1·35 V, P>0·05). These data suggest that 10 min of ischaemia during normothermia is insufficient to relax fully cutaneous resistance vessels and that maximal forearm blood‐flow is underestimated by this procedure.
Muscle ammonia and amino acid metabolism during dynamic exercise in man
Authors: Katz A. , Broberg S. , Sahlin K. , Wahren J.
Published: April 2008

Summary.The effect of dynamic exercise on muscle and blood ammonia (NH3) and amino acid contents has been investigated. Eight healthy men cycled at 50% and 97% of maximal oxygen uptake for 10 min and 5·2 min (to fatigue), respectively. Biopsies (quadriceps femoris muscle), arterial and femoral venous blood samples were obtained at rest and during exercise. Muscle NH3at rest and after submaximal exercise was (x̄±SE) 0·5±0·1 mmol/kg dry muscle (d.m.) and increased to 4·1 ±0·5 mmol/kg d.m. at fatigue (P<0·001). The total adenine nucleotide (TAN) pool (TAN=ATP+ADP+AMP) did not change after submaximal exercise but decreased significantly at fatigue (P<0·01). The decrease in TAN was similar to the increase in NH3. Muscle lactate was 3±1 mmol/kg d.m. at rest and increased to 104±5 mmol/kg d.m. at fatigue. Whole blood and plasma NH3did not change significantly during submaximal but both increased significantly during maximal exercise (P<0·001). During maximal exercise the leg released 7,120 μmol/min of lactate, whereas only 89 μmol/min of NH3were released. NH3accumulation in muscle could buffer only 3% of the hydrogen ions released from lactate, and NH3release could account for only 1% of the net hydrogen ion transport out of the cell. Muscle glutamine was constant throughout the study, whereas glutamate decreased and alanine increased during exercise (P<0·001). No significant changes in either arterial whole blood glutamine or glutamate were observed. Arterial plasma glutamine and glutamate concentrations, however, increased and decreased (P<0·001), respectively, during exercise. It is concluded that (1) muscle and blood NH3levels increase only during strenuous exercise and (2) NH3accumulation is of minor importance for regulating acid‐base balance in body fluids during exercise.
Fibre orientation in the left ventricle and its influence on local pressure—length loop analysis in cats
Authors: Matre K. , Hexeberg E. , Lekven J.
Published: April 2008

Summary. Deviation from local fibre orientation may seriously affect quantification of myocardial segment work, as measured by implanted ultrasound crystals. Crystal pairs were positioned in mid‐wall layers with known directions to the long axis of the heart. One transmitter and four receiving crystals covered a sector on the anterior ventricular wall of 100°. The results show a strong influence of alignment to fibre direction on the pressure‐length loop area; the relation followed a cos2ψ function where ψ denotes the angle between the crystal pair direction and fibre direction established by microscopy. The angle between the mid‐wall muscle fibres on the anterior aspect of the left ventricle and the long axis of the heart varied between 62° and 90° with a mean value of 76°. This study shows that pressure‐length loop quantitation depends strongly on crystal alignment to cardiac muscle fibres through which the ultrasound passes.
Use of vectorcardiography in determination of the left ventricular muscle mass
Authors: Granfeldt H. , Nylander E.
Published: April 2008

Summary. Many studies have investigated different ECG and vectorcardiographic (VCG): criteria for diagnosis of left ventricular hypertrophy (LVH). In some investigations VCG was more sensitive than ECG in this respect. This study was performed to elucidate whether it is possible also to determine the degree of LVH using VCG. Eighty cardiovascularly healthy subjects aged 15–39 were investigated with ECG, VCG (Frank system) and echocardiography. The echocardiographic left ventricular (LV) mass has been shown by others to correlate closely to the anatomical and the angiographically determined LV mass and was used as reference standard. Thirty‐eight of the subjects were endurance sportsmen and had a LV mass above standard reference limits.

The measured ECG variables were R‐amplitude in aVL, I, V5, V6, S‐amplitude in VI and SV1 + RV5/V6 and the VCG variables were QRS spatial area and circumference and left maximal spatial vector.

The sensitivity and specificity of single criteria tested were similar for ECG and VCG in the quantitative determination of LVH. The correlations between ECG‐amplitudes and the magnitude of the LV mass were weak. The correlations were higher with the VCG‐variables, QRS spatial circumference being superior to the others, but not good enough to permit an estimation of the LV mass in individual subjects. In conclusion, normal VCG variables were highly specific for a normal LV mass but in individuals with LVH, VCG was not useful for the estimation of the LV mass.
Human cardiovascular adjustments to acute hypoxaemia
Authors: Rowell L. B. , Blackmon J. R.
Published: April 2008

Summary. Traditionally, cardiovascular adjustments to hypoxaemia are viewed as resultants of competing local vasodilation and vasoconstriction via arterial chemo‐reflexes with net effects of increased cerebral and coronary blood flows (local) and reduced flow to visceral organs and muscle (reflex). Although true in asphyxia, breathing activates lung mechanoreceptors which reduce vagal outflow and apparently, in humans, abolishes sympathetic vasomotor activity (SNA). During rest, moderate to severe hypoxaemia (Pao2= 35 to 27 mmHg) caused no splanchnic, cutaneous or muscle vasoconstriction. Local vasodilator effects of hypoxaemia were not sufficient to overwhelm vasoconstriction; splanchnic arterioles responded normally to infused noradrenalin (NA) during hypoxaemia. Possibly, central effects of hypoxaemia blunt SNA or peripheral, prejunctional effects impair neuronal release of NA. Persistent orthostatic tolerance with normal skeletal muscle vasoconstriction and retained spinal venomotor reflexes during hypoxaemia argue against prejunctional inhibition of NA release. Results so far suggest that beyond a certain threshold, hypoxaemia centrally inhibits SNA. In contrast to rest, even moderate hypoxaemia during exercise markedly increases plasma NA concentration (and SNA), but the usual relationship among splanchnic blood flow, plasma NA and heart rate was not observed—NA and heart rate rose together, whereas the predicted splanchnic vasoconstriction was not observed. In moderate hypoxaemia, muscle blood flow and cardiac output are greater than in normoxia at a given submaximal oxygen uptake; but at maximal oxygen uptake, blood pressure, total vascular conductance and maximal cardiac output are unaffected. Given the fixed upper limit to cardiac output and the greater capacity of active muscle to vasodilate and exceed cardiac pumping capacity during hypoxaemia, we conclude that blood pressure is maintained by baroreflex‐ (not chemoreflex‐) mediated vasoconstriction in the active muscle which must be the primary target of increased SNA and the source of NA.
A comparison between 133Xenon washout technique and Laser Doppler flowmetry in the measurement of local vasoconstrictor effects on the microcirculation in subcutaneous tissue and skin
Authors: Kastrup J. , Bülow J. , Lassen N. A.
Published: April 2008

Summary. Changes in skin blood flow measured by Laser Doppler flowmetry and changes in subcutaneous blood flow measured by 133Xenon washout technique were compared during activation of the local sympathetic mediated veno‐arteriolar vasoconstrictor reflex by lowering the area of investigation below heart level. The measurements were performed in tissue with and without sympathetic innervation. In five subjects, who all had been cervically sympathectomized for manual hyperhidrosis, the Laser Doppler and 133Xenon blood flow measurements were performed simultaneously on the sympathetically denervated forearm, and on the calf with preserved sympathetic nerve supply. The Laser Doppler method registered a 23% reduction in skin blood flow during lowering of the extremities independently of the sympathetic nerve supply to the skin. The ‘“Xenon method recorded a 44% decrease in blood flow in innervated and unchanged blood flow in denervated subcutaneous tissue during lowering of the extremities. Our results indicate that the Laser Doppler method and 133Xenon method are not comparable, and that the Laser Doppler method is not useful in measuring local sympathetic mediated blood flow changes.
Effects of extracellular fluid volume changes on renal response to low‐dose dopamine infusion in normal women
Authors: Agnoli G. C. , Cacciari M. , Garutti C. , Ikonomu E. , Lenzi P. , Marchetti G.
Published: April 2008

Summary. Dopamine (DA) i.v. infused in a low dose (0·1 (μg/kg/min) in healthy women during sustained hypotonic polyuria, produced different renal functional effects as variations in extracellular fluid volume occurred. (1) In hydro‐saline retention (n= 23), induced by desoxycorticosterone acetate treatment, DA produced typical vasodilator and hydro‐natriuretic effects (Goldberg, 1972). (2) In hydro‐saline depletion (n= 19), induced by diuretic treatment and low dietary sodium intake, DA lost its vasodilator and natriuretic efficacy, manifesting, on the other hand, renal sodium conserving effects mainly dependent on the increase in distal sodium reabsorption and a trend towards afferent arteriolar vasoconstriction. (3) Treatment with prazosin (n= 9) or propranolol (n= 9) in hydro‐saline depletion, was efficacious in partly restoring the typical vasodilator and natriuretic effects of DA. Thus, in hydro‐saline depletion, DA produced sympathomimetic effects which were sufficiently intense to outweigh those due to activation of specific DA renal receptors.
Hypocapnia and hypercapnia in the dog: effects on myocardial blood‐flow and haemodynamics during beta‐ and combined alpha‐ and beta‐adrenoceptor blockade
Authors: Wexels J. C. , Myhre E. S. P.
Published: April 2008

Summary. We have recently demonstrated an increase in myocardial blood‐flow (MBF) during systemic hypercapnia independent of myocardial oxygen consumption. During hypocapnia no significant decrease of MBF was observed; however, a significant increase of myocardial oxygen extraction resulted. The present study was undertaken to examine whether these effects were caused by changes in the sympathoadrenal activity. During beta‐adrenoceptor blockade and combined alpha‐ and beta‐blockade the effects of hypocapnia and hypercapnia on MBF and haemodynamics were examined. Closed‐chest dogs were anaesthetized with pentobarbital and hypocapnia was induced by hyperventilation. Carbon dioxide was added to the inspiratory gas to create normocapnia and hypercapnia. Hypocapnia did not result in any changes of MBF, coronary vascular resistance or myocardial oxygen extraction, neither during beta‐adrenoceptor blockade nor during combined alpha‐ and beta‐blockade. Hypercapnia did not increase MBF, neither during beta‐blockade nor during combined alpha‐ and beta‐blockade. However, both myocardial oxygen consumption and mechanical performance of the heart were reduced during hypercapnia. Thus, a relative myocardial overperfusion, indicated by decreased coronary vascular resistance and myocardial oxygen extraction, was observed during hypercapnia. In conclusion, the unaltered MBF during hypocapnia and the coronary overperfusion during hypercapnia were not related to changes in the sympathoadrenal activity.
Changes in coronary haemodynamics and myocardial metabolism at rest and during exercise after a cardiotonic drug (prenalterol) in patients with coronary artery disease
Authors: Westheim A. , Bae E. , Christensen C. C. , Fønstelien E. , Grendahl H. , Muller O.
Published: April 2008

Summary. To elucidiate the myocardial metabolic and haemodynamic effects of an inotropic drug in patients with coronary artery disease (CAD) without evident congestive heart failure (CHF), the acute effects of prenalterol were studied in nine patients. Patients with documented CAD by leftsided cardioangiography and end‐diastolic pressure >15 mm Hg were included in the study. They were examined at rest and during supine exercise at a level just below their anginal threshold before and after prenalterol.

At rest, rate pressure product (RPP) increased by 40% (P<0·01), cardiac index rose 20% (P<0·01), cardiac venous flow (CVF) increased by 18% (P<0·05), and myocardial oxygen consumption (MVO2) increased by 20% (P<0·05) after prenalterol administration. Despite a decrease in mean pulmonary capillary venous pressure (PCV) of 40% (P<0·01), myocardial lactate extraction fell significantly (P<0·01) and lactate production was observed in three of nine patients compared to before prenalterol administration. During exercise, RPP increased by 20% (P<0·01), cardiac index remained unchanged, CVF increased by 25% (NS) and MV02 showed a tendency to an increase (NS) after prenalterol administration. Mean PCV pressure decreased by 30% (P<0·01). Myocardial lactate extraction was markedly reduced during exercise (P<0·01) and five of nine patients showed lactate production compared to that before prenalterol administration. Thus, despite a decrease in left ventricular filling pressure, increased myocardial oxygen demand occurred after acute administration of prenalterol. Prenalterol and probably similar inotropic drugs should be used cautiously in patients with CAD without clinical evidence of congestive heart failure.
Effects of propranolol and verapamil on plasma ionized calcium and parathyroid hormone in short‐term intense isokinetic leg exercise
Authors: Joborn H. , Bergström R. , Rastad J. , Wide L. , Åkerström G. , Ljunghall S.
Published: April 2008

Summary. Physical exercise, beta‐adrenergic stimulation and calcium channel blockade can affect calcium homeostasis. The present study investigated, in eight healthy males, the effects of orally administered propranolol or verapamil during a 2‐min maximal, isokinetiC., leg exercise.

Immediately after exercise the plasma ionized calcium concentrations were increased, in control and drug tests, by 5–6%, and within 5 min of recovery they were almost returned to baseline. Serum parathyroid hormone (PTH) concentrations were unchanged at termination of exercise, but they increased during the first 5 min of recovery, coincident with the decline in calcium concentrations, which, however, were still elevated. Neither verapamil nor propranolol selectively changed basal or exercise plasma ionized calcium or serum PTH concentrations. Muscle strength, blood pH, lactate concentrations and plasma volume changes were not affected by any drug. Verapamil did not have any specific effect on the concentrations of plasma magnesium, phosphate, potassium or sodium while propranolol increased the concentrations of plasma potassium and decreased those of phosphate during exercise as well as recovery.
The low physical working capacity of thyrotoxic patients is not normalized by oral antithyroid treatment
Authors: Sestoft L. , Saltin B.
Published: April 2008

Summary.The low working capacity in thyrotoxic patients has not been quantified and its causes have not been clarified. We studied the working capacity in nine thyrotoxic patients at diagnosis (test 1), after 3 months of oral antithyroid medication (test 2), and in four of them again after 1 year (test 3). The maximum power output was low in thyrotoxic patients (1·65 ±0·15 W/kg‐1) and was not significantly higher after 3 months of treatment (1·84 ±0·15), although plasma thyroid hormone concentrations had been normalized for approximately 3 months. After 1 year's treatment the maximum power output was still somewhat low in the four tested patients (2·75 ±0·34). The rate of oxygen uptake under maximum exercise was low (26 ml/ min‐1/kg‐1) and was not significantly increased at test 2 and 3. The net mechanical efficiency was low at test 1 and 2 (18·9 ±2·1% and 20·1 ± 1·8%, respectively), but was normal at test 3 (25·2%). At all three tests the blood lactate response upon maximum exercise attained only about 50% of normal concentration.

Thus, low work capacity in thyrotoxic patients remained for a long period of time after euthyroid conditions had been attained. The low capacity was due to low aerobic and anaerobic capacities and initially also to a low mechanical efficiency.
Prostacyclin and regional coronary blood flow in experimental myocardial infarction
Authors: Herbaczynska‐Cedro K. , Karwatowska‐Prokopczuk E. , Michalowski J. , Wennmalm Å.
Published: April 2008

Infusion of prostacyclin (PGI2) has been reported to affect infarct size and myocardial blood flow favourably in various animal models of myocardial ischaemia. Recent data suggest that a similar effect of PGI2 may occur also in humans with acute myocardial infarction. We addressed the hypothesis that PGI2 redistributes myocardial blood flow following coronary ligation, and that this effect favours perfusion of myocardium at risk and thereby limits infarct size. Following ligation of a distal branch of the left coronary artery in anaesthetized dogs, PGI2 (2–4 ng/kg/min) was infused for 72 h. Regional myocardial blood flow was assessed immediately after the coronary ligation and at the end of the drug infusion, by injection of 57Co‐ and 113Sn‐labelled microspheres, respectively. Coronary ligation reduced regional coronary blood flow by 40–70%. During the subsequent 72 h the blood flow increased, being at the end of the period 50–70% of the flow in the non‐ischaemic myocardium. PGI2 did not affect the spontaneous improvement of regional myocardial blood flow, as assessed at the end of the infusion. PGI2 also failed to affect infarct size, either when expressed in relation to total left ventricular mass, or in relation to area at risk. We conclude that PGI2, when infused immediately after coronary ligation in dogs in a clinically relevant dose, neither affects regional myocardial blood flow in the ischaemic regions, nor the size of the myocardial infarction.
Regional blood volume in man determined by radiolabeled erythrocytes
Authors: Vissing S. Fløistrup , Nielsen S. Levin
Published: April 2008

The purpose of the present study was to develop a non‐invasive method capable of measuring the regional blood volume in the peripheral circulation. External counting of autologous radiolabeled erythrocytes was performed by dynamic scintigraphy of the calf. During short venous stasis synchronous changes in segmental blood volumes were recorded by plethysmography, thereby obtaining a calibration factor. The recordings were performed with the position of the calf varying between elevated, horizontal and lowered before and after 4·5 min venous stasis with a tourniquet pressure on 57 mmHg applied above the knee. The mean blood volume comprised 3·2 (1·2 ml per 100 ml tissue in the elevated position, 6·0 (1·6) in the horizontal position and 9·8 (2·6) in the lowered position. Correspondingly, the blood volume increase during venous stasis was 120%, 60% and 20% in the three positions. Studies of the reproducibility showed a coefficient of variation of 13.5%. The present study suggests that the method of blood volume measuring should be further evaluated to study the function of capacitance vessels.
Right and left ventricular performance during endotoxin‐induced pulmonary hypertension in sheep
Authors: Hüttemeier P. C. , Eliasen K. , Ringsted C. , Mogensen T. , Jensen H. , Nielsen S. Levin
Published: April 2008

Summary. We investigated right and left ventricular performance by radionuclide angiocardiography in anaesthetized and instrumented sheep following a (1.5 μg/kg) sublethal Escherichia coli endotoxin infusion. Six animals served as controls and five were pre‐treated with intravenous Ibuprofen (12 mg/kg). In control sheep an acute five‐fold increase of pulmonary vascular resistance (PVR) resulted in a significant decrease of right ventricular ejection fraction (RVEF) and stroke volume. Left ventricular ejection fraction (LVEF) was unchanged as was pulmonary capillary wedge pressure (PCWP). The calculated right and left ventricular end‐diastolic volumes (RVEDV; LVEDV) changed significantly in opposite directions during the acute increase of PVR. Right ventricular end‐diastolic pressure increased significantly paralleled by an increase of RVEDV. The decrease of LVEDV with an unchanged PCWP suggested a decrease of left ventricular compliance. Pre‐treatment with Ibuprofen resulted in complete cardiovascular stability after endotoxin.
HYPOTHESES. Coffee, catecholamines and cardiac arrhythmia
Authors: Wennmalm Å. , Wennmalm M.
Published: April 2008

Summary. It is generally agreed that a high release of noradrenaline in the heart may elicit cardiac arrhythmia. Furthermore, administration of aminophylline to patients with ischaemic heart disease frequently elicits ventricular premature beats and ventricular tachycardia. Recent data from animal experiments demonstrate that methylxanthines (aminophylline, caffeine, theophylline) can facilitate noradrenaline release from sympathetic nerve endings. Such facilitation of transmitter release is amplified when myocardial oxygenation is impaired, stressing its clinical significance in relation to ischaemic heart disease. If a similar amplification is also operative in man, a dose of methylxanthine causing a very modest increase in myocardial sympathetic transmitter release in the heart of a healthy subject may be sufficient to cause a three‐to six‐fold elevation in the local myocardial concentration of noradrenaline in a patient with ischaemic heart disease. We hypothesize that such hypoxia‐induced facilitation of sympathetic transmitter release lies behind the reported connection between cardiac events and methylxanthines, for instance sudden cardiac death following coffee consumption.
Single and multiple breath nitrogen wash‐out—closing volume and volume of trapped gas for detection of early airway obstruction
Authors: Dahlqvist M. , Alexandersson R. , Nielsen J. , Hedenstierna G.
Published: April 2008

Summary. Thirty‐eight patients with varying degrees of peripheral airway involvement were studied by flow–volume curves and two nitrogen wash‐out techniques in an on‐site study. Closing capacity (CC), closing volume in percentage of vital capacity (CV%), slope of the alveolar plateau (phase III), volume of trapped gas (VTG), and maximum expiratory flow at 50 and 75% of vital capacity (MEF50, MEF25) were determined and correlation analyses were performed.

A biphasic or exponential correlation was noted between the degree of airway closure and VTG with rapidly increasing VTG at high CC. Although there were correlations between spirometry and the two nitrogen wash‐out techniques, a large scatter precluded the use of the flow–volume variables to predict CC, CV% and VTG.

The coefficient of variation was lower for the measurements of CV% than for the recording of VTG. Since the single breath nitrogen wash‐out technique is also technically simpler it is recommended prior to the multiple breath technique.
Blood volume after coronary artery bypass grafting
Authors: Ivert T. , Pehrsson S. K. , Landou C. , Magder S. , Holmgren A.
Published: April 2008

Summary. Patients with stable angina pectoris are reported to have a markedly reduced blood volume (BV). In the present study, average BV was still 19% less than that predicted in 77 men examined 5 years after coronary artery bypass grafting. Beneficial effects of the operation such as relieved angina, absence of medication, complete revascularization status at repeat angiography, and restored physical fitness were not found to be associated with a normalization of the BV. No significant correlation was found between BV and body weight, heart volume, exercise capacity, ejection fraction or left ventricular end‐diastolic pressure.

The reduced BV in patients with angina pectoris after successful revascularization and the absence of correlation with physiological variables indicate a persisting disturbed regulation mechanism.
Intrathoracic microvascular circulation in haemorrhagically shocked rats. Studies by fluorescence techniques
Authors: Perbeck L. , Lund F. , Thulin L.
Published: April 2008

Summary. The microvascular circulation in the heart, lung and thymus was studied by fluorometry in 32 haemorrhagically shocked rats. Exsanguination to a blood pressure of 35 mmHg for 180 min did not result in any reduction of this circulation in the heart or lung, but in the thymus it was reduced by 52%. Retransfusion of shed blood caused no change in cardiac microcirculation, whereas the microcirculation in the thymus was increased by 59%. In the lungs a heterogeneous fluorescence pattern was observed after retransfusion, with large dark areas alternating with normal fluorescent ones and even some small intensively fluorescent areas. After retransfusion, maldistribution of blood flow seems to be a phenomenon of haemorrhagic shock in the lungs.
Post‐exercise platelet activation—aggregation and release in relation to dynamic exercise
Authors: Naesh O. , Hindberg I. , Trap‐Jensen J. , Lund J. O.
Published: April 2008

Summary. Relatively scarce information is found on the period immediately following physical stress, with special reference to human platelet activity. This, in connection with earlier observations of an increase in platelet release products and hyperaggregability following surgical stress, has initiated the present study. We studied platelet function in eight healthy non‐medicated volunteers during and 1 h after cycle exercise of sub‐maximal intensity. ADP‐induced platelet aggregability was enhanced in the last minute of exercise followed by a decreased aggregability 1 h after. Adrenaline‐induced platelet aggregation showed the same attenuation after exercise but no change during work. The release products β‐thromboglobulin and serotonin in plasma showed significant increases after exercise. This is taken as evidence of an enhanced platelet activity following exercise. A normal stress‐response, measured as increase in cyclic AMP in plasma, was observed. In conclusion, platelets are activated following moderate exercise and it seems valid to include the post‐exercise period in future studies.
Coronary circulation in acute hypoxia
Authors: Kaijser L. , Grubbström J. , Berglund B.
Published: April 2008

Summary. Healthy young men were subjected to different degrees of hypoxia at rest and during increased levels of cardiac work induced by atrial pacing and physical exercise at submaximal and maximal loads. Coronary sinus (cs) blood flow was measured by thermodilution and a‐cs differences of O2 and lactate were obtained. At low cardiac power output (rest, pacing) the reduction in arterial oxygen content was compensated for mainly by a more complete myocardial oxygen extraction producing lowered cs O2 saturation and tension, while at higher cardiac power (exercise) the compensatory mechanism was entirely an increased coronary blood flow. It was possible to compensate fully for a reduction in arterial O2 saturation of 9% even during maximal physical exercise. With a reduction in arterial oxygen content of more than 20–25% the flow increase was sufficient to supply the heart with enough O2 during submaximal (heart rate 157 beats min‐1) but not maximal exercise, in which case anaerobic glycolysis contributed significantly to the myocardial energy metabolism. It is concluded that the normal heart has a ‘coronary flow reserve’ of about 33% above the flow prevailing during maximal physical exercise under air breathing.
Endothelium‐derived constricting factor(s): the last novelty—endothelin
Authors: Karwatowska‐Prokopczuk E. , Wennmalm Å.
Published: April 2008

The vascular endothelium is not merely a passive physical barrier between the blood and the tissue surrounding the blood vessel, but may actively participate in key processes of metabolic, secretory, and vasoregulatory character. In addition, the endothelium plays an important role in the control of platelet activation. Under certain conditions endothelial cells have been shown to produce powerful vasodilators, like endothelium‐derived relaxing factor (EDRF) and prostacyclin (GPI2), and vasoconstrictors like endothelium‐derived constricting factor (EDCF) and endothelin (ET) (Griffith el al., 1988; Vanhoutte & Katusic, 1988). In contrast to the extensive studies performed to characterize the actions and nature of EDRF, recently identified chemically as nitric oxide (Moncada et al., 1988), relatively little is known about EDCF(s). This paper reviews recent data on EDCF, with special emphasis on the newly discovered vasoconstrictor peptide, endothelin (ET).
Muscle strength in hyperthyroid patients before and after medical treatment
Authors: Celsing F. , Westing S. H. , Adamson U. , Ekblom B.
Published: April 2008

Summary. Ten hyperthyroid patients were assessed for muscle strength before and after a period of medical treatment that averaged 12 months. The subjects did not change their habitual level of physical activity between the two test occasions. Maximal voluntary isokinetic knee extensor muscle strength was determined during various concentric, eccentric and isometric conditions. Average increases in strength from before to termination of treatment ranged from 25 to 41% for the concentric and isometric tests (P<0·01, n= 10), and from 19 to 35% for the eccentric tests (P<0·01, n= 6). The present study demonstrates that medical treatment of hyperthyroid patients results in a marked increase in muscle strength.
Diminished meal‐induced thermogenesis in elderly man
Authors: Thörne A. , Wahren J.
Published: April 2008

Summary. The purpose of this study was to examine the possible influence of age on the thermogenic response to a mixed meal in healthy subjects. Twenty‐five healthy male subjects participated in the study and they were divided into three groups, comprising 10 young subjects with an average age of 27 years (22–35 years), seven middle‐aged individuals (51 years, 42–60 years) and eight elderly men (70 years, 67–74 years). They were all studied with continuous indirect calorimetry in the basal state and for 3 h after the ingestion of a mixed meal in liquid form. The size of the meal corresponded to 60% of the individually computed 24‐h basal energy expenditure.

Resting energy expenditure was lower in the elderly men than in the young ones when expressed in absolute values (P<0.001) as well as in relation to body weight (P<0.01) and body surface area (P<0.01). After the meal energy expenditure increased rapidly and reached a relatively constant level after 60 min in all groups; the average increase above the basal level during the whole postprandial period was less in the elderly (21.1±2.5%, P<0.01) and the middle‐aged (24.2±1.7%, P<0.05) than in the young (28.6±1.6%) men.

It is concluded that the thermogenic response during the first 3 h following a mixed meal decreases with age and that this diminished meal‐induced thermogenesis may contribute to lower nutrient requirements in old age.
A morphometrical comparison of right and left whole human vastus lateralis muscle: how to reduce sampling errors in biopsy techniques
Authors: Lexell J. , Taylor C. C.
Published: April 2008

Summary. In studies of the effects of different training programmes, one muscle—most commonly the vastus lateralis—is used for the experiment while the contralateral muscle serves as a control, at the same time as muscle biopsies are taken from both sides. In order to increase the reliability of such studies, the sources and the magnitude of the sampling errors in the biopsy techniques need to be assessed in detail. In this study, cross‐sections of whole right and left vastus lateralis muscle from six young sedentary right‐handed men were prepared, and the total number and size of fibres and the proportion of the different fibre types were caluclated. A significant difference (P < 0·05‐P < 0·001) between the right and the left muscle was found for at least one of the three variables in each of the six men, but there was no systematic difference and, therefore, no significant right‐left difference for the whole group. The maximum difference between the right and the left side for the mean fibre size was 25% and for the fibre type proportion 5%; these differences are much smaller than the known variation within individual muscles. In conclusion, any study involving biopsies from both the right and the left vastus lateralis may use either muscle for the experiment while the contralateral muscle serves as a control without leading to systematic sampling error, whereas the errors involved in taking small samples from each muscle are much more important to control and to reduce.
Oesophageal transit in patients with autonomic dysfunction. The effect of treatment with fludrocortisone
Authors: Jørgensen F. , Boesen F. , Andersen E. B. , Hesse B.
Published: April 2008

Summary. Oesophageal function was examined by radionuclide transit measurements in 15 patients with severe autonomic deficiency and orthostatic hypothension and 23 healthy volunteers. Seven of the patients were re‐examined after treatment for 3 weeks with fludrocortisone acetate (Florinef®). Six patients and five control subjects were evaluated before and after i. v. administration of atropine.

The mean transit time (MTT) was prolonged (P<0.007) and the residual activity increased (P= 0.038) in the patients compared with the control group. Prolonged MTT was associated with oesophageal symptoms.

Treatment of orthostatic hypotension with fludrocortisone acetate significantly reduced MTT. Atropine increased MTT and residual activity. The increase in heart rate after atropine was correlated in the patients with MTT before treatment.

The results demonstrate the frequent presence of impaired oesophageal function in patients with severe autonomic dysfunctiion, irrespective of aetiology. The impairment seems to be closely relatded to parasympathetic insufficiency. The improvement after fludrocortisone may suggest an influence of ion balance on oesophageal function in these patients.
Preserved CO2 response in cerebral and muscular blood vessels during cimetidine treatment
Authors: Saunier C. , Audibert G. , Hartemann D. , Sautegeau A. , Amend P. , Bigard O. , Alvernhe C.
Published: April 2008

Summary. It is known that cimetidine inhibits the hypoxia‐induced increase in cerebral blood flow (CFB) in dogs, but the mechanism of this inhibition is not fully understood.

Since the accepted mechanisms explaining the increase in CBF during hypercapnia are very different from those active during hypoxia, acute hypercapnia was induced in 12 conscious dogs in order to study the cimetidine effect in this condition. Six dogs were given i.v. saline (control group) and the other six, i.v. cimetidine (4 mg kg1). After 15 min, CBF and various muscular blood flow measurements were performed, using the microspheres technique under two conditions: (1) breathing air and (2) after 2 h inhalation of a gas mixture with Fico2 0·10, Fio2 0·21 in nitrogen. The CBF increase was similar in both series with or without cimetidine. The changes in muscular blood flow were unaffected by the H2blocker. We conclude that cimetidine has no effect on the CBF and on muscular blood flow during acute hypercapnia.
Effect of coronary bypass surgery on anaerobic myocardial lactate metabolism during pacing‐induced angina pectoris
Authors: Kaijser L. , Gunnes S. , Berglund B.
Published: April 2008

Myocardial lactate metabolism was studied by coronary sinus catheterization in nine patients before and 8–12 months after coronary bypasss surgery. Measurements were performed at rest and during atrial pacing increased to a heart rate which produced strong chest pain. The estimation of myocardial lactate extraction and release was facilitated by a constant rate infusion of 14C lactate and coronary sinus blood flow (CSBF) was measured by thermodilution. Pre‐operatively strong chest pain could be elicited in all patients and isotope data indicated a significant myocardial lactate release in all of them, although the net a‐cs difference was negative in only half of them. After bypass surgery the maximum tolerable heart rate was increased by 23 beats min1 and chest pain both at heart rate 110 beats min1 and at the highest heart rate achieved was reduced or absent in eight of the nine patients. The increase in chest pain during pacing was quantitatively related to the increase in myocardial lactate release, and the correlation between these two variables followed the same course after the operation as it did before. It is concluded that the improvement in chest pain limited cardiac performance after bypass surgery is well correlated with the improvement in myocardial aerboic metabolism.
Ischaemic heart disease and the changes in the QRS and ST segments during exercise: a pilot study with a novel vectorcardiographic system
Authors: Pilhall M. , Riha M. , Jem S.
Published: April 2008

Summary. In order to find new ischaemic parameters, the spatial changes of the Frank vectorcardiogram were continuously analysed with a new, highly precise vectorcardiographic method during, and immediately after a maximal exercise test. This was done in 18 young healthy males, and 18 patients with scintigraphic reversible ischaemia.

During exercise, different patterns between the groups were noted for the changes in the mean QRS magnitude in the Y‐lead (P< 0.005), the QRS‐integral (P<0.05), and the QRS‐duration (P<0.05). Immediately after exercise, several QRS parameters in the normal group continued to change according to the same pattern as during exercise (P<0.05), which was in contrast with the patterns of the ischaemic group (P<0.01). The spatial ST difference at J+20 ms discriminated well between the groups, especially when corrected for QRS‐magnitudes at rest and heart rate (P< 0.0005).

In short, this pilot study supports previous findings in that changes in amplitude and duration of the QRS complex during exercise discriminated between healthy young males and patients with ischaemic heart disease. Moreover, rapid discriminating changes were seen in the QRS segment during cessation of exercise. These changes deserve attention since they may be of importance for the conflicting results on the diagnostic value of QRS changes during exercise.
Non‐invasive assessment of vessel‐wall changes in hypertensives and normotensive controls
Authors: Lemne C. , Jogestrand T. , de Faire U.
Published: April 2008

Summary The aim of this study was to evaluate the feasibility of non‐invasive assessment of vessel wall changes in early, untreated hypertension. Measurement of intimal+medial (I‐M) thickness in the common carotid artery (CCA) using B‐mode ultrasound imaging showed no differences between 12 patients with untreated, newly diagnosed hypertension and 9 age‐matched controls (0.63 mm vs 0.63 mm just proximal to the carotid bulb).

Echocardiography showed that the hypertensive group had thicker left ventricular walls (LVW) than the normotensive group. Correlation analyses disclosed that I‐M thickness was significantly associated with age (r= 0.63; P<0.05) for the whole material but not with blood pressure levels, serum lipids, or LVW thickness. These results imply that the arterial I‐M layers of the CCA are less responsive to pressure overload than the left ventricle.

The feasibility of using I‐M thickness as an early marker of structural vessel wall changes in hypertensive patients must await results from large scale prospective studies. In view of the present results, age homogenous materials should be selected for such studies.