bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of glomerular filtration rate in adults: accuracy of five single‐sample plasma clearance methods
Authors: Rehling M. , Rabøl A.
Published: April 2008

Summary. After an intravenous injection of a tracer that is removed from the body solely by filtration in the kidneys, the glomerular filtration rate (GFR) can be determined from its plasma clearance. The method requires a great number of blood samples but collection of urine is not needed. In the present investigation the total plasma clearance of 51Cr‐EDTA (ethylenediaminetetra‐acetate) was assessed from 13 blood samples taken 5–300 min post‐injection in 44 adult patients with GFR>15 ml min‐1. In 34 of these patients the plasma clearance of 99Tcm‐DTPA (diethylenetri‐aminepenta‐acetate) was determined simultaneously. Using these clearance values as reference the accuracy of six simplified methods were studied: five single‐sample methods and one five‐sample method. The standard error of estimate (SEE) of the single‐sample methods ranged from 4·2 to 7·5 ml min‐1 using EDTA, and from 3·8 to 6·3 ml min‐1 using DTPA. SEE of the five‐samples method was 3·0 ml min‐1 (EDTA) and 3·1 ml min‐1 (DTPA). The single‐sample methods given by Christensen & Groth (1986) and by Tauxe (1986) are recommended for daily use, as SEE was small even at low GFR values. In patients with GFR < 80 ml min‐1, in whom a highly accurate determination is needed, a multiple samples method is recommended, e.g., Brøchner‐Mortensen (1972).
Arm and leg composition determined by computed tomography in young and elderly men
Authors: Rice C. L. , Cunningham D. A. , Paterson D. H. , Lefcoe M. S.
Published: April 2008

Summary. Five computed tomography (CT) scans were taken at measured intervals of the legs and arms of young (n=7) and elderly (n=13) men. Cross‐sectional areas (CSA) of the total limb, muscle plus bone and bone were measured in each scan, and skin plus subcutaneous tissue areas were calculated by subtraction. In addition, in the arm scans the CSA of the extensor and flexor compartments were measured, and in the leg the CSA of the plantar flexor compartment. A value for lean muscle within these compartments was calculated by excluding non‐muscle tissue using density measurements based on Hounsfield units. Related volumes for the various components were also calculated using geometric formulae. The results showed that elderly limbs were of a similar overall size as the young, but elderly muscles were smaller (28–36%) with greater amounts of non‐muscle tissue located within a muscle, particularly in the plantar flexors (81% more than in the young). Elderly arms had a greater amount of skin plus subcutaneous tissue than the young, but there was no difference in the legs. Muscle volumes were similar to in vitro results reported from cadaver studies and can be predicted from single mid‐limb CT scans using regression equations. These results illustrate that, due to the substantially reduced amount of ‘pure’ muscle tissue in the elderly, comparisons of relative strength with other populations may be misleading unless appropriate measurements of muscle size are considered. Methods to estimate in vivo physiological CSA, which is considered the best means of normalizing strength, have been demonstrated in this study.
On the consistency of ECG reports from two different computer‐based ECG recorders
Authors: Jakobsson A. , Pahlm O. , Reichert L. , Edenbrandt L. , Nilsson B.
Published: April 2008

Summary. Four consecutive computer‐based ECG recordings/interpretations were made on each of 100 patients. Two of the recordings were made with the MAC II recorder (Marquette Electronics Inc., Milwaukee, USA) and two with the Cardisuny IC503FA (Fukuda M‐E Kogyo Co. Ltd, Tokyo, Japan). Computer measurements of PQ interval, Q‐width in III, R‐amplitude in V5 and QRS axis in the frontal plane were compared between recordings, as also were diagnostic statements pertaining to the presence of atrial fibrillation and myocardial infarction.

The MAC II was found to be more consistent than the Cardisuny as regards the measurements. There was a tendency that the MAC II was more specific than the Cardisuny and the Cardisuny more sensitive than the MAC II. The MAC II gave no false positive reports of atrial fibrillation and only one false positive report of myocardial infarction.
Exercise thallium‐201 scintigraphy in the localization of myocardial ischaemia
Authors: Korkeila P. , Hietanen E. , Parviainen S. , Virkki R. , Hartiala J.
Published: April 2008

Summary. We performed a retrospective study in order to study the ability of thallium‐201 exercise scintigraphy to detect and to localize coronary artery perfusion defects (in comparison with a recent coronary angiogram). We studied 81 patients (67 males); their average age was 52.3 years (men 50.5 and women 54.1 years). They performed a pulse‐conducted cycle exercise test, and 2 min before end of exercise 75 MBq of thallium‐201 was infused intravenously, and tomographic images were reconstructed by using a Siemens‐Rota SPECT gamma camera immediately and 4 h after exercise. The thallium‐201 uptake defects were attributed to different coronary arteries, and the results were compared with a coronary angiogram made afterwards in 48 patients. The groups of one‐, two‐ and three‐vessel disease were 27, 21, and 21 patients, and only 12 patients did not have significant (over 50%) stenoses. The latter had the highest ejection fraction and working capacity. Sensitivity of thallium‐201 exercise scintigraphy was 65%, whereas that of exercise ECG was 41% in patients with a low ejection fraction, while in the whole material the sensitivity of thallium‐201 scintigraphy was 91% and that of exercise ECG was 54%. A stenosis in the right coronary artery was best localized by the thallium‐201 scintigram (86% correctly); a stenosis in the left anterior descending artery was localized correctly in 75% of the cases, but a stenosis in left circumflex artery was localized correctly only in 44%. We conclude that exercise thallium‐201 scintigraphy is a useful method not only in detecting but also in localizing coronary artery disease.
Discrepancy between estimated energy intake and requirement in female dancers
Authors: Dahlström M. , Jansson E. , Nordevang E. , Kaijsery L.
Published: April 2008

Summary. Dietary intake of energy, protein, fat and carbohydrates in female dance students compared to female music students was estimated by a dietary history method. Energy requirement was estimated from body weight and physical activity both by a standard formula and from the measured work intensity during dance training. Meal patterns showed significant differences in four types of meals on weekdays and in one type on weekends. The intake of protein, fat and carbohydrates in absolute amounts and the percentage of energy derived from protein were not significantly different between the two groups. The fraction of energy derived from carbohydrates was higher and that from fat was lower in the dancers than in the musicians. Energy intake was of similar magnitude for the dancers and the musicians (8·3±1·9 MJ vs. 8·3 ±1·7 MJ), while the estimated energy requirement was greater for the dancers (10·3±0·7 MJ vs. 8·9±0·4 MJ). The reason for the apparent discrepancy between energy intake and energy requirement of approximately 2 MJ in the dancers is not obvious. The energy intake may have been underestimated. Alternatively, the energy requirement may have been overestimated. The resting metabolic rate may have been depressed by years of low energy intake. In addition, as suggested by some authors, training as such may lower the resting metabolic rate as well as the diet‐induced thermogenesis.
Atrial natriuretic factor and central venous pressure during intermittent and continuous lower‐body positive pressure in healthy humans
Authors: Kellers N.
Published: April 2008

Summary. In eight healthy volunteers undergoing 16 experiments in a cross‐over design central venous pressure (CVP) and atrial natriuretic factor (ANF) in central venous plasma were measured during a 30 min control period followed by three separated periods of 10 min lower‐body positive pressure (LBPP) or 90 min continuous LBPP induced by inflation of a military anti‐G suit to evaluate the effect of short repeated and of extended increases in right atrial pressure on plasma ANF levels. CVP increased significantly during each of three separate periods of intermittent LBPP, and 15 min after application of continuous LBPP (P<0·025 for all). Blood pressure and heart rate did not change. During intermittent LBPP plasma ANF levels increased 10 min after the first inflation of the MAGT‐suit (P= 0·013), but not after the second or third inflation. During continuous LBPP plasma ANF remained unchanged until 90 min after application of LBPP where a significant rise was observed (P= 0·023). The data demonstrate that the ANF response to short‐term increases in right atrial pressure, as small as 2·5 mmHg, is maximal within 10 min and that repeated pressure stimuli may decrease ANF release. Sustained increases in right atrial pressure are not associated with increases in plasma ANF until long after initiation of the pressure stimulus suggesting rapid receptor‐binding of ANF and that the ANF receptors might be saturated during continuously elevated ANF levels.
Influence of local β‐adrenoceptor blockade on exchange of fat and glucose in the human leg after surgery
Authors: Håkanson E. , Rutberg H. , Jorfeldt L.
Published: April 2008

Summary. The metabolic effects of the local administration of propranolol were determined in seven patients undergoing cholecystectomy. Measurements were carried out in the early postoperative period before and after infusion of 2 mg of intraarterial propranolol into the femoral artery of one leg using the other leg as control. Blood flow and arterio‐venous concentration differences for oxygen, glucose, lactate, alanine, glycerol and total FFAs were determined. Uptake and release of FFAs were determined by using a tracer technique. The statistical analyses were based on differences between the test and the control leg in changes following the blockade.

Glycerol release was significantly more suppressed in the test leg than in the control leg. No difference between the legs was seen in the uptake of oxygen, FFA and glucose or the release of lactate and alanine. The arterial concentration of propranolol was 6·07 ± 0·72 ng ml‐1 (mean ± SEM).

This study indicates that a local β‐blockade by intra‐arterial propranolol infusion after surgery slightly reduces the postoperative lipolysis in leg tissues but does not influence or only marginally influences leg blood flow and oxygen uptake or the exchange of glucose, lactate and alanine after moderate surgical trauma.
Small accumulation of inosine monophosphate (IMP) despite high lactate levels in latissimus dorsi during transplantation
Authors: Norman B. , Hedén P. , Jansson E.
Published: April 2008

Summary. The effects of prolonged ischaemia and subsequent reperfusion during and after reconstructive microsurgery on energy metabolism were studied. Repeated skeletal muscle biopsies were taken and analysed for high energy phosphates and their degradation products by high performance liquid chromatography and for lactate by a fluorometric procedure. Moderate changes in adenine nucleotides occurred during the first 4 h of ischaemia. After 6 h of ischaemia, when the creatine phosphate store was almost depleted and the lactate level had increased to 111 mmol kg1 dry muscle, ATP content decreased and inosine monophosphate started to accumulate. The inosine monophosphate accumulation was however small, in spite of a high lactate level, which suggests that the increase in H+ associated with lactate formation is not important for the activation of AMP‐deaminase during the present conditions. In spite of the accelerating metabolic deterioration during the later period of ischaemia, the reperfusion of the muscle resulted in a rapid normalization of all the studied metabolites, thereby indicating a rapid restoration of the muscle energy stores.
The forearm and leg perfusion techniques in man do not give the same metabolic information
Authors: Möller‐Loswick A.‐C. , Bennegård K. , Lundholm K.
Published: April 2008

Summary. The present study evaluates whether forearm and leg perfusion techniques give the same metabolic information. Seven patients hospitalized for operation of uncomplicated disease were investigated pre‐operatively in the fasted state, while seven other patients who were on intravenous nutrition were studied in the fed state. Blood flow and the extremity exchange of glucose, lactate, glycerol, free fatty acids and amino acids were measured simultaneously across the forearm and the leg in all individuals.

In the fasted state the arteriovenous difference (a‐v) of glucose uptake was statistically significant across the forearm while it was statistically insignificant across the. leg (0·27 ± 0·06 vs. ‐0·04±0·13 mmol l1). The a‐v differences of glycerol (0·025 ± 0·028 vs. ‐0·043 ± 0·013 mmol l1) and free fatty acids (0·10 ± 0·03 vs. ‐0·10 ± 0·04 mmol l1) were positive across the forearm while they were negative across the leg (P < 0·01). In the fasted state the a‐v difference of oxygen uptake (3·93 ± 0·67 vs. 3·21 ± 0·44 mmol l1) and blood flow (4·1 ± 1·0 vs. 4·0 ± 0·7 ml min1 100 g1) did not differ between the arm and the leg, but the a‐v difference in carbon dioxide production was significantly higher (P<0.05) across the forearm (2·43 ± 0·37 vs. 1·29 ± 0·29 mmol l1) compared to the leg. In the fed state all the above‐mentioned differences between forearm and leg became statistically insignificant. In the fed state the a‐v difference of the sum of all amino acids was not significantly different from zero balance across the forearm (‐146 ± 103 mmol l1) while there was a significant release from the leg (‐175 ± 6 mmol l1, P<0.05). In the fed state the flux of the sum of all amino acids became significantly positive across the arm while it was not significantly different from zero balance across the leg. In the fed state, forearm blood flow was significantly higher than leg blood flow (6·2 ± 0·5 vs. 4·0 ± 0·2 ml min1 100 g1, P<0.001).

The results in the present study demonstrate that the metabolic balance across regions of peripheral tissues may simultaneously differ considerably, i.e. being positive across the forearm and negative across the leg. This fact may imply that some previous claims may need reconsideration about ‘peripheral tissue metabolism’ associated with a certain clinical condition.
QRS scoring with the Mason‐Likar lead system at rest and during ischaemia
Authors: Walamies M.
Published: April 2008

Summary. The stability of the post‐infarction simplified 29‐point Selvester QRS score during maximal exercise testing was studied using both standard 12 and Mason‐Likar (modified standard, M‐L) ECG lead systems. Thirty‐eight patients participated in the standard exercise test (mean interval after single infarction 4 months) and a total of 54 patients underwent exercise 201thallium emission tomography with M‐L lead system 2 months later. None had electrocardiographic features complicating the scoring. There were no significant differences between the (paired) mean QRS scores, except between the M‐L score at rest (2·3 ± 2·4) and at exercise (3·2 ± 2·6, P< 0·01). The correlation coefficient (r) between resting scores was 0·87, between rest and exercise 0·90 (standard leads) and 0·80 (M‐L leads). In 78% nuclear imaging revealed ischaemia, but this had no significant effect on the mean scores or correlation between rest and exercise scores. It is concluded that the QRS score is relatively stable during exercise with standard leads if the limb leads are recorded immediately after the exercise. Scoring with the M‐L lead system is somewhat inaccurate, especially during exercise, and is not recommended for stratification of clinical risk. The QRS score is protected against ischaemia, which emphasizes its value as an independent prognostic tool.
Cholesterol metabolism in distance runners
Authors: Sutherland W. H. F. , Nye E. R. , Macfarlane D. J. , Williamson S. A. , Robertson M. C.
Published: April 2008

Summary. Faecal steroid excretion, including betasitosterol excretion, whole‐body cholesterol synthesis, plasma lipids, and lipoprotein concentrations and habitual diet, were determined in 14 male distance runners and 14 sedentary men. The proportion of cholesterol‐derived steroids excreted as bile acids, and the quantity of betasitosterol excreted in the faeces were significantly (P< 0.05) higher in the runners compared with the sedentary men. Faecal betasitosterol excretion and the proportion of cholesterol‐derived steroids excreted as bile acids were correlated significantly in the distance runners and the sedentary men (r= 0.774, n= 28, P<0.001). These results suggest that greater dietary intake of plant sterols may contribute to the higher proportion of cholesterol‐derived steroids excreted as bile acids in distance runners.
Formation of prostacyclin during administration of β1‐selective and non‐selective β‐adrenergic antagonists in healthy humans
Authors: Wennmalm Å.
Published: April 2008

Summary. Vascular formation of prostacyclin is increased by propranolol in patients with essential hypertension. However the possible effect of β‐adrenoceptor blocking drugs in healthy subjects is, however, not known. We studied this issue by analysis of the urinary excretion of the prostacyclin metabolite, 2,3‐dinor‐6‐keto‐prostaglandin Fla during intake of a (β1‐selective (metoprolol) or a non‐selective (propranolol) (3‐adrenoceptor antagonist. After 14 days of metoprolol treatment (100 mg d‐1) the urinary excretion of PGI‐M did not differ from control (253 ± 77 vs. 220 ± 33 pg mg‐1 creatinine, respectively). Five days of randomized cross‐over treatment with propranolol (80 mg day‐1) or placebo did not affect urinary PGI‐M significantly either (177 ± 11 vs. 202 ± 11 pg mg‐1 creatinine, respectively). Furthermore, a daily increasing dose of propranolol (80–480 mg) progressively lowered resting blood pressure and heart rate, but failed to influence urinary excretion of PGI‐M. The data demonstrate that metoprolol and propranolol do not affect basal cardiovascular formation of prostacyclin in healthy subjects. Thus, the biosynthesis of prostacyclin does not appear to be regulated by p‐adrenoceptor activity under normal conditions.
Detection of microvascular impairment in type I diabetics by laser Doppler flowmetry
Authors: Wilson S. B. , Jennings P. E. , Belch J. J. F.
Published: April 2008

Summary. The use of a laser Doppler flowmeter to detect microcirculatory impairment and abnormalities in sympathetic neural control of blood flow in the hands and feet was evaluated. Measurements were carried out in 15 insulin dependent diabetic patients with retinopathy, 14 uncomplicated diabetics and 15 normal subjects. Three tests were assessed (1) the hyperaemic response of the skin microcirculation to local heating at 44°C; (2) the reactive hyperaemic response of the skin microcirculation to 2 min arterial occlusion; and (3) the peripheral vasoconstrictor reflexes to cold challenge and inspiratory gasp. Tests (1) and (2) were applied to the dorsum of the hand and foot and test (3) to the pulp of the fingertip and toe. All tests were carried out with the subjects peripherally vasodilated by indirect heating. At the hand no differences were found between the groups for any of the measures. The hyperaemic response to local heating at the dorsum of the foot showed that the maximum flow in complicated diabetics was significantly lower than that in uncomplicated patients (P<0.01) and in normal subjects (P<0.002). A new measure, the time for flow to increase to 3 times basal flow, was longer in the complicated group compared with the uncomplicated (P<0.02) and the normal groups (P<0.001). This test also showed that the response in the uncomplicated group was slower than in the normal group (P<0.01). The post‐occlusive hyperaemic response did not differ between groups. Measurement of vasoconstrictor reflexes showed that the complicated group had a poorer response to cold challenge at the big toe than the uncomplicated group (P<0.02) and the complicated group generally tended to have poorer responses than the other two groups. In conclusion, we have found that the hyperaemic response to local heating can detect microvascular impairment in diabetes before other complications become apparent and that the vasoconstriction test may be able to identify individuals with peripheral sympathetic neuropathy.
Subtraction of extra‐renal background in 99mTc‐DTPA renography: comparison of various regions of interest
Authors: Moonen M. , Granerus G.
Published: April 2008

Summary Quantitative evaluation of renal function in 99mTc‐DTPA isotope renography is hampered by high background activity. This study compares various background regions of interest (ROIs) to obtain the most accurate estimate of the extra‐renal background, taking both total counts (integral value) and change by time (slope) into account. Gamma camera renography was performed in 21 patients with a single kidney. Time‐activity histograms obtained from 8 different background ROIs were compared in the time interval corresponding to the uptake phase of the renogram with the histogram obtained from a ROI over the empty kidney area. A significant difference could be demonstrated between the slope values of the histograms of the right and left empty kidney ROIs, but not for the integral values. Backgrounds taken over the heart, liver, between the kidneys, and under the kidneys had significantly different characteristics than the one in the empty kidney area. Only background ROIs surrounding each kidney area gave integral and slope values with close resemblance to those recorded over the empty kidney area. The results emphasize the necessity for an individual background ROI for each kidney and the need to separate extra‐ and intra‐renal background activities before subtraction.
The laser Doppler analysis of posturally induced changes in skin blood flow at elevated temperatures
Authors: Rendell M. S. , Giitter M. , Bamisedun O. , Davenport K. , Schultz R.
Published: April 2008

Summary Recently, it has become possible to use laser Doppler techniques to separately quantitate the two components of blood flow, microvascular volume and red blood cell velocity. We used these techniques in 21 normal volunteers to quantitate the effect of postural changes in skin blood flow and its components at 35°C and at 44°C. Postural skin blood flow changes have ben studied extensively at basal skin temperature, but not at elevated temperatures. We contrasted changes at sites with arteriovenous anastomotic (AVA) blood flow (toe and finger pulps) with changes at sites with primarily nutritive flow (elbow and knee). Skin blood flow increased markedly with increasing temperature. The increases at the elbow and knee were the products of equivalent increases in both microvascular volume and velocity. In contrast, the increases on the finger and toe pulps were mainly due to increases in velocity. Elevation of both upper and lower extremities brought about a decrease in skin blood flow. Dependency increased blood flow. The magnitudes of observed changes were greater on the lower extremity than on the upper extremity and greater at 44°C than at 35°C. Once again, with postural change, the nutritive areas exhibited similar changes in volume and velocity while the AVA areas primarily showed velocity alterations. The correlation of systolic pulse pressures with blood flow was greater at the AVA areas than at nutritive areas and greater at 44°C than at 35°C. This correlation was with the velocity rather than with the volume component. The contrast of skin blood flow changes at nutritive and AVA sites at high temperatures may furnish a useful index of regional microvascular perfusion.
Heart‐rate variation: what are we measuring?
Authors: Niklasson U. , Wiklund U. , Bjerle P. , Olofsson B.‐O.
Published: April 2008

Summary. Many methods have been proposed during the last two decades for the assessment of autonomic nervous system function by quantification of the heart‐rate variation (HRV). Relatively little has been written about the HRV in relation to physiological models of the heart‐rate regulation. The integral pulse frequency model (IPFM) is a simple model that describes the genesis of heartbeats under the influence of the autonomic nervous system. By comparing simulated HRV data generated with the IPFM model with data from healthy volunteers we found similarities indicating that the model accurately reflects real data. Furthermore, we found a considerable difference between HRV measurements based on beat‐by‐beat heart‐rate and measurements based on the heartbeat interval. Our results suggest that the commonly used electrocardiographic RR interval representation of heart‐rate variation might possess an inherent nonlinear, mean heart‐rate‐dependent property indicating that analysis directly based on RR intervals can give biased results with respect to the underlying autonomic activity. The conclusions embrace all measurements of variation that are directly based on RR intervals including simple indices as well as higher‐level quantification such as spectral analysis.
The effect of increasing temperature on skin blood flow and red cell deformability
Authors: Rendell M. S. , Kelly S. T. , Bamisedun O. , Luu T. , Finney D. A. , Knox S.
Published: April 2008

Summary. Using laser Doppler techniques in nine healthy volunteers, we contrasted the effect of increasing local skin temperature at the elbow, a skin site with nutritive microvasculature, and the finger pulp, with predominantly arteriovenous anastomic (AVA) perfusion). We also assessed flow at the finger dorsum, with contributions of both types of microvasculature. In parallel with the laser Doppler studies, we determined the effect of increasing temperature on the red cell deformability of our subjects, using the new technique of Cell Transit Time Analysis (CTTA). Thermal stimulation produced very large increases in skin blood flow at all three sites tested. However, the magnitude and the pattern of increase were different at the three sites. At the finger pulp, there was a linear approximately threefold increase in flow as temperature increased from the basal level to 44°C. At the elbow, basal flow was considerably lower than at the finger pulp and increased very slowly until skin temperature reached 38°C. From that point, flow increased sharply, reaching tenfold the basal level at 44°C. The thermally induced increase at the finger dorsum was intermediate between the other two sites, with a pattern resembling the elbow more than the finger pulp. These differences among the sites were attributable to substantially different patterns of change in the two components of flow, microvasvular volume and velocity. At the finger pulp, there was very little increase in microvascular volume with increasing temperature. The curve was practically flat from basal temperature to 44°C. In contrast, there was a linear increase in red blood cell velocity of about 300%. At the elbow, both microvascular volume and red blood cell velocity exhibited a parallel curvilinear pattern of equivalent increase, on the order of 300% for each. There was only a small increase in both parameters until the temperature reached 38°, at which point there was a sharp increase in both. At the finger dorsum, the situation was intermediate, again resembling the elbow more than the finger pulp.

Cell Transit Time Analysis revealed a progressive decrease in red cell transit time (TT), from 3.28 ms at 28°C to 2.48 m at 44°C, an overall change of 24%. The decrease in TT was accompanied by an increase in transit frequency, measured as counts s‐1 (C s‐1), from 3.1 to 5.3, an overall change of 71%. The changes in both TT and C/S were essentially linear.

Our present findings demonstrate that cutaneous AVA beds differ significantly from nutritive capillary beds in the mechanisms of thermally induced flow change. The 24% observed increase in red cell transit time on CTTA would suggest only a small potential rheological contribution to increased red blood cell velocity. However, the increase in counts s‐1 of about 70% suggests that improved red cell entry into capillaries is a factor in the thermally induced increase in microvascular volume.
Maintained hyperexcretion of thromboxane A2 metabolite in healthy young cigarette smokers: results from a prospective study in randomly sampled males with stable smoking habits
Authors: Wennmalm Å. , Benthin G. , GranstrÖm E. F. , Persson L. , Winell S.
Published: April 2008

Summary. Although several studies have identified cigarette smoking as a factor increasing platelet formation of thromboxane A2 (TxA2), no prospective data on this issue have been presented in a defined population with stable smoking habits. Therefore, we analysed the relation between smoking habits and urinary excretion of the 2, 3‐dinor metabolites of thromboxane A2 (Tx‐M) and prostacyclin (PGI‐M) in 87 males, randomly sampled from a population of 18–19‐year‐old men, at two different occasions separated by 31–49 months. The daily cigarette consumption among the smokers was unchanged between the study occasions (11 vs. 11 cigarettes day‐1), but 9 of 43 initial smokers had quit. None of the initial non‐smokers had begun smoking. Tx‐M was higher in the smokers than in the non‐smokers and correlated with the daily cigarette consumption both at the initial (176 vs. 123 pg mg‐1 creatinine; P = 0.01) and the second (214 vs. 164 pg mg‐1; P = 0.002) study occasion. Those who had quit smoking since the initial study did not differ in Tx‐M from the non‐smokers at the second study occasion. Urinary PGI‐M did not differ between cigarette smokers, non‐smokers and quitters at either of the study occasions. We conclude that cigarette smoking elicits an increased formation of thromboxane A2, indicating platelet activation, that is stable during an observation period of up to 4 years. The increased platelet activity is reversible upon quitting.
Middle cerebral artery velocity during head‐up tilt induced hypovolemic shock in humans
Authors: Jørgensen L. G. , Perko M. , Perko G. , Secher N. H.
Published: April 2008

Summary. Middle cerebral artery mean velocity (Vmean) and pulsatility index (PI) were followed during head‐up tilt induced hypovolaemic shock in nine subjects. Mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP) and thoracic (TI) electrical impedance were also recorded. Vmean, PI, and CVP did not change during head‐up tilt to 50°, while MAP increased from 92 (81–106) (median and range) to 100 (97–112) mmHg, HR from 63 (53–74) to 84 (68–89) beats min‐1 and Tl100kHz from 30 (27–36) to 32 (30–39) Ohm (P < 0.01) (n= 8). During maintained tilt, Vmean decreased from 52 (32–72) to 34 (16–59) cms‐1, whereas HR increased to 87 (52–108) beats min‐1 and Tl100kHz to 33 (31–39) Ohm (P < 0.01). Presyncopal symptoms appeared after 33 (3–46) min and were associated with a MAP of 65 (32–84) mmHg (P < 0.01) and a HR of 58 (52–71) beats min‐1 (P < 0.05).Vmean decreased to 25 (16–36) cms‐1, and cerebral conductance index (Vmean/MAPbrain) and PI increased (P < 0.01). Arterial collapse was observed (diastolic velocity of zero) in one subject at a brain (diastolic) blood pressure of 21 mmHg and he developed tachycardia (131 beats min‐1) during presyncope. PaCO2 did not change. Maintained tilt resulted in central volume depletion reflected by changes in MAP, HR, and thoracic electrical impedance but not in CVP. Transcranial Doppler derived indices of cerebral perfusion demonstrated critically low values despite marked increase in conductance index.
Changes in the QRS segment during exercise: effects of acute β‐blockade with propranolol
Authors: Pilhall M. , Riha M. , Jern S.
Published: April 2008

Summary. Changes in the QRS complex during exercise may provide information with respect to ischaemic heart disease. The intention with present investigation was to shed light on mechanisms behind QRS changes and to study the possibly confounding effects of β‐blockade on such alterations with exercise. Placebo or propranolol respectively was infused in randomized and double‐blinded order in seven young healthy men before a maximum exercise test. Advanced computerized vectorcardiography and impedance cardiography was recorded continuously together with blood pressures and blood samples.

The Y‐lead magnitude increased significantly with propranolol infusion (P<0–05), but it tended to decrease in the Z‐lead (P<0.07). While the serum potassium concentrations increased (P< 0.0005), the spatial QRS magnitude tended to decrease irrespective of treatment (P<0.07). These changes correlated with changes in QR‐duration (adj r2>0.58).

With exercise, the mean spatial QRS magnitude decreased with similar amounts irrespective of treatment. However, propranolol made the magnitude decrease earlier (P<001). No effect of treatment was detected on the decrease in QRS‐duration.

Immediately after exercise, the QRS complex continued to change as during exercise in the placebo investigations, but did not with propranolol (P<0.05). These different patterns were most obvious in the first half of the QRS complex in the Y‐lead.

It is concluded that acute β‐blockade modifies QRS alterations both during and after exercise in healthy subjects. This indicates that such drugs may have confounding effects in evaluations of the diagnostic value of QRS alterations.
Spontaneous baroreflex by sequence and power spectral methods in humans,
Authors: Hughson R. L. , Quintin L. , Annat G. , Yamamoto Y. , Gharib C.
Published: April 2008

Summary. Beat‐by‐beat variations in blood pressure and RR‐interval are interrelated by the actions of baroreflex and non‐baroreflex responses. This study had two purposes: (1) to examine the spontaneous relationships between RR‐interval and systolic blood pressure to determine the relative occurrence of baroreflex and non‐baroreflex responses in humans, and (2) to compare the beat‐sequence method with a cross spectral estimate of the baroreflex response slope. Eight healthy men were studied during 10 h of quiet, seated rest, and six men and three women were studied during rest, rest plus fixed pace breathing, and a cold pressor test. RR‐interval and continuous, non‐invasive arterial blood pressure were measured with a computerized system. A baroreflex sequence was defined by a series of at least three consecutive heart beats in which systolic pressure and the following RR‐interval either both increased or both decreased. A non‐baroreflex relationship was defined by sequences of at least three beats by opposite directional changes of RR‐interval and systolic pressure of that beat. The results showed that there were approximately 30% as many non‐baroreflex compared to baroreflex slopes. Individual subject mean baroreflex and non‐baroreflex slopes were highly correlated (r= 0–72, P < 0–001). Absolute slope values were not different, and they were unaffected by time, fixed pace breathing, or cold pressor test. The data showed the relatively simple beat‐by‐beat sequence method to yield spontaneous baroreflex response slopes that were quantitatively similar to, and highly correlated with (r= 0–85‐0‐94), baroreflex response slopes calculated by spectral analysis methods.
Effect of exposure to heat and intake of ethanol on the skin circulation and temperature in ischaemic limbs
Authors: Proano E. , Perbeck L.
Published: April 2008

Summary. The question of whether alcohol intake increases skin circulation is controversial. The study described here was undertaken to examine the effect on skin circulation and skin temperature in ischaemic limbs of exposure to external heat, and of alcohol intake together with such exposure. Fourteen patients with occlusive arterial disease, mean age of 65 years (range 47–80), underwent measurements of blood flow by laser Doppler flowmetry (LDF) and of skin temperature 1–2 days before and 8–10 days after vascular reconstruction. LDF and skin temperature were measured in the plantar region of the mid‐forefoot with the subject supine. After 30 min of exposure to external heat, the measurements were repeated. Each subject then drank 15 ml of 50% alcohol and after a further 30 min of heat exposure the same measurements were performed again. Similarly, fourteen healthy subjects, mean age 33 years (range 21–43), were studied. In the patients there was no increase in skin blood flow or skin temperature after heat exposure alone or after combined heat exposure and alcohol intake, either before or after vascular reconstruction. In the healthy subjects LDF showed a 126% increase (P<0–01) in skin blood flow after 30 min of exposure to external heat and a further increase by 81% after alcohol intake and an additional 30 min of heat exposure (P<0–01). The corresponding increases in skin temperature were 3–0°C (P<0–05) and 2–9°C (P<0–05). Thus, external heat and alcohol intake increased plantar skin blood flow and skin temperature in healthy subjects but not in patients with ischaemic limbs. The reason for this difference is unclear, but it is possible that the skin vessels in the patients were fully dilated even before heat exposure or alcohol intake.
PET in cardiology: current status and clinical expectations
Authors: Nienaber C. A.
Published: April 2008

Summary. The development of positron emission tomography (PET) in the clinical environment along with the synthesis of biologically active molecules and tracer kinetic principles has provided a diagnostic tool for in vivo tissue characterization in humans. Moreover, based on the growing knowledge of cellular function on the molecular level of diseases PET biological imaging has stimulated the synthesis of numerous metabolic compounds labelled with the four primary positron‐emitting radioisotopes C‐ll, F‐18, N‐13 and 0–15. While the concept of biological imaging has gained attraction for probing both the central nervous system and neoplastic tissues, current diagnostic benefit from PET is probably best defined in cardiovascular medicine.
Biphasic pulmonary clearance of 99mTc‐DTPA in smokers
Authors: Wollmer P. , Evander E.
Published: April 2008

Summary. We measured the pulmonary clearance of 99mTc‐labelled diethylene triamine penta‐acetate (99mTc‐DTPA) for 3 h in 17 non‐smokers and in 16 healthy smokers. We found the clearance of 99mTc‐DTPA to be well described by a mono‐exponential equation in 14 non‐smokers, the half‐life being 66 ± 17 min (mean ± SD). In all smokers, a bi‐exponential equation yielded a significantly better curve fit. The half‐life of the slow and fast clearance components was 83 ± 19 and 13 ± 4 min, respectively. The relative amount of radioactivity cleared by the fast component was 57 ± 15% and correlated significantly with cumulated tobacco consumption (r= 0–58, P<0.02) and forced expiratory volume in 1 s in percentage of predicted value (r= ‐ 0–60, P<0–02). We conclude that smoking induces a rapidly clearing pool of 99mTc‐DTPA in the lung, the size of which may be related to smoking habits.
Normal limits of the derived vectorcardiogram in Caucasians
Authors: Yang T.‐F. , Macfarlane P. W.
Published: April 2008

Summary. The derived vectorcardiogram (dVCG) can be obtained from three orthogonal leads X, Y, Z, which are synthesized from the conventional 12‐lead ECG by one of a number of mathematical techniques. The application of the dVCG in routine cardiological practice has the advantage of not requiring extra recording electrodes other than those used for the conventional 12 electrocardiographic leads, and offers the simultaneous availability of additional dVCG diagnostic information. In this study, the dVCGs were obtained using the inverse Dower method from 1555 apparently healthy Caucasian individuals (884 men and 671 women) and were analysed to determine the age and sex dependent normal ranges of vector measurements in a Caucasian population. The vectorcardiographic parameters measured included the directions of inscription of the QRS vector loops, the magnitude of initial 20 and 30 ms QRS vectors and the direction of the initial 20 ms QRS vector. The maximal spatial QRS vector magnitude, as well as the maximal QRS and T vector magnitudes in the frontal, horizontal, and right sagittal planes, were observed to decrease significantly with advancing age in both sexes (P<0–001) and were significantly larger in men in all age groups (P<0–001). The observations from the current study illustrate the significant age and sex dependent differences in the normal ranges of dVCG parameters. These are of potential importance for diagnostic applications.
Repeated measurements of transfer factor in rabbits: an animal model suitable for evaluation of short‐term exposure
Authors: Dahlqvist M. , Lagerstrand L. , Nilsen A.
Published: April 2008

Summary. Acute temporary changes in lung function may be of use as a biological exposure indicator. However, studies of humans occupationally exposed to complex airborne irritants are often expensive and time demanding. Therefore, an animal model could be a valuable complement. A rabbit model has been evaluated where transfer factor was measured twice during the same day, and with the rabbit awake and available for exposure, in between.

Anaesthesia and intubation in 22 rabbits (2–6 [0–2] kg [Mean (SD)]) were immediately followed by two measurements of transfer factor and alveolar volume. Transfer factor was estimated by the single breath CO‐technique used in humans. The samples were analysed for CO and He on a gas chromatograph. After one pair of measurements the rabbit was allowed to wake up and after 5 h the duplicate measurements were repeated.

The mean values of transfer factor, alveolar volume and transfer constant were 0–50 (0–09) mmol min‐1 kPa‐1, 127 (8) ml and 3–9 (0–6) mmol min‐1 kPa‐11‐1, respectively. The intraindividual coefficients of variation were 7‐3%, 5‐3% and 6–7%, respectively. Five hours later when the duplicate measurements were repeated, transfer factor, alveolar volume and transfer constant were unchanged still.

The results suggest that relatively small changes in transfer factor may be detected without losing power, and thus that this model could be used as a biological exposure indicator.,
Does digital chest radiography assess regional ventilation?
Authors: Denbratt L. , Bergman B. , Bake B. , Angelhed J.‐E. , Björk L.
Published: April 2008

Summary. Digital radiography of the chest was evaluated for estimation of regional ventilation disturbances. Thirty‐three patients with suspected bronchial carcinomas were examined. Objective measurements of regional density changes during breathing correlated significantly with standardized regional lung function tests (133Xe ventilation scintigraphy), but did not permit reliable individual estimations of regional ventilation. About 35% of the density variations could be explained by regional ventilation. Thus, factors other than ventilation, e.g. changes in the geometry of the thorax, have a major impact on the density variation at digital radiography.,
Effects of glucocorticoids and sympathomimetic agents on basal and insulin‐stimulated glucose metabolism
Authors: Paquot N. , Schneiter Ph. , Jéquier E. , Tappy L.
Published: April 2008

Summary. The mechanisms responsible for glucocorticoid‐induced insulin resistance remain unclear. Glucocorticoids show several interactions with the sympatho‐adrenal system which may contribute to this decrease in insulin sensitivity: they enhance the synthesis and actions of catecholamines, but abolish insulin‐induced activation of muscle sympathetic nerve activity. The present study was performed in order to investigate the effects of the interactions between glucocorticoids and the sympatho‐adrenal system on insulin sensitivity. Basal and insulin‐stimulated glucose metabolism was measured in healthy human subjects during four 2‐h clamp studies as follows: control (C); after taking oral dexamethasone (2 mg daily) for 2 days (D); after taking oral ephedrine sulphate (40 mg daily) for 2 days (E); and after taking dexamethasone+ephedrine (D+E). Glucose uptake, production and oxidation were calculated from plasma 13C glucose and exhaled 13CO2 during constant tracer infusion of U‐13C glucose. Basal glucose production, utilization and oxidation were similar in all four studies. During hyperinsulinaemia, glucose uptake was reduced by 51.5% with treatment D, by 25.9% with treatment E, and by 49.6% with D+E. Glucose oxidation was reduced by 54.0% with treatment D, by 24.0% with treatment E, and by 57.2% with D+E. Hepatic glucose production was completely suppressed in all four studies. It is concluded that both dexamethasone and ephedrine decrease insulin‐mediated glucose uptake and oxidation. Co‐administration of ephedrine does not suppress the glucocorticoid‐induced alterations of glucose metabolism. This indicates that glucocorticoid‐induced insulin resistance is not related to the inhibition of muscle sympathetic nerve activity. These results suggest instead that glucocorticoids and sympathomimetic agents may impair glucose metabolism by common actions.
Basal and exercise‐induced changes in plasma catecholamines: relationship to age, smoking habits and sampling times
Authors: Jensen E. W. , Espersen K. , Kanstrup I.‐L. , Christensen N. J.
Published: April 2008

Summary. Contrary to earlier investigations, we have previously shown that the initial increase in venous plasma noradrenaline (NA) during exercise did not differ in young and elderly non‐smoking subjects exercising at the same relative workload (75%), and that the greatest increase at maximal workload was observed in the young subjects. In order to determine whether the observed discrepancy could be explained by long‐term smoking, plasma NA and adrenaline (A) were evaluated in eight elderly male smokers (mean age 67 years). The results were compared with data reported previously [Jensen et al. (1994) Exercise‐induced changes in plasma catecholames and neuropeptide Y: relation to age and sampling times. J Appl Physiol, 76, 1269–1273] in seven young (mean age 27 years) and seven elderly (mean age 61 years) non‐smoking male subjects. As shown earlier, basal plasma NA was significantly increased in elderly smokers compared to young and elderly non‐smokers. During exercise at 75% of maximal work capacity, no difference was observed between elderly smokers and non‐smokers. No difference in plasma A was found between elderly smokers and non‐smokers either at rest or during exercise. These findings indicate that the exercise‐induced increase in plasma NA did not differ in elderly smokers and non‐smokers despite increased resting levels in the former group, and that the increase in the elderly subjects was not augmented compared to that in young subjects.
Heart rate and blood pressure variability and baroreflex sensitivity in hypercholesterolemia
Authors: Koskinen P. , Kupari M. , Virolainen J. , Stjernvall J. , Jolkkonen J. , Tuomilehto J. , Tikkanen M. J.
Published: April 2008

Summary. To evaluate cardiovascular autonomic function in hypercholesterolaemia, we studied 16 age‐matched pairs of healthy males with elevated serum cholesterol and normocholesterolaemic control subjects (altogether 37 men, aged 27–56 years). We used power spectral analysis to measure short‐term heart rate and blood pressure variability, and the phenylephrine method to determine baroreceptor reflex sensitivity. The mean (SD) serum cholesterol concentration was 6.43 (1.22) among the hypercholesterolaemic subjects and 4.30 (0.44) mmol/1 among the control men (P<0.001). The respective low density lipoprotein (LDL) cholesterol concentrations were 4.44 (1.22) and 2.46 (0.38) mmol/1 (P<0.001). The total power (0.0‐0.5 Hz) of heart rate and blood pressure variability did not differ between the groups, and neither did the high‐frequency (0.15‐0.5 Hz) and medium‐frequency components (0.07‐0.15 Hz). Mean (SD) baroreceptor reflex sensitivity was 18.1 (7.9) in hypercholesterolaemic and 19.4 (6.3) ms mmHg‐1 in normocholesterolaemic subjects (P=0.352). When all the subjects were analysed together, we observed a slight inverse trend between serum LDL cholesterol and baroreceptor reflex sensitivity (r= ‐0.235, P=0.161). In conclusion, hypercholesterolaemia does not alter autonomic neural regulation of the cardiovascular system as assessed by heart rate and blood pressure variability and baroreflex sensitivity.