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Biomedical subjects

J Bülow

Publications and source records attributed to J Bülow.

At least 109 records · Page 6Linked to original sources
PubMed1986

Exercise-induced increase in dog adipose tissue blood flow before and after denervation.

Subcutaneous adipose tissue blood flow was examined during rest and exercise in the inguinal fat pads of four female dogs using the Xe wash-out technique. The experiments were performed before and after denervation of one of the pads. No difference between the resting flows in the two pads could be demonstrated either before or after denervation. The flow increased about two-fold on average from rest to exercise. This response was similar before and after denervation. It is concluded that direct sympathetic innervation is not involved in the regulation of adipose tissue blood flow during exercise.

Adipose Tissue↗
PubMed1986

Facultative thermogenesis induced by carbohydrate: a skeletal muscle component mediated by epinephrine.

In addition to the obligatory thermogenesis due to processing and storage, carbohydrate ingestion is accompanied by a facultative thermogenesis mediated by catecholamines via beta-adrenoceptors. The anatomical origin of facultative thermogenesis has hitherto not been determined. The possible involvement of skeletal muscle was examined in lean, healthy subjects by measuring the response in forearm oxygen consumption to an oral glucose load. The study demonstrates an early component of skeletal muscle thermogenesis coinciding with the local glucose uptake, followed by a late facultative thermogenesis. The arterial epinephrine concentration increased to a maximum of 200% above base-line values 4 h after glucose. This value greatly exceeds the physiological threshold for the thermogenic action of epinephrine. In forearm venous blood the corresponding increase in epinephrine was only approximately 50% due to enhanced peripheral extraction, which accompanies an increase in arterial epinephrine levels. Due to venous sampling previous studies have overlooked the magnitude of the late postglucose increase in arterial epinephrine, and its potential thermogenic effect has been disregarded. The facultative thermogenesis in skeletal muscle may be of importance for the regulation of body weight in humans.

Adult↗
PubMed1986

Cerebral effects of scalp cooling and extracerebral contribution to calculated blood flow values using the intravenous 133Xe technique.

With the intravenous 133Xe technique we measured cerebral blood flow (CBF) in eight healthy subjects during normal subcutaneous temperatures and during extracranial cooling. This gave rise to the possibility of evaluating the contribution of the extracerebral blood flow to the calculation of CBF values. With a two-compartmental analysis of the wash-out curves during cooling there was a significant reduction of the CBF indices f1, representing mainly fast blood flow in the grey matter and f2, representing blood flow in the slowly perfused white matter and extracerebral structures. The reduction of f1 was due to the 'slippage' phenomenon:calculation of f1 was affected by a reduction in f2 due to a considerably reduced extracerebral blood flow. The initial slope index (ISI) calculated from 30 to 90 s of the first part of the presumed mono-exponential 133Xe wash-out curve was not affected by slippage as the ISI remained unchanged in spite of reduced extracerebral blood flow. It is concluded that CBF was unaffected by extracranial cooling. Extracranial cooling can be used to reduce the extracerebral blood flow contribution to the calculated CBF values.

Adult↗
PubMed1986

Microcirculation of the juvenile knee in chronic arthritis.

In order to investigate pathogenetic factors in growth abnormalities of the knee in hemophilic arthropathy and juvenile rheumatoid arthritis, the hemodynamic changes of the knee following chronic synovial inflammation and elevated joint pressure were studied in puppies. Unilateral arthritis was induced by intraarticular injections of carrageenan solution. Regional blood flow (RBF) was measured by tracer microsphere technique. Microvascular volume (VV) was estimated from the distribution volumes of Cr51-labelled erythrocytes and I125 fibrinogen. Mean transit times (TT) of blood components were calculated from volume/flow ratios. The arthritic joint capsules were characterized by high RBF rates, increased VV, low tissue hematocrit (HCT) and short TT of blood. In the juxtaarticular epiphyses and the patella, RBF was largely unchanged, whereas VV was significantly elevated and TT of blood prolonged. The growth plates formed borders for the extension of these changes. The increased permeability and surface area between blood and bone in arthritis may accelerate the resorption and subsequent destruction of subchondral bone in chronic arthropathies of the juvenile knee.

Animals↗
PubMed1985

The effect of non-esterified long-chain fatty acids on blood flow and thermogenesis in brown adipose tissue in the young dog.

In vitro experiments have demonstrated that increasing the molar ratio of extracellular non-esterified fatty acids (NEFA) to albumin stimulates thermogenesis in brown adipocytes. To test these results, in vivo blood flow and local temperature were measured in perirenal brown adipose tissue (BAT) in puppies during thermogenesis induced by increasing the plasma NEFA: albumin ratio by injection of intralipid and heparin. Plasma NEFA concentration increased to 1.5 mmol X 1-I and plasma NEFA:albumin ratio to 4. Concomitantly, the whole body oxygen consumption rose on average about 100% above baseline level. Plasma noradrenaline concentration increased about three-fold and plasma adrenaline concentration about six-fold. The BAT temperature increased by an average of 0.9 degrees C. However, since BAT blood flow was simultaneously reduced by about 50%, it can be calculated that the local heat production was also reduced. Consequently, the increase in whole body oxygen consumption was not due to stimulation of BAT thermogenesis. It is concluded that in vivo assessment of BAT thermogenesis requires concomitant measurements of both local BAT temperature and blood flow.

Adipose Tissue↗
PubMed1985

Vasoconstrictor effect of high FFA/albumin ratios in adipose tissue in vivo.

Subcutaneous or perirenal adipose tissue blood flow was measured with the 133Xe-washout technique before and after intravenous injection or infusion of Intralipid in six anesthetized, otherwise intact mongrel dogs. In four anesthetized mongrel puppies adipose tissue blood flow was measured with the radioactive microsphere method in seven different adipose tissue depots before a bolus injection of Intralipid and at the time after the injection when the thermogenic effect of the Intralipid was maximal. The results showed that the vascular resistance increased in all the examined adipose depots in adult as well as in young dogs after this treatment. The administration of Intralipid did not per se induce the vasoconstriction. The vasoconstriction took place simultaneously with increasing FFA/albumin molar ratios. The results support our previous findings in perfused fat pads that high molar FFA/albumin ratios increase vascular resistance in adipose tissue and they give further support to our suggestion that this vasoconstriction may be a link in a negative-feedback mechanism regulating FFA-mobilization in relation to FFA utilization.

Adipose Tissue↗
PubMed1985

Contribution of BAT and skeletal muscle to thermogenesis induced by ephedrine in man.

This investigation was performed to examine the role of brown adipose tissue (BAT) in thermogenesis induced by ephedrine in man. Light microscopy of biopsies from necropsy cases showed BAT to occur most frequently in the perirenal fat. Perirenal BAT thermogenesis was investigated in five lean men before and during stimulation with 1 mg ephedrine orally X kg body wt-1. Perirenal BAT thermogenesis was assessed by continuous measurements of local temperature and blood flow with the 133xenon clearance method. In the same study the effect of ephedrine on skeletal muscle oxygen consumption was estimated by measurements of leg blood flow and arteriovenous oxygen difference. The perirenal adipose tissue blood flow increased approximately twofold, whereas the local temperature increased approximately 0.1 degrees C on an average. Assuming that man possesses 700 g of BAT with a similar thermogenic capacity, this tissue contributed only 10 ml X min-1 to the 40 ml X min-1 increase in oxygen consumption in the subject whose perirenal BAT showed the most pronounced response to ephedrine. The leg oxygen consumption increased on an average 60% after ephedrine. By extrapolation of this value to whole body skeletal muscle, approximately 50% of the increase in oxygen consumption induced by ephedrine may take place in skeletal muscle. It is concluded that skeletal muscle is a tissue of importance with respect to the thermogenic effect of sympathomimetics in man, whereas the results do not support a major role for perirenal BAT.

Adipose Tissue, Brown↗
PubMed1985

Frontal subcutaneous blood flow, and epi- and subcutaneous temperatures during scalp cooling in normal man.

Cooling of the scalp has been found to prevent hair loss following cytostatic treatment, but in order to obtain the hair preserving effect the subcutaneous temperature has to be reduced below 22 degrees C. In order to establish the relationship between epicutaneous and subcutaneous temperatures during cooling and rewarming and to measure the effect of scalp cooling on subcutaneous scalp blood flow, subcutaneous blood flow and epi- and subcutaneous temperatures were measured in the frontal region at the hairline border before and during cooling with a cooling helmet, during spontaneous rewarming of the cooling helmet and after removal of the rewarmed helmet in 10 normal subjects. Subcutaneous blood flow was reduced to about 25% of the postcooling control level during cooling. The flow was constantly reduced until the subcutaneous temperature exceeded 30-32 degrees C. A linear relationship between epicutaneous and subcutaneous temperatures could be demonstrated with the regression equation: s = 0.9 c + 4.9 (r = 0.99). In eight of the 10 subjects the subcutaneous temperature could be reduced below 22 degrees C with the applied technique. It is concluded that the hair preserving effect of scalp cooling during cytostatic treatment is mainly due to the metabolic effect of cooling, and only to a minor extent due to the flow reducing effect.

Adult↗
PubMed1985

The double isotope technique for in vivo determination of the tissue-to-blood partition coefficient for xenon in human subcutaneous adipose tissue--an evaluation.

Local subcutaneous 133xenon (133Xe) elimination was registered in the human forefoot in 34 patients. The tissue/blood partition coefficient for Xe was estimated individually by simultaneous registration of 133Xe and [131I]antipyrine ([131I]AP) washout from the same local depot. When measured in this way, an average partition coefficient for Xe was found to be 4.3 +/- 1.23 ml g-1. This value is significantly lower than the partition coefficient found in a previous in vitro study in which a Xe partition coefficient of 7.5 +/- 1.57 ml g-1 was found. Thus, if the local blood flow is calculated using the partition coefficient found by the double isotope technique, significantly lower values are obtained than if the in vitro determined coefficient is used. This difference is explained mainly by local dilution when injecting xenon subcutaneously. In short-term studies, utilization of the double isotope technique reduces the coefficient of variation on average flow determinations, thus an improvement in accuracy of local blood flow estimation can be obtained compared to the method in which an average partition coefficient is used. For long-term studies a partition coefficient of 7.5 ml g-1 seems valid.

Adipose Tissue↗
PubMed1984

Interscapular brown adipose tissue blood flow in the rat. Determination with 133xenon clearance compared to the microsphere method.

The xenon clearance method was adapted to continuous measurement of interscapular brown adipose tissue (ISBAT) blood flow in anesthetized rats. The ISBAT-blood partition coefficient for xenon was determined to 3.6 ml X g-1. The blood flow values obtained by Xe clearance were compared with flow values obtained concomitantly by the microsphere technique in 17 cold acclimated rats, at ISBAT blood flows between 0.1 and 6 ml X g-1 X min-1. Variations in blood flows were obtained by infusion of noradrenaline at different rates. The blood flow values obtained from the xenon clearance method showed a close correlation to the blood flow values determined with microspheres. Y = 0.98. X + 0.15 (r = 0.96, P less than 0.001). The Xe clearance method has the advantages compared to the microsphere technique that it permits continuous monitoring of the blood flow and does not require the sacrifice of the animal.

Adipose Tissue, Brown↗
PubMed1984

Ephedrine-induced thermogenesis in man: no role for interscapular brown adipose tissue.

The warmest interscapular skin areas were located by thermography in six healthy subjects during ephedrine-induced thermogenesis. In these interscapular areas, and in lumbar control areas, the skin temperature, subcutaneous temperature and adipose tissue blood flow were measured before and during ephedrine-induced thermogenesis. The skin and subcutaneous temperatures increased in the interscapular area as well as in the lumbar area, by about 0.7-1.2 degrees C. The interscapular skin temperature remained about 1 degree C higher than the lumbar; the subcutaneous temperatures in the two areas were identical during the experiments. Although the interscapular subcutaneous adipose tissue blood flow increased about sixfold and the lumbar increased twofold, the absolute flows were higher in the lumbar area. The oxygen uptake increased to a maximum of 30% above control level. Plasma glucose and glycerol concentrations remained unchanged, and plasma non-esterified fatty acids, lactate and noradrenaline concentrations increased slightly but significantly. Biopsies taken from the hot interscapular areas did not contain brown adipose tissue. It is concluded that the high interscapular skin temperature may be due to a lower insulating fat thickness and that the increases in skin and subcutaneous temperatures during ephedrine-induced thermogenesis are caused by an increased blood flow. These observations weigh against the hypothesis that the interscapular temperature increase is due to functional, interscapular brown adipose tissue.

Adipose Tissue↗
PubMed1984

Inhibitory effect of pentobarbital anesthesia on venous stasis induced arteriolar vasoconstriction in the dog hindleg.

The effect of close intra-arterial administration of pentobarbital in the concentration of about 2 X 10(-4) mol/l on the venous stasis induced arteriolar constriction in the dog hindleg was studied in 6 neurolept anesthetized dogs. It was found that the blood flows and vascular resistances in the legs before pentobarbital infusion were equal and the vasoconstrictor responses to venous stasis were the same. Pentobarbital infusion into the femoral artery in one of the legs increased the total leg blood flow compared to the control leg and abolished the increase in vascular resistance during venous stasis. In another experimental series the effect of general pentobarbital anesthesia on the vasoconstrictor activity in response to venous stasis locally in subcutaneous and muscle tissue in the hind limb was examined in 6 dogs. It was found that during the first 2-3 h of anesthesia the vasoconstrictor response was present in both tissues although the response in muscle tissue exhibited a great variation between the dogs during this period. However, after 4-5 h of anesthesia the response was abolished in both tissues. During neurolept anesthesia with fentanyl/N2O the same vasoconstrictor response was demonstrated in the hindleg 1 h and 5 h after induction of the anesthesia. It is concluded that pentobarbital anesthesia abolishes the arteriolar constriction induced by venous stasis. The mechanism may be blockade of the local sympathetic vasoconstrictor fibres or interference with myogenic vasoconstrictor mechanism of the vascular smooth muscle cells or both. It is suggested that fentanyl/N2O anesthesia is better suited for this kind of studies.

Anesthesia, General↗
PubMed1984

Evaluation of a method for determination of the subcutaneous blood flow in the forefoot continuously over 24 h.

A method is presented which allows for continuous registration of forefoot blood flow over 24 h. Blood flow was estimated by the radioactive Xenon washout method and a portable CdTe detector system was used to measure the tracer disappearance rate. Since the semiconductor detector is placed very close to the tracer depot the washout rates registered are a mixture of rate constants due to tracer removal by blood flow and diffusion of the tracer depot away from the detector. Rate constants only due to diffusion were obtained over 24 h from amputated feet and similarly from normal feet with circulatory arrest in several 20 min periods during 24 h. The rate constants due to blood flow could thus be calculated by subtraction of the appropriate diffusion rate constants from the recorded rate constants. Blood flow in the forefoot during 24 h was measured in 10 experimental subjects with normal peripheral circulation. Blood flow during daytime did not differ between the first and second day. Blood flow during night-time was about twice that during daytime.

Conductometry↗
PubMed1983

Hemodynamics of the juvenile dog knee in relation to increased venous outlet resistance.

Tissue blood flow was measured by the tracer microsphere technique in the juxta-articular bones of the immature knee, knee joint capsule and skeletal muscles of the hind limbs after unilateral bone cannulation of the distal femoral epiphysis, surgical exploration of the popliteal vessels and unilateral isolated increase of venous outlet resistance in the distal femoral epiphysis during Halothane anaesthesia. Pressure registration was performed in a liquid-filled electromanometric pressure recording system. Significant regional differences in bone blood flow was found within the different bone compartments of both control and test limb. Bone cannulation resulted in insignificant hyperaemia in the distal femoral epiphysis. No changes of distribution pattern of bone blood flow followed the surgical procedure. Ligation of the medial genicular vein caused a three fold increase of venous outlet resistance measured after 5 min, while an insignificant decrease of arterial inlet resistance was calculated. After one hour a significant decrease of both arterial inlet resistance and venous outlet resistance was found. In addition evidence of a veno-arterial reflex mechanism causing a significant unilateral decrease of distal skeletal muscle blood flow was found. The results demonstrate the presence of both venous and arterial regulation, predominantly metabolic, of bone blood flow in the knee.

Animals↗
PubMed1983

Bone blood flow in conscious dogs at rest and during exercise.

Using the microsphere technique bone blood flow was measured in different anatomical and functional regions in long bones in conscious dogs. The measurements were performed during physical exercise upon a treadmill, and the bone blood flow values were obtained as prework resting values after 1 and 2 hours of exercise and after 1 hour of rest. The perfusion rates increased 50 per cent from 1.6 to 2.5 ml X 100 g tissue-1 X min-1 in the femoral and tibial cortical bones during work. In the cancellous bone of the femoral head an increase from 12.6 to 20.6 ml X 100 g tissue-1 X min-1 was found. Equal flow responses were determined in the fat-filled tibia-condylar and femoral supracondylar bone. The increase took place after 2 hours' exercise, but nonstatistically verified increased perfusion was found after 1 hour's work. The alternation in bone blood flow suggests that bone has a capability of physical vasodilation during muscular work but the flow response is slow and therefore the vasodilatation seems mediated by a metabolically induced stimulus.

Animals↗
PubMed1983

Hemodynamics of the juvenile knee in relation to increasing intra-articular pressure. An experimental study in dogs.

The relationships between intraosseous pressure and regional blood flow in the juxta-articular epiphyses were determined in the knees of immature dogs. Intraosseous pressures were continuously registered in one knee. Regional blood flow rates were simultaneously determined by the microsphere technique before and after venous tamponade of both knee joint capsules. During complete venous tamponade the intraosseous pressure of the distal femoral epiphyses rose 268%, while flow increased 122%. A concurrent 20-fold flow increase of the knee capsule and 3-4-fold flow increase of the proximal femoral bone was observed. Evacuation of the knee joints resulted in an immediate drop of the intraosseous pressure of the distal femoral epiphyses, whereas hyperaemia prevailed for at least half an hour and was most pronounced in the distal femoral epiphyses and knee joint capsule. Intraosseous pressure registration did not significantly influence regional blood flow. It is suggested that the changes of intraosseous pressures during knee joint tamponade reflect changes in the venous outlet resistance. The results demonstrate the significance of intra-articular pressure increase on the hemodynamics of the juxta-articular tissues of the knee and proximal femoral bone. These findings may be of importance in the pathogenesis of growth disturbances observed in juvenile degenerative arthritis.

Animals↗
PubMed1983

Blood flow in the juvenile hip in relation to changes of the intraarticular pressure. An experimental investigation in dogs.

The blood flow in the hip joint of puppies was studied by means of the microsphere technique. The flow was determined before, during and after intraarticular pressure increase. A venous tamponade of 50 mmHg resulted in a significantly reduced flow in the femoral head and after an arterial tamponade of 150 mmHg the flow almost ceased. The proximal femoral metaphysis, the acetabulum and the hip joint capsule, on the contrary, showed varying degrees of flow increase. It is suggested that the significantly increased blood flow in the hip joint capsule during the intraarticular pressure increase of 50 mmHg and 150 mmHg is caused by an autoregulatory mechanism tending to restore the blood flow in the suffering femoral head. The demonstrated disturbance of the circulation in the juvenile femoral head after venous tamponade supports the theory that synovitis may be the basic mechanism in the production of Calvé-Legg-Perthes' disease.

Acetabulum↗