bluuebunny/crossref_metadata_2025 huggingface dataset:
Urinary excretion of prostaglandin F2α and 6‐keto‐prostaglandin F1α during volume expansion in man
Authors: LINNÉ TOMMY , OLIW ERNST , APERIA ANITA
Published: December 2008

Renal function and the urinary excretion of immunoreactive prostaglandin F2α (PGF2α) and 6‐keto‐prostaglandin F1α (6‐keto‐PGF1α) were investigated during volume expansion (VE) in 9 healthy young adults. The studies were started after at least 17 h of food and fluid deprivation. Volume expansion (3% of body weight) was achieved by a continuous infusion of Ringer's solution (0.22 ml/kg/min). This increased the urinary excretion of sodium from 195±25 to 714±55 μmol/min/1.73 m2(mean ± S.E.) and decreased the excretion of potassium by 24% and plasma renin activity by 60% (P<0.01). The clearance of inulin increased slightly (from 102.4±3.7 to 114.5±6.2 ml/min/1.73 m2, P<0.025), whüe clearance of PAH did not change. The excretion of immunoreactive PGF2α decreased in 8 out of 9 individuals during VE, from 1.58±0.15 to 0.97±0.10 ng/min/1.73 m2(P<0.01). In contrast, excretion of immunoreactive 6‐keto‐PGF1α increased in 8 out of 9 subjects, from 2.32±0.20 to 3.47±0.48 ng/min/1.73 m2(P<0.05). Urinary excretion of PGF2α and 6‐keto‐PGF1α may reflect renal synthesis of prostaglandins (PGs) and prostacyclin (PGI2), respectively. The results indicate that synthesis of PGs is decreased and that of PGI2 is increased during VE in man. However, no simple relationship could be found between the prostaglandins and the renal functional parameters.
Effect of vasoactive intestinal polypeptide (VIP) upon myometrial blood flow in non‐pregnant rabbit
Authors: OTTESEN BENT , FAHRENKRUG JAN
Published: December 2008

Vasoactive intestinal polypeptide (VIP) containing nerve fibres have previously been demonstrated in the female genital tract of several mammalian species including the rabbit. These nerve fibres seemingly innervate vascular and non‐vascular smooth muscle. For that reason we investigated the dose‐relationship between VIP (5, 50, 500 pmol min‐1 kg‐1) and myometrial blood flow (MBF) using Xenon‐133 washout technique. VIP increased MBF dose‐dependently. VIP was on molar base 100 times more potent than acetylcholine. The action of VIP seems to be direct on vascular smooth muscle rather than mediated by other neurotransmitters, because the MBF increase was not antagonized by atropine, adrenergic blocking agents or naloxone. These findings make it likely that VIP plays a role in the local nervous control of myometrial blood flow.
Effects of neurotensin and neurotensin analogues on the migrating myoelectrical complexes in the small intestine of rats
Authors: AL‐SAFFAR A. , ROSELL S.
Published: December 2008

The purpose of the present experiments was to study the effect of neurotensin and neurotensin analogues on the migrating myoelectrical complexes in the small intestine of rats. Four bipolar electrodes were implanted into the muscular wall of the small intestine. The electrodes were placed 5, 15, 25 and 35 cm distal to the pylorus. 7–10 days after the operation the animals were fasted for 48 h with free access to water. Some experiments were performed on conscious rats and in others the rats were anesthetized with pentobarbital, 30 mg/kg. I.v. infusion of either neurotensin (NT) or (Gln4)‐neurotensin at doses of 1.8, 3.6 and 7.1 pmol kg‐1· min‐1abolished the migrating myoelectric complexes, which were replaced by increased spiking activity along the whole length of the small intestine from which activity was recorded. The changes in myoelectrical activity were observed within 2–4 min after commencement of the infusion. The activity returned to control levels within 5–15 min after the end of the infusion period. The neurotensin sequences NT 9–13, NT 8–13, NT 4–13, NT 1–9 and (Gln4)‐NT 1–11 did not induce any changes in the electrical activity in the small intestine. The effects of NT and (Gln4)‐neurotensin on the myoelectrical activity in the small intestine were indistinguishable. The changes induced by NT or (Gln4)‐NT resemble those found after the ingestion of food. The present data indicate that the intact NT sequence, rather than smaller NT fragments, is necessary to induce changes in myoelectrical activity in the small intestine.
Effect of apomorphine and haloperidol on plasma cortisol levels in conscious dogs
Authors: UVNÄS‐WALLENSTEN KERSTIN , GOINY MICHEL , ORIOWO M. A. , CEKAN STEN
Published: December 2008

Cortisol levels were measured in peripheral plasma of conscious dogs after i. v. administration of apomorphine, a dopaminergic agonist, haloperidol, a dopaminergic antagonist, or apomorphine in combination with haloperidol. Apomorphine in a dose of 0.001 and 0.005 mg/kg did not cause any release of cortisol whereas 0.01 and 0.05 mg/kg caused a dose dependent and peakshaped increase of plasma cortisol levels from 20 to 30 and from 20 to 60 ng/ml respectively. Basal levels were reached again within 1 h. Haloperidol (0.1 mg/kg), when given alone, induced a continuous rise of plasma cortisol levels. After 60 min the levels were ˜80 ng/ml and still tended to rise. Jf apomorphine (0.01 mg/kg) was given 30 min after the injection of haloperidol (0.1 mg/kg) no further effect of the apomorphine injections was observed. We therefore speculate that apomorphine activates central dopaminergic receptors which cause a release of ACTH from the pituitary into the circulation, which in turn stimulates the release of cortisol from the adrenals. The fact that not only apomorphine but also haloperidol stimulated cortisol release suggests a complex role of dopamine transmission involving different dopaminergic pathways as well as different dopamine receptors. It is also possible that injection of haloperidol induces a stress reaction in the dogs, which causes a release of cortisol from the adrenals.
Central blood volume in spontaneously hypertensive rats and Wistar‐Kyoto normotensive rats
Authors: LUNDIN S. , FOLKOW B. , RIPPE B.
Published: December 2008

Central blood volume and total blood volume were determined in spontaneously hypertensive rats and Wistar Kyoto rats at two ages, 6 and 12 weeks, representing ‘borderline’ hypertension and early ‘established’ hypertension, respectively. A technique was used where plasma and erythrocyte indicators were injected into conscious rats. Blood volume in the cardiopulmonary compartment, present in the ‘resting’ awake steady‐state, could then be estimated by sudden freezing of the entire rat. 12 week‐old spontaneously hypertensive rats showed a decreased total blood volume, while the fraction of blood contained in the cardiopulmonary area was significantly increased compared with that of normotensive Wistar Kyoto rats. In 6‐week‐old spontaneously hypertensive rats, total blood volume was only marginally decreased but also here a tendency towards centralization of the blood was seen. Thus, along with the development of hypertension in the spontaneously hypertensive rat their decreasing blood volume tends to become increasingly centralized to the cardiopulmonary area. Both neurohormonal influences and structural wall changes in the low‐pressure capacitance side may contribute to this.
On the presence of serotonin in the gut lumen and possible release mechanisms
Authors: AHLMAN H. , BHARGAVA H. N. , DAHLSTRÖM A. , LARSSON I. , NEWSON B. , PETTERSSON G.
Published: December 2008

The possible presence of a luminal release of serotonin (5‐HT) from gut enterochromaffin cells (EC) of the rat. was studied after the injection of the tritiated 5‐HT precursor 5‐hydroxytryptophan [3H]‐5‐HTP by electron microscopic autoradiography. The uptake of 5‐HTP into gut epithelial cells was also studied by fluorescence histochemistry according to the Hillarp‐Falck technique at the same post‐injection interval as in the autoradiography experiments. 3 h after the injection of 5‐HTP (100 mg/kg i. v.) the fluorescence intensity of EC was increased and numerous, probably enteroendocrine, cells had an increased yellow tryptamine induced fluorescence due to an uptake of 5‐HTP and probably decarboxylation to 5‐HT. However, the labelled precursor [3H]‐5‐HTP was taken up not only into granules of enteroendocrine cells but also incorporated into the cytoplasm and nucleus of nonendocrine cells when studied by autoradiography. After 10 min of efferent electrical stimulation of the vagal nerve much of the label was found in the gut lumen suggesting a release of the amine. The hypothesis of a luminal release of 5‐HT was further corroborated in starved cats, where considerable amounts of 5‐HT were detected by fluorimetric assays in the lumen of isolated jejunal loops under resting conditions. The experiments demonstrate that: (i) 5‐HTP is taken up not only into typical EC but also into other enteroendocrine cells, and most probably decarboxylated to 5‐HT. (ii) Also intestinocytes take up [3H]‐5‐HTP and incorporate the amino acid into peptides to a certain extent, (iii) Following vagal nerve stimulation labelled material, probably 5‐HT, is secreted into the gut lumen, (iv) 5‐HT normally occurs in the gut lumen.
Role of adenosine in adipose tissue circulation
Authors: SOLLEVI ALF , FREDHOLM BERTIL B.
Published: December 2008

The vasodilatory effect of adenosine and some related compounds were studied in subcutaneous adipose tissue in situ. The effects of three drugs that inhibit adenosine elimination; two adenosine uptake blockers, dipyridamole and dilazep, the adenosine deaminase inhibitor, EHNA, were also studied. Plasma levels of adenosine were simultaneously determined by HPLC. Adenosine was a potent vasodilator and 2‐and 6‐substituted analogues were even more potent. Tissue blood flow was linearly related to the venous plasma concentrations of adenosine. An elevation of adenosine in plasma from 0.25 to 0.5 μM enhanced blood flow by approximately 50%. A further increase to 1 μM was associated with a doubling of adipose tissue blood flow. Adenosine also increased the vascular conductance and the capillary filtration coefficient, indicating that it is active on all sections of the vascular bed. Theophylline and caffeine (30–100 μM in arterial plasma) antagonized the vasodilatory effect of exogenous adenosine, abolished vasodilatation due to EHNA + dipyridamole and reduced resting blood flow. The results suggest that adenosine plays a physiological role in regulating adipose tissue blood flow.
Aromatic amino acid incorporation into proteins in rat brain slices: influences of other amino acids affecting transport
Authors: KORPI E. R.
Published: December 2008

Incorporation of [3H]tryptophan, [3H]tyrosine and [3H]phenylalanine into proteins has been studied in cerebral coronal slices from adult and 1‐day‐old rats. Unlabelled amino acids greatly increased (histidine) or decreased (leucine, phenylalanine, tyrosine, tryptophan) intracellular levels of the [3H]amino acids, but only slightly decreased their incorporation rates. Effects on uptake were similar in experiments with adult and newborn rats, but patterns of protein synthesis inhibition seemed to differ. Amino acid uptake and subsequent incorporation into proteins were thus not closely associated. Incorporation in slices from adult rats was much slower than in those from newborn rats, and moreover, one half of it was cycloheximide‐insensitive. The different inhibition patterns by other amino acids may thus be explained by multiple mechanisms in cerebral amino acid incorporation into proteins.
A mathematical model of fluid transport in the kidney
Authors: JENSEN PETER KOCH , CHRISTENSEN OVE , STEVEN KENNETH
Published: December 2008

A mathematical model of the rat kidney is developed from glomerular and tubular submodels. It is assumed that all nephrons are identical, that the hydraulic pressure in the tubules obeys Hagen‐Poiseuille's law, that the rate of fluid reabsorption depends on the flow rate of tubular fluid, and that the tubules are distensible. The independent variables of the model are selected to comply with experimental measurements in the hydropenic rat. The model is used to evaluate the mechanism of glomerulotubular balance: changing the mean ultrafiltration pressure in the glomerular capillaries has a substantial influence on glomerular filtration rate (GFR). A change in the rate of fluid reabsorption in the proximal tubules has a strong influence on GFR notwithstanding that the change in GFR is smaller than that in the rate of fluid reabsorption. The calculated values for the hydraulic pressure profile in the tubular system and the interstitial pressure during ureteral obstruction are in close agreement with experimental measurements. Increasing the arterial haematocrit above normal causes a substantial decrease in GFR, whilst reducing it below normal has only a small effect on GFR.
Conversion of exogenous arachidonic acid to prostaglandins in the pulmonary circulation in vivo A human and animal study
Authors: NOWAK JACEK , RADOMSKI MAREK , KAIJSER LENNART , GRYGLEWSKI RYSZARD J.
Published: December 2008

The capacity of human lungs to synthetize prostaglandins (PGs) from exogenous arachidonic acid (AA) was investigated in healthy male volunteers. 14C‐labelled AA was infused at a constant rate into the right atrium under simultaneous sampling of blood from the ascending aorta. The arterial content of 14C‐AA metabolites was extracted, separated with thin‐layer chromatography and quantified using fractionated liquid scintillation spectrometry. Conversion of exogenous AA to prostacyclin (PGI2) was also studied in the lungs of anaesthetized cats. In these experiments different doses of unlabelled AA were administered intravenously. Simultaneously PGI2‐activity in the arterial blood was assayed using a technique for continuous measurement of platelet aggregation on blood superfused collagen strip. Radiochromatograms of the human arterial plasma revealed no clearly defined peaks corresponding to any of the unlabelled standards of PGD2, PGE2, 6‐keto‐PGF1α, PGF2α or TxB2. The 14C‐activity in the chromatograms materialized only in one (apart from AA) prominent peak in parallel to 13,14‐dihydro‐15‐keto‐PGE2. Neither in cats did significant amounts of PGI2 appear in the arterial blood after administration of AA in moderate doses. Only very high AA doses caused a slight increase in arterial PGI2‐activity. The results demonstrate that human lungs do not convert exogenous AA to PGs under physiological conditions. In cats the reluctance of the lungs to utilize exogenous precursor can only be overcome with high, non‐physiological AA doses. The data may suggest the existence of special regulatory mechanisms which control release of PGs from the lungs and promote utilization of endogenous precursor.
Effect of β‐adrenergic receptor blockade on development of training‐induced bradycardia in rats
Authors: NYLANDER EVA
Published: December 2008

Metoprolol‐treated and untreated rats were subjected to the same treadmill running program for 12 weeks. After training and withdrawal of metoprolol, the treated rats had a more pronounced bradycardia during submaximal exercise than non‐treated rats, although they had a lower heart weight/body weight ratio. The intrinsic heart rate (IHR) was slightly but not significantly lower in trained than in untrained untreated animals. The IHR was not altered by a period of metoprolol treatment neither alone nor in combination with training. It is concluded that chronic cardioselective β‐blockade during training augments the training‐induced bradycardia but may impair the development of cardiac hypertrophy. The training‐induced bradycardia is thus not related to the degree of heart rate increase during exercise for its development.
Structural and mechanical alterations in hypertrophic venous smooth muscle
Authors: UVELIUS BENGT , ARNER ANDERS , JOHANSSON BÖRJE
Published: December 2008

Portal hypertension was induced in rats by partial ligation of the hepatic branches of the portal vein. After 5 days the transluminal pressure of the portal vein was measured, and the vessel was fixed in situ for electron‐microscopy, or dissected out and mounted in an apparatus recording force and shortening. Portal veins from sham‐operated animals were used as controls. Portal venous pressure had increased about twofold after the partial ligation and the cross‐sectional area of the longitudinal muscle layer about twofold. Number of muscle cells per mm2 cross‐sectional area decreased to half of the control value, whereas extracellular space in the muscle layer and the dry weight of the preparations were unaltered. Number of cells was unchanged suggesting that no hyperplasia had occurred. Length‐passive force relations were shifted towards higher force values in the hypertrophic vessels, whereas passive stress‐strain characteristics were similar. The structures that carry passive tension have thus increased in proportion to the vessel as a whole. Length‐active tension curves obtained by stimulation with AC current or high K+ solutions indicated that the hypertrophic vessels could not, in relation to optimal length for active force, shorten to the same extent as control vessels. Maximum active tension per vessel was unaltered whereas force per unit muscle area and force per cell had decreased. As the preparations were supramaximally stimulated and had optimal extracellular Ca2+ concentrations we suggest that the amount of functional contractile proteins has not increased in proportion to the increase in size of the muscle cells.
Adaptive changes in work capacity, skeletal muscle capillarization and enzyme levels during training and detraining
Authors: KLAUSEN KLAUS , ANDERSEN LARS BO , PELLE INGE
Published: December 2008

Six male subjects exercised on a bicycle ergometer 30 min with left leg and 30 min with right leg 3 times a week for 8 weeks. This training resulted in a 14.6% increase in V̇o2 max with two‐leg exercise and a 23.1% increase with one‐leg exercise. A significant decrease towards pretraining V̇o2 max was seen during the following 8 weeks of detraining. Muscle biopsy samples were obtained at rest from m. vastus lateralis before and after training and 4 and 8 weeks after training. During training the number of capillaries per mm2 and the number of capillaries per fiber increased about 20%. The number of capillaries around each fibre type (CA) increased 20–30%. The average area of each fibre type increased only about 5%. The fibre area per CA decreased by about 10%. During 8 weeks of detraining decreases were seen in the number of capillaries per fibre, CA and in fibre area, while fibre area per CA and number of capillaries per mm2 were almost unchanged at the end of the detraining period. Pronounced increases in activities of oxidative enzymes were observed after training, while only minor increases were seen in glycolytic enzyme activities. All enzyme activities decreased towards pre‐training levels during detraining. The results indicate that the training‐induced improvement in oxidative capacity and in muscle capillarization expressed as capillaries per fibre and CA disappears within 8 weeks after cessation of training. However, the fibre area per CA and number of capillaries per mm2 point at a favourable long term effect on the average diffusion distance between capillaries and muscle fibres.
Further studies on the gonadotrophin‐induced inhibition of respiration in the preovulatory rat cumulus oophorus
Authors: MAGNUSSON C. , HILLENSJÖ T.
Published: December 2008

It has been shown earlier that LH decreases the oxygen consumption of the rat cumulus oophorus cells, i.e. the granulosa cells immediately surrounding the follicular oocyte. The decrease occurs in the preovulatory period at the time when the oocyte resumes and completes meiosis. This study examines in more detail the time‐course of LH‐induced inhibition of cumulus respiration. The results show that when isolated cumuli were exposed to LH during in vitro culture a significant inhibition of respiration occurred within one hour. When follicle‐enclosed cumuli were exposed to LH, in vivo or in vitro, the decrease in respiration was not evident until 4 hours after the hormone exposure. By this time oocyte maturation was already in progress. The results suggest that the decrease in cumulus respiration may not be directly linked to the onset of oocyte meiosis.
A study of the effect of stimulated endogenous prostaglandin synthesis on urine flow, osmolar excretion rate, and renin release in hydropenic and saline loaded, anesthetized rats
Authors: LEYSSAC PAUL P. , CHRISTENSEN POUL
Published: December 2008

The purpose of the study was to investigate the effects on urine flow and osmolar excretion of arachidonic acid (C20: 4) infused into the renal artery of anaesthetized rats under conditions in which indomethacin previously was found to reduce urine flow and to prevent the development of a moderate saline diuresis. C20: 4 caused a reversible increase in the urinary excretion rates of PGE2 and PGF2α both in hydropenic rats and in rats during a saline diuresis. Renal venous plasma concentration of PGE2 increased significantly while the increase in PGF2α was insignificant. C20: 4 infusion was followed by an increase in urine flow and osmolar excretion rate in hydropenic rats, and it augmented urine flow (but not solute excretion) in saline‐loaded rats. This latter effect was blunted by indomethacin treatment and inactin anaesthesia. Increased endogenous PG‐levels were associated with only a modest (insignificant) increase in renin release under the present conditions. Saline loading acutely depressed PGE2 and PGF2α urinary excretion rates and plasma renin concentration (PRC). The fall in PRC was unaffected by indomethacin. The main conclusions are that endogenous renal PG's have a diuretic effect in the amytal anaesthetized rat, while an effect on osmolar excretion rate is apparent only under hydropenic conditions. Acute saline loading depresses renal PG‐synthesis, but this depression is not the only cause of the fall in PRC following saline loading. The saline diuresis is caused by a mechanism(s) not involving prostaglandins.
Electrophysiology of cultured parathyroid cells from the goat
Authors: SAND O. , OZAWA S. , HOVE K.
Published: December 2008

The membrane potential and resistance of goat parathyroid (PT) cells in culture were 44.7±6.8 mV and 503±218 MΩ (mean ±S.D., n= 24) in 2.4 mM Ca2+ solution. The corresponding values in 0.8 mM Ca2+ solution were 29.2±12.2 mV and 290± 198 MΩ (n= 22). The current/voltage relation showed a pronounced outward rectification for membrane potentials more positive than ‐40 mV. Current injection produced graded, regenerative responses in half of the penetrated cells. Regenerative responses were also obtained in Na+‐free solution, and these responses were reversibly inhibited by the Ca2+ blocker D‐600. The results support the notion that PT cells possess voltage sensitive K+ and Ca2+ channels, and that exocytosis of stored PT hormone depends on influx of extracellular Ca2+ as in other secretory cells.
Blood pressure in the fetal guinea‐pig
Authors: KIHLSTRÖM INGEMAR
Published: December 2008

Mean arterial blood pressure and heart rate in guinea‐pig fetuses during late gestation have been recorded in situ under maternal pentobarbitone anesthesia. The measurements were performed via a catheter in one of the umbilical arteries. Mean arterial umbilical pressure and heart rate were 28±5 mmHg and 282±30 beats/min, respectively. It is suggested that the recorded pressure is consistent with the rise in systemic arterial pressure in other species during gestation and postnatal life.
The antilipolytic effect of endogenous and exogenous adenosine in canine adipose tissue in situ
Authors: SOLLEVI ALF , FREDHOLM BERTIL B.
Published: December 2008

The effects of adenosine, 2‐Cl‐adenosine, two adenosine uptake inhibitors (dipyridamole and dilazep) and the adenosine deaminase (ADA) inhibitor erythro‐9‐(2‐hydroxy‐3‐nonyl) adenine (EHNA) were studied on basal and stimulated lipolysis in subcutaneous adipose tissue. The basal lipolysis was unaffected by all agents. Lipolysis induced by nerve stimulation (4 Hz, 5 min) was dose‐dependently antagonized (up to 100%) by close i.a. infusions of adenosine (1–40 μM in blood); if the nerve induced vasoconstriction was prevented by α‐adrenoceptor‐blockade. 2‐Cl‐adenosine was a more potent antilipolytic agent than adenosine. EHNA (3–10 μM in blood) did not inhibit stimulated lipolysis in vivo possibly because of the low ADA activity in fat cells. Dipyridamole (0.5‐1.5 μM in blood) in combination with EHNA increased the venous plasma concentration of adenosine from 0.3±0.05 to 0.7±0.1 μM and enhanced the tissue concentration close to 3‐fold. Lipolysis induced by nerve stimulation (4 Hz) was reduced by about 40% by dipyridamole + EHNA and that induced by close i.a. noradrenaline injection (20 nmol) by approximately 60%. It is concluded that adenosine is an antagonist of stimulated lipolysis in subcutaneous adipose tissue in situ in concentrations that are reached during prolonged sympathetic nerve stimulation.
Blood pressure and heart rate response to static exercise in relation to electromyographic activity and force development
Authors: SCHIBYE B. , MITCHELL J. H. , PAYNE F. C. , SALTIN B.
Published: December 2008

5 healthy men performed static knee extension (90° knee angle) with one leg for 5 min. In one series of experiments the force was held constant at 20% of the isometric maximal voluntary contraction. In the other the initial force development was also 20%, but the smoothed, rectified electromyographic activity, (SREMG) recorded after 5 s of contraction was kept constant. Heart rate (HR), arterial mean blood pressure (MBP) (measured 20 cm proximally to the elbow in a. brachialis), EMG (surface electrodes) from the lateral portion of m. quadriceps femoris, and force were continuously recorded.

HR and MBP increased approximately 40% in the force‐constant experiments and approximately 20% in the SREMG‐constant experiments. The greatest increase occurred during the first two minutes of contraction. In the force‐constant experiments SREMG doubled, with the most marked increases occurring during the very early and late parts of the contraction. SREMG correlated with both HR (r=0.85) and MBP (r=0.98). In the SREMG‐constant experiments force declined quickly during the first minute and remained at about 12% MVC thereafter.

The observed cardiovascular responses to static contraction can best be explained as the result of the combined action of central and peripheral drives, the central drive being related to the central activity for the recruitment of motor units, and the peripheral drive being mediated through chemoreceptors in the exercising muscles.
Classification of β‐adrenoceptors in the microcirculation of skeletal muscle
Authors: HILLMAN JAHN , LUNDVALL JAN
Published: December 2008

Nervous and humoral β‐adrenergic, postjunctional effects on microvascular resistance, on precapillary sphincter tone, and on transcapillary fluid exchange in cat skeletal muscle (Lundvall & Järhult 1974, 1976 a, Lundvall & Hillman 1978 a, b) were evaluated with regard to the β1‐or β2,‐specificity of the adrenoceptors. Marked β2‐dilator responses but no significant β1‐effects were observed. The conclusion was therefore reached that neurogenic as well as humoral β‐adrenergic control of the microcirculation in skeletal muscle is exerted via activation of β2‐adrenoceptors.
Axonal transport in transplanted frog sciatic nerve
Authors: HANSON MATS
Published: December 2008

Axonal transport was studied in transplanted frog sciatic nerves‐dorsal ganglia for periods up to three months. The ganglia were either labeled prior to, or after varying periods of transplantation and the distribution of labeled proteins compared. The survival of the preparations was assessed by studying their ability to transmit compound action potentials, to maintain axonal transport and by their ultrastructural appearance. The sensory neurons retained their fast axonal transport and excitability during the transplantation periods. Morphologically about 30% of the axons appeared normal after one month of transplantation. The amount and distribution of protein incorporated radioactivity in the ganglia and the nerve changed with time but the decrease in the ganglia was not accompanied by a corresponding increase in the nerve. There was no evidence for a distinct slow phase of transport in spite of a functional fast transport system. The results indicate that either slow transport stops when the normal balance between release, degradation and recirculation is disturbed by the presence of a ligature or that there is a continuous change in the composition of transported material with time after labeling which is not reflected in altered transport characteristics.
Adipose tissue perfusion and fatty acid release in exercising rats
Authors: LARSEN TERJE , MYHRE KJELL , VIK‐MO HARALD , MJØS OLE D.
Published: December 2008

Arterial concentrations of free fatty acids (FFA), glycerol and lactate were measured in male Wistar rats before, during and after 30 minutes exercise on a treadmill. The arterial concentration of glycerol increased 120% and lactate 340% during exercise, but fell immediately upon its termination. The arterial concentration of FFA increased only 20% during the exercise, but was followed by a sharp rise in the recovery period. Maximum FFA concentration was found after 6 minutes of recovery, reaching 70% above the preexercise level, whereafter plasma FFA fell. Using radioactively labelled microspheres it was found that the fraction of cardiac output reaching adipose tissue after 10 min of exercise was reduced by 30–90% in relation to the resting value. After 3 min recovery, however, the fractional distribution to the same tissue was in average 300% above the value measured 3 min before termination of exercise. It is concluded that the increase in plasma FFA observed during the early recovery period is caused by increased FFA release from adipose tissue, as a consequence of increased adipose tissue perfusion in the recovery period.
Reflex cardiovascular responses to graded stimulations of low‐ and high‐threshold afferents in the carotid sinus and aortic nerves in the cat
Authors: ÖBERG BENGT , KENDRICK ED , THORÉN PETER , WENNERGREN GÖRAN
Published: December 2008

Reflex responses to electrical stimulation of low‐threshold and high‐threshold afferents in the aortic and carotid sinus nerves were investigated in chloralose‐anesthetized cats. Changes in blood pressure, heart rate and muscle resistance were recorded. Low‐threshold stimulation induced depressor responses of moderate magnitude. When stimulation intensity was increased to engage also the high threshold aortic nerve afferents a more pronounced reflex response was seen even with stimulation frequencies <10 Hz. Furthermore, stimulation of low‐ and high‐threshold aortic nerve afferents induced different reflex patterns. For a given fall in blood pressure, the low‐threshold afferents induced a greater reflex decrease in muscle vascular resistance compared with the high‐threshold afferents, which reduced heart rate more. The effects seen at low frequency stimulation of high‐threshold aortic nerve afferents were interpreted to reflect activation of the non‐medullated baroreceptor afferents, while the depressor reflexes at low‐threshold stimulation were induced by medullated baroreceptor afferents. Also the reflex effects of continuous and intermittent stimulation patterns of the various afferents were compared. At the same number of imp/s an intermittent stimulation of the low‐threshold afferents induced greater reflex changes in blood pressure and muscle vascular resistance but smaller changes in heart rate. No such difference was observed when high‐threshold afferents were similarly stimulated.
Specific permeability properties of demyelinated rat nerve fibres
Authors: BRISMAR TOM
Published: December 2008

The specific permeability properties of isolated rat fibres with diphtheria toxin induced paranodal demyelination were investigated in potential clamp experiments. Nodal widening (4 to 6 μm) and paranodal demyelination (20 to 90 μm) were associated with a very large increase in the normally low delayed K‐permeability (>10 times). The resting K‐permeability (which was comparatively large in the rat fibres) was similarly increased, which decreased action potential amplitude and excitability. Fibres with paranodal demyelination had, in addition, a large increase in the maximum peak Na‐permeability (2 to 5 times the normal), which indicated that excitability was upheld by formation of new Na‐permeability sites. The conduction defects in demyelinated fibres can therefore not be related to the size of the demyelination, but to the specific permeability changes in the demyelinated segment.
Cholinergic responses in different sections of rat airways
Authors: VORNANEN M. , TIRRI R.
Published: December 2008

Effect of cholinergic agonists on rat airway smooth muscle were studied. 4 different preparations were used: the trachea and the bronchus representing the extrapulmonary airways, the bronchiole and the parenchymal strip representing the intrapulmonary airways. The dose‐dependent isometric contractile responses of these 4 preparations to acetylcholine (ACh) and carbacholine (CCh) were determined. A significant difference in sensitivity to both ACh and CCh was observed between the extrapulmonary and intrapulmonary airways. When pD2‐values of these preparations were compared, the trachea and the bronchus showed to be 10–100 times more sensitive to these drugs than the bronchiole and the parenchyma] strip. A significant difference between the trachea and the bronchus was also found in the pD2‐values to ACh, the bronchus being more sensitive than the trachea. This difference in sensitivity was probably due to a greater activity of cholinesterase (ChE) in the tracheal tissue, for the difference was not seen in response to ACh with physostigmine or to CCh. It is suggested that there are more cholinergic receptors in the tracheal and bronchial smooth muscles than in the muscles of the bronchioles and the parenchymal tissue.
Protection of the rat gastric mucosa by prostaglandin E2: Possible relation to stimulation of the alkaline secretion
Authors: KOLLBERG B. , ALY A. , JOHANSSON C.
Published: December 2008

Exogenous prostaglandins have specific protective effects on the gastric mucosa called cytoprotection which is proposed to be connected to the stimulatory effects of prostaglandins on the gastric nonparietal secretions. The protection by oral prostaglandin E2 (PGE2) against indomethacin‐induced gastric erosions was studied in the rat, as was the effect on the protection of blocking the gastric alkaline secretion by acetazolamide. PGE2 reduced dose‐dependently the indomethacin gastric erosion formation, confirming previous results from others. Acetazolamide caused very little damage when given alone but potentiated the indomethacin erosion formation in a dose‐related way. PGE2 was less protective or without effect against lesions caused by indomethacin when given together with acetazolamide, but protection could be obtained by increasing the doses of PGE2. Indomethacin and acetazolamide are both blockers of the gastric bicarbonate secretion, which is stimulated by PGE2. The potentiation of indomethacin induced lesions by acetazolamide and the antagonistic actions between acetazolamide and PGE2 on mucosal protection are compatible with the hypothesis that stimulation of the alkaline secretion is one mechanism of cytoprotection of the gastric mucosa by PGE2.
Stimulatory effects of Ba2+on contractile activity in the smooth muscle of the rat portal vein
Authors: UVELIUS BENGT , SIGURDSSON STEFAN B.
Published: December 2008

The effects on mechanical activity in rat portal vein of adding Ba2+, Sr2+or Mg2+(0.3–10 mM) to a tris‐buffered solution (Na‐tris) with 2.5 mM Ca2+was investigated and compared to the effects of addition of Ca2+. Ba2+induced a continuous tetanical activity and increased integrated force from threefold (0.3 mM) to sevenfold (10 mM). Addition of Sr2+and Ca2+had only minor effects on mechanical activity, whereas Mg2+in increasing concentrations exerted an inhibitory effect. Contractures were elicited in K+‐high tris solution with 2.5 mM Ca2+. The amplitudes of the contractures were not affected by added Mg2+, whereas Ca2+, Sr2+, and Ba2+increased contracture force to some extent, the increase being highest for Ba2+(twofold in 10 mM). Sucrose gap recordings of electrical and mechanical activity showed that added Ba2+(0.3 mM) to Na‐tris with 2.5 mM Ca2+increased spike discharge and force/spike, the latter almost twofold. A corresponding addition of 0.3 mM Ca2+had no effect. The effects of adding Sr2+ are very similar to that of added Ca2+. Mg2+decreased spontaneous mechanical activity. Relaxation rates after K‐contractures with 2.5 mM Ca2+, Ba2+, or Sr2+were determined. No difference was found after K‐tris with Ca2+or Ba2+, whereas the veins relaxed faster after K‐tris with Sr2+. We conclude that Ba2+acts as a constrictor of the smooth muscle in rat portal vein partly by initiating an increased spike discharge, and partly by increasing the entry or release of Ca2+per spike, whereas the removal of Ca2+is unaffected.
Enhancement of active tension during release phase of slow stretch‐release cycle of quail oviduct
Authors: ARJAMAA O. , TALO A.
Published: December 2008

There occur strong spontaneous contractions in the avian oviduct. These contractions are considered to effect the locus of the ovum during ovum transport. It is not known how these contractions are regulated and no comprehensive description of the contractions exists. When a transversal strip cut from the magnum part of the oviduct was first stretched to a length of about 275% Lo (Lo = length in situ) and then released to a length of Lo at a rate of 1.7 mm/min, it was found that contractions were different during release from those found during stretch. The rate of stretch and release, and the change in length, were physiological. i.e. they can be recorded under normal transport circumstances in vitro. The amplitude of active tension was usually larger during release than during stretch at comparable lengths. The duration of a single contraction on the other hand was significantly longer during stretch than during release, but the number of contractions was smaller. The total area of active tension was 1.34 times greater during release than during stretch. Passive tension always increased with stretching, while during release passive tension was smaller. It is discussed whether the changes are of membraneous origin or if they result directly from the contractile apparatus.
Transcellular and intercellular transport of anions in the kidney tubules of dogs
Authors: STEEN PETTER A. , SEJERSTED OLE M. , HARTMANN ANDERS , KIIL FREDRIK
Published: December 2008

Fractional reabsorption of 4 anions was measured in anesthetized dogs either during inhibition of bicarbonate‐dependent intercellular NaCl transport by acetazolamide or man‐nitol, or during inhibition of transcellular NaCl reabsorption in the diluting segment by ethacrynic acid or ouabain. When administered subsequent to ethacrynic acid, acetazolamide reduced fractional reabsorption of SCN, Br, CI and I by 0.28±0.03, 0.28±0.02, 0.27±0.03 and 0.31±0.03. Mannitol given after ethacrynic acid reduced fractional reabsorptions by 0.23±0.04, 0.20±0.04, 0.20±0.05 and 0.20±0.05, respectively. Thus, the bicarbonate‐dependent reabsorption system does not discriminate between these anions. Ethacrynic acid reduced fractional reabsorption of SCN, Br and CI by 0.28±0.05, 0.24±0.03, 0.22±0.03 in one group, by 0.32±0.04, 0.34±0.03, 0.31±0.04 in another group, with significantly smaller reductions for I, 0.07±0.03, in both groups. Ouabain reduced fractional reabsorption of Br, CI and I by 0.48±0.04, 0.46±0.04 and 0.24±0.03, respectively. Thus, anion permeability or transport affinity for bromide, chloride and iodide are equal both for inter‐ and transcellular transport, while iodide transport is slow along the transcellular route. No specific transport mechanism for chloride was detected.
On the Ca2+‐permeability of neurons and glia
Authors: SELLSTRÖM ÅKE , HENN FRITZ , JACOBSON INGMAR , VENEMA RICK
Published: December 2008

Fractions enriched in pinched‐off nerve terminals and astrocytic glial cells were used to analyse the permeability of Ca++of the two membranes. Three experimental models were used to illustrate a principle difference of the excitatory versus the non‐excitatory cell membrane, with respect to Ca‐permeability. The effect of an increased [Ca++] on 86Rb+and 3H‐GABA transport was measured in medium containing low and high [K+]. The possibility of GABA stimulation of release of preaccumulated 45Ca++with low and high [K+] was compared in neurons and glia. Finally, the effect of depolarizing [K+] on the transmembranal Ca++‐gradient was measured by comparing the efficacy of the Ca‐ionophore A23187 to depolarize or to inhibit the 3H‐GABA uptake at these different [K+]. The data essentially confirms the picture of a potential dependent Ca++‐permeability in the neuron, while the permeability of the glial cells seems a “true” constant. It might be relevant to suggest the astrocyte a role as a “Ca‐buffer” with possibilities to control extracellular Ca++in cases of hyperactivity, this in analogy with what has been suggested for K+.
Nervous control of pancreatic endocrine secretion in pigs V. Influence of the sympathetic nervous system on the pancreatic secretion of insulin and glucagon, and on the insulin and glucagon response to vagal stimulation
Authors: HOLST JENS J. , GRØNHOLT RIKKE , DE MUCKADELL OVE B. SCHAFFALITZKY , FAHRENKRUG JAN
Published: December 2008

Electrical stimulation of the splanchnic nerves in anesthetized pigs was found to stimulate markedly the pancreatic secretion of glucagon. The response pattern was glucose dependent, the glucagon responses at blood glucose concentrations below 4.5 mmol×l–1being significantly greater than those noted during stimulation at higher concentrations. Insulin secretion was stimulated weakly and variably and only at higher glucose levels. The magnitude of the glucagon response was comparable to that obtained by electrical stimulation of the thoracic vagus nerves with the same frequency. The glucagon response to combined vagal and splanchnic stimulation was nearly identical to the sum of the responses to the two types of stimulation, whereas splanchnic stimulation abolished or reduced the increase in insulin secretion elicited by vagal stimulation. Combined α‐ and β‐adrenergic blockade markedly reduced the glucagon responses to splanchnic stimulation.
Degeneration release of noradrenaline in skin flaps in rats
Authors: JURELL GÖRAN , HJEMDAHL PAUL
Published: December 2008

To study if noradrenaline released from degenerating sympathetic nerves may contribute to metabolic stimulation and low blood flow in an experimental skin flap, we have determined noradrenaline levels in such skin flaps. Attempts to use radioenzymatic methodology for the determination of noradrenaline in rat skin extracts were unsuccessful due to interference with the assay. High performance liquid chromatography with electrochemical detection was, however, found to give accurate estimates of rat skin noradrenaline contents. Rat skin contained approximately 2.7 nmol (455 ng) noradrenaline per gram dry weight. Extensive depletion of skin flap noradrenaline, occurring mainly between 6 and 24 h postoperatively, was found. At 48 h nearly all sympathetic nerves in the skin flaps had degenerated as evidenced by noradrenaline levels of 0.13 nmol/g. The degeneration of sympathetic nerve endings appears to proceed from the sides towards the middle of the flap, indicating a segmental distribution of the nerves. Noradrenaline released from degenerating sympathetic nerves may adversely affect the survival of critical skin flaps by causing vasoconstriction and metabolic stimulation.
Cerebrovascular effects of ammonia in vitro
Authors: ANDERSSON KARL‐ERIK , BRANDT LENNART , HINDFELT BENGT , LJUNGGREN BENGT
Published: December 2008

The effect of ammonia (ammonium salts) upon human and rabbit cerebral arteries was studied in vitro. Ammonia (NH3/NH1+) caused relaxation of cerebrovascular smooth muscle which was transient and occurred irrespective of how the vessels were preconstricted (potassium‐Krebs solution, noradrenaline, serotonin, prostaglandin F2α). The effect was independent of ammonia‐induced extracellular changes in pH. It is concluded that ammonia may contribute to the vasodilatation and increase in cerebral blood flow which occurs under certain pathophysiological conditions.
Effects of exogenous angiotensin II in the Atlantic cod, Gadus morhua Observations on gastric acid secretion, gastric sham drinking, and gastric mucosal plasma flow (14C‐aniline clearance)
Authors: HOLSTEIN B. , BRIGEL B.
Published: December 2008

Cods were equipped with cannulae for drainage of the stomach and for the separate perfusion of the stomach (pure seawater containing phenol red as a volume marker) and intestine (diluted seawater). Acidity of the gastric effluence was titrated, its volume calculated from the phenol red concentration. Gastric mucosal plasma flow (MPF) was estimated by gastric 14C‐aniline clearance, I.m. injection of angiotensin II (AII) depressed basal acid secretion in a dose‐dependent fashion. Also the MPF was reduced, but relatively less than the secretory depression. Therefore, the AII‐induced secretory inhibition could not be explained by restrained mucosal blood flow. Perfusion of the intestine with diluted seawater, or a continuous i.m. infusion of 0.6% NaCl both rendered the fishes non‐drinking. A high dose of All (150 μg/kg·h) induced drinking in intestinally perfused cod while lower doses (15, 50 μg/kg·h) did not. In i.m. saline‐injected cod, all three doses were dipsogenic. The results suggest that 0.6% saline infusion induces a permanent satiety and that intestinal perfusion in addition induces a preabsorptive satiety. The preabsorptive satiety appears more resistant to the dipsogenic action of AII than the permanent one.
Positive feedback facilitation of external intercostal and phrenic inspiratory activity by pulmonary stretch receptors
Authors: DIMARCO A. F. , von EULER C. , ROMANIUK J. R. , YAMAMOTO Y.
Published: December 2008

Both in lightly pentobarbitone anesthetized and decerebrate cats increments in lung volume (V) during inspiration caused facilitation of inspiratory activity both in phrenic (Phr) and external intercostal (EI) motoneurons. This effect had low volume threshold, well below eupnoeic tidai volumes. It was readily reduced or abolished by small additional doses of pentobarbitone. This facilitatory effect appeared with considerably greater magnitude in El than in Phr. The response magnitude was linearly related to the corresponding increments in V̇ but not to increments in airflow (V̇). Sustained elevation of V at zero V caused sustained facilitation of EI and Phr. This positive feedback facilitation which was similarly obtained in spontaneously breathing and paralysed cats occurred continuously with great regularity in every breath. It was abolished by bilateral vagotomy but could then be elicited by electrical stimulation of the central end of the vagus nerve at the same threshold strengths required to elicit a just detectable shortening of inspiratory duration. The results indicate that the slowly adapting pulmonary stretch receptors are responsible for this positive feedback facilitation prior to the negative feedback effect on the inspiratory ‘off‐switch’ elicited by the same receptors. Clear distinctions are described between the reflex characteristics of this ‘low‐threshold’ volume dependent facilitatory reflex and the ‘high‐threshold’ transient excitatory reflex effects provoked by large and rapid inflations.