bluuebunny/crossref_metadata_2025_split huggingface dataset:
Depressor and pressor actions of purine nucleosides and nucleotides in the anaesthetized rat
Authors: DELBRO D. , BURNSTOCK G. 
Published: December 2008

Depressor and pressor actions of purine nucleosides and nucleotides in the anaesthetized rat.Acta Physiol Scand130, 373–380. Received 12 May 1986, accepted 28 January 1986. ISSN 0001–6772. Departments of Physiology, University of Goteborg, Sweden and Anatomy & Embryology and Centre for Neuroscience, University College, London, UK.In pentobarbitone‐chloralose anaesthetized rats, the effects of aortic administration of various purine compounds on systemic arterial pressure were investigated. All animals were pretreated with atropine and guanethidine to (largely) eliminate reflex neurogenic cardiovascular adjustments, and drugs influencing purine receptors, prostaglandin synthesis, etc. were used for analytical purposes. The compounds used were adenosine (AD) and its slowly degradable analogue, 2‐chloroadenosine (2‐chloro), adenosine‐5′‐triphosphate (ATP) and its slowly degradable analogues β,γ‐methyleneATP (β,γ‐meATP) and α,β‐methyleneATP (α,β‐meATP). Control cardiac output measurements before, at and after the peak pressure changes in some experiments revealed that they were at least 80% due to changes in systemic resistance, i.e. dominated by shifts in resistance vascular tone. Adenosine, 2‐chloro, ATP and β,γ‐meATP all elicited depressor (vasodilator) responses. 2‐chloro was more potent than AD. Furthermore, the results suggest that the depressor action of ATP involves P1‐purinoceptors, following the rapid degradation of ATP to AD, and probably also other mechanisms. The stable ATP analogues caused prompt pressor (vasoconstrictor) responses, where α,β‐meATP was more potent than β,γ‐meATP. The latter compound also produced delayed (probably P1‐purinoceptormediated) depressor actions, presumably via slow degradation to AD.
Renal degradation and distribution between urinary and venous output of prostaglandins E2and I2
Authors: BUGGE J. F. , VIKSE A. , DAHL E. , KIIL F. 
Published: December 2008

Renal degradation and distribution between urinary and venous output of prostaglandins E2and I2Acta Physiol Scand130, 467–474. Received 25 November 1986, accepted 11 February 1987. ISSN 0001–6772. University of Oslo, Institute for Experimental Medical Research, Ullevaal Hospital, Oslo, Norway.To examine renal degradation and distribution between urine and renal venous blood, prostaglandins E2and I2(PGE2and PGI2), and a metabolite of PGI2, bketo‐PGF1α, were infused into the suprarenal aorta of anaesthetized dogs after blocking prostaglandin synthesis by indomethacin, 10 mg kg‐1body wt iv. During one passage through the kidney 80% of PGE, and only 25% of PGI2and 6‐keto‐PGF1α, were metabolized. Prostaglandin degradation and arterial input were proportional (r> 0.90). To stimulate the intrarenal prostaglandin synthesis in unblocked kidneys, arachidonic acid was infused at rates ranging from 24 to 160 μg min‐1kg‐1body wt. During arachidonic acid and PGE2infusion the urinary excretion of PGE2was about 20% of the renal venous output over a wide range of infusion rates. During arachidonic acid and PGI2infusion urinary excretion of bketo‐PGF1αwas about 10% of total renal output, but failed to increase further when total renal output exceeded 70 pmol min‐1. Further increase in output occurred only in the renal vein. In contrast, during 6‐keto‐PGF1αinfusion the urinary excretion and the renal venous output of this metabolite were related as 1:2 over a wide range of infusion rates. Thus, PGI2is much less degraded by renal tissue than PGE2, and the distribution patterns differ. Similar distributions between urine and renal venous blood during aortic infusion and stimulated intrarenal synthesis suggest a pre‐glomerular vascular origin of both prostaglandins.
Intrathecal noradrenaline has a dose‐dependent inhibitory or facilitatory effect on the flexion reflex in the rat
Authors: WIESENFELD‐HALLIN Z. 
Published: December 2008

Intrathecal noradrenaline has a dosedependent inhibitory or facilitatory effect on the flexion in the rat.Acta Physiol Scand130, 507–511. Received 15 January 1987, accepted 27 February 1987. ISSN 0001–6772. Department of Clinical Physiology and Neurophysiology, Huddinge University Hospital, Sweden.The effect of intrathecal noradrenaline (NA) on the hamstring flexion reflex to subcutaneous electrical shocks was examined in unanaesthetized, decerebrate, spinalized rats. Low doses of NA (200 ng and 2 μg) depressed and high doses (20 μg and 200 μg) facilitated the reflex. It is suggested that the primary effect of NA in the dorsal horn is inhibitory and in the ventral horn excitatory. Furthermore, the neurons mediating these effects are more sensitive to NA in the dorsal horn than in the ventral horn.
Altered shape and size of red blood cells in obese hyperglycaemic mice
Authors: ENGSTRÖM K. G. , TÄLJEDAL I.‐B. 
Published: December 2008

Altered shape and size of red blood cells in obese hyperglycaemic mice. Acta Physiol Scand130, 535–543. Received 31 October 1986, accepted 2 March 1987. ISSN 0001–6772. Department of Histology and Cell Biology, University of Umeå, Sweden.Red blood cells (RBCs) from hyperglycaemic ob/ob‐mice, normoglycaemic controls, and a healthy man were sucked into a narrow capillary, photographed and measured. Mouse RBCs had a smaller diameter than human ones. Although of normal diameter, the ob/ob‐mouse RBCs exhibited increased area and volume, and more frequently than control RBCs had a minimum cylindrical diameter greater that 3 μm. Cross‐sectional profiles with minimum bending resistance were computed for RBCs of mean area and volume. The diameters of these theoretical profiles agreed closely with those empirically observed, in both mice and man. The profile of ob/ob‐mouse RBCs predicted a greater resistance to corpuscle bending than the control profile. It is concluded that changes in shape and size explain the decreased filtrability of diabetic ob/ob‐mouse RBCs. The results also suggest that the actually occuring smooth biconcavity is in general the RBC shape with maximum flexibility.
Effect of L‐Dopa, dopamine, dihydroxyphenyl acetic acid and homovanillic acid on Na, K‐ATPase activity in rat proximal tubule segments
Authors: BERTORELLO A. , APERIA A. 
Published: December 2008

Effect of L‐Dopa, dopamine, dihydroxyphenyl acetic acid and homovanillic acid on Na, K‐ATPase activity in rat proximal tubule segments.Acta Physiol Scand130, 571–574. Received 6 November 1986, accepted 16 February 1987. ISSN 0001–6772. Department of Developmental Physiology, St Görans Children's Hospital, Stockholm, Sweden.We have recently demonstrated that dopamine (DA) inhibits Na, K‐ATPase in single proximal tubule (PCT) segments dissected from previously collagenase perfused rat kidney. The aim of the present study was to ascertain whether this effect was directly mediated by DA or if DA was the precursor of an inhibitor. When PCT segments were incubated with I.‐Dopa, Na,K‐ATPase was significantly lower than in vehicle incubated tubules. Inhibition of dopa decarboxylase abolished the effect of L‐Dopaon Na,K‐ATPase activity. The metabolites of DA, 3, 4‐dihydroxyphenyl acetic acid (DPAC) and homovanillic acid (HVA) both inhibited Na,K‐ATPase activity in doses higher than 10‐‐6M. Both HVA and DPAC 10‐‐4M caused approximately 35% inhibition. Dopamine inhibited Na,K‐ATPase activity even in a dose as low as 10‐‐7M. Maximal inhibition (>60%) was found with DA‐5M. Na,K‐ATPase activity was significantly lower in tubules exposed to DA 10‐‐4and 10‐‐5M than in tubules exposed to DPAC or HVA 10‐‐4and 10‐‐5m. Dopamine produced in proximal tubule cells from L‐Dopa, is an active inhibitor of the Na,K‐pump in these cells. The DA metabolites DPAC and HVA are less potent Na,K‐pump‐inhibitors.
Comparison of atriopeptins II and III, VIP andβ2‐‐adrenoceptor‐evoked relaxations of the two layers of smooth muscle in the rat portal vein
Authors: BRÅTVEIT M. , RYDNINGEN H. T. , HELLE K. B. 
Published: December 2008

Comparison of atriopeptins II and III, VIP andβ2‐‐adrenoceptor‐evoked relaxations in the two layers of smooth muscle in the rat portal vein.Acta Physiol Stand130, 593–599. Received II November 1986, Accepted 26 February 1987. ISSN 0001–6772. Department of Physiology, University of Bergen, Norway.The relative importance of vascular relaxations induced by atriopeptins (AP), theβ‐adrenoceptor agonist isoprenaline and of the neuropeptide VIP was studiedin uitroon circular and longitudinal preparations of the rat portal vein. Two members of the rat atriopeptins (AP II and III) were equipotent with respect to relaxation of the spontaneously contracting outer, longitudinal layer and of theα1‐‐contracted inner, circular layer. The potency for AP II was about 13 times lower in the inner (pD2= 7.48±0.73,n= 6) than in the outer layer (pD2= 8.60 ±0.34,n =6). No significant difference was apparent between the intrinsic activities for AP II in the two layers. The potencies for AP II were for both layers higher than those for VIP while the intrinsic activities for AP II were significantly lower than for VIP and for the reference agonist, isoprenaline in both layers. Atriopeptin II was equally efficient in relaxing the K+‐depolarized anda1‐‐contracted longitudinal segments. Neither theβ‐antagonist, propranolol nor the guanylate cyclase inhibitor, methylene blue, modified the potency or the intrinsic activity of AP II. These results suggest that concentrations of circulating atriopeptins above 10 nM may contribute to reduction of vascular tone by the methylene blue insensitive receptors for AP II and III in the portal‐mesenteric vein region.
Effect of neuroactive agents on cholecystokinin release from the isolated, perfused porcine duodenum
Authors: CANTOR P. , HOLST J. J. , KNUHTSEN S. , REHFELD J. F. 
Published: December 2008

Effect of neuroactive agents on cholecystokinin release from the isolated, perfused porcine duodenum. Acta Physiol Scand130, 627–632. Received 26 April 1986, accepted 8 March 1987, ISSN 0001–6772. Departments of Clinical Chemistry and Surgery C, Rigshospitalet, and Institute of Medical Physiology C, The Panum Institute, University of Copenhagen, Denmark.To elucidate the mechanisms involved in the regulation of CCK release from the small intestine, the effect of neuroactive agents on the release of CCK from the isolated, perfused porcine duodenum has been studied. CCK in the venous effluent was measured by three radio‐immunoassays specific for the N‐terminus, the tyrosin‐o‐sulphated region and the C‐terminus of CCK‐33. Gastrin‐releasing peptide (GRP) at concentrations of 10‐‐10 and 10‐‐9 M in the arterial line increased the CCK output by about 100 and 500%, respectively, as measured with the assay specific for the sulphated region of CCK. Pilocarpine and physostigmine at concentrations of 10‐‐5 m reduced the CCK output to 24 and 40% of basal, respectively, and also abolised the GRP‐stimulated CCK response. Atropine (10‐‐6 M) increased CCK output about 100%. The results suggest that both stimulatory and inhibitory nervous impulses may be transmitted to the intestinal CCK cell, mediated by intramural GRP neurons and cholinergic pathways, respectively.
Adrenal function of the rat in relation to peroral administration of xylitol: depression of aldosterone
Authors: HÄMÄLÄINEN M. M. , MÄKINEN K. K. 
Published: December 2008

Adrenal function of the rat in relation to peroral administration of xylitol: depression of aldosterone.Acta Physiol Scand130, 687–693. Received I September, 1986, accepted 10 March 1987. ISSN 0001–6772. Department of Biochemistry, Institute of Dentistry, University of Turku, Finland, and School of Dentistry, The University of Michigan, Ann Arbor, Michigan, USA.The effect of peroral administration of xylitol (5% or 20% in food) on adrenal function was investigated in thirty‐five Long‐Evans male rats. The control rats were fed either a non‐substituted stock diet or a 20% glucose diet. Glucose elevated and 20% xylitol reduced the growth of the rats (P0.001), but 5% xylitol had no effect on the body weight. The concentrations of serum glucose and lactic acid decreased in rats fed 20% and 5% xylitol, respectively, but those of insulin, glucagon, corticosterone and aldosterone were not affected. In the adrenal glands, 20% xylitol loading was associated with increased epinephrine (P0.05) and norepinephrine (P0.001), but with decreased aldosterone (P0.001) concentrations. The weights and histological picture of adrenal glands were normal. The urinary pH of xylitol‐fed rats decreased significantly (P0.01). Although peroral xylitol affected the levels of aldosterone and catechola‐mines, a normal glucocorticoid metabolism was permitted. The reduced aldosterone levels were regarded as secondary reactions, possibly resulting from alterations in electrolyte and/or acid‐base balance. The increased catecholamine synthesis may be associated with the promoting effect of xylitol on intestinal calcium absorption.
On the nature of endogenous purines modulating cholinergic neurotransmission in the guinea‐pig ileum
Authors: WIKLUND N. P. , GUSTAFSSON L. E. 
Published: December 2008

By means of agonist and enzyme experiments, the relative importance of endogenous adenosine, adenine nucleotides or other purines as modulators of cholinergic neuroeffector transmission in preparations of guinea‐pig ileum muscle has been examined. Adenosine, 2‐chloroadenosine, AMP, ADP, ATP and AMPPNP reversibly inhibited contractile responses to transmural stimulation of the guinea‐pig ileum longitudinal muscle. 5′‐adenylate deaminase dose‐dependently antagonized the inhibitory effect of adenosine, AMP, ADP, ATP and AMPPNP, but not that of 2‐chloroadenosine. 8‐p‐sulphophenyltheophylline, adenosine deaminase and 5′‐adenylate deaminase enhanced contractile responses to transmural nerve stimulation. Adenosine deaminase and 5′‐adenylate deaminase were virtually equiactive whereas 8‐p‐sulphophenyltheophylline was much more effective, and the theophylline derivative also enhanced contractile responses in preparations pretreated with adenosine deaminase or 5′‐adenylate deaminase. Moreover, 8‐p‐sulphophenyltheophylline abolished the inhibition by dipyridamole, whereas adenosine deaminase and 5′‐adenylate deaminase only partly antagonized the inhibitory effect of dipyridamole. Application of 5′‐adenylate deaminase did not enhance the nerve‐induced contractions in preparations pretreated with adenosine deaminase or a combination of dipyridamole and adenosine deaminase.In conclusion, adenosine deaminase and 5′‐adenylate deaminase enhanced the nerve‐induced contractions in the ileum, and, since 5′‐adenylate deaminase was inactive after pretreatment with adenosine deaminase, this suggests that endogenous adenosine rather than 5′‐adenine nucleotides modulated cholinergic neurotransmission in the ileum. However, the adenosine receptor antagonist 8‐p‐sulphophenyltheophylline was much more effecctive than the enzymes, suggesting that endogenous purines other than both adenosine pr classical 5′‐adenine nucleotides were involved in the purine modulation of neurotransmission in ileum muscle.
Functionalα‐adrenoceptors in human atrial preparations in the presence ofβ‐receptor blockade
Authors: ASK J. A. , STENE‐LARSEN G. , HELLE K. B. , RESCH F. 
Published: December 2008

Inotropic effects via cardiacα‐adrenoceptors were studied in electrically driven auricular strips (1 Hz, 37 °C) from patients treated withβ‐blockers for months prior to open heart surgery. Markedα‐mediated positive inotropic effects were demonstrated with adrenaline (A), noradrenaline (NA) and phenylephrine (PHE) in the presence ofβ‐blocker and with blockers of the muscarinic receptor and of the neuronal and extraneuronal uptake mechanisms for the catecholamines. In the presence of ± 10‐6mpropranolol the maximal effects as well as the potencies (pD2‐values) for A and NA were not significantly different while higher than for PHE. Theα1‐blocker, prazosin (10‐6m), markedly reduced the pD2values but not the intrinsic activities (α‐values) for A, NA and PHE in theβ‐blocked preparations. Methoxamine, however, induced negative inotropic responses at normal and low frequencies (1, 0.5 and 0.1 Hz) of stimulation, suggestive of non‐specific, cardiodepressant effects. Other agonists withα‐effects in other types of tissue (oxymethazoline, xylomethazoline and clonidine) were without effects on the force and velocity of contraction in the auricular strips under the present experimental conditions.The results showα1‐type of adrenoceptor‐induced inotropic effects for A, NA and PHE duringβ‐blockade in human auricular strips, indicating that cardiacα1‐receptors may have clinical importance by increasing the inotropy of the human myocardium treated withβ‐blocking agents.
α‐Adrenoceptor stimulation, but not muscarinic stimulation, increases cyclic AMP accumulation in brain slices due to protein kinase C mediated enhancement of adenosine receptor effects
Authors: FREDHOLM B. B. , LINDGREN E. , LINDSTRÖM K. , NORDSTEDT C. 
Published: December 2008

In the present study, using rat hippocampal slices, we have further examined the stimulatory effect ofα1adrenoceptors on the accumulation of cyclic AMP, which is known to depend on calcium and adenosine. The addition of noradrenaline (NA) stimulated the accumulation of [3H]inositol phosphates in [3H]inositol‐treated slices. This effect was shared by carbachol (10–100μmol l‐1) but not by the adenosine receptor agonist 2‐chloroadenosine (100μmol l‐1). The stimulatory effect of theα‐agonists (phenylephrine or NA + propranolol) on cyclic AMP was shared by a diacylglycerol derivative,sn‐1‐oleyl‐2‐acetyl glycerol (OAG), and by the tumour‐promoting phorbol esters phorboldibutyrate (PDiBu) and tetradecanoyl phorbol acetate (TPA). PDiBu caused a translocation of protein kinase C from soluble to particulate fractions. The effects of PDiBu andα‐adrenoceptor stimulation on cyclic AMP were not additive. Surprisingly, carbachol (1–1000μmol l‐1) did not stimulate cyclic AMP accumulation in rat hippocampal slices either in the presence or in the absence of an adenosine receptor agonist.The results are compatible with the opinion that a‐adrenoceptor stimulating drugs enhance the formation of inositol phosphates and diacylglycerol, which synergistically activate protein kinase C, which in turn augments the stimulation of cyclic AMP formation. Thus, a neurotransmitter whose principal biological effect is to stimulate inositol phosphate formation can influence cyclic AMP formation by virtue of an interaction with the actions of the ubiquitous neuromodulator adenosine. The fact that the effect of theα‐receptor stimulation was not mimicked by a muscarinic agonist could indicate that other factors besides activation of inositol phospholipid hydrolys are important for this receptor–receptor interaction.
Influence of reduced muscle temperature on metabolism in type I and type II human muscle fibres during intensive exercise
Authors: BLOMSTRAND E. , ESSÉN‐GUSTAVSSON B. 
Published: December 2008

Six male subjects performed intensive cycle exercise to exhaustion after cooling their legs in water at 10–12 °C (muscle temperature (Tm) 28±2.6 °C, mean ±SD). Exercise at exactly the same rate and duration (370±34 W, 1.5±0.2 min) was then repeated by each subject 2–5 weeks later at normal Tm (35 ± 1.0 °C). Muscle biopsies were taken from the vastus lateralis muscle at rest and after exercise. The muscle tissue was freeze‐dried and fragments of single fibres were dissected out. The fibres were classified and pooled into groups of type I and type II. Analyses of glycogen, glucose 6‐phosphate, lactate and phosphagens were performed on pools of type‐identified fibres.After exercise at reduced Tm, all subjects had higher concentrations of glucose 6‐phosphate and lactate in both type I and type II fibres, and in most subjects the concentrations of ATP and phosphocreatine were lower as compared with the findings after exercise at normal Tm. During exercise the glycogen content of both fibre types decreased to a greater extent at reduced than at normal Tm in most subjects.The results suggest that during intensive dynamic exercise at reduced. Tm there is a higher degree of glycolysis from glycogen in the muscle than in the normal situation. In some subjects the cause of fatigue may be related to a more rapid accumulation of lactate in the cold muscle, while in others fatigue may be related to alternative factors, e.g. low levels of ATP and phosphocreatine.
Agonist and antagonist characterization of the P2‐purinoceptors in the guinea pig ileum
Authors: WIKLUND N. PETER , GUSTAFSSON LARSE. 
Published: December 2008

When adenine nucleotides were administered to isolated guinea pig ileum longitudinal muscle, two immediate effects were observed: a contractile effect and a concomitant inhibition of the responses elicited by transmural nerve stimulation. At concentrations up to 10‐4mthe order of potency for the contractile effect was α,β‐MeADP =α,β ‐MeATP > ADP = ATP = AMPPNP =β,t‐MeATP > 2′‐deoxy AMP = 2′‐deoxy ADP. AMP and adenosine did not show any contractile effect, whereas both compounds dose‐dependently and reversibly inhibited the nerve‐induced contractile responses. ADP, ATP, β,t‐MeATP and AMPPNP also inhibited contractile responses to transmural nerve stimulation, whereas 2′‐deoxy AMP, 2′‐deoxy ADP, α,β ‐MeADP and α,β ‐MeATP showed but weak inhibitory effects, 2′‐deoxyadenosine, IMP, IDP, ITP, 8‐BrATP and TDP lacked significant contractile effects and did not exert a significant inhibition on nerve‐induced contractions.p‐chloromercuribenzene sulphonic acid (PCMBS) irreversibly antagonized the contractile effects of ADP, ATP and the α,β ‐methylene derivatives, whereas dantrolene sodium, tetrodotoxin, scopolamine and 8‐p‐sulphophenyltheophylline were without effect on nucleotide‐induced contractions.The contractile effect of ADP or ATP was unaffected by indomethacin, whereas the contractile effect by α,β ‐methylene derivatives was abolished by indomethacin. ADP, ATP and α,β ‐MeADP enhanced contractile responses to exogenous acetylcholine, α,β‐MeADP being most effective. This enhancement was blocked by indomethacin. We suggest that ADP and ATP contracted the guinea pig ileum by an action at postjunctional P2‐purinoceptors with different characteristics from prejunctional P1‐purinoceptors. The α,β‐methylene analogues seemed to act at least at one different excitatory site and promotion of prostaglandin biosynthesis was critical for their effect.