bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulation of Adrenergic Nerve Fibres to the Urinary Bladder of the Rat
Authors: Elmér Mats 
Published: December 2008

AbstractThe contraction of the rat detrusor muscle caused by electrical stimulation of the hypogastric or pelvic nerves was followed by relaxation when the nerves were stimulated for a short period. The relaxation was more pronounced when the initial contraction was reduced by atropine. It was found to be mediated by adrenergic fibres acting on inhibitory β2‐receptors. Stimulation of the hypogastric or pelvic nerves at high frequencies increased the contractile response probably via adrenergic fibres activating excitatory α‐receptors.
Affinity of Noradrenaline and Dopamine for Neural α‐Receptors Mediating Negative Feedback Control of Noradrenaline Secretion in Human Vasoconstrictor Nerves
Authors: Stjärne Lennart , Brundin Jan 
Published: December 2008

AbstractIsolated superfused field stimulated biopsy specimens of human peripheral arteries and veins, preincubated with3H‐(‐)‐noradrenaline (NA) to label the neural stores of NA, were used to study the potency of dopamine (DA) and of NA as triggers of α‐adrenoceptor mediated negative feedback control of sympathetic neurotransmitter secretion, evoked by stimulation with trains of 300 shocks at 1 Hz. In this preparation DA was found to be only slightly less potent than NA in depressing both the secretion of3H‐NA, and the contractile response, evoked by nerve stimulation. DA depressed the contraction evoked by exogenous NA as well, but to a very much smaller extent. On the other hand, DA was a very weak agonist on the α‐receptors of the smooth muscle; nearly 1 000 times higher concentrations of DA were required to mimick contractions evoked by exogenous NA. The results show that the neural α‐receptor function involved in control of NA secretion differs considerably from the α‐receptors ofe.g.smooth muscle, with respect to sensitivity to DA. It seems possible that the observed depressing effect of DA on NA secretion may be of pharmacological and clinical interest; it may at least in part explain the vasodilating effect of DA infusions in man.
Intracellular Distribution of Amines Taken up by Rat Mast Cells In Vitro
Authors: Bergendorff Anders 
Published: December 2008

AbstractMast cells isolated from rat peritoneal and pleural cavities were incubatedin vitrowith radioactively‐labelled histamine (Hi), 5‐hydroxytryptamine (5‐HT), dopamine (DA), noradrenaline (NA), tyramine (TA), phenylethylamine (PhEA), tryptamine (TrpA), ephedrine (Eph) or amphetamine (Amph). All these amines were taken up by the mast cells. The dose‐response curves for the compound 48/80‐induced release of endogenous Hi and for the various amines taken up by the cells were compared. The release curves for Hi, 5‐HT, DA, NA and TA were found to be similar to that for endogenous Hi, while those for PhEA, TrpA, Eph and Amph were different from that for endogenous Hi. The uptake of Hi, 5‐HT, DA, PhEA, TrpA and Eph into granules in mast cells was studied. Membrane‐bound granules were obtained by sonication of mast cells incubated with the respective amine, followed by differential centrifugation. The amine content of these granules was then measured. Hi, 5‐HT and DA were found to be mainly localized to the granules, while a smaller proportion of the PhEA, TrpA and Eph was found there, the rest being located extragranularly. The present results suggest that, when taken up by rat mast cells, even amines which are not endogenous to the cells are stored in the same way as the endogenous amines Hi and 5‐HT.
The Spread of the Action Potential through the T‐System in Hagfish Twitch Muscle Fibres
Authors: Nicolaysen Kåre 
Published: December 2008

AbstractThe input impedance of twitch muscle fibres of the Atlantic hagfish has been measured with sinusoidal transmembrane currents. The apparent specific membrane resistance and capacitance decreased markedly with frequency, and were relatively independent of fibre diameter. A model of the T‐system based on anatomical observations, was used to predict the input impedance in the normal solution (artificial sea water). The changes in input impedance produced by glycerol treatment, low chloride solution, reduced pH and isotonic solutions with low ionic strength were easily interpreted in terms of the same model. The model predicts severe attenuation of the action potential if conducted electrotonically by the transverse tubules towards the center of the fibre.
N‐Acetyltransferase and Hydroxyindole‐O‐Methyltransferase Activity in Intraocular Pineal Transplants: Diurnal Rhythm as Evidence for a Functional Sympathetic Adrenergic Innervation
Authors: Bäckström Maria , Olson Lars , Seiger ÅKe 
Published: December 2008

AbstractImmature rat pineal grafts were transplanted bilaterally to the anterior eye chamber of adult male rats. The transplants matured and became sympathetically innervated from the host iris and synthesized 5‐hydroxytryptamine as revealed by fluorescence histochemistry. Transplants were used to investigate whether the newly formed nerve terminals were functional and thus could induce a rhythm in pineal N‐acetyltransferase (NAT) enzyme activity and hydroxyindole‐O‐methyl transferase (HIOMT) enzyme activity. Thein situpineal glands from the recipient animals exhibited NAT and HIOMT levels and diurnal variations of enzyme activities no different from control rats without transplants. Sympathetically innervated transplants showed lower NAT enzyme activity than thein situpineals but did yield a highly significant increase in darkness NAT activity as compared to light NAT activity (20:1). Sympathetically denervated transplants showed a much smaller rise in darkness NAT enzyme activity as compared to light values (1.8:1) but the rhythm was still statistically significant (p < 0.01). Sympathetically innervated transplants had a higher HIOMT activity in darkness than in light (2.7:1). The HIOMT activity of the sympathetically denervated grafts was invariably low. Protein contents of transplants were found to be significantly lower thanin situpineal protein content but failed to show a diurnal variation.
Phenylethanolamine‐N‐methyl Transferase (PNMT) Activity and Catecholamine Content in Chromaffin Tissue and Sympathetic Neurons in the Cod,Gadus morhua1
Authors: Abrahamsson Tommy , Nilsson Stefan 
Published: December 2008

AbstractThe activity of phenylethanolamine‐N‐methyl transferase (PNMT) has been measured in the chromaffin tissue of the head kidney and in the sympathetic neurons of the coeliac ganglion/splanchnic nerve in the cod. The content of adrenaline and noradrenaline in these tissues and in other adrenergically innervated tissues and blood plasma was also determined. Adrenaline dominates over noradrenaline in most sympathetically innervated tissues, in the chromaffin tissue and in blood plasma, but not in the muscularis mucosae of the swimbladder. High PNMT activity was found in the chromaffin tissue in the walls of the posterior cardinal veins, and also in sympathetic neurons. It is concluded that the adrenaline found in the sympathetic nerves may originate from intraneuronal adrenaline synthesis, but also from circulating adrenaline which is taken up and stored.
Adenosine 3‘, 5’‐cyclic Monophosphate in Perfused Rat Hearts Exposed to Isoprenaline and Dopamine
Authors: Osnes Jan‐Bjørn , ØYe Ivar 
Published: December 2008

AbstractIsoprenaline and dopamine increased cyclic AMP (cAMP) content and contracile activity of isolated perfused rat hearts. The changes of cAMP levels depended on the mode of drug administration. Isoprenaline (4 × 10‐10mol) administered to the perfused heart as a relatively concentrated bolus, caused a substantial, rapid and transient increase of cAMP. Isoprenaline (2 × 10‐10mol and 4 × 10‐10mol) and dopamine (10‐7mol) diluted in 40 ml of perfusate which was continuously recirculated through the heart, caused a gradual increase of cAMP content which approached an apparent steady state. cAMP accumulation occurred at isoprenaline concentrations above 10‐9M and at dopamine concentrations above 10‐6M. Both agents also increased cAMP labelling from14C‐adenine in the perfusate, probably indicating increased cAMP synthesis. Isoprenaline at 2 × 10‐8M and 10‐7M increased labellingmorethan content of cAMP. Isoprenaline and dopamine also increased phosphorylaseaactivity. An association between increased cAMP contents and increased contractile activity was revealed by both the time‐response and the dose‐response curves of hearts exposed to isoprenaline and dopamine. Since both agents stimulate adrenergic β‐receptors in cardiac muscle, the results are concordant with the hypothesis that cAMP is involved as a mediator of the inotropic response to adrenergic β‐stimulation.
Sympathetic Control of Cerebral Blood Flow in Acute Arterial Hypertension
Authors: Bill Anders , Linder Jan 
Published: December 2008

AbstractThe cervical sympathetic chain on one side was stimulated electrically at 10–20 Hz and an acute rise in arterial blood pressure was produced by: intravenous injection of angiotensin, ligation of the thoracic aorta, or ligation of the aorta combined with injection of metaraminol. The blood flow through the cerebrum and the cerebellum was determined by using labelled microspheres. At high blood pressures there was multifocal breakdown of the blood‐brain barrier in the cerebrum as indicated by leakage of Evans blue. The breakdown was restricted to the control side or much more marked on that side than on the stimulated side. Sympathetic stimulation prevented also breakdown of the blood‐aqueous barrier. The blood flow through the cerebrum on the control side was higher than that on the stimulated side in all experiments. Regions with breakdown of the blood‐brain barrier had flow rates which were about 10 times normal values. Cerebellar blood flow was less affected by the hypertension and did not react significantly to sympathetic stimulation. The results indicate that stimulation of the sympathetic nerves to the brain tends to prevent forced dilatation of the arterioles with a resulting regional overperfusion with blood and breakdown of the blood‐brain barrier. It is concluded that one role of the sympathetic nerves supplying the brain is to extend the pressure region with autoregulation in its upper part under conditions of a general increase in sympathetic vasomotor activity.
Influence of phenobarbital on changes in the metabolites of the energy reserve of the cerebral cortex following complete ischemia
Authors: Nordström Carl‐Henrik , Siesjö Bo K. 
Published: December 2008

AbstractThe present study, which concerns the rate of changes in the cerebral cortex concentrations of phosphocreatine (PCr), ATP, ADP, AMP, lactate and pyruvate during complete ischemia, had the objective of finding out whether or not phenobarbital retards depletion of tissue energy reserves during ischemia. Ischemia was induced for periods of 10 s to 10 min in animals maintained on 70% N2O or given 150 mg. kg‐l of phenobarbital. The results showed that the barbiturate anaesthesia delayed utilization of ATP during the first 2 min. However, after 5 min of ischemia PCr and ATP concentrations, as well as the calculated adenylate energy charge, were identical in animals anaesthetized with nitrous oxide and phenobarbital. Thus, phenobarbital induces a very moderate delay in the depletion of cerebral energy reserves that occurs during complete ischemia. The results obtained after 5–20 s of ischemia allowed calculation of energy (˜P) utilization according to Lowry et al (1964). The closed system method gave values for Putilization which were not far from those obtained by CMRo, measurements. However, with normal values for metabolic rate (70% N2O) valid estimates are obtained only with very short ischemic periods (5–10 s) and, with such short periods, the oxygen content of the tissue may introduce an error.
Effect of sympathetic stimulation on the blood brain barrier dysfunction induced by amphetamine and by epileptic seizures
Authors: Johansson Barbro B. , Lund Staffan 
Published: December 2008

AbstractStimulation of the sympathetic nerves to the brain is known to make the resistance vessels able to with stand a higher blood pressure,i.e. to prevent blood‐brain harrier (BBB) dysfunction and overpcrfusion in acute hypertension. When hypertension occurs concomitantly with a metabolic vasodilatatione.g. during epileptic seizures and after amphetamine‐administration, protein leakage in the brain is more pronounced than in hypertensionper se. Unilateral stimulation of the cervical sympathetic chain during the administration of amphetamine or bicuculline—the latter a GABA‐receptor blocking substance that induces epileptic activity—attenuated the leakage of Evans blue‐albumin and125IHSA into the brain. Our results thus indicate a prophylactic effect of sympathetic stimulation also when hypertension is combined with a nletabolically induced vasodilatation. The sympathetic nerves may constrict both extracerebral arteries and intracerebral resistance vessels. Unexpectedly the effect on the BBB of unilateral stimulation was to a great extent bi lateral under the present experimental conditions.
Estrogen induced inhibition of3H‐noradrenaline release in the uterus and portal vein of the rat
Authors: Bengtsson Bengt 
Published: December 2008

AbstractThe influence of estrogen treatment on3H‐noradrenaline release, induced by potassium or calcium, was studied in isolated preparations of the uterus and the portal vein of the rat. Uterine strips of oophorectomized rats responded with contraction followed by transient relaxation when immersed in a medium containing 127 mM potassium. The transient relaxation was accompanied by an increased rate of3H‐nor‐adrenaline efflux. When the uterine strips were bathed in calcium‐free potassium solution, addition of calcium (3 mM) evoked an increased outflow of3H‐noradrenaline coinciding with a relaxation phase of the contractile response to calcium. After estrogen treatment of the rats the pattern of response was altered. The uterus then responded to potassium and calcium with sustained contractures and with a relatively small (potassium) or with no (calcium) increase of3H‐noradrenaline efflux. Normetanephrine (5 × 10‐‐5M) did not influence the uptake or release of3H‐noradrenaline in either non‐estrogenized or estrogen treated rats uterus. Calculations, based on the amounts of3H‐noradrenaline released by potassium and on the inhibitory effects of desipramine (10‐‐5M) on neuronal uptake of noradrenaline, suggested that similar amounts of tracer were accumulated in the adrenergic nerves of both non‐estrogenized and estrogen treated preparations. Tyramine (10‐‐4M) had a weaker stirnulatory effect on3H‐noradrenaline release than potassium, and the tyramine induced release was not inhibited by estrogen treatment. Strips of the rat portal vein responded to potassium with an increased rate of3H‐noradrenaline efflux. As in the uterus, estrogen treatment reduced the release of3H‐noradrenaline in response to potassium. The adrenolytic effect of estrogen is possibly due to reduced entry of calcium ions into the nerve terminal.
Vasopressin release induced by hemorrhage in the goat
Authors: Larsson B. , Olsson K. , Fyhrquist F. 
Published: December 2008

AbstractEffects of moderate hemorrhage were studied in normovolemic and hydrated conscious goats. Plasma arginine vasopressin (AVP) in jugular vein blood did not rise in response to bleeding of 8 and 12 ml/kg b.wt. After a blood loss of 16 ml/kg an abrupt and conspicuous rise in plasma AVP (to > 10 times basic level) was seen in 50% of the experiments, whereas no rise in AVP occurred in the remaining experiments. Bleeding at 20 and 24 ml/kg gave a more consistent AVP response. Hydration did apparently not reduce the AVP‐responsiveness to bleeding. The plasma vasopressin concentration returned to pre‐hemorrhage level about 3 h after bleeding,i.e. before the blood was re‐transfused. A minor, and inconsistent rise in plasma renin activity occurred in response to bleeding. Central venous pressure fell during hemorrhage and stayed depressed until the blood was re‐transfused. Since the depression was of the same order in all experiments, and was still present when plasma AVP had returned to pre‐hemorrhage level, the fall in venous pressure was obviously not the main cause of the AVP‐response. However, the pronounced riseinplasma vasopressin was correlated to a fall in the arterial pressure and to hyperventilation. No urge to drink developed during any of the hemorrhage experiments. It is concluded that the goat does not readily respond to hemorrhage with vasopressin liberation. When it happens, pressor amounts of the hormone are released, and a fall in arterial pressure and/or increased stimulation of respiratory chemoreceptors (hypoxia?) appear(s) to be the ultimate cause(s) of the release. This thirst‐independent regulation of vasopressin secretion is obviously of no importance in day to day control of water balance, but may help to maintain the arterial blood pressure in emergency situations.
Simultaneous measurements of capillary diffusion and filtration exchange during shifts in filtration‐absorption and at graded alterations in the capillary permeability surface area product (PS)
Authors: Rippe Bengt , Kamiya Akira , Folkow Björn 
Published: December 2008

AbstractThe diffusion exchange of Cr‐EDTA, using the single injection indicator diffusion method, was followed simultaneously with estimations of the capillary filtration capacity (CFC) in an “isogravimetric” rat hindquarter preparation during artificial perfusion and maximal dilatation. Measurements were performed at constant flow and during 1) shifts in filtration‐absorbtion, 2) alterations of perfused capillary wall area (graded rarification of capillary network by microsphere injection) and 3) during alterations of permeability (i.a. infusion of histamine). At maximal vasodilatation CFC was 0.037 ± 0.001 ml/min × mmHg × 100 g and PS for Cr‐EDTA 5.67 ± 0.13 ml/min × 100 g. During filtration or absorbtion, Cr‐EDTA transfer from vessels to interstitium changed only slightly but the situation may well be different for solute transfer from interstitium to vessels. Alterations in capillary wall area resulted in proportional changes in PS for Cr‐EDTA while the CFC changes were always relatively smaller. Histamine increased CFC some threefold with a marked increase in protein transfer, while PS for Cr‐EDTA increased only marginally. This hista mine effect could be ascribed mainly to an increase in the number of large pores which, because of their relative paucity, are of little importance for small molecular diffusion exchange but highly important for convective and macromolecular exchange.
Effects of dopaminergic agonists and antagonists on isolated cerebral blood vessels
Authors: Edvinsson L. , Hardebo J. E. , Mcculloch J. , Owman Ch. 
Published: December 2008

AbstractThe vasomotor response of dopamine and dopaminergic agonists was studiedin vitroon middle cerebral arteries from cat and pial arteries from humans. The action of various inhibitors was tested in order to define the receptors involved. A contractile response could be obtained by epinine, apomorphine and dopamine in the mentioned order of potency. The effect was blocked byalpha‐receptor as well as serotonin receptor antagonists. The mode of inhibition suggested that serotonin receptors rather thanalpha‐adrenoceptors mediated the dopamine‐induced contraction. A dose‐dependent dilatation could be evoked by the dopaminergic agonists on actively contracted pial arteries. The relative potency was epinine > dopamine > apomorphine. The order of potency for the agonists, together with blocking experiments (including a parallel shift in the log dose‐response curve induced by bulbocapnine), indicated that the vasodilatation is mediated by specific dopamine receptors.
Blood flow in the rabbit tenuissimus muscle Influence of preparative procedures for intravital microscopic observation
Authors: LINDBOM L. , TUMA R. F. , ARFORS K.‐E. 
Published: December 2008

LINDBOM, L., TUMA, R. F. & ARFORS, K.‐E.: Blood flow in the rabbit tenuissimus muscle: Influence of preparative procedures for intravital microscopic observation. Acta Physiol Scand 1982,114:121–127. Received 21 April 1981. ISSN 0001–6772. Department of Experimental Medicine, Pharmacia AB, Uppsala, Sweden.The tenuissimus muscle in the rabbit and the cat is a suitable tissue for intravital microscopic investigation of skeletal muscle blood flow. In this study the influence of surgical procedures necessary for direct microscopic observation on the physiological state of the rabbit tenuissimus muscle was assessed by means of blood flow measurements. Mean resting blood flow was 2.8±0.8 (mean ± S.D.) ml. min‐1. 100 g‐1in the left tenuissimus muscle when prepared for microscopic observation as determined by the radioactive microsphere method. This value was not significantly different from that in the intact unexposed muscle in the contralateral leg, 3.3 ±1.1 ml. min‐1. 100 g‐1. Exposure of the muscle to atmospheric oxygen tension resulted in a reduction of blood flow to 0.7±0.4 ml. min‐l. 100g‐l, suggesting that local metabolic control mechanisms were active. The normal range of vascular control seemed to be maintained, as demonstrated by an increase in blood flow to 64.2± 18.8 ml. min‐1. 100 g‐lduring “maximal” vasodilation induced by topical application of PGE1. The tenuissimus muscle showed a marked sensitivity to mechanical stimulation. Slight stretching of the muscle, similar to what may occur during surgical preparation, resulted in an increase in blood flow to 17.5±5.7 ml. min‐1. 100 g‐1. Flow values calculated from data obtained by direct microscopic measurements in the tenuissimus muscle agreed well with those obtained by the microsphere method.
Transport of glucose across the blood‐brain barrier: Reevaluation of the accelerative exchange diffusion
Authors: CHRISTENSEN OVE , LUND‐ANDERSEN HENRIK , BETZ A. LORRIS , GILBOE DAVID D. 
Published: December 2008

In an earlier study of glucose transport across the blood‐brain barrier it was concluded that the kinetic transport constants increase as the brain glucose concentration increases, a finding that was attributed to accelerative exchange diffusion (Betz et al. 1975). The conclusion, however, relied upon application of a commonly used simplified treatment of tracer extraction data. In this study it is demonstrated that the simplified treatment is applicable only in the case of zero brain glucose concentration, and a more general model for determination of the kinetic constants is developed. Re‐analysis by this model of the data of Betz et al. (1975)—comprising a range of brain glucose concentrations—gave kinetic constants which did not vary significantly over a wide range of brain glucose concentrations. For brain glucose concentrations up to about 12 mmol l‐1, the kinetic constants obtained for glucose transport across the blood‐brain barrier areKm =6.18±0.38mmol l‐1Vmax= 1.65±0.06 μmol g‐1 min‐1