bluuebunny/crossref_metadata_2025_split huggingface dataset:
Repeated isokinetic plantar flexions at different angular velocities
Authors: GERDLE B. , LÅNGSTRÖM M. 
Published: December 2008

Repeated isokinetic plantar flexions at different angular velocities. Acta Physiol Scand 130,495–500. Received 29 October 1986, accepted 23 February 1987. ISSN 0001–6772. Work Physiology Division, National Board of Occupational Safety and Health, and Department of Physical Medicine and Rehabilitation, University of Umeå, Sweden.Peak torque (PT), contraction work (CW) and mean power (CP) were measured for each of zoo repetitive isokinetic (maximum effort) plantar flexions. Simultaneous recording of integrated electromyograms (iEMG) were obtained from the three parts of the triceps surae muscle. Four tests at different angular velocities (30, 60, 120 and 180 degrees s‐1 (°.s‐1)) were performed with at least 2 weeks between each test. The subjects were eight clinically healthy females (24–36 years). At all four angular velocities CW, CP and PT decreased steeply during the first approximately 70 contractions, followed by a steady‐state level with no further significant decreases. The relative decreases of PT and CP were significantly smaller than for CW at all velocities. The relative CW decline increased with angular velocity; the relative PT and CP decreases were not velocity dependent. Also iEMG activity decreased in two phases during the zoo contractions and were on a significantly lower relative level at 180°.s‐1. However the reduction of range of motion was significantly greater at 180°.s‐1 and when the iEMG activity was compensated for this decrease the relative decreases in electromyographic activity were similar at the four angular velocities. The results indicated that CW was more sensitive to fatigue than PT and CP and that CW fatigue was dependent on angular velocity.
Comparison of VIP and β2‐‐adrenoceptor‐induced relaxations in the circular and longitudinal smooth muscle layers of the rat portal vein
Authors: RYDNINGEN H. T. , OMLAND T. , OPSTAD P. K. , HELLE K. B. 
Published: December 2008

Comparison of VIP and β2‐‐adrenoceptor‐induced relaxations in the circular and longitudinal smooth muscle layers of the rat portal vein. Acta Physiol Scand 130, 601–607. Received I I November 1986, accepted 26 February 1987. ISSN 00014772. Department of Physiology, University of Bergen, Norwegian Defence Research Establishment, Kjeller, Norway.The relative importance of VIP in reduction of vascular tone was studied in circular and longitudinal preparations of the VIP‐innervated rat portal vein. Exogenous VIP inhibited the methoxamine‐evoked contractures in the atropine‐blocked preparations with a lower potency in the inner, circular (pD2= 6.4±0.5, n= 6) than in the outer, longitudinal layer (pD2= 7.7 ± 0.1, n = 6). VIP was also a less efficient relaxant (intrinsic activity (a) = 0.60 ±0.16, n = 6) of the inner than of the outer layer (a= I. 00). The selective (salbutamol) and the non‐selective (isoproterenol) β2‐‐agonists completely relaxed the methoxamine contractures in both layers and the potency (isoproterenol) was higher in the inner (pD2= 6.39 ± 0.32, n = 6) than in the outer layer (pD2= 5.67 ±0.34, n= 6). Plasma from the portal‐mesenteric vein of anaesthetized, fasting rats contained 0.036 nM VIP (median, n= 17). that is, several orders of magnitude lower than the range of VIP concentrations relaxing the methoxamine contracted vein preparations via VIP receptors of the apamin‐blockable category. The results support the hypothesis that a1‐‐adrenoceptor‐induced contractions in the circular layer are predominately relaxed via β2‐‐adrenoceptors while relaxation of the outer layer may occur via VIP receptors, probably activated by local release of the neuropeptide.
Morphology of the isolated rat hindquarter preparation: tissue preservation, perfusion heterogeneity and a note on the effect of fixative osmolality
Authors: JOHANSSON B. R. , HARALDSSON B. 
Published: December 2008

The isolated rat hindquarter preparation often used for physiological studies was subjected to morphological examination. A two‐hour perfusion with balanced oxygenated dextran solution was followed by perfusion fixation with aldehydes. Fixation was performed at isogravimetry when an isotonic fixative was used (2.5 % glutaraldehyde in 0.05 M Na cacodylate + 4% dextran 70). Muscle specimens were prepared for light and electron microscopy.Most muscle tissue was well perfused but a limited tissue volume could retain blood after the perfusion period. Within perfused tissue the perfusion result varied macroscopically with some regions apparently not being reached by fixative. Non‐fixed tissue was estimated to amount to maximally one fourth of the total tissue mass. Also within macroscopically well‐fixed tissue the microscopy indicated varying patency of perfused capillaries. Thus a marked perfusion flow heterogeneity prevailed in the fixed specimens which is compatible with earlier functional findings of a 50% reduction of capillary surface area during isogravimetric fixation. The possible relation with prefixation flow heterogeneity in the vasodilated preparation is discussed. There were no obvious alterations of endothelial ultrastructure after prolonged artificial perfusion. Isogravimetrically fixed muscle had narrow extracellular spaces which were evidently compressed further after use of absorbing hyperosmolar fixative. Extracellular expansion and intracellular oedema followed after hypo‐osmolar fixation. Muscle cells often exhibited insufficient mitochondrial fixation, probably as a result of tissue hypoxia.
Positive inotropic effect on the rat atrial myocardium compressed to 5, 10 and 30 bar
Authors: ASK J. A. , TYSSEBOTK I. 
Published: December 2008

The contractile activity of spontaneously beating auricular preparations from the rat was studied during and after pressure exposure to 5, 10 and 30 bar in three series of experiments (compression and decompression rate: I bar min‐1). The preparations were mounted in an organ bath within a pressure chamber and perfused with oxygenated preheated Krebs‐Henseleit solution (37 °C, pH = 7.45) containing α, β‐ and muscarinic‐receptor blockers and blockers of the neuronal and extraneuronal uptake mechanisms. No change in chronotropy of the cardiac preparations were observed during or after exposures to the pressures tested. Significant increase in cardiac contractility (20–40%, P < 0.01) described by the peak tension (Tmax), the maximal velocity of tension rise (T'max) and fall (T'max) were apparent at 5 and 10 bar. Further significant elevations (6–80%, P < 0.05) in T'max, T' and T'min were detected during exposure to 30 bar.The cardiac contractility increased rapidly with pressure, was approximately unchanged during stable elevated pressures at 5, 10 and 30 bar, but was maintained above control values 15 min after completed decompression. Since no change in chronotropy and loading of the preparations occurred, it is concluded that the increased contractility is due to a positive inotropy generated by the hydrostatic pressure. Furthermore, it is indicated that this positive inotropy is not related to adrenoceptor activation since the effect was achieved in the presence of α, and β‐adrenoceptor blockade.
Effects of neuropeptides and capsaicin on tracheobronchial blood flow of the pig
Authors: MATRAN R. , ALVING K. , MARTLING C.‐R. , LACROIX J.S. , LUNDBERG J.M. 
Published: December 2008

Blood flow changes upon systemic i. v.injections in the pig of various neuropeptides, capsaicin, bradykinin and histamine were directly monitored by a Transonic blood flowmeter in the superior laryngeal, bronchial and femoral arteries and indirectly in the larynx and skin using laser Doppler flowmetry. To minimize influence of compensatory reflexes and indirect effects, the pigs were pre‐treated with atropine, guanethidine, chlorisondamine and capsaicin. Substance P (SP), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), calcitonin gene‐related peptide (CGRP), capsaicin, bradykinin and histamine all decreased vascular resistance, suggesting vasodilation in the superior laryngeal and bronchial arteries. All peptides and histamine when given i. v.exerted vasodilatory effects independent of autonomic motor nerves and capsaicin‐sensitive afferents. SP was the most potent vasodilator agent tested in both tracheal and bronchial circulation, being about 1000‐fold more active than histamine. VIP was about 10‐fold more potent than PHI in decreasing vascular resistance and had a preferential action on the SLA compared to CGRP.In the femoral artery capsaicin and also SP in the highest dose increased vascular resistance. Capsaicin increased the laser Doppler signal in both laryngeal mucosa and skin, while i. v.peptides caused variable effects.In conclusion, SP and CGRP mimicked capsaicin‐induced vasodilation in the tracheobronchial circulation while VIP had a preferential effect on the tracheal circulation.
Renal interaction between sympathetic activity and ANP in rats with chronic ischaemic heart failure
Authors: PETTERSSON A. , HEDNER J. , HEDNER T. 
Published: December 2008

The diuretic and natriuretic effects of r‐α‐ANP (99–126) were investigated in rats with chronic ischaemic heart failure (IHF) produced by left coronary artery ligation. The plasma concentration of immunoreactive ANP (IrANP) was significantly higher, 91.8 ± 16.0 pm in the IHF rats compared to 31.0 ± 4.9 pm in sham‐operated controls. In the control rats, ANP infusion (0.25–1.0 μg kg‐1 min‐1) increased urine flow rate (V) and urinary sodium (UNaV) excretion. At the highest dose level, both V and UNaV were increased approximately fivefold. The diuresis and natriuresis seen in the control group after the infusion of ANP were blunted in the IHF rats. A bilateral surgical renal denervation in the IHF rats did not alter the renal dopamine levels, but induced a significant decrease in renal noradrenaline content, and almost completely restored the renal responsiveness to the ANP infusions.We conclude that renal denervation reversed the blunted renal excretory response to ANP in IHF rats. Thus, in experimental IHF, there seems to be a functional antagonism between efferent renal sympathetic nerve activity and ANP.
Interaction between gastrin‐17 and oxytocin on plasma levels of insulin, glucagon and glucose in conscious dogs
Authors: STOCK S. , UVNÄS‐MOBERG K. 
Published: December 2008

The aim of the present study was to investigate how infusion of gastrin‐17 and oxytocin affects plasma levels of insulin, glucagon and glucose in order to elucidate how the two hormones contribute to metabolic changes seen in situations where they are released, e.g. feeding and suckling during lactation. Thus, gastrin‐17 (0.5 and 2.0 nmol kg‐1 h‐1) and oxytocin (0.1 i and 1.1 nmol kg‐1 h‐1) were infused separately or simultaneously into conscious dogs.Both gastrin‐17 and oxytocin induced significant, dose‐dependent increases in insulin levels. An additive effect on insulin levels was obtained when gastrin‐17 and oxytocin were infused simultaneously. Glucagon levels were not affected by gastrin‐17 whereas infusion of 1.1 nmol kg‐1 h‐1 of oxytocin was followed by a significant increase. In contrast to a slight transient increase in the glucose level induced by oxytocin, infusion of gastrin‐17 caused a sustained period of hypoglycaemia. Thus, infusion of gastrin‐17 and oxytocin, respectively, gave rise to different ratios between circulating concentrations of insulin and glucagon reflected in different effects on the glucose level. The gastrin‐induced hypoglycaemia could reflect that gastrin, via a release of insulin, promotes storing of glucose, e.g. in connection with feeding. That infusion of oxytocin caused a parallel increase in insulin and glucagon levels together with a slight increase in the glucose level could imply that oxytocin favours mobilization of glucose, e.g. during lactation.
Differential effect of bombesin on intraluminal and intravascular release of gastric gastrin and somatostatin in anaesthetized rats
Authors: ALINO S. F. , UVNÄS‐MOBERG K. 
Published: December 2008

The aim of the present investigation was to study how bombesin, gastrin‐17, cholecystokinin‐8 (CCK‐8) and electrical vagal stimulation influence the release of gastrin and somatostatin into the gastric lumen. Bombesin (3 and 30 nmol kg‐1 h‐1), gastrin‐17 and CCK‐8 (to nmol kg‐1h‐1) were infused i.v. and vagal stimulations at 5 V, 2 ms, 5 Hz were performed in anaesthetized rats, in which the stomach was perfused with a dextran solution (pH˜ 6 or ˜ 1.5). pH, gastrin and somatostatin levels were measured in the perfusate after having passed the stomach. In addition, blood samples were drawn from the jugular vein in the experiments in which bombesin was infused. Gastrin and somatostatin levels were determined with radioimmunoassay, and gastrin‐ and somatostatin‐like immunoreactivity will be referred to as gastrin and somatostatin below. Infusion of bombesin, 3 and 30 nmol kg‐1 h‐1, did not influence acid secretion as evidenced by an unchanged intraluminal pH. Nor was the intraluminal secretion of gastrin or somatostatin influenced by bombesin, whereas plasma gastrin and somatostatin levels were significantly increased at the higher dose. In contrast, infusion of CCK‐8 and gastrin‐17 (to nmol kg‐1 h‐1), as well as electrical vagal stimulation, significantly decreased the pH and increased the somatostatin levels in the perfusate. Vagal activation in addition increased the gastrin levels.The present results, demonstrating that bombesin influences plasma and perfusate levels of gastrin and somatostatin differently, indicate that intraluminal and intravascular gastrin and somatostatin release may be separately regulated.
Increased cardiac contractility in rats exposed to 5 bar
Authors: STUHR L.E.B. , ASK J. A. , TYSSEBOTN I. 
Published: December 2008

The left ventricular pressure, arterial blood pressure and heart rate were studied in three series of pentobarbital‐anaesthetized rats exposed to 5‐bar normoxic (Po2= 0.2 bar) environments: nitrogen‐oxygen (15 and 60 min) and helium‐oxygen (15 min). The maximal left ventricular pressure (LVP max) and the maximal velocities of LVP rise (+ dP/dt max) and fall (‐ dP/dt) were significantly (P < 0.01) increased immediately after reaching normoxic 5 bar (He, 13–28%; N2, 13–23%) and during the exposure at 5 bar (He, 22–44%; N2, 13–18%). The pulse pressure increased significantly (He, 50–62%; N2, 30–34%; P 0.01) during the hyperbaric exposure. No changes in heart rate or end‐diastolic and mean arterial pressure were detected.The present findings indicate an enhanced cardiac contractility (+ dP/dt max) at 5 bar, with the greatest increase found when He was used as inert gas. The increased contractility was of significant duration (at least 60 min), and was not completely‐reversed until 5–10 min after decompression.
Effects of β‐adrenergic agonists in the parotid gland of the rat–an electrophysiological study
Authors: THESLEFF P. 
Published: December 2008

The effects of some β‐adrenergic agonists were studied in the parotid gland of the rat by electrophysiological techniques. In the unoperated gland, isoprenaline caused depolarizations which were slowly developing, long‐lasting and of low amplitude. The same response was seen when noradrenaline was combined with α‐adrenoceptor blocking drugs. A greater number of cells responded to this combination than to isoprenaline.After either parasympathetic or sympathetic denervation 1–3 weeks in advance, to induce supersensitivity, the number of cells responding to β‐adrenoceptor stimulating drugs was significantly increased. In the latter case the threshold dose required to evoke a response was also significantly lowered. Atropine did not have any effect on the isoprenaline‐evoked response. The combined parasympathetic and sympathetic denervation did not further increase the responsiveness.It is concluded that β‐adrenoceptor stimulation in the parotid gland of the rat may cause membrane depolarizations. The response is mediated by β1‐ adrenoceptors. The responsiveness is increased in the denervated gland.Secretory studies have demonstrated a supersensitivity to β‐adrenergic agonists as a result of denervation. On the other hand, β‐adrenoceptor stimulation is believed mainly to activate the adenylate cyclase/cyclic AMP system independent of membrane potential changes. It is thus not known if the present ‘supersensitivity’ is correlated to the increased secretory response earlier demonstrated in this gland.
Mechanism of action of calcitonin on secretion in rat submandibular gland
Authors: SAGULIN G.‐B. , MÜLLER R. M. , WESTLIND‐DANIELSSON A. , NILSSON T. , BERGGREN P.‐O. , ROOMANS G. M. 
Published: December 2008

Calcitonin (CT) was found to reduce the initial flow of pilocarpine‐stimulated saliva from the submandibular glands in the rat. Although there was a concomitant increase of the concentration of calcium and protein in the saliva, the calcium/protein ratio was not significantly affected. CT also caused a significant increase of the potassium concentration in submandibular saliva. Both in vivo and in vitro, CT inhibited the production of cyclic AMP (cAMP) both in the absence and in the presence of forskolin. This decrease in intracellular cAMP levels could result in an inhibition of mucus secretion, which would explain the previously observed calcitonin‐induced intracellular accumulation of mucus in the submandibular gland acinar cells. CT did not affect the cytoplasmic free Ca2+ concentration (as measured with fura 2) in isolated submandibular acini either in the absence or in the presence of cholinergic or adrenergic agonists. These results indicate that the inhibition of fluid secretion in the submandibular gland by calcitonin must be located distal to changes in [Ca2+]i.It can be concluded that CT affects both mucus and fluid secretion in the submandibular gland, but that only the inhibition of mucus secretion can as yet be explained by an effect at the level of the second messenger.
Renal function in different forms of renovascular hypertension in rats
Authors: EKLÖF A.‐C. , APERIA A. 
Published: December 2008

This study examines renal function in different rat models of renovascular hypertension. Hypertension was induced by constriction of the aorta proximal to the renal artery (PAC), by PAC and nephrectomy (PAC + Nx) or by renal artery stenosis (RAS). PAC + Nx is equivalent to the Goldblatt 1 kidney‐i clip hypertension model. The PAC rats were studied 3 weeks after surgery. Hypertension was by then well established. GFR, measured as the clearance of inulin, was significantly lower in PAC rats than in control (C) rats. GFR was the same in PAC + Nx rats as in C rats, but significantly lower in PAC + Nx than in Nx rats. Kidney weight was significantly higher in PAC + Nx rats than in C rats. Filtration fraction (FF), measured as the ratio between GFR and the clearance of PAH, was significantly higher in PAC and PAC + Nx rats than in C and Nx rats. In RAS rats hypertension was not established until 6 weeks after surgery, and RAS is equivalent to Goldblatt 2 kidney‐i clip hypertension. Renal artery constriction was moderate as judged from the weight ratio between the stenosed and contralateral kidneys. The GFR in the stenosed kidney was not significantly lower in the contralateral kidney. FF was significantly higher in RAS rats than in C rats in both the stenosed and the contralateral kidneys, but the increase was less pronounced than in PAC and PAC + Nx rats. Conclusions. An increase in FF is typical of renovascular hypertension. GFR is normal or decreased. In Goldblatt 1 kidney‐i clip hypertension, compensatory hypertrophy blunts the decrease in GFR.
Capsaicin‐induced vasodilatation of human coronary arteries in vitro is mediated by calcitonin gene‐related peptide rather than substance P or neurokinin A
Authors: FRANCO‐CERECEDA A. , RUDEHILL A. 
Published: December 2008

In the present study the possible influence of capsaicin on human arterial coronary tone in vitro was studied in relation to the vasodilatory properties of calcitonin gene‐related peptide (CGRP), substance P (SP) or neurokinin A (NKA). In addition, the influence of vasoactive intestinal polypeptide (VIP) and somatostatin (SOM) on the arteries was investigated.CGRP application to potassium‐pre‐contracted human epicardial coronary arteries (0.4–0.6 mm in inner diameter) induced a concentration‐dependent, long‐lasting relaxation. SP also relaxed these pre‐contracted arteries, but the relaxation was transient and tachyphylaxis developed rapidly upon repeated administration. SP tachyphylaxis did not influence the relaxatory effects of CGRP. Furthermore, pre‐incubation with gossypol, an inhibitor of the formation and release of endothelium‐derived relaxing factors (EDRF), completely abolished the effects of SP without influencing the dilatory action of CGRP. NKA only induced a very minor relaxation of the pre‐contracted arteries. Both VIP and SOM concentration‐dependently relaxed the pre‐contracted arteries.Capsaicin evoked a relaxation of the potassium‐pre‐contracted arteries. This effect was not influenced by SP tachyphylaxis or gossypol incubation. Thus, CGRP but not SP mimics the vasodilatory effects of capsaicin on human coronary arteries. This suggests that CGRP rather than SP is likely to mediate the relaxatory effects seen upon activation of cardiac sensory nerves.
Actions of the CI‐ channel blocker NPPB on absorptive and secretory transport processes of Na+ and CI‐ in rat descending colon
Authors: DIENER M. , RUMMEL W. 
Published: December 2008

The effects of the Cl‐ channel blocker, NPPB (5‐nitro‐2‐(3‐phenylpropylamino)‐benzoate), on the transport of Na+ and Cl‐ in the descending colon of the rat were studied in the Ussing chamber. In control tissue, NPPB administered at the mucosal side of the epithelium increased the short‐circuit current (Isc) and inhibited the unidirectional mucosa‐to‐serosa fluxes of Na+ and CI‐. In HCO‐3‐‐ or Cl‐‐free media or in the presence of SITS (4‐acetamido‐4′‐isothiocyanato‐stilbene‐2,2′‐disulphonic acid), this increase in Isc caused by mucosal NPPB was not observed. The serosal administration of NPPB was without effect.Mhdcosal NPPB (10‐‐4 mol l‐1hd decreased the forskolin‐induced increase in Isc by only about 60%. However, the activation of the serosa‐to‐mucosa flux of Cl‐ caused by forskolin was inhibited completely. NPPB decreased the mucosa‐to‐serosa fluxes of Na+ and Cl‐ reduced additionally by forskolin. Serosal NPPB decreased Isc and JNasm, but had no effect on JNasm or JNasm. In HCO‐3‐free buffer the increase in Isc induced by forskolin was inhibited completely by NPPB.The inhibition of Cl‐ secretion by NPPB fits well with the capacity of the drug to block Cl‐ channels. For the inhibition of neutral NaCl absorption two sites of action are discussed: an interaction with the Cl‐/HCO‐3 exchanger or an interference with the extrusion of Cl‐ through the basolateral membrane.,