bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interference of a neutrophil recruitment inhibitory factor upon the accumulation of inflammatory cells and airway hyperreactivity in sensitized guinea‐pigs after intranasal antigen challenge
Authors: Tavares‐Murta B.M. , Lefort J. , Cunha F.Q. , Ferreira S.H. , Vargaftig B.B. 
Published: July 2012

A neutrophil recruitment inhibitory factor (NRIF) recovered from the crude supernatant of lipopolysaccharide (LPS)‐stimulated macrophages inhibited neutrophil migration following both intratracheal and intravenous administration of LPS, but did not alter the pattern of leukopenia/leucocytosis induced by intravenous LPS.
The correlation between airway infiltration by inflammatory cells and hyperreactivity in lungs from actively sensitized and challenged guinea‐pigs was investigated by use of NRIF.
Increased eosinophil counts were found in the bronchoalveolar lavage fluid from guinea‐pigs sensitized with 10 μg ovalbumin and challenged at day 14 by the intranasal administration of the antigen. The increase was evident 5 h after challenge and persisted at 24 h. Neutrophil numbers were also increased at this time. Pretreatment with NRIF suppressed the leucocyte increase in the bronchoalveolar lavage fluid.
Bronchoconstriction and histamine release induced by 3 ng PAF injected into the isolated lungs were increased in challenged guinea‐pigs as compared to sensitized but unchallenged controls. Pretreatment of the animals with NRIF did not interfere with this response, but significantly reduced the bronchoconstriction induced by ovalbumin injection.
Even though the increased number of inflammatory cells in bronchoalveolar lavage and airway hyperresponsiveness were concomitant, NRIF inhibited cellular infiltration but failed to alter airway hyperreactivity to PAF, demonstrating that these events may occur independently. Conversely, the inhibition of antigen‐induced bronchoconstriction by NRIF suggests that this response is dependent upon the emigration of granulocytes.
Role of the endothelium in the response to cholinoceptor stimulation of rabbit ear and femoral arteries during cooling
Authors: Monge L. , García‐Villalón A.L. , Montoya J.J. , García J.L. , Fernández N. , Gómez B. , Diéguez G. 
Published: July 2012

The role of the endothelium in the effects of cooling on the response to cholinoceptor stimulation of the rabbit central ear (cutaneous) and femoral (non‐cutaneous) arteries was studied using 2 mm long cylindrical segments.
Concentration‐response curves for acetylcholine (10−9‐10−5 m), methacholine (10−9‐10−5 m) and sodium nitroprusside (10−9‐10−4 m) were isometrically recorded in arteries under conditions, with and without endothelium or following pretreatment with the nitric oxide‐synthesis inhibitor NG‐nitro‐l‐arginine methyl ester (l‐NAME, 10−6‐3 x 10−4 m) at 37°C and at 24°C (cooling).
Ear and femoral arteries showed endothelium‐dependent relaxation to acetylcholine and methacholine at 37°C and 24°C. The extent of relaxation of the control ear arteries, but not of the control femoral arteries, to acetylcholine and methacholine increased during cooling.
l‐NAME (10−6−3 × 10−4 m) reduced in a concentration‐dependent way the response of ear arteries to acetylcholine at both 37°C and 24°C, this reduction being more potent at 37°C. l‐Arginine (10−5‐10−3 m) reversed in a concentration‐dependent manner the inhibitor effects of 10−5 m l‐NAME at both temperatures.
Sodium nitroprusside caused a concentration‐dependent relaxation in both arteries that was endothelium‐independent. However, the extent of relaxation to this nitrovasodilator in ear and femoral arteries was lower at 24°C.
These results suggest that cooling augments the reactivity of cutaneous (ear) arteries, but not that of non‐cutaneous (femoral) arteries to cholinoceptor stimulation by endothelium‐mediated mechanisms. Cooling could therefore facilitate the stimulated release of endothelial nitric oxide in cutaneous vessels.
Sensory nerve‐mediated relaxation of guinea‐pig isolated pulmonary artery: prejunctional modulation by α2‐adrenoceptor agonists but not sumatriptan
Authors: Butler A. , Worton S.P. , O'Shaughnessy C.T. , Connor H.E. 
Published: July 2012

Effects of the α2‐adrenoceptor agonists, UK14304 and clonidine, the 5‐HT1 receptor agonist, sumatriptan and the κ‐opioid receptor agonist, GR103545, on sensory neurotransmission in histamine‐contracted guinea‐pig isolated pulmonary artery (GPPA) have been studied.
Electrical field stimulation (EFS) induced frequency‐dependent relaxations of histamine‐contracted GPPA, which were attenuated by tetrodotoxin and capsaicin pretreatment but not by the nitric oxide synthase inhibitor, Nω‐nitro‐l‐arginine methyl ester (l‐NAME).
Substance P (0.3 μm) induced relaxations which were subject to rapid tachyphylaxis. Neither the NK1 receptor antagonist, (±)‐CP 96,345, nor desensitization to substance P had any effect of EFS‐induced relaxations of histamine‐contracted GPPA.
Calcitonin gene‐related peptide (CGRP; 3 and 30 nm) induced concentration‐dependent relaxations of histamine‐contracted GPPA. The putative CGRP receptor antagonist, CGRP8–37 (1 μm), markedly attenuated EFS‐induced relaxations as well as relaxations induced by a low concentration of CGRP.
Sumatriptan (0.1 and 1 μm) and the selective K‐opioid receptor agonist, GR103545 (10 and 100 nm) had no effect on EFS‐induced relaxations of histamine‐contracted GPPA. In contrast, the α2‐adrenoceptor agonists UK14304 (1–100 nm) and clonidine (300 nm) attenuated responses to EFS, the attenuation of UK14304 (100 nm) being reversed by yohimbine (300 nm).
It is concluded that in GPPA, where a presynaptic inhibition of sensory neurotransmission by α2‐adrenoceptor activation could be shown, there was no evidence for such modulation by either sumatriptan‐sensitive 5‐HT1 receptors or κ‐opioid receptors.
Modulation by histamine of the delayed outward potassium current in guinea‐pig ventricular myocytes
Authors: Yazawa Kazuto , Abiko Yasushi 
Published: July 2012

Histamine receptor‐mediated modulation of the delayed outward potassium current (IK) was investigated in guinea‐pig single ventricular cells by the whole‐cell voltage clamp.
Histamine increased IK in a dose‐ dependent manner with a half‐maximum dose of 3.8 × 10−8 M. Histamine (10−6 m) increased IK by a factor of 3.02 without a significant change in the current kinetics. The threshold dose of histamine for increasing IK was 10−9 m and this value was similar to that for calcium current.
Cimetidine decreased IK in the presence of histamine, by shifting the dose‐response curve to histamine to the right. The pA2 value of cimetidine against histamine was 6.38.
Forskolin did not increase IK after application of 10−6 m histamine, and histamine scarcely increased IK in the presence of a heat‐stable inhibitor of cyclic AMP‐dependent protein kinase (PKI).
We conclude that stimulation by histamine of IK is mainly by way of the H2‐receptor, and is mediated by cyclic AMP‐dependent phosphorylation.
Stimulation of insulin secretion and improvement of glucose tolerance in rat and dog by the P2y‐purinoceptor agonist, adenosine‐5′‐O‐(2‐thiodiphosphate)
Authors: Hillaire‐Buys D. , Bertrand G. , Chapal J. , Puech R. , Ribes G. , Loubatières‐Mariani M.M. 
Published: July 2012

In vivo effect of a P2y‐purinoceptor agonist, adenosine‐5′‐O‐(2‐thiodiphosphate) (ADPβS), on insulin secretion and glycaemia were studied both in rats and dogs.
In anaesthetized rats, i.v. administered ADPβS (0.2 mg kg−1) produced an insulin response dependent on the nutritional state of the animals, since we observed only a transient increase in overnight‐fasted rats and a sustained insulin secretion followed by a reduction in plasma glucose levels in fed rats. During an i.v. glucose tolerance test, ADPβS enhanced insulin release and thus increased the glucose disappearance rate.
In anaesthetized fasted dogs, i.v. administered ADPβS (0.1 mg kg−1) increased pancreaticoduodenal insulin output and slightly decreased blood glucose levels.
In conscious fasted dogs, orally administered ADPβS (0.1 mg kg−1) transiently increased insulinemia and punctually reduced glycaemia. Furthermore, during an oral glucose tolerance test, orally administered ADPβS at the same dose markedly enhanced insulin secretion and consequently reduced the hyperglycaemia.
In conclusion, the P2y‐agonist, ADPβS, is a potent insulin secretagogue in vivo, improves glucose tolerance and is effective after oral administration. Thus, the P2y‐purinoceptors of the β cell may be a target for new antidiabetic drugs.
Pharmacology of GAB A ρ1 and GAB A α/β receptors expressed in Xenopus oocytes and COS cells
Authors: Kusama T. , Spivak C.E. , Whiting P. , Dawson V.L. , Schaeffer J.C. , Uhl G.R. 
Published: July 2012

The ρ1 protein, which we previously cloned from retina, assembles as a homooligomer that transduces the binding of γ‐aminobutyric acid (GABA) into robust chloride currents. However, its insensitivity to bicuculline, pentobarbitone and benzodiazepines, all potent agents at typical GABAA receptors, suggested that it may react atypically to other GABA agonists and antagonists.
cDNAs for the ρ1 and the α5β1 receptors for GABA were expressed as homo‐ and heterooligomers, respectively, in Xenopus oocytes. The selectivities of the respective receptors for various agonists were investigated using concentration‐response experiments in voltage clamped cells.
The most potent agonists at the ρ1 receptor were trans‐4‐aminocrotonic acid (TACA) > GABA > muscimol; at the α5β1 receptor the rank order was muscimol > GABA > 4,5,6,7‐tetrahydroisoxazole[4,5‐c]pyridine‐3‐ol (THIP). The most specific agonists were cis‐(2‐(aminomethyl)‐cyclopropyl‐carboxylic acid (CAMP) and THIP for the ρ1 and the α5β1 receptors, respectively.
Comparing GABA, TACA and cis‐aminocrotonic acid (CACA) at ρ1 receptors expressed in COS cells gave results almost indistinguishable from those found at oocytes; the pharmacology of ρ1 seems independent of the expression system.
Agonists THIP, piperidine‐4‐sulphonic acid (P4S), and isoguvacine, whose C‐C‐C‐N chains are constrained by rings into a folded conformation and were potent at the α5β1 receptor, were among the weakest at the ρ1 receptor. However CACA and CAMP, which align better with the extended than the folded conformation, were weakest at the α5β1 receptor but moderately potent at the ρ1 receptor. These findings suggest that the ρ1 receptor recognizes agonists in the extended conformation, in contrast to GABAA receptors, which are believed to recognize agonists in the partially folded conformation.
In contrast to the α5β1 receptor, gradations in maximum responses were apparent in the ρ1 receptor, suggesting various degrees of partial agonism. In particular, imidazole‐4‐acetic acid (I4AA), whose maximum response was only 3% of GABA's maximum, had an apparent Kd for activating the ρ1 receptor of 16 μm; but it had an apparent Kd for competitively blocking the receptor of 0.64 μm. This difference suggests that steric constraints in the activated (open channel) receptor are tighter than in the resting receptor.
Hill coefficients approached 2 at the ρ1 receptor, but were closer to unity at the α5β1 receptor. Thus, the ρ1 receptor displayed higher cooperativity.
Unlike typical GABAA receptors, the ρ1 receptor was insensitive to the competitive antagonists bicuculline, SR95531, securinine, and (+)‐tubocurarine.
Novel regulation of muscarinic receptors and their coupling with G proteins in smooth muscle: transient resensitization during desensitizing process
Authors: Hishinuma Shigeru , Matsumoto Yukio , Uchida Masaatsu K. , Kurokawa Masanori 
Published: July 2012

Muscarinic stimulation of the smooth muscle of guinea‐pig taenia caeci was produced with 10−4 m carbachol for 15 s, 30 s, 1 min, 2 min and 30 min, and the time course of developing desensitization was studied by measuring the muscle contractility and the binding characteristics of muscarinic receptors.
The contractile response to carbachol was analyzed using dose‐response curves. The response to 10−7 m carbachol was reduced by treatment for 15 s with 10−4 m carbachol (fast desensitization), but recovered partially after 30 s treatment and completely after 1 min treatment (resensitization). Contractility was reduced again after 2 min and 30 min treatment (re‐desensitization).
The affinity of carbachol for muscarinic receptors was changed by the carbachol treatment in a manner similar to the contractility. Thus, the affinity was reduced at 15 s, restored slightly at 30 s and completely at 1 and 2 min, and was reduced again at 30 min.
5′‐Guanylylimidodiphosphate (GppNHp), a non‐hydrolysable analogue of guanosine triphosphate (GTP) reduced the affinity of muscarinic receptors for carbachol via guanine nucleotide‐binding regulatory proteins (G proteins). A similar effect was observed in tissues desensitized by 15 s carbachol treatment. This effect disappeared after 30 s, recovered completely after 1 and 2 min, and disappeared again after 30 min carbachol treatment.
Neither the dissociation constant (Kd value) nor the maximal binding (Bmax) of [3H]‐quinuclidinyl benzilate ([3H]‐QNB) to muscarinic receptors were changed by the carbachol treatment.
These results indicate that the whole process of desensitization, resensitization and re‐desensitization are related to changes in the binding ability of muscarinic receptors, in their coupling with G proteins and in the post‐receptor steps of the signal transduction. We emphasize that the desensitizing process involves an early transient phase of resensitization that could be caused by restoration of both the affinity of carbachol for muscarinic receptors and their coupling with G proteins. This novel resensitization mechanism may have some physiological significance for cellular homoeostasis by modulating cellular responsiveness transiently or even in an oscillatory manner during the process of desensitization.
The superficial buffer barrier in venous smooth muscle: sarcoplasmic reticulum refilling and unloading
Authors: Chen Qian , van Breemen Cornelis 
Published: July 2012

The interaction of Ca2+ transport in the plasmalemma and the sarcoplasmic reticulum (SR) was investigated in smooth muscle of the rabbit inferior vena cava. We tested the possibility of direct refilling of the SR with extracellular Ca2+ and of the existence of a vectorial Ca2+ extrusion pathway from the SR lumen to the extracellular space suggested by earlier results.
After depletion with caffeine the SR was loaded with Ca2+ to increasing levels by incubation in a high potassium 1.5 mm Ca2+ solution and a 10 mm Ca2+ zero Na+ solution, respectively. Thapsigargin, 2 μm, (a specific SR Ca2+‐ATPase blocker) completely blocked refilling of the SR in either of the above solutions, indicating that the SR Ca2+‐ATPase is essential for this process.
Three different agents, caffeine, ryanodine and thapsigargin, which inhibit Ca2+ accumulation by the SR, increased the steady state intracellular Ca2+ concentration in the rabbit inferior vena cava.
Measurements of Mn2+ induced quenching of the intracellular fura‐2 signal during pharmacological manipulation of the SR content showed that these three agents did not stimulate divalent cation entry.
On the other hand, stimulation with noradrenaline caused a marked increase in Mn2+ influx, which was blocked by 2 mm Ni2+. Mn2+ entry stimulated by high K+ solution was blocked by 1 μm diltiazem.
We conclude that the SR refilling has to be mediated by the SR Ca2+‐ATPase. Inhibition of Ca2+ accumulation by the SR causes an increase in the steady state intracellular Ca2+ concentration. This observation cannot be explained by an increase in Ca2+ influx into the smooth muscle cells of the rabbit inferior vena cava. Alternatively these results suggest the existence of a continuous vectorial release of Ca2+ from the SR lumen to the extracellular space.
Sodium modulation of 3H‐agonist and 3H‐antagonist binding to α2‐adrenoceptor subtypes
Authors: MacKinnon A.C. , Spedding M. , Brown C.M. 
Published: July 2012

The α2‐adrenoceptors on human platelets and neonatal rat lung were characterized with the agonist and antagonist ligands [3H]‐adrenaline and [3H]‐RS‐15385‐197 respectively. A correlation of affinities for 3H‐antagonist binding showed the receptors to be of the α2A‐(platelet) and α2B‐(neonatal rat lung) adrenoceptor subtypes, whereas a correlation of affinities for 3H‐agonist binding showed the receptors to have similar characteristics (r = 0.88).
NaCl (100 mm) had no effect on [3H]‐RS‐15385‐197 binding in the human platelet, but increased the density of sites labelled with [3H]‐RS‐15385‐197 in neonatal rat lung by 52%. NaCl increased the density of sites labelled by [3H]‐adrenaline in neonatal rat lung, but there was a consequent 3.5 fold decrease in affinity. In the human platelet, no specific [3H]‐adrenaline binding was observed in the presence of 100 mm NaCl.
In the neonatal rat lung, NaCl had no significant effect on the affinity of prazosin for [3H]‐RS‐15385‐197 binding; however, imiloxan affinity was increased 13 fold. The affinity of the catecholamines, adrenaline and noradrenaline was significantly decreased, whereas the imidazolines, oxymetazoline and UK‐14,304 were much less affected. The affinity of prazosin and imiloxan for [3H]‐adrenaline binding was significantly increased in the presence of 10 and 100 mm NaCl. Conversely, the affinity of adrenaline and noradrenaline was decreased in the presence of NaCl, and there was no change in the affinity of the imidazoline agonists.
In the human platelet, NaCl had no effect on the affinity of prazosin for [3H]‐RS‐15385‐197 binding but the affinity of imiloxan was significantly increased. NaCl significantly decreased the affinity of the catecholamines adrenaline and noradrenaline, whereas the affinity of UK‐14,304 and oxymatazoline was much less affected. Competition experiments with [3H]‐adrenaline in the presence of NaCl in platelets were difficult to characterize as there was no specific binding under these conditions.
The results show that both the α2A‐ and α2B‐adrenoceptor subtypes are allosterically regulated by Na+, but only the α2B‐subtype showed a significant increase in density. Interestingly, there is a differential regulation of imidazoline (unchanged) and catecholamine (decreased affinity) agonist interactions with these subtypes. Na+ may therefore critically affect receptor subtype selectivity of drugs. The implications for receptor subclassification are discussed.
Caffeine and related compounds block inhibitory amino acid‐gated Cl− currents in freshly dissociated rat hippocampal neurones
Authors: Uneyama Hisayuki , Harata Nobutoshi , Akaike Norio 
Published: July 2012

The effects of caffeine and related compounds on responses mediated by inhibitory amino acids were investigated in freshly dissociated rat hippocampal pyramidal neurones by conventional and nystatin perforated patch‐clamp techniques.
Glycine and γ‐aminobutyric acid (GABA) evoked Cl− currents in hippocampal neurones. The half‐maximum effective concentrations (EC50) of glycine and GABA were 8.5 × 10−5 and 5 × 10−6 m, respectively.
Caffeine reversibly inhibited both 10−4 m glycine‐ and 10−5 m GABA‐induced Cl− currents in a concentration‐dependent manner. The half‐maximum inhibitory concentrations (IC50) of caffeine were 4.5 × 10−4 m for the glycine response and 3.6 × 10−3 m for the GABA response.
Caffeine shifted the concentration‐response curve of IGly to the right without affecting the maximum response.
The inhibitory action of caffeine did not show voltage‐dependency.
The blocking action of caffeine was not affected by intracellular perfusion with 5 mm BAPTA or by pretreatment with the protein kinase A inhibitor, H‐8. This excludes the participation of Ca2+ or cyclic AMP in the inhibitory action of caffeine.
Caffeine failed to inhibit the augmentations of aspartate‐ and N‐methyl‐d‐aspartate (NMDA) ‐gated current by glycine, suggesting that caffeine has no effect on the allosteric glycine binding site on the NMDA receptor.
The inhibitory effects of some xanthine derivatives on IGly were compared. The inhibitory potency of those compounds on IGly was in the order of pentoxifylline > theophylline ≥ caffeine > paraxanthine > IBMX ≥ theobromine > dyphylline. Xanthine had no effect.
The results indicate that methylxanthines including caffeine may act directly on the glycine receptor Cl− channel complex in rat hippocampal pyramidal neurones. The blockade of the inhibitory amino acid response by methylxanthines may be involved in the excitatory side effects of methylxanthines in the mammalian central nervous system.
Activation by calcium alone of chloride secretion in T84 epithelial cells
Authors: Kachintorn Udom , Vajanaphanich Mana , Traynor‐Kaplan Alexis E. , Dharmsathaphorn Kiertisin , Barrett Kim E. 
Published: July 2012

The goal of this study was to determine if an increase in cytoplasmic calcium concentration ([Ca2+]i), in the absence of additional second messengers derived from membrane phospholipid turnover, is a sufficient signal to induce chloride secretion across monolayers of the human colonic epithelial line, T84.
Thapsigargin was used to increase [Ca2+]i by inhibiting the endomembrane Ca2+‐ATPase. [Ca2+]i was monitored in monolayers by fura‐2 fluorescence spectroscopy, chloride secretion by measuring changes in short circuit current (Isc) in modified Ussing chambers, and inositol phosphates were measured by radio‐h.p.l.c. of extracts of cells prelabelled with [3H]‐inositol.
Thapsigargin increased [Ca2+]i and Isc in parallel, without increasing any inositol phosphates. The effect of thapsigargin on Isc was abolished by the intracellular calcium chelator, bis‐(o‐aminophenoxy)‐ethane‐N,N,N′,N′‐tetraacetic acid (BAPTA).
Increasing [Ca2+]i with thapsigargin did not prevent a subsequent calcium response to carbachol or histamine if extracellular calcium was available. In the absence of extracellular calcium, only one such release of calcium to hormonal stimulation occurred when cells were pretreated with thapsigargin, and a second response to either carbachol or histamine was essentially abolished.
Addition of carbachol or histamine to thapsigargin‐treated cells mounted in Ussing chambers caused a transient further increase in Isc followed by termination of the response, even though [Ca2+]i continued to rise.
We conclude that an elevation in [Ca2+]i is a sufficient signal to induce chloride secretion in T84 cells. Rather than being required to stimulate secretory responses, additional second messengers induced by hormonal secretagogues (such as inositol phosphates) may in fact serve to limit the secretory response.