bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acute effects of the β3‐adrenoceptor agonist, BRL 35135, on tissue glucose utilisation
Authors: Liu Yong‐Ling , Stock Michael J. 
Published: July 2012

The acute effects of BRL 35135 (BRL) on tissue glucose utilisation index (GUI) in vivo were investigated in anaesthetized rats by use of 2‐deoxy‐[3H]‐glucose.
Intravenous injection of BRL caused a dose‐dependent increase in GUI in skeletal muscle, and white and brown adipose tissue; plasma insulin and fatty acid concentrations were also increased. Chronic treatment with BRL added to the diet caused a 34 fold increase in basal GUI of brown adipose tissue (BAT), but had no effect on GUI in other tissues. After chronic treatment, the acute tissue response to an intravenous maximal dose of BRL had disappeared completely in all tissues apart from the soleus muscle.
A high dose (20 mg kg−1) of the non‐selective β‐antagonist, propranolol, inhibited the acute effect of BRL on GUI in BAT, but failed to affect GUI in muscle. A lower dose (1 mg kg−1) of the antagonist also inhibited the BAT response, but had little or no effect on the response in Type I (working) muscles such as soleus and adductor longus (ADL), and potentiated the response in Type II (non‐working) muscles such as tibialis and extensor digitorium longus (EDL).
A low dose (1 mg kg−1) of the selective β1‐antagonist, atenolol, had no effect on the BRL response but the same dose of the selective β2‐antagonist, ICI 118551, potentiated significantly the effect of BRL on GUI in most muscles without altering plasma insulin levels.
It is concluded that: (i) the heterogeneous tissue responses of different muscle fibre types in the presence of β‐antagonists indicates that BRL affects muscle GUI directly, in addition to effects mediated by increases in plasma insulin concentration; (ii) the resistance of the BRL response to conventional β‐adrenoceptor antagonists implicates an atypical adrenoceptor mediating the GUI response in skeletal muscle, but this may not be identical to the adipose tissue β3‐adrenoceptor; (iii) the potentiation of BRL responses by ICI 118551 indicates an inhibitory β2‐adrenoceptor‐mediated component in the muscle GUI response to BRL.
Anaesthetic modulation of nicotinic ion channel kinetics in bovine chromaffin cells
Authors: Charlesworth P. , Richards C.D. 
Published: July 2012

We have investigated the action of the anaesthetics methoxyflurane, methohexitone and etomidate on the nicotinic acetylcholine receptor channel of bovine adrenal chromaffin cells using the whole cell patch clamp technique.
Spectral analysis of macroscopic currents evoked by 25 μm carbachol revealed that each of the agents tested reduced the lifetime of the channel open state in a dose‐dependent manner. The whole cell current was inhibited in a concentration‐dependent fashion by each agent.
Channel gating parameters were calculated from single channel studies and the results used to test models explaining the modulation of nicotinic acetylcholine receptor channels by anaesthetics.
Each of the agents studied reduced the mean channel open time in a concentration‐dependent manner. Anaesthetic concentrations reducing mean open time by 50% were: 370 μm methoxyflurane, 30 μm methohexitone or 23 μm etomidate.
Methohexitone and etomidate produced an increase in the number of brief closures within bursts, while no such increase was observed with methoxyflurane. Despite these inter‐burst gaps, mean burst length was reduced by each of the agents tested.
It is concluded that a simple sequential blocking model fails to account for the action of these anaesthetics. An extended model, in which blocked channels can close, may be applicable.
Activation by ATP of a P2U‘nucleotide’ receptor in an exocrine cell
Authors: Martin Shaun C. , Shuttleworth Trevor J. 
Published: July 2012

We employed the perforated patch whole‐cell technique to investigate the effects of ATP and other related nucleotides on membrane conductances in avian exocrine salt gland cells.
ATP (10μm‐1 mM) evoked an increase in maxi‐K+ and Cl− conductances with a reversal potential of −35mV. At lower concentrations of ATP (≤100 μm) responses were generally oscillatory with a sustained response observed at higher concentrations (≥200 μm).
Both oscillatory and sustained responses were abolished by the removal of bath Ca2+. In cells preincubated in extracellular saline containing reduced Ca2+, the application of ATP resulted in a transient increase in current.
As increasing concentrations of ATP (and related nucleotides) evoked a graded sequence of events with little run‐down we were able to establish a rank order of potency in single cells. The order of potency of ATP analogues and agonists of the various P2‐receptor subtypes was UTP>ATP = 2‐methylthio‐ATP>ADP. Adenosine (1μm‐1mm), AMP (1μm‐1μm), α,β‐methylene‐ATP (1 μM−1 mm) and α,β‐methylene‐ATP (1μm‐ mm) were without effect.
In conclusion, although unable to preclude a role for a P2Y‐receptor, our results suggest that ATP binds to a P2U‐receptor increasing [Ca2+]i and subsequently activating Ca2+‐sensitive K+ and Cl−currents.
Blockade by sigma site ligands of high voltage‐activated Ca2+ channels in rat and mouse cultured hippocampal pyramidal neurones
Authors: Church John , Fletcher Elizabeth J. 
Published: July 2012

The effects of a series of structurally‐dissimilar σ site ligands were examined on high voltage‐activated Ca2+ channel activity in two preparations of cultured hippocampal pyramidal neurones.
In mouse hippocampal neurones under whole‐cell voltage‐clamp, voltage‐activated Ca2+ channel currents carried by barium ions (IBa) were reduced with the rank order (IC50 values in μm): 1S,2R‐(–)‐cis‐N‐methyl‐N‐[2‐(3,4‐dichlorophenyl)ethyl]‐2‐(1‐pyrrolidinyl)cyclohexylamine (7.8) > rimcazole (13) > haloperidol (16)>ifenprodil (18)>opipramol (32)>carbetapentane (40)=1‐benzylspiro[1,2,3,4‐tetrahy‐dronaphthalene‐1,4‐piperidine] (42) >caramiphen (47) >dextromethorphan (73). At the highest concentrations tested, the compounds almost abolished IBa in the absence of any other pharmacological agent.
The current‐voltage characteristics of the whole‐cell IBa were unaffected by the test compounds. The drug‐induced block was rapid in onset and offset, with the exceptions of carbetapentane and caramiphen where full block was achieved only after two to three voltage‐activated currents and was associated with an apparent increase in the rate of inactivation of IBa
In rat hippocampal neurones loaded with the Ca2+‐sensitive dye Fura‐2, rises in intracellular free Ca2+ concentration evoked by transient exposure to 50 mM K+‐containing medium, either in the absence or in the presence of 10 μm nifedipine (to block L‐type high voltage‐activated Ca2+ channels), were also reversibly attenuated by the σ ligands. The rank order potencies for the compounds in these experimental paradigms were similar to that observed for blockade of IBa in the electrophysiological studies.
These results indicate that, at micromolar concentrations, the compounds tested block multiple subtypes of high voltage‐activated Ca2+ channels. These actions, which do not appear to be mediated by high‐affinity σ binding sites, may play a role in some of the functional effects previously described for the compounds.
The promotion of patent airways and inhibition of antigen‐induced bronchial obstruction by endogenous nitric oxide
Authors: Persson Magnus G. , Friberg Sten G. , Gustafsson Lars E. , Hedqvist Per 
Published: July 2012

The aim of the present study was to investigate the role of nitric oxide (NO), histamine and leukotrienes in bronchial obstruction. For this, guinea‐pigs immunised against ovalbumin were studied under anaesthesia during challenge with antigen or agonists.
Challenge with nebulised antigen (0.1‐1 mg) elicited dose‐dependent increases in insufflation pressure which were abolished by combined administration of histamine and leukotriene antagonists.
Challenge with nebulised antigen (0.1‐1 mg) also elicited dose‐dependent increases in the concentration of endogenous nitric oxide in the exhaled air. After an initial peak, exhaled NO concentrations returned to pre‐challenge levels.
The increase in insufflation pressure and in exhaled NO caused by ovalbumin challenge was inhibited by combined administration of histamine and leukotriene antagonists.
In non‐immunised guinea‐pigs, challenge of the airways with nebulised histamine (10–1000 nmol) or leukotriene C4 (LTC4, 30–300 pmol) elicited dose‐dependent increases in insufflation pressure and in concentrations of endogenous NO in exhaled air.
The increase in exhaled NO correlated with the increase in insufflation pressure in response to ovalbumin, histamine and LTC4. An inhibitor of endogenous NO synthesis, Nω‐nitro‐l‐arginine methylester (l‐NAME, 30 mg kg−1 i.v.) abolished NO exhalation, and markedly augmented the airway responses to ovalbumin, histamine, or LTC4.
The potentiation by l‐NAME of the increase in insufflation pressure in response to ovalbumin or histamine was prevented by exogenous NO (20 p.p.m.) in the inhaled air.
The results indicate that endogenous NO has an inhibitory effect on bronchial obstruction. Increased NO release during allergen challenge is likely to be due to actions of histamine and leukotrienes.
Stereoselective uptake of β‐lactam antibiotics by the intestinal peptide transporter
Authors: Wenzel Uwe , Thwaites David T. , Daniel Hannelore 
Published: July 2012

The stereoselective transport of β‐lactam antibiotics has been investigated in the human intestinal epithelial cell line, Caco‐2, by use of D‐ and L‐enantiomers of cephalexin and loracarbef as substrates.
The L‐isomers of cephalexin, loracarbef and dipeptides displayed a higher affinity for the oligopeptide/H+‐symporter in Caco‐2 cells than the D‐isomers. This was demonstrated by inhibition of the influx of the β‐lactam, [3H]‐cefadroxil.
By measurement of the substrate‐induced intracellular acidification in Caco‐2 cells loaded with the pH‐sensitive fluorescent dye BCECF (2′,7′‐bis(2‐carboxyethyl)‐5‐(6)‐carboxy‐fluorescein), it was demonstrated for the first time that L‐isomers of β‐lactams not only bind to the peptide transporter with high affinity but are indeed transported.
Efficient proton‐coupled transport of L‐β‐lactam antibiotics was also shown to occur in Xenopus laevis oocytes expressing the cloned peptide transporter PepTl from rabbit small intestine.
Both cell systems therefore express a stereoselective transport pathway for β‐lactam antibiotics with very similar characteristics and may prove useful for screening rapidly the oral availability of peptide‐derived drugs.
Cytokine‐mediated induction of cyclo‐oxygenase‐2 by activation of tyrosine kinase in bovine endothelial cells stimulated by bacterial lipopolysaccharide
Authors: Akarasereenont P. , Bakhle Y.S. , Thiemermann C. , Vane J.R. 
Published: July 2012

The induction of cyclo‐oxygenase‐2 (COX‐2) afforded by bacterial lipopolysaccharide (LPS, endotoxin) in bovine aortic endothelial cells (BAEC) is mediated by tyrosine kinase. LPS also causes the generation of several cytokines including interleukin‐1β (IL‐1β), tumour necrosis factor‐α (TNF‐α), epidermal growth factor (EGF) and platelet‐derived growth factor (PDGF). This study investigates whether endogenous IL‐1β, TNF‐α, EGF or PDGF contribute to the induction of COX‐2 elicited by LPS in BAEC and if their action is due to activation of tyrosine kinase. Furthermore, we have studied the induction of COX‐2 by exogenous cytokines.
Accumulation of 6‐oxo‐prostaglandin (PG) F1α in cultures of BAEC was measured by radioimmunoassay at 24 h after addition of either LPS (1 μg ml−1) alone or LPS together with a polyclonal antibody to one of the various cytokines. In experiments designed to measure ‘COX activity’, 6‐oxo‐PGF1α generated by BAEC activated with recombinant human IL‐1β, TNF‐α, EGF or PDGF for 12 h was measured after incubation of washed cells with exogenous arachidonic acid (30 μM for 15 min). Western blot analysis determined the expression of COX‐2 protein in BAEC.
The accumulation of 6‐oxo‐PGF1α caused by LPS in BAEC was attenuated by co‐incubation with one of the polyclonal antibodies, anti‐IL‐1β, anti‐TNF‐α, anti‐EGF, anti‐PDGF or with the IL‐1 receptor antagonist, in a dose‐dependent manner. Exogenous IL‐1β, TNF‐α or EGF also caused an increase in COX activity, while PDGF was ineffective. The increase in COX activity elicited by IL‐1β (10 ng ml−1), TNF‐α (100 ng ml−1) or EGF (1000 ng ml−1) in BAEC was attenuated by erbstatin (0.005 to 5 μg ml−1), as was the expression of COX‐2 protein measured by Western blot analysis.
PDGF (10 ng ml−1) significantly augmented the rise in COX activity and COX‐2 protein caused by shorter incubation of BAEC with LPS (1 μg ml−1 for 3 h). Combination of PDGF (10 ng ml−1) with a low concentration of IL‐1β (1 ng ml−1) for 12 h, also increased ‘COX activity’, but combination of PDGF and TNF‐α (10 ng ml−1) did not show any increased activity.
These results suggest that (i) the induction of COX activity and COX‐2 protein elicited by LPS in BAEC is mediated by TNF‐α with lesser contributions from PDGF, EGF or IL‐1β; (ii) exogenous IL‐1β, TNF‐α or EGF alone induce COX‐2 activity and protein in BAEC; (iii) PDGF synergizes with IL‐1β, but not TNF‐α, to cause expression of COX‐2; and (iv) the induction of COX‐2 protein and activity caused by these cytokines involves the activation of tyrosine kinase.
Effect of enalaprilat on bradykinin and des‐Arg9‐bradykinin release following reperfusion of the ischaemic rat heart
Authors: Lamontagne Daniel , Nadeau Réginald , Adam Albert 
Published: July 2012

The release of bradykinin (BK) and its metabolite, des‐Arg9‐bradykinin (des‐Arg9‐BK), was studied following reperfusion of a globally ischaemic rat heart.
BK‐like immunoreactivity increased from 13±3 (preischaemic value) to 48±12 fmol min−1 g−1 (P<0.05, n = 14) 30 s after reperfusion. No difference in BK release was found between control hearts and hearts pretreated with the angiotensin converting enzyme (ACE or kininase II) inhibitor, enalaprilat (50 ng ml−1).
No significant change in des‐Arg9‐BK‐like immunoreactivity during reperfusion was observed in control hearts. In contrast, des‐Arg9 ‐ BK ‐ like immunoreactivity rose from 44 ± 15 to 177 ± 61 fmol min−1 g−1 (P<0.05, n = 7) 30 s after reperfusion in enalaprilat‐treated hearts.
In conclusion, BK is released upon reperfusion of the globally ischaemic rat heart. ACE inhibitors, through the inhibition of kininase II, increase the formation of the active metabolite, des‐Arg9‐BK.
Regulation of kinin‐induced contraction and DNA synthesis by inflammatory cytokines in the smooth muscle of the rabbit aorta
Authors: Levesque Luc , Larrivée Jean‐François , Bachvarov Dimcho R. , Rioux Francis , Drapeau Guy , Marceau Francois 
Published: July 2012

In rabbit aortic rings, the contractile response to kinins is mediated by the B1 receptors for kinins; the response is upregulated from an initial null level in a time‐ and protein synthesis‐dependent manner. Incubation (3 h) with human recombinant interleukin‐lβ (IL‐lβ) selectively amplified the contractile response to the B1 receptor agonist Sar‐[D‐Phe8]des‐Arg9‐BK, while it did not affect the contractile effect of other agents (angiotensin II, endothelin‐1, phenylephrine).
Oncostatin M (OSM), but not macrophage migration inhibitory factor (MIF), increased the contractile response to the B1 receptor agonist, des‐Arg9‐bradykinin (des‐Arg9‐BK).
Cultured smooth muscle cells derived from the rabbit aorta exhibit a significant des‐Arg9‐BK‐induced increase in [3H]‐thymidine incorporation if pretreated with a cyclo‐oxygenase inhibitor (diclofenac) and concomitantly treated with the cytokines IL‐1 or OSM. Angiotensin II, endothelin‐1 or phenylephrine, alone or in the presence of IL‐lβ, exerted little effect on DNA synthesis in these cells.
The pharmacological characterization of the mitogenic response to kinins using a set of agonist and antagonist analogues is consistent with mediation by B1 receptors. Des‐Arg9‐BK‐induced DNA synthesis is suppressed by prostaglandin E2 by a prostacyclin mimetic (iloprost), by the Ser/Thr protein kinase inhibitor, H‐7, and by a tyrosine kinase inhibitor (i.e. an erbstatin analogue).
B1 receptor‐mediated responses and their capacity to be regulated by cytokines, are retained in rabbit aortic smooth muscle cells. Such responses could be relevant to tissue repair mechanisms and hypertrophic medial responses to injury in arteries.
Structural requirements at the melatonin receptor
Authors: Sugden David , Chong Nelson W.S. , Lewis David F.V. 
Published: July 2012

High affinity, specific binding sites for the pineal hormone, melatonin (5‐methoxy N‐acetyltryptamine) can be detected in chick brain membranes by use of the radiolabeled agonist, 2‐[125I]‐iodomelatonin (2‐[125I]‐aMT).
The affinity of a number of analogues of melatonin at the 2‐[125I]‐aMT binding site was determined and compared with an analysis of their electronic structure and significant quantitative relationships obtained.
The best correlations indicated that binding affinity was correlated with ΔE, the difference between the frontier orbital energies, and QNH, the electron density in the highest occupied molecular orbital of the side‐chain nitrogen atom.
These findings suggest that ligand binding may involve hydrogen bonding between the 5‐methoxy and amide moieties of melatonin and complementary amino acid residues, and charge transfer interactions between the indole ring of melatonin and an aromatic amino acid in the receptor binding site.
A molecular model of a putative binding site is proposed based on the predicted amino acid sequence of the cloned Xenopus laevis melanophore melatonin receptor and the quantitative structure‐affinity relationships observed in the present study.
Sustained negative inotropism mediated by α‐adrenoceptors in adult mouse myocardial developmental conversion from positive response in the neonate
Authors: Tanaka Hikaru , Manita Shigeru , Matsuda Tomoyuki , Adachi Mika , Shigenobu Koki 
Published: July 2012

Inotropic responses to α‐adrenoceptor stimulation and the effects of antagonists were examined in isolated ventricular preparations from neonatal and adult mice.
Phenylephrine, in the presence of propranolol, produced positive inotropic responses in neonates up to 1 week after birth, while it produced negative inotropic responses in mice older than 3 weeks.
Both positive and negative responses to phenylephrine in neonates and adults, respectively, were antagonized by prazosin, WB4101 (2‐([2,6‐dimethoxyphenoxyethyl]aminomethyl)‐1,4‐benzodioxane) and 5‐methylurapidil, but not by atropine, yohimbine or chlorethylclonidine.
Noradrenaline (NA) produced positive inotropic responses both in the neonate and adult; the responses were observed in a lower concentration‐range in the neonate than in the adult. WB4101 produced a significant leftward shift of the concentration‐response curve for noradrenaline in adult preparations while only a slight rightward shift was observed in the neonate.
Our results demonstrate the presence of α‐adrenoceptor‐mediated inotropic responses in the mouse ventricular myocardia. The response to phenylephrine changes from a positive to a negative effect during postnatal development. The responses are mediated by α1‐adrenoceptors, and modulate the overall inotropic response to NA in the adult.
Pharmacological analysis of the local and reflex responses to bradykinin on rat urinary bladder motility in vivo
Authors: Lecci A. , Giuliani S. , Meini S. , Maggi C.A. 
Published: July 2012

The topical application of bradykinin (BK) (0.05–5000 pmol/rat) onto the serosal surface of the urinary bladder in urethane‐anaesthetized rats, evoked low amplitude tonic contractions (not exceeding 25 mmHg) or high amplitude (about 50 mmHg), phasic reflex contractions (chemoceptive micturition reflex) which were abolished by bilateral ablation of the pelvic ganglia. In ganglionectomized rats, BK induced only a local, tonic‐type contraction.
Systemic capsaicin pretreatment (164 μmol kg−1, 4 days before) reduced the incidence of chemoceptive reflex induced by BK (500 pmol/rat) but had no effect on the magnitude of the tonic‐type contraction elicited by BK in ganglionectomized rats. Indomethacin (11 μmol kg−1, 20 min before) reduced the incidence but not the amplitude of the reflex contractions induced by topical application of BK (500 pmol/rat). In ganglionectomized rats, indomethacin (11 μmol kg−1, 20 min before) decreased the amplitude of the tonic contraction evoked by BK. Indomethacin did not affect the chemoceptive reflex induced by topical application of capsaicin (15 nmol/rat) onto the bladder.
Intrathecal administration of the tachykinin NK1 receptor antagonists, RP 67,580 (10 nmol/rat) or SR 140,333 (10 nmol/rat), abolished the chemoceptive reflex induced by BK without modifying the magnitude of the tonic contraction. SR 140,333 (10 nmol/rat) also abolished the occurrence of the chemoceptive reflex induced by capsaicin.
Intravenous administration of the B2 receptor antagonist, Hoe 140 (35 nmol kg−1, 10 min before) abolished the reflex and local effects induced by BK on bladder motility but failed to modify the chemoceptive reflex induced by topical application of capsaicin (15 nmol/rat).
Intrathecal administration of Hoe 140 (10 nmol/rat) reduced the incidence of the chemoceptive reflex induced by BK but had no effect on the amplitude of the local motor response. Likewise, Hoe 140 (10 nmol/rat, i.t.) reduced the incidence of reflex bladder contractions induced by topical application of capsaicin (15 nmol/rat) without affecting the magnitude of the tonic‐type contraction.
These findings indicate that BK stimulates motility through B2 receptors in the rat urinary bladder. BK activates the reflex response by stimulating capsaicin‐sensitive afferent nerves with a contribution from prostanoids. At the spinal cord level, tachykinin NK1 and BK B2 receptors could also be involved in the chemoceptive reflex induced by BK or capsaicin.