bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of human platelet activation by polymorphonuclear leukocytes
Authors: Schattner Mirta A. , Geffner Jorge R. , Isturiz Martin A. , Lazzari Maria A. 
Published: July 2012

The effect of unstimulated human polymorphonuclear leukocytes (PMNs) on platelet activation was examined.
Human platelet aggregation and adenosine 5′‐triphosphate (ATP) release induced by collagen (1–2 μg ml−1); thrombin (0.01–0.02 u ml−1) or arachidonic acid (AA) (0.1–0.2 mm) were markedly inhibited when conducted in the presence of unstimulated PMNs.
Platelet inhibition induced by PMNs was dependent on the number of PMNs and on the incubation time of the mixed cell suspension.
Platelet inhibition was not reversed in time when PMNs were depleted from the mixed‐cell suspension.
PMN‐mediated platelet‐inhibition was not mediated by AA metabolites, oxygen reactive intermediates, nitric oxide or proteases.
The factor(s) accounting for the platelet inhibition mediated by PMNs are not yet characterized.
Role of epithelium in agonist‐induced contractile responses of guinea‐pig trachealis: influence of the surface through which drug enters the tissue
Authors: Iriarte C.F. , Pascual R. , Villanueva M.M. , Román M. , Cortijo J. , Morcillo E.J. 
Published: July 2012

A method has been used in guinea‐pig isolated tracheal rings to achieve selective drug entry from the adventitial or mucosal surface. A study has been made of the effects of epithelium removal on responses to spasmogens entering the tissue solely from the adventitial or the mucosal surface.
Cumulative concentration‐response curves for KCl (1 to 100 mm), acetylcholine (0.1 μm to 10 mm) and histamine (1 μm to 1 mm) were constructed in intact and epithelium‐denuded tracheal rings in circumstances where drug entry was unrestricted or restricted to the adventitial or mucosal surface.
Epithelium removal did not alter the responsiveness or sensitivity of tracheal rings to KCl either when drug entry was unrestricted or when drug entry was restricted to the adventitial or mucosal surface.
When acetylcholine entered from the mucosal or adventitial surfaces of intact tracheal rings its concentration‐response curve was displaced to the right with respect to that obtained for unrestricted drug entry. A greater rightward shift was observed for mucosal drug entry than for adventitial drug entry. Epithelium removal potentiated acetylcholine entering from the mucosal surface to a greater extent (27.5 fold) than it potentiated acetylcholine entering from both surfaces (4 fold). Epithelium removal did not potentiate effects of acetylcholine entering from the adventitial surface alone.
In intact tracheal segments, concentration‐response curves for histamine entering from the mucosal surface were displaced to the right compared with those for histamine entering in an unrestricted fashion or from the adventitial surface alone. This displacement was absent in epithelium‐denuded preparations. Epithelium removal potentiated (2–3 fold) histamine entering from the mucosal surface or entering in an unrestricted way. It did not potentiate histamine entering from the adventitial surface alone.
Our findings suggest that the epithelium does not modulate tracheal responses to KCl. Its ability to modulate responses to acetylcholine and histamine is observed when these spasmogens enter the tissue from the mucosal surface but not when they enter from the adventitial surface. The mechanism by which epithelium removal preferentially potentiates acetylcholine and histamine entering from the mucosal rather than the adventitial surface remains to be determined.
Effects of morphine, H‐Tyr‐d‐Arg‐Phe‐Lys‐NH2 (DALDA) and B‐HT920 on non‐cholinergic nerve‐mediated bronchoconstriction in pithed guinea‐pigs
Authors: Rechtman M.P. , Boura A.L.A. , King R.G. , Olley J.E. , Schiller P.W. 
Published: July 2012

Electrical stimulation (1 ms, 5 Hz, 80 V) for 5 or 15 s at the level of C4‐T1 in the spinal canal of artificially respired pithed guinea‐pigs (which had received intravenously (i.v.) (+)‐tubocurarine chloride 2 mg kg−1, atropine sulphate 2 mg kg−1 and pentolinium tartrate 5 mg kg−1) caused constriction of airways, indicated by increased insufflation pressure.
This non‐cholinergic constriction was inhibited by morphine (1–3 mg kg−1, i.v.), the peripherally acting μ‐receptor agonist, H‐Tyr‐d‐Arg‐Phe‐Lys‐NH2 (DALDA, 0.1–1 mg kg−1, i.v.) or the α2‐adrenoceptor agonist B‐HT920 (1–3 mg kg−1, i.v.)
The effects of either morphine (3 mg kg−1, i.v.) or DALDA (1 mg kg−1, i.v.) were inhibited by naloxone (3 mg kg−1, i.v.). Idazoxan (3 mg kg−1, i.v.) inhibited the anti‐constrictor effect of B‐HT920 (3 mg kg−1, i.v.), but not that of DALDA (0.1 mg kg−1, i.v.).
Thus activation of peripheral μ‐opioid receptors or α2‐adrenoceptors inhibits airways constriction induced by non‐cholinergic nerve stimulation in the pithed guinea‐pig. This preparation therefore provides a further method for the in vivo examination of the effects of drugs on non‐cholinergic tracheobronchial constrictor nerve function.
Effects of diltiazem on calcium concentrations in the cytosol and on force of contractions in porcine coronary arterial strips
Authors: Hirano Katsuya , Kanaide Hideo , Abe Shimako , Nakamura Motoomi 
Published: July 2012

Using front‐surface fluorometry with fura‐2‐loaded porcine coronary arterial strips, we simultaneously measured effects of a Ca2+ antagonist, diltiazem, on cytosolic Ca2+ concentrations ([Ca2+]i) and on tension development.
In the presence of extracellular Ca2+ (1.25 mm), histamine concentration‐dependently induced abrupt (the first component) and then sustained (the second component) elevations of [Ca2+]i. In the absence of extracellular Ca2+, histamine induced transient elevations of [Ca2+]i, and the time course was similar to that of the first component observed in the presence of extracellular Ca2+. Histamine caused a greater contraction for a given change in [Ca2+]i than did potassium, at [Ca2+]i over 300 nm.
Diltiazem, 10−8 m to 10−5 m, concentration‐dependently inhibited the second component of [Ca2+]i elevation and tension development induced by histamine (10−5 m). Only at higher concentrations (over 10−5 m) did diltiazem inhibit the first component of increases in [Ca2+]i and tension development induced by histamine, both in the presence and absence of extracellular Ca2+.
Diltiazem (10−6 m) inhibited increases in [Ca2+]i and tension development induced by cumulative applications of extracellular Ca2+ during K+‐depolarization. The curve of [Ca2+]i against tension of these Ca2+‐induced contractions obtained in diltiazem‐treated strips overlapped with that obtained in untreated strips. This suggests that diltiazem has no direct effects on contractile elements.
In contrast, the histamine‐induced Ca2+‐tension curve (second component) was shifted in parallel to the left by diltiazem.
We conclude that diltiazem, at therapeutic concentrations, specifically inhibits extracellular Ca2+‐dependent increases in [Ca2+]i, with no effects on the release of Ca2+ from intracellular store sites or on Ca2+‐sensitivity of the contractile elements involved in the contractions induced by elevations of [Ca2+]i.
Zacopride and BRL 24924 induce an increase in EEG‐energy in rats
Authors: Boddeke Hendrik W.G.M. , Kalkman Hans O. 
Published: July 2012

The substituted benzamides, zacopride and BRL 24924 induced dose‐dependent increases of the total EEG‐energy of rats when applied intracerebroventricularly (i.c.v.) with ED50 values of 8.0 ± 0.6 and 3.6 ± 0.9 μg, respectively. Not only the energy of the low frequency hippocampal theta rhythm but also that of the other frequency bands was increased.
In contrast to i.c.v. application intraperitoneal administration of zacopride or BRL 24924 (1 and 10 mg kg−1) did not lead to an increase in EEG‐energy.
The increase in EEG‐energy induced by zacopride (10 μg, i.c.v.) was blocked by ICS 205–930 (1 μg, i.c.v.). Neither the 5‐HT3 receptor agonist 2‐methyl‐5‐hydroxytryptamine (30 μg, i.c.v.) nor the selective 5‐HT3 receptor antagonist MDL 72222 (30 μg, i.c.v.) had any effect upon rat EEG.
Scopolamine (0.01 μg and 0.1 μg, i.c.v.) dose‐dependently antagonized the effect of zacopride (10 μg, i.c.v.).
An agonist action of zacopride and BRL 24924 and inhibition of these effects by ICS 205–930 but not by MDL 72222 was recently described in isolated colliculi neurones from neonatal mice. The receptor involved was described as ‘5‐HT4’. The present results indicate that the central effects of zacopride and BRL 24924 may be due to activation of such a 5‐HT receptor.
High‐ and low‐affinity binding sites for [3H]‐α,β‐methylene ATP in rat urinary bladder membranes
Authors: Bo Xuenong , Burnstock Geoffrey 
Published: July 2012

The characteristics of [3H]‐α,β‐methylene adenosine 5′‐triphosphate ([3H]‐α,β‐MeATP) binding to membrane preparations of rat urinary bladder detrusor were studied.
The rat bladder membrane preparation was obtained by multiple centrifugation. [3H]‐quinuclidinyl benzilate ([3H]‐QNB) binding to this preparation demonstrated that the muscarinic receptor density was 4.32 times higher than that in the homogenate. [3H]‐α,β‐MeATP binding was increased 3.88 times.
Saturation analysis revealed that the rat bladder membrane contained a high density of [3H]‐α,β‐MeATP binding sites, which could be divided into a high‐affinity component (Kd = 8.1–8.9 nm) and a low‐affinity component (Kd = 67.0–119.8 nm).
Magnesium ions inhibited the maximum binding in a concentration‐dependent manner. The maximum high‐affinity binding was reduced from 10.32 pmol mg−1 protein in magnesium‐free buffer to 4.62 pmol mg−1 protein with 25 mm MgCl2, while the maximum low‐affinity binding was reduced from 58.84 pmol mg−1 protein to 14.24 pmol mg−1 protein. Kd values were not greatly affected.
The binding was a rapid reversible process. The association rate constants were 7.64 × 107 m−1 min−1 for high‐affinity binding, and 7.31 × 106 m−1 min−1 for low‐affinity binding. The dissociation rate constants were 0.2896 min−1 for high‐affinity binding, and 0.6348 min−1 for the low‐affinity binding.
Displacement experiments with unlabelled purinoceptor ligands confirmed that [3H]‐α,β‐MeATP mainly binds to P2X‐purinoceptors. The potency order was: α,β‐methylene ATP > β,γ‐methylene ATP > suramin > ATP > ADP > 2‐methylthio ATP ≫ adenosine.
The results indicate that [3H]‐α,β‐MeATP is a radioligand for the P2X‐purinoceptor, which satisfies the basic criteria for use in radioligand binding assay.
Binding of [125I]‐endothelin‐1 to rat cerebellar homogenates and its interactions with some analogues
Authors: Hiley C. Robin , Jones C. Richard , Pelton John T. , Miller Robert C. 
Published: July 2012

[125I]‐endothelin‐1, over the concentration range 6 pm–10 nm, bound to a single site in homogenates of rat cerebellum with high affinity (Kd = 2.8 ± 0.6 × 10−10 m). The site was present in a concentration of 321 ± 58 fmol mg−1 protein.
The rates of association and dissociation of [125I]‐endothelin‐1 with the binding site were slow (at 25°C, k+1 = 8.0 ± 1.3 × 105m−1 s−1; k−1 = 2.6 × 10−4 s−1) and, on addition of a maximally displacing concentration of endothelin‐1 (100 nm), 94.0 ± 8.4% of the [125I]‐endothelin‐1 was still bound after 14h.
[125I]‐endothelin‐1 binding was inhibited by a number of naturally occurring or genetically encoded members of the endothelin/sarafotoxin family of peptides. The order of potency was endothelin‐3 = sarafotoxin S6b > endothelin‐2 = endothelin‐1 ≫ porcine proendothelin1–39.
Binding was also inhibited by analogues in which either one or both of the cystine disulphide bridges had been replaced by substitution with 2 or 4 alanine residues. The tetra‐alanyl substituted analogue, [Ala1,3,11,15]endothelin‐1, was equipotent with endothelin‐1 at inhibiting the binding of [125I]‐endothelin‐1. [Ala3,11]endothelin‐1 and [Ala1,15]endothelin‐1, analogues which each contained one of the disulphide bridges from the parent peptide, were respectively 3 and 14 times less potent than the parent peptide. An analogue in which the Glu10 residue had been anisylated was 25 fold less potent than endothelin‐1.
It is concluded that the structural requirements for binding to the cerebellar sites for [125I]‐endothelin‐1 do not require the presence of the disulphide bridges characteristic of the endothelin/sarafotoxin family. Rather, the binding may be more sensitive to the presence of bulky side chain substituents, at least in the smaller intramolecular loop.
Characterization of the l‐arginine: nitric oxide pathway in human platelets
Authors: Radomski M.W. , Palmer R.M.J. , Moncada S. 
Published: July 2012

The activation of the l‐arginine:nitric oxide (NO) pathway during aggregation of human platelets by adenosine 5′‐diphosphate (ADP), arachidonic acid, thrombin and the calcium ionophore A23187 and its inhibition by NG‐monomethyl‐l‐arginine (l‐NMMA), NG‐nitro‐l‐arginine methyl ester (l‐NAME) and N‐iminoethyl‐l‐ornithine (l‐NIO) were studied. The inhibition of the cytosolic platelet NO synthase by these compounds was also examined.
Platelet aggregation induced by ADP (1–10 μm) and arachidonic acid (0.1–10 μm), but not that induced by thrombin (1–30 mu ml−1) or A23187 (1–10 nm), was inhibited by l‐, but not d‐arginine (1–30 μm). However, in the presence of a subthreshold concentration of prostacyclin (0.1 nm) or of M & B 22948 (1 μm), a selective inhibitor of guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) phosphodiesterase, l‐arginine caused concentration‐dependent inhibition of aggregation induced by all of these aggregating agents.
l‐NMMA, l‐NAME and l‐NIO (all at 1–30 μm), but not their d‐enantiomers, enhanced to the same extent platelet aggregation induced by ADP, arachidonic acid and thrombin without affecting that induced by A23187.
In the presence of 300 μm l‐arginine, the NO synthase in platelet cytosol was inhibited by l‐NMMA, l‐NAME and l‐NIO with IC50s of 74 ± 9, 79 ± 8 and 8.5 ± 1.5 μm (n = 3), respectively.
These results indicate that the l‐arginine: NO pathway in human platelets plays a role in the modulation of platelet aggregation.
Bradykinin‐induced vasoconstriction of rat mesenteric arteries precontracted with noradrenaline
Authors: Fasciolo Juan C. , Vargas Leonor , Lama M. Cristina , Nolly Héctor 
Published: July 2012

Administration of bradykinin caused dose‐dependent vasoconstriction in rat isolated perfused mesenteric arteries precontracted with noradrenaline.
The vasoconstrictor response was not mediated by BK1‐bradykinin receptors.
Inhibition of cyclo‐oxygenase with indomethacin, aspirin or meclofenamate abolished the vasoconstrictor effect of bradykinin, showing that a member of the arachidonic acid cascade may be involved.
Inhibitors of thromboxane synthesis (imidazole and UK 38485) did not affect or only reduced the bradykinin‐induced vasoconstriction.
The endoperoxide H2/thromboxane A2 receptor antagonist SQ 29548 significantly reduced the vasoconstrictor effect of bradykinin, but did not affect the vasoconstrictor response to noradrenaline, adrenaline, vasopressin, 5‐hydroxytryptamine or prostaglandins.
The eicosanoid(s) that mediate bradykinin‐induced vasoconstriction appear to be synthesized outside the arterial endothelium.
The data suggest that the vasoconstrictor effect of bradykinin in the rat isolated mesenteric artery is mediated by vasoconstrictor arachidonic acid metabolites including the cyclic endoperoxides and/or the thromboxanes.
Effects of organophosphorus anticholinesterases on nicotinic receptor ion channels at adult mouse muscle endplates
Authors: Tattersall John E.H. 
Published: July 2012

The effects of a range of organophosphorus anticholinesterases on the nicotinic acetylcholine receptor ion channel at the adult mouse muscle endplate were investigated by use of single‐channel recording techniques. Diisopropylfluorophosphate (DFP), sarin and soman had no effect on open times at concentrations of up to 100 μm, but ecothiopate (Eco) and O‐ethyl S‐[2‐(diisopropylamino)ethyl]methyl phosphonothiolate (VX) were found to have voltage‐ and concentration‐dependent open channel‐blocking actions at concentrations of 1–50 μm. In addition to its channel‐blocking action, Eco (50 μm) had a weak agonist effect: it is suggested that this may be attributable to thiocholine produced by hydrolysis of Eco.
Rate constants for blockade by Eco and VX were determined according to a sequential model. The greater voltage‐dependence of the block by Eco was due to a greater voltage sensitivity of the blocking rate constant compared to VX: the voltage‐dependence of the unblocking rate constant was similar for both compounds.
In control recordings, the frequency of channel opening declined exponentially with time after formation of the gigaseal. Sarin and soman both increased the rate of this decline, indicating that they accelerated the rate of desensitization of the receptors. Eco and VX reduced the initial frequency of opening, which may have been due to enhancement of a fast phase of desensitization during gigaseal formation, or to blockade of closed channels.
It is concluded that the direct actions of organophosphates on nicotinic receptor ion channels are of little importance for their toxicity under normal conditions, since they occur only at much higher concentrations than those which cause inhibition of acetylcholinesterase. Such actions may become apparent, however, when therapies against the anticholinesterase effects of organophosphates increase their lethal dose sufficiently. These direct actions should also be taken into account when the effects of organophosphates on cholinergic transmission are studied.
Positive inotropic effect of porcine left ventricular extract on canine ventricular muscle
Authors: Navaratnam S. , Chau T. , Agbanyo M. , Bose D. , Khatter J.C. 
Published: July 2012

We previously isolated an extract from porcine left ventricle that possessed digitalis‐like properties such as inhibition of cardiac and kidney Na+, K+‐ATPase, displacement of [3H]‐ouabain from its binding sites and cross reactivity with digoxin antibodies. The extract also had a positive inotropic effect on the guinea‐pig heart.
In the present study the positive inotropic response of the extract was characterized in canine right ventricular trabeculae. Maximum inotropic response (501 ± 20%) was produced by 300 μl and the half maximal increase occurred with 125 μl of the extract.
Ouabagenin produced aftercontractions in rapidly paced trabeculae. Equipotent and even greater amounts of the extract did not produce aftercontractions.
The extract increased the amplitude of the delayed component (P2) of biphasic contractions produced by replacing about 92–96% of the external Ca with Sr. A smaller increase in the size of the early component (P1) was also seen.
The extract decreased post‐rest potentiation after rest for 30 s and 2 min. After 8 min of rest, post‐rest potentiation was converted to post‐rest depression.
The extract (20 μl) produced a decrease in the amplitude of the post‐rest rapid cooling contracture (RCC) at all rest intervals. The steady state RCC, although greater than that in the control muscle, was increased to a lesser extent than the size of the steady state electrically driven contractions.
It is suggested that the extract from porcine left ventricle produces a positive inotropic response by increasing the trans‐sarcolemmal influx of Ca. It also has additional effect(s) on the sarcoplasmic reticulum in that it may facilitate the loss of Ca from the sarcoplasmic reticulum and/or inhibit the uptake of Ca by the organelle.
The effects of ryanodine and caffeine on Ca‐activated current in guinea‐pig ventricular myocytes
Authors: White Edward , Terrar Derek A. 
Published: July 2012

Action potentials from guinea‐pig single ventricular myocytes were interrupted by application of a 300 ms voltage clamp to −40 mV in order to evoke the Ca‐activated tail current which is thought to be carried by Na: Ca exchange. Stimulation frequency was 1 Hz and temperature 36°C.
The actions of ryanodine (1 μm and 10 μm) and caffeine (1 mm and 10 mm) on Ca‐activated tail currents were investigated.
Exposure to 10 mm caffeine and ryanodine reduced tail currents associated with very abbreviated (12 ms duration) action potentials and greatly reduced the difference between first and steady‐state tail currents at this action potential duration. These observations were interpreted in terms of suppression of Ca release from the sarcoplasmic reticulum (SR) stores.
Tail current decay during the voltage clamp is thought to reflect the fall in [Ca]i which accompanies muscle relaxation. Current decay is dependent on Ca extrusion via Na:Ca exchange and on Ca accumulation by the SR stores. Time constants of tail current decay were seen to decrease with increasing action potential duration. This relationship was not affected by 1 mm caffeine or 1 μm ryanodine. Ryanodine at 10 μm and 10 mm caffeine abolished this relationship and increased the time constants of current decay. An increase in the time constant of tail current decay was thought to reflect a reduction in the rate of Ca accumulation by the sarcoplasmic reticulum.
The actions of caffeine and ryanodine on the Ca‐activated tail currents are consistent with a dose‐dependent leakage of Ca from the SR Ca stores. The Ca‐activated tail current appears to be a useful tool in the study of Ca homeostasis.
Inhibitory effect of streptozotocin‐induced diabetes on non‐cholinergic motor transmission in rat detrusor and its prevention by sorbinil
Authors: Luheshi G.N. , Zar M.A. 
Published: July 2012

Non‐cholinergic motor transmission in the urinary bladder of streptozotocin (STZ)‐diabetic rats was studied by recording contractile activity of strips of detrusor in vitro.
The neurogenic contractile responses to electrical field stimulation (EFS) of atropine‐treated detrusor strips were decreased in 4, 8 and 12 week STZ‐diabetic rats. The decrease was most marked in 12 week diabetic rats and least in 4 week ones.
Concentration‐response curves showed no change in sensitivity of the detrusor to acetylcholine (ACh) in diabetic rats. The maximum tension generated by ACh was similar in diabetic and non‐diabetic animals.
The contractile responses to EFS at frequencies ≥ 1 Hz were not maintained during stimulation. The ‘fade’ was significantly greater in detrusor strips of diabetic rats.
The contractile response of detrusor to EFS was significantly greater in 12 week diabetic rats treated with the aldose reductase inhibitor sorbinil, than in untreated 12 week diabetic rats. The sensitivity to ACh was similar in the two groups.
It is concluded that the reduction of the neurogenic non‐cholinergic responses of detrusor to EFS in STZ‐diabetic rats is probably caused by a reduction in the release of the non‐cholinergic motor transmitter. The results are discussed in relation to bladder dysfunction in human diabetes mellitus.