bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dependence on temperature of the effect of dinitrophenol on the release of transmitter quanta at neuromuscular junctions in the mouse diaphragm
Authors: Nishimura Masakazu , Taquahashi Yuhji , Fujita Keiko , Satoh Eiki , Shimizu Yoshio 
Published: July 2012

The frequencies (F, s−1) of miniature endplate potentials and the quantal content (m) of endplate potentials were measured intracellularly and simultaneously at mouse diaphragm endplates in a bathing solution that contained 0.6 mM Ca2+ ions and 5 mM Mg2+ ions.
Twin pulses at 4 ms intervals gave the quantal contents of the first (m1) and second (m2) responses. The ratio of m2/m1 was taken as an indicator of the temporal facilitation of the release of transmitter.
Dinitrophenol (DNP, 10 μm) increased the values of F and m at 36°C. This effect did not depend on extracellular Ca2+ ions.
The potentiating effect of DNP disappeared at 24°C but the value of m2/m1 remained constant.
These results suggest that the effect of DNP is modifiable by temperature which can affect systems that control the intracellular metabolism of Ca2+ ions.
Effect of niflumic acid on noradrenaline‐induced contractions of the rat aorta
Authors: Criddle D.N. , de Moura R. Soares , Greenwood I.A. , Large W.A. 
Published: July 2012

The effects of niflumic acid, an inhibitor of calcium‐activated chloride channels, were compared with the actions of the calcium channel antagonist nifedipine on noradrenaline‐evoked contractions in isolated preparations of the rat aorta.
The cumulative concentration‐effect curve to noradrenaline (NA) was depressed by both nifedipine and niflumic acid in a reversible and concentration‐dependent manner. The degree of inhibition of the maximal contractile response to NA (1 μm) produced by 10 μm niflumic acid (38%) was similar to the effect of 1 μm nifedipine (39%).
Contractions to brief applications (30 s) of 1 μm NA were inhibited by 55% and 62% respectively by 10 μm niflumic acid and 1 μm nifedipine.
In the presence of 0.1 μm nifedipine, niflumic acid (10 μm) produced no further inhibition of the NA‐evoked contractions. Thus, the actions of niflumic acid and nifedipine were not additive.
In Ca‐free conditions the transient contraction induced by 1 μm NA was not inhibited by niflumic acid (10 μm) and therefore this agent does not reduce the amount of calcium released from the intracellular store or reduce the sensitivity of the contractile apparatus to calcium.
Niflumic acid 10 μm did not inhibit the contractions produced by KCl (up to 120 mM) which were totally blocked by nifedipine. Contractions induced by 25 mM KCl were completely inhibited by 1 μm levcromakalim but were unaffected by niflumic acid.
It was concluded that niflumic acid produces selective inhibition of a component of NA‐evoked contraction which is probably mediated by voltage‐gated calcium channels. These data are consistent with a model in which NA stimulates a calcium‐activated chloride conductance which leads to the opening of voltage‐gated calcium channels to produce contraction.
Bradykinin and changes in microvascular permeability in the hamster cheek pouch: role of nitric oxide
Authors: Félétou M. , Bonnardel E. , Canet E. 
Published: July 2012

The objective of this study in the hamster cheek pouch was to investigate the role of nitric oxide in bradykinin‐induced microvascular leakage. The cheek pouch microcirculatory bed of the anaesthetized hamster was directly observed under microscope and vascular leakage was evidenced by dextran‐fluorescein isothiocyanate (FITC‐dextran) extravasation.
Bradykinin superfusion (but not [des‐Arg9]‐bradykinin up to 3 × 10−6 m) induced an increase in microvascular permeability (log EC50: −6.5 ± 0.4) which was exclusively located on the post‐capillary venule. Plasma extravasation was blocked by intravenous pretreatment with Hoe 140, a bradykinin B2 receptor antagonist (estimated log ID50: −9.5 ± 0.2).
The effects of bradykinin (3 × 10−7 m) superfusion were partially but significantly inhibited by indomethacin (10−5 m, P < 0.05) and abolished by pretreatment with L‐nitro‐arginine (L‐NOARG; 10−5 m).
Acetylcholine (10−6 m, which releases endothelial nitric oxide (NO)) and sodium nitroprusside (10−6 m, a nitrovasodilator) superfusion did not induce any changes in permeability, per se. Cromakalim (10−5 m, a potassium channel opener) superfusion induced a moderate but significant plasma extravasation.
The effects of bradykinin, blocked by L‐NOARG pretreatment, were restored by the co‐perfusion of either sodium nitroprusside or cromakalim. Conversely vasoconstriction, produced by a stable analogue of thromboxane A2 (U46619, 3 × 10−7 m), inhibited the increase in permeability produced by bradykinin.
The measurement of arteriolar diameter showed that bradykinin induced a vasodilatation which was blocked by L‐NOARG. L‐NOARG in itself was a powerful vasoconstrictor. Sodium nitroprusside and cromakalim, in the presence of L‐NOARG, were able to restore the inhibited vasodilator response to bradykinin.
These results suggest: (1) bradykinin‐induced microvascular leakage is mediated by bradykinin B2 receptor activation; (2) the increase in permeability is due to two different independent phenomena, i.e. post‐capillary venular endothelial gap formation and arteriolar vasodilatation which increases the post‐capillary venular transmural pressure; (3) NO is only involved in the arteriolar dilatation component of the bradykinin‐induced increase in microvascular permeability.
α1a‐Adrenoceptor polymorphism: pharmacological characterization and association with benign prostatic hypertrophy
Authors: Shibata Katsushi , Hirasawa Akira , Moriyama Nobuo , Kawabe Kazuki , Ogawa Satoshi , Tsujimoto Gozoh 
Published: July 2012

Two restriction fragment length polymorphisms of the human α1a‐adrenoceptor gene digested with PstI restriction enzyme exist; the nucleotide change causes the substitution of C residue for T at nucleotide 1441, thereby Arg492 to Cys492 transition, which might confer an additional putative palmitoylation site in the carboxy‐terminal segment of the α1a‐adrenoceptor. In the present study, we compared their pharmacological properties and examined whether this α1a‐adrenoceptor polymorphism is associated with benign prostatic hypertrophy (BPH).
The frequency of α1a‐adrenoceptor polymorphism was not differently distributed between patients with benign prostatic hypertrophy (BPH) and normal subjects in Japan; thus, the relative frequencies of the C and T alleles were 0.90: 0.10 in normal male subjects (n = 45) and 0.87: 0.13 in BPH patients (n = 222), respectively. However, the frequency distribution of this polymorphism was significantly different between the Japanese and U.S. populations; thus, C and T alleles were 0.34 and 0.66 in U.S. populations.
Utilizing Chinese hamster ovary (CHO) cells stably expressing the two polymorphic α1a‐adrenoceptors (Arg492 and Cys492), we compared their binding affinity and signal transduction. Radioligand binding studies with 2‐[β‐(4‐hydroxy‐3[125I]‐iodophenyl) ethylamino‐methyl]tetralone ([125I]‐HEAT) showed no marked difference in the antagonist or agonist binding affinities between the two receptors. Also, both receptors were found to be coupled to the calcium signaling, and the concentration‐cytosolic Ca2+ concentrations ([Ca2+]i response relationships for noradrenaline were similar for the two polymorphic receptors. Furthermore, the receptor‐mediated [Ca2+]i response was markedly desensitized after a 2 h exposure of phenylephrine (10 μm), and the extent of the desensitization was not significantly different between the two receptors.
In summary, the results showed that the two α1a‐adrenoceptors generated by genetic polymorphism have similar pharmacological characteristics, and the receptor‐mediated [Ca2+]i response can be desensitized in a similar manner. The study did not provide any evidence to support the hypothesis that α1a‐adrenoceptor gene polymorphism is associated with BPH.
P2‐purinoceptor‐mediated formation of inositol phosphates and intracellular Ca2+ transients in human coronary artery smooth muscle cells
Authors: Strøbæk Dorte , Olesen Søren‐Peter , Christophersen Palle , Dissing Steen 
Published: July 2012

. The effects of extracellular adenosine 5′‐triphosphate (ATP) on smooth muscles are mediated by a variety of purinoceptors. In this study we addressed the identity of the purinoceptors on smooth muscle cells (SMC) cultured from human large coronary arteries. Purinoceptor‐mediated increases in [Ca2+]i were measured in single fura‐2 loaded cells by applying a digital imaging technique, and the formation of inositol phosphate compounds was quantified after separation on an anion exchange column.
. Stimulation of the human coronary artery SMC (HCASMC) with extracellular ATP at concentrations of 0.1–100 μ induced a transient increase in [Ca2+]i from a resting level of 49 ± 21 nM to a maximum of 436 ± 19 nM. The effect was dose‐dependent with an EC50 value for ATP of 2.2 μm.
. The rise in [Ca2+]i was independent of the presence of external Ca2+, but was abolished after depletion of intracellular stores by incubation with 100 nM thapsigargin.
. [Ca2+]i was measured upon stimulation of the cells with 0.1–100 μm of the more specific P2‐purinoceptor agonists α,β‐methyleneadenosine 5′‐triphosphate (α,β‐MeATP), 2‐methylthioadenosine 5′‐triphosphate (2MeSATP) and uridine 5′‐triphosphate (UTP). α,β‐MeATP was without effect, whereas 2MeSATP and UTP induced release of Ca2+ from internal stores with 2MeSATP being the most potent agonist (EC50 = 0.17 μ), and UTP having a potency similar to ATP. The P1 purinoceptor agonist adenosine (100 μm) did not induce any changes in [Ca2+]i.
. Stimulation with a submaximal concentration of UTP (10 μm) abolished a subsequent ATP‐induced increase in [Ca2+]i, whereas an increase was induced by ATP after stimulation with 10 μm 2MeSATP.
. The phospholipase C (PLC) inhibitor U73122 (5 μm) abolished the purinoceptor‐activated rise in [Ca2+]i, whereas pretreatment with the Gi protein inhibitor pertussis toxin (PTX, 500 ng ml−1) was without effect on ATP‐evoked [Ca2+]i increases.
. Receptor activation with UTP and ATP resulted in formation of inositol phosphates with peak levels of inositol 1,4,5‐trisphosphate (Ins(1,4,5)P3) observed 5–20 s after stimulation.
. These findings show, that cultured HCASMC express G protein‐coupled purinoceptors, which upon stimulation activate PLC to induce enhanced Ins(1,4,5)P3 production causing release of Ca2+ from internal stores. Since a release of Ca2+ was induced by 2MeSATP as well as by UTP, the data indicate that P2Y‐ as well as P2U‐purinoceptors are expressed by the HCASMC.
Influence of dopamine as noradrenaline precursor on the secretory function of the bovine corpus luteum in vitro
Authors: Kotwica J. , Skarzynski D. , Bogacki M. , Miszkiel G. 
Published: July 2012

. Dopamine is assumed to affect the ovary function after its conversion into noradrenaline (NA).
. To study this bovine luteal slices from 11–14 days of the oestrous cycle were preincubated for 24 h to recover β‐receptors and next they were incubated for 1, 2 or 4 h with (a) different doses of dopamine; (b) dopamine together with a β‐antagonist (propranolol) or with a dopamine receptor blocker (droperidol); (c) dopamine with a dopamine‐β‐hydroxylase inhibitor.
. Dopamine stimulated the luteal content of oxytocin (OT) and progesterone. This effect was inhibited by propanolol but not by droperidol.
. Dopamine added to the medium was followed by an increase of noradrenaline there. This rise was dose and time‐dependent.
. The dopamine‐β‐hydroxylase inhibitor, inhibited the stimulating effect of dopamine on luteal progesterone and OT content.
. Bovine corpus luteum can synthesize de novo NA from dopamine as a precursor.
Carbon monoxide‐induced relaxation of the ductus arteriosus in the lamb: evidence against the prime role of guanylyl cyclase
Authors: Coceani F. , Kelsey L. , Seidlitz E. 
Published: July 2012

. We have previously found that carbon monoxide (CO) potently relaxes the lamb ductus arteriosus and have ascribed this response to inhibition of a cytochrome P450‐based mono‐oxygenase reaction which sustains contractile tone. Our proposal, however, has been questioned on the evidence of findings in other blood vessels implicating the guanylyl cyclase‐based relaxing mechanism as the target for CO. To investigate this issue further, we have carried out experiments in the isolated ductus from near‐term foetal lambs and have examined the effect of CO concomitantly on muscle tone and cyclic GMP content, both in the absence and presence of guanylyl cyclase inhibitors, or during exposure to monochromatic light at 450 nm.
. CO (65 μm) reversed completely, or nearly completely, the tone developed by the vessel in the presence of oxygen (30%) and indomethacin (2.8 μm). Cyclic GMP content tended to increase with the relaxation, but the change did not reach significance. Sodium nitroprusside (SNP), a NO donor, mimicked CO in relaxing the ductus. Contrary to CO, however, SNP caused a marked accumulation of cyclic GMP with levels being positively correlated with the relaxation.
. Methylene blue (10 μm) reduced marginally the CO relaxation, whilst LY‐83583 (10 μm) had an obvious, albeit variable, inhibitory effect. Basal cyclic GMP content was lower in tissues treated with either compound and rose upon exposure to CO. However, the levels attained were still within the range of values for tissues prior to any treatment. Furthermore, the elevation in cyclic GMP was not related to the magnitude of the CO relaxation.
. Illumination of the ductus with monochromatic light at 450 nm reversed the CO relaxation and any concomitant increase in cyclic GMP. In the absence of CO, light by itself had no effect.
. Ductal preparations with only muscle behaved as the intact preparations in reacting to CO, both in the absence and presence of guanylyl cyclase inhibitors, or during illumination.
. We conclude that the primary action of CO in the ductus arteriosus is not exerted on the guanylyl cyclase heme and that cyclic GMP may only have an accessory role in the relaxation to this agent. This finding reasserts the importance of a cytochrom P450‐based mono‐oxygenase reaction for generation of tone and as a target for CO in the ductus.
Modulation of the hepatic α1‐adrenoceptor responsiveness by colchicine: dissociation of free cytosolic Ca2+‐dependent and independent responses
Authors: Butta Nora , Martin‐Requero Angeles , Urcelay Elena , Parrilla Roberto , Ayuso Matilde S. 
Published: July 2012

. The cytoskeletal depolymerizing agent, colchicine, prevents the hepatic α1‐adrenoceptor‐mediated stimulation of respiration, H+ and Ca2+ release to the effluent perfusate, intracellular alkalosis, and glycogenolysis. Unlike the other parameters, colchicine does not perturb the α1‐agonist‐induced stimulation of gluconeogenesis or phosphorylase ‘a’ activation, and enhances the increase in portal pressure response. The lack of effect of colchicine on the hepatic α2‐adrenoceptor‐mediated effects indicates that its actions are α1‐specific.
. Colchicine enhances the acute α1‐adrenoceptor‐mediated intracellular Ca2+ mobilization and prevents the activation of protein kinase C. This differential effect on the two branches of the α1‐adrenoceptor signalling pathway is a distinctive feature of the colchicine action.
. The lack of effect of colchicine in altering the α1‐adrenoceptor ligand binding affinity suggests that it might interact with some receptor‐coupled regulatory element(s).
. The acuteness of the colchicine effect and the ability of its isomer β‐lumicolchicine to prevent all the α1‐adrenoceptor‐mediated responses but the increase in vascular resistance, indicate that its action cannot be merely ascribed to its effects in depolymerizing tubulin.
. Colchicine perturbs the hepatic responses to vasoactive peptides. It enhances the vasopressin‐induced rise of cytosolic free Ca2+ in isolated hepatocytes and prevents the sustained decrease of Ca2+ in the effluent perfusate. It also inhibits the stimulation of glycogenolysis, without altering the stimulation of gluconeogenesis.
. It is concluded that there are at least two major α1‐adrenoceptor signalling pathways. One is colchicine‐sensitive, independent of variations in free cytosolic Ca2+, and protein kinase C‐independent; the other one is colchicine‐insensitive, dependent on variations in free cytosolic Ca2+, and protein kinase C‐independent.
Differential presynaptic modulation of noradrenaline release in human atrial tissue in normoxia and anoxia
Authors: Münch Götz , Kurz Thomas , Urlbauer Thomas , Seyfarth Melchior , Richardt Gert 
Published: July 2012

. Presynaptic modulation of noradrenaline release in human atrial tissue specimens was investigated under normoxic and anoxic conditions.
. Noradrenaline release was induced by electrical stimulation and release during experimental intervention (S2) was compared with release during a preceding control stimulation (S1). The results were expressed as the geometric means and 95% confidence intervals of the S2/S1 ratio.
. The α2‐adrenoceptor agonist, UK 14304 (0.1 μmol 1−1) significantly inhibited noradrenaline release, resulting in a S2/S1 ratio of 0.49 (0.40‐0.59), and the α2‐adrenoceptor antagonist, yohimbine (1 μmol 1−1) increased noradrenaline release (S2/S1 1.83 [1.43‐2.35]) during normoxia. Both compounds were ineffective during anoxia.
. Adenosine (30 μmol 1−1) inhibited noradrenaline release with a S2/S1 ratio of 0.54 (0.42‐0.66). The adenosine antagonist, 8‐phenyltheophylline, alone had no effect during normoxia. During anoxia, neither adenosine nor 8‐phenyltheophylline altered noradrenaline release.
. The β2‐adrenoceptor agonist, terbutaline (1 μmol 1−1) increased (1.53 [1.14‐2.01]) and the β‐adrenoceptor antagonist, pindolol (1 μmol 1−1) suppressed noradrenaline release (0.62 [0.49‐0.79]) under normoxic conditions. During anoxia, pindolol significantly inhibited noradrenaline release with a S2/S1 ratio of 0.66 (0.51‐0.85), whereas terbutaline did not influence noradrenaline release.
. Angiotensin II (0.1 μmol 1−1) enhanced noradrenaline release resulting in a S2/S1 ratio of 1.44 (1.34‐1.54), while the angiotensin II antagonist, losartan (1 μmol 1−1) had no effect on noradrenaline release during normoxia. Conversely, angiotensin II did not increase noradrenaline release and losartan significantly inhibited noradrenaline release to a S2/S1 ratio of 0.60 (0.46‐0.77) during anoxia.
. In conclusion, human cardiac tissue possesses presynaptic inhibitory α2‐adrenoceptors and adenosine receptors, as well as facilitatory β2‐adrenoceptors and angiotensin II receptors regulating noradrenaline release under normoxic conditions. During anoxia the responses to α2‐adrenoceptors and adenosine receptor stimulation are lost, whereas facilitatory responses to β2‐adrenoceptors and angiotensin II receptor stimulation are maintained and these receptors appear to be maximally stimulated. This differential presynaptic modulation in anoxia may contribute to enhanced sympathetic activity in ischaemia.
Differences in hypolipidaemic effects of two statins on Hep G2 cells or human hepatocytes in primary culture
Authors: Clerc Thierry , Sbarra Véronique , Domingo Nicole , Rault Jean Philippe , Diaconescu Nicolas , Moutardier Vincent , Hasselot Nicole , Lafont Huguette , Jadot Guy , Laruelle Claude , Chanussot Françoise 
Published: July 2012

. The objective of this study was to compare in cultured human hepatocytes or Hep G2 cells, changes in the fate of unesterified low density lipoprotein (LDL)‐cholesterol induced by crilvastatin, a new cholesterol lowering drug and a reference statin, simvastatin.
. The experiments were carried out for 20 h, each well contained 4.2 × 105/cm2 Hep G2 cells or 0.5 × 105/cm2 human hepatocytes, 130 μm ursodeoxycholate, 0.68 μCi or 1.59 μCi unesterified human [14C]‐LDL‐cholesterol, crilvastatin or simvastatin at 0 or 50 μm (both cell types) or 300 μm (Hep‐G2 cells). Incubation with the two drugs resulted in increased amounts of unesterified [14C]‐LDL‐cholesterol taken by the two cell types, compared to control.
. Crilvastatin 50 μm led to significantly higher quantities of [14C]‐glyco‐ and [14C]‐tauro‐conjugated bile salts, compared to simvastatin. Statins reduced the apo B100 level secreted by the two cell types (simvastatin) or human hepatocytes (crilvastatin). Crilvastatin enhanced both the level of apo A1 secreted by the Hep G2 cells and the level of APF, a high density lipoprotein (HDL) and biliary apoprotein.
. Crilvastatin not only acts by stimulating LDL‐cholesterol uptake by hepatocytes, but also by enhancing the catabolism of LDL‐cholesterol in bile salts and probably by stimulating HDL and/or bile component secretion. Such a mechanism was not previously described for HMG CoA reductase inhibitors. Our results on APF show that this apoprotein could be considered also as an indicator of changes in bile and/or HDL compartments.
. The human hepatocyte model appeared to be a suitable and relevant model in the pharmacological***metabolic experiments carried out in this study. It led to more consistent data than those obtained with Hep G2 cells.
The role of TNF‐α in fever: opposing actions of human and murine TNF‐α and interactions with IL‐β in the rat
Authors: Stefferl Andreas , Hopkins Stephen J. , Rothwell Nancy J. , Luheshi Giamal N. 
Published: July 2012

The role of tumour necrosis factor‐α (TNF‐α) in fever is controversial. Some studies have indicated that TNF‐α acts as a cryogen to inhibit fever, while others suggest that TNF‐α is an endogenous pyrogen which mediates fever. The majority of studies in experimental animals supporting a cryogenic action have been conducted using human (h)TNF‐α, which has been shown to bind only to one (p55) of the two TNF‐α receptors in rodents.
The aim of the present investigation was to study the role of TNF‐α in fever by comparing effects of hTNF‐α, which binds only to the p55 receptor, with those of murine (m)TNF‐α, which binds to both p55 and p75 TNF‐α receptors, and to investigate the relationship between TNF‐α and interleukin‐1 (IL‐1), an important endogenous pyrogen.
Injection of hTNF‐α (0.3–10 μg kg−1, i.p.) had no effect on core temperature in conscious rats (measured by remote radiotelemetry), whereas mTNF‐α (3 μg kg−1) induced fever which was maximal 1 h after the injection (38.2 ± 0.2°C compared to 37.3 ± 0.1°C in controls). Intracerebroventricular (i.c.v.) administration of either form of TNF‐α elicited dose‐dependent fever at doses higher than 0.12 μg kg−1.
Peripheral injection of hIL‐1β (1 μg kg−1) resulted in fever (38.3 ± 0.2°C compared to 37.2 ± 0.1°C in controls at 2 h), which was significantly attenuated (P < 0.01) by co‐administration of a sub‐pyrogenic dose of hTNF‐α (1 μg kg−1), but was unaffected by co‐administration of mTNF‐α (0.1 or 0.3 μg kg−1, i.p.). In contrast, intracerebroventricular (i.c.v.) co‐administration of a sub‐pyrogenic dose (0.12 μg kg−1) of hTNF‐α did not attenuate fever induced by intraperitoneal (i.p.) injection of IL‐1β, and sub‐pyrogenic dose (0.12 μg kg−1, i.c.v.) of mTNF‐α significantly prolonged the febrile response to IL‐1β. Pretreatment of animals with anti‐TNF‐α antiserum (i.c.v.) did not affect the febrile response to systemic IL‐1β.
Animals injected i.p. with a pyrogenic dose of mTNF‐α developed fever (38.2 ± 0.2°C compared to 37.3 ± 0.1°C in controls 2 h after the injection) that was completely abolished by peripheral administration of IL‐***1ra (2 mg kg−1, P < 0.001), while i.c.v. administration of IL‐***1ra (400 μg/rat) did not affect mTNF‐α‐induced fever.
These data indicate that endogenous TNF‐α is probably a pyrogen and that previous results suggesting cryogenic actions of TNF‐α resulted from the use of a heterologous protein in the rat. The markedly contrasting effects of mTNF‐α and hTNF‐α could result from different interactions with the two TNF‐α receptor subtypes. The data also suggest that fever induced by exogenous TNF‐α is mediated via release of IL‐1β in peripheral tissues, but not in the brain.