bluuebunny/crossref_metadata_2025 huggingface dataset:
Diamagnetic and nonlinear Zeeman shifts in spatially separated electron and hole layers of semiconductor heterostructures with disorder
Authors: Desforges J. , Singh M. R.
Published: May 2003

The effect of the diamagnetic shift on the formation of excitons is investigated for double layer semiconductor systems in which electrons and holes are spatially separated. The effect of disorder due to interface roughness of the double layer structures is included in the calculation of exciton density. Numerical calculations are performed based on an effective lattice‐gas model where the electron–hole system is divided into unit cells. The exciton density is calculated by using the partition function method. The effect of the nonlinear Zeeman splitting is also included in the numerical calculations. It is found that the density of the optically allowed exciton states (excitons with Sz = 0) increases under the influence of either or both the diamagnetic and the nonlinear Zeeman shifts.
High‐pressure phase transitions in semimagnetic semiconductor I: Pb1–xMnxS
Authors: Srivastava Anurag , Singh R. K. , Ahuja R. , Johansson B.
Published: May 2003

Pressure‐induced structural phase transitions in Pb1–xMnxS (0 < x < 0.05), from the rocksalt (B1) to the CsCl (B2) type phase, have been calculated. The present study of the phase transition is based on the three‐body potential (TBP) approach, which includes long‐range as well as short‐range interactions. The long‐range part consists of a Coulomb and three‐body interactions, whereas the short‐range part includes the van der Waals and overlap repulsive interactions. In order to strengthen the significance of our results and verify the presence of intermediate orthorhombic phase during B1 to B2 structural transition in the host binary compound PbS we performed first principles full potential linear muffin tin orbital approach and provided a good support to our TBP results. Our first‐principles calculations, based on the full potential muffin tin orbital (FPLMTO) method, successfully predicts the TlI type phase and supports the TBP results.
Optical properties and concentration dependence of the luminescence of Pr3+ion in fluoroindate glass
Authors: Mazurak Z. , Pisarski W. A. , Gabryś‐Pisarska J. , Żelechower M.
Published: May 2003

Optical absorption and emission spectra are presented for Pr3+and Pr3++ Cr3+ions in fluoroindate glass. Also, X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) measurements are carried out in order to characterize investigated materials. The measured oscillator strengths and radiative rates for several transitions of the Pr3+ion are compared with calculated values. Radiative transition rates for the excited states are determined by using the Judd–Ofelt theory. Energy transfer effects account for the non‐radiative transitions. Although the Judd–Ofelt analysis does not yield the same excellent consistency for Pr3+as for Nd3+and Er3+, the experimental observations are consistent with Judd–Ofelt calculations. The linear concentration quenching and exponential decay times of the1D2level are explained assuming cross‐relaxation and energy transfer between the Pr3+ions. Energy level diagrams of Cr3+and Pr3+reveal that the1G4level of Pr3+lies close in energy to the4T2fluorescent level of Cr3+, and hence will expect a portion of excitation energy from Cr3+. Unfortunately, the mismatch in energy of this Pr3+level with the4T2level of Cr3+(∼3000 cm–1) cannot be compensated for by the phonons of the host, having an energy of about 500 cm–1.
Splitting of X‐ray photoelectron spectra in incommensurate ferroelectric TlInS2 crystals
Authors: Grigas J. , Talik E.
Published: May 2003

This paper presents the first observation of the resolved splitting of X‐ray photoelectron spectra (XPS) in the incommensurate phase of the ferroelectric semiconductor TlInS2 single crystal. The XPS were measured with monochromatised Al Kα radiation in the energy range 0–1400 eV and the temperature range 195–300 K. At room temperature, the valence band is located 1–9 eV below the Fermi level. The chemical shifts in the TlInS2 crystal for the Tl, In and S states are obtained. The mechanism of the XPS splitting in the incommensurate phase is discussed.
The semimetallic S = 1/2 antiferromagnetic chain Yb4As3: quantum transfer‐matrix simulations and experimental field‐dependent specific‐heat data
Authors: Matysiak R. , Kamieniarz G. , Gegenwart P. , Aoki H. , Ochiai A. , Steglich F.
Published: May 2003

The S=1/2 antiferromagnetic Heisenberg model with the Dzyaloshinsky–Moriya interaction is applied to Yb4As3. In this paper we calculate the specific heat of this model, mapped onto the isotropic Heisenberg model with both uniform field Bx and staggered field Bys, by the numerical quantum transfer‐matrix (QTM) method and we present new experimental results for the polydomain sample in the applied field.
Elastic relaxation of a truncated circular cylinder with uniform dilatational eigenstrain in a half space
Authors: Glas Frank
Published: May 2003

We give a fully analytical solution for the displacement and strain fields generated by the coherent elastic relaxation of a type of misfitting inclusions with uniform dilatational eigenstrain lying in a half space, assuming linear isotropic elasticity. The inclusion considered is an infinitely long circular cylinder having an axis parallel to the free surface and truncated by two arbitrarily positioned planes parallel to this surface. These calculations apply in particular to strained semiconductor quantum wires. The calculations are illustrated by examples showing quantitatively that, depending on the depth of the wire under the free surface, the latter may significantly affect the magnitude and the distribution of the various strain components inside the inclusion as well as in the surrounding matrix.
Elastic relaxation of a truncated circular cylinder with uniform dilatational eigenstrain in a half space
Authors: Glas Frank
Published: May 2003

Our Editor's Choice [1] presents results of analytical calculations of the displacement and strain field induced by a linear inclusion such as a strained semiconductor quantum wire in an isotropically elastic half‐space solid. The cover picture shows the total dilatation distribution in the plane perpendicular to a crescent‐shape wire which is parallel to the free surface, marked by the straight red line, and, as thick curved red lines, the sections of the two truncated cylinders used to generate the wire.

Frank Glas is currently in charge of the research group ‘Elaboration and Physics of Epitaxial Structures’ at the Laboratoire de Photonique et de Nanostructures, CNRS Marcoussis. His activities include experimental and theoretical studies of the structural, elastic and thermodynamical properties of III–V semiconductor alloys and epitaxial structures, analytical elasticity calculations as well as electron microscopy and microanalysis.
In vitro DNA‐binding properties of VirB, the Shigella flexneri virulence regulatory protein
Authors: McKenna Sorcha , Beloin Christophe , Dorman Charles J.
Published: May 2003

The DNA‐binding activity of the Shigella flexneri VirB transcription factor was studied in vitro. The protein was found to bind non‐specifically to DNA, but showed preferential binding to VirB‐dependent promoter sequences. DNA binding was contingent on the presence of an intact helix‐turn‐helix motif. While high molecular mass protein–DNA complexes were formed in both specific and non‐specific interactions with DNA, mutant derivatives of VirB lacking a leucine zipper domain or a carboxyl‐terminal‐located oligomerisation domain formed discrete complexes, indicating that an ability to oligomerise on DNA was responsible for the formation of high molecular mass complexes by the wild‐type protein.
Mitochondria‐derived glutamate at the interplay between branched‐chain amino acid and glucose‐induced insulin secretion
Authors: Broca Christophe , Brennan Lorraine , Petit Pierre , Newsholme Philip , Maechler Pierre
Published: May 2003

In pancreatic β‐cells, glutamate has been proposed to mediate insulin secretion as a glucose‐derived factor, although it is also considered for its sole catabolic function. Hence, changes in cellular glutamate levels are a matter of debate. Here, we investigated the effects of glucose and the glutamate precursor glutamine on kinetics of glutamate levels together with insulin secretion in INS‐1E β‐cells. Preincubation at low (1 mM) glucose resulted in reduced cellular glutamate levels, which were doubled by exposure to glutamine. In glutamine‐deprived cells, 5 mM glucose restored glutamate concentrations. Incubation at 15 mM glucose increased cellular glutamate, along with stimulation of insulin secretion, following both glutamine‐free and glutamine‐rich preincubations. Nuclear magnetic resonance (NMR) spectroscopy of INS‐1E cells exposed to 15 mM D‐[1‐13C]glucose revealed glutamate as the major glucose metabolic product. Branched‐chain amino acids, such as leucine, reduced cellular glutamate levels at low and intermediate glucose. This study demonstrates that glucose stimulates glutamate generation, whereas branched‐chain amino acids promote competitive glutamate expenditure.
Duration of ruptured membranes and extended labor are risk factors for HIV transmission
Authors: Garcia‐Tejedor A. , Perales A. , Maiques V.
Published: May 2003

Objectives: To determine the effects of duration of ruptured membranes (DRM) and duration of labor in HIV transmission. Methods: A retrospective cohort study of 366 HIV‐infected pregnant women and their infants analyzed the effects of these two variables; the cut‐off point for transmission increase was estimated using a ROC curve. A multivariate analysis was performed with the most important risk factors according to the literature: maternal age, lymphocyte count, use of invasive procedures during gestation, antiretroviral treatment during pregnancy and labor, mode of delivery, newborn weight, DRM, labor duration, and the interaction of these last two factors. Results: The cut‐off points were estimated at 6 h for DRM and at 5 h for labor duration. A lymphocyte count below 500 cells/ml, use of invasive procedures, use of antiretroviral treatment during pregnancy and interaction between DRM, and labor duration remained significant in perinatal HIV transmission (P<0.05). Conclusions: An increased DRM increased perinatal HIV transmission when it was associated with prolonged labor.
Hemodynamic and metabolic effects after nifedipine and ritodrine tocolysis
Authors: Papatsonis D.N.M. , van Geijn H.P. , Bleker O.P. , Adèr H.J. , Dekker G.A.
Published: May 2003

Objectives: The purpose of this study is to compare the hemodynamic and metabolic changes after ritodrine and nifedipine tocolysis. Methods: For an open randomized study, patients with preterm labor (N=185) were allocated to groups to receive ritodrine intravenously (N=90) or nifedipine orally (N=95). Results: The mean diastolic blood pressure was significantly lower in the ritodrine group 24 h (65±12 vs. 70±8, P=0.001) and 48 h (65±12 vs. 71±8, P=0.004) after starting tocolysis compared with the nifedipine group. Mean maternal heart rate was significantly higher in the ritodrine group 24 h (105±17 vs. 86±13, P<0.0001) and 48 h (100±21 vs. 85±12, P<0.0001) after starting tocolysis compared with the nifedipine group. Mean fasting glucose levels were higher (6.68±2.53 vs. 4.93±1.23, P=0.0016), while mean potassium levels were lower (3.52±0.84 vs. 3.81±0.45, P=0.04) in the ritodrine group 48 h after starting tocolysis compared with the nifedipine group. Conclusions: Use of nifedipine for preterm labor is associated with a lower incidence of adverse hemodynamic and metabolic changes compared with ritodrine after 24 and 48 h of tocolysis. In our opinion nifedipine is the preferred drug of choice for the treatment of preterm labor.
Eukaryotic release factors (eRFs) history
Authors: Inge‐Vechtomov Sergei , Zhouravleva Galina , Philippe Michel
Published: May 2003

In the present review, we describe the history of the identification of the eukaryotic translation termination factors eRF1 and eRF3. As in the case of several proteins involved in general and essential processes in all cells (e.g., DNA replication, gene expression regulation…) the strategies and methodologies used to identify these release factors were first established in prokaryotes. The genetic investigations in Saccharomyces cerevisiae have made a major contribution in the field. A large amount of data have been produced, from which it was concluded that the SUP45 and SUP35 genes were controlling translation termination but were also involved in other functions important for the cell organization and the cell cycle accomplishment. This does not seem to be restricted to yeast but is also probably the case in eukaryotes in general. The biochemical studies of the proteins encoded by the higher eukaryote homologs of SUP45 and SUP35 were efficient and permitted the identification of eRF1 as being the key protein in the termination process, eRF3 having a stimulating role. Around 25 years were needed after the identification of sup45 and sup35 mutants for the characterization of their gene products as eRF1 and eRF3, respectively. It also has to be pointed out that if the results came first from bacteria, the identification of RF3 and eRF3 was made practically at the same time. Moreover, eRF1 was the first crystal structure obtained for a class‐1 release factor, the bacterial RF2 structure came later. The goal is now to understand at the molecular level the roles of both eRF1 and eRF3 in addition to their translation termination functions.
Placental Tissue Interleukin‐10 Receptor Distribution in Pre‐eclampsia
Authors: Hennessy A. , Painter D. M. , Orange S. , Horvath J. S.
Published: May 2003

PROBLEM: Reduced placental (trophoblast) cytokine interleukin‐10 (IL‐10) occurs in human pre‐eclampsia. Along with an increase in inflammatory cytokines this may play an important role in the development of hypertension in pregnancy. It is not clear whether the changes in placental IL‐10 are due to a change in the placental cell production of IL‐10 or a result of changes in cytokine receptor status in adjacent tissues. This study is aimed at qualifying the presence and distribution of IL‐10 receptors in women with a pre‐eclamptic outcome compared to normal pregnancy and gestational hypertension.

METHOD OF STUDY: Patients at the KGV Hospital, Sydney was selected for the study. Placentas were collected fresh and paraffin serial sections made. Sections were stained with IL‐10 receptor antibody (10 μg/mL) using avidin–biotin immunohistochemistry. Tissues of patients with pre‐eclampsia (n = 11) were compared with normal pregnancy (n = 12). Pre‐eclampsia was defined as a blood pressure >140/90 mmHg on two occasions and de novo proteinuria > 300 mg per day which resolved post‐partum. The fetal weights, gestational ages and maternal ages at delivery were compared (ANOVA) and the differences in staining of decidual and villous tissues were graded according to density. Statistical comparisons were made using the Kruskal–Wallis test.

RESULTS: The groups were similar for maternal gestational age but delivered at earlier gestation and with lower fetal weight. There was significantly less villous cytotrophoblast staining for IL‐10 receptor in all groups (P = 0.012) compared to decidual trophoblast cells. There was equal intensity and density of extravillous staining observed in normal pregnancy (45 ± 12%) positive cells compared to pre‐eclampsia (27 ± 12%).

CONCLUSION: IL‐10 receptors are present in greater concentration in the extravillous (decidual) trophoblast compared to villi. The decrease in IL‐10 produced by trophoblast cells in pre‐eclampsia is not explained by a difference in the IL‐10 receptor distribution compared to normal pregnancy.
Thymidine phosphorylase induces angiogenesis in vivo and in vitro: an evaluation of possible mechanisms
Authors: Sengupta Shiladitya , Sellers Lynda A , Matheson Hugh B , Fan Tai‐Ping D
Published: May 2003

Thymidine phosphorylase (TP) is elevated in the plasma of cancer patients, and has been implicated in pathophysiological angiogenesis. However, the downstream signals underlying this implication remain obscure. The purpose of the present study was to examine the effects of TP on the neovascularisation response in vitro and in vivo.

Both TP and its catalytic product, 2‐deoxy‐D‐ribose‐1‐phosphate, and downstream 2‐deoxy‐D‐ribose (2‐DDR) promoted endothelial tubulogenesis in vitro, and the regeneration of a wounded monolayer of endothelial cells without exerting any mitogenic effect. In vivo, both TP and 2‐DDR promoted the development of functional vasculature into an avascular sponge. A TP inhibitor, 6‐amino‐5‐chlorouracil, was able to partially reverse the effects of TP, but had no effect on the 2‐DDR‐induced angiogenesis.

Enhanced monolayer regeneration was observed with TP‐cDNA‐transfected bladder carcinoma cells. The transfection of TP‐cDNA, however, did not confer any proliferative advantage. The regeneration of TP overexpressing cells was associated with a time‐dependent expression of the enzyme haeme‐oxygenase (HO‐1).

The present study demonstrates that both TP and its ribose‐sugar metabolites induce angiogenesis by mediating a cohesive interplay between carcinoma and endothelial cells. The induction of HO‐1 in TP‐transfected cells suggests that it could be a possible downstream signal for the angiogenic effects of TP. Furthermore, reducing sugars have been shown to induce oxidative stress, and ribose could be a possible cause for the upregulation of HO‐1, which has been implicated in the release of angiogenic factors. Therefore, we postulate that 2‐DDR could be mediating the angiogenic effects of TP possibly through an oxidative stress mechanism and additionally getting integrated in the endothelial metabolic machinery.

British Journal of Pharmacology (2003) 139, 219–231. doi:10.1038/sj.bjp.0705216
Binding and effect of KATP channel openers in the absence of Mg2+
Authors: Russ Ulrich , Lange Ulf , Löffler‐Walz Cornelia , Hambrock Annette , Quast Ulrich
Published: May 2003

Openers of ATP‐sensitive K+ channels (KATP channels) are thought to act by enhancing the ATPase activity of sulphonylurea receptors (SURs), the regulatory channel subunits. At higher concentrations, some openers activate KATP channels also in the absence of MgATP. Here, we describe binding and effect of structurally diverse openers in the absence of Mg2+ and presence of EDTA.

Binding of openers to SUR2B was measured using a mutant with high affinity for [3H]glibenclamide ([3H]GBC). In the absence of Mg2+, ‘typical' openers (benzopyrans, cyanoguanidines and aprikalim) inhibited [3H]GBC binding with Ki values ∼200 × higher than in the presence of MgATP. Minoxidil sulphate and nicorandil were inactive, whereas binding of diazoxide was unaffected by MgATP.

In the absence/presence of MgATP, N‐cyano‐N′‐(1,1‐dimethylpropyl)‐N″‐3‐pyridylguanidine (P1075) activated the Kir6.2/SUR2B channel in inside–out patches with EC50=2000/67nM and Emax=32/134%. In the absence of Mg2+, responses were variable with only a small part of the variability being explained by a decrease in channel responsiveness with time after patch excision and to differences in the ATP sensitivity between patches.

The rank order of efficacy of the openers was P1075>rilmakalim ∼nicorandil>diazoxide>minoxidil sulphate.

The data show that structurally diverse openers are able to bind to, and to activate the Kir6.2/SUR2B channel by a pathway independent of ATP hydrolysis. These effects are observed at concentrations used to define the biochemical mechanism of the openers in the presence of MgATP and allow the openers to be classified into ‘typical’ and ‘atypical’ KCOs with diazoxide standing apart.

British Journal of Pharmacology (2003) 139, 368–380. doi:10.1038/sj.bjp.0705238
Curcumin, the major component of food flavour turmeric, reduces mucosal injury in trinitrobenzene sulphonic acid‐induced colitis
Authors: Ukil A , Maity S , Karmakar S , Datta N , Vedasiromoni J R , Das Pijush K
Published: May 2003

Inflammmatory bowel disease (IBD) is characterized by oxidative and nitrosative stress, leucocyte infiltration and upregulation of proinflammatory cytokines. In this study, we have investigated the protective effects of curcumin, an anti‐inflammatory and antioxidant food derivative, on 2,4,6‐ trinitrobenzene sulphonic acid‐induced colitis in mice, a model for IBD.

Intestinal lesions (judged by macroscopic and histological score) were associated with neutrophil infiltration (measured as increase in myeloperoxidase activity in the mucosa), increased serine protease activity (may be involved in the degradation of colonic tissue) and high levels of malondialdehyde (an indicator of lipid peroxidation).

Dose–response studies revealed that pretreatment of mice with curcumin (50 mg kg−1 daily i.g. for 10 days) significantly ameliorated the appearance of diarrhoea and the disruption of colonic architecture. Higher doses (100 and 300 mg kg−1) had comparable effects.

In curcumin‐pretreated mice, there was a significant reduction in the degree of both neutrophil infiltration (measured as decrease in myeloperoxidase activity) and lipid peroxidation (measured as decrease in malondialdehyde activity) in the inflamed colon as well as decreased serine protease activity.

Curcumin also reduced the levels of nitric oxide (NO) and O2− associated with the favourable expression of Th1 and Th2 cytokines and inducible NO synthase. Consistent with these observations, nuclear factor‐κB activation in colonic mucosa was suppressed in the curcumin‐treated mice.

These findings suggest that curcumin or diferuloylmethane, a major component of the food flavour turmeric, exerts beneficial effects in experimental colitis and may, therefore, be useful in the treatment of IBD.

British Journal of Pharmacology (2003) 139, 209–218. doi:10.1038/sj.bjp.0705241
Altered prejunctional modulation of intestinal cholinergic and noradrenergic pathways by α2‐adrenoceptors in the presence of experimental colitis
Authors: Blandizzi Corrado , Fornai Matteo , Colucci Rocchina , Baschiera Fabio , Barbara Giovanni , Giorgio Roberto De , Ponti Fabrizio De , Breschi Maria Cristina , Tacca Mario Del
Published: May 2003

This study investigates the influence of intestinal inflammation on: (1) the control of intestinal neurotransmission and motility by prejunctional α2‐adrenoceptors and (2) the expression of intestinal α2‐adrenoceptors. Experimental colitis was induced by intrarectal administration of 2,4‐dinitrobenzenesulphonic acid (DNBS) to rats.

UK‐14,304 inhibited atropine‐sensitive electrically evoked contractions of ileal and colonic longitudinal muscle preparations. UK‐14,304 acted with similar potency, but higher efficacy, on tissues from DNBS‐treated animals; its effects were antagonized with greater potency by phentolamine than rauwolscine.

Electrically induced [3H]noradrenaline release from ileal preparations was reduced in the presence of colitis. Tritium outflow was decreased by UK‐14,304 and stimulated by rauwolscine or phentolamine: these effects were enhanced in preparations from animals with colitis.

Reverse transcription–polymerase chain reaction and Western blot assay demonstrated the protein expression of α2A‐adrenoceptors in mucosal and muscular tissues isolated from ileum and colon. The induction of colitis increased α2A‐adrenoceptor expression in both ileal and colonic muscular layers, without concomitant changes in mucosal tissues.

Induction of colitis reduced gastrointestinal propulsion of a charcoal suspension in vivo. In this setting, the gastrointestinal transit was inhibited by intraperitoneal (i.p.) UK‐14,304 and stimulated by i.p. rauwolscine. After pretreatment with guanethidine, the stimulant action of rauwolscine no longer occurred, and UK‐14,304 exerted a more prominent inhibitory effect that was antagonized by rauwolscine.

The present results indicate that, in the presence of intestinal inflammation, prejunctional α2‐adrenoceptors contribute to an enhanced inhibitory control of cholinergic and noradrenergic transmission both at inflamed and noninflamed distant sites. Evidence was obtained that such modulatory actions depend on an increased expression of α2A‐adrenoceptors within the enteric nervous system.

British Journal of Pharmacology (2003) 139, 309–320. doi:10.1038/sj.bjp.0705249
Mechanisms involved in the stimulation of prostacyclin synthesis by human lymphocytes in human umbilical vein endothelial cells
Authors: Merhi‐Soussi Faten , Dominguez Zury , Macovschi Olga , Dubois Madeleine , Nemoz Georges , Lagarde Michel , Prigent Annie‐France
Published: May 2003

Endothelial cells play an important role in the modulation of vascular tone because of their ability to produce vasoactive substances such as prostacyclin (PGI2). Cell–cell contact between human umbilical vein endothelial cells (HUVEC) and peripheral blood lymphocytes has been shown to stimulate endothelial PGI2 synthesis by increasing free arachidonic acid availability through endothelial cytosolic phospholipase A2 (cPLA2) activation. In this study, we sought to determine whether phospholipase C (PLC) and D (PLD) activation also contributes, besides cPLA2, to the lymphocyte‐induced PGI2 synthesis in HUVEC, and to delineate further the potential mechanisms of cPLA2 activation triggered by the interaction of HUVEC with lymphocytes.

Pretreatment of endothelial cells with the PI‐PLC inhibitor U‐73122 before the coincubation with lymphocytes markedly inhibited the PGI2 output whereas the diacylglycerol (DAG) lipase inhibitor RHC 80267 and ethanol had no effect. These results suggest that PLC may be involved through inositol trisphosphate generation and calcium mobilization, and that neither DAG nor phosphatidic acid (PtdOH) was used as sources of arachidonic acid.

The stimulated PGI2 synthesis was protein kinase C (PKC)‐independent but strongly inhibited by the mitogen‐activated protein kinase kinase (MEK) inhibitors PD98059 and U‐0126 and by the Src kinase inhibitor PP1.

Immunoblot experiments showed an increased phosphorylation of the extracellular signal‐regulated kinases 1/2 (ERK1/2) upon lymphocyte addition till 4 h coincubation. Phosphorylation was markedly inhibited by U‐0126 and PP1 addition.

Collectively, these results suggest that the signaling cascade triggered by lymphocytes in endothelial cells involves an Src kinase/ERK1/2 pathway leading to endothelial cPLA2 activation.

British Journal of Pharmacology (2003) 139, 321–328. doi:10.1038/sj.bjp.0705253
Deletion of the UT receptor gene results in the selective loss of urotensin‐II contractile activity in aortae isolated from UT receptor knockout mice
Authors: Behm David J , Harrison Stephen M , Ao Zhaohui , Maniscalco Kristeen , Pickering Susan J , Grau Evelyn V , Woods Tina N , Coatney Robert W , Doe Christopher P A , Willette Robert N , Johns Douglas G , Douglas Stephen A
Published: May 2003

Urotensin‐II (U‐II) is among the most potent mammalian vasoconstrictors identified and may play a role in the aetiology of essential hypertension. Currently, only one mouse U‐II receptor (UT) gene has been cloned. It is postulated that this protein is solely responsible for mediating U‐II‐induced vasoconstriction.

This hypothesis has been investigated in the present study, which assessed basal haemodynamics and vascular reactivity to hU‐II in wild‐type (UT(+/+)) and UT receptor knockout (UT(−/−)) mice.

Basal left ventricular end‐diastolic and end‐systolic volumes/pressures, stroke volumes, mean arterial blood pressures, heart rates, cardiac outputs and ejection fractions in UT(+/+) mice and in UT(−/−) mice were similar.

Relative to UT(+/+) mouse isolated thoracic aorta, where hU‐II was a potent spasmogen (pEC50=8.26±0.08) that evoked relatively little vasoconstriction (17±2% 60 mM KCl), vessels isolated from UT(−/−) mice did not respond to hU‐II. However, in contrast, the superior mesenteric artery isolated from both the genotypes did not contract in the presence of hU‐II. Reactivity to unrelated vasoconstrictors (phenylephrine, endothelin‐1, KCl) and endothelium‐dependent/independent vasodilator agents (carbachol, sodium nitroprusside) was similar in the aorta and superior mesenteric arteries isolated from both the genotypes.

The present study is the first to directly link hU‐II‐induced vasoconstriction with the UT receptor. Deletion of the UT receptor gene results in loss of hU‐II contractile action with no ‘nonspecific’ alterations in vascular reactivity. However, as might be predicted based on the limited contractile efficacy recorded in vitro, the contribution that hU‐II and its receptor make to basal systemic haemodynamics appears to be negligible in this species.

British Journal of Pharmacology (2003) 139, 464–472. doi:10.1038/sj.bjp.0705254
Dihydroergotamine and its metabolite, 8′‐hydroxy‐dihydroergo‐tamine, as 5‐HT1A receptor agonists in the rat brain
Authors: Hanoun N , Saurini F , Lanfumey L , Hamon M , Bourgoin S
Published: May 2003

In addition to stopping migraine attacks, dihydroergotamine (DHE) is an efficient drug for migraine prophylaxis. Whether 5‐HT1A receptors could contribute to the latter action was assessed by investigating the effects of DHE and its metabolite, 8′‐OH‐DHE, on these receptors in the rat brain.

Membrane binding assays with [3H]8‐OH‐DPAT and [3H]WAY 100635 as radioligands showed that both DHE (IC50=28–30 nM) and 8′‐OH‐DHE (IC50=8–11 nM) are high‐affinity 5‐HT1A receptor ligands.

Both DHE and 8′‐OH‐DHE enhanced the specific binding of [35S]GTP‐γ‐S to the dorsal raphe nucleus and the hippocampus in brain sections, but to a lower extent than 5‐carboxamido‐tryptamine (5‐CT) in the latter area.

Both DHE (EC50=10.9±0.3 nM) and 8′‐OH‐DHE (EC50=30.4±0.8 nM) inhibited the firing of serotoninergic neurons in the dorsal raphe nucleus within brain stem slices.

Intracellular recording showed that 8′‐OH‐DHE was more potent than DHE to hyperpolarize CA1 pyramidal cells in rat hippocampal slices.

Both the stimulatory effects of DHE and 8′‐OH‐DHE on [35S]GTP‐γ‐S binding and their electrophysiological effects were completely prevented by the selective 5‐HT1A receptor antagonist WAY 100635.

As expected of 5‐HT1A receptor partial agonists, DHE and 8′‐OH‐DHE prevented any subsequent hyperpolarization of CA1 pyramidal cells by 5‐HT or 5‐CT.

Through their actions at 5‐HT1A auto‐ (in the dorsal raphe nucleus) and hetero‐(notably in the hippocampus) receptors, DHE, and even more its metabolite 8′‐OH‐DHE, can exert both an inhibitory influence on neuronal excitability and anxiolytic effects which might contribute to their antimigraine prophylactic efficiency.

British Journal of Pharmacology (2003) 139, 424–434. doi:10.1038/sj.bjp.0705258
Cellular actions of opioids on periaqueductal grey neurons from C57B16/J mice and mutant mice lacking MOR‐1
Authors: Vaughan Christopher W , Bagley Elena E , Drew Geoffrey M , Schuller Alwin , Pintar John E , Hack Stephen P , Christie MacDonald J
Published: May 2003

Patch clamp recordings were made from periaqueductal grey (PAG) neurons in vitro to investigate the cellular actions of opioids in wild‐type C57B16/J mice and mutant mice lacking the first exon of the μ‐opioid (MOP) receptor.

In wild‐type mice, the κ‐(KOP) agonist U‐69593 (300 nM) and the mixed μ/δ‐opioid agonist met‐enkephalin (10 μM), but not the δ‐(DOP) agonist deltorphin (300 nM), reduced the amplitude of evoked GABAA‐mediated inhibitory postsynaptic currents (IPSCs). Met‐enkephalin and U‐69593 also reduced the rate of spontaneous miniature IPSCs, but had no effect on their amplitude and kinetics. In μ‐receptor‐deleted mice, only U‐69593 (300 nM) reduced the amplitude of evoked IPSCs.

In wild‐type mice, the MOP agonist DAMGO (3 μM) produced an outward current in 76% of the neurons. Deltorphin and U‐69593 produced outward currents in 24 and 32% of the neurons, respectively. In μ‐receptor‐deleted mice, deltorphin and U‐69593 produced similar outward currents in 32 and 27% of the neurons, respectively, while DAMGO was without effect. All neurons in both the wild‐type and μ‐receptor‐deleted mice responded with similar outward currents to either the GABAB receptor agonist baclofen (10 μM), or the opioid‐like receptor ORL1 (NOP) agonist nociceptin (300 nM).

The DAMGO‐, deltorphin‐, U‐69593‐, baclofen‐ and nociceptin‐induced currents displayed inward rectification and reversed polarity at −109 to −116 mV.

These findings indicate that μ‐, δ‐ and κ‐opioid receptor activation has complex pre‐ and postsynaptic actions within the mouse PAG. This differs to the rat PAG where only μ‐opioid receptor actions have been observed.

British Journal of Pharmacology (2003) 139, 362–367. doi:10.1038/sj.bjp.0705261
Receptor signaling mechanisms underlying muscarinic agonist‐evoked contraction in guinea‐pig ileal longitudinal smooth muscle
Authors: Unno T , Kwon S‐C , Okamoto H , Irie Y , Kato Y , Matsuyama H , Komori S
Published: May 2003

In guinea‐pig ileal longitudinal muscle, muscarinic partial agonists, 4‐(N‐[3‐chlorophenyl]‐carbomoyloxy)‐2‐butynyl‐trimethylammonium (McN‐A343) and pilocarpine, each produced parallel increases in tension and cytosolic Ca2+ concentration ([Ca2+]c) with a higher EC50 than that of the full agonist carbachol. The maximum response of [Ca2+]c or tension was not much different among the three agonists. The Ca2+ channel blocker nicardipine markedly inhibited the effects of all three agonists

The contractile response to any agonist was antagonized in a competitive manner by M2 receptor selective antagonists (N,N′‐bis[6‐[[(2‐methoyphenyl)methyl]amino]hexyl]‐1,8‐octanediamine tetrahydrochloride and 11‐[[2‐[(diethlamino)methyl]‐1‐piperidinyl]acetyl]‐5,11‐dihydro‐6H‐pyrido[2,3‐b][1,4] benzodiazepine‐6‐one), and the apparent order of M2 antagonist sensitivity was McN‐A343>pilocarpine>carbachol. M3 receptor selective antagonists, 1,1‐dimethyl‐4‐diphenylacetoxypiperidinium iodide and darifenacin, both severely depressed the maximum response for McN‐A343, while darifenacin had a similar action in the case of pilocarpine. Both M3 antagonists behaved in a competitive manner in the case of the carbachol response.

McN‐A343 failed to release Ca2+ from the intracellular stores, and the Ca2+‐releasing action of pilocarpine was very weak compared with that of carbachol. All three agonists were capable of increasing Ca2+ sensitivity of the contractile proteins.

McN‐A343 rarely produced membrane depolarization, but always accelerated electrical spike discharge. Pilocarpine effect was more often accompanied by membrane depolarization, as was usually seen using carbachol.

The results suggest that muscarinic agonist‐evoked contractions result primarily from the integration of Ca2+ entry associated with the increased spike discharge and myofilaments Ca2+ sensitization, and that Ca2+ store release may contribute to the contraction indirectly via potentiation of the electrical membrane responses. They may also support the idea that an interaction of M2 and M3 receptors plays a crucial role in mediating the contraction response.

British Journal of Pharmacology (2003) 139, 337–350. doi:10.1038/sj.bjp.0705267
Do fluorescent drugs show you more than you wanted to know?
Authors: McGrath J C , Daly C J
Published: May 2003

British Journal of Pharmacology (2003) 139, 187–189. doi:10.1038/sj.bjp.0705288
Consequences of removing a keystone herbivore for the abundance and diversity of arthropods associated with a cruciferous shrub
Authors: González‐Megías Adela , Gómez José M.
Published: May 2003

Abstract. 1. The effect of the removal of Timarcha lugens (Chrysomelidae), one of the main herbivores of Hormathophylla spinosa (Cruciferae), on the abundance of co‐occurring phytophagous insects, the abundance of non‐phytophagous arthropods (detritivores, predators, and parasitoids), and the structure and diversity of the entire arthropod community, was studied for 3 years (1999–2001).

2. There was competition between T. lugens and co‐occurring herbivores; the removal of T. lugens was correlated with an increase in the abundance of sap‐suckers, flower‐feeders, and, above all, folivores.

3. Timarcha lugens also had an indirect effect on arthropods belonging to other trophic levels; the abundance of predators increased significantly after the removal of T. lugens.

4. Community composition was affected by the experimental removal. In addition, the diversity of the overall community increased after removal of T. lugens.

5. The study demonstrated experimentally that T. lugens has a significant effect not only on other species belonging to the same trophic level, but also on the abundance of species belonging to higher trophic levels, and, consequently, on the entire structure and diversity of the complex community in which it is immersed.
Dispersal between host populations in field conditions: navigation rules in the parasitoid Venturia canescens
Authors: Desouhant E. , Driessen G. , Lapchin L. , Wielaard S. , Bernstein C.
Published: May 2003

Abstract. 1. Dispersal is a life‐history trait that can have great ecological and evolutionary consequences, however understanding of how insects disperse is limited.

2. Navigation rules of the solitary koinobiont parasitoid of the pyralid moth larvae Venturia canescens (Gravenhorst) were studied in conditions that it is likely to meet when dispersing between host populations and in the absence of cues related directly to the presence of hosts.

3. Mark–release–recapture experiments were conducted in a natural host‐free habitat, and letting the animals disperse for different periods.

4. In the presence of vegetation, wasps seemed to disperse rapidly (1 h for an area of ≥ 1 ha) and capture rates were independent of both dispersal time and distance from the release point.

5. The navigation rules of V. canescens during dispersal between tree stands can be summarised as: move up‐ or down‐wind, avoid or pass through open, sunny areas, and go for shady and dense vegetation.

6. The consequences of the navigation rules for host–parasitoid dynamics are discussed in relation to different spatial scales.
The use of field–based social information in eusocial foragers: local enhancement among nestmates and heterospecifics in stingless bees
Authors: Slaa E. Judith , Wassenberg Jacoba , Biesmeijer Jacobus C.
Published: May 2003

Abstract. 1. Foragers of social insects can be guided to profitable food sources by social information transfer within the nest. This study showed that in addition to such an information‐centre strategy, social information in the field also plays an important role in individual foraging decisions. The effect of the presence of a nestmate on individual decision‐making on where to forage was investigated in six species of stingless bee that differ in their recruitment system. Some species preferred to feed close to a nestmate (local enhancement) whereas other species actively avoided landing close to a nestmate. The term local inhibition is introduced for this avoidance behaviour.

2. Local enhancement and local inhibition were species specific but were not related to the species' recruitment system.

3. Local enhancement and local inhibition were affected by the individual's experience with the food source. Newly recruited foragers of Trigona amalthea showed local enhancement whereas experienced foragers showed local inhibition.

4. These individual decision‐making rules explained accurately the spatial distribution of recruited nestmates: foraging groups of T. amalthea, which shows local inhibition, were more dispersed than foraging groups of Oxytrigona mellicolor, which shows local enhancement.

5. The effect of heterospecifics on stingless bee flower choice was investigated for 18 species combinations. Landing decisions were influenced significantly by the aggressiveness and the body size of the resident bee. Larger and more aggressive heterospecifics were avoided, whereas in some cases less aggressive bees acted as an attraction cue.
Temporal priority and intra‐guild predation in temporary waters: an experimental study using Namibian desert dragonflies
Authors: Padeffke Tanja , Suhling Frank
Published: May 2003

Abstract. 1. Intra‐guild predation between early larval instars of two co‐existing dragonflies, Sympetrum fonscolombii and Trithemis kirbyi, was investigated with respect to temporal advantage and growth. Three situations were simulated experimentally: (1) Sympetrum fonscolombii began development 11 days before T. kirbyi. (2) Trithemis kirbyi began development 11 days before S. fonscolombii. (3) Both species began on the same day.

2. With a temporal advantage of 11 days to the second species, the resulting larval density of the respective first species was significantly higher than that of the second species.

3. Without a temporal advantage, the survival of S. fonscolombii was higher than that of T. kirbyi, and S. fonscolombii had a larger size due to faster growth than T. kirbyi. Hence, it is assumed that survival depended on early oviposition as well as on larval growth.

4. To test the relevance of the laboratory results, observations at artificial ponds in the Namibian semi‐desert were conducted. Trithemis kirbyi was the first species colonising these ponds while S. fonscolombii arrived 15 days later. In field samples, many more Trithemis larvae than Sympetrum larvae were found, a pattern similar to the laboratory experiments in which T. kirbyi enjoyed a temporal advantage.
Calling behaviour of the potato aphid Macrosiphum euphorbiae oviparae under laboratory and field conditions
Authors: Goldansaz Seyed H. , McNeil Jeremy N.
Published: May 2003

Abstract.  1. The calling behaviour of virgin oviparae of the potato aphid Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) was studied at three different constant temperatures under laboratory conditions. The mean age of calling for the first time decreased with a decrease in temperature from 2.9 days at 20 °C to 2.1 days at 10 °C. At all temperature regimes, the mean onset time of calling advanced from about 5 to 3 h after the onset of the photophase, and the mean time spent calling increased by > 4 h over the 8 days.

2. Cohorts of oviparae were also observed at two different periods in late summer–early autumn in the field, to examine the effects of fluctuating abiotic conditions (temperatures, wind velocity, rain) and age on calling behaviour. As under constant laboratory conditions, the mean age of calling for the first time declined with declining temperature, from 3.7 days in early September to 1.6 days at the end of September. Age‐related changes in the mean onset time of calling and the mean time spent calling were much less evident under field conditions, due to the inhibitory effects of low temperatures, high winds, and rain on female calling activity.

3. The results are discussed within the context of reproductive success and address a previously proposed hypothesis suggesting that species‐specific calling windows may serve as a reproductive isolating mechanism for sympatric aphid species.
Interactions of the antCrematogaster scutellariswith the fig/fig wasp mutualism
Authors: Schatz Bertrand , Hossaert‐Mckey Martine
Published: May 2003

Abstract.1. A classical example of specialised pollination mutualisms is the relationship between fig trees and their pollinating wasps, in which each partner depends completely on the other for its reproduction; however the fig/fig wasp association is also the target of a great diversity of other species, ranging from specialised parasites to opportunistic foragers, among them ants.

2. The ant community and the sources of ant attraction observed on the Mediterranean fig treeFicus caricawere characterised.

3. A guild of ants attracted by homopterans tended on the plant was distinguished from a second guild composed of two co‐dominant ant species (Crematogaster scutellarisandPheidole pallidula) that prey mostly on pollinating wasps, abundant during certain parts of the fig cycle.

4. Foraging workers ofC. scutellarissearch for prey on the fig inflorescence (syconium), capturing pollinating wasps mostly at the peak of wasp emergence and at a rate estimated to reach 600 prey per day for an entire tree.

5. Detailed study of the predatory sequences displayed under experimental conditions showed that ant workers captured 100% of the pollinating wasps offered, while they captured only 5.5% of the parasitoid wasp specific to the pollinator. The respective impacts of the interaction on ants and on the figs are discussed, as well as several behavioural traits of predation by the dominant ant on pollinators.
Performance of a spring‐feeding moth in relation to time of oviposition and bud‐burst phenology of different host species
Authors: Klemola Tero , Ruohomäki Kai , Tanhuanpää Miia , Kaitaniemi Pekka
Published: May 2003

Abstract. 1. As a spring‐feeding moth committed to immature foliage, the autumnal moth Epirrita autumnata (Lepidoptera, Geometridae) must have egg hatch synchronised with the bud‐burst of its host plants. Due to large individual variation in the length of the pupal period, however, E. autumnata populations exhibit a prolonged period of flight and oviposition. Because the timing of oviposition in autumn is associated with the timing of egg hatch in the following spring, the time window for egg hatch expands and more potential hosts may become attainable. This suggestion was evaluated under field conditions by rearing E. autumnata eggs and larvae on four different hosts.

2. The performance of E. autumnata was measured by using estimates for fecundity (pupal mass) as well as survivorship of eggs and larvae. Based on the availability of foliage and phenological synchrony between larval and leaf development, early‐laid eggs and the larvae originating from them were predicted to perform better on the hosts that have early‐flushing leaves. On the late‐flushing hosts, the larvae that hatched later were predicted to perform better than the larvae that hatched earlier. Half of the trials were exposed to predators and parasitoids, while the rest were conducted inside mesh‐bags preventing larval dispersal and mortality due to natural enemies.

3. The results of the experiment did not support the simple predictions. In particular, host‐plant quality and natural enemies appeared to operate discordantly between early‐ and late‐laid eggs. Larvae from the late‐laid eggs had rapid development during the larval stages and pupated at the same time and with the same pupal mass as the larvae hatched from the early‐laid eggs.

4. The results indicate an occurrence of several, unknown selective forces in E. autumnata populations maintaining variation in the length of the pupal period, timing of oviposition, and timing of egg hatch.