bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation and linkage analysis of expressed disease-resistance gene analogues of sugar beet (Beta vulgarisL.)
Authors: Hunger Sandra , Gaspero Gabriele Di , Möhring Silke , Bellin Diana , Schäfer-Pregl Ralf , Borchardt Dietrich C , Durel Charles-Eric , Werber Martin , Weisshaar Bernd , Salamini Francesco , Schneider Katharina
Published: February 2003

Sequence conservation among resistance genes (R genes) was exploited to identify 47 R gene analogues (RGAs) from sugar beet (Beta vulgaris L.). Using degenerate primers, 11 RGAs were amplified from genomic DNA and 7 from leaf or beet cDNA. Twenty-nine were selected from an EST sequencing program. Twenty-one RGAs contained structures similar to the nucleotide binding site (NBS)  leucine rich repeat (LRR) domain, a motif commonly found in several R genes. Among the remaining RGAs, 19 revealed similarity to the serine (threonine) protein kinase domain of R genes, 4 showed features related to the LRR region of the rice disease resistance gene Xa21, 1 RGA resembled the sugar beet nematode resistance gene Hs1pro-1, and 2 had homologies to other gene products associated with disease resistance. For 20 EST-derived RGAs, transcript levels were compared in leaf and root tissue revealing organ-specific transcription in 7 cases. Thirty-three RGAs were spread over all nine sugar beet chromosomes, except for a cluster of nine closely linked RGAs on chromosome 7. The analysis of linkage between RGAs and loci for rhizomania and Cercospora resistance identified alleles associated with resistance in both cases.Key words: RGA, Beta vulgaris, NBSLRR, genetic linkage map, molecular marker.
Absence of microspore polarity, symmetric divisions and pollen cell fate inBrachiaria decumbens(Gramineae)
Authors: Filho Roberto Gargione Junqueira , Mendes-Bonato Andréa Beatriz , Pagliarini Maria Suely , Bione Nilton Cesar Pires , Borges do Valle Cacilda , de Oliveira Penteado Maria Isabel
Published: February 2003

Meiotic division and male gametophyte development were analyzed in one tetraploid (2n = 4x = 36) accession of Brachiaria decumbens cv. Basilisk that showed some pollen sterility. Meiotic process was typical of polyploids in that it consisted of multiple chromosome associations. Precocious chromosome migration to the poles, laggards, and micronucleus formation were abundant in both meiosis I and II and resulted in tetrads with micronuclei. After callose dissolution, microspores were released into the anther locule and had the semblance of being normal. Although each microspore initiated its differentiation by pollen mitosis, in 43.24% of the microspores, nuclear polarization was not observed and the typical hemispherical cell plate was not detected. Division was symmetric and microspores lacked differentiation between the vegetative and the generative cell. Both nuclei were of equal size, presented equal chromatin condensation, and had a spherical shape. After the first pollen mitosis and cytokinesis, each cell underwent a new symmetric mitosis without nuclear polarization. At the end of the second pollen mitosis, four equal nuclei were observed in each pollen grain. After the second cytokinesis, the cells gave rise to four equal-sized pollen grains with a similar tetrad configuration that initially remained together. Sterile pollen grains resulted from abnormal pollen mitosis. This anomaly may be explained by a mutation, probably affecting microtubule cytoskeleton formation. The importance of this male-sterile mutation for Brachiaria breeding programs is discussed.Key words: Brachiaria decumbens, male sterility, pollen mitosis, microspore polarity, symmetric division, pollen cell fate, grasses.
Flow resistance in skimming flows in stepped spillways and its modelling
Authors: Chanson H , Yasuda Youichi , Ohtsu Iwao
Published: February 2003

Dams and weirs must be equipped with adequate flood-release facilities for a safe dissipation of the kinetic energy of the flow. With stepped spillway design, it is essential to accurately predict the flow-resistance contribution of the steps. The authors investigate the flow resistance of skimming flows and associated form losses. Recent laboratory experiments were systematically performed with channel slopes ranging from 5.7° up to 55° and the results are compared with existing laboratory and prototype data. The results provide a better understanding of the basic flow patterns and flow-resistance mechanisms and emphasize that form loss is dominant. Simple analytical models provide a reasonable order of magnitude of the pseudo-boundary shear stress and the recirculation cavity ejection frequency. Altogether, more than 38 model studies and four prototype investigations (for a total of more than 700 data points) are reanalysed.Key words: stepped spillway, flow resistance, skimming flow, form drag, physical and analytical modelling.
Strength and ductility of laterally confined concrete columns
Authors: Chung Heon-Soo , Yang Keun-Hyeok , Lee Young-Ho , Eun Hee-Chang
Published: February 2003

The objective of this study is to determine experimentally and analytically the magnitude of the strength enhancement of concrete confined by lateral ties. Sixty-five reinforced concrete columns with a 200 mm square cross section were tested. Experimental parameters include the compressive strength of concrete; the volumetric ratio, strength, and confinement type of rectilinear ties; and the distribution of longitudinal reinforcement bars. The confinement effects are explained by utilizing an effectively confined distance ratio. Tie stress caused by lateral concrete pressure is presented as a function of the volumetric ratio and configuration of ties, and the strength of concrete based on the experimental data and the nonlinear multiple regression method. Based on the empirical data and the nonlinear multiple regression method, this paper presents an empirical equation to determine the strength enhancement as a function of the tie stress, the effectively confined distance ratio, the volumetric ratio of ties, and the strength of concrete. The validity of the American Concrete Institute and Canadian Standards Association specifications for minimum tie spacing and the design of cross ties are examined.Key words: high-strength concrete, ductility, strength enhancement factor, confinement type of ties, volumetric ratio of ties, effectively confined distance ratio, nonlinear multiple regression method.
Monitoring corrosion rate for ordinary portland concrete (OPC) and high-performance concrete (HPC) specimens subjected to chloride attack
Authors: Ismail Mohamed E , Soleymani Hamid R
Published: February 2003

This paper presents the results and the applicability of an electrochemical technique, the Tafel plot method, for determining the corrosion rate of reinforcing steel embedded in laboratory ordinary portland concrete (OPC) and high-performance concrete (HPC) specimens. Fifty-two OPC and 52 HPC concrete cylinders, each with a single embedded reinforcing steel rod, have been subjected to various laboratory conditions, and the corrosion rate of each specimen has been monitored. Results indicate that HPC specimens performed much better than OPC specimens in terms of resisting corrosion, as the corrosion rates were far lower for the HPC specimens than for the OPC specimens. Sodium chloride concentration played an important role in the propagation of corrosion: the higher the NaCl concentration, the higher the corrosion rate. In addition, different cycles of wetting and drying of concrete specimens had different impacts on corrosion rates. Results for the chloride concentration based on the American Society for Testing and Materials (ASTM) destructive testing method C1218 were in agreement with the corrosion rate results from the Tafel plot method used in the study.Key words: corrosion, electrochemical, reinforced concrete, Tafel method, high-performance concrete.
An experimental investigation of steel-free deck slabs
Authors: Hassan Ammar , Kawakami Makoto , Niitani Kyoji , Yoshioka Tamio
Published: February 2003

The steel-free deck slab developed in Canada used straps as a confinement system and relied on the stiffness of this confinement system rather than its strength. In this paper, a new approach, using the strength of a confinement system comprising unbonded prestressed bars, was investigated. In addition, the effect of the concrete strength and the steel ratio of the confinement system was examined. Seven large-scale one-way steel-free deck slabs were built using normal- and high-strength concrete, prestressed to different levels, and statically tested up to failure. The overall behaviour of the slabs was similar to that of slabs confined by straps. Cracking strength was not considerably enhanced. The slabs failed in punching shear mode with high loads. The new approach was not able to overcome the problem of the longitudinal crack, which developed in the tested slabs and reportedly appeared in all the steel-free slabs built or tested previously in Canada. Prestressing had a definite effect, however, on delaying the occurrence of this longitudinal crack, thereby enhancing serviceability. The paper recommends that the serviceability limit state of the steel-free slabs would be better assessed by the occurrence of the longitudinal crack, even though the ultimate capacity of the slabs is high.Key words: arch action, cracking, external prestressing, high-strength concrete, punching shear, steel-free deck slab.
Stochastic nature of freeway capacity and its estimation
Authors: Polus Abishai , Pollatschek Moshe A
Published: February 2003

The main purpose of this study was to investigate the meaning of freeway capacity, in particular to explore its stochastic nature and to estimate its distribution. The evaluation is based on traffic data from three busy urban freeway sections over 3 full days. Momentary capacity is defined as the intersection of the best-fit regression lines calculated for the dense- and unstable-flow regimes close to the maximum flow. An algorithm was developed for the selection of the relevant pairs for each regression line and is discussed. It is argued that momentary capacity values are stochastic in nature and distributed according to the shifted gamma distribution. Estimation of the parameters of this distribution for the three urban freeway sections is studied. It is proposed that the 5th percentile of the distribution, found to be approximately 2330 vehicles per hour per lane for the prevailing conditions of the basic section, could be adopted as the representative design value of capacity. Another conclusion is that the average distribution of capacities for all three through lanes is relatively close to the distribution of capacities in the middle lane.Key words: freeway flow, capacity, flow breakdown, dense flow, unstable flow.
Study of the bending hysteretic behaviour of ductile steel plates for seismic energy dissipation
Authors: Escobar J Alberto , Sánchez-Ramírez A Roberto , Dyer Juan N
Published: February 2003

A study is presented of the nonlinear behaviour of a system of ductile steel plates subjected to bending cyclic loads which could be used as a seismic damper. Evaluation is carried out through laboratory tests, and a nonlinear analytical model is presented. The mechanical properties and deformation capacity of dissipation of the system of steel plates are determined from the experimental data, and a mathematical technique is proposed to fit the data to an analytical model. The results show that, using this technique, the hysteretic model proposed can predict the forcedisplacement relationship of the plates and the hysteretic energy dissipated by the nonlinear behaviour of the plates.Key words: seismic damper, experimental data fit, analytical loaddisplacement, laboratory tests, analytical model.
Experimental study on the effect of flange geometry on the shear strength of reinforced concrete T-beams subjected to concentrated loads
Authors: Giaccio Craig , Al-Mahaidi Riadh , Taplin Geoff
Published: February 2003

This paper presents results of an experimental investigation into the effect of flange geometry on the shear strength of point-loaded, reinforced concrete T-beams. A procedure to normalise the ultimate strength and calculate a concrete contribution is implemented. This is used to discuss the effect of varying the ratio of flange width to web width and the ratio of flange depth to effective depth on the shear strength of a reinforced concrete T-beam. An increase in the ratio of flange width to web width is shown to produce an accompanying increase in the ultimate strength of a reinforced concrete T-beam, providing the ratio of flange depth to effective depth is above a certain minimum value. This increase in shear resistance with an increase in the ratio of flange width to web width continues until the flange is wide enough to allow formation of a failure mechanism whereby the load point punches through the flange.Key words: shear, T-beams, flange, reinforcing, strength, failure mechanisms.
Modeling of the microenvironment of activated sludge floc with experimental and theoretical methods
Authors: Li B , Bishop Paul L
Published: February 2003

In this study, an integrated model of the microenvironment and boundary layers of the activated sludge floc was developed for the floc from aeration tanks at two wastewater treatment plants (Mill Creek Plant and Muddy Creek Plant, Cincinnati, Ohio) for dynamic simulation of combined biological processes for chemical oxygen demand (COD) and nitrogen removal. The model takes into consideration the mass transfer of substrate and oxygen, the biological reaction within the floc particles, biomass hydrolysis, and the endogenous respiration process. The coefficients in the model were set according to the Activated Sludge Model (ASM) and the data acquired from experiments at these two wastewater treatment plants. The simulated substrate and dissolved oxygen (DO) profiles were compared with the microelectrode-measured profiles from the activated sludge floc. The model simulation results and measured profiles show the heterogeneous and gradient-governed microenvironment of activated sludge floc under different substrate and bulk oxygen concentrations. The anoxic and substrate concentration increase zones dominated in the influent activated sludge floc (Mill Creek Plant, medium pollutant strength), with only the outer layer participating in the metabolism of the pollutants. The radius of the substrate concentration increase zone inside the sludge floc decreased with pollutant removal. When the pollutant concentration in the bulk wastewater was low (Muddy Creek Plant), the substrate concentration increase zone disappeared; the whole floc was aerobic and in a high redox status. The boundary layer (0.6 mm) outside the sludge floc was involved in substrate biodegradation and contributed to the dissolved oxygen concentration drop in this layer. Key words: Activated sludge floc, mathematical modeling, microelectrode, computer simulation, microenvironment, nutrient removal, redox potential (ORP), dissolved oxygen.
Mass transfer analysis in ozone bubble columns
Authors: El-Din M Gamal , Smith Daniel W
Published: February 2003

An impinging-jet bubble column has been tested for the ozone mass transfer applications in water treatment. Two venturi injectors were utilized to create turbulent gas-liquid jets in the ambient fluid by placing them at an intersecting angle of 125°. The intersecting of the jets caused an increase in the turbulence produced in the ambient fluid and therefore, increased the gasliquid mass transfer rate. The steady-state one-phase axial dispersion model (1P-ADM) was applied to analyze the dissolved ozone concentration profiles measured in the bubble column by fitting these profiles to the predicted profiles, using the 1P-ADM, to determine the column-average overall mass transfer coefficient (kLa) and liquid-phase axial dispersion coefficient (DL). Two minimization approaches were applied to solve the differential equation representing the 1P-ADM: two-parameter (kLa and DL) and one-parameter (kLa) minimization techniques. To examine the sensitivity of the predicted kLa to changes in DL, DL was estimated first from the tracer experiments. Then, the one-parameter minimization technique was applied to determine kLa. As a result, kLa varied only slightly (<11%) between the two types of minimization techniques. Using the two-parameter minimization technique, kLa and DL values were correlated to the superficial gas and liquid velocities uG and uL, respectively) by power-law relationships. The following correlations were obtained: kLa = 20.54 uG1.13uL0.07 and DL = 2.94 x 102uG0.03uL0.18. The 1P-ADM has proven to be an accurate and easy-to use tool for describing the ozonation process in the impinging-jet bubble column as an excellent conformity between the measured and the predicted dissolved ozone concentration profiles was observed. Key words: axial dispersion model, impinging-jet bubble column, mass transfer, ozone.
Regulation of expression of theRhizopusoryzaeuricase and urease enzymes
Authors: Farley Peter C , Santosa Sugiarto
Published: February 2003

The regulation of intracellular urease and uricase activities was examined in Rhizopus oryzae. Urease activity (2.4 U/mg protein) was present in R. oryzae mycelium grown in minimal medium containing NH4Cl as sole nitrogen source. This activity increased threefold under nitrogen derepression conditions, but no induction by urea was detected. Control of urease activity in R. oryzae differs from that found in Neurospora crassa but resembles the situation in Aspergillus nidulans. No uricase activity was detected in R. oryzae mycelium grown in minimal medium containing NH4Cl as sole nitrogen source. Uricase activity was increased 10- to 40-fold under derepression conditions and was induced by exogenous uric acid (60- to 78-fold). Control of the R. oryzae uricase differs from that found in N. crassa and A. nidulans. This is the first analysis of the regulation of enzymes from the purine catabolic pathway in any member of the Zygomycetes.Key words: Rhizopus oryzae, uricase, urease, nitrogen metabolism.
Activity of sulfate-reducing bacteria in human periodontal pocket
Authors: Boopathy R , Robichaux M , LaFont D , Howell M
Published: February 2003

Samples of subgingival dental tissues were examined for the presence of sulfate-reducing bacteria (SRB). Using enrichment cultures, SRBs were detected in 9 of 17 individuals. A pure culture of SRB was obtained from one sample collected from a patient with type IV periodontal disease. The characterization of this isolate showed that it belongs to the genus Desulfovibrio. The isolate used pyruvate, lactate, glucose, fructose, and ethanol as the sole source of carbon. However, the isolate was unable to use acetate and methanol as a carbon source, indicating it as an incomplete oxidizer unable to carry out the terminal oxidation of substrates. Apart from using sulfate as electron acceptor, the isolate also used thiosulfate and nitrate as an electron acceptor. It has the ability to use a variety of nitrogen sources, including ammonium chloride, nitrate, and glutamate. The optimum growth temperature of the isolate was 37°C and the optimum pH for growth was 6.8. The SRB isolate contained the electron carrier desulfoviridin. The numbers of SRB in the mouth are assumed to be limited by sulfate. Potential sources of sulfate in the subgingival area include free sulfate in pocket fluid and glycosaminoglycans and sulfur-containing amino acids from periodontal tissues.Key words: sulfate-reducing bacteria, periodontal pocket, Desulfovibrio, subgingival tissues, electron acceptor.
Hemoglobin in five genetically diverseFrankiastrains
Authors: Beckwith Jason , Tjepkema John D , Cashon Robert E , Schwintzer Christa R , Tisa Louis S
Published: February 2003

Five strains of Frankia were selected to represent a wide range of genetic diversity and examined for presence of hemoglobin. All five strains produced hemoglobin when grown on media without (N) or with (+N) combined nitrogen. This indicates that hemoglobin is common in Frankia and is not directly associated with nitrogen fixation. Frankia strain EAN1pecwas examined in more detail. It showed greater hemoglobin concentration when grown at 2% O2than at 20% O2in the N treatment but no effect of oxygen on hemoglobin concentration in the +N treatment. At both oxygen levels, it produced substantially more biomass in +N than in N culture. It also produced significantly more biomass when the medium contained 0.2% CO2than in the absence of CO2. The molecular mass of the hemo- globin as determined by size exclusion chromatography was 13.4 ± 0.2 kDa (mean ± SE, n = 3) and is consistent with that of a truncated hemoglobin. The hemoglobin had absorption spectra that were typical of a hemoglobin. The oxygen dissociation rate constants for the hemoglobin were 131.2 ± 5.8 s1for N culture and 166 ± 8.2 s1for +N culture. These rapid rates are consistent with a function in facilitated diffusion of oxygen.Key words: Frankia, hemoglobin, truncated hemoglobin.
Ralstonia basilensisM91-3, a denitrifying soil bacterium capable of usings-triazines as nitrogen sources
Authors: Stamper David M , Radosevich Mark , Hallberg Kevin B , Traina Samuel J , Tuovinen Olli H
Published: February 2003

The purpose of this study was to characterize the phylogenetic and phenotypic traits of M91-3, a soil bacterium capable of mineralizing atrazine (2-chloro-4-N-isopropyl-6-N-ethyl-s-triazine). The isolate was identified as Ralstonia basilensis based on 99.5% homology of the 16S rRNA sequence and various chemotaxonomic data. The isolate used atrazine as the sole source of energy, carbon, and nitrogen. It could also use several other s-triazines as nitrogen sources. Ralstonia basilensis M91-3 was capable of denitrification, which was confirmed by gas chromatographic analysis of nitrous oxide under acetylene blockage conditions.Key words: atrazine biodegradation, denitrification, herbicide degrader, Ralstonia basilensis, triazine degradation.
Scanning electron microscopy of native biofilms on mung bean sprouts
Authors: Fett William F , Cooke Peter H
Published: February 2003

Native biofilms present on the adaxial surface of cotyledons of mung bean sprouts (Vigna radiata) were studied by use of scanning electron microscopy. Biofilms were abundant on the cotyledon surfaces and were comprised of rod-shaped bacteria, cocci-shaped bacteria, or yeasts, often with one type of microbe predominant. In contrast to our earlier study of biofilms on green sprouts (alfalfa, clover, broccoli, and sunflower), yeast and cocci were abundant on mung bean. Filamentous fungi were not observed. Sheet-like or fibrillar material (presumably composed of secreted microbial polysaccharides, proteins, lipids, and nucleic acids) fully or partially covered the biofilms. Biofilms up to 5 mm in length were observed, and some biofilms were comprised of more than just a monolayer of microbial cells. Native biofilms on sprout surfaces undoubtedly play an important role in the ecology of plant epiphytic microbes and may also afford protected sites for plant and human bacterial pathogens.Key words: mung bean sprouts, biofilms, native microflora, scanning electron microscopy, food safety.
Antibacterial activity of Cry- and Cyt-proteins fromBacillus thuringiensisssp.israelensis
Authors: Yudina Tatyana G , Konukhova Anna V , Revina Lyudmila P , Kostina Lyubov I , Zalunin Igor A , Chestukhina Galina G
Published: February 2003

Mosquitocidal endotoxins Cry4B, Cry11A, and CytA from Bacillus thuringiensis ssp.israelensis as well as the products of their limited proteolysis display antibacterial activity relative to Micrococcus luteus. The endotoxin Cry11A also induces the lysis of the micrococcus protoplasts. Potassium and sodium ions and N-acetylgalactosamine increased the antibacterial effect of Cry11A, whereas glucose and N-acetylglucosamine inhibited it. The endotoxin Cry11A displays the antibacterial effect on some other microorganisms.Key words: Bacillus thuringiensis, Micrococcus luteus, δ-endotoxins, antibacterial activity.
Cardiovascular effects of 1,8-cineole, a terpenoid oxide present in many plant essential oils, in normotensive rats
Authors: Lahlou Saad , Figueiredo André Fernandes , Magalhães Pedro Jorge Caldas , Leal-Cardoso José Henrique
Published: February 2003

The cardiovascular effects of i.v. treatment with 1,8-cineole, a monoterpenic oxide present in many plant essential oils, were investigated in normotensive rats. This study examined (i) whether the autonomic nervous system is involved in the mediation of 1,8-cineole-induced changes in mean aortic pressure (MAP) and heart rate (HR) and (ii) whether the hypotensive effects of 1,8-cineole could result from its vasodilatory effects directly upon vascular smooth muscle. In both pentobarbital-anesthetized and conscious, freely moving rats, bolus injections of 1,8-cineole (0.310 mg/kg, i.v.) elicited similar and dose-dependent decreases in MAP. Concomitantly, 1,8-cineole significantly decreased HR only at the highest dose (10 mg/kg). Pretreatment of anesthetized rats with bilateral vagotomy significantly reduced the bradycardic responses to 1,8-cineole (10 mg/kg) without affecting hypotension. In conscious rats, i.v. pretreatment with methylatropine (1 mg/kg), atenolol (1.5 mg/kg), or hexamethonium (30 mg/kg) had no significant effects on the 1,8-cineole-induced hypotension, while bradycardic responses to 1,8-cineole (10 mg/kg) were significantly reduced by methylatropine. In rat isolated thoracic aorta preparations, 1,8-cineole (0.0062.6 mM) induced a concentration-dependent reduction of the contraction induced by potassium (60 mM). This is the first physiological evidence that i.v. treatment with 1,8-cineole in either anesthetized or conscious rats elicits hypotension; this effect seems related to an active vascular relaxation rather than withdrawal of sympathetic tone.Key words: 1,8-cineole, essential oil, cardiovascular effects, autonomic nervous system, isolated thoracic aorta.
Specific electromechanical responses of cardiomyocytes to individual and combined components of ischemia
Authors: Tissier Cindy , Bes Sandrine , Vandroux David , Fantini Elisabeth , Rochette Luc , Athias Pierre
Published: February 2003

The main factors of myocardial ischemia are hypoxia, substrate deprivation, acidosis, and high extracellular potassium concentration ([K+]e), but the influence of each of these factors has not yet been evaluated in a cardiomyocyte (CM) culture system. Electromechanical responses to the individual and combined components of ischemia were studied in CM cultured from newborn rat ventricles. Action potentials (APs) were recorded using glass microelectrodes and contractions were monitored photometrically. Glucose-free hypoxia initially reduced AP duration, amplitude, and rate and altered excitationcontraction coupling, but AP upstroke velocity ([Formula: see text]max) remained unaffected. Early afterdepolarizations appeared, leading to bursts of high-rate triggered impulses before the complete arrest of electromechanical activity after 120 min. Acidosis reduced [Formula: see text]max, whereas AP amplitude and rate were moderately decreased. Combining acidosis and substrate-free hypoxia also decreased [Formula: see text]max but attenuated the effects of substrate-free hypoxia on APs and delayed the cessation of the electrical activity (180 min). Raising [K+]e reduced the maximal diastolic potential and [Formula: see text]max. Total ischemia (substrate deletion, hypoxia, acidosis, and high [K+]e) decreased AP amplitude and [Formula: see text]max without changing AP duration. Moreover, delayed afterdepolarizations appeared, initiating triggered activity. Ultimately, 120 min of total ischemia blocked APs and contractions. To conclude, glucose-free hypoxia caused severe functional defects, acidosis delayed the changes induced by substrate-free hypoxia, and total ischemia induced specific dysfunctions differing from those caused by the former conditions. Heart-cell cultures thus represent a valuable tool to scrutinize the individual and combined components of ischemia on CMs. Key words: cell culture, cardiomyocytes, membrane potential, cell contraction, ischemia.
Carbachol interactions with nonsteroidal anti-inflammatory drugs
Authors: Miranda H F , Sierralta F , Pinardi G
Published: February 2003

The inhibition of cyclooxygenase enzymes by nonsteroidal anti-inflammatory drugs (NSAIDs) does not completely explain the antinociceptive efficacy of these agents. It is known that cholinergic agonists are antinociceptive, and this study evaluates the interactions between carbachol and some NSAIDs. Antinociceptive activity was evaluated in mice by the acetic acid writhing test. Doseresponse curves were constructed for NSAIDs and carbachol, administered either intraperitoneally (i.p.) or intrathecally (i.t.). The interactions of carbachol with NSAIDs were evaluated by isobolographic analysis after the simultaneous administration of fixed proportions of carbachol with each NSAID. All of the drugs were more potent after spinal than after systemic administration. The combinations of NSAIDs and carbachol administered i.p. were supra-additive; however, the i.t. combinations were only additive. Isobolographic analysis of the coadministration of NSAIDs and carbachol and the fact that atropine antagonized the synergistic effect suggest that carbachol may strongly modulate the antinociceptive activity of NSAIDs; thus, central cholinergic modulation would be an additional mechanism for the antinociceptive action of NSAIDs, unrelated to prostaglandin biosynthesis inhibition.Key words: antinociception, nonsteroidal anti-inflammatory drugs, cholinergic, carbachol, writhing test.
Vitamin C lowers blood pressure and alters vascular responsiveness in salt-induced hypertension
Authors: Ettarh R R , Odigie I P , Adigun S A
Published: February 2003

The present study was undertaken to investigate the effect of vitamin C treatment on blood pressure and vascular reactivity in salt-induced hypertension. Male SpragueDawley rats were fed a normal rat diet, a high-sodium (8% NaCl) diet, a normal rat diet plus vitamin C treament (100 mg·kg1·day1), or a high-sodium diet plus vitamin C treatment for 6 weeks. Salt loading significantly increased blood pressure, which was attenuated by vitamin C treatment. Aortic rings from the different groups were suspended for isometric-tension recording. The contractile response to noradrenaline was significantly increased in the salt-loaded rats. Vitamin C reduced the sensitivity of aortic rings to noradrenaline in rats on normal and high-sodium diets. In noradrenaline-precontracted rings, the relaxation response to acetylcholine, which was attenuated in the salt-loaded rats, was restored by vitamin C treatment. Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) abolished the enhanced response to acetylcholine caused by vitamin C. The results suggest that the antihypertensive effect of vitamin C is associated with a reduction in vascular sensitivity to noradrenaline and enhancement of endothelium-dependent relaxation due to increased nitric oxide bioavailability. Key words: vitamin C, salt, hypertension, vascular reactivity.
Effects of clozapine on the efflux of serotonin and dopamine in the rat brain: the role of 5-HT1A receptors
Authors: Hagino Yoko , Watanabe Masayuki
Published: February 2003

In vivo microdialysis in conscious rats was used to examine the effect of clozapine on serotonin (5-hydroxy tryptamine, 5-HT) efflux in the prefrontal cortex and dorsal raphe nucleus and dopamine efflux in the prefrontal cortex. Both systemic and local administration of clozapine (systemic,10 or 20 mg/kg, i.p.; local, 100 μM) increased 5-HT efflux in the dorsal raphe. However, in the prefrontal cortex, dialysate 5-HT increased when clozapine (100 μM) was administered through the probe, while no effect was observed when it was administered systemically. By pretreatment with the selective 5-HT1A receptor antagonist p-MPPI (3 mg/kg, i.p.), systemic treatment of clozapine (10 mg/kg, i.p.) significantly increased 5-HT efflux in the prefrontal cortex. This result suggests that the ability of clozapine to enhance the extracellular concentrations of 5-HT in the dorsal raphe attenuates this drug's effect in the frontal cortex, probably through the stimulation of 5-HT1A somatodendritic autoreceptors in the dorsal raphe. We also found that pretreatment with p-MPPI (3 mg/kg, i.p.) attenuated by 45% the rise in cortical dopamine levels induced by clozapine (10 mg/kg, i.p.). These findings imply that the reduction in serotonergic input from the dorsal raphe nucleus induced by clozapine could lead to an increase in dopamine release in the prefrontal cortex. Key words: 5-HT1A receptor, clozapine, microdialysis, 5-HT, dopamine.
Regulation of insulin-like growth factor-1 by the reninangiotensin system during regression of cardiac eccentric hypertrophy through angiotensin-converting enzyme inhibitor and AT1 antagonist
Authors: Haddad G E , Blackwell K , Bikhazi A
Published: February 2003

Angiotensin II (Ang II) mediates its effects through its non-tyrosine-kinase G protein coupled Ang-II type 1 receptor (AT1). Growing evidence indicates that a functional insulin-like growth factor-1 (IGF-1) tyrosine kinase receptor is required for Ang-II-induced mitogenesis. Along with Ang II, we have previously shown that changes in IGF-1 receptor binding at myofibers are causative agents for cardiac eccentric hypertrophy. This study investigated the interaction of the reninangiotensin system with the IGF-1 receptor during the development and regression of cardiac hypertrophy. Alterations in IGF-1 binding were evaluated in the CHAPS-pretreated perfused heart. Four weeks of aortocaval shunt increased relative heart mass by 76% without a major change in body mass or systolic blood pressure. Binding studies showed that IGF-1 has a higher affinity for the cardiac myofibers of shunt than sham rats. Two weeks of treatment with the angiotensin-converting enzyme (ACE) inhibitor captopril (0.5 g/L in drinking water) or the AT1-antagonist losartan (10 mg/(kg·day)) reduced cardiac hypertrophy by 54 and 42%, respectively. However, while both ACE inhibition and AT1-antagonist treatments produced equivalent regression in ventricular hypertrophy, captopril was more efficacious than losartan in the regression of atrial hypertrophy. Regression of cardiac hypertrophy in the shunt by either captopril or losartan was accompanied with a reduction or normalization of the elevated IGF-1 affinity. Thus, the induction and regression of cardiac eccentric hypertrophy seems to be largely dependent on cross talk between the reninangiotensin system and the IGF-1 axis at the receptor level.Key words: volume overload, cardiac eccentric hypertrophy, reninangiotensin system, IGF-1.
Both endothelin-A and endothelin-B receptors are present on adult rat cardiac ventricular myocytes
Authors: Allen Bruce G , Phuong Luu Lien , Farhat Hala , Chevalier Dominique
Published: February 2003

Endothelin-A (ETA) and endothelin-B (ETB) receptors have been demonstrated in intact heart and cardiac membranes. ETAreceptors have been demonstrated on adult ventricular myocytes. The aim of the present study was to determine the presence of ETBand the relative contribution of this receptor subtype to total endothelin-1 (ET-1) binding on adult ventricular myocytes. Saturation binding experiments indicated that ET-1 bound to a single population of receptors (Kd= 0.52 ± 0.13 nM, n = 4) with an apparent maximum binding (Bmax) of 2.10 ± 0.25 sites (× 105)/cell (n = 4). Competition experiments using 40 pM [125I]ET-1 and nonradioactive ET-1 revealed a Kiof 660 ± 71 pM (n = 10) and a Hill coefficient (nH) of 0.99 ± 0.10 (n = 10). A selective ETAantagonist, BQ610, displaced 80% of the bound [125I]ET-1. No displacement was observed by concentrations of an ETB-selective antagonist, BQ788, up to 1.0 μM. However, in the presence of 1.0 μM BQ610, BQ788 inhibited the remaining [125I]ET-1 binding. Similarly, in the presence of 1.0 μM BQ788, BQ610 inhibited the remaining specific [125I]ET-1 binding. Binding of an ETB1-selective agonist, [125I]IRL-1620, confirmed the presence of ETB. ETBbound to ET-1 irreversibly, whereas binding to ETAdemonstrated both reversible and irreversible components, and BQ610 and BQ788 bound reversibly. Reducing the incubation temperature to 0°C did not alter the irreversible component of ET-1 binding. Hence, both ETAand ETBreceptors are present on intact adult rat ventricular myocytes, and the ratio of ETA:ETBbinding sites is 4:1. Both receptor subtypes bind to ET-1 by a two-step association involving the formation of a tight receptorligand complex; however, the kinetics of ET-1 binding to ETAversus ETBdiffer.Key words: cell communication, endothelins, receptors, inotropic agents, signal transduction
Modulation of L-type Ca2+ channels in neonatal rat heart by a novel Ca2+ channel agonist
Authors: Chahine Mohamed , Sculptoreanu Adrian , Varma Daya R
Published: February 2003

L-type Ca2+ channels are essential in triggering the intracellular Ca2+ release and contraction in heart cells. In this study, we used patch clamp technique to compare the effect of two pure enantiomers of L-type Ca2+ channel agonists: (+)-CGP 48506 and the dihydropyridine (+)-SDZ-202 791 in cardiomyocytes from rats 25 days old. The predominant Ca2+ current activated by standard step pulses in these myocytes was L-type Ca2+ current. The di hy dro py ri dine antagonist (+)-PN200-110 (5 μM) blocked over 90% of Ca2+ currents in most cells tested. CGP 48506 lead to a maximum of 200% increase in currents. The threshold concentration for the CGP effect was at 1 μM and the maximum was reached at 20 μM. SDZ-202 791 had effects in nanomolar concentrations and a maximum effect at about 2 μM. The maximal effect of (+)-SDZ-202 791 was a 400% increase in the amplitude of Ca2+ currents and was accompanied by a 1015 mV leftward shift in the voltage dependence of activation. CGP 48506 increased the currents equally at all voltages tested. Both compounds slowed the deactivation of tail currents and lead to the appearance of slowly activating and slowly deactivating current components. However, SDZ-202 791 had larger effects on deactivation and CGP 48506 had larger effect on the rate of Ca2+ current activation. The effect of SDZ-202 791 was fully additive to that of CGP 48506 even after maximum concentrations of CGP. This observation suggests that the two Ca2+ channel agonists may act at two different sites on the L-type Ca2+ channel. We suggest that CGP 48506 would be a potential cardiotonic agent without the deleterious proarrhythmic effects attributable to the dihydropyridine agonists.Key words: heart failure, calcium channels, dihydropyridine, CGP 48506 (5-methyl-6-phenyl-1, 3,5,6-tetra hydro-3,6-methano-1,5-benzodiazocine-2,4-dione).
Redox-dependent MAP kinase signaling by Ang II in vascular smooth muscle cells: role of receptor tyrosine kinase transactivation
Authors: Touyz Rhian M , Cruzado Montserrat , Tabet Fatiha , Yao Guoying , Salomon Steven , Schiffrin Ernesto L
Published: February 2003

We investigated the role of receptor tyrosine kinases in Ang II-stimulated generation of reactive oxygen species (ROS) and assessed whether MAP kinase signaling by Ang II is mediated via redox-sensitive pathways. Production of ROS and activation of NADPH oxidase were determined by DCFDA (dichlorodihydrofluorescein diacetate; 2 μmol/L) fluorescence and lucigenin (5 μmol/L) chemiluminescence, respectively, in rat vascular smooth muscle cells (VSMC). Phosphorylation of ERK1/2, p38MAP kinase and ERK5 was determined by immunoblotting. The role of insulin-like growth factor-1 receptor (IGF-1R) and epidermal growth factor receptor (EGFR) was assessed with the antagonists AG1024 and AG1478, respectively. ROS bioavailability was manipulated with Tiron (105mol/L), an intra cellular scavanger, and diphenylene iodinium (DPI; 106mol/L), an NADPH oxidase inhibitor. Ang II stimulated NADPH oxidase activity and dose-dependently increased ROS production (p < 0.05). These actions were reduced by AG1024 and AG1478. Ang II-induced ERK1/2 phosphorylation (276% of control) was decreased by AG1478 and AG1024. Neither DPI nor tiron influenced Ang II-stimulated ERK1/2 activity. Ang II increased phosphorylation of p38 MAP kinase (204% of control) and ERK5 (278% of control). These effects were reduced by AG1024 and AG1478 and almost abolished by DPI and tiron. Thus Ang II stimulates production of NADPH-inducible ROS partially through transactivation of IGF-1R and EGFR. Inhibition of receptor tyrosine kinases and reduced ROS bioavaliability attenuated Ang II-induced phosphorylation of p38 MAP kinase and ERK5, but not of ERK1/2. These findings suggest that Ang II activates p38MAP kinase and ERK5 via redox-dependent cascades that are regulated by IGF-1R and EGFR transactivation. ERK1/2 regulation by Ang II is via redox-insensitive pathways.Key words: ERK1/2, p38MAP kinase, EGFR, IGF-1R, signal transduction.
Pharmacological characterization of putative β1-β2-adrenergic receptor heterodimers
Authors: Lavoie Catherine , Hébert Terence E
Published: February 2003

In the last few years, significant experimental evidence has accumulated showing that many G protein coupled receptors (GPCRs) are structurally and perhaps functionally homodimers. Recently, a number of studies have demonstrated that many GPCRs, notably GABAB, somatostatin, and δ and κ opioid receptors form heterodimers, as well. Based on these observations, we undertook a pharmacological and functional analysis of HEK 293 cells transiently transfected with the β1AR or β2AR or with both subtypes together. High-affinity binding for subtype-specific ligands (betaxolol and xamoterol for the β1AR, and ICI 118,551 and procaterol for the β2AR) was detected in cells expressing the cognate receptors alone with values similar to those reported in the literature. However, a significant portion of these high-affinity interactions were lost when both receptors were expressed together while nonspecific ligands (propranolol and isoproterenol) retained their normal affinities. When competition assays were performed with each subtype-specific ligand in the presence of a constant concentration of the other subtype-specific ligand, the high-affinity binding site was rescued, suggesting that the two receptor subtypes were interacting in a fashion consistent with positive cooperativity. Our data suggest that the β1AR and β2AR can form heterodimers and that these receptors have altered pharmacological properties from the receptor homodimers.Key words: G protein coupled receptor, signalling, G protein, dimerization, heterodimer, adrenergic.
Dose-dependent protection of cardiac function by propofol during ischemia and early reperfusion in rats: effects on 15-F2t-isoprostane formation
Authors: Xia Zhengyuan , Godin David V , Chang Thomas K.H , Ansley David M
Published: February 2003

We examined the effects of propofol (2,6-diisopropylphenol) on functional recovery and 15-F2t-isoprostane generation during ischemiareperfusion in Langendorff-perfused rat hearts. Before the induction of 40 min of global ischemia, hearts were perfused (10 min) with propofol at 5 (lo-P) or 12 μg/mL (hi-P) in saline or with saline only (control). During ischemia, saline, lo-P, or hi-P was perfused through the aorta at 60 μL/min. During the first 15 min of reperfusion, propofol (5 or 12 μg/mL) was continued, followed by perfusion with 5 μg/mL propofol for 75 min in both propofol-treated groups. After 90 min of reperfusion (Rep-90), heart tissues were harvested for assessment of antioxidant status. In hi-P, we observed increased latency to and greater reduction of ischemic contracture relative to the lo-P or control groups. 15-F2t-Isoprostane concentrations increased during ischemia and were significantly lower in hi-P and lo-P than in control (P < 0.01). At Rep-90, myocardial functional recovery was greater in both propofol-treated groups relative to control, and it correlated positively with tissue antioxidant capacity preservation. Tissue antioxidant capacity was better preserved in hi-P than in lo-P treatment (P < 0.05). We conclude that oxidant injury occurs during ischemia and reperfusion, and propofol provides dose-dependent protection primarily by enhancing tissue antioxidant capacity and reducing lipid peroxidation.Key words: propofol, myocardium, ischemiareperfusion, 15-F2t-isoprostane.
Ventilation and metabolism during propofol anesthesia in rats
Authors: Saiki Chikako , Kamio Takayuki , Furuya Hideki , Matsumoto Shigeji
Published: February 2003

Many anesthetics are known to decrease ventilation (VdotE) and metabolic rate (MR). Because MR is known to contribute to the VdotE level, one would expect some parallelism between the changes in VdotE and MR during anesthesia. We tested this hypothesis in normoxia and hypoxia (12% O2) on male Wistar rats (n = 10; 221288 g) by using a short-acting intravenous anesthetic, propofol. Propofol anesthesia was induced with a 77.5 mg kg1 (6070 s) dose and maintained with a 2022 mg kg1 h1 (<40 min) dose. In normoxia, propofol significantly decreased VdotE and MR and maintained the VdotE/MR ratio. In hypoxia, propofol decreased MR without a significant decrease in VdotE, and the VdotE/MR ratio tended to increase. As a result, both in normoxia and hypoxia, propofol did not significantly increase the partial pressure of CO2 in arterial blood (PaCO2). Propofol was also associated with decreased body temperature and mean arterial pressure. The results suggest that during anesthesia, a large part of the drop in VdotE can be accounted for by the drop in MR, and that in both normoxia and hypoxia the VdotE/MR ratios and PaCO2values are maintained close to the levels of the conscious state. Key words: anesthesia, propofol, metabolism, ventilation, hypoventilation.
Renal responses to chronic cold exposure
Authors: Sun Zhongjie , Zhang Zhonge , Cade Robert
Published: February 2003

The aim of this study was to assess our hypothesis that the release of antidiuretic hormone (ADH), the renal concentrating response to ADH, or both is decreased by prolonged cold exposure. Six groups (n = 6/group) of rats were used. Three groups were exposed to cold (5°C), while the remaining three groups were kept at room temperature (25°C). It was found that urine osmolality decreased significantly and serum osmolality increased significantly during cold exposure. The ratio of water/food intake was not affected by prolonged cold exposure. However, prolonged cold exposure increased the ratio of urine output/food intake in the cold-exposed rats, indicating that more urine flow is required by the cold-exposed rats to excrete the osmotic substance at a given food intake. The difference between water intake and urine output decreased significantly in the cold-exposed rats. Thus, prolonged cold exposure increases water loss from excretion. Renal concentrating responses to 24-h dehydration and Pitressin were decreased significantly in the cold-exposed rats. Plasma ADH levels remained unchanged, but renal ADH receptor (V2 receptor) mRNA was decreased significantly in the cold-exposed rats. The results strongly support the conclusion that cold exposure increases excretive water loss, and this may be due to suppression of renal V2 receptors rather than inhibition of ADH release.Key words: renal concentrating response, cold-induced dehydration, serum and urine osmolality, ADH, renal V2 receptor mRNA.