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Potential Differences (potential + difference)
Selected AbstractsRufinamide: Clinical pharmacokinetics and concentration,response relationships in patients with epilepsyEPILEPSIA, Issue 7 2008Emilio Perucca Summary Rufinamide is a new, orally active antiepileptic drug (AED), which has been found to be effective in the treatment of partial seizures and drop attacks associated with the Lennox-Gastaut syndrome. When taken with food, rufinamide is relatively well absorbed in the lower dose range, with approximately dose-proportional plasma concentrations up to 1,600 mg/day, but less than dose-proportional plasma concentrations at higher doses due to reduced oral bioavailability. Rufinamide is not extensively bound to plasma proteins. During repeated dosing, steady state is reached within 2 days, consistent with its elimination half-life of 6,10 h. The apparent volume of distribution (Vd/F) and apparent oral clearance (CL/F) are related to body size, the best predictor being body surface area. Rufinamide is not a substrate of cytochrome P450 (CYP450) enzymes and is extensively metabolized via hydrolysis by carboxylesterases to a pharmacologically inactive carboxylic acid derivative, which is excreted in the urine. Rufinamide pharmacokinetics are not affected by impaired renal function. Potential differences in rufinamide pharmacokinetics between children and adults have not been investigated systematically in formal studies. Although population pharmacokinetic modeling suggests that in the absence of interacting comedication rufinamide CL/F may be higher in children than in adults, a meaningful comparison of data across age groups is complicated by age-related differences in doses and in proportion of patients receiving drugs known to increase or to decrease rufinamide CL/F. A study investigating the effect of rufinamide on the pharmacokinetics of the CYP3A4 substrate triazolam and an oral contraceptive interaction study showed that rufinamide has some enzyme-inducing potential in man. Findings from population pharmacokinetic modeling indicate that rufinamide does not modify the CL/F of topiramate or valproic acid, but may slightly increase the CL/F of carbamazepine and lamotrigine and slightly decrease the CL/F of phenobarbital and phenytoin (all predicted changes were <20%). These changes in the pharmacokinetics of associated AEDs are unlikely to make it necessary to change the dosages of these AEDs given concomitantly with rufinamide, with the exception that consideration should be given to reducing the dose of phenytoin. Based on population pharmacokinetic modeling, lamotrigine, topiramate, or benzodiazepines do not affect the pharmacokinetics of rufinamide, but valproic acid may increase plasma rufinamide concentrations, especially in children in whom plasma rufinamide concentrations could be increased substantially. Conversely, comedication with carbamazepine, vigabatrin, phenytoin, phenobarbital, and primidone was associated with a slight-to-moderate decrease in plasma rufinamide concentrations, ranging from a minimum of ,13.7% in female children comedicated with vigabatrin to a maximum of ,46.3% in female adults comedicated with phenytoin, phenobarbital, or primidone. In population modeling using data from placebo-controlled trials, a positive correlation has been identified between reduction in seizure frequency and steady-state plasma rufinamide concentrations. The probability of adverse effects also appears to be concentration-related. [source] Indirect evidence for increased mechanosensitivity of jejunal secretomotor neurones in patients with idiopathic bile acid malabsorptionACTA PHYSIOLOGICA, Issue 2 2009A. Bajor Abstract Aim:, The interdigestive motor rhythm, the migrating motor complex (MMC), is accompanied by active secretion of chloride during periods of distally propagating maximal motor activity (MMC phase III). We studied the behaviour of this system in bile acid malabsorption (BAM), a relative common cause of chronic diarrhoea. We measured motor activity and transmucosal potential difference (PD, reflecting active chloride secretion), in the proximal jejunum in healthy controls (n = 18) and in a group of patients with BAM (n = 11). The phase III-generated voltage was related to the degree of BAM quantified by the 75SeHCAT test. Methods:, We used a multi-channel intestinal infusion system to simultaneously measure jejunal pressure and PD. Saline passing calomel half-cells was infused into the jejunum and subcutaneously. Pressure and PD were recorded in the fasting state and after a test meal. Results:, In the absence of motor activity, jejunal PD was not significantly different from zero in either group. During MMC phase III, PD reached significantly higher mean and peak levels in BAM patients. The product of MMC phase III length multiplied by voltage, over 3 h, was also significantly higher in BAM patients (controls: median 307 mV × cm, range 70,398; BAM: median 511, range 274,2271, P < 0.01). This value was also significantly correlated with the degree of BAM as reflected by the 75SeHCAT test (P < 0.05). Conclusion:, Phase III induced jejunal secretion may be upregulated in BAM patients, resulting in overload of colonic reabsorption capacity. [source] Gap junctional coupling between progenitor cells at the retinal margin of adult goldfishDEVELOPMENTAL NEUROBIOLOGY, Issue 3 2001Fuminobu Tamalu Abstract We prepared living slice preparations of the peripheral retina of adult goldfish to examine electrical membrane properties of progenitor cells at the retinal margin. Cells were voltage-clamped near resting potential and then stepped to either hyperpolarizing or depolarizing test potentials using whole-cell voltage-clamp recordings. Electrophysiologically examined cells were morphologically identified by injecting both Lucifer Yellow (LY) and biocytin. All progenitor cells examined (n = 37) showed a large amount of passively flowing currents of either sign under suppression of the nonjunctional currents flowing through K+ and Ca2+ channels in the cell membrane. They did not exhibit any voltage-gated Na+ currents. Cells identified by LY fills were typically slender. As the difference between the test potential and the resting potential increased, 13 out of 37 cells exhibited symmetrically voltage- and time-dependent current decline on either sign at the resting potential. The symmetric current profile suggests that the current may be driven and modulated by the junctional potential difference between the clamping cell and its neighbors. The remaining 24 cells did not exhibit voltage dependency. A gap junction channel blocker, halothane, suppressed the currents. A decrease in extracellular pH reduced coupling currents and its increase enhanced them. Dopamine, cAMP, and retinoic acid did not influence coupling currents. Injection of biocytin into single progenitor cells revealed strong tracer coupling, which was restricted in the marginal region. Immature ganglion cells closely located to the retinal margin exhibited voltage-gated Na+ currents. They did not reveal apparent tracer coupling. These results demonstrate that the marginal progenitor cells couple with each other via gap junctions, and communicate biochemical molecules, which may subserve or interfere with cellular differentiation. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 204,214, 2001 [source] Dual-asymmetry electrokinetic flow focusing for pre-concentration and analysis of catecholamines in CE electrochemical nanochannelsELECTROPHORESIS, Issue 14 2009Ren-Guei Wu Abstract In this research, a technique incorporating dual-asymmetry electrokinetic flow (DAEKF) was applied to a nanoCE electrochemical device for the pre-concentration and detection of catecholamines. The DAEKF was constructed by first generating a ,-potential difference between the top and bottom walls, which had been pre-treated with O2 and H2O surface plasma, respectively, yielding a 2-D gradient shear flow across the channel depth. The shear flow was then exposed to a varying ,-potential along the downstream direction by control of the field-effect in order to cause downward rotational flow in the channel. By this mechanism, almost all of the samples were effectively brought down to the electrode surface for analysis. Simulations were carried out to reveal the mechanism of concentration caused by the DAEKF, and the results reasonably describe our experiment findings. This DAEKF technique was applied to a glass/glass CE electrochemical nanochip for the analysis of catecholamines. The optimum detection limit was determined to be 1.25 and 3.3,nM of dopamine and catechol, respectively. A detection limit at the zeptomole level for dopamine can be obtained in this device, which is close to the level released by a single neuron cell in vitro. [source] On-column conductivity detection in capillary-chip electrophoresisELECTROPHORESIS, Issue 24 2007Zhi-Yong Wu Professor Abstract On-column conductivity detection in capillary-chip electrophoresis was achieved by actively coupling the high electric field with two sensing electrodes connected to the main capillary channel through two side detection channels. The principle of this concept was demonstrated by using a glass chip with a separation channel incorporating two double-Ts. One double-T was used for sample introduction, and the other for detection. The two electrophoresis electrodes apply the high voltage and provide the current, and the two sensing electrodes connected to the separation channel through the second double-T and probe a potential difference. This potential difference is directly related to the local resistance or the conductivity of the solution defined by the two side channels on the main separation channel. A detection limit of 15,,M (600,ppb or 900,fg) was achieved for potassium ion in a 2,mM Tris-HCl buffer (pH,8.7) with a linear range of 2 orders of magnitude without any stacking. The proposed detection method avoids integrating the sensing electrodes directly within the separation channel and prevents any direct contact of the electrodes with the sample. The baseline signal can also be used for online monitoring of the electric field strength and electroosmosis mobility characterization in the separation channel. [source] Comparative Electrochemical Study of Unsubstituted and Substituted Bis(phthalocyaninato) Rare Earth(III) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2004Peihua Zhu Abstract The electrochemistry of homoleptic substituted phthalocyaninato rare earth double-decker complexes M(TBPc)2 and M(OOPc)2 [M = Y, La...Lu except Pm; H2TBPc = 3(4),12(13),21(22),30(31)-tetra- tert -butylphthalocyanine, H2OOPc = 3,4,12,13,21,22,30,31-octakis(octyloxy)phthalocyanine] has been comparatively studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in CH2Cl2 containing 0.1 M tetra- n -butylammonium perchlorate (TBAP). Two quasi-reversible one-electron oxidations and three or four quasi-reversible one-electron reductions have been revealed for these neutral double-deckers of two series of substituted complexes, respectively. For comparison, unsubstituted bis(phthalocyaninato) rare earth analogues M(Pc)2 (M = Y, La...Lu except Pm; H2Pc = phthalocyanine) have also been electrochemically investigated. Two quasi-reversible one-electron oxidations and up to five quasi-reversible one-electron reductions have been revealed for these neutral double-decker compounds. The three bis(phthalocyaninato)cerium compounds display one cerium-centered redox wave between the first ligand-based oxidation and reduction. The half-wave potentials of the first and second oxidations and first reduction for double-deckers of the tervalent rare earths depend on the size of the metal center. The difference between the redox potentials of the second and third reductions for MIII(Pc)2, which represents the potential difference between the first oxidation and first reduction of [MIII(Pc)2],, lies in the range 1.08,1.37 V and also gradually diminishes along with the lanthanide contraction, indicating enhanced ,,, interactions in the double-deckers connected by the smaller, lanthanides. This corresponds well with the red-shift of the lowest energy band observed in the electronic absorption spectra of reduced double-decker [MIII(Pc,)2], (Pc, = Pc, TBPc, OOPc). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Atomic Structure and Electrical Properties of In(Te) Nanocontacts on CdZnTe(110) by Scanning Probe MicroscopyADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Gili Cohen-Taguri Abstract Understanding complex correlations between the macroscopic device performance (largely dependent on the character of the metal,semiconductor contact) and the metallurgy of contact formation on the atomic level in cadmium zinc telluride (CdZnTe) radiation detectors remains a formidable challenge. In this work, an effort towards bridging that macro,nano knowledge gap is made by conducting a series of controlled experiments aimed at correlating electrical properties of the In contact to n-type CdZnTe(110) surface with the step-by-step process of contact formation. This can only be achieved by using high spatial resolution techniques, capable of conducting highly localized measurements on the nano- and sub-nanoscale, such as scanning probe microscopy. Scanning tunneling microscopy is used in situ to monitor the behavior of various In atom coverages on an atomically flat and ordered CdZnTe surface under well-controlled molecular beam epitaxial conditions in ultra-high vacuum. Electrical derivatives of atomic force microscopy are used to measure the electrical contact properties, such as contact potential difference and spreading resistance in torsion resonance tunneling mode. It is concluded that In atoms preferentially reacted with Te atomic-rows already at room temperature, forming nanometric patches of indium,telluride Schottky-type contacts. The methods developed in this study, in terms of both nanocontact fabrication and characterization (especially in terms of electrical properties) should benefit basic and applied research of any metal,semiconductor system. [source] Metallurgical characterization, galvanic corrosion, and ionic release of orthodontic brackets coupled with Ni-Ti archwiresJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2007Myrsini S. Darabara Abstract In orthodontics, a combination of metallic alloys is placed into the oral cavity during medical treatment and thus the corrosion resistance and ionic release of these appliances is of vital importance. The aim of this study is to investigate the elemental composition, microstructure, hardness, corrosion properties, and ionic release of commercially available orthodontic brackets and Copper Ni-Ti archwires. Following the assessment of the elemental composition of the orthodontic wire (Copper Ni-TiÔ) and the six different brackets (Micro Loc, Equilibrium, OptiMESHXRT, Gemini, Orthos2, and Rematitan), cyclic polarization curves were obtained for each material to estimate the susceptibility of each alloy to pitting corrosion in 1M lactic acid. Galvanic corrosion between the orthodontic wire and each bracket took place in 1M lactic acid for 28 days at 37°C and then the ionic concentration of Nickel and Chromium was studied. The orthodontic wire is made up from a Ni-Ti alloy with copper additions, while the orthodontic brackets are manufactured by different stainless steel grades or titanium alloys. All tested wires and brackets with the exception of Gemini are not susceptible to pitting corrosion. In galvanic corrosion, following exposure for 28 days, the lowest potential difference (,250 mV) appears for the orthodontic wire Copper Ni-Ti and the bracket made up from pure titanium (Rematitan) or from the stainless steel AISI 316 grade (Micro Loc). Following completion of the galvanic corrosion experiments, measurable quantities of chromium and nickel ions were found in the residual lactic acid solution. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Comparison of lipid-rich necrotic core size in symptomatic and asymptomatic carotid atherosclerotic plaque: Initial resultsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2008Vincent C. Cappendijk MD Abstract Purpose To investigate the potential difference in the size of the lipid-rich necrotic core (LRNC) in carotid plaques of symptomatic patients versus asymptomatic patients. Pathological studies established that a large LRNC is an important feature of vulnerable atherosclerotic plaque. Previously, we have demonstrated a high correlation between semiquantitative analysis of the LRNC size in T1-weighted (w) turbo field echo (TFE) MR images and histology. Materials and Methods Thirty-seven patients with carotid stenosis >70% with (n = 26) or without (n = 11) symptoms were included. Three independent MR readers quantified the amount of LRNC with a T1w TFE pulse sequence. The relative amount of LRNC (LRNC score) was defined as sum of cross-sectional area percentages LRNC per carotid plaque. Results Interreader agreement for the three MR readers was good, with an intraclass correlation coefficient (ICC, 95% confidence interval [CI]) of 0.72 (0.57,0.83). All three MR readers on average found a larger LRNC in the symptomatic group of patients, although this was not statistically significant. The mean LRNC score was 116 ± 129 and 59 ± 62 for symptomatic and asymptomatic patients, respectively (P = 0.13). Symptomatic patients showed wide ranges in LRNC scores (0,424), while the range was much lower in the asymptomatic group (0,170). Conclusion Single-sequence T1w TFE may be a promising technique to study atherosclerotic plaque at risk of stroke. Larger studies are warranted to confirm these promising results. J. Magn. Reson. Imaging 2008;27:1356,1361. © 2008 Wiley-Liss, Inc. [source] Amino acids protect epithelial cells from local toxicity by absorption enhancer, sodium laurateJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2001Takashi Yata Abstract To develop the safe absorption-enhancing formulation attenuating the local toxicity caused by an absorption enhancer, sodium laurate (C12), the effects of amino acids on the local toxicity by C12 were examined in rats. The absorption of phenol red, an unabsorbable marker drug, was significantly enhanced by 10 mM C12 in an in situ colon loop study and the addition of L -glutamine (L -Gln), L -arginine, or L -methionine at 10 mM did not change the promoting effect of C12. However, C12 significantly increased the elution of phospholipids, total protein, and lactate dehydrogenase, which are markers for local toxicity, from colon, but these amino acids attenuated the local toxicity caused by C12 significantly. Transport study using an Ussing-type chamber showed that the permeability of colonic membrane to phenol red was significantly enhanced by C12 and that L -Gln did not decrease the permeability enhanced by C12. Transmucosal electrical resistance was extensively decreased by C12, indicating that C12 could enhance the drug absorption at least partly by expanding the paracellular route. L -Gln significantly, but not completely, recovered resistance lowered by C12. Electrical potential difference was markedly reduced by C12, suggesting that C12 lowered the viability of mucosal cells, but 10 mM L -Gln significantly recovered potential difference almost to the control level. These results suggested the possibility that absorption-enhancing formulation with low local toxicity, which is low enough to be used practically, could be developed by using an amino acid like L -Gln as an ingredient attenuating the local toxicity caused by C12. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1456,1465, 2001 [source] Uniform corrosion of titanium in alkaline hydrogen peroxide conditions: influence of transition metals and inhibitors calcium and silicateMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2002J. Rämö Uniform corrosion of titanium was studied in alkaline hydrogen peroxide environments simulating pulp bleaching conditions. Corrosion rates of unalloyed Grade 2 and alloyed Grade 5 were determined as a function of hydrogen peroxide anion (HOO,) concentration. Influences of calcium and silicate inhibitors and iron and manganese were investigated. Without inhibition titanium corroded at HOO, content of 200 mg/l: Grade 2 0.4 mm/y and Grade 5 1.4 mm/y. Addition of calcium (Ca2+) and silicate (SiO32,) diminished the corrosion of Grade 2 to critical anion level 400 mg/l, but could not protect Grade 5 even at the HOO, concentration of 300 mg/l. Presence of iron and manganese raised the critical levels of the both grades. High HOO, anion level was observed as a notable potential difference between titanium and platinum. Gleichmäßige Flächenkorrosion von Titan unter alkalischen Wasserstoffperoxidbedingungen: Einfluss der Übergangsmetalle und der Inhibitoren Kalzium und Silikat Gleichmäßige Flächenkorrosion von Titan wurde in alkalischen Wasserstoffperoxidbedingungen, die Papierbleichbedingungen simulieren, untersucht. Die Korrosionsgeschwindigkeiten von unlegierter Güteklasse 2 und legierter Güteklasse 5 wurden als Funktion der Wasserstoffperoxidanionen(HOO,)konzentration bestimmt. Einflüsse von Kalzium- und Silikatinhibitoren sowie von Eisen und Mangan wurden untersucht. Ohne Inhibierung betrug die Korrosion von Titan bei einem HOO, -Gehalt von 200 mg/l bei der Güteklasse 2 0,4 mm/Jahr und bei der Güteklasse 5 1,4 mm Jahr. Die Zugabe von Kalzium (Ca2+) und Silikat (SiO32,) verminderte die Korrosion der Güteklasse 2 auf ein kritisches Anionenniveau von 400 mg/l; konnte aber Güteklasse 5 selbst bei einer HOO, -Konzentration von 300 mg/l nicht schützen. Die Anwesenheit von Eisen und Mangan erhöhte die kritischen Niveaus für beide Güteklassen. Hohe HOO, -Anionengehalte wurden als beträchtliche Potentialdifferenz zwischen Titan und Platin beobachtet. [source] Membrane depolarization induces K+ efflux from subapical maize root segmentsNEW PHYTOLOGIST, Issue 1 2002Fabio F. Nocito Summary ,,The role of potassium efflux from maize (Zea mays) root segments in maintaining transmembrane electric potential difference (Em) was studied in vivo, together with the involvement of outward rectifying K+ channels (ORCs). ,,Measurements were made of the efflux of potassium (K+) from roots when its uptake was competitively inhibited by rubidium (Rb+), of the Em of the root cells by microelectrodes and of the unidirectional fluxes of monovalent cations. ,,The influx of Rb+, caesium (Cs+) or ammonium (NH4+) into the segments induced an efflux of K+. Lithium (Li+) and sodium (Na+) were not taken up and did not induce K+ efflux. The permeating cations induced membrane depolarizations, which were closely related to the values of K+ efflux. Two K+ -channel blockers, tetraethylammonium-chloride and quinidine, inhibited K+ efflux. The inhibition was accompanied by a higher membrane depolarization induced by Rb+, whose influx was not affected. ,,The results suggest that a depolarizing event caused by cation uptake increased K+ efflux from the cells, probably through the activation of ORCs involved in restoration and stabilization of Em. [source] Standardized procedure for measurement of nasal potential difference: An outcome measure in multicenter cystic fibrosis clinical trials,PEDIATRIC PULMONOLOGY, Issue 5 2004Thomas A. Standaert PhD Abstract Patients with cystic fibrosis (CF) can be discriminated from healthy subjects by measurement of the nasal potential difference, which has become a useful outcome measure for therapies directed toward correcting defective electrolyte transport in CF. A standard operating procedure was developed by a CF Foundation clinical trials network, to be followed by all sites performing collaborative studies. Key variables in the measurement included type of voltmeter, exploring probe, reference electrodes, and solutions used to assess both sodium transport and chloride conductance. Eight sites submitted data on 3,8 normal and 4,5 CF subjects. Baseline voltage, an index of sodium transport, was ,18.2,±,8.3 mV (mean,±,SD) for normals, and ,45.3,±,11.4 mV for CF patients. There was no CFTR-mediated chloride secretion in CF subjects, as evidenced by the lack of response to perfusion with zero chloride,+,beta agonist solutions (+3.2,±,3.5 mV) vs. that in normals (,23.7,±,10.2 mV). The standardized nasal potential difference measurement minimizes variability between operators and study sites. Valid and consistent results can be attained with trained operators and attention to technical details. These data demonstrate the procedure to be sufficient for multicenter studies in the CF Foundation network. Pediatr Pulmonol. 2004; 37:385,392. © 2004 Wiely-Liss, Inc. [source] Influence of adsorbates on the piezoresponse of KNbO3PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2006F. Peter Abstract We report on the reduction of piezoresponse in KNbO3 originating from a surface layer. An analysis with surface sensitive measurements shows that this layer consists of chemisorbates and physisorbates. Heating the sample under ultra high vacuum conditions removes the surface layer on the perovskite to a large extend. This treatment has a drastic effect on the piezoresponse as the potential difference applied to the sample is no longer reduced by a voltage drop across the adsorbate layer, leading to a higher electric field compared to the case with an adsorbate layer. Experiments and simulations are presented confirming this postulation on KNbO3. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electron transport properties in InAs four-terminal ballistic junctions under weak magnetic fieldsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2009M. Koyama Abstract We report on the electron transport properties based on ballistic electrons under magnetic fields in four-terminal ballistic junctions fabricated on an InAs/AlGaSb heterostructure. The four-terminal junction structure is composed of two longitudinal stems with two narrow wires slanted with 30 degree from the perpendicular axis. The electron focusing peak was obtained with the bend resistance measurement. Then it was investigated the nonlinear electron transport property of potential difference between longitudinal stems due to ballistic electrons with applying direct current from narrow wires. Observed nonlinearity showed clear rectification effects which have negative polarity regardless of input voltage polarity. Although this nonlinearity was qualitatively changed due to the Lorentz force under magnetic fields, the degradation of ballistic effects on nonlinear properties were observed when the current increased to higher strength. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electric current as a control variable in the electrospinning processPOLYMER ENGINEERING & SCIENCE, Issue 7 2006Ravikant Samatham In the electrospinning process submicron-diameter polymer fibers can be produced when a high potential difference is applied to a polymer drop suspended at the tip of a capillary. The electrospinning process is affected by a wide range of parameters, because of which controlling the properties of the fibers is difficult. This is the major hurdle in the development of practical applications of electrospun fibers along with its low productivity. Here we are proposing to use the electric current in the electrospinning process to control the "quality of the fibers". Electrospinning of a solution of polyacrylonitrile in dimethylformamide (PAN/DMF) was done by applying a programmed variable flow rate at different constant voltages. The electric current in the process was measured in real time. Four types of jet regimes were observed, electric current and the morphology of the fibers corresponding to these regimes were analyzed. A relation between the electric current, type of jet and morphology of the fibers has been established. The mechanical properties of electrospun fiber mats were also measured by a tensile testing method. POLYM. ENG. SCI. 46:954,959, 2006. © 2006 Society of Plastics Engineers [source] Ion chemistry of chloroethanes in air at atmospheric pressureRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2001Anna Nicoletti Ion chemistry at atmospheric pressure is of major relevance to novel methods for the abatement of volatile organic compounds (VOCs) that employ non-thermal plasmas. For this reason, positive and negative APCI (atmospheric pressure chemical ionization) mass spectra of all six di-, tri- and tetrachloroethanes diluted in air (500,1500,ppm) at atmospheric pressure were investigated at 30,°C and at 300,°C. Spectral changes due to collisional activation of the ions achieved by increasing ,V, the potential difference between sampling and skimmer cones, are informative of structures and ion-molecule reactions. Positive ion chemistry of the chloroethanes (M) can, in general, be ascribed to C-C and C-Cl cleavages of the molecular ion, M+·, never detected but likely formed via exothermic charge exchange from primary ions of the APCI plasma. Exceptions to this characteristic pattern were observed for 1,1-dichloroethane and 1,1,2,2-tetrachloroethane, which give [M,,,H]+ and [M,,,HCl]+· species, respectively. It is suggested that both such species are due to ionization via hydride transfer. Upon increasing ,V, the [M,,,HCl]+· ion formed from 1,1,2,2-tetrachloroethane undergoes the same fragmentation and ion-molecule reactions previously reported for trichloroethene. A nucleophilic reaction of water within the [C2H4Cl+](H2O)n ionic complexes to displace HCl is postulated to account for the [C2H5O+](H2O)m species observed in the positive APCI spectra of the dichloroethanes. Negative ion spectra are, for all investigated chloroethanes, dominated by Cl, and its ion-neutral complexes with one, two and, in some cases, three molecules of the neutral precursor and/or water. Another common feature is the formation of species (X,)(M)n where X, is a background ion of the APCI plasma, namely O2,,O3, and, in some cases, (NO)2,. Peculiar to 1,1,1-trichloroethane are species attributed to Cl, complexes with phosgene, (Cl,)(Cl2C=O)n(n,=,1,2). Such complexes, which were not observed for either the isomeric 1,1,2-trichloroethane or for the tetrachloroethanes, are of interest as oxidation intermediates in the corona-induced decomposition process. No conclusions can be drawn in the case of the dichloroethanes, since, for these compounds, the ions (Cl,)(Cl2C=O)n and (Cl,)(M)n happen to be isobaric. Copyright © 2001 John Wiley & Sons, Ltd. [source] The bioflavonoid compound, sinupret, stimulates transepithelial chloride transport in vitro and in vivo,,§THE LARYNGOSCOPE, Issue 5 2010Frank Virgin MD Abstract Objectives/Hypothesis: Dehydration of airway surface liquid (ASL) disrupts normal mucociliary clearance in sinonasal epithelium leading to chronic rhinosinusitis. Abnormal chloride (Cl,) transport is one mechanism that contributes to this disorder, as demonstrated by the disease cystic fibrosis. Identifying safe compounds that stimulate transepithelial Cl, transport is critical to improving hydration of the ASL and promoting mucociliary transport. Sinupret (Bionorica, LLC, San Clemente, CA), a combination of naturally occurring bioflavonoids, is a widely used treatment for respiratory ailments in Europe. However, the effects of Sinupret on target respiratory epithelium have yet to be fully investigated. The present study evaluated the mechanisms underlying this bioflavonoid therapeutic on transepithelial Cl, transport in respiratory epithelium. Study Design: In vitro and in vivo investigation. Methods: Well characterized murine nasal septal epithelial (MNSE) cultures, and murine nasal potential difference (NPD) techniques were used to evaluate the effects of Sinupret on Cl, secretion. Results: The change in Sinupret-stimulated current (, ISC expressed as ,A/cm2) in MNSE, representing Cl, secretion, was significantly increased when compared to controls (19.04 ± 1.67 ,A/cm2 vs. 1.8 ± 0.35 ,A/cm2, respectively; P = .00005). Transepithelial Cl, transport measured in the murine NPD in vivo assay (n = 42) was also significantly enhanced when compared to controls (,0.8 mV vs. ,0.9 mV; P = .0004). Importantly, Sinupret-stimulated Cl, transport was substantially more robust in vivo than forskolin, a compound among the strongest known cystic fibrosis transmembrane conductance regulator activators (,3.8 mV vs. ,1.65 mV; P = .01). Conclusions: Sinupret strongly activates transepithelial Cl, secretion through a mechanism known to hydrate the ASL of respiratory epithelium. This is one means by which the medication is likely to exert therapeutic benefit. Laryngoscope, 2010 [source] Regulation of restitution after superficial injury in isolated guinea pig gastric mucosaAPMIS, Issue 4-5 2004ARUN BHOWMIK The immediate response of the gastrointestinal epithelium to superficial (i.e. microscopic) injury is primarily directed towards restoring the disturbed epithelial continuity. Both structural (i.e. cytoskeleton) and humoral (i.e. growth factors and cytokines) involvement in the process has recently been documented. Yet it is unclear whether humoral signaling regulating mucosal recovery after superficial injury is associated with tyrosine phosphorylation, and whether there are other signs of downstream activation of the signaling pathway. To evaluate the effects of exogenous genistein and phorbol-myristate acetate in the assessment of the role of tyrosine receptor-mediated signaling in the immediate repair of gastric mucosa after superficial injury. Guinea pig gastric mucosa was mounted in a Ussing chamber, injured with 1.25 M NaCl, and perfused for 4 h. Simultaneously, potential difference and tissue resistance were recorded. In some sets of experiments the tissue was exposed bilaterally either to genistein in order to inhibit tyrosine receptor-mediated signaling or to 4-phorbol-myristate 13-acetate (PMA) in order to enhance PKC signaling during the 4 h recovery. Phosphotyrosine (PTYR) and protein kinase C (PKC) immunoreactivity were assessed by immunoblotting and by immunohistochemistry. Proliferative activity was determined morphometrically after staining of the tissue for Ki-67 nuclear antigen and expressed as proliferative index (PI). The inhibition of tyrosine kinases with exogenous genistein resulted in a significant decrease of the PTYR and the stimulation of PKC with PMA increased the PTYR. Nevertheless, no change in the PTYR was observed by immunoblotting after superficial injury alone. Several PKC isoenzymes were found in the guinea pig gastric mucosa, including PKC-,, -,, -, and -,. They were unaffected either by the injury or the PMA treatment. The mean PI of tissues subjected to NaCl-injury was higher than that of uninjured control tissues (p<0.05) (n=7). Exposure of tissue to genistein during recovery decreased the PI, while stimulation with PMA increased it (p<0.05 for both) (n=6). Both electrophysiologic and morphologic restitution were sensitive to genistein, but not to PMA. Superficial injury alone does not influence tyrosine phosphorylation to a degree which could be assessed by immunoblotting. Nevertheless, exogenous modulation of tyrosine receptor-mediated signaling results in downstream signaling effects. The injury-associated induction of proliferation is sensitive to modulation of tyrosine phosphorylation and PKC, suggesting that superficial epithelial injury results in endogenous activation of the epithelium, presumably after paracrine stimulation of the neighboring cells. [source] A map of the common chimpanzee genomeBIOESSAYS, Issue 6 2002Derek E. Wildman The completion of the chimpanzee genome will greatly help us determine which genetic changes are unique to humanity. Chimpanzees are our closest living relative, and a recent study has made considerable progress towards decoding the genome of our sister taxon.1 Over 75,000 common chimpanzee (Pan troglodytes) bacterial artificial chromosome end sequences were aligned and mapped to the human genome. This study shows the remarkable genetic similarity (98.77%) between humans and chimpanzees, while highlighting intriguing areas of potential difference. If we wish to understand the genetic basis of humankind, the completion of the chimpanzee genome deserves high priority. BioEssays 24:490,493, 2002. © 2002 Wiley Periodicals, Inc. [source] Glutathione transport in the endo/sarcoplasmic reticulum,BIOFACTORS, Issue 1-4 2003Miklós Csala Glutathione transport through the endo/sarcoplasmic reticulum (ER/SR) membrane might play a role in the maintenance of the thiol redox potential difference between the lumen and the cytosol. The transport of glutathione (both GSH and glutathione disulfide, GSSG) is entirely different in the ER and SR membranes. The transport measurements based on either rapid filtration or light scattering techniques revealed that the SR membrane transports glutathione much faster than the hepatic ER membrane or microsomal membranes prepared from heart or brain. The fastest transport has been measured in the membrane of muscle terminal cisternae, which is enriched in ryanodine receptor type 1 (RyR1). All the studied membranes have been found to be equally impermeable to various hydrophilic substances of similar size to glutathione, thus the glutathione transport in muscle microsomes and terminal cysternae as well as the correlation between the rate of glutathione transport and the abundance of RyR1 are specific. In both muscle microsomes and terminal cysternae, glutathione influx can be either inhibited or activated by antagonists and agonists of the ryanodine receptor, respectively, while these agents do not influence the transport of other small permeant molecules. These findings strongly suggest that the ryanodine receptor channel activity is directly associated with glutathione transport activity in the skeletal muscle sarcoplasmic reticulum membrane. [source] On the electrodetection threshold of aquatic vertebrates with ampullary or mucous gland electroreceptor organsBIOLOGICAL REVIEWS, Issue 3 2007Rob C. Peters Abstract Reinterpretation of research on the electric sense in aquatic organisms with ampullary organs results in the following conclusions. The detection limit of limnic vertebrates with ampullary organs is 1 ,Vcm,1, and of marine fish is 20 nVcm,1. Angular movements are essential for stimulation of the ampullary system in uniform d.c. fields. Angular movements in the geomagnetic field also generate induction voltages, which exceed the 20 nVcm,1 limit in marine fish. As a result, marine electrosensitive fish are sensitive to motion in the geomagnetic field, whereas limnic fish are not. Angular swimming movements generate a.c. stimuli, which act like the noise in a stochastic resonance system, and result in a detection threshold in marine organisms as low as 1 nVcm,1. Fish in the benthic space are exposed to stronger electric stimuli than fish in the pelagic space. Benthic fish scan the orientation plane for the maximum potential difference with their raster of electroreceptor organs, in order to locate bioelectric prey. This behaviour explains why the detection threshold does not depend on fish size. Pelagic marine fish are mainly exposed to electric fields caused by movements in the geomagnetic field. The straight orientation courses found in certain shark species might indicate that the electric sense functions as a simple bisensor system. Symmetrical stimulation of the sensory raster would provide an easy way to keep a straight course with respect to a far-field stimulus. The same neural mechanism would be effective in the location of a bioelectric prey generating a near-field stimulus. The response criteria in conditioning experiments and in experiments with spontaneous reactions are discussed. [source] Electro-membrane filtration for the selective isolation of bioactive peptides from an ,s2 -casein hydrolysateBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2002Gerrald Bargeman Abstract For the isolation of the ingredients required for functional foods and nutraceuticals generally membrane filtration has too low a selectivity and chromatography is (too) expensive. Electro-membrane filtration (EMF) seems to be a breakthrough technology for the isolation of charged nutraceutical ingredients from natural sources. EMF combines the separation mechanisms of membrane filtration and electrophoresis. In this study, positively charged peptides with antimicrobial activity were isolated from an ,s2 -casein hydrolysate using batch-wise EMF. ,s2 -Casein f(183,207), a peptide with strong antimicrobial activity, predominated in the isolated product and was enriched from 7.5% of the total protein components in the feed to 25% in the permeate product. With conventional membrane diafiltration using the same membrane (GR60PP), isolation of this and other charged bioactive peptides could not be achieved. The economics of EMF are mainly governed by the energy costs and the capital investment, which is affected by the flux of the desired peptide. A maximum average transport rate of ,s2 -casein f(183,207) during batch-wise EMF of 1.2 g/m2 · h was achieved. Results indicate that an increase in the hydrolysate (feed) concentration, the applied potential difference and the conductivity of the permeate and electrode solutions, and a reduction in the conductivity of the feed result in a higher transport rate of ,s2 -casein f(183,207). This is in line with the expectation that the transport rate is improved when the concentration, the electrical field strength, or the electrophoretic mobility is increased, provided that the electrophoretic transport predominates. The expected energy consumption of the EMF process per gram of peptide transported was reduced by approximately 50% by applying a low overall potential difference and by processing desalinated hydrolysate. Considerable improvements in transport rate, energy efficiency, and process economics seem to be attainable by additional optimization of the process parameters and the EMF module design. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 599,609, 2002. [source] Psoriasis genomics: analysis of proinflammatory (type 1) gene expression in large plaque (Western) and small plaque (Asian) psoriasis vulgarisBRITISH JOURNAL OF DERMATOLOGY, Issue 4 2004W. Lew Summary Background, Type 1 T cells are hypothesized to be central in the immunopathogenesis of psoriasis. Through elaboration of interferon (IFN)-,, type 1 T cells regulate the expression of many ,downstream' inflammatory genes, including an array of chemokines that regulate leucocyte trafficking and activation in skin lesions. Accordingly, disease progression and/or severity might be controlled by the degree to which differing cytokines and chemokines are overexpressed in focal skin regions. To examine this possibility, we studied two forms of chronic psoriasis vulgaris that differ significantly in overall severity and progression: small plaque (SP) psoriasis occurring in Korean patients, and large plaque (LP) psoriasis occurring in North American patients. Objectives, To characterize LP and SP psoriasis vulgaris with respect to expression of proinflammatory genes that define the type 1 T-cell axis in skin lesions [genes encoding interleukin (IL)-12, IFN-,, and IFN-,-regulated chemokines or inflammatory mediators]. Methods, Total cellular RNA of skin samples from groups of patients with LP or SP psoriasis was analysed by quantitative reverse transcription-polymerase chain reaction (TaqMan analysis) to compare the differences in mRNA expression of genes related to the IFN-, pathway. Results, The mRNA expression of keratin 16, CD25, IFN-,, IL-12 p40, signal transducer and activator of transcription-1, inducible nitric oxide synthase, IL-8, macrophage inflammatory protein-3,, monocyte chemoattractant protein-1, S100A12, IFN-,-inducible protein of 10 kDa, IFN-inducible T-cell ,-chemoattractant and monokine induced by IFN-, was increased in the lesions of both LP psoriasis and SP psoriasis. However, IL-18 mRNA expression was significantly different in the lesions of LP psoriasis in comparison with those of SP psoriasis. Conclusions, The results indicate that proinflammatory type 1 genes regulated by IFN-, are similarly increased in both SP and LP psoriasis, but a potential difference in IL-18 exists between these disease forms. The consistent activation of this set of genes argues for a central role of IFN-, as a molecular regulator of inflammation in these distinct subtypes of psoriasis vulgaris. In contrast, disease extent/severity must be controlled by yet other factors. [source] Extraction of Proteins from Biological Fluids by Use of an Ionic Liquid/Aqueous Two-Phase SystemCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2007Zhuo Du Abstract An ionic liquid/aqueous two-phase system based on the hydrophilic ionic liquid 1-butyl-3-methylimidazolium chloride (BmimCl) and K2HPO4 has been employed for direct extraction of proteins from human body fluids for the first time. Proteins present at low levels were quantitatively extracted into the BmimCl-rich upper phase with a distribution ratio of about 10 between the upper and lower phase and an enrichment factor of 5. Addition of an appropriate amount of K2HPO4 to the separated upper phase results in a further phase separation, giving rise to an improved enrichment factor of 20. FTIR and UV spectroscopy demonstrated that no chemical (bonding) interactions between the ionic liquid and the protein functional groups were identifiable, while no alterations of the natural properties of the proteins were observed. The partitioning of proteins in the two-phase system was assumed to have been facilitated by the electrostatic potential difference between the coexisting phases, as well as by salting out effects. The system could be applied successfully for the quantification of proteins in human urine after on-line phase separation in a flow system. The use of an ionic liquid, as a green solvent, offers clear advantages over traditional liquid,liquid extractions, in which the use of toxic organic solvents is unavoidable. [source] Covalent Attachment of Bacteriorhodopsin Monolayer to Bromo-terminated Solid Supports: Preparation, Characterization, and Protein StabilityCHEMISTRY - AN ASIAN JOURNAL, Issue 7 2008Yongdong Jin Dr. Abstract The interfacing of functional proteins with solid supports and the study of related protein-adsorption behavior are promising and important for potential device applications. In this study, we describe the preparation of bacteriorhodopsin (bR) monolayers on Br-terminated solid supports through covalent attachment. The bonding, by chemical reaction of the exposed free amine groups of bR with the pendant Br group of the chemically modified solid surface, was confirmed both by negative AFM results obtained when acetylated bR (instead of native bR) was used as a control and by weak bands observed at around 1610,cm,1 in the FTIR spectrum. The coverage of the resultant bR monolayer was significantly increased by changing the pH of the purple-membrane suspension from 9.2 to 6.8. Although bR, which is an exceptionally stable protein, showed a pronounced loss of its photoactivity in these bR monolayers, it retained full photoactivity after covalent binding to Br-terminated alkyls in solution. Several characterization methods, including atomic force microscopy (AFM), contact potential difference (CPD) measurements, and UV/Vis and Fourier transform infrared (FTIR) spectroscopy, verified that these bR monolayers behaved significantly different from native bR. Current,voltage (I,V) measurements (and optical absorption spectroscopy) suggest that the retinal chromophore is probably still present in the protein, whereas the UV/Vis spectrum suggests that it lacks the characteristic covalent protonated Schiff base linkage. This finding sheds light on the unique interactions of biomolecules with solid surfaces and may be significant for the design of protein-containing device structures. [source] ,-Cyclodextrin Incorporated Carbon Nanotube-coated Electrode for the Simultaneous Determination of Dopamine and EpinephrineCHINESE JOURNAL OF CHEMISTRY, Issue 3 2005Wang Ge-Yun Abstract An ,-cyclodextrin (,-CD) incorporated carbon nanotube (CNT)-coated electrode was fabricated and applied to the simultaneous determination of dopamine (DA) and epinephrine (EP). It has been found that the modified electrode shows strong catalytic effects on the electro-separation of DA and EP, and the cathodic potential difference between DA and EP is about 390 mV. The reducing peak current is proportional to DA and EP concentrations in the range of 2.0×10 -6,1.0×10 -3 and 1.0×10 -6,1.0×10 -3 mol·L -1, respectively. Their detection limits can reach 1×10 -6 and 5×10 -7 mol·L -1, respectively. Because the oxidation of ascorbic acid (AA) is an irreversible reaction in ,-CD/CNT film, the interference of AA in determination of DA and EP is eliminated. [source] Negotiating Personal and Cultural Significance: A Theoretical Framework for Art Museum EducationCURATOR THE MUSEUM JOURNAL, Issue 4 2007Olga M. Hubard This article presents a theoretical framework for those who facilitate engagements with works of art. The aim is to help facilitators negotiate potential differences between the original meaning(s) of an artwork and the fresh interpretations spectators articulate. The author applies Umberto Eco's ideas about literary texts to instances of interpretation in the visual arts. Eco suggests that the implications of unexpected readings change in different situations. Therefore, the facilitators' challenge is in discovering how to handle each individual encounter. To this end, facilitators may wish to ponder: What meaning does the new interpretation conflict with? And what is the distance between the cultural conventions of spectators and the conventions that framed the creation of the work? Real world examples are used to shed light on these questions and their significance. [source] Inhibitory functioning across ADHD subtypes: Recent findings, clinical implications, and future directionsDEVELOPMENTAL DISABILITIES RESEARCH REVIEW, Issue 4 2008Zachary W. Adams Abstract Although growing consensus supports the role of deficient behavioral inhibition as a central feature of the combined subtype of ADHD (ADHD/C; Barkley 1997 Psychol Bull 121:65,94; Nigg 2001 Psychol Bull 127:571,598), little research has focused on how this finding generalizes to the primarily inattentive subtype (ADHD/I). This question holds particular relevance in light of recent work suggesting that ADHD/I might be better characterized as a disorder separate from ADHD/C (Diamond 2005 Dev Psychopathol 17:807,825; Milich et al. 2001 Clin Psychol Sci Pract 8:463,488). This article describes major findings in the area of inhibitory performance in ADHD and highlights recent research suggesting important areas of divergence between the subtypes. In particular, preliminary findings point to potential differences between the subtypes with respect to how children process important contextual information from the environment, such as preparatory cues that precede responses and rewarding or punishing feedback following behavior. These suggestive findings are discussed in the context of treatment implications, which could involve differential intervention approaches for each subtype targeted to the specific deficit profiles that characterize each group of children. Future research avenues aimed toward building a sound theoretical model of ADHD/I and a better understanding of its relation to ADHD/C are also presented. Specifically, investigators are encouraged to continue studying the complex interplay between inhibitory and attentional processes, as this area seems particularly promising in its ability to improve our understanding of the potentially distinct pathologies underlying the ADHD subtypes. © 2008 Wiley-Liss, Inc. Dev Disabil Res Rev 2008;14:268,275. [source] Energy efficiency in gait, activity, participation, and health status in children with cerebral palsyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 3 2008Claire Kerr BSc (Hons) Physio PhD The aim of the study was to establish if a relationship exists between the energy efficiency of gait, and measures of activity limitation, participation restriction, and health status in a representative sample of children with cerebral palsy (CP). Secondary aims were to investigate potential differences between clinical subtypes and gross motor classification, and to explore other relationships between the measures under investigation. A longitudinal study of a representative sample of 184 children with ambulant CP was conducted (112 males, 72 females; 94 had unilateral spastic C P, 84 had bilateral spastic C P, and six had non-spastic forms; age range 4-17y; Gross Motor Function Classification System Level I, n=57; Level II, n=91; Level III, n=22; and Level IV, n=14); energy efficiency (oxygen cost) during gait, activity limitation, participation restriction, and health status were recorded. Energy efficiency during gait was shown to correlate significantly with activity limitations; no relationship between energy efficiency during gait was found with either participation restriction or health status. With the exception of psychosocial health, all other measures showed significant differences by clinical subtype and gross motor classification. The energy efficiency of walking is not reflective of participation restriction or health status. Thus, therapies leading to improved energy efficiency may not necessarily lead to improved participation or general health. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||