bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion Performance of SS-304L Exposed to LiBr-H2O Solution at 70{degree sign}C Applying the Electrochemical Noise Technique, Polarization Curves and Optical Transmitance Measurements.
Authors: Cuevas Cecilia , Castrellón Jesus , Trujillo Ariadna
Published: August 2007

A corrosion study of SS-304L was carried out exposing the material to LiBr-H2O solution 50% (wt.) at 70{degree sign}C for 20 days, applying the electrochemical noise technique and polarization curves. The aim of this work was to determine the corrosion rate and the type of corrosion of SS-304L. The corrosion evaluation was supported by optical observations of corroded specimens and EDX analysis of corrosion products. The dissolved corrosion products in LiBr solution were also analyzed by the atomic absorption technique. To obtain the corrosion rates, the noise resistance from ENT was calculated, and then the Stern-Geary equation and the Faraday Law were used. In general, the results of corrosion rates showed an oscillatory behavior, obtaining a cumulative mass loss of 6.11 mg/cm2. The electro-chemical signals showed important evidences of localized corrosion, showing significant transients of high magnitude, but also low amplitude and high frequency noise. The pitting indexes mainly lie in the mixed corrosion zone, being in agreement with visual observations of corroded samples. Optical transmittance measurements of corrosive solution with dissolved Fe, Cr, and Ni species are also presented.
Smart Nanoporous Membranes
Authors: Smirnov Sergei , Vlassiouk Ivan , Takmakov Pavel , Rios Fabian , Gust Devens
Published: August 2007

Ability to control ion current flow through membranes is important from the fundamental point of view and potentially has a broad range of practical applications including bichemical sensors. In this article we review our results on studying various response mechanisms (such as absorption, fluorescence, electrical conductance) in nanoporous alumina membranes modified with molecular monolayers that are responsive to different physical and chemical stimuli such as light, pressure, and analyte binding.
Electrochemical Response of BDD/IrOx in Presence of As (III), Sb (III), Pb (II) and Cd (II)
Authors: Davila Martin Marino Martin M. , Flores Maria S. , Elizalde Maria P. , Mattusch Juergen , Wennrich Rainer
Published: August 2007

In this work BDD electrode electrochemically modified with iridium oxide was utilized for simultaneous electrochemical measurements at micromolar-level concentrations of As, Sb, Cd and Pb standards for the study of their interferences. The influence of deposition potential of the metals on the anodic stripping voltammetry (ASV) and square-wave anodic stripping voltammetry (SWASV) was also studied with the aim to understand the possible detection of trace metals at the iridium oxide modified diamond electrode. The study showed that for the mixture solutions of Pb, Cd, Sb and As, the mutual interferences due to Pb-Cd, Cd-Sb and Sb-As depend on the type of the substrate and on the deposition time.
Kinetic and Adsorption Studies of Biogenic Amine Neurotransmitters at Polycrystalline Diamond Microelectrodes
Authors: Halpern Jeffrey M. , Xie Songtao , Schreiber Jessica L. , Martin Heidi B.
Published: August 2007

High sensitivity, 1-10 nM detection, of biogenic amine neurotransmitters was achieved using fast-scan cyclic voltammetry at hydrogen-terminated diamond microelectrodes. This reduced to 1-10 μM after 5-10 runs. To attempt to understand the sensitivity decrease, electron transfer kinetics, baseline current, and rate-limiting step for high (μM) and low (nM) concentrations were compared. Dopamine oxidation kinetics slowed after repeated scans, ΔEp increased from 0.142 to 0.805 V. Baseline current decreased by 50%. The rate-limiting step, measured only at the conditioned surface, was diffusion limiting. The high quality of our electrodes was verified by the voltage window in 0.5 M H2SO4 and by Raman spectroscopy. Dopamine and serotonin oxidation kinetics were characterized at more sensitive, sulfophenyl-terminated diamond microelectrodes; the responses were diffusion limited. These data were qualitatively consistent with surface chemistry changes after scanning, but do not adequately explain the sensitivity decrease. Additional testing of hydrogen- terminated surfaces is needed to provide insight.
Evolution of Surface Terminations and Electrochemical Behaviors of Boron Doped Diamond Electrodes Induced by Controlled Anodic and Cathodic Pretreatements
Authors: Simon Nathalie , Girard Hugues , Ballutaud Dominique , De la Rochefoucauld Emmanuel , Etcheberry Arnaud
Published: August 2007

This paper is concerned with the study of the influence of electrochemical pre-treatments on the behavior of highly boron doped diamond electrodes. Anodic and cathodic preconditioning performed either with 10-4 A.cm-2 or 10-1 A.cm-2, have been studied. Cyclic voltammetry at as-deposited, anodically and cathodically treated electrodes, in presence of 2 redox couples serving as electrochemical probes is analyzed in the light of the surface characterization given by XPS chemical analysis and wetting angle measurements. Ce4+/3+ and Fe(CN)63-/4- redox couples in 0.5 M H2SO4 medium, have been studied before and after the different treatments. The results of Mott-Schottky plots and current voltage curves are reported and show that the electrochemical response of BDD electrodes is very dependent on the current density involved in the process. The modification of surface bond termination studied by XPS analyses and contact angle measurements is also strongly dependent on electrochemical pre-treatment.
Characterization of Oxidized Reticulated Vitreous Carbon for Generation of H2O2 from Flowing Acid Solutions
Authors: Saleh Mahmoud M. , Awad Mohamed I. , Ohsaka Takeo
Published: August 2007

The oxidation of reticulated vitreous carbon (RVC) and its impact on the oxygen reduction reaction (ORR) in H2SO4 solutions has been studied and compared with that of a planar glassy carbon (GC) electrode. The oxidation process was characterized using different electrode configurations; GC (planar) and RVC electrodes both with flooded and flow-through assembly. Voltammetric techniques were used for the characterization of the ORR. Anodically oxidized GC and flooded RVC are similar in that the ORR on both electrodes gave a more defined limiting current plateau. For the flow- through porous electrode, the oxidation process caused a distribution of the oxidation extent within the bed thickness, as evident from the SEM images and X-ray photoelectron spectroscopy measurements, and only about half of the porous electrode was utilized in the oxidation process. Oxidation of RVC led to an enhancement of its electrocatalytic properties towards ORR. H2O2 production was tested at the oxidized RVC from flowing acid solutions. The oxidation of RVC resulted in higher current efficiencies and higher outlet concentrations of the H2O2 acid solutions.
Structural Factors Affecting the Reactivity of the Natural a-Hydroxy Benzoquinones. An electrochemical and ESR Study.
Authors: Frontana Carlos E. , González Ignacio
Published: August 2007

The electrochemical study of a series of natural occurring a- hydroxyquinones (2-hydroxy-1,4-naphthoquinone, Perezone, Horminone and 7a-O-methyl-Conacytone), revealed that a selfprotonation mechanism occurs at the first voltammetric reduction signal. The voltammetric analysis for this signal revealed a dependence of the structure of the chemical compound bearing the a-hydroxy-moiety in the reduction mechanism. However, the first electrogenerated radical anion disproportionates readily in solution, and it was not possible to analyze its structural properties by coupled electrochemical - ESR experiments. Nevertheless, since during the selfprotonation process an important amount of deprotonated quinone is produced, the spectroelectrochemical study at the second reduction process for this type of compounds showed well resolved ESR spectra, corresponding to the radical dianion structures. The differences in chemical behavior showed that the abietanic skeleton of natural occurring quinones Horminone and 7a-O-methyl-Conacytone induces changes in the spin structure which prove valuable in determining the stability and reactivity of the electrogenerated radical species.
Determination of Hydrogen Solubility Values in Some Human Fluids by Using an Electrochemical Sensor
Authors: Raposo Raquel R. , Calviño Elyn , Esteso Miguel A.
Published: August 2007

Hydrogen solubility data in some biological liquids (urine, serum and physiological saline solution) were experimentally determined by using an electrochemical sensor. Such solubility is expressed through the Bunsen empiric coefficient, alpha . Human beings produce H2 gas in the large intestine as a final product during the microbial fermentation of carbohydrates. This gas dissolves in the urine and can be quantitatively determined in this liquid since it is excreted by this way also. The gas removal rate fundamentally depends on its solubility in the different corporeal fluids.
Electrochemical Study of Methyl 2-[p-Nitrophenyl(Hydroxy)-Methyl] Acrylate, an Anticancer Drug, in the Presence of GSH and dsDNA
Authors: Goulart Marilia O. , de Souza Antonio A. , Sales Ecio M. , de Paula Francine S. , de Abreu Fabiane C. , Almeida Wanda P.
Published: August 2007

Electrochemical experiments (CV, DPV, SWV, CPE) with methyl 2- [p-nitrophenyl(hydroxy) methyl] acrylate (1) were performed in protic (EtOH + phosphate buffer 1:9, 0.1 mol L-1, pH 6.9 and EtOH + phosphate buffer: 1:9, 0.1 mol L-1, pH 9.4) and aprotic (DMF + TBAP, 0.1 mol L-1) media. The reduction behaviours were typical of nitroaromatics, with an additional wave, in aprotic medium, related to the reduction of the olefin. Electrolysis, in protic media, furnished a reduced dimer. The incubation of 1 into a dsDNA biosensor revealed, that, after reduction of the nitroaromatic function, diagnostic oxidation peaks of the nucleobases were observed, indicative of interaction between them. GSH influenced the reduction behaviour of 1. Direct reduction of 1, in phosphate buffer, pH 9.38, to a stable nitroso/GSH adduct is facilitated. These electrochemical results help in the understanding of the anticancer activity of 1 that can be considered a hypoxia targeted bioreductive agent with a glutathione depleting function.
Spectroelectrochemical Study of the Hemin - Glutathione Interaction in the Absence and Presence of Surfactants
Authors: Toader Ana M. , Diaconu Carmen , Volanschi Elena
Published: August 2007

The interaction of hemin with reduced glutathione (GSH) was studied using cyclic and linear sweep voltammetry with stationary and rotating disc electrodes and UV-VIS spectroelectrochemical experiments. A 1:1 global stoichiometry and similar values for the hemin - GSH binding constant were obtained in aqueous media in the presence of sodium dodecyl sulfate (SDS) with those in dimethylsulphoxide (DMSO). A comparison between the family of curves obtained during the electrochemical reduction of hemin with that recorded at the hemin - GSH interaction points to different absorption bands, leading to the idea of a complexation of the FeIII by GSH, rather than a Fe III → Fe II reduction. The biochemical relevance of the hemin-glutathione interaction is related to the presence of GSH in normal erythrocytes in high concentrations (1 - 4 mM), being involved as an agent in the trapping of free hemin from the cell cytosol.
Interaction of Antiprotozooal Drugs with Biomolecules. An ESR and UV-Vis Spectroelectrochemical Study.
Authors: Sanchez Urban Guadalupe Diana , Diaz de Leon-Luna Pedro , Bautista Martinez Jose Antonio A. , Frontana Carlos E. , Gonzalez I. , Aguilar-Martinez Martha
Published: August 2007

Cyclic voltammetric study in aprotic medium of antiprotozooal nitro compounds, Nifurtimox, Benznidazol and Niclosamide in the presence of glutathione and triolein, compounds that mimic the cellular constituents of the living being, were carried out in order to investigate the interactions of these compounds with the electrogenerated intermediaries in the reduction of the nitro compounds. Glutathione caused an important shift potential of the dianion radical (peak IIc) of nifurtimox and benznidazol and a minimum interaction with the radical anions (peak Ic). However, a significant change in the voltammetric behavior of nifurtimox was observed for both peaks Ic and IIc with triolein. Niclosamide presented more complicated responses. ESR experiments with nifurtimox showed that the nitro radical anion is interacting with triolein, even at very small concentrations.
Functional significance of channels and transporters expressed in the inner ear and kidney
Authors: Lang Florian , Vallon Volker , Knipper Marlies , Wangemann Philine
Published: August 2007

A number of ion channels and transporters are expressed in both the inner ear and kidney. In the inner ear, K+ cycling and endolymphatic K+, Na+, Ca2+, and pH homeostasis are critical for normal organ function. Ion channels and transporters involved in K+ cycling include K+ channels, Na+-2Cl−-K+ cotransporter, Na+/K+-ATPase, Cl− channels, connexins, and K+/Cl− cotransporters. Furthermore, endolymphatic Na+ and Ca2+ homeostasis depends on Ca2+-ATPase, Ca2+ channels, Na+ channels, and a purinergic receptor channel. Endolymphatic pH homeostasis involves H+-ATPase and Cl−/HCO3− exchangers including pendrin. Defective connexins (GJB2 and GJB6), pendrin (SLC26A4), K+ channels (KCNJ10, KCNQ1, KCNE1, and KCNMA1), Na+-2Cl−-K+ cotransporter (SLC12A2), K+/Cl− cotransporters (KCC3 and KCC4), Cl− channels (BSND and CLCNKA + CLCNKB), and H+-ATPase (ATP6V1B1 and ATPV0A4) cause hearing loss. All these channels and transporters are also expressed in the kidney and support renal tubular transport or signaling. The hearing loss may thus be paralleled by various renal phenotypes including a subtle decrease of proximal Na+-coupled transport (KCNE1/KCNQ1), impaired K+ secretion (KCNMA1), limited HCO3− elimination (SLC26A4), NaCl wasting (BSND and CLCNKB), renal tubular acidosis (ATP6V1B1, ATPV0A4, and KCC4), or impaired urinary concentration (CLCNKA). Thus, defects of channels and transporters expressed in the kidney and inner ear result in simultaneous dysfunctions of these seemingly unrelated organs.
Live cell imaging of interleukin-6-induced targeting of “transcription factor” STAT3 to sequestering endosomes in the cytoplasm
Authors: Xu Fang , Mukhopadhyay Somshuvra , Sehgal Pravin B.
Published: August 2007

Signal transducer and activator of transcription (STAT) family transcription factors are classically viewed as transducing cytokine- and growth factor-activated signals from the plasma membrane to the cell nucleus for the purpose of activating transcription. We report live cell imaging studies of fluorescently labeled STAT3 expressed in Hep3B hepatocytes that reveal interleukin (IL)-6-activated targeting of STAT3 and PY-STAT3 to relatively long-lived sequestering endosomes in the cytoplasm. This targeting was rapid but transient, required phosphorylation and integrity of Tyr 705 in STAT3, and was blocked by nocodazole, geldanamycin, and indirubin E804 and by overexpression of wild-type caveolin-1. Strikingly, overexpression of the dominant-negative (DN) mutant K44A of the GTPase dynamin II led to marked constitutive accumulation of STAT3 in the endocytic compartment with depletion of the STAT3 nuclear pool. Subsets of the native and K44A-generated STAT3- and PY-STAT3-sequestering endosomes colocalized with MyD88, an adapter protein that integrates pathways of Toll-like receptor and IL-1 transcriptional signaling and stabilization of mRNAs. These data provide direct evidence for the cytokine-induced “signal transduction” by STAT3 from the plasma membrane to a cytoplasmic membrane destination for yet to be elucidated function(s) in the cytoplasm including prolongation of signaling and/or cross talk.
Membrane-type-1 matrix metalloproteinase transcription and translation in myocardial fibroblasts from patients with normal left ventricular function and from patients with cardiomyopathy
Authors: Spruill Laura S. , Lowry Abigail S. , Stroud Robert E. , Squires Christina E. , Mains Ira M. , Flack English C. , Beck Christy , Ikonomidis John S. , Crumbley A. Jackson , McDermott Paul J. , Spinale Francis G.
Published: August 2007

Past studies have identified that a unique type of matrix metalloproteinase, the membrane-type-1 MMP (MT1-MMP), is increased within the left ventricle (LV) of patients with dilated cardiomyopathy (DCM). However, the cellular and molecular basis for this induction of MT1-MMP with DCM is unknown. LV myocardial biopsies from nonfailing, reference normal patients (defined as LV ejection fraction >50%, elective coronary bypass surgery, no perfusion defect at biopsy site, n = 6) and DCM patients (LV ejection fraction <20%, at transplant, n = 5) were used to establish fibroblast cultures (FIBROS). Confluent LV FIBROS from culture passages 2–5 were measured with respect to MT1-MMP mRNA and protein levels and the distribution of the MT1-MMP mRNA pool in ribosomal fractions. Total MT1-MMP mRNA within DCM FIBROS increased by over 140%, and MT1-MMP protein increased by over 190% from reference normal FIBROS (both P < 0.05). MT1-MMP mRNA in monosome fractions decreased by over twofold in DCM FIBROS compared with reference normal ( P < 0.05) and remained lower in polyribosomal fractions (i.e., 15.7 ± 5.2 vs. 1.4 ± 0.6% in polysomal fraction 6, P < 0.05). These differences in DCM MT1-MMP FIBROS transcription and translation persisted throughout passages 2–5. The unique findings from this study demonstrated that elevated steady-state MT1-MMP mRNA and protein levels occurred in DCM FIBROS despite a decline in translational deficiency. These phenotypic changes in DCM fibroblasts may provide the basis for developing cell specific pharmacological targets for control of MT1-MMP expression.
Oral polyamine administration modifies the ontogeny of hexose transporter gene expression in the postnatal rat intestine
Authors: Wild G. E. , Searles L. E. , Koski K. G. , Drozdowski L. A. , Begum-Hasan J. , Thomson A. B. R.
Published: August 2007

Gastrointestinal mucosal polyamines influence enterocyte proliferation and differentiation during small intestinal maturation in the rat. Studies in postnatal rats have shown that ornithine decarboxylase (ODC) protein and mRNA peak before the maximal expression of brush-border membrane (BBM) sucrase-isomaltase (SI) and the sugar transporters sodium-dependent glucose transporter 1 (SGLT1) and glucose transporter 2 (GLUT2). This study was undertaken to test the hypothesis that the oral administration of spermidine in postnatal rats upregulates the expression of ODC, thereby enhancing the expression of SI and SGLT1 in the brush-border membrane as well as basolateral membrane-facilitative GLUT2 and Na+-K+-ATPase. Northern and Western blot analyses were performed with antibodies and cDNA probes specific for SI, SGLT1, GLUT2, α1- and β1-subunits of Na+-K+-ATPase, and ODC. Postnatal rats fed 6 μmol spermidine daily for 3 days from days 7 to 9 were killed either on postnatal day 10 (Sp10) or day 13 following a 3-day washout period (Sp13). Sp10 rats showed a precocious increase in the abundance of mRNAs for SI, SGLT1, and GLUT2 and Na+-K+-ATPase activity and α1- and β1-isoform gene expression compared with controls. ODC activity and protein and mRNA abundance were also increased in Sp10 animals. The increased expression of these genes was not sustained in Sp13 rats, suggesting that these effects were transient. Thus, 3 days of oral polyamine administration induces the precocious maturation of glucose transporters in the postnatal rat small intestine, which may be mediated by alterations in ODC expression.11 Supplemental material for this article is available online at the American Journal of Physiology-Gastrointestinal and Liver Physiology website.
Intact female stroke-prone hypertensive rats lack responsiveness to mineralocorticoid receptor antagonists
Authors: Rigsby Christiné S. , Burch Ashley E. , Ogbi Safia , Pollock David M. , Dorrance Anne M.
Published: August 2007

Data from the Framingham Heart Study suggest that women may be more sensitive to the deleterious cardiovascular remodeling effects of aldosterone. Previous studies from our laboratory have shown that chronic treatment with spironolactone, a mineralocorticoid receptor (MR) antagonist, decreases ischemic cerebral infarct size and prevents remodeling of the middle cerebral artery (MCA) in male spontaneously hypertensive stroke-prone rats (SHRSP). Therefore, we hypothesized that MR antagonism would reduce ischemic infarct size and prevent MCA remodeling in female SHRSP. Six-week-old female SHRSP were treated for 6 wk with spironolactone (25 or 50 mg·kg−1·day−1) or eplerenone (100 mg·kg−1·day−1) and compared with untreated controls. At 12 wk, cerebral ischemia was induced for 18 h using the intraluminal suture occlusion technique, or the MCA was isolated for analysis of passive structure using a pressurized arteriograph. MR antagonism had no effect on infarct size or passive MCA structure in female SHRSP. To study the potential effects of estrogen, the above experiments were repeated in bilaterally ovariectomized (OVX) female SHRSP treated with spironolactone (25 mg·kg−1·day−1). Infarct size and vessel structure in OVX SHRSP were not different from control SHRSP. Spironolactone had no effect on infarct size in OVX SHRSP. However, MCA lumen and outer diameters were increased in spironolactone-treated OVX SHRSP, suggesting an effect of estrogen. Cerebral artery MR expression, assessed by Western blotting, was increased in female, compared with male, SHRSP. These studies highlight an apparent sexual dimorphism of MR expression and activity in the cerebral vasculature from hypertensive rats.
Distinct roles for renal particulate and soluble guanylyl cyclases in preserving renal function in experimental acute heart failure
Authors: Martin Fernando L. , Supaporn Thanom , Chen Horng H. , Sandberg Sharon M. , Matsuda Yuzuru , Jougasaki Michihisa , Burnett John C.
Published: August 2007

Worsening renal function in the setting of human acute heart failure (AHF) predicts poor outcomes, such as rehospitalization and increased mortality. Understanding potential renoprotective mechanisms is warranted. The guanylate cyclase (GC) enzymes and their second messenger cGMP are the target of two important circulating neurohumoral systems with renoprotective properties. Specifically, natriuretic peptides (NP) released from the heart with AHF target particulate GC in the kidney, while the nitric oxide (NO) system is an activator of renal soluble GC. We hypothesized that both systems are essential to preserve renal excretory and hemodynamic function in AHF but with distinct roles. We investigated these roles in three groups of anesthetized dogs (6 each) with AHF induced by rapid ventricular pacing. After a baseline AHF clearance, each group received intrarenal vehicle (control), NG-monomethyl-l-arginine (l-NMMA), a competitive NO inhibitor (50 μg·kg−1·min−1) or a specific NP receptor antagonist, HS-142-1 (0.5 mg/kg). We observed that intrarenal l-NMMA decreased renal blood flow (RBF) without significant decreases in glomerular filtration rate (GFR), urinary sodium excretion (UNaV), or urinary cGMP. In contrast, HS-142-1 resulted in a decrease in UNaV and cGMP excretion together with a reduction in GFR and an increase in distal fractional tubular sodium reabsorption. We conclude that in AHF, the NP system plays a role in maintaining sodium excretion and GFR, while the function of NO is in the maintenance of RBF. These studies have both physiological and therapeutic implications warranting further research into cardiorenal interactions in this syndrome of AHF.
Sodium self-inhibition of human epithelial sodium channel: selectivity and affinity of the extracellular sodium sensing site
Authors: Bize Vincent , Horisberger Jean-Daniel
Published: August 2007

The epithelial Na+channel (ENaC) is present in the apical membrane of “tight” epithelia in the distal nephron, distal colon, and airways. Its activity controls the rate of transepithelial sodium transport. Among other regulatory factors, ENaC activity is controlled by the concentration of extracellular Na+, a phenomenon named self-inhibition. The molecular mechanism by which extracellular Na+concentration is detected is not known. To investigate the properties of the extracellular Na+sensing site, we studied the effects of extracellular cations on steady-state amiloride-sensitive outward currents in Na+-loaded oocytes expressing human ENaC and compared them with self-inhibition of inward current after fast solution changes. About half of the inhibition of outward Na+currents was due to self-inhibition itself and the rest might be attributed to conduction site saturation. Self-inhibition by extracellular Li+was similar to that of Na+except for slightly slower kinetics. Ionic selectivity of the inhibition for steady-state outward current was Na+≥ Li+> K+. We estimated an apparent inhibitory constant ( KI) of ∼40 mM for extracellular Na+and Li+and found no evidence for a voltage dependence of the KI. Protease treatment induced the expected increase of the amiloride-sensitive current measured in high-Na+concentrations which was due, at least in part, to abolition of self-inhibition. These results demonstrate that both self-inhibition and saturation play a significant role in the inhibition of ENaC by extracellular Na+and that Na+and Li+interact in a similar way with the extracellular cation sensing site.
Descending vasa recta endothelia express inward rectifier potassium channels
Authors: Cao Chunhua , Lee-Kwon Whaseon , Payne Kristie , Edwards Aurélie , Pallone Thomas L.
Published: August 2007

Descending vasa recta (DVR) are capillary-sized microvessels that supply blood flow to the renal medulla. They are composed of contractile pericytes and endothelial cells. In this study, we used the whole cell patch-clamp method to determine whether inward rectifier potassium channels (KIR) exist in the endothelia, affect membrane potential, and modulate intracellular Ca2+ concentration ([Ca2+]cyt). The endothelium was accessed for electrophysiology by removing abluminal pericytes from collagenase-digested vessels. KIR currents were recorded using symmetrical 140 mM K+ solutions that served to maximize currents and eliminate cell-to-cell coupling by closing gap junctions. Large, inwardly rectifying currents were observed at membrane potentials below the equilibrium potential for K+. Ba2+ potently inhibited those currents in a voltage-dependent manner, with affinity k = 0.18, 0.33, 0.60, and 1.20 μM at −160, −120, −80, and −40 mV, respectively. Cs+ also blocked those currents with k = 20, 48, 253, and 1,856 μM at −160, −120, −80, and −40 mV, respectively. In the presence of 1 mM ouabain, increasing extracellular K+ concentration from 5 to 10 mM hyperpolarized endothelial membrane potential by 15 mV and raised endothelial [Ca2+]cyt. Both the K+-induced membrane hyperpolarization and the [Ca2+]cyt elevation were reversed by Ba2+. Immunochemical staining verified that both pericytes and endothelial cells of DVR express KIR2.1, KIR2.2, and KIR2.3 subunits. We conclude that strong, inwardly rectifying KIR2.x isoforms are expressed in DVR and mediate K+-induced hyperpolarization of the endothelium.
Hypoxia transduction by carotid body chemoreceptors in mice lacking dopamine D2 receptors
Authors: Prieto-Lloret J. , Donnelly D. F. , Rico A. J. , Moratalla R. , González C. , Rigual R. J.
Published: August 2007

Hypoxia-induced dopamine (DA) release from carotid body (CB) glomus cells and activation of postsynaptic D2 receptors have been proposed to play an important role in the neurotransmission process between the glomus cells and afferent nerve endings. To better resolve the role of D2 receptors, we examined afferent nerve activity, catecholamine content and release, and ventilation of genetically engineered mice lacking D2 receptors (D2−/− mice). Single-unit afferent nerve activities of D2−/− mice in vitro were significantly reduced by 45% and 25% compared with wild-type (WT) mice during superfusion with saline equilibrated with mild hypoxia (Po2 ∼50 Torr) or severe hypoxia (Po2 ∼20 Torr), respectively. Catecholamine release in D2−/− mice was enhanced by 125% in mild hypoxia and 75% in severe hypoxia compared with WT mice, and the rate of rise was increased in D2−/− mice. We conclude that CB transduction of hypoxia is still present in D2−/− mice, but the response magnitude is reduced. However, the ventilatory response to acute hypoxia is maintained, perhaps because of an enhanced processing of chemoreceptor input by brain stem respiratory nuclei.
Cross contamination of intramyocellular lipid signals through loss of bulk magnetic susceptibility effect differences in human muscle using 1H-MRSI at 4 T
Authors: Cui Min-Hui , Hwang Jong-Hee , Tomuta Vlad , Dong Zhengchao , Stein Daniel T.
Published: August 2007

Cross contamination of intramyocellular lipid (IMCL) signals through loss of bulk magnetic susceptibility (BMS) differences was detected in human muscles using proton magnetic resonance spectroscopic imaging (1H-MRSI) at 4 T by varying nominal voxel sizes on healthy subjects. In soleus muscle the IMCL content estimated in 1.00-ml-sized voxels was 15% and 30% higher than that in 0.25-ml voxels for nonobese ( P < 0.05) and obese ( P < 0.01) subjects, respectively, whereas no effect was observed on IMCL estimation in tibialis posterior (TP) and tibialis anterior (TA) regions for different voxel sizes. The unbiased 0.25-ml voxel size 1H-MRSI method was applied to measure IMCL content in nonobese sedentary (NOB-Sed), moderately trained (Ath), sedentary obese (OB), and Type 2 diabetic mellitus (DM) subjects. IMCL content in soleus was greatest in OB, with decreasing content in DM, Ath, and NOB-Sed, respectively (12.6 ± 1.6, 9.7 ± 1.8, 7.4 ± 1.0, 4.9 ± 0.5 mmol/kg wet wt; P < 0.05 by ANOVA; P < 0.05 OB vs. NOB-Sed or Ath). In TA, IMCL was equivalently elevated in DM and OB, which was higher than in Ath or NOB-Sed, respectively (4.2 ± 0.4 and 4.2 ± 0.7 vs. 2.7 ± 0.5 and 1.5 ± 0.3 mmol/kg wet wt; ANOVA, P < 0.05; P < 0.05 DM or OB vs. NOB-Sed). We conclude that IMCL content is overestimated when voxel size exceeds 0.25 ml despite measurement by optimized high-resolution 1H-MRSI at high field. When IMCL is measured unbiased by concomitant obesity, we find that it is strongly influenced by muscle type, training status, and the presence of obesity and Type 2 diabetes.
Decoding Visual Inputs From Multiple Neurons in the Human Temporal Lobe
Authors: Quiroga R. Quian , Reddy L. , Koch C. , Fried I.
Published: August 2007

We investigated the representation of visual inputs by multiple simultaneously recorded single neurons in the human medial temporal lobe, using their firing rates to infer which images were shown to subjects. The selectivity of these neurons was quantified with a novel measure. About four spikes per neuron, triggered between 300 and 600 ms after image onset in a handful of units (7.8 on average), predicted the identity of images far above chance. Decoding performance increased linearly with the number of units considered, peaked between 400 and 500 ms, did not improve when considering correlations among simultaneously recorded units, and generalized to very different images. The feasibility of decoding sensory information from human extracellular recordings has implications for the development of brain–machine interfaces.
Pharmacodynamic and pharmacokinetic study of chronic low-dose metronomic cyclophosphamide therapy in mice
Authors: Emmenegger Urban , Shaked Yuval , Man Shan , Bocci Guido , Spasojevic Ivan , Francia Giulio , Kouri Andrew , Coke Robert , Cruz-Munoz William , Ludeman Susan M. , Colvin O. Michael , Kerbel Robert S.
Published: August 2007

Prolonged, frequently administered low-dose metronomic chemotherapy (LDM) is being explored (pre)clinically as a promising antiangiogenic antitumor strategy. Although appealing because of a favorable side effect profile and mostly oral dosing, LDM involves new challenges different from conventional maximum tolerated dose chemotherapy. These include possible altered pharmacokinetic characteristics due to long-term drug exposure potentially resulting in acquired resistance and increased risk of unfavorable drug interactions. We therefore compared the antitumor and antivascular effects of LDM cyclophosphamide (CPA) given to mice that had been pretreated with either LDM CPA or normal saline, obtained blood 4-hydroxy-CPA (activated CPA) concentrations using either gas chromatography/mass spectrometry or liquid chromatography/tandem mass spectrometry in mice treated with LDM CPA, and measured hepatic and intratumoral activity of enzymes involved in the biotransformation of CPA and many other drugs [i.e., cytochrome P450 3A4 (CYP3A4) and aldehyde dehydrogenase]. Exposure of mice to LDM CPA for ≥8 weeks did not compromise subsequent activity of LDM CPA therapy, and biologically active 4-hydroxy-CPA levels were maintained during long-term LDM CPA administration. Whereas the effects on CYP3A4 were complex, aldehyde dehydrogenase activity was not affected. In summary, our findings suggest that acquired resistance to LDM CPA is unlikely accounted for by altered CPA biotransformation. In the absence of reliable pharmacodynamic surrogate markers, pharmacokinetic parameters might become helpful to individualize/optimize LDM CPA therapy. LDM CPA-associated changes of CYP3A4 activity point to a potential risk of unfavorable drug interactions when compounds that are metabolized by CYP3A4 are coadministered with LDM CPA. [Mol Cancer Ther 2007;6(8):2280–9]
Activation of a Nuclear Factor κB/Interleukin-1 Positive Feedback Loop by Amphiregulin in Human Breast Cancer Cells
Authors: Streicher Katie L. , Willmarth Nicole E. , Garcia Jose , Boerner Julie L. , Dewey T. Gregory , Ethier Stephen P.
Published: August 2007

We have recently shown that an amphiregulin-mediated autocrine loop is responsible for growth factor–independent proliferation, motility, and invasive capacity of some aggressive breast cancer cells, such as the SUM149 breast cancer cell line. In the present study, we investigated the mechanisms by which amphiregulin activation of the epidermal growth factor receptor (EGFR) regulates these altered phenotypes. Bioinformatic analysis of gene expression networks regulated by amphiregulin implicated interleukin-1α (IL-1α) and IL-1β as key mediators of amphiregulin's biological effects. The bioinformatic data were validated in experiments which showed that amphiregulin, but not epidermal growth factor, results in transcriptional up-regulation of IL-1α and IL-1β. Both IL-1α and IL-1β are synthesized and secreted by SUM149 breast cancer cells, as well as MCF10A cells engineered to express amphiregulin or MCF10A cells cultured in the presence of amphiregulin. Furthermore, EGFR, activated by amphiregulin but not epidermal growth factor, results in the prompt activation of the transcription factor nuclear factor–κB (NF-κB), which is required for transcriptional activation of IL-1. Once synthesized and secreted from the cells, IL-1 further activates NF-κB, and inhibition of IL-1 with the IL-1 receptor antagonist results in loss of NF-κB DNA binding activity and inhibition of cell proliferation. However, SUM149 cells can proliferate in the presence of IL-1 when EGFR activity is inhibited. Thus, in aggressive breast cancer cells, such as the SUM149 cells, or in normal human mammary epithelial cells growing in the presence of amphiregulin, EGFR signaling is integrated with NF-κB activation and IL-1 synthesis, which cooperate to regulate the growth and invasive capacity of the cells. (Mol Cancer Res 2007;5(8):847–62)
Endothelial-Dependent Mechanisms of Leukocyte Recruitment to the Vascular Wall
Authors: Rao Ravi M. , Yang Lin , Garcia-Cardena Guillermo , Luscinskas Francis W.
Published: August 2007

Inflammation is a fundamental process that protects organisms by removing or neutralizing injurious agents. A key event in the inflammatory response is the localized recruitment of various leukocyte subsets. Here we address the cellular and regulatory mechanisms of leukocyte recruitment to the vessel wall in cardiovascular disease and discuss our evolving understanding of the role of the vascular endothelium in this process. The vascular endothelium is the continuous single-cell lining of the cardiovascular system that forms a critical interface between the blood and its components on one side and the tissues and organs on the other. It is heterogeneous and has many synthetic and metabolic functions including secretion of platelet-derived growth factor, von Willebrand factor, prostacyclin, NO, endothelin-1, and chemokines and the expression of adhesion molecules. It also acts as a nonthrombogenic and selective permeable barrier. Endothelial cells also interact closely with the extracellular matrix and with adjacent cells including pericytes and smooth muscle cells within the vessel wall. A central question in vascular biology is the role of the endothelium in the initiation of inflammatory response, the extent of its “molecular conversations” with recruited leukocytes, and its influence on the extent and/or outcome of this response.
Translation and Comparison
Authors: Kontler László
Published: August 2007

This article attempts to refine the understanding of translation, thus contributing to evaluate its role in reception theory and in the history of ideas. A discussion of on the character, theories, and practices of translation in early-modern times is its entry point of analysis. During this period, what mattered in the first place was not the extent to which the translated text succeeded or failed in making the source text and its "original" ideas accessible in the target language, but rather the extent and the way in which the source text was instrumental in pursuing the agenda set by the translator or others in compliance with specific contexts. Such a perspective on translation seems also appropriate to current modes of inquiry for which translation is not an instance of inter-cultural communication, aiming to penetrate the Other in its fullness and make it intelligible in its otherness, but a communicative act whose purposes are predominantly intra-cultural and consist in supporting domestic agendas to which the translated text looks instrumental.
A Model of the Air–Sea Momentum Flux and Breaking-Wave Distribution for Strongly Forced Wind Waves
Authors: Kukulka Tobias , Hara Tetsu , Belcher Stephen E.
Published: August 2007

Under high-wind conditions, breaking surface waves likely play an important role in the air–sea momentum flux. A coupled wind–wave model is developed based on the assumption that in the equilibrium range of surface wave spectra the wind stress is dominated by the form drag of breaking waves. By conserving both momentum and energy in the air and also imposing the wave energy balance, coupled equations are derived governing the turbulent stress, wind speed, and the breaking-wave distribution (total breaking crest length per unit surface area as a function of wavenumber). It is assumed that smaller-scale breaking waves are sheltered from wind forcing if they are in airflow separation regions of longer breaking waves (spatial sheltering effect). Without this spatial sheltering, exact analytic solutions are obtained; with spatial sheltering asymptotic solutions for small- and large-scale breakers are derived. In both cases, the breaking-wave distribution approaches a constant value for large wavenumbers (small-scale breakers). For low wavenumbers, the breaking-wave distribution strongly depends on wind forcing. If the equilibrium range model is extended to the spectral peak, the model yields the normalized roughness length (Charnock coefficient) of growing seas, which increases with wave age and is roughly consistent with earlier laboratory observations. However, the model does not yield physical solutions beyond a critical wave age, implying that the wind input to the wave field cannot be dominated by breaking waves at all wavenumbers for developed seas (including field conditions).
Analysis of Supercritical Stratified Tidal Flow in a Scottish Fjord
Authors: Stashchuk Nataliya , Inall Mark , Vlasenko Vasiliy
Published: August 2007

The baroclinic tidal regime of the fjord Loch Etive (Scotland) is studied. Analysis is performed on the basis of both in situ data and numerical simulations, with the use of a fully nonlinear nonhydrostatic fine-resolution model. It was found that the crest of the sill that separates Loch Etive into inner and outer parts is subjected to a supercritical flow regime with maximum Froude numbers in excess of 5. Strong supercritical conditions lead to the formation of flow separation just above the sill’s crest. As is inherent to jet-type fjordic systems, this, in turn, leads to a weak nonlinear baroclinic wave response. On the other hand, observations and numerical results also revealed the presence of propagating internal tidal waves with amplitudes up to 10 m, several kilometers from the constriction. It is shown that these baroclinic tidal waves are excited during the ebb phase over a section of the inner flank of the sill, at a depth below 30 m, where the local Froude number is substantially less than unity. Thus Loch Etive simultaneously exhibits both weak nonlinear response due to strong supercritical conditions with flow separation over the sill and a significant linear baroclinic tidal response due to the deeper flank of the sill. In this respect, exhibiting both jet- and wave-type behavior, Loch Etive can be referred to as a “hybrid type” fjord: the authors suggest that many jet-type fjords will also generate a significant baroclinic response and should correctly fit into this new category.
Energy Transport by Nonlinear Internal Waves
Authors: Moum J. N. , Klymak J. M. , Nash J. D. , Perlin A. , Smyth W. D.
Published: August 2007

Winter stratification on Oregon’s continental shelf often produces a near-bottom layer of dense fluid that acts as an internal waveguide upon which nonlinear internal waves propagate. Shipboard profiling and bottom lander observations capture disturbances that exhibit properties of internal solitary waves, bores, and gravity currents. Wavelike pulses are highly turbulent (instantaneous bed stresses are 1 N m−2), resuspending bottom sediments into the water column and raising them 30+ m above the seafloor. The wave cross-shelf transport of fluid often counters the time-averaged Ekman transport in the bottom boundary layer. In the nonlinear internal waves that were observed, the kinetic energy is roughly equal to the available potential energy and is O(0.1) megajoules per meter of coastline. The energy transported by these waves includes a nonlinear advection term 〈uE〉 that is negligible in linear internal waves. Unlike linear internal waves, the pressure–velocity energy flux 〈up〉 includes important contributions from nonhydrostatic effects and surface displacement. It is found that, statistically, 〈uE〉 ≃ 2〈up〉. Vertical profiles through these waves of elevation indicate that up(z) is more important in transporting energy near the seafloor while uE(z) dominates farther from the bottom. With the wave speed c estimated from weakly nonlinear wave theory, it is verified experimentally that the total energy transported by the waves is 〈up〉 + 〈uE〉 ≃ c〈E〉. The high but intermittent energy flux by the waves is, in an averaged sense, O(100) watts per meter of coastline. This is similar to independent estimates of the shoreward energy flux in the semidiurnal internal tide at the shelf break.
Vertical Structure of Dissipation in the Nearshore
Authors: Feddersen Falk , Trowbridge J. H. , Williams A. J.
Published: August 2007

The vertical structure of the dissipation of turbulence kinetic energy was observed in the nearshore region (3.2-m mean water depth) with a tripod of three acoustic Doppler current meters off a sandy ocean beach. Surface and bottom boundary layer dissipation scaling concepts overlap in this region. No depth-limited wave breaking occurred at the tripod, but wind-induced whitecapping wave breaking did occur. Dissipation is maximum near the surface and minimum at middepth, with a secondary maximum near the bed. The observed dissipation does not follow a surfzone scaling, nor does it follow a “log layer” surface or bottom boundary layer scaling. At the upper two current meters, dissipation follows a modified deep-water breaking-wave scaling. Vertical shear in the mean currents is negligible and shear production magnitude is much less than dissipation, implying that the vertical diffusion of turbulence is important. The increased near-bed secondary dissipation maximum results from a decrease in the turbulent length scale.
Wave Breaking Dissipation in the Wave-Driven Ocean Circulation
Authors: Restrepo Juan M.
Published: August 2007

If wave breaking modifies the Lagrangian fluid paths by inducing an uncertainty in the orbit itself and this uncertainty on wave motion time scales is observable as additive noise, it is shown that within the context of a wave–current interaction model for basin- and shelf-scale motions it persists on long time scales. The model of McWilliams et al. provides the general framework for the dynamics of wave–current interactions. In addition to the deterministic part, the vortex force, which couples the total flow vorticity to the residual flow due to the waves, will have a part that is associated with the dissipative mechanism. At the same time the wave field will experience dissipation, and tracer advection is affected by the appearance of a dissipative term in the Stokes drift velocity. Consistency leads to other dynamic consequences: the boundary conditions are modified to take into account the diffusive process and proper mass/momentum balances at the surface of the ocean. In addition to formulating how a wave–current interaction model is modified by the presence of short-time events that induce dissipation, this study proposes a stochastic parameterization of dissipation. Its relation to other alternative parameterizations is given. Two focal reasons make stochastic parameterizations attractive: one can draw from extensive practical modeling experience in other fields, and it ties in a very natural way to a wealth of observational data via statistics.
The Influence of Racial Identity Profiles on the Relationship Between Racial Discrimination and Depressive Symptoms
Authors: Banks Kira Hudson , Kohn-Wood Laura P.
Published: August 2007

This study examined the association between racial identity profiles, discrimination, and mental health outcomes. African American college students (N = 194) completed measures of racial discrimination, racial identity, college hassles, and depressive symptoms. Four meaningful profiles emerged through a cluster analysis of seven dimensions of racial identity assessed using the Multidimensional Inventory of Black Identity (MIBI). Results suggested racial identity moderates the relation between discrimination and depressive symptoms. Students whose racial identity profile involves the goal of blending with the mainstream and focusing on shared human qualities rather than race as a core ideological concept had a significantly stronger association between racial discrimination and depressive symptoms. The results hold implications for investigating the experience of racial discrimination and conceptualization of racial identity.