bluuebunny/crossref_metadata_2025 huggingface dataset:
Behavioral Alterations in Arctic Char (Salvelinus alpinus) Briefly Exposed to Sublethal Chlorine Levels
Authors: Jones Keith A. , Hara Toshiaki J.
Published: November 2009

Changes in the locomotor behavior of Arctic char (Salvelinus alpinus) exposed inadvertently to sublethal chlorine concentrations (> 19μg total residual chlorine/L) for 6 d are described. Compared with their preexposure behavior, the char became hypoactive, much more strongly thigmotactic, and less responsive to a food extract during the exposure. After the high chlorine levels subsided, the char continued to be hypoactive for at least 1 wk and failed to respond positively to the food extract for 20 d. There is evidence that some individuals displayed chlorine stress behavior for at least 46 d after the return of nonstressful conditions.
A Stratified Random Transect Design for Acoustic Surveys of Fish Stocks
Authors: Jolly G. M. , Hampton I.
Published: November 2009

The differences between design-based and model-based inference are examined briefly and some recent applications of model-based procedures in fishery surveys are discussed. It is shown that valid estimates of mean and variance can be obtained by taking a stratified random sample, where the primary sampling units in each stratum are parallel transects randomly-spaced within certain non-critical limits. The strata are defined on the basis of the expected fish density or the expected variance in fish density within the region. Formulae are developed for the optimum allocation of transects to strata according to the density or variance in density within each stratum. To illustrate that such designs are entirely feasible, an example is given of a stratified random acoustic survey of South African anchovy (Engraulis capensis), in which the strata were defined on the basis of anchovy distribution encountered on previous surveys of the region. Through a two-phase approach, the transect allocation was adjusted during the survey for differences between the expected and observed distributions. It is demonstrated that in this survey, stratification, with uniform allocation of effort between strata, would have increased precision by an estimated factor of 2.4 compared with an unstratified random sample, while optimising effort within strata gave a further potential increase of 1.4. The coefficient of variation actually achieved was 16%
Metabolic Effects of Bovine Growth Hormone and Genetically Engineered Rainbow Trout Growth Hormone in Rainbow Trout (Oncorhynchus mykiss) Reared at a High Temperature
Authors: Danzmann Roy G. , Kraak Glen J. Van Der , Chen Thomas T. , Powers Dennis A.
Published: November 2009

The growth promoting ability of bovine growth hormone purified from natural sources (bGH) and genetically engineered rainbow trout growth hormone (rtGH) were compared in rainbow trout (Oncorhynchus mykiss) reared at 17.0 °C. Fish were fed high (on-demand feeding) and low (2.8–4.6% of body weight/d) rations. On both rations, length specific growth rates were significantly higher in bGH treated fish than in all other treatments. No significant differences in weight specific growth rates were detected between treatments. Testosterone levels in fish fed the high ration and treated with 1.0 μg/g rtGH or bGH were significantly elevated compared with controls as were 17-β-estradiol levels in females. bGH significantly reduced condition factors of low ration fish, and bGH and rtGH significantly depressed hepatosomatic indicies of high ration fish compared with controls. In a second experiment, weight and length specific growth rates were higher in rtGH and bGH injected fish than in saline controls but these differences were not significant. DNA standardized RNA levels were higher in rtGH and bGH treated fish than in saline control fish and these differences were significant in bGH treated fish. Results indicate that at high rearing temperatures GH administration does not have a major influence on growth but does stimulate steroidogenic and metabolic activity.
Pumping Rates, Water Pressures, and Oxygen Use in Eight Species of Marine Bivalve Molluscs from British Columbia
Authors: Bernard F. R. , Noakes D. J.
Published: November 2009

Pumping characteristics and oxygen utilization for Solemya reidi, Yoldia thraciaeformis, Chlamys hastata, Mytilus edulis, Crassostrea gigas, Clinocardium nuttallii, Saxidomus giganteus, and Mya truncata were studied. Pressures were recorded using a Yale A79 spinal tap needle inserted in the pallial cavity or siphonal aperture. Pumping volumes were determined through particulate analysis using a Model B Coulter counter and oxygen consumption by standard Winkler titration modified for small samples. The species chosen were selected to represent progressive increases in gill complexity and siphon length. The minimum pressure differential across the gill (20 Pa) was observed for Y. thraciaeformis while the maximum pressure gradient (600 Pa) was recorded for M. truncata. Pumping rates varied from 1.41 L∙h−1∙g−1 (Y. thraciaeformis) to 4.71 L∙h−1∙g−1 (C. hastata) and species with siphons tended to pump at lower rates. The deeply burrowing M. truncata consumed 3.5 times as much oxygen (0.63 mL O2∙h−1∙g−1) as S. reidi (0.18 mL O2∙h−1∙g−1) which inhabits anoxic environments. For all species, the metabolic cost of pumping was less than 1% of the total oxygen uptake.
Use of Extant Populations of Scaled Chrysophytes for the Inference of Lakewater pH
Authors: Siver Peter A. , Hamer Josephine S.
Published: November 2009

Abundance of living populations of scaled chrysophytes were used to develop multiple regression models for inferring lakewater pH. Until now, all such inference models had been prepared with surface sediment remains and used to reconstruct historical (down-core) changes. We demonstrate that highly significant models can be prepared from living populations of scaled-chrysophytes which could be valuable for monitoring chronic, episodic and/or long-term changes in lakewater pH. Average weighted-mean pH and a cluster analysis technique were used to divide 33 taxa found in 26 Connecticut lakes into groups according to their distribution along a pH gradient. Two calculations of average weighted-mean pH were made; one based on data from this study and one from literature records. Inference models were developed using a single sample from each lake as well as for multiple samples collected throughout the year. The best model based on a single discrete sample yielded an R2 = 0.58 (p < 0.05); multiple samples from each lake yielded significantly higher R2 values, (between 0.75 and 0.83). Scaled chrysophytes appear to be a very valuable assemblage of indicator organisms for the long-term monitoring of lakes.
A Possible Eddy Retention Mechanism for Ichthyoplankton in Hecate Strait
Authors: Crawford William R. , Tyler Albert V. , Thomson Richard E.
Published: November 2009

The cause of the high rate of production of groundfish in Hecate Strait is uncertain. It is likely that the large, shallow areas of the Strait contribute to the high productivity because of their suitability as juvenile habitat. In winter, however, when many groundfish species spawn, a strong current flows northward through the Strait into Dixon Entrance and likely carries many of the pelagic larvae out of the Strait. A recent study shows that the recruitment rate of Pacific cod varies inversely with this current, which is to be expected if the larvae are swept out of the Strait by the flow. We examine current and wind data from a variety of field programs in Hecate Strait, and find evidence for a return flow toward the southwest in Hecate Strait, counter to the wind-driven transport. This return flow is driven by the set-up of sea level along the Strait by the wind, and its strength increases with the intensity of southeast storm winds. We believe the return flow will recirculate a significant fraction of the larvae in the Strait, increasing their residence time sufficiently to allow settling out, thus enhancing recruitment.
Impact of Ice Algae on Inorganic Nutrients in Seawater and Sea Ice in Barrow Strait, NWT, Canada, During Spring
Authors: Cota Glenn F. , Anning Jeffrey L. , Harris Leslie R. , Harrison W. Glen , Smith Ralph E. H.
Published: November 2009

Except in "bottom ice" (lowest few centimetres) and surface waters impacted by autotrophs, the major inorganic nutrients behave conservatively in seawater and sea ice. From mid- to late spring, steep and persistent nutrient gradients were observed in the "well-mixed surface layer" with minima near the ice–water interface. Nitrate, ammonium, and phosphate are highly concentrated in heavily colonized bottom ice relative to seawater and the remainder of the ice sheet; concentrations in darkened, weakly colonized bottom ice are similar to the ice sheet. These nutrients also display strong vertical stratification over millimetre scales. Nitrate and phosphate in the bottom ice layer display strong positive relationships with chlorophyll. The accumulation of these nutrients in bottom ice must be biologically mediated and constitutes a significant sink. In contrast, silicic acid concentrations in bottom ice are close to those expected for sea ice formed from the source seawater, are only weakly related to algal biomass, and vary much less seasonally. Ice algae are apparently shocked osmotically and release their intracellular pools of dissolved nutrients. Intracellular pools of nitrate averaged 1.4–9.5% of total particulate nitrogen. Nitrient stresses, during periods of high biomass and sluggish supply, may be alleviated by pooling.
Interpretable Statistical Tests for Growth Comparisons using Parameters in the von Bertalanffy Equation
Authors: Cerrato Robert M.
Published: November 2009

Likelihood ratio, t-, univariate χ2-, and T2-tests have been proposed to compare von Bertalanffy parameters among stocks. As commonly applied, all of these tests are approximate, with the accuracy of each dependent on the nonlinearity of the von Bertalanffy equation, sample size, and if present, the degree of heterogeneity in the error variances. An empirical comparison of these procedures shows that the likelihood ratio test often differs in outcome from the others. Analysis of the conflicting cases by confidence region comparisons and Monte Carlo simulations almost always resolved the outcome in favor of the likelihood ratio test. The parameter effects component of nonlinearity was found to be the principal factor biasing the t-, univariate χ2-, and T2-tests. Reparameterizations of the von Bertalanffy equation substantially reduced, but did not completely eliminate, conflicting outcomes. It is concluded that the likelihood ratio test is the most accurate of the procedures considered in this study, and whenever possible, it should be the approach of choice.
Influence of Upwellings, Storms, and Generating Station Operation on Water Chemistry and Plankton in the Nanticoke Region of Long Point Bay, Lake Erie
Authors: Dunstall T. G. , Carter J. C. H. , Monroe B. P. , Haymes G. T. , Weiler R. R. , Hopkins G. J.
Published: November 2009

Storms and upwellings resulted in significant alterations to the aquatic environment in the Long Point Bay region of Lake Erie, contributing to short-term variability in water chemistry and plankton. Both storms and upwellings resulted in nutrient enrichment (filtered reactive phosphorus, total inorganic nitrogen, reactive silicates and organic nitrogen) in lake surface waters during the period of lake warming, prior to mid-August. Storms and upwellings also differentially affected the distributions of specific zooplankton taxa in the lake surface stratum. The most prominent effect was the increased abundance of Diacyclops bicuspidatus thomasi during upwellings, particularly towards shore. The once-through cooling process of the generating station also affected zooplankton distributions, most notably that of D. bicuspidatus thomasi, with a nearshore increase in abundance that was similar to the influence exerted by upwelling.
An Errors-In-Variables Bias Model with an Application to Salmon Hatchery Data
Authors: Schnute J. T. , Mulligan T. J. , Kuhn B. R.
Published: November 2009

This paper presents an errors-in-variables (EV) model for assessing differences between two measurements of the same phenomenon, where each measurement is subject to error. The model, equivalent to a classical EV model, specifically includes parameters associated with the relative bias between the two measurements. We derive a complete statistical theory for this errors-in-variables bias (EVB) model, including analytical formulas for confidence intervals that are exact when the error lies in one variable alone and approximate otherwise. The model is used to compare two methods of estimating the number of salmon that return to their hatchery of origin. One method involves direct counting, while the other is based on fish marked with coded wire tags (CWTs). We conclude that, for coho (Oncorhynchus kisutch) and chinook (Oncorhynchus tshawytscha) hatcheries in British Columbia, Canada, estimates from CWTs are, on average, 22% lower than comparable counting estimates.
SPONTANEOUS SYMMETRY BREAKDOWN IN FUZZY SPHERES
Authors: DAS C. R. , DIGAL S. , GOVINDARAJAN T. R.
Published: November 2009

We study and analyse the questions regarding breakdown of global symmetry on noncommutative sphere. We demonstrate this by considering a complex scalar field on a fuzzy sphere and isolating Goldstone modes. We discuss the role of nonlocal interactions present in these through geometrical considerations.
DIRECT PHOTON PRODUCTION IN d+A AND A+A COLLISIONS AT RHIC
Authors: ZHANG BEN-WEI , VITEV IVAN
Published: November 2009

Direct photon production in minimum bias d+Cu and d+Au and central Cu+Cu and Au+Au collisions at center-of-mass energies [Formula: see text] and 200 GeV at RHIC is systematically investigated. We study the jet quenching effect, the medium-induced photon bremsstrahlung and jet-photon conversion in the hot QGP. We account for known cold nuclear matter effects, such as the isospin effect,the Cronin effect, shadowing and cold nuclear matter energy loss. It is shown that at high pT the nuclear modification factor for direct photons [Formula: see text] is dominated by cold nuclear matter effects and there is no evidence for large cross-section amplification due to medium-induced photon bremsstrahlung and jet-photon conversion in the medium. Comparison of numerical simulations to experimental data also rules out large Cronin enhancement and incoherent photon emission in the QGP but the error bars in the current experimental data cannot provide further constraints on the magnitudes of other nuclear matter effects.
ON EQUIVALENCE OF TWO HURWITZ MATRIX MODELS
Authors: MOROZOV A. , SHAKIROV SH.
Published: November 2009

In Ref. 1 a matrix model representation was found for the simplest Hurwitz partition function, which has Lambert curve ϕe-ϕ= ψ as a classical equation of motion. We demonstrate that Fourier–Laplace transform in the logarithm of external field Ψ converts it into a more sophisticated form, recently suggested in Ref. 2.
QUANTUM CURRENT MAGNIFICATION EFFECTS FOR MUTUAL INDUCTANCES: THERMODYNAMIC CONSIDERATIONS
Authors: FLORES J. C.
Published: November 2009

The robustness of quantum electrical current magnification in the face of thermodynamical decoherence is studied. Thermodynamical calculations for the specific heat, internal energy and electrical current suggest that magnification is decimated by temperature. The range of validity of the phenomenon is at order of the equivalent spectral band. With respect to the Milburn theory of decoherence, electrical current magnification is robust. Moreover, magnification phenomenon is widely exhibited in a large variety of quantum circuits and a wide variety of experimental setups can be envisaged.
INFLUENCE OF SAMARIUM SUBSTITUTION ON DIELECTRIC PROPERTIES OF BARIUM TITANATE BASED CERAMICS
Authors: KUMAR PARVEEN , SINGH SANGEETA , JUNEJA J. K. , PRAKASH CHANDRA , RAINA K. K.
Published: November 2009

In this paper we report samarium substituted Ba 0.80 Pb 0.20 Ti 0.90 Zr 0.10 O 3 (BPZT) ceramics. The material series with compositional formula Ba 0.80-x Sm x Pb 0.20 Ti 0.90 Zr 0.10 O 3 with x varying from 0 to 0.01 in the steps of 0.0025 was chosen for investigations. The material was synthesized by solid state reaction method. Reacted powders compacted in the form of circular discs were sintered at 1325°C. All the samples were subjected to X-ray analysis and found to be single phase. Dielectric behavior was studied as a function of frequency and temperature and Curie temperature (Tc) was determined. Tc was found to decrease with increasing x. The details are discussed and presented here.
APPLICATION OF IMPROVED AMPLITUDE-FREQUENCY FORMULATION TO NONLINEAR DIFFERENTIAL EQUATION OF MOTION EQUATIONS
Authors: DAVODI A. G. , GANJI D. D. , AZAMI R. , BABAZADEH H.
Published: November 2009

This paper presents an approach for solving accurate approximate analytical solutions for strong nonlinear oscillators called improved amplitude-frequency formulation. For illustrating the accuracy of the method, we also solved equations with He's energy balance method and compared results. New algorithms offer promising approaches, which are useful for nonlinear oscillations. We find that these attained solutions not only benefit from a high degree of accuracy, but are also uniformly valid in the whole solution domain which is so simple to do and effective. The studied equations are the general motion equation and the non-dimensional nonlinear differential equation of motion for the relativistic oscillator, which their solution can be useful for researchers to extend this ability into their other works.
CLASSICAL FLUID DYNAMICS UNDER MOLECULAR SCALE CONFINEMENT
Authors: PERCUS J. K.
Published: November 2009

This is a review of some recent developments in the theory of classical nanoscale fluid dynamics, with tagged particle dynamics as the signature of transport properties. A heuristic analysis of the time asymptotic regime in strictly one-dimensional flow is followed by an exact treatment of the same system, with arbitrary non-interacting point particle dynamics. Stretched time and space coordinates allow us to obtain a universal form — the telegrapher's equation — for the self-dynamics after transients have died down. Attention then shifts to one-particle diffusion in a spatially modulated tubular enclosure, which is analyzed by increasingly sophisticated approximation methods. With this background, single-file fluid flow in modulated enclosures is studied, and preliminary analysis of the "passing region" carried out as well.
DYNAMIC BACKGROUND SUBTRACTION BASED ON LOCAL DEPENDENCY HISTOGRAM
Authors: ZHANG SHENGPING , YAO HONGXUN , LIU SHAOHUI
Published: November 2009

Traditional background subtraction methods perform poorly when scenes contain dynamic backgrounds such as waving tree branches, spouting fountain, illumination changes, camera jitters, etc. In this paper, from the view of spatial context, we present a novel and effective dynamic background method with three contributions. First, we present a novel local dependency descriptor, called local dependency histogram (LDH), to effectively model the spatial dependencies between a pixel and its neighboring pixels. The spatial dependencies contain substantial evidence for differentiating dynamic background regions from moving objects of interest. Second, based on the proposed LDH, an effective approach to dynamic background subtraction is proposed, in which each pixel is modeled as a group of weighted LDHs. Labeling a pixel as foreground or background is done by comparing the LDH computed in current frame against its model LDHs. The model LDHs are adaptively updated by the current LDH. Finally, unlike traditional approaches using a fixed threshold to judge whether a pixel matches to its model, an adaptive thresholding technique is also proposed. Experimental results on a diverse set of dynamic scenes validate that the proposed method significantly outperforms traditional methods for dynamic background subtraction.
ARGOS — A VIDEO SURVEILLANCE SYSTEM FOR BOAT TRAFFIC MONITORING IN VENICE
Authors: BLOISI DOMENICO , IOCCHI LUCA
Published: November 2009

Visual surveillance in dynamic scenes is currently one of the most active research topics in computer vision, many existing applications are available. However, difficulties in realizing effective video surveillance systems that are robust to the many different conditions that arise in real environments, make the actual deployment of such systems very challenging.

In this article, we present a real, unique and pioneer video surveillance system for boat traffic monitoring, ARGOS. The system runs continuously 24 hours a day, 7 days a week, day and night in the city of Venice (Italy) since 2007 and it is able to build a reliable background model of the water channel and to track the boats navigating the channel with good accuracy in real-time. A significant experimental evaluation, reported in this article, has been performed in order to assess the real performance of the system.
FAST TRACKING OF OBJECT CONTOUR BASED ON COLOR AND TEXTURE
Authors: CAI LING , GE CHENG , ZHAO YU-MING , YANG XIN
Published: November 2009

This paper presents an efficient algorithm to track the object contour in image sequences. Firstly, the probability distributions of color feature and texture feature are approximated by different schemes. Secondly, the object and the background pixels are distinguished by calculating their posterior probability in light of Bayesian formula based on the two models. Finally, an energy functional is proposed and solved by gradient descent flow to evolve the initial contour which is estimated by motion feature, so that minimum energy contour corresponds to the object contour. In order to save the computational resource, a new texture descriptor is applied to analyze pixels merely in the neighborhood of a contour rather than the whole image. Furthermore, the algorithm's implementation based on the narrow band level set scheme can help to reduce the processing time further. In some experiments, the contours of various objects such as human, car and body organ are successfully tracked by our algorithm and the processing time is short enough for practical application.
STOCHASTIC GALERKIN DISCRETIZATION OF THE LOG-NORMAL ISOTROPIC DIFFUSION PROBLEM
Authors: GITTELSON C. J.
Published: November 2009

The stochastic Galerkin method is developed for the isotropic diffusion equation with an unbounded random diffusion coefficient. The logarithm of the diffusion coefficient is assumed to be an infinite series of Gaussian random variables.

Well-posed weak formulations of the model problem are derived on standard Bochner–Lebesgue spaces. The Galerkin solution is shown to be almost quasi-optimal in the sense that the error of the Galerkin projection can be estimated by a best approximation error in a slightly stronger norm. As a result, convergence analysis of the stochastic Galerkin method is reduced to the problem of approximating the Hermite coefficients of the exact solution by standard finite elements.
Mechanisms of disease pathogenesis in long QT syndrome type 5
Authors: Harmer Stephen C. , Wilson Andrew J. , Aldridge Robert , Tinker Andrew
Published: November 2009

KCNE1 associates with the pore-forming α-subunit KCNQ1 to generate the slow ( IKs) current in cardiac myocytes. Mutations in either KCNQ1 or KCNE1 can alter the biophysical properties of IKs and mutations in KCNE1 underlie cases of long QT syndrome type 5 (LQT5). We previously investigated a mutation in KCNE1, T58P/L59P, which causes severe attenuation of IKs. However, how T58P/L59P acts to disrupt IKs has not been determined. In this study, we investigate and compare the effects of T58P/L59P with three other LQT5 mutations (G52R, S74L, and R98W) on the biophysical properties of the current, trafficking of KCNQ1, and assembly of the IKs channel. G52R and T58P/L59P produce currents that lack the kinetic behavior of IKs. In contrast, S74L and R98W both produce IKs-like currents but with rightward shifted voltage dependence of activation. All of the LQT5 mutants express protein robustly, and T58P/L59P and R98W cause modest, but significant, defects in the trafficking of KCNQ1. Despite defects in trafficking, in the presence of KCNQ1, T58P/L59P and the other LQT5 mutants are present at the plasma membrane. Interestingly, in comparison to KCNE1 and the other LQT5 mutants, T58P/L59P associates only weakly with KCNQ1. In conclusion, we identify the disease mechanisms for each mutation and reveal that T58P/L59P causes disease through a novel mechanism that involves defective IKs complex assembly.
Extracellular osmolarity modulates G protein-coupled receptor-dependent ATP release from 1321N1 astrocytoma cells
Authors: Blum Andrew E. , Corbett Walsh B. , Dubyak George R.
Published: November 2009

We previously reported that ATP release from 1321N1 human astrocytoma cells could be stimulated either by activation of G protein-coupled receptors (GPCR) or by hypotonic stress. Cheema et al. (Cheema TA, Ward CE, Fisher SK. J Pharmacol Exp Ther 315: 755–763, 2005) have demonstrated that thrombin activation of protease-activated receptor 1 (PAR1) in 1321N1 cells and primary astrocytes acts synergistically with hypotonic stress to gate the opening of volume-sensitive organic osmolyte and anion channels (VSOAC) and that hypertonic stress strongly inhibits PAR1 gating of VSOAC. We tested the hypothesis that a VSOAC-type permeability might comprise a GPCR-regulated pathway for ATP export by determining whether PAR1-sensitive ATP release from 1321N1 cells is similarly potentiated by hypotonicity but suppressed by hypertonic conditions. Strong hypotonic stress by itself elicited ATP release and positively modulated the response to thrombin. Thrombin-dependent ATP release was also potentiated by mild hypotonic stress that by itself did not stimulate ATP export. Notably, PAR1-sensitive ATP export was greatly inhibited in hypertonic medium. Neither the potency nor efficacy of thrombin as an activator of proximal PAR1 signaling was affected by hypotonicity or hypertonicity. 1,9-Dideoxyforskolin and carbenoxolone similarly attenuated PAR1-dependent ATP release and suppressed the PAR1-independent ATP elicited by strong hypotonic stress. Probenecid attenuated PAR1-stimulated ATP release under isotonic but not mild hypotonic conditions and had no effect on PAR1-independent release stimulated by strong hypotonicity. PAR1-dependent ATP export under all osmotic conditions required concurrent signaling by Ca2+ mobilization and Rho-GTPase activation. In contrast, PAR1-independent ATP release triggered by strong hypotonicity required neither of these intracellular signals. Thus, we provide the new finding that GPCR-regulated ATP release from 1321N1 astrocytoma cells is remarkably sensitive to both positive and negative modulation by extracellular osmolarity. This supports a model wherein GPCR stimulation and osmotic stress converge on an ATP release pathway in astrocytes that exhibits several features of VSOAC-type channels.
The GPA-dependent, spherostomatocytosis mutant AE1 E758K induces GPA-independent, endogenous cation transport in amphibian oocytes
Authors: Stewart Andrew K. , Vandorpe David H. , Heneghan John F. , Chebib Fouad , Stolpe Kathleen , Akhavein Arash , Edelman E. Jennifer , Maksimova Yelena , Gallagher Patrick G. , Alper Seth L.
Published: November 2009

The previously undescribed heterozygous missense mutation E758K was discovered in the human AE1/SLC4A1/band 3 gene in two unrelated patients with well-compensated hereditary spherostomatocytic anemia (HSt). Oocyte surface expression of AE1 E758K, in contrast to that of wild-type AE1, required coexpressed glycophorin A (GPA). The mutant polypeptide exhibited, in parallel, strong GPA dependence of DIDS-sensitive 36Cl− influx, trans-anion-dependent 36Cl− efflux, and Cl−/HCO3− exchange activities at near wild-type levels. AE1 E758K expression was also associated with GPA-dependent increases of DIDS-sensitive pH-independent SO42− uptake and oxalate uptake with altered pH dependence. In marked contrast, the bumetanide- and ouabain-insensitive 86Rb+ influx associated with AE1 E758K expression was largely GPA-independent in Xenopus oocytes and completely GPA-independent in Ambystoma oocytes. AE1 E758K-associated currents in Xenopus oocytes also exhibited little or no GPA dependence. 86Rb+ influx was higher but inward cation current was lower in oocytes expressing AE1 E758K than previously reported in oocytes expressing the AE1 HSt mutants S731P and H734R. The pharmacological inhibition profile of AE1 E758K-associated 36Cl− influx differed from that of AE1 E758K-associated 86Rb+ influx, as well as from that of wild-type AE1-mediated Cl− transport. Thus AE1 E758K-expressing oocytes displayed GPA-dependent surface polypeptide expression and anion transport, accompanied by substantially GPA-independent, pharmacologically distinct Rb+ flux and by small, GPA-independent currents. The data strongly suggest that most of the increased cation transport associated with the novel HSt mutant AE1 E758K reflects activation of endogenous oocyte cation permeability pathways, rather than cation translocation through the mutant polypeptide.
Calcineurin activates interleukin-6 transcription in mouse skeletal muscle in vivo and in C2C12myotubes in vitro
Authors: Allen David L. , Uyenishi Jill J. , Cleary Allison S. , Mehan Ryan S. , Lindsay Sarah F. , Reed Jason M.
Published: November 2009

Expression of the cytokine interleukin-6 (IL-6) by skeletal muscle is hugely increased in response to a single bout of endurance exercise, and this appears to be mediated by increases in intracellular calcium. We examined the effects of endurance exercise on IL-6 mRNA levels and promoter activity in skeletal muscle in vivo, and the role of the calcium-activated calcineurin signaling pathway on muscle IL-6 expression in vivo and in vitro. IL-6 mRNA levels in the mouse tibialis anterior (TA) were increased 2–10-fold by a single bout of treadmill exercise or by 3 days of voluntary wheel running. Moreover, an IL-6 promoter-driven luciferase transgene was activated in TA by both treadmill and wheel-running exercise and by injection with a calcineurin plasmid. Exercise also increased muscle mRNA expression of the calcineurin regulatory gene MCIP1, as did treatment of C2C12myotubes with the calcium ionophore A23187. Cotransfection of C2C12myotubes with a constitutively active calcineurin construct significantly increased while cotransfection with the calcineurin inhibitor CAIN inhibited activity of a mouse IL-6 promoter-reporter construct. Cotransfection with a myocyte enhancer-factor-2 (MEF-2) expression construct increased basal IL-6 promoter activity and augmented the effects of calcineurin cotransfection, while cotransfection with the MEF-2 antagonist MITR repressed calcineurin-activated IL-6 promoter activity in vitro. Surprisingly, cotransfection with a dominant-negative form of another calcineurin-activated transcription factor, nuclear factor activator of T cells (NFAT), greatly potentiated both basal and calcineurin-stimulated IL-6 promoter activity in C2C12myotubes. Mutation of the MEF-2 DNA binding sites attenuated, while mutation of the NFAT DNA binding sites potentiated basal and calcineurin-activated IL-6 promoter activity. Finally, CREB and C/EBP were necessary for basal IL-6 promoter activity and sufficient to increase IL-6 promoter activity but had minimal roles in calcineurin-activated IL-6 promoter activity. Together, these results suggest that IL-6 transcription in skeletal muscle cells can be activated by a calcineurin-MEF-2 axis which is antagonized by NFAT.
CFTR mediates apoptotic volume decrease and cell death by controlling glutathione efflux and ROS production in cultured mice proximal tubules
Authors: l'Hoste Sebastien , Chargui Abderrahmen , Belfodil Radia , Corcelle Elisabeth , Duranton Christophe , Rubera Isabelle , Poujeol Chantal , Mograbi Baharia , Tauc Michel , Poujeol Philippe
Published: November 2009

We have previously shown that despite the presence of mRNA encoding CFTR, renal proximal cells do not exhibit cAMP-sensitive Cl−conductance (Rubera I, Tauc M, Bidet M, Poujeol C, Cuiller B, Watrin A, Touret N, Poujeol P. Am J Physiol Renal Physiol 275: F651–F663, 1998). Nevertheless, in these cells, CFTR plays a crucial role in the control of the volume-sensitive outwardly rectifying (VSOR) activated Cl−currents during hypotonic shock. The aim of this study was to determine the role of CFTR in the regulation of apoptosis volume decrease (AVD) and the apoptosis phenomenon. For this purpose, renal cells were immortalized from primary cultures of proximal convoluted tubules from cftr+/+and cftr−/−mice. Apoptosis was induced by staurosporine (STS; 1 μM). Cell volume, Cl−conductance, caspase-3 activity, intracellular level of reactive oxygen species (ROS), and glutathione content (GSH/GSSG) were monitored during AVD. In cftr+/+cells, AVD and caspase-3 activation were strongly impaired by conventional Cl−channel blockers and by a specific CFTR inhibitor (CFTRinh-172; 5 μM). STS induced activation of CFTR conductance within 15 min, which was progressively replaced by VSOR Cl−currents after 60 min of exposure. In parallel, STS induced an increase in ROS content in the time course of VSOR Cl−current activation. This increase was impaired by CFTRinh-172 and was not observed in cftr−/−cells. Furthermore, the intracellular GSH/GSSG content decreased during STS exposure in cftr+/+cells only. In conclusion, CFTR could play a key role in the cascade of events leading to apoptosis. This role probably involves control of the intracellular ROS balance by some CFTR-dependent modulation of GSH concentration.
Simvastatin and tempol protect against endothelial dysfunction and renal injury in a model of obesity and hypertension
Authors: Knight Sarah F. , Yuan Jianghe , Roy Siddhartha , Imig John D.
Published: November 2009

Obesity and hypertension are risk factors for the development of chronic kidney disease. The mechanisms by which elevated blood pressure and fatty acids lead to the development of renal injury are incompletely understood. Here, we investigated the contributions of cholesterol and oxidative stress to renal endothelial dysfunction and glomerular injury in a model of obesity and hypertension. Male Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were fed a normal diet, a high-fat diet, a high-fat diet with tempol, or a high-fat diet with simvastatin for up to 10 wk. Blood pressure was not altered by a high-fat diet or treatments. After 3 wk, renal afferent dilatory responses to acetylcholine were impaired in WKY rats and SHR fed a high-fat diet. Tempol treatment prevented this vascular dysfunction in both strains; however, simvastatin treatment demonstrated greater beneficial effects in the SHR. Albuminuria was observed in the SHR and was exacerbated by a high-fat diet. Tempol and simvastatin treatment significantly ameliorated albuminuria in the SHR fed a high-fat diet. Ten weeks on a high-fat resulted in an increase in urinary 8-isoprostane in WKY rats and SHR, and tempol and simvastatin treatment prevented this increase, indicating a reduction in renal oxidative stress. Monocyte chemoattractant protein-1 (MCP-1) excretion was significantly elevated by a high-fat diet in both strains, and tempol prevented this increase. Interestingly, simvastatin treatment had no effect on MCP-1 levels. These data indicate that tempol and simvastatin treatment via a reduction in oxidative stress improve renal endothelial function and decrease glomerular injury in a model of obesity and hypertension.
Postobstructive regeneration of kidney is derailed when surge in renal stem cells during course of unilateral ureteral obstruction is halted
Authors: Park H. C. , Yasuda K. , Ratliff B. , Stoessel A. , Sharkovska Y. , Yamamoto I. , Jasmin J.-F. , Bachmann S. , Lisanti M. P. , Chander P. , Goligorsky M. S.
Published: November 2009

Unilateral ureteral obstruction (UUO), a model of tubulointerstitial scarring (TIS), has a propensity toward regeneration of renal parenchyma after release of obstruction (RUUO). No information exists on the contribution of stem cells to this process. We performed UUO in FVB/N mice, reversed it after 10 days, and examined kidneys 3 wk after RUUO. UUO resulted in attenuation of renal parenchyma. FACS analysis of endothelial progenitor (EPC), mesenchymal stem (MSC) and hematopoietic stem (HSC) cells obtained from UUO kidneys by collagenase-dispersed single-cell suspension showed significant increase in EPC, MSC, and HSC compared with control. After RUUO cortical parenchyma was nearly restored, and TIS score improved by 3 wk. This reversal process was associated with return of stem cells toward baseline level. When animals were chronically treated with nitric oxide synthase (NOS) inhibitor at a dose that did not induce hypertension but resulted in endothelial dysfunction, TIS scores were not different from control UUO, but EPC number in the kidney decreased significantly; however, parenchymal regeneration in these mice was similar to control. Blockade of CXCR4-mediated engraftment resulted in dramatic worsening of UUO and RUUO. Similar results were obtained in caveolin-1-deficient but not -overexpressing mice, reflecting the fact that activation of CXCR4 occurs in caveolae. The present data show increase in EPC, HSC, and MSC population during UUO and a tendency for these cells to decrease to control level during RUUO. These processes are minimally affected by chronic NOS inhibition. Blockade of CXCR4-stromal cell-derived factor-1 (SDF-1) interaction by AMD3100 or caveolin-1 deficiency significantly reduced the UUO-associated surge in stem cells and prevented parenchymal regeneration after RUUO. We conclude that the surge in stem cell accumulation during UUO is a prerequisite for regeneration of renal parenchyma.
Stretch reduces nephrin expression via an angiotensin II-AT1-dependent mechanism in human podocytes: effect of rosiglitazone
Authors: Miceli Ilaria , Burt Davina , Tarabra Elena , Camussi Giovanni , Perin Paolo Cavallo , Gruden Gabriella
Published: November 2009

Increased glomerular permeability to proteins is a characteristic feature of diabetic nephropathy (DN). The slit diaphragm is the major restriction site to protein filtration, and the loss of nephrin, a key component of the slit diaphragm, has been demonstrated in both human and experimental DN. Both systemic and glomerular hypertension are believed to be important in the pathogenesis of DN. Human immortalized podocytes were subjected to repeated stretch-relaxation cycles by mechanical deformation with the use of a stress unit (10% elongation, 60 cycles/min) in the presence or absence of candesartan (1 μM), PD-123319 (1 μM), and rosiglitazone (0.1 μM). Nephrin mRNA and protein expression were assessed using quantitative real-time PCR, immunoblotting, and immunofluorescence, and the protein expression of AT1receptor and angiotensin II secretion were evaluated. Exposure to stretch induced a significant ∼50% decrease in both nephrin mRNA and protein expression. This effect was mediated by an angiotensin II-AT1mechanism. Indeed, podocyte stretching induced both angiotensin II secretion and AT1receptor overexpression, podocyte exposure to angiotensin II reduced nephrin protein expression, and both the AT-1 receptor antagonist candesartan and a specific anti-angiotensin II antibody completely abolished stretch-induced nephrin downregulation. Similar to candesartan, the peroxisome proliferator-activated receptor (PPAR)-γ agonist, rosiglitazone, also inhibited stretch-induced nephrin downregulation, suggesting interference with stretch-induced activation of the angiotensin II-AT1receptor system. Accordingly, rosiglitazone did not alter stretch-induced angiotensin II secretion, but it prevented AT1upregulation in response to stretch. These results suggest a role for hemodynamic stress in loss of nephrin expression and allude to a role of PPAR-γ agonists in the prevention of this loss.
Is the stabilization of quiet upright stance in humans driven by synchronized modulations of the activity of medial and lateral gastrocnemius muscles?
Authors: Vieira Taian M. M. , Windhorst Uwe , Merletti Roberto
Published: November 2009

A matrix of 120 electromyogram (EMG) electrodes (8 rows and 15 columns) was used to investigate individual activation patterns of the medial (MG) and lateral gastrocnemius (LG) muscles during forward sways of the body in human quiet stance. This matrix was positioned on the right calf of eight subjects after identification of the MG and LG contours with ultrasound scanning. Gray-scale images were generated with the maxima and minima of the cross-correlation function between the envelope of each EMG signal and the body center of pressure (CoP) for individual forward sways. These images were automatically segmented to reduce the data set into representative and local values of EMG-CoP cross-correlation for each muscle. On average, modulations in EMG amplitude preceded the onset of forward sways with a variable timing, with both gastrocnemius muscles being similarly and synchronously modulated in 193 out of 236 sways. Variations in the timing of activation between muscles were less frequent, although consistent across subjects and significantly correlated with changes in the direction and velocity of body sways. Interestingly, the time shift between EMG and CoP traces sometimes varied consistently along different channels of the same column of electrodes, either in proximal-to-distal or distal-to-proximal direction. The variable EMG-CoP cross-correlation delay was not congruent with the delay expected for the propagation of surface potentials along muscle fibers. Comparison of surface EMGs with intramuscular EMGs recorded from six subjects demonstrated that surface potentials provide high spatial selectivity, thus supporting the notion of selective activation of motor units during quiet standing. Hence, the stabilization of the quiet standing posture likely relies on flexible rather than stereotyped mechanisms of control.
Effect of acute sleep deprivation on vascular function in healthy subjects
Authors: Sauvet Fabien , Leftheriotis Georges , Gomez-Merino Danièlle , Langrume Christophe , Drogou Catherine , Van Beers Pascal , Bourrilhon Cyprien , Florence Geneviève , Chennaoui Mounir
Published: November 2009

Sleep disorders are associated with inflammation and sympathetic activation, which are suspected to induce endothelial dysfunction, a key factor in the increased risk of cardiovascular disease. Less is known about the early effects of acute sleep deprivation on vascular function. We evaluated microvascular reactivity and biological markers of endothelial activation during continuous 40 h of total sleep deprivation (TSD) in 12 healthy men (29 ± 3 yr). The days before [ day 1 (D1)] and during TSD (D3), at 1200 and 1800, endothelium-dependent and -independent cutaneous vascular conductance was assessed by iontophoresis of acetylcholine and sodium nitroprusside, respectively, coupled to laser-Doppler flowmetry. At 0900, 1200, 1500, and 1800, heart rate (HR) and instantaneous blood pressure (BP) were recorded in the supine position. At D1, D3, and the day after one night of sleep recovery (D4), markers of vascular endothelial cell activation, including soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, and interleukin-6 were measured from blood samples at 0800. Compared with D1, plasma levels of E-selectin were raised at D3, whereas intercellular adhesion molecule-1 and interleukin-6 were raised at D4 ( P < 0.05). The endothelium-dependent and -independent CVC were significantly decreased after 29 h of TSD ( P < 0.05). By contrast, HR, systolic BP, and the normalized low-frequency component of HR variability (0.04–0.15 Hz), a marker of the sympathetic activity, increased significantly within 32 h of TSD ( P < 0.05). In conclusion, acute exposure to 40 h of TSD appears to cause vascular dysfunction before the increase in sympathetic activity and systolic BP.
How Motion Signals Are Integrated Across Frequencies: Study on Motion Perception and Ocular Following Responses Using Multiple-Slit Stimuli
Authors: Hayashi Ryusuke , Sugita Yuko , Nishida Shin'ya , Kawano Kenji
Published: November 2009

Visual motion signals, which are initially extracted in parallel at multiple spatial frequencies, are subsequently integrated into a unified motion percept. Cross-frequency integration plays a crucial role when directional information conflicts across frequencies due to such factors as occlusion. We investigated the human observers' open-loop oculomotor tracking responses (ocular following responses, or OFRs) and the perceived motion direction in an idealized situation of occlusion—multiple-slits viewing (MSV)—in which a moving pattern is visible only through an array of slits. We also tested a more challenging viewing condition, contrast-alternating MSV (CA-MSV), in which the contrast polarity of the moving pattern alternates when it passes the slits. We found that changes in the distribution of the spectral content of the slit stimuli, introduced by variations of both the interval between the slits and the frame rate of the image stream, modulated the OFR and the reported motion direction in a rather complex manner. We show that those complex modulations could be explained by the weighted sum of the motion signal (motion contrast) of each spatiotemporal frequency. The estimated distribution of frequency weights (tuning maps) indicate that the cross-frequency integration of supra-threshold motion signals gives strong weight to low spatial frequency components (<0.25 cpd) for both OFR and motion perception. However, the tuning map estimated with the MSV stimuli were significantly different from those estimated with the CA-MSV (and from those measured in a more direct manner using grating stimuli), suggesting that inter-frequency interactions (e.g., interaction producing speed-dependent tuning) was involved.
Homomeric RDL and Heteromeric RDL/LCCH3 GABA Receptors in the Honeybee Antennal Lobes: Two Candidates for Inhibitory Transmission in Olfactory Processing
Authors: Dupuis Julien Pierre , Bazelot Michaël , Barbara Guillaume Stéphane , Paute Sandrine , Gauthier Monique , Raymond-Delpech Valérie
Published: November 2009

γ-Aminobutyric acid (GABA)–gated chloride channel receptors are abundant in the CNS, where their physiological role is to mediate fast inhibitory neurotransmission. In insects, this inhibitory transmission plays a crucial role in olfactory information processing. In an effort to understand the nature and properties of the ionotropic receptors involved in these processes in the honeybee Apis mellifera, we performed a pharmacological and molecular characterization of GABA-gated channels in the primary olfactory neuropile of the honeybee brain—the antennal lobe (AL)—using whole cell patch-clamp recordings coupled with single-cell RT-PCR. Application of GABA onto AL cells at −110 mV elicited fast inward currents, demonstrating the existence of ionotropic GABA-gated chloride channels. Molecular analysis of the GABA-responding cells revealed that both subunits RDL and LCCH3 were expressed out of the three orthologs of Drosophila melanogaster GABA-receptor subunits encoded within the honeybee genome (RDL, resistant to dieldrin; GRD, GABA/glycine-like receptor of Drosophila ; LCCH3, ligand-gated chloride channel homologue 3), opening the door to possible homo- and/or heteromeric associations. The resulting receptors were activated by insect GABA-receptor agonists muscimol and CACA and blocked by antagonists fipronil, dieldrin, and picrotoxin, but not bicuculline, displaying a typical RDL-like pharmacology. Interestingly, increasing the intracellular calcium concentration potentiated GABA-elicited currents, suggesting a modulating effect of calcium on GABA receptors possibly through phosphorylation processes that remain to be determined. These results indicate that adult honeybee AL cells express typical RDL-like GABA receptors whose properties support a major role in synaptic inhibitory transmission during olfactory information processing.