bluuebunny/crossref_metadata_2025 huggingface dataset:
TWO-ELECTRON SYSTEM IN THE FIELD OF GENERALIZED SCREENED POTENTIAL
Authors: GHOSHAL ARIJIT , HO Y. K.
Published: March 2011

Ground states of a two-electron system in generalized screened potential (GSP) with screening parameter λ: [Formula: see text] where ∊ is a constant, have been investigated. Employing highly correlated and extensive wave functions in Ritz's variational principle, we have been able to determine accurate ground state energies and wave functions of a two-electron system for different values of the screening parameter λ and the constant ∊. Convergence of the ground state energies with the increase of the number of terms in the wave function are shown. We also report various geometrical expectation values associated with the system, ground state energies of the corresponding one-electron system and the ionization potentials of the system. Such a calculation for the ground state of a two-electron system in GSP is carried out for first time in the literature.
SCATTERING AND TUNNELING IN ACTIVE SYSTEMS
Authors: BENNABI Y. , HAMMOU A. B. , ZEKRI N.
Published: March 2011

The scattering properties of one-dimensional potential with gain are studied by using a Schrödinger-like equation. The corresponding Hamiltonian is non-Hermitian with a real energy spectrum. The amplification-absorption duality previously observed is interpreted in terms of the transmission and reflection phases. For a rectangular barrier, the transmission phase oscillates with the barrier width as for passive systems, but the oscillations period is significantly reduced in the absorption region. In this region the reflection phase vanishes and the multiple scattering and interferences dominate. The gain effect is also investigated for double barrier structures as well as superlattices with active potentials. It is found that resonant tunneling energy and the mini-band width are not influenced by the gain, but the transmission is enhanced for small values of the potential imaginary part. For large values, the resonant transmission significantly decreases and the mini-bands disappear.
OFF-LINE SIGNATURE AUTHENTICATION USING RADIAL BASIS FUNCTION
Authors: RADHIKA K. R. , SHEELA S. V. , SEKHAR G. N.
Published: March 2011

A system is proposed that considers minimal features using subpattern analysis which leads to less response time in a real time scenario. Using training samples, with a high degree of certainty, the minimum variance quadtree components [MVQC] of a signature for a person are listed to be applied on a testing sample. Initially the experiment was conducted on wavelet decomposed information for a signature. The non-MVQCs and core components were analyzed. To characterize the local details Gaussian-Hermite moment was applied. Later Hu moments were applied on the selected subsections. The summation values of the subsections are provided as feature to radial basis function [RBF] and feed forward neural network classifiers. Results indicate that the RBF classifier yielded 7% false rejection rate and feed forward neural network classification technique produced 9% false rejection rate. Promising results were achieved, by experimenting on the list of most prominent minimum variance components which are core components using RBF.
AN INTEGRATED APPROACH TO THE RECOGNITION OF A WIDE CLASS OF CONTINUOUS HAND GESTURES
Authors: BHUYAN M. K. , BORA P. K. , GHOSH D.
Published: March 2011

The gesture segmentation is a method that distinguishes meaningful gestures from unintentional movements. Gesture segmentation is a prerequisite stage to continuous gesture recognition which locates the start and end points of a gesture in an input sequence. Yet, this is an extremely difficult task due to both the multitude of possible gesture variations in spatio-temporal space and the co-articulation/movement epenthesis of successive gestures. In this paper, we focus our attention on coping with this problem associated with continuous gesture recognition. This requires gesture spotting that distinguishes meaningful gestures from co-articulation and unintentional movements. In our method, we first segment the input video stream by detecting gesture boundaries at which the hand pauses for a while during gesturing. Next, every segment is checked for movement epenthesis and co-articulation via finite state machine (FSM) matching or by using hand motion information. Thus, movement epenthesis phases are detected and eliminated from the sequence and we are left with a set of isolated gestures. Finally, we apply different recognition schemes to identify each individual gesture in the sequence. Our experimental results show that the proposed scheme is suitable for recognition of continuous gestures having different spatio-temporal behavior.
HOMOCLINIC BIFURCATION AND CHAOS IN Φ6-RAYLEIGH OSCILLATOR WITH THREE WELLS DRIVEN BY AN AMPLITUDE MODULATED FORCE
Authors: SIEWE M. SIEWE , TCHAWOUA C. , RAJASEKAR S.
Published: March 2011

With amplitude modulated excitation, the effect on chaotic behavior of Φ6-Rayleigh oscillator with three wells is investigated in this paper. The Melnikov theorem is used to detect the conditions for possible occurrence of chaos. The results show that the domain of the appearance of chaos is enlarged as both amplitudes of modulated and unmodulated forces increase. The effect of these two amplitudes, when both frequencies of modulated and unmodulated forces are different, on bifurcation diagram and Poincaré map is also investigated, in addition to the surface of Maximal Lyapunov exponent versus modulated and unmodulated parameters for suppressing chaos being shown.
STABILITY AND BIFURCATION FOR A CLASS OF TRI-NEURON NETWORKS WITH BIDIRECTIONALLY DELAYED CONNECTIONS AND SELF-FEEDBACK
Authors: YUAN SHAOLIANG , LI XUEMEI
Published: March 2011

In this paper, a tri-neuron network with bidirectionally delay and self-feedback is considered. We derive some sufficient conditions dependent or independent of delays for the local stability and instability of this model. Regarding the self-connection delay as the parameter, the Hopf bifurcation analysis is carried out. The direction and stability of the Hopf bifurcation are worked out by applying the normal form theory and the center manifold theory. An example is given and numerical simulations are presented to illustrate the obtained results.
LOCAL AND GLOBAL BIFURCATIONS IN THREE-DIMENSIONAL, CONTINUOUS, PIECEWISE SMOOTH MAPS
Authors: DE SOMA , DUTTA PARTHA SHARATHI , BANERJEE SOUMITRO , ROY AKHIL RANJAN
Published: March 2011

In this work, we study the dynamics of a three-dimensional, continuous, piecewise smooth map. Much of the nontrivial dynamics of this map occur when its fixed point or periodic orbit hits the switching manifold resulting in the so-called border collision bifurcation. We study the local and global bifurcation phenomena resulting from such borderline collisions. The conditions for the occurrence of nonsmooth period-doubling, saddle-node, and Neimark–Sacker bifurcations are derived. We show that dangerous border collision bifurcation can also occur in this map. Global bifurcations arise in connection with the occurrence of nonsmooth Neimark–Sacker bifurcation by which a spiral attractor turns into a saddle focus. The global dynamics are systematically explored through the computation of resonance tongues and numerical continuation of mode-locked invariant circles. We demonstrate the transition to chaos through the breakdown of mode-locked torus by degenerate period-doubling bifurcation, homoclinic tangency, etc. We show that in this map a mode-locked torus can be transformed into a quasiperiodic torus if there is no global bifurcation.
SYNCHRONOUS/ASYNCHRONOUS PATTERNS IN THREE-CELL NETWORKS WITH MULTIPLE TIME DELAYS
Authors: YUAN YUAN , LI LEI
Published: March 2011

Some patterns of synchrony/asynchrony in the dynamics of coupled cell systems can be predicted by symmetry. However, in the system without symmetry, the different patterns of periodic solutions may exist as well. We consider a general model including three cells with multiple time delays that connect in any possible manner. Our approach is based on the analytic construction by using a perturbation procedure together with the Fredholm alternative theory. Then we employ the Poincaré–Lindstedt series expansion to compute the Floquet exponents which determine the stability. Finally, we resort to numerical computation to get some insights about the leading term in the Floquet exponents, and the numerical simulations are given to confirm the theoretical results.
HYPERCHAOS IN A SPACECRAFT POWER SYSTEM
Authors: LI QINGDU , YANG XIAO-SONG , CHEN SHU
Published: March 2011

This paper presents some rigorous arguments on a chaotic strange attractor in a spacecraft power system, which is a 3D system with hysteresis switching. By carefully picking a suitable cross-section with respect to the attractor, we find a topological horseshoe of the corresponding third-returned Poincaré map, thus giving a rigorous verification of the existence of chaos in this system. Numerical computation shows that the two Lyapunov exponents of the Poincaré map are both positive and that there exists a two-directional expansion in this horseshoe, suggesting that this attractor is hyperchaotic in nature.
PERIODIC AND CHAOTIC MOTIONS OF FGM THIN PLATE WITH TWO SIMPLY SUPPORTED OPPOSITE AND TWO FREE EDGES
Authors: HAO Y. X. , ZHANG W. , YANG J.
Published: March 2011

An analysis on the nonlinear forced vibration of thermally loaded FGM plate with two simply supported opposite and two free edges subjected to the in-plane and transversal excitations is presented. The material properties of the FGM plates are assumed to be temperature dependent and change continuously throughout the thickness of the plate, according to the volume fraction of the constituent materials based on the power law function. The temperature is assumed to be constant in the plane and varied only in the thickness direction of the plate. The plate is modeled by using the Von Karman hypothesis and the equations of motion are obtained by using an energy approach. It is our aim to choose a suitable mode function to satisfy the first two modes of transverse nonlinear oscillations and the boundary conditions for the FGM rectangular plates with two simply supported opposite and two free edges. The equations of motion can be reduced into a two-degree-of-freedom nonlinear system of transverse motion under combined thermal and external excitations by using the Galerkin's method. By the numerical method, the nonlinear dynamical equations are analyzed to find the nonlinear responses of the FGM plate with two simply supported opposite and two free edges. Under certain conditions the periodic motions and the chaotic motions of the FGM plate are found. The bifurcation diagram demonstrates that for a certain geometric and material properties the chaotic responses of the plate exist as the transverse excitation changes. Moreover, numerical simulations also illustrate that the deflections of the nonlinear dynamic of the FGM rectangular plate are larger than that of the periodic motions.
GLOBAL STABILITY, LIMIT CYCLES AND CHAOTIC BEHAVIORS OF SECOND ORDER INTERPOLATIVE SIGMA DELTA MODULATORS
Authors: HO CHARLOTTE YUK-FAN , LING BINGO WING-KUEN , REISS JOSHUA D. , YU XINGHUO
Published: March 2011

It is well known that second order lowpass interpolative sigma delta modulators (SDMs) may suffer from instability and limit cycle problems when the magnitudes of the input signals are at large and at intermediate levels, respectively. In order to solve these problems, we propose to replace the second order lowpass interpolative SDMs to a specific class of second order bandpass interpolative SDMs with the natural frequencies of the loop filters very close to zero. The global stability property of this class of second order bandpass interpolative SDMs is characterized and some interesting phenomena are discussed. Besides, conditions for the occurrence of limit cycle and fractal behaviors are also derived, so that these unwanted behaviors will not happen or can be avoided. Moreover, it is found that these bandpass SDMs may exhibit irregular and conical-like chaotic patterns on the phase plane. By utilizing these chaotic behaviors, these bandpass SDMs can achieve higher signal-to-noise ratio (SNR) and tonal suppression than those of the original lowpass SDMs.
CDO TERM STRUCTURE MODELLING WITH LÉVY PROCESSES AND THE RELATION TO MARKET MODELS
Authors: SCHMIDT THORSTEN , ZABCZYK JERZY
Published: March 2011

This paper considers the modelling of collateralized debt obligations (CDOs). We propose a top-down model via forward rates generalizing Filipović, Overbeck and Schmidt (2009) to the case where the forward rates are driven by a finite dimensional Lévy process. The contribution of this work is twofold: we provide conditions for absence of arbitrage in this generalized framework. Furthermore, we study the relation to market models by embedding them in the forward rate framework in spirit of Brace, Gatarek and Musiela (1997).
PERFORMANCE OF ROBUST HEDGES FOR DIGITAL DOUBLE BARRIER OPTIONS
Authors: OBŁÓJ JAN , ULMER FRÉDÉRIK
Published: March 2011

We analyze the performance of robust hedging strategies of digital double barrier options of Cox and Obłój (2011) against that of traditional hedging methods such as delta and delta/vega hedging. Digital double barrier options are financial derivative contracts which pay out a fixed amount on the condition that the underlying asset remains within or breaks into a range defined by two distinct barrier levels. We perform the analysis in hypothetical forward markets driven by models with stochastic volatility and jumps, calibrated to the AUD/USD foreign exchange rate market. Our findings are strikingly unanimous and suggest that, in the presence of model uncertainty and/or transaction costs, robust hedging strategies typically outperform in a substantial way model-specific hedging methods.
INSIDER TRADING UNDER DISCRETENESS
Authors: SCOTTI MASSIMO
Published: March 2011

This paper analyzes a version of the static Kyle's (1985) model of insider trading where both the distribution of the liquidation value of the risky asset and the distribution of the order flow of noise traders are discrete. We derive necessary and sufficient conditions for the existence of perfect Bayesian equilibria where the insider's strategy is increasing in the value of the asset, and show that such equilibria can be constructed if and only if the variance of the asset is not too extreme. The results in this paper are relevant in contexts where a discrete version of the static Kyle's (1985) model might be a convenient modelling choice.
CONIC FINANCE AND THE CORPORATE BALANCE SHEET
Authors: MADAN DILIP B. , SCHOUTENS WIM
Published: March 2011

Markets are modeled as passively accepting a convex cone of cash flows that contain the nonnegative cash flows. Different markets are modeled using different cones that reflect the clientele of the market. Conditions are established to exclude the possibility of arbitrage between markets. Operationally these cones are defined by a positive expectation under a concave distortion of the distribution function of the cash flow delivered to market. Under conic finance firms may access risky assets and risky liabilities but regulatory bodies need to ensure that sufficient capital is put at stake to make the risk of excess loss acceptable to taxpayers. Firms approach equity markets for funding and can come into existence only if they can raise equity capital sufficient to meet regulatory requirements. Firms that are allowed to exist may approach debt markets for favorable funding opportunities. The costs of debt limit the amount of debt. Firms with lognormally distributed and correlated assets and liabilities are analysed for their required capital, their optimal debt levels, the value of the option to put losses back to the taxpayer, the costs of debt and equity, and the level of finally reported equity in the balance sheet. The relationship between these entities and the risk characteristics of a firm are analyzed and reported in detail.
Protein kinase G signaling disrupts Rac1-dependent focal adhesion assembly in liver specific pericytes
Authors: Routray Chittaranjan , Liu Chunsheng , Yaqoob Usman , Billadeau Daniel D. , Bloch Kenneth D. , Kaibuchi Kozo , Shah Vijay H. , Kang Ningling
Published: March 2011

Nitric oxide (NO) regulates the function of perivascular cells (pericytes), including hepatic stellate cells (HSC), mainly by activating cGMP and cGMP-dependent kinase (PKG) via NO/cGMP paracrine signaling. Although PKG is implicated in integrin-mediated cell adhesion to extracellular matrix, whether or how PKG signaling regulates the assembly of focal adhesion complexes (FA) and migration of HSC is not known. With the help of complementary molecular and cell biological approaches, we demonstrate here that activation of PKG signaling in HSC inhibits vascular tubulogenesis, migration/chemotaxis, and assembly of mature FA plaques, as assessed by vascular tubulogenesis assays and immunofluorescence localization of FA markers such as vinculin and vasodilator-stimulated phosphoprotein (VASP). To determine whether PKG inhibits FA assembly by phosphorylation of VASP at Ser-157, Ser-239, and Thr-278, we mutated these putative phosphorylation sites to alanine (VASP3A, phosphoresistant mutant) or aspartic acid (VASP3D, phosphomimetic), respectively. Data generated from these two mutants suggest that the effect of PKG on FA is independent of these three phosphorylation sites. In contrast, activation of PKG inhibits the activity of small GTPase Rac1 and its association with the effector protein IQGAP1. Moreover, PKG activation inhibits the formation of a trimeric protein complex containing Rac1, IQGAP1, and VASP. Finally, we found that expression of a constitutively active Rac1 mutant abolishes the inhibitory effects of PKG on FA formation. In summary, our data suggest that activation of PKG signaling in pericytes inhibits FA formation by inhibiting Rac1.
Improving murine embryonic stem cell differentiation into cardiomyocytes with neuregulin-1: differential expression of microRNA
Authors: Sun Maoyun , Yan Xinhua , Bian Yun , Caggiano Anthony O. , Morgan James P.
Published: March 2011

Identification of factors that direct embryonic stem (ES) cell (ESC) differentiation into functional cardiomyocytes is essential for successful use of ESC-based therapy for cardiac repair. Neuregulin-1 (NRG1) and microRNA play important roles in the cardiac differentiation of ESCs. Understanding how NRG1 regulates microRNA will provide new mechanistic insights into the role of NRG1 on ESCs. It may also lead to the discovery of novel microRNAs that are important for ESC cardiac differentiation. The objective of this study was to assess the microRNA expression profile during NRG1-induced ESC cardiac differentiation. Murine ESCs were incubated with a recombinant NRG1β or an inhibitor of ErbB2 or ErbB4 during hanging drop-induced cardiac differentiation. The expression of cardiac-specific markers and microRNAs was analyzed by RT-PCR and microRNA array, respectively. We found that the expression of NRG1 and the ErbB receptors was increased during hanging drop-induced cardiac differentiation of ESCs. NRG1 stimulation during a specific developmental window enhanced, while inhibition of the ErbB2 or ErbB4 receptor inhibited, cardiac differentiation of ESCs. NRG1 increased the expression of mmu-miR-296–3p and mmu-miR-200c*, and decreased mmu-miR-465b-5p. Inhibition of mmu-miR-296–3p or mmu-miR-200c* decreased, while inhibition of mmu-miR-465–5p increased, the differentiation of ESCs into the cardiac lineage. This is the first report demonstrating that microRNAs are differentially regulated by NRG1-ErbB signaling during cardiac differentiation of ESCs. This study has also identified new microRNAs that are important for ESC cardiac differentiation.
Methods for stable recording of short-circuit current in a Na+-transporting epithelium
Authors: Gondzik Veronika , Awayda Mouhamed S.
Published: March 2011

Epithelial Na+ transport as measured by a variety of techniques, including the short-circuit current technique, has been described to exhibit a “rundown” phenomenon. This phenomenon manifests as time-dependent decrease of current and resistance and precludes the ability to carry out prolonged experiments aimed at examining the regulation of this transport. We developed methods for prolonged stable recordings of epithelial Na+ transport using modifications of the short-circuit current technique and commercial Ussing-type chambers. We utilize the polarized MDCK cell line expressing the epithelial Na+ channel (ENaC) to describe these methods. Briefly, existing commercial chambers were modified to allow continuous flow of Ringer solution and precise control of such flow. Chamber manifolds and associated plumbing were modified to allow precise temperature clamp preventing temperature oscillations. Recording electrodes were modified to eliminate the use of KCl and prevent membrane depolarization from KCl leakage. Solutions utilized standard bicarbonate-based buffers, but all gasses were prehydrated to clamp buffer osmolarity. We demonstrate that these modifications result in measurements of current and resistance that are stable for at least 2 h. We further demonstrate that drifts in osmolarity similar to those obtained before prior to our modifications can lead to a decrease of current and resistance similar to those attributed to rundown.
The area postrema in hindbrain is a central player for regulation of drinking behavior in Japanese eels
Authors: Nobata Shigenori , Takei Yoshio
Published: March 2011

It is recognized that fish will drink the surrounding water by reflex swallowing without a thirst sensation. We evaluated the role of the area postrema (AP), a sensory circumventricular organ (CVO) in the medulla oblongata, in the regulation of drinking behavior of seawater (SW) eels. The antidipsogenic effects of ghrelin and atrial natriuretic peptide and hypervolemia and hyperosmolemia (1 M sucrose or 10% NaCl) as well as the dipsogenic effects of angiotensin II and hypovolemia (hemorrhage) were profoundly diminished after AP lesion (APx) in eels compared with sham controls. However, the antidipsogenic effect of urotensin II was not influenced by APx, possibly due to the direct baroreflex inhibition on the swallowing center in eels. When ingested water was drained via an esophageal fistula, water intake increased 30-fold in sham controls but only fivefold in APx eels, suggesting a role for the AP in continuous regulation of drinking by SW eels. After transfer from freshwater to SW, APx eels responded normally with an immediate burst of drinking, but after 4 wk these animals showed a much greater increase in plasma osmolality than controls, suggesting that the AP is involved in acclimation to SW by fine tuning of the drinking rate. Taken together, the AP in the hindbrain of eels plays an integral role in SW acclimation, acting as a conduit of information from plasma for the regulation of drinking, probably without a thirst sensation. This differs from mammals in which sensory CVOs in the forebrain play pivotal roles in thirst regulation.
Female stem cells are superior to males in preserving myocardial function following endotoxemia
Authors: Manukyan Mariuxi C. , Weil Brent R. , Wang Yue , Abarbanell Aaron M. , Herrmann Jeremy L. , Poynter Jeffrey A. , Brewster Benjamin D. , Meldrum Daniel R.
Published: March 2011

Mesenchymal stem cells (MSCs) may offer therapeutic benefit in the setting of sepsis and endotoxemia. Previous studies suggest that MSCs from female donors may possess better protective capabilities than their male counterparts. The present study examined whether female MSCs may offer a greater protective advantage in the setting of endotoxemic cardiac dysfunction compared with male MSCs. Adult male Sprague-Dawley rats were injected intraperitoneally with LPS and then treated with intraperitoneal injections of either saline, female MSCs, or male MSCs. Hearts and serum were then collected for analysis of myocardial function, myocardial protein, and myocardial and serum cytokines. Compared with male MSC or vehicle-treated animals, female MSC treatment resulted in greater preservation of myocardial function ( P < 0.001). Serum and myocardial levels of all measured cytokines were comparable between rats given MSCs from male or female donors but substantially improved over rats given vehicle ( P < 0.05). Reduced myocardial inflammation correlated with reduced levels of phosphorylated p38 MAPK expression in the myocardium of animals injected with MSCs of either sex ( P < 0.05). The Bcl-xL/Bax ratio was increased to a greater extent following treatment with female MSCs vs. male MSCs ( P < 0.05). Intraperitoneal administration of MSCs is effective in limiting myocardial inflammation and dysfunction in the rat endotoxemia model. Compared with treatment with their male counterparts, MSC treatment from female donors is associated with greater cardiac protection against acute endotoxemic injury.
Thermal sensitivity of mitochondrial functions in permeabilized muscle fibers from two populations of Drosophila simulans with divergent mitotypes
Authors: Pichaud Nicolas , Ballard J. William O. , Tanguay Robert M. , Blier Pierre U.
Published: March 2011

In ectotherms, the external temperature is experienced by the mitochondria, and the mitochondrial respiration of different genotypes is likely to change as a result. Using high-resolution respirometry with permeabilized fibers (an in situ approach), we tried to identify differences in mitochondrial performance and thermal sensitivity of two Drosophila simulans populations with two different mitochondrial types ( siII and siIII) and geographical distributions. Maximal state 3 respiration rates obtained with electrons converging at the Q junction of the electron transport system (ETS) differed between the mitotypes at 24°C. Catalytic capacities were higher in flies harboring siII than in those harboring siIII mitochondrial DNA (2,129 vs. 1,390 pmol O2·s−1·mg protein−1). The cytochrome c oxidase activity was also higher in siII than siIII flies (3,712 vs. 2,688 pmol O2·s−1·mg protein−1). The higher catalytic capacity detected in the siII mitotype could provide an advantage in terms of intensity of aerobic activity, endurance, or both, if the intensity of exercise that can be aerobically performed is partly dictated by the aerobic capacity of the tissue. Moreover, thermal sensitivity results showed that even if temperature affects the catalytic capacity of the different enzymes of the ETS, both mitotypes revealed high tolerance to temperature variation. Previous in vitro study failed to detect any consistent functional mitochondrial differences between the same mitotypes. We conclude that the in situ approach is more sensitive and that the ETS is a robust system in terms of functional and regulatory properties across a wide range of temperatures.
Neurosteroid modulation of benzodiazepine-sensitive GABAA tonic inhibition in supraoptic magnocellular neurons
Authors: Jo Ji Yoon , Jeong Ji Ae , Pandit Sudip , Stern Javier E. , Lee Seul Ki , Ryu Pan Dong , Lee So Yeong , Han Seong Kyu , Cho Chung-Hyun , Kim Hyun Woo , Jeon Byeong Hwa , Park Jin Bong
Published: March 2011

Interactions between neurosteroids and GABA receptors have attracted particular attention in the supraoptic nucleus (SON). Although GABAA receptors (GABAAR) mediate a sustained tonic inhibitory current (Itonic), as well as conventional phasic inhibitory postsynaptic currents (IPSCs, Iphasic) in the SON, whether the steroid modulation on Itonic is present in SON magnocelluar neurosecretory cells (MNCs) is unknown. Here, we addressed this question and gained insights into the potential molecular configuration of GABAA receptors mediating Itonic and conferring its neurosteroids sensitivity in SON MNCs. 4,5,6,7-tetrahydroisoxazolo[5,4-c]-pyridin-3-ol (THIP) (1 μM), a relatively selective extrasynaptic GABAAR agonist, facilitated Itonic without affecting the main characteristics of IPSCs, while DS-2, a relatively selective modulator of GABAAR δ-subunits, caused minimal changes in Itonic of SON MNCs. l-655,708, a relatively selective GABAAR α5-subunit inverse agonist, blocked ∼35% of the total Itonic both under basal and elevated ambient GABA concentration (3 μM). Facilitation of Itonic by benzodiazepines further supported the role of GABAAR γ2-subunit in Itonic of SON MNCs. Quantitative RT-PCR analysis showed much lesser expression of GABAAR δ-subunit than the α5 or γ2-subunit in the SON. Allopregnanolone and 3α,5α-tetrahydrodeoxycorticosterone increased both Itonic and Iphasic in SON MNCs, respectively, although more than 90% of the current increase was mediated by Itonic during the neurosteroid facilitation. Finally, l-655,708 attenuated the neurosteroid facilitation of Itonic but not of Iphasic. Altogether, our results suggest that Itonic, mediated mainly by benzodiazepine-sensitive GABAARs containing α5-, β-, and γ2-, and to a lesser extent, δ-subunits, is a potential target of neurosteroid modulation in SON neurons.
Tubuloglomerular feedback response in the prenatal and postnatal ovine kidney
Authors: Brown Russell D. , Turner Anita J. , Carlström Mattias , Persson A. Erik G. , Gibson Karen J.
Published: March 2011

The tubuloglomerular feedback mechanism (TGF) plays an important role in regulating single-nephron glomerular filtration rate (GFR) by coupling distal tubular flow to arteriolar tone. It is not known whether TGF is active in the developing kidney or whether it can regulate renal vascular tone and thus GFR during intrauterine life. TGF characteristics were examined in late-gestation ovine fetuses and lambs under normovolemic and volume-expanded (VE) conditions. Lambs and pregnant ewes were anesthetized and the fetuses were delivered via a caesarean incision into a heated water bath, with the umbilical cord intact. Under normovolemic conditions, mean arterial pressure of the fetuses was lower than lambs (51 ± 1 vs. 64 ± 3 mmHg). The maximum TGF response (ΔPSFmax) was found to be lower in fetuses than lambs when tubular perfusion was increased from 0 to 40 nl/min (5.4 ± 0.7 vs. 10.6 ± 0.4 mmHg). Furthermore, the flow rate eliciting half-maximal response [turning point (TP)] was 15.7 ± 0.9 nl/min in fetuses compared with 19.3 ± 1.0 nl/min in lambs, indicating a greater TGF sensitivity of the prenatal kidney. VE decreased ΔPSFmax (4.2 ± 0.4 mmHg) and increased TP to 23.7 ± 1.3 nl/min in lambs. In fetuses, VE increased stop-flow pressure from 26.6 ± 1.5 to 30.3 ± 0.8 mmHg, and reset TGF sensitivity so that TP increased to 21.3 ± 0.7 nl/min, but it had no effect on ΔPSFmax. This study provides direct evidence that the TGF mechanism is active during fetal life and responds to physiological stimuli. Moreover, reductions in TGF sensitivity may contribute to the increase in GFR at birth.
Coupled ATP and potassium efflux from intercalated cells
Authors: Holtzclaw J. David , Cornelius Ryan J. , Hatcher Lori I. , Sansom Steven C.
Published: March 2011

Increased flow in the distal nephron induces K secretion through the large-conductance, calcium-activated K channel (BK), which is primarily expressed in intercalated cells (IC). Since flow also increases ATP release from IC, we hypothesized that purinergic signaling has a role in shear stress (τ; 10 dynes/cm2) -induced, BK-dependent, K efflux. We found that 10 μM ATP led to increased IC Ca concentration, which was significantly reduced in the presence of the P2receptor blocker suramin or calcium-free buffer. ATP also produced BK-dependent K efflux, and IC volume decrease. Suramin inhibited τ-induced K efflux, suggesting that K efflux is at least partially dependent on purinergic signaling. BK-β4 small interfering (si) RNA, but not nontarget siRNA, decreased ATP secretion and both ATP-dependent and τ-induced K efflux. Similarly, carbenoxolone (25 μM), which blocks connexins, putative ATP pathways, blocked τ-induced K efflux and ATP secretion. Compared with BK-β4−/−mice, wild-type mice with high distal flows exhibited significantly more urinary ATP excretion. These data demonstrate coupled electrochemical efflux between K and ATP as part of the mechanism for τ-induced ATP release in IC.
Effect of ACE inhibition on glomerular permselectivity and tubular albumin concentration in the renal ablation model
Authors: Sangalli Fabio , Carrara Fabiola , Gaspari Flavio , Corna Daniela , Zoja Carla , Botti Lorenzo , Remuzzi Giuseppe , Remuzzi Andrea
Published: March 2011

Despite the central role of tubular plasma proteins that characterize progressive kidney diseases, protein concentrations along the nephron in pathological conditions have not been quantified so far. We combined experimental techniques and theoretical analysis to estimate glomerular and tubular levels of albumin in the experimental model of 5/6 nephrectomy (Nx) in the rat, with or without angiotensin-converting enzyme (ACE) inhibition. We measured glomerular permselectivity by clearance of fluorescent Ficoll and albumin and used theoretical analysis to estimate tubular albumin. As expected, 5/6 Nx induced an elevation of the fractional clearance of the largest Ficoll molecules (radii >56 Å, P < 0.05), increasing the importance of the shunt pathway of the glomerular membrane and the albumin excretion rate (119 ± 41 vs. 0.6 ± 0.2 mg/24 h, P < 0.01). ACE inhibition normalized glomerular permselectivity and urinary albumin (0.5 ± 0.3 mg/24 h). Theoretical analysis indicates that with 5/6 Nx, an increased albumin filtration overcomes proximal tubule reabsorption, with a massive increase in average albumin concentration along the tubule, reaching the highest value of >2,500 μg/ml at the end of the collecting duct. ACE inhibition improved glomerular permselectivity, limiting albumin filtration under proximal tubule reabsorption capacity, with low albumin concentration along the entire nephron, averaging <13 μg/ml at the end of the collecting duct. These results reinforce our understanding of the mechanisms of renal disease progression and the effects of angiotensin II antagonism. They also suggest that evaluation of tubular protein concentration levels could help to identify patients at risk of kidney disease progression and to improve clinical management.
Conservation of Na+vs. K+by the rat cortical collecting duct
Authors: Frindt Gustavo , Houde Véronique , Palmer Lawrence G.
Published: March 2011

Regulation of transport by principal cells of the distal nephron contributes to maintenance of Na+and K+homeostasis. To assess which of these ions is given a higher priority by these cells, we investigated the upregulation of epithelial Na+channels (ENaC) in the rat cortical collecting duct (CCD) during Na depletion with and without simultaneous K depletion. ENaC activity, assessed as whole cell amiloride-sensitive current in split-open tubules, was 260 ± 40 pA/cell in K-repleted but virtually undetectable (3 ± 1 pA/cell) in K-depleted animals. This difference was confirmed biochemically by the reduced amounts of the cleaved forms of both the α-ENaC and γ-ENaC subunits measured in immunoblots. In contrast, in K-depleted rats, simultaneously reducing Na intake did not affect the activity of ROMK channels, assessed as tertiapin-Q-sensitive whole cell currents, in the CCDs. The lack of Na current in K-depleted animals was the result of reduced levels of aldosterone in plasma, rather than a reduced sensitivity to the hormone. However, rats on a low-Na, low-K diet for 1 wk did not excrete more Na than those on a low-Na, control-K diet for the same period of time. Immunoblot analysis indicated increased levels of the thiazide-sensitive NaCl cotransporter and the apical Na-H exchanger NHE3. This suggests that with reduced K intake, Na balance is maintained despite reduced aldosterone and Na+channel activity by upregulation of Na+transport in upstream segments. Under these conditions, Na+transport by the aldosterone-sensitive distal nephron is reduced, despite the low-Na intake to minimize K+secretion and urinary K losses.
A spatial explicit strategy reduces error but interferes with sensorimotor adaptation
Authors: Benson Bryan L. , Anguera Joaquin A. , Seidler Rachael D.
Published: March 2011

Although sensorimotor adaptation is typically thought of as an implicit form of learning, it has been shown that participants who gain explicit awareness of the nature of the perturbation during adaptation exhibit more learning than those who do not. With rare exceptions, however, explicit awareness is typically polled at the end of the study. Here, we provided participants with either an explicit spatial strategy or no instructions before learning. Early in learning, explicit instructions greatly reduced movement errors but also resulted in increased trial-to-trial variability and longer reaction times. Late in adaptation, performance was indistinguishable between the explicit and implicit groups, but the mechanisms underlying performance improvements remained fundamentally different, as revealed by catch trials. The progression of implicit recalibration in the explicit group was modulated by the use of an explicit strategy: these participants showed a lower level of recalibration as well as decreased aftereffects. This phenomenon may be due to the reduced magnitude of errors made to the target during adaptation or inhibition of implicit learning mechanisms by explicit processing.
A new type of recording chamber with an easy-to-exchange microdrive array for chronic recordings in macaque monkeys
Authors: Galashan F. Orlando , Rempel Hanna C. , Meyer Anneke , Gruber-Dujardin Eva , Kreiter Andreas K. , Wegener Detlef
Published: March 2011

In monkeys, long-term recordings with chronically implanted microelectrodes frequently suffer from a continuously decreasing probability to record single units or even small multiunit clusters. This problem is associated with two technical limitations of the available devices: first, restrictions for electrode movement, and second, absent possibility to exchange electrodes easily on a regular basis. Permitting to adjust the recording site and to use new recording tracks with proper electrodes may avoid these problems and make chronic more similar to acute recordings. Here, we describe a novel type of implant tackling this issue. It consists of a new type of recording chamber combined with an exchangeable multielectrode array that precisely fits into it. The multielectrode array is reversibly fixed to the chamber, and within a minute it can be exchanged against another array equipped with new electrodes at the awake animal. The array allows for bidirectional movement of six electrodes for a distance of up to 12 mm. The recording chamber enables hermetical isolation of the intracranial space, resulting in long-lasting aseptic conditions and reducing dural thickening to a minimum, as confirmed by microbiological and histopathological analysis. The device has a simple design and is both easy to produce and low in cost. Functionality has been tested in primary and secondary visual cortex of three macaque monkeys over a period of up to 15 mo. The results show that even after more than a year, single and multiunit responses can be obtained with high incidence.
Metabotropic glutamate receptor 5 regulates excitability and Kv4.2-containing K+ channels primarily in excitatory neurons of the spinal dorsal horn
Authors: Hu Hui-Juan , Gereau Robert W.
Published: March 2011

Metabotropic glutamate (mGlu) receptors play important roles in the modulation of nociception. Previous studies demonstrated that mGlu5 modulates nociceptive plasticity via activation of ERK signaling. We have reported recently that the Kv4.2 K+ channel subunit underlies A-type currents in spinal cord dorsal horn neurons and that this channel is modulated by mGlu5-ERK signaling. In the present study, we tested the hypothesis that modulation of Kv4.2 by mGlu5 occurs in excitatory spinal dorsal horn neurons. With the use of a transgenic mouse strain expressing enhanced green fluorescent protein (GFP) under control of the promoter for the γ-amino butyric acid (GABA)-synthesizing enzyme, glutamic acid decarboxylase 67 (GAD67), we found that these GABAergic neurons express less Kv4.2-mediated A-type current than non-GAD67-GFP neurons. Furthermore, the mGlu1/5 agonist, (R,S)-3,5-dihydroxyphenylglycine, had no modulatory effects on A-type currents or neuronal excitability in this subgroup of GABAergic neurons but robustly modulated A-type currents and neuronal excitability in non-GFP-expressing neurons. Immunofluorescence studies revealed that Kv4.2 was highly colocalized with markers of excitatory neurons, such as vesicular glutamate transporter 1/2, PKCγ, and neurokinin 1, in cultured dorsal horn neurons. These results indicate that mGlu5-Kv4.2 signaling is associated with excitatory dorsal horn neurons and suggest that the pronociceptive effects of mGlu5 activation in the spinal cord likely involve enhanced excitability of excitatory neurons.
Serotonergic modulation of startle-escape plasticity in an African cichlid fish: a single-cell molecular and physiological analysis of a vital neural circuit
Authors: Whitaker K. W. , Neumeister H. , Huffman L. S. , Kidd C. E. , Preuss T. , Hofmann H. A.
Published: March 2011

Social life affects brain function at all levels, including gene expression, neurochemical balance, and neural circuits. We have previously shown that in the cichlid fish Astatotilapia burtoni brightly colored, socially dominant (DOM) males face a trade-off between reproductive opportunities and increased predation risk. Compared with camouflaged subordinate (SUB) males, DOMs exposed to a loud sound pip display higher startle responsiveness and increased excitability of the Mauthner cell (M-cell) circuit that governs this behavior. Using behavioral tests, intracellular recordings, and single-cell molecular analysis, we show here that serotonin (5-HT) modulates this socially regulated plasticity via the 5-HT receptor subtype 2 (5-HTR2). Specifically, SUBs display increased sensitivity to pharmacological manipulation of 5-HTR2 compared with DOMs in both startle-escape behavior and electrophysiological properties of the M-cell. Immunohistochemistry showed serotonergic varicosities around the M-cells, further suggesting that 5-HT impinges directly onto the startle-escape circuitry. To determine whether the effects of 5-HTR2 are pre- or postsynaptic, and whether other 5-HTR subtypes are involved, we harvested the mRNA from single M-cells via cytoplasmic aspiration and found that 5-HTR subtypes 5A and 6 are expressed in the M-cell. 5-HTR2, however, was absent, suggesting that it affects M-cell excitability through a presynaptic mechanism. These results are consistent with a role for 5-HT in modulating startle plasticity and increase our understanding of the neural and molecular basis of a trade-off between reproduction and predation.
Immunohistochemical Evaluation of p63, E‐Cadherin, Collagen I and III Expression in Lower Limb Wound Healing under Honey
Authors: Barui Ananya , Banerjee Provas , Das Raunak Kumar , Basu Shyamal Kumar , Dhara Santanu , Chatterjee Jyotirmoy
Published: March 2011

Honey is recognized traditionally for its medicinal properties and also appreciated as a topical healing agent for infected and noninfected wounds. This study evaluates impact of honey‐based occlusive dressing on nonhealing (nonresponding to conventional antibiotics) traumatic lower limb wounds (n = 34) through clinicopathological and immunohistochemical (e.g., expression of p63, E‐cadherin, and Collagen I and III) evaluations to enrich the scientific validation. Clinical findings noted the nonadherence of honey dressing with remarkable chemical debridement and healing progression within 11–15 days of postintervention. Histopathologically, in comparison to preintervention biopsies, the postintervention tissues of wound peripheries demonstrated gradual normalization of epithelial and connective tissue features with significant changes in p63+ epithelial cell population, reappearance of membranous E‐cadherin (P < .0001), and optimum deposition of collagen I and III (P < .0001). Thus, the present study for the first time reports the impact of honey on vital protein expressions in epithelial and connective tissues during repair of nonhealing lower limb wounds.
Contemporaneous Portal-Arterial Reperfusion during Liver Transplantation: Preliminary Results
Authors: Adani G. L. , Rossetto A. , Bresadola V. , Lorenzin D. , Baccarani U. , De Anna D.
Published: March 2011

We prospectively compared sequential portal-arterial revascularization (SPAr, group 1 no. 19) versus contemporaneous portal-hepatic artery revascularization (CPAr, group 2 no. 21) in 40 consecutive liver transplantation (LT). There were no differences in the demographics characteristics, MELD score, indication to LT, and donor's parameters between the two groups. CPAr had longer warm ischemia66±8versus37±7min (P<.001), while SPAr had longer arterial ischemia103±42 min (P=.0004). One-year patient's and graft survival were, respectively, 89% and 95% versus 94% and 100% (P=.29). At median followup of13±6versus14±7months biliary complications were anastomotic stenosis in 15% versus 19% (P=.78), and intrahepatic nonanastomotic biliary strictures in 26% versus none (P=.01), respectively, in SPAr and CPAr. CPAr reduces the incidence of intrahepatic biliary strictures by decreasing the duration of arterial ischemia.
Impact of Common Property (E.A.) on Fixed Point Theorems in Fuzzy Metric Spaces
Authors: Gopal D , Imdad M , Vetro C
Published: March 2011

We observe that the notion of common property (E.A.) relaxes the required containment of range of one mapping into the range of other which is utilized to construct the sequence of joint iterates. As a consequence, a multitude of recent fixed point theorems of the existing literature are sharpened and enriched.
Selectivity of Inhibition of N-Succinyl-l,l-Diaminopimelic Acid Desuccinylasein Bacteria: The product of dapE-gene Is Not the Target ofl-Captopril Antimicrobial Activity
Authors: Uda Narasimha Rao , Creus Marc
Published: March 2011

The emergence of bacterial strains that are resistant to virtually all currently available antibiotics underscores the importance of developing new antimicrobial compounds. N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) is a metallohydrolase involved in the meso-diaminopimelate (mDAP)/lysine biosynthetic pathway necessary for lysine biosynthesis and for building the peptidoglycan cell wall. Because DapE is essential for Gram-negative and some Gram-positive bacteria, DapE has been proposed as a good target for antibiotic development. Recently,l-captopril has been suggested as a lead compound for inhibition of DapE, although its selectivity for this enzyme target in bacteria remains unclear (Gillner et al. (2009)). Here, we tested the selectivity ofl-captopril against DapEin bacteria. Since DapE knockout strains of gram-negative bacteria are viable upon chemical supplementation with mDAP, we reasoned that the antimicrobial activity of compounds targeting DapE should be abolished in mDAP-containing media. Althoughl-captopril had modest antimicrobial activity inEscherichia coliand inSalmonella enterica, to our surprise, inhibition of bacterial growth was independent both of mDAP supplementation and DapE over-expression. We conclude that DapE is not the main target ofl-captopril inhibition in these bacteria. The methods implemented here will be useful for screening DapE-selective antimicrobial compounds directly in bacterial cultures.