bluuebunny/crossref_metadata_2025 huggingface dataset:
AUTOASSOCIATIVE MEMORY DESIGN USING INTERCONNECTED GENERALIZED BRAIN-STATE-IN-A-BOX NEURAL NETWORKS
Authors: OH CHEOLHWAN , ŻAK STANISLAW H. , ZHAI GUISHENG
Published: July 2005

A class of interconnected neural networks composed of generalized Brain-State-in-a-Box (gBSB) neural subnetworks is considered. Interconnected gBSB neural network architectures are proposed along with their stability conditions. The design of the interconnected neural networks is reduced to the problem of solving linear matrix inequalities (LMIs) to determine the interconnection parameters. A method for solving LMIs is devised generating the solutions that, in general, are further away from zero than the corresponding solutions obtained using MATLAB's LMI toolbox, thus resulting in stronger interconnections between the subnetworks. The proposed architectures are then used to construct neural associative memories. Simulations are performed to illustrate the results obtained.
PLAUSIBLE IMAGE MATCHING: DETERMINING DENSE AND SMOOTH MAPPING BETWEEN IMAGES WITHOUT A PRIORI KNOWLEDGE
Authors: YAMAZAKI SHUNTARO , IKEUCHI KATSUSHI , SHINAGAWA YOSHIHISA
Published: July 2005

This paper presents a method for automatic determination of dense and smooth mapping between two images without a priori knowledge of either the camera pose or the objects in the images. We designed an algorithm to find the mapping between a pair of arbitrary images, and accomplish automatic image morphing. In order to extract image features which look natural to human, we use a set of linear filters similar to those that are used in early vision. Then the derived vector fields consisting of filter responses are matched with each other through a minimization of the cost function which expresses the similarity of transformed images and mapping smoothness, in a multiresolutional hierarchy. Since the cost function in general is highly nonlinear, we avoid excessive distortion in the estimated mapping by providing a local convexity of mapping in nonlinear optimization. In this paper, a variety of experimental results are discussed for various data sets, including images of rotating objects, static objects, human faces and texture patterns, to demonstrate the performance of the proposed method.
FACE RECOGNITION UNDER GENERIC ILLUMINATION BASED ON HARMONIC RELIGHTING
Authors: QING LAIYUN , SHAN SHIGUANG , GAO WEN , DU BO
Published: July 2005

The performances of the current face recognition systems suffer heavily from the variations in lighting. To deal with this problem, this paper presents an illumination normalization approach by relighting face images to a canonical illumination based on the harmonic images model. Benefiting from the observations that human faces share similar shape, and the albedos of the face surfaces are quasi-constant, we first estimate the nine low-frequency components of the illumination from the input facial image. The facial image is then normalized to the canonical illumination by re-rendering it using the illumination ratio image technique. For the purpose of face recognition, two kinds of canonical illuminations, the uniform illumination and a frontal flash with the ambient lights, are considered, among which the former encodes merely the texture information, while the latter encodes both the texture and shading information. Our experiments on the CMU-PIE face database and the Yale B face database have shown that the proposed relighting normalization can significantly improve the performance of a face recognition system when the probes are collected under varying lighting conditions.
MULTI-GHzSiGe BiCMOS FPGAs WITH NEW ARCHITECTURE AND NOVEL POWER MANAGEMENT TECHNIQUES
Authors: ZHOU K. , GUO J.-R. , YOU C. , MAYEGA J. , KRAFT R. P. , ZHANG T. , McDONALD J. F. , GODA B. S.
Published: July 2005

The availability of Silicon Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) devices has opened a door for GHz Field Programmable Gate Arrays (FPGAs).1,2 The integration of high-speed SiGe HBTs and low-power CMOS gives a significant speed advantage to SiGe FPGAs over CMOS FPGAs. In the past, high static power consumption discouraged the pursuit of bipolar FPGAs from being scaled up significantly. This paper details new ideas to reduce power in designing high-speed SiGe BiCMOS FPGAs. The paper explains new methods to reduce circuitry and utilize a novel power management scheme to achieve a flexible trade-off between power consumption and circuit speed. In addition, new decoding logic is developed with shared address and data lines. A SiGe FPGA test chip based on the Xilinx 6200 architecture has been fabricated for demonstration.
SINGLE CFA-BASED NICs WITH IMPEDANCE SCALING PROPERTIES
Authors: KESKIN ALI ÜMIT
Published: July 2005

Negative impedance converter circuits (NICs) are important building blocks in design and manufacturing of analog and mixed mode integrated circuits. In this paper, a catalogue of single-current feedback amplifier-based negative impedance converter circuits having impedance scaling properties is proposed. Various examples are presented to illustrate the versatility of the proposed NIC circuits.
A NOVEL DIVISION ALGORITHM AND ARCHITECTURES FOR PARALLEL AND SEQUENTIAL PROCESSING
Authors: TATAS K. , SOUDRIS D. J. , SIOMOS D. , THANAILAKIS A.
Published: July 2005

A new algorithm for reducing the division operation to a series of smaller divisions is introduced. Partitioning the dividend into segments, we perform divisions, shifts, and accumulations taking into account the weight of dividend bits. Each partial division can be performed by any existing division algorithm. From an algorithmic point of view, computation analysis is performed in comparison with the existing algorithms. From an implementation point of view, since the division can be performed by any existing divider, the designer can choose the divider which best meets his specifications. Although the algorithm is presented for integer numbers, it can be easily generalized for fractions, since it is only a matter of representation. Two possible implementations of the algorithm, namely the sequential and parallel are derived, with several variations, allowing performance, cost, and cost/performance trade-offs. Exhaustive comparisons of the derived implementations with many existing implementations in terms of area cost, performance, and cost/performance are done. A plethora of alternative implementations can be derived due to a variable number of partitions.
VOLTAGE-CONTROLLED CURRENT CONVEYORS: APPLICATIONS TO RESISTANCE-CONTROL
Authors: ERRO M. A. , DÍAZ S. , ALASTRUEY C. F. , SANDOVAL J. M.
Published: July 2005

Variable gain Current Conveyors have been proposed to allow control of the value on fixed resistors. In this paper, procedures will be described, taking into account the stability of different configurations when a practical CCII- is applied. Correction circuits will modify the control range. Frequency response and transients are shown.
STEADY-STATE METHODS OF DIFFERENTIAL-ALGEBRAIC EQUATIONS IN CIRCUIT SIMULATION
Authors: JIANG YAO-LIN
Published: July 2005

In the paper, we study the steady-state methods of large dynamic systems. For a nonlinear system of differential-algebraic equations with a known period T, we decouple it, in function space, into linear subsystems by quasilinearization. The resulting linear dynamic systems can be solved by a waveform Krylov subspace method. For the autonomous case, that is, the period T is unknown, the well-known shooting process can be applied where Newton iterations are computed with pseudo-inverse.
IMPULSIVE SYNCHRONIZATION BETWEEN TWO MIXED-MODE CHAOTIC CIRCUITS
Authors: KILIÇ RECAİ
Published: July 2005

So far, impulsive synchronization method has been applied to several well-known chaotic circuits and systems such as Chua's circuit, Lorenz system and hyperchaotic circuit. Here, we present a study of impulsive synchronization of another chaotic circuit, namely mixed-mode chaotic circuit which oscillates both autonomous and nonautonomous chaotic dynamics. By choosing two mixed-mode chaotic circuits as driving and driven chaotic circuits, we investigated whether these circuits are synchronized impulsively or not by evaluating the minimum length of impulse width (Q), and the ratio of impulse width to impulse period (Q/T). The results of our investigation confirm that two mixed-mode chaotic circuits can be synchronized impulsively with very narrow impulse width.
AN FPGA IMPLEMENTATION OF THE GPRS ENCRYPTION ALGORITHM 3 (GEA3)
Authors: KITSOS P. , GALANIS M. D. , KOUFOPAVLOU O.
Published: July 2005

The General Packet Radio Service (GPRS) uses the GPRS Encryption Algorithm 3 (GEA3) for data encryption. In this paper, alternative hardware implementations of the GEA3 algorithm are described. GEA3 algorithm is based on the KASUMI block cipher. Various KASUMI block cipher hardware implementations have been examined in order to provide information about the required silicon area and throughput. In order to achieve a significant performance improvement, Double Edge Triggered pipeline technique is used. The S-BOXes, which are fundamental elements of the KASUMI cipher, have been implemented by using combinational logic and ROM memories. The proposed GEA3 algorithm hardware implementation achieves throughput up to 837Mbps, which is much faster comparing to the previous designs. The whole system is implemented and evaluated by using Field Programmable Gate Array (FPGA) devices.
AN EVOLUTIONARY ALGORITHM FOR THE ALLOCATION PROBLEM IN HIGH-LEVEL SYNTHESIS
Authors: HARMANANI HAIDAR M. , SALIBA RONY
Published: July 2005

This paper presents an evolutionary algorithm to solve the datapath allocation problem in high-level synthesis. The method performs allocation of functional units, registers, and multiplexers in addition to controller synthesis with the objective of minimizing the cost of hardware resources. The system handles multicycle functional units as well as structural pipelining. The proposed method was implemented using C++ on a Linux workstation. We tested our method on a set of high-level synthesis benchmarks, all yielding good solutions in a short time. An integration path to Field Programmable Gate Arrays (FPGAs) is provided through VHDL.
A NEW DIGITAL SCAN CONVERSION ARCHITECTURE FOR ULTRASONIC IMAGING SYSTEMS
Authors: KASSEM ABDALLAH , SAWAN MOHAMAD , BOUKADOUM MOUNIR
Published: July 2005

Digital scan conversion (DSC) is the process of converting received ultrasound signals, or echoes, in multi-scan lines, at varying angles (polar coordinate), to a Cartesian raster format for displaying. In this paper, we propose a new DSC technique that uses nearest-neighbor interpolation and the linear interpolation between adjacent scan lines to reduce artifacts on the far field, with smaller angular separation between the interpolated lines. A hardware implementation is described that uses only a FIFO register and a display memory. Rapid prototyping using an ARM processor with FPGA resources is achieved to validate the operation of the described system. Experimental results of the implemented design demonstrated the expected operation of the reduced complexity architecture in term of needed memory. Also, the performance of retrieved images were increased.
UBIC2 — TOWARDS UBIQUITOUS BIO-INFORMATION COMPUTING: DATA PROTOCOLS, MIDDLEWARE, AND WEB SERVICES FOR HETEROGENEOUS BIOLOGICAL INFORMATION INTEGRATION AND RETRIEVAL
Authors: HONG PENGYU , ZHONG SHENG , WONG WING H.
Published: July 2005

The Ubiquitous Bio-Information Computing (UBIC2) project aims to disseminate protocols and software packages to facilitate the development of heterogeneous bio-information computing units that are interoperable and may run distributedly. UBIC2 specifies biological data in XML formats and queries data using XQuery. The UBIC2 programming library provides interfaces for integrating, retrieving, and manipulating heterogeneous biological data. Interoperability is achieved via Simple Object Access Protocol (SOAP) based web services. The documents and software packages of UBIC2 are available at .
A LANGUAGE-BASED APPROACH FOR COMPREHENSIVELY SUPPORTING THEIN SILICOEXPERIMENTAL PROCESS
Authors: TRÖGER ANE , FERNANDES ALVARO A. A.
Published: July 2005

One of the challenges for bioinformaticians is to approximate, in silico, tried and tested research methods used in vitro. One of the problems standing in their way is the lack of a concrete framework for designing and expressing in silico experiments that aim at being isomorphic to in vitro experiments. This paper introduces such a framework in the form of a specification language called ISXL. ISXL projects to biologists a model of in silico experiments that approximates the research method they are most familiar with, as follows. An ISXL-specified experiment (1) conforms to a conceptual model that explicitly captures the basic constituents of experiments in the empirical sciences; (2) may be defined in relation to explicit hypothesis formulation and validation rather than simply taking the form of an evidence gathering process as in alternative approaches; (3) may be long-lived and evolve over time, in the sense that there is built-in support for denoting past versions of specifications, past results, past hypotheses, past validation criteria; (4) may denote other experiments and their constituent parts, thereby reflecting the interrelatedness of scientific processes. Features (1)-(4) above are made possible by endowing ISXL with certain characteristics of a persistent workflow environment. This allows ISXL experiments to be rich in metadata without imposing too great a burden on the biologist. The metadata in turn open the way for ISXL experiments to be capable of introspection and reflection. This paper focuses on describing of ISXL conceptually and syntactically, and indicates how ISXL experiments are given a formal semantics.
LIE SYMMETRIES OF THE ENERGY–MOMENTUM TENSOR FOR PLANE SYMMETRIC STATIC SPACETIMES
Authors: SAIFULLAH K.
Published: July 2005

Matter collineations (MCs) are the vector fields along which the energy–momentum tensor remains invariant under Lie transport. Invariance of the metric, the Ricci and the Riemann tensors have been studied extensively and the vectors along which these tensors remain invariant are called Killing vectors (KVs), Ricci collineations (RCs) and curvature collineations (CCs), respectively. In this paper, plane symmetric static spacetimes have been studied for their MCs. Explicit form of MCs together with the Lie algebra admitted by them has been presented. Examples of spacetimes have been constructed for which MCs have been compared with their RCs and KVs. The comparison shows that neither of the sets of RCs and MCs contains the other, in general.
THREE COMPONENTS EVOLUTION IN A SIMPLE BIG BOUNCE COSMOLOGICAL MODEL
Authors: XU LIXIN , LIU HONGYA
Published: July 2005

We consider a five-dimensional Ricci flat Bouncing cosmology and assume that the four-dimensional universe is permeated smoothly by three minimally coupled matter components: CDM + baryons ρm, radiation ρr and dark energy ρx. Evolutions of these three components are studied and it is found that dark energy dominates before the bounce, and pulls the universe contracting. In this process, dark energy decreases while radiation and the matter increases. After the bounce, the radiation and matter dominates alternatively and then decreases with the expansion of the universe. At present, the dark energy dominates again and pushes the universe accelerating. In this model, we also obtain that the equation of state (EOS) of dark energy at present time is wx0≈-1.05 and the redshift of the transition from decelerated expansion to accelerated expansion is zT≈0.37, which are compatible with the current observations.
SPHERICAL AND NON-SPHERICAL GRAVITATIONAL COLLAPSE IN HUSAIN SPACETIME
Authors: PATIL K. D. , THOOL U. S.
Published: July 2005

We investigate the nature of singularities arising in Husain solution. We analyze both spherical and non-spherical gravitational collapse in Husain spacetime. An interesting feature that emerges is that gravitational collapse of spherical cosmological Husain solution leads to the formation of naked singularities, while non-spherical cosmological collapse proceeds to form a black hole. Further strength of naked singularities arising in these spacetimes has been analyzed. It is found that these naked singularities are strong in Tipler's sense.
QUASI-STATIONARY ELECTROMAGNETIC EFFECTS IN CONDUCTORS AND SUPERCONDUCTORS IN SCHWARZSCHILD SPACE–TIME
Authors: AHMEDOV B. J. , FATTOYEV F. J.
Published: July 2005

The general principles needed to compute the effect of a stationary gravitational field on the quasistationary electromagnetic phenomena in normal conductors and superconductors are formulated from general relativistic point of view. Generalization of the skin effect, that is the general relativistic modification of the penetration depth (of the time-dependent magnetic field in the conductor) due to its relativistic coupling to the gravitational field is obtained. The effect of the gravitational field on the penetration and coherence depths in superconductors is also studied. As an illustration of the foregoing general results, we discuss their application to superconducting systems in the outer core of neutron stars. The relevance of these effects to electrodynamics of magnetized neutron stars has been shown.
THE PHYSICAL PROPERTIES OF XeCl EXCIMER PULSED LASER DEPOSITED n-C:P/p-Si PHOTOVOLTAIC SOLAR CELLS
Authors: RUSOP M. , SOGA T. , JIMBO T.
Published: July 2005

This paper reports on the successful deposition of phosphorus (P) -doped n-type (p-C:P) carbon (C) films, and fabrication of n-C:P/p-Si cells by pulsed laser deposition (PLD) using graphite target at room temperature. The cells performances have been given in the dark I–V rectifying curve and I–V working curve under illumination when exposed to AM 1.5 illumination condition (100mW/cm2, 25°C). The n-C:P/p-Si cell fabricated using a target with the amount of P by 7 weight percentages (Pwt%) shows the highest energy conversion efficiency η = 1.14% and fill factor FF = 41%. The quantum efficiency (QE) of the n-C:P/p-Si cells are observed to improve with Pwt%. The dependence of P content on the electrical and optical properties of the deposited films and the photovoltaic characteristics of the n-C:P/p-Si heterojunction solar cell are discussed.
A STUDY OF RECOVERY STAGES IN SOME PLASTICALLY DEFORMED ALUMINUM ALLOYS BY POSITRON LIFETIME SPECTROSCOPY
Authors: ABDEL-RAHMAN M. A. , ABDALLAH M. S. , BADAWI EMAD A.
Published: July 2005

Positron annihilation was performed to study the isochronal annealing of wrought (2024, 7075) and casting ( AlSi 11.35 Mg 0.23, AlSi 10.9 Mg 0.17 Sr 0.06) aluminum alloys in the temperature range from room temperature to 773 K after they had been deformed at room temperature with 25% deformation. Two annealing stages of microstructures were distinguished which were attributed to recovery in 2024, and AlSi 11.35 Mg 0.23, AlSi 10.9 Mg 0.17 Sr 0.06 due to point and dislocations respectively, and only one due to dislocations in 7075.
X-RAY PHOTOELECTRON SPECTROSCOPY STUDIES ON THE BONDING PROPERTIES OF AMORPHOUS CARBON NITRIDE FILMS SYNTHESIZED BY PULSED LASER DEPOSITION WITH DIFFERENT SUBSTRATE TEMPERATURES
Authors: RUSOP M. , SOGA T. , JIMBO T.
Published: July 2005

Amorphous carbon nitride films ( a-CN x) were deposited by pulsed laser deposition of camphoric carbon target with different substrate temperatures (ST). The influence of ST on the synthesis of a-CN x films was investigated. The nitrogen-to-carbon (N/C) and oxygen-to-carbon (O/C) atomic ratios, bonding state, and microstructure of the deposited a-CN x films were characterized by X-ray photoelectron spectroscopy and were confirmed by other standard measurement techniques. The bonding states between C and N , and C and O in the deposited films were found to be significantly influenced by ST during the deposition process. The N/C and O/C atomic ratios of the a-CN x films reached the maximum value at 400°C. ST of 400°C was proposed to promote the desired sp 3-hybridized C and the C 3 N 4 phase. The C–N bonding of C–N , C=N and C≡N were observed in the films.
ZrO2-COATED SiC NANOWIRES PREPARED BY PLASMA-ENHANCED ATOMIC LAYER CHEMICAL VAPOR DEPOSITION
Authors: TAK YOUNGJO , YONG KIJUNG
Published: July 2005

Plasma-enhanced atomic layer deposition (PE-ALCVD) of ZrO 2 was performed to coat SiC nanowires and prepare a SiC-ZrO 2 core-shell nanowire structure. Zirconium tertiary butoxide (ZTB) and hydrogen plasma pulse cycles were used to grow ZrO 2 films. The growth temperature of ZrO 2 PE-ALCVD was 150°C with a growth rate of 1.3 Å/cycle. SEM and TEM images showed uniform coating of SiC nanowires with ZrO 2. The thickness of ZrO 2 coat layer could be controlled by the total number of the pulse cycles. After being annealed at 900°C, a polycrystalline structure of ZrO 2 layer was observed.
SURFACE COATING OF CONCRETE MATERIALS BY DEPOSITION PROCESS
Authors: RYOU J. , MONTEIRO P. J. M.
Published: July 2005

A deposition process for coating concrete surface was presented in this study. This can be accomplished by feeding a weak direct current between the steel in a concrete and an electrode located in the external solution. The test was conducted using reinforced concrete prism specimens of 10 × 10 × 40 cm . Cracked specimens were immersed in an electrolyte magnesium acetate solution, and were applied with a constant current for 14 days. The results indicate that deposit materials are capable of coating the concrete surface and that this technique is effective for the improvement of the impermeability of concrete materials.
CORROSION PROTECTION OF AZ91D Mg ALLOY COATING WITH MICRO-ARC OXIDATION FILM EVALUATED BY IMMERSION AND ELECTROCHEMICAL TESTS
Authors: ZHANG X. P. , CHEN G.
Published: July 2005

This paper describes the preliminary results of corrosion protection of AZ91D Mg alloy coated with a micro-arc oxidation (MAO) coating. The corrosion behavior of coated substrates was evaluated by means of immersion and electrochemical tests in 5 wt.% NaCl solution. The immersions tests include weight loss measurement after full or partial immersion with the whole coat and full immersion with the damaged coat. The electrochemical tests include polarization curves and electrochemical impedance spectroscopy (EIS) measurements. The results of immersion and electrochemical tests show that micro-arc oxidation (MAO) surface treatment can significantly improve the corrosion resistance of the AZ91D Mg alloy in 5% NaCl solution, and the corrosion protection effect of the MAO coating is not sensitive to pores or cracks in the coating. The charge transfer resistance R ct , increases from about 1.669Ωcm2 for the uncoated alloy to about 1113Ωcm2 after being coated with MAO coat.
STUDY OF A BIMATERIAL SYSTEM BY AN IMPROVED DYNAMICAL THERMAL MODEL
Authors: OLIVA A. I. , MALDONADO R. D. , CEH O. , CORONA J. E. , RIVEROS H. G.
Published: July 2005

We present an improved dynamical thermal model and the corresponding experimental efforts to determine thermal profiles of thin metallic films deposited on thick substrates (bimaterial system) as are usually used in microelectronics. A dynamical thermal model to characterize the Joule heating of a metallic film/substrate system, as a function of the applied energy and the thickness is discussed. Good agreement between theoretical and measured thermal profiles on different bimaterial systems support the theoretical model obtained by solving a harmonic oscillator equation. By combining the thermal model and the experimental results it is possible to determine the convective coefficient of the room conditions, the diffusive time constant, and to quantify the different mechanisms of heat loss as a function of the physical properties and the geometrical parameters. The improved thermal model can be useful to rapidly predict a thermal behavior of film/substrate systems that are used for microelectronics.
WETLAND RESOURCES: Status, Trends, Ecosystem Services, and Restorability
Authors: Zedler Joy B. , Kercher Suzanne
Published: July 2005

▪ Abstract  Estimates of global wetland area range from 5.3 to 12.8 million km2. About half the global wetland area has been lost, but an international treaty (the 1971 Ramsar Convention) has helped 144 nations protect the most significant remaining wetlands. Because most nations lack wetland inventories, changes in the quantity and quality of the world's wetlands cannot be tracked adequately. Despite the likelihood that remaining wetlands occupy less than 9% of the earth's land area, they contribute more to annually renewable ecosystem services than their small area implies. Biodiversity support, water quality improvement, flood abatement, and carbon sequestration are key functions that are impaired when wetlands are lost or degraded. Restoration techniques are improving, although the recovery of lost biodiversity is challenged by invasive species, which thrive under disturbance and displace natives. Not all damages to wetlands are reversible, but it is not always clear how much can be retained through restoration. Hence, we recommend adaptive approaches in which alternative techniques are tested at large scales in actual restoration sites.
A common mitchondrial DNA variant is associated with thinness in mothers and their 20-yr-old offspring
Authors: Parker Ellen , Phillips D. I. W. , Cockington Richard A. , Cull Carole , Poulton Jo
Published: July 2005

A common mitochondrial (mt)DNA variant that is maternally inherited, the 16189 variant, is associated with type 2 diabetes and thinness at birth. To elucidate the association of the variant with thinness, we studied the 16189 variant in a well-characterized Australian cohort ( n = 161) who were followed up from birth to age 20 yr. PCR analysis and mtDNA haplotyping was carried out on DNA from 161 offspring from consecutive, normal, singleton pregnancies followed from birth to age 20 yr. The 16189 mtDNA variant was present in 14 of the 161 20 yr olds (8.7%). Both the mothers with the 16189 variant and their 20-yr-old offspring were thinner than those without. Median (interquartile range) BMI was 21.9 kg/m2(20.4 to 22.9) in mothers with the variant compared with 23.5 (21.4 to 26.6) in those without ( P = 0.013) and 22.2 (21.1 to 23.8) in 20 yr olds with the variant compared with 22.7 (20.8 to 25.6) in those without ( P = 0.019). The 16189 variant was also associated with a high placental weight and high placental-to-birth weight ratio ( P = 0.051 and P = 0.0024, respectively). Insulin sensitivity was normal in 20 yr olds with the 16189 variant. This contrasts with 20 yr olds who did not have the variant but who had been thin or small at birth and who had normal BMI and normal placental-to-birth weight ratio, but were insulin resistant. This study suggests that the 16189 mtDNA variant is associated with maternally inherited thinness in young adults. This may be mediated by effects on mtDNA replication and, thence, placental function. Further research is required to confirm these hypotheses.
Defective water and glycerol transport in the proximal tubules of AQP7 knockout mice
Authors: Sohara Eisei , Rai Tatemitsu , Miyazaki Jun-ichi , Verkman A. S. , Sasaki Sei , Uchida Shinichi
Published: July 2005

The aquaporin-7 (AQP7) water channel is known as a member of the aquaglyceroporins, which facilitate the transport of glycerol as well as water. Although AQP7 is abundantly expressed on the apical membrane of the proximal straight tubules in the kidney, the physiological role of AQP7 is still unknown. To investigate this, we generated AQP7 knockout mice. The water permeability of the proximal tubule brush-border membrane measured by the stopped-flow method was slightly but significantly reduced in the AQP7 knockout mice compared with that of wild-type mice (AQP7, 18.0 ± 0.4 × 10−3cm/s vs. wild-type, 20.0 ± 0.3 × 10−3cm/s). Although AQP7 solo-knockout mice did not exhibit a urinary concentrating defect, AQP1/AQP7 double-knockout mice had a reduction in urinary concentrating ability compared with AQP1 solo-knockout mice, suggesting that the amount of water reabsorbed through AQP7 in the proximal straight tubules is physiologically substantial. On the other hand, AQP7 knockout mice showed marked glyceroluria (AQP7, 1.7 ± 0.34 mg/ml vs. wild-type, 0.005 ± 0.002 mg/ml). This identified a novel glycerol reabsorption pathway in the proximal straight tubules. In two mouse models of proximal straight tubule injury, the cisplatin-induced acute renal failure (ARF) model and the ischemic ARF model, an increase in urine glycerol was observed (pretreatment, 0.007 ± 0.005 mg/ml; cisplatin, 0.063 ± 0.043 mg/ml; ischemia, 0.076 ± 0.02 mg/ml), suggesting that urine glycerol could be used as a new biomarker for detecting proximal straight tubule injury.
Renal 20-HETE inhibition attenuates changes in renal hemodynamics induced byl-NAME treatment in pregnant rats
Authors: Huang Hui , Zhou Yiqiang , Raju Venugopal T. , Du Juan , Chang Hsin-Hsin , Wang Cong-Yi , Brands Michael W. , Falck John R. , Wang Mong-Heng
Published: July 2005

We previously reported that inhibition of nitric oxide (NO) synthesis by N-nitro-l-arginine methyl ester (l-NAME) during late pregnancy leads to increased production of renal vascular 20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P-450 (CYP) 4A-derived vasoconstrictor, in pregnant rats. However, the effect of upregulation of vascular 20-HETE production on renal function after NO inhibition is not known. To test the hypothesis that increased gestational vascular 20-HETE synthesis after NO inhibition is involved in mediating blood pressure and renal functional changes, we first determined the IC50value of the effect of nitroprusside (SNP), a NO donor, on renal 20-HETE production in cortical microsomes. We then divided pregnant rats and age-matched virgin rats into a vehicle control group, an l-NAME treatment group (0.25 mg/ml in drinking water), and a group treated with l-NAME plus N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS; CYP4A-selective inhibitor, 10 mg·kg−1·day−1iv). After 4 days of treatment, we measured blood pressure, renal blood flow (RBF), renal vascular resistance (RVR), and glomerular filtration rate (GFR) in each group. The addition of SNP (IC50= 22 μM) decreased renal cortical 20-HETE production. In pregnant rats, l-NAME treatment led to significantly higher mean arterial pressure (MAP) and RVR, and lower RBF and GFR. Combined treatment with DDMS and l-NAME significantly attenuated the increases in MAP and RVR and the decrease in GFR, but not the reduction in RBF induced by l-NAME treatment. l-NAME and l-NAME plus DDMS had no significant impact on renal hemodynamics in virgin rats. In addition, chronic treatment with DDMS selectively inhibited cortical 20-HETE production without a significant effect on CYP4A expression in l-NAME-treated pregnant rats. In conclusion, NO effectively inhibits renal cortical microsomal 20-HETE production in female rats. In pregnant rats, the augmentation of renal 20-HETE production after NO inhibition is associated with increased MAP and RVR, whereas decreased GFR is negated by treatment of a selective and competitive CYP4A inhibitor. These results demonstrate that the interaction between renal 20-HETE and NO is important in the regulation of renal function and blood pressure in pregnant rats.
Renocortical mRNA expression of vasoactive factors during spironolactone protective effect in chronic cyclosporine nephrotoxicity
Authors: Pérez-Rojas Jazmin M. , Derive Stephanie , Blanco Jorge A. , Cruz Cristino , de la Maza Lilia Martínez , Gamba Gerardo , Bobadilla Norma A.
Published: July 2005

We showed that spironolactone reduced structural damage and prevented renal dysfunction in chronic cyclosporine (CsA) nephrotoxicity. These findings evidenced an aldosterone renal vascular effect under this condition. To investigate aldosterone’s role in modulating renal vascular tone, renocortical vasoactive pathways mRNA levels in chronic CsA nephrotoxicity as well as spironolactone’s effect on renal function in acute CsA nephrotoxicity were evaluated. Two experimental sets were designed. For chronic nephrotoxicity, rats fed with low-sodium diet were divided into groups receiving vehicle, spironolactone (Sp), CsA, and CsA+Sp, for 21 days. Creatinine clearance, survival percentage, and renocortical mRNA levels of pro-renin, angiotensinogen (Ang), angiotensin receptors (AT1A, AT1B, and AT2), preproendothelin, endothelin receptors (ETA, ETB), cyclooxygenase-2 (COX-2), and adenosine receptors (Ad1, Ad2A, Ad2B, and Ad3) were analyzed. For acute nephrotoxicity, similar groups fed with a standard chow diet for 7 days were included. Serum potassium and sodium, glomerular filtration rate (GFR), and renal blood flow (RBF) were determined. In chronic model, CsA produced pro-renin and ET upregulation, altered adenosine receptors expression, and reduced Ang, AT1A, AT1B, ETB, and COX-2 mRNA levels. Spironolactone protective effect in chronic nephrotoxicity was associated with prevention of pro-renin upregulation and increased AT2, together with ETBreduction. In acute nephrotoxicity, spironolactone completely prevented GFR and RBF reduction induced by CsA. Our results suggest that aldosterone contributes to renal vasoconstriction observed in CsA nephrotoxicity and that renoprotection conferred by spironolactone was related to modification of renocortical vasoactive pathways expression, in which pro-renin normalization was the most evident change in chronic nephropathy. Finally, our data point to spironolactone as a potential treatment to reduce CsA nephrotoxicity in transplant patients.
A critical role for enhanced TGF-α and EGFR expression in the initiation of parathyroid hyperplasia in experimental kidney disease
Authors: Cozzolino Mario , Lu Yan , Sato Tetsuhiko , Yang Jing , Suarez Ignacio Gonzalez , Brancaccio Diego , Slatopolsky Eduardo , Dusso Adriana S.
Published: July 2005

The parathyroid hyperplasia secondary to kidney disease is associated with enhanced expression of the growth promoter transforming growth factor-α (TGF-α). TGF-α stimulates growth through activation of its receptor, the epidermal growth factor receptor (EGFR), normally expressed in the parathyroid glands. Because enhanced coexpression of TGF-α and EGFR causes aggressive cellular growth, these studies utilized highly specific inhibitors of EGFR tyrosine kinase, a step mandatory for TGF-α-induced EGFR activation, to assess the contribution of growth signals from enhanced expression of TGF-α exclusively or both TGF-α and EGFR to the rapid parathyroid growth induced by kidney disease and exacerbated by high-phosphorus (P) and low-calcium (Ca) diets in rats. The enhancement in parathyroid gland weight and proliferating activity (proliferating cell nuclear antigen/Ki67) induced by kidney disease and aggravated by either high P or low Ca intake, within the first week after 5/6 nephrectomy, in rats, coincided with simultaneous increases (2- to 3-fold) in TGF-α and EGFR content. Conversely, prevention of the increases in both TGF-α and EGFR paralleled the efficacy of either P restriction or high-Ca intake in ameliorating uremia-induced parathyroid hyperplasia. More importantly, suppression of TGF-α/EGFR signaling, through prophylactic administration of potent and highly selective inhibitors of ligand-induced EGFR activation, completely prevented both high-P- and low-Ca-induced parathyroid hyperplasia as well as TGF-α self-upregulation. Thus enhanced parathyroid TGF-α/EGFR expression, self-upregulation, and growth signals occur early in kidney disease, are aggravated by low-Ca and high-P intake, and constitute the main pathogenic mechanism of the severity of parathyroid hyperplasia.
Mesangial cell-reduced Ca2+signaling in high glucose is due to inactivation of phospholipase C-β3by protein kinase C
Authors: Frecker Helena , Munk Snezana , Wang Hong , Whiteside Catharine
Published: July 2005

In high glucose, glomerular mesangial cells (MCs) demonstrate impaired Ca2+signaling in response to seven-transmembrane receptor stimulation. To identify the mechanism, we first postulated decreased release from intracellular stores. Intracellular Ca2+was measured in fluo-3-loaded primary cultured rat MCs using confocal fluorescence microscopy. In high glucose (HG) 30 mM for 48 h, the 25 nM ionomycin-stimulated intracellular Ca2+response was reduced to 82% of that observed in normal glucose (NG). In NG 5.6 mM, Ca2+responses to endothelin (ET)-1 and platelet-derived growth factor (PDGF) were unchanged in cells cultured in 50 nM Ca2+vs. 1.8 mM Ca2+. Depletion of intracellular Ca2+stores with thapsigargin eliminated ET-1-stimulated Ca2+responses. Incubation in 30 mM glucose (HG) for 48 h or stimulation with phorbol myristate acetate (PMA) for 10 min eliminated the Ca2+response to ET-1 but had no effect on the PDGF response. Downregulation of protein kinase C (PKC) with 24-h PMA or inhibition with Gö6976 in HG normalized the Ca2+response to ET-1. Because ET-1 and PDGF stimulate Ca2+signaling through different phospholipase C pathways, we hypothesized that, in HG, PKC selectively phosphorylates and inhibits PLC-β3. Using confocal immunofluorescence imaging, in NG, a 1.6- to 1.7-fold increase in PLC-β3Ser1105phosphorylation was observed following PMA or ET-1 stimulation for 10 min. In HG, immunofluorescent imaging and immunoblotting showed increased PLC-β3phosphorylation, without change in total PLC-β3, which was reversed with 24-h PMA or Gö6976. We conclude that reduced Ca2+signaling in HG cannot be explained by reduced Ca2+stores but is due to conventional PKC-dependent phosphorylation and inactivation of PLC-β3.
Vitamin D receptor-independent FGF23 actions in regulating phosphate and vitamin D metabolism
Authors: Shimada Takashi , Yamazaki Yuji , Takahashi Motoo , Hasegawa Hisashi , Urakawa Itaru , Oshima Takeshi , Ono Kaori , Kakitani Makoto , Tomizuka Kazuma , Fujita Toshiro , Fukumoto Seiji , Yamashita Takeyoshi
Published: July 2005

FGF23 suppresses both serum phosphate and 1,25-dihydroxyvitamin D [1,25D] levels in vivo. Because 1,25D itself is a potent regulator of phosphate metabolism, it has remained unclear whether FGF23-induced changes in phosphate metabolism were caused by a 1,25D-independent mechanism. To address this issue, we intravenously administered recombinant FGF23 to vitamin D receptor (VDR) null (KO) mice as a rapid bolus injection and evaluated the early effects of FGF23. Administration of recombinant FGF23 further decreased the serum phosphate level in VDR KO mice, accompanied by a reduction in renal sodium-phosphate cotransporter type IIa (NaPi2a) protein abundance and a reduced renal 25-hydroxyvitamin D-1α-hydroxylase (1αOHase) mRNA level. Thus FGF23-induced changes in NaPi2a and 1αOHase expression are independent of the 1,25D/VDR system. However, 24-hydroxylase (24OHase) mRNA expression remained undetectable by the treatment with FGF23. We also analyzed the regulatory mechanism for FGF23 expression. The serum FGF23 level was almost undetectable in VDR KO mice, whereas dietary calcium supplementation significantly increased circulatory levels of FGF23 and its mRNA abundance in bone. This finding indicates that calcium is another determinant of FGF23 production that occurs independently of the VDR-mediated mechanism. In contrast, dietary phosphate supplementation failed to induce FGF23 expression in the absence of VDR, whereas marked elevation in circulatory FGF23 was observed in wild-type mice fed with a high-phosphate diet. Taken together, FGF23 works, at least in part, in a VDR-independent manner, and FGF23 production is also regulated by multiple mechanisms involving VDR-independent pathways.
Two Populations of Layer V Pyramidal Cells of the Mouse Neocortex: Development and Sensitivity to Anesthetics
Authors: Christophe Elodie , Doerflinger Nathalie , Lavery Daniel J. , Molnár Zoltán , Charpak Serge , Audinat Etienne
Published: July 2005

Previous studies have shown that layer V pyramidal neurons projecting either to subcortical structures or the contralateral cortex undergo different morphological and electrophysiological patterns of development during the first three postnatal weeks. To isolate the determinants of this differential maturation, we analyzed the gene expression and intrinsic membrane properties of layer V pyramidal neurons projecting either to the superior colliculus (SC cells) or the contralateral cortex (CC cells) by combining whole cell recordings and single-cell RT-PCR in acute slices prepared from postnatal day (P) 5–7 or P21–30 old mice. Among the 24 genes tested, the calcium channel subunits α1B and α1C, the protease Nexin 1, and the calcium-binding protein calbindin were differentially expressed in adult SC and CC cells and the potassium channel subunit Kv4.3 was expressed preferentially in CC cells at both stages of development. Intrinsic membrane properties, including input resistance, amplitude of the hyperpolarization-activated current, and action potential threshold, differed quantitatively between the two populations as early as from the first postnatal week and persisted throughout adulthood. However, the two cell types had similar regular action potential firing behaviors at all developmental stages. Surprisingly, when we increased the duration of anesthesia with ketamine–xylazine or pentobarbital before decapitation, a proportion of mature SC cells, but not CC cells, fired bursts of action potentials. Together these results indicate that the two populations of layer V pyramidal neurons already start to differ during the first postnatal week and exhibit different firing capabilities after anesthesia.
Anticonvulsant Action of GABA in the High Potassium–Low Magnesium Model of Ictogenesis in the Neonatal Rat Hippocampus In Vivo and In Vitro
Authors: Isaev Dmytro , Isaeva Elena , Khazipov Rustem , Holmes Gregory L.
Published: July 2005

Previous developmental studies in vitro suggested that the inhibitory neurotransmitter GABA exerts depolarizing and excitatory actions on the immature neurons and that depolarizing GABA is causally linked to ictal activity during the first weeks of postnatal life. However, remarkably little is known on the role of GABA in the generation of neonatal seizures in vivo. Here, using extracellular recordings from CA3 hippocampus, we studied the effects of GABAA-acting drugs on electrographic seizures induced by local intrahippocampal injection of the epileptogenic agents (high K+/low Mg2+) in the nonanesthetized rats in vivo and in the hippocampal slices in vitro during the second postnatal week (postnatal days P8-12). We found that in vivo, the induction of ictal-like events was facilitated by co-infusion of high-K+/low Mg2+ together with the GABAA antagonist bicuculline or gabazine. Moreover, the infusion of bicuculline alone caused ictal-like activity in ∼30% of cases. Co-infusion of the GABAA receptor agonist isoguvacine or the GABAA-positive allosteric modulator diazepam completely prevented high-K+/low Mg2+-induced seizures. In in vitro studies using hippocampal slices, we also found that high-K+/low Mg2+ produced ictal activity that was exacerbated by bicuculline and gabazine and reduced by isoguvacine. Thus in the model of high-K+/low Mg2+-induced seizures both in in vivo and in vitro conditions, GABA, acting via GABAA receptors, has an anticonvulsant effect during the critical developmental period of enhanced excitability.
Disparity-Tuning Characteristics of Neuronal Responses to Dynamic Random-Dot Stereograms in Macaque Visual Area V4
Authors: Tanabe Seiji , Doi Takahiro , Umeda Kazumasa , Fujita Ichiro
Published: July 2005

Stereo processing begins in the striate cortex and involves several extrastriate visual areas. We quantitatively analyzed the disparity-tuning characteristics of neurons in area V4 of awake, fixating monkeys. Approximately half of the analyzed V4 cells were tuned for horizontal binocular disparities embedded in dynamic random-dot stereograms (RDSs). Their response preferences were strongly biased for crossed disparities. To characterize the disparity-tuning profile, we fitted a Gabor function to the disparity-tuning data. The distribution of V4 cells showed a single dense cluster in a joint parameter space of the center and the phase parameters of the fitted Gabor function; most V4 neurons were maximally sensitive to fine stereoscopic depth increments near zero disparity. Comparing single-cell responses with background multiunit responses at the same sites showed that disparity-sensitive cells were clustered within V4 and that nearby cells possessed similar preferred disparities. Consistent with a recent report by Hegdé and Van Essen, the disparity tuning for an RDS drastically differed from that for a solid-figure stereogram (SFS). Disparity-tuning curves were generally broader for SFSs than for RDSs, and there was no correlation between the fitted Gabor functions' amplitudes, widths, or peaks for the two types of stereograms. The differences were partially attributable to shifts in the monocular images of an SFS. Our results suggest that the representation of stereoscopic depth in V4 is suited for detecting fine structural features protruding from a background. The representation is not generic and differs when the stimulus is broad-band noise or a solid figure.
Development of a Robust Central Auditory Synapse in Congenital Deafness
Authors: Youssoufian M. , Oleskevich S. , Walmsley B.
Published: July 2005

Within the medial nucleus of the trapezoid body (MNTB) in the auditory brain stem, there is a large central synapse known as the calyx of Held, which mediates high-fidelity glutamatergic transmission. We investigated the effects of congenital deafness on the development of pre- and postsynaptic parameters of synaptic strength at the calyx of Held. Whole cell recordings of evoked excitatory postsynaptic currents (EPSCs) and immunohistochemistry of GluR1–4 subunits were performed using brain stem slices from congenitally deaf or hearing mice at postnatal days P5 and P12. In both hearing and deaf mice there was a similar developmental decrease in the NMDA component of the evoked EPSC. There was a concurrent increase in release probability and number of release sites, contributing to a fivefold increase in evoked AMPA-mediated EPSC amplitude. The increase in release probability is opposite to that found in previous studies at the calyx of Held in the rat. There was also a seven- to eightfold increase in the size of the readily releasable pool of vesicles and a decrease in tetanic depression. The postsynaptic glutamate receptor subunits were similarly developmentally regulated and unaffected by deafness. GluR1 and 4 dominated at both ages. There was a decrease in expression of GluR1–3 from P5 to P12 and a shift from GluR2 to GluR3, indicating that AMPA receptor complexes at P12 are predominantly calcium-permeable. These results demonstrate that early development at this robust synapse proceeds normally with congenital deafness, suggesting that auditory nerve activity does not affect the development of synaptic strength at the calyx of Held.