bluuebunny/crossref_metadata_2025 huggingface dataset:
Q2S2: A New Methodology for Merging Quantitative and Qualitative Information in Experimental Design
Authors: Rai Rahul , Campbell Matthew
Published: April 2009

Sequential sampling refers to a set of experimental design methods where the next sample point is determined by information from previous experiments. This paper introduces a new sequential sampling method where optimization and user knowledge are used to guide the efficient choice of sample points. This method combines information from multiple sources of varying fidelity including actual physical experiments, computer simulation models of the product, and first principles involved in design and designer’s qualitative intuition about the design. Both quantitative and qualitative information from different sources are merged together to arrive at a new sampling strategy. This is accomplished by introducing the concept of a confidence function C, which is represented as a field that is a function of the decision variables x and the performance parameter f. The advantages of the approach are demonstrated using different example cases. The examples include design of a bistable microelectro mechanical system switch, a complex and relevant mechanical system.
Topological and Geometrical Synthesis of Three-Degree-of-Freedom Fully Parallel Manipulators by Instantaneous Kinematics
Authors: Wang Xiaoyu , Baron Luc , Cloutier Guy
Published: April 2009

This paper presents a new synthesis procedure of fully parallel manipulators (PMs) of three degrees of freedom (DOFs) that could be implemented in a computer-aided synthesis process. Possible designs of PMs are represented by a set of unit joint twists at an initial configuration, called here topological and geometric parameters (TGPs). This makes it possible to represent PMs of all topologies and geometries in an easy and consistent way. The kinematic bond between the end effector (EE) and the base is then formulated as a set of equations involving TGPs, actuated-joint variables, and non-actuated-joint variables (passive joints). To achieve the required type of EE motion, possible topologies are first derived from tangent space analysis, and then the feasible topologies are retained by further displacement analysis. The geometries are determined such that the set of equations should be isoconstrained when passive-joint variables are taken as unknowns. The synthesis procedure of 3DOF PMs is illustrated with three numerical examples: one producing a new architecture of one translation and two rotations, while the other two producing existing architectures of translational PMs.
Kinematic Synthesis of Planar, Shape-Changing Rigid-Body Mechanisms
Authors: Murray Andrew P. , Schmiedeler James P. , Korte Brian M.
Published: April 2009

This paper presents a kinematic procedure to synthesize planar mechanisms, composed of rigid links and revolute joints, capable of approximating a shape change defined by a set of curves. These “morphing curves”, referred to as design profiles, differ from each other by a combination of rigid-body displacement and shape change. Design profiles are converted to piecewise linear curves, referred to as target profiles, that can be readily manipulated. In the segmentation phase, the geometry of rigid links that approximate the shapes of corresponding segments from each target profile is determined. In the mechanization phase, these rigid links are joined together at their end points with revolute joints to form a single chain. Dyads are then added to reduce the number of degrees of freedom (DOF’s) to any desired value, typically 1. The approach can be applied to any number of design profiles that can be approximated with any number of rigid links, which can then be used to construct a mechanism with any number of DOF’s. Naturally, greater difficulty is encountered for larger numbers of design profiles and/or links and for more dramatic changes in shape. The procedure is demonstrated with examples of single-DOF mechanisms approximating shape changes between two and three design profiles.
Tooth Root Strength of Spur and Helical Gears Manufactured With Gear-Shaper Cutters
Authors: Kawalec Andrzej , Wiktor Jerzy
Published: April 2009

At the beginning of gear transmission design, mainly simplified methods of gear strength analysis based on ISO or AGMA standards are used. However, they allow for calculation of approximate and sometimes biased stresses. Moreover, ISO standard is generally focused on using racks for gear manufacturing. A method proposed in this paper allows for computation of the parameters of critical section, strength coefficients YF, YS, and tooth root stress σF according to the procedure from ISO standard also in the case of machining gears with gear type tools. The proposed improvement of ISO standard leads to replacement of real gear tool with rack with substitute tip radius ρa0*. The developed method maintains basic assumptions and advantages of ISO standard, including its simplicity. Simultaneously, it allows for computing the maximum tooth root stresses σF: (i) very close to results of accurate geometric analysis and finite element analysis, and (ii) much closer, compared to conventional ISO procedure, to results obtained using AGMA standard.
Gear Windage: A Review
Authors: Eastwick Carol N. , Johnson Graham
Published: April 2009

The efficiency of power and propulsive systems is increasingly being targeted as a means of reducing environmental impact. This has caused a renewed interest in industry in the losses associated with meshing gears. Gearbox efficiency varies from 98% to 99% for the best designed high power applications, but that can still equate to losses in megawatts. There are different mechanisms for losses that have been identified within gearboxes; these are meshing losses, bearing losses, windage losses, and churning losses. Depending on the application, the relative importance of these mechanisms varies. This paper reviews information on windage power loss. The motivation for this is that for some applications, this power loss can be a significant component, particularly lightly loaded high-speed applications. For instance, within some aeroengines, gears are mounted internally within bearing chambers. The component of windage power loss becomes significant in this case, and the flows associated with windage power loss have a significant impact on the amount of heat transferred to the oil within the chamber, which is a critical design consideration. This paper provides a review of experimental investigations and available models of gear windage power loss for spur, helical, and bevel gears. The aim of the review is to provide a comprehensive compilation of published information on windage power loss to assist gearbox designers in identifying relevant experimental and modeling information. While it is clear from the review of published work that the rotational speed, gear geometrical parameters, degree of confinement, and density of the fluid surrounding the gear are important, the degree of effect and general solutions for reducing power loss are less clear.
Numerical and Experimental Investigation of Secondary Flow in a High-Speed Compressor Stator
Authors: Ohkita Y. , Kodama H. , Nozaki O. , Kikuchi K. , Tamura A.
Published: April 2009

A series of numerical and experimental studies have been conducted to understand the mechanism of loss generation in a high-speed compressor stator with inlet radial shear flow over the span. In this study, numerical simulation is extensively used to investigate the complex three-dimensional flow in the cascades and to interpret the phenomena that appeared in the high-speed compressor tests. It has been shown that the inlet radial shear flow generated by the upstream rotor had a significant influence on the stator secondary flow, and consequently on the total pressure loss. Redesign of the stator aiming at the reduction of loss by controlling secondary flow has been carried out and the resultant performance recovery was successfully demonstrated both numerically and experimentally.
Rotor Blade-to-Blade Measurements Using Particle Image Velocimetry
Authors: Tisserant D. , Breugelmans F. A. E.
Published: April 2009

The study of turbomachinery flow fields requires detailed experimental data. The rotating parts of turbomachines greatly limit the measurement techniques that can be used. Particle Image Velocimetry (PIV) appears to be a suitable tool to investigate the blade-to-blade flow in a rotor. The facility is a subsonic axial-flow compressor. The experimental apparatus enables the recording of a double-exposed photograph in a circumferential plane located at 85 percent of the blade height. The illumination plane has an axial direction and is provided by a pulsed ruby laser. The tracers used are submicron glycerine oil droplets. Data are processed by Young’s fringes method. Measurements were performed at 3000, 4500, and 6000 rpm with velocities in the range of 30 to 70 m/s. Steady operating conditions are chosen in such a way that the effect of radial velocity on PIV measurements can be neglected. Experimental problems encountered included homogeneous seeding of the flow field and laser light scattering from blade surfaces. The uncertainty affecting the velocity determination corresponds to 2 percent of the measured value. For a given set of operating conditions, 10 PIV pictures are recorded. The periodic flow field is approximated by averaging the experimental data point by point. Upstream and downstream velocity triangles are confirmed by measurements obtained from pressure probes. PIV measurement results were found to be similar to those of a blade-to-blade potential-flow calculation.
Influence of Leading-Edge Geometry on Profile Losses in Turbines at Off-Design Incidence: Experimental Results and an Improved Correlation
Authors: Benner M. W. , Sjolander S. A. , Moustapha S. H.
Published: April 2009

The most recent correlations for turbine profile losses at off-design incidence include the leading-edge diameter as the only aspect of the leading-edge geometry that influences the losses. Cascade measurements are presented for two turbine blades that differ primarily in their leading-edge geometries. The incidence was varied over a range of ±20 deg and the results show significant discrepancies between the observed profile losses and those predicted by the available correlations. Using data from the present experiments, as well as cases from the literature for which sufficient geometric data are given, a revised correlation has been developed. The new correlation is a function of both the leading-edge diameter and the wedge angle, and it is significantly more successful than the existing correlations. It is argued that the off-design loss behavior of the blade is influenced by the magnitude of the discontinuity in curvature at the points where the leading-edge circle meets the rest of the blade profile. The wedge angle appears to be an approximate and convenient measure of the discontinuity in curvature at these blend points.
Throughflow Method for Turbomachines Applicable for All Flow Regimes
Authors: Damle S. V. , Dang T. Q. , Reddy D. R.
Published: April 2009

A new axisymmetric throughflow method for analyzing and designing turbomachines is proposed. This method utilizes body-force terms to represent blade forces and viscous losses. The resulting equations of motion, which include these body-force terms, are cast in terms of conservative variables and are solved using a finite-volume time-stepping scheme. In the inverse mode, the swirl schedule in the bladed regions (i.e., the radius times the tangential velocity rVθ) is the primary specified flow quantity, and the corresponding blade shape is sought after. In the analysis mode, the blade geometry is specified and the flow solution is computed. The advantages of this throughflow method compared to the current family of streamline curvature and matrix methods are that the same code can be used for subsonic/transonic/supersonic throughflow velocities, and the proposed method has a shock capturing capability. This method is demonstrated for designing a supersonic throughflow fan stage and a transonic throughflow turbine stage.
Finite Volume Scheme With Quadratic Reconstruction on Unstructured Adaptive Meshes Applied to Turbomachinery Flows
Authors: Delanaye M. , Essers J. A.
Published: April 2009

This paper presents a new finite volume cell-centered scheme for solving the two-dimensional Euler equations. The technique for computing the advective derivatives is based on a high-order Gauss quadrature and an original quadratic reconstruction of the conservative variables for each control volume. A very sensitive detector identifying discontinuity regions switches the scheme to a TVD scheme, and ensures the monotonicity of the solution. The code uses unstructured meshes whose cells are polygons with any number of edges. A mesh adaptation based on cell division is performed in order to increase the resolution of shocks. The accuracy, insensitivity to grid distortions, and shock capturing properties of the scheme are demonstrated for different cascade flow computations.
Heat Transfer Predictions for Two Turbine Nozzle Geometries at High Reynolds and Mach Numbers
Authors: Boyle R. J. , Jackson R.
Published: April 2009

Predictions of turbine vane and endwall heat transfer and pressure distributions are compared with experimental measurements for two vane geometries. The differences in geometries were due to differences in the hub profile, and both geometries were derived from the design of a high rim speed turbine (HRST). The experiments were conducted in the Isentropic Light Piston Facility (ILPF) at Pyestock at a Reynolds number of 5.3 x 106, a Mach number of 1.2, and a wall-to-gas temperature ratio of 0.66. Predictions are given for two different steady-state three-dimensional Navier–Stokes computational analyses. C-type meshes were used, and algebraic models were employed to calculate the turbulent eddy viscosity. The effects of different turbulence modeling assumptions on the predicted results are examined. Comparisons are also given between predicted and measured total pressure distributions behind the vane. The combination of realistic engine geometries and flow conditions proved to be quite demanding in terms of the convergence of the CFD solutions. An appropriate method of grid generation, which resulted in consistently converged CFD solutions, was identified.
Flow Characteristics and Aerodynamic Losses of Film-Cooling Jets With Compound Angle Orientations
Authors: Lee Sang Woo , Kim Yong Beom , Lee Joon Sik
Published: April 2009

Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate the flow characteristics and aerodynamic loss distributions of film-cooling jets with compound angle orientations. For a fixed inclination angle of the injection hole, measurements are performed at various orientation angles to the direction of the mainstream in the case of three velocity ratios of 0.5, 1.0, and 2.0. Flow visualizations for the velocity ratio of 2.0 show that the increase in the orientation angle furnishes better film coverage on the test surface, but gives rise to large flow disturbances in the mainstream. A near-wall flow model has been proposed based on the surface flow visualizations. It has also been found from the flow measurements that as the orientation angle increases, a pair of count-errotating vortices turn to a single strong one, and the aerodynamic loss field is closely related to the secondary flow. Even in the case of the velocity ratio of 2.0, aerodynamic loss is produced within the jet region when the orientation angle is large. Regardless of the velocity ratio, the mass-averaged aerodynamic loss increases with increasing orientation angle, the effect of which on aerodynamic loss is pronounced when the velocity ratio is large.
Multiple Jets in a Crossflow: Detailed Measurements and Numerical Simulations
Authors: Ajersch P. , Zhou J.-M. , Ketler S. , Salcudean M. , Gartshore I. S.
Published: April 2009

The fluid mechanics and heat transfer characteristics of film cooling are three-dimensional and highly complex. To understand this problem better, an experimental study was conducted in a low-speed wind tunnel on a row of six rectangular jets injected at 90 deg to the crossflow (mainstream flow). The jet-to-crossflow velocity ratios (blowing ratios) examined were 0.5, 1.0, and 1.5, and the jet spacing-to-jet width ratio was 3.0. No significant temperature difference between jet and crossflow air was introduced. Mean velocities and six flow stresses were measured using a three-component laser-Doppler velocimeter operating in coincidence mode. Seeding of both jet and cross-stream air was achieved with a commercially available smoke generator. Flow statistics are reported in the form of vector plots, contours, and x-y graphs, showing velocity, turbulence intensity, and Reynolds stresses. To complement the detailed measurements, flow visualization was accomplished by transmitting the laser beam through a cylindrical lens, thereby generating a narrow, intense sheet of light. Jet air only was seeded with smoke, which was illuminated in the plane of the light sheet. Therefore, it was possible to record on video tape the trajectory and penetration of the jets in the crossflow. Selected still images from the recordings are presented. Numerical simulations of the observed flow field were made by using a multigrid, segmented, k–ε CFD code. Special near-wall treatment included a nonisotropic formulation for the effective viscosity, a low-Re model for k, and an algebraic model for the length scale. Comparisons between the measured and computed velocities show good agreement for the nonuniform mean flow at the jet exit plane. Velocities and stresses on the jet centerline downstream of the orifice are less well predicted, probably because of inadequate turbulence modeling, while values off the centerline match those of the experiments much more closely.
Adiabatic Effectiveness, Thermal Fields, and Velocity Fields for Film Cooling With Large Angle Injection
Authors: Kohli A. , Bogard D. G.
Published: April 2009

The film cooling performance and velocity field were investigated for discrete round holes inclined at an injection angle of 55 deg. Results are compared to typical round film cooling holes, with an injection angle of 35 deg. All experiments in this study were performed at a density ratio of DR = 1.6, using cryogenic cooling of the injected air. Centerline and lateral distributions of effectiveness were obtained for a range of momentum flux ratios. Thermal field and two component mean velocity and turbulence intensity measurements were made at a momentum flux ratio that was within the range of maximum spatially averaged effectiveness. Compared to round holes with 35 deg injection angle, the 55 deg holes showed only a slight degradation in centerline effectiveness for low momentum flux ratios, while a significant reduction in effectiveness was seen at high momentum flux ratios. The thermal field for the 55 deg round holes indicated a faster decay of cooling capacity for the 55 deg round holes. The high turbulence levels for the 55 deg round hole coincided with the sharp velocity gradients between the jet and free stream, and the decay of turbulence levels with downstream distance was found to be similar to those for a 35 deg hole.
Flow and Heat Transfer in a Preswirl Rotor–Stator System
Authors: Wilson M. , Pilbrow R. , Owen J. M.
Published: April 2009

Conditions in the internal-air system of a high-pressure turbine stage are modeled using a rig comprising an outer preswirl chamber separated by a seal from an inner rotor-stator system. Preswirl nozzles in the stator supply the “blade-cooling” air, which leaves the system via holes in the rotor, and disk-cooling air enters at the center of the system and leaves through clearances in the peripheral seals. The experimental rig is instrumented with thermocouples, fluxmeters, pitot tubes, and pressure taps, enabling temperatures, heat fluxes, velocities, and pressures to be measured at a number of radial locations. For rotational Reynolds numbers of Reφ ≃ 1.2 × 106, the swirl ratio and the ratios of disk-cooling and blade-cooling flow rates are chosen to be representative of those found inside gas turbines. Measured radial distributions of velocity, temperature, and Nusselt number are compared with computations obtained from an axisymmetric elliptic solver, featuring a low-Reynolds-number k–ε turbulence model. For the inner rotor-stator system, the computed core temperatures and velocities are in good agreement with measured values, but the Nusselt numbers are underpredicted. For the outer preswirl chamber, it was possible to make comparisons between the measured and computed values for cooling-air temperatures but not for the Nusselt numbers. As expected, the temperature of the blade-cooling air decreases as the inlet swirl ratio increases, but the computed air temperatures are significantly lower than the measured ones. Overall, the results give valuable insight into some of the heat transfer characteristics of this complex system.
Prediction and Measurement of the Total Pressure Loss in an Engine Representative Diffuser System
Authors: Little A. R. , Denman P. A. , Manners A. P.
Published: April 2009

An experimental and computational investigation of the flow in an engine representative diffuser system has been performed. Many parametric changes to the system were considered including inlet conditions, prediffuser geometry, cowl geometry and prediffuser strut position. The focus of this paper is an overview of the results from the twelve configurations that were both predicted and experimentally tested. It was shown that the CFD predictions contained a high degree of numerical error and that to reduce this to a low level would currently be impractical for a parametric study of this type. However, by carefully maintaining approximately the same degree of numerical error in the predictions, it was shown that a valid parametric study could be performed to the extent that the same conclusions about the parametric changes can be drawn equally from the predictions or measurements with one small exception. It was recognized that the level of agreement between the predicted and measured losses was to a degree fortuitous and that the k–ε turbulence model performs poorly for this type of flow.
Penultimate Deglacial Sea-Level Timing from Uranium/Thorium Dating of Tahitian Corals
Authors: Thomas Alex L. , Henderson Gideon M. , Deschamps Pierre , Yokoyama Yusuke , Mason Andrew J. , Bard Edouard , Hamelin Bruno , Durand Nicolas , Camoin Gilbert
Published: April 2009

Early Riser

How glacial-interglacial cycles and the long-term variability of sea level depend on the amount of energy received by Earth from the Sun is unclear.

Thomas
et al.

(p.
1186
, published online 23 April; see the cover) report results from fossil corals found in Tahiti that indicate that sea level began to rise when insolation at 65° North latitude was near a minimum, not after it had begun to rise, as predicted by the Milankovitch theory. In contrast, the timing of the last deglaciation agrees well with the Milankovitch theory. Thus, glacial cycles do not behave as simply as the Milankovitch theory suggests.
Phasic Firing in Dopaminergic Neurons Is Sufficient for Behavioral Conditioning
Authors: Tsai Hsing-Chen , Zhang Feng , Adamantidis Antoine , Stuber Garret D. , Bonci Antonello , de Lecea Luis , Deisseroth Karl
Published: April 2009

Rewarding Bursts of Dopamine

Dopaminergic neurons are thought to be involved in the cognitive and hedonic underpinnings of motivated behaviors. However, it is still unclear whether dopaminergic neuron activation is sufficient to elicit reward-related behavior and which type of neuronal activity pattern serves this purpose.

Tsai
et al.

(p. 1080; published online 23 April) directly compared tonic versus phasic firing of dopaminergic cells in the ventral tegmental area, and the effects on both behavior and dopamine release. Using a transgenic system and virus injection in mice, they targeted the dopaminergic cells with rhodopsin. Light stimulation was then used to drive dopaminergic cells either with a tonic low level of pulses or bursts of high-frequency pulses, with the number of pulses being equal across conditions. Only the high-frequency phasic firing induced a conditioned place preference and dopamine release.
Molecular and biochemical characterization of Iranian surfactin-producingBacillus subtilisisolates and evaluation of their biocontrol potential againstAspergillus flavusandColletotrichum gloeosporioides
Authors: Mohammadipour Matin , Mousivand Maryam , Salehi Jouzani Gholamreza , Abbasalizadeh Saeed
Published: April 2009

The characterization of surfactin-producing Bacillus subtilis isolates collected from different ecological zones of Iran is presented. Characterization was performed using blood agar, PCR, drop-collapse, and reverse-phase high-performance liquid chromatography (HPLC) analyses, and the isolates’ biocontrol effects against the aflatoxin-producing agent Aspergillus flavus and the citrus antracnosis agent Colletotrichum gloeosporioides were studied. In total, 290 B. subtilis isolates were isolated from phylosphere and rhizosphere samples collected from fields and gardens of 5 provinces of Iran. Blood agar assays showed that 185 isolates produced different biosurfactants. Isolates containing the sfp gene, coding for surfactin, were detected using the PCR method. It was found that 14 different isolates contained the sfp gene. Drop-collapse assays, which detect isolates with high production of surfactin, showed that 7 isolates produced high levels of surfactin. It was found from HPLC analysis that the isolates containin the sfp gene produced between 55 and 1610 mg of surfactin per litre of broth medium. Four isolates, named BS119m, BS116l, N3dn, and BS113c, produced more than 1000 mg of surfactin per litre of broth. The highest surfactin production level was observed for isolate BS119m (1610 mg/L). The antagonistic potential of the sfp gene-containing isolates was determined using dual culture and chloroform vapour methods. Our bioassay results indicated that isolate BS119m showed high inhibitory effects against A. flavus (100%) and C. gloeosporioides (88%). Furthermore, the effect of purified surfactin on the growth of A. flavus was evaluated. Mycelia growth was considerably reduced with increasing concentration of surfactin, and 36%, 54%, 84%, and 100% inhibitions of mycelia growth were, respectively, observed at 20, 40, 80, and 160 mg/L after 7 days of incubation.
ALT1-encoded alanine aminotransferase plays a central role in the metabolism of alanine inSaccharomyces cerevisiae
Authors: García-Campusano Florencia , Anaya Víctor-Hugo , Robledo-Arratia Luis , Quezada Héctor , Hernández Hugo , Riego Lina , González Alicia
Published: April 2009

In the yeast Saccharomyces cerevisiae , the paralogous genes ALT1 and ALT2 have been proposed to encode alanine aminotransferase isozymes. Although in other microorganisms this enzyme constitutes the main pathway for alanine biosynthesis, its role in S. cerevisiae had remained unclear. Results presented in this paper show that under respiratory conditions, Alt1p constitutes the sole pathway for alanine biosynthesis and catabolism, constituting the first example of an alanine aminotransferase that simultaneously carries out both functions. Conversely, under fermentative conditions, it plays a catabolic role and alanine is mainly synthesized through an alternative pathway. It can thus be concluded that ALT1 has functions in alanine biosynthesis and utilization or only alanine utilization under respiratory and fermentative conditions, respectively. ALT2 expression was repressed under all tested conditions, suggesting that Alt2p biosynthesis is strictly controlled and only allowed to express under peculiar physiological conditions.
Characterization of bacterial and fungal communities in composted biosolids over a 2 year period using denaturing gradient gel electrophoresis
Authors: Novinscak Amy , DeCoste Nadine J. , Surette Céline , Filion Martin
Published: April 2009

Composting is a microbial process that converts organic waste into a nutrient-rich end product used in horticultural and agricultural applications. The diversity and long-term succession of microorganisms found in composted biosolids has been less characterized than other composts. In this study, bacterial and fungal communities found in composted biosolids aging from 1 to 24 months were studied using denaturing gradient gel electrophoresis (DGGE) and sequencing. The results revealed high levels of diversity, where 53 bacterial species belonging to 10 phyla and 21 fungal species belonging to 4 phyla were identified. Significant differences were observed when comparing the bacterial DGGE patterns of young compost samples, whereas no differences were observed in samples over 8 months. For fungal patterns, no significant differences were observed during the first 4 months of composting, but the diversity then significantly shifted until 24 months. The results indicate that patterns of bacterial species vary during the first few months of composting, whereas fungal patterns generally vary throughout the whole process, except during early stages. The description of the main microbial groups found in composted biosolids could find various applications, including the discovery of biotechnologically relevant microorganisms and the development of novel markers allowing quantitative monitoring of key microorganisms.
Dibutylphthalate and Tween 80 alter ultrastructure inCandida albicans: implications for peroxisome proliferation
Authors: Blaize Jonathan , L’Amoreaux William J. , Downey Maureen , McCoy Elena C.
Published: April 2009

Phthalates are ubiquitous environmental pollutants associated with endocrine disruption and peroxisome proliferation in experimental animals. In yeasts exposed to environmental chemicals, including phthalates, alterations in cell growth, cellular morphology, and H2O2detoxification occur. Nutrient availability also influences diverse cellular processes. Differences in responses to environmental stress between Candida albicans and the model yeast, Saccharomyces cerevesiae , have been reported. In this study, we chose C. albicans as an alternate model for testing estrogen-like chemicals because of its high affinity estrogen-binding protein and, in contrast to S. cerevesiae, estrogens are not growth inhibitory for C. albicans. Cultures were grown in either yeast nitrogen dextrose (YND; phosphate limiting) or YNDP (YND plus 100 mmol/L inorganic phosphate). For chemical testing, 0.5% dibutylphthalate (DBP), 0.05% Tween 80, or a combination of the two (DBPT) were incorporated in growth media to investigate the effects of these estrogenic agents on cell proliferation, morphology, and catalase demonstration. We observed significant differences in cell growth related to DBP and changes in cell wall thickness related to both Tween 80 and phosphate. We describe ultrastructural changes including detachment of the outer yeast cell wall layer and presence of putative peroxisomes. Our findings support the proposal that C. albicans may be particularly suitable for use in studies involving cellular responses associated with exposure to estrogenic chemicals contained in complex mixtures.
Visualization of sporopollenin-containing pathogenic green micro-algaPrototheca wickerhamiiby fluorescent in situ hybridization (FISH)
Authors: Ueno Ryohei
Published: April 2009

Fluorescent in situ hybridization (FISH) using taxon-specific, rRNA-targeted oligonucleotide probes is one of the most powerful tools for the rapid identification of harmful microorganisms. However, eukaryotic algal cells do not always allow FISH probes to permeate over their cell walls. Members of the pathogenic micro-algal genus Prototheca are characterized by their distinctive cell-wall component, sporopollenin, an extremely tough biopolymer that resists acid and alkaline hydrolysis, enzyme attack, and acetolysis. To our knowledge, there has been no report of the successful permeation by the oligonucleotide probes over the cell walls of unicellular green micro-algae, which contain sporopollenin. The DNA probes passed through the cell wall of Prototheca wickerhamii after treating the algal cells with cetyltrimethylammonium bromide (CTAB). Most cells in the middle logarithmic growth phase culture fluoresced when hybridized with the rRNA-targeted universal probe for eukaryotes, though individual cells included in this culture differed in the level of cell-wall vulnerability to attack by the polysaccharide-degrading enzyme, thus reflecting the different stages of the life cycle. This is the first report regarding the visualization of sporopollenin-containing, green micro-algal cells by FISH.
Follicle-stimulating hormone increases cholangiocyte proliferation by an autocrine mechanism via cAMP-dependent phosphorylation of ERK1/2 and Elk-1
Authors: Mancinelli Romina , Onori Paolo , Gaudio Eugenio , DeMorrow Sharon , Franchitto Antonio , Francis Heather , Glaser Shannon , Carpino Guido , Venter Julie , Alvaro Domenico , Kopriva Shelley , White Mellanie , Kossie Ashley , Savage Jennifer , Alpini Gianfranco
Published: April 2009

Sex hormones regulate cholangiocyte hyperplasia in bile duct-ligated (BDL) rats. We studied whether follicle-stimulating hormone (FSH) regulates cholangiocyte proliferation. FSH receptor (FSHR) and FSH expression was evaluated in liver sections, purified cholangiocytes, and cholangiocyte cultures (NRICC). In vivo, normal female and male rats were treated with FSH or immediately after BDL with antide (a gonadotropin-releasing hormone antagonist blocking FSH secretion) or a neutralizing FSH antibody for 1 wk. We evaluated 1) cholangiocyte proliferation in sections and cholangiocytes and 2) changes in secretin-stimulated cAMP (functional index of cholangiocyte growth) levels, and ERK1/2 and Elk-1 phosphorylation. NRICC were stimulated with FSH before evaluation of proliferation, cAMP/IP3levels, and ERK1/2 and Elk-1 phosphorylation. To determine whether FSH regulates cholangiocyte proliferation by an autocrine mechanism, we evaluated the effects of 1) cholangiocyte supernatant (containing FSH) on NRICC proliferation and 2) FSH silencing in NRICC before measuring proliferation and ERK1/2 and Elk-1 phosphorylation. Cholangiocytes and NRICC express FSHR and FSH and secrete FSH. In vivo administration of FSH to normal rats increased, whereas administration of antide and anti-FSH antibody to BDL rats decreased 1) ductal mass and 2) secretin-stimulated cAMP levels, proliferation, and ERK1/2 and Elk-1 phosphorylation in cholangiocytes compared with controls. In NRICC, FSH increased cholangiocyte proliferation, cAMP levels, and ERK1/2 and Elk-1 phosphorylation. The supernatant of cholangiocytes increased NRICC proliferation, inhibited by preincubation with anti-FSH antibody. Silencing of FSH gene decreases cholangiocyte proliferation and ERK1/2 and Elk-1 phosphorylation. Modulation of cholangiocyte FSH expression may be important for the management of cholangiopathies.
Portal pressure responses and angiotensin peptide production in rat liver are determined by relative activity of ACE and ACE2
Authors: Herath Chandana B. , Lubel John S. , Jia Zhiyuan , Velkoska Elena , Casley David , Brown Lindsay , Tikellis Chris , Burrell Louise M. , Angus Peter W.
Published: April 2009

Angiotensin converting enzyme (ACE) 2 activity and angiotensin-(1-7) [Ang-(1-7)] levels are increased in experimental cirrhosis; however, the pathways of hepatic Ang-(1-7) production have not been studied. This study investigated the role of ACE2, ACE, and neutral endopeptidase (NEP) in the hepatic formation of Ang-(1-7) from angiotensin I (Ang I) and Ang II and their effects on portal resistance. Ang I or Ang II were administered to rat bile duct ligated (BDL) and control livers alone and in combination with the ACE inhibitor lisinopril, the ACE and NEP inhibitor omapatrilat, or the ACE2 inhibitor MLN4760 ( n = 5 per group). BDL markedly upregulated ACE, ACE2, and NEP. Ang-(1-7) was produced from Ang II in healthy and in BDL livers and was increased following ACE inhibition and decreased by ACE2 inhibition. In contrast, Ang-(1-7) production from Ang I was minimal and not affected by ACE or NEP inhibition. Surprisingly, ACE2 inhibition in BDLs dramatically increased Ang-(1-7) production from Ang I, an effect abolished by ACE2/NEP inhibition. Ang II and Ang I induced greater portal pressure increases in BDL livers than controls. The effects of Ang I were closely correlated with Ang II production and were strongly attenuated by both ACE and ACE/NEP inhibition. These findings show that the major substrate for hepatic production of Ang-(1-7) is Ang II and this is catalyzed by ACE2. Ang I is largely converted to Ang II by ACE, and net conversion of Ang I to Ang-(1-7) is small. NEP has the ability to generate large amounts of Ang-(1-7) in the BDL liver from Ang I only when ACE2 activity is greatly decreased or inhibited.
Molecular and functional characterization of Kv7 K+channel in murine gastrointestinal smooth muscles
Authors: Jepps Thomas A. , Greenwood Iain A. , Moffatt James D. , Sanders Kenton M. , Ohya Susumu
Published: April 2009

Members of the Kv7 voltage-gated K+channel family are important determinants of cardiac and neuronal membrane excitability. Recently, we and others have shown that Kv7 channels are also crucial regulators of smooth muscle activity. The aim of the present study was to assess the Kv7 expression in different parts of the murine gastrointestinal (GI) tract and to assess their functional roles by use of pharmacological agents. Of KCNQ/Kv7 members, both KCNQ4/Kv7.4 and KCNQ5/Kv7.5 genes and proteins were the most abundantly expressed Kv7 channels in smooth muscles throughout the GI tract. Immunohistochemical staining also revealed that Kv7.4 and Kv7.5 but not Kv7.1 were expressed in the circular muscle layer of the colon. In segments of distal colon circular muscle exhibiting spontaneous phasic contractions, the nonselective Kv7 blockers XE991 and linopirdine increased the integral of tension. Increases in the integral of tension were also observed under conditions of neuronal blockade. Similar effects, although less marked, were observed in the proximal colon. As expected, the Kv7.1-selective blocker chromanol 293B had no effect in either type of segment. These data show that Kv7.x especially Kv7.4 and Kv7.5 are expressed in different regions of the murine gastrointestinal tract and blockers of Kv7 channels augment inherent contractile activity. Drugs that selectively block Kv7.4/7.5 might be promising therapeutics for the treatment of motility disorders such as constipation associated with irritable bowel syndrome.
HCl-activated neural and epithelial vanilloid receptors (TRPV1) in cat esophageal mucosa
Authors: Cheng Ling , de la Monte Suzanne , Ma Jie , Hong Jie , Tong Ming , Cao Weibiao , Behar Jose , Biancani Piero , Harnett Karen M.
Published: April 2009

To test whether transient receptor potential channel vanilloid subfamily member-1 (TRPV1) mediates acid-induced inflammation in the esophagus, a tubular segment of esophageal mucosa was tied at both ends, forming a sac. The sac was filled with 0.01 N HCl (or Krebs buffer for control) and kept in oxygenated Krebs buffer at 37°C. The medium around the sac (supernatant) was collected after 3 h. Supernatant of the HCl-filled sac abolished contraction of esophageal circular muscle strips in response to electric field stimulation. Contraction was similarly abolished by supernatant of mucosal sac filled with the TRPV1 agonist capsaicin (10−6M). These effects were reversed by the selective TRPV1 antagonist 5′-iodoresiniferatoxin (IRTX) and by the platelet-activating factor (PAF) receptor antagonist CV9388. Substance P and CGRP levels in mucosa and in supernatant increased in response to HCl, and these increases were abolished by IRTX and by tetrodotoxin (TTX) but not affected by CV9388, indicating that substance P and CGRP are neurally released and PAF independent. In contrast, the increase in PAF was blocked by IRTX but not by TTX. Presence of TRPV1 receptor was confirmed by RT-PCR and by Western blot analysis in whole mucosa and in esophageal epithelial cells enzymatically isolated and sorted by flow cytometry or immunoprecipitated with cytokeratin antibodies. In epithelial cells PAF increased in response to HCl, and the increase was abolished by IRTX. We conclude that HCl-induced activation of TRPV1 receptors in esophageal mucosa causes release of substance P and CGRP from neurons and release of PAF from epithelial cells.
Hepatic bile acid metabolism in the neonatal hamster: expansion of the bile acid pool parallels increased Cyp7a1 expression levels
Authors: Burke Katie T. , Horn Paul S. , Tso Patrick , Heubi James E. , Woollett Laura A.
Published: April 2009

Intraluminal concentrations of bile acids are low in newborn infants and increase rapidly after birth, at least partly owing to increased bile acid synthesis rates. The expansion of the bile acid pool is critical since bile acids are required to stimulate bile flow and absorb lipids, a major component of newborn diets. The purpose of the present studies was to determine the mechanism responsible for the increase in bile acid synthesis rates and the subsequent enlargement of bile acid pool sizes (BAPS) during the neonatal period, and how changes in circulating hormone levels might affect BAPS. In the hamster, pool size was low just after birth and increased modestly until 10.5 days postpartum (dpp). BAPS increased more significantly (∼3-fold) between 10.5 and 15.5 dpp. An increase in mRNA and protein levels of cholesterol 7α-hydroxylase (Cyp7a1), the rate-limiting step in classical bile acid synthesis, immediately preceded an increase in BAPS. In contrast, levels of oxysterol 7α-hydroxylase (Cyp7b1), a key enzyme in bile acid synthesis by the alternative pathway, were relatively elevated by 1.5 dpp. farnesyl X receptor (FXR) and short heterodimeric partner (SHP) mRNA levels remained relatively constant at a time when Cyp7a1 levels increased. Finally, although simultaneous increases in circulating cortisol and Cyp7a1 levels occurred, precocious expression of Cyp7a1 could not be induced in neonatal hamsters with dexamethasone. Thus the significant increase in Cyp7a1 levels in neonatal hamsters is due to mechanisms independent of the FXR and SHP pathway and cortisol.
Hepatocyte nuclear factor 4α contributes to an intestinal epithelial phenotype in vitro and plays a partial role in mouse intestinal epithelium differentiation
Authors: Babeu Jean-Philippe , Darsigny Mathieu , Lussier Carine R. , Boudreau François
Published: April 2009

Hepatocyte nuclear factor 4α (HNF4α) is a regulator of hepatocyte and pancreatic transcription. Hnf4α deletion in the mouse is embryonically lethal with severe defects in visceral endoderm formation. It has been concluded in the past that the role of Hnf4α in the developing colon was much less important than in the liver. However, the precise role of Hnf4α in the homeostasis of the small intestinal epithelium remains unclear. Our aim was to evaluate the potential of Hnf4α to support an intestinal epithelial phenotype. First, Hnf4α potential to dictate this phenotype was assessed in nonintestinal cell lines in vitro. Forced expression of Hnf4α in fibroblasts showed an induction of features normally restricted to epithelial cells. Combinatory expression of Hnf4α with specific transcriptional regulators of the intestine resulted in the induction of intestinal epithelial genes in this context. Second, the importance of Hnf4α in maintaining the homeostasis of the intestinal epithelium was investigated in mice. Mice conditionally deficient for intestinal Hnf4α developed normally throughout adulthood with an epithelium displaying normal morphological and functional structures with minor alterations. Subtle but statistical differences were observed at the proliferation and the cytodifferentiation levels. Hnf4α mutant mice displayed an increase in the number of goblet and enteroendocrine cells compared with controls. Given the fundamental role of this transcription factor in other tissues, these findings dispute the crucial role for this regulator in the maintenance of intestinal epithelial cell function at a period of time that follows cytodifferentiation but may suggest a functional role in instructing cells to become specific to the intestinal epithelium.
Clinical assessment of left ventricular rotation and strain: a novel approach for quantification of function in infarcted myocardium and its border zones
Authors: Helle-Valle Thomas , Remme Espen W. , Lyseggen Erik , Pettersen Eirik , Vartdal Trond , Opdahl Anders , Smith Hans-Jørgen , Osman Nael F. , Ihlen Halfdan , Edvardsen Thor , Smiseth Otto A.
Published: April 2009

Left ventricular (LV) circumferential strain and rotation have been introduced as clinical markers of myocardial function. This study investigates how regional LV apical rotation and strain can be used in combination to assess function in the infarcted ventricle. In healthy subjects ( n = 15) and patients with myocardial infarction ( n = 23), LV apical segmental rotation and strain were measured from apical short-axis recordings by speckle tracking echocardiography (STE) and MRI tagging. Infarct extent was determined by late gadolinium enhancement MRI. To investigate mechanisms of changes in strain and rotation, we used a mathematical finite element simulation model of the LV. Mean apical rotation and strain by STE were lower in patients than in healthy subjects (9.0 ± 4.9 vs. 12.9 ± 3.5° and −13.9 ± 10.7 vs. −23.8 ± 2.3%, respectively, P < 0.05). In patients, regional strain was reduced in proportion to segmental infarct extent ( r = 0.80, P < 0.0001). Regional rotation, however, was similar in the center of the infarct and in remote viable myocardium. Minimum and maximum rotations were found at the infarct borders: minimum rotation at the border zone opposite to the direction of apical rotation, and maximum rotation at the border zone in the direction of rotation. The simulation model reproduced the clinical findings and indicated that the dissociation between rotation and strain was caused by mechanical interactions between infarcted and viable myocardium. Systolic strain reflects regional myocardial function and infarct extent, whereas systolic rotation defines infarct borders in the LV apical region. Regional rotation, however, has limited ability to quantify regional myocardial dysfunction.