bluuebunny/crossref_metadata_2025 huggingface dataset:
GRE Pipeline Installation Procedures: A Field Case Study
Authors: Khalaf A. , Al-Tartoor Y. , Seibi A. C. , Karrech A.
Published: July 2010

Field layout Glass Reinforced Epoxy (GRE) pipeline is generally handled by unskilled workers with limited or no background of the mechanics of pipes subjected to large deformation. This paper, therefore, presents working envelops for field operators to avoid any potential GRE pipe failure during installation through finite element modeling using ANSYS. The finite element models consist of various pipe sizes subjected to typical loading conditions similar to field pipeline layout. The models were used to estimate the pipe deflection and the induced stresses. The analysis was based on the assumption that the pipeline acts as a cantilever beam. The internal normal force, shear force, and bending moment were obtained for each section along the pipe length under study. The maximum normal stress was calculated and compared to the failure strength of GRE for various lifting scenarios. A sensitivity analysis on the various parameters affecting the structural integrity of the pipeline was also performed. It was found that the threshold lifting height causing potential pipe failure is 2 m for all pipe sizes. Moreover, the results showed that the minimum threshold height increases for smaller pipe sizes.
Stochastic Fracture Analysis of Three-Dimensional Functionally Graded Materials Employing Concurrent Multiscale Model
Authors: Chakraborty Arindam , Rahman Sharif
Published: July 2010

This article presents a stochastic multiscale fracture analysis of three-dimensional functionally graded, particle-matrix composites with random microstructures employing a moment-modified polynomial dimensional decomposition method. The stochastic model is based on a level-cut, inhomogeneous, filtered Poisson random field for representing spatially-varying random microstructures and a moment-modified polynomial dimensional decomposition for calculating the probabilistic characteristics of crack-driving forces. The decomposition involves Fourier-polynomial expansions of component functions by orthonormal polynomial bases, an additive control variate in conjunction with Monte Carlo simulation for calculating the expansion coefficients, and a moment-modified random output to account for the effects of particle locations and geometry. A numerical problem involving a horizontally placed, planar edge-crack in a three-dimensional functionally graded specimen under a mixed-mode deformation was efficiently calculated by the univariate dimensional decomposition to calculate the statistical moments and distribution functions of crack-driving forces and the conditional probability of fracture initiation. The fracture results show significant variation of the stress intensity factors and fracture initiation probability along the crack front of the fracture specimen.
A Universal Design Method Based on Analysis for Cylindrical Shells With Nozzles Due to Internal Pressure, External Forces and Moments: Part I
Authors: Xue Ming-De , Du Qing-Hai , Hwang Keh-Chih , Xiang Zhi-Hai
Published: July 2010

An improved version is presented for analytical solution developed by the authors and the applicable ranges of the theoretical solutions for two normally intersecting cylindrical shells are successfully extended from d/D≤0.8 and λ=d/(DT)1/2≤8 up to d/D ≤0.9 and λ≤12. The thin shell theoretical solution is obtained by solving a complex boundary value problem for a pair of 4-th order complex-valued partial differential equations (exact Morley equations) for the shell and the nozzle. The accuracy of results is improved by some additional terms to the expressions for resultant forces and moments in terms of complex-valued displacement-stress function. The presented theoretical stress concentration factors due to pressure are in agreement with the test results in literatures. The presented theoretical results are in good agreement with those by 3-D finite element method for all the seven load cases, i.e., internal pressure and six external branch pipe load components involving axial tension, two kinds of transverse shear forces, longitudinal and circumferential bending and torsion moments.
Crack Growth Analysis in Alloy 82/182 Butt Weld by Using the Finite Element Alternating Method
Authors: Kim Maan-Won , Kim Young-Jong , Kim Byoung Chul
Published: July 2010

Primary water stress corrosion cracking (PWSCC) of Alloy 82/182 butt welds has been a concern for pressurized water reactor (PWR) plants worldwide for the past decade. A lot of works have been performed to calculate exact welding residual stresses and PWSCC growth rate for Alloy 82/182 butt welds. The PWSCC growth analysis of Alloy 82/182 butt welds has been performed by using the Raju-Newman type solutions for the crack tip stress intensity factors (SIFs). In this study, a finite element alternating method (FEAM) was used to calculate the SIFs and crack propagation in Alloy 82/182 butt weld. The FEAM is consisted of two solution parts: an exact theoretical SIF solution for a crack embedded in infinite body and a simple finite element analysis model with coarse mesh for finite body. In this study, the theoretical SIFs were derived by using a dislocation density function. Finite element (FE) analysis was performed to obtain the welding residual stress distribution for a nozzle with Alloy 82/182 butt weld and PWSCC growth analysis was performed by using the FEAM with PWSCC growth model described in MRP reports under welding residual stress along the nozzle thickness.
Hydrogen Effects on Fracture Toughness of Type 316L Stainless Steel From 175 K to 425 K
Authors: Morgan Michael J. , Chapman Glenn K.
Published: July 2010

The effects of hydrogen on the fracture-toughness properties of Type 316L stainless steel from 175 K to 425 K were measured. Fracture-toughness samples were fabricated from Type 316L stainless steel forgings and hydrogen-charged with hydrogen at 34 MPa and 623 K for two weeks prior to testing. The effect of hydrogen on the J-Integral vs. crack extension behavior was measured at various temperatures by fracturing non-charged and hydrogen-charged samples in an environmental chamber. Hydrogen-charged steels had lower toughness values than non-charged ones, but still retained good toughness properties. The fracture-toughness values of hydrogen-charged samples tested near ambient temperature were about 70% of non-charged values. For hydrogen-charged samples tested at 225 K and 425 K, the fracture-toughness values were 50% of the non-charged values. In all cases, fracture occurred by microvoid nucleation and coalescence, although the hydrogen-charged samples had smaller and more closely spaced microvoids. The results suggest that hydrogen effects on toughness are greater at 225 K than they are at ambient temperature because of strain-induced martensite formation. At 425 K, the hydrogen effects on toughness are greater than they are at ambient temperature because of the higher mobility of hydrogen.
Effects of Cladding on Reactor Pressure Vessel Integrity Based on the Revised PTS Rule (10 CFR 50.61)
Authors: Marthandam Vikram , Griesbach Timothy J. , Spanner Jack
Published: July 2010

This paper provides a historical perspective of the effects of cladding and the analyses techniques used to evaluate the integrity of an RPV subjected to pressurized thermal shock (PTS) transients. A summary of the specific requirements of the draft revised PTS rule (10 CFR 50.61) and the role of cladding in the evaluation of the RPV integrity under the revised PTS Rule are discussed in detail. The technical basis for the revision of the PTS Rule is based on two main criteria: (1) NDE requirements and (2) Calculation of RTMAX-X and ΔT30. NDE requirements of the Rule include performing volumetric inspections using procedures, equipment and personnel qualified under ASME Section XI, Appendix VIII. The flaw density limits specified in the new Rule are more restrictive than those stipulated by Section XI of the ASME Code. The licensee is required to demonstrate by performing analysis based on the flaw size and density inputs that the through wall cracking frequency does not exceed 1E−6 per reactor year. Based on the understanding of the requirements of the revised PTS Rule, there may be an increase in the effort needed by the utility to meet these requirements. The potential benefits of the Rule for extending vessel life may be very large, but there are also some risks in using the Rule if flaws are detected in or near the cladding. This paper summarizes the potential impacts on operating plants that choose to request relief from existing PTS Rules by implementing the new PTS Rule.
Reliability of Onsite Emergency Power for the New Generation and Advanced Nuclear Power Plants
Authors: Sanwarwalla Mansoor H.
Published: July 2010

The nuclear steam supply system (NSSS) design for the new generation PWR and BWR reactor designs and advanced high temperature gas reactor design consider different onsite emergency power sources required to bring the nuclear plant to a safe shutdown condition following a design basis event concurrent with a loss of offsite power. This paper will discuss the various onsite power generation sources, i.e., diesel, gas and battery based on existing operating experience and information available for existing plants. It will discuss the merits and demerits of each of these sources as related to maintenance and reliability. The paper will compare the three sources and attempt to determine which design would be more cost effective for the power plants.
Dispelling the Myths Behind Regulatory Issue Summary 2008-30 (Nuclear Plant Component Fatigue Sensitivity Analyses)
Authors: Herrmann Terry J. , Novotny Tyler D. , Stevens Gary L.
Published: July 2010

In April of 2008, the U.S. Nuclear Regulatory Commission’s Office of Nuclear Regulation released a draft Regulatory Issue Summary (RIS) regarding fatigue analysis of nuclear power plant components. The final RIS was published in December of 2008 with little modification. At issue in the RIS was the use of a single stress term for use with Green’s Functions, as opposed to the ASME Code, Section III method of combining all six stress components, which could potentially lead to non-conservative results in a fatigue usage evaluation. Single stress term Green’s Functions have been commonly deployed in on-line fatigue monitoring systems, and they have been used to quickly generate thermal transient stress histories in place of more rigorous finite element analysis of transients. The conclusions of the RIS were based on a comparison of results from a single-stress term Green’s Function analysis and a follow-on six-stress component confirmatory analysis performed on a BWR-4 feedwater nozzle. The confirmatory analysis considered all six stress components in accordance with ASME Code, Section III, Subsection NB, Subarticle NB-3200 methodology, and yielded higher fatigue usage in the nozzle corner region, thus calling into question the adequacy of the Green’s Function analysis and its associated judgments. Further concerns were raised because of the use of the single stress term Green’s Function approach in some on-line fatigue monitoring systems. However, the RIS did not address the many differences in inputs that were used in the confirmatory analysis that also contributed to the increase in fatigue usage. This paper re-investigates the BWR-4 feedwater nozzle analysis that originally motivated the promulgation of the subject RIS. The paper parametrically investigates the different inputs that were used in each analysis to further understand the differences between the single stress term Green’s Function and follow-on confirmatory analyses, and to clarify some of the misunderstandings about single stress term Green’s functions that may have been created by the publication of RIS 2008-30 [1].
Characterization of Two
Paenibacillus amylolyticus
Strain 27C64 Pectate Lyases with Activity on Highly Methylated Pectin
Authors: Boland Whitney E. , Henriksen Emily DeCrescenzo , Doran-Peterson Joy
Published: July 2010

Two pectate lyases were identified from
Paenibacillus amylolyticus
27C64; both enzymes demonstrated activity on methylated pectin in addition to polygalacturonic acid. PelA is in a subclass of the pectate lyase family III. PelB shows some features of pectate lyase family I but is highly divergent.
Identification and Characterization of a NovelTerrabacter ginsenosidimutanssp. nov. β-Glucosidase That Transforms Ginsenoside Rb1 into the Rare Gypenosides XVII and LXXV
Authors: An Dong-Shan , Cui Chang-Hao , Lee Hyung-Gwan , Wang Liang , Kim Sun Chang , Lee Sung-Taik , Jin Fengxie , Yu Hongshan , Chin Young-Won , Lee Hyeong-Kyu , Im Wan-Taek , Kim Song-Gun
Published: July 2010

A new β-glucosidase from a novel strain ofTerrabacter ginsenosidimutans(Gsoil 3082T) obtained from the soil of a ginseng farm was characterized, and the gene,bgpA(1,947 bp), was cloned inEscherichia coli. The enzyme catalyzed the conversion of ginsenoside Rb1 {3-O-[β-d-glucopyranosyl-(1-2)-β-d-glucopyranosyl]-20-O-[β-d-glucopyranosyl-(1-6)-β-d-glucopyranosyl]-20(S)-protopanaxadiol} to the more pharmacologically active rare ginsenosides gypenoside XVII {3-O-β-d-glucopyranosyl-20-O-[β-d-glucopyranosyl-(1-6)-β-d-glucopyranosyl]-20(S)-protopanaxadiol}, gypenoside LXXV {20-O-[β-d-glucopyranosyl-(1-6)-β-d-glucopyranosyl]-20(S)-protopanaxadiol}, and C-K [20-O-(β-d-glucopyranosyl)-20(S)-protopanaxadiol]. A BLAST search of thebgpAsequence revealed significant homology to family 3 glycoside hydrolases. Expressed inE. coli, β-glucosidase had apparentKmvalues of 4.2 ± 0.8 and 0.14 ± 0.05 mM andVmaxvalues of 100.6 ± 17.1 and 329 ± 31 μmol·min−1·mg of protein−1againstp-nitrophenyl-β-d-glucopyranoside and Rb1, respectively. The enzyme catalyzed the hydrolysis of the two glucose moieties attached to the C-3 position of ginsenoside Rb1, and the outer glucose attached to the C-20 position at pH 7.0 and 37°C. These cleavages occurred in a defined order, with the outer glucose of C-3 cleaved first, followed by the inner glucose of C-3, and finally the outer glucose of C-20. These results indicated that BgpA selectively and sequentially converts ginsenoside Rb1 to the rare ginsenosides gypenoside XVII, gypenoside LXXV, and then C-K. Herein is the first report of the cloning and characterization of a novel ginsenoside-transforming β-glucosidase of the glycoside hydrolase family 3.
Extraction of mRNA from Soil
Authors: Mettel Carsten , Kim Yongkyu , Shrestha Pravin Malla , Liesack Werner
Published: July 2010

Here, we report an efficient method for extracting high-quality mRNA from soil. Key steps in the isolation of total RNA were low-pH extraction (pH 5.0) and Q-Sepharose chromatography. The removal efficiency of humic acids was 94 to 98% for all soils tested. To enrich mRNA, subtractive hybridization of rRNA was most efficient. Subtractive hybridization may be followed by exonuclease treatment if the focus is on the analysis of unprocessed mRNA. The total extraction method can be completed within 8 h, resulting in enriched mRNA ranging from 200 bp to 4 kb in size.
Stable Isotope Probing Analysis of the Diversity and Activity of Methanotrophic Bacteria in Soils from the Canadian High Arctic
Authors: Martineau Christine , Whyte Lyle G. , Greer Charles W.
Published: July 2010

The melting of permafrost and its potential impact on CH
4
emissions are major concerns in the context of global warming. Methanotrophic bacteria have the capacity to mitigate CH
4
emissions from melting permafrost. Here, we used quantitative PCR (qPCR), stable isotope probing (SIP) of DNA, denaturing gradient gel electrophoresis (DGGE) fingerprinting, and sequencing of the 16S rRNA and
pmoA
genes to study the activity and diversity of methanotrophic bacteria in active-layer soils from Ellesmere Island in the Canadian high Arctic. Results showed that most of the soils had the capacity to oxidize CH
4
at 4°C and at room temperature (RT), but the oxidation rates were greater at RT than at 4°C and were significantly enhanced by nutrient amendment. The DGGE banding patterns associated with active methanotrophic bacterial populations were also different depending on the temperature of incubation and the addition of nutrients. Sequencing of the 16S rRNA and
pmoA
genes indicated a low diversity of the active methanotrophic bacteria, with all methanotroph 16S rRNA and
pmoA
gene sequences being related to type I methanotrophs from
Methylobacter
and
Methylosarcina
. The dominance of type I methanotrophs over type II methanotrophs in the native soil samples was confirmed by qPCR of the 16S rRNA gene with primers specific for these two groups of bacteria. The 16S rRNA and
pmoA
gene sequences related to those of
Methylobacter tundripaludum
were found in all soils, regardless of the incubation conditions, and they might therefore play a role in CH
4
degradation
in situ
. This work is providing new information supporting the potential importance of
Methylobacter
spp. in Arctic soils found in previous studies and contributes to the limited body of knowledge on methanotrophic activity and diversity in this extreme environment.
Systems-Level Metabolic Flux Profiling Elucidates a Complete, Bifurcated Tricarboxylic Acid Cycle in
Clostridium acetobutylicum
Authors: Amador-Noguez Daniel , Feng Xiao-Jiang , Fan Jing , Roquet Nathaniel , Rabitz Herschel , Rabinowitz Joshua D.
Published: July 2010

Obligatory anaerobic bacteria are major contributors to the overall metabolism of soil and the human gut. The metabolic pathways of these bacteria remain, however, poorly understood. Using isotope tracers, mass spectrometry, and quantitative flux modeling, here we directly map the metabolic pathways of
Clostridium acetobutylicum
, a soil bacterium whose major fermentation products include the biofuels butanol and hydrogen. While genome annotation suggests the absence of most tricarboxylic acid (TCA) cycle enzymes, our results demonstrate that this bacterium has a complete, albeit bifurcated, TCA cycle; oxaloacetate flows to succinate both through citrate/α-ketoglutarate and via malate/fumarate. Our investigations also yielded insights into the pathways utilized for glucose catabolism and amino acid biosynthesis and revealed that the organism's one-carbon metabolism is distinct from that of model microbes, involving reversible pyruvate decarboxylation and the use of pyruvate as the one-carbon donor for biosynthetic reactions. This study represents the first
in vivo
characterization of the TCA cycle and central metabolism of
C. acetobutylicum
. Our results establish a role for the full TCA cycle in an obligatory anaerobic organism and demonstrate the importance of complementing genome annotation with isotope tracer studies for determining the metabolic pathways of diverse microbes.
Overlapping Repressor Binding Sites Result in Additive Regulation ofEscherichia coliFadH by FadR and ArcA
Authors: Feng Youjun , Cronan John E.
Published: July 2010

Escherichia coli fadHencodes a 2,4-dienoyl reductase that plays an auxiliary role in β-oxidation of certain unsaturated fatty acids. In the 2 decades since its discovery, FadH biochemistry has been studied extensively. However, the genetic regulation of FadH has been explored only partially. Here we report mapping of thefadHpromoter and document its complex regulation by three independent regulators, the fatty acid degradation FadR repressor, the oxygen-responsive ArcA-ArcB two-component system, and the cyclic AMP receptor protein-cyclic AMP (CRP-cAMP) complex. Electrophoretic mobility shift assays demonstrated that FadR binds to thefadHpromoter region and that this binding can be specifically reversed by long-chain acyl-coenzyme A (CoA) thioesters.In vivodata combining transcriptionallacZfusion and real-time quantitative PCR (qPCR) analyses indicated thatfadHis strongly repressed by FadR, in agreement with induction offadHby long-chain fatty acids. Inactivation ofarcAincreasedfadHtranscription by >3-fold under anaerobic conditions. Moreover,fadHexpression was increased 8- to 10-fold under anaerobic conditions upon deletion of both thefadRand thearcAgene, indicating that anaerobic expression is additively repressed by FadR and ArcA-ArcB. UnlikefadM, a newly reported member of theE. coli fadregulon that encodes another auxiliary β-oxidation enzyme,fadHwas activated by the CRP-cAMP complex in a manner similar to those of the prototypicalfadgenes. In the absence of the CRP-cAMP complex, repression offadHexpression by both FadR and ArcA-ArcB was very weak, suggesting a possible interplay with other DNA binding proteins.
ON IMPLEMENTING EFFICIENT MODULO 2n + 1 ARITHMETIC COMPONENTS
Authors: VERGOS HARIDIMOS T. , BAKALIS DIMITRIS
Published: July 2010

It is shown that a diminished-1 adder, with minor modifications, can be also used for the modulo 2n + 1 addition of two n-bit operands in the weighted representation, if the sum of its input operands is decreased by one. This modified diminished-1 adder can perform n-bit modulo 2n + 1 addition in less area and time than solutions that are based on the use of binary adders and/or weighted modulo 2n + 1 adders. Therefore, it can be applied effectively to all weighted modulo 2n + 1 arithmetic components that finally derive two n-bit addends. A small number of weighted arithmetic components have in the past adopted such a scheme without presenting this general theory. By applying this idea, we propose novel multi-operand modulo 2n + 1 adders (MOMAs) and residue generators (RGs). Experimental results indicate that the resulting arithmetic components offer significant savings in delay, implementation area and average power consumption compared to the currently most efficient solutions.
Microrobots for Minimally Invasive Medicine
Authors: Nelson Bradley J. , Kaliakatsos Ioannis K. , Abbott Jake J.
Published: July 2010

Microrobots have the potential to revolutionize many aspects of medicine. These untethered, wirelessly controlled and powered devices will make existing therapeutic and diagnostic procedures less invasive and will enable new procedures never before possible. The aim of this review is threefold: first, to provide a comprehensive survey of the technological state of the art in medical microrobots; second, to explore the potential impact of medical microrobots and inspire future research in this field; and third, to provide a collection of valuable information and engineering tools for the design of medical microrobots.
Characterization of Biological Processes through Automated Image Analysis
Authors: Rittscher Jens
Published: July 2010

The systems-level analysis of complex biological processes requires methods that enable the quantification of a broad range of phenotypical alterations, the precise localization of signaling events, and the ability to correlate such signaling events in the context of the spatial organization of the biological specimen. The goal of this review is to illustrate that, when combined with modern imaging platforms and labeling techniques, automated image analysis methods can provide such quantitative information. The article attempts to review necessary image analysis techniques as well as applications that utilize these techniques to provide the data that will enable systems-level biology. The text includes a review of image registration and image segmentation methods, as well as algorithms that enable the analysis of cellular architecture, cell morphology, and tissue organization. Various methods that enable the analysis of dynamic events are also presented.
Topography, Cell Response, and Nerve Regeneration
Authors: Hoffman-Kim Diane , Mitchel Jennifer A. , Bellamkonda Ravi V.
Published: July 2010

In the body, cells encounter a complex milieu of signals, including topographical cues, in the form of the physical features of their surrounding environment. Imposed topography can affect cells on surfaces by promoting adhesion, spreading, alignment, morphological changes, and changes in gene expression. Neural response to topography is complex, and it depends on the dimensions and shapes of physical features. Looking toward repair of nerve injuries, strategies are being explored to engineer guidance conduits with precise surface topographies. How neurons and other cell types sense and interpret topography remains to be fully elucidated. Studies reviewed here include those of topography on cellular organization and function as well as potential cellular mechanisms of response.
Effects of a novel cystine-based glutathione precursor on oxidative stress in vascular smooth muscle cells
Authors: Sinha-Hikim Indrani , Shen Ruoqing , Paul Lee Wai-Nang N. , Crum Albert , Vaziri Nosratola D. , Norris Keith C.
Published: July 2010

Chronic kidney disease (CKD) is associated with accelerated atherosclerosis and cardiovascular disease, which is largely mediated by oxidative stress. We investigated the effect of three glutathione (GSH) precursors: N-acetyl-cysteine (NAC), cystine as the physiological carrier of cysteine in GSH with added selenomethionine (F1), and NAC fortified with selenomethionine (F2) on oxidative stress induced by spermine (a uremic toxin) in cultured human aortic vascular smooth muscle cells (VSMC). VSMC were exposed to spermine (15 μM) with or without the given antioxidants (dose 50, 100, 200, and 500 μg/ml) or vehicle (control) and assessed for intracellular GSH levels, 4-hydroxy-trans-2-nonenal (4-HNE), and incorporation of 13C from glucose into alanine and protein. Spermine exposure reduced intracellular GSH levels, increased 4-HNE, and impaired glucose metabolism through reduction in pyruvate generation and/or transamination. Treatment with NAC had no effect on intracellular glutathione level. In contrast, F1 maintained intracellular GSH at control levels at all four doses. Subsequent studies performed with 200 μg/ml of F1, F2, or NAC (optimal dose) revealed normalization of 4-HNE, whereas restoration of 13C from glucose to alanine or protein to control values was only noted in the F1 group. Spermine-induced alterations in VSMC ultrastructure were prevented in ∼90% of cells treated with F1 but only ∼50% of cells treated with either NAC or F2. In conclusion, F1 was more effective than NAC or F2 in ameliorating spermine-induced reduction in intracellular GSH levels and cellular alterations in VSMC. The cystine-based GSH precursor (F1) is a promising antioxidant, and further studies are needed to examine the effect of this compound in preventing CKD-associated vascular disease.
Origin and propagation of human gastric slow-wave activity defined by high-resolution mapping
Authors: O'Grady Gregory , Du Peng , Cheng Leo K. , Egbuji John U. , Lammers Wim J. E. P. , Windsor John A. , Pullan Andrew J.
Published: July 2010

Slow waves coordinate gastric motility, and abnormal slow-wave activity is thought to contribute to motility disorders. The current understanding of normal human gastric slow-wave activity is based on extrapolation from data derived from sparse electrode recordings and is therefore potentially incomplete. This study employed high-resolution (HR) mapping to reevaluate human gastric slow-wave activity. HR mapping was performed in 12 patients with normal stomachs undergoing upper abdominal surgery, using flexible printed circuit board (PCB) arrays (interelectrode distance 7.6 mm). Up to six PCBs (192 electrodes; 93 cm2) were used simultaneously. Slow-wave activity was characterized by spatiotemporal mapping, and regional frequencies, amplitudes, and velocities were defined and compared. Slow-wave activity in the pacemaker region (mid to upper corpus, greater curvature) was of greater amplitude (mean 0.57 mV) and higher velocity (8.0 mm/s) than the corpus (0.25 mV, 3.0 mm/s) ( P < 0.001) and displayed isotropic propagation. A marked transition to higher amplitude and velocity activity occurred in the antrum (0.52 mV, 5.9 mm/s) ( P < 0.001). Multiple (3–4) wavefronts were found to propagate simultaneously in the organoaxial direction. Frequencies were consistent between regions (2.83 ± 0.35 cycles per min). HR mapping has provided a more complete understanding of normal human gastric slow-wave activity. The pacemaker region is associated with high-amplitude, high-velocity activity, and multiple wavefronts propagate simultaneously. These data provide a baseline for future HR mapping studies in disease states and will inform noninvasive diagnostic strategies.
c-Jun NH2-terminal kinase-2 mediates osmotic stress-induced tight junction disruption in the intestinal epithelium
Authors: Samak G. , Suzuki T. , Bhargava A. , Rao R. K.
Published: July 2010

Gastrointestinal epithelium faces osmotic stress, both at physiological and pathophysiological conditions. JNK activation is an immediate cellular response to osmotic stress. We investigated the effect of osmotic stress on intestinal epithelial barrier function and delineated the role of JNK2 in osmotic stress-induced tight junction (TJ) regulation in Caco-2 cell monolayers and ileum of Jnk−/−and Jnk2−/−mice. The role of JNK activation in osmotic stress-induced TJ disruption was evaluated using JNK-specific inhibitor and antisense oligonucleotides. Furthermore, the effect of cold restraint stress in vivo on TJ integrity was determined in rats. Osmotic stress disrupted TJs and barrier function in Caco-2 cell monolayers without affecting cell viability. Osmotic stress activated JNK1 and JNK2 and the inhibition of JNK by SP600125 attenuated osmotic stress-induced TJ disruption. TJ disruption and barrier dysfunction by osmotic stress was associated with JNK-dependent remodeling of actin cytoskeleton. Knockdown of JNK2 accelerated TJ assembly and attenuated osmotic stress-induced TJ disruption in Caco-2 cell monolayers. In mouse ileum in vitro, osmotic stress increased paracellular permeability, which was attenuated by SP600125. Osmotic stress disrupted actin cytoskeleton and TJs and increased paracellular permeability in the ileum of wild-type and JNK1−/−mice, but not in JNK2−/−mouse ileum. Cold restraint stress activated JNK in rat ileum and caused JNK-dependent remodeling of actin cytoskeleton and redistribution of occludin and zona occluden-1 from the intercellular junctions. These results reveal the role of JNK2 in the mechanism of osmotic stress-induced TJ disruption in the intestinal epithelium.
Arrhythmogenesis by single ectopic beats originating in the Purkinje system
Authors: Deo Makarand , Boyle Patrick M. , Kim Albert M. , Vigmond Edward J.
Published: July 2010

Cells in the Purkinje system (PS) are known to be more vulnerable than ventricular myocytes to secondary excitations during the action potential (AP) plateau or repolarization phases, known as early afterdepolarizations (EADs). Since myocytes have a lower intrinsic AP duration than the PS cells to which they are coupled, EADs occurring in distal branches of the PS are more likely to result in propagating ectopic beats. In this study, we use a computer model of the rabbit ventricles and PS to investigate the consequences of EADs occurring at different times and places in the cardiac conduction system. We quantify the role of tissue conductivity and excitability, as well as interaction with sinus excitation, in determining whether an EAD-induced ectopic beat will establish reentrant activity. We demonstrate how a single ectopic beat arising from an EAD in the distal PS can give rise to reentrant arrhythmia; in contrast, EADs in the proximal PS were unable to initiate reentry. Clinical studies have established the PS as a potential substrate for reentry, but the underlying mechanisms of these types of disorder are not well understood, nor are conditions leading to their development clearly defined; this work provides new insights into the role of the PS in such circumstances. Our findings indicate that simulated EADs in the distal PS can induce premature beats, which can lead to the tachycardias involving the conduction system due to interactions with sinus activity or impaired myocardial conduction velocity.
PPARγ regulates hypoxia-induced Nox4 expression in human pulmonary artery smooth muscle cells through NF-κB
Authors: Lu Xianghuai , Murphy Tamara C. , Nanes Mark S. , Hart C. Michael
Published: July 2010

NADPH oxidases are a major source of superoxide production in the vasculature. The constitutively active Nox4 subunit, which is selectively upregulated in the lungs of human subjects and experimental animals with pulmonary hypertension, is highly expressed in vascular wall cells. We demonstrated that rosiglitazone, a synthetic agonist of the peroxisome proliferator-activated receptor-γ (PPARγ), attenuated hypoxia-induced pulmonary hypertension, vascular remodeling, Nox4 induction, and reactive oxygen species generation in the mouse lung. The current study examined the molecular mechanisms involved in PPARγ-regulated, hypoxia-induced Nox4 expression in human pulmonary artery smooth muscle cells (HPASMC). Exposing HPASMC to 1% oxygen for 72 h increased Nox4 gene expression and H2O2 production, both of which were reduced by treatment with rosiglitazone during the last 24 h of hypoxia exposure or by treatment with small interfering RNA (siRNA) to Nox4. Hypoxia also increased HPASMC proliferation as well as the activity of a Nox4 promoter luciferase reporter, and these increases were attenuated by rosiglitazone. Chromatin immunoprecipitation assays demonstrated that hypoxia increased binding of the NF-κB subunit, p65, to the Nox4 promoter and that binding was attenuated by rosiglitazone treatment. The role of NF-κB in Nox4 regulation was further supported by demonstrating that overexpression of p65 stimulated Nox4 promoter activity, whereas siRNA to p50 or p65 attenuated hypoxic stimulation of Nox4 promoter activity. These results provide novel evidence for NF-κB-mediated stimulation of Nox4 expression in HPASMC that can be negatively regulated by PPARγ. These data provide new insights into potential mechanisms by which PPARγ activation inhibits Nox4 upregulation and the proliferation of cells in the pulmonary vascular wall to ameliorate pulmonary hypertension and vascular remodeling in response to hypoxia.
Intrarenal urothelium proliferation: an unexpected early event following ischemic injury
Authors: Vinsonneau C. , Girshovich A. , M'rad M. Ben , Perez J. , Mesnard L. , Vandermersch S. , Placier S. , Letavernier E. , Baud L. , Haymann J.-P.
Published: July 2010

Identification of renal cell progenitors and recognition of the events contributing to cell regeneration following ischemia-reperfusion injury (IRI) are a major challenge. In a mouse model of unilateral renal IRI, we demonstrated that the first cells to proliferate within injured kidneys were urothelial cells expressing the progenitor cell marker cytokeratin 14. A systematic cutting of the injured kidney revealed that these urothelial cells were located in the deep cortex at the corticomedullary junction in the vicinity of lobar vessels. Contrary to multilayered bladder urothelium, these intrarenal urothelial cells located in the upper part of the medulla constitute a monolayered barrier and express among uroplakins only uroplakin III. However, like bladder progenitors, intrarenal urothelial cells proliferated through a FGF receptor-2 (FGFR2)-mediated process. They strongly expressed FGFR2 and proliferated in vivo after recombinant FGF7 administration to control mice. In addition, IRI led to FGFR phosphorylation together with the selective upregulation of FGF7 and FGF2. Conversely, by day 2 following IRI, renal urothelial cell proliferation was significantly inhibited by FGFR2 antisense oligonucleotide administration into an intrarenal urinary space. Of notice, no significant migration of these early dividing urothelial cells was detected in the cortex within 7 days following IRI. Thus our data show that following IRI, proliferation of urothelial cells is mediated by the FGFR2 pathway and precedes tubular cell proliferation, indicating a particular sensitivity of this structure to changes caused by the ischemic process.
Aerobic exercise training improves skeletal muscle function and Ca2+ handling-related protein expression in sympathetic hyperactivity-induced heart failure
Authors: Bueno C. R. , Ferreira J. C. B. , Pereira M. G. , Bacurau A. V. N. , Brum P. C.
Published: July 2010

The cellular mechanisms of positive effects associated with aerobic exercise training on overall intrinsic skeletal muscle changes in heart failure (HF) remain unclear. We investigated potential Ca2+ abnormalities in skeletal muscles comprising different fiber compositions and investigated whether aerobic exercise training would improve muscle function in a genetic model of sympathetic hyperactivity-induced HF. A cohort of male 5-mo-old wild-type (WT) and congenic α2A/α2C adrenoceptor knockout (ARKO) mice in a C57BL/6J genetic background were randomly assigned into untrained and trained groups. Exercise training consisted of a 8-wk running session of 60 min, 5 days/wk (from 5 to 7 mo of age). After completion of the exercise training protocol, exercise tolerance was determined by graded treadmill exercise test, muscle function test by Rotarod, ambulation and resistance to inclination tests, cardiac function by echocardiography, and Ca2+ handling-related protein expression by Western blot. α2A/α2CARKO mice displayed decreased ventricular function, exercise intolerance, and muscle weakness paralleled by decreased expression of sarcoplasmic Ca2+ release-related proteins [α1-, α2-, and β1-subunits of dihydropyridine receptor (DHPR) and ryanodine receptor (RyR)] and Ca2+ reuptake-related proteins [sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)1/2 and Na+/Ca2+ exchanger (NCX)] in soleus and plantaris. Aerobic exercise training significantly improved exercise tolerance and muscle function and reestablished the expression of proteins involved in sarcoplasmic Ca2+ handling toward WT levels. We provide evidence that Ca2+ handling-related protein expression is decreased in this HF model and that exercise training improves skeletal muscle function associated with changes in the net balance of skeletal muscle Ca2+ handling proteins.
Bicuculline-Induced Chorea Manifests in Focal Rather Than Globalized Abnormalities in the Activation of the External and Internal Globus Pallidus
Authors: Bronfeld Maya , Belelovsky Katya , Erez Yaara , Bugaysen Jenia , Korngreen Alon , Bar-Gad Izhar
Published: July 2010

Chorea is a basal-ganglia (BG) related hyperkinetic movement disorder characterized by irregular continuous involuntary movements. Chorea and related hyperbehavioral disorders may be induced in behaving primates by local microinjections of the GABAA antagonist bicuculline to the globus pallidus externus (GPe). We performed multielectrode extracellular recordings in the GPe and in the globus pallidus internus (GPi) before, during, and after bicuculline microinjections. Bicuculline led to an increase in the firing rate and a change in the firing pattern of GPe neurons. Two types of abnormal neuronal firing patterns were detected in GPe neurons close to the bicuculline microinjection site: continuous high-frequency activity and bistable activity, in which neurons transitioned between high-frequency and complete cessation of firing. Neuronal activity remained uncorrelated within and between the GPe and the GPi, with no evidence for propagation of the focal GPe abnormal activity downstream to the GPi. Despite reduction in the information capacity of bicuculline-affected GPe neurons, the ability to encode behavioral events was maintained. We found similar responses of GPe neurons to bicuculline in vitro in the rat, suggesting a basic cellular mechanism underlying these abnormal firing patterns. These results demonstrate that chorea is associated with focal neuronal changes that are not complemented by global changes in the BG nuclei. This suggests a mechanism of stochastic phasic alteration of BG control leading to the chaotic nature of chorea. Thus rather than imposing a globalized state of cortical excitability, chorea might be associated with changes in internal information processing within the BG.
Generation and Preservation of the Slow Underlying Membrane Potential Oscillation in Model Bursting Neurons
Authors: Franklin Clarence C. , Ball John M. , Schulz David J. , Nair Satish S.
Published: July 2010

The underlying membrane potential oscillation of both forced and endogenous slow-wave bursting cells affects the number of spikes per burst, which in turn affects outputs downstream. We use a biophysical model of a class of slow-wave bursting cells with six active currents to investigate and generalize correlations among maximal current conductances that might generate and preserve its underlying oscillation. We propose three phases for the underlying oscillation for this class of cells: generation, maintenance, and termination and suggest that different current modules coregulate to preserve the characteristics of each phase. Coregulation of IBurst and IA currents within distinct boundaries maintains the dynamics during the generation phase. Similarly, coregulation of ICaT and IKd maintains the peak and duration of the underlying oscillation, whereas the calcium-activated IKCa ensures appropriate termination of the oscillation and adjusts the duration independent of peak.
Paired-Pulse Transcranial Magnetic Stimulation During Preparation for Simple and Choice Reaction Time Tasks
Authors: Soto Oscar , Valls-Solé Josep , Kumru Hatice
Published: July 2010

Motor preparation for execution of both simple and choice reaction time tasks (SRT and CRT) involves enhancement of corticospinal excitability (CE). However, motor preparation also implies changes in inhibitory control that have thus far been much less studied. Short-interval intracortical inhibition (SICI) has been shown to decrease before CE increases. Therefore we reasoned that, if SICI contributes to inhibitory control of voluntary movement during the preparatory phase, it would be larger in CRT than in SRT because of the need to keep the movement unreleased until the uncertainty resolves on which task is required. We measured changes in SICI and in CE at different time points preceding motor reaction in normal subjects. Single-pulse transcranial magnetic stimulation (spTMS) and paired-pulse transcranial magnetic stimulation (ppTMS) produced time-dependent changes in both SRT and CRT, with shortening when applied close to the presentation of the imperative signal (“early”) and lengthening when applied near the expected reaction (“late”). In addition, at all stimulation time points, reaction time was shorter with ppTMS than that with spTMS, but there was no consistent association between the amount of SICI and reaction time changes. At early stimulation time points, CE was reduced in CRT but not in SRT. However, SICI in CRT was not different from SICI in SRT. At late stimulation time points, SICI decreased just before enhancement of CE. Our findings indicate that inhibitory circuits other than SICI are responsible for setting the level of CE at earlier parts of the reaction time period. Although the decrease in SICI may contribute to the increase in CE at the last part of the premotor period, the two phenomena are not dependent on each other.
Major Impairments of Glutamatergic Transmission and Long-Term Synaptic Plasticity in the Hippocampus of Mice Lacking the Melanin-Concentrating Hormone Receptor-1
Authors: Pachoud Bastien , Adamantidis Antoine , Ravassard Pascal , Luppi Pierre-Hervé , Grisar Thierry , Lakaye Bernard , Salin Paul-Antoine
Published: July 2010

The hypothalamic neuropeptide melanin-concentrating hormone (MCH) plays important roles in energy homeostasis, anxiety, and sleep regulation. Since the MCH receptor-1 (MCH-R1), the only functional receptor that mediates MCH functions in rodents, facilitates behavioral performance in hippocampus-dependent learning tasks, we investigated whether glutamatergic transmission in CA1 pyramidal cells could be modulated in mice lacking the MCH-R1 gene (MCH-R1−/−). We found that both α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-d-aspartate (NMDA) receptor-mediated transmissions were diminished in the mutant mice compared with their controls. This deficit was explained, at least in part, by a postsynaptic down-regulation of these receptors since the amplitude of miniature excitatory postsynaptic currents and the NMDA/AMPA ratio were decreased. Long-term synaptic potentiation (LTP) was also impaired in MCH-R1−/− mice. This was due to an altered induction, rather than an impaired, expression because repeating the induction stimulus restored LTP to a normal magnitude. In addition, long-term synaptic depression was strongly diminished in MCH-R1−/− mice. These results suggest that MCH exerts a facilitatory effect on CA1 glutamatergic synaptic transmission and long-term synaptic plasticity. Recently, it has been shown that MCH neurons fire exclusively during sleep and mainly during rapid eye movement sleep. Thus these findings provide a mechanism by which sleep might facilitate memory consolidation.
Stimulus Novelty, and Not Neural Refractoriness, Explains the Repetition Suppression of Laser-Evoked Potentials
Authors: Wang A. L. , Mouraux A. , Liang M. , Iannetti G. D.
Published: July 2010

Brief radiant laser pulses selectively activate skin nociceptors and elicit transient brain responses (laser-evoked potentials [LEPs]). When LEPs are elicited by pairs of stimuli (S1–S2) delivered at different interstimulus intervals (ISIs), the S2-LEP is strongly reduced at short ISIs (250 ms) and progressively recovers at longer ISIs (2,000 ms). This finding has been interpreted in terms of order of arrival of nociceptive volleys and refractoriness of neural generators of LEPs. However, an alternative explanation is the modulation of another experimental factor: the novelty of the eliciting stimulus. To test this alternative hypothesis, we recorded LEPs elicited by pairs of nociceptive stimuli delivered at four ISIs (250, 500, 1,000, 2,000 ms), using two different conditions. In the constant condition, the ISI was identical across the trials of each block, whereas in the variable condition, the ISI was varied randomly across trials and single-stimulus trials were intermixed with paired trials. Therefore the time of occurrence of S2 was both less novel and more predictable in the constant than in the variable condition. In the constant condition, we observed a significant ISI-dependent suppression of the biphasic negative–positive wave (N2–P2) complex of the S2-LEP. In contrast, in the variable condition, the S2-LEP was completely unaffected by stimulus repetition. The pain ratings elicited by S2 were not different in the two conditions. These results indicate that the repetition-suppression of the S2-LEP is not due to refractoriness in nociceptive afferent pathways, but to a modulation of novelty and/or temporal predictability of the eliciting stimulus. This provides further support to the notion that stimulus saliency constitutes a crucial determinant of LEP magnitude and that a significant fraction of the brain activity time-locked to a brief and transient sensory stimulus is not directly related to the quality and the intensity of the corresponding sensation, but to bottom-up attentional processes.
Mild Hydrothermal Synthesis of Ni–Cu Nanoparticles
Authors: Mohamed Saeed G. H. , Radiman S. , Gasaymeh S. S. , Lim H. N. , Huang N. M.
Published: July 2010

Magnetic Ni‐rich Ni–Cu nanoparticles with Ni : Cu mass ratio (S) of 2.0 and 2.6 were prepared using a mixture of polyoxyethylene (10) isooctylphenyl ether (Triton X‐100) and sodium dodecyl sulfate (SDS) in a mild hydrothermal condition at 95ºC. X‐ray diffractometry (XRD) showed that the nanoparticles prepared at S = 2.0 possessed Ni–Cu alloy characteristic whereas the characteristic was absent at S = 2.6. The XRD data was enhanced by Fourier transform infrared spectroscopy (FTIR) which exhibited metal‐metal (Ni–Cu) band at 455 cm−1. Based on transmission electron microscopy (TEM), the average particle sizes for the nanoparticles prepared at S = 2.0 and 2.6 were in the range of 19–23 nm. The as‐prepared nanoparticles exhibited paramagnetic behaviour measured using a vibrating sample magnetometer (VSM) and the specific saturation magnetization decreased at the higher concentration of Ni.