bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of stress inducible protein 1 (Stip1) in the mouse testis
Authors: Mizrak S.C. , Bogerd J. , Lopez‐Casas P.P. , Párraga M. , del Mazo J. , de Rooij D.G. 
Published: August 2006

AbstractPhthalate esters are considered endocrine disruptors that interfere with the endocrine balance and development of the mammalian testis. Mono‐2‐ethylhexyl phthalate (MEHP), the active metabolite of the ubiquitously used plasticizer di‐2‐ethylhexyl phthalate (DEHP), acts upon Sertoli cells as initial target. By subtractive cDNA libraries we identified genes deregulated as response to MEHP in primary cultures of mouse Sertoli cells. The expression of mouse stress inducible protein 1 (Stip1) was detected as upregulated as a result of MEHP exposure. Stip1 is a cochaperone protein that is homologous to the human heat shock cognate protein 70 (hsc70)/heat shock protein 90 (hsp90)—organizing protein (Hop). To assess the presence and localization of Stip1 in mouse testis and its potential role in stress defense, we studied the expression pattern of the Stip1 protein by immunohistochemistry and of the mRNA by in situ hybridization. Both the protein and the mRNA of Stip1 were mainly found in the cytoplasm of all types of spermatogonia and spermatocytes up till zygotene, the expression decreased during late pachytene and was very weak in diplotene spermatocytes and round spermatids. Interestingly, this expression pattern resembled the pattern of stress sensitivity of spermatogenic cells in that the most sensitive cell types show the weakest expression of Stip1. This suggests an important role for Stip1 in the ability of germ cells to survive in stress conditions including high temperatures. Mol. Reprod. Dev. 73: 1361–1366, 2006. © 2006 Wiley‐Liss, Inc.
Effects of cryopreservation on the developmental competence, ultrastructure and cytoskeletal structure of porcine oocytes
Authors: Wu Caihong , Rui Rong , Dai Jianjun , Zhang Chunyan , Ju Shiqiang , Xie Bing , Lu Xiao , Zheng Xiaofeng 
Published: August 2006

AbstractThe purpose of this study was to determine ultrastructural and cytoskeletal changes that result from vitrification of porcine germinal vesicle‐ (GV‐) and meiosis II‐ (MII‐) stage oocytes. To investigate the effects of vitrification on developmental competence, oocytes were divided into three groups: fresh GV‐oocytes (control), vitrified GV‐oocytes, and vitrified MII‐oocytes. In both GV‐ and MII‐oocytes, vitrification resulted in a high proportion with normal morphology (92.4 vs. 94.2%, P > 0.05), while vitrified GV‐oocytes yielded a higher survival rate than did vitrified MII‐oocytes (56.8 vs. 41.9%, P < 0.05). In vitrified GV‐oocytes, 12 of 154 oocytes underwent cleavage after fertilization in vitro, and 6 of these developed to the 8‐cell stage, 3 developed to the 16‐cell stage, and 3 developed into morulae. No cleavage was obtained from vitrified MII‐oocytes. For ultrastructural analysis of oocytes, fresh and vitrified‐warmed GV‐ and MII‐oocytes were randomly selected for transmission electron microscopy (TEM). Results showed that vitrification caused various degrees of cryodamage in GV‐oocytes. Cumulus cells of some oocytes were separated from the cumulus‐oocyte complex (COC), and the zona pellucida adjacent to cumulus cells was fractured. The gap junctions between cumulus cells were ruptured, and many microvilli were disrupted or disappeared. Only homogeneous lipid droplets were observed. After vitrification, cortical granules still lined the oolemma of MII‐oocytes. Only morphologically irregular, nonhomogeneous lipid droplets surrounding large vacuoles were found. To examine cytoskeletal structures, fresh and vitrified‐warmed MII‐oocytes were analyzed by laser‐scanning confocal microscopy (LSCM); vitrified‐warmed GV‐oocytes were cultured for 42–44 hr before LSCM. Of 58 control oocytes, 79.5% displayed normal spindles with chromosomes aligned along the equatorial plate. In vitrified oocytes the percentage with normal spindle organization was decreased significantly in both vitrified GV‐oocytes and MII‐oocytes (10.1 and 12.9%, respectively, P < 0.05). The proportion of oocytes with normal distribution of F‐actin was lower for vitrified GV‐ and MII‐oocytes than for controls (16.9 and 37.2% vs. 72.3%). Results of this experiment suggest that irreversible damage to the cytoskeleton of porcine GV‐ and MII‐oocytes after vitrification could be an important factor affecting developmental competence. Mol. Reprod. Dev. 73: 1454–1462, 2006. © 2006 Wiley‐Liss, Inc.
The histamine H1 receptor activates the nitric oxide pathway at fertilization
Authors: Leguia Mariana , Wessel Gary M. 
Published: August 2006

AbstractSperm fusion with the egg initiates a signaling cascade that releases intracellular calcium (Ca) from the endoplasmic reticulum (ER). In sea urchins, Ca2+ is released as a single, large transient via two distinct pathways. The first depends on inositol 1,4,5‐triphosphate (IP3) production and triggers the initial phase of Ca2+ release, while the second depends on nitric oxide (NO) production and is thought to maintain the duration of the Ca2+ wave. We identified a sea urchin homolog of the seven trans‐membrane G protein‐coupled receptor for histamine (suH1R) on the egg cell surface that activates NO production. Treatment with histamine (HA) causes fluctuations in the resting levels of NO in the egg, while antagonists or antibodies of H1R inhibit the rise of NO normally observed at fertilization. Inhibition of suH1R function decreases the maintenance, but not the amplitude, of the Ca2+ transient and suggests that it is an integral part of the overall pathway leading to egg activation at fertilization in sea urchins. Mol. Reprod. Dev. 73: 1550–1563, 2006. © 2006 Wiley‐Liss, Inc.
Two‐point water‐fat imaging with partially‐opposed‐phase (POP) acquisition: An asymmetric Dixon method
Authors: Xiang Qing‐San 
Published: August 2006

AbstractA novel two‐point water‐fat imaging method is introduced. In addition to the in‐phase acquisition, water and fat magnetization vectors are sampled at partially‐opposed‐phase (POP) rather than exactly antiparallel as in the original Dixon method. This asymmetric sampling encodes more valuable phase information for identifying water and fat. From the magnitudes of the two complex images, a big and a small chemical component are first robustly obtained pixel by pixel and then used to form two possible error phasor candidates. The true error phasor is extracted from the two error phasor candidates through a simple procedure of regional iterative phasor extraction (RIPE). Finally, least‐squares solutions of water and fat are obtained after the extracted error phasor is smoothed and removed from the complex images. For noise behavior, the effective number of signal averages NSA* is typically in the range of 1.87–1.96, very close to the maximum possible value of 2. Compared to earlier approaches, the proposed method is more efficient in data acquisition and straightforward in processing, and the final results are more robust. At both 1.5T and 0.3T, well separated and identified in vivo water and fat images covering a broad range of anatomical regions have been obtained, supporting the clinical utility of the method. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Delayed changes in T1‐weighted signal intensity in a rat model of 15‐minute transient focal ischemia studied by magnetic resonance imaging/spectroscopy and synchrotron radiation X‐ray fluorescence
Authors: Wang Xuxia , Qian Junchao , He Rui , Wei Li , Liu Nianqing , Zhang Zhiyong , Huang Yuying , Lei Hao 
Published: August 2006

AbstractPrevious studies have found that rats subjected to 15‐min transient middle cerebral artery occlusion (MCAO) show neurodegeneration in the dorsolateral striatum only, and the resulting striatal lesion is associated with increased T1‐weighted (T1W) signal intensity (SI) and decreased T2‐weighted (T2W) SI at 2–8 weeks after the initial ischemia. It has been shown that the delayed increase in T1W SI in the ischemic region is associated with deposition of paramagnetic manganese ions. However, it has been suggested that other mechanisms, such as tissue calcification and lipid accumulation, also contribute to the relaxation time changes. To clarify this issue, we measured changes in relaxation times, lipid accumulation, and elemental distributions in the brain of rats subjected to 15‐min MCAO using MRI, in vivo 1H MR spectroscopy (MRS), and synchrotron radiation X‐ray fluorescence (SRXRF). The results show that a delayed (2 weeks after ischemia) increase in T1W SI in the ischemic striatum is associated with significant increases in manganese, calcium, and iron, but without evident accumulation of MRS‐visible lipids or hydroxyapatite precipitation. It was also found that 15‐min MCAO results in acutely reduced N‐acetylaspartate (NAA)/creatine (Cr) ratio in the ipsilateral striatum, which recovers to the control level at 2 weeks after ischemia. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
SENSE optimization of a transceive surface coil array for MRI at 4 T
Authors: Pinkerton Robert G. , McKinnon Graeme C. , Menon Ravi S. 
Published: August 2006

AbstractParallel imaging (PI) techniques employ the use of multiple radiofrequency (RF) channels to transmit and/or receive the NMR signal. In the current study we use a finite difference time domain (FDTD) method to simulate the electromagnetic fields of a RF coil array operating in transmit‐receive (transceive) mode and receive‐only mode. Optimization of these configurations for PI is studied as well. Our results suggest that a coil array can effectively be used for transceive or receive‐only PI techniques. For a head coil configuration, the sensitivity encoding (SENSE) optimized coil array gap size and PI acceleration factor for MRI are shown to be a function of the physiological‐to‐intrinsic‐noise ratio (PhINR) with a much stronger dependence on acceleration factor than gap size. The results provide a means to optimize any PI sequence by varying the acceleration factor based on the measured PhINR. In addition, an example design for an eight‐element transceive coil array for heads at 4 T is given. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Efficient visualization of vascular territories in the human brain by cycled arterial spin labeling MRI
Authors: Günther Matthias 
Published: August 2006

AbstractIntracranial vascular territories are usually visualized with the use of angiographic techniques. However, because it is difficult to visualize the distal vascular bed with any angiographic technique, it is also difficult to infer the parenchymal borders of vascular territories. Arterial spin labeling (ASL) MRI provides information on cerebral perfusion, and a regional ASL (regASL) approach offers the potential to visualize perfusion of the anterior and posterior circulation separately. Current techniques perform the labeling in each feeding artery as a separate experiment, which is very time‐consuming. In this work a very time‐efficient regASL technique is presented that acquires all vascular territories within the same experiment. Images with different combinations of labeled arteries are combined to delineate the vascular territory of interest. Five subjects were examined with a clinical 1.5T MR scanner. A sharp delineation of the middle cerebral artery (MCA) and posterior cerebral artery (PCA) territories with whole‐brain coverage was achieved in all subjects. The resulting signal‐to‐noise ratios (SNRs) for conventional regASL and the proposed cycled regASL were 9.3 ± 2.4 and 15.3 ± 5.1, respectively. An optimized setup was achieved by combining the regional labeling scheme with an efficient readout technique, which yielded a total measurement time of 2 min for three vascular territories. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
An Eulerian‐Lagrangian method for option pricing in finance
Authors: Wang Zheng , Al‐Lawatia Mohamed , Wang Hong 
Published: August 2006

AbstractThis article is devoted to the development and application of an Eulerian‐Lagrangian method (ELM) for the solution of the Black‐Scholes partial differential equation for the valuation of European option contracts. This method fully utilizes the transient behavior of the governing equations and generates very accurate option's fair values and their derivatives also known as option Greeks, even if coarse spatial grids and large time steps are used. Numerical experiments on two standard option contracts are presented which show that the ELM method (favorably) compares in terms of accuracy and efficiency to many other well‐perceived methods. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 293–329, 2007
Proteomic analysis of the autoantibody response following immunization with a single autoantigen
Authors: Mouquet Hugo , Drouot Laurent , Charlionnet Roland , Arnoult Christophe , Bonnet‐Bayeux Florence , Thomas Marlène , Leprince Jérôme , Joly Pascal , Tron François , Gilbert Danièle 
Published: August 2006

AbstractIn most autoimmune diseases, the autoantibody response is directed against several antigens of the target organ whose identification is crucial for understanding the physiopathological process. Thus, technologies allowing a characterization of the whole autoantibody pattern of both human and experimental autoimmune diseases are required. Here we have used immunoproteomic analysis of human epidermal extracts to characterize the diversity of the anti‐desmosome antibody response induced in normal mice immunized with desmoglein 1, the major autoantigen of pemphigus foliaceus, an autoimmune blistering skin disease. In particular, this analysis enables us to characterize the binding properties of anti‐desmosome mAbs derived from these mice and to show that the autoantibody response induced upon immunization with a single autoantigen targets different epidermal autoantigens with a pattern similar to that observed in certain variety of human pemphigus.
Preparation and characterization of chitosan‐graft‐poly (ϵ‐caprolactone) with an organic catalyst
Authors: Feng Hao , Dong Chang‐Ming 
Published: August 2006

AbstractChitosan‐graft‐poly(ϵ‐caprolactone) was prepared via the ring‐opening graft polymerization of ϵ‐caprolactone (CL) through chitosan with 4‐dimethylaminopyridine as a catalyst and water as a swelling agent. The graft content of PCL within the graft copolymer was adjusted by the feed ratio of CL to chitosan, and the highest grafting concentration of PCL was up to about 400%. Fourier transform infrared, 1H NMR, and two‐dimensional heteronuclear single quantum coherence analyses indicated that the amino group (NH2CH‐2) of chitosan initiated the graft polymerization of CL through the backbone of chitosan, and the hydroxyl group (HOCH2–6) of chitosan did not participate in initiating the graft polymerization. The percentage of amino groups initiating the graft polymerization decreased with an increasing molar ratio of CL to chitosan in the feed, and this was attributed to the fact that the graft polymerization system increasingly became heterogeneous with an increasing feed ratio of CL to chitosan. The physical properties of the graft copolymers were characterized by thermogravimetric analysis and wide‐angle X‐ray diffraction, respectively. These suggested that the introduction of PCL grafts through the chitosan backbone would to some extent destroy the crystalline structure of chitosan, and the PCL grafts existed in an amorphous structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5353–5361, 2006
Elaboration of well‐defined Rasta resins and their use as supported catalytic systems for atom transfer radical polymerization
Authors: Fournier David , Pascual Sagrario , Montembault Véronique , Fontaine Laurent 
Published: August 2006

AbstractNew supported catalytic systems based on the immobilization of a ligand onto supported (co)polymers were prepared, allowing copper immobilization onto a solid support during the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). These supported catalysts were elaborated by the ATRP of 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone and/or styrene onto a Wang resin initiator. Two different approaches were used, involving well‐defined architectures synthesized by ATRP. First, a supported electrophilic homopolymer [Wang‐g‐poly(2‐vinyl‐4,4‐dimethyl‐5‐oxazolone)] was synthesized to obtain an azlactone ring at each repetitive unit, and a supported statistical copolymer [Wang‐g‐poly(2‐vinyl‐4,4‐dimethyl‐5‐oxazolone‐stat‐styrene)] was synthesized to introduce a distance between the azlactone rings. The azlactone‐based (co)polymers were then modified by a reaction with N,N,N′,N′‐tetraethyldiethylenetriamine (TEDETA) to create supported complexing sites for copper bromide. The ATRP of MMA was studied with these supported ligands, and a first‐order kinetic plot was obtained, but high polydispersity indices of the obtained poly(methyl methacrylate) were observed (polydispersity index > 2). On the other hand, the supported ATRP of styrene was performed, followed by the nucleophilic substitution of bromine by TEDETA (Wang‐g‐polystyrene–N,N,N′,N′‐tetraethyldiethylenetriamine) at the chain end of the grafted polystyrene chains. This strategy led the ligand away from the core bead, depending on the length of the polystyrene block (number‐average molecular weight determined by size exclusion chromatography = 1100–2250 g/mol). These supported complexes mediated a controlled polymerization of MMA, yielding polymers with controlled molar masses and low polydispersity indices. Moreover, after the polymerization, 96% of the initial copper was kept in the beads. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5316–5328, 2006
Multiscale dynamics of an interacting sheet by a bond‐fluctuating Monte Carlo simulation
Authors: Pandey R. B. , Anderson Kelly L. , Farmer B. L. 
Published: August 2006

AbstractThe conformation and dynamics of sheets with attractive and repulsive node–node interactions (nn) are examined in an effective solvent medium using Monte Carlo simulations. A bond‐fluctuating coarse grained description is used to model the sheet by a set of nodes (N) tethered together by flexible bonds in a planar structure with linear scaleLs= 16–64,N=Lon a cubic lattice with characteristic dimensions ofL3= 643–2003. Variations of the mean square displacement of the center of mass of the sheet (R) and that of its center node (R) and radius of gyration (Rg) of the sheet with the time step (t) are analyzed to characterize the nature of its global motion, segmental dynamics, and conformational relaxation at a low (T= 2) and a high (T= 10) temperature with the range (r= √8) of interactionnn= 1, –1. We find that sheets achieve their global diffusive motion, that is,R∝t, in the long‐time (asymptotic) regime while their segmental dynamics exhibits a range of power‐law behaviorR∝tνwith ν = 1/4−1 from short to long‐time regimes. The magnitude of the exponent ν and their crossover (and relaxation) from one power‐law to the next depend on temperature, interaction, and molecular weightNof the sheet. The radius of gyration of the sheet relaxes well to its equilibrium with its distinct patterns of expansion (swelling with relatively stiffer bonds (nn= 1)) and contraction (crumpling withnn= −1). Both the relaxation time and the rate of change ofRgdepends onN, Ls, andT. Data for the equilibrium value of the gyration radius scale with its sizeRg∝N1/2suggesting that sheets remain nearly flat with localized wrinkles and crumpling.© 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2512–2523, 2006
Exploring the relationship between funneled energy landscapes and two‐state protein folding
Authors: Konermann Lars 
Published: August 2006

AbstractIt should take an astronomical time span for unfolded protein chains to find their native state based on an unguided conformational random search. The experimental observation that folding is fast can be rationalized by assuming that protein energy landscapes are sloped towards the native state minimum, such that rapid folding can proceed from virtually any point in conformational space. Folding transitions often exhibit two‐state behavior, involving extensively disordered and highly structured conformers as the only two observable kinetic species. This study employs a simple Brownian dynamics model of “protein particles” moving in a spherically symmetrical potential. As expected, the presence of an overall slope towards the native state minimum is an effective means to speed up folding. However, the two‐state nature of the transition is eradicated if a significant energetic bias extends too far into the non‐native conformational space. The breakdown of two‐state cooperativity under these conditions is caused by a continuous conformational drift of the unfolded proteins. Ideal two‐state behavior can only be maintained on surfaces exhibiting large regions that are energetically flat, a result that is supported by other recent data in the literature (Kaya and Chan, Proteins: Struct Funct Genet 2003;52:510–523). Rapid two‐state folding requires energy landscapes exhibiting the following features: (i) A large region in conformational space that is energetically flat, thus allowing for a significant degree of random sampling, such that unfolded proteins can retain a random coil structure; (ii) a trapping area that is strongly sloped towards the native state minimum. Proteins 2006. © 2006 Wiley‐Liss, Inc.
A substitution matrix for structural alphabet based on structural alignment of homologous proteins and its applications
Authors: Tyagi Manoj , Gowri Venkataraman S. , Srinivasan Narayanaswamy , de Brevern Alexandre G. , Offmann Bernard 
Published: August 2006

AbstractAnalysis of protein structures based on backbone structural patterns known as structural alphabets have been shown to be very useful. Among them, a set of 16 pentapeptide structural motifs known as protein blocks (PBs) has been identified and upon which backbone model of most protein structures can be built. PBs allows simplification of 3D space onto 1D space in the form of sequence of PBs. Here, for the first time, substitution probabilities of PBs in a large number of aligned homologous protein structures have been studied and are expressed as a simplified 16 × 16 substitution matrix. The matrix was validated by benchmarking how well it can align sequences of PBs rather like amino acid alignment to identify structurally equivalent regions in closely or distantly related proteins using dynamic programming approach. The alignment results obtained are very comparable to well established structure comparison methods like DALI and STAMP. Other interesting applications of the matrix have been investigated. We first show that, in variable regions between two superimposed homologous proteins, one can distinguish between local conformational differences and rigid‐body displacement of a conserved motif by comparing the PBs and their substitution scores. Second, we demonstrate, with the example of aspartic proteinases, that PBs can be efficiently used to detect the lobe/domain flexibility in the multidomain proteins. Lastly, using protein kinase as an example, we identify regions of conformational variations and rigid body movements in the enzyme as it is changed to the active state from an inactive state. Proteins 2006. © 2006 Wiley‐Liss, Inc.