bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of free amino acids in islets of Langerhans by high‐performance liquid chromatography using pre‐column derivatization with 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole
Authors: Yang Cailing , Jiang Xiaoman , Guo Linyuan , Zhang Haixia , Liu Mancang 
Published: November 2007

AbstractA simple high‐performance liquid chromatographic method with pre‐column derivatization and fluorescence detection was developed and used for the analysis of free amino acids in islets of Langerhans; 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐Cl) served as pre‐column derivatization reagent. Islets of Langerhans were separated from the pancreas of normal and obese rats, treated with pre‐cooling methanol–water (80:20, v/v), and ultrasonicated to fragmentize the islets and effect deproteination. Several parameters influencing the derivatization reaction and chromatographic separation were optimized. Amino acid derivatives obtained under optimal conditions were separated on a C18 column with acetonitrile–acetate buffer as mobile phase and detected at 470 nm/540 nm (Ex/Em). Matrix effects were investigated and good linearities with correlation coefficients better than 0.9972 were obtained over a wide range of 0.42–42.11 μM for most of the amino acids. The detection limits (S/N = 3) were within the range of 6.1–51 nM. The precision of the method and recoveries were in the ranges of 1.43–10.76% (RSD%) and 85.07–108.82%, respectively. The analytical results showed that the serine content was markedly higher in normal rats than in obese rats, whereas methionine was of relatively lower content in both normal and obese rats.
Qualitative and quantitative study of nitrogen‐containing compounds in heavy gas oil using comprehensive two‐dimensional gas chromatography with nitrogen phosphorus detection
Authors: von Mühlen Carin , de Oliveira Eniz C. , Morrison Paul D. , Zini Claudia A. , Caramão Elina B. , Marriott Philip J. 
Published: November 2007

AbstractIn this work, a GC×GC–nitrogen–phosphorus detection (NPD) methodology was developed to separate and quantitate nitrogen‐containing compounds in Brazilian heavy gas oil. First, the NPD performance was improved in order to achieve best GC×GC performance. The geometry of this detector was also evaluated. The use of an extended jet improved significantly the peak shape. The GC×GC separation was studied using both first and second dimension columns with different internal diameters. The use of a thicker film in both dimensions provided better performance. LODs of 0.16–8.49 pg of individual compounds were achieved. Two different extraction techniques of the neutral and basic nitrogen‐containing compounds were also evaluated. The method using ion‐exchange resins to separate neutral and basic nitrogen‐containing compounds was more efficient than the method using modified silica. As an example, the amounts (μg/g) of each class reported were: indole (2.77), alkyl carbazoles ranging from C0 to C6+ (1.467), alkyl benzocarbazoles from C0 to C4+ (793), alkyl quinolines (31.2) and alkyl benzoquinolines (21.6) were quantitated.
Effect of organic modifier and temperature on the resolution of betamethasone and dexamethasone using a porous graphitic carbon column: Application to their identification and confirmation in human urine by LC‐ESI‐MS/MS
Authors: Oueslati Fethi , Hamida Najib Ben , Toumi Amor , Trabelsi Hassen 
Published: November 2007

AbstractThe effects of temperature, organic modifier and the type of acid on the retention factor, the resolution and peak shape of betamethasone and dexamethasone are described. The study is performed using narrow bore porous graphitic carbon (PGC) columns online with diode‐array detector (DAD) and ESI MS/MS. The results show that temperature affects the retention behaviour of the two compounds and ACN yields the best separation while no effect is obtained by changing the type of organic acid. The developed method is applied for the confirmation of dexamethasone and betamethasone in human urine.
HPLC method for preliminary analysis of constituents in rat blood after oral administration of the extract of Acanthopanax senticosus
Authors: Sun Hui , Lv Haitao , Zhang Yanmei , Meng Xiangcai , Sui Jinting , Wang Xijun , Bi Kaishun 
Published: November 2007

AbstractAn HPLC with SPE method has been developed for analysis of constituents in rat blood after oral administration of the extract of Acanthopanax senticosus (ASE). The plasma sample was prepared by SPE method equipped with Oasis HLB cartridge (3cc, 60 mg). The analysis was performed on a Dikma Diamonsil RP18 column (4.6 mm×150 mm, 5 μm) with the gradient elution of solvent A (ACN) and solvent B (0.1% aqueous phosphoric acid, v/v) and the detection wavelength was set at 270 nm. The calibration curve was linear over the range of 0.156–15.625 μg/mL. The LOD was 60 ng/mL. The intraday precision was less than 5.80%, and the interday precision was less than 6.0%. The recovery was (87.30 ± 1.73)%. As a result, 19 constituents were detected in rat plasma after oral administration of the ASE, including 11 original compounds in ASE and eight metabolites, and three of the metabolites originated from syringin in ASE. Six constituents were identified by comparing with the corresponding reference compounds.
Silicon as an emissive optical medium
Authors: Shainline J.M. , Xu J. 
Published: November 2007

AbstractOne of the great challenges in photonics has been to modify silicon to enhance light emission properties. In this review article we survey recent studies which have generated light from silicon in a variety of ways including introduction of emissive centers, anodization, fabrication of quantum‐confined structures and by utilizing non‐linear effects. Each method offers insight into silicon as an emissive medium, but no one method has proven effective enough a light source to compete with established technologies based on III‐V and II‐VI compound semiconductors, and in particular no one method of inducing light emission in silicon has made possible an electrically‐pumped silicon laser.
Biodegradable and Biomimetic Poly(ε‐caprolactone)/Poly(lactobionamidoethyl methacrylate) Biohybrids: Synthesis, Lactose‐Installed Nanoparticles and Recognition Properties
Authors: Zhou Wei , Dai Xiao‐Hui , Dong Chang‐Ming 
Published: November 2007

AbstractBiodegradable and biomimetic SPCL‐PLAMA biohybrids were synthesized via ATRP and characterized by FT‐IR, 1H NMR, GPC and DSC. Biohybrids with small PDI were obtained, and the block length of the PLAMA glycopolymer could be varied linearly by the varying the molar ratio of glycomonomer to macroinitiator. The outer PLAMA glycopolymer restrained the crystallization of inner PCL segments. The self‐assembly properties of amphiphilic biohybrids were studied. Lactose‐installed aggregates were fabricated in aqueous solution; they changed from spherical micelles to vesicles with increasing weight fraction of hydrophobic PCL. The SPCL‐PLAMA biohybrids showed specific recognition for RCA120 lectin.magnified image
Basic Law Controlling the Growth Regime of Layer‐by‐Layer Assembled Polyelectrolyte Multilayers
Authors: Jiang Xiuming , Chen Zhichun , Lv Deshui , Wu Qi , Lin Xianfu 
Published: November 2007

AbstractA mathematical expression describing the growth regime of multilayers formed layer by layer and the correlation between the nature of the growth process and the distribution of the charges in the polyelectrolyte deposited on the surface of the film is reported. Two typical polyelectrolyte pairs were chosen such that one of them causes the film to grow linearly while the other causes the film to grow exponentially. The growth processes were monitored by UV‐Vis spectrophotometry and the experimental data was analyzed. The influence of the polyelectrolyte and NaCl concentration on the fabrication of PAH/PSS and PDDA/PSS films is discussed by analyzing the change of model parameters.magnified image
Why is Stereoregular Polyacrylonitrile Obtained by Polymerization in Urea Canals Isotactic?
Authors: Yang Hyungchol , El‐Shafei Ahmed , Schilling Frederic C. , Tonelli Alan E. 
Published: November 2007

AbstractBecause stereoregular i‐PAN is obtained from the constrained polymerization of acrylonitrile monomer in expandable urea clathrates, we studied the inclusion compounds formed between guest AN and PANs and host cyclodextrins whose rigid channel diameters are in the range of the canals in urea clathrates. ICs of AN were successfully formed with α‐ and γ‐CDs but did not yield PANs, and only ICs between γ‐CD, and a‐ and i‐PANs were formed in solution. Modeling of AN and s‐ and i‐PAN‐CD‐ICs were performed using PM3 parameters to estimate their stabilities. We conclude that the polymerization of AN in urea clathrate channels produces predominantly i‐PAN as a consequence of its improved fit compared with s‐PAN.magnified image
Free Radical Grafting of Polyethylene with Vinyl Monomers by Reactive Extrusion
Authors: Zhang Guofang , Jia Yuxi , Sun Sheng , Wu Lili , Zhao Guoqun , An Lijia 
Published: November 2007

AbstractThe free radical grafting of polyethylene with vinyl monomers by reactive extrusion was studied numerically. Numerical computation expressions of key variables, such as the concentrations of the initiator and polymer, grafting degree, average molecular weight and apparent viscosity, were deduced. The evolutions of the above variables were predicted by means of an uncoupled semi‐implicit iterative algorithm. The monomer conversion monotonically increases with decreasing throughput or increasing initial initiator concentration; with increasing barrel temperature, the monomer conversion first increases then decreases. The simulated results are nearly in good agreement with the experimental results.magnified image
Impaired sexual behavior in male mice deficient for the β1–3 N‐Acetylglucosaminyltransferase‐I gene
Authors: Biellmann Franziska , Henion Timothy R. , Bürki Kurt , Hennet Thierry 
Published: November 2007

AbstractThe β1–3 N‐acetylglucosaminyltransferase‐1 (B3gnt1) gene encodes a poly‐N‐acetyllactosamine synthase which can initiate and extend poly‐N‐acetyllactosamine chains [Gal(β1–4)GlcNAc (β1–3)n]. Previous investigations with heterozygous and homozygous null mice for this gene have revealed the importance of poly‐N‐acetyllactosamine chains for the formation of olfactory axon connections with the olfactory bulb and the migration of gonadotropin releasing hormone neurons to the hypothalamus. The possible long‐term effects of these developmental defects, however, has not yet been studied. Here we have examined a reproductive phenotype observed in B3gnt1‐null mice. Whereas the B3gnt1 null females were fertile, the B3gnt1 null males were not able to sire litters at the expected rate when mated to either wildtype or B3gnt1‐null females. We assessed male sexual behavior as well as male reproduction parameters such as testes size, spermatogenesis, sperm number, morphology, and the development of early embryos in order to identify the source of a reduced rate of reproduction. Our findings show that the B3gnt1 null male reproductive organs were functional and could not account for the lower rate at which they produced offspring with wildtype conspecifics. Hence, we propose that the phenotype observed resulted from an impaired sexual response to female mating partners. Mol. Reprod. Dev. 75: 699–706, 2008. © 2007 Wiley‐Liss, Inc.
Models of sensor operations for border surveillance
Authors: Szechtman Roberto , Kress Moshe , Lin Kyle , Cfir Dolev 
Published: November 2007

AbstractThis article is motivated by the diverse array of border threats, ranging from terrorists to arms dealers and human traffickers. We consider a moving sensor that patrols a certain section of a border with the objective to detect infiltrators who attempt to penetrate that section. Infiltrators arrive according to a Poisson process along the border with a specified distribution of arrival location, and disappear a random amount of time after their arrival. The measures of effectiveness are the target (infiltrator) detection rate and the time elapsed from target arrival to target detection. We study two types of sensor trajectories that have constant endpoints, are periodic, and maintain constant speed: (1) a sensor that jumps instantaneously from the endpoint back to the starting‐point, and (2) a sensor that moves continuously back and forth. The controlled parameters (decision variables) are the starting and end points of the patrolled sector and the velocity of the sensor. General properties of these trajectories are investigated. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2008
HRK inactivation associated with promoter methylation and LOH in prostate cancer
Authors: Higuchi Tomonori , Nakamura Mitsutoshi , Shimada Keiji , Ishida Eiwa , Hirao Kazuya , Konishi Noboru 
Published: November 2007

AbstractOBJECTIVESRecent studies in selected human tumors have demonstrated reduced expression of HRK with hypermethylation. Because no similar study has been performed specifically in prostatic lesions, we examined whether the methylation status of HRK is altered in prostate cancers.METHODSWe chose to analyze the hypermethylation status of HRK, the expression of HRK protein and mRNA with 12q13.1 loss of heterozygosity (LOH) and with p53 mutation, and lesion apoptotic indices as determined by transferase‐mediated digoxigenin‐tagged 16‐desoxy‐uridine‐triphosphate nick end‐labeling (TUNEL) assays in 53 prostate cancers.RESULTSTwenty of the 53 prostate cancers (38%) demonstrated hypermethylation in either the promoter or in exon 1 and, more significantly, the loss of HRK expression observed in 14 cancers by immunohistochemistry (IHC) was associated with promoter methylation. In addition, high apoptotic indices in tumors were related to positive HRK expression. Prostate cancers demonstrating HRK methylation also showed methylation of multiple other genes, such as p14ARF, p16INK4a, O6‐MGMT, and GTS‐P, but, with the exception of one case, p53 mutations were not detected. When compared to tumors having a Gleason score (GS) of 5–6, a significant difference in the apoptotic indices was found among prostate cancers of GS 7 (P < 0.001) or GS 8–9 (P = 0.007). We also detected a close correlation between the loss of HRK expression and decreased apoptosis in GS 5–6 and GS 7 tumors (P = 0.008, P < 0.001, respectively).CONCLUSIONSHRK appears to be inactivated principally by promoter hypermethylation in prostate cancers. We further suggest that the decreased expression of HRK may play an important role in tumor progression by modulating apoptotic cell death. Prostate 68: 105–113, 2008. © 2007 Wiley‐Liss, Inc.
Involvement of decreased Galectin‐3 expression in the pathogenesis and progression of prostate cancer
Authors: Merseburger Axel S. , Kramer Mario W. , Hennenlotter Jörg , Simon Perikles , Knapp Judith , Hartmann Jörg T. , Stenzl Arnulf , Serth Jürgen , Kuczyk Markus A. 
Published: November 2007

AbstractBACKGROUNDAltered expression or loss of function of Galectin‐3 (Gal‐3) was suggested to be involved in the pathogenesis and progression of various human cancer entities. The aim of the present study is to determine the expression of Gal‐3 in prostate tissue emerging from a benign to a malignant, in the beginning hormone‐sensitive and finally hormone‐refractory status to further elucidate the role of this carbohydrate‐binding protein for the pathogenesis and/or progression of malignant prostatic disease.MATERIALS AND METHODSFive hundred and eighty three tissue samples from malignant, tumor adjacent benign, and histologically benign intra‐prostatic areas, retrieved out of 25 whole mounted prostate cancer (CaP) specimens and additional 95 samples of hormone‐refractory CaP, were processed to tissue microarrays. Immunohistochemical Gal‐3 expression was correlated with clinicopathological parameters among the different tissue entities.RESULTSGal‐3 expression was significantly decreased in the hormone‐sensitive CaP specimens when compared with the respective benign tissue either localized far distant from the malignant lesion (P < 0.0001, Wilcoxon test) or directly neighboring the primary tumor (P < 0.0001). The staining reaction in the benign tissue areas directly neighboring the primary cancerous lesions differed significantly from the benign glands localized distant from the primary tumors (P < 0.001). A statistically highly significant, almost complete loss of Gal‐3 was observed in the hormone‐refractory when compared with the hormone‐sensitive tumors (P < 0.0001; mean staining score: 27.7% vs. 8.5%).CONCLUSIONSThe present investigation clearly indicates decreased expression of Gal‐3 to be substantially involved in the pathogenesis and further progression of CaP from benign prostate glands to a finally hormone‐refractory malignant disease. Prostate 68: 72–77, 2008. © 2007 Wiley‐Liss, Inc.
Downregulation of androgen receptor expression by luteolin causes inhibition of cell proliferation and induction of apoptosis in human prostate cancer cells and xenografts
Authors: Chiu Feng‐Lan , Lin Jen‐Kun 
Published: November 2007

AbstractBACKGROUNDAndrogen receptor (ARs) play a crucial role in the development and progression of prostate cancer. Recent studies have suggested that prostate cancer cell proliferation is inhibited by AR downregulation. Our aim was to investigate how luteolin, a natural flavonoid, affects cell growth and AR expression in prostate cancer cells and xenografts.METHODSWe assessed prostate cancer cell (LNCaP, DU145, and PC‐3) proliferation and apoptosis by MTT assay, flow cytometric analysis, and Western analysis. AR function was measured by evaluating the AR target molecule, prostate‐specific antigen (PSA), by RT‐PCR, Western blotting, and enzyme‐linked immunosorbent assay. We determined the mechanism of AR downregulation with cycloheximide chase assays, proteasome inhibitor, and coimmunoprecipitation experiments. The effects of luteolin on growth inhibition in vivo were examined by LNCaP xenografts in SCID mice.RESULTSLuteolin significantly repressed prostate cancer cell proliferation and induced apoptosis in LNCaP cells. PC‐3 and DU145 cells were less susceptible to luteolin‐mediated growth inhibition. Luteolin simultaneously suppressed intracellular and secreted PSA levels and repressed AR mRNA and protein expression in a dose‐ and time‐dependent manner. Luteolin reduced the association between AR and heat‐shock protein 90, causing AR degradation through a proteasome‐mediated pathway in a ligand‐independent manner. Luteolin also suppressed LNCaP xenograft tumor growth in SCID mice.CONCLUSIONLuteolin‐mediated AR downregulation contributes to the inhibition of cell proliferation and the induction of apoptosis in LNCaP human prostate cancer cells, suggesting that AR is a molecular target for luteolin‐mediated anticancer activity. Luteolin may act as a chemopreventive or chemotherapeutic agent for prostate cancer. Prostate 68: 61–71, 2008. © 2007 Wiley‐Liss, Inc.
Reaction mechanism of HSH and CH3SH with NH2CH2COCH2X (X = F and Cl) molecules
Authors: Vijayakumar S. , Kolandaivel P. 
Published: November 2007

AbstractThe reaction mechanism of model compounds H2S and CH3SH for cysteine proteases with NH2CH2COCH2X (X = F and Cl) molecules has been investigated using DFT methods with B3LYP and B3PW91 hybrid density functionals at 6‐31+G* basis sets. The single point energy has been calculated for the above reactions with B3LYP and B3PW91 functionals using aug‐cc‐PVDZ infinite basis set in both gas and solution phases. The intrinsic reaction coordinates calculations have been performed to confirm that each transition state is linked by the desired reactants and products. The geometries and relative energies for various stationary points have been determined and discussed. The zero point vibrational energy corrections have been made to predict the reliable energy. The negative value of reaction energy indicates that the overall reaction profile is found to be exothermic. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Development and validation of an assay for the quantitative determination of cladribine nucleotides in MDCKII cells and culture medium using weak anion‐exchange liquid chromatography coupled with tandem mass spectrometry
Authors: Jansen Robert S. , Rosing Hilde , de Wolf Cocky J. F. , Beijnen Jos H. 
Published: November 2007

AbstractThe development and validation of an assay for the quantitative analysis of cladribine mono‐, di‐ and triphosphate (2‐chloro, 2′‐deoxyadenosine 5′‐mono‐, di‐ and triphosphate or 2CdAMP, 2CdADP and 2CdATP) in culture medium (Optimem) and cell lysate is described. Cladribine mono‐ and diphosphate reference compounds were obtained by thermal degradation of cladribine triphosphate. The reference compounds were characterized using ion‐pairing reversed‐phase high‐performance liquid chromatography with ultraviolet detection. The bioanalytical assay for 2CdAMP, 2CdADP and 2CdATP is based on weak anion‐exchange liquid chromatography coupled with tandem mass spectrometry in the positive ion mode (WAXLC/MS/MS). A fused‐silica electrospray capillary was used instead of a stainless steel electrospray capillary to minimize adsorption of analytes and thus decrease variation in the analyte signals. Dynamic ranges of 1.11–27.7, 0.550–55.0 and 1.31–52.3 nM for 2CdAMP, 2CdADP and 2CdATP, respectively, were validated in culture medium and cell lysate. Optimem samples required stabilization with 30% methanol to prevent conversion of 2CdATP into 2CdAMP and 2CdADP. All intra‐ and interday accuracies and precisions were within ±20%. The stability of the compounds was assessed under various analytically relevant conditions. The method was successfully used to investigate cladribine nucleotide transport in vitro in Madin‐Darby canine kidney II (MDCKII) cells. Copyright © 2007 John Wiley & Sons, Ltd.
A Chemically Amplified Fullerene‐Derivative Molecular Electron‐Beam Resist
Authors: Gibbons Francis , Zaid Hasnah M. , Manickam Mayandithevar , Preece Jon A. , Palmer Richard E. , Robinson Alex P. G. 
Published: November 2007

AbstractCurrent lithographic resists depend on large polymeric materials, which are starting to limit further improvements in line‐width roughness and feature size. Fullerene molecular resists use much smaller molecules to avoid this problem. However, such resists have poor radiation sensitivity. Chemical amplification of a fullerene derivative using an epoxy crosslinker and a photoacid generator is demonstrated. The sensitivity of the material is increased by two orders of magnitude, and 20‐nm line widths are patterned.