bluuebunny/crossref_metadata_2025_split huggingface dataset:
The JNK pathway modulates expression and phosphorylation of 4E‐BP1 in MIN6 pancreatic β‐cells under oxidative stress conditions
Authors: Tominaga Ryu , Yamaguchi Suguru , Satake Chihiro , Usui Masahiro , Tanji Yasuhiro , Kondo Keiichi , Katagiri Hideki , Oka Yoshitomo , Ishihara Hisamitsu 
Published: June 2010

AbstractStress‐mediated apoptosis may play a crucial role in loss of pancreatic β‐cell mass, contributing to the development of diabetes. We have recently identified that translational control involving the translational suppressor eIF4E binding protein‐1 (4E‐BP1) which is important for β‐cell survival under endoplasmic reticulum (ER) stress. The Eif4ebp1 gene, encoding 4E‐BP1, is a direct target of a transcription factor activating transcription factor‐4 (ATF4), a master regulator of gene expression in stress responses. In the current study, we investigated 4E‐BP1 expression in mouse insulinoma line 6 (MIN6) cells treated with arsenite, an inducer of oxidative stress which is another contributor of β‐cell loss. We found that arsenite‐induced 4E‐BP1 expression level was lower than that induced by thapsigargin, an ER stress inducer, although ATF4 was similarly induced by these agents. The ratio of the dephosphorylated form of 4E‐BP1, which has the highest activity, to phosphorylated forms was, however, greater in MIN6 cells treated with arsenite as compared to that in thapsigargin‐treated cells. Arsenite‐induced 4E‐BP1 mRNA and protein expressions were augmented by simultaneous treatment with a c‐Jun N‐terminal kinase (JNK) specific inhibitor, SP600125. The agent also suppressed the level of the dephosphrylated form of 4E‐BP1 in arsenite‐treated MIN6 cells. Thus, JNK activated by oxidative stress is involved in the modulation of 4E‐BP1 expression and phosphorylation in MIN6 cells, which may contribute to fine tuning of translational control under stress conditions. Copyright © 2010 John Wiley & Sons, Ltd.
Melatonin attenuates methotrexate‐induced oxidative stress and renal damage in rats
Authors: Abraham Premila , Kolli Viswa Kalyan , Rabi Suganthy 
Published: June 2010

AbstractNephrotoxicity is an adverse side effect of methotrexate (MTX) chemotherapy. The present study verifies whether melatonin, an endogenous antioxidant prevents MTX‐induced renal damage. Adult rats were administered 7 mg/kg body weight MTX intraperitoneally for 3 days. In the melatonin pretreated rats, 40 mg/ kg body weight melatonin was administered daily intraperitoneally 1 h before the administration of MTX. The rats were killed 12 h after the final dose of MTX/vehicle. The kidneys were used for light microscopic and biochemical studies. The markers of oxidative stress were measured along with the activities of the antioxidant enzymes and myeloperoxidase activity in the kidney homogenates. Pretreatment with melatonin reduced MTX induced renal damage both histologically and biochemically as revealed by normal plasma creatinine levels. Melatonin pretreatment reduced MTX induced oxidative stress, alteration in the activity of antioxidant enzymes as well as elevation in myeloperoxidase activity. The results suggest that melatonin has the potential to reduce MTX induced oxidative stress, neutrophil infiltration as well as renal damage. As melatonin is an endogenous antioxidant and is non‐toxic even in high doses it is suggested that melatonin may be beneficial in minimizing MTX induced renal damage in humans. Copyright © 2010 John Wiley & Sons, Ltd.
Speciation analysis of arsenic and selenium compounds by CE‐dynamic reaction cell‐ICP‐MS
Authors: Hsieh Meng‐Wei , Liu Chen‐Ling , Chen Jing‐Huan , Jiang Shiuh‐Jen 
Published: June 2010

AbstractA dynamic reaction cell ICP‐MS was used as a CE detector for the speciation analysis of arsenic and selenium. Samples containing arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, selenite, selenate, selenocysteine, selenomethione, and Se‐methylselenocysteine were subjected to electrophoretic separation before being introduced into the microconcentric nebulizer (CEI‐100) for their determination by ICP‐MS. The separation has been achieved in a 60 cm length×75 μm id fused‐silica capillary. The electrophoretic buffer used was 25 mmol/L CAPS, and 0.5 mmol/L SDS at pH 9.5, whereas the applied voltage was set at 25 kV. The potentially interfering 38Ar40Ar+ and 40Ar40Ar+ at the selenium masses m/z 78 and 80 were reduced in intensity by approximately three orders of magnitude by using 1.4 mL/min CH4 as reactive cell gas in the dynamic reaction cell. Arsenic was determined as the adduct ion 75As12CH at m/z 89. The LOD for arsenic and selenium was in the range of 0.6–1.8 ng/mL, and 0.5–1.4 ng/mL, respectively, based on peak height. This method has been applied to determine various arsenic and selenium compounds in NIST SRM 1633a Coal Fly Ash and NRCC DOLT‐3 Dogfish Liver reference materials and a selenium dietary supplement. The arsenic and selenium compounds were extracted from fish liver and dietary supplement by using Protease XIV and Lipase, and from coal fly ash with HF solution. The spike recoveries were in the range 91–103% for all the species studied.
Differentiation of organic goat's milk based on its hippuric acid content as determined by capillary electrophoresis
Authors: Carpio Azahara , Rodríguez‐Estévez Vicente , Sánchez‐Rodríguez Manuel , Arce Lourdes , Valcárcel Miguel 
Published: June 2010

AbstractOrganic foods have lately aroused interest by virtue of their quality and their essential, exclusive characteristics. In this study, we assessed the potential of CE to detect a marker that is able to identify the particular food given to the goats and develop an effective method to determine directly the most abundant organic acid in goat's milk (viz. hippuric acid). In addition, we examined the use of the hippuric acid content of goat's milk as a general marker for authenticating organic goat's milk. The feeding of these goats can be influenced by the time of the year. For this reason, we have collected samples from 20 conventionally fed goats and 20 organically fed goats over a period of 2 months. A threshold value dependent on the hippuric acid content was thus established for the first time with a view to discriminating between conventional and organic goat's milk. Organic acids in goat's milk were separated in a running buffer consisting of 120 mM sodium tetraborate decahydrate and 0.5 mM CTAB set to pH 8. The precision of the ensuing method is acceptable for hippuric acid; thus, the RSD for peak area and migration time was less than 10 and 4%, respectively. Also, calibration curves were linear throughout the studied concentration range.
Simultaneous determination of six non‐polar heterocyclic amines in meat samples by supercritical fluid extraction–capillary electrophoresis under fluorimetric detection
Authors: De Andrés Fernando , Zougagh Mohammed , Castañeda Gregorio , Ríos Angel 
Published: June 2010

AbstractA novel, sensitive and selective method for the separation and quantification of a group of non‐polar heterocyclic amines (9H‐pyrido‐[3,4‐b] indole, norharmane; 1‐methyl‐9H‐pyrido‐[3,4‐b] indole, harmane; 2‐amino‐9H‐pyrido‐[2,3‐b] indole, AαC; 2‐amino‐3‐methyl‐9H‐pyrido‐[2,3‐b] indole, MeAαC; 3‐amino‐1,4‐dimethyl‐5H‐pyrido‐[4,3‐b] indole, Trp‐P‐1 and 3‐amino‐1‐methyl‐5H‐pyrido‐[4,3‐b] indole, Trp‐P‐2) in commercial meat samples has been developed. This methodology is faster than others previously described. The method is based on the combination of a supercritical fluid extraction procedure, followed by the analysis of the extracted plug by CE with fluorescence detection. The supercritical fluid extraction procedure was optimized for the clean‐up of the samples and the extraction of the analytes. For the electrophoretic separation, the effect of composition, pH and concentration of buffer, organic modifier content, pressure and time of injection, capillary temperature and voltage applied were studied. A 10 mmol/L formic acid–ammonium formate–ACN (10%, v/v) solution at pH 1.5 was selected as the running electrolyte. With 5‐s hydrodynamic injection, linear responses in the range from 100 to 1000 ng/mL and detection limits ranging from 15.9 to 28.1 ng/mL were obtained for different amines in less than 13 min. ACN–water (1:1 in volume) was used as a sample solvent. Fluorescence detection enhances the sensitivity and avoids interferences coming from non‐fluorescent compounds present in the matrices of the sample extracts.
Normal biventricular function, volumes, and mass in children aged 8 to 17 years
Authors: Robbers‐Visser Daniëlle , Boersma Eric , Helbing Willem A. 
Published: June 2010

AbstractPurposeTo assess normal values for biventricular function, volumes, and mass with current cardiovascular magnetic resonance (CMR) imaging sequences in children.Materials and MethodsIncluded in the study were 60 healthy children aged 8–17 years. A short axis set of contiguous slices was acquired with CMR imaging employing steady‐state free precession. Biventricular end‐diastolic volume (EDV), end‐systolic volume (ESV), ejection fraction (EF), and mass were determined. Uni‐ and multivariate linear regression analyses were performed to study the interrelation of age, gender, and body surface area (BSA) on biventricular volumes and mass. The coefficient of variation was calculated for intra‐ and interobserver variability.ResultsEF did not differ between boys and girls (mean LV‐EF 69 ± (SD) 5%, mean RV‐EF 65 ± 5%). BSA had good (EDV, mass) and modest (ESV) correlation with biventricular measurements. Gender appeared a significant modifier of these relations, whereas age had no independent contribution. The intra‐ and interobserver coefficient of variation was in the range 2.1%–13.9% for biventricular EDV, ESV, and mass.ConclusionThis study reveals gender‐specific normative data for biventricular function, volumes, and mass in children age 8–17 years that can be used as reference data in the follow‐up of pediatric cardiac patients. J. Magn. Reson. Imaging 2009;29:552–559. © 2009 Wiley‐Liss, Inc.
Dynamic birefringence of polyolefins
Authors: Sasaguri K. , Stein R. S. 
Published: June 2010

AbstractThe use of the dynamic birefringence method was extended to the study of the relationship between structural changes and mechanical properties for polyethylene, atactic and isotactic polypropylene, and polybutene‐1. The phase angle between birefringence and strain was measured which permitted the resolution of the strain‐optical coefficient into real and imaginary parts. The real and imaginary parts of the dynamic relaxation modulus were also measured and compared with the optical data. Results for the crystalline polymers were interpreted in terms of the two‐stage mechanism of deformation, involving spherulite deformation followed by internal crystalline reorientation. For the atactic polymer, the viscoelastic flow of amorphous regions contributes to the birefringence. The temperature dependence of birefringence and stress is similar for this mechanism but not for the crystalline contribution.
Differential thermal analysis of synthetic fibers
Authors: Schwenker Robert F. , Zuccarello Robert K. 
Published: June 2010

AbstractThe application of differential thermal analysis (DTA) for the characterization and the investigation of the thermal degradation of synthetic textile fibers, to include polyester, nylon 6, propropylene, and polytetrafluoroethylene fibers, has been studied. The temperature range was from 50 to 650°C. using laboratory‐built DTA apparatus. Experimental considerations and techniques are discussed and such variables as sample preparation, size, cell packing, atmosphere control, and heating rate have been investigated. The conventional technique of grinding or milling DTA samples is shown to cause significant changes in certain samples, particularly in undrawn fibers. The control of sample atmosphere by dynamic gas flow through the sample cell gave peaks that were generally sharper and larger than those found when control was by gas diffusion. Data are given on the various low temperature transitions found in such fibers. Significant differences in low temperature transitions were observed between polypropylene fiber and the bulk polymer as well as between drawn and undrawn nylon 6 fibers. The interpretation of the DTA curves for the decomposition and other reactions at elevated temperatures is discussed. Nylon 6 and polypropylene showed only endothermic reactions indicative of depolymerization processes whereas other fibers showed both endothermic and exothermic reactions in the decomposition range.
Crystallization of polypropylene measured by differential thermal analysis
Authors: Donald H. J. , Humes E. S. , White L. W. 
Published: June 2010

AbstractThe crystallization of polypropylene has been studied by DTA in a linear thermal gradient type furnace. The crystallization rate was found to be linear with temperature, and the rate data were correlated on an Arrhenius type plot. The rate of crystallization of the low molecular weight fraction was lower at the same temperature than the rate for a higher molecular weight fraction.
Application of infrared spectrometry to the study of some polymer problems
Authors: Sibilia J. P. , Paterson A. R. 
Published: June 2010

AbstractInfrared spectroscopy has been applied as a major tool for the investigation of a number of polymer problems. The major products of thermal degradation (300°C.) of polymonochlorotrifiuoroethylene and copolymers with vinylidene fluoride have been Identified and are considerably different depending upon whether or not degradation occurs in nitrogen or oxygen. A mechanism based on random chain cleavage has been proposed for both the homopolymer and copolymer system. A method has also been developed for the determination of the vinylidene fluoride content in vinylidene fluoride‐monochlorotrifluoroethylene copolymers by measuring the —CH— stretching absorption of the —CH2CF2— units in solid films. Absolute values of —CH2CF2‐ content have been determined by high‐resolution NMR and melting point techniques. It has been shown that the intensity of the —CH— stretching absorptions is dependent on the local chain conformation about the —CH2— unit. In another problem the “hardness” of polyethylene waxes has been found to be dependent, on the degree of branching as measured by the methyl absorption at 1378 cm.−1. Molecular weight has been shown to have little effect on the hardness.
Determination of polyacrolein labeled with tritium or carbon‐14
Authors: Carr Robert J. , Gordon B. E. 
Published: June 2010

AbstractThis paper describes methods of analysis for radioactively labeled polyacrolein in solutions, powders, and on paper. The tracers, tritium and carbon‐14, were used because of interferences encountered in some of the analyses. Briefly, the methods involve combustion of the sample in the Sohöniger flask, absorption of the desired product of combustion in a suitable solvent, followed by liquid scintillation counting. For tritium analysis, ethanolic toluene was the absorbent for the product water, and for carbon‐14 methanolic benzylamine was used to absorb the carbon dioxide. Two sources of error in the analysis were discovered, namely, soot and dissolved oxygen. These seriously affected the accuracy and precision of the results. A filtration step followed by an equilibration with air resulted in satisfactory analyses. The use of benzylamine to absorb carbon dioxide has the added advantage of permitting the determination of the weight per cent of carbon by a simple titration with base. The advantages of the tracer method for polyacrolein are (1) specificity, (2) multiple analyses (>20 combustions per day), (3) convenience, and (4) low cost in combustion equipment.
Polymer analysis by high‐resolution NMR, with applications to poly(vinylidene fluoride) and poly(vinyl fluoride)
Authors: Wilson C. W. , Santee E. R. 
Published: June 2010

AbstractHigh‐resolution nuclear magnetic resonance (NMR) spectroscopy has been used for the past several years quite effectively in both the qualitative and quantitative determination of the molecular chain structures and compositions of various polymeric systems. Valuable structural information obtained from such NMR studies has included: (1) detailed stereo chemical configuration (both tacticities and stereoblock sizes) of the polymer chains, (2) copolymer compositions, (5) sequence distribution studies in copolymers, (4) determination of modes of monomer addition in both homopolymers and copolymers, and (5) extent of head‐to‐head structures. Currently, only H1 and F19 NMR techniques are being used in the elucidation of organic polymer structures, for reasons primarily of instrumental sensitivity but also involving general applicability. Examples of the utility of F19 and H1 NMR, as well as double‐resonance techniques, to determine chain structure and composition of fluorine‐containing polymers are presented in this paper. In particular, conclusive proof of a substantial amount (10–12%) of head‐to‐head structure and the detailed assignment of the F19 chemical shifts in poly(vinylidene fluoride) is presented. The existence of a very large amount (26–32%) of he ad‐to‐head structure in both experimental and commercial samples of poly(vinyl fluoride) is also shown (although the detailed assignment of the F19 NMR spectral peaks has not yet been completed); this indicates that about one monomer unit in every six or so is added “backwards” to the growing polymer chains during free‐radical homopolymerizations. Increase in the amount of head‐to‐head structure with increase in polymerization temperature is also observed for poly(vinyl fluoride).
Characterization of polymer orientation by birefringence
Authors: Stein Richard S. 
Published: June 2010

AbstractThe birefringence of a polymer may be used for studying orientation, crystallization, and mobility in a polymeric solid. It is a measure of the average of an orientation distribution for the anisotropic molecular segments of a polymer. Its interpretation is complicated by the lack of knowledge of the absolute birefringence of a polymer segment and by the extent of its dependence upon environment. For crystalline polymers, the birefringence may be resolved into contributions from the crystalline and amorphous components. By measurement, together with measurement of crystalline orientation by the x‐ray technique it may be used to resolve the orientational contribution of these two phases. This is complicated by the uncertain effect of disorder within the crystal upon its birefringence. Also form birefringence of the crystalline amorphous interface and by voids must be considered. Birefringence measurements must be made by compensator or by intensity measurement techniques. The latter are susceptible to automatic recording. Measurements may be made on films or fibers. The time dependence of birefringence may be followed during relaxation or during deformation of a sample. When measured as a function or frequency during vibrational deformation the results characterize the orientation processes possible in a given polymer which depend upon morphology, orientation, and sample treatment.
The molecular structure of polyethylene. XVI. Analytical column fractionation
Authors: Kokle V. , Billmeyer F. W. 
Published: June 2010

AbstractAn analytical procedure for the solvent‐gradient elution fractionation of polyethylene has been devised and applied to both linear and branched polyethylenes. The procedure utilizes selective polymer deposition, programmed solvent composition to keep the polymer:solvent ratio below 1:10,000 at all stages, and reparation of the sampler into several hundred fractions. A smaller number of these fractions is characterized by dilute solution viscosity. New, self‐consistent viscosity‐molecular weight relations are derived which give improved agreement in weight‐average molecular weights observed directly by light scattering, derived from whole polymer viscosities, and derived from fractionation date. Number‐average molecular weights derived from fractionation data are in good agreement with those measured directly. Digital computer techniques are described for deriving integral and differential distribution curves, as well as average molecular weights. Typical results are presented. The broad molecular weight distribution curves in linear polyethylenes are confirmed. For many samples, the differential distribution curve has no peak above the lowest, molecular weight measured, in the neighborhood of 1,000.
Crystalline character in polymers
Authors: Peterlin A. 
Published: June 2010

AbstractThe original fringed micelle model of a crystalline polymer solid assumed two phases, submicroscopical bundled chain crystals embedded in an amorphous matrix. Every macromolecule passed alternately through crystalline and amorphous regions. This model ideally represented the crystallization with highly stretched rubber, but failed to explain spherulites and lamellar single crystals. The folded chain model of the lamellae grown from dilute solution postulated in a polymer solid the inclusion of all the material in single crystals (one phase model). The amorphous x‐ray diffraction pattern and the density defect were due to crystal defects, particularly to the chain folds at the crystal surfaces. Later development has brought both models closer together. In spite of rather regular chain folds with immediate re‐entry there are some chains folding back in a switchboard manner. In a sample crystallized from melt there are still more chains incorporated in two different crystals so that the intervening portion is prevented from crystallization. Together with uncrystallizable components, such tied molecules are constituting an amorphous phase of the very same type as assumed by the fringed micelle model. The basic improvement of the new model is just the comprehension of the important role of chain folds in establishing a discontinuity between the crystals and the amorphous material. A particularly important problem in crystalline polymers is the plastic deformation and the resulting high orientation in drawn fibers and films. From the experiments with single crystals, one learned the basic mechanism of deformation, i.e., phase transformation, twinning, chain tilt, and slip which finally leads to complete break up of original crystals into smaller blocks which are incorporated in the pulled out fibrils. The tied molecules in such highly oriented material are markedly strained and aligned which show up in a decrease of entropy and enthalpy as compared with a completely relaxed amorphous phase. The decrease in enthalpy quantitatively explains the conspicuous depression of sorption, dyeability, diffusion, and permeability of drawn fibers and films.
The diffusion of gases through filled polymers
Authors: Kwei T. K. , Arnheim W. M. 
Published: June 2010

AbstractThe diffusion of oxygen and arson through poly(vinyl acetate) filled with 12% by volume of titanium dioxide was studied. It was found that the activation energy of gas diffusion in each case was about 56% of the corresponding value fur diffusion in the unfilled polymer above its glass transition temperature. Furthermore, the activation energies for diffusion in the filled polymer appeared to be the same at temperatures above and below the transition temperature, in contrast with the observation by Meares that the activation energy for diffusion in the unfilled polymer has a higher value above Tg. The decrease in the activation energy of gas diffusion as a result of filler incorporation is discussed in terms of the possible decrease in the internal pressure of the filled system. It is postulated that a decrease in the configurational entropy of the polymer accompanies the incorporation of the filler. The explanation is consistent with the results of organic vapor sorption experiments.