bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytotrophoblasts Up-Regulate Soluble Fms-Like Tyrosine Kinase-1 Expression under Reduced Oxygen: An Implication for the Placental Vascular Development and the Pathophysiology of Preeclampsia
Authors: Nagamatsu Takeshi , Fujii Tomoyuki , Kusumi Maki , Zou Li , Yamashita Takahiro , Osuga Yutaka , Momoeda Mikio , Kozuma Shirou , Taketani Yuji 
Published: July 2004

AbstractSufficient cytotrophoblast (CT) invasion into the uterine wall and subsequent remodeling of maternal uterine vasculature is critical to establish uteroplacental circulation. The production of vascular endothelial growth factor (VEGF) family molecules is confirmed in placental cells including CTs, but it is not elucidated how the VEGF system in CTs is controlled by oxygen tension and how it is involved in the development of placental circulation. To address this, we explored the effect of oxygen tension on the expression of VEGF, placenta growth factor (PlGF), and their antagonist, soluble fms-like tyrosine kinase-1 (sFlt-1) using ELISA and real-time PCR in a primary CT cell culture. For comparison, the same was conducted in parallel using other cells comprising placenta, such as human umbilical vein endothelial cells (HUVECs) and villous fibroblasts (VFs). Reduced oxygen resulted in a pronounced increase in sFlt-1 mRNA amount and sFlt-1 release into the culture media in CTs, whereas this was not the case with HUVECs and VFs. Free (not bound to sFlt-1) VEGF was not detected in CT culture media regardless of oxygen concentration, even though VEGF expression was stimulated by reduced oxygen in CTs, which was similar to the stimulation in HUVECs and VFs. Free PlGF was also diminished in CT culture media by reduced oxygen. These results implicate that CTs possess a unique property to enhance sFlt-1 production under reduced oxygen, which could consequently antagonize angiogenic activity of VEGF and PlGF. The presented findings might provide a framework with which to understand the mechanism of uterine vascular remodeling and its perturbations as exemplified in preeclampsia.
Ghrelin Inhibits the Proliferative Activity of Immature Leydig Cells in Vivo and Regulates Stem Cell Factor Messenger Ribonucleic Acid Expression in Rat Testis
Authors: Barreiro M. L. , Gaytan F. , Castellano J. M. , Suominen J. S. , Roa J. , Gaytan M. , Aguilar E. , Dieguez C. , Toppari J. , Tena-Sempere M. 
Published: July 2004

AbstractGhrelin has emerged as putative regulator of an array of endocrine and nonendocrine functions, including cell proliferation. Recently, we provided evidence for the expression of ghrelin in mature, but not in undifferentiated, Leydig cells of rat and human testis. Yet testicular actions of ghrelin, other than modulation of testosterone secretion, remain unexplored. In the present study we evaluated the effects of ghrelin on proliferation of Leydig cell precursors during puberty and after selective elimination of mature Leydig cells by treatment with ethylene dimethane sulfonate. In these settings, intratesticular injection of ghrelin significantly decreased the proliferative activity of differentiating immature Leydig cells, estimated by 5-bromodeoxyuridine labeling. This response was selective and associated, in ethylene dimethane sulfonate-treated animals, with a decrease in the mRNA levels of stem cell factor (SCF), i.e. a key signal in spermatogenesis and a putative regulator of Leydig cell development. Thus, the effects of ghrelin on SCF gene expression were evaluated. In adult rats, ghrelin induced a significant decrease in SCF mRNA levels in vivo. Such an inhibitory action was also detected in vitro using cultures of staged seminiferous tubules. The inhibitory effect of ghrelin in vivo was dependent on proper FSH input, because it was detected in hypophysectomized rats only after FSH replacement. Overall, it is proposed that acquisition of ghrelin expression by Leydig cell precursors during differentiation may operate as a self-regulatory signal for the inhibition of the proliferative activity of this cell type through direct or indirect (i.e. SCF-mediated) mechanisms. In addition, we present novel evidence for the ability of ghrelin to modulate the expression of the SCF gene, which may have implications for the mode of action of this molecule in the testis as well as in other physiological systems.
Leptin Enhances Oocyte Nuclear and Cytoplasmic Maturation via the Mitogen-Activated Protein Kinase Pathway
Authors: Craig Jesse , Zhu Hai , Dyce Paul W. , Petrik Jim , Li Julang 
Published: July 2004

AbstractRecent studies have suggested that leptin has a central role in female reproduction, including ovarian function. The leptin receptor (Ob-R) has six isoforms and can signal through either the MAPK or the Janus-activated kinase/signal transducer and activator of transcription signal-transduction pathway, depending on the isoform. Expression of Ob-R has been reported in human and mouse oocytes; however, the physiological role of leptin during follicular development and oocyte maturation is largely unknown. In the current study, expression of Ob-R during oocyte growth and maturation was investigated in porcine oocytes from small, medium, and large follicles and in oocytes in the germinal vesicle (GV), GV breakdown, and metaphase II (MII) stages at both the mRNA and protein levels. The proportion of oocytes expressing Ob-R was maximal in oocytes from medium follicles and at the GV breakdown stage (P &lt; 0.05), whereas the proportion of oocytes expressing the long isoform, Ob-Rb, was found to be consistently low throughout growth and maturation. When included in oocyte maturation medium, leptin significantly increased the proportion of oocytes reaching MII (P &lt; 0.01), elevated cyclin B1 protein content in MII-stage oocytes (P &lt; 0.05), and enhanced embryo developmental potential (P &lt; 0.05), suggesting that leptin plays a role in both nuclear and cytoplasmic maturation. During oocyte maturation, leptin increased phosphorylated MAPK content by 2.8-fold (P &lt; 0.05), and leptin-stimulated oocyte maturation was blocked when leptin-induced MAPK phosphorylation was suppressed by a specific MAPK activation inhibitor, U0126 (P &lt; 0.01), demonstrating that leptin enhances nuclear maturation via activation of the MAPK pathway.
Study of the Adsorption of Copper(II) Ions from Water onto Wood Sawdust, Pulp and Lignin
Authors: Sciban Marina , Klasnja Mile 
Published: July 2004

The adsorption of copper(II) ions from aqueous solution onto sawdusts from different kinds of wood, pulp and Kraft lignin has been studied. The results of batch studies showed that Kraft lignin was a good adsorbent over the whole concentration range studied, hard woods (oak and black locust) were good when the Cu(II) ion concentration in the aqueous solution was high, while soft woods (poplar, willow, fir) and pulp were good for the adsorption of Cu(II) ions when the latter were present over the low concentration range. The maximum adsorption capacities of the adsorbents investigated towards Cu(II) ions were in the 1.77–9.35 mg/g range. Isotherms were used to obtain the corresponding thermodynamic parameters. Almost complete Cu(II) ion desorption was achieved using 0.1 M mineral acid solutions. The regenerated adsorbents could be used in several adsorption/desorption cycles.
Competitive Sorption of Cu(II), Pb(II) and Hg(II) Ions from Aqueous Solution Using Coconut Shell-Based Activated Carbon
Authors: Goel Jyotsna , Kadirvelu Krishna , Rajagopal Chitra 
Published: July 2004

Many adsorbents have been studied for their adsorption properties towards one-component metal ion solutions. However, if these materials are to be used for treating wastewater, their performance has to be determined in multi-component solutions. In the present work, multi-component metal sorption by coconut shell-based activated carbon has been studied using single, binary and ternary systems composed of Cu(II), Pb(II) and Hg(II) ions. The influence of solution pH was also demonstrated. A set of desorption studies was also performed for the same metal ions with the aim of investigating the mechanism involved. It was found that chemisorption, surface chelation and complexation might be a possible metal ion removal mechanism. Scanning electron micrographs (SEM) and the EDAX spectrum of the activated carbon surface before and after equilibration of the adsorbent with the metal ion solution clearly showed the presence of Cu(II), Pb(II) and Hg(II) ions. An attempt was made to quantify the interaction behaviour of the metal ion on the adsorbent and to correlate such observations with the chemical and physical properties of the metal ions. The ability of isotherm models such as those of Freundlich and Langmuir to predict the equilibrium uptake of Cu(II), Pb(II) and Hg(II) ions from one-component, binary and ternary systems was also tested. Both the Langmuir and Freundlich models were found to fit the experimental data well. The applicability of the extended Langmuir model was also evaluated for multi-component systems.
Modified Granular Activated Carbon: A Carrier for the Recovery of Nickel Ions from Aqueous Wastes
Authors: Satapathy D. , Natarajan G.S. , Sen Raja 
Published: July 2004

Granular Activated Carbon (GAC) is widely used for the removal and recovery of toxic pollutants including metals because of its low cost and high affinity towards the scavenging of metal ions. Activated carbon derived from bituminous coal is preferred for wastewater treatment due to its considerable hardness, a characteristic needed to keep down handling losses during re-activation. Commercial grade carbon, viz. Filtrasorb (F-400), was used in the present work. The scavenging of precious metals such as nickel onto GAC was studied and a possible attempt made to recover the adsorbed Ni2+ ions through the use of some suitable leaching processes. As part of the study, the role of complexing agents on the surface of the carbon was also investigated. The use of organic complexing agents such as oxine and 2-methyloxine in the recovery process was found to be promising. In addition, the surface of the carbon was modified with suitable oxidising agents that proved to be more effective than chelating agents. Several attempts were made to optimise the recovery of metal ions by carrying out experiments with oxidising agents in order to obtain maximum recovery from the minimum quantity of carbon. Experiments with nitric acid indicated that not only was the carbon surface modified but such modification also helped in carbon regeneration.
Adsorption of Bovine Serum Albumin onto Radiation-Crosslinked Poly(Acrylamide/Acrylic Acid)
Authors: Öztop H. Nursevin , Saraydın Dursun , Şolpan Dilek , Güven Olgun 
Published: July 2004

Poly(acrylamide/acrylic acid) (AAm/AAc) hydrogels were prepared at initial acrylic acid compositions of 70, 80 and 85 mol%, respectively. Mixtures of AAm and AAc monomers were irradiated in a 60Co γ-ray source at a dosage of 8 kGy. These hydrogels were used in experiments associated with the swelling, diffusion and adsorption of bovine serum albumin (BSA) from aqueous solution. The data obtained allowed the swelling and diffusion parameters for the hydrogels to be calculated. In the BSA adsorption experiments, the adsorption kinetics together with the influence of the pH of the medium, the initial BSA concentration and the composition of the hydrogels on the adsorption efficiency of the AAm/AAc hydrogels were all studied. The rates of BSA adsorption were found to conform to pseudo-first-order kinetics and a kinetic model was used to calculate the corresponding rate constant for the adsorption processes. The adsorption of BSA onto AAm/AAc hydrogels decreased with increasing pH, with the maximum adsorption being observed at a pH value of 3.7. In terms of the Giles classification, the adsorption was of type C. BSA adsorption increased as the AAc content of the hydrogels increased. Significant amounts of adsorbed BSA (up to 95%) were eluted when an elution medium containing 1.0 M NaSCN was employed at a pH value of 8.0.
Synthesis of polyborosilazane and its utilization as a precursor to boron nitride
Authors: Chu Zeng‐Yong , Feng Chun‐Xiang , Song Yong‐Cai , Li Xiao‐Dong , Xiao Jia‐Yu 
Published: July 2004

AbstractA new kind of polyborosilazane was synthesized from hexamethylcyclotrisilazane by exposure to boron trichloride. The pyrolysis of the precursor was carried out at 1250, 1600, and 1800°C in nitrogen for a dwelling time of 1 h. Characterizations were performed with Fourier transform infrared, X‐ray photoelectron spectroscopy, thermogravimetric analysis, and XRD techniques, and the results showed that the boron content of the precursor increased as the exposure time increased, whereas the C/Si ratio remained constant. Minor amounts of Si and C remained in residue pyrolyzed at 1250°C, but they were completely removed when their residue was further sintered at 1800°C. At that point, it only consisted of hexagonal BN crystals. Therefore, the polymer could be used as a precursor to BN in some special applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 105–109, 2004
Synthesis and characterization of 3‐(2,3‐dihydroxypropoxy)propyl‐terminated polydimethylsiloxanes
Authors: Feng Shengyu , Zhang Jie , Wang Dake , Wu Mingyan , Yu Zhaotan 
Published: July 2004

Abstract3‐(2,3‐Dihydroxypropoxy)propyl‐terminated polydimethylsiloxanes (DHT‐PDMS) samples were prepared through the copolymerization of 1,1,3,3,5,5,7,7‐octamethylcyclotetrasiloxane (D4) and 1,3‐bis[3‐(2,3‐dihydroxypropoxy)propyl]‐1,1,3,3‐tetramethyldisiloxane by acid‐catalyzed equilibration. Their structures were characterized with IR and 1H‐NMR spectra. The molecular weights were determined with gel permeation chromatography and 1H‐NMR spectra, respectively. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermodynamic properties and thermal degradation of DHT‐PDMS. The effects of various factors on the synthesis of DHT‐PDMS were also examined. However, the preparation of DHT‐PDMS through the base‐catalyzed equilibrium copolymerization of D4 and 1,3‐bis[3‐(2,3‐epoxypropoxy)propyl]‐1,1,3,3‐tetramethyldisiloxane, followed by the hydrolysis of the epoxy groups, was unsuccessful. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 110–115, 2004
Effect of nano‐Mg(OH)2 on the mechanical and flame‐retarding properties of polypropylene composites
Authors: Mishra S. , Sonawane S. H. , Singh R. P. , Bendale A. , Patil K. 
Published: July 2004

AbstractNano‐Mg(OH)2 was synthesized with an in situ deposition technique, and its size was confirmed by X‐ray diffraction. A polypropylene–Mg(OH)2 composite was prepared by melt‐extrusion processing. The addition of a small quantity of a nanofiller (up to 10 wt %) increased Young's modulus up to 433% with respect to the modulus of virgin polypropylene. The addition of up to 4 wt % Mg(OH)2 produced the maximum increase, and a further decrease in the tensile strength was observed with an increase in the concentration of nano‐Mg(OH)2. Increases in the hardness and other properties were due to higher nucleation and the intercalation of polymer chains in the nanolayer galleries. The flame‐retarding property was demonstrated by the rate of burning. The time required to burn the nanofilled composite was greater than the time required for virgin polypropylene. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 116–122, 2004
Effect of some metal salt pretreatments on acrylic printing
Authors: Gabry L. K. El , Hakeim O. A. 
Published: July 2004

AbstractAcrylic fabrics were pretreated with metal salts (aluminum sulfate, copper sulfate, ferrous sulfate, and potassium dichromate) in different concentrations. The tensile strength, elongation, and moisture regain of pretreated and untreated samples were examined. The effects of various concentrations of the metal salts, the pH of the printing paste, and the thickening agent on the color strength and fastness properties of the printed fabrics were studied to determine the optimum printing conditions. The pretreatment improved the printability of acrylic modified with a cationic dye and the fastness properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 130–134, 2004
A rheometrical technique to study the swelling kinetics of vulcanized rubber particles by paraffinic solvents using a torque rheometer
Authors: Gaulliard Vincent , Leblanc Jean L. 
Published: July 2004

AbstractThe solvent uptake by vulcanized rubber particles was studied through a swelling technique by using a torque rheometer to record torque versus time curves, with good repeatability. Several experiments were performed to study the effects of varying the solvent/rubber ratio, the solvent type, and the rubber nature. The effects of the materials alone were also studied. A four‐parameter mathematical model was developed, with a physical significance assigned to each of the parameters, and was compared with experiments. The model was found to fit well with the experimental results, therefore, allowing the physical processes involved in the solvent swelling of rubber particles to be investigated through model parameters. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 142–153, 2004
Sago starch and its acrylamide modified products as coating material on handsheets made from recycled pulp fibers
Authors: Yeng Wong Sin , Tahir Paridah Md. , Chiang Liew Kang , Yunus Wan Md. Zin Wan , Zakaria Sarani 
Published: July 2004

AbstractThis study was carried out to determine the suitability of sago starch as a paper additive. The basic properties (i.e., pH, viscosity, and solid content) of the 5% weight over volume basis of unmodified and modified sago starch (sago starch blended with acrylamide, sago starch grafted with acrylamide in an acidic and adjusted to alkaline conditions) were determined. The starches were then used to coat laboratory handsheets made from recycled pulp fibers. The incorporation of acrylamide into sago starch through grafting significantly reduced the viscosity of the solution. Generally, coating the handsheets with unmodified sago starch significantly improved some properties as compared to the uncoated handsheets. Among the three types of sago starch modification methods, blending gave superior performance when coated on the handsheets, except for smoothness and air permeance, due to insufficient curing shown by the micrographs. FTIR spectra showed that the interactions between the blended acrylamide–starch solutions and the pulp fiber were weak. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 154–158, 2004
Influence of polymer viscosity on the morphological and opto‐electronic behavior of polysiloxane dispersed ferroelectric liquid crystal composite thin films
Authors: Sumana G. , Raina K.K. 
Published: July 2004

AbstractPoly(dimethyl)siloxanes of different viscosity have been synthesized by hydrolytic condensation of dimethyldichloro silane. Polysiloxane dispersed ferroelectric liquid crystal (PDFLC) composite films were prepared simultaneously by solvent induced and polymer induced phase separation techniques (SIPS and PIPS, respectively). These composite films were prepared by mixing polymer and ferroelectric liquid crystal mixture in diethyl ether and then adding 0.2% of room temperature vulcanizer for crosslinking. Film morphology, droplet size, and electro‐optic parameters of PDFLC systems have been studied by using polysiloxanes of different viscosity. We show that the polymer viscosity affects the droplet size, morphological uniformity, electro‐optic properties, and also the extent to which the phase separation is complete. These composite systems show the switching time of few microseconds. Structure‐property correlation in these materials have been studied and explained on the basis of polysiloxane viscosity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 159–166, 2004
Structural properties of γ‐irradiated poly(vinyl alcohol)/poly(ethylene glycol) polymer blends
Authors: Abd Alla Safaa G. , Said Hossam M. , El‐Naggar Abdel Wahab M. 
Published: July 2004

AbstractThe effect of various doses of γ radiation on the structural properties of water‐soluble polymer blends based on poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) has been investigated. Although the aqueous solutions of individual PVA and PEG homopolymers were homogeneous and clear, films transparent to visual observation were only formed by solution casting of pure PVA and those blends containing low ratios of PEG up to 30%. The structure‐property behavior of this range of blends before and after γ irradiation was investigated by light reflectance and UV absorbance, differential scanning calorimetry (DSC), IR spectroscopy, and tensile mechanical testing. The DSC thermograms of PVA/PEG blends, before or after γ irradiation, showed a solely endothermic peak over the temperature range 40–140°C, which may have arisen from the melting of the PEG component or from the glass transition of PVA/PEG as a miscible blend in accordance with those calculated on the basis of the theoretical Fox equation. Also, these thermograms did not clearly show any transition that arised from the pure PVA component. However, the improvement in tensile mechanical properties of PVA/PEG blends, the reflectance, and the optical absorption measurements support the idea of improved miscibility after γ irradiation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 167–176, 2004
The effects of lignocellulosic fiber surface area on the dynamics of lignin oxidation and diffusion
Authors: Mancosky Douglas G. , Lucia Lucian A. , Deng Yulin 
Published: July 2004

AbstractA novel preliminary experimental approach was developed to determine the effect of maximizing pulp fiber surface area for the regulation of the oxidation and diffusion of lignin through the carbohydrate matrix. The approach entailed liquid nitrogen freezing of mature black spruce kraft pulp fibers and subsequent mechanical grinding to a fine powder to test the effect of enhanced pulp fiber surface area on the efficiencies of lignin oxidation and lignin diffusion. It was found that the liquid nitrogen ground pulp samples provided higher optical reflectance (brightness) after both oxygen and hydrogen peroxide oxidation, which appears to be from chromophoric (chemical) differences and not light scattering differences as supported by UV/Vis spectroscopy. BET (absorption) experiments indicated a dramatic difference in the surface area of the pulp as a result of the grinding, although no differences existed among the pore sizes between the samples, as determined from SEM experiments. Lignin diffusion experiments demonstrated that differences did exist in the kinetics of lignin diffusion into a bulk solution between a control and liquid nitrogen ground samples. Lignin uptake into bulk solutions was enhanced by the liquid nitrogen/pulp‐grinding technique albeit not from chemical changes in the lignin because the subsequent NMR spectra did not point to any major chemical differences as a result of liquid nitrogen freezing and grinding. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 177–181, 2004