bluuebunny/crossref_metadata_2025_split huggingface dataset:
The zebrafish dyrk1b gene is important for endoderm formation
Authors: Mazmanian Gohar , Kovshilovsky Michael , Yen Debbie , Mohanty Aditya , Mohanty Sudipta , Nee Alex , Nissen Robert M. 
Published: December 2009

AbstractNodal‐signaling is required for specification of mesoderm, endoderm, establishing left–right asymmetry, and craniofacial development. Wdr68 is a WD40‐repeat domain‐containing protein recently shown to be required for endothelin‐1 (edn1) expression and subsequent lower jaw development. Previous reports detected the Wdr68 protein in multiprotein complexes containing mammalian members of the dual‐specificity tyrosine‐regulated kinase (dyrk) family. Here we describe the characterization of the zebrafish dyrk1b homolog. We report the detection of a physical interaction between Dyrk1b and Wdr68. We also found perturbations of nodal signaling in dyrk1b antisense morpholino knockdown (dyrk1b‐MO) animals. Specifically, we found reduced expression of lft1 and lft2 (lft1/2) during gastrulation and a near complete loss of the later asymmetric lft1/2 expression domains. Although wdr68‐MO animals did not display lft1/2 expression defects during gastrulation, they displayed a near complete loss of the later asymmetric lft1/2 expression domains. While expression of ndr1 was not substantially effected during gastrulation, ndr2 expression was moderately reduced in dyrk1b‐MO animals. Analysis of additional downstream components of the nodal signaling pathway in dyrk1b‐MO animals revealed modestly expanded expression of the dorsal axial mesoderm marker gsc while the pan‐mesodermal marker bik was largely unaffected. The endodermal markers cas and sox17 were also moderately reduced in dyrk1b‐MO animals. Notably, and similar to defects previously reported for wdr68 mutant animals, we also found reduced expression of the pharyngeal pouch marker edn1 in dyrk1b‐MO animals. Taken together, these data reveal a role for dyrk1b in endoderm formation and craniofacial patterning in the zebrafish. genesis 48:20–30, 2010. © 2009 Wiley‐Liss, Inc.
One‐Pot Catalytic Glycosidation/Fmoc Removal – An Iterable Sequence for Straightforward Assembly of Oligosaccharides Related to HIV gp120
Authors: Pastore Antonello , Adinolfi Matteo , Iadonisi Alfonso , Valerio Silvia 
Published: December 2009

AbstractThe removal of a transient Fmoc protecting group can be simply performed by the addition of excess Et3N just after the accomplishment of a Bi(OTf)3‐promoted glycosidation reaction. The obtained oligosaccharide can be directly employed as a glycosyl acceptor for further elongation of the saccharide. The preparation of biologically important, linear and branched mannans incorporated into HIV gp120 demonstrates that the iteration of this one‐pot sequence leads to a very straightforward oligosaccharide assembly.
Isomerization of all‐(E)‐Retinoic Acid Mediated by Carbodiimide Activation – Synthesis of ATRA Ether Lipid Conjugates
Authors: Christensen Mikkel S. , Pedersen Palle J. , Andresen Thomas L. , Madsen Robert , Clausen Mads H. 
Published: December 2009

AbstractTreatment of the lysolipid 1‐O‐hexadecyl‐sn‐phosphatidylcholine with all‐(E)‐retinoic acid, DCC and DMAP resulted in poor acylation and caused (Z)/(E) isomerization of the α–β double bond. In the presence of a proton source, the carbodiimide‐activated all‐(E)‐retinoic acid undergoes fast isomerization to give a final mixture of (13E)/(13Z) isomers in a 3:1 ratio. Similar treatment of (13Z)‐retinoic acid leads to the same isomer ratio. The isomerization was circumvented successfully by using a Mitsunobu reaction, which provided an efficient synthesis of all‐(E)‐retinoic acidsn‐2‐conjugated to phosphatidylcholine and phosphatidylglycerol etherlipids.
Electrochemical, In Situ Spectroelectrochemical, In Situ Electrocolorimetric and Electrocatalytic Characterization of Metallophthalocyanines Bearing Four Dioctylaminocarbonyl Biphenyloxy Substituents
Authors: Koca Atif , Kalkan Ayfer , Altuntaş Bayır Zehra 
Published: December 2009

AbstractThis study describes the electrochemical, in situ spectroelectrochemical, in situ electrocolorimetric and electrocatalytic characterization of metallophthalocyanines bearing four dioctylaminocarbonyl biphenyloxy groups (MPc's). While CoPc gives both metal‐based and ring‐based redox processes, ZnPc and CuPc show only ring‐based reduction and oxidation processes. In‐situ electrocolorimetric method was applied to investigate color of the electrogenerated anionic and cationic forms of the complexes. Perchloric acid titrations monitored by cyclic voltammetry and spectrophotometry represent possible electrocatalytic activities of the complexes for hydrogen evolution reaction. CuPc having inactive metal center incorporated into a Nafion film on GCE decreases overpotential of the electrode for H+ reduction in aqueous solution.
Electrochemical Reduction of S(IV) Compounds in Water‐Ethanol Solutions at Nafion/Tetraruthenated Porphyrins Glassy Carbon Modified Electrodes
Authors: Calfumán Karla , García Macarena , Aguirre Maria J. , Matsuhiro Betty , Mendoza Leonora , Isaacs Mauricio 
Published: December 2009

AbstractThis work describes electrocatalytic detection of S(IV) compounds in water‐ethanol solutions under acidic conditions, on a glassy carbon electrode modified with Co(II) tetraruthenated porphyrin electrostatically assembled onto a Nafion film. The Ipc current shows a linear relationship with the concentration of S(IV) oxo‐anions. Controlled potential electrolysis shows that thiosulfate was detected as reaction product. Rotating disk electrode and UV‐visible spectroelectrochemistry experiments showed a kinetic limitation to the electron transfer controlled by charge propagation in the film and the formation of an intermediary between Co center and S(IV) species. The reproducibility of the modification methodology presents a RSD of 4.1%.
A Simple Layer‐by‐Layer Assembly Strategy for a Reagentless Biosensor Based on a Nanocomposite of Methylene Blue‐Multiwalled Carbon Nanotubes
Authors: Zhang Yiming , Liu Lijun , Xi Fengna , Wu Tianxing , Lin Xianfu 
Published: December 2009

AbstractA simple layer‐by‐layer (LBL) assembly strategy was established for constructing a novel reagentless biosensor based on a nanocomposite of methylene blue multiwalled carbon nanotubes (MB‐MWNTs). A nanocomposite of MB‐MWNTs was obtained by direct premixing and possessed good dispersion in barbital‐HCl buffer. Through electrostatic interactions, the nanocomposite of MB‐MWNTs could alternately be assembled with horseradish peroxidase (HRP) on the Au electrode modified with precursor films. UV/Vis spectra and scanning electron microscopy (SEM) were applied to reveal the formation of the nanocomposite of MB‐MWNTs. The LBL assembly process was also verified by electrochemical impedance spectroscopy (EIS). The MB is a well‐established mediator and efficiently facilitated the electron shuttle between the HRP and the electrode, as demonstrated by the cyclic voltammetry (CV) measurements. The as‐prepared reagentless biosensor exhibited a fast response for the determination of hydrogen peroxide (H2O2) and reached 95% of the steady‐state current within 3 s. It was found that the linear response range of the reagentless biosensor for H2O2 was from 4.0 μM to 3.78 mM with a detection limit of 1.0 μM and a sensitivity of 22.5 μA mM−1. The biosensor exhibited a high reproducibility and stability.
Electrocatalytic Oxidation of Glucose by the Glucose Oxidase Immobilized in Graphene‐Au‐Nafion Biocomposite
Authors: Zhou Kangfu , Zhu Yihua , Yang Xiaoling , Li Chunzhong 
Published: December 2009

AbstractGraphene was successfully prepared and well separated to individual sheets by introducing SO3−. XRD and TEM were employed to characterize the graphene. UV‐visible absorption spectra indicated that glucose oxidase (GOx) could keep bioactivity well in the graphene‐Au biocomposite. To construct a novel glucose biosensor, graphene, Au and GOx were co‐immobilized in Nafion to further modify a glassy carbon electrode (GCE). Electrochemical measurements were carried out to investigate the catalytic performance of the proposed biosensor. Cyclic voltammograms (CV) showed the biosensor had a typical catalytic oxidation response to glucose. At the applied potential +0.4 V, the biosensor responded rapidly upon the addition of glucose and reached the steady state current in 5 s, with the present of hydroquinone. The linear range is from 15 μM to 5.8 mM, with a detection limit 5 μM (based on the S/N=3). The Michaelis‐Menten constant was calculated to be 4.4 mM according to Lineweaver–Burk equation. In addition, the biosensor exhibits good reproducibility and long‐term stability. Such impressive properties could be ascribed to the synergistic effect of graphene‐Au integration and good biocompatibility of the hybrid material.
Effect of Parasitic Capacitance on Impedance Measurement and Model Extraction
Authors: Zhang Guoping , Zhu Rong 
Published: December 2009

AbstractImpedance spectroscopy has been widely used for the characterization of materials and structures. An impedance model can be employed to extract electrical parameters ascribed to the electrical properties of material interiors, boundaries, and external material/electrode interfaces. In an impedance model, a parasitic capacitance exerts an important effect, and is thus an essential to be added. In this paper, dramatic impact of parasitics on impedance spectra and parameter extraction is investigated using theoretical analyses, simulations, and physical experiments. A complex nonlinear least squares fitting method based on a parasitic model together with an I‐V assisted estimation method is proposed for providing more accurate and efficient parameter extraction than previously available solutions. The results also reveal that the low frequency band (below 1 kHz) is not recommended to be used because the impedance measurements are influenced badly by noise. The moderate frequency band (1 kHz–1 MHz) is a recommended range for parameter extraction.
Amperometric Response of Hydrogen Peroxide at Carbon Nanotubes Paste Electrodes Modified with an Electrogenerated Poly(Fe(III)‐5‐amino‐phenantroline). Analytical Applications for Glucose Biosensing
Authors: Lozano Maria L. , Rodríguez Marcela C. , Herrasti Pilar , Galicia Laura , Rivas Gustavo A. 
Published: December 2009

AbstractThis work reports the catalytic activity of a polymer electrogenerated from Fe(III)‐5‐amino‐1,10‐phenantroline solution at a carbon nanotubes paste electrode (CNTPE) towards the oxidation and mainly the reduction of hydrogen peroxide. The important role of carbon nanotubes on the generation of poly(Fe(III)‐5‐amino‐1,10‐phenantroline) is demonstrated through the comparison with the behavior of graphite paste electrode (CPE). The polymer electrogenerated at CNTPE largely improves the amperometric detection of hydrogen peroxide at −0.100 V. The analytical application of the resulting electrode is demonstrated in connection with the design of a glucose biosensor based on the deposition of GOx and diluted Nafion on the top of the polymer‐modified CNTPE. The quantification of glucose in human serum samples showed a good correlation with the values obtained by the spectrophotometric technique.
Electrochemical Investigation of Na‐Salt of 2‐Methyl‐3‐(4‐nitrophenyl)acrylate on Glassy Carbon Electrode
Authors: Shah Afzal , Diculescu Victor C. , Muhammad Niaz , Qureshi Rumana , Ali Saqib , Oliveira‐Brett Ana Maria 
Published: December 2009

AbstractThe electrochemical behavior of Na‐salt of 2‐methyl‐3‐(4‐nitrophenyl)acrylate (NPA) and its reduction product was studied by cyclic (CV), differential pulse(DPV) and square wave voltammetry (SWV) using a glassy carbon electrode (GCE). The results revealed that NPA is irreversibly reduced leading to the formation of a reduction product (PNPA). For pH<9.0 the peak potential was linearly dependent on pH. For pH>9.0 the peak potential was pH‐independent and the value of pKb≈9.0 was determined. The adsorbed PNPA exhibited reversible redox reaction. The reduction of PNPA was pH dependent. To ensure that the electrochemical behavior of NPA is due to the reducible moiety, NO2, closely related compounds to NPA were also studied, and a redox mechanism was proposed for NPA.
New Anthraquinone Derivatives as Electrochemical Redox Indicators for the Visualization of the DNA Hybridization Process
Authors: Kowalczyk Agata , Nowicka Anna Maria , Jurczakowski Rafal , Niedzialkowski Pawel , Ossowski Tadeusz , Stojek Zbigniew 
Published: December 2009

AbstractInteractions of dsDNA and ssDNA, at the surface of gold and silver electrodes, with three novel anthraquinone derivatives: 3‐(9′,10′‐dioxo‐9′,10′‐dihydro‐anthracen‐1‐yl)‐7,11‐di(carboxymethyl)‐3,7,11‐triazatridecanedioic acid, (AQ‐1); 1‐(9′,10′‐dioxo‐9′,10′‐dihydro‐anthracen‐1yl)‐9‐carboxymethyl‐5‐methyl‐1,5,9‐triazaundecanoicacid, (AQ‐2); and N‐(2‐(9,10‐dioxo‐9,10‐dihydro‐anthracen‐1‐ylamino)ethyl)‐2‐(1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecan‐7‐yl)acetamide, (AQ‐3) are studied. These derivatives are well soluble in water and phosphate buffer solutions. The square wave voltammetric behavior of these redox indicators is described and the parameters of interactions with DNA are reported. It is also pointed out that these compounds can be employed as the hybridization indicators. The difference in the binding ability of the particular redox indicator to single and double stranded DNA can be used for the detection of the complementary nucleic acids.
Evaluation of Poly(o‐phenylenediamine) Films for Application as Insulating Layers upon Carbon Substrates for Use within Sonochemically Fabricated Microelectrode Arrays
Authors: Gornall Davinia D. , Collyer Stuart D. , Higson Séamus P. J. 
Published: December 2009

AbstractThe formation of insulating layers of poly(o‐phenylenediamine) via electropolymerization was performed on single carbon screen‐printed electrodes. The effects of experimental parameters on the properties of the film were investigated, allowing for technique optimization. These conditions were then used to deposit films upon surfaces of 100 interconnected electrodes, with cyclic voltammetry used to study the electroactivity of the resulting electrodes. The insulating property of the film, for use in the formation of microelectrode array amperometric sensors, was evaluated. Finally, the insulated sensors were exposed to ultrasonic ablation to form microelectrode arrays, and these were subsequently assessed using optical and electrochemical techniques.
Anti‐Clostridium tetani Antibody Determination in Serum Samples by Amperometric Immunosensing
Authors: Patris S. , De Vriese C. , Prohoroff F. , Calvo E. Burgoa , Martínez J. Arcos , Kauffmann J.‐M. 
Published: December 2009

AbstractAn electrochemical (EC) immunosensing assay for anti‐Clostridium tetani antibody determination in serum has been developed. The antigen tetanus toxoid was immobilized on superparamagnetic nanobeads. The immunoreaction occurred in Eppendorf minitubes. The anti‐tetani antibody was incubated in the presence of the toxoid functionalized nanobeads, then reacted with horseradish peroxidase‐labeled anti‐IgG. The resulting immunobeads were retained onto the carbon paste working electrode with a magnet. Hydroquinone served as redox label. The level of anti‐Clostridium tetani antibody in guinea pig serum samples was determined by amperometry using a carbon based screen‐printed electrode (cSPE) housed onto a magnetic support. The EC response was proportional to the logarithm of the antibody concentration comprised between 0.0046 IU/mL and 0.175 IU/mL with a limit of detection of 0.0046 IU/mL. In order to minimize the matrix effect, the standard addition method was applied. The assay was validated by comparing the EC immunosensing data with those obtained by applying the ELISA method described in the European Pharmacopoeia.
Enhanced Performance of Edge‐Plane Pyrolytic Graphite (EPPG) Electrodes over Glassy Carbon (GC) Electrodes in the Presence of Surfactants: Application to the Stripping Voltammetry of Copper
Authors: Shishmarev Dmitry S. , Rees Neil V. , Compton Richard G. 
Published: December 2009

AbstractThe voltammetric performance of glassy carbon (GC) and edge‐plane pyrolytic graphite (EPPG) electrodes was investigated for the oxidation of potassium ferrocyanide in aqueous solution both with and without the addition of surfactant (sodium dodecyl sulfate and Triton X‐100). The heterogeneous electron transfer kinetics were determined for all cases, and it was found that the GC electrode surface was far more sensitive to the presence of surfactant than the more hydrophilic EPPG surface. This result was then applied to the electroanalysis of copper via adsorptive stripping voltammetry in the presence of Triton X‐100 and it was observed that the EPPG electrode response was unaffected by up to 100 μM of surfactant, whilst the voltammetry on the GC electrode was significantly affected by only 10 μM.
Quantitative Determination of High Charge Density Polyanion Contaminants in Biomedical Heparin Preparations Using Potentiometric Polyanion Sensors
Authors: Wang Lin , Meyerhoff Mark E. 
Published: December 2009

AbstractQuantification of oversulfated chondroitin sulfate (OSCS) in biomedical heparin preparations is achieved using a recently described potentiometric polyanion sensor‐based approach operated in a kinetic mode of analysis. This is accomplished by adjusting the concentration of the test sample to a range where the OSCS level is low enough for the sensor not to achieve a full and rapid equilibrium phase boundary potential change at the membrane/sample interface upon exposure to the heparin sample. Using this method, the OSCS wt% determined within heparin samples containing OSCS are shown to be in good agreement with those determined by an accepted NMR method.
The tectonic regime along the Andes: Present‐day and Mesozoic regimes
Authors: Ramos Victor A. 
Published: December 2009

AbstractThe analyses of the main parameters controlling the present Chile‐type and Marianas‐type tectonic settings developed along the eastern Pacific region show four different tectonic regimes: (1) a nearly neutral regime in the Oregon subduction zone; (2) major extensional regimes as the Nicaragua subduction zone developed in continental crust; (3) a Marianas setting in the Sandwich subduction zone with ocean floored back‐arc basin with a unique west‐dipping subduction zone and (4) the classic and dominant Chile‐type under compression. The magmatic, structural and sedimentary behaviours of these four settings are discussed to understand the past tectonic regimes in the Mesozoic Andes based on their present geological and tectonic characteristics. The evaluation of the different parameters that governed the past and present tectonic regimes indicates that absolute motion of the upper plate relative to the hotspot frame and the consequent trench roll‐back velocity are the first order parameters that control the deformation. Locally, the influences of the trench fill, linked to the dominant climate in the forearc, and the age of the subducted oceanic crust, have secondary roles. Ridge collisions of seismic and seismic oceanic ridges as well as fracture zone collisions have also a local outcome, and may produce an increase in coupling that reinforces compressional deformation. Local strain variations in the past and present Andes are not related with changes in the relative convergence rate, which is less important than the absolute motion relative to the Pacific hotspot frame, or changes in the thermal state of the upper plate. Changes in the slab dip, mainly those linked to steepening subduction zones, produce significant variations in the thermal state, that are important to generate extreme deformation in the foreland. Copyright © 2009 John Wiley & Sons, Ltd.
Blueberry supplementation attenuates microglial activation in hippocampal intraocular grafts to aged hosts
Authors: Willis Lauren M. , Freeman Linnea , Bickford Paula C. , Quintero E. Matthew , Umphlet Claudia D. , Moore Alfred B. , Goetzl Laura , Granholm Ann‐Charlotte 
Published: December 2009

AbstractTransplantation of central nervous tissue has been proposed as a therapeutic intervention for age‐related neurodegenerative diseases and stroke. However, survival of embryonic neuronal cells is hampered by detrimental factors in the aged host brain such as circulating inflammatory cytokines and oxidative stress. We have previously found that supplementation with 2% blueberry in the diet increases graft growth and neuronal survival in intraocular hippocampal grafts to aged hosts. In the present study we explored possible biochemical mechanisms for this increased survival, and we here report decreased microglial activation and astrogliosis in intraocular hippocampal grafts to middle‐aged hosts fed a 2% blueberry diet. Markers for astrocytes and for activated microglial cells were both decreased long‐term after grafting to blueberry‐treated hosts compared with age‐matched rats on a control diet. Similar findings were obtained in the host brain, with a reduction in OX‐6 immunoreactive microglial cells in the hippocampus of those recipients treated with blueberry. In addition, immunoreactivity for the pro‐inflammatory cytokine IL‐6 was found to be significantly attenuated in intraocular grafts by the 2% blueberry diet. These studies demonstrate direct effects of blueberry upon microglial activation both during isolated conditions and in the aged host brain and suggest that this nutraceutical can attenuate age‐induced inflammation. © 2009 Wiley‐Liss, Inc.
Ammonia triggers exocytotic release of L‐glutamate from cultured rat astrocytes
Authors: Görg Boris , Morwinsky Anke , Keitel Verena , Qvartskhava Natalia , Schrör Karsten , Häussinger Dieter 
Published: December 2009

AbstractAmmonia toxicity to the brain involves NMDA receptor overactivation and glutamate excitotoxicity. The mechanisms underlying glutamate release from astrocytes in response to ammonia were addressed in this study. In cultured rat astrocytes, glutamate immunoreactivity (IR) was punctate and partly colocalized with transfected VAMP2‐YFP. NH4Cl (5 mmol/L) and hypoosmotic exposure (205 mosmol/L) induced a rapid colchicine‐sensitive loss of cellular glutamate and glutamate appearance in the extracellular space. The NH4Cl‐induced glutamate loss from astrocytes was strongly blunted after transfection of the cells with VAMP2 siRNA. Ammonia‐induced exocytosis of VAMP2‐YFP expressing vesicles was shown by total internal reflection fluorescence microscopy (TIRF‐M). Glutamate exocytosis in response to ammonia was sensitive to chelation of Ca2+, cyclooxygenase inhibition by indomethacin and colchicine. Ammonia triggered the rapid formation of prostanoids, which were identified as upstream events in ammonia‐induced glutamate exocytosis. Also, addition of prostaglandin E2 or of tumor necrosis factor (TNF)‐α triggered glutamate exocytosis. Inhibition of ammonia‐induced glutamate exocytosis after transfection of VAMP2 siRNA inhibited ammonia‐induced RNA oxidation. It is concluded that ammonia triggers a prostanoid‐ and Ca2+‐dependent glutamate exocytosis, which is essential for induction of ammonia‐induced RNA oxidation. © 2009 Wiley‐Liss, Inc.