bluuebunny/crossref_metadata_2025 huggingface dataset:
Fourier Transformed Large Amplitude Square‐Wave Voltammetry as an Alternative to Impedance Spectroscopy: Evaluation of Resistance, Capacitance and Electrode Kinetic Effects via an Heuristic Approach
Authors: Sher Anna A. , Bond Alan M. , Gavaghan David J. , Gillow Kathryn , Duffy Noel W. , Guo Si‐Xuan , Zhang Jie
Published: July 2005

A detailed simulation of Fourier transformed large amplitude square‐wave voltammetry is presented in the frequency domain for the process Red⇌Ox+e−. The simulation takes into account the influence of the electrode kinetics (Butler–Volmer model), uncompensated resistance (Ru) and double layer capacitance (Cdl). Of particular significance is the prediction that the even harmonic responses are only detected in the presence of quasi‐reversibility or uncompensated resistance, and also are essentially devoid of charging current. In contrast, the DC and odd harmonic AC components exhibit much larger faradaic currents and also contain charging current. Conveniently, detailed analysis of the simulated DC and AC harmonic components reveals the presence of readily recognised patterns of behaviour with unique levels of sensitivity to electrode kinetics,RuandCdl, that facilitate quantitative analysis of these terms. These electrochemical parameters are generally calculated by small amplitude impedance spectroscopy and utilisation of linear analysis of equivalent circuits. Experimental studies on the one electron oxidation of ferrocene in dichloromethane (0.1 M Bu4NPF6) and the one electron reduction of [Fe(CN)6]3−in aqueous 0.5 M KCl electrolyte analysed via heuristic forms of data analysis based on recognition of patterns of behaviour, are presented as examples of a reversible process with significant uncompensated resistance and a quasi‐reversible process with minimal ohmic drop, respectively. Results demonstrate the advantages of a more intuitively implemented form of data analysis than presently available with conventional forms of impedance spectroscopy.
Voltammetry of Dissolved Iron(III)–Nitrilotriacetate–Hydroxide System in Water Solution
Authors: Cuculić Vlado , Pižeta Ivanka , Branica Marko
Published: July 2005

The investigation of the dissolved iron(III)–nitrilotriacetate–hydroxide system in the water solution (I=0.1 mol L−1 in NaClO4; pH 8.0±0.1) using differential pulse cathodic voltammetry, cyclic voltammetry, and sampled direct current (DC) polarography, was carried out on a static mercury drop electrode (SMDE). The dissolved iron(III) ion concentrations varied from 2.68×10−6 to 6×10−4 mol L−1 and nitrilotriacetate concentrations were 1×10−4 and 5×10−4 mol L−1. By deconvoluting of the overlapped reduction voltammetric peaks using Fourier transformation, four relatively stable, dissolved iron(III) complex species were characterized, as follows: [Fe(NTA)2]3−, mixed ligand complexes [FeOHNTA]− and [Fe(OH)2NTA]2−, showing a one‐electron quasireversible reduction, and binuclear diiron(III) complex [NTAFeOFeNTA]2−, detected above 4×10−4 mol L−1 of the added iron(III) ions, showing a one‐electron irreversible reduction character. The calculations with the constants from the literature were done and compared with the potential shifts of the voltammetric peaks. Fitting was obtained by changing the following literature constants: log β2([Fe(NTA)2]3−) from 24 to 27.2, log β1([FeNTA]−) from 8.9 to 9.2, log β2([Fe(NTA)2]4−) from 11.89 to 15.7 and log β2([Fe(OH)2NTA]3−) from 15.63 to 19. The determination of the electrochemical parameters of the mixed ligand complex [FeOHNTA]−, such as: transfer coefficient (α), rate constant (ks) and formal potential (E°') was done using a sampled DC polarography, and found to be 0.46±0.05, 1.0±0.3×10−3 cm s−1, and −0.154±0.010 V, respectively. Although known previously in the literature, these four species have now for the first time been recorded simultaneously, i.e. proved to exist simultaneously under the given conditions.
Comparison of the Electrochemical Behavior of the High Molecular Mass Cadmium Proteins in Arabidopsis thaliana and in Vegetable Plants on Using Preparative Native Continuous Polyacrylamide Gel Electrophoresis (PNC‐PAGE)
Authors: Kastenholz Bernd
Published: July 2005

In Arabidopsis cytosol (supernatant) and in supernatants of vegetable plants high molecular mass cadmium proteins with molecular mass 200 kDa were isolated by using preparative native continuous polyacrylamide gel electrophoresis (PNC‐PAGE). Because of a different electrochemical behavior of the Cd proteins in Arabidopsis and endive supernatants on using the same PAGE method, it is concluded that the high molecular mass cadmium proteins of Arabidopsis and endive possess different isoelectric points. Consequently, different chemical structures of the Cd proteins with molecular mass 200 kDa are present in Arabidopsis thaliana and in endive. During the electrophoretic separation of vegetable metalloproteins by using the Model 491 Prep Cell from BioRad, electroanalytical processes like electrode reactions may play an important role.
Electrochemically‐Induced Deposition of Amine‐Functionalized Silica Films on Gold Electrodes and Application to Cu(II) Detection in (Hydro)Alcoholic Medium
Authors: Walcarius Alain , Sibottier Emilie
Published: July 2005

Well‐adherent amine‐functionalized porous silica films have been deposited on gold electrodes by combining the self‐assembly technology, the sol–gel process, and the electrochemical modulation of pH at the electrode/solution interface. A partial self‐assembled monolayer of mercaptopropyl‐trimethoxysilane (MPTMS) was first formed on disposable gold electrodes from recordable CDs (Au‐CDtrodes). The so pretreated MPTMS‐Au‐CDtrodes were immersed in a stable sol solution (pH 3) containing (3‐aminopropyl)‐triethoxysilane (APTES) and tetraethoxysilane (TEOS). Polycondensation of the APTES and TEOS precursors was then achieved by applying a negative potential for a given period of time to generate a local pH increase at the electrode/solution interface and promote the deposition of the amine functionalized silica film adhering well to the electrode surface owing to the MPTMS monolayer acting somewhat as a “molecular glue”. Various parameters affecting the electrodeposition process have been studied and the film permeability to redox probes in solution was characterized by cyclic voltammetry. The amine‐functionalized silica film electrodes were then applied to the preconcentration of copper(II) species prior to their electrochemical detection by anodic stripping differential pulse voltammetry. Getting high sensitivity has however required the application of an electrochemical pre‐activation step as the majority of the organo‐functional groups were in the form of ammonium moieties (because the film was prepared from an acidic sol). This was achieved by applying a sufficiently negative potential to the electrode surface to reduce protons and increase consequently the amine‐to‐ammonium ratio within the film and, thus, the efficiency of the precocentration process. The resulting device was then optimized for copper(II) determination in hydroalcoholic medium, giving rise to a linear response in the 0.1–10 μM concentration range.
Electrochemically Deposited Polymer‐Coated Gold Electrodes Selective for 2,4‐Dichlorophenoxyacetic Acid
Authors: Weetall Howard H. , Hatchett David W. , Rogers Kim R.
Published: July 2005

Electropolymerized membranes on gold electrodes doped with 2,4‐dichlorophenoxyacetic acid (2,4‐D) were prepared from a solution containing resorcinol, o‐phenylenediamine and 2,4‐D. Fourier Transform Infrared (FTIR) spectroscopy was used to evaluate the incorporation and interaction of 2,4‐D with the polymer matrix prior to and after the sensing experiments. The FTIR data indicate that 2,4‐D does not leach appreciably from the polymer matrix under experimental conditions employed for the sensing studies. The electrochemical current response for 2,4‐D is compared for the doped polymer‐coated and control polymer‐coated electrode. The response of the doped polymer‐electrode was dependent on increasing concentrations of 2,4‐D and 2,4‐dichlorophenol while unresponsive to benzoic acid.
Thinly Insulated Wire Cells – A New Device for Sensitive Contactless Conductivity Detection in Flow Analyses
Authors: Hoherčáková Zuzana , Opekar František , Štulík Karel
Published: July 2005

Very simple contactless conductivity cells have been designed, suitable for detection in flow analytical techniques (classical HPLC, FIA, SIA, continuous flow, etc.) in which this detection has so far rarely been used. The cells consist of two wire electrodes covered with a very thin layer (units of μm) of an insulating material (the dielectric) and punctured through the walls of a plastic tubing at a close mutual distance (from tenths to units of a mm) and placed either across the tube or along the tube axis, so that the detection occurs within the space limited by the two electrodes. As the thickness of the dielectric layer is substantially smaller than that in common contactless conductivity cells used in CE, the AC current flowing between the electrodes is higher and the measuring sensitivity is enhanced. The principal operational characteristics of these detectors have been tested using KCl solutions and compared with those calculated from a simple theoretical model. It has been shown that this model permits theoretical description of these cell types and reasonable prediction of their behavior. Practical application has been demonstrated on a FIA determination of inorganic carbonate.
Performance of Impedimetric Biosensors Based on Anodically Formed Ti/TiO2 Electrodes
Authors: Mantzila Aikaterini G. , Prodromidis Mamas I.
Published: July 2005

The advantages and limitations of impedimetric sensors based on Ti/TiO2 architectures are described. Titanium dioxide (titania) was potentiostatically formed onto titanium electrodes of 2 mm diameter, at 10 and 30 V in 1 M H2SO4. The thickness of the titania layers was ellipsometrically determined to be 30 and 86 nm respectively and they are highly insulating with charge‐transfer resistances in the MΩ range, as they were measured with electrochemical impedance spectroscopy under specific experimental conditions. Low voltage anodization (<10 V) results to amorphous TiO2, whereas at higher applied voltages (>25 V), anatase is the predominant form. SEM images are indicative of quite smooth, compact coatings without any severe cracks.
Polymeric Membrane Lanthanum(III)‐Selective Electrode Based on N,N′‐Adipylbis(5‐phenylazo salicylaldehyde hydrazone)
Authors: Shamsipur Mojtaba , Ershad Sohrab , Samadi Naser , Esmaeilbeig Ahmad Reza , Kia Reza , Abdolmaleki Amir
Published: July 2005

A recently synthesized azao‐containing Schiff's base N,N′‐adipylbis(5‐phenylazo salicylaldehyde hydrazone) was used as a suitable neutral ion carrier in construction of a highly selective La3+‐PVC membrane electrode. The electrode exhibits a Nernstian response with a slope of 19.4 mV decade−1 over a wide concentration range (1.0×10−6–1.0×10−2 M) and a limit of detection of 4.0×10−7 M (0.05 ppm). The electrode possesses a fast response time of ca. 10 s and can be used for at least 3 months without observing any deviation. The proposed electrode revealed excellent selectivity for La3+ over a wide variety of alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.0–8.0. The practical utility of the electrode has been demonstrated by its use as an indicator electrode in the potentiometric titration of La3+ ions with EDTA and in determination of F− ion in some pharmaceutical preparations.
Simultaneous Determination of Platinum and Rhodium with Hydroxylamine and Acetone Oxime by Catalytic Adsorptive Stripping Voltammetry (CAdSV)
Authors: Huszał Sylwester , Kowalska Joanna , Sadowska Monika , Golimowski Jerzy
Published: July 2005

This paper describes a very sensitive catalytic adsorptive stripping voltammetry (CAdSV) procedure for the simultaneous determination of traces of platinum and rhodium in new supporting electrolyte containing hydroxylamine or acetone oxime and formaldehyde in sulfuric acid medium. Platinum and rhodium were pre‐accumulated simultaneously and after 120 s of accumulation time at 0.0 V, the achieved detection limits were equal 0.1 ng L−1and 0.2 ng L−1for platinum and rhodium respectively in the presence of acetone oxime and 0.6 ng L−1and 0.2 ng L−1for platinum and rhodium respectively in the presence of hydroxylamine. Described reagents were successfully applied to the determination of platinum and rhodium in plant material. Inductively coupled plasma mass spectrometry (ICP MS) was used as a reference method to the CAdSV measurements.
Use of DPPH⋅|DPPH Redox Couple for Biamperometric Determination of Antioxidant Activity
Authors: Milardovic Stjepan , Iveković Damir , Rumenjak Vlatko , Grabarić Božidar S.
Published: July 2005

A novel electrochemical method for selective determination of antioxidant activity based on 2,2‐diphenyl‐1‐picrylhydrazyl | 2,2‐diphenyl‐1‐picrylhydrazin (DPPH⋅|DPPH) redox couple and biamperometric technique is proposed. Two identical glassy carbon disk electrodes were mounted in a classic electrochemical cell and the tested working potential difference was between 50 and 200 mV. The DPPH⋅|DPPH redox couple exhibited a high degree of reversibility. Selectivity of detector was tested by different antioxidant compounds in ethanol‐phosphate buffer solution, pH 7.40. The results of antioxidant activity of pure antioxidant compounds and of actual samples of beverages, expressed as Trolox equivalents and determined by proposed biamperometric and spectroscopic measurements, were in good correlation (R=0.9959). The detection limit for Trolox established by the applied biamperometry was 0.05 μM while the resulting current was linear up to 25 μM of Trolox.
Electrochemical Study of the Interactions of DNA with Redox‐Active Molecules Based on the Immobilization of dsDNA on the Sol‐Gel Derived Nano Porous Hydroxyapatite‐Polyvinyl Alcohol Hybrid Material Coating
Authors: Wang Huai‐Sheng , Wang Gui‐Xiang , Pan Qian‐Xiu
Published: July 2005

A novel type of sol‐gel inorganic‐organic hybrid material coated on glassy carbon electrode used for immobilization of double‐stranded DNA (dsDNA) and study of dsDNA with redox‐active molecules was developed. The hybrid material coating was produced by sol‐gel method with nano hydroxyapatite (HAp)‐polyvinyl alcohol (PVA). The optimum composition of the hybrid material was first examined, and the morphology of the nano HAp‐PVA coatings was investigated with the help of Scanning Electron Microscope (SEM). DsDNA was immobilized in/on the nano HAp‐PVA hybrid coatings by adsorption and the characteristics of the dsDNA/HAp‐PVA/GCE were studied by cyclic voltammetry (CV) using the probes of Co(phen)$\rm{ {_{3}^{3+}}}$ and Fe(CN)$\rm{ {_{6}^{3-}}}$. The results indicate that the dsDNA can be immobilized on the nano porous HAp‐PVA coating effectively and its stability can satisfy the necessity of study on the interactions of dsDNA with redox‐active molecules on the electrode surface. Co(bpy)$\rm{ {_{3}^{3+}}}$ and Co(phen)$\rm{ {_{3}^{3+}}}$ were used as the model molecule to study the interactions of dsDNA with redox‐active molecules. Information such as ratio (KOx/KRed) of the binding constant for the oxidized and reduced forms of a bound species, interaction mode, including change in the mode of interaction, and “limiting” ratio K$\rm{ {_{Ox}^{^{o}}}}$/K$\rm{ {_{Red}^{^{o}}}}$ at zero ionic strength (μ) can be obtained using dsDNA/HAp‐PVA/GCE with about 2 μg of DNA samples.
Electrochemical Study of the Lipid‐Transfer Protein
Authors: Gorjanović Stanislava , Beljanski Miloš V. , Sužnjević Desanka
Published: July 2005

Electrochemical study of barley grain lipid‐transfer protein (LTP) revealed that it may belong to the metal‐binding protein class. Using differential pulse polarography the presence of Cu(II) and Zn(II) ions in the native LTP structure was proved, as well as its affinity for binding Ni(II) ion. Application of a more sensitive electroanalytical technique, such as anodic stripping voltammetry with analyte preconcentration, revealed the presence of Pb(II) and Cd(II) ions and also enabled the following Hg(II) ion binding. Possible biological role of LTP in plant stress response and its contribution to barley phytoextraction potential are discussed.
Incorporation of Disposable Screen‐Printed Electrodes for Use in Capillary Electrophoresis End‐Column Amperometric Detection System
Authors: Tsai Dong‐Mung , Tai Hsiu‐Wen , Shih Pei‐Rong , Chang Ren‐Lin , Wu Han , Conte Eric D. , Zen Jyh‐Myng
Published: July 2005

The development and performance of an end‐column amperometric detection system integrated with disposable screen‐printed electrodes for capillary electrophoresis is presented. In this system, the electrode and capillary can be easily replaced and the capillary/electrode alignment procedure is straightforward. The use of easily replaceable screen‐printed electrodes offers a tremendous benefit for capillary electrophoresis applications requiring frequent replacement of the working electrode due to fouling. This simple and convenient system is very attractive for routine analyses by capillary electrophoresis with electrochemical detection. The separation and determination of uric acid in human urine is presented.
Electrochemical Characterization of Archaeological Tin‐Opacified Lead‐Alkali Glazes and Their Corrosion Processes
Authors: Doménech‐Carbó A. , Doménech‐Carbó M. T.
Published: July 2005

The electrochemical response of weathered and unweathered archaeological tin‐opacified glazes attached to paraffin‐impregnated graphite electrodes is described. Upon comparison with the square wave voltammetric response of SnO2, PbO and PbO2, Sn‐ and Pb‐centered reduction processes can be characterized. Reduction of Sn(IV) involves the stepwise formation of solid Sn(II) and Sn metal, successively, at potentials of −0.08 and −0.55 V vs. AgCl/Ag. Reduction of network‐modifier Pb(II) in glazes occurs at −0.5 V and is accompanied by the reduction of network‐forming Pb(IV) at potentials ranging from +0.65 to +0.20 V, confirming the presence of such centers in glazes. Voltammetric data suggest the presence of small amounts of Sn(II) resulting from the reduction of cassiterite during the firing process. A series of correlations between the peak currents can be established, indicating that the weathering process obeys a kinetic process rather than a equilibrium‐like situation.
A local‐analytic‐based discretization procedure for the numerical solution of incompressible flows
Authors: Pontaza J. P. , Chen H. C. , Reddy J. N.
Published: July 2005

An Erratum has been published for this article in International Journal for Numerical Methods in Fluids 2005, 49(8): 933.

We present a local‐analytic‐based discretization procedure for the numerical solution of viscous fluid flows governed by the incompressible Navier–Stokes equations. The general procedure consists of building local interpolants obtained from local analytic solutions of the linear multi‐dimensional advection–diffusion equation, prototypical of the linearized momentum equations. In view of the local analytic behaviour, the resulting computational stencil and coefficient values are functions of the local flow conditions. The velocity–pressure coupling is achieved by a discrete projection method. Numerical examples in the form of well‐established verification and validation benchmarks are presented to demonstrate the capabilities of the formulation. The discretization procedure is implemented alongside the ability to treat embedded and non‐matching grids with relative motion. Of interest are flows at high Reynolds number, 𝒪(105)–𝒪(107), for which the formulation is found to be robust. Applications include flow past a circular cylinder undergoing vortex‐induced vibrations (VIV) at high Reynolds number. Copyright © 2005 John Wiley & Sons, Ltd.
Generic head models for atlas‐based EEG source analysis
Authors: Darvas Felix , Ermer John J. , Mosher John C. , Leahy Richard M.
Published: July 2005

We describe a method for using a generic head model, in the form of an anatomical atlas, to produce EEG source localizations. The atlas is fitted to the subject by a nonrigid warp using a set of surface landmarks. The warped atlas is used to compute a finite element model (FEM) of the forward mapping or lead‐fields between neural current generators and the EEG electrodes. These lead‐fields are used to localize current sources from the subject's EEG data and the sources are then mapped back to the anatomical atlas. This approach provides a mechanism for comparing source localizations across subjects in an atlas‐based coordinate system, which can be used in the large fraction of EEG studies in which MR images are not available. The Montreal brain atlas was used as the reference anatomical atlas and 10 individual MR volumes were used to evaluate the method. The atlas was fitted to each subject's head by a thin‐plate‐spline (TPS) warp. The spatial locations of a generic 155‐electrode configuration were used to constrain the warp. For the purposes of evaluation, dipolar sources were placed on the inner cortical surface in the atlas geometry and transferred to each subject's brain space using a polynomial warp. The parameters of the warp were computed using an intensity‐based matching of the atlas and subject brains, thus ensuring that the sources were placed at approximately the same anatomical location in each case. Data were simulated in the subject geometry and a dipole fit was performed on these data using an FEM of the TPS warped atlas. The source positions found in the warped atlas were transferred back to the original atlas and compared to the original position. Sources were simulated at 972 locations evenly distributed over the inner cortical surface of the atlas. The mean error over all 10 subjects was 8.1 mm in the subject space and 15.2 mm in the atlas space. In comparison, using an affine transformation of the electrodes into atlas space and an FEM model generated from the atlas produced mean errors of 22.3 mm in subject space and 19.6 mm in atlas space. With a standard three‐shell spherical model the errors were 27.2 mm in the subject space and 34.7 mm when mapped to atlas space. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
VPAC1 Expression Is Regulated by FXR Agonists in the Human Gallbladder Epithelium *
Authors: Chignard Nicolas , Mergey Martine , Barbu Véronique , Finzi Laetitia , Tiret Emmanuel , Paul Annick , Housset Chantal
Published: July 2005

Vasoactive intestinal peptide receptor-1 (VPAC1) is the high-affinity receptor of vasoactive intestinal peptide (VIP), a major regulator of bile secretion. To better define the level at which VPAC1 stimulates bile secretion, we examined its expression in the different cell types participating in bile formation (

i.e.

, hepatocytes, bile duct, and gallbladder epithelial cells). Because VPAC1 expression was previously shown to be regulated by nuclear receptors, we tested the hypothesis that it may be regulated by the farnesoid X receptor (FXR). Quantitative RT-PCR and immunoblot analyses of cell isolates indicated that VPAC1 is expressed in all three cell types lining the human biliary tree, with predominant expression in the gallbladder. In primary cultures of human gallbladder epithelial cells, VIP induced cAMP production and chloride secretion. Analysis of the VPAC1 gene revealed the presence of potential FXR response element sequences, and both FXR and RXRα expressions were detected in gallbladder epithelial cells. In these cells, the FXR pharmacological agonist GW4064 upregulated VPAC1 expression in a dose-dependent manner, and this effect was antagonized by the RXRα ligand, 9-cis retinoic acid. Chenodeoxycholate activated endogenous FXR in gallbladder epithelial cells, as ascertained by electromobility shift assay and upregulation of the FXR target gene, small heterodimer partner. Chenodeoxycholate also provoked an increase in VPAC1 mRNA and protein content in these cells.
In conclusion
, FXR agonists may increase gallbladder fluid secretion through transcriptional activation of VPAC1, which may contribute to the regulation of bile secretion by bile salts and to a protective effect of FXR pharmacological agonists in gallstone disease. (Hepatology 2005.)
Proteasome Inhibition Sensitizes Hepatocellular Carcinoma Cells, But Not Human Hepatocytes, to TRAIL *
Authors: Ganten Tom M. , Koschny Ronald , Haas Tobias L. , Sykora Jaromir , Li-Weber Min , Herzer Kerstin , Walczak Henning
Published: July 2005

TRAIL exhibits potent anti-tumor activity on systemic administration in mice. Because of its proven

in vivo

efficacy, TRAIL may serve as a novel anti-neoplastic drug. However, approximately half of the tumor cell lines tested so far are TRAIL resistant, and potential toxic side effects of certain recombinant forms of TRAIL on human hepatocytes have been described. Pretreatment with the proteasome inhibitor MG132 and PS-341 rendered TRAIL-resistant hepatocellular carcinoma (HCC) cell lines but not primary human hepatocytes sensitive for TRAIL-induced apoptosis. We investigated the different levels of possible MG132-induced interference with resistance to apoptotic signal transduction. Although proteasome inhibition efficiently suppressed nuclear factor-kappaB (NF-κB) activity, specific suppression of NF-κB by mutIκBα failed to sensitize TRAIL-resistant cell lines for TRAIL-induced apoptosis. In contrast to the previously reported mechanism of sensitization by 5-fluorouracil (5-FU), cellular FLICE-inhibitory protein (cFLIP)L and cFLIPS were markedly upregulated in the TRAIL death inducing signaling complex (DISC) by proteasome inhibitor pretreatment. Compared with 5-FU pretreatment, caspase-8 was more efficiently recruited to the DISC in MG132 pretreated cells despite the presence of fewer death receptors and more cFLIP in the DISC. But downregulation of cFLIP by short interference RNA (siRNA) further sensitized the HCC cell lines.
In conclusion
, these results show that otherwise chemotherapy-resistant tumor cells can be sensitized for TRAIL-induced apoptosis at the DISC level in the presence of high levels of cFLIP, which suggests the existence of an additional factor that modulates the interaction of FADD and the TRAIL death receptors. Of clinical relevance, proteasome inhibitors sensitize HCC cells but not primary human hepatocytes for TRAIL-induced apoptosis. (Hepatology 2005.)
LKM1 Autoantibodies in Chronic Hepatitis C Infection: A Case of Molecular Mimicry? *
Authors: Marceau Gabriel , Lapierre Pascal , Béland Kathie , Soudeyns Hugo , Alvarez Fernando
Published: July 2005

Anti-liver-kidney microsome type 1 (LKM1) autoantibodies directed against the cytochrome P450 2D6 (CYP2D6) are considered specific markers of type 2 autoimmune hepatitis, but are also found in 5% of sera from patients chronically infected by hepatitis C virus (HCV). Molecular mimicry between HCV proteins and CYP2D6 has been proposed to explain the emergence of these autoantibodies. Anti-LKM1 autoantibodies from hepatitis C–infected patients were affinity-purified against immobilized CYP2D6 protein and used to screen a phage display library. CYP2D6 conformational epitopes were identified using phage display analysis and the identification of statistically significant pairs (SSPs). Cross-reactivity between CYP2D6 and HCV protein candidates was tested by immunoprecipitation. Nineteen different clones were isolated, and their sequencing resulted in the mapping of a conformational epitope to the region of amino acids 254-288 of CYP2D6. Candidate HCV proteins for molecular mimicry included: core, E2, NS3 and NS5a. Affinity-purified autoantibodies from HCV+/LKM1+ patients immunoprecipitated either NS3, NS5a, or both, and these reactivities were specifically inhibited by immobilized CYP2D6.
In conclusion
, HCV+/LKM1+ sera recognize a specific conformational epitope on CYP2D6 between amino acids 254 to 288, the region that contains the major linear epitope in type 2 autoimmune hepatitis patients. Cross-reactivity due to molecular mimicry at the B-cell level was shown between the CYP2D6 and the HCV NS3 and NS5a proteins and could explain the presence of anti-LKM1 in patients chronically infected with HCV. Further investigation of the role played by this molecular mimicry in HCV-infected patients may lead to more specific strategies for diagnosis and treatment. (Hepatology 2005.)
Spectrum of NAFLD and Diagnostic Implications of the Proposed New Normal Range for Serum ALT in Obese Women *
Authors: Kunde Sachin S. , Lazenby Audrey J. , Clements Ronald H. , Abrams Gary A.
Published: July 2005

The upper limit of normal for ALT activity has been recommended to be lowered to ≤30 U/L in men and ≤19 U/L in women. These changes have been suggested to be diagnostically useful in subjects with nonalcoholic fatty liver disease (NAFLD). Our aim was to investigate the prevalence and spectrum of NAFLD with regard to the new ALT guidelines in 233 women with class II/III obesity. We compared our prior reference range for ALT (ULN ≤ 30 U/L in women) with the new standard. Our study demonstrates that only 86 patients (36.9%) would be classified as having normal ALT levels compared with 169 patients (72.5%) by the new and old standards, respectively. In patients with normal ALT activity (new vs. old standard), the prevalence of fatty liver (FL: 39.5% vs 40.2%), portal fibrosis, and steatosis (IPF: 37.2% vs. 33.7%) and nonalcoholic steatohepatitis (NASH: 23.3% vs. 26%) were similar. In comparison, newly defined patients with elevated ALT levels (>19 U/L) demonstrated an increased prevalence of FL (36%) and IPF (11.6%) but a 23.8% decrease in the prevalence of NASH as compared with the old standard. The sensitivity and specificity for NASH were 42% and 80% (ALT > 30 U/L) compared with 74% and 42% (ALT > 19 U/L).
In conclusion
, a significant increase in the prevalence of FL and IPF is detected in subjects with elevated ALT levels with the application of the new standard. However, the diagnostic utility for ALT to identify NASH or IPF remains poor, and significant healthcare expenditures may be incurred if this standard is adopted. (Hepatology 2005.)
Imparting mineral affinity to proteins with thiol–labile disulfide linkages
Authors: Bansal Geeti , Wright Jennifer E. I. , Zhang Sufeng , Zernicke Ronald F. , Uludag Hasan
Published: July 2005

Chemical conjugation of bisphosphonates (BPs) to proteins is an effective means to enhance binding of proteins to mineral‐containing biomaterials. BPs linked to proteins with reversible (i.e., cleavable) linkages were considered desirable over the conjugates linked with stable linkages because cleavable linkages allow protein release in free form from the mineral‐containing biomaterials. To explore the feasibility of creating cleavable BP‐protein conjugates, an amine‐ and a thiol‐containing BP were conjugated to the model protein Bovine Serum Albumin (BSA) with N‐succinimidyl‐3‐(2‐pyridyldithio)propionate (SPDP), which resulted in disulfide‐linked BP–BSA conjugates. Although disulfide‐linked conjugates were stable under aqueous conditions, the conjugates in solution were readily cleaved in the presence of physiological concentrations (∼ 0.3 mM) of the thiol compound, cysteine. The imparted mineral affinity as a result of BP conjugation, as assessed by hydroxyapatite (HA) binding in vitro, was lost upon cleavage of the disulfide‐linked BP. The conjugates bound to HA were also cleavable with cysteine, but their cleavage rate was significantly reduced as compared to the conjugates in solution. In conclusion, disulfide‐linked BP conjugates were shown to be readily cleavable by the amino acid cysteine and this resulted in the loss of imparted mineral affinity of the proteins. The proposed approach will be useful for modulating in vivo delivery of proteins implanted with mineral‐containing biomaterials. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
New experimental approach to study host tissue response to surgical mesh materials in vivo
Authors: Laschke M. W. , Häufel J. M. , Thorlacius H. , Menger M. D.
Published: July 2005

Implantation of surgical meshes is a common procedure to increase abdominal wall stability in hernia repair. To improve biocompatibility of the implants, sophisticated in vivo animal models are needed to study inflammation and incorporation of biomaterials. Herein, we have established a new model that allows for the quantitative analysis of host tissue response and vascular ingrowth into surgical mesh materials in vivo. Ultrapro meshes were implanted into dorsal skinfold chambers of Syrian golden hamsters. Angiogenesis, microhemodynamics, microvascular permeability, and leukocyte–endothelial cell interaction of the host tissue were analyzed in response to material implantation over a 2‐week period using intravital fluorescence microscopy. Mesh implantation resulted in a short‐term activation of leukocytes, reflected by leukocyte accumulation and adherence in postcapillary venules. This cellular inflammatory response was accompanied by an increase of macromolecular leakage, indicating loss of integrity of venular endothelial cells. Angiogenesis started at day 3 after implantation by protrusion of capillary sprouts, originating from the host microvasculature. Until day 10, these sprouts interconnected with each other to form a new microvascular network. At day 14, the inflammatory response had disappeared and the vascular ingrowth was completed. Histology confirmed the formation of granulation tissue with adequate incorporation of the mesh filaments within the host tissue. We conclude that this novel model of surgical mesh implantation is a useful experimental approach to analyze host tissue response and vascular ingrowth of newly devised materials for hernia repair. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
The role of adsorbed fibrinogen in platelet adhesion to polyurethane surfaces: A comparison of surface hydrophobicity, protein adsorption, monoclonal antibody binding, and platelet adhesion
Authors: Wu Yuguang , Simonovsky Felix I. , Ratner Buddy D. , Horbett Thomas A.
Published: July 2005

Ten specially synthesized polyurethanes (PUs) were used to investigate the effects of surface properties on platelet adhesion. Surface composition and hydrophilicity, fibrinogen (Fg) and von Willebrand's factor (vWf) adsorption, monoclonal anti‐Fg binding, and platelet adhesion were measured. PUs preadsorbed with afibrinogenemic plasma or serum exhibited very low platelet adhesion, while adhesion after preadsorption with vWf deficient plasma was not reduced, showing that Fg is the key plasma protein mediating platelet adhesion under static conditions. Platelet adhesion to the ten PUs after plasma preadsorption varied greatly, but was only partially consistent with Fg adsorption. Thus, while very hydrophilic PU copolymers containing PEG that had ultralow Fg adsorption also had very low platelet adhesion, some of the more hydrophobic PUs had relatively high Fg adsorption but still exhibited lower platelet adhesion. To examine why some PUs with high Fg adsorption had lower platelet adhesion, three monoclonal antibodies (mAbs) that bind to sites in Fg thought to mediate platelet adhesion were used. The antibodies were: M1, specific to γ‐chain C‐terminal; and R1 and R2, specific to RGD containing regions in the α‐chain N‐ and C‐terminal, respectively. Platelet adhesion was well correlated with M1 binding, but not with R1 or R2 binding. When these mAbs were incubated with plasma preadsorbed surfaces, they blocked adhesion to variable degrees. The ability of the R1 and R2 mAbs to partially block adhesion to adsorbed Fg suggests that RGD sites in the alpha chain may also be involved in mediating platelet adhesion and act synergistically with the C‐terminal of the γ‐chain. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Bioresorbable composites prepared by supercritical fluid foaming
Authors: Mathieu L. M. , Montjovent M.‐O. , Bourban P‐E. , Pioletti D. P. , Månson J.‐A. E.
Published: July 2005

Bone is a natural composite construct, with a gradient structure going from a loose interconnected cellular core to an outer dense wall, thus minimizing bone weight while keeping a high mechanical resistance. Due to this unique and complex structure, bone defects are difficult to replace or repair. Tissue engineering aims at providing artificial bone grafts. Several techniques have been proposed to produce porous structures or scaffolds, but, as yet, with no optimal solutions. This article focuses on bioresorbable ceramic–polymer composite foams obtained by supercritical fluid foaming. This flexible technique enables an adequate morphology and suitable properties for bone tissue engineering to be obtained. Composite scaffolds are biocompatible, allowing cell proliferation and differentiation. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Thermogelling emulsions for vascular embolization and sustained release of drugs
Authors: Kan Pei , Lin Xi‐Zhang , Hsieh Ming‐Fa , Chang Ken‐Yuen
Published: July 2005

Thermogelling emulsion system was developed to function as an embolic agent and sustained release system. PEG‐PLGA‐PEG triblock copolymer was synthesized, and blended with oily phase (Lipiodol®) to constitute the thermogelling emulsions. Because the polymer‐rich aqueous phase dramatically increases viscosity in response to temperature change, especially within the range between 20 and 30°C, the emulsions produce a stop‐flowing gel with oil droplets entrapped. Thereafter, paclitaxels were released from the oily reservoir of gelled emulsions in a controlled manner. Reduced burst effect and steady drug release with near zero‐order release kinetics were observed. Human umbilical vein endothelial cells (HUVEC) were collected from fresh umbilical cords for in vitro antiangiogenesis test. It demonstrated that the sustained release of paclitaxel from emulsions inhibited growth of HUVEC and that the IC50, calculated according to release rate, was consistent with that obtained from free drug study. In addition, the emulsions forming a depot in situ inside the injection site of the blood vessel in rabbit ear obstructed the blood flow, and being monitored under X‐ray angiography. Taken together, this study proved the feasibility of the thermogelling emulsions for vascular embolization and sustained drug release. The results presented a potential system for arterial transcatheter embolization on hepatocellular carcinoma combined with antiangiogeneic treatment. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Degradation of poly‐L/DL‐lactide versus TCP composite pins: A three‐year animal study
Authors: Prokop Axel , Höfl Andreas , Hellmich Martin , Jubel Axel , Andermahr Jonas , Emil Rehm Klaus , Hahn Ulrich
Published: July 2005

Biodegradable polylactide implants allow secure fixation of osteochondral fractures. This quasirandomized parallel‐group animal study investigates whether a composite implant of poly‐L/DL‐lactide (PLDLLA) with additional 10% β‐tricalcium phosphate produces an osteoconductive effect, whether the admixture positively influences implant degradation (assessed by comparing time to implant degradation), and whether the pin sites of degraded implants are replaced with bone tissue. On 36 medial femoral condyles of sheep, osteotomies were fixed with either three PLDLLA pins or three composite pins. At 3, 18, and 36 months, the pin sites were measured histologically and the state of degradation assessed according to Pistner's classification. All fractures healed without clinically relevant complications and without displacement. Both pin types led to asymptomatic pin‐site enlargement at 18 months, which disappeared by 36 months. At 18 months, 14 of 18 PLDLLA pins were no longer evident, whereas 16 of 18 composite pins showed only peripheral degradation. By 36 months, all implants from both groups were completely degraded and replaced with scar (2/18) or bone tissue (16/18). At 36 months there was no evidence for significant improvement of either degradation performance or osseointegration through use of the 10% TCP composite mixture. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Physiologically clotted fibrin‐calcined bone composite—A possible bone graft substitute
Authors: Noorjahan S. E. , Sastry T. P.
Published: July 2005

Fibrin plays a major role in blood clotting and is important in wound healing. In the present study, physiologically clotted fibrin (PF) and calcined bone (CB) both of bovine origin were used in the preparation of a bone graft material with chitosan (C) as a binder. This bone graft (PF‐CB) was characterized by stress‐strain analysis, X‐ray diffraction (XRD) studies, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and FTIR spectroscopy. Thermal studies revealed that the incorporation of CB into PF did not alter the thermal stability of fibrin, although it affects the total loss percentage. The composition containing 24:1:15 (PF:C:CB) on dry weight basis exhibited maximum compressive strength, and the same composite was used for characterization studies. The XRD studies have shown the amorphous nature of the implant. SEM pictures revealed the heterogeneity and porous nature of the implant. PF in combination with CB is expected to exhibit osteoinductivity because fibrin, the osteoinductive protein, acts as an angiogenic factor, whereas CB provides calcium and phosphate ions that are needed for new bone formation. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Validation of a micro‐CT technique for measuring volumetric wear in retrieved acetabular liners
Authors: Bowden A. E. , Kurtz S. M. , Edidin A. A.
Published: July 2005

In this study, a novel micro‐CT–based technique for evaluating wear in retrieved acetabular liners was introduced and validated. Six UHMWPE acetabular components ranging in implantation time from 2.7 to 14.4 years were collected and evaluated with the use of a high‐resolution micro‐CT scanner. The components were scanned with a uniform volumetric resolution of 74 microns (16‐bit precision) with the use of a 1024 × 1024 in‐plane image matrix. Manual rigid 3D image registration of the interior hemispherical portion of the acetabular cup with geometric primitives by trained observers allowed for isolation, visualization, and measurement of the wear volume. Results for these six components indicated an average wear rate of 65 mm3/year. Overall scanner error was quantified gravimetrically and associated with a maximum uncertainty of 0.6%. Intra‐ and interobserver uncertainty analysis showed the method to be both accurate and repeatable. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Injectable gels of anionic collagen: Rhamsan composites for plastic correction: Preparation, characterization, and rheological properties
Authors: de Paula Márcio , Goissis Gilberto , Martins Virgínia C. A. , da Silva Trindade José Carlos
Published: July 2005

The present article describes the preparation and characterization of anionic collagen gels obtained from porcine intestinal submucosa after 72 h of alkaline treatment and in the form of rhamsan composites to develop injectable biomaterials for plastic reconstruction. All materials were characterized by SDS/polyacrylamide gel electrophoresis, infrared spectroscopy, thermal stability, potentiometric titration, rheological properties, and fluidity tests. Biocompatibility was appraised after the injection of anionic collagen:rhamsan composites at 2.5% in 60 North Folk rabbits. Independently of processing, the collagen's secondary structure was preserved in all cases, and after 72 h of hydrolysis the collagen was characterized by a carboxyl group content of 346 ± 9, which, at physiological pH, corresponds to an increase of 106 ± 17 negative charges, in comparison to native collagen, due to the selective hydrolysis of asparagine and glutamine carboxyamide side chain. Rheological studies of composites at pH 7.4 in concentrations of 2, 4, and 6% (in proportions of 75:1 and 50:1) showed a viscoelastic behavior dependent on the frequency, which is independent of concentration and proportion. In both, the concentration of the storage modulus always predominated over the loss modulus (G′ > G″ and δ < 45°). The results from creep experiments confirmed this behavior and showed that anionic collagen:rhamsan composites at pH 7.4 in the proportion of 50:1 are less elastic and more susceptible to deformation in comparison to gels in the proportion of 75:1, independent of concentration. This was further confirmed by flow experiments, indicating that the necessary force for the extrusion of anionic collagen:rhamsan composites, in comparison to anionic collagen, was significantly smaller and with a smooth flow. Biocompatibility studies showed that the tissue reaction of anionic collagen:rhamsan composites at 2.5% in the proportion of 75:1 was compatible with the application of these gels in plastic reconstruction. These results suggest that the association of collagen with rhamsan may be a good alternative in the replacement of glutaraldehyde to stabilize the microfibril assembly of commercial collagen gel preparations. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Discerning alumina ball wear from confounding metal transfer artifact
Authors: Brown S. S. , Kawanabe K. , Manaka M. , Williams P. , Good V. , Clarke I. C.
Published: July 2005

On dismounting a ceramic femoral ball from its metal trunnion, there is usually a range of gray metallic bands transferred to the trunnion bore inside the ball. This creates an artifact that may compromise detection by weight of the exceedingly low wear rates of ceramic balls. The objective of this study was to compare the weight trending of the metal trunnions and their ceramic balls during conditioning studies. Our hypothesis was that a pretest conditioning protocol would eliminate or greatly reduce the metal transfer artifact. The balls and tapers were placed on a hip simulator under 300–600 load cycles but with no articulation. The balls were then dismounted from the trunnions, and both were cleaned and weighed. This was repeated 6–23 times. We developed a novel hydraulic method for dismounting balls from trunnions that proved to be safe and efficient. There was significant weight loss in the trunnions after the ball removal, but there was no corresponding weight gain in the alumina balls. The weight effect of the metal transfer appeared to have been removed from the balls with our standard cleaning procedures. Therefore, wear rates for alumina balls may be gravimetrically determined without compensating for the metal transfer from trunnion to ball. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2005
Modification of wool fabric using ecologically acceptable UV‐assisted treatments
Authors: El‐Sayed H , El‐Khatib E
Published: July 2005

Wool fabric was modified using ecologically acceptable treatments in order to enhance its shrinkage and pilling resistance. Wool fabrics were irradiated with ultraviolet light for different period of times. The UV‐irradiated wool fabrics were then treated with an oxidising agent (hydrogen peroxide or sodium monoperoxyphthalate) or a protease enzyme (papain or savinase 16L type EX). Treatment of wool fabric with these systems was found to be effective in reducing its pilling and shrinkage without severe loss in weight and strength of the fabric. Chemical and mechanical analyses of the treated samples compared with the untreated one are reported. Transmission electron microscopy investigation of the untreated and treated wool samples was used to identify the histological component in wool keratin affected by these treatments. Copyright © 2005 Society of Chemical Industry
Biosorption of heavy metals by chemically‐activated alga Fucus vesiculosus
Authors: Rincón J , González F , Ballester A , Blázquez ML , Muñoz JA
Published: July 2005

The sorption capacity of the brown alga Fucus vesiculosus for copper, cadmium, lead and nickel was investigated. Metal sorption yields were modified using different kinds of pretreatment reagents: HCl, CaCl2, formaldehyde, Na2CO3 and NaOH. The Langmuir isotherm was applied to both the non‐treated and all treated biomass tests. Calcium chloride was the only chemical that improved the maximum sorption capacity of the biomass. Copyright © 2005 Society of Chemical Industry