bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of the chiral and achiral related substances of methotrexate by cyclodextrin‐modified micellar electrokinetic chromatography
Authors: Gotti Roberto , El‐Hady Deia Abd , Andrisano Vincenza , Bertucci Carlo , El‐Maali Nagwa Abo , Cavrini Vanni
Published: August 2004

A cyclodextrin‐modified micellar electrokinetic chromatographic (CD‐MEKC) method for the determination of the most important potential impurities of methotrexate (MTX): 2,4‐diamino‐6‐(hydroxymethyl)pteridine, aminopterine hydrate, 4‐[N‐(2‐amino‐4‐hydroxy‐6‐pteridinylmethyl)‐N‐methylamino] benzoic acid, 4‐[N‐(2,4‐diamino‐6‐pteridinylmethyl)‐N‐methylamino] benzoic acid, and the distomer D‐MTX is presented. The MEKC separation of these compounds was optimized by applying a step‐by‐step approach. The addition of β‐CD to a conventional MEKC system, based on sodium dodecyl sulfate (SDS) as surfactant, showed to be essential for the enantioresolution of racemic MTX as well as for the separation of the achiral impurities. To achieve high‐resolution factor between the peaks adjacent to the main component (L‐MTX), as required in the analysis of related impurities, the separation conditions were stressed; in particular, the addition of methanol to the CD‐MEKC system resulted in a very effective choice. Under the optimized final conditions (100 mM SDS and 45 mM β‐CD in a mixture of 50 mM borate buffer, pH 9.30‐methanol (75:25 v/v)), the method was validated showing a general adequate accuracy (93–106% recovery) in the determination of L‐MTX related substances at the impurity level of 0.12% w/w with a relative standard deviation (RSD)% lower than 8% (n = 4). The method was successfully applied to the analysis of pharmaceuticals (tablets and injections) which showed to contain the distomer D‐MTX as major impurity and aminopterine hydrate as a further related substance in the commercial tablets.
Enantioseparations by capillary electro‐chromatography: Differences exhibited by normal‐ and reversed‐phase versions of polysaccharide stationary phases
Authors: Mangelings Debby , Maftouh Mohamed , Massart D. Luc , Vander Heyden Yvan
Published: August 2004

The influence of using normal‐phase and reversed‐phase versions of four commercial polysaccharide stationary phases on chiral separations was investigated with capillary electrochromatography (CEC). Both versions of the stationary phases, Chiralcel OD, OJ, and Chiralpak AD, AS were tested for the separation of two basic, two acidic, a bifunctional, and a neutral compound. Different background electrolytes were used, two at low pH for the acid, bifunctional and neutral substances, and three at high pH for the basic, bifunctional and neutral ones. This setup allowed evaluating differences between both stationary‐phase versions and between mobile‐phase compositions on a chiral separation. Duplicate CEC columns of each stationary phase were in‐house prepared and tested, giving information about the intercolumn reproducibility. In general, reversed‐phase versions of the current commercial polysaccharide stationary phases are found to be best for reversed‐phase CEC, even though at high pH no significant differences were seen between both versions. Most differences were observed at low pH. For acidic compounds, it was seen that an ammonium formate electrolyte performed best, which is also an excellent electrolyte if coupling with mass spectrometry is desired. For basic, bifunctional and neutral compounds, no significant differences between the three tested electrolytes were observed at high pH. Here, a phosphate buffer is preferred as electrolyte because of its buffering capacities. However, if coupling to mass spectrometry is wanted, the more volatile ammonium bicarbonate electrolyte can be used as an alternative.
Chiral capillary electrophoresis applied to the determination of phenylglycidol enantiomers obtained from cinnamyl alcohol by asymmetric epoxidation using new titanium(IV) alkoxide compounds as catalysts
Authors: Morante‐Zarcero Sonia , Crego Antonio L. , Sierra Isabel , Fajardo Mariano , Marina M. Luisa
Published: August 2004

A capillary electrophoresis method for the simultaneous determination of phenylglycidol enantiomers in the presence of an excess of cinnamyl alcohol was developed. The effects of the nature, pH and concentration of the buffer, the nature and concentration of chiral selector, the addition of methanol or acetonitrile, and the capillary temperature on the chiral resolution of phenylglycidol enantiomers were studied. Separations were achieved using 20 mM succinylated β‐cyclodextrin dissolved in a 10 mM borate buffer (pH 10.0). Chiral resolution for the phenylglycidol enantiomers in the optimized electrophoretic conditions was higher than 2.0 with an analysis time less than 7 min. The method developed was validated in terms of selectivity, linearity, precision (instrumental repeatability, method repeatability, intermediate precision), the limits of detection and quantitation, and accuracy. Limits of detection of 6.5 mg/L and 8.3 mg/L for (2S,3S)‐(−)‐3‐phenylglycidol ((S,S)‐PG) and (2R,3R)‐(+)‐3‐phenylglycidol ((R,R)‐PG), respectively, were obtained. The method was applied to study the asymmetric epoxidation of cinnamyl alcohol with titanium(IV) alkoxide compounds as catalysts in order to evaluate their catalytic activity and stereoselectivity of the epoxidation processes.
Evaluation of chiral purity for a substituted imidazole p38 MAP kinase inhibitor and its intermediates using a single chiral capillary electrophoresis method
Authors: Zhou Lili , Thompson Richard , Ellison Dean , Wyvratt Jean M.
Published: August 2004

The chiral separation of a substituted imidazole p38 MAP kinase inhibitor and its intermediates was investigated using capillary electrophoresis (CE) with various sulfated cyclodextrins. After initial screens, a single CE chiral method with a randomly sulfated β‐CD was selected for the evaluation of chiral purity for all three compounds. Operational parameters, such as the concentration of the chiral selectors, background electrolyte (or mobile phase) pH, organic modifiers, and temperature were varied in order to achieve an optimized method. The optimal method was validated in terms of linearity, sensitivity, precision, ruggedness, and specificity.
Enantiomeric separation of basic compounds using heptakis(2,3‐di‐O‐methyl‐6‐O‐sulfo)‐β‐cyclodextrin in combination with potassium camphorsulfonate in nonaqueous capillary electrophoresis: Optimization by means of an experimental design
Authors: Servais Anne‐Catherine , Fillet Marianne , Chiap Patrice , Dewé Walthère , Hubert Philippe , Crommen Jacques
Published: August 2004

The enantiomeric separation of a series of basic pharmaceuticals (β‐blockers, local anesthetics, sympathomimetics) has been investigated in nonaqueous capillary electrophoresis (NACE) systems using heptakis(2,3‐di‐O‐methyl‐6‐O‐sulfo)‐β‐cyclodextrin (HDMS‐β‐CD) in combination with potassium camphorsulfonate (camphorSO3−). For this purpose, a face‐centered central composite design with 11 experimental points was applied. The effect of the concentrations of HDMS‐β‐CD and camphorSO3− on enantioresolution was statistically evaluated and depended largely on the considered analyte. The presence of camphorSO3− was found to be particularly useful for the enantioseparation of compounds with high affinity for the anionic CD. CamphorSO3− seems to act as a competitor, reducing the affinity for the CD, probably by ion‐pair formation with these analytes. For compounds with lower affinity for HDMS‐β‐CD, the combination of camphorSO3− and the CD appeared to have a favorable effect on enantioresolution only if the optimal CD concentration could be reached. On the other hand, for compounds characterized by a very low affinity for the anionic CD, the association of camphorSO3− and HDMS‐β‐CD is always unfavorable. Finally, experimental conditions were selected by means of the multivariate approach in order to obtain the highest resolution (Rs) value for each studied compound.
Enantioseparation of aromatic amino acids and amino acid esters by capillary electrophoresis with crown ether and prediction of enantiomer migration orders by a three‐dimensional quantitative structure‐property relationship/comparative field analysis model
Authors: Park Hyun‐Ju , Choi Youngmie , Lee Wonjae , Kim Kyoung‐Rae
Published: August 2004

The complete enantioseparations of eight aromatic amino acids and four alkyl esters of 2‐phenylglycine were achieved by chiral capillary electrophoresis employing 20 mM Tris‐citric acid background electrolyte (pH 2.50) containing 5.0 mM of (+)‐18‐crown‐6‐tetracarboxylic acid. The relative migration times (RMTs) to that of 6‐aminonicotinic acid were characteristic of each enantiomer with good within‐day precisions (% relative standard deviation (RSD) ≤ 2.0). Quantitative structure‐property relationship (QSPR) modeling based on comparative molecular field analysis (CoMFA) was performed to investigate the correlation between the molecular field descriptor values of each enantiomer studied as analyte and its RMT. The resulting CoMFA model allowed reliable prediction for the RMT values (q2 = 0.406, r2 = 0.996), thus being expected to become a valuable tool to predict enantiomer migration orders (EMOs) of amino acids and amines whose pure enantiomers are unavailable. The CoMFA steric fields supported the well‐established chiral recognition mechanism based on molecular interaction between chiral selector (+)‐18‐crown‐6‐tetracarboxylic acid and amino acid enantiomers.
Evaluation of balhimycin as a chiral selector for enantioresolution by capillary electrophoresis
Authors: Jiang Zhengjin , Kang Jingwu , Bischoff Daniel , Bister Bojan , Süssmuth Roderich D. , Schurig Volker
Published: August 2004

The glycopeptide antibiotic balhimycin and its haloanalogue bromobalhimycin were evaluated as chiral selectors for enantioresolution by capillary electrophoresis. In order (i) to eliminate the adsorption of the glycopeptide antibiotics on the capillary wall, (ii) to shorten the separation time and (iii) to improve the detection sensitivity, a combined approach of the dynamic surface coating technique, the co‐electroosmotic flow electrophoresis technique and the partial filling technique was employed for the enantioresolution of 16 acidic racemates. The effect of experimental parameters (plug length of the partial filling solution containing the chiral selector, selector concentration and buffer pH) on enantiorecognition was investigated. Furthermore, the enantiorecognition ability imparted by balhimycin, bromobalhimycin and vancomycin were compared. For most tested compounds, the highest enantiorecognition was obtained with balhimycin as chiral selector. Only in the case of the enantioresolution of tiaprofenic acid, vancomycin showed a superior enantiorecognition.
Enantioseparations of hydrobenzoin and structurally related compounds in capillary zone electrophoresis using heptakis(2,3‐dihydroxy‐6‐O‐sulfo)‐β‐cyclodextrin as chiral selector and enantiomer migration reversal of hydrobenzoin with a dual cyclodextrin system in the presence of borate complexation
Authors: Lin Ching‐Erh , Lin Sheng‐Li , Fang I‐Ju , Liao Wei‐Ssu , Chen Chia‐Chong
Published: August 2004

We investigated the enantioseparations of racemic hydrobenzoin, together with benzoin and benzoin methyl ether, in capillary electrophoresis (CE) using the single‐isomer heptakis(2,3‐dihydroxy‐6‐O‐sulfo)‐β‐cyclodextrin (SI‐S‐β‐CD) as a chiral selector in the presence and absence of borate complexation and enantiomer migration reversal of hydrobenzoin with a dual CD system consisting of SI‐S‐β‐CD and β‐CD in the presence of borate complexation at pH 9.0 in a borate buffer. The enantioselectivity of hydrobenzoin increased remarkably with increasing SI‐S‐β‐CD concentration and the enantioseparation depended on CD complexation between hydrobenzoin‐borate and SI‐S‐β‐CD. The (S,S)‐enantiomer of hydrobenzoin‐borate complexes interacted more strongly than the (R,R)‐enantiomer with SI‐S‐β‐CD. The enantiomers of hydrobenzoin could be baseline‐resolved in the presence of SI‐S‐β‐CD at a concentration as low as 0.1% w/v, whereas the three test analytes were simultaneously enantioseparated with addition of 0.3% w/v SI‐S‐β‐CD or at concentrations >2.0% w/v in a borate buffer and 0.5% w/v in a phosphate background electrolyte at pH 9.0. Compared with the results obtained previously using randomly sulfated β‐CD (MI‐S‐β‐CD) in a borate buffer, enantioseparation of these three benzoin compounds is more advantageously aided by SI‐S‐β‐CD as the chiral selector. The enantioselectivity of hydrobenzoin depended greatly on the degree of substitution of sulfated β‐CD. Moreover, binding constants of the enantiomers of benzoin compounds to SI‐S‐β‐CD and those of hydrobenzoin‐borate complexes to SI‐S‐β‐CD were evaluated for a better understanding of the role of CD complexation in the enantioseparation and chiral recognition. Enantiomer migration reversal of hydrobenzoin could be observed by varying the concentration of β‐CD, while keeping SI‐S‐β‐CD at a relatively low concentration. SI‐S‐β‐CD and β‐CD showed the same chiral recognition pattern but they exhibited opposite effects on the mobility of the enantiomers.
Comparative study on the chiral separation of phenyl alcohols by capillary electrophoresis and liquid chromatography
Authors: Zhang Yu‐Ping , Lee Kwang‐Pill , Kim Sang‐Ho , Choi Seong‐Ho , Gopalan Anantha I. , Yuan Zhuo‐Bin
Published: August 2004

Structurally related phenyl alcohols were separated by capillary electrophoresis and liquid chromatography. A statistical experimental design was used in order to optimize the main electrophoretic parameters such as pH, concentration of selector and separation voltage in capillary electrophoresis (CE). Response surfaces were derived using the mathematical model and used for a selection of the optimal experimental conditions. Concentration of the chiral selector, the distance between the aromatic group and asymmetric center of the analytes, were identified as the factors influencing the complexation, selectivity and resolution. Experiments were also performed by high‐performance liquid chromatography (HPLC) and the results of CE and HPLC were compared.
Effects of partial/asymmetrical filling of micelles and chiral selectors on capillary electrophoresis enantiomeric separation: Generation of a gradient
Authors: Tesařová Eva , Ševčík Juraj , Gaš Bohuslav , Armstrong Daniel W.
Published: August 2004

The effect of several experimental parameters on enantiomeric separations in micellar capillary electrophoresis (MCE) was studied. A model separation system was tested. It was composed of an acidic phosphate buffer with sodium dodecyl sulfate (SDS) and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) as the chiral selector. A substituted angelicin was used as a chiral analyte. Changes in the concentration of SDS micelles/SDS monomers in the presence of HP‐β‐CD and their impact on the enantioselective separation were investigated. Variation of the composition of electrolytes in the individual compartments of the separation system (inlet vial, capillary, and outlet vial) affected both the migration times and the resolution of the enantiomers. Current vs. time dependencies also were monitored during the separations. A mathematical model of electromigration in micellar systems with chiral selector present was proposed and a computer simulation was used to explain the observed phenomena and to confirm the generation of a CD/SDS‐micelle concentration gradient under certain experimental conditions. This is the reported first attempt of a computer simulation of the complex, dynamic chiral environment of the CD‐SDS‐MCE system.
Influence of methanol on the enantioresolution of antihistamines with carboxymethyl‐β‐cyclodextrin in capillary electrophoresis
Authors: Van Eeckhaut Ann , Detaevernier Marc Robert , Crommen Jacques , Michotte Yvette
Published: August 2004

According to the model of Wren and Rowe, the separation between two enantiomers in capillary electrophoresis (CE) decreases if an organic modifier is added to the run buffer containing a neutral cyclodextrin (CD) in a concentration below its optimal value in a solvent‐free system. In previous work, however, it was observed that the addition of methanol to the background electrolyte (BGE) containing not charged carboxymethyl‐β‐CD in a concentration below its optimal value, increased the enantioresolution of dimetindene maleate. The enantioresolution decreased when other organic modifiers (ethanol, isopropanol or acetonitrile) were added and/or when other neutral (β‐CD, hydroxypropyl‐β‐CD) or chargeable (carboxyethyl‐β‐ and succinyl‐β‐CD) CDs were used. In this CE study further attempts are made to elucidate the observed phenomena through investigating other basic drugs. The effect of organic modifier and CD concentration on the enantioseparation was studied by means of central composite designs. It is shown that obtaining this increase in enantioresolution depends upon the type of CD, the type of organic modifier, and the structure of the analytes. It was also observed that small differences in the structure of the analytes or the CD could have an influence on the enantioresolution. The addition of methanol also resulted in different effects on the resolution of closely related analytes.
Development and validation of a capillary electrophoresis method for the enantiomeric purity determination of SLV307, a basic potential antipsychotic compound
Authors: Muijselaar Pim G. , Lammers Norbert G. F. M. , Gerding Thijs K.
Published: August 2004

A capillary electrophoresis method for the enantiomeric purity determination of SLV307, a basic potential antipsychotic compound, has been developed and validated. It is shown that the presence of the eutomer in the sample solution may have a significant effect on the peak shape of the distomer, due to electrodispersion. The method is shown to give good performance with respect to the validation parameters specificity, linearity, accuracy, precision, determination limits, stability of solutions, and robustness of extraction.
A screening strategy for the development of enantiomeric separation methods in capillary electrophoresis
Authors: Jimidar M. Ilias , Van Ael Willy , Van Nyen Patrick , Peeters Margot , Redlich Dirk , De Smet Maurits
Published: August 2004

Method development of enantiomeric separations in capillary electrophoresis (CE) is a time‐consuming task, since finding the appropriate chiral selector is usually a “trial and error” process. It is impossible to predict the selectivity of a selector towards a certain enantiomer. Therefore, the affinity of all selectors has to be examined one at a time. In order to speed up this process, a strategy is proposed based on simple experimental design methodology. The approach includes first a screening in function of the pH to determine the optimal migration conditions followed by a selection of the right chiral selector by means of Taguchi designs. In the approach several variables, such as the type and concentration of cyclodextrin, the concentration of buffer electrolyte, and the percentage of organic modifier, are varied simultaneously to find initial separation conditions rapidly. The resulting initial separation conditions can be optimized in further steps to be more reproducible. We discuss the results of the approach when applied on a number of selected compounds that are recently in development at Johnson & Johnson – Pharmaceutical Research and Development. Parameters, such as quality of the separation and analysis time, are evaluated to determine initial separation conditions for each compound.
Editorial: Electrophoresis 16/2004
Authors: Fanali Salvatore , Chankvetadze Bezhan
Published: August 2004

No abstracts.
Maximum ozone concentration forecasting by functional non‐parametric approaches
Authors: Aneiros‐Pérez Germán , Cardot Hervé , Estévez‐Pérez Graciela , Vieu Philippe
Published: August 2004

Prediction of maximum ozone concentration is of great importance, especially to alert the population and to allow the authorities to take preventive measures soon enough. Ozone concentration and meteoro‐logical variables are now observed each hour or every 10 min so that we nearly get continuous observations along time, i.e. functions, as covariates. Much work has been done in the statistical community to propose effective models for predicting ozone concentration one day ahead, but there has been much less effort to study methods that take the functional nature of these data into account. We propose here two non‐linear models based on kernel estimators that handle the functional characteristics of the data by means of a measure of proximity between observed functions. In addition, we use additive ideas to take exogeneous variables into account without being too sensitive to dimensionality effects.

Such procedures are called multivariate functional non‐parametric approaches, since our models/estimates are non‐parametric (because of the non‐linear structure linking the explanatory and the response variables), functional (because the variables are curves) and multi‐dimensional (because we can have many functional explanatory variables).

These models are used to forecast maximum ozone concentration in Toulouse (France). We compare them to more classical techniques and the results are promising. Copyright © 2004 John Wiley & Sons, Ltd.
A multiblock operator‐splitting algorithm for unsteady flows at all speeds in complex geometries
Authors: Thakur Siddharth , Wright Jeffrey
Published: August 2004

This paper describes a non‐iterative operator‐splitting algorithm for computing all‐speed flows in complex geometries. A pressure‐based algorithm is adopted as the base, in which pressure, instead of density, is a primary variable, thus allowing for a unified formulation for all Mach numbers. The focus is on adapting the method for (a) flows at all speeds, and (b) multiblock, non‐orthogonal, body‐fitted grids for very complex geometries. Key features of the formulation include special treatment of mass fluxes at control volume interfaces to avoid pressure–velocity decoupling for incompressible (low Mach number limit) flows and to provide robust pressure–velocity–density coupling for compressible (high‐speed) flows. The method is shown to be robust for all Mach number regimes for both steady and unsteady flows; it is found to be stable for CFL numbers of order ten, allowing large time steps to be taken for steady flows. Enhancements to the method which allow for stable solutions to be obtained on non‐orthogonal grids are also discussed. The method is found to be very reliable even in complex engineering applications such as unsteady rotor–stator interactions in turbulent, all‐speed turbomachinery flows. Copyright © 2004 John Wiley & Sons, Ltd.
Spontaneous regression of lung metastasis in the absence of tumor necrosis factor receptor p55
Authors: Tomita Yoshiharu , Yang Xiaoqin , Ishida Yuko , Nemoto‐Sasaki Yoko , Kondo Toshikazu , Oda Makoto , Watanabe Go , Chaldakov George N. , Fujii Chifumi , Mukaida Naofumi
Published: August 2004

In order to clarify the roles of tumor necrosis factor (TNF)‐α in lung metastasis, we injected Renca cells intravenously into TNF receptor p55‐deficient (TNF‐Rp55 KO) and wild‐type (WT) mice. Microscopic and macroscopic metastasis foci appeared in lungs at 7 and 14 days after the tumor injection, respectively. Moreover, metastasis foci expanded at similar rates in both WT and TNF‐Rp55 KO mice until 21 days, and lungs were occupied with metastasis foci. However, later than 21 days after the injection, metastasis foci spontaneously regressed in TNF‐Rp55 KO mice, whereas WT mice exhibited a progressive growth of metastasis foci. Moreover, metastasis foci remained reduced sizes in TNF‐Rp55 KO mice even at 26 days, when all WT mice died with lungs filled with metastasis foci. Later than 21 days after the tumor injection, the number of apoptotic tumor cells was increased in TNF‐Rp55 KO mice. In contrast, neovascularization was less evident in TNF‐Rp55 KO than WT mice, with depressed hepatocyte growth factor (HGF) gene in TNF‐Rp55 KO mice at 21 days after the tumor injection. Thus, TNF‐Rp55‐mediated signals can maintain tumor neovascularization at least partly by inducing HGF expression, and eventually support lung metastasis process. © 2004 Wiley‐Liss, Inc.
MAZ51, an indolinone that inhibits endothelial cell and tumor cell growth in vitro, suppresses tumor growth in vivo
Authors: Kirkin Vladimir , Thiele Wilko , Baumann Petra , Mazitschek Ralph , Rohde Katrin , Fellbrich Guido , Weich Herbert , Waltenberger Johannes , Giannis Athanassios , Sleeman Jonathan P.
Published: August 2004

We have recently described MAZ51, an indolinone that blocks the ligand‐induced autophosphorylation of VEGFR‐3, a receptor tyrosine kinase that plays a central role in the regulation of lymphangiogenesis. Here we show that MAZ51 is able to block the proliferation of VEGFR‐3‐expressing human endothelial cells and is less potently able to induce their apoptosis. MAZ51 also inhibits the proliferation and induces the apoptosis of a variety of non‐VEGFR‐3‐expressing tumor cell lines. These data suggest that MAZ51 blocks the activity of tyrosine kinases in addition to VEGFR‐3. In vivo, MAZ51 significantly inhibits the growth of rat mammary carcinomas. These data establish MAZ51 as a compound with antitumor properties that inhibits tumor growth directly and also indirectly by interfering with tumor‐host interactions. © 2004 Wiley‐Liss, Inc.
Electrolytic deposition of calcium etidronate drug coating on titanium substrate
Authors: Duan Ke , Fan Yuwei , Wang Rizhi
Published: August 2004

Wear debris‐induced osteolysis is the major cause of aseptic loosening and failure of hip implants. One of the promising therapeutic interventions to improve the longevity of hip implants is to administrate bisphosphonate drug to inhibit osteoclastic bone resorption. This study aimed at developing new techniques of directly combining bisphosphonate with implants to achieve local delivery and controlled release of the drug. Instead of using soluble sodium salt, we proposed to apply sparingly soluble calcium salt of bisphosphonate as a potential long‐term antiosteolysis coating on hip implants. Calcium salt of etidronate, a member of the bisphosphonate family of potent osteoclast inhibitors, was used in this pilot study. By adopting the electrolytic deposition (ELD) technique, which was developed for ceramic coatings including calcium phosphates, we demonstrated that a thin layer of calcium bisphosphonate could be deposited onto titanium surface. The drug coating is amorphous as characterized with X‐ray diffraction, and has globular morphology under the scanning electron microscope. Electrospray‐ionization mass‐spectrometry (ESI‐MS) and Fourier‐transformed infrared spectroscopy confirmed that the molecular structure of the etidronate (m/z 205, H3L−, the single dissociated form of parent etidronic acid, denoted as H4L) was preserved after the ELD process. In vitro release into a “physiological” buffer solution confirmed that the etidronate concentration was limited by its low solubility. The etidronate concentration was 8 × 10−5 M at day 1 and kept relatively stable at ∼6 × 10−5 M from day 2 to day 8. The deposition mechanisms of the drug coating and its potential efficacy as an antiosteolytic release source were discussed. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 43–51, 2005
Predicting in vivo failure of pseudoelastic NiTi devices under low cycle, high amplitude fatigue
Authors: Young Jeremy M. , Van Vliet Krystyn J.
Published: August 2004

Due to the large reversible strains achievable through the stress‐induced austenite–martensite phase transformation in NiTi alloys, NiTi has replaced stainless steel in the majority of large‐strain biomedical applications such as root canal enlargement. However, the pseudoelasticity of NiTi is currently overshadowed by the short fatigue life of NiTi wires used in this low cycle (200–2000 rpm), high amplitude (εa > 2.5%) application, resulting in in vivo fracture or premature retirement of otherwise reusable NiTi‐based wire devices. In this study, the failure of pseudoelastic 55.8 wt % Ni‐Ti wire is investigated experimentally, as a function of experimental parameters that include the clinically relevant regime. The effects of radius of curvature, angle of curvature, wire diameter, strain amplitude, cyclic frequency, volume under strain, and specific heat of the surrounding environmental fluid are considered systematically. These data indicate that the lifetime or cycles to failure Nf of a rotating NiTi wire can be predicted via a modified Coffin‐Manson relation that is a strong function of both strain amplitude and volume under strain, and a weaker function of frequency and fluid specific heat. The resulting quantitative relation can be used to predict useful device lifetime under clinically relevant conditions and thereby reduce incidences of in vivo failure. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 17–26, 2005
The parameterization and validation of generalized born models using the pairwise descreening approximation
Authors: Michel Julien , Taylor Richard D. , Essex Jonathan W.
Published: August 2004

Generalized Born Surface Area (GBSA) models for water using the Pairwise Descreening Approximation (PDA) have been parameterized by two different methods. The first method, similar to that used in previously reported parameterizations, optimizes all parameters against the experimental free energies of hydration of organic molecules. The second method optimizes the PDA parameters to compensate only for systematic errors of the PDA. The best models are compared to Poisson–Boltzmann calculations and applied to the computation of potentials of mean force (PMFs) for the association of various molecules. PMFs present a more rigorous test of the ability of a solvation model to correctly reproduce the screening of intermolecular interactions by the solvent, than its accuracy at predicting free energies of hydration of small molecules. Models derived with the first method are sometimes shown to fail to compute accurate potentials of mean force because of large errors in the computation of Born radii, while no such difficulties are observed with the second method. Furthermore, accurate computation of the Born radii appears to be more important than good agreement with experimental free energies of solvation. We discuss the source of errors in the potentials of mean force and suggest means to reduce them. Our findings suggest that Generalized Born models that use the Pairwise Descreening Approximation and that are derived solely by unconstrained optimization of parameters against free energies of hydration should be applied to the modeling of intermolecular interactions with caution. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1760–1770, 2004
Evidence of reciprocal regulation between the high extracellular calcium and RANKL signal transduction pathways in RAW cell derived osteoclasts
Authors: Xu Jiake , Wang Cathy , Han Renzhi , Pavlos Nathan , Phan Tony , Steer James H. , Bakker Anthony J. , Joyce David A. , Zheng Ming H.
Published: August 2004

During bone resorption, osteoclasts are exposed to high Ca2+ concentrations (up to 40 mM). The role of high extracellular Ca2+ in receptor activator of NF‐κB ligand (RANKL)‐mediated osteoclast survival and their functional interrelationship is unclear. In this study, we show that RANKL enhances osteoclast tolerance to high extracellular Ca2+ by protecting the cell from cell death in a dose dependent manner. We have provided evidence that RANKL does this by attenuating high extracellular Ca2+‐induced Ca2+ elevations. Moreover, we have found that high extracellular Ca2+‐induced cell death was partially inhibited by a caspase‐3 inhibitor, suggesting caspase‐3‐mediated apoptosis is involved. Conversely, using reporter gene assays and Western blot analysis, we have demonstrated that high extracellular Ca2+ desensitizes the RANKL‐induced activation of NF‐κB and c‐Jun N‐terminal kinase (JNK), and inhibits constitutive and RANKL‐stimulated ERK phosphorylation, indicating a negative feed‐back mechanism via specific RANKL signaling pathways. Taken together, this study provides evidence for a reciprocal regulation between high extracellular Ca2+ and RANKL signaling in RAW cell derived osteoclasts. Our data imply a cross talk mechanism of extracellular Ca2+ on osteoclast survival through the regulation of RANKL. © 2004 Wiley‐Liss, Inc.
Molecular and cellular regulation of glucose transporter (GLUT) proteins in cancer
Authors: Macheda Maria L. , Rogers Suzanne , Best James D.
Published: August 2004

Malignant cells are known to have accelerated metabolism, high glucose requirements, and increased glucose uptake. Transport of glucose across the plasma membrane of mammalian cells is the first rate‐limiting step for glucose metabolism and is mediated by facilitative glucose transporter (GLUT) proteins. Increased glucose transport in malignant cells has been associated with increased and deregulated expression of glucose transporter proteins, with overexpression of GLUT1 and/or GLUT3 a characteristic feature. Oncogenic transformation of cultured mammalian cells causes a rapid increase of glucose transport and GLUT1 expression via interaction with GLUT1 promoter enhancer elements. In human studies, high levels of GLUT1 expression in tumors have been associated with poor survival. Studies indicate that glucose transport in breast cancer is not fully explained by GLUT1 or GLUT3 expression, suggesting involvement of another glucose transporter. Recently, a novel glucose transporter protein, GLUT12, has been found in breast and prostate cancers. In human breast and prostate tumors and cultured cells, GLUT12 is located intracellularly and at the cell surface. Trafficking of GLUT12 to the plasma membrane could therefore contribute to glucose uptake. Several factors have been implicated in the regulation of glucose transporter expression in breast cancer. Hypoxia can increase GLUT1 levels and glucose uptake. Estradiol and epidermal growth factor, both of which can play a role in breast cancer cell growth, increase glucose consumption. Estradiol and epidermal growth factor also increase GLUT12 protein levels in cultured breast cancer cells. Targeting GLUT12 could provide novel methods for detection and treatment of breast and prostate cancer. © 2004 Wiley‐Liss, Inc.
Oncostatin M stimulates proliferation and functions of mouse fetal liver cells in three‐dimensional cultures
Authors: Ehashi Tomo , Miyoshi Hirotoshi , Ohshima Norio
Published: August 2004

In order to develop a tissue engineered bioartificial liver (BAL), long‐term three‐dimensional (3‐D) culture of fetal liver cells (FLCs) utilizing porous polymer as a scaffold was performed for up to 1 month. The effects of the basal medium and supplementation with oncostatin M (OSM) on the proliferation and differentiation of mouse FLCs were examined in both 3‐D culture and conventional monolayer dish culture. Compared with monolayer culture, cell numbers and hepatic function of FLCs were better maintained by 3‐D culture. When two kinds of basal media were tested in this study, Williams' medium E (WE) was superior to minimum essential medium alpha (αMEM) in expressing hepatic function of FLCs in both 3‐D and monolayer cultures, although higher cell densities were obtained with αMEM. OSM potently stimulated both cell growth and metabolic activity, especially in 3‐D culture. When WE supplemented with OSM was used for 3‐D culture, albumin secretion by FLCs increased dramatically after day 5, and a high level of secretion was maintained until the end of culture. During a period of over 1 month, no decrease of albumin secretion was observed. In conclusion, this 3‐D culture method was expected to be one of the realistic attempts to develop a tissue engineered BAL. © 2004 Wiley‐Liss, Inc.
LiCl inhibits the establishment of left‐right asymmetry in larvae of the direct‐developing echinoid Peronella japonica
Authors: Kitazawa Chisato , Takai Kaori Kajihara , Nakajima Yoko , Fujisawa Hirosuke , Amemiya Shonan
Published: August 2004

The effect of LiCl on the establishment of left‐right (LR) asymmetry in larvae of the direct‐developing echinoid Peronella japonica was investigated with special attention to the location of the amniotic opening and ciliary band pattern. The larvae of echinoids are LR symmetric, but shortly before metamorphosis the larval LR symmetry is lost as a result of the formation of an amniotic cavity (vestibule), part of the adult rudiment, on the left side of the body. P. japonica has been considered to be the only exception among the echinoids, because the amniotic cavity forms at the midline of the larval body. In the present study we discovered the following two different LR asymmetric traits in larvae of P. japonica: the opening of the amniotic cavity initially forms at the midline of the larval body but shifts to the left dorsal side, and a looped ciliary band that initially forms with LR symmetry becomes LR asymmetric as a result of the formation of a bulge on left dorsal side. The establishment of LR asymmetry in both the location of the amniotic opening and the change in the shape of the ciliary band was influenced by exposing embryos to LiCl. Quantitative analysis of the shift in amniotic opening showed that exposure of embryos to LiCl causes repression of leftward shifting of the amniotic opening in earlier stage larvae, and leftward or rightward shifting in later stage larvae. These findings suggest that LiCl is an effective means of impairing the establishment of LR asymmetry in sea urchin embryos. J. Exp. Zool. 301A:707–717, 2004. © 2004 Wiley‐Liss, Inc.
Scaling effects on metabolism of a teleost
Authors: Tripathi G. , Verma Priyanka
Published: August 2004

Scaling effects on citrate synthase (CS), glucose‐6‐phosphate dehydrogenase (G6‐PDH), RNA. RNA/DNA ratio and protein contents of brain, liver and skeletal muscle were studied in a teleost, Clarias batrachus. The activity of white skeletal muscle CS decreased significantly as a function of increasing body mass of the fish. It shows that the fulfilment of energy demand in white skeletal muscle is not dependent on aerobic metabolism. The activity of liver G6‐PDH decreased with the increasing body mass showing reduction in NADPH generation for lipogenic activity. However, increase in G6‐PDH activity showed enhancement in reductive synthesis in skeletal muscle of the larger‐sized individuals. A positive scaling of RNA, RNA/DNA ratio and protein contents reflects changes in macromolecular turnover for ATP‐supplying enzymes and proteins. J. Exp. Zool. 301A:718–726, 2004. © 2004 Wiley‐Liss, Inc.
Species‐specific effects on hemolymph glucose control by serotonin, dopamine, and L‐enkephalin and their inhibitors in Squilla mantis and Astacus leptodactylus (crustacea)
Authors: Lorenzon Simonetta , Brezovec Sara , Ferrero Enrico A.
Published: August 2004

Hemolymph glucose level is controlled by crustacean Hyperglycemic Hormone (cHH) released from the eyestalk neuroendocrine centers under conditions of both physiological and environmental stress. Biogenic amines and enkephalin have been found to mediate the release of several neurohormones from crustacean neuroendocrine tissue. We investigated the effect of serotonin, dopamine, and Leucine‐enkephalin in vivo—injected into the stomatopod Squilla mantis and the decapod Astacus leptodactylus—whether increasing or depressing glycemia. Serotonin had a marked effect in elevating glucose level compared with initial values in both species. 5–HT1–like receptors are more involved in mediating serotonin action as co‐injected cyproheptadine was a more effective antagonist than ketanserin (5–HT2–like receptor inhibitor). Dopamine injection in intact animals produced a decrease below initial levels of hemolymph glucose. This effect was significantly antagonized by domperidone. No significant effect of both amines occurred in eyestalkless animals. L‐enkephalin shows a differential effect: in S. mantis it induced hypoglycemia while in A. leptodactylus it caused an increase of glucose level. Co‐injected antagonist naloxone affected the direction of the response. Serotonin appears to provide a major control on glucose mobilization, whereas dopamine and L‐enkephalin act as modulators whose plasticity in use or action varies among species. J. Exp. Zool. 301A:727–736, 2004. © 2004 Wiley‐Liss, Inc.
Yolk partitioning in embryos of the lizard, Calotes versicolor: Maximize body size or save energy for later use?
Authors: Radder Rajkumar S. , Shanbhag Bhagyashri A. , Saidapur Srinivas K.
Published: August 2004

The hatchlings of Calotes versicolor and other congeners retain residual yolk for immediate post‐hatching needs. Excision of 8% yolk (≌residual yolk) from the eggs resulted in smaller hatchlings when compared to those emerging from sham operated eggs. However, hatchlings in both groups retained the same amount of residual yolk. The findings suggest that residual yolk in hatchlings of C. versicolor is an important part of the energy budget set aside by developing embryos and that the advantages of large hatchling size are counter balanced by selection for residual yolk. J. Exp. Zool. 301A:783–785, 2004. © 2004 Wiley‐Liss, Inc.
A field study of group diversity, workgroup context, and performance
Authors: Jehn Karen A. , Bezrukova Katerina
Published: August 2004

We explore how the context of an organizational workgroup affects the relationship between group diversity and various performance outcomes. In particular, we theorize and empirically examine the moderating effects of three categories of workgroup context variables: cultures (people‐ and competition‐oriented), strategies (stability‐, growth‐ and customer‐oriented), and human resource practices (diversity‐ and training‐oriented). We perform analyses on 1528 workgroups from a Fortune 500 information‐processing firm. The results showed, for example, that members of groups diverse in functional background were paid higher composite bonuses when their workgroup context emphasized people‐oriented cultures and lower levels of bonuses in contexts with a focus on stability‐oriented strategies. In addition, members of groups diverse in level of education were awarded higher amounts of bonuses in workgroup environments that emphasized customer‐ and growth‐oriented strategies. However, members of such groups had lower levels of composite bonuses in environments that focused on training‐ and diversity‐oriented human resource practices. We discuss future research directions regarding diversity, workgroup context, and performance outcomes and outline some implications for managers and group leaders. Copyright © 2004 John Wiley & Sons, Ltd.
Diversity in social context: a multi‐attribute, multilevel analysis of team diversity and sales performance
Authors: Jackson Susan E. , Joshi Aparna
Published: August 2004

Prior research on demographic diversity in work teams has yielded mixed results, with the effects of team diversity ranging from positive to neutral to negative. This article shows that an improved understanding of the relationship between team diversity and team performance can be reached by considering the combined effects of team diversity and demographic social context. We hypothesized that three aspects of the social context would moderate the effects of demographic diversity on performance: the combination of diversity dimensions within a team, the demographic characteristics of the team manager, and the demography of the work unit. In a study of 365 sales teams distributed across 42 sales districts in a large U.S. company, we found support for the general proposition that the demographic social context moderates relationships between team diversity and team performance. We discuss the practical implications of these results as well as the research implications for future studies of team diversity. Copyright © 2004 John Wiley & Sons, Ltd.
A field study of group diversity, participation in diversity education programs, and performance
Authors: Ely Robin J.
Published: August 2004

This study examined the impact of four dimensions of diversity—tenure, age, sex, and race—on performance in 486 retail bank branches and assessed whether employee participation in the firm's diversity education programs influenced these relationships. Data came from archives of the demographic composition of branches, an employee attitude–satisfaction poll, and branch performance assessed as part of the bank's bonus incentive plan. Race and sex diversity were unrelated to performance. The direct effects of tenure and age diversity were largely negative, but were moderated by quality of team processes, suggesting that cooperation and teamwork may suppress potentially task‐enhancing differences associated with these aspects of diversity. Diversity education programs had minimal impact on performance. The results of this study suggest that there is a complex relationship between age and tenure diversity and performance and that, even in firms with characteristics that should be conducive to performance benefits from diversity, other conditions must be in place to foster such effects. Copyright © 2004 John Wiley & Sons, Ltd.
Topographical properties of polymer films deposited in capillaries for electrophoretic separations of large organic molecules
Authors: Guryča Vilém , Pacáková Veřa , Tlust'áková Marie , Štulík Karel , Michálek Jiří
Published: August 2004

Topography and thickness of hydrophilic polymer coatings of fused‐silica capillaries for capillary electrophoresis (CE) were investigated using atomic force microscopy (AFM), scanning electron microscopy (SEM), and profilometry. Three hydrogels, poly(2‐hydroxyethyl methacrylate) [poly(HEMA)], poly(diethylene glycol monomethacrylate) [poly(DEGMA)], and poly(triethylene glycol monomethacrylate) [poly‐(TEGMA)], were deposited using two procedures, either by simple physical sorption of the polymers, or by derivatization of the capillary wall surface with glycidyl methacrylate (EPMA) followed by polymerization of the appropriate monomers. The performance of the modified capillaries was tested under CE conditions (decrease in the electroosmotic flow, EOF dependence on pH, separation of milk and standard proteins). It has been found that the most important property of the polymer coating is its thickness, whereas its topography and the degree of its hydrophobicity are less significant. Film deposition by physical adsorption is preferable to polymerization on the derivatized surface.
Retention modelling in liquid chromatographic separation of simvastatin and six impurities using a microemulsion as eluent
Authors: Malenovic Andjelija , Ivanovic Darko , Medenica Mirjana , Jancic Biljana , Markovic Slavko
Published: August 2004

A novel and unique approach was used for retention modelling in the separation of simvastatin and six impurities by liquid chromatographic using a microemulsion as mobile phase. A microemulsion is a modification of a micellar system where a lipophilic organic solvent is dissolved in the micelles; for that reason, microemulsions are usually treated as solvent‐modified micellar solutions. When microemulsions are used as eluents in HPLC separations, solutes partition between the charged oil droplets and the aqueous buffer phase. The complexity of the composition of the microemulsion permits extensive manipulations to be made during method development in order to achieve acceptable resolution of such a complex mixture of substances. In order to avoid a laborious “trial and error” procedure, a 23 full factorial design was applied for choosing an optimal microemulsion composition to obtain good separation in a reasonable run time. Organic solvent, sodium dodecyl sulphate, and n‐butanol content were varied within defined experimental domain. Optimal conditions for the separation of simvastatin and its six impurities were obtained using an X TerraTM 50×4.6 mm, 3.5 μm particle size column at 30°C. The mobile phase consisted of 0.9% w/w of diisopropyl ether, 2.2% w/w of sodium dodecylsulphate (SDS), 7.0% w/w of co‐surfactant such as n‐butanol, and 89.9% w/w of aqueous 25 mM disodium phosphate pH 7.0.