bluuebunny/crossref_metadata_2025 huggingface dataset:
The unified equation for the evaluation of degenerated first‐order reactions in dynamic electrophoresis
Authors: Trapp Oliver
Published: June 2006

An analytical solution for the unified equation for degenerated (pseudo‐) first‐order reactions, e.g., enantiomerization processes, in dynamic CE is presented, and validated with a dataset of 31 250 elution profiles covering typical experimental parameters. The unified equation was applied to determine the enantiomerization barrier of the hypnotic glutarimide derivative thalidomide (Contergan®) by dynamic capillary electrokinetic chromatography (DEKC). The enantiomer separation of thalidomide was performed in an aqueous 50 mM sodium borate buffer at pH 9.3 in the presence of the chiral mobile phase additive carboxymethyl‐β‐CD. Interconversion profiles featuring pronounced plateau formation were observed. Activation parameters ΔH≠ and ΔS≠ were obtained from temperature‐dependent measurements between 20.0 and 37.5°C in 2.5K steps. From the activation parameters the enantiomerization barrier of thalidomide at 37°C under basic conditions were calculated to be ΔG≠ = 93.2 kJ/mol. Comparison of the kinetic data with results obtained at pH 8.0 reveals the catalytic influence of the base on the enantiomerization barrier.
QM/MM calculations with DFT for taking into account protein effects on the EPR and optical spectra of metalloproteins. Plastocyanin as a case study
Authors: Sinnecker Sebastian , Neese Frank
Published: June 2006

A detailed study of the influence of the surrounding protein on magnetic and optical spectra of metalloproteins is presented using the quantum‐mechanical/molecular mechanical (QM/MM) approach. The well‐studied type I copper site in plastocyanin in the cupric oxidation state is taken as a test case because its spectroscopic properties have been extensively studied and are well understood. The calculations have been performed using nonrelativistic and scalar relativistic (at the level of the zeroth order regular approximation, ZORA) calculations (B3LYP functional). Linear response theory has been used to calculate first‐ and second‐order properties, namely the EPR g‐tensor, the central metal hyperfine couplings (HFCs), the HFCs of the directly coordinating ligands, as well as superhyperfine couplings (1H, 14N) from remote nuclei, transition energies, and oscillator strengths. Two different model systems have been defined that do not and do include important amino acids from the second coordination sphere, respectively. For comparison, calculations have been carried out in the gas phase and in a dielectric continuum (conductor like screening model, COSMO) with a dielectric constant of four. The best results were obtained at the scalar relativistic ZORA level for the largest model in conjunction with explicit modeling of the protein environment through the QM/MM procedure, which is also considered to be the highest level of theory used in this work. The protein effects beyond the second coordination sphere were found to be quite substantial (up to 30% changes on some properties), and were found to require an explicit treatment of the protein beyond the second coordination sphere. In addition, the embedding water cage was found to have a nonnegligible influence on the calculated spectroscopic data, which is of the same order as the influence of the protein backbone charges. However, while qualitatively satisfactory, the errors in the calculated spectroscopic parameters are still substantial, and can all be traced back to the fact that the linear‐response of the presently available functionals is “too stiff” with respect to the external perturbations at least for the model systems studied here. Ligand field‐based approaches are used to correct for systematic errors in the DFT procedures. As a consequence, we propose a new breakdown of the copper hyperfine interaction into Fermi‐contact, spin‐dipolar and spin‐orbit contributions. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1463–1475, 2006
Performance of DFT in modeling electronic and structural properties of cobalamins
Authors: Kuta Jadwiga , Patchkovskii Seguei , Zgierski Marek Z. , Kozlowski Pawel M.
Published: June 2006

Computational modeling of the enzymatic activity of B12‐dependent enzymes requires a detailed understanding of the factors that influence the strength of the CoC bond and the limits associated with a particular level of theory. To address this issue, a systematic analysis of the electronic and structural properties of coenzyme B12 models has been performed to establish the performance of three different functionals including B3LYP, BP86, and revPBE. In particular the cobalt–carbon bond dissociation energies, axial bond lengths, and selected stretching frequencies have been analyzed in detail. Current analysis shows that widely used B3LYP functional significantly underestimates the strength of the CoC bond while the nonhybrid BP86 functional produces very consistent results in comparison to experimental data. To explain such different performance of these functionals molecular orbital analysis associated with axial bonds has been performed to show differences in axial bonding provided by hybrid and nonhybrid functionals. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1429–1437, 2006
A DFT study of the mechanism of Ni superoxide dismutase (NiSOD): Role of the active site cysteine‐6 residue in the oxidative half‐reaction
Authors: Prabhakar Rajeev , Morokuma Keiji , Musaev Djamaladdin G.
Published: June 2006

In the present DFT study, the catalytic mechanism of H2O2 formation in the oxidative half‐reaction of NiSOD, E‐Ni(II) + O + 2H+ → E‐Ni(III) + H2O2, has been investigated. The main objective of this study is to investigate the source of two protons required in this half‐reaction. The proposed mechanism consists of two steps: superoxide coordination and H2O2 formation. The effect of protonation of Cys6 and the proton donating roles of side chains (S) and backbones (B) of His1, Asp3, Cys6, and Tyr9 residues in these two steps have been studied in detail. For protonated Cys6, superoxide binding generates a Ni(III)–O2H species in a process that is exothermic by 17.4 kcal/mol (in protein environment using the continuum model). From the Ni(III)–O2H species, H2O2 formation occurs through a proton donation by His1 via Tyr9, which relative to the resting position of the enzyme is exothermic by 4.9 kcal/mol. In this pathway, a proton donating role of His1 residue is proposed. However, for unprotonated Cys6, a Ni(II)–O species is generated in a process that is exothermic by 11.3 kcal/mol. From the Ni(II)–O species, the only feasible pathway for H2O2 formation is through donation of protons by the Tyr9(S)–Asp3(S) pair. The results discussed in this study elucidate the role of the active site residues in the catalytic cycle and provide intricate details of the complex functioning of this enzyme. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1438–1445, 2006
Correlation between computed gas‐phase and experimentally determined solution‐phase infrared spectra: Models of the iron–iron hydrogenase enzyme active site
Authors: Tye Jesse W. , Darensbourg Marcetta Y. , Hall Michael B.
Published: June 2006

Gas‐phase density functional theory calculations (B3LYP, double zeta plus polarization basis sets) are used to predict the solution‐phase infrared spectra for a series of CO‐ and CN‐containing iron complexes. It is shown that simple linear scaling of the computed CO and CN stretching frequencies yields accurate predictions of the the experimentally determined ν(CO) and ν(CN) values for a variety of complexes of different charges and in solvents of varying polarity. As examples of the technique, the resulting correlation is used to assign structures to spectroscopically observed but structurally ambiguous species in two different systems. For the (μ‐SCH2CH2CH2S)[Fe(CO)3]2 complex in tetrahydrofuran solution, our calculations show that the initial electrochemical reduction process leads to a simple one‐electron reduced product with a structure very similar to the (μ‐SCH2CH2CH2S)[Fe(CO)3]2 parent complex. For the iron–iron hydrogenase enzyme active site, our computations show that the absence or presence of a water molecule near the distal iron center (the iron center further from the [4Fe4S] cluster and protein backbone) has very little effect on the predicted infrared spectra. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1454–1462, 2006
Treatment of paper and pulp wastewater and removal of odorous compounds by a Fenton‐like process at the pilot scale
Authors: Tambosi José L , Di Domenico Michele , Schirmer Waldir N , José Humberto J , Moreira Regina de FPM
Published: June 2006

A Fenton‐like process, involving oxidation and coagulation, was evaluated for the removal of odorous compounds and treatment of a pulp and paper wastewater. The main parameters that govern the complex reactive system [pH and Fe(III) and hydrogen peroxide concentrations] were studied. Concentrations of Fe(III) between 100 and 1000 mg L−1 and of H2O2 between 0 and 2000 mg L−1 were chosen. The main mechanism for color removal was coagulation. The maximum COD, color and aromatic compound removals were 75, 98 and 95%, respectively, under optimal operating conditions ([Fe(III)] = 400 mg L−1; [H2O2] = 500–1000 mg L−1; pH = 2.5; followed by coagulation at pH 5.0). The biodegradability of the wastewater treated increased from 0.4 to 0.7 under optimal conditions and no residual hydrogen peroxide was found after treatment. However, partially or non‐oxidized compounds present in the treated wastewater presented higher acute toxicity to Artemia salina than the untreated wastewater. Based on the optimum conditions, pilot‐scale experiments were conducted and revealed a high efficiency in relation to the mineralization of organic compounds. Terpenes [(1S)‐α‐pinene, β‐pinene, (1R)‐α‐pinene and limonene] were identified in the wastewater and were completely eliminated by the Fenton‐like treatment. Copyright © 2006 Society of Chemical Industry
Humoral immune responses against minute virus of mice vectors
Authors: Lang Susanne I. , Giese Nathalia A. , Rommelaere Jean , Dinsart Christiane , Cornelis Jan J.
Published: June 2006

Background

Owing to their oncolytic properties, autonomous rodent parvoviruses and derived vectors constitute potential anti‐tumor agents.

Methods

Humoral immune responses to minute virus of mice (MVMp) were characterized. In particular, the generation of neutralizing antibodies on subsequent therapeutic virus applications was evaluated in a mouse melanoma model. Mice bearing subcutaneous melanomas were injected intratumorally with virus and re‐injected 10 days later in a second tumor on the other flank. Four days after the first or second injection, the tumors and lymph nodes were analyzed by RT‐PCR for gene expression.

Results

Injection of MVMp in tumor‐bearing B6 mice resulted in viral gene expression in tumors and draining lymph nodes. A repeated virus administration did not lead to detectable viral transcription if it was preceded by a virus infection 10 days earlier. This protection correlated with the induction of virus‐neutralizing antibodies following the first virus application. The restrictions on viral gene expression after a consecutive MVMp injection could be alleviated in subsequent applications by the use of viruses consisting of MVMp genomes packaged into capsids of a related parvovirus. Neutralizing antibody induction was irrespective of the route of administration and of the presence of a tumor and persisted at significant levels at least up to 26 weeks after the viral infection. MVMp infection of B6 mice stimulated the generation of IgM and IgG anti‐viral antibodies, the latter mainly of the T‐helper (Th) 1‐dependent IgG2, and the T‐cell‐independent IgG3 subclasses.

Conclusions

Neutralizing antibodies impede the effectiveness of a subsequent virus administration, but can be overcome by pseudotyping. Copyright © 2006 John Wiley & Sons, Ltd.
Recent progress in the assays of xylanolytic enzymes
Authors: Biely Peter , Puchart Vladimír
Published: June 2006

Increasing industrial importance of xylanolytic enzymes together with recent evidence for cereal endoxylanase inhibitors having a negative impact on the application of enzymes in fodder and food industries, brings challenges to facilitate and simplify the procedures to follow these enzymes. This article gives a critical evaluation of current methods and outlines new methodological alternatives to follow the major depolymerising enzyme, endo‐β‐1,4‐xylanase using chromogenic substrates. Attention is paid also to assays of three accessory xylanolytic enzymes α‐glucuronidase, acetylxylan esterase and feruloyl esterase, for which new enzyme‐coupled assays were elaborated. Copyright © 2006 Society of Chemical Industry
New Fluorene‐Acceptor Random Copolymers: Towards Pure White Light Emission from a Single Polymer
Authors: Wu Wen‐Chung , Lee Wen‐Ya , Chen Wen‐Chang
Published: June 2006

Summary: Two kinds of fluorene‐acceptor copolymers containing three emitting segments have been synthesized and explored as the emissive layer in white‐light‐emitting devices (WLEDs). The light‐emitting copolymers PFQTP and PFBTTP either contain blue‐emitting (9,9‐dihexyl‐fluorene, F), green‐emitting (quinoxaline, Q) (or yellow‐emitting (2,1,3‐benzothiadiazole, BT)), and red‐emitting (thieno[3,4‐b]‐pyrazine, TP) units in the backbone. The energy‐transfer processes between the emitting units are investigated by their absorption, photoluminescence, time‐resolved photoluminescence, and electroluminescence. The experimental results suggest that only a relatively small faction of the acceptor moiety incorporated into the fluorene can achieve white light emission through energy transfer. The energy transfer from BT to TP is more efficient that that of Q to TP because of the degree of spectroscopic overlap between absorption and luminescence. The electroluminescent device with PFBTTP1 (0.1% of BT and 0.25% of TP) as an emissive layer exhibits the Commission Internationale de L'Eclairage (CIE) 1931 coordinates of (0.33, 0.34), a luminance of 1 870 cd · m−2 under the condition of maximum luminance yield of 1.92 cd · A−1, and without significant variation with driving voltages. The present study suggests that the single polymers based on three fluorene‐acceptor segments could be potentially used for pure‐white‐light‐emitting diodes.

The fluorene‐acceptor copolymers, PFQTP and PFBTTP, and the normalized EL spectra of their devices (left) and their CIE 1931 coordinates (x, y).

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The fluorene‐acceptor copolymers, PFQTP and PFBTTP, and the normalized EL spectra of their devices (left) and their CIE 1931 coordinates (x, y).
Brand personality: Exploring the potential to move from factor analytical to circumplex models
Authors: Sweeney Jillian C. , Brandon Carol
Published: June 2006

With the proliferation of products and brands in the marketplace, brand personality has emerged as an important means of brand differentiation and thus of increasing consumer preference. However, little research has investigated this important construct, with the significant exceptions of Aaker's (1997) work, which is based on a factoranalytical approach. In response to the limitations of the factor approach to brand personality, this study explores the potential for advancing understanding of brand personality through a circumplex model derived from the fields of social and personality psychology and interpersonal psychiatry. The model is based on relationships between interpersonal personality traits or emotions and can assist academics and practitioners in understanding the brand personality concept. © 2006 Wiley Periodicals, Inc.
Measuring consumer vanity: A cross‐cultural validation
Authors: Wang Paul Z. , Waller David S.
Published: June 2006

Given the unmistakable trend toward a more integrated global economy and the tremendous impact of consumer vanity on demand for countless goods and services, there exists a need for more cross‐cultural research on the important psychological construct known as consumer vanity (Netemeyer, Burton, & Lichtenstein, 1995). This article examines four components of the vanity construct: appearance concern, appearance perception, achievement concern, and achievement perception. To test the vanity construct cross‐culturally, a survey was undertaken in the United States and China. This article illustrates the use of the comprehensive analytical framework proposed by Steenkamp and Baumgartner (1998) to assess measurement invariance in cross‐cultural consumer research. The results provided a rigorous cross‐cultural validation test of the vanity scale that has implications for both academics and practitioners in cross‐cultural consumer research and marketing. © 2006 Wiley Periodicals, Inc.
New Stimuli Responsive Poly(1‐vinylpyrrolidin‐2‐one) Bearing Pendant Activated Disulfide Groups
Authors: Bencini Marco , Ranucci Elisabetta , Ferruti Paolo , Manfredi Amedea
Published: June 2006

Summary: A novel functionalised poly(1‐vinylpyrrolidin‐2‐one) (PVP) derivative, carrying a pre‐determined amount of 2‐(2‐pyridinyldithio)ethylamine moieties as side substituents, P(VP‐co‐VP‐SS‐Py), has been prepared from carboxylated VP copolymers, in turn obtained by copolymerising 1‐vinylpyrrolidin‐2‐one with 3,3‐di‐(ethoxycarbonyl)‐1‐vinylpyrrolidin‐2‐one in the presence of radical initiators. Using reaction solvents acting in the mean time as chain transfer agents could control its molecular weight. P(VP‐co‐VP‐SS‐Py) proved to be extremely reactive towards exchange reactions with molecules containing mercapto functions, including bioactive peptides. The exchange derivative with reduced glutathione, chosen as a model compound, was easily prepared.

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A Fluorescence Ratiometric Protein Assay Using Light‐Harvesting Conjugated Polymers
Authors: An Lingling , Tang Yanli , Wang Shu , Li Yuliang , Zhu Daoben
Published: June 2006

Summary: A highly selective protein assay was created which combines the fluorescent ratiometric technique based on FRET with the light‐harvesting properties of conjugated polymers. The cationic poly[(9,9‐bis(6′‐N,N,N‐trimethylammonium)‐hexyl)‐fluorene phenylene] bromide (PFP‐NMe) and the negatively charged biotinylated fluorescein probe (Fl‐B) were used to detect the target protein streptavidin optically. The strong electrostatic interactions between PFP‐NMe and fluorescein result in efficient FRET from PFP‐NMe to fluorescein. In the presence of streptavidin, however, the biotin moiety of Fl‐B specifically associates with streptavidin and the fluorescein molecule is buried deeply in the adjacent vacant binding sites. This separates the fluorescein spatially from the PFP‐NMe moiety, resulting in inefficient FRET from PFP‐NMe to fluorescein. Although a nonspecific protein, such as BSA, shows nonspecific interactions with PFP‐NMe, it does not affect the fluorescent ratio value of PFP‐NMe to fluorescein. Hence, the charged neutral complex of two oppositely charged conjugated polymers can eliminate the nonspecific interactions, and thus optimize their application in protein assays.

A schematic representation of the protein assay operation.

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A schematic representation of the protein assay operation.
Mechanical characteristics of functionally graded biodegradable implants for skull bone reconstruction
Authors: Wehmöller M. , Neuking K. , Epple M. , Annen T. , Eufinger H.
Published: June 2006

A functionally graded implant was developed to substitute the function of the skull for geometry and for protection of the brain. The implant consists of polylactide/amorphous calcium phosphate as mechanically stable external structure and of polylactide/calcium carbonate as porous internal structure for the ingrowth of bone. For the examination of this protective mechanical function implant fragments were compared with bone fragments of the corresponding calvarium with a 3‐point bending test.
Silicon‐substituted hydroxyapatite ceramics (Si‐HAp): densification and grain growth through the prism of sintering theories
Authors: Putlayev V. , Veresov A. , Pulkin M. , Soin A. , Kuznetsov V.
Published: June 2006

Ceramics based on calcium phosphates is known to be a prospective material for biomedical applications. Noticeable attention is paid to hydroxyapatite Ca10(PO4)6(OH)2 (HAp) due to its affinity to a bone mineral. It was recognized recently that Si‐doped HAp is a highly promising material in sense of bioactivity improvement. In the frame of distinct research activity structured around this subject, some special problems are to be solved: (1) solubility of Si in the bulk of HAp lattice (and its limit) vs. segregation of Si to free surfaces and grain boundaries, (2) rationalization of Si effect on sintering of HAp ceramics, (3) charge compensation over aliovalent doping of HAp with Si and its interplay with thermal stability of HAp phase.

The work was focused on a fabrication of Si‐HAp with Ca10(Po4)6‐x(SiO4)x(OH)2‐x (x=0..1) nominal composition and evaluation the effect of Si on sintering of HAp ceramics. The limit of Si solubility in HAp lattice was estimated to be not higher than x=0.1 in the formula above (at 1000 °C, according to XRD and SEM/EDX). The essence of the silicon influence consists in significant suppression of grain growth during the initial stage of sintering. Silicon doping reduces grain boundary mobility (increasing activation energy of lattice diffusion) along with the increase of pore mobility (in fact, increasing grain boundary diffusion). We believe that the effect of Si on sintering behaviour can be treated in terms of its segregation to grain boundaries, the phenomenon arising from a lattice instability of Si‐HAp due to the charge compensation in the course of aliovalent doping.
Deposition of functionalized calcium phosphate nanoparticles on functionalized polymer surfaces
Authors: Urch H. , Geismann C. , Ulbricht M. , Epple M.
Published: June 2006

Calcium phosphate nanoparticles were functionalized using two polymeric additives: polyallylamine hydrochloride, PAH, giving them a positive charge, and polyacrylic acid, PAA, giving them a negative charge. These particles were deposited on surface‐functionalized polymers (polyethylene terephthalate track‐etch membranes; PET) by dip‐coating. If the charge of the nanoparticles and the charge of the polymer membrane had an opposite sign, efficient adsorption was observed, whereas on unfunctionalized polymer surfaces, no adsorption occurred.
The skeleton and pharyngeal teeth of zebrafish (Danio rerio) as a model of biomineralization in vertebrates
Authors: Neues F. , Arnold W. H. , Fischer J. , Beckmann F. , Gaengler P. , Epple M.
Published: June 2006

Zebrafish (Danio rerio) has become one of the most common models for genetics, and developmental research in the biosciences. Synchrotron radiation micro computer tomography (SRμCT), scanning electron microscopy, polarized light microscopy, and energy‐dispersive X‐ray analysis were applied to visualize the biomineralization in teeth and bones in high spatial resolution.
In vitro pH‐controlled calcification of biological heart valve prostheses
Authors: Krings M. , Kanellopoulou D. , Mavrilas D. , Glasmacher B.
Published: June 2006

Background: Bioprosthetic heart valves still suffer from calcification. In the department of Cryobiology & Biomaterials, we have established an in vitro calcification test method which is suitable for the investigation of calcification patterns of heart valves. In a modified test protocol we use the pH‐dependency of the calcification process to control and stabilise the process by keeping the calcification ions more constant than in the established test protocol. Methods: Five glutaraldehyde‐fixed porcine heart valve bioprostheses underwent accelerated dynamic in vitro calcification individually. Three valves were tested according to the established test protocol. Two valves were studied with the new pH‐controlled loop system. pH drop was used as an index for the consumption of the calcification ions. The degree of calcification was determined by means of μX‐ray (high resolution x‐ray on mammography machine), conventional and micro computer tomography (CT, μ‐CT). Results: We determined the average degree of calcification after 12 million cycles. The value was calculated to be 12 % vs. 67 % (established vs. pH‐controlled group) using μX‐ray (2D), 3 % vs. 16 % using CT, and 3 % vs. 33 % using μ‐CT. Conclusion: A new faster and more potent in vitro calcification method has been developed. Optimisation of this pH‐controlled method in order to implement an additional direct calcification ion concentration control is under construction.
Synthesis and characterization of DNA‐functionalized calcium phosphate nanoparticles
Authors: Sokolova V. , Prymak O. , Meyer‐Zaika W. , Cölfen H. , Rehage H. , Shukla A. , Epple M.
Published: June 2006

Calcium phosphate nanoparticles were prepared by precipitation from aqueous solution. A stable colloid was formed by coating with DNA. The properties of the colloidal dispersion can be adjusted by variation of the inorganic nanoparticles. In particular, the partial substitution of calcium by magnesium or aluminum led to stable dispersions of nanoparticles. By a multi‐step precipitation process, it is also possible to include DNA into the particles in order to protect it from intracellular biochemical degradation. The dispersions were analyzed by dynamic light scattering, zeta potential measurements, analytical ultracentrifugation, and transmission electron microscopy.
Numerical computation of the porosity of bone substitution materials from synchrotron micro computer tomographic data
Authors: Vanis S. , Rheinbach O. , Klawonn A. , Prymak O. , Epple M.
Published: June 2006

Different porous bone substitution materials were studied by synchrotron micro computer tomography (SRμCT). The digital data were analyzed with respect to the geometrical parameters of the samples, i.e., porosity, specific surface, and connectivity of the pores. For most samples (both from natural and synthetic sources), there is a truly interconnecting porosity, i.e., topologically, they contain only one single pore.
Magnesium‐substituted hydroxyapatite ceramics
Authors: Zyman Z. , Tkachenko M. , Epple M. , Polyakov M. , Naboka M.
Published: June 2006

The effect of the addition of magnesium (up to 10 wt%, expressed as MgO) on the phase composition, the microstructure and the mechanical properties of hydroxyapatite‐based ceramics (HA) was studied by X‐ray powder diffraction, infrared spectroscopy, scanning electron microscopy, and mechanical testing. Doping with magnesium did not change the crystal lattice of HA but, due to an isomorphous substitution of Mg2+for Ca2+, it caused a decrease in the average grain size, an increase of microporosity, a removal of the texture, and the formation of a weak intergranular boundary. The transcrystallite fracture pattern of pure HA was changed to a predominantly intercrystallite one. This resulted in a decrease in density (down to 2.93 g cm‐3), in microhardness (down to 400 MPa), in compressive strength (down to 190 MPa) and in improved plastic properties of the material (increasing the fracture toughness$ K_{1_C} $up to 2.7 MPa m1/2, close to that of the bone). It is interesting that the$ K_{1_C} $increase could be only observed for a small concentration of additives (up to 1 wt%), i.e. close to the Mg concentration in natural bone mineral.
Needs and trends for biomaterials and biodevices in oral and maxillofacial surgery
Authors: Muster D. , Meyer C.
Published: June 2006

The evolution of the devices used for the fracture fixation is now oriented toward the bioresorbable materials (PLA, PGA, PDX) which should gradually replace the metallic materials (titanium, SS) in the next 10‐15 years. The osteosynthesis devices will have to fulfil more precise biomechanical criteria, in certain anatomical zones (i.e. trapezoidal plates for the mandibular condyle).

The most known TMJ prostheses are either definitive prostheses (no more available on the European market, only in the American market) or temporary condylar prostheses. In this field the lag compared with the orthopaedics is certainly over 20 years. Very few biomechanical studies have been performed and there is few interest from the industrials in Europe for this type of prostheses because of the small number of cases and the scarcity of the indications.

Numerous materials of all classes have been tried as bone substitutes but all are lacking of osteoinductivity and therefore combined materials are largely studied. Actually, in maxillofacial surgery, the most used materials are HA, TCP, Coral eventually enriched with growth factors. Concerning tissue engineering, nice models are elaborated in various laboratories in the world but huge difficulties remain regarding the optimal molecular environment and the biomechanical functionality.
O‐phospho‐L‐serine modified calcium phosphate cements – material properties, in vitro and in vivo investigations
Authors: Reinstorf A. , Hempel U. , Olgemöller F. , Domaschke H. , Schneiders W. , Mai R. , Stadlinger B. , Rösen‐Wolff A. , Rammelt S. , Gelinsky M. , Pompe W.
Published: June 2006

One of the most important requirements for calcium phosphate bone cements (CPBC) is remodelling in vivo. Degradation of the artificial material and the formation of native new bone matrix have to interdigitate to avoid instability. The remodelling process should not last longer than one year. In this study a CPBC was modified with O‐phospho‐L‐serine (phosphoserine) to improve the material properties in order to speed up remodelling in vivo. The results showed that the modified cements exhibit a nano‐crystalline microstructure with a high specific surface area and increased compressive strength (about 50 %). Metabolic activity of osteoblasts was improved on the modified material. Monocytes were found to be highly activated on the cements containing phosphoserine. In addition the formation of multinucleated giant cells (osteoclast‐like cells) was not impaired on phosphoserine modified cement composites. In vivo experiments in Wistar rats and mini pigs clearly revealed that phosphoserine modified cements showed a higher capability of remodelling compared to the cements without phosphoserine.
A novel synthetic vascular prosthesis: effect of plasma protein adsorption on blood‐ and cyto‐compatibility
Authors: Knetsch M.L.W. , Aldenhoff Y.B.J. , Hanssen H.H.L. , Koole L. H.
Published: June 2006

The development of a genuinely functional small diameter vascular prosthesis remains one of the toughest problems in biomedical engineering. Most current small diameter vascular grafts fail because of thrombotic complications or neo‐intimal hyperplasia. Here were present a novel synthetic vascular prosthesis with a polymer coated luminal surface. The coating can be tuned for its hydrophilicity by varying the molar ratio of the monomers, N‐vinyl‐pyrrolidinone and butyl‐methacrylate. Additionally these polymeric coatings can be loaded with anticoagulant drugs, like heparin. Especially surface exposed heparin dramatically improved blood‐compatibility of the coating, reducing thrombin generation. For long‐term functionality of vascular prostheses, formation of an endothelial cell layer is vital. In vitro, the hydrophobic coatings in particular supported formation of an endothelial cell layer. Upon adsorption of blood plasma proteins, endothelial cells grew equally well on all surfaces, irrespective of the hydrophilicity. It was found that high density lipoprotein (HDL) is responsible for transforming hydrophilic coatings into good cell‐compatible surfaces. Furthermore, HDL can reduce surface‐induced thrombin generation and therefore can be used to modify the lumen of a vascular prosthesis.
Bioavailability and genotoxicity of soluble and particulate nickel compounds in cultured human lung cells
Authors: Schwerdtle T. , Hartwig A.
Published: June 2006

Nickel compounds are well known human and animal carcinogens, but the carcinogenic potential depends largely on the actual species. Within the present study, water soluble nickel chloride and poorly water soluble nickel oxide were compared with respect to uptake, intracellular distribution and genotoxicity as determined by the induction of DNA strand breaks and DNA base modifications recognized by the bacterial formamidopyrimidine DNA glycosylase (Fpg). The results show that both compounds were taken up by A549 cells. Furthermore, both compounds increase the nickel content in the nucleus and the cytoplasm yielding concentration ratios nucleus/cytoplasm of up to 0.18 and >0.5 for NiCl2 and black NiO, respectively. Also, the induction of DNA lesions was evident for water soluble and particulate nickel(II), even though pronounced effects were restricted to cytotoxic concentrations. Thus, it is proposed that nickel ions appear to be the ultimate species exerting both direct and indirect genotoxicity. The higher carcinogenic potential of particulate nickel(II) may thus be due to much longer retention times in vivo, not to different mechanisms of action on the cellular level.
The influence of foreign ions on the crystal lattice of hydroxyapatite upon heating
Authors: Zyman Z. , Rokhmistrov D. , Ivanov I. , Epple M.
Published: June 2006

The influence of foreign ions on the crystal lattice of hydroxyapatite (precipitated from aqueous solution by a conventional method at 96 °C with a given ratio of Ca/P=1.67:1) was studied during heating in air in the temperature range of 25‐1250 °C. The lattice constants decreased to those of stoichiometric hydroxyapatite by a complex dependence during heating. This dependence was correlated to a simultaneous release of gaseous products. These products resulted from the decomposition of foreign ions which were incorporated into the hydroxyapatite lattice during precipitation, i.e. ammonium, nitrate and carbonate. Stoichiometric hydroxyapatite with correct lattice constants was obtained at 1100 °C. Further heating to 1250 °C resulted in only minor changes in the lattice characteristics.
Anti‐infective surfaces based on tetraether lipids for peritoneal dialysis catheter systems
Authors: Frant M. , Stenstad P. , Johnsen H. , Dölling K. , Rothe U. , Schmid R. , Liefeith K.
Published: June 2006

To prevent bacterial growth on silicone catheters and other medical devices a new coating concept based on covalent immobilisation of a group of bipolar membrane spanning tetraether lipids from archaebacterium Thermoplasma acidophilum was developed. A lipophilic layer with optional further functionality was introduced to the surface of commercially available medical silicone elastomer slides and tubes. Physico‐chemical characterisation of the different surface modified polymers represents the basis for the optimisation of the monomolecular coatings. The new tetraether lipid coated catheter surfaces showed a successful reduction of bacterial adherence associated with an excellent biocompatibility.
Regulation of leukocyte adhesion molecules by leukocyte/biomaterial‐conditioned media: A study with calcium‐phosphate‐coated and non‐coated NiTi‐shape memory alloys
Authors: Köller M. , Esenwein St. A. , Bogdanski D. , Prymak O. , Epple M. , Muhr G.
Published: June 2006

To evaluate the role of soluble mediators released after interaction of leukocytes with biomaterials on cells of the implant microenvironment, the surface expression of adhesion molecules (CD11b, CD62L, CD66b, ICAM‐1) on freshly isolated whole blood leukocytes (WBL) was analyzed by flow cytometry after incubation in leukocyte/nickel‐titanium shape‐memory alloy (NiTi‐SMA)‐conditioned media. NiTi‐SMA samples were either coated with calcium phosphate by dipping in oversaturated calcium phosphate solution (CaP‐coating) or were non‐coated. Peripheral blood mononuclear cells (PBMC) and polymorphonuclear neutrophil leukocytes (PMN) were isolated and seeded on both samples to generate respective conditioned media. In comparison with conditioned media obtained by non‐coated NiTi‐SMA, the expression of CD11b, CD66b, and ICAM‐1 on WBL was upregulated by conditioned media obtained from CaP‐coated samples. In contrast, the expression of CD62L on WBL was decreased after incubation in conditioned medium obtained from CaP‐coated NiTi‐samples compared to non‐coated NiTi. These data demonstrate the possible influence of released mediators elicited by leukocyte‐biomaterial interactions on cells of the implant microenvironment.
The impact of nanocolloidal wear‐particles on human mononuclear cells
Authors: Podleska L. E. , Weuster M. , Dose E. , Kühne Chr. A. , Nast‐Kolb D. , Ruchholtz St. , Taeger G.
Published: June 2006

This article investigates the effects of metallic wear‐medium prepared from 316L stainless steel and titanium alloy (TiAl6V4) in vitro. Wear was generated by a tribometer, under sterile conditions, disc‐on‐pin submersed in cell culture medium. Wear medium was separated into a particle fraction (>200 nm) and a nanocolloidal fraction (< 200 nm). A standardized cell culture model was employed using isolated mononuclear cells from peripheral human blood cells were incubated with increasing amounts of wear medium containing particles or nanocolloids. Vitality was assayed using MTT and inflammatory reactions were measured by TNF‐α ELISA. In a second step wear‐medium was aged over two weeks in an incubator to simulate passivation of the implant / particle surfaces.

Dose dependant toxic reactions induced by nanocolloids from titanium alloy and even more from stainless steel were identified with the vitality decreasing to 50 % compared to untreated cells. Nanocolloids did not induce inflammatory effects. Particles had no apparent toxic effects on cells. On the other hand, particles from titanium alloy induced a higher secretion of TNF‐α in the supernatants than 316L.

Aged nanocolloids lost their toxic potential, but aged particles did still show a strong inflammatory reaction with titanium alloy being the stronger inflammatory agent.

This study demonstrates that particles from titanium alloy can not be assumed as to be an inert biomaterial. In fact, titanium alloy particles induced a stronger inflammatory reaction rather than stainless steel. We conclude that both particles and nanocolloids show specific interactions with mononuclear cells in a sense of toxicity and inflammation. Furthermore, it seems to be of great importance to critically consider fabrication processes and age of particles used for cell culture settings in future research.
Inflammation in white matter: Clinical and pathophysiological aspects
Authors: Pleasure David , Soulika Athena , Singh Sunit K. , Gallo Vittorio , Bannerman Peter
Published: June 2006

While the central nervous system (CNS) is generally thought of as an immunopriviledged site, immune‐mediated CNS white matter damage can occur in both the perinatal period and in adults, and can result in severe and persistent neurological deficits. Periventricular leukomalacia (PVL) is an inflammatory white matter disease of premature infants that frequently results in cerebral palsy (CP). Clinical and experimental studies show that both hypoxic/ischemic and innate immune mechanisms contribute to the destruction of immature oligodendroglia and of axons in the deep cerebral white matter in PVL. No data are yet available as to whether there is any genetic predisposition to PVL or to its neurological sequelae. Multiple sclerosis (MS) is an inflammatory white matter disease that often begins in young adulthood, causes multifocal destruction of mature oligodendroglia and of axons, and eventually leads to substantial cumulative neurological disability. Certain genetic polymorphisms contribute to susceptibility to MS, and adaptive immune responses to myelin‐associated self antigens, or to exogenous antigens that mimic these self antigens, play a central role in the pathophysiology of this disease. MRDD Research Reviews 2006;12:141–146. © 2006 Wiley‐Liss, Inc.
The Yin and Yang of cell cycle progression and differentiation in the oligodendroglial lineage
Authors: Nguyen Laurent , Borgs Laurence , Vandenbosch Renaud , Mangin Jean‐Marie , Beukelaers Pierre , Moonen Gustave , Gallo Vittorio , Malgrange Brigitte , Belachew Shibeshih
Published: June 2006

In white matter disorders such as leukodystrophies (LD), periventricular leucomalacia (PVL), or multiple sclerosis (MS), the hypomyelination or the remyelination failure by oligodendrocyte progenitor cells involves errors in the sequence of events that normally occur during development when progenitors proliferate, migrate through the white matter, contact the axon, and differentiate into myelin‐forming oligodendrocytes. Multiple mechanisms underlie the eventual progressive deterioration that typifies the natural history of developmental demyelination in LD and PVL and of adult‐onset demyelination in MS. Over the past few years, pathophysiological studies have mostly focused on seeking abnormalities that impede oligodendroglial maturation at the level of migration, myelination, and survival. In contrast, there has been a strikingly lower interest for early proliferative and differentiation events that are likely to be equally critical for white matter development and myelin repair. This review highlights the Yin and Yang principles of interactions between intrinsic factors that coordinately regulate progenitor cell division and the onset of differentiation, i.e. the initial steps of oligodendrocyte lineage progression that are obviously crucial in health and diseases. MRDD Research Reviews 2006;12:85–96. © 2006 Wiley‐Liss, Inc.
Astrocytes and developmental white matter disorders
Authors: Sen Ellora , Levison Steven W.
Published: June 2006

There is an increasing awareness that the astrocytes in the immature periventricular white matter are vulnerable to ischemia and respond to inflammation. Here we provide a synopsis of the articles that have evaluated the causes and consequences of developmental brain injuries to white matter astrocytes as well as the consequences of several genetic mutations that result in abnormal astrocyte development. Emerging data suggest that the astrocytes are not simply responding to the injury but are likely victims as well as culprits. Given the important roles that astrocytes play in maintaining ionic, neurotransmitter, and metabolic homeostasis in the brain, a more thorough understanding of the mechanisms that lead to their incapacitation, demise, or reactions as well as a better understanding of the stimuli that regulate their neuroprotective and regenerative properties will enable these cells to be manipulated to preserve the integrity of white matter and to potentially provide therapeutics to enhance neonatal regeneration and recovery from brain injury. MRDD Research Reviews 2006;12:97–104. © 2006 Wiley‐Liss, Inc.
Perinatal white matter injury: The changing spectrum of pathology and emerging insights into pathogenetic mechanisms
Authors: Back Stephen A.
Published: June 2006

Perinatal brain injury in survivors of premature birth has a unique and unexplained predilection for periventricular cerebral white matter. Periventricular white‐matter injury (PWMI) is now the most common cause of brain injury in preterm infants and the leading cause of chronic neurological morbidity. The spectrum of chronic PWMI includes focal cystic necrotic lesions (periventricular leukomalacia; PVL) and diffuses myelination disturbances. Recent neuroimaging studies support that the incidence of PVL is declining, whereas focal or diffuse noncystic injury is emerging as the predominant lesion. Factors that predispose to PVL during prematurity include hypoxia, ischemia, and maternal–fetal infection. In a significant number of infants, PWMI appears to be initiated by perturbations in cerebral blood flow that reflect anatomic and physiological immaturity of the vasculature. Ischemic cerebral white matter is susceptible to pronounced free radical‐mediated injury that particularly targets immature stages of the oligodendrocyte lineage. Emerging experimental data supports that pronounced ischemia in the periventricular white matter is necessary, but not sufficient to generate PWMI. The developmental predilection for PWMI to occur during prematurity appears to be related to both the timing of appearance and regional distribution of susceptible oligodendrocyte progenitors. Injury to oligodendrocyte progenitors may contribute to the pathogenesis of PWMI by disrupting the maturation of myelin‐forming oligodendrocytes. Chemical mediators that may contribute to white‐matter injury include reactive oxygen species glutamate, cytokines, and adenosine. As our understanding of the pathogenesis of PWMI improves, it is anticipated that new strategies for directly preventing brain injury in premature infants will develop. MRDD Research Reviews 2006;12:129–140. © 2006 Wiley‐Liss, Inc.
Canavan disease: A white matter disorder
Authors: Kumar Shalini , Mattan Natalia S. , de Vellis Jean
Published: June 2006

Breakdown of oligodendrocyte‐neuron interactions in white matter (WM), such as the loss of myelin, results in axonal dysfunction and hence a disruption of information processing between brain regions. The major feature of leukodystrophies is the lack of proper myelin formation during early development or the onset of myelin loss late in life. These early childhood WM diseases are described as hypomyelination or dysmyelination arising from a primary block in normal myelin synthesis because of a genetic mutation expressed in oligodendrocytes, or failure in myelination secondary to neuronal or astroglial dysfunctions (van der Knaap2001Dev. Med. Child Neurol. 43:705–712). Here, we describe the pathophysiological parameters of Canavan disease (CD), caused by genetic mutations of the aspartoacylase (ASPA) gene, a metabolic enzyme restricted in the central nervous system (CNS) to oligodendrocytes. CD presents pathophysiological dysfunctions similar to diseases caused by myelin gene mutations, such as Pelizaeus‐Merzbacher disease (PMD) and several animal models, such as myelin deficient rat (md), jimpy (jp), shiverer (sh), and quaking (qk viable) mutant mice. These single gene mutations have pleiotropic effects, whereby the alteration of one myelin gene expression disrupts functional expression of other oligodendrocyte genes with an outcome of hypomyelination/dysmyelination. Among all of the known leukodystrophies, CD is the first disorder, which was approved and tested for the adeno‐associated virus vector (AAV)‐ASPA gene therapy (Leone et al.2000Ann. Neurol. 48:27–38; Janson et al.2001Trends Neurosci. 24:706–712) without much success following the first two attempts.ASPAgene delivery attempts in animal models have shown a lowering ofN‐acetylL‐aspartate and a change in motor functions, while sponginess of the WM, a characteristic of CD remained unchanged (Matalon et al.2003Mol. Ther. 7 (5, Part 1):580–587; McPhee et al.2005Brain Res. Mol. Brain Res. 135:112–121) even with better viral serotype and delivery of the gene during early phase of development (Klugmann et al.2005Mol. Ther. 11:745–753). While different approaches are being sought for the success of gene therapy, there are pivotal developmental questions to address regarding the specific regions of the CNS and cell lineages that become the target for the onset and progression of CD symptoms from early to late stages of development. © 2006 Wiley‐Liss, Inc. MRDD Research Reviews 2006;12:157–165.