bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure Ionization of Atoms in Plasmas
Authors: Ebeling W. , Richert W.
Published: July 2007

It is shown that the main physical reason leading to the ionization of the atoms in plasmas at high densities (pressures) is the Pauli exclusion principle for the electrons which is responsible for the big spatial extension of atoms. Especially for the example of hydrogen the theory is extended to include those effects. Spatial and energetic variants for the definition of the species atom are discussed. The quantum theory of bound states in plasmas is compared with the classical theory of ion association in electrolytes.
Estimation of the Current Density in Cathode Arc Spots
Authors: Hantzsche E.
Published: July 2007

Probable values of the (averaged) current density j in cathode arc spots are calculated using simple physical models of relevant processes. From six independent estimations results (in case of clean copper cathodes): j=(10 ± 5) · 107 A/cm2, possibly somewhat more.
Energy Selecting Action of Limiters on Particle Fluxes Penetrating into the SOL‐Plasma
Authors: Hildebrandt D.
Published: July 2007

A simple model of the penetration of particle effluxes from the core plasma into the SOL‐plasma of tokamaks is proposed. The assumptions made are free streaming of particles parallel to the magnetic field and anomalous particle transport perpendicular to the toroidal field with a constant radial velocity. The model has been proved for measured particle fluxes of Li which was injected into the core plasma of the tokamak T‐10. The dependence of the Li‐particle flux on the minor radius as well as toroidal asymmetries in the SOL‐plasma can be explained by the results of the calculations.
Effects of Higher‐Order Terms on the Nonlinear Propagation of Electron Acoustic Waves
Authors: Sarma S. N. , Kalita M. K. , Bujarbarua S.
Published: July 2007

The contribution of higher‐order terms on the nonlinear propagation of electron acoustic waves has been investigated, using the reductive perturbation technique. A modified KdV equation for the first order perturbed potential and a linear inhomogeneous equation for the second order perturbed potential have been derived. The soliton width and amplitude have been calculated.
Diagnostics of Pulsed Discharge Plasma in Electrolyte
Authors: Radovanov S. B. , Tripković M. R. , Holclajtner‐Antunović I. D.
Published: July 2007

Two experimental methods are applied to determine electron temperature: the method of calculating temperature from the slope of the continuum's relative intensity, and the Boltzmann plot of the relative line intensity of oxygen OII, in a pulsed discharge in an electrolyte (PDE). Electron density is determined using the electron impact widths of magnesium ionic lines.
Quasi‐Classical and Classical Cross Sections for the Scattering of Electrons on the Coulomb Cut‐Off Potential
Authors: Mihajlov A. A. , Dimitrijević M. S. , Djordjević D. , Luft M. , Kraeft W. D.
Published: July 2007

The elastic scattering of electrons on the cut‐off Coulomb potential Uc(r) = −1/r + 1/rc, for r ≦ rc and Uc(r) = 0, for r > rc, has been considered. It has been shown that for ε > 0.5/rc (ε is the energy of free electrons in atomic units) the analytical quasi‐classical expressions describe quite well the behaviour of transport, differential and total cross sections for elastic scattering. It has been shown moreover, that in the energy range considered, transport cross section could be determined with practically the same accuracy already by means of classical, analytical expressions. Born approximations show larger deviations from exact quantum calculations.
Gravitational Instability of Fluid of Finite Electrical and Thermal Conductivity Flowing through Porous Medium
Authors: Vaghela D. S. , Chhajlani R. K.
Published: July 2007

In view of the importance of porosity in astrophysical context the problem of gravitational instability of fluid of finite electrical and thermal conductivity flowing through porous medium is studied. Equations of the problem are stated and from them linearized perturbation equations are derived. Dispersion relations are obtained and Jeans' criterion of instability is discussed taking properties of the medium in different combinations for parallel and perpendicular directions to the magnetic field. Thermal conductivity modifies the Jeans' expression. Magnetic field and porosity of the medium also modify the Jeans' expression in case of wave propagation in perpendicular direction to the magnetic field but finite electrical conductivity neutralizes the effect of porosity on Jeans' criterion of instability.
Electron Kinetics in the Cathode Region of a Glow Discharge and in Hollow Cathodes
Authors: Valentini H.‐B.
Published: July 2007

On the basis of an improved cascade model a multi‐group theory for studying the electron kinetics in the cathode region of a glow discharge and in hollow cathodes is developed. The secondary electrons newly created by ionization are taken into account. The electrons are divided in groups with respect to the interval where they were created or where they made an inelastic collision. The inelastic collisions and the forward scattering are assumed to dominate. The mean energies of two neighbouring groups are taken to be different by the ionization energy or by parts of it. For the flux densities of the various electron groups a set of ordinary first order differential equations and corresponding boundary conditions are obtained and solved for He. These formulae are valid for any electric potentials. The results relatively well agree with those of Monte Carlo simulations. The first Townsend ionization coefficient differs substantially from that resulting from the Townsend formula. The velocity distribution function spatially varies and contains several groups of fast electrons. Using the detour factor the angular scattering can be included in the calculations.
Comparative Studies of the Exchange‐Correlation Potential Formulas for Coulomb Systems
Authors: Stolzmann W. , Rösler M.
Published: July 2007

The exchange‐correlation part (xc) to the free energy is numerical evaluated in the RPA at arbitrary degree of degeneracy. The results are compared with numerical data of easy‐to‐use analytic fit‐formulas or Padé approximants of the xc‐term. All together results show very high accuracy at extremly high densities (rs ≈ 1). The agreements disappear between the several formulas for increasing Brueckner parameter rs. Numerical results for the xc‐potentials (pressure and chemical potential) at finite temperatures for an electron‐ion system are given. The xc‐part of the ground state energy of our electron‐ion model is compared with the ground state energy for metallic hydrogen and with Monte‐Carlo calculations.
Partial Cross Sections for Dissoziative Ionization of Fluorinated Compounds by Electron Impact
Authors: Poll H. U. , Meichsner J.
Published: July 2007

Ionization cross sections of fragment ions of CF4, C2F6, C3F8, n‐C4F10, C2F4, 1‐C4F8, SiF4, COF2. CHF3 were determined in dependence on electron energy up to 125 eV by means of a quadrupol mass spectrometer. Tails at the low energy part of the characteristics are interpreted as a result of kinetic energy depending on molecular weight of fragments. Parent ions are only detected for chemically unsaturated compounds showing characteristic curves of ionization efficiency. Total cross sections obey the additive rule.
Muscle development in a biphasic animal: The frog
Authors: Elinson Richard P.
Published: July 2007

Knowledge of muscle development in a vertebrate reflects strengths of the particular model system. For example, the origin of mesoderm is very well characterized in Xenopus laevis, where development of somites is less well understood. The major problem in muscle development, presented by frogs, is the complete replacement of larval muscles by adult muscles at thyroid hormone–dependent metamorphosis. All tail muscles die, all leg muscles form de novo, and muscles in the jaw and trunk show both processes. The nature of adult muscle progenitors remains unclear. Comparison of X. laevis development with divergent amphibian patterns, such as direct developers, which lack the larval tadpole, should highlight important steps in adult muscle formation. Developmental Dynamics 236:2444–2453, 2007. © 2007 Wiley‐Liss, Inc.
Robust CD4+ and CD8+ T cell responses to SIV using mRNA‐transfected DC expressing autologous viral Ag
Authors: Melhem Nada M. , Liu Xiang Dong , Boczkowski David , Gilboa Eli , Barratt‐Boyes Simon M.
Published: July 2007

A potentially powerful strategy for therapeutic HIV vaccination is the use of DC transfected with mRNA encoding autologous viral Ag, as epitopes presented by transfected DC would exactly reflect those expressed by infected cells in the individual. Using human and rhesus macaque monocyte‐derived DC, we show that nucleofection is a superior method for mRNA transfection, resulting in high‐level protein expression and DC maturation. DC transfected with SIV gag isolated from an infected monkey stimulated robust Ag‐specific recall T cell responses of similar magnitude to those induced by peptide‐pulsed PBMC that were predominantly CD8+ T cell mediated. Enhanced CD4+ T cell responses were stimulated when Gag was redirected into the lysosomal pathway via the targeting signal derived from lysosome‐associated membrane protein‐1 (LAMP‐1). Rhesus DC transfected with lysosome‐targeted gag encoding an escape mutation in an immunodominant CTL epitope stimulated CD4+ and CD8+ T cell responses of almost equivalent magnitude directed towards undefined epitopes outside of the mutated region. Finally, gag‐transfected DC from SIV‐infected monkeys stimulated significant Ag‐specific recall T cell responses in an entirely autologous system. These findings demonstrate that mRNA‐transfected DC expressing SIV Ag derived from infected monkeys stimulate broad and relevant T cell responses, supporting this approach for therapeutic HIV vaccine development.
MGL‐mediated internalization and antigen presentation by dendritic cells: A role for tyrosine‐5
Authors: van Vliet Sandra J. , Aarnoudse Corlien A. , Broks‐van den Berg Venice C. M. , Boks Martine , Geijtenbeek Teunis B. H. , van Kooyk Yvette
Published: July 2007

Professional antigen‐presenting cells are essential for the initiation of adaptive immune responses; however, they also play a vital role in the maintenance of tolerance towards self‐antigens. C‐type lectins can function as antigen receptors by capturing carbohydrate ligands for processing and presentation. Here, we focused on the dendritic cell (DC)‐expressed macrophage galactose‐type lectin (MGL), a C‐type lectin with a unique specificity for terminal GalNAc residues, such as the tumor‐associated Tn antigen. Soluble model antigens are efficiently internalized by MGL and subsequently presented to responder CD4+ T cells. The tyrosine‐5 residue in the YENF motif, present in the MGL cytoplasmic domain, was essential for the MGL‐mediated endocytosis in CHO cells. In conclusion, MGL contributes to the antigen processing and presentation capacities of DC and may provide a suitable target for the initiation of anti‐tumor immune responses.
Acetate inhibits NFAT activation in T cells via importin β1 interference
Authors: Ishiguro Kazuhiro , Ando Takafumi , Maeda Osamu , Ohmiya Naoki , Niwa Yasumasa , Goto Hidemi
Published: July 2007

Acetate is a principal short chain fatty acid produced by bacterial fermentation in the colon and a major end product of alcohol metabolism. In the present study, we assessed the effects of acetate on T cell activation and found that acetate inhibited NFAT activation but not NF‐κB activation. Moreover, acetate impaired the nuclear translocation of NFAT but not that of NF‐κB. Unlike cyclosporin A (CsA), acetate did not affect the dephosphorylation of NFAT and calcineurin activity. Acetate impaired the binding of NFAT to importin β1, which is involved in NFAT nuclear translocation. NFAT is a critical transcription factor in cytokine and early response gene expression in activated T cells. Agents targeting NFAT such as CsA are used to suppress harmful immune responses in inflammatory diseases. Therefore, we also evaluated the efficacy of acetate in murine models of inflammatory diseases, and found that acetate administration (as well as administration of dexamethasone) attenuated trinitrobenzenesulfonic acid‐induced colitis and dinitrofluorobenzene‐induced dermatitis. These findings indicate for the first time that acetate inhibits NFAT activation by interfering with the interaction between NFAT and importin β1 in T cells and that acetate can potentially act as an anti‐inflammatory agent.
(Arene)ruthenium(II) Complexes Containing Substituted Bis(pyrazolyl)methane Ligands – Catalytic Behaviour in Transfer Hydrogenation of Ketones
Authors: Carrión M. Carmen , Jalón Félix A. , Manzano Blanca R. , Rodríguez Ana M. , Sepúlveda Francisco , Maestro Miguel
Published: July 2007

A new and safer methodology has been developed for the synthesis of bis(pyrazol‐1‐yl)methane ligands (NN). Several ligands containing different phenyl groups on the central carbon atom have been obtained. Ruthenium derivatives of the type [Ru(arene)Cl(NN)]BPh4 (arene = benzene, p‐cymene) have been synthesised using these ligands. One or two isomers that differ regarding the axial or equatorial disposition of the phenyl group on the metallacycle have been obtained. Their formation is rationalised by considering steric effects. The structures of five derivatives were determined by X‐ray diffraction. In four complexes the phenyl substituent is in the axial disposition of the metallacycle and in one case in the equatorial orientation. The dihedral angle formed by the planes of the two pyrazole rings is always bigger for the complexes containing unsubstituted pyrazolyl heterocycles. The behaviour of the new derivatives in the transfer hydrogenation of benzophenone in the presence of KOH was studied. The benzene derivatives showed higher activity than the p‐cymene complexes. A marked and positive effect of the methyl groups on the pyrazolyl rings was observed. The effect of the substituents on the benzyl carbon atom was also important. It has been observed that the benzophenone hydrogenation was possible without the addition of complexes. The effect of the KOH concentration was evaluated and a concentration that leads to negligible conversion in a base‐only process was chosen. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Controlled Chemical Reduction of Uranyl Salts into UX4(MeCN)4 (X = Cl, Br, I) with Me3SiX Reagents
Authors: Berthet Jean‐Claude , Siffredi Gérald , Thuéry Pierre , Ephritikhine Michel
Published: July 2007

UO2I2(thf)3 or UO2(OTf)2 are easily reduced by Me3SiX (X = Cl, Br, I) in acetonitrile into the tetravalent UX4(MeCN)4 complexes, which are useful precursors in uranium chemistry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Kinetics and Magnetism of Phosphane Diadducts of Diruthenium(II,III) Tetraacetate
Authors: Burchell Tara J. , Cameron T. Stanley , Macartney Donal H. , Thompson Laurence K. , Aquino Manuel A. S.
Published: July 2007

The kinetic parameters for the axial‐ligand‐substitution reactions of [Ru2(μ‐O2CCH3)4(MeCN)2]+ in acetonitrile (MeCN) with PCy3 and PCy2Ph (Cy = cyclohexyl and Ph = phenyl) were investigated under pseudo first‐order conditions of excess phosphane. The rate‐determining formation of [Ru2(μ‐O2CCH3)4(MeCN)(PCy2R]+ appears independent of the nature of the incoming phosphane with an average k1 (25.0 °C) = (1.25 ± 0.06) × 103 M–1 s–1. A dissociatively activated mechanism is proposed for substitution of the axially coordinated acetonitrile, and the rate parameters are compared to earlier measurements carried out on [Rh2(μ‐O2CCH3)4(MeCN)2]. Variable‐temperature magnetic susceptibility measurements were carried out on the two phosphane diadducts, [Ru2(μ‐O2CCH3)4(PCy3)2]PF6, (1) and [Ru2(μ‐O2CCH3)4(PCy2Ph)2]PF6 (2), and showed behaviour unique to a Boltzmann distribution of states over the temperature range 2–300 K. To support the magnetic measurements, the single‐crystal X‐ray structure of 1 was redetermined at various temperatures down to –150 °C and showed a distinct decrease in the Ru–Ru bond length with decreasing temperature, consistent with a σ2π4δ2π*3 configuration at low temperature (ground state) and a σ2π4δ2π*2δ*1 configuration at room temp. In addition, the structure redeterminations of 1 were better resolved than the earlier reported structure and also corrected a minor error in that the molecule of solvation was found to be 1,2‐dichloroethane instead of dichloromethane. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Exploration of meso‐Substituted Formylporphyrins and Their Grignard and Wittig Reactions
Authors: Dahms Katja , Senge Mathias O. , Bakar M. Bakri
Published: July 2007

Formylporphyrins were prepared by using either the 1,3‐dithian‐2‐yl residue as a precursor for the CHO group or by the Vilsmeier reaction. Two synthetic routes for the introduction of the 1,2‐dithian‐2‐yl group were explored. Furthermore, reactions of the 1,3,5‐trithian‐2‐yl group with porphyrins were examined as well as spirobisdithiane derivatives as precursors for the ultimate assembly of porphyrin spirobisdithanyl‐linked bioconjugates. The obtained formylporphyrins were reacted with organomagnesium or organophosphorus compounds. A series of hydroxyporphyrins resulting from the Grignard reaction of 5,15‐substituted porphyrins were synthesised in high yields. Several porphyrins with unsaturated residues introduced by the Wittig reaction were obtained in moderate yields. The less sterically hindered 5,15‐substituted porphyrins show increased reactivity and give higher yields; their reaction products are higher in stability relative to other porphyrin systems.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Activity and Reaction Mechanism of the Initial Enzymatic Step Specifying the Microbial Degradation of 2,4‐Dichlorophenoxyacetate
Authors: Müller R. H.
Published: July 2007

The capability of Delftia acidovorans MC1010 (SdpA+, RdpA–) to degrade the herbicides 2,4‐dichlorophenoxyacetate (2,4‐D) and 4‐chloro‐2‐methylphenoxyacetate (MCPA) was investigated in batch degradation experiments and interpreted in the light of the catalytic activity of the initial enzyme SdpA, an α‐ketoglutarate‐dependent dioxygenase, catalyzing the cleavage of the ether bond. Dense inocula of this strain degraded high initial 2,4‐D concentrations quickly to below the detection limit. The specific degradation rate became slower and the degradation remained incomplete when low initial biomass concentrations and/or 2,4‐D concentrations were used. With low initial 2,4‐D concentrations, the degradation rate became nearly concentration‐independent. This effect was less pronounced with MCPA, a substrate that is more readily degraded by SdpA than 2,4‐D. (S)‐2‐(2,4‐dichlorophenoxy)propionate ((S)‐2,4‐DP), the favored substrate of SdpA used as comparison, was almost completely utilized under the various conditions. The observed differences were attributed to the easier regeneration of the essential co‐substrate α‐ketoglutarate with MCPA and above all (S)‐2,4‐DP as a substrate compared to 2,4‐D. Decreasing SdpA activity, which was observed during the starvation of MC1010, will contribute to the apparent recalcitrance of 2,4‐D. Degradation of 2,4‐D by Bradyrhizobium sp. RD5‐C2, a strain initiating 2,4‐D cleavage by a monooxygenase not requiring an organic intermediate as a co‐substrate, proceeded to completion despite the approximately 20‐fold lower degradation rates compared to those obtained with strain MC1010. However, lowering of biomass concentrations resulted in restricted degradation also with strain RD5‐C2. The results were discussed in terms of the kind of co‐substrate in the cleavage reaction, the availability of essential intracellular metabolites, and the cells' maintenance demands.
Development of a Pilot Plant Facility for the Conversion of Renewables in Biotechnological Processes
Authors: Venus J. , Richter K.
Published: July 2007

The experience of recent years has shown that a swift transfer of new biotechnological processes into practice often fails due to the lack of a reference facility that can be used for multiple applications. Besides the basic research there is a need for investigations at different scales from the laboratory to the industrial scale. The construction of a pilot plant facility for the production of lactic acid at the Leibniz Institute for Agricultural Engineering Potsdam‐Bornim (ATB) consequently fills a gap in the various phases of bioprocess engineering from applied fundamental via application research to the launch of biotechnological processes in practice. An example of a biorefinery is presented, which produces 10 t lactic acid in 200 days per year. The steps of project development from the idea and concept up to the planning and installation of the plant are described. First results for the manufacture of lactic acid from rye wholemeal illustrate the conformity with existing investigations. Further research may lead to an increase in the long‐term stability of the fermentation and to an adaptation of the process to the demands of product quality. The availability of product samples should familiarize interested partners in industry with the specific product requirements and win them as cooperation partners for research projects.
A Halophilic and Osmotolerant Azospirillum brasilense Strain from Algerian Soil Restores Wheat Growth under Saline Conditions
Authors: Nabti E. , Sahnoune M. , Adjrad S. , Van Dommelen A. , Ghoul M. , Schmid M. , Hartmann A.
Published: July 2007

A new bacterial isolate (NH) from salt‐affected soil was identified as Azospirillum brasilense using phenotypic analyses and 16S rDNA‐based phylogeny. This isolate showed resistance towards 3,4‐dehydroproline and optimal growth at 200 mmol/L NaCl, tolerating salt stress of 300 mmol/L NaCl in the absence of osmoprotectants and up to 600 mmol/L NaCl in the presence of glycine betaine and Ulva lactuca extracts. This effect was enhanced with extracts of the marine algae Ulva lactuca. A. brasilense strain NH can produce auxin indole acetic acid under saline conditions. The hypothesis was tested that the inoculation of this osmotolerant rhizosphere strain could improve the growth of wheat under saline stress conditions. Normal wheat growth was restored in the presence of both 150 mmol/L and 200 mmol/L NaCl after inoculation with A. brasilense NH. Under saline conditions, its effect of promoting plant growth of wheat was significantly superior to that of A. brasilense Sp7, the non‐halotolerant type strain. A. brasilense NH restored wheat growth at elevated salt concentrations in pot and field experiments even better in the presence of osmoprotective Ulva lactuca extracts.
Dynamics of Benzene and Toluene Degradation in Pseudomonas putida F1 in the Presence of the Alternative Substrate Succinate
Authors: Rüegg I. , Hafner T. , Bucheli‐Witschel M. , Egli T.
Published: July 2007

In batch and continuous culture, the regulation of benzene and toluene degradation by Pseudomonas putida F1 was investigated in the presence of the alternative carbon and energy source succinate. In batch culture, benzene and toluene were used simultaneously, whereas succinate suppressed benzene consumption under carbon excess conditions resulting in diauxic growth. In carbon‐limited continuous culture mixed substrate growth was observed. Since in nature low substrate concentrations and ever changing conditions prevail, this paper focuses on the dynamics of benzene/toluene degradation, biomass synthesis, and the regulation of benzene/toluene‐degrading enzymes in cultures growing continuously at a dilution rate of 0.1 h–1, when shifting the supply of the carbon and energy source from succinate to various mixtures of succinate and benzene/toluene, or to benzene only. When the succinate concentration was kept constant (1.25 mM) and the medium was supplemented with benzene (2 mM), growth with benzene began already two hours after the shift. In contrast, replacing succinate with benzene only led to a wash out of biomass for more then ten hours, before biomass production from benzene started. A striking and reproducible transition pattern was observed for all shifts where the succinate concentration was reduced or succinate was omitted. After an initial period of biomass production from benzene, the culture collapsed and a wash‐out of biomass was observed. However, this wash‐out was not accompanied by an increase in benzene in the cultivation liquid, indicating a benzene uptake without conversion into biomass. Another possibility is that in phases of low biomass concentrations, cells were only able to use the low amounts of benzene/toluene dissolved in the cultivation liquid yielding low biomass concentrations whereas in phases of high biomass concentrations, they were able to rapidly utilize the aromatic solvents so that additional benzene from the gas phase diffused into the cultivation liquid resulting in more biomass production. In most cases, growth resumed again after 10 to 80 h. Currently, the reasons for the decrease in biomass after the first rise are unknown. However, several indications rule out intoxication of the cells by either the solvents benzene or toluene themselves, or by toxic degradation intermediates, or by‐products.
Parosteal osteosarcoma: Case report and review of the literature
Authors: Hewitt Kim M. , Ellis Gary , Wiggins Richard , Bentz Brandon G.
Published: July 2007

Background.

The majority of osteosarcoma cases of the head and neck are high‐grade lesions. We present a case and discuss the diagnostic and therapeutic implications of a rare low‐grade parosteal osteosarcoma of the maxilla.

Methods.

A 32‐year‐old man presenting to the Head and Neck Surgical Oncology clinic with a 1‐year history of a firm palatal mass. Evaluation clinically and radiographically raised the suspicion of an osteosarcoma.

Results.

A partial maxillectomy revealed a parosteal osteosarcoma with negative margins. No adjuvant therapy was recommended, and the patient remains without evidence of local recurrence after 3 years.

Conclusions.

Parosteal osteosarcomas of the head and neck region are rare, low‐grade variants of osteosarcoma, but have the potential to recur with simple local excision. Clinical and radiographic features are diagnostically helpful. Definitive diagnosis comes from histopathology, and wide local resection should be employed as the optimal treatment. © 2007 Wiley Periodicals, Inc. Head Neck, 2008
Results of a pilot study of the effects of celecoxib on cancer cachexia in patients with cancer of the head, neck, and gastrointestinal tract
Authors: Lai Victor , George Jonathan , Richey Luther , Kim Hong J. , Cannon Trinitia , Shores Carol , Couch Marion
Published: July 2007

Background.

Animal models suggest that cyclooxygenase‐2 (COX‐2) inhibitors may be beneficial in suppressing cancer cachexia. We investigated the effect of short‐course celecoxib on body composition, inflammation, and quality of life (QOL) in patients with cancer cachexia in a phase II clinical pilot trial.

Methods.

Eleven cachectic patients with head and neck or gastrointestinal cancer were randomly assigned to receive placebo or celecoxib for 21 days while awaiting the initiation of cancer therapy. Body composition, resting energy expenditure, QOL, physical function, and inflammatory markers were measured on days 1 and 21.

Results.

Patients receiving celecoxib experienced statistically significant increases in weight and body mass index (BMI), while patients receiving placebo experienced weight loss and a decline in BMI. Patients receiving celecoxib also had increases in QOL scores.

Conclusions.

Cachectic patients receiving celecoxib gained weight, experienced increased BMI, and demonstrated improved QOL scores. Compliance was good and no adverse events were seen. © 2007 Wiley Periodicals, Inc. Head Neck, 2008
Alginate/lactose‐modified chitosan hydrogels: A bioactive biomaterial for chondrocyte encapsulation
Authors: Marsich Eleonora , Borgogna Massimiliano , Donati Ivan , Mozetic Pamela , Strand Berit L. , Salvador Santiago Gomez , Vittur Franco , Paoletti Sergio
Published: July 2007

A new bioactive scaffold was prepared from a binary polysaccharide mixture composed of a polyanion (alginate) and a polycation (a lactose‐modified chitosan, chitlac). Its potential use for articular chondrocytes encapsulation and cartilage reconstructive surgery applications has been studied. The hydrogel combines the ability of alginate to act as a 3D supporting structure with the capability of the second component (chitlac) to provide interactions with porcine articular chondrocytes. Physico‐chemical characterization of the scaffold was accomplished by gel kinetics and compression measurements and demonstrated that alginate‐chitlac mixture (AC‐mixture) hydrogels exhibit better mechanical properties when compared with sole alginate hydrogels. Furthermore, biochemical and biological studies showed that these 3D scaffolds are able to maintain chondrocyte phenotype and particularly to significantly stimulate and promote chondrocyte growth and proliferation. In conclusion, the present study can be considered as a first step towards an engineered, biologically active scaffold for chondrocyte in vitro cultivation, expansion, and cell delivery. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Reduced medical infection related bacterial strains adhesion on bioactive RGD modified titanium surfaces: A first step toward cell selective surfaces
Authors: Maddikeri R.R. , Tosatti S. , Schuler M. , Chessari S. , Textor M. , Richards R.G. , Harris L.G.
Published: July 2007

Ideally, implants should inhibit nonspecific protein adsorption, bacterial adhesion, and at the same time, depending on the final application be selective toward cellular adhesion and spreading for all or only selected cell types. Poly(L‐lysine)‐grafted‐poly(ethylene glycol) (PLL‐g‐PEG) polymers have been shown to adsorb from aqueous solution onto negatively charged metal oxide surfaces, reducing protein adsorption as well as fibroblast, osteoblast and epithelial cell adhesion significantly. PLL‐g‐PEG can be functionalized with bioligands such as RGD (Arg‐Gly‐Asp), which then restores host cell adhesion, but the surface remains resistant to nonspecific protein adsorption. Previously, it was also shown that both nonfunctionalized PLL‐g‐PEG and RGD‐peptide functionalized PLL‐g‐PEG reduced the adhesion of Staphylococcus aureus to titanium (Ti) surfaces. The present study looked at the effect of other implant associated infection relevant bacteria, Staphylococcus epidermidis, Streptococcus mutans and Pseudomonas aeruginosa towards the same surface chemistries. The different surfaces were exposed to the bacteria for 1–24 h, and bacteria surface density was evaluated using scanning electron microscopy (SEM) and fluorescence light microscopy (FM). The adhesion of all bacteria strains tested was reduced on Ti surfaces coated with PLL‐g‐PEG compared to uncoated Ti surfaces even in the presence of RGD. The percentage reduction in bacterial adhesion over the 24‐h culture time investigated was 88%–98%, depending on the bacteria type. Therefore, coating surfaces with PLL‐g‐PEG/PEG‐RGD allows cells such as fibroblasts and osteoblasts to attach but not bacteria, resulting in a selective biointeractive pattern that may be useful on medical implants. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Characterization of polyelectrolyte multilayer films on polyethylene terephtalate vascular prostheses under mechanical stretching
Authors: Rinckenbach Simon , Hemmerlé Joseph , Dieval Florence , Arntz Youri , Kretz Jean‐Georges , Durand Bernard , Chakfe Nabil , Schaaf Pierre , Voegel Jean‐Claude , Vautier Dominique
Published: July 2007

Layer‐by‐layer (LBL) polyelectrolyte films offer extensive potentials to enhance surface properties of vascular biomaterials. From the time of implantation, PET prostheses are continuously subjected to multiple mechanical stresses such as important distorsions and blood pressure. In this study, three LBL films, namely (1) poly(sodium 4‐styrenesulfonate)/poly(allylamine hydrochloride), (2) poly(L‐lysine)/hyaluronan, and (3) poly(L‐lysine)/poly(L‐glutamic acid) were built on to isolated PET filaments, thread, and vascular prostheses. The three LBL films uniformly covered the surface of the PET samples with rough, totally smooth, and “wrinkled” appearances respectively for (PAH/PSS)24, (PLL/HA)24, and (PLL/PGA)24 systems. We then assessed the behavior of these LBL films, in an aqueous environment [by environmental scanning electronic microscopy (ESEM)], when subjected to unidirectional longitudinal stretches. We found that stretching induces ruptures in the multilayer films on isolated filaments for longitudinal stretches of 14% for (PSS/PAH)24, 13% for (PLL/PGA)24, and 30% for (PLL/HA)24 films. On threads, the rupture limit is enhanced to be respectively 26, 20, and 28%. Most interestingly, we found that on vascular prosthesis no rupture is visible in any of the three multilayers types, even for elongations of 200% (200% undergone by the PET prostheses is representative of those encountered during graft deployment) which by far exceeds elongations observed under physiological conditions (10–20%, blood pressure). In term of mechanical behaviors, these preliminary data constitute a first step toward the possible use of LBL film to coat and functionalize vascular prosthesis. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Magnetic targeting after femoral artery administration and biocompatibility assessment of superparamagnetic iron oxide nanoparticles
Authors: Ma Hui‐Li , Qi Xian‐Rong , Ding Wu‐Xiao , Maitani Yoshie , Nagai Tsuneji
Published: July 2007

Ferrofluids are attractive candidates for magnetic targeting system because of their fluidity and magnetism. The magnetic nanoparticles in ferrofluids should have combined properties of superparamagnetic behavior, target localization, and biocompatibility. The magnetic targeting and biocompatibility of superparamagnetic iron oxide nanoparticles stabilized by alginate (SPION‐alginate) was investigated in vitro and in vivo. The localization of SPION‐alginate by an external magnetic field in vitro was quantitatively evaluated by determining the iron content, and the results revealed that the localization ratio of SPION‐alginate was 56%. Magnetic targeting of the SPION‐alginate after femoral artery administration with the magnetic field in rats was quantitatively investigated by iron content and qualitatively confirmed by histological evaluation and magnetic resonance imaging. The ratio of iron content between the target site and the nontarget site were 8.88 at 0.5 h and 7.50 at 2 h, respectively. The viability of RAW264.7 cells and L929 cells was apparently unaltered upon exposure to SPION‐alginate. The incubation with erythrocytes indicated that the SPION‐alginate did not induce erythrocytes hemolysis and aggregation. In conclusions, the SPION‐alginate had magnetic targeting with an external magnetic field and did not be detained at the injection site without the magnetic field. The SPION‐alginate was generally considered to be biocompatible in cytotoxicity and hemolysis aspects. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Acute oral toxicity evaluation of biodegradable and pH‐sensitive hydrogel based on polycaprolactone, poly(ethylene glycol) and methylacrylic acid (MAA)
Authors: Chen Xian , Qian ZhiYong , Gou MaLing , Chao GuoTao , Zhang YangDe , Gu YingChun , Huang MeiJuan , Wang JiWei , Pan YiFeng , Wei YuQuan , Chen JianPing , Tu MingJing
Published: July 2007

In this article, a novel biodegradable and pH‐sensitive hydrogel based on polycaprolactone, poly(ethylene glycol) and methylacrylic acid (MAA), was prepared by UV‐initiated free radical polymerization. The obtained hydrogel was characterized by 1H NMR and FTIR. The acute toxicity tests and histopathological study were performed in BALB/c mice. In acute oral toxicity test, mice were orally administered with a total 15 g/kg body weight (b.w.) of P(CL‐MAA‐EG) hydrogels, and were observed continuously for 14 days. For histopathologic study, samples including heart, liver, lung, kidneys, spleen, stomach, and intestine, were histochemically prepared and stained with hematoxylin‐eosin for histopathologic examination. No mortality or significant signs of acute toxicity was observed during the whole observation period, and no macroscopic alteration was found in the organs. Histopathological analysis of various organs also did not show any significant pathological changes. Thus, the maximal tolerance dose of P(CL‐MAA‐EG) hydrogels was calculated to be higher than 15 g/kg b.w. in BALB/c mice. It was suggested that the studied P(CL‐MAA‐EG) hydrogel in this article were nontoxic after acute oral administration and it might be a promising candidate as a novel oral drug carrier. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
A study on polysialic acid as a biomaterial for cell culture applications
Authors: Stark Yvonne , Bruns Stephanie , Stahl Frank , Kasper Cornelia , Wesemann Maike , Grothe Claudia , Scheper Thomas
Published: July 2007

Polysialic acid (PSA) was investigated for its applicability as coating material for mammalian cell cultivation. PSA is involved in post‐translational modification of the vertebrate neural cell adhesion molecule (NCAM). It is biocompatible and degradation‐controlled. Thus, it becomes interesting for use as a coating and scaffold material for tissue engineering applications, especially for peripheral nerve regeneration. As a preliminary study of the use of PSA as scaffold material it was tested in its soluble form as coating material. The cytotoxicity was investigated and compared to another polysaccharide β‐glucan, to widely used coating substances (collagen I, poly‐L‐lysine, hyaluronic acid) and uncoated tissue culture plastic material. The interactions between the modified cell culture surface and the cells were investigated using a model liver cell line Hep‐G2 and a neurobiological cell line PC‐12. The PSA coating itself was analyzed by immunoanalysis. Viability of the cells was investigated by the MTT assay. The number and distribution of adhered cells were studied by cell nuclei staining. Furthermore, the differentiation status of the PC‐12 cells was monitored, as well as glucose and lactate levels in the cell culture medium from the Hep‐G2 cells. Comparable viability and similar numbers of attached cells were observed. Growth in cell clusters was observed for PSA, β‐glucan, and hyaluronic acid coated materials. In general, the results indicate that PSA is comparable to other well‐established coating materials (e.g. collagen I, hyaluronic acid, and poly‐L‐lysine). Moreover, as a key substance in vertebrate development it offers interesting features for nerve regeneration, especially as an insoluble, modified scaffold material. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
In vitro biological evaluation of β–TCP/HDPE—A novel orthopedic composite: A survey using human osteoblast and fibroblast bone cells
Authors: Homaeigohar S. SH. , Shokrgozar M. A. , Khavandi A. , Sadi A. Yari
Published: July 2007

Beta‐tricalcium phosphate reinforced high density polyethylene (β‐TCP/HDPE) was prepared to simulate bone composition and to study its capacity to act as bone tissue. This material was produced by replacing the mineral component and collagen soft tissue of the bone with β‐TCP and HDPE, respectively. The biocompatibility of the composite samples with different volume fractions of TCP (20, 30 and 40 vol %) was examined in vitro using two osteoblast cell lines G‐292 and Saos‐2, and also a type of fibroblast cell isolated from bone tissue, namely human bone fibroblast (HBF) by proliferation, and cell adhesion assays. Cell‐material interaction with the surface of the composite samples was examined by scanning electron microscopy (SEM). The effect of β‐TCP/HDPE on the behavior of osteoblast and fibroblast cells was compared with those of composite and negative control samples; polyethylene (PE) and tissue culture polystyrene (TPS), respectively. In general, the results showed that the composite samples containing β‐TCP as reinforcement supported a higher rate of proliferation by various bone cells after 3, 7, and 14 days of incubation compared to the composite control sample. Furthermore, more osteoblast cells were attached to the surface of the composite samples when compared to the composite control samples after the above incubation periods (p < 0.05), while in the case of HBF an equal or even higher number of cells adhered to PE was observed. The number of adhered osteoblast cells was almost equal and in some days even higher than the number of adhered cells on negative control sample, while in the case of fibroblast this difference was significantly higher than TPS (p < 0.05). Adhered cells presented a normal morphology by SEM and many of the cells were observed to be undergoing cell division. These findings indicate that β‐TCP/HDPE composites are biocompatible, nontoxic, and act to stimulate proliferation and adhesion of the cells, whether osteoblast or fibroblast. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Relationship between tissue stiffness and degree of mineralization of developing trabecular bone
Authors: Mulder Lars , Koolstra Jan Harm , den Toonder Jaap MJ , van Eijden Theo MGJ
Published: July 2007

It is unknown how the degree of mineralization of bone in individual trabecular elements is related to the corresponding mechanical properties at the bone tissue level. Understanding this relationship is important for the comprehension of the mechanical behavior of bone at both the apparent and tissue level. The purpose of the present study was, therefore, to determine the tissue stiffness and degree of mineralization of the trabecular bone tissue and to establish a relationship between these two variables. A second goal was to assess the change in this relation during development. Mandibular condylar specimens of four fetal and four newborn pigs were used. The tissue stiffness was measured using nanoindentation. A pair of indents was made in the cores of 15 trabecular elements per specimen. Subsequently, the degree of mineralization of these locations was determined from microcomputed tomography. The mean tissue stiffness was 11.2 GPa (±0.5 GPa) in the fetal group and 12.0 GPa (±0.8 GPa) in the newborn group, which was not significantly different. The degree of mineralization of the fetal trabecular cores was 744 mg/cm3 (±28 mg/cm3). The one in the newborn bone measured 719 mg/cm3 (±34 mg/cm3). Again, the difference was statistically insignificant. A significant relationship between tissue stiffness and degree of mineralization was obtained for fetal (R = 0.42, p < 0.001) and newborn (R = 0.72, p < 0.001) groups. It was concluded that woven bone tissue in fetal and newborn trabecular cores resembles adult trabecular bone in terms of tissue properties and is strongly correlated with degree of mineralization. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Cotton wool‐like nanocomposite biomaterials prepared by electrospinning: In vitro bioactivity and osteogenic differentiation of human mesenchymal stem cells
Authors: Schneider Oliver D. , Loher Stefan , Brunner Tobias J. , Uebersax Lorenz , Simonet Marc , Grass Robert N. , Merkle Hans P. , Stark Wendelin J.
Published: July 2007

The present study evaluates the in vitro biomedical performance of an electrospun, flexible, and cotton wool‐like poly(lactide‐co‐glycolide) (PLGA)/amorphous tricalcium phosphate (ATCP) nanocomposite. Experiments on in vitro biomineralization, applicability in model defects and a cell culture study with human mesenchymal stem cells (hMSC) allowed assessing the application of the material for potential use as a bone graft. Scaffolds with different flame made ATCP nanoparticle loadings were prepared by electrospinning of a PLGA‐based composite. Immersion in simulated body fluid showed significant deposition of a hydroxyapatite layer only on the surface of ATCP doped PLGA (up to 175% mass gain within 15 days for PLGA/ATCP 60:40). Proliferation and osteogenic differentiation of hMSC on different nanocomposites were assessed by incubating cells in osteogenic medium for 4 weeks. Proper adhesion and an unaffected morphology of the cells were observed by confocal laser scanning microscopy for all samples. Fluorometric quantification of dsDNA and analysis of ALP activity revealed no significant difference between the tested scaffolds and excluded any acute cytotoxic effects of the nanoparticles. The osteocalcin content for all scaffolds was 0.12–0.19 ng/ng DNA confirming osteogenic differentiation of human mesenchymal stem cells on these flexible bone implants. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
Thermal reactions of brushite cements
Authors: Bohner M. , Gbureck U.
Published: July 2007

The thermal reactions of a brushite cement made of β‐tricalcium phosphate (β‐TCP), monocalcium phosphate monohydrate (MCPM), and an aqueous solution were followed in situ with an isothermal calorimeter at 37°C. The investigated parameters were the β‐TCP/MCPM weight ratio, the liquid‐to‐powder ratio, the synthesis route and milling duration of the β‐TCP powder, as well as the presence of sulfate, citrate, and pyrophosphate ions in the mixing liquid. The thermograms were complex, particularly for mixtures containing an excess of MCPM or additives in the mixing solution. Results suggested that the endothermic MCPM dissolution and the highly exothermic β‐TCP dissolution occurred simultaneously, thereby leading to the formation of a large exothermic peak at early reaction time. Both reactions were followed by the exothermic crystallization of brushite and in the presence of an excess of MCPM by the endothermic crystallization of monetite. Additives generally widened the main exothermic reaction peak, or in some cases with pyrophosphate ions postponed the main exothermic peak at late reaction time. Generally, the results could be well explained and understood based on thermodynamic and solubility data. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008
Uniaxial and biaxial properties of terminally sterilized porcine urinary bladder matrix scaffolds
Authors: Freytes Donald O. , Stoner Richard M. , Badylak Stephen F.
Published: July 2007

Scaffolds composed of extracellular matrix have been successfully used to support the reconstruction of a variety of tissues in preclinical studies and in clinical applications. As an off‐the‐shelf product, extracellular matrix (ECM) scaffolds must be subjected to terminal sterilization before use. The choice of sterilization method may alter the integrity of the ECM's composition and structure such that the mechanical and material properties are adversely affected. The present study evaluated selected structural properties of an ECM scaffold derived from the urinary bladder termed urinary bladder matrix after being sterilized by three different methods: ethylene oxide (ETO) (750 mg/h for 16 h), gamma irradiation (2.0 Mrads), or electron beam irradiation (e‐beam) (2.2 Mrads). The structural properties that were evaluated include maximum force, maximum elongation, maximum tangential stiffness, energy dissipation, and ball‐burst strength. All sterilization methods affected at least two of the measured properties. ETO was shown to have the least detrimental effect upon the measured properties. Gamma and e‐beam irradiation were shown to decrease the uniaxial and biaxial strength, maximum tangential stiffness, and the energy dissipation of the ECM scaffolds. The present study showed that the choice of terminal sterilization method affects the structural properties of scaffolds composed of extracellular matrix. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008