bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative studies for the effect of dual‐ and mono‐organic modifiers on the physical properties of polyimide‐clay nanocomposite membranes
Authors: Lai Mei‐Chun , Jang Guang‐Way , Chang Kung‐Chin , Hsu Sheng‐Chieh , Hsieh Ming‐Fa , Yeh Jui‐Ming
Published: April 2008

In this study, a series of nanocomposite membranes consisted of organic polyimide and organo‐modified clay were successfully prepared by an in situ polymerization through thermal imidization reactions using a dual‐ (i.e., CTAB/melamine) and mono‐organic modifier as swelling agent of clay mineral. A sequential comparative study was performed to investigate the effect of various feeding ratios of dual‐ and mono‐organic modifiers on the physical properties of as‐prepared samples. The as‐synthesized nanocomposite membranes were subsequently characterized by WAXRD and TEM. It should be noted that all the nanocomposite membranes prepared from a dual‐organic modifier system exhibited a better dispersion of silicate layers in PI matrices as compared with that of mono‐organic modifier system. Comparative studies for the effect of various feeding ratios of dual‐ and mono‐organic modifiers on the thermal stability, mechanical strength, molecular barrier properties, and optical clarity of PI‐clay nanocomposite membranes were performed with measurements of TGA, DSC, DMA, GPA, VPA, and UV–visible transmission spectroscopy, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A novel process to develop modified polymeric surfaces for the analysis of bacterial adhesion: Surface properties and adhesion test
Authors: Anjum N. , Bellon‐Fontaine M.‐N. , Herry J.‐M. , Riquet A.‐M.
Published: April 2008

Surface of polypropylene (PP) sheets were modified by radiation induced graft polymerization of a mixture of two monomers, a quaternary ammonium salt ([2‐(methacryloyloxy)ethyl]‐trimethyl ammonium chloride) (QAS) and acrylic acid(AA) to control the bacterial adhesion. Electron beam radiation was used to activate PP sheets prior to the grafting reaction. Depth concentration profile of nitrogen on modified PP up to 10 nm was performed by XPS. However, XPS has revealed no significant changes in the concentration profile of nitrogen for the grafted PP prepared under different parameters. Energetic characteristics (Lifshitz‐van der Waals (γLW), electron acceptor (γ+), and electron donor (γ−) components) of these modified surfaces (with different ratio of comonomer mixtures) were calculated by using contact angle measurements. The PP surfaces prepared under one specific ratio of comonomer mixture (AA : QAS) 20 : 40 (M‐4) has been compared with the surfaces modified with 20% AA (AA‐20) and 40% QAS (QAS‐40). The surface charge and isoelectric point have been determined by zeta potential measurements. AA‐20 and comonomer mixture modified PP (M‐4) surfaces exhibit negative charges of −27 and −16, respectively, while QAS‐40 modified PP surfaces show positive charge of +16. The physicochemical properties of Listeria monocytogenes (LM) were obtained by microbial adhesion to solvent method. Finally, adhesion of LM on unmodified and modified PP surfaces was observed by electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Using COC as pharmaceutical or cosmetic storage material. II. Effect of electron beam radio‐sterilization
Authors: Saunier J. , Aymes Chodur C. , Leclerc B. , Larbes L. , Yagoubi N.
Published: April 2008

This study was performed on cycloolefin materials. These polymers are more and more used in the cosmetic and pharmaceutical fields. Samples were subjected to an electron beam radio‐sterilization. Different irradiation doses ranging from 25 to 150 kGy were used to study the irradiation effect on the structure and properties of the material. In this study, we were mainly interested in additive degradation, and in the modification of polymer thermomechanical properties, as elasticity, glass transition temperature, and swelling ability. Although the modification of the polymer chains was important, effect on thermomechanical properties was quite weak. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of water on Bombyx mori regenerated silk fibers and its application in modifying their mechanical properties
Authors: Plaza Gustavo R. , Corsini Paola , Pérez‐Rigueiro José , Marsano Enrico , Guinea Gustavo V. , Elices Manuel
Published: April 2008

The effect of water on regenerated silkworm silk fibers has been studied and compared with that of water on natural silkworm silk fibers. Regenerated fibers are spun from an N‐methylmorpholine‐N‐oxide (NMMO) fibroin solution through a wet‐spinning process, leading to fibers with two distinct tensile behaviors, labeled as brittle and ductile, respectively. Regenerated fibers show a significant contraction when immersed in water. Contraction increases further after drying. In contrast, natural silkworm silk fibers show a negligible contraction when submerged in water. Regenerated fibers tested in water are considerably more compliant than samples tested in air, though their stiffness and tensile strength are significantly reduced. It has been shown that the tensile properties of brittle regenerated fibers can be modified by a wet‐stretching process, which consists of deforming the fiber while immersed in water. Regenerated wet‐stretched fibers always show a ductile behavior independent from their initial tensile behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Properties of reactive hot melt polyurethane adhesives with acrylic polymer or macromonomer modifications
Authors: Jung Jin Su , Kim Jae Hoon , Kim Min Seok , Jeong Han Mo , Kim Yong Sung , Kim Tae Kyoon , Hwang Jeong Mi , Lee Sang Yun , Cho Yang Lae
Published: April 2008

The properties of reactive hot melt polyurethane adhesives (RHAs) modified by dihydroxyl‐terminated reactive acrylic macromonomers were examined and compared with those of RHAs modified with a nonreactive commercial acrylic copolymer. The melt viscosity and initial bond strength was increased when a portion of the polyols and tackifier was replaced by macromonomers or acrylic copolymers, which have higher glass transition temperatures. When RHA was modified by macromonomer, the storage modulus at low shear rate was reduced and set time was increased, which suggests that the chain entanglement was diminished by short‐chain branches created by the macromonomers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and characterization of fluorescent polymer magnetic particles
Authors: Baharvand H.
Published: April 2008

Magnetic iron oxide (maghemite, Fe3O4) particles were encapsulated with fluorescent polymer phase. The resulting fluorescent magnetic polymer particles were characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimeter analysis (TGA), reflection optical microscopy, differential scanning calorimeter (DSC), Fritsch particle sizer, scanning electron microscopy (SEM), powder X‐ray diffractometer (XRD), and vibrating sample magnetometer (VSM) measurements. FTIR and XRD confirmed the presence of iron oxide in polymer phase. The TGA and DSC measurements indicated that the magnetic polymer particles have more than 50% iron oxide content and high thermal stability. SEM and reflection optical microscopy under UV light revealed that all maghemite particles were embedded in the polymer spheres and have fluorescent characteristics. The size‐distribution analysis of prepared magnetic particles was shown that the means diameter of the particles slightly increased. According to our magnetometry data, shape of the loops evidences the ferromagnetic character of the material and no evidence of superparamagnetism was seen. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of Platensimycin Analogues and Their Antibiotic Potency
Authors: Krauss Jürgen , Knorr Veronika , Manhardt Vera , Scheffels Stefanie , Bracher Franz
Published: April 2008

Platensimycin is a natural product isolated from various strains of Streptomyces platensis which exhibits antimicrobial activity against Gram positive bacteria, including vancomycin‐ and linezolide‐resistant species. Analogues of platensimycin were synthesized from 3‐aminobenzoic acid or other aniline derivatives and several alkyl‐ and aryl‐carboxylic acids. The resulting compounds were tested in an agar diffusion assay against several bacteria and fungi.
Unanticipated Acyloxymethylation of Sumatriptan Indole Nitrogen Atom and its Implications in Prodrug Design
Authors: Rodrigues Tiago , Moreira Rui , Guedes Rita C. , Iley Jim , Lopes Francisca
Published: April 2008

Sumatriptan is a potent and selective 5‐HT1B and 5‐HT1D agonist used in the symptomatic treatment of migraine; it shows poor oral bioavailability ascribed, in part, to its low lipophilicity. In an attempt to develop acyloxymethyl prodrugs of sumatriptan suitable for oral administration, we carried out the reaction of sumatriptan with chloromethyl esters. To our surprise, acyloxymethylation occurred preferentially at the indole nitrogen rather than at sulfonamide nitrogen, reflecting a difference either in product stability or in the nucleophilicities of the indole and sulfonamide anions. The hydrolysis of the corresponding N1‐acyloxymethyl derivatives was studied in aqueous buffers and in human plasma, by HPLC. N1‐Acyloxymethyl derivatives of sumatriptan are rapidly hydrolysed to the chemically stable N1‐hydroxymethylsumatriptan at pH 1‐13. Slow formation of the parent drug was observed only at high pH values. Hydrolysis of sumatriptan derivatives is slower in human plasma than in phosphate buffer and also generates N1‐hydroxymethylsumatriptan rather than the parent drug. These results indicate that N1‐acyloxymethyl derivatives of sumatriptan cannot be considered as true prodrugs of sumatriptan.
Self‐Assembly of [B‐SbW9O33]9− Subunit with Transition Metal Ions (Mn2+, Cu2+, Co2+) in Aqueous Solution: Syntheses, Structures and Magnetic Properties of Sandwich Type Polyoxometalates with Subvalent SbIII Heteroatom
Authors: Wang Jing‐Ping , Ma Peng‐Tao , Li Jie , Niu Hong‐Yu , Niu Jing‐Yang
Published: April 2008

Rational self‐assembly of Sb2O3 and Na2WO4, or (NH4)18[NaSb9W21O86] with transition‐metal ions (Mn2+, Cu2+, Co2+), in aqueous solution under controlled conditions yield a series of sandwich type complexes, namely, Na2H2[Mn2.5W1.5(H2O)8(B‐β‐SbW9O33)2]⋅32 H2O (1), Na4H7[Na3(H2O)6Mn3(μ‐OAc)2(B‐α‐SbW9O33)2]⋅20 H2O (OAc=acetate anion) (2), NaH8[Na2Cu4Cl(B‐α‐SbW9O33)2]⋅21 H2O (3), Na8K[Na2K(H2O)2{Co(H2O)}3(B‐α‐SbW9O33)2]⋅ 10 H2O (4), and Na5H[{Co(H2O)2}3W(H2O)2(B‐β‐SbW9O33)2]⋅11.5 H2O (5). These structures are determined by using the X‐ray diffraction technique and further characterized by obtaining IR spectra and performing elemental analysis. Structure analysis reveals that polyoxoanions in 1 and 5 comprise of two [B‐β‐SbW9O33]9− building units, whereas 2, 3, and 4 consist of two isomerous [B‐α‐SbW9O33]9− building blocks, which are all linked by different transition‐metal ions (Mn2+, Cu2+, or Co2+) with different quantitative nuclearity. It should be noted that compound 2 represents the first one‐dimensional sinusoidal chain based on sandwich like tungstoantimonate building blocks through the carboxylate‐bridging ligands. Additionally, 3 is constructed from sandwiched anions [Na2Cu4Cl(B‐α‐SbW9O33)2]9− linked to each other to form an infinitely extended 2D network, whereas 5 shows an interesting 3D framework built up from offset sandwich type polyoxoanion [{Co(H2O)2}3W(H2O)2(B‐β‐SbW9O33)2]6− linked by Co2+ and Na+ ions. EPR studies performed at 110 K and room temperature reveal that the metal cations (Mn2+, Cu2+, Co2+) reside in a square‐pyramidal geometry in 2, 3, and 4. The magnetic behavior of 1–4 suggests the presence of weak antiferromagnetic coupling interactions between magnetic metal centers with the exchange integral J=−0.552 cm−1 in 2.
Synthesis of Novel Monodentate Phosphoramidites and Their Application in Iridium‐Catalyzed Asymmetric Hydrogenations
Authors: Erre Giulia , Junge Kathrin , Enthaler Stephan , Addis Daniele , Michalik Dirk , Spannenberg Anke , Beller Matthias
Published: April 2008

New monodentate H8‐binaphthol based phosphoramidites 6 b–i have been prepared. Starting from (S)‐3,3′‐dibromo‐5,5′,6,6′,7,7′,8,8′‐octahydro‐1,1′‐binaphthyl‐2,2′‐diol 3, a general protocol for the synthesis of ligands 6 is presented. A small ligand library bearing aryl substituents in the 3,3′‐position of the binaphthol core was synthesized and successfully tested in the iridium‐catalyzed asymmetric hydrogenation of 2‐amidocinnamates to obtain different α‐amino acid derivatives in up to 99 % ee.
Kinetically Controlled Ring‐Closing Metathesis: Synthesis of a Potential Scaffold for 12‐Membered Salicylic Macrolides
Authors: Matsuya Yuji , Takayanagi Sho‐ichi , Nemoto Hideo
Published: April 2008

For the synthesis of a 12‐membered salicylic macrolide scaffold, ring‐closing metathesis (RCM) of a ω‐diene compound was planned. The stereochemical outcome of the RCM reaction changed depending on the type of Ru catalyst that was used; a “first‐generation” Grubbs catalyst produced exclusively theEisomer and “second‐generation” catalysts provided a mixture of theEandZisomers under kinetic control (not thermodynamic control). Considerations for theE/Zselectivity are described.
Factors predicting additional disease in the axilla in patients with positive sentinel lymph nodes after neoadjuvant chemotherapy
Authors: Jeruss Jacqueline S. , Newman Lisa A. , Ayers Gregory D. , Cristofanilli Massimo , Broglio Kristine R. , Meric‐Bernstam Funda , Yi Min , Waljee Jennifer F. , Ross Merrick I. , Hunt Kelly K.
Published: April 2008

BACKGROUND.

The utility of sentinel lymph node (SNL) biopsy (SLNB) as a predictor of axillary lymph node status is similar in patients who receive neoadjuvant chemotherapy and patients who undergo surgery first. The authors of this study hypothesized that patients with positive SLNs after neoadjuvant therapy would have unique clinicopathologic factors that would be predictive of additional positive non‐SLNs distinct from patients who underwent surgery first.

METHODS.

One hundred four patients were identified who received neoadjuvant chemotherapy, had a positive SLN, and underwent axillary dissection between 1997 and 2005. At the time of presentation, 66 patients had clinically negative lymph nodes by ultrasonography, and 38 patients had positive lymph nodes confirmed by fine‐needle aspiration. Eighteen factors were assessed for their ability to predict positive non‐SLNs using chi‐square and logistic regression analysis with a bootstrapped, backwards elimination procedure. The resulting nomogram was tested by using a patient cohort from another institution.

RESULTS.

Patients with clinically negative lymph nodes at presentation were less likely than patients with positive lymph nodes to have positive non‐SLNs (47% vs 71%; P = .017). On multivariate analysis, lymphovascular invasion, the method for detecting SLN metastasis, multicentricity, positive axillary lymph nodes at presentation, and pathologic tumor size retained grouped significance with a bootstrap‐adjusted area under the curve (AUC) of 0.762. The resulting nomogram was validated in the external patient cohort (AUC, 0.78).

CONCLUSIONS.

A significant proportion of patients with positive SLNs after neoadjuvant chemotherapy had no positive non‐SLNs. The use of a nomogram based on 5 predictive variables that were identified in this study may be useful for predicting the risk of positive non‐SLNs in patients who have positive SLNs after chemotherapy. Cancer 2008. © 2008 American Cancer Society.
Completion of adjuvant radiation therapy among women with breast cancer
Authors: Srokowski Tomasz P. , Fang Shenying , Duan Zhigang , Buchholz Thomas A. , Hortobagyi Gabriel N. , Goodwin James S. , Giordano Sharon H.
Published: April 2008

BACKGROUND.

Optimal treatment for breast cancer often involves lengthy multimodality care including 5 to 6 weeks of radiotherapy, but few studies have evaluated adherence to radiotherapy outside the context of a therapeutic clinical trial.

METHODS.

Using a SEER‐Medicare database, the authors identified women age 66 years or older with Stage I to III breast cancer diagnosed between 1992 and 2002. They evaluated rates of completion of radiotherapy, defined as a minimum of 25 sessions. Multivariate logistic regression analyses were performed to determine factors associated with completion of radiotherapy, and Cox multivariate models were used to determine the impact of radiotherapy completion on local recurrence.

RESULTS.

Some 24,510 patients were included in the study. Eighty‐seven percent of patients completed 25 or more radiotherapy sessions. In multivariate logistic regression models, mastectomy (HR 1.26, 95% CI 1.10‐1.43), hospitalization during treatment (2.87, 2.49‐3.31), earlier year of diagnosis, and black race (1.36, 1.14‐1.63) were associated with increased risk of non‐completion of radiotherapy. Among 21,269 patients treated with breast conservation, incomplete radiotherapy was associated with higher risk of local recurrence. A total of 98.7% of patients who did not complete radiation therapy were free of recurrence at 5 years vs. 97.5% of patients who completed radiation therapy (HR 1.46, CI 1.09‐1.95).

CONCLUSION.

This study demonstrates relatively high rates of completion of radiation therapy among a population of older woman with breast cancer. However, those who did not complete a full course of radiotherapy had small but statistically significant higher risk of breast cancer recurrence. Future efforts should focus on intervening with women at high risk of not receiving adjuvant radiotherapy and increasing rates of radiotherapy completion. Cancer 2008. © 2008 American Cancer Society.
A mixed sensitivity method for structural damage detection
Authors: Yang Q. W.
Published: April 2008

Structural damage detection using measured dynamic data has emerged as a new research area in civil, mechanical and aerospace engineering communities in recent years. In this paper, a mixed sensitivity method is presented to identify structural damage by combining the eigenvalue sensitivity with the flexibility sensitivity. The sensitivity of structural flexibility matrix is firstly derived by Neumann series expansion and then the eigenvalue sensitivity together with the flexibility sensitivity are combined to calculate the elemental damage parameters. The presented mixed perturbation approach is demonstrated and compared with the eigenparameter sensitivity method on a 31‐bar truss structure. It has been shown that the proposed procedure is simple to implement and may be useful for structural damage identification. Copyright © 2008 John Wiley & Sons, Ltd.
Comparative study between two numerical methods for oxygen diffusion problem
Authors: Gülkaç Vildan
Published: April 2008

Two approximate numerical solutions of the oxygen diffusion problem are defined using three time‐level of Crank–Nicolson equation and Gauss–Seidel iteration for three time‐level of implicit method.

Oxygen diffusion in a sike cell with simultaneous absorption is an important problem and has a wide range of medical applications. The problem is mathematically formulated through two different stages. At the first stage, the stable case having no oxygen transition in the isolated cell is searched, whereas at the second stage the moving boundary problem of oxygen absorbed by the tissues in the cell is searched. The results obtained by three time‐level of implicit method and Gauss–Seidel iteration for three time‐level of implicit method and the results gave a good agreement with the previous methods (J. Inst. Appl. Math. 1972; 10:19–33; 1974; 13:385–398; 1978; 22:467–477). Copyright © 2008 John Wiley & Sons, Ltd.
Equilibrium Kinetics of Chemisorption Processes
Authors: Ledovskikh Alexander , Danilov Dimitry , Notten Peter H. L.
Published: April 2008

A new approach to describe the equilibrium kinetics of chemisorption is proposed. The description of the system is based on first‐principles chemical reaction kinetics and statistical thermodynamics. The rate constants are described by using a novel way of activation energy characterization. General expressions for equilibrium gas pressure isotherms and forward/backward reaction rates are obtained as a function of surface coverage. A strong influence of attraction and repulsion interaction energies between the adsorbed species on the equilibrium kinetics is found.
Short‐Range Interactions in Na Coadsorption with CO and O on Ni(111)
Authors: Politano Antonio , Agostino Raffaele G. , Formoso Vincenzo , Chiarello Gennaro
Published: April 2008

The coadsorption of Na with CO and O on Ni(111) is studied by high‐resolution electron energy loss spectroscopy. Experimental evidence for a very short‐range interaction between Na and coadsorbates is reported, in contrast with recent theoretical predictions overestimating nonlocal alkali‐induced effects. Loss spectra show distinct features, as a consequence of different local [CO]:[Na] and [O]:[Na] stoichiometries.
Early postnatal lethality and cardiovascular defects in CXCR7‐deficient mice
Authors: Gerrits Han , van Ingen Schenau Dorette S. , Bakker Nicole E.C. , van Disseldorp Ad J.M. , Strik Ankie , Hermens Laura S. , Koenen Tim B. , Krajnc‐Franken Magda A.M. , Gossen Jan A.
Published: April 2008

CXCR7 is a G‐protein coupled receptor that was recently deorphanized and shown to have SDF1 and I‐TAC as high affinity ligands. Here we describe the characterization of CXCR7‐deficient mice that were generated to further investigate the function of this receptor in vivo. Expression analysis using a LacZ reporter knockin revealed that postnatally Cxcr7 was specifically expressed in cardiomyocytes, vascular endothelial cells of the lung and heart, the cerebral cortex and in osteocytes of the bone. Adult tissues revealed high expression in cardiomyocytes and osteocytes. The observation that 70% of the Cxcr7−/− mice died in the first week after birth coincides with expression of Cxcr7 in vascular endothelial cells and in cardiomyocytes. An important role of CXCR7 in the cardiovascular system was further supported by the observation that hearts of the Cxcr7−/− mice were enlarged, showed myocardial degeneration and fibrosis of postnatal origin, and hyperplasia of embryonic origin. Despite high expression in osteocytes no apparent bone phenotype was observed, neither in combination with ovariectomy nor orchidectomy. Thus as CXCR7 does not seem to play an important role in bone our data indicate an important function of CXCR7 in the cardiovascular system during multiple steps of development. genesis 46:235–245, 2008. © 2008 Wiley‐Liss, Inc.
Fluid–structure interaction in lower airways of CT‐based lung geometries
Authors: Wall Wolfgang A. , Rabczuk Timon
Published: April 2008

In this study, the deformability of airway walls is taken into account to study airflow patterns and airway wall stresses in the first generations of lower airways in a real lung geometry. The lung geometry is based on CT scans that are obtained from in vivo experiments on humans. A partitioned fluid–structure interaction (FSI) approach, realized within a parallel in‐house finite element code, is employed. It is designed for the robust and efficient simulation of the interaction of transient incompressible Newtonian flows and (geometrically) non‐linear airway wall behavior. Arbitrary Lagrangian–Eulerian‐based stabilized tetrahedral finite elements are used for the fluid and Lagrangian‐based 7‐parametric mixed/hybrid shell elements are used for the airway walls using unstructured meshes due to the complexity of the geometry. Airflow patterns as well as airway wall stresses in the bronchial tree are studied for a number of different scenarios. Thereby, both models for healthy and diseased lungs are taken into account and both normal breathing and mechanical ventilation scenarios are studied. Copyright © 2008 John Wiley & Sons, Ltd.
Incompressible SPH simulation of water entry of a free‐falling object
Authors: Shao Songdong
Published: April 2008

In this paper an incompressible smoothed particle hydrodynamics (Incom‐SPH) model is used to simulate the interactions between the free surface flow and a moving object. Incom‐SPH method is a two‐step semi‐implicit hydrodynamic formulation of the SPH algorithm and is capable of accurately treating the free surface deformations and impact forces during the solid–fluid interactions. For a free‐falling object, its motion is tracked by an additional Lagrangian algorithm based on Newton's law to couple with the Incom‐SPH program. The developed model is employed to investigate the water entry of a free‐falling wedge. The accuracy of the computations is validated by the good agreement in predicting the relevant hydrokinematic and hydrodynamic parameters. Finally, a numerical test is performed to study the influence of spatial resolution on the water entry features. The Incom‐SPH modeling coupled with the solid–fluid interaction algorithm could provide a promising computational tool to predict the slamming problems in coastal and offshore engineering. Copyright © 2008 John Wiley & Sons, Ltd.
A coupled lattice Boltzmann model for the shallow water‐contamination system
Authors: Li Yineng , Huang Ping
Published: April 2008

A coupled numerical method for the direct simulation of shallow water dynamics and pollutant transport is formulated and implemented. The conservation equations of shallow water dynamics equations and the convection–diffusion equations are solved using the lattice Boltzmann (LB) method. The local equilibrium distribution of the pollutant has no terms of second order in flow velocity. And the relaxation time of the pollutant deviates from a constant for the flows with variable free surface water depth. The numerical tests show that this scheme strictly obeys the conservation law of mass and momentum. Excellent agreement is obtained between numerical predictions and analytical solutions in the pure diffusion problem and convection–diffusion problem. Furthermore, the influences on the accuracy of the lattice size and the diffusivity are also studied. The results indicate that the variation in the free surface water depth cannot affect the conservation of the model, and the model has the ability to simulate the complex topography problem. The comparison shows that the LB scheme has the capacity to solve the complex convection–diffusion problem in shallow water. Copyright © 2008 John Wiley & Sons, Ltd.
Microglial dystrophy in the aged and Alzheimer's disease brain is associated with ferritin immunoreactivity
Authors: Lopes Kryslaine O. , Sparks D. Larry , Streit Wolfgang J.
Published: April 2008

Degeneration of microglial cells may be important for understanding the pathogenesis of aging‐related neurodegeneration and neurodegenerative diseases. In this study, we analyzed the morphological characteristics of microglial cells in the nondemented and Alzheimer's disease (AD) human brain using ferritin immunohistochemistry. The central hypothesis was that expression of the iron storage protein ferritin increases the susceptibility of microglia to degeneration, particularly in the aged brain since senescent microglia might become less efficient in maintaining iron homeostasis and free iron can promote oxidative damage. In a primary set of 24 subjects (age range 34–97 years) examined, microglial cells immunoreactive for ferritin were found to constitute a subpopulation of the larger microglial pool labeled with an antibody for HLA‐DR antigens. The majority of these ferritin‐positive microglia exhibited aberrant morphological (dystrophic) changes in the aged and particularly in the AD brain. No spatial correlation was found between ferritin‐positive dystrophic microglia and senile plaques in AD tissues. Analysis of a secondary set of human postmortem brain tissues with a wide range of postmortem intervals (PMI, average 10.94 ± 5.69 h) showed that the occurrence of microglial dystrophy was independent of PMI and consequently not a product of tissue autolysis. Collectively, these results suggest that microglial involvement in iron storage and metabolism contributes to their degeneration, possibly through increased exposure of the cells to oxidative stress. We conclude that ferritin immunohistochemistry may be a useful method for detecting degenerating microglia in the human brain. © 2008 Wiley‐Liss, Inc.
The chemokine receptor CXCR2 is differentially regulated on glial cells in vivo but is not required for successful remyelination after cuprizone‐induced demyelination
Authors: Lindner Maren , Trebst Corinna , Heine Sandra , Skripuletz Thomas , Koutsoudaki Paraskevi N. , Stangel Martin
Published: April 2008

Unravelling the factors that can positively influence remyelination is one of the major challenges in multiple sclerosis research. Expression of the chemokine receptor CXCR2 on oligodendrocytes both in vitro and in MS lesions has suggested a possible role for CXCR2 in the recruitment of oligodendrocyte precursor cells (OPC). To investigate the function of CXCR2 during remyelination in vivo, we studied this receptor in cuprizone‐induced demyelination and subsequent remyelination. We found that CXCR2 is constitutively expressed on OPC, whereas on macrophages/microglia CXCR2 is upregulated upon activation during demyelination. Hence, the expression of CXCR2 is differentially regulated in oligodendrocytes and macrophages/microglia. Furthermore, we subjected CXCR2−/− mice to the cuprizone model demonstrating that remyelination was not altered in comparison to wildtype controls. In addition, the number of OPC and the amount of microglial accumulation were similar in both CXCR2−/− and wildtype animals during the whole demyelination and remyelination process. These results suggest that despite expression on OPC and microglia CXCR2 plays only a minor role during remyelination. © 2008 Wiley‐Liss, Inc.
Activated microglia modulate astroglial enzymes involved in oxidative and inflammatory stress and increase the resistance of astrocytes to oxidative stress in Vitro
Authors: Röhl Claudia , Armbrust Elisabeth , Kolbe Karola , Lucius Ralph , Maser Edmund , Venz Simone , Gülden Michael
Published: April 2008

Neuropathological processes in the central nervous system are commonly accompanied by an activation of microglia and astrocytes. The involvement of both cell populations in the onset and progress of neurological disorders has been widely documented, implicating both beneficial and detrimental influences on the neural tissue. Nevertheless, little is known about the interplay of these glial cell populations, especially under diseased conditions. To examine the effects of activated microglia on astrocytes purified rat astroglial cell cultures were treated with medium conditioned by purified quiescent (MCM[−]) or lipopolysaccharide (LPS)‐activated rat microglia (MCM[+]) and subjected to a comparative proteome analysis based on two‐dimensional gel electrophoresis. No significant down regulation of proteins was observed. The majority of the 19 proteins identified by means of nano HPLC/ESI‐MS/MS in the 12 most prominent protein spots significantly overexpressed (≥2‐fold) in MCM[+] treated astrocytes are involved in inflammatory processes and oxidative stress response: superoxide dismutases (Sod), peroxiredoxins, glutathione S‐transferases (Gst), nucleoside diphosphate kinase B, argininosuccinate synthase (Ass), and cellular retinol‐binding protein I (Rbp1). Sod2, Rbp1, Gstp1, and Ass were also significantly increased on the mRNA level determined by quantitative RT‐PCR. The upregulation of antioxidative enzymes in astrocytes was accompanied by a higher resistance to oxidative stress induced by H2O2. These results show that activated microglia change the expression of antioxidative proteins in astrocytes and protect them against oxidative stress, which might be an effective way to increase the neuroprotective potential of astrocytes under pathological conditions associated with oxidative stress and inflammation. © 2008 Wiley‐Liss, Inc.
Sodium signals in cerebellar Purkinje neurons and Bergmann glial cells evoked by glutamatergic synaptic transmission
Authors: Bennay Mustapha , Langer Julia , Meier Silke D. , Kafitz Karl W. , Rose Christine R.
Published: April 2008

Glial cells express specific high‐affinity transporters for glutamate that play a central role in glutamate clearance at excitatory synapses in the brain. These transporters are electrogenic and are mainly energized by the electrochemical gradient for sodium. In the present study, we combined somatic whole‐cell patch‐clamp recordings with quantitative Na+ imaging in fine cellular branches of cerebellar Bergmann glial cells and in dendrites of Purkinje neurons to analyze intracellular Na+ signals close to activated synapses. We demonstrate that pressure application of glutamate and glutamate agonists causes local Na+ signals in the mM range. Furthermore, we analyzed the pharmacological profile, as well as the time course and spatial distribution of Na+ signals following short synaptic burst stimulation of parallel or climbing fibers. While parallel fibers stimulation resulted in local sodium transients that were largest in processes close to the stimulation pipette, climbing fibers stimulation elicited global sodium transients throughout the entire cell. Glial sodium signals amounted to several mM, were mainly caused by sodium influx following inward transport of glutamate and persisted for tens of seconds. Sodium transients in dendrites of Purkinje neurons, in contrast, were mainly caused by activation of AMPA receptors and had much faster kinetics. By reducing the driving force for sodium‐dependent glutamate uptake, intracellular sodium accumulation in glial cells upon repetitive activity might provide a negative feedback mechanism, promoting the diffusion of glutamate and the activation of extrasynaptic glutamate receptors at active synapses in the cerebellum. © 2008 Wiley‐Liss, Inc.
Inhibition of Rho‐dependent pathways by Clostridium botulinum C3 protein induces a proinflammatory profile in microglia
Authors: Hoffmann Anja , Hofmann Fred , Just Ingo , Lehnardt Seija , Hanisch Uwe‐Karsten , Brück Wolfgang , Kettenmann Helmut , Ahnert‐Hilger Gudrun , Höltje Markus
Published: April 2008

Successful regeneration in the central nervous system crucially depends on the adequate environment. Microglia as brain immune‐competent cells importantly contribute to this task by producing pro‐ and anti‐inflammatory mediators. Any environmental change transforms these cells towards an activated phenotype, leading to major morphological, transcriptional and functional alterations. Rho GTPases affect multiple cellular properties, including the cytoskeleton, and C3 proteins are widely used to study their involvement. Especially C3bot from Clostridium botulinum has been considered to promote neuronal regeneration by changing Rho activity. Yet C3bot may exert cellular influences through alternative mechanisms. To determine the role of Rho‐dependent pathways in microglia we investigated the influence of C3bot on functional properties of cultivated primary mouse microglial cells. Nanomolar concentrations of C3bot transformed microglia towards an activated phenotype and triggered the release of nitric oxide and several proinflammatory cyto‐ and chemokines. These inductions were not mediated by the ROCK‐kinase pathway, since its selective inhibitors Y27632 and H1152 had no effect. C3‐induced and Rho‐mediated NO release was instead found to be under the control of NFκB, as revealed by treatment with the NFκB inhibitor PDTC. Thus, C3bot induces a proinflammatory response in microglia resembling the classical proinflammatory phenotype elicited by bacterial LPS. The findings are relevant for the use of C3bot in regenerative approaches. © 2008 Wiley‐Liss, Inc.
Prognostic impact of bcl‐2 expression on advanced nasopharyngeal carcinoma
Authors: Chen Mu‐Kuan , Lai Jui‐Chung , Chang Cheng‐Chuan , Chang Julia H. , Chang Yu‐Jun , Chen Hui‐Chuan
Published: April 2008

Background

Our aim was to evaluate the prognostic impact of bcl‐2 expression on patients with advanced nasopharyngeal carcinoma (NPC).

Methods

One hundred five patients with advanced NPC treated with high‐dose radiotherapy were included. The relationship between bcl‐2 expression, TNM stage, and disease‐specific survival was analyzed.

Results

Within the same stage III and IV, patients with negative bcl‐2 expression had better disease‐free survival. The disease‐free survival of patients with stage IV NPC with negative bcl‐2 expression was paradoxically better than that of patients with stage III NPC with positive bcl‐2 expression. In the advanced NPC, the disease‐free survival of patients with stage III cancer was better than that of patients with stage IV cancer (p = .06); in contrast, patients with bcl‐2‐positive tumors had a worse disease‐free 5‐year survival (p = .02). The Cox regression model revealed that only bcl‐2 expression was statistically significant (p = .03).

Conclusion

In advanced staged NPC, bcl‐2 expression represented an important prognostic factor. © 2008 Wiley Periodicals, Inc. Head Neck, 2008
Using multiple‐variable indicator kriging to assess groundwater quality for irrigation in the aquifers of the Choushui River alluvial fan
Authors: Jang Cheng‐Shin , Chen Shih‐Kai , Ching‐Chieh Lin
Published: April 2008

This work attempted to locate clean and safe groundwater for irrigation use in the Choushui River alluvial fan. Multiple‐variable indicator kriging (MVIK) was adopted to evaluate numerous hydrochemical parameters for a standard of water quality for irrigation in Taiwan. Many hydrochemical parameters in groundwater were distinguished into three main categories—salinity/sodium hazard, nitrogen hazard and heavy metal hazard. Safe and potential hazardous regions of groundwater for irrigation were delineated according to different probabilities estimated by MVIK. The probabilistic results of the classifications gave an opportunity to explore the spatial uncertainty of the hazards and helped government administrators establish a sound policy associated with the development and management of groundwater resources. Analysis of the results indicate that the central distal‐fan and mid‐fan aquifers are the best places to extract clean and safe groundwater for irrigation, and the deep aquifer (exceeding 200 m depth) has wider regions with clean and safe groundwater for irrigation than shallow aquifers. The northern and southern aquifers, with multiple hazards, limit groundwater use for irrigation. Although the proximal‐fan aquifer is a zone of groundwater recharge, the high nitrogen content seriously affects the environment and is not suitable for irrigation use. Copyright © 2008 John Wiley & Sons, Ltd.
The mechanical strength of collagen gels containing glycosaminoglycans and populated with fibroblasts
Authors: Saddiq Ziad A. , Barbenel Joseph C. , Grant M. Helen
Published: April 2008

Collagen gels provide a biocompatible matrix for replacing soft tissues, but it is essential to determine whether the mechanical properties of the matrix can be retained after cell ingrowth into the collagen scaffold. We have determined the mechanical strength of four collagen gel compositions (plain collagen; collagen‐chrondroitin‐6‐sulphate glycosaminoglycan (GAG); collagen crosslinked with carbodiimide and putrescine, and collagen‐GAG with the crosslinkers) in the presence of either 3T3 mouse fibroblasts or human skin fibroblasts, to determine whether cellular activity influences the mechanical properties of the matrix, and whether the crosslinking processes alter the effects of the cells. The presence of GAG and the crosslinkers increased the strength and stiffness of the unseeded gels, but there was no evidence for synergy between these treatments. In all cases, the gels became significantly weaker after 6 days in the presence of either human or mouse fibroblasts, as judged by the decrease in the values of the maximum load and stress before failure, and the stiffness decreased as shown by the lower values of the incremental modulus. With most parameters, the effect of the cells was independent of gel composition, and the presence of crosslinkers or GAG did not impart resistance to the cell‐induced decrease in strength. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Selective protein adsorption modulates platelet adhesion and activation to oligo(ethylene glycol)‐terminated self‐assembled monolayers with C18 ligands
Authors: Gonçalves Inês C. , Martins M. Cristina L. , Barbosa Mário A. , Naeemi Esmaeel , Ratner Buddy D.
Published: April 2008

This study focuses on the selective binding of albumin to a nanostructured surfaces to inhibit other blood proteins from adsorbing thereby reducing platelet adhesion and activation. Tetra (ethylene‐glycol)‐terminated self‐assembled monolayers (EG4 SAMs) with different percentages of C18 ligands on the surface were characterized by contact angle measurements, X‐ray photoelectron microscopy, infrared reflection‐absorption spectroscopy, and ellipsometry. A specific surface (2.5% C18 SAM) was found to be selective for human serum albumin (HSA) in the presence of both albumin and fibrinogen (HFG). The importance of this concentration of C18 ligands was stressed in reversibility studies since that surface exchanged almost all the preadsorbed HSA by HSA in solution, but not by HFG. The effect of protein adsorption in the subsequent adhesion and activation of platelets was studied by pre‐immersing the surfaces in albumin and plasma before contact with platelets. Scanning electron microscopy and glutaraldehyde induced fluorescence technique images showed that as surfaces got more hydrophobic due to the immobilization of C18 ligands, the number of adherent platelets increased and their morphology changed from round to fully spread. Pre‐immersion in HSA led to an 80% decrease in platelet adhesion and reduction of activation. Pre‐immersion in 1% plasma was only relevant in 2.5% C18 SAMs since this was the only surface that demonstrated less adhesion of platelets comparing with buffer pre‐immersion. However, they still adsorb more platelets then when HSA was preadsorbed. This was confirmed in competition studies between HSA and plasma that suggested that other plasma proteins were also adsorbing to this surface. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Mineral apposition rates provide significant information on long‐term effects in BMP‐induced bone regeneration
Authors: Schopper Christian , Moser Doris , Spassova‐Tzekova Else , Russmueller Guenter , Goriwoda Walter , Lagogiannis Georgios , Ewers Rolf , Redl Heinz
Published: April 2008

In this study, a CaP biomaterial was used as a carrier for rhBMP‐2. Biomaterials were investigated in calvarial and femoral defects using a rabbit animal model, with unloaded biomaterials serving as control. Fluorochrome labels were administered at days 14 and 70. Specimens were retrieved after 12 weeks for histological analysis. When area fractions were assessed by conventional histomorphometry, no significant effect of rhBMP‐2 on the amounts of regenerated bone and residual biomaterial were seen by 12 weeks. After mineral appositional rate (MAR) measurement using double labels, calculation yielded significantly higher MARs for defects at both implantation sites, when compared with surrounding bone, whether or not biomaterials were loaded with rhBMP‐2. Analyzing the effect of rhBMP‐2, both defect sites showed significantly higher MARs in the rhBMP‐2 group. MARs of bone surrounding the defects had also been elevated significantly by rhBMP‐2 at calvarial and femoral implantation sites. It is concluded that MAR measurement is suitable to identify long‐term effects of rhBMP‐2 on bone formation at a time when conventional histomorphometry using fractional area determination is inadequate. Also, by MAR assessment, effects of rhBMP‐2 on surrounding bone can be documented. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Gentamicin‐eluting bioresorbable composite fibers for wound healing applications
Authors: Zilberman Meital , Golerkansky Esty , Elsner Jonathan J. , Berdicevsky Israela
Published: April 2008

New gentamicin‐eluting bioresorbable core/shell fiber structures were developed and studied. These structures were composed of a polyglyconate core and a porous poly(DL‐lactic‐co‐glycolic acid) (PDLGA) shell loaded with the antibiotic agent gentamicin, prepared using freeze drying of inverted emulsions. These unique fibers are designed to be used as basic elements of bioresorbable burn and ulcer dressings. The investigation focused on the effects of the emulsion's composition (formulation) on the shell's microstructure, on the drug release profile from the fibers, and on bacterial inhibition. The release profiles generally exhibited an initial burst effect accompanied by a decrease in release rates with time. Albumin was found to be the most effective surfactant for stabilizing the inverted emulsions. All three formulation parameters had a significant effect on gentamicin's release profile. An increase in the polymer and organic:aqueous phase ratio or a decrease in the drug content resulted in a lower burst release and a more moderate release profile. The released gentamicin also resulted in a significant decrease in bacterial viability and practically no bacteria survived after 2 days when using bacterial concentrations of 1 × 107 CFU/mL. Thus, our new fiber structures are effective against the relevant bacterial strains and can be used as basic elements of bioresorbable drug‐eluting wound dressings. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Microfabricated poly(ethylene glycol) templates enable rapid screening of triculture conditions for cardiac tissue engineering
Authors: Iyer Rohin K. , Chiu Loraine L. Y. , Radisic Milica
Published: April 2008

The purpose of this study was to design a simple system for cultivation of micro‐scale cardiac organoids and investigate the effects of cellular composition on the organoid function. We hypothesized that cultivation of cardiomyocytes (CM) on preformed networks of fibroblasts (FB) and endothelial cells (EC) would enhance the structural and functional properties of the organoids, compared to simultaneously seeding the three cell types or cultivating enriched CM alone. Microchannels for cell seeding were created by photopolymerization of poly(ethylene glycol) diacrylate. In the preculture group the channels were seeded with a mixture of NIH 3T3 FB and D4T EC, following by addition of neonatal rat CM after 2 days of FB/EC preculture. The control microchannels were seeded simultaneously with FB/EC/CM (simultaneous triculture) or with enriched CM alone (enriched CM). Preculture resulted in cylindrical, contractile, and compact cardiac organoids that contained elongated CM expressing connexin‐43 and cardiac troponin I. In contrast, simultaneous triculture resulted in noncontractile organoids with clusters of CM growing separately from elongated FBs and ECs. The staining for Connexin‐43 was absent in the simultaneous triculture group. When fixed or frozen FB/EC were utilized as a preculture substrate for CM, noncontractile organoids were obtained; while preculture on a single cell type (either FB or EC) resulted in contractile organoids but with inferior properties compared to preculture with both FB/EC. These results emphasize the importance of living cells, presence of both nonmyocyte cell types as well as sequential seeding approach for cultivation of functional multicell type cardiac organoids. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009