bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combination of ascorbate and growth factor (TGF β‐3) in thermo‐reversible hydrogel constructs embedded with rabbit chondrocytes for neocartilage formation
Authors: Choi Seong‐Jun , Na Kun , Kim Sungwon , Woo Dae Gyun , Sun Bo Kyung , Chung Hyung‐Min , Park Keun‐Hong 
Published: June 2007

AbstractThis study evaluated the potential of using poly(NiPAAm‐co‐AAc) as an injectable drug delivery carrier and a cell therapeutic agent in the form of a supporting matrix for the chondrogenic differentiation of rabbit chondrocytes. In particular, rabbit chondrocytes were embedded in hydrogels containing a combination of ascorbate and transforming growth factor β‐3 (TGF β‐3). Hydrogel constructs containing embedded cells either without ascorbate or a combination of ascorbate and TGF β‐3 were used as controls to determine the effects of ascorbate and TGF β‐3 on chondrogenic differentiation. The level of cartilage associated ECM proteins was examined using immunohistochemical staining for collagen type II as well as by Safranin‐O and Alcian blue (GAG) staining. The results showed that ascorbate is an important factor for preparing cartilage constructs because of its action on chondrocyte phenotype modulation and proliferation. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Material dependent differences in inflammatory gene expression by giant cells during the foreign body reaction
Authors: Luttikhuizen D.T. , Dankers P.Y.W. , Harmsen M.C. , van Luyn M.J.A. 
Published: June 2007

AbstractMultinucleated giant cells (GCs) are often observed in the foreign body reaction against implanted materials. The in vivo function of GCs in this inflammatory process remains to be elucidated. GCs degrade collagen implants in rats and may also orchestrate the inflammatory process via the expression and secretion of modulators, such as cytokines and chemokines. In this study, we show that the gene expression of PMN chemoattractants, CXCL1/KC and CXCL2/MIP‐2, is high in GCs micro‐dissected from explanted Dacron, cross‐linked collagen (HDSC), and bioactive ureido‐pyrimidinone functionalized oligocaprolactone (bioactive PCLdiUPy). Conversely, the gene expression levels of TGFβ and pro‐angiogenic mediators VEGF and FGF were found to be low in these GCs as compared with the expression levels in total explants. GCs in bioactive PCLdiUPy displayed high cytokine and angiogenic mediator expression compared with GCs isolated from the two other studied materials, whereas chemokine gene expression in GCs isolated form HDSC was low. Thus, GCs adopt their expression profile in response to the material that is encountered. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Collagen stiffness regulates cellular contraction and matrix remodeling gene expression
Authors: Karamichos D. , Brown R.A. , Mudera V. 
Published: June 2007

AbstractCell‐level mechanical and 3D spatial cues are essential to the organization and architecture of new tissues that form during growth, repair or in bioreactors. Fibroblast‐seeded 3D collagen constructs have been used as bioartifical extracellular matrix (ECM) providing a 3D environment to embedded resident cells. As cells attach to scaffold fibrils, they generate quantifiable contractile forces which depend on cell type, cell attachment, cell density, growth factors, and matrix stiffness. The aim of this study was to quantify the cytomechanical and molecular responses of human dermal (HDF) and neonatal foreskin fibroblasts (HNFF) seeded in constructs of increased stiffness. We also tested the effect of blocking early attachment using serum starvation on these outputs. Constructs were placed under uniaxial strains of 0–10% to increase scaffold stiffness, prior to gel contraction, and force generation was monitored using a tensional culture force monitor (t‐CFM). Increased matrix stiffness reduced generation of quantifiable cellular force (up to 70%) over 24 h in both cell types and delayed the onset of measurable contraction (upto sevenfold). The delay of measurable force generation was cell lineage dependent but not FCS dependent. Gene expression of MMP‐2, TIMP‐2, and collagen type III expression in HDFs were significantly upregulated in constructs of increased stiffness. HNFFs did not show any significant changes in these gene expressions indicating a lineage specific response. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
COMP mutations: Domain‐dependent relationship between abnormal chondrocyte trafficking and clinical PSACH and MED phenotypes
Authors: Chen Tung‐Ling L. , Posey Karen L. , Hecht Jacqueline T. , Vertel Barbara M. 
Published: June 2007

AbstractMutations in cartilage oligomeric matrix protein (COMP) produce clinical phenotypes ranging from the severe end of the spectrum, pseudoachondroplasia (PSACH), which is a dwarfing condition, to a mild condition, multiple epiphyseal dysplasia (MED). Patient chondrocytes have a unique morphology characterized by distended rER cisternae containing lamellar deposits of COMP and other extracellular matrix proteins. It has been difficult to determine why different mutations give rise to variable clinical phenotypes. Using our in vitro cell system, we previously demonstrated that the most common PSACH mutation, D469del, severely impedes trafficking of COMP and type IX collagen in chondrocytic cells, consistent with observations from patient cells. Here, we hypothesize that PSACH and MED mutations variably affect the cellular trafficking behavior of COMP and that the extent of defective trafficking correlates with clinical phenotype. Twelve different recombinant COMP mutations were expressed in rat chondrosarcoma cells and the percent cells with ER‐retained COMP was assessed. For mutations in type 3 (T3) repeats, trafficking defects correlated with clinical phenotype; PSACH mutations had more cells retaining mutant COMP, while MED mutations had fewer. In contrast, the cellular trafficking pattern observed for mutations in the C‐terminal globular domain (CTD) was not predictive of clinical phenotype. The results demonstrate that different COMP mutations in the T3 repeat domain have variable effects on intracellular transport, which correlate with clinical severity, while CTD mutations do not show such a correlation. These findings suggest that other unidentified factors contribute to the effect of the CTD mutations. J. Cell. Biochem. 103: 778–787, 2008. © 2007 Wiley‐Liss, Inc.
Benchmarking approximate density functional theory for s/d excitation energies in 3d transition metal cations
Authors: Schultz Nathan E. , Zhao Yan , Truhlar Donald G. 
Published: June 2007

AbstractHolthausen has recently provided a comprehensive study of density functional theory for calculating the s/d excitation energies of the 3d transition metal cations. This study did not include the effects of scalar relativistic effects, and we show here that the inclusion of scalar relativistic effects significantly alters the conclusions of the study. We find, contrary to the previous study, that local functionals are more accurate for the excitation energies of 3d transition method cations than hybrid functionals. The most accurate functionals, of the 38 tested, are SLYP, PBE, BP86, PBELYP, and PW91. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
pyVib, a computer program for the analysis of infrared and Raman optical activity
Authors: Zerara Mohamed 
Published: June 2007

AbstractA new program called pyVib has been developed as a tool for the analysis of Gaussian (Gaussian 03, Gaussian Inc., Pittsburgh, PA) outputs of vibrational absorption (IR), Raman as well as vibrational optical activity (VOA) spectra calculations. This program has been designed to help the computational chemistry practitioner in the task of analyzing and visualizing molecular vibrations and cross sections. In particular, the analysis of absorption and scattering cross sections can be done using new tools such as group coupling matrices (GCMs) and atomic contribution patterns (ACPs) as either 2D or 3D representations, respectively (Hug, Chem Phys 2001, 264, 53). It reads the Hessian, the atomic polar tensors (APTs), the atomic axial tensors (AATs) (Nafie, J Chem Phys 1983, 79, 4950), and the gradients of the various polarizability tensors involved in VOA calculations and stored in Gaussian fchk ascii files. pyVib is capable of picking suitably chosen atoms or group of atoms for evaluating the contribution of each atom or defined groups of atoms to the calculated VOA scattered intensities. All the results generated by pyVib can be visualized in real‐time but can also be transferred to text editors and electronic spreadsheets, which facilitate a detailed subsequent analysis and the visualization by other graphical user interfaces (GUIs).This program is coded in Python and used the visualization toolkit (VTK) library. It is freely available under the terms of the general GNU public license (GPL) for Linux platforms. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
Interval Tournaments
Authors: Brown David E. , Busch Arthur H. , Lundgren J. Richard 
Published: June 2007

AbstractA tournament is an orientation of a complete graph. A directed graph is an interval digraph if for each vertex v there corresponds an ordered pair of intervals (Sv, Tv) such that u → v if and only if Su ∩ Tv ≠ ∅︁. A bipartite graph is an interval bigraph if to each vertex there corresponds an interval such that vertices are adjacent if and only if their corresponding intervals intersect and each vertex belongs to a different partite set. We use the equivalence of the models for interval digraphs and interval bigraphs to characterize tournaments that are interval digraphs via forbidden subtournaments and prove that a tournament on n vertices is an interval digraph if and only if it has a transitive (n − 1)‐subtournament. We also characterize the obstructions to the existence of a transitive subtournament of order n − 1 in a tournament of order n. © 2007 Wiley Periodicals, Inc. J Graph Theory 56: 72–81, 2007
The crossing number of K11 is 100
Authors: Pan Shengjun , Richter R. Bruce 
Published: June 2007

AbstractThe crossing number of Kn is known for n ⩽ 10. We develop several simple counting properties that we shall exploit in showing by computer that cr(K11 = 100, which implies that cr(K12) = 150. We also determine the numbers of non‐isomorphic optimal drawings of K9 and K10. © 2007 Wiley Periodicals, Inc. J Graph Theory 56: 128–134, 2007
Characterization of the glycosidic linkage of underivatized disaccharides by interaction with Pb2+ ions
Authors: Firdoussi Ahlam El , Lafitte Marie , Tortajada Jeanine , Kone Omar , Salpin Jean‐Yves 
Published: June 2007

AbstractElectrospray ionization in combination with tandem mass spectrometry and lead cationization is used to characterize the linkage position of underivatized disaccharides. Lead(II) ions react mainly with disaccharides by proton abstraction to generate [Pb(disaccharide)m− H]+ ions (m = 1–2). At low cone voltages, an intense series of doubly charged ions of general formula [Pb(disaccharide)n]2+ are also observed. Our study shows that MS/MS experiments have to be performed to differentiate Pb2+‐coordinated disaccharides. Upon collision, [Pb(disaccharide) − H]+ species mainly dissociate according to glycosidic bond cleavage and cross‐ring cleavages, leading to the elimination of CnH2nOn neutrals (n = 2–4). The various fragmentation processes allow the position of the glycosidic bond to be unambiguously located. Distinction between glc‐glc and glc‐fru disaccharides also appears straightforward. Furthermore, for homodimers of D‐glucose our data demonstrate that the anomericity of the glycosidic bond can be characterized for the 1 → n linkages (n = 2, 4, 6). Consequently, Pb2+ cationization combined with tandem mass spectrometry appears particularly useful to identify underivatized disaccharides. Copyright © 2007 John Wiley & Sons, Ltd.
Influence of extracellular osmolarity and mechanical stimulation on gene expression of intervertebral disc cells
Authors: Wuertz K. , Urban J.P.G. , Klasen J. , Ignatius A. , Wilke H.‐J. , Claes L. , Neidlinger‐Wilke C. 
Published: June 2007

AbstractIntervertebral discs (IVD) have a higher extracellular osmolarity than most other tissues; moreover their osmolarity changes by around 25% during each diurnal cycle. In this study, changes in aggrecan, collagen I and collagen II expression of IVD cells were examined after exposure to osmotic environment alterations or mechanical stimulation under different osmotic conditions. Human and bovine IVD cells seeded in three‐dimensional (3D) collagen type I matrices were cultured under hypo‐osmotic (300 mOsm), iso‐osmotic (400 mOsm), or hyperosmotic (500 mOsm) conditions. Osmolarity‐induced changes in gene expression of IVD cells were measured after 5 days. Load‐induced changes in gene expression under the different osmotic conditions were measured after application of hydrostatic pressure (0.25 MPa, 0.1 Hz, 30 min) or cyclic strain (4%, 1 Hz, 24 h). The results showed that IVD cells respond strongly to changes in the osmotic environment by altering mRNA expression. Human cells cultured over 5 days increased expression of aggrecan and collagen II in both nucleus and annulus cells under increasing osmolarity. In contrast, collagen I expression was inhibited at high osmolarity in both cell types. Mechanically induced alterations in gene expression appear to have only modest effects on matrix protein expression, but the same stimulus partly resulted in an inhibition or stimulation of gene expression, depending on the osmotic conditions. This study showed that the osmotic environment does not only have an appreciable effect on gene expression but also affects responses to mechanical stimuli. This suggests that the osmotic conditions cannot be ignored when examining physiological and pathological behavior of IVD cells. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1513–1522, 2007
Reactivity of tert‐butylperoxyl radical with manganese(III), cobalt(II), and nickel(II) salicylidene Schiff base chelates
Authors: Tavadyan Levon A. , Tonikyan Hakob Gh. , Musaelyan Makich V. , Barsegyan Aram E. , Minasyan Seyran H. , Sorenson John R. J. 
Published: June 2007

AbstractSalicylidene Schiff base chelates (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediaminomanganese(III) chloride, (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediaminocobalt(II), N,N′‐bis(salicylidene)‐ethylenediaminocobalt(II), N,N′‐bis(salicylidene)ethylenediaminonickel(II), and N,N′‐bis(salicylidene)ethylenediaminoaquacobalt(II), as well as (R,R)‐(–)‐N,N′‐bis(3,5‐di‐tert‐butylsalicylidene)1,2‐cyclohexanediamine, were kinetically examined as antioxidants in the scavenging of tert‐butylperoxyl radical (tert‐butylOO•). Absolute rate constants and corresponding Arrhenius parameters were determined for reactions of tert‐butylOO• with these chelates in the temperature range −52.5 to −11°C. High reactivity of tert‐butylOO• with Mn(III) and Co(II) salicylidene Schiff base chelates was established using a kinetic electron paramagnetic resonance method. These salicylidene Schiff base chelates react in a 1:1 stoichiometric fashion with tert‐butylOO• without free radical formation. Ultraviolet–visible spectrophotometry and differential pulse voltammetry established that the rapid removal rate of tert‐butylOO• by these chelates is the result of Mn(III) oxidation to Mn(IV) and Co(II) oxidation to Co(III) by tert‐butylOO•. It is concluded that removal of alkylperoxyl radical by Mn(III) and Co(II) salicylidene Schiff base chelates may partially account for their biological activities. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 431–439, 2007
The use of the IKP method for evaluating the kinetic parameters and the conversion function of the thermal decomposition of NaHCO3 from nonisothermal thermogravimetric data
Authors: Janković Bojan , Adnađević Borivoj 
Published: June 2007

AbstractThree linear isoconversional methods (Friedman, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose) and the invariant kinetic parameters (IKP) method were used in order to examine the kinetics of the nonisothermal decomposition of a sodium bicarbonate (NaHCO3). The objective of the paper is to show the usefulness of the IKP method to determine both the kinetic parameters and the kinetic model of the investigated process. The activation energy (Ea) value obtained by the IKP method is in good agreement with the values obtained by isoconversional methods. The IKP method associated with the criterion of coincidence of kinetic parameters for all heating rates led us to the following kinetic triplet: Ea = 95.5 kJ mol−1, A = 2.65 × 1010 min−1, and conversion function f(α) = (1 − α) (first‐order reaction model, F1). © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 462–471, 2007
The kinetics of complex formation between Ti(IV) and hydrogen peroxide
Authors: O'Sullivan Daniel W. , Tyree Michael 
Published: June 2007

AbstractThe kinetics of the formation of the titanium‐peroxide [TiO2+2] complex from the reaction of Ti(IV)OSO4 with hydrogen peroxide and the hydrolysis of hydroxymethyl hydroperoxide (HMHP) were examined to determine whether Ti(IV)OSO4 could be used to distinguish between hydrogen peroxide and HMHP in mixed solutions. Stopped‐flow analysis coupled to UV‐vis spectroscopy was used to examine the reaction kinetics at various temperatures. The molar absorptivity (ε) of the [TiO2+2] complex was found to be 679.5 ± 20.8 L mol−1 cm−1 at 405 nm. The reaction between hydrogen peroxide and Ti(IV)OSO4 was first order with respect to both Ti(IV)OSO4 and H2O2 with a rate constant of 5.70 ± 0.18 × 104 M−1 s−1 at 25°C, and an activation energy, Ea = 40.5 ± 1.9 kJ mol−1. The rate constant for the hydrolysis of HMHP was 4.3 × 10−3 s−1 at pH 8.5. Since the rate of complex formation between Ti(IV)OSO4 and hydrogen peroxide is much faster than the rate of hydrolysis of HMHP, the Ti(IV)OSO4 reaction coupled to time‐dependent UV‐vis spectroscopic measurements can be used to distinguish between hydrogen peroxide and HMHP in solution. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 457–461, 2007
Charged Polymers via Controlled Radical Polymerization and their Implications for Gene Delivery
Authors: Heath William H. , Senyurt Askim F. , Layman John , Long Timothy E. 
Published: June 2007

AbstractNon‐viral gene delivery agents are notorious for their poor nucleic acid transfection efficiency and relatively high cell cytotoxicity. Thus, many investigators are exploring the important parameters involved in charged polymer‐mediated gene delivery, such as chemical composition, molecular weight, structural architecture, surface charge, etc. It is important to develop clear structure‐property relationships in order to design successful nucleic acid delivery agents for gene therapy. To elucidate these relationships, well‐defined materials are necessary. Controlled radical polymerization methods offer a facile route to systematically produce well‐defined, structurally distinct gene delivery agents. The use of charged polymers prepared via controlled radical polymerizations to elucidate transfection mechanisms or develop new delivery vectors will be reviewed herein.magnified image
New Results on the Collapse Transition(s) of Flexible Homopolymers
Authors: Paul Wolfgang , Rampf Federica , Strauch Thomas , Binder Kurt 
Published: June 2007

AbstractSummary:We analyze the collapse transition of flexible homopolymer chains in the bond‐fluctuation model employing the Wang‐Landau Monte Carlo algorithm. The coil‐globule transition is followed by a first order transition into a solid state occurring in the collapsed globule. In the thermodynamic limit (chain length to infinity) the topology of the phase diagram depends on the range of the attractive interaction between the monomers. For sufficiently large interaction range anormalbehaviour of a continuous coil‐globule transition at the Θ‐temperature followed by a crystallization transition at lower temperature is observed. For short interaction range the first‐order transition asymptotically can pre‐empt the coil‐globule transition such that a first‐order collapse from a random‐coil into a crystalline globule occurs. This vanishing of the liquid globule state is similar to the vanishing of the vapour‐liquid coexistence found for colloidal suspensions interacting by a short‐ ranged attraction.
Monte Carlo Computer Simulation of a Single Semi‐Flexible Macromolecule at a Plane Surface
Authors: Ivanov Victor A. , Martemyanova Julia A. 
Published: June 2007

AbstractSummary: The properties of a single semiflexible mushroom chain at a plane surface with a long‐ranged attracting potential are studied by means of lattice Monte Carlo computer simulation using the bond fluctuation model, configurational bias algorithm for chain re‐growing and the Wang‐Landau sampling technique. We present the diagram of states in variables temperature T vs. strength of the adsorption potential, εw, for a quite short semiflexible chain consisting of N = 64 monomer units. The diagram of states consists of the regions of a coil, liquid globule, solid isotropic globule, adsorbed coil and cylinder‐like liquid‐crystalline globule. At low values of the adsorption strength εw the coil–globule and the subsequent liquid–solid globule transitions are observed upon decreasing temperature below the adsorption transition point. At high values of εw these two transitions change into a single transition from an adsorbed coil to a cylinder‐like liquid‐crystalline solid globule. We conclude that for a semiflexible chain the presence of a plane attracting surface favors the formation of a globule with internal liquid‐crystalline ordering of bonds.
Polymer Brushes on Flat and Curved Substrates: Scaling Concepts and Computer Simulations
Authors: Dimitrov Dimitar , Milchev Andrey , Binder Kurt 
Published: June 2007

AbstractSummary:The scaling concepts for isolated flexible macromolecules in good solvent grafted with one chain end to a flat surface (“polymer mushrooms”) as well as for layers of many overlapping end‐grafted chain molecules (“polymer brushes”) are introduced. Monte Carlo attempts to test these concepts are briefly reviewed. Then the extension of these concepts to polymer brushes grafted to the interior of a cylinder surface is discussed. Molecular Dynamics results on chain average linear dimensions in the direction normal to the grafting surface and in axial direction are described, as well as distribution functions for the density of end monomers and of all monomers of the chains. It is argued that under typical conditions reachable in either simulation or experiment the data fall in a crossover regime, where no simple power‐laws (as derived from the scaling description) hold. Moreover, extensions of the Daoud‐Cotton blob picture to the cylinder geometry, implying that each chain in such a cylindrical brush is confined into a conical sector, are invalid; thus, chain ends in densely filled cylinders are not restricted to stay in the “hemicylinder” containing the grafting site of the chain.