bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adhesion and cytokine production by monocytes on poly(2‐methacryloyloxyethyl phosphorylcholine‐co‐alkyl methacrylate)‐coated polymers
Authors: Defife K. M. , Yun J. K. , Azeez A. , Stack S. , Ishihara K. , Nakabayashi N. , Colton E. , Anderson J. M. 
Published: December 2004

AbstractHuman monocytes isolated from peripheral venous blood were assayed for their ability to adhere to various polymers. The culture supernatants were also assayed for the cytokines, interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6), and tumor necrosis factor‐α (TNF‐α). The polymers evaluated for adherence and cytokine production included Pellethane®, polyethylene and poly[n‐butyl methacrylate (BMA)] coated with poly[2‐methacryloyloxyethyl phosphorylcholine (MPC)‐co‐alkyl methacrylate] copolymers. In some experiments the test polymers were adsorbed with fibrinogen or IgG prior to the addition of monocytes. MPC copolymer‐coated materials inhibited monocyte and macrophage adhesion after 1 and 8 days of culture relative to corresponding uncoated polymers and tissue culture polystyrene (TCPS). The degree of inhibition by coated Pellethane compared to uncoated Pellethane was the greatest, while inhibition of adhesion by coated poly(BMA) was the least compared to uncoated poly(BMA). However, adhesion was significantly decreased on both coated and uncoated poly(BMA) by day 8. While IL‐1β, IL‐6, and TNF‐α release was variably influenced by polymer coating, release was consitently inhibited relative to TCPS on day 1. However, cytokine production was not inhibited compared to corresponding uncoated polymers on day 1. With or without protein preadsorption, IL‐1β release was not detectable in the supernatants of any polymer on day 8, IL‐6 production was diminished on day 8, and TNF‐α production was sustained on day 8. Overall, MPC copolymercoated and uncoated poly(BMA) were the least stimulating, while TCPS was the most stimulating. These studies suggest that MPC copolymers may improve the cell adhesion‐resistant properties of a biomaterial while variably influencing the activation of cells which may contact the coated surface. © 1995 John Wiley & Sons, Inc.
Effect of carbon content on the resistance to localized corrosion of as‐cast cobalt‐based alloys in an aqueous chloride solution
Authors: Montero‐Ocampo C. , Salinas Rodriguez A. 
Published: December 2004

AbstractThe effect of carbon content on the resistance to localized corrosion of ASTM‐F75, as‐cast cobalt‐based alloys, was studied using potentiostatic polarization tests in Ringer's solution. Critical pitting potentials were estimated from the potentiostatic polarization curves and were found to increase with decreasing carbon content. The highest resistance to pitting corrosion observed at low C contents was attributed to a greater chemical and microstructural homogeneity in the as‐cast condition. The results of the investigation led to the conclusion that the use of low C content ASTM‐F75 as‐cast alloys in the manufacture of orthopedic implants may result in a lower release rate of corrosion products which should improve the “in vivo” performance of the implants. © 1995 John Wiley & Sons, Inc.
Bacteria/blood/material interactions. I. Injected and preseeded slime‐forming Staphylococcus epidermidis in flowing blood with biomaterials
Authors: Brunstedt M. R. , Sapatnekar S. , Rubin K. R. , Kieswetter K. M. , Ziats N. P. , Merritt K. , Anderson J. M. 
Published: December 2004

AbstractBlood‐material interactions were studied using in vitro recirculation with human blood, slime‐forming Staphylococcus epidermidis, and cardiovascular materials. Staphylococcus epidermidis, under preseeded or injected conditions, adhered to nonsmooth materials and elevated plasma levels of fibrinopeptide A (FpA) and C3a in the presence of all materials. Increased white blood cell (WBC) and platelet adhesion and thrombospondin and platelet factor 4 (PF4) release were noted for respective materials in the presence of injected bacteria. Materials that adhered significant quantities of injected S. epidermidis exhibited low levels of adsorbed proteins. Materials with high levels of preseeded S. epidermidis showed high levels of adsorbed proteins. Adhesion of preseeded bacteria and blood plasma elevations of C3a and FpA were lowest on semicrystalline polymer substrates, intermediate on halogenated substrates, and highest on amorphous substrates. In the presence of injected bacteria, WBCs and platelets adhered at earlier recirculation times to amorphous substrates than to semicrystalline substrates. © 1995 John Wiley & Sons, Inc.
Hydrogel‐based three‐dimensional matrix for neural cells
Authors: Bellamkonda Ravi , Ranieri John P. , Bouche Nicolas , Aebischer Patrick 
Published: December 2004

AbstractThe ability to organize cells in three dimensions (3D) is an important component of tissue engineering. This study sought to develop an extracellular matrix (ECM) equivalent with a physicochemical structure capable of supporting neurite extension from primary neural cells in 3D. Rat embryonic day 14 striatal cells and chick embryonic day 9 dorsal root ganglia extended neurites in 3D in agarose hydrogels in a gel concentration‐dependent manner. Primary neural cells did not extend neurites above a threshold agarose gel concentration of 1.25% wt/vol. Gel characterization by hydraulic permeability studies revealed that the average pore radius of a 1.25% agarose gel was 150 mm. Hydraulic permeability studies for calculating average gel pore radius and gel morphology studies by environmental and scanning electron micrography showed that the average agarose gel pore size decreased exponentially as the gel concentration increased. It is hypothesized that the average gel porosity plays an important role in determining the ability of agarose gels to support neurite extension. Lamination of alternating nonpermissive, permissive, and nonpermissive gel layers facilitated the creation of 3D neural tracts in vitro. This ability of agarose hydrogels to organize, support, and direct neurite extension from neural cells may be useful for applications such as 3D neural cell culture and nerve regeneration. Agarose hydrogel substrates also offer the possibility of manipulating cells in 3D, and may be used as 3D templates for tissue engineering efforts in vitro and in vivo.
Microstructural investigation of bone—cement interface
Authors: Savarino L. , Stea S. , Ciapetti G. , Paganetto G. , Donati M. E. , Alvergna P. , Pizzoferrato A. 
Published: December 2004

AbstractWe evaluated the microstructural characteristics of newly formed bone tissue at the interface with cement. The bone‐cement interfaces of the femoral components of nine hip prostheses retrieved after loosening were investigated by means of X‐ray diffraction on microareas and microhardness. The bone far from the interface of two stable prostheses was used as a control. The newly formed bone adjacent to cement in the loosened prostheses showed a maturity degree lower than that of bone adjacent to cement in stable prostheses. The lattice parameters of bone apatite did not show significant variations as compared to the reference values. Bone trabeculae at the interface with loosened prostheses often showed an osteoid lining characterized by a strongly demineralized lamellar and haversian structure. Radioopaque cement particles are sometimes found in the trabecular bone tissue around the prosthesis. © 1995 John Wiley & Sons, Inc.
Monosize poly(ethylcyanoacrylate) microspheres: Preparation and degradation properties
Authors: Tuncel A. , Çiçek H. , Hayran M. , Pişkin E. 
Published: December 2004

AbstractMonosize, biodegradable poly(ethylcyanoacrylate) (PECA) microspheres in the size range of 0.5–2.5 μm were prepared by a relatively new polymerization technique, the so‐called dispersion polymerization. The polymerizations were performed by using a stabilizer system containing a poly(ethyleneoxide)/poly(propyleneoxide) (PEO/PPO) copolymer and dextran in the aqueous HCl solution as a dispersion medium. Phosphoric acid was used as a catalyst, stabilizer, monomer concentrations, and the pH of dispersion medium on the monomer conversion, average size, and size distribution of the PECA microspheres were studied. The resultant microspheres size was mainly controlled by PEO/PPO copolymer and HCl concentrations. To explain the degradation mechanism, the degradation of monosize PECA microspheres was studied in in vitro conditions. The partially degraded beads were observed by electron microscopy. The results indicated that the degradation of monosize PECA microspheres occurred mainly by surface erosion. © 1995 John Wiley & Sons, Inc.
Platelet and monoclonal antibody binding to fibrinogen adsorbed on glow‐discharge‐deposited polymers
Authors: Kiaei David , Hoffman Allan S. , Horbett Thomas A. , Lew Ken R. 
Published: December 2004

AbstractThe state of fibrinogen adsorbed on untreated and glow‐discharge‐treated surfaces was examined by measuring platelet adhesion, monoclonal antibody (mAb) binding, the amount of fibrinogen adsorbed, and the amount of adsorbed fibrinogen which could be eluted with sodium dodecyl sulfate (SDS). Tetrafluoroethylene (TFE) glow‐discharge‐treated polymers have a lower surface free energy (in air) and retain a larger fraction of adsorbed fibrinogen than untreated surfaces after SDS elution. Platelet adhesion was lowest on the TFE‐treated surfaces which retain the highest amounts of fibrinogen after SDS elution. Fibrinogen may undergo unfolding or spreading on the TFE‐treated surfaces to minimize interfacial free energy (in water) and maximize protein–;surface interactions. When it is adsorbed on the TFE‐treated surfaces, fibrinogen evidently assumes a state which somehow prevents its recognition and binding by platelet receptors. Monoclonal antibodies that bind to the three regions in fibrinogen thought to be involved in platelet adhesion were therefore used to detect changes in adsorbed fibrinogen. These regions and the antibodies which bind to them are: the COOH‐terminal of the γ‐chain, mAb M1; the RGD peptide sequence at Aα 95–98, mAb R1; the RDG sequence at Aα 572–575, mAb R2. For fibrinogen adsorbed on the untreated or TFE‐treated surfaces, M1 and R2 binding was relatively high compared to background, while R1 binding was low. However, the amount of binding of each mAb to fibrinogen adsorbed on the TFE‐treated surfaces was equal to or greater than fibrinogen adsorbed to the untreated surfaces. Therefore, antibody‐detectable changes in the platelet binding regions of adsorbed fibrinogen that might have been caused by conformational or orientational rearrangements were not observed for the TFE‐treated surfaces. The data suggest that the tight binding of fibrinogen on a surface may directly affect the ability of the fibrinogen to interact with the platelet receptors—i.e., that fibrinogen must be loosely held to facilitate maximal interaction with platelet receptors. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of fluoropolymeric substrata with immobilized minimal peptide sequences for cell adhesion studies. I
Authors: Vargo T. G. , Bekos E. J. , Kim Y. S. , Ranieri J. P. , Bellamkonda R. , Aebischer P. , Margevich D. E. , Thompson P. M. , Bright F. V. , Gardella J. A. 
Published: December 2004

AbstractIn this work, poly(tetrafluoroethylene‐cosubstrathexafluoropropylene) (also known as fluorinated ethylene propylene; FEP) was functionalized at the surface using a radio frequency glow discharge plasma. This particular surface modification produced controlled densities of hydroxyl functionality on the FEP surface. These surface hydroxyl groups provided sites for the covalent attachment of minimal peptide sequences, that are specific for neuronal attachment. FSCA, ATR‐FTIR, ToFsubstratSIMS, and fluorescence spectroscopy were used to evaluate peptide reaction efficiencies and to verify that intact peptide sequences were covalently attached to the FEP surfaces. These modified substrata were then used to study the cell attachment and response to covalently bound minimal peptide sequences. Cell attachment and differentiation results using NG108–15 and PC12 neuronal cell lines are presented in the adjoining paper by Ranieri et al. © 1995 John Wiley & Sons, Inc.
Neuronal cell attachment to fluorinated ethylene propylene films with covalently immobilized laminin oligopeptides YIGSR and IKVAV. II
Authors: Ranieri John P. , Bellamkonda Ravi , Bekos Evan J. , Vargo Terrence G. , Gardella Joseph A. , Aebischer Patrick 
Published: December 2004

AbstractMaterial surfaces that can mediate cellular interactions by the coupling of specific cell membrane receptors may allow for the design of a biomaterial that can control cell attachment, differentiation, and tissue organization. Cell adhesion proteins have been shown to contain minimum oligopeptide sequences that are recognized by cell surface receptors and can be covalently immobilized on material surfaces. In this study, cell attachment to fluorinated ethylene propylene (FEP) films functionalized with the laminin‐derived oligopeptides, YIGSR and a 19‐mer IKVAV‐containing sequence, was assessed using NG108–15 neuroblastoma and PC12 cells. A radiofrequency glow discharge (RFGD) process that replaces the FEP surface fluorine atoms with reactive hydroxyl functionalities was used to activate the film surfaces. The oligopeptides were then covalently coupled to the surface by their C‐terminus using a standard nucleophilic substitution reaction. The covalent attachment of the oligopeptides to the FEP surface was verified using electron spectroscopy for chemical analysis (ESCA). Receptor‐mediated NG108–15 cell attachment on the YIGSR‐modified films was determined using competitive binding assays. Average cell attachment on the oligopeptide immobilized films in medium containing soluble CDPGYIGSR was reduced by approximately a factor of 2, compared to cell attachment in serum‐free medium alone. No significant decrease in cell attachment was noted in medium containing the mock oligopeptide sequence CDPGYIGSK. FEP films immobilized with the 19‐mer IKVAV sequence demonstrated a higher percentage of receptor mediated cell attachment on the film surfaces. A sixfold decrease in PC12 cell attachment occurred on the oligopeptide immobilized films in a competitive binding assay medium containing the soluble IKVAV oligopeptide compared to cell attachment in serum‐free medium alone. These results demonstrate that laminin oligopeptides can be covalently immobilized on an FEP material surface and analytically verified, and can mediate the receptor specific coupling of neuronal cells onto its surface. © 1995 John Wiley & Sons, Inc.
Contact activation of the plasma coagulation cascade. II. Protein adsorption to procoagulant surfaces
Authors: Vogler Erwin A. , Graper Jane C. , Sugg Harry W. , Lander Lorraine M. , Brittain William J. 
Published: December 2004

AbstractA study of blood protein adsorption to procoagulant surfaces utilizing a coagulation time assay, contact angles, Wilhelmy balance tensiometry, and electron spectroscopy (ESCA) is presented. Using a new contact angle method of measuring protein adsorption termed “adsorption mapping” it was demonstrated that protein‐adsorbent surfaces were inefficient activators of the intrinsic pathway of the plasma coagulation cascade whereas water‐wettable, protein‐repellent surfaces were efficient procoagulants. Repeated use of fully water‐wettable (spreading) glass procoagulants in the coagulation time assay demonstrated that putative “activating sites” were not consumed in the coagulation of platelet‐poor porcine plasma. Furthermore, these procoagulant surfaces retained water‐wettable surface properties after incubation with blood proteins and saline rinse. The interpretation of these observations was that plasma and serum proteins were not adsorbed to water‐wettable surfaces. However, ESCA of these same surfaces revealed the presence of a thin protein layer. Wilhelmy balance tensiometry resolved these seemingly divergent observations by demonstrating that protein was “associated” with a bound hydration layer, but not formally adsorbed through a surface dehydration or ionic interaction mechanism. © 1995 John Wiley & Sons, Inc.
Assessments of thrombogenicity by three in vitro techniques
Authors: Skarada Douglas J. , Erickson Geoffrey R. , Warnecke Kindra L. , du Laney Tracey V. , Greenberg Charles S. , Ritter Edmond F. , Klitzman Bruce 
Published: December 2004

AbstractThis study assessed three in vitro techniques designed to measure the thrombogenicity of vascular grafts. All techniques immersed vascular grafts in rotating blood. In the gravimetric analysis, the weight of adherent thrombi was recorded at 2 min intervals for 20 min. In the torque analysis, a microviscometer continuously recorded the amount of torque developed as the graft rotated for 20 min. In the thrombin analysis, the blood sample was analyzed for fibrinopeptide A production indicating fibrinogen clevage. Expanded polytetrafluoroethylene grafts were treated by removal of air nuclei (denucleation), binding of heparin, or binding of polyethylene oxide (PEO). The gravimetric analysis determined that the time at which each group experienced clot initiation was as follows: control after 6 min, denucleation after 14 min, heparin after 18 min, and PEO after 10 min. Similarly, in the torque analysis all treatment groups significantly delayed the initial increase in torque from 8.0 min for control to 12.5 min for denucleation (P < .01), > 20 min for heparin (P < 0.1), and 12 min for PEO (P < .05). The thrombin analysis determined that coagulation activity was reduced relative to control at 12 min with the denucleation group (P < .05) and heparin group (P < .01) and at 18 min with all treatment groups (P < .01). The similarity of results among the techniques increases confidence that each measurement accurately predicts in vitro thrombogenicity. © 1995 John Wiley & Sons, Inc.
Characterization of thin hydroxyapatite layers formed on anodic titanium oxide films containing Ca and P by hydrothermal treatment
Authors: Ishizawa Hitoshi , Ogino Makoto 
Published: December 2004

AbstractAn anodic titanium oxide film containing Ca and P (AOFCP) was formed on commercially pure titanium which was anodized in an electrolytic solution of dissolved β‐glycerophosphate (β‐GP) and calcium acetate (CA). Hydroxyapatite (HA) crystals were precipitated by hydrothermally heating the AOFCP at 300°C. After hydrothermal treatment, the film was characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray microanalysis (EDX), and tensile tests. The morphology, composition, and amount of HA crystals precipitated were significantly affected by the composition of the electrolytes. Nearstoichiometric HA crystals with high crystallinity were precipitated completely covering the AOFCP surface at specific electrolyte concentrations. The HA layers were thin at 1–2 μm in thickness. The adhesive strength of the film increased with decreasing electrolyte concentration and the maximum value was about 40 MPa. In vitro tests for 300 days suggested that the stability of the film was high. The high adhesive strength may result from the AOFCP existing as an intermediate layer between the HA layer and a titanium substrate. The intervention of the AOFCP may have prevented abrupt changes in Ca and P content at an HA coating‐titanium interface as seen in a plasma‐sprayed one. The porous TiO2 matrix of the AOFCP may be suitable for nucleation sites of HA crystals, as well as SiO2 matrix of silicate bioactive glasses or glass ceramics. © 1995 John Wiley & Sons, Inc.
Cellular responses to chemical and morphologic aspects of biomaterial surfaces. II. The biosynthetic and migratory response of bone cell populations
Authors: Chesmel K. D. , Clark C. C. , Brighton C. T. , Black J. 
Published: December 2004

AbstractThe biosynthetic and migratory response of bone cells to changes in both surface composition and morphology of polystyrene (PS) substrates was examined. A system was devised wherein micromachined silicon wafers were used as templates to solvent‐cast PS replicas [using 0, 1, or 2 wt % styrene (S) monomer additions] with either 0.5‐ or 5.0‐ μm‐deep surface grooves. Smooth replicas (0% S) served as the control surfaces. The chemical and morphologic characteristics of the nine unique model biomaterial surfaces (MBSs) produced using this system were documented and were found to be distinct. For the biosynthetic studies, bone cells isolated from neonatal rat calvaria were plated onto the MBSs and labeled at postconfluence with [14C]proline for 24 h. Total DNA per surface, total newly synthesized collagenous (CP), and noncollagenous protein (NCP) (cell associated and secreted) were determined. Cell‐associated CP was found to increase significantly for the bone cells cultured on the substrates with 0.5‐μm grooves and 2% S (P < .05). Cell‐associated NCP was found to be elevated for all 2% S substrates and for the 0.5‐μm grooves substrates with 1% S. For the migration studies, bone cells were plated first onto 5‐mm nitrocellulose disks that were attached to standard Petri dishes using a plasma clot. At confluence, the disks were removed aseptically and placed on the replicas. The cellular area occupied as a result of the outward migration of the bone cells was measured after 4 days of culture using an image analysis system. An average velocity for the leading edge of bone cell populations on each of the nine MBSs was calculated: Cells on surfaces with either 1% S or 5.0‐μm grooves displayed significantly higher velocities than did the control cultures. A significant interaction effect between chemistry and morphology was observed. The biosynthetic and migratory responses of in vitro cultures of bone cells were not predictable from the observations of the cellular responses to the individual features, but appeared to depend on cellular responses to more than one substrate factor. © 1995 John Wiley & Sons, Inc.
Study of aging of silicone rubber biomaterials with NMR
Authors: Pfleiderer Bettina , Xu Ping , Ackerman Jerome L. , Garrido Leoncio 
Published: December 2004

AbstractMultinuclear nuclear magnetic resonance (NMR) spectroscopy (29Si, 13C, 1H) is used to characterize the aging process of silicone rubber‐based biomaterials in a rat model. 1H NMR relaxation measurements (spin‐lattice, T1, and spinspin, T2, relaxation times) were performed to better understand the molecular dynamics of polysiloxane chains in implants. After 1 year of implantation in animals, changes in the 1H T2 relaxation times and the NMR spectra were observed in polydimethylsiloxane, Silastic® sheets and chin implants, while these measurements remain unchanged in finger joints. Very small amounts of fat were detected in all types of silicone rubber implants at the end of the implantation period. This work shows that free silicone migrates from the implants to adjacent tissues and distant sites, such as spleen or liver, and is chemically modified. © 1995 John Wiley & Sons, Inc.
Dictyostelium Chemotactic Response to Spatial and Temporal Gradients. Theories of the Limits of Chemotactic Sensitivity and of Pseudochemotaxis
Authors: Futrelle R.P. 
Published: December 2004

AbstractFour aspects of ameboid cell chemotaxis are discussed: 1) Ameboid cells (Dictyostelium discoideum, leukocytes) might orient to chemotaxin gradients by sensing a spatial gradient or a temporal change in the concentration. Using a moving micropipette source of cAMP, we show the D discoideum cells can orient toward a gradient in which the concentration is everywhere decreasing with time–implying a spatial mechanism. 2) The number of molecules N that must be released by a source to orient a cell is limited by the natural concentration “noise” due to diffusion. N is shown to be simply related to the cell size and the distance from the source. 3) We show that previous diffusion equations for cell population movement have not taken the speed variations (klinokinesis) into account properly, and we present a new result that does. 4) We briefly discuss reaction‐diffusion models of cell orientation.