bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bioactive material template for in vitro, synthesis of bone
Authors: El‐Ghannam Ahmed , Ducheyne Paul , Shapiro Irving M. 
Published: December 2004

AbstractWe describe the synthesis of a new, porous, modified bioactive glass for use as a template for bone formation in vitro. The porosity of the glass was 36.4%; the pore size ranged from 10–160 mm, and there was no incipient devitrification. Prior to seeding the glass with cells, it was necessary to condition the disks. Optimum conditioning was achieved by immersing the templates in a tris buffer at pH 6.8 for 48 h and then treating the glass with tissue culture medium for 1 h at 37°C. The conditioned glass disks were seeded with 106 neonatal rat calvaria osteoblast‐like cells; cells on the substrate were maintained in culture for 3–7 days. To prevent pH shifts due to corrosion of the conditioned glass, the medium:glass ratio was maintained at 90 ml/g. We found that the templates were rapidly invaded by cells which maintained the osteoblast phenotype; thus, they exhibited high alkaline phosphatase activity and synthesized type I collagen and osteocalcin. SEM‐EDAX showed that the cells elaborated substantial amounts of extracellular matrix and a bonelike tissue was present throughout the entire template thickness. FTIR analysis of material formed in the glass indicated that the mineral phase was a biologic hydroxyapatite. Controls (cells without substrate and substrate without cells) exhibited none of these features. Results of the study suggest that this porous glass can function as a template for generating bone in vitro. © 1995 John Wiley & Sons, Inc.
Computer‐Assisted three‐dimensional reconstruction of epithelial cells attached to percutaneous implants
Authors: Chehroudi B. , Soorany E. , Black N. , Weston L. , Brunette D. M. 
Published: December 2004

AbstractIt is generally accepted that cell shape plays a pivotal role in many aspects of cell behavior including proliferation, differentiation, and gene expression. Although previous reports have shown that implant‐surface topography can alter cell shape in vitro, in vivo evidence for such an effect is largely based on intuitive interpretation of two‐dimensional histological sections. The objective of this in vivo, study was to develop a method to reconstruct in three dimensions the shape of epithelial cells attached to smooth and micromachined implant surfaces. Titanium‐coated epoxy replicas of smooth and 10‐μm‐deep micromachined grooved surfaces were implanted percutaneously in the parietal of region of rats. After 7 days the implants and attached tissue were removed and processed for light and electron microscopy. One‐micrometer‐thick serial histological sections were used to trace and digitize cells and their nuclei into a Hewlett Packard computer. Three‐dimensional images were reconstructed and rotated to measure length, width, height, area, orientation index and the angle cells or nuclei formed with the long axis of the grooves (XY angle), and the angle cells or nuclei formed with the long axis of the implant (XZ angle). Epithelial cells attached to the smooth surfaces were found to be significantly (P, < .05) flatter and more spread than were the cells attached to the grooved surfaces. Cells on the smooth surfaces were aligned parallel with the long axis of the implant, whereas on the grooved surfaces cells were oriented obliquely with the implant. There was a strong correlation (r = 0.9) between measurements of parameters of cells and those of nuclei on the smooth surfaces, but little correlation was found for the cells and their nuclei on grooved surfaces. These measurements indicated that cell shape is altered by the topography of the implant surface in vivo, but that one cannot necessarily predict the shape of a cell from the shape of its nucleus. © 1995 John Wiley & Sons, Inc.
Glass Wool–H2O2/CoCl2 test system for in vitro evaluation of biodegradative stress cracking in polyurethane elastomers
Authors: Zhao Qinghong , Casas‐Bejar Jesus , Urbanski Peter , Stokes Ken 
Published: December 2004

AbstractEnvironmental stress cracking (ESC) in polyetherurethanes has been demonstrated in animal models. However, duplication of this phenomenon in vitro has been a challenge. The glass wool‐H2O2/CoCl2 test system was designed to provide oxidation components found in vivo, i.e., hydroxyl radical (HO·), molecular oxygen (O2), and superoxide (O) required for auto‐oxidation of polyetherurethanes. The in vitro test is not only reliable in duplicating the characteristics of in vivo stress cracking in polyetherurethanes at 37°C, but also accelerates ESC as much as seven times. The test results on several types of polyurethanes showed that Tecothane 80A was as vulnerable to biodegradative stress cracking in vitro as Pellethane 2363‐80A, while the new generation of polyurethanes, Corethane, demonstrated great resistance against stress cracking. © 1995 John Wiley & Sons, Inc.
Mediator interactions in macrophage/particulate bone resorption
Authors: Horowitz Stephen M. , Purdon Marie A. 
Published: December 2004

AbstractThe purpose of this study was to examine the mechanism by which mediators released from macrophages exposed to cement particles may interact with cells in bone to ultimately lead to bone resorption. Macrophages were exposed to cement particles, and then this conditioned medium was exposed to rat calvarial bones in vitro. The macrophage conditioned medium contained increased levels of tumor necrosis factor, but not interleukin 1 or prostaglandin E2. Exposure of this medium to the calvaria led to release of prostaglandin E2 by the calvaria, but not tumor necrosis factor or interleukin 1. Bone resorption was assessed by measuring the release of calcium 45 from the newborn rat calvarial bones. At 48, 72, and 96 h of incubation, the macrophage/cement particle‐conditioned medium led to the release of both prostaglandin E2 and calcium 45 from the calvaria. To determine whether the release of calcium 45 was dependent on prostaglandin E2 production by the cells in bone, the calvaria were incubated with 600 ng/ml of indomethancin in addition to the macrophage‐conditioned medium. The addition of indomethacin was effective in inhibiting both prostaglandin E2 and calcium 45 release from the calvaria, even after 96 h of exposure to the macrophage‐conditioned medium. This study suggests that tumor necrosis factor produced in association with macrophage/cement particle osteolysis arises from macrophages and not cells in bone, and that prostaglandin E2 originates from cells in bone and not from macrophages. Interleukin 1 was not found to be produced by macrophages or bone, and appears to have a lesser role. This study also suggests that the production of prostaglandin E2 by cells in bone plays an important role in the bone resorption which accompanies aseptic loosening. Macrophage exposure to bone‐cement particles leads to the release of mediators which stimulates bone resorption, at least in part, through a prostaglandin E2‐dependent mechanism. © 1995 John Wiley & Sons, Inc.
Creep characteristics of hand‐ and vacuum‐mixed acrylic bone cement at elevated stress levels
Authors: Norman T. L. , Kish V. , Blaha J. D. , Gruen T. A. , Hustosky K. 
Published: December 2004

AbstractCompressive creep testing of cylindrical specimens machined from two commercial self‐polymerizing acrylic bone cements demonstrated measurable creep strains with higher creep strains for the hand‐mixed cement specimens compared to vacuum‐mixed cement ones. The average creep strains of hand‐mixed cement, after 6 h of constant load, ranged from 0.11° at 10.5 MPa to 14.0° at 50 MPa of applied stress. Vacuum mixing reduced the average creep strain to 6.7° after 6 h of applied stress at 50 MPa. There were no significant differences in the creep response between the two types of acrylic cements. The difference in creep resistance of the two cements was reduced after vacuum mixing (P = .013), which also significantly reduced the cement's internal porosity. © 1995 John Wiley & Sons, Inc.
Characterization of nodules induced by bioactive glass on cultured periodontal‐ligament fibroblasts
Authors: Kubo Kohji , Kamada Tetsuro , Matsuyama Takashi , Tsukasa Nobuyuki , Uehara Mayumi , Izumi Yuichi , Kitano Motoo , Ogino Makoto , Sueda Takeshi 
Published: December 2004

AbstractWe previously reported that materials leached from bioactive glass (BG) and vitamin D3 induced the formation of nodules on cultured periodontal‐ligament fibroblasts (PLF). In this study, we have investigated the relationship between the conditions of the materials and nodule formation, analyzed morphologically, and also studied whether the production of nodules was specific to cultured PLF. PLF and skin fibroblasts were cultured in the presence or absence of BG. The amounts of calcium, phosphate, sodium and silicon in the culture medium and the number of nodules were measured at the 55th day. The nodules were observed microscopically and analyzed using an X‐ray microanalyzer. In PLF, nodules were formed regardless of the presence or absence of BG; however, they were more numerous in the presence of BG. In skin fibroblasts, nodules were not observed. The amounts of calcium and silicon were higher in the presence of BG, while the amount of phosphate was lower. The nodules appeared crystalline with a spongy structure and contained calcium and phosphorus. Our results show that the nodules were associated with PLF and precipitated by the materials (higher concentrations of calcium and silicon), and they were spongy crystal composed of calcium and phosphorus. © 1995 John Wiley & Sons, Inc.
Cranial bone apposition and ingrowth in a porous nickel–titanium implant
Authors: Simske S. J. , Sachdeva R. 
Published: December 2004

AbstractA 5 × 5 × 1‐mm uncoated porous nickel‐titanium (nitinol) implant was placed 4 mm to either side of the midsection of the frontal bone and 4 mm anterior to the coronal suture of the cranial bone of New Zealand White rabbits. In the other frontal location, a 5 × 5 × 1‐mm coralline hydroxyapatite (HA) (Interpore 200, a well‐known craniofacial implant material) implant was fitted. Rabbits were killed at each of three postsurgical intervals (2, 6, and 12 weeks), and the implants were evaluated for gross biocompatibility, bony contact, and ingrowth. No adjacent macrophage cells were observed for either implant type, and overlaying soft tissues and connective tissues readily adhered to the implants even after 2 weeks. Both materials made bone contact with the surrounding cranial hard tissue, and percent ingrowth increased with surgical recovery time. Measurements of microhardness and bone histologic parameters indicated that bone in contact with and grown into the implants was similar in properties to the surrounding cranial bone. Porous nitinol implants therefore appear to allow for significant cranial bone ingrowth after as few as 12 weeks, and thus nitinol appears to be suitable for craniofacial applications. Compared to HA, the nitinol implants demonstrated a trend for less total apposition and more total ingrowth after 6 and 12 weeks of implantation. © 1995 John Wiley & Sons, Inc.
Preservation of surface‐dependent properties of viral antigens following immobilization on particulate ceramic delivery vehicles
Authors: Kossovsky Nir , Gelman Andrew , Sponsler Edward , Rajguru Samir , Torres Mariel , Mena Ed , Ly Khan , Festekjian Ara 
Published: December 2004

AbstractB‐cell stimulation for the purpose of evoking an effective neutralizing humoral immune response is a surface phenomenon that is exquisitely specific to antigen conformation. Consequently, successful delivery of antigen, such as would be desired in a vaccine, entails preservation of an antigen's apparent native surface (conformational) properties. Prior to testing the actual vaccinating efficacy of delivered antigens, the surface properties could be assessed through a variety of in vitro and in vivo assays in which the measurement standard would be the properties of the antigens in their native state (whole virus). Using surface modified nanocrystalline carbon and calcium‐phosphate ceramic particulates (carbon ceramics and brushite), we evaluated the surface activity of immobilized non‐nuclear material extracted from HIV‐1. Physical characterization showed that the particles with immobilized antigen („HIV decoys”︁) measured 50 nm in diameter (HIV = 50–100 nm) and exhibited the same ξ potentials as whole (live) HIV. In vitro testing showed that the HIV decoys were recognized by both conformationally nonspecific and specific monoclonal antibodies, were recognized by human IgG from HIV antibody‐positive patients, and could promote surface agglomeration among malignant T‐cells similar to live HIV. Last, in vivo testing in three vaccinated animal species showed that the HIV decoys elicited humoral and cellular immune responses similar to that evoked by whole (live) HIV. © 1995 John Wiley & Sons, Inc.
Assessment of viability and proliferation of in vivo silicone‐primed lymphocytes after in vitro re‐exposure to silicone
Authors: Ciapetti Gabriela , Granchi Donatella , Stea Susanna , Cenni Elisabetta , Schiavon Patrizia , Giuliani Renzo , Pizzoferrato Arturo 
Published: December 2004

AbstractThe functional response of peripheral blood lymphocytes isolated from 22 patients with silicone gel‐filled breast implants was assessed after in vitro re‐exposure to silicone. Using cell culture test methods to quantify proliferation and viability and/or activation of lymphocyte microcultures, i.e., the uptake of tritiated thymidine (3H‐TdR uptake test) and the reduction of formazan salts (MTT assay), interesting data were obtained. Peripheral blood lymphocytes purified from patients wearing silicone gel‐filled breast implants react in vitro to silicone showing a statistically significant increase of both proliferation and viability, while healthy subjects do not respond on in vitro exposure to silicone. Differences resulted even more statistically significant when patients were divided into two groups depending on the type of surgery they underwent: patients with breast augmentation for aesthetic reasons seem to have an increased responsiveness in vitro to silicone compared to patients who experienced a reconstructive surgery of the breast. Although they are still preliminary, being referred to a limited population, these results suggest that the lymphocytes of patients with silicone gel‐filled breast implants could be sensitized in vivo toward silicone; the re‐exposure of these cells to silicone leads to a higher functional response which could be looked for by using quantitative in vitro test methods. © 1995 John Wiley & Sons, Inc.
Role of cyclic plastic deformation in the wear of UHMWPE acetabular cups
Authors: Wang A. , Stark C. , Dumbleton J. H. 
Published: December 2004

AbstractThe mechanisms of wear in ultra‐high‐molecular‐weight polyethylene (UHMWPE) acetabular cups were investigated on both laboratory simulator‐tested cups and a clinically retrieved component. Two different levels of wear process were identified: one characterized by the formation and detachment of platelet‐like flakes from initial machining marks, and the other by the formation of fine ripples and fibrils by repeated passes of microscopic asperities on the femoral head. Both wear processes could be described by a criterion of critical plastic strain. A theoretical model was developed to account for the generation of the microscopic wear particles based on such a critical strain criterion. Its predictions of the dependence of the UHMWPE wear rate on surface roughness and applied load were in excellent agreement with previously published experimental correlations. © 1995 John Wiley & Sons, Inc.
Hydroxyapatite‐clay bone fixation for loaded implants
Authors: Maruyama Masaaki 
Published: December 2004

AbstractA clay containing hydroxyapatite (HA clay), which was made by mixing HA granules (range of sizes: 0.1–0.3 mm) and a saline solution of sodium alginate, was inserted into the medullary canal of an osteotomized rabbit's tibia with a Ti‐6Al‐4V titanium alloy implant. Each implant had a conical portion for bearing load. The shear strength of the bone‐implant interface for the implant with HA clay was significantly greater than that for the implant without HA clay 3 months postoperatively (P < .02), while there was no significant difference between the two strengths 1 week postoperatively. Under microscopic observation, the percentage of area of newly developed bone was also significantly greater for the implant with HA clay than for the implant without HA clay 3 months postoperatively (P < .04). This study suggests that HA clay encouraged adequate bone fixation of the loaded implant in 3 months, while the clay was not effective for immediate fixation. © 1995 John Wiley & Sons, Inc.
Bovine serum albumin conformation on methyl and amine functionalized surfaces compared by scanning force microscopy
Authors: Taborelli M. , Eng L. , Descouts P. , Ranieri J. P. , Bellamkonda R. , Aebischer P. 
Published: December 2004

AbstractWe investigated the adsorption of albumin on chemically modified gold surfaces by scanning force microscopy operating both in contact and noncontact mode. The surface modification was performed with thiol‐based selfassembling molecules carrying amine or methyl groups. The albumin on the aminoethanethiol‐coated gold formed a uniform layer and single molecules could be distinguished. On the dodecanethiol‐coated surface the protein adsorbed in aggregates or single isolated molecules depending on the incubation time. The width of the albumin molecule on both surfaces was similar, but the height was much lower on the amine than on the methyl surface. This was interpreted as a difference in the conformation of albumin depending on the substrate, and could explain the promotion of cell adhesion on amine‐treated polymers coated with albumin. © 1995 John Wiley & Sons, Inc.
Protein‐rejecting ability of surface‐bound dextran in end‐on and side‐on configurations: Comparison to PEG
Authors: Österberg E. , Bergström K. , Holmberg K. , Schuman T. P. , Riggs J. A. , Burns N. L. , Van Alstine J. M. , Harris J. M. 
Published: December 2004

AbstractThere is much interest in attaching polyethylene glycol (PEG) and other hydrophilic, neutral polymers to surfaces to reduce the extent of protein and cell adsorption. Interestingly, these same surface‐bound polymers are effective in masking surface charge and reducing electrokinetic effects such as particle electrophoretic mobility, streaming potential, and electroosmosis. It is apparent that similar molecular properties are responsible for both protein and cell rejection and reduction of electrokinetic effects. In this work we compared the fibrinogen‐rejecting ability and the effect on electrophoretic mobility of three polymer coatings bound to polystyrene. The three polymers were side‐bound dextran, end‐bound dextran, and end‐bound PEG. The results of these measurements were used to elucidate the importance of polymer packing density and polymer layer thickness on protein adsorption and reduction of electrokinetic effects. Protein adsorption appears not to be sensitive to polymer layer thickness or the presence of dilute polymer tails in a surface coating, while electrokinetic effects are. Protein adsorption is, however, very sensitive to the availability of exposed surface. Finally, the unique effectiveness of PEG is apparent in this research as in previous studies. © 1995 John Wiley & Sons, Inc.
The resorption of bone‐implanted corals varies with porosity but also with the host reaction
Authors: Roudier M. , Bouchon C. , Rouvillain J. L. , Amédée J. , Bareille R. , Rouais F. , Ch. Fricain J. , Dupuy B. , Kien P. , Jeandot R. , Basse‐Cathalinat B. 
Published: December 2004

AbstractThree different exoskeletons of coral species Porites astreoides (P), Montastrea annularis (M), and Dichocoenia stokesi (D) were implanted for 2–20 weeks in rabbits. At 2, 4, 8, or 20 weeks, the exoskeletons presented variations in their resorptions depending on the species. To understand the variations in the decreasing speed of the implants despite their similar chemical composition, a study of the surface and architecture of the coral was carried out using scanning electronic microscopy, porosity was evaluated, and growth and differentiation of osteogenic cells cultured in vitro were observed for more than 1 month. At the cellular level, the surface of the implants was identical. Three‐dimensional structures of the implants were variable, but the porosity values [P = 42.7%, M = 40.7%, and D = 17.4%] could not completely account for the differences in the resorbing process of the species. Standard histologic studies performed at 2, 4, 8, and 20 weeks after implantation produced the same pattern with P or M, showing aspects of rapid resorption; however, with D there were images resembling those of a foreign‐body reaction. It seems that when resorption is not quick enough, a foreign body reaction develops which further slows down the process. This work focuses on the importance of porosity when using coral as bone substitute. © 1995 John Wiley & Sons, Inc.
Studies on a new strategy for surface modification of polymeric biomaterials
Authors: Aldenhoff Yvette B. J. , Koole Leo H. 
Published: December 2004

AbstractA new methodology to improve the hemocompatibility of polyurethane (medical grade Pellethane D‐55) surfaces is reported. The approach is essentially based on a photochemical immobilization reaction. Two new conjugate molecules, compounds 2 and 3, were prepared. They consist of (i) dipyridamole, a well‐known inhibitor of platelet activation, and a vasodilating drug with clinical application, for instance before and during pecutaneous transluminar coronary angioplasty (Dottering); and (ii) an aryl azide, a moiety that exhibits marked photoreactivity. In 2, the dipyridamole unit is directly linked to the aryl azide (via an ester bond), while a short spacer chain separates both units in 3. Upon irradiation of 2 or 3, adsorbed onto the polyurethane foil, the aryl azide is converted into a highly reactive species which reacts with a nucleophilic group on the polymer surface. In this way, the dipyridamole is covalently linked to the polymer. The underlying principle is also used in photoaffinity labeling, a well‐known technique in biochemical studies on enzyme structure and function. From UV extinction experiments it could be deduced that the surfacedensity of immobilized 2 is 4.9 nmol/cm2. The surface density for 3 was 14.6 nmol/cm2. The surfaces were subjected to an in vitro thrombin generation assay. This assay gives a valuable impression about the hemocompatibility of artificial surfaces. These experiments revealed that the clotting times were substantially prolonged as a result of the photoimmobilization of dipyridamole. This was especially the case for immobilized 3. This effect cannot be readily explained. Possibly, the enhanced activity of immobilized 3 is due to the spacer chain. An alternative explanation is that the surface density is larger for 3 than for 2. In addition, the photomodified surfaces were incubated with platelet‐rich blood plasma (37°C, 30 min) and subsequently examined by scanning electron microscopy. The morphology of the blood platelets adhered to the surface also showed that hemocompatibility increased in the order untreated polyurethane < polyurethane with immobilized 2 < polyurethane with immobilized 3. Future work will concentrate on evaluation of the role of the spacer (length, hydrophilicity, etc.), as well as on the possible use of this approach with respect to the construction of biomaterials with improved in vivo biocompatibility, in particular hemocompatibility. © 1995 John Wiley & Sons, Inc.