bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the surface geometry of smooth and porous‐coated titanium alloy on the orientation of fibroblasts in vitro
Authors: Inoue T. , Cox J. E. , Pilliar R. M. , Melcher A. H. 
Published: December 2004

AbstractThe migration and orientation of human gingival fibroblasts in relation to the rim of smooth‐surfaced and porous‐coated titanium discs placed on multilayers in vitro was investigated. Samples were examined after 6 h, 24 h, 3 days, and 7 days of culture using phase‐contrast and scanning electron microscopy. The cells migrated from the multilayer onto the smooth‐surfaced discs forming bridges between them, and orientated along parallel circumferential grooves in the rim of the discs. This resulted in the cellular bridges orientating at an acute angle to the rim of the disc, and adjacent cells in the multilayer orientating parallel to the rim. Cellular bridges were also formed between the porous‐coated discs and the multilayer but, because the cells that migrated onto, and between, the spheres of the porous‐coat showed no preferred orientation, the bridges retained their orientation at right angles to the surface of the rim. This in turn resulted in the cells of the adjacent multilayer becoming similarly orientated. These observations suggest that the geometrical configuration of the surface of implants could influence whether a capsule or an orientated fibrous attachment is developed in relation to implants in vivo.
Localized prevention of postsurgical adhesion formation and reformation with oxidized regenerated cellulose
Authors: Shimanuki Takao , Nishimura Kazunori , Montz Fredrick J. , Nakamura Robert M. , Dizerega Gere S. 
Published: December 2004

AbstractWe evaluated oxidized regenerated cellulose (ORC) in experimental rabbit and dog models to assess its potential for reducing or preventing adhesion formation and reformation. Evaluation was performed in the following anatomical sites: (1) uterine horn trauma; (2) small bowel resection and anastomosis; (3) parietal peritoneum excision; and (4) adhesion reformation in the uterine horn. Ten to 14 days after ORC treatment, adhesion formation was macroscopically and microscopically evaluated. Results demonstrate that ORC produced graded reduction in adhesion formation and significantly prevented adhesion reformation.
Bone‐particle‐impregnated bone cement: An in vitro study
Authors: Liu Y. K. , Park J. B. , Njus G. O. , Stienstra D. 
Published: December 2004

AbstractBone‐particle‐impregnated bone cement specimens (up to 30% by weight) were characterized by various test methods. The experimental bone cement showed decreased crack propagation rates and increased Young's modulus, while the ultimate tensile strength and impact strength were decreased. The viscosity could be adjusted by adding initiators lost when substituting the PMMA powder with bone particles. The present study warranted fur‐ther in vivo experiments on the possibility of tissue ingrowth for which the new bone cement was developed.
Luminal surface fabrication for cardiovascular prostheses
Authors: Deininger William D. , Gabriel Stephen B. 
Published: December 2004

AbstractMethods to produce highly ordered, specific surface morphologies on polytetrafluoroethylene (PTFE Teflon) surfaces were developed. These methods included the use of photolithographic techniques for pattern definition and directed argon ion beam sputter etching to produce the desired surface morphology. Use of these techniques resulted in the formation of regular arrays of sharply defined hexagonal pillars with smooth, vertical walls with heights of up to 80 μm. Pillar height‐to‐width ratios ranged up to 5.2–1. Surface hole depths of up to approximately 80 μm were also obtained. These surface morphologies could have an important application in medicine for improving the patency of cardiovascular prostheses. This would be accomplished by creating a luminal surface in the implant which promotes the development of a healthy neointima lining.
In vitro and in vivo kinetics of regulated drug release from polymer matrices by oscillating magnetic fields
Authors: Edelman E. R. , Brown L. , Taylor J. , Langer R. 
Published: December 2004

AbstractThe kinetics of drug release from polymerdrug matrices containing an embedded magnet was continuously monitored in vitro and in vivo. The application of an oscillating magnetic field increased the rate of drug release from the polymer matrices. Within the limits of detection the increase in release occurred immediately, remained stable for as long as the field was applied, and returned exactly to baseline upon withdrawal of the field. The increase in release was directly proportional to field amplitude. The same pattern of results were observed in vivo as in vitro, though higher strength fields were required in vivo to achieve the same effect observed in vitro.
Wear‐accelerated corrosion of Ti‐6Al‐4V and nitrogen‐ion‐implanted Ti‐6Al‐4V: Mechanisms and influence of fixed‐stress magnitude
Authors: Buchanan R. A. , Rigney E. D. , Williams J. M. 
Published: December 2004

AbstractWear‐accelerated corrosion rates at constant anodic potentials were evaluated for unimplanted and nitrogen‐ion‐implanted surgical Ti‐6Al‐4V while wearing against ultrahigh‐molecular‐weight polyethylene at stress levels up to 6.90 MPa (1000 psi). The ion implantation processing was found to reduce the wear corrosion rates in both saline and serum solutions at all applied stress levels. During wear testing, all of the ion‐implanted surfaces remained visually unchanged from the polished condition. However, many of the unimplanted surfaces developed damage zones characterized by wear tracks and black wear debris. A surface‐damage mechanism is proposed and discussed which involves disruption of the Ti‐6Al‐4V protective oxide film, subsequent entrapment of oxide particles in the polyethylene, then self‐perpetuating damage due to the abrasive action of the embedded particles.
The effect of injection of powdered biomaterials on mouse peritoneal cell populations
Authors: Pizzoferrato A. , Vespucci A. , Ciapetti G. , Stea S. , Tarabusi C. 
Published: December 2004

AbstractThe authors suggest an experimental model for the assaying, before implantation, of the tissue reaction that wear particles from artificial joints can cause in the human body. Mice were intraperitoneally injected with biomaterial powders in suspension in saline. The materials used were chromium, chromium oxide, nickel, nickel oxide, aluminium, alumina, alumina‐titania, cobalt, molybdenum, titanium, silver, zirconium oxide, iron oxide, and stainless steel. Peritoneal lavage was performed a week after injection. A thorough morphological and quantitative analysis of the cell suspension thus obtained was made both immediately after collection and after a 24 h culture.
Surface characterization of heparin‐complexing poly(amido amine) chains grafted on polyurethane and glass surfaces
Authors: Barbucci Rolando , Baszkin Adam , Benvenuti Manuela , Costa Maria De Lourdes , Ferruti Paolo 
Published: December 2004

AbstractPoly(amido‐amine) chains grafted onto polyurethanes and glass form stable complexes with heparin yielding potential nonthrombogenic surfaces. The characterization of the surfaces, and the product of each chemical reaction including final heparinized surfaces, has been studied by contact angle data and scanning electron microscopy (SEM). Air in water, octane in water, and drop‐on‐plate contact angle data were used to estimate surface (γsv) and interfacial (γsw) free energies. Solid–water work of adhesion (Wa) and its dispersive (W) and polar (I) components were calculated for all studied surfaces. It has been found that the viscosity of polyurethane solution used for film casting influences wetting properties of these films. It has also been found that a direct correlation exists between the I/W values and the degree of coverage of the surfaces by cellular deposits after their exposure to platelet‐rich plasma. Final heparinized polyurethane and glass materials are hydrophilic, their I/W ratio is high, and little or no cellular deposit is observed on their surfaces.
Tissue reactions to wear products from polyacetal (Delrin®) and UHMW polyethylene in total hip replacement
Authors: Mathiesen E. B. , Lindgren J. U. , Reinholt F. P. , Sudmann E. 
Published: December 2004

AbstractThe tissue reaction to implanted materials and their wear products is important for the long‐term fixation of a total hip replacement (THR). Recent reports indicate a relatively high incidence of aseptic loosening with Christiansen total hip prostheses. We examined tissue reactions to wear products in two groups of prostheses: (1) 16 Christiansen prostheses with polyacetal (Delrin) sockets, and (2) 18 Charnley‐Müller total hip prostheses with ultrahigh‐molecular‐weight polyethylene (UHMWP) sockets. Specimens from these 34 patients were compared in a combined qualitative and semiquantitative morphological study. We saw similar histological changes in specimens of both groups, but specimens from the bone–cement interfaces of the acetabulum and femur shaft in the polyacetal group showed more inflammation and necrosis.
A histological comparison of the tissue interface of bioglass and silica glass
Authors: Ito G. , Matsuda T. , Inoue N. , Kamegai T. 
Published: December 2004

AbstractThe objectives of the present article are to confirm the bone bonding phenomenon of Bioglass (BG) developed by Hench et al., and to observe the singularity of tissue reaction to it. BG and nonreactive silica glass (SG) were implanted in the femurs of rabbits and rats. Histological examination revealed that a relatively acellular zone with little inflammation was formed on BG surface at 1 day after implantation. Neither fibrous tissue nor a distinct boundary was observed between BG and bone after 7 days. On the contrary, a moderate post‐operative inflammatory reaction was observed on SG at 1 day, and fibrous tissue was observed between SG and bone after 7 days. From these findings, it was confirmed that BG bonded directly with bone. As the relatively acellular zone observed on BG surface at 1 day was replaced by bone after 7 days, the formation of this zone might play an important role in bone‐bonding process. Further research should be focused on the mechanism and biological meaning of bone bonding, for this phenomenon can not be explained by the conventional pathological theory of foreign body encapsulation.
Studies of poly(ether)urethane pacemaker lead insulation oxidation
Authors: Thoma R. J. , Phillips R. E. 
Published: December 2004

AbstractPublished reports suggest that silver ions may catalyze the oxidation of poly‐(ether)urethane soft‐segments resulting in the failure of urethane insulations of specific models of pacemaker leads. Attempted oxidation of soft‐segment models, poly‐(tetra‐methylene ether)glycols, by silver nitrate has shown that metal‐ion catalyzed oxidative‐reduction (MICOR) does not adequately explain observed failures unless antioxidants are removed in process. Such cracking can, however, be explained in terms of a metal ion enhanced environmental stress cracking.
In vitro and in vivo characterization of synthetic polymer/biopolymer composites
Authors: Gilbert Donna L. , Lyman Donald J. 
Published: December 2004

AbstractCollagen, extracted from rat tail tendons using dilute acetic acid, was fabricated into films for subsequent characterization and biocompatibility testing. The reconstituted collagen was characterized with infrared spectroscopy, solution viscosity, contact angle, and tensile testing techniques and was found to be pure with molecular and physical properties consistent with findings of previous researchers. Composites composed of collagen coated on urethane and Silastic Rubber® films were fabricated to give improved tear resistance.The biocompatibility of the composites and individual polymers was evaluated by discs implanted in the paravertebral muscle of rabbits. After four weeks none of the materials induced any gross changes in the muscle. Histopathological evaluation revealed a fibrous capsule around all of the materials. Collagen and collagen composites exhibited a stronger reaction as evidenced by a larger fibroblast layer and a variety of inflammatory cells, lymphocytes, eosinophils, and macrophages. The urethane was rated with a response index of 1.5 versus 3.25 for the urethane/collagen composite; Silastic Rubber® rated a response index of 1.67 versus 3.12 for the Silastic Rubber®/collagen composite; collagen rated a response index of 3.3. The polyester sutures also induced a reaction with a larger fibrous capsule but fewer inflammatory cells as compared to collagen and collagen composites.
The determination of Al, Cr, Co, Fe, and Ni in whole blood by electrothermal atomic absorption spectrophotometry
Authors: Lugowski S. , Smith D. C. , van Loon J. C. 
Published: December 2004

AbstractProcedures for the determination of aluminum, chromium, cobalt, nickel, and iron in whole blood are presented and discussed. Chromium, cobalt, nickel, and iron were determined from one sample after decomposition of the blood with a mixture of nitric and perchloric acids. A graphite furnace was used for the determination of chromium, cobalt and nickel, and flame AAS was used for iron. The determination of Al was done from separate samples by GFAAS after dilution with 1% Triton TX‐100. The normal concentration of these elements was measured in rabbit and dog blood.
The influence of protein adsorption on interactions of cultured human endothelial cells with polymers
Authors: van Wachem P. B. , Vreriks C. M. , Beugeling T. , Feijen J. , Bantjes A. , Detmers J. P. , van Aken W. G. 
Published: December 2004

AbstractA systematic study of the effects of polymer surface properties on the interaction with human endothelial cells (HEC) may lead to the development of small‐diameter vascular grafts. HEC, suspended in culture medium containing 20% serum adhered and spread onto moderately wettable polymers such as TCPS (tissue culture polystyrene). Reduced or no adhesion of HEC was observed upon the hydrophobic polymers PETP (polyethyleneterephthalate, Dacron) and FEP (fluoroethylenepropylene copolymer, Teflon). Polymers precoated with the proteins albumin (Alb), high density lipoprotein (HDL), and immunoglobulin G (IgG) inhibited the adhesion of HEC, whereas fibronectin (Fn) coátings promoted cell adhesion. Endothelialization of PETP and FEP only occurred after precoating of these materials with Fn. The adsorption of Fn, Alb, HDL, and IgG from solutions of different serum concentrations onto TCPS, PETP, and FEP was related to the adhesion of HEC. Serum Fn only adsorbed onto TCPS, with the maximum at 0.1% serum concentration. Maximal cell adhesion onto TCPS was also observed after pretreatment with a solution containing 0.1% serum. The cell adhesion inhibiting proteins Alb and HDL preferentially adsorbed at higher serum concentrations. Desorption of these proteins and exchange for, e. g., cellular Fn may result in cell spreading and proliferation of HEC upon TCPS.
Comparison of the mechanical properties of simplex P, zimmer regular, and LVC bone cements
Authors: Davies Jeff. P. , O'Connor Daniel O. , Greer James A. , Harris William H. 
Published: December 2004

AbstractThe mechanical properties of the three cement preparations most widely used in the United States were compared by conducting tensile and fatigue tests on Simplex P, LVC, and Zimmer Regular bone cements. Specimens of all three cement preparations were prepared for mechanical testing with and without centrifugation of the cement immediately after mixing. Although the results of the tensile testing revealed a few specific instances of significant differences in the tensile properties of the three cement preparations, there was no consistent evidence that one cement was superior in tension to the others. However, the fatigue properties of Simplex P were consistently and significantly superior to the fatigue properties of both LVC and Zimmer Regular bone cements. Centrifugation of the cement immediately after mixing significantly improved both the tensile and fatigue properties of all three bone cements. However, the fatigue strength of centrifuged Simplex P was substantially and significantly superior to the fatigue strength of the centrifuged LVC and Zimmer Regular bone cements. Since in total joint replacements bone cement is subjected to cyclic loading, these data suggest that centrifuged Simplex P is a preferable bone cement to LVC and to Zimmer Regular cement with or without centrifugation.
Complement activation by hydroxyethylmethacrylate‐ethylmethacrylate copolymers
Authors: Payne Mark S. , Horbett Thomas A. 
Published: December 2004

AbstractCertain biomaterials, including nylon oxygenator and cellulosic dialysis membranes, are potent activators of human complement. In this study, the effect of polymers containing 2‐hydroxyethyl methacrylate (HEMA) on the human complement system was investigated. Copolymers of HEMA with ethylmethacrylate (EMA) varying from 100 to 40% HEMA in the monomer made by radiation initiation were used to coat glass discs. These were equilibrated with human plasma in vitro and the degree of complement activation was quantitated by C3a radio immunoassay. Significant activation was caused by copolymers made from monomers containing 60% or greater HEMA. A direct relationship between the amount of activation and the percentage of HEMA was found. The degree of activation by poly HEMA, when corrected for surface area, was quite similar to that observed for dialysis and oxygenator membranes. Similar observations were made when solid casts of crosslinked HEMA/N‐vinylpyrrolidone (NVP) copolymer gels were tested, but the magnitude of activation was much greater. The results are significant because complement activation may play an important role in the response to foreign surfaces, in both extravascular and intravascular settings. A new concept of molecular biocompatibility is proposed in which surfaces eliciting molecular transformations in any of the biological defense systems are deemed nonbiocompatible. By this criterion, the hydrogel poly‐HEMA, which has so frequently been thought of as biocompatible, is considered to be a molecularly nonbiocompatible material.
Shear creep of injectable collagen biomaterials
Authors: Wallace Donald G. , Rhee Woonza , Weiss Barbara 
Published: December 2004

AbstractShear creep experiments in a parallel‐plate apparatus were carried out on two injectable forms of collagen: semidilute nonfibrillar solutions (32 and 45 mg protein/mL) and aqueous fibrillar suspensions (at 35 and 65 mg/mL). Nonfibrillar solutions were more easily deformed than fibrillar suspensions, and both materials continued to deform slowly, even at long times (up to 6 × 104 sec). When the creep compliance, J(t), was plotted versus t1/3, regions of linear dependence were identified, which indicated that the materials were undergoing Andrade creep. At higher stress levels, J(t) diverged from t1/3, and true viscous flow occurred. A delayed viscosity could be calculated which agreed with viscosities derived from measurements under conditions of steady shear Couette flow. The time of onset of viscous flow was identified with a specific strain for each material, suggesting yield strain behavior. An analysis of recovery curves showed that at low stress levels or for short experimental times, the Boltzmann superposition was approximately obeyed, indicating linear behavior. At high stress levels and times >103 sec, both nonfibrillar solutions and fibrillar suspensions showed marked curvature of stress‐strain curves, which indicated that the materials are nonlinear in creep.
The electrochemical behavior of metallic implant materials as an indicator of their biocompatibility
Authors: Zitter H. , Plenk H. 
Published: December 2004

AbstractThis study introduces a simple in vitro arrangement to measure current densities of implant metals. The in vivo condition of a metallic implant lying in tissues exhibiting different redox potentials is simulated in so‐called straddle tests by applying a constant potential difference of 250 mV in saline containing the stable, fast‐reacting redox system K4Fe(CN)6/K3Fe(CN)6. From a variety of corrosion‐resistant implant metals and alloys, gold showed the highest current densities, followed by the stainless steel, the cobalt‐based alloy, and the TiAIV‐alloy. The pure metals titanium, niobium, and tantalum showed the lowest values. This can be explained by the stable oxide layer on these base metals, preventing an exchange of electrons and thus any redox reaction. This rating of metallic implant materials based on in vitro measurements of current densities is in good accordance with their biocompatibility rating reported from in vivo experiences. It seems that simple and cheap electrochemical tests allow an even more precise differentiation of the suitability of metallic materials for implant purposes than most of the conventional implantation tests, considering that biocompatibility is not only determined by corrosion products, but also by exchange currents and reaction products of redox processes involving tissue compounds.
Enhanced in vitro fibrinolytic activity of immobilized plasmin on collagen beads
Authors: Shankar Hariharan , Senatore Fred , Zuniga Pat , Venkataramani Edamanal 
Published: December 2004

AbstractPlasmin was immobilized on collagenous substrates using carbodiimide as a linking agent. The kinetics of soluble and immobilized plasmin were monitored by reacting them with the chromogenic substrate S‐2251 (H‐D‐Val‐Leu‐Lys‐pNA) in the presence and absence of a2‐antiplasmin (a2‐PI). The ability of immobilized plasmin to lyse synthetic clots formed from fibrinogen and thrombin was determined by detecting the formation of fibrin degradation products (FDP). The activity of immobilized plasmin was 0.02 casein units (CU)/mg of collagen. The kinetic analysis of soluble and immobilized plasmin in the presence and absence of a2‐PI shows that while soluble plasmin activity was inhibited by the presence of a2‐PI, the plasmin inhibitor did not interfere with the ability of immobilized plasmin to attack fibrin. In the absence of a2‐PI, the ability of the immobilized plasmin to lyse synthetic clots was the same as that of soluble plasmin. In the presence of a2‐PI, immobilized plasmin produced twice the amount of FDP as did soluble plasmin. The immobilized plasmin activity was stable for a period of at least 3 months.
Cell responses to biomaterials I: Adhesion and growth of vascular endothelial cells on poly(hydroxyethyl methacrylate) following surface modification by hydrolytic etching
Authors: McAuslan B. R. , Johnson G. 
Published: December 2004

AbstractHydrogels of poly(hydroxyethyl methacrylate) (polyHEMA) homopolymer do not normally support the attachment and growth of mammalian cells. By altering the surface it has been possible to dramatically change this cell–substratum interaction so that vascular endothelial cells can attach and completely populate a poly HEMA surface. While this can be achieved by copolymerisation of polyHEMA with methacrylic acid or diethylaminoethyl methacrylate, it is most conveniently achieved by brief treatment of polyHEMA hydrogel with concentrated sulphuric acid. The resultant creation of surface—COOH groups, revealed by electron spectroscopy for chemical analysis, is consistent with the hydrolytic formation of methacrylic acid on the surface layer. Surface—COOH groups created by treatment with chloric or hydrofluoric acids were not effective. Following sulfuric acid treatment, cell adhesion and growth on polyHEMA hydrogel were better than on Teflon and approached those attained on glow–discharge‐treated polystyrene. The capacity of acid‐treated polyHEMA to adsorb albumin or fibronectin was of the order of 100‐fold or 10‐fold lower respectively than either polystyrene, Teflon, or segmented polyurethane. Hydrolytic “etching” in this way is proposed as an efficient means of expanding the use of polyHEMA hydrogel as a biomaterial without modifying the overall physicochemical properties of the bulk of the material.