bluuebunny/crossref_metadata_2025_split huggingface dataset:
Difference in tissue response to nitrogen‐ion‐implanted titanium and c.p. titanium in the abdominal wall of the rat
Authors: Röstlund Tord , Thomsen Peter , Bjursten Lars Magnus , Ericson Lars E. 
Published: December 2004

AbstractIon implantation modifies the surface properties of different materials. We have compared the biological properties of titanium implanted with nitrogen with those of pure titanium. Implants were inserted in the abdominal wall of rats. The implants with surrounding tissue were excised after 1 and 6 weeks, and embedded in epoxy resin. The bulk metal was removed electrochemically and the tissue cut for light and electron microscopy. Using this technique the implant surface, formed by a thin oxide layer, remains and appears in sections as a dense line. After 1 week both types of implants were surrounded by a fluid space containing proteins and scattered macrophages but few polymorphonuclear granulocytes. The fluid space was wider around ionimplanted titanium (52 ± 22 μm) than around pure titanium implants (15 ± 3 μm). After 6 weeks the fluid space had largely disappeared around both type of implants. Around pure titanium implants macrophages and fibroblasts, quantified in 1‐μm‐thick sections in the light microscope, were present in about the same concentration in the inner tissue zone (within 25 μm from the implant surface). Around ion‐implanted titanium macrophages predominated in the inner zone and multinuclear giant cells were present in almost all sections. Around both type of implants fibroblasts increased and macrophages decreased with increasing distance from the surface. In the electron microscope macrophages close to the surface of pure titanium were of small size and had an ultrastructure indicating a low activity. Macrophages close to ion‐implanted titanium were large and had an active appearance as indicated by the presence of large amounts of endoplasmic reticulum and large Golgi areas in the cytoplasm. Our observations indicate that modification of the surface properties of titanium implants by ion implantation changes the biological properties.
Study of the effect of the surface state on the cytocompatibility of a Co‐Cr alloy using human osteoblasts and fibroblasts
Authors: Naji Abdessamad , Harmand Marie‐Françoise 
Published: December 2004

AbstractCobalt‐chromium‐based alloys are widely used in oral and orthopedic implantology. Although they are relatively well tolerated, biological complications could occur which sometimes are due to the insufficient biocompatibility of the alloy. This study shows the effects of an alloy (Co (base), 28% Cr, 5.5% Mo, 1% Ni, 0.95% Si, 0.7% Fe, 0.65% Mn, 0.25% C), on differentiated human cells derived from an oral implantation site, specifically alveolar bone osteoblasts and gingival fibroblasts. The cytocompatibility of the alloy is determined by the study of cell proliferation, determination of total cell protein and in tracellular alkaline phosphatase contents, cytoskeleton, and cell morphology. The alloy is presented to the cells in four different surface states: rough cast specular polished, microbead blasted, and RF sputtered. The results demonstrate that the same material has different effects on the basal and specific cellular functions, according to its surface state. For this alloy we can classify its cytocompatibility according to its surface state in such an order: Microbead blasted ≥ specular polished > RF sputtered > rough cast.
Suspension polymerization of 2‐hydroxyethyl methacrylate in the presence of polymeric diluents: A novel route to spherical highly porous beads for biomedical applications
Authors: Jayakrishnan J. , Thanoo B. Chithambara 
Published: December 2004

AbstractSpherical, highly porous beads of poly(2‐hydroxyethyl methacrylate) (PHEMA) crosslinke with ethylene glycol dimethacrylate (EGDM) were prepared by suspension polymerization of HEMA in concentrated NaCl solutions in presence of toluene, poly(methyl methacrylate) (PMMA) in toluene, and poly(tetramethylene glycol) (PTMG). Magnesium hydroxide prepared in situ in the dispersion medium gave the best stabilization effect for the monomer droplets. In the presence of PTMG, beads having nearly 1.0 mm in diameter could be prepared, while toluene alone as the diluent produced beads of very small size. Removal of PMMA or PTMG from the beads after polymerization using suitable solvents gave rise to highly porous PHEMA microspsheres. Polymerization in the presence of PTMG produced microspsheres with better spherical geometry as compared to those generated in the presence of PMMA. The effect of various factors such as NaCl concentration, concentration of Mg(OH)2, and the concentration of PMMA or PTMG in the monomer phase on the stability of the suspension and the particle size distribution was investigated.
Tissue reactivity and degradation patterns of absorbable vascular ligating clips implanted in peritoneum and rectus fascia
Authors: Chegini Nasser , Metz Stephen A. , Masterson Byron J. 
Published: December 2004

AbstractAbsorbable vascular ligating clips are finding increasing use in intraabdominal surgery. We report the results of a light and scanning electron microscope investigation of the tissue reactivity and clip degradation patterns of two such materials, Absolok (polydioxanone) and Lactomer (copolymer of glycolic and lactic acid), implanted in the fascia and peritoneum of rabbits for intervals of 2 to 70 days. Cellular response to the clips, defined as the number of inflammatory cells/104 μm2, was maximum at day 4 postimplantation, then gradually declined as the duration of implantation increased. This pattern, seen with both types of clips, was similar to that seen with polydioxanone (PDS) suture, but significantly greater than that associated with polypropylene (Prolene) suture. Although cellular response to the clips was greater in peritoneum than in fascia, especially on two occasions associated with adhesion formation, this was not statistically significant. Based on our morphological observations, the signs of clip degradation which were indicated by the appearance of surface crazing and cracks occurred earlier in peritoneum than in fascia.
Study of soft tissue ingrowth into canine porous coated femoral implants designed for osteosarcomas management
Authors: LaBerge M. , Bobyn J. D. , Rivard C. H. , Drouin G. , Duval P. 
Published: December 2004

AbstractThe objective of this project was to characterize soft tissue bonding to porous coated implants such as those that would be used for resection‐reconstruction of osteosarcoma cases. We were interested in determining conditions which would provide both mechanical attachment of the implant to the surrounding tissue and produce a vascularized interface. In a bilateral canine implant model, both femoral midshafts were replaced with a porous coated cobalt‐chrome segmental implant fabricated with average pore sizes of 300 μm or 900 μm. Twelve implants, six of each pore size, were used in six dogs. Two dogs were sacrificed at 2, 4, and 6 months after implantation. The soft tissue‐implant interface was characterized mechanically with peel tests and histologically using light microscopy and immunohistochemistry. At all periods, a nonvascularized fibrous membrane surrounded the smaller pore size implants, without ingrowth or mechanical bonding. In contrast, a vascularized membrane developed within and around the larger pore size implants; the attachment strength increasing with implantation time. The vascularity increased in size and quantity with time. This study demonstrates the feasibility of obtaining vascularized soft tissue attachment to tumor replacement implants with appropriate porous coated implant design.
Detection of surface‐adsorbed (lipo)proteins by means of a two‐step enzyme‐immunoassay: A study on the Vroman effect
Authors: Poot A. , Beugeling T. , van Aken W. G. , Bantjes A. 
Published: December 2004

AbstractIn view of reports on the involvement of high‐molecular‐weight (HMW) kininogen and high‐density lipoprotein (HDL) in the Vroman effect, we studied the adsorption of fibrinogen, HMW kininogen, HDL and several other proteins from pooled human plasma and congenitally HMW kininogen‐deficient plasma onto glass and low‐density polyethylene, both as a function of the plasma concentration and the contact time. Mixtures of purified (lipo)proteins were also included in the study. Protein adsorption was determined by means of a two‐step enzyme‐immunoassay. Our results support the hypothesis that HMW kininogen is involved in the displacement of fibrinogen, which is almost instantly adsorbed from normal plasma onto glass. On hydrophobic polymers like polyethylene, the low amounts of adsorbed fibrinogen and HMW kininogen from plasma and concentrated plasma solutions may be due to a preferential adsorption of HDL.
Mechanical property studies of human gallstones
Authors: Stranne Steven K. , Cocks Franklin H. , Gettliffe Roland 
Published: December 2004

AbstractThe recent development of gallstone fragmentation methods has increased the significance of the study of the mechanical properties of human gallstones. In the present work, fracture strength data and microhardness values of gallstones of various chemical compositions are presented as tested in both dry and simulated bile environments. Generally, both gallstone hardness and fracture strength values were significantly less than kidney stone values found in previous studies. However, a single calcium carbonate stone was found to have an outer shell hardness exceeding those values found for kidney stones. Diametral compression measurements in simulated bile conclusively demonstrated low gallstone fracture strength as well as brittle fracture in the stones tested. Based on the results of this study, one may conclude that the wide range of gallstone microhardnesses found may explain the reported difficulties previous investigators have experienced using various fragmentation techniques on specific gallstones. Moreover, gallstone mechanical properties may be relatively sensitive to bile‐environment composition.
Differential effects of eight metal ions on lymphocyte differentiation antigens in vitro
Authors: Bravo Isabel , Carvalho Graça S. , Barbosa Mário A. , de Sousa Maria 
Published: December 2004

AbstractIn vitro studies were conducted to determine the effects of metal ions known to be released from metallic implants in vivo on the expression of lymphocyte surface antigens. Normal human peripheral blood lymphocytes were exposed to various concentrations of metal ions (Fe3+, Ni2+, Co2+, Mo6+, V5+, Cr6+, Cr3+, and Ti3+) for 30 min at 37°C in a 5% CO2 atmosphere, and then analyzed for their ability to form rosettes with sheep red blood cells. Following this preliminary analysis, lymphocytes were exposed to the metal ions found to inhibit the E‐rosette reaction (Fe3+, Ni2+, and Co2+) in order to determine which of the following surface antigens were affected: CD2, CD3, CD4, CD8, CD1, CD22, CD10, and HLA‐DR. Our results showed that the in vitro treatment of lymphocytes with Fe3+ or Co2+ caused inhibition of CD2 only, whereas Ni2+ caused inhibition of both CD2 and CD3 antigens. These findings suggest that Fe3+, Co2+, and Ni2+ ions may interfere with T cell activation since both CD2 and CD3 are involved in that process.
Reduced thrombogenicity of polymers having phospholipid polar groups
Authors: Ishihara Kazuhiko , Aragaki Runa , Ueda Tomoko , Watenabe Akihiko , Nakabayashi Nobuo 
Published: December 2004

AbstractThe thrombogenicity of polymers having a phospholipid polar group, poly(2‐methacryloyloxyethyl phosphorylcholine (MPC)‐co‐n‐butyl methacrylate (BMA)), was evaluated by a microsphere‐column method with attention to the activation and adhesion of platelets on the polymer surface. When citrated platelet‐rich plasma (PRP) contacted with the polymers, a large number of platelets adhered and aggregated on poly(BMA). The number of adherent platelets decreased and deformation and aggregation were suppressed with increasing MPC composition. The same tendency was noted when Ca2+‐re‐added PRP came in contact with the polymers. In the case of poly(MPC‐co‐BMA) with 0.320 mole fraction of MPC, activation of platelets and formation of fibrin were completely suppressed. Therefore, MPC moieties in the polymer play an important role in the reduction of thrombogenicity of the polymer.
In vitro properties of crosslinked, reconstituted collagen sheets
Authors: Morykwas Michael J. 
Published: December 2004

AbstractReconstituted, 100‐μm‐thick collagen sheets were crosslinked with either UV light, chromium, or cysteine for use as a burn covering. The sheets were also exposed to a “surface agent” (hydroxyproline, fibronectin, or soluble basement membrane matrix containing Type IV collagen) as a preliminary step in planned adherence studies. Since some chemicals render the collagen toxic, the modified sheets were tested for cytotoxicity using human keratinocytes and fibroblasts. Autoradiography and 3H‐thymidine incorporation were used to quantitate the proliferative rate of these cells in vitro. There was a universal depression of keratinocyte incorporation of 3H‐thymidine following a 1‐day exposure to any collagen sheet when compared to cells not exposed to any collagen. This effect had lessened by 5 days' exposure to the collagen. Conversely, the fibroblasts showed an enhancement in rate of incorporation after 1‐day exposure, especially for cells exposed to collagen sheets crosslinked by UV light. This effect had also lessened by 5 days' exposure. Autoradiography showed few significant variations for any of the cells exposed for either time period. Chromium leaching was determined, with no values greater than 30% of the allowable maximum set by both the British and American Pharmacopeia.
Sequential polydepsipeptides as biodegradable carriers for drug delivery systems
Authors: Yoshida Masaru , Asano Masaharu , Kumakura Minoru , Katakai Ryoichi , Mashimo Tooru , Yuasa Hisako , Imai Kyoichi , Yamanaka Hidetoshi 
Published: December 2004

AbstractSequential polydepsipeptides containing both peptide and ester bonds, poly[(L‐alanyl)n‐γ‐ethyl L‐glutamyl‐L‐lactyl] (n = 0, 1, 2, and 3) (poly[(Ala)n‐Glu(OEt)‐Lac]), were prepared for application as biodegradable carriers for drug delivery systems. The in vivo degradation of these polymers was evaluated by subcutaneous implantation in the backs of male rats, and was strongly influenced by the number (n) of Ala units in poly[(Ala)n‐Glu(OEt)‐Lac]. The resulting poly(Ala‐Ala‐Glu(OEt)‐Lac) gave the highest degradability, in which 100% degradation was observed 24 weeks from the start of implantation. A luteinizing‐hormone‐releasing hormone agonist des‐Gly10‐[D‐Leu6]‐LH‐RH ethylamide (LH‐RH agonist), was incorporated into a sequential poly(Ala‐Ala‐Glu(OEt)‐Lac) carrier by the melt‐pressing technique, which gave fine cylindrical polymer formulations with different structures of drug dispersion, e.g., blend‐type and sandwich‐type formulations. The rate of in vivo release of LH‐RH agonist from a blend‐type formulation showed a linear decrease with time until its release was finished after 6 weeks' implantation. In contrast, in a sandwichtype formulation, the in vivo release rate was apparently maintained constant over a period of 16 weeks (24 ± 14 μg/day).
Postadsorptive transitions in fibrinogen: Influence of polymer properties
Authors: Rapoza Richard J. , Horbett Thomas A. 
Published: December 2004

AbstractChanges in the fibrinogen molecule after its adsorption to biomaterials may be important in determining blood compatibility. Previously, postadsorptive transitions were detected by measuring the elutability of adsorbed proteins with surfactant solutions. The elutability decreased with increased residence time, suggesting that protein—surface interactions increased with residence time. In this study, we have examined the effects of polymer structure and composition, chain mobility, and hydrophobicity on the postadsorptive transitions of fibrinogen. Glassy, rigid polymers showed high fibrinogen adsorption, regardless of whether the polymer was hydrophilic or hydrophobic. However, the binding strength (as measured by elutability) was much lower on hydrophilic polymers and oxygen‐containing hydrophobic polymers. Short‐term transitions, requiring 2 h or less after adsorption, were observed only on hydrophobic polymers that contained no oxygen. More gradual transitions were observed on hydrophobic polymers containing oxygen, but only after a lag time of 1–4 h.
Modulation of cell adhesion by modification of titanium surfaces with covalently attached self‐assembled monolayers
Authors: Sukenik Chaim N. , Balachander Natarajan , Culp Lloyd A. , Lewandowska Kristine , Merritt Katherine 
Published: December 2004

AbstractThe surface of titanium has been modified by covalent attachment of an organic monolayer anchored by a siloxane network. This coating completely covers the metal and allows controlled modification of surface properties by the exposed chemical end‐groups of the monolayer forming surfactant. The attachment of such a film allows different bulk materials (e.g., glass and titanium) to have identical surface properties and this can be used in regulating cell adhesion responses. This control over surface functionality can modulate the functions of fibronectin in regulating attachment and neurite formation by neuronal cells. The effect on bacterial adherence that is achieved by using such monolayers to vary surface hydrophilicity is also assessed.
Study of the mineral—organic linkage in an apatitic reinforced bone cement
Authors: Dandurand J. , Delpech V. , Lebugle A. , Lamure A. , Lacabanne C. 
Published: December 2004

AbstractIn order to increase mechanical properties of surgical cements, an apatitic filler has been linked to the polymethylmethacrylate (PMMA) matrix. We report here the study of the linkage between the mineral and organic components by a dielectric spectroscopy: Thermally Stimulated Current. First, the mineral—organic interface between apatitic—octocalcic phosphate and hydroxyethylmethacrylate (HEMA) has been investigated. Second, the filler—matrix interface between grafted apatite and PMMA has been examined. It has been shown that the filler is chemically linked to the matrix and stiffens the PMMA bone cement.
In vivo thrombus formation induced by complement activation on polymer surfaces
Authors: Hayashi K. , Fukumura H. , Yamamoto N. 
Published: December 2004

AbstractTo clarify involvement of complement activation in thrombus formation on polymer surfaces, in vitro complement activation was evaluated for polyethylene (PE) tubes radiation‐graft copolymerized with acrylamide (AAm), acrylic acid (AC), 2‐hydroxyethyl methacrylate (HEMA), Nvinylpyrrolidone (NVP), and vinyl alcohol (VOH), and compared to their in vivo antithrombogenicity and cell adherence in canine peripheral veins. The complement‐activating surfaces (NVP and VOH) cause preferential adhesion of leukocytes and were more thrombogenic than the low complement‐activating surfaces (AAm, PE, and HEMA). Infusion of naja haje cobra venom factor depressed leukocyte adhesion, followed by a marked decrease in thrombogenesis, for the strong classical‐pathway‐activating surface (NVP). Although estimation of in vitro activation for AC was inconclusive because of a large effect of adsorption, AC behaved like VOH in vivo. These results suggest that C5a(des Arg) mediated activation of leukocytes may play a role in thrombus formation by complement activation on polymer surfaces.
Rapidly degraded terpolymers of DL‐lactide, glycolide, and ϵ‐caprolactone with increased hydrophilicity by copolymerization with polyethers
Authors: Sawhney Amarpreet S. , Hubbell Jeffrey A. 
Published: December 2004

AbstractA series of 66 terpolymers of dl‐lactide, glycolide, and ϵ‐caprolactone was synthesized for the purpose of identifying those materials which exhibited rapid degradation in vitro. Polymers having half‐lives from a few weeks to several months were identified. The morphology of each material was scanning calorimetry. A terpolymeric composition of 60% glycolide, 30% dl‐lactide, and 10% ϵ‐caprolactone, which exhibited a half‐life of 17 days, was selected for further investigation. The hydrophilicity of this material was increased by performing the polymerization in the presence of a polyether prepolymer, Pluronic F‐68, with the motivation of concomitantly reducing cell and tissue adhesion. An increase in the hydrophilicty of the material was apparent from contact angle measurements. Copolymerization with the prepolymer also resulted in a stronger and partly crystalline material which was mechanically stable at physiological temperature in water. A slight increase was observed in the half‐life of the polymer relative to the base polymer due to the presence of the prepolymer.
The wear behavior of ion‐implanted Ti‐6Al‐4V against UHMW polyethylene
Authors: McKellop H. A. , Röstlund T. V. 
Published: December 2004

AbstractNitrogen‐ion‐implanted Ti‐6Al‐4V against UHMW polythylene was tested on a joint simulator to evaluate the wear behavior under different conditions. It was concluded that the polymer wear rate was not affected by ion implantation. The metallic wear, on the other hand, was substantially reduced by this treatment. It was also found that ion implantation resulted in good protection of the metal surface against third‐body wear by PMMA, while the introduction of C.P. titanium particles in the joint initiated tremendious wear. Although ion implantation improved the wear of titanium alloy against UHMW polyethylene, the durability of the implanted layer needs further study.
Poly(anhydride) administration in high doses in vivo: Studies of biocompatibility and toxicology
Authors: Laurencin C. , Domb A. , Morris C. , Brown V. , Chasin M. , McConnell R. , Lange N. , Langer R. 
Published: December 2004

AbstractPoly(anhydrides) proposed for use as vehicles for controlled drug delivery were administered subcutaneously in Sprague‐Dawley rats at two dosage levels (800 mg/kg rat and 2400 mg/kg rat) for a period of eight weeks. Biocompatibility was assessed using a number of methods. Thirtysix clinical chemistry and hematology parameters were monitored throughout the study. Blood values were statistically analyzed for any possible effects due to the implanted polymer. After 8 weeks, rats were sacrificed and complete necropsies were performed. Histological evaluations of 33 organ sites including heart, lung, liver, kidney, and brain were performed. In addition, subcutaneous implant sites were excised and examined both grossly and microscopically. Results from evaluations of blood chemistry and hematology data, organ analyses and local implant site analyses overall demonstrated that the poly(anhydride) biomaterial possessed excellent in vivo biocompatibility.
A parametric study of the factors affecting the fatigue strength of porous coated Ti‐6A1‐4V implant alloy
Authors: Kohn David H. , Ducheyne Paul 
Published: December 2004

AbstractThe high cycle fatigue strength of porous coated Ti‐6Al‐4V is approximately 75% less than the fatigue strength of uncoated Ti‐6Al‐4V. This study separates the effects of three parameters thought to be responsible for this reduction: interfacial geometry, microstructure, and surface alternations brought about by sintering. To achieve the goal of one parameter variations, hydrogen‐alloying treatments, which refined the lamellar microstructure of β‐annealed and porous coated Ti‐6Al‐4V, were formulated. The fatigue strength of smooth‐surfaced Ti‐6Al‐4V subjected to hydrogen‐alloying treatments is 643–669 MPa, significantly greater than the fatigue strength of β‐annealed Ti‐6Al‐4V (497 MPa) and also greater than the fatigue strength of preannealed, equiaxed Ti‐6Al‐4V (590 MPa). The fatigue strength of porous coated Ti‐6Al‐4V, however, is independent of microstructure. This leads to the conclusion that the notch effect of the surface porosity does not allow the material to take advantage of the superior fatigue crack initation resistance of a refined α‐grain size. Thus, sinternecks act as initiated microcracks and fatigue of porous coated Ti‐6Al‐4V is propagation controlled.