bluuebunny/crossref_metadata_2025_split huggingface dataset:
Degradation of adsorbed fibrinogen by surface‐generated plasmin
Authors: Brash J. L. , Chan B. M. C. , Szota P. , Thibodeau J. A. 
Published: December 2004

AbstractAn investigation of the physical status of fibrinogen that has been adsorbed to glass and then eluted has been conducted. Exposure of Kabi fibrinogen to glass was carried out using a glass bead column experiment. The fibrinogen was eluted sequentially, first by 1 M Tris and then by SDS. The initially eluted fibrinogen showed considerable degradation (SDS polyacrylamide gel electrophoresis) while the later fractions were less degraded. Fibrinogen purified by chromatography on either DEAE‐cellulose or Sepharose‐lysine to remove plasminogen was less degraded. When purfied plasminogen was added to fibrinogen, degradation of column eluates was very extensive in all eluted fractions. These results are interpreted in terms of a surface‐mediated activation of plasminogen to plasmin followed by fibrinogenolysis. Although such an effect remains to be demonstrated as a general property of surfaces, it is speculated that surfaces may vary in their activation of fibrinolysis as well as their activation of clotting, and that maximization of fibrinolysis is a worthwhile goal in the development of blood‐compatible surfaces.
Evaluation of in vivo adsorption of blood elements onto hydrogel‐coated silicone rubber by scanning electron microscopy and fourier transform infrared spectroscopy
Authors: Seifert Linda M. , Greer Raymond T. 
Published: December 2004

AbstractThree hydrogel formulations consisting of 2‐hydroxyethyl methacrylate (HEMA) copolymerized with N‐vinyl pyrrolidone (NVP) were incorporated into silicone rubber by irradiation‐induced polymerization. These coatings were chosen to represent different degrees of hydrophilicity, and they changed the hydrophobic character of the silicone rubber surface to that of hydrophilic. These composite materials and the silicone rubber comparison material were used as femoral artery‐to‐vein (A‐V) shunts and were removed at 15 min, an approximate time representative of an initial buildup stage of blood elements on test surfaces. Data obtained by scanning electron microscopy (SEM) were used to determine the type and amount of adhering blood cells and fibrin at the time interval described. One‐half of each specimen was used for Fourier Transform Infrared (FT‐IR) analysis to provide a direct comparison of the relative amounts of protein present on the silicone rubber and the three hydrogel composite samples. The combined SEM and FT‐IR analyses were performed on A‐V samples from three dogs. Differences in the response of blood to the surfaces were found by the combined SEM and FT‐IR analyses. The more hydrophilic a hydrogel grafted surface, the less fibrin and cellular elements were seen deposited on it. This is not interpreted as an indication of less reactivity, but is more likely due to thrombus buildup and a degree of subsequent embolization (a tearing of sections of the platelet matting away from a surface, revealing an area that again can be covered).
Modification of polyetherurethane for biomedical application by radiation‐induced grafting. I. Grafting procedure, determination of mechanical properties, and chemical modification of grafted films
Authors: Jansen B. , Ellinghorst G. 
Published: December 2004

AbstractRadiation grafting of monomers onto suitable trunk polymers is a useful tool for tailoring new polymers for special purposes. This technique has been used in the past for the development of biocompatible materials, e.g., by grafting hydrogels onto mechanically stable polymers. In this first part of our work, the radiation grafting of hydrophilic or reactive monomers onto a polyetherurethane film using the preswelling technique is described. Following this technique the trunk polymer was swollen in the monomer before irradiation. As monomers 2‐hydroxyethyl methacrylate (HEMA), 2,3‐epoxypropyl methacrylate (GMA), 2,3‐dihydroxypropyl methacrylate (GOMA), and acrylamide (AAm) were used. The kinetics of the grafting reactions were examined, and the distribution of the graft component inside the trunk polymer was investigated by means of infrared (IR) spectroscopy. Surface‐grafted as well as bulk‐ and surface‐grafted products could be obtained. The mechanical behavior of the grafted films—especially in the water‐swollen state—was examined and compared with that of the pure trunk polymer. In nearly all cases it was found that the tensile strength σB and the elongation at break εR decreases as the grafting yield increases. Modification of GMA‐ and AAm‐grafted films via chemical reactions was performed to create new functional groups of biomedical interest. In this manner a diol structure, a carboxylic acid structure, and a sulfonic acid group could be introduced in the grafted polymer. The water uptake of such modified films is increased markedly when compared with that of the unmodified samples.
Rat peritoneal macrophage adhesion to hydroxyethyl methacrylate–ethyl methacrylate copolymers and hydroxystyrene–styrene copolymers
Authors: Lentz Anthony J. , Horbett Thomas A. , Hsu Lawrence , Ratner Buddy D. 
Published: December 2004

AbstractMacrophage adhesion to a wide variety of substrates has been measured, but no systematic study of the influence of specific substrate chemical properties on adhesion is available. These studies were conducted using two series of materials, copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) and copolymers of hydroxystyrene and styrene, to determine the effect of a single chemical property, polar character, on adhesion. Rat periotoneal macrophages were allowed to contact polymer substrates for periods ranging from 1 to 240 min before being subjected to a shear stress of 60–120 dynes/cm2 in a thin‐channel flow cell. Percentage adhesion was calculated from the number of cells that remained adherent to the substrate after 30 s of applied shear stress. Macrophages remained adherent to 100% EMA and all hydroxystyrene–styrene copolymer surfaces after only 1 min of contact. In copolymers of the HEMA‐EMA series, the time required to attain peak adhesion levels increased with increasing substrate hydrophilicity (increasing HEMA content). Cells did not attach to the 20% EMA/80% HEMA copolymer and the 100% HEMA polymer. The results demonstrate that there is a time delay between contact and adhesion of the cells to surfaces of increasing hydrophilicity within the HEMA‐EMA series and no time delay with the hydroxystyrene–styrene series. The time delay is thought to be a function of the excluded volume provided by polymers that are able to undergo significant chain rotation and or swelling in the solvent, water. Small excluded volumes present in copolymers of high EMA content and all hydroxystyrene–styrene copolymers offer little or no resistance to formation of adhesive bonds by macrophages, whereas copolymers with large excluded volumes (high HEMA content) prevent contact and/or adhesion. A mechanism based on the net excluded volumes of both the cell and substrate surface macromolecule is proposed to explain this phenomenon.
Microheterophase structure, permeability, and biocompatibility of A‐B‐A triblock copolymer membranes composed of poly(γ‐ethyl L‐glutamate) as the A component and polybutadiene as the B component
Authors: Sato H. , Nakajima A. , Hayashi T. , Chen G.‐W. , Noishiki Y. 
Published: December 2004

AbstractA‐B‐A block copolymers (EBE) consisting of poly(γ‐ethyl L‐glutamate) as the A component and polybutadiene as the B component were synthesized. The microheterophase structure of these block copolymers, as observed microscopically, was less distinct than that of the block copolymer (GBG) composed of poly(γ‐benzyl L‐glutamate) as the A component. This was attributed to the better compatibility of the ethyl group with polybutadiene block, compared with the benzyl group. The observed micelle size of various microheterophase structures ranged from 350 to 480 Å, which agreed well with the micelle size estimated from a thermodynamic study. From the measurement of water permeation through the EBE block copolymer membranes, the contributions of the interfacial region between the α‐helical polypeptide domain and polybutadiene domain to the permeability coefficient were concluded to be higher than those of poly(γ‐methyl L‐glutamate)‐polybutadiene block copolymer (MBM) membranes, i.e., more hydrophilic domain seemed to exist in EBE membranes than in MBM membranes. The results of in vivo tests on the tissue compatibility indicate that the EBE block copolymer membranes have good biocompatibility.
The removal of residuals and oligomers from poly(2‐hydroxyethylmethacrylate)
Authors: Brynda E. , Štol M. , Chytrý V. , Cífková I. 
Published: December 2004

AbstractPoly(2‐hydroxyethyl methacrylate) gels obtained by the cross‐linking polymerization using four different free‐radical initiators were washed with water. Chromatographically, the eluate appeared to be a mixture of low‐molecular‐weight compounds and of a small amount of the high‐molecular‐weight component. The UV and IR absorption spectra of compounds present in the eluate were compared with those of model compounds that were assumed to exist in the gel as impurities after the polymerization (monomers and oligomers of hydroxyethyl methacrylate, decomposition products of initiators). Time dependences of the removal of impurities from the gels by washing were measured. Most of the impurities were washed out within a few hours. In addition to the assumed impurities, the eluate was found to contain an unidentified compound that was still washed out after several months. Intracutaneous applications of this compound did not produce local irritation of the tested tissue.
Alginate dental impression materials: Chemistry, structure, and properties
Authors: Cook Wayne 
Published: December 2004

AbstractThe setting behavior of calcium alginate impression materials was investigated by monitoring the viscosity, calcium ion activity, and shear modulus during the reaction. Structural information was also obtained from the dependence of viscosity and compressive modulus on the calcium concentration in model systems. The gelation time is primarily controlled by the concentration of Na4P2O7 in solution acting as a retarder, while the level and particle size of the alginate and CaSO4 · 2H2O also affect the kinetics through the dissolution rates and concentration effects. The Ca2+ crosslinks bridging the alginate chains in the network appear to be labile. Although this process of bond interchange and that of continued polymerization during deformation may be contributory mechanisms to permanent set, bond rupture appears to be the primary mechanism. Bond rupture can be reduced by increasing the alginate content in the system which also raises the tear energy. Both the permanent set and tear energy are affected by the filler particle morphology.
Adhesion behavior of rat lymphocyte subpopulations (B cell and T cell) on the surface of polystyrene/polypeptide graft copolymer
Authors: Maeda Mizuo , Kimura Masatoshi , Inoue Shohei , Kataoka Kazunori , Okano Teruo , Sakurai Yasuhisa 
Published: December 2004

AbstractPolyvinyl/polypeptide graft copolymers having microdomain structure on their surfaces were newly synthesized for the development of a specific cell separator, and the adhesion behavior of rat lymphnode lymphocytes with these materials was examined by column method. Morphologic change of lymphocytes adherent to the graft copolymers was found to be less than that of cells adherent to corresponding homopolymers, i.e., polystyrene and poly(γ‐benzyl L‐glutamate). Separation of lymphocyte subpopulations (B cell and T cell) was examined in the absence of serum proteins. The adhesion selectivity for B cell was found to depend on the microdomain structure, since the highest value, 2,2, was observed for the graft copolymer with the polypeptide content of 50 wt%. Synthetic polypeptide derivatives may be promising materials which substitute for a conventional system with nylon fiber and fetal calf serum.
In vivo biocompatibility studies. VII. Inflammatory response to polyethylene and to a cytotoxic polyvinylchloride
Authors: Marchant R. E. , Anderson J. M. , Dillingham E. O. 
Published: December 2004

AbstractThe cellular biocompatibility of low‐density polyethylene and a cytotoxic polyvinylchloride were investigated using an in vivo cage implant system. Components of the inflammatory response (white cells, extracellular alkaline and acid phosphatase, the complement component C3, and total protein content) were monitored over a 21‐day implantation period. Scanning electron microscopy was used to evaluate the morphologic condition of leukocytes adherent to the implanted polymers. Prior to implantation, each polymer was evaluated using an established primary acute toxicity screen. The results showed that the cytotoxic polyvinylchloride stimulated an intense acute phase inflammatory response, and at later observation periods, an intense and increasing chronic inflammatory response. In constrast, the polyethylene promoted relatively small increases in the acute and chronic phases of inflammation; the overall cellular response being essentially resolved by the third week after implantation. The initial toxicity screen of each polymer suggested that the observed differences in inflammation were primarily caused by the release from the polyvinylchloride of the added cytotoxic agent (dioctyltinbisoctylmercaptoacetate).
Bioerodible polyanhydrides as drug‐carrier matrices. II. Biocompatibility and chemical reactivity
Authors: Leong K. W. , D'Amore P. , Marletta M. , Langer R. 
Published: December 2004

AbstractThe biocompatibility of bioerodible polyanhydrides and toxicology of the polymer breakdown products were assessed. Poly‐[bis (p‐carboxy‐phenoxy) propane anhydride] (PCPP), Poly(terephthalic acid anhydride) (PTA), and their copolymers with sebacic acid were tested. The polymers did not provoke inflammatory responses in the corneas of rabbits over a six week implantation period. Subcutaneous implantation studies of PCPP in rats over a six month period showed no evidence of inflammatory cells and only slight tissue encapsulation by layers of fibroblastic cells. The degradation products of the polymers were nonmutagenic, noncytotoxic, and had a low teratogenic potential. The in vitro growth of mammalian cells on the polymers was unaffected as measured by cell morphology and cell growth rate. The chemical reactivity of the polyanhydrides with reactive model drugs, para substituted anilines, was also examined. Amides were formed when the drugs were injection molded with the polyanhydrides at 120°C. However, no reaction was observed using compression molding at room temperature. No reaction occurred between the polymer and the drug during the hydrolytic degradation of the matrix at 37°C.
Use of tricalcium phosphate or electrical stimulation to enhance the bone–porous implant interface
Authors: Berry J. L. , Geiger J. M. , Moran J. M. , Skraba J. S. , Greenwald A. S. 
Published: December 2004

AbstractImplant stabilization by biologic ingrowth into a porous surface offers a durable method of prosthetic fixation. These systems, however, lack the immediate stability offered by the use of acrylic bone cement. The interface strength of porous coated CoCrMo in a canine model does not approach that of acrylic bone cement until two weeks postoperatively. It is expected that this would be a minimum time period in clinical applications. Both chemical and electrical means have been advocated as methods to affect tissue ingrowth. A study using a canine model was undertaken to determine tissue ingrowth rates utilizing examples of these two methods: (1) impregnation of the porous structures with tricalcium phosphate powder (TCP); or (2) the application of an electrical stimulator to the implant with the implant itself serving as the cathode. Ten implants were coated with TCP, two each at weekly intervals from 1 to 5 weeks. Plain porous rods were likewise implanted, serving as the controls. While histology did reveal a slightly more dense bony structure, the interface bond strength was not affected by TCP. Electrical stimulation of the implant was similarly investigated with an additional time period of 10 weeks. Compared to the controls, the electrically stimulated implants reveal no statistically demonstratable difference in interface strength. Histologic specimens indicate larger areas of calcification than are observed in the controls.
A comparative study of the biologic and immunologic response to medical devices derived from dermal collagen
Authors: DeLustro Frank , Condell Richard A. , Nguyen Mai Anh , McPherson John M. 
Published: December 2004

AbstractWe examined collagen materials for soft tissue augmentation [Zyderm® Collagen Implant (ZCI), glutaraldehyde cross‐linked (GAX) collagen, and Koken Atelocollagen (Atelocollagen)]; hemostatic collagens [Gelfoam® Gelatin Powder (Gelfoam), Avitene® Microfibrillar Collagen Hemostat (Avitene), and Collastat® Collagen Hemostat (Collastat)]; and reconstituted, intact fibrillar collagen from bovine skin in a subcutaneous guinea pig model. After 11, 25, and 39 days in situ, explants from animals injected with GAX collagen demonstrated greater wet‐weight persistence than all other materials. Conversely, at all time points, the explants of Atelocollagen were the least persistent. Following 25 days in vivo, explants were examined using differential scanning calorimetry; ZCI and Atelocollagen displayed thermal transition temperatures of 58°C. Avitene and Gelfoam explants displayed transition points of 30°C and 32°C, indicating denatured or cleaved collagen. By contrast, GAX collagen explants had a high (68°C) transition temperature, reflecting its cross‐linking. With respect to immunogenicity, day 39 sera from ZCI treated animals showed significantly lower titers in the ELISA to their respective implant collagen than all other groups examined, while antibody activity in the GAX collagen, Gelfoam, Atelocollagen, and intact collagen groups were not significantly different. Collastat elicited antibodies with a greater affinity than observed in these previous groups. Sera from Avitene treated animals demonstrated the highest antibody levels and were the only sera which reacted with bovine serum albumin. Thus, Avitene was the most immunogenic of the collagen materials examined, while GAX collagen demonstrated the greatest persistence and minimal immunogenicity, and ZCI was the least immunogenic.
Fracture toughness determination of dental amalgams through microindentation
Authors: Hassan R. , Vaidyanathan T. K. , Schulman A. 
Published: December 2004

AbstractA microindentation technique was used to study and estimate the fracture toughness of six amalgams. A significant difference is observed between fracture toughness at the bulk and the margin of amalgams. All amalgams show significant differences in fracture toughness as a function of distance from the margin. Microindentation measurement of fracture toughness appears to be an effective method of evaluating the localized brittleness of amalgams.
Clinical study of urokinase‐bound fibrocollagenous tubes
Authors: Senatore Fred , Bernath Fred , Meisner Ken 
Published: December 2004

AbstractDacron‐reinforced fibrocollagenous tubes (FCT) were synthesized from canine mongrels using the mandril‐rod technique in order to develop a small diameter (i.e., 4 mm i.d.) vascular graft. They were rendered fibrinolytic by immobilizing urokinase on to the inner surface of the tubes. Urokinase‐bound fibrocollagenous tubes (UK‐FCT), control FCTs (i.e., no bound enzyme), Perloff grafts (Dr. Perloff, Department of Surgery, University Medical Center, Sidney Australia, has developed a mandril‐derived collagenous tube from goats. Samples were implanted for comparative purposes.) and autogeneous saphenous veins, were interposed in the carotid or femoral artery in chronic studies involving 21 canine mongrels. On the basis of Doppler auscultation and palpation, the UK‐FCTs were statistically more patent than other candidate prostheses. Fibrin degradation product (FDP) increased in the dogs' systemic circulation with a postoperative peak of 5 days. The host's increase in fibrinolytic activity was shown to be local to the anastamosis. A carotid arterial extracorporeal shunt was designed to evaluate acute patency. Results indicated a rapid thrombosis but no platlet or fibrin adherence to the graft surface was observed, as evidenced by scanning electron microscopy.
Synthesis and bioevaluation of a rapidly biodegradable tissue adhesive: 1,2‐Isopropylidene glyceryl 2‐cyanoacrylate
Authors: Jaffe H. , Wade C. W. R. , Hegyeli A. F. , Rice R. M. , Hodge J. 
Published: December 2004

AbstractA rapidly biodegradable tissue adhesive, 1,2‐isopropylidene glyceryl 2‐cyanoacrylate, was synthesized and characterized by NMR. Bond strength was determined. Three types of corresponding polymers were prepared and evaluated for in vitro and in vivo toxicity. The polymers were generally found to be in the moderately toxic and toxic groups similar to the lower alkyl 2‐cyanoacrylates.
Thrombin uptake and inhibition on endothelium and surfaces with a stable heparin coating: A comparative in vitro study
Authors: Arnander C. , Dryjski M. , Larsson R. , Olsson P. , Swedenborg J. 
Published: December 2004

AbstractThe endothelial lining and two differently heparin‐coated surfaces were compared in vitro regarding thrombin uptake and inhibition. One heparin surface was based on stabilized ionic binding of heparin, the other on covalent binding of partially degraded heparin. Both heparin surfaces have previously been shown to have pronounced thromboresistant properties. The two heparinized polyethylene surfaces and the endothelial surface of segments of the porcine aorta were studied. After exposure to the surfaces, thrombin disappeared from the solution and appeared bound to the surfaces. The disappearance rate of thrombin from the solution was the same on exposure to the endothelium and the covalently bonded heparin surface, but less following exposure to the ionically bonded heparin surface. The thrombin activity appearing on the endothelium was lower than on the heparin surfaces, indicating that the endothelium exerted a slow thrombin inhibiting capacity. On exposure of the thrombin‐loaded endothelium to plasma, thrombin was rapidly inhibited. Thrombin bound to the covalently bonded heparin surface was inhibited at a slower rate than on the ionically bonded surface, but still faster than the rate at which free thrombin was inhibited in nonheparinized plasma. It is concluded that the endothelium and stabilized heparin coatings bind thrombin and accelerate its inhibition by plasma.
In vitro calcification and in vivo biocompatibility of the cross‐linked polypentapeptide of elastin
Authors: Wood S. A. , Lemons J. E. , Prasad K. U. , Urry D. W. 
Published: December 2004

AbstractThe in vitro calcifiability and molecular weight dependence of calcification of the polypentapeptide, (L · Val1‐L· Pro2‐Gly3‐L · Val4‐Gly5)n, which had been γ‐irradiation cross‐linked have been determined when exposed to dialyzates of normal, nonaugmented fetal bovine serum. The material was found to calcify: calcifiability was found to be highly molecular weight dependent and to be most favored when the highest molecular weight polymers (n ≈240) had been used for cross‐linking. The in vivo biocompatibility, biodegradability, and calcifiability of the γ‐irradiation cross‐linked polypentapeptide were examined in rabbits in both soft and hard tissue sites. The material was found to be biocompatible irrespective of its physical form and to be biodegradable but with n of 200 or less it was not shown to calcify or ossify in the rabbit tibial nonunion model.