bluuebunny/crossref_metadata_2025_split huggingface dataset:
The in vitro and in vivo behavior of urokinase immobilized onto collagen‐synthetic polymer composite material
Authors: Watanabe S. , Shimizu Y. , Teramatsu T. , Murachi T. , Hino T. 
Published: December 2004

AbstractWith a view to developing biomaterials for semipermanent substitution, we have studied a composite material constituted with collagen and a synthetic polymer which possesses high tissue compatibility. This collagen—synthetic polymer composite was applied as a support for immobilization of enzymes for the purpose of providing a material surface with biological function. The enzymes, urokinase and trypsin, were successfully bound to the collagen membrane layer which had been activated by acyl azide formation of its carboxyl groups. The enzyme‐bearing composite material showed excellent catalytic activity toward a protein substrate as well as a low‐molecular‐weight synthetic substrate. The immobilized urokinase was characterized enzymatically and compared with native urokinase. The apparent affinity of immobilized urokinase for the substrate was slightly decreased, but its intrinsic kinetic properties were not significantly affected. No decrease in its esterase activity was observed both on repeated use and on long‐term storage, and its fibrinolytic activity was stable on heat or disinfection treatment. When this urokinase‐bearing composite material was applied into rabbit blood vessels, its in vivo fibrinolytic activity was maintained. Thus, enzyme—collagen—synthetic polymer composites may find wide application for biomaterials and artificial organs as functional biomaterials.
Biodegradation of a poly(α‐amino acid) hydrogel. I.In vivo
Authors: Dickinson H. R. , Hiltner A. , Gibbons D. F. , Anderson J. M. 
Published: December 2004

AbstractA new hydrogel material has been prepared by crosslinking a hydrophilic, nonionic poly(amino acid), poly(2‐hydroxyethyl‐L‐glutamine). The material properties of the hydrogel can be controlled by variation in the crosslink density, and the swelling ratio was found to be a sensitive and convenient method for measuring the extent ofin vivobiodegradation of implanted specimens. Degradation of the material was observed only during the first 2 weeks of subcutaneous implantation in rats, and is attributed to hydrolysis by proteolytic enzymes released during the acute and chronic stages of the normal inflammatory response.
The in‐vitro degradation of poly(glycolic acid) sutures — effect of pH
Authors: Chu C. C. 
Published: December 2004

AbstractTensile strength of poly(glycolic acid) suture (PGA) of size 2–0 was examined as a function of three pH levels, 5.25,7.44, and 10.09 of the buffer. Cord and yarn grip was used to eliminate grip‐induced failure of breaking strength tests. It was found that Dexon sutures degraded significantly faster in pH = 10.09 buffer than the other two lower pH buffers. There was no significant difference in degradation rate at pH = 5.25 and 7.44. At 7 days, PGA sutures lost almost half of its original tensile strength at pH = 10.09, while the same sutures still remained more than 95% of their original breaking strength at buffers of pH = 5.25 and 7.44. After 21 days, no trace of sutures could be detected in the buffer of pH = 10.09 while about 20% strength still remained in the buffers of pH = 7.44 and 5.25. Cage effect in the crystalline phase and pH dependent hydrogen bonding were introduced to explain the difference in degradation phenomenon of PGA at buffers of various pH.
Toxicology and biocompatibility of bioglasses
Authors: Wilson June , Pigott G. H. , Schoen F. J. , Hench L. L. 
Published: December 2004

AbstractEvidence for the lack of toxicity of various bioglass formulations has been deduced from studies carried out, both in vivo and in vitro, in several different centers. Recent studies of the authors, described here, include testing of solid bioglass implants in the soft tissues of rats and rabbits for time periods of up to eight weeks. Two new techniques are described for the toxicological testing of particulate biomaterials. These tests, which involve rat peritoneal macrophages in culture and a mouse pulmonary biomaterial embolus model, indicate the biocompatibility of bioglass powders. Thus, the surface activity so critical in bone adhesion is without toxic effect in nonosseous tissues in contact with solid bioglass implants. Should wear occur and produce particulate bioglass, the material should be eliminated without consequence.
Work hardening and forming behavior of cast dental alloys
Authors: Baran George , Woodland Everan C. 
Published: December 2004

AbstractThe work hardening characteristics of several casting alloys were determined from true stress‐true strain data. A regression technique was used to fit the data to linear or nonlinear mathematical expressions. Manipulation of the expressions made it possible to calculate the work necessary to deform the alloys. Several nonprecious alloys proved to be as easy to cold form as a conventional, high gold containing alloy.
SEM ultrastructure studies of N‐acyl‐ and N‐benzylidene‐chitosan and chitosan membranes
Authors: Hirano Shigehiro , Tobetto Kenzi , Noishiki Yasuharu 
Published: December 2004

AbstractFine ultrastructures of the cross sections of membranes, which are derived from chitosan and utilizable as artificial kidney, are examined by scanning electron microscopy (SEM). Three types of unique ultrastructure of the membrane cross sections are present: N‐acylchitosan membranes [N‐acetyl (1), N‐propionyl (2), N‐butyryl (3), N‐pentanoyl (4), N‐hexanoyl (5), N‐octanoyl (6), and N‐benzoyl (7)], N‐benzylidenechitosan membranes (8) and chitosan membranes (9). The vertical cross sections of membranes 1–7 consist of orderly arranged layers that are formed by an assembly of particle units of fibrils. Neither fibrils nor layers are present and a smooth surface is characteristic of the cross sections of (8). On the other hand, the particle units of fibrils are absent and a nappy rough surface is characteristic of the cross sections of (9). N‐Acetylation of (9) affords the particle units of fibrils that are disorderly oriented. Low‐ and middle‐molecular compounds (MW < 2000) pass through small pores among these fibrils present in orderly arranged layers of the membranes. Properties of these N‐acylchitosan membranes well meet the requirements of artificial kidney membranes.
Surface roughness and edge geometries in hemolysis with rotating disk flow
Authors: Monroe Joseph M. , True Douglas E. , Williams Michael C. 
Published: December 2004

AbstractJudging biocompatibility of materials with blood includes assessment of hemolysis resulting from flow in contact with those materials. Such hemolysis is influenced in part by the surface roughness and specific hydrodynamic features of the device used. Using a rotating‐disk device, with polyethylene disks and human blood, it was shown that roughness under 4 μm has negligible effect and that hemolysis increases sharply for roughness above about 11 μm. Gross roughness (65 μm) causes qualitatively different hemolysis kinetics but not as severe hemolysis as extrapolated from low‐roughness data. In the disk geometry, the corner is a key region which generates high hemolysis and thus minor alterations cause hemolytic variations which may tend to obscure materials influences. A series of corner‐beveled polycarbonate disks were tested in comparison with the normal square corner and were found always to cause greater hemolysis. Tapering the bevel inward, so the taper angle was on the order of 2°−4°, reduced hemolysis relative to the 45° bevel but still was more hemolytic than the flat disk. Evidence suggests that glassy plastics can be machined with more reproducibility at the corners than plastics above their Tg such as polyethylene. General device design problems regarding hemolysis are discussed.
Irradiation crosslinking of the polytetrapeptide of elastin and compounding to dacron to produce a potential prosthetic material with elasticity and strength
Authors: Urry D. W. , Harris R. D. , Long M. M. 
Published: December 2004

AbstractThe poly(tetra peptide), H‐ (L·Val1‐L·Pro2‐Gly3‐Gly4)n‐L·Val‐OMe, which is a recurring sequence in tropoelastin the precursor protein of the elastic fiber, has been irradiation crosslinked to produce an elastomeric material with limited strength. When a material such as a Dacron fabric is impregnated by the coacervate phase of the poly(tetra peptide) prior to irradiation crosslinking at 50 Mrad, the crosslinked product exhibits stress–strain curves with good elastomeric properties and high strength. In addition to the stress‐strain curves, the material is characterized by scanning electron microscopy.
Evaluation of a chemical technique for determining the oxygen permeability of synthetic membranes
Authors: Alexander B. , Fleming J. S. 
Published: December 2004

AbstractThe biocompatibility and high gas transfer characteristics of gas‐permeable membranes have led to their use for total and supportive cardiopulmonary bypass. The gas transfer rates, particularly of oxygen, have previously been measured with sophisticated apparatus and this has restricted accurate measurements to a few laboratories. A simple chemical technique for measuring the oxygen permeability of synthetic membranes is described, in which sodium hydrosulfite is used to provide the highest possible oxygen gradient and the volume of oxygen crossing the membrane is measured volumetrically. Results agreed with those obtained with orthodox apparatus and replacement of the reducing agent with blood gave much lower oxygen transfer rates demonstrating the rheological influences of the blood upon oxygen transfer.
The influence of heparinized polymers on the retention of platelets aggregability during storage
Authors: Mori Yuichi , Nagaoka Shoji , Kikuchi Tetsuya , Tanzawa Hiroshi 
Published: December 2004

AbstractThe change in aggregability of the platelets stored in the storage tube fabricated from a newly developed heparinized hydrophilic polymer (H‐RSD) has been studied in comparison with plasticized poly(vinyl chloride) (PVC) which is widely used for blood bags. Rabbit blood was directly withdrawn into the storage tube containing an anticoagulant from the carotid. Then the tube was mechanically sealed with screw cocks and centrifugated to prepare platelet‐rich plasma (PRP) in the tube and again mechanically clamped to separate the PRP from the residual precipitate. The PRP was stored in situ in the storage tube at room temperature under agitation. During storage, the change in the aggregability of the PRP induced by adenosine diphosphate (ADP) was studied and the morphological change in the platelets adhered onto the inner surface of the storage tube was observed by scanning electron microscopy. In the H‐RSD tube, the aggregability was maintained during two‐day storage, while in the PVC tube, the aggregability was completely lost after one‐day storage. The scanning electron microscopic studies demonstrated that the reduction in the aggregability of the stored platelets is closely correlated with the morphological deformation of the platelets adhered onto the surface of the storage tube.
Wetting characteristics and blood clotting on surfaces of acylated chitins
Authors: Kaifu Katsuaki , Komai Takashi 
Published: December 2004

AbstractVarious acylated chitins, including formyl, acetyl, propionyl, butyryl, caproyl, capryl, lauroyl, and benzoylchitin, were evaluated as materials for blood contact surfaces by means of contact angle and blood‐clotting time measurements. Critical surface tensions of acylated chitins varied within the range of 20–30 dyn cm−1 and were dependent on the length of the acyl side chains. Furthermore, the dispersion and nondispersion components of the surface tension show remarkable differences which are dependent on the type of acyl group attached to chitin. The chitin derivative with 2.0 acetyl groups per N‐acetylglucosamine residue gave values of the dispersive and nondispersive components of the surface tension that are very close to those obtained for glutaraldehyde‐treated umbilical cord vessels. All of the acylated chitin surfaces show longer clotting times than the original chitin surface.
Correlation between strength of bonding to enamel and mechanical properties of dental composites
Authors: Boyer Daniel B. , Chalkley Yvonne , Chan Kai Chiu 
Published: December 2004

AbstractThe strength of bonding of dental composites to enamel was measured in shear. The compressive strength, proportional limit, elastic modulus, and tensile strength of the composites were measured for correlation with the bond strength. Conventional and microfilled composites with a range of filler concentrations were studied. The densities of the composites and their fillers and the concentrations of the fillers were determined. The mechanical properties that were most highly correlated with bond strength to enamel were proportional limit and elastic modulus. Tensile strength and filler concentration had lower correlation coefficients, and compressive strength was not correlated with bond strength. Using unfilled resins as bonding agents between the composites and enamel resulted in increased bond strength with half of the composites.
Biological evaluation of dental restorative materials—a comparison of different test methods
Authors: Wennberg A. , Mjör I. A. , Hensten‐Pettersen A. 
Published: December 2004

AbstractThree restorative materials–two composite resins and zinc oxide‐eugenol cement–were subjected to three cytotoxicity tests–chromium release, millipore filter, and agar overlay–one implantation test, and a pulp study. In the cytotoxicity test the materials were evaluated freshly prepared and after storage at 37°C for 24 h. In the implant test polyethylene tubes holding freshly prepared materials were inserted subcutaneously into rats. After 30 and 90 days the tissue response at the end of the tube and at a window site along the side of the tube was assessed. In the pulp study the materials were placed in cavities prepared in newly erupted monkey teeth. After 7 and 78 days the reaction of the pulp tissue was studied. Comparison of the results from the cytotoxicity tests revealed a varying degree of correlation, indicating that the three tests were not interchangeable. When data from the pulp study were compared to those of the cytotoxicity tests and implantation test, the correlation was not as good. This emphasizes that the final biological evaluation of dental restorative materials still has to be carried out as pulp studies.
Preparation of a biocompatible albumin‐coated ion exchange resin for bilirubin removal from the blood of jaundiced newborns
Authors: Sideman S. , Mor L. , Brandes J. M. , Lupovitch S. 
Published: December 2004

AbstractRemoval of bilirubin by hemoperfusion with ion exchange resin particles is suggested to replace exchange transfusion of blood of jaundiced infants in some cases of unconjugated hyperbilirubinemia. The hemoperfusion system developed here consists of a packed bed of a macroreticular resin which is made biocompatible by a coating of a monomolecular layer of albumin. The choice of the appropriate ionic form of the resin and the proper albumin coating and crosslinking procedure assures a high bilirubin adsorption capacity and excellent blood compatibility of the resin. The albumin coated resin removes in vitro 80–90% of the bilirubin initially present in the plasma. The results encourage in vivo clinical studies.
Effect of surface texture on the soft tissue response to polymer implants
Authors: Taylor S. R. , Gibbons D. F. 
Published: December 2004

AbstractIon beam etching has provided a system which can produce a controllable surface morphology in the micron range without altering surface chemistry or surface energy. PTFE (polytetrafluoroethylene) develops a surface texture having conical projections with average dimensions: height = 12 μm, base width = 4 μm, tip radius = 0.1 μm. Smooth and textured PTFE disks (1 cm diam. × 250 μm thick) were implanted subcutaneously into the dorsum of Sprague‐Dawley rats for time periods of 1 and 3 days and 1,2,3,4, and 8 weeks. Smooth control samples consisted of untreated surfaces and surfaces that were exposed to an ion beam environment producing a smooth surface. All smooth surfaces behaved identically by both histochemical and histological methods. Consequently, the ion beam environment had no effect on the soft tissue response. Textured surfaces, however, demonstrated increased cell adhesion and increased succinic dehydrogenase and acid phosphatase staining in the interfacial cells. Interfacial cells consisted of foreign body giant cells and macrophages. These macrophages possessed increases in the cytoplasmic‐to‐nuclear ratio, number and interdigitation of filopodia, and vacuolization as demonstrated by TEM. The textured surfaces also influence the kinetics of fibrous capsule formation. At 8 weeks, capsules associated with textured interfaces were reduced in thickness by 30% when compared to smooth surfaces. The results of this investigation demonstrate that the surface texture of an implant is a critical variable in determining the soft tissue response to a material.
Development of a new orthopedic wire fatigue tester
Authors: Sander Thomas W. , Treharne Richard W. , Baswell Imogene , Oh Indong 
Published: December 2004

AbstractEven though orthopedic wire is commonly used in orthopedic surgery, very little is known about its fatigue properties. This article describes the development of a simple, effective testing machine that simulates the in situ fatigue loading of orthopedic wire. A mathematical analysis has predicted the maximum stress that is generated in wires in the fatigue machine. The fatigue resistance of intact monofilament wires made from different materials was studied. It was found that F90 was more resistant than F562, which in turn was more resistant than F138, grade 2. Also studied was the effect of cold‐forming different notch sizes on the wire surface. It was found that even the slightest notch (1% of wire diameter) reduced the fatigue life by 63%.
A newly prepared surface‐treated oxystarch for removal of urea
Authors: Shimizu Toshimi , Fujishige Shoei 
Published: December 2004

AbstractThere is an urgent need to develop an efficient technique to remove urea from the blood or gastrointestinal tract of uremic patients. Activated charcoals have a low sorption capacity for urea although they effectively remove other uremic toxic substances. To provide an urea‐reactive adsorbent, a chemically modified oxystarch with albumin or gelatin has been prepared. Elemental analysis and Fourier transform infrared (FT‐IR) spectroscopic analysis demonstrate that the reaction of a small amount of protein (albumin or gelatin) with oxystarch has taken place possibly by chemical combination. The influence of the dialdehyde content of the oxystarch on urea sorption, its sorption isotherm, and the adsorption rates have been investigated. It was found that the swelling factor of the oxystarch is closely related to the sorption activity under physiological conditions (pH 7.2–7.4 at 37°C). Adsorption studies have shown that sorption capacity is increased by surface treatment and can reach 6–8.2 g urea/kg‐dried adsorbent (initial urea concentration was 70 mg/dL). The oxystarch had 49.2% of glucose unit oxidized and was surface treated with albumin. These results suggest that the newly prepared surface‐treated oxystarch would be utilized as an effective chemisorbent for urea removal under physiological conditions.
Surface properties determine bioadhesive outcomes: Methods and results
Authors: Baier R. E. , Meyer A. E. , Natiella J. R. , Natiella R. R. , Carter J. M. 
Published: December 2004

AbstractThis investigation developed experimental evidence for the influence of different surface energy states on tissue incorporation of biomedical materials. Implants of two smooth metals, each with three different surface energy states, were placed in the subdermal fascial plane of the backs of New Zealand White rabbits and were allowed healing times of 10 and 20 days. The implant surfaces were thoroughly characterized by physical‐chemical criteria prior to surgical placement and again following removal from the tissue capsules generated by the host animals. Quantitative histopathologic analysis, using standard morphometric criteria, of the adjacent tissues revealed up to a threefold increase of fibroblastic‐fibrocytic cells against the initially scrupulously cleaned, high‐surface‐energy materials. The cells were flattened and active, producing tenacious bonds through a thin pre‐adsorbed protein‐dominated “conditioning” film, that could be broken only by cohesive failure in the tissue itself. In contrast, the lower‐surface‐energy materials typical of standard dental implants were “walled off” by a cell‐poor, nonadhesive capsule with a fibrous interface separated from a thicker “conditioning” film by a lipid‐rich mucus zone. The advantages of proper surface treatment to favor the desired degree of biological adhesion are apparent.
Some aspects of macrophage behavior at the implant interface
Authors: Salthouse Thomas N. 
Published: December 2004

AbstractThe macrophage plays a pivotal role in both wound healing and cellular response to implants, including percutaneous devices. Within twenty‐four hours macrophages were found in close contact with the implant surface. Eventually fibroplasts and connective tissue proliferate, and finally the implant will be encapsulated. The presence of macrophages is essential for the activation of collagen synthesis by fibroplasts. Implant shape and surface can profoundly affect macrophage behavior. At rough implant surfaces macrophages with giant cells are present for many months with the possibility of chronic granulomatous reactions. Superior tissue compatibility should be associated with smooth, well contoured implants with no acute angles.
The influence of temperature and specimen size on the flexural properties of pmma bone cement
Authors: Brown S. A. , Bargar W. L. 
Published: December 2004

AbstractA three‐stage investigation was undertaken to examine the influence of specimen size and polymerization environment on the flexural properties of PMMA. In the first stage, specimens were cut from large pieces of commercially cast acrylic (Lucite) and self‐curing dental acrylic. The material properties of the cast acrylic as calculated from the results of flexural testing were not influenced by specimen size in the range of 1 × 10 × 30 to 3 × 10 × 60 mm, whereas 1‐mm thick dental cement specimens had 12% (p < 0.001) higher stress and 24% (p < 0.001) higher strain to failure than 3‐mm specimens cut from the same sample. In the second stage, self‐curing dental cement and Simplex P bone cement were molded in different thicknesses. These experiments demonstrated that molding thin 1.6‐mm specimens resulted in increases of 14% (p < 0.001) in stress and 30% (p < 0.001) in strain to failure as compared with 3.2‐mm specimens, which were greater differences than those due to the specimen thickness effects alone. In the third stage, temperatures of cement were monitored during polymerization, and cements were molded at different temperatures. These results demonstrated that thicker cement samples reached higher temperatures and that cement samples polymerized at lower temperatures (21 versus 37°C) had 12% (p < 0.001) greater stress and 105% (p < 0.001) greater strain to failure.