bluuebunny/crossref_metadata_2025_split huggingface dataset:
Free radical decay kinetics in PMMA bone cement
Authors: Turner R. C. 
Published: December 2004

AbstractElectron‐spin resonance has been used to measure the decay of the concentration of polymerization radicals in polymethyl methacrylate (PMMA) bone cement and the kinetics of the decay determined. Thermal annealing at various temperatures has shown that the logarithm of the concentration of radicals varies linearly with time, but with a nonzero intercept. These results have been analyzed by including both first‐ and second‐order decay processes. The first‐order process has an activation energy of 39 ± 2 kcal/mol and is probably due to a diffusion‐limited termination. The second‐order process has an activation energy of 36 ± 5 kcal/mol and is probably due to bimolecular termination.
The healing of hamster skin ulcers treated with n‐butyl‐2‐cyanoacrylate (Histoacryl blue)
Authors: Galil K. A. , Wright G. Z. , Schofield I. D. 
Published: December 2004

AbstractThis study was undertaken to examine the effectiveness of a commercially available n‐butyl‐2‐cyanoacrylate (Histoacryl blueTri‐Hawk International, 1570 Barré, Montréal, H4L 4M6 Quebec.
) as a local treatment for cutaneous ulcers. Two ulcers, approximately 0.5 cm2 each, were made on the backs of 30 hamsters. The right side was covered with a thin film of tissue adhesive, while the left side was left untreated as a control. Animals were sacrificed at various times post‐operatively, the tissue excised, processed, and examined with the light microscope. Results showed that cyanoacrylate decreased the inflammatory exudate early in the experiment, and epithelial migration occurred slightly earlier in experimental tissue. Scab formation was absent in experimental sites until the layer of adhesive was lost. After 2 days, healing was comparable in both experimental and control, and the sites were indistinguishable histologically at day 5.
Convex‐lens‐on‐slide: A simple system for the study of human plasma and blood in narrow spaces
Authors: Adams A. L. , Fischer G. C. , Munoz P. C. , Vroman L. 
Published: December 2004

AbstractOn clot‐promoting surfaces, intact normal blood or plasma deposits fibrinogen and then supplants it with high molecular weight kininogen (HMWK). On glass, plasma layers of less than about 25 μm thick, while still containing enough fibrinogen to coat the surrounding surfaces, lack sufficient HMWK per surface area to remove this fibrinogen deposit. Thus normal intact citrated plasma allowed to enter the space between a glass slide and a convex lens resting belly‐down on the slide will leave a disc of fibrinogen where the thickness of plasma layer was below this “critical height” H. The discs of fibrinogen left by plasma that lacks HMWK pathologically or by activation or dilution, are larger—the required H being greater. The present study shows that plasma dilution (final volume divided by original plasma volume) plotted against H yields a straight line. In preliminary series, the slope of this line increases with the atomic weight of five metals whose oxidized surfaces were used as substrates. In whole blood collected in either heparin or ACD, a circle of platelets adheres to oxidized silicon, anodized tantalum, or glass; this circle is similar in size to the one of fibrinogen left by plasma.
Equilibrium adsorption of human serum albumin and human fibrinogen on hydrophobic and hydrophilic surfaces
Authors: Brynda E. , Cepalova N. A. , Štol M. 
Published: December 2004

AbstractThe adsorption of human serum albumin and human fibrinogen on flat surfaces was quantitatively determined by measuring the decrease in UV absorption in the adsorption solution. The applicability of the method is discussed for hydrophilic and hydrophobic materials. The values of equilibrium adsorption are presented—albumin on polyethylene, and fibrinogen on polyethylene, carbon, poly(2‐hydroxyethyl methacrylate), and cellophane.
Toxic reactions evoked by glutaraldehyde‐fixed pericardium and cardiac valve tissue bioprosthesis
Authors: Gendler E. , Gendler S. , Nimni M. E. 
Published: December 2004

AbstractBovine pericardial tissue and tissue‐derived bioprosthesis fixed in glutaraldehyde and stored in either glutaraldehyde or formaldehyde can induce cytotoxic reactions even after prolonged washing due to the slow leaching of the chemicals used for crosslinking and sterilizing. Sequential rinsing for up to 60 min was still not sufficient to eliminate cytotoxic effects. On the other hand, satisfactory results were obtained when cardiac valves made from glutaraldehyde fixed pericardium were stored in a solution containing 0.02% of propyl‐hydroxy‐benzoate and 0.18% methyl‐hydroxy‐benzoate. The valves stored in this solution and rinsed three times for 1 min in normal saline showed few signs of residual cytotoxicity. Rinsing in a solution containing glycine was partially effective in neutralizing the cytotoxic effect, and this or similar approaches offer good possibilities. The use of Chang cells grown in culture provides an excellent quantitative assay for the assessment of residual cytotoxicity and for evaluating the host response to different methods of fixation, storage, and rinsing of tissue derived bioprosthesis.
Intraocular‐lens—endothelial interface: Adhesive force measurements
Authors: Reich S. , Levy M. , Meshorer A. , Blumental M. , Yalon M. , Sheets J. W. , Goldberg E. P. 
Published: December 2004

AbstractAn instrument for measuring the force of adhesion between intraocular lens materials and the endothelium of excised rabbit corneas was constructed. The adhesion force was measured for polymethylmethacrylate (PMMA), polyhydroxyethylmethacrylate (PHEMA), Duragel (amino‐polyamide hydrogel), PMMA surface grafted with polyvinylpyrolidone, and PMMA surface treated with sodium hyaluronate (Healon). The force of adhesion was reduced considerably when the PMMA surface was modified with a hydrophilic polymer coating. This is consistent with previous studies showing reduced endothelium cell damage for hydrophilic polymer coated intraocular lenses. Adhesive forces were also decreased by addition of polyvinyl alcohol or gelatin to the saline solution in which the corneas were immersed. Extension of this type of measurement to pericardium, vascular endothelium, and peritoneum surfaces may also be important to understand tissue damage problems in general surgery.
Significance of the inner‐surface structure of small‐caliber prosthetic blood vessels in relation to the development, presence, and fate of a neo‐intima. A morphological evaluation
Authors: Hess F. , Jerusalem C. , Grande P. , Braun B. 
Published: December 2004

AbstractMicrovascular prostheses with three different inner surface structures were examined morphologically 1–18 months after implantation to evaluate the presence and structure of the neo‐intima. Fibrous polyurethane tubes (length: 5–10 mm, inner diameter: 1.5 mm) were implanted in the rat abdominal aorta in group A with a fibrillar inner structure (pore sizes 20–50 m̈m), and in group B the inner fibrillar structure was coated with an impermeable continuous silicon sheet. Expanded polytetrafluorethylene vascular prostheses (length: 40 mm, inner diameter: 4 mm) were implanted in the dog carotid artery (group C). The specimens were examined by light microscopy and scanning electron microscopy. A continuous and permanent neointima was only found in the prostheses with the porous fibrillar inner structure (group A). The thin new lining sheet was well attached to the prosthetic wall by cellular protrusions. In the silicon‐coated prostheses (group B) also a continuous neo‐intima had developed which, however, was irregular, thicker, and not anchored to the prosthetic wall. The expanded polytetrafluorethylene prostheses (group C) showed also after 1 year only incomplete lining with a neo‐intima. Fresh blood cell deposits could be observed in the unlined prosthetic wall. It is concluded that a continuous lining of vascular grafts with a thin neo‐intima is only achieved if the cells invading the prostheses from the anastomotic areas can anchore their cytoplasmic protrusions onto an appropriately structured inner surface. If these anchoring facilities are not provided, the unattached neo‐intima will thicken, interfering with the patency of these microvascular prostheses, or fragments of the neo‐intima or alternatively mural thrombi may constantly strip off and embolize.
Development of topical BAPN delivery system for acute spinal cord injury in dogs
Authors: Chvapil Milos , Weinstein Philip R. , Misiorowski Ronald L. , Telles David , Rankin Lucinda , Stoy Vladimir 
Published: December 2004

AbstractTopical sustained release of various medications by a subdurally implantable device at the site of spinal cord injury is considered advantageous in the treatment of early symptoms of tissue damage. A typical case is the interference with collagenous scar by β‐aminopropionitrile, inhibiting collagen polymerization. Four materials, silicone, polyethylene, polytetrafluoroethylene (PTFE), and polyacrylonitrile‐based hydrogel were evaluated for biocompatibility in subcutaneous implantations. The hydrogel, the least reactive, was then compared with silicone sheets as subcural implants. The histology favored the hydrogel as the most inert material, which was then used for the construction of soft, pliable pouches, releasing the drug through the hydrated wall at a rate controlled by an osmotic pump.
Bond strength and hardness of light‐activated composite resins
Authors: Schulein Thomas M. , Boyer Daniel B. , Chalkley Yvonne 
Published: December 2004

AbstractThe bond strength of visible light‐activated composites to etched enamel was measured as a function of exposure time. Studies have shown that the bottom surface may not be as hard as the top after customary cure times. Therefore this study also measured hardness and related it to enamel bonding. Plexiglas molds were used to simulate extracoronal applications where light is not attenuated by enamel. Bond strength and hardness of the bottom surfaces reached maximum values after the same exposure times with two of the three composites. More exposure time than normally recommended by manufacturers was needed to obtain maximum bond strength to enamel.
Inhibition of thrombus formation on intravascular sensors by electrical polarization
Authors: Schmitt J. M. , Baer M. , Meindl J. D. , Anderson M. F. , Mihm F. G. 
Published: December 2004

AbstractImplantable biomedical sensors built on a silicon substrate capped with glass are currently being developed for intravascular applications. Electrical techniques for inhibiting thrombus formation on the surface of a proposed optical sensor in direct contact with blood have been investigated. Glass‐on‐silicon specimens (4 × 1.2 × 0.4 mm3) were coated with indium–tin oxide, a transparent conductor, and implanted in the vena cava and iliac veins of three dogs for 10, 20, or 33 days. The equilibrium surface—blood interface potentials of the specimens were modified by implanted current sources which supplied either direct current (8–15 m̈A) or 100 KHz alternating current (5 m̈A, root mean square). Light‐microscopic and scanning electron‐microscopic analyses showed each of the DC‐polarized specimens to be free of thrombus, in contrast to nonpolarized (control) specimens on which varying amounts of adsorbed protein and thrombus deposits were found. Like the control specimens, the AC‐polarized specimens formed thrombus, but the appearance of the deposits differed. These findings support the view that the polarity, magnitude and time dependence of the potential across conducting surface—blood interface significantly influence thrombogenicity. Further work is necessary to determine the roles of electrochemical and electrostatic factors in preventing thrombus formation on foreign materials.
Marginal leakage of class V cavity preparations
Authors: Dumsha Thomas C. , Biron George 
Published: December 2004

AbstractDentin‐bonding materials, ferric oxylate (FO), addition reaction between N‐phenylglycine and glycidyl methacrylate (NPG—GMA), and addition reaction product of pyromellitic acid dianhydride and 2‐hydroxyethyl methacrylate (PMDM), were tested together for their ability to inhibit marginal leakage in Class V composite restorations in vitro. Sixteen experimental teeth were pretreated with FO, NPG—GMA, PMDM, and restored with composite. Sixteen control teeth were treated conventionally with composite. The teeth were then thermally cycled (5 and 55°C) for 7 days, silver stained, and evaluated blindly for degree of marginal leakage on a scale of 0 (no leakage) to 7 (leakage into the pulp). The experimental group displayed significantly greater leakage values (p ≤ 0.01) than controls. The results of this study support the hypothesis that FO, NPG—GMA, and PMDM, together with composite inhibit marginal leakage.
An in vivo method for the biological evaluation of metal implants
Authors: Keller J. C. , Marshall G. W. , Kaminski E. J. 
Published: December 2004

AbstractThe peritoneal cavity of the rat was used as an implantation site in order to study the quantitative, cellular response and the qualitative, histopathological response to three metals (Ag, Sn, Cu). The effects of the metals on the cells were correlated with the cellular concentrations of the metal as determined by chemical analysis. Small variations in the cell population and a minimal foreign body reaction was observed with an implanted control material (silicone polymer). Large increases in the number of cells and an intense foreign body reaction was observed with Cu implants. Decreases in the number of cells were seen with Sn and Ag implants, but only Sn elicited a foreign body reaction. Implantation of Ag failed to elicit a foreign body reaction. Significant concentrations of all three metals were detected in the retrieved cells.
Demineralization and ion binding action of polycarboxylate cement liquid on human dental enamel
Authors: Vaidyanathan J. , Vaidyanathan T. K. , Schulman A. 
Published: December 2004

AbstractThe demineralization and ion binding effects on dental tissues due to poly(acrylic) acid attack under different dilution conditions of the latter are studied by scanning electron microscope (SEM) and infrared (IR) spectroscopy. The results indicate that in addition to the general demineralization effects such as preferential prism core attack, prism periphery attack, and protruding prism rods, competing ion binding effects also occur. Using optimum dilution conditions, the microstructural effects of demineralization and ion binding are shown and the effects are related to IR spectral observations.
Effects of immersion in cholesterol‐lipid solution on the tensile and fatigue properties of elastomeric polymers for blood pump applications
Authors: Hayashi K. , Matsuda T. , Takano H. , Umezu M. 
Published: December 2004

AbstractTensile and fatigue properties were studied on three kinds of segmented polyether polyurethanes developed for blood pump applications. To study the effects of plasma constituents, specimens were immersed in a cholesterol‐lipid solution whose composition is similar to that of plasma. The results obtained were compared with those observed in a saline solution which had been reported previously. Immersion in the cholesterol‐lipid solution has influence on the mechanical properties of Toyobo TM5 polyurethane and Avcothane 51: Its effect is enhanced by cyclic deformation. Cholesterol‐lipids change the mechanical characteristics of Avcothane 51 more remarkably than those of Toyobo TM5 polyurethane possibly because the former contains about 10% silicone. On the other hand, there is little effect of the constituents of the cholesterollipid solution on the static and dynamic mechanical properties of Biomer, although moisture and cyclic deformation have some influence on the mechanical characteristics.
Covalent coupling of polysaccharides to silicon and silicon rubber surfaces
Authors: Elam Jan H. , Nygren Håken , Stenberg Manne 
Published: December 2004

AbstractA method to produce a hydrogel by covalently coupling dextran polysaccharide to silicon and silicon rubber surfaces is described. A bifunctional epoxysilane was used as coupling mediator and the conditions for the reaction were optimized. Coupling of the silane to silicon rubber was possible only after oxidation of the surface by plasma etching. The reaction between the epoxy‐group and dextran was concentration dependent and required high concentrations of dextran. The turnover rate of fibrinogen in solution at the hydrophilic surface was found to be high when measured by ellipsometry.
Determination of extractable methylene dianiline in thermoplastic polyurethanes by HPLC
Authors: Mazzu A. L. , Smith C. P. 
Published: December 2004

AbstractPolyurethanes are finding increasing utilization in biomedical applications. Recently, the reported finding of methylene dianiline (4,4′‐diaminodiphenylmethane, MDA) in the aqueous extracts of autoclaved 4,4′‐diphenylmethane diisocyanatebased polyurethanes promoted our investigation of the origin and extent of extractable methylene dianiline in polyurethanes. A high‐pressure liquid chromatography procedure using precolumn derivatization is utilized to selectively monitor the appearance of this diamine in the aqueous extracts of polyurethanes subjected to water immersion, heat aging, and various sterilization techniques. No MDA was found in the aqueous extracts of the treated polyurethane except for the case of prolonged steam autoclaving. The appearance of 3–5 ppb MDA in the extract under these conditions is attributed to hydrolysis of the polymer. The stability of the polyurethanes under most conditions renders these materials useful in biomedical applications.
Improved photochemical bonding of composites to dentin using 4‐methacryloxyethyl trimellitate anhydride
Authors: Nagata K. , Lundeen T. F. , Turner D. T. 
Published: December 2004

AbstractThe main objective was to evaluate the use of 4‐methacryloxyethyl trimellitate anhydride (4‐META) to improve bonding of composite materials to dentin. Bowen's resin, containing camphoroquinone, was polymerized by exposure to visible light. In composites, made with a silanated silicate, inclusion of 4‐META (3%) had little effect in increasing mechanical strength or adhesion to bovine teeth. However, direct application of 4‐META via acetone solution was found to be an effective way of increasing tensile adhesive strength; by 240% to dentin (to 7.2 MPa) and by 160% to enamel (to 10.8 MPa). Applying the experience mentioned above, 4‐META was used to bond a proprietary photocuring microfilled composite material to Class V cavities in freshly extracted human teeth. After thermal cycling between water baths held at 5°C and 60°C, all dentin restorations without 4‐META failed, as judged by marginal leakage of a dyestuff. In contrast, using 4‐META there was no leakage in 9 out of 10 cases. In restorations involving enamel, 4‐META failed to prevent marginal leakage at the enamel margins but did prevent penetration along the dentin/composite interface. It is concluded that 4‐META shows great promise for preventing marginal leakage at dentin/composite interfaces.
Property changes of UHMW polyethylene hip cup endoprostheses during implantation
Authors: Eyerer Peter , Ke Yu Cai 
Published: December 2004

AbstractIn this study it is demonstrated that the combined chemical and mechanical influences of the implant situation cause property changes of ultra‐high‐molecular‐weight polyethylene (UHMW PE) hip joint cups. Nearly 30 out of 48 loosened cups, retrieved 3 weeks to 11 years after implantation, were investigated. Density measurements show a density increase with implantation time and a dependence of these changes from implant position and loading conditions. The rate of extractable constituents also increases with course of time. An increased in vivo conditioned oxidation of the UHMW PE can be demonstrated by infrared (IR) spectrometry. The density increase can be explained by post‐crystallization, which is the result of oxidative chain scission. This leads to a reduction of the average molecular weight of the PE and to an increased extractability of constituents. Since these changes have been recognized as the reasons for aging and failing of UHMW PE, the methods of material characterization used in this study for retrieved implants will help to develop suitable in vitro testing and simulating methods. They are the prerequisite for the necessary improvements of the material properties of UHMW PE.
Immunogenicity of glutaraldehyde‐treated bovine pericardial tissue xenografts in rabbits
Authors: Salgaller M. L. , Bajpai P. K. 
Published: December 2004

AbstractXenograft valves of glutaraldehyde‐treated bovine pericardial tissue have been claimed to be an excellent choice for the replacement of malfunctioning human heart valves. These valves exhibit low thrombogenicity, hemodynamic function, and transvalvular gradients superior to their mechanical and tissue counterparts. However, there are differences of opinion concerning the immunogenic properties of these valvular devices. This study was conducted to evaluate the immune reactivity of such implants. Data obtained indicated that whole xenograft sections of both untreated and treated valvular tissue remain immunogenic following initial and secondary subcutaneous implantations in rabbits. Homologous and cross‐reacting antibodies were detected by means of indirect hemagglutination test 30 days after initial implantation of the grafts. Presence of cellular immune response as judged by skin reaction and leukocyte migration inhibition tests indicated that glutaraldehyde treatment of tissues does not destroy cellular immunity. Data obtained also suggest that chemical modification of such implants by glutaraldehyde probably alters, but does not abolish some antigenic determinant sites on the tissue surface. Glutaraldehyde treatment of bovine pericardial tissue does not render the tissue immunologically inert.