bluuebunny/crossref_metadata_2025_split huggingface dataset:
Can a small blood vessel prosthesis be derived from heterologous foreign body reactive tissue?
Authors: Schoen F. J. , Normann S. J. , Brunswick R. A. , Diacoff G. R. 
Published: December 2004

AbstractThis study investigated as a small diameter vascular replacement the tissue formed adjacent to an implanted cylindrical foreign body, heterologously transplanted. Grafts of 4 mm i.d. were grown in rabbits and transplanted to dogs as segmental carotid and femoral artery replacements. These maintained 50% patency after 3 weeks. Variables in the further development of this concept are discussed.
Thermally induced time dependence of mechanical properties in biomedical grade polyurethanes
Authors: Wilkes G. L. , Dziemianowicz T. S. , Ophir Z. H. , Artz E. , Wildnauer R. 
Published: December 2004

AbstractThe time dependence of the mechanical properties of segmented urethanes as well as urethane‐urea systems were monitored after the materials had been given a short thermal treatment followed by rapid cooling. Both linear and crosslinked materials were studied but the major focus was on many of the common biomedical grade urethanes. As had been noted in earlier studies on nonmedical segmented urethanes from this laboratory, many of the biomedical grade materials also showed time‐dependent changes in mechanical properties that can be directly related to time‐dependent changes in the degree of domain structure (microphase separation) that may occur in these segmented copolymers. Interestingly, those systems possessing significant amounts of urea linkage show little or no significant time‐dependent changes in structure or properties following thermal treatment. The effect of chemical crosslinking can also influence the domain formation process and its thermal stability. The ramifications of these time dependent effects may have bearing on the biomaterial applications of segmented urethane polymers.
Thrombus formation and microaggregate removal during extracorporeal membrane oxygenation
Authors: Guidoin R. G. , Kenedi R. M. , Trudell L. , Galleti P. , Blais P. 
Published: December 2004

AbstractContemporary microporous membrane oxygenators have adequate gas transfer capacity and even prolonged oxygenation is relatively atraumatic to the blood elements. However, even with adequate heparinization, thrombus formation still takes place, albeit to a lesser degree than in direct blood‐gas contact devices. In this work, scanning electron microscopy of the dissected devices in the extracorporeal circuit was performed on devices used during four aorto‐coronary bypasses and two cardiac valve replacements. Membrane surfaces remained free of major deposits although thrombotic material could still be observed in parts of the oxygenators and the filters. Blood filtration from the cardiotomy reservoir may be more critical as it removes surgical debris and cells injured by suction which appear to enhance thrombus formation within the oxygenator. The return line arterial filter appears more useful as a bubble remover; its value appears much diminished as microemboli do not leave the device in large quantities.
Adsorption of human serum albumin to amberlite XAD‐7 resin
Authors: Ton H. Y. , Hughes R. D. , Silk D. B. A. , Williams Roger 
Published: December 2004

AbstractIn the present study the conditions leading to tight binding of human serum albumin to the Amberlite XAD‐7 resin without the use of chemical coupling agents have been defined. Optimal binding (10.97 mm/kg dry XAD‐7) was achieved at pH 5.0 and adsorption conformed to a Langmuir isotherm. Theoretical analysis of the data suggest adsorption of a monolayer of albumin which is suported by the absence of visual surface coating on scanning electron micrographs. Binding of human serum albumin was reduced when two chemical coupling agents, glutaraldehyde and carbodiimide were included in the human serum albumin solution, the elution of adsorbed HSA from the resins under severe flow conditions was reduced, and the amount eluted was minimal in all instances.
Role of catheter surface morphology on intravascular thrombosis of plastic catheters
Authors: Libsack Craig V. , Kollmeyer Kenneth R. 
Published: December 2004

AbstractThe role of catheter surface roughness in initiation and propagation of intravascular catheter thrombosis was studied in dogs, utilizing the scanning electron microscope. Catheters were inserted in major arteries and veins for 200 min and the animals then sacrificed. Catheter segments, both with and without associated thrombi, were scrutinized with the scanning electron microscope. No correlation was found between catheter surface roughness and thrombus formation, suggesting that the inherent chemical characteristics of the catheter is most important in the initiation of intravascular catheter thrombus formation.
Sustained drug delivery systems. I. The permeability of poly(ϵ‐caprolactone), poly(DL‐lactic acid), and their copolymers
Authors: Pitt Colin G. , Jeffcoat A. Robert , Zweidinger Ruth A. , Schindler Anton 
Published: December 2004

AbstractThe maximum steady state flux, diffusion coefficients, and solubilities of five contraceptive steroids in homopolymers and copolymers of ϵ‐caprolactone and DL‐lactic acid were determined. The permeabilities of polymers of ϵ‐caprolactone were comparable to silicone rubber and, by inference, are suitable for the construction of drug delivery devices. Poly(DL‐lactic acid) was 104 times less permeable, although its permeability was significantly enhanced by additives.
In vitro blood compatibility of glycosaminoglycan‐precipitated collagens
Authors: Silver F. H. , Yannas I. V. , Salzman E. W. 
Published: December 2004

AbstractPrecipitation of bovine hide collagen by chondroitin 6‐sulfate at low pH and subsequent crosslinking enhances the blood compatibility of native collagen. Both dehydrothermal crosslinking and complexation with chondroitin 6‐sulfate separately decrease the platelet‐aggregating activity of collagen. Crosslinking also decreases the number of free acidic and free basic residues on collagen, which suggests that crosslinking involves these residues in condensation reactions with formation of intrachain and interchain synthetic peptide bonds. Clotting times for collagen precipitated with chondroitin 6‐sulfate indicate the this surface does not activate or interfere with coagulation via either the intrinsic or extrinsic pathway. These findings support further consideration of collagen modified by chondroitin 6‐sulfate as a blood compatible material.
Surface ultrastructure and pressure dynamics of tracheal tube cuffs
Authors: Wu Wen‐Hsien , Arteaga Margaret , Mlodozeniec Arthur R. , Poppers Paul J. 
Published: December 2004

AbstractThe outer and inner surfaces of six commercial endotracheal tube cuffs were characterized using scanning electron microscopy (SEM) and energy dispersive x‐ray analysis. Lateral tracheal wall pressure (LWP) was measured at various steps of cuff inflation using a mock‐trachea system. The surface characteristics of the cuffs were found to vary widely. The surface of the Lanz cuff was relatively smooth but showed a regular array of circular depressions 0.8 μm in diameter. Uniform spheres also 0.8 μm in diameter were distributed through the thickness of the membrane. The American Hi‐Lo cuff surface was also relatively smooth but was covered widely with flakes of material which x‐ray showed to be a clay‐like substance containing aluminum, silica, and potassium. The Harlake cuff was covered widely with roughly spherical, 5‐μm‐diam particles, probably starch granules. The membrane itself was smooth even at 3,000X. The Foregger cuff had a rough surface and was covered with the same clay‐like particles seen on the American cuff. The inner surface with irregular, uneven areas were surrounded by fissures. The Rusch Armored tube cuff was completely covered by a continuous 2‐μm‐thick chlorinated coating. The surface was highly convoluted and irregular. The three cuff membranes showing relatively smooth surfaces, Lanz, American and Harlake, also produced relatively low LWP at various points of cuff inflation. While we have no data to indicate that cuff surface smoothness correlates with tracheal morbidity, it would seem prudent to select cuffs that produce low LWP's with smooth surfaces for clinical use.
Design of an artificial skin. II. Control of chemical composition
Authors: Yannas I. V. , Burke J. F. , Gordon P. L. , Huang C. , Rubenstein R. H. 
Published: December 2004

AbstractDetailed methodology is described for the reproducible preparation of collagen‐glycosaminoglycan (GAG) membranes with known chemical composition. These membranes have been used to cover satisfactorily large experimental full‐thickness skin wounds in guinea pigs over the past few years. Such membranes have effectively protected these wounds from infection and fluid loss for over 25 days without rejection and without requiring change or other invasive manipulation. When appropriately designed for the purpose, the membranes have also strongly retarded wound contraction and have become replaced by newly synthesized, stable connective tissue. In our work, purified, fully native collagen from two mammalian sources is precipitated from acid dispersion by addition of chondroitin 6‐sulfate. The relative amount of GAG in the coprecipitate varies with the amount of GAG added and with the pH. Since coprecipitated GAG is generally eluted from collagen fibers by physiological fluids, control of the chemical composition of membranes is arrived at by crosslinking the collagen‐GAG ionic complex with glutaraldehyde, or, alternately, by use of high‐temperature vacuum dehydration. Appropriate use of the crosslinking treatment allows separate study of changes in membrane composition due to elution of GAG by extracellular fluid in animal studies from changes in composition due to enzymatic degradation of the grafted or implanted membrane in these studies. Exhaustive in vitro elution studies extending up to 20 days showed that these crosslinking treatments insolubilize in an apparently permanent manner a fraction of the ionically complexed GAG, although it could not be directly confirmed that glutaraldehyde treatment covalently crosslinks GAG to collagen. By contrast, the available evidence suggests strongly that high‐temperature vacuum dehydration leads to formation of chemical bonds between collagen and GAG. Procedures are described for control of insolubilized and “free” GAG in these membranes as well as for control of the molecular weight between crosslinks (Mc). The insolubilized GAG can be controlled in the range 0.5–10 wt. % while “free” GAG can be independently controlled up to at least 25 wt. %; Mc can be controlled in the range 2500–40,000. Studies by infrared spectroscopy have shown that treatment of collagen‐GAG membranes by glutaraldehyde or under high‐temperature vacuum does not alter the configuration of the collagen triple helix in the membranes. Neither do these treatments modify the native banding pattern of collagen as viewed by electron microscopy. Collagen‐GAG membranes appear to be useful as chemically well‐characterized, solid macromolecular probes of biomaterial‐tissue interactions.
Fracture toughness concept applied to methyl methacrylate
Authors: Sih G. C. , Berman A. T. 
Published: December 2004

AbstractPolymethyl methacrylate bone cement is tested at the Institute of Fracture and Solid Mechanics Laboratory, Lehigh University. Standard tensile coupon and compact tension specimens are molded under varying conditions of temperature and pressure. Test results are obtained for the strength and toughness of bone cement involved in total hip replacement operations.
Measurement of the activation time for platelet adhesion to foreign surfaces
Authors: Predecki Paul , Life L. , Russell P. A. , Newman M. M. 
Published: December 2004

AbstractAn apparatus is described which permitted a perfusant (lactated Ringer's solution) to be passed through a porous sample in a pulsatile manner with a square wave pressure profile. The “on” time, “off” time, number of cycles and pressure amplitude were separately controllable. Using this apparatus and immersing the sample in stirred, heparinized, human blood, there was a certain “off” time below which platelet adhesion to the sample abruptly ceased. The values of this “off” time, termed the activation time ta for platelet adhesion were ∼0.5 sec for 0.2 μm pore size cellulose diacetate/nitrate (millipore filter) and ˜0.3 sec for 0.2 μm polycarbonate (nuclepore filter). After a single cycle with a 5 sec “off” time, adhered platelets on both these materials showed pseudopodia, varying degrees of spreading and membrane perforation.
Methyl methacrylate concentrations in tissues adjacent to bone cement
Authors: Petty William 
Published: December 2004

AbstractThe amount of methyl methacrylate monomer present in bone tissue immediately adjacent to implanted bone cement that has polymerized in vivo has been determined. Poly(methyl methacrylate) was implanted into the distal femoral condyle of the dog and allowed to polymerize. At various times following polymerization, samples were removed and sections adjacent to the cement were cut and subjected to homogenization followed by liquid gas chromatographic determination of the amount of methyl methacrylate monomer present. The highest concentration of methyl methacrylate monomer present in bone tissue was 0.140% in the 1000 μm of bone tissue adjacent to bone cement immediately after polymerization of the cement. The concentration was very similar (0.137%) 1 hr after cement polymerization, but dropped off rapidly following that with no free methyl methacrylate monomer present in bone tissue adjacent to cement after 4 hr following cement polymerization.
Interaction of human α‐thrombin with artificial surfaces and reactivity of adsorbed α‐thrombin
Authors: Chuang H. Y. K. , Mohammad S. F. , Sharma N. C. , Mason R. G. 
Published: December 2004

AbstractThrombin adsorbed onto Cuprophane or poly(vinyl chloride) (PVC) was shown to be inactive with respect to amidase activity. Desorbed thrombin from these two artificial surfaces showed only low amidase activity. However, in the presence of albumin, the surface‐bound thrombin appeared to exhibit increased amidase activity. This apparent activity may be due to the action of thrombin displaced from the surfaces by albumin. Thrombin bound to Cuprophane or PVC was shown to be capable of reacting with antithrombin III (AT III) only in the presence of heparin. On the other hand, AT III bound to Cuprophane or PVC was unable to react with thrombin in either the absence or presence of heparin. Fibrin formation on or at surfaces was demonstrated by phase contrast microscopy when Cuprophane or PVC pretreated with thrombin and carefully rinsed was incubated in a fibrinogen solution. This fibrin formation is time dependent and likely is the result of direct interaction of adsorbed thrombin with fibrinogen in solution. Glass, Cuprophane, and PVC pretreated with thrombin were shown to attract more platelets than respective untreated surfaces. The enhancing effect of adsorbed thrombin on platelet adhesion was similar to the enhancing effect of adsorbed fibrinogen. Thrombin adsorbed onto PVC and crosslinked by glutaraldehyde treatment was shown to be antigenically active with a 125I‐labeled monospecific antithrombin IgG produced in rabbits. No other plasma proteins adsorbed singly or from plasma or serum onto PVC reacted significantly with the antithrombin IgG preparation. The possible significance of these observations is discussed.
Design of an artificial skin. Part III. Control of pore structure
Authors: Dagalakis N. , Flink J. , Stasikelis P. , Burke J. F. , Yannas I. V. 
Published: December 2004

AbstractSeveral methods are compared for preparing collagen‐glycosaminoglycan (GAG) membranes of high or low porosity. Collagen‐GAG membranes have been used to cover satisfactorily large experimental full‐thickness skin wounds in guinea pigs over the past few years. Methods studies as means for controlling pore size are confined to purely physical processes which do not require use of additives or chemical reagents to form the porous membrane. We find that membranes, initially swollen in distilled water or saline, shrink linearly to no less than 94% of original dimension after freeze drying; to 75% after critical point drying (from CO2, following water‐ethanol exchange); and to 41% of original dimension following air drying from the swollen state. Scanning electron microscopic study of the pore structure resulting from each drying procedure confirms our major conclusion: A carefully designed freeze drying process, two variants of which are described in detail, yields membranes with the highest mean pore size, as measured by quantitative stereological procedures. Critical point drying gave significantly more shrinkage and a lower mean pore size than either one of the two freeze drying procedures used.
Factors affecting surgical alloy/bone cement interface adhesion
Authors: Keller John C. , Lautenschlager Eugene P. , Marshall Grayson W. , Meyer Paul R. 
Published: December 2004

AbstractInterfaces were formed between acrylic bone cement and three commonly used surgical alloys (316L SS, CoCrMo, and Ti6A14V), in an attempt to further define cementation parameters of acrylic bone cement for use in orthopaedic surgery. Metal/cement interfaces were made at three distinct times during the setting cycle of the cement and were cured for 1 hr, 1 day, and 1 week. The metals were prepared with roughly polished or finely polished prepassivated surfaces. Tensile bond strengths and residual cement on metal coverage data indicated that, for each metal system, interfaces created prior to and at the onset of the dough stage formed superior interfaces for implanation compared to those formed late in the dough stage. Furthermore, electropolishing plus prepassivation offered a more efficient bonding surface than mechanical polishing.
The use of 99Tc‐pyrophosphate for imaging and measuring of calcification caused by implanted polymers
Authors: Cífková I. , Šprincl L. 
Published: December 2004

AbstractPyrophosphate labeled with 99Tc was evaluated as an indicator of the calcification which occurs after implantation of polymeric materials in rats. Poly(2‐hydroxyethyl methacrylate), both porous and homogeneous, had been implanted. 99Tc pyrophosphate was applied intravenously to rats in intervals from 14 days to 15 months. Scintigraphy, x‐ray examination, and histology were carried out. The ratio of specific activity in the capsule around the implant to specific activity in the reference tissue was determined. The cumulation of activity was parallel with the development of calcification as revealed by histology. The method can be used not only in the screening test of new polymeric materials, but also in a quantitative determination of the degree of calcification in general.
The use of polyamide coatings for selective adsorption control on activated charcoal
Authors: Wicks S. R. , Richardson N. E. , Meakin B. J. 
Published: December 2004

AbstractPolymer‐coated, activated charcoal granules have found considerable use for the direct detoxification of blood in cases of uraemia and drug overdose. Although polymer coating materials are presently selected for their biocompatibility, more selective polymers could be used to increase the adsorption capacity for specific drugs and toxins. To gain an understanding of the fundamental factors influencing these adsorbent systems, we have investigated a possible selective coating material, nylon 6 and studied its influence on adsorption rates of simple model compounds when applied as a thin coat to activated charcoal granules. Thermodynamic studies have shown that phenolic compounds interact with the polymer by a hydrogen bonding mechanism, whereas nonphenolic compounds probably bind less strongly due to Van der Waals type interactions. Kinetic studies have shown that the selectivity of charcoal granules for phenolic compounds was increased by coating the granules with a thin layer of nylon 6. The increase in selectivity is probably a result of the different binding mechanism between solute and the polymer. These studies have shown that possible selective coatings may be evaluated more effectively on the basis of simple preliminary drug‐plastics interaction studies.
Experimental design in the clinical evaluation of amalgam restorations
Authors: Goldberg Jon , Munster Edward , Rydinge Elisabeth , Sanchez Luis , Lambert Kenneth 
Published: December 2004

AbstractIn a clinical evaluation of marginal deterioration, 475 amalgram restorations were equally distributed in a 6 × 4 × 2 × 3 factorial design, based on alloy, operator, tooth, and number of restored surfaces. All factors except the last had a statistically significant effect after 6, 12 and 18 months. There were no consistent two‐way interactions over time.
Effect of applied dc currents on experimental tumor growth in rats
Authors: Habal Mutaz B. 
Published: December 2004

AbstractMorris Hepatoma experimental tumor in ACI rats is treated with small anodal direct current via an implantable power pack unit. There was major retardation in tumor growth when the treatment was started early. There was enhancement of tumor growth when the treatment was started early and then was discontinued. There was no statistical difference in growth control of the experimental tumor when the electrotherapy was given after the half‐life of the tumor was achieved. This last point will be the most important to the clinician scientist, for it simulates the clinical situation that faces the treating physician.
Adsorption of proteins from plasma to a series of hydrophilic‐hydrophobic copolymers. I. Analysis with the in situ radioiodination technique
Authors: Horbett Thomas A. , Weathersby Paul K. 
Published: December 2004

AbstractThe adsorption of proteins affects cellular interactions with foreign surfaces and thus plays an important role in determining the biocompatibility of implants. Previous studies have indicated differences in the affinity of various proteins for a given polymer, and differences in the affinity of fibrinogen for a series of polymers varying in hydrophilicity. These studies suggest that differences in the composition of the protein layer adsorbed to polymers from plasma might exist. To examine this hypothesis, the proteins adsorbed from plasma to a series of polymers varying in hydrophilicity were analyzed with the iodogram technique. Copolymers of hydroxyethyl methacrylate and ethyl methacrylate made by the radiation grafting technique were exposed to plasma for 0.5 or 150 min. The adsorbed proteins were iodinated, eluted with SDS, and separated with polyacrylamide gel electrophoresis. Fibrinogen, immunoglobulin G, hemoglobin, and a peak tentatively ascribed to prothrombin were the major proteins detected. Very little iodine was incorporated into adsorbed albumin, even though it was shown to be present by a separate experiment using dye binding. The fraction of total radioactivity associated with each of nine proteins was found to vary markedly and systematically among the surfaces. The distribution of radioactivity into the proteins was very different on 0.5 and 150‐min plasma exposed polymers. The results reflect both compositional differences in the adsorbed protein layer on the polymers and differences in the accessibility of proteins to the labeling reagent in the adsorbed state. Differences in the organization of the adsorbed protein layer may play a key role in determining whether cell surface receptors can come in contact with the specific plasma protein able to further stimulate the cell.