bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of gamma irradiation on injectable human amnion collagen
Authors: Liu Bingci , Harrell Randall , Davis Robert H. , Dresden Marc H. , Spira Melvin 
Published: December 2004

AbstractThe effect of gamma irradiation on the physicochemical properties of injectable human amninon collagen was investigated. Pepsin‐extracted human amnion collagen was purified, reconstituted, and irradiated with varying doses of gamma irradiation (0.25 Mrads to 2.5 Mrads). Gamma irradiation had a significant impact on the physical characteristics of the collagen. The neutral solubility of collagen in PBS at 45°C was decreased from 100% for the nonirradiated control sample to 16% for the 2.5 Mrads irradiated sample. SDS polyacrylamide gel electrophoresis also demonstrated the dose‐dependent effect of gamma irradiation on collagen crosslinks. Electron microscopic observation revealed that even at low irradiation dose (0.25 Mrads), collagen fibril diameter increased. The average diameter was 50 nm for nonirradiated control fibrils, while 4.4% percent of the irradiated collagen fibrils had a diameter greater than 100 nm. Irradiated collagen showed little evidence of damage. Well‐preserved cross‐strations were found in collagen fibrils at all doses of irradiation. Native amnion collagen irradiated with gamma rays demonstrated a slight increase in resistance to collagenase degradation compared with nonirradiated native collagen samples. Increased resistance to collagenase did not correlate with increasing irradiation dose. After 30 min of incubation at 37°C, both irradiated and non‐irradiated collagen was completely digested by collagenase. However, gamma‐irradiated collagen did become more sensitive to hydrolysis by trypsin. The higher the irradiation doses used, the greater sensitivity to trypsin was observed. At 0.25 Mrads irrdiation only a slight increase was found. No marked differences in amino acid composition were noted among the high dose irradiated, low dose irradiated and control amnion collagen.
Heparinizable segmented polyurethanes containing poly‐amidoamine blocks
Authors: Tanzi M. C. , Levi M. 
Published: December 2004

AbstractA poly‐ether‐urea‐urethane was synthesized by copolymerization of 4,4′‐diphenylmethanediisocyanate (MDI), propanediamine, and poly‐oxytetra‐methylene glycol (M.W. 1000). Two other corresponding copolymers were also synthesized by adding amino terminated poly‐amidoamine macromonomers, purposely synthesized, so as to insert relatively small amounts (6 and 15 weight %) of two types of poly‐amidoamine segments in the final product. Of the three copolymers several physicochemical and mechanical properties have been determined, and their heparin adsorption ability, blood compatibility, and cytotoxicity evaluated.
Transformation of biphasic calcium phosphate ceramicsin vivo: Ultrastructural and physicochemical characterization
Authors: Daculsi G. , Legeros R. Z. , Nery E. , Lynch K. , Kerebel B. 
Published: December 2004

AbstractSpecially prepared biphasic calcium phosphate (BCP) macroporous ceramics consisting of an intimate association of beta tricalcium phosphate (b̃‐TCP) and hydroxyapatite (HA) with b̃‐TCP/HA weight ratios of 15/85, 35/65, and 85/15 were implanted in surgically created periodontal osseous defects in dogs and recovered after 6 months. A decrease in average size of crystals in BCP ceramics and an increase in the size of microporosities in the surface and at the core of the ceramic after implantation were observed, indicating thatin vivodissolution has taken place. The resorbability (reflectingin vivodissolution) of BCP ceramics depended on their b̃‐TCP/HA ratios, the higher the ratio, the greater the resorbability. The formation of microcrystals with crystallographic properties and Ca/P ratio similar to those of bone apatite crystals were also observed. The abundance of these crystals were directly related to the b̃‐TCP/HA ratio of the BCP ceramic before implantation. The formation of the bone apatite‐like crystals may be due to the precipitation of calcium and phosphate ions released from the dissolving ceramic crystals (the b̃‐TCP component dissolving preferentially to the HA component). Results from this study suggested that one of the means of controlling resorbability (in vivodissolution) of BCP ceramic is by varying its b̃‐TCP/HA ratio.
Foreign body reaction against cellophane in the athymic nude mice
Authors: Smetana K. , Holub M. , Slavčev A. 
Published: December 2004

AbstractThere are no differences in the multinucleate cell formation in normal and athymic mice after the subcutaneous implantation of a cellophane strip. The number of Ia+ epitheloid cells and multinucleate foreign body giant cells was lower and the number of epitheloid cells sharing the marker of activated macrophages (M 57) was higher in athymic compared to normal mice. The epitheloid cells of athymic and euthymic animals exhibited no difference in the expression of Mac‐2 molecule. The difference of the expression of surface markers between athymic and euthymic animals does not influence the foreign body giant cell formation.
Bioabsorption of polylactides with different molecular properties
Authors: Nakamura T. , Hitomi S. , Watanabe S. , Shimizu Y. , Jamshidi K. , Hyon S.‐H. , Ikada Y. 
Published: December 2004

AbstractIn order to study the effects of factors governing the bioabsorption rate of polylactides, implantation tests were carried out in rabbits using various samples (20 × 10 × 2 mm3) differing in their chemical composition, residual monomer content, and molecular orientation. Copolymer samples with a higher lactic acid content showed a lower rate of absorption, whereas those with a higher unreacted monomer content were absorbed faster and showed a more drastic decrease in molecular weight. In contrast, degradation of the purified polymers was slow; the purified poly‐L‐lactide showed no weight change and a 50% reduction in molecular weight after 6 months of implantation. Scanning electron microscopy of the samples containing monomers showed a microporous structure extending from the surface to the inner region a few days after implantation, whereas the purified poly‐L‐lactide did not exhibit a microporous structural change even after 10 months of implantation.
Mechanical properties of BIS‐GMA resin short glass fiber composites
Authors: Krause William R. , Park Sang‐Hyun , Straup Robert A. 
Published: December 2004

AbstractThe use of short glass fibers as a filler for dental restorations or cement resins have not been examined extensively. The mechanical properties and untreated glass fibers (5 μm dia × 25 μm) in Bis‐phenol A glycidyl methacrylate (BIS‐GMA) diluted with triethylene‐glycol dimethacrylate (TEGDMA) resin were investigated for possible use as a restorative dental composite or bone cement. Compression, uniaxial tension and fracture toughness tests were conducted for each filler composite mixtures of 40, 50, 60 and 70%. Set time and maximum temperature of polymerization were determined. The results show that the elastic modulus, tensile strength and compressive strength are dependent on the percent of filler content. Elastic modulus and compressive yield (0.2%) strength of silane treated glass fibers filled composite increased from 2.26 to 4.59 GPa and 43.3 to 66.6 MPa, respectively, with increasing the filler content while the tensile strength decreased from 26.7 to 18.6 MPa. The elastic modulus of the untreated composite was less than that of the silane treated fiber composite. The tensile strength and compressive strengths were 20 to 50% lower than those of silane treated composites. The fracture toughness of the silane treated glass fiber additions were not significantly different from the untreated additions. The highest fracture toughness was obtained at 50% filler content with 1.65 MPa m.5. Set time increased from 3.5 to 7.7 minutes with increased filler content and peak temperature dropped from 68.3 to 34°C. The results of this study indicate that the addition of silane coated glass fiber to BIS‐GMA resin increased the elastic modulus, tensile and compressive strengths compared with non‐treated fibers. The addition of either treated or non‐treated fibers increased the set time of the material and decreased the maximum temperature.
In vivo and in vitro degradation of glycine/DL‐lactic acid copolymers
Authors: Schakenraad J. M. , Nieuwenhuis P. , Molenaar I. , Helder J. , Dijkstra P. J. , Feijen J. 
Published: December 2004

AbstractA series of copolymers of glycine and DL‐lactic acid with various compositions was synthesized and their in vivo and in vitro degradation behavior was studied. For the in vivo examination, discs of the copolymer films were subcutaneously implanted in rats. The in vitro studies were carried out in phosphate buffer at pH = 7.4 and 37°C. The decrease in molecular weight, the loss of weight, and the tissue reactions of the different copolymers were determined after 2, 5, and 10 weeks. Poly(DL‐lactic acid) was used as reference material. The in vivo and in vitro degradation behavior of the polymers was comparable. The decrease of molecular weight of the copolymers and poly(DL‐lactic acid) in time was similar. The weight loss for copolymers with a higher mole fraction of glycine units started earlier. The copolymer with the highest content of glycine units disappeared completely within 10 weeks both in vivo and in vitro. The poly(DL‐lactic acid) implant lost only 25% weight over the same period. Tissue reactions against all materials started with an acute inflammatory reaction caused by the trauma of implantation, followed by wound‐healing processes, ending in a very mild foreign body reaction for the poly(DL‐lactic acid) and a more excessive macrophage mediated foreign body reaction for the glycine/DL‐lactic acid copolymers. The tissue reaction was more severe for polymers having a higher rate of degradation.
Embolization: Critical thrombus height, shear rates, and pulsatility. Patency of blood vessels
Authors: Basmadjian Diran 
Published: December 2004

AbstractThe present article builds on elementary fluid dynamics and previous analyses by the author to delineate approximate boundaries of mural thrombus height HP, maximum shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma _{{\rm Max}} $\end{document}, and flow pulsatility beyond which thrombi are subject to either very high or very low probabilities of embolization. A thrombus height of ∼0.1 mm emerges as a critical dividing line: Below it, the maximum embolizing shear stress τs is independent of thrombus height and varies only linearly with shear rate. Above it, τs quickly approaches a strong quadratic dependence on both thrombus height and shear rate: \documentclass{article}\pagestyle{empty}\begin{document}$ \tau _{\rm s} \sim (H_{\rm p} \dot \gamma)^2 $\end{document}, significantly increasing the likelihood of an embolizing event. By contrast, convective‐diffusive removal of blood components during the initial stages of thrombus formation varies only weakly with \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma ^{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}} $\end{document} in all but the smallest vessels. These maximum embolizing stresses are due principally to fluid drag. Acceleration (pulsatile) forces only begin to make their presence felt at \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma} $\end{document} < 500 s−1 and reach parity with fluid drag at \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma} $\end{document} ∼ 10 s−1, i.e., at a level where the presence of pulsatility is questionable. The results are used to provide maps of domains with high and low probabilities of an embolytic event and of vessel patency. The maps reveal that relatively modest changes in shear rate and/or vessel lumen can cause shifts from high to low likelihood of vessel patency, opening up possible ways of controlling blockage by manipulation of these variables.
Preadsorption of polymers on glass and silica to reduce fibrinogen adsorption
Authors: Maechling‐Strasser C. , Déjardin Ph. , Galin J. C. , Schmitt A. 
Published: December 2004

AbstractGlass and silica beads were precoated with various polymers to obtain steric exclusion chromatography (SEC) supports which are nonadsorbant for hydrophilic macromolecules. The efficiency of this treatment was estimated by subsequent radiolabeled fibrinogen adsorption. The result obtained with a block copolymer was better than with various hydrophilic homopolymers. This ABA type block copolymer, where A is a poly(N‐acetylethyleneimine) (PAEI) sequence and B a polyethylene oxide (PEO) sequence was preadsorbed at pH 4.5 and 25°C; the fibrinogen adsorption was reduced to less than 5% of the value observed on untreated solid surfaces. Thus the hemocompatibility of solid supports should be increased by precoating with this block copolymer. Results for nonporous glass beads and porous silica particles were in good correlation.
Synthesis and adsorption of a poly(n‐acetylethyleneimine)‐polyethyleneoxide‐poly (n‐acetylethyleneimine) triblock‐copolymer at a silica/solution interface. influence of its preadsorption on platelet adhesion and fibrinogen adsorption
Authors: Maechling‐Strasser C. , Déjardin Ph. , Galin J. C. , Schmitt A. , Housse‐Ferrari V. , Sébille B. , Mulvihill J. N. , Cazenave J. P. 
Published: December 2004

AbstractThe synthesis of a triblock copolymer poly‐(N‐acetylethyleneimine)‐polyethylenoxide‐poly(N‐acetylethyleneimine) includes two successive steps: the first is the functionalization of a poly(ethyleneglycol) precursor by creating sulfonic esters at its chain ends, the second uses these esters to initiate the cationic polymerization of 2‐methyl‐2‐oxazoline. Homopolymers appear in the raw product; hence successive selective extractions of the copolymer with benzene and dioxane are necessary. The final yield in pure copolymer was 11%. The copolymer was characterized by UV and 1H‐NMR spectrometry and light scattering. Adsorption isotherms were determined on silica, for varying pH and salt concentration. Optimum conditions for coating silica with the polymer were determined. The efficiency of this precoating to reduce the adsorption of fibrinogen was very high (99.2% reduction with respect to bare silica). Steric exclusion chromatography of a variety of proteins gave a satisfactory calibration curve. Platelet accumulation on copolymer precoated glass was reduced to 10–20% of its value on bare glass, a result superior to that obtained by albumin passivation of the same glass surface.
A micromechanical technique for monitoring cell—substrate adhesiveness: Measurements of the strength of red blood cell adhesion to glass and polymer test surfaces
Authors: Bowers V. M. , Fisher L. R. , Francis G. W. , Williams K. L. 
Published: December 2004

AbstractWe report a novel method for rapid comparison of the relative strength of adhesion of cells to different solid surfaces. A vertically oscillating micropipette is brought above an individual cell in such a manner that it makes contact with the cell at the lower limit of its travel. The pressure within the micropipette is gradually reduced until the cell attaches to the micropipette by suction and is lifted from the solid surface. The reduction in pressure required to detach a cell depends on the specific cell‐substrate combination and serves as a relative measure of the strength of cell adhesion. A particular advantage of this approach over conventional methods is the ability to select particular cells from a population. As a test of the reproducibility of the method and its ability to distinguish the strength of adhesion of cells to different solid surfaces, we have used it to measure the adhesiveness of human red blood cells to hydrophilic glass, tissue culture grade polystyrene, polyethylene terephthalate, and polymethyl methacrylate. We find that results for the same surface are highly reproducible and that the method is capable of distinguishing small differences in the adhesiveness of red blood cells to the above surfaces.
Identification of plasma proteins adsorbed to hemodialyzers during clinical use
Authors: Mulzer S. R. , Brash J. L. 
Published: December 2004

AbstractAn investigation has been made of the protein layers formed on hemodialysis membranes during clinical use. Dialyzers having membranes of polymethylmeth‐acrylate (PMMA), Cuprophane, cellulose acetate (CA), and saponified cellulose ester (SCE) were examined. Immediately following dialysis the dialyzers were washed free of blood and the membranes eluted with 2% SDS. The eluates were examined by SDS‐PAGE followed by protein immunoblotting. Antisera to 16 common plasma proteins were used to probe for the presence of these proteins in the eluates. Most of the proteins tested for were found in the different eluates, suggesting that the protein layers are extremely complex. The protein compositions were qualitatively different on the different membranes. Except for HMWK the contact phase clotting factors were present in very small amounts and were largely activated. The clear presence of HMWK and the relatively small amounts of fibrinogen provide support for the occurrence of the Vroman effect. Fibrinogen was found to be degraded and this may be related to the observation that plasminogen was activated to plasmin. Complement C3 was an abundant component of all eluates. It was degraded to small fragments in a way which could not be related to complement activation. Many of the other proteins, particularly those of high molecular weight, were extensively degraded. It is speculated that this heretofore unremarked phenomenon may be due to the action of enzymes released by cell damage.
Thermodynamic study of phase transfer of precipitates on SiC whisker reinforced glass ceramics
Authors: Imai K. , Yuge T. , Ito S. , Kawase T. , Saito S. 
Published: December 2004

AbstractPhysicochemical properties of glass ceramics in weakly buffered, supersaturated, metastable calcium and phosphate solution were studied. Formations of calcium phosphate precipitates were also analyzed thermodynamically. All biomaterials examined here showed primarily dissolution process and subsequent nucleation. Dissolution was enhanced in those which contained Na2O and/or SiC. The dissolution of calcium and phosphate ions from biomaterials and subsequent nucleation of calcium phosphate salts after induction time resulted in a stable equilibrium having solubility characteristics similar to octacalcium phosphate (OCP). The most soluble material, CPSN‐SiC, showed an initial transient equilibrium with amorphous calcium phosphate (ACP). From above results, calcium phosphate ceramics had certain driving force of its own which kept the equilibrium of solution to OCP thermodynamically for 7 days. Despite the favorable solubility equilibrium attained, there still remain problems for clinical application.
The effects of heat treatments and bead size on the corrosion of porous F75 in saline and serum
Authors: Hughes P. J. , Brown S. A. , Payer J. H. , Merritt K. 
Published: December 2004

AbstractAn accelerated anodic corrosion method was used to study the effects of heat treatment and bead size on corrosion and metal ion release of porous coated F75 cylinders in saline and serum. Three heat treatments were used: a standard process for F75 implants (HTA), the standard plus an additional hour in air to produce a thin oxide film (HTA′), and a sintering in high vacuum to produce a chromium‐depleted surface (HTB). Three bead sizes of similar composition were used, with approximate sizes of 215, 300, and 560 μm. The results demonstrated that HTA′ had the lowest corrosion rate and that of HTB was significantly greater than either HTA or HTA′. The corrosion rates of HTA and HTA′ were significantly greater in serum as compared with saline, whereas that of HTB was not affected by the presence of serum, suggesting an interaction between chromium and serum proteins. Bead size had a minimal effect on the corrosion rate of HTA′. For HTA, the small beads had the highest corrosion rate; the lowest was with the medium‐sized beads. Bead size had the most significant effect with HTB, with that of the smaller beads having the higher corrosion rates. The effects of bead size were less consistent in serum, suggesting that protein adsorption may mask some of the surface area effects. It is concluded that the oxide film does reduce corrosion, that proteins do have an influence on the corrosion of F75, and that this method can be a suseful tool for studying the effects of improved heat treatment methods on the corrosion rate of F75 implants.
A fractographic analysis of in vivo poly(methyl methacrylate) bone cement failure mechanisms
Authors: Topoleski L. D. Timmie , Ducheyne Paul , Cukler John M. 
Published: December 2004

AbstractCementing with poly(methyl methacrylate) (PMMA) is a common means of fixing total hip prostheses. Bone cement fails mechanically, and subsequent loosening frequently requires correction via revision surgery. An initial step in optimizing bone cement properties is to establish which properties are critical to the material's in vivo performance. The objectives were to discern the critical in vivo failure mechanisms of bone cement. Fracture surfaces of bone cement specimens that failed in vivo were compared with fatigue and rapid fracture surfaces created in vitro. In vivo fracture processes of bone cement were positively identified and explained by the elucidation of PMMA fracture micromechanisms. The ex vivo fracture surfaces are remarkably similar to in vitro fatigue fracture surfaces. The fractographic data document that the primary in vivo failure mechanism of bone cement is fatigue, and the fatigue cracks grow by developing a microcraze shower damage zone. Agglomerates of BaSO4 particles can be implicated in some bone cement failures, large flaws or voids in vivo can lead to a rapid, unstable fracture, pores in the PMMA mass have a clear influence on a propagating crack, and wear of the fracture surfaces occurs, and may produce PMMA debris, exacerbating bone destruction.
Surface passivation by human albumin of plasmaperesis circuits reduces platelet accumulation and thrombus formation. Experimental and clinical studies
Authors: Mulvihill Juliette N. , Faradji Albert , Oberling Francis , Cazenave Jean‐Pierre 
Published: December 2004

AbstractThe contact of flowing blood with an artificial surface leads to adsorption of plasma proteins, followed by platelet adhesion and aggregation and thrombus formation. This phenomenon is enhanced by turbulent flow at joints, bifurcations, and constrictions. In therapeutic plasmapheresis using an IBM blood cell separator, blockage of the extracorporeal circulation system by platelet‐fibrin thrombi imposed a halt in treatment for manual clearance of the circuit for 66 in 149 cases (44%). Thus it was decided to passivate the surface of the extracorporeal circuit by filling the tubing with 4% human serum albumin 15–20 min before the treatment session and then displacing the albumin solution with the patient's blood without creating an air–liquid interface. After introduction of this technique, a blockage was observed for only 11 in 239 cases (5%). In vitro measurements of platelet accumulation on the internal surface of the circulation system were carried out using washed human platelets labeled with 111In‐oxine in the presence of a 40% hematocrit. Preadsorption of the surface with albumin reduced platelet deposition to 4–5% that observed for an equivalent pretreatment with physiological saline.