bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vivo evaluation of protein adsorption to sterically stabilised colloidal carriers
Authors: Norman Maria E. , Williams Paul , Illum Lisbeth 
Published: May 2005

AbstractA diffusion chamber implanted intraperitoneally in the rabbit was employed as an in vivo model to evaluate the interaction of peritoneal proteins with block copolymer (poloxamer and poloxamine)‐coated polystyrene microspheres (PS). Using a desorption technique followed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, six proteins of 94, 86, 66, 53, 40, and 20 kDa were desorbed from the carrier systems after incubation with peritoneal fluid in vitro. The 40‐ and 20‐kDa proteins dominated the protein profile. A similar pattern was observed when proteins were desorbed from PS microspheres removed after 24‐h implantation in chambers in the peritoneal cavity, although the protein profile was dominated by the 94‐ and 53‐kDa proteins. In general, coating of PS with block copolymers reduced the amount of protein bound to the microspheres in vitro and in vivo but did not change the types of proteins bound. © 1993 John Wiley & Sons, Inc.
Porous collagen sponge for esophageal replacement
Authors: Natsume Tohru , Ike Osamu , Okada Toshiyuki , Takimoto Nobuyuki , Shimizu Yasuhiko , Ikada Yoshito 
Published: May 2005

AbstractA new artificial esophagus with a bilayered structure made of porous collagen sponge and silicone was studied. The concept of this study was not to replace an esophageal defect permanently with prosthesis but to promote tissue regeneration by collagen. Five centimeters of cervical esophagus were replaced by this artificial esophagus in 19 adult mongrel dogs. Two weeks after implantation, the collagen sponge was replaced by autologous tissue and regeneration of the “neoesophagus” was observed in all animals. The inner surface of the neoesophagus was covered with mature mucosal epithelium similar to the intact esophagus 4–5 weeks after implantation. The replacement site was not complicated by infection, anastomotic leakage, or exuberant granulation tissue development on the luminal surface. In a long‐term survival study, animals showed moderategrade stenosis but could take normal feed orally and with no clinical problems observed. © 1993 John Wiley & Sons, Inc.
Gentamicin sulfate attachment and release from anodized Ti‐6Al‐4V orthopedic materials
Authors: Dunn D. S. , Raghavan S. , Volz R. G. 
Published: May 2005

AbstractA novel method has been developed to attach, retain, and release antibiotics from titanium based materials. This technique consists of forming porous surface coatings by anodizing and using the surface chemical properties of the oxide coatings to attach antibiotics. Coatings with pores in the size range 0.1–0.5 μm have been formed in acid solutions. The attachment and retainment of gentamicin sulfate, a cationic antibiotic, to the coatings has been investigated using microbiological methods. In vitro test results have shown that the duration of antimicrobial activity on the surface of anodized materials is dependent on the porosity and isoelectric point of the coatings. Using microporous oxide coatings formed in phosphoric acid solutions, it has been found that antimicrobial activity could be retained for more than 2 weeks. © 1993 John Wiley & Sons, Inc.
Use of polyphosphazenes for skeletal tissue regeneration
Authors: Laurencin Cato T. , Norman Maria E. , Elgendy Hoda M. , El‐Amin Saadiq F. , Allcock Harry R. , Pucher Shawn R. , Ambrosio Archel A. 
Published: May 2005

AbstractThe hydrolytically unstable polyphosphazenes, poly [(imidazolyl) (methylphenoxy) phosphazenes] and poly [ethyl (glycinato) (methylphenoxy) phosphazenes], were studied as potential polymeric supports for cells in tissue regeneration. For bone repair, their specific function would be to support osteoblast growth, forming a bone–polymer matrix. MC3T3–E1 cells (an osteogenic cell line) were seeded onto polymer matrices and cell adhesion and growth as well as polymer degradation were examined. Both imidazoly‐ and ethyl glycinato‐substituted polyphosphazenes supported the growth of MC3T3–E1 cells. An increase in the content of the imidazolyl side group resulted in a reduction in cell attachment and growth on the polymer surface and an increase in the rate of degradation of the polymer. In contrast, substitution with the ethyl glycinato group favored increased cell adhesion and growth and also an increase in the rate of degradation of the polymers. Thus, the polyphosphazenes represent a system whereby cell growth and degradation can be modulated by varying the nature of the hydrolytically unstable side chain. This in vitro evaluation suggests that the polyphosphazenes may be suitable candidate biomaterials for the construction of a cell–polymer matrix for tissue regeneration. © 1993 John Wiley & Sons, Inc.
Polyvinyl alcohol plasma deposited nylon 4 membrane for hemodialysis
Authors: Shih C. Y. , Lai J. Y. 
Published: May 2005

AbstractPolyvinyl alcohol (PVA) is a hydrophilic and blood compatible material, but it is easily hydrolyzed in aqueous solution. Various methods, including chemical crosslinking and γ‐ray irradiation, have been investigated by many researchers for overcoming the instability of PVA in aqueous solution. This study suggests a new hemodialysis membrane, which is prepared by plasma depositing vinylacetate (VAc) onto annealled nylon 4 membrane, followed by hydrolysis treatment. This improves the blood compatibility of nylon 4 and overcomes the hydrolysis problem of PVA. In addition to conventional plasma deposition, the plasma initiated interpenetrating network (IPN) method is also investigated.The new hemodialysis membranes prepared by both conventional plasma deposited VAc onto nylon 4 (PPVA/N4) and IPN polymer of plasma initiated VAc onto nylon 4 (PIPVA/N4 IPN) show significant improvement in blood compatibility. However, the solute permeabilities of PIPVA/N4 IPN membranes are higher than those of PPVA/N4 membranes. The permeabilities of NaCl, vitamin B12, and albumin for membranes prepared by IPN at 80 W, 30 sec plasma deposited conditions, i.e., the optimized conditions, are 3.614, 0.070, and 0.000 × 10−5 cm2/min, respectively. The mole ratio of adsorbed fibrinogen to adsorbed albumin (the mole ratio F/A) for this membrane is 0.20, and it also shows excellent blood compatibility in this study. © 1993 John Wiley & Sons, Inc.
Adsorption/desorption of human serum albumin at the surface of poly(lactic acid) nanoparticles prepared by a solvent evaporation process
Authors: Verrecchia T. , Huve P. , Bazile D. , Veillard M. , Spenlehauer G. , Couvreur P. 
Published: May 2005

AbstractBiocompatible and biodegradable nanoparticles of poly‐(lactic acid) 100% L‐lactic units = PLA) were prepared by an emulsion, microfluidization, and solvent evaporation method using human serum albumin (HSA) as a surface agent. A radiolabeling technique was employed to quantify the serum albumin bound to the nanoparticles and to measure its desorption kinetics in various media at 22°C and 37°C (Phosphate buffer pH 7.4, serum albumin 40 g/L in phosphate buffer pH 7.4 and fetal calf serum). The amount of serum albumin bound to the nanoparticles was found to be a linear fur ction of 1/D (where D is the nanoparticle mean diameter) and was related to the total developed area of the nanoparticles. The adsorption/desorption behavior of serum albumin at the surface of the nanoparticles suggested a multilayer adsorption model. Moreover, a part of the serum albumin molecules was irreversibly bound regardless of the incubation conditions. Consequently, the classical Langmuirian theories of equilibria could not be applied. © 1993 John Wiley & Sons, Inc.
Dacron vascular biomaterial triggers macrophage ectoenzyme activity without change in cell membrane fluidity
Authors: Chignier Elza , Guidollet Jeanine , Freyria Anne Marie , Ardail Dominique , McGregor John Louis , Louisot Pierre 
Published: May 2005

AbstractBiomaterials induce an inflammatory reaction characterized by a rapid recruitment at the implantation site of polymorphonuclear cells and macrophages. In the course of the inflammatory response, the cellular activation triggers expression of a number of enzymes, such as 5′‐nucleotidase, which is widely distributed in animal cell membranes as an ectoenzyme. It is now well established that 5′‐nucleotidase activity decreses following the contact of inflammatory cells with foreign particles. In this paper we investigate a possible correlation between the enzymatic activities and the dynamic properties of the cell membrane bilayer. Dacron pieces were introduced into rats' peritoneal cavities for a period of 6 h, after which the peritoneal cells were harvested, and various enzyme assays performed, including those for cytoplasmic, lysosomal, and ectoenzymes. In parallel, we studied cell membrane fluidity, using fluorescence polarization of 1‐(4‐trimethylammoniumphenyl)‐6‐phenyl‐1,3,5‐hexatriene (TMA‐DPH), and cellular ultrastructural alteration resulting from the cell‐biomaterial interactions using scanning and transmission electron microscopy. Our results show that: (1) macrophages spread around the Dacron fibers with cytoplasmic finger‐like projections, but no phagolysosomes, (2) 5′‐nucleotidase levels decrease with surgical trauma in comparison with the resident cell exudate, (3) implantation of biomaterials slightly modify the 5′‐nucleotidase levels observed in the sham animal, (4) no differences in the anisotropy values indicating that membrane lipid order within the cells could not account for the observed decrease of 5′‐nucleotidase activity. Thus, we can suggest that 5′‐nucleotidase expression may reflect a particular feature of cell activation without a phagocytic process. © 1993 John Wiley & Sons, Inc.
Comparison of human and canine external femoral morphologies in the context of total hip replacement
Authors: Bloebaum Roy D. , Ota Doug T. , Skedros John G. , Mantas John P. 
Published: May 2005

AbstractThe canine is frequently used as a model for human hip arthroplasty research. In order to better understand the appropriateness of the canine as a model for human total hip replacement studies, the external morphology of canine and human femurs were examined and compared. Several differences were found between canine and human femora, including angular measurements, anterior bow, and femoral head position relative to the femoral diaphysis. In addition, the human femur was noted to undergo age‐related changes in several of the measured parameters. The canine femur did not exhibit any age‐related changes in the measured parameters. This study suggests that there are limitations to the use of the canine model in human hip arthroplasty research, and that discretion must be exercised when attempting to extrapolate results from a canine study to the human clinical condition. © 1993 John Wiley & Sons, Inc.
Tumorigenicity of poly‐L‐lactide (PLLA) plates compared with medical‐grade polyethylene
Authors: Nakamura Tatsuo , Shimizu Yasuhiko , Okumura Norihito , Matsui Teruo , Hyon Suong‐Hyu , Shimamoto Takeshi 
Published: May 2005

AbstractPoly‐L‐lactide (PLLA) plates, 20 × 10 × 1 mm in size, with flat surfaces, were implanted into 50 young male Wistar rats subcutaneously, and the incidence of tumors for 2 years under specific pathogen‐free (SPF) conditions was evaluated. Tumors arose in 22 rats (at the implant sites in 20, and distant from the implantation site in 2). As a control, plates of medical‐grade polyethylene of the same shape were implanted into 50 rats. Tumors appeared in 23 of these rats (21 at the sites of the plates, and 2 ectopically). In 30 rats given sham operations, no tumors appeared in the 2 year observation period. Histologically, all the tumors were mesenchymal malignant tumors resembling fibrosarcoma or malignant fibrous histocytoma (MFH) in humans. In 6 of the PLLA tumors and 3 of the PE tumors, bone formation was observed. There was no significant difference between the incidence of tumors caused by PLLA plates and that of tumors caused by medical‐grade polyethylene plates. Macroscopically, PLLA plates retained their initial shape for 2 years. Scanning electron microscopy revealed small holes on the surfaces of the plates, and their molecular weight was reduced to 8% of the initial value. © 1994 John Wiley & Sons, Inc.
The formation of hydroxyapatite‐gelatin composites at 38°C
Authors: TenHuisen Kevor S. , Brown Paul W. 
Published: May 2005

AbstractComposites comprised of calcium deficient hydroxyapatite (CA/P = 1.5) and gelatin form in about 4 h at 38°C. The solid reactants used are CaHPO4 and Ca4(PO4)2O and the liquid reactant is gelatin solution. The reaction forming hydroxyapatite occurs in several steps. Based on the measurement of heat liberation, there is an initial period where the reaction rate is low. This is followed by a period of constant reaction until the reaction is complete. Analysis of the variation in pH shows that hydroxyapatite formation occurs at a steady state pH near 8.2. Analyses of the evolution of crystalline phases indicates that Ca4(PO4)2O is consumed prior to complete reaction resulting in a phase assemblage of hydroxyapatite (CA/P > 1.5) and CaHPO4. Further reaction results in compositional adjustments in hydroxyapatite as CaHPO4 is consumed. Microstructurally, the composites which form consist of clusters of hydroxyapatite embedded in a gelatin network. The presence of gelatin does not influence the morphology of the hydroxyapatite which forms nor does it retard its rate of formation. © 1994 John Wiley & Sons, Inc.
Physicochemical properties of calcific deposits isolated from porcine bioprosthetic heart valves removed from patients following 2–13 years function
Authors: Tomazic B. B. , Brown W. E. , Schoen F. J. 
Published: May 2005

AbstractThe purpose of this study was to characterize the physicochemical properties of calcific deposits that cause the failure of tissue‐derived heart valve bioprostheses. This was done in an effort to understand the mechanism of pathologic biomineralization in the cardiovascular system and potentially prevent deterioration of bioprostheses. Calcific deposits taken from 10 failed bioprosthetic valves that had been implanted in patients for 2–13 years were characterized by chemical analysis, x‐ray diffraction, FTIR spectroscopy, scanning electron microscopy, polarized light microscopy, and solubility measurements. The combined results identified the biomineral as an apatitic calcium phosphate salt with substantial incorporation of sodium, magnesium and carbonate. The average Ca/PO4 ratio for this “young” pathologic biomineral was ∼1.3, considerably lower than ∼1.7 found in mature atherosclerotic plaque biomineral and mature skeletal biomineral, both of which approximate hydroxyapatite in composition. Deproteinated calcific deposits from bioprostheses had thermodynamic solubilities comparable to those of both atherosclerotic plaque, typical pathologic biomineral and hydrolyzed octacalcium phosphate (OCP, Ca4H(PO4)3 · 2.5 H2O), a proposed precursor phase to biomineral apatite. This later finding, together with chemical composition and structrual details of the bioprostetic deposits themselves, supports a mechanism of cardiovascular calcification in which OCP plays a crucial role in the formation of the final apatitic phase. This suggests an approach toward prevention of bioprosthetic tissue calcification through control of the formation of the kinetically favored OCP precursor and/or its transformation into bioapatite. © 1994 John Wiley & Sons, Inc.This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
Anisotropic elasticity and strength of glutaraldehyde fixed bovine pericardium for use in pericardial bioprosthetic valves
Authors: Zioupos P. , Barbenel J. C. , Fisher J. 
Published: May 2005

AbstractUniaxial tensile tests were performed on glutaraldehyde fixed bovine pericardial strips prepared from chemically modified pericardial samples. These samples originated from an area which demonstrated anisotropic mechanical properties in the native material and which is suitable for the construction of leaflets for pericardial bioprostheses. After glutaraldehyde fixation the tissue had retained its anisotropicity in stiffness and strength in two orthogonal directions. In the range of the functional stresses for a heart valve leaflet (> 1 MPa) the unconstrained fixation regime had modified the initial anisotropic elastic behavior into a more isotropic one. The implications of these findings are that leaflets manufactured from bovine pericardium can be made to resemble, to a degree, the well known anisotropy found in two orthogonal direction in natural human heart valve leaflets, or porcine bioprosthetic heart valve leaflets. © 1994 John Wiley & Sons, Inc.
Calcium phosphate precipitation on the surface of HA‐G‐Ti composite under physiologic conditions
Authors: Ban S. , Maruno S. , Iwata H. , Itoh H. 
Published: May 2005

AbstractHydroxyapatite‐glass‐titanium (HA‐G‐Ti) functionally gradient composite plates bound face‐to‐face by nylon wire were soaked in a simulated body fluid. The gap between the plates was filled with the precipitates after soaking for 6 months, and a tight chemical bond was formed between them. Field emission‐type (FE) scanning electron microscopy (SEM) and transmission electron microscopy observations revealed that the growth rate and morphology of the precipitates differed widely from the outside portion to the inside one on the surface region of the composite plates. In the portion relatively near the outside, the mutually bonded portion, needle‐like precipitates with preferred orientation to the c‐axis were markedly observed. From the results of Fourier transform infrared spectroscopy and energy dispersive x‐ray microanalysis, it was found that the precipitates were Ca‐deficient carbonate apatite with low crystallinity. On the other hand, HA‐G‐Ti composite rods were implanted in the femur of beagle dogs for 3 months. FE‐SEM observations demonstrated that needle‐like precipitates were deposited on both the surfaces of the composite and bone at the portion having a narrow gap, about 0.1–0.2 mm between them prepared deliberately before implantation. It was found that both the morphologies and the composition of the precipitates in vivo were similar to those in vitro. It is concluded that the HA particles on the surface of the composite act as nucleation sites for precipitation in physiologic environments, whereas the glass matrix is independent to it. © 1994 John Wiley & Sons, Inc.
Effects of hyaluronan on collagen fibrillar matrix contraction by fibroblasts
Authors: Huang‐Lee Lynn L. H. , Wu Julia H. , Nimni Marcel E. 
Published: May 2005

AbstractHyaluronan, found in high concentrations in fetal tissues, appears to have a major role in preventing scar formation in fetal wounds. Nevertheless, its role in inhibiting wound contractures associated with scar formation has not been clearly demonstrated. Our current study evaluated the effects of hyaluronan using an in vitro floating collagen fibrillar matrix (CFM) contraction model. The results demonstrated that the contraction of CFM by fibroblasts was significantly reduced when high concentrations (>1 mg/mL) of hyaluronan were present in the media. This phenomenon is unique to hyaluronan, because chondroitin sulfate was ineffective in this connection. Fibroblast migration and proliferation studies indicated that high concentrations of hyaluronan stimulated cell migration and had no cytotoxic effects.Some possible mechanisms by which high concentrations of hyaluronan reduced CFM contraction by fibroblasts were proposed. Because the viscosity of a hyaluronan solution is much greater than that of chondroitin sulfate, and this increases with concentration, we investigated whether this property in itself was an important factor in inhibiting CFM contraction. No direct correlation was found between the viscosity of glycosaminoglycans and their ability to reduce CFM contraction. © 1994 John Wiley & Sons, Inc.
Screening of matrices and fibers for reinforced thermoplastics intended for dental applications
Authors: Goldberg A. Jon , Burstone Charles J. , Hadjinikolaou Ioannis , Jancar Joseph 
Published: May 2005

AbstractPlastic reinforced with continuous fibers (FRC) are being developed for dental applications, such as prosthodontic frameworks and orthodontic retainers. Flexure properties, stress relaxation and hydrolytic stability of FRC based on six thermoplastic matrices, three types of fibers, and three fiber volume fractions were evaluated. Samples with clinically relevant dimensions were tested. Polycarbonate was the preferred matrix material. Polycarbonate reinforced with 42 volume percent glass fibers exhibited the highest combination of flexure modulus (17.9 ± 2.6 GPa), flexure strength (426 ± 40 MPa), reinforcing efficiency (0.79), and resistance to stress relaxation.No statistically significant difference was observed between E and S2 glass reinforced composites under the experimental conditions used. Kevlar reinforced materials exhibited a low flexure modulus and strength. The apparent flexure moduli of all composites decreased with span length in the range of clinical interest. Generally, the prevalent mode of failure for all FRC investigated was brittle failur under flexure loading. Relatively large sample‐to‐sample variation in both composition and properties indicated that improved fabrication methods will be needed in future studies.The combination of good flexure properties, formability, and translucency suggests that novel appliance designs for dentistry are feasible with FRC, but further studies of its properties and particularly the effects of fiber/ matrix interfacial quality are needed. © 1994 John Wiley & Sons, Inc.
Fatigue crack propagation behavior of ultra high molecular weight polyethylene under mixed mode conditions
Authors: Elbert K. E. , Wright T. M. , Rimnac C. M. , Klein R. W. , Ingraffea A. R. , Gunsallus K. , Bartel D. L. 
Published: May 2005

AbstractAnalytical studies of the stresses on and within ultra high molecular weight polyethylene joint components suggest that damage modes associated with polyethylene fatigue failure are caused by a combination of surface and subsurface crack propagation. Fatigue crack propagation tests under mixed mode loading conditions were conducted on center‐cracked tension specimens machined from extruded blocks of sterilized polyethylene in an attempt to determine how fatigue cracks change direction in this material. Cyclic testing was performed using a sinusoidal wave form at a frequency of 5 Hz and an R‐ratio (minimum load/ maximum load) of 0.15. Specimens had the notch oriented perpendicular to the direction of applied load and at angles of 60° and 45° to the loading direction. Numerical analyses were used to interpret the experimental test and to predict the fatigue behavior of polyethylene under mixed mode conditions. It was found that all cracks eventually propagated horizontally, regardless of the initial angle of inclination of the notch to the direction of applied cyclic load. In fact, the extent of the curvilinear crack growth was quite limited. An effective range of cyclic stress intensity factor was calculated for correlation with the rate of crack growth. The results followed a Paris relation, with crack growth rate linearly related to a power of the range of stress intensity, for all three crack orientations. The numerical analyses adequately modeled the experimental fatigue crack growth results. © 1994 John Wiley & Sons, Inc.