bluuebunny/crossref_metadata_2025_split huggingface dataset:
Guided bone tissue elaboration by osteogenic cells in vitro
Authors: Gomi K. , Davies J. E. 
Published: May 2005

AbstractPrimary rat bone marrow cells were cultured for 2 weeks in polystyrene dishes whose surfaces had been roughened using 600‐ or 320‐grit silicon carbide paper. Eight samples were prepared of each of the three groups of dishes, to include a nontreated control suface. Following the culture period, the dishes were stained by von Kossa's method. The distribution of bone formed during the culture period was examined by light microscopy and the area of bone formed quantified. Results demonstrated that both the amount and spatial distribution of bone were influenced by the roughness of the underlying substratum. Differences between the smooth and roughened surfaces were statistically different at P < .05. © 1993 John Wiley & Sons, Inc.
Hydroxylapatite/poly(L‐lactide) composites: An animal study on push‐out strengths and interface histology
Authors: Verheyen C. C. P. M. , de Wijn J. R. , van Blitterswijk C. A. , de Groot K. , Rozing P. M. 
Published: May 2005

AbstractIn the development of new materials for resorbable systems for bone fixation and replacement, composites of hydroxylapatite and poly (L‐lactide) (HA/PLLA) were tested. In a transcortical implantation model in goats the interactions at the bone‐implant interface were studied with post‐operative intervals up to 1 year. Push‐out testing of the implants indicated that PLLA reinforced with 50 wt% hydroxylapatite coating of 50 μm thickness increases interfacial shear strength at 3 months of implantation when compared to unfilled poly(L‐lactide) (P < .01). Scanning electron microscopy showed that the failure mode was predominantly at the coating‐implant interface. Implantation periods longer than 3 months did not result in a significant increase in push‐out strength because of the resorbing PLLA matrix. In support of the above findings there was histological evidence, on a light microscopical level, of increased bone contact at the interface for the composites, HA incorporated in or coated on PLLA, compared to unfilled poly(L‐lactide). © 1993 John Wiley & Sons, Inc.
Patency and blood flow in gas denucleated arterial prostheses
Authors: Vann Richard D. , Ritter Edmond F. , Plunkett Mark D. , Wyble Charles W. , Bensen Christopher V. , Gerth Wayne A. , Barwick William J. , Klitzman Bruce 
Published: May 2005

AbstractBiomaterials exposed to blood often fail due to thrombosis. Gas nuclei (air) in the material are thrombogenic and a potential cause of failure. The effects of gas nuclei on patency and blood flow were studied in 4 mm diameter arterial grafts (Gore ePTFE; Johnson and Johnson Vitagraft ePTFE; Bard ACG EXS) in the femoropopliteal position of dogs. Control and denucleated (air‐free) grafts were implanted bilaterally. Grafts were denucleated by immersion in degassed saline and exposure to 4 torr vacuum and 3,000–20,000 psig pressure. Graft patency was determined at harvest in 46 dogs. Blood flow was measured with acoustic flow probes in eight dogs. Denucleated graft patency was 60% after 2 days of implant while control patency was 22% (P < .05). Measured blood flow was higher in denucleated grafts than in control grafts (P < .02) in 4 of 5 dogs which had significantly different flows. Patency and flow decreased to zero for both control and denucleated grafts over periods of up to 80 days. Air in the control grafts may have been absorbed within several days, leading to late similarity with the denucleated grafts. Thus, removing the air from 4 mm ePTFE grafts decreased acute thrombosis and increased the patency. © 1993 John Wiley & Sons, Inc.
Strain distribution in the proximal femur with flexible composite and metallic femoral components under axial and torsional loads
Authors: Otani Takuya , Whiteside Leo A. , White Stephen E. 
Published: May 2005

AbstractThis study investigated strain distribution changes in the proximal femur after implantation of a flexible composite femoral component (carbon composite material, modulus of elasticity = 18.6 GPa), a titanium alloy implant (E = 100 GPa), and a stainless steel implant (E = 200 GPa). Transverse as well as longitudinal strain was measured using bipolar strain gauges at eight locations on the proximal femur under both physiologic axial (1000 N and 2000 N) and physiologic torsional (10 N‐m and 20 N‐m) loads. Under axial load, longitudinal compressive strain at the calcar region was significantly greater in intact femurs and the carbon composite stem specimens than in the two metal stem specimens. The difference between intact femurs and the carbon composite stem specimens was not significant. Stress shielding in the proximal lateral region of the femur, however, was still apparent even in the carbon composite stem specimens. Without seating of the stem collar on the femoral neck, longitudinal compressive strain was not generated at the calcar region, and transverse tensile strain at this region was increased. With conventional implant design, the stem collar was still necessary even in the flexible composite stem to provide near normal longitudinal compressive strain in the calcar region. Under torsional load, proximal strain in intact femurs was small and the proximal strain levels observed after either carbon composite or titanium alloy stem implantation were greater than strain levels before implantation. It seemed unlikely that torsional stress relief played a significant role in proximal bone loss after total hip arthroplasty. Both longitudinal and transverse strains at the calcar region under torsional load were significantly greater in the carbon composite stem specimens than in both intact femurs and the titanium alloy stem specimens, suggesting that these abnormally high proximal stresses may cause high proximal micromotion of the implant, and even bone fracture. Proximal implant design seems to be of paramount importance with flexible composite femoral components to avoid excessive proximal stress concentration under torsional load and‐to provide near normal strain distribution in the proximal femur. © 1993 John Wiley & Sons, Inc.
Histologic investigation of the biologic behavior of different hydroxyapatite plasma‐sprayed coatings in rabbits
Authors: Jansen J. A. , van der Waerden J. P. C. M. , Wolke J. G. C. 
Published: May 2005

AbstractThe aim of this study was to investigate bone response to and biostability of three different hydroxyapatite (HA)‐coatings. Therefore, coated and uncoated titanium implants were inserted into the tibia of rabbits. Implantation times were at 3 and 12 weeks. The histological evaluation included measurement of the amount of bone apposition to the various implant surfaces. The results demonstrated at 3 and 12 weeks no marked differences in bony reaction at the cortical level to the different implant materials. However, compared with the 3‐week specimens, at 12 weeks extensive maturation of the woven bone callus had occurred. In addition, all 12‐week implants induced bone formation in the medullary cavity. It was also noted that all HA‐coatings showed loss of coating thickness. Quantitative determination of bone contact demonstrated that all 12‐week implants showed the same high amount of bone apposition. © 1993 John Wiley & Sons, Inc.
Polymethylmethacrylate particles enhance DNA and protein synthesis of human fibroblasts in vitro
Authors: Frondoza Carmelita G. , Tanner Kamaryn T. , Jones Lynne C. , Hungerford David S. 
Published: May 2005

AbstractAseptic loosening of polymethylmethacrylate (PMMA) fixed prosthesis is characterized by formation of a radiolucent fibrous membrane, accumulation of inflammatory cells and osteolysis. Since this membrane is produced by fibroblasts, it is likely that these connective tissue cells play a critical role in the loosening process. Whether fibroblasts form the radiolucent membrane in response to stimulation by PMMA has not yet been established, nor is it known whether fibroblasts play a role in attracting inflammatory cells to the bone‐cement interface by secreting chemical mediators. To address this question, we analyzed the in vitro response of normal human fibroblasts to PMMA. Cells were plated with 105/mL Dulbecco minimal essential medium and were incubated 4 h later with PMMA particles, polystyrene (PS) particles, or medium alone. Proliferative capacity monitored by incorporation of 3H‐thymidine was significantly increased following a 48 h exposure to PMMA. Protein synthesis determined by incorporation of 14C‐leucine and 14C‐proline was also increased. In contrast, levels of secreted prostaglandin (PG) E2 assayed immunoenzymatically was not altered by PMMA. Fibroblasts exposed to control PS did not change their proliferative or protein synthetic activity. Fibroblasts internalized PMMA and PS particles without detectable ultrastructural damage. PMMA enhancement of fibroblast proliferative capacity and protein synthetic ability observed in our in vitro assay system suggests similar effects on fibroblasts in vivo. © 1993 John Wiley & Sons, Inc.
Conformational changes of fibronectin induced by polystyrene derivatives with a heparin‐like function
Authors: Stanislawski L. , Serne H. , Stanislawski M. , Jozefowicz M. 
Published: May 2005

AbstractIt was previously reported that polystyrene substituted with the sulfonate group, PSSO3, which has anticoagulant heparin‐like properties, and then coated with fibronectin supports the growth of human umbilical vein endothelial cells. On the other hand, polystyrene substituted with the amino acid sulfamide group, PSSO2‐Asp, which has a higher anticoagulant activity, and then coated with fibronectin no longer supported the growth of endothelial cells. We report here that, while the affinity of fibronectin to either polymer is of the same order of magnitude, fibronectin is adsorbed onto the PSSO2‐Asp polymer in a different conformation compared to the PSSO3 polymer. This was shown by a higher binding of polyclonal antifibronectin antibodies to fibronectin‐coated PSSO2‐Asp polymer, and by a decreased susceptibility of the coated fibronectin to proteolysis by thermolysin. This study provides evidence that a solid phase substrate with a strong heparin‐like function may influence the conformation and biological properties of fibronectin. © 1993 John Wiley & Sons, Inc.
Relationship between arterial thrombosis and neutralization of a polyethylene ionomer
Authors: Goggins Jean A. , Hiltner Anne , Jones Paul K. , Jones Richard D. 
Published: May 2005

AbstractThe influence of three levels of sodium neutralization of an ethylene/ methacrylic acid copolymer on in vivo blood compatibility was studied in a canine arterial model. Effects due to sample fabrication methods (thermal pressing versus solution casting) were also monitored. Sodium content, sodium release, hydrogen dissociation, and localization of anionic groups were noted. Polymer surface energy, surface morphology, water uptake, and thermal properties were characterized.Material characterization and in vivo implantation disclose the following: (1) Thermal pressing generated oxidation degradation products that decreased in vivo blood compatibility. Solution‐cast samples adhered and activated fewer blood elements. (2) Platelets and leukocytes were sensitive to differences in shear rate in the carotid and femoral arteries, with the femoral site tending toward higher shear, more platelet deposition and fewer leukocytes. (3) The surface properties of the polyethylene control, 0% Na, and 50% Na samples tended to be similar. These properties were different from the 100% Na ionomer was more hydrophilic, had a higher polar component for its surface energy, and was unique in exhibiting discrete ionic clusters 1–10 μm in diameter on its surface. (4) These differences were manifested in vivo by platelet activation and thrombus development on the polyethylene, 0% Na, and 50% Na implants, while the 100% Na implant surfaces were predominantly covered by singly adherent, unactivated platelets. (5) It is proposed that the improvement in biocompatibility for the 100% Na ionomer is due to the cluster development in the neutralized methacrylic component and that either directly, or through appropriate protein adsorption and/or conformational adjustment to the cluster regions, platelets are not activated and do not initiate the coagulation mechanism. © 1993 John Wiley & Sons, Inc.
Analysis of the extractive and hydrolytic behavior of microthane poly(ester‐urethane) foam by high pressure liquid chromatography
Authors: Amin Prafulla , Wille John , Shah Kishore , Kydonieus Agis 
Published: May 2005

AbstractMicrothane foam, a poly(ester‐urethane) (PU) used in the manufacture of Meme/ Replicon breast implants, was analyzed by an HPLC method to determine whether 2,4‐ and 2,6‐toluenediamine (TDA) were formed under a variety of physiological and nonphysiological and nonphysiological extraction and hydrolytic conditions. At our detection limit of 20 ppb, no 2,4‐ or 2,6‐TDA was observed in either methyl tert‐butyl ether (MTBE), or aqueous buffer extracts of PU foam. The predominant extractable components identified by HPLC UV‐analysis, were a mixture of nonaromatic and aromatic PU fragments. Moreover, no detectable amounts of TDA were found in foam or MTBE extract of foam incubated in phosphate buffer, pH 7.4, at 37°C for 5 days. By contrast, 2,4‐ and 2,6‐TDA were found in foam and foam extracts exposed to low concentrations of either strong mineral acid or base; higher levels were found at higher acidity, treatment temperature, or durations of incubation. Moreover, 2,4‐ and 2,6‐TDA were found in oligomers isolated by preparative HPLC and exposed to alkaline conditions. Finally, 1–2 ppm of 2,4‐TDA was detected when PU foam extracts were prepared by the Snyder‐Breder method, which employs acidic and alkaline conditions in the work‐up procedure. Based on these findings, we suggest that published observations of 2,4‐TDA formation from in vitro and ex vivo extractions of PU foam are artifacts resulting from pH effects on oligomeric PU fragments present in or extracted from the foam. © 1993 John Wiley & Sons, Inc.
Incorporation of polylactide–polyglycolide in a cortical defect: Neoosteogenesis in a bone chamber
Authors: Winet H. , Hollinger J. O. 
Published: May 2005

AbstractOne hundred‐micron‐thick threads of 40‐kDa copolymer polylactide : polyglycolide (PLGA) in a 50 : 50 molar ratio in bone chambers were implanted in rabbit tibias. Weekly intravital microscopic observations were used to assess trabecular ingrowth and PLGA absorption, processes referred to as incorporation. Nineteen rabbits were observed from the 3rd (W3) to the 10th or 12th (W10/W12) week postimplantation. Analysis of digitally processed video images obtained weekly showed that PLGA absorption was completed in about 8–10 weeks and trabecular ingrowth delayed to about 1 week slower than its control value. Four of the bone chambers showed PLGA unraveled by week 3, no trabecular ingrowth, and significantly reduced neovascularization. No such apparent inhibitory effects were observed in bone chambers that displayed PLGA absorption. No causal link could be established between the rate of neoosteogenesis and the rate of PLGA absorption, but it was clear that incorporation slowed and rapid degradation inhibited bone regeneration. It was concluded that copolymer synthesis and postsynthesis processing must result in a synthetic with a predictable micro‐ and macro‐molecular structure before one can predict its incorporability in a given reconstruction or fixation site. © 1993 John Wiley & Sons, Inc.
Mechanical and histological evaluation of amorphous calcium phosphate and poorly crystallized hydroxyapatite coatings on titanium implants
Authors: Maxian Suzanne H. , Zawadsky Joseph P. , Dunn Michael G. 
Published: May 2005

AbstractThe effect of amorphous calcium phosphate (Ca/P) and poorly crystallized (60% crystalline) hydroxyapatite (HA) coatings on bone fixation to “smooth” and “rough” (Ti‐6Al–4V powder sprayed) titanium‐6Al‐4V (Ti) implants was investigated. Implants were evaluated histologically, mechanically, and by scanning electron microscopy (SEM) after 4 and 12 weeks of implantation in a rabbit transcortical femoral model. Histological evaluation of amorphous vs. poorly crystallized HA coatings showed significant differences in bone apposition (for rough‐coated implants only) and coating resorption (for smooth‐ and rough‐coated implants) that were increased within cortical compared to cancellous bone. The poorly crystallized HA coatings showed most degradation and least bone apposition. Mechanical evaluation, however, showed no significant differences in push‐out shear strengths between the two types of coatings evaluated. Differences between 4 and 12 weeks were significant for coating resorption and push‐out shear strength but not for bone apposition. Significant enhancement in interfacial shear strengths for bioceramic coated as compared to uncoated implants were seen for smooth‐surfaced implants (3.5–5 times greater) but not for rough‐surfaced implants at 4 and 12 weeks. Rough implants showed greater mean interfacial strengths than uncoated smooth implants at 4 and 12 weeks (seven times greater) and to coated smooth implants at 12 weeks only (two times greater). Mechanical failure of the bone/coating/implant interface consistently occurred within the bone, even in the case of the poorly crystallized HA coatings, which had almost completely resorbed on rough implants. These results suggest that once early osteointegration is achieved biodegradation of a bioactive coating should not be detrimental to the bone/coating/implant fixation. © 1993 John Wiley & Sons, Inc.
Effect of polyol type on the surface structure of sulfonate‐containing polyurethanes
Authors: Silver James H. , Lewis Ken B. , Ratner Buddy D. , Cooper Stuart L. 
Published: May 2005

AbstractPolyurethanes based upon polytetramethylene oxide (PTMO) as the polyol and derivatized with propyl sulfonate functionality pendant from the urethane nitrogen have previously been shown to possess good bloodcontacting properties. Other investigators have shown that sulfonated polyurethanes containing polyethylene oxide (PEO) as the soft segment are much more thrombogenic than those containing PTMO as the soft segment. In this article, the surface properties of sulfonated polyurethanes based upon either PTMO or PEO are compared. Dynamic contact angle measurements show a significant decrease in the receding angles of the sulfonated PTMO‐containing polyurethane as compared to its nonsulfonated precursor polymer. No significant difference is seen between the receding contact angles of either the sulfonated PEO‐based polyurethane or its nonsulfonated analog. Variableangle electron spectroscopy for chemical analysis (ESCA) studies of sulfonated PTMO‐based polyurethane performed at room temperature show that there is a significant decrease in sulfur content at the surface. In contrast, the sulfonated PEO‐based polyurethane showed little change in sulfur content with take‐off angle. Finally, ESCA studies of freeze‐dried surfaces show a significant increase in sulfur near the surface of the sulfonated PTMO‐based polymer as compared to vacuum‐dried samples but show no such increase for the sulfonated PEO‐based polyurethane. It is suggested that the ability of the sulfonate functionality to be expressed at the surface may explain the observed differences in blood compatibility between the sulfonated polyurethanes based upon polyols of varying hydrophilicity. © 1993 John Wiley & Sons, Inc.
In vitro study on the integrity of a hydroxylapatite coating when challenged with staphylococci
Authors: Verheyen C C. P. M. , Dhert W. J. A. , Petit P. L. C. , Rozing P. M. , de Groot K. 
Published: May 2005

AbstractAn in vitro study was performed to evaluate the effect of Staphylococcus aureus and Staphylococcus epidermidis on the integrity of a hydroxylapatite coating. The coating plasmasprayed on poly(L‐lactide), showed dissolution during a 24 h incubation period. This was indicated by an increase in pH and calcium release in the buffer solution., After 4 h of incubation, calcium levels decreased due to the precipitation of calcium phosphate complexes on the coating. The bacteria digested or dissolved the coating, creating irregularly shaped holes. Although the integrity of the hydroxylapatite coating was focally damaged within 2–4 h of incubation with staphylococci, the extent of the damage was only marginal. Due to the formation of a layer of CaP precipitates though, bacteria could not be counted accurately after 4–8 h of incubation. This model could reveal part of the failure mechanism of infected hydroxylapatite coated implants. © 1993 John Wiley & Sons, Inc.
Particle microelectrophoresis of calcium‐deficient hydroxyapatite: Solution composition and kinetic effects
Authors: Kowalchuk Roman M. , Pollack Solomon R. , Ducheyne Paul , King Linda A. 
Published: May 2005

AbstractConcurrent work demonstrates that the zeta potential of bone is multivalued and systematically alterable by changes in sample preparation, steeping fluid composition, and steeping time. Since bone mineral is a mixture of carbonated calcium‐deficient hydroxyapatites, and since the zeta potential of calcium‐deficient hydroxyapatite (CDHA) is altered by pH and time in HNO3‐KOH solutions, the zeta potential of CDHA in physiologic Neuman's fluid (NF) compared with that seen in bone could reveal important information on the contribution of the mineral phase to the zeta potential of bone. In addition, such information may be valuable in designing and evaluating calcium‐phosphate ceramics for increased bone ingrowth. Results demonstrate that the zeta potential of CDHA in NF is negative. With increasing calcium in NF, the zeta potential magnitude of CDHA decreases and inverts to positive values given sufficient calcium concentration and steeping time. This result is opposite to that seen in bone, suggesting that exposed CDHA is not the predominant bone microsurface and implicating a bone surface protein component. With increasing phosphate in NF, the zeta potential magnitude increases to more negative values. While low concentrations of fluoride showed no effect, the possibility of an effect with higher concentrations is still to be determined. © 1993 John Wiley & Sons, Inc.
Elastomeric polytetrapeptide matrices: Hydrophobicity dependence of cell attachment from adhesive (GGIP)n to nonadhesive (GGAP)n even in serum
Authors: Nicol Alastair , Channe Gowda D. , Parker Timothy M. , Urry Dan W. 
Published: May 2005

AbstractThe cross‐linked polytetrapeptide matrices based on the repeating amino acid sequences, GGAP, GGVP and GGIP, were prepared and tested for cell adhesion promoting activity in both the absence and presence of fetal bovine serum. For comparison, X20‐poly(GVGVP), a matrix previously shown to be a poor support for cell attachment and spreading, was included. In the absence of serum, all three polytetrapeptide‐based matrices and the polypentapeptide‐based matrix were negative for the adhesion of fibroblasts and endothelial cells. In the presence of serum, various sub‐maximal levels of cell adhesion were found for all matrices except for the matrix based on GGAP. An apparent correlation was noted between the degree of cell attachment to the different polytetrapeptide‐based matrices and the hydrophobicity of those matrices where increased hydrophobicity results in increased cell attachment. The property of being refractory to ligamentum nuchae fibroblast and human umbilical vein endothelial cell adhesion in the presence of serum indicates a potential use for X20‐poly(GGAP) in the development of, for example, additional physical barriers for the prevention of post‐surgical and post‐trauma adhesions. © 1993 John Wiley & Sons, Inc.