bluuebunny/crossref_metadata_2025_split huggingface dataset:
A critical evaluation of the purification of biominerals by hypochlorite treatment
Authors: Tomazic Branko B. , Brown Walter E. , Eanes Edward D. 
Published: May 2005

AbstractThe quantitative deproteination of calcific deposits from surgically explanted heart valve bioprostheses was carried out by both hypochlorite and hydrazine extraction to establish which is the better procedure for preparing purified mineral suitable for detailed chemical and structural characterization. Hypochlorite treatment resulted in a material with a higher Ca/PO4 ratio than that of the untreated deposits. The hydrazine treatment did not produce such an effect. A systematic comparison of x‐ray diffraction patterns of calcific deposits showed an increase in crystallinity of hypochlorite‐treated versus native material, while the crystallinity of hydrazine‐treated materials did not change. One other result of the hypochlorite treatment was a pronounced disaggregation of well‐ground calcific deposits into a particle populations ranging from 50–300 nm in size, as shown by scanning electron microscopy. Results comparable to the above findings were also obtained when the two treatments were applied to other bioapatites. On the other hand, mineral solubilities were comparable, regardless of which deprotenation treatment was used. The principal conclusion from this study is that hydrazine deproteination is preferable to hypochlorite extraction in isolating pathologic mineral deposits from bioprosthetic materials for further study. © 1993 John Wiley & Sons, Inc.
The functional equivalence of demineralized bone and tooth matrices in ectopic bone induction
Authors: Katz Ronald W. , Hollinger Jeffrey O. , Reddi A. H. 
Published: May 2005

AbstractThe objective of this study was to determine whether demineralized rat incisor matrices were a more potent inducer of ectopic endochondral bone formation than demineralized diaphyseal bone matrices derived from the same donors. Twenty‐five‐milligram disks of demineralized bone or tooth matrix obtained from adolescent Long‐Evans rats were implanted in a standardized ectopic site. Biochemical and histometric measurements of bone formation revealed that the two matrices were functionally equivalent inducers of endochondral bone formation. The induced pellicle of bone reached a maturation point 18 days after implantation. Dentin matrix implants generated a significantly greater amount of mineralized tissue than did bone matrix implants. This difference could be explained on the basis of remineralization of the dentin particles to a greater degree than the bone matrix particles. Initial observations suggesting a more robust osteoinductive activity in demineralized incisor matrix can be attributed to the decreasing activity of bone matrix from older donors when compared to younger donors. The extent of osteoinduction by the two substrata was equivalent when the matrices were matched for age. © 1993 John Wiley & Sons, Inc.
Ingrowth of bone into pores in titanium chambers implanted in rabbits: Effect of pore cross‐sectional shape in the presence of dynamic shear
Authors: Goodman Stuart , Toksvig‐Larsen Søren , Aspenberg Per 
Published: May 2005

AbstractThe micromotion chamber consists of a titanium outer cylinder and a central core, which are pierced by a transverse 1‐mm canal for tissue ingrowth. Six weeks after implantation in the proximal tibia in mature rabbits, the outer cylinder is osseointegrated; the central core can then be moved in relation to the fixed outer cylinder. Thus, the tissue growing through the pore, from the cylinder into the core, can be subjected to motion of a predetermined amplitude and frequency. In this study we investigate the influence of pore cross‐sectional shape on tissue ingrowth in the canal. In six animals, the outer cylinder was pierced by a square 1‐mm hole that was congruent with the square hole in the core; in five animals, the hole in the cylinder was round. The cross‐sectional area of the square hole in the cylinder was about 21% greater than in a round hole. In all cases, the channel in the inner core was a 1 × 1 × 5‐mm quadrate. All chambers underwent 20 cycles/day of micromotion for a 3‐week period. The amplitude of the micromotion was 0.5 mm. Chambers containing cylinders with a round hole demonstrated less bone ingrowth as compared to cylinders with a square hole. This observation may be due to several factors including the greater cross‐sectional area of the several factors including the greater cross‐sectional area of the square versus the round hole in the cylinder and the enhanced congruity provided by the square outer and inner holes, versus a round outer and square inner hole. © 1993 John Wiley & Sons, Inc.
Histological and biochemical evaluation of osteoblasts cultured on bioactive glass, hydroxylapatite, titanium alloy, and stainless steel
Authors: Vrouwenvelder W. C. A. , Groot C. G. , de Groot K. 
Published: May 2005

AbstractWe investigated the behavior of fetal rat osteoblasts cultured on four bone replacing materials: bioactive glass, hydroxylapatite, a titanium alloy, and stainless steel. The cultures were histologically examined for individual cell morphology and osteoblast expression after several periods of time using scanning electron, fluorescence, and normal light microscopy. Other cultures were used for biochemical determinations of alkaline phosphatase activity (APA) and DNA content. Osteoblasts cultured on bioactive glass showed a better osteoblast‐like morphology and a higher proliferation rate, leading to confluent cultures with higher cell density and a generally better expression of the osteoblast phenotype in comparison with the other substrates. The confluent bioactive glass cultures also showed significantly higher DNA content and APA as well as the calculated APA/DNA ratio. Based on the evaluation of histological and biochemical parameters we conclude that osteoblasts cultured on bioactive glass show a generally better osteoblast character than on the other materials. © 1993 John Wiley & Sons, Inc.
Attachment and proliferation of bovine aortic endothelial cells onto additive modified poly(ether urethane ureas)
Authors: Brunstedt Michael R. , Ziats Nicholas P. , Rose‐Caprara Veronica , Hiltner P. Anne , Anderson James M. , Lodoen Gary A. , Payet C. R. 
Published: May 2005

AbstractTo better understand endothelial cell interactions with poly(ether urethane urea) (PEUU) materials, and to assess bovine aortic endothelial cell attachment, films were incubated for 24 h with BAEC in media containing 5% fetal bovine serum. Other films were allowed to incubate for 4 more days in media containing 5% fetal bovine serum without cells to assess BAEC proliferation. The assay was performed on PEUU films modified with acrylate and methacrylate polymer and copolymer additives that spanned a wide range on the hydrophobicity/hydrophilicity scale. Tissue culture polystyrene (TCPS) was used as a control. The assay showed that PEUU films loaded with Methacrol 2138F [copoly(diisopropylaminoethyl methacrylate][DIPAM]/decyl methacrylate [DM]) (3/1) or with its hydrophilic component, DIPAM, in homopolymer form (i. e., h‐DIPAM), significantly enhanced BAEC attachment (∼80% of TCPS values) and proliferation (∼80%) when compared to unloaded PEUU films (attachment, 73%; proliferation, 47%) or to PEUU films loaded with the more hydrophobic acrylate or methacrylate polymer additives (attachment, 32–69%; proliferation, 18–57%). The assay also showed that PEUU films coated with homopoly(diisopropylaminoethyl acrylate) (h‐DIPAA) significantly enhanced BAEC attachment and proliferation when compared to PEUU films coated with h‐decyl acrylate (h‐DA); films coated with the copolymer of these two acrylates (i.e., co‐[DIPAA/DA] [3/1]) showed intermediate behavior. To explain the enhancement of BAEC interaction with films loaded with Methacrol 2138F or h‐DIPAM, when compared to unmodified PEUU films or to PEUU films loaded with more hydrophobic acrylate and methacrylate polymer additives, it was assumed that the additives near the surface region of the solvent swollen PEUU matrix may have migrated to, or near to, the PEUU‐air interface during film formation, creating an additive enriched PEUU surface region. It is suggested that, once at this surface region, dynamic reorientation in response to an aqueous medium ensured the additives were able significantly to influence protein adsorption, and concomitant endothelial cell behavior, but only if they interacted with aqueous media more favorably than the PEUU. The ability of Methacrol and h‐DIPAM additives to enhance endothelial cell behavior is argued to be the result of increased hydrophilicity. This is the result of exposed, hydrogen‐bonding DIPAM moieties and increased surface flexibility, which is itself due to the hydration of unhindered Methacrol chains, which may create an additive enriched PEUU‐water interfacial zone. © 1993 John Wiley & Sons, Inc.
Toxicity of L‐ascorbic acid to L929 fibroblast cultures: Relevance to biocompatibility testing of materials for use in wound management
Authors: Schmidt Richard J. , Chung Lip Yong , Andrews Andrea M. , Turner Terence D. 
Published: May 2005

AbstractFibroblast cultures are often used to evaluate materials intended for medical use, cytotoxicity being taken as an indicator of bioincompatibility. Such an approach has previously been taken with ascorbic acid in determining its value in wound healing. We have now reexamined the toxicity of L‐ascorbic acid to L929 fibroblast cells in culture. Concentrations of ascorbic acid between 0.5 mM and 11 mM were tested. At concentrations above 2 mM, ascorbic acid was found to inhibit cell proliferation, with cell viability decreasing as the concentration was increased. This effect could be prevented by the addition of either superoxide dismutase or catalase to the culture medium. Assays of glutathione and glutathione disulfide were carried out on 8 day old cultures exposed for 24 h to the same concentrations of ascorbic acid. A dose‐related depletion of glutathione occurred whilst glutathione disulfide levels remained essentially constant. Lactate dehydrogenase and glucose‐6‐phosphate dehydrogenase activities were induced by ascorbic acid at all concentrations tested but the ratio of NADP to NADPH nevertheless increased as the concentration of ascorbic acid increased. Finally, ATP in cells from 8‐day‐old cultures became depleted in the presence of ascorbic acid at concentrations in excess of about 5 mM when assayed after 24 h incubation. These biochemical changes and the concomitant cytostatic/cytotoxic effects may be ascribed to the reactive oxygen species produced by the autoxidation of ascorbic acid in the culture medium. Ascorbic acid breakdown products appeared not to be directly involved. In addition, our results suggested that superoxide acted cooperatively with hydroxyl to elicit these effects on the fibroblasts. It is evident from this study that the microenvironment surrounding fibroblasts in culture may differ fundamentally from that surrounding fibroblasts in a healing wound, making it impossible to extrapolate directly to an in vivo situation and hence to make any recommendations from these results concerning the use of ascorbic acid in wound healing. © 1993 John Wiley & Sons, Inc.
Comparison of bone–implant interface shear strength of solid hydroxyapatite and hydroxyapatite‐coated titanium implants
Authors: Hayashi K. , Inadome T. , Mashima T. , Sugioka Y. 
Published: May 2005

AbstractThe interface shear strength of uncoated Ti‐6Al‐4V, dense sintered hydroxyapatite (HA), and HA‐coated Ti‐6Al‐4V were compared. Interface shear strength was determined using a transcortical push‐out model in dogs 4 and 12 weeks after implantation. The interface shear strength of dense sintered HA and HA‐coated Ti‐6Al‐4V was significantly higher than that of uncoated Ti‐6Al‐4V (P < .001). There was no significant difference between the interface shear strength of dense sintered HA and HA‐coated Ti‐6Al‐4V. After the push‐out test for HA‐coated implants, the regions fractured at the bone‐coating interface and at the coating‐titanium interface coexisted at 4 weeks after implantation. At 12 weeks, the fracture site was, in all cases, the HA coating‐titanium interface, and, in a few samples, fractures inside the coating layer also were visible. © 1993 John Wiley & Sons, Inc.
Biotolerance of a semisolid hydrophobic biodegradable poly(ortho ester) for controlled drug delivery
Authors: Bernatchez Stéphanie F. , Merkli Alain , Tabatabay Cyrus , Gurny Robert , Zhao Qinghong H. , Anderson James M. , Heller Jorge 
Published: May 2005

AbstractWe evaluated the biotolerance of a new semisolid poly(ortho ester) (POE) intended for controlled drug delivery. Two different investigations were carried out in rats: subcutaneous injections and the cage‐implant system. Sodium hyaluronate (SH), 1%, in phosphate buffer was used as a noninflammatory control. When injected subcutaneously in rats, the POE induced a mild and local inflammation at 3 and 7 days followed by a minimal chronic inflammation at 14 and 21 days. When using the cage‐implant system, we quantified the inflammatory components of the exudate surrounding the implanted material within the cage system at 3, 7, 14, and 21 days. The total leukocyte and macrophage concentrations were higher only at 7 days for both SH and POE compared to the control (empty cage). The other parameters were not significantly different from the control. These results show that POE is well‐tolerated by rats when used subcutaneously. © 1993 John Wiley & Sons, Inc.
Integrin receptors and platelet adhesion to synthetic surfaces
Authors: Goodman Steven L. , Cooper Stuart L. , Albrecht Ralph M. 
Published: May 2005

AbstractThe activation‐independent and ‐dependent integrin receptors—glycoproteins GPIc–IIa (α5–β1) and GPIIb–IIIa (αIIb–β3)—are involved in platelet adhesion and thrombus growth on damaged subendothelium through interactions with fibrinogen, fibronectin, von Willebrand factor, and other adhesive proteins. Because these receptors are used in normal in vivo hemostatic adhesion, they may also have a role for adhesion onto synthetic surfaces in the vasculature. Platelet adhesion in vitro was examined onto Formvar, glass, and four polyurethaneureas with various soft segment chemistries and surface properties. Platelets were pretreated with RGD peptides before and after adhesion. RGD peptide pretreatment inhibited spreading and close contact formation compared to treatment with saline or control RGE peptides, with no observable effect on the number of adherent platelets per area. High‐voltage electron microscopy showed abnormally sparse and short microfilament structures with RGD peptide treatment, suggesting an indirect inhibition of actin filament formation. Video‐enhanced light microscopy showed a cessation of spreading and a partial reversal of close contacts following RGD peptide application to adherent platelets. Because minimal amounts of plasma proteins are present in column‐washed platelet suspensions, and as platelet secretion appeared to be minimal in these experiments, these observations suggest that RGD binding integrin receptors may function in platelet spreading even in the absence of exogenous ligand. As RGD peptides did not affect the numbers of adherent platelets, while producing substantial decreases in the extent of spreading, we suggest that platelet integrins, possibly GPIIb–IIIa, are involved in spreading on synthetic surfaces but not for initial adhesion. © 1993 John Wiley & Sons, Inc.
Mapping of glutaraldehyde‐treated bovine pericardium and tissue selection for bioprosthetic heart valves
Authors: Simionescu Dan , Simionescu Agneta , Deac Radu 
Published: May 2005

AbstractGlutaraldehyde‐crosslinked bovine pericardium is widely used in bioprosthetic heart valve fabrication. In an attempt to set a scientific basis for more reproducible tissue selection, we produced and analyzed topographical maps of glutaraldehyde‐treated bovine pericardium. Whole pericardia were divided into specific anatomical areas and their thickness was measured and mapped on templates. In each area, the suture holding power was determined in both parallel and perpendicular (to the base‐apex line) directions; analyses of the tearing patterns in each fragment were used to evaluate predominant fiber orientation, and observations were confirmed by polarized light microscopy. Complete maps were superimposed graphically to aid in the selection of certain areas that would have known fiber orientation, high suture holding power, and suitable thickness. Our results describe regional heterogeneity of bovine pericardial structure and mechanical properties, specifically demonstrating variations in thickness, suture holding power, and collagen fiber orientation. Two areas of choice (representing about 35% of the total) were described as suitable for use in bioprosthetic heart valve fabrication. © 1993 John Wiley & Sons, Inc.
RINm5F cell culture on sephadex derivatives
Authors: Oturan N. , Serne H. , Reach G. , Jozefowicz M. 
Published: May 2005

AbstractInteractions between polystyrene sodium sulfonate and insulin‐secreting RINm5F cells have been previously described. When cultured on these microcarriers, cells exhibited normal growth, altered morphology, and inhibition of the insulin secretion was observed. For the sake of comparison, interactions of RINm5F cells with Sephadex derivatives, namely, carboxymethyl Sephadex (CM Seph), benzylaminated CM Seph (CMB Seph), and sulfonated CMB Seph (CMBS Seph), as well Sephadex, were studied. Cells attached poorly and did not spread onto Sephadex and CM Seph microcarriers, but all other characteristics were normal. In contrast, with cells cultured on CMB Seph and CMBS Seph microcarriers cell attachment, morphology, and growth rate were comparable to those of cells grown on classic plastic wells. But, in the latter case, surprisingly, insulin secretion was enhanced. This effect is composition of the microcarriers dependent. The insulin secretion per cell‐microcarriers composition relationship suggests a specific interaction between an unknown membrane receptor of RINm5F cells and a composite ligand site made of a combination of different chemical functional groups present at the microcarriers surface. © 1993 John Wiley & Sons, Inc.
Time‐dependent changes in the mechanical properties of zirconia ceramic
Authors: Shimizu K. , Oka M. , Kumar P. , Kotoura Y. , Yamamuro T. , Makinouchi K. , Nakamura T. 
Published: May 2005

AbstractZirconia has received special attention, mainly because of its high strength and toughness. However, there is some controversy about the time‐dependent deterioration of its mechanical properties. To examine the change in mechanical properties of zirconia ceramics in vivo and in vitro, tetragonal zirconia polycrystal pieces were introduced into the medullary cavity of the tibia in Japanese rabbits and animals were sacrificed after 2, 4 and 6 weeks and 6, 12, and 30 mo, respectively. Alumina ceramic and hydroxyapatite (HAP) pieces were used as controls to investigate the differences in biocompatibility. Zirconia showed a bending strength of over 1000 MPa initially, and little time‐dependent change in strength was found in both in vivo environments. x‐Ray analysis showed little change in the transformation rate, i.e., less than 5 mol % in vivo and in vitro over a period of 3 years. To estimate time‐dependent changes in zirconia over a longer period, zirconia pieces were placed in 95°C saline solution for over 3 years and their mechanical properties examined at chosen intervals. No serious decrease of bending strength was found over the 3‐year period under these conditions. It is concluded that zirconia can be used clinically because it retains a bending strength of over 700 MPa under any experimental conditions for over 3 years. © 1993 John Wiley & Sons, Inc.
Hardness and young's modulus determined by nanoindentation technique of filler particles of dental restorative materials compared with human enamel
Authors: Willems G. , Celis J. P. , Lambrechts P. , Braem M. , Vanherle G. 
Published: May 2005

AbstractThe recently developed nanoindentation technique was used to measure hardness and Young's modulus of small filler particles in resin composites and other dental restoratives. This technique eliminates the need to visualize indentations. Load and displacement are continuously monitored during a loading–unloading sequence, and hardness as well as Young's modulus are then calculated from the load–displacement curves taking into account the geometry of the indenter. Thirteen posterior composites, 3 dental ceramics for CAD/CAM restorations, 1 sintered porcelain, and 1 amalgam were investigated in this study. The results were compared to the hardness and Young's modulus determined by nanoindentation of human enamel. Of the dental materials tested, only five materials contain inorganic filler particles with a nanohardness not statistically different from that of enamel. The predominant fillers in all other materials, except amalgam and the prepolymerized resin fillers in Bell Firm PX, were found to be significantly harder. The dental restorative materials, except the alloy phase in amalgam, were composed of particles with a Young's modulus significantly lower than that of human enamel. The alloy phase in amalgam had a Young's modulus value comparable to that of enamel. © 1993 John Wiley & Sons, Inc.
Immobilization of high‐affinity heparin oligosaccharides to radiofrequency plasma‐modified polyethylene
Authors: Yuan Shengmei , Szakalas‐Gratzl Gyongyi , Ziats Nicholas P. , Jacobsen Donald W. , Kottke‐Marchant Kandice , Marchant Roger E. 
Published: May 2005

AbstractOligosaccharides of heparin with high affinity for antithrombin III (ATIII) have been immobilized onto surface‐modified NHLBI Primary Reference low density polyethylene (PE). PE was modified by radiofrequency plasma polymerized (<150 nm thick) films derived from N‐vinyl‐2‐pyrrolidone (PPNVP) or allyl alcohol (PPAA), and coupled by chemical derivatization to either 3‐aminopropyltriethoxysilane or amino‐terminated poly ethylene oxide). High affinity heparin oligosaccharides (HA‐heparin, anti‐factor Xa activity of 592 ± 120 IU/mg) prepared by partial deaminative cleavage of commercial crude heparin and fractionated by agarose‐ATIII affinity chromatography, were immobilized to surface‐modified PE by reductive amination. The anticoagulant activity, as determined by a chromogenic assay for the inhibition of factor Xa, was estimated to be 30–70 mIU/cm2, with binding estimated to be 56–119 ng/cm2. The highest activity was obtained for the HA‐heparin immobilized to PE modified by PPNVP with a PEO spacer. Visual confirmation of ATIII binding to immobilized HA‐heparin was demonstrated by a goldlabeled double antibody method with imaging by SEM. © 1993 John Wiley & Sons, Inc.