bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shear force modulates osteoblast response to surface roughness
Authors: Bannister S. R. , Lohmann C. H. , Liu Y. , Sylvia V. L. , Cochran D. L. , Dean D. D. , Boyan B. D. , Schwartz Z. 
Published: August 2002

AbstractPrevious studies have shown that osteoblasts are sensitive to surface roughness. When cultured on Ti, MG63 osteoblast‐like cells exhibit decreased proliferation and increased differentiation with increasing surface roughness. In vivo, osteoblasts also are subjected to shear force during osseointegration. To examine how shear force modulates osteoblast response to surface roughness, MG63 cells were cultured on glass disks or Ti disks with three different Ra values and topographies (PT: Ra = 0.60 μm; SLA: Ra = 3.97 μm; TPS: Ra = 5.21 μm) in a continuous flow device, resulting in shear forces of 0, 1, 5, 14, and 30 dynes/cm2. Confluent cultures were exposed to fluid flow for 1 h. After an additional 23 h, cell number, alkaline‐phosphatase‐specific activity, and levels of osteocalcin, TGF‐β1, and PGE2 in the conditioned media were determined. Cell numbers on smooth surfaces (glass and PT) were unaffected by shear force. In contrast, shear force caused a dose‐dependent reversal of the decrease in cell numbers seen on rough SLA and TPS surfaces. Alkaline‐phosphatase‐specific activity was unaffected on glass or PT, but shear force caused a biphasic reduction in the roughness‐dependent increase on SLA and TPS that was maximal at 14 dynes/cm2. There was a similar effect seen with TGF‐β1 levels. Osteocalcin was unaffected on smooth surfaces; shear force caused a dose‐dependent reduction in the roughness‐stimulated increase seen on SLA and TPS. PGE2 production was increased by shear force on all surfaces. There was a twofold increase in PGE2 levels in the media of MG63 cells cultured on glass and PT in response to 14 dynes/cm2, but on SLA and TPS, 14 dynes/cm2 shear force caused a 9–10‐fold increase. These results show that osteoblastic response to shear force is modulated by surface topography. The shear‐force‐mediated decrease in osteoblast differentiation seen in cultures on rough surfaces may be due to increased production of PGE2. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 167–174, 2002
Interlaboratory validation of oxidation‐index measurement methods for UHMWPE after long‐term shelf aging
Authors: Kurtz S. M. , Muratoglu O. K. , Gsell R. , Greer K. , Shen F. W. , Cooper C. , Buchanan F. J. , Spiegelberg S. , Yau S. S. , Edidin A. A. 
Published: August 2002

AbstractAn international oxidation index standard would greatly benefit the orthopedic community by providing a universal scale for reporting oxidation data of ultra‐high molecular weight polyethylene (UHMWPE). We investigated whether severe oxidation associated with long‐term shelf aging affects the repeatability and reproducibility of area‐based oxidation index measurement techniques based on normalization with the use of 1370‐ or 2022‐cm−1 infrared (IR) absorption reference peaks. Because an oxidation index is expected to be independent of sample thickness, subsurface oxidation was examined with the use of both 100‐ and 200‐μm‐thick sections from tibial components (compression‐molded GUR 1120, gamma irradiated in air) that were shelf aged for up to 11.5 years. Eight institutions in the United States and Europe participated in the present study, which was administered in accordance with ASTM E691. On average, the 100‐μm‐thick samples were associated with significantly greater interlaboratory relative standard uncertainty (40.3%) when compared with the 200‐μm samples (21.8%, p = 0.002). In contrast, the intralaboratory relative standard uncertainty was not significantly affected by the sample thickness (p = 0.21). The oxidation index method did not significantly influence either the interlaboratory or intralaboratory relative standard uncertainty (p = 0.32 or 0.75, respectively). Our interlaboratory data suggest that with the suitable choice of specimen thickness (e.g., 200 μm) and either of the two optimal oxidation index methods, interlaboratory reproducibility of the most heavily oxidized regions in long‐term shelf‐aged components can be quantified with a relative standard uncertainty of 21% or less. Therefore, both the 1370‐cm−1 and the 2022‐cm−1 reference peaks appear equally suitable for use in defining a standard method for calculating an oxidation index for UHMWPE. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 15–23, 2002
Use of Ti‐coated replicas to investigate the effects on fibroblast shape of surfaces with varying roughness and constant chemical composition
Authors: Wieland Marco , Chehroudi Babak , Textor Marcus , Brunette Donald M. 
Published: August 2002

AbstractA two‐stage replica technique with a subsequent titanium (Ti)‐coating treatment was used to faithfully replicate topographies of polished, acid‐etched, machined‐like, finely blasted, coarsely blasted, coarsely blasted and acid‐etched, and Ti plasma‐sprayed Ti surfaces. The replicas were used to study the influence of different rough surface topographies on the response of human fibroblasts in vitro under conditions of constant surface chemistry for all surfaces. The surface topographies of the replicas were characterized using non‐contact laser profilometry, scanning electron microscopy (SEM), and stereo‐SEM, whereas surface chemistry was examined using X‐ray photoelectron spectroscopy. Fibroblasts were trypsinized and plated onto the Ti‐coated epoxy‐resin replica surfaces for 24 h and observed with SEM. Fluorescein‐5‐thiosemicarbazide was used to stain the cell components including cell membrane, and the stained cells were optically sectioned using epifluorescent microscopy. The optical sections were computationally reconstructed to obtain three‐dimensional images and cell volume and cell thickness determined. The different surface topographies were found to alter cell thickness and cell morphology. However, cell volume as computed from three‐dimensional reconstructions was not affected by surface features. The results suggest that cells distort themselves to accommodate to rough surfaces but their volume is not significantly altered. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 434–444, 2002; DOI 10.1002/jbm.10059
Biocompatibility assessment of silicone oil and perfluorocarbon liquids used in retinal reattachment surgery in rat retinal cultures
Authors: Malchiodi‐Albedi Fiorella , Morgillo Antonio , Formisano Giuseppe , Paradisi Silvia , Perilli Roberto , Scalzo Giovanna Carnovale , Scorcia Giovanni , Caiazza Salvatore 
Published: August 2002

AbstractThe effects of silicone oil and perfluorocarbon liquids used in retinal reattachment surgery were studied in vitro using rat retinal cultures seeded on microporous inserts. These inserts allow the cell layer to be in contact with the material to be tested on the apical side and with the nutrient medium on the basal side. The materials tested were silicone oil, the perfluorocarbons perfluorophenanthrene and perfluoroctane, and hydroxypropylmethylcellulose. Perfluorophenanthrene, the heaviest of the compounds, induced a very precocious detachment of the cell layer. All the other tested biomaterials were compatible with cell survival and did not alter the structural organization of the retinal cultures, as revealed by scanning electron microscopy. By immunocytochemical techniques we evaluated the cell composition and the differentiation state of each of the cultures. In both control and treated samples, neuronal cells were well preserved. The expression of microtubule−asso‐ ciated protein 2, a marker of differentiated neuronal cytoskeleton, was not affected. Amacrine neurons, immunolabeled for γ‐aminobutyric acid, still were detectable after treatment. Synapses, marked by immunoreactivity for synapthophysin, were equally preserved. Vimentin‐positive glial cells did not show modifications. The apoptotic rate, as determined by the terminal transferase‐mediated dUTP–biotin nick end‐labeling assay, was similar in treated and control samples. The results confirm that the use of biomaterials with a specific gravity close to intraocular fluids is compatible with retinal cell survival and differentiation in vitro. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 548–555, 2002
Accelerated aging studies of UHMWPE. I. Effect of resin, processing, and radiation environment on resistance to mechanical degradation
Authors: Edidin A. A. , Herr M. P. , Villarraga M. L. , Muth J. , Yau S. S. , Kurtz S. M. 
Published: August 2002

AbstractThe resin and processing route have been identified as potential variables influencing the mechanical behavior, and hence the clinical performance, of ultra‐high molecular weight polyethylene (UHMWPE) orthopedic components. Researchers have reported that components fabricated from 1900 resin may oxidize to a lesser extent than components fabricated from GUR resin during shelf aging after gamma sterilization in air. Conflicting reports on the oxidation resistance for 1900 raise the question of whether resin or manufacturing method, or an interaction between resin and manufacturing method, influences the mechanical behavior of UHMWPE. We conducted a series of accelerated aging studies (no aging, aging in oxygen or in nitrogen) to systematically examine the influence of resin (GUR or 1900), manufacturing method (bulk compression molding or extrusion), and sterilization method (none, in air, or in nitrogen) on the mechanical behavior of UHMWPE. The small punch testing technique was used to evaluate the mechanical behavior of the materials, and Fourier transform infrared spectroscopy was used to characterize the oxidation in selected samples. Our study showed that the sterilization environment, aging condition, and specimen location (surface or subsurface) significantly affected the mechanical behavior of UHMWPE. Each of the three polyethylenes evaluated seem to degrade according to a similar pathway after artificial aging in oxygen and gamma irradiation in air. The initial ability of the materials to exhibit post‐yield strain hardening was significantly compromised by degradation. In general, there were only minor differences in the aging behavior of molded and extruded GUR 1050, whereas the molded 1900 material seemed to degrade slightly faster than either of the 1050 materials. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 312–322, 2002
Ce‐TZP/Al2O3 nanocomposite as a bearing material in total joint replacement
Authors: Tanaka Kenji , Tamura Jiro , Kawanabe Keiichi , Nawa Masahiro , Oka Masanori , Uchida Masaki , Kokubo Tadashi , Nakamura Takashi 
Published: August 2002

AbstractThe objectives of this study were to investigate the biocompatibility, phase stability, and wear properties of a newly developed Ce‐TZP/Al2O3 nanocomposite, as compared to conventional ceramics, and to determine whether the new composite could be used as a bearing material in total joint prostheses. In tests of mechanical properties, this composite showed significantly higher toughness than conventional Y‐TZP. For biocompatibility tests, cylindrical specimens of both the Ce‐TZP/Al2O3 nanocomposite and monolithic alumina were implanted into the paraspinal muscles of male Wistar rats. The tissue reactions were almost the same, and at 24 weeks after implantation, thin fibrous capsules with almost no inflammation were observed around both of them. There were no significant differences in membrane thickness between the two ceramics. After hydrothermal treatment in 121 °C vapor for 18 h, the new composite showed complete resistance to aging degradation, whereas Y‐TZP showed a phase transformation of 25.3 vol% (initial 0.4%) to the monoclinic form. According to the results of pin‐on‐disk tests, the wear rates of Ce‐TZP/Al2O3 nanocomposite and alumina were 0.55 ± 0.04 × 10−7 and 2.12 ± 0.37 × 10−7mm3/Nm, respectively. The results of this study suggest that the Ce‐TZP/Al2O3 nanocomposite is a promising alternative ceramic component for total joint replacement. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 262–270, 2002
Preparation of albumin preferential surfaces on poly(vinyl chloride) membranes via surface self‐segregation
Authors: Ji Jian , Feng Linxian , Shen Jiacong , Barbosa M. A. 
Published: August 2002

AbstractPoly(vinyl chlorides)‐graft‐[ω‐stearyl‐poly(ethylene oxide)] (PVC‐g‐SPEO), which has a poly(vinyl chloride) (PVC) backbone, poly(ethylene oxide) (PEO) side chain, and stearyl end groups, has been synthesized. Self‐organizing blends of the amphiphilic comb polymer in poly(vinyl chlorides) have been examined as a means to create albumin preferential surfaces on polymer films. X‐ray photoelectron spectroscopy (XPS) analysis indicates substantial surface segregation of the PVC‐g‐SPEO. A surface concentration of 59.9 EO wt % is achieved by the solution casting and heat treatment of a film with a bulk concentration of only 3.78 EO wt %. In the aqueous environment, the surface rearrangement of PVC‐g‐SPEO/PVC blend film is limited and presents a high interfacial energy and high depolar component of interfacial energy due to the “tail‐like” SPEO side chain. Protein adsorption tests confirm that PVC‐g‐SPEO/PVC blend films absorb high levels of albumin and dramatically resist fibrinogen adsorption. Surfaces to attract and reversibly bind albumin, which might diminish the occurrence of thrombosis, inflammation, and infection, are developed by self‐organizing blends of the amphiphilic comb polymer in poly(vinyl chlorides). © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 252–259, 2002
Hydroxylapatite with substituted magnesium, zinc, cadmium, and yttrium. I. Structure and microstructure
Authors: Ergun Celaletdin , Webster Thomas J. , Bizios Rena , Doremus Robert H. 
Published: August 2002

AbstractHydroxylapatite (HA) was made containing magnesium, zinc, cadmium, and yttrium. Salts of these cations were added to precipitating HA; the precipitates were dried and sintered at 1100°C for 1 h. Lattice parameters from X‐ray diffraction spectra showed that these elements were incorporated into the apatite structure at a level of 2% added fraction of calcium in HA and up to 7% for yttrium. The densities of different substituted apatites were close to theoretical for pressed and sintered samples, which is evidence for low bulk porosity. The grain sizes of substituted apatites were smaller than those of pure HA except for cadmium‐containing apatite. Surfaces of etched samples showed no second phases, whereas surfaces of unetched samples showed second phases and higher porosity than etched surfaces. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 305–311, 2002
Effects on articular cartilage of subchondral replacement with polymethylmethacrylate and calcium phosphate cement
Authors: Hisatome Takashi , Yasunaga Yuji , Ikuta Yoshikazu , Fujimoto Yoshinori 
Published: August 2002

AbstractBone defects were created in rabbit medial femoral condyle in a model where subchondral bone was completely removed or about 2 mm of subchondral bone was maintained. Groups without augmentation and augmented with autogenous bone, polymethylmethacrylate, or calcium phosphate cement were sacrificed at 3, 12, and 24 weeks for evaluation of articular cartilage and observation of bone formation. In the model in which subchondral bone was completely removed, collapse of the subchondral bone together with exfoliation and prolapse of cartilage developed early in all cases. In the model in which 2 mm of subchondral bone was maintained, degeneration of articular cartilage developed at 12 weeks in the group augmented with polymethylmethacrylate, showing a significant difference when compared to the contralateral untreated control group. The group augmented with calcium phosphate cement did not demonstrate any evident difference from the control group. Mechanical properties after subchondral replacement did not differ between the groups augmented with polymethylmethacrylate and calcium phosphate cement, although calcium phosphate cement was considered histologically superior. Calcium phosphate cement was a reliable subchondral replacement material when the bone defect is adjacent to the articular cartilage. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 490–498, 2002
Effect of adsorbed fibronectin concentration on cell adhesion and deformation under shear on hydrophobic surfaces
Authors: Goldstein Aaron S. , DiMilla Paul A. 
Published: August 2002

AbstractTo facilitate tissue integration with biomaterials proteins and peptides frequently are immobilized on the biomaterial surface. In particular, extracellular matrix proteins—which interact specifically with integrin adhesion receptors on the cell surface—can stimulate initial cell attachment by serving both as a ligand for receptor‐mediated attachment and as a stimulant of focal adhesion formation and cytoskeletal reorganization. Consequently, the strength of cell adhesion should depend both on the strength of cell/surface contacts and cytoskeleton‐dependent properties of the cell (i.e., morphology, compliance). To examine this dual role of extracellular matrix proteins, murine fibroblasts were seeded onto self‐assembled monolayers (SAMs) of dodecanethiolate coated with 0 to 0.45 μg/cm2 of fibronectin (Fn) and then detached by hydrodynamic shear using a radial‐flow chamber (RFC). Cell adhesion was characterized in terms of the critical wall shear stress for detachment (τwc), and the compliance was evaluated from measurements of cell displacement and elongation as a function of the fibronectin concentration. Critical wall shear stress and cell displacement were found to be insensitive to Fn at concentrations below 0.23 μg/cm2 while above this threshold τwc increased and displacement decreased with increasing Fn concentration. Elongation of the cells in the direction of flow was independent of Fn concentration, but correlated linearly with τwc for Fn densities below 0.23 μg/cm2. These studies show that Fn concentration affects both τwc and cell displacement under shear, and that τwc is sensitive to cell compliance. In addition, they suggest that the dominant mechanism of cell detachment from hydrophobic substrates involves cell displacement. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 665–675, 2002
Cell density dependent regulation of AP‐1 activity is important for chondrogenic differentiation of C3H10T1/2 mesenchymal cells
Authors: Seghatoleslami M. Reza , Tuan Rocky S. 
Published: August 2002

AbstractThe multipotential C3H10T1/2 mesenchymal cells undergo chondrogenic differentiation only when seeded as high‐density micromass cultures, particularly upon treatment with bone morphogenetic protein‐2 (BMP‐2). The molecular mechanism(s) responsible for the cell density‐dependent onset of cartilage‐specific gene expression is presently unknown. Interestingly, a number of recent studies have indicated that activating protein‐1 (AP‐1), a well known downstream target of the mitogenic activated protein kinase (MAP kinase) signaling pathway, is a target of chondrogenic/osteogenic growth factors such as BMP‐2, and plays a role in osteogenic gene regulation as well as in chondrogenic differentiation. The aim of this study is to examine the density‐dependent alteration in the level and binding activity of AP‐1 and its functional involvement in C3H10T1/2 mesenchymal chondrogenesis. To measure the activity of the AP‐1 transcription factor, we generated a pool of stable C3H10T1/2 cell lines harboring a luciferase expression vector driven by a concatamer of an efficient AP‐1 response element (AP1‐10T1/2 cells). Luciferase activity of AP1‐10T1/2 cultures was found to decrease sharply with increase in cell density, either as a function of culture time or initial cell seeding densities. In C3H10T1/2 micromass cultures undergoing chondrogenesis, AP‐1 activity was further reduced and then maintained at a low, steady level for the entire 3–4 day culture period. AP‐1 activity in micromass cultures was not significantly affected by BMP‐2 treatment, but chondrogenesis was compromised upon competitive inhibition of AP‐1 activity with a double‐stranded AP‐1 binding oligonucleotide. The level of AP‐1 binding correlated with the activity of its response element but not with the levels of its leucine‐zipper containing subunits, c‐Jun and c‐Fos. These findings suggest that a cell density‐dependent, low but steady level of AP‐1 binding and activity is required for promoting the chondrogenic potential of C3H10T1/2 cells. J. Cell. Biochem. 84: 237–248, 2002. © 2001 Wiley‐Liss, Inc.
Estrogen‐induced osteogenesis in mice is associated with the appearance of Cbfa1‐expressing bone marrow cells
Authors: Plant Andrea , Samuels Abigail , Perry Mark J. , Colley Shane , Gibson Rachel , Tobias Jonathan H. 
Published: August 2002

AbstractCbfa1 is a transcription factor recognised as being involved in early osteoblast differentiation during embryonic skeletogenesis. To determine whether Cbfa1 plays a similar role in bone formation in the adult, we analysed whether its expression is altered during estrogen‐induced osteogenesis, following our recent studies which suggest that this response involves the generation of early osteoblast precursors within bone marrow. To facilitate identification of Cbfa1‐expressing cells, these studies were performed in mice heterozygous for a cbfa1 gene deletion (cbfa1+/−) using β‐galactosidase (lacZ) as a genetic marker. Cbfa1‐expressing cells were identified by lacZ staining of longitudinal sections of the proximal tibial metaphysis. Treatment of cbfa1+/− mice with 17β‐estradiol 0.5 mg/week for 24 days led to the appearance of new cancellous bone surfaces. This response was associated with a marked increase in number of Cbfa1‐expressing cells within the metaphysis, consisting not only of osteoblasts on bone surfaces but also of cells within the adjacent bone marrow. We subsequently enumerated Cbfa1‐expressing cells at earlier time‐points following estrogen, in sections co‐stained for ALP activity. After 4 days of estrogen treatment, a population of cells appeared within the marrow cavity which expressed Cbfa1, but were negative for ALP. At later time‐points, large numbers of Cbfa1 + bone marrow cells were still present, but the majority of these were close to new trabecular bone surfaces at sites which showed high levels of ALP activity. An equivalent distribution of Cbfa1‐expressing cells was observed in further studies where Cbfa1 expression was analysed in wild‐type mice by immunohistochemistry. We conclude that estrogen‐induced osteogenesis is associated with the appearance of a population of Cbfa1‐expressing cells within bone marrow, which we hypothesize to represent the osteoblast precursor population responsible for subsequent new bone formation. J. Cell. Biochem. 84: 285–294, 2002. © 2001 Wiley‐Liss, Inc.