Thirteen male rats, 7 or 10 months old, were given 0.005% NaF in the diet or 0.025 NaF in the drinking water fro periods of 3 to 20 weeks. Femur/tibia bones were demineralized in 3.25% HNO3, the process being watched ...
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Thirteen male rats, 7 or 10 months old, were given 0.005% NaF in the diet or 0.025 NaF in the drinking water fro periods of 3 to 20 weeks. Femur/tibia bones were demineralized in 3.25% HNO3, the process being watched on radiographs. As soon as all radiopaque material representing mineralized bone had disappeared, demineralization was discontinued. In some instances the process was stopped while some radiopaque material was still present. Hematoxylin-eosin stained paraffin sections from all bones showed deep blue granules, fluoride granules. Transmission electron microscopy and selected area diffraction revealed that the fluoride granules contain microcrystalline CaF2. X-ray diffraction of hydrazine-deproteinated, demineralized fluorotic bones revealed the presence of CaF2 and a minor unidentified component. The results are discussed in relation to (1) the identity of the fluoride granules, and (2) their inconsistent presence in demineralized hard tissues.
Digital image-based finite element meshing is an alternative approach to time-consuming conventional meshing techniques for generating realistic three-dimensional (3D) models of complex structures. Although not limite...
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Digital image-based finite element meshing is an alternative approach to time-consuming conventional meshing techniques for generating realistic three-dimensional (3D) models of complex structures. Although not limited to biological applications, digital image-based modeling has been used to generate structure-specific (i.e., nongeneric) models of whole bones and trabecular bone microstructures. However questions remain regarding the solution accuracy provided by the digital meshing approach, particularly at model or material boundaries. The purpose of this study was to compare the accuracy of digital and conventional smooth boundary models based on theoretical solutions for a two-dimensional (2D) compression plate and a 3D circular cantilever beam. For both the plate and beam analyses, the predicted solution at digital model boundaries was characterized by local oscillations, which produced potentially high errors within individual boundary elements. Significantly, however, the digital model boundary solution oscillated approximately about the theoretical solution. A marked improvement in solution accuracy was therefore achieved by considering average results within a region composed of several elements. Absolute errors for Von Mises stress averaged over the beam cross section, for example, converged to less than 4 percent, and the predicted free-end displacement of the cantilever beam was within 1 percent of the theoretical solution, Analyses at several beam orientations and mesh resolutions suggested a minimum discretization of three to four digital finite elements through the beam cross section to avoid high numerical stiffening errors under bending.
Previous studies have shown that the actions of IGF-II in bone are determined not only by its concentration, but also by the concentration of IGFBP-4 as well as other IGFBPs. In this study, we sought to determine by W...
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Previous studies have shown that the actions of IGF-II in bone are determined not only by its concentration, but also by the concentration of IGFBP-4 as well as other IGFBPs. In this study, we sought to determine by Western ligand blotting the effects of growth hormone, IGF-I and IGF-II on the production of IGFBP-3 and IGFBP-4 in TE89 human osteosarcoma cells and in untransformed normal human bone cells derived from rib. Human growth hormone at 10 mug/l decreased the amount of IGFBP-4 but had no effect on the IGFBP-3 level in the conditioned medium of low density cultures of TE89 cells and human bone cells derived from rib. Human growth hormone had no effect on IGFBP-3 or IGFBP-4 levels in the conditioned medium of high density human bone cell cultures. IGF-I and IGF-II, which increased human bone cell proliferation, decreased the level of IGFBP-4 (30% of control at 100 mug/IIGF-I and IGF-II) but increased the level of IGFBP-3 (3-10 fold at 100 mug/l IGF-I and IGF-II) after 48 h of treatment in the conditioned medium of both low and high density TE89 cell cultures. Similar changes in IGFBP-3 and IGFBP-4 levels were also seen in the conditioned medium of human bone cells derived from rib after treatment with IGF-I and IGF-II. Studies to determine the underlying molecular mechanisms by which IGF-II decreased the amount of IGFBP-4 in the conditioned medium revealed that IGF-II decreased the IGFBP-4 mRNA abundance and increased the IGFBP-3 mRNA abundance in human bone cells. Based on the above findings, we conclude that the production of both IGFBP-3 and IGFBP-4 is regulated in bone cells and that local and systemic agents may modulate the responsiveness of bone cells to IGFs by regulated secretion of IGFBP-3 and IGFBP-4.
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