Three Dimensional Mapping of Texture in Dental Enamel

We have used synchrotron x-ray diffraction to study the crystal orientation in human dental enamel as a function of position within intact tooth sections. Keeping tooth sections intact has allowed us to construct 2D and 3D spatial distribution maps of the magnitude and orientation of texture in dental enamel. We have found that the enamel crystallites are most highly aligned at the expected occlusal points for a maxillary first premolar, and that the texture direction varies spatially in a three dimensional curling arrangement. Our results provide a model for texture in enamel which can aid researchers in developing dental composite materials for fillings and crowns with optimal characteristics for longevity, and will guide clinicians to the best method for drilling into enamel, in order to minimize weakening of remaining tooth structure, during dental restoration procedure

Semiallogenic fusions of MSI+ tumor cells and activated B cells induce MSI-specific T cell responses

<p>Abstract</p> <p>Background</p> <p>Various strategies have been developed to transfer tumor-specific antigens into antigen presenting cells in order to induce cytotoxic T cell responses against tumor cells. One approach uses cellular vaccines based on fusions of autologous antigen presenting cells and allogeneic tumor cells. The fusion cells combine antigenicity of the tumor cell with optimal immunostimulatory capacity of the antigen presenting cells.</p> <p>Microsatellite instability caused by mutational inactivation of DNA mismatch repair genes results in translational frameshifts when affecting coding regions. It has been shown by us and others that these mutant proteins lead to the presentation of immunogenic frameshift peptides that are - in principle - recognized by a multiplicity of effector T cells.</p> <p>Methods</p> <p>We chose microsatellite instability-induced frameshift antigens as ideal to test for induction of tumor specific T cell responses by semiallogenic fusions of microsatellite instable carcinoma cells with CD40-activated B cells. Two fusion clones of HCT116 with activated B cells were selected for stimulation of T cells autologous to the B cell fusion partner. Outgrowing T cells were phenotyped and tested in functional assays.</p> <p>Results</p> <p>The fusion clones expressed frameshift antigens as well as high amounts of MHC and costimulatory molecules. Autologous T cells stimulated with these fusions were predominantly CD4⁺, activated, and reacted specifically against the fusion clones and also against the tumor cell fusion partner. Interestingly, a response toward 6 frameshift-derived peptides (of 14 tested) could be observed.</p> <p>Conclusion</p> <p>Cellular fusions of MSI⁺carcinoma cells and activated B cells combine the antigen-presenting capacity of the B cell with the antigenic repertoire of the carcinoma cell. They present frameshift-derived peptides and can induce specific and fully functional T cells recognizing not only fusion cells but also the carcinoma cells. These hybrid cells may have great potential for cellular immunotherapy and this approach should be further analyzed in preclinical as well as clinical trials. Moreover, this is the first report on the induction of frameshift-specific T cell responses without the use of synthetic peptides.</p

2D mapping of texture and lattice parameters of dental enamel

We have used synchrotron X-ray diffraction to study the texture and the change in lattice parameter as a function of position in a crosssection of human dental enamel. Our study is the first to map changes in preferred orientation and lattice parameter as a function ofposition within enamel across a whole tooth section with such high resolution. Synchrotron X-ray diffraction with a micro-focused beamspot was used to collect two-dimensional (2D) diffraction images at 150 mm spatial resolution over the entire tooth crown. Contour mapsof the texture and lattice parameter distribution of the hydroxyapatite phase were produced from Rietveld refinement of diffractionpatterns generated by azimuthally sectioning and integrating the 2D images. The 002 Debye ring showed the largest variation inintensity. This variation is indicative of preferred orientation. Areas of high crystallite alignment on the tooth cusps match the expectedbiting surfaces. Additionally we found a large variation in lattice parameter when travelling from the enamel surface to the enameldentinejunction. We believe this to be due to a change in the chemical composition within the tooth. The results provide a new insight onthe texture and lattice parameter profiles within enamel

2D mapping of texture and lattice parameters of dental enamel

We have used synchrotron X-ray diffraction to study the texture and the change in lattice parameter as a function of position in a cross section of human dental enamel. Our study is the first to map changes in preferred orientation and lattice parameter as a function of position within enamel across a whole tooth section with such high resolution. Synchrotron X-ray diffraction with a micro-focused beam spot was used to collect two-dimensional (2D) diffraction images at 150 μm spatial resolution over the entire tooth crown. Contour maps of the texture and lattice parameter distribution of the hydroxyapatite phase were produced from Rietveld refinement of diffraction patterns generated by azimuthally sectioning and integrating the 2D images. The 002 Debye ring showed the largest variation in intensity. This variation is indicative of preferred orientation. Areas of high crystallite alignment on the tooth cusps match the expected biting surfaces. Additionally we found a large variation in lattice parameter when travelling from the enamel surface to the enamel-dentine junction. We believe this to be due to a change in the chemical composition within the tooth. The results provide a new insight on the texture and lattice parameter profiles within ename

Three dimensional mapping of texture in dental enamel

We have used synchrotron x-ray diffraction to study the crystal orientation in humandental enamel as a function of position within intact tooth sections. Keeping tooth sections intacthas allowed us to construct 2D and 3D spatial distribution maps of the magnitude and orientation oftexture in dental enamel. We have found that the enamel crystallites are most highly aligned at theexpected occlusal points for a maxillary first premolar, and that the texture direction varies spatiallyin a three dimensional curling arrangement. Our results provide a model for texture in enamel whichcan aid researchers in developing dental composite materials for fillings and crowns with optimalcharacteristics for longevity, and will guide clinicians to the best method for drilling into enamel, inorder to minimize weakening of remaining tooth structure, during dental restoration procedures

Phase-specific magnetic ordering in BiFeO3-PbTiO3

The multiferroic 0.7 BiFeO3–0.3 PbTiO3 has been fabricated in both sintered ceramic and powder form using conventional mixed oxide synthesis. Rietveld’s analysis of neutron powder diffraction data has shown that the sintered ceramic and powder are predominantly R3c and P4mm phases, respectively. It is shown explicitly that magnetic ordering does not occur for the P4mm phase at room temperatur

Pressure induced para-antiferromagnetic switching in BiFeO -PbTiO as determined using in-situ neutron diffraction

BiFeO-PbTiO exhibits both ferroelectric and antiferromagnetic order, depending on the composition. Moderate hydrostatic pressures have been used at room temperature to transform the crystallographic phase from P4mm to R3c for the compositions 0.7BiFeO-0.3PbTiO and 0.65BiFeO-0.35PbTiO, as determined using in-situ neutron diffraction. Using Rietveld refinements, the resultant data showed that, for both compositions, a transformation from para- to G-type antiferromagnetic order accompanied the structural transition. The transformation occurred over the range 0.4-0.77 and 0.67-0.88 GPa for 0.7BiFeO-0.3PbTiO and 0.65BiFeO-0. 35PbTiO, respectively; at intermediate pressures, a mixture of P4mm and R3c phases were evident. These pressures are far lower than required to induce a phase transition in either the BiFeO or PbTiO end members. The driving force for this pressure induced first order phase transition is a significant difference in volume between the two phases, P4mm > R3c of 4-5, at ambient pressure. Upon removal of the pressure, 0.65BiFeO-0.35PbTiO returned to the paramagnetic tetragonal state, whereas in 0.7BiFeO-0.3PbTiO antiferromagnetic ordering persisted, and the structural phase remained rhombohedral. Using conventional laboratory x-ray diffraction with a hot-stage, the phase readily reverted back to a tetragonal phase, at temperatures between 100 and 310 °C for 0.7BiFeO-0.3PbTiO, far lower than the ferroelectric Curie point for this composition of 632 °C. To our knowledge, the reported pressure induced para- to antiferromagnetic transition is unique in the literature