Effects of pH and acid concentration on erosive dissolution of enamel, dentine, and compressed hydroxyapatite

The aims of this study were to determine the effects of pH and acid concentration on the dissolution of enamel, dentine, and compressed hydroxyapatite (HA) in citric acid solutions (15.6 and 52.1 mmol l(-1) ; pH 2.45, 3.2, and 3.9), using a pH-stat system. After an initial adjustment period, the dissolution rates of enamel and HA were constant, while that of dentine decreased with time. The dissolution rate increased as the pH decreased, and this was most marked for enamel. To compare substrates, the rate of mineral dissolution was normalized to the area occupied by mineral at the specimen surface. For a given acid concentration, the normalized dissolution rate of HA was always less than that for either dentine or enamel. The dissolution rate for dentine mineral was similar to that for enamel at pH 2.45 and greater at pH 3.2 and pH 3.9. The concentration of acid significantly affected the enamel dissolution rate at pH 2.45 and pH 3.2, but not at pH 3.9, and did not significantly affect the dissolution rates of dentine or HA at any pH. The variation in response of the dissolution rate to acid concentration/buffer capacity with respect to pH and tissue type might complicate attempts to predict erosive potential from solution composition.

Interaction of the receptor FGFRL1 with the negative regulator Spred1

FGFRL1 is a member of the fibroblast growth factor receptor family. It plays an essential role during branching morphogenesis of the metanephric kidneys, as mice with a targeted deletion of the Fgfrl1 gene show severe kidney dysplasia. Here we used the yeast two-hybrid system to demonstrate that FGFRL1 binds with its C-terminal, histidine-rich domain to Spred1 and to other proteins of the Sprouty/Spred family. Members of this family are known to act as negative regulators of the Ras/Raf/Erk signaling pathway. Truncation experiments further showed that FGFRL1 interacts with the SPR domain of Spred1, a domain that is shared by all members of the Sprouty/Spred family. The interaction could be verified by coprecipitation of the interaction partners from solution and by codistribution at the cell membrane of COS1 and HEK293 cells. Interestingly, Spred1 increased the retention time of FGFRL1 at the plasma membrane where the receptor might interact with ligands. FGFRL1 and members of the Sprouty/Spred family belong to the FGF synexpression group, which also includes FGF3, FGF8, Sef and Isthmin. It is conceivable that FGFRL1, Sef and some Sprouty/Spred proteins work in concert to control growth factor signaling during branching morphogenesis of the kidneys and other organs.

The cell surface receptor FGFRL1 forms constitutive dimers that promote cell adhesion

FGFRL1 is a novel member of the fibroblast growth factor (FGF) receptor family. Utilizing the FRET (fluorescence resonance energy transfer) technique, we demonstrate that FGFRL1 forms constitutive homodimers at cell surfaces. The formation of homodimers was verified by co-precipitation of differentially tagged FGFRL1 polypeptides from solution. If overexpressed in cultivated cells, FGFRL1 was found to be enriched at cell-cell contact sites. The extracellular domain of recombinant FGFRL1 promoted cell adhesion, but not cell spreading, when coated on plastic surfaces. Adhesion was mediated by heparan sulfate glycosaminoglycans located at the cell surface. It could specifically be blocked by addition of soluble heparin but not by addition of other glycosaminoglycans. When the amino acid sequence of the putative heparin-binding site was modified by in vitro mutagenesis, the resulting protein exhibited decreased affinity for heparin and reduced activity in the cell-binding assay. Moreover, a synthetic peptide corresponding to the heparin-binding site was able to neutralize the effect of heparin. With its dimeric structure and its adhesion promoting properties, FGFRL1 resembles the nectins, a family of cell adhesion molecules found at cell-cell junctions.

A propensity score-matched comparison between Cardia and Amplatzer PFO closure devices - insights from the SOLUTION registry (Swiss percutaneOus patent foramen ovale cLosUre in recurrent clinical events prevenTION)

Aims: To compare clinical outcome of Amplatzer PFO (APFO) to Cardia PFO (CPFO) occluder. Percutaneous patent foramen ovale (PFO) closure prevents stroke recurrence in stroke due to paradoxical embolism. Methods and results: The primary endpoint was a composite of stroke, TIA, or peripheral embolism at follow-up. The secondary endpoint was residual shunt. Outcome was compared among 934 (APFO: 712; CPFO: 222) patients, and in 297 propensity score-matched patients. The primary endpoint occurred in 29 patients (0.71/100 patient-years): four (2%) with the CPFO (0.31/100 patient-years), and 25 (4%) with the APFO (0.89/100 patient-years) (p=0.20). Residual shunt at six months was more frequent with the CPFO (31% versus 9%, p<0.001). No differences in residual shunts were seen at the last available echocardiographic follow-up (9±18 months): APFO 11%, CPFO 14%, p=0.22. Conclusions: This study suggests that PFO closure with APFO or CPFO is equally effective for the prevention of recurrent events. Residual shunt was more frequent at six months with CPFO, but was similar to APFO at later follow-up.

From In Situ towards In Operando Conditions: Scanning Tunneling Microscopy Study of Hydrogen Intercalation in Cu(111) during Hydrogen Evolution

We used electrochemical scanning tunneling microscopy to study the intercalation of hydrogen into a Cu(111) model electrode under reactive (in operando) conditions. Hydrogen evolution causes hydrogen intermediates to migrate into the copper lattice as function of the applied potential and the resulting current density. This H-inclusion is demonstrated to be reversible. The presence of subsurface hydrogen leads to a significant surface relaxation/reconstruction affecting both the geometric and electronic structure of the electrode surface.

A Convex Solution to Disparity Estimation from Light Fields via the Primal-Dual Method

We present a novel approach to the reconstruction of depth from light field data. Our method uses dictionary representations and group sparsity constraints to derive a convex formulation. Although our solution results in an increase of the problem dimensionality, we keep numerical complexity at bay by restricting the space of solutions and by exploiting an efficient Primal-Dual formulation. Comparisons with state of the art techniques, on both synthetic and real data, show promising performances.