Absence of the BRAF V600E mutation in pheochromocytoma.

PURPOSE: Pheochromocytomas (PCCs) are rare endocrine tumors originating from the adrenal medulla. These tumors display a highly heterogeneous mutation profile, and a substantial part of the causative genetic events remains to be explained. Recent studies have reported presence of the activating BRAF V600E mutation in PCC, suggesting a role for BRAF activation in tumor development. This study sought to further investigate the occurrence of the BRAF V600E mutation in these tumors. METHODS: A cohort of 110 PCCs was screened for the BRAF V600E mutation using direct Sanger sequencing. RESULTS: All cases investigated displayed wild-type sequences at nucleotide 1799 in the BRAF gene. CONCLUSIONS: Taken together with all previously screened tumors up to date, only 1 BRAF V600E mutation has been found among 361 PCCs. These findings imply that the BRAF V600E mutation is a rare event in pheochromocytoma.

Ultrastructural characterization of tooth-biomaterial interfaces prepared with broad and focused ion beams.

UNLABELLED: Current available techniques for transmission electron microscopy (TEM) of tooth-biomaterial interfaces are mostly ineffective for brittle phases and impair integrated chemical and morphological characterization. OBJECTIVES: The aims of this study were (1) to determine the applicability of new focused ion beam (FIB) and broad ion beam (BIB) techniques for TEM preparation of tooth-biomaterial interfaces; (2) to characterize the interfacial interaction with enamel and dentin of a conventional glass-ionomer (Chemfil Superior, DeTrey Dentsply, Germany), a 2-step self-etch (Clearfil SE, Kuraray, Japan) and a 3-step etch-and-rinse (OptiBond FL, Kerr, USA) adhesives; and (3) to characterize clinically relevant interfaces obtained from actual Class-I cavities. METHODS: After bonding to freshly extracted human third molars, non-demineralized and non-stained sections were obtained using the FIB/BIB techniques and examined under TEM. RESULTS: The main structures generally disclosed in conventional ultramicrotomy samples were recognized in FIB/BIB-based ones. There were not any major differences between FIB and BIB concerning the resulting ultrastructural morphology. FIB/BIB-sections enabled to clearly resolve sub-micron hydroxyapatite crystals on top of hard tissues and the interface between matrix and filler in all materials, even at nano-scale. Some investigated interfaces disclosed areas with a distinct "fog" or "melted look", which is probably an artifact due to surface damage caused by the high-energy beam. Interfaces with enamel clearly disclosed the distinct "keyhole" shape of enamel rods sectioned at 90 degrees , delimited by a thin electron-lucent layer of inter-rod enamel. At regions where enamel crystals ran parallel with the interface, we observed a lack of interaction and some de-bonding along with interfacial void formation. SIGNIFICANCE: The FIB/BIB methods are viable and reliable alternatives to conventional ultramicrotomy for preparation of thin sections of brittle and thus difficult to cut biomaterial-hard tissue interfaces. They disclose additional ultrastructural information about both substrates and are more suitable for advanced analytic procedures.

Structural change of biomimetic hydroxyapatite coatings due to heat treatment.

Biomimetic deposition of hydroxyapatite (HA) coatings on implants could be done for two reasons, one is to study their possible bioactivity, and one is to generate bioactive coatings on implants before implantation surgery to improve the osseointegration. Heat treatment of coated implants can be performed for several reasons, for example, to ensure coating sterility and to increase the adhesion. This paper describes the morphology and crystalline structure changes occurring due to the heat treatment of biomimetic HA coatings on rutile TiO2. Rutile TiO2 surfaces were produced on titanium (Ti) plates by heating at 800 degrees C. Afterwards, these samples were immersed in a phosphate buffer saline solution for 7 days at 37 degrees C in order to deposit HA coatings on their surfaces. These HA coatings were then either untreated or heat treated at 600 or 800 degrees C for 1 hr. The coatings microstructural changes were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cross-sectional TEM samples were produced using a sample preparation method based on focused ion beam microscopy (FIB). Rutile was found to be bioactive due to HA formation on the surface. The 600 degrees C heat treatment of the HA coating changed its morphology, increased its grain size and also increased the porosity. At 800 degrees C the coating was completely transformed to beta-TCP according to XRD. Sample preparation using FIB and TEM analysis proved to be a useful method for high-resolution analysis of biomimetic coatings in cross-section.