Collective cell migration and metastases induced by an epithelial-to-mesenchymal transition in Drosophila intestinal tumors.

Metastasis underlies the majority of cancer-related deaths yet remains poorly understood due, in part, to the lack of models in vivo. Here we show that expression of the EMT master inducer Snail in primary adult Drosophila intestinal tumors leads to the dissemination of tumor cells and formation of macrometastases. Snail drives an EMT in tumor cells, which, although retaining some epithelial markers, subsequently break through the basal lamina of the midgut, undergo a collective migration and seed polyclonal metastases. While metastases re-epithelialize over time, we found that early metastases are remarkably mesenchymal, discarding the requirement for a mesenchymal-to-epithelial transition for early stages of metastatic growth. Our results demonstrate the formation of metastases in adult flies, and identify a key role for partial-EMTs in driving it. This model opens the door to investigate the basic mechanisms underlying metastasis, in a powerful in vivo system suited for rapid genetic and drug screens

Size Effects in MgO Cube Dissolution

Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg2+-O2- surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)(2) nanosheets. At a pH >= 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)(2) nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 n

Size Effects in MgO Cube Dissolution

Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg2+-O2- surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)(2) nanosheets. At a pH >= 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)(2) nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 n

Photoluminescence properties of alkaline-earth oxide nanoparticles

Previous experiments have demonstrated that photoluminescence properties, both excitation and emission spectra, of powdered MgO depend strongly on the powder preparation and treatment. Similar dependencies have been found for CaO, SrO, and BaO powders. The observed broad photoemission bands have been attributed to the low-coordinated surface sites. Recent advances in nanoscale science and technology have made it possible to produce nearly monodispersed alkaline-earth oxide nanoparticles of very high surface area and investigate their optical properties in details. Here we present the results of our theoretical and experimental work in this area and present new results. ©The Electrochemical Society

Bulk and Surface Excitons in Alloyed and Phase-Separated ZnO–MgO Particulate Systems

The rational design of composite nanoparticles with desired optical and electronic properties requires the detailed analysis of surface and bulk contributions to the respective overall function. We use flame spray pyrolysis (FSP) to generate nanoparticles of the ternary Zn–Mg–O system the compositions of which range from solid solutions of Zn2+ ions in periclase MgO to phase separated particle mixtures which consist of periclase (cubic) MgO and wurtzite (hexagonal) ZnO phases. The structure and composition of the composite ZnxMg1–xO (0 ≤ x ≤ 0.3) particles are investigated using X-ray diffraction and high-resolution transmission electron microscopy, whereas UV diffuse reflectance and photoluminescence (PL) spectroscopy are used for the investigation of their optical properties. Vacuum annealing has been carried out to track the effects of stepwise elimination of surface adsorbates on the photoexcitation and PL emission properties. We demonstrate that for Zn0.1Mg0.9O particles, the admixed ZnO suppresses the MgO specific surface excitons and produces a PL emission band at 470 nm. Although gaseous oxygen partially reduces the emission intensity of hydroxylated particles, it leads to entire quenching in completely dehydroxylated samples after vacuum annealing at 1173 K. Consequently, surface hydroxyls at the solid–gas interface play a significant role as protecting groups against the PL-quenching effects of O2. The obtained results are relevant for the characterization of ZnO-based devices as well as for other metal oxide materials where the impact of the surface composition on the photoelectronic properties is usually neglected