Activation of adenosine A2A receptors induces TrkB translocation and increases BDNF-mediated phospho-TrkB localization in lipid rafts : implications for neuromodulation

Copyright © 2010 the authorsBrain-derived neurotrophic factor (BDNF) signaling is critical for neuronal development and transmission. Recruitment of TrkB receptors to lipid rafts has been hown to be necessary for the activation of specific signaling pathways and modulation of neurotransmitter release by BDNF. Since TrkB receptors are known to be modulated by adenosine A2A receptor activation, we hypothesized that activation of A2A receptors could influence TrkB receptor localization among different membrane microdomains. We found that adenosine A2A receptor agonists increased the levels of TrkB receptors in the lipid raft fraction of cortical membranes and potentiated BDNF-induced augmentation of phosphorylated TrkB levels in lipid rafts. Blockade of the clathrin-mediated endocytosis with monodansylcadaverine(100µM) did not modify the effects of theA2A receptor agonists but significantly impairedBDNFeffects on TrkB recruitment to lipid rafts. The effect of A2A receptor activation in TrkB localization was mimicked by 5 µM forskolin, an adenylyl cyclase activator. Also, it was blocked by the PKA inhibitors Rp-cAMPs and PKI-(14 –22), and by the Src-family kinase inhibitor PP2. Moreover, removal of endogenous adenosine or disruption of lipid rafts reduced BDNF stimulatory effects on glutamate release from cortical synaptosomes. Lipid raft integrity was also required for the effects of BDNF on hippocampal long-term potentiation at CA1 synapses. Our data demonstrate, for the first time, a BDNF-independent recruitment of TrkB receptors to lipid rafts induced by activation of adenosine A2A receptors, with functional consequences for TrkB phosphorylation and BDNF-induced modulation of neurotransmitter release and hippocampal plasticity.Supported by Fundacão para a Ciência e a Tecnologia (SFRH/BD/21374/2005 for N.A.L., SFRH/BD/21359/2005 for V.C.S., and SFRH/BPD/11528/2002 for D.B.P.) and by the European Union [European Cooperation in Science and Technology (COST) COST B30 concerted action, Neural Regeneration and Plasticity (NEREPLAS)]

Exploring the high-temperature thermoelectric performance of la-substituted Ca3Co4O9 bulk ceramics

It is well-known that the electrical properties of the Ca3Co4O9 thermoelectric (TE) compound are strongly influenced by the valence of the substituting cation, while its solubility and “functional” impact depend largely on the preparation and/or processing methods used. Furthermore, this material’s hybrid crystal structure allows for different cation substitutions in/from different sublattices. This research work presents the relevant effects of different La substitutions for the Ca ions from the insulating rock salt type [Ca2CoO3] crystal component (considered as a “charge reservoir” for the conductive [CoO2] layers) for a series of bulk samples prepared and processed via a solid-state method, chosen for simplicity. The results show that the actual level of La substitutions does not exceed 0.03 (x < 0.03), in Ca3-xLaxCo4O9 samples with x = 0.01, 0.03, 0.05 and 0.07, and that beyond this limit, simultaneous Ca3Co4O9 phase decomposition and secondary Ca3Co2O6 and (La,Ca)CoO3 phase formation take place. The morpho-structural features were found to be quite moderate, with a negligible effect on the charge carries transport. The electrical measurements and average oxidation state of cobalt (~3.11) suggest that the substitutions with La have only a minor effect on the charge carrier concentration. The electrical resistivity of the samples with x = 0.01, 0.03 and 0.05 is found to be ~1.3 times lower than of pristine Ca3Co4O9, while the changes in the Seebeck coefficient values are only moderate in the whole measured temperature range. The highest power factor, representing the electrical counterpart of the TE performance, was found for the Ca2.99La0.01Co4O9 samples (~0.28 mW/K2m, at 800 C), being among the best found in the literature for similar materials. Our results suggest that low substitutions with rare-earth cations in the “charge reservoir” layers of the Ca3Co4O9 compound can be promising in designing and improving these p-type oxides, provided by the strongly correlated nature of their conduction mechanism.publishe

Direct processing of cellular ceramics from a single red mud precursor

The feasibility of recycling red mud waste by its direct transformation into highly-porous cellular ceramics was successfully demonstrated. Ceramic materials with designed cellular porosity were processed by emulsification of red mud suspensions with liquid paraffin. Taguchi method was used to study the effects provided by varying the red mud load in the suspension, gelatine content and emulsion stirring time on the micro structural features of the cellular ceramics. Additional experiments analysed the effects of the organic to suspension ratio and firing temperature. Emulsification of paraffin followed by gelatine consolidation, drying, elimination of the droplets of the discontinuous organic phase and firing, allowed one to design cellular ceramic pieces with open porosity up to 75%, consisting in interconnected cells with adjustable cell size and low resistance to percolation. These results allow one to consider prospective applications of red mud-based cellular ceramics with designed microstructures as highly-porous membranes for the capture of pollutants.publishe

Electrochemical reduction of hematite-based ceramics in alkaline medium: challenges in electrode design

Electrochemical reduction of low-conductive hematite-based ceramics represents a novel approach for iron recovery and waste valorisation. The process itself allows a flexible switching between hydrogen generation and iron reduction, important for the intermittent renewable-energy-powered electrolytic process. The present study focuses on the direct electrochemical reduction of aluminium-containing hematite in strong alkaline media. Within this scope, the reduction mechanisms of porous and dense cathodes, with 60%, 37% and 3% of open porosity, were investigated using different types of electrodes configuration: nickel-foil and Ag-modified nickel-foil supported configuration (cathodes facing or against the counter electrode), and nickel-mesh supported configuration. The efficiency of the iron reduction was compared for different electrode concepts. The results highlight the importance of electrolyte access to the interface between the metallic current collector and ceramic cathode for attaining reasonable electroreduction currents. Both excessively porous and dense ceramic cathodes are hardly suitable for such reduction process, showing a necessity to find a compromise between mechanical strength of the electrode and its open porosity, essential for the electrolyte access.publishe

Alkaline electrochemical reduction of a magnesium ferrospinel into metallic iron for the valorisation of magnetite-based metallurgical waste

The electrochemical reduction of iron oxides in alkaline media arises as a novel approach for ironmaking and iron-rich waste valorisation. Strong advantages and attractive aspects of alkaline electroreduction include lower electric energy consumption, absence of CO2 emissions, and non-polluting valuable by-products such as H2 and O2. Another potential advantage originates from the compatibility of this concept with intermittent renewable energies. However, to bring this technology to a competitive level, especially compared to the traditional steelmaking, innovative approaches and developments in materials processing and their appropriate integration into the electrolysis process are required. This research work explores the prospects for electrochemical reduction of a magnesium-containing ferrospinel, as a potential component in iron-containing wastes. The experimental approach considers bulk cathode- and suspension-based electrolysis concepts, which allow reaching 55% and 20% Faradaic efficiencies of the reduction to metallic iron, respectively. The effects imposed by the magnesium presence on the electroreduction kinetics, phase composition and morphology of the electroreduction products are evaluated and discussed. The obtained results open new perspectives for the recovery of metallurgical residues with low magnesium impurities content.publishe

Exploring the high-temperature electrical performance of Ca3-xLaxCo4O9 thermoelectric ceramics for moderate and low substitution levels

Aliovalent substitutions in Ca3Co4O9 often result in complex effects on the electrical prop-erties and the solubility, and impact of the substituting cation also depends largely on the prepara-tion and processing method. It is also well-known that the monoclinic symmetry of this material’s composite crystal structure allows for a significant hole transfer from the rock salt-type Ca2CoO3 buffer layers to the hexagonal CoO2 ones, increasing the concentration of holes and breaking the electron–hole symmetry from the latter layers. This work explored the relevant effects of relatively low La-for-Ca substitutions, for samples prepared and processed through a conventional ceramic route, chosen for its simplicity. The obtained results show that the actual substitution level does not exceed 0.03 (x < 0.03) in Ca3-xLaxCo4O9 samples with x = 0.01, 0.03, 0.05 and 0.07 and that further introduction of lanthanum results in simultaneous Ca3Co4O9 phase decomposition and secondary Ca3Co2O6 and (La,Ca)CoO3 phase formation. The microstructural effects promoted by this phase evolution have a moderate influence on the electronic transport. The electrical measurements and determined average oxidation state of cobalt at room temperature suggest that the present La sub-stitutions might only have a minor effect on the concentration of charge carriers and/or their mobil-ity. The electrical resistivity values of the Ca3-xLaxCo4O9 samples with x = 0.01, 0.03 and 0.05 were found to be ~1.3 times (or 24%) lower (considering mean values) than those measured for the pris-tine Ca3Co4O9 samples, while the changes in Seebeck coefficient values were only moderate. The highest power factor value calculated for Ca2.99La0.01Co4O9 (~0.28 mW/K2m at 800 °C) is among the best found in the literature for similar materials. The obtained results suggest that low rare-earth substitutions in the rock salt-type layers can be a promising pathway in designing and improving these p-type thermoelectric oxides, provided by the strong interplay between the mobility of charge carriers and their concentration, capable of breaking the electron–hole symmetry from the conduc-tive layers.publishe

Genetic Polymorphisms of the Epidermal Growth Factor and Related Receptor in Non-Small Cell Lung Cancer—A Review of the Literature

Learning Objectives After completing this course, the reader will be able to: Describe the role played by EGF and EGFR in lung carcinogenesis.Discuss how different polymorphic alleles from the EGF and EGFR genes may affect drug response.Evaluate the value of determining the presence of EGF and EGFR polymorphisms in NSCLC patients for daily clinical practice. CME Access and take the CME test online and receive 1 AMA PRA Category 1 Credit™ at CME.TheOncologist.co

Prospects for electrical performance tuning in Ca3Co4O9 materials by metallic Fe and Ni particles additions

This work further explores the possibilities for designing the high-temperature electrical performance of the thermoelectric Ca3Co4O9 phase, by a composite approach involving separate metallic iron and nickel particles additions, and by employing two different sintering schemes, capable to promote the controlled interactions between the components, encouraged by our recent promising results obtained for similar cobalt additions. Iron and nickel were chosen because of their similarities with cobalt. The maximum power factor value of around 200 µWm−1K−2 at 925 K was achieved for the composite with the nominal nickel content of 3% vol., processed via the twostep sintering cycle, which provides the highest densification from this work. The effectiveness of the proposed approach was shown to be strongly dependent on the processing conditions and added amounts of metallic particles. Although the conventional one-step approach results in Feand Ni-containing composites with the major content of the thermoelectric Ca3Co4O9 phase, their electrical performance was found to be significantly lower than for the Co-containing analogue, due to the presence of less-conducting phases and excessive porosity. In contrast, the relatively high performance of the composite with a nominal nickel content of 3% vol. processed via a two-step approach is related to the specific microstructural features from this sample, including minimal porosity and the presence of the Ca2Co2O5 phase, which partially compensate the complete decomposition of the Ca3Co4O9 matrix. The obtained results demonstrate different pathways to tailor the phase composition of Ca3Co4O9 -based materials, with a corresponding impact on the thermoelectric performance, and highlight the necessity of more controllable approaches for the phase composition tuning, including lower amounts and different morphologies of the dispersed metallic phases.publishe

Projeto de Para-sol com Embalagens Tetra Pak

A reutilização das embalagens tetra pak, como uma barreira física para conter a entrada da luz solar direta no interior de veículos, vem ao encontro de dois benefícios, o primeiro deles seria, como mais um meio de reciclar as embalagens tetra pak, ou melhor dizendo, aumentar o ciclo de vida do produto, antes de ser descartado. E o segundo benefício, seria bloquear a ação da radiação ultravioleta e infravermelho no interior dos veículos que acelera a desagregação de cor dos materiais, reduzindo a vida útil dos componentes internos. A título de curiosidade, estes componentes internos, que na maioria das vezes são de cor preta, aumenta a temperatura interna do veículo, quando exposto ao sol, chegando a 80°C, devido ao efeito estufa criado, pela reflexão dos raios infravermelhos do painel e tecidos dos bancos, refletindo no vidro, quando é impedido de sair, causando um desconforto térmico aos usuários. Sendo, portanto, uma solução de custo baixo e excelente benefício à aplicação do para-sol com embalagens de tetra pak

Photocatalytic removal of benzene over Ti3C2Tx MXene and TiO2–MXene composite materials under solar and NIR irradiation

MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separation and suppressing the exciton recombination. Titanium-containing MXenes are well compatible with the classical TiO2 photocatalyst. The TiO2 component can be directly grown on MXene sheets by in situ oxidation, representing a mainstream processing approach for such composites. In this study, an essentially different approach has been implemented: a series of TiO2-MXene composite materials with controlled composition and both reference end members were prepared, involving two different strategies for mixing sol-gel-derived TiO2 nanopowder with the Ti3C2Tx component, which was obtained by HF etching of self-propagating high-temperature synthesis products containing modified MAX phase Ti3C2Alz (z > 1) with nominal aluminium excess. The prospects of such composites for the degradation of organic pollutants under simulated solar light, using benzene as a model system, were demonstrated and analysed in combination with their structural, microstructural and optical properties. A notable photocatalytic activity of bare MXene under near infrared light was discovered, suggesting further prospects for light-to-energy harvesting spanning from UV-A to NIR and applications in biomedical imaging and sensors.publishe