Shape-controlled synthesis and cathodoluminescence properties of elongated α-Fe_2O_3 nanostructures

α-Fe_2O_3 (hematite) nanostructures with various morphologies have been grown by thermal oxidation of compacted iron powder at temperatures between 700 and 900 degrees C. Different thermal treatments have been found to induce the growth of single-crystalline nanowires, nanobelts, nanoplates and featherlike structures, free and caped nanopillars, and pyramidal microcrystals or cactuslike microstructures. The experimental conditions leading to the different morphologies have been systematically investigated, as well as the possible growth mechanisms. The obtained nanostructures have been characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy, x-ray diffraction, and cathodoluminescence (CL) spectroscopy in the SEM. The formation of the nanostructures induces changes in the intensity and spectral distribution of the CL emission, as compared with the bulk material. Ligand to metal charge transfer transitions as well as Fe^(3+) ligand field transitions are thought to be involved in the observed luminescence. The evolution of the panchromatic CL intensity in the visible range as a function of temperature shows some anomalies that may be induced by magnetic ordering effects

Oxidative stress is tightly regulated by cytochrome c phosphorylation and respirasome factors in mitochondria

Respiratory cytochrome c has been found to be phosphorylated at tyrosine 97 in the postischemic brain upon neuroprotective insulin treatment, but how such posttranslational modification affects mitochondrial metabolism is unclear. Here, we report the structural features and functional behavior of a phosphomimetic cytochrome c mutant, which was generated by site-specific incorporation at position 97 of p-carboxymethyl-l-phenylalanine using the evolved tRNA synthetase method. We found that the point mutation does not alter the overall folding and heme environment of cytochrome c, but significantly affects the entire oxidative phosphorylation process. In fact, the electron donation rate of the mutant heme protein to cytochrome c oxidase, or complex IV, within respiratory supercomplexes was higher than that of the wild-type species, in agreement with the observed decrease in reactive oxygen species production. Direct contact of cytochrome c with the respiratory supercomplex factor HIGD1A (hypoxia-inducible domain family member 1A) is reported here, with the mutant heme protein exhibiting a lower affinity than the wild-type species. Interestingly, phosphomimetic cytochrome c also exhibited a lower caspase-3 activation activity. Altogether, these findings yield a better understanding of the molecular basis for mitochondrial metabolism in acute diseases, such as brain ischemia, and thus could allow the use of phosphomimetic cytochrome c as a neuroprotector with therapeutic applications.España, Junta de Andalucía BIO-198España MINECO BFU2015-71017/BM

Cannabinoid CB₂ Receptor Modulation by the Transcription Factor NRF2 is Specific in Microglial Cells

Nuclear factor erythroid 2-related factor 2 (NRF2) is a pleiotropic transcription factor that has neuroprotective and anti-inflammatory effects, regulating more than 250 genes. As NRF2, cannabinoid receptor type 2 (CB2) is also implicated in the preservation of neurons against glia-driven inflammation. To this concern, little is known about the regulation pathways implicated in CB2 receptor expression. In this study, we analyze whether NRF2 could modulate the transcription of CB2 in neuronal and microglial cells. Bioinformatics analysis revealed an antioxidant response element in the promoter sequence of the CB2 receptor gene. Further analysis by chemical and genetic manipulations of this transcription factor demonstrated that NRF2 is not able to modulate the expression of CB2 in neurons. On the other hand, at the level of microglia, the expression of CB2 is NRF2-dependent. These results are related to the differential levels of expression of both genes regarding the brain cell type. Since modulation of CB2 receptor signaling may represent a promising therapeutic target with minimal psychotropic effects that can be used to modulate endocannabinoid-based therapeutic approaches and to reduce neurodegeneration, our findings will contribute to disclose the potential of CB2 as a novel target for treating different pathologies.This work was supported by the Spanish Ministry of Economy and Competitiveness (Grants Refs. SAF2016-76520-R to ILB and BFU2016-75973-R to MDG)

Magnetic transitions in alpha-Fe_2O_3 nanowires

Magnetic transitions in single-crystal alpha-F_2O_3 (hematite) nanowires, grown by thermal oxidation of iron powder, have been studied in the range of 5-1023 K with a superconducting quantum interference device below room temperature and with a vibrating sample magnetometer at higher temperatures. The broad temperature range covered enables us to compare magnetic transitions in the nanowires with the transitions reported for bulk hematite. Morin temperatures (T-M) of the nanowires and of hematite bulk reference powder were found to be 123 and 263 K, respectively. Also the Neel temperature (T-N) of the nanowires, 852 K, was lower than the bulk T-N value. Measurements of the magnetization as a function of temperature show an enhanced signal in the nanowires, which suggests a decrease in the anti ferromagnetic coupling. A coercive field observed below T-M in the hysteresis loops of the nanowires is tentatively explained by the presence of a magnetic phase

Caprellids (Crustacea: Amphipoda: Caprellidae) from shallow waters of the Caribbean coast of Venezuela

AbstractThe caprellidean fauna of Venezuela is investigated. Twenty-seven stations in shallow waters of the states Falcón, Carabobo, Aragua, Anzoátegui, Sucre and Nueva Esparta were sampled, and the caprellids were sorted and identified. A total of 3984 specimens were identified; 12 species in eight genera are reported. Two species, Caprella penantis Leach, 1814 and Paracaprella digitimanus Quitete, 1971, are new records for Venezuelan waters. The electronic supplement to this paper includes illustrations and a key to all caprellid species known from Venezuela, as well as comments on their distribution and ecology

Structural basis of mitochondrial dysfunction in response to cytochrome c phosphorylation at tyrosine 48

Regulation of mitochondrial activity allows cells to adapt to changing conditions and to control oxidative stress, and its dysfunction can lead to hypoxia-dependent pathologies such as ischemia and cancer. Although cytochrome c phosphorylation—in particular, at tyrosine 48—is a key modulator of mitochondrial signaling, its action and molecular basis remain unknown. Here we mimic phosphorylation of cytochrome c by replacing tyrosine 48 with p-carboxy-methylL-phenylalanine (pCMF). The NMR structure of the resulting mutant reveals significant conformational shifts and enhanced dynamics around pCMF that could explain changes observed in its functionality: The phosphomimetic mutation impairs cytochrome c diffusion between respiratory complexes, enhances hemeprotein peroxidase and reactive oxygen species scavenging activities, and hinders caspase-dependent apoptosis. Our findings provide a framework to further investigate the modulation of mitochondrial activity by phosphorylated cytochrome c and to develop novel therapeutic approaches based on its prosurvival effects.España, MINECO BFU2015-71017-P/BMC and BFU2015- 19451/BMCUnión Europea, Bio-NMR-00130 and CALIPSO-312284España, Ministerio de Educación AP2009-409

Structural basis of mitochondrial dysfunction in response to cytochrome c phosphorylation at tyrosine 48

Regulation of mitochondrial activity allows cells to adapt to changing conditions and to control oxidative stress, and its dysfunction can lead to hypoxia-dependent pathologies such as ischemia and cancer. Although cytochrome c phosphorylation—in particular, at tyrosine 48—is a key modulator of mitochondrial signaling, its action and molecular basis remain unknown. Here we mimic phosphorylation of cytochrome c by replacing tyrosine 48 with p-carboxy-methyl-L-phenylalanine (pCMF). The NMR structure of the resulting mutant reveals significant conformational shifts and enhanced dynamics around pCMF that could explain changes observed in its functionality: The phosphomimetic mutation impairs cytochrome c diffusion between respiratory complexes, enhances hemeprotein peroxidase and reactive oxygen species scavenging activities, and hinders caspase-dependent apoptosis. Our findings provide a framework to further investigate the modulation of mitochondrial activity by phosphorylated cytochrome c and to develop novel therapeutic approaches based on its prosurvival effects.Financial support was provided by the Spanish Ministry of Economy and Competitiveness (Grants BFU2015-71017-P/BMC and BFU2015-19451/BMC, cofounded by FEDER EU), European Union (Bio-MR-00130 and CALIPSO-312284), Ramon Areces Foundation, and Andalusian Government (BIO198). B.M.-B. was awarded a PhD fellowship from the Spanish Ministry of Education (AP2009-4092) and a short-term traveling fellowship from the European Bio-NMR Project. A.G.-C. was awarded a PhD fellowship from the CSIC (JaePre-2011-01248).Peer reviewe

Efecto de la discretización espacial sobre las simulaciones de caudal con el modelo distribuido CEQUEAU

El presente trabajo analiza el efecto que tiene la discretización espacial de unacuenca sobre los resultados de las simulaciones de caudal con el modeloCEQUEAU. Este modelo es de tipo distribuido, y se desarrolló por el Instituto Nacional de Investigación Científica de la Universidad de Quebec, Canadá.CEQUEAU ha sido empleado en varios países para la modelación de escurrimientos y utilizado en estudios de comparación de modelos efectuada por la Organización Meteorológica Mundial (OMM). El modelo discretiza la cuenca en elementos cuadrados y el balance hídrico se realiza cuadro por cuadro, tomando en cuenta precipitación, temperatura, porcentaje de lagos, porcentaje de bosque, etcétera. El principal objetivo del trabajo consistió en identificar criterios para determinar el tamaño de cuadro óptimo de discretización de una cuenca, asumiendo una representación adecuada de la precipitación. Se analizaron ocho cuencas de diferentes tamaños y con diferentes climas en la república mexicana. Las características fisiográficas han sido determinadas con el SIG-Idrisi. Además,CEQUEAU fue calibrado y validado todos los días, con varios tamaños de cuadro, evaluando el nivel de certidumbre de los resultados con los criterios numérico de Nash y gráficos. Con base en los resultados obtenidos bajo el diseño experimental propuesto, se construyó un adecuado modelo matemático de tipo regresivo para obtener el tamaño óptimo del cuadro de discretización espacial, utilizando como variables explicativas parámetros fisiográficos de fácil obtención

Aplicación del enfoque integral de la labor educativa y político ideológica en la carrera de medicina. Application of the comprehensive approach for the educational and political-ideological work in medical studies

Con el propósito de hacer algunas consideraciones acerca de la aplicación de los Proyectos Integrales de Trabajo Educativo, sus bases teóricas y sus particularidades en los dos primeros años de la carrera de Medicina, basados en las experiencias obtenidas en la aplicación de los mismos en los primeros años de la carrera de Medicina, durante tres cursos académicos, se realiza un análisis del rol del colectivo de año como célula fundamental para el desarrollo del trabajo educativo, así como se exponen nuestras experiencias en el diseño de dichos proyectos y en la ejecución de sus tareas. Se reconoce al Enfoque Integral de la Labor Educativa y Político Ideológica de los estudiantes, como un escalón cualitativamente superior en la formación integral del futuro profesional revolucionario y se argumentan las limitaciones del currículo de la carrera de Medicina en cuanto al protagonismo de la disciplina principal integradora, que afectan el funcionamiento de los colectivos de años y de carrera. DeCS: TRABAJO EDUCATIVO, EDUCACIÓN MÉDICA, EDUCACIÓN SUPERIOR.ABSTRACT A study was conducted with the purpose of establishing new considerations about the application of Comprehensive Projects for Educational Work, its theoretical bases and particular features on the first two academic courses of Medical Studies were analyzed from the experiences of their applications in the first years of Medical Studies, along three academic courses. An examination of the role played by the teaching group as a core to develop the educational work was carried out, the experiences regarding the design of such projects to perform the tasks, recognizing the Comprehensive Approach of the Educational and Political-Ideological Work of the students, a higher qualitative step on the comprehensive training of the future revolutionary health professional. The limiting factors of the syllabus regarding the leading role of the main comprehensive disciplines which affect the function of the teaching group in the academic courses of the medical studies were recognized as well. DeCS: Educational work; Medical Education; Higher Education