Role of Robo1 receptor in semaphorin signalling system and cortical interneuron migration

En route to the cerebral cortex, interneurons encounter the developing striatum and avoid it. It has been shown that these cells express neuropilin (Nrp) as well as PlexinA receptors, which allow these cells to respond to Sema3A and Sema3F chemorepulsive cues expressed in the developing striatum and as consequence they migrate around it and into their proper tangential migratory paths. Robo proteins (receptors for the chemorepulsive family of ligands Slit) have also been observed in cortical interneurons, and they are thought to modulate the morphology of migrating interneurons as well as to play a role in their migration. In the present work, I found that Robo1, but not Robo2 or Slit1/Slit2, deficient (Robo1-/-) mice contain a significant number of cortical interneurons migrating aberrantly through their developing striatum. In vitro experiments showed that dissociated cells taken from the medial ganglionic eminence (MGE, major source of cortical interneurons) of Robo1-/- mice do not respond to either Sema3A or Sema3F induced chemorepulsion. Moreover, I observed significant down regulation of Nrp and PlexinA receptors, as well as reduced levels of Sema3F expression and of some intracellular effectors activated by Sema3A and Sema3F in Robo1-/- cortical interneurons. Using a cell line as an in vitro model, I confirmed that perturbation of Robo1 signalling results in loss of responsiveness to Sema3A and Sema3F, as well as down regulation of their receptors. Additionally, I found that Robo1 can bind directly to Nrp and PlexinA proteins. Taken together, the data presented here suggest a novel role for Robo1 receptor in controlling the expression of distinct components of the class 3 semaphorin signalling system and thus, the migration of cortical interneurons. They also suggest that the migration of cortical interneurons around the striatum might result from the collaborative effort of Robo1receptors and the class 3 semaphorin signalling system

Reseña de "La formación de redes de conocimiento. Una perspectiva regional desde México" de Rosalba Casas (coord.)

En el libro se presentan los resultados de una investigación colectiva realizada bajo la coordinación de Rosalba Casas con las colaboraciones de Rebeca de Gortari, Matilde Luna, María Josefa Santos y Ricardo Tirado. El trabajo se sitúa en el análisis de las relaciones interactivas en la producción y aplicación de conocimientos como un paso metodológico previo al análisis de los procesos de innovación. En este sentido, el texto es un esfuerzo enorme para actualizar los estudios sociales de la ciencia y la tecnología

Catalytic secondary methods for the removal of tar derived from biomass gasification: use of low-cost materials and study of the effect of sulfur species on the steam reforming activity of the catalysts

Biomass gasification could potentially mitigate the actual dependency on fossil fuels. The practical application of this technology still faces many challenges to be considered a sustainable and profitable energy production source. One of the drawbacks of this technology is the production of undesirable by-products such as high molecular weight hydrocarbons collectively known as “tar” and sulfur compounds. These unwanted compounds must be removed before syngas end-use applications as they can foul pipes and reduced the performance of equipment downstream the gasifier as well as poison the catalyst used for upgrading the syngas. Catalytic steam reforming stands as an appealing tar removal technology in the small and medium sized gasification plants where heat management is crucial and recovery of the energy content within the tar compounds is desirable avoiding wastewater effluents and disposal of adsorbents. Nickel based catalysts have been the preferred choice in industrial applications for the reforming reactor. However, deactivation by carbon deposition is at present an unresolved problem which must be addressed before commercial application of biomass gasification technology. Moreover, the presence of sulfur compounds even at the low concentration found in most biomass feedstocks is deleterious for the steam reforming activity of the catalyst. This thesis comprises four experimental studies, each of them deal with a specific arguments of the hot gas cleanup technology of biomass syngas. The main focus was on the steam reforming activity of nickel-based catalyst and the effect of sulfur and the potassium-sulfur interactions on the steam reforming performance of the catalyst. The main contributions from these studies are; 1) the development of a less time and energy consuming synthesis procedure for the production of a mayenite-supported nickel catalyst using low-cost precursors. This new method involves the addition of the nickel precursor during the mayenite synthesis procedure. Compared to the “wet impregnation” technique the developed method showed slightly lower toluene steam reforming activity but greater stability, which was ascribed to a higher carbon deposition tolerance. 2) Better understanding on the sulfur poisoning of catalysts under steam reforming conditions at laboratory scale. The results evidenced that for a deeper knowledge of the sulfur poisoning, the calculation of the sulfur coverage should be more accurate and new methods for its measurement are required. 3) Comprehension of the mechanism of interaction between potassium and sulfur on a sulfur passivated commercial nickel catalyst under reforming conditions using real biomass syngas. The preferential adsorption site for sulfur and potassium was determined for the applied experimental conditions and catalyst and a mechanism involving the interaction of potassium with the sulfur chemisorbed on the active sites was propose

CO(2) in the spotlight

Optogenetic techniques have revealed that retrotrapezoid neurons are essential for sensitivity to carbon dioxide

¿Es Global o Local la Investigación? La Proliferación Situada de Polímeros, Transgénicos y Colectivos

El presente artículo presenta la construcción sociotécnica de dos experiencias de investigación: polímeros cerámicas y papas transgénicas. Ambas tienen por objeto constituirse en una alternativa de análisis a los estudios que resaltan el papel fundamental de la tecnología en la explicación de la globalización. El trabajo muestra dos etnografías de laboratorio. En el caso de los polímeros se muestra cómo la construcción de un saber lo cal se expande internacionalmente; en el segundo, las papas transgénicas, siendo un saber que ha comenzado a ser conocido mundialmente, es necesario situarlo localmente en su proceso de investigación.El presente artículo presenta la construcción sociotécnica de dos experiencias de investigación: polímeros cerámicas y papas transgénicas. Ambas tienen por objeto constituirse en una alternativa de análisis a los estudios que resaltan el papel fundamental de la tecnología en la explicación de la globalización. El trabajo muestra dos etnografías de laboratorio. En el caso de los polímeros se muestra cómo la construcción de un saber lo cal se expande internacionalmente; en el segundo, las papas transgénicas, siendo un saber que ha comenzado a ser conocido mundialmente, es necesario situarlo localmente en su proceso de investigación

Fugas

Por razones prácticamente obvias, únicamente se analizan las fugas de agua relativas a la Ciudad de México, las cuales oscilan entre 40% y 60% de la red de suministro público. A medida que los avances tecnológicos permiten la detección de fugas no visibles se ha estimado un gran impacto en el sistema de abastecimiento público (CONAGUA, 2010). En el caso de las fugas perceptibles, los usuarios, las autoridades y medios de comunicación han planificado la problemática hasta un punto tal que podrían incidir en las políticas públicas de inversión y abastecimiento, así como los conflictos entre usuarios y autoridades por la regularización del servicio público de abastecimiento.Por razones prácticamente obvias, únicamente se analizan las fugas de agua relativas a la Ciudad de México, las cuales oscilan entre 40% y 60% de la red de suministro público. A medida que los avances tecnológicos permiten la detección de fugas no visibles se ha estimado un gran impacto en el sistema de abastecimiento público (CONAGUA, 2010). En el caso de las fugas perceptibles, los usuarios, las autoridades y medios de comunicación han planificado la problemática hasta un punto tal que podrían incidir en las políticas públicas de inversión y abastecimiento, así como los conflictos entre usuarios y autoridades por la regularización del servicio público de abastecimiento.Unidad Académica Profesional Chimalhuacá

RESULTADOS OBSTÉTRICOS DE LAS PACIENTES CON DIABETES GESTACIONAL EN EL HOSPITAL GENERAL DE ECATEPEC “LAS AMÉRICAS” EN EL PERIODO COMPRENDIDO DE ENERO A DICIEMBRE DE 2011.

Antecedentes: La Diabetes Gestacional es definido como la intolerancia a la glucosa que aparece o es reconocido por primera vez durante el embarazo. El desarrollo de esta patología incrementa el riesgo de morbimortalidad materno - fetal con diversas complicaciones para el binomio, con resultados obstétricos que difieren del resto de la población que no padece Diabetes gestaciona

Use of low-cost materials for tar abatement process

In the present work char, olivine and mayenite were used as bed materials to study ability to remove tar produced in biomass thermal processing. The tar gases formed from the pyrolysis reactions of the olive pomace biomass were forced to pass through the bed material. Nitrogen was used as carrier gas. The temperature of the bed was set at 660 °C and no oxidizing agent was added during the tests. The char was produced from the pyrolysis of olive pomace biomass. Olivine was used without any pre-treatment. Mayenite was synthesized in laboratory using CaCO3 and Al2O3 as precursors. Among the tested materials, mayenite showed the best tar removal capacity and stability, with a total tar removal of about 60% after 60 min time on stream, while in the case of char and olivine the attained value was 15%. The measured average nitrogen-free gas flow value in the tests carried out with mayenite was 0.84 NL min-1, whereas in the case of char and olivine the obtained average gas flow values were 0.65 and 0.55 NL min-1, respectively. Accordingly, the higher average hydrogen amount was measured in the tests using mayenite as bed material (36%)

The dorsal spinal cord and hindbrain: from developmental mechanisms to functional circuits

Neurons of the dorsal hindbrain and spinal cord are central in receiving, processing and relaying sensory perception and participate in the coordination of sensory-motor output. Numerous cellular and molecular mechanisms that underlie neuronal development in both regions of the nervous system are shared. We discuss here the mechanisms that generate neuronal diversity in the dorsal spinal cord and hindbrain, and emphasize similarities in patterning and neuronal specification. Insight into the developmental mechanisms has provided tools that can help to assign functions to small subpopulations of neurons. Hence, novel information on how mechanosensory or pain sensation is encoded under normal and neuropathic conditions has already emerged. Such studies show that the complex neuronal circuits that control perception of somatosensory and viscerosensory stimuli are becoming amenable to investigations