Species interactions and random dispersal rather than habitat filtering drive community assembly during early plant succession

Theory on plant succession predicts a temporal increase in the complexity of spatial community structure and of competitive interactions: initially random occurrences of early colonising species shift towards spatially and competitively structured plant associations in later successional stages. Here we use long-term data on early plant succession in a German post mining area to disentangle the importance of random colonisation, habitat filtering, and competition on the temporal and spatial development of plant community structure. We used species co-occurrence analysis and a recently developed method for assessing competitive strength and hierarchies (transitive versus intransitive competitive orders) in multispecies communities. We found that species turnover decreased through time within interaction neighbourhoods, but increased through time outside interaction neighbourhoods. Successional change did not lead to modular community structure. After accounting for species richness effects, the strength of competitive interactions and the proportion of transitive competitive hierarchies increased through time. Although effects of habitat filtering were weak, random colonization and subsequent competitive interactions had strong effects on community structure. Because competitive strength and transitivity were poorly correlated with soil characteristics, there was little evidence for context dependent competitive strength associated with intransitive competitive hierarchies.

A legacy of human-induced ecosystem changes: spatial processes drive the taxonomic and functional diversities of testate amoebae in Sphagnum peatlands of the Galápagos

Aim Our aims were to compare the composition of testate amoeba (TA) communities from Santa Cruz Island, Galápagos Archipelago, which are likely in existence only as a result of anthropogenic habitat transformation, with similar naturally occurring communities from northern and southern continental peatlands. Additionally, we aimed at assessing the importance of niche-based and dispersal-based processes in determining community composition and taxonomic and functional diversity. Location The humid highlands of the central island of Santa Cruz, Galápagos Archipelago. Methods We survey the alpha, beta and gamma taxonomic and functional diversities of TA, and the changes in functional traits along a gradient of wet to dry habitats. We compare the TA community composition, abundance and frequency recorded in the insular peatlands with that recorded in continental peatlands of Northern and Southern Hemispheres. We use generalized linear models to determine how environmental conditions influence taxonomic and functional diversity as well as the mean values of functional traits within communities. We finally apply variance partitioning to assess the relative importance of niche- and dispersal-based processes in determining community composition. Results TA communities in Santa Cruz Island were different from their Northern Hemisphere and South American counterparts with most genera considered as characteristic for Northern Hemisphere and South American Sphagnum peatlands missing or very rare in the Galápagos. Functional traits were most correlated with elevation and site topography and alpha functional diversity to the type of material sampled and site topography. Community composition was more strongly correlated with spatial variables than with environmental ones. Main conclusions TA communities of the Sphagnum peatlands of Santa Cruz Island and the mechanisms shaping these communities contrast with Northern Hemisphere and South American peatlands. Soil moisture was not a strong predictor of community composition most likely because rainfall and clouds provide sufficient moisture. Dispersal limitation was more important than environmental filtering because of the isolation of the insular peatlands from continental ones and the young ecological history of these ecosystems.

Jack-of-all-trades effects drive biodiversity–ecosystem multifunctionality relationships in European forests

There is considerable evidence that biodiversity promotes multiple ecosystem functions (multifunctionality), thus ensuring the delivery of ecosystem services important for human well-being. However, the mechanisms underlying this relationship are poorly understood, especially in natural ecosystems. We develop a novel approach to partition biodiversity effects on multifunctionality into three mechanisms and apply this to European forest data. We show that throughout Europe, tree diversity is positively related with multifunctionality when moderate levels of functioning are required, but negatively when very high function levels are desired. For two well-known mechanisms, ‘complementarity’ and ‘selection’, we detect only minor effects on multifunctionality. Instead a third, so far overlooked mechanism, the ‘jack-of-all-trades’ effect, caused by the averaging of individual species effects on function, drives observed patterns. Simulations demonstrate that jack-of-all-trades effects occur whenever species effects on different functions are not perfectly correlated, meaning they may contribute to diversity–multifunctionality relationships in many of the world’s ecosystems.

Intrinsic pH-Sensitivity of Cells in the Retrotrapezoid Nucleus: Possible Role of Glia in Respiratory Drive

An increase in carbon dioxide (CO2) and protons (H+) are the primary signals for breathing. Cells that sense changes in CO2/H+ levels and increase breathing accordingly are located in a region of the caudal medulla oblongata called the retrotrapezoid nucleus (RTN). Specifically, select RTN neurons are intrinsically pH sensitive and send excitatory projections to the respiratory rhythm generator to drive breathing. Glial cells in the RTN are thought to contribute to this respiratory drive, possibly by releasing ATP in response to increases in CO2/H+ levels. However, pH sensitivity of RTN glial cells has yet to be determined. Therefore, the goal of my thesis is to determine if acutely dissociated RTN cells can respond to changes in pH in isolation. To make this determination I used ratiometric fluorescent microscopy to measure intracellular calcium in dissociated RTN cells during changes in bath pH. I found that a small percentage of RTN cells (16%) respond to bath acidification from pH 7.3 to pH 6.9 with an increase in fluorescence indicating an increase in intracellular calcium. Preliminary electrophysiological findings suggest that responsive cells are unable to make action potentials, thus suggesting their identity to be glia. These results indicate that a subset of pH sensitive cells in the RTN are intrinsically pH sensitive and that glia cells may possibly play a role in central chemoreception.

A MOLECULAR APPROACH FOR DETECTING GENETIC DAMAGE USING THE ECO R1 FAMILY OF HUMAN DNA (SEQUENCING)

A clone of the primary Eco R1 family of human DNA sequences has been used as an indicator sequence for detecting alterations induced by a toxic agent. Specific clones of this family have been examined and compared to the consensus sequence to determine the normal variability of this family. Though variations were observed, data indicated that such clones can be used to study induced DNA modifications. This DNA was exposed to the toxic agent dimethyl sulfate under various conditions and a distinct pattern of aberrations was shown to occur. It is suggested that this approach be used to characterize patterns of damage induced by various agents in the ultimate development of a system capable of monitoring human genotoxic exposure. ^

αvβ8 Integrin Interacts with RhoGDI1 to Regulate Rac1 and Cdc42 Activation and Drive Glioblastoma Cell Invasion

As an interface between the circulatory and central nervous systems, the neurovascular unit is vital to the development and survival of tumors. The malignant brain cancer glioblastoma multiforme (GBM) displays invasive growth behaviors that are major impediments to surgical resection and targeted therapies. Adhesion and signaling pathways that drive GBM cell invasion remain largely uncharacterized. Here we have utilized human GBM cell lines, primary patient samples, and pre-clinical mouse models to demonstrate that integrin αvβ8 is a major driver of GBM cell invasion. β8 integrin is overexpressed in many human GBM cells, with higher integrin expression correlating with increased invasion and diminished patient survival. Silencing β8 integrin in human GBM cells leads to impaired tumor cell invasion due to hyperactivation of the Rho GTPases Rac1 and Cdc42. β8 integrin associates with Rho GDP Dissociation Inhibitor 1 (RhoGDI1), an intracellular signaling effector that sequesters Rho GTPases in their inactive GDP-bound states. Silencing RhoGDI1 expression or uncoupling αvβ8 integrin-RhoGDI1 protein interactions blocks GBM cell invasion due to Rho GTPase hyperactivation. These data reveal for the first time that αvβ8 integrin, via interactions with RhoGDI1, suppresses activation of Rho proteins to promote GBM cell invasiveness. Hence, targeting the αvβ8 integrin-RhoGDI1 signaling axis may be an effective strategy for blocking GBM cell invasion.

Coordenadas de lo posmoderno : un texto fundacional: El nombre de la rosa de U. Eco

Fil: Corti, Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas

Funcionalidad de la articulación Glenohumeral en el golpe de Drive en pelota a paleta

El propósito de esta ponencia, es realizar un análisis del gesto técnico denominado "Drive", golpe determinante en la disciplina de Pelota a Paleta, a partir del estudio Anatómico y Biomecánico de la articulación Glenohumeral. Se destacará la importancia de los conocimientos anatomo-funcionales en la formación del Profesor en Educación Física, como base para el análisis del movimiento en cuestión, ya sea con fines de rendimiento deportivo o para mejorar la intervención docente. La articulación Glenohumeral es parte de un complejo de articulaciones que corresponde a la Cintura Escapular. Esta, posee 3 grados de libertad, lo que permite orientar al miembro superior en relación a los 3 planos del espacio, a disposición de tres ejes principales, y de esa manera, combinarlos gracias a su característica de articulación en esfera (Diartrosis-Enartrosis). A partir de Aquí, los movimientos principales que puede realizar son: La Flexión y la Extensión en el plano Sagital en torno al eje transversal; la Aducción y la Abducción en el plano frontal con su eje anteroposterior; la Rotación Interna y la Rotación Externa en el plano horizontal, alrededor del eje vertical, y por último, el movimiento de circunduccion, que resulta de la combinación de los precedentes. Los principios básicos para el desarrollo del golpe, establecen que éste debe comenzar desde la empuñadura de la paleta, la posición del cuerpo en sus diferentes instancias, hasta llegar al momento del golpe para realizar un correcto impacto. Este último momento se realiza llevando el miembro superior desde atrás hacia delante, con el codo extendido en el momento del golpeo y a la altura del hombro. Es un golpe para imprimir fuerza y dirección a la pelota

El asedio : Eco del mundo novelesco de Arturo Pérez Reverte

El asedio (2010), de Arturo Pérez Reverte, ofrece una multiplicidad de entradas posibles, ya que se trata de una voluminosa novela coral, que concentra la experiencia de su autor. Proponemos, para este encuentro, un enfoque centrado en analizar los universos de los personajes y su trabazón caleidoscópica. Pérez Reverte utiliza siempre una tercera persona que se cuela en las zonas oscuras y recónditas de tipos humanos inmersos en una ciudad y un tiempo hostiles: Cádiz en 1811. Despliega las condiciones de asedio militar a ese territorio, que se replican de variados modos en individuos asediados por sus propios conflictos. La naturalidad con la que los personajes se encuentran en puntos de unión y de fuga conforma una telaraña, cuyos hilos representan la trabazón de esta novela de novelas

Reflexiones desde la eco-antropología sobre el terroir

El Terroir constituye en la actualidad un concepto clave en el pensamiento sobre la producción de alimentos y de bebidas de calidad. En este texto, consideramos esta noción con un punto de vista eco-antropológico apoyándonos sobre ejemplos sacados principalmente de la historia y de la actualidad de ciertos vinos. Estudiamos sucesivamente su construcción, sus usos (en particular en el marco de los procesos de denominación de origen) y sus representaciones.

Reflexiones desde la eco-antropología sobre el terroir

El Terroir constituye en la actualidad un concepto clave en el pensamiento sobre la producción de alimentos y de bebidas de calidad. En este texto, consideramos esta noción con un punto de vista eco-antropológico apoyándonos sobre ejemplos sacados principalmente de la historia y de la actualidad de ciertos vinos. Estudiamos sucesivamente su construcción, sus usos (en particular en el marco de los procesos de denominación de origen) y sus representaciones.

Funcionalidad de la articulación Glenohumeral en el golpe de Drive en pelota a paleta

El propósito de esta ponencia, es realizar un análisis del gesto técnico denominado "Drive", golpe determinante en la disciplina de Pelota a Paleta, a partir del estudio Anatómico y Biomecánico de la articulación Glenohumeral. Se destacará la importancia de los conocimientos anatomo-funcionales en la formación del Profesor en Educación Física, como base para el análisis del movimiento en cuestión, ya sea con fines de rendimiento deportivo o para mejorar la intervención docente. La articulación Glenohumeral es parte de un complejo de articulaciones que corresponde a la Cintura Escapular. Esta, posee 3 grados de libertad, lo que permite orientar al miembro superior en relación a los 3 planos del espacio, a disposición de tres ejes principales, y de esa manera, combinarlos gracias a su característica de articulación en esfera (Diartrosis-Enartrosis). A partir de Aquí, los movimientos principales que puede realizar son: La Flexión y la Extensión en el plano Sagital en torno al eje transversal; la Aducción y la Abducción en el plano frontal con su eje anteroposterior; la Rotación Interna y la Rotación Externa en el plano horizontal, alrededor del eje vertical, y por último, el movimiento de circunduccion, que resulta de la combinación de los precedentes. Los principios básicos para el desarrollo del golpe, establecen que éste debe comenzar desde la empuñadura de la paleta, la posición del cuerpo en sus diferentes instancias, hasta llegar al momento del golpe para realizar un correcto impacto. Este último momento se realiza llevando el miembro superior desde atrás hacia delante, con el codo extendido en el momento del golpeo y a la altura del hombro. Es un golpe para imprimir fuerza y dirección a la pelota