Colaboración científica entre países de la región latinoamericana

An analysis of the scientific collaboration among Latin American countries registered between 1975 and 2004 in the Science Citation Index database, Web of Science online version, revealed a steady increase in the number of publications, more marked in the last decade, as well as in the percentages that these represent in the total number of publications authored by regional scientists. Differences were found between countries in the magnitude of these increases, the smaller countries showing the highest levels of collaboration, especially with respect to those publications also involving scientists from institutions outside the Latin American region. The most common subject areas of intra-regional collaboration were Biology, Health, Physics, and Chemistry. Participating institutions from outside the region in intra-regional co-authorship were most commonly European (40% of cases) and North American (38%). The impact of papers as measured by a normalized h-index, involving scientists from outside the region was greater than that found for all intra-regional publications. The dominant bilateral regional collaboration was between Brazil and Argentina which in recent years has focused on topics in the Health Sciences and Astronomy. A detailed analysis of Physics papers showed that institutions from Brazil and Argentina are the most productive in intra-regional collaborations and Condensed Matter, the most studied subject.Un análisis de la colaboración científica entre los países de América Latina a través de documentos registrados de 1975-2004 en el Science Citation Index versión Web of Science, revela un aumento paulatino en el número total de trabajos principalmente en la última década, así como en los porcentajes de éstos del total de publicaciones registradas por la región. La magnitud de estos aumentos varía; los países más pequeños mostraron los niveles más altos de colaboración, en especial aquellas colaboraciones intra-regionales que involucran países fuera de la región. Los temas más abordados por el esfuerzo intra-regional son de las áreas de la Biología, la Salud, la Física, y la Química. En cuanto a la participación de los países fuera de la región en las colaboraciones intra-regionales, el 40% corresponden a países europeos y el 38% a América del Norte. El impacto de los trabajos intra-regionales con la presencia de por los menos un país de fuera de la región calculado a través de un índice h normalizado, fue superior al impacto de los trabajos en colaboración intra-regional en su conjunto. La colaboración Brasil-Argentina domina las colaboraciones bilaterales intra-regionales que en la última década se han enfocado a temas en las Ciencias de la Salud y Astronomía. Las instituciones brasileñas y argentinas son las más productivas en el área de Física y la categoría de mayor contribución en las colaboraciones intra-regionales, es la Materia Condensada

Global human footprint on the linkage between biodiversity and ecosystem functioning in reef fishes

Copyright: © 2011 Mora et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas

Demographic History of Indigenous Populations in Mesoamerica Based on mtDNA Sequence Data

The genetic characterization of Native American groups provides insights into their history and demographic events. We sequenced the mitochondrial D-loop region (control region) of 520 samples from eight Mexican indigenous groups. In addition to an analysis of the genetic diversity, structure and genetic relationship between 28 Native American populations, we applied Bayesian skyline methodology for a deeper insight into the history of Mesoamerica. AMOVA tests applying cultural, linguistic and geographic criteria were performed. MDS plots showed a central cluster of Oaxaca and Maya populations, whereas those from the North and West were located on the periphery. Demographic reconstruction indicates higher values of the effective number of breeding females (Nef) in Central Mesoamerica during the Preclassic period, whereas this pattern moves toward the Classic period for groups in the North and West. Conversely, Nef minimum values are distributed either in the Lithic period (i.e. founder effects) or in recent periods (i.e. population declines). The Mesomerican regions showed differences in population fluctuation as indicated by the maximum Inter-Generational Rate (IGRmax): i) Center-South from the lithic period until the Preclassic; ii) West from the beginning of the Preclassic period until early Classic; iii) North characterized by a wide range of temporal variation from the Lithic to the Preclassic. Our findings are consistent with the genetic variations observed between central, South and Southeast Mesoamerica and the North-West region that are related to differences in genetic drift, structure, and temporal survival strategies (agriculture versus hunter-gathering, respectively). Interestingly, although the European contact had a major negative demographic impact, we detect a previous decline in Mesoamerica that had begun a few hundred years before

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Clustering methodologies for identifying country cor

D-cycloserine improves synaptic transmission in an animal mode of Rett syndrome

<div><p>Rett syndrome (RTT), a leading cause of intellectual disability in girls, is predominantly caused by mutations in the X-linked gene <i>MECP2</i>. Disruption of <i>Mecp2</i> in mice recapitulates major features of RTT, including neurobehavioral abnormalities, which can be reversed by re-expression of normal <i>Mecp2</i>. Thus, there is reason to believe that RTT could be amenable to therapeutic intervention throughout the lifespan of patients after the onset of symptoms. A common feature underlying neuropsychiatric disorders, including RTT, is altered synaptic function in the brain. Here, we show that <i>Mecp2</i>^{<i>tm1</i>.<i>1Jae/y</i>} mice display lower presynaptic function as assessed by paired pulse ratio, as well as decreased long term potentiation (LTP) at hippocampal Schaffer–collateral-CA1 synapses. Treatment of <i>Mecp2</i>^{<i>tm1</i>.<i>1Jae/y</i>} mice with D-cycloserine (DCS), an FDA-approved analog of the amino acid D-alanine with antibiotic and glycinergic activity, corrected the presynaptic but not LTP deficit without affecting deficient hippocampal BDNF levels. DCS treatment did, however, partially restore lower BDNF levels in the brain stem and striatum. Thus, treatment with DCS may mitigate the severity of some of the neurobehavioral symptoms experienced by patients with Rett syndrome.</p></div

Administration of DCS (20 mg/kg/day IP) to <i>Mecp2</i>^{<i>tm1</i>.<i>1Jae/y</i>} mice, beginning at 3 weeks of age, improved the breathing pattern and spontaneous locomotor activity, but did not affect neurological function, walking gate, tremors or grip strength compared to <i>Mecp2</i>^{<i>tm1</i>.<i>1Jae/y</i>} mice receiving vehicle (VEH) injection (n = 5 per group), at 18 weeks of age.

<p>Administration of DCS (20 mg/kg/day IP) to <i>Mecp2</i>^{<i>tm1</i>.<i>1Jae/y</i>} mice, beginning at 3 weeks of age, improved the breathing pattern and spontaneous locomotor activity, but did not affect neurological function, walking gate, tremors or grip strength compared to <i>Mecp2</i>^{<i>tm1</i>.<i>1Jae/y</i>} mice receiving vehicle (VEH) injection (n = 5 per group), at 18 weeks of age.</p

Administration of DCS (20 mg/kg/day IP) to <i>Mecp2</i>^{<i>tm1</i>.<i>1Jae/y</i>} mice did not alter body weight compared to <i>Mecp2</i>^{<i>tm1</i>.<i>1Jae/y</i>} mice receiving vehicle (VEH) injection (n = 5 per group).

<p>Mice were injected daily beginning at 3 weeks of age and continued throughout the life of the animal.</p