72 research outputs found
AnĂĄlisis multiescala de las comunidades de coral hermatĂpico del PacĂfico Central Mexicano
The Mexican Central Pacific is located in a zone of oceanographic transition between two biogeographic provinces with particular conditions that affect the associated fauna. The objective of this study was to evaluate the variation of hermatypic coral assemblages in this region and to determine their relationship with the heterogeneity of the benthonic habitat and spatial variables. A total of 156 transects were carried out at 41 sites in the years 2010 and 2011. The sampling effort returned 96.7% of the coral richness expected for the area, with a total of 15 species recorded. The results showed that richness, diversity and cover of corals varied only at the site and state scales. However, the composition and coverage of all coral species, as well as the benthonic habitat structure, differed significantly across the study scales (i.e. sites, zones and states). Canonical redundancy analysis showed that variation in the richness, diversity and assemblages of corals was explained by the cover of live corals, articulated calcareous algae, sandy substrate, sponges and fleshy macroalgae. This study suggests that local scale (i.e. site) variation in the coral assemblages of the Mexican Central Pacific is the result of the heterogeneity of the benthonic habitat, while geomorphological and oceanographic characteristics play a greater role at regional scale.El PacĂfico Central Mexicano se localiza en una zona de transiciĂłn oceanogrĂĄfica entre dos provincias biogeogrĂĄficas con condiciones ambientales particulares que afectan la fauna asociada. El objetivo del estudio fue evaluar la variaciĂłn de las comunidades de coral hermatĂpico de esta regiĂłn y determinar su relaciĂłn con la heterogeneidad del hĂĄbitat bentĂłnico y variables espaciales. Se realizaron 156 transectos en 41 sitios en los años 2010 y 2011. El esfuerzo de muestreo representĂł el 96.7% de la riqueza de coral esperada para el ĂĄrea, con un total de 15 especies registradas. Los resultados mostraron que la riqueza, diversidad y cobertura de corales variaron sĂłlo en las escalas de sitio y de estado. En cambio, la composiciĂłn y cobertura de todas las especies de coral, asĂ como la estructura del hĂĄbitat bentĂłnico, fueron significativamente diferentes en todas las escalas estudiadas (i.e. sitio, zona y estado). Los anĂĄlisis de redundancia canĂłnica mostraron que la variaciĂłn de la riqueza, diversidad y de las comunidades de corales eran explicadas por la cobertura de coral vivo, algas calcĂĄreas articuladas, sustrato arenoso, esponjas y macroalgas carnosas. Este trabajo sugiere que la variaciĂłn de las comunidades de coral en el PacĂfico Central Mexicano a escala local (i.e. sitio) se debe a la heterogeneidad del hĂĄbitat bentĂłnico, mientras que a escala regional, las caracterĂsticas geomorfolĂłgicas y oceanogrĂĄficas desempeñan un papel mĂĄs importante
Ensamblajes bacterianos asociados a especies de coral del PacĂfico central mexicano
The functional role of coral-associated bacteria and their contribution to coral health is still largely unknown. The first necessary step to address this gap in the knowledge is based on characterization of the microbial assemblage of the coral and the species-specific, temporal and spatial variation in its diversity. Branched corals (e.g., genus Pocillopora), are the main builders of coral reefs worldwide. This study evaluated the bacteria associated with the mucus and tissues of Pocillopora damicornis and Pocillopora verrucosa, as well as that of the seawater and surrounding sediments, in 6 sites of the Mexican Central Pacific during summer and winter seasons. The molecular techniques DGGE and RFLP were used with the 16S rDNA to assess the most abundant bacterial OTUs. The relationships between the bacterial-coral assemblage and environmental and spatial variables of the reef surroundings were also evaluated, using the multivariate analyses. Twenty different Operational Taxonomic Units (OTU) were obtained, with the highest number presented by the sediments. Specificity of bacterial groups was found for each coral species, as well as between the tissue and mucus of each species. The results showed that the bacterial dominant groups were similar between seasons, but these showed significant spatial variations among substrates within sites, as well as per substrate across all sites. The environmental variables that explained the variation of the dominant bacterial groups in corals and sea water were the coverages of fleshy macroalgae, live coral and sponge. In contrast, variation in the sediments was explained by the coverages of sand, rubble and rock.El papel funcional de las bacterias asociadas a corales y su contribuciĂłn a la salud del coral es aĂșn desconocido en gran medida. Es necesario que primero se caracterice el ensamblaje microbiano del coral y sus cambios en la diversidad a travĂ©s de las especies de coral, el espacio y tiempo. Los corales ramificados (e.g., gĂ©nero Pocillopora) son los principales constructores arrecifales a nivel mundial. Este estudio evaluĂł la estructura bacteriana asociada al mucus y tejidos de Pocillopora damicornis y Pocillopora verrucosa, asĂ como del agua de mar y sedimentos circundantes en 6 sitios del PacĂfico central mexicano. Se emplearon las tĂ©cnicas DGGE y RFLP del ADNr 16S para generar los perfiles de bandeo o evaluar la diversidad. AdemĂĄs, se evaluĂł la relaciĂłn del ensamblaje bacteriano-coral con variables ambientales y espaciales del entorno arrecifal (de cada sitio), utilizando anĂĄlisis multivariados. Se obtuvieron 20 Unidades TaxonĂłmicas Operacionales (OTU) diferentes, siendo los sedimentos los que presentaron mayor nĂșmero. Se encontrĂł una especificidad de grupos bacterianos para cada especie de coral, asĂ como entre el tejido y mucus de cada especie. Los resultados mostraron que los grupos de bacterias dominantes variaron entre sustratos y entre sitios, encontrando, sĂłlo una variaciĂłn espacial significativa. Las variables ambientales que explican la variaciĂłn de los grupos bacterianos dominantes en corales y agua de mar fueron las coberturas de macroalgas carnosas, coral vivo y esponja. En cambio, la variaciĂłn en los sedimentos fue explicada por las coberturas de arena, escombro y roc
Gas Accretion and Star Formation Rates
Cosmological numerical simulations of galaxy evolution show that accretion of
metal-poor gas from the cosmic web drives the star formation in galaxy disks.
Unfortunately, the observational support for this theoretical prediction is
still indirect, and modeling and analysis are required to identify hints as
actual signs of star-formation feeding from metal-poor gas accretion. Thus, a
meticulous interpretation of the observations is crucial, and this
observational review begins with a simple theoretical description of the
physical process and the key ingredients it involves, including the properties
of the accreted gas and of the star-formation that it induces. A number of
observations pointing out the connection between metal-poor gas accretion and
star-formation are analyzed, specifically, the short gas consumption time-scale
compared to the age of the stellar populations, the fundamental metallicity
relationship, the relationship between disk morphology and gas metallicity, the
existence of metallicity drops in starbursts of star-forming galaxies, the
so-called G dwarf problem, the existence of a minimum metallicity for the
star-forming gas in the local universe, the origin of the alpha-enhanced gas
forming stars in the local universe, the metallicity of the quiescent BCDs, and
the direct measurements of gas accretion onto galaxies. A final section
discusses intrinsic difficulties to obtain direct observational evidence, and
points out alternative observational pathways to further consolidate the
current ideas.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dav\'e, to be published by
Springe
BIOETHANOL POTENTIAL FROM HIGH DENSITY SHORT ROTATION WOODY CROPS ON MARGINAL LANDS IN CENTRAL CHILE
Correction to: A nonsynonymous mutation in PLCG2 reduces the risk of Alzheimer's disease, dementia with Lewy bodies and frontotemporal dementia, and increases the likelihood of longevity
Genome sequencing analysis identifies new loci associated with Lewy body dementia and provides insights into its genetic architecture
The genetic basis of Lewy body dementia (LBD) is not well understood. Here, we performed whole-genome sequencing in large cohorts of LBD cases and neurologically healthy controls to study the genetic architecture of this understudied form of dementia, and to generate a resource for the scientific community. Genome-wide association analysis identified five independent risk loci, whereas genome-wide gene-aggregation tests implicated mutations in the gene GBA. Genetic risk scores demonstrate that LBD shares risk profiles and pathways with Alzheimer's disease and Parkinson's disease, providing a deeper molecular understanding of the complex genetic architecture of this age-related neurodegenerative condition
Pathogenic Huntingtin Repeat Expansions in Patients with Frontotemporal Dementia and Amyotrophic Lateral Sclerosis.
We examined the role of repeat expansions in the pathogenesis of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) by analyzing whole-genome sequence data from 2,442 FTD/ALS patients, 2,599 Lewy body dementia (LBD) patients, and 3,158 neurologically healthy subjects. Pathogenic expansions (range, 40-64 CAG repeats) in the huntingtin (HTT) gene were found in three (0.12%) patients diagnosed with pure FTD/ALS syndromes but were not present in the LBD or healthy cohorts. We replicated our findings in an independent collection of 3,674 FTD/ALS patients. Postmortem evaluations of two patients revealed the classical TDP-43 pathology of FTD/ALS, as well as huntingtin-positive, ubiquitin-positive aggregates in the frontal cortex. The neostriatal atrophy that pathologically defines Huntington's disease was absent in both cases. Our findings reveal an etiological relationship between HTT repeat expansions and FTD/ALS syndromes and indicate that genetic screening of FTD/ALS patients for HTT repeat expansions should be considered
Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic
This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic
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