69 research outputs found
Inhibidores de monoamino oxidasas para el control de la enfermedad de Alzheimer
60 p.La enfermedad del Alzheimer (EA) es uno de los trastornos neurológicos de más
prevalencia en la actualidad, caracterizado por el deterioro lento y progresivo de la
capacidad cognitiva. Es una enfermedad multifactorial que no tiene una etiología
definida, sin embargo, existen teorías que intentan explicar su origen, como lo son:
(i) hipótesis colinérgica, basada en que la degradación de las neuronas
colinérgicas puede alterar la memoria y funciones cerebrales; (ii) hipótesis
amiloide, en la cual se acumulan los depósitos del péptido Aβ que contribuyen al
desarrollo de la enfermedad; y (iii) hipótesis de hiperfosforilación de la proteína
Tau, donde la hiperfosforilación de Tau conduce a la formación de ovillos
neurofibrilares (NFT) que reducen la sinapsis y producen neurotoxicidad junto a
disfunción celular. A la fecha, la EA no tiene cura, por lo cual los fármacos
disponibles se encargan de tratar los síntomas de la enfermedad y de retrasar el
deterioro neuronal. En los últimos años, se han realizados diversos estudios sobre
las enzimas monoamino oxidasas (MAO) como blanco terapéutico en la EA. Las
MAO son flavoenzimas que catalizan reacciones de desaminación oxidativa y
metabolizan neurotransmisores como dopamina, entre otras. La inhibición a MAO
ha tenido resultados favorables para el tratamiento de la depresión y síntomas de
la enfermedad de Parkinson. Según la evidencia reciente, los inhibidores de MAOs
(iMAOs) tienen la capacidad de proporcionar neuroprotección para la EA,
mediante la mejora del deterioro cognitivo, regulando la hidrólisis de proteína
precursora amiloide (APP) disminuyendo los niveles de depósitos de Aβ que
puede generar neurotoxicidad en el cerebro. Es por esto, que en la presente
revisión se presentan la acción de los iMAOs para controlar la EA, tanto los que
son usados tradicionalmente para el control de enfermedades neurodegenerativas como los que están presentando reciente evidencia como terapia para la EA
Efectos de un programa de intervención de acceso al léxico en adultos mayores con envejecimiento típico
Tesis (Fonoaudiólogo)Durante la vejez se van evidenciando diferentes cambios tanto físicos, psicológicos, fisiológicos y cognitivos. Dentro de este último, están los problemas para elicitar palabras específicas en diferentes contextos, manifestándose como fenómeno de “Punta de Lengua” (PDL) que es, más bien, un problema en la capacidad de acceso al léxico de los individuos. La terapia fonoaudiológica, actualmente, cuenta con escasa evidencia empírica con respecto a cómo la intervención fonoaudiológica permite incrementar la capacidad del acceso al léxico del adulto mayor (AM). El propósito de esta investigación fue determinar el efecto que tiene un programa de intervención en acceso al léxico en adultos mayores con envejecimiento típico. La muestra constó de 12 adultos mayores autovalentes a quienes se les aplicó una prueba fonoaudiológica de evaluación previa a la implementación del programa de intervención para contar con una línea de base. Los test FAS World Fluency y el Test de vocabulario de Boston. Estos test fueron aplicados nuevamente al finalizar el programa de intervención fonoaudiológico para evaluar los avances. El programa en cuestión constó de 10 sesiones de 45 minutos cada una, dividida en 3 actividades por sesión, 3 veces a la semana. Los resultados analizados con la prueba T de Student indican que no existe evidencia estadísticamente significativa para establecer que el programa de intervención aplicado generó un efecto en la capacidad de acceso al léxico en los AM.During old age different physical, psychological, physiological and cognitive changes are evident.
Within this last one, there are the problems to elicit specific words in different contexts, manifesting
itself as "Tip of Tongue" (TOT) phenomenon that is, rather, a problem in the ability of lexical
access of older adults. The speech therapy, today, has limited empirical evidence about the speech
therapy can increase the skills for lexical access in older adults (OA), therefore, the purpose of this
research was to determine the effect that has an intervention program in lexical access in elderly
with typical aging. The study group consisted of 12 self-sustaining seniors who underwent an
evaluation test prior to the intervention program to have a reference base through the FAS World
Fluency tests and the Boston Vocabulary Test. These same evaluations were applied again after the
speech therapy to evaluate the advances. The program consisted in 10 sessions of 45 minutes each,
divided into 3 activities per session, 3 times a week. According to the results analyzed with the
Student's T test, they indicate that there is no statistically significant evidence to establish that the
applied intervention program generates an effect in the lexical access ability in OA
Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates
Unidad de excelencia María de Maeztu CEX2019-000940-MAim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types
Local hydrological conditions influence tree diversity and composition across the Amazon basin
Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures
Estimating the global conservation status of more than 15,000 Amazonian tree species
Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict thatmost of the world’s >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century
Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates
Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis).
Time period: Tree-inventory plots established between 1934 and 2019.
Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm.
Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield.
Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes.
Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests.
Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types
Geography and ecology shape the phylogenetic composition of Amazonian tree communities
AimAmazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types.LocationAmazonia.TaxonAngiosperms (Magnoliids; Monocots; Eudicots).MethodsData for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny.ResultsIn the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types.Main ConclusionNumerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions
Geography and ecology shape the phylogenetic composition of Amazonian tree communities
Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types.
Location: Amazonia.
Taxon: Angiosperms (Magnoliids; Monocots; Eudicots).
Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran\u27s eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny.
Results: In the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R = 28%). A greater number of lineages were significant indicators of geographic regions than forest types.
Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions
Mapping density, diversity and species-richness of the Amazon tree flora
Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution
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