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A Contribution to Pollen Rain Characterization in Forest-Savanna Mosaics of the Venezuelan Guayana and Its Use in Vegetation Reconstructions from Sedimentary Records

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American Journal of Plant Sciences 2013年第7期4卷 33-52页

作者： leal alejandra Bilbao Bibiana Berrío Juan Carlos Department of Environmental Studies Universidad Simón Bolívar Sartenejas. Edo. Caracas Venezuela 2Department of Geo- graphy University of Leicester Leicester UK.

The main results of a study of pollen representation in surface soils from different plant communities in the upland savannas of Guayana were presented. The representation of savanna herb pollen mainly belonging to the Poaceae and Cyperaceae was high in open communities such as fernlands, grasslands and Mauritia palm swamps, but decreased as vegetation structure became more closed and woody;from savanna-forest borders to secondary forests and lastly, evergreen montane forests;mimicking the gradient of vegetation openness observed in living plant communities. Thus, the proportion of savanna herb pollen in herbaceous communities: swamps, fernlands and grasslands, reached over 80% and arboreal pollen contributed less than 10%. This ratio changed in savanna-forest borders where savanna herb pollen decreased to 60% or less and the proportion of arboreal pollen rose to 30% or higher. Lastly, in forest soils, pollen abundances from trees (Dimorphandra, Protium, Schefflera), shrubs (Miconia and other Melastomataceae) and lianas contributed higher than 60% of the pollen sum, even in open gallery forests and fallows. The lack of pollen from cassava, the main crop in the forests of the region, at these sites was remarkable. The ordination of sediment samples from 4 records from the Late Holocene with respect to the soil surface samples studied, showed that the characterization of pollen rain was useful for identifying long-term compositional and structural changes in the sedimentary records, thus providing objective indicators for the interpretation of past vegetation structure.

关键词： Pollen Representation Savanna-Forest Dynamics Upland Guayana Gran Sabana Poaceae Pollen

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Role of cytokines and other factors involved in the Mycobacterium tuberculosis infection

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World Journal of Immunology 2015年第1期5卷 16-50页

作者： Tania Beatriz Romero-Adrian Jorymar leal-Montiel Gerardo Fernández alejandra Valecillo Graduate Studies in Immunology Institute of Biological Research Faculty of Medicine University of Zulia Service of Pediatric Southern General Hospital Rheumatology and Immunology Service University Hospital

Mycobacterium tuberculosis （Mtb） is a pathogen that is widely distributed geographically and continues to be a major threat to world health. Bacterial virulence factors, nutritional state, host genetic condition and immune response play an important role in the evolution of the infection. The genetically diverse Mtb strains from different lineages have been shown to induce variable immune system response. The modern and ancient lineages strains induce different cytokines patterns. The immunity to Mtb depends on Th1-cell activity [interferon- γ （IFN- γ ）, interleukin-12 （IL-12） and tumor necrosis factor-α （TNF-α）]. IL-1β directly kills Mtb in murine and human macrophages. IL-6 is a requirement in host resistance to Mtb infection. IFN- γ , TNF-α, IL-12 and IL-17 are participants in Mycobacterium-induced granuloma formation. Other regulating proteins as IL-27 and IL-10 can prevent extensive immunopathology. CXCL 8 enhances the capacity of the neutrophil to kill Mtb . CXCL13 and CCL19 have been identified as participants in the formation of granuloma and control the Mtb infection. Treg cells are increased in patients with active tuberculosis （TB） but decrease with anti-TB treatment. The increment of these cells causes down- regulation of adaptive immune response facilitating the persistence of the bacterial infection. Predominance of Th2 phenotype cytokines increases the severity of TB. The evolution of the Mtb infection will depend of the cytokines network and of the infuence of other factors aforementioned.

关键词： Mycobacterium tuberculosis, Strains Virulence Host genetic Immune response T lymphocytes Cytokines

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Quantification of the Mixture of Hydrothermal and Fresh Water in Tectonic Valleys

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Journal of Earth Science 2020年第5期31卷 1007-1015页

作者： Janete Moran-Ramirez Jose Ivan Morales-Arredondoc Maria Aurora Armienta-Hernandez Jose Alfredo Ramos-leal National Council of Science and Technology National Autonomous University of MexicoInstitute of GeophysicsScientific Research CircuitUniversity CityCoyoacan 04150Mexico CityMexico National Autonomous University of Mexico Institute of GeophysicsUniversity CampusMexico CityMexico Potosino Institute for Scientific and Technological Research 78216 San Luis PotosiS.L.P.Mexico

This study was conducted to identify the origin, hydrogeochemical processes and evolution of groundwater in a tectonic valley. This study was carried out with the aim of quantifying the proportions of groundwater flows contributing to the water chemistry abstracted in a zone of convergence favored by the presence of active faults. The study area is located in the Trans-Mexican Volcanic Belt. End members methodology was applied to identify the mixing of hydrothermal with fresh groundwater, where changes in the aquifer geology result in distinct groundwater chemical signatures. Ternary mixing was quantified using conservative elements. Moreover, other evolutionary processes, such as ion exchange and silicate weathering occur due to changes in the geology of the area. In ternary mixing, each of the end members is associated with the lithology through which it circulates. The local flow contributes 70% of the water to the system, the intermediate flow contributes 14%, and the regional flow contributes 16%. Three types of water are produced: Na-HCO3, due to the interaction of water with volcanic rocks of rhyolitic composition, Na-Mg-HCO3, due to the interaction of water with volcanic rocks of basaltic-andesite composition, and Ca-HCO3, due to the interaction of water with sedimentary calcareous rocks.

关键词： hydrogeochemistry ternary mixing end members conservative elements local flow Mexico

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