Estudio sobre la tosca. Parte I: Evidencias de un movimiento descendente del carbonato en base a la interpretación de características macro y geomorfológicas

En base a la interpretación de características morfológicas y geomorfológicas de perfiles con tosca pertenecientes a tres áreas climáticas diferentes del S.E. pampeano, se intentó dilucidar el tipo de movimiento del carbonato de calcio en el perfil. La aparición de capas calcáreas más potentes, con mayor grado de evolución de la estructura y contenidos de CaC03 en zonas elevadas del terreno, hablan en contra de una acumulación por capilaridad del carbonato. La existencia de al menos una de las características morfológicas consideradas como indicadoras inequívocas de un movimiento descendente del carbonato ("barbas" de calcáreo debajo de clastos, tosca sobre granito y tendencia horizontal de la estructura) en cada uno de los 16 perfiles estudiados, confirman una acumulación del mismo por acción de aguas de infiltración. Otras características de interpretación dudosa (disminución de los contenidos de carbonato de calcio en profundidad, limites tosca-subyacente difusos, saltos granométricos, concreciones excéntricas) que tienen aparición conjunta con las anteriores, quedan por lo tanto confirmadas como producidas por este tipo de proceso. La existencia de un clima más húmedo con posterioridad a la acumulación y endurecimiento, del calcáreo, produjo presumiblemente el transporte de materia es más finos hacia los bajos y el lavado del CaC03 de éstos, así romo la formación de pequeñas cubetas de disolución y lamelas por movimiento lateral del agua sobre la superficie de la tosca.Trabajo extractado de "Uritersuchug über die Calcrete-Bildung in SO-Argentinien". Tesis Doctoral, Universitát Hobenheim, Alemania Federal, 1983-1985; llevado a cabo con el apoyo de CONICET (Beca Externa). Publicado en Ciencia del Suelo 4(1):55-65. 1986. Bs. As

Estudio sobre la tosca. PARTE II: Evidencia de un movimiento descendente del carbonato en base a la interpretación de características micromorfológicas

A fin de confirmar o rechazar la hipótesis que atribuye a las toscas del SE pampeano una génesis debida a un arrastre del bicarbonato por agua de infiltración (y en parte a transporte lateral) a favor de la cual hablan resultados deducidos en base a la interpretación de diversas características macromorfológicas y geomorfológicas (Buschiazzo, 1986) se llevaron a cabo estudios micromorfológicos complementarios. Se utilizaron para ello observaciones de cortes delgados con microscopio petrográfico y de muestras sin alterar con microscopio de barrido electrónico (en algunos casos complementados con determinaciones de la composición elemental con microsonda así como roentgenográficos) de muestras de toscas representativas.Indicadores de un movimiento descendente del calcáreo resultaron:1. Cementos:1.1. Microestalactitas ("pendants") y cristales idiomórficos de calcita con crecimiento concéntrico.1.2. Formas de lixiviación con componentes calcíticos, arcillosos y clásticos entre agregados de CaCo31.3. Calcanes y silanes (globoidos, bandas y silanes propiamente dichos) dispuestos alternadamente en poros de tosca.2. Cristales:2.1. Forma, tamaño y ordenamiento de los cristales: en tosca fuertemente laminar (láminas superiores más modernas) cristales isomórficos y mejor ordenados en profundidad.2.2. Grado de cristalización: en toscas débilmente laminares (láminas inferiores más modernas) calcita mejor cristalizada en general en superficie y cristales de calcita de no más de 40 u de diámetro.Indican Un movimiento lateral de calcáreo:1. Ooidos de calcita en poros de lamelas calcáreas eh toscas de zonas semiáridas.2. Ordenamiento laminar horizontal de los ooidos.Trabajo extractado de "Uritersuchug über die Calcrete-Bildung in SO-Argentinien". Tesis Doctoral, Universitát Hobenheim, Alemania Federal,Tesis Doctoral, financiado por CONICET (Beca Externa) y la Duetsche Forchungsgemeinchaft (DFG). Enviado para su publicación a Ciencia Suelo. Bs. As

Aplicación del método de reconstrucción y balance de sustancias al estudio de la degradación de la fertilidad de suelos en la Región Semiárida Pampeana

The bas is of the method of reconstruction and balance sheet of substances are given. The required parameters for this application to soil degradation studies in the semiarid region are considered. A CaC03- balancesheet of an Ustipsamment is given as an example.Se detallan los fundamentos del método de reconstrucción y balance de sustancias y se consideran las posibles aplicaciones a estudios de degradación de suelos en la región semiárida pampeana, así como los parámetros utilizables a tal fin. El método se ejemplifica por medio de un balance de CaCo3 en un Ustipsamment

Management discriminant properties in semiarid soils

The physical properties of coarse - textured soils in semiarid regions often deteriorate with use. We hypostatized that the changes in the physical properties of the soil were related to the cropping sistem employed. 5urface sampled of 52 Entic Haplustolls under three diferents uses (24 under continuous cultivation), 18 under rotation wuth grass Ieys (R), and 10 virgin soils M were analyzed for c1ay, silt, organic malter anrd water content, bulk density, compaction and aggregate stability. Data were analyzed statistically using principal components, canonical variables, and discriminant functions. A satisfactory segregation of the soils according to discriminant properties (coarse organic matter, aggregate stability, and suceptibility lo compaction) was obtained. The model developed satisfactory classified the soils under different uses (100% R, 83% e, and 88% V). Principal component analysis also showed that bulck density, compaction, and wet aggregate salability are related lo organic matter content. We conclude that, in the studied region, the lower the ratio of organic matter lo clay + soil content, the more severe the physical deterioration of the soils.Resúmenes de Trabajos presentados en otras publicaciones (por docentes de la UNLPam.)Publicado en Soil Science, Vol 163 N°7

Visual versus semi-quantitative analysis of 18F-FDG-PET in amnestic MCI. An European Alzheimer\u27s Disease Consortium (EADC) project

We aimed to investigate the accuracy of FDG-PET to detect the Alzheimer\u27s disease (AD) brain glucose hypometabolic pattern in 142 patients with amnestic mild cognitive impairment (aMCI) and 109 healthy controls. aMCI patients were followed for at least two years or until conversion to dementia. Images were evaluated by means of visual read by either moderately-skilled or expert readers, and by means of a summary metric of AD-like hypometabolism (PALZ score). Seventy-seven patients converted to AD-dementia after 28.6?19.3 months of follow-up. Expert reading was the most accurate tool to detect these MCI converters from healthy controls (sensitivity 89.6%, specificity 89.0%, accuracy 89.2%) while two moderately-skilled readers were less (p < 0.05) specific (sensitivity 85.7%, specificity 79.8%, accuracy 82.3%) and PALZ scorewas less (p < 0.001) sensitive (sensitivity 62.3%, specificity 91.7%, accuracy 79.6%). Among the remaining 67 aMCI patients, 50 were confirmed as aMCI after an average of 42.3 months, 12 developed other dementia, and 3 reverted to normalcy. In 30/50 persistent MCI patients, the expert recognized the AD hypometabolic pattern. In 13/50 aMCI, both the expert and PALZ score were negative while in 7/50, only the PALZ score was positive due to sparse hypometabolic clusters mainly in frontal lobes. Visual FDG-PET reads by an expert is the most accurate method but an automated, validated system may be particularly helpful to moderately-skilled readers because of high specificity, and should be mandatory when even a moderately-skilled reader is unavailable

Perspectives on the Trypanosoma cruzi-host cell receptor interaction

Chagas disease is caused by the parasite Trypanosoma cruzi. The critical initial event is the interaction of the trypomastigote form of the parasite with host receptors. This review highlights recent observations concerning these interactions. Some of the key receptors considered are those for thromboxane, bradykinin, and for the nerve growth factor TrKA. Other important receptors such as galectin-3, thrombospondin, and laminin are also discussed. Investigation into the molecular biology and cell biology of host receptors for T. cruzi may provide novel therapeutic targets

Influencias del material original y la acción antrópica sobre características morfológicas, físicas y contenidos de materia orgánica de suelos cultivados y vírgenes de la región semiárida pampeana central (Argentina)

En este estudio se evaluó la incidencia de las características heredadas del material original y aquellas condicionadas por el laboreo sobre propiedades morfológicas, físicas (granulometría, densidad aparente y poros) y contenidos de materia orgánica de horizontes A de suelos cultivados y vírgenes de la región semiárida pampeana central argentina. Este estudio se llevó a cabo sobre 12 perfiles de zonas planas, media loma alta y baja de dos toposecuencias cultivadas y dos vírgenes. Los resultados muestran que las diferencias textura les entre perfiles determinan la proporción de poros chicos y medianos &lt; 10 µ) y posiblemente de materia orgánica, mientras que el laboreo condiciona la densidad aparente y los poros grandes (10-1000 u) de los diferentes horizontes A. Los espesores del solum hasta la acumulación secundaria de CaCo y la acumulación residual de arena son, las características morfológicas que más fehacientemente indicaron la degradación mientras que los espesores de los horizontes superiores y las características morfológicas dependientes de los contenidos de materia orgánica principalmente color y estructura) no son indicadores confiables.Estudio financiado por SECYT dentro del Plan de Expansión de Fronteras Agropecuarias. Enviado para publicar a Anales de Edafología y Agrobiología. Madrid, España

Sialic Acid Glycobiology Unveils Trypanosoma cruzi Trypomastigote Membrane Physiology.

Trypanosoma cruzi, the flagellate protozoan agent of Chagas disease or American trypanosomiasis, is unable to synthesize sialic acids de novo. Mucins and trans-sialidase (TS) are substrate and enzyme, respectively, of the glycobiological system that scavenges sialic acid from the host in a crucial interplay for T. cruzi life cycle. The acquisition of the sialyl residue allows the parasite to avoid lysis by serum factors and to interact with the host cell. A major drawback to studying the sialylation kinetics and turnover of the trypomastigote glycoconjugates is the difficulty to identify and follow the recently acquired sialyl residues. To tackle this issue, we followed an unnatural sugar approach as bioorthogonal chemical reporters, where the use of azidosialyl residues allowed identifying the acquired sugar. Advanced microscopy techniques, together with biochemical methods, were used to study the trypomastigote membrane from its glycobiological perspective. Main sialyl acceptors were identified as mucins by biochemical procedures and protein markers. Together with determining their shedding and turnover rates, we also report that several membrane proteins, including TS and its substrates, both glycosylphosphatidylinositol-anchored proteins, are separately distributed on parasite surface and contained in different and highly stable membrane microdomains. Notably, labeling for α(1,3)Galactosyl residues only partially colocalize with sialylated mucins, indicating that two species of glycosylated mucins do exist, which are segregated at the parasite surface. Moreover, sialylated mucins were included in lipid-raft-domains, whereas TS molecules are not. The location of the surface-anchored TS resulted too far off as to be capable to sialylate mucins, a role played by the shed TS instead. Phosphatidylinositol-phospholipase-C activity is actually not present in trypomastigotes. Therefore, shedding of TS occurs via microvesicles instead of as a fully soluble form

Genome of the Avirulent Human-Infective Trypanosome—Trypanosoma rangeli

Background: Trypanosoma rangeli is a hemoflagellate protozoan parasite infecting humans and other wild and domestic mammals across Central and South America. It does not cause human disease, but it can be mistaken for the etiologic agent of Chagas disease, Trypanosoma cruzi. We have sequenced the T. rangeli genome to provide new tools for elucidating the distinct and intriguing biology of this species and the key pathways related to interaction with its arthropod and mammalian hosts.  Methodology/Principal Findings: The T. rangeli haploid genome is ,24 Mb in length, and is the smallest and least repetitive trypanosomatid genome sequenced thus far. This parasite genome has shorter subtelomeric sequences compared to those of T. cruzi and T. brucei; displays intraspecific karyotype variability and lacks minichromosomes. Of the predicted 7,613 protein coding sequences, functional annotations could be determined for 2,415, while 5,043 are hypothetical proteins, some with evidence of protein expression. 7,101 genes (93%) are shared with other trypanosomatids that infect humans. An ortholog of the dcl2 gene involved in the T. brucei RNAi pathway was found in T. rangeli, but the RNAi machinery is non-functional since the other genes in this pathway are pseudogenized. T. rangeli is highly susceptible to oxidative stress, a phenotype that may be explained by a smaller number of anti-oxidant defense enzymes and heatshock proteins.  Conclusions/Significance: Phylogenetic comparison of nuclear and mitochondrial genes indicates that T. rangeli and T. cruzi are equidistant from T. brucei. In addition to revealing new aspects of trypanosome co-evolution within the vertebrate and invertebrate hosts, comparative genomic analysis with pathogenic trypanosomatids provides valuable new information that can be further explored with the aim of developing better diagnostic tools and/or therapeutic targets

Design and Implementation of Degenerate Microsatellite Primers for the Mammalian Clade

Microsatellites are popular genetic markers in molecular ecology, genetic mapping and forensics. Unfortunately, despite recent advances, the isolation of de novo polymorphic microsatellite loci often requires expensive and intensive groundwork. Primers developed for a focal species are commonly tested in a related, non-focal species of interest for the amplification of orthologous polymorphic loci; when successful, this approach significantly reduces cost and time of microsatellite development. However, transferability of polymorphic microsatellite loci decreases rapidly with increasing evolutionary distance, and this approach has shown its limits. Whole genome sequences represent an under-exploited resource to develop cross-species primers for microsatellites. Here we describe a three-step method that combines a novel in silico pipeline that we use to (1) identify conserved microsatellite loci from a multiple genome alignments, (2) design degenerate primer pairs, with (3) a simple PCR protocol used to implement these primers across species. Using this approach we developed a set of primers for the mammalian clade. We found 126,306 human microsatellites conserved in mammalian aligned sequences, and isolated 5,596 loci using criteria based on wide conservation. From a random subset of ∼1000 dinucleotide repeats, we designed degenerate primer pairs for 19 loci, of which five produced polymorphic fragments in up to 18 mammalian species, including the distinctly related marsupials and monotremes, groups that diverged from other mammals 120–160 million years ago. Using our method, many more cross-clade microsatellite loci can be harvested from the currently available genomic data, and this ability is set to improve exponentially as further genomes are sequenced