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

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 < 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

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

Molecular and Structural Discrimination of Proline Racemase and Hydroxyproline-2-Epimerase from Nosocomial and Bacterial Pathogens

The first eukaryotic proline racemase (PRAC), isolated from the human Trypanosoma cruzi pathogen, is a validated therapeutic target against Chagas' disease. This essential enzyme is implicated in parasite life cycle and infectivity and its ability to trigger host B-cell nonspecific hypergammaglobulinemia contributes to parasite evasion and persistence. Using previously identified PRAC signatures and data mining we present the identification and characterization of a novel PRAC and five hydroxyproline epimerases (HyPRE) from pathogenic bacteria. Single-mutation of key HyPRE catalytic cysteine abrogates enzymatic activity supporting the presence of two reaction centers per homodimer. Furthermore, evidences are provided that Brucella abortus PrpA [for ‘proline racemase’ virulence factor A] and homologous proteins from two Brucella spp are bona fide HyPREs and not ‘one way’ directional PRACs as described elsewhere. Although the mechanisms of aminoacid racemization and epimerization are conserved between PRAC and HyPRE, our studies demonstrate that substrate accessibility and specificity partly rely on contraints imposed by aromatic or aliphatic residues distinctively belonging to the catalytic pockets. Analysis of PRAC and HyPRE sequences along with reaction center structural data disclose additional valuable elements for in silico discrimination of the enzymes. Furthermore, similarly to PRAC, the lymphocyte mitogenicity displayed by HyPREs is discussed in the context of bacterial metabolism and pathogenesis. Considering tissue specificity and tropism of infectious pathogens, it would not be surprising if upon infection PRAC and HyPRE play important roles in the regulation of the intracellular and extracellular amino acid pool profiting the microrganism with precursors and enzymatic pathways of the host

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

Data publication with the structural biology data grid supports live analysis

Access to experimental X-ray diffraction image data is fundamental for validation and reproduction of macromolecular models and indispensable for development of structural biology processing methods. Here, we established a diffraction data publication and dissemination system, Structural Biology Data Grid (SBDG; data. sbgrid. org), to preserve primary experimental data sets that support scientific publications. Data sets are accessible to researchers through a community driven data grid, which facilitates global data access. Our analysis of a pilot collection of crystallographic data sets demonstrates that the information archived by SBDG is sufficient to reprocess data to statistics that meet or exceed the quality of the original published structures. SBDG has extended its services to the entire community and is used to develop support for other types of biomedical data sets. It is anticipated that access to the experimental data sets will enhance the paradigm shift in the community towards a much more dynamic body of continuously improving data analysis

Data Publication with the Structural Biology Data Grid Supports Live Analysis

Access to experimental X-ray diffraction image data is fundamental for validation and reproduction of macromolecular models and indispensable for development of structural biology processing methods. Here, we established a diffraction data publication and dissemination system, Structural Biology Data Grid (SBDG; data.sbgrid.org), to preserve primary experimental data sets that support scientific publications. Data sets are accessible to researchers through a community driven data grid, which facilitates global data access. Our analysis of a pilot collection of crystallographic data sets demonstrates that the information archived by SBDG is sufficient to reprocess data to statistics that meet or exceed the quality of the original published structures. SBDG has extended its services to the entire community and is used to develop support for other types of biomedical data sets. It is anticipated that access to the experimental data sets will enhance the paradigm shift in the community towards a much more dynamic body of continuously improving data analysis

The Infection of Chicken Tracheal Epithelial Cells with a H6N1 Avian Influenza Virus

Sialic acids (SAs) linked to galactose (Gal) in α2,3- and α2,6-configurations are the receptors for avian and human influenza viruses, respectively. We demonstrate that chicken tracheal ciliated cells express α2,3-linked SA, while goblet cells mainly express α2,6-linked SA. In addition, the plant lectin MAL-II, but not MAA/MAL-I, is bound to the surface of goblet cells, suggesting that SA2,3-linked oligosaccharides with Galβ1–3GalNAc subterminal residues are specifically present on the goblet cells. Moreover, both α2,3- and α2,6-linked SAs are detected on single tracheal basal cells. At a low multiplicity of infection (MOI) avian influenza virus H6N1 is exclusively detected in the ciliated cells, suggesting that the ciliated cell is the major target cell of the H6N1 virus. At a MOI of 1, ciliated, goblet and basal cells are all permissive to the AIV infection. This result clearly elucidates the receptor distribution for the avian influenza virus among chicken tracheal epithelial cells and illustrates a primary cell model for evaluating the cell tropisms of respiratory viruses in poultry