Los conocimientos previos en el proceso de aprendizaje de contenidos históricos en el contexto escolar

Es de interés psicológico y didáctico estudiar la actividad cognoscitiva de los niños involucrada en el proceso de adquisición de conocimientos específicos en el contexto escolar. A partir de los presupuestos epistemológicos del constructivismo genético, de la concepción interaccionista del proceso lector y de una aproximación a la complejidad disciplinar de la Historia se abordan los procesos de interpretación de conocimientos históricos en la lectura de un texto enseñado en clase. El análisis cualitativo puso en evidencia el dinamismo de la actividad cognoscitiva en el proceso de establecimiento de relaciones de significado a partir de los conocimientos previos infantiles de la información textual. En función de ello se caracterizó su originalidad y cierto grado de organización y sistematicidad en su funcionamientoIt is of psychological and educational interest to study the cognitive activity of children in-volved in the process of acquiring specific knowledge in the school context. The process of in-terpretation of historical knowledge in the reading of a text taught in class are addressed based on the epistemological presuppositions of genetic constructivism, the interactionist con-ception of the reading process and an approach to the disciplinary complexity of History. The qualitative analysis revealed the dynamism of the cognitive activity in the process of meaning relations between children's prior knowledges and the textual information. It was found that prior knowledges are characterized by its originality and certain degree of organization and systematic functionin

Glucocorticoids Exert Direct Toxicity on Microvasculature: Analysis of Cell Death Mechanisms

Glucocorticoids (GCs) are routinely administered systemically or injected into the eye when treating numerous ocular diseases; however, their toxicity on the retinal microvasculature has not been previously investigated. In this article, the effects of hydrocortisone (Hydro), dexamethasone, dexamethasone-phosphate and triamcinolone acetonide (TA) were evaluated in vitro on human skin microcirculation cells and, bovine endothelial retinal cells, ex-vivo, on flat mounted rat retinas. The degree of GCs induced endothelial cell death varied according to the endothelial cell type and GCs chemical properties. GCs toxicity was higher in skin microvascular endothelial cells and for hydrophobic GC formulations. The mechanism of cell death differed between GCs, Hydro and TA activated the leukocyte elastase inhibitor/L-DNase II pathways but did not activate caspases. The mechanisms of cell death observed in cell cultures were similar to those observed in rat retinal explants. Taken together these results indicate that particular attention should be paid to the potential vascular side effects when administrating GCs clinically and in particular when developing sustained-release intraocular device

Condiciones didácticas y reflexión sobre el lenguaje en la elaboración de textos para recomendar libros. Una indagación con alumnos de 1º EGB

En el marco de una indagación didáctica en el contexto escolar con alumnos de 1º de Educación Básica elaboramos secuencias de enseñanza y formas de intervención docente para el aprendizaje de procedimientos de composición de textos para recomendar libros. El presente trabajo analiza las condiciones de organización de la actividad de enseñanza e intervenciones didácticas que favorecen la actividad metalingüística de los niños sobre diferentes niveles del lenguaje escrito. Observamos la relevancia de algunos criterios de organización de la secuencia de enseñanza e intervenciones docentes que desencadenaron interacciones áulicas para el trabajo cognitivo-lingüístico relativo a observar, verbalizar, reflexionar y sistematizar algunos conocimientos sobre qué escribir y cómo hacerlo.AbstractIn the frame of a didactic investigation in the school context with pupils of 1º of Basic Education we elaborate sequences of education and forms of educational intervention for the learning procedure of composition of texts to recommend books. The present work analyzes the conditions of organization of the activity of education and didactic interventions that favor the metalinguistic activity of the children on different levels of the written language. We observe the relevancy of some criteria of organization of the sequence of education and educational interventions that unleashed interactions for the cognitive - linguistic work relative to observing, verbalizing, thinking and systematizing some knowledge on what to write and how to do it

Necesariedad Teórica y Validación de la Práctica Psicopedagógica: algunos problemas

The psychopedagogical task focused on learning difficulties has legitimatedits intervention by tuming to different conceptual marks that served as itsstarting point for the understanding of the learning problem and for the legitimizationof its clinicai intervention. Serious consequences for the development of thepsychopedagogical practice were arisen from a certain tendency of applying conceptsand methods that were built in the midst of theories which are not specifically dedicatedto the psychopedagogical field, and from the lack of an epistemological reflectionabout that fact. This article attempts to enlighten the historical origin of thepsychopedagogical practice and to redefine both its object of study and its field ofproblems, as well as to reflect about some obstacles and possibilities for the developmentof an intervention theory.EI quehacer psicopedagógico dedicado a atender la dificultadpara aprender ha legitimado su intervención recurriendo a diferentes marcos conceptualesque le sirvieron como punto de partida para la comprensión deI problema deaprendizaje y para legitimar su intervención clínica. Una cierta tendencia a aplicarconceptos y métodos construídos en el seno de teorías que no se dedican específicamenteaI campo psicopedagógico y la falta de una reflexión epistemológica sobre ello, hantenido serias consecuencias para el desarrollo de la práctica psicopedagógica. Este artículotiene la intención de dar luz sobre el origen histórico de la práctica psicopedagógica yredefinir su objeto de estudio y su campo de problemas; así también como reflexionarsobre algunos obstáculos y posibilidades para el desarrollo de una teoría de la intervención

Effects of triamcinolone acetonide on vessels of the posterior segment of the eye

PURPOSE: This study investigates the effects of triamcinolone acetonide (TA) on retinal endothelial cells in vitro and explores the potential vascular toxic effect of TA injected into the vitreous cavity of rats in vivo. METHODS: Subconfluent endothelial cells were treated with either 0.1 mg/ml or 1 mg/ml TA in 1% ethanol. Control cells were either untreated or exposed to 1% ethanol. Cell viability was evaluated at 24 h, 72 h, and five days using the tetrazolium 3-(4,5-dimethylthiazol-2-yl)-2,5 phenyltetrazolium bromide test (MTT) and lactate dehydrogenase (LDH) assays. Cell proliferation was evaluated by 5-bromo-2-deoxyuridine (BrdU) test. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling assay (TUNEL assay), annexin-binding, and caspase 3 activation. Caspase-independent cell deaths were investigated by immunohistochemistry using antibodies against apoptosis inducing factor (AIF), cytochrome C, microtubule-associated protein (MAP)-light chain 3 (MAP-LC3), and Leukocyte Elastase Inhibitor/Leukocyte Elastase Inhibitor-derived DNase II (LEI/L-DNase II). In vivo, semithin and ultrathin structure analysis and vascular casts were performed to examine TA-induced changes of the choroidal vasculature. In addition, outer segments phagocytosis assay on primary retinal pigment epithelium (RPE) cells was performed to assess cyclooxygenase (COX-2) and vascular endothelial growth factor (VEGF) mRNAs upregulation with or without TA. RESULTS: The inhibitory effect of TA on cell proliferation could not explain the significant reduction in cell viability. Indeed, TA induced a time-dependent reduction of bovine retinal endothelial cells viability. Annexin-binding positive cells were observed. Cytochrome C was not released from mitochondria. L-DNase II was found translocated to the nucleus, meaning that LEI was changed into L-DNase II. AIF was found nuclearized in some cells. LC3 labeling showed the absence of autophagic vesicles. No autophagy or caspase dependent apoptosis was identified. At 1 mg/ml TA induced necrosis while exposure to lower concentrations for 3 to 5 days induced caspase independent apoptosis involving AIF and LEI/L-DNase II. In vivo, semithin and ultrathin structure analysis and vascular casts revealed that TA mostly affected the choroidal vasculature with a reduction of choroidal thickness and increased the avascular areas of the choriocapillaries. Experiments performed on primary RPE cells showed that TA downregulates the basal expression of COX-2 and VEGF and inhibits the outer segments (OS)-dependent COX-2 induction but not the OS-dependent VEGF induction. CONCLUSIONS: This study demonstrates for the first time that glucocorticoids exert direct toxic effect on endothelial cells through caspase-independent cell death mechanisms. The choroidal changes observed after TA intravitreous injection may have important implications regarding the safety profile of TA use in human eyes

A Search for Star-Disk Interaction Among the Strongest X-ray Flaring Stars in the Orion Nebula Cluster

The Chandra Orion Ultradeep Project observed hundreds of young, low-mass stars undergoing highly energetic X-ray flare events. The 32 most powerful cases have been modeled with the result that the magnetic structures responsible for these flares can be many stellar radii in extent. In this paper, we model the observed spectral energy distributions of these 32 stars in order to determine, in detail for each star, whether there is circumstellar disk material situated in sufficient proximity to the stellar surface for interaction with the large magnetic loops inferred from the observed X-ray flares. Our spectral energy distributions span the wavelength range 0.3-8 um (plus 24 um for some stars), allowing us to constrain the presence of dusty circumstellar material out to >10 AU from the stellar surface in most cases. For 24 of the 32 stars in our sample the available data are sufficient to constrain the location of the inner edge of the dusty disks. Six of these (25%) have spectral energy distributions consistent with inner disks within reach of the observed magnetic loops. Another four stars may have gas disks interior to the dust disk and extending within reach of the magnetic loops, but we cannot confirm this with the available data. The remaining 14 stars (58%) appear to have no significant disk material within reach of the large flaring loops. Thus, up to ~40% of the sample stars exhibit energetic X-ray flares that possibly arise from a magnetic star-disk interaction, and the remainder are evidently associated with extremely large, free-standing magnetic loops anchored only to the stellar surface.Comment: Accepted to the ApJ; 26 pages, 6 tables, 6 figure

Identifying Ancient Settlement Patterns through LiDAR in the Mosquitia Region of Honduras

The Mosquitia ecosystem of Honduras occupies the fulcrum between the American continents and as such constitutes a critical region for understanding past patterns of socio-political development and interaction. Heavy vegetation, rugged topography, and remoteness have limited scientific investigation. This paper presents prehistoric patterns of settlement and landuse for a critical valley within the Mosquitia derived from airborne LiDAR scanning and field investigation. We show that (i) though today the valley is a wilderness it was densely inhabited in the past; (ii) that this population was organized into a three-tiered system composed of 19 settlements dominated by a city; and, (iii) that this occupation was embedded within a human engineered landscape. We also add to a growing body of literature that demonstrates the utility of LiDAR as means for rapid cultural assessments in undocumented regions for analysis and conservation. Our ultimate hope is for our work to promote protections to safeguard the unique and critically endangered Mosquitia ecosystem and other similar areas in need of preservation

Identification of hepatitis a virus mimotopes by phage display, antigenicity and immunogenicity

A phage-displayed peptide approach was used to identify ligands mimicking antigenic determinants of hepatitis A virus (HAV) for the first time. Bacteriophages displaying HAV mimotopes were isolated from a phage-display peptide library by affinity selection on serum antibodies from hepatitis A patients. Selected phage-peptides were screened for reactivity with sera from HAV infected patients and healthy controls. Four cloned peptides with different sequences were identified as mimotopes of HAV; three of them showed similarity in their amino acid sequences with at least one of the VP3 and VP1 antigenic proteins of HAV. One clone was recognised by 92% of the positive sera. The phagotopes competed effectively with HAV for absorption of anti-HAV-specific antibodies in human sera, as determined by ELISA. The four phage clones induced neutralising anti-HAV antibodies in immunised mice. These results demonstrate the potential of this method to elucidate the disease related epitopes of HAV and to use these mimotopes in diagnostic applications or in the development of a mimotope-based hepatitis A vaccine without the necessity of manipulation of the virus