El aprendizaje de distintos dominios notacionales según niños de preescolar y primer grado

Se investiga si las concepciones de los niños acerca del aprendizaje adoptan matices diferentes según tres dominios notacionales: dibujo, escritura y notación numérica. Se entrevistó individualmente a 120 alumnos de preescolar (60) y primer grado (60) de escuelas públicas en Argentina. Se aplicó la lexicometría a las transcripciones de sus respuestas completas a tres preguntas referidas a la actividad, dificultades y metas en relación al propio aprendizaje del dibujo, escritura o notación numérica. Los resultados revelan diferencias significativas en cómo los niños refieren el contenido de aprendizaje y a sí mismos como aprendices según el dominio, indicando una teoría interpretativa del aprendizaje en relación al dibujo y la notación numérica, y una teoría directa en relación a la escritura.-1. Introducción. -2. Objetivos. -3. Método. -4. Análisis y resultados. -5. Conclusión. Lista de referencias

Single-cell analysis of cardiogenesis reveals basis for organ-level developmental defects.

Organogenesis involves integration of diverse cell types; dysregulation of cell-type-specific gene networks results in birth defects, which affect 5% of live births. Congenital heart defects are the most common malformations, and result from disruption of discrete subsets of cardiac progenitor cells1, but the transcriptional changes in individual progenitors that lead to organ-level defects remain unknown. Here we used single-cell RNA sequencing to interrogate early cardiac progenitor cells as they become specified during normal and abnormal cardiogenesis, revealing how dysregulation of specific cellular subpopulations has catastrophic consequences. A network-based computational method for single-cell RNA-sequencing analysis that predicts lineage-specifying transcription factors2,3 identified Hand2 as a specifier of outflow tract cells but not right ventricular cells, despite the failure of right ventricular formation in Hand2-null mice4. Temporal single-cell-transcriptome analysis of Hand2-null embryos revealed failure of outflow tract myocardium specification, whereas right ventricular myocardium was specified but failed to properly differentiate and migrate. Loss of Hand2 also led to dysregulation of retinoic acid signalling and disruption of anterior-posterior patterning of cardiac progenitors. This work reveals transcriptional determinants that specify fate and differentiation in individual cardiac progenitor cells, and exposes mechanisms of disrupted cardiac development at single-cell resolution, providing a framework for investigating congenital heart defects

Spatial effects on species persistence and implications for biodiversity

Natural ecosystems are characterized by striking diversity of form and functions and yet exhibit deep symmetries emerging across scales of space, time and organizational complexity. Species-area relationships and species-abundance distributions are examples of emerging patterns irrespective of the details of the underlying ecosystem functions. Here we present empirical and theoretical evidence for a new macroecological pattern related to the distributions of local species persistence times, defined as the timespans between local colonizations and extinctions in a given geographic region. Empirical distributions pertaining to two different taxa, breeding birds and herbaceous plants, analyzed in a new framework that accounts for the finiteness of the observational period, exhibit power-law scaling limited by a cut-off determined by the rate of emergence of new species. In spite of the differences between taxa and spatial scales of analysis, the scaling exponents are statistically indistinguishable from each other and significantly different from those predicted by existing models. We theoretically investigate how the scaling features depend on the structure of the spatial interaction network and show that the empirical scaling exponents are reproduced once a two-dimensional isotropic texture is used, regardless of the details of the ecological interactions. The framework developed here also allows to link the cut-off timescale with the spatial scale of analysis, and the persistence-time distribution to the species-area relationship. We conclude that the inherent coherence obtained between spatial and temporal macroecological patterns points at a seemingly general feature of the dynamical evolution of ecosystems.Comment: 5 pages, 5 figures. Supplementary materials avaliable on http://www.pnas.org/content/108/11/434

Protein degradation by ubiquitin-proteasome system in formation and labilization of contextual conditioning memory

The ubiquitin-proteasome system (UPS) of protein degradation has been evaluated in different forms of neural plasticity and memory. The role of UPS in such processes is controversial. Several results support the idea that the activation of this system in memory consolidation is necessary to overcome negative constrains for plasticity. In this case, the inhibition of the UPS during consolidation impairs memory. Similar results were reported for memory reconsolidation. However, in other cases, the inhibition of UPS had no effect on memory consolidation and reconsolidation but impedes the amnesic action of protein synthesis inhibition after retrieval. The last finding suggests a specific action of the UPS inhibitor on memory labilization. However, another interpretation is possible in terms of the synthesis/degradation balance of positive and negative elements in neural plasticity, as was found in the case of long-term potentiation. To evaluate these alternative interpretations, other reconsolidation-interfering drugs than translation inhibitors should be tested. Here we analyzed initially the UPS inhibitor effect in contextual conditioning in crabs. We found that UPS inhibition during consolidation impaired long-term memory. In contrast, UPS inhibition did not affect memory reconsolidation after contextual retrieval but, in fact, impeded memory labilization, blocking the action of drugs that does not affect directly the protein synthesis. To extend these finding to vertebrates, we performed similar experiments in contextual fear memory in mice. We found that the UPS inhibitor in hippocampus affected memory consolidation and blocked memory labilization after retrieval. These findings exclude alternative interpretations to the requirement of UPS in memory labilization and give evidence of this mechanism in both vertebrates and invertebrates.Fil: Fustiñana, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: de la Fuente, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Federman, Maria Noel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Freudenthal, Ramiro A. M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Romano, Arturo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentin

SST-GATE: A dual mirror telescope for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) will be the world's first open observatory for very high energy gamma-rays. Around a hundred telescopes of different sizes will be used to detect the Cherenkov light that results from gamma-ray induced air showers in the atmosphere. Amongst them, a large number of Small Size Telescopes (SST), with a diameter of about 4 m, will assure an unprecedented coverage of the high energy end of the electromagnetic spectrum (above ~1TeV to beyond 100 TeV) and will open up a new window on the non-thermal sky. Several concepts for the SST design are currently being investigated with the aim of combining a large field of view (~9 degrees) with a good resolution of the shower images, as well as minimizing costs. These include a Davies-Cotton configuration with a Geiger-mode avalanche photodiode (GAPD) based camera, as pioneered by FACT, and a novel and as yet untested design based on the Schwarzschild-Couder configuration, which uses a secondary mirror to reduce the plate-scale and to allow for a wide field of view with a light-weight camera, e.g. using GAPDs or multi-anode photomultipliers. One objective of the GATE (Gamma-ray Telescope Elements) programme is to build one of the first Schwarzschild-Couder prototypes and to evaluate its performance. The construction of the SST-GATE prototype on the campus of the Paris Observatory in Meudon is under way. We report on the current status of the project and provide details of the opto-mechanical design of the prototype, the development of its control software, and simulations of its expected performance.Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223

NGC 2660: Gaia DR2, ASteCA and the end of controversies?

NGC 2660, un cumulo abierto viejo y muy compacto localizado a aproximadamente 3 kpc del Sol en una región de absorción moderada, ha sido objeto de varios estudios fotométricos y espectroscopicos en el pasado. Surgen controversias en cuanto a su distancia, antigüedad y contenido metalice. Las comparaciones llevadas a cabo por investigaciones anteriores con modelos sintéticos de cúmulos no las resolvieron. Decidimos analizar este objeto combinando paralaje de alta precisión, movimientos propios y magnitudes procedentes del Gaia Second Data Release (Gaia DR2) para mejorar los parámetros fundamentales del cumulo. Para ello seleccionamos los datos de Gaia DR2 en una región de 1 grado de lado centrada en NGC 2660. Para la identificación de miembros utilizamos el código pyUPMASK y completamos el análisis general del cumulo con el código ASteCA. La secuencia principal del cumulo muestra un turn-off point bien definido, aunque algunas estrellas se ubican por encima de el, en la posición típica de las estrellas blue stragglers. Hay un evidente ensanchamiento de la secuencia principal, que es difícil de atribuir solo a errores fotométricos, siendo mas probable que ella se deba a un alto porcentaje de estrellas binarias.NGC 2660, an old and very compact open cluster placed at about 3 kpc from the Sun in a region ofmoderate absorption, has been subject of several photometric and spectroscopic studies in the past. Controversies arise in terms of its distance, age and metal content. Previous comparisons with cluster synthetic models carried out did not resolve them. We decided to analyze this object combining high precision parallax, proper motions and magnitudes coming from the Gaia Second Data release (Gaia DR2), in order to improve the cluster fundamental parameters. So we collect Gaia DR2 data in region 1 deg on a side, centered in NGC 2660. For the membership estimation, we run the pyUPMASK code and completed the overall cluster analysis with the ASteCA code. The cluster main sequence shows a well-defined turn-off point although some stars are placed above it, resembling the typical position of blue straggler stars. There is an evident widening of the main sequence hard to be explained by just photometric errors becoming more probable that it is produced by a high percentage of binary stars.Fil: Giorgi, E. E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Perren, Gabriel Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: De Laurenti, M. A.. No especifíca;Fil: Solivella, Gladys Rebeca. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Pera, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Cruzado, Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Vazquez, Ruben Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina62º Reunión Anual de la Asociación Argentina de AstronomíaRosarioArgentinaAsociación Argentina de Astronomí

Muscle, functional and cognitive adaptations after flywheel resistance training in stroke patients : a pilot randomized controlled trial

Resistance exercise (RE) improves neuromuscular function and physical performance after stroke. Yet, the effects of RE emphasizing eccentric (ECC; lengthening) actions on muscle hypertrophy and cognitive function in stroke patients are currently unknown. Thus, this study explored the effects of ECC-overload RE training on skeletal muscle size and function, and cognitive performance in individuals with stroke. Thirty-two individuals with chronic stroke (≥6 months post-stroke) were randomly assigned into a training group (TG; n = 16) performing ECC-overload flywheel RE of the more-affected lower limb (12 weeks, 2 times/week; 4 sets of 7 maximal closed-chain knee extensions; <2 min of contractile activity per session) or a control group (CG; n = 16), maintaining daily routines. Before and after the intervention, quadriceps femoris volume, maximal force and power for each leg were assessed, and functional and dual task performance, and cognitive functions were measured. Quadriceps femoris volume of the more-affected leg increased by 9.4 % in TG. Muscle power of the more-affected, trained (48.2 %), and the less-affected, untrained limb (28.1 %) increased after training. TG showed enhanced balance (8.9 %), gait performance (10.6 %), dual-task performance, executive functions (working memory, verbal fluency tasks), attention, and speed of information processing. CG showed no changes. ECC-overload flywheel resistance exercise comprising 4 min of contractile activity per week offers a powerful aid to regain muscle mass and function, and functional performance in individuals with stroke. While the current intervention improved cognitive functions, the cause-effect relationship, if any, with the concomitant neuromuscular adaptations remains to be explored. Clinical Trial

Computational Stem Cell Biology: Open Questions and Guiding Principles

Computational biology is enabling an explosive growth in our understanding of stem cells and our ability to use them for disease modeling, regenerative medicine, and drug discovery. We discuss four topics that exemplify applications of computation to stem cell biology: cell typing, lineage tracing, trajectory inference, and regulatory networks. We use these examples to articulate principles that have guided computational biology broadly and call for renewed attention to these principles as computation becomes increasingly important in stem cell biology. We also discuss important challenges for this field with the hope that it will inspire more to join this exciting area

Feasibility of laparoscopy for small bowel obstruction

<p>Abstract</p> <p>Background</p> <p>Adherential pathology is the most common cause of small bowel obstruction. Laparoscopy in small bowel obstruction does not have a clear role yet; surely it doesn't always represent only a therapeutic act, but it is always a diagnostic act, which doesn't interfere with abdominal wall integrity.</p> <p>Methods</p> <p>We performed a review without any language restrictions considering international literature indexed from 1980 to 2007 in Medline, Embase and Cochrane Library. We analyzed the reference lists of the key manuscripts. We also added a review based on international non-indexed sources.</p> <p>Results</p> <p>The feasibility of diagnostic laparoscopy is high (60–100%), while that of therapeutic laparoscopy is low (40–88%). The frequency of laparotomic conversions is variable ranging from 0 to 52%, depending on patient selection and surgical skill. The first cause of laparotomic conversion is a difficult exposition and treatment of band adhesions. The incidence of laparotomic conversions is major in patients with anterior peritoneal band adhesions. Other main causes for laparotomic conversion are the presence of bowel necrosis and accidental enterotomies. The predictive factors for successful laparoscopic adhesiolysis are: number of previous laparotomies ≤ 2, non-median previous laparotomy, appendectomy as previous surgical treatment causing adherences, unique band adhesion as phatogenetic mechanism of small bowel obstruction, early laparoscopic management within 24 hours from the onset of symptoms, no signs of peritonitis on physical examination, experience of the surgeon.</p> <p>Conclusion</p> <p>Laparoscopic adhesiolysis in small bowel obstruction is feasible but can be convenient only if performed by skilled surgeons in selected patients. The laparoscopic adhesiolysis for small bowel obstruction is satisfactorily carried out when early indicated in patients with a low number of laparotomies resulting in a short hospital stay and a lower postoperative morbidity. Although a higher small bowel obstruction recurrence remains the major postoperative risk of the laparoscopic management of these patients.</p