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Upon interaction with immobilized antigens B cells form an immune synapse, where actin remodeling and re-positioning of the microtubule-organizing center (MTOC) together with lysosomes can facilitate antigen extraction. B cells have restricted cytoplasmic space, mainly occupied by a large nucleus, yet the role of nuclear morphology in the formation of the immune synapse has not been addressed. Here we show that, upon activation, B cells re-orientate and adapt the size of their nuclear groove facing the immune synapse, where the MTOC sits and lysosomes accumulate. Silencing nuclear envelope proteins, Nesprin-1 and Sun-1, impairs nuclear reorientation towards the synapse and leads to defects in actin organization at this level. Consequently, B cells are unable to internalize the BCR after antigen activation. Nesprin-1 and Sun-1-silenced B cells also fail to accumulate the tethering factor Exo70 at the center of the synaptic membrane and display defective lysosome positioning, impairing efficient antigen extraction at the immune synapse. Thus, changes in nuclear morphology and positioning emerge as critical regulatory steps to coordinate B cell activation.

18 páginas This research examined challenges faced by novice principals in Colombia in connecting to their school communities through their socialisation processes. Interviews with 37 newly appointed principals in rural and urban schools revealed that the complexity of their school contexts accentuated the need to work on the relational dimension of their jobs. Forging relationships with teachers and parents based on trust and communication, introspection and knowledge about their school communities emerged as crucial factors to foster social justice and to transcend deficit views of their communities. The article questions the role of supporting services for novice principals, emphasises the importance of organisational socialisation, and stresses the role of preparation programs in providing principals with tools for learning during this phase of their professional careers.

Resumen Objetivos: Realizar el análisis estructural de fragmentos de bosque seco tropical encontrados en la ecorregión estratégica de la Tatacoa y su área de influencia en el sur del departamento del Tolima; y detallar los patrones de estructura vertical, horizontal y total para generar conocimiento que permita enriquecer los pocos estudios existentes y contribuir al uso sostenible, conservación y restauración de los bosques secos del valle interandino del Magdalena. Metodología: Se seleccionaron 12 relictos boscosos y se estableció una parcela de ¼ de ha en cada uno; se midieron e identificaron los árboles con DAP ≥ 5 cm, caracterizando la estructura horizontal mediante el índice de valor de importancia y cociente de mezcla; se realizaron perfiles de vegetación, diagramas de dispersión de Ogawa; se calcularon distribuciones diamétricas y área basal. Resultados: Se encontró que los bosques tienden a ser homogéneos con dominancia de especies tales como Curatella americana, Astronium graveolens, Anacardium excelsum, Trichilia sp., Anadenanthera peregrina, Guazuma ulmifolia y Tabebuia chrysantha. La estructura vertical mostró dos tendencias, una de bosques de porte bajo en áreas planas a onduladas y otra con bosques más altos en áreas de pendiente. La mayoría de los bosques tienen tres estratos y pocos árboles emergentes. La distribución diamétrica tiende a tener estructura de modelo exponencial en j invertida a excepción de dos bosques. El área basal por hectárea osciló entre 3-23 m2. Los bosques presentan patrones similares a bosques del norte del Tolima, la Costa Atlántica y otras regiones neotropicales como Bolivia y Perú. Conclusiones: Estos bosques presentan estados sucesionales intermedios, aunque son muy intervenidos aún tienen un potencial importante de biodiversidad forestal y podrían tomarse como ecosistemas de referencia para procesos de restauración ecológica del valle interandino del Magdalena. Abstract Objectives: to carry out the structural analysis of fragments of tropical dry forest found in the Strategic Ecoregion of La Tatacoa and its area of influence in the south of the department of Tolima, and to detail the vertical, horizontal and total structure patterns to generate knowledge that allows enriching the few existing studies and contribute to the sustainable use, conservation and restoration of the dry forests of the inter-Andean valley of Magdalena. Methodology: Twelve forest relicts were selected and a plot of ¼ ha was established in each one. They were measured and trees with DBH ≥ 5 cm were identified characterizing the horizontal structure by means of the Importance Value Index (IVI) and mixing ratio. Vegetation profiles and Ogawa scatter diagrams were made; diametric distributions and basal area were calculated. Results: It was found that forests tend to be homogeneous, with dominance of species such as Curatella americana, Astronium graveolens, Anacardium excelsum, Trichilia sp, Anadenanthera peregrina, Guazuma ulmifolia and Tabebuia crhysantha. The vertical structure showed two tendencies, one of low forests on flat to undulated areas, and another with higher forests in steep areas. Most forests have three arboreal strata and few emerging trees. The diameter distribution tends to have an exponential model structure in reversed J shape curve with the exception of two forests. The basal area per hectare ranged from 3 to 23 m2. Forests have similar patterns to forest in northern Tolima, the Atlantic coast and other neotropical regions such as Bolivia and Peru. Conclusions: these forests have intermediate successional stages and, although they are heavily intervened, still have an important potential for forest biodiversity and could be considered as reference ecosystems for ecological restoration processes in the Andean valleys of the Magdalena River.

Resumen El presente artículo presenta un estudio realizado con 25 estudiantes de primer año de educación primaria, a los cuales se les se implementó una secuencia didáctica con actividades basadas en el enfoque de “Respuesta Física Total” para mejorar la inteligibilidad en la pronunciación del inglés. En esta secuencia didáctica los estudiantes observaron imágenes y escucharon vocabulario mediante videos y canciones, relacionándolos con movimientos corporales e interactuando a través de breves diálogos. La recolección de datos se obtuvo de un pre-test y post-test de pronunciación oral conformados por tres ítems: repetición de palabras, descripción de objetos y presentación oral, cuyos datos se procesaron mediante un análisis de frecuencia y porcentual. Asimismo, se llevó a cabo un análisis temático para las notas de campo y las entrevistas realizadas. Los resultados reflejaron un mejoramiento en la pronunciación a nivel de palabras, frases y oraciones en inglés, lo que permitió que los participantes produjeran mensajes inteligibles. Abstract English pronunciation for first year primary school students: a didacticsequence implementation for its improvement This article presents a study conducted on 25 first-year primary school students. A didactic sequence was implemented utilizing activities that allowed participants to improve their intelligibility in the English pronunciation. The activities were primarily based on the Total Physical Response method for English teaching. In this didactic sequence the students observed images and listened to vocabulary through videos and songs, relating them to body movements and interacting through brief dialogues. The data collection was carried out with a Pre and Post-Oral Pronunciation test, which included three items: Repetition of Words, Description of Objects, and Oral Presentation; the data obtained was processed by frequency and percentage. Likewise, a thematic analysis was conducted for field notes and interviews. The results revealed an improvement in the pronunciation at word, phrase, and sentence levels in English, and participants achieved an intelligible message.