Diseño de una propuesta de enseñanza del concepto reacción química que permita la relación de los 3 niveles de representación propuesto por Johnstone en estudiantes de octavo grado.

En el presente trabajo de grado se expondrá una propuesta educativa a través del diseño de una unidad didáctica para fortalecer la enseñanza- aprendizaje del concepto de reacciones químicas, relacionando los 3 niveles de representación propuestos por Johnstone a estudiantes de Octavo grado de básica secundaria. Por tanto, lo anterior se desarrolló a través de una metodología cualitativa, y como técnica de recolección el análisis de contenido, con un enfoque interpretativo, se recopiló información sobre los elementos necesarios para la construcción de la unidad didáctica, se planificó estrategias y actividades para promover la enseñanza--aprendizaje del concepto de reacciones químicas y su relación con los niveles de representación; con el objetivo de comprender los fenómenos del entorno, resolver problemas de su cotidianidad y fortalecer la enseñanza de los contenidos de la química. Por último, se elaboró la unidad didáctica para la enseñanza ¿ aprendizaje del tema ya anteriormente mencionado, para el cual se utilizó un modelo que reúne cuatro categorías: Análisis científico, didáctico, selección de objetivos y estrategias didácticas. Y así ofrecer aportes a los docentes para que puedan transformar la planificación de sus experiencias educativas y poder mejorar su proceso de enseñanza-aprendizaje.PregradoLICENCIADO(A) EN CIENCIAS NATURALES Y EDUCACIÓN AMBIENTA

Cyclin D1 promotes neurogenesis in the developing spinal cord in a cell cycle-independent manner

Neural stem and progenitor cells undergo an important transition from proliferation to differentiation in the G1 phase of the cell cycle. The mechanisms coordinating this transition are incompletely understood. Cyclin D proteins promote proliferation in G1 and typically are down-regulated before differentiation. Here we show that motoneuron progenitors in the embryonic spinal cord persistently express Cyclin D1 during the initial phase of differentiation, while down-regulating Cyclin D2. Loss-of-function and gain-offunction experiments indicate that Cyclin D1 (but not D2) promotes neurogenesis in vivo, a role that can be dissociated from its cell cycle function. Moreover, reexpression of Cyclin D1 can restore neurogenic capacity to D2-expressing glial-restricted progenitors. The neurogenic function of Cyclin D1 appears to be mediated, directly or indirectly, by Hes6, a proneurogenic basic helic-loop-helix transcription factor. These data identify a cell cycle-independent function for Cyclin D1 in promoting neuronal differentiation, along with a potential genetic pathway through which this function is exerted

Zebrafish Her8a Is Activated by Su(H)-Dependent Notch Signaling and Is Essential for the Inhibition of Neurogenesis

Understanding how diversity of neural cells is generated is one of the main tasks of developmental biology. The Hairy/E(spl) family members are potential targets of Notch signaling, which has been shown to be fundamental to neural cell maintenance, cell fate decisions, and compartment boundary formation. However, their response to Notch signaling and their roles in neurogenesis are still not fully understood. In the present study, we isolated a zebrafish homologue of hairy/E(spl), her8a, and showed this gene is specifically expressed in the developing nervous system. her8a is positively regulated by Su(H)-dependent Notch signaling as revealed by a Notch-defective mutant and injection of variants of the Notch intracellular regulator, Su(H). Morpholino knockdown of Her8a resulted in upregulation of proneural and post-mitotic neuronal markers, indicating that Her8a is essential for the inhibition of neurogenesis. In addition, markers for glial precursors and mature glial cells were down-regulated in Her8a morphants, suggesting Her8a is required for gliogenesis. The role of Her8a and its response to Notch signaling is thus similar to mammalian HES1, however this is the converse of what is seen for the more closely related mammalian family member, HES6. This study not only provides further understanding of how the fundamental signaling pathway, Notch signaling, and its downstream genes mediate neural development and differentiation, but also reveals evolutionary diversity in the role of H/E(spl) genes

Cancer stem cells (CSCs) : metabolic strategies for their identification and eradication

Phenotypic and functional heterogeneity is one of the most relevant features of cancer cells within different tumor types and is responsible for treatment failure. Cancer stem cells (CSCs) are a population of cells with stem cell-like properties that are considered to be the root cause of tumor heterogeneity, because of their ability to generate the full rep- ertoire of cancer cell types. Moreover, CSCs have been invoked as the main drivers of metastatic dissemination and therapeutic resistance. As such, targeting CSCs may be a useful strategy to improve the effectiveness of classical anticancer therapies. Recently, metabolism has been considered as a relevant player in CSC biology, and indeed, onco- genic alterations trigger the metabolite-driven dissemination of CSCs. More interestingly, the action of metabolic pathways in CSC maintenance might not be merely a conse- quence of genomic alterations. Indeed, certain metabotypic phenotypes may play a causative role in maintaining the stem traits, acting as an orchestrator of stemness. Here, we review the current studies on the metabolic features of CSCs, focusing on the bio- chemical energy pathways involved in CSC maintenance and propagation. We provide a detailed overview of the plastic metabolic behavior of CSCs in response to microenvironment changes, genetic aberrations, and pharmacological stressors. In addition, we describe the potential of comprehensive metabolic approaches to identify and selectively eradicate CSCs, together with the possibility to ‘force’ CSCs within certain metabolic dependences, in order to effectively target such metabolic biochemical inflexibilities. Finally, we focus on targeting mitochondria to halt CSC dissemination and effectively eradicate cancer

Chronic Mitochondrial Translation Inhibition Alters Metabolic Phenotype and Stemness Properties of a Leukemic Cell Line

Recently, we demonstrated that the anti-bacterial agent tigecycline preferentially induces death in leukemia cells through the inhibition of mitochondrial protein synthesis. To better understand the mechanisms of sensitivity and resistance to mitochondrial translation inhibition, we treated TEX leukemia cells with increasing concentrations of tigecycline over 4 months, and selected a population of cells resistant to tigecycline (RTEX+TIG). Compared to their wild type counterparts, the resistant RTEX+TIG cells had an altered metabolic profile with diminished oxidative phosphorylation and a greater reliance on glycolysis. Upon removal of tigecycline from RTEX+TIG cells, the cells re-established aerobic metabolism and oxidative phosphorylation to wild type levels. At the molecular level, these cells had increased levels of HIF1a. Strikingly, tigecycline-resistant cells had decreased expression of CD34 and CD117, clonogenic growth potential and engraftment capabilities in vivo. Thus, chronic inhibition of mitochondrial translation leads to the establishment of rho-zero-like metabolic phenotype, and is associated with differentiation of leukemia cells.MAS

Development of an electrode mediated glucose sensor using iridium oxide nanoparticles

Bibliography: p. 109-119An optimized thin film of Iridium oxide (IrOx) nanoparticles with the presence of Nafion was used to encapsulate the redox enzyme, glucose oxidase (GOx). The resulting films showed an excellent response towards the detection of glucose in both an oxygenated and deoxygenated environment. It was shown that IrOx nanoparticles are mediating the direct transfer of electrons from GOx, and functioning as 4th generation glucose sensors. These sensors (0.2 to 0.008 cm2 ) demonstrated excellent stability and precision when they were tested for glucose strictly under deoxygenated environments; with a linear response up to 40 mM glucose and a sensitivity of 0.5 ?A/cm2/mM (in< 0.3 ?M of dissolved 0 2). In parallel work, an immobilized enzyme kinetic model was derived and the implication of the IrOx/GOx film properties on the apparent Km was presented. This model was also applied to experimental data to assess the interpretation of the parameter

Regulation of cortical neuron and astrocyte differentiation by the basic helix loop helix protein Hes6

During development of the mammalian cerebral cortex, pluripotent neural progenitor cells located in the ventricular zone lining the lateral ventricles give rise to neurons, astrocytes, and oligodendrocytes. Neurogenesis precedes astrocyte differentiation, followed by oligodendrocyte differentiation. The mechanisms regulating the transition of undifferentiated progenitor cells into the differentiated state are regulated in part by basic-helix-loop-helix (bHLH) transcription factors of the Hairy/Enhancer of split (Hes) family. A number of Hes proteins are induced in response to the activation of the Notch signaling pathway. Notch-activated Hes proteins, like Hes1 or Hes5, are transcriptional repressors that inhibit cortical neurogenesis and promote astrocyte differentiation. Another Hes family member, termed Hes6, is not activated in response to Notch signaling and promotes neurogenesis, in contrast to Notch-activated Hes1 and Hes5. The objectives of the present studies were a) to elucidate the molecular mechanisms underlying the pro-neuronal activity of Hes6, and b) to determine whether or not Hes6 is also involved in glial cell differentiation. To pursue these goals, a structure function analysis was performed in which mutated forms of Hes6 were examined for their ability to promote neurogenesis using primary cultures of cortical neural progenitor cells. Moreover, Hes6 and mutated forms thereof were tested to determine whether they would inhibit astrocyte differentiation. It is shown here that Hes6 inhibits astrogenesis in addition to inducing neuronal differentiation. These two activities require separate structural domains, suggesting that that they are mediated by different molecular mechanisms.Durant le développement du cortex cérébral mammifère, des cellules souches neuronales situées dans la zone ventriculaire se différencient en neurones, astrocites, et oligodendrocites. Durant ce développement la neurogenèse prend place en premier, suivi par la différenciation des astrocites et celle des oligodendrocites. Les mécanismes régulateurs de la différenciation sont en parti sous le control des facteurs de transcriptions « basic-helix-loop-helix » (bHLH) appartenant au groupe « Hairy/Enhancer of split » (Hes). Plusieures protéines Hes sont activées par la signalisation de Notch. Ces protéines, tel Hes1 et Hes5, sont des inhibiteurs de transcription durant la neurogenèse corticale et promeuvent la différentiation des astrocites. Par contre Hes6, insensible aux signaux de Notch, promeut la neurogenèse. Les objectifs de cette étude consistent à: 1) mieux comprendre les mécanismes moléculaires de l'activité de Hes6 ; 2) étudier le rôle potentiel de Hes6 dans la différenciation des cellules glies. Nous avons analysé l'habileté de différents mutants de Hes6 à promouvoir la neurogenèse en employant un système de culture cellulaire primaire de cellules souches neuronales. De plus, ces différentes formes de Hes6 ont été testées pour leur effet sur l'inhibition de la différenciation des astrocites. Nous démontrons que Hes6 inhibe l'astrogenèse et promeut la différenciation neuronale. Ces deux activités requèrent différentes domaines structurelles, laissant présager différents mécanismes moléculaires

Development of a best-fit algorithm for feature based assembly

Traditionally, domestic water pump assembly is often carried out manually using dedicated fixed systems. These are inflexible, have long manufacturing lead time and can lead to capital bottlenecks. One way of introducing flexibility is by incorporating robots. Background literature suggested that there has been limited work on the use of flexible robot-based assembly applications. But they all required sophisticated expensive software and hardware for their implementation. The paper ismainly focus on the development of best fit algorithms for feature based assembly and a process of proving the feasibility of robotic assembly applications. This research, feature-based assembly technique was used as the main method for the assembly of the components since a feature contains much more information than just geometry. A metrology system was used to locate the component and measure the position of the assembly features before assembly. Similarly, the metrology system was used to locate features on the counter part. The acquired data was processed using a mathematical algorithm to calculate the relative component positions required for optimal assembly. The data can also be used to check for the quality of the components and to reject those outside the specification limits. The paper demonstrates that with a combination of metrology and mathematical processing algorithms can be used for the assembly of water pump components within the tolerances limits. The developed system is flexible and reconfigurable due to reduce reliance of fixtures

Glucose detection based on electrochemically formed Ir oxide films

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