Browsing by Author "Lopez, Ximena"

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    A Monitoring and Evaluation Scheme for an ICT-Supported Education Program in Schools
    (NATL TAIWAN NORMAL UNIV, TAIWAN, 2010) Rodriguez, Patricio; Nussbaum, Miguel; Lopez, Ximena; Sepulveda, Marcos
    More than 20 years after ICTs were introduced in schools, solid evidence of their impact on student attainment is still lacking. Reasons for this include the mismatch between the methods used to measure the effects and the type of learning promoted, the absence of information regarding the specific types of ICT used, and the scarce attention paid to the monitoring and evaluation of ICT for Education (ICT4E) programs. A monitoring and evaluation scheme would provide qualitative and quantitative data to refine, adjust and improve an ICT4E project, to learn from the experience gained, and to determine whether the program has served its client communities and how it might be replicated.
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    A physiologic rise in cytoplasmic calcium ion signal increases pannexin1 channel activity via a C-terminus phosphorylation by CaMKII
    (2021) Lopez, Ximena; Palacios-Prado, Nicolas; Guiza, Juan; Escamilla, Rosalba; Fernandez, Paola; Vega, Jose L.; Rojas, Maximiliano; Marquez-Miranda, Valeria; Chamorro, Eduardo; Cardenas, Ana M.; Maldifassi, Maria Constanza; Martinez, Agustin D.; Duarte, Yorley; Gonzalez-Nilo, Fernando D.; Saez, Juan C.
    Pannexin1 (Panx1) channels are ubiquitously expressed in vertebrate cells and are widely accepted as adenosine triphosphate (ATP)-releasing membrane channels. Activation of Panx1 has been associated with phosphorylation in a specific tyrosine residue or cleavage of its C-terminal domains. In the present work, we identified a residue (S394) as a putative phosphorylation site by Ca2+/calmodulin-dependent kinase II (CaMKII). In HeLa cells transfected with rat Panx1 (rPanx1), membrane stretch (MS)-induced activation- measured by changes in DAPI uptake rate-was drastically reduced by either knockdown of Piezo1 or pharmacological inhibition of calmodulin or CaMKII. By site-directed mutagenesis we generated rPanx1S394A-EGFP (enhanced green fluorescent protein), which lost its sensitivity to MS, and rPanx1S394D-EGFP, mimicking phosphorylation, which shows high DAPI uptake rate without MS stimulation or cleavage of the C terminus. Using whole-cell patch-clamp and outside-out excised patch configurations, we found that rPanx1EGFP and rPanx1S394D-EGFP channels showed current at all voltages between +/- 100 mV, similar single channel currents with outward rectification, and unitary conductance (similar to 30 to 70 pS). However, using cell-attached configuration we found that rPanx1S394D-EGFP channels show increased spontaneous unitary events independent of MS stimulation. In silico studies revealed that phosphorylation of S394 caused conformational changes in the selectivity filter and increased the average volume of lateral tunnels, allowing ATP to be released via these conduits and DAPI uptake directly from the channel mouth to the cytoplasmic space. These results could explain one possible mechanism for activation of rPanx1 upon increase in cytoplasmic Ca2+ signal elicited by diverse physiological conditions in which the C-terminal domain is not cleaved.
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    Designing and implementing a test for measuring cultural dimensions in primary school
    (2018) Gelerstein, Damian; Nussbaum Voehl, Miguel; Lopez, Ximena; Cortes, Ana; Castillo, Cristobal; Chiuminatto, Pablo; Ovalle, Francisca
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    Differences in Views of School Principals and Teaches regarding Technology Integration
    (2017) Claro, Magdalena; Nussbaum, Miguel; Lopez, Ximena; Contardo, Victoria
    This paper studies the similarities and differences among the views of school principals and teachers regarding a mobile computer lab (MCL) initiative implemented in 1,591 public schools in Chile. It also characterizes the aspects in which their views diverge. A mixed methods study was carried out in two stages: first, a quantitative stage, where a self- administered (web-based) questionnaire was sent to the schools; and second, a qualitative stage, where a case study was conducted with three schools. The results show a greater convergence of the teachers' and school principals' views regarding the contribution of ICT resources to teaching, with more divergence when it comes to the implementation process. More specifically, these differences were related to two points: (1) how appropriate the conditions were for using and learning how to use the new resources within the context of the school, and (2) who should be held accountable for integrating ICT resources within the school organization. Furthermore, the qualitative results revealed that school principals only had vague information on the pedagogical integration of the MCLs in their schools. These findings suggest that in order to have more effective technology integration processes in schools, a closer presence of school leaders in the teachers' everyday pedagogical activities is required.
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    Endogenous pannexin1 channels form functional intercellular cell-cell channels with characteristic voltage-dependent properties
    (2022) Palacios-Prado, Nicolas; Soto, Paola A.; Lopez, Ximena; Choi, Eun Ju; Marquez-Miranda, Valeria; Rojas, Maximiliano; Duarte, Yorley; Lee, Jinu; Gonzalez-Nilo, Fernando D.; Saez, Juan C.
    The occurrence of intercellular channels formed by pannexin1 has been challenged for more than a decade. Here, we provide an electrophysiological characterization of exoge-nous human pannexin1 (hPanx1) cell-cell channels expressed in HeLa cells knocked out for connexin45. The observed hPanx1 cell-cell channels show two phenotypes: O-state and S-state. The former displayed low transjunctional voltage (Vj) sensitivity and single -channel conductance of -175 pS, with a substate of -35 pS; the latter showed a pecu-liar dynamic asymmetry in Vj dependence and single-channel conductance identical to the substate conductance of the O-state. S-state hPanx1 cell-cell channels were also iden-tified between TC620 cells, a human oligodendroglioma cell line that endogenously expresses hPanx1. In these cells, dye and electrical coupling increased with temperature and were strongly reduced after hPanx1 expression was knocked down by small interfer-ing RNA or inhibited with Panx1 mimetic inhibitory peptide. Moreover, cell-cell cou-pling was augmented when hPanx1 levels were increased with a doxycycline-inducible expression system. Application of octanol, a connexin gap junction (GJ) channel inhibi-tor, was not sufficient to block electrical coupling between HeLa KO Cx45-hPanx1 or TC620 cell pairs. In silico studies suggest that several arginine residues inside the chan-nel pore may be neutralized by hydrophobic interactions, allowing the passage of DAPI, consistent with dye coupling observed between TC620 cells. These findings demonstrate that endogenously expressed hPanx1 forms intercellular cell-cell channels and their unique properties resemble those described in innexin-based GJ channels. Since Panx1 is ubiquitously expressed, finding conditions to recognize Panx1 cell-cell channels in different cell types might require special attention.
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    Introducing 1 to 1 in the Classroom: A Large-scale Experience in Chile
    (2013) Claro, Magdalena; Nussbaum, Miguel; Lopez, Ximena; Diaz, Anita
    This paper presents the results of a study that sought to understand how a strategy of Mobile Computer Labs (MCL) has been integrated into 3rd and 4th grade teaching-learning practices in 1,591 state schools in Chile. In particular, the study aims to identify the most important factors related to MCL integration into these practices a year after its implementation. The findings obtained by applying a survey and performing classroom observations show that, although the schools are willing to use this resource, it has been used sporadically for searching information and drilling and practicing contents related to Mathematics and Language, in addition to motivating students. Furthermore, the classroom observations do not reveal any innovative teaching strategies, related to the use of this new technology. The study shows that amongst the main reasons for this traditional and sporadic use of the MCL are a lack of targeted teacher training and preparation time, and insufficient technical and pedagogical support during the phases of implementation and integration to the pedagogical practices.