La enseñanza de las ciencias mediante proyectos didácticos en la Universidad de los Andes - Venezuela

Los paradigmas de la pedagogía científica incorporan estrategias activas, pero, en el trabajo de aula sigue prevaleciendo el modelo pasivo. En contraposición a esto, el presente ensayo describe la experiencia que hemos acumulado desde 1999 con el desarrollo de una metodología denominada Proyectos Didácticos para la Enseñanza de la Ciencia que tiene por finalidad principal aportar diferentes propuestas metodológicas para abordar el trabajo de aula y fuera de ésta, para el caso especial de la enseñanza de las ciencias. Esta estrategia implica la participación activa del estudiante diseñando propuestas prácticas o juegos para el desarrollo de diversos contenidos típicos de la ciencia en el contexto de la formación inicial de docentes en la Universidad de Los Andes

The histone deacetylase inhibitor valproic acid attenuates phospholipase Cγ2 and IgE-mediated mast cell activation.

Mast cell activation through the high-affinity IgE receptor (FcεRI) plays a central role in allergic reactions. FcεRI-mediated activation triggers multiple signaling pathways leading to degranulation and synthesis of different inflammatory mediators. IgE-mediated mast cell activation can be modulated by different molecules, including several drugs. Herein, we investigated the immunomodulatory activity of the histone deacetylase inhibitor valproic acid (VPA) on IgE-mediated mast cell activation. To this end, bone marrow-derived mast cells (BMMC) were sensitized with IgE and treated with VPA followed by FcεRI cross-linking. The results indicated that VPA reduced mast cell IgE-dependent degranulation and cytokine release. VPA also induced a significant reduction in the cell surface expression of FcεRI and CD117, but not other mast cell surface molecules. Interestingly, VPA treatment inhibited the phosphorylation of PLCγ2, a key signaling molecule involved in IgE-mediated degranulation and cytokine secretion. However, VPA did not affect the phosphorylation of other key components of the FcεRI signaling pathway, such as Syk, Akt, ERK1/2, or p38. Altogether, our data demonstrate that VPA affects PLCγ2 phosphorylation, which in turn decreases IgE-mediated mast cell activation. These results suggest that VPA might be a key modulator of allergic reactions and might be a promising therapeutic candidate

An AGAMOUS-related MADS-box gene, XAL1 (AGL12), regulates root meristem cell proliferation and flowering transition in Arabidopsis

11 pages, 5 figures, 1 table.-- PMID: 18203871 [PubMed].-- PMCID: PMC2259045.-- Supplementary information available at: http://www.plantphysiol.org/cgi/content/full/pp.107.108647/DC1MADS-box genes are key components of the networks that control the transition to flowering and flower development, but their role in vegetative development is poorly understood. This article shows that the sister gene of the AGAMOUS (AG) clade, AGL12, has an important role in root development as well as in flowering transition. We isolated three mutant alleles for AGL12, which is renamed here as XAANTAL1 (XAL1): Two alleles, xal1-1 and xal1-2, are in Columbia ecotype and xal1-3 is in Landsberg erecta ecotype. All alleles have a short-root phenotype with a smaller meristem, lower rate of cell production, and abnormal root apical meristem organization. Interestingly, we also encountered a significantly longer cell cycle in the strongest xal1 alleles with respect to wild-type plants. Expression analyses confirmed the presence of XAL1 transcripts in roots, particularly in the phloem. Moreover, XAL1beta-glucuronidase expression was specifically up-regulated by auxins in this tissue. In addition, mRNA in situ hybridization showed that XAL1 transcripts were also found in leaves and floral meristems of wild-type plants. This expression correlates with the late-flowering phenotypes of the xal1 mutants grown under long days. Transcript expression analysis suggests that XAL1 is an upstream regulator of SOC, FLOWERING LOCUS T, and LFY. We propose that XAL1 may have similar roles in both root and aerial meristems that could explain the xal1 late-flowering phenotype.This work was supported by Consejo Nacional de Ciencia y Tecnología (CONACYT), México (grant nos. CO1.41848/A–1, CO1.0538/A–1, and CO1.0435.B–1); Dirección General de Asuntos del Personal Académico (DGAPA)-Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica (PAPIIT), Universidad Nacional Autónoma de México (UNAM; grant nos. IN230002 and IX207104); and the University of California-MEXUS ECO IE 271 to E.R.A.-B. R.T.-L. was a recipient of CONACYT and DGAPA-PAPIIT-UNAM fellowships (no. IX225304). J.G.D. was supported by DGAPA-PAPIIT-UNAM (grant nos. IN210202 and IN225906) and CONACYT (grant no. 49267).Peer reviewe

Valproic acid restricts mast cell activation by Listeria monocytogenes.

Mast cells (MC) play a central role in the early containment of bacterial infections, such as that caused by Listeria monocytogenes (L.m). The mechanisms of MC activation induced by L.m infection are well known, so it is possible to evaluate whether they are susceptible to targeting and modulation by different drugs. Recent evidence indicates that valproic acid (VPA) inhibits the immune response which favors L.m pathogenesis in vivo. Herein, we examined the immunomodulatory effect of VPA on L.m-mediated MC activation. To this end, bone marrow-derived mast cells (BMMC) were pre-incubated with VPA and then stimulated with L.m. We found that VPA reduced MC degranulation and cytokine release induced by L.m. MC activation during L.m infection relies on Toll-Like Receptor 2 (TLR2) engagement, however VPA treatment did not affect MC TLR2 cell surface expression. Moreover, VPA was able to decrease MC activation by the classic TLR2 ligands, peptidoglycan and lipopeptide Pam3CSK4. VPA also reduced cytokine production in response to Listeriolysin O (LLO), which activates MC by a TLR2-independent mechanism. In addition, VPA decreased the activation of critical events on MC signaling cascades, such as the increase on intracellular Ca2+ and phosphorylation of p38, ERK1/2 and -p65 subunit of NF-κB. Altogether, our data demonstrate that VPA affects key cell signaling events that regulate MC activation following L.m infection. These results indicate that VPA can modulate the functional activity of different immune cells that participate in the control of L.m infection

Hojas de Leucaena leucocephala en la alimentación de patos en crecimiento

To evaluate the productive behavior of growing ducks with different levels of substitution of the concentrate by leaves of Leucaena leucocephala, 90 ducks of 27 days of age were used with a weight of 328 ± 12 g distributed in 9 groups of 10 animals under a completely design randomized, divided into 3 treatments: a control with concentrate; while the remaining two consisted of restrictions of 10 and 20% respectively, in both cases with supply of Leucaena leaves at will. The evaluation period lasted 40 days, which included weighings every 10 days. The data obtained during the study showed that there were no significant differences for consumption, daily gain and feed conversion. On the other hand, for the total conversion of the food, significant differences were obtained (P <0.05), with values ​​of 4.05; 5.34 and 5.56 g of DM / kg of weight gain in 0; 10 and 20% substitution of the concentrate, respectively. The channel yield behaved in the same way (P <0.01) with 48.4; 43.1 and 44.0%. Producing 1 t of meat with the control treatment diet costs $11.2; while with the experimental ones, the cost is$ 10.8, all in local currency, according to the economic analysis. These results show that the use of Leucaena leucocephala in the feeding of growing ducks is feasible, replacing up to 20% the concentrate.Para evaluar el comportamiento productivo de patos en crecimiento con diferentes niveles de sustitución del concentrado por hojas de Leucaena leucocephala, se utilizaron 90 patos de 27 días de edad con un peso de 328 ± 12 g distribuidos en 9 grupos de 10 animales bajo un diseño completamente aleatorizado, divididos en 3 tratamientos: un control con concentrado; mientras que los dos restantes consistieron en restricciones de 10 y 20% respectivamente, en ambos casos con suministro de hojas de Leucaena a voluntad. El periodo de evaluación duró 40 días, que incluyó pesajes cada 10 días. Los datos obtenidos durante el estudio demostraron que no existieron diferencias significativas para el consumo, la ganancia diaria y la conversión del pienso. Por otra parte para la conversión total del alimento se obtuvieron diferencias significativas (P<0,05), con valores de 4,05; 5,34 y 5,56 g de MS /kg de aumento de peso en 0; 10 y 20% de sustitución del concentrado, respectivamente. El rendimiento en canal se comportó de igual forma (P<0,01) con 48,4; 43,1 y 44,0 %. Producir 1 t de carne con la dieta del tratamiento control cuesta $11,2; mientras que con las experimentales el costo es de$10,8, todo ello en moneda nacional, según el análisis económico. Estos resultados demuestran que es factible el uso de la Leucaena leucocephala en la alimentación de patos en crecimiento, sustituyendo hasta un 20% el concentrado

Nucleation of (4)R^{(4)}R Brane Universes

The creation of brane universes induced by a totally antisymmetric tensor living in a fixed background spacetime is presented, where a term involving the intrinsic curvature of the brane is considered. A canonical quantum mechanical approach employing Wheeler-DeWitt equation is done. The probability nucleation for the brane is calculated taking into account both an instanton method and a WKB approximation. Some cosmological implications arose from the model are presented.Comment: 19 pages, 2 figure

Molecular Processing of Tau Protein in Progressive Supranuclear Palsy : Neuronal and Glial Degeneration

ACKNOWLEDGMENTS This work was supported by Fondo Nacional de Ciencia y Tecnologia, FONDOCyT, from the Ministry of Higher Education, Science and Technology, Dominican Republic (2015-3A2-127 to MP-H) and (2018-2019-2A3-208 to JL-M and MP-H). The authors want to express their gratitude to the following: Dr. P. Davies† (Albert Einstein College of Medicine, Bronx, NY, USA) and Lester I. Binder† (North Western, Chicago, IL, USA) for the generous gift of mAbs TG–3 and Alz–50, and Tau–1, Tau–5 and Tau–7, respectively; Tec. Amparo Viramontes Pintos for the handling of the brain tissue; support in the confocal microscopy unit of CIIDIR Durango, Instituto Politecnico Nacional; Union Medica Uni- A. Mart´ınez-Maldonado et al. / Molecular Processing of Tau Protein in Progressive Supranuclear Palsy 1529 versity Clinic, Dominican Republic, for their support and collaboration in the development of this research project. We also want to express our gratitude to the Mexican families who have donated the brain of their loved ones affected with Alzheimer’s disease and made our research possible. This work is dedicated to the memory of Professor Dr. Jose Ra ´ ul Mena L ´ opez ´ †. †Deceased. Authors’ disclosures available online (https:// www.j-alz.com/manuscript-disclosures/20-1139r2).Peer reviewedPublisher PD