Acceso y habilitación en TIC en jóvenes universitarios: ¿transición a la interactividad en el aprendizaje y a una socialidad en RED?

1 archivo PDF (38 páginas)Esta ponencia se deriva de un proyecto de investigación más amplio. Tiene como referente conceptual a la llamada sociedad del conocimiento y versa, desde una perspectiva empírica comparada, sobre los estudiantes de la UAM-A y de las FES-A matriculados en seis programas de formación profesional que esos establecimientos tienen en común. Se finca en datos obtenidos de una encuesta desarrollada y aplicada ex profeso en esos espacios universitarios en el marco del proyecto de investigación intitulado “Identidades, contexto societal y trayectorias de jóvenes universitarios de la ZMVM: región norte“. Se destaca el tema de la formación de habilidades y saberes que posibilitan insertarse de modo propositivo en la sociedad del conocimiento. Se considera que el proceso de globalización influye de modo directo en el contexto en que se desenvuelve la educación. En lo particular se propone la hipótesis de que la difusión de las TIC, correlativa a la sociedad global del conocimiento, representa uno de los rasgos más sobresalientes que se corresponde con un nuevo paradigma educacional y, que el acceso a éstas constituye una condición de apropiación y participación en los códigos de la modernidad para desempeñar funciones denominadas de “análisis simbólico” que realizan planificadores de todo tipo, consultores de comunicación, asesores en acopio e interpretación de conocimientos, estrategas simbólicos, etc. El análisis considera las siguientes dimensiones con relación a las TIC: acceso; habilitación; intensidad; aplicaciones disciplinares; formas de socialidad; e-currículo y transición de la difusión a la interactividad (de la enseñanza al aprendizaje). Lo anterior se realiza comparando instituciones, carreras, género y nivel socioeconómico

Molecular dynamics simulations of mixed DOPC–β-sitosterol bilayers and their interactions with DMSO

ell membrane phospholipid bilayers can be damaged by the large amounts of dimethyl sulphoxide (DMSO) commonly used in cryopreservation. The interaction of DMSO with model bilayers consisting of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and ß-sitosterol has been studied using molecular dynamics simulations. Initially the effect of sterol concentration and temperature upon bilayers solvated in pure water was determined, and membranes containing ß-sitosterol were compared with membranes containing cholesterol. These simulations showed that the presence of sterols has a condensing effect on the phospholipids, causing a reduction in the area per lipid as the sterol concentration increases, up to a phospholipid–sterol ratio of 2[thin space (1/6-em)]:[thin space (1/6-em)]1. The incorporation of sterols into the bilayer also increased the thickness and order of the phospholipid acyl tails. DOPC–ß-sitosterol bilayers at different relative concentrations were simulated in solutions of 2.5 and 25.0 mol% DMSO. The interaction of DMSO with the bilayers caused the bilayers to expand laterally, while thinning normal to the plane of the bilayer expansion. The same qualitative behaviour has been shown to occur in pure phosphocholine bilayers. However, the presence of sterols made the membranes more resistant to the effects of DMSO, to the extent that the membranes where able to maintain their integrity in 25.0 mol% DMSO, a concentration that would otherwise cause the destruction of a pure DOPC bilayer. Increasing the concentration of ß-sitosterol within the bilayers reduced the rate of DMSO diffusion across the bilayer and, if the concentration was large enough, caused the diffusion mechanism to change. DMSO was observed to disorder the membranes enough to cause an increase in the number of sterol “flip–flops”. The findings of this work provide a more realistic description of how DMSO interacts with cell membranes and the role of the composition of the membrane

Revisiting the Interaction of Melittin with Phospholipid Bilayers: The Effects of Concentration and Ionic Strength.

Melittin is an anti-microbial peptide (AMP) and one of the most studied membrane-disrupting peptides. There is, however, a lack of accurate measurements of the concentration-dependent kinetics and affinity of binding of melittin to phospholipid membranes. In this study, we used surface plasmon resonance spectroscopy to determine the concentration-dependent effect on the binding of melittin to 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) bilayers in vesicles. Three concentration ranges were considered, and when combined, covered two orders of magnitudes (0.04 µM to 8 µM), corresponding to concentrations relevant to the membrane-disrupting and anti-microbial activities of melittin. Binding kinetics data were analysed using a 1:1 Langmuir-binding model and a two-state reaction model. Using in-depth quantitative analysis, we characterised the effect of peptide concentration, the addition of NaCl at physiological ionic strength and the choice of kinetic binding model on the reliability of the calculated kinetics and affinity of binding parameters. The apparent binding affinity of melittin for POPC bilayers was observed to decrease with increasing peptide/lipid (P/L) ratio, primarily due to the marked decrease in the association rate. At all concentration ranges, the two-state reaction model provided a better fit to the data and, thus, a more reliable estimate of binding affinity. Addition of NaCl significantly reduced the signal response during the association phase; however, no substantial effect on the binding affinity of melittin to the POPC bilayers was observed. These findings based on POPC bilayers could have important implications for our understanding of the mechanism of action of melittin on more complex model cell membranes of higher physiological relevance

Cryopreservation of threatened native Australian species—what have we learned and where to from here?

Cryogenic storage techniques have been developed and adopted for more than 100 (mainly agricultural) plant species worldwide, and within Australia, at least 30 critically endangered plants have been stored long term using cryogenic approaches. Nevertheless, there are many species that are very difficult to store using current procedures, and organizations involved in plant germplasm conservation (such as botanic gardens, agricultural institutions, etc.) that utilise cryogenic storage techniques are in some respects at a crossroads in their endeavours to cheaply and effectively store a wide selection of species and genotypes for conservation and agricultural/horticultural purposes. For taxa that are not amenable to current cryogenic approaches, new ways of developing cryogenic storage techniques need to be investigated, including research into the ways in which cell membranes interact and change when cooled to cryogenic temperatures (−196°C in liquid nitrogen) in the presence of various cryoprotective agents. This review highlights the current state of cryogenic research both within Australia and internationally, provides a case study on threatened plant species and also describes several new research initiatives that aim to provide answers to why some native species are quite amenable to widely utilised cryogenic approaches whilst others are currently non-responsive. New approaches aim to integrate laboratory and membrane modelling paradigms to provide guidelines for the development of new cryopreservation protocols and to assess the robustness of theoretical models in predicting optimum cryogenic conditions

Identification and characterisation of putative drug binding sites in human ATP-binding cassette B5 (ABCB5) transporter.

The human ATP-binding cassette B5 (ABCB5) transporter, a member of the ABC transporter superfamily, is linked to chemoresistance in tumour cells by drug effluxion. However, little is known about its structure and drug-binding sites. In this study, we generated an atomistic model of the full-length human ABCB5 transporter with the highest quality using the X-ray crystal structure of mouse ABCB1 (Pgp1), a close homologue of ABCB5 and a well-studied member of the ABC family. Molecular dynamics simulations were used to validate the atomistic model of ABCB5 and characterise its structural properties in model cell membranes. Molecular docking simulations of known ABCB5 substrates such as taxanes, anthracyclines, camptothecin and etoposide were then used to identify at least three putative binding sites for chemotherapeutic drugs transported by ABCB5. The location of these three binding sites is predicted to overlap with the corresponding binding sites in Pgp1. These findings will serve as the basis for future in vitro studies to validate the nature of the identified substrate-binding sites in the full-length ABCB5 transporter

Cold-induced changes affect survival after exposure to vitrification solution during cryopreservation in the south-west Australian Mediterranean climate species Lomandra sonderi (Asparagaceae)

There is limited knowledge of the effects of exposure to low temperatures in the unique Mediterranean climate plant species of Western Australia. We have thus investigated the effect of low temperature on cryogenic tolerance in Lomandra sonderi, an endemic perennial species of southwest Western Australia. Lomandra sonderi plants were preconditioned in tissue culture at constant 23 °C (12 h light/dark cycle) or alternating 20/-1 °C (16 h light and 8 h dark cycle). Shoot tips from both conditions were analysed for their phospholipid, sterol and soluble sugar compositions. Shoot tips were also cryoexposed via a droplet-vitrification protocol. Survival in both preconditioning regimes for cryoexposed and non-cryoexposed samples was the same, but plants from the 20/-1 °C regime displayed an improved tolerance to the overall cryopreservation process in both cryoexposed and non-cryoexposed samples, thereby eliminating exposure to liquid nitrogen as a primary cause of reduced post-cryogenic viability. Preconditioning of in vitro shoots of L. sonderi at 20/-1 °C induced significant increases in phosphatidylcholine (from 7.30 ± 3.46 to 22.2 ± 7.80 ng mg-1 FW) and increases in several soluble sugars (fructose, galactose, glucose, sucrose) compared to shoots incubated at 23 °C—changes consistent with known cold acclimation responses in plant species generally—but sterol content remained largely unchanged. Analysis of electrolyte leakage in shoot tips from both preconditioning regimes generated a significantly lower LT50 value in the 20/-1 °C samples (-5.45 ± 0.53 °C) over the 23 °C samples (-2.5 ± 0.08 °C). Increased tolerance to cryoexposure in L. sonderi appears to lie mainly with acclimation-induced changes in membrane composition and promotion of membrane stability and hence increased resistance to freeze damage

Development of cryopreservation for Loxocarya cinerea - an endemic Australian plant species important for post-mining restoration

We report the development of a cryopreservation protocol for the endemic Western Australian plant species Loxocarya cinerea (Restionaceae). Shoot tips from two genotypes, SXH404 and SXH804, were cryopreserved using the droplet-vitrification technique. Control explants, which were cryoprotected, but not cooled, showed regeneration for both genotypes (SXH404, 22.1 ± 5.9%; SXH804, 67.7 ± 9.6%). Extension of incubation in PVS2 from 30 to 60 min did not lead to survival after cryopreservation. Thermal analysis using differential scanning calorimetry confirmed the beneficial effect of a loading phase but also revealed no or very little ice formation after cryoprotection of shoot tips in other treatments. Regeneration following cryopreservation was obtained for genotype SXH804 (4.3 ± 2.1%) but not for SXH404. Regenerated explants of L. cinerea SXH804 were morphologically identical to tissue-cultured plants. As an alternative to shoot tips, callus tissues of clone SXH404 were successfully cryopreserved (>66.7% post LN survival) using the same protocol

Exploring the origin of ultra-diffuse galaxies in clusters from their primordial alignment

We find that the minor axes of the ultra-diffuse galaxies (UDGs) in Abell 2634 tend to be aligned with the major axis of the central dominant galaxy, at a $\gtrsim 95\%$ confidence level. This alignment is produced by the bright UDGs with the absolute magnitudes $M_r<-15.3$ mag, and outer-region UDGs with $R>0.5R_{200}$. The alignment signal implies that these bright, outer-region UDGs are very likely to acquire their angular momenta from the vortices around the large-scale filament before they were accreted into A2634, and form their extended stellar bodies outside of the cluster; in this scenario, the orientations of their primordial angular momenta, which are roughly shown by their minor axes on the images, should tend to be parallel to the elongation of the large-scale filament. When these UDGs fell into the unrelaxed cluster A2634 along the filament, they could still preserve their primordial alignment signal before violent relaxation and encounters. These bright, outer-region UDGs in A2634 are very unlikely to be the descendants of the high-surface-brightness dwarf progenitors under tidal interactions with the central dominant galaxy in the cluster environment. Our results indicate that the primordial alignment could be a useful probe of the origin of UDGs in large-scale structures.Comment: Accepted for publication in MNRAS Lette