Showing papers by "National University of Cuyo published in 2022"

Synaptotagmin-1 C2B domains cooperatively stabilize the fusion stalk <i>via</i> a master-servant mechanism

Abstract: Synaptotagmin-1 is a low-affinity Ca2+ sensor that triggers synchronous vesicle fusion. It contains two similar C2 domains (C2A and C2B) that cooperate in membrane binding, being the C2B domain mainly responsible for the membrane fusion process due to its polybasic patch KRLKKKKTTIKK (321-332). In this work, a master-servant mechanism between two identical C2B domains is shown to control the formation of the fusion stalk in a calcium-independent manner. Two regions in C2B are essential for the process, the well-known polybasic patch and a recently described pair of arginines (398 399). The master domain shows strong PIP2 interactions with its polybasic patch and its pair of arginines. At the same time, the servant analogously cooperates with the master to reduce the total work to form the fusion stalk. The strategic mutation (T328E, T329E) in both master and servant domains disrupts the cooperative mechanism, drastically increasing the free energy needed to induce the fusion stalk, however, with negligible effects on the master domain interactions with PIP2. These data point to a difference in the behavior of the servant domain, which is unable to sustain its PIP2 interactions neither through its polybasic patch nor through its pair of arginines, and in the end, losing its ability to assist the master in the formation of the fusion stalk.

Contrasting climate influences on Nothofagus pumilio establishment along elevational gradients

Abstract: Predicted warmer temperatures and more frequent extreme climatic events in the southern Andes may affect the dynamics of the Patagonian forests. These environmental changes may differentially alter the probability of Nothofagus pumilio establishment across its altitudinal range of distribution. We monitored fruit fall, seedling emergence and survival at altitudinal distribution range of N. pumilio forests in Santa Cruz (49°22′ S—72°56′ W), Argentina. Fruit fall, seedling emergence and survival were tested in relation to drought, based on the SPEI (Standardized Precipitation Evapotranspiration Index), interacting with elevation. Fruit fall was consistently higher at low elevation and the abundance of fruits was not affected by drought intensity. Density of new-born seedlings was ~ 9 to 24 times lower at low- than at high-elevation plots in our first observations (2014 and 2016), characterized by warm-dry climatic conditions in spring-early summers. In contrast, seedling abundance was ~ 1.5 times larger at low elevations during relatively cold-wet growing seasons. Survival probability was explained by the interaction between SPEI and elevation. At low elevation and in dry periods, survival probability was lower (CI 54–72%) than in wet periods (CI 68–84%) but at high elevation similar survival was registered even with positive or negative SPEI values. Our results show interacting effects of elevation and drought on tree establishment at the elevation limits, with positive and negative drought effects at high and low elevations, respectively. Predicted increase of extreme drought events during the XXI century could be detrimental for N. pumilio establishment at dry, low-elevation forests.

Plant dry weight and nutritive value of genetically diverse germplasm of false Rhodes grass [ <i>Leptochloa crinita</i> (Lag.) P.M. Peterson and N.W. Snow], a native forage grass from arid regions of the Americas

Abstract: The native forage, false Rhodes grass [Leptochloa crinita (Lag.) P.M. Peterson and N.W. Snow], represents an important component of the arid and semi-arid rangelands of the Americas, due to its large area of distribution and its tolerance to drought and cattle grazing. Precise information on nutritive value and the factors that influence this trait is relevant for effective utilization as a forage in arid regions of the world. Here, we characterized dry matter (DM) per plant and nutritive value parameters in leaves, stems, and panicles of 21 genetically diverse L. crinita accessions, in a 2-yr partially replicated trial. Dry matter, crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), ash, fat, phosphorus, and calcium concentrations were determined. Significant (p < .01), substantial variation was found among accessions for DM, CP, NDF, ADF, ash, and fat content. Whole-plant DM varied ∼three-fold among the accessions. Variation was also found among the plant parts (p < .001) for all traits, with leaves and panicles having greater CP content than stems, and leaves being the less fibrous organs. In general, the range values found for DM (117–342 g DM plant−1), CP (76–109 g kg−1), NDF (747–839 g kg−1), and ADF (425–479 g kg−1) partially overlapped the range of variation reported for these traits in other forage grasses of arid regions, although some L. crinita accessions had greater CP and DM than most of the compared species; suggesting that L. crinita is an adequate forage grass for cattle grazing.

DNA Damage Repair Proteins, HSP27, and Phosphorylated-HSP90α as Predictive/Prognostic Biomarkers of Platinum-based Cancer Chemotherapy: An Exploratory Study

Abstract: Platinum analogs are commonly used for cancer treatment. There is increasing interest in finding biomarkers which could predict and overcome resistance, because to date there is no reliable predictive/prognostic marker for these compounds. Here we studied the immunohistochemical expression of proteins involved in DNA damage response and repair (γH2AX, 53BP1, ERCC1, MLH1, and MSH2) in primary tumor tissues from patients treated with platinum-based chemotherapy. Levels and localization of Heat Shock Protein (HSP)27 and phospho-(Thr5/7)-HSP90α (p-HSP90α) were also determined. The implications in clinical response, disease-free survival and overall survival were analyzed. High γH2AX and 53BP1 expressions were associated with poor clinical response. Nuclear p-HSP90α, as well as nuclear absence and low cytoplasmic expression of HSP27 correlated with good response. Patients with high γH2AX and high cytoplasmic HSP27 expressions had shorter overall survival and disease-free survival. MLH1, MSH2, or ERCC1 were not associated with clinical response or survival. We report the potential utility of p-HSP90α, HSP27, γH2AX, and 53BP1 as predictive/prognostic markers for platinum-based chemotherapy. We present the first study that evaluates the predictive and prognostic value of p-HSP90α in primary tumors. Our research opens new possibilities for clinical oncology and shows the usefulness of immunohistochemistry for predicting chemotherapy response and prognosis in cancer.

Nanocrystalline superconducting γ-Mo2N ultra-thin films for single photon detectors

Abstract: We analyze the influence of the surface passivation produced by oxides on the superconducting properties of γ-Mo2N ultra-thin films. The superconducting critical temperature of thin films grown directly on Si (100) with those using a buffer and a capping layer of AlN are compared. The results show that the cover layer avoids the presence of surface oxides, maximizing the superconducting critical temperature for films with thicknesses of a few nanometers. We characterize the flux-flow instability measuring current-voltage curves in a 6.4 nm thick Mo2N film with a superconducting critical temperature of 6.4 K. The data is analyzed using the Larkin and Ovchinnikov model. Considering self-heating effects due to finite heat removal from the substrate, we determine a fast quasiparticle relaxation time ≈ 45 ps. This value is promising for its applications in single-photon detectors.

Genotypic and environmental effects on the compounds associated with garlic flavor, health‐enhancing properties, and postharvest conservation

Abstract: To estimate genetic and environmental effects on traits associated with garlic (Allium sativum L.) functional value and postharvest quality, the content of total organosulfur compounds, phenolics, and solids were determined in selected garlic cultivars grown at four locations in Mendoza, Argentina. An initial experiment considered five cultivars grown in two locations and 2 yr, and a second experiment evaluated 12 cultivars across four locations. Among all the cultivars and locations, pyruvate levels, an estimator of total organosulfur content, varied more than fourfold (with a range of 24.7–111.1 μmol/g fresh weight), phenolics varied ∼fivefold (132.1–703.1 mg gallic acid equivalents/kg fresh weight), and solids varied within a range of 28.4 to 41.2%. Strong environmental influence and genotype × environment interactions were found for all traits, together accounting for 54.8 to 63.2% of the variation found for pyruvate, 63.3 to 81% for phenolics, and 35.1 to 50.8% for solids. The impact of genotype was higher for solids (31.9–50.9% of total variation) than for pyruvate (33.6–40.4%) and phenolics (16.1–34.1%). Despite the substantial environmental influence and genotype × environment interaction found, individual garlic cultivars with consistently high levels for all of these compounds were identified. We conclude that garlic pyruvate, phenolic, and solids levels are genetically and environmentally conditioned. The identified genotypes with consistently high phytochemicals content are valuable to breeders aiming at increasing garlic flavor, functional value, and postharvest quality, whereas locations yielding contrastingly high or low pyruvate levels are of interest for producing pungent and mild garlics, respectively.

Dispersive waves and radiation trapping in optical fibers with a zero-nonlinearity wavelength

Abstract: The formation of dispersive waves and radiation trapping are two most relevant phenomena in supercontinuum generation. In spite the fact that the nonlinear coefficient of many waveguides depends strongly on wavelength and even changes sign, the influence of a frequency-dependent nonlinearity on these phenomena have seldom been studied. The goal of this work is to fill this gap in the literature by thoroughly studying the behavior of dispersive waves and radiation trapping in the presence of a zero-nonlinearity wavelength (ZNW). Although the generalized nonlinear Schrödinger equation (GNLSE) is widely used to model optical pulse propagation in waveguides, it has been shown that the GNLSE may lead to unphysical results in the case of frequency-dependent nonlinearities. For this reason, we perform our analysis by resorting to the newly introduced photon-conserving generalized nonlinear Schrödinger equation (pcGNLSE). Further, we discuss results obtained with both equations and put in evidence the inadequacy of the GNLSE to appropriately account for radiation trapping.

La no-imagen, la constelación fantasmal y el escotoma : ¿hacia un modelo fantasmal de la historia del arte?

Abstract: Este texto tiene una estructura abierta y flexible que no parte de un problema central, sino que aborda un problema fantasma compuesto a su vez por varios problemas. Tampoco busca corroborar o desmentir una hipótesis determinada, sino que plantea una especie de hipótesis fantasmal(es). Esta(s) hipótesis se encuentra(n) articulada(s) a la forma del montaje. A partir del análisis de los fenómenos clínicos del ojo fantasma y del miembro fantasma, este texto problematiza los alcances de la historia del arte en cuanto a su objeto de estudio. En ese orden de ideas, se propone la visibilización de lo invisible como una posible indagación de la historia del arte, a lo cual apela justamente el término modelo fantasmal de la historia del arte. La apertura y flexibilidad de la estructura textual implican que el documento tiene distintos niveles, que a su vez abren distintas posibilidades de lectura. Esos distintos niveles pueden hacer aparecer hipótesis diversas.

Global seasonal distribution of CH₂Br₂ and CHBr₃ in the upper troposphere and lower stratosphere

Abstract: Abstract. Bromine released from the decomposition of short-lived brominated source gases contributes as a sink of ozone in the lower stratosphere. The two major contributors are CH2Br2 and CHBr3. In this study, we investigate the global seasonal distribution of these two substances, based on four High Altitude and Long Range Research Aircraft (HALO) missions, the HIAPER Pole-to-Pole Observations (HIPPO) mission, and the Atmospheric Tomography (ATom) mission. Observations of CH2Br2 in the free and upper troposphere indicate a pronounced seasonality in both hemispheres, with slightly larger mixing ratios in the Northern Hemisphere (NH). Compared to CH2Br2, CHBr3 in these regions shows larger variability and less clear seasonality, presenting larger mixing ratios in winter and autumn in NH mid to high latitudes. A clear CH2Br2 maximum is observed in the NH during autumn with a less pronounced similar feature in the Southern Hemisphere (SH). This suggests that transport processes may be different in both hemispheric autumn seasons, which implies that the influx of tropospheric air ("flushing") into the NH lowermost stratosphere is more efficient than in the SH. However, the SH database is insufficient to quantify this difference. We further compare the observations to model estimates of TOMCAT and CAM-Chem, both using the same emission inventory. The pronounced tropospheric seasonality of CH2Br2 in the SH is not reproduced by the models, presumably due to erroneous seasonal emissions or atmospheric photochemical decomposition efficiencies. In contrast, model simulations of CHBr3 show a pronounced seasonality in both hemispheres, which are not confirmed by observations. The distributions of both species in the lowermost stratosphere of the Northern and Southern Hemispheres are overall well captured by the models with the exception of southern hemispheric autumn, where both models present a bias that maximizes in the lowest 40 K above the tropopause, with considerably lower mixing ratios in the observations. Thus, both models reproduce equivalent "flushing" in both hemispheres, which is not confirmed by the available observations. Our study emphasises the need for more extensive 20 observations in the SH to fully understand the impact of CH2Br2 and CHBr3 on lowermost stratospheric ozone loss and to help constraining emissions.

Use of pulsed electric fields in white grape processing

Abstract: In recent decades, much research on nonthermal food processing technologies has been carried out to combat spoilage and pathogenic microorganisms, reduce the use of chemical preservatives, improve the functionality of foods, and optimize process efficiency. One of these innovative technologies that aim to achieve these objectives is pulsed electric fields (PEFs). This technique causes the electroporation of cytoplasmic membranes of microorganisms and eukaryote cells of plant and animal tissues using low energy requirements, thus minimizing quality deterioration of the food compounds. Intense fundamental research efforts have been addressed in recent years to understand the electroporation mechanisms and to identify the critical factors affecting electroporation. In parallel, many studies have been conducted to demonstrate the electroporation efficacy on the inactivation of microbial cells, enhancing mass transfer, and the modification of food structure. The attractive effects deriving from PEF processing have driven the development of pulse power generators that meet the requirements for food processing, and currently, different commercial applications of PEF are available in the market. Wineries are an industrial sector that can take advantage of the attractive effects deriving from PEF. The electroporation of the cells of the grapes before vinification or of the microbial cells involved in winemaking may have a beneficial impact on the different stages involved in winemaking in terms of optimizing process efficiency, reducing the use of chemical preservatives, or saving energy. The objective of this chapter is to describe potential applications of PEF technology in different stages of the white winemaking

Climate-Sensitive Architecture, Is Natural Comfort Possible?

Abstract: Comfort is a perception that evidences a state of well-being in a given environment. In practice, the achievement of comfort is the result of a complex phenomenon in which objective space parameters – such as thermal, visual or acoustical – coexist with subjective physiological, sociological, cultural and psychological factors. Comfort can be achieved by using auxiliary energy, usually from non-renewable and pollutant sources, that powers energy-intensive mechanisms with almost immediate response. Nevertheless, building comfort by natural means should be our main goal to protect the environment for future generations. In this holistic approach, well-designed climate-sensitive architecture will play a very important role, but also occupant’s expectations and willingness to adapt to architectural possibilities and its response times will be key. Comfort in architecture is not a given, users must be involved in the process of achieving it by interacting with their building over time.

The Production of Neoliberal Subjectivity in an Argentine Public University

Abstract: Argentina’s public university system has shifted from the indelible reformist tradition of 1918, with its emancipatory and Latin American perspective, to a commodified education in line with the global logic introducing neoliberal rationality and the neoliberal subject into the Universidad Nacional de Cuyo. A review of recent reforms and a description of the university’s institutional measures is followed by possible lines of resistance, combining ideas from the 1918 reformist movement and the current Argentine feminist movement. La universidad pública argentina está sufriendo una conversión de la tradición de indeleble marca reformista desde 1918 (de horizonte emancipatorio y latinoamericano) a una educación mercantilizada según la lógica global de la racionalidad neoliberal y del sujeto neoliberal, visible en la Universidad Nacional de Cuyo. Repaso reformas nacionales recientes, y describo las disposiciones institucionales de la universidad para llegar a una discusión sobre coordenadas posibles de resistencia entrecruzando ideas del movimiento reformista de 1918 y el actual movimiento feminista argentino.