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Search Results: 1 - 10 of 463311 matches for " Josep A. Villena "
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Rosiglitazone-Induced Mitochondrial Biogenesis in White Adipose Tissue Is Independent of Peroxisome Proliferator-Activated Receptor γ Coactivator-1α
Rosario Pardo, Natàlia Enguix, Jaime Lasheras, Juan E. Feliu, Anastasia Kralli, Josep A. Villena
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026989
Abstract: Background Thiazolidinediones, a family of insulin-sensitizing drugs commonly used to treat type 2 diabetes, are thought to exert their effects in part by promoting mitochondrial biogenesis in white adipose tissue through the transcriptional coactivator PGC-1α (Peroxisome Proliferator-Activated Receptor γ Coactivator-1α). Methodology/Principal Findings To assess the role of PGC-1α in the control of rosiglitazone-induced mitochondrial biogenesis, we have generated a mouse model that lacks expression of PGC-1α specifically in adipose tissues (PGC-1α-FAT-KO mice). We found that expression of genes encoding for mitochondrial proteins involved in oxidative phosphorylation, tricarboxylic acid cycle or fatty acid oxidation, was similar in white adipose tissue of wild type and PGC-1α-FAT-KO mice. Furthermore, the absence of PGC-1α did not prevent the positive effect of rosiglitazone on mitochondrial gene expression or biogenesis, but it precluded the induction by rosiglitazone of UCP1 and other brown fat-specific genes in white adipose tissue. Consistent with the in vivo findings, basal and rosiglitazone-induced mitochondrial gene expression in 3T3-L1 adipocytes was unaffected by the knockdown of PGC-1α but it was impaired when PGC-1β expression was knockdown by the use of specific siRNA. Conclusions/Significance These results indicate that in white adipose tissue PGC-1α is dispensable for basal and rosiglitazone-induced mitochondrial biogenesis but required for the rosiglitazone-induced expression of UCP1 and other brown adipocyte-specific markers. Our study suggests that PGC-1α is important for the appearance of brown adipocytes in white adipose tissue. Our findings also provide evidence that PGC-1β and not PGC-1α regulates basal and rosiglitazone-induced mitochondrial gene expression in white adipocytes.
The db/db Mouse: A Useful Model for the Study of Diabetic Retinal Neurodegeneration
Patricia Bogdanov, Lidia Corraliza, Josep A. Villena, Andrea R. Carvalho, José Garcia-Arumí, David Ramos, Jesús Ruberte, Rafael Simó, Cristina Hernández
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0097302
Abstract: Background To characterize the sequential events that are taking place in retinal neurodegeneration in a murine model of spontaneous type 2 diabetes (db/db mouse). Methods C57BLKsJ-db/db mice were used as spontaneous type 2 diabetic animal model, and C57BLKsJ-db/+ mice served as the control group. To assess the chronological sequence of the abnormalities the analysis was performed at different ages (8, 16 and 24 weeks). The retinas were evaluated in terms of morphological and functional abnormalities [electroretinography (ERG)]. Histological markers of neurodegeneration (glial activation and apoptosis) were evaluated by immunohistochemistry. In addition glutamate levels and glutamate/aspartate transporter (GLAST) expression were assessed. Furthermore, to define gene expression changes associated with early diabetic retinopathy a transcriptome analyses was performed at 8 week. Furthermore, an additional interventional study to lower blood glucose levels was performed. Results Glial activation was higher in diabetic than in non diabetic mice in all the stages (p<0.01). In addition, a progressive loss of ganglion cells and a significant reduction of neuroretinal thickness were also observed in diabetic mice. All these histological hallmarks of neurodegeneration were less pronounced at week 8 than at week 16 and 24. Significant ERG abnormalities were present in diabetic mice at weeks 16 and 24 but not at week 8. Moreover, we observed a progressive accumulation of glutamate in diabetic mice associated with an early downregulation of GLAST. Morphological and ERG abnormalities were abrogated by lowering blood glucose levels. Finally, a dysregulation of several genes related to neurotransmission and oxidative stress such as UCP2 were found at week 8. Conclusions Our results suggest that db/db mouse reproduce the features of the neurodegenerative process that occurs in the human diabetic eye. Therefore, it seems an appropriate model for investigating the underlying mechanisms of diabetes-induced retinal neurodegeneration and for testing neuroprotective drugs.
El mercado hidrotérmico chileno: un enfoque de teoría de juegos
Vega Mauricio A.,Villena Mauricio
Cuadernos de Economía , 2006,
Abstract: Este trabajo analiza los efectos y consecuencias potenciales de la desregulación del mercado chileno de generación eléctrica. Propone un modelo del sistema de generación que aplica la teoría de juegos no cooperativos en un contexto estático y dinámico. En Chile se han hecho estudios similares para sistemas puramente térmicos, donde las decisiones de operación sólo dependen de los costos de combustible y otros costos operativos, lo que permite usar modelos estáticos. Las centrales hidráulicas a aden una nueva e importante dimensión que se debe incorporar en el modelo: el uso del agua y la fuerte dependencia temporal de las decisiones, lo que implica el uso de modelos dinámicos. Este trabajo es un primer intento de elaborar un modelo dinámico del sistema hidrotérmico chileno. El modelo es genérico y se puede utilizar para simular un sistema hidrotérmico basado en una Bolsa de energía. La pérdida de generalidad se evita suponiendo que las centrales térmicas e hidráulicas pueden hacer ofertas a la Bolsa y comportarse estratégicamente.
Dietary Supplementation with Probiotic Strain Improves Immune-Health in Aged Mice  [PDF]
Verónica Molina, Marta Médici, Julio Villena, Graciela Font, Maríaa Taranto
Open Journal of Immunology (OJI) , 2016, DOI: 10.4236/oji.2016.63008
Abstract: Ageing is associated with several anatomical and physiological changes of the organism, and the increase in global elderly population promotes the research to develop strategies to improve their quality of life. In this work, we characterized the immunological alterations naturally produced during aging in a mice model, and evaluated the effect of probiotic Lactobacillus (L.) rhamnosus CRL1505 administration on those immunological parameters. We demonstrated that L. rhamosus CRL1505 was able to improve peritoneal macrophages phagocytic activity, and the number of intestinal IgA+ cells in aged mice, reaching values of those parameters similar to young adult mice. The results of this work indicate that is plausible that the immunobiotic CRL1505 strain may find applications as a beneficial immunomodulator in aging to reinforce the intestinal and systemic immunity. The immune modulation in aging induced by L. rhamnosus CRL1505 could lead to the development of new strategies for functional foods specifically tailored for the elderly.
EL MERCADO HIDROTéRMICO CHILENO: UN ENFOQUE DE TEORíA DE JUEGOS
Vega,Mauricio A; Villena,Mauricio G.;
Cuadernos de Economía , 2006,
Abstract: this work analyses the effects and potential consequences of deregulating the chilean electricity generating market. it proposes a model generation system to which non-cooperative game theory is applied within a static and dynamic context. similar studies for purely thermal systems have been carried out in chile where operational decisions only depend on the costs of fuel and other operating costs, meaning that static models can be used. hydraulic power stations add a new important dimension which should be incorporated into the model: using water and strong temporal dependence on decision-making, implying using dynamic models. this work is a first attempt to draw up a dynamic model of the chilean hydrothermal system. the model is generic and can be used for simulating an energy stock-exchange-based hydrothermal system. a loss of generality can be avoided by supposing that thermal and hydraulic power stations can supply such stock-market and behave strategically.
Iberian-Tartessian scripts/graffiti in Iruna-Veleia (Basque Country, North Spain): findings in both Iberia and Canary Islands-Africa
A Arnaiz-Villena, D Rey
International Journal of Modern Anthropology , 2012,
Abstract: 760 officially recognized scripts on ceramics from Iru a-Veleia excavated by the archaeology firm Lurmen S.L. (approximately between years 2002-2008)have been analyzed. A number of these ceramics contains scripts which may be assimilated to Iberian/Tartessian writings. This number may be underestimated since more studies need to be done in already available and new found ceramics. This is the second time that Iberian writing is found by us in an unexpected location together with the Iberian-Guanche inscriptions of Lanzarote and Fuerteventura (Canary Islands). On the other hand, naviform scripting, usually associated to Iberian rock or stone engraving may have also been found in Veleia. Strict separation, other than in time and space stratification, between Iberian and (South) Tartessian culture and script is doubted.
Evolución de Preferencias bajo escenarios de Información Completa e Incompleta: Teoría y Evidencia Experimental
César A. Salazar,Mauricio G. Villena
Estudios de Economia , 2005,
Abstract: La presente investigación tiene dos objetivos básicos. Primero, se utilizarán elementos de la Teoría de Juegos Evolutivos para evaluar la estabilidad de distintos tipos de preferencias en el contexto de la explotación de un recurso de propiedad común. En particular, analizaremos la evolución de preferencias egoístas, altruistas y envidiosas usando un enfoque evolutivo indirecto como el propuesto por Bester y Güth (1998). Los resultados básicos de nuestro modelo teórico plantean que en un escenario de información completa las preferencias evolutivamente estables serán envidiosas, las que implican un nivel de esfuerzo por sobre el nivel sugerido por el equilibrio Nash. En cambio, en términos de información incompleta las preferencias que prevalecerán serán las egoístas. Un segundo objetivo es evaluar experimentalmente las predicciones teóricas encontradas en la primera parte de este trabajo. Para este propósito se realizan dos tratamientos distintos del experimento estándar de un juego de explotación de un recurso de propiedad: uno con información completa y otro con información incompleta. Para ello se tiene como base el trabajo de Walter et al. (1990), quienes simulan el modelo clásico del problema de extracción de un recurso de propiedad común como una decisión abstracta de inversión. Comparando por medio de criterios de significancia estadística las distintas predicciones teóricas con los resultados experimentales encontramos que nuestras predicciones teóricas basadas en un enfoque evolutivo explican de mejor manera los resultados experimentales que las predicciones basadas solamente en la teoría de juegos no-cooperativa.
Option Pricing of Twin Assets
Marcelo J. Villena,Axel A. Araneda
Quantitative Finance , 2014,
Abstract: How to price and hedge claims on nontraded assets are becoming increasingly important matters in option pricing theory today. The most common practice to deal with these issues is to use another similar or "closely related" asset or index which is traded, for hedging purposes. Implicitly, traders assume here that the higher the correlation between the traded and nontraded assets, the better the hedge is expected to perform. This raises the question as to how \textquoteleft{}closely related\textquoteright{} the assets really are. In this paper, the concept of twin assets is introduced, focusing the discussion precisely in what does it mean for two assets to be similar. Our findings point to the fact that, in order to have very similar assets, for example identical twins, high correlation measures are not enough. Specifically, two basic criteria of similarity are pointed out: i) the coefficient of variation of the assets and ii) the correlation between assets. From here, a method to measure the level of similarity between assets is proposed, and secondly, an option pricing model of twin assets is developed. The proposed model allows us to price an option of one nontraded asset using its twin asset, but this time knowing explicitly what levels of errors we are facing. Finally, some numerical illustrations show how twin assets behave depending upon their levels of similarities, and how their potential differences will traduce in MAPE (mean absolute percentage error) for the proposed option pricing model.
Stability and Chaos in a Multi-Market Oligopoly with Economies of Scale
Marcelo J. Villena,Axel A. Araneda
Quantitative Finance , 2015,
Abstract: In an oligopolistic setting under a Cournot scheme, the strategy of each economic player depends on its own quantity decision, but also on its rivals' reaction. Since Puu's seminal work, different oligopoly games have been studied in terms of their stability, as nonlinear discrete time varying systems. Most works in this line of research have concentrated on single markets with linear production structures (i.e. assuming constant returns to scale). Nevertheless, oligopolistic competition seems today to present multi-market phenomena, exhibiting, in some cases, important economies of scale, especially in the retail and service industry. In this paper, we study the stability of a multi-market Cournot-Nash equilibrium with global economies of scale. In other words, we look at the scale level that is related to the total production of firms, in all markets, as opposed to local economies of scale presented at each store individually. The modeling confirms the fact that economies and diseconomies of scale make the Cournot equilibrium very unstable for certain values of the scale of the producers. On the other hand, stability is achieved when the firm reaches absolute advantage with respect to its competition.
Pectinases yeast production using grape skin as carbon source  [PDF]
María Arévalo-Villena, Mercedes Fernández, Jesús López, Ana Briones
Advances in Bioscience and Biotechnology (ABB) , 2011, DOI: 10.4236/abb.2011.22014
Abstract: Pectinases are used in Enology for some different utilities. Enzymatic preparations from moulds are a mixed of different enzymes with strong and unspe-cific activities. Some Saccharomyces cerevisiae pro-duce pectinases which can be used instead of com-mercial preparations. The objectives of this work were to study the enzyme secretion by one Saccharo-myces cerevisiae (CECT 11783) for growing on grape skin (industry oenological by-product) as carbon source. Preliminary experiments showed that the strain produced pectinases for growing on grape skin without any other carbon source. Statistical treat-ment (factorial design 25) was applied to evaluate the influences of related factors (agitation, temperature, presence of peptone and detergent in the medium and time of growth) Variables with the most significant interactions for pectinase production were agitation and nitrogen source concentration. Response surface methodology showed that a first order model was not adequate for results. Nevertheless, the built of a sec-ond order model offered a polynomial equation which surface predicted a maximum of activity (52.68 enzymatic units) for specific values of the studied variables (147.8 rpm of agitation and 15.9 g of pep-tone/ L culture medium).
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