la volatilidad de los mercados en el escenario de la crisis de las hipotecas basura y la deuda soberana

Trabajo de fin de Grado. Grado en Economía. Curso académico 2013-1014La volatilidad de los mercados financieros ha experimentado un gran incremento durante las crisis subprime y de deuda pública. No obstante y a pesar de la presencia de no normalidad de los activos financieros en estos escenarios, muchas instituciones financieras todavía consideran medidas del valor al riesgo (VAR) basadas en la distribución gausiana. Este trabajo ilustra el mal comportamiento de tales medidas y muestra la ganancia en términos de ajuste que se obtiene al asumir distribuciones leptocúrticas como la T-Student. Nuestro análisis se realiza en 3 pasos. En primer lugar revisaremos las características empíricas de las series financieras y mostraremos que la no normalidad depende principalmente de la frecuencia de los datos. En segundo lugar, analizaremos el comportamiento del VAR con una metodología basada en la distribución normal y T-Student. Concluiremos que la primera subestima el riesgo de los activos financieros mientras que la segunda lo captura con mayor exactitud para niveles de confianza altos (1%). Sin embargo, para un nivel de confianza del 5%, la T-Student podría ser demasiado conservadora en lo que respecta a la medición del riesgo, lo que abre la posibilidad de estudiar otras alternativas no gausianas que sean más flexibles. En tercer lugar, pondremos de manifiesto que las mejoras obtenidas con la T-Student aparecen en un contexto de alta volatilidad, consecuencia de la reciente crisis. Los resultados se han obtenido al emplear índices de Bolsa de diferentes áreas económicas: Europa (IBEX35 y DAX30), Norte América (DOW JONES) y economías emergentes (HANG SENG)[EN] The volatility in financial markets has experienced a dramatically increased during the subprime and sovereign debt crises. Nevertheless, and despite the wellknown fact of the non-normality of asset returns in these scenarios, most financial institutions still report value at risk (VAR) measures based on the gaussian distribution. This paper illustres the Underperformance of such measures and shows the gains in accuracy obtained by assuming more leptokurtic student's innovations. Our analyses proceeded in three steps. First, we revise the salient empirical features of fi-nancial data and show that the non-normality depends basically on the high frequency of the data. Second, we compare the relative VAR performance of the methodologies based on either normal oo a student's T Distributions. We show that the former systematically underestimates risk measures but the latter captures more accurately the risk for high confidence levels (1%). At 5% confidence level, however, the student's T are particulary achieved in the context of the highly volatile scenario of the recent crisis. Our resultats are obtained by using stock índices from different economic áreas: Europe (IBEX35 and DAX30), North America (DOW JONES) and emerging markets (HANG SENG

Mejoramiento barrial en Itaca

La propuesta se basa principalmente en dos ejes: la ordenación del territorio de una forma natural, eficiente y ordenada, con una ocupación del espacio y expectativas de mejora progresivas a partir de unos centros de servicios comunes entorno al agua; y el desarrollo y conexión de los centros de producción, tanto los ya existentes en Matola y los previstos en entorno inmediato, como los propuestos en la actuación

Role of S-adenosylmethionine on the hepatobiliary homeostasis of glutathione during cyclosporine A treatment

[EN] The effects of cyclosporine A (CyA) treatment on the hepatic content and biliary output of reduced (GSH) and oxidized (GSSG) glutathione and lipid peroxidation in the liver, and the ability of S-adenosylmethionine (SAMe) to antagonize the CyA-induced alterations were studied in male Wistar rats. To evaluate the efficacy of SAMe, three CyA and SAMe protocols were used: Cotreatment with SAMe plus CyA, pretreatment with SAMe before starting cotreatment, and post-treatment with SAMe after beginning treatment with CyA alone. CyA treatment for one and four weeks depleted liver GSH, decreased the GSH/GSSG ratio and significantly reduced GSH and GSSG biliary concentrations and secretion rates. Additionally, long-term treatment enhanced lipid peroxidation. By contrast, when the rats were treated with CyA plus SAMe using any of the administration protocols, SAMe was seen to be efficient in antagonizing the GSH hepatic depletion, the changes in hepatic GSH/GSSG ratio and the increase induced by CyA in lipid peroxidation. Furthermore, SAMe also abolished the effects of CyA on the biliary secretion rates of GSH and GSSG. The efficacy of SAMe was similar, regardless of the administration protocols used. In conclusion, our results clearly demonstrate that SAMe is good for preventing, antagonizing and reversing the CyA-induced alterations in the hepatobiliary homeostasis of glutathione

Effects of S-adenosylmethionine on intrabiliary glutathione degradation induced by long-term administration of cyclosporin A in the rat

[EN] We investigate the ability of S-adenosylmethionine (SAMe) to antagonize the cyclosporine A (CyA)-induced inhibition of biliary glutathione efflux induced by long-term administration of CyA (10 mg/kg per day-CyA10 or 20 mg/kg per day-CyA20 for 4 weeks) in rats. CyA treatment reduced the liver content of total glutathione and caused a significant increase in the oxidized-to-reduced glutathione ratio and the thiobarbituric acid-reactive substances (TBARS) concentration. When the rats were concurrently treated with SAMe (10 mg/kg twice daily) and CyA, all these parameters did not significantly differ from control values. Treatment with CyA induced a significant increase in liver GGT activity that was attenuated by coadministration of SAMe. Biliary efflux of total glutathione was significantly reduced in animals treated with CyA. These changes were abolished by SAMe administration. Following inhibition of the intrabiliary catabolism of the tripeptide by acivicin, glutathione efflux rates increased to a lesser extent in animals cotreated with SAMe when compared to those receiving only CyA. The significant decrease in biliary efflux of oxidized glutathione induced by CyA was totally (S+CyA10) or partially (S+CyA20) prevented by coadministration of SAMe. Our observations confirm that SAMe cotreatment in rats antagonizes CyA-induced inhibition in the biliary efflux of glutathione and suggest that protection against intrabiliary glutathione degradation plays a major role in this protective effect

Effects of aging on the susceptibility to the toxic effects of cyclosporin A in rats. Changes in liver glutathione and antioxidant enzymes

[EN] Free radicals are involved in aging and cyclosporin A-induced toxicity. The age-related changes in the liver oxidative status of glutathione, lipid peroxidation, and the activity of the enzymatic antioxidant defense system, as well as the influence of aging on the susceptibility to the hepatotoxic effects of cyclosporin (CyA) were investigated in rats of different ages (1, 2, 4, and 24 months). The hepatic content of reduced glutathione (GSH) increased with aging, peaked at 4 months, and decreased in senescent rats. By contrast, glutathione disulfide (GSSG) and thiobarbituric acid-reactive substances (TBARS) concentrations and superoxide dismutase, catalase, and glutathione peroxidase activities were higher in the oldest than in the youngest rats. CyA treatment, besides inducing the well-known cholestatic syndrome, increased liver GSSG and TBARS contents and the GSSG/GSH molar ratio, and altered the nonenzymatic and enzymatic antioxidant defense systems. The CyA-induced cholestasis and hepatic depletion of GSH, and the increases in the GSSG/GSH ratio, and in GSSG and TBARS concentrations were higher in the older than the mature rats. Moreover, superoxide dismutase and catalase activities were found to be significantly decreased only in treated senescent rats. The higher CyA-induced oxidative stress, lipoperoxidation, and decreases in the antioxidant defense systems in the aged animals render them more susceptible to the hepatotoxic effects of cyclosporin. © 2001 Elsevier Science Inc

Glutathione Metabolism In Cyclosporine A‐Treated Rats: Dose‐ And Time‐Related Changes In Liver And Kidney

[EN] 1. We investigated the simultaneous effects of cyclosporine A (CsA) treatment in rats on glutathione metabolism, oxidative status and their interorgan relationship in the liver and kidney. 2. Reduced and oxidized glutathione (GSH and GSSG, respectively), lipid peroxidation and the activity of several enzymes of the glutathione cycle were evaluated in adult Wistar rats treated daily (i.p.) with saline, CsA vehicle (olive oil) or CsA (10 and 20 mg/kg per day) for either 1 or 4 weeks (short- and long-term treatments, respectively). 3. Cyclosporine A treatment elicited a significant depletion in liver GSH content and a decrease in the GSH/GSSG ratio that was unrelated to either the time of treatment or the dose used; these effects were already evident after I week of treatment. Renal GSH levels remained unaffected or increased, while those of GSSG increased markedly in all CsA-treated rats, leading to decreases in the GSH/GSSG ratio, except in rats treated in the short term with the lower dose of CsA. These changes in the GSH/GSSG ratio were time and dose dependent. Short-term CsA treatment using the higher dose and long-term treatment with both doses of CsA progressively enhanced lipid peroxidation, which was reflected by increased levels of thiobarbituric acid-reactive substances in both hepatic and renal homogenates. Hepatic γ-glutamylcysteine synthetase activity was increased after long-term treatment with both doses of CsA, whereas the activity of GSH hepatic peroxidase and GSH transferase was not significantly modified in any of the experimental groups. In contrast, renal γ-glutamyl transpeptidase activity decreased in a progressive fashion, with the magnitude of this decrease being dose and time dependent. The plasma levels of total glutathione increased only in rats treated in the long term, regardless of the dose of CsA used, and remained unaltered in animals treated in the short term. 4. In summary, the data collected indicate that CsA treatment alters the interorgan homeostasis of glutathione and the oxidative status of the rat liver and kidney, which is associated with increases in lipid peroxidation in both organs, and also induces modifications in the activity of some enzyme related to the glutathione cycle

Effects of aging and cyclosporin treatment on the hepatobiliary efflux of glutathione

[EN] The aim of this study was to investigate the effects of cyclosporin (CyA) treatment on biliary glutathione efflux in rats of different ages (1, 2, 4, and 24 months). CyA treatment reduced the liver content of total glutathione in 1-, 2- and 24 month old rats ( 30%, 43% and 30%, respectively). By contrast, oxidized glutathione (GSSG) concentration in liver tended to increase, although non significantly, in the rats aged 4 and 24 month ( + 36% and + 28%, respectively). The oxidized-to-reduced glutathione ratio was significantly increased in 2-, 4- and 24 month old animals ( + 23%, + 36% and >100%, respectively). Regarding biliary glutathione, our data indicate that efflux rates of total glutathione in control (untreated) rats increased to a maximum at 4 months, and decreased ( 56%) in 24 month old rats, although values were still higher than those from young animals. CyA treatment significantly reduced biliary glutathione secretion except in 24 month old rats ( 98%, 66% and 32%, at 1, 2 and 4 month, respectively). In addition, following inhibition of the intrabiliary catabolism of the tripeptide by acivicin, glutathione efflux rates into bile were significantly reduced by the drug only in 1- and 2 month old rats ( 29% and 55%, respectively) and even tended to increase, although non significantly, in oldest animals. Our data indicate that inhibition of biliary glutathione efflux by CyA was greater in younger rats and support the view that increased intrabiliary catabolism of the tripeptide and inhibition of its canalicular transport could contribute to the decline in biliary glutathione secretion induced by the drug

Susceptibility to the toxic effects of cyclosporin in the rat: effects of aging

[ES] Sumario de la revista Journal of Hepatology: Susceptibilidad a los efectos tóxicos de la ciclosporina en la rata: efectos del envejecimiento

The Control of Zoonotic Soil-Transmitted Helminthoses Using Saprophytic Fungi

Soil-transmitted helminths (STHs) are parasites transmitted through contact with soil contaminated with their infective eggs/larvae. People are infected by exposure to human-specific species or animal species (zoonotic agents). Fecal samples containing eggs of Ascaris suum or Lemurostrongylus sp. were sprayed with spores of the soil saprophytic filamentous fungi Clonostachys rosea (CR) and Trichoderma atrobrunneum (TA). The antagonistic effect was assessed by estimating the viability of eggs and their developmental rate. Compared to the controls (unexposed to fungi), the viability of the eggs of A. suum was halved in CR and decreased by two thirds in TA, while the viability of the eggs of Lemurostrongylus sp. was reduced by one quarter and one third in CR and TA treatments, respectively. The Soil Contamination Index (SCI), defined as the viable eggs that attained the infective stage, reached the highest percentages for A. suum in the controls after four weeks (66%), with 21% in CL and 11% in TA. For Lemurostrongylus sp., the values were 80%, 49%, and 41% for control, CR and TA treatments, respectively. We concluded that spreading spores of C. rosea or T. atrobrunneum directly onto the feces of animal species represents a sustainable approach under a One Health context to potentially reduce the risk of zoonotic STHs in humansThis research was funded by the Research Projects CTM2015-65954-R and RYC-2016-21407 (Ministerio de Economía y Competitividad, Spain; FEDER), and ED431F 2018/03 (Consellería de Cultura, Educación e Ordenación Universitaria, Xunta de Galicia, Spain). María Sol Arias Vázquez is recipient of a Ramón y Cajal (Ministerio de Economía y Competitividad, Spain) contractS

Advantageous Fungi against Parasites Transmitted through Soil

Although many fungal specimens are responsible for human and/or animal infection, other species are advantageous for preventing the infection by soil-transmitted zoonotic parasites. Infection occurs by the accidental ingestion of parasitic stages (cysts, oocysts, eggs, and larvae), their active penetration through the skin or through direct contact. Numerous species of helminths develop an external phase in the soil where the infective stages are attained, thus mammals become infected when grazing, drinking, or accidentally. Ectoparasites as ticks perform also in the soil the phase from egg to larva. Different soil saprophytic fungi that turn into predatory agents when parasitic stages are near have been isolated and described. These species are capable of destroying the pathogens or irreversibly decreasing their viability, providing thus a very interesting and sustainable tool to reduce environmental contamination by pathogenic agents. In the last year, a profound knowledge on the most appropriate fungal species, together with the proper way to disseminate them, has been acquired