José Hernández

Lipids and Oxidative Stress Associated with Ethanol-Induced Neurological Damage

The excessive intake of alcohol is a serious public health problem, especially given the severe damage provoked by chronic or prenatal exposure to alcohol that affects many physiological processes, such as memory, motor function, and cognitive abilities. This damage is related to the ethanol oxidation in the brain. The metabolism of ethanol to acetaldehyde and then to acetate is associated with the production of reactive oxygen species that accentuate the oxidative state of cells. This metabolism of ethanol can induce the oxidation of the fatty acids in phospholipids, and the bioactive aldehydes produced are known to be associated with neurotoxicity and neurodegeneration. As such, here we will review the role of lipids in the neuronal damage induced by ethanol-related oxidative stress and the role that lipids play in the related compensatory or defense mechanisms.

Global financial crisis and dependence risk analysis of sector portfolios: a vine copula approach

ABSTRACT We use regular vine (r-vine), canonical vine (c-vine) and drawable vine (d-vine) copulas to examine the dependence risk characteristics of three 20-stock portfolios from the retail, manufacturing and gold-mining equity sectors of the Australian market in periods before, during and after the 2008–2009 global financial crisis (GFC). Our results indicate that the retail portfolio is less risky than the manufacturing counterpart in the crisis period, while the gold-mining portfolio is less risky than both the retail and manufacturing sector portfolios. Both the retail and gold stocks display a higher propensity to yield positively skewed returns in the crisis periods, contrary to the manufacturing stocks. The r-vine is found to best capture the multivariate dependence structure of the stocks in the retail and gold-mining portfolios, while the d-vine does it for the manufacturing stock portfolio. These findings could be used to develop dependence risk- and investment risk-adjusted strategies for investment, rebalancing and hedging which more adequately account for the downside risk in various market conditions.

Multivariate dependence and portfolio optimization algorithms under illiquid market scenarios

We propose a model for optimizing structured portfolios with liquidity-adjusted Value-at-Risk (LVaR) constraints, whereby linear correlations between assets are replaced by the multivariate nonlinear dependence structure based on Dynamic conditional correlation t-copula modeling. Our portfolio optimization algorithm minimizes the LVaR function under adverse market circumstances and multiple operational and financial constraints. When considering a diversified portfolio of international stock and commodity market indices under multiple realistic portfolio optimization scenarios, the obtained results consistently show the superiority of our approach, relative to other competing portfolio strategies including the minimum-variance, risk-parity and equally weighted portfolio allocations.

Alcoholism: Common and Oxidative Damage Biomarkers

For many years it has been assumed that moderate alcohol intake might provide health benefits to humans, while alcohol abuse generally produces some systemic complications, even when physical and mental dependence on alcohol has not developed. Many studies have focused on distinct molecules that might serve as useful early or late biomarkers in individuals that consume important amounts of alcohol. Indeed, the diversity of molecules postulated as biomarkers is quite wide and this is the direct reflection of the broad range of mechanisms involved in the impact that alcohol has on human health, either as a result of acute or chronic intake, the latter being a cause death. In this review, we have considered most of the molecules that have been followed-up in individuals who drink large amounts of alcohol, as well as some of those that have been less intensely studied, and we present a pair of oxidative biomarkers that could be used to evaluate early stage alcoholism.

Nitric oxide and inducible nitric oxide synthase expression are downregulated in acute cholestasis in the rat accompanied by liver ischemia

Hepatic blood flow decreases under cholestasis and there is evidence that NO regulates liver microvascular perfusion. Thus, the aim of the present study was to evaluate NO synthesis in cholestasis. Cholestasis was induced by bile-duct ligation (BDL) in male Wistar rats. Bilirubins and enzyme activities were measured in serum. Lipid peroxidation, GSH, GSSG and glycogen were determined in liver. Histopathological analysis was performed. Serum NO2- + NO3- concentration was measured by the Gries reaction. iNOS immunoblot analysis was carried out using an iNOS polyclonal antibody. After 7 days of BDL lipid peroxidation increased while GSH/GSSG ratio decreased. Serum NO2- + NO3- and liver iNOS protein were reduced, accompanied by ischemia as revealed by the histopathological analysis. GSH upregulates NO synthesis by increasing iNOS mRNA levels and iNOS activity, thus the reduction of GSH/GSSG ratio may be responsible for the downregulation of iNOS protein and NO synthesis, which in turn may explain the observed ischemia and the decreased hepatic blood perfusion in cholestasis reported by others.

Oxidative dehydrogenation of n-octane over Mg-containing SBA-15 material

Abstract In this study, it is proposed the incorporation of MgO into of SBA-15 via the direct synthesis different atomic ratios of Si/Mg (20, 40 and 80). Although the incorporation of Mg did not affect the mesoporous character of SBA-based materials, it was found dramatic changes in the SBA-15 characteristic honeycomb structure even after the incorporation of small amount of Mg. The creation of more basic sites in SBA-15, because of the addition of Mg, improved ODH conversion of n-octane with respect to SBA-15, used as reference. Sample with a Si/Mg molar ratio of 20 showed the best catalytic performance in the oxidative dehydrogenation of n-octane, while the sample with a Si/Mg molar ratio of 40 achieve the highest productions of olefins.

HPLC Method for Quantification of Caffeine and Its Three Major Metabolites in Human Plasma Using Fetal Bovine Serum Matrix to Evaluate Prenatal Drug Exposure

Caffeine is recognized as the first-line therapeutic agent for apnea of prematurity. The dosage regimen is 10 mg/kg loading dose and 2.5 mg/kg maintenance dose. However, the plasma concentration achieved, not always, is therapeutically useful. It makes necessary to increase the doses to reach plasma concentration up to 30 or 35 μg/mL or even higher to attain therapeutic effect. To study why neonates have these differences, and whether these effects are linked to prenatal caffeine exposure, we had to develop an analytical method for an accurate measurement of caffeine and metabolites concentration. The analysis was carried out using fetal bovine serum (FBS) as biological matrix in a high-performance liquid chromatography with an ultraviolet detector method. This method allows acceptable chromatographic resolution between analytes in 15 minutes. It was validated and proved to be linear in the 0.1–40 µg/mL range for caffeine, paraxanthine, theobromine, and theophylline in the same chromatographic analysis. Accuracy for quality control samples for intra- and interday assays was ranged from 96.5 to 105.2% and 97.1 to 106.2%. Precision had CV no more than 10% in all concentration levels for all analytes. No differences were observed between quantification in human and FBS. This method was applied to quantify plasma drug concentration in mothers and their newborns in a Mexican northeast population. In our study, we confirmed self-reported caffeine maternal intake in 85.2% (n=23); meanwhile, in their newborns plasma, it was detected only in 78% (n=21). Caffeine plasma concentrations in mother and newborn had a linear relationship, and no differences were observed between groups (mothers versus children). These results suggest that our analytical method and substitution of biological matrix was linear, precise, and accurate for caffeine quantification and could be used for measuring prenatal exposure and let us to study, in the future, concentration differences observed during apnea clinical treatment.