Rate of free-radical oxidation of C18 diene and triene fatty acids in aqueous micellar solutions and effectiveness of beta-carotene as an inhibitor of their oxidation

The rate of accumulation of conjugated dienes of polyunsaturated fatty acids was measured during free-radical oxidation of linoleic acid (18:2n-6, LA), -linolenic acid (18:3n-3, -LNA), and -linolenic acid (18:3n-6, -LNA) initiated by 2,2"-azo-bis-(2-amidinopropane) hydrochloride in aqueous micellar solutions of sodium dodecyl sulfate and sodium cholate. It was shown that, unlike homogeneous solutions, the oxidative stability of PUFAs in aqueous dispersions increased with an increase in the extent of unsaturation. The rate of LA oxidation was more than tenfold greater than that of - and -LNA. The antioxidant activity of -carotene, in contrast to homogeneous solutions, in both micellar systems studied depended on the degree of PUFA unsaturation. We found that 5 M -carotene effectively inhibited the LA oxidation (almost by 90%), whereas the oxidation of -LNA and -LNA was not inhibited by -carotene even at much greater concentration (30 M). The paradoxical discrepancy between the extent of unsaturation and the PUFA oxidation rate, as well as a decrease in the efficiency of -carotene-dependent inhibition of oxidation of more polyunsaturated fatty acids in reactions conducted in aqueous dispersions is consistent with the model according to which the peroxyl radicals of LA and fatty acids with the doublebond number greater than two exhibit different polarity.     

Comparative study of antioxidant properties and cytoprotective activity of flavonoids

Antioxidant properties and cytoprotective activity of flavonoids (rutin, dihydroquercetin, quercetin, epigallocatechin gallate (EGCG), epicatechin gallate (ECG)) were studied. All these compounds inhibited both NADPH- and CCl₄-dependent microsomal lipid peroxidation, and the catechins were the most effective antioxidants. The I ₅₀ values calculated for these compounds by regression analysis were close to the I ₅₀ value of the standard synthetic antioxidant ionol (2,6-di-tert-butyl-4-methylphenol). The antiradical activity of flavonoids to O ₂ was studied in a model photochemical system. Rate constants of the second order reaction obtained by competitive kinetics suggested flavonoids to be more effective scavengers of oxygen anion-radicals than ascorbic acid. By competitive replacement all flavonoids studied were shown to be chelating agents capable of producing stable complexes with transition metal ions (Fe²⁺, Fe³⁺, Cu²⁺). The flavonoids protected macrophages from asbestos-induced damage, and the protective effect increased in the following series: rutin < dihydroquercetin < quercetin < ECG < EGCG. The cytoprotective effect of flavonoids was in strong positive correlation with their antiradical activity to O ₂ .     

Oxidative damage following cerebral ischemia depends on reperfusion - a biochemical study in rat

The extent of brain injury during reperfusion appears to depend on the experimental pattern of ischemia/reperfusion. The goals of this study were: first, to identify the rate of free radicals generation and the antioxidant activity during ischemia and reperfusion by means of biochemical measurement of lipid peroxidation (LPO) and both enzymatic (superoxid dismutase - SOD, catalase - CAT, glutathion peroxidase - GPx) and non-enzymatic antioxidants activity (glutathione - GSH); and second, to try to find out how the pattern of reperfusion may influence the balance between free radical production and clearance. Wistar male rats were subject of four-vessel occlusion model (Pulsinelly & Brierley) cerebral blood flow being controlled by means of two atraumatic arterial microclamps placed on carotid arteries. The level of free radicals and the antioxidant activity were measured in ischemic rat brain tissue homogenate using spectrophotometrical techniques. All groups subjected to ischemia shown an increase of LPO and a reduction of the activity of enzymatic antioxidative systems (CAT, GPx, SOD) and non-enzymatic systems (GSH). For both groups subjected to ischemia and reperfusion, results shown an important increase of LPO but less significant than the levels found in the group with ischemia only. Statistically relevant differences (p<0.01) between continuous reperfusion and fragmented reperfusion were observed concerning the LPO, CAT, SOD and GSH levels, oxidative aggresion during fragmented reperfusion being more important.     

Study of the first hours of microvinification by the use of osmotic stress-response genes as probes

When yeast cells are inoculated into grape must for vinification they find stress conditions because of osmolarity, which is due to very high sugar concentration, and pH lower than 4. In this work an analysis of the expression of three osmotic stress induced genes (GPD1, HSP12 and HSP104) under microvinification conditions is shown as a way to probe those stress situations and the regulatory mechanisms that control them. The results indicate that during the first hours of microvinification there is an increase in the GPDI mRNA levels with a maximum about one hour after inoculation, and a decrease in the amount of HSP12 and HSP104 mRNAs, although with differences between them. The RNA steady-state levels of all the genes considered, and in some cases the microvinification progress are significantly affected by the composition of the must (pH, nature of the osmotic agent and carbon source). These results point out the importance of the control of these parameters and the yeast molecular response during the first hours of vinification for an accurate winemaking process.     

The role of astroglia on the survival of dopamine neurons

Glial cells play a key role in the function of dopamine (DA) neurons and regulate their differentiation, morphology, physiological and pharmacological properties, survival, and resistance to different models of DA lesion. Several studies suggest that glial cells may be important in the pathogenesis of Parkinson’s disease (PD), a common neurodegenerative disorder characterized by degeneration of the nigrostriatal DA system. In this disease the role of glia could be due to the excessive production of toxic products such as nitric oxide (NO) or cytokines characteristic of inflammatory process, or related to a defective release of neuroprotective agents, such as small antioxidants with free radical scavenging properties or peptidic neurotrophic factors.     

Modulation of rat liver cytochrome P450 activity by prolonged red wine consumption

Cytochrome P450-dependent oxidation of lauric acid, p-nitrophenol and ethanol by liver microsomal fractions were studied in control rats and in animals given either ethanol, red wine, or alcohol-free red wine for 10 weeks. Ethanol increased the total cytochrome P450 and the isoenzyme 2E1 content, as well as the p-nitrophenol hydroxylation and ethanol oxidation. These effects of ethanol treatment were attenuated by red wine administration. Red wine increased the total antioxidant capacity of plasma, whereas the alcohol-free red wine decreased the cytochrome P450 content and decreased the oxidation of lauric acid, p-nitrophenol and ethanol to values lower than control. It is concluded that red wine administration attenuates the ethanol-induced enhancement in liver microsomal parameters dependent on cytochrome P450 2E1 activity, an affect that seems to be accomplished by the non-alcoholic constituents of red wine known to have antioxidant properties.     

Influence of the yeast strain on the changes of the amino acids,peptides and proteins during sparkling wine production by the traditional method

The influence of five yeast strains on the nitrogen fractions, amino acids, peptides and proteins, during 12 months of aging of sparkling wines produced by the traditional or Champenoise method, was studied. High-performance liquid chromatography (HPLC) techniques were used for analysis of the amino acid and peptide fractions. Proteins plus polypeptides were determined by the colorimetric Bradford method. Four main stages were detected in the aging of wines with yeast. In the first stage, a second fermentation took place; amino acids and proteins plus polypeptides diminished, and peptides were liberated. In the second stage, there was a release of amino acids and proteins, and peptides were degraded. In the third stage, the release of proteins and peptides predominated. In the fourth stage, the amino acid concentration diminished. The yeast strain used influenced the content of free amino acids and peptides and the aging time in all the nitrogen fractions. Received 25 March 2002/ Accepted in revised form 31 July 2002     

Physiological thiols as promoters of glutathione oxidation and modifying agents in protein S-thiolation.

Glutathione is one of the most relevant antioxidants present in cells. It exerts its scavenging action through the involvement of efficient and ubiquitous enzymes. GSH on the other hand, because of its chemical features, can scavenge reactive oxygen species without the involvement of enzymatic systems. The study deals with the mobilization of GSH pool in a nonenzymatic antioxidant system by other physiological thiols (i.e., cysteine and cysteinyl-glycine), which are far more sensitive than GSH to oxidative conditions. These thiol compounds, in the presence of iron/EDTA, can promote oxygen activation through their oxidation to disulfides. GSH, through trans-thiolation reactions, can regenerate Cys and CysGly, which can then recycle, thus inducing a massive GSH oxidation. In these conditions, making use of bovine lens aldose reductase as a protein model, evidence is given that Cys and CysGly promote specific protein S-thiolation reactions. The possibility that GSH may be recruited in controlling cellular oxygen tension is considered.     

Population genetic variation in genome-wide gene expression

Evolutionary biologists seek to understand which traits display variation, are heritable, and influence differential reproduction, because such traits respond to natural selection and underlie organic evolution. Selection acts upon individual differences within a population. Whether individual differences within a natural population include variation in gene expression levels has not yet been addressed on a genome-wide scale. Here we use DNA microarray technology for measuring comparative gene expression and a refined statistical analysis for the purpose of comparing gene expression levels in natural isolates of the wine yeast Saccharomyces cerevisiae. A method for the Bayesian analysis of gene expression levels is used to compare four natural isolates of S. cerevisiae from Montalcino, Italy. Widespread variation in amino acid metabolism, sulfur assimilation and processing, and protein degradation-primarily consisting of differences in expression level smaller than a factor of 2-is demonstrated. Genetic variation in gene expression among isolates from a natural population is present on a genomic scale. It remains to be determined what role differential gene expression may play in adaptation to new or changing environments.