Biomedical subjects

José M Vega

Publications and source records attributed to José M Vega.

6 recordsLinked to original sources

PubMed2004

Phenomenological model of weakly damped Faraday waves and the associated mean flow.

A phenomenological model of parametric surface waves (Faraday waves) is introduced in the limit of small viscous dissipation that accounts for the coupling between surface motion and slowly varying streaming and large-scale flows (mean flow). The primary bifurcation of the model is to a set of standing waves (stripes, given the functional form of the model nonlinearities chosen here). Our results for the secondary instabilities of the primary wave show that the mean flow leads to a weak destabilization of the base state against Eckhaus and transverse amplitude modulation instabilities, and introduces a longitudinal oscillatory instability which is absent without the coupling. We compare our results with recent one-dimensional amplitude equations for this system systematically derived from the governing hydrodynamic equations.

Journal Article↗

PubMed2004

UV-A mediated induction of carotenoid accumulation in Dunaliella bardawil with retention of cell viability.

The effect of adding UV-A radiation (320-400 nm) to photosynthetically active radiation (PAR, 400-700 nm) during growth of the photosynthetic marine microalga Dunaliella bardawil was investigated in this work in terms of cell growth and carotenoid production. Although signs of slow cell growth (slight reduction of chlorophyll and protein content) were observed after 24 h of cell exposure to UV-A (40 micromol photons m(-2) s(-1) and 70 micromol photons m(-2) s(-1)) plus 140 micromol photons m(-2) s(-1) PAR , 84 h exposure to these UV-A conditions slightly stimulated cell growth and increased the photosynthetic efficiency of the exposed cultures. The enhanced cell growth was coupled with an increase in total carotenoid content. Besides beta-carotene as the major pigment, increases in the well-known antioxidants lutein and zeaxanthin of about 3-fold and 5-fold, respectively, were determined in cultures exposed to UV-A radiation of 70 micromol photons m(-2) s(-1)for 84 h. As a consequence, far from being negative to cell growth, low and medium UV-A radiation are stress factors that could be successfully applied to long-term processes for large scale carotenoid production using D. bardawil cultures with retention of cell viability. UV-A exposure has the advantage of being a factor either easily applied or removed as required, in contrast to other nutrient stresses, which require medium replacement for their application.

Cell Survival↗

PubMed2003

Characterization of anthocyanins from the fruits of baguaçu (Eugenia umbelliflora Berg).

Anthocyanin pigments in the berries of baguaçu (Eugenia umbelliflora Berg), a tropical fruit from Brazil, were extracted with 0.1% HCl in ethanol, and the crude anthocyanin extract was purified by Amberlite XAD-7 open-column chromatography. Six major anthocyanins were isolated by preparative HPLC, and their chemical structures were identified by spectroscopic methods (TLC, UV-vis, MS, and (1)H NMR). Delphinidin 3-O-beta-glucopyranoside, cyanidin 3-O-beta-glucopyranoside, petunidin 3-O-beta-glucopyranoside, pelargonidin 3-O-beta-glucopyranoside, peonidin 3-O-beta-glucopyranoside, and malvidin 3-O-beta-glucopyranoside were identified. On the basis of chromatographic data the total anthocyanin content was 342 mg/100 g of fresh baguaçu berries. Therefore, the concomitant presence of six anthocyanins in a single plant species makes this product promising as a new pigment source.

Anthocyanins↗

PubMed2003

Metal toxicity in Chlamydomonas reinhardtii. Effect on sulfate and nitrate assimilation.

Cadmium (Cd(2+)) or copper (Cu(2+)) ions are toxic for Chlamydomonas reinhardtii growth, at 300 microM, and the alga may accumulate about 0.90+/-0.02 and 0.64+/-0.02% of its dry weight, respectively. Metal contamination changes the elemental composition of dried alga biomass, which indicates the possibility to use C. reinhardtii as biosensor and bioremediator of the aquatic contamination by heavy metals. Either, Cd(2+) or Cu(2+), inhibits about 20% of the nitrate consumption rate by the cells, while only Cd(2+) increases about 40% the sulfate consumption rate. The presence of 1 mM calcium (Ca(2+)) in the culture medium increases the C. reinhardtii productivity (about 50%), the nitrate uptake rate (about 20%) and the sulfate uptake rate (about 30%). In addition, Ca(2+) overcomes the Cd(2+) (300 microM) toxicity by decreasing (about 35%) the intracellular accumulation of metal. Sulfur-starvation induces in C. reinhardtii the expression of serine acetyltransferase and O-acetylserine(thiol)lyase activities, but decreases 50% the consumption rate of nitrate by the cells. Sulfate is also required for the full expression of the nitrate reductase (NR), nitrite reductase (NiR) and glutamate synthase activities.

Animals↗

PubMed2003

Carotenoids as protective response against oxidative damage in Dunaliella bardawil.

In the present work the relation between carotenoids production and cell response mechanisms to oxidative damage was studied. High light intensity and nitrogen starvation, both conditions, which may increase the oxidative damage in microalgae, significantly increased total carotenoids content in Dunaliella bardawil, the effect of N-starvation being more noticeable when acting synergetically with light on carotenoid production. S-starvation stimulated carotenoids production as much as N-starvation. The use of norflurazon, inhibitor of phytoene desaturase that blocks formation of epsilon-carotene from phytoene, caused a decrease of carotenoid content down to 5% that of the control cells incubated without the inhibitor. The decrease in the oxygen consumption rate of D. bardawil cells exposed to norflurazon suggests a connection between carotenoids desaturation and chloroplastic oxygen species dissipation processes reported in the literature for other algae. It is an indication of the carotenoids involvement in chloroplastic response mechanisms to oxidative damage.

Carotenoids↗

PubMed2002

Coupled mean flow-amplitude equations for nearly inviscid parametrically driven surface waves.

Nearly inviscid parametrically excited surface gravity-capillary waves in two-dimensional periodic domains of finite depth and both small and large aspect ratio are considered. Coupled equations describing the evolution of the amplitudes of resonant left- and right-traveling waves and their interaction with a mean flow in the bulk are derived, and the conditions for their validity established. In general the mean flow consists of an inviscid part together with a viscous streaming flow driven by a tangential stress due to an oscillating viscous boundary layer near the free surface and a tangential velocity due to a bottom boundary layer. These forcing mechanisms are important even in the limit of vanishing viscosity, and provide boundary conditions for the Navier-Stokes equation satisfied by the mean flow in the bulk. The streaming flow is responsible for several instabilities leading to pattern drift.

Journal Article↗