José David Sepúlveda-Sánchez

Airborne particulate matter PM2.5 from Mexico City affects the generation of reactive oxygen species by blood neutrophils from asthmatics: an in vitro approach

BackgroundThe Mexico City Metropolitan Area is densely populated, and toxic air pollutants are generated and concentrated at a higher rate because of its geographic characteristics. It is well known that exposure to particulate matter, especially to fine and ultra-fine particles, enhances the risk of cardio-respiratory diseases, especially in populations susceptible to oxidative stress. The aim of this study was to evaluate the effect of fine particles on the respiratory burst of circulating neutrophils from asthmatic patients living in Mexico City.MethodsIn total, 6 subjects diagnosed with mild asthma and 11 healthy volunteers were asked to participate. Neutrophils were isolated from peripheral venous blood and incubated with fine particles, and the generation of reactive oxygen species was recorded by chemiluminescence. We also measured plasma lipoperoxidation susceptibility and plasma myeloperoxidase and paraoxonase activities by spectrophotometry.ResultsAsthmatic patients showed significantly lower plasma paraoxonase activity, higher susceptibility to plasma lipoperoxidation and an increase in myeloperoxidase activity that differed significantly from the control group. In the presence of fine particles, neutrophils from asthmatic patients showed an increased tendency to generate reactive oxygen species after stimulation with fine particles (PM2.5).ConclusionThese findings suggest that asthmatic patients have higher oxidation of plasmatic lipids due to reduced antioxidant defense. Furthermore, fine particles tended to increase the respiratory burst of blood human neutrophils from the asthmatic group.On the whole, increased myeloperoxidase activity and susceptibility to lipoperoxidation with a concomitant decrease in paraoxonase activity in asthmatic patients could favor lung infection and hence disrupt the control of asthmatic crises.

Crystallochemical characterization of calcium oxalate crystals isolated from seed coats ofPhaseolus vulgaris and leaves ofVitis vinifera

Calcium oxalate crystals are a major biomineralization product in higher plants. Their biological function and use are not well understood. In this work, we focus on the isolation and crystallochemical characterization of calcium oxalate crystals from seed coats of Phaseolus vulgaris (prisms) and leaves of Vitis vinifera (raphides and druses) using ultrastructural methods. A proposal based on crystal growth theory was used for explaining the existence of different morphologies shown by these crystals grown inside specialized cells in plants.

Chitosan-based microcapsules containing grapefruit seed extract grafted onto cellulose fibers by a non-toxic procedure

A novel non-toxic procedure is described for the grafting of chitosan-based microcapsules containing grapefruit seed oil extract onto cellulose. The cellulose was previously UV-irradiated and then functionalized from an aqueous emulsion of the chitosan with the essential oil. The novel materials are readily attained with durable fragrance and enhanced antimicrobial properties. The incorporation of chitosan as determined from the elemental analyses data was 16.08+/-0.29 mg/g of sample. Scanning electron microscopy (SEM) and gas chromatography-mass spectroscopy (GC-MS) provided further evidence for the successful attachment of chitosan microcapsules containing the essential oil to the treated cellulose fibers. The materials thus produced displayed 100% inhibition of Escherichia coli and Staphylococcus epidermidis up to 48 h of incubation. Inhibition of bacteria by the essential oil was also evaluated at several concentrations.

Calcium carbonate precipitation by heterotrophic bacteria isolated from biofilms formed on deteriorated ignimbrite stones: influence of calcium on EPS production and biofilm formation by these isolates.

Heterotrophic CaCO3-precipitating bacteria were isolated from biofilms on deteriorated ignimbrites, siliceous acidic rocks, from Morelia Cathedral (Mexico) and identified as Enterobacter cancerogenus (22e), Bacillus sp. (32a) and Bacillus subtilis (52g). In solid medium, 22e and 32a precipitated calcite and vaterite while 52g produced calcite. Urease activity was detected in these isolates and CaCO3 precipitation increased in the presence of urea in the liquid medium. In the presence of calcium, EPS production decreased in 22e and 32a and increased in 52g. Under laboratory conditions, ignimbrite colonization by these isolates only occurred in the presence of calcium and no CaCO3 was precipitated. Calcium may therefore be important for biofilm formation on stones. The importance of the type of stone, here a siliceous stone, on biological colonization is emphasized. This calcium effect has not been reported on calcareous materials. The importance of the effect of calcium on EPS production and biofilm formation is discussed in relation to other applications of CaCO3 precipitation by bacteria.

Effect of Lactobacillus plantarum and chitosan in the reduction of browning of pericarp Rambutan (Nephelium lappaceum)

The effects of Lactobacillus plantarum alone or in combination with chitosan were evaluated on quality and color retention in rambutan fruits (Nephelium lappaceum) stored at 25 degrees C and 10 degrees C with 75+/-2.5% of relative humidity for 10 and 15 days, respectively. The development of the microorganisms was evidenced by viability analyses and lactic acid production. The application of L. plantarum significantly improved color retention (a* and L*), and reduced weight losses. The lactobacilli, alone or in combination with chitosan, preserved fruit quality characteristics such as firmness, total soluble solids and titratable acidity. The lactobacilli application on rambutan pericarp produced acidification of pericarp and avoided the browning; thereby desiccation was prevented due to biofilm formation.

Electrochemical and atomic force microscopy investigations of new materials from N-trifluoromethanesulfonyl-1-azahexa-1,3,5-trienes derivatives

Thin films have been created on the surface of highly oriented pyrolytic graphite electrodes from chemically synthesized p-donor species by using the cyclic voltammetry technique and in situ electrochemistry-atomic force microscopy. Results indicate that it is possible to form new compounds called molecular materials from the coupling of electro-oxidized N-trifluoromethanesulfonyl-1-azahexa-1,3,5-triene species and a [Cr(C2O4)3]3- anion. Different techniques such as AFM, SEM and EDS were employed to characterize the films morphology and composition. Results indicate that the new materials exhibited a particular electrochemical response and a different film texture depending on the chemical composition of the starting compounds.

In Situ Atomic Force Microscopy Imaging of a Heteropolyanion onto a HOPG Electrode during Its Cyclic Voltammetry

The voltammetric electrodeposition of the heteropolyanion (HPA) [CoMo 6 O 18 (OH) 6 ] 3 on the surface of highly oriented pyrolytic graphite (HOPG) was studied by in situ atomic force microscopy (AFM). The electrochemical behavior of the HPA showed voltammetric plots similar to those found on the growth mechanism of organic conducting polymers. The combined electrochemical behavior and the AFM images revealed that electroreduced species of HPA (ranging from 1.5 to 0.6 V vs. Ag wire) were deposited on the graphite surface in an irregular aggregation. The depth and morphology of the deposit changed as the number of potential cycles and concentration were modified. Additionally, the electrodeposits were characterized by scanning electron microscopy-energy dispersive spectroscopy techniques. These results show that electrochemical studies of inorganic compounds by electrochemistry-AFM provide a strong evidence of electrodeposition for heteropolyanions such as the HPA molecule.