Transferência trófica de mercúrio e selênio na costa norte do Rio de Janeiro

Trophic transfer of trace elements along marine food chains has been recognized as an important process influencing metal and metalloid bioaccumulation. The trophic transfer of mercury was observed between trophic levels from prey (considering fish with different feeding habits and squid) to top predator (dolphin) in a Northern coastal food chain of Rio de Janeiro. Selenium showed some evidence of trophic transfer between lower trophic levels. Dolphin presented the highest mercury concentrations whereas the benthic carnivorous fish showed the highest selenium concentrations. Mercury is biomagnified through the food chain while selenium does not present the same behavior.

Physical properties of Brazil nuts

The Brazil-nut, also known as Para-nut, is widely used as food and in cosmetic industries. The seeds are rich in lipids and protein, and also present a considerable amount of selenium. Limited research has been conducted on postharvest of the Brazil nut, being an important information to design equipment related to aeration, drying, storage and transportation steps. Thus, the objective of this study was to determine the physical properties of the Brazil-nut with and without tegument. The dimensions found for the almonds with tegument were 39.35 mm in the X axis, 24.19 mm in the Y axis, and 17.88 mm in the Z axis. However for the almond without tegument the values were 31.05 mm in X, 14.38 in Y and 15.91 mm in Z axis. The sphericity was 66.40% and 51.59% for the kernels with and without seed tegument respectively. The kernels with and without tegument presented sphericity of 63.00% and 47.72% respectively. The mass of 1000 almonds was 6.13 kg for almond with teguments and 3.18 kg for almonds without teguments. Specific mass of 0.947 g.cm-3 and 1.003 g.cm-3 for the kernels with and without tegument, coupled with a porosity of 46.88% and 37.60% and, resulting on a bulk density of 0.504 g.cm-3 and 0.626 g.cm-3 for almonds with and without teguments respectively. Finally, the angle of repose for the kernels with teguments was 36.37°.

Reaction of diphenyl diselenide with hydrogen peroxide and inhibition of delta-aminolevulinate dehydratase from rat liver and cucumber leaves

The interaction of the product of H2O2 and (PhSe)2 with delta-aminolevulinate dehydratase (delta-ALA-D) from mammals and plants was investigated. (PhSe)2 inhibited rat hepatic delta-ALA-D with an IC50 of 10 µM but not the enzyme from cucumber leaves. The reaction of (PhSe)2 with H2O2 for 1 h increased the inhibitory potency of the original compound and the IC50 for animal delta-ALA-D inhibition was decreased from 10 to 2 µM. delta-ALA-D from cucumber leaves was also inhibited by the products of reaction of (PhSe)2 with H2O2 with an IC50 of 4 µM. The major product of reaction of (PhSe)2 with H2O2 was identified as seleninic acid and produced an intermediate with a lambdamax at 265 nm after reaction with t-BuSH. These results suggest that the interaction of (PhSe)2 with mammal delta-ALA-D requires the presence of cysteinyl residues in close proximity. Two cysteine residues in spatial proximity have been recently described for the mammalian enzyme. Analysis of the primary structure of plant delta-ALA-D did not reveal an analogous site. In contrast to (PhSe)2, seleninic acid, as a result of the higher electrophilic nature of its selenium atom, may react with additional cysteinyl residue(s) in mammalian delta-ALA-D and also with cysteinyl residues from cucumber leaves located at a site distinct from that found at the B and A sites in mammals. Although the interaction of organochalcogens with H2O2 may have some antioxidant properties, the formation of seleninic acid as a product of this reaction may increase the toxicity of organic chalcogens such as (PhSe)2.

Antioxidant dietary deficiency induces caspase activation in chick skeletal muscle cells

Apoptosis and necrosis are two distinct forms of cell death that can occur in response to different agents and stress conditions. In order to verify if the oxidative stress induced by dietary selenium and vitamin E deficiencies can lead muscle cells to apoptosis, one-day-old chicks were reared using diets differing in their vitamin E (0 or 10 IU/kg) and selenium (0 or 0.15 ppm) supplementation. Chick skeletal muscle tissue was obtained from 28-day-old animals and used to verify apoptosis occurrence based on caspase activity detection and DNA fragmentation. Antioxidant deficiency significantly increased caspase-like activity assessed by the hydrolysis of fluorogenic peptide substrates (Abz-peptidyl-EDDnp) at lambdaexc = 320 nm and lambdaem = 420 nm. Proteolytic activation was not accompanied by typical internucleosomal DNA fragmentation detected by field inversion gel electrophoresis. Although the general caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp(O-Me) fluoromethyl ketone (Z-VAD-fmk) (0 to 80 muM) did not block caspase-like activity when preincubated for 30 min with muscle homogenates, the hydrolyzed substrates presented the same cleavage profile in HPLC (at the aspartic acid residue) when incubated with the purified recombinant enzyme caspase-3. These data indicate that oxidative stress causes caspase-like activation in muscle cells and suggest that cell death associated with exudative diathesis (dietary deficiency of selenium and vitamin E) can follow the apoptotic pathway.

Effect of (-)-∆9-tetrahydrocannabinoid on the hepatic redox state of mice

(-)-∆9-Tetrahydrocannabinol (∆9-THC), a psychoactive component of marijuana, has been reported to induce oxidative damage in vivo and in vitro. In this study, we administered ∆9-THC to healthy C57BL/6J mice aged 15 weeks in order to determine its effect on hepatic redox state. Mice were divided into 3 groups: ∆9-THC (N = 10), treated with 10 mg/kg body weight ∆9-THC daily; VCtrl (N = 10), treated with vehicle [1:1:18, cremophor EL® (polyoxyl 35 castor oil)/ethanol/saline]; Ctrl (N = 10), treated with saline. Animals were injected ip twice a day with 5 mg/kg body weight for 10 days. Lipid peroxidation, protein carbonylation and DNA oxidation were used as biomarkers of oxidative stress. The endogenous antioxidant defenses analyzed were glutathione (GSH) levels as well as enzyme activities of superoxide dismutase, catalase, glutathione S-transferase, glutathione reductase, and glutathione peroxidase (GPx) in liver homogenates. The levels of mRNA of the cannabinoid receptors CB1 and CB2 were also monitored. Treatment with ∆9-THC did not produce significant changes in oxidative stress markers or in mRNA levels of CB1 and CB2 receptors in the liver of mice, but attenuated the increase in the selenium-dependent GPx activity (Δ9-THC: 8%; VCtrl: 23% increase) and the GSH/oxidized GSH ratio (Δ9-THC: 61%; VCtrl: 96% increase), caused by treatment with the vehicle. Δ9-THC administration did not show any harmful effects on lipid peroxidation, protein carboxylation or DNA oxidation in the healthy liver of mice but attenuated unexpected effects produced by the vehicle containing ethanol/cremophor EL®.

Investigation of glutathione peroxidase activity in chicken meat under different experimental conditions

Due to the fact that previous studies on the enzymatic activity of Glutathione peroxidase (GSH-Px) diverge widely in their methodology and results, this study aimed to investigate the influence of different analytical conditions on GSH-Px activity in chicken thighs from broilers that were fed different diets with different sources and concentrations of selenium. GSH-Px activity was evaluated six hours after slaughter and 120 days after frozen storage at -18 ºC. The different analytical conditions included time of pre-incubation (0, 10 and 30 minutes), reaction medium, types of substrate (H2O2 (0.72 mM, 7.2 mM, and 72 mM) and Terc-butil hydroperoxide 15 mM), and different buffer concentrations (buffer 1, potassium phosphate 50 mM pH 7.0 + EDTA 1 mM + mercaptoethanol 1 mM, and buffer 2, tris-HCl 50 mM pH 7.6 + EDTA 1 mM + mercapthanol 5 mM). The results show that the highest GSH-Px activity was observed when enzyme and substrate were in contact at 22 ºC without any pre-incubation, and that, when used at concentrations above 0.72 mM, hydrogen peroxide saturated the GSH-Px enzyme and inhibited its activity. The enzyme presented higher affinity to hydrogen peroxide when compared to terc-butil peroxide, and the addition of a buffer containing mercaptoethanol did not increase GSH-Px enzymatic activity. The activity of GSH-Px was not influenced by the source and concentration of selenium in the diet either. The obtained results allowed the determination of the best temperature of contact between the enzyme and substrate (22 ºC), the optimum concentration, and the type of substrate and buffer to be used. This information is extremely useful for future studies on GSH-Px activity in meat due to the divergence and little information found in the literature.

Physicochemical properties and mineral and protein content of honey samples from Ceará state, Northeastern Brazil

This study evaluated the physicochemical properties and protein and mineral content of honey samples from Ceará State, Northeastern Brazil, one of the major honey exporters in the country. Nutritional importance of the minerals detected was also analyzed. Physicochemical properties were examined according to the AOAC and CAC official methods; the protein content was determined using the Bradford method, and the minerals were analyzed by atomic absorption spectrometry. All analyses were performed in triplicate. The levels of macrominerals sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) varied from 1.80-47.20, 21.30-1513.30, 14.58-304.82, and 2.48-28.33 mg/kg, respectively, and the trace elements iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), selenium (Se), and chromium (Cr) varied from 0.12-8.76, 0.07-1.29, 0.06-1.96, 0.07-1.85 mg/kg, 0.36 × 10-3-62.00 × 10-3 and 22.50 × 10-3-170.33 × 10-3 µg/kg, respectively. Myracrodruon urundeuva honey sample had high contents of macrominerals (Na, K, Ca, and Mg). Protein content of the Anacardium occidentale honey sample was the highest (1121.00 µg/g) among the samples analyzed. Among the minerals detected in the honey samples, K showed the highest concentration, followed by Ca, Na, and Mg. The presence of trace elements can show environmental contamination. The honey samples studied were free of trace elements contamination, except for Mn; the Piptadenia moniliformis was the only honey sample that was in compliance with the law requirements. The variations of the chemical constituents in the honey samples are probably related to differences in the floral origin and mineral and protein contents and confirm the nutritional importance of Ceará State honey.