907 resultados para selenium concentration


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Effects of pulsing with different concentrations of gibberellin plus benzyladenine (GA(4+7) + BA), a proprietary mixture of GA(4+7) plus BA in a commercial floral preservative (GA(4+7) + BA + preservative), or a propriety mixture of sugar plus acidifier developed for bulbous flowers (floral bulb preservative) were studied on postharvest performance and quality of cut lily (Lilium hybrids) and gladiolus ( Gladiolus hybrids) flowers. Pulsing of cut stems of lily with GA(4+7) + BA at 5 or 2 mL.L-1 GA(4+7) + BA + preservative for 20 hours at 3 +/- 1 degrees C extended the vase life and controlled leaf chlorosis of 'Cobra'oriental lily and 'Cappuccino'and Pot Corn'asiatic lily. Cut 'Orange Art'asiatic lily performed best when pulsed with GA(4+7) + BA at 10 mg.L-1. For cut gladiolus, pulsing with GA(4+7) + BA at 10 mg.L-1 extended the vase life of 'Alice', 'Mammoth', and 'Passion', while 'Scarlet'had the longest vase life when pulsed with 5 mg.L-1 GA(4+7) + BA. GA(4+7) + BA + preservative also extended the vase life and controlled leaf chlorosis, but the floral bulb preservative had no effect on vase life extension or preventing leaf chlorosis of lilies. Gladiolus cultivars had no or minor leaf chlorosis during vase period. Overall, overnight pulsing with GA(4+7) + BA + or GA(4+7) + BA + preservative extended the vase life and prevented leaf chlorosis

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Objetives: The aim of this study was to verify the anticariogenic effect of acidulate solutions with low NaF concentration, using pH-cycling model and bovine enamel. Material and Methods: Enamel blocks were submitted to the surface microhardness (SMH) test and randomly divided in 12 experimental and one placebo groups. The blocks were submitted to pH cycling for 7 days, with daily applications once/day of 0.05% NaF and 0.1% NaF and twice/day of 0.02% NaF solutions. Four different pH: 4.0, 5.0, 6.0 and 7.0 were used. Next, SMH test was again used to determine the surface microhardness percentage change (%SMH). Data obtained for %SMH were homogeneous and passed through variance analyses and Tukey's test (5%) as far as fluoride concentrations and pH. Results: The results showed that pH influenced %SMH in 0.02% NaF and 0.05% NaF solutions with pH 4.0, which had less mineral loss compared to pH 7.0 (p<0.05). The 0.02% NaF - pH 4.0, and 0.05% NaF – pH 7.0 groups showed similar results (p>0.05). A dose-response relationship was observed among the tested solutions, with better anticariogenic effect for the 0.1% NaF solution. Conclusion: The results suggest that the addition of citric acid to acidulate mouth rinses reduce mineral loss.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The aim of this clinical randomized double-blind split-mouth study was to assess the effectiveness of a 6% hydrogen peroxide with nitrogen-doped titanium dioxide light activated bleaching agent. 31 patients were treated with: one upper hemiarcade with a 35% hydrogen peroxide bleaching agent and the other hemiarcade with a 6% hydrogen peroxide. Two applications were completed each treatment session and three sessions were appointed, with one week interval between them. Tooth colour was registered each session and 1 week and 1 months after completing the treatment by spectrophotometer, registering parameters L*, a* and b*, and subjectively using VITA Classic guide. Tooth sensitivity was registered by VAS and patient satisfaction and self-perception result was determined using OHIP-14. Tooth colour variation and sensitivity were compared between both bleaching agents. Both treatment showed a change between baseline colour and all check-points with a ΔE=5.57 for 6% and of ΔE=7.98 for the 35% one month after completing the (p<0.05). No statistical differences were seen when subjective evaluations were compared. Also, no differences were seen in tooth sensitivity between bleaching agents. OHIP-14 questionnaire demonstrated a significant change for all patients after bleaching. A 6% hydrogen peroxide with nitrogen-doped titanium dioxide light activated agent is effective for tooth bleaching, reaching a ΔE of 5.57 one month after completing the treatment, with no clinical differences to a 35% agent neither in colour change or in tooth sensitivity. A low concentration hydrogen peroxide bleaching agent may reach good clinical results with less adverse effects.

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Reactive oxygen species (ROS) are reactive molecules containing oxygen, that form as byproducts of aerobic metabolism, including immune system processes. Too much ROS may cause oxidative stress. In this study, we examined whether it can also limit the production of immune system compounds. To assess the relationship between antioxidant status and immunity we evaluated the effect of dietary supplementation with organic selenium, given at various levels for 10 days, on the antioxidant and immune system of the pacu fish (Piaractus mesopotamicus). Fish fed a diet containing 0.6 mg Se-yeast kg(-1) showed significant improvement in antioxidant status, as well as in hematological and immunological profiles. Specifically, they had the highest counts for catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), red blood cells, and thrombocytes; the highest leukocyte count (particularly for monocytes); and the highest serum lysozyme activity. There was also a positive correlation between GPx and lysozyme in this group of fish. These findings indicate that short-term supplementation with 0.6 mg Se-yeast kg(-1) reestablished the antioxidative status, allowing the production of innate components which can boost immunity without the risk of oxidative stress. This study shows a relationship between oxidative stress and immunity, and, from a practical perspective, shows that improving immunity and health in pacu through the administration of selenium could improve their growth performance.

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Reservoirs are artificial environments built by humans, and the impacts of these environments are not completely known. Retention time and high nutrient availability in the water increases the eutrophic level. Eutrophication is directly correlated to primary productivity by phytoplankton. These organisms have an important role in the environment. However, high concentrations of determined species can lead to public health problems. Species of cyanobacteria produce toxins that in determined concentrations can cause serious diseases in the liver and nervous system, which could lead to death. Phytoplankton has photoactive pigments that can be used to identify these toxins. Thus, remote sensing data is a viable alternative for mapping these pigments, and consequently, the trophic. Chlorophyll-a (Chl-a) is present in all phytoplankton species. Therefore, the aim of this work was to evaluate the performance of images of the sensor Operational Land Imager (OLI) onboard the Landsat-8 satellite in determining Chl-a concentrations and estimating the trophic level in a tropical reservoir. Empirical models were fitted using data from two field surveys conducted in May and October 2014 (Austral Autumn and Austral Spring, respectively). Models were applied in a temporal series of OLI images from May 2013 to October 2014. The estimated Chl-a concentration was used to classify the trophic level from a trophic state index that adopted the concentration of this pigment-like parameter. The models of Chl-a concentration showed reasonable results, but their performance was likely impaired by the atmospheric correction. Consequently, the trophic level classification also did not obtain better results.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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In order to avoid that contaminated frog farms animals escaping in the environment and become potential vector of emergent diseases, studies with disinfection protocol are strictly necessary. The formaldehyde is one of the compounds tested in fungal disinfection protocols and also used in aquaculture. This study aimed to determine the median lethal concentration (LC50-96h) of formaldehyde in bullfrog tadpoles and to evaluate the possible genotoxic effects in acute exposition. Accordingly, the animals were exposed to formaldehyde in the concentrations of 6, 9, 12, 15, and 18 mg L(-1), and after 96 h blood samples were drawn for the micronucleus (MN) test. The LC50-96h was 10.53 mg L(-1), and the MN frequency increased in proportion to the formaldehyde concentrations, with an estimated frequency in the negative control being 1.35 MN/individual. We concluded that formaldehyde is genotoxic to tadpoles of bullfrogs in the tested concentrations, and the choice of this chemical should be contemplated before its use in animals in captivity.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Deficient antioxidant defenses in preterm infants have been implicated in diseases such as bronchopulmonary dysplasia, retinopathy of prematurity, necrotizing enterocolitis, periventricular leukomalacia, and intraventricular hemorrhage. The antioxidant properties of selenium, vitamin A, and vitamin E make these elements important in the nutrition of Very Low-Birth Weight (VLBW) infants. Selenium is a component of glutathione peroxidase, an enzyme that prevents the production of free radicals. The decrease in plasma selenium in VLBW infants in the first month after birth makes evident that preterm infants have low selenium store and require supplementation by parenteral and enteral nutrition. A meta-analysis, with only three trials, showed that selenium supplementation did not affect mortality, and the incidence of neonatal chronic lung disease or retinopathy of prematurity, but was associated with a reduction in lateonset sepsis. Most VLBW infants and extremely Low-Birth Weight Infants (ELBW) are born with low vitamin A stores and need vitamin A supplementation by intramuscular or enteral route. Low plasma retinol concentrations increase the risk of chronic lung disease/bronchopulmonary dysplasia and long-term respiratory disabilities in preterm infants. There is evidence that vitamin A supplementation decreases the mortality or oxygen requirement at one month of age, and oxygen requirement at 36 weeks’ postmenstrual age. Vitamin E blocks natural peroxidation of polyunsaturated fatty acids from lipid layers of cell membranes. VLBW infants have a decrease in plasma concentrations in the first month after birth suggesting the need of vitamin E supplementation. A meta-analysis on vitamin E supplementation concluded that vitamin E did not affect mortality, risk of bronchopulmonary dysplasia, and necrotizing enterocolitis but reduced the risk of intraventricular hemorrhage and increased the risk of sepsis. Serum vitamin E concentrations higher than 3.5 mg/dL are associated with a decrease in the risk of severe retinopathy of prematurity, and blindness, but also with an increase in neonatal sepsis. Caution is recommended with the supplementation of high doses of parenteral vitamin E and supplementation that increases serum levels above 3.5 mg/dL. In conclusion: although it is known that preterm infants are deficient in selenium, vitamin A and E, more studies are required to determine the best way to supplement and the impact of supplementation on neonatal outcome.

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Mineral elements are essential to animal health, survival and production because they are part of physiological, structural, catalytic and regulatory organism functions. Therefore, they should be present in diet. However, these minerals when ingested in excessive doses due to errors in balancing mineral supplements and/or complete ration, intake of plants with high mineral concentration, resulting from addition of fertilizers, herbicides, insecticides and fungicides in pasture or tillage where plants and/or grains will be used to feed animals, decomposition of urban and industrial wastes, leaks and accidental spills of pollutants may result in accumulation of toxic mineral elements in the environment poisoning the animals and may lead them to death. However, toxic doses, physiological changes during poisoning, symptoms and mineral concentration in tissues of poisoned animals to confirm diagnosis are not completely known. Thus, this study reviews mineral element doses that some authors considered toxic for animals intake, as its concentration in tissues of poisoned animals and its physiological effects, symptoms, diagnostic procedures and treatment for poisoning by cadmium, lead, copper, chromium, iodine, manganese, molybdenum, selenium and zinc.

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This study evaluated the relationship between Se supplementation and serum cortisol in repeatedly handled cattle. Sixty Nellore calves were randomly distributed into four experimental groups, which were fed a mineral-protein mixture added with Se to achieve individual daily supplementation of 0 (Gc), 3.6 (G3.6), 5.4 (G5.4) and 6.4 (G6.4) mg Se. Stressful handling procedures and blood sampling were performed on days 0, 15, 30, 60, 90 and 120. Serum cortisol increased until day 90 and decreased on day 120, irrespective of Se supplementation. This finding shows that cattle reached a stress state but adapted. Cortisol and Se levels were not markedly correlated. Serum Se increased over the course of the experiment in the supplemented groups. However, because serum Se decreased in Gc, it may have mobilized to form the selenoproteins needed to remove metabolic wastes from handling-related oxidative stress.