1000 resultados para concentração


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Despite the fact that the processes of embryo development and implantation of mammals do not occur in atmospheric tension in vivo, it is common practice in laboratories for in vitro fertilization (IVF) the culture of embryos in an oxygen tension of 20%. The discrepancy between the tensions of oxygen leads to important discussions about their effects in vitro embryo development. It is believed that the culture of embryo in atmospheric oxygen tension can be detrimental to the quality of the data for predisposing them to the negative interference of reactive oxygen species (ROS), resulting in oxidative stress, leading to deleterious effects on metabolism embryo gene expression and blastocysts grown in those conditions. Faced with arguments for and against the culture of embryos in vitro oxygen tensions similar to those found in vivo, this revies article aims to condense and discuss the literature concerning the influence of oxygen tension on the quality of in vitro culture.

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This trial was conducted in order to determine the 50% lethal concentration (LC (I) 50-96h) of the aqueous extract of dried leaves of Terminalia catappa, a plant with antifungal, antibacterial and antiparasitic activity. Due to the increasing use of herbal medicines in aquaculture, its use is an option for controlling diseases in fish. Toxicity tests are important before recommending any treatment, since some products have therapeutic concentration close to lethal. To conduct the study used 135 fish species Guarus (Phalloceros caudimaculatus), exposed to increasing concentrations of: 0.0, 50.0, 100.0, 150.0, 200.0, 250.0, 300.0 mL of stock solution per liter of water. The results were calculated by the method Trimmed Spearman Karbo, demonstrating that the 50% lethal concentration (LC (I) 50-96h) estimated was 208.52 mL / L, with lower limit of 187.79 mL / L and higher 231.54 mL / L. Observed changes in behavior of the test organisms at concentrations above 250 mL / L decrease in the levels of dissolved oxygen and pH. Concentrations below 250 mL /L result in mortality rate near zero, so the aqueous extract shown low toxicity.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Agronomia (Ciência do Solo) - FCAV

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Agronomia (Energia na Agricultura) - FCA

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)