122 resultados para Minimal lethal concentration


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

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

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Pós-graduação em Aquicultura - FCAV

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Natural products have been studied aiming to understand their biological properties. Thus, this study aimed to investigate the antimicrobial activity of twenty-seven essential oils (EOs) used in aromatherapy procedures, a natural therapy with great emphasis currently used against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa strains. The agar dilution method was carried out and minimal inhibitory concentration against 50% and 90% of strains (MIC50% and MIC90% values) were reported. The S.aureus strains were highly susceptible with MIC90% from 0.21mg/mL to black pepper (Piper nigrum) and tea tree (Melaleuca alternifolia) to 26.52mg/mL with copaiba (Copaifera officinalis) EO. Cinnamon (Cinnamomum cassia) and clove (Syzygium aromaticum) EOs were effective against E.coli (2.0mg/mL) while the S.aromaticum EO was against P.aeruginosa (8.29mg/mL). Thus, the higher susceptibility of Gram-positive bacteria when compared with Gram-negative strains was found, and a large variability in the potential antibacterial has also been observed.

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Apis mellifera honeybees are social insects of economic importance, by providing honeybee products, and by the pollination of natural areas of vegetation or agricultural areas. The constant use of pesticides, including the thiamethoxam, which is an insecticide belonging to the class of neonicotinoids with neurotoxic action, is subjecting pollinators to situations of severe stress, which has been evidenced by the decrease in the density of honeybees in many parts of the world. By these considerations, the present study aimed to assess the acute toxicity of thiamethoxam for newly emerged workers of A. mellifera, and to investigate the effect of sublethal doses of this insecticide on the survival time and its cytotoxicity to the brain and midgut to the honeybees. It was established the value of the lethal concentration 50 (LC50) equal to 4.28 ng thiamethoxam/μL of food and from it, the sublethal concentrations of 0.428 ng thiamethoxam/μL (CL50/10) and 0.0428 ng thiamethoxam/μL (CL50/100), which were used in bioassays of intoxication of the honeybees. After the bioassays the bees were dissected and the brain and midguts were collected to analyze possible morphological (staining with Hematoxylin-Eosin) and histochemical alterations (Xylidine Ponceau technique, and Feulgen and PAS reactions) caused by exposure to thiamethoxam, and to calculate the lethal time (LT50) for the workers. The duration of the bioassays was 8 days after beginning of feeding. The results obtained showed that the thiamethoxam is toxic to newly-emerged workers of A. mellifera, causing changes in survival time of individuals. This study also shown that the thiamethoxam causes morphological and histochemical alterations on the midgut and brain of workers. These alterations may be reflected in physiological and behavioral changes that can modify the operation of the colony

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Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

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