ICB - Artigos publicados em periódicos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/52
Navegar
477 resultados
Resultados da Pesquisa
- ItemMolecular typing of Mycobacterium bovis isolated in the south of Brazil(2014) Soares, Daniela Fernandes Ramos; Silva, Ana Bárbara Scholante; Fagundes, Michel Quevedo; Groll, Andrea Von; Silva, Pedro Eduardo Almeida da; Dellagostin, Odir AntonioBovine tuberculosis is a major infectious disease of the cattle. In this study, 85 M. bovis isolates from 162 lymph nodes, obtained from a herd of cattle on a farm in southern Brazil, were evaluated using spoligotyping and VNTR. The strains were grouped into five clusters and five orphans, showing a heterogenic genetic profile, what could represent diverse geographic origins of the introduced cows and/or the frequent movement of cattle between different properties.
- ItemExiste relação entre governança corporativa e volatilidade? um estudo a partir da formação de carteiras(2010) Monte, Paulo Aguiar do; Rezende, Isabelle Carlos Campos; Teixeira, Gibran da Silva; Besarria, Cássio da NobregaEm finanças, a relação entre risco e retorno é estabelecida pela incerteza associada aos retornos esperados de uma decisão de investimento. Nesse contexto, as boas práticas de Governança Corporativa, que objetivam proporcionar uma maior transparência na divulgação de seus resultados econômicos e financeiros, auxiliam na redução dos riscos de uma decisão. Para avaliar a relação entre transparência/informação e risco/retorno, o presente trabalho tem como objetivo geral analisar a composição, o risco e a persistência da volatilidade de três carteiras de variância mínima formadas, respectivamente, por ativos de empresas que fazem parte dos níveis de Governança listadas na BM&FBOVESPA: N1 (nível 1), N2 (nível 2) e NM (Novo Mercado). Nesse intuito, foi desenvolvida uma pesquisa exploratório-descritiva, utilizando-se de técnicas econométricas aplicadas sobre as informações primárias obtidas no sítio do BM&FBOVESPA. Os dados foram tratados com o auxílio do Excel, especificamente das ferramentas Solver, e com a aplicação do modelo CAPM e dos modelos da família ARCH. Os principais resultados encontrados revelam que a formação da carteira de variância mínima reduz, significativamente, o risco diversificável. Também se observou que, quanto maior o nível de Governança, maior é o seu risco não sistemático (NM>N2>N1). O estudo comparativo das carteiras formadas confirmou a tese de menor persistência de volatilidade das empresas do Novo Mercado. Concluiu-se, portanto, que a carteira formada por ativos de empresas do Novo Mercado é menos arriscada, comparativamente às formadas por ativos das empresas dos níveis 1 e 2
- ItemPhysiological effects of chronic silver exposure in Daphnia magna(2002) Bianchini, Adalto; Wood, ChrisDaphnia magna were exposed to a total concentration of 5.0"0.04 mg Agyl, added as AgNO (dissolved concentration, 3 as defined by 0.45 mm filtration s 2.0"0.01 mg Agyl) in moderately hard synthetic water under static conditions (total organic carbon s 4.80"1.32 mgyl) with daily feeding and water renewal, for 21 days. There was no mortality in control daphnids and 20% mortality in silver-exposed animals. Silver exposure caused a small but significant reduction of reproductive performance manifested as a 13.7% decrease in the number of neonates produced per adult per reproduction day over the 21-day exposure. However, silver exposed daphnids also exhibited a much more marked ionoregulatory disturbance, which was characterized by a 65% decrease in whole body Na concentration, and an 81% inhibition of q unidirectional whole body Na uptake. Previous work on the acute toxicity of Ag to daphnids has shown that Na q q q uptake inhibition is directly related to inhibition of Na ,K -ATPase activity. Therefore, we suggest that the Na uptake q q q inhibition seen in response to chronic silver exposure was explained by an inhibition of the Na channels at the apical q ‘gill’ membrane, since a 60% increase in whole body Na ,K -ATPase activity was observed in the chronically silver- q q exposed daphnids. Our findings demonstrate that, in broad view, the key mechanism involved in chronic silver toxicity in D. magna, the most acutely sensitive freshwater organism tested up to now, resembles that described for acute toxicity—i.e. ionoregulatory disturbance associated with inhibition of active Na uptake, though the fine details may q differ. Our results provide encouragement for future extension of the current acute version of the Biotic Ligand Model (BLM) to one that predicts chronic silver toxicity for environmental regulation and risk assessment. The results strongly suggest that Na uptake inhibition is the best endpoint to determine sensitivity to both acute and chronic toxicity in the q scope of future versions of the BLM for silver
- ItemMetal sulfides in oxygenated aquatic systems: implications for the biotic ligand model(2002) Bianchini, Adalto; Bowles, KarlThe Biotic Ligand Model (BLM) attempts to predict metal toxicity to aquatic organisms on the basis ofmetal speciation and effects at the cell surface. Current versions of the BLM for silver and copper consider metal binding by inorganic ligands, dissolved organic matter (DOM) and also competition at the cell surface from calcium and protons (pH). Recent studies reported in the geochemical and ecotoxicological literature have indicated the importance ofsulfide as a ligand, even in fully oxygenated aquatic systems. Speciation calculations for oxygenated waters do not currently include reduced sulfur as a ligand and as a consequence, no version of the BLM model has been published including reduced sulfur. This reflects the limitations on our knowledge regarding reduced sulfur in aquatic systems. In this paper we highlight the need to include reduced sulfur in the Biotic Ligand Model, with the interaction between silver and inorganic metal sulfides as a specific example. The geochemical importance of metal sulfides as ligands for silver and the effect of ‘dissolved’ metal sulfide and other ligands on metal toxicity and accumulation are described and reviewed. Recommendations are made for future work needed to incorporate sulfide ligands into the BLM’s modeling framework
- ItemAcute silver toxicity in the euryhaline copepod Acartia tonsa: influence of salinity and food(2007) Pedroso, Mariana Saia; Bersano Filho, José Guilherme; Bianchini, AdaltoThe euryhaline copepod Acartia tonsa was exposed to silver (AgNO(3)) in either the absence or the presence of food (diatom Thalassiosira weissflogii; 2 x 10(4) cells/ml). Standard static-renewal toxicity tests that included a fixed photoperiod of 16: 8 h light:dark and temperature (20 degrees C) were run in three different salinities (5, 15, and 30 ppt) together with measurements of pH, ions (Na(+), Cl(-), K(+), SO(4)(2-), Mg(2+), and Ca(2+)), alkalinity, dissolved organic carbon, and total and dissolved (0.45 microm) silver concentrations in the experimental media. In the absence of food, the 48-h EC50 (concentration causing effect to 50% of the individuals tested) values based on total and dissolved silver concentrations were 11.6, 87.2, and 163.2 microg Ag/L and 7.1, 79.2, and 154.6 microg Ag/L at salinities 5, 15, and 30 ppt, respectively. In the presence of food, they were 62.1, 98.5, and 238.4 microg Ag/L and 48.4, 52.3, and 190.9 microg Ag/L, respectively. In all experimental conditions, most of the toxic silver fraction was in the dissolved phase, regardless of salinity or the presence of food in the water. In either the absence or the presence of food, acute silver toxicity was salinity dependent, decreasing as salinity increased. Data indicate that changes in water chemistry can account for the differences in acute silver toxicity in the absence of food, but not in the presence of food, suggesting that A. tonsa requires extra energy to cope with the stressful conditions imposed by acute silver exposure and ionoregulatory requirements in low salinities. These findings indicate the need for incorporation of both salinity and food (organic carbon) in a future biotic ligand model (BLM) version for estuarine and marine conditions, which could be validated and calibrated using the euryhaline copepod A. tonsa
- ItemCorynosoma spp. (Acanthocephala, Polymorphidae) in Mirounga leonina (Pinnipedia, Phocidae) of South Shetlands Islands: a new host for Corynosoma cetaceum(2014) Silveira, Tony Leandro Rezende da; Robaldo, Ricardo Berteaux; Pinto Colares, Elton; Bianchini, Adalto; Muelbert, Monica Mathias Costa; Martínez, Pablo Elías; Pereira, Eliane Machado; Valente, Ana Luisa SchifinoCorynosoma bullosum is a parasite of pinnipeds while Corynosoma cetaceum is considered a parasite of cetaceans. Until now, there were no records of parasitism by C. cetaceum in phocids. This study reports C. bullosum and the first record of C. cetaceum in Mirounga leonina from Antarctica
- ItemEffects of metacercariae (Digenea: Microphallidae) on the hepatopancreas of Chasmagnathus granulata (Decapoda: Grapsidae)(1999) Robaldo, Ricardo Berteaux; Monserrat, José María; Cousin, João Carlos Brahm; Bianchini, AdaltoWe analysed the effects of lnfection by Microphallus szldati metacercarlae on carbohydrate (glucose and glycogen) levels and histopathology of the hepatopan- cieas of the estuarine crab Chasmagnathus granulata No slg- nlflcant differences In infection were found between the left and nght sides of the hepatopancreas and infection intensity ranged from 2 to 802 The mean intensi ty of rlletacercarlae cysts was 54 79 k 12 64 (k1 SE) wlth a prevalence of 90 1% Hepatopancreat~c glycogen was higher In infected crabs (28 2 t 2 2 m g g-l tlssue) than in non-lnfected ones (21 7 2 1 9 my g ' tissue) Further, hlgh intensltles of infection (>6 parasites per tissue section) promoted necrosls of the hepatopancreatlc tubules and hemocytic infiltration around the cysts Thus the presence of M szjdatj metacercarlae in the hepatopancreas of C granulata can cause structural damage to the tissue altering its glycogen levels and can be considered as a potential physiological stress factor
- ItemLipid peroxidation induced by Clinostomum detruncatum in muscle of the freshwater fish Rhamdia quelen(2000) Belló, André Ricardo Ribeiro; Fortes, Elinor; Klein, Adriane Belló; Belló, Antonio Andréa; Llesuy, Susana Francisca; Robaldo, Ricardo Berteaux; Bianchini, AdaltoThe effect of Clinostomum detruncatum metacercaria infection on the activities of the antioxidant enzymes superoxide dismutase and catalase in muscle of the freshwater fish Rhamdia quelen was analyzed. Tert-butyl hydroperoxide-initiated chemiluminescence, a measure of lipid peroxidation, was also investigated. Enzyme activities were similar in infected and uninfected fishes. However, the chemiluminescence was almost 2-fold higher in muscle of infected fishes than in muscle of uninfected ones. These results indicate that parasite infection induces oxidative stress and a higher level of membrane damage in the fish muscle due to an imbalance between pro-oxidants and non-enzymatic antioxidants. Our results suggest that fish response to parasite infection could involve, as in other vertebrates, reactive oxygen intermediates
- ItemEffects of diphenylamine-2-carboxylate on the transepithelial potential difference and Cl- fluxes in gills of the chinese crab Eriocheir sinensis(1989) Bianchini, Adalto; Gilles, RaymondThe effects of DPC (diphenylamine-2-carboxylate-10-4 M) have been studied on the transepithelial potential difference of anterior and posterior gills and on the Cl- fluxes in posterior gills of the Chinese crab Eriocheir sinensis acclimated to fresh water. DPC is effective only on the serosal side of the posterior gills. It induces a marked depolarization of the epithelium and largely reduces the Cl- uptake which takes place in these gills. The observed effects of DPC are consistent with a role of serosal Cl- channels in the transepithelial transport of Cl- taking place in the posterior gills of Eriocheir sinensis
- ItemAcute copper toxicity in juvenile fat snook Centropomus parallelus (Teleostei: Centropomidae) in sea water(2014) Oliveira, Bruno de Laquila; Fernandes, Luiz Fernando Loureiro; Bianchini, Adalto; Chippari-Gomes, Adriana Regina; Silva, Bruno Ferreira; Athayde, Geisamanda Pedrini Brandão; Gomes, Levy de CarvalhoThree experiments were designed to assess the accumulation and acute toxicity of copper (Cu) in juvenile fat snook Centropomus parallelus. The first experiment was performed to determine the 96-h lethal concentration (LC50) of Cu. The second experiment was designed to assess the effects of sublethal concentrations of Cu (0.47 and 0.94 mg/L), while the third one allowed us to test the recovery capacity of fish exposed to the sublethal concentrations Cu and kept in sea water without Cu addition. The LC50 value for Cu was found to be 1.88 mg/L Cu. Fish exposed to the sublethal concentrations of Cu showed a significant accumulation of Cu in gills at 96 h respect to the control ones (0.43 µg/g Cu). No significant difference was observed in the accumulation of Cu in gills between fish exposed to 0.47 mg/L (1.09 µg/g Cu) and 0.94 mg/L (1.26 µg/g Cu). Exposure (24 and 96 h) to the sublethal concentrations of Cu tested induced DNA damage in the erythrocytes. The results show that acute exposure to sublethal concentrations induces Cu accumulation and DNA damage in fish, these effects being recovered after 240 h in sea water without Cu addition