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Data of Dissertation


Author: Rodrigo de Cássio da Silva.

Title: Study of oxidative stress caused by cylindrospermopsin in tilapia (Oreochromis niloticus) under laboratory conditions.

Year: 2003.    Full text (in Portuguese)


Cylindrospermopsin is a cyanotoxin which can be produced by different species of cyanobacteria. Therefore their presence in water bodies is a public health concern worldwide. In mammals its action is systemic, but little is known about their toxicity in fish. Thus, the use of an experimental model of native tropical fish - Hoplias malabaricus - was used for this purpose in the present work. This thesis is organized into three chapters: the first and the second with exposure in vivo where after exposure to a single dose of CYN (aqueous extract and purified toxin) damage and its accumulation in the brain and muscle tissue after 14 days were assessed. In the brain and muscle were no significant changes in the activity of acetylcholinesterase. In addition, oxidative damage (lipid peroxidation) in the brain indicated that CYN is capable to crossing the blood brain barrier. In Chapter II, CYN concentration, biochemical biomarkers of oxidative stress, damage to macromolecules and histopathological aspects were evaluated. Injuries were corroborated by histological and biochemical biomarkers. Some damage to macromolecules, such as increase in the concentration of hydroperoxides and protein carbonylation, were observed. In vitro assays constituted the third chapter, in which a reduction in cellular viability of hepatocytes exposed to either extract and purified toxin was observed. The responses of different biomarkers indicated a change in the redox milieu of hepatocytes, which was more pronounced in cells exposed to the aqueous extract. In conclusion, this work presents novel aspects since there are few data regarding the toxicology of CYN in tropical fish species.