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| Author(s): |
Camila Queiroz Moreira
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2007-09-28 |
| Examining board members: |
Helenice de Souza Spinosa;
Silvana Lima Górniak;
Ernani Pinto Junior
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| Advisor: | Helenice de Souza Spinosa |
| Abstract | |
Cyanobacteria (blue-green algae) are prokaryotic and photosynthetic organisms found in practically every type of liquid habitat and that can form great superficial masses of intense green color called blooms. The development of algal blooms on water surface occurs with a higher incidence and is recognised as being a potential health hazard due to the toxic nature of some algae. Cyanobacteria can produce hepatotoxins, neurotoxins and dermatotoxins, which already caused adverse effects and death of animals and human beings. Most of the hepatotoxins are microcystins (MCs), a family of toxins produced by species of freshwater cyanobacteria. MC-LR was the first to be identified and is the more studied, therefore, it has been associated to most of the cases of intoxication involving cyanotoxins. The present study was performed to evaluate the toxicity in mice after prolonged exposure to a cyanobacteria bloom extract containing microcystins. For this, male Swiss mice were treated with the extract (300 or 900 mg/kg) for four weeks and was evaluated: weight gain, food and water consumption, behavior in the open field (OF) and in the elevated plus-maze (EPM), blood count, clinical biochemistry, anatomopathological findings and presence of MC in the plasma and liver. Besides, the MCs present in the extract were quantified and the cellular death of leukocytes exposed in vitro to MC and to the extract was evaluated. The chemical analysis of the extract showed that it presented, besides MCs, anabaenopeptins; the MCs found were MC-LR, MC-RR, MC-YR and [D-Asp3] MC-LR. The prolonged exposure to the extract for 28 days did not alter the weight gain and the relative weight of organs. At necropsy, macroscopic alterations were not observed, however, histopathological alterations were found in the liver and in the kidney. In the liver, discreet necrosis focuses associated with neutrophils and mononuclear cells were found. In the kidney, the treatment with the extract increased significantly the intensity of tubular nephrosis, and this was more accentuated in the animals treated with the largest dose. The prolonged treatment with both doses caused dose-dependent behavioral effects in the OF: significant increase of moved distance, number of entries, time moving and rearing in the center of the OF, besides an increase of time spent in the center, with consequent decrease of this parameter in the periphery. None of the parameters evaluated in EPM were altered. The prolonged exposure to the extract caused subtle alterations in hematological and biochemical parameters, characterized by tendency for leukocyte decrease and increase of the levels of serum creatinine in the animals treated with the largest dose of the extract. The prolonged treatment with the extract allowed the detection of MC just in the liver. As much MC-LR as the extract promoted increase of the apoptosis levels in mouse leukocytes in vitro. Concluding, it was observed that the prolonged exposure to the cyanobacteria bloom containing MCs caused low toxicity and dose-dependent behavioral effects, showing that animal behavior is useful to evaluate subtler effects of toxic agents on the central nervous system. (AU) | |