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Copper sulfate (CuSO(4))is an inorganic chemical product worldwide used as an algaecide and a fungicide in aquaculture and agriculture and being discharged into freshwater environments where it can affect the freshwater fauna, especially fishes. The impact of copper on fish cardiac function was analyzed in two groups of Nile tilapias, Oreochromis niloticus (control group and group exposed to 1 mg l(-1) of CuSO(4) for 96 h). Structural and ultra-structural changes were studied and related to perturbations of the inotropic and chronotropic responses of ventricle strips. Fish of Cu exposed group did not show significant alterations in the medium diameter and in the percentage of collagen in the cardiac myocytes when evaluated through the light microscope. However, the ultrastructural analysis revealed cellular swelling followed by mitochondrial swelling. The myofibrils did not show significant variations among groups. Force contraction was significantly decreased, and rates of time to tension increase (contraction) and decrease (relaxation) were significantly augmented after copper exposure. The results suggest that the copper sulfate impairs the oxidative mitochondrial function and consequently alters the cardiac performance of this species.

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Amplification of the 16S rRNA gene from a blood sample obtained from a dog in southeastern Brazil was used to confirm a naturally acquired Ehrlichia (E.) canis infection. Following isolation and culturing of the new bacterial strain called Uberlândia, partial sequences of the dsb and p28 genes were obtained. The dsb partial sequence of the novel strain was 100% similar to dsb gene sequences of E. canis obtained from different geographic areas around the world. Conversely, the p28 partial sequence for the E. canis Uberlândia strain differed at several nucleotides from other sequences available in GenBank. To confirm the antigenic profile of the Uberlândia strain, an indirect immunofluorescence assay against E. canis antigens was performed using dog sera collected from two different areas in Brazil (Uberlândia and São Paulo). The results suggest that both antigens were able to identify animals seropositive for E. canis in Brazil since these Brazilian strains appear to be highly conserved.