The effects of heavy metals on the incidence of morphological deformities in Chironomidae (Diptera)

ABSTRACT Streams in urban areas are strongly impacted by the input of organic matter and metals, for instance copper (Cu) and zinc (Zn). These metals are essential for the aquatic biota, but when absorbed in excess they are toxic. In Chiro nomidae larvae, the deleterious effects of heavy metals can be ascertained by analyzing the morphological deformities of the larval mentum, a structure of the oral cavity. In this study, we evaluated I) the bioavailability of Cu and Zn in urban stream sediments and II) the relationship between Cu and Zn concentrations and the incidence of deformities in the mentum of Chironomus larvae. Chironomid flies were collected from four locations in two streams at an urban area in southern Brazil. They were identified and the incidence of deformities in the mentum was quantified. Sediment samples were collected at the same locations where larvae were collected, to quantify the bioavailable fractions of Cu and Zn. The concentrations of Cu in the sediment were similar between the collection sites. However, Zn concentrations varied among sites, being greater in the stretch directly influenced by the input of the organic waste. In total, 2,895 Chironomid larvae were collected. The incidence of deformities in the mentum was above 30% and was correlated with the concentrations of Cu (r = 0.68) and Zn (r = 0.87). This correlation indicates that the municipal waste that is thrown into the city’s streams has influenced the occurrence of deformities

The effects of heavy metals on the incidence of morphological deformities in Chironomidae (Diptera)

Streams in urban areas are strongly impacted by the input of organic matter and metals, for instance copper (Cu) and zinc (Zn). These metals are essential for the aquatic biota, but when absorbed in excess they are toxic. In Chironomidae larvae, the deleterious effects of heavy metals can be ascertained by analyzing the morphological deformities of the larval mentum, a structure of the oral cavity. In this study, we evaluated I) the bioavailability of Cu and Zn in urban stream sediments and II) the relationship between Cu and Zn concentrations and the incidence of deformities in the mentum of Chironomus larvae. Chironomid flies were collected from four locations in two streams at an urban area in southern Brazil. They were identified and the incidence of deformities in the mentum was quantified. Sediment samples were collected at the same locations where larvae were collected, to quantify the bioavailable fractions of Cu and Zn. The concentrations of Cu in the sediment were similar between the collection sites. However, Zn concentrations varied among sites, being greater in the stretch directly influenced by the input of the organic waste. In total, 2,895 Chironomid larvae were collected. The incidence of deformities in the mentum was above 30% and was correlated with the concentrations of Cu (r = 0.68) and Zn (r = 0.87). This correlation indicates that the municipal waste that is thrown into the city’s streams has influenced the occurrence of deformities

Trypanosoma Cruzi Response To The Oxidative Stress Generated By Hydrogen Peroxide.

As an intracellular parasite, Trypanosoma cruzi is exposed to reactive oxygen species. The study of the proteins involved in the hydroperoxide detoxification cascade, tryparedoxin peroxidase included, may lead to the development of a more specific chemotherapy for Chagas'disease. In this work, the involvement of TcCPX in T. cruzi resistance to oxidant-mediated injury was investigated. At low concentrations of hydrogen peroxide cell proliferation was stimulated and parasites increased their resistance to sub-lethal doses of H2O2 (100 microM) if previously treated with a non-toxic concentration of H2O2 (20 microM). Incubation of cells with different H2O2 concentrations induced a dose-dependent increase in TcCPX levels, as detected by Western blotting analysis. The increase in TcCPX levels in the presence of high H2O2 concentrations possibly reflects an initial cell attempt to promote detoxification. To further demonstrate TcCPX involvement in T. cruzi response to oxidative stress, TcCPX overexpressing cells were produced. Compared to pTEX transformed cells, pTEX-TcCPX mutant cells showed a higher mRNA level (129%), without a corresponding increase in protein production (11%), suggesting that regulation of gene expression occurs at post-transcriptional levels. Furthermore, parasite treatment with 200 microM H2O2 for 30 min, led to an increase in mRNA (192%), but not in protein levels (24%). Higher mRNA levels correlated to protein levels were observed only after longer H2O2 incubation periods (1-2 h), suggesting that protein translation occurs accordingly to parasite needs. An increase in glucose-6-phosphate dehydrogenase activity was observed in pTEX-TcCPX epimastigotes that could provide cells with extra reducing power and a higher growth index.13337-4