DNA methylation in Daphnia Magna

Daphnia magna is gaining interest as a model for epigenetic research. It is easy to maintain under laboratory conditions and has low genetic diversity due to parthenogenetic reproduction. The D. magna genome is responsive to a wide range of stimuli and genomics resources are being developed for this species. Despite these great advantages, information regarding the epigenome of D. magna and its regulation is still lacking. Thus, the main aim of this work was to describe the methylome of D.magna and investigate its regulation and responsiveness to environmentally relevant exposure conditions. Despite the low levels of global DNA methylation, a defined profile could be identified. DNA methylation in D. magna is sporadic and mainly found at coding regions. These data suggest that D. magna encodes a complete set of genes for DNA methylation reactions. Evidence of direct effects on the DNA methylation profile were found in animals exposed to the DNA methylation inhibitor 5-azacytidine and these changes were persistent after the removal of the stressor. Acute and chronic exposures to environmentally relevant concentrations of stressors (arsenic and hypoxia) also induced changes in gene transcription levels and concentrations of onecarbon pathway metabolites. These findings indicate that the epigenome of D. magna is responsive to changes in the environment, supporting its use as an environmentally relevant model organism for epigenetics research. Furthermore, the maintenance of some of the epigenetic changes in the absence of the initial stressor supports the concept of ‘epigenetic memory’ and its potential use in chemical risk assessment

Water Quality of Urban Streams: The Allium cepa

The present study investigates the genotoxic, mutagenic, and cytotoxic potential of surface waters in urban streams using Allium cepa and analyzes the applicability of this assay for environmental monitoring. Water samples were collected from three streams located in the urban area of a municipality in the south of Brazil. For each stream, two samples were collected, one upstream and one downstream of the pollution discharge site. Physicochemical evaluation indicated that all samples had various degrees of environmental impact, but substantial impact was seen for the downstream samples of the Preto and Pedras streams. All samples increased the frequency of chromosome aberrations (P<0.05). The sample from Pedras downstream site also caused a decrease in mitotic index (P<0.08) and increase in micronuclei (P<0.08) frequency, indicating potential cytotoxicity and mutagenicity. The Pedras stream receives mixed industrial and urban wastewater, while the Lajeado and Preto streams receive wastewater predominantly domestic in nature, which may partially explain the difference in toxicity among the samples. Moreover, the Allium cepa seeds/seedlings were shown to be extremely sensitive in detecting the genotoxicity of environmental water samples and can be applied as the first tool for environmental health hazard identification and prediction

ANÁLISE GENOTÓXICA DE EFLUENTE DE LAVANDERIA HOSPITALAR: ENSAIO COMETA COM Daphnia magna STRAUS, 1820

Considerando que os efluentes hospitalares possuem carga poluidora potencialmente tóxica e genotóxica, o objetivo do presente trabalho foi desenvolver a metodologia do Ensaio Cometa com um organismo-teste amplamente utilizados em teste de toxicidade, Daphnia magna, a fim de avaliar a genotoxicidade de efluente provindo do setor de lavanderia de um hospital do Vale do Rio Pardo, RS. Foram realizadas coletas mensais do efluente entre os meses de maio e julho de 2011. Após a padronização do Ensaio Cometa, os organismos foram expostos a concentrações subletais do efluente (0,195; 0,39; 0,78; 1,56%) por um período de 48 h. O ensaio foi realizado com modificações. Os resultados mostraram diferenças significativas (