Second, the method can give an accurate relative quantification of the total demethylation potential of the aquatic sample extracts with 5-AZA-CdR DTE, which is more convenient for the direct comparison of health risks for different food samples.
If the aquatic sample extract has strong total demethylation potential to the promoter, its methylation level will decrease, and increased green fluorescence will be observed under microscopy after TDQ co-incubation.
In summary, the aquatic samples were transported at 4 °C to the laboratory and processed within a maximum period of 24 h.
The aquatic sampling sites were located around the estuary of the Haihe River in the Bohai Bay area.
Semi-aquatic or terrestrial taxa collected during the aquatic sampling (Lepidoptera, Araneae, Collembola) were not included either, since they are not likely to play an important role in the aquatic community.
The relatively low frequencies of quinolone TRAs found within waste samples are not significantly higher than those found in soil and are only marginally significantly higher than those found in the aquatic samples (FDR-corrected P = 0.673 and FDR-corrected P = 0.05, respectively, supplementary table S2, Supplementary Material online).
DNA methylation changes in whole blood are associated with exposure to environmental contaminants such as cadmium, mercury, lead, and bisphenol A [ 20], implying that the demethylation potential of the aquatic samples from heavily polluted marine areas should be a focus of health risk assessments of the local residents.
At Hour 30, the cells were treated with different concentrations of 5-AZA-CdR (Sigma, MO, USA), a positive demethylation agent for myelodysplastic syndrome therapy [ 31], and the target extract of the aquatic samples which was freshly dissolved in PBS and filtered through a 0.2-μm membrane.
The obtained results have been confirmed both by timed natural aquatic sample analysis and laboratory simulations using water from Moldovan small rivers (Isnovat, Raut, and Bic).
It is calculated by subtracting the 14C age of a terrestrial sample 14 C T from the 14C age of the contemporaneous aquatic sample 14 C A : R = 14 C A − 14 C T. (1).
