Gene expression and biochemical responses in brain of zebrafish Danio rerio exposed to organic nanomaterials: carbon nanotubes (SWCNT) and fullerenol (C60(OH)18-22(OK4)).

Nanomaterials (NM) industry had grown in the last decade, although there are few studies concerning its potential toxicity effects on aquatic organisms. In this study the freshwater zebrafish (Danio rerio) was exposed to two kinds of carbon NM, single-wall carbon nanotubes (SWCNT) and fullerenol [C60(OH)18-22(OK4)] to analyze oxidative stress responses on fish brain. Adult zebrafish (mean mass: 0.52±0.01g) were submitted to intraperitoneal injections of SWCNT suspension and fullerenol solution (30mg/kg of fish), receiving one or two doses with a time interval of 24h. Results showed that total antioxidant capacity was lowered in brains of fish exposed 24h to fullerenol when compared to those from SWCNT treatment (p<0.05). After 48h, fullerenol induced higher expression of both catalytic and regulatory subunits of enzyme glutamate cysteine ligase when compared to control group (p<0.05), indicating an antioxidant behavior. In vitro assays showed a dual effect of SWCNT, since a pro-oxidant behavior was observed at low concentrations (0.1 and 1.0mg/L) and an antioxidant one at the highest concentration (10.0mg/L). Few biological responses were altered by this NM: decrease in total antioxidant capacity and induction of the expression of the transcription factor Nrf2 when compared to control group.

Biochemical and behavioral responses in the estuarine polychaete Perinereis gualpensis (Nereididae) after in situ exposure to polluted sediments.

In situ translocation experiments are advantageous relative to traditional laboratory experiments, particularly for understanding the bioavailability of trace metals like mercury (Hg). Individuals of the polychaete Perinereis gualpensis were translocated from a reference site (Raqui estuary, Chile) to an estuarine site with significant sediment Hg concentrations (Lenga estuary: 1.78-9.89 mg/kg). Individuals were exposed in polluted and non-polluted sediments for 21 days and sampled every 7 days with cages deployed at three different depths. Tissue Hg concentrations were measured in conjunction with oxidative stress responses. Translocated polychaetes rapidly accumulated Hg. Glutathione S-transferase (GST) activities measured from posterior body regions were 2-fold higher than control activities after 21 days of exposure. Other antioxidant measures were idiosyncratic. Distinct burrowing behavior differences were observed; control polychaetes exhibited more homogenous vertical distributions, whereas in Lenga, worms tended to remain in upper layers. These studies demonstrate that under natural conditions, Hg is highly bioavailable to polychaetes affecting both biochemical and behavioral responses after relatively short-term exposure.