Integrated biological responses of zebrafish (Danio rerio) to analyze water quality in regions under anthropogenic influence.

This study analyzed water quality in regions around Patos lagoon (Southern Brazil) that are under anthropogenic pressure. Water samples were collected from five different sites, including one used as a source for human consumption (COR) and others known to be influenced by human activities (IP). Danio rerio (Teleostei, Cyprinidae) organisms were exposed for 24h to these water samples, plus a control group. It was observed that: (1) reactive oxygen species levels were lower in COR and IP than in the control group; (2) glutamate-cysteine ligase (catalytic subunit) expression was higher in COR than in other sites; (3) exposure to all water samples affected long-term memory (LTM) when compared to control group. Thus, some water samples possess the ability to modulate the antioxidant system and to induce a decline in cognitive functions, as measured by LTM. The obtained results indicate that a combination of variables of different organization level (molecular, biochemical and behavioral) can be employed to analyze water quality in impacted regions.

Microcystin-induced oxidative stress in Laeonereis acuta (Polychaeta, Nereididae).

Oxidative stress induced by microcystins was evaluated in an estuarine worm, Laeonereis acuta (Nereididae). Ten organisms were exposed to lyophilized cells of a toxic Microcystisaeruginosa strain RST9501 ( approximately 2 microg/mL microcystins, MC); 10 were exposed to lyophilized cells of a nontoxic Aphanotece sp. strain RSMan92 and 10 were maintained without cyanobacterial cells. Exposure time was 48 h. The enzymatic antioxidant defenses, as well as the oxidative damage, were analyzed. Toxic and nontoxic cyanobacteria lowered catalase activity with no changes in glutathione reductase and glutathione-S-transferase activities. This may have led to toxin intracellular accumulation, which should favor oxidative stress generation, observed by the high lipid peroxide and DNA-protein crosslink levels in the group exposed to MC.

The benefits and drawbacks of nicotine exposure in the cortex and hippocampus of old rats.

Nicotine is the main alkaloid of tobacco and possesses well-established stimulant effects. Previous reports show that nicotine at low doses improves memory functions, while high doses impair memory. This study aims to analyze the effects of nicotine (NIC) on inhibitory avoidance task and on DNA damage, reactive oxygen species (ROS) concentration, total antioxidant capacity, and lipid peroxidation in cortex and hippocampus of old rats. Male Wistar rats of 24-26 months old (620-700g) were exposed i.p. to two doses (0.3 and 1mg/kg) of NIC daily during 9 days. The treatment NIC 0.3 enhanced long-term memory (p<0.05), whereas NIC 1 improved both short and long-term memories (p<0.05). DNA damage was observed only in hippocampus (p<0.05) after NIC 1 exposure. A similar result was obtained for ROS: higher levels were detected at NIC 1 treatment in hippocampus (p<0.05). No alterations in the total antioxidant capacity were verified after NIC exposure (0.3 and 1mg/kg) in both tissues (p>0.05). Finally, evidence of oxidative damage was observed in terms of lipid peroxides levels, being higher at NIC 1 in hippocampus (p<0.05). Overall the results indicate that deleterious effects paralleled the improved short and long-term memories at the highest NIC dose, since augmented DNA damage, ROS concentration and lipid peroxides levels were registered.

Effects of microcystins over short- and long-term memory and oxidative stress generation in hippocampus of rats.

Microcystins produced by cyanobacteria are potent inhibitors of some protein phosphatases, but recent evidence also indicates its potential to generate oxidative stress. In the present study, the effects of microcystin raw extracts (Mic; 0.01 and 20microg/L) and purified okadaic acid (OA; 0.01 and 10microg/L) on short- and long-term memory alteration and antioxidant and oxidative damage were investigated in hippocampus of rats. The results showed an amnesic effect with 0.01 and 20microg/L Mic on retrieval and only with 0.01microg/L Mic on spatial learning. Parallel to these effects oxidative damage was observed as evidenced by augmented levels of lipid peroxides and DNA damage and the absence of antioxidant responses in terms of total oxyradical scavenging capacity. Phase II reactions catalyzed by glutathione-S-transferase were not modified after microcystins exposure. Overall this study showed physiological events (retrieval and spatial learning) that can be related to the classical toxic effects of microcystins (i.e., phosphatase inhibition). In addition, evidence of alternative toxicity mechanisms via oxidative stress generation was also obtained. The fact that organic anion transporter polypeptides (OATP) involved in microcystins uptake are expressed not only in liver but also in brain points to the environmental relevance of the observed effects.

Histological and morphological alterations induced by copper exposure in Laeonereis acuta (Polychaeta, Nereididae).

Laeonereis acuta (Polychaeta, Nereididae) was collected in an unpolluted (UP) and an polluted (P) site at the Patos Lagoon estuary (Southern Brazil) and maintained under control conditions (UPC and PC, respectively) or exposed to waterborne copper (UPCu and PCu; 500 microg Cu/l), for 48 h. Four groups (aaUPC, aaPC, aaUPCu, and aaPCu) were also pre-exposed for 48 h to ascorbic acid (aa; 0.1 mM) before copper exposure. Histological and morphological alterations, as well as oxygen consumption changes were evaluated. Independently of the sampling site and the pre-exposure to the ascorbic acid, morphological abnormalities were evident in more than 80% of worms exposed to copper. Conspicuous histological changes (coeloma obliteration, cuticle separation from the epidermis, and absence of dorsal vessel) were also observed. In addition, PCu worms showed loss of the digestive epithelium and coiling behavior. Similar oxygen consumption values were observed in control and copper exposed worms.

Oxidative stress responses in two populations of Laeonereis acuta (Polychaeta, Nereididae) after acute and chronic exposure to copper.

Acute (4 days) and chronic (14 days) effects of copper were evaluated on the antioxidant defenses of Laeonereis acuta (Polychaeta) collected in unpolluted (UP) and polluted (P) sites. In the acute assay (125 and 250 micro g Cu/l) superoxide dismutase (SOD) and glutathione S-transferase (GST) activities did not change, whereas catalase (CAT) increased in worms from both the sites. Lipid peroxidation was higher in copper exposed worms from the P site. In the chronic assay (62.5 micro g Cu/l) polychaetes from the P site showed enhanced activities of SOD, GST and CAT and higher contents of metallothionein-like proteins and sulfhydrils compared to worms from UP. Differences in responses between polychaetes from UP and P sites suggest that organisms from the polluted site, P, are more susceptible to oxidative stress conditions.

Determination of lipid peroxides in invertebrates tissues using the Fe(III) xylenol orange complex formation.

Reactive oxygen species (ROS) are subproducts of the oxidative metabolism known to initiate chain reactions with polyunsaturated fatty acids that generate lipid peroxides (LPO). The objective of this work was to adapt the ferrous oxidation/xylenol orange (FOX) assay to measure LPO in invertebrate tissues i.e.: from polychaeta (Laeonereis acuta) and crab (Chasmagnathus granulata) species. Whole polychaetes were homogenized in methanol 100%, being determined the optimal sample volume and the time required for color development. It was tested five sample volumes (8-30 microl), following color development up to 215 min. Absorbance stabilization was observed after 90 min, being linearly related with sample volume. A similar procedure was adopted for crab tissues (anterior gills, posterior gills, and hepatopancreas). Differences between species and between organs of the same species were observed when analyzed nonspecific absorbance increments after adding the standard cumene hydroperoxide (CHP). In polychaeta and crab anterior gills tissue, absorbance increments were lower (21-25%) than samples without tissue extracts (blanks) that received CHP. In crab posterior gills and hepatopancreas, the nonspecific increment was almost negligible. Correction formulae are given to account for these differences and simplified protocols for each tissue and species are also included. Great differences in the lipid peroxides content was detected between worms (127.05 +/- 19.32 nmoles CHP/g of wet tissue) respect to anterior gills, posterior gills, and hepatopancreas from the crab species (52.65 +/- 3.59, 30.54 +/- 4.73, and 48.51 +/- 8.78 nmoles CHP/g of wet tissue, respectively).