Evaluation of the lethal and sub-lethal toxicity and potential endocrine disrupting effect of nonylphenol on the zebra mussel (Dreissena polymorpha)

Uranium (238U)-induced ROS and cell cycle perturbations, antioxidant responses and erythrocyte nuclear abnormalities in the freshwater iridescent shark fish Pangasius sutchi

The strategic plan of this study is to analyze any possible radiological impact on aquatic organisms from forthcoming uranium mining facilities around the Nagarjuna Sagar Dam in the future. The predominantly consumed and dominant fish species Pangasius sutchi, which is available year-round at Nagarjuna Sagar Dam, was selected for the study. To comprehend the outcome and to understand the mode of action of ²³⁸U, the fish species Pangasius sutchi was exposed to ¼ and ½ of the LC₅₀ doses of waterborne ²³⁸U in a static system in duplicate for 21 days. Blood and organs, including the gills, liver, brain and muscles, were collected at different time periods-0h, 24h, 48h, 72h, 96h, 7, days 14days and 21 days-using ICP-MS to determine the toxic effects of uranium and the accumulation of ²³⁸U concentrations. The bioaccumulation of ²³⁸U in P. sutchi tissues was dependent on exposure time and concentration. The accumulation of uranium was, in order of magnitude, measured as gills>liver>brain>tissue, with the highest accumulation in the gills. It was observed that exposure to ²³⁸U significantly reduced antioxidant enzymes such as superoxide dismutase, catalase, and lipid peroxidase. The analysis of DNA fragmentation by comet assay and cell viability by flow cytometry was performed at different time intervals. DNA histograms by flow cytometry analysis revealed an increase in the G2/M phase and the S phase. The long-term ²³⁸U exposure studies in fish showed increasing micronucleus frequencies in erythrocytes with greater exposure time. The higher the concentration of ²³⁸U is, the greater is the effect observed, suggesting a close relationship between accumulation and toxicity. A possible ROS-mediated ²³⁸U toxicity mechanism and antioxidant responses have been proposed.

Endocrine-disrupting effects of compounds in Danish streams

Effluents from municipal wastewater-treatment plants and scattered dwellings, as well as runoff from agricultural fields, are sources of endocrine-disrupting compounds (EDCs) in the aquatic environment. The present study investigated the correlation between the occurrence of EDCs in nine Danish streams using passive samplers (polar organic integrative samplers and silicone membranes) and determined their possible biological effects as assessed by mammal cell cultures and the mussel (Unio tumidus). The passive samplers and mussels were exposed simultaneously at the study sites. The extracts from the passive samplers were used to measure the concentrations of EDCs and the biological effects on the estrogen (ER), androgen (AR), and aryl hydrocarbon (AhR)-receptor transactivation. Male mussels were investigated for biomarkers of endocrine effects, such as the levels of vitellogenin-like proteins measured as alkali-labile phosphate (ALP). EDC concentrations, hormone-receptor transactivation (ER, AR, AhR), and level of ALP were greater downstream of wastewater-treatment plants compared with upstream sites and sites supposed to be relatively nonimpacted by wastewater. Furthermore, there was a significant positive correlation between in vitro AhR transactivation and frequency of ALP of male mussels. We conclude that wastewater effluent is an important source of endocrine-disrupting effects in the aquatic environment and that the combination of biological effect measurements and chemical analyses based on passive sampling is useful in the assessment of the ecological state of the aquatic environment.

Effects of the pharmaceuticals gemfibrozil and diclofenac on the marine mussel (Mytilus spp.) and their comparison with standardized toxicity tests

Human pharmaceuticals, like the lipid lowering agent gemfibrozil and the non-steroidal anti-inflammatory drug diclofenac are causing environmental concern. In this study, the marine mussel (Mytilus spp.) was exposed by injection to environmentally relevant and elevated (1 μg/L and 1000 μg/L) concentrations of both compounds and biomarker expression was observed. Gemfibrozil exposure induced biomarkers of stress (glutathione S-transferase and metallothionein) at both concentrations 24h and 96 h after exposure, respectively. Biomarkers of damage (lipid peroxidation (LPO) and DNA damage) were significantly affected, as well as the biomarker for reproduction, alkali-labile phosphate assay, indicating the potential oxidative stress and endocrine disrupting effect of gemfibrozil. Diclofenac significantly induced LPO after 96 h indicating tissue damage. Additionally standard toxicity tests using the marine species Vibrio fischeri, Skeletonema costatum and Tisbe battagliai showed differences in sensitivity to both drugs in the mg/L range. Results indicate a suite of tests should be used to give accurate information for regulation.

Development of an in vitro culture method for cells and tissues from the zebra mussel (Dreissena polymorpha)

Despite the successful transfer of mammalian in vitro techniques for use with fish and other vertebrates, little progress has been made in the area of invertebrate tissue culture. This paper describes the development of an in vitro technique for the culture of both cells in suspension and tissue explants from the gill, digestive gland and mantle of the zebra mussel (Dreissena polymorpha) and their successful maintenance in culture for up to 14 days. Cell suspensions from the gills and digestive gland were the most successful technique developed with viability >80% maintained for up to 8 days in culture, suitable for use in short term toxicity tests. Tissue explants from the mantle were also maintained in culture for up to 14 days. This paper describes the challenges involved in the development of a novel in vitro culture technique for aquatic invertebrates.

Anti-androgenic effects of sewage treatment plant effluents in the prosobranch gastropod Nucella lapillus

Recent studies performed under laboratory conditions have shown that single exposure to high levels of several xenoestrogens is able to induce imposex in at least two neogastropod species. In an attempt to evaluate if xenoestrogens, at environmentally relevant conditions, do contribute to imposex induction, we have tested the effects of a mixture containing xenoestrogens (municipal sewage effluents) on imposex development in the dogwhelk Nucella lapillus. Exposure for 3 months to the raw (0.25% and 1%) and the final sewage effluent (12.5% and 50%) rendered no increase in the severity of imposex. Conversely, as exposure to high concentrations of natural steroids, estradiol and estrone, had previously been shown to partially rescue imposex development under laboratory conditions, we have also tested if exposure to the final sewage effluent could ameliorated the severity of imposex induction by tributyltin (TBT). The results demonstrated that co-exposure to the final sewage effluent leads to a decrease trend in the severity of imposex in the presence of TBT. Within the studied imposex parameters, the Relative Penis Size index (RPSI) was the most affected with a 50% decrease in the effluent 12.5% plus TBT exposed group and 25% decrease in the effluent 50% plus TBT, if compared with the TBT alone. Overall, our results give further support to the use of imposex in N. lapillus as a specific biomarker of TBT contamination. However, in areas of high inputs of sewage effluents, the assessment of TBT contamination by the use of the imposex phenomenon should ideally also include data on the tissue levels of butyltins.

The pesticide heptachlor affects steroid hormone secretion in isolated follicular and luteal cells of rat

Heptachlor, a chlorinated hydrocarbon pesticide, suppresses the production of progesterone and estradiol in the female rat in vivo or in isolated ovaries in vitro. In this study the effect of heptachlor on steroid hormone production by isolated rat luteal and follicular cells, in the presence of two precursor hormones was investigated. Ovaries were isolated from anesthetized mature normocyclic virgin rats (3 to 4 months old), under sterile conditions. Corpora lutea and follicles were microscopically dissected out and separately enzymatically dispersed with collagenase at 37 degrees C. Viable cells collected after centrifugation were used at a concentration of approximately 2.5 x 10(5) cells/10 mL. Both luteal and follicular cell preparations were separately incubated overnight (15 h) at 37 degrees C in the presence of pregnenolone (P5) and androstenedione (A4) at a concentration of 6.0 nmol/L each, and heptachlor at either 0.12 microg/mL (low dose) or 1.20 microg/mL (high dose) (test cells) or in the absence of heptachlor (control cells). At the end of the incubations, progesterone and estradiol 17beta levels were analyzed in the incubation media. The results indicate that heptachlor significantly suppressed the production of both progesterone and estradiol in both cell types in a dose related manner even in the presence of A4 and P5 as precursor hormones (P<0.05).

Are endocrine disrupting compounds a health risk in drinking water?

There has been a great deal of international discussion on the nature and relevance of endocrine disrupting compounds in the environment. Changes in reproductive organs of fish and mollusks have been demonstrated in rivers downstream of sewage discharges in Europe and in North America, which have been attributed to estrogenic compounds in the effluent. The anatomical and physiological changes in the fauna are illustrated by feminization of male gonads. The compounds of greatest hormonal activity in sewage effluent are the natural estrogens 17Beta-estradiol, estrone, estriol and the synthetic estrogen ethinylestradiol. Androgens are also widely present in wastewaters. Investigations of anthropogenic chemical contaminants in freshwaters and wastewaters have shown a wide variety of organic compounds, many of which have low levels of estrogenic activity. In many highly populated countries the drinking water is sourced from the same rivers and lakes that are the recipients of sewage and industrial discharge. The River Thames which flows through London, England, has overall passed through drinking water and sewage discharge 5 times from source to mouth of the river. Under these types of circumstance, any accumulation of endocrine disrupting compounds from sewage or industry potentially affects the quality of drinking water. Neither basic wastewater treatment nor basic drinking water treatment will eliminate the estrogens, androgens or detergent breakdown products from water, due to the chemical stability of the structures. Hence a potential risk to health exists; however present data indicate that estrogenic contamination of drinking water is very unlikely to result in physiologically detectable effects in consumers. Pesticide, detergent and industrial contamination remain issues of concern. As a result of this concern, increased attention is being given to enhanced wastewater treatment in locations where the effluent is directly or indirectly in use for drinking water. In some places at which heavy anthropogenic contamination of drinking water sources occurs, advanced drinking water treatment is increasingly being implemented. This treatment employs particle removal, ozone oxidation of organic material and activated charcoal adsorption of the oxidation products. Such processes will remove industrial organic chemicals, pesticides, detergents, pharmaceutical products and hormones. Populations for which only basic wastewater and drinking water treatment are available remain vulnerable.