Biomedical subjects

Anja Coors

Publications and source records attributed to Anja Coors.

4 recordsLinked to original sources

PubMed2006

Application of in-situ bioassays with macrophytes in aquatic mesocosm studies.

Aquatic mesocosm studies assess ecotoxicological effects of chemicals by using small artificial ponds as models of lentic ecosystems. In this study, methods of controlled insertion of macrophytes within an outdoor mesocosm study were explored. Although analytically confirmed concentrations of the model herbicide terbuthylazine were high enough to expect direct effects on phytoplankton, functional parameters and dominant taxa abundance indicated only minor and transient effects. In-situ assays with Lemna minor, Myriophyllum spicatum, Potamogeton lucens and Chara globularis revealed adverse effects at concentrations in accordance with literature data. Complex interactions such as nutrient limitation and competition were possible reasons for the observed growth promotion at the lower concentration of about 5 microg/l terbuthylazine. The approach of macrophyte in-situ bioassays within a mesocosm study proved to be applicable. Presumed advantages are simultaneous acquisition of toxicity data for several species of aquatic plants under more realistic conditions compared to laboratory tests and inclusion of macrophytes as important structural and functional components in mesocosms while limiting their domination of the model ecosystem.

Animals↗

PubMed2006

Nonylphenol isomers differ in estrogenic activity.

Nonylphenol belongs to the most investigated xenohormones acting at the estrogen receptor. Technical nonylphenol contains approximately 20 para-substituted isomers. Because of limitations in testing and quantifying all 20 isomers in the mixture, the linear form, 4n-NP, is often used as a reference substance, even though it is not present in the technical mixture. Here, we report on the synthesis and estrogenic potency of six nonylphenol isomers that occur at different proportions in technical nonylphenol mixtures. The relative potency of each isomer was determined by use of the MVLN transcriptional activation cell assay. As well, a subset of isomers was tested in the E-screen assay. One isomer, p353-NP, exhibited the same relative potency as the nonylphenol mixture, whereas the other isomers were found to be less potent. Two isomers, p22-NP and p262 NP, and the linear 4n-NP were found to be weak ER agonists with responses near the detection limit in the MVLN assay. Two isomers, p262-NP and 4n-NP, exhibited measurable activity in the E-screen. Our results demonstrate that defined p-NP isomers are most suitable for reflecting the estrogenic potency of technical NP mixtures. Among other applications, they should be used in the future to explain differences in estrogenic potency due to NPs as detected by various in vitro assays.

Biological Assay↗

PubMed2004

Adaptation to environmental stress in Daphnia magna simultaneously exposed to a xenobiotic.

In standardized ecotoxicological testing chemicals are investigated under optimal conditions for the test organisms despite the fact that environmental factors such as predation pressure and food availability are important parameters regulating natural populations. Food limitation and predator presence can induce shifts in life-history traits in various Daphnia species, especially trade-offs in reproductive biomass allocation. These adaptive responses are thought to ensure survival of the population in a highly variable environment. A xenobiotic dispersant (used in textile dyeing processes) also shifted the biomass allocation of Daphnia magna. To assess whether the dispersant could hinder D. magna adaptation to varying environmental conditions, we conducted experiments with food level and presence of Chaoborus larvae as environmental factors and simultaneous exposure to the dispersant. At low food level and in presence of the predator, D. magna produced fewer but larger sized neonates, regardless of dispersant exposure. The dispersant shifted biomass allocation towards more but smaller sized offspring in all experiments. However, the adaptive response to the environmental factors and the dispersant effect cancelled each other out in that they induced independently from each other opposite shifts in biomass allocation. In summary, the dispersant exposure resulted not in an inhibition of the adaptive response but in a reduction of the value of the response. Our study with this model substance demonstrates that xenobiotics can affect the adaptation of organisms to environmental stress which can result in effects likely to be overlooked in standardized testing.

Acclimatization↗

PubMed2003

Removal of estrogenic activity from municipal waste landfill leachate assessed with a bioassay based on reporter gene expression.

The leachate of a municipal waste landfill was tested for estrogenic activity using a reporter-gene-based bioassay with a human breast-cancer-derived cell line (MVLN cells). The leachate was processed with two different membrane-employing processes operating in parallel. One process consists of aerobic biological degradation, ultrafiltration, and subsequent adsorption to activated carbon. The second process was a reverse osmosis treatment of the raw leachate. Both processes are common in the treatment of landfill leachate. Here, the efficacy of the two processes to remove "estrogenicity" was compared. Both treatment processes removed more than 97% of the estrogenic activity, calculated as estradiol equivalents (EEQs), but they were not equally effective. After adsorption to activated carbon, no estrogenicity was detected, whereas concentrated effluent of the reverse osmosis treatment still elicited an estrogenic response in the bioassay. On the basis of chemical analysis, it is proposed that bisphenol A was responsible for the majority of estrogenic activity in the raw and treated leachate. Although the contribution of treated leachate to the estrogenic load on the aquatic environment seems to be low compared to that of sewage treatment works, the high estrogenic activity in raw landfill leachate stresses the necessity for the appropriate treatment of these leachates.

Benzhydryl Compounds↗