Validation of a two-generational reproduction test in Daphnia magna: An interlaboratory exercise.

Effects observed within one generation disregard potential detrimental effects that may appear across generations. Previously we have developed a two generation Daphnia magna reproduction test using the OECD TG 211 protocol with a few amendments, including initiating the second generation with third brood neonates produced from first generation individuals. Here we showed the results of an inter-laboratory calibration exercise among 12 partners that aimed to test the robustness and consistency of a two generation Daphnia magna reproduction test. Pyperonyl butoxide (PBO) was used as a test compound. Following experiments, PBO residues were determined by TQD-LC/MS/MS. Chemical analysis denoted minor deviations of measured PBO concentrations in freshly prepared and old test solutions and between real and nominal concentrations in all labs. Other test conditions (water, food, D. magna clone, type of test vessel) varied across partners as allowed in the OECD test guidelines. Cumulative fecundity and intrinsic population growth rates (r) were used to estimate "No observed effect concentrations "NOEC using the solvent control as the control treatment. EC10 and EC-50 values were obtained regression analyses. Eleven of the twelve labs succeeded in meeting the OECD criteria of producing >60 offspring per female in control treatments during 21days in each of the two consecutive generations. Analysis of variance partitioning of cumulative fecundity indicated a relatively good performance of most labs with most of the variance accounted for by PBO (56.4%) and PBO by interlaboratory interactions (20.2%), with multigenerational effects within and across PBO concentrations explaining about 6% of the variance. EC50 values for reproduction and population growth rates were on average 16.6 and 20.8% lower among second generation individuals, respectively. In summary these results suggest that the proposed assay is reproducible but cumulative toxicity in the second generation cannot reliably be detected with this assay.

Optimizing the design of a reproduction toxicity test with the pond snail Lymnaea stagnalis.

This paper presents the results from two ring-tests addressing the feasibility, robustness and reproducibility of a reproduction toxicity test with the freshwater gastropod Lymnaea stagnalis (RENILYS strain). Sixteen laboratories (from inexperienced to expert laboratories in mollusc testing) from nine countries participated in these ring-tests. Survival and reproduction were evaluated in L. stagnalis exposed to cadmium, tributyltin, prochloraz and trenbolone according to an OECD draft Test Guideline. In total, 49 datasets were analysed to assess the practicability of the proposed experimental protocol, and to estimate the between-laboratory reproducibility of toxicity endpoint values. The statistical analysis of count data (number of clutches or eggs per individual-day) leading to ECx estimation was specifically developed and automated through a free web-interface. Based on a complementary statistical analysis, the optimal test duration was established and the most sensitive and cost-effective reproduction toxicity endpoint was identified, to be used as the core endpoint. This validation process and the resulting optimized protocol were used to consolidate the OECD Test Guideline for the evaluation of reproductive effects of chemicals in L. stagnalis.

Visualizing Compound Distribution during Zebrafish Embryo Development: The Effects of Lipophilicity and DMSO.

The predictability of the zebrafish embryo model is highly influenced by internal exposure of the embryo/larva. As compound uptake is likely to be influenced by factors such as lipophilicity, solvent use, and chorion presence, this article focuses on investigating their effects on compound distribution within the zebrafish embryo. To visualize compound uptake and distribution, zebrafish embryos were exposed for 96 hr, starting at 4 hr postfertilization, to water-soluble dyes: Schiff's reagent (logP -4.63), Giemsa stain (logP -0.77), Van Gierson stain (logP 1.64), Cresyl fast violet (logP 3.5), Eosine Y (logP 4.8), Sudan III (logP 7.5), and Oil red O (logP 9.81), with and without 1% dimethyl-sulfoxide (DMSO). Three additional compounds were used to analytically determine the uptake and distribution: Acyclovir (logP -1.56), Zidovudine (logP 0.05), and Metoprolol Tartrate Salt (logP 1.8). Examinations were performed every 24 hr. Both methods (visualization and specific analysis) showed that exposure to higher logP values results in higher compound uptake. Specific analysis showed that for lipophilic compounds >90% of compound is taken up by the embryo. For hydrophilic compounds, >90% of compound within the complete egg could not be associated to embryo or chorion and is probably distributed into the perivitelline space. Overall, internal exposure analyses on at least two occasions (i.e., before and after hatching) is crucial for interpretation of zebrafish embryotoxicity data, especially for compounds with extreme logP values. DMSO did not affect exposure when examined with the visualization method, however, this method might be not sensitive enough to draw hard conclusions.

From cutting edge to guideline: A first step in harmonization of the zebrafish embryotoxicity test (ZET) by describing the most optimal test conditions and morphology scoring system.

In the last couple of years, the interest in the zebrafish embryotoxicity test (ZET) for use in developmental toxicity assessment has been growing exponentially. This is also evident from the recent proposal for updating the ICHS5 guideline. The methodology of the ZET used by the different groups varies greatly. To further evaluate its successfulness and to take the ZET to the next level, harmonization of procedures is crucial. In the present study, based on literature and empirical data, the most optimal study design regarding temperature, test chamber, exposure period, presence of chorion, solvent use, exposure method, choice of concentrations, and teratogenic classification is proposed. Furthermore, our morphology scoring system is reported in detail as protocol to further enhance study design harmonization.

A European perspective on alternatives to animal testing for environmental hazard identification and risk assessment.

Tests with vertebrates are an integral part of environmental hazard identification and risk assessment of chemicals, plant protection products, pharmaceuticals, biocides, feed additives and effluents. These tests raise ethical and economic concerns and are considered as inappropriate for assessing all of the substances and effluents that require regulatory testing. Hence, there is a strong demand for replacement, reduction and refinement strategies and methods. However, until now alternative approaches have only rarely been used in regulatory settings. This review provides an overview on current regulations of chemicals and the requirements for animal tests in environmental hazard and risk assessment. It aims to highlight the potential areas for alternative approaches in environmental hazard identification and risk assessment. Perspectives and limitations of alternative approaches to animal tests using vertebrates in environmental toxicology, i.e. mainly fish and amphibians, are discussed. Free access to existing (proprietary) animal test data, availability of validated alternative methods and a practical implementation of conceptual approaches such as the Adverse Outcome Pathways and Integrated Testing Strategies were identified as major requirements towards the successful development and implementation of alternative approaches. Although this article focusses on European regulations, its considerations and conclusions are of global relevance.