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PubMed2004

The use of embryonic stem cells for regulatory developmental toxicity testing in vitro--the current status of test development.

The future chemical policy of the European Union as well as the 7th amendment of the cosmetic directive is calling for the development of alternative tests to animal experimentation for toxicological safety testing. In the field of embryotoxicity one of the most promising in vitro models are based on embryonic stem cells. The embryonic stem cell test has already been validated in comparison to in vivo results in an international blind collaboration study. The presented review is discussing the use, limitations and further needs for the test in order to be fully suitable for regulatory acceptance. In this context, it is summarized which requirements for an in vitro embryotoxicity test have to be fulfilled for regulatory toxicity testing. In addition, an overview about the current status of test development of other embryonic stem cell tests is presented. Several workshops have reviewed the progress of in vitro tests for developmental toxicity testing. A general consensus of these workshops has been that one single test will not be sufficient to cover all manifestations of developmental toxicity. The establishment of a test battery for developmental toxicity is required. This will be even more challenging since the principles of a composing test strategy and its validation have not been defined yet. Finally, the unique possibility of combining the human embryonic stem cell technology and the microarray techniques might lead to a deeper understanding of the toxicological mechanisms of human developmental toxicants.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

Interlaboratory variability of amphipod sediment toxicity tests in a cooperative regional monitoring program.

Marine sediment toxicity tests are widely applied in monitoring programs, yet relatively little is known about the comparability of data from different laboratories. The need for comparability information is increased in cooperative monitoring programs, where multiple laboratories (often with variable skill levels) perform toxicity tests. An interlaboratory comparison exercise was conducted among seven laboratories in order to document the comparability of sediment toxicity measurements during the Bight '98 regional sediment survey in southern California. Sediments from four stations in Los Angeles and Long Beach Harbors were tested using a 10-day survival test of the amphipod Eohaustorius estuarius. All laboratories successfully performed the sediment test and associated reference toxicant test. Statistically significant differences were found in mean amphipod survival rates among some laboratories for the field-collected sediments, but there was little evidence of a consistent bias among laboratories. Although the reference toxicant test indicated a five-fold variation in test sensitivity among laboratories, these results were not accurate predictors of interlaboratory performance for the sediment tests. The laboratories demonstrated excellent concordance (Kendall's W = 0.91) in ranking the field-collected sediments by toxicity. Agreement on classifying the sediments into categories (nontoxic, moderately toxic, and highly toxic) based upon the percent of survival was best for highly toxic sediments. An analysis of test precision based upon the variance among replicates within a test indicated that the measured survival rate for a sample may vary by up to 12 percentage points from the actual response.

Amphipoda↗
PubMed2001

Assessment of sublethal endpoints for toxicity testing with the nematode Caenorhabditis elegans.

Toxicity tests in invertebrates often use sublethal endpoints, which may exhibit different sensitivity for various toxicants. Our objective was to characterize the sensitivity of movement, feeding, growth, and reproduction as endpoints for heavy metal toxicity testing with Caenorhabditis elegans. Growth and feeding were assessed in the same nematode samples used to assess movement and reproduction. Median effective concentrations (EC50s) for 24-h exposures to Pb, Cu, and Cd were determined for movement, feeding, and growth and a 72-h EC50 was derived for reproduction. The order of toxicity was Cu > Pb > Cd for each endpoint, including lethality and movement. There were no differences in sensitivity among endpoints for any metal. When exposed for 4 h at (sublethal) concentrations that were 14 times the 24-h EC50 value, Pb and Cu reduced feeding to the same extent while movement was reduced significantly more by Pb than by Cu. Thus, a difference in sensitivity of endpoints was apparent at 4 h, which was not evident at 24 h. These observations suggest potentially different mechanisms of toxicity for 24- and 4-h tests.

Animals↗
PubMed2003

Comparison of the sensitivity of three nematode species to copper and their utility in aquatic and soil toxicity tests.

Nematodes are useful organisms for aquatic and soil toxicity testing because of their abundance and diversity as well as their ease of culturing and maintenance in the laboratory. The nematode Caenorhabditis elegans has been used extensively in toxicity testing, but its sensitivity to metal exposures in relation to other nematodes remains unclear. In this study, we compare the sensitivity and ease of use of two other rhabditid nematodes, Panagrellus redivivus and Pristionchus pacificus, to C. elegans. Toxicity endpoints were chosen to investigate the effects of Cu on the survival of these nematodes after soil exposures and on the survival, reproduction, movement, and feeding behavior of nematodes after exposures in aquatic medium. In all lethality testing, P. pacificus was the most sensitive, C. elegans exhibited intermediate sensitivity, and P. redivivus was the least sensitive. Reproduction and movement of C. elegans and reproduction of P. pacificus were decreased 50% by similar concentrations of Cu (EC50s approximately 2 mg/L), but P. pacificus movement was less sensitive to Cu exposures (EC50 = 8 mg/L). Although all nematodes may be useful in lethality assays, using P. redivivus in toxicity tests is complicated by the presence of two sexes and difficulties in obtaining age-synchronized cultures. Pristionchus pacificus is an ideal acute toxicity-testing organism because of its sensitivity and ease of culturing. However, C. elegans appears to be more sensitive and therefore most useful in behavioral assays. Future studies of the relative sensitivities of nematodes in toxicity testing should continue to investigate additional toxicants, nematode species, and quantifications of sublethal effects after soil exposures.

Animals↗
PubMed2003

Photothermal bioanalytical methods for pesticide toxicity testing.

This paper describes bioanalytical methods and biosensors which rely on cholinesterase (ChE) inhibition and can be used to detect and test the toxicity of organophosphate (OP) and carbamate pesticides. Particular attention is given to the combined use of these methods and photothermal detection that has recently led to improved sensitivity and increased sample throughput of ChE bioanalytical assay. Following a rapid and simple sample preparation procedure, this assay can detect organophosphate pesticides such as paraoxon in the sub ng/mL concentration range. The AChE bioanalytical method demonstrated different sensitivity to various pesticides, which correlated well with pesticide toxicity expressed as LD50 for rats. Similarly, the same pesticide yielded different ChE inhibition in different organisms. This opens the possibility of applying these bioanalytical methods to evaluate the acute toxicity of OP compounds or of environmental samples to particular organisms.

Biosensing Techniques↗
PubMed2004

Sulfide as a confounding factor in toxicity tests with the sea urchin Paracentrotus lividus: comparisons with chemical analysis data.

Sperm cell and embryo toxicity tests with the sea urchin Paracentrotus lividus were performed to assess the toxicity of sulfide, which is considered a confounding factor in toxicity tests. For improved information on the sensitivity of these methods to sulfide, experiments were performed in the same aerobic conditions used for testing environmental samples, with sulfide concentrations being monitored at the same time by cathodic stripping voltammetry. New toxicity data for sulfide expressed as median effective concentration (EC50) and no-observed-effect concentration (NOEC) are reported. The EC50 value for the embryo toxicity test (total sulfide at 0.43 mg/L) was three times lower than for the sperm cell test (total sulfide at 1.20 mg/L), and the NOEC values were similar (on the order of total sulfide at 10(-1) mg/L) for both tests. The decrease in sulfide concentration during the bioassay as a consequence of possible oxidation of sulfide by dissolved oxygen was determined by voltammetric analysis, indicating a half-life of about 50 min in the presence of gametes. To check the influence of sulfide concentrations on toxicity effects in real samples, toxicity (with the sperm cell toxicity test) and chemical analyses also were performed in pore-water samples collected with an in situ sampler in sediments of the Lagoon of Venice (Italy). A highly positive correlation between increased acute toxicity and increased sulfide concentration was found. Examination of data revealed that sulfide is a real confounding factor in toxicity testing in anoxic environmental samples containing concentrations above the sensitivity limit of the method.

Animals↗
PubMed2003

A comparison of the daphnids Ceriodaphnia dubia and Daphnia ambigua for their utilization in routine toxicity testing in the Southeastern United States.

U.S. regulatory agencies commonly require effluent toxicity testing with Ceriodaphnia dubia--a practice that has led to the criticism that this species and test protocol often does not reflect local taxa or site-specific conditions. Using an indigenous test species may produce a more realistic model of local effects and may minimize test endpoint variance due to regional differences in water quality. This study addressed the substitution of C. dubia with Daphnia ambigua for toxicity testing in the southeastern United States. This investigation determined that D. ambigua could be laboratory cultured with only minimal changes to established regulatory protocol and that the life-cycle characteristics of this species were conducive to traditional acute and chronic aquatic toxicity test methods used with other daphnids. Acute toxicity tests showed that D. ambigua was less sensitive to some toxicants (sodium chloride, copper sulfate, and sodium lauryl sulfate) but more sensitive to others (chlorpyrifos). Chronic tests with copper sulfate and sodium chloride resulted in lower EC50S for D. ambigua reproduction with both compounds. When exposed to low-alkalinity, low-pH stream waters typical of many southeastern United States watersheds, C. dubia demonstrated a significant reproductive depression in two of three streams tested, whereas D. ambigua experienced no chronic effect. These results suggest that D. ambigua may serve as a suitable surrogate for C. dubia as an toxicity indicator species in these types of receiving streams.

Animals↗
PubMed1997

Evaluation of bleached kraft mill process water using Microtox(R), Ceriodaphnia dubia, and Menidia beryllina toxicity tests.

To determine whether a 7- to 10-d embryo toxicity/teratogenicity test with the inland silverside fish, Menidia beryllina, is a sensitive indicator for evaluation of bleached kraft mill effluents, we compared this test with the Microtox(R) 15-min acute toxicity test and the Ceriodaphnia dubia 7-d chronic toxicity test. Water samples used in each test were collected from three areas in a bleached kraft pulp and paper mill using a 100% chlorine dioxide bleaching process: 1) river water prior to use in the mill; 2) the combined acid/base waste stream from the pulping process prior to biological treatment in the aerated stabilization basin (ASB); and 3) the effluent from the ASB with a retention time of approximately 11 d. Relative toxicity determined by the three tests for each water sampling location was compared. All three toxicity tests were predictive indicators of toxicity; however, the C. dubia and M. beryllina tests were the more similar and sensitive indicators of toxicity. Process water (ASB influent) prior to biological treatment in the ASB was toxic at all concentrations using the Microtox(R) and C. dubia tests. The fish embryo test showed no toxicity at 1% concentrations, slight toxicity at 10%, and acute toxicity at the 100% ASB influent concentration. Tests with biologically-treated ASB effluent indicated a substantial reduction in observed toxicity to Microtox(R) bacteria, C. dubia, and M. beryllina. No toxic responses were observed in any test at a 1% ASB effluent concentration which was the approximate effluent concentration in the receiving river following mixing. No relationship was found among any toxicological response and effluent levels of adsorbable organic halides, polychlorinated phenolic compounds, 2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3,7,8-tetrachlorodibenzofuran, total suspended solids, color, chemical oxygen demand, or total organic carbon.

Abnormalities, Drug-Induced↗
PubMed1993

Regulatory agency considerations and requirements for validation of toxicity test alternatives.

When developing an alternative toxicity test, one must first determine whether the alternative assay is to be used as a screen or as a replacement for the traditional toxicity test. An assay used as a screen will require less stringent acceptance criteria, for it is designed to answer fewer and less complex questions (e.g., the assessment of only potential teratogenicity). An assay used as a replacement will be used to establish hazard or lack thereof (safety). In other words, a replacement assay must clearly establish whether or not a chemical is a teratogen. One should also have knowledge of and experience with the in vivo assay to be replaced. This knowledge should be of not only the procedural aspects of the test but also the regulatory information it provides (i.e., how the results are used for hazard determination). Thorough consideration of the regulatory information is critical for a test intended to be used as a replacement. Validation should include intralaboratory and interlaboratory reproducibility of results from a standard protocol, an assessment of the qualitative and quantitative aspects of the test responses, and the use of a sufficient number of chemicals representative of the defined category of interest.

Animals↗
PubMed1997

Predator-prey relationships in a two-species toxicity test system.

In a two-species toxicity test system survival and reproduction of both the predator Hypoaspis aculeifer (Gamasida) and the prey Folsomia fimetaria (Collembola) were studied after 21 days of residual exposure to a soil contamination of the insecticide dimethoate. Additional experiments were run to analyze which species-species and compound-species relationships determine the outcome of this two-species experiment. Number of adult F. fimetaria were reduced by both predation and dimethoate exposure, whereas mites preyed less efficiently on adults than on juveniles. At 0.357 mg dimethoate/kg soil, numbers of juvenile F. fimetaria were mainly reduced by predation on adults and juveniles. At 0.7 mg/kg, an additional dimethoate effect was found, which was attributed to an effect on the reproduction of F. fimetaria, mainly due to lethality of adults. It was reasoned that lethal effects on juvenile springtails are less important. Adult H. aculeifer was not affected by dimethoate exposure, whereas numbers of juvenile H. aculeifer demonstrated a decline only at the highest concentration of 0.7 mg/kg. It is hypothesized that this latter effect is possibly due to food depletion caused by a decreased availability of prey, rather than to the lethal effects of dimethoate on juvenile mites. Such a secondary effect of a pesticide application could not have been derived from a single-species toxicity experiment and demonstrates the additional value of a two-species toxicity test system.

Animals↗
PubMed2004

Short-term algal toxicity test based on phosphate uptake.

In order to develop a short-term algal toxicity test, the growth of and the phosphate uptake by the green alga Selenastrum capricornutum during batch culture were observed. In the control medium, S. capricornutum took up phosphate earlier than it grew. It was also observed that the phosphate uptake was inhibited by the presence of a toxicant. From these results, phosphate uptake was considered as one of the useful effect parameters for a short-term algal toxicity test. As the removal rate of phosphate from the medium is a function of the amount of algal cell initially inoculated, the test period is variable. The relationship between the amount of inoculation and phosphate uptake was examined and the test conditions suitable for a 3-h toxicity test were established as one example. According to this test procedure, the inhibitory effect of some toxicants on the phosphate uptake was determined. For comparison, a conventional algal assay based on algal growth was also performed. The EC50s for both tests were close. This indicated that the algal toxicity test method proposed in this paper would be useful for the uses where rapidity is required.

Carbon↗
PubMed1994

A critical review of the optimum duration of chronic rodent testing for the determination of non-tumourigenic toxic potential: a report by the BTS Working Party on Duration of Toxicity Testing.

This review indicates that for the detection of non-neoplastic toxic effects: 1. Four decades of accumulated literature provide no lead as to the optimum duration of repeat dose toxicity testing required for all classes of chemicals, although 6 months repeated administration appears adequate for pharmaceuticals. 2. Three month studies predicted the 2 year outcome for 70% of the compounds evaluated in this pilot study using data published by the US National Toxicology Program. 3. In spite of the limitations of this pilot study, this finding is considered encouraging as it is close to that generated previously on more detailed confidential pharmaceutical data. This suggests that the exercise should now be expanded using confidential surveys of industrial data to determine the concordance resulting from the evaluation of a larger group of chemicals.

Animals↗
PubMed2003

Application of toxicity tests into discharges of the pulp-paper industry in Turkey.

The aim of this study was to investigate the acute toxicity of pulp-paper industry wastewater using traditional and enrichment toxicity tests and to emphasize the importance of toxicity tests in wastewater discharge regulations. Enrichment toxicity tests are novel applications and give an idea of whether there is potential toxicity or growth-limiting and -stimulating conditions. Different organisms were used such as bacteria (floc and coliform bacteria), algae (Chlorella sp.), protozoa (Vorticella sp.), and fish (Lepistes sp.) to represent four trophic levels. Furthermore, chemical oxygen demand (COD) fractionation results were compared with these tests to assess the effect of COD subcategories on the determination of possible toxicity. The pulp-paper industry results revealed acute toxicity to at least two organisms in 6 of 20 effluent samples. The toxicity test results were assessed with chemical analyses such as COD, biochemical oxygen demand (BOD), color, absorbable organic halogen (AOXs), and phenol. It was observed that the toxicity of the effluents could not be explained by using physicochemical analyses in four cases for the pulp-paper industry. The results clearly indicate that bioassay tests provide additional information on the toxicity potential of industrial discharges and effluents.

Animals↗