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TETRATOX


The TETRATOX database is a collection of toxic potency data for more than 2,400 industrial organic compounds of which more than 1,600 have been published. The assay {Schultz, T.W. 1997. TETRATOX: Tetrahymena pyriformis population growth impairment endpoint-A surrogate for fish lethality. Toxicol. Methods 7: 289-309}is a short-term, static protocol using the common freshwater ciliate Tetrahymena pyriformis (strain GL-C). The 50% impairment growth concentration (IGC50) is the recorded endpoint.

Briefly, cultures are reared in 50 ml of a semi-defined medium in 250 ml Erlenmeyer flasks. In the TETRATOX assay, a range-finding assay followed by three replicate definitive tests is performed on each test material. Definitive test replicates consist of a minimum of five different concentrations of each test material with duplicate flasks of each concentration. Thus, a minimum of 30 data points comprises each analysis. Duplicate controls, which have no test material but were inoculated with T. pyriformis, and a blank are used to provide a measure of the acceptability of the test by indicating the suitability of the medium and test conditions, and a basis for interpreting data from other treatments. While several different time points were used over the course of more than 15 years, each was used with a medium and test condition regime to allow for 8 to 9 cell cycles in controls. Duplicate flasks are inoculated with an initial density of 2,500 cells/ml with log-growth-phase ciliates. Following 40 hours of incubation at 27 1C, population density is measured spectrophotometrically and 50% effect levels determined.

The 50% inhibitory growth concentration in mg/l (IGC50) and the 95% fiducial interval are determined for each test compound. The IGC50 is calculated by probit analysis using the percent control-normalized absorbance as the dependent variable and the toxicant concentration in mg/l as the independent variable. Both the slope and intercept of the probit regression equation is recorded as well as the Chi-squared value. The latter is an indicator of the fit of the data to the probit model. Normally the Chi-squared value is greater than 0.9.

In the majority (> 85%) of the more than 2,100 tests completed, it is possible to generate a statistically valid concentration-response curve. However, some chemicals (e.g., neutral organics with 1-octanol/water partition coefficients greater than 5.0) are not toxic at saturation; others do not attain the measured 50% effect endpoint at saturation, and still other chemicals (e.g., highly bioreactive toxicants) have a very narrow concentration-response range that precludes proper statistical analyses.

  Toxicity and chemical descriptor data for 500 aliphatic chemicals

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AUTHOR & CONTACT: 

Schultz, T.W., M. S., Ph.D.
Department of Comparative Medicine
College of Veterinary Medicine
The University of Tennessee
2407 River Dr.
Knoxville, TN 37996- 4500

Tel: 1- 865- 974- 5826
Fax: 1- 865- 974-5640
Email:
Web: http://www.vet.utk.edu/faculty/schultz.shtml

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