Toxicity testing with protozoans

Protoxkit . Freshwater Toxicity Test with a Ciliate Protozoan. Standard Operational Procedure, Creasel Deinze, Belgium, 1998 18 pp. 

Over the years a numbo of alternative test systems have been described in the literature. These include the use of tissue culture, excised animal organs, bactoial systems, computer modeling, protozoan mortality inhibition, chorioallantoic membrane inflammation, and specific biochemical reactions [23]. Most of these alternative test procedures have been proposed or developed with the objective of reducing or replacing animal LDjg toxicity tests and the controversial Draize rabbit eye irritancy test [24]. 

In Europe tests with rotifers, cysts from aquatic invertebrates (Calleja et al., 1994), development of onion roots have been tried but none have been accepted (Persoone et al., 1994 Snell and Persoone, 1989 Fresjog, 1985 Gaggi et al. 1995). Jaffe (1995) has proposed a method using the survival of a protozoan. Toxic chemicals kill the protozoa. The test requires a Coulter particle counter to determine the numbers of viable protozoa. 

Aptula et al. used multiple linear regression to investigate the toxicity of 200 phenols to the ciliated protozoan Tetrahymena pyriformis Using their MLR model, they then predicted the toxicity of another 50 phenols. Here we present a comparative study for the entire set of 250 phenols, using multiple linear regression, artificial neural networks, and SVM regression methods. Before computing the SVM model, the input vectors were scaled to zero mean and unit variance. The prediction power of the QSAR models was tested with complete cross-validation leave-5%-out (L5%0), leave-10%-out (L10%O), leave-20%-out (L20%O), and leave-25%-out (L25%0). The capacity parameter C was optimized for each SVM model. 

Bogaerts, P. Bohatier, J. Bonnemoy, E. Use of the ciliated protozoan Tetrahymena pyriformis for the assessment of the toxicity and quantitative structure-activity relationships of xenobiotics comparison with the microtox test. Ecotox. Environ. Safe. 2001, 49, 293-301. 

This test identifies the substance to be examined as a salt of antimony(III), Sb +, or antimony(V), Sb +. Antimony(III) and antimony(V) were formerly used in the oral treatment of intestinal worms and topically in the treatment of infections of protozoan parasites in the skin. But since especially tetrava-lent antimony is poisonous, they have generally been replaced by less toxic alternatives. At present, there are no monographs of antimony compounds in the European Pharmacopoeia. Antimony forms both tetra- and pentavalent ions, but the pentavalent is mainly found in oxides containing the antimonate ion, Sb04. Antimony(III), on the other hand, can be found as the free dissociated ion, Sb +, but, as also for example bismuth, since it reacts with water at neutral pH, forming antimonate. 

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