Comparison of two screening bioassays, based on the frog sciatic nerve and yeast cells, for the assessment of herbicide toxicity

Abstract

Two different test systems, one based on the isolated sciatic nerve of an amphibian and the other on a microbial eukaryote, were used for the assessment of herbicide toxicity. More specifically, we determined the deleterious effects of increasing concentrations of herbicides of different chemical classes (phenoxyacetic acids, triazines, and acetamides), and of 2,4-dichlorophenol (2,4-DCP), a degradation product of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), on electrophysiological parameters and the vitality of the axons of the isolated sciatic nerve of the frog (Rana ridibunda) and on the growth curve of the yeast Saccharomyces cerevisiae based on microtiter plate susceptibility assays. The no-observed-effect-concentration (NOEC), defined as the maximum concentration of the tested compound that has no effect on these biological parameters, was estimated. In spite of the different methodological approaches and biological systems compared, the NOEC values were identical and correlated with the lipophilicity of the tested compounds. The relative toxicity established here, 2,4-DCP > alachlor, metolachlor >> metribuzin > 2,4-D, 2-methyl-4-chlorophenoxyacetic acid (MCPA), correlates with the toxicity indexes reported in the literature for freshwater organisms. Based on these results, we suggest that the relatively simple, rapid, and low-cost test systems examined here may be of interest as alternative or complementary tests for toxicological assessment of herbicides.

On the Mechanism of Biotransformation of the Anthraquinonic Dye Acid Blue 62 by Laccases

“…The use of the eukaryotic model Saccharomyces cerevisiae could provide meaningful clues on the potential cytotoxicity of these compounds for mammals or aquatic eukaryotic organisms. [19] Our results show that AB62 causes a significant inhibitory effect on yeast growth (Figure 4) and values of LOEC and IC 50 of around 7 and 420 mm (3 and 177 mg/L) respectively, were estimated.…”

Phototransformation Processes of Emerging Contaminants in Surface Water

“…Furthermore, they can be formed as secondary pollutants upon environmental transformation of various pesticides, mainly the chlorophenoxy-acetic and propionic acids [15,16] and the antimicrobial agent triclosan [17,18]. Chlorophenol direct photolysis shows an interesting difference between ortho-and para-substituted isomers.…”

“…16 reports the log 10 (k) vs. s (Hammett) plot for CO 3 À in the case of phenolates and anilines. The good linear trends suggest that reactivity with CO 3 À is heavily influenced by the nature of the substituents on the aromatic ring.…”

Oxidative Stress Induced by the 2,4-Dichlorophenoxyacetic Herbicide

“…Indeed, yeast has proved to be a useful experimental model for the study of basic molecular mechanisms underlying the toxicological effects of the important agrochemical 2,4-D and the associated adaptive responses (Papaefthimiou et al, 2004).…”