Bioassays systems

Several recent expert reviews and workshops have discussed the effects of endocrine disruption on wildlife and especially invertebrate species. These include the EU workshop on the impact of endocrine disrupters on human health and wildlife (Weybridge, 1996), the lEH workshop (Leicester, May 1997), the Environment Agency Consultative report (January 1998) and the Tyndall Forum at the Royal Institution (February 1998). They have concluded that endocrine disruption may have far-reaching adverse consequences for biodiversity and the sustainability of natural ecosystems. More comprehensive bioassay systems are required to identify and assess chemicals alleged to produce endocrine modulating effects. 

Mancy, K.H. Allen, H.E. A Controlled Bioassay System for Measuring Toxicity of Heavy Metals. U.S. Environmental Protection Agency Washington D.C., 1977. 

Thns far, the discussion has dealt primarily with biomarker responses in living organisms. In the next section, consideration will be given to the exploitation of this principle in the development of bioassay systems that can be nsed in environmental monitoring and environmental risk assessment. 

Persoone, G., Janssen, C., and De Coen, W. (Eds.) (2000). New Microbiotests for Routine Toxicity Testing and Screening—An extensive review of bioassay systems and toxicity tests that also contains some valuable discussion of the principles that underlie them. 

Garrison, P.M., Tullis, K., and Aarts J.M.M.J.G. et al. (1996). Species specific recombinant cell lines as bioassay systems for the detection of dioxin-like chemicals. Fundamental and Applied Toxicology 30, 194-203. 

In our efforts to detect and isolate the allelcpathic agents from tall fescue and several other grass species, we extracted the detached plant material with water and/or organic solvents. Either solvent extraction method yielded extracts that were inhibitory to the seed germination and seedling growth in our bioassay systems. 

Cost. Most bioassay systems, in particular those involving whole animals, are extremely expensive to undertake. 

Fig. 6. Conceptual integration of a micro-reactor with a bioassay system...

Despite the uncertainties in HOP for the toxins, there is reason to suspect that their mouse intraperitoneal potencies (MIP), the ri for the standard mouse bioassay system, do not bear a uniform relationship to them. Early pharmacological work ( ) on the paralytic shellfish toxins was conducted with shellfish extracts. 

Denison, M.S., Rogers, W.J., Fair, M., Ziccardi, M., Clark, G., Murk, A.J., Brouwer, A. (1996). Application of the CALUX bioassay system for the detection of dioxin-like chemicals (Ah receptor ligands) in whole serum samples and in extracts fiom commercial and consumer products. Organohalogen Compounds 27 280-284. 

Butler, J. P., T. J. Kneip, and J. M. Daisey, An Investigation of Interurban Variations in the Chemical Composition and Mutagenic Activity of Airborne Particulate Organic Matter Using an Integrated Chemical Class/Bioassay System, Atmos. Environ., 21, 883-892 (1987). 

BioAssay Systems, QuantiChrom Magnesium Assay Kit(DIMG-250), BioAssay Systems, Hayward, CA, USA. (http //www.bioassaysys.com/DIMG.pdf). 

Destruction of nitric oxide by superoxide in the buffers is more likely to account for the short half-life of nitric oxide in vitro. Superoxide dismutase (15-100 U/ml) substantially increased the apparent half-life of EDRF, strongly suggesting that superoxide contributes to the short biological half-life of nitric oxide. In the perfusion cascade bioassay system, the buffers are bubbled with 95% oxygen, contain 11 mM glucose as well as trace iron plus copper contamination and are incubated under the weak ultraviolet (UV) radiation of fluorescent lights. These are prime conditions for the autoxidation of glucose to form small amounts of superoxide in sufficient amounts to account for the short half-life of nitric oxide in nanomolar concentrations. The rate of reaction between superoxide and nitric oxide is 6.7 X 10 M sec L The shortest half-life of nitric oxide measured is approximately 6 sec. To achieve a half-life of 6 sec, the steady state concentration of superoxide would only need to be 17 pM, calculated as ln(2)/ (6 sec X 6.7 X 10 M" sec )-... 

Possibly, cellular thiols may be oxidized by the inactive adduct of nitric oxide and oxygen to regenerate a nitrosothiol or related species with EDRF activity. Some of the inconsistent results observed in bioassay systems may be due to the secondary and nonenzymatic formation of a nitrosothiols or other species capable of regenerating nitric oxide, which are leached into perfusion cascades. Consequently, bioassay systems should not be the gold standard to distinguish whether nitric oxide is the EDRF, because secondary reactions of nitric oxide decomposition products may regenerate nitric oxide. 

Inorganic cations, although probably isolated by ion exchange, should not be soluble in the dichloromethane extract of the aqueous eluents and should probably remain therein. The experiment with lead(II) nitrate, which yielded <0.2 of the spiked Pb ion, supported this expectation. Therefore, heavy metal toxicity to bioassay systems should not be a problem for testing organic residues. Conversely, when inclusion of inorganics in a test residue is desirable, other recovery techniques should be considered. 

Table 1. Bioassay Systems for Screening of Compounds with Antitumor-Promotion, Anti-Inflammatory and Anti-Allergic Activities Described in This Review...

Most of the semi-synthetic compounds listed were prepared from natural products by simple chemical modification. The bioassay systems in which the compounds exhibited inhibitory effects, together with the major sources of the compounds, are included in the Table. 

Table 2. Triterpenoids, and Sterols and Their Oxygenated Derivatives from Plants and Fungi and the Bioassay Systems in which the Compounds Exhibited Inhibitory Activities... 

Compound Code Source and Occurrence TPA° Bioassay System" Other Assays References... 

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