Bioassays detection

Bioassay detection limit Mouse bioassay 20 pg SIX eq/100 g Mouse bioassay 20 pg STX eq/lOOg Neuroblastoma assay 2 pg STX eq/ 100 g Mouse bioassay 20 pg STX eq/100 g Protein-phosphatase inhibition assay 20 pg STX eq/100 g Unknown Unknown Neuroblastoma assay 10 ng/mL... 

Table II. Comparison of HPLC and Mouse Bioassay Detection Limits...

Bioassay Detected effects Endpoint Levels Of indication Known active toxic compounds Performance characteristics (sensitivity detection limit variability reproducibility) Confounding factors Percentage false positive data... 

The observations that cytokinins have activity in the tobacco bioassay detectable at concentrations as low as 10 H M, and that the promotion of such activity can depend on structural parameters... 

In the early 1990s, routine bioassays detected the presence of a fast-acting toxin in extracts of shellfish from sites along the southeastern coast of Nova Scotia, Canada [11]. Two new toxins of the cyclic imine group, named spirolide B and spirolide D, were isolated from the viscera of scallops (Placopecten magellanicus) and mussels (M. edulis) and their structures determined [12]. Subsequently, spirolides A, C, E, and F were described, along with 13-desmethyl spirolide C [13,14]. 

M. W. F. Nielen, T. F. H. Bovee, et al.. Urine testing for designer steroids by liquid chromatography with androgen bioassay detection and electrospray quadrupole time-of-flight mass spectrometry identification. Anal. Chem. 78, 424-431 (2006). 

It is obvious from the provisional risk assessment values for microcystins, and, being of the same order of magnitude of mammalian toxicity, similar values may be calculated for the cyanobacterial neurotoxins, that sensitive detection methods are required to detect these low concentrations of toxins. Of the biological methods of detection discussed earlier, the mouse and invertebrate bioassays are not sensitive enough without concentration of water samples, in that they are only able to detect mg of microcystins per litre. Only the immunoassays (ng-/rg 1 and the protein phosphatase inhibition assays (ng O... 

Not all cyanobacterial blooms and scums contain detectable levels of toxins. Indeed, the incidence of toxicity detection by mouse bioassay, and toxin detection by HPLC among environmental samples, ranges from about 40% to However, in view of this high occurrence, it is the policy of regulatory authorities and water supply operators in some countries to assume that blooms of cyanobacteria are toxic until tested and found to be otherwise. In the absence of available analytical facilities or expertise or for logistical reasons, this precautionary principle should be regarded as sensible and prudent. 

Bioassays can be used for cost-effective biomonitoring and rapid screening of environmental samples to detect the presence of mixtures of toxic chemicals and to identify hot spots. 

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. 

Some Chemical Considerations Relevant to the Mouse Bioassay. Net toxicity, determined by mouse bioassay, has served as a traditional measure of toxin quantity and, despite the development of HPLC and other detection methods for the saxi-toxins, continues to be used. In this assay, as in most others, the molar specific potencies of the various saxitoxins differ, thus, net toxicity of a toxin sample with an undefined mixture of the saxitoxins can provide only a rough approximation of the net molar concentration. Still, to the extent that limits can be placed on variation in toxin composition, the mouse assay can in principle provide useful data on trends in net toxin concentration. However, the somewhat protean chemistry of the saxitoxins makes it difficult to define conditions under which the composition of a mixture of toxins will remain constant thus, attaining a reproducible level of mouse bioassay toxicity is difficult. It is therefore useful to review briefly some of the chemical factors that should be considered when employing the mouse bioassay for the saxitoxins or when interpreting results. Similar concepts will apply to other assays. 

Mouse Bioassay. The mouse is the traditional animal of choice for detecting biological activity due to STX and TTX. Mice receive an intraperitoneal injection of sample and are observed for symptoms of intoxication, i.e., dypsnea, convulsions, and death. This method is effective for detecting biological activity of STX and TTX in numerous samples. For the standard STX assay, one mouse unit is defined as that quantity of STX injected i.p. in 1 ml solution that will... 

It is emphasized that some investigations show that bacterial cultures contain TTX-like substances which are not detected by mouse bioassay and are "difficult to detect" by HPLC and GC-MS analyses. Structural analyses of these substances with other techniques was not reported. 

Experimental evidence indicates that many marine bacteria produce TTXs. However, TTX production by some bacteria has not been validated since TTX and anhydro-like TTX are described as "difficult to detect" by using HPLC and GC-MS methods, and show no activity in the mouse bioassay. 

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