Toxins cyanobacterial

Detection, Analysis and Risk Assessment of Cyanobacterial Toxins... 

The detection and analysis, including quantification, of cyanobacterial toxins are essential for monitoring their occurrence in natural and controlled waters used for agricultural purposes, potable supplies, recreation and aquaculture. Risk assessment of the cyanobacterial toxins for the protection of human and animal health, and fundamental research, are also dependent on efficient methods of detection and analysis. In this article we discuss the methods developed and used to detect and analyse cyanobacterial toxins in bloom and scum material, water and animal/clinical specimens, and the progress being made in the risk assessment of the toxins. 

The detection and quantification of cyanobacterial toxins quoted in the above examples required methods which have been undergoing rapid development in recent years, and as the need for greater understanding of the properties and occurrence of the toxins continues to grow, these are continuing to be developed. This has resulted in methods of cyanobacterial toxin detection which are more sensitive, quantitative, reliable, specific and humane. Many of these methods are presented and discussed in the proceedings of a recent conference. 

Methods for the detection and analysis of cyanobacterial toxins fall into two... 

In vitro cytotoxicity assays using isolated cells have been applied intermittently to cyanobacterial toxicity testing over several years." Cells investigated for suitability in cyanobacterial toxin assays include primary liver cells (hepatocytes) isolated from rodents and fish, established permanent mammalian cell lines, including hepatocytes, fibroblasts and cancerous cells, and erythrocytes. Earlier work suggested that extracts from toxic cyanobacteria disrupted cells of established lines and erythrocytes," but studies with purified microcystins revealed no alterations in structure or ion transport in fibroblasts or erythrocytes,... 

An enzymatic assay can also be used for detecting anatoxin-a(s). " This toxin inhibits acetylcholinesterase, which can be measured by a colorimetric reaction, i.e. reaction of the acetyl group, liberated enzymatically from acetylcholine, with dithiobisnitrobenzoic acid. The assay is performed in microtitre plates, and the presence of toxin detected by a reduction in absorbance at 410 nm when read in a plate reader in kinetic mode over a 5 minute period. The assay is not specific for anatoxin-a(s) since it responds to other acetylcholinesterase inhibitors, e.g. organophosphoriis pesticides, and would need to be followed by confirmatory tests for the cyanobacterial toxin. 

C. Edwards, L.A. Lawton and G. A. Codd, in Detection Methods for Cyanobacterial Toxins, ed. 

After screening for toxicity, identification and/or quantification assays may need to be carried out if the screening method is not specific for the cyanobacterial toxin(s) under investigation. Suitable assays for these purposes include the physicochemical assays, HPLC, MS, and CE, and to some extent the immunoassays and protein phosphatase inhibition assays summarized in Section 2. 

The ability to identify and quantify cyanobacterial toxins in animal and human clinical material following (suspected) intoxications or illnesses associated with contact with toxic cyanobacteria is an increasing requirement. The recoveries of anatoxin-a from animal stomach material and of microcystins from sheep rumen contents are relatively straightforward. However, the recovery of microcystin from liver and tissue samples cannot be expected to be complete without the application of proteolytic digestion and extraction procedures. This is likely because microcystins bind covalently to a cysteine residue in protein phosphatase. Unless an effective procedure is applied for the extraction of covalently bound microcystins (and nodiilarins), then a negative result in analysis cannot be taken to indicate the absence of toxins in clinical specimens. Furthermore, any positive result may be an underestimate of the true amount of microcystin in the material and would only represent free toxin, not bound to the protein phosphatases. Optimized procedures for the extraction of bound microcystins and nodiilarins from organ and tissue samples are needed. 

In order to counter the hazards presented to health by cyanobacterial toxins, management actions concerning potable and recreational waters are required. These actions include risk assessment and monitoring programmes which rely on sensitive, accurate toxin analysis methods. 

Table 1 Characteristics of biological assays for cyanobacterial toxins...

Specificity of the assay depends on the specificity (cross-reactivity) of the antibodies. Of the known cyanobacterial toxins, only hepatotoxins are detected and are, therefore, able to be screened for by protein phosphatase inhibition. 

In reality, the demands upon most freshwaters, whether from human potable supply, animal watering, aquaculture, recreation, or amenity are increasing, and a need exists to monitor the types, location and levels of cyanobacterial toxins. 

The final article, by S. G. Bell and G. A. Codd of the University of Dundee Department of Biological Services, is concerned with detection, analysis, and risk assessment of cyanobacterial toxins. These can be responsible for animal, fish, and bird deaths and for ill-health in humans. The occurrence of toxic cyanobacterial blooms and scums on nutrient-rich waters is a world-wide phenomenon and cases are cited from Australia, the USA, and China, as well as throughout Europe. The causes, indentification and assessment of risk, and establishment of criteria for controlling risk are discussed. 

G. A. Codd, Cyanobacterial toxins occuixance, properties and biological significance . WaterSci. Technol. 32 149-156(1995). 

R. W. MacKintosh, K. N. Dalby, D. G. Campbell, P. T. W. Cohen, P. Cohen and C. MacKintosh, The cyanobacterial toxin microcystin binds covalently to cysteine-273 on protein phosphatase 1 , FEBS Lett. 371 236-240 (1995). 

Algal and cyanobacterial toxins Brominated flame retardants Disinfection by-products Gasoline additives... 

There are two major classes of freshwater cyanobacterial toxins, broadly categorized according to their physiological effects on vertebrates hepatotoxins and neurotoxins. Although these hydrophilic toxins are highly soluble, they are typically released only upon cell lysis following mechanical damage or cell senescence (Sivonen and Jones 1999). 

Carmichael WW, Azevedo SFMO, An JS, Molica RJR, Jochimsen EM, Lau S, Rinehart KL, Shaw GR, Eaglesham GK (2001) Human fatalities from cyanobacteria chemical and biological evidence for cyanotoxins. Environ Health Persp 109 663-668 Codd GA, Bell SG, Kaya K, Ward CJ, Beattie KA, Metcalf JS (1999) Cyanobacterial toxins, exposure routes and human health. Eur J Phycol 34 405 115 Cronin G, Hay M (1996) Induction of seaweed chemical defenses by amphipod grazing. Ecology 77 2287-2301... 

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