Toxicity, chemical assay

Of the various chemical assays that have been developed for the saxitoxins (75,76), that described by Bates and Rapoport, based on the oxidation of saxitoxin to a fluorescent derivative, has proved to be the most useful. Other assay methods have been developed from it (77-79). The Bates and Rapoport method is virtually insensitive to the N-l-hydroxyl saxitoxins as originally described and so, like the presently available immunoassays, fails as a general assay for either concentration or toxicity. However, it is quite sensitive for those toxins it does detect and has been the basis for other useful methods. 

Standardized procedures were adopted with regard to sample preparation, recovery of toxicant, and chemical assay. In order to determine the nature and magnitude of penetrated residues, it was necessary to disassociate all extra-surface residues. The techniques originally developed to effect this separation and which were used in most of the DDT penetration studies have been described by Gunther 11). Certain modifications which have been developed subsequently in connection with the parathion studies are described in detail below since this phase of penetration studies assumes singular importance (see also 14). 

The assay microorganisms in Polytox are a blend of bacterial strains originally isolated from wastewater [48]. The Polytox kit (Microbiotest Inc., Nazareth, Belgium), specifically designed to assess the effect of toxic chemicals on biological waste treatment, is based on the reduction of respiratory activity of rehydrated cultures in the presence of toxicants. The commercially available kit is specihcally designed for testing wastewaters. Quantative results can be obtained in just 30 minutes. 

As mentioned above we obtained most of the poison for our chemical and biological work from the Alaska butter clam. However our search for a dinoflagellate or any other poisonous organism in the water as a source of the poison in the clams was never definitely accomplished. In 1948, and in some years following, along with a survey for toxic butter clams in Southeastern Alaska by the staff at the Fishery Products Research Laboratory at Ketchikan, 1 collected plankton in areas where the clams were found to be toxic. Mouse assays of the plankton showed no toxicity. Microscopic examination of the water in these areas showed heavy growth of microscopic plankton but little or no evidence of... 

Preference is obviously for a simple chemical assay for PSP. Unfortunately the more specific the chemical test, the narrower is the window of compounds it can assay. The Paralytic Shellfish Poison is not just Saxitoxin (STX) as originally believed, but is a mixture of compounds closely related to STX Q) and the mix varies widely with location and with time ( ). It would seem, therefore that a chemical assay should determine at least the ratios of the several compounds, and that the relative toxicity of each of the compounds must be known. An effective assay must evaluate the actual biological toxicity of the shellfish being tested. For the chemical assay this requires the summated toxicity of all the... 

HPLC instrumentation and column technology have undergone major advances since the early 1970s, when HPLC made its debut in the field of vitamin analysis. Yet sample preparation in food analysis continues to rely largely on manual wet-chemical techniques, which are time consuming and labor intensive, require considerable analytical skill, and constitute the major source of error in the assay procedure. There is also the serious problem of environmental pollution and the exposure of laboratory personnel to toxic chemicals. 

Analytical toxicology is a branch of analytical chemistry concerned with the identification and assay of toxic chemicals and their metabolites in biological and environmental materials. 

Botsford, J.L. (1998) A simple assay for toxic chemicals using a bacterial indicator, World Journal of Microbiology and Biotechnology 14 (3), 369-376. 

Bioassays appeared to fit the bill to perform this service to monitor chemical contamination. They have been around for a while. Until relatively recently, however, they remained in the realm of the laboratory. Only over the last two decades have they found a niche in testing for toxic chemicals in water and sediment, but not yet specifically as a tool for routine water quality monitoring. As Small-scale Freshwater Toxicity Investigations, Volumes 1 and 2 amply demonstrates, the science has now come of age. Assays based on bacteria, microscopic or multi-cellular algae, protozoa, invertebrates and vertebrates (freshwater fish cell cultures) are discussed in... 

Another important contributor to the development of toxicology was the Spanish physician Orfila (1787-1853). He was one of the first scientists to make systematic use of test animals and autopsy material. Orfila was the first to treat toxicology as a separate scientific subject and was also responsible for the development of numerous chemical assays for detecting the presence of poisons, thus providing an early foundation for forensic toxicology. In 1815 Orfila published the first major work dealing with the toxicity of natural agents. 

Frequently, the first sign of hepatotoxicity is breakdown of the outer cell plasma membrane. If the cell membrane is full of holes , it allows the internal contents of the hepatocyte to leak out into the culture medium. By taking an ahquot of the cell culture supernatant following exposure to a toxic chemical and incubating the sample with a reagent that recognizes LDH, the amount of LDH that leaks out of the damaged cell can be determined. This assay is based on a coupled enzymatic assay that results in the conversion of resazurin into the fluorescent compound, resorufm. 

The TBA method has been used not only to assay glycosylated hemoglobin, but also almost exclusively for the following glycosylated proteins plasma albumin (D22, El, NIO, M12), plasma proteins and albumin (K6), capillary whole-blood protein collected on filter paper (L14), erythrocyte spectrin (M13), skin collagen (P2), lens basement membrane (M5), and crystallins (M28). In assays on hair and epidermal keratin, cyclohexanone extraction of the color developed with TBA and reading the absorbance of the cyclohexanone layer at 433 nm has provided increased sensitivity and accuracy (T4). A possible objection to the procedure is the use of oxalic and thiobarbituric acids, which are potentially toxic chemicals. 

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