Toxicity assay

Figure 9. Observed increases in mouse assay toxicity of test mixtures of shellfish meat and toxin Cl (4), hydrolyzed with varying concentrations of HCI acid. Two series of experiments are shown. The initial concentration of toxin Cl was uniform for all samples in a series. Toxicity is expressed on the vertical axis as percentage of the maximum toxicity attained for that series.

See also Ames Test Analytical Toxicology Aneuploidy Carcinogen-DNA Adduct Formation and DNA Repair Chromosome Aberrations Developmental Toxicology Dominant Lethal Tests Host-Mediated Assay Molecular Toxicology - Recombinant DNA Technology Mouse Lymphoma Assay Toxicity Testing, Mutagenicity. 

See also Ames Test Analytical Toxicology Animal Models Dominant Lethal Tests Dose-Response Relationship Host-Mediated Assay In Vitro Test In Vivo Test Mouse Lymphoma Assay Toxicity, Acute Toxicity, Chronic Toxicity Testing, Irritation Toxicity Testing, Modeling Toxicity, Subchronic Toxicity Testing, Validation. 

Daphnia is commonly maintained in laboratories for assaying toxic substances in water. Water fleas are often of great importance in the diets of fishes, especially young fishes, and predaceous insects, such as many of the Diptera larvae. 

Toxicity. Initial assessment of the toxicity of these aryl dye molecules using a modification of the agar disk diffusion antibiotic sensitivity was inconclusive because of the limited diffusion of the compound and its intense binding to the cellulose disks. Liquid cultures supplemented with 1 mg of aryl dye dissolved in 1 ml of DMF were used to assay toxicity. Comparison of the growth of Candida lipolvtica (GSU 37-1) and Candida maltosa (GSU R-42) was made by observing the optical density at 595 nm in a Turner spectrophotometer model 380. Determination of the absorption by compound was made for uninoculated GYNB. The increase in absorbance in cultures with and without analogue was compared. 

Manufacture, Shipment, and Analysis. In the United States, sodium and potassium thiocyanates are made by adding caustic soda or potash to ammonium thiocyanate, followed by evaporation of the ammonia and water. The products are sold either as 50—55 wt % aqueous solutions, in the case of sodium thiocyanate, or as the crystalline soHds with one grade containing 5 wt % water and a higher assay grade containing a maximum of 2 wt % water. In Europe, the thiocyanates may be made by direct sulfurization of the corresponding cyanide. The acute LD q (rat, oral) of sodium thiocyanate is 764 mg/kg, accompanied by convulsions and respiratory failure LD q (mouse, oral) is 362 mg/kg. The lowest pubhshed toxic dose for potassium thiocyanate is 80—428 mg/kg, with hallucinations, convulsions, or muscular weakness. The acute LD q (rat, oral) for potassium thiocyanate is 854 mg/kg, with convulsions and respiratory failure. 

Mycotoxins, toxic metaboUtes of some fungi, can be assayed by immunochemical techniques to determine concentration in animal feed and foodstuffs. Some of the analytes assayed in kits and the detection limits are Hsted in Table 4 (45). These assays are especially advantageous for routine analysis of large samples of foodstuffs (45,46). 

Physicochemical properties requked include melting/boiling point, vapor pressure, solubiUty, and flammabiUty/explosion characteristics. The toxicological studies include acute toxicity tests, oral, inhalation, and dermal skin and eye kritation skin sensiti2ation subacute toxicity, oral, inhalation, and dermal and mutagenicity tests. In vitro reverse mutation assay (Ames test) on Salmonella typhimurium and/or E.scherichia coli and mammalian cytogenic test. In vivo mouse micronucleus test. 

The brine shrimp (Anemia salina) has been evaluated as an alternative to the mouse bioassay for use in cyanobacterial toxicity screening assays." " " As in the... 

Daphnia assay, the brine shrimps are exposed to different concentrations of toxicant, and the toxicity is expressed as the LCjo value. Extracts of cyanobacterial blooms and laboratory cultures, containing microcystins or anatoxin-a, have been found to be toxic towards brine shrimp," and fractionation of such extracts resulted in brine shrimp fatalities only with fractions containing microcystins." " ... 

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,... 

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. 

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... 

Each interferon preparation was ultracentrifuged at 20,000 revolutions per minute for one hour to remove tissue debris and inactivated virus. The supernatant was dialyzed against distilled water (1 400) for 24 hours at4°C. The material was then freeze-dried. The dried product was reconstituted in one-tenth of the original volume in distilled water and dispensed into ampoules. Reconstituted solutions were assayed for interferon activity, examined for toxicity, and tested for sterility. 

---