Effect of an unknown toxin isolated from Dinophysis sp.-contaminated French mussels, on the electrical and mechanical activity of frog heart.

The effects of an unknown toxin, isolated along with okadaic acid from the hepatopancreas of French mussels contaminated by Dinophysis sp., producing ataxia, neurologic symptoms, bradycardia, arrhythmias, electrocardiographic changes, and cardiac arrest, have been studied in terms of the electrical and mechanical activity of frog atrial heart muscle. The toxin, in a dose-dependent manner, decreased the amplitude of the stimulated peak tension of isolated fibers.

Cooked mussels contaminated by Dinophysis sp.: a source of okadaic acid.

A method was developed for fractionation and isolation of toxic components present in extracts prepared from Dinophysis-contaminated mussels. The major toxin present in French mussels was identified as okadaic acid by its chromatographic properties and spectral data. Large amounts of mussel tissue (digestive glands and remaining meat) can be treated easily if they are cooked, or cooked and dried and are useful for isolating significant amounts of okadaic acid.

The use of Daphnia magna for detection of okadaic acid in mussel extracts.

Okadaic acid (OA), the main toxin responsible for diarrheic shellfish poisoning (DSP) has toxicity for Daphnia magna (EC50 = 15 +/- 1.8 micrograms/l). A Daphnia bioassay was developed and used to analyse okadaic acid in mussel extracts.