If the toxin is not present, nothing happens. It can't be much fun for the mice, hence the interest in developing assays that do not require the unfortunate test rodents. The two-year project, financed by the Marine Institute, has just got under way with two postgraduate researchers and the collaboration of Dr Marion Boland of Trinity College. The group is concentrating on two tests, one giving a rapid response if the toxin is present, and a more comprehensive test which uses animal cells in vitro to measure toxin levels. It involves laying down a substrate on to which the enzyme, phosphatase, can be fixed.
Samples are first mixed with a test solution and then applied to the enzyme dipstick.
The phosphatase reacts with the solution, changing colour if no toxin is present, but this reaction is blocked if okadaic acid is in the sample. Testing for levels of toxin using cultured cell lines is a much more complex process. The toxin will change or kill off cells and these morphological changes can be detected using a microscope. However, another system under study repeats the process of mixing a sample with a test solution that is then put in contact with the cells. The goal would be to establish a scale of expected change in growth, physiology or cell death rate based on the level of toxin present.