Bioassays measure the effects of a substance on living things, often used to predict human reactions. In vitro tests use living matter, while in vivo tests use the whole organism. Animal rights activists criticize biotests, but they are necessary when developing new drugs or dealing with toxins. In France, in vivo tests on oysters were stopped in 2010 due to objections from oyster fishermen.
A bioassay, short form of bioassay, is a type of test in which scientists measure the effects a substance has on living things. Sometimes, they try to predict what a substance will do to humans by observing other creatures’ reactions to it. In other cases, the reaction of a certain organism or cell type is used to identify an unknown substance. Biotests are often criticized by animal rights activists and manufacturers of the products they test, who say they sometimes give skewed results.
There are two main reasons for using a biological approach rather than an inorganic test. First, when developing a new drug or dealing with the effects of toxins that have not been studied before, it is difficult to approximate the effects the substance will have on living creatures without testing it on living creatures. Inorganic tests can tell scientists what molecules are in a substance, but life forms and the cells of living creatures react in unpredictable ways. The different components of a substance can interact with each other, for example, so the most relevant outcome when predicting the effect something will have on a person is the effect it had on another being, rather than what its individual components we are.
The second reason is that inorganic tests may not be available. Sometimes, a substance causes a reaction, but scientists are unable to identify the precise compound that caused it. In these cases, it is often impossible to develop an inorganic test because scientists do not know which molecule they are testing for. A scientist may think a plant is toxic, for example, but has no way of knowing which toxin might be active. Then, he could run a biological test to see if ingesting the plant is toxic to a rat.
A bioassay is any test in which scientists apply a substance to living material and quantify the results. There are two categories of these tests. In vitro tests use living matter, such as cells. In vivo tests use the whole organism.
Scientists often use in vitro bioassays to check for the presence of certain toxins. A common in vitro bioassay is the Limulus test, named for the horseshoe crab genus. Scientists mix a test culture with horseshoe crab blood cells. They clot in the presence of endotoxins, which are poisons found within some gram-negative bacteria that are released when bacterial cells break down. This test can help scientists identify the bacteria they are dealing with.
In vivo tests are often used for predictive testing, and the most commonly used animal in biological testing is the mouse. For example, scientists can inject drugs into pregnant mice to see if those particular drugs pass from the mother to the fetus. They can then make recommendations for pregnant women to take the drug.
In France, in vivo tests have been used each season to test for toxins in oysters. The mice were injected with oyster juice and the product could not be shipped if two-thirds of the mice died within a day. Oyster fishermen objected on the grounds that rats often died of other causes, condemning safe products. France acknowledged its objections by announcing the end of the practice in January 2010. This does mean, however, that future oyster tests will be limited to a certain number of toxins, at thresholds scientists believe can cause disease.
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