ecture. For example, very thin slices of liver and kidney can be used to study possible effects of drugs on these organs. This type can also be very economical because human tissue obtained after surgery can be used in tissue culture. However, these cultures have a limited lifespan and a high level of technical skill is needed to set up and maintain them. The latest breakthrough has come with the development of three-dimensional tissue equivalents, which essentially mimic the real tissue. These equivalents are made by culturing tissues on an artificial support matrix. A lot of human skin equivalents have been developed and work is in progress on tissue equivalents for other organs. One alternative, Testskin, is actual human skin grown in a sterile plastic bag. This test is used to measure irritancy, and is being used by Avon, Amway, and Estee Lauder. Epipack, which also uses cloned human tissue, is designed to work much like the Testskin. Finally, the Neutral Red Bioassay test, which is a test performed on cultured human cells, is used to compute the absorption of water-soluble dyes. This can help determine the relative toxicity of the dye (9).Organ cultures have an advantage in that they allow all of the interactions that take place in the organ. These in vitro procedures are used in a lot of pharmacology studies. The disadvantage, once again, is that they are hard to maintain and are short-lived. Organ cultures also involve killing an animal for an organ, and only one organ can be taken from each of the animals, with the exception of the kidneys.One in vitro procedure, Corrositex, was developed as an alternative to the rabbit skin test. The test assesses chemical corrosivity using a protein membrane designed to function like the skin. When exposed to a potentially corrosive substance, the biomembrane becomes colored. Results to a Corrositex test are available in as little as three minutes and no longer than four hours...
