The level of a protein that actually affects prions is the secondary structure. There are two forms of prions, a normal cellular prion, and an infectious form. The prion is encoded by a single gene on the 20th human chromosome. The normal prion is converted by an unknown sequence of events in which the coiled structure is refolded into a beta-sheet. In the infectious form, the prion is insoluble and the plaques are surrounded by spongy holes causing spongiform encephalopathy. The prions induce death in the host without any signs of immune response to the infectious agent.
Prions cause mad cow disease, which then causes Creutzfeldt-Jacob disease, and believed to be connected to Alzheimer’s disease. After some analyses of autopsies of these diseases, a great similarity was found in brain malformations. The diseases caused by prions have first been documented in animals. Among the animals, the sheep were the first to have brain malformations that look like sponges. Scrapie was the first known prion disease. Signs for the diseases are loss of appetite, seizures, paralysis, blindness, and then eventually death.
Bovine spongiform encephalopathy was then seen in cows in 1984. It was described as the new scrapie-like syndrome. The disease was thought to be transferred by ingestion of sheep by-products from sheep that had scrapie. There are other forms found in mink, elk, and deer. Meat products from infected animals contained bits if offal before being banned, which was put into pharmaceuticals, supplements, and cosmetics. One way to become infected is to ingest food, or one of these products contaminated with the insoluble prions. The second way to get this form of the prion is from a tainted pituitary gland of an affected cadaver. Mad Cow disease is obviously very serious and always fatal.
Bibliography
Alpher, Jennifer. Forwood, Nellie. Frock, Kristen. Mad Cow disease, and new variant _ Creutzfeldt-Jacob disease: pharmaceutical excipients from bovine sources may be tainted _ with Transmissible Spongiform Encephalopathy. Alternate sources for these excipients must be found. Advanstar Communications, Inc. 2006