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A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
In 1835 it was discovered that a disease of silkworms known as muscardine could be transferred from one silkworm to another, and was caused by a fungus.
Normal urine is sterile. It contains fluids, salts, and waste products. It is free of bacteria, viruses, and fungi.
Interferon was scarce and expensive until 1980, when the interferon gene was inserted into bacteria using recombinant DNA technology, allowing for mass cultivation and purification from bacterial cultures.