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More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
In 1886, William Bates reported on the discovery of a substance produced by the adrenal gland that turned out to be epinephrine (adrenaline). In 1904, this drug was first artificially synthesized by Friedrich Stolz.
IgA antibodies protect body surfaces exposed to outside foreign substances. IgG antibodies are found in all body fluids. IgM antibodies are the first type of antibody made in response to an infection. IgE antibody levels are often high in people with allergies. IgD antibodies are found in tissues lining the abdomen and chest.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
There are approximately 3 million unintended pregnancies in the United States each year.