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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 the United States, there is a birth every 8 seconds, according to the U.S. Census Bureau's Population Clock.
HIV testing reach is still limited. An estimated 40% of people with HIV (more than 14 million) remain undiagnosed and do not know their infection status.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
Prostaglandins were first isolated from human semen in Sweden in the 1930s. They were so named because the researcher thought that they came from the prostate gland. In fact, prostaglandins exist and are synthesized in almost every cell of the body.