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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.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
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.
Alzheimer's disease affects only about 10% of people older than 65 years of age. Most forms of decreased mental function and dementia are caused by disuse (letting the mind get lazy).
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.