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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
There are major differences in the metabolism of morphine and the illegal drug heroin. Morphine mostly produces its CNS effects through m-receptors, and at k- and d-receptors. Heroin has a slight affinity for opiate receptors. Most of its actions are due to metabolism to active metabolites (6-acetylmorphine, morphine, and morphine-6-glucuronide).
In 1864, the first barbiturate (barbituric acid) was synthesized.
Malaria was not eliminated in the United States until 1951. The term eliminated means that no new cases arise in a country for 3 years.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.