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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.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
In the United States, there is a birth every 8 seconds, according to the U.S. Census Bureau's Population Clock.
During the twentieth century, a variant of the metric system was used in Russia and France in which the base unit of mass was the tonne. Instead of kilograms, this system used millitonnes (mt).