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After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
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.
On average, the stomach produces 2 L of hydrochloric acid per day.
Bacteria have been found alive in a lake buried one half mile under ice in Antarctica.
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).