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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
The liver is the only organ that has the ability to regenerate itself after certain types of damage. As much as 25% of the liver can be removed, and it will still regenerate back to its original shape and size. However, the liver cannot regenerate after severe damage caused by alcohol.
Interferon was scarce and expensive until 1980, when the interferon gene was inserted into bacteria using recombinant DNA technology, allowing for mass cultivation and purification from bacterial cultures.
The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.
The strongest synthetic topical retinoid drug available, tazarotene, is used to treat sun-damaged skin, acne, and psoriasis.