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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.
Multiple experimental evidences have confirmed that at the molecular level, cancer is caused by lesions in cellular DNA.
Urine turns bright yellow if larger than normal amounts of certain substances are consumed; one of these substances is asparagus.
Common abbreviations that cause medication errors include U (unit), mg (milligram), QD (every day), SC (subcutaneous), TIW (three times per week), D/C (discharge or discontinue), HS (at bedtime or "hours of sleep"), cc (cubic centimeters), and AU (each ear).
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.