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For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
Each year in the United States, there are approximately six million pregnancies. This means that at any one time, about 4% of women in the United States are pregnant.
In 2012, nearly 24 milliion Americans, aged 12 and older, had abused an illicit drug, according to the National Institute on Drug Abuse (NIDA).
Warfarin was developed as a consequence of the study of a strange bleeding disorder that suddenly occurred in cattle on the northern prairies of the United States in the early 1900s.
Amoebae are the simplest type of protozoans, and are characterized by a feeding and dividing trophozoite stage that moves by temporary extensions called pseudopodia or false feet.