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Multiple experimental evidences have confirmed that at the molecular level, cancer is caused by lesions in cellular DNA.
Nearly 31 million adults in America have a total cholesterol level that is more than 240 mg per dL.
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.
Acute bronchitis is an inflammation of the breathing tubes (bronchi), which causes increased mucus production and other changes. It is usually caused by bacteria or viruses, can be serious in people who have pulmonary or cardiac diseases, and can lead to pneumonia.
Intradermal injections are somewhat difficult to correctly administer because the skin layers are so thin that it is easy to accidentally punch through to the deeper subcutaneous layer.