Areola: 1. The small darkened area around the nipple of the breast. 2. The colored part of the iris around the pupil of the eye. 3. Any small space in a tissue.
Arenavirus: One of a family of viruses called Arenaviridae whose members are generally associated with diseases transmitted by rodents to humans. Each arenavirus is usually associated with a particular rodent host species in which it is maintained. Arenavirus infections are relatively common in humans in some areas of the world and can cause severe illnesses. […]
Argentaffinoma: A tumor which secretes large amounts of the hormone serotonin. Argentaffinoma is also called carcinoid tumor. The tumor usually arises in the gastrointestinal tract, anywhere between the stomach and the rectum (the favorite spot is in the appendix) and from there may metastasize (spread) to the liver. In the liver the tumor produces and […]
Arginine: An essential amino acid and a key component of protein. Lack of arginine in the diet impairs growth, and in adult males it decreases the sperm count. Arginine is available in turkey, chicken, and other meats, and as L-arginine in supplements. Babies born without the enzyme phosphate synthetase have arginine deficiency syndrome; adding arginine […]
- Argon laser
Argon laser: A laser with ionized argon as the active medium. Argon lasers are used for photocoagulation in ophthalmology.
Argyria: Silver poisoning, resulting in ashen, gray, discolored skin, and damage to other tissues of the body. Caused by long-term use of silver salts or other preparations containing silver.