Alopecia, traumatic
Alopecia, traumatic: Hair loss caused by injury to the scalp. Common causes include the use of caustic hair straighteners, especially those that include lye as an ingredient; stress traction injury from tight rollers and braiding; overheating of the hair shafts; and compulsive pulling out of hair (trichotillomania).
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- Alpha blocker
Alpha blocker: A drug that blocks receptors in arteries and smooth muscle. This action relaxes the blood vessels and leads to an increase in blood flow and a lower pressure for the control of hypertension. The action in the urinary tract enhances urinary flow in prostatic hypertrophy (enlarged prostate). The alpha blockers include doxazosin (Cardura), […]
- Alpers disease
Alpers disease: A progressive disease of the nervous system characterized by spasticity (tightness), myoclonus and dementia and by liver problems with jaundice and cirrhosis. This disorder, first described by Alpers in 1931 as “Diffuse progressive degeneration of gray matter of cerebrum”, usually begins early in life with convulsions. A continuous seizure (status epilepticus) is often […]
- Alpha cell, pancreatic
Alpha cell, pancreatic: A type of cell found in areas within the pancreas called the islets of Langerhans. Alpha cells make and release glucagon, which raises the level of glucose (sugar) in the blood.
- Alpha error
Alpha error: The statistical error made in testing a hypothesis when it is concluded that a result is positive, but it really is not. Also known as false positive.
- Alpha helix
Alpha helix: The coiled structure of many proteins consisting of a single chain of amino acids stabilized by hydrogen bonds. The alpha helix was first proposed by Linus Pauling and Robert Corey in a brilliant series of paper in the early 1950s. It is also known as the Pauling-Corey helix. See also: Pauling, Linus.