alpha

alpha

 [al´fah]

the first letter of the Greek alphabet, α; used to denote the first position in a classification system; as, in names of chemical compounds, to distinguish the first in a series of isomers, or to indicate the position of substituent atoms or groups; also used to distinguish types of radioactive decay, brain waves or rhythms, adrenergic receptors, and secretory cells that stain with acid dyes, such as the alpha cells of the pancreas.

alpha-adrenergic blocking agent (alpha-blocker) (alpha-blocking agent) any of a group of drugs that selectively inhibit the activity of alpha receptors in the sympathetic nervous system. As with beta-adrenergic blocking agents, alpha-blocking agents compete with the catecholamines at peripheral autonomic receptor sites. This group includes ergot and its derivatives, and phentolamine.

alpha chain disease the most common heavy chain disease, occurring predominantly in young adults in the Mediterranean area, and characterized by plasma cell infiltration of the lamina propria of the small intestine resulting in malabsorption with diarrhea, abdominal pain, and weight loss, or, exceedingly rarely, by pulmonary involvement. The gastrointestinal form is immunoproliferative small intestine disease.

alpha-fetoprotein (AFP) a plasma protein produced by the fetal liver, yolk sac, and gastrointestinal tract and also by hepatocellular carcinoma, germ cell neoplasms, and other cancers in adults; elevated levels may also be seen in benign liver disease such as cirrhosis and viral hepatitis. The serum AFP level is used to monitor the effectiveness of cancer treatment.

During pregnancy some AFP crosses from the amniotic fluid to the mother's blood. If the fetus has a neural tube defect, large amounts of AFP will be found in the amniotic fluid and maternal blood. Blood screening tests for serum AFP can thus be done as a first step in the screening process; if test results are positive, further testing is indicated to diagnose the defect.

alpha particles a type of emission produced by the disintegration of a radioactive substance. The atoms of radioactive elements such as uranium and radium are very unstable, continuously breaking apart with explosive violence and emitting particulate and nonparticulate types of radiation. The alpha particles, consisting of two protons and two neutrons, have an electrical charge and form streams of tremendous energy when they are released from the disintegrating atoms. These streams of energy (alpha rays) can be used in treatment of various malignancies. See also radiation and radiation therapy.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

α

1. First letter of the Greek alphabet, alpha (α), used as a classifier in the nomenclature of many sciences.

2. Symbol for Bunsen solubility coefficient.

3. In chemistry, denotes the first in a series, a position immediately adjacent to a carboxyl group, the first of a series of closely related compounds, an aromatic substituent on an aliphatic chain, or the direction of a chemical bond away from the viewer.

4. Abbreviation for alpha particle.

5. In chemistry, symbol for angle of optic rotation; degree of dissociation. For terms beginning with this prefix, see the specific term.

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[α]

Symbol for specific optic rotation.

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al·pha

(al'fă), The spelling alpha is used in chemical names, the spelling alfa in pharmaceutical names.

First letter of the Greek alphabet, α.

Farlex Partner Medical Dictionary © Farlex 2012

ALPHA

Abbreviation for:
Access to Learning for the Public Health Agenda (Medspeak-UK)
Agenda for Leadership in Programs for Healthcare Accreditation (obsolete)
Antenatal Psychosocial Health Assessment

Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

α

Abbreviation for alpha.

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al·pha

(α) (al'fă)

1. First letter of the Greek alphabet; used as a classifier in the nomenclature of many sciences.

2. Bunsen solubility coefficient

3. chemistry Denotes the first in a series, a position immediately adjacent to a carboxyl group, the first of a series of closely related compounds, an aromatic substituent on an aliphatic chain, or the direction of a chemical bond away from the viewer.

4. Alpha (α) particle.

5. chemistry Symbol for angle of optic rotation; degree of dissociation.

Medical Dictionary for the Health Professions and Nursing © Farlex 2012