melanin

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melanin

 [mel´ah-nin]
any of several closely related dark, sulfur-containing pigments normally found in the hair, skin, ciliary body, choroid of the eye, pigment layer of the retina, and certain nerve cells. They occur abnormally in the tumors known as melanomas and may be excreted in the urine when such tumors are present (melanuria).
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

mel·a·nin

(mel'ă-nin),
Any of the dark brown to black polymers of indole-5,6-quinone and/or 5,6-dihydroxyindole 2-carboxylic acid that normally occur in the skin, hair, pigmented coat of the retina, and inconstantly in the medulla and zona reticularis of the adrenal gland. Melanin may be formed in vitro or biologically by oxidation of l-tyrosine or l-tryptophan, the usual mechanism being the enzymatic oxidation of l-tyrosine to 3,4-dihydroxy-l-phenylalanine (dopa) and dopaquinone by monophenol monooxygenase, and the further oxidation (probably spontaneous) of this intermediate to melanin. Compare: eumelanin, pheomelanin.
Synonym(s): melanotic pigment
[G. melas (melan-), black]
Farlex Partner Medical Dictionary © Farlex 2012

melanin

(mĕl′ə-nĭn)
n.
Any of a group of naturally occurring dark pigments, especially the pigment found in skin, hair, fur, and feathers.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

melanin

A dark natural pigment found in the epidermis or skin adnexal structures. It is a complex polymer of oxidised tyrosine synthesised from DOPA and dopaquinone in response to actinic stimulation and bound to a carrier protein by melanocytes—in the skin, mucous membrane, pia arachnoid, retina, inner ear and mesentery. Melanin is detected in tissue sections by the Fontana-Masson stain.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

melanin

 Physiology A dark natural body pigment found in the epidermis or skin adnexal structures. See Albinism, DOPA, Melanoma.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

mel·a·nin

(mel'ă-nin)
Any of the dark brown to black pigments that occur in the skin, hair, pigmented coat of the retina, and medulla and zona reticularis of the suprarenal gland.
[G. melas (melan-), black]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

melanin

The body's natural colouring (pigment) found in the skin, hair, eyes, inner ears and other parts. In body cells, melanin is bound to protein. It is a complex POLYMER formed from the amino acid TYROSINE (4-hydroxphenylalanine) by oxidation via dopa and dopaquinone.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

melanin

a dark brown or black pigment found in skin or hair and in the iris and choroid layer of the EYE. Melanin is found in special cells called MELANOPHORES. See ALBINISM, DOPA.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Melanin

A dark insoluble pigment found in humans in the skin, hair, choroid layer of the eye, and a part of the brain called the substantia nigra.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

melanin

Dark brown to black pigment normally present in the skin, the hair, the choroid, the iris, the retina, the ciliary body, the cardiac tissue, the pia mater and the substantia nigra of the brain. It is absent in albinos. See albinism; fuscin; melanocyte; melanosis; choroidal naevus; retinal pigment epithelium.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann

mel·a·nin

(mel'ă-nin)
Any of the dark brown to black pigments that occur in the skin, hair, pigmented coat of the retina, and medulla and zona reticularis of the suprarenal gland.
[G. melas (melan-), black]
Medical Dictionary for the Dental Professions © Farlex 2012