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).

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]

melanin

(mĕl′ə-nĭn)
n.
Any of a group of naturally occurring dark pigments, especially the pigment found in skin, hair, fur, and feathers.

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.

melanin

 Physiology A dark natural body pigment found in the epidermis or skin adnexal structures. See Albinism, DOPA, Melanoma.

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]

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.

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.

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.

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.

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]
References in periodicals archive ?
The spectral curves of phaeomelanin and eumelanin differ in such a way that the absorbance of phaeomelanin is lower than the absorbance of eumelanin at 650 nm (Fig.
They found that eumelanin rather than phaeomelanin was the major factor influencing incorporation.
(19) measured both eumelanin and phaeomelanin in addition to phencyclidine and showed that the incorporation of phencyclidine into rodent hair was related to eumelanin rather than phaeomelanin, and Mars (26) showed that the in vitro binding capacity of eumelanin is somewhat higher than that of phaeomelanin.
In humans, the shades of hair color are the result of a mixed melanogenesis, and the resulting pigment is a combination of eumelanin and phaeomelanin. Considering this wide range of hair color shades in humans, it is necessary not only to accurately determine the color shade of the hair but also to quantitatively measure the pigmentation and at least qualitatively determine the type of pigmentation.
As a qualitative trait, the plumage colour of poultry is determined by the relative content and distribution of eumelanin and phaeomelanin produced in melanocytes.
A Japanese study (32) of the hairs of tyrosinase-positive albinos showed phaeomelanin only, unlike the hairs of the single tyrosinase-negative albino which contained neither eumelanin nor phaeomelanin.
Phaeomelanin as well as eumelanin is present in human epidermis.
Phaeomelanin versus eumelanin as a chemical indicator of ultraviolet sensitivity in fair-skinned subjects at high risk for melanoma: a pilot study.