(n.) A black pigment found in the pigment-bearing cells of the skin (particularly in the skin of the negro), in the epithelial cells of the external layer of the retina (then called fuscin), in the outer layer of the choroid, and elsewhere. It is supposed to be derived from the decomposition of hemoglobin.
Example Sentences:
(1) Although the mechanism(s) by which melanin augments inflammation has not been defined, these data suggest that the binding of serum components (such as antibodies) to melanin may contribute to its proinflammatory effect.
(2) An unusual case of medullary carcinoma of the thyroid gland with melanin production is described.
(3) The melanins examined show significant differences in conductivity, thermal activation energy and photocurrent intensity values.
(4) The total number of neuronal cell bodies was 25% lower in AIDS (P less than 0.01) than in 12 age-matched controls, although the volume density of neuronal melanin did not differ from that of controls because the percentage of pigmented cell bodies was higher (P less than 0.01) and the cell bodies were more fully packed with melanin in AIDS.
(5) Comparison of the melanin-related metabolites excreted in urine of people with different capacities for melanin biosynthesis indicates that, of all measured substances, 5H6MI2C is the best urinary marker of melanin formation in the skin pigmentary system.
(6) Since neuromelanin in SN is the end-product of nonenzymatic dopamine degradation, the amount of melanin probably depends on the overall amount of dopamine produced during life.
(7) 1 After the injection of labelled procaine and lidocaine in mice, the location and concentration of radioactivity was demonstrated by autoradiographical methods.2 An accumulation in some endocrine cells such as the pancreatic islets, the hypophysis, the adrenal medulla and certain cells of the thyroid (probably representing the calcitonin-producing parafollicular cells) was shown.3 After the injection of [(14)C]-procaine in chicks, an accumulation of radioactivity was observed in the ultimobranchial gland (which produces calcitonin in birds), but not in the thyroid.4 Radioactivity was also shown to be strongly concentrated in structures containing melanin, such as the pigment of the eye, skin and hair and in some organs involved in the metabolism and excretion of these drugs.
(8) Microautoradiography showed that melanin-containing cells in the trunk and head kidney and in the olfactory rosettes also accumulated high amounts of radioactivity.
(9) In all cases there was a reduction of the melanin of the basal layer.
(10) Two melanotropic peptides, melanin concentration hormone (MCH) and alpha-melanocyte stimulating hormone (alpha-MSH), exert opposing actions on melanosome (melanin granule) movements within teleost pigment cells, melanocytes (melanophores).
(11) The varying epidermal melanin content that produces racial pigmentation determines the number of photons that reach the lower (malpighian) cellular layers, where vitamin D3 synthesis takes place.
(12) The synthesis of melanin involves the oxidation of phenolic substrates by the enzyme tyrosinase.
(13) Since such rats supposedly have a normal pigment distribution and a normal pattern of decussation at the optic chiasm, this finding appears to undermine the suggested role played by stalk melanin in establishing the laterality of retinal fibre projections in other mammalian species.
(14) The MNT was composed mainly of two cell types: small immature neuroblast-like cells and large columnar or cuboidal epithelial-like cells with or without melanin granules.
(15) L-tyrosine, a precurosr to melanin, has recently been shown to be a regulator of the melanogenic pathway in some cultured melanoma cell lines.
(16) By analysis of co-variance, the melanin content of melanocytes of black and white subjects was significantly (p less than 0.05) associated with susceptibility to UVA killing; melanocytes with high melanin content had high resistance to UVA cytotoxicity and those with low melanin content had low resistance to UVA cytotoxicity.
(17) Melanin biosynthesis is a multistep process with the first step being the conversion of L-tyrosine to L-Dopa catalyzed by the enzyme tyrosinase.
(18) The results showed that there was no correlation between the GABA concentration and the number of melanin-rich nigral cell bodies.
(19) These fluorescent substances were heterogeneous: fluorescence was detected both in main high molecular fraction and in low molecular substances (fluorescence was absent in the initial melanin and its fractions).
(20) Melanocyte cultures have already shed new light on keratinocyte-melanocyte interactions within the epidermal melanin unit by showing that keratinocytes produce "melanotrophic factors" which modulate growth, melanin production, and dendricity of melanocytes.
Pigment
Definition:
(n.) Any material from which a dye, a paint, or the like, may be prepared; particularly, the refined and purified coloring matter ready for mixing with an appropriate vehicle.
(n.) Any one of the colored substances found in animal and vegetable tissues and fluids, as bilirubin, urobilin, chlorophyll, etc.
(n.) Wine flavored with species and honey.
Example Sentences:
(1) The results also suggest that the dispersed condition of pigment in the melanophores represents the "resting state" of the melanophores when they are under no stimulation.
(2) Differences between the albino vs pigmented strains were observed following injections of saline.
(3) Two lectins, wheat germ agglutinin (WGA) and peanut agglutinin (PNA), were used to compare domains within the interphotoreceptor matrices (IPM) of the cat and monkey, two species where the morphological relationship between the retinal pigment epithelium (RPE) and photoreceptors is distinctly different.
(4) Uptake studies with 22Na were performed in cultured bovine pigmented ciliary epithelial cells, in order to characterize mechanisms of Na+ transport.
(5) CW Nd:YAG light transmitted by fiber optic cable and sapphire crystal was applied transsclerally to the ciliary body of pigmented and albino rabbits.
(6) The evolution and function of multiple forms of a given photosynthetic pigment in vivo are discussed.
(7) Changes in protein phosphorylation induced by phagocytic challenge were identified in cultured rat retinal pigment epithelium (RPE) following exposure to isolated rat rod outer segments (ROS) or to polystyrene latex microspheres (PSL).
(8) Both categories frequently showed pellagrous pigmentation and mucocutaneous signs of B-vitamin deficiency.
(9) We show that, in digitonin-permeabilized goldfish xanthophores, the pigment organelles can be induced to disperse by a combination of cAMP, ATP, and xanthophore cytosol.
(10) A red pigment produced by the actinomycete strain B 4358 was identified as butyl-meta-cycloheptylprodiginine (4) by 1H, 13C and correlation via long range coupling NMR spectra.
(11) Two unusual types of oral mucosal pigmentation are reported.
(12) These results are consistent with the idea that RPE pigment dispersion is triggered by a substance that diffuses from the retina at light onset.
(13) Rhabdomeres are substantially smaller and visual pigment is nearly eliminated when Drosophila are carotenoid-deprived from egg to adult.
(14) It is hypothesized that deposition of bilirubin in tissues takes place as an ongoing event, the deposited pigment being eliminated by bilirubin oxidase in healthy infants.
(15) The calculated separation between the centers of these two pigments (using an extended version of the exciton theory) is about 10 A, the pigments' molecular planes are tilted by about 20 degrees, and their N1-N3 axes are rotated by 150 degrees relative to each other.
(16) We have investigated enhancement of pigmentation in inbred C3H- mice using tail skin as a model for testing the effects of phosphorylated DOPA (DP) and ultraviolet radiation.
(17) Although mucocutaneous pigmentation was not present in two of the three patients, the features of intestinal polyposis are consistent with those of Peutz-Jeghers syndrome.
(18) Cytochromes b, c(555), possibly c(1), cytochrome oxidase, a carbon monoxide-binding pigment, and flavoproteins were detectable in the spectra of both intact cells and mitochondria.
(19) The addition of alcohol to the drinking-water resulted in the formation of stones rich in pigment.
(20) The total number of neuronal cell bodies was 25% lower in AIDS (P less than 0.01) than in 12 age-matched controls, although the volume density of neuronal melanin did not differ from that of controls because the percentage of pigmented cell bodies was higher (P less than 0.01) and the cell bodies were more fully packed with melanin in AIDS.