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PubMed2002

Changes in the proliferative activity of epidermal melanocytes in serum-free primary culture during the development of ultraviolet radiation B-induced pigmented spots in hairless mice.

Long-term exposure to ultraviolet radiation B (UVB) induced pigmented spots in the dorsal skin of hairless mice of strain (HR-1 X HR/De)F1. To clarify the cellular mechanism for the development of these UVB-induced pigmented spots, we investigated changes in the proliferative activity of epidermal melanoblasts and melanocytes in the dorsal skin at various weeks after UVB irradiation. Epidermal cell suspensions from the dorsal skin of hairless mice were cultured in a serum-free medium supplemented with dibutyryl adenosine 3':5'-cyclic monophosphate (DBcAMP) and basic fibroblast growth factor (bFGF). The suspensions were prepared from dorsal skins of mice exposed to UVB for 4 weeks (the stage of hyperpigmentation). Suspensions were also prepared from mice at 3 (the stage of depigmentation), 8 (the stage of appearance of pigmented spots), 20 (the stage of development of small-sized pigmented spots) and 37 (the stage of development of medium-sized pigmented spots) weeks after the cessation of 8-week UVB exposure. At the stage of hyperpigmentation the proliferative activity of melanoblasts and melanocytes was suppressed. With the development of pigmented spots, the proliferative activity of undifferentiated melanoblasts gradually increased, and then followed the increase in the proliferative activity of differentiated melanocytes. These results suggest that the proliferative activity of epidermal melanoblasts and melanocytes in UVB-irradiated skin increases with the development of pigmented spots.

Animals↗
PubMed1992

Absorption spectra of human cone pigments.

Human colour vision is mediated by three light-sensitive pigments, each found in a different cone-cell type. The absorption spectra of the human cone pigments have been sought for over a century using techniques such as psychophysical colour matching, reflection densitometry, electroretinography, single-cell action spectra and, most directly, microspectrophotometry. We report here a direct determination of the human cone pigment photobleaching difference absorption spectra after the production of each cone pigment apoprotein in tissue culture cells transfected with the corresponding complementary DNA clones. The mean values for the wavelength of maximal absorption are 426 nm for the blue pigment, 530 nm for the green pigment, and 552 nm and 557 nm for two polymorphic variants of the red pigment.

Amino Acid Sequence↗
PubMed2001

Morphologic features of melanocytes, pigmented keratinocytes, and melanophages by in vivo confocal scanning laser microscopy.

Confocal scanning laser microscopy (CSLM) represents a novel imaging technique for in vivo microscopic analysis of skin lesions at a level of resolution that allows morphologic analysis of microanatomic structures. We investigated the feasibility of recognizing the cellular constituents of pigmented skin lesions, such as pigmented keratinocytes, melanocytes, and melanophages, by CSLM. Fifteen pigmented lesions (five pigmented seborrheic keratoses, and 10 compound melanocytic nevi) from 15 patients were studied, as well as normal skin. After the clinical lesions were imaged by CSLM, they were biopsied or excised for examination by conventional histology for comparison of the morphologic features. In images obtained by CSLM, pigmented keratinocytes were seen as polygonal cohesive cells with variably bright granular cytoplasm. Melanocytes appeared as bright round, oval, fusiform, or dendritic cells. The architectural growth pattern of melanocytes could be analyzed. Melanocytes were identified by their nested growth pattern as aggregates of bright round to oval structures at the dermoepidermal junction or in the superficial dermis. Melanocytes were also recognizable as single cells along the dermoepidermal junction, usually separated from each other by a variable number of keratinocytes. Melanophages appeared as large bright plump cells with ill-defined cytoplasmic borders, usually located around or near vessels of the superficial dermis. Our results demonstrate that the cellular constituents of pigmented lesions can be recognized by CSLM. This technique sets a new paradigm for noninvasive quasihistologic examination of pigmented lesions in vivo and merits further evaluation for diagnostic use.

Diagnosis, Differential↗
PubMed2003

Role of visual pigment properties in rod and cone phototransduction.

Retinal rods and cones share a phototransduction pathway involving cyclic GMP. Cones are typically 100 times less photosensitive than rods and their response kinetics are several times faster, but the underlying mechanisms remain largely unknown. Almost all proteins involved in phototransduction have distinct rod and cone variants. Differences in properties between rod and cone pigments have been described, such as a 10-fold shorter lifetime of the meta-II state (active conformation) of cone pigment and its higher rate of spontaneous isomerization, but their contributions to the functional differences between rods and cones remain speculative. We have addressed this question by expressing human or salamander red cone pigment in Xenopus rods, and human rod pigment in Xenopus cones. Here we show that rod and cone pigments when present in the same cell produce light responses with identical amplification and kinetics, thereby ruling out any difference in their signalling properties. However, red cone pigment isomerizes spontaneously 10,000 times more frequently than rod pigment. This high spontaneous activity adapts the native cones even in darkness, making them less sensitive and kinetically faster than rods. Nevertheless, additional factors are probably involved in these differences.

Animals↗
PubMed2003

A green cone-like pigment in the 'blind' mole-rat Spalax ehrenbergi: functional expression and photochemical characterization.

The degenerate subcutaneous eye of the blind mole rat belonging to the Spalax ehrenbergi superspecies has been shown to contain a long wavelength sensitive (LWS) cone pigment. Baculovirus expression of this LWS pigment and subsequent IMAC purification yields a photosensitive protein, that according to absorbance maximum (530 +/- 2 nm), kinetics of late phototransitions, and transducin activation, has all characteristics of a functional green cone pigment. The absorbance spectrum of the Spalax pigment is strongly red-shifted relative to the very homologous mouse, rabbit and rat green cone pigments (508-510 nm). Also in contrast to the rodent pigments, the Spalax pigment exhibits anion-dependent spectral properties, displaying a 12 nm blue-shift upon substitution of chloride ions by nitrate ions. Finally, the slow part of the photocascade deviates in some aspects from that of sighted mammals. The possible relevance of these findings for the evolutionary adaptation of Spalax to a subterranean ecotope is discussed.

Animals↗
PubMed2003

Pigmented melanocytes are protected against ultraviolet-A-induced membrane damage.

The dominant skin pigment melanin is believed to protect human skin against several harmful effects of ultraviolet radiation. It is not clear, however, how melanin located inside melanin-producing melanocytes modulates the effect of ultraviolet radiation on melanocytes themselves. We have determined membrane damage in pigmented and unpigmented albino mouse melanocytes after ultraviolet A radiation, which is suspected to induce melanoma. Unpigmented cells were much more susceptible to ultraviolet-A-induced membrane permeability than pigmented cells. Unpigmented cells were also more susceptible to ultraviolet-A-induced lipid peroxidation than strongly pigmented cells. Furthermore, unpigmented cells were much more susceptible to ultraviolet-A-induced depletion of glutathione than pigmented cells. Reduced glutathione is known to be a major antioxidant of unpigmented skin cells such as fibroblasts and keratinocytes. To examine whether or not glutathione is also a major antioxidant in melanocytes, melanocytes were depleted of glutathione by means of buthionine sulfoximine. We found that depletion of glutathione in pigmented melanocytes did not change lipid damage induced by ultraviolet A radiation. In unpigmented melanocytes, however, depletion of glutathione significantly increased lipid damage induced by ultraviolet A radiation. Thus, pigmented melanocytes apparently contain antioxidants more potent than glutathione, protecting them from ultraviolet-A-induced membrane damage.

Albinism↗
PubMedDate not supplied

Developmental constraints on an adaptive plasticity: reaction norms of pigmentation in adult segments of Drosophila melanogaster.

Variation of dark pigmentation according to developmental temperature was investigated in two geographic populations (France and India) with the isofemale line technique (20 lines for each population). The response curves called the reaction norms, were established in females for seven different segments: the mesothorax and abdomen segments 2-7 (Abd 2-7). In all cases the response curves were non-linear and had to be described either by a quadratic convex polynomial for thorax and Abd 2-5, or by a cubic polynomial for Abd 6 and 7. Among abdomen segments, increasing antero-posterior gradients were observed for several traits, including average pigmentation, overall phenotypic plasticity, the temperature of minimum pigmentation, and the curvature parameter of quadratic norms. Genetic correlations between abdomen segments were high when adjacent segments were considered, but became nil when more distant segments were correlated, suggesting that different pigmentation genes are expressed in the anterior and the posterior part of the abdomen. Characteristic values of reaction norms provided information either on trait value (i.e., the extension of pigmentation) or on plasticity. Correlations between plasticity and pigmentation were generally low and non-significant, suggesting their genetic independence. The overall darker pigmentation which is observed at low temperatures is assumed to be an adaptive plasticity. However, the differences which are evidenced among segments reveal strong interactions with developmental genes. These interactions are less likely to be a consequence of natural selection and are better interpreted as developmental constraints. The reaction norms analysis reveals the complexity of these interactions and should help, in the future, in the identification of the responsible thermosensitive genes.

Adaptation, Physiological↗
PubMed2001

Tissue distribution of NS-49, a phenethylamine class alpha 1A-adrenoceptor agonist, in pigmented rats.

After a single oral administration of 1 mg/kg of 14C-NS-49 ((R)-(-)-3'-(2-amino-1-hydroxyethyl)-4'-fluoromethanesulfonanilide hydrochloride, CAS 137431-04-0), the radioactivity distribution in tissues of male pigmented rats was studied and compared with that in male albino rats. One eye of each pigmented rat was divided into melanin-containing structures (uvea, pigmented epithelium and sclera) and others without melanin (cornea and lens), and the radioactivity concentration in each ocular tissue was measured. In all the pigmented rat body tissues tested, maximum radioactivity concentrations (Cmax) were reached within 4 h after administration. At 1 h, the kidney showed the highest concentration (11 times the plasma concentration), followed by the urethra, liver, urinary bladder and lung. Concentrations in the other tissues were similar to or less than the plasma concentration. The radioactivity concentrations in most tissues decreased rapidly, being less than 10% of the Cmax 24 h after administration. These characteristics of the 14C-NS-49 tissue distribution in the pigmented and albino rats did not differ. In the eye, however, the radioactivity concentration decreased more slowly in the pigmented than in the albino rats. Most of the radioactivity in the eyes of the pigmented rats was present in melanin-containing structures indicating that NS-49 binds to ocular melanin. The radioactivity concentration in the melanin-containing structures reached a maximum 4 h after administration, then decreased as did that for the whole eye with a t1/2, beta of 66.8 h.

Adrenergic alpha-1 Receptor Agonists↗
PubMed1990

Convergent evolution of the red- and green-like visual pigment genes in fish, Astyanax fasciatus, and human.

We have isolated and sequenced genes from the blind cave fish, Astyanax fasciatus, that are homologous to the human red and green visual pigment genes. The data strongly suggest that, like human, these fish have one red-like visual pigment gene and multiple green-like visual pigment genes. By comparing the DNA sequences of the human and fish visual pigment genes and knowing their phylogenetic relationship, one can infer the direction of amino acid substitutions in the red and green visual pigments. The results indicate that the red pigments in human and fish evolved from the green pigment independently by identical amino acid substitutions in only a few key positions.

Amino Acid Sequence↗
PubMed2004

Microphthalmia transcription factor induces both retinal pigmented epithelium and neural crest melanocytes from neuroretina cells.

Mitf encodes a basic helix-loop-helix transcription factor that plays an essential role in the differentiation of the retinal pigmented epithelium (RPE) and neural crest-derived melanocytes. As cells containing melanogenic enzymes (TRP2) are found in Mitf mouse mutants, it is not clear whether Mitf is a downstream factor or a master regulator of melanocyte differentiation. To further study the role of Mitf in committing cells to the melanocyte lineage, we express Mitf in the cultured quail neuroretina cells. This leads to the induction of two types of pigmented cells: neural crest-derived melanocytes, according to their dendritic morphology, physiology, and gene expression pattern are observed together with pigmented epithelial RPE-like cells. The expression of Mitf is lower in pigmented epithelial RPE-like cells than in neural crest-derived melanocytes. Accordingly, overexpression of Mitf in cultured quail RPE causes cells to develop into neural crest-like pigmented cells. Thus, Mitf is sufficient for the proper differentiation of crest-like pigmented cells from retinal cells and its expression level may determine the type of pigment cell induced.

Animals↗
PubMedDate not supplied

Differential accumulation and pigmenting ability of dietary carotenoids in colorful finches.

Many animals develop bright red, orange, or yellow carotenoid pigmentation that they use to attract mates. Colorful carotenoid pigments are acquired from the diet and are either directly incorporated as integumentary colorants or metabolized into other forms before deposition. Because animals often obtain several different carotenoids from plant and animal food sources, it is possible that these pigments are accumulated at different levels in the body and may play unique roles in shaping the ultimate color expression of individuals. We studied patterns of carotenoid accumulation and integumentary pigmentation in two colorful finch species--the American goldfinch (Carduelis tristis) and the zebra finch (Taeniopygia guttata). Both species acquire two main hydroxycarotenoids, lutein and zeaxanthin, from their seed diet but transform these into a series of metabolites that are used as colorful pigments in the plumage (goldfinches only) and beak (both species). We conducted a series of carotenoid-supplementation experiments to investigate the relative extent to which lutein and zeaxanthin are accumulated in blood and increase carotenoid coloration in feathers and bare parts. First, we supplemented the diets of both species with either lutein or zeaxanthin and measured plasma pigment status, feather carotenoid concentration (goldfinches only), and integumentary color. Zeaxanthin-supplemented males grew more colorful feathers and beaks than lutein-supplemented males, and in goldfinches incorporated a different ratio of carotenoids in feathers (favoring the accumulation of canary xanthophyll B). We also fed goldfinches different concentrations of a standard lutein-zeaxanthin mix and found that at physiologically normal and high concentrations, birds circulated proportionally more zeaxanthin over lutein than occurred in the diet. Collectively, these results demonstrate that zeaxanthin is preferentially accumulated in the body and serves as a more potent substrate for pigmentation than lutein in these finches.

Alabama↗
PubMed1997

Altered expression of a novel adaptin leads to defective pigment granule biogenesis in the Drosophila eye color mutant garnet.

Drosophila eye pigmentation defects have thus far been attributed to mutations in genes encoding enzymes required for biosynthesis of pigments and to ABC-type membrane transporters for pigments or their precursors. We report here that a defect in a gene encoding a putative coat adaptor protein leads to the eye color defect of garnet mutants. We first identified a human cDNA encoding delta-adaptin, a structural homolog of the alpha- and gamma-adaptin subunits of the clathrin coat adaptors AP-1 and AP-2, respectively. Biochemical analyses demonstrated that delta-adaptin is a component of the adaptor-like complex AP-3 in human cells. We then isolated a full-length cDNA encoding the Drosophila ortholog of delta-adaptin and found that transcripts specified by this cDNA are altered in garnet mutant flies. Examination by light and electron microscopy indicated that these mutant flies have reduced numbers of eye pigment granules, which correlates with decreased levels of both pteridine (red) and ommachrome (brown) pigments. Thus, the eye pigmentation defect in the Drosophila garnet mutant may be attributed to compromised function of a coat protein involved in intracellular transport processes required for biogenesis or function of pigment granules.

Adaptor Protein Complex alpha Subunits↗
PubMed1991

The rosy locus in Drosophila melanogaster: xanthine dehydrogenase and eye pigments.

The rosy gene in Drosophila melanogaster codes for the enzyme xanthine dehydrogenase (XDH). Mutants that have no enzyme activity are characterized by a brownish eye color phenotype reflecting a deficiency in the red eye pigment. Xanthine dehydrogenase is not synthesized in the eye, but rather is transported there. The present report describes the ultrastructural localization of XDH in the Drosophila eye. Three lines of evidence are presented demonstrating that XDH is sequestered within specific vacuoles, the type II pigment granules. Histochemical and antibody staining of frozen sections, as well as thin layer chromatography studies of several adult genotypes serve to examine some of the factors and genic interactions that may be involved in transport of XDH, and in eye pigment formation. While a specific function for XDH in the synthesis of the red, pteridine eye pigments remains unknown, these studies present evidence that: (1) the incorporation of XDH into the pigment granules requires specific interaction between a normal XDH molecule and one or more transport proteins; (2) the structural integrity of the pigment granule itself is dependent upon the presence of a normal balance of eye pigments, a notion advanced earlier.

Animals↗
PubMed2001

The effect of acidified soapstocks on feed conversion and broiler skin pigmentation.

The effect of different soapstocks (corn, sunflower, canola, and soybean) on productive performance and skin broiler pigmentation was investigated. Soapstock was added to reach 1.0% polyunsaturated fatty acids in the diet. The addition of soybean soapstock significantly improved live body weight gain of the birds from 1 to 7 wk of age. A live body weight gain of 1,736 g/bird was calculated for broilers fed with the soybean soapstock diet. Feed conversion was significantly higher for broilers fed with the soybean soapstock diet, and no negative effect was observed. Compared to broilers fed with Pixtafil (100.0% pigmentation), those fed soybean soapstock (when added as a supplement of 1.0% polyunsaturated fatty acids in the diet) reached 48.0% pigmentation, and those fed corn soapstock reached only 7.3%. When the diets were complemented with Pixtafil to reach 100% of calculated pigmentation, the soybean soapstock diet reached 100.8% pigmentation compared to a canola soapstock diet that reached 72.0% pigmentation. Acidified soybean soapstock could be a source of polyunsaturated fatty acids and of xantophyl pigments in broiler feeding.

Animal Feed↗
PubMed1985

Cirrhosis and alcoholism as pathogenetic factors in pigment gallstone formation.

The association of cirrhosis with pigment gallstones has been noted in numerous autopsy studies. However a direct relationship between alcoholism and pigment cholelithiasis has not been previously demonstrated. We have classified 123 cholecystectomy patients according to stone type and correlated the resulting categories with hepatic morphology, drinking history, and hematological data. Pigment stones were found in 79% of biopsy-verified cirrhotic patients but in only 26% of noncirrhotics. In patients without cirrhosis a positive history of alcoholism was found associated with pigment gallstones more often than with cholesterol or mixed stones (36% vs. 10%). Similarly, the mean red cell volume (MCV), a sensitive marker of alcoholism, was significantly increased in patients with pigment stones (93.6 mu 3 vs. 89.6 mu 3). We conclude that both cirrhosis and alcoholism predispose to pigment gallstone formation and that the effect of alcoholism may occur independent of cirrhosis. This suggests that the apparent association of cirrhosis with pigment stones may, in fact, result from a direct effect of long-term ethanol ingestion on red blood cells, liver, or bile.

Adult↗
PubMed1997

Indocyanine green angiographic evaluation of retinal pigment epithelial tears.

BACKGROUND: Although choroidal neovascularization has a recognized role in the formation of retinal pigment epithelial tears in the setting of age-related macular degeneration, there frequently was no fluorescein angiographic evidence of choroidal neovascularization in published series. METHODS: Three consecutive patients with a folded retinal pigment epithelium in a subfoveal location, which was associated with a serous macular detachment in the setting of age-related macular degeneration, were studied with intravenous fluorescein angiography and indocyanine green angiography. RESULTS: Fluorescein angiography demonstrated no well-defined choroidal neovascular membrane, although there was evidence of occult choroidal neovascularization. The folded retinal pigment epithelium blocked fluorescence. Indocyanine green angiography demonstrated placoid subfoveal hyperfluorescence consistent with choroidal neovascularization in the region of the folded retinal pigment epithelium and fibrovascular pigment epithelial detachment. Hypofluorescence was noted within the region of the retinal pigment epithelial tear. CONCLUSION: Indocyanine green angiography in our cases clearly demonstrated the presence of presumed choroidal neovascularization in the setting of retinal pigment epithelial tears secondary to age-related macular degeneration.

Aged↗
PubMed1986

Photoactive retinal pigments in haloalkaliphilic bacteria.

Light-induced fast transient absorbance changes were detected by time-resolved spectroscopy in 38 of 51 haloalkaliphilic isolates from alkaline salt lakes in Kenya and the Wadi Natrun in Egypt. They indicate the presence of two retinal pigments, Pf and Ps, which undergo cyclic photoreactions with half-times of 2 ms and 500 ms respectively. Pf absorbs maximally near 580 nm and Ps near 500 nm. The pigments differ in their sensitivity to hydroxylamine and detergent bleaching and the photoreactions of Pf are strongly dependent on chloride concentration. Of the 38 pigment-containing strains, 29 possess both Pf and Ps, 9 possess only Ps. Inhibition of retinal synthesis with nicotine blocks pigment formation and addition of retinal restores it. Hydroxylamine-bleached pigments can be reconstituted with retinal or retinal analogues. Their similarity to the retinal pigments of Halobacterium halobium strongly suggests that they are also rhodopsin-like retinyledene proteins. Pf in all properties tested is almost identical to halorhodopsin, the light-driven chloride pump of H. halobium, and may serve the same function in the haloalkaliphiles. Ps has photocycle kinetics similar to sensory rhodopsin and a far-blue-shifted long-lived photocycle intermediate, but its ground state absorption maximum is near 500 nm instead of 587 nm. We have not found a bacteriorhodopsin-like pigment in the haloalkaliphiles.

Bacteriorhodopsins↗
PubMed1995

Ectopic expression of the Streptomyces coelicolor whiE genes for polyketide spore pigment synthesis and their interaction with the act genes for actinorhodin biosynthesis.

The whiE gene cluster of Streptomyces coelicolor is normally expressed shortly before sporulation in the aerial mycelium, leading to production of the grey polyketide spore pigment. By placing the whiE genes under the control of the thiostrepton-inducible tipA promoter, they were artificially expressed on plasmids or in the chromosome during vegetative growth in a strain deleted for the act genes, which control biosynthesis of the polyketide antibiotic actinorhodin. Certain combinations of whiE-ORFI-VII led to production of mycelial pigments; these were exported into the medium when whiE-ORFI was absent, but poorly in its presence. Combined with comparative sequence data, the results allowed deductions to be made, or confirmed, about the normal roles of the eight known genes, whiE-ORFI-VIII, as follows: whiE-ORFIII, IV, V encode the three components (ketosynthase, chain length factor and acyl carrier protein) of the whiE 'minimal' polyketide synthase (PKS) needed for assembly of the carbon chain of the spore pigment precursor; whiE-ORFII, VI, VII are likely to be involved in cyclizations of the nascent carbon chain; whiE-ORFVIII controls a late step in the spore pigment biosynthetic pathway, probably a hydroxylation; and whiE-ORFI may encode a protein needed for correct targeting or retention of spore pigment at an appropriate cellular location. In other experiments, genes encoding components of the act-PKS and whiE-PKS were artificially co-expressed. Each of the three whiE minimal PKS subunit genes could complement lesions in the corresponding act-PKS genes to produce actinorhodin or related mycelial pigments, and each of the three act minimal PKS genes could complement lesions in the whiE minimal PKS genes to cause spore pigmentation. Thus the two sets of PKS subunits, which are encoded by genes that have presumably diverged from a common ancestor, are still capable of biochemical 'cross-talk', but this is normally prevented because the gene sets are expressed in different 'tissues' of the differentiated Streptomyces colony. Ectopic expression of sets of whiE-PKS genes presumed to be sufficient to assemble a carbon chain caused inhibition of early growth of the strains, perhaps by causing interference with fatty acid biosynthesis; this yielded circumstantial evidence that the whiE-PKS gene products can also interact with those of the fatty acid synthase(s) of the organism.

Anthraquinones↗