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PubMed1998

Topical trans-4-aminomethylcyclohexanecarboxylic acid prevents ultraviolet radiation-induced pigmentation.

We have studied the effect of a plasmin inhibitor, trans-4-aminomethylcyclohexanecarboxylic acid (trans-AMCHA), on skin pigmentation induced by ultraviolet (UV) exposure in Weiser-Maples guinea pigs. When guinea pigs are exposed to UV radiation (840 mJ cm-2), skin pigmentation is clearly observed from seven days after exposure and continued to increase to 29 days. Post-exposure applications of 2 and 3% solutions of trans-AMCHA to the exposed regions prevent or inhibit the pigmentation process. When the skin is removed and stained by the Fontana-Masson method, melanin content in the basal layer of UV-exposed epidermis is significantly reduced in the regions to which 2 and 3% trans-AMCHA solutions have been applied, compared with the vehicle control. As plasmin is known to contribute to the release of arachidonic acid (AA) and the production of prostaglandins (PGs), we have examined the effects of trans-AMCHA on AA-induced pigmentation in guinea pig skin. Topical application of trans-AMCHA causes a dose-dependent decrease in AA-induced pigmentation. These results suggest that trans-AMCHA reduces melanocyte tyrosinase activity by suppressing the production of PGs, UV-induced melanogens, through the suppression of the UV-induced increase in epidermal plasmin activity.

Administration, Topical↗
PubMedDate not supplied

Minocycline pigmentation of heart valves.

Minocycline, a derivative of tetracycline, is a broad spectrum antibiotic used in the treatment of gram-positive and gram-negative infections. Benitz et al. (1) were the first to report black discoloration of the thyroid gland in rats, dogs, and monkeys given minocycline. Since that time, there have been numerous reports in the literature describing minocycline related black pigmentation of the skin, thyroid gland, and other sites. We report an unusual case of minocycline induced pigmentation of the cardiac valves and coronary vessels. The pigment stained with Fontana-Masson and was reduced with bleaching. The exact nature of the pigment is unclear; however, various theories have been advocated. Ochronosis is another cause of black pigmentation of the heart valves; the clinical history should allow distinction between the two.

Aged↗
PubMed2003

Lutein-based plumage coloration in songbirds is a consequence of selective pigment incorporation into feathers.

Many birds obtain colorful carotenoid pigments from the diet and deposit them into growing tissues to develop extravagant red, orange or yellow sexual ornaments. In these instances, it is often unclear whether all dietary pigments are used as integumentary colorants or whether certain carotenoids are preferentially excluded or incorporated into tissues. We examined the carotenoid profiles of three New World passerines that display yellow plumage coloration-the yellow warbler (Dendroica petechia), common yellowthroat (Geothlypis trichas) and evening grosbeak (Coccothraustes vespertinus). Using high-performance liquid chromatography, we found that all species used only one carotenoid-lutein-to color their plumage yellow. Analyses of blood carotenoids (which document those pigments taken up from the diet) in two of the species, however, revealed the presence of two dietary xanthophylls-lutein and zeaxanthin-that commonly co-occur in plants and animals. These findings demonstrate post-absorptive selectivity of carotenoid deposition in bird feathers. To learn more about the site of pigment discrimination, we also analyzed the carotenoid composition of lipid fractions from the follicles of immature yellow-pigmented feathers in G. trichas and D. petechia and again detected both lutein and zeaxanthin. This suggests that selective lutein incorporation in feathers is under local control at the maturing feather follicle.

Animals↗
PubMedDate not supplied

Evaluation of the analgesic efficacy of EMLA cream in volunteers with differing skin pigmentation undergoing venipuncture.

BACKGROUND AND OBJECTIVES: Lidocaine/prilocaine cream (EMLA) applied to intact skin for 60 minutes has been shown to reduce venipuncture pain. Recent studies have suggested that lidocaine/prilocaine cream is less effective on heavily pigmented skin. The objective of this study was to evaluate the topical anesthetic efficacy of lidocaine/prilocaine cream in volunteers with varying skin pigmentation types. METHODS: Sixty volunteers were enrolled into each of three groups based on skin pigmentation history. Subjects were randomized to receive lidocaine/prilocaine cream onto the antecubital fossa of one arm and placebo cream on the comparable location of the other arm for either 60, 90, or 120 minutes prior to venipuncture. Assessments of perceived pain associated with each venipuncture were made by the subject using a visual analog scale. RESULTS: Lidocaine/prilocaine cream applied for 60 minutes significantly (P < .0001) reduced the pain of venipuncture compared to placebo regardless of the skin pigmentation type. Pain reduction did not differ significantly across skin types (P = .7986). Additional exposure up to 120 minutes did not change the efficacy of EMLA cream. CONCLUSIONS: Lidocaine/prilocaine cream is a safe and effective topical anesthetic for reducing pain associated with venipuncture in individuals, regardless of skin pigmentation.

Administration, Topical↗
PubMed1994

Effects of the white allele of the mi locus on coat pigmentation in chimeric mice.

To investigate the cellular action of the Miwh allele in the mouse with regard to its effects upon coat color patterns, we generated a series of aggregation chimeras, using embryos that differ in their mi locus genotype. We have obtained 11 chimeras Miwh/+C/C<==>+/+ c/c and 8 chimeras +/+ C/C<==>+/+ c/c. Chimerism was determined by coat and retinal pigment epithelium mosaicism and by the electrophoretic analysis of GPI-1 isoenzymes. In Miwh/+ C/C<==>+/+ c/c mice white coat color prevailed due to the higher percentage of unpigmented areas and the higher percentage of unpigmented hairs in pigmented areas. Our data indicate that a single Miwh gene dose decreases the melanoblast proliferative activity, causing the lightening of coat pigmentation. In Miwh/+ C/C<==>+/+ c/c mice a few pigmented hairs were often detected on the belly where Miwh/+ mice always had a white spot. This suggests that in the chimeras the presence of some non-Miwh cells in the skin of the belly allows pigment cells to develop. Using embryos of two substrains of Miwh/Miwh mice that differ in their Gpi-1 locus genotype we have produced 8 Miwh/+<==>Miwh/Miwh chimeras. In all these chimeras coat color patterns resembled those of Miwh/+ heterozygotes despite the higher percentage of the Miwh/Miwh component in three chimeras. Mosaic hairs were absent in the chimeras. This shows that the chimeras have only one Miwh/+ melanoblast population which actively proliferates and colonizes almost all hair follicles. Thus the Miwh/Miwh dermis and epidermis do not suppress proliferation and differentiation of the Miwh/+ melanoblasts except the certain area on the belly.

Alleles↗
PubMedDate not supplied

Pigment granule migration in crustacean photoreceptors requires calcium.

We have investigated the role of calcium in the regulation of pigment granule migration in photoreceptors of the semi-terrestrial crab, Sesarma cinereum. Isolated crab eyes (eyecup plus eyestalk) were maintained in crustacean Ringer either prepared normally or calcium-free plus 50 mM EGTA. Pigment granule movement was indirectly observed by monitoring reflectance from the eye during light stimuli using intracellular optical physiological techniques. Electroretinograms (ERGs) were also measured during light stimuli. EGTA treatment caused gradual loss of centripetal migration of pigment granules (normally leading to pupillary closure), and photoreceptors eventually became locked in the open-pupil, dark-adapted state despite repeated stimuli. In contrast, ERG responses continued throughout EGTA treatment, although the size and shape of the response was altered. Normal ERG responses and pigment granule movements returned after replacing EGTA-Ringer with normal-calcium medium. These results suggest that centripetal migration of pigment granules in crustacean photoreceptors requires calcium.

Animals↗
PubMed1992

Microspectrophotometric determinations of rod visual pigments in some adult and larval Australian amphibians.

Visual pigments from the red rods of adults of eight species of Australian anuran amphibians, from a variety of habitats, were analyzed by microspectrophotometry. The lambda max in all cases fell between 502 nm and 506 nm, and the absorption spectra were well fitted by an A1-based visual pigment template curve. Red rod pigments were also analyzed for a number of tadpoles. In some cases the data were best fitted with an A1-based visual pigment template, in other cases with an A2-based template, and finally some tadpoles appeared to have mixtures of the two pigments.

Animals↗
PubMedDate not supplied

Visual pigments and dichroism of anchovy cones: a model system for polarization detection.

The retinas of anchovies have two unique photoreceptor types: "bifid" and "long" cones (Fineran & Nicol, 1976). The outer segments of these cells contain multiple layers of membranes (lamellae) oriented longitudinally (axially). This orientation is distinct from that in all other vertebrate rods and cones, where the lamellae are stacked transversely with their planes perpendicular to the incident light path. Although the common arrangement provides optimal absorption for normally incident light rays, it is also insensitive to the rays' direction of vibration (i.e. their polarization). In contrast, the two mutually perpendicular sets of axially oriented lamellae segregated into bifid and long cones could function as the principal analyzers for linearly polarized light, as previously hypothesized (Fineran & Nicol, 1976, 1978). Here, we report on a microspectrophotometric study that shows (1) the presence of two spectrally distinct visual pigments in the three photoreceptor types of the bay anchovy retina; these are typical vertebrate pigments in that they bleach, when exposed to light, and have absorption spectra like all other vitamin A1-based visual pigments; (2) that the rods and cones exhibit dichroic absorption of light in accordance with their lamellar orientation, and (3) that the two cone types of the retina contain a spectrally indistinguishable pigment with peak absorbance (lambda(max)) around 540 nm, while the rods contain a rhodopsin-like pigment with lambda(max) near 500 nm. Compared to other vertebrates, anchovies are remarkable for using a monochromatic cone system with unusual specializations supportive of a polarization detection system.

Animals↗
PubMed1992

In vitro reconstitution of a light-harvesting gene product: deletion mutagenesis and analyses of pigment binding.

AB96, a gene encoding a Pisum sativum chlorophyll a/b binding protein [Coruzzi et al. (1983) J. Biol. Chem. 258, 1399-1402], can be expressed in Escherichia coli and reconstituted with pigments by the procedure described by Plumley and Schmidt [(1987) Proc. Natl. Acad. Sci. U.S.A. 84, 146-150]. Following purification by polyacrylamide gel electrophoresis, the reconstituted pigment-protein complex (CP2) is shown to have similar pigment-binding characteristics to native CP2 complexes isolated from thylakoid membranes. Therefore, the AB96 gene product contains binding sites for chlorophylls a and b and xanthophylls, all of which are necessary for optimal reconstitution in vitro. Absorption, fluorescence, and circular dichroism spectroscopy indicate that the pigments are oriented accurately and that chlorophylls a and b are adjoined for energy transfer. Studies with proteins produced after deletion mutagenesis of AB96 indicate that NH2-terminal amino acids 1-21 and COOH-terminal amino acids 219-228 do not play a role in pigment binding. In contrast, amino acids 50-57 and 204-212 (encompassing one of three conserved histidine residues) are essential for reconstitution. Residues near the presumed NH2- and COOH-terminal alpha-helix boundaries (22-49 and 213-218, respectively) affect the stability of reconstituted CP2 during electrophoresis at 4 degrees C. Correlation of diminished chlorophyll a binding with disappearance of a negative circular dichroism near 684 nm suggests that amino acids 213-218 near the COOH-terminal boundary of the third membrane-spanning helix affect the binding of some chlorophyll a molecules.

Amino Acid Sequence↗
PubMed2000

Thermooptic effect in chloroplast thylakoid membranes. Thermal and light stability of pigment arrays with different levels of structural complexity.

In chloroplast thylakoid membranes, chiral macrodomains, i.e., large arrays of pigment molecules with long-range chiral order, have earlier been shown to undergo light-induced reversible and irreversible structural changes; such reorganizations did not affect the short-range, excitonic pigment-pigment interactions. These structural changes and similar changes in lamellar aggregates of the main chlorophyll a/b light-harvesting complexes exhibited a linear dependence on the intensity of light that was not utilized in photosynthesis. It has been hypothesized that the light-induced rearrangements are driven by a thermooptic effect, i.e., thermal fluctuations due to the dissipation of excess excitation energies [Barzda, V., et al. (1996) Biochemistry 35, 8981-8985]. To test this hypothesis, we have utilized circular dichroism (CD) spectroscopy to investigate the structural stability of the chiral macrodomains and the constituent bulk pigment-protein complexes of granal thylakoid membranes against heat and prolonged, intense illumination. (i) In intact thylakoid membranes, the chiral macrodomains displayed high stability below 40 degrees C, but they were gradually disassembled between 50 and 60 degrees C; the thermal stability of the chiral macrodomains could be decreased substantially by suspending the membranes in reaction media that were hypotonic or had low ionic strength. (ii) The chiral macrodomains were also susceptible to high light: prolonged illumination with intense white light (25 min, 2500 microE m(-)(2) s(-)(1), 25 degrees C) induced similar, irreversible disassembly to that observed at high temperatures; in different preparations, lower thermal stability was coupled to lower light stability. (iii) The light stability depended significantly on the temperature: between about 5 and 15 degrees C, the macrodomains in the intact thylakoids were virtually not susceptible to high light; in contrast, the same preillumination at 35-40 degrees C almost completely destroyed the chiral macrodomains. (iv) As testified by the excitonic CD bands, the molecular organization of the pigment-protein complexes in all samples exhibited very high thermal stability between about 15 and 65 degrees C, and virtually total immunity against intense illumination. These data are fully consistent with the hypothesis of a thermooptic effect, and are interpreted within the frame of a simple model.

Chlorophyll↗
PubMed1994

A covalent link between the chromophore and the protein backbone of bacteriorhodopsin is not required for forming a photochemically active pigment analogous to the wild type.

Bacteriorhodopsin pigments lacking the retinal-Lys-216 covalent bond were prepared by reconstituting the K216G mutant protein with retinal alkylamine Schiff bases. The procedure follows the approach of Zhukovsky et al. [Zhukovsky, E., Robinson, P., & Oprian, D. (1991) Science 251, 558-560] in the case of visual (rhodopsin) pigments. Reconstitution leads to a mixture of three pigments. One of them, bR(K216G)/566a, absorbs (pH = 6.9) at 566 nm. Its absorption is pH-dependent, exhibiting a purple to blue transition. The pigment's laser-induced photocycle patterns are similar to those of wild-type all-trans-bR. A second component, bR(K216G)/566b, exhibits an independent photocycle reminiscent of that of wild-type 13-cis-bR. A third pigment component, bR(K216G)/630, absorbs around 630 nm. Experiments in the presence of a pH dye indicator show that illumination of bR(K216G)/566 produces a detectable proton gradient. It is concluded that a covalent bond between the retinal chromophore and the protein backbone is not a prerequisite for the basic structure and photochemical features of bR or for its proton pump activity.

Bacteriorhodopsins↗
PubMed1990

Comparative study on the chromophore binding sites of rod and red-sensitive cone visual pigments by use of synthetic retinal isomers and analogues.

A comparative study on the chromophore (retinal) binding sites of the opsin (R-photopsin) from chicken red-sensitive cone visual pigment (iodopsin) and that scotopsin) from bovine rod pigment (rhodopsin) was made by the aid of geometric isomers of retinal (all-trans, 13-cis, 11-cis, 9-cis, and 7-cis) and retinal analogues including fluorinated (14-F, 12-F, 10-F, and 8-F) and methylated (12-methyl) 11-cis-retinals. The stereoselectivity of R-photopsin for the retinal isomers and analogues was almost identical with that of scotopsin, indicating that the shapes of the chromophore binding sites of both opsins are similar, although the former appears to be somewhat more restricted than the latter. The rates of pigment formation from R-photopsin were considerably greater than those from scotopsin. In addition, all the iodopsin isomers and analogues were more susceptible to hydroxylamine than were the rhodopsin ones. These observations suggest that the retinal binding site of iodopsin is located near the protein surface. On the basis of the spectral properties of fluorinated analogues, a polar group in the chromophore binding site of iodopsin as well as rhodopsin was estimated to be located near the hydrogen atom at the C10 position of the retinylidene chromophore. A large difference in wavelength between the absorption maxima of iodopsin and rhodopsin was significantly reduced in the 9-cis and 7-cis pigments. On the assumption that the retinylidene chromophore is anchored rigidly at the alpha-carbon of the lysine residue and loosely at the cyclohexenyl ring, each of the two isomers would have the Schiff-base nitrogen at a position altered from that of the 11-cis pigments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Phosphorylation of iodopsin, chicken red-sensitive cone visual pigment.

The amino acid sequence has been determined for the carboxyl-terminal 41 amino acids of chicken red-sensitive cone pigment, iodopsin. This sequence is distinct from but structurally homologous to that of other visual pigments. It contains a region rich in the hydroxy amino acids serine and threonine. In the related rod cell visual pigment, rhodopsin, such serines and threonines have previously been identified as sites for phosphorylation by rhodopsin kinase. Phosphorylation of photolyzed rhodopsin serves to terminate its ability to function in visual transduction as an activator of G-protein. We have purified and reconstituted both chicken rhodopsin and chicken iodopsin and shown them to be phosphorylated by bovine rhodopsin kinase. Chicken iodopsin has a Km and Vmax similar to but distinguishably different from that for bovine rhodopsin. These results, in conjunction with other data, suggest that visual pigments in cone cells, upon absorption of light, undergo functional processes similar to those of the visual pigments in rod cells.

Amino Acid Sequence↗
PubMed1976

Visual-pigment spectra: implications of the protonation of the retinal Schiff base.

Various models of visual-pigment spectra are critically discussed in terms of the spectral properties of protonated Schiff bases and the common structural features of most proteins. The opsin apoprotein is capable of regulating visual pigment wavelengths in ways that are difficult or impossible to reproduce in model systems. Theories based on solvent effects of the spectra of protonated Schiff bases may be misleading. Careful parameterization using known polyene spectra allows accurate calculation of the spectral properties of protonated Schiff bases. It is shown that an isolated protonated Schiff base of retinal should absorb near 600 nm and that blue-shifted spectra seen in solution arise from associated counterions or solvent molecules. We conclude that the most plausible specific model of chromophore-protein interactions is one in which the protonated Schiff base is closely associated with its counterion and where additional negatively charged or polar groups are positioned by the protein in the vicinity of the ring half of the chromophore. Pigment absorption maxima, bandwidths, and the A2-A1 pigment absorption differences arise naturally from these simple models of pigment spectra.

Animals↗
PubMed2020

Chemical Imaging of Retinal Pigment Epithelium in Frozen Sections of Zebrafish Larvae Using ToF-SIMS.

Variants of the SLC24A5 gene, which encodes a putative potassium-dependent sodium-calcium exchanger (NCKX5) that most likely resides in the melanosome or its precursor, affect pigmentation in both humans and zebrafish (Danio rerio). This finding suggests that genetic variations influencing human skin pigmentation alter melanosome biogenesis via ionic changes. Gaining an understanding of how changes in the ionic environment of organelles impact melanosome morphogenesis and pigmentation will require a spatially resolved way to characterize the chemical environment of melanosomes in pigmented tissue such as retinal pigment epithelium (RPE). The imaging mass spectrometry technique most suited for this type of cell and tissue analysis is time-of-flight secondary ion mass spectrometry (ToF-SIMS) because it is able to detect many biochemical species with high sensitivity and with submicron spatial resolution. Here, we describe chemical imaging of the RPE in frozen-hydrated sections of larval zebrafish using cryo-ToF-SIMS. To facilitate the data interpretation, positive and negative polarity ToF-SIMS image data were transformed into a single hyperspectral data set and analyzed using principal component analysis. The combination of a novel protocol and the use of multivariate data analysis allowed us to discover new marker ions that are attributable to leucodopachrome, a metabolite specific to the biosynthesis of eumelanin. The described methodology may be adapted for the investigation of other classes of molecules in frozen tissues from zebrafish and other organisms.

Animals↗
PubMed2001

Changes in chloroplast pigments of olive varieties during fruit ripening.

Changes in chlorophyll and carotenoid pigments of five olive (Olea europaea L.) varieties destined for milling were investigated at six consecutive ripening stages. There was a manifest dependence between olive variety, moment of picking, and chloroplast pigment composition of the fruits. Although the content of chlorophylls and carotenoids differed with fruit variety, ripening always involved their gradual loss, which becames more pronounced with increased presence of anthocyanin compounds. The relative rates of disappearance of chlorophylls and carotenoids were markedly different between varieties, implying that the catabolism of these pigments takes place at a relative rate inherent to each variety. The varieties less rich in pigments showed the most extreme behavior. The highest relative rate of disappearance was observed in fruits of the Blanqueta variety, and the lowest was observed in those of Arbequina. The chlorophyll a/chlorophyll b ratio remained practically constant during ripening, with a value very similar for Hojiblanca, Picual, Cornicabra, and Blanqueta, but much higher for Arbequina, implying that the structure of the photosynthetic apparatus is different in the latter variety. In the five varieties studied, lutein was the slowest carotenoid to be degraded, so that its percentage in the fruits increased with ripening, whereas beta-carotene was the fastest to disappear. In ripe fruits covered with anthocyanins, chloroplast pigments were retained in both skin and pulp, with the rate of disappearance being much higher in the latter.

Carotenoids↗
PubMed2001

Color and stability of pigments derived from the acetaldehyde-mediated condensation between malvidin 3-O-glucoside and (+)-catechin.

A pigment derived from the acetaldehyde-mediated condensation between (+)-catechin and malvidin 3-O-glucoside has been prepared and isolated by semipreparative HPLC, and its characteristics of color and stability have been studied and compared with that of malvidin glucoside in aqueous solutions. When the pH was increased from 2.2 to 5.5, the solution of the pigment became progressively more violet (lambda(max) = 560 nm at pH 5.5), whereas similar solutions of the anthocyanin were almost colorless at pH 4.0. This behavior indicated that the anthocyanin moiety of the pigment was more protected against water attack, and thus the formation of its quinonoidal forms was favored. The color of the pigment also showed more stability with regard to bleaching by SO(2) than that of malvidin glucoside. Nevertheless, the pigment was more sensitive to degradation in aqueous solution than the anthocyanin. The cleavage of the ethyl bridge that links the anthocyanin and the catechin constituted the first step in its degradation, as demonstrated by the formation of malvidin glucoside as a major product.

Acetaldehyde↗
PubMed2002

Identification of anthocyanin-flavanol pigments in red wines by NMR and mass spectrometry.

Three newly formed Port wine pigments were isolated by Toyopearl HW-40(s) gel chromatography and semipreparative HPLC. Furthermore, the pigments were identified by mass spectrometry (LC/MS) and NMR techniques (1D and 2D). These anthocyanin-derived pigments showed UV-visible spectra different from those of the original grape anthocyanins. These pigments correspond to malvidin 3-glucoside linked through a vinyl bond to either (+)-catechin, (-)-epicatechin, or procyanidin dimer B3 [(+)-catechin-(+)-catechin]. NMR data of these pigments are reported for the first time.

Anthocyanins↗