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At least 109 records · Page 6Linked to original sources
PubMed1994

Is chicken green-sensitive cone visual pigment a rhodopsin-like pigment? A comparative study of the molecular properties between chicken green and rhodopsin.

Chicken green is a visual pigment present in chicken green-sensitive cones and has an amino acid sequence more similar than any other cone visual pigments to the rod visual pigments, rhodopsins. Here we have investigated the molecular properties of chicken green and compared them with those of rhodopsin to elucidate whether or not chicken green is a rhodopsin-like pigment. While chicken green has a molecular extinction coefficient and a photosensitivity very similar to those of rhodopsin, it displays faster regeneration from 11-cis-retinal and opsin and faster formation and decay of the physiologically active meta II intermediate than rhodopsin. These differences correlate with the physiological difference between cones and rods. Thus in spite of the similarity in amino acid sequence, chicken green displays molecular properties required for a cone visual pigment that are clearly different from those of rhodopsin.

Animals↗
PubMed1966

A protein-protochlorophyll complex obtained from inner seed coats of Cucurbita pepo. The resolution of its two pigment groups into true protochlorophyll and a pigment related to bacterial protochlorophyll.

1. The inner seed coats of Cucurbita pepo were extracted with aqueous acetone and found to contain pigments with spectra similar to that of protochlorophyll. 2. When the fruits of C. pepo were stored the amount of protochlorophyll-like material in the inner seed coats increased and a form of protochlorophyll absorbing at longer wavelength was apparently formed. 3. The pigment was resolved into two forms of protochlorophyll by chromatography on sugar columns. One form with absorption maxima in ether at 432, 535, 571 and 623mmu was spectroscopically identical with plant protochlorophyll; the other, with absorption maxima at 438, 537, 574 and 624mmu, was spectroscopically identical with bacterial protochlorophyll isolated from the tan mutant of Rhodopseudomonas spheroides. The two phaeoporphyrins obtained from the seed-coat pigments closely resemble the corresponding phaeoporphyrin derivatives of plant protochlorophyll and bacterial protochlorophyll in spectroscopic and partition properties. 4. The pigment in the cells of inner seed coat of C. pepo is concentrated in discrete particles of about 1.7mu diameter. Extracts of the seed coats in a glycerol-glycine buffer were similar in spectroscopic properties to the crude protochlorophyll holochrome, but were not light-transformable. 5. After partial purification of the glycerol-glycine buffer extracts a pigment-protein complex was obtained with absorption maxima at considerably longer wavelengths than in organic solvents. 6. Preparations of the seed-coat protochlorophyll, in the presence of bovine serum albumin, adsorbed on filter paper or in colloidal solution, did not have absorption bands shifted so far to the red region as the natural protein complex isolated from the seed coat. 7. It is suggested that bacterial protochlorophyll (magnesium 2,4-divinylphaeoporphyrin a(5) methyl ester) is involved in the biosynthesis of chlorophyll in both plants and photosynthetic bacteria.

Chlorophyll↗
PubMed2000

Ultraviolet pigments in birds evolved from violet pigments by a single amino acid change.

UV vision has profound effects on the evolution of organisms by affecting such behaviors as mating preference and foraging strategies. Despite its importance, the molecular basis of UV vision is not known. Here, we have transformed the zebra finch UV pigment into a violet pigment by incorporating one amino acid change, C84S. By incorporating the reverse mutations, we have also constructed UV pigments from the orthologous violet pigments of the pigeon and chicken. These results and comparative amino acid sequence analyses of the pigments in vertebrates demonstrate that many avian species have achieved their UV vision by S84C.

Amino Acid Sequence↗
PubMed1995

Pigmentation of the posterior lens capsule central to Wieger's ligament and the Scheie line: a possible indication of the pigment dispersion syndrome.

Observation of pigment deposition on the posterior lens central to Wieger's ligament and the position of the so-called Scheie line is reported as a clinical sign of the pigment dispersion syndrome (PDS). Although abnormal pigmentation of the posterior lens surface is well-known to occur as scattered deposition among the zonule insertions as well as in the shape of a line formed within the crevice just anterior to the junction between the posterior capsule and the anterior hyaloid face, pigmentation has not been well-known to occur more centrally, nearer the polar capsular region. Pigment in this location is a relatively unknown finding in PDS and may lead to suspicion and diagnosis of this disorder.

Adolescent↗
PubMed1990

Hairless pigmented guinea pigs: a new model for the study of mammalian pigmentation.

A stock of hairless pigmented guinea pigs was developed to facilitate studies of mammalian pigmentation. This stock combines the convenience of a hairless animal with a pigmentary system that is similar to human skin. In both human and guinea pig skin, active melanocytes are located in the basal layer of the interfollicular epidermis. Hairless albino guinea pigs on an outbred Hartley background (CrI:IAF/HA(hr/hr)BR; designated hr/hr) were mated with red-haired guinea pigs (designated Hr/Hr). Red-haired heterozygotes from the F1 generation (Hr/hr) were then mated with each other or with hairless albino guinea pigs. The F2 generation included hairless pigmented guinea pigs that retained their interfollicular epidermal melanocytes and whose skin was red-brown in color. Following UV irradiation, there was an increase in cutaneous pigmentation as well as an increase in the number of active epidermal melanocytes. An additional strain of black hairless guinea pigs was developed using black Hr/Hr animals and a similar breeding scheme. These two strains should serve as useful models for studies of the mammalian pigment system.

Animals↗
PubMed1988

Influence of source and physical form of xanthophyll pigment on broiler pigmentation and performance.

Two experiments were conducted using 21-day-old, commercial-strain broilers to determine the effect of various commercial pigmentation products on pigmentation and bird performance. Birds received finisher/withdrawal diets that included 8% corn gluten meal or either a 2.5 or 5.0% substitution of gluten meal with Liquid OroGlo5, Dry Oroglo10, or Cromophyl-oro. When birds were slaughtered at either 48 or 51 days of age there were no differences in the birds' breast skin hue (dominant wavelength) or brightness (luminosity). Data indicated similar levels of pigmentation among birds in all treatments. Color intensity (excitation purity) values of shank and breast skin samples suggested that the liquid form of OroGlo was more effective than the dry form in pigmenting broiler skin when both forms were fed at equal calculated levels. Data indicated that actual xanthophyll intake was higher when the liquid source was fed. Body weight gain and feed efficiency among the treatments, in general, indicated that commercial pigment sources can be substituted for corn gluten meal without appreciably altering broiler performance.

Animals↗
PubMed1983

Retinomotor pigment migration in the teleost retinal pigment epithelium. II. Cyclic-3',5'-adenosine monophosphate induction of dark-adaptive movement in vitro.

The retinal pigment epithelium (RPE) and photoreceptors of teleosts exhibit dramatic examples of cell motility (called retinomotor movements) in response to diurnal changes in lighting conditions. In darkness the pigment granules of the RPE migrate to the scleral base of the RPE cell and cone photoreceptors elongate. In the light these movements are reversed; pigment granules disperse into the long apical projections of the RPE cell and cones contract. It is reported here that treatments that elevate cytoplasmic cyclic AMP induce dark-adaptive movements (pigment aggregation and cone elongation) in light-adapted retinas cultured in the light. Treatments designed to elevate cGMP had no effect. In dose-response studies with the cAMP analog, dibutyryl cyclic AMP (dbcAMP), we found that the RPE pigment did not exhibit intermediate states of aggregation with increasing concentrations of dbcAMP but instead changed abruptly from the fully light-adapted to the fully dark-adapted retinomotor positions between 10 microM and 50 microM exogenous dbcAMP concentrations. Cones, on the other hand, elongated to intermediate extents in proportion to increasing dbcAMP concentration between 10 microM and 500 microM. These observations suggest that cytoplasmic cAMP plays a role in regulating retinomotor position in both RPE and cones.

1-Methyl-3-isobutylxanthine↗
PubMed2004

Pigmented pleomorphic adenoma, a novel melanin-pigmented benign salivary gland tumor.

This paper reports a pleomorphic adenoma with grossly visible pigmentation resulting in the macroscopic appearance of melanotic lesion in a 33-year-old Japanese male. In addition to the characteristic histopathological features of a benign pleomorphic adenoma, variously formed and -sized cells, many of which were considered to be melanocytes, containing melanin pigment in their cytoplasm, were distributed in the epithelial component. In addition, melanin pigment was deposited in tumor cells of duct structures. Furthermore, condensed secretory substances with marked pigmentation were frequently seen in the tubular lumina. Perusal of the English language literature revealed only two cases of parenchymal pigmentation of salivary gland tumors: both were mucoepidermoid carcinoma. The possible histogenesis of melanocytes in the salivary gland lesions is discussed, though no firm conclusion could be drawn.

Adenoma, Pleomorphic↗
PubMed1994

Pigment-dependent differences in the stria vascularis of albino and pigmented guinea pigs and rats.

Functional models of the stria vascularis (SV) have ascribed roles for the marginal and basal cells, but not for the intermediate cells, which remain poorly understood. Intermediate cells have been identified as melanocytes, which produce melanin in most pigmented animals including humans. The relationship of melanin to intermediate cell function may be addressed through comparisons with the albino inner ear. Albinos have a normal distribution of melanocytes that are unable to synthesize melanin pigment. In the present study, the SV was compared between albino and pigmented littermates in both the guinea pig and the rat. Photomicrographic montages of the SV were analyzed from each of 7 cochlear regions in the guinea pig and 5 regions in the rat. Stereological procedures were used to determine the volume density (Vv) for each of the three main cell types in the stria, the surface density (Sv) of the marginal cells, and to derive estimates of absolute cell volume and surface area. In the guinea pig, comparisons between pigment groups showed that marginal cell Vv was larger across cochlear turns in the albinos, while intermediate cell Vv was smaller. Intermediate cell cytoplasmic and total cell volumes were smaller in the albino guinea pigs; however, marginal cell Sv and absolute area were larger. In the rat, intermediate cell Vv was alos smaller across cochlear turns in the albinos. Similarly, intermediate cell cytoplasmic and total cell volumes were smaller in the albinos, while marginal cell total surface area per radial cross-section of the SV was larger. These results demonstrate that amelanotic melanocytes occupy significantly less volume than do pigmented melanocytes, and suggest that melanin may influence the structure and function of the SV.

Albinism↗
PubMed2005

Construction of pigmented skin equivalent and its application to the study of congenital disorders of pigmentation.

We have constructed a pigmented skin equivalent and used it to study the hyperpigmentation seen in café-au-lait macules to elucidate whether the pigmented skin equivalent could be used as a model of congenital hyperpigmentary disorders. When we used fibroblasts derived from café-au-lait macules of neurofibromatosis type 1, the amount of pigment was significantly greater than in models using cells derived from normal skin. Quantities of pigment were not seen when keratinocytes derived from solitary café-au-lait macules were used, a possible reason being that keratinocytes on the skin equivalent are in a proliferating condition and are not well-differentiated enough to act on other cells. Our results suggested that our pigmented skin equivalent is useful for the study of congenital hyperpigmentary disorders, although insufficient differentiation of keratinocytes might be a disadvantage.

Cafe-au-Lait Spots↗
PubMed1995

Analysis of the pigment stoichiometry of pigment-protein complexes from barley (Hordeum vulgare). The xanthophyll cycle intermediates occur mainly in the light-harvesting complexes of photosystem I and photosystem II.

The carotenoid zeaxanthin has been implicated in a nonradiative dissipation of excess excitation energy. To determine its site of action, we have examined the location of zeaxanthin within the thylakoid membrane components. Five pigment-protein complexes were isolated with little loss of pigments: photosystem I (PSI); core complex (CC) I, the core of PSI; CC II, the core of photosystem II (PSII); light-harvesting complex (LHC) IIb, a trimer of the major light-harvesting protein of PSII; and LHC IIa, c, and d, a complex of the monomeric minor light-harvesting proteins of PSII. Zeaxanthin was found predominantly in the LHC complexes. Lesser amounts were present in the CCs possibly because these contained some extraneous LHC polypeptides. The LHC IIb trimer and the monomeric LHC II a, c, and d pigment-proteins from dark-adapted plants each contained, in addition to lutein and neoxanthin, one violaxanthin molecule but little antheraxanthin and no zeaxanthin. Following illumination, each complex had a reduced violaxanthin content, but now more antheraxanthin and zeaxanthin were present. PSI had little or no neoxanthin. The pigment content of LHC I was deduced by subtracting the pigment content of CC I from that of PSI. Our best estimate for the carotenoid content of a LHC IIb trimer from dark-adapted plants is one violaxanthin, two neoxanthins, six luteins, and 0.03 mol of antheraxanthin per mol trimer. The xanthophyll cycle occurs mainly or exclusively within the light-harvesting antennae of both photosystems.

Carotenoids↗
PubMed1985

The nature of pigment in pigmented apocrine hidrocystoma.

Apocrine hidrocystomas are often pigmented clinically. The cause of this pigmentation is not known. A case of pigmented apocrine hidrocystoma is presented with evidence of melanin as the underlying mechanism of the pigmentation. Review of an additional 150 cases suggests that this is rare. The Tyndall effect, analogous to that seen in blue dome cysts of fibrocystic disease of the breast may be the likely explanation of the pigmentation seen clinically in most cases of apocrine hidrocystomas.

Aged↗
PubMed1996

Pigmented lateral periodontal cyst and other pigmented odontogenic lesions.

OBJECTIVE: To report a case of lateral periodontal cyst (LPC) with marked melanin pigmentation in a 38-year-old Black male and to discuss the phenomenon of melanin pigmentation in odontogenic cysts and tumors. RESULTS: Histologically, the epithelial lining of the LPC contained an abundant amount of melanin granules throughout the entire epithelium. Ultrastructurally, epithelial cells contained mature melanosomes (stage IV melanosomes). Melanophages containing aggregates of melanosomes were identified in the connective tissue cyst wall. Perusal of the literature revealed that melanin pigmentation in odontogenic lesions is uncommon. Melanin has been reported in calcifying odontogenic cyst (18 cases), odontogenic keratocyst (8 cases), adenomatoid odontogenic tumor (3 cases), ameloblastic fibroma (3 cases), odontoma (2 cases), and ameloblastic fibro-odontoma, odonto-ameloblastoma, and odontogenic fibroma (1 case each). CONCLUSIONS: Almost all pigmented odontogenic lesions; occurred in Blacks and Asians; they are almost non-existent in Whites. Thus, racial pigmentation probably plays an important role in such lesions.

Adult↗
PubMed1998

Two visual pigments in a single photoreceptor cell: identification and histological localization of three mRNAs encoding visual pigment opsins in the retina of the butterfly Papilio xuthus.

This paper describes the localization of newly identified visual pigment opsins in the tiered retina of the Japanese yellow swallowtail Papilio xuthus. We first cloned three cDNAs encoding visual pigment opsins, PxRh1, PxRh2 and PxRh3, and then carried out histological in situ hybridization to localize their mRNAs in the retina. By combining the present data with our previous electrophysiological results, we concluded that both PxRh1 and PxRh2 correspond to visual pigments expressed in photoreceptor cells sensitive in the green wavelength region (green receptors), whereas PxRh3 corresponds to a pigment in red receptors. The in situ hybridization studies showed that some photoreceptor cells express two opsin mRNAs. In the ventral half of the eye, all green receptors in the distal tier were labelled by both PxRh1 and PxRh2 probes. The labelling by the PxRh2 and PxRh3 probes was detected throughout the eye in the proximal tier; in 18 % of ommatidia, the probes labelled the same photoreceptor cell. These results suggest that the possible co-localization of two different visual pigments will broaden the sensitivity spectrum of the photoreceptor cells.

Amino Acid Sequence↗
PubMedDate not supplied

Photodecomposition of Pigment Yellow 74, a pigment used in tattoo inks.

Tattooing has become a popular recreational practice among younger adults over the past decade. Although some of the pigments used in tattooing have been described, very little is known concerning the toxicology, phototoxicology or photochemistry of these pigments. Seven yellow tattoo inks were obtained from commercial sources and their pigments extracted, identified and quantitatively analyzed. The monoazo compound Pigment Yellow 74 (PY74; CI 11741) was found to be the major pigment in several of the tattoo inks. Solutions of commercial PY74 in tetrahydrofuran (THF) were deoxygenated using argon gas, and the photochemical reaction products were determined after exposure to simulated solar light generated by a filtered 6.5 kW xenon arc lamp. Spectrophotometric and high-pressure liquid chromatography (HPLC) analyses indicated that PY74 photodecomposed to multiple products that were isolated using a combination of silica chromatography and reversed-phase HPLC. Three of the major photodecomposition products were identified by nuclear magnetic resonance and mass spectrometry as N-(2-methoxyphenyl)-3-oxobutanamide (o-acetoacetanisidide), 2-(hydroxyimine)-N-(2-methoxyphenyl)-3-oxobutanamide and N,N''-bis(2-methoxyphenyl)urea. These results demonstrate that PY74 is not photostable in THF and that photochemical lysis occurs at several sites in PY74 including the hydrazone and amide groups. The data also suggest that the use of PY74 in tattoo inks could potentially result in the formation of photolysis products, resulting in toxicity at the tattoo site after irradiation with sunlight or more intense light sources.

Aniline Compounds↗
PubMed1999

Current understanding on the role of retinal pigment epithelium and its pigmentation.

Retinal pigment epithelium (RPE) is a monolayer of cuboidal cells that is strategically placed between the rod and cone photoreceptors and the vascular bed of the choriocapillaris. It has many important functions, such as phagocytic uptake and breakdown of the shedded photoreceptor membranes, uptake, processing, transport and release of vitamin A (retinol), setting up the ion gradients within the interphotoreceptor matrix, building up the blood-retina barrier, and providing all transport from blood to the retina and back. This short review focuses on the role of the pigment granules in RPE. Although the biology of the pigment granules has been neglected in the past, they do seem to be involved in many important functions, such as protection from oxidative stress, detoxification of peroxides, and binding of zinc and drugs, and, therefore, serve as a versatile partner of the RPE cell. Melanin plays a role in the development of the fovea and routing of optic nerves. New findings show that the melanin granules are connected to the lysosomal degradation pathway. Most of these functions are not yet understood. Deficit of melanin pigment is associated with age-related macula degeneration, the leading cause of blindness.

Age Factors↗
PubMed1993

Allotransplantation of rabbit retinal pigment epithelial cells double-labelled with 5-bromodeoxyuridine (BrdU) and natural pigment.

To facilitate identification of transplanted retinal pigment epithelial (RPE) cells, we sought to double-label the cells with 5-bromodeoxyuridine (BrdU) and with natural pigment. The BrdU is not lost during cell division but does require immunohistochemical methods for visualization; the pigment, on the other hand, allows immediate, obvious identification, but is gradually lost with cell division. Together they provide a convenient, long-term double label. Herein we report the successful allotransplantation of double-labelled RPE cells onto Bruch's membrane of albino rabbits. The labelled cells were localized by anti-BrdU antibody and the avidin biotin-alkaline phosphatase complex (ABC-AP) method, and by visible inclusions of pigment. Using this double-label method, allotransplanted RPE cells could be readily and reliably identified on the recipient Bruch's membrane eight months after transplantation. The cells had distinct basal and apical morphology, and were in close contact with the photoreceptor outer segments of the host. This successful allotransplantation raises the possibility that the subretinal space of the rabbit might enjoy some degree of immunologic privilege.

Animals↗
PubMedDate not supplied

Histochemistry of B663 pigmentation: ceroid-like pigmentation in macrophages.

Histochemical studies were made of pigmented cutaneous lesions from three cases of lepromatous leprosy treated with B663 to determine the nature and histogenesis of the brown pigmentation which develops as a side effect of the drug. One case of DDS-treated leprosy and four cases of untreated leprosy were also investigated histochemically as controls. The brown pigmentation of the skin is due to deposition of a ceroid-like substance in the macrophages, which is a yellowish-brown, acid-fast lipid pigment. It is insoluble in fat solvents and accepts lipid dyes even after lipid extraction by fat solvents. The macrophages in the B663-treated leprosy contain more neutral fat and less phospholipid than the untreated lepromatous leprosy tissues. Ceroid in the macrophages probably originated from unsaturated fatty acids of the leprosy bacilli through oxidation or their binding with the drug. Crystals of the drug were not found in the macrophages in this series, even on the tissues embedded in carbowax or frozen sections.

Ceroid↗