Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PIGMENTATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77Linked to original sources
PubMed1996

Characterization of non-pigmented Staphylococcus chromogenes.

A large number of non-pigmented Staphylococcus chromogenes were isolated from the skin of piglets with exudative epidermitis and healthy pigs. Their characteristics were homologous with S. chromogenes type strain, except for pigment production. Strains of non-pigmented S. chromogenes exhibited high levels of DNA homology with S. chromogenes type strain. The colony morphology and pigmentation of non-pigmented S. chromogenes was very similar to S. hyicus type strain, but their characteristics differ in hyaluronidase production, heat stable DNase, Tween 80 hydrolysis and bacitracin resistance. Further, DNA homology drew a distinction between non-pigmented S. chromogenes and S. hyicus type strain.

Animals↗
PubMed1999

Morphological study on pigmented cells in the horse testis.

One of the most attractive characteristics of a horse testis is the change of the weight during development. As the testicular weight changes and the number of Leydig cells decreases, pigments appear in interstitial tissues. In the present study, the characteristics of the pigments found in the interstitial tissues were examined histochemically and ultrastructurally. Specific stainings indicated that the pigmented granules showed almost all of the histological and histochemical characteristics of ceroid or ceroid-like pigment. The cells showed positive reaction for acid phosphatase while the pigmented cells contained a lot of lysosomes ultrastructurally. These results suggest that macrophages might phagocytize Leydig cells, and store their digested materials as ceroid-like pigment.

Animals↗
PubMed2004

Fuzzy logic for identifying pigments studied by Raman spectroscopy.

Fuzzy logic and linguistic variables are used for the automatic interpretation of Raman spectra obtained from pigments found in cultural heritage art objects. Featured bands are extracted from a Raman spectrum of a reference pigment and the methodology for constructing the library is illustrated. An unknown spectrum is then interpreted automatically and a process for identifying the corresponding pigment is described. A reference library consisting of 32 pigments was built and the effectiveness of the algorithm was tested by the Raman spectroscopic analysis of 10 pigments that are known to have been extensively used in Byzantine hagiography. Binary mixtures of these pigments were also tested. The algorithm's level of identification was good even though extra peaks, noise, and background signals were encountered in the spectra.

Journal Article↗
PubMed1999

Organisation of xanthophyll-lipid membranes studied by means of specific pigment antisera, spectrophotometry and monomolecular layer technique lutein versus zeaxanthin

The structure of the xanthophyll pigments lutein and zeaxanthin differs in the position of one double bond and refers to one of the ionon rings. Specific antibodies to zeaxanthin were used to analyse the localisation and orientation of these two xanthophyll pigments in lipid membranes formed with egg yolk lecithin. Bimolecular and monomolecular layers were used. Antibody-antigen interaction was demonstrated and analysed by the bathochromic shift of the absorption spectra of both pigments and by the increase of light-scattering of the pigmented liposome suspension. It appeared that the extent of the spectral effects accompanying the interaction of the antiserum to zeaxanthin, injected to the liposome suspension which was pigmented with either zeaxanthin or lutein, was different in spite of their similar molecular structures. The results are interpreted in terms of a localisation and distribution of lutein, in the hydrophobic phase of liposomes within two essentially different pigment pools, one oriented horizontally and the other vertically with respect to the membrane plane. This interpretation is supported by the analysis of isotherms of the compression of monomolecular layers of lutein and zeaxanthin formed at the air-water interface and of mixed xanthophyll-lipid monolayers as well as by analysis of the penetration of antibody proteins dissolved in the subphase into the mixed xanthophyll-lipid films.

Journal Article↗
PubMed1992

[Cutaneous pigmentation induced by minocycline: ultrastructural analysis and X-ray microanalysis].

The authors report a case of cutaneous pigmentation induced by minocycline. The patient (aged 59) presented with a bluish-grey pigmentation on her face, legs and nails. She had been receiving minocycline for 8 years for asthma. The cumulative dose was 400 g. Skin biopsy specimens from the pigmented areas were examined by light and electron microscopy. Light microscopy displayed hyperpigmentation with Fontana's stain in the dermis, macrophages and basal layer of the epidermis. Electron microscopy showed an increase in melanosomes within the basal keratinocytes, and dense granules in macrophages of the dermis. An X-ray microanalysis of the electron-dense granules showed the presence of larger quantities of iron and smaller quantities of sulphur and calcium. The different types of pigmentation are reviewed. Several pigments are thought to be responsible for the pigmentation but the underlying mechanism remains unclear.

Female↗
PubMed1992

Introduction of hydroxyl-bearing amino acids causes bathochromic spectral shifts in rhodopsin. Amino acid substitutions responsible for red-green color pigment spectral tuning.

Comparisons of the deduced amino acid sequences of eight primate photopigment genes led to the proposal that three amino acid substitutions produce the approximately 1,000 cm-1 difference in the absorption maxima of human red and green pigments (Neitz, M., Neitz, J., and Jacobs, G.H. (1991) Science 252, 971-974). We tested this proposal by mutating these three residues in rhodopsin and evaluating the effects on spectral properties. Nonpolar residues normally present in rhodopsin and in the green pigment were substituted by hydroxyl-bearing residues normally present in the red pigment. Two of these substitutions (Phe-261 to Tyr or Ala-269 to Thr) caused significant red shifts in the absorption maxima of the resulting mutant pigments. A third substitution (Ala-164 to Ser) caused only a slight effect. Combinations of substitutions caused additive shifts in absorption maxima. A double mutant (Phe-261 to Tyr/Ala-269 to Thr) displayed an absorption maximum that was red-shifted by 775 cm-1. Wavelength modulation in the visual pigments responsible for red-green color vision is likely to be governed by retinal-protein interactions involving primarily these two amino acid residues. Furthermore, interactions of hydroxyl-bearing amino acids with the chromophore may be a general mechanism of the opsin shift in visual pigments.

Amino Acid Sequence↗
PubMed1992

[Central areolar pigment epithelium dystrophy. Its differentiation from other dominant macular dystrophies].

Central areolar pigment epithelial dystrophy (CAPE dystrophy) is a rare, dominantly transmitted, dystrophy of the retinal pigment epithelium. The disease does not cause severe loss of function. This is partly due to the slightly eccentric localization of the dystrophy (the pigment epitheliopathy has a paramacular temporal localization). The disease is not progressive. Characteristic features are near-normal or normal visual acuity, undisturbed colour vision and normal ERG and EOG. Because of the eccentric position of the dystrophy, we suggest renaming this hereditary dystrophy of the macula as "paramacular areolar pigment epithelial dystrophy". The most important conditions that must be considered in the differential diagnosis are all dominantly inherited macular dystrophies. The most decisive criteria of paramacular areolar pigment epithelial dystrophy are good visual acuity, intact colour vision and normal electrophysiological findings. Because of the dominant transmission with high expressivity and high penetrance, it must be assumed that this dystrophy occurs more frequently than it is diagnosed. Because of the lack of complaints in patients it can easily be overlooked. However, the paramacular areolar pigment epithelial dystrophy should be included in every differential diagnosis of inherited macular dystrophy.

Adolescent↗
PubMed1985

Pigmented variant of calcifying odontogenic cyst. Report of an additional case and review of the literature.

A case of the pigmented variant of calcifying odontogenic cyst occurring in a 21-year-old Japanese male is reported, and a review of previously reported cases of the lesion is included. In addition to the characteristic histopathologic features of calcifying odontogenic cyst, dendritic cells containing melanin pigment were widely distributed in the epithelial layer and melanin pigment was also found in the epithelial cells including ghost cells in the present case. Although no conclusion could be drawn from the present examination as to the origin of melanin pigment in the calcifying odontogenic cyst, it is thought that the role of racial pigmentation is one of the important factors in occurrence of pigmented odontogenic lesions.

Adult↗
PubMed1982

[Corneal pigmentation after removal of the eye in Rana temporaria L. larvae].

Pigmentation of the cornea has been studied in the Rana temporaria larvae at the 22d-27th stages of development macroscopically (total corneal preparations with the surrounding skin) and microscopically. Dynamics of the pigment cells transfer that fill the transparent cornea is compared to the histological rearrangement of the latter. The corneal pigmentation is demonstrated to occur with a constant velosity and is well described by means of the linear regression equation. At initial stages of transformation, the corneal pigmentation overtakes the histological processes, then the two processes run in parallel and only towards the metamorphosis period the corneal histological changes slightly overtake the pigmentation process. As a whole, the pigment cells arrangement demonstrates the transformation degree of the external corneal into the skin after the eye has been extirpated. A suggestion is made explaining the necessity of a constant inducing retinal influence on the skin in Anura larvae.

Animals↗
PubMed1996

Cellular signalling in vertebrate pigment cells.

Chromatophores are specialized integumental stellate cells that synthesize and store pigments. Pigment granules are translocated within chromatophores of poikilothermic vertebrates and crustaceans in response to photic, thermal and/or neurohormonal stimuli, allowing the animal to rapidly change color for thermoregulation, adaptation to light and background, and social behavior display. Birds and mammals do not show color changes, but may present slow long-term responses, such as melanocyte proliferation, melanin synthesis and melanin granule translocation into feathers, hair and surrounding keratinocytes. Pigment translocation in lower vertebrates as well as pigment production in all vertebrates are modulated by a variety of hormones and neurotransmitters acting on transmembrane receptors located on the cell surface. Alpha-melanocyte-stimulating hormone (alpha-MSH), melanin-concentrating hormone (MCHA), melatonin and catecholamines are the most important pigment cell agonist in vertebrates. The major signalling pathway leading to pigment dispersion and melanin synthesis appears to be involve stimulation of adenylate cyclase followed by an increase in the cAMP level and activation of cAMP-dependent protein kinases (PKAs). Another melanogenesis-related intracellular pathway involves the activation of protein kinase C (PKC) by diacylglycerol, and the increase in cytosolic Ca2+ by inositol triphosphate. Growth factors such as basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF) and mast cell growth factor (MGF or KIT ligand), and UV radiation modulate the melanogenic and mitogenic processes in vertebrate melanocytes as well.

Adaptation, Physiological↗
PubMed1975

Rethingking human pigmentation.

Though pigmentation has been of interest to anthropologists for a long time, its inheritance, and particularly the reasons for the incomplete correlation of skin, hair and eye, is poorly understood. It is suggested that this is largely due to lack of genetically plausible hypotheses. Taking into account racial and individual variation in pigment traits, and knowledge of pigmentation in other mammals, a minimum set of genetic factors for pigmentation in man is suggested. These include: (1) a set of polygenes affecting skin color only; (2) one locus for depigmentation of the eye, not affecting skin or hair, (3) one pleiotropic gene for reduction of pigment at all sites, and (4) one or more loci with multiple alleles producing blondness or rufosity of the hair in symmetrical patterns over the body.

Eye Color↗
PubMed2002

Development of pigment cells in the zebrafish embryo.

In recent years, the zebrafish Danio rerio has emerged as a powerful model organism for the study of vertebrate embryogenesis. Zebrafish, like other vertebrates, possess pigment cells that arise from two distinct embryonic sources: those of the dermis and epidermis originate from the neural crest, while those that comprise the outermost layer of the retina, the retinal pigment epithelium or RPE, derive from the optic cup. A better understanding of processes behind the specification and differentiation of these cells will provide insight to the evolutionary diversification of all classes of vertebrates and will have clinical relevance to human disorders of pigmentation and certain retinopathies. In the first part of this review, the present knowledge of the ontogeny of both of these populations of pigment cells in the embryonic zebrafish is summarized, in terms of both genetics and molecular markers. The final part of the review focuses on duplicate zebrafish genes encoding orthologs of the basic helix-loop-helix/leucine zipper protein Mitf (Microphthalmia-associated transcription factor), and presents a hypothesis concerning their divergent roles in neural crest and retinal pigment cells.

Animals↗
PubMed1995

Pigmentation-dependent side effects to copper vapor laser and argon laser treatment.

BACKGROUND AND OBJECTIVE: Melanin is a limiting factor for obtaining beneficial results in dermatological treatment of vascular malformations. The aim of our study was to establish a relation between pretreatment skin pigmentation and the occurrence of side effects. STUDY DESIGN/MATERIALS AND METHODS: Thirteen human volunteers selected to have a varying degree of skin pigmentation were laser-treated on the inside of the brachium with an argon laser (AL, 488 nm and 514.5 nm) and a copper vapor laser (CVL, 578 nm), both connected to a Hexascan. Total exposure areas were 1.26 cm2 and beam diameters were 1 mm. Three intensities were used, 0.7, 1.0, and 1.3 W. Pulse duration was 200 ms, resulting in fluences of 17.8, 25.5, and 33.1 J/cm2. Pretreatment skin pigmentation was objectified by skin reflectance measurements. RESULTS: At 1, 2, and 6 months after laser treatment, significant correlations were demonstrated between pretreatment skin pigmentation and laser-induced pigmentary changes and scar formation. At the 6-month assessment, the AL induced significantly higher scores of clinically evaluated scar formation as compared with the CVL (1.0 and 1.3 W/spot) and tended to induce higher clinical scores of pigmentary changes (not significant, ns). CONCLUSIONS: We recommend skin pigmentation to be taken into consideration in dermatological laser treatment of vascular malformations.

Adult↗
PubMed1977

Pigmented preretinal membranes.

Continuous growth and an increase in pigmentation of a preretinal membrane occurred in a 46-year-old woman after a scleral buckling procedure for rhegmatogenous retinal detachment. Ten additional patients had pigmented preretinal membranes in eyes treated for rhegmatogenous retinal detachment. Although we made no attempts to determine the incidence of pigmented preretinal membrane formation in eyes with retinal detachments, these 11 cases, in a consecutive series of 500 eyes treated for rhegmatogenous retinal detachment, indicated that the development of pigmented preretinal membranes is not uncommon. Our clinical observations supported recent experimental findings implicating retinal pigment epithelial cells as a cause of preretinal membrane formation.

Female↗
PubMed1989

Development of lipofuscin-like fluorescence in the retinal pigment epithelium in response to protease inhibitor treatment.

Experiments were conducted to determine whether photoreceptor outer segment components contain precursors for lipofuscin fluorophores that accumulate in the retinal pigment epithelium (RPE) during senescence. Intravitreal injection of the lysosomal protease inhibitor leupeptin caused a rapid accumulation of inclusions with lipofuscin-like autofluorescence in the RPE of albino rats. These inclusions appeared to be derived from photoreceptor outer segments, which are normally phagocytosed and degraded by the RPE. The tripeptide leu-gly-gly, which is similar to leupeptin except that it does not inhibit proteolysis, had no effect on RPE autofluorescent pigment content. Likewise, netilmicin, a purported inhibitor of lysosomal phospholipases, did not enhance autofluorescent pigment deposition in the RPE. These findings are consistent with other experiments suggesting that RPE age-pigment fluorophores are derived from molecular components of the photoreceptor outer segments. The effect of leupeptin suggests that outer segment proteins may be among the precursors for these fluorophores. The RPE appears to differ from other cell types that accumulate lipofuscin in that the majority of the precursors for this pigment in the RPE are taken up by phagocytosis rather than being generated within the cells themselves.

Aging↗
PubMed2006

Pigmented episcleral deposits after brachytherapy of uveal melanoma.

PURPOSE: To describe the characteristics and evolution of pigmented episcleral deposits after brachytherapy for uveal melanoma to determine their origin and association with melanoma-related mortality. DESIGN: Noncomparative case series. PARTICIPANTS: Two hundred eleven patients (108 males, 103 females; median age, 61 years; range, 14-88 years) who were treated with a single ruthenium and iodine plaque therapy (median dose to tumor base, 475 Gy and 392 Gy, respectively) for a choroidal and ciliary body melanoma. Median tumor diameter and height were 12 mm and 5.5 mm, respectively. Eighty-eight patients were treated prospectively during the study. METHODS: The number and location of pigmented episcleral deposits were recorded under the slit lamp during each visit after brachytherapy. The association of the deposits with tumor characteristics and survival was analyzed with logistic regression and Kaplan-Meier analysis, respectively. MAIN OUTCOME MEASURES: Number and location of episcleral deposits, melanoma-related mortality. RESULTS: The pigmented episcleral deposits ranged from black and brownish spots to slightly thickened patches. Most deposits appeared within the first 6 months after brachytherapy. By 1 year, 85% (95% confidence interval, 77-93) of eyes had at least 1 deposit (median, 6). The deposits increased in number until 7 years from irradiation, and decreased with increasing distance from tumor center. An association between the number of deposits at 1 and 2 years and subsequent melanoma-related mortality could not be confirmed (P = 0.80 and P = 0.31, respectively). CONCLUSIONS: Pigmented macrophage-related episcleral deposits are found in most eyes with uveal melanoma after brachytherapy. Their association with plaque size and isotope rather than with tumor size suggests that radiation atrophy of retinal pigment epithelium and choroid in addition to tumor regression contributes to the formation of the deposits. Knowledge of their existence may save patients from unnecessary enucleation.

Adolescent↗
PubMed1987

Foveal cone pigments and sensitivity in young patients with Usher's syndrome.

Psychophysical and reflection retinal densitometric techniques were used to investigate foveal function of three patients (ages 14, 16, and 19 years) with Usher's syndrome who had good central visual acuity and, by ophthalmoscopic examination, normal foveal areas. During dark adaptation foveal sensitivity and its relation to proportion of cone pigment present were normal, but the kinetics of regeneration of the pigments were markedly abnormal. Measurements were made to consider the possibilities that the disorders of regeneration were associated with altered light-catching capacities of the patients' cone pigments, deranged transport of visual cycle substances between the retinal pigment epithelium and photoreceptors, or lingering photoproducts. None of the mechanisms fully accounted for the observed kinetics. The results suggested that abnormal kinetics of regeneration are among the earliest signs of malfunction of the foveal photoreceptor-pigment epithelial complex in some of the retinal degenerative disorders.

Adolescent↗
PubMed1980

Lipofuscin of human retinal pigment epithelium.

Analysis of the fluorescent spectra of chloroform-methanol extracts of human retinal pigment epithelium confirmed the presence of lipofuscin pigments in the pigment epithelium of older individuals. Similar fractions in the pigment epithelium of young individuals were present in insufficient quantities for spectral analysis. Electron microscopy of the pigment epithelium of these eyes showed few or no lipofuscin granules in young eyes but large numbers in older eyes.

Adult↗