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 1,189 records · Page 66Linked to original sources
PubMed2002

Pigmentation and mate choice in Drosophila.

Many species of the fruitfly Drosophila are either sexually dimorphic for abdominal pigmentation (the posterior segments in males are black and those of females have thin dark stripes) or sexually monomorphic for this pigmentation (both sexes show striping). Kopp et al. report a correlation in two Drosophila clades between the expression of the bric-à-brac (bab) gene, which represses male-specific pigmentation in D. melanogaster females, and the presence of sexually dimorphic pigmentation. They suggest that sexual selection acted to produce sexual dichromatism in Drosophila by altering the regulation of bab, on the grounds that D. melanogaster males show a strong mate preference for females with lightly pigmented abdomens, and that this discrimination helps to maintain sexual dichromatism by preventing males from wasting time by courting other (darkly pigmented) males. Here we show that the mate discrimination observed by Kopp et al. may in fact have resulted from the nature of the strains and comparisons they used in their study and so could be irrelevant to mate choice in nature.

Abdomen↗
PubMed1999

Position of a 'green-red' hybrid gene in the visual pigment array determines colour-vision phenotype.

The X-linked red- and green-pigment genes are arranged in a head-to-tail tandem array. The colour-vision defect of deuteranomaly (in 5% of males of European descent) is associated with a 5'-green-red-3' visual-pigment hybrid gene, which may also exist in males with normal colour vision. To explain why males with a normal red, a normal green and a green-red hybrid gene may have either normal or deutan colour vision, we hypothesized that only the first two genes are expressed and deuteranomaly results only if the green-red hybrid gene occupies the second position and is expressed preferentially over normal green-pigment genes occupying more distal positions. We used long-range PCR amplification and studied 10 deutan males (8 deuteranomalous and 2 deuteranopic) with 3 visual pigment genes (red, green and green-red hybrid) to investigate whether position of the hybrid gene in the array determined gene expression. The green-red hybrid gene was always at the second position (and the first position was always occupied by the red gene). Conversely, in two men with red, green and green-red hybrid genes and normal colour vision, the hybrid gene occupied the third position. When pigment gene mRNA expression was assessed in post-mortem retinae of three men with the red, green and green-red genotype, the green-red hybrid gene was expressed only when located in the second position. We conclude that the green-red hybrid gene will only cause deutan defects when it occupies the second position of the pigment gene array.

Color Perception↗
PubMed1985

A plasmid for diffusible pigment production in Staphylococcus aureus.

Production of diffusible pigment in a strain of Staphylococcus aureus (WG260) has been associated with a plasmid of c.26 megadaltons which can be co-transduced with inducible erythromycin and spectinomycin resistance. However, the diffusible pigment plasmid can be lost from the transductants without loss of inducible erythromycin and spectinomycin resistance. The evidence suggests that the resistance determinants are located on an element similar or identical to transposon Tn554, and, during transduction of the diffusible pigment plasmid, a copy of the resistance determinants always inserts into the chromosome of the transductant. This is the first report of such an element occurring on a plasmid in a clinical isolate of S. aureus. To date, the diffusible pigment plasmid has been isolated only as the open-circular conformation of plasmid DNA and is probably a highly relaxable plasmid. The production of the orange, diffusible pigment was shown to be independent of colony pigmentation.

Chromosome Mapping↗
PubMed2006

Genetics, development and evolution of adaptive pigmentation in vertebrates.

The study of pigmentation has played an important role in the intersection of evolution, genetics, and developmental biology. Pigmentation's utility as a visible phenotypic marker has resulted in over 100 years of intense study of coat color mutations in laboratory mice, thereby creating an impressive list of candidate genes and an understanding of the developmental mechanisms responsible for the phenotypic effects. Variation in color and pigment patterning has also served as the focus of many classic studies of naturally occurring phenotypic variation in a wide variety of vertebrates, providing some of the most compelling cases for parallel and convergent evolution. Thus, the pigmentation model system holds much promise for understanding the nature of adaptation by linking genetic changes to variation in fitness-related traits. Here, I first discuss the historical role of pigmentation in genetics, development and evolutionary biology. I then discuss recent empirically based studies in vertebrates, which rely on these historical foundations to make connections between genotype and phenotype for ecologically important pigmentation traits. These studies provide insight into the evolutionary process by uncovering the genetic basis of adaptive traits and addressing such long-standing questions in evolutionary biology as (1) are adaptive changes predominantly caused by mutations in regulatory regions or coding regions? (2) is adaptation driven by the fixation of dominant mutations? and (3) to what extent are parallel phenotypic changes caused by similar genetic changes? It is clear that coloration has much to teach us about the molecular basis of organismal diversity, adaptation and the evolutionary process.

Adaptation, Biological↗
PubMed2004

Divergent mechanisms for the tuning of shortwave sensitive visual pigments in vertebrates.

Of the four classes of vertebrate cone visual pigments, the shortwave-sensitive SWS1 class shows the shortest lambda(max) values with peaks in different species in either the violet (390-435 nm) or ultraviolet (around 365 nm) regions of the spectrum. Phylogenetic evidence indicates that the ancestral pigment was probably UV-sensitive (UVS) and that the shifts between violet and UV have occurred many times during evolution. This is supported by the different mechanisms for these shifts in different species. All visual pigments possess a chromophore linked via a Schiff base to a Lys residue in opsin protein. In violet-sensitive (VS) pigments, the Schiff base is protonated whereas in UVS pigments, it is almost certainly unprotonated. The generation of VS from ancestral UVS pigments most likely involved amino acid substitutions in the opsin protein that serve to stabilise protonation. The key residues in the opsin protein for this are at sites 86 and 90 that are adjacent to the Schiff base and the counterion at Glu113. In this review, the different molecular mechanisms for the UV or violet shifts are presented and discussed in the context of the structural model of bovine rhodopsin.

Amino Acid Substitution↗
PubMed1998

The measurement of constitutive and facultative skin pigmentation and estimation of sun exposure in Caucasians with basal cell carcinoma and cutaneous malignant melanoma.

In two identical and simultaneously performed case-control studies of basal cell carcinoma (BCC) and cutaneous malignant melanoma (CMM) with age-matched, sex-matched and residence-matched controls, skin pigmentation was measured objectively by skin reflectance spectroscopy in 145 BCC patients and 174 matched controls and in 168 CMM patients and 176 matched controls. Measurements were performed at the forehead, the upper chest, the upper back, the lateral and medial aspects of the upper arm, and the buttocks. Self-estimation of sun exposure in childhood, in youth and in adulthood was performed by all subjects. There were no statistically significant differences in constitutive skin pigmentation at the buttocks between BCC patients and controls (P = 0.96) or between CMM patients and controls (P = 0.13). Facultative skin pigmentation in ultraviolet-exposed sites was not significantly different between BCC patients and controls except that women patients had higher pigmentation at the lateral side of the upper arm. For CMM, men patients had higher pigmentation at the lateral side of the upper arm. Self-estimations of sun exposure did not show differences between patients and controls but indicated high exposure levels in childhood and youth and in adult leisure time. Sun exposure estimated by increase in facultative pigmentation above the constitutive level (the Sun Exposure Index) was not significantly different between BCC patients and controls, whereas CMM men patients had higher estimates for the lateral side of the upper arm, the chest and the back.

Adolescent↗
PubMed2000

Growth, pigment production and protease activity of Monascus purpureus as affected by salt, sodium nitrite, polyphosphate and various sugars.

The effect of different levels of salt, sodium nitrite, polyphosphate and various sugars on growth, pigment production, protease activity and culture pH caused by Monascus purpureus was studied in broth medium and ground meat. The addition of sodium chloride (> 50.0 g l(-1)) and polyphosphate (> 3.0g l(-1)) to broth medium decreased mycelial growth, pigment production and protease activity of M. purpureus, whereas low concentrations of sodium nitrite (< 0.2 g l(-1)) promoted mycelial growth and pigment production. When the basal medium and ground meat contained salt, 150.0 g l(-1), the mould growth was stopped. The medium with fructose as carbon source proved to be the most suitable for mycelium growth and pigment production, with maltose and glucose being the second most productive. When sucrose and lactose were used as carbon sources, mycelium growth and pigment production were inhibited but the protease activity increased significantly. The mould showed more tolerance to salt and polyphosphate in ground meat than in broth medium and used sucrose as a carbon source as well as glucose for growth and pigment production in the meat mixture.

Animals↗
PubMed1999

Unbiased morphometrical measurements show loss of pigmented nigral neurones with ageing.

This study used the dissector method to evaluate pigmented nigral neuronal loss in the substantia nigra pars compacta with age. Dissector counts can be used to estimate the absolute and accurate total neurone numbers. In addition, the area and diameter of the neuronal cell body was estimated by using a computerized morphometric analysis in a single section of the substantia nigra pars compacta. Brain samples from 26 people with an age range from 17 to 90 years were studied. A significant decrease in the total number of pigmented neurones (r=-0.83, P<0.001) and their density (r=-0.83, P<0.001) with age was found in the substantia nigra pars compacta. The number of pigmented neurones counted from a single section also showed an age-dependent decline (r=-0.76, P<0.001). According to the regression equations, the total number of pigmented neurones estimated by dissector counts decreased by 9.8% per decade and the neuronal density decreased by 7.4% per decade. The area of the neuronal cell body decreased by 3.2% per decade. This latter change corresponds to an approximate 4.4% decrease per decade in neuronal volume. These findings show that both the number of pigmented neurones and their size in the substantia nigra pars compacta decreases with age. However, the reductions in the total number of pigmented neurones are more dramatic than the reduction in neurone size with ageing.

Adolescent↗
PubMed2000

Oral pigmentation.

Oral pigmentation may be physiological or pathological in nature. It may represent a localized anomaly of limited significance or the presentation of potentially life-threatening multisystem disease. Evaluation of a patient with oral pigmentation requires a systematic approach with resource to appropriate investigations in certain circumstances. A full history of evolution of the pigmentary changes, as well as inquiring into family history, drug ingestion and systemic symptoms of concurrent disease are clearly important in the assessment. The duration, pattern, hue and distribution of colour changes can provide useful diagnostic clues. Special attention is given to newly appearing lesions, or those that have changed significantly in appearance, and biopsy may be needed to validate the clinical impression. This review should enable the reader to increase their familiarity with the assessment of oral pigmentation, the common causes of oral pigmentary change and the rarer disorders of pigmentation seen in this area. The systemic diseases that may give rise to oral pigmentation are detailed and the early signs of oral melanoma are highlighted, as well as the drugs which may cause pigmentary changes in this area and the different pattern of pigmentation they may induce.

Biopsy, Needle↗
PubMed2001

Polysaccharide production by a reduced pigmentation mutant of Aureobasidium pullulans NYS-1.

AIMS: To isolate a reduced pigmentation mutant of Aureobasidium pullulans NYS-1 and characterize its cellular pigmentation plus its polysaccharide and biomass production relative to carbon source. METHODS AND RESULTS: Cellular pigmentation, polysaccharide levels and biomass production by the isolated mutant NYSRP-1 were analysed relative to carbon source. Cellular pigmentation of the mutant was lower than its parent strain using either carbon source. The mutant elaborated higher polysaccharide levels on sucrose than on corn syrup. The pullulan content of the polysaccharide synthesized and biomass production by the mutant rose as the carbon source concentration was increased. CONCLUSION: It is feasible to isolate a reduced pigmentation mutant from strain NYS-1 that exhibits elevated polysaccharide production using corn syrup as a carbon source. SIGNIFICANCE AND IMPACT OF THE STUDY: The mutant provides an advantage for commercial pullulan production because of its reduced pigmentation and enhanced polysaccharide synthesis.

Biomass↗
PubMed2002

Treatment of pigmented hypertrophic scars with the 585 nm pulsed dye laser and the 532 nm frequency-doubled Nd:YAG laser in the Q-switched and variable pulse modes: a comparative study.

BACKGROUND: Pigmented hypertrophic scars are a difficult condition to treat. They may result from traumatic injuries or from surgical and cosmetic procedures. The 585 nm flashlamp-pumped pulsed dye laser (FLPDL) has been used to treat this condition, with significant improvement of varying degrees. It remains to be determined whether other laser modalities may have a similar or even greater success in the treatment of pigmented hypertrophic scars. OBJECTIVE: To determine the efficacy of the 532 nm frequency-doubled Nd:YAG laser in the treatment of pigmented hypertrophic scars as compared to the 585 nm FLPDL. METHODS: Six patients with pigmented hypertrophic scars and skin phototypes II-IV were chosen. A scar was selected for treatment in each patient and divided into four equal 2 cm segments. Three segments were each treated with a different laser modality and one was left untreated to serve as the control. A 585 nm FLPDL was used with an energy of 3.5 J, a pulse duration of 450 microsec, and a 10 mm spot size. A 532 nm Q-switched frequency-doubled Nd:YAG laser was set to an energy of 2.8 J, a 10-nsec pulse, and a 3 mm spot size. The same 532 nm laser was set to the variable pulse mode to treat a 2 cm scar segment, with an energy of 9.5 J, a 10-msec pulse, and a 4 mm spot size. An average of 3.3 treatments were performed on each scar segment, at intervals of 4-6 weeks and long-term follow-up at 22 weeks. Treatment outcome was graded by a blind observer using the Vancouver General Hospital (VGH) Burn Scar Assessment Scale. A SigmaStat t-test was used to determine the statistical significance of the values obtained. RESULTS: Treatment of pigmented hypertrophic scars with the 532 nm Q-switched Nd:YAG laser led to a significant improvement of 38% in the VGH scores when compared to baseline (P =.005). The 585 nm FLPDL also had a favorable effect on the scars, with an average improvement of 36.1% in the VGH scores. There was no significant difference noted between the outcome of treatment with either of these two lasers. Treatment with the 532 nm variable pulse Nd:YAG laser led to a 19% improvement in the VGH scores of scars, which did not differ significantly from the 16.1% improvement observed in control scars on the last follow-up visit. No side effects or complications from treatment were noted or reported during the course of the study. At the conclusion of the study, five of six patients chose the segment treated with the 532 nm Q-switched Nd:YAG laser as the best segment overall. CONCLUSION: The 532 nm Q-switched Nd:YAG laser and the 585 nm FLPDL offer comparable favorable results in the treatment of pigmented hypertrophic scars. The 532 nm Q-switched Nd:YAG laser may be preferred by patients particularly distressed by the dark color of their scars.

Adolescent↗
PubMed2003

Lightening effect on ultraviolet-induced pigmentation of guinea pig skin by oral administration of a proanthocyanidin-rich extract from grape seeds.

Antioxidants such as vitamins C and E have been reported to inhibit the progression of ultraviolet (UV) radiation-induced pigmentation in the skin of hairless mice. However, little is known of the lightening effect of proanthocyanidin, a powerful polyphenolic antioxidant, on UV-induced pigmentation of the skin. We investigated the lightening effect of oral administration of a proanthocyanidin-rich grape seed extract (GSE) using guinea pigs with UV-induced pigmentation. These pigmented guinea pigs were fed diets containing 1% GSE or 1% vitamin C (w/w) for 8 weeks. GSE-feeding had an apparent lightening effect on the guinea pigs' pigmented skin. Histologic evaluation demonstrated a decrease in the number of 3,4-dihydroxyphenylalanine (DOPA)-positive melanocytes as well as 8-hydroxy-2'-deoxyguanosine (8-OHdG)-positive, Ki-67-positive, proliferating cell nuclear antigen (PCNA)-positive melanin-containing cells in the basal epidermal layer of the UV-irradiated skin in GSE-fed guinea pigs. In contrast, these parameters did not change in the skin of vitamin C-fed or control guinea pigs. GSE inhibited the activity of mushroom tyrosinase and also inhibited melanogenesis without inhibiting the growth of cultured B16 mouse melanoma cells. In conclusion, we demonstrated that oral administration of GSE is effective in lightening the UV-induced pigmentation of guinea pig skin. This effect may be related to the inhibition of melanin synthesis by tyrosinase in melanocytes and the reactive oxygen species (ROS)-related proliferation of melanocytes.

Administration, Oral↗
PubMed2004

Comparison of long-term survival of pigmented epidermal reconstructs cultured in vitro vs. xenografted on nude mice.

Epidermal reconstructs incorporating pigment cells have been used in vitro over the last decade to study the physiology of the epidermal melanin unit. However, the major limitation of this technology is the duration of the assays, which need to be completed within 2-3 weeks to obviate the problem of epidermal senescence and excessive terminal differentiation. This becomes a major problem for studying long-term biological phenomena in photoprotection and epidermal skin cancers. We report here a simplified surgical technique in immunotolerant mice allowing long-term studies. The creation of a vascularized mouse skin flap is the key point of the surgical procedure. Long-term pigmentation of the xenografts seemed macroscopically successful, but surprisingly microscopy at 11 and 16 weeks postgrafting showed mostly dermal pigment aggregates and rare Melan-A positive dermal and epidermal pigment cells. In the same reconstructs maintained in vitro, dermal pigment and dermal pigment cells were never noted. It could be speculated that in our model, the colonization of the xenografted dead human dermis by murine cells influences melanocyte survival.

Animals↗
PubMed2001

[Diagnosis and differential diagnosis of the combined hamartoma of the retina and retinal pigment epithelium].

BACKGROUND: The combined hamartoma of the retina and the retinal pigment epithelium (CHR-RPE) is an important differential diagnosis of retinal and choroidal diseases with variable degrees of pigmentation. PATIENTS: The clinical picture and typical fluorescence angiography findings of two adult patients who were first diagnosed to have a combined hamartoma of the retina and retinal pigment epithelium are presented. The referral diagnosis macular pucker and malignant melanoma of the choroid, respectively, are discussed regarding severe therapeutic interventions such as pars plana vitrectomy with membrane peeling (macular pucker), and radiotherapy, or enucleation (malignant melanoma of the choroid) as well as other important differentials. RESULTS: The combined hamartoma of the retina and the retinal pigment epithelium is a benign congenital, mostly unilateral retinal lesion. The presenting symptom is a painless, unilateral, often silent loss of vision. Histologically, three cell populations can be identified: glial, vascular, and pigmented cells. Variations in composition of these three cell types are responsible for the heterogeneous clinical picture and thus diagnostic challenges. The greyish retinal tumor located peripapillary in most cases with varying degrees of pigmentation and surrounding vascular tortuosity can result in secondary changes at the vitreoretinal interface with deterioration of vision. Combined fluorescein-/indocyaningreen angiography and ultrasound are crucial for diagnostic evaluation. Documentation and regular clinical follow-up examinations are essential for successful management of this disorder. CONCLUSION: Recognition of this rare clinical entity is crucial for administering the appropriate therapy.

Adult↗
PubMed2006

Is pigmentation important for face recognition? Evidence from contrast negation.

It is extraordinarily difficult to recognize a face in an image with negated contrast, as in a photographic negative. The variation among faces can be partitioned into two general sources: (a) shape and (b) surface reflectance, here termed 'pigmentation'. To determine whether negation differentially affects the processing of shape or pigmentation, we made two sets of faces where the individual faces differed only in shape in one set and only in pigmentation in the other. Surprisingly, matching performance was significantly impaired by contrast negation only when the faces varied in pigmentation. This provides evidence that the perception of pigmentation, not shape, is selectively disrupted by negation and, by extension, that pigmentation contributes to the neural representation of face identity.

Adolescent↗
PubMed1986

Pigmented spots in the wool-bearing skin on white merino sheep induced by ultraviolet light.

Black-grey pigmented skin spots, some of which contained pigmented wool fibres, were observed in a flock of 8.5-year-old white Merino ewes. The spots were concentrated along the backline and increased in number following shearing, suggesting exposure to sunlight to be of importance in the development of these non-congenital pigmented skin spots in genetically white Merino sheep. To test the effect of ultraviolet light, white Merino sheep, ranging in age from 3 to 8 years, had a closely clipped midside area of wool-bearing skin irradiated on each of 28 consecutive days. Pigmented skin spots developed in 6 of the 16 white Merino sheep irradiated. Spots first appeared after 10 days of irradiation, the number subsequently increasing with time, and two skin spots were found to contain sparse numbers of black-grey pigmented wool fibres. Histological examination showed both the naturally occurring and irradiation-induced pigmented skin spots resulted from an increase in both number and activity of melanocytes localized along the epidermal-dermal border of the epidermis. With time, the melanocytes were observed to have entered, to varying depths, the outer-root sheath of follicles still producing white wool fibres. These ultraviolet-light-induced changes to epidermal melanocytes in white Merino sheep presumably occur due to alterations within the local tissue environment in which the melanocytes lie.

Aging↗
PubMed2002

Role of a locus control region in the mutually exclusive expression of human red and green cone pigment genes.

Trichromacy in humans and other Old World primates evolved from a dichromatic color vision system approximately 30-40 million years ago. One essential part of this evolution was the duplication and divergence of sequences on the X chromosome to create the present-day red and green cone pigment genes. Earlier work demonstrated that a locus control region (LCR) located upstream of these genes is essential for their expression. In the present work, we have generated a variety of modified human red and green pigment gene arrays that direct the expression of distinguishable histochemical reporters from each gene promoter. Transgenic mice carrying a single copy of each modified array were studied to define the role of three variables in producing mutually exclusive expression of red and green pigment transgenes: the distance between the promoter and the LCR, the identity of the visual pigment promoter, and LCR copy number. The results support a model in which the mutually exclusive expression of these genes in their respective cone types is controlled by competition between visual pigment promoters for pairing with the LCR, and they suggest a facile mechanism for the evolution of trichromacy after visual pigment gene duplication.

Animals↗
PubMed2004

Vertebrate ultraviolet visual pigments: protonation of the retinylidene Schiff base and a counterion switch during photoactivation.

For visual pigments, a covalent bond between the ligand (11-cis-retinal) and receptor (opsin) is crucial to spectral tuning and photoactivation. All photoreceptors have retinal bound via a Schiff base (SB) linkage, but only UV-sensitive cone pigments have this moiety unprotonated in the dark. We investigated the dynamics of mouse UV (MUV) photoactivation, focusing on SB protonation and the functional role of a highly conserved acidic residue (E108) in the third transmembrane helix. On illumination, wild-type MUV undergoes a series of conformational changes, batho --> lumi --> meta I, finally forming the active intermediate meta II. During the dark reactions, the SB becomes protonated transiently. In contrast, the MUV-E108Q mutant formed significantly less batho that did not decay through a protonated lumi. Rather, a transition to meta I occurred above approximately 240 K, with a remarkable red shift (lambda(max) approximately 520 nm) accompanying SB protonation. The MUV-E108Q meta I --> meta II transition appeared normal but the MUV-E108Q meta II decay to opsin and free retinal was dramatically delayed, resulting in increased transducin activation. These results suggest that there are two proton donors during the activation of UV pigments, the primary counterion E108 necessary for protonation of the SB during lumi formation and a second one necessary for protonation of meta I. Inactivation of meta II in SWS1 cone pigments is regulated by the primary counterion. Computational studies suggest that UV pigments adopt a switch to a more distant counterion, E176, during the lumi to meta I transition. The findings with MUV are in close analogy to rhodopsin and provides further support for the importance of the counterion switch in the photoactivation of both rod and cone visual pigments.

Amino Acid Sequence↗