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PubMed1983

Firm structural associations between migratory pigment granules and microtubules in crayfish retinula cells.

The morphology of associations between mobile pigment granules and microtubules of the crayfish retinula cells was examined with transmission electron microscopy. Many pigment granules were found associated with microtubules through linkages of fuzzy appearance in thin sections. The linkages were revealed as discrete strands of variable shape in rotary-shadowed replicas of freeze-fractured and deep-etched specimens. The only feature of constant morphology among these connections consisted of 2-4-nm filaments projecting laterally from the microtubules. The firmness of the pigment granule-microtubule associations was judged by their ability to hold up during cell disruption procedures of increasing disaggregation effects in a low-Ca++ stabilization buffer. The results of these tests were inspected with scanning electron microscopy and with transmission electron microscopy of negatively stained preparations. Numerous pigment granules remained associated with a stable microtubule framework after the plasma membrane had been stripped away. Moreover, granule-microtubule attachments survived breakdown of this framework into free fascicles of microtubules. The pigment granules were associated with the free microtubules either individually or as clusters entangled in a fibrous material interwoven with 10-nm filaments. These findings attest that many pigment granules are bound to microtubules through linkages that constitute effective attachments. Further, it is demonstrated that a highly cohesive substance associates the pigment granules with one another. These conclusions are discussed in terms of a pigment transport mechanism in which a network of interconnected granules would establish firm transient interactions with a supporting skeleton of microtubules.

Animals↗
PubMed1974

Pigment migration and adaptation in the eye of the squid, Loligo pealei.

The migration of the screening pigment was investigated in the retina of the intact squid. The action spectrum of pigment migration corresponds to the action spectrum of the visual pigment, rhodopsin, rather than to the absorption spectrum of the screening pigment. The total number of quanta required for a fixed criterion of pigment migration is the same, when the quanta are delivered over any period of time from 6 s to an hour or more. When less than 3-10% of the rhodopsin is isomerized, the screening pigment migrates out to the tips of the receptors with a time-course of 5-15 min, and back again over the same period of time. When rather more than 10% is isomerized, the outward migration takes 5-15 min, but the screening pigment does not migrate inwards, even after several hours in the dark. Indirect evidence suggests that the band of screening pigment, when it reaches the tips of the receptors, is approximately equivalent to a filter of 0.6 log units. The spectral sensitivity of the optic nerve response was measured, and was found to be broader than the absorption spectrum of squid rhodopsin in vitro; the broadness could be explained by self-screening, assuming a density of rhodopsin of 0.6 log units at 500 nm.

Animals↗
PubMed1979

The contribution of a sensitizing pigment to the photosensitivity spectra of fly rhodopsin and metarhodopsin.

Most of the photoreceptors of the fly compound eye have high sensitivity in the ultraviolet (UV) as well as in the visible spectral range. This UV sensitivity arises from a photostable pigment that acts as a sensitizer for rhodopsin. Because the sensitizing pigment cannot be bleached, the classical determination of the photosensitivity spectrum from measurements of the difference spectrum of the pigment cannot be applied. We therefore used a new method to determine the photosensitivity spectra of rhodopsin and metarhodopsin in the UV spectral range. The method is based on the fact that the invertebrate visual pigment is a bistable one, in which rhodopsin and metarhodopsin are photointerconvertible. The pigment changes were measured by a fast electrical potential, called the M potential, which arises from activation of metarhodopsin. We first established the use of the M potential as a reliable measure of the visual pigment changes in the fly. We then calculated the photosensitivity spectrum of rhodopsin and metarhodopsin by using two kinds of experimentally measured spectra: the relaxation and the photoequilibrium spectra. The relaxation spectrum represents the wavelength dependence of the rate of approach of the pigment molecules to photoequilibrium. This spectrum is the weighted sum of the photosensitivity spectra of rhodopsin and metarhodopsin. The photoequilibrium spectrum measures the fraction of metarhodopsin (or rhodopsin) in photoequilibrium which is reached in the steady state for application of various wavelengths of light. By using this method we found that, although the photosensitivity spectra of rhodopsin and metarhodopsin are very different in the visible, they show strict coincidence in the UV region. This observation indicates that the photostable pigment acts as a sensitizer for both rhodopsin as well as metarhodopsin.

Animals↗
PubMedDate not supplied

The influence of carotenoid acquisition and utilization on the maintenance of species-typical plumage pigmentation in male American goldfinches (Carduelis tristis) and northern cardinals (Cardinalis cardinalis).

Birds display a tremendous variety of carotenoid-based colors in their plumage, but the mechanisms underlying interspecific variability in carotenoid pigmentation remain poorly understood. Because vertebrates cannot synthesize carotenoids de novo, access to pigments in the diet is one proximate factor that may shape species differences in carotenoid-based plumage coloration. However, some birds metabolize ingested carotenoids and deposit pigments that differ in color from their dietary precursors, indicating that metabolic capabilities may also contribute to the diversity of plumage colors we see in nature. In this study, we investigated how the acquisition and utilization of carotenoids influence the maintenance of species-typical plumage pigmentation in male American goldfinches (Carduelis tristis) and northern cardinals (Cardinalis cardinalis). We supplemented the diet of captive goldfinches with red carotenoids to determine whether males, which are typically yellow in color, were capable of growing red plumage. We also deprived cardinals of red dietary pigments to determine whether they could manufacture red carotenoids from yellow precursors to grow species-typical red plumage. We found that American goldfinches were able to deposit novel pigments in their plumage and develop a striking orange appearance. Thus, dietary access to pigments plays a role in determining the degree to which goldfinches express carotenoid-based plumage coloration. We also found that northern cardinals grew pale red feathers in the absence of red dietary pigments, indicating that their ability to metabolize yellow carotenoids in the diet contributes to the bright red plumage that they display.

Animals↗
PubMed1993

Pl-Bh, an anthocyanin regulatory gene of maize that leads to variegated pigmentation.

Anthocyanins are purple pigments that can be produced in virtually all parts of the maize plant. The spatial distribution of anthocyanin synthesis is dictated by the organ-specific expression of a few regulatory genes that control the transcription of the structural genes. The regulatory genes are grouped into families based on functional identity and DNA sequence similarity. The C1/Pl gene family consists of C1, which controls pigmentation of the kernel, and Pl, which controls pigmentation of the vegetative and floral organs. We have determined the relationship of another gene, Blotched (Bh), to the C1 gene family. Bh was originally described as a gene that conditions blotches of pigmentation in kernels homozygous for recessive c1, suggesting that Bh could functionally replace C1 in the kernel. Our genetic and molecular analyses indicate that Bh is an allele of Pl, that we designate Pl-Bh. Pl-Bh differs from wild-type Pl alleles in two respects. In contrast to the uniform pigmentation observed in plants carrying Pl, the pattern of pigmentation in plants carrying Pl-Bh is variegated. Pl-Bh leads to variegated pigmentation in virtually all tissues of the plant, including the kernel, an organ not pigmented by other Pl alleles. To address the molecular basis for the unusual pattern of expression of Pl-Bh, we cloned and sequenced the gene. The nucleotide sequence of Pl-Bh showed only a single base-pair difference from that of Pl. However, genomic DNA sequences associated with Pl-Bh were found to be hypermethylated relative to the same sequences around the wild-type Pl allele. The methylation was inversely correlated with Pl mRNA levels in variegated plant tissues. Thus, we conclude that DNA methylation may play a role in regulating Pl-Bh expression.

Alleles↗
PubMed2005

Effects of skin pigmentation on pulse oximeter accuracy at low saturation.

BACKGROUND: It is uncertain whether skin pigmentation affects pulse oximeter accuracy at low HbO2 saturation. METHODS: The accuracy of finger pulse oximeters during stable, plateau levels of arterial oxygen saturation (Sao2) between 60 and 100% were evaluated in 11 subjects with darkly pigmented skin and in 10 with light skin pigmentation. Oximeters tested were the Nellcor N-595 with the OxiMax-A probe (Nellcor Inc., Pleasanton, CA), the Novametrix 513 (Novametrix Inc., Wallingford, CT), and the Nonin Onyx (Nonin Inc., Plymouth, MN). Semisupine subjects breathed air-nitrogen-carbon dioxide mixtures through a mouthpiece. A computer used end-tidal oxygen and carbon dioxide concentrations determined by mass spectrometry to estimate breath-by-breath Sao2, from which an operator adjusted inspired gas to rapidly achieve 2- to 3-min stable plateaus of desaturation. Comparisons of oxygen saturation measured by pulse oximetry (Spo2) with Sao2 (by Radiometer OSM3) were used in a multivariate model to determine the interrelation between saturation, skin pigmentation, and oximeter bias (Spo2 - Sao2). RESULTS: At 60-70% Sao2, Spo2 (mean of three oximeters) overestimated Sao2 (bias +/- SD) by 3.56 +/- 2.45% (n = 29) in darkly pigmented subjects, compared with 0.37 +/- 3.20% (n = 58) in lightly pigmented subjects (P < 0.0001). The SD of bias was not greater with dark than light skin. The dark-light skin differences at 60-70% Sao2 were 2.35% (Nonin), 3.38% (Novametrix), and 4.30% (Nellcor). Skin pigment-related differences were significant with Nonin below 70% Sao2, with Novametrix below 90%, and with Nellcor at all ranges. Pigment-related bias increased approximately in proportion to desaturation. CONCLUSIONS: The three tested pulse oximeters overestimated arterial oxygen saturation during hypoxia in dark-skinned individuals.

Adult↗
PubMed2004

Perilimbal bulbar conjunctival pigmentation in vernal conjunctivitis: prospective evaluation of a new clinical sign in an Indian population.

OBJECTIVES: To prospectively evaluate the occurrence of perilimbal conjunctival pigmentation in patients with vernal conjunctivitis and normal controls; to document the location, extent, density, and color of such pigmentation; and to correlate these changes with disease severity. METHODS: Prospective, noninterventional case-control study. Demographic data, disease symptoms and duration, clinical signs of disease severity and extent, and characteristics of the perilimbal pigmentation were recorded. RESULTS: Twenty-five patients with vernal conjunctivitis and 30 controls were studied. The mean age of the patients (21 M, 4 F) and controls (18 M, 12 F) was 7.5 +/- 3.7 years and 10.3 +/- 3.1 years, respectively. Perilimbal pigmentation was seen in all patients with vernal conjunctivitis and in none of the controls. The palpebral conjunctival changes and patient symptoms correlated with the severity of the disease in patients with vernal conjunctivitis. However, the extent of perilimbal pigmentation did not correlate with the symptoms and signs of vernal conjunctivitis or the density of palisadal pigment. CONCLUSIONS: Perilimbal bulbar conjunctival pigmentation appears to be a consistent finding in patients with vernal conjunctivitis that is both specific and sensitive. It is also present in eyes with inactive disease and hence is a useful clinical sign that aids diagnosis in patients with mild or quiescent disease. Further studies are required to establish the histopathologic correlation of this finding and its etiopathogenesis. It is also important to establish whether this finding occurs with the same frequency in eyes of whites, as this study was performed in a cohort of Asian patients who have greater limbal pigmentation and a higher incidence of limbal changes in vernal conjunctivitis.

Case-Control Studies↗
PubMed1997

Choroidal findings in the course of idiopathic serous pigment epithelium detachment detected by indocyanine green videoangiography.

PURPOSE: To analyze the choroidal alterations associated with idiopathic serous pigment epithelium detachment. METHODS: Twenty-five consecutive patients affected by idiopathic serous pigment epithelium detachment underwent ophthalmoscopy, fluorescein angiography, and indocyanine green videoangiography. RESULTS: On indocyanine green videoangiography an early, complete, and homogeneous filling of the pigment epithelium detachment was always observed. In the late phases, the indocyanine green pattern depended on the size of the detachment. An idiopathic serous pigment epithelium detachment larger than the diameter of one optic disk was still hyperfluorescent in the late phases of indocyanine green videoangiography and was surrounded by a ring of brighter hyperfluorescence. An idiopathic serous pigment epithelium detachment smaller than the diameter of one optic disk usually could be visualized in the late phases as a hypofluorescent area surrounded by a hyperfluorescent ring. In 30 eyes (83.3%), choroidal hyperpermeability was observed. An irregular dilatation of the choroidal veins at the site or within an area the size of one disk diameter from the detachments could be visualized on indocyanine green videoangiography in 12 of 36 affected eyes (33.3%); in three cases an active focus of central serous chorioretinopathy with subretinal leakage developed in the follow-up period. CONCLUSION: The observation that pigment epithelium detachments frequently are associated with choroidal leakage and venous dilatation supports the hypothesis that an idiopathic serous pigment epithelium detachment is a variant of central serous chorioretinopathy. Moreover, the choroidal permeability alterations detected by indocyanine green videoangiography would support the theory of Gass that idiopathic serous pigment epithelium detachments could be caused by exudation of fluids from the choroidal vessels.

Adult↗
PubMed2000

Induced pigmentation in zooplankton: a trade-off between threats from predation and ultraviolet radiation.

Ultraviolet (UV) radiation is harmful to all life, and the ongoing depletion of the ozone layer is likely to affect interactions among both terrestrial and aquatic organisms. Some organisms have evolved adaptations to reduce radiation damage, such as the various types of protective pigmentation of freshwater zooplankton. However, strong pigmentation also increases vulnerability to visually hunting predators. Hence, where both UV radiation and predation are intense, zooplankton may be sandwiched between conflicting selective pressures: to be pigmented and to be transparent at the same time. Here, I show that the level of pigmentation in copepods is up to ten times higher in lakes without predatory fishes than where fishes are present. Moreover, animals from the same population exposed to either UV light or predator scent showed a 10% difference in pigmentation after only four days, suggesting that pigmentation is an inducible trait. Hence, individual copepods are not passive victims of selective predation or radiation damage, but adjust the level of pigmentation according to the prevailing threat. The ability to adjust pigmentation level rapidly may be especially useful in situations where risk assessment is difficult due to strong seasonal and spatial variation in risk variables, such as in Arctic regions. With progressive thinning of the ozone layer, the ability of some but not other organisms to adjust protection against UV radiation may lead to counter-intuitive, large-scale alterations in freshwater food webs.

Adaptation, Physiological↗
PubMed1989

Cloning and expression of Rhodococcus genes encoding pigment production in Escherichia coli.

Pigment was produced by Escherichia coli cells carrying recombinant plasmids pNIL100, pNIL200 and pNIL400 containing DNA from Rhodococcus sp. E. coli cells containing pNIL100 or pNIL200 (with DNA inserts from Rhodococcus sp. JL10 and Rhodococcus sp. ATCC 21145 respectively) produced both blue and pink pigments, while cells containing pNIL400 (with a DNA insert from Rhodococcus sp. ATCC 21145) produced only pink pigment. Colonies of E. coli(pNIL100) and E. coli(pNIL200) were dark blue, whereas E. coli(pNIL400) colonies were pink. No pigment was detected in Streptomyces griseus transformants containing pNIL100, pNIL200 or pNIL400. Restriction endonuclease mapping indicated that the cloned DNA fragments were different. The pigment gene(s) in pNIL200 producing both the blue and pink pigments were contained within a 2.8 kb DNA fragment. The pigments produced by E. coli transformants containing pNIL200 were characterized by visible and UV spectroscopy. No similar pigments were detected in Rhodococcus sp. ATCC 21145.

Cloning, Molecular↗
PubMed1988

Giant pigmented tumour of the scalp--a diffuse neurofibroma or a congenital naevus showing neurofibromatous changes? Immunohistochemical and electron microscopic studies.

A case of giant pigmented tumour of the scalp which developed in a 47-year-old woman is reported. Macroscopically, the tumour showed a peculiar two-layered structure, consisting of an upper non-pigmented and a lower pigmented portion. Histologically, it was composed of elongated neurofibromatous tumour cells with abundant collagen fibres in the non-pigmented portion and round naevus-like cells with abundant melanin pigment in the pigmented portion. S-100 protein and neurone-specific enolase were demonstrated in most of the tumour cells, but neurofilament and myelin basic protein were not detected. Electron microscopy revealed melanosomes in the tumour cells of the pigmented portion. These findings might support a melanocytic origin for the tumour, but the lack of superficial pigmentation and the associated hair loss were against this. The tumour may represent an example of duality of neural crest differentiation.

Carboxylesterase↗
PubMed2005

Locally differentiated cryptic pigmentation in the freshwater isopod Asellus aquaticus.

A repeated pattern of background colour matching in animals is an indication that pigmentation may be cryptic. Here, we examine the relationship between pigmentation of the freshwater isopod Asellus aquaticus and background darkness in 29 lakes, wetlands and ponds in Southern Sweden. The results show that Asellus pigmentation was correlated with substrate darkness across all localities. In seven localities, in which two contrasting substrate types were noted, Asellus populations were differentiated with respect to pigmentation. These findings thus provide phenomenological support for cryptic pigmentation in Asellus. Pigmentation generally increased with body size, but the relationship between pigmentation and size differed among localities, possibly as a result of differences in correlational selection on pigmentation and size. Selection thus appears to have resulted in local differentiation over a small spatial scale, even within lakes and wetlands. This differentiation is a likely cause behind elevated phenotype variation noted in localities with two substrate types, suggesting that habitat heterogeneity promotes genetic diversity.

Adaptation, Physiological↗
PubMed1980

Interrelationships between the retinal pigment epithelium and the neurosensory retina.

The role of the retinal pigment epithelium in regulating transport between the choriocapillariss and sensory retina was studied by examining the diffusion fluorescent across the intact rabbit retinal pigment epithelium and the retinal pigment epithelium damaged by intravenous injection of sodium iodate. Destruction of the tight junctions of the retinal pigment epithelium allowed free diffusion of fluorescein from the choroid into the retina. The electrical characteristics of the cat retinal pigment epithelium which play an important role in governing transport of substances across the retinal pigment epithelium were studied. The apical membrane of the cat retinal pigment epithelium resembled that of the frog in having high sensitivity to apical K+, greater sensitivity to apical Na+, and less sensitivity to apical HCO3-. The apical membrane was sensitive to oubain which produced a rapid fall in the transepithelial potential. Previous studies of the electrical properties of the retinal epithelium in cold blooded preparations are summarized with emphasis on the important interactions between the retinal pigment epithelium and sensory retina and the implications that these studies have with regard to the regulation of photoreceptor function.

Animals↗
PubMed1986

Investigation and prognosis in the retinal pigment epitheliopathies.

Eighty-three patients with retinal pigment epitheliopathy have been identified from the photographic and fluorescein records of the Tennent Institute of Ophthalmology in Glasgow. Many have been brought back for follow-up assessment. Twenty-seven patients had placoid lesions, 22 geographic lesions and 15 a condition which we propose to rename the 'not ocular histoplasmosis' (NOH) syndrome. Patients with placoid lesions could be divided into typical acute multifocal placoid pigment epitheliopathy (AMPPE), where the long-term visual prognosis was poor because of recurrent disease leading to extensive areas of atrophy, and acute diffuse placoid pigment epitheliopathy which seemed to be self-limiting. No consistent evidence of viral or immunological abnormality was found in either group of patients. Geographic lesions appeared to result either from a coalescence of focal lesions or from a slow (serpiginous) spread from a single focus. Four patients with helicoid atrophy lost central vision from disciform lesions. Seven patients had pigment epithelial disorder associated with sarcoidosis. The pigment epithelial disease was unresponsive to systemic corticosteroid therapy and tended to be complicated by disciform lesions. Disciform lesions may occur in any type of pigment epitheliopathy, as may serous retinal detachment or pigment epithelial detachment. A technique for the biopsy of choroid and retinal pigment epithelium is described. This may lead to a better understanding of these disorders.

Eye Diseases↗
PubMed1977

The action of melatonin on single amphibian pigment cells in tissue culture.

1. Neural crest material from neurula stage Xenopus embryos was tissue cultured as small aggregates of cells or a single cell suspension. Isolated pigment cells differentiated after 2 days in culture. 2. Melatonin (10(-15) to 10(-13) M) induced pigment granule condensation; it was 10,000 times more effective than any other compound tested. 3. Tests with appropriate agents showed the pigment cells to have beta-adrenoceptors and 5-hydroxytryptamine receptors; these sites could be blocked without affecting the response to melatonin. Phentolamine blocked the effect of melatonin. 4. Removal of Na+ or Ca2+ from the bathing medium inhibited melatonin-induced pigment granule condensation; 10 mM K+ induced pigment granule condensation. D600, Mn2+ and La3+, which inhibit Ca2+ entry, blocked the effect of melatonin. 5. Cyclic GMP induced pigment condensation and cyclic AMP pigment dispersion (10(-2) to 10(-4) M). 6. It is suggested that the action of melatonin is accompanied by depolarization and the entry of calcium ions. 7. Pigment cells in tissue culture could provide a useful bioassay method for melatonin.

Animals↗
PubMed1994

Correlation of serum ferritin levels and postsclerotherapy pigmentation. A prospective study.

BACKGROUND: Postsclerotherapy pigmentation is a common sequela of sclerotherapy to varicose and telangiectatic leg veins. This pigmentation is thought to be due to hemosiderin deposition in the dermis. A preliminary study indicated that serum ferritin was a good indicator of susceptibility to postsclerotherapy pigmentation. OBJECTIVE: To clarify the relationship between serum ferritin and postsclerotherapy pigmentation using a prospective study. METHODS: Serum ferritin levels were taken from 233 consecutive patients prior to commencement of sclerotherapy. Patients were assessed clinically for the presence of pigmentation at 3, 6, and 12 months. RESULTS: There was a linear relationship between pretreatment serum ferritin level and the occurrence of pigmentation at each posttreatment assessment date. CONCLUSION: The results confirm a relationship between serum ferritin levels and postsclerotherapy pigmentation. This indicates that a significant predisposing factor to the development of persistent postsclerotherapy pigmentation is a high level of total body iron stores.

Adult↗
PubMed2006

Diagnosing and managing cutaneous pigmented lesions: primary care physicians versus dermatologists.

BACKGROUND: Primary care physicians (PCPs) are often expected to screen for melanomas and refer patients with suspicious pigmented lesions to dermatologists. OBJECTIVE: To assess whether there is a difference between dermatologists and PCPs in accurately diagnosing melanoma and appropriately managing (based on decisions to refer/biopsy) suspicious pigmented lesions. DESIGN, PARTICIPANTS: A survey based on a random sample of 30 photographs of pigmented lesions with known pathology was administered to 101 dermatologists and 115 PCPs from October 2001 to January 2003. MEASUREMENTS: Likelihoods that a photographed lesion was melanoma and that the lesion should be biopsied/referred were scored on a 1 to 10 scale. Accuracy of melanoma diagnosis and appropriateness of pigmented lesion management were compared between dermatologists and PCPs by using the areas under (AUC) the receiver operating characteristic (ROC) curves. RESULTS: Dermatologists were superior to PCPs in diagnosing melanomas (AUC 0.89 vs 0.80, P<.001) and appropriately managing pigmented lesions (AUC .84 vs 0.76, P<.001). PCPs who tended to biopsy lesions themselves did better at managing pigmented lesions than PCPs who did not perform biopsies. Dermatology training during residency did not significantly improve the diagnostic accuracy of PCPs nor their management of pigmented lesions. CONCLUSIONS: Dermatologists have both better diagnostic accuracy and ability to manage pigmented lesions than PCPs. Yet, there is a shortage of dermatologists to meet the demand of accurate melanoma screening. More innovative strategies are needed to better train PCPs and enhance skin cancer screening.

Biopsy↗
PubMed1982

Epidemiologic study of excessive oral melanin pigmentation with special reference to the influence of tobacco habits.

The prevalence of oral melanin pigmentation was studied in a population of 30 118 adult individuals in Sweden. Among these, 9.9% showed melanin pigmentation in the oral mucosa. The anterior labial gingiva in the mandible was the most frequently pigmented location. The presence of melanin pigmentation was positively correlated to tobacco smoking. Among tobacco smokers 21.5% were pigmented as compared to 3.0% among individuals not using tobacco. The smoking-related oral pigmentation, smokers' melanosis, could thus be calculated at a prevalence of 18.5% among smokers and the total frequency of smokers' melanosis was calculated at 6.8%. The prevalence of pigmentation was found to increase prominently during the first year of smoking but also to decrease to the level found among non-tobacco users about 3 years after cessation of smoking. Snuff dipping did not significantly elevate the prevalence of oral melanin pigmentation.

Adolescent↗