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PubMed1972

Psychophysical estimates of visual pigment densities in red-green dichromats.

1. The spectral sensitivity of red-green dichromats was determined using heterochromatic flicker photometric matches (25-30 c/s) on the fovea. These matches are upset after a bright bleach and consequently the spectral sensitivity is altered.2. Preliminary experiments indicate that under the conditions in which these experiments were performed, the blue cone mechanism of deuteranopes and protanopes cannot follow 20 c/s flicker. If dichromats lack one of the normal pigments then the upset of these matches monitors the change in spectral sensitivity of a single mechanism.3. After a bleach which removes all the cone pigments, the spectral sensitivity recovers with the time course of pigment kinetics as measured by densitometry.4. An intense background also changes the relative spectral sensitivity of the dichromats. On real equilibrium backgrounds, the changes in spectral sensitivity follow those predicted by the pigment changes measured by densitometry. The predicted changes are obtained by modifying the Rushton equilibrium equation to take into account the density of pigment.5. The relationship of these changes to the luminance of the background is independent of the colour of the background light.6. In contradistinction the effect is dependent on the colour of the lights which were flickered. These experiments indicate that a narrowing of the spectral sensitivity curves takes place on both sides of the dichromats' lambda(max).7. The change in relative spectral sensitivity as a function of background intensity was also determined by increment threshold measurements. These changes can be expressed in terms of deviations from Weber's law (DeltaI/I = const.) if DeltaI and I represent the number of chromophores destroyed by the test and background.8. The relative spectral sensitivity of the dichromat was changed by decentering the point of pupil entry. This upset was abolished by bleaching. The size of the upset was correlated with the magnitude of the S-C I effect.9. Given the hypothesis of pigment density (self-screening), the results of expts. (3)-(8) are consistent and allow the calculation of a maximum optical density for those pigments which underlie the dichromats' long-wave mechanism. For the deuteranope a D(lambdamax) of 0.5-0.6 is calculated and for the protanope a D(lambdamax) of 0.4-0.5 is obtained.

Color Perception↗
PubMed1977

The gecko visual pigments: a microspectrophotometric study.

1. A dual system of visual pigments having absorbance maxima in the green and blue respectively has been found in the retinas of geckos both by single cell microspectrophotometry and by the method of extraction. Microspectrophotometry has shown the system to be present in four species of geckos representing four genera. Along with previous work with extracts (Crescitelli, 1972) this indicates a fundamental property in this family of lizards. No other photopigments have been detected.2. For Gekko gekko, the species most intensively studied, the two pigments have absorbance maxima at 521 and 467 nm respectively. Both are based on vitamin A(1) and both are characterized by absorbance spectra that nearly conform to the Dartnall nomogram.3. In situ, the 521-pigment is not temperature-sensitive, and has virtually the same absorbance spectrum at 23 degrees C as at 5 degrees C. On extraction into digitonin solution, however, the absorbance spectrum of the pigment becomes temperature-dependent and, though identical when measured at low temperature (2-5 degrees C) with the constant in situ curve, is displaced to shorter wave-lengths at higher temperatures (10-25 degrees C). Thus the extract spectrum is relevant to the in situ spectrum only at low temperature (and in the presence of chloride ions).4. Unlike the rhodopsins of several vertebrates, the gecko 521-pigment displays no evidence of a meta-III stage in the sequence of products following photic bleaching, even at low temperatures. This is true for the pigment in situ as well as in the extracted condition.

Animals↗
PubMedDate not supplied

Blood stasis contributions to the perception of skin pigmentation.

The chromatic characteristics of skin color arise from the interactions of light (primarily absorption and scattering) with the epidermis and the dermis. The primary light absorbers in skin are hemoglobin and melanin. Most of scattering is attributed to collagen fibers and in pigmented skin to melanosomes. Traditionally skin redness is considered to arise due to locally elevated concentrations of hemoglobin, whereas skin pigmentation is attributed to melanin. In this study we attempt to understand better the contributions of these chromophores to the perceived skin color using spectral analysis of skin color reactions induced by ultraviolet (UV) irradiation or pressure. In the first experiment 12 individuals with skin phototypes III-IV were irradiated on the back using a solar simulator with doses ranging from 0.7 to 3 MED. The skin reactions were evaluated on days 1, 7, 14, and 21 after irradiation. Evaluations included diffuse reflectance spectroscopy (DRS) and clinical assessment of the erythema and the pigment reaction. Apparent concentrations of melanin, oxy-, and deoxy-hemoglobin were calculated from the absorption spectra. In the second experiment the levels of deoxy-hemoglobin of the volar forearm of ten volunteers were selectively altered by either application of a pressure cuff or by topical application of 3% H(2)O(2). Changes in skin color appearance were documented by photography, colorimetry, and DRS. In the UV exposure experiment all reactions were dose dependent. Oxy-hemoglobin values increased to a maximum on day 1, correlating well with the clinical evaluation of erythema, and then decreased exponentially to base line. Melanin showed a significant increase on day 7 and remained relatively constant for the next 3 weeks, correlating well with the clinical evaluation of pigmentation (tanning). Deoxy-hemoglobin increased slightly on day 1 and remained elevated for the next 2 weeks. Thus, deoxy-hemoglobin correlated moderately with the clinical erythema scoring on day 1 only, while it contributes significantly to what is clinically perceived as skin tanning on days 7 and 14. Application of pressure below the diastolic level increased deoxy-hemoglobin concentration as measured by DRS. This increase corresponded to a decrease of a "pigmentation" parameter (based on the L(*)a(*)b(*) scale) in a similar fashion that has been documented for increases in melanin concentration. Topical H(2)O(2) application reduced deoxy-hemoglobin levels as measured by DRS. This reduction coincided kinetically with a visible skin blanching. Application of pressure or H(2)O(2) did not significantly alter the levels of oxy-hemoglobin or melanin. In this report we present compelling evidence that deoxy-hemoglobin significantly contributes to the skin color appearance. Blood pooling, expressed as increased deoxy-hemoglobin, can contribute to what is visually perceived as pigmentation. Furthermore, we present that measurement of its contribution to the skin color appearance can only be accomplished with DRS.

Administration, Topical↗
PubMed1986

Molecular genetics of human color vision: the genes encoding blue, green, and red pigments.

Human color vision is based on three light-sensitive pigments. The isolation and sequencing of genomic and complementary DNA clones that encode the apoproteins of these three pigments are described. The deduced amino acid sequences show 41 +/- 1 percent identity with rhodopsin. The red and green pigments show 96 percent mutual identity but only 43 percent identity with the blue pigment. Green pigment genes vary in number among color-normal individuals and, together with a single red pigment gene, are proposed to reside in a head-to-tail tandem array within the X chromosome.

Amino Acid Sequence↗
PubMed1986

Red pigment in Bacillus megaterium spores.

Bacillus megaterium QM B1551 spores contained a unique red pigment in their membranes that was not found in other species. This red pigment, presumably a carotenoid, was synthesized about the time of dipicolinic acid synthesis during sporulation and was associated with the forespores. A yellow pigment was synthesized during sporulation in rich medium and was found in the mother cell compartment. Although the yellow pigment was also associated with spores, it could be removed by two different extraction procedures without impairing germination; it was absent when sporulation occurred in a minimal medium. Although the yellow pigment of the mother cell appeared to be dispensable, the red pigment may serve a more critical function, such as membrane stabilization.

Bacillus megaterium↗
PubMed2003

Contrasting patterns of phytoplankton community pigment composition in two salt marsh estuaries in southeastern United States.

Phytoplankton community pigment composition and water quality were measured seasonally along salinity gradients in two minimally urbanized salt marsh estuaries in South Carolina in order to examine their spatial and temporal distributions. The North Inlet estuary has a relatively small watershed with minimal fresh water input, while the Ashepoo, Combahee, and Edisto (ACE) Basin is characterized by a relatively greater influence of riverine drainage. Sampling stations were located in regions of the estuaries experiencing frequent diurnal tidal mixing and had similar salinity and temperature regimens. Phytoplankton community pigment composition was assessed by using high-performance liquid chromatography (HPLC) and multivariate statistical analyses. Shannon diversity index, principal-component, and cluster analyses revealed that phytoplankton community pigments in both estuaries were seasonally variable, with similar diversities but different compositions. The temporal pigment patterns indicated that there was a relatively weak correlation between the pigments in ACE Basin and the relative persistence of photopigment groups in North Inlet. The differences were presumably a consequence of the unpredictability and relatively greater influence of river discharge in the ACE Basin, in contrast to the greater environmental predictability of the more tidally influenced North Inlet. Furthermore, the timing, magnitude, and pigment composition of the annual phytoplankton bloom were different in the two estuaries. The bloom properties in North Inlet reflected the predominance of autochthonous ecological control (e.g., regenerated nutrients, grazing), and those in ACE Basin suggested that there was greater influence of allochthonous environmental factors (e.g., nutrient loading, changes in turbidity). These interestuarine differences in phytoplankton community structure and control provide insight into the organization of phytoplankton in estuaries.

Animals↗
PubMed2005

Mutations of toluene-4-monooxygenase that alter regiospecificity of indole oxidation and lead to production of novel indigoid pigments.

Broad-substrate-range monooygenase enzymes, including toluene-4-monooxygenase (T4MO), can catalyze the oxidation of indole. The indole oxidation products can then condense to form the industrially important dye indigo. Site-directed mutagenesis of T4MO resulted in the creation of T4MO isoforms with altered pigment production phenotypes. High-pressure liquid chromatography, thin-layer chromatography, and nuclear magnetic resonance analysis of the indole oxidation products generated by the mutant T4MO isoforms revealed that the phenotypic differences were primarily due to changes in the regiospecificity of indole oxidation. Most of the mutations described in this study changed the ratio of the primary indole oxidation products formed (indoxyl, 2-oxindole, and isatin), but some mutations, particularly those involving amino acid G103 of tmoA, allowed for the formation of additional products, including 7-hydroxyindole and novel indigoid pigments. For example, mutant G103L converted 17% of added indole to 7-hydroxyindole and 29% to indigoid pigments including indigo and indirubin and two other structurally related pigments. The double mutant G103L:A107G converted 47% of indole to 7-hydroxyindole, but no detectable indigoid pigments were formed, similar to the product distribution observed with the toluene-2-monooxygenase (T2MO) of Burkholderia cepacia G4. These results demonstrate that modification of the tmoA active site can change the products produced by the enzyme and lead to the production of novel pigments and other indole oxidation products with potential commercial and medicinal utility.

Binding Sites↗
PubMed1984

Differential primary plating medium for enhancement of pigment production by Pseudomonas aeruginosa.

A cost-effective and more rapid means of detection of Pseudomonas aeruginosa in cultures from clinical specimens would be very advantageous. We have developed a modified MacConkey agar (MMA), which enhances pigment production of P. aeruginosa and which, if pyocyanin pigment is present, provides a relatively rapid and very cost-effective identification. The MMA medium inhibits the gram-positive organisms, while lactose- and non-lactose-fermenting gram-negative rods are easily distinguishable from pigment-producing pseudomonads. Organisms that produce pyocyanin, pyoverdin, or pyorubin, or both pyocyanin and pyoverdin, are easily recognized on the medium. Pyocyanin production is clearly distinguishable from other Pseudomonas pigments on MMA. In a comparative study, MMA identified 97% of the P. aeruginosa strains 24 h earlier than routine laboratory biochemical methods. Highly mucoid strains which did not produce detectable pigments on standard biochemicals produced detectable pigments on the MMA within 48 h. This medium can provide a very practical, reliable, and cost-effective means for early characterization of P. aeruginosa.

Culture Media↗
PubMed2001

Bile bilirubin pigment analysis in disorders of bilirubin metabolism in early infancy.

BACKGROUND: Early and accurate diagnosis of Crigler-Najjar syndrome, which causes prolonged unconjugated hyperbilirubinaemia in infancy, is important, as orthotopic liver transplantation is the definitive treatment. AIM: To determine whether bilirubin pigment analysis of bile in infants with prolonged unconjugated hyperbilirubinaemia provides useful diagnostic information in the first 3 months of life. METHODS: Retrospective review of patients with prolonged unconjugated hyperbilirubinaemia referred to the liver unit, Birmingham Children's Hospital, for the diagnosis of Crigler-Najjar syndrome. Bile bilirubin pigment composition was determined by high performance liquid chromatography. Initial diagnoses were made based on the result of bile bilirubin pigment composition. Final diagnoses were made after reviewing the clinical course, response to phenobarbitone, repeat bile bilirubin pigment composition analysis, and genetic studies. RESULTS: Between 1992 and 1999, nine infants aged less than 3 months of age with prolonged hyperbilirubinaemia underwent bile bilirubin pigment analyses. Based on these, two children were diagnosed with Crigler-Najjar syndrome (CNS) type 1, six with CNS type 2, and one with Gilbert's syndrome. Five children whose initial diagnosis was CNS type 2 had resolution of jaundice and normalisation of serum bilirubin after discontinuing phenobarbitone, and these cases were thought to be normal or to have Gilbert's syndrome. One of the initial cases of CNS type 1 responded to phenobarbitone with an 80% reduction in serum bilirubin consistent with CNS type 2. In all, the diagnoses of six cases needed to be reviewed. CONCLUSIONS: Early bile pigment analysis, performed during the first 3 months of life, often shows high levels of unconjugated bilirubin or bilirubin monoconjugates, leading to the incorrect diagnosis of both type 1 and type 2 Crigler-Najjar syndrome.

Bile Pigments↗
PubMed1981

Tears of detached retinal pigment epithelium.

Ripping of detached pigment epithelium appears to be a common sight-threatening complication of pigment epithelial detachments and occurs at the junction of the detachment and flat pigment epithelium. The characteristics of the detachment prior to the rip suggest that the tear occurs in pigment epithelium which is detached without its basement membrane. The tear is followed by retraction of the pigment epithelium, revealing bare Bruch's membrane. The defect may remain apparently unaltered, or may be recovered by normal looking pigment epithelium, but most commonly is replaced by a fibrous plaque. Most patients had a profound reduction in visual acuity.

Aged↗
PubMed1983

Plasmodial pigmentation of placenta and outcome of pregnancy in West African mothers.

In a region where falciparum malaria is endemic and where pregnant women traditionally receive only curative treatment for parasitaemias and no chemoprophylaxis 65 placental biopsy specimens were examined histologically for malaria pigment. Twenty seven placentas had pigment, but parasitaemias had been diagnosed antenatally in only 12 of these women despite their frequent attendance at antenatal and other clinics. The incidence of parasitaemia in pregnant primigravidas was 17.7%, seven times greater than that in lactating primiparous mothers; pregnant primigravidas also had the highest incidence (67%) of pigmented placentas. First born babies with pigmented placentas had a mean (SD) birth weight of 2580 (260) g, significantly less than the 3150 (400) g of unaffected first babies. All babies weighing less than 2500 g at birth had pigmented placentas. Pigmentation was associated with parasitaemias in the second half of pregnancy, and, although some recovery from early parasitaemias may occur, the fetoplacental unit is inadequately protected by curative treatment alone. Chemoprophylaxis currently remains the procedure of choice.

Birth Weight↗
PubMed1991

Characterization of the pigment from homogentisic acid and urine and tissue from an alkaptonuria patient.

When urine samples from alkaptonuria patients are allowed to stand, they turn black, presumably owing to the oxidation of homogentisic acid to a melanin-like substance. We report the characterization of the pigments formed by polymerization of (a) the components in the urine from a patient with alkaptonuria and (b) homogentisic acid. The absorption spectra and electron spin resonance signals of these pigments are similar to those of eumelanins. Irradiation of the pigments with nitroblue tetrazolium caused reduction of the tetrazolium; this was partially inhibited by superoxide dismutase. Irradiation of Ehrlich ascites carcinoma cells with the pigments from homogentisic acid or urine caused cell lysis. Since this lysis was inhibited by catalase, we have concluded that it was mediated by H2O2. A similar pigment was also extracted from the tissue from an alkaptonuria patient. It is suggested that the degeneration of tissue in vivo may be due to the deposition of melanin-like pigments in the tissues, probably in combination with metal ions.

Alkaptonuria↗
PubMed1978

Electron-microscopic studies on primate neurons: microtubule-pigment associations.

The relationship between microtubules and the lipoprotein pigment found in senile Cynomolgus brain and senile human brain biopsy material was investigated. Numerous microtubules were present in all parts of the cytoplasm and within the pigment areas, running parallel or obliquely to the pigment bodies and being associated with its lateral aspects. Microtubules also occurred in the periphery of neurons or appearing to enter the perineuronal oligodendrocytes. These observations indicate a possible role of microtubules in the transport of pigment bodies. The oligodendrocyte from human brain biopsy material has definitely taken the role of a phagocyte in ingesting pigment bodies. Its numerous microtubules may offer a fasting moving system for disposing off pigment residures to the capillary endothelium.

Animals↗
PubMed1978

Comparative aspects of pigmented nevi in children, youths and adults.

Clinicomorphological correlations in children of different ages, youths, and adults with various pigmented nevi are analyzed to determine the diagnostic significance of certain structures. The study included 129 pigmented nevi surgically removed from 122 children, 27 from youths, and 133 from adult subjects. A comparative analysis of the reasons that caused the removal of the pigmented nevi made it possible to clarify a number of peculiarities of pigmented nevi in children that play an important role in the clinical and diagnostic aspects, as well as the decision of management policy. For diagnostic purposes, in the evaluation of pigmented nevi in children, particular attention should not be paid to the marked cellular proliferation of junctional melanoblasts, invasion of the epidermis by nevus cells, and pigmentation of the epidermis by melanin.

Adolescent↗
PubMed2003

Temporal and cellular requirements for Fms signaling during zebrafish adult pigment pattern development.

Ectothermic vertebrates exhibit a diverse array of adult pigment patterns. A common element of these patterns is alternating dark and light stripes each comprising different classes of neural crest-derived pigment cells. In the zebrafish, Danio rerio, alternating horizontal stripes of black melanophores and yellow xanthophores are a prominent feature of the adult pigment pattern. In fms mutant zebrafish, however, xanthophores fail to develop and melanophore stripes are severely disrupted. fms encodes a type III receptor tyrosine kinase expressed by xanthophores and their precursors and is the closest known homologue of kit, which has long been studied for roles in pigment pattern development in amniotes. In this study we assess the cellular and temporal requirements for Fms activity in promoting adult pigment pattern development. By transplanting cells between fms mutants and either wild-type or nacre mutant zebrafish, we show that fms acts autonomously to the xanthophore lineage in promoting the striped arrangement of adult melanophores. To identify critical periods for fms activity, we isolated temperature sensitive alleles of fms and performed reciprocal temperature shift experiments at a range of stages from embryo to adult. These analyses demonstrate that Fms is essential for maintaining cells of the xanthophore lineage as well as maintaining the organization of melanophore stripes throughout development. Finally, we show that restoring Fms activity even at late larval stages allows essentially complete recovery of xanthophores and the development of a normal melanophore stripe pattern. Our findings suggest that fms is not required for establishing a population of precursor cells during embryogenesis but is required for recruiting pigment cell precursors to xanthophore fates, with concomitant effects on melanophore organization.

Alleles↗
PubMed2003

A novel function for Hedgehog signalling in retinal pigment epithelium differentiation.

Sonic hedgehog is involved in eye field separation along the proximodistal axis. We show that Hh signalling continues to be important in defining aspects of the proximodistal axis as the optic vesicle and optic cup mature. We show that two other Hedgehog proteins, Banded hedgehog and Cephalic hedgehog, related to the mouse Indian hedgehog and Desert hedgehog, respectively, are strongly expressed in the central retinal pigment epithelium but excluded from the peripheral pigment epithelium surrounding the ciliary marginal zone. By contrast, downstream components of the Hedgehog signalling pathway, Gli2, Gli3 and X-Smoothened, are expressed in this narrow peripheral epithelium. We show that this zone contains cells that are in the proliferative state. This equivalent region in the adult mammalian eye, the pigmented ciliary epithelium, has been identified as a zone in which retinal stem cells reside. These data, combined with double labelling and the use of other retinal pigment epithelium markers, show that the retinal pigment epithelium of tadpole embryos has a molecularly distinct peripheral to central axis. In addition, Gli2, Gli3 and X-Smoothened are also expressed in the neural retina, in the most peripheral region of the ciliary marginal zone, where retinal stem cells are found in Xenopus, suggesting that they are good markers for retinal stem cells. To test the role of the Hedgehog pathway at different stages of retinogenesis, we activated the pathway by injecting a dominant-negative form of PKA or blocking it by treating embryos with cyclopamine. Embryos injected or treated at early stages display clear proximodistal defects in the retina. Interestingly, the main phenotype of embryos treated with cyclopamine at late stages is a severe defect in RPE differentiation. This study thus provides new insights into the role of Hedgehog signalling in the formation of the proximodistal axis of the eye and the differentiation of retinal pigment epithelium.

Animals↗
PubMed2003

Formation of the adult pigment pattern in zebrafish requires leopard and obelix dependent cell interactions.

Colour patterns are a prominent feature of many animals and are of high evolutionary relevance. In zebrafish, the adult pigment pattern comprises alternating stripes of two pigment cell types, melanophores and xanthophores. How the stripes are defined and a straight boundary is formed remains elusive. We find that mutants lacking one pigment cell type lack a striped pattern. Instead, cells of one type form characteristic patterns by homotypic interactions. Using mosaic analysis, we show that juxtaposition of melanophores and xanthophores suffices to restore stripe formation locally. Based on this, we have analysed the pigment pattern of two adult specific mutants: leopard and obelix. We demonstrate that obelix is required in melanophores to promote their aggregation and controls boundary integrity. By contrast, leopard regulates homotypic interaction within both melanophores and xanthophores, and interaction between the two, thus controlling boundary shape. These findings support a view in which cell-cell interactions among pigment cells are the major driving force for adult pigment pattern formation.

Animals↗
PubMed1996

Mutations affecting xanthophore pigmentation in the zebrafish, Danio rerio.

In a large-scale screen for mutants with defects in embryonic development we identified 17 genes (65 mutants) specifically required for the development of xanthophores. We provide evidence that these genes are required for three different aspects of xanthophore development. (1) Pigment cell formation and migration (pfeffer and salz); (2) pigment synthesis (edison, yobo, yocca and brie) and (3) pigment translocation (esrom, tilsit and tofu). The number of xanthophore cells that appear in the body is reduced in embryos with mutations in the two genes, salz and pfeffer. In heterozygous and homozygous salz and pfeffer adults, the melanophore stripes are interrupted, indicating that xanthophore cells have an important function in adult melanophore pattern formation. Most other genes affect only larval pigmentation. In embryos mutant for edison, yobo, yocca and brie, differences in pteridine synthesis can be observed under UV light and by thin-layer chromatography. Homozygous mutant females of yobo show a recessive maternal effect. Embryonic development is slowed down and embryos display head and tail truncations. Xanthophores in larvae mutant in the three genes esrom, tilsit and tofu appear less spread out. In addition, these mutants display a defect in retinotectal axon pathfinding. These mutations may affect xanthophore pigment distribution within the cells or xanthophore cell shape. Mutations in seven genes affecting xanthophore pigmentation remain unclassified.

Animals↗