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PubMed1989

Light-induced dopamine release from teleost retinas acts as a light-adaptive signal to the retinal pigment epithelium.

In the retinal pigment epithelium (RPE) of lower vertebrates, melanin pigment granules migrate in and out of the cells' long apical projections in response to changes in light condition. When the RPE is in its normal association with the retina, light onset induces pigment granules to disperse into the apical projections; dark onset induces pigment granules to aggregate into the cell bodies. However, when the RPE is separated from the retina, pigment granule movement in the isolated RPE is insensitive to light onset. It thus seems likely that a signal from the retina communicates light onset to the RPE to initiate pigment dispersion. We have examined the nature of this retina-to-RPE signal in green sunfish, Lepomis cyanellus. In isolated retinas with adherent RPE, light-induced pigment dispersion in the RPE is blocked by treatments known to block Ca2+-dependent transmitter release in the retina. In addition, the medium obtained from incubating previously dark-adapted retinas in the light induces light-adaptive pigment dispersion when added to isolated RPE. In contrast, the medium obtained from incubating dark-adapted retinas in constant darkness does not affect pigment distribution when added to isolated RPE. These results are consistent with the idea that RPE pigment dispersion is triggered by a substance that diffuses from the retina at light onset. The capacity of the conditioned medium from light-incubated retinas to induce pigment dispersion in isolated RPE is inhibited by a D2 dopamine antagonist, but not by D1 or alpha-adrenergic antagonists. Light-induced pigment dispersion in whole RPE-retinas is also blocked by a D2 dopamine antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1973

Production of a sporulation pigment by Streptomyces venezuelae.

Streptomyces venezuelae S13 produced a pH-indicating sporulation pigment on a glucose-salts-agar medium consisting of glucose, KNO(3), MgSO(4), and Na(2)HPO(4), pH 7. Pigmentation on this medium appeared to be closely associated with sporulation, which normally required 5 to 7 days at 30 C. The pigment was soluble in water as well as in a number of organic solvents. Butanol-extracted pigment exhibited absorption maxima at 430 and 520 nm at pH 3 and 12, respectively. Although many salts of organic acids and amino acids could replace glucose as the sole carbon source in basal salts-agar medium for growth and pigmentation, most sugars that were tested supported good growth but negligible pigmentation. Among the nitrogenous substances tested, KNO(3) was most desirable for pigmentation. The organism did not exhibit any specific requirements for divalent cations with respect to growth and pigmentation. In the absence of MgSO(4), however, glucose-salts-agar prepared by autoclaving all components together failed to support growth. The production of the sporulation pigment on glucose-salts-agar was comparable to that obtained on tomato paste-oatmeal-agar medium. Incorporation of partially purified pigment material into broth medium that did not normally support sporulation induced sporulation, and amino acid-salts-agar medium could induce vegetative mycelia to pigment when transferred from medium that did not support either pigmentation or sporulation.

Agar↗

PubMed1986

Cloning and regulation of Erwinia herbicola pigment genes.

The genes coding for yellow pigment production in Erwinia herbicola Eho10 (ATCC 39368) were cloned and localized to a 12.4-kilobase (kb) chromosomal fragment. A 2.3-kb AvaI deletion in the cloned fragment resulted in the production of a pink-yellow pigment, a possible precursor of the yellow pigment. Production of yellow pigment in both E. herbicola Eho10 and pigmented Escherichia coli clones was inhibited by glucose. When the pigment genes were transformed into a cya (adenylate cyclase) E. coli mutant, no expression was observed unless exogenous cyclic AMP was provided, which suggests that cyclic AMP is involved in the regulation of pigment gene expression. In E. coli minicells, the 12.4-kb fragment specified the synthesis of at least seven polypeptides. The 2.3-kb AvaI deletion resulted in the loss of a 37K polypeptide and the appearance of a polypeptide of 40 kilodaltons (40K polypeptide). The synthesis of the 37K polypeptide, which appears to be required for yellow pigment production, was not repressed by the presence of glucose in the culture medium, as was the synthesis of other polypeptides specified by the 12.4-kb fragment, suggesting that there are at least two types of gene regulation involved in yellow pigment synthesis. DNA hybridization studies indicated that different yellow pigment genes exist among different E. herbicola strains. None of six pigmented plant pathogenic bacteria examined, Agrobacterium tumefaciens C58, Cornyebacterium flaccumfaciens 1D2, Erwinia rubrifaciens 6D364, Pseudomonas syringae ATCC 19310, Xanthomonas campestris 25D11, and "Xanthomonas oryzae" 17D54, exhibited homology with the cloned pigment genes.

Cloning, Molecular↗

PubMed1985

Clonal separation of mature melanocytes from premelanocytes in a diploid human cell strain: spontaneous and induced pigmentation of premelanocytes.

Strains of pigmented melanocytes can be derived reproducibly from normal human skin. Published procedures have been modified here to yield a strain, 'Nohm-1', comprising many unpigmented cells as well as cells with various degrees of pigmentation observable by light microscopy. The unpigmented cells contain early melanosomes (pigment organelles) and the specific enzyme tyrosinase. They are on average smaller and less dendritic than the pigmented cells. Nohm-1 cells show normal chromosomal banding patterns and normal proliferative behaviour, including senescence. They form no tumours in immunodeficient (nude) mice. Nohm-1 cells have been cloned and yield two distinct types of colony, depending on the progenitor cell. Well-pigmented melanocytes engender pure colonies of pigmented cells, but cells with little or no pigment can produce both unpigmented and pigmented progeny. Thus there is a separate cell type, or premelanocyte, which can differentiate spontaneously and stably in culture; this cell type includes both unpigmented and faintly pigmented cells. Usefully, most premelanocytes are viable after frozen storage, unlike well-pigmented melanocytes. Some components of the culture medium affect the proportion of pigmented cells in Nohm-1 cultures, and hence probably the ratio of mature melanocytes to premelanocytes. Rapid pigmentation can be induced artificially and simply, by using a medium with increased extracellular pH and tyrosine concentration.

Cell Differentiation↗

PubMed1993

The role of microtubules in pigment translocation in goldfish xanthophores.

In xanthophores, microtubules were observed to radiate out from the microtubule organization center which was also the center of a central pigment mass. A similar pattern of microtubules was identified in both cells with dispersed or aggregated pigments. Brief vinblastine incubation, which depolymerized the microtubules of pigment-aggregated cells, failed to disrupt the central pigment mass. Subsequent removal of the vinblastine and the addition of ACTH dispersed pigment granules before the reassembly of microtubules. These results suggest that a radiating microtubular system is not essential to the maintenance or the dispersion of the aggregated pigment mass. Prolonged incubation with vinblastine eventually dispersed the aggregated pigment mass even in an ACTH-free medium, suggesting that certain components responsible for pigment association were finally destroyed by vinblastine. Moreover, these dispersed pigments could be induced to reaggregate into small clusters in the absence of microtubules, and finally into a large, tight aggregate when the microtubule system was fully reconstituted. We thus conclude that microtubules may serve to guide the centripedal movement of small pigment clusters toward the cell center, and they may not be essential to pigment dispersion and the maintenance of the central pigment mass.

Adrenocorticotropic Hormone↗

PubMed2000

Macular pigment optical density in a Southwestern sample.

PURPOSE: Increasing evidence implicates macular pigment in protecting the retina and retinal pigment epithelium from light-initiated oxidative damage. Little information, however, is available regarding "average" levels of macular pigment in the general population. This study was designed to assess macular pigment in a high-light environment and to determine what personal characteristics influence macular pigment density in that sample. METHODS: Macular pigment optical density was measured psychophysically using a 1 degree, 460-nm test stimulus. Personal data were collected using a questionnaire. RESULTS: 217 subjects (79 men, 138 women) were recruited from the Phoenix metropolitan area (age range = 17-92 years). The average macular pigment density was 0.22 +/- 0.13. There was a slight tendency for macular pigment density in this sample to decline with age (r = -0.14, P < 0.02). Average macular pigment density was significantly lower in women versus men (P < 0.05), lower in individuals with light-colored irises versus dark-colored irises (P < 0.009), and lower in heavy smokers compared to light (P < 0.0045) and never (P < 0.034) smokers. CONCLUSIONS: Macular pigment density was lower than average levels obtained from the Northeast but similar to average values obtained in a recent study of adults recruited from Indianapolis. Consistent with past studies, MP density was 13% lower in women and 18% lower in individuals with light- versus dark-colored irises. The relation of smoking to macular pigment density was only significant for those current smokers who smoked more than 10 cigarettes per day (about a 25% reduction). The large number of individuals in this sample with low macular pigment density motivates the need for population-based assessment of the possibly poor nutritional state of the average American's retina.

Adolescent↗

PubMed1977

Pigment versus cholesterol cholelithiasis: identification and quantification by infrared spectroscopy.

We previously reported that 27% of 92 cholecystectomized patients had pigment stones (Am J Dig Dis 19:585-590, 1974). Using standard biochemical methods, we found that cholesterol accounted for an average of 77% of the dry weight of cholesterol stones, but that unconjugated bilirubin represented a mean of only 7% of pigment stones. This quantitation of pigment stones was limited because approximately 66% of their weight was insoluble. To characterize pigment and cholesterol stone composition further, we used infrared spectroscopy--a technique requiring neither crystallinity nor solubilization--to quantitate pigment, carbonate, and cholesterol in gallstones. Other organic and inorganic components of stones were measured by standard methods. By infrared spectroscopy, two types of pigment stones were identified: carbonate-containing and noncarbonate pigment stones. Carbonate pigment stones contained significantly more calcium, carbonate, and phosphate, but less pigment than noncarbonate stones. Compared to our initial report, the total measured components of all pigment stones were increased 6-fold from 10 to 63%. Cholesterol was the major component of cholesterol stones by chemical assay or infrared spectroscopy. Among five cholesterol stones with limited solubility, 80% of the insoluble residue was identified as cholesterol by infrared spectroscopy. This study extends our knowledge of pigment stone and cholesterol stone composition by the use of quantitative infrared spectroscopy in conjunction with standard biochemical methods; furthermore, it confirms that pigment and cholesterol stones differ in composition and form by different mechanisms.

Carbonates↗

PubMedDate not supplied

Composition of pigmented centers of cholesterol gallstones.

Most cholesterol gallstones have visually pigmented centers, but it is unclear whether this represents simple co-precipitation of pigment with cholesterol during stone nidation or nidation on a true pigment stone center. To clarify this issue, we selected from among 67 sets of cholesterol gallstones, 12 sets with the most conspicuously pigmented centers. The composition of the centers and the peripheries of these 12 stones was analyzed using infrared spectroscopy and compared with that of 10 black pigment gallstones. The pigmented centers of cholesterol stones contained 80.1 +/- 7.9% (mean +/- S.E.) cholesterol, 6.2 +/- 3.4% calcium bilirubinate (only 4 of the 12 centers had measurable calcium bilirubinate), trace amounts of calcium phosphate and no calcium carbonate or calcium palmitate. The peripheral areas of the cholesterol stones contained 91.6 +/- 2.3% cholesterol and no detectable calcium salts. For comparison, the composition of the centers of 10 black pigment gallstones was 13.5 +/- 2.2% cholesterol, 28.2 +/- 5.3% calcium bilirubinate, 5.5 +/- 2.4% calcium phosphate and 10.6 +/- 5.8% calcium carbonate. The composition of only one cholesterol stone center (15.8% cholesterol, 26.8% calcium bilirubinate) resembled that of a pigment stone, but even this center differed from that of a typical pigment stone in that it contained only a trace amount of calcium phosphate and no calcium carbonate. Thus, the chemical composition of pigmented centers of cholesterol gallstones is quantitatively different from that of black pigment stones, suggesting that cholesterol gallstones do not form on a pigment stone nidus.

Bilirubin↗

PubMed2006

Interactions of pigments and opacifiers on color stability of MDX4-4210/type A maxillofacial elastomers subjected to artificial aging.

STATEMENT OF PROBLEM: The color instability and degradation of maxillofacial elastomers limit the function and cosmetic quality of facial prostheses. PURPOSE: The purpose of this study was to measure the interactions of oil pigments plus dry earth opacifiers at 5%, 10%, and 15% by volume in stabilizing the color of MDX4-4210/type A silicone elastomers before and after artificial aging. MATERIAL AND METHODS: In the first part of the study, each of 5 opacifiers (Georgia kaolin powder neutral, kaolin powder calcined, Artskin white, dry pigment titanium (Ti) white, or Ti white artists' oil color) at 10% concentrations were combined with each of 5 oil pigment types (no pigment, cadmium-barium red deep, yellow ochre, burnt sienna, or a mixture of the 3 pigments), for a total of 25 experimental groups of elastomers. In the second part of the study, 50 experimental groups of elastomers were made by combining 1 of 5 opacifiers at 5% and 15% concentrations with 1 of 5 oil pigments as in Part 1. Five specimens of each elastomer were tested, for a total of 375 specimens. In each part of the study, all specimens were aged in an artificial aging chamber. CIE L*a*b* values were measured by a spectrophotometer. The color differences (DeltaE*) were subjected to repeated-measures analysis of variance. Mean values were compared by Tukey-Kramer intervals (alpha = .05). RESULTS: In Part 1, when the opacifiers were tested at 10% concentration, Ti white oil color had the most color change, and dry pigment Ti white had the least; all other opacifiers were not significantly different from each other. In Part 2, at 5%, Ti white oil color had the most color change; all other opacifiers were not significantly different from the others. At 15%, Ti white oil color again had the most color change, followed by Artskin white, kaolin powder calcined, and Georgia kaolin; Ti white dry earth pigment had the least color change. Overall, 5% Artskin white had less color change than the 15%, whereas 15% dry pigment Ti white had less color change than the 5% (P < .001). The 5% and 15% of other opacifiers were not significantly different. CONCLUSIONS: At all 3 concentrations, oil pigments mixed with opacifiers helped protect the MDX4-4210/type A silicone elastomer from color degradation over time. Dry pigment Ti white remained the most color stable over time, followed by the pigments mixed with kaolin powder calcined, Georgia kaolin, Artskin white, and Ti white artists' oil color.

Barium Sulfate↗

PubMed1999

Ultraviolet radiation-induced color shifts occurring in oil-pigmented maxillofacial elastomers.

STATEMENT OF PROBLEM: Oil-based pigments are added to a maxillofacial prosthesis either as base colorants present within the elastomer or as surface tints that are painted on with an adhesive. Color stability of the pigments and pigmented prosthetic materials on exposure to ultraviolet radiation are unknown. PURPOSE: This study measured DeltaE* color changes caused by ultraviolet radiation for materials colored with 5 oil pigments, applied either as base colorants (intrinsic) or surface tints (extrinsic) to a silicone elastomer. MATERIAL AND METHODS: One of 5 oil pigments was added to polydimethyl siloxane disks to serve as a base colorant (0.2 weight percent present throughout a 2 mm thick disk) or as a concentrated surface tint (2.0 weight percent concentrated in upper 0.3 mm thickness). Pigmented disks, along with pigment-only and elastomer-only control disks, were exposed to ultraviolet radiation for 400, 600 and 1800 hours. DeltaE* color changes were measured at baseline and for each time interval. RESULTS: Control samples underwent minimum color changes after 1800 hours (DeltaE* </= 2.0), whereas samples containing oil pigments as base colorants demonstrated a wide range of susceptibility to ultraviolet radiation, with the greatest changes occurring for pigments cadmium red, cadmium yellow, and yellow ochre (7.1 </= DeltaE* </= 9.4). Elastomers coated with the same oil pigments as concentrated surface tints demonstrated significantly lower color shifting after 1800 hours of radiation exposure (maximum DeltaE* = 4.2, P </= .05). CONCLUSION: Customizing a prosthesis with an oil-pigmented surface tint may reduce the incidence of color change, provided a sufficient amount of pigment is present.

Coloring Agents↗

PubMed1998

Large-scale production and purification of the human green cone pigment: characterization of late photo-intermediates.

We present the first characterization of the late photo-intermediates (Meta I, Meta II and Meta III) of a vertebrate cone pigment in a lipid environment. Marked differences from the same pathway in the rod pigment were observed. The histidine-tagged human green cone pigment was functionally expressed in large-scale suspension cultures in Sf9 insect cells using recombinant baculovirus. The recombinant pigment was extensively purified in a single step by immobilized metal affinity chromatography and displays the expected spectral characteristics. The purified pigment was able to activate the rod G-protein transducin at about half the rate of the rod pigment. Following reconstitution into bovine retina lipid proteoliposomes, identification and analysis of the photo-intermediates Meta I, Meta II and Meta III was accomplished. Similar to the rod pigment, our results indicate the existence of a Meta I-Meta II equilibrium, but we find no evidence for pH dependence. Replacement of native Cl- by NO3- in the anion-binding site of the cone pigment affected the spectral position of the pigment itself and of the Meta I intermediate, but not that of Meta II and Meta III. The decay rate of the 'active' intermediate Meta II did not differ for the Cl- and NO3- state. However, in qualitative agreement with results reported before for chicken cone pigments, the rate of Meta II decay was significantly higher in the human cone pigment than in the rod pigment.

Animals↗

PubMed2004

Pigment cells trigger the onset of gastrulation in tropical sea urchin Echinometra mathaei.

In the tropical sea urchin Echinometra mathaei, pigment cells are just detectable before the onset of gastrulation, owing to an early accumulation of red pigment granules. Taking advantage of this feature, behavior of pigment cells was studied in relation to the processes of gastrulation. Before the initiation of primary invagination, pigment cells were arranged in a hemi-circle in the dorsal half of the vegetal plate. Inward bending of the vegetal plate first occurred at the position occupied by pigment cells, while the bending was not conspicuous in the ventral half of the blastopore. Rhodamine-phalloidin staining showed that actin filaments were abundant at the apical corticies of pigment cells. It was also found that the onset of gastrulation was considerably delayed in the NiCl2-treated embryos, in which pigment cells were drastically reduced in number. It is notable that the NiCl2-treated embryos began to gastrulate on schedule if they contained a number of pigment cells in spite of treatment. This shows that pigment cells are the bottle cells that trigger the onset of gastrulation. In the embryos devoid of pigment cells, a short stub-like gut rudiment formed in a delayed fashion, and several secondary mesenchyme cells (SMC) appeared at the tip of the rudiment and elongated gradually until its tip reached the apical plate. This observation suggests that the SMC that pull the gut rudiment upward are not pigment cells but blastocoelar cells, because pigment cells change their fate to blastocoelar cells upon NiCl2-treatment.

Animals↗

PubMed1968

Isolation and characterization of carotenoid pigments of Micrococcus roseus.

In addition to canthaxanthin, seven pigment fractions were isolated from Micrococcus roseus. They were purified by solvent partitioning and by column and thin-layer chromatography. Visible absorption spectra, chromatographic behavior, and partition coefficients of the pigments and derivatives prepared from the pigments were used in characterizing them. Both alpha- and beta-carotene derivatives were present. The structure of one pigment was suggested as phoenicoxanthin (3-hydroxy-4,4'-diketo-beta-carotene). Four other pigments were tentatively characterized as a dihydroxy-3,4-dehydro-alpha-carotene, a dihydroxy-alpha-carotene, a diketo-alpha-carotene, and a polyhydroxy-beta-carotene. Two pigments were isolated in trace amounts and could not be characterized. All the pigments studied were isolated as mixtures of cis-trans isomers and all except the diketo-alpha-carotene were isolated as esters from M. roseus. Quantitation of the pigments showed that canthaxanthin (4,4'-diketo-beta-carotene) represented 85% of the pigment recovered from extracts. Three of the other pigments contributed a significant proportion of the remaining pigments, whereas the other four were present in only small amounts. beta-Carotene derivatives comprised 96% and alpha-carotene derivatives 4% of the pigments recovered from extracts.

Carotenoids↗

PubMed1996

Pigment in prostatic epithelium and adenocarcinoma: a potential source of diagnostic confusion with seminal vesicular epithelium.

Granular cytoplasmic pigment is frequently observed in prostatic epithelium, and may cause confusion with ejaculatory ductal and seminal vesicular epithelium. We evaluated the distribution and histochemical and immunohistochemical phenotype of pigment in nine serially sectioned, whole-mounted prostatectomy specimens with carcinoma. Golden yellow-brown pigment was found in prostatic glandular epithelium in eight cases (89%) of nine, varying from inconspicuous and focal to extensive and diffuse. It was usually located in the basal portion of the secretory (lumenal) cell layer, but was also observed throughout the cytoplasm, and rarely seen in basal cells. Stromal pigment was observed in seven cases (78%) of nine and was patchy and inconspicuous. Epithelial pigment was observed throughout the prostate (transition zone, 67%; central zone, 56%; peripheral zone, 89%; and periurethral glands, 56%). Focal pigment was observed in high-grade prostatic intraepithelial neoplasia in seven cases (78%) of nine and one case (11%) of nine cases of adenocarcinoma. The epithelial pigment was histochemically similar to lipofuscin pigment (Fontana-Masson positive, bleached by permanganate reaction, Prussian blue negative, and Ziehl-Neelsen positive); S100 protein immunohistochemical stains were negative. Our results indicate that pigment is frequently present in the prostatic epithelium of all zones, at least focally, and has histochemical similarities to pigment in the seminal vesicular epithelium. Awareness of prostatic epithelial pigment is important, and the differential diagnosis of pigmented epithelium in scant specimens such as those obtained from needle biopsies includes normal and neoplastic prostatic epithelium, seminal vesicle epithelium, and ejaculatory duct epithelium.

Adenocarcinoma↗

PubMed1959

A light-sensitive yellow pigment from the housefly.

Extraction of house-fly heads with neutral phosphate buffer yielded a dark brown solution from which a number of pigments were separated, either wholly or partially, by chromatography on a column of calcium phosphate mixed with celite. One of the pigments was light-sensitive, and had a yellow color, with a spectral absorption maximum at 437 mmicro in phosphate buffer at pH 6.5. Several consecutively eluted fractions from each chromatogram of the house-fly head extract showed the characteristic absorption curve of this pigment with no trace, spectroscopically, of the other pigments of the extract. The products of bleaching the pigment at pH 6.5 had an absorption curve showing plateaus at 440 to 460 mmicro and 350 to 360 mmicro and an inflection at about 250 mmicro. Above pH 8.0 the pigment bleached in the dark giving an absorption maximum at about 380 mmicro, and inflections at 290 mmicro and at about 250 mmicro. With 2.5 to 5 N HCl or H(2)SO(4) an absorption maximum at 470 to 475 mmicro was obtained with either the unbleached or the bleached pigment. With sulfosalicylic acid, ethanol, or heating at 100 degrees C., a part of the pigment was precipitated, leaving a light-stable yellow supernatant. This light-sensitive house-fly pigment cannot as yet be identified with any of the previously known insect pigments or with the photosensitive pigments of other animals, though these latter compounds exhibit some similarity in their spectroscopic properties.

Animals↗

PubMedDate not supplied

Behavior and differentiation process of pigment cells in a tropical sea urchin Echinometra mathaei.

The behavior and differentiation processes of pigment cells were studied in embryos of a tropical sea urchin Echinometra mathaei, whose egg volume was one half of those of well-known sea urchin species. Owing to earlier accumulation of pigments, pigment cells could be detected in the vegetal plate even before the onset of gastrulation, distributed dorsally in a hemi-circle near the center of the vegetal plate. Although some pigment cells left the archenteron during gastrulation, most of them remained at the archenteron tip. At the end of gastrulation, pigment cells left the archenteron and migrated into the blastocoele. Unlike pigment cells in typical sea urchins, however, they did not enter the ectoderm, and stayed in the blastocoele even at the pluteus stage. It is of interest that the majority of pigment cells were distributed in the vicinity of the larval skeleton. Aphidicolin treatment revealed that eight blastomeres were specific to pigment cell lineage after the eighth cleavage, one cell cycle earlier than that in well-known sea urchins. The pigment founder cells divided twice, and the number of pigment cells was around 32 at the pluteus stage. It was also found that the differentiation of pigment cells was blocked with Ni2+, whereas the treatment was effective only during the first division cycle of the founder cells.

Animals↗

PubMedDate not supplied

Effect of the barring gene on eye pigmentation in the fowl.

Pigment cells of the iris, pecten, retinal pigment epithelium, and choroid of the wild-type jungle fowl (JF) and the barred Plymouth rock (BPR) breeds of adult chickens were studied at both light and electron microscopic levels. BPR choroidal tissues had 2.8 times fewer melanophores than the JF choroid, and BPR melanophores also contained 2.4 times fewer melanosomes, which tended to clump together in variously sized clusters. The melanosomes were often irregular in shape, smaller in diameter, and less mature (stage III) than those granules in the JF. The retinal pigment epithelium of both JF and BPR breeds contained a single epithelial layer of columnar cells. Rod-shaped melanosomes were present in the more apical regions of this cell type in both breeds. Both JF and BPR irides contained a multilayered posterior pigmented epithelium of columnar shaped cells that were densely filled with large spherical granules. Intercellular spaces with interdigitating cytoplasmic projections were present between pigment cells of both breeds. The pecten melanophores of both breeds were dendritic with melanosomes that were larger and fewer in numbers than those pigment cells of the iris and choroid. Intercellular spaces were present between cells in both breeds, with numerous villous-like pigment cell extensions. Choroid melanophores contained very little, if any, acid phosphatase activity. Approximately one-half of the retinal pigment epithelial cells observed contained small amounts of diffuse acid phosphatase activity in both breeds. The iris and pecten melanophores of both breeds contained profuse acid phosphatase activity scattered throughout their cytoplasms. Sparse tyrosinase activity was seen in iris and pecten pigment cells, whereas no tyrosine activity was observed in choroid melanophores or in retinal pigment epithelial cells in the two breeds, indicating that little new melanogenesis occurs in adult pigmented eye tissues. The results show that the barring gene reduces the number and melanin content of the choroidal melanophores in homozygous male BPR chickens as compared to the wild-type JF chickens. Whether this gene prevents the initial migration of embryonic neural crest cells (future melanophores) to the choroid or whether some of the choroidal melanophores prematurely degenerate in the embryo of young birds is yet to be determined. If the latter is the case, this choroid system may serve as a model for a genetic hypomelanotic disease such as vitiligo.

Acid Phosphatase↗

PubMed1995

Retinal pigment epithelial wound healing in vivo.

OBJECTIVE: To develop an in vivo rabbit model of retinal pigment epithelial wound healing that preserves the overlying retina. METHODS: Hydraulic débridement of the retinal pigment epithelium was performed in one eye of 35 pigmented rabbits by means of a pars plana vitrectomy approach. Five of the 35 eyes were examined by stereoscopic color fundus photography, fluorescein angiography, and light microscopy on each of the following postoperative days: 0, 2, 4, 7, 14, 28, and 56. RESULTS: Retinal pigment epithelial débridement with this technique results in apical decapitation of the retinal pigment epithelial cells followed by subsequent hydraulic removal of the residual nucleus-containing basal cellular debris. The retinal pigment epithelium-denuded Bruch's membrane was resurfaced mostly by a monolayer of flattened, hypopigmented retinal pigment epithelial cells within 4 days after débridement. Progressive retinal pigment epithelial hyperplasia also occurred beginning between postoperative days 2 and 4. CONCLUSIONS: Retinal pigment epithelial wound healing after hydraulic débridement occurs rapidly and in a manner initially consistent with sliding migration. Progressive retinal pigment epithelial hyperplasia also occurs and may contribute to this repair process. Further investigation of retinal pigment epithelial repair by means of this in vivo model may provide important insight into the pathogenesis and treatment of outer retinal disorders.

Animals↗