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PubMed2004

Height changes associated with pigment aggregation in Xenopus laevis melanophores.

Melanophores are pigment cells found in the skin of lower vertebrates. The brownish-black pigment melanin is stored in organelles called melanosomes. In response to different stimuli, the cells can redistribute the melanosomes, and thereby change colour. During melanosome aggregation, a height increase has been observed in fish and frog melanophores across the cell centre. The mechanism by which the cell increases its height is unknown. Changes in cell shape can alter the electrical properties of the cell, and thereby be detected in impedance measurements. We have in earlier studies of Xenopus laevis melanophores shown that pigment aggregation can be revealed as impedance changes, and therefore we were interested in investigating the height changes associated with pigment aggregation further. Accordingly, we quantified the changes in cell height by performing vertical sectioning with confocal microscopy. In analogy with theories explaining the leading edge of migrating cells, we investigated the possibility that the elevation of plasma membrane is caused by local swelling due to influx of water through HgCl2-sensitive aquaporins. We also measured the height of the microtubule structures to assess whether they are involved in the height increase. Our results show that pigment aggregation in X. laevis melanophores resulted in a significant height increase, which was substantially larger when aggregation was induced by latrunculin than with melatonin. Moreover, the elevation of the plasma membrane did not correlate with influx of water through aquaporins or formation of new microtubules, Rather, the accumulation of granules seemed to drive the change in cell height.

Animals↗
PubMed2006

Melanin granule models for the processes of laser-induced thermal damage in pigmented retinal tissues. I. Modeling of laser-induced heating of melanosomes and selective thermal processes in retinal tissues.

The computer modeling was applied for investigation of the processes of laser-induced tissue damage. The melanin granule models for the processes of laser-induced thermal damage and the results of computer modeling of the optical, thermophysical, and thermochemical processes during selective laser interaction with melanoprotein granules (melanosomes) in retinal pigment epithelium are presented in this paper. Physical-mathematical model and system of equations are formulated which describe thermal interaction processes for "short" laser pulses of duration t (p)<10(-6) s and for " long' pulses of duration t(p) > 10(-6) s. Results of numerical simulation of the processes give the space-time distributions of temperature and degrees of thermodenaturation of the protein molecules inside and around melanosomes and in the volume of irradiated tissues. Energy absorption, heat transfer and thermochemical (thermodenaturation, coagulation) processes occurring during the interaction of laser pulses with pigmented spherical and spheroidal granules in heterogeneous tissues are theoretically investigated. The possibility for selective interaction of short laser pulses with pigmented granules is discussed which results in the formation of denaturation microregions inside and near the pigmented granules (granular thermodenaturation) without origination of a continuous macroscopic thermodenaturation lesion in tissue. Analytical model of heating of single spherical and spheroidal granule under laser pulse is presented. Simple equations for time dependencies of particle temperature are obtained. The presented results are of essential interest for laser applications in and can be used for investigation of laser interaction with pigmented tissues in different fields of laser medicine.

Computer Simulation↗
PubMed1977

Pattern dystrophy of the pigment epithelium.

Three generations of a family showed alterations in the retinal pigment epithelium along with mild visual disturbance. Younger members had granular pigment dispersed beneath the fovea while older members showed a reticular pigment pattern. The electro-oculogram was subnormal in most affected individuals, but visual fields, color vision, dark adaptation, and the electroretinogram were normal. The pigmentary changes in these patients are similar to those seen in other pigment epithelial dystrophies such as reticular dystrophy and butterfly-shaped dystrophy. Until these disorders can be separated pathophysiologically, we suggest the definition of a more inclusive clinical term, "pattern dystrophies of the pigment epithelium.

Adolescent↗
PubMed1982

Lipids of pigment gallstones.

The lipids of pigment gallstones were analyzed. In contrast to previous reports, pigment stones were found to contain a wide variety of free fatty acids. In addition, pigment stones contained unhydrolyzed phospholipids. Both free fatty acids and phospholipids were present in much higher concentrations in a brown stone obtained from a patient with a biliary tract infection than in a black stone obtained from a patient with sterile bile and a long-standing hemolytic anemia. However, the phospholipids in both kinds of stone consisted primarily of phosphatidylcholine. Separation of stone and bile phosphatidylcholines into their individual molecular species by high performance liquid chromatography indicated that the phosphatidylcholines in stones closely resemble those in bile. The data suggest that both the free fatty acids and the phosphatidylcholine of pigment stones derive from bile phosphatidylcholine, but that the extent of bile phosphatidylcholine participation in pigment stone formation may be variable.

Adult↗
PubMed1983

A subcortical, pigment-containing structure in Xenopus eggs with contractile properties.

An accumulation of insoluble, finely granular material has been observed under the pigmented surface of Xenopus eggs by a specialized "dry fracture" technique and scanning electron microscopy. Cortical granules and pigment granules can be recognized with the techniques and can be seen to be embedded in the material. Thin sections show that the region also contains mitochondria and membranous vesicles or reticula. Yolk platelets are largely excluded from the heaviest accumulations of the material. The substance is most dense just under the cortex and grades off gradually into the more diffuse, yolk-containing network of the endoplasm. The accumulation of material is much thicker in the animal hemisphere of the egg than in the vegetal hemisphere, and the pigment embedded in it defines the pigmented area of the animal hemisphere. In the pigmented area the material excludes yolk for a thickness of 3-7+ microns from the surface. In the vegetal hemisphere there is no such accumulation and yolk platelets can be found almost touching the plasmalemma. Cortical contractions have been experimentally induced in eggs. Their relative strength correlates with the relative thickness of the finely granular, subcortical material. During contraction the material accumulates to much greater thicknesses, excluding yolk from thicknesses of 15-30+ microns from the surface. The contracting entity is, or is in, the finely granular material. Injection of cytochalasins into the eggs inhibits cleavage furrow operation but does not inhibit the induced cortical contractions. The thus do not seem to be dependent on actin microfilamentogenesis as is the operation of the contractile ring of the cleavage furrow. The differential sensitivity to cytochalasins of the contractile ring and the system responding in the induced cortical contractions, suggests a two-component system for cortical contractions in the egg. A model is presented which accommodates the available data.

Animals↗
PubMed1987

Growth and development of the mouse retinal pigment epithelium. II. Cell patterning in experimental chimaeras and mosaics.

The retinal pigment epithelium (PE), with pigmentation as a cell-autonomous marker, was analyzed in three types of mice: congenic pigmented----albino chimaeras, X-inactivation mosaics (Cattanach's translocation), and mosaics homozygous for the pink-eyed unstable mutation, which contain rare fully pigmented cells. In 10 chimaeric and 34 X-inactivation eyes, the proportionate mix in the right and left eyes of an individual animal was similar, the mix was approximately constant in all parts of a given eye, average patch size was larger toward the periphery of the PE, and peripheral patches tended to be elongated in the radial dimension. In all 44 whole mounts from pink-eyed unstable mutants, patches of 1-12 pigmented cells, each representing a single clone, were scattered throughout the PE; they tended to be larger with increasing distance from the optic nerve head. The collective data are consistent with significant cell mixing prior to specification of the two eye fields, during early organ-forming stages, and during later development of the PE. The tendency of peripheral patches to orient radially reflects the edge-biased pattern of cell proliferation in the PE. Cell mixing appears to be more prominent posteriorly in the PE sheet; growth proceeds anteriorly for more generations.

Animals↗
PubMed1983

Cytochemical evaluation of anionic sites on the surface of cultured pigment epithelium cells from normal and dystrophic RCS rats.

Anionic sites on the surface of cultured pigment epithelium cells from normal and dystrophic rats were studied. Cytochemical procedures and quantitative analysis were employed in order to determine distribution patterns and labeling densities. Anionic sites, in general, were localized with cationized ferritin at pH 7.0. The presence and density of sialic acid residues on the pigment epithelium cell surface were evaluated with colloidal iron at pH 1.8. Dystrophic cells contained 20% more cationized ferritin-binding sites as compared with normal pigment epithelium cells. With colloidal iron, an 18% increase in labeling density was measured in dystrophic pigment epithelium cells. Pretreatment with neuraminidase reduced subsequent labeling with colloidal iron by 93-97%. Thus, the presence of sialic acid residues on the surface of pigment epithelium cells and a significant increase in its content on the surface of dystrophic cells were established.

Animals↗
PubMed1990

Expression of the cell surface antigens RET-PE2 and N-CAM by rat retinal pigment epithelial cells during development and in tissue culture.

Invagination of the optic vesicle to form the optic cup results in the formation of two apposed layers of neuroepithelium which follow divergent developmental pathways. Changes in the expression of cell surface molecules may be either the cause or result of important inductive signals during this process. We have used immunological reagents to study the expression of two molecules in the rat: the neural cell adhesion molecule N-CAM, and a cell membrane-associated protein which is specific for pigment epithelium in the adult, RET-PE2. Both N-CAM and RET-PE2 are present in both layers of the optic cup at embryonic age E13, but they become restricted to inner retina and pigment epithelium, respectively, by E17 and maintain that pattern of expression in the normal adult. Culture of pigment epithelial cells results in the reexpression of N-CAM and the continued expression of RET-PE2. Western blotting reveals that the size and relative proportions of the 180- and 140-kDa N-CAM molecules synthesized by rat pigment epithelial cells in vitro differ from that made by rat brain, retina and liver. Embryonic RPE N-CAM contains the sulfated carbohydrate recognized by the HNK-1 antibody, but this epitope was not present on N-CAM synthesized by cultured RPE cells. The reexpression of an embryonic antigen when placed in culture suggests that pigment epithelial cells retain some degree of plasticity in the adult state.

Animals↗
PubMed1992

Kynurenine identified as the short-wave absorbing lens pigment in the deep-sea fish Stylephorus chordatus.

A number of deep-sea fish have bright yellow lenses whose coloration is attributable to a variety of largely unidentified short-wave absorbing pigments. Here the pigment of the deep-sea fish Stylephorus chordatus has been isolated and identified by NMR and mass spectroscopy as kynurenine; a pigment also found in the human lens. The degree of this pigmentation is greater in older animals. The fact that the lenses of both a deep-sea fish and man contain the same pigment is of interest, given the vastly different light environments they inhabit.

Animals↗
PubMed1991

The differential diagnosis of Crigler-Najjar disease, types 1 and 2, by bile pigment analysis.

Phenobarbital response, bile pigment composition, and the fractional biliary excretion ratio of bilirubin were studied in nine children with Crigler-Najjar disease. In five children, serum bilirubin levels decreased during phenobarbital treatment by 26% or more and the pigment composition in bile changed with a decrease in the proportion of unconjugated bilirubin from 33% +/- 12% to 13% +/- 1% and an increase in monoconjugates and diconjugates from 57% +/- 14% and 10% +/- 2%, respectively, to 72% +/- 4% and 16% +/- 3%. In four children, serum bilirubin levels did not change significantly during phenobarbital treatment. In these patients, bile pigments comprised 91% +/- 10% unconjugated bilirubin, 9% +/- 11% monoconjugates, and 1% +/- 1% diconjugates. On the basis of these differences, the former group can be classified as having type 2 Crigler-Najjar disease and the latter, type 1. Bile pigment analysis in parents of patients with Crigler-Najjar disease showed an increased proportion of monoconjugates in at least one of the partners in three of four couples tested, despite normal serum bilirubin levels. Serum bilirubin levels were about the same in type 1 and 2 patients and amounted to 236 +/- 62 mumol/L and 214 +/- 82 mumol/L, respectively. In addition the fractional bilirubin excretion ratio, calculated as the ratio ([bilirubin in bile]/[bilirubin in serum])/([bile acid in bile]/[bile acid in serum]) could not differentiate between these two groups. However, there was a 10-fold and 100-fold difference of this ratio between patients with Crigler-Najjar disease and those with Gilbert's syndrome and between patients with Crigler-Najjar disease and controls. The fractional bilirubin excretion ratio proved an excellent tool to differentiate between Gilbert's syndrome and Crigler-Najjar disease, whereas Crigler-Najjar disease types 1 and 2 could be differentiated on the basis of bile pigment analysis.

Bile↗
PubMed1989

Oral calcium promotes pigment gallstone formation.

Dietary calcium supplementation has been recommended for prevention of osteoporosis and has become a standard component of most "health food" diets. Biliary calcium has been recognized to play a central role in the formation of pigment gallstones. We have recently demonstrated that 5 days of oral calcium supplementation significantly increases biliary calcium in the prairie dog (K. D. Lillemoe, T. H. Magnuson, G. E. Peoples, et al., Gastroenterology 94: A563, 1988). We hypothesized, therefore, that long-term oral calcium supplementation would promote pigment gallstone formation. Sixteen adult male prairie dogs were maintained on a standard nonlithogenic diet. Eight animals received calcium supplementation (2.5 x control levels) in their water, while the remaining eight animals served as controls. After 8 weeks, cholecystectomy was performed, and the common bile duct was cannulated. Bile was examined microscopically and analyzed for ionized calcium, bilirubin, glycoprotein, and biliary lipids. The cholesterol saturation index (CSI) was calculated. Pigment stones and calcium bilirubinate sludge were present in all animals receiving calcium supplementation. Only one control animal had evidence of pigment stones (P less than 0.001). Biochemical analysis of gallbladder bile demonstrated a significant increase in total bilirubin and bilirubin monoglucuronide (P less than 0.01) as well as bile glycoprotein content (P less than 0.05) after oral calcium supplementation. Gallbladder bile ionized calcium was also increased although not significantly. These data suggest that oral calcium supplementation promotes gallbladder sludge and pigment gallstone formation in the prairie dog. This observation raises concern that oral calcium supplementation, especially in the older female population, may enhance gallstone formation.

Animals↗
PubMed1990

More unusual pigmentations of the gingiva.

Three unusual types of oral pigmentation are presented. The first is a brown orange pigmentation caused by the habit of using the bark of Juglans regia for teeth cleaning. The second is a bright yellow pigmentation associated with the habit of chewing the seeds of Cola nitida. The third is a generalized mousy brown pigmentation related to the habit of chewing the leaves of Catha edulis. The purpose of this article is to describe the nature of these pigmentations and to present their clinical and histologic features.

Adult↗
PubMed1985

Placental malaria and foetoplacental function: low plasma oestradiols associated with malarial pigmentation of the placenta.

Placental biopsies were taken immediately post partum from 65 Gambian mothers who had not received anti-malaria chemoprophylaxis during pregnancy whilst living in an area hyperendemic for Plasmodium falciparum malaria. The biopsies were examined without knowledge of the mothers' health or the outcome of pregnancies. Histologically, they were divided into two groups: those with macrophages containing malarial pigment in the inter-villous spaces, and those without such pathology. Babies with pigmented placentae had a mean (SD) weight for gestational age of 83.3 (10.6)%, which was significantly lower (p less than 0.01) than that of 91.2 (7.7)% in the non-pigmented group. The plasma oestradiol concentrations in the mothers who later delivered pigmented placentae were significantly lower from 32 weeks of gestation onwards, and did not continue to rise in the last trimester as they did in the non-pigmented group. The last trimester appears to be the critical time for protection of the foeto-placental unit against malaria. Anti-malaria chemoprophylaxis should be given to all pregnant women.

Birth Weight↗
PubMedDate not supplied

Intraleucocytic malaria pigment and prognosis in severe malaria.

The quantity of malaria pigment liberated into the circulation at schizogony reflects the pathogenic sequestered parasite burden in Plasmodium falciparum malaria, and may therefore be a measure of disease severity. Among 300 consecutive adult patients with severe falciparum malaria, the 40 who died had significantly higher proportions of malaria pigment-containing neutrophils on admission (mean = 7.7%, standard deviation (SD) = 5.9%) and pigment-containing monocytes (mean = 8.6%, SD = 5.9%) than did survivors (mean 3.2%, SD = 4.1% and mean 4.8%, SD = 4.6%, respectively) (P < 0.0001). This proved a better indicator of prognosis than the peripheral parasite count. A count of peripheral neutrophils containing visible pigment > or = 5% predicted a fatal outcome with 73% sensitivity and 77% specificity (relative risk 6.2, 95% confidence interval (CI) 3.2-11.8) compared to 60% sensitivity and 57% specificity for parasitaemia > 100,000/microL (relative risk 1.8, 95% CI 1.0-3.3). The peripheral blood count of pigment-containing neutrophils in severe malaria is a rapid, simple, and practical prognostic test.

Adipose Tissue↗
PubMed1982

Range of modulation of light sensitivity by accessory pigments in the crayfish compound eye.

The compound eye of the crayfish during dark adaptation undergoes an enhancement of light sensitivity within a range of 3 log units. Only 1 log unit can be explained by the increase in responsiveness of the retinula cells. The rest can be accounted for by the migration of the proximal and distal accessory pigments. In isolated retinas, with the distal pigment paralysed in light-adapted position and the proximal pigment only partially responsive, the sensitivity enhancement in darkness is reduced in more than 1 log unit. By hormonally inducing the expansion of the distal pigment while the rest of the system remains dark-adapted, there is a shift of one log unit in the V-log 1 curve. In a crayfish mutant devoid of the two dark accessory pigments, the sensitivity enhancement in dark adaptation only covers one log unit.

Animals↗
PubMed1983

Seasonal variation of the vitamin A2-based visual pigment in the retina of adult bullfrog, Rana catesbeiana.

Visual pigment composition was determined by HPLC analysis over a one-year period in the adult bullfrog (Rana catesbeiana). In Japan, the vitamin A2-based pigment was only 5% of the total visual pigment from the middle of July to October. The vitamin A2-based pigment increased in November and reached a maximum of 32-36% between January and June. This seasonal variation may relate to the average of outdoor temperature rather than the daylight hours. The amount of vitamin A2-based pigment began to increase when the average temperature became lower than 20 degrees C and it decreased rapidly as the average temperature was higher than 20 degrees C.

Animals↗
PubMed1983

Determination of human cone pigment density difference spectra in spatially resolved regions of the fovea.

A new method was developed to measure spectrally and spatially resolved cone pigment optical density difference in normal human subjects. Using digitized television images of human retinas scanned before and after bleaching the cone pigments with a bright light, unique high-resolution images of cone pigment density difference were produced. The spectral peak density difference within the fovea was found to be at 560 nm. These measurements demonstrate a decrease in cone pigment optical density difference with increased distance from the subject's central fixation point in the fovea. The cone pigment density difference was asymmetrically distributed in the fovea with higher amounts on the nasal side.

Dark Adaptation↗
PubMed1984

Annual variations in the visual pigments of brown trout inhibiting lochs providing different light environments.

Visual pigments were extracted at regular intervals over the year from trout (Salmo trutta) inhabiting three Scottish lochs. Measurements of the spectral quality of the light in the lochs were also made. In all cases only A2-based pigment was found in the winter, with A1-based pigment appearing as well in summer. Fish from Loch Turret had significantly less A1-based pigment than fish from the other two lochs. Loch Turret differs from the other two lochs in being dystrophic, as opposed to eutrophic, and the light penetrating into it has more long wavelength energy. Possible correlations between this environmental difference and the visual pigments of the three trout populations are discussed.

Animals↗