Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PIGMENTATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,621 records · Page 90Linked to original sources
PubMed1992

Protein kinase C activation antagonizes melatonin-induced pigment aggregation in Xenopus laevis melanophores.

The pineal hormone, melatonin (5-methoxy N-acetyltryptamine) induces a rapid aggregation of melanin-containing pigment granules in isolated melanophores of Xenopus laevis. Treatment of melanophores with activators of protein kinase C (PKC), including phorbol esters, mezerein and a synthetic diacylglycerol, did not affect pigment granule distribution but did prevent and reverse melatonin-induced pigment aggregation. This effect was blocked by an inhibitor of PKC, Ro 31-8220. The inhibitory effect was not a direct effect on melatonin receptors, per se, as the slow aggregation induced by a high concentration of an inhibitor of cyclic AMP-dependent protein kinase (PKA), adenosine 3',5'-cyclic monophosphothioate, Rp-diastereomer (Rp-cAMPS), was also reversed by PKC activation. Presumably activation of PKC, like PKA activation, stimulates the intracellular machinery involved in the centrifugal translocation of pigment granules along microtubules. alpha-Melanocyte stimulating hormone (alpha-MSH), like PKC activators, overcame melatonin-induced aggregation but this response was not blocked by the PKC inhibitor, Ro 31-8220. This data indicates that centrifugal translocation (dispersion) of pigment granules in Xenopus melanophores can be triggered by activation of either PKA, as occurs after alpha-MSH treatment, or PKC. The very slow aggregation in response to inhibition of PKA with high concentrations of Rp-cAMPS, suggests that the rapid aggregation in response to melatonin may involve multiple intracellular signals in addition to the documented Gi-mediated inhibition of adenylate cyclase.

Adenosine Monophosphate↗
PubMed1966

The effect of strychnine and light on pigmentation in Blepharisma undulans Stein.

The effect of strychnine sulfate and light on pigmentation in the ciliate protozoan Blepharisma undulans has been determined. Upon exposure of cells to strychnine, the pigment granules become loosened from their surrounding membranes. Eventually these membranes break and the granules are simultaneously released from the cell. At the cell surface, a fusion occurs between adjacent membraneless granules with the incorporation of membrane fragments. This fusion of granules and membrane fragments results in the formation of a pigmented "capsule" around the organism. After elimination of the pigment, the granule membranes remaining in the cytoplasm fuse to form apparently empty vesicles. Other cell organelles are generally undisturbed. A similar situation occurs upon exposure of cells to artificial light for 12 to 18 hr, however, the slow elimination of granules from the cells under these conditions does not result in the formation of a pigmented "capsule." The possible mechanisms of these reactions are discussed.

Ciliophora↗
PubMed1969

Lipofuscin (aging) pigment granules of the newborn human liver.

We have observed pigmented cytoplasmic granules, with the characteristic staining properties of lipofuscin (ceroid, "wear-and-tear") pigment, in newborn human liver. The pigment is found at the periphery of the lobule in hepatocytes and some bile ductular cells. It is acid-fast, PAS-positive after diastase digestion, slightly argyophilic and sudanophilic, and markedly Schmorl's- and peroxidase positive in paraffin sections. Difficult to see in sections stained with hematoxylin and eosin, the pigment can be detected in unstained sections. The granules also resemble lipofuscin found in adult tissues, in their ultra-structural and enzymatic properties. They are polymorphic, contain granular material of moderate and high electron opacity, and are delimited by a single membrane. Acid phosphatase and beta-glucuronidase activities are visualized in the newborn granules, identifying them as lysosomes. The granules also contain copper and, to a much lesser extent, iron. The accumulation of lipofuscin pigment in lysosomes in many tissues correlates well with aging, and this process has been interpreted as a reflection of cellular degeneration or wear-and-tear. However, the presence of lipofuscin granules as a constant component of neonatal liver suggests that they are not a measure of cellular senescence.

Acid Phosphatase↗
PubMed1974

Effects of cyclic AMP and Sephadex fractions of chick embryo extract on cloned retinal pigmented epithelium in tissue culture.

The effects of dibutyryl cyclic 3',5'-adenosine monophosphate (BcAMP) and Sephadex G-25 fractions of chick embryo extract on the growth rate, morphology, and pigmentation of normal chick retinal pigmented epithelium (PE) were investigated. Seven cloned PE cell lines were each grown in modified Ham's F-12 medium alone (F-12), or in F-12 supplemented with either high molecular weight (H) or low molecular weight (L) fractions of chick embryo extract. Cells grown in F-12 alone or in L medium formed compact epithelial sheets, whereas cells grown in H had a fibrocytic appearance and formed poorly organized monolayers. In H plus BcAMP, cell morphology was more epithelioid than in H alone, and generally the monolayers appeared more differentiated. Under each of these three culture conditions, 2 x 10(-4) M BCAMP retarded the increase in cell number and decreased the final number of cells per culture dish, but had little effect on plating efficiency. BcAMP also increased the rate of cell adhesion to a plastic substratum. Pigmentation was marked in cultures grown in F-12 or in L alone, but the addition of BcAMP dramatically reduced visible pigmentation. This effect was reversed when BcAMP was removed from the culture medium. Thus BcAMP modifies cell and colonial morphology, rate of cell accumulation, adhesive properties, and pigmentation of normal PE cells.

Animals↗
PubMed1979

Evidence for rapid structural and functional changes of the melanophore microtubule-organizing center upon pigment movements.

Melanophores of the angelfish, pterophyllum scalare, have previously been shown to display approximately 2,400 microtubules in cells wih pigment dispersed; these microtubules radiate from a presumptive organizing center, the central apparatus (CA), and their number is reduced to approximately 1,000 in the state with aggregated pigment (M. Schliwa and U. Euteneuer, 1978, J. Supramol. Struct. 8:177-190). In an attempt to elucidate the factors controlling this rapid reorganization of the microtubule apparatus, structure and function of the CA have been investigated under different physiological conditions. As a function of the state of pigment distribution, melanophores differ markedly with respect to CA organization. A complex of dense amorphous aggregates and associated fuzzy material, several micrometers in diameter, surrounds the centrioles in cells with pigment dispersed, and numerous microtubules emanate from this complex in a radial fashion. In the aggregated state, on the other hand, few microtubules are observed in the pericentiolar region, and the amount of fibrous material is greatly reduced. These changes in CA morphology as a function of the state of pigment distribution are associated with a marked difference in its capacity to initiatiate the assembly of microtubules from exogenous pure porcine brain tubulin in lysed cell preparations. After complete removal of preexisting microtubules, cells lysed in the dispersed state into a solution of 1-2 mg/ml pure tubulin have numerous microtubules associated with the CA in radial fashion, while cells lysed in the aggregated state nucleate the assembly of only a few microtubules. We conclude that it is the activity of the CA that basically regulates the expression of microtubules. This regulation is achieved through a variation in the capacity to initiate microtubule assembly. Increase or decrease in the amount of dense material, as readily observed in the cell system studied here, seems to be a morphologic expression of such a physiologic function.

Animals↗
PubMed1981

Demonstration of contractility of circumferential actin bundles and its morphogenetic significance in pigmented epithelium in vitro and in vivo.

Each pigmented epithelial cell bears circumferential actin bundles at its apical level when the pigmented epithelium is established in eyes in situ or in culture in vitro. Well-differentiated pigmented epithelia in culture were treated with a 50% glycerol solution containing 0.1 M KCl, 5 mM EDTA, and 10 mM sodium phosphate buffer, pH 7.2, for 24 h or more at 4 degrees C. When the glycerinated epithelium was transferred to the ATP solution, each cell constituting the epithelium began to contract. The epithelium was cleaved into many cell groups as a result of contraction of each cell. The periphery of each cell group was lifted to form a cup or vesicle and eventually detached from the substratum. However, those cells that had not adhered tightly and not formed a monolayer epithelium with typical polygonal cellular pattern contracted independently as observed in the glycerinated fibroblasts. Contraction of the glycerinated pigmented epithelial cells was inhibited by N-ethylmaleimide but not by cytochalasin B. ITP and UTP also effected the contraction of the glycerinated cells, but GTP and ADP did not. Ca2+ was not required. This contractile model of pigmented epithelium provides a useful experimental system for analyzing the function of actin in cellular morphogenesis.

Actins↗
PubMedDate not supplied

Marginal differentiation between the sexual and general carotenoid pigmentation of guppies (Poecilia reticulata) and a possible visual explanation.

We present the first detailed analysis of carotenoid pigmentation of the integument of guppies (Poecilia reticulata Peters), quantifying variation in carotenoid content and composition of wild guppies from three drainages on Trinidad (1) between the sexual and general pigmentation of males, (2) between the sexes, and (3) geographically in relation to carotenoid availability. We report that the carotenoid pigments in the integument of guppies are predominantly esters of tunaxanthin. The peak wavelength of carotenoids in the orange spots of males lay only ca. 2.8 nm higher than that of pigments outside of the orange spots, and the peak wavelength of carotenoids in the male whole integument does not differ from that in the female whole integument. Carotenoid composition of the general integument of females and the non-orange spot fraction of males, but not of the orange spot fraction of males, varied with diet, correlating with the ratio beta-carotene to lutein in the different streams. Male guppies deposit higher concentrations of carotenoids in their orange spots than in the rest of the integument (five to nine times higher), but not at the expense of the general integument, which was similarly endowed as the general integument of females, even in carotenoid-poor streams. Presumably males absorb/retain more pigments than females. Photoreceptor-based simulations suggest that tunaxanthin provides both greater brightness and chroma than would 4-keto-carotenoids such as astaxanthin.

Analysis of Variance↗
PubMed1989

Effects of adrenergic agents on alpha-chymotrypsin-induced ocular hypertension in albino and pigmented rabbits: a comparative study.

Alpha-chymotrypsin-induced ocular hypertension in albino rabbits is widely used as an experimental model to screen potential antiglaucoma drugs. The present study compares the intraocular pressure (IOP) response following the ocular application of single or repeated adrenergic agents in conscious albino and pigmented rabbits. A single instillation of clonidine was not as effective in lowering the IOP in pigmented hypertensive rabbit eyes as in albino hypertensive eyes. Similarly, betaxolol moderately lowered the IOP in albino rabbits but induced a slight response when pigmented rabbits were used as an experimental model. Twice-a-day applications of betaxolol in pigmented hypertensive eyes permitted an identical level of IOP decrease to be reached, as observed in a one-day study in albino rabbits, after at least 6 days of treatment. It has been suggested that the pigmented layers of the iris-ciliary body may act as sites for topically applied antiglaucoma drugs. Non-specific binding could explain in part the frequent discrepancy observed between the preclinical results obtained in albino hypertensive rabbit eyes and clinical results obtained in glaucomatous human eyes.

Adrenergic beta-Antagonists↗
PubMed1989

Cytotoxic and neoplastic transforming effects of industrial hexavalent chromium pigments in Syrian hamster embryo cells.

Twenty eight moderately water-soluble to insoluble chromium (VI) compounds, such as zinc and lead chromate, industrial and laboratory synthesized pigments, and the analytical reagents strontium, barium and calcium chromate, were physicochemically characterized and studied for cytotoxicity and morphological transformation in cultured Syrian hamster embryo (SHE) cells. In vivo validation of malignancy of transformed SHE cells was performed. A high physicochemical diversity among the complex chromium pigments was revealed. The solubility of the compounds was greatly increased after incubation in a complete medium and even higher under cell culture conditions. The cytotoxic effects appeared to be due principally to extracellular solubilized chromium because the most solubilized compounds. Zn, Ca and Sr chromates, were equitoxic at about the same Cr concentration treatment and 8-fold more cytotoxic than less soluble compounds such as some Pb chromates and Ba chromate. However, certain physicochemical properties of lead chromate pigments could also influence their cytotoxic activity. All test compounds were, in a dose-dependent manner, efficient in inducing morphological transformation of SHE cells. Many of the Cr pigments, although physicochemically different, were similarly effective in transformation induction. Nevertheless, compounds among Zn and Pb chromates had various transforming potencies. Ba chromate was the least active in inducing transformation. Certain physicochemical properties could mediate the transforming activity but no particular relationship could be established between any one of the physicochemical parameters and the transforming potency. Cloned morphologically-transformed colonies of SHE cells were grown in soft agar medium and showed true neoplastic behaviour by tumour formation in syngeneic animals. These results show that various chromate pigments containing either Zn or Pb, of medium to very low aqueous solubility, induced neoplastic transformation of SHE cells.

Animals↗
PubMed2005

A motion-sensitive area in ferret extrastriate visual cortex: an analysis in pigmented and albino animals.

In search of the neuronal substrate for motion analysis in the ferret (Mustela putorius furo), we extracellularly recorded from extrastriate visual cortex in five pigmented and two albino ferrets under general anaesthesia and paralysis. Visual stimulation consisted of large area random dot patterns moving either on a circular path in the frontoparallel plane or expanding and contracting radially. Strongly direction-selective neurons were recorded in a circumscribed area in and just posterior to the suprasylvian sulcus, thus named by us the posterior suprasylvian area (area PSS). Altogether, we recorded 210 (90%) and 95 (72%) PSS neurons in pigmented and albino ferrets, respectively, that were direction selective. In these neurons responses during random dot pattern stimulation in the preferred direction were at least twice as strong than stimulation in the non-preferred direction. Response strength in preferred direction and tuning sharpness of PSS neurons in albinos were significantly reduced when compared to pigmented animals (median values: 34.1 versus 14.8 spikes/s and 142 versus 165 degrees for pigmented and albino ferrets, respectively). Inter-spike-intervals during visual stimulation were significantly shorter in pigmented (median 9 ms) than in albino PSS neurons (median 14 ms). Our data indicate that area PSS may play a crucial role in motion perception in the ferret.

Action Potentials↗
PubMed1998

Dominant defects in Drosophila eye pigmentation resulting from a euchromatin-heterochromatin fusion gene.

We have isolated a dominant mutation, pugilistDominant (pugD), that causes variegated reductions in pteridine and ommochrome pigmentation of the Drosophila eye. The effect of pugD on pteridine pigmentation is most dramatic: the only remaining pigment consists of a thin ring of pigment around the periphery of the eye with a few scattered spots in the center. The pugD mutation disrupts a gene that encodes a Drosophila homolog of the trifunctional enzyme methylenetetrahydrofolate dehydrogenase (MTHFD; E.C.1.5.1.5, E.C.3.5. 4.9, E.C.6.3.4.3). This enzyme produces a cofactor that is utilized in purine biosynthesis. Because pteridines are derived from GTP, the pigment defect may result from an impairment in the production of purines. The mutant allele consists of a portion of the MTHFD coding region fused to approximately 1 kb of highly repetitive DNA. Transcription and translation of both parts are required for the phenotype. The repetitive DNA consists of approximately 140 nearly perfect repeats of the sequence AGAGAGA, a significant component of centric heterochromatin. The unusual nature of the protein produced by this gene may be responsible for its dominance. The repetitive DNA may also account for the variegated aspect of the phenotype. It may promote occasional association of the pugD locus with centric heterochromatin, accompanied by inactivation of pugD, in a manner similar to the proposed mode of action for brownDominant.

Animals↗
PubMed2000

Defective pigment granule biogenesis and aberrant behavior caused by mutations in the Drosophila AP-3beta adaptin gene ruby.

Lysosomal protein trafficking is a fundamental process conserved from yeast to humans. This conservation extends to lysosome-like organelles such as mammalian melanosomes and insect eye pigment granules. Recently, eye and coat color mutations in mouse (mocha and pearl) and Drosophila (garnet and carmine) were shown to affect subunits of the heterotetrameric adaptor protein complex AP-3 involved in vesicle trafficking. Here we demonstrate that the Drosophila eye color mutant ruby is defective in the AP-3beta subunit gene. ruby expression was found in retinal pigment and photoreceptor cells and in the developing central nervous system. ruby mutations lead to a decreased number and altered size of pigment granules in various cell types in and adjacent to the retina. Humans with lesions in the related AP-3betaA gene suffer from Hermansky-Pudlak syndrome, which is caused by defects in a number of lysosome-related organelles. Hermansky-Pudlak patients have a reduced skin pigmentation and suffer from internal bleeding, pulmonary fibrosis, and visual system malfunction. The Drosophila AP-3beta adaptin also appears to be involved in processes other than eye pigment granule biogenesis because all ruby allele combinations tested exhibited defective behavior in a visual fixation paradigm.

Adaptor Protein Complex alpha Subunits↗
PubMed1990

The effect of inhibitors of glycoprotein synthesis and processing on the phagocytosis of rod outer segments by cultured retinal pigment epithelial cells.

Retinal pigment epithelial cells selectively phagocytize rod outer segments by a process that may be mediated by specific cell surface receptors. Since many receptors are glycoproteins, we have studied the effect of tunicamycin, an inhibitor of N-linked oligosaccharide synthesis, and of castanospermine and swainsonine, which are inhibitors of oligosaccharide processing, on the ability of cultured retinal pigment epithelial cells to phagocytize rod outer segment. Tunicamycin inhibits the glycosylation of newly synthesized glycoproteins by 85-90%; concomitantly, the phagocytosis of rod outer segments is inhibited by 70-80%. The effect of tunicamycin is to initially reduce rod outer segments binding, and therefore the subsequent ingestion of rod outer segments. SDS-PAGE analysis and autoradiography of [35S]methionine labelled extracts of tunicamycin-treated cells, demonstrates the disappearance of a number of glycoprotein bands, and the appearance of a number of protein bands of lower Mr. Kinetic analysis of the disappearance and reappearance of specific glycoproteins suggests that the lower Mr bands are the non-glycosylated forms of the higher Mr bands. By contrast, castanospermine and swainsonine have no effect on the ability of retinal pigment epithelial cells to phagocytize rod outer segments, or on the SDS-PAGE pattern of treated cells, although they were shown to inhibit oligosaccharide processing as expected. These results support the hypothesis that rod outer segment phagocytosis by retinal pigment epithelial cells is mediated by specific glycoprotein receptors. N-Glycosylation of these receptors is required for their function, or for their insertion into the plasma membrane, whereas processing of the N-linked oligosaccharide chains of these receptors is not crucial for rod outer segment phagocytosis by retinal pigment epithelial cells.

Animals↗
PubMed2006

The genetic architecture of normal variation in human pigmentation: an evolutionary perspective and model.

Skin pigmentation varies substantially across human populations in a manner largely coincident with ultraviolet radiation intensity. This observation suggests that natural selection in response to sunlight is a major force in accounting for pigmentation variability. We review recent progress in identifying the genes controlling this variation with a particular focus on the trait's evolutionary past and the potential role of testing for signatures of selection in aiding the discovery of functionally important genes. We have analyzed SNP data from the International HapMap project in 77 pigmentation candidate genes for such signatures. On the basis of these results and other similar work, we provide a tentative three-population model (West Africa, East Asia and North Europe) of the evolutionary-genetic architecture of human pigmentation. These results suggest a complex evolutionary history, with selection acting on different gene targets at different times and places in the human past. Some candidate genes may have been selected in the ancestral human population, others in the 'out of Africa' proto European-Asian population, whereas most appear to have selectively evolved solely in either Europeans or East Asians separately despite the pigmentation similarities between these two populations. Selection signatures can provide important clues to aid gene discovery. However, these should be viewed as complements, rather than replacements of, functional studies including linkage and association analyses, which can directly refine our understanding of the trait.

Asian People↗
PubMed2005

Reconstitution of ancestral green visual pigments of zebrafish and molecular mechanism of their spectral differentiation.

We previously reported that zebrafish have four tandemly duplicated green (RH2) opsin genes (RH2-1, RH2-2, RH2-3, and RH2-4). Absorption spectra vary widely among the four photopigments reconstituted with 11-cis retinal, with their peak absorption spectra (lambda(max)) being 467, 476, 488, and 505 nm, respectively. In this study, we inferred the ancestral amino acid (aa) sequences of the zebrafish RH2 opsins by likelihood-based Bayesian statistics and reconstituted the ancestral opsins by site-directed mutagenesis. The ancestral pigment (A1) to the four zebrafish RH2 pigments and that (A3) to RH2-3 and RH2-4 showed lambda(max) at 506 nm, while that (A2) to RH2-1 and RH2-2 showed a lambda(max) at 474 nm, indicating that a spectral shift had occurred toward the shorter wavelength on the evolutionary lineages A1 to A2 by 32 nm, A2 to RH2-1 by 7 nm, and A3 to RH2-3 by 18 nm. Pigment chimeras and site-directed mutagenesis revealed a large contribution (approximately 15 nm) of glutamic acid to glutamine substitution at residue 122 (E122Q) to the A1 to A2 and A3 to RH2-3 spectral shifts. However, the remaining spectral differences appeared to result from complex interactive effects of a number of aa replacements, each of which has only a minor spectral contribution (1-3 nm). The four zebrafish RH2 pigments cover nearly an entire range of lambda(max) distribution among vertebrate RH2 pigments and provide an excellent model to study spectral tuning mechanisms of RH2 in vertebrates.

Amino Acid Sequence↗
PubMedDate not supplied

Blonde, a new mutation in Peromyscus maniculatus affecting fur, skin, and eye pigmentation.

An autosomal recessive mutation affecting hair and eye pigmentation was discovered in the F2 progeny of wild-type deer mice, (Peromyscus maniculatus), trapped near East Lansing, Michigan. When homozygous, the mutation (designated as blonde, bl), reduces both black and yellow pigmentation deposited in the fur, reduces or eliminates pigmentation in the non-follicular melanocytes of the outer ear, peri-orbital skin and tail, slightly reduces the amount of pigmentation in the choroidal melanocytes, and completely eliminates pigmentation of the retinal epithelium.

Animals↗
PubMed1998

Effects of lighting conditions on sleep and wakefulness in albino Lewis and pigmented Brown Norway rats.

STUDY OBJECTIVES: Previous studies have demonstrated that albino but not pigmented rats show acute increases in REM sleep following light-to-dark transitions. Light and dark have also been shown to have direct effects on NREM sleep and wakefulness in albino rats. Little is known, however, about the direct light-dark effects on sleep patterns in pigmented animals. The purpose of the present study was to compare the direct effects of light and dark on REM sleep, NREM sleep, and waking in albino Lewis and pigmented Brown Norway (BN) rats. DESIGN: Groups of albino Lewis and pigmented Brown Norway (BN) rats were exposed to various light-dark (LD) schedules. In the first experiment, the lighting schedules were LD 12:12 and LD 3:3. The second experiment compared LD 12:12 with an irregular schedule consisting of short light and dark periods of unequal length. MEASUREMENTS AND RESULTS: Both Lewis and BN rats slept more during the light and were awake more during the dark on all schedules. REM sleep patterns in light and dark periods were opposite, however. Lewis rats spent more of their sleep in REM sleep during dark than the light, whereas BN rats had a higher proportion of REM sleep in the light. CONCLUSIONS: The results suggest that there are substantial direct effects of light and dark on sleep in pigmented as well as in albino rats, although these effects are not always the same in magnitude or even in direction.

Animals↗
PubMed2001

Pigmented epidermal cysts.

There are few reports documenting the presence of melanin or melanocytes in epidermal cysts. One hundred and twenty five epidermal cysts from Indian patients were analyzed for the presence of melanin pigment and their sites were noted. A Masson's Fontana stain and immunohistochemistry for S-100 protein and HMB 45 was performed for localization of melanin and melanocytes within the epidermal cysts. Seventy-nine (63%) of the epidermal cysts showed presence of melanin pigment or melanocytes to a variable extent. Melanin was not present in epidermal cysts occurring along lines of fusion of skin folds during embryonogenesis (e.g., ventral midline, inner canthus, nose, upper lip and in the distal most parts like leg and foot and also scrotum). Ten of the 79 epidermal cysts showed extensive accumulation of melanin pigment and infiltration with melanophages in the cyst wall. Four of these patients gave history of trauma and the follow-up was uneventful in two of them. Pigmentation of epidermal cysts thus follows a definite anatomic pattern and is dependent on the natural skin color. Large amount of pigment accumulation within epidermal cysts occurs after cyst rupture and is not associated with hemochromatosis as was believed in the past.

Adolescent↗