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Pigment Cells (pigment + cell)

Distribution by Scientific Domains

Life Sciences	60%
Medical Sciences	20%

Selected Abstracts

Back to black: Pigment Cell & Melanoma Research

PIGMENT CELL & MELANOMA RESEARCH, Issue 3 2007
Colin Goding
First page of article [source]

Localization of Sepiapterin Reductase in Pigment Cells of Oryzias latipes

PIGMENT CELL & MELANOMA RESEARCH, Issue 5 2003
Sumiko Negishi
Body colors of poikilothermal vertebrates are derived from three distinct types of pigment cells, melanophores, erythro/xanthophores and irido/leucophores. It is well known that melanin in melanophores is synthesized by tyrosinase within a specific organelle termed the melanosome. Although sepiapterin reductase (SPR) is an important enzyme involved in metabolizing biopterin and sepiapterin (a conspicuous pteridine as a coloring pigment in xanthophores) the distribution of SPR has not been shown in pigment cells. An antibody raised in rabbits against rat SPR was used to demonstrate the presence of SPR in pigment cells of Oryzias latipes. This study, which used immunohistochemistry with fluorescence or peroxidase/diaminobenzidine as markers, revealed that SPR could be detected readily in xanthophores, but only faintly in melanophores. These results suggest that sepiapterin is metabolized within xanthophores. Moreover, these experiments show that a protein sharing immunological cross-reactivity with rat SPR is located in teleost O. latipes xanthophores, which is significant considering the relationship of pteridine metabolism between poikilothermal vertebrates and mammals. Further progress in investigations of the roles of pteridines in vertebrates will be promoted by using these fish which can be bred in mass rather easily in the laboratory. [source]

Expression of Cre Recombinase in Pigment Cells

PIGMENT CELL & MELANOMA RESEARCH, Issue 4 2002
Laurence Guyonneau
Conditional gene targeting using the Cre/loxP system enables specific deletion of a gene in a tissue of interest. For application of Cre-mediated recombination in pigment cells, Cre expression has to be targeted to pigment cells in transgenic mice. So far, no pigment cell-specific Cre transgenic line has been reported and we present and discuss our first results on use of Cre recombinase in pigment cells. A construct was generated where Cre recombinase is controlled by the promoter of the mouse dopachrome tautomerase (Dct) gene. The construct was functionally tested in vitro and introduced into mice. Following breeding to two reporter mouse strains, we detected Cre recombinase activity in telencephalon, melanoblasts, and retinal pigment epithelium (RPE). Our data demonstrate the feasibility of pigment cell-specific Cre/loxP-mediated recombination. [source]

European Society for Pigment Cell Research 14th Meeting , Bari, 14 , 17 October 2007 Sheraton Nicolaus , Bari ,,Pigment cells and their environment"

PIGMENT CELL & MELANOMA RESEARCH, Issue 5 2007
Article first published online: 10 SEP 200
First page of article [source]

Structure of the skin of an air-breathing mudskipper, Periophthalmus magnuspinnatus

JOURNAL OF FISH BIOLOGY, Issue 6 2002
J. Y. Park
The epidermis of the mudskipper Periophthalmus magnuspinnatus consisted of three layers: the outermost layer, middle layer and stratum germinativum. Extensive vascular capillary networks were present near the superficial layer of epidermis and outermost layer. The diffusion distance between the vascular capillaries and the surface of epidermis was c. 1.5 ± 0.9,m. The middle layer consisted of small or voluminous cells swollen by epidermal cells. Due to the swollen cells, the thickness of the epidermis increased and the epidermis appeared web-like. The swollen cells contained tonofilaments, lucent contents and desmosomes. Fine blood capillaries were also discernible in this layer. Well-developed lymphatic spaces containing lymphocytes existed in the stratum germinativum. Numerous blood capillaries were present under the basement membrane. The dermis consisted of a stratum laxum and stratum compactum, and there was a definite area with acid mucopolysaccharides and a small scale in the stratum laxum. The skin had an epidermal pigment cell, dendritic melanophores (-cytes) containing melanin granules within their cytoplasm, and two kinds of dermal pigment cells, melanophores and colourless pigments containing reflecting platelets. [source]

Surgical Approaches for Stable Vitiligo

DERMATOLOGIC SURGERY, Issue 10 2005
Rafael Falabella MD
Background. Vitiligo therapy is difficult. Depending on its clinical presentation, unilateral or bilateral vitiligo lesions respond well with different repigmentation rates, according to age, affected anatomic area, extension of lesions, time at onset, timing of depigmentation spread, and other associated factors. When stable and refractory to medical treatment, vitiligo lesions may be treated by implanting pigment cells on depigmented areas. Objective. To describe the main events of depigmentation and the fundamentals of surgical techniques for repigmenting vitiligo by implanting noncultured cellular or tissue grafts, in vitro cultured epidermis-bearing pigment cells, or melanocyte suspensions. Methods. A description of the available techniques for repigmentation of vitiligo is done, emphasizing the most important details of each procedure to obtain the best repigmentation and minimize side effects. Results. With most of these techniques, adequate repigmentation is obtained, although there are limitations when applying some methods to clinical practice. Conclusions. Restoration of pigmentation may be accomplished with all available surgical procedures in most anatomic locations, but they are of little value for acral areas. Unilateral vitiligo responds well in a high proportion of patients, and bilateral disease may also respond when stable. Appropriate patient selection is important to achieve the best results. [source]

RNA interference by expressing short hairpin RNA in the Ciona intestinalis embryo

DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 6 2008
Aya Nishiyama
We carried out RNA interference by expressing short hairpin RNA (shRNA) in the Ciona intestinalis embryo. For this purpose, we identified a gene encoding U6 small nuclear RNA (snRNA) in the C. intestinalis genome. The 1-kb sequence upstream of the U6 snRNA gene was sufficient for directing transcription of short RNA as revealed by Northern blot hybridization. An shRNA-expressing plasmid vector was constructed, in which shRNA-encoding oligonucleotides are inserted downstream of the U6 promoter. An shRNA that contained a sequence homologous to the C. intestinalis tyrosinase gene (Ci-tyrosinase) suppressed melanization of pigment cells in the brain of morphologically normal tailbud embryos. An shRNA that perfectly matched the translated sequence of enhanced green fluorescent protein (EGFP) (a mutant type of Aequorea victoria green fluorescent protein) suppressed the expression of the coelectroporated EGFP transgene. These results suggest that the expression of shRNA interferes with functions of both endogenous and exogenous genes. The shRNA-expressing plasmid constructed in the present study provides an easy and inexpensive alternative for the functional analysis of genes in ascidian embryos. [source]

Gastrulation in the sea urchin embryo: A model system for analyzing the morphogenesis of a monolayered epithelium

DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 4 2004
Tetsuya Kominami
Processes of gastrulation in the sea urchin embryo have been intensively studied to reveal the mechanisms involved in the invagination of a monolayered epithelium. It is widely accepted that the invagination proceeds in two steps (primary and secondary invagination) until the archenteron reaches the apical plate, and that the constituent cells of the resulting archenteron are exclusively derived from the veg2 tier of blastomeres formed at the 60-cell stage. However, recent studies have shown that the recruitment of the archenteron cells lasts as late as the late prism stage, and some descendants of veg1 blastomeres are also recruited into the archenteron. In this review, we first illustrate the current outline of sea urchin gastrulation. Second, several factors, such as cytoskeletons, cell contact and extracellular matrix, will be discussed in relation to the cellular and mechanical basis of gastrulation. Third, differences in the manner of gastrulation among sea urchin species will be described; in some species, the archenteron does not elongate stepwise but continuously. In those embryos, bottle cells are scarcely observed, and the archenteron cells are not rearranged during invagination unlike in typical sea urchins. Attention will be also paid to some other factors, such as the turgor pressure of blastocoele and the force generated by blastocoele wall. These factors, in spite of their significance, have been neglected in the analysis of sea urchin gastrulation. Lastly, we will discuss how behavior of pigment cells defines the manner of gastrulation, because pigment cells recently turned out to be the bottle cells that trigger the initial inward bending of the vegetal plate. [source]

Blocking Dishevelled signaling in the noncanonical Wnt pathway in sea urchins disrupts endoderm formation and spiculogenesis, but not secondary mesoderm formation

DEVELOPMENTAL DYNAMICS, Issue 7 2009
Christine A. Byrum
Abstract Dishevelled (Dsh) is a phosphoprotein key to beta-catenin dependent (canonical) and beta-catenin independent (noncanonical) Wnt signaling. Whereas canonical Wnt signaling has been intensively studied in sea urchin development, little is known about other Wnt pathways. To examine roles of these beta-catenin independent pathways in embryogenesis, we used Dsh-DEP, a deletion construct blocking planar cell polarity (PCP) and Wnt/Ca2+ signaling. Embryos overexpressing Dsh-DEP failed to gastrulate or undergo skeletogenesis, but produced pigment cells. Although early mesodermal gene expression was largely unperturbed, embryos exhibited reduced expression of genes regulating endoderm specification and differentiation. Overexpressing activated beta-catenin failed to rescue Dsh-DEP embryos, indicating that Dsh-DEP blocks endoderm formation downstream of initial canonical Wnt signaling. Because Dsh-DEP-like constructs block PCP signaling in other metazoans, and disrupting RhoA or Fz 5/8 in echinoids blocks subsets of the Dsh-DEP phenotypes, our data suggest that noncanonical Wnt signaling is crucial for sea urchin endoderm formation and skeletogenesis. Developmental Dynamics 238:1649,1665, 2009. © 2009 Wiley-Liss, Inc. [source]

Iris as a recipient tissue for pigment cells: Organized in vivo differentiation of melanocytes and pigmented epithelium derived from embryonic stem cells in vitro

DEVELOPMENTAL DYNAMICS, Issue 9 2008
Hitomi Aoki
Abstract Regenerative transplantation of embryonic stem (ES) cell-derived melanocytes into adult tissues, especially skin that includes hair follicles or the hair follicle itself, generally not possible, whereas that of ES cell-derived pigmented epithelium was reported previously. We investigated the in vivo differentiation of these two pigment cell types derived from ES cells after their transfer into the iris. Melanocytes derived from ES cells efficiently integrated into the iris and expanded to fill the stromal layer of the iris, like those prepared from neonatal skin. Transplanted pigmented epithelium from either ES cells or the neonatal eye was also found to be integrated into the iris. Both types of these regenerated pigment cells showed the correct morphology. Regenerated pigment epithelium expressed its functional marker. Functional blocking of signals required for melanocyte development abolished the differentiation of transplanted melanocytes. These results indicate successful in vivo regenerative transfer of pigment cells induced from ES cells in vitro. Developmental Dynamics 237:2394,2404, 2008. © 2008 Wiley-Liss, Inc. [source]

Pigment cell distributions in different tissues of the zebrafish, with special reference to the striped pigment pattern

DEVELOPMENTAL DYNAMICS, Issue 2 2005
Masashi Hirata
Abstract The orderly pigment pattern of zebrafish (Danio rerio) is a good model system for studying how spatial patterns form in animals. Recent molecular genetic studies have shown that interactions between the pigment cells play major roles in pattern formation. In the present study, we performed comparative transmission electron microscopy of pigment cells, in order to clarify the structural interactions of pigment cells in tissues with and without a striped pattern. In patterned tissues, pigment cells were distributed as a one-cell-thick sheet. The layer order of the sheets is always kept strictly. In tissues without a striped pattern, the layer order was often disturbed or the cells were distributed in a scattered, double-sheeted, or an accumulated pile. Our observations suggest that the underlying mechanism that controls the vertical order of the pigment cells is related to that controlling the stripe pattern. Developmental Dynamics 234:293,300, 2005. © 2005 Wiley-Liss, Inc. [source]

Histopathological effects in tissues of snail Lymnaea stagnalis (Gastropoda, Pulmonata) exposed to sublethal concentration of Thiodan® and recovery after exposure

JOURNAL OF APPLIED TOXICOLOGY, Issue 6 2005
Erhan Ünlü
Abstract Histopathological alterations induced by Thiodan® in three tissues, namely, digestive gland, foot and mantle, of the freshwater snail Lymnaea stagnalis were investigated. Specimens of Lymnaea stagnalis were exposed to 0.36% and 0.72% Thiodan® 35 EC, a commercial grade of endosulfan, for 96 h followed by a recovery period of 30 days. Thiodan® caused significant dose dependent histopathological changes in all the tissues of the snail. Irreversible necrotic changes occurred in the digestive gland of the snail following Thiodan® exposure. Degenerative changes in the muscle fiber of the foot, protein and pigment cells of the foot and the connective tissue element of the mantle were recovered after 30 days of recovery of the snail in pesticide-free freshwater. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Kojic acid reduces the cytotoxic effects of sulfur mustard on cultures containing human melanoma cells in vitro

JOURNAL OF APPLIED TOXICOLOGY, Issue 6 2001
C. N. Smith
Abstract In vivo experiments have shown that melanocytes are more sensitive than keratinocytes to the cytotoxic effects of sulfur mustard when it is applied topically to pig skin.1 It has been hypothesized that this is caused by the uncoupling of the melanogenic pathway by depletion of cellular glutathione, resulting in the uncontrolled production of cytotoxic quinone free-radical species by tyrosinase.2. In the present study, the feasibility of blocking the melanogenic pathway as a means of reducing the cytotoxicity of sulfur mustard was evaluated using kojic acid. Kojic acid is a topically applied depigmenting agent that exerts its effect by acting as a slow-binding, competitive inhibitor of tyrosinase.3 Preincubation of G361 pigmented melanoma cells and mixed cultures of G361 cells and SVK keratinocytes with 2.5 mM kojic acid resulted in significant increases in the viability of these cultures as determined by neutral red (NR) and gentian violet (GV) dye binding assays for up to 48 h following exposure to 50 µM sulfur mustard. The highest levels of protection were seen in the G361 cultures, with a 26.8% increase in culture viability (NR assay) compared with the sulfur-mustard-only controls at 24 h. Preincubation of SVK cells alone with kojic acid resulted in lower increases in viability (2.5% at 24 h by the NR assay). Inhibition of the melanogenic pathway reduces the sensitivity of cultures containing pigment cells to sulfur mustard. © Crown copyright 2001. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source]

The evolution of teleost pigmentation and the fish-specific genome duplication

JOURNAL OF FISH BIOLOGY, Issue 8 2008
I. Braasch
Teleost fishes have evolved a unique complexity and diversity of pigmentation and colour patterning that is unmatched among vertebrates. Teleost colouration is mediated by five different major types of neural-crest derived pigment cells, while tetrapods have a smaller repertoire of such chromatophores. The genetic basis of teleost colouration has been mainly uncovered by the cloning of pigmentation genes in mutants of zebrafish Danio rerio and medaka Oryzias latipes. Many of these teleost pigmentation genes were already known as key players in mammalian pigmentation, suggesting partial conservation of the corresponding developmental programme among vertebrates. Strikingly, teleost fishes have additional copies of many pigmentation genes compared with tetrapods, mainly as a result of a whole-genome duplication that occurred 320,350 million years ago at the base of the teleost lineage, the so-called fish-specific genome duplication. Furthermore, teleosts have retained several duplicated pigmentation genes from earlier rounds of genome duplication in the vertebrate lineage, which were lost in other vertebrate groups. It was hypothesized that divergent evolution of such duplicated genes may have played an important role in pigmentation diversity and complexity in teleost fishes, which therefore not only provide important insights into the evolution of the vertebrate pigmentary system but also allow us to study the significance of genome duplications for vertebrate biodiversity. [source]

Structure of the skin of an air-breathing mudskipper, Periophthalmus magnuspinnatus

Melanophores: A model system for neuronal transport and exocytosis?

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 12 2007
Sara Aspengren
Abstract Black pigment cells, melanophores, from lower vertebrates are specialized in bidirectional and coordinated translocation of pigment granules, melanosomes, in the cytoplasm. Melanophores develop from the neuronal crest and are most abundant in the dermal and epidermal layers of the skin, where the intracellular distribution of the pigment significantly influences the color of the animal. The transport of pigment is dependent on an intact cytoskeleton and motor proteins associated with cytoskeletal components. The easily cultured melanophores have proved to be excellent models for organelle transport because the intracellular movements of pigment can be visualized via light microscopy, and the granules move in response to defined chemical signals. The ease of achieving a combination of morphological and functional transport studies is the advantage of the melanophore system, and studies on pigment cells have revealed new components of the transport machinery, including molecular motors, their adapters, and transfer of vesicles to other cells. Many cellular components are transported with a combination of the actin- and microtubule-based transport systems, and, since all eukaryotic organisms rely on functional intracellular transport and an intact cytoskeleton, studies on melanophores are important for many aspects of cell biology, including axonal transport. In this review, we present an overview of the research on the pigment transport system and the potential use of pigment cells as a model system. © 2006 Wiley-Liss, Inc. [source]

Autoimmunity as an aetiological factor in vitiligo

JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 7 2007
N Rezaei
Abstract Vitiligo is a common dermatological disorder characterized by the presence on the skin of depigmented macules resulting from the destruction of cutaneous melanocytes. Autoimmunity is an important hypothesis with regard to vitiligo aetiology and the evidence for autoimmune responses being involved in the pathogenesis of this disorder will be discussed in the present review. All immune system compartments, including innate and adaptive immunity have been implicated in vitiligo development. Particularly relevant are autoantibodies and autoreactive T cells in vitiligo patients that have cytotoxic effects upon pigment cells. Furthermore, predisposition to vitiligo appears to be associated with certain alleles of the major histocompatibility complex class II antigens as well as with other autoimmune-susceptibility genes. Moreover, the association of vitiligo with autoimmune disorders, the animal models of the disease, and the positive response to immunosuppressive therapeutic agents emphasize the role of autoimmunity in the development of this disorder. [source]

Pigment pattern formation in zebrafish: A model for developmental genetics and the evolution of form

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2002
Ian K. Quigley
The zebrafish Danio rerio is an emerging model organism for understanding vertebrate development and genetics. One trait of both historical and recent interest is the pattern formed by neural crest,derived pigment cells, or chromatophores, which include black melanophores, yellow xanthophores, and iridescent iridophores. In zebrafish, an embryonic and early larval pigment pattern consists of several stripes of melanophores and iridophores, whereas xanthophores are scattered widely over the flank. During metamorphosis, however, this pattern is transformed into that of the adult, which comprises several dark stripes of melanophores and iridophores that alternate with light stripes of xanthophores and iridophores. In this review, we place zebrafish relative to other model and non-model species; we review what is known about the processes of chromatophore specification, differentiation, and morphogenesis during the development of embryonic and adult pigment patterns, and we address how future studies of zebrafish will likely aid our understanding of human disease and the evolution of form. Microsc. Res. Tech. 58:442,455, 2002. © 2002 Wiley-Liss, Inc. [source]

Melanoma development and pigment cell transformation in xiphophorus

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2002
Claudia Wellbrock
As early as 1927, it was recognised that hybridisation of platyfish (Xiphophorus maculatus) and swordtails (Xiphophorus helleri) results in offspring that develop tumours according to Mendelian laws. Most obviously, the primary event, namely the cell lineage-specific overexpression of a structurally altered receptor tyrosine kinase, finds its parallel in many tumours of birds and mammals. Once expressed at high levels, this receptor, the Xiphophorus melanoma inducing receptor kinase Xmrk, shows constitutive activation. By using different pathways, Xmrk induces both proliferative as well as anti-apoptotic signalling in pigment cells finally leading to cell transformation, tumour induction, and progression. Analyses of the different signalling cascades induced by the Xmrk-receptor led to the identification of the src-kinase Fyn, the MAP kinases ERK1 and ERK2, the "Signal Transducer and Activator of Transcription" STAT5, and the PI3-kinase as its major downstream substrates. This review describes some of the genetic findings, as well as the results from the recent molecular analyses of the factors involved in the initiation and manifestation of pigment cell transformation and melanoma development in Xiphophorus. Microsc. Res. Tech. 58:456,463, 2002. © 2002 Wiley-Liss, Inc. [source]