Browsing by Subject "Melanocyte"

Now showing 1 - 5 of 5
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    Genetics of pigment cells, lessons from the tyrosinase gene family
    (Murcia : F. Hernández, 2006) Murisier, F.; Beermann, Friedrich
    In mammals, the melanin pigment is produced in two cell types of distinct developmental origins. The melanocytes of the skin originate form the neural crest whereas the retinal pigment epithelium (RPE) of the eye originates from the optic cup. The genetic programs governing these two cell types are thus quite different but have evolved to allow the expression of pigment cell-specific genes such as the three members of the tyrosinase-related family. Tyrosinase, Tyrp1 and Dct promoters contain a motif termed E-box which is bound by the transcription factor Mitf. These E-boxes are also found in the promoters of the corresponding fish genes, thus highlighting the pivotal role of Mitf in pigment cell-specific gene regulation. Mitf, which displays cell type-specific isoforms, transactivates the promoters of the tyrosinase gene family in both pigment cell lineages. However, specific DNA motifs have been found in these promoters, and they correspond to binding sites for RPE-specific factors such as Otx2 or for melanocyte-specific factors such as Sox10 or Pax3. The regulation of pigment cell-specific expression is also controlled by genetic elements located outside of the promoter, such as the tyrosinase distal regulatory element located at -15 kb which acts as a melanocytespecific enhancer but also protects from spreading of condensed chromatin. Thus, by using the tyrosinase gene family as a model, it is possible to define the transcription factor networks that govern pigment production in either melanocytes or RPE.
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    Human skin reconstruct models: A new application for studies of melanocyte and melanoma biology
    (Murcia : F. Hernández, 2001) Berking, C.; Herlyn, M.
    Studies of melanocyte and melanoma biology using monocultures of cells are limited because of culture-induced morphology changes and expression of genes related to growth, migration, and invasion, which do not reflect the in situ phenotype of normal melanocytes, nevus cells, or melanoma cells from biologically early progression stages. The development of organotypic cultures of human skin, in which culture artifacts are greatly diminished and cell-matrix and cellcell interactions between different cell types can be investigated in a three-dimensional system, has opened a new era for melanoma research. Long-term in vivo studies, especially important for melanomagenesis and melanoma metastasis have become possible through grafting of skin reconstructs to immuno.deficient laboratory animals. In this review, principles and different methods of skin reconstruction are introduced with focus on the application for pigment cell biology
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    Structure and function of melanocytes, Microscopic
    (Murcia : F. Hernández, 1995) Hirobe, T.
    Melanocytes characterized by their tyrosinase activity, melanosomes and dendrites locate in the basa1 layer of epidermis and hair bulb in the skin of mice. Melanocytes differentiate from undifferentiated melanoblasts derived from embryonic neural crest. Melanocyte-stimulating hormone plays an important role in the regulation of the differentiation of mouse melanocytes in the epidermis and hair bulb by inducing tyrosinase activity, melanosome formation, transfer of melanosomes and increased dendritogenesis. The proliferative activity of differentiating epidermal melanocytes of newborn mice during the healing of skin wounds is regulated by semidominant genes, suggesting that the genes are involved in regulating the proliferative activity of epidermal melanocytes during differentiation. The morphology and differentiated functions of mouse melanocytes are shown to be influenced by environmental factors such as ultraviolet and ionizing radiations. From the results of serum-free culture of mouse epidermal melanoblasts, basic fibroblast growth factor is shown to stimulate the sustained proliferation of melanoblasts in the presence of dibutyryl adenosine 3 ' 3 - cyclic monophosphate and keratinocytes. In contrast, melanocyte differentiation in serum-free culture is induced by melanocyte-stimulating hormone in the presence of keratinocytes. These results suggest that the structure and function of mouse melanocytes in the epidermis and hair bulb are controlled by both genetic factors and local tissue environment, such as hormones and growth factors.
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    The intracellular origin of the melanosome in pigment cells. A review of ultrastructural data
    (Murcia : F. Hernández, 1996) Schraerrneyer, U.
    This paper is a review about the ultrastructural data dealing with the origin of the melanin granules in retina1 pigment epithelial cells, in melanocytes, in the ink gland of cuttle fish, in Kupffer cells of the liver, in neurona1 tissues, in cultured pigment cells. The role and structure of lysosomes in melanogenesis are discussed in a separate chapter. The early steps of melanogenesis are ultrastructurally very heterogeneous, even in the same cell types. With respect to this heterogeneity and the considerably different views on melanosome origin in the literature, the author hypothesizes that pigment cells may use protein matrices originated from different cellular pathways. 1) They may either produce a specific protein matrix and be converted into melanin in the classical way, or 2) altematively, a matrix resulting from lysosomal protein degradation or endocytotic pathways may be used and converted into melanin, as found in fibroblasts transfected with the tyrosinase gen or in Kupffer cells. The very heterogeneous ultrastructure of the polymerizing melanin may be influenced by the amount and sterical availability of tyrosine residues in the protein moieties and the activity of tyrosinase.
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    The skin injury induced by high energy dose of ultraviolet in hairless descendants of Mexican hairless dogs
    (Murcia : F. Hernández, 1997) Ishii, Y.; Kimura, T.; Itagaki, S.; Doi, K.
    Histopathological changes in the dorsal skin of hairless descendants of Mexican hairless dogs (MHDs) exposed to artificial irradiation with high energy dose ( 1 8 0 k ~ l m ~of) ultraviolet (UV) rays (UVA+B) were investigated. Macroscopically, erythema and edema were observed in the irradiated skin at 1 day after irradiation (DAI), and blister formation occurred except one dog at 2 DAI. Erythema almost disappeared at 5 DAI, and at 6 DAI, the skin recovered to almost normal state. Light microscopically, sunburn cells were observed at 1 DAI. Then intercellular edema and blister formation in the epidermis and dermal edema were evident at 2 and 3 DAI. At 6 DAI, the skin showed almost normal features except for slight epidermal thickening, but melanin granules, which were distributed in almost the whole length of the epidermis before UV irradiation, were detected only in cells which seemed to be melanocytes except one dog. Dihydroxyphenylalanine (D0PA)- positive melanocytes almost disappeared at 1 and 2 DAI, and at 6 DAI, the number of DOPA-positive melanocytes increased over the leve1 before UV irradiation. The ultrastructural features of melanocytes were characterized by vacuolated cytoplasm, decreased melanosomes, irregular-shaped nuclei and shortened dendrites at 1 DAI, and returned to normal at 6 DAI. These findings of melanocytes reflect the severity of the skin injury and support weak suntan reaction in this case. In conclusion, severe form of UV-induced skin injury seen in humans could be reproduced in hairless descendants of MHDs exposed to high energy dose of artificial UVA+B.