摘要:

Melanocyte‐stimulating hormone plays an important role in the regulation of melanocyte differentiation in the mouse epidermis by inducing tyrosinase activity, melanosome formation, translocation of melanosomes, and increased dendritogenesis. The proliferative activity of differentiating epidermal melanocytes of newborn mice during the healing of skin wounds is regulated by semi‐dominant genes, suggesting that the genes are involved in regulating the proliferative activity of epidermal melanocytes during differentiation. From the results of serum‐free culture of epidermal cell suspensions from neonatal mouse skin, basic fibroblast growth factor is shown to stimulate the sustained proliferation of melanoblasts in the presence of dibutyryl adenosine 3′,5′‐cyclic monophosphate and keratinocyte‐derived factors. Moreover, each step of melanocyte differentiation is controlled by numerous coat color genes. These genes control melanocyte differentiation by regulating the differentiation of neural crest cells into melanoblasts in embryonic skin, or by regulating the differentiation of neural crest cells into melanoblasts in embryonic skin, or by regulating transcription and/or translation of the tyrosinase gene in the differentiating melanocytes. These results suggest that melanocyte proliferation and differentiation in the mouse epidermis are controlled by both genetic factors and local tissu

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00776.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The purpose of this study was to examine the differentiation of variant tumors of the B16 metastatic melanoma when tumors were grown serially under different culture conditions and transplanted into C57BL/6J black mice, lethal yellowAy/a, albinoc/c, andC+/cmutant mice. Morphological and biochemical markers of melanogenesis were examined in cells in culture and in the corresponding tumors. Cellular pigmentation was assessed in terms of the levels of DOPA and 5‐S‐CD and in terms of tyrosinase activity in the various cell lines and tumors. The observed change from high to low metastatic capacity, which was dependent on culture conditions, appeared to be unrelated to melanogenesis even though changes were observed in the biochemical melanotic phenotype. Overall, tumor cells from spontaneous pulmonary metastases appear to differentiate in ways that are unrelated to the instability of experimental metastatic capacity. The melanotic phenotype in albinoc/candC+/cmice was dependent on the phenotype of the parental tumors. A marked difference was observed between two pigmentation compartments, one of which was stable in the B16 control, while the other was unstable in YB16 and MB16 variant cells and in the tumors derived from them. It appears, therefore, that the metastatic capacity of B16 metastatic variants is changeable and is independent of the unstable melanogenic behavior. The production of metastases and the differentiation of tumors in the present experiments appeared to be related to the genetic background of the mice and the epigenetic metabolic environment of tumors and ce

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00777.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Five cell lines (one parental, two transformed melanin producing, and two transformed non‐melanin producing) were evaluated for the responses to 2‐ and 4‐hydroxyanisole (2HA, 4HA) alone or combined with hyperthermia or radiation. All cells exhibited a non‐specific toxic response to the two compounds and the effect was exposure time and concentration dependent and was greater for 4HA compared to 2HA. In addition, the two melanin‐producing cell lines were more sensitive, demonstrating specific toxicity to such cell lines. The treatment with either 2HAor4HA combined with heat and radiation resulted mostly in additive or antagonistic effects, except for one combination of 2HA plus radiation in the melanin‐producing R25 cells. Thus, while these compounds may be useful in therapy for pigmented melanomas, combined treatment with radiation is not

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00778.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

This report describes morphological alterations of the chinchilla stria vascularis seen 30 days after exposure to impulse noise. The observed changes included a dramatic increase in strial melanin content which occurred in 7 of 36 animals exposed to electronically synthesized impulses presented in various temporal patterns at either 135 or 150 dB peak SPL. In these animals, densely pigmented areas of stria 1.5 to 3 mm in length were found in the basal cochlear turn. Light and electron microscopic study revealed that these areas contained large numbers of melanin granules situated primarily in pale‐staining cells of the middle layer of the stria. Unlike the pigment granules present in normal chinchilla stria, the melanosomes found in the noise‐exposed material clearly showed ultrastructural features characteristic of eumelanin. Melanin granules were also observed in marginal and basal cells of the noise‐exposed stria. In some cases, pigment granules which had apparently been expelled from the marginal cells were present in the endolymphatic space beneath Reissner's membrane and on the strial surface. These findings support the view that the melanin‐bearing cells of the inner ear are capable of markedly increased activity in response to stressful con

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00779.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00780.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

4‐Methyl catechol and catechol, at concentrations ranging from 0.03 to 9 mM and 0.066 to 20 mM, respectively, have a synergistic effect on the rate of DL‐DOPA oxidation by mushroom tyrosinase to material absorbing at 475 nm. The synergism results from the ability of 4‐methyl catechol‐o‐quinone (4‐methyl‐o‐benzoquinone) and of catechol‐o‐quinone (o‐benzoquinone) to oxidize DL‐DOPA non‐enzymatically to dopaquinone, with the latter being immediately converted to d

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00781.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY