ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00039.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Human TRP‐1 has been immunopurified from normal human melanocytes cultured from black neonatal subjects and used to investigate the catalytic function of TRP‐1 for the two substrates, L‐tyrosine and L‐DOPA. Immunopurified TRP‐1 did not demonstrate DOPA staining on SDS/PAGE nor DOPA oxidase (DO) activity with either routine or modified assays. The purified TRP‐1 also demonstrated no tyrosine hydroxylase (TH) activity using the routine Pomerantz assay. However, there was apparent TH activity exhibited by immunopurified TRP‐1 under conditions with low tyrosine concentration (≤0.8 μCi/ml of3H‐tyrosine), prolonged incubation time (i.e., overnight) and in the absence of the cofactor L‐DOPA. Using these latter specific conditions, TH activity was also detected in cell lysates from a tyrosinase‐negative albino melanocyte line which exhibited no TH activity with the routine Pomerantz assay. In addition, TH activity under low substrate assay conditions was not exhibited in a melanocyte line derived from a TRP‐1 deficient, Brown albino individual. However, the absence of TH in this Brown albino cell line could be compensated for by the addition of L‐DOPA to the assay. These results suggested that TRP‐1 has some tyrosine hydroxylase but no DOPA oxidase activity. We propose that one function of TRP‐1 is to modulate tyrosinase activity by making DOPA available as a cofactor to perpetuate the

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00040.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Microanalysis of eumelanin is based on the formation of pyrrole‐2,3,5‐tricarboxylic acid (PTCA) on permanganate oxidation followed by its HPLC determination. A problem in this method was that the oxidation gave concave, exponential curves when the amounts of PTCA formed were plotted against the amounts of sample oxidized. The problem has been mostly overcome by adding a homogenate of 5 mg of a mouse liver to the oxidation medium. Sepia melanin, C57BL black mouse hair, B16 mouse melanoma, and MM418 human melanoma cells were oxidized in the absence or presence of the liver homogenate. The yields of PTCA increased about 1.5‐fold by adding the liver homogenate and the calibration curves became linear or almost linear. With the improved method the PTCA values from various types of samples can be reliably com

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00041.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Melanin precursors and free radicals, cytotoxic substances, are produced during melanin synthesis by tyrosinase. We compared these cytotoxic effects of L‐dopa and oxygen on the cell cycle of melanotic retinal pigment epithelial (RPE) cells with amelanotic RPE cells because of the differences of tyrosinase activities between melanotic and amelanotic RPE cells. Flow cytometric DNA analysis of RPE cells exposed to L‐dopa (100 μM and 250 μM) were conducted at several oxygen concentrations (20%, 10%, and 5%). The dose‐dependent effect of L‐dopa to arrest the cell cycle (the S phase) was more pronounced in melanotic than in amelanotic RPE cells, and oxygen caused arrest in th

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00042.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Dominant black‐eyed white phenotypes are one of the most commonly observed traits in domestic animals. Their genetic control mechanisms, however, have not been elucidated. As the first step to approach the problem, we examined histologically the patterns of the distribution of pigment cells in Shiba goats (two each of day‐73‐postcoitum and day‐112‐postcoitum fetuses, and a 15‐week‐old kid) with the dominant black‐eyed white phenotype. Melanocytes were present and fully pigmented in the choroid and the sclera of eyes, as well as in dorsal skin epidermis of the fetuses and of the kid. Melanocytes were also found in approximately 6% of the hair bulbs in the fetal dorsal skin, while the rest (94%) lacked them. Hair follicles of the kid did not harbor melanocytes except for some in the early anagen stage. The results suggest that the survival of melanocytes was inhibited specifically in the hair follicles of the Shiba goat with the dominant black‐eyed white phenotype and that the ostensibly similar phenotypes in the Shiba goat and in theSIorWmutants of the mouse, where melanocytes die en route to the hair bulbs, are regulated by dif

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00043.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The transfer mechanism of melanosome from the melanocyte into the keratinocyte was investigated in mildly photodamaged Caucasian facial skin by electron microscopy. Three ways of transfer are suggested by our observations. The first mechanism probably occurs through the following process: 1) protrusion and insertion of the thick dendrite of the melanocyte into the basal keratinocyte, 2) formation of sac‐dendrite complex in the subnuclear region, 3) digestion and segregation of the enclosed dendrite, 4) formation of the cistern in the paranuclear region, and 5) pinching‐off of the melanosomes in single or aggregated form from the tip of the cistern. The second mechanism probably takes place through a membrane fusion between the melanocyte and the keratinocyte. Such a membrane fusion possibly forms a passage way for release of the melanosome from the former cell to the latter. The third mechanism is considered to include exocytosis of the single melanosome from the melanocyte followed by the endocytosis through the formation of coated‐pit in the keratin

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00044.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Scanning electron microscopy with immunogold labeling was used to demonstrate the in vivo distribution of molecules of basic fibroblast growth factor (bFGF) that were expressed and/or present on the surface of the cells of the normal epidermis and dermal connective tissue of humans. We found that molecules of bFGF, seen as deposits of gold particles, were present densely on the surfaces of the melanocytes but not the epidermal keratinocytes. In connective tissue, these molecules were present exclusively on the surfaces of the fibroblasts, macrophages, vascular endothelial cells, and the basement membrane surrounding the endothelial tube. The selective deposition of bFGF molecules on the melanocytes suggests that the dermal connective tissue may be involved in controlling the proliferation of melanocytes by means of bFGF molecules in vivo, since these melanocytes require bFGF to proliferate in vitro. The latter is synthesized and stored exclusively in the connective tissue.

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00045.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Using selective antagonists, including pirenzepine, adiphenine, AF‐DX116, gallamine, and 4‐DAMP we attempted to characterize the muscarinic cholinoceptors on the melanophores of the translucent glass catfishKryptopterus bicirrhisand the mailed catfishCorydoras paleatus.The M3receptor‐selective antagonist, 4‐DAMP, potently inhibited the acetylcholine‐induced aggregation of pigment in both species. It appeared, therefore, that the receptors that mediated the cholinergically evoked aggregation of melanosomes in these species were of the M3muscarini

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00046.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The morphological characteristics and ommochrome quantity in the integument of red, white, and wild type (black‐grey)Armadillidium vulgarewere studied. The red phenotype was found to possess two kinds of immature ommochrome pigment granules within its pigment cells, in addition to mature pigment granules. The immature granules seemed to contain uniformly distributed fibrilles, or to have an electron‐dense central region surrounded by an electron‐lucent outer edge. Since these immature pigment granules were typically observed to be distributed along with the mature ones, and were also more easily extractable than the wild type's, it is hypothesized that ommochrome granule maturation in the red phenotype may occur slowly due to a defect in the pigment granule internal process which combines pigments with matrix proteins. Regarding the white phenotype, although its pigment cells were undeveloped, several large‐sized vesicles containing a small amount of electron‐dense material appeared in the pigment cell cytoplasm. The wild and red type males ofA. vulgarewere found to have an ommochrome content twice as large as that of the corresponding females, with no ommochrome pigment being detected in the white phenotype. The genetic relationship between the white and red phenotypes was discussed using as a basis the observed pigment granule

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00047.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1994.tb00048.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY