摘要:

Homeotherms are generally considered to lack classical active dermal pigment cells (chromatophores) in their integument, attributable to the development of an outer covering coat of hair or feathers. However, bright colored dermal pigment cells, comparable to chromatophores of lower vertebrates, are found in the irides of many birds. We propose that, because of its exposed location, the iris is an area in which color from pigment cells has sustained a selective advantage and appears to have evolved independently of the general integument. In birds, the iris appears to have retained the potential for the complete expression of all dermal chromatophore types. Differences in cell morphology and the presence of unusual pigments in birds are suggested to be the result of evolutionary changes that followed the divergence of birds from reptiles. By comparison, mammals appear to have lost the potential for producing iridophores, xanthophores, or erythrophores comparable to those of lower vertebrates, even though some species possess brightly colored irides. It is proposed that at least one species of mammal (the domestic cat) has recruited a novel iridial reflecting pigment organelle originally developed in the choroidal tapetum lucidum. The potential presence of classical chromatophores in mammals remains open, as few species with bright irides have been examined.

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00564.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A new method for rapidly evaluating the effects of drugs on receptors that regulate intracellular cAMP in a cell line derived fromXenopus laevismelanophores has been developed. Melanophores were plated into sterile 96 well microtiter plates, and 3 days later the cells were treated with melatonin for 30 min to induce melanosome aggregation. Subsequent exposure to MSH or adrenergic agonists caused dose dependent pigment dispersion that peaked within 30 min. The cumulative pigment displacement from cells could be quantitated by using a microplate reader to measure changes in transmittance of light through the wells. The acquired data enabled detailed and reproducible dose response curves and time course analyses to be generated. In addition, the assay followed for the rapid characterization of the effects of antagonists upon the (β adrenergic receptor (β AR). The assay has the potential to test the effects of ligands upon any receptor capable of mediating pigment translocation in the melanophore cell lin

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00565.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The autoxidation of dopa to melanin in culture media causes toxicity to retinal pigment epithelial (RPE) cells and endothelial cells. The damage is specific to cell type and to the ambient oxygen concentration. To determine whether RPE cells influence the oxidation of dopa to media, we compared light absorbing dopa derivatives in the media exposed to cells with those found in the media incubated without cells. Dopa was extensively oxidized in the presence of RPE cells, and more light absorbing substances were generated with higher dopa and oxygen concentrations. However, an increase in ambient oxygen concentration decreased the quantity of several dopa derivatives which had been formed. The data provided evidence that RPE modulated dopa metabolism. Quinolic derivatives produced from a tyrosinase reaction and dopa‐melanin formation moved the peak absorbance wavelength of dopa into the visible range. The spectrum between the dopa‐derived compounds in the media has an absorbance at 240–275 nm and a maximum around 300 nm wth a shoulder near 375 nm. Gaussian analysis (peak separation) resolved these spectra into five components: a sharp band at 248 nm, a band at 295 nm, a large band at 359 nm, and two broad bands at 459 and 5

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00566.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

B700 is a murine melanoma antigen that is closely related to, but distinct from, serum albumin. The present study examined the metabolic fate and anatomic distribution of radioiodinated B700 and mouse serum albumin (MSA) administered s.c. to mice. In blood, both proteins were associated with the plasma fraction where the halflife of B700, a glycoprotein, was 0.5 days, compared to 2.7 days for MSA. Of particular interest was the observation that B700, a 67 kD anionic protein, was excreted primarily in urine. The selective B700‐proteinuria did not alter urinary volumes or produce hematuria or edema. SDS‐polyacrylamide gel electrophoresis and western blot analysis using the H‐2‐3‐3 B700‐specific monoclonal antibody revealed that B700 proteinuria occurred in B‐16 murine melanoma bearing animals but not in control mice. These studies demonstrate that the tumor‐bearing host readily distinguishes between very similar normal protein (MSA) and tumor‐associated antigen (B700) molecules and processes

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00567.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Sodium iodate damages retinal pigment epithelium specifically, but the reason for this specificity is not well understood. The work reported here describes an effect of sodium iodate on melanin, a major component of the retinal pigment epithelium. Sodium iodate increases the ability of melanin to convert glycine to glyoxylate. Almost ten times as much glyoxylate is formed when sodium iodate is present compared to the amount formed with melanin alone, although iodate alone does not convert glycine to glyoxylate. A chemical reaction between sodium iodate and melanin is suggested as a partial explanation of the specificity of iodate toxicity towards retinal pigment epithelium.

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00568.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

L‐DOPA had no effect on the endogenous phosphorylation of proteins after extraction with 1% Triton X‐100 from hamster melanoma. When proteins were purified further by wheat germ‐agglutinin chromatography, however, a dramatic and dose‐dependent inhibitory effect of DOPA on glycoprotein phosphorylation was observed in the presence

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00569.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The antifungal reagent Fungizone (amphotericin B and deoxycholate) caused an activation in dopachrome tautomerase and dopa oxidase activities of B16/F10 melanoma cells at the routine concentration (2.5 μg/ml) used for preventing molds and yeast growth in cultures of animal cells. However, higher amphotericin B concentrations caused a significant cell death and the inhibition of enzymatic activities. At the optimal concentration of Fungizone, the enzymatic activities and melanin content were augmented as incubation time increased. The detergent sodium deoxycholate alone exerted no effect on these melanogenic parameters, eliminating the possibility that this detergent was partially responsible for melanogenic modifications produced by Fungizone. After withdrawal of Fungizone from the reaction medium, the recovery of melanogenic parameters to normal values was slower for DCT than for tyrosinase. The behavior of dopa oxidase was very similar to that reported by Johnson and Bagnara (Pigment Cell Res. 3, 173–175) for tyrosine hydroxyla

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00570.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

This study on five patients has revealed more extensive alterations to melanocytes than previously reported, and emphasizes the fact that depigmentation is an essential element of the condition. In hyperpigmented areas, melanocytes were increased in number along the basal layer of the epithelium, were hyperactive, and in some cases contained bizarre melanosomes. In two cases there was suggestion of a defect in melanosome transfer to keratinocytes. Lymphocytes were closely apposed to melanocytes, and, in hypopigmented areas, were clearly involved in their disintegration. In depigmented areas, there was complete absence of melanocytes and of melanosomes in keratinocytes, and lymphocytes were present in the basal layer. In general, the appearances did not resemble melanoma in situ with spontaneous regression, although a second biopsy of one patient after one year did reveal features of melanocytes suggestive of an early stage of this condition. The study has provided no clear information as to the initial cause of the condition, but the manner of destruction of melanocytes suggests an immune reaction. Neither has it been of assistance in suggesting a more precise name for it.

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1992.tb00571.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.tb00572.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.tb00573.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY