摘要:

The yellow pigment observed in older axanthic(ax/ax)mutant Mexican axolotls (Ambystoma mexicanum) was analyzed by thin layer chromatography and by spectrofluorometry of its acetyl derivative. Ethanol extracts from the skin of axanthic animals were acetylated and the chloroform‐soluble portion of the product mixture was compared with a chloroform solution of an authentic riboflavin tetraacetateo standard prepared in the same manner. The pigment in these two solutions behaved identically on thin layer chromatograms and in fluorescent emission spectroscopy. This confirms that the yellow pigment seen in these genetically axanthic animals is riboflavin and, since it cannot be synthesized by the animal, must be derived from the die

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00275.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The morphological and biochemical characteristics of pigment accumulations found in the kidney, liver, spleen, and mesentery of three different species of teleost fishes have been studied. There are significant differences in number, distribution, and morphology of pigment accumulations in different organs of the three species. Biochemical studies have shown the existence of tyrosinase activity in the mesentery ofMugil cephalusand in the kidney and mesentery ofSparus auratus.No tyrosinase activity was found in any internal organs ofDicertranchus labrax.That activity was assayed using three methods: tyrosine hidroxylation, dopa oxidation, and melanin formation. The morphological and biochemical observations are in agreement. In those organs in which we have demonstrated melanin synthetic activity, the pigment cells are morphologically and like melanophores, while in the organs that show no melanin synthetic activity, the pigment cells resemble macrophages.

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00276.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Norepinephrine (NE) and phenylephrine (Phe) were employed to study the ionic requirements for alpha adrenoceptor activation in the teleostPoecilia reticulatamelanophores.As expected the beta adrenoceptor blocker, propranolol, increased the sensitivity of the preparation to NE (5.8 times), and was therefore employed in all the experimental procedures. Neither cocaine (a neuronal uptake blocker) nor dexamethasone (an extraneuronal uptake blocker) enhanced the sensitivity of the preparation to NE, suggesting that these inactivating mechanisms would not play a role inP. reticulatapigmentary system. However, in the absence of calcium, the dose‐response curve (DRC) to NE was displaced to the left about 3.5 times, whereas the DRC to Phe was not affected. These results indicate that a neuronal uptake is active, but was not demonstrated by the classical pharmacological tools, probably due to an assymmetric display of the nervous endings.The DRC to NE was rightward displaced (14.1 times) in the presence of the calcium channel blocker Verapamil, whereas the DRC to Phe was not affected. These data suggest thatP. reticulatamelanophores possess a mixed population of alpha1and alpha2adrenoceptors, the activation of the latter eliciting an extracellular calcium influx.In sodium‐free saline, the DRC to NE was rightward shifted (6.6 times) and the response to Phe was impaired in such a way that the maximal response was not achieved. The DRC to both NE and Phe were rightward displaced (7.9 and 2.7 times respectively) in the presence of the sodium channel blocker tetrodotoxin (TTX) 10−7M.In potassium‐free saline, the melanophore sensitivity to Phe was increased, whereas the responses to NE were not affected, suggesting a differential sensitivity of the two alpha adrenoceptor subtypes to the resulting membrane hyperpolarization.Based on the literature and on our data we propose thatP. reticulatamelanophores possess a mixed population of alpha1and alpha2receptors. The activation of both subtypes of alpha adrenoceptors elicits a Na+ion influx through TTX‐sensitive sodium channels. The stimulation of alpha2adrenoceptors also requires an extracellular calcium influx, through the opening of slow calcium

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00277.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

45Ca uptake was studied in isolated chick retinal pigment epithelial cells.45Ca was accumulated by a saturable, temperature‐dependent system with a KMof 400 μM and a Vmax of 0.13 μmoles/mg protein/min, which depends on the external sodium concentrations. The transport system was present early during embryonic development. RPE cells of three breeds of chicks with different degrees of pigmentation accumulated calcium proportionally to the melanin content of the cells, suggesting that pigment granules participate in the storage and regulation of intracellular calc

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00278.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A phenolic amine compound, 4‐S‐cysteaminylphenol (4‐S‐CAP), was found to cause a selective destruction of follicular melanocytes. It was also recently found that 4‐S‐CAP can be a substrate for both tyrosinase and plasma monoamine oxidase (MAO). Both of these enzymes are capable of producing cytotoxic intermediates through their interaction with 4‐S‐CAP. To study the mechanism of selective melanocytotoxicity of phenolic amine compounds, we compared the in vivo depigmenting potency of 4‐S‐CAP and its three analogues; i.e., 4‐S‐HomoCAP, α‐methyl(Me)‐4‐S‐CAP and N,N‐dimethyl(DiMe)‐4‐S‐CAP, using black hair follicles. All four of these phenolic amine compounds possessed depigmenting potency. In this study we examined the kinetics of tyrosinase and MAO by these four compounds. 4‐S‐CAP and 4‐S‐HomoCAP were the substrates of both tyrosinase and MAO, whereas α‐Me‐4‐S‐CAP and N,N‐DiMe‐4‐S‐CAP were the substrates of tyrosinase alone. The rate ofo‐quinone formation by tyrosinase was not in parallel to the in vivo depigmenting potency of the tested compounds. It is therefore indicated that plasma MAO is not the enzyme directly responsible for the production of the melanocytotoxic intermediates from the phenolic amine compounds. We also found that the observed in vivo depigmentation results from complex processes involving the amount ofo‐quinone form

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00279.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A stock of hairless pigmented guinea pigs was developed to facilitate studies of mammalian pigmentation. This stock combines the convenience of a hairless animal with a pigmentary system that is similar to human skin. In both human and guinea pig skin, active melanocytes are located in the basal layer of the interfollicular epidermis. Hairless albino guinea pigs on an outbred Hartley background (CrI:IAF/HA(hr/hr)BR; designatedhr/hr) were mated with red‐haired guinea pigs (designatedHr/Hr). Red‐haired heterozygotes from the F1generation(Hr/hr)were then mated with each other or with hairless albino guinea pigs. The F2generation included hairless pigmented guinea pigs that retained their interfollicular epidermal melanocytes and whose skin was red‐brown in color. Following UV irradiation, there was an increase in cutaneous pigmentation as well as an increase in the number of active epidermal melanocytes. An additional strain of black hairless guinea pigs was developed using blackHr/Hranimals and a similar breeding scheme. These two strains should serve as useful models for studies of the mammalian pigment s

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00280.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The in vitro radiosensitivity of one murine melanoma cell line (Cloudman S91 CCL 53.1) and three human melanoma cell strains (C8146C, C8161, and R83‐4) were studied. Cells were irradiated by single dose X‐rays and plated either in agar or on plastic. The survival curves were fitted by the single‐hit multitarget, two‐hit multitarget, and quadratic models. Multiple comparisons of the residual sum of squares suggested that the two‐hit model was clearly inferior to the single‐hit and quadratic models. No statistically significant difference was suggested for either the single‐hit or quadratic models. Furthermore, on examination of the differences in correlations between the observed and predicted values, the residual plots (observed minus predicted over dose) failed to suggest a clear advantage of either the single‐hit multitarget or the quadratic models. Either model could be recommended for analysis of in vitro

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00281.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Three human melanoma cell lines of varying invasive and metastatic potential were analyzed for their ability to express HLA‐DR antigens on the cell surface as well as transcriptionally at the mRNA level in the presence and absence of IFN‐γ treatment. Cells of low and intermediate metastatic and invasive potential showed a high percentage of HLA‐DR surface expression, both before (91.2‐99.9%) and after (97.8‐99.9%) IFN‐γ treatment, as quantitated by flow cytometry. In contrast, cells of high metastatic and invasive potential expressed barely detectable levels of HLA‐DR‐positive cells before IFN‐γ treatment (0.3‐0.6%) and displayed elevated levels following treatment (42.3‐89.4%(. Allowing the highly metastatic cells to recover for 7 or 14 days following IFN‐γ treatment resulted in barely detectable levels of HLA‐DR‐positive cells. Northern blot analyses of HLA‐DR transcription levels showed a strong expression in cells of low and intermediate metastatic and invasive potential. HLA‐DR mRNA levels were not detectable in control cells of high metastatic potential nor in those cells which had undergone 7‐ and 14‐day recovery periods following IFN‐γ treatment. There was, however, an induction of HLA‐DR expression in the cells that had been treated with IFN‐γ for 72 hr and allowed no recovery period. In addition, a punctate, receptor‐like pattern of immunofluorescence staining pattern for cell surface HLA‐DR was seen after a 72 hr IFN‐γ treatment in the highly metastatic cells. In contrast, cells of low and intermediate metastatic potential expressed

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00282.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Pigmented tissues from bovine eye were used as a source for isolation of tyrosinase from normal melanocytes. Tyrosinase is highly hydrophobic and the isolation procedure is mainly based on the use of hydrophobic interaction chromatography. The bovine enzyme is, in contrast to the human melanoma tyrosinase, mainly soluble. The predominant part of the ocular enzyme from cow has a molecular weight and isoelectric behavior similar to that of the soluble tyrosinase in the human melanoma cells. The N‐terminal amino acid sequence of isolated bovine tyrosinase was determined by automated Edman degradation. The N‐terminal amino acid sequence from normal bovine tyrosinase was identical to the sequence of an N‐terminal region of mouse melanoma tyrosinase predicted from a c‐DNA clone by Kwon et al. (1988). The amino acid sequence of bovine tyrosinase shows homology to that of human tyrosinase (Wittbjer et al., 1989), but three amino acids of the 16 residues determined by us differed. Histidine was the N‐terminal a

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00283.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00284.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY