摘要:

The types and amounts of pigments in fibers from variously colored Tajik, Hissar, and Caracul sheep were determined by three methods: high‐performance liquid chromatography, electron spin resonance spectroscopy, and light microscopic evaluation of mel‐anosomes. In both dominant and recessive black lambs the color is due to eumelanin pigment. Brown and red phenotypes are the result of interaction of Awtand EBI, EBr, or EYalleles, and these colors are caused by mixtures of eumelanin and pheomelanin in varying ratios. The HPLC and ESR measurements detected these differences in melanin type, while direct characterization of melanosomes generally failed to distinguish between melanin type or relative ratio of melanin t

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00286.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Fast atom bombardment was applied to the study of the intermediates of the reaction dopamine‐tyrosinase after treatment with diazomethane. The identification of trimeth‐oxyindoline, dopamine‐o‐quinone and dimethoxyindole was easily achieved by this ionization method, together with accurate mass measurements and collision experiments. The structures of these compounds are in agreement with those already hypothesized in studies on melano

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00287.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A series of experiments was performed on lyophylized melanosomes in order to analyze the melanin in the natural state as polymerized into these organdies and to verify in such biological amorphous material the possibility of obtaining intensity scattering curves from which Bragg distances can be calculated. The results confirm the feasibility of the method and show that melanins in melanosomes maintain many structural features of the purified form and that the biochemical composition of the organelles can be responsible for the observed differences in the diffractograms. The presence in melanosomes of supramolecular paracrystalline aggregates was also clearly demonstrated.

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00288.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effects of β‐adrenergic agonists and antagonists on the pigmentary state of denervated melanophores in isolated, split, caudal fins of the gobyTridentiger obscuruswere examined to investigate the function and the subtype of the β‐adrenoceptors of the melanophores. Salbutamol, terbutaline, and dobutamine partially inhibited the pigment‐aggregating response of melanophores to norepinephrine. The effects of these β‐agonists were inhibited by propranolol. It was confirmed that the melanophores possess both α‐and β‐adrenoceptors, and that the activation of the β‐adrenoceptors induces the dispersion of pigment in the melanophores. Norepinephrine, epinephrine, isoproterenol, dobutamine, salbutamol, and terbutaline evoked the dispersion of pigment in the melanophores in which pigment had previously been aggregated by treatment with verapamil in the presence of phentolamine. The pigment‐dispersing effects of two β1‐selective agonists, norepinephrine and dobutamine, were effectively inhibited by metoprolol, a selective antagonist of β1‐receptors. By contrast, the pigment‐dispersing effects of two β2‐selective agonists, salbutamol and terbutaline, were not inhibited by metoprolol. Both the effects of nonselective agonists, epinephrine and isoproterenol, were partially inhibited by metoprolol. The actions of all of the β‐agonists used were effectively inhibited by propranolol, and they were partially inhibited by butoxamine. These results suggest coexistence of β1‐ and β2‐adrenoceptors in the melanophores. The relative numbers of β1‐ and β2‐adrenoreceptors as a percentage of the total population of β‐adrenoceptors were estimated to be 18.6% and 81.4%, respectively, from analyses of Hofstee plots of the effects of the β‐agonists on the mel

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00289.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Linoleic acid has been shown to inhibit melanogenesis in cultured B16 mouse melanoma cells. We report here the possible involvement of protein kinase C (PKC) in linoleic acid‐induced inhibition of melanogenesis in B16 cells. A single PKC subspecies (α‐PKC) was detected in B16 cells. The enzyme was activated by linoleic acid in vitro. The effective concentrations at which PKC was activated (25 μM; maximum response) were consistent with those for the inhibition of melanogenesis in cell culture system. In addition, the permeable diacylglycerol 1‐oleoyl‐2‐acetyl glycerol that activates PKC also inhibits melanogenesis at 100 μM. These results suggest that activation of PKC plays a pivotal role in the linoleic acid‐induced inhibition of melanogenesi

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00290.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effects of 3′‐5’cyclic AMP and ATP upon tyrosinase induction inNeurospora crassawere examined. Northern analysis of total cellular RNA revealed rapid de novo synthesis of protyrosinase after addition of these substances to stationary‐phase mycelia. The maturation of protyrosinase in crude extracts of mycelia was followed by Western analysis. Polyclonal rabbit antiserum directed against the denatured carboxyl‐terminal extension of protyrosinase does recognize the proform and several intermediate forms of different molecular weight but not mature tyrosinase. Disruption of ATP‐induced mycelia in sodium phosphate buffer (pH 6.0) demonstrate processing at the carboxyl‐terminal end of protyrosinase. The activity assays revealed that protyrosinase is an inactive precursor and that at least two active forms of slightly different molecular weight are present in crude extracts. Maturation of protyrosinase thus involves specific and sequential proteolytic cleavage at the carboxyl‐terminus. These results suggest the presence of a tyrosinase activator inNeurospora crassamycelia, which is kept apart from protyrosinase in the

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00291.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Psoralens (8‐methoxypsoralen, 5‐methoxypsoralen and 4,5,8‐trimethylpsoralen) stimulate mouse melanoma cell (S91 and B16/F10) tyrosinase activity in vitro in a dose‐related manner. Stimulation of enzyme activity by the psoralens was evoked in the presence or absence of light. In the presence of a melanotropin the actions of the psoralens were generally at least additive compared to the individual actions of the two agonists. The actions of the psoralens were acute and depended upon the constant presence of the agents to maintain enhanced melanoma tyrosinase activity. Tyrosinase activation by the psoralens, like that of α‐melanotropin, was blocked by actinomycin‐Dor cycloheximide demonstrating that the actions of the drugs may have involved both transcriptional and translational events in the stimulation of melanogenesis. Psoralens also stimulated an immediate darkening of frog skins in vitro. Topically applied psoralens were transdermally delivered to the systemic circulation resulting in a conversion from pheomelanogenesis to eumelanogenesis within follicular melanocytes throughout the entire skin of mice (C57BL/ 6JAymaintained in the dark. Taken together, these results demonstrate that psoralens activate processes within melanocytes resulting in both an immediate translocation of melanosomes within the cell (frog) or in a slower genomic event involving tyrosinase activation (melanoma cells) and eumelanin formation (mouse follicular

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1990.tb00292.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.tb00293.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY