摘要:

A pigment‐dispersing hormone (PDH) from eyestalks of the crayfishProcambarus clarkiiwas purified by gel filtration, cation‐exchange chromatography, partition chromatography, and reversed‐phase HPLC. Based on automated sequencing and by the identical chromatographic behavior of the native PDH and the synthetic amidated form of the deduced sequence, the primary structure ofProcambarusPDH has been established as: Asn‐Ser‐Glu‐Leu‐Ile‐Asn‐Ser‐Ile‐Leu‐Gly‐Leu‐Pro‐Lys‐Val‐Met‐Asn‐Glu‐Ala‐NH2. This peptide differs from β‐PDH of the fiddler crabUca pugilatorat a single position, Glu17in place of Asp17. Because of this substitution,ProcambarusPDH was 4 to 7‐fold less potent than β‐PDH in causing pigment dispersion in the erythrophores, leucophores, and melanophores ofUca. In contrast,ProcambarusPDH was 4‐fold more potent than β‐PDH in eliciting pigment dispersion in the erythrophores of Procambarus. These peptides displayed less marked differences in potency in triggering leucophore pigment dispersion and light‐adaptational distal eye pigment movement inProcambarus. These findings indicate that the structural requirements for PDH‐receptor interactions vary with the sp

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The iridescence from the cornea of the sand goby (Pomatoschistus minutus) occurs because of thin layer interference from the platelet‐like cells in the stroma. It is suggested that ionic pumps across the epithelium control the water content in the stroma and thus the spectral reflection. A saline was perfused over goby eyes and simple ion manipulation was carried out to observe any changes in the iridescent characteristics. It was found that removal of CI−and K+ions reduced the peak reflected wavelength to the blue end of the spectrum, whereas Na+had little effect. The removal of K+also caused a dramatic change to the normal shift in reflected spectral intensity. The iridescence was also found to be sensitive to pH, and the buffer HEPES was detrimental to the cornea compared to controls. These results suggest similarities to amphibian and mammalian corneal hydration cont

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

This paper deals with the nuclear magnetic resonance characterization of a soluble derivative (melanin free acid) ofSepiamelanin obtained by a peroxidative treatment of the parent (insoluble) species. High resolution13C and15N solid state NMR spectroscopies allow the assessment of the chemical changes occurring in the macromolecule upon solubilization.1H and13C NMR solution spectra are discussed in light of the results obtained from the solid state spectra.Furthermore, the coordination properties of melanin have been investigated through27Al NMR spectroscopy and proton relaxation enhancement studies of the paramagnetic gadolinium complex of melanin free acid. Through these experiments it has been possible to evaluate the molecular reorientational time τR (and from it an estimated molecular weight close to 20 KDa) and the strength of the metal‐macromolecule interacti

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00443.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Concentration of melanosomes in various tissues has been unknown because of the impracticability of their direct quantification. Using an indirect approach comprising the estimation of melanin both in freeze‐dried tissue samples and in isolated melanosomes, we obtained data on the amount of melanosomes in various pigment tissues. The concentrations of melanosomes found in the tissues were relatively high, not only reflecting the dark color of pigment tissues but also explaining their capacity to perform various functions ascribed to the presence of melani

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00444.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Verapamil, a calcium channel antagonist, inhibits murine B16 melanoma and colon adenocarcinoma C26 tumor metastasis by altering platelet aggregation [Tsuruo, T., et al. (1985) Cancer Chemother. Pharmacol., 14:30–33]. However, the role of calcium homeostasis in regulating several biochemical pathways implicated in other steps of the meta‐static cascade suggests that calcium channel antagonists could also inhibit metastasis by other mechanisms. In this report, non‐toxic doses of verapamil reversibly decreased human A375M and C8161 melanoma cell invasion and metastasis in a dose‐dependent manner. Verapamil reduced cellular invasion and metastases by up to 96% (range 78–96%). Concomitantly, verapamil disrupts microtubule and microfilament organization and inhibits unidirectional cell migration but does not affect cellular adhesion to endothelial mono‐layers or reconstituted basement membranes. In addition, tumor cells treated with verapamil have a decrease in mRNA of type IV collagenase, a proteinase important in tumor cell degradation of basement membranes. Collectively, these data offer additional evidence regarding the mechanisms of action of verapamil as an anti‐met

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00445.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

High levels of intracellular glutathione (GSH) may result in resistance of tumor cells to cytotoxic drugs. Because of the innate refractory nature of melanoma cells to chemotherapy, we have used a syngeneic murine system consisting of nontumorigenic Mel‐ab melanocytes, tumorigenic H‐ras‐transformed melanocytes (C9.1), and the highly meta‐static BL6 melanoma cells to examine the GSH content, glutathione S‐transferase (GST) activity, and sensitivity to buthionine sulfoximine (BSO) and other cytotoxic drugs. Compared to the nontumorigenic melanocytes, both C9.1 and BL6 melanoma cells have nearly fivefold higher GSH content, and BL6 cells have increased GST activity. C9.1 and BL6 cells are more resistant to the cytotoxic effects of BCNU and adriamycin; however, the degrees of resistance do not reflect the increased GSH content in these cells. Pretreatment of BL6 melanoma cells with 50 μM BSO depleted over 90% of their GSH content and enhanced the growth‐inhibitory effects ofl‐dopa methylester, BCNU, bleomycin, and dacarbazine. Exposure to BSO alone was not toxic to the tumor cells for up to 24 hr, but was significantly cytotoxic in the melanocytes after 9 hr. The sensitivity of these cells to BSO appears to depend on a critical level of GSH depletion which is not related to the initial GSH content. These studies suggest that the resistance of melanoma cells to cytotoxic drugs is only partially attributed to changes in the GSH system caused during cellular

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00446.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Electron micrographs of skin from xanthic (gold) sailfin mollies revealed numerous xanthophores, as well as scattered melanophores. The melanophores were seen to contain premelanosomes in various stages of development. This is consistent with the fact that xanthic mollies have been shown to be tyrosinase positive. Melanosomes in xanthic mollies appear to develop by one of two pathways: 1) from an endoplasmic reticulumderived vesicle which develops an internal lamellar framework, and 2) by fusion of multiple Golgi‐derived vesicles which lack an internal lamellar framework. Analysis of the pigments in the skin of the xanthic mollies identified four colorless pteridine pigments (xanthopterin, isoxanthopterin, neopterin, and pterin) and a carotenoid with an absorbance spectrum similar to β‐carotene. It appears that, unlike some other poeciliid fishes, sailfin mollies do not use pteridine pigments for orange coloration. Rather, they appear to rely primarily on caroten

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00447.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Effects of dexamethasone on melanogenesis and tyrosinase mRNA levels were determined in B16/F10 melanoma cells. Melanin content of B16 cells increased in a dosedependent manner by the addition of dexamethasone to the culture medium. After 72 hr exposure, dexamethasone (10−6M) produced a 2.4‐fold increase in melanin content. Northern blot analysis revealed that tyrosinase mRNA level also increased by the addition of dexamethasone to the culture medium. After 24 hr exposure, dexamethasone (10−6M) caused a 1.8‐fold increase in tyrosinase mRNA levels. A tumor promoter, 12‐O‐tetradecanoyl phorbol‐13‐acetate (TPA) decreased tyrosinase mRNA level at 30 nM concentration. Dexamethasone antagonized this TPA mediated decrease in tyrosinase mRNA. It is suggested that glucocorticoids are involved in the regulation of tyrosinase activity at the transc

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00448.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Melanophores of isolated fish scales survive for weeks in a culture medium. During this isolation period a progressive increase in sensitivity to noradrenaline (NA) takes place. In the present study, a 100‐fold increase in sensitivity to NA was found after 9 days. However, at the same time, a 12‐fold decrease in sensitivity to MCH was detec

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00449.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0893-5785    

DOI:10.1111/j.1600-0749.1991.tb00450.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY