中药对黑素生物合成影响研究I.82味中药乙醇提取物对酪氨酸酶活性的抑制作用

对中医治疗色素增加性皮肤病方剂６９首进行计算机拆方排序,选出高频次出现中药８２ 味,观察这些中药乙醇提取物对蘑菇酪氨酸酶和无细胞系统多巴色素自动氧化生成黑素量的影 响。结果显示１１味中药乙醇提取物在３个不同浓度对酪氨酸酶活性和黑素生成量呈剂量依赖性 抑制,其中白术、白僵蚕、藁本、白芨、白附子、沙苑子、六月雪、柿叶对酪氨酸酶活性抑制率与单体 化合物熊果苷无统计学差异（Ｐ＞０．０５）。进－步研究这些中药的皮肤脱色机制与评估其临床应用 价值是必要的。     

二花鲜汁膜治疗黄褐斑的实验研究

目的：观察二花鲜汁膜对紫外线照射致黄褐斑模型小鼠皮肤中黑色素细胞的分布和数量及超氧化物歧化酶（SOD）活性和丙二醛（MDA）含量的影响。方法：紫外线照射法制作黄褐斑小鼠模型；检测应用二花鲜汁膜后，小鼠皮肤中SOD和MDA的含量、黑色素细胞的分布及数量。结果：实验组皮肤中SOD活性较对照组明显升高，MDA含量降低，黑色素细胞的数量及分布也明显减少。结论：二花鲜汁膜对黄褐斑有明显的抑制作用。     

Direct effects on proliferation,antigen expression and melanin synthesis of cultured normal human melanocytes in response to UVB and UVA light

BACKGROUND/PURPOSE: Ultraviolet (UV) radiation; induces a variety of responses in the skin, including tanning and inflammation, and may also act as a carcinogen. As epidermal melanocytes are seen as the major targets of UV light, the present study was conducted to evaluate the direct effects of UVA and UVB irradiation on melanocytes in vitro. METHODS: Normal human epidermal melanocytes (NHM) were exposed on 3 consecutive days to UVA (0.072-7.2 J/cm2) and UVB (7.2-48 mJ/cm2), respectively, and changes of morphology, cell number, melanin synthesis and antigen expression (APAAP technique) were determined 5 days after the first exposure. RESULTS: UVA radiation caused only minimal effects on NHM by slightly inducing expression of the activation marker HMB-45 and decreasing expression of the proliferation marker Ki-67. No changes of morphology, cell number or melanin synthesis were detectable with any of the applied doses. On the other hand, UVB radiation significantly induced dendrite formation and decreased the number of NHM in a dose-dependent manner (74% of the controls at 7.2 mJ/cm2, 64% at 14.4 mJ/cm2 and 28% at 36 mJ/cm2). Significant induction of the activation marker HMB-45 was found in parallel to decreased expression of the differentiation marker K.1.2.58. UVB doses >or=9.6 mJ/cm2 also resulted in significant downregulation of the proliferation marker Ki-67, confirming the data of the cell counts, and melanin content was increased in NHM (20% over the controls, P<0.01) after applying 7.2 mJ/cm2 UVB. CONCLUSION: Our results may suggest that the effect of UVB radiation in skin is due to direct activation of melanocytes, whereas skin tanning caused by UVA is mediated rather in an indirect way.     

Melanin production in medullary thyroid carcinoma

A case of melanin-producing medullary thyroid carcinoma is reported in a 51-year-old man. Histologically, the tumour had a typical pattern of medullary thyroid carcinoma with numerous scattered pigmented cells which contained large amounts of melanin pigment as confirmed by bleached Fontana-Masson stain. Immunohistochemical staining revealed positivity of almost all tumour cells for calcitonin and chromogranin, whereas S-100 protein and HMB-45 staining was positive only in the pigmented tumour cells. This finding confirms the ability of medullary thyroid carcinoma cells to have multidirectional differentiation, although melanocytic differenciation remains an exceptional phenomenon.     

Effect of melanin, oxyhemoglobin and bilirubin on transcutaneous bilirubinometry

To determine the effect of skin pigments on transcutaneous bilirubinometer readings, we measured the effect of bilirubin, melanin, and oxyhemoglobin solutions on transcutaneous bilirubinometer readings in vitro. Our results showed that the variability of the readings in vitro was related to the instrument's non-linear response to bilirubin and melanin concentration and an inacurate oxyhemoglobin correction factor. These factors should be considered in developing a more accurate non-invasive method of monitoring serum bilirubin concentration.     

Histopathological parameters determining lesion colours in the naevus of Ota: a morphometric study using computer-assisted image analysis

BACKGROUND: Naevus of Ota manifests various colours ranging from light brown to blue. Naevus colours have been claimed to reflect the depth of melanin pigments but the claim has rarely been substantiated by quantitative studies. OBJECTIVES: We attempted both quantitative and qualitative analyses of the naevus of Ota to find out relations between histological patterns or parameters of melanin/melanocytes and lesion colours. METHODS: Lesion colours were determined by one of the authors and were confirmed by a separate panel of dermatologists. Forty biopsy specimens of naevus of Ota were evaluated by both computer-assisted quantitative image analysis and a previously proposed conventional pattern analysis. RESULTS: The mean area fraction (AFmean) of melanin, the depth of the maximum area fraction of melanin (level of AFmax) and the depth of the deepest infiltrating melanocyte were significantly greater or deeper for bluish lesions than brownish lesions. Based on the qualitative pattern analysis we found that all the brownish lesions demonstrated superficial dermal melanin pigments, whereas bluish lesions tended to show more heterogeneous histological patterns. Eyelid lesions, all of which were bluish, revealed greater AF(mean) value than cheek lesions, presenting as either brownish or bluish colours. CONCLUSIONS: Quantitative analysis indicated that pigment density measures such as AFmean could be as important as the depth of melanocytes in the explanation of the lesion colours in naevus of Ota. However, qualitative pattern analysis failed to link specific patterns with lesion colours, especially in bluish lesions, probably due to the lack of consideration of the pigment density.     

Assessing macular pigment from SLO images

PURPOSE: To assess the spectral characteristics and spatial distribution of macular pigment by comparing relative retinal reflectance at four different wavelengths. METHODS: A Rodenstock scanning laser opththalmoscope (SLO) with four spectral beams, 488, 544, 633 and 780 nm, was used to obtain images of the normal macula from five eyes of three normal subjects. The relative spectral reflectance was determined along a horizontal path extending from nasal to temporal retina through the fovea for each image. A comparison of this data provided an indication of the relative density and the actual spatial extent of macular pigmentation. RESULTS: There is an area of hyper-pigmentation obtained from averaging the data from all five eyes that extends from about 6 deg symmetrically into nasal and temporal macula surrounding a small zone of greater hyper-pigmentation that extends about 3 deg on each side of the fovea. The smaller central zone has a relatively high absorption for blue light and is considered to represent macular pigment. The larger less hyper-pigmented zone is considered to represent melanin in the retinal pigment epithelium. CONCLUSION: The circularly symmetrical hyper-pigmented central macula including the yellow macular pigment can be assessed by comparing different spectral images obtained from an SLO.     

Binding Affinity of Bunazosin,Dorzolamide, and Timolol to Synthetic Melanin

Purpose The purpose of this study was to compare the binding affinity of bunazosin and dorzolamide to synthetic melanin relative to that of timolol.Methods Synthetic melanin was prepared from dopa by the action of tyrosinase. Timolol, dorzolamide, and bunazosin were incubated separately at a concentration of 10^–4M in 2ml of 0.066M phosphate buffer containing 5mg of synthetic melanin. After centrifugation, the absorbance of each free drug in the supernatant was measured at its optimum wavelength. The percentage of each drug bound to melanin was calculated directly from the change in absorbance relative to the initial value.Results The increase in the binding rates of all three drugs seemed to reach a plateau after 30min. After incubating for 60min, the binding rate of timolol was 22.2% ± 4.9%, bunazosin 36.3% ± 2.5%, and dorzolamide 8.5% ± 1.9%. There were statistically significant differences between the binding rates of each drug.Conclusions Under our study conditions, the order of binding affinity of these ocular hypotensive agents to synthetic melanin seems to be as follows: bunazosin timolol dorzolamide. Jpn J Ophthalmol 2004;48:34–36 © Japanese Ophthalmological Society 2004     

Binding of Memantine to Melanin: Influence of Type of Melanin and Characteristics

Purpose. The objectives of this study were to characterize sepia, synthetic, and bovine melanin and to determine their binding characteristics to the drug memantine. Methods. Physical methods were used to characterize sepia, synthetic, and bovine melanin. Their binding properties toward memantine were determined in deionized water and phosphate-buffered saline (PBS) at 37°C. Melanin-memantine binding was measured indirectly by determining the unbound fraction of memantine. Curve fitting according to the Langmuir binding isotherm for one binding site was used for the determination of binding capacity (B _Lmax ) and dissociation constant (K _D ). Results. Synthetic and sepia melanin had comparable Gaussian particle size distributions, whereas bovine melanin showed a heterogeneous distribution profile. The suspension medium had a small effect on the particle size distribution of synthetic and bovine melanin. There were characteristic differences in the infrared spectra of the melanins. The rank order for B _Lmax in deionized water was sepia > bovine > synthetic melanin. However, when the melanins were suspended in PBS, the B _Lmax values were lower, and the rank order was bovine > sepia > synthetic. Whereas the K _D values for sepia and synthetic melanin remained largely the same in deionized water and PBS, the K _D value for bovine melanin in PBS was more than twice than in deionized water. Conclusions. This study showed that the physical characteristics of the melanins investigated differ markedly. The binding of memantine to melanin is thought to be determined by the different chemistries of the melanins, particle size, and buffer electrolytes.