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.     

Loss of melanin from human RPE with aging: possible role of melanin photooxidation

The pigment melanin, which is believed to play a photoprotective role, was quantified here in human RPE cells from donors of different age. Electron spin resonance (ESR) spectroscopy was shown to provide a quantitative measure of melanin and was used as a non-destructive measure of melanin content. Results indicated an age-related melanin loss in RPE cells, with melanin content diminishing 2.5-fold between the first and the ninth decade of life. To determine whether photo-oxidation may contribute to age-related changes in RPE melanin, RPE in human eyecups, isolated human and bovine RPE cells, purified melanin granules, or synthetic dopa melanin were irradiated with various wavelengths and intensities of visible light. Samples were analysed for changes in melanin content by ESR spectroscopy, and by absorption and emission spectrophotometry. The concentration of hydrogen peroxide was measured in some samples, and some human eyecups were examined by transmission electron microscopy. Irradiation of RPE in eyecups with intense visible light was found to produce a time-dependent photobleaching of melanosomes that was accompanied by the formation of hydrogen peroxide. Photobleaching of isolated RPE melanosomes and synthetic dopa melanin resulted in enhanced melanin fluorescence, as previously shown for melanin from aged donors by others, and significantly reduced ESR signal intensity, resembling the changes in melanin with aging observed here. We conclude that the content of melanin in RPE cells undergoes an age-related change to which photo-oxidation may contribute. This observation raises the question of whether age-related changes in melanin reduce the photoprotective role of the pigment in aging RPE cells.     

Effect of oral administration ofHypericum perforatum extract (St. John's Wort) on skin erythema and pigmentation induced by UVB,UVA, visible light and solar simulated radiation

Hypericin from St John's wort (Hypericum perforatum L.) is a photosensitizing agent that may cause a severe photodermatitis when higher amounts of St John's wort are ingested by animals. Although Hypericum extracts are widely used in the treatment of depressive disorders, only a little information on the photosensitizing capacity of St John's wort in humans is available. In the present prospective randomized study we investigated the effect of the Hypericum extract LI 160 on skin sensitivity to ultraviolet B (UVB), ultraviolet A (UVA), visible light (VIS) and solar simulated radiation (SIM). Seventy two volunteers of skin types II and III were included and were divided into six groups, each consisting of 12 volunteers. In the single-dose study the volunteers (n = 48) received 6 or 12 coated tablets (5400 or 10 800 microgram hypericin). In the steady-state study the volunteers (n = 24) received an initial dose of 6 tablets (5400 microgram hypericin), and subsequently 3 x 1 tablets (2700 microgram hypericin) per day for 7 days. Phototesting was performed on the volar forearms prior to medication and 6 h after the last administration of Hypericum extract. The erythema-index and melanin-index were evaluated photometrically using a mexameter. After both single-dose and steady-state administration, no significant influence on the erythema-index or melanin-index could be detected, with the exception of a marginal influence on UVB induced pigmentation (p = 0.0471) in the single-dose study. The results do not provide evidence for a phototoxic potential of the Hypericum extract LI 160 in humans when administered orally in typical clinical doses up to 1800 mg daily. This is in accordance with previous pharmacokinetic studies that found hypericin serum and skin levels after oral ingestion of Hypericum extract always to be lower than the assumed phototoxic hypericin threshold level of 1000 ng/mL.     

Esophageal blue nevus: an isolated endoscopic finding

BACKGROUND: The occurrence of blue nevus has seldom been reported in extracutaneous sites and with no record in the esophagus. CASE REPORT: A blue nevus was reported in the esophagus of a 58-year-old Chinese woman. On endoscopic examination, the lesion presented as linear patches of bluish pigmentation in the esophagus. The patient was free of symptoms 3 years after the endoscopic examination. CONCLUSIONS: We believe this represents the first reported case of blue nevus in the esophagus. The clinicopathologic features, differential diagnoses, and the nature of the lesion are discussed, along with a review of the literature.     

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）。进一步研究这些中药的皮肤