Is abnormal retinal development in albinism only a mammalian problem? Normality of a hypopigmented avian retina

The central retina in hypopigmented mammals is underdeveloped. In the outer retina this deficit is confined to rods. Also, many ganglion cells in temporal regions project inappropriately to the contralateral hemisphere. This study addresses the question of whether pigment-related abnormalities occur in the central retina of a non-mammal, the bird. Birds have a highly developed central retina, but unlike most mammals they do not have a significant uncrossed retinal projection. Consequently, examination of the retinae of hypopigmented birds will reveal whether there is a relationship between the two abnormalities. Also if one of the primary effects of albinism is centred on rods, then albino birds may not show a deficit, because their retinae are cone dominated. Retinae from normally pigmented and two forms of hypopigmented budgerigars (Melopsittacus undulatus) were studied. Measurements of layer thickness, cell density and cell size were made at a range of locations in the ganglion cell layer and in the inner and the outer nuclear layers. Estimates of cone numbers were also made. Each strain of bird had an area of increased retinal layer thickness in dorso-temporal regions, but not a fovea. Although there were variations in the measurements undertaken between the strains, none were pigment related or consistent with the abnormality found in the central retina in albino mammals. Consequently, the underdevelopment of the central retina seen in hypopigmented mammals does not occur in this bird. There are two possible explanations for this result. First, normal mammalian retinal development may depend partly on time-dependent interactions in the maturation of the retinal pigment epithelium and the neural retina. Although there is a common time table for the development of the mammalian visual system when expressed in terms of the caecal period, which is between conception and eye opening, the pace of retinal development in birds is accelerated, which may alter interactions between these regions. Second, as the bird retina is cone dominated, any deficits in albino strains may be relatively minor.     

Protection of melanoma cells against superoxide radicals by melanins

Summary Human melanoma cells transplanted into immunocompetent mice by the 6-day subrenal capsule technique are characterized by high resistance against immunological attack. This resistance is suggested to be the consequence of scavenging of superoxide free radicals by melanin. Scavenging of superoxide radicals by the melanoma cells was clearly demonstrated using electron spin resonance techniques. From comparison with synthetic melanins it is concluded that the scavenger effect can be attributed mainly to low-molecular-mass melanins synthesized in the melanoma cells whereas high-molecular-mass melanins are practically ineffective.Abbreviations ESR electron spin resonance - DMSO dimethylsulfoxide - TEMPOL 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl     

褪黑素通过调控p53介导的细胞早衰抑制紫外线诱导的HaCaT细胞中黑色素合成

目的 探索褪黑素对中波紫外线（UVB）引起人永生化表皮角质形成（HaCaT）细胞黑色素合成的影响及机制,为褪黑素的皮肤保护机制提供理论基础。方法 80 mJ/cm² UVB照射10^-5 mol/L褪黑素预处理的HaCaT细胞,照后48和72 h,利用NaOH法检测细胞黑色素水平。照后72 h,利用β-半乳糖苷酶染色试剂盒检测早衰阳性细胞并分析其比例,蛋白免疫印迹法检测衰老相关蛋白p53和酪氨酸酶（TYR）的表达变化。80 mJ/cm² UVB照射分别经毛细血管扩张性共济失调突变激酶/毛细血管扩张性共济失调Rad3相关激酶（ATM/ATR）抑制剂、p53抑制剂和褪黑素预处理的HaCaT细胞,照后72 h检测细胞早衰阳性比例和黑色素水平变化。结果 褪黑素抑制UVB诱导的黑色素水平增加（t=56.65、13.39,P<0.05）,同时抑制UVB诱导的TYR表达增加（t=16.46,P<0.05）;并可缓解UVB诱导的HaCaT细胞早衰（t=6.37,P<0.05）,抑制UVB诱导的p53表达增加（t=19.08,P<0.05）;ATM/ATR抑制剂、p53抑制剂和褪黑素预处理均可抑制UVB诱导的HaCaT细胞黑色素水平升高（t=13.88、7.86、8.96,P<0.05）。结论 褪黑素通过调控p53介导的细胞早衰,抑制UVB诱导的HaCaT细胞黑色素水平增加。     

The Influence of Eye Colour upon Temporary Threshold Shift

Controversy has arisen over the claim that melanin content of the iris as determined by eye colouration bears a direct relationship to susceptibility to temporary threshold shift (TTS). A more comprehensive investigation of TTS has now been carried out which not only confirms the relationship but also indicates that earlier discordant results can be attributed to differences in methodology. The new evidence suggests that for stimulus intensities below 110 dB. (HTL re ISO, 1964) melanin content of the iris exerts its influence predominantly upon auditory adaptation while fatigue effects only become apparent at intensities above this level. The relevance of these findings to hearing conservation measures aimed at the prevention of noise-induced hearing loss is discussed.     

微生物来源的黑色素生物合成抑制剂H7264的研究

通过建立的用链霉菌X59为鉴定菌的黑色素生物合成抑制剂筛选模型，从4000余个微生物代谢产物中找到一株活性化合物产生菌。该菌从四川省宜 地区土壤中分离，编号SIIA－H7264。该菌种经鉴定为链霉菌，其代谢产物H7264A和H7264B结构论证与化合物Enopeptin A,B同质，但Enopeptin尚未发现其有抑制黑色素生物合成活性。     

Inhibitory effects of arbutin on melanin biosynthesis of α-melanocyte stimulating hormone-induced hyperpigmentation in cultured brownish guinea pig skin tissues

Arbutin has been used as a whitening agent in cosmetic products. Melanin, the major pigment that gives color to skin, may be over-produced with sun exposure or in conditions such as melasma or hyperpigmentary diseases. Tyrosinase is a key enzyme that catalyzes melanin synthesis in melanocytes; therefore, inhibitors of the tyrosinase enzyme could be used for cosmetic skin whitening. A recent study has reported that arbutin decreases melanin biosynthesis through the inhibition of tyrosinase activity. However, this inhibitory mechanism of arbutin was not sufficiently demonstrated in skin tissue models. We found that arbutin both inhibits melanin production in B16 cells induced with α-MSH and decreases tyrosinase activity in a cell-free system. Furthermore, the hyperpigmentation effects of α-MSH were abrogated by the addition of arbutin to brownish guinea pig and human skin tissues. These results suggest that arbutin may be a useful agent for skin whitening.     

Influence of macular pigment and melanin on incident early AMD in a white population

Background The protective effect of macular pigment (MP) and melanin against age-related macular degeneration (AMD) is still controversial from cross-sectional studies. In an attempt to clarify this issue, we performed a population-based longitudinal study. Methods MP optical density (MPOD) and melanin optical density (MOD) data were collected during the second follow-up phase of the Rotterdam Study in 1999 in a random subset of 435 participants. Data from 419 participants (98% white) was available for analysis. AMD diagnosis was based on standardized fundus photographs according to the International Classification System, and AMD cases were subdivided into five mutually exclusive stages. In the three follow-up phases, incident AMD (iAMD), defined as absence of any AMD at baseline and the presence of stage 2 or higher at follow-up, was determined. We used Cox regression analysis to study the effect of an assumedly stable MPOD and MOD on early iAMD. Results During a mean follow-up of 9.82 years, 13 male and 17 female participants developed early iAMD and two male participants late iAMD. Because only two participants developed late iAMD, we had to restrict our analyses to early iAMD. Cox regression analysis adjusted for age and gender showed no significant effect of MPOD [hazard ratio (HR) 0.37; 95% confidence interval (CI) 0.04, 3.57] and MOD (HR 0.56; 95% CI 0.09, 3.60) on early iAMD. Additional adjustment for smoking did not change these associations. Conclusions This unique but quantitatively limited material leads to the conclusion that no major protective effect of MPOD or MOD was seen on early iAMD. The authors have no financial interest in this study. The authors have full control of all primary data, and they agree to allow Graefe’s Archive for Clinical and Experimental Ophthalmology to review their data upon request.     

泰和乌骨鸡黑色素及其Cu2+、Fe3+配合物的红外光谱研究

目的:考察从泰和乌骨鸡分离提取的黑色素非均匀体系中乌鸡黑色素与Cu2 和Fe3 在不同pH值条件下的相互作用。方法:黑色素及其Cu2 和Fe3 配合物与KBr压片用红外光谱测定。结果:图谱解析表明Cu2 和Fe3 与2个黑色素大分子中的2个羰基以及羟基键合。结论:通常条件下,黑色素中的羰基能与金属离子相互作用,乌骨鸡的黑色素是真黑色素和异黑色素的混合物。     

Dual T1 and T2 weighted magnetic resonance imaging based on Gd3+ loaded bioinspired melanin dots

In this report, a novel T₁/T₂ dual modal nanoprobe based on highly efficient and bioinspired melanin dots (M-dots) with directly loading gadolinium (Gd-M-dots) for magnetic resonance imaging (MRI) is described. In vitro and in vivo investigations have revealed that Gd-M-dots showed nontoxicity and good biocompatibilitity. Gd-M-dots relaxivity values on 3 T were determined to be r₁?=?23.4 and r₂?=?123.3 mM^?1 s^?1, which were much higher than both Gd-DTPA (r₁?=?5.1, r₂?=?6.2 mM^?1 s^?1) and Fe-M-dots (r₁?=?1.2, r₂?=?2.1 mM^?1 s^?1). For in vivo MRI, after injection of Gd-M-dots, simultaneous T₁ and T₂ contrast enhancement have been observed in the MRI of mice abdomen and mice bearing U87MG tumors. Furthermore, all the veins showed high signal intensity on T₁-weighted MRI and remained for 2 h. Overall, in vitro and in vivo studies indicate that Gd-M-dot with high r₁ relaxivity and r₂ relaxivity has high potential to be a promising nanoprobe for MR venography and molecular imaging.