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Melanin Content (melanin + content)

Distribution by Scientific Domains

Medical Sciences	52%
Life Sciences	47%

Selected Abstracts

Temperature Effects on Survival and DNA Repair in Four Freshwater Cladoceran Daphnia Species Exposed to UV Radiation

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2009
Sandra J. Connelly
The biological responses of four freshwater daphniid species, Daphnia middendorffiana, D. pulicaria, D. pulex and D. parvula, to a single acute dose of ultraviolet B radiation (UVB) were compared. In addition to survival, we compared the induction of DNA damage (i.e. cyclobutane pyrimidine dimers) between species as well as the ability to repair this damage in the presence or absence of photoreactivating light. All four species showed high levels of shielding against DNA damage when compared to damage induced in purified DNA dosimeters at the same time and dose. Significant variation in survival was observed between species depending on temperature and light conditions. Contrary to our expectations, all species showed significantly higher survival and light-dependent DNA damage removal rates at 10°C compared to 20°C, suggesting that the enhanced rate of photoenzymatic repair (PER) at the lower temperature contributed significantly to the recovery of these organisms from UVB. PER was highly effective in promoting survival of three of the four species at 10°C, but at 20°C it was only partially effective in two species, and ineffective in two others. None of the species showed significant dark repair at 20°C and only D. pulicaria showed a significant capacity at 10°C. Two species, D. middendorffiana and D. pulex, showed some short-term survival at 10°C in absence of PER despite their inability to repair any appreciable amount of DNA damage in the dark. All species died rapidly at 20°C in absence of PER, as predicted from complete or near-absence of nucleotide excision repair (NER). Overall, the protective effects of tissue structure and pigmentation were similar in all Daphnia species tested and greatly mitigated the absorption of UVB by DNA and its damaging effects. Surprisingly, the visibly melanotic D. middendorffiana was not better shielded from DNA damage than the three non-melanotic species, and in fact suffered the highest damage rates. Melanin content in this species was not temperature dependent under the experimental growth conditions, and so did not contribute to temperature-dependent responses. It is evident that different species within the same genus have developed diverse biological responses to UVB. Our data strongly suggest that DNA damage is lethal to Daphnia and that photoenzymatic repair is the primary mechanism for removing these lesions. In the absence of light, few species are capable of removing any DNA damage. Surprisingly, the single species in which significant excision repair was detected did so only at reduced temperature. This temperature-dependence of excision repair is striking and may reflect adaptations of certain organisms to stress in a complex and changing environment. [source]

Recurrence of kernicterus in term and near-term infants in Denmark

ACTA PAEDIATRICA, Issue 10 2000
F Ebbesen
Classical acute bilirubin encephalopathy (kernicterus) in term and near-term infants had not been seen in Denmark for at least 20 y until 1994. From 1994 to 1998, however, six cases were diagnosed. Aetiology of the hyperbilirubinaemia was known in two infants; spherocytosis and galactosaemia, most likely known in two infants; possible A-O blood type immunization, and unknown in two infants. However, one of these last-mentioned infants had a gestational age of only 36 wk. The maximum plasma total bilirubin concentrations were 531,745 ,mol/L. The increase in the number of cases of kernicterus was considered to have been caused by: (i) a decreased awareness of the pathological signs, (ii) a change in the assessment of the risk of bilirubin encephalopathy, (iii) early discharge of the infants from the maternity ward, (iv) so-called breastfeeding-associated jaundice, (v) demonstration of bilirubin being an antioxidant, and (vi) difficulty in estimating the degree of jaundice in certain groups of immigrants. Accordingly, for prevention: (a) Attempt to change the healthcare workers' understanding of the risk of bilirubin encephalopathy, (b) give further instructions, both orally and in writing, to mothers before discharge from the maternity ward, (c) be more liberal in giving infant formula supplements, (d) conduct home visits by the community nurse at an earlier stage, (e) follow authorized guidelines for phototherapy and exchange transfusion, (f) lower plasma bilirubin concentration limits as an indication for phototherapy and exchange transfusion, (g) screen all term and near-term infants, and (h) measure the skin's yellow colour with a device that corrects for the skin's melanin content. Conclusions: Audit of the six cases presented indicates that measures are necessary in both the primary and secondary healthcare sectors if the risk of kernicterus is to be avoided. Screening may be considered, but in order to identify the problems it would first be reasonable to perform a larger prospective study in which audit is performed on all newborn infants, born at term and near-term, who develop a plasma bilirubin concentration above the exchange transfusion limit. [source]

Histologic and Ultrastructural Analysis of Ultraviolet B Laser and Light Source Treatment of Leukoderma in Striae Distensae

DERMATOLOGIC SURGERY, Issue 4 2005
David J. Goldberg MD
Background. Lasers and light sources emitting ultraviolet B (UVB) irradiation have been shown to repigment striae distensae. Objective. The purpose of this study was to analyze the histologic and ultrastuctural changes seen after UVB laser, or light source,induced repigmentation of striae distensae. Methods. Ten subjects with hypopigmented striae were selected. Five subjects were treated with an XeCl excimer UVB laser, and five subjects were treated with a UVB light device. Six months after the final treatment, the biopsies were evaluated for both standard and electron microscopic changes in melanocytes. Results. Analyses of biopsied skin after treatment with both the UVB laser and light source showed increased melanin content, hypertrophy of melanocytes, and an increase in the number of melanocytes in all patients. Conclusions. Repigmentation of striae distensae with either a UVB laser or light source is due to an increase in melanin pigment, hypertrophy of melanocytes, and an increase in melanocytes. DAVID J. GOLDBERG, MD, ELLEN S. MARMUR, MD, CHRYSALINE SCHMULTS, MD, MUSSARRAT HUSSAIN, MD, AND ROBERT PHELPS, MD, HAVE INDICATED NO SIGNIFICANT INTEREST WITH COMMERCIAL SUPPORTERS. [source]

Antimelanogenesis effect of Tunisian herb Thymelaea hirsuta extract on B16 murine melanoma cells

EXPERIMENTAL DERMATOLOGY, Issue 12 2007
Mitsuko Kawano
Abstract:, Skin pigmentation is the result of melanogenesis that occurs in melanocytes and/or melanoma cells. Although melanogenesis is necessary for the prevention of DNA damage and cancer caused by UV irradiation, excessive accumulation of melanin can also cause melanoma. Thus, we focused on the antimelanogenesis effect of an extract from Thymelaea hirsuta, a Tunisian herb. Murine melanoma B16 cells were treated with T. hirsuta extract, and then cell viability and synthesized melanin content were measured. We found that the T. hirsuta extract decreased the synthesized melanin content in B16 cells without cytotoxicity. Tyrosinase is a key enzyme of melanogenesis and extracellular signal-regulated kinase (ERK)-1/2 phosphorylation is known to be related to melanogenesis inhibition. To clarify its mechanism, we also determined ERK1/2 phosphorylation and tyrosinase expression level. ERK1/2 was immediately phosphorylated in cells just after treatment with the extract. The tyrosinase expression was inhibited after 24 h of stimulation with the extract. The T. hirsuta extract was fractionated, and we found that one fraction considerably decreased the melanin synthesis in B16 cells and that this fraction contains daphnanes as the main component. This indicates that our findings might be attributable to daphnanes. [source]

Linear and whorled nevoid hypermelanosis associated with developmental delay and generalized convulsions

INTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 2 2004
Ahmad A. Alrobaee MD
A 2-year-old Saudi boy was seen in our dermatology clinic with symmetrical, brown, linear macules over the legs, trunk, and arms (Figs 1,3). He was a product of a full-term vaginal delivery following an uneventful first pregnancy in a 22-year-old mother. The birth weight was 2.3 kg. The hyperpigmented macules followed the lines of Blaschko and were noticed a few months after birth; they had enlarged with body growth until the age of 18 months. There was no family history of a similar condition and the boy's parents were unrelated. No blistering or inflammatory changes preceded the hyperpigmentation. The palms, soles, nails, scalp, mucous membranes, and teeth were normal. In addition to the hyperpigmented macules, the patient started to have generalized convulsions at the age of 2 months. Figure 1. Linear hyperpigmented macules following the lines of Blaschko Figure 2. Close up view of the hyperpigmented macules Figure 3. Trunk: Hyperpigmented macules in whorled distribution Physical examination revealed delayed developmental milestones, microphthalmia, depressed nose, and high arched palate with no other abnormalities. Blood tests were normal. Magnetic resonance imaging of the brain showed changes suggestive of a demyelinating process at the parieto-occipital white matter. Echocardiography revealed an atrial septal defect. Electroretinography (ERG), visual evoked potentials (VEP), and auditory evoked potentials (AEP) were normal. Electroencephalogram (EEG) showed multifocal epileptic discharge in the posterior region. A punch skin biopsy taken from the hyperpigmented lesions showed an increase in the melanin content of the basal layer with no incontinence of pigment or melanophages in the dermis. [source]

Acral lentiginous melanoma: an immunohistochemical study of 20 cases

INTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 2 2003
You Chan Kim MD
Background Though acral lentiginous melanoma (ALM) is a major type of malignant melanoma, no immunohistochemical study on this type of melanoma has been reported. Objective The purpose of this study is to analysis the immunohistochemical findings of ALM using routinely used immune markers. Methods An immunohistochemical study was performed on paraffin sections of 20 ALMs using S-100 protein, HMB-45, MART-1, vimentin, epithelial membrane antigen (EMA) and CAM 5.2. Results S-100 protein (95%) was found to be a more sensitive marker than either HMB-45 (80%) or MART-1 (70%) for recognizing ALM. Melanin bleaching was useful for recognizing heavily pigmented ALM using both S-100 protein and HMB-45. The intensity of HMB-45 correlated well with the melanin content. However, there was no significant correlation between the intensity of S-100 protein and the melanin content. One and two out of 20 cases stained focally with EMA and CAM5.2, respectively, but these cases stained also with HMB-45 and/or S-100 protein. Conclusions S-100 protein and HMB-45 were relatively sensitive markers for recognizing ALM. Despite the occasional positivity for the epithelial markers in ALM, all epithelial marker-positive cases stained also with HMB-45 and/or S-100 protein. Therefore, we recommend that the panel of antibodies used for recognizing ALM should contain at least S-100 protein and HMB-45. [source]

Application of computerized image analysis in pigmentary skin diseases

INTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 1 2001
Eun-So Lee MD
Background Melanocyte number and the amount of melanin pigment are related to diagnosis and treatment of pigmentary skin diseases. Various histologic methods are used, such as Fontana-Masson stain for melanin pigment or immunohistochemical stain for melanocytes. Recently, computerized image analysis has been applied to many fields to avoid interobserver bias. In this study, we applied a computerized image analysis to assess the melanin content and melanocyte density of human epidermis. Methods We evaluated the skin biopsy specimens (paraffin blocks) from normal human skin (33 ± 6.6, n = 11) and diseased skins; vitiligo (32 ± 10.0, n = 8), melasma (35 ± 8.6, n = 11), and lentigo senilis (40 ± 7.2, n = 11) (mean age ± SD). Each specimen was stained with Fontana,Masson for melanin pigments and immunohistochemical method for melanocytes. Quantitative analysis of melanin pigment and melanocyte number (density) were investigated through two methods: (1) two dermatologists measured the visual scales; and (2) computerized image analysis was used to measure melanin content indices (MCI). The data were evaluated using one-way anova. Results The visual scale of the Fontana,Masson stain was the highest for lentigo senilis (3.8 ± 0.40), followed by melasma (2.6 ± 0.67), normal skin (1.8 ± 0.60) and vitiligo (0) (P < 0.05). These findings were consistent with objective measurements made by computerized image analysis. MCI values were 120.3 ± 20.74 for lentigo senilis, 81.1 ± 19.27 for melasma, 45.5 ± 16.92 for normal skin, and 0.3 ± 0.30 for vitiligo in decreasing order (P < 0.05). MC/1E (melanocyte number per 1 mm epidermis) was about two fold larger in lentigo senilis (18.1 ± 8.92) than melasma (9.7 ± 2.40) or normal skin (9.3 ± 2.67) (P < 0.05). MC/1B (melanocyte number per 1 mm basal layer) was about 1.5 fold higher in lentigo senilis (13.5 ± 4.17), compared to normal skin (9.0 ± 3.55) (P < 0.05). Melasma showed increased melanocyte numbers compared to normal skin, but it was not statistically significant (P > 0.05). Conclusion We believe this computerized image analysis could be useful tool for diagnosis and comparison of interval changes in pigmentary diseases like melasma or lentigo senilis by quantifying melanin pigments or melanocytes in skin biopsy specimens. [source]

Standardization of In Vitro Macrophotography for Assessment of Cutaneous Responses

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009
Sergio G. Coelho
The increased popularity of commercially available three-dimensional human skin equivalents in recent years has allowed for assessment of melanogenesis modulated by compounds topically applied to the skin or directly incorporated from the medium. These skin equivalents provide a suitable model for elucidating the mechanisms of action of various factors that modulate skin pigmentation or other properties of the skin. As such, researchers need to objectively quantify cutaneous responses at the macroscopic level. A simple method to standardize macrophotography images is reported that can quantify cutaneous responses in human skin equivalents of Asian, Black or African American, and Caucasian or White racial/ethnic origin. Macrophotographs are analyzed using the Commission Internationale de l'Eclairage L*a*b* color space system in combination with a personal computer and image editing software. Pigmentation changes monitored over a 9 day period showed a high correlation with melanin content evaluated in Fontana,Masson-stained sections. These results indicate the feasibility of using a macrophotography setup in a sterile tissue culture environment to objectively assess in vitro cutaneous responses in human skin equivalents. This serves as an adjunct tool to biochemical and morphological methods to effectively quantify changes in pigmentation over time. [source]

DNA Damage, Apoptosis and Langerhans Cells,Activators of UV-induced Immune Tolerance,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2008
Laura Timares
Solar UVR is highly mutagenic but is only partially absorbed by the outer stratum corneum of the epidermis. UVR can penetrate into the deeper layers of the epidermis, depending on melanin content, where it induces DNA damage and apoptosis in epidermal cells, including those in the germinative basal layer. The cellular decision to initiate either cellular repair or undergo apoptosis has evolved to balance the acute need to maintain skin barrier function with the long-term risk of retaining precancerous cells. Langerhans cells (LCs) are positioned suprabasally, where they may sense UV damage directly, or indirectly through recognition of apoptotic vesicles and soluble mediators derived from surrounding keratinocytes. Apoptotic vesicles will contain UV-induced altered proteins that may be presented to the immune system as foreign. The observation that UVR induces immune tolerance to skin-associated antigens suggests that this photodamage response has evolved to preserve the skin barrier by protecting it from autoimmune attack. LC involvement in this process is not clear and controversial. We will highlight some basic concepts of photobiology and review recent advances pertaining to UV-induced DNA damage, apoptosis regulation, novel immunomodulatory mechanisms and the role of LCs in generating antigen-specific regulatory T cells. [source]

Melanin Offers Protection Against Induction of Cyclobutane Pyrimidine Dimers and 6,4 Photoproducts by UVB in Cultured Human Melanocytes,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2001
Nico P. M. Smit
ABSTRACT The goal of this investigation was to correlate the melanin content in human pigmentary cells with the generation of UVB-induced photoproducts and to examine the relationship between the melanin content and the removal of the photoproducts. Cultured melanocytes from light-skinned individuals synthesized less melanin and produced more cyclobutane pyrimidine dimers and 6,4 photoproducts upon UVB exposure than did melanocytes from black skin. Tyrosine-stimulated melanogenesis provided protection against DNA damage in both cell types. In another set of pigmented cell lines a ratio between eumelanin and pheomelanin was determined. The assessment of association between DNA damage induction and the quantity and quality of melanin revealed that eumelanin concentration correlated better with DNA protection than pheomelanin. Skin type,I and skin type,VI melanocytes, congenital nevus (CN)-derived cells and skin type,II melanocytes from a multiple-melanoma patient were grown in media with low or high l -tyrosine concentration. The cells were irradiated with 200 J/m2 UVB, and the levels of the photoproducts were determined immediately and after 6 and 24 h. Once again the induction of the photoproducts was mitigated by increased melanogenesis, and it was inversely correlated with the skin type. No significant differences were found for the removal of photoproducts in the cultures of skin types I and VI and CN cells. No indications of a delay in the removal of photoproducts in the melanocytes from the multiple-melanoma patient were found either. [source]

Inhibitory effects of Hoelen extract on melanogenesis in B16/F1 melanoma cells

PHYTOTHERAPY RESEARCH, Issue 9 2010
Mun Seog Chang
Abstract Melanin synthesis is regulated by melanogenic proteins, such as tyrosinase, tyrosinase-related protein 1 (TRP-1) and TRP-2. The effects of Hoelen extract on melanogenesis were investigated in B16Fl murine melanoma cells. Specifically, tyrosinase activity, cell viability and melanin content were assayed, and western blotting and RT-PCR for tyrosinase, TRP-1 and TRP-2 conducted. The results show that Hoelen significantly inhibited melanin synthesis through inhibition of TRP-2 expression, while it did not affect tyrosinase activity or its expression. Taken together, RT-PCR results showed that the depigmentation effect of Hoelen may be due to inhibition of TRP-2 gene transcription. These results suggest that Hoelen may be a useful inhibitor for the attenuation of melanogenesis and hyperpigmentation in skin cells. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Correlation between melanogenic and catalase activity in in vitro human melanocytes: a synergic strategy against oxidative stress

PIGMENT CELL & MELANOMA RESEARCH, Issue 2 2008
Vittoria Maresca
Summary UV-induced DNA damage can lead to melanoma, the most dangerous form of skin cancer. Understanding the mechanisms employed by melanocytes to protect against UV is therefore a key issue. In melanocytes, catalase is the main enzyme responsible for degrading hydrogen peroxide and we have previously shown that that low basal levels of catalase activity are associated with the light phototype in in vitro and ex vivo models. Here we investigate the possible correlation between its activity and melanogenesis in primary cultures of human melanocytes. We show that while the total melanin concentration is directly correlated to the level of pigmentation, the more the degree of pigmentation increased, the lower the proportion of pheomelanin present. Moreover, in human melanocytes in vitro, catalase-specific mRNA, protein and enzymatic activity were all directly correlated with total cellular melanin content. We also observed that immediately after a peroxidative treatment, the increase in reactive oxygen species was inversely associated with pigmentation level. Darkly pigmented melanocytes therefore possess two protective strategies represented by melanins and catalase activity that are likely to act synergistically to counteract the deleterious effects of UV radiation. By contrast, lightly pigmented melanocytes possess lower levels of melanogenic and catalase activity and are therefore more susceptible to accumulate damage after UV exposition. [source]

Quercetin Enhances Melanogenesis By Increasing the Activity and Synthesis of Tyrosinase in Human Melanoma Cells and in Normal Human Melanocytes

PIGMENT CELL & MELANOMA RESEARCH, Issue 1 2004
Hidetaka Nagata
Quercetin (3,3,,4,,5,7-pentahydroxyflavone) is a diphenyl propanoid widely distributed in edible plants. In this study, we examined the effect of quercetin on melanogenesis in human HMVII melanoma cells and in normal human epidermal melanocytes (NHEM) in the absence of ultraviolet radiation. Upon the addition of quercetin to the culture medium, the melanin content in melanoma cells (HMVII) increased remarkably in time- and dose-dependent manners. In addition, quercetin induced melanogenesis in cultured NHEM. As compared with controls, melanin content was increased about sevenfold by treatment with 20 ,M (HMVII) or 1 ,M (NHEM) quercetin for 7 d. Tyrosinase activity was also increased, to 61.8-fold higher than the control. The expression of tyrosinase protein was slightly increased by the addition of quercetin. However, quercetin did not affect the expression of tyrosinase mRNA. Tyrosinase activation by quercetin was blocked by actinomycin-D or by cycloheximide demonstrating that its actions in stimulating melanogenesis may involve both transcriptional and translational events. Tyrosinase activity was increased dramatically whereas the level of melanogenic inhibitor was remarkably decreased following quercetin treatment. Taken together, these results demonstrate that in human melanoma cells and in NHEM, quercetin stimulates melanogenesis by increasing tyrosinase activity and decreasing other factors such as melanogenic inhibitors. [source]

Plumage colour mutations and melanins in the feathers of the Japanese quail: a first comparison

ANIMAL GENETICS, Issue 6 2009
F. Minvielle
Summary The absorbance of melanin content from dorsal feathers was compared between wild-type Japanese quail and nine other quail plumage colours determined by single mutations in one of seven genes: extended brown (MC1R), yellow (ASIP), silver (MITF), lavender (MLPH), roux (TYRP1), imperfect albinism (SLC45A2) and rusty. As compared with wild-type quail, all mutations but extended brown decreased total melanins. The largest decrease was observed in quail with one of the dilution mutations at TYRP1, MLPH or SLCA45A2. No difference in eumelanins was found between the 10 plumage colours. Despite visible colour differences, homozygous and heterozygous mutants at MITF, or the two imperfect albino (white) and cinnamon (pale yellow) alleles at SLC45A2, could not be differentiated on the basis of melanins. In contrast, the two white phenotypes caused by mutations at MITF and SLC45A2, or the two reddish plumage colours caused by the roux and rusty non-allelic mutations had different total melanin contents. The results showed that rusty was not likely to be a dilution mutation. [source]

The patterns of melanosome distribution in keratinocytes of human skin as one determining factor of skin colour

BRITISH JOURNAL OF DERMATOLOGY, Issue 3 2003
H.-Y. Thong
Summary Background One determining factor of skin colour is the distribution pattern of melanosomes within keratinocytes. Melanosomes in keratinocytes of light skin as in Caucasians are distributed as membrane-bound clusters, whereas the melanosomes in keratinocytes of dark skin as in African/American individuals tend to be larger and distributed individually. It has been shown that melanin content, melanin composition and the size of melanosomes in the human epidermis vary considerably with both ethnicity and chronic sun exposure. Objectives To assess quantitatively the distribution pattern of melanosomes that have been transferred to keratinocytes in the photoprotected (volar forearm) skin from normal Asian individuals and to compare these data with those from light-skinned Caucasian and dark-skinned African/American individuals. Methods Electron microscopy was used. Results We have demonstrated that melanosomes within keratinocytes of Asian skin are distributed as a combination of individual and clustered melanosomes with a proportion of 62·6% vs. 37·4%, respectively. This contrasts with dark and light skin keratinocytes where melanosomes are predominantly individual (88·9%) and clustered (84·5%), respectively. Analysis of mean ± SD melanosome size also revealed a progressive variation in size with ethnicity, melanosomes in dark skin being the largest (1·44 ± 0·67 ,m2 × 10,2) followed in turn by those in Asian skin (1·36 ± 0·15 ,m2 × 10,2) and Caucasian skin (0·94 ± 0·48 ,m2 × 10,2). In addition, it was shown that the melanosomes that are individually distributed tend to have a larger size than the clustered melanosomes. Conclusions The present data indicate that there may be a size gradient of melanosomes encompassing the global complexion coloration and that the melanosome distribution in keratinocytes of Asian skin is intermediate between that in light Caucasian and dark African/American skin. [source]