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1
Youngchim, Sirida, Roderick J. Hay i Andrew J. Hamilton. "Melanization of Penicillium marneffei in vitro and in vivo". Microbiology 151, nr 1 (1.01.2005): 291–99. http://dx.doi.org/10.1099/mic.0.27433-0.
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Melanins are found universally in nature and are implicated in the pathogenesis of several important human fungal pathogens. This study investigated whether the conidia and the yeast cells of the thermally dimorphic fungal pathogen Penicillium marneffei produce melanin or melanin-like compounds in vitro and during infection. Treatment of conidia with proteolytic enzymes, denaturant and concentrated hot acid yielded dark particles that were similar in size and shape to the conidia. A melanin-binding monoclonal antibody (mAb) labelled pigmented conidia, yeast cells and the isolated particles as determined by immunofluorescence microscopy. Electron spin resonance spectroscopy revealed that particles derived from pigmented conidia contained a stable free radical compound, consistent with their identification as melanins. Skin tissue from penicilliosis marneffei patients contained yeast cells that were labelled by melanin-binding mAb. Additionally, sera from P. marneffei-infected mice developed a significant antibody response (both IgG and IgM) against melanin. Phenoloxidase activity capable of synthesizing melanin from l-DOPA was detected in cytoplasmic yeast cell extracts. These findings indicate that P. marneffei conidia and yeast cells can produce melanin or melanin-like compounds in vitro and that the yeast cells can synthesize pigment in vivo. Accordingly this pigment may play some role in the virulence of P. marneffei.
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Mokrzynski, Krystian, Shosuke Ito, Kazumasa Wakamatsu, Theodore G. Camenish, Tadeusz Sarna i Michal Sarna. "Photoreactivity of Hair Melanin from Different Skin Phototypes—Contribution of Melanin Subunits to the Pigments Photoreactive Properties". International Journal of Molecular Sciences 22, nr 9 (24.04.2021): 4465. http://dx.doi.org/10.3390/ijms22094465.
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Photoreactivity of melanin has become a major focus of research due to the postulated involvement of the pigment in UVA-induced melanoma. However, most of the hitherto studies were carried out using synthetic melanin models. Thus, photoreactivity of natural melanins is yet to be systematically analyzed. Here, we examined the photoreactive properties of natural melanins isolated from hair samples obtained from donors of different skin phototypes (I, II, III, and V). X-band and W-band electron paramagnetic resonance (EPR) spectroscopy was used to examine the paramagnetic properties of the pigments. Alkaline hydrogen peroxide degradation and hydroiodic acid hydrolysis were used to determine the chemical composition of the melanins. EPR oximetry and spin trapping were used to examine the oxygen photoconsumption and photo-induced formation of superoxide anion, and time-resolved near infrared phosphorescence was employed to determine the singlet oxygen photogeneration by the melanins. The efficiency of superoxide and singlet oxygen photogeneration was related to the chemical composition of the studied melanins. Melanins from blond and chestnut hair (phototypes II and III) exhibited highest photoreactivity of all examined pigments. Moreover, melanins of these phototypes showed highest quantum efficiency of singlet oxygen photogeneration at 332 nm and 365 nm supporting the postulate of the pigment contribution in UVA-induced melanoma.
3
Nosanchuk, Joshua D., Beatriz L. Gómez, Sirida Youngchim, Soraya Díez, Philip Aisen, Rosely M. Zancopé-Oliveira, Angela Restrepo, Arturo Casadevall i Andrew J. Hamilton. "Histoplasma capsulatum Synthesizes Melanin-Like Pigments In Vitro and during Mammalian Infection". Infection and Immunity 70, nr 9 (wrzesień 2002): 5124–31. http://dx.doi.org/10.1128/iai.70.9.5124-5131.2002.
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ABSTRACT Melanin is made by several important pathogenic fungi and has been implicated in the pathogenesis of a number of fungal infections. This study investigated whether the thermally dimorphic fungal pathogen Histoplasma capsulatum var. capsulatum produced melanin or melanin-like compounds in vitro and during infection. Growth of H. capsulatum mycelia in chemically defined minimal medium produced pigmented conidia. Growth of H. capsulatum yeast in chemically defined minimal medium with l-3,4-dihydroxyphenylalanine (DOPA) or (-)-epinephrine produced pigmented cells. Treatment of the pigmented cells with proteolytic enzymes, denaturant, and hot concentrated acid yielded dark particles that were similar in size and shape to their respective propagules. Melanin-binding monoclonal antibodies (MAb) labeled pigmented conidia, yeast, and the isolated particles as determined by immunofluorescence microscopy. Electron spin resonance spectroscopy revealed that pigmented yeast cells and particles derived from pigmented cells were stable free radicals consistent with their identification as melanins. Tissues from mice infected with H. capsulatum and from biopsy specimens from a patient with histoplasmosis contained fungal cells that were labeled by melanin-binding MAb. Digestion of infected mouse tissues yielded dark particles that reacted with the melanin-binding MAb and were similar in appearance to H. capsulatum yeast cells. Additionally, sera from infected mice contained antibodies that bound melanin particles. Phenoloxidase activity capable of synthesizing melanin from L-DOPA was detected in cytoplasmic yeast cell extracts. These findings indicate that H. capsulatum conidia and yeast can produce melanin or melanin-like compounds in vitro and that yeast cells can synthesize pigment in vivo. Since melanin is an important virulence factor in other pathogenic fungi, this pigment may have a similar role to play in the pathogenesis of histoplasmosis.
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Morris-Jones, Rachael, Sirida Youngchim, Beatriz L. Gomez, Phil Aisen, Roderick J. Hay, Joshua D. Nosanchuk, Arturo Casadevall i Andrew J. Hamilton. "Synthesis of Melanin-Like Pigments by Sporothrix schenckii In Vitro and during Mammalian Infection". Infection and Immunity 71, nr 7 (lipiec 2003): 4026–33. http://dx.doi.org/10.1128/iai.71.7.4026-4033.2003.
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ABSTRACT Melanin has been implicated in the pathogenesis of several important human fungal pathogens. Existing data suggest that the conidia of the dimorphic fungal pathogen Sporothrix schenckii produce melanin or melanin-like compounds; in this study we aimed to confirm this suggestion and to demonstrate in vitro and in vivo production of melanin by yeast cells. S. schenckii grown on Mycosel agar produced visibly pigmented conidia, although yeast cells grown in brain heart infusion and minimal medium broth appeared to be nonpigmented macroscopically. However, treatment of both conidia and yeast cells with proteolytic enzymes, denaturant, and concentrated hot acid yielded dark particles similar in shape and size to the corresponding propagules, which were stable free radicals consistent with identification as melanins. Melanin particles extracted from S. schenckii yeast cells were used to produce a panel of murine monoclonal antibodies (MAbs) which labeled pigmented conidia, yeast cells, and the isolated particles. Tissue from hamster testicles infected with S. schenckii contained fungal cells that were labeled by melanin-binding MAbs, and digestion of infected hamster tissue yielded dark particles that were also reactive. Additionally, sera from humans with sporotrichosis contained antibodies that bound melanin particles. These findings indicate that S. schenckii conidia and yeast cells can produce melanin or melanin-like compounds in vitro and that yeast cells can synthesize pigment in vivo. Since melanin is an important virulence factor in other pathogenic fungi, this pigment may have a similar role in the pathogenesis of sporotrichosis.
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Youngchim, Sirida, Soraya Pornsuwan, Joshua D. Nosanchuk, Wiyada Dankai i Nongnuch Vanittanakom. "Melanogenesis in dermatophyte species in vitro and during infection". Microbiology 157, nr 8 (1.08.2011): 2348–56. http://dx.doi.org/10.1099/mic.0.047928-0.
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Dermatophytes are keratinophilic fungi that are the most common cause of fungal skin infections worldwide. Melanin has been isolated from several important human fungal pathogens, and the polymeric pigment is now recognized as an important virulence determinant. This study investigated whether dermatophytes, including Trichophyton rubrum, Trichophyton mentagrophytes, Epidermophyton floccosum and Microsporum gypseum, produce melanin or melanin-like compounds in vitro and during infection. Digestion of the pigmented microconidia and macroconidia of dermatophytes with proteolytic enzymes, denaturant and hot concentrated acid yielded dark particles that retained the size and shape of the original fungal cells. Electron spin resonance spectroscopy revealed that particles derived from pigmented conidia contained a stable free radical signal, consistent with the pigments being a melanin. Immunofluorescence analysis demonstrated reactivity of a melanin-binding mAb with the pigmented conidia and hyphae, as well as the isolate particles. Laccase, an enzyme involved in melanization, was detected in the dermatophytes by an agar plate assay using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as the substrate. Skin scrapings from patients with dermatophytoses contained septate hyphae and arthrospores that were reactive with the melanin-binding mAb. These findings indicate that dermatophytes can produce melanin or melanin-like compounds in vitro and during infection. Based on what is known about the function of melanin as a virulence factor of other pathogenic fungi, this pigment may have a similar role in the pathogenesis of dermatophytic diseases.
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Solano, F. "Melanins: Skin Pigments and Much More—Types, Structural Models, Biological Functions, and Formation Routes". New Journal of Science 2014 (18.03.2014): 1–28. http://dx.doi.org/10.1155/2014/498276.
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This review presents a general view of all types of melanin in all types of organisms. Melanin is frequently considered just an animal cutaneous pigment and is treated separately from similar fungal or bacterial pigments. Similarities concerning the phenol precursors and common patterns in the formation routes are discussed. All melanins are formed in a first enzymatically-controlled phase, generally a phenolase, and a second phase characterized by an uncontrolled polymerization of the oxidized intermediates. In that second phase, quinones derived from phenol oxidation play a crucial role. Concerning functions, all melanins show a common feature, a protective role, but they are not merely photoprotective pigments against UV sunlight. In pathogenic microorganisms, melanization becomes a virulence factor since melanin protects microbial cells from defense mechanisms in the infected host. In turn, some melanins are formed in tissues where sunlight radiation is not a potential threat. Then, their redox, metal chelating, or free radical scavenging properties are more important than light absorption capacity. These pigments sometimes behave as a double-edged sword, and inhibition of melanogenesis is desirable in different cells. Melanin biochemistry is an active field of research from dermatological, biomedical, cosmetical, and microbiological points of view, as well as fruit technology.
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Pralea, Ioana-Ecaterina, Radu-Cristian Moldovan, Alina-Maria Petrache, Maria Ilieș, Simona-Codruța Hegheș, Irina Ielciu, Raul Nicoară i in. "From Extraction to Advanced Analytical Methods: The Challenges of Melanin Analysis". International Journal of Molecular Sciences 20, nr 16 (13.08.2019): 3943. http://dx.doi.org/10.3390/ijms20163943.
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The generic term “melanin“ describes a black pigment of biological origin, although some melanins can be brown or even yellow. The pigment is characterized as a heterogenic polymer of phenolic or indolic nature, and the classification of eu-, pheo- and allo- melanin is broadly accepted. This classification is based on the chemical composition of the monomer subunit structure of the pigment. Due to the high heterogeneity of melanins, their analytical characterization can be a challenging task. In the present work, we synthesized the current information about the analytical methods which can be applied in melanin analysis workflow, from extraction and purification to high-throughput methods, such as matrix-assisted laser desorption/ionization mass-spectrometry or pyrolysis gas chromatography. Our thorough comparative evaluation of analytical data published so far on melanin analysis has proven to be a difficult task in terms of finding equivalent results, even when the same matrix was used. Moreover, we emphasize the importance of prior knowledge of melanin types and properties in order to select a valid experimental design using analytical methods that are able to deliver reliable results and draw consistent conclusions.
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Łopusiewicz, Łukasz. "Antioxidant, antibacterial properties and the light barrier assessment of raw and purified melanins isolated from Citrullus lanatus (watermelon) seeds". Herba Polonica 64, nr 2 (1.06.2018): 25–36. http://dx.doi.org/10.2478/hepo-2018-0008.
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Summary Introduction: The nutritive value and terapeuthic activity of watermelon seeds is known, but up to day no studies on isolation and characterisation of their melanin were conducted. Objective: The aim of the study was to evaluate the antioxidant, antibacterial and light barrier properties of raw and purified melanins isolated from watermelon seeds. Methods: Native melanin was isolated from seeds by alkaline extraction. Obtained pigment was purified by acid hydrolysis. Chemical tests and FT-IR analysis were conducted to determine the melanin nature of the isolated pigments. UV-Vis, transmittance and colour properties were evaluated spectrophotometrically. Antioxidant activity was determined using ABTS and antibacterial activity through a well diffusion method. Results: The results of the study demonstrated that melanins isolated from watermelon seeds had antioxidant, light barrier and antibacterial properties. A purified form of melanin had higher antioxidant activity and light barrier properties than the raw form. Both melanins inhibited the growth of Enterococcus faecalis and Pseudomonas aeruginosa. Conclusions: Watermelon seeds may be considered as a promising source of natural melanin which possess remarkable therapeutic action that can support the traditional use of this plant in the ethnomedicine.
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Sułkowski, Maciej, Marta Kot, Bogna Badyra, Anna Paluszkiewicz, Przemysław M. Płonka, Michał Sarna, Dominika Michalczyk-Wetula, Fabio A. Zucca, Luigi Zecca i Marcin Majka. "Highly Effective Protocol for Differentiation of Induced Pluripotent Stem Cells (iPS) into Melanin-Producing Cells". International Journal of Molecular Sciences 22, nr 23 (26.11.2021): 12787. http://dx.doi.org/10.3390/ijms222312787.
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Melanin is a black/brown pigment present in abundance in human skin. Its main function is photo-protection of underlying tissues from harmful UV light. Natural sources of isolated human melanin are limited; thus, in vitro cultures of human cells may be a promising source of human melanin. Here, we present an innovative in vitro differentiation protocol of induced pluripotent stem cells (iPS) into melanin-producing cells, delivering highly pigmented cells in quantity and quality incomparably higher than any other methods previously described. Pigmented cells constitute over 90% of a terminally differentiated population and exhibit features characteristic for melanocytes, i.e., expression of specific markers such as MITF-M (microphthalmia-associated transcription factor isoform M), TRP-1 (tyrosinase-related protein 1), and TYR (tyrosinase) and accumulation of black pigment in organelles closely resembling melanosomes. Black pigment is unambiguously identified as melanin with features corresponding to those of melanin produced by typical melanocytes. The advantage of our method is that it does not require any sophisticated procedures and can be conducted in standard laboratory conditions. Moreover, our protocol is highly reproducible and optimized to generate high-purity melanin-producing cells from iPS cells; thus, it can serve as an unlimited source of human melanin for modeling human skin diseases. We speculate that FGF-8 might play an important role during differentiation processes toward pigmented cells.
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Hellinen, Laura, Sina Bahrpeyma, Anna-Kaisa Rimpelä, Marja Hagström, Mika Reinisalo i Arto Urtti. "Microscale Thermophoresis as a Screening Tool to Predict Melanin Binding of Drugs". Pharmaceutics 12, nr 6 (16.06.2020): 554. http://dx.doi.org/10.3390/pharmaceutics12060554.
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Interactions between drugs and melanin pigment may have major impacts on pharmacokinetics. Therefore, melanin binding can modify the efficacy and toxicity of medications in ophthalmic and other disease of pigmented tissues, such as melanoma. As melanin is present in many pigmented tissues in the human body, investigation of pigment binding is relevant in drug discovery and development. Conventionally, melanin binding assays have been performed using an equilibrium binding study followed by chemical analytics, such as LC/MS. This approach is laborious, relatively slow, and limited to facilities with high performance quantitation instrumentation. We present here a screening of melanin binding with label-free microscale thermophoresis (MST) that utilizes the natural autofluorescence of melanin. We determined equilibrium dissociation constants (Kd) of 11 model compounds with melanin nanoparticles. MST categorized the compounds into extreme (chloroquine, penicillin G), high (papaverine, levofloxacin, terazosin), intermediate (timolol, nadolol, quinidine, propranolol), and low melanin binders (atropine, methotrexate, diclofenac) and displayed good correlation with binding parameter values obtained with the conventional binding study and LC/MS analytics. Further, correlation was seen between predicted melanin binding in human retinal pigment epithelium and choroid (RPE-choroid) and Kd values obtained with MST. This method represents a useful and fast approach for classification of compounds regarding melanin binding. Thus, the method can be utilized in various fields, including drug discovery, pharmacokinetics, and toxicology.
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Suryani, Adelia. "Faktor-Faktor yang Memengaruhi Pigmentasi Manusia". Cermin Dunia Kedokteran 47, nr 11 (1.11.2020): 682. http://dx.doi.org/10.55175/cdk.v47i11.1195.
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<p>Warna kulit manusia ditentukan oleh pigmen kulit yakni melanin. Melanin juga memiliki beberapa fungsi penting, yakni berperan pada proses pigmentasi, melindungi kulit dari sinar UV dan perlindungan dari panas.</p><p>Human skin color is determined by the skin pigment melanin. Melanin has several important role: in pigmentation process, UV and heat protection</p>
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Gómez, Beatriz L., Joshua D. Nosanchuk, Soraya Dı́ez, Sirida Youngchim, Philip Aisen, Luz E. Cano, Angela Restrepo, Arturo Casadevall i Andrew J. Hamilton. "Detection of Melanin-Like Pigments in the Dimorphic Fungal Pathogen Paracoccidioides brasiliensis In Vitro and during Infection". Infection and Immunity 69, nr 9 (1.09.2001): 5760–67. http://dx.doi.org/10.1128/iai.69.9.5760-5767.2001.
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ABSTRACT Melanins are implicated in the pathogenesis of several human diseases, including some microbial infections. In this study, we analyzed whether the conidia and the yeasts of the thermally dimorphic fungal pathogen Paracoccidioides brasiliensis produce melanin or melanin-like compounds in vitro and during infection. Growth of P. brasiliensis mycelia on water agar alone produced pigmented conidia, and growth of yeasts in minimal medium withl-3,4-dihydroxyphenylalanine (l-DOPA) produced pigmented cells. Digestion of the pigmented conidia and yeasts with proteolytic enzymes, denaturant, and hot concentrated acid yielded dark particles that were the same size and shape as their propagules. Immunofluorescence analysis demonstrated reactivity of a melanin-binding monoclonal antibody (MAb) with the pigmented conidia, yeasts, and particles. Electron spin resonance spectroscopy identified the yeast-derived particles produced in vitro when P. brasiliensis was grown in l-DOPA medium as a melanin-like compound. Nonreducing polyacrylamide gel electrophoresis of cytoplasmic yeast extract revealed a protein that catalyzed melanin synthesis from l-DOPA. The melanin binding MAb reacted with yeast cells in tissue from mice infected with P. brasiliensis. Finally digestion of infected tissue liberated particles reactive to the melanin binding MAb that had the typical morphology of P. brasiliensis yeasts. These data strongly suggest that P. brasiliensis propagules, both conidia and yeast cells, can produce melanin or melanin-like compounds in vitro and in vivo. Based on what is known about the function of melanin in the virulence of other fungi, this pigment may play a role in the pathogenesis of paracoccidioidomycosis.
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Zhang, Yinqiao, Hu Li, Juan Du, Junzheng Zhang, Jie Shen i Wanzhi Cai. "Three Melanin Pathway Genes, TH, yellow, and aaNAT, Regulate Pigmentation in the Twin-Spotted Assassin Bug, Platymeris biguttatus (Linnaeus)". International Journal of Molecular Sciences 20, nr 11 (3.06.2019): 2728. http://dx.doi.org/10.3390/ijms20112728.
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Pigmentation plays a vital role in insect survival and reproduction. Many melanin pathway genes have been studied in holometabolous insects; however, they have only been studied in two hemimetabolous insect genera, Oncopeltus and Periplaneta. Here we analyzed three melanin pathway genes (TH, yellow, and aaNAT) using RNA interference (RNAi) in another hemimetabolous insect, namely the twin-spotted assassin bug, Platymeris biguttatus. TH was highly expressed in freshly molted nymphs and adults. TH RNAi resulted in a complete loss of black pigment, with yellow coloration maintained. Therefore, black pigment in this assassin bug is solely generated from the melanin pathway, whereas yellow pigment is generated from other unknown pigmentation pathways. yellow and aaNAT were highly expressed in the white spot of the hemelytra. Downregulation of yellow caused a brown phenotype with high mortality, indicating an important role of yellow functions in cuticle formation and in the process of converting melanin from brown to black. Interestingly, aaNAT RNAi caused not only loss of white pigment, but also loss of yellow and red pigments. This phenotype of aaNAT has not been reported in other insects. Our results provide new information for understanding the melanin pathway in which aaNAT is essential for the formation of colorless patterns.
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Panichakul, Tasanee, Teerapat Rodboon, Prasit Suwannalert, Chanchai Tripetch, Rittipun Rungruang, Nattaporn Boohuad i Piyawan Youdee. "Additive Effect of a Combination of Artocarpus lakoocha and Glycyrrhiza glabra Extracts on Tyrosinase Inhibition in Melanoma B16 Cells". Pharmaceuticals 13, nr 10 (14.10.2020): 310. http://dx.doi.org/10.3390/ph13100310.
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Artocarpus lakoocha (Al) and Glycyrrhiza glabra (Gg) extracts have been reported to show tyrosinase inhibitory activity and melanin pigment reduction. This is the first study to assess the combination of Al and Gg extracts in enhancing inhibition of tyrosinase and reduction of melanin pigments. Al and Gg extracted by maceration in 70% and 95% ethanol were analyzed for oxyresveratrol and glabridin using Ultra High Performance Liquid Chromatography. Extracts of Al and Gg singly and combinations of Al95 and Gg95 were tested for cytotoxicity, tyrosinase inhibitory activity, and reduction of melanin pigments in melanoma B16 cells. Al95 had higher antioxidant, tyrosinase inhibitory activity and reduced more melanin pigments in B16 cells compared to Al70, and exhibited higher levels of oxyresveratrol. Gg95 inhibited oxidative stress and mushroom tyrosinase better than Gg70, and exhibited higher levels of glabridin. Combinations of Al95 and Gg95 at various ratios (concentration of 0.1 mg/mL) were not cytotoxic to B16 cells. Interestingly, Al95 and Gg95 combined at a ratio 9:1 reduced melanin pigment up to 53% in B16 cells. This combination of Al95 and Gg95 extracts exhibited the additive effect of reducing melanin pigments by suppressing the expression of microphthalmia-associated transcription factor (MITF), tyrosinase (TYR) and tyrosinase-related protein-2 (TRP-2) in B16 cells. The combination of Al and Gg extracts could be developed as skin care products for hyperpigmentation treatment.
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El-Naggar, Noura El-Ahmady, i WesamEldin I. A. Saber. "Natural Melanin: Current Trends, and Future Approaches, with Especial Reference to Microbial Source". Polymers 14, nr 7 (25.03.2022): 1339. http://dx.doi.org/10.3390/polym14071339.
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Melanin is a universal natural dark polymeric pigment, arising in microorganisms, animals, and plants. There is a couple of pieces of literature on melanin, each focusing on a different issue, the goal of the present review is to focus on microbial melanin. It has numerous benefits with very few drawbacks. The current situation and expected trends are discussed. Intriguing, numerous studies have provoked a serious necessity for a comprehensive assessment of microbial melanin pigments. So that, such review would help scholars from diverse backgrounds to realize the importance of melanin pigments isolated from microorganisms, with this aim in mind, information, and hypothesis from this review could be the paradigm for studies on melanin in the next era.
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Harlisa, Pasid, Sita Mahardika i Suryani Yuliyanti. "The Effect of Corncob (Zea mays) Extract Cream on the Number of Melanin Pigments of Guinea Pig Exposed to Ultraviolet". Berkala Ilmu Kesehatan Kulit dan Kelamin 33, nr 3 (30.11.2021): 194. http://dx.doi.org/10.20473/bikk.v33.3.2021.194-199.
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Background: Exposure to Ultraviolet B (UVB) rays on the skin causesmany problems, including pigmentation and aging effect. Hence, protection against it is needed. Purpose: The study aimedto determine the effect of corncob extract cream on the number of melanin pigments in guinea pig skins exposed to UVB rays. Methods: Anexperimental post-test-only control group study was conducted on the 25 guinea pigs. The guinea pigs were divided randomly into five groups: group I without cream, group II cream base, group III hydroquinone cream, group IV 30% corncob extract cream, and group V 40% corncob extract cream. The cream was given daily for 20 minutes before UVB exposure and 4 hours after UVB exposure. The total dose of UVB exposure was 780 mJ / cm2 for 28 days. The amount of melanin pigment was calculated using the CX21 image J. Result: The number of melanin pigment in groups I, II, III, IV, and V were 22.8±0.4 cells, 18±0.3 cells, 6.3±3.1 cells, 13.8±0.2 cells, and 9.4±0.5 cells, respectively. Asignificantlydifferent value of One way ANOVA test was <0.05. Thus, there was a difference in the number of melanin pigments between the five groups. LSD post-hoc test showed differences in each group (p <0.05). Conclusion: 40% corn cobs extract cream effectively decreased the number of melanin pigment in guinea pigs exposed to UVB rays.
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Chrissian, Christine, Emma Camacho, Man Shun Fu, Rafael Prados-Rosales, Subhasish Chatterjee, Radames J. B. Cordero, Jennifer K. Lodge, Arturo Casadevall i Ruth E. Stark. "Melanin deposition in two Cryptococcus species depends on cell-wall composition and flexibility". Journal of Biological Chemistry 295, nr 7 (2.01.2020): 1815–28. http://dx.doi.org/10.1074/jbc.ra119.011949.
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Cryptococcus neoformans and Cryptococcus gattii are two species complexes in the large fungal genus Cryptococcus and are responsible for potentially lethal disseminated infections. These two complexes share several phenotypic traits, such as production of the protective compound melanin. In C. neoformans, the pigment associates with key cellular constituents that are essential for melanin deposition within the cell wall. Consequently, melanization is modulated by changes in cell-wall composition or ultrastructure. However, whether similar factors influence melanization in C. gattii is unknown. Herein, we used transmission EM, biochemical assays, and solid-state NMR spectroscopy of representative isolates and “leaky melanin” mutant strains from each species complex to examine the compositional and structural factors governing cell-wall pigment deposition in C. neoformans and C. gattii. The principal findings were the following. 1) C. gattii R265 had an exceptionally high chitosan content compared with C. neoformans H99; a rich chitosan composition promoted homogeneous melanin distribution throughout the cell wall but did not increase the propensity of pigment deposition. 2) Strains from both species manifesting the leaky melanin phenotype had reduced chitosan content, which was compensated for by the production of lipids and other nonpolysaccharide constituents that depended on the species or mutation. 3) Changes in the relative rigidity of cell-wall chitin were associated with aberrant pigment retention, implicating cell-wall flexibility as an independent variable in cryptococcal melanin assembly. Overall, our results indicate that cell-wall composition and molecular architecture are critical factors for the anchoring and arrangement of melanin pigments in both C. neoformans and C. gattii species complexes.
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Ferraz, Ana Rita, Rita Pacheco, Pedro D. Vaz, Cristina S. Pintado, Lia Ascensão i Maria Luisa Serralheiro. "Melanin: Production from Cheese Bacteria, Chemical Characterization, and Biological Activities". International Journal of Environmental Research and Public Health 18, nr 20 (9.10.2021): 10562. http://dx.doi.org/10.3390/ijerph182010562.
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Pigments are compounds of importance to several industries, for instance, the food industry, where they can be used as additives, color intensifiers, and antioxidants. As the current trend around the world is shifting to the use of eco-friendly commodities, demand for natural dyes is increasing. Melanins are pigments that are produced by several microorganisms. Pseudomonas putida ESACB 191, isolated from goat cheese rind, was described as a brown pigment producer. This strain produces a brown pigment via the synthetic Müeller-Hinton Broth. This brown compound was extracted, purified, analyzed by FTIR and mass spectrometry, and identified as eumelanin. The maximum productivity was 1.57 mg/L/h. The bioactivity of eumelanin was evaluated as the capacity for scavenging free radicals (antioxidant activity), EC50 74.0 ± 0.2 μg/mL, and as an acetylcholinesterase inhibitor, with IC50 575 ± 4 μg/mL. This bacterial eumelanin did not show cytotoxicity towards A375, HeLa Kyoto, HepG2, or Caco2 cell lines. The effect of melanin on cholesterol absorption and drug interaction was evaluated in order to understand the interaction of melanin present in the cheese rind when ingested by consumers. However, it had no effect either on cholesterol absorption through an intestinal simulated barrier formed by the Caco2 cell line or with the drug ezetimibe.
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Ahmadi, Ali. "The Effect of Various Genetic Diseases and Eye Surgeries on Iris Discoloration". Biomedical Research and Clinical Reviews 7, nr 1 (15.06.2022): 01–02. http://dx.doi.org/10.31579/2692-9406/120.
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The color of human eyes is often the same as the iris of the eye, which itself consists of two parts: the anterior layer of iris stroma and the posterior layer or posterior pigment epithelium. Based on experiments, it is believed that iris color is determined based on four factors: pigment granules in the posterior pigment epithelium, pigment concentration in iris stromal melanocytes, melanin pigments in iris melanocytes, and the scattering and absorption of light from the extracellular matrix properties of the stroma. Becomes. In general, melanocytes in the iris stroma have a greater effect on iris color. These types of cells contain a biopolymeric and inert substance called melanin, which itself has two types: brown-black or Eumelanin and red-yellow or Pheomelanin.
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Al Khatib, Maher, Jessica Costa, Daniele Spinelli, Eliana Capecchi, Raffaele Saladino, Maria Camilla Baratto i Rebecca Pogni. "Homogentisic Acid and Gentisic Acid Biosynthesized Pyomelanin Mimics: Structural Characterization and Antioxidant Activity". International Journal of Molecular Sciences 22, nr 4 (9.02.2021): 1739. http://dx.doi.org/10.3390/ijms22041739.
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Pyomelanin mimics from homogentisic acid (HGA) and gentisic acid (GA) were biosynthesized by the oxidative enzyme T. versicolor laccase at physiological pH to obtain water soluble melanins. The pigments show brown-black color, broad band visible light absorption, a persistent paramagnetism and high antioxidant activity. The EPR approach shows that at least two different radical species are present in both cases, contributing to the paramagnetism of the samples. This achievement can also shed light on the composition of the ochronotic pigment in the Alkaptonuria disease. On the other hand, these soluble pyomelanin mimics, sharing physico-chemical properties with eumelanin, can represent a suitable alternative to replace the insoluble melanin pigment in biotechnological applications.
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Grabolus, Dominika, Patrycja Wacławik i Magdalena Zatoń-Dobrowolska. "Differences in melanin type and content among color variations in American mink (Neovison vison)". Canadian Journal of Animal Science 100, nr 3 (1.09.2020): 418–25. http://dx.doi.org/10.1139/cjas-2019-0196.
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Coat colour is one of the most important qualitative traits of fur animals. Determining melanin pigments forming the basics of visible coat colour may contribute to a better understanding of the process of creating different coat colour variations in fur-bearing animals. This study aimed to (i) isolate pigment cells from the hair of American mink of 11 colour variations (standard brown, silverblue, palomino, black, wild type, sapphire, black cross, pearl, palomino cross, glow, and amber) using acid and alkali; and (ii) characterise the melanin pigments obtained. The purified pigment cells were observed under a light microscope and verified by spectrophotometry scanning and nuclear magnetic resonance spectroscopy. The method allowed for obtaining pure melanin specimens. Using acid and alkali to extract eumelanosomes did not affect their shape and structure; it also allowed for obtaining pheomelanin from the hair. The results have proven that the hair colour of the American mink is based on all types of melanin, and that its variations differ in terms of how much eumelanin and pheomelanin the hair contains.
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M, Dr Leo Caroline, Dr Serena Francis, Dr A. Beeula, Dr R. Sathish Muthukumar, Dr Sreeja C i Dr Nachiammai. "Melanin pigment: A review". International Journal of Applied Dental Sciences 6, nr 4 (1.10.2020): 219–24. http://dx.doi.org/10.22271/oral.2020.v6.i4d.1068.
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Zhou, Mengkai, Ze Li, Yanjie Liu, Ping Zhang, Xiaoran Hao i Xudong Zhu. "Transcription Factors Pmr1 and Pmr2 Cooperatively Regulate Melanin Biosynthesis, Conidia Development and Secondary Metabolism in Pestalotiopsis microspora". Journal of Fungi 8, nr 1 (31.12.2021): 38. http://dx.doi.org/10.3390/jof8010038.
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Melanins are the common fungal pigment, which contribute to stress resistance and pathogenesis. However, few studies have explored the regulation mechanism of its synthesis in filamentous fungi. In this study, we identified two transcription factors, Pmr1 and Pmr2, in the filamentous fungus Pestalotiopsis microspora. Computational and phylogenetic analyses revealed that Pmr1 and Pmr2 were located in the gene cluster for melanin biosynthesis. The targeted deletion mutant strain Δpmr1 displayed defects in biosynthesis of conidia pigment and morphological integrity. The deletion of pmr2 resulted in reduced conidia pigment, but the mycelial morphology had little change. Moreover, Δpmr2 produced decreased conidia. RT-qPCR data revealed that expression levels of genes in the melanin biosynthesis gene cluster were downregulated from the loss of Pmr1 and Pmr2. Interestingly, the yield of secondary metabolites in the mutant strains Δpmr1 and Δpmr2 increased, comparing with the wild type, and additionally, Pmr1 played a larger regulatory role in secondary metabolism. Taken together, our results revealed the crucial roles of the transcription factors Pmr1 and Pmr2 in melanin synthesis, asexual development and secondary metabolism in the filamentous fungus P. microspora.
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Frases, Susana, Angela Salazar, Ekaterina Dadachova i Arturo Casadevall. "Cryptococcus neoformans Can Utilize the Bacterial Melanin Precursor Homogentisic Acid for Fungal Melanogenesis". Applied and Environmental Microbiology 73, nr 2 (10.11.2006): 615–21. http://dx.doi.org/10.1128/aem.01947-06.
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ABSTRACT Cryptococcus neoformans melanizes in the environment and in mammalian tissues, but the process of melanization in either venue is mysterious given that this microbe produces melanin only from exogenous substrates. Understanding the process of melanization is important because melanization is believed to protect against various stresses in the environment, including UV radiation, and pigment production is associated with virulence. Melanization in C. neoformans requires the availability of diphenolic precursors. In contrast, many bacteria synthesize melanin from homogentisic acid (HGA). We report that C. neoformans strains representing all four serotypes can produce a brown pigment from HGA. The brown pigment was acid resistant and had the electron paramagnetic resonance spectrum of a stable free radical, qualities that identified it as a melanin. Melanin “ghost”-like particles obtained from pigmented C. neoformans cells were hydrophobic, fluorescent under a variety of irradiation wavelengths, negatively charged, insoluble in organic solvents and alcohols, resistant to degradation by strong acids, and vulnerable to bleaching. HGA melanization was laccase dependent and repressed by high concentrations of glucose. The ability of C. neoformans to utilize a bacterial melanin precursor compound suggests a new substrate source for melanization in the environment.
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McGraw, Kevin J., Kazumasa Wakamatsu, Shosuke Ito, Paul M. Nolan, Pierre Jouventin, F. Stephen Dobson, Richard E. Austic i in. "You Can't Judge a Pigment by its Color: Carotenoid and Melanin Content of Yellow and Brown Feathers in Swallows, Bluebirds, Penguins, and Domestic Chickens". Condor 106, nr 2 (1.05.2004): 390–95. http://dx.doi.org/10.1093/condor/106.2.390.
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Abstract The two main pigment types in bird feathers are the red, orange, and yellow carotenoids and the black, gray, and brown melanins. Reports conflict, however, regarding the potential for melanins to produce yellow colors or for carotenoids to produce brown plumages. We used high-performance liquid chromatography to analyze carotenoids and melanins present in the yellow and brown feathers of five avian species: Eastern Bluebirds (Sialia sialis), Barn Swallows (Hirundo rustica), King Penguins (Aptenodytes patagonicus), Macaroni Penguins (Eudyptes chrysolophus), and neonatal chickens (Gallus domesticus). In none of these species did we detect carotenoid pigments in feathers. Although carotenoids are reportedly contained in the ventral plumage of European Barn Swallows (Hirundo rustica rustica), we instead found high concentrations of both eumelanins and phaeomelanins in North American Barn Swallows (H. r. erythrogaster). We believe we have detected a new form of plumage pigment that gives penguin and domestic- chick feathers their yellow appearance. No Puedes Juzgar un Pigmento por su Color: Contenido de Carotenoide y Melanina de Plumas Amarillas y Marrones en Golondrinas, Azulejos, Pingüinos y Gallinas Domésticas Resumen. Los dos tipos principales de pigmentos que las aves incorporan en sus plumas son carotenoides, para desarrollar plumajes rojo, naranja o amarillo, y melaninas, para adquirir coloración negra, marrón, gris o tonalidades color tierra. Sin embargo, existe información conflictiva sobre la potencial coloración de plumas amarillas basadas en melanina y la presencia de caroteniodes en el plumaje marrón de ciertas especies. En este estudio, usamos cromatografía líquida de alto rendimiento para analizar los tipos y cantidades de carotenoides y melaninas presentes en las plumas amarillas y marrones de cinco especies de aves: el azulejo Sialia sialis y la golondrina Hirundo rustica, los pingüinos Aptenodytes patagonicus y Eudyptes chrysolophus y el plumón natal amarillo de la gallina doméstica Gallus domesticus. En ninguna de estas especies detectamos pigmentos carotenoides en las plumas. A pesar de que los carotenoides han sido encontrados en el plumaje ventral de la golondrina Hirundo rustica rustica, nosotros en cambio encontramos altas concentraciones de eumelaninas y feomelaninas en H. r. erythrogaster y en azulejos que variaron entre individuos y regiones de plumaje. Creemos que hemos detectado una nueva forma de pigmento de plumaje que le da a las plumas de pingüinos y pollos domésticos su apariencia amarilla.
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Mattoon, Ellie Rose, Radames J. B. Cordero i Arturo Casadevall. "Fungal Melanins and Applications in Healthcare, Bioremediation and Industry". Journal of Fungi 7, nr 6 (18.06.2021): 488. http://dx.doi.org/10.3390/jof7060488.
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Melanin is a complex multifunctional pigment found in all kingdoms of life, including fungi. The complex chemical structure of fungal melanins, yet to be fully elucidated, lends them multiple unique functions ranging from radioprotection and antioxidant activity to heavy metal chelation and organic compound absorption. Given their many biological functions, fungal melanins present many possibilities as natural compounds that could be exploited for human use. This review summarizes the current discourse and attempts to apply fungal melanin to enhance human health, remove pollutants from ecosystems, and streamline industrial processes. While the potential applications of fungal melanins are often discussed in the scientific community, they are successfully executed less often. Some of the challenges in the applications of fungal melanin to technology include the knowledge gap about their detailed structure, difficulties in isolating melanotic fungi, challenges in extracting melanin from isolated species, and the pathogenicity concerns that accompany working with live melanotic fungi. With proper acknowledgment of these challenges, fungal melanin holds great potential for societal benefit in the coming years.
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Cubo, Teresa, Francisco Romero, Jose M. Vinardell i Jose E. Ruiz-Sainz. "Expression of the Rhizobium leguminosarum biovar phaseoli melA Gene in Other Rhizobia Does Not Require the Presence of the nifA Gene". Functional Plant Biology 24, nr 2 (1997): 195. http://dx.doi.org/10.1071/pp96076.
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Many different Rhizobium strains produce melanin (Mel+) when grown on solid media supplemented with L-tyrosine. The composition of the media and the culture conditions are of great importance for pigment production. Previous reports showed that some Rhizobium leguminosarum biovar phaseoli strains that produce the pigment in complete solid media (TY) failed to produce the pigment in minimal media (SY) supplemented with L-tyrosine or in TY liquid media. In this paper we have investigated different R. fredii, R. meliloti, R. etli and R. leguminosarum bv. trifolii and phaseoli strains (all of them Mel+ in solid media) for their ability to produce the pigment in liquid media. All Rhizobium species tested, except Rhizobium etli, were Mel+ in liquid media and in all cases the pigment yielded maximum absorption peaks at 280 and 315 nm. Melanin production by other bacteria (such as Vibrio, Streptomyces or Azospirillum) is enhanced by the presence of amino acids other that tyrosine. In this paper we show that the addition of L-methionine, which is not a precursor of rhizobial melanins, stimulated pigment production by Rhizobium cultures supplemented with L-tyrosine. The role of melanin production by Rhizobium strains is unclear. One hypothesis is that the Rhizobium tyrosinase, a bifunctional copper-containing enzyme that is essential for melanin biosynthesis, could detoxify polyphenolic compounds which might accumulate in senescing nodules. We show here that R. etli and R. fredii bacteroids produced melanin, which supports the idea that bacteroids contain the enzyme tyrosinase. Previous reports showed that, in R. leguminosarum bv. phaseoli strain 8002, the expression of the tyrosinase gene (melA) is dependent on the presence of nifA, a regulatory gene that is located in the symbiotic plasmid. However, transfer of R. leguminosarum bv. phaseoli melA gene to pSym-cured derivatives of R. leguminosarum bv. trifolii and viciae, R. fredii and Rhizobium sp. (Hedysarum) produced Mel+ transconjugants. DNA-hybridisation experiments showed that the pSym-cured strains did not contain any copy of nifA. Therefore, in contrast to the results reported on R. leguminosarum bv. phaseoli strain 8002, the expression of the melA gene in other rhizobia is not nifA-dependent. Key words: Rhizobium, melanin.
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Almeida-Paes, Rodrigo, Susana Frases, Glauber de Sousa Araújo, Manoel Marques Evangelista de Oliveira, Gary J. Gerfen, Joshua D. Nosanchuk i Rosely Maria Zancopé-Oliveira. "Biosynthesis and Functions of a Melanoid Pigment Produced by Species of the Sporothrix Complex in the Presence of l-Tyrosine". Applied and Environmental Microbiology 78, nr 24 (5.10.2012): 8623–30. http://dx.doi.org/10.1128/aem.02414-12.
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ABSTRACTSporothrix schenckiiis the etiological agent of sporotrichosis, the main subcutaneous mycosis in Latin America. Melanin is an important virulence factor ofS. schenckii, which produces dihydroxynaphthalene melanin (DHN-melanin) in conidia and yeast cells. Additionally,l-dihydroxyphenylalanine (l-DOPA) can be used to enhance melanin production on these structures as well as on hyphae. Some fungi are able to synthesize another type of melanoid pigment, called pyomelanin, as a result of tyrosine catabolism. Since there is no information about tyrosine catabolism inSporothrixspp., we cultured 73 strains, including representatives of newly describedSporothrixspecies of medical interest, such asS. brasiliensis,S. schenckii, andS. globosa, in minimal medium with tyrosine. All strains but one were able to produce a melanoid pigment with a negative charge in this culture medium after 9 days of incubation. AnS. schenckiiDHN-melanin mutant strain also produced pigment in the presence of tyrosine. Further analysis showed that pigment production occurs in both the filamentous and yeast phases, and pigment accumulates in supernatants during stationary-phase growth. Notably, sulcotrione inhibits pigment production. Melanin ghosts of wild-type and DHN mutant strains obtained when the fungus was cultured with tyrosine were similar to melanin ghosts yielded in the absence of the precursor, indicating that this melanin does not polymerize on the fungal cell wall. However, pyomelanin-producing fungal cells were more resistant to nitrogen-derived oxidants and to UV light. In conclusion, at least three species of theSporothrixcomplex are able to produce pyomelanin in the presence of tyrosine, and this pigment might be involved in virulence.
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Smith, C. N., i C. D. Lindsay. "Stimulation of C32 and G361 melanoma cells using oleoyl acetyl glycerol and its effect on sulphur mustard cytotoxicity". Human & Experimental Toxicology 20, nr 8 (sierpień 2001): 418–25. http://dx.doi.org/10.1191/096032701682692991.
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Epidermal melanocytes have a higher sensitivity to sulphur mustard (HD) compared with other skin cell types.1 This may be due to the enzymatic production of melanin precursors exerting an additional cytotoxic effect following HD depletion of the cellular protectant, GSH.2,3 Stimulation of the protein kinase C pathway in melanocytes is known to increase melanin production in melanocytes and melanoma cell lines.4,5 In order to investigate the role of pigment synthesis in HD toxicology, cultures of an unpigmented melanoma cell line (C32) and of a pigmented melanoma line (G361) were treated with the potent diacyl glycerol analogue, oleoyl acetyl glycerol (OAG), in order to determine if protein kinase C-mediated increases in pigment production could increase sensitivity to subsequent HD exposure. Stimulation of C32 cells with OAG exerted a significant protective effect against the cytotoxic effects of HD. However, this was not due to increased melanin synthesis because this cell line cannot synthesize melanin pigments. The protective action observed is postulated to be due to modulation of protein kinase C activity. In contrast, stimulation of G361 melanoma cells with OAG resulted in an increased level of cytotoxicity upon subsequent exposure to HD. Protein kinase C controls several cellular pathways including checkpoints in the cell cycle, stalling the cell in G1 and promoting transition through the G2 /M boundary. Given the genotoxic properties of HD, these two points in the cell cycle are important in determining the overall cytotoxic effect of HD. Control of the cell cycle by protein kinase C modulation and manipulation of melanin synthetic pathways may have therapeutic benefits.
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Suthar, Malika, Laurent Dufossé i Sanjay K. Singh. "The Enigmatic World of Fungal Melanin: A Comprehensive Review". Journal of Fungi 9, nr 9 (31.08.2023): 891. http://dx.doi.org/10.3390/jof9090891.
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Synthetic dyes are generally not safe for human health or the environment, leading to the continuous search and growing demand for natural pigments that are considered safer, biodegrade more easily, and are environmentally beneficial. Among micro-organisms, fungi represent an emerging source of pigments due to their many benefits; therefore, they are readily viable on an industrial scale. Among all the bioactive pigments produced by fungi, melanin is an enigmatic, multifunctional pigment that has been studied for more than 150 years. This dark pigment, which is produced via the oxidative polymerization of phenolic compounds, has been investigated for its potential to protect life from all kingdoms, including fungi, from biotic and abiotic stresses. Over time, the research on fungal melanin has attracted a significant amount of scientific interest due to melanin’s distinct biological activities and multifarious functionality, which is well-documented in the literature and could possibly be utilized. This review surveys the literature and summarizes the current discourse, presenting an up-to-date account of the research performed on fungal melanin that encompasses its types, the factors influencing its bioactivity, the optimization of fermentation conditions to enhance its sustainable production, its biosynthetic pathways, and its extraction, as well as biochemical characterization techniques and the potential uses of melanin in a wide range of applications in various industries. A massive scope of work remains to circumvent the obstacles to obtaining melanin from fungi and exploring its future prospects in a diverse range of applications.
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Chan, Alexander Chak Lam, Luen Cheung Ho, William Wai Lun Yip i Fung Ching Cheung. "Pigmented Ependymoma With Lipofuscin and Neuromelanin Production". Archives of Pathology & Laboratory Medicine 127, nr 7 (1.07.2003): 872–75. http://dx.doi.org/10.5858/2003-127-872-pewlan.
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Abstract We report an unusual case of ependymoma with pigmentation, a phenomenon that has only been described in a few cases, to our knowledge. This tumor occurred in the fourth ventricle of a 45-year-old man. It showed the typical histologic appearance of ependymoma with perivascular pseudorosettes and rare ependymal rosettes. Some tumor cells contained brown cytoplasmic pigment, which was shown histochemically to represent a mixture of lipofuscin and neuromelanin. The pigment was positive for acid-fast and periodic acid–Schiff stains and was also focally positive for Masson-Fontana and Schmorl stains (bleached by pretreatment with potassium permanganate). In addition, some other tumor cells showed a signet ring morphology as a result of prominent intracytoplasmic vacuolation. Immunohistochemically, all the tumor cells expressed glial fibrillary acidic protein, and rare pigmented tumor cells also expressed HMB-45. Ultrastructural examination showed irregularly shaped heterogeneous electron-dense bodies corresponding to the pigment, and the cytoplasmic vacuoles were formed by dilatation of intracytoplasmic lumens lined by microvilli. Since lipofuscin production can occur in normal ependymal cells and neuromelanin has been suggested to be a melanized form of lipofuscin, it is not surprising that these 2 pigments can be found in ependymoma. In all the previously reported cases, the pigment was shown to represent melanin only. In our case, the HMB-45 positivity in rare tumor cells indicated that there might also be a minor melanin component in the pigment in addition to lipofuscin and neuromelanin.
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Mednick, Aron J., Joshua D. Nosanchuk i Arturo Casadevall. "Melanization of Cryptococcus neoformans Affects Lung Inflammatory Responses during Cryptococcal Infection". Infection and Immunity 73, nr 4 (kwiecień 2005): 2012–19. http://dx.doi.org/10.1128/iai.73.4.2012-2019.2005.
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ABSTRACT The production of melanin pigments is associated with virulence for many microbes. Melanin is believed to contribute to microbial virulence by protecting microbial cells from oxidative attack during infection. However, there is also evidence from various systems that melanins have immunomodulatory properties, which conceivably could contribute to virulence by altering immune responses. To investigate the effect of melanin on the immune response, we compared the murine pulmonary responses to infection with melanized and nonmelanized Cryptococcus neoformans cells. Infection with melanized cells resulted in a greater fungal burden during the early stages of infection and was associated with higher levels of interleukin-4 and MCP-1 and greater numbers of infiltrating leukocytes. Infection with laccase-positive (melanotic) C. neoformans cells also elicited higher MCP-1 levels and more infiltrating leukocytes than did infection with laccase-negative cells. Melanization interfered with phagocytosis in vivo for encapsulated C. neoformans but not for nonencapsulated cells. The results provide strong evidence that cryptococcal melanization can influence the immune response to infection and suggest that immunomodulation is an additional mechanism by which the pigment contributes to virulence.
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Nganvongpanit, Korakot, Piyatida Kaewkumpai, Varankpicha Kochagul, Kidsadagon Pringproa, Veerasak Punyapornwithaya i Supamit Mekchay. "Distribution of Melanin Pigmentation in 33 Organs of Thai Black-Bone Chickens (Gallus gallus domesticus)". Animals 10, nr 5 (30.04.2020): 777. http://dx.doi.org/10.3390/ani10050777.
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The black-bone chicken (Gallus gallus domesticus) is a breed of chicken that is commonly found in Thailand. This breed is known for having a number of black colored organs. Consumers have been notably attracted to the black-bone chicken breed for the characteristic darkness that is observed in many of its organs. However, the degree of darkness in all organs of the black-bone chicken is still in question. Importantly, there have not yet been any published reports on the distribution of melanin pigment in the organs of the black-bone chicken. This research study aims to examine the distribution of the melanin pigment in 33 organs of the Thai black-bone chicken. Ten black-bone chickens (five male, five female) were included in this study. Thirty-two organs including the brain, spinal cord, sciatic nerve, larynx, trachea, syrinx, lungs, heart, pericardium, aorta, brachial vein, kidney, cloaca, oviduct, testis, gastrocnemius muscle, femur, tongue, esophagus, crop, proventriculus, gizzard, duodenum, jejunum, ileum, cecum, pancreas, liver, gall bladder, omentum, abdominal fat, spleen, and skin were examined in this study. Histological sections taken from tissue samples of each of these organs were studied. The findings revealed that the presence of the melanin pigment was not significantly different (p > 0.005) between male and female specimens. Notably, the liver was the only organ in which the melanin pigment had not accumulated. Consequently, there was not a uniform pattern of melanin pigment accumulation throughout the organs of the chickens. The melanin pigment was present in all of the tissue layers of most organs, while the melanin pigment was found in only specific layers of some of the organs. In conclusion, the distribution of melanin pigmentation in the organs of each of the animals in this study was found to be different. However, in some tissue samples, such as those obtained from the liver, no accumulation of the melanin pigment was observed.
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Glagoleva, A. Y., L. A. Novokreschenov, O. Y. Shoeva, O. N. Kovaleva i E. K. Khlestkina. "Studying grain color diversity in the barley collection of VIR". Proceedings on applied botany, genetics and breeding 183, nr 3 (3.10.2022): 76–84. http://dx.doi.org/10.30901/2227-8834-2022-3-76-84.
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Background. Dark color of barley grain (Hordeum vulgare L.) can be caused by the synthesis and accumulation of two types of polyphenolic pigments – anthocyanins and melanins, which perform important functions in plant life, participating in the regulation of growth and development, and protecting plants from adverse environmental conditions. The aim of this study was to investigate the diversity of barley in the VIR collection in the context of grain color.Materials and methods. To analyze the pigment composition of the grain, 150 barley accessions with colored grains were selected from the VIR collection. Anthocyanins and melanins in grain husk were identified using qualitative reactions.Results and discussion. It was shown that in 60% of the accessions the dark color of their grain was induced by independent accumulation of melanin, while the accessions characterized by accumulation of only anthocyanins, and those with combined accumulation of anthocyanins and melanins, were 14.6% and 14%, respectively. For 11.3% of the accessions the presence of anthocyanins and melanins in grain husk was not found; their pigmentation could presumably be associated with an increased content of other polyphenolic pigments – proanthocyanidins. Accessions with melanin in grain predominated in all identified geographic groups, while other types of pigmentation were most evenly represented in the regions with the widest genetic diversity of barleys – Africa, East Asia, and the Middle East.Conclusion. Dark pigmentation of barley grain was shown to be mainly associated with the accumulation of melanin, and this type of pigmentation prevails in all geographical regions identified. The results obtained made it possible to describe the barley collection more fully and expand the possibilities of its utilization.
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Busolini, Fabricio Ivan, Graciela Beatriz Rodríguez, Verónica Palmira Filippa i Fabian Heber Mohamed. "Pigmented Cells in the Pineal Gland of Female Viscacha (Lagostomus maximus maximus): A Histochemical and Ultrastructural Study". International Journal of Endocrinology 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/7492960.
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The presence of pigment has been demonstrated in different nervous structures such as those of retina, substantia nigra, and locus coeruleus. These pigments have also been described in the pineal gland of different mammal species. Histochemical and ultrastructural studies of the pineal gland of female viscacha (Lagostomus maximus maximus) were performed to analyze the presence of pigmented cells under natural conditions and to evaluate a probable relation between pigment content and glandular activity during pregnancy. The following techniques were applied: hematoxylin-eosin, phosphotungstic acid-hematoxylin, Masson-Fontana silver, DOPA histochemistry, Schmorl’s reaction and toluidine blue. Estradiol and progesterone serum levels were determined by RIA. The ultrastructural features of the pineal pigment granules were also analyzed. Pigment granules were observed in a random distribution, but the pigmented cells were frequently found near blood vessels. The pineal pigment was histochemically identified as melanin. Differences in the amount of pigmented cells were found between pregnant and nonpregnant viscachas. The ultrastructural analysis revealed the presence of premelanosomes and melanosomes. Estradiol and progesterone levels vary during pregnancy. In conclusion, the changes in the amount of pigment content and hormone levels may indicate that the pineal gland of female viscacha is susceptible to endocrine variations during pregnancy.
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Carney, Bonnie C., Taryn E. Travis, Lauren T. Moffatt, Laura S. Johnson, Melissa M. McLawhorn, Cynthia M. Simbulan-Rosenthal, Dean S. Rosenthal i Jeffrey W. Shupp. "Hypopigmented burn hypertrophic scar contains melanocytes that can be signaled to re-pigment by synthetic alpha-melanocyte stimulating hormone in vitro". PLOS ONE 16, nr 3 (25.03.2021): e0248985. http://dx.doi.org/10.1371/journal.pone.0248985.
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There are limited treatments for dyschromia in burn hypertrophic scars (HTSs). Initial work in Duroc pig models showed that regions of scar that are light or dark have equal numbers of melanocytes. This study aims to confirm melanocyte presence in regions of hypo- and hyper-pigmentation in an animal model and patient samples. In a Duroc pig model, melanocyte presence was confirmed usingen facestaining. Patients with dyschromic HTSs had demographic, injury details, and melanin indices collected. Punch biopsies were taken of regions of hyper-, hypo-, or normally pigmented scar and skin. Biopsies were processed to obtain epidermal sheets (ESs). A subset of ESs wereen facestained with melanocyte marker, S100β. Melanocytes were isolated from a different subset. Melanocytes were treated with NDP α-MSH, a pigmentation stimulator. mRNA was isolated from cells, and was used to evaluate gene expression of melanin-synthetic genes. In patient and pig scars, regions of hyper-, hypo-, and normal pigmentation had significantly different melanin indices. S100βen facestaining showed that regions of hyper- and hypo-pigmentation contained the same number of melanocytes, but these cells had different dendricity/activity. Treatment of hypo-pigmented melanocytes with NDP α-MSH produced melanin by microscopy. Melanin-synthetic genes were upregulated in treated cells over controls. While traditionally it may be thought that hypopigmented regions of burn HTS display this phenotype because of the absence of pigment-producing cells, these data show that inactive melanocytes are present in these scar regions. By treating with a pigment stimulator, cells can be induced to re-pigment.
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Kurkiewicz, Sławomir, Anna Dzierżęga-Lęcznar, Agata Stanek-Widera i Dariusz Lange. "Development of a method for isolation of melanin from archival FFPE tissues of human melanoma for structural studies by pyrolysis-gas chromatography-tandem mass spectrometry". Postępy Higieny i Medycyny Doświadczalnej 76, nr 1 (1.01.2022): 122–27. http://dx.doi.org/10.2478/ahem-2022-0006.
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Abstract Introduction There is some evidence that pheomelanin produced in skin melanocytes may be involved in the development of cutaneous melanoma, particularly in individuals with a light skin/red hair phenotype. However, nothing is known about possible correlation between the type and/or clinical stage of melanoma and the content of pheomelanin in the tumor tissue. We believe that archival formalin-fixed and paraffin-embedded (FFPE) melanoma tissues could be a good source of melanin pigment for future large-scale research on that issue. Aim The aim of this work was to develop a method for isolation and purification of melanin from FFPE samples of human melanoma. To test the suitability of the isolation protocol for planned structural studies, the obtained melanin was analyzed for pheomelanin content by the method based on pyrolysis (Py) coupled with gas chromatography and tandem mass spectrometry (GC/MS/MS). Material and methods For melanin isolation, microtome sections of FFPE tissue of primary lesion and lymph node metastases were subjected to a multistep procedure of paraffin removal, tissue rehydration, homogenization, and digestion with the set of proteolytic enzymes. The pigment samples were then pyrolyzed at 500 °C, and the GC-separated thermal degradation products were identified using a triple quadrupole mass spectrometer operating in the multiple reaction monitoring mode. Results GC/MS/MS analysis of the pyrolysis products revealed the presence of pheomelanin markers, which allowed quantitation of a pheomelanin component of each of the isolated pigments. Melanin from the FFPE primary melanoma was found to contain 6.6%, and the pigment from FFPE metastatic lymph node 7.5% of pheomelanin. Conclusions The developed protocol allows for the isolation of melanin from FFPE melanoma specimens. The pigment can be successfully studied for pheomelanin content by Py-GC/MS/MS method. The results of our study indicate that archival FFPE tumor tissues can be used as a good source of melanin for future structural studies aimed at shedding more light on the role of pheomelanin in the pathomechanism of cutaneous melanoma.
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Farahani, Shokoufeh Shahrabi, i Mohammadtaghi Lotfalian. "A Pigmented Dentigerous Cyst in a Patient with Multiple Dentigerous Cysts of the Jaws: A Case Report". Journal of Contemporary Dental Practice 8, nr 5 (2007): 85–91. http://dx.doi.org/10.5005/jcdp-8-5-85.
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Abstract Aim The aim of this article is to report an unusual and interesting case of non-syndromic multiple dentigerous cysts of the maxilla and mandible associated with melanin pigment and melanocytes in the epithelial lining in one of the cysts. In addition, embryologic aspect and origin of melanocytes are briefly discussed. Background Dentigerous cysts are the second most common odontogenic cysts after radicular cysts. They are usually solitary with multiple cysts reported on occasion in association with syndromes. While melanocytes and melanin-pigment are widely distributed in the skin, the nervous system, certain types of mucosa, uveal tract, and other areas, they are not normally present within bone in mammals. Report A 37-year-old Iranian male was referred to an oral surgeon by his dentist for evaluation and treatment of multiple cyst-like radiolucent lesions around the crowns of some unerupted permanent teeth in both maxillary and mandibular anterior areas. The biopsy revealed numerous granules of melanin-pigment distributed throughout the epithelial lining of one of these cysts in addition to the characteristic histopathologic features of adentigerous cyst. Histochemical analysis confirmed the pigment was melanin, and many of the cells containing melanin were immunohistochemically positive for s-100 protein. Summary Although the specific origin and pathologic significance of the melanocytes described here cannot be explained, it may be of interest for future investigations. Citation Shahrabi Farahani S, Lotfalian M. A Pigmented Dentigerous Cyst in a Patient with Multiple Dentigerous Cysts of the Jaws: A Case Report. J Contemp Dent Pract 2007 July;(8)5:085-091.
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Almeida-Paes, Rodrigo, Maria HG Figueiredo-Carvalho, Leandro BR da Silva, Gary Gerfen, Glauber R. de S Araújo, Susana Frases, Rosely M. Zancopé-Oliveira i Joshua D. Nosanchuk. "Candida glabrata produces a melanin-like pigment that protects against stress conditions encountered during parasitism". Future Microbiology 16, nr 7 (maj 2021): 509–20. http://dx.doi.org/10.2217/fmb-2020-0228.
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Aim: Melanin has been linked to pathogenesis in several fungi. They often produce melanin-like pigments in the presence of L-dihydroxyphenylalanine (L-DOPA), but this is poorly studied in Candida glabrata. Methods & materials: C. glabrata was grown in minimal medium with or without L-DOPA supplementation and submitted to a chemical treatment with denaturant and hot acid. Results: C. glabrata turned black when grown in the presence of L-DOPA, whereas cells grown without L-DOPA supplementation remained white. Biophysical properties demonstrated that the pigment was melanin. Melanized C. glabrata cells were effectively protected from azoles and amphotericin B, incubation at 42°C and macrophage killing. Conclusion: In the presence of L-DOPA, C. glabrata produces melanin, increases antifungal resistance and enhances host survival.
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Takeda, Yasunori, Atsumi Suzuki, Masafumi Kuroda i Yoshiyuki Yamazaki. "Melanin-pigment in complex odontoma". International Journal of Oral and Maxillofacial Surgery 16, nr 2 (kwiecień 1987): 222–26. http://dx.doi.org/10.1016/s0901-5027(87)80135-2.
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Plonka, Przemyslaw M., Dominika Michalczyk, Malgorzata Popik, Bori Handjiski, Andrzej Slominski i Ralf Paus. "Splenic eumelanin differs from hair eumelanin in C57BL/6 mice." Acta Biochimica Polonica 52, nr 2 (25.06.2005): 433–41. http://dx.doi.org/10.18388/abp.2005_3456.
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The presence of melanin in spleens of black C57BL/6 mice has been known for long. Although its origin and biological functions are still obscure, the relation of splenic melanin to the hair follicle and skin pigmentation was suggested. Here, we demonstrated using for the first time electron paramagnetic resonance spectroscopy that black-spotted C57BL/6 spleens contain eumelanin. Its presence here is a "yes or no" phenomenon, as even in the groups which revealed the highest percentage of spots single organs completely devoid of the pigment were found. Percentage of the spotted spleens decreased, however, with the progress of telogen after spontaneously-induced hair growth. The paramagnetic properties of the spleen eumelanin differed from the hair shaft or anagen VI skin melanin. The splenic melanin revealed narrower signal, and its microwave power saturability betrayed more heterogenous population of paramagnetic centres than in the skin or hair shaft pigment. Interestingly, the pigment of dry hair shafts and of the wet tissue of depilated anagen VI skin revealed almost identical properties. The properties of splenic melanin better resembled the synthetic dopa melanin (water suspension, and to a lesser degree -- powder sample) than the skin/hair melanin. All these findings may indicate a limited degradation of splenic melanin as compared to the skin/hair pigment. The splenic eumelanin may at least in part originate from the skin melanin phagocyted in catagen by the Langerhans cells or macrophages and transported to the organ.
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Frases, Susana, Stuart Chaskes, Ekaterina Dadachova i Arturo Casadevall. "Induction by Klebsiella aerogenes of a Melanin-Like Pigment in Cryptococcus neoformans". Applied and Environmental Microbiology 72, nr 2 (luty 2006): 1542–50. http://dx.doi.org/10.1128/aem.72.2.1542-1550.2006.
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ABSTRACT While studying the interaction of Cryptococcus neoformans with Dictyostelium discoideum, we noticed that yeast colonies in agar with a feeder lawn of Klebsiella aerogenes were brown. This finding was intriguing because C. neoformans colonies are not pigmented unless they are provided with precursors for melanization. Strains of all C. neoformans serotypes produced brown pigment in response to K. aerogenes at 22, 30, and 37°C. Pigment production required fungal laccase and was suppressed by high concentrations of glucose. Treatment of brown cells with guanidinium isothiocyanate and hot concentrated HCl yielded particulate material that had the physical and chemical characteristics of melanins. No pigment formation was observed when C. neoformans was exposed to live Escherichia coli or heat-killed K. aerogenes. Analysis of K. aerogenes supernatants revealed the presence of dopamine, which can be a substrate for melanin synthesis by C. neoformans. Our findings illustrate a remarkable interaction between a pathogenic fungus and a gram-negative bacterium, in which the bacterium produces a substrate that promotes fungal melanization. This observation provides a precedent that could explain the source of a substrate for C. neoformans melanization in the environment.
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Argenziano, Rita, Maria Laura Alfieri, Noemi Gallucci, Gerardino D’Errico, Lucia Panzella i Alessandra Napolitano. "A Model Eumelanin from 5,6-Dihydroxyindole-2-Carboxybutanamide Combining Remarkable Antioxidant and Photoprotective Properties with a Favourable Solubility Profile for Dermo-Cosmetic Applications". International Journal of Molecular Sciences 24, nr 4 (20.02.2023): 4241. http://dx.doi.org/10.3390/ijms24044241.
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The search for new synthetic melanin-related pigments that maintain the antioxidant and photoprotective properties of naturally occurring dark eumelanins, while overcoming their unfavorable solubility, and molecular heterogeneity is presently a very active issue for dermo-cosmetic purposes. In this work, we explored the potential of a melanin obtained from the carboxybutanamide of a major eumelanin biosynthetic precursor, 5,6-dihydroxyindole-2-carboxylic acid (DHICA), by aerobic oxidation under slightly alkaline conditions. Analysis of the pigment by EPR, ATR-FTIR and MALDI MS indicated a substantial structural similarity to DHICA melanin, while investigation of the early intermediates confirmed unchanged regiochemistry of the oxidative coupling. The pigment exhibited a UVA–visible absorption even more intense than that of DHICA melanin, and a noticeable solubility in polar solvents of dermo-cosmetic relevance. The hydrogen- and/or electron-donor ability, and the iron (III) reducing power as determined by conventional assays provided evidence for marked antioxidant properties not merely ascribable to the more favorable solubility profile, while the inhibitory action of the radical- or photosensitized solar light-induced lipid peroxidation was more marked compared to that of DHICA melanin. Overall, these results hint at this melanin, which remarkable properties are, in part, due to the electronic effects of the carboxyamide functionality as a promising functional ingredient for dermo-cosmetic formulations.
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Kriangwanich, Wannapimol, Promporn Piboon, Wirakorn Sakorn, Kittisak Buddhachat, Varankpicha Kochagul, Kidsadagon Pringproa, Supamit Mekchay i Korakot Nganvongpanit. "Consistency of dark skeletal muscles in Thai native black-bone chickens (Gallus gallus domesticus)". PeerJ 9 (13.01.2021): e10728. http://dx.doi.org/10.7717/peerj.10728.
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Black-bone chickens (Gallus gallus domesticus) have become economically valuable, particularly in Southeast Asia as a consequence of popular traditional Chinese medical practices. Chickens with whole body organ darkness are considered to have higher value and are, therefore, more often requested. This research study aimed to investigate the darkness in 34 skeletal muscles of 10 Thai black-bone chickens (five males and five females). The evaluation of muscle darkness was done on two levels: (i) a color chart was employed at the macroanatomical level and (ii) by using melanin pigment to evaluate the structure at the microanatomy level. The results revealed that the accumulation of melanin pigment in the muscle tissue was observed in the endomysium, perimysium and epimysium. With respect to the results of the color chart test, iliotibialis lateralis pars preacetabularis, gastrocnemius, fibularis longus and puboischiofemoralis pars medialis showed the highest degree of darkness, while serratus profundus, pectoralis, iliotibialis cranialis, flexor cruris lateralis, and flexor cruris medialis appeared to be the least dark. In addition, we found that the highest and lowest amounts of melanin pigment was noted in the flexor carpi ulnaris and pectoralis (p < 0.05), respectively; however, there was no significant difference (p > 0.05) observed between the sexes. These results reveal that the 34 specified muscles of black-bone chickens showed uneven distribution of darkness due to the differing accumulations of melanin pigments of each muscle.This information may provide background knowledge for a better understanding of melanin accumulation and lead to breeding improvements in Thai black-bone chickens.
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Menon, I. Aravind, Suruj D. Persad, Herbert F. Haberman, Prasanta K. Basu, Joseph F. Norfray, Christopher C. Felix i B. Kalyanaraman. "Characterization of the pigment from homogentisic acid and urine and tissue from an alkaptonuria patient". Biochemistry and Cell Biology 69, nr 4 (1.04.1991): 269–73. http://dx.doi.org/10.1139/o91-041.
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When urine samples from alkaptonuria patients are allowed to stand, they turn black, presumably owing to the oxidation of homogentisic acid to a melanin-like substance. We report the characterization of the pigments formed by polymerization of (a) the components in the urine from a patient with alkaptonuria and (b) homogentisic acid. The absorption spectra and electron spin resonance signals of these pigments are similar to those of eumelanins. Irradiation of the pigments with nitroblue tetrazolium caused reduction of the tetrazolium; this was partially inhibited by superoxide dismutase. Irradiation of Ehrlich ascites carcinoma cells with the pigments from homogentisic acid or urine caused cell lysis. Since this lysis was inhibited by catalase, we have concluded that it was mediated by H2O2. A similar pigment was also extracted from the tissue from an alkaptonuria patient. It is suggested that the degeneration of tissue in vivo may be due to the deposition of melanin-like pigments in the tissues, probably in combination with metal ions.Key words: alkaptonuria, homogentisic acid, pigmentation, melanin, photosensitization.
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Trias, Joaquim, Miquel Viñas, Jesus Guinea i José G. Lorèn. "Brown pigmentation in Serratia marcescens cultures associated with tyrosine metabolism". Canadian Journal of Microbiology 35, nr 11 (1.11.1989): 1037–42. http://dx.doi.org/10.1139/m89-172.
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Serratia marcescens produced a brown pigment when grown in minimal medium in the presence of tyrosine and high concentrations of copper(II) ion. The pigment was not related to the melanin pigments, but was similar to the pigment produced by autooxidation and polymerization of 3,4-dihydroxyphenylacetate, which is synthesized in S. marcescens from tyrosine through the 3,4-dihydroxyphenylacetate catabolic pathway. The enzymes of this pathway were induced under pigment production conditions; however, 3,4-dihydroxyphenylacetate 2,3-dioxygenase remained at low activity levels, permitting the accumulation and excretion of the substrate. Mutants unable to use tyrosine as a sole carbon and energy source were able to produce brown pigments only if the step blocked by the mutation was after the synthesis of 3,4-dihydroxyphenylacetate. The ability to produce brown pigments was common to all the S. marcescens strains tested.Key words: brown pigment, 3,4-dihydroxyphenylacetate 2,3-dioxygenase, Serratia marcescens, tyrosine, aromatic amino acid catabolism.
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Liu, Chia-Hsing, Chih-Hung Lin, Min-Jan Tsai, Yu-Hsuan Chen, Sheau-Fang Yang i Kun-Bow Tsai. "Melanin Bleaching With Warm Hydrogen Peroxide and Integrated Immunohistochemical Analysis: An Automated Platform". International Journal of Surgical Pathology 26, nr 5 (21.02.2018): 410–16. http://dx.doi.org/10.1177/1066896918756998.
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Objective. Diagnosing melanocytic lesions is among the most challenging problems in the practice of pathology. The difficulty of physically masking melanin pigment and the similarity of its color to commonly used chromogens often complicate examination of the cytomorphology and immunohistochemical staining results for tumor cells. Melanin bleach can be very helpful for histopathological diagnosis of heavily pigmented melanocytic lesions. Although various depigmentation methods have been reported, no standardized methods have been developed. This study developed a fully automated platform that incorporates hydrogen peroxide–based melanin depigmentation in an automated immunohistochemical analysis. Methods and Materials. The utility of the method was tested in 1 cell block of malignant melanoma cells in pleural effusion, 10 ocular melanoma tissue samples, and 10 cutaneous melanoma tissue samples. Our results demonstrated that the proposed method, which can be performed in only 3 hours, effectively preserves cell cytomorphology and immunoreactivity. Results. The method is particularly effective for removing melanin pigment to facilitate histopathological examination of cytomorphology and for obtaining an unmasked tissue section for immunohistochemical analysis.
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van der Heijden, A., J. E. van Dijk, A. G. Lemmens i A. C. Beynen. "Spleen pigmentation in young C57BL mice is caused by accumulation of melanin". Laboratory Animals 29, nr 4 (1.10.1995): 459–63. http://dx.doi.org/10.1258/002367795780740113.
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It has been previously reported that in 2 C57BL mouse sublines a dark pigmentation of the cranial part of the spleen occurs in up to 30% of the animals within the populations. It was not clear whether this discoloration is caused by melanosis, lipofuscinosis or haemosiderosis. With the use of light and electron microscopy of stained spleen sections, we identified the pigment in 14 out of 60 C57BL mice aged 8-10 wks. In the mice with pigmented spleens there was accumulation of melanin, predominantly in melanophores. Literature data indicate that apart from melanin, lipofuscin and haemosiderin can be observed in splenic macrophages provided that the mice are older than those studied by us. We conclude that melanin is the principal pigment causing spleen discoloration in young C57BL mice. Splenic melanosis displays inter-individual variation, but its relevance from a pathophysiological point of view remains obscure.
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Zadlo, Andrzej, Anna Pilat, Michal Sarna, Anna Pawlak i Tadeusz Sarna. "Redox Active Transition Metal ions Make Melanin Susceptible to Chemical Degradation Induced by Organic Peroxide". Cell Biochemistry and Biophysics 75, nr 3-4 (11.04.2017): 319–33. http://dx.doi.org/10.1007/s12013-017-0793-6.
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Abstract With aging, retinal pigment epithelium melanosomes, by fusion with the age pigment lipofuscin, form complex granules called melanolipofuscin. Lipofuscin granules may contain oxidized proteins and lipid hydroperoxides, which in melanolipofuscin could chemically modify melanin polymer, while transition metal ions present in melanin can accelerate such oxidative modifications. The aim of this research was to examine the effect of selected transition metal ions on melanin susceptibility to chemical modification induced by the water-soluble tert-butyl hydroperoxide used as an oxidizing agent. Synthetic melanin obtained by DOPA autooxidation and melanosomes isolated from bovine retinal pigment epithelium were analyzed. To monitor tert-butyl hydroperoxide-induced oxidative changes of DMa and BMs, electron paramagnetic resonance spectroscopy, UV-vis absorption spectroscopy, dynamic light scattering, atomic force microscopy and electron paramagnetic resonance oximetry were employed. These measurements revealed that both copper and iron ions accelerated chemical degradation induced by tert-butyl hydroperoxide, while zinc ions had no effect. Strong prooxidant action was detected only in the case of melanosomes and melanin degraded in the presence of iron. It can be postulated that similar chemical processes, if they occur in situ in melanolipofuscin granules of the human retinal pigment epithelium, would modify antioxidant properties of melanin and its reactivity.
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Morris-Jones, Rachael, Beatriz L. Gomez, Soraya Diez, Martha Uran, Stephen D. Morris-Jones, Arturo Casadevall, Joshua D. Nosanchuk i Andrew J. Hamilton. "Synthesis of Melanin Pigment by Candida albicans In Vitro and during Infection". Infection and Immunity 73, nr 9 (wrzesień 2005): 6147–50. http://dx.doi.org/10.1128/iai.73.9.6147-6150.2005.
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ABSTRACT Melanins are implicated in the pathogenesis of several important human diseases. This study confirmed the presence of melanin particles in Candida albicans in vitro and during infection. Dark particles were isolated from the digestion of C. albicans cultures and from infected tissue, as established by electron microscopy and immunofluorescence techniques.