The Incorporation of Various Metal Ions into in Vivo- and in Vitro-Produced Melanin

Bruenger, F. W.; Stover, Betsy J.; Atherton, D.R.

doi:10.2307/3572300

Cited by 79 publications

(25 citation statements)

References 6 publications

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“…4C) (18). In addition, melanin complexes metals with an affinity that increases with increasing valence and atomic weight of the metal (19,20).1 this explains reports of highly variable and sometimes excessive Amounts of heavy metals in pigmented tissues and fias'led to the proposal that one function of melanin is to scavenge potentially harmful metals (20,21). Whenl Ca was inclUded in those studies, its binding to melanin was found to be rather weak and reversible as compared to heavier metals; the alkali metals did not bind at all (18,20 (24)(25)(26).…”

Section: Methods and Resultsmentioning

confidence: 99%

Calcium binding in pigmented and albino eyes.

Drager¹

1985

Proc. Natl. Acad. Sci. U.S.A.

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The localization of calcium binding sites in eyes was determined autoradiographically after extracting endogenous Ca from tissue sections and replacing it with 45Ca.The strongest labeling was associated with pigmented tissues due to the high concentration of melanin, which was shown to bind Ca effectively and in a pH-dependent fashion. The second strongest binding was over the tapetum lucidum of the cat eye, and moderate labeling was associated with eye muscles and epithelium and endothelium of the cornea. The neural retina was generally more lightly labeled than the surrounding tissue of the eye; here the plexiform layers stood out in comparison to the nuclear layers, as did a band located internal to the photoreceptor outer segments. The possibility that the Ca buffering capacity of melanin may represent the common denominator for the various neurological defects found in hypopigmentation mutants is discussed.Hypopigmentation mutants in mammals have two types of visual abnormalities that cannot be explained by insufficient light screening but point to another, unidentified function of pigment. The first abnormality is due to miswiring of optic connections; it includes the extensively studied defect in optic nerve crossing (1, 2) and probably also the eye movement defects (3-5). The second type is a dynamic defect that depends on direct contact of the neural retina with the retinal pigment epithelium (RPE): in optic nerve recordings from intact pearl mice, a hypopigmentation mutant not allelic with the albino, visual thresholds were elevated about 100 times at dim backgrounds, as compared to fully pigmented mice, but were about normal at bright ambient illumination (6); when recordings were done from ganglion cells in isolated retinas, however, visual thresholds of normal and pearl mice were indistinguishable (7). Defects in optic nerve crossing and eye movements are caused by mutations at any of several genes involved in pigmentation; severity of defects correlates roughly with the degree of impairment in pigmentation of the RPE and not with pigment in any other tissues (8)(9)(10). This is consistent with the notion that the defects are expressed in the embryo, because the RPE becomes pigmented at early stages of eye development, long before any other pigment appears in the organism; the choroid of the eye, for instance, assumes pigment only several days after birth in mice, at a time when optic connections are for the most part well established. It is not known with which pigment, if any, the light sensitivity defect may correlate, as it has only been described in pearl mice; a similar defect does seem to be present in albino mice (unpublished observations) and it may also be reflected in visual abnormalities found in albinos of several species, including humans, which cannot be explained by light scatter or aberrant crossing (11, 12). METHODS AND RESULTSMice were perfused with paraformaldehyde and (in some cases) glutaraldehyde, and their eyes were dissected as eye cups, cut on a cryostat at 10 ,m, e...

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Section: Methods and Resultsmentioning

confidence: 99%

Calcium binding in pigmented and albino eyes.

Drager¹

1985

Proc. Natl. Acad. Sci. U.S.A.

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“…Using radioactive isotopes to determine the metal ion binding properties of melanins, Bruenger et al (1967) concluded many years ago that the reaction characteristics of melanin and of weak acid cation-exchange resins were very similar. Evidence for the existence of several specific types of metal binding sites in choroidal eumelanin from bovine eyes was obtained in an ESR study, in which lanthanide ions were employed as molecular probes (Sarna et al, 1976a,b).…”

Section: Ion-exchange Propertiesmentioning

confidence: 99%

The physical and chemical properties of eumelanin

Meredith

Sarna

2006

Pigment Cell Research

908

1,045

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SummaryIn this article, we review the current state of knowledge concerning the physical and chemical properties of the eumelanin pigment. We examine properties related to its photoprotective functionality, and draw the crucial link between fundamental molecular structure and observable macroscopic behaviour. Where necessary, we also briefly review certain aspects of the pheomelanin literature to draw relevant comparison. A full understanding of melanin function, and indeed its role in retarding or promoting the disease state, can only be obtained through a full mapping of key structure-property relationships in the main pigment types. We are engaged in such an endeavor for the case of eumelanin.

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“…Several studies shown that fungal melanin has a capacity to bind heavy metal ions [15]. However, the understanding of the role of fungal melanin in heavy metal tolerance of DSE is still lacking.…”

Section: Introductionmentioning

confidence: 99%

The Response of Dark Septate Endophytes (DSE) to Heavy Metals in Pure Culture

et al. 2012

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Dark septate endophytes (DSE) occur widely in association with plants exposed to heavy metal stress. However, little is known about the response of DSE exposed to heavy metals. In this study, five DSE were isolated from the roots of Astragalus adsurgens Pall. seedlings growing on lead-zinc mine tailings in China. Based on morphological characteristics and DNA sequence analyses, the isolates were identified as Gaeumannomyces cylindrosporus, Paraphoma chrysanthemicola, Phialophora mustea, Exophiala salmonis, and Cladosporium cladosporioides. G. cylindrosporus was selected to explore responses to Pb stress. Scanning electron microscopic observations of G. cylindrosporus grown on solid medium revealed curling of hyphae and formation of hyphal coils in response to Pb. In contrast, in liquid medium, hyphae became thick and swollen with an increase in Pb (II) concentration. We interpret that these changes are related to the variation in cell wall components. We also demonstrated that fungal melanin content increased with the addition of Pb(II). Melanin, as an important component in the cell wall, is known to be an essential antioxidant responsible for decreasing heavy metal toxicity. We also measured the total soluble protein content and glutathione (GSH) concentrations in G. cylindrosporus and found that they initially increased and then decreased with the increase of Pb(II) concentrations. The antioxidant enzyme activities were also examined, and the results showed that superoxide dismutase (SOD) activity was significantly positively correlated with Pb(II) concentrations (r = 0.957, P<0.001). Collectively, our observations indicate that the intracellular antioxidant systems, especially fungal melanin, play an important role in abating the hazards of heavy metals.

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The Incorporation of Various Metal Ions into in Vivo- and in Vitro-Produced Melanin

Cited by 79 publications

References 6 publications

Calcium binding in pigmented and albino eyes.

Calcium binding in pigmented and albino eyes.

The physical and chemical properties of eumelanin

The Response of Dark Septate Endophytes (DSE) to Heavy Metals in Pure Culture

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