Distribution of copper and zinc in mammalian eyes. Occurrence of metals in melanin fractions from eye tissues

Bowness, J. M.; Morton, R. A.; Shakir, M.; Stubbs, A. L.

doi:10.1042/bj0510521

Cited by 88 publications

(38 citation statements)

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“…1953, 53 assumed to combine with its own weight of protein, as was shown to be the case for the natural cattle melanin-protein complex (Bowness et al 1952), then the amount of zinc bound to the synthetic complex is of the same order as that which is combined with the pigment material obtained from perch and frog eyes (Bowness & Morton, 1952), which contains the highest concentration of zinc yet found in biological material.…”

Section: Discussionmentioning

confidence: 94%

“…Evidence of an association of zinc with melanin pigmentation in the eyes ofmany vertebrates, and of a number of other metals occurring in melaninprotein fractions from the pigmented eye tissues, has been presented by Bowness et al (1952) and Bowness & Morton (1952). Some findings of other workers such as the occurrence of barium in cattle choroids (Ramnage & Sheldon, 1931) and the occurrence of high concentrations of copper in the ink of Sepia offlcinalis (Giuliani, 1938) were also mentioned.…”

Section: Discussionmentioning

confidence: 95%

“…Assuming, however, that the conversion was complete, the minimum concentration of zinc in a pigment-protein complex analogous to those isolated from cattle and perch eyes can be calculated. The melanin in these complexes was combined with roughly its own weight of protein (Bowness et al 1952); the total weight of pigment-protein complex I953 must therefore be a maximum of 20 mg. The amount of zinc combined by this material must be 250 {lg., giving a concentration of 1-25 %.…”

Section: Experimental and Resultsmentioning

confidence: 99%

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The association of zinc and other metals with melanin and a melanin-protein complex

Bowness

Morton

1953

Biochemical Journal

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two last-mentioned papers it was shown that zinc and a number of other metals occurred in nondialysable form in melanin-protein fractions from the eyes of cattle and perch. The accumulation in these fractions was sufficient to account for most of the zinc in the pigmented tissues.The present work attempts to throw light on the combination between metallic ions and melanin or melanin-protein complexes. The interactions of zinc and other metals with various systems which transform tyrosine or 3:4-dihydroxyphenyl-Lalanine (dopa) to melanin have been studied. Arnow (1938a) showed that a pigment could be obtained by bubbling atmospheric oxygen through an alkaline solution of dopa. Raper (1927) showed that dopa is an intermediate product in the oxidation of tyrosine to melanin by tyrosinase. It is probable that most animal melanins are synthesized by this series of reactions. As the absorption spectrum of the pigment produced by the oxidation of dopa resembles that of natural melanins (Arnow, 1938b) the structures are probably analogous, if not identical. The artificial pigment is therefore suitable for investigating the combination between metals and melanin in the absence of protein.Winternitz (1918) showed that an extract of pig uveal tract catalysed the darkening of tyrosine suspensions, and Calkins (cited by Lerner & Fitzpatrick, 1950) reported the presence of tyrosinase and dopa-oxidase in ox ciliary bodies. It was therefore decided to try to extract from cattle irises and ciliary bodies an enzyme system catalysing the oxidation of tyrosine to melanin, and to use this system to study, in vitro, the effect of metals on melanin formed from tyrosine in the presence of protein. MATERIALS AND METHODSReagents and apparatus. Reagents of A.R. grade were used whenever possible. All aqueous solutions were prepared with twice-distilled water, the final distillation being from, and into, Pyrex-glass vessels. All glass vessels were washed first with 50 % (v/v) HNO3, then with twice-distilled water, and dried in a stainless-steel oven. Subsequently they were scrubbed or rinsed in hot tap water, and then rinsed with twice-distilled water and dried.Preparation of dopa-melanin solution. An aqueous solution of dopa (approx. 0-01 %) was allowed to oxidize in air for several months. The resulting solution was diluted to approximately the original volume. On evaporating 10 ml.of the diluted solution at 500, a dry residue (8-2 mg.) was obtained. The absorption spectrum ofthe solution is given in Fig. 1. The curve corresponds well with that given by Arnow (1938b) for the absorption in the visible region of his dopamelanin. The small peak at 280 m,u. may be due to unchanged dopa (cf. Mason, 1948).

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 95%

Section: Experimental and Resultsmentioning

confidence: 99%

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The association of zinc and other metals with melanin and a melanin-protein complex

Bowness

Morton

1953

Biochemical Journal

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“…Desferrioxamine toxicity is thought to arise secondary to chelation of metals, such as iron, copper, zinc, cobalt, and nickel, which are essential for normal retinal function [5,7,10,11]. In particular, copper fluxes induced by desferrioxamine may induce retinal toxicity by oxidative cell membrane damage, interrupting monoaminergic neurotransmission in the retina, impairing antioxidant synthesis, and promoting oxidative enzyme reactions in the retina [10,12]. Furthermore iron is found deposited in the peripheral retina, choroid, and sclera.…”

Section: Discussionmentioning

confidence: 99%

Desferrioxamine related maculopathy: A case report

2004

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Desferrioxamine is used for the treatment of chronic iron overload, acute iron poisoning, and certain anaemias. Ocular toxicity secondary to prolonged treatment with desferrioxamine may result in night blindness, visual field constriction, cataract, pigmentary retinopathy and optic neuropathy. To avoid such complications an ophthalmic screening has been suggested for patients taking desferrioxamine. We report an 81-year-old patient who developed irreversible ocular toxicity despite undergoing ophthalmic screening.

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“…Zinc depletion results in poor dark adaptation and reduced photopic and scotopic responses. Copper is necessary for the synthesis of melanin, a storage protein for iron, zinc, and copper in RPE and melanocytes (77,78). The cellular homeostasis of iron, zinc, and copper is tightly interlinked.…”

Section: Introductionmentioning

confidence: 99%

The Age-Related Eye Disease 2 Study: Micronutrients in the Treatment of Macular Degeneration

Gorusupudi

Nelson

Bernstein

2017

Advances in Nutrition

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Age-related macular degeneration (AMD) is one of the leading causes of vision loss in the elderly. With an increasingly aged population worldwide, the need for the prevention of AMD is rising. Multiple studies investigating AMD with the use of animal models and cell culture have identified oxidative stress-related retinal damage as an important contributing factor. In general, diet is an excellent source of the antioxidants, vitamins, and minerals necessary for healthy living; moreover, the general public is often receptive to recommendations made by physicians and health care workers regarding diet and supplements as a means of empowering themselves to avoid common and worrisome ailments such as AMD, which has made epidemiologists and clinicians enthusiastic about dietary intervention studies. A wide variety of nutrients, such as minerals, vitamins, v-3 (n-3) fatty acids, and various carotenoids, have been associated with reducing the risk of AMD. Initial results from the Age-Related Eye Disease Study (AREDS) indicated that supplementation with antioxidants (b-carotene and vitamins C and E) and zinc was associated with a reduced risk of AMD progression. The AREDS2 follow-up study, designed to improve upon the earlier formulation, tested the addition of lutein, zeaxanthin, and v-3 fatty acids. In this review, we examine the science behind the nutritional factors included in these interventional studies and the reasons for considering their inclusion to lower the rate of AMD progression. Adv Nutr 2017;8:40-53.

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Distribution of copper and zinc in mammalian eyes. Occurrence of metals in melanin fractions from eye tissues

Abstract: Cattle and sheep eyes were obtained from the abattoir and dissected within 12 hr. of the death of the animals. Whale eyes were obtained from sperm whales caught in the Antarctic region, and had been stored (whaling ship 521l

Cited by 88 publications

References 6 publications

The association of zinc and other metals with melanin and a melanin-protein complex

The association of zinc and other metals with melanin and a melanin-protein complex

Desferrioxamine related maculopathy: A case report

The Age-Related Eye Disease 2 Study: Micronutrients in the Treatment of Macular Degeneration

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