The function of melanin or six blind people examine an elephant

Hill, Helene Z.

doi:10.1002/bies.950140111

Cited by 306 publications

(235 citation statements)

References 34 publications

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“…radiation to the retina and is associated with less dense choroidal melanin, which may mean less protection of the nuclei of choroidal melanocytes against solar radiation. 45 These effects might be expected to increase ocular sensitivity to incident solar radiation and may explain the association we observed between ocular melanoma and squinting as a child. They also suggest indirectly that incident solar radiation is a cause of choroidal and ciliary body melanoma, which is also supported by the lower risk of choroidal and ciliary body melanoma in people born in other than Australia and New Zealand.…”

Section: Discussionmentioning

confidence: 80%

Eye color and cutaneous nevi predict risk of ocular melanoma in Australia

Vajdic¹,

Kricker

Giblin

et al. 2001

Int. J. Cancer

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Ethnicity, cutaneous nevi and eye color are generally accepted risk factors for melanoma of the eye, although casecontrol studies have produced conflicting results. We sought to determine the constitutional risk factors for melanomas of the choroid, ciliary body, iris and conjunctiva in Australia. A population-based case-control study was conducted, with case ascertainment from a prospective national incidence survey and randomly selected community controls. Two hundred and ninety cases aged 18 -79 years and diagnosed between 1st January 1996 and 31st July 1998 were enrolled with 916 controls frequency matched by age, sex and State or Territory of residence. Risk of choroidal and ciliary body melanoma (n ‫؍‬ 246) was increased in people with grey (OR 2.9, 95% CI 1.5-5.5), hazel (OR 2.2, 95% CI 1.4 -3.7) and blue eyes (OR 1.7, 95% CI 1.0 -2.7) compared with brown eyes. Risk was also increased in those with 4 or more nevi on their back, those unable to tan, and those who squinted when outdoors as a child. Risk was reduced in people born other than in Australia and New Zealand (OR 0.7, 95% CI 0.5-1.0). Non-brown eye color was a risk factor for iris melanoma (n ‫؍‬ 25). No risk factors were identified for conjunctival melanoma (n ‫؍‬ 19). Eye color is the strongest constitutional predictor of choroidal and ciliary body melanoma, and may indicate a protective effect of melanin density at these sites. An independent association with cutaneous nevi suggests a role for other genetic factors.

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Section: Discussionmentioning

confidence: 80%

Eye color and cutaneous nevi predict risk of ocular melanoma in Australia

Vajdic¹,

Kricker

Giblin

et al. 2001

Int. J. Cancer

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“…Melanin is a skin pigment that plays a variety of roles, including protection of the germinative layer of the skin from the harmful effects of UV irradiation [71]. Melanin is produced in specialized cells (melanocytes) in the skin and its appendages (the basal layer of the skin and the hair follicle), in the eye (choroidal melanocytes and retinal pigment epithelial cells), the inner ear, the brain meninges and in other tissues and organs, such as the liver, the heart, the bone and the adipose tissue.…”

Section: Radioprotective Properties Of Melaninmentioning

confidence: 99%

“…Melanin is an efficient converter of electromagnetic energy. It participates readily in processes of electron transfer and is an efficient free-radical scavenger [71][72][73]. Beverages such as tea, coffee and cocoa and foodstuffs such as grapes, bananas and edible fungi contain melanin-like pigments [74,75].…”

Section: Radioprotective Properties Of Melaninmentioning

confidence: 99%

“…Melanin exerts its protective action at the initial stage of irradiation, absorbing and converting high-energy electromagnetic radiation and reducing the levels of free radical species, thereby preventing DNA damage [71,86]. Thus, individual characteristics such as melanin content may affect individualized biodosimetrical measurements.…”

Section: Radioprotective Properties Of Melaninmentioning

confidence: 99%

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Some problems and errors in cytogenetic biodosimetry

Mosse

Kilchevsky

Nikolova

et al. 2016

Biotechnology & Biotechnological Equipment

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Human radiosensitivity is a quantitative trait that is generally subject to binomial distribution. Individual radiosensitivity, however, may deviate significantly from the mean (by 2-3 standard deviations). Thus, the same dose of radiation may result in different levels of genotoxic damage (commonly measured as chromosome aberration rates) in different individuals. There is significant genetic component in individual radiosensitivity. It is related to carriership of variant alleles of various single-nucleotide polymorphisms (most of these in genes coding for proteins functioning in DNA damage identification and repair); carriership of a different number of alleles producing cumulative effects; amplification of gene copies coding for proteins responsible for radioresistance, mobile genetic elements and others. Among the other factors influencing individual radioresistance are: the radioadaptive response; the bystander effect; the levels of endogenous substances with radioprotective and antimutagenic properties and environmental factors such as lifestyle and diet, physical activity, psychoemotional state, hormonal state, certain drugs, infections and others. These factors may have radioprotective or sensibilizing effects. Apparently, there are too many factors that may significantly modulate the biological effects of ionizing radiation. Thus, conventional methodologies for biodosimetry (specifically, cytogenetic methods) may produce significant errors if personal traits that may affect radioresistance are not accounted for.

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“…The ability of C. neoformans to make melanin was discovered in the early 1960s (Staib, 1962(Staib, , 1963 and was associated with virulence in the 1980s Rhodes et al, 1982). Melanins are rigid, acid-resistant polymers of uncertain structure that are found in all biological kingdoms (Hill, 1992). The synthesis of melanin by C. neoformans occurs only in the presence of phenolic compounds, such as L-3,4-dihydroxyphenylalanine (L-dopa), and is catalysed by a laccase Williamson, 1994).…”

Section: Introductionmentioning

confidence: 99%

Budding of melanized Cryptococcus neoformans in the presence or absence of l-dopa

Nosanchuk

Casadevall

2003

Microbiology

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Cryptococcus neoformans is a pathogenic fungus that produces melanin when incubated in the presence of certain phenolic substrates such as L-3,4-dihydroxyphenylalanine (L-dopa). Melanin is an enigmatic polymer that is deposited in the cell wall and contributes to virulence. Substantial progress has been made in understanding the synthesis of melanin and the mechanisms by which it contributes to virulence, but relatively little is known about how melanin is rearranged during growth and budding. In this study we used transmission and scanning electron microscopy and immunofluorescence of melanized cells and melanin 'ghosts' to study the process of melanization during replication. Budding in melanized C. neoformans results in focal disruption of cell-wall melanin at the bud site. In the presence of L-dopa, bud-related melanin defects are repaired and daughter cells are melanized. However, in the absence of substrate, mother cells cannot repair their melanin defects and daughter cells are non-melanized. Hence, melanin in the parent cell is not carried to the daughter cells, but rather is synthesized de novo in buds. These results imply that melanin remodelling occurs during cell growth in a process that involves degradation and synthesis at sites of budding. INTRODUCTIONCryptococcus neoformans is an encapsulated, environmental fungus that can cause life-threatening meningitis, particularly in immunocompromised individuals. The ability of C. neoformans to make melanin was discovered in the early 1960s (Staib, 1962(Staib, , 1963 and was associated with virulence in the 1980s Rhodes et al., 1982). Melanins are rigid, acid-resistant polymers of uncertain structure that are found in all biological kingdoms (Hill, 1992). The synthesis of melanin by C. neoformans occurs only in the presence of phenolic compounds, such as L-3,4-dihydroxyphenylalanine (L-dopa), and is catalysed by a laccase Williamson, 1994). The C. neoformans laccase has recently been shown to be tightly associated with the cell wall by a hydrolysable bond (Zhu et al., 2001). When the fungus grows in the presence of phenolic compounds, melanin is deposited in the cell wall (Wang et al., 1995) and comprises approximately 15 % of the dry weight of late-stationary-phase melanized C. neoformans (Wang & Casadevall, 1996). C. neoformans is melanized in the environment (Nosanchuk et al., 1999b) and during human infection (Nosanchuk et al., 2000). In the environment melanin is thought to protect the fungus against extremes of temperature (Rosas & Casadevall, 1997), ultraviolet light (Wang & Casadevall, 1994a), heavy metals (Garcia-Rivera & Casadevall, 2001) and amoeboid predators (Steenbergen et al., 2001). During infection melanin appears to function in virulence by protecting fungal cells against microbicidal oxidants (Wang & Casadevall, 1994b) and peptides (Doering et al., 1999) produced by immune effector cells. Furthermore, melanin may interfere with the development of effective cellmediated responses (Huffnagle et al., 1995) and could affect the activation ...

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The function of melanin or six blind people examine an elephant

Cited by 306 publications

References 34 publications

Eye color and cutaneous nevi predict risk of ocular melanoma in Australia

Eye color and cutaneous nevi predict risk of ocular melanoma in Australia

Some problems and errors in cytogenetic biodosimetry

Budding of melanized Cryptococcus neoformans in the presence or absence of l-dopa

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