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Direct Ultraviolet Effects on Biological Systems
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
Eumelanins and pheomelanins are two classes of these polymers, the former found in brown/black hair and the retina; the latter in red hair and feathers. Melanin pigments are tyrosine-based polymers formed in melanocytes within specialized organelles called melanosomes. From these latter two statements and (some of) our experience with tanning, we may guess another instance of UV-induced cross-linking is at hand. We cannot seriously deal with all of the issues of melanin and skin pigmentation, but we should disavow ourselves of the notion that melanin is a simple material with merely cosmetic implications. One of the world’s long-time melanin experts has posted his most important conclusions about a century or more of melanin studies (not all his): The chemical study of melanins have given poor results until now because of using of raw material in chemical and physical analyses and scarce knowledge of solid state by chemists and biologists. The discovery of theparticle[my emphasis] may change our strategy in the study of structure and function of melanins. Melanin is necessary for brain, ear, eyes, skin to function. It would not be possible to see blue or green colours in animal or plant kingdom without melanin. No blue or green eyes to admire.… If you don’t believe it imagine to remove the melanin from the biological tissue and observe what happens.Rodolfo Alessandro Nicolaus23
Nonionizing Radiation
Published in Martin B., S.Z., of Industrial Hygiene, 2018
Erythema is an inflammatory reaction of the superficial blood vessels involving dilation and increased permeability of the vessels, increased blood flow, and cellular exudation. A composite action spectrum shows that, for humans with moderate levels of pigmentation, the most effective wavelengths are between 250 and 300 nm. The dose necessary to produce erythema increases into the UV-A, where the erythemal doses are about a factor 1000 to 10,000 times greater. Erythema follows a dose-dependent latency period of 2 to 10 hours, although some physiological changes, e.g., vasodilation, may be detected very soon after exposure. In addition to redness associated with vascular changes, erythema produces cellular damage and may also produce edema and blistering. Following UV exposure, the epidermal layers of the skin thicken, melanosomes (pigment granules) migrate to the topmost layers of the skin, and the melanocytes produce more melanin. Both measures afford added UV protection to the skin.
Fractal Dimension of Skin Lesions
Published in Dinesh K. Kumar, Sridhar P. Arjunan, Behzad Aliahmad, Fractals, 2017
Dinesh K. Kumar, Sridhar P. Arjunan, Behzad Aliahmad
Melanocytes are the cells that produce melanin, the darkening pigment which is responsible for the skin and hair color and is stored in specialized cellular vesicles called melanosomes. Everyone has almost the same amount of melanocytes, however, the size and amount of melanin granules differs immensely in humans with different races and skin colors. Even in a single person the density of melanin can differ from one anatomical location to the other. In some areas such as the palm and soles of the feet where the skin color is lighter, the density of melanocytes and melanin content is much lower compared to areas with darker color.
Effects of anti-wrinkle and skin-whitening fermented black ginseng on human subjects and underlying mechanism of action
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Jin Ju Park, Junmin An, Jung Dae Lee, Hyang Yeon Kim, Jueng Eun Im, Eunyoung Lee, Jaehyoun Ha, Chang Hui Cho, Dong-Wan Seo, Kyu-Bong Kim
The skin is a protective outer covering extending throughout the human body which protects internal tissues and organs. Human skin is composed of three primary layers; the epidermis, dermis, and hypodermis. The epidermis, the outermost layer of the skin, functions by protecting the body and is predominantly composed of keratinocytes, melanocytes, Langerhans, and Merkel cells. Keratinocytes are the most abundant cells found in the epidermis and function as a barrier against the external environment (McGrath, Eady, and Pope 2004; Winkelmann and Breathnach 1973). Melanocytes produce the colored pigment of melanin. Melanin occurs in two forms in human skin: eumelanin and pheomelanin. Eumelanin is black and brown melanin and common throughout the body, while pheomelanin is a red or yellow melanin pigment (Wakamatsu and Ito 2002). Melanin is biosynthesized from tyrosine. Tyrosine is converted to DOPA (3,4-dihydroxy-L-phenylalanine), which is then oxidized to DOPA-quinone and subsequently converted to DOPA-chrome. Melanin is finally generated through several intermediates and a series of biochemical steps. Tyrosinase plays a key role in the melanin biosynthetic pathway by converting tyrosine to DOPA (Choi et al. 2001; D’Mello et al. 2016; Kong et al. 2000). The inhibition of tyrosinase leads to blockade of melanin production. The reaction of tyrosinase (activity or inhibition) with test material is used as a measure of efficacy of the compound. Melanin, which is synthesized and matures in the melanosome, is transferred to keratinocytes where pigmentation occurs. Skin color is determined by melanin in the melanocytes. Melanocytes function predominantly by producing melanin pigment, which protects against and absorbs harmful ultraviolet (UV) radiation (D’Mello et al. 2016).
Effects of anti-wrinkle and skin-whitening fermented black ginseng on human subjects and underlying mechanism of action
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Jin Ju Park, Junmin An, Jung Dae Lee, Hyang Yeon Kim, Jueng Eun Im, Eunyoung Lee, Jaehyoun Ha, Chang Hui Cho, Dong-Wan Seo, Kyu-Bong Kim
The skin is a protective outer covering extending throughout the human body which protects internal tissues and organs. Human skin is composed of three primary layers; the epidermis, dermis, and hypodermis. The epidermis, the outermost layer of the skin, functions by protecting the body and is predominantly composed of keratinocytes, melanocytes, Langerhans, and Merkel cells. Keratinocytes are the most abundant cells found in the epidermis and function as a barrier against the external environment (McGrath, Eady, and Pope 2004; Winkelmann and Breathnach 1973). Melanocytes produce the colored pigment of melanin. Melanin occurs in two forms in human skin: eumelanin and pheomelanin. Eumelanin is black and brown melanin and common throughout the body, while pheomelanin is a red or yellow melanin pigment (Wakamatsu and Ito 2002). Melanin is biosynthesized from tyrosine. Tyrosine is converted to DOPA (3,4-dihydroxy-L-phenylalanine), which is then oxidized to DOPA-quinone and subsequently converted to DOPA-chrome. Melanin is finally generated through several intermediates and a series of biochemical steps. Tyrosinase plays a key role in the melanin biosynthetic pathway by converting tyrosine to DOPA (Choi et al. 2001; D’Mello et al. 2016; Kong et al. 2000). The inhibition of tyrosinase leads to blockade of melanin production. The reaction of tyrosinase (activity or inhibition) with test material is used as a measure of the efficacy of the compound. Melanin, which is synthesized and matures in the melanosome, is transferred to keratinocytes where pigmentation occurs. Skin color is determined by melanin in the melanocytes. Melanocytes function predominantly by producing melanin pigment, which protects against and absorbs harmful ultraviolet (UV) radiation (D’Mello et al. 2016).