Skin image analysis for vitiligo assessment
Ahmad Fadzil Mohamad Hani, Dileep Kumar in Optical Imaging for Biomedical and Clinical Applications, 2017
Skin functions are insulation and temperature regulation, sensation, vitamin D and B synthesis, and protection against pathogens. Skin has three primary layers: epidermis, dermis and hypodermis (subcutaneous tissue) (Rosebury, 1969). The epidermis provides protection against infection. The dermis serves as location for the appendages of skin. The hypodermis serves as the basement of skin membrane. The epidermis consists of keratinocytes, melanocytes, Langerhans cells and Merkel cells. There are no blood vessels in the epidermis and it is nourished by diffusion from the dermis. Epidermis is divided into five sublayers (strata), which are (from superficial to deep) strata corneum, strata lucidum, strata granulosum, strata spinosum, and strata basale. Epidermis cells are formed through mitosis at the innermost layers (Figure 3.1). Skin has a pigment melanin that absorbs some of the potentially dangerous ultraviolet radiation in sunlight. Melanin is a colour pigment found in skin, eyes and hair. It is produced by melanocytes through processes called melanogenesis. Melanocytes are epidermis cells that are located in the bottom layer of the epidermis, as shown in Figure 3.2. The density of melanocytes in skin does not vary among different ethnic origins; however, skin pigmentation differs due to variations in the rate of melanin production. The dermis is the second primary layer of skin and is located beneath the epidermis. It is connected to the epidermis by a basement membrane. There are many sensors and glands located in the dermis. The nerves that are related to sense of touch and heat, hair follicles, sweat glands, sebaceous glands, apocrine glands and blood vessels are all located in the dermis. The blood vessels in the dermis provide nourishment and removes waste. The hypodermis is the last layer of skin and lies below the dermis. It attaches the skin to underlying bone and muscle, and supplies skin with blood vessels and nerves.
The Integumentary (Dermatologic) System and Its Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
The skin, which covers the body's entire surface, is its largest organ. It is composed primarily of two layers. The outer layer is the epidermis, named for the prefix epi-, meaning "upon" (as in epigastric, the area "upon" the stomach, and epidural, on or over the dura mater) and the root derm. The second layer is the dermis or corium, the thicker layer of connective tissue beneath the epidermis and named for the Greek word for skin (see Figure 8.1). The epidermis is composed of up to five layers called strata. There are no blood vessels in these epithelial tissues, and the epidermis contains the melanocytes that produce the pigment melanin and dead cells containing the fibrous protein keratin. Skin pigmentation results from the presence of melanin (mela = black), the yellow pigment carotene (the yellow pigment in carrots), and the color of blood reflected through the epidermis. The main function of melanin is to screen out excessive ultraviolet radiation. The thickness and number of these layers of the epidermis varies throughout the body. The dermis or "true skin" is a strong, flexible meshwork of fibrous connective tissue. The upper or papillary layer derives its name from the Greek word for pimple, the same root denoting the bumps in a "maculopapular rash"; the papillary layer contains numerous small projections that join it to the epidermis. The lower reticular layer contains blood and lymph vessels, nerves, fat (or adipose cells), oil glands, and hair roots (see Figure 8.1). The hypodermis or subcutaneous layer of loose, fibrous connective tissue lies below the dermis. It contains lymph and blood vessels, nerves, sweat gland ducts, and hair follicle bases, as well as the adipose cells. The sudoriferous or sweat glands are found over almost the entire surface of the skin, particularly on the palms of the hands and soles of the feet. These glands function to regulate body temperature. There are two types of sweat glands; the eccrine glands are embedded in the hypodermis, and the apocrine glands are found in the armpits, dark region around the nipples, and the anal and genital regions. Apocrine glands are larger and more deeply located than the eccrine glands and respond to stress rather than heat.
Melanotropic Peptides: Biomedical Applications
Mac E. Hadley in The Melanotropic Peptides, 2018
The human skin is populated by pigment cells, melanocytes, whose function is to produce melanin. Melanin provides a sunscreen to protect the skin from the harmful (cancer-producing) rays of the sun. Sun tanning is, in fact, an adaptive response in which these pigment cells produce even more melanin to protect the skin under conditions of continued solar exposure. Unfortunately, these pigment cells are themselves vulnerable to the mutagenic (carcinogenic) actions of solar (ultraviolet) radiation. Melanocytes are converted into cancer cells, specifically, melanoma cells. Melanoma cells proliferate to form tumors in the skin, but then melanoma cells almost invariably metastasize to other parts of the body. Early surgical removal is important, since chemotherapeutic treatment strategies are presently ineffective in eradicating the cancer. Melanoma is notorious for its difficulty of early detection and refractoriness to chemotherapy. Worldwide statistics indicate that the incidence of melanoma is increasing. The cutaneous melanomas are a group of malignancies for which there is a premium on diagnosis at the in situ and early invasive phases. There is a definate association between progressive depth of invasion and a worse prognosis. Clearly there is a mandate to (1) provide a method for early diagnosis, and, if metastasis has occurred to (2) provide a means for localizing the disseminated lesion as well as (3) provide a method of directing chemotherapeutic agents for eradication of the melanoma; it is also paramount to (4) understand more clearly the cellular physiology of the melanoma cell so that the above objectives can be approached with some realistic hope of success.
Melanin as a potential cryptococcal defence against microbicidal proteins
Published in Medical Mycology, 1999
T.L. DOERING, J. D. NOSANCHUK, W. K. ROBERTS, A. CASADEVALL
Cryptococcus neoformans is an important fungal pathogen that synthesizes melanin when grown in the presence of phenolic substrates. The ability of C. neoformans to produce melanin is associated with virulence, but the specific role of melanin in the pathogenesis of infection is not clear. In this study the ability of C. neoformans melanin to bind proteins and protect against microbicidal peptides was investigated. Melanin was shown to bind a variety of proteins of fungal and mammalian origin. Melanin-protein interactions were dependent on the pH of the solution and on the amount of protein and melanin present. Melanized cells were less susceptible to killing by three microbicidal peptides: a defensin, a protegrin, and a magainin. Incubation of the microbicidal peptides with melanin particles, followed by removal of the melanin, reduced or abolished fungicidal activity, demonstrating interactions between peptides and melanin. The ability of melanin to bind proteins and to protect against microbicidal peptides suggests a protective function for melanin, whereby it sequesters microbicidal peptides and abrogates their activity.
Effect of melanin biosynthesis inhibiting compounds on
Published in Mycologia, 1995
Inhibition of melanin production was observed in Gaeumannomyces isolates treated with DHN-melanin inhibiting compounds (tricyclazole, pyroquilon, fthalide and chlobenthiazone) but not with DOPA-melanin inhibiting compounds (tropolone, kojic acid, 2-mercaptobenzimidazole and diethyldithiocarbamate). This indicates that the melanin associated with cell walls of G. graminis and G. incrustans is DHN-melanin. Depending on the compound, consistent inhibition of melanin was observed at levels that were not inhibitory to fungal growth. In vitro pathogenicity to wheat by these isolates was not affected by the DHN-melanin compounds.
Isoimperatorin (ISO) reduces melanin content in keratinocytes via miR-3619/CSTB and miR-3619/CSTD axes
Published in Bioscience, Biotechnology, and Biochemistry, 2020
Bijun Zeng, Kai Li, Zhibo Yang, Haizhen Wang, Chang Wang, Pan Huang, Yi Pan
ABSTRACT Melanin metabolism disorders may cause severe impacts on the psychological and social activities of patients. Different from the other two steps of melanin metabolism, namely synthesis and transport, little has been known about the mechanism of melanin degradation. Isoimperatorin (ISO) suppressed the activity of tyrosinase, an essential enzyme in melanin biosynthesis, hence, we investigated the effects and mechanism of ISO in melanin reduction. ISO stimulation significantly reduces the melanin contents and PMEL 17 protein levels; meanwhile, the activity and the protein levels of two critical lysosomal enzymes, Cathepsin B and Cathepsin D, can be significantly increased by ISO treatment. MiR-3619 inhibited the expression of CSTB and CSTD, therefore affecting ISO-induced degradation of melanin. In summary, ISO reduces the melanin content via miR-3619/CSTB and miR-3619/CSTD axes. ISO could be a potent skin-whitening agent, which needs further in vivo and clinical investigation.