By Ashley H. Robins
Dermis colour might be the main decisive and abused actual attribute of humankind. This publication offers a multidisciplinary evaluate of ways and why human populations differ so markedly of their dermis colour. The organic features of the pigment mobilephone and its construction of melanin are reviewed. The features of melanin within the dermis, mind, eye and ear are thought of, and the typical scientific abnormalities of pigmentation, similar to albinism, are defined and illustrated. specific reflectance facts from around the world surveys of dermis colour also are offered. subsequent, old and modern backgrounds of the phenomenon are explored on the subject of the so-called colour challenge in society. eventually, the potential evolutionary forces that form human pigmentation are assessed.
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Extra resources for Biological Perspectives on Human Pigmentation
Moreover, as Everett et al. (1979) have demonstrated, both single and aggregated melanosomes are observed in all racial groups from light-skinned Caucasoids to dark-skinned Negroids. The partitioning of melanosomes into either a single or an aggregated state is determined not by race but by melanosome size. The latter factor seems to be the critical one, and a cut-off point was defined by Toda et al. (1972). lSjum (along the major axis) were always aggregated. , 1979). , 1979) the latter occurred in complexes of only two or three, whereas those of Caucasoids consisted of five or more melanosomes.
These subunits are the intermediate compounds in the tyrosine-melanin pathway (from dopaquinone onwards) which randomly co-polymerize to form the highly irregular three-dimensional configuration that is eumelanin (Fig. 1). Melanin is bound to protein within the melanosomes to become melanoprotein, a binding that reinforces the nightmare of chemical analysis. Phaeomelanin The biosynthesis of phaeomelanin follows the same route as that of eumelanogenesis up to dopaquinone. Dopaquinone then combines with the sulphydryl-containing amino acid cysteine to form 5-5-cysteinyldopa.
192). Recent work has shown that many patients with melanoma have oestrogen receptors in their tumours, although the role of these is undetermined. It is still not clear how the sex steroids enhance pigmentation, although it is possible that they interact with MSH peptides. In certain mammals ovarian hormones have been shown to stimulate the secretion of MSH by the pituitary (Friedmann & Thody, 1986). Modifications in hormone balance Pregnancy One of the early signs of pregnancy is darkening of the nipples and areolae and, to a lesser extent, of the face, anterior abdominal wall and genitalia.