Hair follicles human skin

Ahsan MK, Urano Y, Kato S, (Dura H, Arase S. Immunohistochemical localization of thyroid hormone nuclear receptors in human hair follicles and in vitro effect of L-triiodothyronine on cultured cells of hair follicles and skin. J Med Invest 1998 44(3 ) 179-84. 

Nickel salts penetrate very slowly into the human skin [272-274] and little enhancement by sweat or detergents has been observed [272]. In addition, an initial rapid phase of uptake through the sweat ducts and hair follicles has been suggested [271, 275],... 

Grams, Y. Y. and Bouwstra, J. A., Penetration and distribution of three lipophilic probes in vitro in human skin focusing on the hair follicle. J. Control. Release, 83, 253-62, 2002. 

Although most patch testing is done with nickel sulfate because it is less irritating than nickel chloride, exposure of the skin to nickel alloys results in the release of nickel chloride from the influence of human sweat. Therefore, nickel chloride is the more relevant form of nickel for examining threshold concentrations (Menne 1994). Menne and Calvin (1993) examined skin reactions to various concentrations of nickel chloride in 51 sensitive and 16 nonsensitive individuals. Although inflammatory reactions in the sweat ducts and hair follicles were observed at 0.01% and lower, positive reactions to nickel were not observed. To be scored as a positive reaction, the test area had to have both redness and infiltration, while the appearance of vesicles and/or a bullous reaction were scored as a more severe reaction. At 0.1%, 4/51 and 1/51 tested positive with and without 4% sodium lauryl sulfate. Menne et al. (1987) examined the reactivity to different nickel alloys in 173 nickel-sensitive individuals. With one exception (Inconel 600), alloys that released nickel into synthetic sweat at a rate of <0.5 pg/cmVweek showed weak reactivity, while alloys that released nickel at a rate of >1 pg/cm /week produced strong reactions. 

Grams, Y.Y., et al. 2003. Permeant lipophilicity and vehicle composition influence accumulation of dyes in hair follicles of human skin. Eur J Pharm Sci 18 329. 

Keratins are insoluble proteins that make up such structures as hair, skin, nails, wool, and feathers and form the cytoskeleton structures in all cells of epithelial origin. Along with other fibrous proteins of the same dimensions (e.g., neurofilaments), keratin has been referred to as intermediary filament (IF). In the human being, keratin is one of the more abundant proteins. The basic keratin unit is a relatively small protein with a molecular weight of 40,000-70,000. About 20 different keratin polypeptides have been identified in human hair follicles, various epithelial cells, and tumor cells. They have been assigned numbers 1-20 and have been divided into two classes acidic (type 1) and neutral/base (type 2). A given tissue or cell line will have a characteristic keratin polypeptide distribution, as shown in Table 8.2. However, both types of peptides are always present in a given cell. 

Little information is available regarding the toxieokineties of lewisite. Lewisite is readily absorbed by mueous membranes and, beeause of its lipophilicity, dermal absorption is signitieant (HSDB, 2004). Dermal absorption is reportedly more rapid than for sulfur mustard (Hurst and Smith, 2008). Axehod and Hamilton (1947) reported that radiolabeled ( " As) lewisite applied to a 0.4S em area of human skin was primarily fixed on the epidermis and that very little was found in the dermis most was detected in hair and hair follicles. In experiments with guinea pigs, histological examination revealed that lewisite applied to skin entered epidermis within 2 min and penetrated into the dermis within 10 min (Ferguson and Silver, 1947). Only trace amounts were detectable in the dermis at 24 h post-application. 

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