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Body Systems: The Basics
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
Humans are distinct from other mammals because we are basically naked (Jablonski, 2006). While most mammals have a layer of protective hair on their bodies, the hair on the bodies of humans is very fine and often unnoticeable with the exception of some areas, like the head. Dermal layer sebaceous glands (only found associated with hair follicles) produce sebum, a combination of fatty compounds and cellular debris. The oily, waxy sebum flows along the hair shaft to the surface, to lubricate the hair and skin. Sweat glands also lie in the dermis and exit to the skin. Apocrine sweat glands are found in the armpits and groin. Eccrine sweat glands are found all over the body. Sweat glands produce a water-based solution of many different salts and body chemicals. Sweat from apocrine glands differs in composition from eccrine gland sweat. The composition of sweat and sebum produced by the skin has to be considered when designing products like hats and shirts with fitted collars that are in close contact with the skin and may easily pick up body oil and perspiration. Some materials are difficult to clean when they absorb body oils.
Optimized protocol for the biocompatibility testing of compression stockings and similar products with close skin contact in vitro
Published in The Journal of The Textile Institute, 2018
Cornelia Wiegand, Tanja Hansen, Johanna Köhnlein, Ines Exner, Marlen Damisch-Pohl, Peter Schott, Ulrike Krühner-Wiesenberger, Uta-Christina Hipler, Ernst Pohlen
A further step to create more in vivo-like testing conditions was to change the extraction medium from the cell culture medium (DMEM with FCS) to an acidic sweat solution. Sweat solutions, both acidic and alkaline, are applied for testing color fastness of textiles (DIN ISO 105-E04, 2008). Sweat is produced in the body as a secretion from eccrine and apocrine sweat glands. The main components of eccrine sweat are water and salts with only little proteins. At low sweat rates and maximal time for HCO3− reabsorption, the sweat acidifies to pH values approaching 5.0 and below (Burry et al., 2001). A shift of the pH of the eccrine sweat up to pH 6.0 may occur with excessive sweating. The eccrine sweat glands are distributed all over the body and there are only specific areas with apocrine sweat glands as armpits, nipples, genital and anal area. In these areas, the pH may shift to a more alkaline value due to a mixing of eccrine and apocrine sweat (Nagel, 2012). Here, only the acidic sweat solution was used as it is more likely that compression stockings come into contact with eccrine sweat in a pH range of about 4.5–6.0. It could be shown that the artificial acidic sweat solution is suitable extraction media. However, direct application of the extracts on the cells should be avoided because due to a nutrient deficiency in the sweat solution cells die when incubated over a longer period with sweat solution alone (Lee et al., 2011; Shin, Bakin, Rodeck, Brunet, & Arteaga, 2001). An apoptotic mode of action is probable, supported by the fact of increasing cellular ATP content. This theory has to be validated by corresponding assays e.g. measurement of the induction of the effector-caspase 3/7. Here, to avoid this effect, the preparation of a double-concentrated extract at a ratio of 2.5 cm2:mL followed by augmentation with cell culture medium (ratio 1:1) was employed. This approach is in accordance with DIN EN ISO 10993-5 which states to mix the extraction medium with cell culture medium if the extraction medium is non-physiologic (e.g. not containing nutrients) and therefore detrimental to the cells. Thereby, cells are supplied with enough nutrients to keep them sustained over the study period. In addition, augmentation of the extract with culture medium also has an influence on the pH raising it from 5.5 to 6.2 and therefore, establishing conditions cultured cells are more used to. Extracts of the products A to F prepared in acidic sweat solution exhibited no negative influence on HaCaT keratinocyte viability in vitro and no direct cytotoxic effects were observed for the extracts of the compression stockings tested measured as release of LDH. Hence, it can be concluded that the extraction force is a function of the pH. While similar effects were observed for the compression stocking extracts using DMEM (pH 7.4) or an alkaline sweat solution with pH 8.0 (data not shown), the extracts with the acidic sweat solution (pH 5.5) of the products A to F showed good cell compatibility. Under the acidic conditions, potentially toxic residues such as dyes and other additives possess a lower solubility and can therefore be expected to remain in the material.