Abstract
Bloor 1 has shown relationships between physiological activity and the nature of the lipids in various tissues of the animal body. A high degree of activity is paralleled by a high phospholipid to cholesterol ratio. Since cells of the epidermis undergo a marked change in physiological activity during keratinization, we determined some of the lipids in epidermal cells before and after this process. The epidermis was separated from the cutis by digesting the skin, from which all subcutaneous fat had been removed, in cold 1% acetic acid. The completeness of the separation was confirmed by microscopic examination of sections of the skin. Several samples of epidermis were analyzed separately. Since it was impossible to obtain sufficiently large samples composed entirely of stratum germinativum, material containing considerable but varying quantities of this layer of active cells was scraped from the proximal surface of the epidermis and analyzed. Samples composed entirely of stratum corneum, trimmed from the soles of feet, were obtained from chiropodists and the lipids in keratinized cells determined. Skin from palms and soles of human cadavers was used because of the absence of hair and sebaceous glands and the greater thickness of the epidermis on these parts.
The material for analysis was cut into fine bits with scissors, or by passing it through a meat chopper, and extracted with hot alcohol vapors in a continuous extractor for 12 hours, changing the alcohol every 3 hours. The combined alcohol extracts were evaporated under diminished pressure and the residue extracted with ethyl ether. The ether extract was made up to volume in a volumetric flask and aliquots were used for the analyses.
The con~pleteness of this extraction method was tested by saponifying several samples of extracted material with concentrated sodium hydroxide and extracting the remaining lipids with petroleum ether after acidification.
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