THE SKIN OF HAIRLESS MICE .2. AGEING CHANGES AND THE ACTION OF 20-METHYLCHOLANTHRENE

[摘要] Ageing skin of hairless mice shows an increase in the number of cysts and a progressive accumulation of Schiff-reactive cells in the dermis. Animals 7 months or older acquire numerous multinucleated, foreign body giant cells, the cytoplasm of which is Schiff-reactive and stains metachromatically. In old animals these cells form spherules which contain a mucoid residue. Four days after the application of methylcholanthrene, the sebaceous glands are destroyed and their ducts, the former pilosebaceous canals, form solid epithelial cords. Ten days after the application of the carcinogen, the epidermis is repaired and it is thicker and more basophilic than untreated control skin. Sebaceous glands redifferentiate and the epithelial cords become patent. Of the 24 mice used in this experiment, 19 developed skin growths after the application of the carcinogen. The first growths appeared 31 to 46 days after treatment in mice aged 1.5-4.5 months at the time of treatment. Most of the small growths were aggregates of hyperplastic sebaceous glands and the larger ones resembled sebaceous adenomas. The few typical papill-omas developed on the scars of biopsy wounds. Since these areas are free of epidermal appendages, papillomas could have arisen only from the epidermis. Several months after treatment, skin growths appeared also in areas which were not painted with the carcinogen. Two hairless mice developed squamous cell carcinomas 18 months after treatment with methylcholanthrene.