Search

everythinglearnresearchcommunity

for

Search:↓

The study investigated the effects of multiple exposures to 12-O-tetradecanoylphorbol-13-acetate (TPA), mezerein, and ethyl phenylpropriolate (EPP) on murine epidermal cells, focusing on the induction of ornithine decarboxylase (ODC) activity. While single applications of these agents caused similar hyperplasia and ODC induction, multiple treatments revealed significant differences in ODC activity, with TPA and mezerein inducing more than EPP. Immunocytochemical analysis showed distinct patterns of ODC-positive cells, with TPA prominently affecting perifollicular cells, mezerein affecting both interfollicular and perifollicular areas, and EPP affecting only interfollicular cells. Flow cytometry identified three keratinocyte subpopulations, with TPA causing the expansion of an intermediate-sized subpopulation not seen with EPP or mezerein. The findings suggested that TPA, a potent tumor promoter, selectively expanded a keratinocyte subpopulation hyperinducible for ODC, potentially important for neoplastic transformation, while mezerein and EPP were less effective in this regard.

The study investigated the expression of ornithine decarboxylase (ODC) in mouse skin treated with the tumor promoter TPA. It was found that ODC expression was heterogeneous, with high levels predominantly in suprabasal cells around hair follicles shortly after TPA treatment. This expression was transient, disappearing within 16 to 24 hours, but persisted in some cells within benign papillomas a week after TPA application. Pretreatment with retinoic acid or cycloheximide inhibited ODC expression. The findings suggested that both normal and tumor tissues in mice exhibited varied ODC expression.

In this study, researchers investigated the effects of a mutant Adenovirus E1a oncoprotein, NTdl646, on keratinocyte growth and differentiation in transgenic mice. The protein was expressed specifically in the skin using a keratin 5 promoter, resulting in two lines of mice with abnormal hair phenotypes, including short, crooked hair shafts and dystrophic or absent inner root sheaths. Despite these hair follicle maturation disturbances, the interfollicular epidermis remained normal, and there was no increase in spontaneous or chemically induced skin tumors. The study concluded that while the transgene disrupted keratinocyte maturation, it did not lead to increased epidermal proliferation or neoplastic growth.

The study presented a tracheal xenotransplantation assay as a simple in vivo system to evaluate epithelialization, hair follicle formation, and tumorigenesis using primary epidermal cells from wild-type and transgenic mice. This method involved seeding epithelial cells into deepithelialized rat tracheas, which were then transplanted into athymic nude mice. The study found that keratinocytes overexpressing ornithine decarboxylase (ODC) and infected with v-Ha-ras became invasive, penetrating all layers of the tracheal wall, similar to malignant skin carcinomas in ODC/Ras transgenic mice. The assay also demonstrated its utility in hair follicle reconstitution, showing that freshly harvested epithelial cells were more effective than cultured ones in forming hair follicles. The method proved advantageous for studying keratinocyte stem cell colonies and factors affecting hair follicle development, especially when cell numbers were limited.