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The document discussed the distinction between hirsutism and hypertrichosis, emphasizing the role of androgens produced by the ovaries and adrenal glands in female hair growth. It highlighted that while treatments for hirsutism can prevent or slow new hair growth, existing hair must be removed through methods like electrolysis or laser removal. Eflornithine, a topical drug, was noted for its ability to inhibit an enzyme essential for hair growth, showing visible improvement within weeks.

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.

The study demonstrated that ornithine decarboxylase (ODC) played a significant role in hair follicle development and hair growth by being associated with cell proliferation and commitment. ODC was expressed in embryonic epidermis at sites of follicle development and persisted in proliferating bulb cells of anagen follicles, except at the base of the bulb. Its expression decreased as follicles entered catagen and resumed with new follicle initiation. In vibrissae, ODC showed a complex expression pattern, being present in both the bulb and hair shaft, and in outer root sheath cells near the follicle bulge, suggesting a link to hair follicle stem cells.

The study developed a transgenic mouse model to investigate the role of ornithine decarboxylase (ODC) in tumor promotion. By overexpressing ODC in hair follicle keratinocytes of C57Bl/6 mice using a tetracycline-regulated system, researchers found that high levels of ODC activity led to significant epidermal hyperplasia and increased sensitivity to tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA). This effect was reversible with doxycycline, which repressed transgene expression. The findings indicated that enhanced ODC expression converted the typically tumor-resistant C57Bl/6 mice to a tumor-sensitive phenotype, highlighting the potential role of ODC in tumor promotion.

The study developed a transgenic mouse model to investigate the role of ornithine decarboxylase (ODC) in tumor promotion. By using a tetracycline-regulated system, researchers were able to overexpress ODC specifically in hair follicle keratinocytes of C57Bl/6 mice. In the absence of doxycycline, these mice showed high levels of epidermal ODC activity and hyperplasia when exposed to the tumor promoter TPA, particularly affecting hair follicles. This increased ODC expression made the typically tumor-resistant C57Bl/6 mice more sensitive to tumor-promoting effects. However, when doxycycline was used to repress ODC expression, the number of papillomas was significantly reduced, demonstrating the critical role of ODC in tumor promotion.

The study investigated the role of ornithine decarboxylase (ODC) in skin carcinogenesis by using genetically modified mice to direct ODC expression to specific epidermal compartments. It was found that K6-driven ODC over-expression in the outer root sheath of hair follicles significantly increased tumorigenesis compared to K14-driven ODC expression in inter-follicular epidermal keratinocytes. Mice with K6-ODC expression developed an average of 15 tumors per mouse, while K14-ODC mice developed 6.8 tumors per mouse. The K6-ODC mice also showed higher UVB-induced proliferation, pro-inflammatory responses, and a greater number of stem-like cells, with reduced Notch1 expression linked to stem cell expansion. The study concluded that ODC enhances tumorigenesis by negatively regulating the Notch pathway, leading to an expansion of the stem cell compartment.

The study investigated the role of polyamines in hair follicle function and fiber composition in sheep. It found that inhibiting ornithine decarboxylase with alpha difluoromethylornithine altered fiber characteristics but did not inhibit wool follicle growth in culture. Conversely, inhibiting S-adenosylmethionine decarboxylase with methylglyoxal (bis)guanylhydrazone completely inhibited fiber growth, which could be reversed by adding spermidine, but not spermine. The study concluded that polyamines, particularly spermidine, were crucial for hair growth, as evidenced by the ability of spermidine to partially counteract growth depression in methionine-deficient conditions.

The study investigated hair regrowth in C3H mice of varying ages by examining enzyme activities in different skin areas after shaving. It was found that hair regrowth was irregular and delayed as the mice aged, with older mice showing more significant delays. Biochemical analysis of 18 mice revealed that enzyme activities, specifically ornithine decarboxylase (ODC), transglutaminase (TGase), and alkaline phosphatase (Al-P), were significantly higher in areas where hair was regrowing compared to non-growing areas. This suggested that these enzymes played a role in hair regrowth, with increased activity in follicle-rich regions.

The study demonstrated that overexpression of ornithine decarboxylase (ODC) in mouse skin was sufficient to promote tumor formation. Transgenic mice with high levels of ODC expression in epidermal keratinocytes were more susceptible to tumor initiation with a single low dose of carcinogen, and they did not require additional tumor promoters for tumor development. The research suggested that the primary target cells for chemical carcinogens in the skin were located in hair follicles, and that ODC overexpression could activate these cells to form epidermal tumors.

The study investigated the expression of ornithine decarboxylase (ODC) and keratins in early papillomas in SENCAR mice to identify markers for early stages of skin tumorigenesis. Tumors were induced using 7,12-dimethylbenzanthracene and promoted with 12-O-tetradecanoylphorbol-13-acetate. In early papillomas, keratin 1 (K1) showed patchy staining, while keratin 10 (K10) was minimally expressed, indicating altered differentiation patterns. ODC expression was intense and diffuse in suprabasal cells of papillomas, correlating with decreased K1 and K10 expression. These findings suggested that high ODC expression and reduced K1 and K10 could serve as phenotypic markers for early tumorigenesis in mouse skin.

The study investigated the effects of expressing a mutant H-ras oncogene in different epidermal cell types in mice, revealing that targeting hair follicle cells led to the development of benign skin tumors that often progressed to malignant squamous and spindle carcinomas. This contrasted with previous findings where expression in interfollicular cells did not lead to spontaneous malignancy. The study involved 464 animals, with 30% developing skin tumors, highlighting the significant influence of the targeted cell type on the malignant potential of tumors, with hair follicle cells being a primary source of tumors at high risk of malignant conversion.