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Unformatted text preview: Skin and Carcinogenesis Question 1; Skin Power Point Slides Ficks Law (simplified): Assuming low concentrations of organic compounds, the amount of uptake through the skin is proportional to: 1. Time of exposure 2. Surface area exposed 3. Concentration of the agent 4. Flux of the agent - the speed of travel through the skin barrier in units of distance per time; a property of the agent. Amount absorbed = (time of exposure)(surface area)(concentration of the agent)(flux) Amount absorbed = (2 hours)(10,000 cm 2 )(2ug/ml)(0.125 cm/hours) = 5000 ug = 5 mg Recall: cm 3 = 1 ml Question 2: Syllabus Skin Carcinogenesis p 4-5; Liver Carcinogenesis p 2-3 Initiation: Stable, heritable change -- DNA damage (point mutations, insertions/deletions, chromosomal breaks). Initiators are also known as genotoxic carcinogens. Promotion: Clonal expansion of initiated cells. Promoters are also known as nongenotoxic carcinogens (do not directly damage DNA). Complete Carcinogen: Causes cancer by itself; acts at both initiation and promotion stages. Initiators are generally complete carcinogens because they can cause cancer at high doses. They have intrinsic promoting activity, but are not pure promoters. Diethylnitrosamine Liver cancer Necrosis at high doses leads to regenerative repair process. Liver cells, which normally dont divide in the absence of damage, are stimulated to divide to fill in the gaps for the dead cells. Since the cells are dividing rapidly, DNA damage is often not repaired, and mutations result. DNA damage is often not repaired, and mutations result....
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- Winter '06