Questions and Answers
Which factor is known to stimulate the expression of ornithine decarboxylase (ODC)?
What type of chemicals are known to partially inhibit the activity of ornithine decarboxylase?
Which of the following is NOT a stimulant for ornithine decarboxylase expression?
Which of the following factors is known to inhibit ornithine decarboxylase expression?
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What is the effect of eflornithine on cancer in animal models?
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Which of the following is a hormone that stimulates ornithine decarboxylase expression?
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Which environmental factor is known to stimulate ODC expression?
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Which of the following treatments is known to block the induction of ODC activity?
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What type of skin condition is mentioned to have hyperproliferation related to the inhibition of ODC?
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Which category of substances includes compounds that stimulate ornithine decarboxylase expression?
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Study Notes
Skin Structure and Cells
- Melanocytes are present in relatively fewer numbers in the epidermis, accounting for 3-5% of total skin cells.
- Meissner's corpuscles are located in the papillary dermal tips, contributing to touch sensation.
- Dermal collagen increases with reduced spacing between bundles, indicating denser connective tissue.
- The epidermis lacks pilosebaceous units (hair follicles and sebaceous glands) in the stratum spinosum (Malpighian layer).
Epidermal Cell Types
- Keratinocytes constitute 90-95% of the epidermal cells; they are essential for producing keratin filaments that form the cytoskeleton.
- Melanocytes contribute to skin pigmentation, with neural crest origins.
- Langerhans cells and Merkel cells are other important epidermal cell types, derived from mesoderm.
Keratinocyte Characteristics
- Keratinocytes regenerate continually through division and differentiation.
- They exhibit tennis racket-shaped nuclei, an indicator of their specialized structure.
- E-cadherin receptors are crucial for intercellular connections among keratinocytes.
Ornithine Decarboxylase (ODC) Expression
- ODC expression is stimulated by several factors linked to cellular proliferation:
- Trauma and UV radiation (particularly UVB).
- EGF (Epidermal Growth Factor).
- Hormones such as androgens (and estrogens).
- Tumor promoters, including some chemicals and cytokines.
- Asbestos exposure is linked to increased ODC activity in miners.
- ODC expression is partially inhibited by:
- Retinoic acid, corticosteroids, and vitamin D3.
- In psoriatic skin, ODC hyperproliferation occurs, impacting keratinocyte growth.
- Eflornithine (difluoro-methylornithine) is noted for its efficacy in reducing cancer in animal studies.
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Description
This quiz explores key aspects of skin anatomy, focusing on the role of melanocytes, Meissner's corpuscles, and the characteristics of dermal collagen. Additionally, it highlights changes in skin structure relevant to health and aging. Enhance your understanding of skin physiology with this informative quiz.
