Pathophys-Day 2 Photobiology Flashcards
What UV spectrum does the ozone layer block out and what is its wavelength range? Which one is fairly dependent on ozone concentration?
UVC, 290-200
UVB dep on ozone [ ]
Which UV spectrum causes sunburn?
UVB, 290-320
Which UV spectrum is filtered out by window glass?
UVB, 290-320
What does SPF 50 tell you?
Would take 50x long to get as burned as without the sunscreen
Does UVA penetrate glass?
Yes
UVA range
320-400
Which UV is the least potent?
UVA
UV light from the sun is __% UVB and __ % UVA
5, 95
Photoaging is caused by:
UVA (penetrates deeper)
Which UV gives you wrinkles?
UVA
Which UV spectrum penetrates the skin deepest?
UVA
What are some modifiers of UVR?
Altitude (4% with 1000 ft)
Surface reflection (water<snow)
Cloud cover only scatters
What is the deepest layer that C, B, and A get to
C gets to top of epidermis
B gets to top of dermis
A gets deep into dermis (vessels)
What is an action spectrum?
determined by UV absorbing properties of molecule that initiates the response: chromophore
What are some major UVB chromophores?
DNA, urocanic acid, aromatic AAs
Which wavelength is used to treat psoriasis?
310 nm
Which spectrum is most responsible for photodamage / effects of UV on skin?
UVB
What are some acute effects of UVR on skin?
Inflammation/sunburn Immunomodulation Tanning (A immediate) Epidermal hyperplasia Vit D synthesis DNA damage/apoptosis
Explain erythema, heat, swelling, and pain of sunburn
Erythema: vasodilation
Heat: inc blood flow
Swelling: vasoperm inc
Pain: cytokine release
Sunburn cells are what type and look like what
keratinocytes, purple blobs with fuzzy red halos
Immediate tanning is caused by:
UVA and visible light cause oxidation and melanin redistribution (NOT production)
Not proective like a UVB tan
Delayed tanning is caused by
UVB, 3 days or so later, inc melanin and inc transfer of melanosomes to keratinocytes
Photoprotective
What is solar elastosis?
Accumulation of abnormal elastin in the skin as a result of photodamage
What are some features of photoaging?
Inelastic Telangiectasia Irregular pigmentation: ephelides/freckles, solar lentigo/age spot, hypo pigmentation Comedones and cysts Actinic keratosis and malignancy Benign growths
Favre-Racouchot syndrome is?
skin disease in sun damaged individuals characterized by yellowish thickening of skin with nodules, comedones and follicular cysts
WITCH FACE
Compare UVB and UVA radiation damage
UVB is 20-50x more potent, but UVA is higher in quantity and penetrates deeper
Which UV causes most DNA damage and how so?
UVB, through direct absorption (chromophore) and exposure to nearby chromophores
What happens to DNA upon UV exposure?
covalent dimers of adjacent pyrimidines, either as cyclobutane dimers or 6,4 products (UVB specifically for 6,4)
What are some signature UV mutations?
C->T
CC-> TT
What mechanisms protect against UVR and what layer are they in?
Stratum corneum: reflection Melanin - absorption Tumor suppressors - p53, PTCH, CDKN2A DNA repair Apoptosis
What is the defect in xeroderma pigmentosum?
Usually defects in nucleotide excision repair
AR
What three areas are involved in XP?
Skin, eyes, CNS
What are the most common causes of death in XP?
Metastatic skin cancer and neurologic degeneration
What cells are particularly vulnerable to DNA damage?
Lymphocytes and Langerhans - immunosuppression
Langerhans disappear
Describe why tanning bads are bad emk?
UVA mostly, 5x normal
10x less protective
strong assoc w melanoma and non-mel skin cancer
