Pathophys-Day 2 Photobiology

Question 1

What UV spectrum does the ozone layer block out and what is its wavelength range? Which one is fairly dependent on ozone concentration?

Answer 1

UVC, 290-200

UVB dep on ozone [ ]

Question 2

Which UV spectrum causes sunburn?

Answer 2

UVB, 290-320

Question 3

Which UV spectrum is filtered out by window glass?

Answer 3

UVB, 290-320

Question 4

What does SPF 50 tell you?

Answer 4

Would take 50x long to get as burned as without the sunscreen

Question 5

Does UVA penetrate glass?

Answer 5

Yes

Question 6

UVA range

Answer 6

320-400

Question 7

Which UV is the least potent?

Answer 7

UVA

Question 8

UV light from the sun is __% UVB and __ % UVA

Answer 8

5, 95

Question 9

Photoaging is caused by:

Answer 9

UVA (penetrates deeper)

Question 10

Which UV gives you wrinkles?

Answer 10

UVA

Question 11

Which UV spectrum penetrates the skin deepest?

Answer 11

UVA

Question 12

What are some modifiers of UVR?

Answer 12

Altitude (4% with 1000 ft)
Surface reflection (water<snow)
Cloud cover only scatters

Question 13

What is the deepest layer that C, B, and A get to

Answer 13

C gets to top of epidermis
B gets to top of dermis
A gets deep into dermis (vessels)

Question 14

What is an action spectrum?

Answer 14

determined by UV absorbing properties of molecule that initiates the response: chromophore

Question 15

What are some major UVB chromophores?

Answer 15

DNA, urocanic acid, aromatic AAs

Question 16

Which wavelength is used to treat psoriasis?

Answer 16

310 nm

Question 17

Which spectrum is most responsible for photodamage / effects of UV on skin?

Answer 17

UVB

Question 18

What are some acute effects of UVR on skin?

Answer 18

Inflammation/sunburn
Immunomodulation
Tanning (A immediate)
Epidermal hyperplasia
Vit D synthesis
DNA damage/apoptosis

Question 19

Explain erythema, heat, swelling, and pain of sunburn

Answer 19

Erythema: vasodilation
Heat: inc blood flow
Swelling: vasoperm inc
Pain: cytokine release

Question 20

Sunburn cells are what type and look like what

Answer 20

keratinocytes, purple blobs with fuzzy red halos

Question 21

Immediate tanning is caused by:

Answer 21

UVA and visible light cause oxidation and melanin redistribution (NOT production)

Not proective like a UVB tan

Question 22

Delayed tanning is caused by

Answer 22

UVB, 3 days or so later, inc melanin and inc transfer of melanosomes to keratinocytes

Photoprotective

Question 23

What is solar elastosis?

Answer 23

Accumulation of abnormal elastin in the skin as a result of photodamage

Question 24

What are some features of photoaging?

Answer 24

Inelastic
Telangiectasia
Irregular pigmentation: ephelides/freckles, solar lentigo/age spot, hypo pigmentation
Comedones and cysts
Actinic keratosis and malignancy
Benign growths

Question 25

Favre-Racouchot syndrome is?

Answer 25

skin disease in sun damaged individuals characterized by yellowish thickening of skin with nodules, comedones and follicular cysts WITCH FACE

Question 26

Compare UVB and UVA radiation damage

Answer 26

UVB is 20-50x more potent, but UVA is higher in quantity and penetrates deeper

Question 27

Which UV causes most DNA damage and how so?

Answer 27

UVB, through direct absorption (chromophore) and exposure to nearby chromophores

Question 28

What happens to DNA upon UV exposure?

Answer 28

covalent dimers of adjacent pyrimidines, either as cyclobutane dimers or 6,4 products (UVB specifically for 6,4)

Question 29

What are some signature UV mutations?

Answer 29

C->T | CC-> TT

Question 30

What mechanisms protect against UVR and what layer are they in?

Answer 30

``` Stratum corneum: reflection Melanin - absorption Tumor suppressors - p53, PTCH, CDKN2A DNA repair Apoptosis ```

Question 31

What is the defect in xeroderma pigmentosum?

Answer 31

Usually defects in nucleotide excision repair AR

Question 32

What three areas are involved in XP?

Answer 32

Skin, eyes, CNS

Question 33

What are the most common causes of death in XP?

Answer 33

Metastatic skin cancer and neurologic degeneration

Question 34

What cells are particularly vulnerable to DNA damage?

Answer 34

Lymphocytes and Langerhans - immunosuppression Langerhans disappear

Question 35

Describe why tanning bads are bad emk?

Answer 35

UVA mostly, 5x normal 10x less protective strong assoc w melanoma and non-mel skin cancer