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Fitz 9th > 17 - Cutaneous Photobiology > Flashcards

17 - Cutaneous Photobiology Flashcards

1
Q

Radiation can only cause a photobiologic response if

A

It is first absorbed by a molecule (chromophore) in the skin

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2
Q

UV-signature mutations

A

C to T and CC to TT mutations at dipyrimidine sites

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3
Q

Y/N: Photoaging is reversible.

A

No

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4
Q

Carries sufficient photon-energy to completely remove an electron from an atom or molecule

A

Ionizing electromagnetic radiation

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5
Q

Examples of ionizing electromagnetic radiation

A

X-rays

Gamma rays

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8
Q

Shortest wavelength of solar electromagnetic radiation reaching the earth’s surface

A

290 nm

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9
Q

Y/N: Longer wavelengths of UVR are highly damaging to animals and plants

A

No - shorter wavelengths

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10
Q

Energy (increases/decreased) with increasing wavelength

A

Decreases

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11
Q

ROYGBIV is arranged according to increasing

A

Wavelength

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12
Q

Spectrum of electromagnetic radiation from lowest to highest energy

A 
Radio waves
Infrared
Visible
Ultraviolet
X-rays
Gamma rays

Roman men Invented Very Unusual Xray Guns

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13
Q

(Shorter/longer) wavelengths of visible light are more filtered by a linger passage through the atmosphere

A

Shorter

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14
Q

Fraction of UVA relative to UVB (increases/decreases) with lower angles of solar radiation

A

Increases

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15
Q

Y/N: UVA and UVB are less abundant early or late in the day

A

Yes

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16
Q

States that light must be first absorbed by a chemical substance for a photochemical reaction to take place

A

Grotthuss-Draper law

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17
Q

One wavelength that is most likely to excite a chromophore

A

Absorption maximum

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18
Q

Well characterized chromophores in the skin (3)

A

DNA
Porphyrins
Melanin

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19
Q

Process in which energy from an excited chromophore is transferred to another molecule

A

Photosensitized reaction

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20
Q

States that the wavelength of fluorescence is always longer (=less energetic) than the exciting wavelength

A

Stokes law

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21
Q

Photon emission from return of triplet excited states to ground states

A

Phosphorescence

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22
Q

Major role of vitamin D

A

Increase the flow of calcium into the bloodstream

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23
Q

Safe upper limit for adult intake of vitamin D

A

10,000 IU/day

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24
Q

Chronic toxic dose of vitamin D

A

50,000 IU/day

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25
Q

When obtained from food or supplements, vitamin D is absorbed in the

A

Small intestine

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26
Q

Central role in photoaging

A

UVA

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27
Q

Immediate erythema and pigment darkening

A

UVA

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28
Q

Major role in drug induced photosensitivity

A

UVA

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29
Q

Major role in carcinogenesis

A

UVB

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30
Q

Role in vitamin D production

A

UVB

31
Q

25(OH)D-1alpha-hydroxylase activity is increased by (2)

A

Parathyroid hormone

Low phosphate

32
Q

In tropical areas, adequate amounts if vitamin D3 can be made in the skin with

A

10 to 15 minutes of biweekly sun exposure to the face, arms and hands, or the back

33
Q

Most of the immunosuppressive effects of UVR are caused by

A

UVB

34
Q

Chromophore for the sunburning and tanning reaction

A

DNA

35
Q

Plant-based chromophores related to psoralens

A

Furocoumarins

36
Q

Chromophore is the perfume ingredient bergamot oil (5-methoxy psoralen)

A

Berloque dermatitis

37
Q

Most common indication for phototherapy

A

Psoriasis

38
Q

Chromophore that mediates the antipsoriasis therapeutic efficacy

A

DNA

39
Q

Much less energetic and produces much less pyrimidine dimers (UVA/UVB)

A

UVA

40
Q

Chromophore that mediates the therapeutic effect of PDT

A

Protoporphyrin IX

41
Q

Can penetrate through window glass

A

UVA

42
Q

Almost monochromatic emissions at 311-312 nm

A

Phillips TL01 fluorescent lamp

43
Q

Advantage of MAL vs 5-ALA

A

Better uptake into cells because of is more lipophilic properties

43
Q

Protoporphyrin is most effectively excited by (blue/red light)

A

Blue light

44
Q

Deeper penetration of PDT with (blue/red light)

A

Red light

45
Q

PDT modality more effective for thicker skin lesions, for example, infiltrating skin cancers

A

Methyl aminolevulinic acid (MAL) with red light

46
Q

Y/N: Photoabsorbing molecules are usually larger and aromatic and are therefore less likely to be internalized by cells

A

Yes

Except chromophore of current PDT

47
Q

Two main types of DNA photoproducts

A

Cyclobutane pyrimidine dimers

6,4-pyrimidine-pyrimidone photoproducts

48
Q

Absorption maximum of DNA

A

260 nm

49
Q

SCC and AK genetic mutations

A

p53

50
Q

BCC genetic mutations

A

Sonic hedgehog signaling pathways (ptch, shh, smo)

p53

51
Q

Melanoma genetic mutations

A

CDKN2A
PTEN
TERT promoter
p53

52
Q

Mechanisms by which UVR induces formation of pyrimidine dimers (2)

A

Direct absorption of photons by DNA bases

Photoexcitation of melanin, particulary pheomelanin leading to formation of “dark cyclobutane pyridimine dimers”

53
Q

Non-exposed cells in the vicinity of irradiated cells
also demonstrate stress responses similar to exposed
cells

A

Bystander effect

54
Q

Most of the oxidative DNA damage after exposure to natural sunlight is caused by

A

UVA

55
Q

Much higher abundance in natural sun (UVA/UVB)

A

UVA

56
Q

Generating the majority of solar radiation-induced pyrimidine dimers (UVA/UVB)

A

UVB

57
Q

Does not induce a robust cellular DNA damage response (UVA/UVB)

A

UVA

58
Q

Melanomas that are not UVR-induced

A

Mucosal

Acral

59
Q

Melanomas on chronically sun-damaged skin often arise from

A

Lentigo maligna

60
Q

Non-chronically sun-damaged skin melanomas are most common on the _____ in wowen and on the _____ in men

A

Lower legs

Back

61
Q

Damaged nucleotide is removed and

replaced with undamaged DNA

A

Nucleotide excision repair

62
Q

Defects in nucleotide excision repair genes can cause

A

Xeroderma pigmentosum

Cockayne syndrome Trichothiodystrophy

63
Q

Simpler type of DNA damage involving chemical changes in a single DNA base

A

Oxidative base modifications

64
Q

DNA repair pathway for oxidative base modifications

A

Base excision repair

65
Q

Guardian of the genome

A

Tumor suppressor p53

66
Q

Group of cysteine proteases that are central regulators of apoptosis

A

Caspases

67
Q

Only nonproliferative feature of photoaged skin that is not observed in intrinsically aged skin

A

Actinic elastosis

68
Q

Accumulation of fibrillary basophilic material in the upper and middermis

A

Actinic elastosis

69
Q

Progerin is found in high concentrations in cells from patients with

A

Hutchinson Gilford progeria

Fitz 9th (108 decks)

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