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I. Ocular Physiology > Retinal Pigment Epithelium Physiology (F) > Flashcards

Retinal Pigment Epithelium Physiology (F) Flashcards

1
Q

What is the organelle responsible for light absorption? 1. When is it formed? 2

A
  1. Melanosome

2. development and none after that

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2
Q

What is a lack of melanin pigment in the RPE called? 1. What does it result in? 2

A
  1. Ocular Albinism

2. improper routing of ganglion cells through the optic chiasm (binocular)

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3
Q

What fails to develop in eyes without melanosomes?

A

the fovea

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4
Q

What are melanosomes derivatives of? 1. How do they mature? 2

A
  1. early sorting endosomes

2. intracellular vesicular trafficking and incorporation of vesicles containing melanosome specific proteins

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5
Q

What are the first two stages of melanosome formation characterized by?

A

intralumenal proteinaceous fibrils that begin to form in stage I and are completed by stage II

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6
Q

What stage is melanin deposited? 1. What is the enzyme that initiates melanin synthesis? 2

A
  1. III and IV

2. Tyrosinase

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7
Q

What are the non-enzymatic antioxidants to neutralize ROS in the RPE?

A

Superoxide dismutase, catalase, Glutathione, ascorbate, melanin

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8
Q

What are the non-enzymatic antioxidants to neutralize ROS in the RPE?

A

Superoxide dismutase, catalase, Glutathione, ascorbate, melanin

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9
Q

What are the glucose transporters in the RPE? 1. Which one has increased expressing in the presence of HIF-1? 2.

A
  1. GLUT1, GLUT3

2. GLUT1

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10
Q

What is incorporated into glycerolipids for synthesis and storage of fatty acids and is essential for the renewal process of the photoreceptor out segment membranes?

A

Docosahexaenoic acid (DHA)

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11
Q

What is the driving force of the constant removal of water from the RPE?

A

chloride ions

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12
Q

What transport water from the inner retina? 1. From the outer retina? 2

A
  1. Muller cells

2. RPE cells

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13
Q

Where are the Na+-K+-ATPase (NKA) channels? 1. What do they move and where? 2. Do they require ATP? 3.

A
  1. apical
  2. 3 Na+ out, 2 K+ in
  3. yes
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14
Q

Where are the rectifying potassium channels (Kir)? 1. What do they move and where? 2. Do they require ATP? 3.

A
  1. apical
  2. K+ out
  3. no
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15
Q

Where are the rectifying potassium channels (Kir)? 1. What do they move and where? 2. Do they require ATP? 3.

A
  1. apical
  2. K+ out
  3. no
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16
Q

Where are the NKCC co-transporters? 1. What do they move and where? 2. Do they require ATP? 3.

A
  1. apical
  2. Na+ in, K+ in, 2 Cl-
  3. no
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17
Q

What drives water into the RPE cells via aquaporins (AQP1)?

A

intracellular chloride ions

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18
Q

Where are the CLC-2 Cl- channels? 1. What do they move and where? 2. Do they require ATP? 3.

A
  1. basal
  2. Cl- out
  3. no
19
Q

Where are the Ca2+ dependent Cl- channels? 1. What do they move and where? 2. Do they require ATP? 3.

A
  1. basal
  2. Cl- out
  3. no
20
Q

Where are the cAMP regulated Cl- channels? 1. What do they move and where? 2. Do they require ATP? 3.

A
  1. basal
  2. Cl- out
  3. require cAMP
21
Q

Does water flow in or out of the RPE cell on the basal end?

22
Q

What happens in the light to the Na+, K+ and H2O in the subretinal space?

A
  1. Decrease in subretinal K+
  2. Increase in Na+
  3. Increase in H2O
23
Q

What happens in the light to the Na+, K+ and H2O in the subretinal space?

A
  1. Decrease in subretinal K+
  2. Increase in Na+
  3. Increase in H2O
24
Q

Where are the Na+/H+ exchangers? 1. What do they move and where? 2. What is the driver? 3

A
  1. apical
  2. Na+ in, H+ out
  3. sodium gradient
25
Q

Where are the MCT1 (monocarboxylate transporter) cotransporters? 1. What do they move and where? 2. What is the driver? 3

A
  1. apical
  2. H+ and lactate in
  3. pH gradient and the high [lactate-] in the subretinal space
26
Q

Where are the MCT3 (monocarboxylate transporter) cotransporters? 1. What do they move and where? 2.

A
  1. basal

2. H+ and lactate out

27
Q

When the extracellular pH is high what is the movement of HCO3-? 1. When low? 2

A
  1. retina to choroid

2. choroid to retina

28
Q

What channel is pH sensitive?

29
Q

An increase in the transport of lactate leads to what regarding the intracellular pH? 1. Cl-? 2. Water transport? 3

A
  1. intracellular acidification
  2. increase
  3. increase
30
Q

An increase in the transport of lactate leads to what regarding the intracellular pH? 1. Cl-? 2. Water transport? 3

A
  1. intracellular acidification
  2. increase
  3. increase
31
Q

What do rod photoreceptors depend on for the conversion of 11-trans to 11 cis and as a source of 11-cis-retinal? 1. What do cones depend on? 2

A
  1. completely on RPE cells

2. RPE cells and have an alternative pathway which CAN regenerate all-trans to 11-cis retinal

32
Q

After hydrolysis where does all-trans retinal become embedded?

A

the lumen (minority) or cytosolic membrane face (majority)

33
Q

Where is all-trans retinal found in the lumen side is “flipped” to? 1. What mediates this? 2

A
  1. cytosolic side

2. disc membrane localized ABCA4

34
Q

What retinal disorders are linked to mutation of the ABCA4 gene?

A
  1. Stargardt disease
  2. Cone-rod dystrophy
  3. Age-related macular degeneration
35
Q

What is all-trans retinal converted to in the outer segment of the rod? 1. What mediates this? 2. What is required for this? 3

A
  1. all-trans retinol
  2. all-trans retinol dehydrogenase (RDH) enzyme
  3. NADPH
36
Q

What delivers all-trans retinol to RPE cells?

A

interphotoreceptor matrix retinal binding protein (IRBP)

37
Q

Wat converts 11-cis retinOL to 11-cis retinAL? 1. Where does this occur? 2

A
  1. retinol dehydrogenase (RDH)

2. Retinosomes

38
Q

Wat converts 11-cis retinOL to 11-cis retinAL? 1. Where does this occur? 2

A
  1. retinol dehydrogenase (RDH)

2. Retinosomes

39
Q

11-cis retinAL is transported back to the rod outer segment while bound to what? 1. What does this protein do? 2

A
  1. interphotoreceptor matrix retinal binding protein (IRBP)

2. protects against oxidation

40
Q

Vitamin A (all-trans retinOL) is provided to the RPE cells from what? 1. What mediated this uptake? 2

A
  1. choroid vasculature

2. STRA6

41
Q

When is phagocytotic activity the highest in the retina?

A

in morning and peaks within 1-2 hours

42
Q

How often is a whole length of a photoreceptor outer segment renewed?

43
Q

What is required for engulfment and mutations of this gene cause Retinitis Pigmentosa (breakdown of rod photoreceptors)?

A

tyrosine kinase receptor MerTK

44
Q

What are membrane bound organelles with lysosomal properties found in the RPE? 1. What happens to these with age? 2

A
  1. Lipofuscin vesicles

2. increase abundance

I. Ocular Physiology (20 decks)

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