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epithelial > L3 > Flashcards

L3 Flashcards

1
Q

what does ASL stand for?

A

airway surface liquid

- made up of periciliary layer and mucous layer

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2
Q

what is the PL and why is this important?

A

periciliary layer - the layer of ASL which the cilia project into
- the height of the PL is important as it is required to be at a certain height for cilia to beat and clear mucous efficiently

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3
Q

what is the convergance issue?

A

As you move up the airways SA decreases - is a mucb larger SA in alveoli than the bronchus

  • the height of the PL should be consistent in all cells - so when move u the airways get and accumulation of ASL as more mucous/liquid is required lower in the airways to cover large SA
  • this excess liquid needs to be reabsorbed as move up airways, as otherwise ASL/PL would be too high
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4
Q

how can ASL be controlled?

A

Passive - musouc layer acts as a resovoir

Active - active ion transport controlling salt level in PCL

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5
Q

what role does ENaC have in newborn babies?

A

Newborn baby lung clearance - Absorb liquid with Na+ (ENaC stimulates Na+ absorption

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6
Q

what is the optimum PCL height in the lungs and in cultured h epithelial cells?

A
  • in culture - 7um (2 exp showed this)
  • in vivo/lungs - 14um
    lungs are not static which stimulates extra secretion due to shear stress
  • cells in culture are static so do not undergo sheer stress
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7
Q

what transport / channels function to determine the height of the liquid layer?

A
  • at high ASL levels, ENaC has high function to absorb Na which stimulates H2O absorption
  • as optimum height, Cl- secretion predominates effect of ENaC - via NKCC1
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8
Q

what balance determines the height of the liquid layer??

A

The balance between Na+ absorption and Cl- secretion in the epithelial cells of the airway
- anything that disrupts Na+ abs or Cl- secretion disrupts the height of the ASL as it disrupts water movement

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9
Q

What does bumetanide do?

A

blocks NKCC1

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10
Q

what does NKCC1 do and where is it?

A

NKCC1 transports Na, 2Cl and K into the cell via the basolateral membrane
- NKCC1 is on the basolateral membrane of most epithelial cells - e.g. upper airways

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11
Q

What is the main channel where Cl- secretion occurs through?

A

CFTR (on apical membrane of cell)

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12
Q

what is the cell model of the upper airways?

A
  • apical - CFTR (Cl- secretion)
  • apical - ENaC (Na+ absorption)
  • basolateral - Na/K ATPase (3Na out of cell, 2K into cell)
  • basolateral - NKCC1 (Na, 2Cl and K into cell)
  • basolateral - K+ secretion
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13
Q

What happens to Cl secretion when bumetanide is added?

A

Bumetanide inhibits NKCC1 - this creates driving force for Cl- secretion as it brings Cl into the cell
- When bumetanide added Cl- secretion is inhibited

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14
Q

how do ENaC and Cl- drive water?

A

They drive water movement in opposite directions

- water moves paracellularly

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15
Q

what does RSV stand for?

A

respiratory syncytial virus

- major resp pathogen - especially in children

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16
Q

What channel does RSV affect and how was this shown?

A

Measuring SSC(Vte) and I amiloride in mouse trachea

  • RSV inhibits ENaC - shown as response to amiloride much smaller when RSV present and is a shift in Vte - becomes more positive as less Na+ is being absorbed into cell
  • This means less Na+ is absorbed by cell in presence of RSV - less water uptake from liquid layer - more liquid in airway - why get a running nose
17
Q

what components are important for RSVs effect on ENaC and how was this shown?

A

PKC and glyolipids are important

  • If PKC is blocked (by bim), inhibition of ENaC doesn’t occur
  • when virus is inhibited from binding to gycolipids (PPMP) - lose inhibition of ENaC
  • likely that RSV binds to glycolipids on cells, and PKC is activated downstream
18
Q

How was if shown that glycoproteins ARE NOT important in RSVs effect on ENaC?

A

When gycoprotiens are inhibited (NA), still is inhibition of ENaC by RSV- RSV doesn’t need glycoprotein to have an effect

19
Q

What are inhibitors of PKC and glycolipids?

A

PKC inhibitor - BIM

glycolipid inhibitor - PPMP

20
Q

what components does influenza need to have an effect on cells?

A

glyoproteins

PKC

21
Q

what glyoproteins does the infuenza virion contain?

A
  • M1
  • M2
  • haemagglutinin
  • neuraminidase
22
Q

what does haemagglutinin do in influenza?

A
  • activates PKC and transiently inhibits ENaC
23
Q

what does M2 do in influenza?

A

forms acid activated, amantadine inhibited, H+ channel in the apical membrane - long term regulation of ENaC

24
Q

How does M2 contribute to the inhibition of ENaC and it’s current?

A
  • M2 promoting the endocytosis of ENaC
  • when M2 present is less ENaC in the membrane - shown by western blot compared to when M2 is present
  • fewer openings of ENaC as less ENaC in membrane
25
Q

what happens when the lid ENaC mutant is used?

A

lid ENaC mutant - ENaC stuck in the membrane ( cannot be endocytosed)
- there is no difference between IENaC when M2 is present or absent (M2 cannot endocytosis the lid mutant of ENaC)

26
Q

What does the endocytosis of ENaC by M2 require?

A

PKC and ROS

  • When add antioxidant (GSH) inhibition of ENaC is smaller
  • When PKC inhibitors added e.g. BIM - inhibition of ENaC is less
27
Q

what can be caused by loss of function of ENaC?

A

PHA - pseudohypaldosteronism

28
Q

what are the 2 forms of PHA1?

A
  • systemic - autosomal recessive form - effects multiple organs - all ENaC subunits mutated
  • renal - autosomal dominant - effects kidneys
29
Q

Give some features/symptoms of PHA

A
  • salt wasting (inactive ENaC)
  • hypotension - increased urine flow rate
  • hyperkalaemia
  • acidosis
  • high renin and aldosterone
30
Q

What was shown by monitoring PHA1 patients nasal surface liquid?

A
  • in systemic form is more wet weight and an increase in [Na+] in the liquid from nose.
  • is a decrease in Vte in systemic patients
  • % inhibition with amiloride decreased in systemic patients as ENaC function is reduced
  • less functional ENaC in membrane of PHA1 cellsq
31
Q

why does ENaC not reach the membrane in PHA1 cells?

A
  • ENaC is mutated so this is recognised and ENaC is degraded via ENaC - why doesn’t reach membrane
  • less ENaC in membrane - less Na+ reabsorption
  • less H2O reabsorption
  • water moves into lumen through cells - higher liquid layer - higher risk of infection

epithelial (8 decks)

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