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psc2016 > lecture 11 > Flashcards

lecture 11 Flashcards

1
Q

what is pulse chase?

A
  • add radioactive material to cell culture
  • wash cells to remove radioactive material
  • put new media in
  • follow where radioactive material goes
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2
Q

how does HA exit cell?

A
  • HA formed in plasma membrane
  • can exit cell into extracellular matrix
  • ABC transporter that forms and exports the HA
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3
Q

what do the chondrocytes contain lots of and how is it known?

A
  • core protein
  • inhibit protein synthesis, using cyclohexamide
  • pool of core protein as glycoproteins keep appearing
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4
Q

what is glycoproteins synthesised as?

A
  • single polypeptide chain
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5
Q

what is the signal for secretion?

A
  • addition of glycosaminoglycans
  • passes through intracellular pool to become glycosylated and rapidly secreted
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6
Q

what post-translational modifications take place?

A
  • smaller cell free system, dont have enough machinery to do modifications after translation
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7
Q

what is the normal aggregation process?

A
  • release of proteoglycan with link protein attached
    -reelase of hyaluronic acid
  • stable aggregate formed in extracellular matrix
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8
Q

how is this process interfered with?

A
  • by adding 10-20 sugars hylaronase
  • binds proteogylcsn and slows ability
  • isn’t long enough to bind proteoglycan and link protein
  • ## equilibrium between attached and ability of proteoglycan to loose small chain and bind to stable aggregate
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9
Q

what does this tell us?

A
  • more than 20 sugars needed to bind the link protein with the proteoglycan
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10
Q

what is the function of proteoglycans in cartilage?

A
  • highly negatively charged
  • retain large volumes of water in extracellular matrix
  • immobilised in collagen matrix as aggregates
  • restrained from swelling by collagen meshwork
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11
Q

what happens if collagen was removed?

A
  • protoelgycans will expand and form a gel
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12
Q

what can the hydrated proteoglycans do?

A
  • be reversibly compressed by displacement of water from their hydration shells
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13
Q

how does reversible compressibility occur?

A
  • proteoglycan isn’t expanded as much as needed, Ks and Cs closer than should be
  • force trying to push apart (intramolecular force)
  • intermolecular force as proteoglycans too close and hydration spheres are overlapping
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14
Q

what happens if load is applied?

A
  • squash gylcosaminogylcans closer
  • hydration spheres overlap more
  • some water lost
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15
Q

where does the fluid lost go?

A
  • redistributed within tissue away from point of compression
  • redistribution is slow
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16
Q

why is the redistribution slow?

A
  • proteoglycans are entrapped in the collagen meshwork which impedes flow of fluid
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17
Q

how is a large frictional drag caused?

A
  • by bottlebrushes structure sliding past each other
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18
Q

what provides the damping effect?

A
  • cartilage onlu deforming gradually under a load
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19
Q

what occurred in sokoloffs experiments?

A
  • showed cartilage is reversibly compressible
  • set up rig that applies force including cartilage
20
Q

what does the addition of lanthanum chloride cause?

A
  • precipitation of proteoglycans
  • reversible compressibility is lost
21
Q

what occurred in the Thomas experiment?

A
  • injected papain into rabbits ears
  • papain destroys proteoglycans so cartilage support function is lost
22
Q

what is the function of versican?

A
  • important for reversible contractility
  • found in intima of aorta
  • lots found in head
23
Q

what are some other functions of proteoglycans?

A
  • cell adhesion
  • DNA regulation
  • nervous system
  • lipid metabolism
  • cell growth
  • basement membrane permeability
  • killer T lymphocytes
  • platelet adhesion to endothelial surfaces
  • HIV
  • preventing tumour growth in brain
  • amyloid plaque formation
  • embryo implantation
24
Q

what is the role of heparin sulphate proteoglycans in embryo implantation?

A
  • non receptive phase = heparin sulphate protelgycans on surface of embryo but cant reach receptors, mucins expressed on surface (MUC1) so receptors hidden underneath so embryo cant implant
  • receptive phase = MUC1 expression stopped so can implant
25
Q

what is osteoarthritis?

A
  • disease of synovial joints
  • characterised by progressive deterioration and focal erosions
26
Q

what is the appearance of the hyaline cartilage?

A
  • white ish blue
  • glossy in appearance
27
Q

what occurs to hyaline cartilage appearance in osteoarthritis?

A
  • loss of glossy appearance
  • fibrillation
  • erosion of cartilage
  • exposure of subchondral bone
28
Q

what are the first signs of osteoarthiris ?

A
  • joint gets warm
  • changes in collagen and glycosylation
  • causes relax
29
Q

what are the enzyme changes in osteoarthritis?

A
  • shows degree of severity is proportional to level fo. degradative enzyme activity
  • MMPs, ADAMTs and cysteine proteases increased
  • TIMPs cant inhibit all degradative activity
  • aryl sulphatases remove sulphate (levels raised)
30
Q

what does the increased enzyme activity cause?

A
  • faster matrix breakdown
    -degradation fragments diffuse out tissue
  • increased porosity of extracellular matrix
  • degradative enzymes penetrate further
  • synovial fluid can diffuse in and leech out more proteoglycans
  • unsupported collagen looses stiffness
31
Q

what occurs in the acute inflammatory response in oestoarthirits ?

A
  • can get lots of polymorphonuclear leucocytes (damage tissue)
  • produce large quantities of lysosomal enzymes
  • difference in diffusion rates due to size differences
  • enzymes diffuse quick as small, inhibitors diffuse much slower so lots of damage occurs
32
Q

what are the chondrocytes doing in this process?

A
  • increased synthetic activity (increased DNA synthesis, cell division occurring)
33
Q

what does 35S sulphate show?

A
  • increased biosynthesis = increased levels in newly synthesised glycoproteins
34
Q

what is a signal for an immature proteoglycan?

A
  • newly synthesised richer in C4S than C6S
35
Q

what occurs with newly synthesised proteoglycans?

A
  • less associated with matrix
  • more easily degraded
36
Q

why cant degradation occur to all?

A
  • repair fails as cant stop both newly synthesised and adult proteogylcasn
37
Q

what does this lead to?

A

fall in synthetic activity in severe disease
- programmed cell death
- lacunae appear in tissue

38
Q

what are the treatments for osteoarthritis?

A
  • platelet rich plasma taken from patients
  • centrifuged at low speed to bring down RBC, high speed to pellet the platelets
  • platelets taken up in plasma
  • injected into joint
39
Q

what is another treatment method for osteoarthritis?

A
  • intra-articular HA injections
40
Q

why is more HA needed?

A
  • increases concentration in synovial fluid
  • so becomes more viscous
  • increases viscous-elasticity properties
41
Q

how is damaged cartilage repaired?

A
  • open joint up and finding lesion, drilling through subchondral bone- bleeds into split (fibrous cartilage forms to repair)
  • make small tubes of alginate (from seaweed) and fill with chondrocytes culture
42
Q

how is the alginate used?

A
  • culture for week
  • strands of cartilage forned
  • used as substrate for 3d printer
  • able to compose the matrix which can be transplanted into the damaged area
43
Q

how are drugs delivered to articular cartilage using nanoparticles?

A
  • nanoparticles penetrate the cartilage matrix
  • treated cultures with IL-1 to form proteoglycan breakdown
  • tested with fluorescence to see if nanoparticles enter cartilage
44
Q

what is shown in loss of joint space in OA?

A
  • symptoms worsened
  • left side of joint loose fine
  • cartilage disappeared on right side
  • bone articulating on bone causing friction and bone necrosis due to heat from friction
45
Q

what occurs in synovial fluid in OA?

A
  • increased fragments of aggrecan proteogylcan
46
Q

what are the biomarkers of articular cartilage degradation?

A
  • fragments of aggrecan
  • fragments of cartilage

psc2016 (12 decks)

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