Lecture 11 Part 2 - Composition

Question 1

When does viscosity increase?

Answer 1

When proteoglcyans are linked onto the hyaluronic acid, but the complex is not stable you can dissociate it

Question 2

How could there be a drop in viscosity?

Answer 2

If the proteoglcyans join the short chain of hyaluronic acid instead of the long chain, short chain is the same as free protein

Question 3

How can proteoglycan aggregates be investigated?

Answer 3

Using gel filtration

Question 4

What is gel filtration?

Answer 4

A whole series of beads in a column, the beads have holes in them. If you have a small molecule and put it on the top of the column the beads will fit through the hole. If you out something big it can’t go through the beads so will flow around the outside

Question 5

Where would the proteoglycan come out in gel filtration?

Answer 5

It would come out the VO - volume void as it is too big

Question 6

Can you make the proteoglycans smaller?

Answer 6

Can chop the top off, still has G1 and a little bit of glycosylation

Question 7

How much HA (hyaluronan) is present in cartilage?

Answer 7

1% in vivo concentration

Question 8

What is an example for the mechanism of aggregation?

Answer 8

Pulse chase

Question 9

What is the pulse?

Answer 9

The radioactive sulphur (35S)

Question 10

At the end of the pulse mechanism what should you end up with?

Answer 10

Sulphating proteoglycan culture chondrocytes

Question 11

What do chondrocytes contain?

Answer 11

A lot of core protein

Question 12

How can you inhibit protein synthesis?

Answer 12

By cycloheximide by interfering with the translocation step

Question 13

How can you interfere with aggregation?

Answer 13

If you add 10-20 HA - not stable aggregate

Question 14

How many sugars do you need to be able to bind both a proteoglycan and a link protein?

Answer 14

More than 20 sugars, you need 26-30 sugars to form a stable molecular aggregate

Question 15

What is the major function of aggregation?

Answer 15

When the proteoglycans are immobilised in the collagen matrix as aggregates

Question 16

What needs to happen if you want to take the proteoglycans out?

Answer 16

Need to deaggregate them

Question 17

How much in ml will a proteoglycan occult in solution?

Answer 17

30-50ml

Question 18

What can disrupt aggregation?

Answer 18

A high ionic solvent will disrupt the interaction

Question 19

What is an example for a high ionic solvent?

Answer 19

You can use calcium chloride

Question 20

How are proteoglycans restrained from swelling by?

Answer 20

By the collagen meshwork ‘a swelling pressure’

Question 21

What happens if collagen was removed from the matrix?

Answer 21

The proteoglcyans would expand and form a gel

Question 22

What happens in oesteroarthitis to the collagen network?

Answer 22

The collagen network relaxes which enables the proteoglycans to expand more

Question 23

What can the hydrated proteoglycan be?

Answer 23

They can be reversible compressed by displacement of some of the water from their hydration shells

Question 24

What is an Intramolecular force?

Answer 24

When the proteoglcyans are too close together - the hydration cells overlap

Question 25

What happens when you apply a load to the intermolecular force?

Answer 25

You will squash the proteoglycans even closer together and will push the hydration spheres even closer together

Question 26

What happens when you remove the load?

Answer 26

The proteoglycans will spring back up and take the water back up - reversible compressibility

Question 27

What happens to the fluid in cartilage when load is applied?

Answer 27

The fluid will be displaced from the domains of the proteoglycans at that point

Question 28

What is the redistribution of fluid like when pressure is applied?

Answer 28

Is slow because the proteoglycans are trapped in the collagen meshwork

Question 29

What type of effect is caused when cartilage is under pressure?

Answer 29

Cartilage only deforms gradually under pressure is it is a damping effect

Question 30

What happens in SOKKOLOFF’S experiment with the addition of Lanthanium chloride?

Answer 30

It causes precipitation of proteoglycans

Question 31

What destroys proteoglycans in Thomas experiment?

Answer 31

Papain - causes loss in cartilage support function

Question 32

What is versican?

Answer 32

It is a chondroitin sulphate proteoglycan that is helpful in the brain to prevent damage by compressive forces

Question 33

What happens in the receptive stage? Embryo implantation?

Answer 33

You lose mUC1 expression - means that heparin sulphate binding sites at the apical surface of the uterine become accessible