Exam 3 Koh- Vitreous Biochem Flashcards Preview

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Flashcards in Exam 3 Koh- Vitreous Biochem Deck (46):
1

Vitreous is a highly hydrated gel-like _____ _____

Extracellular matrix

2

What is the vitreous made of?

99% water, gel like, virtually acellular apart from a few cells (hyalocytes) in the periphery

3

What does viteous regulate?

Eye growth and shape during development, a barrier to the cellular invasion/migration (transparency), lowers oxygen tensions

4

Vitreous degneration are central to ______ pathologies

Retinal

5

Asteroid hyalosis

A degenerative condition of the eye involving small white opacities in the vitreous humor

6

Synchysis scintillans

Resulting in liquefied vitreous humor and the accumulation of cholesterol crystals within the vitreous

7

What is the biochemical composition of the vitreous?

The main fibrillar proteins are collagen fibrils, the major GAG is is hyaluronan (HA), endows the tissue with shape, strength, flexibility, and resistance to tractional forces

8

Low-level postnatal _____ _____ does occur in vitreous

Collagen synthesis

9

How much collagen synthesis occurs in bovine eyes

About 60 mg/ml

10

How much collagen synthesis occurs in human eyes?

About 300 mg/ml

11

The concentration of collagen ______ as the eye grows

Decreases

12

What types of collagen in the vitreous?

2, 9, 5/11

13

Collagens can assemble into what types of structures?

Triple-helical structure (gly-X-Y), proline and hydroxyproline, lysine and hydroxylysine

14

What is collagen type 2 in the vitreous?

A fibril-forming collagen that accounts for 60-75% of the collagen in vitreous

15

What is Stickler's syndrome?

Premature vitreous degeneration and NSC

16

What is type 9 collagen in the vitreous?

Has a multiple-domain structure, up to 25%, synthesized in proteoglycan form having a single chondroitin sulphate

17

Type 5/11 collagen co-assembles with type ____ to form the core

2

18

How much type 5/11 collagen is in the vitreous?

10-25%

19

What is a ubiquitous component of extracellular matrices?

Type 6 collagen

20

What does type 6 collagen do?

Binds fibrillar collagens and HA, linking together the heterotypic collagen fibrils and HA

21

Marfan's syndrome is caused by mutations in _______

Fibrillin-1

22

Opticin binds what 2 things?

Growth hormone and GAGs

23

What is hyaluronan?

HA is the predominant GAG in mammalian vitreous, not covalently linked to a core protein

24

What is versican?

A large proteoglycan with a central domain that carries multiple CS chains

25

Mutation in ______ causes Wagner's syndrome

Versican

26

What is Wagner's syndrome?

Pre-retinal membranes and chorioretinal atrophy

27

The vitreous has how much more ascorbate than plasma?

10x (0.46 to 0.04)

28

What forms the bulk of the vitreous body?

Central vitreous

29

Collagen fibrils course in an ______ direction

Anterior-posterior

30

The lowest amount of collagen is within the _____ vitreous

Central

31

High about of collagen is at the viterous _____

Base

32

There is no ____ ____ over disc

Vitreous cortex

33

______ ____ via a 'molecular glue' that link the cortical itreous collagen fibrils to the ILL

Vitreoretinal adhesion

34

CS chains of type ____ collagen play a role in both connecting together and spacing apart the collagen fibrils within these bundles

9

35

What is the half-life for the type 9 collagen?

11 years

36

The human vitreous humor undergoes an inevitable processof _____ with aging

Liquefaction (or syneresis)

37

After the age of 40 years, there is a stead _____ in liquid vitreous

Increase

38

What is posterior vitreous detachment?

The cortical vitreous gel splits away from ILL

39

How often does PVD occur?

Occurs in approx 25% of the population during their lifetime

40

What are results of PVD?

Hemorrhage, retinal tears and detachment, macular hole formation, and vitreomacular traction syndrome

41

'Complete" PVD protects against what?

Proliferative diabetic retinopathy

42

Weakening of the _____ ____ is seen with age due to biochemical changes at the vitreoretinal interface

Vitreoretinal adhesion

43

_____ on the surface of cortical vitreous collagen fibrils could bind HS proteoglycans of the ILL

Opticin

44

The extension of the vitreous base into the peripheral retina is due to what?

Synthesis of new 'vitreous' collagen by retinal cells, an unbreakable viteoretinal adhesion

45

Why is vitreous more than just filler?

The concentration of ascorbate in human vitreous, an intact gel vitreous (and crystalline lens) may have some function that protects against POAG, cataract, vitreolysis, vitreous substitutes

46

The are prospects for nonsurgical closure of macular holes with ________

Ocriplasmin