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Anatomy and Biochemisty > Exam 3 Koh- Vitreous Biochem > Flashcards

Exam 3 Koh- Vitreous Biochem Flashcards

1
Q

Vitreous is a highly hydrated gel-like _____ _____

A

Extracellular matrix

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2
Q

What is the vitreous made of?

A

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

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3
Q

What does viteous regulate?

A

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

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4
Q

Vitreous degneration are central to ______ pathologies

A

Retinal

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5
Q

Asteroid hyalosis

A

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

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6
Q

Synchysis scintillans

A

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

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7
Q

What is the biochemical composition of the vitreous?

A

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

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8
Q

Low-level postnatal _____ _____ does occur in vitreous

A

Collagen synthesis

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9
Q

How much collagen synthesis occurs in bovine eyes

A

About 60 mg/ml

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10
Q

How much collagen synthesis occurs in human eyes?

A

About 300 mg/ml

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11
Q

The concentration of collagen ______ as the eye grows

A

Decreases

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12
Q

What types of collagen in the vitreous?

A

2, 9, 5/11

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13
Q

Collagens can assemble into what types of structures?

A

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

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14
Q

What is collagen type 2 in the vitreous?

A

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

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15
Q

What is Stickler’s syndrome?

A

Premature vitreous degeneration and NSC

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16
Q

What is type 9 collagen in the vitreous?

A

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

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17
Q

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

A

2

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18
Q

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

A

10-25%

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19
Q

What is a ubiquitous component of extracellular matrices?

A

Type 6 collagen

20
Q

What does type 6 collagen do?

A

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

21
Q

Marfan’s syndrome is caused by mutations in _______

A

Fibrillin-1

22
Q

Opticin binds what 2 things?

A

Growth hormone and GAGs

23
Q

What is hyaluronan?

A

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

24
Q

What is versican?

A

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

25
Q

Mutation in ______ causes Wagner’s syndrome

A

Versican

26
Q

What is Wagner’s syndrome?

A

Pre-retinal membranes and chorioretinal atrophy

27
Q

The vitreous has how much more ascorbate than plasma?

A

10x (0.46 to 0.04)

28
Q

What forms the bulk of the vitreous body?

A

Central vitreous

29
Q

Collagen fibrils course in an ______ direction

A

Anterior-posterior

30
Q

The lowest amount of collagen is within the _____ vitreous

A

Central

31
Q

High about of collagen is at the viterous _____

A

Base

32
Q

There is no ____ ____ over disc

A

Vitreous cortex

33
Q

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

A

Vitreoretinal adhesion

34
Q

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

A

9

35
Q

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

A

11 years

36
Q

The human vitreous humor undergoes an inevitable processof _____ with aging

A

Liquefaction (or syneresis)

37
Q

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

A

Increase

38
Q

What is posterior vitreous detachment?

A

The cortical vitreous gel splits away from ILL

39
Q

How often does PVD occur?

A

Occurs in approx 25% of the population during their lifetime

40
Q

What are results of PVD?

A

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

41
Q

‘Complete” PVD protects against what?

A

Proliferative diabetic retinopathy

42
Q

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

A

Vitreoretinal adhesion

43
Q

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

A

Opticin

44
Q

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

A

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

45
Q

Why is vitreous more than just filler?

A

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
Q

The are prospects for nonsurgical closure of macular holes with ________

A

Ocriplasmin

Anatomy and Biochemisty (15 decks)

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