Flashcards in Exam 3 Koh- Vitreous Biochem Deck (46)
Vitreous is a highly hydrated gel-like _____ _____
What is the vitreous made of?
99% water, gel like, virtually acellular apart from a few cells (hyalocytes) in the periphery
What does viteous regulate?
Eye growth and shape during development, a barrier to the cellular invasion/migration (transparency), lowers oxygen tensions
Vitreous degneration are central to ______ pathologies
A degenerative condition of the eye involving small white opacities in the vitreous humor
Resulting in liquefied vitreous humor and the accumulation of cholesterol crystals within the vitreous
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
Low-level postnatal _____ _____ does occur in vitreous
How much collagen synthesis occurs in bovine eyes
About 60 mg/ml
How much collagen synthesis occurs in human eyes?
About 300 mg/ml
The concentration of collagen ______ as the eye grows
What types of collagen in the vitreous?
2, 9, 5/11
Collagens can assemble into what types of structures?
Triple-helical structure (gly-X-Y), proline and hydroxyproline, lysine and hydroxylysine
What is collagen type 2 in the vitreous?
A fibril-forming collagen that accounts for 60-75% of the collagen in vitreous
What is Stickler's syndrome?
Premature vitreous degeneration and NSC
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
Type 5/11 collagen co-assembles with type ____ to form the core
How much type 5/11 collagen is in the vitreous?
What is a ubiquitous component of extracellular matrices?
Type 6 collagen
What does type 6 collagen do?
Binds fibrillar collagens and HA, linking together the heterotypic collagen fibrils and HA
Marfan's syndrome is caused by mutations in _______
Opticin binds what 2 things?
Growth hormone and GAGs
What is hyaluronan?
HA is the predominant GAG in mammalian vitreous, not covalently linked to a core protein
What is versican?
A large proteoglycan with a central domain that carries multiple CS chains
Mutation in ______ causes Wagner's syndrome
What is Wagner's syndrome?
Pre-retinal membranes and chorioretinal atrophy
The vitreous has how much more ascorbate than plasma?
10x (0.46 to 0.04)
What forms the bulk of the vitreous body?
Collagen fibrils course in an ______ direction
The lowest amount of collagen is within the _____ vitreous
High about of collagen is at the viterous _____
There is no ____ ____ over disc
______ ____ via a 'molecular glue' that link the cortical itreous collagen fibrils to the ILL
CS chains of type ____ collagen play a role in both connecting together and spacing apart the collagen fibrils within these bundles
What is the half-life for the type 9 collagen?
The human vitreous humor undergoes an inevitable processof _____ with aging
Liquefaction (or syneresis)
After the age of 40 years, there is a stead _____ in liquid vitreous
What is posterior vitreous detachment?
The cortical vitreous gel splits away from ILL
How often does PVD occur?
Occurs in approx 25% of the population during their lifetime
What are results of PVD?
Hemorrhage, retinal tears and detachment, macular hole formation, and vitreomacular traction syndrome
'Complete" PVD protects against what?
Proliferative diabetic retinopathy
Weakening of the _____ ____ is seen with age due to biochemical changes at the vitreoretinal interface
_____ on the surface of cortical vitreous collagen fibrils could bind HS proteoglycans of the ILL
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
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