Term
| What are some functions of the lens capsule? |
|
Definition
| metabolic exchange, filters intermediate sized molecules |
|
|
Term
| How are molecules selected by the lens capsule? |
|
Definition
| Based on size and charge (anions) |
|
|
Term
| What are some metabolites exchanged by the lens capsule? |
|
Definition
| glucose, salts, water, O2, CO2, waste |
|
|
Term
| What kind of collagen is found in lens capsule? |
|
Definition
|
|
Term
| Is the lens capsule thick or thin? |
|
Definition
|
|
Term
| Besides Collagen IV, what else is found in the lens capsule? |
|
Definition
| laminin, nidogen and perlecan |
|
|
Term
| What is stored in the lens capsule? |
|
Definition
| fibroblast growth factors (FGF) for lens development |
|
|
Term
| What MMP's are upregulated in lens cells stressed by cataract surgery? |
|
Definition
|
|
Term
|
Definition
| fibroblast growth factors |
|
|
Term
| What does hyperglycemia do to the lens capsule? |
|
Definition
| stiffens it, makes it brittle |
|
|
Term
| What is the mechanism of lens capsule stiffening? |
|
Definition
| cross linked lysine amine groups |
|
|
Term
| What may be a factor in presbyopia? |
|
Definition
|
|
Term
| What is deep to the lens capsule? |
|
Definition
| epithelium of anterior lens or lens fibers |
|
|
Term
| What way does the apical surface of the lens membrane face? |
|
Definition
|
|
Term
| Where are gap junctions found in the lens? |
|
Definition
|
|
Term
| How big is vit C linearly? |
|
Definition
|
|
Term
| What connexins are found in lens cells? |
|
Definition
|
|
Term
| Do connexins interact with cataracts? |
|
Definition
|
|
Term
| What happens if knock out Cx50? |
|
Definition
|
|
Term
| How does Ca++ accumulation affect lens? |
|
Definition
| activates calpain --> cleaves crystallins |
|
|
Term
| What do cleaved crystallins do? |
|
Definition
| precipitate into a lens opacity |
|
|
Term
| Where are epithelial Na-K-ATPases found? |
|
Definition
|
|
Term
| What is lens nutrient flow? |
|
Definition
| In at the poles, out at the equators |
|
|
Term
|
Definition
| Na-K-ATPase inhibitor, not used to prevent cataract though due to heart failure |
|
|
Term
| What happens if Na+ levels increase in the lens? |
|
Definition
|
|
Term
| What does purinergic receptors do? |
|
Definition
| Sense and regulate Na-K-ATPase |
|
|
Term
| What are CLC-2 and CLC-3? |
|
Definition
| Lens epithelium chloride channels |
|
|
Term
|
Definition
| transports calcum out of lens |
|
|
Term
|
Definition
| Na-H exchangers and Cl-HCO3 exchangers |
|
|
Term
| What water channels are found in lens epithelium? |
|
Definition
|
|
Term
| What is the glucose transporter for lens epithelium? |
|
Definition
| Glut 1; this is NOT dependent on insulin to transport glucose. Glut 4 is however. |
|
|
Term
| What is the glucose metabolism pathways for the lens? |
|
Definition
| aerobic = 40% of ATP yield from only 3-10% of glucose, 80% of glucose = anaerobic |
|
|
Term
| Why is energy needed in the lens? |
|
Definition
| To power the lens pumps and repair fibers |
|
|
Term
| What differentiates differentiateing fibers (DF)? |
|
Definition
| DF have organelles present |
|
|
Term
| What aquaporins are in DF? |
|
Definition
|
|
Term
| What are mature fibers (MF)? |
|
Definition
|
|
Term
| Why do MF cells use O2 when they have lost their mitochondria? |
|
Definition
| ascorbate has high conc. and may consume O2 |
|
|
Term
| What aquaporins are in MF? |
|
Definition
|
|
Term
| What regulates glucose uptake in MF? |
|
Definition
| Na dependent glucose transporter, does not require ATP, driven by Na gradient |
|
|
Term
| What drives lens microcirculation? |
|
Definition
| transmembrane fluid flow via osmosis |
|
|
Term
| What aquaporins let water into and out of the lens? |
|
Definition
| AQP0 lets water in, AQP1 lets water out |
|
|
Term
| What cumulative damage causes cataracts? |
|
Definition
| oxidative damage of crystallin proteins |
|
|
Term
| What prevents oxidative damage to lens? |
|
Definition
| antioxidant enzymes: catalase, superoxide dismutase, glutathione reductase, glutathione peroxidase |
|
|
Term
| What % of the lens is water? |
|
Definition
|
|
Term
| What is unique about lens composition? |
|
Definition
| High protein content, low water content |
|
|
Term
| What is the protein content of the lens? |
|
Definition
|
|
Term
| What are the 3 types of crystallins? |
|
Definition
|
|
Term
| What is the size comparison for the three types of crystallins? |
|
Definition
|
|
Term
| What is the major class of lens proteins? |
|
Definition
|
|
Term
| What is the function of alpha crystallins? |
|
Definition
| heat shock protein, inhibit apoptosis, protect lens from stress |
|
|
Term
| Where else is alpha B crystallin found in the body? |
|
Definition
| Brain, is a factor in parkinsons and alzheimer dx, found lewy body plaques that destroy neurons |
|
|
Term
| What is the form of beta crystallin proteins? |
|
Definition
|
|
Term
| What does the greek key motif facilitate? |
|
Definition
| Binding to calcium, more compact proteins |
|
|
Term
| What is unique about gamma crystallin? |
|
Definition
| high amounts of cysteine, makes disulfide bonds possible |
|
|
Term
| what induces disulfide bonds in gamma crystallins? |
|
Definition
| oxidative damage of crystallin proteins |
|
|
Term
| What are common posttranslational modifications? |
|
Definition
| phosphorylation, oxidation, cross linking, and cleavage of proteins after translation |
|
|
Term
| What tissue is affected greatly by posttranslatoinal modification? |
|
Definition
| crystallins in mature lenses |
|
|
Term
| What crystallins degrade extensively with age? |
|
Definition
|
|
Term
| What property do crystallins lose with age? |
|
Definition
|
|
Term
| What is the biochemical structure of all crystallins? |
|
Definition
| beta sheet, allows for better packing |
|
|
Term
| What is the Hudson-Stahli line? |
|
Definition
| Iron buildup around cornea w/ age |
|
|
Term
| What molecule stores iron? |
|
Definition
|
|
Term
| What molecule allows iron to be used? |
|
Definition
|
|
Term
|
Definition
|
|
Term
| How does caloric restriction prevent oxidative damage? |
|
Definition
| Decreases mitochondrial free radical generation |
|
|
Term
|
Definition
| abnormal ion transport, excessivel proteolysis, low glutathione and excess cytoplasmic Ca++ |
|
|
Term
| What are theories of cataractogenesis? |
|
Definition
| mechanical shearing from accommodation, compromised membrane fluidity, depleted crystallin chaperone activity |
|
|
Term
| What ion channels participate in cataractogenesis? |
|
Definition
|
|
Term
|
Definition
|
|
Term
| What is a diabetic cataract? |
|
Definition
| hyperglycemia causes lens swelling by compromising fiber cells ability to regulate their volume |
|
|
Term
| What two volume regulating pathways does hyperglycemia compromise? |
|
Definition
| Sorbitol conc. and K-Cl cotransporter overstimulation |
|
|
Term
|
Definition
| Improper galactose metabolism |
|
|
Term
| What can galactosemia do to the lens? |
|
Definition
| causes cataracts, often in infants |
|
|
Term
| How do you manage galactosemia? |
|
Definition
|
|
Term
| What is the most common type of cataract? |
|
Definition
|
|
Term
| What percent of cataracts are nuclear? |
|
Definition
|
|
Term
| What lens fibers are most susceptible to oxidative damage? |
|
Definition
|
|
Term
| What is a common cause of cortical cataracts? |
|
Definition
|
|
Term
| What is posterior subcapsular cataract etiolgy? |
|
Definition
| abnormal migration of lens epithelial cells can be caused by radiotherapy or long term steroid use |
|
|
Term
| What % of cataracts are posterior subcapsular? |
|
Definition
|
|
Term
| What is a second cataract? |
|
Definition
| The post capsular bag calcifies around IOL |
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|
