Cell Growth

Question 1

What does EGF do?

Answer 1

Epidermal grwoth factor

Produced by stromal fibroblasts

Stimulates corneal epithlial migration and epithelial and fibroblast proliferation

By increasing fibronectin production

Question 2

What are functions of TGF-beta

Answer 2

TGF-b1 casues dose related inhibtion of epithelial cell proliferation and inhibits stimulatory effect of EGF

TGF-b2 localised to superficial limbal epithelial cells - transdifferentiation of conj and corneal epithelium

TGF b3 stimulates proliferation of stromal fibroblasts and increased collagen and fibronectin synthesis

Question 3

What does PDGF platelet derived growth factor do

Answer 3

Stimulate limbal stem cell proliferation

Question 4

What does fibroblast growth factor do

Answer 4

Stimulates epithelial and fibroblast proliferation and production of ECM by fibroblastsW

Question 5

What proteins make up ECM

Answer 5

Collagen
Laminin
Fibronectin
Plysaccharide glycosaminoglycans (negative charge, repeating disaccharide chain)

Question 6

What is fibronectin structure? Role?

Answer 6

2 polypeptide chains linked by disulphide bond S-S

6 domains on each with binding sites for integrins, proteoglycans and collagen

Found at level of stromal side of Descemet’s

ROLE: Promote adhesion between cells and extracellular matrix via integrin a5b1 in wounded cornea
Forms temporary scaffold in injury for epithelial migration and adjesion

Question 7

What stimualtes fibronectin production

Answer 7

Epidermal growth factor
Tissue growth factor B

Question 8

What are laminin structures? Where found?
Role?

Answer 8

Large multidoamin glycoprotein
3 polypeptide chains

Found in lamina lucida of basal almina

Strctural component of basement membrane

Growth, migration, differentaition

Question 9

What is an important laminin in corneal wound healing

Answer 9

laminin-5

Becomes continuous after wound closure

Question 10

What are integrin structure? Function?

Answer 10

TRansmembrane glycoprotein
alpha and beta subunits

Mediate attachment of cells to ECM and cell-cell adhesion.

Transduce biochemical signals from ECM to the interior of the cell via phosphorylation cascades

Receptors for laminin, collagen, fibronectin, vitronectin, ICAM1, ICAM2

Question 11

What integrin is important in hemodesmosomes

Answer 11

a6b4 integrin

Question 12

What are mechanisms of cell surface signalling

Answer 12

GPCR
Adnylate cyclase - cAMP
Phophoinoitidase C (PIC) - 1,2 DAG, inositol, calcium
Ligand gated ion channels - nAChR
Tyrosine kinase linked receptro - EGF, PDGR

Question 13

Structure/function of GPCRs

Answer 13

Guanin nucleotide - coupling protein
Effector protein - may be enzyme or ion channelW

Question 14

What receptors activate adenylate cyclase?

Answer 14

B1 and B2 adrenergic receptors
TSH
ACTH
Glucagon
H2

Question 15

What receptors inhibit adenylate cyclase?

Answer 15

a2 adrenergic
M muscarinic Ach

Question 16

What receptros activate phosphoinositidase C (PIC) to result in 1,2 - DAG, inostol, claclium?

Answer 16

a1 adrenergic
H1
Endothelin
Platelet activating fators

Question 17

What receptor activates nucleotide phosphodiesterase

Answer 17

RhodopsinW

Question 18

What is a nicotinic ACh receptor? Muscarninic?

Answer 18

Nicotinic - ligand gated ion channel

Muscarinic - inhibits adenylate cyclase

Question 19

What are beta adrenergic receptors

Answer 19

Activate adenylate cyclase

Question 20

What are alpha 1 and alpha 2 adrenergic receptors

Answer 20

alpha 1 - activates PIC

Alpha 2 - inhibits adenylate cyclase

Question 21

What are cadherins

Answer 21

Simpla transmembrane glycoproteins - calcium dependent cell adhesion

Zonula adherens and desmosome connections between epithelial cells

Homophillic binding of cadherins on adjacent cells

Question 22

What are the phases of apoptosis

Answer 22

1. precondensation - gene within cell reposnibel for apoptosis is induced
2. Condensation - cytoplasmic and nuclear volume DECREASE
   Chromatic condenses and interactions between cell and adjacent cells lost
   Development of plasma membrane blebs
3. Fragmentation - non-lysosomal Ca and Mg dependent endonucleases break down DNA into smaller apoptotic bodies
   Nucleus become pyknotic
4. Final phase - phagocytosis of apoptotic bodies and degradation by lesosommal enzymes, no immune reaction

Question 23

Which factors activate apoptosis

Answer 23

Growth factor withdrawal
Glutamage and dopamine
TNF
TGF-beta
Calcium
Glucocorticoids
Iatrogenic factors - radiation, chemotherapy, toxins - ethanol, beta amyloid

Question 24

What gene promots apoptosis?

Answer 24

BAX

Question 25

What gene inhibits apoptosis

Answer 25

Bcl 2