wk1: AED - Cell Injury 1

Question 1

Name 8 common causes of injury/stress to ocular tissues

Answer 1

Hypoxia
Chemicals and Drugs
Physical agents (e.g. FBs)
Microbial agents (e.g. corneal compromise in CL wearer)
Immunological agents (e.g. infective epithelial keratitis)
Genetic defects (e.g. photoreceptor degen in R.P)
Nutritional Imbalances
Ageing

Question 2

Name and describe 5 types of cell adaptation

Answer 2

Atrophy - decrease size, loss of organelles
Hypertrophy - increase size
Hyperplasia - increase in number
Metaplasia - replacement of one cell type with another by differentiation/proliferation
Dysplasia - abnormal change in cell shape/size

Question 3

Describe the features of a reversible injury of a cell [4]

Answer 3

organelles are swelling up
cell is adapting
nucleus begins to clump - distinct dark areas
lysosomes autophagy - cell eats at its own organelles to atrophy and/or reduce metabolic demand

Question 4

Describe the features of a irreversible injury of a cell [4]

Answer 4

mitochondria swell
much greater defects in the cell membrane
cell membrane pores
cell nucleus darkens or fades

Question 5

Describe the changes to corneal epithelium in a reversible injury [3]

Answer 5

Swelling of the stroma - stresses the epithelium (swelling of basal columnar epithelium and nuclear clumping of chromatin)
Loss of polarization of the epithelial tissue - shapes of the cells are less structured and organised
If stromal oedema removed - corneal epithelium returns to normal - as the cells can turn over (in regenerative tissue)

Question 6

Name 2 indicators of a corneal injury becoming irreversible

Answer 6

Nuclear pyknosis and mitochondrial vacuolisation (which significantly reduces corneal thickness)

Question 7

Describe the mediators of cell injury as a result of the following: 
A) Hypoxia, Ischaemia
B) Multiple Injurous Stimuli
C) Mutations, cell stress, infection
D) Radiation, other insults
E) Infections, immunologic disorders

Answer 7

A: Reduced ATP
B: Increased ROS
C: Accumulation of misfolded proteins
D: Damage damage
E: Inflammation

Question 8

What is the difference between apoptosis and necrosis

Answer 8

Apoptosis: active process, programmed process of autonomous cellular dismantling that avoids eliciting inflammation

Necrosis: passive, accidental cell death resulting from environmental pertubations with uncontrolled release of inflammatory cellular contents

Question 9

Describe what happens to the cell when undergoing apoptosis [4]

Answer 9

Cell shrinkage
Chromatin condensation
Cell blebbing
Phagocytosis

Question 10

Describe what happens to the cell when undergoing necrosis [3]

Answer 10

Compromised membrane; cell swelling

cell lysis: release of intracellular components

Question 11

Name 3 situations that could result in necrosis of a cell

Answer 11

Physical trauma
Complement-mediated lysis
Lytic viral infection

Question 12

Name 4 situations that could result in apoptosis of a cell

Answer 12

During development
Tissue homeostasis
Cell-mediated immunity
Hormone-mediated atrophy

Question 13

How much inflammation and tissue disruption occurs in apoptosis?

Answer 13

No inflammation, little tissue degradation

Question 14

Describe the following features of Apoptosis
A: Cell size
B: Nucleus
C: Plasma membrane
D: Cellular components
E: Adjacent inflammation
F: Physiologic or Pathologic role

Answer 14

A: Reduced (shrinkage)
B: Fragmentation into nucleosome-sized fragments
C: intact; altered structure, especially orientation of lipids
D: intact, may be released in apoptotic bodies
E: No
F: Often physiological means of eliminating unwanted cells; may be pathological after some forms of cell injury, especially DNA and protein damage

Question 15

Describe the following features of Necrosis
A: Cell size
B: Nucleus
C: Plasma membrane
D: Cellular components
E: Adjacent inflammation
F: Physiologic or Pathologic role

Answer 15

A: Enlarged (swelling)
B: Pyknosis – Karyorrhexis – Karyolysis
C: Disrupted
D: Enzymatic digestion; may leak out of the cell
E: Frequent
F: Invariably pathologic (culmination of irreversible cell injury)

Question 16

What is the tunica vasculosa lentis?

Answer 16

Is an extensive capillary network. spreading over the posterior and lateral surfaces of the lens of the eye. It disappears shortly after birth.
it wraps around the lens during development and regresses via apoptosis until vascularisation of the lens is reduced to nothing.

Question 17

What happens if regression of tunica vasculosa lentis is incomplete?

Answer 17

Causes remnant or persistent hyaloid artery at vestigial, right at where the central retinal artery enters the optic disc

Question 18

Name the 4 principle targets and biochemical mechanisms of cell injury

Answer 18

1. Mitochondria and their ability to generate ATP and ROS under pathologic conditions
2. Disturbance in calcium homeostasis
3. Damage to cellular (plasma and lysosomal) membranes
4. Damage to DNA and misfolding of proteins

Question 19

Name the 2 major apoptotic pathways

Answer 19

1. Mitochondrial (intrinsic) pathway

2. Death receptor (extrinsic) pathway

Question 20

Describe the process of the cell undergoing necrosis [7ish]

Answer 20

Acute depletion of ATP
Lead to Ca2+ accumulation within the cell – toxicity
Cell will try to counteract Ca2+ accumulation through ionic balancing via ion pumps that require ATP
Leads to further depletion of ATP
Leads to stress on mitochondria – cause dysfunction – result in developing ROS - damage cell - oxidative stress
Leads to protein misfolding and cell membrane compromised
Sets of inflammatory cascade at same time

Question 21

How does Ca2+ accumulation affect endonucleases and DNA degradation?

Answer 21

Activates them

Question 22

What is necrosis characterised as? [3]

Answer 22

Loss of ion channel function (overload of Na+ – activation of Na+/k+/ATPase – dissipation of ATP)
Ca+ dependent activation of endo-, proteo-, phospholip-, ases
Cell swelling, membrane blebbing, cytoskeleton breakdown

Question 23

What do TUNEL assays do?

Answer 23

Detect DNA fragmentation by labeling the terminal end of nucleic acids

Question 24

What is BrdU?

Answer 24

is an analogue of thymidine used in the BrdU assay to identify proliferating cells

Question 25

Do visual field changes appear clinically in visual field tests before or after RGC apoptosis?

Answer 25

After. RGC apoptosis precedes clinically detectable changes in visual field tests

Question 26

What is Annexin V used for?

Answer 26

Used in flow cytometry to detect apoptotic cells by its ability to bind to phosphatidylserine, a marker of apoptosis when it is on the outer leaflet of the plasma membrane

Question 27

Between apoptosis and necrosis, which one involves denaturation of proteins leading to extensive amorphous coagulation of tissue during healing?

Answer 27

Necrosis

Question 28

How much cellular residue is present in apoptosis?

Answer 28

very little cellular residue