myelination

Question 1

myelin

Answer 1

Lipid-rich, living insulating sheath
50% dry weight of white matter
Synthesised by non-neuronal cells
 Conduction velocity
surround only some axons

Question 2

schwann cells (PNS)

Answer 2

myelinate indivudal aons- surround all axons but may not myelinate

Question 3

oligodendrocytes (CNS)

Answer 3

myelinate several axons/parts of axons

Question 4

myelin composition

Answer 4

40% water
70-85% dry lipid
protein= 15-30%

Question 5

in KO mice

Answer 5

myelin forms but develops vacuoles
paralysis seen in ages animals
delamination nof myelin-> pathological probs

Question 6

PNS composition myelin

Answer 6

has less
cerebroside
sulfatide

Question 7

CNS composition myelin

Answer 7

has more spingomyelin

Question 8

two major proteins

Answer 8

myelin basic protein

proteolipid protein

Question 9

PLP (proteolipid protein)

Answer 9

natural mutation

jimpy mouse
v little myelin
die early 
severe loss of olives
PLP produced (little) is toxic
KO mice= milder phenotype

Question 10

MBP (myelin basic protein

Answer 10

induces experimental allergic encepthalomyelitis
used as a model for MS
shiverer mice
die early

Question 11

CNS myelin proteins: enzymes and Ig -like molecules

Answer 11

Enzymes:

• Cyclic nucleotide phosphodiesterase
• Proteases
• Lipid metabolism
• Carbonic anhydrase

Ig – like molecules:

• MOG and MAG
• oligo-axon communication

Question 12

PNS myelin proteins

Answer 12

P0 50+% of PNS myelin protein
Some Charcot-Marie-Tooth syndrome (CMT type 1b)
KO mice - profound myelin defects
Adhesion molecule - compaction

PMP-22
CMT type 1a

Question 13

MS

Answer 13

Onset 20’s – 40’s
Variable severity
Relapsing / remitting MS
May be progressive
MRI - plaques
Periventricular white matter vulnerable
Primary demyelination
i.e. axon - sparing

Question 14

MULTIPLE SCLEROSIS – GENETICS vs ENVIRONMENT

Answer 14

 Caucasians (f:m = 1.5:1)
Monozygotic twins ~ 30% concordance
Linkage studies - immunological factors
Clusters/migration/geographic distribution suggest environment. Vitamin D!
Virally-induction e.g. herpes.

Question 15

AUTO IMMUNITY AND MULTIPLE SCLEROSIS

Answer 15

Generally accepted
Clear inflammatory response
No clear evidence for any particular autoantigen
Macrophage and protease activity degrades myelin

Question 16

MS therapy

Answer 16

Steroids
Interferons
Interfere with immune response
Other immune suppressants e.g. cyclophosphamide, antibodies e.g. alemtuzumab
Haemopoietic stem cells
Dietary e.g. vitamin D

Question 17

GUILLAN-BARRE SYNDROME

Answer 17

rare but serious autoimmune disorder in which the immune system attacks healthy nerve cells in your peripheral nervous system

Post viral/bacterial infection
e.g. Campylobacter jejuni, Zika virus?
Acute inflammatory response
Primary demyelination
Molecular mimicry?
e.g. between LPS of bacterial coat and myelin lipids/proteins

Question 18

treatment of guillan barre syndrome

Answer 18

with anti bodies from donated blood

intravenous immunoglobulin