Myelin & Myelination

Question 1

What myelinates in the PNS?

Answer 1

Schwann cells

Question 2

What myelinates in the CNS?

Answer 2

Oligodendorcytes

Question 3

What do Schwann cells myelinated?

Answer 3

Individual axons, can surround other neurones without myelinating them

Question 4

What do oligodendrocytes myelinate?

Answer 4

Several axons/ Part of axons

Question 5

What is the major period line of the Schwann cell?

Answer 5

Linked internal proteins (dark). Inner protein coat

Question 6

What is the intraperiod line of the Schwann cell?

Answer 6

Linked external proteins (faint). Outer protein coats

Question 7

Is the major period line dark or faint?

Answer 7

Dark

Question 8

Which line in Schwann cells is faint?

Answer 8

Intraperiod line

Question 9

What is periodicity in terms of Schwann cells?

Answer 9

Distance between two lines

Question 10

Greater periodicity in PNS or CNS?

Answer 10

In PNS

Question 11

What is the composition of myelin?

Answer 11

Water
Dry lipid (mainly this)
Protein

Question 12

What is a cerebroside?

Answer 12

Any of a group of complex lipids present in the sheaths of nerve fibres

Question 13

What happens in cerebroside knockout mice?

Answer 13

Myelin forms but develops vacuoles –> paralysis

Question 14

PNS vs CNS: which has less cerebrosides?

Answer 14

PNS

Question 15

PNS vs CNS: which has more sphingomyelin?

Answer 15

CNS

Question 16

PNS vs CNS: which has less sulfotides?

Answer 16

PNS

Question 17

PNS vs CNS: which has more cerebrosides?

Answer 17

CNS

Question 18

PNS vs CNS: which has myelin basic protein (MBP)?

Answer 18

CNS

Question 19

PNS vs CNS: which has proteolipid protein (PLP)?

Answer 19

CNS

Question 20

Which proteins are found in CNS myelin that aren’t in the PNS?

Answer 20

• Myelin basic protein

- Proteolipid protein

Question 21

What can myelin basic protein induce?

Answer 21

Experimental allergic encephalomyelitis (EAE)

Question 22

What is experimental allergic encephalomyelitis (EAE) induced by?

Answer 22

Myelin basic protein

Question 23

What is experimental allergic encephalomyelitis a model for?

Answer 23

Multiple sclerosis

Question 24

What is a natural mutation that can cause EAE?

Answer 24

“Shiverer” mutation

Question 25

What is a natural mutation that affects proteolipid protein?

Answer 25

"Jimpy" in mice

Question 26

What does the jimpy mutation cause?

Answer 26

Little production of myelin --> die early, severe loss of oligos PLP produced is toxic

Question 27

What is the PLP produced like in jimpy mice?

Answer 27

Toxic PLP produced

Question 28

PLP knockout mice or rumpshaker mutants have a stronger or milder phenotype?

Answer 28

Milder

Question 29

What kind of mice produce a milder phenotype than jimpy mice?

Answer 29

KO mice or rumpshaker mutants

Question 30

Give some examples of proteins other than MBP and PLP in CNS myelin

Answer 30

``` Enzymes - cyclic nucleotide phosphodiesterase - proteases - lipid metabolism - carbonic anhydrase Ig-like molecules - MOG and MAG - oligo-axon communication ```

Question 31

What proteins are found in PNS myelin?

Answer 31

- P0 - MBP - PMP-22

Question 32

Which gene codes for P0?

Answer 32

mpz

Question 33

Which syndrome is associated with P0?

Answer 33

Charcot-Marie-Tooth snydrome

Question 34

What is the onset of MS?

Answer 34

20-40s

Question 35

What does an MRI of a patient suffering from multiple sclerosis show?

Answer 35

Shows plaques - areas of demyelination

Question 36

What kind of demyelination occurs in MS?

Answer 36

Primary demyelination which is axon-sparing

Question 37

MS is more common in ____________

Answer 37

Caucasians

Question 38

Autoimmunity and MS

Answer 38

- Clear inflammatory response - No clear evidence for specific auto antigen - Macrophage and protease activity degrades myelin

Question 39

What is used to treat MS?

Answer 39

- Steroids - Interferons - Immune suppressants - Haemopoietic stem cells - Dietary i.e. vitamin D

Question 40

What is Guillan-Barre syndrome caused by?

Answer 40

- Post viral/bacterial infection | Campylobacter jejuni

Question 41

What can infection by campylobacter jejuni cause?

Answer 41

Guuillan-Barre syndrome

Question 42

What is primary demyelination?

Answer 42

Segmental myelin damage without primary changes in the axon

Question 43

What is secondary demyelination?

Answer 43

Both the axoplasm and myelin undergo necrosis