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Neuroscience > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

What are two structural characteristics of myelin?

A
  1. lipid-rich, living insulating sheath

2. 50% dry weight of white matter

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2
Q

Where is myelin synthesized?

A

non-neuronal cells

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3
Q

Can myelin distribution change in learning and memory?

A

yes

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4
Q

Myelin surrounds some axons. Why?

A

High metabolic energy needed to produce myelin

Highly selective when wrapping around axon

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5
Q

What does myelin look like?

A

Dense staining wrapped around peripheral axon
Myelin gives white color to the white matter in the brain
Multi-layered membrane tightly wrapped and has light and dark lines

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6
Q

What is are differences between myelin wrapping between Schwann cells and oligodendrocytes?

A 
Schwann: 
myelinates individual axons
Cell is flattened out - flattened cytosol
tubukar edge
Oligodendrocytes: 
myelinates several axons or several parts of axons
cell body is separate
bumpy cytosol
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7
Q

What does compaction of the membranes contribute to?

A

Allows proteins to crosslink with each other

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8
Q

What does a dense line do?

A

Compresses together

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9
Q

What is periodicity?

A

Distance between lines composition of myelin is different between PNS and CNS

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10
Q

Why does myelin look like what it does?

A
  • protein-lipid-protein repeats
  • linked external proteins = intraperiod line (faint)
  • linked internal proteins = major period (dense) line
  • Periodicity
    PNS: 11.9 nm
    CNS: 10.7 nm
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11
Q

What is myelin composed of and at what proportions?

A

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

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12
Q

What are the dry protein and dry lipid compositions in myelin, white matter and gray matter?

A 
Myelin:
30% protein 70% lipid
White matter:
39% protein 55% lipid
Gray matter:
55% protein 33% lipid
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13
Q

What are the cholesterol, cerebrosides, galactolipid, plasmalogens, phospholipid compositions in lipid in myelin, white matter and gray matter?

A

Myelin:
28% cholesterol 23% cerebrosides 28% galactolipids 12% plasmalogens 43% phospholipids
White matter:
28% cholesterol 20% cerebrosides 29% galactolipids 11% plasmalogens 46% phospholipids
Gray matter
22% cholesterol 5% cerebrosides 7% galactolipids 9% plasmalogens 70% phospholipids

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14
Q

Which does myelin compositions more closely resemble; white matter or gray matter?

A

White matter

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15
Q

What happens when cerebrosides are lacking?

A

Myelin forms but develops vacuoles

Paralysis is seen in aged knockout mice because myelin starts to delaminate

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16
Q

When comparing between PNS and CNS, PNS has less _ and _ while CNS has more _.

A

cerebroside
sufatide
sphingomyelin

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17
Q

What are two major myelin proteins?

A 
myelin basic protein (MBP)
proteolipid protein (PLP)
18
Q

What does a natural mutation of proteolipid protein lead to?

A 
Jimpy mouse: "jerky" motor disturbance
Very little myelin
Die early
Severe loss of oligos
PLP produced is toxic
19
Q

What is a milder knockout mouse of jimpy mouse?

A

Rumpshaker

no PLP toxicity

20
Q

What does Myelin Basic Protein (MBP) induce and what can it be a model for?

A

Induces experimental allergic encephalomyelitis (EAE)

model for MS

21
Q

What is a condition found when MBP is lacking?

A

shiverer mouse

22
Q

What are enzymes found in myelin?

A

Cyclic nucleotide phosphodiesterase
Proteases
Lipid metabolism
Carbonic anhydrase

23
Q

What do Ig like molecules contain?

A

Immunoglobin domain

24
Q

What are Ig-like molecules found in myelin? What do they allow?

A

MOG and MAG

Oligo-axon communication

25
Q

How much do PNS myelin protein take up in the PNS myelin? What is a major protein?

A

over 50%

P0

26
Q

What happens when the PNS myelin protein is being knocked out?

A

Condition: Some Charcot-Marie-Tooth syndrome (CMT 1b)
Profound myelin defects
adhesion molecule compaction

27
Q

PMP-22 is a PNS myelin protein. What gene produces it?

A

CMT 1a

28
Q

What happens when CMT 1a is mutated?

A

Lethal

Tubular loop structure separate too much and widen the node of Ranvier

29
Q

What is the onset age range for MS?

A

20s to 40s

30
Q

What is vulnerable in MS patients?

A

Periventricular white matter

31
Q

What is an example of axon demyelination?

A

axon-sparring

32
Q

Where does demyelination occur in MS?

A

CNS

33
Q

What is the female to male ratio in caucasians with MS?

A

1.5:1

34
Q

What have linkage studies shown in MS?

A

Immunological factors involved

35
Q

What do clusters/migration/geographic distribution suggest?

A

Environment

Vitamin D involvement

36
Q

What virus can induce MS?

A

herpes

37
Q

What activity degrades myelin in MS?

A

macrophage and protease

38
Q

Name five types of therapies for MS?

A
  1. steroids
  2. interferons - interferes with immune system
  3. other immune suppressants
  4. hemopoietic stem cells
  5. dietary
39
Q

Name examples of immune suppressants for MS?

A

cyclophosphamide antibodies e.g. alemtuzumab

40
Q

What is a dietary factor in MS?

A

Vitamin D intake

41
Q

What kind of infections can lead to Guillan-Barre syndrome?

A

Post viral/bacterial infections

e.g. campylobacter jejuni, zika virus (?)

42
Q

What are symptoms if Guillan-Barre Syndrome?

A

Acute inflammatory response
Primary demyelination
Molecular mimicry
e.g. Between LPS of bacterial coat and myelin lipids/proteins

Neuroscience (28 decks)

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