Nervous Tissue

Question 1

What is myelin?

Answer 1

Referred to as White matter in the CNS

Complex, white, fatty, non-living material containing protein, cholesterol, phospholipids, and cerebrosides

Question 2

What are the main chemicals and their purpose in Luxol Fast Blue (what are the colours of the tissue as each chemical is used)?

Answer 2

1. Luxol Fast Blue –> Demonstrates myelin / white matter. All tissue elements - blue.
2. Lithium carbonate & 70% Ethanol (separate steps)–> Differentiates selectively, removes Luxol Fast Blue from the background. Myelin (WM) is blue, all other tissue and grey matter - pale.
3. Eosin –> Counterstain (Acid dye), stains cytoplasm & background with grey matter. Myelin (WM) blue, all other tissue & grey matter - pink.

Question 3

What happens if the lithium carbonate & 70% Ethanol are used too long and over differentiates?

Answer 3

Over differentiation:

No myelin / white matter demonstrated.

Question 4

What happens if the lithium carbonate & 70% Ethanol are used too short and under differentiates?

Answer 4

Under differentiation:

Grey matter is stained

Question 5

What are the characteristics of Luxol Fast Blue stain?

Answer 5

Luxol Fat Blue:

1. Basic dye
2. Alcohol soluble (contrast to Alcian blue which is an water soluble dye).
3. Very slow in action; requires an accelerator of gentle heat, i.e. 37C.

Question 6

What are the purpose of the lithium carbonate and the 70% ethanol being used together as the differentiator?

Answer 6

Lithium carbonate - weak base (acts like a pretreatment before using 70% ethanol). Don’t see any colour change after this step.
70% ethanol - slows process

Question 7

What is the principle of stain for Luxol Fast Blue?

Answer 7

Luxol Fast Blue - Principle:

Acid-Base Reaction of Salt Formation