HIS Staining Theory

Question 1

Auxochrome

Answer 1

IONIZED molecular structure that allows dyes to attach to the tissue

Question 2

T or F: categorizing dyes as acidic/ basic is misleading bc it has nothing to do with the pH of the dye solution

Answer 2

TRUE; categorizing dyes as acidic/ basic is misleading bc it has nothing to do with the pH of the dye solution

Question 3

Auxochromes with carboxyl, hydroxyl, and sulphonic groups are __ auxochromes.

Answer 3

Auxochromes with carboxyl, hydroxyl, and sulphonic groups are ANIONIC auxochromes.

COOH > COO-
OH > O-
SO3H > SO3-

Question 4

Anionic auxochromes will bind __ tissues.

Answer 4

Anionic auxochromes will bind POSITIVELY-CHARGED tissues.

Question 5

What do these dyes have in common: eosin, orange G, Biebrich scarlet, and acid fuchsin ?

Answer 5

ANIONIC dyes stain basic components

Question 6

NH2 is the __ auxochrome.

Answer 6

NH2 is the CATIONIC auxochrome.

NH2 > NH3+

Question 7

What do these dyes have in common: hematoxylin, crystal violet, methylene blue, basic fuchsin ?

Answer 7

CATIONIC dyes stain acidic components

Question 8

Consider trinitrobenzene: It contains three nitro groups (NO2). Why is it NOT a dye ?

Answer 8

It does NOT contain any auxochromes and cannot bind any tissue components

Question 9

Why is picric acid a dye, despite having a similar ring structure as trinitrobenzene ?

Answer 9

• has a ring of nitro groups AND A HYDROXYL GROUP (OH)
• OH has a ability to ionize and react with positively-charged tissue components
• is a chromophore AND an auxochrome = ANIONIC DYE

Question 10

Mordant

Answer 10

• reagent that links dye to tissue
• usually metallic salts; IRON or ALUMINUM

Question 11

Example of a mordanted dye

Answer 11

Hematoxylin; needs mordant to stain nucleus

Question 12

Dye lake

Answer 12

A dye combined with a mordant

Question 13

Metachromasia

Answer 13

• Tissue stains a different color than that of the staining solution
• this is bc Cationic dyes aggregate to negatively-charged tissue in close proximity

Question 14

Examples of metachromatic tissue

Answer 14

• MAST cells
• mucin
• amyloid

Question 15

Selective Solubility

Answer 15

• staining method for LIPIDS based on PHYSICAL PROPERTIES (solubility in solvent vs in lipid)
• dye migrates from solvent to lipids of tissue
  Ie. Oil Red O, Sudan Black B

Question 16

Principle of silver-staining methods

Answer 16

Silver nitrate solutions are easily reduced = metallic silver deposits

Question 17

Argentaffin

Answer 17

Can bind AND REDUCE silver to its metallic form
Ie. melanin, formalin pigment

Question 18

Why is formalin pigment troublesome in silver stains ?

Answer 18

Formalin pigment is a by-product of aging formaldehyde
- can be interpreted as a FALSE POSITIVE for melanoma

Question 19

Argyrophil

Answer 19

• can bind BUT CANNOT REDUCE silver to its metallic form
• chemical reducing agent is needed
  Ie. urates

Question 20

T or F: Argyrophil methods will also demonstrate argentaffin substances

Answer 20

TRUE; Argyrophil methods will also DEMONSTRATE ARGENTAFFIN SUBSTANCES (bind and reduce silver by themselves)

Question 21

What is a preferred DIRECT method over INDIRECT Metallic Substitution of calcium ?

Answer 21

Alizarin red S stain detects calcium DIRECTLY

NOTE: Von Kossa method is an outdated, INDIRECT method to detect calcium