Module 1: Stain theories

Question 1

Physical theories

Answer 1

porosity
adsorption
selective solubility

Question 2

Chemical theories

Answer 2

ionic bonds
covalent bonds
hydrogen bonds
Van der Waal’s forces

Question 3

Porosity

Answer 3

nearly all substances are porous to a degree therefore osmosis and capillarity can account for penetration of dye into interior tissues
Varying porosities can be used to differentially stain them with dye molecules of different sizes

Question 4

Adsorption

Answer 4

Ability of tissue components to attract dye molecules to their surface
Occurs in first step of most staining

Question 5

Selectrive solubility

Answer 5

happens when lysochrome (colored dye substance) is more soluble in tissue than solvent

• Colored substances are hydrophobic and more soluble in lipids and organic solvent than in water
• occurs in fat or lipid staining when lysochromis is more soluble in lipid (only purely physical stain)

Question 6

Lysochrome

Answer 6

strongly colored, very soluble substances intended to color, but doesn’t bond to tissue element

Question 7

Solvent requirements used with lysochromes

Answer 7

Cant dissolve lipid, lysochrome must be less to soluble in solvent than lipid

Question 8

Ionic bonds

Answer 8

electrovalent attraction, couombic bonding or salt linkage
Most common due to coulombic force or electrvalant attraction (initiated when oppositely charged ions come in close proximity)

• complete transfer or electrons from one atom to another occurs to stabilize configuration
• easity disupted by acids or high electrolyte concentration (may be used to limit extent of staining or take out stain)

Question 9

Covalent Bonds

Answer 9

– not commonly found in biological staining (lack of selectivity)
- two atoms held tightly together by sharing electrons

Question 10

Hydrogen bonds

Answer 10

– between hydrogen covalently bonded to oxygen or nitrogen in one molecule and a nonbonding pair of
electrons of nitrogen or oxygen in another molecule.
- not as strong as covalent bonding
- may occur when dyes are applied in non aqueous solvents (ie: Congo Red)

Question 11

Van der Waal’s forces

Answer 11

– found in all staining systems in varying degrees

• exists between electrons of one atom and nucleus of another (only effective when in close proximity)
• weakest force, though thought to be significant in “large molecule dye staining”