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mlsci 250 > stain theory > Flashcards

stain theory Flashcards

1
Q

what is the purpose of staining

A

provide a contrast between tissue components by
1. attaching dyes to the tissue
2. reacting the tissue with organic reagents to produce coloured products
3. depositing metals on tissue components to produce visible insoluble black products

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2
Q

dye colour theory

A

molecules absorb radiation in visible region
electrons move in response to gaining and losing energy
energy levels are unique to each molecule

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3
Q

what are some component of dyes

A

organic compounds
most are coal tar or benzene derivatives
are able to attach to a substance by chemical bonding

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4
Q

dyes can be classified according to their

A

-chromophores
-classficiations in reference books
-colour index numbers
-manufacturing process

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5
Q

chromophores are

A

chemical group that results in colour
- the more numbers = increased colour intensity

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6
Q

an uncoloured molecule +chromophore =

A

chromogen

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7
Q

auxochromes

A

attach dye to tissue
- anionic (acid, net neg)
- cationic (basic, net pos)

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8
Q

chromogen + auxochrome

A

stain

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9
Q

classification of dyes by reaction with tissue

A
  • cationic dyes
  • anionic dyes
  • mordant dyes
  • solvent dyes
  • polychromatic dyes
  • neutral stain solutions
  • amphoretic dyes
  • leuco dyes
  • metachromatic dyes
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10
Q

cationic dyes

A

attach to anionic groups in tissue
stain is basic
substrate is basophillic
stain is acidophillic
often used to stain nuclei, basophil, mast granules, cartilage matrix, cytoplasmic anionic groups

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11
Q

anionic dyes

A

attach to cationic groups in tissue
stain is acidic; substrate acidophilic, stain basophilic
used to stain cytoplasm and extracellular structures

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12
Q

mordant dyes have a

A

weak auxochrome
- they stain tissues indirectly

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13
Q

dye lakes

A

highly basic and act as cationic dyes

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14
Q

cheif mordant dyes:

A

iron and alum

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15
Q

solvent dyes are also known as…

A

lysochromes

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16
Q

what is the use of solvent dyes

A

solvent dyes lacks an auxochrome and are hydrophobic
- when applied to tissue with hydrophobic domain it will get into other hydrophobic areas, helps stains fats, dye will be incorporated with the fat

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17
Q

examples of solvent dyes

A

oil red-o
suban black

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18
Q

solvent dyes are termed

A

selective or preferential solubility

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19
Q

polychromatic dyes

A

spontaneously form other dyes in solution
- use a single solution

20
Q

what is polychromatic dyes often used for

A

rapid diagnosis of cryostat sections

21
Q

examples of a polychromatic dye

A

methylene blue
is oxidized into azure a and azure b (blue and purpe)

22
Q

neutral stain solutions

A

made from the interaction of anionic and cationic dyese

23
Q

example of a neutral stain

A

romanowsky dye in hem

24
Q

leuco dyes

A

colourless clear put into tissue and will change colour due to an occuring chemical reaction
- chromophores are easily reduces
-chemical reaction occurs with reactive tissue groups
- usually easily reversible
eg. periodic acid schiff

25
Q

metachromatic dyes

A

dye certain tissue components a colour different than the colour of the dye itself
- can be basic or cationic
-aqueous mounting media is recommended
- sulfation can induce metachromasia

26
Q

what are the tissue components in a metachromatic dye calles

A

chromotrophs

27
Q

what is the basis of a metachromatic dye

A

stain is based on the tendency to polymerize
- when two or more dye molecules come close together, get a new wavelength of light absorptivity

28
Q

interaction of dye with tissue involves

A

physical factors and chemical factors (electrovalent bonds, covalent bonds, hydrogen bonds, van der waals forces, hydrophobic interaction)

29
Q

physical factors

A

combine by absorption
- dimension of surface area
- density
- permeability
- size of dye molecule

30
Q

electrovalent bonds

A

the electrostatic attraction of oppositely charged ions
known as ionic, electrostatic, salt linkages
disrupted by acids, weak bases, water, alcohol, or high concentration of electrolytes
dissociation = differenciation

31
Q

covalent bonds

A

formed when two atoms share electrons
strongeat and requires lots of energy to disrupt bond
typical of organic chemicals

32
Q

example of covalent bond stain

A

schiff’s reagent
verhoeff’s stain

33
Q

hydrogen bonds

A

bond due to attraction between lone pair of electrons on O or N and partially exposed nucleus of H
- weaker than covalent or ionic bonds
- affect staining in non aqueous solvents

34
Q

van der waals

A

electrostatic attractions that exist between electrons of one atom and nucleus of another
- found in all staining systems to various degrees
- very short range forces
- weakest

35
Q

example of van der waals staining

A

staining of elastin by aldehyde fuchsin

36
Q

hydrophobic interactions

A

affinity of non polar molecules to one another
- stained preparations must be mounted in aqueous mounting media
- the dye must be more soluble in the substrate and the solvent

37
Q

metallic impregnation

A

uses silver in alkaline solution readily able to precipitate

38
Q

what are the 3 types of reactions to occur in a metallic impregnation stain

A

argentaffin
argyrophil
metallic substitution

39
Q

argentaffin

A

reactive groups are capable to reducing silver salts

40
Q

argyrophil

A

tissue elements are not sufficiently reactive to reduce silver
- outside reducer is required

41
Q

metallic substitution

A

ion exchange`

42
Q

progressive staining

A

in each stain until desired effect achieved
- linear (X amount of minutes)

43
Q

regressive staining

A

tissue is overstained
- takes a long time for tissue to stain and then it is gently removed

44
Q

differenciation

A

selective removal of excess dye from a section

45
Q

method of differenciation

A
  • washing in water
  • using of excess mordant
  • oxidizing agents
  • other dyes : dye competition
46
Q

knowing the nature of the dye is important for

A

troubleshooting
- what is the pH of dye solution
- how has fixation affected the method

mlsci 250 (11 decks)

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