fixation, decal, dehy, clearing

Question 1

when uses for clearing tissues during the embedding process, is lower in action than xylene but causes less brittleness

Answer 1

chloroform

Question 2

advantage:
recommended for routine work (6-24hrs)
miscible with absolute alcohol
recommended for rough tissues
suitable for large spx
not inflammable

Disad:
relatively toxic to the liver
clearing is relatively slow
does not make tissues transparent

Answer 2

chloroform

Question 3

most common chrome -osmium acetic acid fixative used. recommended for nuclear preparation.

Answer 3

Flemming’s solution

Question 4

composition:
EDTA disodium salt 250gm
distilled water 1750ml

advantage:
permits excellent staining result
produce minimal cell and tissue distortion

Disad
very slow and therefore not reccommended for urgent and routine biopsies

Answer 4

NEUTRAL EDTA

Question 5

give 6 common dehydrating agents

Answer 5

Alcohol
acetone
dioxane
cellusolve
triethyl phosphate
tetrahydrofuran

Question 6

its use is reserve for the fixation of cryostat sections or for tissues in which enzymes have to be preserved.

Answer 6

acetone

Question 7

advantage:
less shrinkage and hardening than ethyl alcohol
excellent for slow processing
miscible with paraffin

disad
odorous
slow acting
long periods of iniltration
low dehydrating power

Answer 7

Butanol (MP: 117.7C)

Question 8

mercurial fix tissues through an unknown mechanism that increases staining and brightness and gives excellent nuclear detail. however mercurial penetrates poorly and produce tissue shrinkage

Answer 8

metallic fixatives

Question 9

most commonly used. metallic fixative, frequently used in saturated acqueous solutions of 5-7%

Answer 9

mercuric chloride

Question 10

is used in 1-2 aqueous solution. it precipitates proteins and adequately preserves carbohydrates

Answer 10

chromic acid

Question 11

fixation time of regaud’s (muller’s) fluid

Answer 11

12-48hrs

Question 12

examples of metallic fixatives

Answer 12

mercuric chloride and chromate fixatives

Question 13

preserves nuclear structure ( e.g. chromosomes). they usually contains glacial acetic acid and their primary component due to its affinity for nuclear chromatin.
ph 4.6 or less

Answer 13

Nuclear fixative

Question 14

traditionally used for EM. is a good fixative and staining is weak

Answer 14

osmium tetroxide

Question 15

formula:
mercuric chloride 5gm
potassium dichromate 2.5g
distilled water 100ml
acetic acid, glacial 5ml (to be added just before use)
fixation time: 12-24hrs

Answer 15

Zenker’s solution

Question 16

formula:
mercuric chloride 5gm
potassium dichromate 2.5g
distilled water 100ml
40% formaldehyde 5ml (to be added)
fixation time: 24-24hrs

Answer 16

Zenker-formol (Helly’s) solution

Question 17

examples of histochemical fixatives

Answer 17

formol saline 10%
absolute ethyl alcohol
acetone
newcomers fluid

Question 18

fixation time of formol-corrosive

Answer 18

3-24hrs

Question 19

thickness of tissue block should be

Answer 19

1.5mm

Question 20

fixation with formaldehyde is largely complete in _______ hrs

Answer 20

24hrs

Question 21

the tissue may be stored in cold PBS for how short period of time?

Answer 21

2-3days

Question 22

decalcification time of formol nitric acid

Answer 22

1-3 days

Question 23

fastest decalcifying agent

Answer 23

Zenker’s solution

Question 24

excellent bone decalcifier

Answer 24

neutral EDTA

Question 25

volatile oil found in citrus peel

Answer 25

limonene

Question 26

can be dehydrating agent and clearing agent

Answer 26

tetrahydrofuran

Question 27

not normally utilized as a routine clearing agent but recommended in clearing embryos, insects and very delicate specimen.

Answer 27

aniline oil

Question 28

recommended for urgent biopsies

Answer 28

benzene

Question 29

used to remove excess formalin, cosmic acid, and chromates from tissues fixed in Kelly’s, zenkersm and flemming slxn.

Answer 29

tap water

Question 30

advantage
it is miscible with both absolute alcohol and paraffin
acts fairly rapidly and is recommended for routine purpose
clears overnight
not carcinogenic

disadvantage
slower than xylene and benzene
tends to acidify in a particular filled vessel
more expensive
highly concentrated solutions will emit fumes that are toxic upon prolonged exposure

Answer 30

toluene

Question 31

advantage:
recommended for routine work (6-24hrs)
miscible with absolute alcohol
reco for tough tissues ( skin fibroid and decalcified tissues)
suitable for lang tissue spx
not flammable

disad
relatively toxic to the liver

Answer 31

chloroform

Question 32

most widely used fixative for routine histology

Answer 32

10%. neutral buffered formalin