Dehydration and clearing

Question 1

Process of removing intercellular & extracellular water from the tissue following fixation & prior to wax impregnation

Answer 1

dehydration

Question 2

Characteristics of an Ideal Dehydrating Solution:

Answer 2

• It must dehydrate rapidly
• It should not remove stains
• Not evaporate very fast
• not toxic
• be able to dehydrate fatty tissues
• Not be a fire hazard
• It should not harden the tissue

Question 3

• Best dehydrating agent - fast acting
• not expensive
• not poisonous

Answer 3

ethyl alcohol

Question 4

• Primarily employed for blood and tissue
  films and for smear preparation
• toxic

Answer 4

methyl alcohol

Question 5

• slow dehydrating agent
• recommended for tissues which do not require rapid processing

Answer 5

butyl alcohol

Question 6

produces less shrinkage and hardening than ethyl alcohol

Answer 6

butyl alcohol

Question 7

Factors to considered in dehydration:

Answer 7

• Size and nature of tissue
• type of fixative used
• temperature
• ratio

Question 8

alcohol concentration:
make tissues hard brittle and
difficult to cut

Answer 8

above 80%

Question 9

alcohol concentration:
liable to produce considerable
shrinkage and hardening of tissues leading
to distortion

Answer 9

85-95%

Question 10

tend to harden only the surface of the tissue while the deeper parts are not completely penetrated

Answer 10

95% or absolute alcohol

Question 11

Gen. Schedule for Alcohol Dehydration

Answer 11

70% alcohol - 6 hrs
95% alcohol - 12 hrs
100% alcohol - 2 hrs
100% alcohol - 1 hr
100% alcohol - 1 hr

Question 12

dehydration sequence for
specimens not more than 4mm thick

Answer 12

70% - 15 mins
90% - 15 mins
100% - 15 mins
100% - 15 mins
100% - 30 mins
100% - 45 mins

Question 13

Cheap, rapid acting dehydrating agent.

Answer 13

acetone

Question 14

Expensive and extremely dangerous

Answer 14

dioxane (diethyl dioxide)

Question 15

dehydrates in 30 mins to 2 hours

Answer 15

acetone

Question 16

Used to dehydrate sections and smears

Answer 16

triethyl phosphate

Question 17

It may be used for demixing, clearing and dehydrating paraffin sections
before and after staining

Answer 17

tetrahydrofuran

Question 18

Clear, colorless highly flammable and extremely volatile fluid

Answer 18

acetone

Question 19

Not recommended for routine dehydration purposes

Answer 19

acetone

Question 20

Tissues can be left for long periods of time without affecting the
consistency or staining properties of the specimen

Answer 20

dioxane

Question 21

The tissue may be transferred from water or normal saline directly to cellosolve and stored in it for months without producing hardening or distortion

Answer 21

cellosolve

Question 22

combustible at 110°F to 120°F and is toxic

Answer 22

ethylene glycol

Question 23

Triethyl Phosphate is soluble in

Answer 23

• water
  -alcohol
• ether
• benzene
• chloroform
• acetone
• xylene

Question 24

removes water

Answer 24

triethyl phosphate

Question 25

instead of ethylene glycol ether you can use

Answer 25

propylene based glycol

Question 26

It both dehydrates and clears tissues since it is miscible in water and paraffin

Answer 26

tetrahydrofuran (THF)

Question 27

Additives to Dehydrating Agentsd

Answer 27

- 4% Phenol - glycerol alcohol mixture or in “Molliflex)

Question 28

Tissue processing for transmission electron microscopy

Answer 28

ethanol - dehydrating solvent propylene oxide - transition fluid

Question 29

good substitute for propylene

Answer 29

Acetonitrile

Question 30

non-carcinogenic, less toxic and not as flammable as propylene oxide

Answer 30

Acetonitrile

Question 31

dehydrating and clearing agent

Answer 31

DIOXANE Tetrahydrofuran

Question 32

The tissue may be transferred from water or normal saline directly to cellosolve and stored in it for months without producing hardening or distortion.

Answer 32

Cellosolve (Ethylene Glycol Monoethyl Ether)

Question 33

the transition step between dehydration and infiltration with the embedding medium.

Answer 33

clearing

Question 34

Most commonly used clearing agents

Answer 34

xylene, dioxane, chloroform and cedarwood oil.

Question 35

Recommended for routine purposes

Answer 35

- toluene - xylene

Question 36

Not recommended for routine purposes

Answer 36

- aniline oil - cedarwood oil - clove oil

Question 37

Unsuitable for routine clearing

Answer 37

- clove oil

Question 38

Expensive

Answer 38

- toluene - cedarwood oil - clove oil

Question 39

Make tissues transparent

Answer 39

- xylene - benzene - cedarwood oil

Question 40

Does not make tissue transparent

Answer 40

- chloroform - carbon tetrachloride

Question 41

Highly flammable

Answer 41

- xylene - benzene

Question 42

Does not dissolve aniline dyes

Answer 42

- xylene - cedarwood oil