DEHYDRATION

Question 1

Removing intercellular and extracellular water from the tissue following fixation and prior to wax impregnation is known as?

Answer 1

Dehydration

Question 2

Increasing strengths of alcohol for fixed specimen

Answer 2

70% ethyl alcohol in water > 95% ethyl alcohol >100% of ethyl alcohol

Question 3

For delicate tissues, particularly embryonic tissues dehydration, it starts at __________

Answer 3

30% ethanol (recommended)

Question 4

It’s important to keep the dehydration times as _____ as possible to minimize the risk of extracellular constituents.

Answer 4

brief

Question 5

General rule, the amount in each stage should not be __________ the volume of the tissue in order to ensure complete penetration

Answer 5

less than 10 times

Question 6

FIVE COMMONLY USED DEHYDRATING AGENTS:

Answer 6

1. Alcohol (most common)
2. Acetone
3. Dioxane
4. Cellosolve
5. Triethyl phosphate
6. Tetrahydrofuran

Question 7

Recommended for routine dehydration of tissues. Clear, colorless, flammable fluid.

Answer 7

Ethyl alcohol (ethanol)

Question 8

Considered the best dehydrating agent because it is fast-acting, mixes with water and many organic solvents also penetrates tissue easily. Not poisonous and not very expensive.

Answer 8

Ethyl alcohol (ethanol)

Question 9

Toxic, primarily employed for blood and tissue films also smear preparation.

Answer 9

Methyl Alcohol

Question 10

Utilized in plant and animal micro techniques, slow dehydrating agent.

Answer 10

Butyl Alcohol

Question 11

Produces less shrinkage and hardening recommended for
tissue which does not require rapid processing.

Answer 11

Butyl Alcohol

Question 12

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

Answer 12

concentrated alcohols (95% or absolute)

Question 13

Will hasten dehydration and used for tissue sections that require urgent examination such as fragmentary biopsies.

Answer 13

temperature of 37⁰C

Question 14

Ensuring complete dehydration, a layer of
________, about 1/4 inch deep is placed in the bottom of the container and covered with filter paper. This will accelerate dehydration by removing water from the dehydrating fluid.

Answer 14

anhydrous copper sulfate

Question 15

Cheap, rapid-acting dehydrating agent utilized for most urgent biopsies dehydrates in ½ to 2 hours

Answer 15

Acetone

Question 16

More miscible with epoxy but is highly flammable and requires consideration care in handling

Answer 16

Acetone

Question 17

Rapid in action but penetrates tissue poorly and causes brittleness in tissues. Most lipids are removed from tissue

Answer 17

Acetone

Question 18

Limited only to small pieces of tissues due to its extreme volatility and not recommended for routine dehydration.

Answer 18

Acetone

Question 19

Excellent dehydrating and clearing agent readily miscible in water, melted paraffin, alcohol and xylol

Answer 19

Dioxane (Diethylene Dioxide)

Question 20

Tissues can be left in this reagent for long periods of time

Answer 20

Dioxane (Diethylene Dioxide)

Question 21

Miscible with both water and paraffin, tissues may be placed directly into the solution after washing out.

Answer 21

Dioxane (Diethylene Dioxide)

Question 22

Dehydration time for acetone

Answer 22

3-24 hours

Question 22

Tissues are fixed, washed and transferred directly, removes water very readily and produces very little distortion and hardening of tissue

Answer 22

Triethyl phosphate

Question 22

Expensive, extremely dangerous. Vapor produces a cumulative and highly toxic action in man; should not be used routinely.

Answer 22

Dioxane (Diethylene Dioxide)

Question 23

Tissues which have been treated with a ________, or, __________, __________ should be thoroughly washed in running tap water prior to treatment with dioxane in order to remove the chromate.

Answer 23

chromate fixative; Reagents; Moller’s fluid

Question 24

Soluble in alcohol, water, ether, benzene, chloroform, acetone and xylene

Answer 24

Triethyl phosphate

Question 24

Used to dehydrate sections and smears following certain stains and produces minimum shrinkage.

Answer 24

Triethyl phosphate

Question 25

A reagent that both dehydrates and clear tissues since it is miscible in both water and paraffin

Answer 25

Tetrahydrofuran (THF)

Question 26

Can dissolve many substances including fats and is in itself miscible with lower alcohol, water, ether, benzene, chloroform, acetone and xylene

Answer 26

Tetrahydrofuran (THF)

Question 27

Maybe used for demixing, clearing and dehydrating paraffin sections before and after staining.

Answer 27

Tetrahydrofuran (THF)

Question 28

Does not dissolve out aniline dyes and toxic if ingestion or inhaled

Answer 28

Tetrahydrofuran (THF)

Question 29

Dehydrates rapidly and not harmful to tissues. Toxic by inhalation, skin contact and ingestion (Use propylene-based glycol esters)

Answer 29

Cellosolve/ Ethylene Glycol Monoethyl Ether

Question 30

Used to dehydrate sections and smears following certain stains

Answer 30

Triethyl phosphate

Question 31

It is an eye and skin irritant and prolong exposure (up to 6 months) may cause conjunctival irritation

Answer 31

Tetrahydrofuran (THF)

Question 32

Should be used if good grade absolute ethyl alcohol is not easily available

Answer 32

Isopropanol/ Isopropyl Alcohol

Question 33

Acetone chemical formula

Answer 33

CH3COCH3 or (CH3)2CO