MIDTERM LEC: DEHYDRATION

Question 1

Follows fixation, and decalcification (if applicable)

Answer 1

DEHYDRATION

Question 2

It is the removal of water from tissue in preparation for impregnation

Answer 2

DEHYDRATION

Question 3

Since most fixatives are aqueous solutions, placing the fixed tissue in molten paraffin will not achieve impregnation because paraffin wax and water (from fixative) do not mix. Hence, dehydration must be done.

Answer 3

DEHYDRATION

Question 4

Done as brief as possible and at a tissue-to-fixative ratio of 1:10

Answer 4

DEHYDRATION

Question 5

Common Dehydrating Agents:

Answer 5

I. Alcohol
II. Acetone
III. Dioxane
IV. Cellosolve
V. Triethyl phosphate
VI. Tetrahydrofuran

Question 5

Characteristics of Ideal Dehydrating Agents:

Answer 5

1. Rapid action, with minimal tissue shrinkage and distortion
2. Should not evaporate fast
3. Able to dehydrate even fatty tissues
4. Should not harden tissues excessively
5. Should not remove stains
6. Non-toxic, and not a fire hazard

Question 6

Done in ascending grades to avoid distortion of tissue: 70% ROH -> 90% ROH ->100% ROH

Answer 6

ALCOHOLS

Question 7

For delicate tissues, start at 30%

Answer 7

ALCOHOLS

Question 8

ALCOHOLS

Initial alcohol conc. depends on the size and nature of tissue and the fixative used:

Answer 8

 Strong initial conc.  shrinkage and brittleness
 Prolonged dehydration in less than 70% ROH  tissue maceration

Question 9

ALCOHOLS

37C

Answer 9

will hasten dehydration rate (for urgent exams)

Question 10

ALCOHOLS

To ensure complete dehydration:

Answer 10

Add atleast ¼ deep layer of anhydrous Cu2SO4 at bottom of container, and cover with filter paper

Question 11

ALCOHOLS

indicates full saturation of dehydrating fluids with water, thus alcohol must be changed with
a fresh solution

Answer 11

Bluing of copper sulfate crystals

Question 12

ALCOHOLS:

Answer 12

1. Ethyl alcohol (Ethanol)
2. Methanol
3. Butanol

Question 13

Best dehydrant because it is fast-acting, mixes with water and many organic solvents, and penetrates tissues easily

Answer 13

Ethyl alcohol (Ethanol)

Question 14

Not poisonous and not very expensive

Answer 14

Ethyl alcohol (Ethanol)

Question 15

Clear, colorless, flammable

Answer 15

Ethyl alcohol (Ethanol)

Question 16

For blood & tissue films, smears

Answer 16

Methanol

Question 17

Plant and animal microtechniques

Answer 17

Butanol

Question 18

Less tissue shrinkage and hardening but slow

Answer 18

Butanol

Question 19

Fastest dehydrant (1/2 to 2 hours), thus for rapid biopsies

Answer 19

ACETONE

Question 20

Clear, colorless, and more miscible with epoxy resins than alcohol

Answer 20

ACETONE

Question 21

DADV: Flammable, extremely volatile, and not recommended for routine work because of considerable shrinkage and brittleness

Answer 21

ACETONE

Question 22

Lipids are removed from tissue

Answer 22

ACETONE

Question 23

Both a dehydrant and clearing agent

Answer 23

DIOXANE (DIETHYLENE DIOXIDE)

Question 24

ADV: Less tissue shrinkage, prolongation is possible

Answer 24

DIOXANE (DIETHYLENE DIOXIDE)

Question 25

DADV: extremely dangerous because of toxicity, and risk of explosion; expensive, tissues will have poor ribbons

Answer 25

DIOXANE (DIETHYLENE DIOXIDE)

Question 26

DIOXANE (DIETHYLENE DIOXIDE) Methods:

Answer 26

1. Graupner's 2. Weiseberger’s

Question 27

pure dioxane -> paraffin

Answer 27

Graupner's

Question 28

wrapping tissue in gauze and suspension to bottle containing dioxane with anhydrous calcium oxide or quicklime

Answer 28

Weiseberger’s

Question 29

# DIOXANE (DIETHYLENE DIOXIDE) Note: Tissues treated with chromic acid must be ____

Answer 29

thoroughly washed with water prior to dioxane treatment

Question 30

ADV: no shrinkage in prolongation

Answer 30

CELLOSOLVE/ETHYLENE GLYCOL MONOGLYCOL ETHER

Question 31

DADV: Combustible at 110-120F, toxic to reproductive, fetal, urinary, and blood systems

Answer 31

CELLOSOLVE/ETHYLENE GLYCOL MONOGLYCOL ETHER

Question 32

If cannot be avoided, propylene-based glycol ethers should be used instead of ethylene-based

Answer 32

CELLOSOLVE/ETHYLENE GLYCOL MONOGLYCOL ETHER

Question 33

A:rapid, little distortion and hardening

Answer 33

TRIETHYL PHOSPHATE

Question 34

Both a dehydrant and clearing agent

Answer 34

TETRAHYDROFURAN

Question 35

Dissolves fats

Answer 35

TETRAHYDROFURAN

Question 36

Most staining procedures give improved results with THF

Answer 36

TETRAHYDROFURAN

Question 37

Has rather offensive odor, thus room must be well-ventilated

Answer 37

TETRAHYDROFURAN

Question 38

Toxic to eyes (conjunctival irritation) and skin (Teflon gloves may be used, but it is recommended to avoid THF use)

Answer 38

TETRAHYDROFURAN

Question 39

ADDITIVES:

Answer 39

1. 4% phenol 2. Molliflex (glycerol alcohol mixture)

Question 40

added to 95% ETOH; softener for hard tissues

Answer 40

4% phenol

Question 41

softener

Answer 41

Molliflex (glycerol alcohol mixture)