Unit 3.2. Dehydration

Dehydration

a mandatory process of removing water from the tissue following fixation in preparation for wax infiltration

F

T or F

Decalcification can be performed by the autotechnicon

ascending grades of alcohol;

70%

Dehydration is accomplished through the use of _______________ starting with _____ concentration

70%

95%

100%

Dehydration starts by placing the fixed spx in _____ in water, progressing through _____ ethyl alcohol to _____ ethyl alcohol

30% ethanol

For delicate tissues (esp. embryonic tissues), dehydration starting with ___________ is recommended

< 10:1

Dehyrating agent to tissue ratio

incomplete dehydration

most common problem in tissue processing

prevent ingress of the clearing agents to the tissue

soft ;

non-receptive ;

infiltration ;

incomplete dehydration makes the tissue _______ and _____________ to weak _________

1. Ethyl alcohol

2. Methyl alcohol

3. Isopropyl/ Isopropanol

4. Butyl alcohol

5. Acetone

6. Dioxane (Diethylene dioxide)

7. Tetrahydrofuran (THF)

8. Cellosolve

9. Triethyl phosphate

Enumerate DEHYDRATING AGENTS

Ethyl alcohol

DEHYDRATING AGENTS

• most common fast-acting alcohol

• best dehydrating agent

• recommended for routine dehydration of tissues

• fast acting

• mixes w water and many organic solvents

• penetrates tissue easily

Ethyl alcohol characteristics

Denatured alcohol

________________ is a form of ethanol through a mixture with methanol that is unfit for human consumption

anhydrous coper sulfate;

1-4 inches

Along with ethyl alcohol, a layer of ___________________, sized ________, is placed at the bottom of the container and then covered with a filter paper.

• blue = presence of water = incomplete dehydration

• white = absence of water = complete dehydration

• copper sulfate is blue = ________ of water = ___________ dehydration

• copper sulfate is white = ________ of water = ___________ dehydration

methyl alcohol

DEHYDRATING AGENTS

• a toxic dehydrating agent

blood & tissue films

smear preparation

methyl alcohol is used for

Isopropyl alcohol (isopropanol)

DEHYDRATING AGENTS

• best all-around ethanol

• can be used as a substitute to xylene

microwave processing technique

Isopropyl alcohol (isopropanol) is useful in

1. Graupner's Isopropanol

2. Weiseberger's Isopropanol

Ex. of Isopropyl alcohol (isopropanol)

immerse tissue in 3 changes of pure dioxane → 3 changes of paraffin wax → embed in water

How to use Graupner’s Isopropanol

prepare container containing dioxane + anhydrous calcium oxide/quick line → wrap container with gauze

How to use Weiseberger’s Isopropanol

acetone

DEHYDRATING AGENTS

• a fixative & dehydrating agent

• rapid acting

• very cheap

urgent biopsies ;

30 mins - 2 hrs

acetone is best utilized for __________, dehydrate within _________

• evaporates easily

• highly flammable

• not routinely used

Disadvantages of acetone

Dioxane (Diethylene dioxide)

DEHYDRATING AGENTS

• an excellent dehydrating & clearing agent

• may explode upon air exposure

• water

• xylol

• paraffin

• alcohol

Dioxane (Diethylene dioxide) is miscible in what substances

1. explodes upon air exposure (main disadvantage)

2. cumulatively toxic and carcinogenic

3. tend to ribbon poorly (section-cutting problem)

Dioxane (Diethylene dioxide) disadvantages

Tetrahydrofuran (THF)

DEHYDRATING AGENTS

• dehydrates and clears tissue at the same time

• best universal solvent for its fast action and less tissue shrinkage/hardening

Cellosolve

DEHYDRATING AGENTS

• toxic by inhalation, skin contact, and ingestion

• toxic to fetal reproduction, urinary and blood system

Ethylene Glycol Monoethyl Ether

Cellosolve chemical name

110-120 ℉;

sunlight

Cellosolve is combustible at _________, and decomposes easily upon exposure to __________

Triethyl phosphate

DEHYDRATING AGENTS

• causes minimum shrinkage

• dehydrates sections in smears