DEHYDRATION Flashcards
Removing intercellular and extracellular water from the tissue following fixation and prior to wax impregnation is known as?
Dehydration
Increasing strengths of alcohol for fixed specimen
70% ethyl alcohol in water > 95% ethyl alcohol >100% of ethyl alcohol
For delicate tissues, particularly embryonic tissues dehydration, it starts at __________
30% ethanol (recommended)
It’s important to keep the dehydration times as _____ as possible to minimize the risk of extracellular constituents.
brief
General rule, the amount in each stage should not be __________ the volume of the tissue in order to ensure complete penetration
less than 10 times
FIVE COMMONLY USED DEHYDRATING AGENTS:
- Alcohol (most common)
- Acetone
- Dioxane
- Cellosolve
- Triethyl phosphate
- Tetrahydrofuran
Recommended for routine dehydration of tissues. Clear, colorless, flammable fluid.
Ethyl alcohol (ethanol)
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.
Ethyl alcohol (ethanol)
Toxic, primarily employed for blood and tissue films also smear preparation.
Methyl Alcohol
Utilized in plant and animal micro techniques, slow dehydrating agent.
Butyl Alcohol
Produces less shrinkage and hardening recommended for
tissue which does not require rapid processing.
Butyl Alcohol
Tend to harden only the surface of the tissue while the deeper parts are not completely penetrated
concentrated alcohols (95% or absolute)
Will hasten dehydration and used for tissue sections that require urgent examination such as fragmentary biopsies.
temperature of 37⁰C
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.
anhydrous copper sulfate
Cheap, rapid-acting dehydrating agent utilized for most urgent biopsies dehydrates in ½ to 2 hours
Acetone
More miscible with epoxy but is highly flammable and requires consideration care in handling
Acetone
Rapid in action but penetrates tissue poorly and causes brittleness in tissues. Most lipids are removed from tissue
Acetone
Limited only to small pieces of tissues due to its extreme volatility and not recommended for routine dehydration.
Acetone
Excellent dehydrating and clearing agent readily miscible in water, melted paraffin, alcohol and xylol
Dioxane (Diethylene Dioxide)
Tissues can be left in this reagent for long periods of time
Dioxane (Diethylene Dioxide)
Miscible with both water and paraffin, tissues may be placed directly into the solution after washing out.
Dioxane (Diethylene Dioxide)
Dehydration time for acetone
3-24 hours
Tissues are fixed, washed and transferred directly, removes water very readily and produces very little distortion and hardening of tissue
Triethyl phosphate
Expensive, extremely dangerous. Vapor produces a cumulative and highly toxic action in man; should not be used routinely.
Dioxane (Diethylene Dioxide)
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.
chromate fixative; Reagents; Moller’s fluid
Soluble in alcohol, water, ether, benzene, chloroform, acetone and xylene
Triethyl phosphate
Used to dehydrate sections and smears following certain stains and produces minimum shrinkage.
Triethyl phosphate
A reagent that both dehydrates and clear tissues since it is miscible in both water and paraffin
Tetrahydrofuran (THF)
Can dissolve many substances including fats and is in itself miscible with lower alcohol, water, ether, benzene, chloroform, acetone and xylene
Tetrahydrofuran (THF)
Maybe used for demixing, clearing and dehydrating paraffin sections before and after staining.
Tetrahydrofuran (THF)
Does not dissolve out aniline dyes and toxic if ingestion or inhaled
Tetrahydrofuran (THF)
Dehydrates rapidly and not harmful to tissues. Toxic by inhalation, skin contact and ingestion (Use propylene-based glycol esters)
Cellosolve/ Ethylene Glycol Monoethyl Ether
Used to dehydrate sections and smears following certain stains
Triethyl phosphate
It is an eye and skin irritant and prolong exposure (up
to 6 months) may cause conjunctival irritation
Tetrahydrofuran (THF)
Should be used if good grade absolute ethyl alcohol is not easily available
Isopropanol/ Isopropyl Alcohol
Acetone chemical formula
CH3COCH3 or (CH3)2CO
