Dehydration Flashcards
what is dehydration?
process of removing intercellular and extracellular water from the tissue following fixation and prior to wax impregnation
what is the purpose of dehydrating agents?
to remove aqueous tissue fluids with little disruption to the tissue caused by diffusion currents
t or f: most of the dehydrating agents are alcohols
true
dehydration starts by?
placing fixed specimen in 70% ethyl alcohol in water, progressing through 95% ethyl alcohol to 100% ethyl alcohol
recommended alcohol concentration for embryonic tissues
30%
what is the general rule in dehydration?
the amount of dehydrating agent should not be LESS THAN 10 TIMES the volume of the tissue
enumerate the characteristics of an ideal dehydrating solution
IT SHOULD NOT:
1. not dehydrate rapidly w/out producing considerable shrinkage or distortion of tissue
2. not evaporate very fast
3. not be able to dehydrate even fatty tissues
4. not harden tissues excessively
5. not remove stains
6. not be toxic to the body
7. not be a fire hazard
enumerate the commonly used dehydrating reagents
DSATAT
- dioxane4
- cellosolve
- alcohol
- triethyl phosphate
- acetone
- tetrahydrofuran
alcohol reco for routine dehydration of tissues, considered as the best dehydrating agent
ethyl alcohol (ethanol)
methyl alcohol is a toxic dehydrating agent primarily used for?
- blood and tissue films
- for smear preparations
a slow dehydrating agent utilized in plant and animal micro-techniques, producing less shrinkage
butyl alcohol
dehydrating agent recommended for tissues which do not require rapid processing
butyl alcohol
why formalin-fixed tissue should not be transferred directly to higher grades of alcohol?
because this may produce considerable shrinkage and hardening of tissues
these alcohols tend to harden only the surface of the tissue while the deeper parts are not completely penetrated
concentrated alcohols (95% or absolute)
this will make tissues, hard, brittle, and difficult to cut
under dehydration topic
concentrated alcohols above 80%
prolonged storage in lower concentrations of alcohol tends to?
macerate the tissues
dehydration period using 10% formol-saline alcohol, 70% alcohol, 90%, absolute alcohol
13-5
time in hours for dehydration (running water) using the zenker or helly’s fixative
1-12
dehydration (alcohol 70% to absolute) using the bouin’s fluid
13-12
dehydration (alcohol 30% to absolute) using the zenker or helly’s
1-6
dehydration (alcohol 90% to absolute) using the SUSA, Carnoy, or formol-sublimate fixative
1-6 hours
time in hours for flemming’s fluid and the dehydrating agent is running water
1-12
time in hours for flemming’s fluid is 1/2-3, what is the dehydrating agent/s that was used?
30%, 50%, 70%
time in hours for flemming’s using the absolute alcohol
1-3
Temperature that will hasten dehydration and is used for tissue sections that require urgent examinations such as fragmentary biopsies
37C
to ensure complete dehydration, a layer of __ about ___ deep is placed in the bottom of the container and covered with filter paper
to ensure complete dehydration, a layer of ANHYDROUS COPPER SULFATE about 1/4 INCH deep is placed in the bottom of the container and covered with filter paper
purpose of anhydrous copper sulfate and filter paper in dehydration
to accelerate dehydration by removing water from the dehydrating fluid
blue discoloration of ___ will indicate full saturation of dehydrating fluids
copper sulfate crystals
cheap, rapid-acting dehydrating agent utilized for most urgent biopsies
acetone
clear, colorless fluid that mixes with water, ethanol, and most organic solvents
acetone
acetone is more miscible with __ than alcohol but is highly flammable
epoxy resins
effect of prolonged dehydration using acetone
penetrates tissue poorly and causes brittleness in tissues
these are removed from tissues with acetone
lipids
excellent dehydrating and clearing agent readily miscible in water, melted paraffin, alcohol, and xylol
diethylene dioxide
a dehydrating agent not recommended for routine dehydration purposes
acetone
advantage of dioxane
tissues can be left in this reagent for long periods without affecting the consistency or staining properties
disadvantage of dioxane
- expensive
- cumulative
- highly toxic
what is the method in dioxane utilizing the paraffin wax?
Graupner’s method
Graupner’s method:1st pure dioxane - 1 hr2nd pure dioxane - __3rd ___ - 2 hours1st paraffin wax - 2nd paraffin wax - 3rd paraffin wax -
Graupner’s method:1st pure dioxane - 1 hr2nd pure dioxane - 1 hr3rd pure dioxane - 2 hrs1st paraffin wax - 15 mins2nd paraffin wax - 45 mins3rd paraffin wax - 2 hrs
method used in dioxane in which the tissue is wrapped in a gauze bag and suspended in a bottle containing dioxane and a little anhydrous calcium oxide
Weiseberger’s method
dehydration period for weiseberger’s method
3-24 hrs
why Regaud’s or Moller’s fluid should be thoroughly washed in running tap water?
to remove the chromate
this agent dehydrates rapidly
cellosolve (ethylene glycol monoethyl ether)
t or f: you can store the tissue for longer periods of time using cellosolve
true
combustible at 110-120F and are toxic by inhalation, skin contact, and ingestion
ethylene glycol ethers
these systems can be particularly vulnerable for the toxic side effects of ethylene glycol ethers
reproductive, fetal, urinary, and blood systems
other option of ethylene glycol ethers
ethylene-based glycol ethers
this is used to dehydrate sections and smears following certain stains and produces minimum shrinkage
triethyl phosphate
a reagent that both dehydrates and clears tissue since it is miscible in water and paraffin
tetrahydrofuran
tetrahydrofuran can dissolve many substances including fats and is in itself miscible with ___
lower alcohols, ether, chloroform, acetone, benzene, xylene
this may be used for demixing, clearing, and dehydrating paraffin sections with fewer artifacts
tetrahydrofuran
tetrahydrofuran does not dissolve out __ dye
aniline dye
prolonged exposure for this dehydrating agent may cause conjunctival irritation
tetrahydrofuran
an additive that act as a softener for tissues such as tendon, nail, or dense fibrous tissue
phenol (4%)
an additive used for hard tissues
glycerol/alcohol mixture or in Molliflex
enumerate the alcohol reagents
- ethanol / ethyl alcohol
- isopropanol / isopropyl alcohol
- methanol / methyl alcohol
- butanol / butyl alcohol
- acetone
- dioxane / diethylene dioxide
- cellosolve / ethylene glycol monoethyl ether
- triethyl phosphate
- tetrahydrofuran
dehydration time for acetone
1/2 - 2 hrs