LESSON 4: DEHYDRATION Flashcards
eye inflammation
Conjunctivitis
means no water
Anhydrous
solvent for water
Polar
100% alcohol
Absolute
simplest tertiary alcohol
Tearbutanol
carboxylic acid formed from methanol
Formic Acid
solvent for organic molecules
Non-polar
in between cells
Intracellular
aka soluble
Miscible
effect of a higher concentration gradient on the rate of diffusion of molecules
Increased
➢ Removal of fixative and intercellular and extracellular water from tissues in preparation for infiltration
➢ Increasing strengths of the dehydrating agent is used to prevent distortion of tissue structures by diffusion currents (flow of molecules)
DEHYDRATION
Type of Tissue
(eg. embryo): start with 30% ethanol up to 70%
DELICATE TISSUES
Type of Tissue start with 70% up to 95% or Absolute alcohol
NORMAL TISSUES
VOLUME
10X the volume of tissue
On Prolonged Immersion tissues become hard and brittle
High Concentrations
On Prolonged Immersion tissues become macerated
Low Concentrations
increases rate of dehydration and used for tissues that require
urgent examination
37 deg Celsius
Accelerates diffusion of molecules increasing the rate of dehydration
Agitation
¼ inch at the bottom of the container to facilitate the removal
of water molecules from the dehydrating fluid
Anhydrous copper sulfate:
✓ Clear, colorless, flammable liquid
✓ Recommended for routine dehydration
✓ Best dehydrating agent, fast-acting and miscible in water and many organic
solvents
✓ Penetrates tissues easily
✓ Not poisonous, not very expensive
✓ Long Immersion in high concentrations should be avoided
ETHANOL
Substitute for ethanol
ISOPROPYL ALCOHOL
✓ Also referred to as wood alcohol
✓ Toxic dehydrating agent (methanol is converted to formaldehyde and can be further converted to formic acid: both formaldehyde and formic acid are toxic
to the body)
✓ for blood & tissue films and smear preparations
METHANOL
✓ Slow-acting
✓ For plants & animals
✓ Also recommended for tissues which do not require rapid processing
✓ May be used in combination with ethanol
✓ Used to dehydrate slides after staining
BUTYL ALCOHOL
✓ cheap, rapid and used for most urgent biopsies
✓ duration: 30 minutes to 2 hours
✓ removes lipids from tissues
✓ penetration is poor and causes brittleness
ACETONE
✓ Rapid and does not cause any harmful effect on tissues
✓ 4 baths: 30 min → 30-60 min → 60 min → 90 min
✓ Toxic to the reproductive, fetal, urinary and blood systems
✓ Combustible at 110-120 OF
✓ Propylene-based glycol ethers may be used in place of EGME
CELLOSOLVE (Ethylene Glycol Monoethyl Ether)
✓ Excellent dehydrating and clearing agent
✓ Fixatives → Dioxane→paraffin
**dehydration and clearing may be done at the same time using dioxane
✓ Sections ribbon poorly
✓ Expensive and extremely dangerous
✓ Vapor tends to accumulate in the body and is highly toxic
✓ Creates explosive peroxides
✓ Removal of water
DIOXANE (Diethylene dioxide)
uses several changes of pure dioxane
Graupner’s Method
uses pure dioxane and anhydrous calcium
oxide or quicklime to facilitate removal of water
Weiseberg’s Method
✓ May be used as dehydrating and clearing agent
✓ Can dissolve fats in tissues
✓ Vapors cause nausea, dizziness, headache and anesthesia
✓ Skin and eye irritant
✓ Offensive odor; may cause conjunctivitis during prolonged exposure
THF (Tetrahydrofuran)
✓ May be used to dehydrate sections and smears after staining
TRIETHYL PO4
✓ 4% phenol: added to 95% alcohol to soften tissues
ADDITIVES TO DEHYDRANTS
✓ Glycerol-alcohol mixture and Molliflex: used to soften hard tissues
ADDITIVES TO DEHYDRANTS
toxic alcohol dehydrant
Methanol
other name of cellosolve
EGME
dehydrant with an offensive odor
Tetrahydrofuran
non-alcohol-based dehydrant that removes lipids
Acetone
effect of prolonged immersion of tissues in
low concentrations of dehydrants
Maceration
method that uses pure dioxane and anhydrous calcium oxide
Weiseberg’s
type of tissue that is first immersed in 30%
alcohol
Delicate
expensive and may form explosive peroxides
Dioxane
best dehydrating agent for routine processing
Ethanol
best dehydrating agent for routine processing
Softening
T/F Additives are incorporated in the lowest concentration of acetone to prevent tissue maceration.
FALSE
Additives are incorporated in the HIGHEST concentration of ALCOHOL to PROMOTE tissue SOFTENING
T/F Tert-butyl alcohol is a slow-acting dehydrant thus causing less tissue shrinkage
and hardening.
TRUE
T/F Acetone is a rapid-acting dehydrant that penetrates tissue sample well.
FALSE: Acetone is a rapid-acting dehydrant that penetrates tissues POORLY
T/F Tetrahydrofuran can be used as a fixative and dehydrating agent but it causes dissolution of glycogen.
FALSE: Tetrahydrofuran can be used as dehydrating and clearing agent but it causes dissolution of lipids.
T/F Graupner’s method makes use of cellosolve which can act as a decalcifying and dehydrating agent.
FALSE: Graupner’s method makes use of DIOXANE which can act as dehydrating and CLEARING agent
