LESSON 4: DEHYDRATION Flashcards by CANA GIFT CHAVEZ

eye inflammation

Conjunctivitis

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means no water

Anhydrous

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solvent for water

Polar

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100% alcohol

Absolute

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simplest tertiary alcohol

Tearbutanol

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carboxylic acid formed from methanol

Formic Acid

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solvent for organic molecules

Non-polar

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in between cells

Intracellular

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aka soluble

Miscible

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effect of a higher concentration gradient on the rate of diffusion of molecules

Increased

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➢ 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

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Type of Tissue

(eg. embryo): start with 30% ethanol up to 70%

DELICATE TISSUES

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Type of Tissue start with 70% up to 95% or Absolute alcohol

NORMAL TISSUES

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VOLUME

10X the volume of tissue

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On Prolonged Immersion tissues become hard and brittle

High Concentrations

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On Prolonged Immersion tissues become macerated

Low Concentrations

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increases rate of dehydration and used for tissues that require
urgent examination

37 deg Celsius

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Accelerates diffusion of molecules increasing the rate of dehydration

Agitation

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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