Clearing (Supplemental Cards)

Xylene

A colorless clearing agent that is commonly used in histology.

Methyl benzaldehyde

What is the intermediate product of xylene?

• Clearing agent

• Dewaxing agent

Xylene is used as?

Xylene

Its advantage is it does not dissolve celloidin and evaporated rapidly in paraffin oven.

• Nervous tissue

• Lymph nodes

Xylene causes considerable shrinking and hardening. It is not recommended for?

• Xylene

• Cedarwood oil

What are the two clearing agents that can become milky?

Toxic and narcotic

At high levels, xylene is?

Dermatitis

Xylene in contact with skin causes?

30 mins to 1 hour - routine

15 mins to 30 mins - urgent

Clearing time of xylene

Toluene

Better at preserving tissue structures and is more tolerant to leftover water.

Xylene

Benzene

Toluene is used as a substitute for?

Toluene

It is not carcinogenic.

Toluene

It tends to acidify.

It is slower than benzene and xylene.

Benzene

Preferred as clearing agent because it penetrates and clears tissue rapidly

Benzene

It has highly carcinogenic properties. Hence, use is highly discouraged.

15 minutes - 1 hour

Benzene is used in urgent biopsies. What is it clearing time?

• Too long clearing time → tissue shrinkage

• Extremely toxic to man

• Carcinogenic

• Damages bone marrow → aplastic anemia

What are the disadvantages of benzene?

Chloroform

Used as clearing agent in embedding, slower than xylene but cause less brittleness.

Chloroform

Up to 1 cm

It is used for thick tissues.

Indicate the thickness.

No

Can chloroform make tissues translucent?

Chloroform

» skin, fibrinoid, and decalcified tissues

» nervous tissue, lymph nodes, embryos

It is used for tough tissues.

Indicate what these tissues are.

What other tissues does it clear?

• Chloroform

• Dioxane

It is toxic to the liver.

Chloroform

Its vapors attack the rubber seal used in vacuum impregnating bath

Wrapping absorbent cotton gauze to tissues to facilitate sinking

Tissues float in chloroform. How is this avoided?

Cedarwood oil

It clears both paraffin and celloidin

• Central Nervous System Tissues

• Cytological studies of smooth muscle and skin

Where is cedarwood used in?

Cedarwood o

It is miscible with 96% alcohol

2 - 3 days

5 - 6 days

Clearing time of cedarwood oil

Clearing time in celloidin

Cedarwood oil

Its advantage is that it is extremely slow

Transfer the specimen from oil to benzene for 30 mins before placing in wax

Cedarwood oil is hard to eliminate. What is the corrective action?

Superimpose absolute alcohol on the surface of the cedarwood oil.

Then transfer to a new cedarwood oil solution.

The quality of tissues is not uniform in cedarwood oil because it initially floats before sinking to the bottom. Hence, the tissue may dry out before it proceeds. How is it prevented?

• Clear acetic-alcohol fixed tissue

• Crystals

• Heating the tissue at 200 C

Cedarwood oil used to clear what specimen causes?

How is it prevented?

Cedarwood oil

It produces crystals

Aniline oil

This is not normally utilized as a routine clearing agent but it is recommended for clearing embryos, insects and very delicate specimens, due to its ability to clear 70% alcohol without excessive tissue shrinkage and hardening.

Clove oil

Its quality is not guaranteed due to its tendency to become adulterated.

Clove oil

Wax impregnation after clearing is slow and difficult. Tissues become brittle, aniline dyes are removed, and celloidin is dissolved.

Carbon tetrachloride

Similar to chloroform, but cheaper.

Tetrahydrofuran

It is superior to ordinary dehydrating and clearing agents due to its ability to perform 2 processes at a time, which shortens process time.

Tetrahydrofuran

It is nontoxic but odorous.

Dioxane

Tissues dissolved in Bouin’s solution or formalin fixative is transferred to this clearing agent.

Dioxane

It causes greater shrinkage than xylene.

Yes

Is 1.7% dish washing solution considered a xylene substitute?

Terpenes

These are isoprene polymers found in essential oils originally derived from plants, though some are now synthesized.

Terpenes

They are the earliest transition solvents to be used in histology.

Limonene

Lemon zest or Orange zest

Steam distillation

They are found in citrus peels.

They are referred to as?

They are obtained through?

Orange oil based clearing agents

It offers clearing action with lowest hazard rating of all xylene alternatives.

Chlorinated hydrocarbons

It is effective as a solvent but considered toxic.

It is government regulation restricted.

Methyl benzoate

Methyl salicylate

It is a slow acting clearing agent that can be used when double embedding techniques are required.

Coconut oil

Dealcoholization agent

It is an efficient substitute to xylene but it is non-hazardous, less expensive, and cause less shrinkage.

It can be used as?

Solidifies at low temperature

Drawback of coconut oil

Bleached palm oil

It can be a substitute to conventional xylene as clearing and dewaxing agent.

It is nontoxic, nonflammable, biodegradable, and economic.