clearing

Question 1

A process whereby alcohol or a dehydrating agent is
removed from the tissue and replaced with a substance
that will dissolve the wax with which is to be
impregnated or the medium on which the tissue is to be
mounted

Answer 1

clearing (de-alcoholization)

Question 2

✓ For clearing, embedding and mounting procedures
✓ To remove paraffin in slides, not in actual mounting

Answer 2

xylene (xylol)

Question 3

xylene (xylol) is:

✓ Dewaxing agent during staining
✓ Suitable for histologic processing schedules of less than ____, tissue block size _________
✓ Works well for_____ clearing of small tissue
blocks

Answer 3

24hrs, <5mm in thickness, short-term

Question 4

advantages of xylene

Answer 4

o Rapid clearing agent
o Suitable for urgent biopsies
o Clears within 15-30minutes
o Miscible with absolute alcohol and paraffin
o Dissolve celloidin
o Evaporates quickly in paraffin oven
o Cheap

Question 5

xylene clears within _____-

Answer 5

15-30 mins

Question 6

disadvantages of xylene:

o Makes tissues excessively hard and brittle, if used
longer than ______
o Becomes _____ when an incompletely dehydrated
tissue is immersed

Answer 6

3 hrs, milky

Question 7

xylene is an ______

Answer 7

irritant

Question 8

Handling Procedures and Storage Requirements:

✓ Close the container tightly
✓ Store in a ______ area
✓ Store in a ______ storage cabinet
✓ Use ________; in closed containers
and in the _________
✓ Store below _____ for visibility of cracks or leaking
containers and there is less potential for falling onto lab
workers when pulling from shelves
✓ Do not mix ______-

Answer 8

cool and dry, flammable liquid cabinets, chemical transport carriers, smallest amounts, eye level, paraffin and xylene

Question 9

✓ Preserves tissue structure
✓ Expensive and toxic than xylene
✓ Substitute for xylene or benzene for clearing during
embedding and mounting processes

Answer 9

toluene

Question 10

advantage of toluene

Answer 10

Tissues do not become excessively hard and brittle
even if left in toluene for 24 hrs

Question 11

Disadvantages of toluene

o Slower than _____ and _______
o Tends to _____ in a partially filled vessel
o Emit _____in highly concentrated solutions that are
toxic upon prolonged exposure

Answer 11

xylene and benzene, acidify, fumes

Question 12

✓ Penetrates and clears tissues rapidly
✓ Highly carcinogenic (preleukemic state)

Answer 12

benzene

Question 13

advantages of benzene

Answer 13

o Urgent biopsies (15-60minutes)
o Does not make tissues hard and brittle
o Causes minimum shrinkage
o Makes tissues transparent

Question 14

disadvantages of benzene

Answer 14

o Highly flammable
o Excessive exposure may be extremely toxic and may become carcinogenic
o May damage the bone marrow resulting in aplastic anemia

Question 15

benzene may damage bone marrow causing

Answer 15

aplastic anemia

Question 16

benzene may become _____

Answer 16

carcinogenic

Question 17

time interval for benzene in urgent biopsies

Answer 17

15-60 mins

Question 18

✓ Slower in action than xylene, but causes
less brittleness
✓ Thicker tissue blocks can be processed, even those
up to 1 cm in thickness

Answer 18

chloroform

Question 19

in chloroform, thicker tissue blocks can be processed, even those
up to _____ in thickness

Answer 19

1 cm

Question 20

• Recommended for touch tissues (skin, fibroid
  and decalcified tissues) for nervous tissues,
  lymph nodes and embryos
• Suitable for large tissue specimens

Answer 20

chloroform (advantages)

Question 21

Relatively toxic to the liver after prolonged inhalation

Answer 21

chloroform

Question 22

Wax impregnation after _____ clearing is relatively slow

Answer 22

chloroform

Question 23

o Does not make tissues transparent
o Tissues tend to float
o Evaporates quickly from a water bath

Answer 23

chloroform (disadvantages)

Question 24

✓ Used to clear both paraffin and celloidin sections

Answer 24

cedarwood oil

Question 25

✓ Recommended for CNS tissues and cytological studies, especially smooth muscles and skin

Answer 25

cedarwood oil

Question 26

✓ Requires 2 changes in clearing solution ✓ Clearing is usually complete in 2-3days

Answer 26

cedarwood oil

Question 27

cedarwood oil is ____ penetrating

Answer 27

very

Question 28

cedarwood oil clears _____ in ____ days

Answer 28

celloidin, 5-6 days

Question 29

clearing agents wherein tissues may be left in oil definitely without considerable damage and distortion

Answer 29

cedarwood oil

Question 30

o Does not harden tissues o Improves cutting of the sections

Answer 30

cedarwood oil

Question 31

o Extremely slow clearing agent o Quality is not always uniform and good o Filter cedarwood oil before use, it becomes milky upon prolonged storage o Very expensive

Answer 31

cedarwood oil

Question 32

Not normally utilized as a routine clearing agent

Answer 32

analine oil

Question 33

Recommended for clearing embryos, insects, and very delicate specimens, due to its ability to clear 70% alcohol without excessive tissue shrinkage and hardening.

Answer 33

analine oil

Question 34

✓ Causes minimum shrinkage of tissues, but quality is not guaranteed; ✓ Wax impregnation after clearing is slow and difficult; ✓ Unsuitable for routine clearing purposes since tissues become brittle.

Answer 34

clove oil

Question 35

May be used in clearing tissues for embedding

Answer 35

carbon tetrachloride

Question 36

✓ Its properties are very similar to that of chloroform although it is relatively cheaper; ✓ Its disadvantage is the same as that of chloroform;

Answer 36

carbon tetrachloride

Question 37

It produces considerable tissue hardening and is dangerous to inhale on prolonged exposure due to its highly toxic effects.

Answer 37

carbon tetrachloride

Question 38

It is superior to ordinary dehydrating and clearing agents

Answer 38

tetrahydrofuran

Question 39

its ability to perform two processes at the same time, thereby shortening the total processing time and allowing more time for fixation

Answer 39

tetrahydrofuran

Question 40

It is non-toxic but has offensive odor and should be used in a well-ventilated room.

Answer 40

tetrahydrofuran

Question 41

It is miscible both with water and paraffin

Answer 41

dioxane

Question 42

Used primarily when time is important because the tissues may be embedded with paraffin within 4 hours after fixation

Answer 42

dioxane

Question 43

in dioxane; It is changed __ times within ___ hours and the tissues are transferred directly to paraffin;

Answer 43

3times, within 4 hours

Question 44

Found in essential oils originally derived from plants;

Answer 44

terpenes

Question 45

✓ A volatile oil found in citrus peels; ✓ Clear, colorless fluid with a distinctly citrus aroma.

Answer 45

limonene

Question 46

It offer the clearing action with the lowest hazard rating of all xylene alternatives Excellent for preserving fine tissue structure an can often be used in place of xylene with no alteration of protocol.

Answer 46

orange oil-based clearing agents

Question 47

Can be effective solvents but they are toxic chemicals

Answer 47

chlorinated hydrocarbons

Question 48

✓ Efficient substitute for xylene; ✓ Non-hazardous, less expensive and causes less shrinkage of the tissue; ✓ Can be used as dealcoholization agent.

Answer 48

coconut oil

Question 49

It is a clearing agent during tissue processing and as a deqaxing agent during staining;

Answer 49

bleached palm oil

Question 50

other name of xylene

Answer 50

xylol