LESSON 5: CLEARING

Question 1

Removal of dehydrating agent from the tissues and replacing it by a solvent → transparent & translucent tissue

Answer 1

CLEARING

Question 2

what are the clearing agents only?

Answer 2

glycerin, gum syrup and Brun’s solution

Question 3

What are the dealcoholizing agents only?

Answer 3

chloroform and carbon tetrachloride

Question 4

dealcoholize and act as solvent of paraffin

Answer 4

Solvent

Question 5

Done after dehydration & before infiltration

Answer 5

Clearing in Embedding

Question 6

Done after staining & before mounting

Answer 6

Clearing in Mounting

Question 7

Complete the following:
Characteristics of an Ideal Clearing Agent

1. Should be __________ with ______________ and either infiltrating medium or mounting medium
2. Should ____________ & clear quickly without overhardening the tissues

Answer 7

miscible; dehydrating agent
remove alcohol quickly

Question 8

Complete the following:
Characteristics of an Ideal Clearing

✓ Should not dissolve out _________
✓ Should not evaporate quickly in the _________
✓ Evaporates quickly in _________
✓ Could be used in amounts at least __________________

Answer 8

aniline dyes
water baths
paraffin oven
10Xthe volume of tissue

Question 9

does not affect the rate but affects the quality of cleared tissue

Answer 9

Refractive Index

Question 10

This clearing agents is the most rapid (15 - 30 mins/ 30 min – 1 hr)

Answer 10

Xylene/Xylol

Question 11

✓ Excellent clearing agent but tends to make tissues excessively hard & brittle.
✓ Turns milky when dehydration is not complete

Answer 11

Xylene/Xylol

Question 12

✓ Rapid agent (15 – 60 mins)
✓ Carcinogenic, causes aplastic anemia

Answer 12

Benzene

Question 13

Similar to xylene but does NOT harden tissues nearly so much

Answer 13

Toluene/Toluol

Question 14

✓ Slower than xylene or benzene (1 – 2 hrs)
✓ Not carcinogenic but emits toxic fumes

Answer 14

Toluene/Toluol

Question 15

✓ For nervous tissues, lymph nodes & embryos
✓ Tissue do not become translucent
✓ Best for large specimens (up to 1cm thick) and tough tissues
✓ Toxic to the liver on prolonged inhalation
✓ Tissues tend to float: remedy → wrap tissues with absorbent cotton gauze

Answer 15

Chloroform

Question 16

Recommended for CNS, smooth muscles & skin

Answer 16

Cedarwood oil

Question 17

✓ Slow (2 – 3 days); minimal shrinkage
✓ For both celloidin and paraffin sections
✓ Tissue floats – use Absolute alcohol to prevent drying out of tissues
✓ Must be followed by immersion in xylene or benzene to remove oil from tissues
✓ Turns milky on prolonged storage

Answer 17

Cedarwood oil

Question 18

✓ Clears 70% alcohol

✓ Recommended for embryos, insects and delicate specimens

Answer 18

Aniline oil

Question 19

Slow; may be adulterated; removes aniline dyes

Answer 19

Clove Oil

Question 20

Similar to chloroform

Answer 20

CCl4

Question 21

Both dehydrating and clearing

Answer 21

Dioxane

Question 22

For large pieces of tissues & embryonic materials

Answer 22

Amyl acetate

Question 23

Substitute for cedarwood oil

Answer 23

Terpineol

Question 24

Used in double embedding.

Answer 24

Methyl
Benzoate/Salicylate

Question 25

when the tissue is to be cleared directly from water (no de-alcoholization, it merely improves the RI)

Answer 25

Glycerin, Gum syrup & Brun’s solution

Question 26

For materials that are difficult to clear (eg. Thick mucinous Papanicolaou smears)

Answer 26

Carbo - Xylene

Question 27

Should be thoroughly rinsed in xylene prior to mounting

Answer 27

Carbo - Xylene

Question 28

a volatile oil found in citrus peels

Answer 28

Based on limonene:

Question 29

Long chain aliphatic HC

Answer 29

Clearite