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

 Not all dealcoholizing agents act as clearing agents

Question 3

 Clearing agents only:

Answer 3

glycerin, gum syrup and Brun’s solution

Question 4

 Dealcoholizing agents only:

Answer 4

chloroform and carbon tetrachloride

Question 5

 Most rapid (15 - 30 mins/ 30 min – 1 hr)

Answer 5

Xylene/Xylol

Question 6

 Excellent clearing agent but tends to make tissues excessively hard & brittle.

Answer 6

Xylene/Xylol

Question 7

 Turns milky when dehydration is not complete

Answer 7

Xylene/Xylol

Question 8

 Rapid agent (15 – 60 mins)

Answer 8

Benzene

Question 9

 Carcinogenic, causes aplastic anemia

Answer 9

Benzene

Question 10

 Similar to xylene but does NOT harden tissues nearly so much

Answer 10

Toluene/Toluol

Question 11

 Slower than xylene or benzene (1 – 2 hrs)

Answer 11

Toluene/Toluol

Question 12

 Not carcinogenic but emits toxic fumes

Answer 12

Toluene/Toluol

Question 13

 For nervous tissues, lymph nodes & embryos

Answer 13

Chloroform

Question 14

 Tissue do not become translucent

Answer 14

Chloroform

Question 15

 Best for large specimens (up to 1cm thick) and tough tissues

Answer 15

Chloroform

Question 16

 Toxic to the liver on prolonged inhalation

Answer 16

Chloroform

Question 17

 Tissues tend to float: remedy

Answer 17

Chloroform

Question 18

 wrap tissues with absorbent cotton gauze

Answer 18

Chloroform

Question 19

 Recommended for CNS, smooth muscles & skin

Answer 19

Cedarwood oil

Question 20

 Slow (2 – 3 days); minimal shrinkage

Answer 20

Cedarwood oil

Question 21

 For both celloidin and paraffin sections

Answer 21

Cedarwood oil

Question 22

 Tissue floats – use Absolute alcohol to prevent drying out of tissues

Answer 22

Cedarwood oil

Question 23

 Must be followed by immersion in xylene or benzene to remove oil from tissues

Answer 23

Cedarwood oil

Question 24

 Turns milky on prolonged storage

Answer 24

Cedarwood oil

Question 25

 Clears 70% alcohol

Answer 25

Aniline oil

Question 26

Recommended for embryos, insects and delicate specimens

Answer 26

Aniline oil

Question 27

 Slow; may be adulterated; removes aniline dyes

Answer 27

Clove Oil

Question 28

 Similar to chloroform

Answer 28

CCl4

Question 29

 Both dehydrating and clearing

Answer 29

Dioxane

Question 30

 For large pieces of tissues & embryonic materials

Answer 30

Amyl acetate

Question 31

 Substitute for cedarwood oil

Answer 31

Terpineol

Question 32

 Used in double embedding.

Answer 32

Methyl Benzoate/Salicylate

Question 33

 when the tissue is to be cleared directly from water (no dealcoholization, it merely improves the RI)

Answer 33

Glycerin, Gum syrup & Brun’s solution

Question 34

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

Answer 34

Carbo - Xylene

Question 35

✓ Should be thoroughly rinsed in xylene prior to mounting

Answer 35

Carbo - Xylene

Question 36

Others

Answer 36

✓ Oil of bergamot
✓ Phenol in alcohol
✓ Creosote

Question 37

Newer Clearing agents

Answer 37

✓ Based on limonene: a volatile oil found in citrus peels
✓ Clearite - Long chain aliphatic HC