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HISTOPATHOLOGY > CHAPTER 10 CLEARING > Flashcards

CHAPTER 10 CLEARING Flashcards

1
Q

is a colorless clearing agent that is most commonly used in histology laboratories.

A

Xylene (Xylol)

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2
Q

Clearing time is usually 1/2 to 1 hour.

A

Xylene (Xylol)

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3
Q

It is used for clearing, both for embedding and mounting procedures.

A

Xylene (Xylol)

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4
Q

It is generally suitable for most routine histologic processing schedules of less than 24 hours, and when the tissue block size is less than 5 mm. in thickness.

A

Xylene (Xylol)

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5
Q

is reasonably cost effective and works well for short-term clearing of small tissue blocks.

A

Xylene (Xylol)

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6
Q

is one of the routinely used chemical in histology and pathology laboratories because of its vital role in the paraffin wax tissue processing method.

A

Xylene (Xylol)

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7
Q

It is mostly used as a clearing agent during tissue processing and as a dewaxing agent during staining.

A

Xylene (Xylol)

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8
Q

It is also used in cover slipping, in cleaning tissue processors, as solvent to remove synthetic immersion oil from the microscope objective and in recycling of used slides.

A

Xylene (Xylol)

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9
Q

However, several toxicities believed to be caused by intermediate products of its metabolism such as methyl benzaldehyde have been reported. These include central nervous system disorders, respiratory depression, abdominal pain, dryness and redness of skin, dermatitis, liver diseases, nephrotoxicity, conjunctivitis, and teratogenic and fetotoxic effects.

A

Xylene (Xylol)

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10
Q

It is the most rapid clearing agent, suitable for urgent biopsies which it clears within 15-30 minutes.

A

Xylene (Xylol)

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11
Q

It makes tissues transparent.

A

Xylene (Xylol)

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12
Q

It is miscible with absolute alcohol and paraffin.

A

Xylene (Xylol)

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13
Q

It does not extract out aniline dyes.

A

Xylene (Xylol)

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14
Q

For mounting procedures, it does not dissolve celloidin and can, therefore, be used for celloidin sections.

A

Xylene (Xylol)

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15
Q

It evaporates quickly in paraffin oven and can, therefore, be readily replaced by wax during impregnation and embedding.
It is cheap.

A

Xylene (Xylol)

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16
Q

It is highly inflammable and should be appropriately stored.

A

Xylene (Xylol)

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17
Q

If used longer than 3 hours, it makes tissues excessively hard and brittle.

A

Xylene (Xylol)

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18
Q

It causes considerable hardening and shrinkage of tissues; hence, is not suitable for nervous tissues and lymph nodes.

A

Xylene (Xylol)

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19
Q

becomes milky when an incompletely dehydrated tissue is immersed in it

A

Xylene (Xylol)

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20
Q

may irritate eyes, nose and respiratory tract.

A

Xylene (Xylol)

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21
Q

It can be absorbed through the skin and cause dermatitis.

A

Xylene (Xylol)

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22
Q

At high concentrations, it is toxic and narcotic.

A

Xylene (Xylol)

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23
Q

is better at preserving tissue structure and is more tolerant of small amounts of water left behind in the tissues than xylene

A

Toluene

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24
Q

more expensive than xylene and more toxic, so toluene is less commonly used.

A

Toluene

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25
Q

may be used as a substitute for xylene or benzene for clearing both during embedding and mounting processes.

A

Toluene

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26
Q

Time recommended for clearing is 1 -2 hours.

A

Toluene

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27
Q

It is miscible with both absolute alcohol and paraffin.

A

Toluene

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28
Q

It acts fairly rapidly and is recommended for routine purposes.

A

Toluene

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29
Q

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

A

Toluene

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30
Q

Clears overnight.

A

Toluene

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31
Q

It is not carcinogenic.

A

Toluene

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32
Q

It is slower than xylene and benzene.

A

Toluene

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33
Q

It tends to acidify in a partially filled vessel.

A

Toluene

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34
Q

Highly concentrated solutions will emit fumes that are toxic upon prolonged exposure.

A

Toluene

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35
Q

It is more expensive.

A

Toluene

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36
Q

is preferred by some as clearing agent in the embedding process of tissues because it penetrates and clears tissues rapidly.

A

Benzene

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37
Q

It used to be a popular routine clearing agent until recently when its highly carcinogenic properties were recognized.

A

Benzene

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38
Q

Its use for clearing purposes is therefore strongly discouraged.

A

Benzene

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39
Q

It is rapid acting, hence is recommended for urgent biopsies (15-60 minutes) and routine purposes.

A

Benzene

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40
Q

It volatilizes rapidly in paraffin oven and is therefore easily eliminated from the tissue.

A

Benzene

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41
Q

It is miscible with absolute alcohol.

A

Benzene

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42
Q

It does not make tissues hard and brittle. It causes minimum shrinkage.

A

Benzene

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43
Q

It makes tissues transparent. It clears overnight.

A

Benzene

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44
Q

It is highly flammable.

A

Benzene

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45
Q

If a section is left in benzene for a long time, considerable tissue shrinkage may be observed. Hence, tissues should be transferred to paraffin wax as soon as possible.

A

Benzene

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46
Q

Excessive exposure to benzene may be extremely toxic to man and may become carcinogenic or it may damage the bone marrow resulting in aplastic anemia. If ever benzene is to be used for clearing, the laboratory should be well-ventilated.

A

Benzene

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47
Q

slower in action than xylene, but causes less brittleness

A

Chloroform

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48
Q

Thicker tissue blocks, even those up to I cm. in thickness, can be processed.

A

Chloroform

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49
Q

However, tissues placed in it do not become translucent.

A

Chloroform

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50
Q

It is recommended for routine work (6-24 hours).

A

Chloroform

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51
Q

It is miscible with absolute alcohol.

A

Chloroform

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52
Q

It is recommended for tough tissues (e.g. skin, fibroid and decalcified tissues) for nervous tissues, lymph nodes and embryos because it causes minimum shrinkage and hardening of tissues.

A

Chloroform

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53
Q

It is suitable for large tissue specimens.

A

Chloroform

54
Q

It is not inflammable.

A

Chloroform

55
Q

It is relatively toxic to the liver after prolonged inhalation; this may be prevented by adequate room ventilation.

A

Chloroform

56
Q

Wax impregnation after clearing is relatively slow.

A

Chloroform

57
Q

It does not make tissues transparent.

A

Chloroform

58
Q

It is not very volatile in paraffin oven; hence, it is difficult to remove from paraffin sections.

A

Chloroform

59
Q

It may even produce considerable deterioration of the wax.

A

Chloroform

60
Q

Its vapor may attack the rubber seal used in vacuum impregnating bath.

A

Chloroform

61
Q

Complete clearing is difficult to evaluate.

A

Chloroform

62
Q

Tissues tend to float in chloroform; this may be avoided by wrapping the tissues with absorbent cotton gauze to facilitate sinking of the section in solution.

A

Chloroform

63
Q

It evaporates quickly from a water bath.

A

Chloroform

64
Q

is used to clear both paraffin and celloidin sections during
the embedding process.

A

Cedarwood Oil

65
Q

It is especially recommended for central nervous system tissues and cytological studies, particularly of smooth muscles and skin. It requires two changes in clearing solution.

A

Cedarwood Oil

66
Q

Clearing is usually complete in 2-3 days.

A

Cedarwood Oil

67
Q

It is very penetrating.

A

Cedarwood Oil

68
Q

It is miscible with 96% alcohol which it removes readily.

A

Cedarwood Oil

69
Q

It clears celloidin in 5-6 days.

A

Cedarwood Oil

70
Q

It causes minimal shrinkage of tissues.

A

Cedarwood Oil

71
Q

Tissues may be left in oil indefinitely without considerable damage and distortion.

A

Cedarwood Oil

72
Q

It does not dissolve out aniline dyes.

A

Cedarwood Oil

73
Q

It makes tissues transparent.

A

Cedarwood Oil

74
Q

It does not harden tissues.

A

Cedarwood Oil

75
Q

It does not interfere too seriously with paraffin penetration if it is not completely removed.

A

Cedarwood Oil

76
Q

Clearing with cedarwood oil often improves cutting of the sections.

A

Cedarwood Oil

77
Q

It is an extremely slow clearing agent, hence, it is not recommended for routine purposes.

A

Cedarwood Oil

78
Q

It is slightly slower in penetrating than benzene.

A

Cedarwood Oil

79
Q

It is hard to eliminate from the tissues in paraffin bath, making the wax impregnation process very slow.

A

Cedarwood Oil

80
Q

This may be improved or hastened by transferring the specimen from oil to benzene for 1/2 hour before finally placing the tissue in wax.

A

Cedarwood Oil

81
Q

Quality is not always uniform and good. Tissues cleared in it initially float before gradually staying to the bottom as clearing proceeds. Hence, the tissue may dry out before it is completely cleared. This can be prevented by superimposing absolute alcohol on the surface of the clearing agent. Once saturated, the specimen should then be transferred to a fresh solution.

A

Cedarwood Oil

82
Q

It becomes milky upon prolonged storage and should be filtered before use.

A

Cedarwood Oil

83
Q

It that has been previously used to clear acetic-alcohol fixed tissues may produce crystals with a melting point of approximately 35°C and therefore interfere with adequate clearing of tissue. The solution must be heated to 200°C in order to dissolve the crystals and restore the solution to its normal state.

A

Cedarwood Oil

84
Q

It is very expensive.

A

Cedarwood Oil

85
Q

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.

A

Aniline oil

86
Q

This reagent causes minimum shrinkage of tissues.

A

Clove oil

87
Q

However, its quality is not guaranteed due to its tendency to become adulterated.

A

Clove oil

88
Q

Wax impregnation after clearing with it is slow and difficult.

A

Clove oil

89
Q

Tissues become brittle, aniline dyes are removed, and celloidin is dissolved.

A

Clove oil

90
Q

All of these, in addition to the expensiveness of the solution, make it unsuitable for routine clearing purposes.

A

Clove oil

91
Q

may be used in clearing tissues for embedding.

A

Carbon tetrachloride

92
Q

Its properties are very similar to that of chloroform although it is relatively cheaper.

A

Carbon tetrachloride

93
Q

Its disadvantage is the same as that of chloroform.

A

Carbon tetrachloride

94
Q

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

A

Carbon tetrachloride

95
Q

is superior to ordinary dehydrating and clearing agents due
to its ability to perform two processes at the same time, thereby shortening the total processing time and allowing more time for fixation.

A

Tetrahydrofuran

96
Q

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

A

Tetrahydrofuran

97
Q

is miscible both with water and paraffin.

A

Dioxane

98
Q

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

A

Dioxane

99
Q

The tissues are transferred to dioxane straight from Bouin’s fluid or a formalin fixative.

A

Dioxane

100
Q

is changed 3 times within 4 hours and the tissues are transferred directly to paraffin (3 changes are made in a total of 90 minutes)

A

Dioxane

101
Q

causes greater shrinkage than xylene does.

A

Dioxane

102
Q

In addition, it is dangerous.

A

Dioxane

103
Q

Fumes are toxic to human especially to the liver.

A

Dioxane

104
Q

Other Xylene Substitutes:

A
105
Q

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

A

Terpenes

106
Q

They are the earliest transition solvents to be used in histology and include turpentine and oils of bergamot, cedarwood, clove, lemon, oreganum and sandalwood.

A

Terpenes

107
Q

In general the natural oils are not highly pure compounds but contain several substances.

A

Terpenes

108
Q

clear tissues and celloidin sections from 80%-95% alcohol, render tissues transparent and have a slow gentle non-hardening action.

A

Terpenes

109
Q

Most are generally regarded as safe though some have particularly strong odors which can be overpowering, requiring good laboratory ventilation.

A

Terpenes

110
Q

are moderately effective solvents, but they too are considered toxic.

A

Terpenes

111
Q

Solvents in this class also dry slowly, leave an oily residue on slides and are relatively expensive.

A

Terpenes

112
Q

One of the recommended xylene substitutes from the terpene family

A

Limonene

113
Q

a volatile oil found in citrus peels which goes by several trade names.

A

Limonene

114
Q

It is a natural oil found in the skins of citrus fruits, such as lemons or oranges, and in cooking is usually referred to as lemon or orange zest.

A

Limonene

115
Q

is obtained industrially by the steam distillation of orange peel which is a byproduct of the orange juice industry.

A

Limonene

116
Q

It is a clear, colorless fluid with a distinctly citrus aroma, not unpleasant to most people, although some do not like it.

A

Limonene

117
Q

is often sold as a xylene replacement and some technologists substitute it for xylene in other uses, but this is not universally successful.

A

Limonene

118
Q

When used as the clearant immediately prior to cover slipping, there are some reports that the mounting medium, usually dissolved in either toluene or xylene, does not mix well with it.

A

Limonene

119
Q

In such cases, replacing the it with xylene or toluene, or quickly dipping the section in either one just prior to cover slipping should be effective. This does, of course, defeat the purpose of the replacement to a certain degree.

A

Limonene

120
Q

offer the clearing action with the lowest hazard rating of all xylene alternatives.

A

Orange oil based clearing agents

121
Q

It is excellent for preserving fine tissue structure, and can often be used in place of xylene with no alteration of protocol.

A

Orange oil based clearing agents

122
Q

In using a product containing orange oils, it is important to use a product which has been rigorously purified then stabilized.

A

Orange oil based clearing agents

123
Q

[?] that are neither pure nor stable can break down to produce compounds which will interfere with staining procedures.

A

Orange oil based clearing agents

124
Q

can be effective solvents, but they are considered toxic chemicals, posing serious health risks.

A

Chlorinated hydrocarbons

125
Q

Government regulations have restricted most of the effective solvents in this class.

A

Chlorinated hydrocarbons

126
Q

is an efficient substitute for xylene, as it is non-hazardous, less expensive and causes less shrinkage of the tissue.

A

Coconut oil

127
Q

It can be used as a de- alcoholization agent in the histopathological laboratory, without losing the quality of the histological details.

A

Coconut oil

128
Q

The only drawback associated with coconut oil, is its tendency to get solidified at a lower temperature.

A

Coconut oil

129
Q

However, this can be overcome by performing the clearing procedure in an incubator, maintaining the required temperature.

A

Coconut oil

130
Q

Substitution of the conventional xylene with [?] as a clearing agent during tissue processing and as a dewaxing agent during staining gives good tissues, sections and histological slides.

A

bleached palm oil

131
Q

is nontoxic, nonhazardous, nonflammable, bio-degradable, economic, easy to handle, and readily available.

A

bleached palm oil

HISTOPATHOLOGY (14 decks)

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