Clearing II Flashcards
What is chloroform suitable for?
Chloroform is suitable for large tissue specimens.
Is chloroform inflammable?
No, chloroform is not inflammable.
What is a disadvantage of chloroform related to liver toxicity?
Chloroform is relatively toxic to the liver after prolonged inhalation; this may be prevented by adequate room ventilation.
How does chloroform affect wax impregnation?
Wax impregnation after chloroform clearing is relatively slow.
Does chloroform make tissues transparent?
No, chloroform does not make tissues transparent.
What is a challenge with chloroform in a paraffin oven?
Chloroform is not very volatile in a paraffin oven; hence, it is difficult to remove from paraffin sections.
What can chloroform vapor attack?
Chloroform vapor may attack the rubber seal used in vacuum impregnating baths.
What is a challenge in evaluating chloroform clearing?
Complete clearing with chloroform is difficult to evaluate.
What happens to tissues in chloroform?
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.
How quickly does chloroform evaporate?
Chloroform evaporates quickly from a water bath.
What is cedarwood oil used for?
Cedarwood oil is used to clear both paraffin and celloidin sections during the embedding process.
What types of tissues is cedarwood oil especially recommended for?
It is especially recommended for central nervous system tissues and cytological studies, particularly of smooth muscles and skin.
How many changes in clearing solution does cedarwood oil require?
It requires two changes in clearing solution.
How long does clearing usually take with cedarwood oil?
Clearing is usually complete in 2-3 days.
What is one advantage of cedarwood oil?
It is very penetrating.
How does cedarwood oil interact with 96% alcohol?
It is miscible with 96% alcohol which it removes readily.
How long does it take for cedarwood oil to clear celloidin?
It clears celloidin in 5-6 days.
What effect does cedarwood oil have on tissue shrinkage?
It causes minimal shrinkage of tissues.
Can tissues be left in cedarwood oil indefinitely?
Yes, tissues may be left in oil indefinitely without considerable damage and distortion.
Does cedarwood oil dissolve aniline dyes?
No, it does not dissolve out aniline dyes.
What effect does cedarwood oil have on tissue transparency?
It makes tissues transparent.
Does cedarwood oil harden tissues?
No, it does not harden tissues.
How does cedarwood oil affect paraffin penetration?
It does not interfere too seriously with paraffin penetration if it is not completely removed.
What is one disadvantage of cedarwood oil?
It is an extremely slow clearing agent, hence, it is not recommended for routine purposes.
How does the penetration speed of cedarwood oil compare to benzene?
It is slightly slower in penetrating than benzene.
What can be done to hasten the wax impregnation process after using cedarwood oil?
Transferring the specimen from oil to benzene for 1/2 hour before finally placing the tissue in wax may improve the process.
What issue can arise with the quality of tissues cleared in cedarwood oil?
Quality is not always uniform and good; tissues may initially float before gradually sinking.
How can drying out of tissues be prevented during the clearing process?
This can be prevented by superimposing absolute alcohol on the surface of the clearing agent.
What happens to cedarwood oil upon prolonged storage?
Cedarwood oil becomes milky and should be filtered before use.
What issue can arise from using previously used cedarwood oil?
It may produce crystals with a melting point of approximately 35°C, interfering with adequate clearing.
How can the crystals formed in cedarwood oil be dissolved?
The solution must be heated to 200°C in order to dissolve the crystals.
What is Aniline oil used for?
Aniline oil is recommended for clearing embryos, insects, and very delicate specimens due to its ability to clear 70% alcohol without excessive tissue shrinkage and hardening.
What are the drawbacks of Clove oil?
Clove oil causes minimum shrinkage of tissues but is unsuitable for routine clearing due to its tendency to become adulterated, slow wax impregnation, brittleness of tissues, removal of aniline dyes, and expensiveness.
What is the primary use of Carbon tetrachloride?
Carbon tetrachloride may be used in clearing tissues for embedding and is relatively cheaper than chloroform.
What are the disadvantages of Carbon tetrachloride?
It produces considerable tissue hardening and is dangerous to inhale on prolonged exposure due to its highly toxic effects.
What is the advantage of Tetrahydrofuran?
Tetrahydrofuran is superior to ordinary dehydrating and clearing agents as it performs two processes simultaneously, shortening total processing time.
What are the safety considerations for Tetrahydrofuran?
Tetrahydrofuran is non-toxic but has an offensive odor and should be used in a well-ventilated room.
How is Dioxane used in tissue processing?
Dioxane is used primarily when time is important, allowing tissues to be embedded with paraffin within 4 hours after fixation.
What are the risks associated with Dioxane?
Dioxane causes greater shrinkage than xylene and its fumes are toxic to humans, especially to the liver.
Aniline oil is not normally utilized as a routine cleaning agent but it is recommended for
Clearing embryos, insects and very delicate specimens
Why is aniline oil recommended for clearing embryos, insects and very delicate specimens
Due to its ability to clear 70% alcohol without excessive issue shrinkage and hardening
This reagent causes minimum shrinkage of tissues.
Clove oil
Why is clove oil’s not guaranteed
Due to its tendency to become adulterated
Wax impregnation after clearing with clove oil is ____. Tissues become ____, aniline dyes are ____, and celloidin is ____. All of these, in addition to the expensiveness of the solution, make it unsuitable for routine clearing purposes.
Wax impregnation after clearing with clove oil is slow and difficult. Tissues become brittle, aniline dyes are removed, and celloidin is dissolved.
may be used in clearing tissues for embedding. Its properties are very similar to that of chloroform although it is relatively cheaper.
Carbon tetrachloride
Disadvantages a carbon tetrachloride
- same as that of chloroform.
- It produces considerable tissue hardening, and is dangerous to inhale on prolonged exposure due to its highly toxic effects.
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.
Tetrahydrofuran
It is non-toxic but has offensive odor and should be used in a well-ventilated room.
Tetrahydrofuran
Dioxane is miscible both with?
Water and paraffin
J dioxane is used primarily when time is important because the tissues may be embedded with paraffin within ___ hours after fixation.
Within 4 hours
The dioxane is changed ___ within ___ and the tissues are transferred directly to paraffin
3 times within 4 hours
causes greater shrinkage than xylene does. In addition, it is dangerous.
Dioxane
Fumes are toxic to human especially to the liver.
J. Dioxane
Other xylene substitutes
Terpenes, Limonene, Orange oil based clearing agents, Chlorinated hydrocarbons, Coconut oil, bleached palm oil
What led to the substitution of xylene?
The reported toxicity and environmental pollution from unsafe disposal of xylene.
What are some less-toxic substitutes for xylene?
Limonene reagents, mineral oil mixtures, 1.7% dish washing solution, vegetable oils, and coconut oil.
What has hampered the use of xylene substitutes in developing countries?
Their availability in commercial quantities.
What are terpenes?
Isoprene polymers found in essential oils originally derived from plants, some of which are now synthesized.
What are some examples of terpenes used as solvents?
Turpentine and oils of bergamot, cedarwood, clove, lemon, oregano, and sandalwood.
What is the general safety status of terpenes?
Most are regarded as safe, though some have strong odors requiring good laboratory ventilation.
What is Limonene?
A volatile oil found in citrus peels, often used as a xylene replacement.
How is Limonene obtained industrially?
By the steam distillation of orange peel, a byproduct of the orange juice industry.
What is a potential issue when using Limonene as a clearing agent?
It may not mix well with mounting mediums usually dissolved in toluene or xylene.
What are orange oil based clearing agents known for?
Offering the clearing action with the lowest hazard rating of all xylene alternatives.
What is important when using products containing orange oils?
They should be rigorously purified and stabilized to avoid interference with staining procedures.
are isoprene polymers found in essential oils originally derived from plants, though some are now synthesized.
Terpenes
Solvents in this class also dry slowly, leave an oily residue on slides and are relatively expensive.
Terpenes
a volatile oil found in citrus peels which goes by several trade names. 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.
Limonene
Disadvantage of Limonene,
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 the limonene.
offer the clearing action with the lowest hazard rating of all xylene alternatives.
Orange oil based clearing agents
In using a product containing orange oils, it is important to use a product which
has been rigorously purified then stabilized.
can be effective solvents, but they are considered toxic chemicals, posing serious health risks. Government regulations have restricted most of the effective solvents in this class.
Chlorinated hydrocarbon
is an efficient substitute for xylene, as it is non-hazardous, less expensive and causes less shrinkage of the tissue.
Coconut oil
Coconut oil can be used without losing the quality of the histological details the only drawback is
its tendency to get solidified at a lower temperature.
coconut oils tendency to get solidified at a lower temperature. Can be overcome by
Performing the clearing procedure in an incubator, maintaining the required temperature.
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.
Bleached palm oil
is nontoxic, nonhazardous, nonflammable, bio-degradable, economic, easy to handle, and readily available.
Bleached Palm oil
Dying out tissue in cedar wood can be prevented by
Superimposing absolute alcohol on the surface of the clearing agent
Cedarwood oil that has been previously used to clear acetic alcohol fixed tissues may produce crystals with a a melting point of approximately ___ and therefore interfere with adequate clearing of tissue.
35°C
The solution (cedar wood) must be heated to ___ in order to dissolve the crystals and restore the solution to its normal state
200°C
