02 Clearing Flashcards
the process whereby alcohol or a dehydrating agent is removed from the tissue
clearing
in the clearing process, the tissue has a ___ appearance when dehydrating agent has been replaced by the solvent
translucent
function of the clearing agent:
when used after alcohol dehydration
mix with alcohol and remove it from the tissue
function of the clearing agent:
when used after tissue section has been stained
make microscopic tissue preparation transparent
function of the clearing agent:
when the tissue is to be cleared directly from water
improve refractive index of the tissue
T/F: when the function of the clearing agent is for the tissue to be cleared directly from water, dealcoholization is one of the most important process
F (no dealcoholzation required)
in clearing, those with low boiling point are ___ (more/less) readily replaced by melted paraffin
more
in clearing, the viscosity of the agent affects the ___ of penetration
speed
prolonged exposure to clearing agent causes the tissue to become ___
brittle
clearing agent:
colorless and most commonly used
xylene
clearing time of xylene
1/2-1 hour
clearing agent:
used for clearing, both for embedding and mounting procedures
xylene
clearing agent:
generally suitable for routine histologic processing schedules of less than 24 hours and when tissue block is less than 5mm in thickness
xylene
clearing agent:
most rapid
xylene
clearing agent:
makes the tissue excessively hard if used over 3 hours
xylene
clearing agent:
causes considerable shrinkage and hardening on lymph nodes
xylene
clearing agent:
may be used as substitute for xylene or benzene for clearing both during embedding and mounting processes
toluene
clearing time of toluene
1-2 hours
clearing agent:
miscible with both absolute alcohol and paraffin
toluene
clearing agent:
acts fairly rapidly; recommended for routine purposes
toluene
clearing agent:
does not make tissues excessively hard and brittle if left for 24 hours
toluene
T/F: toluene is a faster clearing agent than xylene and benzene
F (slower)
clearing agent:
preferred by some in the embedding process because it penetrates and clears tissues rapidly
benzene
clearing agent:
rapid acting; for urgent biopsies (15-60 mins) and routine purposes
benzene
T/F: benzene causes shrinkage if the tissue is exposed for too long
T
T/F: chloroform is used for clearing and is slower than xylene
T
clearing agent:
can be used for large and thicker tissue blocks - up to 1cm
chloroform
T/F: tissues in chloroform easily become translucent
F (do not become translucent)
clearing agent:
used for routine work (6-24 hours)
chloroform
clearing agent:
used for tough tissues such as skin, dibroid, decalcified tissues, and for nervous tissues, lymph nodes, and embryos
chloroform
clearing agent:
used to clear both paraffin and celloidin sections during the embedding process
cedarwood oil
clearing agent:
especially recommended for CNS tissues and cytological studies
cedarwood oil
cedarwood oil requires __ changes in clearing solution
2
clearing time of cedarwoord oil
2 days
cedarwood oil is ___ miscible with alcohol, which removes readily
96
clearing agent:
tissues may be left indefinitely without causing considerable damage and distortion
cedarwood oil
clearing agent:
not normally utilized as a routine clearing agent
cedarwood oil
clearing agent:
recommended for clearing embryos, insects, and very delicate specimens
cedarwood oil
clearing agent:
has the ability to clear 70% alcohol without excessive shrinkage and hardening
cedarwood oil
clearing agent:
has a tendency to be adulterated; therefore the quality is not guaranteed
clove oil
clearing agent:
has similar properties with chloroform
carbon tetrachloride
clearing agent:
can be used when double embedding techniques are required
methyl benzoate/methyl salicylate
clearing agent:
causes greater shrinkage than xylene does
dioxane
a popular clearing agent is ___ and multiple changes are required to completely displace ethanol
xylene
xylene substitute:
isoprene polymers found in essential oils originally derived from plants
terpenes
xylene substitute:
a volatile oil found in citrus peels which goes by several trade names
limonenes
xylene substitute:
offer the clearing action with the lowest hazard rating of all xylene alternatives
orange oil-based
xylene substitute:
excellent in preserving fine tissue structure, and can often be used in place of xylene with not alteration of protocol
orange oil-based
xylene substitute:
can be effective solvents, but they are considered toxic chemicals, posing serious health risks
chlorinated hydrocarbons
xylene substitute:
non-hazardous, less expensive and causes less shrinkage of the tissue; can be used as a dealcoholization agent in the histopathological laboratory, without losing the quality of the histological details
coconut oil
xylene substitute:
gives good tissues, sections, and histological slides; non-toxic, non-hazardous, non-flammable, biodegradable, economic, easy to handle, and readily available
bleached palm oil
