U3 LAB: DEHYDRATION Flashcards
(76 cards)
1
Q
Tissue processing involves?
A
- dehydration
- clearing
- wax infiltration
- embedding
2
Q
In Rush Frozen Section, this is done simultaneously.
A
- fixing
- embedding
3
Q
Pre-eminent type of tissue processing treatment considered to be the most suitable for routine preparation, sectioning, staining, and subsequent storage of large tissue samples.
A
Paraffin Wax
4
Q
Paraffin Wax utilizes what as dehydrating fluid?
A
series of alcohol
5
Q
This is the removal of water from aqueous fixed tissue.
A
Dehydration
6
Q
What step is introduced since most alcohols and paraffin are not miscible?
A
Clearing
7
Q
Characteristics of an Ideal Dehydrating Solution
A
- dehydrate rapidly without producing shrinkage or distortion
- should not evaporate very fast
- should be able to dehydrate even fatty tissues
- should not harden tissues excessively
- should not remove stains
- should not be toxic to the body
- should not be a fire hazard
8
Q
Characteristics of an Ideal Dehydrating Solution
It should dehydrate rapidly without producing?
A
considerable shrinkage or distortion of tissues
9
Q
Characteristics of an Ideal Dehydrating Solution
It should be able to dehydrate even?
A
fatty tissues
10
Q
Characteristics of an Ideal Dehydrating Solution
It should not?
A
- evaporate very fast
- harden tissues excessively
- not be toxic to the body
- be a fire hazard
11
Q
Commonly used Dehydrating Agents
A
- Alcohol
- Acetone
- Dioxane
- Cellosolve
- Triethyl phosphate
- Tetrahydrofuran
12
Q
Dehydrating agents: Alcohol
A
- Ethanol
- Methanol
- Butanol
13
Q
Recommended for routine dehydration and considered as the best dehydrating agent
A
Ethanol
14
Q
Ethanol is also known as?
A
Ethyl alcohol
15
Q
Ethanol
Characteristics
A
- clear
- colorless
- flammable
16
Q
Ethanol
Advantages
A
- fast acting
- mixes with water and many inorganic solvents
- penetrates tissue easily
- not poisonous and expensive
17
Q
Ethanol
Recommended for?
A
routine dehydration
18
Q
Primarily used for blood and tissue films and for smear preparations.
A
Methanol
19
Q
Methanol is also known as?
A
Methyl alcohol
20
Q
Methanol
Disadvantage
A
Toxic to the body
21
Q
Methanol
If introduced to body, what will be affected first?
A
eyes (blurring of vision)
22
Q
This is utilized in plant and animal micro-techniques/
A
Butanol
23
Q
Butanol is also known as?
A
Butyl alcohol
24
Q
Butanol
Advantages
A
- slow dehydrating agent
- less shrinkage and hardening
25
Butanol
DIsadvantage
slow dehydrating agent (not suitable for rapid processing)
26
Increasing alcohol series
60-70% Ethanol > 90-95% Ethanol
27
99 to 100% Ethanol is also called as?
Absolute Alcohol
28
Points to remember
The strength of initial alcohol required in each concentration will depend on?
size, nature, fixative
29
Smaller and more delicate tissues require ______ concentration and _______ intervals between succeeding ascending grades of alcohol.
lower, shorter
30
These produce shrinkage and make the tissue hard, brittle and difficult to cut.
Concentrated alcohols
31
The tissue may be stored in?
70-80% alcohol
(but not for longer periods of time)
32
Prolonged storage in lower concentrations or below _______ tends to _______ the tissue
70%, macerate
33
Concentrations ranging from 70-80% alcohol at very long periods of time might interfere with the?
staining properties of the specimen
34
Dehydration time will be hastened at?
37C for urgent examinations
35
This serves as an indicator that will accelerate removal of water from the dehydrating fluid and insure complete dehydration.
Anhydrous Copper Sulfate
36
Anhydrous Copper Sulfate ensures?
complete hydration
37
This is a clear, colorless fluid that mixes with water, ethanol and most organic solvent
Acetone
38
Acetone
Advantages
- cheap, rapid-acting dehydrating agent
- more miscible when epoxy resins than alcohol
39
Acetone
Disadvantages
- highly flammable
- penetrate tissues poorly
- causes brittleness (prolonged time)
- most lipids are removed from tissues
- extremely volatile and inflammable (small pieces of tissue)
40
Acetone
dehydrates in how many hours?
1/2 to 2 hours
41
This is an excellent dehydrating and clearing agent, readily miscible in water, melted paraffin, alcohol and xylol
Dioxane
42
Dioxane is also known as?
Diethylene Dioxide
43
Dioxane
Advantages
- less tissue shrinkage
- can be left in this reagent for long period of time without affecting consistency or staining properties of the specimen
- placed directly into solution after washing out
44
Dioxane
Disadvantages
- expensive
- extremely dangerous
- ribbon poorly
- cumulative and highly toxic
45
Dioxane should not be recycled as the risk of _________ increases greatly.
creating explosives
46
Time schedule with Dioxane
Graupner's Method
47
Graupner's method
Pure dioxane solution
1st & 2nd: 1 hour
3rd: 2 hours
48
Graupner's method
Paraffin Wax
1st: 15 minutes
2nd: 45 minutes
3rd: 2 minutes
49
This method is when tissues are wrapped in a gauze bag and suspended in a bottle.
Weiseberg's Method
50
Weiseberg's Method
Bottle contains?
Dioxane and little anhydrous calcium oxide
50
Weiseberg's Method
Water displaced fro tissues is absorbed by?
calcium oxide or quicklime
51
Weiseberg's Method
Dehydration period
3-24 hours
52
Tissues which have been treated with a chromate fixative should be?
thoroughly washed in running tap water prior to treatment with dioxane
53
Examples of Chromate Fixatives
- Regaud's
- Moller's
54
This is an ethylene glycol monoethyl ether which dehydrates rapidly, and can be stored for months without producing hardening or distortion.
Cellosolve
55
Cellosolve
Cautions
- highly flammable (combustible at 110 - 120 F)
- toxic
56
Cellosolve
If cannot be avoided, what should be used instead of ethylene based glycol ethers?
Propylene based glycol ether
57
This removes water very readily and produces very little distortion and hardening.
Triethyl Phosphate
58
Triethyl Phosphate
Used to dehydrate?
sections and smears
59
Triethyl Phosphate
produce?
minimum shrinkage
60
This both dehydrates and clears tissues.
Tetrahydrofuran (THF)
61
Tetrahydrofuran
Dissolve many substances including?
fats
62
Tetrahydrofuran
Miscible with?
- lower alcohols
- ether
- chloroform
- acetone
- benzene
63
Tetrahydrofuran
May be used for?
- demixing
- clearing
- dehydrating
64
T/F: Tetrahydrofuran gives improved results.
True
65
Tetrahydrofuran
Cautions
- toxic
- should be in well ventilated room
- avoid if possible
66
This varies per the fixative used in Fixation.
Dehydrating schedule
67
This fluid and other alcoholic fluids are directly transferred to 90%, 95% or even absolute alcohol
Carnoy's fluid
68
Carnoy's fluid is used in?
fixing brain for rabies pr Negri bodies
69
These tissues are first dehydrated with 1st stage of 50% alcohol, followed by a graded treatment to prevent tissue shrinkage.
Soft tissues
70
Tissues fixed in this fluid is transferred to 90% alcohol.
Susa fluid
71
Susa fluid in lower grades of alcohol may cause?
swelling of fibrous tissues
72
Typical dehydration sequence for specimens not more than 4mm thick
70, 90, 100% Ethanol (x2) - 15 mins
100% Ethanol - 30 mins
100% Ethanol - 45 mins
73
Quality Check for Absolute Alcohol (free of water)
layer of must be employed in dehydrating vessel
Anhydrous copper sulfate
- 2-2-5cm thick
74
Quality Check for Absolute Alcohol (free of water)
Anhydrous copper sulfate layer must be covered by?
filter paper (prevent contamination)
75
Quality Check for Absolute Alcohol (free of water)
Turns ____ if alcohol gets diluted
blue
