infiltration - embedding (quizlet) Flashcards
(134 cards)
1
Q
What is the most common temperature range for paraffin wax impregnation?
A
About 56°C to 58°C.
2
Q
What is the traditional advice regarding the temperature of paraffin wax?
A
To use it at about 2°C above the melting point.
3
Q
What melting point is typically used for routine work with paraffin wax?
A
56°C.
4
Q
What is the recommended melting point range for wax when the laboratory temperature is between 15-18°C?
A
Between 50°C and 54°C.
5
Q
What factors affect wax hardness (viscosity)?
A
The molecular weight of the components and ambient temperature.
6
Q
How can technologists improve tissue infiltration during paraffin wax impregnation?
A
By increasing the temperature above 60°C or 65°C.
7
Q
What does tissue-wax adhesion depend on?
A
The crystal morphology of the embedding medium.
8
Q
Does setting temperature affect crystal size in paraffin wax?
A
No, it does not appreciably affect crystal size.
9
Q
What are the advantages of using paraffin wax for embedding?
A
Thin sections can be cut easily, the process is rapid, and tissues can be stored indefinitely without considerable destruction.
10
Q
What is impregnation in the context of histopathology?
A
The process of replacing the clearing agent with a medium that fills tissue cavities and gives a firm consistency.
11
Q
What is embedding in histopathology?
A
The process of placing impregnated tissue in a mold with medium that solidifies.
12
Q
What are the characteristics of a suitable embedding medium?
A
Soluble in processing fluids, suitable for sectioning, molten between 30°C and 60°C, translucent or transparent, stable, homogenous, non-toxic, odorless, easy to handle, and inexpensive.
13
Q
What are the four types of impregnation and embedding mediums?
A
Paraffin wax, celloidin, gelatin, and plastic.
14
Q
What are the disadvantages of paraffin wax impregnation?
A
Overheating makes specimens brittle, prolonged impregnation causes excessive shrinkage, and inadequate impregnation leads to soft and shrunken tissues.
15
Q
What tissues require long immersion in paraffin for proper support?
A
Bones, teeth, brains, and eyes.
16
Q
Why is paraffin processing not recommended for fatty tissues?
A
Because the dehydrating and clearing agents used dissolve and remove fat from the tissues.
17
Q
What is paraffin wax primarily composed of?
A
A polycrystalline mixture of solid hydrocarbons produced from coal and mineral oils.
18
Q
What is the simplest and most common embedding medium used for routine tissue processing?
A
Paraffin wax.
19
Q
What is the recommended procedure for manual processing of tissues in paraffin wax?
A
At least four changes of wax at 15-minute intervals to ensure complete removal of the clearing agent.
20
Q
What is the fixation time for tissues using 10% buffered formalin?
A
24 hours.
21
Q
What happens to tissues that are difficult to infiltrate if not immersed long enough in paraffin?
A
They may crumble on sectioning.
22
Q
What is the melting point range for paraffin wax?
A
Melts at temperatures up to 65°C or 70°C.
23
Q
What is the effect of prolonged immersion in paraffin wax?
A
It is not advisable as it can lead to excessive tissue shrinkage and hardening.
24
Q
What is the purpose of embedding in histopathology?
A
To provide support for tissue sections during cutting.
25
What is the processing time for 70% alcohol?
6 hours
26
What is the processing time for 95% alcohol?
12 hours
27
What is the processing time for 100% alcohol?
2 hours for the first bath, and 1 hour for subsequent baths.
28
What is the purpose of using xylene or toluene in automatic processing?
They are used for clearing tissues.
29
How long should tissues be cleared with xylene or toluene?
1 hour for each change.
30
What is the duration for paraffin wax impregnation?
15 minutes for each change.
31
What is the total time required for embedding in paraffin wax?
3 hours.
32
What factors determine how often fluids are changed during processing?
The number and sizes of the tissues processed.
33
What indicates that the paraffin wax needs to be changed?
The presence of any odor in the clearing agent during the final paraffin wax bath.
34
What should be done with the first 100% ethanol bath after processing?
It should be discarded.
35
What is the recommended storage condition for processed tissues?
They can be stored in cassettes at room temperature indefinitely.
36
What is the main advantage of vacuum processing in tissue preparation?
It decreases the time and labor needed during processing.
37
What is the purpose of vacuum embedding?
It involves wax impregnation under negative atmospheric pressure to promote rapid wax penetration.
38
What types of tissues are particularly recommended for vacuum embedding?
Urgent biopsies, delicate tissues such as lung, brain, connective tissues, decalcified bones, eyes, spleen, and central nervous system.
39
What temperature should Paraplast be maintained at during winter?
54 to 56°C.
40
What temperature should Paraplast be maintained at during summer?
60 to 63°C, though this should be avoided to prevent 'cooking' the tissue.
41
What is the effect of 'cooked' tissue on sectioning and staining?
It does not section well and does not stain well, destroying most details.
42
What is the reduction in time required for complete impregnation with vacuum embedding?
25% to 75% of the normal time required for tissue processing.
43
What is the maximum degree of vacuum recommended for vacuum embedding?
500 mm Hg.
44
What is bio/aid and its recommended use?
A semisynthetic wax recommended for embedding eyes.
45
What is Tissue Mat and its properties?
A product of paraffin containing rubber, with properties similar to Paraplast.
46
What are the steps for ester wax embedding?
Clear in two changes of xylene, place in molten wax in a vacuum chamber, exhaust air slowly, leave for 15 minutes, readmit air, place in fresh wax, and repeat steps.
47
What must be done to the tissue before embedding it in wax?
The tissue must be brought to normal atmospheric pressure and the exhaustion and readmission of air must be gradual to avoid ruining the specimen.
48
What is a key characteristic of the melting point of ester wax compared to paraffin?
Ester wax has a lower melting point (46-48°C) but is harder than paraffin.
49
In what solvents is ester wax soluble?
Ester wax is not soluble in water but is soluble in 95% Ethyl Alcohol and other clearing agents.
50
What clearing agents can be used for ester wax?
Cellosolve (ethylene glycol monoethyl ether) or xylene may be used as clearing agents.
51
How many changes of wax are required for complete tissue impregnation with ester wax?
Three to four changes of wax are required.
52
What type of microtome should be used for sectioning ester wax-impregnated tissues?
A heavy-duty microtome, such as a sliding or sledge type microtome, should be used due to the relative hardness of the wax.
53
What are water-soluble waxes primarily made of?
Water-soluble waxes are mostly made of plastic polymers, primarily polyethylene glycols.
54
What is Carbowax and its characteristics?
Carbowax is a polyethylene glycol containing 18 or more carbon atoms, appears solid at room temperature, is soluble in water, and is suitable for many enzyme histochemical studies.
55
What is the maximum time tissue should be left in melted paraffin?
Tissue should not be left in the paraffin oven for more than 4 hours to prevent shrinkage and hardening.
56
What temperature range should a paraffin oven be maintained at for impregnation?
The paraffin oven must be maintained at a temperature 2 to 5°C above the melting point of paraffin.
57
What happens if infiltration occurs in overheated paraffin?
Infiltration in overheated paraffin (above 60°C) will produce shrinkage and hardening of tissues and can destroy lymphoid tissues completely.
58
What is Paraplast and its melting point?
Paraplast is a mixture of highly purified paraffin and synthetic plastic polymers with a melting point of 56-57°C.
59
What are the advantages of using Paraplast over traditional paraffin wax?
Paraplast is more elastic and resilient than paraffin wax and reduces infiltration times, facilitating thin sectioning.
60
What is the role of DMSO in tissue embedding?
DMSO scavenges residual transition solvent and alters tissue permeability by substituting for or removing bound water, thus improving infiltration.
61
What is the Wet Celloidin Method recommended for?
The Wet Celloidin Method is recommended for bones, teeth, large brain sections, and whole organs.
62
What is celloidin and its uses?
Celloidin is a purified form of nitrocellulose soluble in many solvents, suitable for specimens with large hollow cavities and for hard and dense tissues.
63
What are the disadvantages of using celloidin for tissue embedding?
Disadvantages include the inability to cut thin sections, the need to store blocks in alcohol, and the speed of the technique which can take several weeks or months.
64
What is the process for celloidin impregnation?
The process involves placing tissue in equal parts of alcohol for 12-24 hours, followed by a series of transfers through thin, medium, and thick celloidin solutions.
65
How long should tissue be transferred to thin celloidin?
Tissue should be transferred to thin celloidin (2-4%) for 5-7 days.
66
What indicates that embedding is complete when using celloidin?
Embedding is complete when the ball of the finger leaves a mark on the surface of the tissue block after evaporation.
67
What is the consistency of the resultant block after celloidin embedding?
The resultant block has a rubbery consistency which provides good support to the tissues.
68
What is the purpose of storing tissue blocks in 70-80% alcohol?
To avoid dehydration and shrinkage until ready for cutting.
69
What is the Dry Celloidin Method preferred for?
Processing of whole eye sections.
70
What is Gilson's mixture composed of in the Dry Celloidin Method?
Equal parts of chloroform and cedarwood oil.
71
What effect does Gilson's mixture have on tissue?
It makes the tissue transparent.
72
What is Nitrocellulose used for in tissue processing?
It allows cutting of thicker tissue sections and is recommended for neurological tissues.
73
What is a key advantage of Nitrocellulose's rubbery consistency?
It allows cutting of tissue blocks of varying consistency without undue distortion.
74
Which types of tissues benefit from Nitrocellulose during sectioning?
Dense tissues like bones and brain, and specimens that tend to collapse easily, such as eyes.
75
What is Low Viscosity Nitrocellulose (L.V.N.)?
A form of celloidin soluble in equal concentrations of ether and alcohol, with a lower viscosity.
76
What is a disadvantage of Nitrocellulose when dry?
It is explosive, requiring it to be marketed with alcohol.
77
What are some disadvantages of Celloidin impregnation?
It is slow, difficult to cut very thin sections, and challenging to prepare serial sections.
78
Why should ether solvent vapors be avoided near open flames?
They are very flammable.
79
What is the tissue-to-agent ratio for Malagamba embedding?
1:25 with 1% phenol to prevent mold growth.
80
What are disposable embedding molds used for?
They allow for easy removal of tissue blocks after sectioning.
81
What is the process for using plastic ice trays in embedding?
Use 10% gelatin with 1% phenol, cool in refrigerator, and remove by bending the tray.
82
What should the embedding medium match in terms of tissue?
The strength and hardness of the tissue type.
83
What are the benefits of using paper boats for embedding?
They are cheap, easy to make, and can be used for both celloidin and paraffin wax blocks.
84
What is the main purpose of gelatin impregnation in tissue processing?
It is suitable for histochemical and enzyme studies and avoids dehydration.
85
What is a common issue with photomicrographs when using Celloidin?
They are difficult to obtain.
86
What must be done to prevent evaporation of volatile solvents like ether?
Keep them in bottles with ground-glass stoppers.
87
What is the significance of using 1% phenol in embedding?
It prevents the growth of molds.
88
What is the recommended duration for embedding with 20% gelatin and 1% phenol?
12 hours.
89
What is a key characteristic of the embedding medium in tissue processing?
It should not cause over-hardening of tissues by heating.
90
What is the recommended temperature for melted paraffin used for embedding?
5-10˚C above its melting point.
91
How should embedded tissue be cooled to solidify?
Rapidly in a fridge at -5˚C or immersed in cold water.
92
What is the purpose of orientation in tissue embedding?
To arrange the tissue in a precise position in the mold during embedding and on the slide before staining.
93
What is Leuckhart's Embedding Mold used for?
To mark the position of small tissues with a lead pencil on the inner surface of the bottom.
94
What information should embedding molds bear?
The case number and other identification data of the tissue block.
95
How long can embedded tissues be stored before cutting?
Indefinitely in a cool place.
96
What factors determine the choice of embedding mold?
The type of chuck in the microtome used to section the tissue.
97
What are some examples of materials used for embedding molds?
Stainless steel, ceramic, paper, plastic, aluminum foil.
98
Describe the structure of the procedure for embedding.
It consists of two L-shaped strips of heavy brass or metal on a flat metal plate, adjustable for various tissue block sizes.
99
What is the advantage of a Compound Embedding Unit?
It embeds more specimens at a time.
100
What is the function of Plastic Embedding Rings and Base Mold?
They hold the tissue block during cutting.
101
What are the benefits of using Tissue Tek for embedding?
It allows for rapid solidification, ease of use, less paraffin wax needed, and permanent identification.
102
What is the first step in the embedding procedure?
Open the cassette to view the tissue sample and choose a mold that best corresponds to the size of the tissue.
103
How much molten paraffin should be added to the mold?
A small amount, enough to cover the tissue adequately.
104
What orientation should the tissue have when placed in the mold?
The cut side should be down, as it was placed in the cassette.
105
What should be done after placing the tissue in the mold?
Add the labeled tissue cassette on top of the mold and press firmly.
106
What is the purpose of cooling the top surface of the Paraplast?
To prevent the tissues from becoming brittle and to ensure proper solidification.
107
What should be done if the paraffin block is not solidified after 30 minutes?
If the wax cracks or the tissues are not aligned well, melt them again and start over.
108
What is the risk of using ice water for final cooling?
It may split the block due to too rapid shrinkage.
109
How can the Paraplast block be removed from the mold?
It can be easily popped out once completely cooled and hardened.
110
What should be done with plastic cups after use in the embedding process?
The Paraplast block can be removed as soon as it is cooled.
111
What happens to the stainless steel mold after cooling?
It should slip off easily and can be reused.
112
What are the advantages of using propylene oxide in tissue infiltration?
Propylene oxide can be obtained pure, has very low viscosity, infiltrates fastest, is easy to prepare, mixes rapidly, and is compatible with ethanol.
113
What is the polymerization temperature for propylene oxide?
60°C
114
What is a disadvantage of the Celloidin or Nitrocellulose Embedding Method?
It is hydrophobic, may produce tissue damage due to oxidation, may reduce antigenicity, and contains toxic components like vinyl cyclohexane dioxide.
115
How are tissues embedded in the Celloidin or Nitrocellulose method?
Tissues are embedded in shallow tins covered by weighted glass sheets, and bell jars can control the evaporation rate of the solvent.
116
What are the characteristics of polyester plastics in embedding?
Originally introduced for electron microscopy in the 1950s, they have been superseded by superior epoxides and are now seldom used.
117
What is the process of Double-Embedding in tissue preparation?
Tissues are first embedded with a supporting medium like agar or nitrocellulose and then embedded again with paraffin wax.
118
What is the purpose of using acrylic plastics in tissue embedding?
Acrylic plastics facilitate cutting of large blocks of dense tissues like the brain and are recommended for making small sections of celloidin blocks.
119
What are the properties of plastic (resin) embedding?
Made of esters of acrylic or methacrylic acid, used extensively for light microscopy, preferable for high resolution, but can act as a barrier during staining.
120
What is Polyglycol methacrylate (GMA) used for?
It is used for light microscopic studies of hard tissues like undecalcified bone and for high resolution light microscopy of thin tissue sections.
121
What are the advantages of using GMA?
It is extremely hydrophilic, allowing many staining methods, requires no hardener, and can be polymerized without crosslinking.
122
What are the types of epoxy plastics mentioned?
Types include Bisphenol A (Araldite) and Glycerol (Epon), and dehydration can occur in aqueous dilutions or organic solvents.
123
What is the polymerization process for GMA?
Infiltration can occur at room temperature or lower, and polymerization can be done at ambient temperatures up to 60°C with UV radiation.
124
What is a significant advantage of Low Acid GMA?
It resists the uptake of stain, reducing non-specific background staining.
125
What is the role of benzoyl peroxide in the embedding process?
It acts as a catalyst that decomposes to form phenyl radicals, facilitating the polymerization of acrylics.
126
What are the storage requirements for benzoyl peroxide?
It should be stored in dark bottles in a cool place to prevent premature polymerization.
127
What is Methyl methacrylate (MMA) used for?
It is used for embedding undecalcified bone.
128
What are the advantages of using MMA over GMA?
MMA penetrates tissues better and provides superior staining characteristics and morphological detail.
129
What is a disadvantage of using MMA?
It causes almost complete loss of enzyme activity and protein antigenicity, precluding histochemical and immunohistological methods.
130
What are practical considerations for processing specimens?
Specimens should be processed under a fume hood, continuously agitated on a roller mixer, and benzoyl peroxide should be handled carefully.
131
What is the recommended method for preparing acrylic plastic mixes?
Prepare only the quantity required using a large glass vial and measure volumes by weight.
132
What is the effect of agar on tissue during embedding?
Agar may cause shrinkage of certain tissues.
133
What is the significance of using a roller mixer during specimen processing?
It ensures continuous agitation for better infiltration and embedding.
134
What safety precautions should be taken when handling benzoyl peroxide?
Avoid direct heat and sunlight, and ensure no water is present before dissolving it in the infiltrating solution.
