STEP 4: IMPREGNATION Flashcards
is the simplest, most common and best embedding medium for routine tissue processing
paraffin wax
tissue blocks and unstained mounted sections may be
stored for an indefinite period of time after impregnation
without considerable tissue destruction
paraffin wax
is not recommended for fatty tissues
paraffin
Paraffin oven or incubator at
55-60°C
temperature of incubator normally used for routine work
56°C
involves wax impregnation under negative atmospheric pressure
vacuum embedding
embedding that gives the fastest result; recommended for urgent biopsies
vacuum embedding
recommended for delicate tissues such as lung, brain, connective tissues, decalcified bones, eyes, spleen, and central nervous system
vacuum embedding
the vacuum chamber of vacuum embedding is maintained at ______ above the melting point of the wax
2-4°C
the degree of the vacuum should not exceed ____________
500 mm Hg
Factors Affecting Paraffin Wax Impregnation:
- Natureofthetissue
- Sizeofthetissue
- Clearing agents to be used
Wax to be reused must be heated at _______
100-105°C
Paraffin wax may be used only ______
twice
▪ a mixture of highly purified paraffin and synthetic plastic polymers
▪ melting point of 56-57°C
▪ more elastic and resilient than paraffin wax
paraplast
- a synthetic wax substitute similar to paraplast with a melting point of 56-58°C
- less brittle, less compressible than paraplast
embeddol
- semisynthetic wax recommened for embedding eyes
bioloid
- a product of paraffin
- contains rubber
- the same property as paraplast
tissue mat
▪ has a lower melting point (46-48°C)
▪ harder than paraffin
▪ cellosolve or xylene may be used as clearing agents
▪ To remove clearing agent: equal portion of clearing agent and wax for 3-6 hours
▪ sectioning of tissues should be done on a heavy duty microtome
ester wax
▪ are mostly polyethylene glycols
▪ melting points of 38-42°C or 45-56°C
water soluble waxes
▪ most commonly used
▪ solid at room temperature
▪ cytologic details are excellently preserved
▪ very easily dissolved in water
▪ Impregnation: Four changes (70%, 90%, 100%, 100%) at 56°C
▪ Embedding: at 50°C and rapidly cooled in a refrigerator
carbowax
▪ a purified form of nitrocellulose soluble in many solvents
▪ suitable for specimens with large hollow cavities
▪ suitable for hard and dense tissues
▪ suitable for large tissue sections of the whole embryo
▪ recommended for processing of neurological tissues
▪ Thin (2%), medium (4%), thick (8%)
celloidin impregnation
permits cutiting of tissue sections which are thicker than in paraffin wax
celloidin
its rubbery consistency allows tissue blocks to be cut without undue distortio
celloidin
impregnation photomicrographs are difficult to obtain
celloidin
celloidin impregnation recommended for bones, teeth ,large brain sections, and whole organs
wet celloidin method
celloidin impregnation preferred for processing of whole eye sections
dry celloidin method
is another form of celloidin soluble in equal concentration of ether and alcohol with a lower
viscosity
Low Viscosity Nitrocellulose (LVN)
the tendency of tissues to crack in nitrocellulose method may be prevented by adding _________
plasticizers (oleum ricini or castor oil)
▪ is rarely used except when dehydration is to be avoided
▪ used when tissues are subjected to histochemical and enzyme studies
▪ used as an embedding medium for delicate specimens and frozen tissue sections
▪ tissues should not be more than 2-3 mm thick
▪ 1% phenol prevents the growth of molds
▪ The volume of the impregnating medium should be at least 25 times the volume of the tissue
gelatin impregnation
