Tissue Embedding Techniques
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Questions and Answers

What is the primary purpose of coarse trimming in tissue processing?

  • to form a truncated pyramid/4-sided prism which helps to reduce the size of the block.
  • To remove excess wax from the block and ensure all sides are parallel. (correct)
  • To expose the entire tissue surface for staining.
  • To create a smooth surface for sectioning and prevent crumbling.

    • Which of the following adhesives is commonly used for immunohistochemistry?

  • Glycerin
  • Mayer's egg albumin
  • 3-APES
  • Poly-L-Lysine (correct)

    • What is the recommended duration for leaving sections on a water bath?

  • Not more than 30 seconds (correct)
  • Not more than 10 seconds
  • As long as necessary to flatten the sections
  • Up to 1 minute

    • In preparing sections for staining, how should the sections be picked from the water bath after they have been flattened?

    <p>Picking up the sections in a vertical position (A)</p> Signup and view all the answers

    What is the purpose of adding thymol crystals to Mayer's egg albumin?

    <p>To prevent the growth of mold. (A)</p> Signup and view all the answers

    Which type of mold is recommended for busy routine laboratories?

    <p>Plastic Ice Trays (B)</p> Signup and view all the answers

    What technique can be used to resolve tissues that tend to crumble during trimming?

    <p>Exhaling gently onto the block surface (A)</p> Signup and view all the answers

    Why are serial dilutions often removed in ribbons of 10 sections?

    <p>To make it easier to identify and retrieve specific sections for further analysis. (A)</p> Signup and view all the answers

    Which embedding method is particularly suited for tissues with large hollow cavities prone to collapse?

    <p>Celloidin (collodion) impregnation (C)</p> Signup and view all the answers

    What is the primary advantage of using vacuum embedding?

    <p>It offers a more rapid embedding process, ideal for urgent biopsies. (D)</p> Signup and view all the answers

    What is the primary component added to paraffin to create Paraplast?

    <p>Synthetic plastic polymers (D)</p> Signup and view all the answers

    Which embedding medium is preferred for processing whole eye sections?

    <p>Dry celloidin method (B)</p> Signup and view all the answers

    Which of the following embedding media is water soluble and suitable for enzyme histochemical studies?

    <p>Carbowax (D)</p> Signup and view all the answers

    What is the primary advantage of using the gelatin method for embedding?

    <p>It prevents tissue fragmentation, particularly for delicate specimens and frozen sections. (C)</p> Signup and view all the answers

    What is the primary reason why Bisphenol A (Araldite) infiltration is slow?

    <p>It is a highly viscous plastic. (D)</p> Signup and view all the answers

    Which of the following embedding media is commonly used in double embedding techniques?

    <p>Celloidin (D)</p> Signup and view all the answers

    Which of the following embedding media is known to be carcinogenic?

    <p>Vinyl cyclohexane dioxide (VCD) (B)</p> Signup and view all the answers

    What is the most rapid type of embedding?

    <p>Vacuum embedding (A)</p> Signup and view all the answers

    What is the advantage of using a Compound Embedding Unit?

    <p>It allows for embedding multiple specimens simultaneously, saving time. (A)</p> Signup and view all the answers

    What is the main purpose of adding 1% phenol to gelatin in the gelatin method?

    <p>To prevent the growth of molds. (C)</p> Signup and view all the answers

    Which embedding method is considered the most suitable for processing hard, dense tissues such as undecalcified bone?

    <p>Plastic method (B)</p> Signup and view all the answers

    What is the volume ratio recommendation when using the gelatin method for embedding?

    <p>The volume of the impregnation medium should be at least 25 times the volume of the specimen. (C)</p> Signup and view all the answers

    Which of the following embedding methods is most commonly used for routine tissue processing?

    <p>Paraffin wax impregnation (C)</p> Signup and view all the answers

    Flashcards

    Paper Boat Mold

    Disposable mold used for embedding tissues in celloidin or paraffin.

    Plastic Ice Trays

    Molds recommended for busy laboratories, often for embedding.

    Coarse Trimming

    Initial trimming to shape tissue into a truncated pyramid or prism.

    Fine Trimming

    Final trimming to expose the entire surface of the tissue.

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    Gently Exhaling into Block

    Technique to resolve crumbling during trimming.

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    Mayer's Egg Albumin

    Common adhesive for sticking tissue sections to slides.

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    Thymol Crystals

    Added to Mayer's egg albumin to prevent mold growth.

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    3-APES (3-aminopropyltriethoxysilane)

    Adhesive used in cytology preparations.

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    Paraffin wax

    A common embedding medium used for tissue processing.

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    Vacuum embedding

    Embedding technique under negative atmospheric pressure for rapid results.

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    Paraplast

    A mixture of purified paraffin and synthetic polymers for large tissue blocks.

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    Celloidin impregnation

    An embedding medium for tissues with large cavities, using no heat.

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    Gelatin method

    An impregnation method that prevents dehydration and fragmentation of tissues.

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    Double embedding method

    Facilitates the embedding of large, dense tissue blocks like the brain.

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    Ester wax

    A harder wax suitable for heavy-duty microtomes that is insoluble in water.

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    Carbowax

    Water-soluble wax suitable for enzyme and cytologic studies.

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    Dry celloidin method

    Uses chloroform and cedarwood oil for processing whole eye sections.

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    Plastic method

    An impregnation method for electron microscopy, superior for hard tissues.

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    Compound Embedding Units

    Interlocking plates for embedding multiple specimens at once.

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    Bioloid

    A semi-synthetic wax specifically for embedding eyes.

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    Peel-away molds

    Disposable plastic molds that are easily removed post-embedding.

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    Syn. plastic polymers

    Added to paraffin to create stronger wax like Paraplast.

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    Gilson's mixture

    Chloroform and cedarwood oil blend used in certain embedding methods.

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    Study Notes

    Tissue Embedding Techniques

    • Paraffin Wax Impregnation: Simplest, most common, and best routine embedding method.
    • Paraffin Wax: Polycrystalline mixture of hydrocarbons, derived from coal and mineral oil refining. Can be reused after melting and filtering. May be used only twice.
    • Automatic Processing: Advantages include constant agitation during embedding.
    • Vacuum Embedding: Fastest method; recommended for urgent biopsies, delicate tissues, decalcified bones, and tissues like CNS, eyes, spleen, and lungs. Impregnation under negative pressure in an embedding oven.
    • Paraplast: Highly purified paraffin wax mixed with synthetic plastic polymers. Best for large, dense tissue blocks like bones and brain.
    • Embeddol: Synthetic wax similar to paraplast, but less brittle and less compressible.
    • Bioloid: Semi-synthetic wax for eye embedding.
    • Tissue Mat: Paraffin product with rubber, similar properties to paraplast.
    • Ester Wax: Harder than paraffin, requires heavy-duty microtome (sliding/sledge type). Insoluble in water, soluble in 95% ethanol; suitable for impregnation without clearing.
    • Carbowax: Water-soluble wax, suitable for enzyme histochemical and cytologic studies. Pearse solution and Blank and McCarthy solution are used for floating sections in water when using Carbowax.
    • Celloidin (Collodion) Impregnation: For tissues with large cavities that may collapse; suitable for hard, dense tissues and large tissue sections or whole embryos. Celloidin is a purified nitrocellulose soluble in many solvents. No heat is used; block has a rubbery consistency. Use wet method to protect from dehydration and shrinkage (70-80% alcohol); dry method uses chloroform and cedarwood oil (Gilson's mixture). Low viscosity nitrocellulose is an option, but is explosive when dry.
    • Double Embedding: Celloidin infiltration, followed by paraffin embedding; used for large blocks of dense, firm tissue like the brain.
    • Gelatin Method: Prevents dehydration, suitable for delicate specimens or frozen sections. Volume of impregnation medium should be at least 25 times the volume of the specimen. 1% phenol added to prevent mold growth.
    • Plastic Method: Preferred for electron microscopy and light microscopy (especially hard tissues like undecalcified bone). Superior results with specific plastics chosen for the application.

    Plastic Types

    • Epoxy Plastics: Carefully balanced mixture of epoxy plastic, catalyst, and accelerators. Vinyl cyclohexane dioxide (VCD) is a component, known to be carcinogenic. Bisphenol A is slow for infiltration due to large molecules.
    • Glycerol (Epon): Lower viscosity, sold as isomer mixture.
    • Cyclohexane Dioxide (Spurr): Pure epoxy with low viscosity; fastest infiltration.
    • Polyester Plastics: Originally for electron microscopy, now less common.
    • Acrylic Plastics: Esters of acrylic or methacrylic acid; used extensively for light microscopy. Include polyglycol methacrylate and methyl methacrylate. A related term Araldite can refer to bisphenol A.

    Embedding Molds

    • Leukhart's Embedding Mold: Two L-shaped brass/metal strips on a flat plate to adjust size.
    • Compound Embedding Units: Interlocking plates on a base with multiple compartments. Advantage: Embedding numerous specimens at once.
    • Plastic Embedding Rings and Base Mold: Stainless steel base with plastic ring, used for block holder.
    • Peel-away: Disposable thin plastic molds for even blocks after solidification.
    • Paper Boat Mold: Disposable mold for celloidin, can be used for paraffin.
    • Plastic Ice Trays: Suitable for busy laboratories.

    Tissue Trimming

    • Coarse Trimming: Cutting excess wax from sides, top, and bottom to create a level, parallel 4-sided prism.
    • Fine Trimming: Removing surface wax exposing tissue. "Set thickness adjuster at 15 mm or advancing the block using the coarse feed mechanism"
    • Slow, Uniform Cuts: Best results for minimal section compression. Exhaling gently onto the block surface for crumbling tissue blocks.

    Sectioning and Mounting

    • Sections cut into ribbons (10).
    • Sections should not remain in the water bath more than 30 seconds.
    • Sections picked up vertically.
    • Sections fixed onto slides with adhesives like Mayer's egg albumin (glycerin, thymol crystals). Other adhesives include Plasma, Poly-L-Lysine, and 3-APES.

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    Description

    Explore the various techniques used in tissue embedding, including paraffin wax impregnation and vacuum embedding. This quiz covers methodologies such as automatic processing and the use of synthetic waxes, highlighting their applications for different tissue types. Test your knowledge on the best practices for preparing tissue samples.

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