HISTOPATHOLOGY

• Reagents that both dehydrates and clears tissue include Tetrahydrofuran, Dioxane (diethylene dioxide), and Chloroform.
• Applications of clearing in histopathology include dealcoholization of tissues preparatory to wax impregnation, dealcoholization of stained sections prior to mounting in Permount, Clarite, and Canada Balsam, and making tissues, embryos, and parasites transparent.
• Clearing agents must be used in amounts not less than 10 times the volume of the tissue.
• An impregnating agent must be used in amounts not less than 20 times the volume of the tissue.
• Xylene (xylol) is the most rapid and most commonly used clearing agent in histology laboratories.
• Incomplete dehydration is the most probable cause when a clearing agent turns milky as soon as the tissue is placed in it.
• Excessive exposure to Xylene (xylol) may be extremely toxic to man and may become carcinogenic or it may damage the bone marrow resulting in aplastic anemia.
• Chloroform is recommended for tough tissues (skin, fibrinoid, and decalcified tissues), nervous tissues, lymph nodes, and embryos.
• Cedarwood oil is especially recommended for CNS tissues and cytological studies, particularly of smooth muscles and skin.
• Poly-L-lysine is widely used as a section adhesive for immunohistochemistry.
• For routine works, paraffin sections are usually cut between 2 to 3 micra in thickness for histologic procedures.
• Mayer's egg albumin is the most commonly used adhesive for paraffin sections.
• Thymol is added to Mayer's egg albumin to prevent the growth of molds.
• For cutting an embedded frozen section, a freezing microtome releases carbon dioxide that freezes tissues.
• Celloidin sections are usually cut between 4 to 6 micra in thickness.
• A plane-wedge knife is recommended for frozen sections or for cutting extremely hard and tough specimens embedded in paraffin blocks using a base-sledge type or sliding microtome.
• Incomplete fixation results in tissue being soft when block is trimmed.
• The cryostat is an apparatus used in fresh tissue microtomy, consisting of a microtome, kept inside a cold chamber which has been maintained at a temperature of -20 °C.
• Coated slides are very useful in cytology, particularly cytospin preparations of proteinaceous or bloody material.
• Freeze-drying is a special way of preserving tissues by rapid freezing (quenching) of fresh tissue and subsequently removing ice water molecules (desiccation) by a physical process of transferring the still frozen tissue block in a vacuum at a higher temperature (sublimation).
• Diamond or glass knives are used to cut block for electron microscopy (EM).
• A biconcave knife is recommended for cutting paraffin embedded sections on the rotary microtome.
• The primary application of frozen sectioning is for rapid diagnosis during surgery.
• Clove oil is an example of a type of tissue impregnation and embedding media.
• Bioloid is a semi-synthetic wax used for embedding the eyes.
• Infiltrated with CELLOIDIN then embedded with PARAFFIN is a method of double embedding.
• Dry celloidin is the preferred method for processing whole eye sections.
• The volume of the impregnating medium should be at least not less than 5 times the volume of the tissue.
• Emphysema is a condition that can occur during vacuum embedding, and it stimulates scarring when examined microscopically.
• Infiltrated with GELATIN then embedded with PARAFFIN is a method of double embedding.
• Ester wax is harder than paraffin but with a lower melting point.
• Gilson's mixture is added to the celloidin blocks before hardening to make the tissues transparent.
• Infiltrated with GELATIN then embedded with PLASTIC is a method of double embedding.
• Paraffin wax is the simplest, most common, and best embedding medium for routine tissue processing.
• The wet celloidin method is recommended for all bones and teeth, large brain sections, and whole organs.
• None of these are correct.
• Celloidin is not the best embedding medium for routine tissue processing.
• Paraffin wax and Celloidin (collodion) are examples of types of tissue impregnation and embedding media.
• Infiltrated with PARAFFIN then embedded with CELLOIDIN is a method of double embedding.
• Gelatin and plastic are examples of types of tissue impregnation and embedding media.