Podcast
Questions and Answers
Which fixative is specifically noted for its effective use in histochemistry and electron microscopy?
Which fixative is specifically noted for its effective use in histochemistry and electron microscopy?
- Glutaraldehyde (correct)
- Cajol's Formol Ammonium Bromide
- Baker's Formol Calcium
- Mercuric Chloride
What is the primary purpose of using 5% sodium thiosulfate in the fixation process?
What is the primary purpose of using 5% sodium thiosulfate in the fixation process?
- To remove excess iodine (correct)
- To fix proteins in the tissue
- To enhance tissue preservation
- To accelerate dehydration of tissues
Which of the following is true about Baker's Formol Calcium?
Which of the following is true about Baker's Formol Calcium?
- It requires a longer fixation time than glutaraldehyde.
- It is effective for preserving lipids. (correct)
- It contains mercuric chloride as a key ingredient.
- It is primarily used for nervous tissue fixation.
What is the typical fixation time range for glutaraldehyde?
What is the typical fixation time range for glutaraldehyde?
Which component is crucial for removing excess iodine during the dezenkerization process?
Which component is crucial for removing excess iodine during the dezenkerization process?
In the context of fixatives, what role does alcoholic iodine serve?
In the context of fixatives, what role does alcoholic iodine serve?
What is the primary benefit of using glutaraldehyde in histopathological preparations?
What is the primary benefit of using glutaraldehyde in histopathological preparations?
What combination is necessary for preparing the alcoholic iodine solution for fixation?
What combination is necessary for preparing the alcoholic iodine solution for fixation?
What is a significant characteristic of Ethanol/Ethyl Alcohol as a dehydrating agent?
What is a significant characteristic of Ethanol/Ethyl Alcohol as a dehydrating agent?
Which dehydrating agent is noted for causing less shrinkage and hardening?
Which dehydrating agent is noted for causing less shrinkage and hardening?
What is the primary disadvantage of using Methanol/Methyl Alcohol?
What is the primary disadvantage of using Methanol/Methyl Alcohol?
Which of the following is true about Isopropanol/Isopropyl Alcohol?
Which of the following is true about Isopropanol/Isopropyl Alcohol?
Which characteristic makes Benzene effective for urgent biopsies?
Which characteristic makes Benzene effective for urgent biopsies?
What indicates the purity requirement for Ethanol in tissue processing?
What indicates the purity requirement for Ethanol in tissue processing?
What is a common characteristic of clearing agents like acetone and xylene?
What is a common characteristic of clearing agents like acetone and xylene?
What kind of hazard should not be present in tissue processing agents?
What kind of hazard should not be present in tissue processing agents?
What is the primary purpose of direct staining?
What is the primary purpose of direct staining?
Which component is essential in the process of indirect staining?
Which component is essential in the process of indirect staining?
What type of tissue affinity do acidic cellular components generally have?
What type of tissue affinity do acidic cellular components generally have?
What is a primary disadvantage of using carbon tetrachloride as a clearing agent?
What is a primary disadvantage of using carbon tetrachloride as a clearing agent?
What role does mordant play in tissue staining?
What role does mordant play in tissue staining?
What is the purpose of using two contrasting stains during microscopic examination?
What is the purpose of using two contrasting stains during microscopic examination?
Which of the following best describes tetrahydrofuran (THF)?
Which of the following best describes tetrahydrofuran (THF)?
What is one of the main uses for methyl benzoate and methyl salicylate?
What is one of the main uses for methyl benzoate and methyl salicylate?
What is silver nitrate primarily used for in histology?
What is silver nitrate primarily used for in histology?
Which statement best represents the quality of clove oil as a clearing agent?
Which statement best represents the quality of clove oil as a clearing agent?
How does impregnation relate to tissue staining methods?
How does impregnation relate to tissue staining methods?
What characterizes a tissue-dye complex formed by the mordant?
What characterizes a tissue-dye complex formed by the mordant?
What is a characteristic of the impregnation process in tissue processing?
What is a characteristic of the impregnation process in tissue processing?
Which of the following tissues is vacuum embedding recommended for?
Which of the following tissues is vacuum embedding recommended for?
Which property distinguishes carbon tetrachloride from benzene?
Which property distinguishes carbon tetrachloride from benzene?
Which is a notable property of clove oil in tissue processing?
Which is a notable property of clove oil in tissue processing?
Which method is primarily used for overstating nuclei in tissue samples?
Which method is primarily used for overstating nuclei in tissue samples?
What is a primary advantage of using the Hematoxylin-eosin method?
What is a primary advantage of using the Hematoxylin-eosin method?
Which component is critical in fixing tissue samples for staining?
Which component is critical in fixing tissue samples for staining?
Which staining method is recommended for sections needing resistance to strong alkaline or acid solutions?
Which staining method is recommended for sections needing resistance to strong alkaline or acid solutions?
What is the purpose of coating slides with dilute celloidin solutions?
What is the purpose of coating slides with dilute celloidin solutions?
Which reagent is critical in demonstrating tissue components containing glycogen?
Which reagent is critical in demonstrating tissue components containing glycogen?
What problem should be avoided when staining with cellulose nitrate?
What problem should be avoided when staining with cellulose nitrate?
What is the main focus of rapid metachromatic staining of frozen sections?
What is the main focus of rapid metachromatic staining of frozen sections?
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Study Notes
Special Formalin Fixatives
- 0.5% iodine in 70% ethanol (alcoholic iodine): Used for 5-10 minutes followed by water and 5% sodium thiosulfate to remove excess iodine.
- Cajol's Formol Ammonium Bromide: Effective fixative for nervous tissue (like astrocytes), requires washing in running water after decolorization.
- Baker's Formol Calcium: Preserves lipids; most formalin fixatives damage lipids.
- Addition of Iodine: Saturated iodine solution in 96% alcohol is used in later stages to decolorize iodine with absolute alcohol.
Glutaraldehyde
- Fixation Time: Ranges from ½ to 2 hours; optimal for histochemistry and electron microscopy.
- Composition: Contains two formaldehyde residues linked by three carbon chains, is effective for protein cross-linking.
- Solution Concentration: 2.5% for small fragments; 4% for larger tissues.
Mercuric Chloride Fixatives
- Should not harden tissues excessively and must retain stain.
- Safety Considerations: Non-toxic and non-carcinogenic; useful in preserving tissue structure without brittleness.
Alcohol Fixatives
- Ethanol (Ethyl Alcohol): Most effective, fast-acting dehydrating agent; should be at least 99.7% pure.
- Methanol (Methyl Alcohol): Toxic, used for blood and tissue films.
- Butanol (Butyl Alcohol): A slow dehydrating agent that produces less shrinkage.
- Isopropanol (Isopropyl Alcohol): Alternative when high-grade ethyl alcohol is unavailable.
Clearing Agents
- Benzene: Rapid-acting; used for urgent biopsies, clears alcohol without excessive brittleness.
- Carbon Tetrachloride: Dangerous upon inhalation, produces hardening but cheaper alternative to chloroform.
- Clove Oil: Expensive, unsuitable for routine use, removes aniline dyes and makes tissues brittle.
- Tetrahydrofuran (THF): Dehydrates and clears simultaneously; miscible in water and paraffin.
- Methyl Benzoate/Salicylate: Slow-acting clearing agents used for double embedding techniques.
Impregnation
- Definition: Clearing agent removed, filling tissue to aid in diagnosis and morphology.
- Techniques: Autotechnicon/Elliot-Bench Type Tissue Processor facilitates all steps.
- Vacuüm Embedding: Recommended for urgent biopsies and delicate tissues by applying negative pressure.
Methods of Staining
- Direct Staining: Color given using aqueous or alcoholic dye solutions (e.g., Methylene blue, Eosin).
- Indirect Staining: Enhanced by mordants to promote dye attachment, e.g., Hematoxylin (basic) and Eosin (acid).
- Silver Staining: Utilizes silver nitrate for impregnating nervous tissue.
Common Staining Techniques
- Hematoxylin-Eosin Method: A key method for microanatomical studies; requires fixing in Zenker's fluid.
- Colloidonization: Coats slides with dilute celloidin solutions to firmly attach sections.
- Eye Dropper Method: Rapid metachromatic staining of frozen sections either on wet slides or solidified sections.
Final Notes
- Preparation for Acidic vs Basic Dyes: Acidic tissues have greater affinity for basic dyes, and vice versa.
- Care with Celloidin: Soluble in absolute alcohol, should be avoided during the dehydration and clearing of stained sections.
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