Cell Fixation Techniques
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Questions and Answers

What is added to gelatin to prevent mold growth during the embedding process?

  • 1% formaldehyde
  • 1% glycerin
  • 1% phenol (correct)
  • 1% alcohol

    • Which characteristic of cyclohexene dioxide makes it distinct compared to other epoxy plastics?

  • It has a higher viscosity
  • It is impure with high viscosity
  • It is pure with very low viscosity (correct)
  • It infiltrates at the slowest rate

    • For what primary application is gelatin rarely used?

  • Microscopic imaging (correct)
  • Avoiding dehydration
  • Embedding delicate specimens
  • Histochemical studies

    • What is the maximum tissue thickness requirement for using gelatin?

    <p>2-3 mm</p> Signup and view all the answers

    Why are polyester plastics now seldom used in comparison to their initial introduction?

    <p>Alternative materials have replaced their usage</p> Signup and view all the answers

    What is the primary purpose of using 10% formalin in routine fixation?

    <p>To preserve the specific elements of the cell</p> Signup and view all the answers

    How long should routine fixation typically last?

    <p>2-6 hours</p> Signup and view all the answers

    What effect does a pH greater than 4.6 have on the fixation process?

    <p>Retards fixation</p> Signup and view all the answers

    What is the rate of penetration for routine fixation?

    <p>1 mm per hour</p> Signup and view all the answers

    What is a major factor that improves the fixation process?

    <p>Moderate agitation during fixation</p> Signup and view all the answers

    What is the consequence of using glacial acetic acid in fixation?

    <p>Destroys mitochondria and Golgi bodies</p> Signup and view all the answers

    Which type of fixative acts on nuclear structures according to action?

    <p>Aldehydes</p> Signup and view all the answers

    Which of the following is true regarding larger tissues in fixation?

    <p>They retard the fixation process</p> Signup and view all the answers

    What is the primary purpose of the impregnation/infiltration process in tissue processing?

    <p>To replace clearing agents with a medium</p> Signup and view all the answers

    Which embedding medium is noted as the simplest and most common?

    <p>Paraffin wax</p> Signup and view all the answers

    At what temperature is the routine melting point of paraffin wax?

    <p>66°C</p> Signup and view all the answers

    What ratio should be maintained between the impregnation agent and tissue during infiltration?

    <p>25:1</p> Signup and view all the answers

    What are Negri bodies primarily associated with?

    <p>Viral infections, specifically rabies</p> Signup and view all the answers

    Which factor is crucial for optimal infiltration temperature when using paraffin wax?

    <p>2-5°C above the melting point</p> Signup and view all the answers

    What is a purity requirement for paraffin wax used in tissue processing?

    <p>Must be free from dust and foreign matter</p> Signup and view all the answers

    Which fixation method is preferred for preserving antigenicity in smears of brain tissue?

    <p>Acetone</p> Signup and view all the answers

    What is the main purpose of using Carnoy's solution in histological studies?

    <p>To coagulate mucus and fix sputum</p> Signup and view all the answers

    Which step directly follows the impregnation of tissue during the processing procedure?

    <p>Embedding/Casting</p> Signup and view all the answers

    What type of structures does Flemming's fixative primarily prepare for examination?

    <p>Nuclear structures</p> Signup and view all the answers

    For laboratory temperatures of 20-24°C, which melting point wax should be used?

    <p>34-58°C</p> Signup and view all the answers

    Which fixative is known for its lipid staining properties?

    <p>Osmium tetroxide</p> Signup and view all the answers

    Which fixing agent acts faster compared to alcoholic formalin?

    <p>Formol-acetic alcohol</p> Signup and view all the answers

    What is the main component of Flemming's fixative when glacial acetic acid is excluded?

    <p>Chromic acid</p> Signup and view all the answers

    What is the ideal temperature range for effective decalcification?

    <p>18-20°C</p> Signup and view all the answers

    Which solution is a mixture of ethanol, chloroform, and glacial acetic acid?

    <p>Carnoy's solution</p> Signup and view all the answers

    Which decalcification method is known for being the fastest?

    <p>Microwave decalcification</p> Signup and view all the answers

    What can be used to inhibit nuclear staining when using strong acids for decalcification?

    <p>Formaldehyde</p> Signup and view all the answers

    What is the primary mechanism of ion exchange resins in decalcification?

    <p>Removes calcium ions</p> Signup and view all the answers

    What is the typical decalcification time required for small specimens?

    <p>1-3 weeks</p> Signup and view all the answers

    What effect does a temperature of 37°C have during the decalcification process?

    <p>Impairs nuclear staining</p> Signup and view all the answers

    What is the volume ratio of decalcifying solution to tissue that is generally recommended?

    <p>20-30 times</p> Signup and view all the answers

    For which type of samples is electrolytic decalcification especially effective?

    <p>Small bone fragments</p> Signup and view all the answers

    Study Notes

    Fixation

    • Purpose of Fixation: To preserve the specific elements of the cell, chemical constituents of cells and tissues, and prevent autolysis of cells
    • Fixation Process: Involves replacing the water content of the tissue with fixative agents, which form cross-links and solidify the tissue
    • Types of Fixation: Nuclear, Cytological (both preserve cell elements), Histochemical (preserve chemical constituents of cells and tissues)
    • Routine Fixation Duration: 2-6 hours
    • Electron Microscopy Fixation Duration: 3 hours
    • Factors Affecting Fixation:
      • **Size & Thickness of tissue:**Larger tissues require more time
      • Agitation: Improves the speed of fixation
      • Moderate Temperature: Ideal temperature is 18-20°C
      • pH: Ideal pH for most fixatives is ≤ 4.6
    • Important Note: Glacial acetic acid is used in some nuclear fixatives, but it destroys mitochondria and Golgi bodies, so it is not used in cytoplasmic fixatives

    Fixative Types

    • Aldehydes: Commonly used fixatives like formaldehyde
    • Metallic Fixatives (Mercuric, Chromate): Also used for fixation
    • Picric Acid: Another type of fixative
    • Glacial Acetic Acid: Used in fixatives for preservation of nuclear structures
    • Formalin-Acetic Alcohol: Faster acting than alcoholic formalin, used for diagnostic cryostat sections
    • Osmic Acid Fixatives: Strong oxidizing solution used in Electron Microscopy, excellent lipid stain
    • Flemming's Solution: Chromic-Osmium Acetic Acid fixative, recommended for nuclear preparation
    • Flemmings Without Glacial Acetic Acid: Recommended for preserving cytoplasmic structures, particularly mitochondria
    • Trichloroacetic Acid: Another type of fixative, most common decalcifying agent

    Decalcification

    • Purpose: To remove calcium salts from bone tissue for sectioning and staining
    • Common Methods: Chemical (using acids) and Electrolytic
    • Decalcification Rate: Can vary, small specimens may take 1-3 weeks, dense cortical bone may take 6-8 weeks or longer
    • Microwaves: Can be used to accelerate decalcification, a newer technique

    Tissue Processing

    • Steps Involved: Fixation, Decalcification, Dehydration, Clearing, Impregnation, Embedding, Trimming, Sectioning, Staining, Mounting, Ringing, Labeling
    • Impregnation: Replacing clearing agents with a medium to fill tissue cavities, ensuring proper support for cutting and staining
    • Embedding: Incorporating tissue into a medium for sectioning, typically paraffin wax

    Embedding Mediums

    • Paraffin Wax: Most common embedding medium, suitable for routine histological studies
    • Celluloidin: Another type of embedding medium, particularly for preserving large tissues
    • Gelatin: Used for delicate specimens and frozen sections, avoids dehydration
    • Plastic: Epoxy resin, used for electron microscopy and special staining techniques

    Paraffin Wax

    • Ideal Infiltration Temperature: 2-5°C above melting point
    • Routine Melting Point: 66°C
    • Viscosity: Lower than other embedding mediums
    • Purity Requirements: Free from dust, water, and foreign matter

    Other Embedding Mediums

    • Cyclohexene Dioxide: Known as SPURR, very low viscosity, rapid infiltration
    • Polyester Plastics: Originally for electron microscopy, now used less frequently

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    Midterm Histopath (2) PDF

    Description

    Explore the process and types of cell fixation in this quiz. Learn about the purpose, routine duration, and factors affecting fixation. Test your knowledge on the specifics of nuclear, cytological, and histochemical fixation methods.

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