Histology and Microscopy Techniques

Study Notes

Fixation Methods

Purpose: To preserve tissue morphology and prevent degradation
Types:
- Chemical fixation: Uses chemicals to denature proteins and preserve tissue structure
  - Formalin: most common fixative, peroxygenic acid-based
  - Methanol: used for delicate tissues, can be used for DNA and RNA preservation
  - Glutaraldehyde: used for electron microscopy, preserves ultrastructure
- Physical fixation: Uses physical methods to preserve tissue structure
  - Freeze-drying: preserves tissue structure and antigens
  - Cryofixation: rapid freezing to preserve ultrastructure

Staining Techniques

Purpose: To enhance contrast and visibility of tissue structures
Types:
- Dyes: Chemical compounds that bind to specific tissue components
  - Hematoxylin and eosin (H&E): most common staining technique, stains nuclei and cytoplasm
  - Special stains: used for specific tissue components, e.g. PAS for glycogen, Masson's trichrome for collagen
- Immunohistochemistry: Uses antibodies to detect specific proteins
  - Direct method: uses labeled antibody
  - Indirect method: uses unlabeled antibody and labeled secondary antibody
- Histological stains: Used for specific tissue structures or components
  - Giemsa stain: used for blood cells and parasites
  - Gram stain: used for bacterial identification

Sectioning Methods

Purpose: To obtain thin sections of tissue for microscopic examination
Types:
- Microtomy: Uses a microtome to cut sections
  - Rotary microtome: most common type, uses a rotating blade
  - Cryomicrotome: used for frozen sections, cuts at -20°C
- Vibratome: Uses a vibrating blade to cut sections
  - Used for fresh tissue, preserves tissue structure
- Laser microtomy: Uses a laser to cut sections
  - Used for delicate tissues, preserves tissue structure

Mounting Media

Purpose: To preserve and stabilize the tissue section on the slide
Types:
- Aqueous mounting media: Water-based, e.g. water, glycerol, or gelatin
  - Used for temporary mounts, can be easily removed
- Organic mounting media: Solvent-based, e.g. xylene, toluene, or DPX
  - Used for permanent mounts, provides better clarity and durability
- Resin-based mounting media: Used for electron microscopy, e.g. Epon or Spurr's resin

Quality Control

Importance: Ensures accurate and reliable results
Steps:
- Tissue selection: Selecting appropriate tissue samples for analysis
- Fixation and processing: Verifying fixation and processing protocols
- Staining and mounting: Verifying staining and mounting techniques
- Microscopic examination: Verifying slide quality and accuracy of interpretation
- Standardization: Standardizing protocols and procedures to ensure consistency and reproducibility

Description

Test your knowledge of histology and microscopy techniques, including fixation methods, staining techniques, sectioning methods, mounting media, and quality control procedures. Learn about the different types of fixation, staining, and sectioning methods used in histology and microscopy.