17 Questions
What is the main purpose of fixation in histotechnology?
To alter tissue by stabilizing the protein
Which type of fixation involves the use of fixative reagents like 10% Neutral buffered formalin (NBF)?
Chemical fixation
What is autolysis in histotechnology?
Enzyme attack on tissues
Which fixative is most commonly used in histotechnology?
Formaldehyde
What can happen if tissues are not fixed promptly to prevent autolysis?
Formation of black acid hematin pigment
What should be maintained to prevent the formation of formalin pigment during fixation?
pH levels
Which of the following stains is used to demonstrate the presence of argyrophil (silver-loving) granules in neurosecretory tumors?
Grimelius Stain
What is the purpose of the Fontana-Masson stain in histology?
To demonstrate the presence of melanin and other argentaffin substances
Which of the following steps is NOT part of the automated staining process described for the Multistainer with CV5030 Glass Coverslipper and TS5025 Transfer Station?
Manually apply coverslips to each slide
What is the primary function of the HistoCore PEGASUS Tissue Processor?
To process and embed tissue samples in paraffin wax
Which of the following is NOT a function of the barcodes used on slides and cassettes in the automated system?
To provide information about the fixative used
Which stain is used to demonstrate the presence of neurofibrillary tangles and senile plaques in Alzheimer's disease?
Bielschowsky stain
What is the primary difference between progressive and regressive staining techniques?
The presence or absence of a differentiation phase using alcohol
Which stain is used for the detection of Mycobacterium leprae, the causative agent of leprosy?
Fite acid-fast stain
Which stain is used for the identification of Helicobacter pylori, a bacterium associated with gastric ulcers?
Giemsa stain
Which stain is used for the demonstration of fungal organisms in tissue samples?
Methenamine-silver nitrate
Which stain is used for the demonstration of spirochetes, a group of spiral-shaped bacteria?
Warthin-Starry stain
Study Notes
Fixation
- Alters tissue by stabilizing protein, making it resistant to further changes
- Can occur physically or chemically using fixative reagents or heat
- Autolysis is a common problem, especially in tissues rich in enzymes, and should be prevented by fixing tissues as soon as possible
- Two factors to consider:
- Size: tissues should not be more than 3 mm thick, and 1 mm for osmium tetroxide
- Volume ratio: 15-20 times greater than the tissue volume
Fixatives
- Formaldehyde: most commonly used fixative, may produce a pigment, and maintenance of pH, appropriate volume ratio, and removal techniques can prevent it
- Prussian blue: detects Ferric ion in tissues
- Fontana-Masson: demonstrates argentaffin substances such as melanin
- Grimelius Stain: demonstrates argyrophil (silver-loving) granules in neurosecretory tumors
Automation
- Barcode labeling on slides and cassettes
- Multistainer with CV5030 Glass Coverslipper and TS5025 Transfer Station: automated staining and coverslip process
- HistoCore PEGASUS Tissue Processor: can hold up to 200 cassettes and takes pictures
Stains
- Mayer Mucicarmine: useful for demonstrating Cryptococcus neoformans
- Alcian blue: used for acid mucopolysaccharides (pH 2.5) and sulfated mucosubstances (pH 1.0)
- Congo red: demonstrates amyloid in tissues with green birefringence under a polarized microscope
- Masson Trichrome Stain: differentiates between collagen and smooth muscle
- Sudan black B: most sensitive of all lipid dyes
- Bielschowsky stain: demonstrates neurofibrillary tangles and senile plaques in Alzheimer's disease
- Cajal stain: demonstrates astrocytes (now replaced by immunohistochemical techniques)
Embedding
- Also referred to as casting or blocking
- Specimen orientation is the most critical step in embedding
Staining
- Progressive vs Regressive staining: differentiated by the differentiation phase, where regressive stain uses an alcohol solvent
Microorganisms
- Acid-fast stain: Ziehl-Neelsen (hot method) and Kinyoun (cold method) for detection of Mycobacterium
- Fite acid-fast stain: detection of Mycobacterium leprae
- Giemsa Stain: identification of Helicobacter pylori
- Methenamine-Silver Nitrate: demonstration of fungal organisms
- Warthin-Starry: demonstration of spirochetes
Test your knowledge on special stains used in histology for demonstrating specific tissue components like Cryptococcus neoformans, acid mucopolysaccharides, sulfated mucosubstances, amyloid, collagen, and smooth muscle. Learn about techniques like Mayer Mucicarmine, Alcian blue, Congo red, and Masson Trichrome Stain.
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