Lecture 5 - Special Stains Flashcards
Why are special stains for tissue morphology often performed on a ventilated bench with a downdraft?
Special stains are done in a well-ventilated area to keep vapors away from workers.
In what situations is it an exception to use only pathological tissue for special stains, and why?
It is an exception when only pathological tissue will exhibit a particular staining, such as the detection of viral proteins.
How do Trichrome stains utilize the density, permeability, and size of dye molecules to stain different tissue areas?
Trichrome stains use different dyes based on their size and permeability. RBCs are least permeable, cytoplasm/muscle are in the middle, and collagen is the most permeable.
Describe the stages involved in Martius Scarlet Blue (MSB) staining for connective tissue.
Stage 1 - Yellow dye for RBCs, Stage 2 - Red dye for collagen, muscle, and cytoplasm, Stage 3 - Phosphotungstic acid differentiation, Stage 4 - Collagen filled with blue dye.
What is the composition of the Van Gieson solution, and how does it selectively stain different tissue components?
Van Gieson solution consists of picric acid and acid fuchsin. It stains muscle, RBCs, and cytoplasm with small picric acid, while collagen is stained with larger acid fuchsin.
Explain metachromasia and how Toluidine Blue utilizes it to stain tissues.
Metachromasia is when a pure dye stains a tissue element a different color. Toluidine Blue, a strong basic dye, stains nuclei blue (orthochromasia) and mast cell granules purple (metachromasia).
What are the three categories of pigments discussed in the lecture, and provide examples of each.
Artefact pigments (formalin, mercury, chrome, osmium), exogenous pigments (carbon, silica, asbestos, tattoo pigments), and endogenous pigments (haematogenous - haemoglobin, haemosiderin; autogenous - melanin, lipofuscin).
How does the Perls Prussian Blue method work, and what does it detect in tissue sections?
Perls Prussian Blue detects iron in tissue, specifically haemosiderin. It involves the reaction of hydrochloric acid and potassium ferrocyanide, forming an insoluble blue compound.
In what pathological condition is Haemosiderin deposition visualized using Perls Prussian Blue, and what diseases are associated with it?
Haemosiderin deposition is visualized in asbestosis, a chronic lung condition associated with pleural disease, mesothelioma, and lung cancer.
How does the Schmorl’s reagent work to detect melanin deposition in tissues?
Schmorl’s reagent, a mix of potassium ferricyanide and ferric chloride, exploits melanin’s ability to reduce potassium ferricyanide, forming an insoluble blue compound.
Describe the Masson-Fontana method for detecting melanin and the steps involved in the process.
The Masson-Fontana method involves silver impregnation, where melanin reduces ammoniacal silver solution to metallic silver. It includes staining with Fontana solution and counterstaining nuclei with neutral red.
What are the general stains for proteins, and why are special stains needed to identify specific proteins?
General stains for proteins include eosin, ponceau red, and Coomassie blue. Special stains are needed for specific protein identification due to their acidophilic and eosinophilic properties.
Name the special stains used to identify fibrin, collagen, elastin, and reticulin in tissue sections.
Fibrin - Haematoxylin & van Gieson, MSB; Collagen - Haematoxylin & van Gieson, MSB; Elastin - Orcein; Reticulin - Silver impregnation.
What is the significance of orcein staining, and how is it used in the diagnosis of certain conditions?
Orcein stains elastic fibres dark brown/purple and copper-associated proteins. It is used in the diagnosis of hepatitis B infection and liver diseases associated with copper.
What is reticulin, and how is it demonstrated in tissue sections?
Reticulin is a type III collagen produced by fibroblasts, providing support in cellular organs. It is demonstrated using silver impregnation, involving a multistep staining process.
