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21 Cards in this Set

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Why fix a slide?
1) Terminates Cell Metabolism
2) Prevents enzyme degredation of cells by a process called autolysis
3) Kills pathogenic viruses, bacteria, and fungi
4) Hardens tissue by cross-linking or denaturing proteins
3 Steps in Slide Preparation
1) Fixation
2) Infiltration with paraffin
3) Staining
Why should you use a neutral, buffered formalin solution in fixation?
The neutral pH prevents the formation of acid hematin crystals in the tissue when formalin reacts with hemoglobin in an acidic environment
How does formaldehyde act as a preservative and why is it preferred?
It preserves cell structure and extracellular components by reacting with amino groups of protein, resulting in a cross-linking between lysine residues. It minimally alters the 3D structure of most proteins, preserving their immunogenicitiy and allowing subsequent use of labeled antibodies in immunofluorescent techniques and immunohistochemistry.
Why are slide tissues infiltrated with paraffin?
To keep the tissue rigid while it is sliced into extremely thin sections.
How do you infiltrate a slide with paraffin?
The slide is washed until free of fixative, then dehydrated in a series of increasingly concentrated alcohols (ending in 100%). It is finally placed in a clearing solution that consists of organic solvent (e.g. xylene or toluol) and immersed in liquid paraffin at 57-59 degree C. The cooled, hardened tissue in a paraffin block is mounted and sectioned.
What is an unstained paraffin block?
A specimen after paraffin infiltration (and before staining) sectioned off from a paraffin block.
What do H&E stand for and which stain is water-soluble?
H= hematoxylin (water soluble)
E= eosin (alcohol soluble)
Following paraffin filtration, what must be done to the slide before it is "ready"?
First paraffin must be dissolved from the tissue with xylol or toluol. The tissue is rehydrated with decreasing alcohol solutions (ending in water). After staining, tissue is dehydrated a second time, re-immersed in xylol or toluol, and covered with a thin glass cover slip held in place by non-aqueous mounting medium.
What histologic structures *cannot* be seen on an H&E slide?
Basement membranes, intra-cellular lipid, elastic connective tissue, and reticular fibers.
Name the histologic structure(s) we look for using Periodic acid Schiff (PAS) stain.
Basement membrane (purple), Glycogen (magenta)
Name the histologic structure we look for using Masson's or Mallory's stain.
Muscle (red)
Name the histologic structure we look for using trichrome stain.
Collagen (blue)
Name the histologic structure we look for using Weigert's stain.
Elastic fibers (black)
Name the histologic structure we look for using silver stain.
Reticular fibers (black)
Name the histologic structure we look for using Oil and red O stain.
Lipid (red)
Name the histologic structure we look for using Wright's or Wright-Giemsa stain.
Blood cells, cytology
Name the histologic structure we look for using Toluidine blue (T-blue) stain.
Mast cell granules (metachromasia)
What are common sources of artifacts in prepared slides?
Insufficient/prolonged tissue fixation (prolonged is especially common when not using formalin), failure to completely dehydrate the tissue prior to paraffin embedding, and use of paraffin that is too hot during the embedding process.
Differentiate between polyclonal and monoclonal antibodies.
Polyclonal antibodies are produced in an immunized animal while monoclonal antibodies are produced in a continuously replicating antibody-producing cell line.
What color does fluorescein appear when viewed under UV light?
Bright apple green