Question | Answer |
what does PASD demonstrate | Glycogen |
What is the principle behind PASD | Diastase (an enzyme) depolymerizes glycogen into small sugars that are washed out.
After glycogen digestion the sections are stained with PAS |
What two things can be used to digest the glycogen | diastase and human saliva |
what fixatives are used for PASD | 10 NBF, formalin alcohol, and absolute alcohol |
what fixatives are least desirable for pasd | picric acid, gluteraldehyde, and osmium tetroxide (they make tissue more resistant to diastase digestion therfore increasing time) |
what is the proper microscope for pasd | light |
what is the preferred thichness | 2 slides with 2 identical sections @ 4-5 microns (liver) one labeled with (digestion) and one W/O |
what are good controls for pasd | liver and cervix (endo and ecto cervix)
the ecto contains squamous epithelium and the endo has glandular epithelium |
what will the 2 epitheliums of cervix stain with the pasd reaction | glandular (endo) will stain positive with schiff, while diastase will remove glycogen from squamous (ecto) therefore negative |
what are the major reagents for pasd (6) | malt diastase, periodic acid, schiff, metabisulfate, running water, harris hematox |
what is the purpose of the malt diastase in pasd | it is for glycogen digestion *contains alpha and beta enzyme* |
what are some problems with malt diastase in pasd | tends to loosen sections and doesn't alway complete glycogen digestion |
what are some possible errors when working with malt diastase | if heat beyond 40○C the digestion will cease, but if not enough heat the enzymes will not work well |
based on PAS what does the P.A., Schiff, metabisulfate, water and harris do | P.A. oxidises glycols to aldehydes, schiff combines with aldehydes, metabisulfate removes excess schiff, water restors schiff color, harris is used for counterstain |