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UND 363 PASD
| 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 |