On Thu, 11 May 2000 Eileen_Dusek@cdh.org wrote:

> Does anyone have a procedure for Pas Diastase without using saliva.  In
> this day and age of safety i am surprised we still use our own saliva.

  In the absence of some active infection of the mouth, such as
  streptococci, herpes simplex or Vincent's angina, it isn't easy
  to think of saliva as unsafe. Even if you're a carrier of
  meningococci or something potentially harmful to some others,
  putting a drop of spit on a slide isn't exactly a promiscuous
  and unregulated kiss-a-thon. For places that are short of cash,
  such as hospitals in the middle of Africa and research laboratories
  in Canada, saliva is a free, safe and very practical source of
  the enzyme amylase (= diastase).

  The arguments for using amylase from a chemical supplier are,
  despite the truths in the preceding paragraph, quite strong.

  (1) It isn't expensive (even in Canada) unless for some reason you
      need some particular highly purified variant of the enzyme.
      For confirming starch or glycogen, you don't.
  (2) With bought amylase you can use a higher concentration than
      your own salivary glands could ever put out, and consequently
      the time to digest glycogen is shorter.
  (3) Amylase isn't the only enzyme in spit. Proteolytic enzymes,
      lysozyme and ribonuclease are other well known ingredients,
      and there are surely many more. After all, this is the liquid
      that cleaned people's teeth before the invention of the
      toothbrush (except in India and perhaps elsewhere, where they
      are lucky enough to have trees with suitably bristly twigs).

  The other enzymes in saliva are unlikely to catalyze the hydrolysis
  of substances in the section that would be stained by a method to
  show glygogen (such as PAS or Best's carmine).

  Instructions for making your own salivary RNase are in the 2nd
  edition of Pearse's Histochemistry (1960). You heat to 90C for
  a while, which inactivates all the other enzymes. I did this
  once, years ago, and it worked: prevented the red staining of
  neuronal RNA (Nissl substance) by methyl green-pyronine.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1