The question about using periodic acid instead of chromic acid for GMS, is
this for basement membrane staining (PAMS aka Jones) or for fungus staining
(GMS)??  

There are caveats about using periodic acid instead of chromic acid for
fungus staining, discussed some time ago on Histonet by Freida Carson and
others, check out archives.  It is a good idea to know what changes in
fungus staining results occur with periodic acid usage (user beware!).
There is a publication in J of Histotechnology pointing out potential false
negative results after using periodic acid substitute in GMS for fungus.  
Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)

email: gcallis@montana.edu