Interesting info provided by the Samurai, in fact, wasn't the original
method done so whoever could go back into tissue/slide archives to do just
this study for endemic Histoplasmosis.  If I remember correctly, Grocott
removed coverslips with xylene soak from H&E slides, then oxidized the
section with chromic acid.  This actually removed hematoxylin by
overoxidation while oxidizing the Histoplasma capsule, and the methenamine
silver steps followed.  So if one ever needs to do a GMS stain on an H&E
slide, it is possible.  I am not sure periodic acid would do this. 

Trying to remember the common name for Histoplasmosis, Missouri Valley
fever, or some such thing. Help on this one Samurai!  and pigeons dooing
their thing in courtyards were suspect or sources of Histoplasmosis.   

>The problem with Histoplasma capsulatum is that the more elderly the 
>organism, the more difficult it is to stain, and organisms scattered in 
>fibrotic or necrotic material are most difficult of all. Before I would 
>believe in a periodic acid oxidation technique, I would want to see someone 
>assemble a series of such cases (some university's autopsy files would 
>probably contain them) and re-stain them with chromic and periodic acids.
>
>>>so if you live in an area where you are likely to have this organism<< 
>Histoplasma is very widely distributed in the eastern half of the USA, and 
>given the mobility of Americans, anybody in North America may be infected.
>

At any rate, we are staying with tried and true GMS using chromic acid.  If
you are worried about hazardous chromium (salts of), look at chrome gelatin
subbing solutions for slide adhesive, it contains chromium too, and if you
sub the slides, air dry, what do you do with used subbing solutions?  Drain
dump them?? Well, that's considered a no no with chromium whether in
chromic acid or subbing solutions. Collecting this material for safe
disposal is no more difficult than collecting DAB, other chromogens, etc.
and silver in GMS solutions.  

Gayle Callis
MT,HT,HTL(ASCP)
Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367
406 994-4303 (FAX)