Re: GMS help
Freida Carson observes about methenamine silver demonstration of Histoplasma:
>>With the usual 1% periodic acid oxidation for 5 minutes, you run the risk
of false negatives with histoplasma. This happen to us, so if you live in an
area where you are likely to have this organism, you should use chromic acid
oxidation or perhaps stronger and longer periodic acid oxidation. Jerry
Fredenburgh and I wrote a paper on this that was published in the Journal of
Histotechnology a couple of years ago. I do not have the reference handy
right now, but will put it on histonet if anyone is interested.<<
Please do post the reference, Dr. Carson, so I can excavate my copy of the
necessary journal out of the garage!
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.
How do you dispose of chromic acid? I would think you'd want to reduce it to
a lower valence state and precipitate it in some insoluble form that you
could accumulate in a jug. Does anyone have a method for this? (Thus one can
precipitate mercury as the sulfide, and silver as the carbonate or sulfate.)
My recycling center now accepts batteries, which contain all kinds of
unpleasant heavy metals such as cadmium, mercury, and lead. Surely whoever
carts that stuff off could deal with properly precipitated heavy metal waste
from histology labs.
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