I am not an expert but the way I understand it is this:

According to Grocott and Luna, the polysaccharides in the fungal cell wall are oxidized to aldehydes by the chromic acid.  Only substances that possess a large quantity of polysaccharides (fungal cell wall, glycogen and mucins) remain reactive with the methenamine silver, reducing it to metallic silver.

Most all of the silver spirochete techniques follow the principle that spirochetes are argryophilic (they have the ability to bind silver ions from a solution) but do not have the ability to reduce the silver to a visible metallic form.  A chemical reducer is used for that purpose. Based on this chemical property it stands to reason that these organisms would appear larger than they actually are.



Hope that helps.

Jeanine Bartlett, BS, HT(ASCP)
Centers for Disease Control and Prevention
1600 Clifton Road, MS/G-32
18/SB-114
Atlanta, GA  30333
(404) 639-3590 
jeanine.bartlett@cdc.hhs.gov


 




-----Original Message-----
From: histonet-bounces@lists.utsouthwestern.edu [mailto:histonet-bounces@lists.utsouthwestern.edu] On Behalf Of Bobbi Pritt
Sent: Monday, April 17, 2006 9:20 PM
To: histonet@lists.utsouthwestern.edu
Subject: [Histonet] Gomori silver versus Warthin-Starry

Could someone explain the difference between silver stains for fungi and those for spirochetes?  I've been told that silver-based fungal stains (such as GMS) do not significantly deposit silver onto the fungal elements, therefore, one can accurately measure their size using such a preparation.  On the other hand, I've been told that the silver stains for spirochetes (eg. Steiner, Warthin-Starry) are "deposition" stains, which make the organisms appear larger and therefore, more easily identifiable.  Presumably, you would not want to measure size of organisms using this stain.  Is all of this true, and can someone explain the differing mechanisms to me?
  Thank you,
  Bobbi Pritt
   

		
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