Hi Nancy,
Due to holidays I am a little behind with Histonet.

I have heard the same problem of vanishing silver reaction product from
people using immunogold-silver staining procedures. This technique is
also dealing with metallic silver grains as final reaction product like
your ISH. Those people also used organic mounting for their slides. For
some funny coincidence I had been using an aqueous mounting medium
(DAKO Glycergel and it appeared that even after 5 years the silver
reaction product was still there. We never found any reason why this
happened.
Just try this aqueous mounting along with the organic mounting you
described and in 1-3 weeks you know the answer if this works for you.
And, perhaps this cheap solution also saves you! Stay cool!

Good luck!
Chris van der Loos
Dept. of Cardiovascular Pathology
Academical Medical Center
Amsterdam - The Netherlands

>Date: 8 Jul 2003 03:15:54 -0500
>From: Nancy.Walker@sanofi-synthelabo.com
>Subject: lost ISH signal
>
>Help histonetter!
>
>Can you imagine it's like "now you see it now you don't"! A vanishing
>act that's flipping me out!!
>
>The pb appears at the photographic emulsion stage, that is the films
>are great. It's our silver grains that once devllopped dissappear with
>time (ie 1-3 weeks depending on the strength of the signal). We
>haven't been able to pinpoint any change to our protocol. And
>sometimes we don't lose the signal! Is it VOODOO! That is we've
>changed from Kodak NBT emulsion to Amersham LM1, it's not changed the
>pb. We've had no change in products that we know of (ie devellopper
>and fixateur are KODAK LX24 ,  Xylene clearing with ENTELLAN mounting
>medium).
>
>I would appreciate a discussion on the actual process that could
>explain this loss and might help pinpoint the cause. Or has anybody
>experienced this.
>
>My psychological health and professional reputation depends on this!
>Please Help.
>
>Nancy Walker
>Molecular Biology Scientist