Celia,

How does your positive control look?
Have you changed anything in your protocol for
processing or staining?  Have you checked the pH of
your DI water before acidulation and then after? 
Warthin Starry is ultra sensitive, one small change
can alter your results.  It could be anything from a
change in temperature in processing to not having the
tissue sufficiently cleared or hydrated.  If you have
spirochetes in your positive control and not a lot of
precipitate meaning it's clean) it could be that your
processing may have something to do with it.  If the
processor gets too hot during the dehydration phase it
sort of "burns" the tissue.  Also are you using
control material from an outside source or one that
has been processed in your lab?  

Warthin Starry is among the more sensitive silver
stains and it has well earned the second name it was
given "Worthless & Sorry" for a very good reason.  

As a last resort, do a Giemsa it will give you the
same results with half the grief.

Vikki Baker
Institute for Cancer Prevention
Valhalla, New York

__________________________________
Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com

_______________________________________________
Histonet mailing list
Histonet@lists.utsouthwestern.edu
http://lists.utsouthwestern.edu/mailman/listinfo/histonet