I hesitated to respond to this, because I haven't used subbed slides for
brain.  However, my experience might help.  My usual practice is to make
subbed slides that I need just before I need them.  There been occasions,
however, when I have subbed slides remaining after mounting sections.  Thus,
I have successfully used subbed slides at least a year old for mounting
5-7um sections of mixed tissues [BUT never adipose tissue].  I have never
used subbed slides that have stood around for longer times.  Furthermore, I
never felt the need to seriously entertain the issue of microbial breakdown
of the gelatin, given the presence of so much Cr.  My use of subbed slides
was confined to those instances when I performed autoradiography on
radioactively labeled tissues.  I have never used subbing for any other
experimental purpose.  Old subbed slides were used for sections to add to a
'demonic' histology slide box I prepared for my histology students.

The first time I used subbed slides (following the directions, "Chrome alum
("lavender crystals ONLY, please!!!") into a ?% solution of gelatin"), I was
struck by the absence of wetting of the slides.  Adhesion, however, was not
then, and never has been, a problem.  In recent years, because of changing
regulations about the handling of chemical waste and the availability of
better adhesive substances, I have refrained from making subbing solution,
even for autoradiography.

This reminiscence is the substance of my 'subbing' point.  Having observed
this behavior (non wetting) of subbed slides EVERY time I prepared them, I
learned how to overcome the initial difficulty of 'getting' sections to stay
put (EXTRA drying time).  My initial conclusion that subbing causes a degree
of hydrophobicity still stands.  Your problem may be a combination of this,
insufficient drying of the section-subbed slide on the slide warmer, or the
extra lipid content of brain. 

Hope this helps, because it is simply too long to be totally irrelevant.

Regards,

Fred Monson

Frederick C. Monson, PhD   
Center for Advanced Scientific Imaging
Schmucker II Science Center
West Chester University
South Church Street 
West Chester, Pennsylvania, USA, 19383
Phone:  610-738-0437
FAX:  610-738-0437
fmonson@wcupa.edu
CASI URL:  http://darwin/wcupa.edu/casi/
WCUPA URL:  http://www.wcupa.edu/
Visitors URL:  http://www.wcupa.edu/_visitors/


> ----------
> From: 	Knight, Brandon
> Sent: 	Wednesday, April 10, 2002 2:37 PM
> To: 	'histonet@pathology.swmed.edu'
> Subject: 	How long are subbed slides good?
> 
> I've been having a problem with 40um mouse brain sections coming off of
> subbed slides when placed in any liquid (for instance, when going through
> the staining process).  The edges may fold over, they may wrinkle, or
> slide
> off completely.  They were sufficiently dried (some for a couple of
> weeks).
> The slides that I'm using were subbed in August of 2000.  Is it possible
> that the gelatin has degraded and that these slides are no longer subbed,
> or
> could there be another explanation?
> 
> Brandon Knight
> Children's Research Institute
> Center for Genetic Medicine
> Children's National Medical Center
> Washington, D.C.
> 
>