Dear Rebecca,

	One of the great problems with precutting & storing tissue is that you
expose the tissue to oxidation (sp) & reduction reactions with the
surrounding environment.  This is also true of blocks.  However, by the
time you have trimmed the surface of a block you are into the unaffected
tissue.  While there are many people who can report that they have stored
unstained slides forever without detrimental effect, it depends on the
staining.  H&E no problem, many histochemical & some immuno staining - no
problem.  BUT, for the really important stuff - big problems.  In some
cases the chemical reactions that have taken place can be reversed, ie
antgen retrieval (if your lucky).  I was taught to always store blocks, &
only store unstained slides for short periods (weeks to months depending on
what they were for).  Refrigeration slows chemical reactions it doesn't
prevent them.  If you must store unstained slides & must get good results
from them I can only suggest placing them immediately in a container filled
with nitrogen gas, temperature of storage - probably cold.
	Long term storage of tissue in fixative creates similar problems.

	Regards

	Rob W.

At 07:48 12/07/1999 -0500, you wrote:
>Hi.  I've got some mouse spinal cord tissue that has been sitting on slides
>in a freezer for two years.  I need to stain it for oligodendricytes with a
>cc-1 antibody.  The procedure that was prepared workes beautifully on
>tissue that has been UNCUT in a freezer for a long time, and was cut only
>recently to practice for this stain.  However, when the precut old tissue
>(the important stuff) is used with the same procedure, the background
>staining is terribly high.  Oh yeah, it's developed with DAB.  The
>oligodendricytes are too light to be seen clearly against the background
>stain, making them uncountable.  Our head histotech thinks its due to
>freezer burn, or something similar to it. Does anyone have any ideas as to
>how I can salvage the rest of this tissue?
>Thanks,
>Rebecca LoVerso
>Dept. of Neuroscience
>The Ohio State University


R. Wadley, B.App.Sc. M.L.S, Grad.Dip.Sc.MM
Laboratory Manager
Cellular Analysis Facility
School of Microbiology & Immunology
UNSW, New South Wales, Australia, 2052
Ph (BH) 	+61 (2) 9385 3517
Ph (AH)	+61 (2) 9555 1239
Fax 	+61 (2) 9385 1591
E-mail	r.wadley@unsw.edu.au
www	http://www.micro.unsw.edu.au/caf.html