I always wonder if the tissue from autopsy is suitable for apoptosis
assay or not.
It usually takes a few  to 24 hours before fixing the tissue in
formalin.  It is enough for inducing apoptosis in any tissue and
probably more important factor than fixation time.

TUNEL method can pick up not only apoptotic nuclei, but also simple DNA
damage.  Simple DNA damage can be caused by sectioning, improper
fixation, and etc.  

The Tdt enzyme concentration varys in each kit.  I don't like
Boehringer's kit, which tends to have higher background.  

Depends on the tissue you use, you have to modify the condition.  If
normal? control sample get high background with reasonable modification,
you might better question whether tissue were hundled carefully.

LINDA MARGRAF MD wrote:
> Dear Histonetters:
> The brains (mostly fetal and infant) are fixed for 1-2 weeks in 20% formalin prior to processing and paraffin embedding. Does anyone know if this amount of fixation will create too much DNA fragmentation to invalidate the procedure. I would also love to hear from anyone doing

-- 
Masayuki Miyagishima, MD
University of Pittsburgh, 
Department of Surgery
412-647-2345, and ask the hospital operator to page 3228, please.