I am trying to stain a monolayer of cells growing on a 12 mm glass
coverslip with propidium iodide.  We fixed the monolayer with either
ethanol or 2% paraformaldehyde and then stained overnite with 5 ug/ml
propidium iodide, rinsed,  mounted using mowiol, and examined using an
MRC600.  The ethanol fixed cells had intensely stained nucleoli but the
nuclei themselves were still dark against a lightly stained cytoplasm.
QUESTION:  Can anybody tell me why the nuclei themselves aren't staining?
Nuclei in 1 um JB-4 methacrylate sections of paraformaldehyde fixed cells
stain beautifully and homogeneously using 5 ug/ml PI.
 
The paraformaldehyde fixed cells had a general light diffuse staining with
no specific staining of the nuclei or nucleoli.  I assume this is because
the paraformaldehyde didn't permeabilize these cells.  Alternative
explanations welcomed.
 
Thanks in advance for any advice or comments.
 
 
Thomas E. Phillips, Ph.D.
Associate Professor of Biological Sciences
Director, Molecular Cytology Core Facility
3 Tucker Hall
University of Missouri
Columbia, MO 65211
(314)-882-4712 (voice)
(314)-882-0123 (fax)