Permeabilization of cell membranes (Hermina Borgerink)

I would greatly appreciate it if somenone could explain to me why it is
necessary to permeabilize the cell membrane of cells in a cut tissue
section, whether that be a paraffin or frozen section?  It would seem to
me that only whole cells with their membrane intact would require
permeabilization with either a detergent such as Tween or Triton or
Saponin.  Along the same lines, I tend to question why it is necessary
to digest with Proteinase K in a paraffin section when doing In Situ
detection using Tunel or Isel: the 3'-OH ends of DNA are already exposed
as a result of cleavage which takes place during programmed cell death. 
I have tried it with and without, at room temperature and at 37 degrees
Celsius, and I found that there is little if any, difference.  And when
using ethanol as a fixative rather than an aldehyde, it has been my
experience that a ton of cells will stain which are not necessarily

Any comments in favor of detergents other than as a "background
cleanser" would be greatly appreciated.

Hermina Borgerink, BA, HT(ASCP)IHQ
Department of Pathology
Wake Forest University School of Medicine
Winston-Salem, N.C. 27157
PH (336) 716-1538
Fax (336) 716-1515

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