Re: [ PI staining live cells? ]

Robert:
Hi!
I don't know of any cases where PI staining is not an indicator of cell 
death. In the context of this ignorance, I must tell you that I do not 
understand how your definition of live/dead works in with PI (I am assuming 
your dividing vs dead dichotomy is for the sake of the argument, since as a 
general statement I think most would say it is not true).

PI, as you said, is used to probe membrane integrity. How does that connect 
with a cell being able to divide? Sure, PI staining means that the cell is 
about to die, so it won't be diving any more; and a cell that is divinding 
is clearly alive so it should be able to exclude PI. But that is the trivial 
case. What I want to get to is that if your criterion of eligibility is 
dividing vs not dividing, I think you would be better off looking at a probe 
or assay that can tell you something about mitosis and not about membrane 
permeability. We all commonly use probes that assay X while actually wanting 
to know about Y, but use them because we know X and Y are connected or 
correlated in a given way. In this case, you are taking two different 
definitions, division as a measure of viability and membrane integrity as a 
measure of viability, mixing 1/2 - 1/2, and then equating "not dead" by one 
definition as "not dead" by the other. I think that these two phenomena, a 
cell being capable of dividing and capable of excluding PI, are so separated 
than trying to marry them together would be problematic. You are taking a 
probe that measures membrane permeability and trying to make it say 
something about a cellular process completely different. That is a 
conceptual link that I don't know how you support it (besides the trivial 
case mentioned before). Maybe you can elaborate a little more about the idea 
behind your proposition?

Regards,

Uriel.
Uriel Trahtemberg
MD/PhD student
The Laboratory for Cellular and Molecular Immunology
The Hebrew University - Hadassah Medical Organization
Jerusalem - ISRAEL

"God does not care about our mathematical difficulties. He integrates 
empirically."
 Albert Einstein

----- Original Message ----- 
From: "Robert J. Palmer Jr." <rjpalmer@dir.nidcr.nih.gov>
To: cyto-inbox
Sent: Friday, April 28, 2006 8:27 PM
Subject: [ PI staining live cells? ]


> PI has a tradition in eukaryotic biology as an indicator of cell death 
> through membrane disruption.	I am interested in whether any list watchers 
> can tell me of cases in which strong PI staining is not an indicator of 
> cell death.  If many examples of PI staining of growing (or 
> growth-capable) cells exist, then of what is PI staining indicative other 
> than a (transient) membrane permeability difference compared to untreated 
> controls?
> FYI, my definition of cell death is the inability of cells to divide when 
> provided with appropriate conditions.  I am less interested in other 
> measurements of viability - "dividing or dead" is my motto...
> Thanks for your opinions.....
> Rob Palmer
> -- 
> Robert J. Palmer Jr., Ph.D.
> Natl Inst Dental Craniofacial Res - Natl Insts Health
> Oral Infection and Immunity Branch
> Bldg 30, Room 310
> 30 Convent Drive
> Bethesda MD 20892
> ph 301-594-0025
> fax 301-402-0396