RE: [ PI staining live cells? ]

In eukaryotes as well as in prokaryotes PI represents a marker for cell
membrane permeability. However, as Howard says so nicely in his book, it
makes a difference if you are permeabilised by several 22g needles or
22calibre bullet holes. Survival becomes a question of balance, like in
a ship that sinks if the water comes in faster than it can be pumped
out. Thus membrane integrity is a suitable target for the detection of
cell death as long as the circumstances are considered. Electro or
chemoporation are classical examples probed for by PI uptake where it
does not indicate cell death.

The viewpoint of dividing or dead is too simplistic. Of the eukaryotic
cells terminally differentiated granulocytes provide a crucial function
in the immune system and are definitively not dead. Viable bacteria can
be divided into :
Reproductive viability
Metabolically active
Intact and
Permeabilised
(see http://www1.elsevier.com/homepage/sah/mimet/speciss/1378.pdf)

Cells that are dead do definitively not divide, but you can not say that
cells that do not divide are definitively dead

Regards

Gerhard





-----Original Message-----
From: Robert J. Palmer Jr. [mailto:rjpalmer@dir.nidcr.nih.gov] 
Sent: 28 April 2006 19:27
To: cyto-inbox
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