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Carl, Charles,

The response Charles described is to be expected using Hoechst, if UV 
(=< 405 nm) excitation is used. Same goes for DAPI, with the 
additional problem that DAPI requires permeabilized cells making it 
unsuitable for most live cell experiments.

I have not tried this but I am sure someone out there probably has, 
namely, multi-photon confocal either 2 P or 3 P to excite Hoechst, 
which is PM permeable. UV by itself will elicit radical generation 
and strand breaking. Hoechst being a minor groove DNA dye could lead 
to a lower risk of scission when using 2 P or 3 P to get excitation, 
and might pose less risk of collateral DNA damage including unwanted 
crosslinking.

Further, I would be interested to know whether Hoechst added to cells 
in culture with no light excitation and maintained through what would 
be a couple of passages would permit any cell division. I.E., does 
the dye+light abolish cell division or dye by itself?

Regards All,
Mario

PS I know that MP illumination can really cook cells, too. Guys what 
about using DRAQ5 to watch mitosis?


>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>Dear all,
>What is the consensus on using either DAPI or Hoechst staining on 
>live cells?  Are there effects on mitosis and/or chromosome movement?
>Thanks,
>
>Carl
>
>Carl A. Boswell, Ph.D.
>Molecular and Cellular Biology
>University of Arizona
>520-954-7053
>FAX 520-621-3709


-- 
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Mario M. Moronne, Ph.D.

cell (510) 367-8497

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