I've been using Hoechst 33342 at 100-200ng/ml. In my tests, this
concentration did not noticeably impair growth of mammalian
fibroblastic and epithelial cell lines over a period of 4 days.
(5-10ug/ml of as proposed by Ramin will act as a mitotic blocker as
far as I remember. I didn't do the experiment myself, though, and I
don't remember the reference).

Cheers,

        Beat


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