> >Is there a publication or series of papers showing the superiority of >single parameter propidium iodine S phase determinations versus the >combined use of Brdu and PI. I realize that two parameter anlaysis should >permit better resolution of S phase cells but am unable to cite a reference >(s). Thank you. > I don't think a "controlled trial" has been done on this issue. One problem has been that the DNA denaturation required for BrdU detection with anti-BrdU antibody tends to degrade the quality of the PI histogram. The strand break detection method for BrdU developed by the Darzynkiewicz group (Li X, Traganos F, Melamed MR, Darzynkiewicz Z: Detection of 5-bromo-2-deoxyuridine incorporated into DNA by labeling strand breaks induced by photolysis (SBIP). Intl J Oncol 4:1157-61, 1994) doesn't require denaturation and should avoid this problem. The per cent S phase obtained from a DNA histogram cannot identify cells arrested in S phase, which are encountered in some tumors; tracer methods (originally thymidine incorporation detected autoradiographically, and now BrdU incorporation detected by antibody incorporation, strand breaks, or cytochemistry) are necessary to catch cells in the act of DNA synthesis, and to estimate cell turnover rates. -Howard
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