Multivariate Cell Analysis: Techniques for Correlated Measurements of DNA and Other Cellular Constituents

Analysis of the cell cycle was significantly advanced by the development of photometric methods for quantitative measurement of biochemical constituents in single cells. Population biochemical analysis could then be performed on a cell-by-cell basis, and distinct subpopulations discriminated and quantified. Such methods as used in early studies by Casperson and Schultz (10 ) and others [see review by Swift (84 )] demonstrated the potential of ultraviolet (260 nm) absorption cytophotometry for determining cellular nucleic acids content. Interestingly, Kamentsky et al. (51 ), in one of the earliest reports on flow cytometry, utilized this analytical technique along with cellular light scattering measurement. Cytochemical analysis incorporating colorometric procedures, such as the Feulgen reaction (33 ), allowed for microspectrophotometric quantitation of DNA in single cells. Pyronin Y staining was used by Brachet (7 ) and later by Kurnick (54 ) for RNA determinations. The quantitative cytophotometric methods employed in these early studies (9 ) accurately established that both nucleic acid as well as protein contents were elevated in rapidly growing cells compared to cells in stationary phase-correlated biochemical events that are now well established for the cell cycle.