The objectives of this study are three-fold. The first is to continue development of new cytochemical, biochemical and biophysical probes and techniques to measure amount and/or state or conformation of various constituents of individual cells. These probes (techniques) will be designed for cell analysis by flow cytometry and cell sorting, and are expected to have clinical application in cancer screening, diagnosis, classification and prognosis, in evaluation of drug sensitivity of tumors and in monitoring treatment effects. Techniques measuring the following cell features: (1) total DNA, RNA and protein content; also RNA/DNA and RNA/protein ratios of whole cells and isolated nuclei; (2) mass and membrane potential of mitochondria; (3) ratio of ds/ss RNA; (4) accessibility of DNA in situ to various intercalating and externally binding probes as an indicator of DNA superstructure; (5) polysomal vs ribosomal RNA; (6) selected nuclear proteins specific for proliferating or transformed cells detected by monoclonal antibodies; (7) structures of nuclear chromatin analysed by dye combinations exploiting energy transfer and fluoresence polarization; (8) presence and accessibility of SH groups; (9) chromatin sensitivity to steroid hormones; and (10) DNA in situ sensitivity to denaturation as an indicator of chromatin structure will be either refined, adapted to clinical use or developed. The second objective is to study the cell features described above in a variety of cell types, to apply the developed probes in relation to cell growth, progression through the mitotic cycle or differentiation. The data will be correlated with kinetics of those processes and analysed for each cell type. The analyses will provide a more complete description of metabolic changes and cell heterogenity and should give new clues to the regulatory mechanisms of the cell cycle and differentiation. The developed probes will be also applied to study mechanisms of action of certain antitumor or drugs in relation to the cell cycle, quiescence, differentiation or unbalanced growth. The third objective is, by using biochemical and biophysical methods to study molecular interactions between the probes and various cell constituents, predominantly nucleic acids. Because many probes are either antitumor drugs themselves or drug analogs, these studies in addition to being helpful in developing new diagnostic techniques are expected to reveal information on mechanisms of drug action on cells at the molecular level. Correlating these data with the drug studies on whole cells will provide a comprehensive view on intercellular drug targets, mechanisms involved in drug binding, modulations of binding and effects related to cell kinetics or metabolic state are mechanisms of cytotoxicity. This in turn will help to assess the cellular features predicting susceptibility to particular drugs and aid in new drugs design.