Flow sorting in the study of teratocarcinoma cell differentiation

Flow cytometry is a technique by which particles (cells, subcellular fragments, bacteria) in aqueous suspension are passed one by one through a sensing region where optical (or electrical) signals are generated. These signals for each individual cell are collected and processed, and may be stored to yield the distr1bution of the property measured for the population of cells analyzed. Most often cells are fluorescently labelled (with fluorescent dyes, particles or antibodies) and fluorescence signals are measured. Instruments called flow sorters in addition have a sorting capability which allows physical separation of a desired subpopulation for further analysis. This thesis is concerned with the cell biological application of such an instrument with particular emphasis on the use of the sorting capabilities. The process of cell specialization which occurs when a multicellular organism develops from one cell into the mature organism is called cell differentiation. Mouse teratocarcinoma cells share many properties with early embryonic cells and can be used as an tn vitro cell model system to study the early events of cell differentiation. Some aspects of teratocarcinoma cell differentiation may especially profitable be studied by making use of the sorting capabilities of the cell sorter and this is what the main part of this thesis is about. Teratocarcinoma cells can be induced to differentiate by treatment with chemical inducers. Analysis of properties changing upon differentiation can yield information about their role in the differentiation process. One of these properties is the "fluidity" of the plasma membrane. A part of this thesis describes the flow cytophotometric measurement of this change after induction of differentiation.