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Unformatted text preview: 9.5 Isolation, Culture, and Differentiation of Metazoan Cells Most animal and plant tissues contain multiple types of cells, hut biochemical and molecular investigations are best accomplished on homogenous cell populations. In the first part of this section we describe a powerful instrument, the fluorescence- activated cell sorter ( FACS) , in which - cells that express specific cell-surface proteins can be separated from a complex mixture of cells. - With this instrument, an investigator can isolate homogenous populations of specific cell types for study. Next we discuss techniques for culturing primary cells —that is, maintaining cells directly isolated from an animal in the laboratory under conditions that permit their survival and growth for at least several divisions. Certain types of primary cells, especially those from embryos , can undergo differentiation in culture. As an example. we will describe how muscle cell precursors grown in culture can differentiate and form apparently normal muscle cells, providing a good system for studying this developmental process. Although many types of primary cells undergo only a limited number of divisions in culture, some accumulate cancer- causing (oncogenic) mutations that allow them to be cultured indefinitely دو¡حم ل . In many cases a single cell can be readily grown into a colony of identical cells, a process called cell cloning. Because these cells are genetically homogeneous, they are particularly suitable for many types of biochemical and genetic studies. Certain cloned cells can undergo differentiation into specific cells types such as adipocytes (fat- storing cells), nerve, or muscle, allowing studies on the mechanism of cell differentiation to be conducted يرجأ on homogenous cell populations. Many times in this chapter we have shown how monoclonal antibodies facilitate cell biological experiments; at the end of this section we describe how special cultured cells are used to generate these antibodies. Flow Cytometry Separates Different Cell Types Some cell types differ sufficiently in density that they can be separated on the basis of this physical property. White blood cells (leukocytes) and red blood cells (erythrocytes), for instance, have very different densities because erythrocytes have no nucleus; thus these cells can be separated by equilibrium density centrifugation (described shortly). Because most cell types cannot be 1 differentiated so easily, other techniques such as flow cytometry must be used to separate them. A flow cytometer identifies different cells by measuring- the light that they scatter and - the fluorescence that they emit as they flow through a laser beam; thus it can quantify the numbers of cells of a particular type from a mixture....
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- Spring '10
- cells, Cellular differentiation, Cell culture, FACS