Cell cycle time of murine neopallial cells in vitro

Disaggregated glial cells from newborn CD1 mouse neopallia were cultured in low concentration (4.2 x 10(3) cells/cm2) for 72 hr and then either pulse labeled with BrdU by one 2-hr pulse at various times of culturing or continuously labeled for various lengths of time. At the end of incubation, the cells were fixed and immunoreacted with BrdU. All BrdU+ and BrdU- cell nuclei were counted in an area of 4.84 cm2. A three-compartment model for interpretation of the experimental data was developed consisting of active proliferating cells, non-active cells with proliferating potential, and nonproliferating cells. The model is based on assumptions of time invariance of culture conditions, random re-entry of cells into cell cycle and random exit from the proliferating pool. Furthermore, it is assumed that average values are representative for describing the numbers of cells in specific compartments as functions of time. A set of relationships representing the numbers of labeled cells for pulse labeling and continuous labeling assays is derived from these assumptions and the generally accepted representation of cell progress through the cell cycle, i.e., a genetically predetermined sequence of post-mitosis rest phase, S-phase, pre-mitosis rest phase, and mitosis. These relationships are used to evaluate the S-phase time tau s and cell cycle time tau c of proliferating cells. Under our particular conditions, we obtain approximately tau s = 8 hr and tau c = 16 hr, respectively. The applicability of the model and possible distorting factors are discussed.