The RMS from the C57BL/6J and A/J mice was reconstructed selleck chemicals from serial sagittal sections to compare their three-dimensional course and to determine the total numbers of RMS cells in each strain. Our immunohistological staining analysis and imaging revealed that the general configuration of the RMS in both strains was similar (Fig. 3). Moreover, A/J had
approximately 40% more cells in the RMS than C57BL/6J (A/J = 52659 ± 535 and C57BL/6J = 37130 ± 731; Fig. 3B and C). At the cellular level, we wanted to determine if the differences in BrdU-labeled cells between A/J and C57BL/6J are due to differences in cell cycle parameters as explored in the dentate gyrus by Hayes & Nowakowski (2002). First, we determined the LI at each time point under study for both parental strains (Fig. 4). There was an initial increase of LI with lengthening BrdU exposure time, indicative of a constantly dividing cell population. For both strains, the LI reached a plateau of ∼0.2, suggesting
that the actively dividing populations in the RMS accounts for approximately 20% of the total RMS cell population. Using the total RMS cell numbers described in Fig. 3 and a GF value (i.e. the proportion of proliferating cells to the total number of cells in the population) of 0.2, we estimated that the total numbers of actively dividing cells in the RMS were 10531 ± 107 and 7426 ± 146 PARP inhibitor for A/J and C57BL/6J, respectively. Moreover, the quantitative analysis of the LI curves showed that there were
no significant differences in the cell cycle parameters of the two RMS Forskolin purchase populations. The ratio of Ts/Tc was similar (∼0.57), indicating that the relative length of the S-phase (Ts) to the whole cell cycle (Tc) was the same for the two strains. The length of the cell cycle for the proliferative populations in the RMS ranged from 10.5 h (A/J) to 14.5 h (C57BL/6J), and these values overlap with the cell cycle length for the proliferative population in the dentate gyrus (12–14 h) and are also within the 8–18 h range of cell cycle lengths detected in progenitor cells lining the ventricular cavity of the developing cerebral neocortex (Hayes & Nowakowski, 2002; Takahashi et al., 1995). Although the lengths of cell cycle and S-phase for the proliferative population in A/J RMS appeared to be shorter than the lengths detected in the C57BL/6J RMS, such differences did not reach statistical significance. Therefore, the differences in the number of BrdU-labeled cells in the RMS of the two strains reflected differences in the actual number of proliferative cells and was not due to differences in cell cycle or S-phase lengths. In line with this conclusion, the proliferative population size in the A/J RMS was ∼40% larger than C57BL/6J RMS.