CELL-PROLIFERATION IN THE SUBEPENDYMAL LAYER OF THE ADULT-MOUSE IN-VIVO AND IN-VITRO

Pulse labelling experiments with [H-3] thymidine (dT) and double label ling experiments with [H-3]dT and bromodeoxyuridine (BrdUrd) were carr ied out on cells of the subependymal layer in the brain of adult norma l mice in vivo, in vivolin vitro and in vitro. The results should (i) lead to information about cell cycle parameters of these cells in the brain of adult mice, since these cells have been studied mostly in the rat brain up to now and (ii) answer the question whether results conc erning cell proliferation obtained in vivo correspond with those from brain slices incubated in vitro with or without prelabelling in vivo. In vivo an LI of 20.2 +/- 2.7% ((X) over bar +/- SEM) and T-s = 7.2 +/ - 0.7h were found. Furthermore, grain count halving experiments led to a surprisingly short cycle time (T-c) of 11.2-14.2h. The longer T-c v alues (18-20h) reported in the literature for subependymal cells in th e rat brain seem to be due to evaluations of different areas around th e lateral ventricle without considering the migrating behaviour of the se cells which is quite different regionally. The in vitro studies (wi th or without prelabelling in vivo) showed a significantly reduced LI due to the fact that about 20% of the S phase cells, possibly lying in the middle of S, stopped further DNA synthesis after transfer to cult ure. This was shown by comparing the cell fluxes at the G(1)/S and S/G (2) borders of in vivo vs. in vitro studies.