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Autoradiographic investigations of glial proliferation in the brain of adult mice. II. Cycle time and mode of proliferation of neuroglia and endothelial cells
Author(s) -
Korr Hubert,
Schultze Brigitte,
Maurer Werner
Publication year - 1975
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901600405
Subject(s) - biology , neuroglia , neuroscience , astrocyte , microbiology and biotechnology , central nervous system
The cycle time of the proliferating glial cells outside the subependymal layer of the lateral ventricle as well as that of endothelial cells was studied autoradiographically in the brains of adult and untreated mice. To determine the mean cycle time two independent methods were used. A mean cycle time of about 20 hours was obtained for glial and endothelial cells from the decrease of the mean grain number/nucleus as a function of time after tritiated thymidine ( 3 H‐TdR) injection. Another group of experiments utilized the “method of labeled S phases.” With this method the passage of labeled cells through successive S phases is observed. Passing through S phase following 3 H‐TdR injection the 3 H‐labeled cells are double labeled by an additional 14 C‐TdR injection. This method again resulted in a cycle time of 20 hours for glial and endothelial cells. From the present work and a former study (Korr et al., 11973) the following cell cycle parameters were derived: Cycle time 20 hours; S phase 9.4 hours; G 2 less than three hours; (G 2 + M) five hours; G 1 five hours. The growth fraction of glial cells related to all glial cells is only 0.004. Furthermore, the present experiments show that in the case of glial cells 17% of the daughter cells after mitosis become pyknotic and are eliminated from the glial cell population. Apart from this cell loss, after mitosis about onefourth of the daughter cells do not enter the next S phase. These cells leave the growth fraction and are replaced by a corresponding number of non‐proliferating glial cells. There is a relatively extensive permanent exchange of cells between the growth fraction and non‐growth fraction of glial cell.