Autoradiographic investigations of glial proliferation in the brain of adult mice. II. Cycle time and mode of proliferation of neuroglia and endothelial cells

Abstract

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 (3H-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 3H-TdR injection the 3H-labeled cells are double labeled by an additional 14C-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., '73) the following cell cycle parameters were derived: Cycle time 20 hours; S phase 9.4 hours; G2 less than three hours; (G2+M) five hours; G1 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 one-fourth 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.

The Two Patterns of Reactive Astrocytosis in Postischemic Rat Brain

“…Thymidine uptake was confined to a few subependymal cells, as previously reported by Korr et al (1975). Labeled nuclei in brain parenchyma were exceedingly rare (one GF AP-negative cell in cerebral cortex in one of three brains).…”

Endothelial-cell proliferation in experimental tumours

“…Cell proliferation in the endothelium may give rise to wider or longer individual vessels in which the blood flow may be slowed and/or the blood will become depleted in nutrients. Furthermore, some of the endothelial cells may be lost soon (Korr et al, 1975) and in tumours (Hirst et al, 1982). Capillary budding (Ausprunk & Folkman, 1977) (Tannock, 1968) but we were unable to obtain a better definition in autoradiographs with this stain than with conventional haematoxylin and eosin.…”

Expression of Myelin Protein Genes and Other Myelin Components in an Oligodendrocytic Cell Line Conditionally Immortalized with a Temperature‐Sensitive Retrovirus

“…To insure a high number of stably transfected oligodendrocytes, we used the recombinant retrovirus ZIPSVtsA58 (Frederiksen et al, 1988;Jat et al, 1989) in conjunction with enriched populations of oligodendrocytes. Efficient integration of retroviral sequences into host genomic DNA requires that cells proceed through the S phase of the cell cycle [-9 h in mouse glia (Korr et al, 1975)]. We isolated oligodendrocytes at a time in culture when they were transitioning from immature to mature oligodendrocytes (Amur-Umarjee et al, 1990~).…”