Radioautographic investigation of gliogenesis in the corpus callosum of young Rats I. Sequential changes in oligodendrocytes

Abstract

The corpus callosum of young rats was examined to clarify the behavior of the three subtypes of oligodendrocytes (the large organelle-rich "light oligodendrocytes," the smaller and more densely stained cells referred to as "medium oligodendrocytes," and the even smaller and denser "dark oligodendrocytes"). It was hoped to find out whether cells of the three subtypes undergo division and how they are related to one another. 3H-thymidine was given intraperitoneally as single or three shortly spaced injections to a first group of 19- to 20-day old rats weighing about 40 g, and to a second group of 25-day old rats weighing about 80 g. The animals were sacrificed at various time intervals from 2 hours to 35 days after 3H-thymidine administration. Pieces of corpus callosum were taken near the superior lateral angle of the lateral ventricles; and semithin sections were radioautographed and stained with toluidine blue. Two hours after 3H-thymidine injection, label is virtually absent from light, medium and dark oligodendrocytes, from microglia, and probably from astrocytes, but is present in about 10% of the immature glial cells, which include the poorly differentiated glioblasts and the partially differentiated oligodendroblasts and astroblasts. Hence, the cells undergoing DNA synthesis and mitosis in the corpus callosum are these three types of immature cells. During the week that follow the administration of 3H-thymidine, label appears in oligodendrocytes and astrocytes, which presumably have arisen from the initially labeled immature cells. The oligodendrocytes acquire label in a sequential manner: the light cells show label first and their labeling index reaches a peak at the seven-day interval; the medium oligodendrocytes become labeled next with a labeling peak toward the 14- and 21-day intervals and, finally, the dark oligodendrocytes with a peak around the 28-day interval. Analysis by the method of Zilversmit et al. ('42-'43) provides precise details on the sequence: immature cells presumed to be oligodendroblasts give rise to light oligodendrocytes which, after four to seven days, transform into medium oligodendrocytes which, after another 11 to 18 days, transform into dark oligodendrocytes. The dark cells may persist indefinitely or turn over at a very slow rate. It is concluded that oligodendrocytes arise from the last division of oligodendroblasts and develop in three main periods: a light stage lasting less than a week, a medium stage lasting about two weeks, and a very long lasting dark stage.

Expression of Neural RNA-Binding Proteins in the Postnatal CNS: Implications of Their Roles in Neuronal and Glial Cell Development

“…Subsequently, these immature astrocytes migrate into the overlying parenchyma dorsal and lateral to the corpus callosum, and finally a population of these cells become dispersed in almost all regions of the forebrain where they have terminally differentiated and undergone morphological changes or acquired GFAP immunoreactivity. This developmental profile of astrocytes from SVZ precursor cells is also supported by previous 3 H-thymidine labeling studies (Paterson et al, 1973;Imamoto et al, 1978) and lineage tracing of retroviral-labeled SVZ precursor cells Zerlin et al, 1995).…”

Mitotic neuroblasts in the 9-day-old and 11-month-old rodent hippocampus

“…These cells do not resemble neuroglia cells, since they lack the irregular contours of protoplasmic astrocytes and microglia and the bundles of filaments of fibrous astrocytes (Peters et al, 1976). Neither do neuroblasts resemble immature forms of astrocytes or oligodendrocytes (Skoff et al, 1976;Imamoto et al, 1978;Kaplan and Hinds, 1980). Although the dissimilar features are outlined in Kaplan and Hinds (1980), it is interesting to note that immature neurons have an electron-dense cytoplasm (present study), unlike immature oligodendrocytes which have a light-staining cytoplasm.…”

Olig2 Directs Astrocyte and Oligodendrocyte Formation in Postnatal Subventricular Zone Cells

“…1 A) (Altman, 1966;Paterson et al, 1973;Imamoto et al, 1978;Levison and Goldman, 1993;Luskin et al, 1993;Suzuki and Goldman, 2003). The synchronization of SVZ cell phenotype and migration behavior is not understood.…”