Histochemistry of glycogen deposition in perinatal rat brain: importance of radial glial cells

Abstract

Changes in the glycogen content and patterns of deposition in the developing rat brain were studied using a light microscopic periodic acid-Schiff method on embryonic days (ED) 14, 16, 18, 20 and postnatal days (PD) 1, 3, 7, 12, 16 and 21. Regional and temporal differences were quantified with an automatic image analyser by estimation of stained material in subpial regions of cerebral cortex, thalamus, superior colliculus and medulla. The cellular localization of glycogen particles was investigated by electron microscopy on ED 18, ED 20 and PD 2. On ED 14 the first signs of glycogen storage were found in parts of the immature choroid plexus and in radial glial cells in the midbrain and medullary raphé. With advancing foetal age these structures retained their high capacity for glycogen storage but, in addition, an increasing number of radial fibres in most of the brain stem regions and in the cerebral cortex of older foetuses (ED 18-20) showed significant amounts of glycogen. The storage of glycogen in cerebral cortex was relatively low at all foetal age intervals studied. In new born animals the distribution of glycogen particles was similar to that found in the late foetal brain. A decrease of glycogen content commenced from PD 1 to 3 and reached the pattern of the adult brain between PD 7 and 21. Glycogen storage by radial glial cells in the developing rat brain might indicate their possible role as an energy source in perinatal carbohydrate metabolism.

Secretory activity in the floor plate neuroepithelium of the developing human spinal cord: Morphological evidence

“…Altman and Bayer (1984) suggested that the floor plate neuroepithelium may be one source of non-neuronal cells such as radial glial cells. Accumulation of glycogen has been noted in radial glial cells (Bruckner and Biesold, 1981;Uehara and Ueshima, 1984); however, we have not found a report that neuroepithelial cells in the developing spinal cord possess secretory activity. Although we have obtained morphological evidence for cellular secretory activity in the floor plate neuroepithelium, the physiological significance of this activity during the embryonic development remains the subject of further study.…”

The Glial Nature of Embryonic and Adult Neural Stem Cells

“…Progressive thickening of the cortex throughout neurogenesis is accompanied by lengthening of the pial-directed radial processes of RG. These morphological changes are accompanied by the acquisition of 24-nm microtubules and 9-nm intermediate filaments within the radial fiber, as well as glycogen storage granules in the subpial end feet (Choi & Lapham 1978, Bruckner & Biesold 1981, Gadisseux & Evrard 1985). The RG cells also begin to express astroglial markers such as the astrocyte-specific glutamate transporter (GLAST), brain lipid-binding protein (BLBP), and Tenascin C (TN-C) (for review, see Campbell & Gotz 2002).…”

Shaping Our Minds: Stem and Progenitor Cell Diversity in the Mammalian Neocortex

“…During this transformation, NECs lose some of their epithelial properties in favor of certain glial characteristics, but retain contacts with the ventricular and pial surfaces that give them their radial morphology; hence the term RGC. Among the changes characterizing the NEC-to-RGC transition are the loss of tight junctions (Aaku-Saraste et al, 1996), the acquisition of glycogen storage granules (Brückner and Biesold, 1981; Gadisseux and Evrard, 1985), and the expression of astroglial genes such as brain lipid-binding protein (BLBP), astrocyte-specific glutamate transporter (GLAST) and tenascin-C (Hartfuss et al, 2001; Heins et al, 2002; Noctor et al, 2002). RGCs still retain many NEC characteristics, however, and the two cell types likely co-exist for some time (Götz and Huttner, 2005).…”