FIGURE 4.

Proto-astrocytes (cephalic sheath, or CEPsh glial cells) of roundworm C. elegans. A: a cartoon of an adult worm showing the four CEPsh glial cells (green) positioned in the anterior of the worm (inset). The CEPsh cell bodies with their velate processes are positioned around the central nerve ring (red), which they enwrap along with the proximal section of the ventral nerve cord. Additionally, each CEPsh glial cell possesses a long anterior process, projecting to the anterior sensory tip, which closely interacts with the dendritic extension of a nearby cephalic neuron (blue). Arrows indicate the dorsal (red arrow) and ventral (orange arrow) side of the worm. B: a confocal image showing green fluorescent protein expression driven by the hlh-17 promoter to visualize the four CEPsh glial cells (worm strain VPR839). The anterior (head) of a juvenile (larval stage 4) worm is shown; the worm is turned ~45 degrees from “upright” such that all four CEP sheath cells are visible. The sheath portion of the cells that form a tube around the dendritic endings of the CEP neurons are seen at the left of the image. The dorsal (red arrow) and ventral (orange arrow) CEPsh cell bodies are seen. The thin sheetlike extensions that surround and invade the nerve ring are seen in the rightmost part of the image. Scale bar, 20 µm. [From Stout et al. (1683).]