Neurites grow in bundles and are surrounded by cellular processes. (A E) Electron micrographs of retinal explants grown in EN2 for 4 days. (A) Low magnification image of the edge of the explant in cross-section shows the close association of retinal ganglion cell (RGC) and putative astrocyte (AS) cell bodies as well as several neurite bundles (arrows) surrounded by cellular processes. (B C) Higher magnification images of areas both near (B) and distant (C) to the explant in cross-section show neurite bundles (arrows) surrounded by cellular processes, some of which appear to be putative Müller cell processes (MP) and putative astrocyte processes (AP) (B). (D E) Low magnification (D) and high magnification of a distal process from the explant in longitudinal section shows a microtubule rich neurite axonal process (arrow) in contact with astrocyte processes (AP). A junction complex can be seen between the neurite process (JC) and putative astrocyte process (AP) in (E). Identification of putative glial processes were based on criteria established by Hogan et al . Scale bars equal 2 μm (A), 500 nm (B C, E), and 1 μm (D), m=mitochondria.