Fig. 3. Transmission electron microscopy of wild-type and GFAP^–/– Vim^–/– retinas. (A) In wild-type retinas, large Müller-cell endfeet (MC) form a continuous straight zone at the vitreal surface of the retina; the endfeet contain abundant rough endoplasmic reticulum and a few IFs (arrowheads), are closely apposed to the basal lamina (BL) and form a boundary between optic axons (ax) and the vitreous body (vit). (B) In GFAP^–/– Vim^–/– retinas, the basal lamina is separated from the retina by many micrometers and is not visible (arrow), and the Müller cell processes lack IFs. The Müller cell processes and endfeet are both irregularly shaped and, often, only very thin lamellae are visible (top left). (C) A lower-magnification image shows the irregularity of the inner surface of the remaining retina. Many blood vessels (bv) are not covered by Müller-cell endfeet (as they are in wild-type retinas; not shown). Instead, the basal lamina of pericytes (pc) forms the innermost surface of the remaining retina (arrowheads). (D) A large blood vessel containing many erythrocytes (ery) is incompletely covered by Müller-cell processes (MC) and is detached, along with a large axon bundle, from the rest of the retina (arrow). (E) Rarely, a Müller-cell process (asterisks) had a disrupted membrane and missing cytoplasm.