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. 2019 Jan 3;78(2):140–156. doi: 10.1093/jnen/nly121

FIGURE 2.

FIGURE 2.

Reactive astrocytes and astrocyte endfeet in intact tissue. (A, B) GFAP-positive AQP4-positive reactive stellate astrocytes in intact myelinated tissue bordering an actively demyelinating plaque. (B) The wall of a capillary stains positively for AQP4. The spaces around oligodendrocytes (“halos”) are a postmortem artefact. (C) The space around the vessel is a common post mortem artefact. It lies outside the true perivascular space and is formed by grossly swollen, partly ruptured, astrocyte foot processes, leaving AQP4-positive remnants in the space. (D) A vessel located in a postphagocytic plaque shows an absence of GFAP-positive astrocyte foot processes within the artefactual perivascular space. (E) Perfusion-fixed rat central nervous system tissue. The tissue is compact with no spaces around neurons or other cells. The only “spaces” visible are capillary lumens. (F) Intact periplaque tissue. Perineuronal spaces, another autolytic artefact formed by swollen ruptured astrocyte foot processes, are lined with AQP4-positive membranes. (A: GFAP, ×250; B: AQP4, ×250; C: AQP4, ×125; D: GFAP, ×250; E: 1-µm-thick epoxy section, toluidine blue, ×375; F: AQP4, ×250).