Fig. 1. Astrocytes derived from embryonic or newborn animals produce morphologically different laminin matrices. Confluent monolayers of astrocytes isolated at embryonic day 16 (A,C-E) or at birth (B,F,G) were quickly fixed to preserve the associated extracellular matrix and processed for laminin immunocytochemistry (white in panels A and B and red in panels C-G). Cell nuclei were labeled with DAPI (blue staining). Note that laminin on E16 monolayers presented a periodical shape, made of polygons, which are better visualized in panels A and E (amplification of the field delimited by the larger frame in panel C). The P0 matrix forms webs that protrude from the cell surface (best seen in B and F). Panel D (field delimited by the smaller frame in C) shows the delicacy of the laminin mesh secreted by embryonic astrocytes, not comparable to the dense protein aggregates observed on P0 (G; amplification of the field delimited by the frame in F). Bars, 50 µm.