C and D display examples of wagon-wheel or rosette formation of GFAP filaments in the vascular end feet, whereas E and F are ... Wolburg H, Risau W ( 1995) Formation of the blood-brain barrier. In: Neuroglia (Kettenmann H, Ransom B, eds), pp 763-776. New ... lines of evidence have suggested that the role of astrocytes is to provide appropriate environmental signals for the formation ...