Ex vivo crush disrupts geometry. A, Phase-contrast photomicrograph of a horizontal cryostat section (the longitudinal axis is from left to right) containing spinal cord white matter (wm) that had been bilaterally crushed with forceps prior to freezing. The crushed white matter is evident from its increased optical density. The edges of the crushed segment of white matter are indicated by white arrowheads. A line of complete disruption can be seen near the middle of the crushed segment (white arrow). The optical density of crushed gray matter (gm) was not increased by the crush. B, GFAP immunoreactivity within the same field shown in panel A. Disruption of the normally parallel orientation of GFAP-labelled processes can be seen within the crush. C, An adjacent section of crushed spinal cord stained with Luxol-Fast Blue shows similar disruption to myelin. D, Phase-contrast photomicrograph of a longitudinal cryostat section of sciatic nerve that had been crushed with forceps prior to freezing. The crushed nerve tissue is evident from its increased optical density. The edges of the crushed segment of nerve are indicated by white arrowheads. Scale bars: A, B, 200 μm; C, 50 μm; D, 200 μm.