Relationship of growing axons to white matter myelin and astrocytes. a, b, Electron microscope images of GFP-immunolabeled regenerating adult DRG axons in intimate contact (arrowheads) with degenerating myelin membranes within acutely lesioned dorsal column white matter. Three day survival after transplantation and 1.5 mm distance from the graft ensures that these profiles are near the growing tips of the axons. However, the dense HRP labeling prevented the ability to distinguish bona fide growth cones from axonal varicosities. Note that the GFP-immunolabeled axon profile in a is also tightly associated with an adjacent host astrocyte (As). Magnification 5000×.