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Figure 2. Ultrastructure of microglial process contacts onto axonal segments following TBI. Electron micrographs of Iba-1 immuno-labeled microglia contacting: A: intact non-injured axons in sham-injured micro pig thalamus; B: injured axonal segment in the thalamus of micro pigs acutely (one day) following diffuse TBI. Iba-1-labeled microglial processes are pseudo-colored blue and the injured axon is pseudo-colored yellow for clarity. While few microglial processes were observed in direct contact with axons normally, microglial processes were observed in direct contact various segments of the neuron, including the soma (N = nucleus), AIS, and the proximal axonal swelling (X) of the injured neuron. Note that the proximal axonal segment of the injured neuron demonstrates ultrastructural characteristics of axonal sprouting (*). Scale bar: 5 μm. AIS: axon initial segment; TBI: traumatic brain injury