Age-related changes in TuJ1 and NF 200 expression in human ears.

<p><b>A:</b> TuJ1⁺ neurons in a paraffin section from the middle turn of a young adult mouse. <b>B–C:</b> TuJ1⁺ neurons in the middle turns from (<b>B</b>) a 38-year-old donor (H18) and (<b>C</b>) a 69-year-old donor (H4). A marked decrease in TuJ1 immunostaining (asterisks) was seen in SGNs of the older ear. The white arrow indicates a neuron with a relatively normal level of TuJ1 immunoreactivity. Nuclei were counterstained with PI (red). <b>D, E, F:</b> A marked decrease of NF200 immunoreactivity was seen in many SGNs of older donors. NF200⁺ neurons (green) from the middle turns of (<b>D</b>) a 46-year-old (H26), (<b>E</b>) a 67-year-old (H19), and (<b>F</b>) a 91-year-old donor (H3). Asterisks indicate SGNs with a lower level of NF200 immunoreactivity. White arrows indicate SGNs with a level of NF200 immunoreactivity more similar to that of SGNs from the 46-year-old donor shown in <b>D</b>. Note the punctuate inclusions (white arrowheads) in the cytoplasm of some NF200⁺ SGNs indicating that neurofilament aggregation occurs in older ears. <b>G, H, I:</b> Confocal images showing a reduction in both the number of NF200⁺ neurons and decreased immunostaining intensity for NF200 in most surviving SGNs in older donors. Asterisks indicate SGNs with a lower level of NF200 immunoreactivity. A white arrow points to an SGN with a normal level of NF200 immunoreactivity. Punctuate inclusions (white arrowheads) were seen in the cytoplasm of many NF200⁺ SGNs in the 91-year-old donor. Scale bars, 8 µm in <b>C</b> (applies to <b>A–C</b>); 7 µm in <b>I</b> (applies to <b>D–I</b>).