FIGURE 2.

Immunolabelling (brown pigment) of phosphorylated tau protein (pTau) using antibody AT180 in the cerebral cortices of odontocetes. When at lower intensities, immunolabelling of pTau was present as cytoplasmic granules within the cell bodies of neurons (a), and with increased intensity of labelling, pTau frequently extended into the axons and dendrites (b,c). Irrespective of the intensity of cytoplasmic labelling, nuclei were consistently devoid of any labelling (c) although neurons that labelled intensely for pTau frequently contained pyknotic nuclei (d, arrowhead). Intensely phospho‐tau‐stained cells were found in animal (Gm5) and present in all sections of cerebral cortex available for examination (e,f). Neuritic plaques were present in both the white and grey matter in all four aged animals examined (Gm1, Gm5, La5 and Tt1) and within the grey matter often colocalized with neuropil threads (g, arrowhead). Similarly, neuritic plaques colocalized with phospho‐tau‐positive cell bodies (h,i, arrowheads). pTau labelling was present predominantly in cerebrocortical layers II and V (j). Positive control sections were composed of human brain tissue from a case of definitely diagnosed Alzheimer's disease (k). Semi‐serial sections were used for the controls (k, positive; l, negative control)