Abnormal neuronal and glial argyrophilic fibrillary structures in the brain of an aged albino cynomolgus monkey (Macaca fascicularis)

Abstract

An aged albino male cynomolgus monkey (Macaca fascicularis) more than 35 years old died after showing neurological signs including gait disturbance, trembling, drowsing tendency and a decrease in activity. Neuropathological examination revealed glial fibrillary tangles (GFTs) mainly distributed in the putamen, caudate nucleus, thalamic nuclei, substantia nigra, red nucleus, globus pallidus, trapezoid body, pyramid, pons and medulla oblongata of the brain, and neurofibrillary tangles (NFTs) in the thalamic nuclei. These structures were positively stained by the modified Gallyas-Braak (GB) method and immunostained for tau. The tau-positive argyrophilic GFTs were morphologically classified into four types, as in human cases, i.e., tufts of abnormal fibers (TAFs), thorn-shaped astrocytes (TSAs), glial coiled bodies (GCBs) and argyrophilic threads (ATs) depending on their GB profiles, and GCBs were the major structures in this case. Some of these structures were also immunoreactive for α-synuclein. The glial cells possessing the structures were negative for glial fibrillary acidic protein, a marker for astrocytes, indicating that the argyrophilic GFTs were present in oligodendroglia. In addition, marked neuronal loss and ubiquitin-positive spheroid bodies were observed in the substantia nigra and globus pallidus. According to the characteristic distribution of the argyrophilic structures in neurons and glial cells as well as clinical signs, the monkey might have suffered from a neurodegenerative disease such as progressive supranuclear palsy (PSP). This is the first report of the occurrence of a neurodegenerative disease in a nonhuman animal.