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Two cases of high-grade glioma comprising sheets of oligodendroglial cells multifocally disrupted by regions of remarkable neuronal differentiation are described. These tumours morphologically resemble 'oligodendroglioma with ganglioglioma-like maturation', a rare tumour of man, but appear to be phenotypically more aggressive. Neuronal markers (synaptophysin, neuron-specific enolase and βIII-tubulin) effectively highlight neuronal elements within these tumours and could potentially help to further investigate the prevalence and biological significance of neuronal differentiation in canine oligodendroglioma., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative disease caused by the expression of mutant ataxin-1 that contains an expanded polyglutamine tract. Overexpression of mutant ataxin-1 in Purkinje cells of transgenic mice results in a progressive ataxia and Purkinje cell pathology that are very similar to those seen in SCA1 patients. Two prominent aspects of pathology in the SCA1 mice are the presence of cytoplasmic vacuoles and dendritic atrophy. We found that the vacuoles in Purkinje cells seem to originate as large invaginations of the outer cell membrane. The cytoplasmic vacuoles contained proteins from the somatodendritic membrane, including mGluR1, GluRDelta1/Delta2, GluR2/3, and protein kinase C (PKC) gamma. Further examination of PKCgamma revealed that its sequestration into cytoplasmic vacuoles was accompanied by concurrent loss of PKCgamma localization at the Purkinje cell dendritic membrane and decreased detection of PKCgamma by Western blot analysis. In addition, the vacuoles were immunoreactive for components of the ubiquitin/proteasome degradative pathway. These findings present a link between vacuole formation and loss of dendrites in Purkinje cells of SCA1 mice and indicate that altered somatodendritic membrane trafficking and loss of proteins including PKCgamma, are a part of the neuronal dysfunction in SCA1 transgenic mice.

In this study of an aged wolverine (Gulo gulo), we document neuropathologic lesions (cerebral amyloid angiopathy (CAA), neuritic plaques (NPs), neurofibrillary tangles (NFTs), and granulovacuolar degeneration strikingly similar to those present in aging and Alzheimer's disease (AD), with the additional finding of concurrent cerebral hemorrhage. A beta immunoreactive cerebral amyloid angiopathy and senile plaques (neuritic and diffuse) were present throughout the cerebral cortex and hippocampus. Ubiquitin immunoreactivity was noted in peripheral portions of some of the plaques. Argyrophilic intracellular neurofibrillary tangles containing abnormally phosphorylated (Ser 202) tau protein were present within cortical and hippocampal neurons. The wolverine should be added to the list of nonhuman species (dogs, nonhuman primates, polar bears) with amyloid deposits similar to those in aged humans and in humans with AD. The aged wolverine appears to be distinct from other nonhuman species in possessing plaques and NFTs, as well as other histologic cerebral lesions frequently associated with AD.

The olfactory bulb (OB), with its comparatively simple and well-delineated connectivity, presents an interesting system for examining cell-specific pathology in neurologic degenerative disorders such as Alzheimer's disease (AD). We have found that in AD the large, efferently projecting neurons (mitral cells) of the OB degenerate, typically without classical Alzheimer neurofibrillary changes. In some cases, with less severe neocortical pathology, the terminal arborizations of olfactory nerve appear hyperplastic and are associated with focal accumulations of A-4 (beta-amyloid) immunoreactivity that are not detectable by standard amyloid stains. These abnormalities may represent a pathologic manifestation of normally occurring plasticity in the olfactory system.

Immunohistochemical localization of tissue specific or cell-specific antigenic markers in neoplastic cells has become an increasingly important tool in the pathologic diagnosis of tumors. The myelin-specific proteins of peripheral nervous system myelin, because they are normally synthesized in Schwann cells, are potentially useful markers for neoplasms arising from peripheral nerves. The authors carried out immunohistochemical studies on 18 cases of Schwann cell neoplasms, including schwannomas, neurofibromas, and granular cell tumors, to determine whether two myelin-specific proteins, myelin basic protein and P2 protein, were present in neoplastic Schwann cells. None of these tumors showed immunostaining for either myelin basic protein or P2 protein in neoplastic cells. In contrast, S-100 protein, which is a well established marker for normal and neoplastic Schwann cells, was localized by immunohistochemistry to neoplastic cells in all 18 neoplasms. Therefore, although myelin basic protein and P2 protein are known to be Schwann-cell-specific proteins, they do not appear to be expressed commonly in neoplastic Schwann cells.

Using two methods of immunization (A and B), 5/10 (A) and 27/45 (B), BALB/c by J mice immunized with human myelin proteolipid protein developed a demyelinating disease with a spectrum of chronic progressive to relapsing-remitting courses. Demyelinative lesions were seen histopathologically in all clinically affected animals that were examined. Many of the clinically unaffected animals also had histopathologic evidence of demyelination. Some of the animals had evidence of multiple ages of foci of activity. Evidence is presented that contamination with myelin basic protein could not account for the disease. This is a new model for multiple sclerosis in mice.