Cases reported "Scrapie"

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1/3. Golgi and electronmicroscopic studies of spongiform encephalopathy.

    Golgi impregnations of cerebral biopsies from two patients suffering from Creutzfeldt-Jakob disease (subacute spongiform encephalopathy) revealed striking loss of dendritic spines of pyramidal neurons and unusual focal spherical distensions of dendritic and axonal processes. light and electronmicroscopic studies disclosed spongiform changes, which seemed to be caused by intracytoplasmic vacuoles and expansion of the plasmalemmal membranes of neurons and astrocytes. Although the diagnostic biopsies were performed at a markedly symptomatic stage of the disease, there was no evidence of neuronal cell loss. Neuronal changes in Golgi impregnations of cerebral cortex from hamsters infected with scrapie were essentially identical to those in the human biopsies. The loss of dendritic spines of pyramidal cells and spherical swellings of axons and dendrites thus seem to be characteristic of spongiform encephalopathies, and probably account in part for the clinical neurologic manifestations, which may be severe in the relative absence of neuronal death.
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keywords = astrocyte
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2/3. Interactions between astrocytes and oligodendroglia in human and experimental Creutzfeldt-Jakob disease and scrapie.

    We report here a rare interaction between reactive astrocytes and oligodendrocytes, first detected in a brain biopsy of human Creutzfeldt-Jakob disease (CJD) and then in experimental CJD in mice and in two models (263K and 22CH) of scrapie in hamsters. In human CJD brain biopsy, low-power electron microscopy revealed numerous examples of astrocytes and oligodendroglial cells in close apposition. At higher magnification, both types of cells were occasionally connected by adhesive plaque junctions (attenuated desmosomes). More complex structures were also seen. Astrocytic cytoplasm was penetrated by oligodendroglial processes or oligodendroglial cells were completely surrounded by astrocytic processes. An analogous phenomenon was identified in the brains of CJD-infected mice and in two models of scrapie-infected hamsters. In the CJD brain biopsy and in brain specimens from CJD-infected mice and scrapie-infected hamsters, GFAP-immunoreactive hypertrophic astrocytes were readily identified, particularly in those areas where the tissue damage was the most extensive. Oligodendrocytes frequently surrounded hypertrophic astrocytic processes or cell bodies and remained unstained in GFAP preparation. The significance of the interactions between astrocytes and oligodendrocytes is unclear at the present time. As in MS and other brain pathologies in which it has been studied, this interaction is not associated with a reaction toward any infectious pathogen but it may be an early cellular event that triggers further brain tissue destruction.
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keywords = astrocyte
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3/3. Myelinated axon undergoes complete demyelination in the panencephalopathic--but it is merely subjected to the wallerian degeneration in the polioencephalopathic type of transmissible spongiform encephalopathies.

    We report here on axon and myelin changes in panencephalopathic type of Creutzfeldt-Jakob disease as opposed to polioencephalopathic models of scrapie. In CJD, myelinated axons presented various pathological changes. Initially the myelin sheath was separated by cytoplasmic tongues into several concentric bands. Cellular processes penetrated between layers of myelin and lifted away the outermost lamellae. Then a complicated labyrinth of concentric cellular processes, clearly belonging to either astrocytes or macrophages invested myelinated axons. In terminal stages axons completely denuded of myelin were seen in the centre of a concentric network of cellular processes or spirals of myelin were seen surrounded by such processes. The myelin fragments penetrated into astrocytes or macrophages where they underwent final digestion. macrophages containing fragments of axons, paracrystalline lamellar bodies and myelin debris were abundant in this model. In two models of scrapie myelin dilatation, not unlike that seen in the panencephalopathic type of CJD was observed. Several altered axons were also seen, but these presented only typical features of wallerian degeneration. Even the most damaged fibres consisted of "empty" vacuoles (the axon itself was lost) surrounded by a narrow rim of oligodendroglial cytoplasm. Thus, myelinated fibre degeneration in this polioencephalopathic model merely represents the sequel to preceding neuronal degeneration. In conclusion, it seems that myelinated fibres are eventually denuded of myelin in the panencephalopathic type of CJD but undergo wallerian degeneration in polioencephalopathic types of scrapie. Because myelin dilatation is observed in both pan- and polioencephalopathic type of TSE and because their formation is probably mediated by cytokines released from astrocytes and microglia, we hypothesised that this mechanism operates early in the fibre destruction and must be supplemented later in the course of the disease by other, currently unknown mechanisms.
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