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Experimental scrapie in mice: ultrastructural observations
Abstract:
Scrapie, kuru, and Creutzfeldt-Jakob disease are characterized by a similar spongiform pathology, prolonged incubation periods, and an agent with unique physical, chemical, and biological properties. Swiss mice were inoculated with the scrapie agent and sacrificed three to five months later for light and electron microscopy. At three months, small vacuoles were seen within the neuropil of the cerebral cortex and basal ganglia. By the fifth month these vacuoles had increased in number and size and were accompanied by moderate astrocytic proliferation. The brainstem, cerebellum, and spinal cord showed variable changes of much less intensity. Many dilated postsynaptic processes contained osmiophilic particles in random or crystalline arrays. The particles, measuring approximately 23 nm in diameter, appeared consistently in postsynaptic processes of brain from scrapie-infected mice, were lacking in controls, and were a size consistent with sedimentation and filtration data for the scrapie agent. Whether these particles represent the scrapie agent must await further studies.
Insights
Researchers observed unique 23 nm particles in the brains of mice infected with the scrapie agent. These particles appeared consistently in infected mice, suggesting a potential role in spongiform encephalopathies.
Area of Science:
- Neuroscience
- Pathology
- Microbiology
Background:
- Scrapie, kuru, and Creutzfeldt-Jakob disease share spongiform pathology and prolonged incubation periods.
- These transmissible spongiform encephalopathies are associated with an unconventional infectious agent.
Purpose of the Study:
- To investigate the ultrastructural changes in the brains of scrapie-infected mice.
- To identify potential physical characteristics of the scrapie agent at the microscopic level.
Main Methods:
- Swiss mice were inoculated with the scrapie agent.
- Brain tissue was examined using light and electron microscopy at three and five months post-inoculation.
Main Results:
- Vacuoles in the neuropil and astrocytic proliferation were observed, increasing in severity by five months.
- Unique 23 nm osmiophilic particles were consistently found within postsynaptic processes of infected mouse brains, but not in controls.
Conclusions:
- The observed 23 nm particles in postsynaptic processes are a consistent feature of scrapie infection in mice.
- These particles' size and consistent presence align with expectations for the scrapie agent, warranting further investigation.