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PubMedDate not supplied

Retinopathy in mice with experimental scrapie.

Scrapie is a naturally occurring neurological disease of adult sheep and goats with an incubation period of several years. Some strains of the causal agent can infect laboratory mice in which the incubation period, as well as the severity and distribution of vacuolar degeneration in the brain, varies according to the strain of the agent and the genotype of the mouse. Retinopathy, involving the partial or complete loss of the photoreceptor layer, was observed in a number of murine scrapie models but was absent in others. The severity of retinopathy depended on both the strain of scrapie and the genotype of mouse used. Some scrapie strains (22C, 87A and 87V) produced minimal or no retinal pathology, others (ME7, 22A and 22L) produced changes in the retinae of only certain mouse genotypes, while the strains 79A and 139A produced degeneration of the photoreceptor layer in every mouse genotype investigated. The severity of retinopathy in the various models did not correlate with the overall intensity of vacuolar degeneration in the brain, with the severity of vacuolation in the centres in the brain controlling pupillary constriction, or with the incubation period.

Animals↗

PubMedDate not supplied

Immunostaining of scrapie cerebral amyloid plaques with antisera raised to scrapie-associated fibrils (SAF).

Brain sections from 16 different mouse scrapie models were immunostained with antisera to scrapie-associated fibrils (SAF) from three experimental scrapie sources (hamster 263K, mouse ME7 and mouse 22L). These models involved seven strains of scrapie injected intracerebrally or intraperitoneally into a range of inbred mouse strains, producing a wide variety of neuropathological changes. The only brain structures which were positively immunostained were amyloid plaque cores in those models in which plaques could be readily identified using traditional amyloid stains. The intensity of immunostaining correlated with the density of amyloid in the cores, as detected by Congo red and thioflavine S staining. No differences in immunostaining specificity were found between antisera or between plaques in different combinations of scrapie strain and mouse genotype. There were also no differences in immunoreactivity between plaques in different parts of the brain. These results strongly suggest that SAF and histologically detectable amyloid in scrapie mice are derived from the same precursor protein. Scrapie-associated cerebrovascular amyloid and plaques in sheep and goats also gave positive immunostaining with SAF antisera, although the lesions in the natural disease could only be stained after formic acid pretreatment. Senile plaques in Alzheimer's disease and Down's syndrome, although structurally similar to scrapie amyloid plaques, were found to be completely negative for SAF, in agreement with previous biochemical and immunocytochemical findings.

Amyloid↗