Factors determining the morphology of beta-amyloid (A beta) deposits in Down's syndrome

Immunostained preparations of the medial temporal lobe from patients with Down's syndrome (DS) were counterstained with cresyl violet to reveal the beta-amyloid (A beta) deposits and their associated cell populations. A beta deposits in the cornu Ammonis (CA) of the hippocampus were, on average, more strongly stained, less often directly associated with neurons and more often associated with glial cells than the adjacent areas of cortex. Cored deposits were more frequently recorded in sulci rather than gyri and were associated with more glial cells than the uncored deposits. Multiple regression analyses suggested there was a positive correlation in the cortex between A beta deposit size and the frequency of closely associated neurons, the correlation being most significant with larger (> 25 microns) neurons. The morphology of A beta deposit was also correlated with the location of deposits in the cortex, CA and dentate gyrus but this factor was of lesser importance. No significant variation in the morphology of the A beta deposits was associated with the presence of blood vessels within or adjacent to the deposit. The data suggest that neuronal cell bodies are important in the initial formation of A beta deposits and glial cells with the development of more mature amyloid deposits.