Ultrastructural Features of Beta-Amyloid Plaques in Aged Transgenic Tg 2576 Mouse Brain with Alzheimer Plaque Pathology

Ultrastructural characteristics for beta-amyloid (A ) plaque and neuronal morphology were obtained from 24 month old (aged) transgenic Tg 2576 mice brains with Alzheimer plaque pathology using immunocytochemical and electron microscopic techniques. Immunoperoxidase staining showed extensive presence of A plaques in the cortex, hippocampus and subcortical areas. There was a homogenous distribution of plaques in the cerebral cortex from the frontal to occipital pole. The entorhinal cortex showed some remarkable presence of plaques. The A plaque morphology was a typical star-shaped appearance of diffuse amyloid plaque with abundant or numerous bundles of extracellular, non-branching and wavy amyloid fibrils radiating from the central dense core. The amyloid fibrils became less closely oriented at the periphery of the plaque. An amyloid interface was also observed in addition to degeneration neurons and dystrophic neurites. The neurites presented as discontinuous surface membranes of cells in the neighbourhood of neuritic plaques, with or without an amyloid core. Neuronal morphology in the cortex and hippocampus were altered in the vicinity of plaques with degenerating neurons showing more of apoptotic signs such as chromatin condensations, cell shrinkage and hyperchromatic nucleus. These data are comparable with some of the reported features in patients with Alzheimer`s Disease (AD) and so the transgenic Tg 2576 mice do represent a reliable animal model for investigating AD related plaque pathology.