In Alzheimer's disease, the plaque is made up of: (E. REPEAT 2010)-
Ans-BRef: Robbins Pathologic Basis of Disease. 8th edition. Pages 1313-7Explanation:MORPHOLOGY OF ALZHEIMER'S DISEASECortical atrophy especially in frontal, temporal and parietal lobes.Compensatory ventricular enlargement due to loss of parenchyma and reduced brain volume - (hydrocephalus ex vacuo).Structures involved early - medial temporal lobe, including the hippocampus, entorhinal cortex, and amygdala.The major microscopic abnormalities: o Neuritic (senile) plaques.o Neurofibrillary tangles.Progressive severe neuronal loss and reactive gliosis.Neuritic PlaquesFocal, spherical collections of dilated, tortuous, neuritic processes (dystrophic neurites) often around a central amyloid core, surrounded by a clear halo.Size from 20 to 200 mm in diameter.Microglial cells and reactive astrocytes are present at their periphery.Plaques are found in the hippocampus, amygdala, and neocortex.The amyloid core, stained by Congo Red. contains several abnormal proteins.The dominant component of the amyloid plaque core is Ab. a peptide derived from, amyloid precursor protein (APP).Other proteins include:o Components of the complement cascadeo Pro-inflammatory cytokineso al-antichymotrypsino Apolipoproteins.Neurofibrillary TanglesBundles of filaments in the cytoplasm of the neurons that displace or encircle the nucleus.In pyramidal neurons, they have an elongated "flame" shape: in rounder cells, the basket weave of fibers around the nucleus takes a rounded contour ("globose" tangles).H&E staining: Basophilic fibrillar structures.Very well demonstrated by silver (Bielschowsky) staining.They are commonly found in cortical neurons, especially in the entorhinal cortex, pyramidal cells of the hippocampus, the amygdala, the basal forebrain, and the raphe nuclei. They are insoluble and resistant to clearance remaining visible in tissue sections as "ghost" or "tombstone" tangles long after the death of the parent neuron.Ultrastructurally, they are composed of paired helical filaments along with some straight filaments.A major component of paired helical filaments is abnormally hyperphosphorylated forms of the protein tau. an axonal microtubule-associated protein that enhances microtubule assembly.Other components include MAP2 (microtubule-associated protein-2) and ubiquitin.Paired helical filaments are also found in the dystrophic neurites that form the outer portions of neuritic plaques and in axons coursing through the affected gray matter as neuropil threads.Other FeaturesCerebral amyloid angiopathy (CAA).Granulovacuolar degeneration: Small (~5 mm in diameter), clear intraneuronal cytoplasmic vacuoles, each of which contains an argyrophilic granule.Hirano bodies are elongated, glassy, eosinophilic bodies consisting of paracrystalline arrays of beaded filaments, with actin as their major component, found most commonly within hippocampal pyramidal cells.Pathologic changes are evident earliest in the entorhinal cortex, then spread through the hippocampal formation and isocortex, and then extend into the neocortex.NIA-Reagan criteria used in the diagnosis.Remember:Amyloid plaques - Extracellular IJ amyloid.Neurofibrillary tangles - Intracellular tau proteins.
Tau protein
Beta amyloid
Huntington
Alpha synnuclein