Dendrites in the context of "Glomerulus (olfaction)"

Neurofibrillary tangles (NFTs) are intracellular aggregates of hyperphosphorylated tau protein that are most commonly known as a primary biomarker of Alzheimer's disease. NFTs also are present in numerous other diseases known collectively as tauopathies. Little is known about their exact relationship to the different pathologies, but it is typically recognized that tauopathy is an important factor in the pathogenesis of several neurodegenerative diseases.

NFTs consist primarily of a misfolded, hyperphosphorylated microtubule-associated protein known as tau, which abnormally polymerizes into insoluble filaments within cells. Under the electron microscope, these polymers of tau are seen to take two basic forms: paired helical filaments (PHFs) and straight filaments. These basic types of tau filaments can vary structurally, especially in different tauopathies. The filaments bundle together to form the neurofibrillary tangles that are evident under the light microscope. Classical NFTs are located within the neuronal cell body, although it is now recognized that abnormal, filamentous tau occurs also in neuronal dendrites and axons (referred to as neuropil threads) and the dystrophic (abnormal) neurites that surround neuritic Abeta plaques. Mature NFTs in cell bodies can have a torch-like or globose appearance, depending on the type of neuron involved. When tangle-containing neurons die, the tangles can remain in the neuropil as extracellular "ghost tangles".

Lewy bodies are inclusion bodies – abnormal aggregations of protein – that develop inside neurons affected by Parkinson's disease, the Lewy body dementias (Parkinson's disease dementia and dementia with Lewy bodies (DLB)), and in several other disorders such as multiple system atrophy. The defining proteinaceous component of Lewy bodies is alpha-synuclein (α-synuclein), which aggregates to form Lewy bodies within neuronal cell bodies, and Lewy neurites in neuronal processes (axons or dendrites). In some disorders, alpha-synuclein also forms aggregates in glial cells that are referred to as 'glial cytoplasmic inclusions'; together, diseases involving Lewy bodies, Lewy neurites and glial cytoplasmic inclusions are called 'synucleinopathies'.

Lewy bodies appear as spherical masses in the neuronal cytoplasm that can displace other cellular components such as the nucleus and neuromelanin. A given neuron may contain one or more Lewy bodies. There are two main kinds of Lewy bodies – classical (brainstem-type) and cortical-type. Classical Lewy bodies occur most commonly in pigmented neurons of the brainstem, such as the substantia nigra and locus coeruleus, although they are not restricted to pigmented neurons. They are strongly eosinophilic structures ranging from 8-30 microns in diameter, and when viewed with a light microscope they are seen to consist of a dense core that is often surrounded by a pale shell. Electron microscopic analyses found that the core consists of a compact mass of haphazard filaments and various particles surrounded by a diffuse corona of radiating filaments. In contrast, cortical-type Lewy bodies are smaller, only faintly eosinophilic, and devoid of a surrounding halo with radial filaments. Cortical-type Lewy bodies occur in multiple regions of the cortex and in the amygdala. Cortical Lewy bodies are a distinguishing feature of dementia with Lewy bodies, but they may occasionally be seen in ballooned neurons characteristic of behavioural variant frontotemporal dementia and corticobasal degeneration, as well as in patients with other tauopathies.