Plaques, Tangles and Amyloid:
Robert E. Becker, Ezio Giacobini in Alzheimer Disease, 2020
Neurites: Neurite is a general term for axonal and dendritic extensions from the perikarya and does not necessarily signify an abnormal process. However, when used in the context of AD, the term ’neurites’ usually refers to abnormally large or misshapen structures in abnormal distributions. These neurites are usually detected using silver-stains, appearing as swollen structures up to 20μm in diameter. Because some routinely used silver-stains detect neurofilaments (Gambetti et al, 1981), presumably many neurites represent dystrophic axons (Wisniewski and Terry, 1973), some of which are axonal terminals. Combined silver-staining and immunohistochemical techniques (Walker et al, 1988), and electron microscopic studies (Wisniewski and Terry, 1973; Struble and Cork, personal observations) detect many more swollen, dystrophic fibers in a SP than can be seen with a silver stain alone. This finding is not surprising as several studies report dendritic processes in SP (Scheibel and Tomyasu, 1978; Probst et al, 1983) and dendritic components may remain unstained by most routinely used silver stains.
Neurological Activities of Seaweeds and their Extracts
Leonel Pereira in Therapeutic and Nutritional Uses of Algae, 2018
Neurite outgrowth is a fundamental neuronal feature and plays an important role in neuronal development during embryogenesis and in the adult brain (Khodosevich and Monyer 2010). Sargassum macrocarpum and its two active components, sargaquinoic acid and sargachromechanol, have been shown to promote neurite outgrowth in pheochromocytoma (PC12) cells in rats (Kamei and Sagara 2002, Tsang and Kamei 2004, Tsang et al. 2005). Structure of sargaquinoic acid and neurite outgrowth promoting relationship has been reported by Tsang et al. (2001). They reported that quinone is the structural moiety of the sargaquinoic acid molecule, which is responsible for the neurite outgrowth-promoting activity. Notably, the hydroxyl group bonded to quinone had a significant effect on neuritogenic activity. In addition, pheophytin a, a chlorophyll-related compound and its analog, vitamin B12 derived from Sargassum fulvellum, also has potential neurite outgrowth-promoting activity (Ina and Kamei 2006, Ina et al. 2007).
Nerve Growth Factor Synthesis and Biological Activity in Malignant Cells
Velibor Krsmanović, James F. Whitfield in Malignant Cell Secretion, 2019
The response of some tumor cells to NGF was the object of extensive studies. Some human neuroblastoma cells extend neurites in the presence of the factor, a morphological differentiating action which is mimicked by retinoic acid.93,95 NGF was found to stimulate either differentiation or division in different clones of murine neuroblastoma.96 Pheochrom-ocytomas, which are tumors of adrenal medullary cells, are also responsive to NGF. Tumor explants from humans or rats97,98 also respond to the factor by extending neurites. The system which is presently the most widely studied was derived by Greene and Tischler99 from a rat pheochromocytoma. It consists of a clonal cell line, referred to as PC 12. Cells of this line grow in vitro in the absence of NGF and differentiate into sympathetic-like neurons in its presence. The factor exerts short-term and long-term effects involving numerous biochemical, physiological, or morphological changes which lead eventually to a prolonged outgrowth of neurites.100 Several other NGF-responsive clonal cell lines were isolated from the same rat pheochromocytoma.101 They differ from PC 12 in that the factor does not cause them to extend neurites, but, like PC 12, they are interesting model systems for the study of the mode of action of NGF.
Developing therapeutic strategies to promote myelin repair in multiple sclerosis
Published in Expert Review of Neurotherapeutics, 2019
Laura E. Baldassari, Jenny Feng, Benjamin L.L. Clayton, Se-Hong Oh, Ken Sakaie, Paul J. Tesar, Yanming Wang, Jeffrey A. Cohen
Neurite orientation dispersion and density imaging (NODDI) is a diffusion imaging technique developed to characterize the complex microstructural arrangement in tissue. Neurites correspond to axons or dendrites. NODDI provides three parameters, the neurite density index, which quantifies the density of neurites, the orientation dispersion index, which quantifies the variability in the orientation of the neurites, and the isotropic volume fraction, which quantifies the amount of free water. NODDI differentiates the density of neurites from their spatial orientations. Therefore, it is a more specific microstructural measure of tissue compared to standard DTI. It is unaffected by crossing fiber tracts and variations in fiber density. It has been shown that neurite density correlated strongly with myelin stain intensity in rat models [117], suggestive of its potential in myelin monitoring.
Cell death assays for neurodegenerative disease drug discovery
Published in Expert Opinion on Drug Discovery, 2019
Jeremy W. Linsley, Terry Reisine, Steven Finkbeiner
Changes in neurite area have also been employed as a morphological readout of early stages of neurodegeneration in imaging assays. Neurite outgrowth occurs in healthy neurons during development and is needed for formation of synapses and neuronal circuits, thus neurite retraction can indicate synapse break down and impaired neuronal health. One problem with this hypothesis is that during synapse formation, pruning can result in neurite retraction even though the neuron itself is functional and healthy. Furthermore, neurite area is in constant flux as the activity of the neuron changes, so static assays that only monitor neurite area at a specific time point might miss the dynamic changes in the neurite over time. However, in general, neurite retraction has been viewed as a measure of impaired neuronal health and has been suggested as a reliable early marker of neurodegeneration [73,74].
PDGF as an Important Initiator for Neurite Outgrowth Associated with Fibrovascular Membranes in Proliferative Diabetic Retinopathy
Published in Current Eye Research, 2022
Evy Lefevere, Inge Van Hove, Jurgen Sergeys, David H. W. Steel, Reinier Schlingemann, Lieve Moons, Ingeborg Klaassen
The observed effects of PDGF on neurite outgrowth confirm the results from previous studies. Cultured primary rat neuronal cells treated with PDGF-BB for 2 days resulted in extended cell survival and increased outgrowth of neurites.18 In addition, prolonged incubation of more than 10 days with PDGF-BB resulted in an extended survival of cultured GABAergic interneurons.32 PDGF-BB was also found to stimulate proliferation of Müller cells and PDGF receptor phosphorylation, which was blocked by a PDGFR-selective tyrosine kinase inhibitor.19 Müller cells may play a role in the formation of FVMs in PDR. Proliferating Müller cells are considered to be a scaffold for neurites to grow on,7,33 and recently, Müller glial–mesenchymal transition was postulated as an alternative fibrinogenic mechanism associated with membrane formation in PDR.11 Another recent study showed that proliferation and migration of cultured Müller cells were stimulated by vitreous of PDR patients (Rezzola et al. 2021).34 Together, this provides further evidence for a role of Müller cells in the formation of FVMs in PDR.
Related Knowledge Centers
- Axon
- Cell Culture
- Dendrite
- Ephrin
- Cellular Differentiation
- Soma
- Neuron
- Netrin
- Semaphorin
- Collapsin Response Mediator Protein Family