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Plaques, Tangles and Amyloid:
Published in Robert E. Becker, Ezio Giacobini, Alzheimer Disease, 2020
Robert G. Struble, H. Brent Clark
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.
Diseases of the Nervous System
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
In cortical degeneration, the disorder starts with focal alterations of neurites followed by a phagocytic response. Later amyloid protein plaques are deposited and surrounded by few macrophages with swollen neurites containing secondary lysosomes. Amyloid plaques are found in almost all elderly patients, but their number is great only when signs of clinical dementia are apparent and neuronal fallout is detectable. Patchy lesions in the white matter in aging brain and dementia have also been reported.86 The presence of abnormal proteins characterizes the manifestation of the Alzheimer’s disease, although its direct cause is still unknown.79,80,81,154,383 The deposition of abnormal proteins in the amyloid plaques is found concentrated near old infarcts and their presence probably represents nonspecific degenerative reactions to the causative agent by focal or individual cortical neurons.38,40 The primary cause may be associated with slowly progressing deterioration of protein synthesis by the endoplasmic reticulum (Nissl substance); its elimination is partly controlled by the production of secondary lysosomes.
Nerve Growth Factor Synthesis and Biological Activity in Malignant Cells
Published in Velibor Krsmanović, James F. Whitfield, Malignant Cell Secretion, 2019
Philippe Brachet, Eleni Dicou, Rémi Houlgatte, Didier Wion
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.
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.
Evaluation of the neuroprotective effects of Vitamin E on the rat substantia nigra neural cells exposed to electromagnetic field: An ultrastructural study
Published in Electromagnetic Biology and Medicine, 2021
Zahra Shabani, Daryoush Mohammad nejad, Tahereh Ghadiri, Mohammad Karimipour
Ultrastructural analysis of the neural cells in the control group revealed many neurites. As shown in Figure 3 (A), the myelinated axons showed smooth regular contours, and the myelin sheaths with normally compacted lamellae regularly covered them. In the Radiation group, the segmental loss of myelin sheath lamellar was dramatically observed. Moreover, the lamellae of the myelin sheath occasionally either demolished or separated in some nerve fibers (Figure 3(B, C, D)). This number significantly increased compared to the control group (p < .001) (Figure 3(G)). Our results revealed that the treatment group, the myelin sheaths, had normally compacted lamellae regularly covered them (Figure 3(E, F)). However, in some nerve fibers, separation of myelin sheathe lamellae has happened but these changes were slighter than the radiation group. The mean number of nerve fibers with abnormal myelin sheath was significantly decreased in EMF + Vitamin E group compared to the EMF group (Figure 3(G)).
Premacular Cells as Source of Neurotrophic Factors in Idiopathic Macular Holes
Published in Current Eye Research, 2020
Denise Vogt, Christos Haritoglou, Luca Mautone, Felix Hagenau, Stefanie R. Guenther, Armin Wolf, Siegfried G. Priglinger, Ricarda G. Schumann
Furthermore, with the expression of the specific proteins anti-neurofilament, anti-calretinin, and anti-melanopsin, which have been described as markers for retinal ganglion cells, our data indicate the presence of neurite processes in premacular membranes.22,23 In the retina, different retinal diseases lead not only to glial cell proliferation and migration but also to neuronal changes including neurite sprouting. These newly generated neurites derive from retinal neurons such as ganglion cells. Although neurite growth is not completely understood, there is evidence that the expression of neurotrophic factors of Müller cells might be associated with the growth of neurite processes.22,23 This underlines the possible potential of neuronal remodeling of human retina.