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Neurosteroids: metabolism and activities
Published in Barry G. Wren, Progress in the Management of the Menopause, 2020
After cryolesion84 (Figure 12a), axons and their accompanying myelin sheaths degenerate quickly in the frozen zone and the distal segments (Wallerian degeneration). However, the intact basal lamina tubes provide an appropriate environment for regeneration. Schwann cells start to proliferate and myelinate the regenerating fibers after 1 week, and, 2 weeks after surgery, myelin sheaths have reached about one-third of their final width. In the damaged portion of the nerve, PREG and PROG levels remain high, and even increase 15 days after lesion (if expressed in pg/cm).
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
These are associated with abnormalities of myelin formation and metabolism. The combination of lipids and proteins to form the myelin sheath is involved in these disorders. Myelin formation takes place on the surface of Schwann cells or oligodendrocytes, where lipid molecules are linked spontaneously to produce multimolecular aggregates. Protein and polysaccharide units are then attached to the lipid particles. The myelin sheath is formed by a spiral winding of these layers around the axis giving rise to the characteristic lamellar structure. The synthesis of adequate lipids and proteins, and the proper aggregation of protein and lipid molecules in order and proportion are important during myelination and remyelination. Myelin sheath proteins are denatured, consequently, the metabolism of the lipid moieties of this membrane is very slow. Only small components, such as phosphatidylinositol, show rapid turnover associated with the control of impermeability of certain areas in the nerve membrane.
Personal Protective Equipment (PPE): Practical and Theoretical Considerations
Published in Brian J. Lukey, James A. Romano, Salem Harry, Chemical Warfare Agents, 2019
Myelination is the second process that continues development throughout childhood. Myelin is an insulating sheath that encapsulates nerves of both the CNS (brain and spinal cord) and the PNS. It is composed of fatty substances and protein, and its purpose is to allow fast electrical conduction along the nerve. Damage to the nerve’s myelin sheath will slow down electrical transmission within the nerve (Kantor, 2015). Research has shown a progressive increase in the white matter (myelin) during ages 4 through 17 years in age in humans in both the internal capsule and the left arcuate fasciculus (both anatomical parts of the brain); the former is involved in motor function, while the latter being involved in speech function (Rice, 2000, p. 520, Figure 10). Thus, myelination of the brain is not complete until adolescence (Bearer, 2000, p. 930). Should damage to this progressive myelination process occur due to neurotoxicants, it could possibly accelerate the rate of age-related decline in nerve function (WHO Training, 2008, Slide 26). Of tremendous concern to investigators is the possibility of delayed latency; that is, exposure to the toxic agent inducing neurotoxicity years after exposure to the agent has ceased (Rice, 2000, p. 525).
Centella asiatica L. Urban protects against morphological aberrations induced by chronic unpredictable mild stress in rat’s hippocampus via attenuation of oxidative stress
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Saravanan Jagadeesan, Samaila Musa Chiroma, Mohamad Aris Mohd Moklas, Mohamad Taufik Hidayat Baharuldin, Che Norma Mat Taib, Zulkhairi Amom, Thirupathirao Vishnumukkala, Warren Thomas, Onesimus Mahdi
The myelin sheath plays a vital role in the central nervous system because of its role in the trophic support of axons and rapid signal conduction [52]. The myelin sheath also has a role in the protection and insulation of axons. Hence, damage to the myelin sheaths could result in severe neurological deficits affecting the normal signaling, and leading therefore to neurological dysfunction. An increase in the number of demyelinated axons and destruction of the myelin sheath around axons were reported in rats exposed to either physiological or physical stressors [53]. It has been reviewed that demyelination is associated with anxiety- and depression-related behaviors in rodents [54]. In this study, CUMS rats also exhibited defects of the myelin sheaths which include detachment from the axons, discontinuous, and bulging of myelin sheath. These structural anomalies of the myelin sheath could be attributed to the depression-like behaviors and cognitive deficits observed in the CUMS rats [6]. Prevention of the structural alterations was seen in fluoxetine and CA (400 and 800 mg/kg) treated groups of rats in the current study. Rao and his team have also reported that CA extract significantly increased the dendritic arborization of hippocampal CA3 neurons in vivo studies on rats [55]. In another study on chronic mild stress-induced rat models of depression, it was observed that fluoxetine delayed the development of white matter demyelination [56].
Effect of massage, passive neural mobilization and transcutaneous electrical nerve stimulation on magnetic resonance diffusion tensor imaging (MR-DTI) of the tibial nerve in a patient with type 2 diabetes mellitus induced neuropathy: a case report
Published in Physiotherapy Theory and Practice, 2022
Goyal Manu, Mittal Amit, Samuel Asir John
In this report, FA and ADC describe/depict the three-dimensional diffusion of water molecules. FA describes the movement in space in the preferred direction whereas ADC quantifies the speed of diffusion of water molecules. Due to the accumulation of fluid in and around the tibial nerve in the tarsal tunnel, the cross-sectional area is increased in patients with DM (Singh, Gupta, and Kaur, 2017). This can lead to abnormal mechanosensitivity of the nerve during functional activities (Boyd, Nee, and Smoot, 2017). FA maps can detect neuropathy at the subclinical stage earlier than nerve conduction studies (NCS). Focal damage/disruption of the myelin sheath can only be detected by FA and not by NCS (Bäumer et al., 2014). Inflammation of the nerve sheath and somatosensory changes may result in the presence of mild axonal damage and trivial morphological changes (Gilbert et al., 2015). However, these changes can still lead to neuropathic pain and dysfunction (Greening and Lynn, 1998).
Honokiol exerts protective effects on neural myelin sheaths after compressed spinal cord injury by inhibiting oligodendrocyte apoptosis through regulation of ER-mitochondrial interactions
Published in The Journal of Spinal Cord Medicine, 2022
Yong Tan, Haijun Yu, Shanquan Sun, Shengwei Gan, Rui Gong, Ke-jie Mou, Jun Xue, Shiye Xu, Jiangfeng Wu, Lan Ma
Due to the complex pathophysiology, high incidence, and severe disability, compressed spinal cord injury (CSCI) has become one of the most common serious spinal disorders worldwide.1 There are many mechanical injuries, such as spinal trauma, epidural hematoma, and intramedullary tumors which may cause CSCI.1 They can result in a series of biochemical changes, such as microcirculatory disturbance and electrolyte imbalance, that ultimately lead to secondary damage including apoptosis and demyelination.2 Once the myelin sheath is lost, axonal dysfunction and degeneration will occur, and nerve impulse conduction is blocked, which affects patients’ motor and sensory functions.3,4 Thus, the key to effective treatment of CSCI is how to avoid or reduce demyelination, and facilitate functional recovery.