China
Africa
Explore chapters and articles related to this topic
Infiltrative Optic Neuropathies
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Aniruddha Agarwal, Sabia Handa, Vishali Gupta
Optic nerve gliomas are low-grade astrocytomas (and not hamartomas as previously thought). Lesions may invade the leptomeninges and result in a desmoplastic reaction consisting of fibroblastic response.18 These tumors have low cellularity especially away from the main tumor bulk. Lesions with a higher grade on histology show an oligodendroglial response. Histopathological studies performed after tumor excision reveal that in several cases, tumors may remain dormant, fail to recur, or even completely involute despite a positive histological resection margin. This may be attributed to reactive gliosis. Immunohistochemical studies using cell proliferation markers such as Ki-67 (MIB-1) and p53 may have a prognostic significance, especially in cases where the resection margin is positive. If the resection margin has values of Ki-67 labeling indices similar to the main bulk of the tumor, there may be higher chances of tumor recurrences and growth.15,19
Comparative Anatomy and Physiology of the Mammalian Eye
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
The predominant glial cell in the optic nerve is the astrocyte. Astrocytes weave together to form tunnels through which the axon bundles must pass. They serve, therefore, in a support role.166 In addition, they also interpose themselves between the optic nerve and all mesodermal elements and, in doing so, presumably serve to moderate the environment.166 Oligodendroglia are also present and serve to form and maintain the myelin sheaths.166
Central Nervous System
Published in Pat Price, Karol Sikora, Treatment of Cancer, 2020
An intermediate radiation reaction can begin within weeks of completing radiotherapy to the brain. Typically, it results in a feeling of somnolence, lethargy, and sometimes recurrence of presenting symptoms and signs. It lasts between 6 and 10 weeks. It is usually self-limiting, and there is no highly effective intervention, although treatment with steroids is often recommended particularly in the presence of neurological deterioration. The pathogenesis is unknown but is believed to correlate with interruption to myelin synthesis secondary to damage to oligodendroglial cells. A corresponding condition occurs after spinal irradiation and presents with Lhermitte’s sign. Neither is believed to indicate an increased risk of developing late effects. Patients with an underlying demyelinating condition such as multiple sclerosis have a relative contraindication for radiotherapy to the brain.
Radiation-induced neuropathological changes in the oligodendrocyte lineage with relevant clinical manifestations and therapeutic strategies
Published in International Journal of Radiation Biology, 2022
Demyelination is one of the histopathological hallmarks of late-delayed radiation-induced damage, implying the involvement of the oligodendrocyte lineage is involved as these cells are responsible for the formation and maintenance of myelin sheaths that surround axons in the CNS. Compared to other glial cells such as astrocytes, oligodendrocytes and oligodendrocyte progenitor cells (OPCs) have been shown to be particularly radiosensitive and undergo ionizing radiation-induced apoptosis (Li, Jay, et al. 1996; Atkinson et al. 2005). Additionally, OPCs communicate with other brain cells such as astrocytes, microglial and endothelial cells (Du et al. 2021), and are involved in modulating brain plasticity and altering neuronal circuitry (Sakry et al. 2014). Oligodendrocyte death results in reduced oligodendroglial densities and demyelination. As white matter integrity (Bull et al. 2017) and myelin plasticity (Begolly et al. 2016) are associated with learning and cognitive functions, alterations in these areas could contribute to radiation-induced cognitive dysfunction (Begolly et al. 2016).
Neuroanniversary 2022
Published in Journal of the History of the Neurosciences, 2022
Heinrich Obersteiner (1847–1922) was an Austrian neurologist born in Vienna. In 1870, he earned his doctorate from the University of Vienna, where he worked in the laboratory of Ernst Wilhelm von Brücke (1819–1892). In 1873, he earned his habilitation for pathology and anatomy of the nervous system at the University of Vienna, becoming an associate professor there in 1880 and a full professor in 1898. He was also the director of a private mental institution at Oberdöbling, outside of Vienna. In 1882, he established an internationally known neurological institute in Vienna. The eponymous Obersteiner–Redlich line is named after him and Emil Redlich (1866–1930). This zone is where the central nervous system and peripheral nervous system meet, as well as the place where Schwann cells meet oligodendroglia cells.
Ultrastructural evidence for presenсe of gap junctions in rare case of pleomorphic xanthoastrocytoma
Published in Ultrastructural Pathology, 2020
Evgeniya Yu. Kirichenko, Sehweil Salah M. M., Zoya A. Goncharova, Aleksei G. Nikitin, Svetlana Yu. Filippova, Sergey S. Todorov, Marina A. Akimenko, Alexander K. Logvinov
Despite the rarity of PXA, a large amount of data concerning the features of the cellular structure of this type of tumor has been accumulated. Nevertheless, the characteristics of intercellular communication in PXA are poorly studied. To date, only a few descriptions of desmosome-like contacts have been obtained.11,12 At the same time, the existence of gap junctions and half-channels, as well as the expression of their constituent proteins in astrocytic tumors, is an urgent topic in modern neurooncology.13–15 Gap junctions (GJ) are hexametric membrane pores, formed by connexins that directly connect cytoplasms of two cells. In nervous tissue, they can be formed either between neuronal cells16, or between astroglial and oligodendroglial cells.17 According to the modern data, GJs occupy a special place among the various types of intercellular contacts and serve as the key structural and functional component of metabolic homeostasis maintenance in the brain.18 The controversial role of GJ in astrocytic tumor pathogenesis has been investigated in a number of studies. On the one hand, GJ possesses such pro-oncogenic properties as tumor cells migration promotion19 and transmission of transforming signals from tumor to nonmalignant tissue.20 On the other hand, connexins proteins have been known for the antiproliferative activity.14