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Neurosurgery: Supratentorial tumors
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Geriatric Neuroanesthesia, 2019
Monica S. Tandon, Kashmiri Doley, Daljit Singh
ST gliomas typically arise in the subcortical WM tracts in the cerebral hemispheres, enlarge rapidly, and spread contiguously to other parts of the brain by infiltrating along the WM tracts, surrounding cortical neurons (satellitosis), subependymal zone, and cerebrospinal fluid (CSF) pathways (subarachnoid seeding) (14) (Figure 5.1).
Regulation of Cerebrovascular Aging
Published in David R. Riddle, Brain Aging, 2007
William E. Sonntag, Delrae M. Eckman, Jeremy Ingraham, David R. Riddle
Understanding the relationship between microvascular plasticity and neural activity, and how aging-related changes in the microvasculature affect metabolic support for neuronal signaling, is essential for clarifying the basis of cognitive changes during senescence. Accumulating evidence suggests that age-related changes in the microvasculature also may influence other critical aspects of neural function and plasticity. As noted previously, new neurons are continually produced in some regions of the adult brain [126–128] (see also Chapter 6), and the microvasculature is critically involved in regulating adult neurogenesis, both as a local source of factors that create an appropriate milieu for neurogenesis and as the source of blood-borne factors that influence proliferation. The production of new granule neurons in the subgranular zone of the adult dentate gyrus occurs within “neuroangiogenic foci” where neuronal, glial, and endothelial precursors divide in tight clusters [129, 130]. Proliferative precursors in other regions of the hippocampus are not found within such a vascular niche and do not give rise to neurons, only glia. Thus, the association between endothelial and neuronal proliferation in the subgranular zone suggests that either signals originating from somatic tissues or from the CNS act simultaneously to stimulate neurogenesis and angiogenesis, or that the initiating signal activates proliferation of one cell type, which then stimulates proliferation of the other. A recent demonstration that intracerebroventricular infusion of VEGF into the adult brain increases the genesis of both endothelial cells and granule neurons is consistent with a mechanistic link between angiogenesis and neurogenesis [131]. Also supporting this hypothesis is evidence that the reduction in neurogenesis that follows whole brain irradiation is due, in part, to alterations in the microenvironment, including disruption of microvascular angiogenesis [132]. More direct evidence that endothelial-produced factors regulate neurogenesis comes from the demonstration that culturing precursor cells from the adult rodent forebrain subependymal zone (SZ) on monolayers of endothelial cells, rather than on astrocytes or fibroblasts, increases neurogenesis and neuronal survival [133]. Thus, much remains to be determined concerning the complex interactions between vasculature and neurons.
Harnessing neuroplasticity: modern approaches and clinical future
Published in International Journal of Neuroscience, 2018
Andrew Octavian Sasmita, Joshua Kuruvilla, Anna Pick Kiong Ling
The most attractive adaptive change is, without a doubt, neurogenesis, generation of neurons of neural cell types from neural stem cells or neural progenitor cells (NPCs) which occurs throughout life [4]. Upon reaching adulthood, it has also been suggested that the dentate gyrus and subependymal zone of the adult hippocampus contain distinct committed NPCs of glial and neuronal cells [5]. In particular, adult neurogenesis is often highlighted as the brain is often regarded as non-renewable [6] and specific illnesses occur almost exclusively in adulthood, namely Parkinson's disease (PD) and multiple sclerosis [7]. Furthermore, 3H-thymidine autoradiography [8], thymidine analog 5-bromo-2′-deoxyuridine (BrdU) labeling test [9] and 14C isotope-based tests [10] on animal and human brains have long disregarded the first speculation of the brain being non-renewable, as more evidences are pointing to the actual presence of neurogenesis in key areas of the adult brain, including substantia nigra, striatum and hypothalamus, although the levels discussed are below those in non-physiological conditions [11].