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Current Status of Alzheimer's Disease in India: Prevalence, Stigma, and Myths
Published in Meenu Gupta, Gopal Chaudhary, Victor Hugo C. de Albuquerque, Smart Healthcare Monitoring Using IoT with 5G, 2021
Surekha Manhas, Zaved Ahmed Khan, Meenu Gupta
During AD, numerous brain cells get affected and the numbers vary with respect to different regions by the expression of neuropeptides and neurotransmitters, including claustrum, substantia nigra, striatum, thalamus, locus ceruleus. Due to degenerative process, usually cells come under this process and thus loss of neuronal cells as a result of cellular atrophy. The pathobiology of this subtle disease also has potential to affect the non-neuronal cells like microglia, astrocytes, oligodendroglia, blood vessels, choroid plexus. The AD models of transgenic mice showed that the presence of amyloid plaques in the brain tissues has a great potential to disturb the normal brain functioning due to the loss of dendrite spines or synaptic dysfunction. Postmortem studies of brain tissues illustrated that individuals who suffer from this deadly disease usually have a strong decline in dendritic spines and density of synapses in the hippocampus region of the brain relative to normal brain tissues. Loss of dendritic spines is directly co-related with the worsening mental status and also acts as an indicator of disease [4].
Laser-Induced Fluorescence Imaging
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
An example of the quality and resolution achievable by single-molecule superresolution fluorescence imaging is exemplified for a STORM measurement in Figure 18.18. The images shown here (in false-color representation, used to label the positional light intensities) revealed a new membrane–skeleton structure in neurons (see Xu et al. 2013). It should be recalled that dendritic spines are cellular structures of small dimensions (with dimension d ~ 500 nm); these are of great importance not only because they compartmentalize the excitation sites of neurotransmission in neurons, but also because their fast morphological changes seem to play an essential role in the plasticity of synaptic transmission.
Nanoscopic Imaging to Understand Synaptic Function
Published in Francesco S. Pavone, Shy Shoham, Handbook of Neurophotonics, 2020
Daniel Choquet, Anne-Sophie Hafner
In the adult central nervous system, dendritic spines receive most glutamatergic excitatory inputs. Presynaptic axon terminals or boutons containing synaptic vesicles of ~40 nm in diameter are opposed and linked to those postsynaptic protrusions to form mature synapses. Dendritic spines are small subcellular organizations connected to the neuron dendritic shaft by a thin spine neck (length ~1 µm, diameter ~100 nm) that acts as a diffusion barrier and leads to a spine head of typically 200 nm to 1 µm in diameter. The spine head contains the postsynaptic density (PSD), a GigaDalton macromolecular structure of typically less than 500 nm2 apposed intracellularly to the postsynaptic membrane and formed of a complex assembly of scaffold proteins responsible for anchoring numerous key players of synaptic transmission such as glutamate receptors, kinases, and phosphatases. The PSD also contains an assembly of adhesion proteins responsible for the adhesion between the post- and pre-synapse. The spine cytoplasm contains an impressive number of proteins both quantitatively and qualitatively. The dimensions of both pre- and post-synapse elements are in the range – or below – the diffraction limit (in the order of half the wavelength of the used light, i.e. 200–400 nm). Thus, for decades, the techniques of choice to study the morphological organization of synapses were electron microscopy or biochemical isolation. Light microscopy techniques harbor many advantages. For instance, compared to electron microscopy, it allows imaging of a large volume, a whole neuron, and the study of structural modifications over time with live-cell imaging. However, only the advent of superresolution microscopy techniques has allowed optical microscopy to deeply investigate synapse structure in live cells.
Neurophysiological and molecular approaches to understanding the mechanisms of learning and memory
Published in Journal of the Royal Society of New Zealand, 2021
Shruthi Sateesh, Wickliffe C. Abraham
The plasticity of functional synaptic properties appears to go hand-in-hand with plasticity of the synaptic structure (Muller et al. 2000; Williams et al. 2003). Dendritic spines, which are the small postsynaptic protrusions where excitatory synaptic contacts are made, are dynamic structures that can be formed, modified in their shape or eliminated under the influence of activity. Matsuzaki et al. (2004) showed that synaptic potentiation is closely related to the enlargement of spine heads, as revealed by two-photon photolysis of caged glutamate and concurrent real-time imaging of spine morphology and electrophysiological recording of synaptic responses at single spines of hippocampal CA1 pyramidal neurons. This key finding has been complemented by static analyses of synaptic structure at fixed times post-HFS using electron microscopy. Bourne and Harris (2011) undertook three-dimensional reconstructions of CA1 dendrites and observed an increase in synapse size and number for both excitatory and inhibitory synapses following induction of LTP. In addition, using a combination of electron microscopy and calcium precipitation, there was an increase in the number of spines making contact with the same presynaptic terminal, indicating that LTP induces the multiplication of existing axonal-dendritic contacts (Toni et al. 1999). Interestingly, changes in number and morphology of neuronal structures have also been captured in behaving animals using high-resolution imaging suggesting that structural plasticity is an ongoing process in the mammalian adult brain (Holtmaat and Svoboda 2009).
The cognitive and neural correlates of written language: a selective review of bilingualism
Published in Journal of the Royal Society of New Zealand, 2021
Karen E. Waldie, Gjurgjica Badzakova-Trajkov, Haeme R. P. Park, Yuxuan Zheng, Denise Neumann, Nasrin Zamani Foroushani
All typically developing children learn to speak at least one language without explicit teaching, leading to the idea that the neural basis of language is innate: a product of about 70,000 years of evolution and natural selection (Pinker 2007). The timing of the emergence of speech in toddlers appears to be both universal and corresponds to maturational changes in the brain (Molfese and Molfese 1979). The structural language networks are mainly established by age 2 years (Wada et al. 1975), with cell division mostly ceasing with the migration of neural cells to their final positions in the cerebral cortex (Changeux and Danchin 1976). The major changes that occur after the age of 2 years are in the interconnections of neurons, involving an increase in the complexity of dendritic spines as well as synaptic pruning.