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Bio-Inspired NoC Fault-Tolerant Algorithms
Published in Muhammad Athar Javed Sethi, Bio-Inspired Fault-Tolerant Algorithms for Network-on-Chip, 2020
Synaptogenesis is a self-adapting mechanism in the human brain where two neurons attempt to connect and communicate with each other. In this phenomenon, the growth cone (having lamellipodium and filopodia) at the top of the axon and dendrites terminals, finds a path to a target neuron. The filopodia actually finds the path for a connection with the target neuron. A chemical attractant is released by the target neuron to attract the growth cone. A synapse is formed between the source and target neuron using this method (Breedlove, Watson, and Rosenzweig 2007). The synaptogenesis process is shown in Figure 4.3.
Nanomaterial-Assisted Tissue Engineering and Regenerative Medical therapy
Published in Gilson Khang, Handbook of Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine, 2017
Nirmalya Tripathy, Rafiq Ahmad, Gilson Khang
Nerve regeneration refers to the regrowth or repair of nervous tissues, cells, or cell products. Such mechanisms may include generation of new neurons (transmit electrochemical signals), glial cells (support neurons), axons, myelin, or synapses. Neurons are comprised of a cell body (or soma), an axon (extended long structure to transmit signals to the synapse, the junction between neurons), and dendrites (branched structure around the cell body for receiving signals from other neurons at the synapse), and axons and dendrites in vitro called neurites collectively. Some axons are covered by a myelin sheath, an insulator helping fast action potential transfer. However, the center of the nervous system, the brain, takes charge of perception and information processing, controls most of motions and behaviors in body, and maintains homeostasis. The significant functions of the brain require electrochemical signal transfer mediated by neurons; therefore, the specific connections between neurons are very important. For the efficient connection and thus effective neuronal process, neurite outgrowth is a fundamental phase in which undifferentiated neurons extend to neurites before differentiating to axons and dendrites subsequently. During neurite outgrowth process, neurons extend leading tips called growth cones, and the growth cone senses the extracellular chemical, mechanical, and topographical environments, which guide the directional structure and movement of an axon and dendrites.92 Precise understanding of extracellular cues influencing neuronal growth is not only crucial for research into development of neurons but also for designing scaffold for nerve tissue regeneration with knowledge about alignment and migration of neuronal cells. Traditionally, chemical cues for guidance of growth cones have received much attention.
Microfluidics in Neuroscience
Published in Tuhin S. Santra, Microfluidics and Bio-MEMS, 2020
Pallavi Gupta, Nandhini Balasubramaniam, Kiran Kaladharan, Fan-Gang Tseng, Moeto Nagai, Hwan-You Chang, Tuhin S. Santra
Coming to the gradient of neurotrophic factors in microfluidic chambers, future experiments could be undertaken to maintain constant gradients via continuous flow of media and chemoattractants for longer periods by employing external pumps. Apart from known guidance cues, such as netrin-1, brain pulp, and slit-2, new guidance molecules, factors affecting growth cone morphology, or axon guiding genes could also be studied using microfluidic gradient channels.
Influence of ionic crosslinkers (Ca2+/Ba2+/Zn2+) on the mechanical and biological properties of 3D Bioplotted Hydrogel Scaffolds
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Md. Sarker, Mohammad Izadifar, David Schreyer, Xiongbiao Chen
Implanted nerve guidance conduits (NGC) featuring micro/nano-scale physical cues across a damaged peripheral nerve have promoted axon regeneration in a number of studies [37,38]. Biofabricated and aligned micro-strands could be used in NGCs to obtain directional outgrowth of axons. In particular, Schwann cells embedded in hydrogel strands facilitate the regeneration process by producing growth factors and guiding the axon growth cone to the distal end of damaged nerves [39,40]. However, complex interactions among various metal ions, mannuronic acid, guluronic acid, and incorporated cells might significantly affect the survival and biological performance of Schwann cells in possible applications for peripheral nerve regeneration. To address this issue, Schwann cells were used in this study in the biofabrication of alginate scaffolds.
Finite element brain deformation in adolescent soccer heading
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Colin M. Huber, Declan A. Patton, Jalaj Maheshwari, Zhou Zhou, Svein Kleiven, Kristy B. Arbogast
Animal models provide the unique opportunity to directly measure tissue-level injury through morphological analysis and neuropathology post-mortem (Sullivan et al. 2013) and estimate thresholds for functional and mechanical axonal injury (Bain and Meaney 2000; Singh et al. 2009). An in vivo axonal stretch model of the guinea pig optic nerve identified a 25% functional injury risk threshold for strains of 0.18 based on delayed visual evoked potentials (VEP) (Bain and Meaney 2000). An in vivo stretch model of rat spinal nerve roots quantified 50% risk of complete conduction block (i.e. loss of neurophysiological utility) at strains of 0.16, 0.10, 0.09 for strain rates of 0.01, 1, 15 mm/s, respectively (Singh et al. 2009). For the current study, the 100th percentile, or maximum, MPS was 0.11; however, the highest 99th percentile strain was 0.08; therefore, for the highest intensity headers, fewer than 1% of brain elements were at risk of functional or mechanical axonal injury based on the thresholds described above. Further, MPS for the brain tissue may not align with axon tracts; therefore, strains along the length of the axon will be lower than MPS values. An in vitro axon stretch model of rat primary cortical neurons found microtubule rearrangement and decreased growth cone size after strains as low as 0.005, and repetitive stretch exposure further exacerbated the effects, indicating a cumulative effect of the insults (Yap et al. 2017). Therefore, repetitive head loading in sports with low values of strain such as those estimated in this study may cause structural changes in axons that build up over time, which could potentially cause electrophysiological deficits or make the cells more susceptible to injury.