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Regeneration: Nanomaterials for Tissue Regeneration
Published in Harry F. Tibbals, Medical Nanotechnology and Nanomedicine, 2017
It is easy to focus on the neurons, with their electrical activity and complex interconnections, to the exclusion of the many supporting cells in the central nervous system, termed glial cells. The glial cells (from the Greek for “glue”) were originally considered merely space fillers providing structural support to the neurons in the brain and spinal cord. Research in neuron cell culture and regeneration has led to a more complete appreciation of the many essential roles of glial cells in maintaining healthy neuron function. It is now known that glial cells participate in calcium channel signaling with neurons and regulate growth, plasticity, and neurotransmitter management in neurons. Star-shaped glial cells called astrocytes perform many functions, including biochemical support of endothelial cells, which form the blood-brain barrier, provision of nutrients to the nervous tissue, and maintenance of extracellular ion balance and repair and scar formation following nerve damage.
Engineered Scaffolds: Materials and Microstructure from Nanostructures to Macrostructures for Tissue Engineering
Published in Claudio Migliaresi, Antonella Motta, Scaffolds for Tissue Engineering, 2014
Venu G. Varanasi, Panayiotis S. Shiakolas, Pranesh B. Aswathc
Tissues are 3D self-assembled constructs developed to serve very specific needs based on their location. Typically the cells in a tissue have a common embryonic origin and similar structure and tend to perform a specific function. The organization of the cells in a tissue is based on function and may be classified into four basic types: (i) epithelial, (ii) connective, (iii) muscle, and (iv) nervous. The epithelial tissue covers the body and all internal cavities with the major function of protection, secretion, absorption, and filtration. The connective tissue is widely dispersed in the human body and serves the function of support and protection and includes loose connective tissues such as fat, dense connective tissue such as cartilage and bone, and vascular tissues such as erythrocytes, leucocytes, and platelets. Muscle tissue includes smooth, skeletal, and cardiac and can be broadly classified as voluntary or involuntary muscle tissue. Smooth muscle tissue and cardiac muscle tissue are involuntary while skeletal tissue is considered to be voluntary tissues. Nervous tissue is made up of specialized cells that constitute the central nervous system including the brain and spinal cord.
Tissue Structure and Function
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
Nervous tissue regulates and coordinates many bodily activities. It detects and responds to changes in the internal and external environments and allows for states of consciousness, learning, memory, and emotions. Nervous tissue is designed to convert stimuli into electrical signals, transfer these signals to the processing center, process the signals, and stimulate tissues and organs based on those signals. The central nervous system, peripheral nervous system, brain, and spinal cord are nervous tissues. Like the other tissues that we have discussed, the function of nervous tissues in the neural system are predicated on the molecules that they are composed of; the main difference lies in function. These tissues contain two types of cells, neurons and neuroglia. Neurons are cells that can conduct impulses. Neurons have cell bodies, which houses the nucleus and other organelles; extensions from the cell body include the dendrites and the axon (Figure 4.24). Dendrites allow the neuron to send and receive signals through neuron-to-neuron connections called synapses. The axon also extends from the cell body and is used to make connections with other neurons using the axon terminals. The axon terminals come into close proximity to dendrites and exchange neurotransmitters, which pass the signal from the axon terminal to the dendrites. From here, the signal travels down the axon of the neuron that received the signal through its dendrites and to the axon terminals. Neurons have different-sized axons depending on their job. Local circuit neurons or interneurons in the brain have shorter axons; projection neurons can have lengths of up to a meter depending on the target, like those that run from the spine to the foot.19 The signal passes from the dendrite, down the axon, to the axon terminals using action potential. Action potentials send electrical impulses down the length of an axon through the movement of ions into the cell through ion gates. An action potential is a fast increase and decrease in voltage across the membrane of a cell.
In vitro study on electrospun lecithin-based poly (L-lactic acid) scaffolds and their biocompatibility
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Zhonghua Xu, Peng Liu, Hongyin Li, Mingkui Zhang, Qingyu Wu
Bioactivity of lecithin is another main reason for the regulation of cell attachment and proliferation. Lecithin is a natural mixture of phospholipids and neutral lipids, and is a significant constituent of nervous tissue and brain substance. It is a typical amphiphilic phospholipid with good biocompatibility, which is capable of mixing with different polymers and maximizing hydrophilic interactions. In addition, phospholipid is one of the main components of cytomembrane and is abundant in human body, so its excellent biocompatibility is favorable for cell growth and tissue regeneration. As we know, polymer blending is one of the several efforts used so far to enhance hydrophilicity and recognized as an easy cost-effective approach for the manipulation physiochemical properties of polymeric biomaterials [10]. The simple solvent blending method adopted by us allowed lecithin to be released slowly from the electrospinning polymeric scaffolds. So the 3D electrospun PLLA/lecithin scaffolds with improved hydrophilicity and cytocompatibility, provided direct fabrication of biologically based scaffolds for tissue engineering blood vessel, without the use of multiple synthetic steps and postprocessing surface treatments.
Stress and strain propagation on infant skull from impact loads during falls: a finite element analysis
Published in International Biomechanics, 2020
F.J. Burgos-Flórez, Diego Alexander Garzón-Alvarado
TBI is produced by impact loads on the skull, known as direct injury, or by the acceleration or deceleration of the head without the direct application of load, known as diffuse injury. However, in most cases, a combination of impact loads and acceleration is present (Hardman and Manoukian 2002). The biomechanical impact on brain structures causes the injury of nervous and vascular tissue through two underlying mechanisms, described as primary and secondary lesions. The primary lesion is defined as the set of nervous and vascular lesions that appear immediately as a consequence of TBI and trigger the transmission of energy to the tissue, producing multidirectional deformations in it. These deformations predominantly affect the neurons and to a lesser extent, the glia and cerebral vascular structures, causing contusions and lacerations in the superficial tissue and axon and vascular stretching in the deeper tissue. The secondary lesion refers to the appearance of new lesions in the nervous tissue of a percentage of the patients hospitalized by TBI, which, instead of improving, present deterioration of their condition. These lesions are triggered by a limited number of biochemical chain reactions that progressively affect brain tissue. Thus, the primary lesion tends to get worse, generating final damage more severe than the one directly caused by the primitive impact (Hardman and Manoukian 2002).
Inflammatory and apoptotic signalling pathways and concussion severity: a genetic association study
Published in Journal of Sports Sciences, 2018
Sarah Mc Fie, Shameemah Abrahams, Jon Patricios, Jason Suter, Michael Posthumus, Alison V. September
Although neuroinflammation is necessary to promote healing in the central nervous system, a prolonged or over-active response can have detrimental effects on the health of nervous tissue (Lenzlinger, Morganti-Kossmann, Laurer, & McIntosh, 2001; Morganti-Kossmann, Rancan, Stahel, & Kossmann, 2002). For example, increased blood brain barrier disruption resulted in prolonged inflammatory stimulation, oedema, and cell death (Schlosberg, Benifla, Kaufer, & Friedman, 2010), while increased neuronal apoptosis caused disruption of white matter networks and neurological difficulties (Kraus et al., 2007). Furthermore, activated microglia and astroglia release several neurotoxic chemicals, including nitric oxide, which can be damaging to the health of surrounding neurons (Brown & Neher, 2010).