Ultra-Structural Analysis of the Intrahepatic Bile Duct System
Gianfranco Alpini, Domenico Alvaro, Marco Marzioni, Gene LeSage, Nicholas LaRusso in The Pathophysiology of Biliary Epithelia, 2020
Alteration of specific cytoskeletal proteins may also have substantial impact on the cellular structure and function. Recently, Fitz and co-authors29 have demonstrated that during warm liver ischemia, cholangiocyte membrane structure appears altered both in vivo and in vitro after ATP depletion. Lateral interdigitations are gready reduced after 120 minutes of ischemia or ATP depletion, and apical microvilli appear to increase in length but become progressively less abundant. In a time course that paralleled the loss of microvilli, the actin membrane linking protein ezrin, progressively dissociated from the microvillar cytoskeleton, suggesting the role of alteration in the membrane-cytoskeletal interactions at the early stages of these events. These studies indicate that the initial cellular response to metabolic inhibition involves early and characteristic changes in the membrane-cytoskeleton and secondary structures of the plasma membrane. Although cell viability and epithelial barrier function remained largely intact, the profound loss of membrane organization and surface area may negatively impair the secretory capacity of intrahepatic bile duct until the membrane domains are re-established.
From cells to systems
Nick Draper, Helen Marshall in Exercise Physiology, 2014
The cytoplasm, meaning cell-forming matter, comprises cytosol, a cytoskeleton and organelles which carry out a wide range of functions within the cell. Cytosol or intracellular fluid is a gel-like substance, largely composed of water that contains suspended and dissolved particles such as ATP, glucose, lipids, amino acids and a variety of different ions. Many metabolic reactions take place within the cytosol including glycolysis, one of the major pathways for synthesising ATP. The cytoskeleton is literally that, a cellular ‘skeleton’ within the cytoplasm which is made out of protein (see Figure 3.2). It includes three main types of protein filament that, among other roles, maintain cell structure and hold in place many of the cell’s organelles. The microtubules are responsible for support and structure within the cell giving the cytoskeleton strength and rigidity. The intermediate filaments give the cell strength, help to maintain the structure and stabilise the position of the cells organelles, while microfilaments (which are illustrated in Figure 3.5) help to give the cell shape by anchoring the cytoskeleton to the plasma membrane. The microfilaments (which are comprised of the protein actin) are also one of the filaments responsible for muscular contraction (see Chapter 5).
Anatomy and Physiology of the Autonomic Nervous System
Kenneth J. Broadley in Autonomic Pharmacology, 2017
The smooth muscle cells (Figure 1.1) are usually described as elongated and tapered at each end, although variations in this general shape are more usual. The size is in the range 2–3 µm diameter and 15–20 µm long in blood vessels, 5–6 µm diameter and 30–40 µm long in the intestine, and up to 0.5 mm long in the uterus. The smooth muscle fibres contain a single centrally located nucleus and, unlike skeletal muscle, have no transverse striations. In skeletal muscle the contractile filaments, myosin and actin, are arranged longitudinally in alternating layers as thick and thin myofilaments, respectively. Their alternating parallel arrangement produces the characteristic dense transverse bands (A bands) where they are both present, and the thin bands (I bands) where only actin occurs (Figure 1.1). In contrast, the actin and myosin of smooth muscle fibres are very thin and arranged more randomly so that no striations are seen. The contractile filaments are seen as fine longitudinal striations. Dense bodies can be observed in the sarcoplasm and these are probably connected to the dense bands attached to the cell membrane. These probably form the point of attachment of the thin filaments. A cytoskeleton of intermediate filaments probably exists, serving as a means of force transduction between the dense bodies and its membrane attachment (Gabella 1981).
Enhanced osteogenic activity and antibacterial ability of manganese–titanium dioxide microporous coating on titanium surfaces
Published in Nanotoxicology, 2020
Quan-Ming Zhao, Yu-Yu Sun, Chun-Shuai Wu, Jian Yang, Guo-Feng Bao, Zhi-Ming Cui
The results of this study are consistent with those previously reported. Plasma proteins that adsorb onto the Mn–TiO2 microporous biotic coating may promote cell spreading by stimulating the expression of cytoskeletal proteins. It is currently known that cytoskeletal proteins play a central and linking role between cell cytoplasm and nuclei and that they are important for signal transduction between them. Also, we found that Mn–TiO2 microporous biotic coatings promoted the expression of cytoskeletal proteins, which confirms the currently reported hypotheses to some extent. However, the regulation of Mn ions on osteoblasts is a complex process, and the mechanism by which Mn ions regulate cell spreading remains unclear and thus demands further research. The results of this study demonstrate that MC3T3-El osteoblasts in the MnII, MnI, and MT groups showed better spreading than those in the PT group, indicating that porous structures can promote cell spreading.
Proteome-based pathology: the next frontier in precision medicine
Published in Expert Review of Precision Medicine and Drug Development, 2021
Michael H. Roehrl, Victor B. Roehrl, Julia Y. Wang
Proteins are the true machines of life. Protein enzymes carry out virtually all complex chemical transformations in living organisms, such as nucleic acid synthesis and replication, posttranslational modifications, carbohydrate and lipid metabolism, hormone biosynthesis, proteolysis, and many more. Proteins provide functional context to cells, tissues, and organisms in the form of receptors, signaling cascades, channels, and transporters. Proteins are also major structural components of the cytoskeleton and extracellular matrices. The pathobiology of virtually all diseases can be understood as the malfunctioning of any one or more of this myriad of actions that proteins perform in a spatially and temporally highly orchestrated manner. By contrast, many diseases, especially cancers, continue to be viewed in a nucleic acid-based genomic and mutation-centric manner, but is this good enough?
Peripheral nerve injury and axonotmesis: State of the art and recent advances
Published in Cogent Medicine, 2018
Rui Alvites, Ana Rita Caseiro, Sílvia Santos Pedrosa, Mariana Vieira Branquinho, Giulia Ronchi, Stefano Geuna, Artur S.P. Varejão, Ana Colette Maurício
Within the endoneurium are myelinated or unmyelinated axons in close relation to the Schwann cells. These glial cells guarantee functional connections with the terminal organs such as muscle fibers or sensorial terminations by ensuring the saltatory propagation of action potentials along the axon (Said & Krarup, 2013). To the set formed by the axons and by the Schwann cells that surround it is given the histological denomination of parenchyma (Mills, 2007). The axon itself has a tubular shape. The axonal cytoskeleton has a microfibrillary structure consisting of three large groups of proteins: microfilaments, microtubules and intermediate filaments including neurofilaments. The function of the cytoskeleton is essentially to maintain the shape and participate in axonal growth (Rigoard et al., 2009), ensuring the transport of proteins and organelles between the cell body and the axon terminals (Josta & Casper, 2015). Some axons develop in close relationship with Schwann cell chains, each one associated with a single axon and responsible for producing their myelin sheaths. These sheets are essentially composed of several layers of Schwann cell membranes associated with secreted proteins. Between two myelin segments, also called internodes, there are demyelinated spaces called Ranvier nodes (Pereira, Lebrun-Julien, & Suter, 2012). The most abundant protein is P0, which mediates the cell-to-cell interactions and those between the neurons and myelin sheaths, being essential in the formation of the latter and in its maintenance (L. Zhao & Zheng, 2010).
Related Knowledge Centers
- Archaea
- Bacteria
- Cytoplasm
- Eukaryote
- Intermediate Filament
- Microfilament
- Cell Membrane
- Cell Nucleus
- Protein Filament
- Cell