Phagocytosis By Human Neutrophils
Hans H. Gadebusch in Phagocytes and Cellular Immunity, 2020
The microfilaments are apparently composed of contractile proteins. Actin, myosin, and an actin-binding protein have been partially purified from both neutrophils7*'81 and macrophages.82,83 The phagocytic myosin has Mg2+-ATPase activity that is increased markedly in the presence of actin;79,80 in the case of macrophages, an additional cofactor is required for this activation.81 It appears as though the actin in leukocytes is capable of a reversible polymerization, resulting in a reversible gelation phenomenon in vitro;79 electron micrographs show the formation of a tangled filamentous network when actin, myosin, and actin-binding protein are mixed in vitro.79-81 The most important direct evidence for the significance of this system to leukocyte mobility lies in the identification of a patient with inadequate ability to polymerize actin.*4 This child was originally observed to have recurrent bacterial infections but minimal signs of inflammation. Studies of cell mobility both in vivo and in vitro showed poor migration and particle ingestion was abnormal. Although the total cellular actin content was normal, it did not polymerize to the usual extent under a normal stimulus (addition of KC1). Thus it appears as though defective actin polymerization leads to a functional defect in cellular locomotion.
White Blood Cell Rheology
Gordon D. O. Lowe in Clinical Blood Rheology, 2019
Experiments have also been performed with the use of cytochalasin B, which disrupts the actin microfilaments. In this case all three elements decrease. These results suggest that both the microfilaments and microtubules are important in governing the passive viscoelastic properties of the WBC; their disruption leads to a decrease in the viscoelastic coefficients of the cell. Furthermore, the results suggest that the microfilaments and the microtubules have different roles in the control of the viscoelastic properties of the cell. The microtubules apparently are not important in determining K1, whereas the disruption of microfilaments has an influence on all three elements. The interrelationship between the chemical and the physical properties of the cell needs to be further studied.
The Aging of the Neuronal Cytoskeleton
Alvaro Macieira-Coelho in Molecular Basis of Aging, 2017
Microfilaments have a diameter of 4 to 6 nm and are composed of actin. As actin is a highly conserved protein, a whole family of actin-associated proteins (AAPs) confers specialized functions to these actin filaments according to the needs of individual cells.1 The 42-kDa actin monomers (G-actin) polymerize into double-helical filaments (F-actin). This polymerization is dependent on ATP hydrolysis. Actin polymerization is a very dynamic process controlled mostly by actin-associated proteins such as profilin (G-actin sequestering) and gelsolin (filament nucleating). Other AAPs such as spectrin and myosin cross-link existing filaments into a network. Ankyrin and spectrin anchor actin filaments to the plasma membrane and to other cellular organelles. Myosin is the motor of cell motility by a sliding filament mechanism. Motility can also appear from transitions between the gel and the sol state of actin filaments interacting with other cytoskeletal filaments and the cell membrane. Through these mechanisms, actin filaments are involved in cell motility, adhesion, membrane stability, determination of cell shape, exocytosis, and cytokinesis.2 Microfilaments, therefore, act simultaneously as the cell “skeleton and muscles”.
Topiramate affords neuroprotection in diabetic neuropathy model via downregulating spinal GFAP/inflammatory burden and improving neurofilament production
Published in Toxicology Mechanisms and Methods, 2023
Mohammed A. Attia, Nema Soliman, Mohamed Ahmed Eladl, Shymaa E. Bilasy, Taghrid B. El-Abaseri, Howaida S. Ali, Faten Abbas, Dalia Ibrahim, Noura M. S. Osman, Abdullah A. Hashish, Asma Alshahrani, Abir S. Mohamed, Sawsan A. Zaitone
In the DN group, scoring of the spinal cord sections revealed a significant increase in histopathological changes as degenerated neurons, eosinophilic foci, and gliosis that was associated with a significant decrease in the Nissl granules and NEFH. Since, neurofilaments, which are exclusively expressed in neurons and function along with other cytoskeleton proteins (like microtubules and microfilament) in forming and maintaining the cell integrity via contributing to particles and organelle delivery within the cytoplasm. In central and peripheral neuronal degenerative diseases, neurofilaments have a crucial role. Reduced size of the myelinated fibers in addition to losing axonal neurofilament content in the peripheral nerve have been reported in diabetic rats. Further, a decline in the neurofilament subunit expression to the distal axon has been proposed as a crucial role in degeneration of the axons (Qiao et al. 2015).
Biomechanical characterization and modeling of human mesenchymal stem cells under compression
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Negar Moghimi, Kaiyuan Peng, Arkady Voloshin
ANSYS Mechanical APDL1 was used as a finite element analysis tool to calculate internal forces and deformations in each of the thirty elements (cables and struts) due to the applied external excitation. In this study, a 30-member tensegrity structure consisting of 6 struts and 24 cables (Figure 6) is used to simulate a cell’s viscoelastic behavior. The mechanical properties of microtubules and microfilaments were assigned on the basis of the experiment implemented by (Gittes et al. 1993). In our study, most of the parameters of cells’ properties were based on this experiment, but the value of the cross section was enlarged to assure that the whole structure is stable under the external force. For the elastic case, the physical and mechanical properties of the cellular members are displayed in Table 3. We modeled stiffer micro-tubules as internal elastic members while more flexible micro-filaments are modeled as internal viscoelastic members of the cell, resulting in a viscoelastic response for the whole cell. In ANSYS one can model viscoelastic behavior by utilizing a Prony series, which describes the Wiechert model.
Graphene 2D platform is safe and cytocompatibile for HaCaT cells growing under static and dynamic conditions
Published in Nanotoxicology, 2022
Iwona Lasocka, Elzbieta Jastrzębska, Agnieszka Zuchowska, Ewa Skibniewska, M. Skibniewski, Lidia Szulc-Dąbrowska, Iwona Pasternak, Jakub Sitek, Marie Hubalek Kalbacova
Cell membrane is also crucial for cell adhesion, because it contains receptors (integrins) that act as sensors of external signals, allowing the cell to respond to environmental cues (Lotfi, Nejib, and Naceur 2013). Integrins (signaling layer of focal adhesion) transmit information to the force transduction layer (vinculin, talin) and further to actin regulatory layer connected to actin stress fibers (actin cytoskeleton). Focal adhesion kinase (FAK) is today recognized as a hub in the interactome of focal adhesions (Martínez, Navajas, and Lietha 2020), thus its visualization could help to reveal the interaction between cells and graphene substrate. As shown in Figure 7, adhesion sites based on FAK and F-actin colocalization are already visible at the third hour of incubation on the graphene covered coverslips (Figure 7(A)) and control coverslips (Figure 7(B)). The cells are spherical in shape and begin to form clusters, but most of them are still single cells. After next 21 hours, the adhesion sites become more pronounced and cells stick tightly to each other and become more spread in clusters consisting of four to six cells (Figure 7(C)). There is a clearly visible „FAK frame” around the cell cluster that colocalizes with actin filaments and organized microfilaments are evenly distributed in the cytoplasm (Figure 7(C)). No more organized structures like microfilament bundles or stress fibers were observed in these cells cultivated on neither substrate.
Related Knowledge Centers
- Actin
- Biopolymer
- Cytoplasm
- Cytoskeleton
- Eukaryote
- Protein
- Cytokinesis
- Protein Filament
- Cell
- Amoeboid Movement