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Genotoxicity of Functionalized Nanoparticles
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials II, 2021
Varsha Dogra, Gurpreet Kaur, Rajeev Kumar, Sandeep Kumar
This is the process of engulfment of a solid particle, typically by macrophages, neutrophils, dendritic cells, monocytes, and mast cells which is instigated by particle opsonization and leads to the stimulation of F-actin-driven pseudopods that ingest the solid particle and forms phagosome. This process can be inhibited by the action of cytochalasin D (Geiser et al. 2005) which blocks actin polymerization (Bronson 1998) that stops the action of pseudopodia. Neutrophils, macrophages, and monocytes are specialized phagocytes, other cells like epithelial cells, fibroblast, etc. can also uptake the solid particles by the process called pinocytosis (Mellman 1996). This process takes places at the site of clathrin-coated pits that are found in most animal cells and includes the intake of particles having a size less than 200nm, along with fluids surrounding the particles.
Optical Cardiovascular Imaging
Published in Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer, Cardiovascular Molecular Imaging, 2007
Crystal M. Ripplinger, Guy Salama, Igor R. Efimov
A significant limitation of optical mapping of the heart is motion artifact introduced by muscle contractions. These “movement” artifacts distort optical action potentials by altering the fluorescence intensity. When the tissue contracts, it can move relative to both the sensor and light source, causing artificial changes in fluorescence. Since muscle contraction begins immediately after the action potential upstroke, motion artifacts are most pronounced during the plateau and repolarization phases. Several methods have been used in the past to minimize the effect of motion artifact. Mechanical restriction of the movement can successfully limit the artifact without affecting the physiology of the heart (18). This method works particularly well with small hearts such as mice, rats, and guinea pigs. A popular alternative is the use of various pharmacological agents, such as calcium channel blockers (19), 2,3-butanedione monoxime (BDM) (20,21) or cytochalasin D (22). However, all of these agents may have effects on the electrical activity of the heart. Calcium channel blockers are often avoided due to the many calcium-dependant cellular processes (23,24). BDM has an effect on a variety of ion channels and may alter action potential duration in a number of species (25,26). Therefore, BDM may not be appropriate for studies of repolarization. Cytochalasin D may provide a promising alternative for some species (22,27). Therefore, the effects of any pharmaceutical agents used need to be taken into consideration for an appropriately designed experiment.
Chapter 10: The Use of Microspheres in the Study of cell Motility
Published in Alan Rembaum, Zoltán A. Tökés, Micro spheres: Medical and Biological Applications, 2017
Godman et al.51 studied the effect of cytochalasin D on the induction and subsequent migration of cell surface blebs on cultured mammalian cells. They observed that 0.8 p-m diameter polystyrene microspheres attached to the HeLa cell surface exhibited irregular patterns of movement. Although the overall vector of movement tended to be toward the cell apex (thickest portion of the cell occupied by the nucleus), no clustering of microspheres was observed. However, treatment with either cytochalasin D (0.25 μg/mℓ) or colcemid (0.6 μg/mℓ) resulted in directed centripetal movement of the microspheres and their clustering at the cell apex. The directed movement of microspheres induced by colcemid treatment occurred at 3 to 4 μm/min.
Astral microtubules determine the final division axis of cells confined on anisotropic surface topography
Published in Journal of Experimental Nanoscience, 2020
Kyunghee Lee, Yen Ling Koon, Jaewon Kim, Keng-Hwee Chiam, Sungsu Park
In this study, we aimed to investigate the interplay between cell geometry and cortical cues in orientating the mitotic spindle for cells cultured on 3D microgratings. We used microgratings of poly(dimethyl siloxane) (PDMS) coated with fibronectin (FN) to manipulate mammalian cell geometry. The gratings are of constant depth (1 μm) with varied groove and ridge widths (1, 2 and 10 μm) that restrict cell width but allow for variable length. Cell adhesion patterns are modified using cytochalasin D (CD) that perturb focal adhesions. We also used RPE-1 and HeLa cells as characteristic normal-cancer pairs like in previous studies to showcase different behaviors between normal and cancer cells [12,17,18]. Through our analysis of cell aspect ratios and spindle angle, we find that spindle orientation is primarily determined by cell geometry attributes such as elongation when placed on 3D gratings. This is especially so for the normal cell line, RPE-1 where greater adherence to Hertwig’s rule is observed compared to cancerous HeLa. We also found that disrupting cortical cues by addition of CD does not lead to misalignment of spindle orientation. Instead, perturbing MTs disrupts the division alignment of RPE-1 and HeLa cells to a greater degree than abolishment of cortical focal adhesion cues. Our results suggest that cell geometry such as elongation plays a more imperative role in mitotic spindle orientation as compared to cortical cues. At the same time, astral MTs are important in maintaining proper spindle orientation for cells plated on anisotropic 3D surfaces since perturbation of MTs leads to spindle misorientation. Lastly, to incorporate our findings of elongation and astral MTs as important determinants of spindle orientation, we develop a computational force balance model that investigates the interplay between cell elongation, astral MTs and spindle orientation, and found good agreement between the model and the experimental data.