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The Type II Pneumocyte
Published in Jacques R. Bourbon, Pulmonary Surfactant: Biochemical, Functional, Regulatory, and Clinical Concepts, 2019
On the other hand, abundant actin-like filaments have been observed in close association with lamellar bodies, especially with those located near the cell surface or in the process of being released.40 Following treatment with cytochalasin D, which alters microfilament organization in many cell types, lamellar bodies were no longer surrounded by actin-like material, and no exocytic lamellar bodies were encountered.40 Conversely, following treatment with isoproterenol, known to stimulate surfactant secretion (see Chapter 7), a greater number of actin-like filaments were associated with lamellar bodies. If cells had been treated with cytochalasin D prior to isoproterenol stimulation, the secretory response to the β-agonist was abolished.145 Actin filaments might therefore be involved in moving lamellar bodies through the cytoplasm and/or in their secretion into alveoli. However, one should note that opposite results were obtained by Rice et al.146 In their hands, following cytochalasin treatment, surfactant secretion was enhanced in a dose-dependent manner.
Intestinal Absorption Of Macromolecules In The Adult *
Published in Károly Baintner, Intestinal Absorption of Macromolecules and Immune Transmission from Mother to Young, 2019
Absorption of macromolecules is an energy-dependent process in both the young and the adult. The absorption is blocked by cold (0°C), uncoupling of oxidative phosphorylation,1524, 1528 and 02-deficiency (N2-atmosphere),446, 1524, 1528 and is decreased by protamine.1401 In vitro absorption is apparently not coupled with sodium transport.571 In organ culture HRP uptake was inhibited by cytochalasin D, but not by cytochalasin B.131
Quantification of Cellular Elasticity
Published in Malgorzata Lekka, Cellular Analysis by Atomic Force Microscopy, 2017
The observed heterogeneity in Young’s modulus observed at small indentations depths can be explained by several phenomena, including non-homogenous cytoskeleton density, removal of a limited number of filaments composing the network or even disruption of cytoskeletal filaments induced by AFM indentations. The narrowing of histograms as indentation depths increases stems from the fact that for larger indentations the information on cell mechanical properties is gathered from a larger volume. In this limit, elastic modulus should reach constant level at very large indentations, above 1–2 microns. Distributions presented in Fig. 4.17 show also cell-type relationship. Fibroblasts, being the cells with highly differentiated cytoskeleton and heterogeneous organization of filaments, reveal wider distribution of the modulus values. The modulus distribution for erythrocytes is much narrower. The incubation of fibroblasts with cytochalasin D, an agent depolymerizing actin filaments, manifests in the narrowest modulus histogram. This relation is observed both when a single cell or a population of cells are considered (Fig. 4.17).
Synthesis and in vitro characterization of oxytocin receptor targeted PEGylated immunoliposomes for drug delivery to the uterus
Published in Journal of Liposome Research, 2019
Mechanisms of cellular uptake were determined in the presence of specific inhibitory agents for different types of endocytosis. hTERT-myo cells were pretreated with specific inhibitory agents for 30 min at 37 °C prior to incubation with liposomes for 1 h at 37 °C. Inhibition of clathrin-mediated endocytosis was tested with chlorpromazine hydrochloride and monodansylcadaverine. Inhibition of caveolin-mediated endocytosis was performed using genistein and filipin. Methyl-β-cyclodextrin was used to deplete cholesterol, which inhibits both clathrin- and caveolin-mediated endocytosis. Cytochalasin D was used to inhibit phagocytosis and macropinocytosis, and nocodazole was used to inhibit macropinocytosis. Alexa FluorTM 488 conjugated transferrin (120 µg/ml) was used together with specific inhibitors as a positive control to investigate clathrin-mediated endocytosis and Alexa FluorTM 488 conjugated cholera toxin subunit B (0.6 µg/ml) with inhibitors as a positive control to analyze caveolin-mediated endocytosis. Fluoresbrite® YG carboxylate microspheres of 1 µm diameter (100 µg/ml) were used together with specific inhibitors as a positive control to evaluate phagocytosis and macropinocytosis. At the end of incubation, cells were washed three times with ice-cold PBS before fluorimetric detection as described above.
Compartmentalisation of cAMP-dependent signalling in blood platelets: The role of lipid rafts and actin polymerisation
Published in Platelets, 2015
Zaher Raslan, Khalid M. Naseem
Having shown that actin filaments played a role in regulating the inhibitory effect of cAMP-elevating agents on platelet aggregation, we examined the effect of cytochalasin D on platelet cAMP concentrations. In these experiments, PGI2 (50 nM) by itself caused a 31 ± 4% increase in cAMP levels over basal levels compared to an 89 ± 24% when platelets were pretreated with cytochalasin D (p < 0.05; Figure 4A). Consistent with a role for actin filaments in regulating AC activity, we found that cytochalasin D potentiated signalling events induced by PGI2, although this effect was less dramatic when compared to that observed with MβCD. Analysis of whole cell PKA substrate phosphorylation events revealed that inhibition of actin polymerisation increased the basal phosphorylation of proteins with apparent molecular weights of 50 and 55 kDa when compared with platelets with intact actin filaments. When platelets were stimulated with PGI2 (1 nM), there were modest increases in phosphorylation of the 90 kDa band, but no sensitisation of any other bands by the presence of cytochalasin D. When we examined signalling induced by 8-CPT-6-Phe-cAMP, the PKA activator was found to increase phosphorylation, but this was not enhanced by the presence of cytochalasin D. Consistent with previous experiments, cytochalasin D did cause a modest increase in basal phosphorylation (Figure 4C). These data suggest that disruption of actin filaments enhances the signalling events mediated by PKA in response to PGI2. These data suggest that actin filament disruption with cytochalasin D results in a significant increase cAMP signalling, which seems to be mediated at the level of AC and cAMP synthesis.
TiO2 nanotubes regulate histone acetylation through F-actin to induce the osteogenic differentiation of BMSCs
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Yanchang Liu, Zhicheng Tong, Chen Wang, Runzhi Xia, Huiwu Li, Haoran Yu, Juehua Jing, Wendan Cheng
To investigate the regulatory role of F-actin in BMSCs osteogenesis, we inoculated rat BMSCs onto the surface of TiO2 nanotube specimens. Then BMSCs were treated with Cytochalasin D and phalloidin daily. Phallus ring peptides bind only to polymerized filaments, not to actin monomers. It interacts with polymerized microfilaments, destroys the dynamic balance of polymerization and depolymerization, inhibits the disintegration of microfilaments and promotes the formation of more robust cytoskeleton. Cytochalasin D exerts the opposite effect [23]. Figure 3(C,E) validated the effects of phalloidin and cytochalasin on BMSCs which were seeded on the surface of TiO2 nanotubes from the aspect of cell morphology. F-actin in the TiO2 + Cytochalasin D group was almost depolymerized and the fibrous structures were rarely seen. But the F-actin in the TiO2 + Phalloidin group further polymerized to form thicker fibre bundles. The fibrous structures were not only concentrated at the edges of the cells, but even filled the entire cells. The content of ALP in BMSCs of TiO2 + Phalloidin group was significantly higher than that of TiO2 + Cytochalasin D group (Figure 3(A)). The results of qRT-PCR and Western blotting showed that the expression of OPN, OCN and RUNX2 in the TiO2 + Cytochalasin D group was lower than that in the TiO2 + Phalloidin (Figure 3(B,F,G)) group. These results confirmed that BMSCs treated with Cytochalasin D inhibited the polymerization of F-actin, thereby inhibiting osteogenesis differentiation, manifested by decreased expression of ALP and related osteogenic differentiation markers (OPN, OCN, RUNX2). On the contrary, Phalloidin promoted the polymerization of F-actin and elevated the expression of F-actin, ALP and osteogenic differentiation markers.