Mechanisms of Cholestasis
Robert G. Meeks, Steadman D. Harrison, Richard J. Bull in Hepatotoxicology, 2020
Low-dose administration of cytochalasin also causes cholestasis, which is accompanied by dilatation of canaliculi and a loss of microvilli (Phillips et al., 1975). Cytochalasin has a number of effects, including detachment of microfilaments from the plasma membrane (Oda and Phillips, 1977) and prevention of the polymerization of actin (McLean-Fletcher and Pollard, 1980). Cytochalasin causes a reversible inhibition of canalicular contractions in the isolated hepatocyte couplets (Phillips et al., 1983), inhibits the transport of taurocholate (Reichen et al., 1981; Kacich et al., 1983), and the receptor-mediated transcytosis of IgA (Gebhart, 1984). The exact mechanism by which it inhibits bile flow is not known. As discussed above for phalloidin, disruption of microfilament function may explain the cholestasis.
Internalization of Lipopolysaccharide by Phagocytes
Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison in Endotoxin in Health and Disease, 2020
Since large LPS aggregates can bind mCD14, another potential LPS internalization mechanism is phagocytosis. We (30) found that the internalization of [3H]LPS aggregates by THP-1 cells was only slightly (25–35%) inhibited by concentrations of cytochalasin D or cytochalasin H that completely inhibited mCD14-mediated phagocytosis of BODIPY-labeled E. coli. Phagocytosis is thus not required for internalization of LPS aggregates that bind to mCD14. Interestingly, the relatively weak inhibition by cytochalasins also suggests that the mechanism of LPS internalization mediated by GPI-anchored CD 14 differs from that of GPI-anchored CD59, which is internalized by a cytochalasin-inhibitable, non-clathrin-dependent pathway in T lymphocytes (47). Internalization of cross-linked CD59 appears to involve an actin-dependent capping mechanism that does not occur during LPS internalization. On the other hand, the fact that cytochalasins partially inhibit LPS internalization points to some role for the actin cytoskeleton in this process.
Optical Cardiovascular Imaging
Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer in Cardiovascular Molecular Imaging, 2007
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.
Chronic low dose exposure of hospital workers to ionizing radiation leads to increased micronuclei frequency and reduced antioxidants in their peripheral blood lymphocytes
Published in International Journal of Radiation Biology, 2019
Zothan Siama, Mary Zosang-zuali, Annie Vanlalruati, Ganesh Chandra Jagetia, Kham Suan Pau, Nachimuthu Senthil Kumar
The blood samples were collected by venipuncture from each volunteer of both groups in individual sterile heparinized tubes. The lymphocyte culture was carried out according to the method described earlier (Jagetia et al. 2001). Briefly, the blood was allowed to sediment and the buffy coat was collected in individual sterile glass tubes. Usually, 106 nucleated cells were inoculated into sterile glass tubes containing RPMI-1640 medium, 10% fetal calf serum and phytohemagglutinin as the mitogen. The cells were allowed to grow for the next 44 h in a humidified atmosphere of 5% CO2 in air at 37 °C. Cytochalasin B was added at a final concentration of 5 μg/ml to block cytokinesis and cells were allowed to grow for another 28 h (Fenech and Morley 1985). Cells were harvested at the end of 72 h after initiation of the lymphocyte culture by centrifugation. A mild hypotonic solution was added to the cell pellet so as to retain the cell membrane. Cells were then fixed in freshly prepared Carnoy’s fixative (methanol: acetic acid, 3:1). The cell suspension was placed onto pre-cleaned coded blinded slides to avoid observer`s bias and spread by air blowing. The cells were stained with acridine orange and scored under a fluorescence microscope (DM 2500, Leica Mikrosysteme Vertrieb GmbH, Wetzlar, Germany) by two individuals. Usually, a total of 1000 binucleate cells (BNC) with well-preserved cytoplasm were scored from each individual for the presence of micronuclei (MN) according to the criteria described earlier (Fenech et al. 2003).
Cytogenetic effects of antidiabetic drug metformin
Published in Drug and Chemical Toxicology, 2022
Deniz Yuzbasioglu, Jalank H. Mahmoud, Sevcan Mamur, Fatma Unal
MN test was applied according to the studies of Fenech (2000) and Palus et al. (2003) with some modifications. Peripheral blood samples were added to Chromosome medium B. The samples were incubated at 37 °C for 72 h. Lymphocytes were exposed to MET at 12.5, 25, 50, 75, 100, and 125 µg/mL concentrations during the last 48 h. At the 44th h of the culture, cytochalasin-B (5.2 μg/mL) was added to arrest cytokinesis. A negative and a positive control (MMC, 0.20 µg/ml) were also included. After a total of 72 h incubation, the cells were treated with the hypotonic solution (0.075 M KCI) for 5 min. Then the cells were fixed in methanol: glacial acetic acid (3:1, v/v) supplemented with formaldehyde. The slides were air-dried and stained in 5% Giemsa.
Prospecting in silico antibacterial activity of a peptide from trypsin inhibitor isolated from tamarind seed
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2023
Gerciane Silva de Oliveira, Amanda Maria de Souza Nascimento, Anna Beatriz Santana Luz, Ana Júlia Felipe Camelo Aguiar, Mayara Santa Rosa Lima, Lídia Leonize Rodrigues Matias, Isabel Rodríguez Amado, Thais Souza Passos, Karla Suzane Florentino da Silva Chaves Damasceno, Norberto de Kássio Vieira Monteiro, Susana Margarida Gomes Moreira, Lorenzo Pastrana, Ana Heloneida de Araújo Morais
Cells were grown to 80% confluence, and the medium was replaced by a fresh medium containing TTI (0.3 and 0.6 mg.mL−1), and cells were incubated for 24 h. Then, the medium was aspirated, and the cells were washed with PBS. Subsequently, a fresh medium supplemented with cytochalasin B (Cyt B; Sigma®, St. Louis, MO, USA) was added, and the cells were incubated for another 24 h. Afterward, the cells were washed with PBS, detached using 200 μL of 0.025% Trypsin (0.05% EDTA) for 5 min, and suspended in a culture medium. After centrifuging, the cells were suspended in fixation buffer at 4 °C, consisting of methanol and glacial acetic acid (9: 1 v/v). Washing in fixation buffer was repeated three times.
Related Knowledge Centers
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