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Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Little is known about melanosome transfer from the melanocyte to neighboring keratinocytes. The melanosomes migrate to the dendritic processes of the melanocyte, which then become pinched off and transferred to the keratinocyte. The area of contact between the keratinocyte and dendritic processes of the melanocyte undulates in vitro. This undulation of the membrane has been attributed to intracellular microfilaments.101 Studies in vitro have demonstrated pigment transfer. When the fungal metabolite cytochalasin B is added to the culture medium, melanocytes shrink, undulations of the keratinocyte membrane cease, and microfilaments disappear. However, the attachment site between melanocytes and keratinocytes remains intact, while desmosomal attachments between keratinocytes split apart. This indicates that the melanocyte-keratinocyte attachment is stable and can withstand the tension, which the keratinocyte-keratinocyte desmosome attachment cannot. Other organelles are not affected by cytochalasin B treatment. The effects of cytochalasin B on microfilaments are reversible 1 h after removal of the drug.90
Native And Acquired Resistance To Infection With Cryptococcus Neoformans
Published in Hans H. Gadebusch, Phagocytes and Cellular Immunity, 2020
The mechanism for the release of lysosomal enzymes from leukocytes is apparently more complex than had hitherto been thought (reviewed by Silverstein et al.,76 Schorlemmer et al.,43 and Zurier et al.77). Acid hydrolase release into the surrounding medium usually is associated with particle ingestion, can be enhanced by compounds that elevate cyclic GMP (cGMP) levels, and is inhibited by removal of Ca2+ from the extracellular medium,72 but may also occur in the absence of ingestion. It has been postulated that free calcium locally available in the cytoplasm leads to fusion of the lysosome with a specific region of the plasma membrane78 resulting in release of enzymes. Cytochalasin B, an inhibitor of phagocytosis, is thought to potentiate this effect.78,79
A Histopathologic Classification of Chemical-Induced Injury of the Liver
Published in Robert G. Meeks, Steadman D. Harrison, Richard J. Bull, Hepatotoxicology, 2020
John M. Cullen, Boris H. Ruebner
“Bland” cholestasis is most often seen in humans after administration of certain drugs such as contraceptive or anabolic steroids (Figure 11). However, a similar pattern is also produced by several naturally occurring compounds such as icterogenin, a triterpene pentacyclic alkaloid found in the plant Lippia rehmani (Arias, 1963). Cattle, sheep, rabbits, and rats are susceptible to this compound (Bullock et al., 1974). Triterpenes, lantadene A and B, which occur in the plant Lantana camara can also produce a similar pattern of cholestasis in ruminants (Seawright, 1972; Gopinath and Ford, 1969). Cytochalasin B, a fungal alkaloid, can, like anabolic steroids, produce canalicular cholestasis through its disruptive action on cytoplasmic microtubules which appear necessary for movement of bile through canaliculi (Phillips et al. 1978, 1983). In low doses, phalloidin, another fungal toxin produced by Amanita phalloides, can also produce cholestasis (Watanabe and Phillips, 1986). Other agents capable of causing cholestasis without associated inflammatory lesion include endotoxins, and manganese in excessive quantities (Zimmerman et al., 1979; Lustig et al., 1982; Witzleben, 1972; Phillips et al., 1978).
Methanol extracts of Teucrium arduini L. and Teucrium flavum L. induce protective effect against mitomycin C in human lymphocytes in vitro
Published in Drug and Chemical Toxicology, 2022
Aleksandra Marković, Jovana Tubić Vukajlović, Darko Grujičić, Marina Radović Jakovljević, Milan Stanković, Katarina Djordjević, Ninoslav Djelić, Milena Radaković, Olivera Milošević-Djordjević
The CBMN assay was performed as previously described by Fenech and Morley (1985), with few modifications. Heparinized whole blood (0.5 mL) was cultivated in the complete medium for lymphocyte cultivation PBMax Karyotyping (Invitrogen, California, USA) and incubated at 37 °C for 72 h. After 24 h of incubation, cultures were treated with methanol extracts of the investigated plants separately, at four different concentrations (125, 250, 500 and 1000 μg/mL) in a small volume (0.1 mL). Mitomycin C (MMC, Sigma, St. Louis, MO, USA) was concomitantly added to cell cultures at the concentration of 0.5 μg/mL. Forty-four hours after the beginning of incubation, cytochalasin B (Sigma, St. Louis, MO, USA) was added at a final concentration of 4 μg/mL. At the same time, negative (untreated cells) and positive (only MMC) controls were set up. At the end of the incubation period the cells were centrifuged and treated with cold (4 °C) hypotonic solution (0.56% KCl). After that the cells were fixed with a fixative methanol : glacial acetic acid = 3 : 1, three times. The suspended cells were dropped onto clean slides, where first dried under a lamp and then in air. Slides stained with 2% Giemsa (Alfapanon, Novi Sad, Serbia).
A comparative study of genotoxicity endpoints for women exposed to different levels of indoor radon concentrations
Published in International Journal of Radiation Biology, 2022
Tiberius Dicu, Piroska Virag, Ioana Brie, Maria Perde-Schrepler, Eva Fischer-Fodor, Bogdan Victor, Alexandra Cucoș, Bety-Denissa Burghele
CBMNA is one of the most used methods for assessing unstable chromosomal aberrations, such as acentric chromosomal fragments, detectable in interphase as micronuclei. The technique, according to Fenech’s protocol (Fenech 2000), uses Cytochalasin B to block the cytokinesis process. PBMCs cultured from both exposed groups and reference groups were treated with Phytohemagglutinin M (PHA) (Sigma-Aldrich, USA) to stimulate cell division and to ensure maximum yield of binucleated cells (20 μg PHA/ml cell culture). Cytochalasin B (Cyt B) (Sigma-Aldrich, USA) was added after 44 h of incubation (6 μg Cyt B/ml cell culture) and cells were harvested by cytocentrifugation at the end of the 28 h incubation with Cytochalasin B. Finally, the cells were stained with Giemsa 10% and examined at 1000× magnification.
Small is beautiful: low activity alpha and gamma sources for small-scale radiation protection research experiments
Published in International Journal of Radiation Biology, 2021
Magdalena Płódowska, Milagrosa Lopez-Riego, Pamela Akuwudike, Daniel Sobota, Mateusz Filipek, Mariusz Kłosowski, Urszula Kaźmierczak, Beata Brzozowska, Agnieszka Baliga, Halina Lisowska, Janusz Braziewicz, Paweł Olko, Lovisa Lundholm, Andrzej Wojcik
For experiments with the low dose gamma source at the Jan Kochanowski University in Kielce cells were seeded out at low density on 90 mm-diameter plastic dishes containing 10 ml of medium and stacked on the source inside an incubator for 192 hours (8 days) resulting in an averaged dose of 10.5 mGy to cells in stack position 1 and 5.9 mGy to cells in stack position 2 (see Section ‘Dosimetry’ below and Table 2 for more details). Control cells were grown in the same incubator but outside the range of gamma radiation. Cells were passaged every 72 h. Cytochalasin B (Sigma-Aldrich) was added at a final concentration of 5.6 µg/ml for the final 24 h of incubation time. After 192 h cells were trypsinised, transferred to centrifuge tubes, spun down and resuspended in warm (37 °C) 0.14 M KCl (Sigma-Aldrich). After a 5 min incubation time at room temperature, the cells were centrifuged and fixed in fixative I (methanol: 0.9% NaCl: acetic acid (Sigma-Aldrich); 12:13:3) and subsequently in fixative II (methanol: acetic acid; 4:1). Following 2–3 washes with fixative II cells were dropped onto clean, dry microscopic slides (Menzel-Glaser, Germany), dried and stained with 5% Giemsa (Merck, Germany) for 10 min. Three independent experiments were performed. Blinded slides were analyzed for MN by two independent scorers and their results were pooled. The total number of scored binucleated cells was 4852 for controls, 4444 for 5.9 Gy and 3897 for 10.5 Gy. A total of 1500 nuclei per treatment group were scored for estimating the percentage of binucleated cells.