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The embryo in recurrent implantation failure
Published in Efstratios M. Kolibianakis, Christos A. Venetis, Recurrent Implantation Failure, 2019
Confocal laser scanning microscopy has also highlighted the presence of tripolar and tetrapolar spindles with the characteristic Y- and cruciform X-shaped organization, at cleavage and early blastocyst stages, respectively, in human embryos, following labeling with antitubulin antibodies and a DNA-specific fluorochrome.9 As there are no checkpoints to monitor excess spindle poles, multipolar spindles progress in the cell cycle and lead to chaotic chromosomal constitutions. This study provided the first direct evidence of spindle abnormalities throughout human preimplantation development, and led to the realization that nuclear and chromosomal aberrations are interrelated through abnormalities in cytokinesis and spindle formation.9
Antitubulin Agents
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
Paclitaxel’s mechanism of action involves the stabilization of microtubules and their protection from disassembly, thus interfering with their normal breakdown during cell division (Figure 4.3). This contrasts with the mechanism of action of colchicine, the Vinca alkaloids, and eribulin which facilitate tubulin disassembly. Chromosomes are thus unable to achieve a metaphase spindle configuration which blocks the progression of mitosis. Prolonged activation of the mitotic checkpoint triggers apoptosis or reversion to the G-phase of the cell cycle without cell division. Thus, morphologically, paclitaxel-treated cells have defects in mitotic spindle assembly, chromosome segregation, and cell division. Interestingly, suppression of microtubule dynamics occurs at concentrations lower than those needed to block mitosis. At higher therapeutic-relevant concentrations, paclitaxel suppresses microtubule detachment from the centrosomes, a process normally activated during mitosis. These observations have led researchers to the conclusion that chromosome mis-segregation on highly abnormal, multipolar spindles may be the cause of cell death rather than mitotic arrest (Figure 4.14). (Left) Molecular model of paclitaxel (shown in yellow) interacting with the β-subunit (blue) of tubulin, itself dimerized to the α-subunit (red). (Right) Details of the paclitaxel-induced hyperstabilization of the β subunit of tubulin that interferes with normal function of microtubule breakdown. The M-loop of the taxane ring is essential for binding, in particular involving residues Pro274, Leu275, Thr276, Ser277, and Arg278. The hydrogen bonds are shown in green.
Strategies for the drug discovery and development of taxane anticancer therapeutics
Published in Expert Opinion on Drug Discovery, 2022
Changwei Wang, Angelo Aguilar, Iwao Ojima
Substantial amount of work has been focusing on determining and understanding the taxane binding site [10]. However, a study using a breast cancer model argues the intratumoral paclitaxel concentration produced by standard paclitaxel treatment regimen is not sufficient to initiate mitotic arrest of breast cancers [64]. It was suggested that it is likely the clustering of multipolar spindles into bipolar spindles that is responsible for paclitaxel resistance, rather than the lower intratumoral paclitaxel concentration. It was shown that longer duration of multipolarity increased instability of chromosome and conversely decreasing its duration increased cell survival and decreased sensitivity to paclitaxel treatment. Thus, the level of chromosomal stability of breast cancer patients was shown as a biomarker to determine whether they are sensitive to multipolar divisions triggered by paclitaxel treatment [64].
Magnetic field direction differentially impacts the growth of different cell types
Published in Electromagnetic Biology and Medicine, 2018
Xiaofei Tian, Dongmei Wang, Meng Zha, Xingxing Yang, Xinmiao Ji, Lei Zhang, Xin Zhang
PC9 cells were plated on coverslips in 35-mm cell culture plates with or without magnetic field exposure. After 3 days, cells were washed once with PBS and fixed by precooled methanol (−20 °C) for 5 min. Then, the coverslips were washed with TBS-Tx (TBS supplemented with 0.1% Triton X-100) and blocked by AbDil-Tx [TBS-Tx with 2% (wt/vol) BSA and 0.5% sodium azide] at room temperature at least for 30 min. Coverslips were stained with anti-β-tubulin antibody (TransGen Biotech) at room temperature for 2 h, followed by fluorescently conjugated secondary antibodies (Thermo Fisher Scientific) at room temperature for 1 h. After washed with TBS-Tx, coverslips were mounted in anti-fade Prolong Gold mounting medium with DAPI (Invitrogen). Leica DMI4000B fluorescent microscope was used to get immunofluorescence images. Then, we used Adobe Photoshop software to count the numbers of cells in different cell cycle stages, including interphase, prophase, prometaphase, metaphase, anaphase and telophase. We also counted the numbers of cells with multipolar spindles. Mitotic index is the percentage of cells in mitosis.
Evaluation of toxicological and antimicrobial activity of lavender and immortelle essential oils
Published in Drug and Chemical Toxicology, 2021
Aner Mesic, Irma Mahmutović-Dizdarević, Emina Tahirović, Irma Durmišević, Izet Eminovic, Anesa Jerković-Mujkić, Renata Bešta-Gajević
The results of the cytogenetic analysis conducted in root meristems of A. cepa showed diverse genotoxic effects when lavender and immortelle oils were evaluated. The observed CAs were sticky chromosomes, chromosome bridges, vagrant chromosomes, chromosome missegregation and mutipolarity. As for genotoxicity testing performed in human lymphocytes, different structural aberrations were detected, with only significant incidence in the frequency of minute fragments induced by the immortelle EO. The chromosome stickiness is one of the major and most frequent alteration observed in the present study. Stickiness indicates a highly toxic and irreversible lesion leading to cell death (Herrero et al. 2012). Chromosome bridges arise from the chromatid or chromosome breaks and fusions, chromosome stickiness, defects in cohesion complex degradation as well as from DNA repair, triggered chromosome fusion (Gomurgen 2005; Eminovic et al. 2016; Pampalona et al. 2016). In the animal somatic cells a chromosome bridge may result in a number of different scenarios including chromosome breakage, aneuploidy, polyploidy and possibly cell cycle arrest (Pampalona et al. 2016). Vagrant chromosomes are indicators of spindle poisoning and irregularity, and lead to the unequal chromosome segregation in the daughter nuclei, as well as formation of daughter cells with unequal sized or irregularly shaped nuclei at interphase (El-Ghamery et al. 2003; Rank 2003). The improper chromosome segregation may indicate mitotic spindle disturbance (Herrero et al. 2012). It has been demonstrated that the cells with more than two centrosomes can undergo anaphase with multipolar spindles and segregate chromosomes incorrectly to more than two daughter cells. This lethal process selectively targets the cancer cells with the extra centrosomes, avoiding normal cells with two centrosomes (Galimberti et al. 2011).