Mass Spectrometric Analysis
Adorjan Aszalos in Modern Analysis of Antibiotics, 2020
Siderophores, compounds that bind iron, are another type of ionophore antibiotic. Pyochelin (8) is a recently studied siderophore whose structure was rigorously elucidated, in part by mass spectrometry [272]. The molecular weight (324) and elemental composition were determined by high-resolution FD. Ferripyochelin, obtained by treating pyochelin with ferric chloride, gave FD ions at m/z 378 (that is, 322 + Fe) and 413 (322 + Fe + Cl). The FD spectrum of pyochelin also gave evidence for a carboxylic acid group with an ion corresponding to (M - COOH)+; this is supported by a mass increase of 14 after reaction of the antibiotic with diazomethane. Ions at m/z 146 and 178 in both FD and El spectra suggest the molecule fragments in two pieces, both capable of carrying a positive charge. Pyochelin is presumed to be biosynthesized from one molecule of salicyclic acid and two of cysteine.
Impact of Probiotics on Animal Health
Marcela Albuquerque Cavalcanti de Albuquerque, Alejandra de Moreno de LeBlanc, Jean Guy LeBlanc, Raquel Bedani in Lactic Acid Bacteria, 2020
Increasing evidences led the World Health Organization (WHO) to become aware of the importance of this subject, suggesting periodically over the last few years the phase out or even the complete banishment of using AGPs (WHO 1997, 2004, 2017). The European Commission (EC) banned the marketing and use of AGPs in feed nutrition since January 1st 2006 (EC Regulation No. 1831/2003), although ionophores continue to be administered (Economou and Gousia 2015). In the United States, the use of fluoroquinolones in poultry was banned in 2005. After that, the rise of fluoroquinolone-resistant Campylobacter infections in humans has significantly decreased (FDA 2018). However, other than this action, little has been effectively done by regulatory authorities to reduce inappropriate and unnecessary use of antibiotics on livestock. In South America, Brazil, known as the second largest poultry producer (Ferreira et al. 2018), following the recommendations of the international agencies such as Food and Agriculture Organization of the United States (FAO), OIE World Organization for Animal Health, and the EC, and based on scientific evidence for the analysis of risks associated with veterinary drug residues in foods, has restricted since 1998 the use of antibiotics avoparcin, amphiphilic, tetracyclines, penicillins, cephalosporins, quinolones, sulfonamides, erythromycin, spiramycin, and recently colistin (Bezerra et al. 2017).
Where Cancer and Bacteria Meet
Ananda M. Chakrabarty, Arsénio M. Fialho in Microbial Infections and Cancer Therapy, 2019
Ionophores promote ion transport across lipid bilayers and include a large number of naturally occurring molecules. External disruption of the ion permeability of membranes disturbs the normal ion balance, a property that can be exploited in the induction of cell death (apoptosis, autophagy, or necrosis), including that of tumor cells, or the elimination of harmful microorganisms. While anion-selective ionophores (anionophores) are much less common than cationophores, they have attracted intense interest over the last two decades. Anionophores are natural products that facilitate transmembrane anion transport across phospholipid bilayers [54]. This capability is crucial for the maintenance of the concentration gradients that form the basis for signaling and cellular regulation.
A retrospective analysis of artificial oocyte activation in patients with low or no fertilisation in intracytoplasmic sperm injection cycles
Published in Journal of Obstetrics and Gynaecology, 2022
Kevin K. W. Lam, Jacki Y. Y. Wong, Tak-Ming Cheung, Raymond H. W. Li, Ernest H. Y. Ng, William S. B. Yeung
Calcium ionophores are lipid soluble molecules. They transport calcium ions across the cell membrane which in turn induce a single transient rise in intracellular calcium level. When used for AOA, the concentration of A23187 varies from 5–10 µM (Montag et al. 2012; Lv et al. 2020). Although the concentration of the ready-to-use A23187 reagent is not disclosed by the manufacturer, it has been shown to induce a single rise in intracellular calcium to a peak within two minutes (Nikiforaki et al. 2016). The safety and efficacy of the ready-to-use A23187 has been proven in previous studies (Ebner et al. 2012; Caglar et al. 2015; Ebner et al. 2015). Exposure of A23187 in conjunction with calcium chloride injection together with spermatozoon has also been reported (Vanden Meerschaut et al. 2012). Our data indicated that the performance of two protocols were comparable. The observation is understandable as the injection of calcium chloride and the subsequent A23187 exposure might increase the intracellular calcium concentration to a level higher than that using A23187 alone, both protocols could not generate calcium oscillations (Nikiforaki et al. 2016). To the best of our knowledge, there is no commercially available mouse embryo-tested calcium chloride for AOA. The calcium chloride solution was mainly prepared from research grade chemicals (Vanden Meerschaut et al. 2012; Nikiforaki et al. 2016), the safety of which is in doubt. Based on the current data, AOA should be performed without the concomitant injection of calcium chloride.
Artificial oocyte activation: physiological, pathophysiological and ethical aspects
Published in Systems Biology in Reproductive Medicine, 2019
George Anifandis, Alexandros Michopoulos, Alexandros Daponte, Katerina Chatzimeletiou, Mara Simopoulou, Christina I. Messini, Nikolas P. Polyzos, Katerina Vassiou, Konstantinos Dafopoulos, Dimitrios G. Goulis
Currently, AOA with ionophores is performed with caution, given the possible risk of epigenetic defects that may emerge from its application. The reason is that the most Ca+2 agents may cause Ca+2 release but not in physiological levels (maybe under- or supra-physiological). Nevertheless, this Ca+2 release drives fundamental downstream events that may result in different gene expression patterns (Ebner and Montag 2016). Moreover, culture media always is a threat and a possible risk for epigenetic defects (Simopoulou et al. 2018). Last, the fact that both gametes and preimplantation embryos have a high metabolizing rate that might regulate the epigenetic process might inevitably lead to epigenetic defects (Koscinski et al. 2018). Many assisted reproduction centers apply AOA only in couples that have recurrent implantation failures after ICSI. Follow-up studies about the health of the newborns are still lacking. In the United Kingdom, AOA has not been prohibited, while in other European countries, AOA is performed whenever is considered appropriate, without any specific legal context. No studies with ionophores have been conducted in the United States, while a study from Korea suggested that AOA is a useful method to ensure fertilization in ICSI cycles, in selected patients with low fertilization rate (Kang et al. 2015).
Ca2+ mediates extracellular vesicle biogenesis through alternate pathways in malignancy
Published in Journal of Extracellular Vesicles, 2020
Jack Taylor, Iman Azimi, Gregory Monteith, Mary Bebawy
Using pharmacological modulators of Ca2+ release together with topographical AFM analysis we show that intracellular calcium mobilization is required for plasma membrane EV biogenesis. The Ca2+ ionophore, A23187 (1 µM) was used to study the effect of increasing intracellular Ca2+ on malignant (MCF-7 and Dx) cell and non-malignant (hCMEC-D3) cell vesiculation (Figure 1). Ca2+ ionophores mobilize Ca2+ through the translocation of Ca2+-ionophore complexes across the plasma membrane, activation of native plasma membrane Ca2+ channels, and via mobilization of Ca2+ from the ER [58].
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