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  • 1
    ISSN: 1573-0646
    Keywords: AZQ ; tumor cells ; cell cycle ; nondividing cells ; synchrony
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The anticancer agent 1,4-cyclohexadiene-1,4-dicarbonic acid, 2,5-bis(aziridinyl)-3,6-dioxo-, diethyl ester (AZQ) (NSC 182986) was studied in vitro to determine survival, cell cycle stage sensitivity, and cell cycle kinetics effects. One hour treatments with AZQ doses ranging from 1 μg/ml to 25 μg/ml revealed that human stomach tumor clones were most sensitive of three cell types studied to the killing effects of AZQ; this sensitivity was followed in order by human astrocytomas and Chinese hamster ovary (CHO) cells. Depending on the AZQ dose, nondividing CHO cells were 10 to 180 times more sensitive than dividing CHO cells. Synchronized CHO cells were most sensitive to AZQ's killing effects when treated at the late S/G2 phase boundary, with the overall order of sensitivity being late S/G2, G2, mid-S, and G1 phase. Mitotic cells were neither killed by doses used in these studies, nor were they inhibited in their progression from mitosis into the G1 phase. Synchronized CHO cells treated in all other phases of the cell cycle were either blocked completely or delayed for up to 2 hours in their progression through the cell cycle. Flow microfluorometry (FMF) studies on exponentially growing CHO cells demonstrated that even at noncytotoxic doses (1 μg/ml), AZQ caused very large, but reversible enrichments of cells in the S and G2 phases of the cell cycle. Since AZQ has already been shown to be effective against a variety of animal and human tumors (especially brain tumors) the data reported here may be useful in designing more effective treatment schedules and drug combination regimens.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2014-02-03
    Description: Total filterable and colloidal metals were measured in the Tamar Estuary. The colloidal fraction (Mc) was highly variable for each metal, both spatially and temporally. In April 2001, Alc and Coc were higher in the river than the estuary, Cdc, Crc and Pb c were lower, and Mnc and Uc were similar. In September 2001, Cdc was higher in the river than the estuary. Colloidal Al and Mn were positively correlated with concentrations of suspended particles, whereas the colloid contents of the other metals were primarily determined by additional factors. The effect of the colloidal metal content on resultant metal filtrate concentrations, as a function of sample volume filtered, was examined. The amount of Al, Cd, Cu, Pb, and U in the filtrate decreased significantly in at least one case, whereas Mn initially increased in some cases. There was no change for Co, Cr, and Zn. The implications of these results for the study of trace metals in moderately turbid estuaries are discussed. © CSIRO 2006.
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2014-02-04
    Description: This work presents the optimisation, validation and field deployment of a voltammetric in situ profiling (VIP) system for the simultaneous determinations of dynamic Cd(II), Cu(II) and Pb(II) in estuarine and coastal waters. Systematic studies in NaNO3 (as a supporting electrolyte) and seawater, indicated that variations in ionic strength, pH and dissolved oxygen did not affect the response of the instrument, whereas an Arrhenius type temperature response was observed. The VIP instrument allows the determination of 2-3 samples h-1, and has a detection limit (defined as 3σ) in seawater for Cd(II): 23 pM, Cu(II): 1.13 nM, and Pb(II): 23 pM. The VIP system accurately measured the total dissolved concentrations of Cd(II), Cu(II) and Pb(II) in two certified reference materials; SLRS-3, a river water, and SLEW-2, an estuarine water. Field evaluation of the instrumentation and analytical methods was achieved through a series of surveys in the Plym Estuary (Devon, UK), from which environmental data are presented.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2014-01-27
    Description: This paper presents the results of an inter-comparison exercise undertaken to test the reliability and performance of a voltammetric in situ profiling system (VIP system) and carried out by partners based in Italy, Sweden, Switzerland and the UK. The VIP system was designed to allow in situ simultaneous monitoring of the dynamic fractions (i.e. the maximum potentially bioavailable fractions) of Cu(II), Pb(II) and Cd(II) in natural waters at a frequency of 2-3 analyses h - 1. The four participating groups used the VIP systems under laboratory conditions to determine dissolved concentrations of Cu, Pb and Cd in river, estuarine and coastal water reference materials (SLRS-3/4, SLEW-2/3 and CASS3/4, respectively). The accuracy of the VIP method was comparable to that of established methodologies, including inductively coupled plasma mass spectrometry and voltammetric methods using mercury-electrodes. The VIP systems were also applied to determine the dynamic fractions of the target analytes in freshly collected samples ex situ, as well as in situ in contrasting European marine waters. There was good agreement between the concentrations of the dynamic metal fractions determined in laboratory analyses, and observed during the simultaneous deployment of up to five VIP instruments for periods of several hours in coastal waters. The simultaneous in situ deployment of two VIP instruments in an estuary showed a consistent analytical performance over several days of continuous operation. The results of this inter-comparison exercise show that the VIP system is a reliable submersible probe for accurate, sensitive and high resolution in situ monitoring of dissolved metal fractions in the picomolar (Cd, Pb) and nanomolar (Cu) concentration ranges. © 2009 Elsevier B.V. All rights reserved.
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2014-08-01
    Description: In recent environmental legislation, such as the Water Framework Directive in the European Union (WFD, 2000/60/EC), the importance of metal speciation and biological availability is acknowledged, although analytical challenges remain. In this study, the Voltammetric In situ Profiler (VIP) was used for high temporal resolution in situ metal speciation measurements in estuarine waters. This instrument simultaneously determines Cd, Cu and Pb species within a size range (ca〈4. nm) that is highly relevant for uptake by organisms. The colloidal metal fraction can be quantified through a combination of VIP measurements and analyses of total dissolved metal concentrations.VIP systems were deployed over tidal cycles in a seasonal study of metal speciation in the Fal Estuary, southwest England. Total dissolved concentrations were 4.97-315. nM Cu, 0.13-8.53. nM Cd and 0.35-5.75. nM Pb. High proportions of Pb (77 ± 17) and Cu (60 ± 25) were present as colloids, which constituted a less important fraction for Cd (37 ± 30). The study elucidated variations in the potentially toxic metal fraction related to river flow, complexation by organic ligands and exchanges between dissolved and colloidal phases and the sediment. Based on published toxicity data, the bioavailable Cu concentrations (1.7-190. nM) in this estuary are likely to severely compromise the ecosystem structure and functioning with respect to species diversity and recruitment of juveniles. The study illustrates the importance of in situ speciation studies at high resolution in pursuit of a better understanding of metal (bio)geochemistry in dynamic coastal systems. © 2011 Elsevier Ltd.
    Type: Article , PeerReviewed
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  • 6
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    American Chemical Society
    In:  In: Environmental Electrochemistry. ACS Symposium Series, 811 . American Chemical Society, pp. 73-101. ISBN 9780841237742
    Publication Date: 2014-02-04
    Description: The increasing environmental pressures on estuarine and coastal waters call for improved monitoring techniques of chemical constituents to aid management decisions. Automated stripping voltammetry is a suitable technique for continuous, near real-time monitoring of trace metals in marine systems. This contribution describes the application of voltammetric monitoring techniques in estuarine and coastal waters of the UK and Spain. The high spatial and temporal resolution of the data obtained, allows a thorough interpretation of the trace metal sources and behaviour. Future trends in this field research include submersible sensors which can be remotely deployed for a period of several weeks.
    Type: Book chapter , NonPeerReviewed
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  • 7
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    Elsevier
    In:  TrAC - Trends in Analytical Chemistry, 22 (11). pp. 828-835.
    Publication Date: 2020-05-04
    Description: Developments in instrument miniaturisation and automation have resulted in the manufacture of portable electrochemical instrumentation for continuous trace-metal measurements from the banks of estuaries and on board ships. The most recent developments in flow cells with gel-coated iridium (Ir) micro-electrode arrays have resulted in submersible in situ voltammetric probes that allow long-term trace-metal monitoring at sub-nanomolar concentrations in coastal waters. This article overviews the design and the application of field-deployable voltammetric instrumentation for trace-metal monitoring. © 2003 Published by Elsevier B.V.
    Type: Article , PeerReviewed
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