A Edwards

Säteilyturvakeskukseen, Helsinki, Uusimaa, Finland

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Publications (9)17.11 Total impact

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    ABSTRACT: The possibility of genotoxicity of radiofrequency radiation (RFR) applied alone or in combination with x-rays was investigated in vitro using several assays on human lymphocytes. The chosen specific absorption rate (SAR) values are near the upper limit of actual energy absorption in localized tissue when persons use some cellular telephones. The purpose of the combined exposures was to examine whether RFR might act epigenetically by reducing the fidelity of repair of DNA damage caused by a well-characterized and established mutagen. Blood specimens from 14 donors were exposed continuously for 24 h to a Global System for Mobile Communications (GSM) basic 935 MHz signal. The signal was applied at two SAR; 1 and 2 W/Kg, alone or combined with a 1-min exposure to 1.0 Gy of 250 kVp x-rays given immediately before or after the RFR. The assays employed were the alkaline comet technique to detect DNA strand breakage, metaphase analyses to detect unstable chromosomal aberrations and sister chromatid exchanges, micronuclei in cytokinesis-blocked binucleate lymphocytes and the nuclear division index to detect alterations in the speed of in vitro cell cycling. By comparison with appropriate sham-exposed and control samples, no effect of RFR alone could be found for any of the assay endpoints. In addition RFR did not modify any measured effects of the x-radiation. This study has used several standard in vitro tests for chromosomal and DNA damage in Go human lymphocytes exposed in vitro to a combination of x-rays and RFR. It has comprehensively examined whether a 24-h continuous exposure to a 935 MHz GSM basic signal delivering SAR of 1 or 2 W/Kg is genotoxic per se or whether, it can influence the genotoxicity of the well-established clastogenic agent; x-radiation. Within the experimental parameters of the study in all instances no effect from the RFR signal was observed.
    No preview · Article · Jun 2006 · International Journal of Radiation Biology
  • P Hone · D Lloyd · M Szłuińska · A Edwards
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    ABSTRACT: Cultured human blood lymphocytes were exposed during the S/G2 phases of the cell cycle to continuous extremely low frequency (50 Hz) electromagnetic fields of 0.23, 0.47 or 0.7 mT either alone or immediately after an acute exposure to 1.0 Gy of gamma rays. The ionising radiation, as expected, induced chromosomal aberrations of the chromatid-type observed at the next metaphase. The field applied alone did not induce chromosomal damage nor did it modify the frequency of aberrations caused by the gamma rays.
    No preview · Article · Feb 2006 · Radiation Protection Dosimetry
  • C Lindholm · A Edwards
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    ABSTRACT: To investigate whether translocations in 'stable' lymphocytes, i.e. those not containing unstable aberrations in any chromosome including counterstained ones, would have a longer persistence with time compared with those measured in all cells. The time-course of chromosomal aberrations in the three most highly exposed radiation victims of an Estonian accident in November 1994 was followed for 7 post-accident years encompassing 15 samples. Chromosome painting was performed using probes for chromosomes 1, 2 and 4 with a pan-centromeric probe, and chromosomal aberrations involving the painted chromosomes were scored using a developed version of the Protocol for Aberration Identification and Nomenclature Terminology (PAINT) nomenclature. Metaphases containing aberrations were captured with an image analyser and stored on a computer. An earlier analysis of aberrations in the painted portion of the genome was performed in all cells, irrespective of the possible aberrations in the unpainted part of the genome. The present analysis has taken into account the 'stable/unstable' nature of the complete cell. Evaluation was performed on images, counting all chromosomes and checking the counterstained chromosomes for unstable aberrations, i.e. dicentrics, acentrics or ring chromosomes. In the original analyses of all cells, a decrease in translocation frequency in the early samples was observed. In the present study of stable cells, the results showed that the yield of translocations is constant with time. The results show that translocations observed in stable cells are persistent with time. This implies that retrospective dosimetry and calibration should be performed using stable cells. To obtain more information on this issue, the stability status of all cells in any future fluorescence in situ hybridization follow-up of a radiation accident should be noted.
    No preview · Article · Sep 2004 · International Journal of Radiation Biology
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    ABSTRACT: The purpose of this paper is to investigate how well various assays on blood can detect radiation dose to people exposed many years previously and, if possible, to estimate that dose. The assays were applied to persons resident close to Chernobyl in 1986. Blood samples were taken 13-15 years after the reactor accident. The assays used were the frequencies of lymphocyte chromosomal translocations, micronuclei, HPRT mutations and apoptotic cells. Translocation yields in the exposed groups were marginally higher than in their respective controls, leading to dose estimates of about 0.2 Gy but with large uncertainties. All other assays showed inconsistency from person to person or other variations apparently not related to dose. The measurement of translocations, it is concluded, is the biological method of choice for retrospective dosimetry.
    No preview · Article · Feb 2004 · Radiation Protection Dosimetry
  • D Lloyd · P Hone · A Edwards · R Cox · J Halls
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    ABSTRACT: G(0) human blood lymphocytes were irradiated with 2.0 Gy gamma-rays and cultured to metaphase whilst held in a 50-Hz power frequency magnetic field of 0.23, 0.47 or 0.7 mT. No differences were found in the frequencies of gamma-induced chromosome aberrations observed in cells held in the EM fields compared with replicates held in a sham coil. Similar field conditions have been reported to increase the frequency of gamma-induced HPRT mutations, leading to a suggestion that the EM fields alter the fidelity of repair of genomic lesions. This was not confirmed by the chromosome aberration assay described here.
    No preview · Article · Feb 2004 · Cytogenetic and Genome Research
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    P Hone · A Edwards · J Halls · R Cox · D Lloyd
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    ABSTRACT: Epidemiology has shown an association between exposure to extremely low frequency (ELF) electromagnetic fields (EMF) and childhood leukaemia. The causal nature and biological basis of this association are however questionable. Studies with aneuploid cell lines raised the hypothesis that ELF EMF may act as a coleukaemogen by compromising DNA damage response to genotoxic agents such as ionising radiation. We examined this hypothesis using gamma-ray-induced dicentric chromosome exchange in human lymphocytes. The results from 12 h post-gamma-ray exposure to fields of 0.23, 0.47 and 0.7 mT provide no support to the hypothesis. The power of the study was sufficient to exclude an ELF enhancement of chromosomal exchange of 10-15% (2SE).
    Full-text · Article · Jul 2003 · British Journal of Cancer
  • C Lindholm · H Romm · G Stephan · E Schmid · J Moquet · A Edwards
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    ABSTRACT: To perform an interlaboratory comparison of FISH chromosome painting and to study the time-course of translocations and dicentrics in three accident victims exposed to radiation. Also, to use the data in the validation of the FISH technique as a retrospective dosimeter. Twelve blood samples were collected during 4 years from three subjects exposed to radiation in an accident in Estonia in 1994 involving gamma-radiation from a 137Cs source. Two of the subjects were exposed during approximately 7 h, both receiving a protracted dose of about 1 Gy and also localized exposure. The third subject received a protracted whole-body dose of 2.7 Gy during 4 weeks as well as a short-term partial-body dose. Preparations from 48-h metaphase cultures were painted by the FISH technique using routine methods and probe cocktails in four laboratories. Samples from each subject were analysed in two different laboratories that used different combinations of whole chromosome probes. The PAINT nomenclature was applied when recording chromosome aberrations. The intercomparison of FISH analysis data showed reasonable similarities between laboratories, the largest discrepancy being 21% in the frequency of two-way translocations in subject 3. Half-time calculations, based on combined data sets from two laboratories, showed that dicentrics decreased rapidly with half-times of approximately 2 years. In all cases, the initial dicentric yields were lower than the initial translocation yields. During the 4-year follow-up, the frequencies of all translocations in cells containing only simple rearrangements fell on average to about 65% of their initial value. Two-way translocations were slightly more persistent than all translocations. The average half-time was about 8 years for two-way translocations and around 6 years for all translocations. Cells containing complex rearrangements were few in number and they disappeared with time. In general, the inclusion of complex cells caused a more rapid fall in aberration yield. In general, the results imply that relatively consistent scoring data were obtained with different chromosome painting protocols. They also support the idea that the reduction of translocations with time is associated with partial-body irradiation.
    No preview · Article · Nov 2002 · International Journal of Radiation Biology
  • A Edwards · N Maznik · J Moquet · P Hone · V Vinnikov · D Lloyd · R Cox
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    ABSTRACT: Data are presented for a subset of lymphocytes characterized by FISH as missing painted chromosomal material. These lymphocytes occur in both control and irradiated subjects. These cells have a much greater frequency of one-way translocations than cells in which all of the painted chromosomal material is present. Their presence contributes to interindividual variability in control translocation yields. These cells do not appear to be more prevalent in persons exposed to high radiation doses. It is suggested that their exclusion when selecting cells for analysis may improve the sensitivity of FISH as a biological dosimeter at low doses. Mechanisms for the production of these one-way translocations in vivo are also discussed, with a proposal that their variable frequency in individuals may be consistent with exposure to chemical clastogens.
    No preview · Article · May 2002 · Radiation Research
  • I Sorokine-Durm · C. Whitehouse · A Edwards
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    ABSTRACT: This paper represents a summary of discussion and an analysis of control data from those groups present at the workshop of the European Union (EU) Concerted Action on FISH biological dosimetry. Despite acknowledged uncertainties there is a reasonable measure of agreement between the laboratories on data interpretation once the strong age dependence on translocation frequency is accounted for. The results give good hope that a generic age-related control level for chromosome translocation can be ascribed for the purposes of retrospective dosimetry using FISH.
    No preview · Article · Mar 2000 · Radiation Protection Dosimetry