The micronucleus assay as a biological dosimeter of in vivo ionising radiation exposure (original) (raw)
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Micronucleus-Centromere Assay to Measure Ionizing Radiation Damage of Low Dose Occupational Exposure
OBM Genetics, 2018
Background: The purpose of study was to assess the cytogenetic effect of chronic low dose radiation exposure of nuclear power plant workers using the micronucleus centromere assay. This method allows the differentiation between centromere-positive micronuclei containing whole chromosome and centromere-negative micronuclei containing acentric fragment pointing to clastogenic action of ionizing radiation. Methods: The effect of low dose occupational exposure was estimated in 32 nuclear power plant workers using in situ hybridization (FISH) with the human pancentromeric DNA probe for peripheral blood lymphocytes. Group of 17 persons from the administrative staff served as reference control group. Results: Data on the number of micronuclei, centromere-positive micronuclei and centromere-negative micronuclei per 1000 binucleated cells for the workers were significantly higher compared with the control group (p = 0.001, p=0.01 and p=0.002 respectively). No differences in the studied indicators between smokers and non-smokers
Molecular Medicine Reports, 2016
The aim of the present study was to perform cytogenetic analysis by means of a semi-automated micronucleus-centromere assay in lymphocytes from medical radiation workers. Two groups of workers receiving the highest occupational doses were selected: 10 nuclear medicine technicians and 10 interventional radiologists/cardiologists. Centromere-negative micronucleus (MNCM-) data, obtained from these two groups of medical radiation workers were compared with those obtained in matched controls. The blood samples of the matched controls were additionally used to construct a 'low-dose' (0-100 mGy) MNCM-dose-response curve to evaluate the sensitivity and suitability of the micronucleus-centromere assay as an 'effect' biomarker in medical surveillance programs. The physical dosimetry data of the 3 years preceding the blood sampling, based on single or double dosimetry practices, were collected for the interpretation of the micronucleus data. The in vitro radiation results showed that for small sized groups, semi-automated scoring of MNCM-enables the detection of a dose of 50 mGy. The comparison of MNCM-yields in medical radiation workers and control individuals showed enhanced MNCM-scores in the medical radiation workers group (P=0.15). The highest MNCM-scores were obtained in the interventional radiologists/cardiologists group, and these scores were significantly higher compared with those obtained from the matched control group (P=0.05). The higher MNCM-scores observed in interventional radiologists/cardiologists compared with nuclear medicine technicians were not in agreement with the personal dosimetry records in both groups, which may point to the limitation of 'double dosimetry' procedures used in interventional radiology/cardiology. In conclusion, the data obtained in the present study supports the importance of cytogenetic analysis, in addition to physical dosimetry, as a routine biomonitoring method in medical radiation workers receiving the highest occupational radiation burdens.
REVIEW The micronucleus assay as a biological dosimeter of in vivo ionising radiation exposure
2010
Biological dosimetry, based on the analysis of micronuclei (MN) in the cytokinesis-block micronucleus (CBMN) assay can be used as an alternative method for scoring dicentric chromosomes in the field of radiation protection. Biological dosimetry or Biodosimetry, is mainly performed, in addition to physical dosimetry, with the aim of individual dose assessment. Many studies have shown that the number of radiation-induced MN is strongly correlated with dose and quality of radiation. The CBMN assay has become, in the last years, a thoroughly validated and standardised technique to evaluate in vivo radiation exposure of occupational, medical and accidentally ex-posed individuals. Compared to the gold standard, the dicentric assay, the CBMN assay has the important advantage of allowing economical, easy and quick analysis.
International Journal of Modern Physics: Conference Series, 2016
In case of a radiation accident, it is well known that in the absence of physical dosimetry biological dosimetry based on cytogenetic methods is a unique tool to estimate individual absorbed dose. Moreover, even when physical dosimetry indicates an overexposure, scoring chromosome aberrations (dicentrics and rings) in human peripheral blood lymphocytes (PBLs) at metaphase is presently the most widely used method to confirm dose assessment. The analysis of dicentrics and rings in PBLs after Giemsa staining of metaphase cells is considered the most valid assay for radiation injury. This work shows that applying the fluorescence in situ hybridization (FISH) technique, using telomeric/centromeric peptide nucleic acid (PNA) probes in metaphase chromosomes for radiation dosimetry, could become a fast scoring, reliable and precise method for biological dosimetry after accidental radiation exposures. In both in vitro methods described above, lymphocyte stimulation is needed, and this limits...
Cytogenetic Biodosimetry for Radiation Disasters: Recent Advances
2005
Potential scenarios of radiation exposure resulting in mass casualties require individual, early, and definitive diagnostic radiation dose assessment to help provide medical aid within days of the occurrence of a catastrophe. The long-range goal of the Armed Forces Radiobiology Research Institute (AFRRI) Biological Dosimetry Team is to identify, develop, and optimize broad dose-range biodosimetry methods, using in vitro models, and to validate those methods, using suitable in vivo models. Of these methods, the cytological biodosimetry methods are capable of assessing radiation dose both in whole-body and partial-body radiation exposure scenarios. Chromosome-aberration analysis in exposed individual's peripheral blood lymphocytes is an internationally accepted "gold standard" cytogenetic biodosimetry method that can be used to assess dose to help develop a treatment strategy within days of a radiation catastrophe. We have established the conventional lymphocyte metaphase-spread dicentric assay, in accordance with international harmonized protocols, and have used the assay to estimate radiation doses in several accidents. Current efforts focus on increasing sample throughput via automation. We systematically addressed the development of an automated cytogenetic laboratory that can triage by exposure group (not life-threatening, potentially life-threatening, and significantly life-threatening) and thereby efficiently differentiate radiation-exposed individuals from the "concerned public" following a disaster. Our studies included concept feasibility, workflow analysis, possible process reengineering, bottleneck elimination in manual processing, and proof-in-principle experiments. With automation, up to 500 samples per week can be analyzed in triage mode in which chromosome aberration analysis is restricted to 20 to 50 metaphase spreads per sample compared with the conventional approach of 500 to 1000 spreads. In another effort, we are developing and validating a novel cytogenetic bioassay, the rapid interphase chromosome aberration (RICA) assay, using suitable in vivo models. In this innovative method, radiation-induced chromosome aberrations in specific chromosomes are studied directly and rapidly in resting peripheral blood lymphocytes after inducing premature chromosome condensation either by fluorescence in situ hybridization or by immuno-enzymatic detection based on bright-field microscopy. The latter method is amenable to automation using image analysis. We used an accidentally radiation-exposed cohort, in Thailand in Feb. 2000, to determine the ability of the RICA assay to assess whole-body equivalent dose; our results indicated that the RICA assay can be used to assess radiation-induced damage to a specific chromosome in interphase cells. We are using a rodent model to determine the persistency of radiation-induced damage and the influence of sampling delay on dose estimation. These studies, in general, will contribute to an improved diagnostic response to a mass-casualty situation and will improve protection and survivability in adverse ionizing radiation environments.
Int J Rad Biol, 2020
Purpose: Inhomogeneous exposures to ionizing radiation can be detected and quantified with the dicentric chromosome assay (DCA) of metaphase cells. Complete automation of interpretation of the DCA for whole-body irradiation has significantly improved throughput without compromising accuracy, however, low levels of residual false positive dicentric chromosomes (DCs) have confounded its application for partial-body exposure determination. Materials and methods: We describe a method of estimating and correcting for false positive DCs in digitally processed images of metaphase cells. Nearly all DCs detected in unirradiated calibration samples are introduced by digital image processing. DC frequencies of irradiated calibration samples and those exposed to unknown radiation levels are corrected subtracting this false positive fraction from each. In partial-body exposures, the fraction of cells exposed, and radiation dose can be quantified after applying this modification of the contaminated Poisson method. Results: Dose estimates of three partially irradiated samples diverged 0.2–2.5 Gy from physical doses and irradiated cell fractions deviated by 2.3%–15.8% from the known levels. Synthetic partial- body samples comprised of unirradiated and 3Gy samples from 4 laboratories were correctly discriminated as inhomogeneous by multiple criteria. Root mean squared errors of these dose estimates ranged from 0.52 to 1.14Gy2 and from 8.1 to 33.3%2 for the fraction of cells irradiated. Conclusions: Automated DCA can differentiate whole- from partial-body radiation exposures and provides timely quantification of estimated whole-body equivalent dose.
Health Physics, 2014
Large scale radiological emergencies require high throughput techniques of biological dosimetry for population triage in order to identify individuals indicated for medical treatment. The dicentric assay is the "gold standard" technique for the performance of biological dosimetry, but it is very time consuming and needs well trained scorers. To increase the throughput of blood samples, semi-automation of dicentric scoring was investigated in the framework of the MULTIBIODOSE EU FP7 project, and dose effect curves were established in six biodosimetry laboratories. To validate these dose effect curves, blood samples from 33 healthy donors (>10 donors/scenario) were irradiated in vitro with 60 Co gamma rays simulating three different exposure scenarios: acute whole body, partial body, and protracted exposure, with three different doses for each scenario. All the blood samples were irradiated at Ghent University, Belgium, and then shipped blind coded to the participating laboratories. The blood samples were set up by each lab using their own standard protocols, and metaphase slides were prepared to validate the calibration curves established by semi-automatic dicentric scoring. In order to achieve this, 300 metaphases per sample were captured, and the doses were estimated using the newly formed dose effect curves. After acute uniform exposure, all laboratories were able to distinguish between 0 Gy, 0.5 Gy, 2.0, and 4.0 Gy (p < 0.001), and, in most cases, the dose estimates were within a range of ± 0.5 Gy of the given dose. After protracted exposure, all laboratories were able to distinguish between 1.0 Gy, 2.0 Gy, and 4.0 Gy (p < 0.001), and here also a large number of the dose estimates were within ± 0.5 Gy of the irradiation dose. After simulated partial body exposure, all laboratories were able to distinguish between 2.0 Gy, 4.0 Gy, and 6.0 Gy (p < 0.001). Overdispersion of the dicentric distribution enabled the detection of the partial body samples; however, this result was clearly dose-dependent. For partial body exposures, only a few dose estimates were in the range of ± 0.5 Gy of the given dose, but an improvement could be achieved with higher cell numbers. The new method of semi-automation of the dicentric assay was introduced successfully in a network of six laboratories. It is therefore concluded that this method can be used as a high-throughput screening tool in a large-scale radiation accident.
Mutagenesis, 2000
of peripheral blood lymphocytes is a valuable and less laborious alternative for large scale L.De Ridder 1 studies . Fluorescence in situ hybridiza-. Pasteurlaan 2, and 2 Occupational preparations allows distinction between the clastogenic and Medicine Service IDEWE, University Hospital Ghent, De Pintelaan 185, aneugenic actions of radiation . Belgium Scoring of micronuclei with and without centromeres has A cytogenetic study was performed in lymphocytes of increased the sensitivity of the technique substantially for hospital workers occupationally exposed to X-and γ-rays monitoring of radiation workers . According using the micronucleus centromere assay. A comparison of to , the micronucleus centromere assay is the data for the exposed group and an age-matched group able to detect the effects of chronic exposure in uranium of non-exposed hospital workers showed a significant (P < miners a long time after exposure.
2012
Cytogenetic biodosimetry is the definitive test for assessing exposure to ionizing radiation. It involves manual assessment of the frequency of dicentric chromosomes (DCs) on a microscope slide, which potentially contains hundreds of metaphase cells. We developed an algorithm that can automatically and accurately locate centromeres in DAPIstained metaphase chromosomes and that will detect DCs. In this algorithm, a set of 200-250 metaphase cell images are ranked and sorted. The 50 top-ranked images are used in the triage DC assay (DCA). To meet the requirement of DCA in a mass casualty event, we are accelerating our algorithm through parallelization. In this paper, we present our finding in accelerating our ranking and segmentation algorithms. Using data parallelization on a desktop system, the ranking module was up to 4-fold faster than the serial version and the Gradient Vector Flow module (GVF) used in our segmentation algorithm was up to 8-fold faster. Large scale data paralleliz...
Mutagenesis, 1999
Acute radiation exposure of humans was observed to induce various forms of cytogenetic damage, including increased frequencies of micronuclei and chromosomal aberrations. However, the cytogenetic effects of chronic low dose radiation exposure in vivo needs further characterization. Sixteen subjects with chronic low dose rates of γ-radiation exposure from 60 Co-contaminated steel in radioactive buildings were compared with seven non-exposed reference subjects for micronucleus frequencies after they relocated. By in situ hybridization using a digoxigenin-labeled anti-α all human centromere probe, the exposed subjects were shown to have a significant increase in cytochalasin B-modulated micronucleus (CBMN) frequencies, as well as a significant increase in centromere-positive (C⍣) CBMN, centromere-negative (C-) CBMN, total C⍣signals, single C⍣ MN signals and multiple C⍣ signals/1000 binucleated cells (BN). However, decreases in the ratios C⍣MN/C-MN and C⍣MN/total CBMN (%) were also noted in the exposed subjects. By mixed effects analysis, considering individuals from the same families, the C-MN and single C⍣ MN/ 1000 BN were both positively and moderately associated with previous cumulative exposure. When the time period of relocation post-exposure (relocation time or RT) was considered, total C⍣MN and multiple C⍣MN/1000 BN were negatively and significantly associated with RT. Moreover, the C⍣MN, C-MN, C⍣MN/C-MN ratio and single C⍣MN/1000 BN were all negatively and moderately associated with RT, but not with exposure dose. This suggested that acentromeric and single or multiple centromeric CBMN cytogenetic damage seems to disappear differentially in human subjects post chronic low dose radiation exposure.