Cytogenetical dose estimation for 3 severely exposed patients in the JCO criticality accident in Tokai-mura

Effect of changing the radiation dose range on the in vitro cytogenetic dose response to gamma-rays

PURPOSE

To examine the distortion of the linear quadratic (LQ) model of in vitro cytogenetic dose response over an extended range of γ-ray doses by analyzing the available literature data, and to establish the dose ranges, in which the LQ dose response curve (DRC) can be most accurately fitted for biological dosimetry.

MATERIALS AND METHODS

Data on yields of dicentrics (Dic) or dicentrics plus centric rings (Dic + CR) induced in vitro in human lymphocytes by acute γ-rays were extracted from 108 open sources. The overall dose response dataset in the dose range up to 50 Gy was fitted to a fractional-rational (FR) model, which included a 'basic' LQ function in the numerator, and a reduction factor dependent on the square of the dose in the denominator. Cytogenetic dose response data obtained at Grigoriev Institute for Medical Radiology, Kharkiv, Ukraine (GIMRO) in the range 0.1 - 20.3 Gy acute γ-rays were fitted to the LQ model with the progressive changing minimum or maximum radiation dose.

RESULTS

The overall dose response, as expected, followed the LQ function in the dose range ≤5 Gy, but in the extended dose range appeared to be S-shaped, with intensive saturation and a plateau at doses ≥22 Gy. Coefficients of the 'basic' LQ equation in FR model were very close to many published DRCs; calculated asymptote was 17. Fitting of the GIMRO dataset to the LQ model with the shift of the dose range showed the increase in linear coefficient with the increment of either minimum or maximum radiation dose, while the decline of the quadratic coefficient was regulated mostly by the increase of the highest dose. The best goodness of fit, assessed by lower χ2 values, occurred for dose ranges 0.1 - 1.0 Gy; 0.5 - 5.9 Gy; 1.0 - 7.8 Gy; 2.0 - 9.6 Gy, 3.9 - 16.4 Gy and 5.9 - 20.3 Gy. The 'see-saw' effect in changes of LQ coefficients was confirmed by re-fitting datasets published by other laboratories.

CONCLUSIONS

The classical LQ model with fixed coefficients appears to have limited applicability for cytogenetic dosimetry at radiation doses >5 Gy due to the saturation of the dose response. Different response of the LQ coefficients to the changes of the dose range must be considered during the DRC construction. Proper selection of minimum and maximum dose in calibration experiments makes it possible to improve the goodness of fit of the LQ DRC.

Optimizing chemical-induced premature chromosome condensation assay for rapid estimation of high-radiation doses

In the event of exposure to high doses of radiation, prompt dose estimation is crucial for selecting appropriate treatment modalities, such as cytokine therapy or stem cell transplantation. The chemical-induced premature chromosome condensation (PCC) method offers a simple approach for such dose estimation with significant radiation exposure, but its 48-h incubation time poses challenges for early dose assessment. In this study, we optimized the chemical-induced PCC assay for more rapid dose assessment. A sufficient number of PCC and G2/M-PCC cells were obtained after 40 h of culture for irradiated human peripheral blood up to 20 Gy. By adding caffeine (final concentration of 1 mM) at 34 h from the start of culture, G2/M-PCC index increased by 1.4-fold in 10 Gy cultures. There was also no significant difference in the G2/M-PCC ring frequency induced for doses 0 to 15 Gy between our 40-h caffeine-supplemented chemical-induced PCC method and the conventional 48-h PCC assay.

Fluorescence in situ hybridisation for interphase chromosomal aberration-based biological dosimetry

Metaphase spreads stained with Giemsa or painted with chromosome-specific probes by fluorescence in situ hybridisation (FISH) have been in use since long for retrospective dose assessment (biological dosimetry). However, in cases of accidental exposure to ionising radiation, the culturing of lymphocytes to obtain metaphase chromosomes and analysis of chromosomal aberrations is time-consuming and problematic after high radiation doses. Similarly, analysing chromosomal damage in G0/G1 cells or nondividing cells by premature chromosome condensation is laborious. Following large-scale radiological emergencies, the time required for analysis is more important than precision of dose estimate. Painting of whole chromosomes using chromosome-specific probes in interphase nuclei by the FISH technique will eliminate the time required for cell culture and allow a fast dose estimate, provided that a meaningful dose-response can be obtained by scoring the number of chromosomal domains visible in interphase nuclei. In order to test the applicability of interphase FISH for quick biological dosimetry, whole blood from a healthy donor was irradiated with 8 Gy of gamma radiation. Irradiated whole blood was kept for 2 h at 37°C to allow DNA repair and thereafter processed for FISH with probes specific for Chromosomes-1 and 2. Damaged chromosomal fragments, distinguished by extra color domains, were observed in interphase nuclei of lymphocytes irradiated with 8 Gy. These fragments were efficiently detected and quantified by the FISH technique utilising both confocal and single plane fluorescence microscopy. Furthermore, a clear dose-response curve for interphase fragments was achieved following exposure to 0, 1, 2, 4 and 8 Gy of gamma radiation. These results demonstrate interphase FISH as a promising test for biodosimetry and for studying cytogenetic effects of radiation in nondividing cells.

Proteomics and secreted lipidomics of mouse-derived bone marrow cells exposed to a lethal level of ionizing radiation

High doses of ionizing radiation (IR) exposure can lead to the development of severe acute radiation syndrome with bone marrow failure. Defining risk factors that predict adverse events is a critical mission to guide patient selection for personalized treatment protocols. Since non-hematopoietic stem cells act as feeder cells in the niche and their secreted lipids may regulate hematopoietic stem cells, we focused on non-hematopoietic stem cells and aimed to discover biomarkers that can assess radiation exposure from their secreted lipids. Bone marrow stromal cells (BMSCs) and osteoblast differentiation-inducing cells (ODICs) isolated from mouse femurs were exposed to lethal doses of IR and the proteomic differences between BMSC and ODIC cell layers were compared. We observed an increased Nrf2-mediated oxidative stress response and IL6 expression in ODICs and decreased expression of mitochondrial proteins in BMSCs. To elucidate secreted factors, lipidomics of the cultures were profiled; the relevant lipids distinguishing IR-exposed and control groups of BMSC were acyl-acyl phosphatidylcholine (PC aa C34:1 and PC aa C34:4), lysophosphatidylcholine (lyso-PC a C18:0 and lyso PC a C17:0) and sphingomyelin (SM C20:2). These analyses suggest that certain lipids are candidate markers for the toxic effects of IR.

Fact-finding survey on the competencies and literacy of radiological technologists regarding radiation disasters

BACKGROUND

Radiological technologists serve as risk communicators who aim to lessen patients' anxiety about radiation exposure, in addition to performing radiological examinations.

OBJECTIVE

We conducted a fact-finding survey on knowledge and awareness of radiation disasters among the radiological technologists to reveal their literacy and competencies regarding radiation disasters.

METHODS

A paper questionnaire was distributed to 1,835 radiological technologists at 166 National Hospital Organization facilities in Japan. The 28-item questionnaire covered knowledge and awareness of radiation protection and radiation disasters. Radiological technologists were divided into 2 groups by regionality: areas where a nuclear power station was present/nearby (NPS areas) and non-NPS areas.

RESULTS

Completed questionnaires were returned from 148 facilities with a facility response rate of 89.2% and from 1,391 radiological technologists with a response rate of 75.8%. There were 1,290 valid responses with a valid response rate of 70.3%. The correct answer rate for knowledge of radiation protection and radiation disasters was high in the 24 NPS areas. There were no differences in awareness of radiation disasters between NPS and non-NPS areas.

CONCLUSIONS

Establishing a nationwide, region-independent training system can be expected to improve literacy regarding radiation disasters among radiological technologists. Willingness to assist during disasters was high among radiological technologists irrespective of area, indicating that the competencies of radiological technologists represent a competency model for radiation disaster assistance.

Application of a semi-automated dicentric scoring system in triage and monitoring occupational radiation exposure

The dicentric chromosome assay (DCA) is considered the gold standard for radiation biodosimetry, but it is limited by its long dicentric scoring time and need for skilled scorers. The automation of scoring dicentrics has been considered a strategy to overcome the constraints of DCA. However, the studies on automated scoring methods are limited compared to those on conventional manual DCA. Our study aims to assess the performance of a semi-automated scoring method for DCA using ex vivo and in vivo irradiated samples. Dose estimations of 39 blind samples irradiated ex vivo and 35 industrial radiographers occupationally exposed in vivo were estimated using the manual and semi-automated scoring methods and subsequently compared. The semi-automated scoring method, which removed the false positives of automated scoring using the dicentric chromosome (DC) scoring algorithm, had an accuracy of 94.9% in the ex vivo irradiated samples. It also had more than 90% accuracy, sensitivity, and specificity to distinguish binary dose categories reflecting clinical, diagnostic, and epidemiological significance. These data were comparable to those of manual DCA. Moreover, Cohen's kappa statistic and McNemar's test showed a substantial agreement between the two methods for categorizing in vivo samples into never and ever radiation exposure. There was also a significant correlation between the two methods. Despite of comparable results with two methods, lower sensitivity of semi-automated scoring method could be limited to assess various radiation exposures. Taken together, our findings show the semi-automated scoring method can provide accurate dose estimation rapidly, and can be useful as an alternative to manual DCA for biodosimetry in large-scale accidents or cases to monitor radiation exposure of radiation workers.

Chromosome length ratio as a biomarker of DNA damage in cells exposed to high dose ionizing radiation

The premature chromosome condensation (PCC) assay is considered as complementary bio-dosimetry tool for chromosome aberration assay and the PCC assay can be used to estimate high dose exposure. Though the PCC ring is considered as prospective biomarker, chromosome length ratio (ratio of longest and shortest chromosome length in PCC spreads) of chemically induced PCC is shown to be very good indicator of ionizing radiation. In view of this, an in-vitro study has been performed using PCC assay to suggest chromosome length ratio (LR) as potential bio-dosimeter induced by high dose ionizing radiation. Blood samples were collected from healthy subjects (n = 3) after prior consent and irradiated to ten different doses ranging between 0 and 20 Gy using 6 MV LINAC X-rays with dose rate of 5.6 Gy/min. Irradiated lymphocytes were cultured and calyculin induced PCC spreads were prepared. PCC spreads were captured using image analysis system and chromosome lengths were measured using open-source ImageJ software. For each dose, LR for 50 chromosome spreads were computed and mean LR value was calculated. LR varies between 6.0 ± 0.08 and 23.6 ± 0.55 for the dose range between 2 and 20 Gy. The dose response curve for LR was observed to be linear with y = 1.02x + 3.36, R² = 0.97. Linear dose response relationship obtained in the present study confirms the prospective use of LR measurement. This study is first of its kind to examine chromosome length ratio as a biomarker of DNA damage in cells exposed to high dose X-ray exposure.

Biological and internal dosimetry for radiation medicine: current status and future perspectives

The International Atomic Energy Agency (IAEA) and Hiroshima International Council for Health Care of the Radiation-Exposed (HICARE) jointly organized two relevant workshops in Hiroshima, Japan, i.e. a Training Meeting 'Biodosimetry in the 21st century' (BIODOSE-21) on 10-14 June 2013 and a Workshop on 'Biological and internal dosimetry: recent advance and clinical applications' which took place between 17 and 21 February 2020. The main objective of the first meeting was to develop the ability of biodosimetry laboratories to use mature and novel techniques in biological dosimetry for the estimation of radiation doses received by individuals and populations. This meeting had a special focus on the Asia-Pacific region and was connected with the then on-going IAEA Coordinated Research Project (CRP) E35008 'Strengthening of "Biological dosimetry" in IAEA Member States: Improvement of current techniques and intensification of collaboration and networking among the different institutes' (2012-17). The meeting was attended by 25 participants, which included 11 lecturers. The 14 trainees for this meeting came from India, Indonesia, Japan, Malaysia, Philippines, Republic of Korea, Singapore, Thailand and Vietnam. During the meeting 13 lectures by HICARE and IAEA invited lecturers were delivered besides eight research reports presented by the IAEA CRP E35008 network centers from the Asia-Pacific region. Two laboratory exercises were also undertaken, one each at Hiroshima University and the Radiation Effects Research Foundation (RERF). The second training workshop aimed to discuss with the participants the use of mature and novel techniques in biological and internal dosimetry for the estimation of radiation effects by accidental, environmental and medical exposures. The workshop was attended by 19 participants from Indonesia, Jordan, Oman, Philippines, Singapore, Syrian Arab Republic, Thailand, UAE, USA and Yemen. The main outcome of both meetings was a review of the state-of-the-art of biodosimetry and internal dosimetry and their future perspectives in medical management. This report highlights the learning outcome of two meetings for the benefit of all stake-holders in the field of biological and internal dosimetry.

Training of clinical triage of acute radiation casualties: a performance comparison ofon-siteversusonlinetraining due to the covid-19 pandemic

A collection of powerful diagnostic tools have been developed under the umbrellas of NATO for ionising radiation dose assessment (BAT, WinFRAT) and estimate of acute health effects in humans (WinFRAT, H-Module). We assembled a database of 191 ARS cases using the medical treatment protocols for radiation accident victims (n= 167) and the system for evaluation and archiving of radiation accidents based on case histories (n= 24) for training purposes of medical personnel. From 2016 to 2019, we trained 39 participants comprising MSc level radiobiology students in an on-site teaching class. Enforced by the covid-19 pandemic in 2020 for the first time, an online teaching of nine MSc radiobiology students replaced the on-site teaching. We found that: (a) limitations of correct diagnostic decision-making based on clinical signs and symptoms were experienced unrelated to the teaching format. (b) A significant performance decrease concerning online (first number in parenthesis) versus on-site teaching (reference and second number in parenthesis) was seen regarding the estimate time (31 vs 61 cases per hour, two-fold decrease,p= 0.005). Also, the accurate assessment of response categories (89.9% vs 96.9%,p= 0.001), ARS (92.4% vs 96.7%,p= 0.002) and hospitalisation (93.5% vs 97.0%,p= 0.002) decreased by around 3%-7%. The performances of the online attendees were mainly distributed within the lower quartile performance of on-site participants and the 25%-75% interquartile range increased 3-7-fold. (c) Comparison of dose estimates performed by training participants with hematologic acute radiation syndrome (HARS) severity mirrored the known limitations of dose alone as a surrogate parameter for HARS severity at doses less than 1.5 Gy, but demonstrated correct determination of HARS 2-4 and support for clinical decision making at dose estimates >1.5 Gy, regardless of teaching format. (d) Overall, one-third of the online participants showed substantial misapprehension and insecurities of elementary course content that did not occur after the on-site teaching.

Medical management of heavily exposed victims: an experience at the Tokaimura criticality accident

A criticality accident occurred at the uranium conversion plant in Tokaimura, Ibaraki Prefecture, Japan on 30 September 1999. When uranyl nitrate was overloaded to a critical mass level, uncontrolled fission reaction occurred. A procedure was carried out according to the JCO manual, although not an officially approved manual. Three workers were heavily exposed to neutrons andγ-rays produced by nuclear fission, and they subsequently developed acute radiation syndrome (ARS). The average doses to the whole body of the three workers were approximately 25, 9, and 3 GyEq (biologically equivalent dose ofγ-exposure), respectively; dose distribution analysis later revealed extreme heterogeneity of these doses in two workers. They were triaged according to the predicted clinical needs. Two of these workers developed severe bone marrow failure and received haematopoietic stem cell transplantation: one with peripheral stem cell transplantation from his Human Leukocyte Antigen compatible sister and the other with umbilical cord blood transplantation. The graft was initially successful in both workers; autologous haematopoietic recovery was observed after donor/recipient mixed chimerism in one of them. Despite of all medical efforts available including haematopoietic stem cell transplantation, investigational drugs, skin graft, two workers died of multiple organ involvement and failure 83 and 211 days after the accident, respectively. Clinically as well as pathologically, the direct cause of death was deemed to be intractable gastrointestinal (GI) bleeding in one, and thoraco-abdominal compartment syndrome due to dermal fibrosis/sclerosis in the other. The third worker also developed bone marrow suppression but was treated with granulocyte colony-stimulating factor. He recovered without major complications and is now under periodical medical follow-up. These experiences suggest that treatment of bone marrow is not a limiting factor for saving the life of ARS victims severely exposed. Successful treatment of other organs such as lungs, skin, and GI tract is also essential. Furthermore, the whole-body dose may not always reflect the prognosis of ARS victims because of the nature of accidental exposure, heterogenous exposure.

Cytogenetic biological dosimetry assays: recent developments and updates

Biological dosimetry is the measurement of radiation-induced changes in the human to measure short and long-term health risks. Biodosimetry offers an independent means of obtaining dose information and also provides diagnostic information on the potential for “partial-body” exposure information using biological indicators and otherwise based on computer modeling, dose reconstruction, and physical dosimetry. A variety of biodosimetry tools are available and some features make some more valuable than others. Among the available biodosimetry tool, cytogenetic biodosimetry methods occupy an exclusive and advantageous position. The cytogenetic analysis can complement physical dosimetry by confirming or ruling out an accidental radiological exposure or overexposures. We are discussing the recent developments and adaptability of currently available cytogenetic biological dosimetry assays.

Editing flagellin derivatives for exploration of potent radioprotective agents

Exploration of medical radiation countermeasures (MRCs) has great implications in protection of mammals from radiation damages. While flagellin has been recently reported to show radioprotective effects, the relationships between flagellin structure and radioprotective activity are rarely explored. Herein, we deliberately edited the amino acid sequence of flagellin in its binding domain with toll-like receptor 5 (TLR5) for exploration of potent flagellin derivatives (Fds). An in vitro screening paradigm was developed to examine the radioprotective effects of six engineered Fds. Notably, mutation of 103 threonine on flagellin into asparagine resulted in a potent MRC candidate (Fd-T103N) displaying 1.28-fold increment of interactions with TLR5. Fd-T103N was able to further activate NF-κB pathway, induce immune protective cytokine (e.g. G-CSF) release, and significantly ameliorate γ-irradiation induced cell death. The protection effects of Fd-T103N were further validated in mice exposed to 10 Gy γ-irradiations. Compared to parent flagellin, Fd-T103N treatment showed higher G-CSF release in mouse blood, lower intestine damages, and 13% increments of mouse survival rates. In short, the established predictive paradigm could greatly reduce the labor-, time- and animal-costs in exploration of MRC candidates. Fd-T103N is a promising candidate of investigational new drug for radioprotection.

Lessons from the Fukushima Daiichi nuclear power plant accident -from a research perspective

Since the accident at Fukushima Daiichi nuclear power plant, there has been a focus on the impact of low-dose radiation exposure due to nuclear disasters and radiology on human bodies. In order to study very low levels of impact on the human body from low-dose radiation exposure, a system with high detection sensitivity is needed. Until now, the most well-established biological radiation effect detection system in the field of emergency radiation medicine has been chromosomal analysis. However, chromosomal analysis requires advanced skills, and it is necessary to perform chromosomal analysis of a large number of cells in order to detect slight effects on the human body due to low-dose radiation exposure. Therefore, in order to study the effects of low-dose radiation exposure on the human body, it is necessary to develop high-throughput chromosome analysis technology. We have established the PNA-FISH method, which is a fluorescence in-situ hybridisation method using a PNA probe, as a high-throughput chromosome analysis technique. Using this method, the detection of dicentrics and ring chromosomes has become very efficient. Using this technology, chromosomal analysis was performed on peripheral blood before and after computed tomography (CT) examination of patients at Hiroshima University Hospital, and it was possible to detect chromosomal abnormalities due to low-dose radiation exposure in the CT examination. Furthermore, it was shown that there may be individual differences in the increase in chromosomal abnormalities due to low-dose radiation exposure, suggesting the need to build a next-generation medical radiation exposure management system based on individual differences in radiation sensitivity. If techniques such as chromosomal analysis, which have been used for biological dose evaluation in emergency radiation medicine, can be used for general radiology, such as radiodiagnosis and treatment, that will be a contribution to radiology from an unprecedented angle. This article will discuss the clinical application of new biological dose evaluation methods that have been developed in the field of emergency radiation medicine.

Construction of dose response curve for 6 MV LINAC X-rays using Premature Chromosome Condensation assay for radiation dosimetry

Quantification of chromosomal aberrations in the exposed personnel blood samples is considered as a 'gold standard' and sensitive biomarker in biological dosimetry. Despite technological developments, culture of cells for 48-52 h remains an unmet need in case of triage biodosimetry. Moreover, it is difficult to get sufficient number of metaphase spreads for scoring after high doses of exposures. The technique which causes condensation of chromatin before mitosis using biological or chemical agent is named as Premature Chromosome Condensation (PCC) assay. This assay is considered as an alternative to chromosome aberration assay, particularly at high acute doses of low and high LET radiation. To establish the PCC assay, blood samples were collected from healthy non-smoking individuals (n = 3) and exposed to various doses (0-20 Gy) of 6 MV X-rays at a dose rate of 5.6 Gy/min, using a high energy Linear accelerator (LINAC). Irradiated blood samples were subjected to Calyculin-A induced PCC. About 500 cells or more than 100 Ring Chromosomes (RC) were scored at each dose. Dicentric chromosomes (DC) and acentric fragments were also scored at each dose; the number of chromosomal aberrations in G1, M, G2/M and M/A phase of cell cycle were recorded and the frequency was used to construct the dose response curve. A dose dependent increase in RC and DC frequency were observed with a slope of 0.049 ± 0.002 and 0.30 ± 0.02 respectively. This study is first of its kind to construct a dose response curve for LINAC X-rays using a PCC assay.

A faster and easier biodosimetry method based on calyculin A-induced premature chromosome condensation (PCC) by scoring excess objects

Dicentric analysis and the ring PCC assay as established biodosimetry methods both have limitations in the estimation of absorbed doses in suspected overexposure cases between 5 and 10 Gy. The proposed method based on calyculin A-induced PCC overcomes these limitations by scoring excess objects as the endpoint. This new scoring method can potentially serve as a faster and up-scalable approach that complements the existing methods with higher accuracy at different dose ranges. It can also potentially be performed by less skilled workers when no automated system is available in mass casualty emergency cases to assist with the triage of patients. Additionally, it offers the possibility to further reduce the sample size and PCC induction time. In this pilot study, a calibration curve for excess objects was constructed using the new scoring method for the first time and a blind validation test composed of three unknown doses was carried out. Almost all the dose estimates were within the 95% confidence limits of the actual test doses by scoring only 50-100 PCC spreads. This method was found to be more accurate than ring PCC for doses below 10 Gy.

Retrospective biodosimetry techniques: Focus on cytogenetics assays for individuals exposed to ionizing radiation

In the absence of physical data, biodosimetry tools are required for fast dose and risk assessment in the event of radiological or nuclear mass accidents or attacks to triage exposed humans and take immediate medical countermeasures. Biodosimetry tools have mostly been developed for retrospective dose assessment and the follow-up of victims of irradiation. Among them, cytogenetics analyses, to reveal chromosome damage, are the most developed and allow the determination of doses from blood samples as low as 100 mGy. Various cytogenetic tests have already allowed retrospective dose assessment of Chernobyl liquidators and military personnel exposed to nuclear tests after decades. In this review, we discuss the properties of various biodosimetry techniques, such as their sensitivity and limitations as a function of the time from exposure, using multiple examples of nuclear catastrophes or working exposure. Among them, chromosome FISH hybridization, which reveals chromosome translocations, is the most reliable due to the persistence of translocations for decades, whereas dicentric chromosome and micronuclei assays allow rapid and accurate dose assessment a short time after exposure. Both need to be adjusted through mathematical algorithms for retrospective analyses, accounting for the time since exposure and the victims' age. The goal for the future will be to better model chromosome damage, reduce the time to result, and develop new complementary biodosimetry approaches, such as mutation signatures.

Modified PNA Telomere and Centromere FISH Protocols

Fluorescence in situ Hybridization (FISH) utilizes peptide nucleic acid (PNA) probes to identify specific DNA sequences. PNA probes have been effectively used to identify chromosome aberrations and have been shown to greatly aid in biodosimetery assays involved in identifying dicentrics. Traditional techniques have required the heat denaturing of the DNA in formamide followed by multiple hours at moderated temperatures to allow the probe to hybridize to its specific target. Over the past 30 years, advancements in both protocols and probes have made FISH a more reliable technique for both biological research and medical diagnostics, additionally the protocol has been shortened to several minutes. We will introduce two modified PNA FISH protocols, a rapid microwave-based approach and nonclassical hybridization protocol.

BABOON RADIATION QUALITY (MIXED-FIELD NEUTRON AND GAMMA, GAMMA ALONE) DOSE-RESPONSE MODEL SYSTEMS: ASSESSMENT OF H-ARS SEVERITY USING HAEMATOLOGIC BIOMARKERS

Results from archived (1986 and 1996) experiments were used to establish a baboon radiation-quality dose-response database with haematology biomarker time-course data following exposure to mixed-fields (i.e. neutron to gamma ratio: 5.5; dose: 0-8 Gy) and 60Co gamma-ray exposures (0-15 Gy). Time-course (i.e. 0-40 d) haematology changes for relevant blood-cell types for both mixed-field (neutron to gamma ratio = 5.5) and gamma ray alone were compared and models developed that showed significant differences using the maximum likehood ratio test. A consensus METREPOL-like haematology ARS (H-ARS) severity scoring system for baboons was established using these results. The data for mixed-field and the gamma only cohorts appeared similar, and so the cohorts were pooled into a single consensus H-ARS severity scoring system. These findings provide proof-of-concept for the use of a METREPOL H-ARS severity scoring system following mixed-field and gamma exposures.

Development of Dose-Response Calibration Curve for Dicentric Chromosome Induced by X-Rays

Chromosome aberration is a biomarker that has been used as a standard tool in biological dosimetry (biodosimetry) of individuals after exposure to ionizing radiation. It is based mainly on the induction of dicentric chromosomes - one of the radiation-induced biological effects, in order to correlate them with radiation dose. In this study, a dose calibration curve for X-rays was generated by using the dicentric assay and by fitting the data to both Chromosomal Aberration Calculation Software and Dose Estimate programs to compare the output of each method. Peripheral blood samples from four nonsmoker healthy donors were irradiated with various doses ranging from 0 to 4 Gy with 250 kV or 122 keV X-rays at a dose rate of 0.17 Gy/min. The irradiated blood was cultured, harvested, and analyzed according to the standard procedure as described by the International Atomic Energy Agency with slight modifications. The dose-response calibration data for dicentrics were fitted with the linear-quadratic model (Y_dic = 0.03987D² + 0.00651D). The dose-response calibration curve obtained in this research was comparable to other estimations with similar radiation quality and dose rates. The results in this research convinced us in sustaining a biodosimetry using a dose-response calibration curve in our laboratory.

Serum miR-375-3p increase in mice exposed to a high dose of ionizing radiation

Exposure to high-doses of ionizing radiation (IR) leads to development of a strong acute radiation syndrome (ARS) in mammals. ARS manifests after a latency period and it is important to develop fast prognostic biomarkers for its early detection and assessment. Analysis of chromosomal aberrations in peripheral blood lymphocytes is the gold standard of biological dosimetry, but it fails after high doses of IR. Therefore, it is important to establish novel biomarkers of exposure that are fast and reliable also in the high dose range. Here, we investigated the applicability of miRNA levels in mouse serum. We found significantly increased levels of miR-375-3p following whole body exposure to 7 Gy of X-rays. In addition, we analyzed their levels in various organs of control mice and found them to be especially abundant in the pancreas and the intestine. Following a dose of 7 Gy, extensive cell death occurred in these tissues and this correlated negatively with the levels of miR-375-3p in the organs. We conclude that high expressing tissues of miR-375-3p may secrete this miRNA in serum following exposure to 7 Gy. Therefore, elevated miR-375-3p in serum may be a predictor of tissue damage induced by exposure to a high radiation dose.

Cytogenetics for Biological Dosimetry

Cytogenetics is the gold-standard in biological dosimetry for assessing a received dose of ionizing radiation. More modern techniques have recently emerged, but none are as specific as cytogenetic approaches, particularly the dicentric assay. Here, we will focus on the principal cytogenetic techniques used for biological dosimetry: the dicentric assay in metaphase cells, the micronuclei assay in binucleated cells, and the premature condensed chromosome (PCC) assay in interphase cells. New fluorescence in situ hybridization (FISH) techniques (such as telomere-centromere hybridization) have facilitated the analysis of the dicentric assay and have permitted to assess the dose a long time after irradiation by translocation analysis (such as by Tri-color FISH or Multiplex-FISH). Telomere centromere staining of PCCs will make it possible to perform dose assessment within 24 h of exposure in the near future.

Fukushima Daiichi-Derived Radionuclides in the Ocean: Transport, Fate, and Impacts

The events that followed the Tohoku earthquake and tsunami on March 11, 2011, included the loss of power and overheating at the Fukushima Daiichi nuclear power plants, which led to extensive releases of radioactive gases, volatiles, and liquids, particularly to the coastal ocean. The fate of these radionuclides depends in large part on their oceanic geochemistry, physical processes, and biological uptake. Whereas radioactivity on land can be resampled and its distribution mapped, releases to the marine environment are harder to characterize owing to variability in ocean currents and the general challenges of sampling at sea. Five years later, it is appropriate to review what happened in terms of the sources, transport, and fate of these radionuclides in the ocean. In addition to the oceanic behavior of these contaminants, this review considers the potential health effects and societal impacts.

Management of ionizing radiation injuries and illnesses, part 4: acute radiation syndrome

To provide proper medical care for patients after a radiation incident, it is necessary to make the correct diagnosis in a timely manner and to ascertain the relative magnitude of the incident. The present article addresses the clinical diagnosis and management of high-dose radiation injuries and illnesses in the first 24 to 72 hours after a radiologic or nuclear incident. To evaluate the magnitude of a high-dose incident, it is important for the health physicist, physician, and radiobiologist to work together and to assess many variables, including medical history and physical examination results; the timing of prodromal signs and symptoms (eg, nausea, vomiting, diarrhea, transient incapacitation, hypotension, and other signs and symptoms suggestive of high-level exposure); and the incident history, including system geometry, source-patient distance, and the suspected radiation dose distribution.

High-throughput sample processing and sample management; the functional evolution of classical cytogenetic assay towards automation

High-throughput individual diagnostic dose assessment is essential for medical management of radiation-exposed subjects after a mass casualty. Cytogenetic assays such as the Dicentric Chromosome Assay (DCA) are recognized as the gold standard by international regulatory authorities. DCA is a multi-step and multi-day bioassay. DCA, as described in the IAEA manual, can be used to assess dose up to 4-6 weeks post-exposure quite accurately but throughput is still a major issue and automation is very essential. The throughput is limited, both in terms of sample preparation as well as analysis of chromosome aberrations. Thus, there is a need to design and develop novel solutions that could utilize extensive laboratory automation for sample preparation, and bioinformatics approaches for chromosome-aberration analysis to overcome throughput issues. We have transitioned the bench-based cytogenetic DCA to a coherent process performing high-throughput automated biodosimetry for individual dose assessment ensuring quality control (QC) and quality assurance (QA) aspects in accordance with international harmonized protocols. A Laboratory Information Management System (LIMS) is designed, implemented and adapted to manage increased sample processing capacity, develop and maintain standard operating procedures (SOP) for robotic instruments, avoid data transcription errors during processing, and automate analysis of chromosome-aberrations using an image analysis platform. Our efforts described in this paper intend to bridge the current technological gaps and enhance the potential application of DCA for a dose-based stratification of subjects following a mass casualty. This paper describes one such potential integrated automated laboratory system and functional evolution of the classical DCA towards increasing critically needed throughput.

Shortening the culture time in cytogenetic dosimetry using PCC-R assay

The fast assessment of the dose received by exposed persons is crucial in radiological accidents, so the 48 h of cell culture in conventional cytogenetic dosimetry in addition to some limitations after high doses becomes a disadvantage. The premature chromosome condensation (PCC) assay permits to analyse enough cells after high radiation exposure, and the score of PCC-R may reduce the culture time up to 40-42 h. Peripheral whole-blood samples were exposed to 1-10 Gy of gamma radiation and cultured during 40 and 42 h. No statistical difference between frequencies was obtained between 40, 42 and 48 h of culture time, and PCC index decreased with the increase of the dose and increased with the culture time. The protocol proposed allows reduce the culture time down to 40 or 42 h when using the PCC-R assay with adequate precision in dose estimation.

Drug-induced premature chromosome condensation (PCC) protocols: cytogenetic approaches in mitotic chromosome and interphase chromatin

Chromosome analysis is a fundamental technique which is used in wide areas of cytogenetic study including karyotyping species, hereditary diseases diagnosis, or chromosome biology study. Chromosomes are usually prepared from mitotic cells arrested by colcemid block protocol. However, obtaining mitotic chromosomes is often hampered under several circumstances. As a result, cytogenetic analysis will be sometimes difficult or even impossible in such cases. Premature chromosome condensation (PCC) (see Note 1) is an alternative method that has proved to be a unique and useful way in chromosome analysis. Former, PCC has been achieved following cell fusion method (cell-fusion PCC) mediated either by fusogenic viruses (e.g., Sendai virus) or cell fusion chemicals (e.g., polyethylene glycol), but the cell fusion PCC has several drawbacks. The novel drug-induced PCC using protein phosphatase inhibitors was introduced about 20 years ago. This method is much simpler and easier even than the conventional mitotic chromosome preparation protocol use with colcemid block and furthermore obtained PCC index (equivalent to mitotic index for metaphase chromosome) is usually much higher than colcemid block method. Moreover, this method allows the interphase chromatin to be condensed to visualize like mitotic chromosomes. Therefore drug-induced PCC has opened the way for chromosome analysis not only in metaphase chromosomes but also in interphase chromatin. The drug-induced PCC has thus proven the usefulness in cytogenetics and other cell biology fields. For this second edition version, updated modifications/changes are supplemented in Subheadings 2, 3, and 4, and a new section describing the application of PCC in chromosome science fields is added with citation of updated references.

A new model of biodosimetry to integrate low and high doses

Biological dosimetry, that is the estimation of the dose of an exposure to ionizing radiation by a biological parameter, is a very important tool in cases of radiation accidents. The score of dicentric chromosomes, considered to be the most accurate method for biological dosimetry, for low LET radiation and up to 5 Gy, fits very well to a linear-quadratic model of dose-effect curve assuming the Poisson distribution. The accuracy of this estimation raises difficulties for doses over 5 Gy, the highest dose of the majority of dose-effect curves used in biological dosimetry. At doses over 5 Gy most cells show difficulties in reaching mitosis and cannot be used to score dicentric chromosomes. In the present study with the treatment of lymphocyte cultures with caffeine and the standardization of the culture time, metaphases for doses up to 25 Gy have been analyzed. Here we present a new model for biological dosimetry, which includes a Gompertz-type function as the dose response, and also takes into account the underdispersion of aberration-among-cell distribution. The new model allows the estimation of doses of exposures to ionizing radiation of up to 25 Gy. Moreover, the model is more effective in estimating whole and partial body exposures than the classical method based on linear and linear-quadratic functions, suggesting their effectiveness and great potential to be used after high dose exposures of radiation.

A novel parameter, cell-cycle progression index, for radiation dose absorbed estimation in the premature chromosome condensation assay

The calyculin A-induced premature chromosome condensation (PCC) assay is a simple and useful method for assessing the cell-cycle distribution in cells, since calyculin A induces chromosome condensation in various phases of the cell cycle. In this study, a novel parameter, the cell-cycle progression index (CPI), in the PCC assay was validated as a novel biomarker for biodosimetry. Peripheral blood was drawn from healthy donors after informed consent was obtained. CPI was investigated using a human peripheral blood lymphocyte (PBL) ex vivo irradiation ((60)Co-gamma rays: ∼0.6 Gy min(-1), or X ray: 1.0 Gy min(-1); 0-10 Gy) model. The calyculin A-induced PCC assay was performed for chromosome preparation. PCC cells were divided into the following five categories according to cell-cycle stage: non-PCC, G1-PCC, S-PCC, G2/M-PCC and M/A-PCC cells. CPI was calculated as the ratio of G2/M-PCC cells to G1-PCC cells. The PCC-stage distribution varied markedly with irradiation doses. The G1-PCC cell fraction was significantly reduced, and the G2/M-PCC cell fraction increased, in 10-Gy-irradiated PBL after 48 h of culture. CPI levels were fitted to an exponential dose-response curve with gamma-ray irradiation [y = 0.6729 + 0.3934 exp(0.5685D), r = 1.0000, p < 0.0001] and X-ray irradiation [y = -0.3743 + 0.9744 exp(0.3321D), r = 0.9999, p < 0.0001]. There were no significant individual (p = 0.853) or gender effects (p = 0.951) on the CPI in the human peripheral blood ex vivo irradiation model. Furthermore, CPI measurements are rapid (< 15 min per case). These results suggest that the CPI is a useful screening tool for the assessment of radiation doses received ranging from 0 to 10 Gy in radiation exposure early after a radiation event, especially after a mass-casualty radiological incident.

The Internet's role in a biodosimetric response to a radiation mass casualty event

Response to a large-scale radiological incident could require timely medical interventions to minimize radiation casualties. Proper medical care requires knowing the victim's radiation dose. When physical dosimetry is absent, radiation-specific chromosome aberration analysis can serve to estimate the absorbed dose in order to assist physicians in the medical management of radiation injuries. A mock exercise scenario was presented to six participating biodosimetry laboratories as one individual acutely exposed to Co under conditions suggesting whole-body exposure. The individual was not wearing a dosimeter and within 2-3 h of the incident began vomiting. The individual also had other medical symptoms indicating likelihood of a significant dose. Physicians managing the patient requested a dose estimate in order to develop a treatment plan. Participating laboratories in North and South America, Europe, and Asia were asked to evaluate more than 800 electronic images of metaphase cells from the patient to determine the dicentric yield and calculate a dose estimate with 95% confidence limits. All participants were blind to the physical dose until after submitting their estimates based on the dicentric chromosome assay (DCA). The exercise was successful since the mean biological dose estimate was 1.89 Gy whereas the actual physical dose was 2 Gy. This is well within the requirements for guidance of medical management. The exercise demonstrated that the most labor-intensive step in the entire process (visual evaluation of images) can be accelerated by taking advantage of world-wide expertise available on the Internet.

Direct DNA and PNA probe binding to telomeric regions without classical in situ hybridization

BACKGROUND

Fluorescence in situ Hybridization (FISH) utilizes peptide nucleic acid (PNA) probes to identify specific DNA sequences. Traditional techniques have required the heat denaturing of the DNA in formamide followed by multiple hours at moderated temperatures to allow the probe to hybridize to its specific target. Over the past 30 years, advancements in both protocols and probes have made FISH a more reliable technique for both biological research and medical diagnostics, additionally the protocol has been shortened to several minutes. These PNA probes were designed to target and hybridize to both DNA and RNA, and PNA-protein interactions still remain unclear.

RESULTS

In this study we have shown that a telomeric single stranded specific PNA probe is able to bind to its target without heat denaturing of the DNA and without formamide. We have also identified a centromere specific probe, which was found to bind its target with only incubation with formamide.

CONCLUSIONS

Certain PNA probes are able to hybridize with their targets with minimal to no denaturing of the DNA itself. This limited denaturing preserves the chromosome structure and may lead to more effective and specific staining.

Assessment of simulated high-dose partial-body irradiation by PCC-R assay

The estimation of the dose and the irradiated fraction of the body is important information in the primary medical response in case of a radiological accident. The PCC-R assay has been developed for high-dose estimations, but little attention has been given to its applicability for partial-body irradiations. In the present work we estimated the doses and the percentage of the irradiated fraction in simulated partial-body radiation exposures at high doses using the PCC-R assay. Peripheral whole blood of three healthy donors was exposed to doses from 0-20 Gy, with ⁶⁰Co gamma radiation. To simulate partial body irradiations, irradiated and non-irradiated blood was mixed to obtain proportions of irradiated blood from 10-90%. Lymphocyte cultures were treated with Colcemid and Calyculin-A before harvest. Conventional and triage scores were performed for each dose, proportion of irradiated blood and donor. The Papworth's u test was used to evaluate the PCC-R distribution per cell. A dose-response relationship was fitted according to the maximum likelihood method using the frequencies of PCC-R obtained from 100% irradiated blood. The dose to the partially irradiated blood was estimated using the Contaminated Poisson method. A new D₀ value of 10.9 Gy was calculated and used to estimate the initial fraction of irradiated cells. The results presented here indicate that by PCC-R it is possible to distinguish between simulated partial- and whole-body irradiations by the u-test, and to accurately estimate the dose from 10-20 Gy, and the initial fraction of irradiated cells in the interval from 10-90%.

Comparative study of radioresistance between feline cells and human cells

Radioresistance of cats has been seen in animal radiotherapy. Feline radioresistance and its underlying mechanism(s) were investigated in fibroblast cells and lymphocytes. We hypothesized that radioresistance was attributable to an increase in the cells ability to repair DNA damage. To investigate this hypothesis, fibroblast cells were exposed to various doses of X rays and then colony formation assays were performed. Survival curves showed that potential lethal damage repair (PLDR) for feline cells were greater than that for human cells. γ-H2AX foci assays were performed to evaluate DNA double-strand breaks (DSBs) formation and repair kinetics. After PLDR, feline cells displayed a decreased residual amount of γ-H2AX foci. Formation of chromosome aberrations (dicentrics) after PLDR as an indicator of radiation-induced DNA damage and repair; human, feline and canine lymphocytes were evaluated. Human and canine lymphocytes showed two to three times the number of dicentrics compared to feline lymphocytes. Finally, micronuclei assays were performed to further confirm the radioresistant nature of feline lymphocytes. In concordance with the results of the chromosome aberration assay, the number of micronuclei in feline lymphocytes was less than observed in human and canine lymphocytes. Taken together, these results show that DNA and chromosome damage induced by X irradiation is more effectively repaired in feline cells, resulting in less residual damage. Our results suggest that both feline fibroblasts and lymphocytes are more radioresistant compared to human cells of similar tissues, and this resistance can be contributed, at least in part, to greater ability for PLDR.

Deoxyribonucleic acid damage-associated biomarkers of ionising radiation: current status and future relevance for radiology and radiotherapy

Diagnostic and therapeutic radiation technology has developed dramatically in recent years, and its use has increased significantly, bringing clinical benefit. The use of diagnostic radiology has become widespread in modern society, particularly in paediatrics where the clinical benefit needs to be balanced with the risk of leukaemia and brain cancer increasing after exposure to low doses of radiation. With improving long-term survival rates of radiotherapy patients and the ever-increasing use of diagnostic and interventional radiology procedures, concern has risen over the long-term risks and side effects from such treatments. Biomarker development in radiology and radiotherapy has progressed significantly in recent years to investigate the effects of such use and optimise treatment. Recent biomarker development has focused on improving the limitations of established techniques by the use of automation, increasing sensitivity and developing novel biomarkers capable of quicker results. The effect of low-dose exposure (0-100 mGy) used in radiology, which is increasingly linked to cancer incidences, is being investigated, as some recent research challenges the linear-no-threshold model. Radiotherapy biomarkers are focused on identifying radiosensitive patients, determining the treatment-associated risk and allowing for a tailored and more successful treatment of cancer patients. For biomarkers in any of these areas to be successfully developed, stringent criteria must be applied in techniques and analysis of data to reduce variation among reports and allow data sets to be accurately compared. Newly developed biomarkers can then be used in combination with the established techniques to better understand and quantify the individual biological response to exposures associated with radiology tests and to personalise treatment plans for patients.

Individual variations in the micronucleus assay for biological dosimetry after high dose exposure

The micronucleus assay is widely used as a biological dosimeter. Due to an inhibitory effect of radiation on cell proliferation the assay yields satisfactory results only when the absorbed dose is below about 5Gy. In 2002 Müller and Rode suggested that a modified version of the test, based on the analysis of the ratio of trinucleated to tetranucleated cells and the frequency of micronuclei (Mn) in binucleated cells containing at least one Mn, can be applied to detect a dose reaching 15Gy (Mutat. Res. 502 (2002) 47-51). Their conclusion was based on the results of experiments with lymphocytes from one donor and nothing is known about the possible influence of individual variability on the applicability of the Mn test to detect high doses of radiation. The aim of the present study was to validate the modified micronucleus assay with lymphocytes of 5 donors. Their blood was exposed to 0, 5, 10, 15 and 20Gy of (60)Co gamma rays. The levels of Mn and of cell proliferation were assessed using various approaches. A strong inter-individual variability was observed for all endpoints. The results clearly show that the assessment of cell proliferation is essential for the interpretation of results. Unfortunately, it was not possible to identify one single proliferation marker that gives all necessary information.

Cytogenetic dose-response in vitro for biological dosimetry after exposure to high doses of gamma-rays

The dose response for dicentrics plus centric rings and total unstable chromosome-type aberrations was studied in the first mitoses of cultured human peripheral blood lymphocytes irradiated in vitro to doses of ∼2, 4, 6, 8, 10, 16 and 20 Gy of acute (60)Со gamma-rays. A dose-dependent increase of aberration yield was accompanied by a tendency to the underdispersion of dicentrics and centric rings among cells distributions compared with Poisson statistics at doses ≥6 Gy. The formal fitting of the data to a linear-quadratic model resulted in an equation with the linear and quadratic coefficients ranged 0.098-0.129×cell(-1)×Gy(-1) and 0.039-0.034×cell(-1)×Gy(-2), respectively, depending on the fitting method. The actual radiation-induced aberration yield was markedly lower than expected from a calibration curve, generated earlier within a lower dose range. Interlaboratory variations in reported dicentric yields induced by medium-to-high radiation doses in vitro are discussed.

A simple and rapid fluorescence in situ hybridization microwave protocol for reliable dicentric chromosome analysis

Fluorescence in situhybridization (FISH) is an extremely effective and sensitive approach to analyzing chromosome aberrations. Until recently, this procedure has taken multiple days to complete. The introduction of telomeric and centromeric peptide nucleic acid (PNA) probes has reduced the procedure's duration to several hours, but the protocols still call for a high temperature (80-90°C) step followed by 1-3 h of hybridization. The newest method to speed up the FISH protocol is the use of a microwave to shorten the heating element to less than a minute; however this protocol still calls for a 1-h hybridization period. We have utilized PNA centromere/telomere probes in conjunction with a microwave oven to show telomere and centromere staining in as little as 30 s. We have optimized the hybridization conditions to increase the sensitivity and effectiveness of the new protocol and can effectively stain chromosomes in 2 min and 30 s of incubation. We have found that our new approach to FISH produces extremely clear and distinct signals. Radiation-induced dicentric formation in mouse and human fibroblast cells was analyzed by two individual scorers and the observed dicentrics matched very well.

Chromatin condensation dynamics and implications of induced premature chromosome condensation

Somatic cell cycle is a dynamic process with sequential events that culminate in cell division. Several physiological activities occur in the cytoplasm and nucleus during each of the cell cycle phases which help in doubling of genetic content, organized arrangement of the duplicated genetic material and perfect mechanism for its equal distribution to the two daughter cells formed. Also, the cell cycle checkpoints ensure that the genetic material is devoid of damages thus ensuring unaltered transmission of genetic information. Two important phenomena occurring during the cell cycle are the DNA condensation and decondensation cycles in the nucleus along with the cyclic expression and functioning of certain specific proteins that help in the same. Several protein families including Cyclins, cyclin dependent kinases, condensins, cohesins and surivins ensure error free, stage specific DNA condensation and decondensation by their highly specific, controlled orchestrated presence and action. Understanding the molecular mechanisms of chromatin compaction towards formation of the structural units, the chromosomes, give us valuable insights into the cellular physiology and also direct us to techniques such as premature chromosome condensation. The techniques of inducing 'prophasing' of interphase cells are undergoing rapid advances which have multidimensional applications for basic research and direct applications.

Estimation of the biological dose received by five victims of a radiation accident using three different cytogenetic tools

The present study aims to estimate the biological doses received by five victims (A, B, C, D and E) of the Shanxi Taiyuan radiation accident in China of 2008 and to investigate the value of the cytokinesis-block micronuclei (CBMN) and premature chromosome condensation (PCC) assays in the estimation of biological doses received by the victims of a radiation accident. Conventional chromosome aberration analysis and the CBMN assay, as well as a drug-induced PCC assay recently established by our group, were performed on peripheral blood and bone marrow samples from five victims after the accident. The biological doses were estimated by scoring dicentrics plus centric rings, micronuclei and PCC rings. A high dose-effect curve and the nuclear division index (NDI) we previously established were used to estimate the dose received by victim A, the most highly affected victim of the five. The doses for the five victims (A, B, C, D and E) were 12.4, 3.4, 2.5, 2.1 and 2.2Gy, respectively, estimated by scoring dicentrics plus rings in peripheral blood lymphocytes. Similar results were obtained by combining the CBMN and NDI (CBMN+NDI) assays and the PCC assay. The doses estimated by the three methods were in accordance with the clinical symptoms observed. The specific dicentric assay with a low background level may be a better indicator for biological dose evaluation than the CBMN and PCC assays. The high dose curve we established is reliable and could become a suitable supplement to traditional biodosimetry for dose estimation. The CBMN and drug-induced PCC assays are simple, rapid and accurate. The two methods reinforce and verify the results observed with chromosome aberration analysis.

A modified system for analyzing ionizing radiation-induced chromosome abnormalities

The analysis of dicentric chromosomes in human peripheral blood lymphocytes (PBLs) by Giemsa staining is the most established method for biological dosimetry. However, this method requires a well-trained person because of the difficulty in detecting aberrations rapidly and accurately. Here, we applied a fluorescence in situ hybridization (FISH) technique, using telomere and centromere peptide nucleic acid (PNA) probes, to solve the problem of biological dosimetry in radiation emergency medicine. A comparison by a well-trained observer found that FISH analysis of PBLs for the dose estimation was more accurate than the conventional Giemsa analysis, especially in samples irradiated at high doses. These results show that FISH analysis with centromeric/telomeric PNA probes could become the standard method for biological dosimetry in radiation emergency medicine.

Mass casualties and health care following the release of toxic chemicals or radioactive material--contribution of modern biotechnology

Catastrophic chemical or radiological events can cause thousands of casualties. Such disasters require triage procedures to identify the development of health consequences requiring medical intervention. Our objective is to analyze recent advancements in biotechnology for triage in mass emergency situations. In addition to identifying persons "at risk" of developing health problems, these technologies can aid in securing the unaffected or "worried well". We also highlight the need for public/private partnerships to engage in some of the underpinning sciences, such as patho-physiological mechanisms of chemical and radiological hazards, and for the necessary investment in the development of rapid assessment tools through identification of biochemical, molecular, and genetic biomarkers to predict health effects. For chemical agents, biomarkers of neurotoxicity, lung damage, and clinical and epidemiological databases are needed to assess acute and chronic effects of exposures. For radiological exposures, development of rapid, sensitive biomarkers using advanced biotechnologies are needed to sort exposed persons at risk of life-threatening effects from persons with long-term risk or no risk. The final implementation of rapid and portable diagnostics tools suitable for emergency care providers to guide triage and medical countermeasures use will need public support, since commercial incentives are lacking.

Infrastructure to support ultra high throughput biodosimetry screening after a radiological event

PURPOSE

After a large-scale radiological event, there will be a pressing need to assess, within a few days, the radiation doses received by tens or hundreds of thousands of individuals. This is for triage, to prevent treatment locations from being overwhelmed, in what is sure to be a resource limited scenario, as well as to facilitate dose-dependent treatment decisions. In addition there are psycho-social considerations, in that active reassurance of minimal exposure is a potentially effective antidote to mass panic, as well as long-term considerations, to facilitate later studies of cancer and other long-term disease risks.

MATERIALS AND METHODS

As described elsewhere in this issue, we are developing a Rapid Automated Biodosimetry Tool (RABiT). The RABiT allows high throughput analysis of thousands of blood samples per day, providing a dose estimate that can be used to support clinical triage and treatment decisions.

RESULTS

Development of the RABiT has motivated us to consider the logistics of incorporating such a system into the existing emergency response scenarios of a large metropolitan area. We present here a view of how one or more centralized biodosimetry readout devices might be incorporated into an infrastructure in which fingerstick blood samples are taken at many distributed locations within an affected city or region and transported to centralized locations.

CONCLUSIONS

High throughput biodosimetry systems offer the opportunity to perform biodosimetric assessments on a large number of persons. As such systems reach a high level of maturity, emergency response scenarios will need to be tweaked to make use of these powerful tools. This can be done relatively easily within the framework of current scenarios.