Calculation of the absorbed dose for the overexposed patients at the JCO criticality accident in Tokai-mura

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.

Neutrons are forever! Historical perspectives

Purpose: Neutrons were an active field of radiobiology at the time of publication of the first issues of the International Journal of Radiation Biology in 1959. Three back-to-back papers published by Neary and his colleagues contain key elements of interest at the time. The present article aims to put these papers into context with the discovery of the neutron 27 years previously and then give a feel for how the field has progressed to the present day. It does not intend to provide a comprehensive review of this enormous field, but rather to provide selective summaries of main driving forces and developments. Conclusions: Neutron radiobiology has continued as a vigorous field of study throughout the past 84 years. Main driving forces have included concern for protection from the harmful effects of neutrons, exploitation and optimization for cancer therapy (fast beam therapy, brachytherapy and boron capture therapy), and scientific curiosity about the mechanisms of radiation action. Effort has fluctuated as the emphasis has shifted from time to time, but all three areas remain active today. Whatever the future holds for the various types of neutron therapy, the health protection aspects will remain with us permanently because of natural environmental exposure to neutrons as well as increased additional exposures from a variety of human activities.

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.

High frequency of simple and complex chromosome aberrations detected in the Tokai-mura survivor four and five years after the 1999 criticality accident

In September 1999 a criticality accident occurred in a uranium processing plant in Tokai-mura, Japan. During the accident, three workers (A, B and C) were exposed to high acute doses of neutrons and γ-rays: workers A and B fatally and worker C to an estimated whole body absorbed dose of 0.81 Gy neutrons and 1.3 Gy γ-rays. We obtained fixed peripheral blood lymphocytes (PBL) preparations from worker C approximately four and five years after the accident and assayed by 24 colour karyotyping (M-FISH) to determine the frequency and complexity of chromosome aberrations present. We observed a high frequency of simple reciprocal translocations, which we used to provide a rough estimation of dose and, in addition, for the assessment of the emergence of any clinically-relevant clonal exchanges. We did not observe any evidence of clonality but did find some evidence suggesting chromosome 1 as being preferentially involved in exchanges in stable cells. We also detected a relatively high frequency of damaged cells containing complex chromosome aberrations, of both the stable and unstable types. Qualitatively these complex aberrations were consistent with those observed to be induced after exposure to low doses of high-LET radiation or moderate doses of low-LET radiation, supporting the suggestion that heavily damaged cells can be quite long-lived in vivo.

Pathological changes in the gastrointestinal tract of a heavily radiation-exposed worker at the Tokai-mura criticality accident

Gastrointestinal syndrome after high-dose acute radiation whole body exposure is difficult to treat, although it is a well-known complication. In this report, we describe the clinical and pathological features of a patient who died after the criticality accident which occurred in Japan on 30 September 1999. The patient was estimated to have been exposed to 16-25 Gy equivalent of gamma ray, and died of multiple organ failure after acute radiation syndrome, especially gastrointestinal syndrome, on day 82. The stomach and small intestine contained a large amount of blood clots and the gastrointestinal epithelial cells were almost totally depleted at autopsy. In addition, the degree of the mucosal damage was dependent on the segment of the gastrointestinal tract; the mucosa of stomach, ileum and ascending colon was entirely depleted, but the esophagus, descending and sigmoid colon and rectum retained a small portion of the epithelial cells. From the posture of the patient at the time of exposure, the absorbed dose was presumed to be highest in the right-anterior abdomen. This agreed with the pathological differences in the mucosal damage by the position in the abdomen, which depended presumably on the radiation dose. This is the first report documenting the relationship between the absorbed dose and the severity of gastrointestinal damages in vivo.

Initial medical management of patients severely irradiated in the Tokai-mura criticality accident

A nuclear criticality accident occurred in Japan on September 30, 1999, which resulted in severe exposure of three victims to mixed flux of neutrons and gamma-rays. Estimated average doses for the three victims were 5.4 Gy of neutrons and 8.5 Gy of gamma-rays for Patient A, 2.9 Gy of neutrons and 4.5 Gy of gamma-rays for Patient B, and 0.81 Gy of neutrons and 1.3 Gy of gamma-rays for Patient C. They then suffered the consequences of the effects of ionizing radiation resulting in acute radiation syndrome. In Patients A and B, bone marrow failure was so severe that they received haematopoietic stem cell transplantation. The graft initially took successfully in both patients, although in Patient B it was later taken over by his own haematopoietic cells. They also suffered from severe skin lesions, later exhibited gastrointestinal bleeding and eventually died of multiple organ failure 82 and 210 days after the accident, respectively. The survival of these patients beyond the period of agranulocytosis means that bone marrow failure per se caused by exposure to ionizing radiation may now be overcome. Patient C also developed bone marrow failure and was treated with granulocyte colony-stimulating factor as well as supportive care. He recovered without major complications and is now under periodical follow-up. Remarkably, during the prodromal phase, all the patients exhibited hypoxaemia, two of whom also showed interstitial oedema of the lungs. In Patient C these manifestations improved within a week. The circumstances of the accident and the initial medical treatment of the victims are described.

Dose estimation by ESR on tooth enamel from two workers exposed to radiation due to the JCO accident

ESR dosimetry is useful to estimate the external dose for the general population as well as for occupational workers in a nuclear emergency. Three teeth were extracted from two exposed workers (A and B) related to the JCO criticality accident. Tooth enamel was carefully separated from other tooth parts and subjected to ESR dosimetry. Doses equivalent to the gamma-ray dose of 60Co were estimated as follows: for worker A, the buccal and lingual sides of the eighth tooth in the upper right side, 11.8 +/- 3.6 and 12.0 +/- 3.6 Gy, respectively; for worker B, the buccal and lingual sides of the fourth tooth in the upper right side and the fifth tooth in the upper left side, 11.3 +/- 3.4 and 10.8 +/- 3.3 Gy, 11.7 +/- 3.5 and 11.4 +/- 3.4 Gy, respectively. The estimated doses were found to be similar and not dependent on the tooth positions, whether the buccal or lingual sides in each tooth.

Transplantation for accidental acute high-dose total body neutron- and gamma-radiation exposure

Accidental exposure to acute high-dose total body neutron radiation is rare. We report a 35-year-old man exposed to a total body dose of 5.4 Gy neutron- and 8.5-13 Gy gamma-radiation in a radiation criticality accident. He received a blood stem cell transplant from his HLA-identical sister. There was bone marrow recovery with complete donor chimerism. Random chromatid breaks were observed in donor cells suggesting a bystander effect of neutron exposure. The subject died 82 days after the accident (75 days post transplant) from multi-organ failure.

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

A dose estimation by chromosome analysis was performed on the 3 severely exposed patients in the Tokai-mura criticality accident. Drastically reduced lymphocyte counts suggested that the whole-body dose of radiation which they had been exposed to was unprecedentedly high. Because the number of lymphocytes in the white blood cells in two patients was very low, we could not culture and harvest cells by the conventional method. To collect the number of lymphocytes necessary for chromosome preparation, we processed blood samples by a modified method, called the high-yield chromosome preparation method. With this technique, we could culture and harvest cells, and then make air-dried chromosome slides. We applied a new dose-estimation method involving an artificially induced prematurely condensed ring chromosome, the PCC-ring method, to estimate an unusually high dose with a short time. The estimated doses by the PCC-ring method were in fairly good accordance with those by the conventional dicentric and ring chromosome (Dic+R) method. The biologically estimated dose was comparable with that estimated by a physical method. As far as we know, the estimated dose of the most severely exposed patient in the present study is the highest recorded among that chromosome analyses have been able to estimate in humans.

Determination of radionuclides produced by neutrons in heavily exposed workers of the JCO criticality accident in Tokai-mura for estimating an individual's neutron fluence

In the Tokai-mura criticality accident, three workers were heavily exposed. Biological materials, such as blood, urine, vomit and hair, were collected from the workers and analyzed for radioactivities, produced by the neutron irradiation. Activation products. such as 24Na, -K and 82Br, were found in these materials by gamma-ray spectrometry. The radionuclide of the highest activity observed in biological materials was 24Na, e.g. the concentrations of this nuclide in the blood samples from the three patients at the accident time were 169, 92 and 23 Bq/ml, respectively. The concentrations of stable sodium in the same samples were determined by ICP-AES to obtain specific activities of 24Na (concentration ratio between the produced 24Na and stable 23Na), which are essential for estimating the neutron fluences and radiation doses. The specific activities of 24Na obtained for the three patients through the blood analysis were 8.2 x 10(4),4.3 x 10(4) and 1.2 x 10(4) Bq24Na/g23Na. Based on these values, individual's neutron fluences were estimated to be 5.7 x 10(11), 3.0 x 10(-1) and 0.85 x 10(11) cm(-2), respectively.