Multidisciplinary European Low Dose Initiative (MELODI): strategic research agenda for low dose radiation risk research.

MELODI (Multidisciplinary European Low Dose Initiative) is a European radiation protection research platform with focus on research on health risks after exposure to low-dose ionising radiation. It was founded in 2010 and currently includes 44 members from 18 countries. A major activity of MELODI is the continuous development of a long-term European Strategic Research Agenda (SRA) on low-dose risk for radiation protection. The SRA is intended to identify priorities for national and European radiation protection research programs as a basis for the preparation of competitive calls at the European level. Among those key priorities is the improvement of health risk estimates for exposures close to the dose limits for workers and to reference levels for the population in emergency situations. Another activity of MELODI is to ensure the availability of European key infrastructures for research activities, and the long-term maintenance of competences in radiation research via an integrated European approach for training and education. The MELODI SRA identifies three key research topics in low dose or low dose-rate radiation risk research: (1) dose and dose rate dependence of cancer risk, (2) radiation-induced non-cancer effects and (3) individual radiation sensitivity. The research required to improve the evidence base for each of the three key topics relates to three research lines: (1) research to improve understanding of the mechanisms contributing to radiogenic diseases, (2) epidemiological research to improve health risk evaluation of radiation exposure and (3) research to address the effects and risks associated with internal exposures, differing radiation qualities and inhomogeneous exposures. The full SRA and associated documents can be downloaded from the MELODI website ( http://www.melodi-online.eu/sra.html ).

An unusual case of extra-abdominal desmoid tumour.

Desmoid tumour is relatively rare and generally non-metastatisizing lesion of mesenchymal origin composed of fibrous tissue and fitting in the group of aggressive fibromatosis; it is a locally aggressive proliferative soft-tissue lesion with controversial nature. This tumour accounts for 0.03% of all tumours and 3% of soft-tissue tumours with annual incidence of two to four cases per million. Although desmoid tumours are more common in persons aged 10-40 years than in others, they do occur in young children and older adults; in children the sex incidence is equal. This is a rare case of extra-abdominal desmoid tumour in a 14-year-old girl affected by spastic tetraparesis. To our knowledge no similar cases are present in literature to date.

DNA fragmentation induced in human fibroblasts by 56Fe ions: experimental data and Monte Carlo simulations.

We studied the DNA fragmentation induced in human fibroblasts by iron-ion beams of two different energies: 115 MeV/nucleon and 414 MeV/nucleon. Experimental data were obtained in the fragment size range 1-5700 kbp; Monte Carlo simulations were performed with the PARTRAC code; data analysis was also performed through the Generalized Broken Stick (GBS) model. The comparison between experimental and simulated data for the number of fragments produced in two different size ranges, 1-23 kbp and 23-5700 kbp, gives a satisfactory agreement for both radiation qualities. The Monte Carlo simulations also allow the counting of fragments outside the experimental range: The number of fragments smaller than 1 kbp is large for both beams, although with a strong difference between the two cases. As a consequence, we can compute different RBEs depending on the size range considered for the fragment counting. The PARTRAC evaluation takes into account fragments of all sizes, while the evaluation from the experimental data considers only the fragments in the range of 1-5700 kbp. When the PARTRAC evaluation is restricted to this range, the agreement between experimental and computed RBE values is again good. When fragments smaller than 1 kbp are also considered, the RBE increases considerably, since gamma rays produce a small number of such fragments. The analysis performed with the GBS model proved to be quite sensitive to showing, with a phenomenological single parameter, variations in double-strand break (DSB) correlation.

Unilateral hydronephrosis due to ureteropelvic junction obstruction in children: long term follow-up.

AIM: Hydronephrosis is one of the most common urological disease detected on prenatal ultrasound; The aim of this study was evaluate the role of long-term follow-up in patients with unilateral hydronephrosis. METHODS: On January 2009, the medical charts of patients observed at the Department and Institution for unilateral hydronephrosis were reviewed, for a long-term follow-up evaluation (10 years). All diagnosis were done prenatally. Long term follow-up is described. RESULTS: One hundred and seventy-four 174 patients were observed. At diagnosis grading of hydronephrosis was: 3% grade 0, 25% grade I, 41% grade II, 31% grade IV. At the end of the study, 94 patients underwent surgery, while 80 were managed conservatively. CONCLUSIONS: Grade of hydronephrosis and renal function still remain the most important variables to decide the surgical management. Long-term follow-up shows that over the years many patients need surgery.

INNOVATIVE SOLUTIONS FOR PERSONAL RADIATION SHIELDING IN SPACE.

Personal radiation shielding is likely to play an important role in the strategy for radiation protection of future manned interplanetary missions. There is potential for the successful adoption of wearable shielding devices, readily available in case of accidental exposures or used for emergency operations in low-shielded areas of the habitat, particularly in case of solar particle events (SPEs). Based on optimization of available resources, conceptual models for radiation protection spacesuits have been proposed, with elements made of different materials, and the first prototype of a water-fillable garment was designed and manufactured in the framework of the PERSEO project, funded by the Italian Space Agency, leading to the successful test of such prototype for ease of use and wearability on-board the International Space Station. We present results of Monte Carlo calculations offering a proof-of-principle validation of the shielding efficacy of such prototype in different SPE environments and shielding conditions.

BIOINFORMATIC ANALYSIS OF DOSE- AND TIME-DEPENDENT miRNome RESPONSES.

The advent of new 'omics' techniques determined a massive boost in the measurement of the whole spectra of molecules within cells, favoring promising new radiobiological studies at low doses. The main aim of this work was to assess the radiation-induced perturbations of miRNA profiles and their temporal dynamics. Human Umbilical Vein Endothelial Cells were irradiated with low doses of γ-rays. At different time points post-irradiation, cells were harvested and miRNAs isolated. A full mapping of the miRNA sequences via Next-Generation-Sequencing analysis was performed followed by bioinformatic analyses. Pathway enrichment analyses on the differentially expressed miRNAs focused both on the averaged effects of different doses over the 24-h experiment and on the altered temporal dynamics of the miRNA profiles. These complementary analyses provided a picture of the dose- and time-dependent miRNAs responses, allowing to better explore the candidate biomarkers linked to radiation exposures and their corresponding pathways and functions.

WHAT ROLES FOR TRACK-STRUCTURE AND MICRODOSIMETRY IN THE ERA OF -omics AND SYSTEMS BIOLOGY?

Ionizing radiation is a peculiar perturbation when it comes to damage to biological systems: it proceeds through discrete energy depositions, over a short temporal scale and a spatial scale critical for subcellular targets as DNA, whose damage complexity determines the outcome of the exposure. This lies at the basis of the success of track structure (and nanodosimetry) and microdosimetry in radiation biology. However, such reductionist approaches cannot account for the complex network of interactions regulating the overall response of the system to radiation, particularly when effects are manifest at the supracellular level and involve long times. Systems radiation biology is increasingly gaining ground, but the gap between reductionist and holistic approaches is becoming larger. This paper presents considerations on what roles track structure and microdosimetry can have in the attempt to fill this gap, and on how they can be further exploited to interpret radiobiological data and inform systemic approaches.

A COMPARISON BETWEEN X-RAY AND CARBON ION IRRADIATION IN HUMAN NEURAL STEM CELLS.

Glioblastoma multiforme (GBM) is characterized by a poor prognosis and a median survival of ~12-18 months. GBM is usually managed by neurosurgery followed by both chemotherapy and radiotherapy. Since GBM develops resistance to conventional therapies, treatment with C-ions is promising to completely eradicate the tumoural mass. During cranial irradiation, exposure of healthy tissues is inevitable. Because of the presence of neural stem cells, a deep investigation on the effects of C-ion irradiation with respect to X-ray induced damage is mandatory to allow a better definition of treatments. In this work, the comparison of X-rays and C-ion irradiation-induced effects on human neural stem cell, focusing on multiple endpoints, such as cell viability, cytokine secretion and spheroid formation is presented. Results show different temporal and dose responses of human neural stem cells to the different radiation qualities, suggesting different underpinning mechanisms of radiation-induced damages.

A New Standard DNA Damage (SDD) Data Format.

Our understanding of radiation-induced cellular damage has greatly improved over the past few decades. Despite this progress, there are still many obstacles to fully understand how radiation interacts with biologically relevant cellular components, such as DNA, to cause observable end points such as cell killing. Damage in DNA is identified as a major route of cell killing. One hurdle when modeling biological effects is the difficulty in directly comparing results generated by members of different research groups. Multiple Monte Carlo codes have been developed to simulate damage induction at the DNA scale, while at the same time various groups have developed models that describe DNA repair processes with varying levels of detail. These repair models are intrinsically linked to the damage model employed in their development, making it difficult to disentangle systematic effects in either part of the modeling chain. These modeling chains typically consist of track-structure Monte Carlo simulations of the physical interactions creating direct damages to DNA, followed by simulations of the production and initial reactions of chemical species causing so-called "indirect" damages. After the induction of DNA damage, DNA repair models combine the simulated damage patterns with biological models to determine the biological consequences of the damage. To date, the effect of the environment, such as molecular oxygen (normoxic vs. hypoxic), has been poorly considered. We propose a new standard DNA damage (SDD) data format to unify the interface between the simulation of damage induction in DNA and the biological modeling of DNA repair processes, and introduce the effect of the environment (molecular oxygen or other compounds) as a flexible parameter. Such a standard greatly facilitates inter-model comparisons, providing an ideal environment to tease out model assumptions and identify persistent, underlying mechanisms. Through inter-model comparisons, this unified standard has the potential to greatly advance our understanding of the underlying mechanisms of radiation-induced DNA damage and the resulting observable biological effects when radiation parameters and/or environmental conditions change.

Maize food allergy: a double-blind placebo-controlled study.

BACKGROUND: Maize allergy is not very common especially in Europe. The number of studies that address IgE mediated maize allergy is all too few. OBJECTIVE: Evaluate subjects with a history of maize allergy by double-blind, placebo-controlled food challenge; identify the spectrum of symptoms manifested during challenge; determine the lowest provocation dose (PD) during challenge; determine the performance characteristics of maize skin prick test and specific IgE. METHODS: Twenty-seven patients with a history of maize allergy were enrolled to be evaluated by skin test, specific IgE and double-blind placebo-controlled maize challenge. RESULTS: Forty-eight percent of the patients were challenge positive. PD range was 0.1-25 g. Fifty-four percent of the maize allergic subjects had a PD that was < or = 2.5 g; two subjects reacted to 100 mg of maize. Comparison of maize specific IgE levels and skin test results to the challenge results revealed the following (specific IgE level/skin testing): sensitivity 1.00/0.846, specificity 0.077/0.384, positive predictive value 0.520/0.579, and negative predictive value 1.00/0.714. CONCLUSION: Maize is a cause of IgE-mediated allergic reactions to foods in adults and children. Nearly half of the subjects recruited were confirmed by challenge to be allergic to maize. Twenty-three percent of the positive challenge patients manifested symptoms that involved two organ systems, thus fulfilling the criteria for maize induced anaphylaxis. Maize is allergenic and can pose a risk for symptomatic food allergy at a dose of 100 mg.

Contralateral exploration for unilateral inguinal hernia in females: risk factors and surgical findings.

BACKGROUND: Controversy continues over the need to explore the asymptomatic contralateral groin in girls with unilateral inguinal hernia. The aim of this study is to identify the incidence and risk factors of developing a contralateral inguinal hernia. MATERIALS AND METHODS: Between July 1997 and July 2006, 364 consecutive girls aged between 1 month and 8 years with unilateral inguinal hernia underwent surgical exploration of the contralateral inguinal side. Inclusion criteria were created. After collection of the surgical findings, the authors analysed the correlation between the patients' medical history and the incidence of contralateral inguinal hernias. The patients were then divided into eight groups following an age range grouping. RESULTS: One hundred and eighteen patients were enrolled in this study, 74 with right-side inguinal hernia and 44 with left-side inguinal hernia. About 47.4% of these patients showed contralateral true inguinal hernias, 38% right-sided and 63% left-sided hernias. There was no correlation between medical history, age at surgery and the presence of contralateral inguinal hernia. CONCLUSIONS: Although the results of this study are in contrast with many other studies in the literature, the authors came to the conclusion that contralateral exploration should be routinely performed in girls with inguinal hernia until they reach 4 years of age.

The role of lifestyle changing to improve the semen quality in patients with varicocele.

AIM: To evaluate the recovery of semen quality in patients with high grade varicocele without hypotrophy and abnormal semen analysis using a simple lifestyle changing protocol. METHODS: Fifty-two patients were eligible for this study. Two semen sample were collected at baseline and other two after treatment. PROTOCOL: patients had to stop or decrease the number of cigarette per day, reduce the coffee and alcohol consumption, introduce fruits and vegetables in the daily diet and have a normal sexual activity with an abstinence of tree days before semen collection. All the variables and the semen parameters were evaluated and correlated between responders and non-responders. RESULTS: Forty patients (76%) had an improvement of semen quality showing a normal semen analysis following the WHO criteria. The other 12 patients had an improvement of the semen quality but without statistical differences. Smokers and drinkers (for both coffee and alcohol) had lower sperm volume, lower sperm motility and vitality when compared to the others. CONCLUSIONS: The analysis of data collected by the spermiograms showed that semen quality could benefit from lifestyle changing. This finding is important for the management of patients with varicocele, suggesting that lifestyle changing could avoid surgery.

AT THE PHYSICS-BIOLOGY INTERFACE: THE NEUTRON AFFAIR.

We present predictions of neutron relative biological effectiveness (RBE) for cell irradiations with neutron beams at PTB-Braunschweig. A neutron RBE model is adopted to evaluate initial DNA damage induction given the neutron-induced charged particle field. RBE values are predicted for cell exposures to quasi-monoenergetic beams (0.56 MeV, 1.2 MeV) and to a broad energy distribution neutron field with dose-averaged energy of 5.75 MeV. Results are compared to what obtained with our RBE predictions for neutrons at similar energies, when a 30-cm sphere is irradiated in an isotropic neutron field. RBE values for experimental conditions are higher for the lowest neutron energies, because, as expected, target geometry determines the weight of the low-effectiveness photon component of the neutron dose. These results highlight the importance of characterizing neutron fields in terms of physical interactions, to fully understand neutron-induced biological effects, contributing to risk estimation and to the improvement of radiation protection standards.

A water-filled garment to protect astronauts during interplanetary missions tested on board the ISS.

As manned spaceflights beyond low Earth orbit are in the agenda of Space Agencies, the concerns related to space radiation exposure of the crew are still without conclusive solutions. The risk of long-term detrimental health effects needs to be kept below acceptable limits, and emergency countermeasures must be planned to avoid the short-term consequences of exposure to high particle fluxes during hardly predictable solar events. Space habitat shielding cannot be the ultimate solution: the increasing complexity of future missions will require astronauts to protect themselves in low-shielded areas, e.g. during emergency operations. Personal radiation shielding is promising, particularly if using available resources for multi-functional shielding devices. In this work we report on all steps from the conception, design, manufacturing, to the final test on board the International Space Station (ISS) of the first prototype of a water-filled garment for emergency radiation shielding against solar particle events. The garment has a good shielding potential and comfort level. On-board water is used for filling and then recycled without waste. The successful outcome of this experiment represents an important breakthrough in space radiation shielding, opening to the development of similarly conceived devices and their use in interplanetary missions as the one to Mars.

Comprehensive track-structure based evaluation of DNA damage by light ions from radiotherapy-relevant energies down to stopping.

Track structures and resulting DNA damage in human cells have been simulated for hydrogen, helium, carbon, nitrogen, oxygen and neon ions with 0.25-256 MeV/u energy. The needed ion interaction cross sections have been scaled from those of hydrogen; Barkas scaling formula has been refined, extending its applicability down to about 10 keV/u, and validated against established stopping power data. Linear energy transfer (LET) has been scored from energy deposits in a cell nucleus; for very low-energy ions, it has been defined locally within thin slabs. The simulations show that protons and helium ions induce more DNA damage than heavier ions do at the same LET. With increasing LET, less DNA strand breaks are formed per unit dose, but due to their clustering the yields of double-strand breaks (DSB) increase, up to saturation around 300 keV/µm. Also individual DSB tend to cluster; DSB clusters peak around 500 keV/µm, while DSB multiplicities per cluster steadily increase with LET. Remarkably similar to patterns known from cell survival studies, LET-dependencies with pronounced maxima around 100-200 keV/µm occur on nanometre scale for sites that contain one or more DSB, and on micrometre scale for megabasepair-sized DNA fragments.

Exploring innovative radiation shielding approaches in space: A material and design study for a wearable radiation protection spacesuit.

We present a design study for a wearable radiation-shielding spacesuit, designed to protect astronauts' most radiosensitive organs. The suit could be used in an emergency, to perform necessary interventions outside a radiation shelter in the space habitat in case of a Solar Proton Event (SPE). A wearable shielding system of the kind we propose has the potential to prevent the onset of acute radiation effects in this scenario. In this work, selection of materials for the spacesuit elements is performed based on the results of dedicated GRAS/Geant4 1-dimensional Monte Carlo simulations, and after a trade-off analysis between shielding performance and availability of resources in the space habitat. Water is the first choice material, but also organic compounds compatible with a human space habitat are considered (such as fatty acids, gels and liquid organic wastes). Different designs and material combinations are proposed for the spacesuits. To quantify shielding performance we use GRAS/Geant4 simulations of an anthropomorphic phantom in an average SPE environment, with and without the spacesuit, and we compare results for the dose to Blood Forming Organs (BFO) in Gy-Eq, i.e. physical absorbed dose multiplied by the proton Relative Biological Effectiveness (RBE) for non-cancer effects. In case of SPE occurrence for Intra-Vehicular Activities (IVA) outside a radiation shelter, dose reductions to BFO in the range of 44-57% are demonstrated to be achievable with the spacesuit designs made only of water elements, or of multi-layer protection elements (with a thin layer of a high density material covering the water filled volume). Suit elements have a thickness in the range 2-6 cm and the total mass for the garment sums up to 35-43 kg depending on model and material combination. Dose reduction is converted into time gain, i.e. the increase of time interval between the occurrence of a SPE and the moment the dose limit to the BFO for acute effects is reached. Wearing a radiation shielding spacesuit of the kind we propose, the astronaut could have up to more than the double the time (e.g. almost 6 instead of 2.5 h) to perform necessary interventions outside a radiation shelter during a SPE, his/her exposure remaining within dose limits. An indicative mass saving thanks to the shielding provided by the suits is also derived, calculating the amount of mass needed in addition to the 1.5 cm thick Al module considered for the IVA scenario to provide the same additional shielding given by the spacesuit. For an average 50% dose reduction to BFO this is equal to about 2.5 tons of Al. Overall, our results offer a proof-of-principle validation of a complementary personal shielding strategy in emergency situations in case of a SPE event. Such results pave the way for the design and realization of a prototype of a water-filled garment to be tested on board the International Space Station for wearability. A successful outcome will possibly lead to the further refining of the design of radiation protection spacesuits and their possible adoption in future long-duration manned missions in deep space.

Inhalation studies of nickel sulfide in pulmonary carcinogenesis of rats.

Two hundred twenty-six specific pathogenfree male and female F344 rats were exposed to nickel sulfide inhalations for 78 weeks (5 days/wk, 6 hr/day) and observed for an adiditional 30-week period. For the same amount of time, 214 rats were exposed to filtered room air and served as controls. Rats exposed to nickel sulfide showed a significantly higher incidence of pulmonary hyperplastic and neoplastic lesions originating from the bronchial and bronchiloo-alveloar segments. The overall incidence of lung tumors in the animals treated with nickel sulfide was 14 percent compared with 1 percent in the controls. Pulmonary inflammatory reactions were also greatly increased. Injection of an agent (hexachlorotetra-fluorobutane) that induced lung infarction did not increase the proportion of animals having lesions, nor did it alter the type of lesions found in animals exposed to nickel sulfide.

Modelling radiation-induced bystander effect and cellular communication.

In the last 10 years evidence has accumulated on the so-called radiation-induced 'non-targeted effects' and in particular on bystander effects, consisting of damage induction in non-irradiated cells most likely following the release of soluble factors by the irradiated ones. These phenomena were observed for different biological endpoints, both lethal and non-lethal for the cell. Although the underlying mechanisms are largely unknown, it is now widely recognised that two types of cellular communication (i.e. via gap junctions and/or release of molecular messengers into the extracellular environment) play a pivotal role. Furthermore, the effects can be significantly modulated by parameters such as cell type and cell-cycle stage, cell density, time after irradiation etc. Theoretical models and simulation codes can be of help to improve our knowledge of the mechanisms, as well as to investigate the possible role of these effects in determining deviations from the linear relationship between dose and risk which is generally applied in radiation protection. In this paper three models, including an approach under development at the University of Pavia, will be presented in detail. The focus will be on the various adopted assumptions, together with their implications in terms of non-targeted radiobiological damage and, more generally, low-dose radiation risk. Comparisons with experimental data will also be discussed.

Role of DNA/chromatin organisation and scavenging capacity in USX- and proton- induced DNA damage.

DNA higher-order structures and (non-histonic) *;OH radical scavengers have well known protective effects in the induction of single- and double-strand breaks by ionising radiation. In a previous work, such protective roles have been quantified for gamma radiation (Valota et al., Int. J. Radiat. Biol. 79, 2003). As a starting base for the simulations, we used the PARTRAC Monte Carlo code, developed within a collaboration involving the University of Pavia and the GSF institute. The code can reproduce the track structure of photons, electrons, protons and heavier ions in liquid water, and it can simulate the DNA content of a human cell at different organisation levels, based on an atom-by-atom approach. In this work we extended the calculations to Ultra-Soft X rays (USX) and protons, separately analysing the effects of different radiation types on various DNA structures (i.e. linear DNA, SV40 'minichromosomes' and compact chromatin) as a function of the *OH scavenging capacity (SC). Both for USX and protons, the calculated damage yields decreased by increasing the SC for the three considered target types. Such decrease can be ascribed to the competition between the reactions *OH-DNA and *OH-scavenger, which becomes more and more likely by increasing the SC. Furthermore, linear DNA was found to be more radiosensitive than SV40 'minichromosomes', which in turn were more radiosensitive than compact chromatin, which is protected by histones. Comparisons with experimental data by Fulford et al. (Int. J. Radiat. Biol. 77, 2001) relative to USX irradiation showed very good agreement. The dependence of the modulating role played by DNA organisation and scavenging capacity on radiation quality is presented and discussed.

Gamma ray-induced bystander effect in tumour glioblastoma cells: a specific study on cell survival, cytokine release and cytokine receptors.

Recent experimental evidence has challenged the paradigm according to which radiation traversal through the nucleus of a cell is a prerequisite for producing genetic changes or biological responses. Thus, unexposed cells in the vicinity of directly irradiated cells or recipient cells of medium from irradiated cultures can also be affected. The aim of the present study was to evaluate, by means of the medium transfer technique, whether interleukin-8 and its receptor (CXCR1) may play a role in the bystander effect after gamma irradiation of T98G cells in vitro. In fact the cell specificity in inducing the bystander effect and in receiving the secreted signals that has been described suggests that not only the ability to release the cytokines but also the receptor profiles are likely to modulate the cell responses and the final outcome. The dose and time dependence of the cytokine release into the medium, quantified using an enzyme linked immunosorbent assay, showed that radiation causes alteration in the release of interleukin-8 from exposed cells in a dose-independent but time-dependent manner. The relative receptor expression was also affected in exposed and bystander cells.