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Space radiation represents one of the major health hazards to crews of interplanetary missions. As the duration of space flight increases, according to International Space Station (ISS) and Mars mission programs, the risk associated with exposure to ionizing radiation also increases. Although physical dosimetry is routinely performed in manned space missions, it is generally accepted that direct measurement of biological endpoints (biological dosimetry) is necessary for a precise assessment of radiation risk in extraterrestrial activities. Chromosomal aberrations (CAs) in peripheral blood lymphocytes (PBLs) are particularly suitable to this purpose, as they can provide estimates of both equivalent radiation dose and risk. In this study, cytogenetic analysis was performed on PBL chromosomes of an Italian astronaut involved in two different 10-day missions on the ISS (Marco Polo, April 2002, and ENEIDE, May 2005). Blood samples were collected before and after flights. CAs were evaluated in either mitotic spreads or in prematurely condensed chromosomes (PCC) by Fluorescence in Situ Hybridization (FISH). In addition, blood samples were exposed to graded doses of X-rays in vitro before and after the flight and cytogenetic damage evaluated to investigate whether the space environment alters the sensitivity of human cells to ionizing radiation. The yield of baseline chromosomal aberrations was not modified following Marco Polo and ENEIDE mission. This is consistent with the low dose absorbed in these short-term space missions. Preliminary results from Marco Polo mission suggested a significant increase in intrinsic radiosensitivity of lymphocytes after landing compared to pre-flight and follow-up (6 months after landing) samples. However, this effect was not observed during the ENEIDE mission. The results suggest that intra-indi-vidual variations in radiosensitivity are significant, but they cannot be related to the space flight.

In this study, we have pre-exposed human peripheral blood lymphocytes to non-ionizing radiofrequency fields (RF, 1950 MHz, UMTS signal, at 0.3 W/kg SAR) and then challenged them with ionizing radiation to examine the induction of adaptive response (AR). The results showed that 20 hours of pre-exposure of the cells to RF resulted in a significant reduction in the frequency of micronuclei induced by 1.0 and 1.5 Gy x-rays. Thus, the data indicated RF-induced AR.

We report results for chromosomal aberrations in human peripheral blood lymphocytes after they were exposed to high-energy iron ions with or without shielding at the HIMAC, AGS and NSRL accelerators. Isolated lymphocytes were exposed to iron ions with energies between 200 and 5000 MeV/nucleon in the 0.1-1-Gy dose range. Shielding materials consisted of polyethylene, lucite (PMMA), carbon, aluminum and lead, with mass thickness ranging from 2 to 30 g/cm(2). After exposure, lymphocytes were stimulated to grow in vitro, and chromosomes were prematurely condensed using a phosphatase inhibitor (calyculin A). Aberrations were scored using FISH painting. The yield of total interchromosomal exchanges (including dicentrics, translocations and complex rearrangements) increased linearly with dose or fluence in the range studied. Shielding decreased the effectiveness per unit dose of iron ions. The highest RBE value was measured with the 1 GeV/nucleon iron-ion beam at NSRL. However, the RBE for the induction of aberrations apparently is not well correlated with the mean LET. When shielding thickness was increased, the frequency of aberrations per particle incident on the shield increased for the 500 MeV/nucleon ions and decreased for the 1 GeV/nucleon ions. Maximum variation at equal mass thickness was obtained with light materials (polyethylene, carbon or PMMA). Variations in the yield of chromosomal aberrations per iron particle incident on the shield follow variations in the dose per incident particle behind the shield but can be modified by the different RBE of the mixed radiation field produced by nuclear fragmentation. The results suggest that shielding design models should be benchmarked using both physics and biological data.

The aim was to evaluate the effect of modelled microgravity on radiation-induced chromosome aberrations (CAs). G(0) peripheral blood lymphocytes were exposed to 60 MeV protons or 250 kV(p) X-rays in the dose range 0 - 6 Gy, and allowed to repair DNA damage for 24 h under either normal gravity or microgravity modelled by the NASA-designed rotating-wall bioreactor. Cells were then stimulated to proliferate by phytohaemagglutinin (PHA) under normal gravity conditions and prematurely condensed chromosomes were harvested after 48 h. CAs were scored in chromosomes 1 and 2 by fluorescence in-situ hybridization. Proliferation gravisensitivity was examined by cell growth curves and by morphological evaluation of mitogen-induced activation. Cell replication rounds were monitored by bromodeoxyuridine labelling. Modelled microgravity markedly reduced PHA-mediated lymphocyte blastogenesis and cell growth. However, no significant differences between normal gravity and modelled microgravity were found in the dose - response curves for the induction of aberrant cells or total interchromosomal exchange frequency. Rotating-wall bioreactor-based microgravity reproduced space-related alterations of mitogen stimulation in human lymphocytes but did not affect the yield of CAs induced by low-linear energy transfer radiation.

Gli effetti radiobiologici della radiazione ionizzante di interesse in radioprotezione e adronterapia dipendono fortemente dalla qualità della radiazione. Ad alto LET, gli effetti della struttura di traccia di ioni accelerati giocano un ruolo che non è stato bene caratterizzato sia dal punto di vsita sperimentale che modellistico. Qui presentiamo dati sulla sopravvivenza clonogenica ottenuti esponendo linee cellulari tumorali intorno al picco di Bragg per fasci di ioni 12C, 16O e 19F accelerati al Tandem TTT-3 del Dipartimento di Scienze Fisiche, Università di Napoli Federico II. I risultati saranno discussi in relazione agli attuali modelli RBE-LET.

Biophysical models are commonly used to evaluate the effectiveness of shielding in reducing the biological damage caused by cosmic radiation in space flights. To improve and validate these codes biophysical experiments are needed. We have measured the induction of chromosomal aberrations in human peripheral blood lymphocytes exposed in vitro to 500 MeV/ n iron ion beams (dose range 0.1–1 Gy) after traversing shields of different material (lucite, aluminium, or lead) and thickness (0–11.3 g/cm 2 ). For comparison, cells were exposed to 200 MeV/ n iron ions and to X-rays. Chromosomes were prematurely condensed by a phosphatase inhibitor (calyculin A) to avoid cell-cycle selection produced by the exposure to high-LET heavy-ion beams. Aberrations were scored in chromosomes 1, 2, and 4 following fluorescence in situ hybridization. The fraction of aberrant lymphocytes has been evaluated as a function of the dose at the sample position, and of the fluence of primary 56 Fe ions hitting the shield. The influence of shield thickness on the action cross-section for the induction of exchange-type aberrations has been analyzed, and the dose average-LET measured as a function of the shield thickness. These preliminary results prove that the effectiveness of heavy ions is modified by shielding, and the biological damage is dependent upon shield thickness and material.

Stress-induced premature senescence (SIPS) is increasingly attracting interest as a cellular response to generalized sublethal stimuli, which include ionizing radiation (IR). Its timing can be modulated by the nature of the toxic agent while its underlying molecular mechanisms are not clear. Low doses of IR have been shown to induce SIPS in vitro in cell lines such as fibroblasts, this phenomenon being accompanied by premature differentiation. For the first time, here we demonstrate the occurrence of ectopic cellular senescence in human endothelial cells and its correlation with shortening of mean telomere length as assessed by Interphase Quantitative (IQ)-FISH. Carbon ions from the plateau region and from the Spread-Out Bragg Peak (SOBP), of interest for normal tissue and tumour vasculature hadrontherapy effects respectively, were accelerated at GSI (Darmstadt). Clonogenically iso-effective doses of low-LET radiation were used as reference. In our hands, the senescent phenotype was found to occur at early times post irradiation and was effectively induced by doses as low as 0.1-0.5 Gy of carbon ions. A persistent occurrence of senescing cells was found also in SOBP-irradiated cells, although at a lesser extent but despite the higher cell lethality known to be induced in SOBP. Mean length of telomeres, whose temporal stability is critical for maintenance of genomic stability and suppression of carcinogenesis, shows a reduction which is inversely related to LET, suggesting telomere length as a driving mechanism for SIPS after low LET irradiation but of no apparent relevance for carbon ion-induced senescence. These results will be discussed in relation to their implications for normal tissue adverse effects as well as desirable tumor vasculature impairment following hadrontherapy.

Carbon-ion irradiation is used to treat deep seated and/or radioresistant tumours because of the ions’ superior ballistic and radiobiological properties compared to low-LET radiation or protons. However, hadrontherapy late effects are undetermined. One such effect may be stress-induced premature senescence (SIPS), a cellular response generally elicited by sublethal insults. By enabling sublethally damaged cells to escape ionising radiation (IR)-induced death, SIPS may lead to genomic instability, hence transformation. Furthermore, in vivo, accumulation of prematurely senescent cells in a normal tissue can affect its performance and accelerate its degeneration. On the other hand, it would be much desirable that lower doses of IR revert the immortalised phenotype to a senescent one or may efficiently impair tumour vasculature. The induction of SIPS and its relationship with telomere length, which drives physiological senescence, were investigated in vitro by exposing model system (HUVEC or human vein endothelial cells) to the GSI carbon ion beam used for therapeutic purposes, at both the LET values incurred by normal (plateau region) and tumour (spread-out Bragg Peak) cells. X-ray irradiation was used as a reference. The aim was two fold: understanding if radiation quality influences SIPS and whether the latter is mechanistically linked with telomere length reduction.

The aim of this preliminary investigation was to assess whether human peripheral blood lymphocytes which have been pre-exposed to non-ionizing radiofrequency fields exhibit an adaptive response (AR) by resisting the induction of genetic damage from subsequent exposure to ionizing radiation. Peripheral blood lymphocytes from four healthy donors were stimulated with phytohemagglutinin for 24 h and then exposed for 20 h to 1950 MHz radiofrequency fields (RF, adaptive dose, AD) at an average specific absorption rate of 0.3 W/kg. At 48 h, the cells were subjected to a challenge dose (CD) of 1.0 or 1.5 Gy X-irradiation (XR, challenge dose, CD). After a 72 h total culture period, cells were collected to examine the incidence of micronuclei (MN). There was a significant decrease in the number of MN in lymphocytes exposed to RF + XR (AD + CD) as compared with those subjected to XR alone (CD). These observations thus suggested a RF-induced AR and induction of resistance to subsequent damage from XR. There was variability between the donors in RF-induced AR. The data reported in our earlier investigations also indicated a similar induction of AR in human blood lymphocytes that had been pre-exposed to RF (AD) and subsequently treated with a chemical mutagen, mitomycin C (CD). Since XR and mitomycin-C induce different kinds of lesions in cellular DNA, further studies are required to understand the mechanism(s) involved in the RF-induced adaptive response.

Among the most important obstacle to long-term space exploration by human beings there is the health risk due to the exposure to high charge and energy ions present in the galactic cosmic rays. The shielding is the simplest solution to protect the crews but the nuclear fragmentation events modify the radiation field. In recent years alternative materials are under investigation in order to enhance the shielding properties: therefore is crucial to measure the interaction cross section because biological effects are related to the radiation quality. In this work we report the measurement of the total charge changing cross section of 1 A GeV iron ions on different targets of interest in space radiation protection. An automatic system, realized in our laboratory, was used to analyze the CR-39 detectors. The system comprises an inverted microscope with motorized stage, a CCD camera, a motion control device and the computer code TRANA written in Labview language. The code uses the Danielsson algorithm for track recognition and determines the geometrical parameters and the central brightness of the tracks. The analysis of an image (about 200 X 300 micron^2) takes 1-3 seconds, depending on the number of observed tracks. Special care is taken for couples of overlapping tracks.

Al fine di garantire un'efficace Radioprotezione degli astronauti, è necessario studiare come la radiazione cosmica interagisce con nuovi materiali che stanno trovando ampie applicazioni nella costruzione di moduli gonfiabili per i veicoli o le stazioni spaziali, in quanto non vengono danneggiati a seguito di eventuali impatti con meteoriti. Prove sull'efficacia di questi materiali, dal punto di vista radioprotezionistico sono in corso sulla Stazione Spaziale Internazionale e sono state effettuate anche presso il Brookhaven National Laboratory per poter valutare la dose dovuta a particelle HZE, poiché nello spazio il campo è misto e le sue componenti sono quindi difficilmente separabili.

La radioterapia intraoperatoria (IORT) è una recente modalità di trattamento che prevede la somministrazione di una singola dose di elettroni in sede di intervento chirurgico. Le condizioni di irraggiamento prevedono ratei di dose e di dose per impulso molto più alti rispetto alle radioterapia convenzionale con LINAC (200 e 20 volte maggiori, rispettivamente), con nuovi problemi dosimetrici e radiobiologici da affrontare. Cellule di carcinoma mammario sono state irraggiate con elettroni prodotti dall???acceleratore per IORT dell???azienda Ospedaliero-Universitaria di Pisa e con raggi X presso l???Università di Napoli Federico II per la misura della sopravvivenza clonogenica e la valutazione dell???efficacia biologica relativa.

The objective of this study was to measure differences in the chromosomal rearrangements found in the progeny of cells exposed to the same dose of X-rays or energetic iron ions, with emphasis on intra-chromosomal exchanges. We hybridized metaphase cells with human DNA probes specific for the p and q arms of the chromosome 1. The arm-specific probes allow a fast and reliable detection of both symmetrical and asymmetrical inter-chromosomal exchanges and inter-arm intra-changes (pericentric inversions) in the painted chromosome pair. We used this method to score aberrations in human peripheral blood lymphocytes exposed to 1 Gy of either 250 kVp X-rays or 1 GeV/n Fe-ions and harvested following 120 h in culture, including 2 h in colcemid for metaphase-block. Although iron ions are much more effective than X-rays in the induction of chromosomal aberrations formed during the first post-exposure cell cycle, we found that the effectiveness drops when daughter cells are scored at a late harvest time. In fact, no significant difference in the yield of simple interchanges or intra-changes was found for the two radiation qualities. On the other hand, complex-type exchanges, including rearrangements involving both intra- and inter-chromosomal exchanges, were much more frequent in the progeny of the population exposed to Fe-nuclei than to photons.

To measure clonogenic death of Chinese hamster V79 cells following exposure to a defined number of 4.3 MeV alpha-particles (track-averaged LET = 105 keV/micron).Cells were irradiated at the radiobiological facility installed at the TTT-3 Tandem accelerator in Naples by using a 'Biostack' approach, which allows the positions of incident tracks relative to cells to be carefully determined. Subcellular structure was identified by fluorescence microscopy, while tracks were visualized by LR-115 solid state nuclear track detectors.Particle hits in the cytoplasm did not significantly affect cell survival, yet survival probability decreased exponentially as a function of the number of nuclear traversals. Measured probability of surviving to exactly one 4.3 MeV alpha-particle traversal in the cell nucleus was 0.67 +/- 0.10. Inactivation cross-section was substantially higher than expected from conventional survival curves. However, folding of the data with Poisson statistics showed that survival level expected if a mean of one alpha-particle goes through a nucleus is higher than the measured value after exactly one particle traversal.V79 cells have about 67% probability to survive a single alpha-particle traversal in the cell nucleus. Single-particle survival curves are consistent with conventional dose-survival relationships, once Poisson distribution of traversals is taken into account.

Computer code calculations based on biophysical models are commonly used to evaluate the effectiveness of shielding in reducing the biological damage caused by cosmic radiation in space flights. Biological measurements are urgently needed to benchmark the codes. We have measured the induction of chromosomal aberrations in human peripheral blood lymphocytes exposed in vitro to 56Fe-ion beams accelerated at the HIMAC synchrotron in Chiba. Isolated lymphocytes were exposed to the 500 MeV/n iron beam (dose range 0.1-1 Gy) after traversal of 0 to 8 g/cm2 of either PMMA (lucite, a common plastic material) or aluminum. Three PMMA shield thickness and one Al shield thickness were used. For comparison, cells were exposed to 200 MeV/n iron ions and to X-rays. Chromosomes were prematurely condensed by a phosphatase inhibitor (calyculin A) to avoid cell-cycle selection produced by the exposure to high-LET heavy ion beams. Aberrations were scored in chromosomes 1, 2, and 4 following fluorescence in situ hybridization. The yield of chromosomal aberrations per unit dose at the sample position was poorly dependent on the shield thickness and material. However, the yield of aberrations per unit ion incident on the shield was increased by the shielding. This increase is associated to the increased dose-rate measured behind the shield as compared to the direct beam. These preliminary results prove that shielding can increase the effectiveness of heavy ions, and the damage is dependent upon shield thickness and material, and heavy ion energy and charge.

Astronauts' radiation exposure limits are based on experimental and epidemiological data obtained on Earth. It is assumed that radiation sensitivity remains the same in the extraterrestrial space. However, human radiosensitivity is dependent upon the response of the hematopoietic tissue to the radiation insult. It is well known that the immune system is affected by microgravity. We have developed a mathematical model of radiation-induced myelopoiesis which includes the effect of microgravity on bone marrow kinetics. It is assumed that cellular radiosensitivity is not modified by the space environment, but repopulation rates of stem and stromal cells are reduced as a function of time in weightlessness. A realistic model of the space radiation environment, including the HZE component, is used to simulate the radiation damage. A dedicated computer code was written and applied to solar particle events and to the mission to Mars. The results suggest that altered myelopoiesis and lymphopoiesis in microgravity might increase human radiosensitivity in space.

In vitro radiobiological studies with ions require an extracted beam in air, uniformly spread over an area of at least 1 cm2 characterised by a good monochromaticity. Moreover an accurate fluence monitoring is needed together to an accurate off line calibration, taking into account the measurement geometry, to determine the absorbed dose. Finally energy, and then LET, following every traversed material, should be determined. In this framework we set up a facility at the 3 MV Tandem HVC TTT-3 accelerator of the University of Naples “Federico II” using light ions up to Z=6 and energy below 0.6 MeV n−1. Survival measurements of the V79 cell line following irradiation with beryllium, boron and carbon showed a good agreement with data from literature.

Bayreuth

St. Paul, Minnesota

Helsinki

To analyse the cell inactivation frequencies induced by low energy protons in human cells with different sensitivity to photon radiation.Four human cell lines with various sensitivities to photon irradiation were used: the SCC25 and SQ20B derived from human epithelium tumours of the tongue and larynx, respectively, and the normal lines M/10, derived from human mammary epithelium, and HF19 derived from a lung fibroblast. The cells were irradiated with y-rays and proton beams with linear energy transfer (LET) from 7 to 33 keV/microm. Clonogenic survival was assessed.Survival curves are reported for each cell line following irradiation with gamma-rays and with various proton LETs. The surviving fraction after 2 Gy of gamma-rays was 0.72 for SQ20B cells, and 0.28-0.35 for the other cell lines. The maximum LET proton effectiveness was generally greater than that of gamma-rays. In particular there was a marked increase in beam effectiveness with increasing LET for the most resistant cells (SQ20B) whose 2 Gy-survival varied from 0.72 with gamma-radiation down to 0.37 with 30 keV/microm protons. The relative biological effectiveness (RBE(2 Gy gamma)) with the 30 keV/microm beam, evaluated as the ratio of 2 Gy to the proton dose producing the same inactivation level as that given by 2 Gy of gamma-rays, was 3.2, 1.8, 1.3 and 0.8 for SQ20B, M/10, SCC25, and HF19, respectively.RBE for inactivation with high-LET protons increased with the cellular radioresistance to gamma-rays. The cell line with the greatest resistance to gamma-rays was the most responsive to the highest LET proton beam. A similar trend has also been found in studies reported in the literature with He, C, N ions with LET in the range 20-125 keV/microm on human tumour cell lines.

Inactivation of mouse C3H 10t½ cells in plateau-phase (7·8 × 104 cells/cm2) was studied by using α-particles from the irradiation facility installed for radiobiological experiments at the 3 MV Tandem accelerator, University of Naples. Silicon detectors and CR39 plastic track detectors were employed for dosimetric purposes. The cells were exposed to high LET monoenergetic α-particles (energy of 1·8 MeV at the centre of the cell nucleus, track-averaged LET of 177 keV/µm and dose-rate of 1·1 Gy/min) and low-LET 80 kVp X-rays. The X-ray survival curve showed a significant shoulder (α/β = 9 Gy) while the survival curve for α-particles was close to exponential. The mean lethal dose of α-particles was 0·77 ± 0·02 Gy and the RBE was 5·2 at 80% survival and 3·0 at 5% survival. Survival of exponentially growing cells (2 × 104 cells/cm2) following irradiation with the α-particle beam is also reported. The nuclear areas of 10T½ cells were measured as 299 ± 9 µm2 and 250 ± 8 µm2 for cells in log phase and plateau phas...

Chromosome aberrations induced by X-rays and alpha-particles (LET = 177 keV/microns) were observed at the first mitosis in C3H 10T1/2 cells released from density-inhibited cultures. X-radiation induced more chromosome exchanges than breaks (71% vs 27% of total aberrations), while a predominance of breaks (63%) was observed after alpha-irradiation. A linear-quadratic dose-response relationship was obtained for X-rays, while that for alpha-particles was linear. The RBE values for total aberration induction (ranging from 5.1 at low doses to 4.4 at high doses) were very similar to the RBE for cell killing (from 5.2 to 4.3). The RBE for dicentric induction (approximately 2) was much lower than the RBE for the induction of both breaks (from 7 to 6) and interstitial deletions (from 9 to 7). This behaviour supports the hypothesis that chromosome deletions play a major role in the malignant transformation of 10T1/2 cells. A high correlation between cell killing and number of acentric fragments per cell was found. The number of acentrics/cell at the mean lethal dose was about 1.4. This number was reduced to 1.0 when asymmetrical interchanges, which generally result in very small deletions, were subtracted from acentrics. It could be hypothesized that very small deletions could not impair cell survival. However, an alternative hypothesis related to the aneuploid state of C3H 10T1/2 cells can be formulated. Robertsonian translocations were also observed at the first mitosis. The dose-response curve of these translocations appears to be very similar to the dose-response curve for induction of sister chromatid exchanges (observed at the second mitosis) reported by other authors studying the same cell line. This similarity could indicate a general mechanism of action of radiation on the process of recombination of genetic material.

We measured residual cytogenetic damage in the progeny of human peripheral blood lymphocytes exposed to 1 GeV/ nucleon iron ions or gamma rays. Arm-specific DNA probes for chromosome 1 were used to detect aberrations as a function of dose in cells harvested 144 h after exposure. In addition, arm-specific mFISH was applied to samples exposed to a single dose of 2 Gy. These methods allowed the detection of interarm intrachanges (pericentric inversions) in addition to interchanges. The ratio of these types of aberrations (F ratio) has been proposed as a fingerprint of exposure to densely ionizing radiation. The fractions of aberrant cells in the progeny of cells exposed to iron ions were similar to those in the population exposed to gamma rays, possibly because many rearrangements induced by heavy ions ultimately lead to cell death. Simple inter- and intrachanges were also similar, but more complex rearrangements were found in cells that survived after exposure to iron ions. We did not find a significant difference in the ratio of simple interchanges to simple intrachanges for the two radiation types. However, iron ions induced a much higher frequency of events involving both inter- and intrachanges. We conclude that these complex rearrangements represent a hallmark of exposure to heavy ions and may be responsible of the decrease of the F ratio with increasing LET reported in the literature in some in vitro and in vivo experiments.

Shielding is the only practical countermeasure for the exposure to cosmic radiation during space travel. It is well known that light, hydrogenated materials, such as water and polyethylene, provide the best shielding against space radiation. Kevlar and Nextel are two materials of great interest for spacecraft shielding because of their known ability to protect human space infrastructures from meteoroids and debris. We measured the response to simulated heavy-ion cosmic radiation of these shielding materials and compared it to polyethylene, Lucite (PMMA), and aluminum. As proxy to galactic nuclei we used 1 GeV n iron or titanium ions. Both physics and biology tests were performed. The results show that Kevlar, which is rich in carbon atoms (about 50% in number), is an excellent space radiation shielding material. Physics tests show that its effectiveness is close (80-90%) to that of polyethylene, and biology data suggest that it can reduce the chromosomal damage more efficiently than PMMA. Nextel is less efficient as a radiation shield, and the expected reduction on dose is roughly half that provided by the same mass of polyethylene. Both Kevlar and Nextel are more effective than aluminum in the attenuation of heavy-ion dose.

La radioprotezione degli astronauti è cruciale per il successo di missioni spaziali di lunga durata come quelle programmate su Marte. La scelta dei materiali per la schermatura della radiazione cosmica va ottimizzata al fine di ridurre il rischio di danno biologico all???equipaggio da essa prodotto. La frammentazione nucleare di ioni di alta energia e alto Z incidenti su tali schermi può infatti modificare la qualità della radiazione. Saranno presentati spettri di frammentazione ottenuti analizzando rivelatori CR-39 esposti a ioni accelerati e schermati con un sistema automatico, sviluppato presso il nostro laboratorio. Particolare cura è stata posta nella misura di coppie di tracce sovrapposte.

Non-cancer biological effects of ionising radiation exposure are of relevance for estimating normal tissue damage arising from radiotherapy as well as for space radiation protection. In particular, as ion-based radiation treatment of cancer is looking increasingly promising, it is necessary to investigate whether charged particles such as carbon ions, whose increased biological effectiveness at causing early cytotoxicity in the form of clonogenic death is well known, are also more effective than photons at inducing late effects, thereby obscuring their beneficial anti-cancer potential. Aside from neoplastic transformation, one such late effect is cellular senescence, which has been shown to be inducible in vitro by a variety of stressors, including ionising radiation at sub-lethal doses. Such a response, termed stress-induced premature senescence (SIPS), manifests itself as a senescent-like phenotype but, unlike physiological loss of reproductive ability leading to death or terminal differentiation that it resembles, is not unambiguously linked with telomere length attrition and can be reversed. Thus, it is possible that SIPS, while representing an escape from radiation-induced death, may be enacted by damage-response pathways and lead ultimately to genome instability and hence transformation. In vivo accumulation of prematurely senescent cells in a normal tissue can impact its performance and accelerate degenerative effects. In order to study the dependence of SIPS upon radiation quality and to examine its mechanistical link with reduced telomere length, we exposed a widely used model system (human vein endothelial cells) to the GSI carbon ion beam at both the LET values incurred by normal (plateau region) and tumour (spread-out Bragg Peak) cells. X-ray irradiation was used as a reference. The onset of cellular senescence was studied in the progeny of irradiated or control cells and related to measurements of telomere length. The latter was performed by means of an automated system that allows recognition of interphase cells labelled by a pan-telomeric fluorescent probe and a centromere-directed probe (IQ-FISH). Relative telomere length was obtained by the fluorescence intensity ratio between the two markers. Our data suggest that ionising radiation causes surviving descendants to enter senescence earlier than do their unirradiated counterparts, exhibiting a complex dependence upon increasing LET values and a non-linear correlation with telomere length reduction.

Complicazioni nel tessuto sano sono inevitabili in radioterapia. Nonostante la loro probabilità si riduca usando ioni carbonio invece dei fotoni, non è noto se la maggiore efficacia biologica dei primi in termini di inattivazione clonogenica si mantenga anche per il danno alla progenie cellulare. Mentre la senescenza cellulare prematura insorge in risposta a vari stress citotossici, non se ne conoscono meccanismi e dipendenza dalla qualità della radiazione. Riportiamo dati sulla senescenza indotta in un sistema modello (HUVEC) da un fascio di ioni carbonio usato a fini terapeutici (GSI, Germania) e da raggi X, rapportandoli a misure della lunghezza telomerica media.

Gli effetti biologici tardivi della radiazione ionizzante sono di interesse per i danni al tessuto sano derivanti dal trattamento radioterapico. Ioni come il carbonio risultano in una dose a queste cellule molto ridotta rispetto ai fotoni, ma la maggiore efficacia di queste particelle nel causare morte clonogenica, essenziale per eradicare tumori radioresistenti, potrebbe tradursi in un???efficacia altrettanto elevata anche per altre forme di danno radioindotto. In vitro la senescenza è inducibile da vari agenti: in questi casi essa non appare come stadio fisiologico che prelude all???esaurimento del potenziale proliferativo e alla differenziazione terminale della cellula, ma si configura come vero e proprio meccanismo alternativo a morte e trasformazione neoplastica. Tuttavia, l???accumularsi di tale fenotipo in vivo può compromettere la funzionalità del tessuto interessato e, in ultima analisi, favorire l???insorgenza di tumori secondari attraverso la destabilizzazione del genoma. Vanno quindi compresi dipendenza di tale risposta dalla qualità della radiazione (ioni vs. fotoni) e meccanismi (ruolo degli oncogeni vs. telomeri). Abbiamo studiato la senescenza nel sistema modello endoteliale HUVEC per un fascio di carbonio usato per radioterapia (GSI, Germania). In parallelo, è stata misurata la lunghezza media telomerica dalle intensità di fluorescenza di un marcatore pantelomerico e uno centromerico. Raggi X hanno funto da radiazione di riferimento. I dati fin qui raccolti indicano che la progenie delle cellule esposte entra in senescenza prima di quanto facciano colture non irraggiate, con una complessa dipendenza sia dal LET che dalla riduzione di lunghezza telomerica.

A brief review of the state of the PIXE technique is given. Principles and recent advances in beam systems, instrumentation and sample handling are covered. A rather comprehensive list of references regarding different methodological aspects and biomedical applications is given. Some applications are discussed. In particular, preliminary results on a preconcentration technique developed by the authors for the determination of manganese in milk are presented.

La quantità di radon che penetra negli ambienti chiusi dipende, oltre che dal contenuto di radio dei materiali e dei suoli anche dall’aliquota di questo che viene trasportato nell’aria. Questo rapporto dipende dalla pressione, dall’umidità e dal altri fattori, ma soprattutto dalle caratteristiche dei materiali la cui caratterizzazione, anche rispetto ad esso, è uno degli elementi principali di un programma di prevenzione e/o di riduzione del rischio radiologico connesso con la radioattività naturale indoor. Viene proposto un metodo capace di eseguire la determinazione del coeffiiciente di emanazione del radon da un materiale, basato sulla rivelazione delle particelle alfa emesse dai suoi discendenti 218Po e 214Po. Le misure vengono eseguite all’interno di una camera di diffusione sigillata del volume di circa un litro le cui pareti sono poste ad una tensione di 3500 V rispetto al rivelatore (un silicio a barriera superficiale), in modo da trasportare verso di esso il 90% del 218Po che è ionizzato. L’alta velocità di deriva degli ioni, rispetto alla loro vita media, fa sì che essi decadano nelle vicinanze del rivelatore, permettendo così la rivelazione delle particelle alfa con una risoluzione energetica migliore del 10%, nonostante la presenza dell’aria all’interno della camera. Eseguendo conteggi a tempi diversi dal momento di chiusura della camera si ricostruisce tutta l’evoluzione del sistema verso l’equilibrio, ottenendo in tal modo anche la misura del rate di emanazione. I coefficienti di emanazione sono ricavati dal confronto tra il valore di saturazione dell’attività nella camera e la concentrazione del radon totale misurato mediante spettrometria gamma dei suoi figli 214Bi e 214Pb su di un’aliquota diversa dello stesso materiale sigillata in un beaker tipo Marinelli per un tempo di circa 3 settimane. I test eseguiti fino a questo momento hanno dimostrato l’assenza di fenomeni di back-diffusion dovuti alle dimensioni finite della camera; un tempo di crescita della curva di 350 ore permette di determinare il valore di saturazione con un errore del 5%. Con questo metodo saranno analizzati i suoli e i materiali da costruzione caratteristici della Campania, tra i quali i materiali di origine vulcanica, quali tufo e pozzolana, che sono stati nel passato e sono tuttora largamente utilizzati.

Inheritable chromosome aberrations (CA) are of concern because cytogenetic damage may trigger the carcinogenic process. Moreover, stability of radiation-induced CA is a prerequisite for meaningful biological dosimetry. CA inheritability arguably depends on the aberration structure, with symmetrical exchanges being favoured over asymmetrical rearrangements, but it is also affected by radiation quality. CA induced by low-LET protons and high-LET 12C ions in G0 peripheral blood lymphocytes were measured in first- , second- and third-generation by combined FISH/harlequin staining of metaphase as well as prematurely condensed interphase chromosomes 1 and 2. As expected, the frequency of non-transmissible (NT) aberrations declined through replication rounds. A radiation-induced arrest occurred prior to first post-irradiation mitosis that prevalently affected aberrant cells. Aberrant cells incurred cycle delays also at subsequent cycles following proton-irradiation but not 12C ion-irradiation. As expected, the frequency of reciprocal translocations remained fairly stable while that of dicentrics was halved at each mitotic round. A significant fraction of complex-type exchanges was found in third-generation cells following both irradiations and appeared to be transmitted relatively more efficiently after protons than 12C ions. A low but stably transmitted frequency of transmissible (T)-type insertions were detected after 12C ions but not after low LET-irradiation. Our data support a differential ability by aberrant cells to progress through post-irradiation mitoses that is influenced by the aberration burden and radiation quality.

The induction of Robertsonian translocations in murine C3H 10T 1 2 embryo fibroblasts after exposure to X-rays and mitomycin C has been investigated. Cells were irradiated in log-phase and harvested at different times for chromosome analysis. The stage of the cell cycle of individual cells at the time of individual cells at the time of irradiation could be determined by differential replication staining. A dose-dependent delay in the progression through S- and G2-phase has been observed. X-rays produced an increase in the freqency of Robertsonian translocations when cells were exposed in G1- or S-phase, but not in G2. The dose-response curve for the induction of Robertsonian translocations both in G1 and S peaked at 2 Gy and slightly declined at higher doses. For G2 cells, an increase compared to the control level was observed only after 1 Gy. Mitomycin C induced chromosomal aberrations and Robertsonian translocations in 10T 1 2 cells, but no significant interaction between ionizing radiation and the alkylating agent was observed for these two endpoints. However, the combined exposure caused satellite associations of chromosomes. Both the number of satellite associations/metaphase (five times the frequency observed after mitomycin C alone) and the number of chromosomes/satellite (up to 10 chromosomes were observed in satellite associations) were greatly enhanced compared to X-rays and mitomycin C alone.