Electron Spin-Lattice Relaxation of Substitutional Nitrogen in Silicon: The Role of Disorder and Motional Effects

In a previous investigation, the authors proposed nitrogen as a possible candidate for exploiting the donor spin in silicon quantum devices. This system is characterized by a ground state deeper than the other group V impurities in silicon, offering less stringent requirements on the device temperature necessary to access the unionized state. The nitrogen donor is slightly displaced from the substitutional site, and upon heating, the system undergoes a motional transition. In the present article, we show the results from our investigation on the spin-relaxation times in natSi and 28Si substrates and discuss the motional effects on relaxation. The stretched exponential relaxation observed is interpreted as a distribution of spin-lattice relaxation times, whose origin is also discussed. This information greatly contributes to the assessment of a nitrogen-doped silicon system as a potential candidate for quantum devices working at temperatures higher than those required for other group V donors in silicon.

Accuracy and reliability of left atrial appendage morphology assessment by new 3D transesophageal echocardiographic rendering modalities: a comparative study with computed tomography

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction. Left atrial appendage (LAA) morphology assessed by contrast-enhanced computed tomography (CT) has been associated to the risk of cardioembolic stroke in non-valvular atrial fibrillation. Subsequent studies with the traditional LAA classification system (CS) into 4 morphologies (Chicken wing, Cauliflower, Cactus and Windsock) yielded mixed results in terms of reliability and stroke risk association. Recently, a simple LAA morphology CS (new-LAAcs) based on the LAA bend angle measurement has been suggested. Three-dimensional transesophageal echocardiography (3D TOE) quality imaging has been improved and new volume rendering modalities developed.

Purpose. Aim of this study was to evaluate the accuracy and reliability of 2D and new 3D TOE rendering modalities compared to CT in assessing LAA morphology. We used and validated a new simple LAA morphology classification system (new-LAAcs) based on the LAA bend angle in contrast to the traditional CS.

Methods. 50 consecutive patients who underwent both cardiac CT and TOE were enrolled. LAA morphology was assessed by three different TEE modalities: (1) 2D TOE inspective evaluation (2D TOE), (2) 3D TOE multiplanar reconstruction (3D TOE MPR) and (3) 3D TOE Philips TrueVue Glass rendering (3D TOE GLASS). We assessed TOE accuracy compared to CT by sensitivity, specificity, accuracy, and Cohen’s kappa. Two trained readers independently adjudicated LAA morphologies in the new-LAAcs and the inter-rater reliability was obtained by percentage agreement and Cohen’s kappa. The reliability of the new- vs. traditional-LAAcs was assessed by CT in terms of reliability rates and influence on LAA morphology prevalence.

Results. CT and TOE imaging analyses were feasible in all patients. 2D TOE was fairly accurate in identifying LAA morphology (κ 0.38, p = 0.022) and had only moderate inter-rater (κ 0.46, p = 0.027) and substantial intra-rater (κ 0.62, p = 0.003) reliability rates. 3D TOE showed high validity: 3D TOE MPR had an almost perfect accuracy (κ 0.84, p < 0.001) and substantial (κ 0.77, p < 0.001) inter-rater reliability; 3D TOE GLASS substantial accuracy (κ 0.67, p < 0.001) and almost perfect (κ 0.82, p < 0.001) inter-rater reliability. Intra-rater agreement was almost perfect for both 3D TOE modalities (κ 0.84, p < 0.001). In the comparison among CS the traditional-LAAcs inter-rater reliability was moderate (κ 0.47, p < 0.001) and the intra-rater reliability substantial (κ 0.68, p < 0.001) while the new-LAAcs yielded an almost perfect reliability level (inter-rater κ 0.84, p < 0.001 and intra-rater κ 0.93, p < 0.001). With the traditional-LAAcs, the prevalence of CW LAA was 30 (60%), while with the new-LAAcs the prevalence of low-risk-LAA was 13 (26%), leading to classify 17 (57%) CW morphologies as high-risk-LAA.

Conclusions. 3D TOE is an accurate, reliable, and feasible alternative to CT in assessing LAA morphology with the new-LAAcs. The new-LAAcs shows higher reliability rates than the traditional one. Abstract Figure.  Abstract Figure.

Adjuvant Systemic Therapies in Patients with Colorectal Cancer: An Audit on Clinical Practice in Italy

Aims and Background

Rarely are conclusions from clinical trials summarized in international consensus conferences and promptly transferred to patient care. The adjuvant therapy for colorectal cancer used in daily clinical practice in Italy is described and compared with the recommendations of the 1990 NIH Consensus Conference.

Patients and Methods

We audited prescriptions of adjuvant systemic therapies for Italian colorectal cancer patients in 82 centers during a fixed one-week period.

Results

Among 434 patients receiving adjuvant chemotherapy there were 139 (42.5%) colon cancer patients with N- and 169 (51.7%) with N+ regional nodal involvement. Treatment at academic centers, a young age, T4 and a low total number of lymph nodes removed at surgery were the factors potentially justifying the decision for adjuvant chemotherapy in stage II colon cancer patients. The most common chemotherapy used was a bolus of 5-fluorouracil/folinic acid for 6 months (75.8%). Adjuvant radiotherapy was not administered to 37 (38.5%) of 96 patients with stage II and III rectal cancer.

Conclusions

The study shows that a substantial proportion of patients on adjuvant treatment at a certain time point in a large enough sample of Italian centers are stage II (potential over-treatment) and that an under-treatment of stage II and III rectal cancer patients (lack of radiotherapy) occurs too often in daily clinical practice in this country.

Weekly Low Dose Epirubicin in Elderly Cancer Patients

Aims and background

The treatment of elderly patients with metastatic solid tumours is still a debated problem. Patients over 75 years are generally excluded from combination chemotherapy trials because of higher toxicity. Several clinical studies have shown that weekly low dose epirubicin is a well tolerated and effective treatment for elderly cancer patients (breast, prostate, lung).

Methods

We report a study of patients aged between 75 and 85 years affected by metastatic anthracyclines-sensible carcinomas, to assess the tolerance of epirubicin given weekly at a dose of 25 mg/m2.

Results

25 patients (13 males, 12 females; ECOG P.S. 0-2) entered the study and were evaluable for side effects. One-hundred and ninety-six cycles of therapy have been administered. Side effects were never severe. Mucositis (9 patients), leucopenia (7 patients), anemia (5 patients) were usually of grade 1 or 2. Grade 1 cardiotoxicity (tachycardia) was observed in only one case. Grade 3 toxicity consisted in anemia (1 patient) and mucositis (1 patient), while grade 4 toxicity never occurred. Nineteen patients were evaluable for response: 0 CR, 4 PR (1 lung, 3 breast), 8 SD (3 lung, 3 breast, 2 prostate) have been observed. Compliance was encouraging and the majority of patients showed a decrease in symptoms and an improvement in performance status.

Conclusions

Weekly low-dose epirubicin is a very well tolerated treatment in elderly cancer patients. In view of the negligible toxicity encountered, it could be of utility to test this regimen in patients aged 75 years or older, affected by anthracyclines-sensible metastatic tumors, also to assess activity.

Evaluation of Symptoms and Prevention of Cancer in Menopause: The Value of Vulvar Exam

Vulvar and vaginal atrophy (VVA), is a chronic medical condition experienced by postmenopausal women, with prevalence estimated ranging from 10% to 50% [1]. VVA is characterized by a constellation of symptoms, that may affect daily activities, sexuality, relationships, and quality of life [3]. Early recognition and effective treatment of VVA may enhance sexual health and the quality of life of women and their partners. Some vulvar conditions such as lichen sclerosus are more prevalent in the postmenopausal years. Lichen sclerosus has been suggested as a precursor of Vulvar squamous cell carcinoma. The vulvar exam in post-menopausal women plays an essential role in prevention of cancer because it allows to identify women who should undergo vulvar skin biopsy in order to early detect pre-neoplastic lesions for early diagnosis of cancer of the vulva.

Results of a round-robin exercise on read-across

A round-robin exercise was conducted within the CALEIDOS LIFE project. The participants were invited to assess the hazard posed by a substance, applying in silico methods and read-across approaches. The exercise was based on three endpoints: mutagenicity, bioconcentration factor and fish acute toxicity. Nine chemicals were assigned for each endpoint and the participants were invited to complete a specific questionnaire communicating their conclusions. The interesting aspect of this exercise is the justification behind the answers more than the final prediction in itself. Which tools were used? How did the approach selected affect the final answer?

Glioblastoma stem cells: radiobiological response to ionising radiations of different qualities

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumour, with very poor prognosis. The high recurrence rate and failure of conventional treatments are expected to be related to the presence of radio-resistant cancer stem cells (CSCs) inside the tumour mass. CSCs can both self-renew and differentiate into the heterogeneous lineages of cancer cells. Recent evidence showed a higher effectiveness of C-ions and protons in inactivating CSCs, suggesting a potential advantage of Hadrontherapy compared with conventional radiotherapy for GBM treatment. To investigate the mechanisms involved in the molecular and cellular responses of CSCs to ionising radiations, two GBM stem cell (GSC) lines, named lines 1 and 83, which were derived from patients with different clinical outcomes and having different metabolic profiles (as shown by NMR spectroscopy), were irradiated with (137)Cs photons and with protons or C-ions of 62 MeV u(-1) in the dose range of 5-40 Gy. The biological effects investigated were: cell death, cell cycle progression, and DNA damage induction and repair. Preliminary results show a different response to ionising radiation between the two GSC lines for the different end points investigated. Further experiments are in progress to consolidate the data and to get more insights on the influence of radiation quality.

Low-radiation environment affects the development of protection mechanisms in V79 cells

Very little is known about the influence of environmental radiation on living matter. In principle, important information can be acquired by analysing possible differences between parallel biological systems, one in a reference-radiation environment (RRE) and the other in a low-radiation environment (LRE). We took advantage of the unique opportunity represented by the cell culture facilities at the Gran Sasso National Laboratories of the Istituto Nazionale di Fisica Nucleare, where environment dose rate reduction factors in the underground (LRE), with respect to the external laboratory (RRE), are as follows: 10(3) for neutrons, 10(7) for directly ionizing cosmic rays and 10 for total γ-rays. Chinese hamster V79 cells were cultured for 10 months in both RRE and LRE. At the end of this period, all the cultures were kept in RRE for another 6 months. Changes in the activities of antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX) and spontaneous mutation frequency at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus were investigated. The results obtained suggest that environmental radiation might act as a trigger of defence mechanisms in V79 cells, specifically those in reference conditions, showing a higher degree of defence against endogenous damage as compared to cells grown in a very low-radiation environment. Our findings corroborate the hypothesis that environmental radiation contributes to the development of defence mechanisms in today living organisms/systems.

Induction and Repair of DNA DSB as Revealed by H2AX Phosphorylation Foci in Human Fibroblasts Exposed to Low- and High-LET Radiation: Relationship with Early and Delayed Reproductive Cell Death

The spatial distribution of radiation-induced DNA breaks within the cell nucleus depends on radiation quality in terms of energy deposition pattern. It is generally assumed that the higher the radiation linear energy transfer (LET), the greater the DNA damage complexity. Using a combined experimental and theoretical approach, we examined the phosphorylation-dephosphorylation kinetics of radiation-induced γ-H2AX foci, size distribution and 3D focus morphology, and the relationship between DNA damage and cellular end points (i.e., cell killing and lethal mutations) after exposure to gamma rays, protons, carbon ions and alpha particles. Our results showed that the maximum number of foci are reached 30 min postirradiation for all radiation types. However, the number of foci after 0.5 Gy of each radiation type was different with gamma rays, protons, carbon ions and alpha particles inducing 12.64 ± 0.25, 10.11 ± 0.40, 8.84 ± 0.56 and 4.80 ± 0.35 foci, respectively, which indicated a clear influence of the track structure and fluence on the numbers of foci induced after a dose of 0.5 Gy for each radiation type. The γ-H2AX foci persistence was also dependent on radiation quality, i.e., the higher the LET, the longer the foci persisted in the cell nucleus. The γ-H2AX time course was compared with cell killing and lethal mutation and the results highlighted a correlation between cellular end points and the duration of γ-H2AX foci persistence. A model was developed to evaluate the probability that multiple DSBs reside in the same gamma-ray focus and such probability was found to be negligible for doses lower than 1 Gy. Our model provides evidence that the DSBs inside complex foci, such as those induced by alpha particles, are not processed independently or with the same time constant. The combination of experimental, theoretical and simulation data supports the hypothesis of an interdependent processing of closely associated DSBs, possibly associated with a diminished correct repair capability, which affects cell killing and lethal mutation.

Few electron limit of n-type metal oxide semiconductor single electron transistors

We report the electronic transport on n-type silicon single electron transistors (SETs) fabricated in complementary metal oxide semiconductor (CMOS) technology. The n-type metal oxide silicon SETs (n-MOSSETs) are built within a pre-industrial fully depleted silicon on insulator (FDSOI) technology with a silicon thickness down to 10 nm on 200 mm wafers. The nominal channel size of 20 × 20 nm(2) is obtained by employing electron beam lithography for active and gate level patterning. The Coulomb blockade stability diagram is precisely resolved at 4.2 K and it exhibits large addition energies of tens of meV. The confinement of the electrons in the quantum dot has been modeled by using a current spin density functional theory (CS-DFT) method. CMOS technology enables massive production of SETs for ultimate nanoelectronic and quantum variable based devices.

MELODI: the 'Multidisciplinary European Low-Dose Initiative'

The importance of research to reduce uncertainties in risk assessment of low and protracted exposures is now recognised globally. In Europe a new initiative, called 'Multidisciplinary European LOw Dose Initiative' (MELODI), has been proposed by a 'European High Level and Expert Group on low-dose risk research' (www.hleg.de), aimed at integrating national and EC (Euratom) efforts. Five national organisations: BfS (DE), CEA (FR), IRSN (FR), ISS (IT) and STUK (FI), with the support of the EC, have initiated the creation of MELODI by signing a letter of intent. In the forthcoming years, MELODI will integrate in a step-by-step approach EU institutions with significant programmes in the field and will be open to other scientific organisations and stakeholders. A key role of MELODI is to develop and maintain over time a strategic research agenda (SRA) and a road map of scientific priorities within a multidisciplinary approach, and to transfer the results for the radiation protection system. Under the coordination of STUK a network has been proposed in the 2009 Euratom Programme, called DoReMi (Low-Dose Research towards Mutidisciplinary Integration), which can help the integration process within the MELODI platform. DoReMi and the First MELODI Open Workshop, organised by BfS in September 2009, are now important inputs for the European SRA.

Monte Carlo evaluation of DNA fragmentation spectra induced by different radiation qualities

The PARTRAC code has been developed constantly in the last several years. It is a Monte Carlo code based on an event-by-event description of the interactions taking place between the ionising radiation and liquid water, and in the present version simulates the transport of photons, electrons, protons, helium and heavier ions. This is combined with an atom-by-atom representation of the biological target, i.e. the DNA target model of a diploid human fibroblast in its interphase (genome of 6 Gigabase pairs). DNA damage is produced by the events of energy depositions, either directly, if they occur in the volume occupied by the sugar-phosphate backbone, or indirectly, if this volume is reached by radiation-induced radicals. This requires the determination of the probabilities of occurrence of DNA damage. Experimental data are essential for this determination. However, after the adjustment of the relevant parameters through the comparison of the simulation data with the DNA fragmentation induced by photon irradiation, the code has been used without further parameter adjustments, and the comparison with the fragmentation induced by charged particle beams has validated the code. In this paper, the results obtained for the DNA fragmentation induced by gamma rays and by charged particle beams of various LET are shown, with a particular attention to the production of very small fragments that are not detected in experiments.

Adaptive response: modelling and experimental studies

Adaptive response (AR) is a term that has been generally accepted to describe the ability of a low 'priming' radiation dose to decrease the cell response to a subsequent higher 'challenging' dose. The main proposed mechanisms to explain AR are: increased efficiency of DNA repair and induction of antioxidant enzymes. A model that considers a modulation of the efficiency of DNA repair activity and of the level of antioxidant enzymes, starting from the framework of a lethal-potentially lethal (LPL) model is proposed. The LPL model has been extended with the inclusion of the dynamic variables representing the efficiency of repair, the levels of radiation induced radicals and of antioxidant enzymes. The model used here is able to describe the protective effect of a priming dose. Moreover, in agreement with the data in the literature, the simulations show that the AR happens in given priming dose and priming dose-rate ranges only, and requires at least 4 h to develop. In order to get more insights into the role of cell-cell communication as factors affecting the AR, experimental studies were planned using sparse or confluent AG1522 cell monolayer. The results obtained after gamma irradiation suggest that cell density is a crucial factor for observing an AR.

DNA fragmentation in V79 cells irradiated with light ions as measured by pulsed‐field gel electrophoresis. II. Simulation with a generalized broken stick model

PURPOSE

To characterize the differences among the experimental DNA fragmentation spectra induced in Chinese hamster V79 cells by gamma-rays, low-energy protons and alpha-particles through the use of a phenomenological model.

MATERIALS AND METHODS

A model of DNA fragmentation was developed as a generalization of the broken-stick model, in which the double-strand breaks induced by radiation were considered randomly placed, but in which the manifestly non-random fragmentation of the control sample was fully taken into account and considered as the initial fragment distribution. Further, an analytical method was introduced that allowed an evaluation of the deviation from randomness of the fragmentation induced by radiation.

RESULTS

The analysis of the experimental distribution of DNA fragments showed that there was a progressive departure from randomness in radiation-induced fragmentation going from gamma-rays to protons and then to alpha-particles. This deviation was characterized by an enhanced induction of fragments, and therefore by a larger correlation of double-strand breaks, in the experimental range of lower molecular weights.

CONCLUSION

The analysis shows that low-energy light ions induce DNA fragmentation, at the loop level of the chromatin organization, that can be significantly non-random. The same analysis can readily be applied at different length scales, and thus it could offer a basis for the study of the link between DNA damage, correlated at various spatial scales and biological end-points.

Direct Comparison between Protons and Alpha-particles of the Same LET: I. Irradiation Methods and Inactivation of Asynchronous V79, HeLa and C3H 10T½ Cells

A direct comparison was carried out of the biological effectiveness of protons and alpha-particles of the same linear energy transfer (LET) under identical conditions with a variety of in vitro biological systems. Monolayers of mammalian cells were irradiated with accelerated beams of protons (1.2 and 1.4 MeV) and alpha-particles (30 and 35 MeV) corresponding to LETs of 23 and 20 keV microns-1 for each particle type. For V79-4 cells it was observed that the linear term of the dose-response for cell inactivation by protons was significantly greater than that for alpha-particles of the same LET. For HeLa and HeLa S3 cells, also, the linear term appeared to be greater for protons, but this was not observed with more limited data for C3H 10T1/2 cells. The result for V79 cells is in agreement with the report of Belli et al. (1989) who observed that the biological effectiveness of protons rose sharply between 17 and 30 keV microns-1 in strong contrast to alpha-particles which reached a peak effectiveness at greater than 100 keV microns-1. These results place new constraints on the biologically relevant features of the microscopic structure of radiation tracks, and have implications for the mechanistic and practical comparison between radiations.

Direct Comparison of Biological Effectiveness of Protons and Alpha-particles of the Same LET. II. Mutation Induction at the HPRT Locus in V79 Cells

Mutation induction at the hprt locus has been studied in V79-4 Chinese hamster cells irradiated with mono-energetic protons and alpha-particles with LET of 20.3 and 23 keV microns-1. The mutation frequency increased linearly with the dose for all the four radiation qualities investigated, so that effectiveness for mutation induction could be expressed by the slope of the relevant curve. This effectiveness did not significantly change with the small change in LET of each kind of particle, while sizeable differences were found between particles. Protons were more effective in mutation induction than alpha-particles with the same LET by a factor of about 2. This finding is similar to, although slightly larger than, the factors 1.5-1.8 found for inactivation of the same cells in the same series of experiments.

Direct Comparison of Biological Effectiveness of Protons and Alpha-particles of the Same LET. III. Initial Yield of DNA Double-strand Breaks in V79 Cells

The results reported form part of a series of experiments to substantiate and extend the findings by Belli et al. (1989) that protons are more biologically effective at cell killing than alpha-particles of the same LET. The irradiations were carried out using the Variable Energy Cyclotron (VEC) at the Harwell Laboratories. V79-4 Chinese hamster cells were exposed to alpha-particles and protons with LETs of 20 and 23 keV microns-1 in the dose range 40-150 Gy. X-rays were also used for comparison. Two methods were used for measurement of initial DNA double-strand breaks: sedimentation and DNA precipitation assays. The dose-response relationships were found to be well fitted by straight lines in all cases. With the sedimentation assay a slightly lower yield of dsb was found from protons than from alpha-particles of the same LET. The yield from X-rays was not significantly different from either. The precipitation assay showed similar yields of DNA damage from both particle types but significantly higher yields from X-rays. This may reflect a difference in the type of lesions scored by the two methods. Since the initial amount of dsb does not account for the observed differences in cellular response to radiations of different qualities, it is likely that these are related to the nature of the dsb (affecting reparability) or to the occurrence of other types of molecular damage.

DNA DSB induced in human cells by charged particles and gamma rays: Experimental results and theoretical approaches

PURPOSE

To quantify the role played by radiation track structure and background fragments in modulating DNA fragmentation in human cells exposed to gamma-rays and light ions.

MATERIALS AND METHODS

Human fibroblasts were exposed in vitro to different doses (in the range from 40 - 200 Gy) of (60)Co gamma-rays and 0.84 MeV protons (Linear Energy Transfer, LET, in tissue 28.5 keV/microm). The resulting DNA fragments were scored under two electrophoretic conditions, in order to optimize separation in the size ranges 0.023 - 1.0 Mbp and 1.0 - 5.7 Mbp. In parallel, DNA fragmentation was simulated both with a phenomenological approach based on the "generalized broken-stick" model, and with a mechanistic approach based on the PARTRAC (acronym of PARticle TRACk) Monte Carlo code (1.32 MeV photons were used for the simulation of (60)Co gamma-rays).

RESULTS

For both gamma-rays and protons, the experimental dose response in the range 0.023 - 5.7 Mbp could be approximated as a straight line, the slope of which provided a yield of (5.3 +/- 0.4) x 10(-9) Gy(-1) bp(-1) for gamma-rays and (7.1 +/- 0.6) x 10(-9) Gy(-1) bp(-1) for protons, leading to a Relative Biological Effectiveness (RBE) of 1.3 +/- 0.2. From both theoretical analyses it appeared that, while gamma-ray data were consistent with double-strand breaks (DSB) random induction, protons at low doses showed significant deviation from randomness, implying enhanced production of small fragments in the low molecular weight part of the experimental range. The theoretical analysis of fragment production was then extended to ranges where data were not available, i.e. to fragments larger than 5.7 Mbp and smaller than 23 kbp. The main outcome was that small fragments (<23 kbp) are produced almost exclusively via non-random processes, since their number is considerably higher than that produced by a random insertion of DSB. Furthermore, for protons the number of these small fragments is a significant fraction (about 20%) of the total number of fragments; these fragments remain undetected in these experiments. Calculations for 3.3 MeV alpha particle irradiation (for which no experimental data were available) were performed to further investigate the role of fragments smaller than 23 kbp; in this case, besides the non-random character of their production, their number resulted to be at least as much as half of the total number of fragments.

CONCLUSION

Comparison between experimental data and two different theoretical approaches provided further support to the hypothesis of an important role of track structure in modulating DNA damage. According to the theoretical approaches, non-randomness of fragment production was found for proton irradiation for the smaller fragments in the experimental size range and, in a significantly larger extent, for fragments of size less than 23 kbp, both for protons and alpha particles.

Superionic conductivity in the Li4C60 fulleride polymer

We report on the extraordinary superionic conductivity in the fulleride polymer Li4C60, a crystalline material with no disorder. 7Li, NMR, and dc frequency dependent conductivity show uncorrelated ionic hopping across small energy barriers (DeltaE_{a} approximately 200 meV) and an ionic conductivity of 10;{-2} S/cm at room temperature, higher than in "standard" ionic conductors. Ab initio calculations of the molecular structure find intrinsic unoccupied interstitial sites that can be filled by Li+ cations in stoichiometric Li4C60 even at low temperatures. The low energy required for the occupation of these sites allows a sizable Li+ diffusion above 130 K. The results suggest novel application of lithium intercalated fullerides as electrodes in Li ions batteries.

The Cosmic Silence experiment: on the putative adaptive role of environmental ionizing radiation

Previously we reported that yeast and Chinese hamster V79 cells cultured under reduced levels of background environmental ionizing radiation show enhanced susceptibility to damage caused by acute doses of genotoxic agents. Reduction of environmental radiation dose rate was achieved by setting up an underground laboratory at Laboratori Nazionali del Gran Sasso, central Italy. We now report on the extension of our studies to a human cell line. Human lymphoblastoid TK6 cells were maintained under identical in vitro culture conditions for six continuous months, at different environmental ionizing radiation levels. Compared to "reference" environmental radiation conditions, we found that cells cultured in the underground laboratories were more sensitive to acute exposures to radiation, as measured both at the level of DNA damage and oxidative metabolism. Our results are compatible with the hypothesis that ultra-low dose rate ionizing radiation, i.e. environmental radiation, may act as a conditioning agent in the radiation-induced adaptive response.

A 244Cm irradiator for protracted exposure of cultured Mammalian cells with alpha particles

A 244Cm alpha-particle irradiator was designed and constructed for radiobiological studies where protracted exposure at a low dose rate of cultured mammalian cells is required. It allows irradiation of a cell monolayer attached to the Mylar bottom of a specially designed Petri dish of 56 mm diameter (approximately 25 cm(2) area). The irradiator is based on a 20-mm-diameter stainless steel chamber containing a 148 kBq 244Cm source. The chamber, flushed with helium gas at a pressure kept slightly above the external pressure, is inserted into a cell incubator where temperature and CO2 concentration are controlled. Spectrometric and dosimetric characterization of the irradiator was carried out by means of an ion-implanted-silicon charged-particle detector, CR39 detectors, and Monte Carlo simulations with the TRIM code. Average LET of particles incident on the cells at the center of the Petri dish was evaluated to be 120 keV microm(-1) at 59 mm from the source, and the average dose rate was 5.69 x 10 Gy s(-1), with +12% and -8% variations at the center and the edge, respectively. The irradiator has been successfully tested and used for several experiments involving 16-d exposure of human fibroblasts monolayers.

DNA fragments induction in human fibroblasts by radiations of different qualities

Experimental data on DNA double strand break (DSB) induction in human fibroblasts (AG1522), following irradiation with several radiation qualities, namely gamma rays, 0.84 MeV protons, 58.9 MeV u(-1) carbon ions, iron ions of 115 MeV u(-1), 414 MeV u(-1), 1 GeV u(-1), and 5 GeV u(-1), are presented. DSB yields were measured by calibrated Pulsed Field Gel Electrophoresis in the DNA fragment size range 0.023-5.7 Mbp. The DSB yields show little LET dependence, in spite of the large variation of the latter among the beams, and are slightly higher than that obtained using gamma rays. The highest yield was found for the 5 GeV u(-1) iron beam, that gave a value 30% higher than the 1 GeV u(-1) iron beam. A phenomenological method is used to parametrise deviation from randomness in fragment size spectra.

DNA DSB induced by iron ions in human fibroblasts: LET dependence and shielding efficiency

This paper reports on DNA DSB induction in human fibroblasts by iron ions of different energies, namely 5, 1 GeV/u, 414 and 115 MeV/u, in absence or presence of different shields (PMMA, Al and Pb). Measure of DNA DSB was performed by calibrated Pulsed Field Gel Electrophoresis using the fragment counting method. The RBE-LET relationships for unshielded and shielded beams were obtained both in terms of dose average LET and of track average LET. Weak dependence on these parameters was observed for DSB induction. The shielding efficiency, evaluated by the ratio between the cross sections for unshielded and shielded beams, depends not only on the shield type and thickness, but also on the beam energy. Protection is only observed at high iron ions energy, especially at 5 GeV/u, where PMMA shield gives higher protection compared to Al or Pb shields of the same thickness expressed in g/cm2.

Li4C60: A Polymeric Fulleride with a Two-Dimensional Architecture and Mixed Interfullerene Bonding Motifs

All known fullerene polymers have interfullerene connections via either [2 + 2] cycloaddition or single C-C bonds. The high-resolution synchrotron X-ray powder diffraction technique was employed here to determine the crystal structure of the Li4C60 fulleride. We find that the ground state of Li4C60 is a two-dimensional polymer with monoclinic crystal symmetry and an unprecedented architecture, combining both the [2 + 2] cycloaddition and the single C-C bridging motifs. The small size of the Li+ cations is crucial in stabilizing the resulting tightly packed polymeric structure.

DNA fragmentation induced by Fe ions in human cells: shielding influence on spatially correlated damage

Outside the magnetic field of the Earth, high energy heavy ions constitute a relevant part of the biologically significant dose to astronauts during the very long travels through space. The typical pattern of energy deposition in the matter by heavy ions on the microscopic scale is believed to produce spatially correlated damage in the DNA which is critical for radiobiological effects. We have investigated the influence of a lucite shielding on the initial production of very small DNA fragments in human fibroblasts irradiated with 1 GeV/u iron (Fe) ions. We also used gamma rays as reference radiation. Our results show: (1) a lower effect per incident ion when the shielding is used; (2) an higher DNA Double Strand Breaks (DSB) induction by Fe ions than by gamma rays in the size range 1-23 kbp; (3) a non-random DNA DSB induction by Fe ions.

Environmental radioactivity in four national parks of the Abruzzo region (central Italy)

Since 1998, the Istituto Zooprofilattico Sperimentale dell'Abruzzo e Molise 'G. Caporale' in Teramo is conducting radioecological surveys in the Abruzzo region (Central Italy), to acquire knowledge on the geochemical and biological mobility of radionuclides derived from the Chernobyl accident. To this end, samples of grasses, fungi, mosses and soils were collected in four national parks (Sirente-Velino, Abruzzo Lazio and Molise, the Gran Sasso and the park of Monti della Laga and Maiella). The results show that the Chernobyl fallout is still detectable in the samples collected in the four parks but the (137)Cs concentrations are present in the semi-natural environments in quantities that do not create concerns from a radiological point of view.

Influence of a low background radiation environment on biochemical and biological responses in V79 cells

We present the results of an experiment aimed at comparing the effects of different background radiation environments on metabolism and responses to gamma-rays and cycloheximide of cultured mammalian cells. Chinese hamster V79 cells were maintained in exponential growth in parallel for up to 9 months at the Istituto Superiore di Sanità (ISS) and at the INFN-Gran Sasso underground Laboratory (LNGS) where exposure due to gamma-rays and to radon was reduced by factors of about 70 and 25, respectively. After 9 months the cells grown at the LNGS (cumulative gamma dose about 30 microGy, average radon concentration around 5 Bq/m(3)), compared to the cells grown at the ISS (cumulative gamma-ray dose about 2 mGy, average radon concentration around 120 Bq/m(3)), exhibited i). a significant increase of the cell density at confluence, ii). a significantly higher capacity to scavenge organic and inorganic hydroperoxides but a reduced scavenging capacity towards superoxide anions and iii). an increase in both the basal hprt mutation frequency and sensitivity to the mutagenic effect of gamma-rays. The cells grown at the LNGS also showed a greater apoptotic sensitivity starting at the third month of culture, that was no longer detected after 9 months. Overall, these data suggest a role of background ionizing radiation in determining an adaptive response, although they cannot be considered conclusive.

137Cs and 40K soil-to-plant relationship in a seminatural grassland of the Giulia Alps, Italy

To examine the soil-to-plant transfer of 137Cs and 40K, we performed a study based on sampling of natural soil and plants from an alpine pasture site situated in the Giulia Alps, Italy, during July 1997. High 137Cs activity was present in the upper most soil layer, and decreased one order of magnitude at a depth of 10 cm. An opposite gradient was observed for 40K. Simultaneous sampling of soil and plant material was performed in order to analyse transfer factor (TF) values. In spite of homogeneous 137Cs activities in soil, grass samples showed a high variability. A negative correlation was detected between 40K- and 137Cs-activities in plants. TF values for 137Cs were highly variable, thus suggesting that this parameter would be independent of 137Cs soil activity. Lower variability was observed for 40K TFs values. Our results suggest that TFs are highly variable parameters that appear to be independent on radionuclide soil activity. Because soil and plant characteristics strongly affect TF values, caution is necessary when TF values are used as the sole parameter to predict radionuclide uptake by plants in semi-natural ecosystems.

An overview of recent charged-particle radiation biology in Italy

Radiobiology with charged particles is being carried out in Italy since several decades, starting with the experiments with protons in Milan. Later, also other groups entered the field, such as those in Naples, in Legnaro (LNL) and in Rome. In the last 10-15 years the activities in the field began to grow in a significant way. This happened in concomitance with the involvement of various researchers and Institutions in European and international projects devoted to radiation protection aspects, such as those aimed at elucidating and modelling radiation action mechanisms (EC/EU) and those aimed at radiation protection in space (NASA). A special role has been played since then by the Laboratori Nazionali di Legnaro of the INFN, where a radiobiology facility for low energy light ions was set up and operated in 1985. A formidable stimulus for charged-particle radiobiology was more recently given by the onset of plans for developing hadrontherapy Centres in Italy. The TERA Foundation first, and than the TOP Project at the Istituto Superiore di Sanità, at the same time favoured the spreading in Italy of radiobiology research with charged particles and encouraged co-operation among various groups. The Italian radiobiology community, though relatively small, developed a number of valuable activities with charged particles, mostly at the cellular and molecular levels, that span from mechanisms of radiation action to radiation protection in space and to therapy with charged hadrons. In this article, due to space limitations, we have just been able to list the present activities and to briefly review some research that forms a common background for the various areas. This includes the work on Chinese hamster V79 cells irradiated with light ions at LNL, that provided extensive data on the relationships between radiation quality, molecular damage and cellular effects, and the related work aimed at possible interpretation by mechanistic models. It appears that the multiplicity of objectives does not represent a factor of weakness for the relatively small Italian radiobiology community. Synergistic effects have been found because the basic radiobiology is the same for different areas such as radiation protection and hadrontherapy, and because the expertise and the methods developed for a given purpose may find useful applications in others. Though it is difficult to forecast the future development in Italy of the various areas that will take advantage of charged-particle radiobiology, it is expected that hadrontherapy and space radiation protection together, independently of their relative weight, will be important driving forces for the future development of the field in our Country.

DNA fragmentation induced in K562 cells by nitrogen ions

This study was aimed at investigating the radiation induced DNA fragmentation pattern as a function of cellular differentiation and radiation quality. DNA double strand breaks (DSB) induced by gamma-rays were analyzed in K562 human proerythroblasts before (AP cells) and after (D cells) differentiation induction while DNA DSB induced by 125 keV/micrometers N-ions have been studied in AP cells. Pulsed-Field Gel Electrophoresis (PFGE) of cellular DNA was used to determine the DSB yield by analysis of the Fraction of Activity Released (FAR) and of the fragmentation pattern in a specific size range (5.7-0.225 Mbp). The results so far obtained show that the DSB induction by gamma-rays is different if evaluated with the FAR or with the fragmentation analysis. The DSB yield obtained with the former method is about 1.4 times higher in AP respect to D cells while the latter method indicates that more fragments are produced in D cells. Comparison between gamma-rays and N-ions in AP cells shows that no significant differences are detected by the FAR analysis; otherwise fragmentation analysis demonstrates a higher effectiveness of nitrogen ions.

DNA fragmentation in V79 cells irradiated with light ions as measured by pulsed-field gel electrophoresis. I. Experimental results

PURPOSE

To compare the results on DNA fragmentation induced in Chinese hamster V79 cells by various doses of gamma-rays and low-energy protons and helium-4 ions.

MATERIALS AND METHODS

V79 cells were irradiated as monolayers with monoenergetic protons and helium-4 ions; gamma-rays were used as the reference radiation. DNA double-strand breaks were evaluated by calibrated pulsed-field gel electrophoresis using conditions covering the range 5.7 Mbp-23.1 kbp.

RESULTS

The fragment-counting method gave double-strand breaks yields and the relative biological effectiveness higher than those obtained by the fraction of activity released method. The frequency distribution of fragments showed that protons and helium ions induced more fragments below the Mbp region than did gamma-rays at the same dose. The distributions for both the irradiated and non-irradiated samples clearly appeared to be non-random.

CONCLUSION

Differences were observed in the yield and spatial correlation, at a molecular size scale characteristic of loop dimensions, of the double-strand breaks induced by gamma-rays and by light ions. These effects may have a role in the observed different cell response to these radiations.

Induction and repair of DNA damage in human cells at different stages of differentiation

Use of cellular systems capable of undergoing in vitro differentiation can give useful information on the basic mechanisms of cellular radiation sensitivity. During differentiation the cellular organisation, including the nuclear structure and the intracellular concentration of several compounds and enzymes change drastically. Accordingly, radiation response to ionising radiation is also expected to change. The human proerythroblastoid cell line K562 can be induced to pseudoerythroid differentiation. This process has been characterised and studies have been carried out on DNA single strand break and double strand break induction and repair before and after differentiation commitment. Rejoining studies have been performed for both types of damage and correct double strand break rejoining has been also measured in particular genomic locations. An overview is presented of these results together with preliminary data recently obtained on radiation induced DNA fragmentation as a function of radiation quality.

Suspended particle adhesion on aquatic plant surfaces: implications for 137Cs and 133Cs uptake rates and water-to-plant concentration ratios

Suspended particle adhesion on aquatic biota can significantly increase the apparent concentration of radionuclides above their endogenous value, leading to an overestimation of the uptake rate and concentration ratios. This study is an attempt to assess quantitatively the importance of suspended particle adhesion on periphyton samples (biological material coating submerged surfaces). The concentrations of 137Cs and stable Cs (133Cs) in periphyton, suspended particles and filtered water were measured to determine the net water-to-periphyton concentration ratios for 137Cs and stable Cs. The net amount of 133Cs (or 137Cs) taken up by periphyton was calculated by subtracting from the total amount of 133Cs (or 137Cs) on the collected material (periphyton + inorganic particles), the 133Cs (or 137Cs) due to the inorganic particles adhering to periphyton. The mass of suspended particles adhering to the periphyton surface was calculated using scandium as an indicator of the mineral fraction of the suspended particles. The relationship between the concentration ratios for 137Cs and stable Cs and suspended particle adhesion on periphyton external surfaces is discussed.

A semi-microscopic model for the evaluation of radiation damage

A model for the biological effects of the energy deposited by ion beams on irradiated tissues is presented. The relevant parameters are the fractions of undamaged cells (where of course the definition of damaged cell depends on the biological end point under consideration, e.g. surviving cells) after the sensitive target of the cells has been traversed by any given number of ionising particles. The experimental parameters of the dose response curves offer a way to determine those of the model. The model can be formulated both for the simpler case of cells traversed by only one radiation quality, i.e. by a monoenergetic beam of a given ion, and for the general case of irradiation by a mixed field. A possible application in experimental data analysis is presented.

Radioecological survey at selected sites hit by depleted uranium ammunitions during the 1999 Kosovo conflict

A field study, organised, coordinated and conducted under the responsibility of the United Nations Environment Programme (UNEP), took place in Kosovo in November 2000 to evaluate the level of depleted uranium (DU) released into the environment by the use of DU ammunition during the 1999 conflict. Representatives of six different scientific organisations took part in the mission and a total of approximately 350 samples were collected. During this field mission, the Italian National Environmental Protection Agency (ANPA) collected water, soil, lichen and tree bark samples from different sites. The samples were analysed by alpha-spectroscopy and in some cases by inductively coupled plasma-source mass spectrometry (ICP-MS). The 234U/238U and 235U/238U activity concentration ratios were used to distinguish natural from anthropogenic uranium. This paper reports the results obtained on these samples. All water samples had very low concentrations of uranium (much below the average concentration of drinking water in Europe). The surface soil samples showed a very large variability in uranium activity concentration, namely from approximately 20 Bq kg(-1) (environmental natural uranium) to approximately 2.3 x 10(5) Bq kg(-1) (approximately 18000 mg kg(-1) of depleted uranium), with concentrations above environmental levels always due to DU. The uranium isotope measurements refer to soil samples collected at places where DU ammunition had been fired; this variability indicates that the impact of DU ammunitions is very site-specific, reflecting both the physical conditions at the time of the impact of the DU ammunition and any physical and chemical alteration which occurred since then. The results on tree barks and lichens indicated the presence of DU in all cases, showing their usefulness as sensitive qualitative bio-indicators for the presence of DU dusts or aerosols formed at the time the DU ammunition had hit a hard target. This result is particularly interesting considering that at some sites, which had been hit by DU ammunition, no DU ground contamination could be detected.

Gemcitabine plus vinorelbine yields better survival outcome than vinorelbine alone in elderly patients with advanced non-small cell lung cancer. A Southern Italy Cooperative Oncology Group (SICOG) phase III trial

OBJECTIVE

This phase III study was aimed at evaluating whether the addition of gemcitabine (G) to vinorelbine (V) could improve the survival and quality of life (QoL) of elderly patients with advanced NSCLC.

PATIENTS AND METHODS

Patients with advanced NSCLC, aged >or=70 years, were randomly allocated to receive V 30 mg/m(2) on days 1 and 8 every 3 weeks or G 1200 mg/m(2) plus V 30 mg/m(2) on days 1 and 8 every 3 weeks. Survival was the main end point of the study. The estimated sample size was 120 patients per arm, but an interim analysis of survival was planned on the first 60 patients per arm.

RESULTS

In May 1999, an interim analysis was performed with the survival data of the first 120 eligible patients (V(arm)=60, G+V(arm)=60). Forty-nine patients had stage IIIB disease and 71 patients stage IV disease, median potential follow-up of 14 months (range; 3-22), 93 patients had died (G+V(arm)=41, V(arm)=52). Median survival time (MST) was 29 weeks and projected 1-year survival was 30% in the G+V(arm); these values were 18 weeks and 13% in the V(arm). At multivariate Cox analysis, the risk of death in the G+V(arm) compared with V(arm) was 0.48 (95% C1=0.29-0.79; P<0.01). Combination therapy was also associated with a clear delay in symptom and QoL deterioration. The ORR was 22 and 15% in the G+V and V(arms), respectively. Toxicity was not irrelevant in both arms.

CONCLUSIONS

G+V treatment is associated with a significantly better survival than V alone in elderly NSCLC patients. The magnitude of the difference justifies the early closure of the study. The G+V regimen is now the SICOG reference regimen in this type of patients.

Fine structure of healthy human gingival mast cells and their immunological characterization

Despite the great number of studies on mast cell population, at the present time few are the studies regarding the structural aspects of mast cells in human gingiva. In order to identify and characterize gingival mast cells, specimens of healthy human gingival tissue have been studied. Subsequently, in order to test mast cell capability of express TNF-alfa, samples of healthy gingiva with antibody anti-TNF-alfa have been incubated. The results showed that in human gingiva mast cells are numerous and ubiquitarious. These cells exhibit several morphological types of cytoplasmic granules with characteristic subgranular content, varying in shape and density. This allows to divide gingival mast cells into two different subpopulations: either cells containing granules with compact coiled scrolls and/or particles and cells showing granules with scrolls and thin parallel bands. The two ultrastructural aspects observed seem to be correlated to the McT (mast cells containing tryptase) and McTC (mast cells containing tryptase and chymase) described in international literature, differing for ultrastructural aspect, biochemical content and response to secretagogue substances. The positivity of the reaction for TNF-alfa seems indeed to confirm that gingival mast cells are able to secrete sensible amounts of TNF-alfa.