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At least 19 recordsLinked to original sources
PubMed2003

In vivo and in vitro measurements of complex-type chromosomal exchanges induced by heavy ions.

Heavy ions are more efficient in producing complex-type chromosome exchanges than sparsely ionizing radiation, and this can potentially be used as a biomarker of radiation quality. We measured the induction of complex-type chromosomal aberrations in human peripheral blood lymphocytes exposed in vitro to accelerated H-, He-, C-, Ar-, Fe- and Au-ions in the LET range of approximately 0.4-1400 keV/micrometers. Chromosomes were analyzed either at the first post-irradiation mitosis, or in interphase, following premature condensation by phosphatase inhibitors. Selected chromosomes were then visualized after FISH-painting. The dose-response curve for the induction of complex-type exchanges by heavy ions was linear in the dose-range 0.2-1.5 Gy, while gamma-rays did not produce a significant increase in the yield of complex rearrangements in this dose range. The yield of complex aberrations after 1 Gy of heavy ions increased up to an LET around 100 keV/micrometers, and then declined at higher LET values. When mitotic cells were analyzed, the frequency of complex rearrangements after 1 Gy was about 10 times higher for Ar- or Fe- ions (the most effective ions, with LET around 100 keV/micrometers) than for 250 MeV protons, and values were about 35 times higher in prematurely condensed chromosomes. These results suggest that complex rearrangements may be detected in astronauts' blood lymphocytes after long-term space flight, because crews are exposed to HZE particles from galactic cosmic radiation. However, in a cytogenetic study of ten astronauts after long-term missions on the Mir or International Space Station, we found a very low frequency of complex rearrangements, and a significant post-flight increase was detected in only one out of the ten crewmembers. It appears that the use of complex-type exchanges as biomarker of radiation quality in vivo after low-dose chronic exposure in mixed radiation fields is hampered by statistical uncertainties.

Biomarkers↗
PubMed1989

Quantitative interpretation of heavy ions effects: models for the biological effects of heavy ions.

Heavy ions are an important part of space radiation. Although they contribute only about 1 percent in number the fraction in terms of energy deposited is much higher. Also the quality of radiation is different from the other components since the LET is generally quite high. This poses the problem of Relative Biological Effectiveness (RBE). It is considerably more important in space than on earth because shielding measures are costly and sometimes not even feasible. Radiation hazards appear to be the limiting factor In long term space flights and their evaluation constitutes a major task. There is still no general agreement about RBE of earthbound radiation, and even less concerning the biological weighting of very heavy and very energetic ions in space. Because of the lack of experimental data--particularly for risk estimates in humans-- theoretical approaches may be very helpful in this respect and provide the only means to judge the radiation protection situation in outer space. In order to be useful careful checks of their consistency are necessary. This paper summarizes some of the more common approaches in a critical manner. The unhappy conclusion at the end will be that at present it is not possible to understand even heavy ion action on survival quantitatively with an acceptable precision.

Animals↗
PubMed2005

Comparison doses of secondary neutron with the heavy ions in a 75-Mev/n heavy ion beam.

The angular distributions for neutrons of energy >6 MeV that are induced by 75 MeV/n 12C6+ and 16O8+ ions were measured with the activation method of Al threshold detectors at the radiobiological terminal of HIRFL. The data were obtained by a high-purity Ge(HpGe) detector. The results show that the neutron angular distributions produced by heavy ion beams are strongly peaked in the forward direction and decreased exponentially with angles in experimental area. The experimental conditions for these measurements were similar to those for biological experiments, so the results should be representative of neutrons produced by heavy ions during the biological experiments and tumour therapy. Comparing with the neutron doses produced by the heavy ion beam, the heavy ion dose is the main factor in biological effects and tumour therapy response, so the contribution of neutron dose can be neglected.

Carbon↗
PubMed1993

Dosimetry and measured differential W values of air for heavy ions.

Heavy-ion irradiation systems were designed and constructed at two cyclotron facilities in Japan for use in various fields of radiation physics and radiation biology. A 135 MeV/u carbon beam as well as 12 MeV/u carbon and helium-3 beams were first used in experiments. We have established a systematic method for heavy-ion dosimetry at both high and low incident energies involving measurements of fluences. We also obtained differential W values (w) of air for those beams by comparing the results of fluence measurement dosimetry with ionization chamber dosimetry. The differential W values of air were found to be 36.2 +/- 1.0, 34.5 +/- 1.0, and 33.7 +/- 0.9 eV for 6.7 MeV/u carbon ions, 10.3 MeV/u 3He ions, and 129.4 MeV/u carbon ions, respectively. The w value for high-energy heavy ions approaches the W value for high-energy electron or photon beams. In ionization chamber dosimetry for a heavy-ion beam, we found a track-size effect. A difference in the track sizes of heavy ions in the gas and solid phases affected the output current of the ion chamber in the case of high-energy heavy ions.

Carbon↗
PubMed1996

Low energy ions in the heavy ions in space (HIIS) experiment on LDEF.

We present data from the Lexan top stacks in the Heavy Ions In Space (HIIS) experiment which was flown for six years (April 1984-Jan 1990) onboard the LDEF spacecraft in 28.5 degrees orbit at about 476 km altitude. HIIS was built of passive (i.e. no timing resolution) plastic track detectors which collected particles continuously over the entire mission. In this paper we present data on low energy heavy ions (10 < or = Z, 20MeV/nuc < E < 200 MeV/nuc). These ions are far below the geomagnetic cutoff for fully ionized ions in the LDEF orbit even after taking into account the severe cutoff suppression caused by occasional large geomagnetic storms during the LDEF mission. Our preliminary results indicate an unusual elemental composition of trapped particles in the inner magnetosphere during the LDEF mission, including both trapped anomalous cosmic ray species (Ne, Ar) and other elements (such as Mg and Fe) which are not found in the anomalous component of cosmic rays. The origin of the non-anomalous species is not understood, but they may be associated with the solar energetic particle events and geomagnetic disturbances of 1989.

Argon↗
PubMed2002

Heavy-ion-induced mutations in the gpt delta transgenic mouse: comparison of mutation spectra induced by heavy-ion, X-ray, and gamma-ray radiation.

Heavy-ion radiation accounts for the major component of absorbed cosmic radiation and is thus regarded as a significant risk during long-term manned space missions. To evaluate the genetic damage induced by heavy particle radiation, gpt delta transgenic mice were exposed to carbon particle irradiation and the induced mutations were compared with those induced by reference radiations, i.e., X-rays and gamma-rays. In the transgenic mouse model, deletions and point mutations were individually identified as Spi(-) and gpt mutations, respectively. Two days after 10 Gy of whole-body irradiation, the mutant frequencies (MFs) of Spi(-) and gpt were determined. Carbon particle irradiation significantly increased Spi(-) MF in the liver, spleen, and kidney but not in the testis, suggesting an organ-specific induction of mutations by heavy-ion irradiation. In the liver, the potency of inducing Spi(-) mutation was highest for carbon particles (3.3-fold increase) followed by X-rays (2.1-fold increase) and gamma-rays (1.3-fold increase), while the potency of inducing gpt mutations was highest for gamma-rays (3.3-fold increase) followed by X-rays (2.1-fold increase) and carbon particles (1.6-fold increase). DNA sequence analysis revealed that carbon particles induced deletions that were mainly more than 1,000 base pairs in size, whereas gamma-rays induced deletions of less than 100 base pairs and base substitutions. X-rays induced various-sized deletions and base substitutions. These results suggest that heavy-ion beam irradiation is effective at inducing deletions via DNA double-strand breaks but less effective than X-ray and gamma-ray irradiation at producing oxidative DNA damage by free radicals.

Aerospace Medicine↗
PubMed2004

Expression of NF-kappaB and ERK following heavy ion irradiation.

Heavy ion irradiation of cells is known to increase cytotoxic, mutagenic, and carcinogenic effects. The increased biological effectiveness of these ions is as yet unexplained, except for the fact that, unlike gamma-radiation, they result in clustered damage. It is likely that the increased biological effectiveness is a consequence of altered signaling pattern, which in turn may be due to the difference in the nature of damage produced. Gamma irradiation has been known to activate both pro- and anti-apoptotic signaling pathways. Nuclear factor-kappaB (NF-kappaB) and extracellular signal regulated kinase (ERK) contribute to the survival of the irradiated cell. Moreover, NF-kappaB acts as a redox sensor. In the present study, we examined NF-kappaB and ERK as antiapoptotic factors that could lead to the inhibition of apoptosis and, consequently, to increased mutagenicity. Both these signaling factors show a fluctuation in their levels with time.

Animals↗
PubMed1996

DNA damage and repair in oncogenic transformation by heavy ion radiation.

Energetic heavy ions are present in galactic cosmic rays and solar particle events. One of the most important late effects in risk assessment is carcinogenesis. We have studied the carcinogenic effects of heavy ions at the cellular and molecular levels and have obtained quantitative data on dose-response curves and on the repair of oncogenic lesions for heavy particles with various charges and energies. Studies with repair inhibitors and restriction endonucleases indicated that for oncogenic transformation DNA is the primary target. Results from heavy ion experiments showed that the cross section increased with LET and reached a maximum value of about 0.02 micrometer2 at about 500 keV/micrometer. This limited size of cross section suggests that only a fraction of cellular genomic DNA is important in radiogenic transformation. Free radical scavengers, such as DMSO, do not give any effect on induction of oncogenic transformation by 600 MeV/u iron particles, suggesting most oncogenic damage induced by high-LET heavy ions is through direct action. Repair studies with stationary phase cells showed that the amount of reparable oncogenic lesions decreased with an increase of LET and that heavy ions with LET greater than 200 keV/micrometer produced only irreparable oncogenic damage. An enhancement effect for oncogenic transformation was observed in cells irradiated by low-dose-rate argon ions (400 MeV/u; 120 keV/micrometer). Chromosomal aberrations, such as translocation and deletion, but not sister chromatid exchange, are essential for heavy-ion-induced oncogenic transformation. The basic mechanism(s) of misrepair of DNA damage, which form oncogenic lesions, is unknown.

Animals↗
PubMed2004

Experimental model for irradiating a restricted region of the rat brain using heavy-ion beams.

Heavy-ion beams have the feature to administer a large radiation dose in the vicinity of the endpoint in the beam range, its irradiation system and biophysical characteristics are different from ordinary irradiation instruments like X-rays or gamma-rays. In order to get clarify characteristic effects of heavy-ion beams on the brain, we have developed an experimental system for irradiating a restricted region of the rat brain using heavy-ion beams. The left cerebral hemispheres of the adult rat brain were irradiated at dose of 50 Gy charged carbon particles (290 MeV/nucleon; 5 mm spread-out Bragg peak). After irradiation, the characteristics of the heavy-ion beams and the animal model were studied. Histological examination and measurement showed that extensive necrosis was observed between 2.5 mm and 7.5 mm depth from the surface of the rat head, suggesting a relatively high dose and uniform dose was delivered among designed depths and the spread-out Bragg peak used here successfully and satisfactorily retained its high-dose localization in the defined region. We believe that our experimental model for irradiating a restricted region of the rat brain using heavy-ion beams is a good model for analyzing regional radiation susceptibility of the brain.

Animals↗
PubMed1993

Micro-PIXE (particle induced X-ray emission) analysis of aluminum in rat-liver using MeV heavy ion microprobes.

Heavy ion microprobes (HIM) such as 3 MeV Si2+ and 3 MeV p2+ have been applied to the elemental analysis by PIXE (proton-induced X-ray emission). It was found that silicon and phosphorus microprobes have several times higher sensitivity for aluminum K alpha X-rays than 2 MeV proton microprobes, and detection limits were more favorable in a phosphorus microprobe. Using a 3 MeV P2+ microprobe, the liver of a rat, which had been injected with aluminum-lactate, was investigated and it was found that aluminum segregates in areas with a dimension of about 10 microns. These areas could hardly be observed with 2 MeV proton microprobes.

Aluminum↗
PubMed2002

Examination of fragment dose contribution in heavy ion radiotherapy.

Heavy-ion radiotherapy is an efficient method for the treatment of deep-seated tumors, because the stopping of ions in a tissue delivers the maximal absorbed dose to the tumor-affected areas with minimal damage to the healthy tissues. However, heavy ions can undergo nuclear reactions, giving products with lower Z-values and hence a longer range in the tissue. This causes a dose increase beyond the mean range of the primary beam. The contribution of such reaction products was examined in an experiment where a stack of tissue-like targets interleaved with CR-39 etched track detectors (ETD) was irradiated with heavy ions. The analysis was performed using a recently developed technique of trajectory tracing, which enables the spectroscopy of fragments with different Z-values.

Carbon Isotopes↗
PubMed2001

The integrating ion imager: a device for determining heavy ion doses during irradiations.

We have designed and built an integrating ion imaging system (I3) that records the spatial distribution of the dose of heavy ions incident on samples irradiated at the radiobiology beamline of the Alternating Gradient Synchrotron at Brookhaven National Laboratory. The images of dose are integrated over the duration of the exposure. Unlike the images formed on X-ray film, these images are linear with the incident dose. Heavy ions are incident on a phosphor that is located just behind the sample position. Visible light emitted from the phosphor is collected by a lens and focused onto a scientific grade charge coupled device (CCD) cooled to about -45 degrees C. The phosphor and CCD camera are integral parts of a modular sample holder designed for irradiating molecular samples, which is easily mounted on the sample platform of the beamline. The imager can be adapted to other types of samples. The present CCD image is digitized to 14 bits (16,384 intensity levels), but the dynamic range is extended by adjusting the aperture of the CCD camera lens. Digital images from the CCD are routinely transferred over the BNL local area network for archival storage on a UNIX server, from which they can be opened from any authorized computer with access to the Internet. Images obtained with no sample in place record the dose at all points on the target field. When a sample is in place, an image of the sample appears providing its exact location with respect to fiducial marks recorded for all images. Areas surrounding the image of the sample are used in comparison with companion no-sample images to get exact doses over the sample. The contrast mechanism responsible for image formation is the shift along the Bragg curve resulting from loss of energy of the ions as they pass through the sample--not from a change in ion flux reaching the phosphor. The sharpness of the images formed with the DNA samples we have recorded indicates that neither scattering of the incident heavy ions or the generation of secondary ions contribute significantly.

Elementary Particles↗
PubMed1996

Effects of absorption by Io on composition of energetic heavy ions.

The Galileo heavy ion counter is sensitive to ions with atomic numbers Z >/= 6 and energies greater than approximately 6 MeV per nucleon. During Galileo's passage through Jupiter's inner magnetosphere, the observed composition of these heavy ions was consistent with the presence of singly ionized iogenic O, Na, and S and highly ionized solar C, O, and Ne. The solar component is absorbed more strongly by Io because its gyroradius is smaller than Io's diameter.

Carbon↗
PubMed1976

Lesional effects of primary cosmic heavy ions on rat brain.

Heavy ions were detected with nuclear emulsions plates fixed on the skulls of 20 rats which were exposed to cosmic rays at an altitude of 32,000 metres. Eight cases are described of correlations between ions tracks and brain lesions. The passage of heavy ions seems to cause functional rather than destructive alterations in the cells. The metabolic disturbances give a dark aspect to the neurons. The lesions generally appear in wide areas around the track and this fact suggests a physiopathological phenomenon of amplification. An evaluation of this biological hazard during flights of long duration at high altitude will be possible when the mechanism of action of heavy ions on nervous tissue is better known, and particularly if experiments carried out in accelerators confirm the small number of results obtained in flight.

Animals↗
PubMed2006

Charge transfer and ionisation by intermediate-energy heavy ions.

The use of heavy ion beams for microbeam studies of mammalian cell response leads to a need to better understand interaction cross sections for collisions of heavy ions with tissue constituents. For ion energies of a few MeV u(-1) or less, ions capture electrons from the media in which they travel and undergo subsequent interactions as partially 'dressed' ions. For example, 16 MeV fluorine ions have an equilibrium charge of 7(+), 32 MeV sulphur ions have an equilibrium charge of approximately 11(+), and as the ion energies decrease the equilibrium charge decreases dramatically. Data for interactions of partially dressed ions are extremely rare, making it difficult to estimate microscopic patterns of energy deposition leading to damage to cellular components. Such estimates, normally obtained by Monte Carlo track structure simulations, require a comprehensive database of differential and total ionisation cross sections as well as charge transfer cross sections. To provide information for track simulation, measurement of total ionisation cross sections have been initiated at East Carolina University using the recoil ion time-of-flight method that also yields cross sections for multiple ionisation processes and charge transfer cross sections; multiple ionisation is prevalent for heavy ion interactions. In addition, measurements of differential ionisation cross sections needed for Monte Carlo simulation of detailed event-by-event particle tracks are under way. Differential, total and multiple ionisation cross sections and electron capture and loss cross sections measured for C(+) ions with energies of 100 and 200 keV u(-1) are described.

Biopolymers↗
PubMed1984

On the quantitative interpretation of cellular heavy ion action.

Current analyses of heavy ion action assume that the survival probability of a cell hit by a heavy ion depends only on the energy absorbed in its critical site. It is known, however, that the efficiency to produce a biological effect depends also on the spatial pattern of energy deposition. This has to be included in the quantitative evaluation of heavy ion action. Based on recent models of lesion formation by ionizing radiation (Goodhead and Brenner, Phys. Med. Biol. 28, 485, 1983) data with lighter ions (LET < 500 keV/micrometer) were re-analysed. It is shown that the behaviour of various cell systems can be described by a common curve which can be used to estimate the contribution of "non-linear" components (i.e. where the distribution of energy deposition plays a role) with heavy ions. It is concluded that even with Uranium ions the regions of non-linear effects does not extend beyond 50 nm from the trade core. These data will be used to assess quantitatively survival curves obtained with very heavy ion exposure.

Heavy Ions↗