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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↗
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↗
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↗
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↗
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↗
PubMed1983

Rapid development of corneal lesions in rats produced by heavy ions.

Scanning electron micrographs of heavy ion irradiated corneas demonstrate a significant correlation with the heavy ion beam: The average number of plasma membrane lesions per unit area of corneal surface is correlated with the particle fluence of the beam. This observation corroborates what has already been suggested theoretically about heavy ion tracks and what has been shown experimentally through etched plastics, developed emulsions, and bubble chambers. But the new data indicate that particle tracks occur in biological tissues as well, and that a single heavy ion is responsible for each membrane lesion.

Animals↗
PubMed2002

Chlorophyll-deficient mutants of rice demonstrated the deletion of a DNA fragment by heavy-ion irradiation.

Heavy-ion irradiation is a new method of mutation breeding to produce new cultivars. We established the application of this method in rice plants to obtain mutants. Rice seeds were irradiated by C or Ne ions (135MeV/u) with a LET (linear energy transfer) of 22.7 or 64.2 keV/microm, respectively. Chlorophyll-deficient mutants (CDM) segregated in M2 progeny were albino, pale-green, yellow or striped-leave phenotypes. The highest rate of CDM with C-ion irradiation, 7.31%, was obtained at 40 Gy among the doses examined. Ne-ion irradiation gave the highest rate, 11.6%, at 20 Gy. We used the RLGS (Restriction Landmark Genomic Scanning) method to analyze DNA deletion in an albino mutant genome. Not I-landmark RLGS profiles detected about 2000 spots in rice. We found that one of the polymorphic spots was strongly linked to the albino phenotypic mutant derived from deleting of a DNA fragment, and demonstrated the high ability to detect of polymorphic regions by the RLGS method.

Carbon↗
PubMed1990

The medical heavy ion therapy project at the Gesellschaft für Schwerionenforschung facility in Darmstadt.

It could be demonstrated that local tumor control is considerably improved by radiation therapy with charged particles (protons or heavier ions). The advantages of heavy ion therapy compared to conventional photon therapy techniques are due to the better physical dose distributions achievable and the radiobiological characteristics of heavy ions. However, because of the expense and complexity of heavy ion therapy it is only carried out at a few facilities throughout the world. The Radiologische Universitätsklinik (Radiological University Hospital) and the Deutsches Krebsforschungszentrum (German Cancer Research Centre, DKFZ) in Heidelberg, in collaboration with the Gesellschaft für Schwerionenforschung (Laboratory for Heavy Ion, GSI) in Darmstadt, have developed a concept to use the new heavy ion synchrotron (Schwerionen-Synchroton SIS) in Darmstadt for medical-clinical irradiations. Due to the high flexibility of the SIS accelerator the medical program can be performed in addition to the planned physical experiments with minor interference only. The close geographical proximity of the three institutes involved and the accelerator which will be completed by the end of 1989 provide the unique opportunity to carry out relevant clinical, medical-physical, physical-technical, and radiobiological research in a relatively short time and, compared to similar projects in other countries, at low cost.

Costs and Cost Analysis↗
PubMed1998

Investigation of lipid peroxidation in liposomes induced by heavy ion irradiation.

Lipid peroxidation induced by heavy ion irradiation was investigated in 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) liposomes. Lipid peroxidation was induced using accelerated heavy ions that exhibit linear energy transfer (LET) values between 30 and 15000 keV/microm and doses up to 100 kGy. With increasing LET, the formation of lipid peroxidation products such as conjugated dienes, lipid hydroperoxides, and thiobarbituric acid-reactive substances decreased. When comparing differential absorption spectra and membrane fluidity following irradiation with heavy ions and x-rays (3 Gy/min), respectively, it is obvious that there are significant differences between the influences of densely and sparsely ionizing radiation on liposomal membranes. Indications for lipid fragmentation could be detected after heavy ion irradiation.

Argon↗