Electric Fields in Liquid Water Irradiated with Protons at Ultrahigh Dose Rates.

We study the effects of irradiating water with 3 MeV protons at high doses by observing the motion of charged polystyrene beads outside the proton beam. By single-particle tracking, we measure a radial velocity of the order of microns per second. Combining electrokinetic theory with simulations of the beam-generated reaction products and their outward diffusion, we find that the bead motion is due to electrophoresis in the electric field induced by the mobility contrast of cations and anions. This work sheds light on the perturbation of biological systems by high-dose radiations and paves the way for the manipulation of colloid or macromolecular dispersions by radiation-induced diffusiophoresis.

A diamond guard ring microdosimeter for ion beam therapy.

A single crystal chemical vapor deposition diamond-based microdosimeter prototype featuring an array of micro-sensitive volumes (µSVs) and surrounded by a so-called guard ring (GR) electrode has been fabricated using various microfabrication techniques available at Diamond Sensors Laboratory of CEA, Saclay. The GR microdosimeter was irradiated by a raster scanning method with 2 MeV proton microbeams. The charge transport properties of the GR sensor were determined with sub-micron spatial resolution by measuring the charge collection efficiency (CCE), the µSV geometry, and the pulse-height spectra. The response of the microdosimeter showed a well-defined and homogeneously active µSV. Appropriate biasing of the µSV structures led toward a full CCE for protons with lineal energies of ∼46 keV/µm. This shows the GR microdosimeter's great potential for applications in microdosimetry in clinical beam conditions.

Advances in microbeam technologies and applications to radiation biology.

Charged-particle microbeams (CPMs) allow the targeting of sub-cellular compartments with a counted number of energetic ions. While initially developed in the late 1990s to overcome the statistical fluctuation on the number of traversals per cell inevitably associated with broad beam irradiations, CPMs have generated a growing interest and are now used in a wide range of radiation biology studies. Besides the study of the low-dose cellular response that has prevailed in the applications of these facilities for many years, several new topics have appeared recently. By combining their ability to generate highly clustered damages in a micrometric volume with immunostaining or live-cell GFP labelling, a huge potential for monitoring radiation-induced DNA damage and repair has been introduced. This type of studies has pushed end-stations towards advanced fluorescence microscopy techniques, and several microbeam lines are currently equipped with the state-of-the-art time-lapse fluorescence imaging microscopes. In addition, CPMs are nowadays also used to irradiate multicellular models in a highly controlled way. This review presents the latest developments and applications of charged-particle microbeams to radiation biology.

No evidence for DNA and early cytogenetic damage in bystander cells after heavy-ion microirradiation at two facilities.

The occurrence of bystander effects has challenged the evaluation of risk for heavy ions, mainly in the context of space exploration and the increasing application of carbon ions in radiotherapy. In the present study, we addressed whether heavy-ion-induced DNA and cytogenetic damage is detectable in bystander cells. The formation of gamma-H2AX foci, sister chromatid exchanges and micronuclei were used as markers of damage to DNA. Normal human fibroblasts were exposed to low fluences of carbon and uranium ions, and alternatively single cells were targeted with heavy ions using the GSI microbeam. We did not observe a significant increase in the bystander formation of gamma-H2AX foci, sister chromatid exchanges or micronuclei. In addition, we performed for the first time parallel experiments at two microbeam facilities (GSI, JAEA) using the same cell line, culture conditions and irradiation protocols. No significant enhancement of the micronucleus frequencies in bystander cells was detected after targeted carbon-ion irradiation, confirming the results. Details regarding the history, culture conditions or support of the cells might be affecting the detection of bystander effects. On the other hand, the potential X-ray- and heavy-ion-induced bystander effects investigated herein clearly do not exceed the experimental error and thus are either lacking or are less pronounced than the effects reported in the literature for similar end points after alpha-particle and X-ray exposure.

Cell cycle-related bystander responses are not increased with LET after heavy-ion irradiation.

Evidence has accumulated that irradiated cells affect their unirradiated neighbors, so that they in turn display cellular responses typically associated with direct radiation exposure. These responses are generally known as bystander effects. In this study, cell cycle-related bystander responses were investigated in three strains of human fibroblasts after exposure to densely ionizing radiation. Varying the linear energy transfer (LET) from 11 to 15,000 keV microm(-1) allowed a study of the impact of the complexity of DNA damage in the inducing cells on the responses of bystander cells. Using both broad-beam and microbeam irradiation, transient bystander responses were obtained for the induction of CDKN1A (p21). The latter was also observed when the transmission of bystander signals was limited to soluble factors. Targeted irradiation of single cells in confluent cell monolayers revealed no correlation between the amount of CDKN1A protein in the bystander cells and the radial distance to the targeted cells. In line with the induction of CDKN1A in bystander cells after irradiation with different LETs, a transient delay in the first G1 phase after irradiation of G0/G1 cells was observed. However, the CDKN1A induction revealed no significant effect on premature terminal differentiation considered to underlie fibrosis in irradiated tissue. Thus the unchanged differentiation pattern in bystander cells does not indicate pronounced, long-lasting effects.

A fast online hit verification method for the single ion hit system at GSI.

For a single ion hit facility built to irradiate specific targets inside biological cells, it is necessary to prove that the ions hit the selected targets reliably because the ion hits usually cannot be seen. That ability is traditionally tested either indirectly by aiming at pre-etched tracks in a nuclear track detector or directly by making the ion tracks inside cells visible using a stain coupled to special proteins produced in response to ion hits. However, both methods are time consuming and hits can be verified only after the experiment. This means that targeting errors in the experiment cannot be corrected during the experiment. Therefore, we have developed a fast online hit verification method that measures the targeting accuracy electronically with a spatial resolution of +/-1 microm before cell irradiation takes place.

[Concurrent mycetoma and chromomycosis: case report from Senegal]. / Association d'un eumycétome et d'une chromomycose: une observation au Sénégal.

A 68-year-old cattle farmer from northern Senegal sought medical attention for tumefaction that had been progressing on the right foot and leg for 20 years. Physical examination of the right extremity revealed very firm tumefaction involving the foot and whole leg associated with numerous nodules. Bone radiographs and CT-scan of the foot and leg disclosed extensive osteolytic involvement. A specimen of squamous tissue from the top of nodules showed the presence of fumagoid cells characteristic of chromomycosis. Histologic examination after skin biopsy demonstrated fungal myocetoma. Due to the extent of involvement surgical and antifungal treatment was proposed but the patient refused to undergo surgery. Only one previous case of concurrent chromomycosis and mycetoma has been described. However the previous case involved actinomycetoma. The rarity of this combination of diseases despite their common contamination mode is due to different geographical distribution with mycetoma being found in the Sahelian region and chromomycosis in the humid equatorial region.