Structure and rheological properties of model microemulsion networks filled with nanoparticles

Model microemulsion networks of oil droplets stabilized by non ionic surfactant and telechelic polymer C18-PEO(10k)-C18 have been studied for two droplet-to-polymer size ratios. The rheological properties of the networks have been measured as a function of network connectivity and can be described in terms of simple percolation laws. The network structure has been characterised by Small Angle Neutron Scattering. A Reverse Monte Carlo approach is used to demonstrate the interplay of attraction and repulsion induced by the copolymer. These model networks are then used as matrix for the incorporation of silica nanoparticles (R=10nm), individual dispersion being checked by scattering. A strong impact on the rheological properties is found for silica volume fractions up to 9%

Social connections predict brain structure in a multidimensional free-ranging primate society

Reproduction and survival in most primate species reflects management of both competitive and cooperative relationships. Here, we investigated the links between neuroanatomy and sociality in free-ranging rhesus macaques. In adults, the number of social partners predicted the volume of the mid–superior temporal sulcus and ventral-dysgranular insula, implicated in social decision-making and empathy, respectively. We found no link between brain structure and other key social variables such as social status or indirect connectedness in adults, nor between maternal social networks or status and dependent infant brain structure. Our findings demonstrate that the size of specific brain structures varies with the number of direct affiliative social connections and suggest that this relationship may arise during development. These results reinforce proposed links between social network size, biological success, and the expansion of specific brain circuits

Oxidative stress in normal cells exposed to carbon ions

The high efficiency of carbon ions versus photons, with an RBE (Relative Biological Efficiency) of 2 to 3, to treat various tumours was demonstrated in the main hadrontherapy centers (GSI, Germany and HIMAC, Japan). However, few extensive studies were performed in order to evaluate the impact of high-LET exposure on healthy tissues. In spite of a better accuracy of a carbon beam as compared to photons, normal cells could also be irradiated in vicinity of the tumours treated. Thus, in order to evaluate the possible secondary effects of a carbon treatment, we compare the exposure of normal human cells to carbon ions (75 MeV/u) and to photons (X-rays). Survival curves were performed to select irradiation doses in both cases, X- or C-exposure. Oxidative stress was assessed in these cells to observe induced early and long-term cellular responses following radiation exposure (hours, days and weeks). Since exposure to high-LET ions is known to create DNA damage that are difficult to repair and that often lead to cell death, DNA damage were measured using global or cell level techniques as comet assay and γ-H2AX immunostaining. These measurements were performed soon after the exposure and also after different periods of recovery (1 and 3 hours). The evaluation of micronuclei in the cell cultures up to 21 days after irradiation was also a good indicator of the global management of DNA injury. Then, lipid peroxidation products (MDA, 4-HNE) were quantified as well as reactive oxygen species production (by flow cytometry using DCFH-DA and HE probes). Enzymatic defence systems (catalase, superoxide dismutase and glutathione peroxidase activities) and non-enzymatic defence systems (vitamin E, reduced/oxidized gluthatione) were also investigated. First results indicated an increased efficiency in producing oxidative damage after carbon ions exposure compared to X-rays

GENOTOXICITY OF HEAVY IONS IN RECOMBINANT BACTERIA

The mutagenic potential of the heavy ion component of the galactic cosmic radiation of space environment is of major concern for astronauts in terms of tumor induction as radiation late effects. The recombinant SWITCH test is based on TA1535 Salmonella typhimurium cells transformed with a bi-cistronic vector harbouring (a) the genes for bioluminescence production from Photobacterium leiognathi under the control of a DNA-damage inducible promoter and (b) the gene for green fluorescent protein from the jellyfish Aequorea victoria under the control of a constitutive promoter. Suchlike genetically modified organism report on the presence of genotoxic conditions by dose dependent increase of bioluminescence induction and on the presence of cytotoxic conditions by dose dependent decrease in GFP fluorescence. By this, it is possible to analyse bacterial inactivation and mutation induction by ionizing radiation in parallel in the same cell within short time. Experiments with heavy ions have been performed with the SWITCH test at GANIL with 75 MeV/A carbon, 95 MeV/A argon, and 29 MeV/A lead. The results obtained clearly show that the numbers of hits (particles per cm2) necessary to inactivate the bacteria (cytotoxicity) depend on LET. The higher the ionisation capacity of the accelerated ion, the less hits resulted in the same test effect, e.g. 37 % survival. For genotoxicity induction it can be seen, that for very high LET radiation the number of hits required is much less then for lower LET radiation (e.g. 1.4x106/cm2 hits for lead versus 1.3x107/cm2 hits for carbon). The power of the genotoxic response seems to be inversely related to LET. While carbon radiation results in a maximal induction of 72.6x, argon radiation leads to a 29.4x value and lead results in only a factor of 4.8. From the experiments with 3 different ions cross sections σ were calculated. Inactivation cross sections (σRCP) rise over the whole LET range under investigation. The same is true for genotoxicity cross sections (σRGP). Cross sections for maximal luminescence emission (σRGP for peak response) differ by a factor of about 10 from cross sections for inactivation; cross sections for doubling the response from untreated cells (σRGP for 2x) are about 3 orders of magnitude higher

Genotoxic and Cytotoxic Responses of Recombinant Salmonella typhimurium TA1535 Induced by Simulated Space Radiation Qualities

Introduction: For risk assessment, the mutagenic potential of the heavy ion component of the galactic cosmic radiation is of major concern for tumor induction as radiation late effects. The genetically modified TA1535 Salmonella typhimurium strain (SWITCH) reports on the presence of genotoxic conditions by dose dependent increase of bioluminescence induction and on the presence of cytotoxic conditions by dose dependent decrease in GFP fluorescence. By this, it is possible to analyze bacterial inactivation and mutation induction by ionizing radiation in parallel in the same cell within short time

Minor contribution of direct ionization to DNA base damage induced by heavy ions

International audienc

Formation of Modified DNA Bases in Cells Exposed either to Gamma Radiation or to High-LET Particles 1

International audienc