Rapid Note Evidence for intrinsic Kerr bistability of high-Q microsphere resonators in superfluid helium

Abstract. Quality factors up to 10 9 have been obtained in the whispering gallery modes (WGMs) of fused silica microspheres immersed in a superfluid helium bath. We have observed a dispersive bistable behaviour of the WGM resonances with a threshold power of 10 µW, due to the intrinsic Kerr nonlinearity of silica. These results open the way to the realization of a thresholdless microlaser and other cavity QED projects with microspheres. PAC

A non-destructive sugar-feeding assay for parasite detection and estimating the extrinsic incubation period of Plasmodium falciparum in individual mosquito vectors

Despite its epidemiological importance, the time Plasmodium parasites take to achieve development in the vector mosquito (the extrinsic incubation period, EIP) remains poorly characterized. A novel non-destructive assay designed to estimate EIP in single mosquitoes, and more broadly to study Plasmodium–Anopheles vectors interactions, is presented. The assay uses small pieces of cotton wool soaked in sugar solution to collect malaria sporozoites from individual mosquitoes during sugar feeding to monitor infection status over time. This technique has been tested across four natural malaria mosquito species of Africa and Asia, infected with Plasmodium falciparum (six field isolates from gametocyte-infected patients in Burkina Faso and the NF54 strain) and across a range of temperatures relevant to malaria transmission in field conditions. Monitoring individual infectious mosquitoes was feasible. The estimated median EIP of P. falciparum at 27 °C was 11 to 14 days depending on mosquito species and parasite isolate. Long-term individual tracking revealed that sporozoites transfer onto cotton wool can occur at least until day 40 post-infection. Short individual EIP were associated with short mosquito lifespan. Correlations between mosquito/parasite traits often reveal trade-offs and constraints and have important implications for understanding the evolution of parasite transmission strategies

Detection of Plasmodium falciparum in laboratory-reared and naturally infected wild mosquitoes using near-infrared spectroscopy.

There is an urgent need for high throughput, affordable methods of detecting pathogens inside insect vectors to facilitate surveillance. Near-infrared spectroscopy (NIRS) has shown promise to detect arbovirus and malaria in the laboratory but has not been evaluated in field conditions. Here we investigate the ability of NIRS to identify Plasmodium falciparum in Anopheles coluzzii mosquitoes. NIRS models trained on laboratory-reared mosquitoes infected with wild malaria parasites can detect the parasite in comparable mosquitoes with moderate accuracy though fails to detect oocysts or sporozoites in naturally infected field caught mosquitoes. Models trained on field mosquitoes were unable to predict the infection status of other field mosquitoes. Restricting analyses to mosquitoes of uninfectious and highly-infectious status did improve predictions suggesting sensitivity and specificity may be better in mosquitoes with higher numbers of parasites. Detection of infection appears restricted to homogenous groups of mosquitoes diminishing NIRS utility for detecting malaria within mosquitoes

Discrimination of Radiotoxic and Chemotoxic Effects of Uranium on Mouse Embryo Fibroblasts

Uranium (U) is a natural radioactive heavy metal used in the nuclear industry, in different forms with different isotopic compositions (natural, depleted or enriched in 235U) and solubilities. Uranium internal exposure is a major risk for the nuclear workers. Uranium uptake can occur accidentally after inhalation, ingestion, or absorption through intact or injured skin. Due to these physical and chemical properties, U toxicity results from both chemical and radiological toxicity. The aim of this work was to find biological markers of internal contamination able to discriminate between chemotoxic and radiotoxic effects of U. The study was carried out in vitro on mouse C3H10T1/2 embryo fibroblasts contaminated either with 0.3% depleted uranium in isotope 235U (DU) or with 12% enriched uranium in isotope 235U (EU). In our experimental conditions, EU has a specific activity 20 times higher than DU. Fibroblasts were grown in culture medium containing various concentrations of DU or EU (0µM, 5µM, 50µM, 500µM and 1000µM). Genotoxic effects of both DU and EU were assessed with the cytokinesis-block micronucleus assay in combination with the fluorescent in situ hybridization of centromeric DNA probes. Binucleated cells with one micronucleus (BN-1MN), binucleated cells with centromere-negative micronucleus (BN-MNC-), mononucleated cells with one MN (Mono-1MN) and nucleoplasmic bridges (NPBs) were scored. Moreover ?-H2AX immunostaining was achieved to detect DNA double-strand breaks (DSB). The percentage of BN-1MN increased with both DU and EU concentration. The percentage of BN-MNC- was significantly higher when cells were contaminated with EU compared to DU for all concentrations (for example, 1,2% and 0,4% for a 50µM EU and DU concentration, respectively), this result confirms clastogen effect of EU. The frequency of NPBs increased with the U concentration. However EU induces more NPBs than DU (for example, 1,35% and 0,25% for a 50µM EU or DU concentration, respectively). In addition, the percentage of Mono-1MN is higher after a contamination with EU compared to DU (for example, 5,5% and 4,5% for a 50µM EU and DU concentration, respectively). The percentage of cells with DSB increased with U concentration. As a conclusion, our experiments show that BN-1MN and DSB seem to be a marker of U genotoxicity (chemical + radiological). The BN-MNC-, NPBs, and to a lesser extent Mono-1MN seem to be a marker of a radiotoxic effect. A microdosimetric calculation is in process and will consolidate these results

A mouse model of cytogenetic analysis to evaluate caesium137 radiation dose exposure and contamination level in lymphocytes

International audienceIn case of external overexposure to ionizing radiation, an estimation of its genotoxic effects on exposed individuals can be made retrospectively by the measurement of radiation-induced chromosome aberrations on circulating lymphocytes. Compared with external irradiation, intakes of radionuclides may, however, lead to specific features influencing dose distribution at the scale of body, of tissue or even of cell. Therefore, in case of internal contamination by radionuclides, experimental studies, particularly using animal models, are required to better understand mechanisms of their genotoxic effects and to better estimate the absorbed dose. The present study was designed to evaluate a cytogenetic method in mouse peripheral blood lymphocytes that would allow determination of yields and complexities of chromosome aberrations after low-dose rate exposure to 137Cs delivered in vitro either by irradiation or by contamination. By using M-FISH analysis, we compared the low-dose rate responses observed in mouse to the high-dose rate responses observed both in mouse and in human. Promising similarities between the two species in the relative biological effect evaluation show that our cytogenetic model established in mouse might be useful to evaluate various radiation exposures, particularly relevant in case of intakes of radionuclides. © 2016, Springer-Verlag Berlin Heidelberg

Impact des facteurs individuels et environnementaux sur le taux d’aberrations chromosomiques de type translocations Partie 1 : âge, sexe, tabac, alcool

L’évaluation de l’exposition aux rayonnements ionisants, effectuée longtemps après l’exposition, est actuellement réalisée en dénombrant les aberrations chromosomiques de type translocations. Le taux de ces translocations observées dans les lymphocytes des personnes exposées est comparé au taux observé au sein d’une population contrôle. Toutefois, la spécificité des translocations vis-à-vis de l’irradiation n’est pas clairement identifiée. Afin d’éviter toute conclusion hâtive, il est nécessaire d’identifier tous les facteurs susceptibles d’induire des translocations. À notre connaissance, aucune synthèse sur l’effet de ces différents facteurs sur le taux de translocations n’a été réalisée à ce jour. Cette recherche bibliographique a confirmé l’impact de certains facteurs personnels sur l’augmentation des translocations. Cette étude corrobore que l’âge s’avère être le facteur ayant le plus d’impact sur le taux de translocations, notamment après 60 ans. À ce jour, le facteur « âge » est déjà considéré dans l’estimation du taux de translocations après suspicion d’exposition aux rayonnements ionisants pour toutes les classes d’âge. L’étude montre également que ce taux varie significativement lorsque le patient est exposé simultanément et de manière importante et chronique à une combinaison alcool et tabac. Ainsi, une courbe du taux de translocations devrait être établie en fonction de la consommation excessive de ce type d’agent pour chaque individu. Ainsi il serait alors possible de déterminer le taux de translocations induit uniquement par une exposition radiologique. Les effets des agents toxiques sur le taux de translocations après exposition professionnelle feront l’objet d’une deuxième partie

029. Romans 8:17

Chapel Sermon by John Schmidtke from Romans 8:17 on Monday, October 31, 2011