Contrasting effects of the alkaloid ricinine on the capacity of Anopheles gambiae and Anopheles coluzzii to transmit Plasmodium falciparum

Background Besides feeding on blood, females of the malaria vector Anopheles gambiae sensu lato readily feed on natural sources of plant sugars. The impact of toxic secondary phytochemicals contained in plant-derived sugars on mosquito physiology and the development of Plasmodium parasites remains elusive. The focus of this study was to explore the influence of the alkaloid ricinine, found in the nectar of the castor bean Ricinus communis, on the ability of mosquitoes to transmit Plasmodium falciparum. Methods Females of Anopheles gambiae and its sibling species Anopheles coluzzii were exposed to ricinine through sugar feeding assays to assess the effect of this phytochemical on mosquito survival, level of P. falciparum infection and growth rate of the parasite. Results Ricinine induced a significant reduction in the longevity of both Anopheles species. Ricinine caused acceleration in the parasite growth rate with an earlier invasion of the salivary glands in both species. At a concentration of 0.04 g l−1 in An. coluzzii, ricinine had no effect on mosquito infection, while 0.08 g l−1 ricinine-5% glucose solution induced a 14% increase in An. gambiae infection rate. Conclusions Overall, our findings reveal that consumption of certain nectar phytochemicals can have unexpected and contrasting effects on key phenotypic traits that govern the intensity of malaria transmission. Further studies will be required before concluding on the putative role of ricinine as a novel control agent, including the development of ricinine-based toxic and transmission-blocking sugar baits. Testing other secondary phytochemicals in plant nectar will provide a broader understanding of the impact which plants can have on the transmission of vector-borne diseases

Realising the European network of biodosimetry: RENEB-status quo

Creating a sustainable network in biological and retrospective dosimetry that involves a large number of experienced laboratories throughout the European Union (EU) will significantly improve the accident and emergency response capabilities in case of a large-scale radiological emergency. A well-organised cooperative action involving EU laboratories will offer the best chance for fast and trustworthy dose assessments that are urgently needed in an emergency situation. To this end, the EC supports the establishment of a European network in biological dosimetry (RENEB). The RENEB project started in January 2012 involving cooperation of 23 organisations from 16 European countries. The purpose of RENEB is to increase the biodosimetry capacities in case of large-scale radiological emergency scenarios. The progress of the project since its inception is presented, comprising the consolidation process of the network with its operational platform, intercomparison exercises, training activities, proceedings in quality assurance and horizon scanning for new methods and partners. Additionally, the benefit of the network for the radiation research community as a whole is addressed

Cytogenetic and molecular characterization of plutonium-induced rat osteosarcomas

The association between ionizing radiation and the subsequent development of osteosarcoma has been well described, but little is known about the cytogenetic and molecular events, which could be involved in the formation of radiation-induced osteosarcomas. Here, we performed comparative genomic hybridization (CGH) to detect chromosomal copy number changes in a series of 16 rat osteosarcomas induced by injection of plutonium-238. Recurrent gains/amplifications were observed at chromosomal regions 3p12-q12, 3q41-qter, 4q41-qter, 6q12-q16, 7q22-q34, 8q11-q23, 9q11-q22, 10q32.1-qter, and 12q, whereas recurrent losses were observed at 1p, 1q, 3q23-q35, 5q21-q33, 8q24-q31, 10q22-q25, 15p, 15q, and 18q. The gained region at 7q22-q34 was homologous to human chromosome bands 12q13-q15/8q24/22q11-q13, including the loci of Mdm2, Cdk4, c-Myc and Pdgf-b genes. The lost regions at 5q21-q33, 10q22-q25 and 15q contained tumor suppressor genes such as p16INK4a/p19ARF, Tp53 and Rb1. To identify potential target gene(s) for the chromosomal aberrations, we compared the expression levels of several candidate genes, located within the regions of frequent chromosomal aberrations, between the tumors and normal osteoblasts by using quantitative RT-PCR analysis. The Cdk4, c-Myc, Pdgf-b and p57KIP2 genes were thought to be possible target genes for the frequent chromosomal gain at 7q22-34 and loss at 1q in the tumors, respectively. In addition, mutations of the Tp53 gene were found in 27% (4 of 15) osteosarcomas. Our data may contribute to further understanding of the molecular mechanisms underlying osteosarcomas induced by ionizing radiation in human

Detection of partial-body exposure to ionizing radiation by the automatic detection of dicentrics

International audienceIn accidental exposure to ionizing radiation, it is essential to estimate the dose received by the victims. Currently dicentric scoring is the best biological indicator of exposure. The standard biological dosimetry procedure (500 metaphases scored manually) is suitable for a few dose estimations, but the time needed for analysis can be problematic in the case of a large-scale accident. Recently, a new methodology using automatic detection of dicentrics has greatly decreased the time needed for dose estimation and preserves the accuracy of the estimation. However, the capability to detect nonhomogeneous partial-body exposures is an important advantage of dicentric scoring-based biodosimetry, and this remains to be tested with automatic scoring. Thus we analyzed the results obtained with in vitro blood dilutions and in real cases of accidental exposure (partial- or whole-body exposure) using manual scoring and automatic detection of dicentrics. We confirmed that automatic detection allows threefold quicker dicentric scoring than the manual procedure with similar dose estimations and uncertainty intervals. The results concerning partial-body exposures were particularly promising, and homogeneously exposed samples were correctly distinguished from heterogeneously exposed samples containing 5 to 75 of blood irradiated with 2 Gy. In addition, the results obtained for real accident cases were similar whatever the methodology used. This study demonstrates that automatic detection of dicentrics is a credible alternative for recent and acute cases of whole- and partial-body accidental exposures to ionizing radiation. © 2012 by Radiation Research Society

Optimization of cytogenetic procedures for population triage in case of radiological emergency

In case of accidental overexposure to ionizing radiation, the scoring of dicentrics in lymphocytes from blood is the current reference method to estimate the dose received. When only few individuals are accidentally overexposed, at least 500 cells are scored to have a good estimation of the dose. But such a practice is too time consuming when many people are exposed such as in a radiological emergency. In order to reduce the time required to estimate a dose, specific strategies have been developed in the laboratory. Population triage based on the adaptation of the dicentrics assay: In order to reduce the analysis time it is possible to have a dose estimation based on only 50 cells analysed in an hour with a 95% confidence limit of 1 Gy. Population triage based on the use of image analysis systems: The metaphase finder increases the speed of the scoring by a factor of 2. It is also possible to detect automatically the dicentrics. The system proposes to the operator some candidate dicentrics which are then verified manually. In this case, 50% of the dicentrics are correctly detected with a 95% confidence limit of 0.4 Gy. Establishment of a network: Biological dosimetry laboratories are small, hence their capacity can be overloaded by a large number of suspected overexposed individuals. That is why international and national networks should be established, they should perform periodically intecomparisons and population triage exercises. Population triage based on micronuclei assay: As micronuclei are easier to score than dicentrics, in an hour 500 binucleated cells can be scored resulting in a 95% confidence limit of about 0.5 Gy versus 1 Gy with the dicentric assay. However, the micronuclei technique is not efficient to estimate accurately the dose because it lacks specificity. Use ofγ -H2AX for population triage: This assay is based on the scoring of double-strand breaks. Whereas with the other technique a cell culture is required, here it is possible to estimate a dose 3 h after receiving the sample in the laboratory with a sensitivity below 0.5 Gy. But one major limitation is the decrease of the signal with time. Therefore, this assay can only be used in case of population triage starting within minutes post-exposure. © 2007 Elsevier Ltd. All rights reserved

Effect of lymphocytes culture variations on the mitotic index and on the dicentric yield following gamma radiation exposure

International audienceFundamentals of biological dosimetry are described in the International Atomic Energy Agency manual, but all over the world each laboratory is using its own protocol. To test the influence of protocol variations, some blood samples were exposed to 0.5 Gy of gamma radiation and mitotic index and dicentric rates were measured under different experimental conditions. The effect of seven parameters [bromodeoxyuridin (BrdU), phytohaemagglutinin and colcemid concentrations, blood and medium volumes, culture duration and incubation temperature] was tested using a Placket and Burman experimental design. The analysis reveals that the mitotic index was influenced by the concentration of BrdU, medium and blood volumes, the culture duration and the temperature. However, none of the factors has a significant impact on the yield of dicentrics. The dicentric assay is robust against reagent variations within the range tested. These results could be used by relevant laboratories as elements of their procedures robustness in any event requiring such demonstration. © The Author 2012. Published by Oxford University Press. All rights reserved

Biological dosimetry by automated dicentric scoring in a simulated emergency

International audienceDicentric chromosome analysis remains the most widely used method in biodosimetry. It has a lower detection limit of about 0.1 Gy, and allows one to distinguish between whole-and partial-body exposures. A drawback of the dicentric analysis is that it is a time consuming method and maybe difficult to implement in a mass casualty event. To try to increase the analysis capacity, automatic dicentric scoring (ADS) using image analysis software is being incorporated in several laboratories. Here we present the results obtained in an emergency exercise simulating 50 victims. The ability to distinguish different radiations scenarios is evaluated. To simulate whole-body exposures peripheral blood samples were irradiated at doses between 0-4.7 Gy, and to simulate partial-body exposures irradiated and nonirradiated blood were mixed in different proportions. With the data obtained from the first slide analyzed (with about 300-400 cells), 32 of 34 simulated whole-body exposures were correctly classified according to radiation exposure levels. For simulated partial-body irradiations, it was possible to detect them as partial exposures at the end of the first slide analyzed but only at the highest doses. In all cases the classification was updated every time the analysis of one additional slide was finished. The comparison between our present results and those reported in the literature for manual scoring shows that for triage purposes the ADS based on 300-400 cells is similar in efficiency to classifying the cases based on manual scoring of 50 cells. However, if one accounts for the associated uncertainties and the time needed for ADS, we suggest that ADS triage scoring should be based on about 1,000 cells. For final dose estimations the number of cells to score will depend on the initial estimated dose, and on the information contributed from physical dose-reconstruction or clinical symptoms. At doses higher than 1 Gy, we propose analysis of 1,500 and for lower doses or suspected partial-body exposures, the number of cells to score should be 3,000. © 2013 by Radiation Research Society. All rights of reproduction in any form reserved

Broad modulation of gene expression in CD4+ lymphocyte subpopulations in response to low doses of ionizing radiation

To compare me responses of the different lymphocyte sub-types after an exposure of whole blood to low doses of ionizing radiation, we examined variations in gene expression in different lymphocyte subpopulations using microarray technology. Blood samples from five healthy donors were independently exposed to 0 (sham irradiation), 0.05 and 0.5 Gy of ionizing radiation. Three and 24 h after exposure, CD56+, CD4+ and CD8+ cells were negatively isolated. RNA from each set of experimental conditions was competitively hybridized on 25k oligonucleotide microarrays. Modifications of gene expression were measured after both intervals and in all cell types. Twenty-four hours after exposure to 0.5 Gy, we observed an induction of the expression of BAX, PCNA, GADD45, DDB2 and CDKNIA. However, the numbers of modulated genes greatly differed between cell types. In particular, 3 h after exposure to doses as low as 0.05 Gy, the number of down-modulated genes was 10 times greater for CD4+ cells than for all other cell types. Moreover, most of these repressed genes were taking part in the cell processes of protein biosynthesis and oxidative phosphorylation. The results suggest that several biological pathways in CD4+ cells could be sensitive to low doses of radiation. Therefore, specifically studying CD4+ cells could help to understand the mechanisms involved in low-dose response and allow their detection

Manual versus automated γ-H2AX foci analysis across five European laboratories Can this assay be used for rapid biodosimetry in a large scale radiation accident?

International audienceThe identification of severely exposed individuals and reassurance of the 'worried well' are of prime importance for initial triage following a large scale radiation accident. We aim to develop the γ-H2AX foci assay into a rapid biomarker tool for use in accidents. Here, five laboratories established a standard operating procedure and analysed 100 ex vivo γ-irradiated, 4 or 24. h incubated and overnight-shipped lymphocyte samples from four donors to generate γ-H2AX reference data, using manual and/or automated foci scoring strategies. In addition to acute, homogeneous exposures to 0, 1, 2 and 4. Gy, acute simulated partial body (4. Gy to 50% of cells) and protracted exposures (4. Gy over 24. h) were analysed. Data from all laboratories could be satisfactorily fitted with linear dose response functions. Average yields observed at 4. h post exposure were 2-4 times higher than at 24. h and varied considerably between laboratories. Automated scoring caused larger uncertainties than manual scoring and was unable to identify partial exposures, which were detectable in manually scored samples due to their overdispersed foci distributions. Protracted exposures were detectable but doses could not be accurately estimated with the γ-H2AX assay. We conclude that the γ-H2AX assay may be useful for rapid triage following a recent acute radiation exposure. The potentially higher speed and convenience of automated relative to manual foci scoring needs to be balanced against its compromised accuracy and inability to detect partial body exposures. Regular re-calibration or inclusion of reference samples may be necessary to ensure consistent results between laboratories or over long time periods. © 2013

Cytogenetic assessment of heterogeneous radiation doses in cancer patients treated with fractionated radiotherapy

cited By 16The purpose of this study was to evaluate the in vivo dose-response relation of chromosome aberration formation and distribution in a context of localised and fractionated radiotherapy. Cytogenetic analysis was applied to eight patients, all treated for the same tumour localisation; the same localisation was used to prevent the variability usually observed between patients treated with radiotherapy and to allow the corresponding roles of the size of irradiation field and of the dose rate to be studied. The yield of dicentrics, centric rings and fragments was measured in blood samples taken before treatment, during the course of radiotherapy and up to 6 months after. After the first fraction of radiotherapy, we observed that the whole-body dose estimated from the yield of dicentrics and rings was higher (0.35±0.2 Gy) than the calculated equivalent whole-body dose (0.07±0.04 Gy). By contrast, the partial-body dose derived from the Qdr (quotient of dicentrics and rings) model was estimated to be 2.2±0.3 Gy, which agreed quite well with the dose delivered to the tumour (2.1±0.1 Gy). We also found a correlation between the yield of induced chromosome aberrations and the target field size (p=0.014). U-value analysis showed that the distribution of dicentrics and rings was overdispersed, despite the fractionation of the exposure, and a positive correlation between the U-value and the dose rate was observed (p=0.017). Overall, these results suggest that the proportion of undamaged lymphocytes could increase with the dose rate. © 2010 The British Institute of Radiology