Effets de l’environnement de vie sur les associations entre déterminants individuels et santé périnatale en Wallonie (Belgique)

Résumé L’association entre les caractéristiques individuelles des mères et la prématurité ou le faible poids à la naissance, tout comme l’effet de l’environnement de vie sur la santé périnatale ont fait l’objet de nombreux travaux. Plus rares sont les études qui se sont penchées sur l’effet que l’environnement de vie pouvait avoir sur l’association entre ces caractéristiques individuelles et la santé périnatale. Dans cet article, nous adoptons une perspective multi-niveaux pour prendre en compte conjointement l’effet de l’environnement de vie et les déterminants individuels des mères sur deux indicateurs de santé périnatale, la prématurité et le faible poids à la naissance en Wallonie. Les analyses portent sur 147 718 naissances vivantes uniques issues de mères qui résidaient en Wallonie de 2010 à 2013. Les variables indépendantes principales sont le niveau d’instruction, le statut professionnel et l’état de cohabitation des mères. Les variables dépendantes sont la prématurité et le faible poids à la naissance. Un indice synthétique des conditions de bien-être (ICBE) est utilisé pour décrire l’environnement de vie et mis en relation avec la prématurité et le faible poids à la naissance grâce à des modèles de régression logistique multivariables à un et plusieurs niveaux. La fréquence de la prématurité et du faible poids s’avère plus élevée dans les communes avec un environnement de vie défavorisé. Les mères ayant un faible niveau d’instruction, n’ayant pas d’activité professionnelle ou déclarant vivre seule courent par ailleurs un risque plus élevé d’accoucher prématurément ou d’avoir un enfant de faible poids à la naissance. Dans les analyses multi-niveaux, les mesures d’association entre les variables socio-économiques de la mère et les deux variables dépendantes restent identiques aux mesures d’association observées dans les régressions classiques. Les conditions de bien-être dans une commune, mesurées par l’ICBE, n’ont pas d’effet additionnel sur les associations entre les caractéristiques socio-économiques de la mère et la prématurité ou le faible poids à la naissance. Abstract The association between the individual characteristics of mothers, preterm birth or low birth weight and the impact of the living environment on perinatal health have been widely studied. Far fewer studies have examined the way the living environment can influence the association between characteristics and perinatal health. In this paper, we adopt a multi-level analysis to simultaneously study the effects of the living environment and the individual characteristics of the mothers on preterm birth and low-birth weight in Wallonia. The study population consists of 147’718 single live births to mothers who resided in Wallonia and delivered between 2010 and 2013. The main independent variables are the mothers’s level of education, their occupational and cohabitation status. The dependent variables are preterm birth and low birth weight. A synthetic index of Well-being condition (ICBE) is used to describe living conditions. The association between these conditions, preterm birth and low birth weight is quantified through multilevel logistic regression models adjusted for mothers’ characteristics. Preterm birth and low birth weight rates are higher in municipalities with a poor living environment. Non-working, single mothers or with low levels of education are at higher risk of delivering a preterm or low birth weight baby. In the multilevel analyses, the association between the socio-economic variables and the two dependent variables is similar to the one observed in the classical regressions (one level-analysis). Well-Being conditions, measured through ICBE, have no additional effect on the association between individual socio-economic characteristics of the mother, preterm birth or low birth weight.&nbsp

Effects of radionuclide contamination on leaf litter decomposition in the Chernobyl exclusion zone

The effects of radioactive contamination on ecosystem processes such as litter decomposition remain largely un- known. Because radionuclides accumulated in soil and plant biomass can be harmful for organisms, the function- ing of ecosystems may be altered by radioactive contamination. Here, we tested the hypothesis that decomposition is impaired by increasing levels of radioactivity in the environment by exposing uncontaminated leaf litter from silver birch and black alder at (i) eleven distant forest sites differing in ambient radiation levels (0.22–15 μGy h−1) and (ii) along a short distance gradient of radioactive contamination (1.2–29 μGy h−1) within a single forest in the Chernobyl exclusion zone. In addition to measuring ambient external dose rates, we estimat- ed the average total dose rates (ATDRs) absorbed by decomposers for an accurate estimate of dose-induced eco- logical consequences of radioactive pollution. Taking into account potential confounding factors (soil pH, moisture, texture, and organic carbon content), the results from the eleven distant forest sites, and from the single forest, showed increased litter mass loss with increasing ATDRs from 0.3 to 150 μGy h−1. This unexpected result may be due to (i) overcompensation of decomposer organisms exposed to radionuclides leading to a higher decomposer abundance (hormetic effect), and/or (ii) from preferred feeding by decomposers on the un- contaminated leaf litter used for our experiment compared to locally produced, contaminated leaf litter. Our data indicate that radio-contamination of forest ecosystems over more than two decades does not necessarily have detrimental effects on organic matter decay. However, further studies are needed to unravel the underlying mechanisms of the results reported here, in order to draw firmer conclusions on how radio-contamination affects decomposition and associated ecosystem processes

Utilisation de l’humour par les soignants : un lien avec la confrontation à la mort ?

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Effects of gamma ionizing radiation exposure on Danio rerio embryo-larval stages - comparison with tritium exposure

International audienceThe objective was to investigate the effects of ionizing radiation induced in zebrafish early life stages by coupling responses obtained at the molecular (genotoxicity, ROS production, gene expression) and phenotypic (tissue alteration, embryo-larval development) levels. Here we present results obtained after exposure of 3 hpf larvae to 10 days of gamma irradiation at 3.3x101, 1.3x102 and 1.2x103 µGy/h. Dose rates used in these studies were chosen to be in the ‘derived consideration reference level’ (DCRL) for gamma irradiation where deleterious effects can appear in freshwater fish. Also, these dose rates were similar to the ones already tested on tritium (beta ionizing radiation) in our previous work, in order to compare both types of ionizing radiation. Results showed that gamma irradiation did not induce any effect on survival and hatching. No effect was observed on DNA damages, but ROS production was increased. Muscle damages were observed for all tested dose rates, similarly to previous results obtained with tritium (beta ionizing radiation) at similar dose rates. Some molecular responses therefore appeared to be relevant for the study of gamma ionizing radiation effects in zebrafish

Effect of chronic low doses of ionizing radiations on central nervous system development of zebrafish

International audienceAfter the nuclear accidents at Chernobyl and Fukushima and due to a growing use of radionuclides, radiation protection of the environment is a major concern. Studies show an increased sensitivity to ionizing radiation (IR) during development. However, there are few data on the molecular mechanisms leading to the effects of IR on embryogenesis and moreover for chronic exposures. In this context, the objective of this thesis is to better understand the effects of exposure to IR on the development of zebrafish (Danio rerio), a model organism in ecotoxicology and in biomedicine. Fertilized eggs were exposed to gamma rays emitted by a 137Cs source at low to moderate dose rates (from 0.005 mGy/h to 50 mGy/h), then analysed from the gastrula stage (6 hours) to the larval stage (5 days) by an integrative approach from molecular effects to behavioural effects. Part of this work has focused on studying the effects of IR at an early stage of zebrafish development after exposure to IR. For this, a multi-omics approach with the study of the transcriptome and the methylome has been implemented. A transcriptomic study at the shield stage with dose rates ranging from 0.005 mGy/h to 50 mGy/h was carried out and demonstrated a moderate but significant effect on the regulation of oxidative stress and mitochondrial activity. At 5 and 50 mGy/h, the genes involved in the development of the central nervous system (CNS) and muscles are affected. The methylome study has revealed hypomethylation of the promoter sequences of genes involved in the development of the CNS and muscles, associated with a modification of gene expression. These results on early embryonic stages, highlight potential effects on the development of the CNS and muscles. The other part of this work focused on assessing the effects of IR exposure at later developmental stages using a system biology approach. For this, analyses were carried out from the molecular scale to the phenotypic scale. At the molecular level, a multi-omics analysis of the transcriptome and the proteome has highlighted the modulation of genes involved in the retinoic acid pathway, the development of the CNS and muscles in embryos and larvae exposed to 0.5; 5 and 50 mGy/h. Labelling by in-situ hybridization confirmed the misregulation of the transcription factors her4.4 in the CNS and myog in the muscles of embryos exposed to IR. At the tissue level, disruption of muscle myofibrils and alteration of neuromuscular junctions are detected in embryos exposed to 5 and 50 mGy/h. In order to assess an individual effect at phenotypic scale, the locomotor behaviour of the larvae was assessed under stress conditions. A significant decrease in larval motility was detected between 0.5 mGy/h and 50 mGy/h. This work has shown effects of IR on the development of the CNS and muscles from early development at the molecular level. These effects are confirmed at later stages of development. This study suggests that the molecular disturbances observed during early development are predictive of the effects observed at later developmental stages. In addition, this thesis work allows us to propose a model of "Adverse Outcome Pathway" where the deregulation of the retinoic acid pathway by exposure to IR will lead to effects on the development of the CNS and muscles

Male frequency in Caenorhabditis elegans increases in response to chronic irradiation

International audienceOutcrossing can be advantageous in a changing environment because it promotes the purge of deleterious mutations and increases the genetic diversity within a population, which may improve population persistence and evolutionary potential. Some species may, therefore, switch their reproductive mode from inbreeding to outcrossing when under environmental stress. This switch may have consequences on the demographic dynamics and evolutionary trajectory of populations. For example, it may directly influence the sex ratio of a population. However, much remains to be discovered about the mechanisms and evolutionary implications of sex ratio changes in a population in response to environmental stress. Populations of the androdioecious nematode Caenorhabditis elegans, are composed of selfing hermaphrodites and rare males. Here, we investigate the changes in the sex ratio of C. elegans populations exposed to radioactive pollution for 60 days or around 20 generations. We experimentally exposed populations to three levels of ionizing radiation (i.e., 0, 1.4, and 50 mGy.h−1). We then performed reciprocal transplant experiments to evaluate genetic divergence between populations submitted to different treatments. Finally, we used a mathematical model to examine the evolutionary mechanisms that could be responsible for the change in sex ratio. Our results showed an increase in male frequency in irradiated populations, and this effect increased with the dose rate. The model showed that an increase in male fertilization success or a decrease in hermaphrodite self-fertilization could explain this increase in the frequency of males. Moreover, males persisted in populations after transplant back into the control conditions. These results suggested selection favoring outcrossing under irradiation conditions. This study shows that ionizing radiation can sustainably alter the reproductive strategy of a population, likely impacting its long-term evolutionary history. This study highlights the need to evaluate the impact of pollutants on the reproductive strategies of populations when assessing the ecological risks

Revealing the Increased Stress Response Behavior through Transcriptomic Analysis of Adult Zebrafish Brain after Chronic Low to Moderate Dose Rates of Ionizing Radiation

International audienceHigh levels of ionizing radiation (IR) are known to induce neurogenesis defects with harmful consequences on brain morphogenesis and cognitive functions, but the effects of chronic low to moderate dose rates of IR remain largely unknown. In this study, we aim at defining the main molecular pathways impacted by IR and how these effects can translate to higher organizational levels such as behavior. Adult zebrafish were exposed to gamma radiation for 36 days at 0.05 mGy/h, 0.5 mGy/h and 5 mGy/h. RNA sequencing was performed on the telencephalon and completed by RNA in situ hybridization that confirmed the upregulation of oxytocin and cone rod homeobox in the parvocellular preoptic nucleus. A dose rate-dependent increase in differentially expressed genes (DEG) was observed with 27 DEG at 0.05 mGy/h, 200 DEG at 0.5 mGy/h and 530 DEG at 5 mGy/h. Genes involved in neurotransmission, neurohormones and hypothalamic-pituitary-interrenal axis functions were specifically affected, strongly suggesting their involvement in the stress response behavior observed after exposure to dose rates superior or equal to 0.5 mGy/h. At the individual scale, hypolocomotion, increased freezing and social stress were detected. Together, these data highlight the intricate interaction between neurohormones (and particularly oxytocin), neurotransmission and neurogenesis in response to chronic exposure to IR and the establishment of anxiety-like behavior

Physiological effects of gamma irradiation in the honeybee, Apis mellifera

International audienceTerrestrial ecosystems are exposed to various kinds of pollutants, including radionuclides. The honeybee, Apis mellifera, is commonly used in ecotoxicology as a model species for evaluating the effects of pollutants. In the present study, honeybees were irradiated right after birth for 14 days with gamma rays at dose rates ranging between 4.38x10-3 and 588 mGy/d. Biological tissues (head, intestine and abdomen) were sampled at D3, D10 and D14. Ten different physiological markers involved in nervous (acetylcholinesterase (AChE)), antioxidative (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST)), immune system (phenoloxidase (PO)) and metabolism (carboxylesterases (CaEs) and alkaline phosphatase (ALP)) were measured. Univariate analyses were conducted to determine whether each individual biomarker response was positively or negatively correlated with the dose rate. Then, multivariate analyses were applied to investigate the relationships between all the biomarker responses. Although no mortality occurred during the experiment, several biomarkers varied significantly in relation to the dose rate. Globally, the biomarkers of antioxidant and immune systems decreased as the dose rate increased. Reversible effects on the indicator of the neural system were found. Concerning indicators of metabolism (carboxylesterases), variations occurred but no clear pattern was found. Taken altogether, these results help better understand the effects of ionizing radiation on bees by identifying relevant physiological markers of effects. These results could improve the assessment of the environmental risk due to ionizing radiation in terrestrial ecosystems

Skin microvascular dysfunction as an early cardiovascular marker in primary hyperoxaluria type I

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A systems biology approach reveals neuronal and muscle developmental defects after chronic exposure to ionising radiation in zebrafish

International audiencecontamination of the environment after the chernobyl and fukushima Daiichi nuclear power plant (npp) disasters led to the exposure of a large number of humans and wild animals to radioactive substances. However, the sub-lethal consequences induced by these absorbed radiological doses remain understudied and the long-term biological impacts largely unknown. We assessed the biological effects of chronic exposure to ionizing radiation (IR) on embryonic development by exposing zebrafish embryo from fertilization and up to 120 hours post-fertilization (hpf) at dose rates of 0.5 mGy/h, 5 mGy/h and 50 mGy/h, thereby encompassing the field of low dose rates defined at 6 mGy/h. Chronic exposure to IR altered larval behaviour in a light-dark locomotor test and affected cardiac activity at a dose rate as low as 0.5 mGy/h. The multi-omics analysis of transcriptome, proteome and transcription factor binding sites in the promoters of the deregulated genes, collectively points towards perturbations of neurogenesis, muscle development, and retinoic acid (RA) signaling after chronic exposure to iR. Whole-mount RnA in situ hybridization confirmed the impaired expression of the transcription factors her4.4 in the central nervous system and myogenin in the developing muscles of exposed embryos. At the organ level, the assessment of muscle histology by transmission electron microscopy (TEM) demonstrated myofibers disruption and altered neuromuscular junctions in exposed larvae at 5 mGy/h and 50 mGy/h. The integration of these multi-level data demonstrates that chronic exposure to low dose rates of iR has an impact on neuronal and muscle progenitor cells, that could lead to motility defects in free swimming larvae at 120 hpf. The mechanistic understanding of these effects allows us to propose a model where deregulation of RA signaling by chronic exposure to IR has pleiotropic effects on neurogenesis and muscle development