Bien que les technologies d’imagerie soient un acquis réel de la médecine moderne, leur introduction ne semble pas avoir été précédée d’une démarche réflexive suffisante qui aurait permis d’anticiper les multiples enjeux que rencontre la pratique radiologique actuelle. En effet, à force de se focaliser sur les acquis techniques et scientifiques, le cadre de radioprotection en place semble ne pas avoir suffisamment considéré l’apport essentiel que représente la connaissance des aspects sociaux, éthiques et humains que peuvent amener des domaines comme la bioéthique. Cette insuffisance fait en sorte que l’on se retrouve aujourd’hui face à des enjeux importants relatifs à la radioprotection du patient comme la surutilisation des examens radiologiques ou encore le manque d’information des acteurs du milieu face aux risques des rayonnements. Après un état des lieux des enjeux éthiques en radiologie diagnostique ayant un impact sur la radioprotection médicale des patients, un enjeu majeur de la pratique actuelle, qui est la justification inadéquate des prescriptions d’examens radiologiques, sera analysé selon une approche par principes. De cet exercice, visant à démontrer comment l’éthique peut concrètement contribuer à la radioprotection, découle l’impératif d’une vision nouvelle et globale permettant de proposer des pistes de solution aux controverses liées à l’utilisation actuelle de l’imagerie. Dans une perspective de santé des populations, il est important de contribuer à la diminution de la banalisation du recours au rayonnement ionisant dans la pratique médicale diagnostique en alliant bioéthique et radioprotection. Ce projet de recherche se veut être une étape limitée, mais nécessaire dans l’établissement de ce dialogue interdisciplinaire. / While imaging technologies represent a real achievement for modern medicine, their introduction seems not to have been preceded by a sufficiently reflective process that would have anticipated the multiple challenges arising in current radiological practice. In focusing on the technical and scientific achievements, the actual radiation protection framework fails to consider sufficiently the essential contribution brought by social, ethical and human dimensions of disciplines such as bioethics. This failure means that today we find ourselves faced with major issues related to patient radiation protection, such as overuse of radiological examinations or medical personnel’s lack of information about the risks of radiation. Following an overview of ethical issues in diagnostic radiology affecting medical radiation protection of patients, a major issue in current practice – i.e., the inadequate justification of radiological examination prescriptions – will be analyzed using a principle-based approach. From this exercise, which aims to demonstrate how ethics can contribute concretely to radiation protection, a need arises for a new and comprehensive vision leading to solutions for controversies related to the current use of medical imaging. In a population health perspective, it is important to contribute to the reduction of the trivialization of the use of ionizing radiation in diagnostic medical practice by combining both bioethics and radiation protection. This research project aims to be a modest but necessary first step in the establishment of such an interdisciplinary dialogue.

Prostate cancer is the fourth most frequent cause of cancer-related deaths in men worldwide. One of current successful approaches to treat prostate cancer is radical prostatectomy followed by radiotherapy. However, this treatment is not 100% successful, as 53% patients develop secondary tumors. Our hypothesis is, that ionizing radiation itself contributes to the development of metastases by inducing changes in cell phenotype, particularly in terms of epithelial-to-mesenchymal transition and stemness. To test this hypothesis, we irradiated the cells of metastatic prostate cancer cell line DU145 by fractionated radiation 2 x 10 Gy and we compared the expression of selected epithelial, mesenchymal and stem-cell markers prior to and after irradiation. Besides we focused on a subpopulation of so called floating cells which arise during irradiation. These cells can survive the radiation treatment and after some time they are able to reattach and give rise to readherent population. We wanted to asses what is the cell cycle profile of these cells and whether and how fast they proliferate. In this thesis we have shown that radiation causes only minor changes in epithelial/mesenchymal and stem-like character of adherent fraction of the DU145 cell line. However, we have also described that small population of...

The promyelocytic leukemia protein (PML) is a tumour suppressor. It has been reported that PML interaction with the p53 protein is involved in the activation of cell cycle checkpoints and, when persistent, may lead to the premature onset of cellular senescence. Cellular senescence is a state of permanent cell growth arrest that is associated with characteristic morphological and metabolic changes and persistent DNA damage signalling. Importantly, PML nuclear bodies coassociate with persistent DNA damage foci in senescent cells; however, the role of this interaction is still obscure. My goal was to characterize the role of PML in DNA damage response (DDR) and the induction of premature cellular senescence after genotoxic stress, namely X-radiation, using both siRNA-mediated PML knock down (PML KD) and complete PML knock out (PML KO) in human cells. The dynamics of DNA damage foci, levels of various proteins involved in DDR, and proliferation rate were measured in both PML KD and KO cells. No significant changes in the formation of DNA damage foci, activated DDR (p53 and Chk2), activated p21CIP1/WAF1 cyclin-dependent kinase inhibitor, senescent morphology, and SA-β-galactosidase activity in PML KO cells were observed. However, PML KO cells displayed higher levels of retinoblastoma protein (Rb) and...

Les rayonnements ionisants sont un facteur de risque reconnu pour les leucémies chez l'homme pour des fortes doses d'exposition médicale ou accidentelle. En revanche, l'hypothèse de l'existence d'un risque associé aux rayonnements ionisants à des niveaux d’exposition inférieurs, habituellement rencontrés dans l'environnement et de manière continue reste à démontrer. Notre travail propose d’évaluer l’hypothèse de l’existence d’une association entre les expositions environnementales aux radiations ionisantes d’origine naturelle et le risque de leucémie de l’enfant (LA) en utilisant des observations réalisées en France métropolitaine.Les cas de leucémie inclus dans ce travail sont toutes les LA du Registre National des Hémopathies malignes de l’Enfant, qui enregistre l'ensemble des cas de moins de 15 ans diagnostiqués en France métropolitaine, sur la période étudiée.Un premier travail a consisté à étudier la répartition spatiale de l’incidence des leucémies de l’enfant au niveau des 1 916 bassins de vie (BV) définis par l’INSEE. Des méthodes de détection de cluster ont été appliquées sur les 7 675 cas de leucémies de l'enfant diagnostiqués entre 1990 et 2006 afin d’identifier les zones potentiellement associées à un plus fort risque de leucémies aiguës de l’enfant. Cette étude n'a pas mis en évidence d’hétérogénéité spatiale des taux d'incidence des LA de l'enfant au cours de la période 1990-2006 au niveau des BV. Cependant, quelques clusters spatiaux ont été identifiés dans des lieux et périodes spécifiques. Bien que les niveaux de significativité de ces clusters ne soutiennent pas fortement l'existence de facteurs de risque localisés, les clusters peuvent montrer un léger impact de facteurs de risque partagés à l'échelle des BV.Pour tester l’hypothèse de l’existence d’une association entre l’exposition aux radiations ionisantes d’origine naturelle et l’incidence des leucémies de l’enfant, une étude d’incidence basée sur les 9 056 cas de LA de la période 1990-2009 a été réalisée. Cette étude a été complétée par une étude cas-témoins en population fondée sur les 2 763 cas de LA enregistrés sur la période 2002-2007 et un ensemble témoin de 30 000 sujets constituant un échantillon contemporain représentatif de la population pédiatrique française. Dans cette approche, la géolocalisation des adresses des cas et des témoins ainsi que celle des sources d'exposition et leur caractérisation permet de définir les critères de l'intensité d'exposition aux facteurs d'intérêt et de les mettre en relation avec le statut cas vs témoins des sujets.Les données concernant l'exposition à la radioactivité d’origine naturelle ont été produites par l'IRSN (Institut de Radioprotection et de Sûreté Nucléaire). Une cartographie du potentiel d’exhalation du radon émis par le sol et un échantillon national de 10 843 points de mesures localisés dans des habitations ont permis d’estimer l’exposition résidentielle au radon au niveau de la commune et du domicile. L’exposition aux rayonnements gamma telluriques et cosmiques a été estimée par zone d’emploi à partir d’un ensemble de 28 000 mesures issues de la campagne nationale IRSN et de mesures réalisées dans approximativement 1 000 sites couvrant la France entière, dans un but de surveillance de la radioactivité ambiante.Notre étude n’a pas montré d’association entre les leucémies de l’enfant et l’exposition aux radiations ionisantes d’origine naturelle estimée au diagnostic et de façon cumulée pendant l’enfance. Elle avait une bonne puissance pour mettre en évidence les risques attendus d’après les modèles de risque actuels (UNSCEAR) issus des études sur les risques observés à forte dose. Cette question reste néanmoins suffisamment importante et peu explorée pour mériter des études complémentaires dans d’autres pays. / Ionizing radiation due to medical or accidental exposure to high doses is an established risk factor for leukemia in humans. However, the evidence of a risk associated with exposure to ionizing radiation at lower levels usually encountered in the environment remains to be demonstrated. Our work aims to evaluate the hypothesis of the existence of an association between natural background ionizing radiation and the risk of childhood leukemia (CL) using observations made in France.Leukemia cases included in this study are all the CL recorded in the National Registry of Childhood Hematological Malignancies, an exhaustive repository of all cases of patients younger than 15 years old in France over the studied period.First step was the study of the spatial distribution of the incidence of CL at the level of the 1,916 Living Zone (LZ) defined by INSEE. Cluster detection methods have been used on 7,675 cases of CL diagnosed during the period 1990-2006 to identify areas potentially associated with a higher risk of acute childhood leukemia. The study did not show any spatial heterogeneity of incidence of CL during the period at LZ level. However, some spatial clusters were highlighted in specific places and times. Although the levels of significance of these clusters do not strongly support the existence of risk factors, localized clusters can show a slight impact of risk factors shared across LZ, including contextual environmental exposures.To test the hypothesis of the existence of an association between environmental exposure to ionizing radiation of natural origin and incidence of childhood leukemia, an incidence study based on 9,056 cases of CL for the period 1990-2009 was conducted. This study was complemented by a record-based cases-controls study based on the 2,763 cases of CL recorded over the 2002-2007 period and a control set of 30,000 subjects constituting a representative sample of the contemporary French pediatric population. In this approach, localizations of cases and controls and exposure identifications were geocoded and compared to the status cases vs control population.Data of exposure to natural background radiation were produced by the IRSN (Institute for Radiological Protection and Nuclear Safety). Mapping of the “potential radon exhalation emitted by the ground” and a national sampling of 10,843 measurement points located in dwellings were used to estimate residential exposure to radon at a level of granularity of cities and houses. Exposure to terrestrial gamma and cosmic rays was estimated by zone d’emploi based on a set of more than 28,000 environmental measurements in approximately 1,000 sites covering whole France, and by the IRSN national campaign data. Our study did not show any association of childhood leukemia with exposures to natural background radiation estimated nor at diagnosis nor cumulatively during childhood. However it had a good power to highlight the risks expected from current models of risk (UNSCEAR) built from studies on the observed high doses risks. If this work does not support the hypothesis that there is an association between exposure to ionizing radiation from natural sources observed and the incidence of childhood leukemia which may be directly observable at the epidemiologic level, this question remains important enough and not investigated enough to merit further complementary studies in countries where it has not been investigated.

Introdução: Na prática clínica se observa que há diferenças na incidência de efeitos colaterais entre pacientes submetidos ao mesmo esquema terapêutico de radioterapia. Tais diferenças podem ser entendidas como uma radiossensibilidade individual determinada geneticamente. Objetivos: Este estudo teve como objetivo avaliar os efeitos tardios na bexiga em pacientes com câncer do colo uterino tratadas com radioterapia, com ou sem cirurgia, e o valor prognóstico de três polimorfismos genéticos de base única com relação ao desenvolvimento de cistite actínica. Material e métodos: Foi realizada uma análise retrospectiva de 50 pacientes com carcinoma cervical tratadas entre 1999 e 2004, com um mínimo de 6,5 anos de seguimento. A dose de radioterapia na bexiga foi considerada como a soma da dose da radioterapia externa com a dose de braquiterapia no ponto de bexiga definido pelo ICRU 38 (Relato número 38 da Comissão Internacional de Unidades e Medidas em Radiação). Para as correlações entre dose e efeito, foi calculada a dose biológica efetiva (BED) para cada caso. Para a avaliação dos efeitos tardios em bexiga, além dos dados descritos em prontuário, foi feito um questionário específico dirigido aos sintomas urinários, foi realizada cistoscopia em todas as pacientes e a escala LENTSOMA (efeitos tardios no tecido normal/ subjetivo-objetivo tratamento e exames) foi aplicada, utilizando o pior grau do efeito encontrado nos diferentes métodos de avaliação. Variantes genéticas do códon 72 da p53 (Arginina / Prolina), MDM2 SNP309 T/G e ATMex39 5557 G>A foram identificadas usando o método de genotipagem de SNP ABI SNaPshot e os resultados foram correlacionados com a incidência e grau de cistite actínica. Resultados: Complicações clínicas tardias da bexiga foram registradas em 17 (34%) pacientes usando dados coletados dos prontuários e em 41 (82%) pacientes pelo questionário de existência e gravidade dos efeitos tardios da irradiação. Essas complicações foram diretamente correlacionadas com a BED. Vinte e oito pacientes (56%) desenvolveram cistite diagnosticada por cistoscopia (16% Grau 2-4). MDM2 SNP309 TT associado a TP53 (P72R) GG foram relacionados com o aumento da incidência de cistite. Conclusões: Cistite actínica, em grau 2 ou maior, foi elevada nessa população e apresentou uma maior incidência quando realizado um questionário específico para tal. Houve associação com maior dose de radioterapia (BED Gy3 > 100 Gy) e com MDM2 SNP309 TT associado a TP53 (P72R) GG. / Introduction: In clinical practice it is observed that there are differences in the incidence of side effects among patients undergoing the same regimen of radiotherapy. Such differences can be understood as a genetically determined individual radiosensitivity. Purposes: This study aimed to evaluate urinary bladder late effects in patients with uterine cervix cancer treated with radiotherapy with or without surgery and the prognostic value of three single nucleotide polymorphisms (SNPs) related to radiation cystitis. Material and methods: retrospective analysis of 50 patients with cervical carcinoma treated between 1999 and 2004 with a minimum of 6.5 years of follow-up was performed. The radiation dose in the bladder was considered as the dose delivered by external beam irradiation plus the brachytherapy dose in the ICRU Report 38 (International Commission of Radiation Units and Measurements report number 38) bladder point. For dose-effect correlations the biological effective dose (BED) was calculated for each case. For evaluation of bladder late effects, besides the data collected from the charts review, a specific query directed to urinary symptoms was applied to the patients and also a cystoscopy was performed in all of them. The LENTSOMA (late effects of normal tissues/subjective-objective management analytic) scale for bladder late effects was applied. Genetic variants of p53 codon72 (arginine/proline) polymorphism, MDM2 SNP309 T/G and ATMex39 5557G>A were identified by using ABI SNaPshot SNP genotyping method. And the results were correlated with the incidence and grade of radiation cystitis. Results: Clinical late bladder complications were recorded in 17 (34%) patients using data collected from the charts and in 41 (82%) patients by the questionnaire for the existence and severity of late irradiation effects. These complications were directly related with the BED. Twenty eight patients (56%) developed cystitis diagnosed by cystoscopy (16% Grade 2-4). MDM2 SNP309 TT associated with TP53 (P72R) GG was related with increased incidence of cystitis. Conclusions: Late radiation cystitis grade 2 or greater were high in this population and presented a higher incidence when a specific questionnaire was used. Higher radiation dose (BED Gy3 > 100 Gy) and MDM2 SNP309 TT associated with TP53 (P72R) GG were correlated with bladder late effects

La relation entre le risque de décès par cancer du poumon et l’exposition au radon est aujourd’hui établie, notamment à partir des études conduites chez les mineurs d’uranium. Mais de nombreuses interrogations persistent sur les risques de cancers extra-pulmonaires et de maladies non-cancéreuses, et sur l'impact sur la santé des autres expositions radiologiques professionnelles. L’objectif général de cette thèse est de contribuer à l’estimation des risques radio-induits aux faibles débits de dose au travers de l'analyse des risques de décès par cancer du rein et par Maladie de l'Appareil Circulatoire (MAC) chez les mineurs d’uranium.Les analyses du risque de décès par cancer du rein ont été réalisées au sein de la cohorte française des mineurs d'uranium (n=5 086 ; période de suivi : 1946-2007), la cohorte post-55 (n=3 377 ; période de suivi : 1957-2007) et la cohorte allemande de la Wismut (n=58 986; période de suivi : 1946-2003) au sein desquelles sont respectivement répertoriés 24, 11 et 174 décès par cancer du rein. L’exposition au radon et à ses descendants à vie courte (exprimée en Working Level Month WLM), aux poussières d’uranium (kBqh.m-3) et aux rayonnements gamma (mSv) a été estimée individuellement et la dose absorbée au rein a été calculée. La relation dose-réponse a été affinée par rapport à l'analyse classique en considérant deux types de réponse : le risque instantané de décès par cancer du rein (analyse classique, Cause-specific Hazard Ratio (CSHR) estimé avec le modèle de Cox) et sa probabilité d'occurrence au cours du suivi (Subdistribution Hazard Ratio (SHR) estimé avec le modèle de Fine & Gray). Un excès de mortalité par cancer du rein était observé dans la cohorte française (SMR = 1,62 IC95%[1,04; 2,41]), mais pas dans la cohorte post-55. Dans la cohorte de la Wismut, un déficit de mortalité par cancer du rein était observé (0,89 [0,78; 0,99]). Pour ces trois populations, aucune relation n'a pu être mise en évidence entre les expositions radiologiques (ou la dose au rein) et le risque de décès par cancer du rein (ex : CSHRWismut_radon/100WLM=1,023 [0,993; 1,053]), ni avec sa probabilité d'occurrence au cours du suivi (ex : SHRWismut_radon /100WLM=1,012 [0,983; 1,042]).L’étude du risque de décès par MAC dans la cohorte française a montré une augmentation significative du risque de décès par MAC (n=442, CSHR/100WLM=1,11 [1,01; 1,22]) et par Maladie CérébroVasculaire (MCeV, n=105, CSHR/100WLM=1,25 [1,09; 1,43]) avec l’exposition au radon. Une enquête cas-témoins nichée au sein de la cohorte a été mise en place pour recueillir dans les dossiers médicaux les facteurs de risque classiques de MAC (surpoids, hypertension, diabète...) pour 313 mineurs (76 décès par MAC (dont 26 par Cardiopathie Ischémique (CI) et 16 par MCeV) et 237 témoins). Pour les trois expositions radiologiques, la relation exposition-risque a été analysée au sein d'une pseudo-cohorte (obtenue en pondérant les observations par l'inverse de la probabilité de sélection, n=1 644 pseudo-individus) avec le modèle de Cox, en ajustant sur les différents facteurs de risque. L’association entre les expositions radiologiques et le risque de décès par MAC, CI ou MCeV n'était pas significative (ex : CSHRMAC_radon/100WLM=1,43 [0,71; 2,87]). La prise en compte des facteurs de risque ne modifiait pas sensiblement cette association.L'absence de relation dose-réponse significative suggère que l'excès de mortalité par cancer du rein chez les mineurs français serait induit par d'autres facteurs, non-disponibles pour cette analyse. La faible variation des coefficients avec l'ajustement sur les facteurs de risque de MAC dans l'enquête cas-témoins nichée soutient l'hypothèse de l'existence d'une augmentation du risque de MCeV dans la cohorte française associée à l’exposition au radon. La poursuite du suivi de la cohorte permettra d'affiner ces résultats. / The relation between lung cancer risk and radon exposure has been clearly established, especially from the studies on uranium miner cohorts. But the association between radon exposure and extrapulmonary cancers and non-cancer diseases remains not well known. Moreover, the health risks associated with the other mining-related ionizing radiation exposures are still under consideration. The aim of this thesis is to contribute to the estimation of the radio-induced health risks at low-doses through the analysis of the kidney cancer and Circulatory System Disease (CSD) mortality risks among uranium miners.Kidney cancer mortality risk analyses were performed from the French cohort of uranium miners (n=5086; follow-up period: 1946-2007), the post-55 cohort (n=3,377; follow-up period: 1957-2007) and the German cohort of the Wismut (n=58,986; follow-up period: 1946-2003) which included 24, 11 and 174 deaths from kidney cancer, respectively. The exposures to radon and its short-lived progeny (expressed in Working Level Month WLM), to uranium ore dust (kBqh.m-3) and to external gamma rays (mSv) were estimated for each miners and the equivalent kidney dose was calculated. The dose-response relation was refined considering two responses: the instantaneous risk of kidney cancer mortality (corresponding to the classical analysis, Cause-specific Hazard Ratio (CSHR) estimated with the Cox model) and its occurrence probability during the follow-up (Subdistribution Hazard Ratio (SHR) estimated with the Fine & Gray model). An excess of kidney cancer mortality was observed only in the French cohort (SMR = 1.62 CI95%[1.04; 2.41]). In the Wismut cohort, a decrease of the kidney cancer mortality was observed (0.89 [0.78; 0.99]). For these three cohorts, the occupational radiological exposures (or the equivalent kidney dose) were significantly associated neither with the risk of kidney cancer mortality (e.g. CSHRWismut_radon/100WLM=1.023 [0.993; 1.053]), nor with its occurrence probability during the follow-up (e.g. SHRWismut_radon /100WLM=1.012 [0.983; 1.042]).CSD mortality risk analyses in the French cohort showed a significant increase of the risks of mortality from CSD (n=442, CSHR/100WLM=1.11 [1.01; 1.22]) and from CerebroVascular Disease (MCeV, n=105, CSHR/100WLM=1.25 [1.09; 1.43]) with radon exposure. A case-control study nested in the French cohort was set up to collect the information related to CSD risk factors (overweight, hypertension, diabetes...) from the medical records of 313 miners (76 deaths from CSD (including 26 from Ischemic Heart Disease (IHD) and 16 from MCeV) and 237 controls). For the three radiological exposures, the exposure-risk relation was analyzed in a pseudo-cohort (n=1,644 pseudo-individuals, obtained from the weighting of the observations by their inverse selection probability) with the Cox model, adjusted for the CSD risk factors. The association between the radiological exposure and the risk of mortality from CSD, IHD or MCeV was not significant (e.g. CSHRCSD_radon/100WLM=1.43 [0.71; 2.87]). The adjustment for CSD risk factors did not substantially change the exposure-risk relation.The lack of a significant dose-response relation suggests that the excess of kidney cancer mortality among the French uranium miners may be induced by other risk factors, unavailable for this study. The small change of the coefficients observed after adjustment for CSD risk factors in the nested case-control study supports the assumption of the existence of the MCeV mortality risk increase associated with radon exposure in the French cohort of uranium miners. Future analyses based on further follow-up updates should allow to confirm or not these results.

This thesis presents numerical optimization of geometries of axially symmetric ion trap mass analyzers. The motivation for this thesis is two fold. First is to demonstrate how the automated scheme can be applied to achieve geometry parameters of axially symmetric ion traps for a desired field configuration. Second is, through the Geometries investigated in this thesis, to present practically achievable geometries for mass spectroscopists to use. Here the underlying thought has been to keep the design simple for ease of fabrication (with the possibility of miniaturization) and still ensure that the performance of these analyzers is similar to the stretched geometry Paul traps. Five geometries have been taken up for investigation: one is the well known Cylindrical ion trap (CIT), three are new geometries and the last is the Paul trap under development in our laboratory. Two of these newer geometries have a step in the region of the midline of the cylindrical ring electrode (SRIT) and the third geometry has a step in its endcap electrodes (SEIT). The optimization has been carried out around deferent objective functions composed of the desired weights of higher order multiples. The Nelder-Mead simplex method has been used to optimize trap geometries. The multipoles included in the computations are quadrupole, octopole, dodecapole, hexadecapole,ikosipole and tetraikosipole having weights A2, A4, A6, A8, A10 and A12, respectively.Poincare sections have been used to understand dynamics of ions in the traps investigated. For the CIT, it has been shown that by changing the aspect ratio of the trap the harmful ejects of negative dodecapole superposition can be eliminated, although this results in a large positive A4=A2 ratio. Improved performance of the optimized CIT is suggested by the ion dynamics as seen in Poincare sections close to the stability boundary. With respect to the SRIT, two variants have been investigated. In the first geometry, A4=A2 and A6=A2 have been optimized and in the second A4=A2, A6=A2 and A8=A2 have been optimized; in both cases, these ratios have been kept close to their values reported for stretched hyperboloid geometry Paul traps. In doing this, however, it was seen that the weights of still higher order multipole not included in the objective function, A10=A2 and A12=A2, are high; additionally, A10=A2 has a negative sign. In spite of this, for both these configurations, the Poincare sections predict good performance. In the case of the SEIT, a geometry was obtained for which A4=A2 and A6=A2 are close to their values in the stretched geometry Paul trap and the higher even multipole (A8=A2, A10=A2 and A12=A2) are all positive and small in magnitude. The Poincare sections predict good performance for this con¯guration too. Direct numerical simulations of coupled nonlinear axial/radial dynamics also predict good performance for the SEIT, which seems to be the most promising among the geometries proposed here. Finally, for the Paul trap under development in our laboratory, Poincare sections and numerical simulations of coupled ion dynamics suggest a stretch of 79:7% is the best choice.

PiRNAs and their Piwi family protein partners are part of a germline specific epigenetic regulatory mechanism essential for proper spermatogenesis, silencing of transposable elements, and maintaining germline genome integrity, yet their role in the response of the male germline to genotoxic stress is unknown. Ionizing radiation (IR) is known to cause transgenerational genome instability that is linked to carcinogenesis. Although the molecular etiology of IR-induced transgenerational genomic instability is not fully understood, it is believed to be an epigenetically mediated phenomenon. IR-induced alterations in the expression pattern of key regulatory proteins involved in the piRNA pathway essential for paternal germline genome stability may be directly involved in producing epigenetic alterations that can impact future generations. Here we show whole body and localized X-irradiation leads to significant altered expression of proteins that are necessary for, and intimately involved in, the proper functioning of the germline specific piRNA pathway in mice and rats. In addition we found that IR-induced alterations to piRNA pathway protein levels were time and dose dependent. / ix, 123 leaves : ill. (some col.) ; 29 cm

BRCA1 est un suppresseur de tumeur majeur jouant un rôle dans la transcription, la réparation de l’ADN et le maintien de la stabilité génomique. En effet, des mutations dans le gène BRCA1 augmentent considerablement le risque de cancers du sein et de l’ovaire. BRCA1 a été en majorité caractérisé pour son rôle dans la réparation de l’ADN par la voie de recombinaison homologue (HR) en présence de bris double brins, par example, induits par l’irradiation gamma (IR). Cependant, la fonction de BRCA1 dans d’autres voies de réparation de l’ADN, comme la réparation par excision de nucléotides (NER) ou par excision de base (BER), demeurent toutefois obscures. Il est donc important de comprendre la régulation de BRCA1 en présence d’agents génotoxiques comme le méthyle méthanesulfonate (MMS) ou l’UV, qui promouvoient le BER et le NER respectivement. Nos observations suggèrent que BRCA1 est dégradée par le protéasome après traitement avec le MMS ou les UV, et non avec l’IR. Par ailleurs, cette dégradation semble compromettre le recrutement de Rad51, suggérant que la voie de HR est inhibée. Nos résultats suggèrent que la HR est inhibée afin d’éviter l’activation simultanée de multiples voies de réparation. Nous avons aussi observé que la dégradation BRCA1 est réversible et que la restauration des niveaux de BRCA1 coïncide avec le recrutement de Rad51 aux sites de dommages. Cela suggère que la HR est réactivée tardivement par les bris double brins générés suite à l’effondrement des fourches de réplication. Ayant observé que BRCA1 est hautement régulé par l’ubiquitination et est ciblé par le protéasome pour dégradation, nous avons émis une hypothèse que BRCA1 est régulé par des déubiquitinases. Cela amène à caractériser plus en profondeur par un criblage en déplétant les déubiquitinases individuellement par RNAi et en observant leur effet sur le recrutement de BRCA1 et des protéines reliées à cette voie. Un criblage préliminaire nous a permi d’identifié candidats potentiels tel que BAP1, CXORF53, DUB3, OTUB1 et USP36. / BRCA1 is a tumour suppressor involved in transcription, DNA repair and maintenance of genomic stability. Indeed, BRCA1 mutation carriers have an exceptionally higher risk of breast and ovarian cancers. BRCA1 is mainly known for its role in homologous recombination repair (HR) by recruiting HR proteins to chromatin upon double strand break (DSBs) formation, e.g., following treatment with ionizing irradiation (IR). However, the function of BRCA1 in other DNA repair pathways such as nucleotide excision repair (NER) or base excision repair (BER) is still obscure. It is thus of fundamental and clinical importance to investigate BRCA1 function following exposure to diverse genotoxic agents. Using human cultured cell, we observed that BRCA1 is downregulated by the proteasome upon treatment with MMS or UV, but not with IR. Moreover, this downregulation prevents Rad51 recruitment to chromatin following exposure to MMS. Given that DNA damage induced by UV and MMS trigger NER and BER pathways respectively, this implies that HR could be inhibited in order to prevent competition between independent DNA repair pathways. We also found that BRCA1 downregulation is reversible and the recovery of BRCA1 levels correlates with the reappearance of BRCA1 and Rad51 on chromatin. This implies that the HR has been reactivated at the late stage of DNA damage for the repair of double strand breaks generated by replication fork collapse. Since BRCA1 stability is highly regulated by ubiquitination and is downregulated following MMS treatment, one would expect that a deubiquitinase is responsible for relieving this downregulation to promote the reactivation of the HR pathway. To characterize this aspect further, we conducted DUB RNAi screens in which a particular DUB is depleted and the localization of BRCA1 and other related proteins were observed. According to a preliminary screen, a few DUBs (BAP1, CXORF53, DUB3, OTUB1, and USP36) were identified as potential regulators of the stability and localization of BRCA1 and proteins involved in homologous recombination.

CAPES / A dosimetria em tomografia computadorizada (TC) envolve desde a determinação de grandezas dosimétricas específicas de TC até a estimativa de dose absorvida e dose efetiva. Entretanto, deve-se considerar que por envolver radiação ionizante no seu processo, este procedimento apresenta riscos inerentes e sua utilização deve ponderar o custo e o benefício propiciado pelo procedimento. A proteção de pacientes submetidos a exames radiológicos, de uma maneira geral, é determinada pelos princípios da “justificação” e “otimização”. Desta forma, torna-se importante o conhecimento dos níveis de radiação nas exposições durante um procedimento tomográfico. Estes níveis foram observados através da estimativa das grandezas específicas para tomografia computadorizada, tais como o Índice de kerma no ar (C100,ar), o Índice de kerma ponderada (Cw) e o produto kerma comprimento (PKL,CT), e em estimados os níveis de dose efetiva e risco para o estudo tomográfico computadorizado de crânio, tórax e abdômen realizado com múltipla varredura. Os valores obtidos foram comparados com os obtidos por simulação computacional por Monte Carlo. Eles foram utilizados, neste estudo, no cálculo da Dose Efetiva e risco e para comparação com o nível de referência de dose estabelecido pela Comunidade Européia. Utilizando-se o programa de simulação computacional Dosecal X_CT e o protocolo ICRP 103, foram determinadas as grandezas de radioproteção relevantes para o estudo que são os valores de dose efetiva referente ao procedimento. O nível do Produto kerma comprimento (PKL,CT), utilizando-se o C100,ar previamente estabelecido, foi também obtido e comparado com o nível de referência de dose estabelecido pela comunidade europeia. Os valores encontrados até agora estão dentro dos limites dos Níveis de Referência. / The computed tomography (CT) dosimetry involves measurements of specific quantities of CT, which are part of CT quality control procedures, as well as calculation of absorbed and effective doses to a patient submitted to CT examinations. Since CT uses ionizing radiation, it should be considered that a precise balance between risks and benefits must be achieved in order to justify the adoption of such technique. Radiation protection of patients undergoing radiological exams is established based on the justification and optimization principles. Nowadays, it is important to know the dose radiation levels to which a patient is exposed during a tomographic procedure. Those are given by the estimation of specific dosimetric quantities called the computed tomography kerma index in air, C100,air, the weighted computed tomography kerma index Cw, kerma length product, PKL,CT and then the levels of effective dose and risk to the computerized CT scan study of skull, thorax and abdomen with a multiple scanning. The values obtained were compared with those obtained by computer simulation using Monte Carlo method. The protection quantities organ absorbed dose, effective dose and risk for comparison with the reference dose level established by the European Community. Using computational simulation program of the Dosecal X_CT and the ICRP 103 Protocol, were certain quantities of radiation protection relevant to study which are the values of effective dose for the procedure. The dose length product PKL,CT level was calculated from the C100,air and compared to the reference dose level established by the European Community. The values found so far are within the limits of the reference levels.