Lake and round whitefish are cold-adapted freshwater species with similar life histories and spawning behaviours. There have been several studies on the embryonic development of both species (particularly for lake whitefish), most utilizing constant temperatures. However, temperatures fluctuate in the field due to natural (e.g. seasonal changes) and anthropogenic (e.g. water discharged from once-through cooling processes) effects. Releases from once-through cooling processes may contain low levels of chemicals (e.g. morpholine) and radiation (e.g. tritium). This thesis examined and compared the impacts of thermal, morpholine, and radiation stressors on lake and round whitefish embryogenesis. To examine the effects of fluctuating incubation temperatures, lake and round whitefish were reared at constant temperatures, with seasonal temperature declines/inclines, transient temperature spikes, or seasonal temperature changes combined with temperature spikes. Round whitefish embryos had significantly higher mortality when reared at 8°C compared to lake whitefish, and seasonal temperature changes impacted development rate, growth, and hatch dynamics for both species. Temperature spikes had relatively little effect on development. The effects on embryonic development of chronic morpholine and low-dose radiation exposures were examined in round whitefish to compare with existing data in lake whitefish. Round whitefish embryos were more impacted by morpholine than lake whitefish (larger effects on growth and mortality at relatively lower concentrations) and v less impacted by low-dose radiation (little effect on growth or hatch dynamics). Post hatch, round whitefish embryos reared at 8°C, with rapid seasonal inclines, or with 500 mg L-1 morpholine had elevated mortality. All irradiated embryos had decreased mortality post-hatch compared to non-irradiated embryos. Thus, embryonic exposure to all stressors examined appears to alter post-hatch survival. This thesis better defines the effects of fluctuating incubation temperatures, chronic morpholine, and chronic radiation exposures on the embryonic development of lake and round whitefish. It also suggests that embryonic incubation conditions are important beyond hatching. / Thesis / Master of Science (MSc) / Lake and round whitefish are cold-adapted freshwater species. Both species play important ecological roles, with lake whitefish generally perceived as more economically and culturally important. Many studies have detailed lake whitefish embryonic development under constant stressors (e.g. temperature) but there are relatively few studies on round whitefish embryonic development. Both species experience seasonal temperature fluctuations in nature and may experience additional anthropogenic temperature, chemical, and radiation stress due to discharge from once-through cooling processes at thermal power plants, which may contain low levels of morpholine and radiation. Our study suggests that round whitefish embryos are more sensitive to elevated temperature and morpholine levels, but less impacted by chronic low-dose irradiation relative to lake whitefish embryos. The growth and development of both species are significantly affected by seasonal temperature changes.

No description available.

Low dose endotoxemia is caused by several health conditions including smoking, alcohol abuse, high fat diets, and aging. Several studies have correlated low dose endotoxemia with increased risks of atherosclerosis, diabetes, and Parkinson's disease. Unlike high doses of endotoxin which induce a strong but transient induction of pro-inflammatory mediators, low doses of endotoxin result in a mild but chronic induction of pro-inflammatory genes. The central hypothesis of our study was that if low doses of endotoxin are capable of inducing mild prolonged inflammation, then a unique signaling circuit must be utilized. In the first study, the molecular mechanisms for the persistent induction of lipocalin 2 (LCN2) in response to 100 ng/mL of lipopolysaccharide (LPS) in kidney fibroblasts was examined. It appears that the intracellular signaling network responsible for the persistent induction of LCN2 requires both activator protein-1 (AP-1) and CCAAT/enhancer binding protein delta (C/ebpδ). Interleukin-1 receptor-associated kinase 1 (IRAK-1) is critical for LCN2 expression. In the second study, the molecular mechanisms governing the persistent induction of interleukin 6 (IL-6) upon a 50 pg/mL challenge of LPS in macrophages was examined. At this dose, only the persistent activation of cJun N-terminal kinase (JNK) and C/ebpδ was observed. IL-6 transcription requires the transient recruitment of activating transcription factor 2 (ATF2) and the persistent recruitment of C/ebpδ to the IL-6 promoter. In the third study, the molecular mechanisms that mediate LPS-induced priming was examined. The results demonstrate that macrophages are able to sense their prior history of exposure to LPS that result in either a priming or tolerance phenotype upon a secondary challenge of LPS. Results suggest that this sensing mechanism involves cross-talk between IRAK-1 and phosphoinositide-3-kinase (PI3K). Collectively, these studies indicate that JNK and C/ebpδ are the primary players responsible for the persistent expression of pro-inflammatory genes during low dose endotoxemia. IRAK-1 is a key intracellular signaling kinase that mediates signaling at low doses of LPS. IRAK-1 is not only critical for low dose induced expression, but also for LPS-induced priming. This research has revealed a novel signaling pathway that could provide new molecular targets for drug development against chronic inflammatory diseases. / Ph. D.

Der niedrig dosierte Dexamethason-Suppressionstest (LDDST) wird als Screeningverfahren in der Diagnostik des Cushing-Syndroms angewendet. Allerdings können Faktoren wie die variable Resorption, sowie ein gesteigerter Metabolismus von Dexamethason die Testergebnisse beeinflussen und zu falsch positiven Resultaten führen. Ein falsch positives Testresultat wird hierbei insbesondere bei adipösen Patienten häufiger beobachtet. In der vorliegenden Arbeit wurde daher der Einfluss des Körpergewichts auf das Ergebnis des Dexamethason-Suppressionstestes (DST) untersucht. Hierzu wurden hospitalisierte Patienten und ein aus gesunden Probanden bestehendes Kontrollkollektiv rekrutiert und diese einem regulären LDDST unterzogen. Es konnte gezeigt werden, dass übergewichtige Menschen im Rahmen des DST signifikant niedrigere Dexamethasonwerte erreichen als normalgewichtige Personen. Es ist daher davon auszugehen, dass Unterschiede im Body-Mass-Index (BMI) Einfluss auf die Resorptionsrate und den Metabolismus von Dexamethason nehmen und daraus resultierend die Serum-Dexamethasonspiegel wesentlich verringern können. Diese Prozesse scheinen allerdings keinen nachhaltigen Einfluss auf die Cortisolsuppression im DST zu haben, da die Cortisolwerte nach Dexamethasongabe zwischen adipösen und nicht adipösen Testpersonen nicht signifikant differierten. Diese Ergebnisse belegen, dass ein Zusammenhang zwischen BMI-Unterschieden und der Dexamethasonkinetik im LDDST besteht. Die erniedrigten Dexamethasonspiegel bei übergewichtigen Patienten scheinen hierbei insbesondere durch das wesentlich höhere Verteilungsvolumen und durch Unterschiede im hepatogenen Metabolismus bedingt zu sein. Trotz der erniedrigten Dexamethasonwerte bleibt die Feed-Back-Sensitivität der Hypothalamus-Hypophysen-Nebennieren-Achse (HHNA) auch bei Adipositas erhalten, weshalb der LDDST als zuverlässiges Screeningverfahren bei adipösen Patienten mit Verdacht auf Cushing-Syndrom einzustufen ist.

Le Strontium 90 (90Sr) est un radionucléide d’origine anthropogénique, relâché en grandes quantités dans l’environnement à la suite d’essais nucléaires aériens ou d’accidents d’installations nucléaires. Le 90Sr persiste à long terme dans l’environnement, ce qui conduit à la contamination chronique par ingestion de populations des territoires contaminés. L’induction de tumeurs osseuses liées à la fixation du 90Sr a été largement décrite. Par contre, l’occurrence d’effets non cancéreux est beaucoup moins connue. Nous avons utilisé un modèle murin avec une contamination chronique par ingestion d’eau contenant 20 kBq/l de 90Sr. Une étude de biocinétique a confirmé l’accumulation de 90Sr dans les os, avec un taux d’accumulation plus rapide durant la croissance osseuse. Cette accumulation est plus élevée dans les os des femelles que chez les males. Les doses absorbées au corps entier varient de 0.33 ± 0.06 mGy (naissance) à 10.6 ± 0.1 mGy (20 semaines). La dose au squelette peut aller jusqu’à 55 mGy. L’ingestion de 90Sr induit une modification de l’expression des gènes impliqués induisant à un déséquilibre favorisant la résorption osseuse, mais sans répercussion sur la morphologie de l’os. Aucun effet majeur n’a été observé pour le système hématopoïétique. Par contre, des modifications mineures du système immunitaire ont été observées. Afin d’évaluer la fonctionnalité du système immunitaire, un test de vaccination avec les antigènes TT et KLH a été utilisé. Les résultats montrent chez les animaux contaminés une diminution significative de la production d’immunoglobulines spécifiques, une modification de la balance Th1/Th2 dans la rate et une différenciation lymphoïde B perturbée. Ces résultats permettent de mieux comprendre certaines des conséquences non cancéreuses de l’exposition chronique à faible dose à des radionucléides à demi-vie longue pouvant être rejetés accidentellement. / Strontium 90 (90Sr) is a radionuclide of anthropogenic origin released in large quantities in the environment as a result of nuclear atmospheric tests or accidents at nuclear facilities. 90Sr persists on a long-term basis in the environment, leading to chronic contamination by ingestion of populations living on contaminated territories. The induction of bone tumours associated with the fixation of 90Sr has been widely described. However, the occurrence of non-cancer effects is much less known. We used a mouse model with chronic contamination by ingestion of water containing 20 kBq/l of 90Sr. A biokinetic study confirmed the accumulation of 90Sr in the bones, with an increased rate of accumulation during bone growth. This accumulation was higher in the bones of females than in males. The whole-body absorbed doses ranged from 0.33 ± 0.06 mGy (birth) to 10.6 ± 0.1 mGy (20 weeks). The absorbed dose for the skeleton was up to 55 mGy. Ingestion of 90Sr induced a change in the expression of genes inducing an imbalance in favour of bone resorption, but without effect on bone morphology. No significant effect was observed for the hematopoietic system. On the other hand, minor modifications were observed for the immune system. To evaluate the functionality of the immune system, a vaccination test with TT and KLH antigens was used. Results showed in contaminated animals a significant decrease in the production of specific immunoglobulins, changes in the Th1/Th2 balance in the spleen and a disrupted B lymphocyte differentiation. These results improve the understanding of some of the non-cancerous consequences of chronic exposure at low dose of radionuclides with a long half-life, which can be accidentally released.

Les maladies cardiovasculaires sont la première cause de mortalité dans le monde, en lien notamment avec la présence et la rupture de plaques d’athérome. Afin d’éviter la survenue d’évènements aigus, un traitement par statines peut être proposé. Cependant, leur utilisation engendre un risque d’effets délétères. Afin de réduire ce risque, une réduction des doses utilisées pourrait être envisagée. Ce travail de thèse étudie les effets potentiels d’un traitement à très faible dose d’atorvastatine et à long terme sur un modèle animal : le lapin Watanabe. Des mesures ont été menées sur des individus contrôles et traités de 3 à 12 mois. Le suivi de la lipidémie et des principaux facteurs biochimiques, de l’adhésion et de l’inflammation a été fait au niveau sanguin. Le développement de l’athérosclérose a été évalué en tomographie par cohérence optique (OCT). Des mesures en histologie ont permis de valider un classement proposé avec l’OCT et de quantifier les macrophages intra plaques. L’élasticité artérielle a été testée in vivo par la mesure de la vitesse de l’onde de pouls et in vitro par un test de traction statique. La fonction vasculaire a été appréhendée en vasoréactivité sur différents territoires (aorte, carotide, mésentérique). Le contenu en élastine et collagène de la paroi des vaisseaux a été effectué en microscopie à deux photons et génération de seconde harmonique. Enfin la respiration mitochondriale du myocarde et sa susceptibilité aux ROS a été évaluée sur fibres cardiaques perméabilisées, l’activité de systèmes antioxydants enzymatiques mesuré, ainsi que la peroxydation lipidique. Les résultats montrent des effets bénéfiques de ce traitement à très faible dose d’atorvastatine sur la fonction cardiovasculaire indépendamment d’un effet hypolipidémiant. / Cardiovascular diseases are the first worldwide causes of death, associated to the presence and rupture of atherosclerotic plaques. To limit acute events, statins may be prescribed. However, its use leads to deleterious effects risk. To reduce this risk, a dose reduction could be considered. The work of this thesis is to study potential effects of a very low dose of atorvastatin, taken in the long term, in an animal model: the Watanabe rabbit. Measurements are made on control and treated animals from the age of 3 to 12 months. Circulating lipids, biochemical parameters and parameters of adhesion and inflammation were studied. Atherosclerosis evolution was evaluated by optical coherence tomography (OCT). Histological measurements allowed to validate a ranking proposed with OCT observations and to quantify intra-plaque macrophage content. Arterial stiffness was tested in vivo with pulse wave velocity and in vitro with a static tensile test. Vascular function was approached with vasoreactivity in different territories (aorta, carotid, mesenteric). Elastin and collagen contents of the artery wall were determined with two-photon and second harmonic generation microscopy. Finally, mitochondrial respiration and its susceptibility to ROS were evaluated in permeabilized cardiac fibers, any enzymatic antioxidant systems and lipid peroxidation were measured. Results show beneficial effects of this very low dose atorvastatin treatment in cardiovascular function, independently of a lipid-lowering effect.Keywords: atherosclerosis,

<p>Transesophageal echocardiography (TEE) has become a useful tool in monitoring the heart in patients during open-heart surgery. This study was undertaken to evaluate whether it is feasible to use TEE to assess left ventricular myocardial viability in anesthetized patients scheduled for coronary artery bypass grafting (CABG).</p><p>A total of 84 patients were studied. To test myocardial viability, TEE and a low-dose dobutamine stress regimen were used. Echocardiographic data were analyzed off-line using a visual or semiautomatic analysis of segmental left ventricular wall motion (LVWM). Visual assessment was performed by readers blinded to the sequence of events. The agreement between readers in visual analysis of segmental LVWM in the transgastric short-axis view was 73% or higher. Segmental LVWM assessed by TEE was compared to hemodynamic data obtained by thermodilution pulmonary artery catheter (PAC) and coronary angiographic data. Also, using the same low-dose dobutamine stress regimen, TEE findings in the anesthetized patient perioperatively were compared with preoperative transthoracic echocardiography (TTE) findings in the awake patient.</p><p>TEE was found to be feasible and adequate for testing left segmental ventricular viability. A concomitant increase in stroke volume assessed by PAC and decrease in LVWM-score assessed by TEE was found with dobutamine stimulation. Abnormal segmental LVWM corresponded to angiographically stenosed supplying coronary artery vessels. During dobutamine stimulation, 69% of the corresponding segments responded which is a sign of viability. The LVWM response to preoperative TTE and perioperative TEE dobutamine stress was comparable except for a significant difference in the apical segments.</p><p>This study showed that perioperative TEE dobutamine stress could be used to test left ventricular viability and was also a valuable supplement to PAC, angiography and TTE. The acquired knowledge is important and suggest that further development of transesophageal ultrasound technology is warranted.</p>

Transesophageal echocardiography (TEE) has become a useful tool in monitoring the heart in patients during open-heart surgery. This study was undertaken to evaluate whether it is feasible to use TEE to assess left ventricular myocardial viability in anesthetized patients scheduled for coronary artery bypass grafting (CABG). A total of 84 patients were studied. To test myocardial viability, TEE and a low-dose dobutamine stress regimen were used. Echocardiographic data were analyzed off-line using a visual or semiautomatic analysis of segmental left ventricular wall motion (LVWM). Visual assessment was performed by readers blinded to the sequence of events. The agreement between readers in visual analysis of segmental LVWM in the transgastric short-axis view was 73% or higher. Segmental LVWM assessed by TEE was compared to hemodynamic data obtained by thermodilution pulmonary artery catheter (PAC) and coronary angiographic data. Also, using the same low-dose dobutamine stress regimen, TEE findings in the anesthetized patient perioperatively were compared with preoperative transthoracic echocardiography (TTE) findings in the awake patient. TEE was found to be feasible and adequate for testing left segmental ventricular viability. A concomitant increase in stroke volume assessed by PAC and decrease in LVWM-score assessed by TEE was found with dobutamine stimulation. Abnormal segmental LVWM corresponded to angiographically stenosed supplying coronary artery vessels. During dobutamine stimulation, 69% of the corresponding segments responded which is a sign of viability. The LVWM response to preoperative TTE and perioperative TEE dobutamine stress was comparable except for a significant difference in the apical segments. This study showed that perioperative TEE dobutamine stress could be used to test left ventricular viability and was also a valuable supplement to PAC, angiography and TTE. The acquired knowledge is important and suggest that further development of transesophageal ultrasound technology is warranted.

On 26 April 1986 an accident occurred in the Chernobyl nuclear power plant resulting in the release of large amount of radionuclides. Almost five percent of the total released caesium-137 was deposited in Sweden. The incidence of malignancies in the most affected counties in Sweden was investigated in three epidemiological studies. In the first study the incidence of malignancies in children and adolescents was studied for the period 1978-1992. The parishes and their inhabitants were classified according to the ground deposition of caesium-137 on an analogue map provided be the Swedish Radiological Protection Authority. A continuous increase of brain tumour incidence observed during the time of the study had no clear relationship to the Chernobyl fallout. A somewhat decreased relative risk of ALL was observed in areas with increased deposition. Other malignancies showed no changes in incidence over time or with regard to the exposure of caesium-137. In study II and III we enlarged the study base by including adults. We improved the methodology by defining a cohort of subjects who lived in the same parish from 31 December 1985 to 31 December 1987. The inhabitants from seven counties were included. Parishes were classified the same way as in study I. Due to the large number of individuals six exposure categories could be created; &lt;3, 3–29, 30–39, 40–59, 60–79, and 80–120 kBq caesium-137/m2. The inhabitants of the 117 non-affected parishes (&lt;3 kBq/m2) served as reference. During the 1988-1996 followup, 22,409 malignancies were recorded. The MH-IRR in the fully adjusted model was 1.00 (reference), 1.05, 1.03, 1.08, 1.10 and 1.21, respectively. ERR was 0.11 per 100 kBq/m2 (95% CL 0.03;0.20). A more advanced method was used in Study III by ignoring the exposure classification for parishes, and instead matching the dwelling coordinate to a digital map of deposition of casesium-137. In spite of a more valid exposure classification the risk estimates were similar in study II and III. Also, the ERR during the longer follow-up of 1988-1999 was almost identical, 0.10 per 100 kBq/m2 (95% CL 0.00;0.23). The strongest dose-response relationship was seen in the first four years (1988-1991). No obvious excess for leukaemia or thyroid cancer was recognised in either study II or III. The estimated number of exposure related cases was calculated to 849 in study II and 1,278 in study III. Our interpretation is that we have shown an increased incidence of total malignancies with dose-response relationship for caesium-137, only a few years after the Chernobyl accident. In study IV we compared the two different ways of classifying the exposure in study II and III. Out of the 450 parishes 111 got a different classification. The similar risk estimates in study II and III could probably be explained by relatively homogenous exposure in the parishes making the intra-parish difference less influential, especially when included in categories. In study V we examined the urinary excretion of 8-OHdG in Belarussian children from areas with high and low fallout of caesium-137, respectively. We found significantly lower urinary 8-OHdG levels in children from rural contaminated areas compared to urban uncontaminated areas, suggesting an urban, rather than a radiation related, risk factor. Using the Hill criteria for causality there is support for a causal inference between the fallout of caesium-137 from the Chernobyl accident and the increased incidence in total malignancies in Northern Sweden.

Fifty percent of solid cancers are treated with radiation therapy (RT). The dose used in RT is adjusted to the most sensitive individuals so that not more than 5% of the patients will have severe adverse healthy tissue effects. As a consequence, the majority of the patients will receive a suboptimal dose, as they would have tolerated a higher total dose and received a better tumor control. Thus, if RT could be individualized based on radiation sensitivity (RS), more patients would be cured and the most severe adverse reactions could be avoided. At present the mechanisms behind RS are not known. The long term aim of this thesis was to develop diagnostic tools to assess the individual RS of breast cancer patients and to better understand the mechanisms behind the RS and radiation effects after low dose exposures. The approach was based on the hypothesis that biomarkers of individual RS, in terms of acute adverse skin reactions after breast cancer RT, can be found in whole blood that has been stressed by low doses of ionizing radiation (IR).  To reach this goal two different approaches to identify biomarkers of RS have been investigated. A protocol for the analysis of differential protein expression in response to low dose in vitro irradiated whole blood was developed (paper I). This protocol was then used to investigate the proteomic profile of radiation sensitive and normo-sensitive patients, using isotope-coded protein labeled proteomics (ICPL). The results from the ICPL study (paper III) show that the two patient groups have different protein expression profiles both at the basal level and after IR. In paper II the potential biomarker 8-oxo-dG was investigated in serum after IR. The relative levels of IR induced 8-oxo-dG from radiation sensitive patients differ significantly from normo-sensitive patients. This indicates that the sensitive patients differ in their cellular response to IR and that 8-oxo-dG is a potential biomarker for RS. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>