Mixing of Rhône River water in Lake Geneva (Switzerland-France) inferred from stable hydrogen and oxygen isotope profiles

Depth profiles were sampled at different locations throughout Lake Geneva on a monthly and seasonal basis over the course of 2 years and analysed for their stable hydrogen and oxygen isotope compositions. The isotopic compositions indicate an isotopic stratification in the metalimnion during summer and fall. This is related to mixing of Rhône River water, which in summer is dominated by snow and glacier melt waters, and lake water, with the latter having a homogenous isotopic composition. The observed interflow layer is 7-15 m thick and can be traced by the distinct stable isotope composition of the water for about 55 km throughout the lake as well as into shallow bay regions. Depth of the interflow layer close to the Rhône River mouth is similar to those previously described based on echo-soundings and turbidity profiles of sediment dispersion. In contrast to previous descriptions of the interflow within Lake Geneva, the stable isotope compositions allow for direct, natural tracing of the Rhône River water even in cases where the turbidity and conductivity measurements do not indicate such an interflow. In addition, the method allows for a quantification of the Rhône River and lake water in the interflow with the fraction of Rhône River water within the interflow estimated to be up to 37% in summer. The isotopic composition further indicates different vertical mixing processes within the two lake basins of Lake Geneva, related to the density gradients and local stability within the water column. The method may be applicable to other lakes in catchments with large differences in the topography as water that originates from high altitudes or glaciers has a distinct oxygen and hydrogen isotope composition compared to other sources of water originating at lower altitudes and/or from direct precipitation over the lake. Stable isotope measurements thus improve the understanding of the circulation of water within the lake, which is fundamental for an evaluation of the water residence times, dissolved pollutant and nutrient transport as well as oxygenation.

Antiretroviral adherence program in HIV patients: a feasibility study in the Swiss HIV Cohort Study.

Objective To evaluate the feasibility of a comprehensive, interdisciplinary adherence program aimed at HIV patients. Setting Two centers of the Swiss HIV Cohort Study: Lausanne and Basel. Method 6-month, pilot, quasi-experimental, 2-arm design (control and intervention). Patients starting a first or second combined antiretroviral therapy line were invited to participate in the study. Patients entering the intervention arm were proposed a multifactorial intervention along with an electronic drug monitor. It consisted of a maximum of six 30-min sessions with the interventionist coinciding with routine HIV check-up. The sessions relied on individualized semi-structured motivational interviews. Patients in the control arm used directly blinded EDM and did not participate in motivational interviews. Main outcome measures Rate of patients' acceptance to take part in the HIV-adherence program and rate of patients' retention in this program assessed in both intervention and control groups. Persistence, execution and adherence. Results The study was feasible in one center but not in the other one. Hence, the control group previously planned in Basel was recruited in Lausanne. Inclusion rate was 84% (n = 21) in the intervention versus 52% (n = 11) in the control group (P = 0.027). Retention rate was 91% in the intervention versus 82% in the control group (P = ns). Regarding adherence, execution was high in both groups (97 vs. 95%). Interestingly, the statistical model showed that adherence decreased more quickly in the control versus the intervention group (interaction group × time P < 0.0001). Conclusion The encountered difficulties rely on the implementation, i.e., on the program and the health care system levels rather than on the patient level. Implementation needs to be evaluated further; to be feasible a new adherence program needs to fit into the daily routine of the centre and has to be supported by all trained healthcare providers. However, this study shows that patients' adherence behavior evolved differently in both groups; it decreased more quickly over time in the control than in the intervention group. RCTs are eventually needed to assess the clinical impact of such an adherence program and to verify whether skilled pharmacists can ensure continuity of care for HIV outpatients.

Hypertoniebehandlung bei Nierenarterienstenose [Hypertension therapy in patients with renal artery stenosis].

Renovascular hypertension is due to reduced renal parenchymal perfusion. The correct diagnosis can be difficult. It is important to note that the demonstration of renal artery stenosis in a patient with hypertension does not necessarily constitute renovascular hypertension. Often, clinically nonsignificant and asymptomatic renal artery stenosis are found in patients with essential hypertension, or renal failure of other origin. Renovascular disease is a complex disorder with various clinical presentations. In patients with significant renovascular hypertension plasma renin is increased. For this reason the therapy aims to block the renin-angiotensin-aldosterone system. Bilateral renal artery stenosis causes renal sodium retention. In this situation a diuretic drug has to be added to the therapy. Endovascular or surgical therapy has to be considered in patients with flash pulmonary edema or fibromuscular dysplasia. The control of cardiovascular risk factors is important.

Origin of cadmium enrichments in carbonate rocks deposited in the Alpine Tethys area during the Middle-Late Jurassic

ABSTRACTThe pollution of air, soil and water by heavy metals through anthropogenic activities is an object of numerous environmental studies since long times. A number of natural processes, such as volcanic activity, hydrothermal fluid circulation and weathering of metal-rich deposits may lead to an additional and potentially important input and accumulation of heavy metals in the environment. In the Swiss and French Jura Mountains, anomalous high cadmium (Cd) concentrations (up to 16 ppm) in certain soils are related to the presence of underlying Cd-enriched (up to 21 ppm) carbonate rocks of Middle to Late Jurassic age. The aim of this study is to understand the processes controlling Cd incorporation into carbonate rocks of Middle and Late Jurassic age and to reconstruct the sedimentary and environmental conditions, which have led to Cd enrichments in these sedimentary rocks.Cd concentrations in studied hemipelagic sections in France vary between 0.1 and 0.5 ppm (mean 0.15 ppm). Trace-element behavior and high Mn concentrations suggest that sediment accumulation occurred in a well-oxygenated environment. Increases in Cd contents in the bulk-rock carbonate sediments may be related to increases in surface-water productivity under oxic conditions and important remineralization of organic matter within the water column. In platform settings preserved in the Swiss Jura Mountains, no correlation is observed between Cd contents and evolution of environmental conditions. Cd concentrations in these platform sections are often below the detection limit, with isolated peaks of up to 21 ppm. These important Cd enrichments are associated with peaks in Zn concentrations and are present in carbonate rocks independently of facies and age. The high Cd contents in these shallow-water carbonate rocks are partly related to the presence of disseminated, Cd-rich (up to 1.8%), sphalerite (ZnS) mineralization. The basement rocks are considered to be the source of metals for sulfide mineralization in the overlying Jurassic strata, as the sphalerite Pb isotope pattern is comparable to that of granite rocks from the nearby southern Black Forest crystalline massif. The Rb-Sr ages of sphalerite samples indicate that a main phase of sphalerite formation occurred near the boundary between the late Middle and early Late Jurassic, at around 162 Ma, as a result of enhanced tectonic and hydrothermal activity in Europe, related to the opening of the Central Atlantic and to the tectonic/thermal subsidence during spreading of the Alpine Tethys. I therefore propose to use unusually high Cd concentrations in carbonates as a tracer of tectonic activity in the Jura Mountains area, especially in the case when important enrichments in Zn co-occur. Paleoproductivity reconstructions based on records of authigenic Cd may be compromised not only by post-depositional redistribution, but also by incorporation of additional Cd from hydrothermal solutions circulating in the rock.The circulation of metal-rich hydrothermal fluids through the sediment sequence, in addition to specific environmental conditions during sedimentation, contributes to the incorporation of Cd into the carbonate rocks. However, only hydrothermal activity has led to the unusually high concentrations of Cd in carbonate rocks of Bajocian-Oxfordian age, through the formation of sphalerite mineralization.

The role of PLK-1 in asynchronous cell division of two-cell stage "C. elegans" embryos

Summary Acquisition of lineage-specific cell cycle duration is an important feature of metazoan development. In Caenorhabditis a/egans, differences in cell cycle duration are already apparent in two-cell stage embryos, when the larger anterior blastomere AB divides before the smaller posterior blastomere P1. This time difference is under the control of anterior-posterior (A-P) polarity cues set by the PAR proteins. The mechanism by which these cues regulate the cell cycle machinery differentially in AB and P1 are incompletely understood. Previous work established that retardation of P1 cell division is due in part to preferential activation of an ATL1/CHK-1 dependent checkpoint in P1 but how the remaining time difference is controlled was not known at the onset of my work. The principal line of work in this thesis established that differential timing relies also on a mechanism that promotes mitosis onset preferentially in AB. The polo-like kinase PLK-1, a positive regulator of mitotic entry, is distributed in an asymmetric manner in two-cell stage embryos, with more protein present in AB than in P1. We find that PLK-1 asymmetry is regulated by anterior-posterior (A-P) polarity cues through preferential protein retention in the embryo anterior. Importantly, mild inactivation of plk-1 by RNAi delays entry into mitosis in P1 but not in AB, in a manner that is independent of ATL-1/CHK-1. Together, these findings favor a model in which differential timing of mitotic entry in C. elegans embryos relies on two complementary mechanisms: ATL-1/CHK-1 dependent preferential retardation in P1 and PLK-1 dependent preferential promotion in AB, which together couple polarity cues and cell cycle progression during early development. Besides analyzing PLK-1 asymmetry and its role in differential timing of two-cells stage embryos, we also characterized t2190, a mutant that exhibits reduced differential timing between AB and P1. We found this mutant to be a new allele of par-1. Additionally, we analyzed the role of NMY-2 in regulating the asynchrony of two-cell stage embryos, which may be uncoupled from its role in A-P polarity establishment and carried out a preliminary analysis of the mechanism underlying CDC-25 asymmetry between AB and P,. Overall, our works bring new insights into the mechanism controlling cell cycle progression in early C. elegans embryos. As most of the players important in C. elegans are conserved in other organisms, analogous mechanisms may be utilized in polarized cells of other species. Résumé Au cours du développement, les processus de division cellulaire sont régulés dans l'espace et le temps afin d'aboutir à la formation d'un organisme fonctionnel. Chez les Métazoaires, l'un des mécanismes de contrôle s'effectue au niveau de la durée du cycle cellulaire, celle-ci étant specifiée selon la lignée cellulaire. L'embryon du nématode Caenorhabditis elegans apparaît comme un excellent modèle d'étude de la régulation temporelle du cycle cellulaire. En effet, suite à la première division du zygote, l'embryon est alors composé de deux cellules de taille et d'identité différentes, appelées blastomères AB et P1. Ces deux cellules vont ensuite se diviser de manière asynchrone, le grand blastomère antérieur AB se divisant plus rapidement que le petit blastomère postérieur P1. Cette asynchronie de division est sous le contrôle des protéines PAR qui sont impliquées dans l'établissement de l'axe antéro-postérieur de l'embryon. A ce jour, les mécanismes moléculaires gouvernant ce processus d'asynchronie ne sont que partiellement compris. Des études menées précédemment ont établit que le retard de division observé dans le petit blastomère postérieur P1 était dû, en partie, à l'activation préférentielle dans cette cellule de ATL-1/CHK-1, protéines contrôlant la réponse à des erreurs dans le processus de réplication de l'ADN. L'analyse des autres mécanismes responsables de la différence temporelle d'entrée en mitose des deux cellules a été entreprise au cours de cette thèse. Nous avons considéré la possibilité que l'asynchronie de division était du à l'entrée préférentielle en mitose du grand blastomère AB. Nous avons établi que la protéine kinase PLK-1 (polo-like kinase 1), impliquée dans la régulation positive de la mitose, était distribuée de manière asymétrique dans l'embryon deux cellules. PLK-1 est en effet enrichi dans le blastomère AB. Cette localisation asymétrique de PLK-1 est sous le contrôle des protéines PAR et semble établie via une rétention de PLK-1 dans la cellule AB. Par ailleurs, nous avons démontré que l'inactivation partielle de plk-7 par interférence à ARN (RNAi) conduit à un délai de l'entrée en mitose de la cellule P1 spécifiquement, indépendamment des protéines régulatrices ATL-1/CHK-1. En conclusion, nous proposons un modèle de régulation temporelle de l'entrée en mitose dans l'embryon deux cellules de C. elegans basé sur deux mécanismes complémentaires. Le premier implique l'activation préférentielle des protéines ATL-1/CHK-1, et conduit à un retard d'entrée en mitose spécifiquement dans la cellule P1. Le second est basé sur la localisation asymétrique de la protéine kinase PLK-1 dans la cellule AB et induit une entrée précoce en mitose de cette cellule. Par ailleurs, nous avons étudié un mutant appelé t2190 qui réduit la différence temporelle d'entrée en mitose entre les cellules AB et P1. Nous avons démontré que ce mutant correspondait à un nouvel allèle du Bene par-1. De plus, nous avons analysé le rôle de NMY-2, une protéine myosine qui agit comme moteur moléculaire sur les filaments d'active; dans la régulation de l'asynchronie de division des blastomères AB et P1, indépendamment de sa fonction dans l'établissement de l'axe antéro-postérieur. Par ailleurs, nous avons commencé l'étude du mécanisme moléculaire régulant la localisation asymétrique entre les cellules AB et P1 de la protéine phosphatase CDC25, qui est également un important régulateur de l'entrée en mitose. En conclusion, ce travail de thèse a permis une meilleure compréhension des mécanismes gouvernant la progression du cycle cellulaire dans l'embryon précoce de C. elegans. Etant donné que la plupart des protéines impliquées dans ces processus sont conservées chez d'autres organismes multicellulaires, il apparaît probable que les mécanismes moléculaires révélés dans cette étude soit aussi utilisés chez ceux-ci.

Sediment budget monitoring of a debris-flow torrent (French Prealps)

The Manival near Grenoble (French Prealps) is a very active debris-flow torrent equipped with a large sediment trap (25 000 m3) protecting an urbanized alluvial fan from debris-flows. We began monitoring the sediment budget of the catchment controlled by the trap in Spring 2009. Terrestrial laser scanner is used for monitoring topographic changes in a small gully, the main channel, and the sediment trap. In the main channel, 39 cross-sections are surveyed after every event. Three periods of intense geomorphic activity are documented here. The first was induced by a convective storm in August 2009 which triggered a debris-flow that deposited ~1,800 m3 of sediment in the trap. The debris-flow originated in the upper reach of the main channel and our observations showed that sediment outputs were entirely supplied by channel scouring. Hillslope debris-flows were initiated on talus slopes, as revealed by terrestrial LiDAR resurveys; however they were disconnected to the main channel. The second and third periods of geomorphic activity were induced by long duration and low intensity rainfall events in September and October 2009 which generate small flow events with intense bedload transport. These events contribute to recharge the debris-flow channel with sediments by depositing important gravel dunes propagating from headwaters. The total recharge in the torrent subsequent to bedload transport events was estimated at 34% of the sediment erosion induced by the August debris-flow.

External urethral sphincter electromyography in asymptomatic women and the influence of the menstrual cycle.

OBJECTIVE: To investigate by electromyography (EMG), the presence of complex repetitive discharges (CRDs) and decelerating bursts (DBs) in the striated external urethral sphincter during the menstrual cycle in female volunteers with no urinary symptoms and complete bladder emptying. SUBJECTS AND METHODS: Healthy female volunteers aged 20-40 years, with regular menstrual cycles and no urinary symptoms were recruited. Volunteers completed a menstruation chart, urinary symptom questionnaires, pregnancy test, urine dipstick, urinary free flow and post-void ultrasound bladder scan. Exclusion criteria included current pregnancy, use of hormonal medication or contraception, body mass index of >35 kg/m(2) , incomplete voiding and a history of pelvic surgery. Eligible participants underwent an external urethral sphincter EMG, using a needle electrode in the early follicular phase and the mid-luteal phase of their menstrual cycles. Serum oestradiol and progesterone were measured at each EMG test. RESULTS: In all, 119 women enquired about the research and following screening, 18 were eligible to enter the study phase. Complete results were obtained in 15 women. In all, 30 EMG tests were undertaken in the 15 asymptomatic women. Sphincter EMG was positive for CRDs and DBs at one or both phases of the menstrual cycle in eight (53%) of the women. Three had CRDs and DBs in both early follicular and mid-luteal phases. Five had normal EMG activity in the early follicular phase and CRDs and DBs in the mid-luteal phase. No woman had abnormal EMG activity in the early follicular phase and normal activity in the luteal phase. There was no relationship between EMG activity and age, parity or serum levels of oestradiol and progesterone. CONCLUSIONS: CRDs and DB activity in the external striated urethral sphincter is present in a high proportion of asymptomatic young women. This abnormal EMG activity has been shown for the first time to change during the menstrual cycle in individual women. CRDs and DBs are more commonly found in the luteal phase of the menstrual cycle. The importance of CRDs and DBs in the aetiology of urinary retention in young women remains uncertain. The distribution and or quantity of abnormal EMG activity in the external urethral sphincter may be important. In a woman with urinary retention the finding of CRDs and DBs by needle EMG does not automatically establish Fowler's syndrome as the explanation for the bladder dysfunction. Urethral pressure profilometry may be helpful in establishing a diagnosis. Opiate use and psychological stress should be considered in young women with urinary retention.