Les effets de l'oxygénation dans un lac eutrophe étudiés par la méthode de l'«enceinte»

Le lac de Comabhio (Lombardie, Italie du Nord) est un lac peu profond (z- = 4,4 m) en comparaison à sa surface (3,44 km2). L'eutrophisation naturelle du lac a été accélérée par l'apport d'effluents domestiques pas traités. Pour améliorer la situation, les effluents conduits par un collecteur circumlacustre, ont été recueillis à l'extérieur du bassin versant.Les effets seront visibles seulement dans plusieurs années et ces interventions ne seront pas suffisantes pour ramener le lac à l'état de mésotrophie. Afin d'accélérer l'assainissement du lac, mais surtout pour éviter la forte mortalité du poisson périodiquement à la fin de l'été, on a pris la décision d'oxygéner artificiellement l'hypolimnion. Pour prévoir les effets de l'oxygénation on a fait une expérience dans le lac avec deux enceintes en PVC (diamètre : 40 m; profondeur : 6 m; volume : 7000 m3). On a gardé une enceinte comme témoin; dans l'autre a été insufflé de l'oxygène pur. On a recueilli, à certains intervalles de temps, des échantillons d'eau et de plancton du lac et des deux enceintes. Les éléments nutritifs ont été analysés; la température, la transparence, la conductivité et le pH ont été mesurés sur place. L'effet le plus visible du traitement consistait dans une augmentation de la concentration de l'oxygène visant à produire des conditions normales pour la vie des poissons. Les effets de l'oxygénation sur les caractéristiques chimiques, physiques et biologiques du milieu sont discutés.Lake Comabbio (Lombardy, Northern Itaty) is a shallow Lake (zmax = 8.0 m; z-= 4.4 m; surface = 3.44 km2). Its naturally high trophic level has been increased by the huge nutrient loading from domestic effluents. Each year (except in winter, when commonly the lake is covered with ice) more phytoplankton blooms are observed and in the late summer oxygen depletion, with a consequent mass mortality of fish, occurs.At present, to reduce the nutrient charge, the effluents are collected in a channel and diverted from the lake watershed. Because of the significant nutrient release from the sediment ("internal eutrophication") the reduction of the external loading may slow the eutrophication rate, but it is not sufficient to restore the lake to an acceptable mesotrophic state within a reasonable time.To prevent the periodic mass mortality of fish and possibly to accelerate the restoration process of the ecosystem, the Lake Comabbio Protection Committee decided to oxygenate the hypolimnetic layer artificially. In order to avoid undesirable effects of aeration (e.g. nitrogen enrichment of lake water), dissolved oxygen injection was preferred. As there is no general agreement on the ecological effects of the oxygen (or air) addition it was decided, before applying oxygenation to the whole lake, to carry out experiments using the "enclosure" method. One experiment was carried out from 26th September to 9th December 1986 and this was replicated in 1987 from 22nd April to 30th November. This paper is concerned with the first experiment, as data treatment of the second is still in progress. Two cylindrical "enclosures" of PVC (diameter = 40.0 m; height = 6.0 m; volume = 7000 m3) were settled in Lake Comabbio to isolate a water column with its sediments. One enclosure was treated with oxygen from 15th November to 6th December, the other was kept as control. The water aspirated from the enclosure was oxygenated (20.3 mg O2/l) and injected in the same enclosure at 4 m depth at a rate of 4 m3/h. During the enclosure settlement the fish escaped from the enclosures. To simulate a complete ecosystem, the plan was to add to each enclosure 60 kg of the most abundant fish species (Scardinius erythrophtalmus). By mistake, fish were added to the enclosure that was to be oxygenated but not to the control. Water and zooplankton were sampled simultaneously from both the enclosures as well as from the Lake. Zooplankton was collected by vertical hauls from the bottom to the water surface. The following parameters were measured : temperature, transparency, pH, electrical conductivity, dissolved oxygen, alkalinity, phosphorus and nitrogen compounds, chlorophyll-a and pheopigments. The injection of water rich in oxygen did not resuspend the sediments and the absence of bubbles showed that the oxygen had completely dissolved.Soon after oxygenation the difference in oxygen concentration in the treated enclosure and in the control was progressively reduced until 26th November, when both the enclosures had the same oxygen concentration. At the end of the experiment (9th December) the oxygen concentration in the control was about 4 mg/l, whereas in the treated enclosure it attained a concentration of 6 mg/l, although in the latter the oxygen consumption was greater than in the control, owing to fish respiration and the increased activity of aerobic microorganisms. The higher concentrations of total phosphorus (TP), soluble reactive phosphorus (SRP) and ammonium (N-NH4) measured in the lake were probably due to the external loading of nutrients. The nutrient concentrations in the treated enclosure were similar to those of the control. The greater concentration of nutrients was probably the cause of more abundant phytoplankton in the lake, which was also demonstrated by the lower values of water transparency, when compared with those measured in both the enclosures. The pH values of the control were similar to those of the treated enclosure. The pattern of abundance and species composition of the zooplankton in the treated enclosure did not differ from that of the control. The Entomostraca populations decreased in the lake as well as in both the enclosures from the beginning to the end of the experiment.From this experiment, carried out when oxygen depletion affected the whole water column, we may conclude that oxygenation can prevent fish mortality, without significantly influencing the structure and biomass of the planktonic community. The variations in the plankton and chemical and physical characteristics of the water (except oxygen concentration) were essentially due to the season and mot to the artificial oxygenation. In addition, oxygenation, by abolishing the periodical mortality of fish, may also prevent the release of a huge amount of organic substances from the dead fish into the water

A (p,q)-deformed Landau problem in a spherical harmonic well: spectrum and noncommuting coordinates

A (p,q)-deformation of the Landau problem in a spherically symmetric harmonic potential is considered. The quantum spectrum as well as space noncommutativity are established, whether for the full Landau problem or its quantum Hall projections. The well known noncommutative geometry in each Landau level is recovered in the appropriate limit p,q=1. However, a novel noncommutative algebra for space coordinates is obtained in the (p,q)-deformed case, which could also be of interest to collective phenomena in condensed matter systems.Comment: 9 pages, no figures; updated reference

The Indo-Pacific ammonite <i>Mayaites</i> in the Oxfordian of the Southern Andes

Oxfordian Iitho- and biostratigraphy of the Chilean and Argentine Andes is reviewed (P. N. Stipanicic). Within the Chacay Group, the Lower to basal Upper Oxfordian La Manga Formation, below, mostly detrital and biogenic, and the Upper Oxfordian Auquilco Formation, above, mainly chemical, are distinguished. The La Manga Formation (with Gryphaea calceola lumachelle) is rich in ammonite faunas, particularly of thc upper Cordatum to lower Canaliculatum Zones. In Neuquén and Mendoza provinces of Argentina, the Plicatilis Zone or Middle Oxfordian has yielded Perísphinctes spp., Euaspidoceras spp., Aspidoceras spp., together with Mayaítes (Araucanites ) stípanícfcí, M. (A.) reyesi, and M. (A.) mulai, Westermann et Riccardi subgen. et spp. nov. The first find of Mayaitidae outside the Indo-Pacific province is discussed in light of _plate-tectonic theory.La revisión Iito- y bioestratigráfica del Oxfordiano de los Andes de Argentina y Chile (P. N. Stipanicic) ha permitido reconocer dentro del Grupo Chacay: 1) abajo, la Formación La Manga, mayormente detrítica y biogénica, del Oxfordiano inferior-superior basa!, y 2) arriba, la Formación Auquilco, mayormente química, del Oxfordiano superior. La Formación La Manga (con lumachelas de Gryphaea calceola) contiene abundante cantidad de amonitas, particularmente de las Zonas de Cordatum superior a Canaliculatum inferior. En las provincias de Mendoza y Neuquén, Argentina, la Zona de Plicatilis (Oxfordiano medio) contiene Perispbinctes spp., Euaspidoceras spp., Aspidoceras spp., conjuntamente con Mayaites (Araucanites) stipanicici, M. (A.) reyesi, y M. (A.) mulai, Westermann et Riccardi subgen. et spp. nov. El primer hallazgo de Mayaitidae fuera de la provincia lndo-Pacífica es discutido tomando en consideración la teoría de tectónica de placas.Universidad Nacional de La Plata (UNLP) - Facultad de Ciencias Naturales y Museo (FCNM

The Indo-Pacific ammonite <i>Mayaites</i> in the Oxfordian of the Southern Andes

Oxfordian Iitho- and biostratigraphy of the Chilean and Argentine Andes is reviewed (P. N. Stipanicic). Within the Chacay Group, the Lower to basal Upper Oxfordian La Manga Formation, below, mostly detrital and biogenic, and the Upper Oxfordian Auquilco Formation, above, mainly chemical, are distinguished. The La Manga Formation (with Gryphaea calceola lumachelle) is rich in ammonite faunas, particularly of thc upper Cordatum to lower Canaliculatum Zones. In Neuquén and Mendoza provinces of Argentina, the Plicatilis Zone or Middle Oxfordian has yielded Perísphinctes spp., Euaspidoceras spp., Aspidoceras spp., together with Mayaítes (Araucanites ) stípanícfcí, M. (A.) reyesi, and M. (A.) mulai, Westermann et Riccardi subgen. et spp. nov. The first find of Mayaitidae outside the Indo-Pacific province is discussed in light of _plate-tectonic theory.La revisión Iito- y bioestratigráfica del Oxfordiano de los Andes de Argentina y Chile (P. N. Stipanicic) ha permitido reconocer dentro del Grupo Chacay: 1) abajo, la Formación La Manga, mayormente detrítica y biogénica, del Oxfordiano inferior-superior basa!, y 2) arriba, la Formación Auquilco, mayormente química, del Oxfordiano superior. La Formación La Manga (con lumachelas de Gryphaea calceola) contiene abundante cantidad de amonitas, particularmente de las Zonas de Cordatum superior a Canaliculatum inferior. En las provincias de Mendoza y Neuquén, Argentina, la Zona de Plicatilis (Oxfordiano medio) contiene Perispbinctes spp., Euaspidoceras spp., Aspidoceras spp., conjuntamente con Mayaites (Araucanites) stipanicici, M. (A.) reyesi, y M. (A.) mulai, Westermann et Riccardi subgen. et spp. nov. El primer hallazgo de Mayaitidae fuera de la provincia lndo-Pacífica es discutido tomando en consideración la teoría de tectónica de placas.Universidad Nacional de La Plata (UNLP) - Facultad de Ciencias Naturales y Museo (FCNM

Dissecting the Pharmacodynamics and Pharmacokinetics of MSCs to Overcome Limitations in Their Clinical Translation

Recently, mesenchymal stromal stem cells (MSCs) have been proposed as therapeutic agents because of their promising preclinical features and good safety profile. However, their introduction into clinical practice has been associated with a suboptimal therapeutic profile. In this review, we address the biodistribution of MSCs in preclinical studies with a focus on the current understanding of the pharmacodynamics (PD) and pharmacokinetics (PK) of MSCs as key aspects to overcome unsatisfactory clinical benefits of MSC application. Beginning with evidence of MSC biodistribution and highlighting PK and PD factors, a new PK-PD model is also proposed. According to this theory, MSCs and their released factors are key players in PK, and the efficacy biomarkers are considered relevant for PD in more predictive preclinical investigations. Accounting for the PK-PD relationship in MSC translational research and proposing new models combined with better biodistribution studies could allow realization of the promise of more robust MSC clinical translation. The number of clinical trials based on MSCs that are publicly available exceeds 800; however, data regarding MSC pharmacodynamics (PD), pharmacokinetics (PK), and biodistribution are still scarce. For this reason, we dissected the PD and PK properties of MSCs, presenting factors that may influence MSC-based PK studies to then conceive a new PK-PD model that would support better and more robust MSC clinical translation

Etiological diagnosis, prognostic significance and role of electrophysiological study in patients with Brugada ECG and syncope.

BACKGROUND: Syncope is considered a risk factor for life-threatening arrhythmias in Brugada patients. Distinguishing a benign syncope from one due to ventricular arrhythmias is often difficult, unless an ECG is recorded during the episode. Aim of the study was to analyze the characteristics of syncopal episodes in a large population of Brugada patients and evaluate the role of electrophysiological study (EPS) and the prognosis in the different subgroups. METHODS AND RESULTS: One hundred ninety-five Brugada patients with history of syncope were considered. Syncope were classified as neurally mediated (group 1, 61%) or unexplained (group 2, 39%) on the basis of personal and family history, clinical features, triggers, situations, associated signs, concomitant therapy. Most patients underwent EPS; they received ICD or implantable loop-recorder on the basis of the result of investigations and physician's judgment. At 62±45months of mean follow-up, group 1 showed a significantly lower incidence of arrhythmic events (2%) as compared to group 2 (9%, p<0.001). Group 2 patients with positive EPS showed the highest risk of arrhythmic events (27%). No ventricular events occurred in subjects with negative EPS. CONCLUSION: Etiological definition of syncope in Brugada patients is important, as it allows identifying two groups with different outcome. Patients with unexplained syncope and ventricular fibrillation induced at EPS have the highest risk of arrhythmic events. Patients presenting with neurally mediated syncope showed a prognosis similar to that of the asymptomatic and the role of EPS in this group is unproven

Postnatal survival after endoscopic equatorial laser for the treatment of twin-to-twin transfusion syndrome

Background Endoscopic laser coagulation of placental anastomoses is the first-line treatment for severe twin-to-twin transfusion syndrome. A recent randomized controlled trial reported that laser coagulation along the entire vascular equator was associated with a similar dual survival and survival of at least 1 twin compared with the group that was treated with the selective technique. In addition, there was a significantly lower incidence of postoperative recurrence of twin-to-twin transfusion syndrome and the development of twin anemia-polycythemia sequence in the equatorial group. Objective The purpose of this study was to report on neonatal survival in twin-to-twin transfusion syndrome pregnancies that were treated with endoscopic laser therapy with the use of the equatorial technique and to examine the relationship between preoperative factors and twin loss. Study Design Endoscopic equatorial laser therapy was carried out as the primary treatment for twin-to-twin transfusion syndrome in all consecutive monochorionic diamniotic twin pregnancies that were referred at a single fetal surgery Center over a 4-year period. All visible placental anastomoses were coagulated; additional laser ablation of the placental tissue between the coagulated vessels was carried out. Pre-laser ultrasound data, periprocedural complications, pregnancy outcome, and postnatal survival at hospital discharge were recorded and analyzed. Results A total of 106 pregnancies were treated during the study period. Median gestational age at laser therapy was 19.7 weeks (range, 15.1-27.6 weeks). There was postoperative recurrence of twin-to-twin transfusion syndrome or the development of twin anemia-polycythemia sequence in 2 (1.9%) and 2 (1.9%) cases, respectively. The survival rates of both and at least 1 twin were 56.6% and 83.0%, respectively. Donor survival was significantly lower compared with the recipient co-twin (64.2% vs 75.5%, respectively; P <.05). The rate of fetal death, which was the most common cause of twin loss, was significantly higher in donors compared with recipient fetuses (23.6% vs 10.4%, respectively; P <.05). In cases with absent or reversed end-diastolic velocity in the donor umbilical artery, dual and donor survival rates were significantly lower compared with the remaining twin-to-twin transfusion syndrome pregnancies (40.0% vs 64.8% and 40.0% vs 76.1%, respectively; P <.05). There were no significant differences between the 2 groups in the survival of at least 1 twin and in the recipient survival. Conclusions Endoscopic equatorial laser therapy was associated with a survival of both and at least 1 twin of approximately 55% and 83%, respectively, with a low rate of recurrent twin-to-twin transfusion syndrome and twin anemia-polycythemia sequence. In addition, the preoperative finding of abnormal donor umbilical artery Doppler on ultrasound identified a subgroup of twin-to-twin transfusion syndrome pregnancies with a lower dual survival rate caused by increased intrauterine deaths of donor twins

Calcium-sensing receptor antagonism or lithium treatment ameliorates aminoglycoside-induced cell death in renal epithelial cells

AbstractThe aminoglycoside antibiotic gentamicin elicits proximal tubular toxicity and cell death. In calcium-sensing receptor (CaR)-transfected HEK-293 (CaR-HEK) cells and CaR-expressing proximal tubule-derived opossum kidney (OK) cells, chronic gentamicin treatment elicits dose-dependent, caspase-mediated apoptotic cell death. Here we investigated whether the renal cell toxicity of the CaR agonist gentamicin could be prevented by CaR antagonism or by lithium cotreatment which may interfere with receptor-mediated signalling. Chronic treatment of OK and CaR-HEK cells with low concentrations of gentamicin elicited cell death, an effect that was ameliorated by cotreatment with the CaR negative allosteric modulator (calcilytic) NPS-89636. This calcilytic also attenuated CaR agonist-induced ERK activation in these cells. In addition, 1 mM LiCl, equivalent to its therapeutic plasma concentration, also inhibited gentamicin-induced toxicity in both cell types. This protective effect of lithium was not due to the disruption of phosphatidylinositol-mediated gentamicin uptake as the cellular entry of Texas red-conjugated gentamicin into OK and CaR-HEK cells was unchanged by lithium treatment. However, the protective effect of lithium was mimicked by glycogen synthase 3β inhibition. Together, these data implicate CaR activation and a lithium-inhibitable signalling pathway in the induction of cell death by gentamicin in renal epithelial cells in culture

Fluctuations of company yearly profits versus scaled revenue: Fat tail distribution of Levy type

We analyze annual revenues and earnings data for the 500 largest-revenue U.S. companies during the period 1954-2007. We find that mean year profits are proportional to mean year revenues, exception made for few anomalous years, from which we postulate a linear relation between company expected mean profit and revenue. Mean annual revenues are used to scale both company profits and revenues. Annual profit fluctuations are obtained as difference between actual annual profit and its expected mean value, scaled by a power of the revenue to get a stationary behavior as a function of revenue. We find that profit fluctuations are broadly distributed having approximate power-law tails with a Levy-type exponent $\alpha \simeq 1.7$, from which we derive the associated break-even probability distribution. The predictions are compared with empirical data.Comment: 6 pages, 6 figure