Continuous ambulatory peritoneal dialysis (CAPD) is used to treat end-stage renal failure in an increasing number of patients. CAPD has an advantage over hemodialysis in that it allows patients greater freedom to perform daily activities; it also provides other clinical benefits. However, the long-term effectiveness of CAPD is limited by complications, which have various causes. Complications with an infectious cause include bacterial peritonitis, tuberculous peritonitis, and infections of the catheter exit site and tunnel. Noninfectious complications include catheter dysfunction, dialysate leakage, hernias, and sclerosing encapsulating peritonitis. Many imaging modalities-radiography, ultrasonography, peritoneal scintigraphy, computed tomography (CT), and magnetic resonance (MR) imaging-are useful for characterizing these complications. CT peritoneography and MR peritoneography are techniques specifically suited to this purpose. Imaging plays a critical role in ensuring that complications are detected early and managed appropriately.
1. Anadromous salmon transport marine-derived nutrients and carbon to freshwater and riparian ecosystems upon their return to natal spawning systems. The ecological implications of these subsidies on the trophic ecology of resident fish remain poorly understood despite broad recognition of their potential importance. 2. We studied the within-year changes in the ration size, composition and stable isotope signature of the diets of two resident salmonids (rainbow trout, Oncorhynchus mykiss; Arctic grayling, Thymallus arcticus) before and after the arrival of sockeye salmon (Oncorhynchus nerka) to their spawning grounds in the Bristol Bay region of southwest Alaska. 3. Ration size and energy intake increased by 480-620% for both species after salmon arrived. However, the cause of the increases differed between species such that rainbow trout switched to consuming salmon eggs, salmon flesh and blowflies that colonized salmon carcasses, whereas grayling primarily ate more benthic invertebrates that were presumably made available because of physical disturbances by spawning salmon. 4. We also observed an increase in the d 15 N of rainbow trout diets post-salmon, but not for grayling. This presumably led to the observed increase in the d 15 N of rainbow trout with increasing body mass, but not for grayling. 5. Using a bioenergetics model, we predicted that salmon-derived resources contributed a large majority of the energy necessary for growth in this resident fish community. Furthermore, the bioenergetics model also showed how seasonal changes in diet affected the stable isotope ratios of both species. These results expand upon a growing body of literature that highlights the different pathways whereby anadromous salmon influence coastal ecosystems, particularly resident fish.
The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we describe the effects of ocean acidification on an upwelling system that already experiences inherently low pH conditions, the California Current. We used an end-to-end ecosystem model (Atlantis), forced by downscaled global climate models and informed by a meta-analysis of the pH sensitivities of local taxa, to investigate the direct and indirect effects of future pH on biomass and fisheries revenues. Our model projects a 0.2-unit drop in pH during the summer upwelling season from 2013 to 2063, which results in wide-ranging magnitudes of effects across guilds and functional groups. The most dramatic direct effects of future pH may be expected on epibenthic invertebrates (crabs, shrimps, benthic grazers, benthic detritivores, bivalves), and strong indirect effects expected on some demersal fish, sharks, and epibenthic invertebrates (Dungeness crab) because they consume species known to be sensitive to changing pH. The model's pelagic community, including marine mammals and seabirds, was much less influenced by future pH. Some functional groups were less affected to changing pH in the model than might be expected from experimental studies in the empirical literature due to high population productivity (e.g., copepods, pteropods). Model results suggest strong effects of reduced pH on nearshore state-managed invertebrate fisheries, but modest effects on the groundfish fishery because individual groundfish species exhibited diverse responses to changing pH. Our results provide a set of projections that generally support and build upon previous findings and set the stage for hypotheses to guide future modeling and experimental analysis on the effects of OA on marine ecosystems and fisheries.
To describe temporal dynamics of stable isotope ratios in fishes, we developed a bioenergetics-based model that links isotope ratios to growth, as influenced by fish size, temperature, diet, and prey quality. The model includes error terms for isotope ratios, diet proportions, and fractionation. The model accurately predicted temporal δ 15 N dynamics of lake trout (Salvelinus namaycush) in a diet-switch experiment but was less successful for δ 13 C, possibly because of variable fractionation. The model was then used in three heuristic applications. In a diet-validation scenario, a model derived from limited knowledge of rainbow smelt (Osmerus mordax) diet reasonably estimated δ 13 C and δ 15 N compared with a null model but inaccurately estimated prey consumption. In a scenario where adult lake trout briefly cannibalized stocked lake trout fingerlings, the detectability of a cannibalism-induced δ 15 N increase depended on predator size, duration of cannibalism, and sample size. In a scenario where seasonal isotopic variability occurred at the base of a food web, variation propagated to higher trophic levels depended on consumer size and diet. Our approach is most valuable when used to examine multiple diet combinations that produce observed stable isotope ratios; one can then identify the most reasonable diets through field tests or other observations. Résumé : Dans le but de décrire la dynamique temporelle des rapports d'isotopes stables chez les poissons, nous avons mis au point un modèle basé sur la bioénergétique qui relie les rapports isotopiques à la croissance, elle-même influencée par la taille du poisson, la température, le régime alimentaire et la qualité des proies. Le modèle comprend des termes d'erreur pour les rapports isotopiques, les proportions du régime alimentaire et le fractionnement. Le modèle a permis de prédire avec précision la dynamique temporelle du δ 15 N chez le Touladi (Salvelinus namaycush) dans une expérience de changement de régime; il a été moins efficace dans la prédiction de δ 13 C, peut-être à cause du fractionnement variable. Le modèle a aussi servi dans trois applications heuristiques. Dans un scénario de validation du régime alimentaire, un modèle élaboré à partir d'une connaissance limitée du régime alimentaire de l'Éperlan arc-enciel (Osmerus mordax) a permis l'estimation adéquate de δ 13 C et de δ 15 N par rapport à un modèle nul, mais n'a pu déterminer correctement la consommation des proies. Dans un second scénario dans lequel des touladis se sont, pendant une courte période, alimentés par cannibalisme d'estivaux de touladis ensemencés, la possibilité de détection de l'augmentation de δ 15 N reliée au cannibalisme dépendait de la taille du prédateur, de la durée du cannibalisme et de la taille de l'échantillon. Dans un dernier scénario où la variation isotopique saisonnière se produisait à la base du réseau alimentaire, la variation qui se propageait aux niveaux trophiques supérieurs dépendait de la taille du consommateur et de son régime alimentaire. C'est dans l'exame...
Ultrasound microbubble contrast agents are effective and safe echo enhancers. An ingenious array of methods are employed to achieve stability and provide a clinically useful enhancement period. Microbubbles enhance ultrasound signals by up to 25 dB (greater than 300-fold increase) due to resonant behaviour. This is used to rescue failed Doppler studies and may be extended to image the microcirculation of tumours and the myocardium using non-linear modes. Functional studies open up a whole range of applications by using a variety of active and passive quantitation techniques to derive indices from the transit of contrast through a tissue of interest. This has been especially successful in the detection of liver metastases and cirrhosis and shows great promise as a clinical tool. It also has great potential in measuring microcirculatory flow velocity. The demonstration that some microbubbles are not just pure blood pool agents but have a hepatosplenic specific phase has extended the versatility of ultrasound. Imaging of this stationary phase with non-linear modes such as phase inversion and stimulated acoustic emission, has improved the sensitivity and specificity of ultrasound in the detection and characterisation of focal liver lesions to rival that of CT and MR.
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