Ecosystem effects of partial fish migration in lakes

Migration is a widespread phenomenon in many ecosystems. Most often, studies on migration have focused on how migration strategies are dependent on ecological parameters, but little attention has been paid to the top-down effect of migration on ecosystem processes. Cyprinid fish in many European lakes undergo partial migration, where a part of the population leaves the lake and enters streams for the winter. In this study, we model the effect of partial migration by fish on lower trophic levels in a lake ecosystem. Our results suggest that spring phyto- and zooplankton dynamics, including occurrences of clear-water phases, can be related to the timing and magnitude of partial migration of planktivorous fish. From our results we conclude that partial migration can influence the dynamics of lower trophic levels in the ecosystem. Furthermore, we hypothesize that partial migration may affect the stability of alternative stable states and transitions between them.     

Reversible alteration of nanosecond reduction of chlorophyll a+II in inside-out thylakoids correlated to inhibition and reconstitution of oxygen-evolving activity

The electron donation to Chl a⁺_II has been studied by measurement of absorbance changes at 824 nm under repetitive excitation conditions. For untreated inside-out thylakoids the electron donation was dominated by 35 and 220 ns kinetics. After salt-washing, both oxygen-evolution and nanosecond phases decreased drastically with corresponding increase in the microsecond time range. On addition of a purified 23 kDa protein, a restoration of the nanosecond phases up to 75% of the orginal level was obtained concomitant with a corresponding restoration of oxygen evolution. The results are consistent with a function of the 23 kDa protein at the oxidizing side of Photosystem II and that the nanosecond donation to Chl-a⁺_II is coupled to the natural path of electrons from water.     

Cost of In-Patient Care over 7 Years among Surgically and Conventionally Treated Obese Patients

Objective: Bariatric surgery improves cardiovascular risk factors and quality of life, but few studies have directly addressed the relation between obesity treatment and hospitalization costs. This prospective controlled study compares in-patient care between surgically and conventionally treated obese patients. Research Methods and Procedures: A total of 962 surgically and conventionally treated obese patients from the intervention study, Swedish Obese Subjects, were followed for 6 years. Changes in days of hospitalization and hospitalization costs were analyzed. Information on hospitalizations for each subject were obtained from the Swedish Hospital Discharge Register. Results: After 6 years, weight change was −16.7% in the surgical group and +0.9% in the control group (p < 0.0001). The cumulated hospital stay over 6 years was 23.4 days in the surgical group and 6.9 days in the control group (p < 0.0001). The average hospital cost for the surgical intervention was US$4300. Incremental costs that could be attributable to obesity surgery averaged US$1200 per year. After exclusion of hospitalizations for the surgical intervention and conditions common after bariatric surgery, there were no significant differences between the groups in number of hospital days or hospitalization costs. Discussion: Our experience from bariatric surgery indicates that average weight reductions of 16% will not reduce hospitalization costs over 6 years. Costs of bariatric surgery are limited and seem to be motivated given the marked improvements of cardiovascular risk factors, cardiac structure, and function and health-related quality of life.     

Susceptibility Loci for Adiposity Phenotypes on 8p, 9p,and 16q in American Samoa and Samoa

Obesity is a complex phenotype affected by genetic and environmental influences such as sociocultural factors and individual behaviors. Previously, we performed two separate genome‐wide investigations for adiposity‐related traits (BMI, percentage body fat (%BF), abdominal circumference (ABDCIR), and serum leptin and serum adiponectin levels) in families from American Samoa and in families from Samoa. The two polities have a common evolutionary history but have lately been influenced by variations in economic development, leading to differences in income and wealth and in dietary and physical activity patterns. We now present a genome‐wide linkage scan of the combined samples from the two polities. We adjust for environmental covariates, including polity of residence, education, cigarette smoking, and farm work, and use variance component methods to calculate univariate and bivariate multipoint lod scores. We identified a region on 9p22 with genome‐wide significant linkage for the bivariate phenotypes ABDCIR–%BF (1‐d.f. lod 3.30) and BMI–%BF (1‐d.f. lod 3.31) and two regions with genome‐wide suggestive linkage on 8p12 and 16q23 for adiponectin (lod 2.74) and the bivariate phenotype leptin‐ABDCIR (1‐d.f. lod 3.17), respectively. These three regions have previously been reported to be linked to adiposity‐related phenotypes in independent studies. However, the differences in results between this study and our previous polity‐specific studies suggest that environmental effects are of different importance in the samples. These results strongly encourage further genetic studies of adiposity‐related phenotypes where extended sets of carefully measured environmental factors are taken into account.     

Semiquantitative estimations of quinacrine fluorescence in intestinal nerve fibres

Summary Quinacrine has been shown to bind selectively to a population of nerves and ganglion cells in the mouse, rat and guinea-pig gut. In the present report a method for semiquantitation of nervous quinacrine contents using semiquantitative estimations of fluorescence intensity and nerve fibre density is presented and evaluated. Estimation of fluorescence intensity and nerve fibre density is based on a scale with eleven steps from 0 to 5. Preparations were incubated in ¹⁴C-labelled quinacrine hydrochloride. Reliability of the scale was expressed as the correlation coefficient between two consecutive blind estimations of the same preparations with recoding and remixing specimens in between. This correlation was found to be 0.95 or higher. Validity was expressed as the correlation between the semiquantitative estimations and ¹⁴C-quinacrine uptake measurements into the same specimens. Also this correlation was found to be strongly positive.It was concluded that nervous quinacrine content and amount of quinacrine binding nerves can be reliably estimated by fluorescence microscopy.     

Computational modelling of the open-state Kv1.5 ion channel block by bupivacaine

Binding of R(+)-bupivacaine to open-state homology models of the mammalian K_v1.5 membrane ion channel is studied using automated docking and molecular dynamics (MD) methods. Homology models of K_v1.5 are built using the 3D structures of the KcsA and MthK channels as a template. The packing of transmembrane (TM) α-helices in the KcsA structure corresponds to a closed channel state. Opening of the channel may be reached by a conformational transition yielding a bent structure of the internal S6 helices. Our first model of the K_v open state involves a PVP-type of bending hinge in the internal helices, while the second model corresponds to a Gly-type of bending hinge as found in the MthK channel. Ligand binding to these models is probed using the common local anaesthetic bupivacaine, where blocker binding from the intracellular side of the channel is considered. Conformational properties and partial atomic charges of bupivacaine are determined from quantum mechanical HF/6-31G* calculations with inclusion of solvent effects. The automated docking and MD calculations for the PVP-bend model predict that bupivacaine could bind either in the central cavity or in the PVP region of the channel pore. Linear interaction energy (LIE) estimates of the binding free energies for bupivacaine predict strongest binding to the PVP region. Surprisingly, no binding is predicted for the Gly-bend model. These results are discussed in light of electrophysiological data which show that the K_v1.5 channel is unable to close when bupivacaine is bound.     

Potential Distribution of Dengue Fever Under Scenarios of Climate Change and Economic Development

Dengue fever is the most important viral vector-borne disease with ~50 million cases per year globally. Previous estimates of the potential effect of global climate change on the distribution of vector-borne disease have not incorporated the effect of socioeconomic factors, which may have biased the results. We describe an empirical model of the current geographic distribution of dengue, based on the independent effects of climate and gross domestic product per capita (GDPpc, a proxy for socioeconomic development). We use the model, along with scenario-based projections of future climate, economic development, and population, to estimate populations at risk of dengue in the year 2050. We find that both climate and GDPpc influence the distribution of dengue. If the global climate changes as projected but GDPpc remained constant, the population at risk of dengue is estimated to increase by about 0.28 billion in 2050. However, if both climate and GDPpc change as projected, we estimate a decrease of 0.12 billion in the population at risk of dengue in 2050. Empirically, the geographic distribution of dengue is strongly dependent on both climatic and socioeconomic variables. Under a scenario of constant GDPpc, global climate change results in a modest but important increase in the global population at risk of dengue. Under scenarios of high GDPpc, this adverse effect of climate change is counteracted by the beneficial effect of socioeconomic development.