Theoretical guidelines for editing ecological communities.

Having control over species abundances and community resilience is of great interest for experimental, agricultural, industrial and conservation purposes. Here, we theoretically explore the possibility of manipulating ecological communities by modifying pairwise interactions. Specifically, we establish which interaction values should be modified, and by how much, in order to alter the composition or resilience of a community towards a favorable direction. While doing so, we also take into account the experimental difficulties in making such modifications by including in our optimization process, a cost parameter, which penalizes large modifications. In addition to prescribing what changes should be made to interspecies interactions given some modification cost, our approach also serves to establish the limits of community control, i.e. how well can one approach an ecological goal at best, even when not constrained by cost.

Chrysosplenol-C Increases Contraction by Augmentation of Sarcoplasmic Reticulum Ca2+ Loading and Release via Protein Kinase C in Rat Ventricular Myocytes.

Naturally found chrysosplenol-C (4',5,6-trihydroxy-3,3',7-trimethoxyflavone) increases the contractility of cardiac myocytes independent of ß-adrenergic signaling. We investigated the cellular mechanism for chrysosplenol-C-induced positive inotropy. Global and local Ca2+ signals, L-type Ca2+ current (ICa), and contraction were measured from adult rat ventricular myocytes using two-dimensional confocal Ca2+ imaging, the whole-cell patch-clamp technique, and video-edge detection, respectively. Application of chrysosplenol-C reversibly increased Ca2+ transient magnitude with a maximal increase of ∼55% within 2- to 3-minute exposures (EC50 ≅ 21 µM). This chemical did not alter ICa and slightly increased diastolic Ca2+ level. The frequency and size of resting Ca2+ sparks were increased by chrysosplenol-C. Chrysosplenol-C significantly increased sarcoplasmic reticulum (SR) Ca2+ content but not fractional release. Pretreatment of protein kinase C (PKC) inhibitor but not Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor abolished the stimulatory effects of chrysosplenol-C on Ca2+ transients and Ca2+ sparks. Chrysosplenol-C-induced positive inotropy was removed by the inhibition of PKC but not CaMKII or phospholipase C. Western blotting assessment revealed that PKC-δ protein level in the membrane fractions significantly increase within 2 minutes after chrysosplenol-C exposure with a delayed (5-minute) increase in PKC-α levels in insoluble membrane. These results suggest that chrysosplenol-C enhances contractility via PKC (most likely PKC-δ)-dependent enhancement of SR Ca2+ releases in ventricular myocytes. SIGNIFICANCE STATEMENT: Study shows that chrysosplenol-C, a natural flavone showing a positive inotropic effect, increases SR Ca2+ releases on depolarizations and Ca2+ sparks with an increase of SR Ca2+ loading but not L-type Ca2+ current in ventricular myocytes. Chrysosplenol-C-induced enhancement in contraction is eliminated by PKC inhibition, and it is associated with redistributions of PKC to the membrane. These indicate that chrysosplenol-C enhances contraction via PKC-dependent augmentations of SR Ca2+ release and Ca2+ loading during action potentials.

Extinction in complex communities as driven by adaptive dynamics.

In a complex community, species continuously adapt to each other. On rare occasions, the adaptation of a species can lead to the extinction of others, and even its own. 'Adaptive dynamics' is the standard mathematical framework to describe evolutionary changes in community interactions, and in particular, predict adaptation driven extinction. Unfortunately, most authors implement the equations of adaptive dynamics through computer simulations that require assuming a large number of questionable parameters and fitness functions. In this study, we present analytical solutions to adaptive dynamics equations, thereby clarifying how outcomes depend on any computational input. We develop general formulas that predict equilibrium abundances over evolutionary time scales. Additionally, we predict which species will go extinct next, and when this will happen.

High resolution whole brain diffusion imaging at 7T for the Human Connectome Project.

Mapping structural connectivity in healthy adults for the Human Connectome Project (HCP) benefits from high quality, high resolution, multiband (MB)-accelerated whole brain diffusion MRI (dMRI). Acquiring such data at ultrahigh fields (7T and above) can improve intrinsic signal-to-noise ratio (SNR), but suffers from shorter T2 and T2(⁎) relaxation times, increased B1(+) inhomogeneity (resulting in signal loss in cerebellar and temporal lobe regions), and increased power deposition (i.e. specific absorption rate (SAR)), thereby limiting our ability to reduce the repetition time (TR). Here, we present recent developments and optimizations in 7T image acquisitions for the HCP that allow us to efficiently obtain high quality, high resolution whole brain in-vivo dMRI data at 7T. These data show spatial details typically seen only in ex-vivo studies and complement already very high quality 3T HCP data in the same subjects. The advances are the result of intensive pilot studies aimed at mitigating the limitations of dMRI at 7T. The data quality and methods described here are representative of the datasets that will be made freely available to the community in 2015.

Evaluation of intra-renal oxygenation during water diuresis: a time-resolved study using BOLD MRI.

Hypoxia of the renal medulla is a possible precursor to the onset of acute renal failure in humans and therefore an understanding of the factors influencing the oxygenation status within the renal medulla is very important. Blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) has been shown to non-invasively evaluate intra-renal oxygenation levels of the renal medulla in humans. A newly implemented three-dimensional (3-D) multiple gradient-recalled echo sequence, which permits examination of temporal responses to physiological or pharmacological stimuli, was used to monitor changes in intra-renal oxygenation status during water diuresis. Five healthy, young subjects (22+/-1.2 years) took part in the study. BOLD MRI data were acquired before and after water loading. Studies were repeated on a separate day after the subjects were pretreated with naproxen. Water diuresis significantly improved renal medullary oxygenation levels in all subjects (pre-waterload=30.3 1/s vs post-waterload 22.8 1/s); however, the temporal response was found to be subject dependent. In the presence of cyclooxygenase (COX) inhibition by naproxen, the improvement in oxygenation during water diuresis was completely abolished (pre-waterload=27.5 1/s vs post-waterload 28.5 1/s). Monitoring of temporal responses for the first time during water loading allowed for an appreciation of subject dependence. Comparison of the temporal response in terms of slopes demonstrated a significant difference between the waterload studies with and without naproxen (with naproxen=0.056 1/(s min) vs without naproxen=0.25 1/(s min)). The observed effects of naproxen were consistent with previous findings with COX inhibition.

DNA vaccination encoding glutamic acid decarboxylase can enhance insulitis and diabetes in correlation with a specific Th2/3 CD4 T cell response in non-obese diabetic mice.

DNA vaccination encoding beta cell autoantigens has been shown very recently to prevent type I diabetes in non-obese diabetic (NOD) mice. However, DNA vaccination encoding microbial or reporter antigens is known to induce specific long-lasting CD4 Th1 and strong cytolytic CD8 T cell responses. As this immune phenotype is associated strongly with beta cell destruction leading to diabetes, we have chosen to study the effects of plasmids encoding glutamic acid decarboxylase (GAD), a crucial beta cell autoantigen, in female NOD mice that developed a 'moderate' diabetes incidence. In the present study, 3-week-old female NOD mice were vaccinated twice in tibialis muscles with plasmid-DNA encoding 65-kDa GAD or betagalactosidase. In GAD-DNA immunized mice, diabetes cumulative incidence (P < 3.10(-3)) and insulitis (P < 7.10(-3)) increased significantly. Simultaneously, DNA immunization induced GAD-specific CD4 T cells secreting interleukin (IL)-4 (P < 0.05) and transforming growth factor (TGF)-beta (P = 0.03). These cells were detected in spleen and in pancreatic lymph nodes. Furthermore, vaccination produced high amounts of Th2 cytokine-related IgG1 (P < 3.10(-3)) and TGF-beta-related IgG2b to GAD (P = 0.015). Surprisingly, diabetes onset was correlated positively with Th2-related GAD-specific IgG1 (P < 10(-4)) and TGF-beta-related IgG2b (P < 3.10(-3)). Moreover, pancreatic lesions resembled Th2-related allergic inflammation. These results indicate, for the first time, that GAD-DNA vaccination could increase insulitis and diabetes in NOD mice. In addition, our study suggests that Th2/3 cells may have potentiated beta cell injury.

Possible role of disturbed Na+ homeostasis in mouse vas deferens contractile hyperreactivity after immunological sensitization.

In the present study we have investigated the involvement of sensitized mice immunoglobulins and some electrophysiological alterations that participate to the antigenic sensitization-induced hyperreactivity of isolated mouse vas deferens. Active sensitization was performed by subcutaneous injection of egg albumen. Contractile responses to noradrenaline were isometrically recorded in the isolated vas deferens. Low external Na(+)-induced contractions and rapid cooling contractures were evaluated. Resting membrane potential (Er) and intracellular Na activity were measured in control and actively sensitized vas deferens by using conventional KCl-filled and Na(+)-sensitive microelectrodes respectively. Active sensitization-induced hyperreactivity to noradrenaline was reproduced by in vitro passive sensitization of control vas deferens with sensitized mice immunoglobulins. The inhibition of the nitric oxide synthesis by N-nitro-L-arginine methyl ester (L-NAME) did not change control vas deferens reactivity in vitro to noradrenaline and acetylcholine. Rapid cooling contractures, performed after lowering external Na+ concentration, were not altered by active sensitization. However, sensitization increased significantly the strength of the low external Na+-induced contractions. In control vas deferens Er was a mean of -49.2+/-0.3 mV (mean+/-SEM). Sensitization resulted in reduction of Er by 14 mV. In sensitized preparations, relative insensitivity of Er to ouabain, external K+ removal and cooling were observed. The intracellular Na+ activity was increased by about 40% in sensitized vas deferens. It is concluded that sensitization-induced hyperreactivity is mediated by immunoglobulins and produced smooth muscle cells depolarisation. The low Er of sensitized muscle may be partly the result of an increase in membrane permeability to Na+ which could interfere with intracellular Ca2+ homeostasis.

Loss of nitric oxide release in passively sensitized guinea-pig aorta with purified immunoglobulin G1.

BACKGROUND: Vascular hyperresponsiveness can be reproduced by in vitro passive sensitization of isolated aorta with immunoglobulin G1 (IgG1) taken from ovalbumen-sensitized BFA guinea-pig. OBJECTIVE: The aim of the present work was to investigate the role of nitric oxide in the sensitization-induced alteration of the contractile and relaxant responses of guinea-pig aorta to noradrenaline (NA) and acetylcholine (ACh), respectively. METHODS: Cumulative concentration-response curves to NA or ACh were established before and after IgG1 sensitization and then after successive treatments. RESULTS: IgG1 in vitro passive sensitization of aorta caused a significant hyperreactivity to NA and completely inhibited the relaxation to ACh. After sensitization, the addition of an intact aortic ring (with endothelium) in the organ chamber restored the maximal response to NA and ACh close to control but was ineffective in the presence of hemoglobin. The restoration of the control reactivity to NA was also inhibited in the presence of L-NAME or when the added aortic ring was endothelium-denuded. Moreover, L-arginine, a nitric oxide (NO) precursor, was able to restore the control reactivity to NA. CONCLUSION: The present results show that IgG1 in vitro sensitization induced a loss of NO release from the vascular endothelium. This loss of NO probably plays a great role in vascular hyperreactivity by increasing the contractile response and decreasing the relaxant response to mediators and would be a component of allergic diseases pathogenesis.

Effect of guinea-pig purified immunoglobulin G1 on the responsiveness of tracheal, aortic, vas deferens and ileum smooth muscles.

BACKGROUND: Smooth muscles hyperresponsiveness is a common feature in anaphylaxis and allergic diseases. OBJECTIVE: The aim of the present work was to investigate the effect of in vitro passive sensitization with highly purified immunoglobulin G1 (IgG1) on the responsiveness of tracheal, aortic, vas deferens and ileum smooth muscles. METHODS: Firstly, IgG1, obtained from actively sensitized BFA guinea-pigs, was purified by Protein A-Sepharose column and characterized by enzyme-linked immunosorbent assay (ELISA) and immunoelectrophoresis analysis. Concentration-response curves to spasmogens (acetylcholine for trachea and vas deferens, noradrenaline for aorta and histamine for ileum) were established before and after in vitro passive sensitization with IgG1. RESULTS: Contractile responses and maximal contractions were significantly enhanced after passive sensitization for all the organs. Maximal contractions were significantly increased in the trachea (+46.7%), aorta (+51%), vas deferens (+114.2%) and ileum (+117.2%). At the end of the experiments, the application of the sensitizing antigen induced a significant Schultz-Dale reaction of the smooth muscles. CONCLUSION: The present results show that the in vitro application of purified IgG1 can produce non-specific smooth muscle hyperreactivity and hypersensitivity. So, IgG1 can be considered as the main factor involved in the genesis of sensitization-induced hyperresponsiveness, and probably play a great role in hyperreactivity observed during allergic diseases and anaphylaxis.

Effect of moderate cooling on contractile responses in mouse vas deferens and its relation to calcium.

Isolated mouse vas deferens preparations were used to study the effect of temperature on noradrenaline-induced contractions. Preparations were suspended in the organ bath containing Krebs-Henseleit solution for isometric tension recording. Contractile responses to noradrenaline were investigated in the mouse vas deferens after moderate cooling from 37 to 26 or 22 degrees C. A significant increase of the phasic contractions to noradrenaline was observed at 26 or 22 degrees C compared with responses obtained at 37 degrees C (about 12.3 and 35.6% increase at 26 and 22 degrees C, respectively). The secondary noradrenaline-induced sustained contraction was also significantly enhanced after moderate cooling to 26 degrees C. The potentiation of noradrenaline-induced contraction at 26 degrees C remained in a Ca(2+)-free EGTA (1 mM)-containing solution. However, sustained contraction was suppressed after removal of the calcium from the medium at 37 and 26 degrees C. Contraction to caffeine was significantly enhanced at 22 degrees C compared with 37 degrees C. By contrast, barium chloride-induced contraction of the vas deferens was markedly decreased after moderate cooling to 22 degrees C. In the presence of ouabain (0.1 mM), the noradrenaline-induced peak contraction was significantly increased at 37 degrees C. However, potentiation of the noradrenaline response at 22 degrees C was unaffected by the Na+/K+ pump inhibitor. Noradrenaline-induced peak contractions were depressed in the presence of vanadate (1 mM) and cyclopiazonic acid (10 microM), two Ca(2+)-ATPase inhibitors, at 37 degrees C and also at 22 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Strain-related differences in the tracheal responsiveness of sensitized guinea pig.

The purpose of this study was to evaluate the strain-related differences in tracheal hyperresponsiveness in control and egg albumen-sensitized guinea pigs. Concentration-response curves to acetylcholine and barium chloride were established from tracheal rings of Dunkin-Hartley and BFA strain guinea pigs. In the Dunkin-Hartley strain, sensitization did not significantly increase the tracheal responsiveness to acetylcholine and barium chloride. By contrast, in the BFA strain, significant sensitization-induced hyperreactivity was achieved as the maximal contractions induced by acetylcholine and barium chloride, were enhanced from 6.5 +/- 1.2 and 3.2 +/- 0.4 mN in control to 10.0 +/- 1.4 and 5.6 +/- 0.8 mN, respectively, in sensitized animals. However, antigen challenge, performed in vitro, exhibited a similar amplitude of contraction in tracheal rings from both strains (Dunkin-Hartley 5.1 +/- 0.8 mN; BFA 5.9 +/- 0.5 mN). Finally, while the two guinea-pig strains developed specific sensitization to allergen, only tracheal rings from the BFA strain developed hyperresponsiveness to acetylcholine and barium chloride. The strain-related difference appears to be partly explained by a lower basal reactivity in the BFA strain both acetylcholine (Em 7.3 +/- 1.7 and 6.5 +/- 1.2 mN for Dunkin-Hartley and BFA, respectively) and barium chloride (Em 9.4 +/- 2.6 and 3.2 +/- 0.4 mN for Dunkin-Hartley and BFA, respectively). As the same procedure of sensitization provides different results in the genesis of hyperreactivity between the two guinea-pig strains used for asthma models, the BFA guinea-pig strain seems to be a better model because sensitized non-challenged animals could easily be dissociated from control ones, similar to that which occurs in asthmatic patients during provocation tests with cholinergic drugs.

Enhancement of the responsiveness of vas deferens and ileum smooth muscle in sensitized guinea pigs: in vitro study.

Changes in the reactivity of the ileum (to histamine and barium chloride) and vas deferens (to acetylcholine and barium chloride), isolated from actively egg albumen-sensitized guinea pigs, have been investigated. The study was performed on 2 guinea pig strains: the Dunkin-Hartley strain, usually used as an airway allergic model, and the BFA strain. In actively sensitized guinea pigs of both strains, concentration-response curves exhibited a significant dose-dependent upward shift compared to those obtained in control guinea pigs. The maximal contraction strength calculated from these curves was significantly enhanced in both sensitized guinea pig strains, without a change in EC50 values. This study showed that the active antigen sensitization procedure involved several smooth muscle functions, and not exclusively the trachea.

Flow field mapping by multi-zone adiabatic passage excitation.

This paper describes a robust method for flow field mapping by multi-zone adiabatic fast passage (AFP). It provides a quick and simple way to simultaneously acquire flow profiles at several locations and arbitrary orientations inside the field-of-view. The flow profile is the time-averaged evolution of the labeled flowing material. Results obtained using a carotid bifurcation and jet phantoms are similar to the previous experimental studies employing Laser Doppler Anemometry (LDA), and other flow visualization techniques. In addition, the preliminary results obtained with a human volunteer support the feasibility of the technique for in vivo flow quantification.