Do herbivorous minnows have “plug-flow reactor” guts? Evidence from digestive enzyme activities, gastrointestinal fermentation, and luminal nutrient concentrations

Few investigations have empirically analyzed fish gut function in the context of chemical reactor models. In this study, digestive enzyme activities, levels of gastrointestinal fermentation products [short chain fatty acids (SCFA)], luminal nutrient concentrations, and the mass of gut contents were measured along the digestive tract in herbivorous and carnivorous minnows to ascertain whether their guts function as “plug-flow reactors” (PFRs). Four of the species, Campostoma anomalum, C. ornatum, C. oligolepis, and C. pauciradii, are members of a monophyletic herbivorous clade, whereas the fifth species, Nocomis micropogon, is a carnivore from an adjacent carnivorous clade. In the context of a PFR model, the activities of amylase, trypsin and lipase, and the concentrations of glucose, protein, and lipid were predicted to decrease moving from the proximal to the distal intestine. I found support for this as these enzyme activities and nutrient concentrations generally decreased moving distally along the intestine of the four Campostoma species. Furthermore, gut content mass and the low SCFA concentrations did not change (increase or decrease) along the gut of any species. Combined with a previous investigation suggesting that species of Campostoma have rapid gut throughput rates, the data presented here generally support Campostoma as having guts that function as PFRs. The carnivorous N. micropogon showed some differences in the measured parameters, which were interpreted in the contexts of intake and retention time to suggest that PFR function breaks down in this carnivorous species

Phosphatidylserine Targets Single-Walled Carbon Nanotubes to Professional Phagocytes In Vitro and In Vivo

Broad applications of single-walled carbon nanotubes (SWCNT) dictate the necessity to better understand their health effects. Poor recognition of non-functionalized SWCNT by phagocytes is prohibitive towards controlling their biological action. We report that SWCNT coating with a phospholipid “eat-me” signal, phosphatidylserine (PS), makes them recognizable in vitro by different phagocytic cells - murine RAW264.7 macrophages, primary monocyte-derived human macrophages, dendritic cells, and rat brain microglia. Macrophage uptake of PS-coated nanotubes was suppressed by the PS-binding protein, Annexin V, and endocytosis inhibitors, and changed the pattern of pro- and anti-inflammatory cytokine secretion. Loading of PS-coated SWCNT with pro-apoptotic cargo (cytochrome c) allowed for the targeted killing of RAW264.7 macrophages. In vivo aspiration of PS-coated SWCNT stimulated their uptake by lung alveolar macrophages in mice. Thus, PS-coating can be utilized for targeted delivery of SWCNT with specified cargoes into professional phagocytes, hence for therapeutic regulation of specific populations of immune-competent cells

Internet-Based Attention Bias Modification for Social Anxiety : A Randomised Controlled Comparison of Training towards Negative and Training Towards Positive Cues

Biases in attention processes are thought to play a crucial role in the aetiology and maintenance of Social Anxiety Disorder (SAD). The goal of the present study was to examine the efficacy of a programme intended to train attention towards positive cues and a programme intended to train attention towards negative cues. In a randomised, controlled, double-blind design, the impact of these two training conditions on both selective attention and social anxiety were compared to that of a control training condition. A modified dot probe task was used, and delivered via the internet. A total of 129 individuals, diagnosed with SAD, were randomly assigned to one of these three conditions and took part in a 14-day programme with daily training/control sessions. Participants in all three groups did not on average display an attentional bias prior to the training. Critically, results on change in attention bias implied that significantly differential change in selective attention to threat was not detected in the three conditions. However, symptoms of social anxiety reduced significantly from pre- to follow-up-assessment in all three conditions (d(within) = 0.63-1.24), with the procedure intended to train attention towards threat cues producing, relative to the control condition, a significantly greater reduction of social fears. There were no significant differences in social anxiety outcome between the training condition intended to induce attentional bias towards positive cues and the control condition. To our knowledge, this is the first RCT where a condition intended to induce attention bias to negative cues yielded greater emotional benefits than a control condition. Intriguingly, changes in symptoms are unlikely to be by the mechanism of change in attention processes since there was no change detected in bias per se. Implications of this finding for future research on attention bias modification in social anxiety are discussed. Trial Registration: ClinicalTrials.gov NCT01463137Funding: Swedish Council for Working Life and Social Research, FAS 2009-0222</p

Contrasting response of European forest and grassland energy exchange to heatwaves

Recent European heatwaves have raised interest in the impact of land cover conditions on temperature extremes. At present, it is believed that such extremes are enhanced by stronger surface heating of the atmosphere, when soil moisture content is below average. However, the impact of land cover on the exchange of water and energy and the interaction of this exchange with the soil water balance during heatwaves is largely unknown. Here we analyse observations from an extensive network of flux towers in Europe that reveal a difference between the temporal responses of forest and grassland ecosystems during heatwaves. We find that initially, surface heating is twice as high over forest than over grassland. Over grass, heating is suppressed by increased evaporation in response to increased solar radiation and temperature. Ultimately, however, this process accelerates soil moisture depletion and induces a critical shift in the regional climate system that leads to increased heating. We propose that this mechanism may explain the extreme temperatures in August 2003. We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates the impact of the most extreme heat and/or long-lasting events