Water uptake by trees in a riparian hardwood forest (Rhine floodplain, France)

Water flow in the soil–root–stem system was studied in a flooded riparian hardwood forest in the upper Rhine floodplain. The study was undertaken to identify the vertical distribution of water uptake by trees in a system where the groundwater is at a depth of less than 1 m. The three dominant ligneous species (Quercus robur, Fraxinus excelsior and Populus alba) were investigated for root structure (vertical extension of root systems), leaf and soil water potential (m), isotopic signal (18O) of soil water and xylem sap. The root density of oak and poplar was maximal at a depth of 20 to 60 cm, whereas the roots of the ash explored the surface horizon between 0 and 30 cm, which suggests a complementary tree root distribution in the hardwood forest. The flow density of oak and poplar was much lower than that of the ash. However, in the three cases the depth of soil explored by the roots reached 1Ð2 m, i.e. just above a bed of gravel. The oak roots had a large lateral distribution up to a distance of 15 m from the trunk. The water potential of the soil measured at 1 m from the trunk showed a zone of strong water potential between 20 and 60 cm deep. The vertical profile of soil water content varied from 0Ð40 to 0Ð50 cm3 cm3 close to the water table, and 0Ð20 to 0Ð30 cm3 cm3 in the rooting zone. The isotopic signal of stem water was constant over the whole 24-h cycle, which suggested that the uptake of water by trees occurred at a relatively constant depth. By comparing the isotopic composition of water between soil and plant, it was concluded that the water uptake occurred at a depth of 20 to 60 cm, which was in good agreement with the root and soil water potential distributions. The riparian forest therefore did not take water directly from the water table but from the unsaturated zone through the effect of capillarit

The effect of exogenous GLP-1 on food intake is lost in male truncally vagotomized subjects with pyloroplasty

Rapid degradation of glucagon-like peptide-1 (GLP-1) by dipeptidyl peptidase-4 suggests that endogenous GLP-1 may act locally before being degraded. Signaling via the vagus nerve was investigated in 20 truncally vagotomized subjects with pyloroplasty and 10 matched healthy controls. Subjects received GLP-1 (7-36 amide) or saline infusions during and after a standardized liquid mixed meal and a subsequent ad libitum meal. Despite no effect on appetite sensations, GLP-1 significantly reduced ad libitum food intake in the control group but had no effect in the vagotomized group. Gastric emptying was accelerated in vagotomized subjects and was decreased by GLP-1 in controls but not in vagotomized subjects. Postprandial glucose levels were reduced by the same percentage by GLP-1 in both groups. Peak postprandial GLP-1 levels were approximately fivefold higher in the vagotomized subjects. Insulin secretion was unaffected by exogenous GLP-1 in vagotomized subjects but was suppressed in controls. GLP-1 significantly reduced glucagon secretion in both groups, but levels were approximately twofold higher and were nonsuppressible in the early phase of the meal in vagotomized subjects. Our results demonstrate that vagotomy with pyloroplasty impairs the effects of exogenous GLP-1 on food intake, gastric emptying, and insulin and glucagon secretion, suggesting that intact vagal innervation may be important for GLP-1's actions.</jats:p

Differential effects of glucagon-like peptide-1 receptor agonists on heart rate

Abstract While glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are known to increase heart rate (HR), it is insufficiently recognized that the extent varies greatly between the various agonists and is affected by the assessment methods employed. Here we review published data from 24-h time-averaged HR monitoring in healthy individuals and subjects with type 2 diabetes mellitus (T2DM) treated with either short-acting GLP-1 RAs, lixisenatide or exenatide, or long-acting GLP-1 RAs, exenatide LAR, liraglutide, albiglutide, or dulaglutide (N\ua0=\ua01112; active-treatment arms). HR effects observed in two independent head-to-head trials of lixisenatide and liraglutide (N\ua0=\ua0202; active-treatment arms) are also reviewed. Short-acting GLP-1 RAs, exenatide and lixisenatide, are associated with a transient (1\u201312\ua0h) mean placebo- and baseline-adjusted 24-h HR increase of 1\u20133\ua0beats per minute (bpm). Conversely, long-acting GLP-1 RAs are associated with more pronounced increases in mean 24-h HR; the highest seen with liraglutide and albiglutide at 6\u201310\ua0bpm compared with dulaglutide and exenatide LAR at 3\u20134\ua0bpm. For both liraglutide and dulaglutide, HR increases were recorded during both the day and at night. In two head-to-head comparisons, a small, transient mean increase in HR from baseline was observed with lixisenatide; liraglutide induced a substantially greater increase that remained significantly elevated over 24\ua0h. The underlying mechanism for increased HR remains to be elucidated; however, it could be related to a direct effect at the sinus node and/or stimulation of the sympathetic nervous system, with this effect related to the duration of action of the respective GLP-1 RAs. In conclusion, this review indicates that the effects on HR differ within the class of GLP-1 RAs: short-acting GLP-1 RAs are associated with a modest and transient HR increase before returning to baseline levels, while some long-acting GLP-1 RAs are associated with a more pronounced and sustained increase during the day and night. Findings from recently completed trials indicate that a GLP-1 RA-induced increase in HR, regardless of magnitude, does not present an increased cardiovascular risk for subjects with T2DM, although a pronounced increase in HR may be associated with adverse clinical outcomes in those with advanced heart failure

Enhancing first responder CBRN capabilities

First responders perform a multitude of life-saving activities, including pre-hospital care, in challenging environments and situations. Responding to mass casualty events is difficult in any setting, but is even more complex during chemical, biological, radiological and nuclear (CBRN) incidents.In light of the growing concern about CBRN risks and the identified gaps in preparedness and response, the European Union (EU) has launched the EU Centers of Excellence (CoE)initiative on CBRN Risk Mitigation. One of the projects within the CoE initiative, Project 14, aims to enhance the capacities of first responders in South East Europe, Caucasus and Moldova. Two training courses have been implemented in the region, and this report aims to highlight some of the key points discussed, including the usability of the specific 'Gamma Ray Dose Constant'

Inability of Some Commercial Assays to Measure Suppression of Glucagon Secretion

Glucagon levels are increasingly being included as endpoints in clinical study design and more than 400 current diabetes-related clinical trials have glucagon as an outcome measure. The reliability of immune-based technologies used to measure endogenous glucagon concentrations is, therefore, important. We studied the ability of immunoassays based on four different technologies to detect changes in levels of glucagon under conditions where glucagon levels are strongly suppressed. To our surprise, the most advanced technological methods, employing electrochemiluminescence or homogeneous time resolved fluorescence (HTRF) detection, were not capable of detecting the suppression induced by a glucose clamp (6 mmol/L) with or without atropine in five healthy male participants, whereas a radioimmunoassay and a spectrophotometry-based ELISA were. In summary, measurement of glucagon is challenging even when state-of-the-art immune-based technologies are used. Clinical researchers using glucagon as outcome measures may need to reconsider the validity of their chosen glucagon assay. The current study demonstrates that the most advanced approach is not necessarily the best when measuring a low-abundant peptide such as glucagon in humans

Inability of Some Commercial Assays to Measure Suppression of Glucagon Secretion

Glucagon levels are increasingly being included as endpoints in clinical study design and more than 400 current diabetes-related clinical trials have glucagon as an outcome measure. The reliability of immune-based technologies used to measure endogenous glucagon concentrations is, therefore, important. We studied the ability of immunoassays based on four different technologies to detect changes in levels of glucagon under conditions where glucagon levels are strongly suppressed. To our surprise, the most advanced technological methods, employing electrochemiluminescence or homogeneous time resolved fluorescence (HTRF) detection, were not capable of detecting the suppression induced by a glucose clamp (6 mmol/L) with or without atropine in five healthy male participants, whereas a radioimmunoassay and a spectrophotometry-based ELISA were. In summary, measurement of glucagon is challenging even when state-of-the-art immune-based technologies are used. Clinical researchers using glucagon as outcome measures may need to reconsider the validity of their chosen glucagon assay. The current study demonstrates that the most advanced approach is not necessarily the best when measuring a low-abundant peptide such as glucagon in humans

Dissecting the physiology and pathophysiology of glucagon-like peptide-1

Copyright © 2018 Paternoster and Falasca. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. An aging world population exposed to a sedentary life style is currently plagued by chronic metabolic diseases, such as type-2 diabetes, that are spreading worldwide at an unprecedented rate. One of the most promising pharmacological approaches for the management of type 2 diabetes takes advantage of the peptide hormone glucagon-like peptide-1 (GLP-1) under the form of protease resistant mimetics, and DPP-IV inhibitors. Despite the improved quality of life, long-term treatments with these new classes of drugs are riddled with serious and life-threatening side-effects, with no overall cure of the disease. New evidence is shedding more light over the complex physiology of GLP-1 in health and metabolic diseases. Herein, we discuss the most recent advancements in the biology of gut receptors known to induce the secretion of GLP-1, to bridge the multiple gaps into our understanding of its physiology and pathology

Floodplain ecohydrology : climatic, anthropogenic, and local physical controls on partitioning of water sources to riparian trees

This research was financially supported by Observatoire Hommes/Milieux Vallee du Rhone, The Royal Society (RG100590), The Carnegie Trust for the Universities of Scotland, and the Rhone-Alpes region via the ARC Environment program 2013. We also acknowledge NERC PhD studentship support to Sargeant and Evans.Seasonal and annual partitioning of water within river floodplains has important implications for ecohydrologic links between the water cycle and tree growth. Climatic and hydrologic shifts alter water distribution between floodplain storage reservoirs (e.g., vadose, phreatic), affecting water availability to tree roots. Water partitioning is also dependent on the physical conditions that control tree rooting depth (e.g., gravel layers that impede root growth), the sources of contributing water, the rate of water drainage, and water residence times within particular storage reservoirs. We employ instrumental climate records alongside oxygen isotopes within tree rings and regional source waters, as well as topographic data and soil depth measurements, to infer the water sources used over several decades by two co-occurring tree species within a riparian floodplain along the Rhône River in France. We find that water partitioning to riparian trees is influenced by annual (wet versus dry years) and seasonal (spring snowmelt versus spring rainfall) fluctuations in climate. This influence depends strongly on local (tree level) conditions including floodplain surface elevation and subsurface gravel layer elevation. The latter represents the upper limit of the phreatic zone and therefore controls access to shallow groundwater. The difference between them, the thickness of the vadose zone, controls total soil moisture retention capacity. These factors thus modulate the climatic influence on tree ring isotopes. Additionally, we identified growth signatures and tree ring isotope changes associated with recent restoration of minimum streamflows in the Rhône, which made new phreatic water sources available to some trees in otherwise dry years.Publisher PDFPeer reviewe