Copolymers enhance selective bacterial community colonization for potential root zone applications.

Managing the impact of anthropogenic and climate induced stress on plant growth remains a challenge. Here we show that polymeric hydrogels, which maintain their hydrous state, can be designed to exploit functional interactions with soil microorganisms. This microbial enhancement may mitigate biotic and abiotic stresses limiting productivity. The presence of mannan chains within synthetic polyacrylic acid (PAA) enhanced the dynamics and selectivity of bacterial ingress in model microbial systems and soil microcosms. Pseudomonas fluorescens exhibiting high mannan binding adhesins showed higher ingress and localised microcolonies throughout the polymeric network. In contrast, ingress of Bacillus subtilis, lacking adhesins, was unaltered by mannan showing motility comparable to bulk liquids. Incubation within microcosms of an agricultural soil yielded hydrogel populations significantly increased from the corresponding soil. Bacterial diversity was markedly higher in mannan containing hydrogels compared to both control polymer and soil, indicating enhanced selectivity towards microbial families that contain plant beneficial species. Here we propose functional polymers applied to the potential root zone which can positively influence rhizobacteria colonization and potentially plant growth as a new approach to stress tolerance.

Longitudinal bioimpedance vector plots add little value to fluid management of peritoneal dialysis patients.

Bioimpedance (BI) has the potential to enable better management of fluid balance, which can worsen over time on peritoneal dialysis (PD) due to loss of residual kidney function and progressive muscle wasting. We undertook a prospective, randomized, open-label, blinded end-point controlled trial to determine whether availability of longitudinal BI measures as vector plots helped clinicians maintain stable fluid status over 12 months in 308 peritoneal dialysis patients from the United Kingdom and Shanghai, China. Patients were recruited into 4 groups nested within a single trial design according to country and residual kidney function. Nonanuric subjects from both countries demonstrated stable fluid volumes irrespective of randomization. Hydration worsened in control anuric patients in Shanghai with increased extracellular/total body water (ECW/TBW) ratio (0.04; 95% CI: 0.01, 0.06) and reduced TBW (-1.76 L 95% CI: -2.70, -0.82), but was stable in the BI intervention group whose dialysate glucose prescription was increased. However, multilevel analysis incorporating data from both countries showed worsening ECW/TBW in active and control anuric patients. Clinicians in the United Kingdom reduced target weight in the nonanuric BI intervention group causing a reduction in TBW without beneficial effects on ECW or blood pressure. Thus, routine use of longitudinal BI vector plots to improve clinical management of fluid status is not supported.

Injection of deuterated water into the pulmonary/alveolar circulation; measurement of HDO in exhaled breath and implications to breath analysis.

The results of experiments are described in which a known quantity of sterile deuterated water is injected directly into the pulmonary circulation via the right internal jugular vein of several haemodialysis patients and the deuterium to hydrogen ratio, D/H, in the exhaled lung water was measured using the flowing afterglow mass spectrometry technique. The breath D/H abundance was measured in sequential breath exhalations before and after the injection, providing data that are sufficiently detailed to follow the production and loss rate of D/H in the exhaled breath. Thus, in principle, considering isotope dilution the volume of water in the lungs and pulmonary circulation can be derived. However, it is seen that the maximum abundance that the breath D/H reached was much lower than anticipated by considering the likely volume of blood/water in the pulmonary circulation and so it is deduced that either 'leakage' of the injected deuterated water rapidly occurs from the pulmonary to the systemic circulation and/or isotope exchange of deuterium with hydrogen along the bronchial tree efficiently occurs, thus reducing the D/H in the exhaled breath. This latter phenomenon has important implications to breath analysis in which it is often assumed that so-called alveolar breath concentrations of metabolites reflect blood/systemic levels. Detailed consideration of the breath D/H abundances when the deuterium is equilibrated amongst the total body water, TBW, of the patients, which occurs about 40 min after injection of the deuterated water, allows the TBW of the patients to be estimated.

Dispersal kinetics of deuterated water in the lungs and airways following mouth inhalation: real-time breath analysis by flowing afterglow mass spectrometry (FA-MS).

Pulmonary oedema is a medical condition characterized by abnormal accumulation of fluid in the extravascular space in the alveoli. Effective oxygenation is impaired and this leads to significant short- and long-term morbidity and mortality. The detection and monitoring of pulmonary oedema by measuring lung water volume is therefore crucial in the initiation and guidance of therapeutic intervention. The current gold standard bedside measurement of extravascular lung water volume (EVLW) is the dilution method using various indicators, but despite the good correlation of the results with those obtained using the post-mortem gravimetric method, the invasiveness of the dilution technique limits its general application in the wider clinical setting. In the present preliminary experiments, the dispersal kinetics of deuterium (actually HDO) in exhaled breath of three healthy participants following the inhalation of deuterium oxide (D(2)O) vapour are explored as monitored using flowing afterglow mass spectrometry (FA-MS). Here, we present the basic ideas of lung water estimation using this novel technique, and briefly discuss its limitations and required future work.