Novel form of collective movement by soil bacteria.

Although migrations are essential for soil microorganisms to exploit scarce and heterogeneously distributed resources, bacterial mobility in soil remains poorly studied due to experimental limitations. In this study, time-lapse images collected using live microscopy techniques captured collective and coordinated groups of B. subtilis cells exhibiting "crowd movement". Groups of B. subtilis cells moved through transparent soil (nafion polymer with particle size resembling sand) toward plant roots and re-arranged dynamically around root tips in the form of elongating and retracting "flocks" resembling collective behaviour usually associated with higher organisms (e.g., bird flocks or fish schools). Genetic analysis reveals B. subtilis flocks are likely driven by the diffusion of extracellular signalling molecules (e.g., chemotaxis, quorum sensing) and may be impacted by the physical obstacles and hydrodynamics encountered in the soil like environment. Our findings advance understanding of bacterial migration through soil matrices and expand known behaviours for coordinated bacterial movement.

Complexity vs. simplicity: groundwater model ranking using information criteria.

A groundwater model characterized by a lack of field data about hydraulic model parameters and boundary conditions combined with many observation data sets for calibration purpose was investigated concerning model uncertainty. Seven different conceptual models with a stepwise increase from 0 to 30 adjustable parameters were calibrated using PEST. Residuals, sensitivities, the Akaike information criterion (AIC and AICc), Bayesian information criterion (BIC), and Kashyap's information criterion (KIC) were calculated for a set of seven inverse calibrated models with increasing complexity. Finally, the likelihood of each model was computed. Comparing only residuals of the different conceptual models leads to an overparameterization and certainty loss in the conceptual model approach. The model employing only uncalibrated hydraulic parameters, estimated from sedimentological information, obtained the worst AIC, BIC, and KIC values. Using only sedimentological data to derive hydraulic parameters introduces a systematic error into the simulation results and cannot be recommended for generating a valuable model. For numerical investigations with high numbers of calibration data the BIC and KIC select as optimal a simpler model than the AIC. The model with 15 adjusted parameters was evaluated by AIC as the best option and obtained a likelihood of 98%. The AIC disregards the potential model structure error and the selection of the KIC is, therefore, more appropriate. Sensitivities to piezometric heads were highest for the model with only five adjustable parameters and sensitivity coefficients were directly influenced by the changes in extracted groundwater volumes.

Quantification of long-term wastewater fluxes at the surface water/groundwater-interface: an integrative model perspective using stable isotopes and acesulfame.

The suitability of acesulfame to trace wastewater-related surface water fluxes from streams into the hyporheic and riparian zones over long-term periods was investigated. The transport behavior of acesulfame was compared with the transport of water stable isotopes (δ(18)O or δ(2)H). A calibrated model based on a joint inversion of temperature, acesulfame, and piezometric pressure heads was employed in a model validation using data sets of acesulfame and water stable isotopes collected over 5months in a stream and groundwater. The spatial distribution of fresh water within the groundwater resulting from surface water infiltration was estimated by computing groundwater ages and compared with the predicted acesulfame plume obtained after 153day simulation time. Both, surface water ratios calculated with a mixing equation from water stable isotopes and simulated acesulfame mass fluxes, were investigated for their ability to estimate the contribution of wastewater-related surface water inflow within groundwater. The results of this study point to limitations for the application of acesulfame to trace surface water-groundwater interactions properly. Acesulfame completely missed the wastewater-related surface water volumes that still remained in the hyporheic zone under stream-gaining conditions. In contrast, under stream-losing conditions, which developed after periods of stagnating hydraulic exchange, acesulfame based predictions lead to an overestimation of the surface water volume of up to 25% in the riparian zone. If slow seepage velocities prevail a proportion of acesulfame might be stored in smaller pores, while when released under fast flowing water conditions it will travel further downstream with the groundwater flow direction. Therefore, under such conditions acesulfame can be a less-ideal tracer in the hyporheic and riparian zones and additional monitoring with other environmental tracers such as water stable isotopes is highly recommended.

Influence of erythropoietin treatment on 2,3-bisphosphoglycerate and O2-affinity of red blood cells in children with renal anemia.

In children with renal anemia the concentration of DPG of red blood cells and the O2-affinity of hemoglobin (P50) were determined before and under treatment with EPO. Before treatment the concentration of DPG was 6.25 mmoles/l cells and the P50 28.9 Torr. A rise of the hematocrit to about 0.30 was accompanied by an increase of DPG to 7.95 mmoles/l cells and of P50 to 32.1 Torr, respectively. Thus improvement of renal anemia by stimulation of erythropoiesis by means of EPO was accompanied by a decreased O2-affinity of hemoglobin and therefore by an additionally improved O2-supply to the tissues.

Erythrocyte sodium content and transport in borderline and mild hypertension.

Sodium content and transport of red blood cells were examined in 98 male blood donors. Regarding their blood pressure they were classified into the following groups: (a) 57 normotensives, (RR less than 140/90 mm Hg); (b) 24 borderline hypertensives (140/90 less than or equal to RR less than 160/95 mm Hg); and (c) 17 hypertensives (RR greater than 160/100 mm Hg). Compared with the normotensives the borderline hypertensives have significantly reduced red cell sodium content. The ouabain-resistant net Na+ uptake and the relative Na+ uptake, as a measure of the Na+/K+ pump, were significantly increased. With rising blood pressures the measured values turn to normal, so that no difference exists between the normotensive and hypertensive groups. It is supposed that in the initial or even prehypertensive state a considerable enhancement of the pump activity occurs, simultaneously accompanied by less marked increases in sodium influx, leading to a reduced intracellular sodium content. In the course of hypertension, possibly caused by the formation of a pump inhibitor, the sodium content of red cells turns to normal or supernormal values.

Determination of the acid-base status in blood of patients on chronic haemodialysis and of bicarbonate in dialysate: comparison of three techniques and their mathematically derived values.

The study deals with the comparison of acid-base parameters in blood of patients on chronic haemodialysis and of bicarbonate dialysate determined by Gas-Check AVL 945, equilibration technique (ET), and a titrimetric method. The results show that an acceptable agreement exists between AVL and ET with respect to measurements of pH, pCO2, HCO3-, and base excess. However, the values obtained for total buffer base related to the actual haemoglobin concentration are significantly lower (P less than 0.001) when determined by AVL. A titrimetric method is proposed for routine measurement of HCO3- in bicarbonate dialysate. Values obtained using this method are 3-4 mmol/l higher than those determined by AVL and ET. However, when the values for pK1' and for the solubility coefficient used in the Henderson-Hasselbalch equation are replaced by those for saline-bicarbonate solutions, results obtained using the titrimetric determined values agree well with those obtained by AVL and ET.

Erythrocyte sodium transport in normotensive and hypertensive patients on chronic hemodialysis, acute effect of treatment.

Patients on chronic hemodialysis were divided into two groups: normotensive patients (group I) and renal hypertensive patients treated with antihypertensives (group II). The sodium and potassium contents in red blood cells ([Na+]i, [K+]i), ouabain-resistant net sodium uptake (ORNa+ uptake, phi Na), the relative ORNa+ uptake (k), the mean cell hemoglobin concentration (MCHC), and acid-base status were examined just before and after dialysis. The results indicate that in treated renal hypertensive patients k is stimulated and causes lower red blood cell sodium content. The reason for this increase remains obscure: the pattern of alterations of the sodium transport components during dialysis is similar in all patients: [Na+]i and phi Na increase significantly during dialysis, and the increases in [Na+]i are closely related to increases in pH and bicarbonate.

[Saralasin test in the differential diagnosis of essential and renal hypertension]. / Der Saralasintest in der Differentialdiagnostik essentieller und renaler Hypertonien.

In a multicentric prospective study should be tested clinically the effectiveness and the tolerance of an angiotensin-II-antagonist (Saralasin-IWF) developed by the Institut für Wirkstofforschung der Akademie der Wissenschaften, its position in the differential-diagnostic step programme of the arterial hypertension should be analysed and with it should be performed pathogenetic investigations for hypertension after kidney transplantation. Taking into consideration international studies our results confirm that the Saralasin test, taking into account strongly standardized methodical prerequisites, is suited to objectify a participation of the RAAS in the hypertension pathogenesis, without, however, thus making an absolutely reliable evidence concerning the etiology of hypertension. The Saralasin test may represent an important diagnostic criterion for an optimization of the therapy of "volume-resistant" hypertension under the conditions of haemodialysis and in connection with selective renin determinations it possesses a high value in the screening diagnostics of the arterial stenosis after allogenic kidney transplantation.

[Comparative studies of the efficiency of MLW-1.3 and 1.8-hollow fiber dialyzers]. / Vergleichende Effektivitätsuntersuchungen an MLW-1.3- und -1.8-Hohlfaserdialysatoren.

Clinically contradictory results in the use of hollow-fibre dialysers with surfaces of 1.3 and 1.8 m2 prompted us to compare their efficiency under standard conditions. It was found that the efficiency does not increase proportionally to the enlargement of the dialyser surface. the reason for this is to be seen in: the supply of rinsing solution in the dialyser, blood flow, insufficient degassing, coating of the membrane with denatured protein and, last but not least, the body mass of the patient himself. For optimum dialysis an individually suited dialysis time can be calculated from these data for each patient.