Pseudohypocalcemia caused by perchlorate (Irenat (R))

Background: Blood gas analysis (BGA), including measurement of ionized calcium, is performed routinely in patients with end stage renal disease on renal replacement therapy, especially when using citrate for regional anticoagulation. After installation of a new blood gas analyzer (RAPIDpoint (R) 405; BGA), we observed lower ionized calcium concentrations in a few patients without signs of hypocalcemia, whereas calcium concentrations were normal using a standard laboratory method. Pseudohypocalcemia was of limited duration and correlated with the short-term intake of sodium perchlorate monohydrate (Irenat (R)). Methods: We prepared dilution series from whole blood samples and stock solutions of calcium and perchlorate with different concentrations of ionized calcium and perchlorate. Measurement of ionized calcium concentrations was performed using two different blood gas analyzers (RAPIDpoint (R) 405; BGA and Roche AVL 9180; standard laboratory method). Results: After addition of different amounts of perchlorate, significant lower ionized calcium concentrations were measured with BGA compared to the standard laboratory method using either preparations from whole blood samples or stock solutions. The addition of potassium or methylene blue known to complex perchlorate had no effect on the concentrations of ionized calcium measured with BGA. Using different mathematical methods, a calculation of the "real" ionized calcium concentration from the value measured with BGA was not possible. Conclusions: Based on our experiments, we confirm the hypothesis that perchlorate can influence the measurement of ionized calcium by BGA. As the effect depends on the ion selective electrode that is used, it is advisable to test the blood gas analyzer with calcium and perchlorate solutions

Evanescent-Wave Spectroscopy on Bulk-Response Optode Membranes

The absorbance of a solvent polymerie bulk optode membrane in contact with sapphire as a wave-guide is studied with the attenuated total reflection (ATR) technique. Utilizing thin (≤ 1 μm) and, therefore, fast-responding membranes, high values of absorbance are obtained by multiple internal reflection (MIR). The approach has an advantage over conventional transmission studies in that the light beam does not pass through the sample solution. Samp1e-induced swelling of the membrane may, however, create problems

Tonotopic organization of the hyperpolarization-activated current (I-h) in the mammalian medial superior olive

Neuronal membrane properties can largely vary even within distinct morphological cell classes. The mechanisms and functional consequences of this diversity, however, are little explored. In the medial superior olive (MSO), a brainstem nucleus that performs binaural coincidence detection, membrane properties at rest are largely governed by the hyperpolarization-activated inward current (I-h) which enables the temporally precise integration of excitatory and inhibitory inputs. Here, we report that I-h density varies along the putative tonotopic axis of the MSO with I-h being largest in ventral, high-frequency (HF) processing neurons. Also I-h half-maximal activation voltage and time constant are differentially distributed such that I-h of the putative HF processing neurons activate faster and at more depolarized levels. Intracellular application of saturating concentrations of cyclic AMP removed the regional difference in hyperpolarization-activated cyclic nucleotide gated (HCN) channel activation, but not I-h density. Experimental data in conjunction with a computational model suggest that increased I-h levels are helpful in counteracting temporal summation of phase-locked inhibitory inputs which is particularly prominent in HF neurons

Activation of G12/G13 Results in Shape Change and Rho/Rho-Kinase–mediated Myosin Light Chain Phosphorylation in Mouse Platelets

Platelets respond to various stimuli with rapid changes in shape followed by aggregation and secretion of their granule contents. Platelets lacking the α-subunit of the heterotrimeric G protein Gq do not aggregate and degranulate but still undergo shape change after activation through thromboxane-A2 (TXA2) or thrombin receptors. In contrast to thrombin, the TXA2 mimetic U46619 led to the selective activation of G12 and G13 in Gαq-deficient platelets indicating that these G proteins mediate TXA2 receptor-induced shape change. TXA2 receptor-mediated activation of G12/G13 resulted in tyrosine phosphorylation of pp72syk and stimulation of pp60c-src as well as in phosphorylation of myosin light chain (MLC) in Gαq-deficient platelets. Both MLC phosphorylation and shape change induced through G12/G13 in the absence of Gαq were inhibited by the C3 exoenzyme from Clostridium botulinum, by the Rho-kinase inhibitor Y-27632 and by cAMP-analogue Sp-5,6-DCl-cBIMPS. These data indicate that G12/G13 couple receptors to tyrosine kinases as well as to the Rho/Rho-kinase–mediated regulation of MLC phosphorylation. We provide evidence that G12/G13-mediated Rho/Rho-kinase–dependent regulation of MLC phosphorylation participates in receptor-induced platelet shape change

Integrated modelling for assessing the risk of groundwater contaminants to human health and surface water ecosystems

The practical implementation of the European Water Framework Directive has resulted in an increased focus on the groundwater-surface water interaction zone. A gap exists with respect to preliminary assessment methodologies that are capable of evaluating and prioritising point sources of contamination. In particular, adaptive management tools designed to work with sparse data sets from preliminary site assessments are needed which can explicitly link contaminant point sources with groundwater, surface water and ecological impacts. Here, a novel integrated modelling approach was employed for evaluating the impact of a TCE groundwater plume, located in an area with protected drinking water interests, to human health and surface water ecosystems. This is accomplished by coupling the system dynamicsbased decision support system CARO-Plus to the aquatic ecosystem model AQUATOX via an analytical volatilisation model for the stream. The model is tested on a Danish case study involving a 750 m long TCE groundwater plume discharging into a stream. The initial modelling results indicate that TCE contaminant plumes with μgL-1 concentrations entering surface water systems do not pose a significant risk to either human or ecological receptors

Standardisierter Datenmanagementplan

Der Artikel beschreibt die Vorgehensweise und den Lernprozess, der bei der Entwicklung eines Standardisierten Datenmanagementplans für die Bildungsforschung (Stamp) im Verbundprojekt Domain-Data-Protokolle für die Empirische Bildungsforschung (DDPBildung) erreicht wurde. Als Ausgangspunkt wird zunächst die Science-Europe-Vorlage (SE-Vorlage) zur Entwicklung des Stamps diskutiert und es werden darin jene Stellen herausgestellt, die domänenspezifische Anpassungen, hier die der Empirischen Bildungsforschung, erfordern. In einem weiteren Schritt skizziert der Artikel die Workshops, die mit externen Expert*innen aus der Empirischen Bildungsforschung – darunter Forscher*innen und Forschungsdatenmanagement-Beauftragte – durchgeführt wurden. Dabei stehen die Ergebnisse aus den Workshops sowie deren Auswirkungen auf die Entwicklung des Stamps im Vordergrund. Danach veranschaulicht der Artikel unter Rückgriff auf die Ergebnisse derWorkshops die an der SE-Vorlage unternommenen Anpassungen