Consumption of nitric oxide by endothelial cells: Evidence for the involvement of a NAD(P)H-, flavin- and heme-dependent dioxygenase reaction

AbstractIn the present study, we investigated the mechanism of nitric oxide (NO) inactivation by endothelial cells. All experiments were performed in the presence of superoxide dismutase to minimize the peroxynitrite reaction. Incubation of the NO donor diethylamine/NO adduct with increasing amounts of intact cells led to a progressive decrease of the NO concentration, demonstrating a cell-dependent consumption of NO. In cell homogenates, consumption of NO critically depended on the presence of NADPH or NADH and resulted in the formation of nitrate. Both NO consumption and nitrate formation were largely inhibited by the heme poisons NaCN and phenylhydrazine as well as the flavoenzyme inhibitor diphenylene iodonium. Further characterization of this NO consumption pathway suggests that endothelial cells express a unique membrane-associated enzyme or enzyme system analogous to the bacterial NO dioxygenase that converts NO to nitrate in a NAD(P)H-, flavin- and heme-dependent manner

Propensity score adjustment of a treatment effect with missing data in psychiatric health services research

Background: Missing values are a common problem for data analyses in observational studies, which are frequently applied in health services research. This paper examines the usefulness of different approaches to tackle the problem of incomplete observational data, focusing whether the Multiple Imputation (MI) strategy yields adequate estimates when applied to a complex analysis framework. Methods: Based on observational study data originally comparing three forms of psychotherapy, a simulation study with different missing data scenarios was conducted. The considered analysis model comprised a propensity score-adjusted treatment effect estimation. Missing values were handled by complete case analysis, different MI approaches, as well as mean and regression imputation. Results: All point estimators of the applied methods lay within the 95% confidence interval of the treatment effect derived from the complete simulation data set. Highest deviation was observed for complete case analysis. A distinct superiority of MI methods could not be demonstrated. Conclusion: Since there was no clear benefit of one method to deal with missing values over another, health services researchers faced with incomplete observational data are well-advised to apply different imputation methods and compare the results in order to get an impression of their sensitivity

Evidence for a magnesium-insensitive membrane resistance increase during NMDA-induced depolarizations in rat neocortical neurons in vitro

The responses of rat neocortical neurons in vitro to iontophoretically applied N-methyl-d-aspartate (NMDA) were investigated by means of intracellular recording in the presence and absence of extracellular magnesium ions (Mg2+). At Mg2+-concentrations of 1.3 mM the neurons responded with a depolarization accompanied by an increase in membrane resistance. Upon removal of Mg2+ the NMDA-induced depolarization was markedly potentiated. However, even in neurons recorded from slices which were incubated in a Mg2+-free solution for 3–7 h, the NMDA response was still associated with a resistance increase, suggesting that the voltage-dependence of the NMDA-activated conductance is not exclusively determined by Mg2+

Modelling of Industrial Hybrid Bonding Processes considering Fluid-Structure-Interaction

The subject of the work presented is focused on self-pierce-riveting and clinching in combination with adhesive bonding. In the industrial process chain the rivets and clinch-points are set before the adhesive is cured. A FEA reference model is developed for the elementary mechanical joining processes. The model is then expanded to consider the displacement of the liquid adhesive, including associated internal pressures. Coupled fluid-structure simulations, which include the interaction of the solid matter influenced in the mechanical joining process and the fluid adhesive, are presented. In a last step a surrogate model for the multi-point hybrid joint is developed and applied to industry-relevant structures

Multi User Context-Aware Service Selection for Mobile Environments - A Heuristic Technique

Modern service systems build on top of service dominant designs which encompass contextualization (value-in-context) and collaboration (value-in-use) between users and service providers. Processes in this domain often require the consideration of both context information (e.g., location or time of day) and multiple participating users where each user probably has its own preferences and constraints (e.g., restricted overall budget). However, selecting a suitable service provider for each action of a process, especially when some of these actions are conducted together by several users, can be a complex decision problem in multi user context-aware service systems. Consequently, exact approaches are not fit to solve such a service selection problem in appropriate time. Thus, the paper proposes a heuristic technique applying a decomposition of the users’ global constraints and a local service selection. In this way, the aim is to determine a feasible service composition for each participating user while taking the users’ individual preferences and constraints as well as context information into account. The evaluation of the heuristic technique shows, based on a real-world scenario in the tourism domain, that the proposed approach is able to achieve close-to-optimal solutions while efficiently scaling with problem size and therefore can support decision makers in multi user context-aware service Systems

Dependence of aptamer activity on opposed terminal extensions : improvement of light-regulation efficiency

Aptamers that can be regulated with light allow precise control of protein activity in space and time and hence of biological function in general. In a previous study, we showed that the activity of the thrombin-binding aptamer HD1 can be turned off by irradiation using a light activatable "caged" intramolecular antisense-domain. However, the activity of the presented aptamer in its ON state was only mediocre. Here we studied the nature of this loss in activity in detail and found that switching from 5'- to 3'-extensions affords aptamers that are even more potent than the unmodified HD1. In particular we arrived at derivatives that are now more active than the aptamer NU172 that is currently in phase 2 clinical trials as an anticoagulant. As a result, we present light-regulatable aptamers with a superior activity in their ON state and an almost digital ON/OFF behavior upon irradiation

Reversible inactivation of endothelial nitric oxide synthase by NG-nitro-l-arginine

AbstractNG-Methyl-l-arginine (L-NMA) and NG-nitro-l-arginine (L-NNA) inhibited NO-induced cGMP accumulation in porcine aortic endothelial cells with half-maximally effective concentrations of 15 and 3.4 μM, respectively. The effects of both compounds were reversible, but the L-NNA-induced inhibition was only reversed by wash-out in the presence of 1 mM l-arginine. In short-term incubations (45 s) of membrane fractions, L-NMA and L-NNA exhibited similar potencies to inhibit endothelial NO synthase, but L-NNA was markedly more potent than L-NMA after prolonged incubation periods (⩾ 3 min) due to induction of a pronounced, reversible enzyme inactivation