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We present an approach to reduce topography-related errors of vertical tropospheric columns (VTC) of NO2 retrieved from the Ozone Monitoring Instrument (OMI) in the vicinity of mountainous terrain. This is crucial for reliable estimates of air pollution levels over our particular area of interest, the Alpine region and the adjacent planes, where the Dutch OMI NO2 product (DOMINO) exhibits significant biases due to the coarse resolution of surface parameters used in the retrieval. Our approach replaces the coarse-gridded surface pressures by accurate pixel-average values using a high-resolution topography data set, and scales the a priori NO2 profiles accordingly. NO2 VTC reprocessed in this way for the period 2006–2007 suggest that NO2 over the Po Valley in Italy and over the Swiss plateau is underestimated by DOMINO by about 15–20% in winter and 5% in summer under clear-sky conditions (cloud radiance fraction, Atmospheric Measurement Techniques, 2 (2), ISSN:1867-1381, ISSN:1867-8548

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Evoked Potentials (EPs) are responses that appear in the EEG due to external stimulation. Findings indicate that changes in EPs can be related to changes in frequencies of the pre-stimulus EEG. Auditory EPs of rats (n=8) were measured in reaction to tone-pip stimuli (90 dB, 10.2 kHz, ISI 2s, n=1500). Trials were ranked according to the percentage of delta (1-4 Hz), theta (5-8), alpha (9-12) or beta power (13-30 Hz) in the pre-stimulus EEG. Consecutive AEPs were computed. An increase in beta and a decrease in delta resulted both in an increase in the N60 and P70 component and a decrease in the P150-200 component. These beta and delta changes have been associated with changes in arousal. The increased N60 and P70 components with increases in beta might reflect increased attention due to an increase in arousal. We found that an increase in delta activity, leads to an increase of the late-latency P150-200 component, possibly due to an increased synchronization in the EEG.

The effect of diazepam on sensory gating was studied in rats by measuring diazepam effects on auditory evoked potentials (AEPs) elicited in a ten-tone paradigm. Trains of 10 repetitive tone-pip stimuli were presented. Rats (n = 8) received 4 mg·kg–1 diazepam subcutaneously or vehicle, counterbalanced over two sessions. Diazepam decreased the amplitude of the middle-latency P30 component and increased the amplitudes of the late-latency N60 and P67 components. The increase in the late-latency components might be due to a diazepam-induced decrease in arousal. Stimulus repetition decreased the amplitudes of the middle-latency N18 and P30 components in both conditions. This suggests that automated neuronal recovery functions underlying sensory gating remain intact with diazepam. In the vehicle condition, the amplitude of the late-latency P67 decreased with stimulus repetition, but not in the diazepam condition. This suggests a diazepam-induced decrease of behaviourally mediated habituation.

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Spike-Wave Discharges (SWDs) occur spontaneously in the EEG of WAG/Rij rats. These SWDs are a model for human absence seizures. In order to examine whether non-linear analysis methods can contribute to the analysis of SWDs, we estimated the correlation dimension of the SWDs and compared the value to that of the phase-randomized signals

Item does not contain fulltext Backqround: most patients subjected to locoregional anaesthesia report "deconnection sensations" once the effect of the local anaesthetic blocks reversibly the connection of peripheral sensors and the central nervous system. Only part of these sensations can be attributed to the effect at the site of action of the local anaesthetics. This study inventories the incidence and type of "deconnection sensations". The objective is to evaluate their cause and clinical relevance. Methods: an inventory questionnaire was composed in a pilot study. The extent of the nerve block was evaluated for each patient using the pinprick method. Results: All (100%) patients feit deconnection sensations in the arm. In addition to simple sensations such as tingling or warmth, the complex sensations were frequentiy reported. These included: telescoping (40 %); kinetic sensations (25%); disproportionate arm (80 %) and perturbed three-dimensional orientation (90 %). Conclusion: there is a striking similarity between the sensations during brachial plexus blockade and phantom limb sensations. Our patients reported on all sensations of this category, except for pain. This proves that these sensations are independent of complex adaptations in the central nervous system such as cortical reorganisation. Rather, our data corroborate the notion that the sensations are generated by a memory. For the clinical practice it is relevant to express information on persistence of sensations, which may help to avoid unnecessary supplementation of the nerve block.

To find a new measure from the EEG that quantifies the effects of anesthetics during surgery, the correlation dimension (CD) of the EEG of eight rats was estimated. To get informed about the anesthetic state, the noxious induced withdrawal reflex (NIWR) was measured, i.e. the force elicited by transcutaneous electrical stimulation of the hind paw. The algorithm of Grassberger and Procaccia (1983) to compute the CD was slightly modified and labeled as "dimensional complexity" (DC). The DC was estimated by applying a fit procedure to find the scaling region in the correlation integral. Experiments were performed under propofol infusion (30 à 40 mg.kg-1.h-1), with repeated bolus injections (3 mg) to induce periods of more profound anesthesia. The DC was compared to the Spectral Edge Frequency (SEF), a linear measure extracted from the power spectrum. The DC and SEF were correlated with the NIWR responses. The DC showed higher and more consistent correlations with the NIWR than the SEF. Correlation coefficients of NIWR and DC mainly varied between 0.6 and 0.8. Conclusion: New parameters from the field of non-linear dynamics can be an aiding tool in detecting effectual changes induced by anesthetics.

Item does not contain fulltext Although monotherapy in epilepsy treatment is frequently advocated, this is not based on studies with equal drug loads. This study was performed to investigate the experimental background of polytherapy with standardized drug loads. Dose-dependent effects on grip strength, accelerod performance, and spontaneous behavior of rats was used to study the effect of combining valproate and ethosuximide. The potency of the drugs (combination) was obtained by fitting the sigmoid E-max equation to the data. Drug interaction was assessed using the isobologram method and quantified by comparing equivalent drug loads with their 95% confidence intervals. We found that the effects of valproate and ethosuximide combine in a simple additive way in the grip strength experiment as well as in the accelerod experiment. In the behavioral studies, however, a higher drug load of the combination was needed to obtain the same amount of sedation, signifying infra-additivity. Infra-additivity of sedative effects is an important finding because this is by far the most frequent side effect mentioned in human studies. However, assessment of the therapeutic effect of the combination will have to be completed before a preference for mono- or polytherapy, based on the balance of adverse effects and efficacy, can be expressed.

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Item does not contain fulltext Within the context of the discussion about rational polytherapy, we determined the effects of four anaesthetics on the binding of [H-3]t-butylbicycloorthobenzoate ([H-3]TBOB) to the GABA(A) receptor complex in the presence of several concentrations of GABA (gamma-aminobutyric acid), in order to build a molecular model that can describe and quantify the interactions between the compounds. The empirical isobole method revealed that GABA and the anaesthetics acted synergically in displacing [H-3]TBOB. This synergy could be described by a simple molecular model in which both GABA and the anaesthetics displaced [H-3]TBOB allosterically and in which GABA allosterically enhanced the binding of the anaesthetics. To get information about the interaction between GABA and anaesthetics, we used [H-3]TBOB as a tracer ligand. The model indicated that GABA enhanced the affinity of thiopental 3.0-fold, propofol 5.0-fold, the neuroactive steroids Org 20599 3.5-fold and Org 20549 13-fold. Insight into the molecular mechanism and strength of these interactions can help clinicians to choose therapeutically optimal drug and dose combinations: a step towards rational polytherapy.

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