Millennium Ecosystem Assessment Scenario drivers (1970-2050): Climate and hydrological alterations

This study was carried out to support and enhance a series of global studies assessing contemporary and future changes in nutrient export from watersheds (Global Nutrient Export from Watersheds (NEWS)). Because hydrography is one of the most important drivers in nutrient transport, it was essential to establish how climatic changes and direct human activities (primarily irrigation and reservoir operations) affect the hydrological cycle. Contemporary and future hydrography was established by applying a modified version of a global water balance and transport model (WBMplus) driven by present and future climate forcing, as described in the Millennium Ecosystem Assessment scenarios (1970-2050). WBMplus represents a major upgrade to previous WBM implementations by incorporating irrigational water uptake and reservoir operations in a single modeling framework. Contemporary simulations were carried out by using both observed climate forcings from the Climate Research Unit of East Anglia (CRU) data sets and from Global Circulation Model (GCM) simulations that are comparable to the future simulations from the same GCM forcings. Future trends in three key human activities (land use, irrigation, and reservoirs operation for hydropower) were taken from the Integrated Model to Assess the Global Environment (IMAGE). The reservoir operation required establishing a realistic distribution of future reservoirs since the IMAGE model provided only the hydropower potentials for the different future scenarios

The Vega debris disc: A view from Herschel

We present five band imaging of the Vega debris disc obtained using the Herschel Space Observatory. These data span a wavelength range of 70-500 mu m with full-width half-maximum angular resolutions of 5.6-36.9 ''. The disc is well resolved in all bands, with the ring structure visible at 70 and 160 mu m. Radial profiles of the disc surface brightness are produced, and a disc radius of 11 '' (similar to 85AU) is determined. The disc is seen to have a smooth structure thoughout the entire wavelength range, suggesting that the disc is in a steady state, rather than being an ephemeral structure caused by the recent collision of two large planetesimals

GABAergic drugs in WAG/Rij rats. Mechanisms underlying spike and wave discharges

Contains fulltext : 27383.pdf (publisher's version ) (Open Access)It was aimed to further evaluate the role of the GABAergic neurotransmission system in the mechanisms underlying absence epilepsy. More specifically, the aim of this thesis is to investigate whether GABAergic neurotransmission is either quantitatively or qualitatively (or both) involved in the mechanisms underlying SWDs and whether this involvement is specifically determined by GABAA or GABAB mediated neurotransmission. To summarise, manipulation of different types of GABA receptors was shown to differentially affect the SWD activity. Systemic administration of GABA agonistic drugs resulted in an enhancement of SWD activity, with the exception of diazepam and loreclezole (discussed in 8.1.3.). It has been predicted that (relatively) enhancing GABAB-related neurotransmission in TC cells should slow down the peak frequency of SWDs (Destexhe, 1999; Destexhe and Sejnowski, 2003), which was confirmed in this thesis (chapter 4). Also, it was shown that hazard rate analysis can be a useful tool for hypothesising about the SWD starting and stopping mechanisms. Moreover, it was shown that this type of analysis might reveal more information on these mechanisms than the standard analysis of averages (of incidence and duration). In general, stimulation of GABAA receptors was shown to increase the probability of the generation of SWDs and to decrease the probability of the cessation of SWDs. Stimulation of GABAB receptors was also shown to increase the probability of SWD generation. Moreover, GABAB receptor activation not only decreased the probability of the stopping of a SWD, but also changed the course of this probability as the SWD lasts. Possible biological mechanisms responsible for these effects were discussed, and some possible types of drugs for the treatment of absence epilepsy were proposed.Promotor : Coenen, A.M.L. Co-promotor : Rijn, C.M. vanRU Radboud Universiteit Nijmegen, 7 februari 2006141 p

The effects of vigabatrin on the beta frequency spectral power in the EEG of rats during sleep and active behaviour

Contains fulltext : 63618.pdf (publisher's version ) (Open Access

Effects of R-baclofen on the delta frequency band during active and passive behavior in rats

Contains fulltext : 64255.pdf (publisher's version ) (Open Access

Effects of vigabatrin on spike and wave discharges in the eeg of rats

Item does not contain fulltextIn the present study, the effects of vigabatrin on type I and type II SWDs in the EEG of rats were studied. Vigabatrin is an irreversible GABA transaminase inhibitor which increases, long lasting, GABA concentrations, thus affecting both GABAA and GABAB conductances. Type I SWDs occur abundantly in WAG/Rij rats, whereas this type is virtually absent in ACI rats. In ACI rats however, type II SWDs do occur. The type I SWDs were studied in WAG/Rij rats after inter-peritoneal injection of 15-500 mg/kg of vigabatrin, 6 hours after injection. The type II SWDs were studied in ACI rats after inter-peritoneal injection of 500 mg/kg of vigabatrin, 6 hours after injection. The incidence of both type I and type II SWDs was significantly increased after vigabatrin as compared to saline. The duration of type II SWDs was also increased after vigabatrin as compared to saline treatment, whereas the duration of type I SWDs was not affected. The peak-frequency of both type I and type II SWDs was decreased after vigabatrin. Thus, vigabatrin alters not only the incidence but also the morphology of both type I and type II SWDs. These results might fit well with predictions of a theoretical model, in which both GABAA and GABAB conductances are modulated, as proposed by Destexhe (1999)

Effects of d-amphetamine on the performance of rats in an animal analogue of the A-X Continuous Performance Test

Schizophrenia patients subjected to the A-X Continuous Performance Test (A-X CPT) show cognitive deficits that are thought to reflect impaired representation and maintenance of context information. An issue deserving attention is to what extent the acute amphetamine model of schizophrenia also models these cognitive deficits. The present experiment examined the effect of acute d-amphetamine (AMP) on the performance of rats in an animal analogue of the A-X CPT. Subjects first learned to solve an A->X+, B->X-, A->Y-discrimination task, with A and B representing visual features; X and Y designating auditory target stimuli; -> signifying a serial presentation; and + and - referring to food reinforcement and non-reinforcement, respectively. Frequency of food-magazine visits was the dependent measure. After mastering the discrimination, rats received test trials under either saline or 0.5 mg/kg AMP (s.c.). At test, the interval between feature and target presentation was varied; reinforcement contingencies were maintained. AMP significantly impaired performance on the A->X+/B->X- discrimination by increasing the response level on B->X- trials. AMP did not significantly affect performance on the A->X+/A->Y- discrimination. However, AMP also increased magazine responding in the absence of the presentation of features and targets. A parsimonious conclusion based on these preliminary results is that acute AMP does not affect processing of context information provided by the visual features in this procedure. It rather has a more non-specific response-enhancing effect, especially with respect to stimuli associated with the delivery of food

Viabatrin alters the spike and wave discharges in the EEG of rats

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GABAergic manipulationin absence epilepsy: WAG/Rij rats and a computational model

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Vigabatrin changes the proprties of spike-and-wave discharges in a rat model for absence epilepsy

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