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Horizontal Slices (horizontal + slice)
Selected AbstractsFenfluramine Blocks Low-Mg2+ -Induced Epileptiform Activity in Rat Entorhinal CortexEPILEPSIA, Issue 8 2000K. Gentsch Summary: Purpose: The entorhinal cortex (EC) represents the main input structure to the hippocampus and seems to be critically involved in temporal lobe epilepsy. Considering that the EC receives a strong serotonergic projection from the raphe nuclei and expresses a high density of serotonin (5-HT) receptors, the effect of the 5-HT,releasing drug fenfluramine (FFA) on epileptiform activity generated in the EC was investigated in an in vitro model of epilepsy. Methods: The experiments were performed on 43 horizontal slices containing the EC, the subiculum, and the hippocampal formation obtained from 230,250 g adult Wistar rats. Using extracellular recording techniques, we investigated the effect of bath-applied FFA (200 ,mol/L to 1 mmol/L) on epileptiform activity induced by omitting MgSO4 from the artificial cerebrospinal fluid. Results: We demonstrate that FFA reversibly blocks epileptiform activity in the EC. Surprisingly, in the presence of the 5-HT uptake blocker paroxetine, the FFA-induced effect was diminished. Coapplication of the 5-HTIA receptor antagonist WAY 100635 prevented the FFA-induced anticonvulsive effect, suggesting that (a) the FFA-induced suppression of epileptiform activity is mediated by the release of 5-HT from synaptic terminals within the EC rather than by an unspecific effect of FFA and (b) released 5-HT most likely blocks the activity by activation of 5-HTIA receptors. Conclusion: FFA, which is primarily used because of its anorectic activity, might get an additional therapeutic value in the treatment of temporal lobe epilepsy with parahippocampal involvement. [source] Synaptic and non-synaptic mechanisms of amygdala recruitment into temporolimbic epileptiform activitiesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2003Julia Klueva Abstract Lateral amygdala (LA) activity during synchronized-epileptiform discharges in temporolimbic circuits was investigated in rat horizontal slices containing the amygdala, hippocampus (Hip), perirhinal (Prh) and lateral entorhinal (LEnt) cortex, through multiple-site extra- and intracellular recording techniques and measurement of the extracellular K+ concentration. Application of 4-aminopyridine (50 µm) induced epileptiform discharges in all regions under study. Slow interictal-like burst discharges persisted in the Prh/LEnt/LA after disconnection of the Hip, seemed to originate in the Prh as shown from time delay analyses, and often preceded the onset of ictal-like activity. Disconnection of the amygdala resulted in de-synchronization of epileptiform discharges in the LA from those in the Prh/LEnt. Interictal-like activity was intracellularly reflected in LA projection neurons as ,-aminobutyric acid (GABA)A/B receptor-mediated synaptic responses, and depolarizing electrogenic events (spikelets) residing on the initial phase of the GABA response. Spikelets were considered antidromically conducted ectopic action potentials generated at axon terminals, as they were graded in amplitude, were not abolished through hyperpolarizing membrane responses (which effectively blocked evoked orthodromic action potentials), lacked a clear prepotential or synaptic potential, were not affected through blockers of gap junctions, and were blocked through remote application of tetrodotoxin at putative target areas of LA projection neurons. Remote application of a GABAB receptor antagonist facilitated spikelet generation. A transient elevation in the extracellular K+ level averaging 3 mm above baseline occurred in conjunction with interictal-like activity in all areas under study. We conclude that interictal-like discharges in the LA/LEnt/Prh spread in a predictable manner through the synaptic network with the Prh playing a leading role. The rise in extracellular K+ may provide a depolarizing mechanism for recruitment of interneurons and generation of ectopic action potentials at axon terminals of LA projection neurons. Antidromically conducted ectopic action potentials may provide a spreading mechanism of seizure activity mediated by diffuse axonal projections of LA neurons. [source] Interpretation of observed fluid potential patterns in a deep sedimentary basin under tectonic compression: Hungarian Great Plain, Pannonian BasinGEOFLUIDS (ELECTRONIC), Issue 1 2001J. Tóth Abstract The , 40 000 km2 Hungarian Great Plain portion of the Pannonian Basin consists of a basin fill of 100 m to more than 7000 m thick semi- to unconsolidated marine, deltaic, lacustrine and fluviatile clastic sediments of Neogene age, resting on a strongly tectonized Pre-Neogene basement of horst-and-graben topography of a relief in excess of 5000 m. The basement is built of a great variety of brittle rocks, including flysch, carbonates and metamorphics. The relatively continuous Endr,d Aquitard, with a permeability of less than 1 md (10,15 m2) and a depth varying between 500 and 5000 m, divides the basin's rock framework into upper and lower sequences of highly permeable rock units, whose permeabilities range from a few tens to several thousands of millidarcy. Subsurface fluid potential and flow fields were inferred from 16 192 water level and pore pressure measurements using three methods of representation: pressure,elevation profiles; hydraulic head maps; and hydraulic cross-sections. Pressure,elevation profiles were constructed for eight areas. Typically, they start from the surface with a straight-line segment of a hydrostatic gradient (,st = 9.8067 MPa km,1) and extend to depths of 1400,2500 m. At high surface elevations, the gradient is slightly smaller than hydrostatic, while at low elevations it is slightly greater. At greater depths, both the pressures and their vertical gradients are uniformly superhydrostatic. The transition to the overpressured depths may be gradual, with a gradient of ,dyn = 10,15 MPa km,1 over a vertical distance of 400,1000 m, or abrupt, with a pressure jump of up to 10 MPa km,1 over less than 100 m and a gradient of ,dyn > 20 MPa km,1. According to the hydraulic head maps for 13 100,500 m thick horizontal slices of the rock framework, the fluid potential in the near-surface domains declines with depth beneath positive topographic features, but it increases beneath depressions. The approximate boundary between these hydraulically contrasting regions is the 100 m elevation contour line in the Duna,Tisza interfluve, and the 100,110 m contours in the Nyírség uplands. Below depths of ,,600 m, islets of superhydrostatic heads develop which grow in number, areal extent and height as the depth increases; hydraulic heads may exceed 3000 m locally. A hydraulic head ,escarpment' appears gradually in the elevation range of ,,1000 to ,,2800 m along an arcuate line which tracks a major regional fault zone striking NE,SW: heads drop stepwise by several hundred metres, at places 2000 m, from its north and west sides to the south and east. The escarpment forms a ,fluid potential bank' between a ,fluid potential highland' (500,2500 m) to the north and west, and a ,fluid potential basin' (100,500 m) to the south and east. A ,potential island' rises 1000 m high above this basin further south. According to four vertical hydraulic sections, groundwater flow is controlled by the topography in the upper 200,1700 m of the basin; the driving force is orientated downwards beneath the highlands and upwards beneath the lowlands. However, it is directed uniformly upwards at greater depths. The transition between the two regimes may be gradual or abrupt, as indicated by wide or dense spacing of the hydraulic head contours, respectively. Pressure ,plumes' or ,ridges' may protrude to shallow depths along faults originating in the basement. The basement horsts appear to be overpressured relative to the intervening grabens. The principal thesis of this paper is that the two main driving forces of fluid flow in the basin are gravitation, due to elevation differences of the topographic relief, and tectonic compression. The flow field is unconfined in the gravitational regime, whereas it is confined in the compressional regime. The nature and geometry of the fluid potential field between the two regimes are controlled by the sedimentary and structural features of the rock units in that domain, characterized by highly permeable and localized sedimentary windows, conductive faults and fracture zones. The transition between the two potential fields can be gradual or abrupt in the vertical, and island-like or ridge-like in plan view. The depth of the boundary zone can vary between 400 and 2000 m. Recharge to the gravitational regime is inferred to occur from infiltrating precipitation water, whereas that to the confined regime is from pore volume reduction due to the basement's tectonic compression. [source] Age-Related Three-Dimensional Morphological Changes in Rat Motoneurons Innervating Diaphragm and Longissimus MusclesANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2008H. Miyata Summary We investigated age-related morphological changes of rat motoneurons innervating diaphragm muscle (DI-MN) and lumber longissimus muscle (LL-MN) in which quite different activation patterns exist. In young (2,4 months) and old (24,26 months) rats, the motoneurons innervating both muscles were labelled retrogradely by intramuscular injection of cholera toxin B subunit. After a 4-day survival, horizontal slices of the spinal cord were processed with immunohistochemical staining (first antibody to cholera toxin B subunit and second antibody with Cy3) and observed with a confocal microscope. Three-dimensional reconstruction of labelled motoneurons was performed to examine soma and dendrite morphology. As compared to the soma volume in young rats, significantly smaller values were found in old rats in both motoneurons and the degrees of decline were 16.1% in DI-MN and 20.3% in LL-MN. Significant decreases in the thickness of primary dendrites were also found in both motoneurons, and the degrees of decline were 17.5% in DI-MN and 22.3% in LL-MN. Smaller changes were found in DI-MN than in LL-MN, indicating the possibility that increased activation by central drives can attenuate age-related morphological changes of the motor system in the spinal cord. [source] Ground-penetrating radar survey over bronze age circular monuments on a sandy soil, complemented with electromagnetic induction and fluxgate gradiometer dataARCHAEOLOGICAL PROSPECTION, Issue 3 2009L. Verdonck Abstract This paper presents a ground-penetrating radar (GPR) survey over two circular structures originally surrounding Bronze Age burial mounds at the site of Koekelare (western Belgium). The region is characterized by sandy soils. Their low water storage capacity and the consequent moisture contrasts in dry summers played an important role in the detection of over 1000 Bronze Age funeral monuments through aerial archaeology in the past few decades. At Koekelare, low attenuation of GPR waves resulted in the detection of a double and single circular ditch. A fluxgate gradiometer survey and electromagnetic induction (EMI) measurements did not clearly reveal the ditches. For the GPR wave velocity analysis, constant velocity migration tests were combined with time-domain reflectometry (TDR). The TDR measurements were made at different depths within the ditches and in the adjacent undisturbed soil, so that the differences in the physical soil parameters could be assessed. At a depth of approximately 0.45 to 0.8,m, the relatively homogeneous ditch fill produces few GPR reflections compared with the undisturbed soil, and is visible as a weak negative anomaly on the horizontal slices. At this depth, the grey or brownish black ditch fill was found in augering samples, clearly distinguishable from the yellowish brown sandy soil outside the ditches. The transition between the ditch and the underlying soil caused a gradual reflection of radar energy at a depth of approximately 0.8 to 1.2,m, although TDR showed no marked differences in relative permittivity between the ditches and the surrounding soil, and no clear steps as a function of depth. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||