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  • 1
    Electronic Resource
    Electronic Resource
    High pressure-jump apparatus for kinetic studies of protein folding reactions using the small-angle synchrotron x-ray scattering technique (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3895-3899 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An apparatus suitable for pressure-jump experiments with variable pressure amplitude and a fast response time to facilitate time-resolved small-angle x-ray scattering at synchrotron facilities is described. The high pressure-jump apparatus is capable of performing bidirectional pressure jumps at a time resolution as high as 5 ms. The high pressure sample cell presented has flat diamond windows and is suited for pressures up to 0.7 GPa operating in the temperature range from −40 to 120 °C. The cell is designed for investigating biological and other soft condensed matter materials. Modifications on the window supports allow also simultaneous wide-angle x-ray scattering data to be taken. We have used the equipment to study the kinetics of protein folding reactions. The performance of the apparatus is demonstrated by presenting data on the pressure-induced un/refolding reaction of the water-soluble protein SNase WT. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1290508
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of Glutamate Application on the Rhythm of Low Magnesium-induced Epileptiform Activity in Hippocampal Slices of Guinea-pigs (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 8 (1996), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The extracellular concentration of glutamate has previously been reported to increase to more than 10-fold the basal level during seizure activity. In the present study, we tested whether localized increases in extracellular glutamate concentration influence the rhythm of epileptiform discharges in the low-magnesium epilepsy model. In hippocampal slices of guinea-pigs, epileptiform activity was induced by omission of magnesium from the bath fluid. Glutamate and its subreceptor agonists N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid (AMPA) were ejected into different strata of the CA3 and CA1 regions using microiontophoretic and micropressure application. Glutamate, NMDA and AMPA applied to the CA3 region, but not to the CA1 region, induced a short-lasting increase in epileptiform discharge frequency, often followed by a transient reduction. The effect was most pronounced with application into the stratum lacunosum-moleculare of the CA3 region and could only be evoked in slices exceeding 400 μm in thickness. The effects on the rhythm of epileptiform discharges induced by NMDA and AMPA were blocked by their specific receptor antagonists. They were not influenced by application of GABAA and GABAB receptor antagonists. Changes in somatic membrane potential of CA3 pyramidal neurons did not correlate with changes in the rhythm of epileptiform discharges elicited in this region. The transient suppression of epileptiform discharges that followed the increase in discharge frequency was abolished by an adenosine A1 receptor antagonist. We propose that localized increases in extracellular glutamate concentration modify the rhythm of epileptiform discharges due to changes in neuronal network activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1996.tb00735.x
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  • 3
    Electronic Resource
    Electronic Resource
    Spontaneous and stimulus-triggered epileptic discharges: delayed antiepileptic effect with triggering (1994)
    Springer
    Experimental brain research 79 (1994), S. 376-384 
    Details
    ISSN: 1432-1106
    Keywords: Verapamil ; Calcium channel blockers Epilepsy ; Hippocampus ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present study was to test whether the organic calcium channel blocker verapamil acts not only on spontaneously occurring epileptiform field potentials (EFP) but also on EFP triggered by single electrical stimuli in the low-Mg2+ epilepsy model. The experiments were carried out on hippocampal slices of guinea pigs. EFP were elicited by omission of Mg2+ from the perfusate and recorded from stratum pyramidale and stratum radiatum in the CA1 subfield. Single electrical stimuli were applied to the Schaffer collateral pathway. Verapamil was added to the bath solution in concentrations of 40 and 60 μmol verapamil/1 at normal (4 mmol/l) and elevated (8 mmol/1) K+ levels. After omission of Mg2+ from the perfusate, spontaneously occurring EFP appeared in all trials. These spontaneously occurring EFP were suppressed dose-dependently upon addition of verapamil to the perfusate. At elevated K+ levels, the latencies to suppression were significantly reduced and the dose dependency was abolished for the two doses of verapamil used. Triggered EFP reappeared upon stimulation after spontaneously occurring EFP had been suppressed, except for trials with 60 /gmmol verapamil/1 bath solution with elevated K+ levels. The stimulus-evoked EFP were abolished with continuing perfusion of verapamil except for trials with 40 μmol/1 at normal extracellular K+ concentrations. This effect was again dose dependent and enhanced by elevating the K+ level. In all experiments, stimulus-evoked EFP reappeared upon wash-out of verapamil. A primary action of verapamil on pacemaker functions in epileptogenic tissue is assumed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229178
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  • 4
    Electronic Resource
    Electronic Resource
    Melatonin reduces low-Mg2+ epileptiform activity in human temporal slices (1995)
    Springer
    Experimental brain research 107 (1995), S. 321-325 
    Details
    ISSN: 1432-1106
    Keywords: Epilepsy ; Melatonin ; Low Mg2+ ; Epileptiform field potentials ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Scizure susceptibility waxes and wanes in an apparently circadian manner in many epileptic patients. Fluctuations of melatonin concentration with highest levels during the night and lowest levels in the early morning could be involved in this phenomenon. Therefore, the action of melatonin on epileptic activity was tested. The experiments were carried out on human temporal neocortical slices cut from tissue resected for surgical treatment of epilepsy. Autoradiographic studies were performed on parallel slices with 100–120 pmol 2-[125I]iodomelatonin/l in the absence or presence of unlabelled melatonin. High-affinity binding sites of melatonin could be demonstrated in layers II–V of the temporal cortex. The binding was saturable, specific and occurred with low capacity. In electrophysiological studies, epileptiform field potentials were elicited by omission of Mg2+ from the superfusate and recorded from layers II–V. The frequency of occurrence of epileptiform field potentials was reduced to 0.5 of the initial value with application of melatonin (10 and 100 nmol/l) in each case. This effect was reversible upon washing. The findings favour the hypothesis that melatonin depresses epileptiform neuronal activity through specific neocortical receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230052
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