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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 10 (1998), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Intracellular recordings were performed in area CA1 pyramidal cells of rat hippocampal slices to determine the effects of certain steroids on inhibitory postsynaptic potentials/currents (IPSP/Cs) mediated by GABAA receptors. Following application of the steroids 5α-pregnan-3α,21-diol-20-one (5α-THDOC), alphaxalone and 5β-pregnan-3α-ol-20-one (pregnanolone) hyperpolarizing PSPs developed into biphasic responses consisting of an early hyperpolarizing and a late depolarizing PSP sequence. Steroid-induced depolarizing PSPs could be elicited in the presence of antagonists to non-NMDA, NMDA, and GABAB receptors, indicating that these receptor types do not contribute significantly to the initiation of these responses. Depolarizing PSPs were completely blocked by both GABAA receptor antagonists bicuculline and t-butylbicyclophosphorothionat (TBPS) providing evidence for their mediation by GABAA receptors. The reversal potential of steroid-induced late inward PSCs, measured in single-electrode voltage clamp, was –29.9 ± 5.3 mV, whereas the early outward current, which corresponded to the early hyperpolarizing component of PSPs, reversed at –68.2 ± 1.5 mV. Depolarizing PSPs and late inward PSCs were sensitive to reduction of extracellular [HCO3–] and block of carbonic anhydrase by application of acetazolamide. The results suggest that certain neuroactive steroids can induce GABAA receptor-mediated depolarizing PSPs, which are dependent on HCO3–.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1912
    Keywords: High potassium ; Ictaform events ; Low calcium ; Low magnesium ; Methysticin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Methysticin is one of the constituents of Piper methysticum which possesses anticonvulsant and neuroprotective properties. Its effects on different in vitro seizure models were tested using extracellular recordings in rat temporal cortex slices containing the hippocampus and the entorhinal cortex. Elevating [K+]o0 induced seizure-like events with tonic and clonic electrographic phases in area CA1. Lowering [Ca2+]0 caused recurrent seizure like episodes with large negative field potential shifts. Lowering Mg2+ induced short recurrent discharges in area CA3 and CA1 while ictaform events lasting for many seconds were induced in the subiculum, entorhinal and temporal neocortex. In the hippocampus the activity stayed stable over a number of hours. In contrast, the ictaform events in the subiculum, entorhinal and temporal cortex changed their characteristics after one to two hours to late recurrent discharges. In a concentration-range from 10 to 100 μM methysticin reversibly blocked all these types of epileptiform activity. Decreases in [Ca2+]0 and associated slow field potentials evoked by repetitive stimulation of the stratum radiatum or the alveus remained almost unaffected by methysticin. A paired pulse stimulus paradigm used to test for effects of methysticin on synaptically evoked transient field potentials in normal medium revealed interference with mechanisms involved in frequency potentiation. While responses to alvear stimulation were largely unaffected, the responses to a paired pulse stimulus to stratum radiatum were depressed over the whole range of tested stimulus intervals. The findings suggest that methysticin has effects on different patterns of epileptiform activity possibly by interfering with processes responsible for frequency potentiation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1912
    Keywords: Key words High potassium ; Ictaform events ; Low calcium ; Low magnesium ; Methysticin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Methysticin is one of the constituents of Piper methysticum which possesses anticonvulsant and neuroprotective properties. Its effects on different in vitro seizure models were tested using extracellular recordings in rat temporal cortex slices containing the hippocampus and the entorhinal cortex. Elevating [K+]0 induced seizure-like events with tonic and clonic electrographic phases in area CA1. Lowering [Ca2+]0 caused recurrent seizure like episodes with large negative field potential shifts. Lowering Mg2+ induced short recurrent discharges in area CA3 and CA1 while ictaform events lasting for many seconds were induced in the subiculum, entorhinal and temporal neocortex. In the hippocampus the activity stayed stable over a number of hours. In contrast, the ictaform events in the subiculum, entorhinal and temporal cortex changed their characteristics after one to two hours to late recurrent discharges. In a concentration-range from 10 to 100 μM methysticin reversibly blocked all these types of epileptiform activity. Decreases in [Ca2+]0 and associated slow field potentials evoked by repetitive stimulation of the stratum radiatum or the alveus remained almost unaffected by methysticin. A paired pulse stimulus paradigm used to test for effects of methysticin on synaptically evoked transient field potentials in normal medium revealed interference with mechanisms involved in frequency potentiation. While responses to alvear stimulation were largely unaffected, the responses to a paired pulse stimulus to stratum radiatum were depressed over the whole range of tested stimulus intervals. The findings suggest that methysticin has effects on different patterns of epileptiform activity possibly by interfering with processes responsible for frequency potentiation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 58 (1971), S. 322-323 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
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    Unknown
    Kingston, R.I., etc. : Periodicals Archive Online (PAO)
    The Historian. 57:4 (1995:Summer) 803 
    ISSN: 0018-2370
    Topics: History
    Description / Table of Contents: THE AMERICAS
    Notes: Book Reviews
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 394 (1998), S. 189-192 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Coherent oscillations, in which ensembles of neurons fire in a repeated and synchronous manner, are thought to be important in higher brain functions. In the hippocampus, these discharges are categorized according to their frequency as theta (4–10 Hz), gamma (20–80 Hz) ...
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0630
    Keywords: 78.70 ; 73.40 ; 75.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The coupling of Cr to Fe in stacked Cr/Fe/Cr trilayers is studied by circular magnetic X-ray dichroism using fluorescence yield to monitor the absorption. From the dichroic spectra, we determine the thickness dependent average magnetic coupling of Cr to Fe for Cr layer thicknesses of 1, 2 and 3 ML. We compare our results to new calculated spectra. Additionally, all Cr spectra show significant contributions due to photon scattering processes at theL 2, 3 absorption edges depending on the degree of circular polarization.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0630
    Keywords: PACS: 78.70; 73.40; 75.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  The coupling of Cr to Fe in stacked Cr/Fe/Cr trilayers is studied by circular magnetic X-ray dichroism using fluorescence yield to monitor the absorption. From the dichroic spectra, we determine the thickness dependent average magnetic coupling of Cr to Fe for Cr layer thicknesses of 1, 2 and 3 ML. We compare our results to new calculated spectra. Additionally, all Cr spectra show significant contributions due to photon scattering processes at the L 2,3 absorption edges, depending on the degree of circular polarization.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 185 (1965), S. 437-455 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract At the Bonn 500 MeV Electronsynchrotron the spectrum of the Bremsstrahlung has been investigated for several maximum-energies between 250 MeV and 450 MeV and under various angles to the axes of theγ-ray. The upper limit of the spectrum has been measured carefully in respect to later experiments with photon difference method. The absolute errors of 4.5% permitted a control of the quantameter calibration or the cross-section for electron pair production.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 402 (1973), S. 225-231 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Crystal Structure of BaMnS2The compound BaMnS2 can be synthesized by heating an equivalent mixture of BaCO3 and Mn under a current of H2S at 1000°C. The crystal structure was determined by X-ray diffraction techniques. BaMnS2 is orthorhombic, D2h16-Pnma, a = 7.000, b = 4.144, c = 14.00 Å, z = 4. MnS4 tetrahedra linked by corners form waved layers, which are connected by barium ions. BaMnS2 has the same type of structure as the oxide SrZnO2. In the series of tetrahedral structures AxByCz in which A corresponds to an alkali metal or alkaline-earth metal and B to a transition metal, BaMnS2 is the first known example for a sulfide which is isostructural with an oxide.
    Notes: Durch Umsetzung von BaCO3 mit Mn im H2S-Strom bei 1000°C konnte BaMnS2 rein erhalten werden. Die Kristallstruktur wurde über röntgenographische Untersuchungen an Einkristallen aufgeklärt. Raumgruppe: D2h16-Pnma. Elementarzelle: a = 7,000 Å, b = 4,144 Å, c = 14,00 Å, sie enthält 4 Formeleinheiten. Die Manganatome sind tetraedrisch von Schwefelatomen umgeben. Durch Eckenverknüpfungen der Tetraeder werden gewellte Schichten ausgebildet, die über die Bariumatome zusammengehalten werden. BaMnS2 entspricht in seinem Aufbau dem SrZnO2 und ist damit aus der Reihe der Tetraedergerüststrukturen AxByCz, in denen A für ein Alkali- oder Erdalkalimetall und B für ein Nebengruppenmetall stehen, das erste Beispiel für ein Sulfid, das mit einem Oxid isotyp ist.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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