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  • 1
    Electronic Resource
    Electronic Resource
    Contribution of single-unit spike waveform changes to temperature-induced alterations in hippocampal population spikes (1996)
    Springer
    Experimental brain research 107 (1996), S. 348-360 
    Details
    ISSN: 1432-1106
    Keywords: Hippocampus ; Temperature ; Granule cell ; Exploration ; Fascia dentata ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Brain temperature changes accompany exploratory behavior and profoundly affect field potential amplitudes recorded in hippocampus. The waveform alterations in fascia dentata include a reduction in population spike area, which might be explained by fewer granule cells firing in response to a given stimulus or by an alteration in the size or shape of the individual action potentials. This study was designed to assess these alternate possibilities. In experiment 1, changes in the shape and firing rates of single cells recorded in the fascia dentata of awake rats were compared with changes in the population spike before and after a bout of activity. Single-unit amplitudes were significantly reduced following exploration, and there was a small (〈 3%) change in unit spike-width. These changes, however, were insufficient to account, in a linear fashion, for the entire decline in the population spike. In experiment 2, radiant heat was used to manipulate brain temperature in anesthetized rats. As in the first experiment, the magnitude of change in the extracellular units was much smaller than the change in population spike amplitude. The spontaneous firing rates of the cells were also modified by brain temperature changes. In experiment 3, the polysynaptic, contralateral commissural response (which covaries with changes in the ipsilateral population spike at a fixed temperature) was measured as a function of either exploratory behavior or radiant heat. The relationship between the ipsilateral population spike and corresponding polysynaptic commissural response was altered following exploration and passive warming in a manner consistent with a reduction in net granule cell output, reduced transmission efficacy through the polysynaptic circuit, or a combination of these. Taken together these data suggest that at least two factors contribute to temperature-dependent changes in the perforant path-evoked population spikes recorded in the fascia dentata: changes in the size of individual action potentials and alterations in discharge of action potentials in response to a given stimulus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230417
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical study of geometrical and electronic structures of various thiophene-based tricyclic polymers (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 10607-10615 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theoretical study of a variety of tricyclic polymers [–(C8H2X2Y)n–] with two different types of bridging groups was performed, X(Double Bond)S and Y(Double Bond)CH2, SiH2, C(Double Bond)O, C(Double Bond)S, or C(Double Bond)CH2 for the fused bithiophene system and vice versa for the thieno-bicyclic system. These two types of the bridging groups are different from each other in that S favors the aromatic form of a cyclic polymer and the other groups prefer the quinonoid form. Geometrical structures of the polymers were obtained from semiempirical self-consistent-field (SCF) band calculations and the electronic properties from the modified extended Hückel band calculations. It is found that the ground-state geometrical structures of the tricyclic polymers are determined by the bridging groups in the outer rings. That is, the fused bithiophene system is aromatic in the ground state and the thieno-bicyclic system is quinonoid. The ground-state band gaps (which correspond to the absorption peaks of π–π* band transition) of the polymers were estimated to be in the range of 0.7–2.0 eV. The band gaps were analyzed in terms of the bond-length alternation along the conjugated carbon backbone, the C1–C4 interactions, and the electronic effect of the bridging groups. We also investigated the geometrical and electronic structures of polydicyanomethylene-cyclopenta-dicyclopentadiene (PDICNCY). Unlike the theoretical predictions of Toussaint and Bredas [Synth. Met. 69, 637 (1995)], PDICNCY in the ground state was estimated to be of the quinonoid form and to possess a large band gap (2.55 eV) comparable with the gap of polythiophene. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474175
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  • 3
    Electronic Resource
    Electronic Resource
    Strain effects in lattice-mismatched InxGa1−xAs/InyAl1−yAs coupled double quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 61-63 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy (TEM) and Raman scattering spectroscopy measurements were performed to investigate strain effects in lattice-mismatched InxGa1−xAs/InyAl1−yAs modulation-doped coupled double quantum wells. The high-resolution TEM images showed that a 100-Å In0.8Ga0.2As deep quantum well and a 100-Å In0.53Ga0.47As shallow quantum well were separated by a 30-Å In0.25Ga0.75As embedded potential barrier. The selected-area electron-diffraction pattern obtained from TEM measurements on the InxGa1−xAs/InyAl1−yAs double quantum well showed that the InxGa1−xAs active layers were grown pseudomorphologically on the InP buffer layer. The values of the strain and the stress of the InxGa1−xAs layers were determined from the electron-diffraction pattern. Based on the TEM results, a possible crystal structure for the InxGa1−xAs/InyAl1−yAs coupled double quantum well is presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121723
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetotransport, magneto-optical, and electronic subband studies in InxGa1−xAs/InyAl1−xAs modulation-doped strained double quantum wells (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4388-4393 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetotransport and magneto-optical measurements on InxGa1−xAs/InyAl1−yAs modulation-doped strained double quantum wells with a 100 Å In0.8Ga0.2As well and a 100 Å In0.53Ga0.47As quantum wells separated by a 35 Å In0.25Ga0.75As potential barrier were carried out to investigate the electrical and the optical properties of the electron gas in the quantum wells. The Shubnikov-de Haas measurements at 1.5 K demonstrated clearly the occupation of three subbands in the quantum wells by a two-dimensional electron gas. The electron effective masses determined from the slopes of the cyclotron resonance peak energies as a function of the magnetic field were 0.06171 and 0.05228me. The electronic subband energies, the subband energy wavefunctions, and the Fermi energy in the quantum wells were self-consistently calculated a transfer matrix method taking into account the exchange-correlation effect, the strain effect, and the nonparabolicity effect, and the results of the cyclotron resonance measurements qualitatively show the nonparabolicity effect in the strained double quantum well. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366165
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of CB1 Receptors on Rat Neuronal Cell Cultures: Binding and Functional Studies Using the Selective Receptor Antagonist SR 141716A (1997)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 68 (1997), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: This study was undertaken to characterize further the central cannabinoid receptors in rat primary neuronal cell cultures from selected brain structures. By using [3H]SR 141716A, the specific CB1 receptor antagonist, we demonstrate in cortical neurons the presence of a high density of specific binding sites (Bmax = 139 ± 9 fmol/mg of protein) displaying a high affinity (KD = 0.76 ± 0.09 nM). The two cannabinoid receptor agonists, CP 55940 and WIN 55212-2, inhibited in a concentration-dependent manner cyclic AMP production induced by either 1 µM forskolin or isoproterenol with EC50 values in the nanomolar range (4.6 and 65 nM with forskolin and 1.0 and 5.1 nM with isoproterenol for CP 55940 and WIN 55212-2, respectively). Moreover, in striatal neurons and cerebellar granule cells, CP 55940 was also able to reduce the cyclic AMP accumulation induced by 1 µM forskolin with a potency similar to that observed in cortical neurons (EC50 values of 3.5 and 1.9 nM in striatum and cerebellum, respectively). SR 141716A antagonized the CP 55940- and WIN 55212-2-induced inhibition of cyclic AMP accumulation, suggesting CB1 receptor-specific mediation of these effects on all primary cultures tested. Furthermore, CP 55940 was unable to induce mitogen-activated protein kinase activation in either cortical or striatal neurons. In conclusion, our results show nanomolar efficiencies for CP 55940 and WIN 55212-2 on adenylyl cyclase activity and no effect on any other signal transduction pathway investigated in primary neuronal cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1997.68010402.x
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  • 6
    Electronic Resource
    Electronic Resource
    Lines of Murine Oligodendroglial Precursor Cells Immortalized by an Activated neu Tyrosine Kinase Show Distinct Degrees of Interaction with Axons In Vitro and In Vivo (1995)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 7 (1995), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Replication-defective retroviruses expressing the t-neu oncogene, or a hybrid protein with the neu tyrosine kinase linked to the external region of the human epidermal growth factor receptor (egfr-neu), were used to establish lines of murine oligodendroglial precursor cells. Differentiation of the t-neu lines into myelin-associated glycoprotein (MAG)-positive oligodendrocytes was induced by dibutyryl cAMP, and the egfr-neu line showed limited differentiation in vitro upon withdrawal of epidermal growth factor. Cerebellar granule cell neurons expressed mitogens for the cell lines. Upon transplantation into demyelinated lesions, t-neu line cells engaged with the demyelinated axons whereas the egfr-neu line cells differentiated further and ensheathed the axons. These cell lines thus interact with neurons in vitro and in vivo and can be used as tools to define the molecules involved in different stages of neuron-glia interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1995.tb01115.x
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetotransport, magneto-optical, and electronic subband studies in InxGa1−xAs/In0.52Al0.48As one-side-modulation-doped asymmetric step quantum wells (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1752-1754 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Shubnikov–de Haas (SdH), Van der Pauw Hall-effect, and cyclotron resonance measurements on InxGa1−xAs/In0.52Al0.48As asymmetric step quantum wells were carried out to investigate the electrical properties of a free electron gas and to determine the effective mass of the electron gas, the subband energies, and the wave functions in the InxGa1−xAs quantum wells. The SdH measurements at 1.5 K demonstrated clearly the existence of a quasi-two-dimensional electron gas in the InxGa1−xAs quantum wells, and the fast Fourier transformation results for the SdH data indicated clearly the occupation by that gas of two subbands in the quantum wells. The electronic effective masses determined from the slopes of the main peak absorption energies as a function of the magnetic field were 0.0477 and 0.053 me for the first excited and the ground subbands, respectively. The electronic subband energies and the wave functions in the InxGa1−xAs/In0.52Al0.48As step quantum wells were calculated by a self-consistent method taking into account exchange-correlation effects together with the strain and nonparabolicity effects. The results of the cyclotron resonance measurements qualitatively satisfied the nonparabolicity effects of the step quantum well. These results can help improve understanding for the application of InxGa1−xAs/In0.52Al0.48As step quantum wells in optoelectronic devices. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117474
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  • 8
    Electronic Resource
    Electronic Resource
    Electronic subband studies in In0.52Al0.48As/InxGa1−xAs one-side-modulation-doped asymmetric coupled double quantum wells (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 508-510 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Shubnikov–de Haas (SdH) and van der Pauw Hall effect measurements on In0.52Al0.48As/InxGa1−xAs coupled double quantum wells grown by metalorganic chemical vapor deposition have been carried out to investigate the magnetotransport properties of an electron gas and to determine the subband energies and wave functions in the coupled quantum wells. Transmission electron microscopy measurements showed that In0.8Ga0.2As and In0.53Ga0.47As quantum wells were separated by an In0.25Ga0.75As potential barrier in an active region. The SdH measurements at 1.5 K demonstrated clearly the existence of a quasi-two-dimensional electron gas in the quantum wells. The fast Fourier transformation results for the SdH data clearly indicate the occupation of three subbands in the In0.52Al0.48As/InxGa1−xAs coupled quantum wells. Electron subband energies and wave functions in the quantum wells were calculated by a self-consistent method taking into account exchange-correlation effects. The first and second excited subband wave functions in the asymmetric quantum well are strongly coupled over both In0.8Ga0.2As and In0.53Ga0.47As wells. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114072
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  • 9
    Electronic Resource
    Electronic Resource
    Regulation of Androgen Action by Receptor Gene Inhibition (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 761 (1995), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1995.tb31372.x
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  • 10
    Electronic Resource
    Electronic Resource
    Cyclospora cayetanensis: First imported infections in Germany (1997)
    Springer
    Infection 25 (1997), S. 167-170 
    Details
    ISSN: 1439-0973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Over the last decade increasing numbers of enteritis cases have been attributed to infection with a new coccidian species that was namedCyclospora cayetanensis in 1993. Diarrhea caused by this agent is clinically indistinguishable from cryptosporidiosis, isosporiasis and microsporidiosis, butCyclospora infections are often very prolonged (up to 15 weeks) and may cause severe weight loss. Diagnosis of infection is important because, in contrast to diarrhea caused byCryptosporidium and microsporidia, treatment with co-trimoxazole is effective. Here we report the cases of two female patients, aged 70 and 58 years old, respectively, who suffered from severe, prolonged diarrhea after a vacation in Singapore, Java and Bali. Routine microbiological laboratory diagnostics were unable to demonstrate the presence of known enteropathogenic bacteria. Modified Ziehl-Neelsen staining of fecal smears revealed oocysts ofCyclospora cayetanensis, and treatment of the patients with co-trimoxazole was promptly effective. We would like to increase awareness of the possibility ofCyclospora infections in patients with prolonged diarrhea who have travelled to endemic areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02113606
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