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  • 11
    Electronic Resource
    Electronic Resource
    Learning abilities depend on NMDA-receptor density in hippocampus in adult rats (1997)
    Springer
    Journal of neural transmission 104 (1997), S. 281-289 
    Details
    ISSN: 1435-1463
    Keywords: Learning ; memory ; NMDA-receptor density ; cerebral cortex ; hippocampus ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The hippocampal NMDA-receptor is predominantly involved to establish long-term potentation (LTP) which is assumed to underlie fundamental molecular mechanisms of learning and memory. In the present study, NMDA-receptor density was investigated in parietotempral cerebral cortex and in hippocampus of commonly bred naive adult male Wistar rats which had performed well or poorly in the passive avoidance paradigm. NMDA-receptor binding was determined in saturation experiments using (3H) MK-801 as a ligand and data for K d and Bmax were calculated from Scatchard plots. In general, higher NMDA receptor density was found in the hippocampus as compared to parietotemporal cerebral cortex. This regional difference became particularly obvious in good performers but was abolished in poor performers. In the hippocampus, a significantly higher NMDA-receptor density could be found in rats which had performed well in the passive avoidance task as compared to poor performers. In contrast, no such differences could be found in parietotemporal cerebral cortex. The data may indicate that the reduction in hippocampal NMDA-receptor density is of functional importance, for cognitive abilities in both physiological and pathophysiological conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01273188
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  • 12
    Electronic Resource
    Electronic Resource
    Electromagnetic fission of238U at 600 and 1000 MeV per nucleon (1995)
    Springer
    The European physical journal 353 (1995), S. 197-204 
    Details
    ISSN: 1434-601X
    Keywords: 25.75.+r ; 25.85.-w ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electromagnetic fission of238U projectiles at E/A =600 and 1000 MeV was studied with the ALADIN spectrometer at the heavy-ion synchrotron SIS. Seven different targets (Be, C, Al, Cu, In, Au and U) were used. By considering only those fission events where the two charges added up to 92, most of the nuclear interactions were excluded. The nuclear contributions to the measured fission cross sections were determined by extrapolating from beryllium to the heavier targets with the concept of factorization. The obtained cross sections for electromagnetic fission are well reproduced by extended Weizsäcker-Williams calculations which include E1 and E2 excitations. The asymmetry of the fission fragments' charge distribution gives evidence for the excitation of the double giant-dipole resonance in uranium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01295898
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  • 13
    Electronic Resource
    Electronic Resource
    On the origin of surface states in a correlated local-moment film (1998)
    Springer
    The European physical journal 2 (1998), S. 249-257 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.70.-i Magnetic films and multilayers - 73.20.At Surface states, band structure, electron density of states - 75.50.Pp Magnetic semiconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The electronic quasiparticle structure of a ferromagnetic local moment film is investigated within the framework of the s-f model. For the special case of a single electron in an otherwise empty energy band being exchange coupled to a fully ordered localised spin system the problem can be solved exactly and, for the spin- electron, some marked correlation effects can be found. We extend our model to incorporate the influence of the surface on the electronic structure. Therefore we modify the hopping integrals in the vicinity of the surface. This leads to the existence of surface states, both for the spin- and the spin- spectral density of states. The interplay between the modification of the hopping integrals and the existence of surface states and correlation effects is discussed in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050247
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  • 14
    Electronic Resource
    Electronic Resource
    On the analytic continuation of rank one eisenstein series (1996)
    Springer
    Geometric and functional analysis 6 (1996), S. 572-586 
    Details
    ISSN: 1420-8970
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02249264
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  • 15
    Electronic Resource
    Electronic Resource
    The trace class conjecture in the theory of automorphic forms. II (1998)
    Springer
    Geometric and functional analysis 8 (1998), S. 315-355 
    Details
    ISSN: 1420-8970
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract. Let G be the group of real points of a reductive algebraic $ \Bbb {Q} $ -group satisfying the assumptions made in [H, Chapter I] and let $ \Gamma $ be an arithmetic subgroup of G. Let $ R_{\Gamma} $ be the right regular representation of G on $ L^2(\Gamma \backslash G) $ and denote by $ R^d_\Gamma $ the restriction of $ R_\Gamma $ to the discrete subspace. In this paper we prove that for every integrable rapidly decreasing function f on G, the operator $ R^d_\Gamma (f) $ is of the trace class.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000390050059
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  • 16
    Electronic Resource
    Electronic Resource
    Molecular evolution: Evidence for the monophyletic origin of multicellular animals (1995)
    Springer
    Naturwissenschaften 82 (1995), S. 36-38 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01167869
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  • 17
    Electronic Resource
    Electronic Resource
    Molecular Evolution: Evidence for the Monophyletic Origin of Multicellular Animals (1995)
    Springer
    Naturwissenschaften 82 (1995), S. 36-38 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01167869
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  • 18
    Electronic Resource
    Electronic Resource
    Differentiation: A Central Topic in Developmental and Cell Biology (1999)
    Springer
    Naturwissenschaften 86 (1999), S. 457-467 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Notes: MyoD/myogenin genes and neural key genes (e.g., achaete scute-C, neurogenin), are switched on which control entire sets of subordinate effector genes. In multiplying cells "cell heredity" based on an epigenetic cellular memory enables transmission of the cell type determining program from parental to daughter cells. This memory can be based on autocatalytic self-activation of cell type specific selector genes and on the enduring action of gene groups such as the Polycomb and thrithorax complexes that code for proteins which bind to DNA sequences called cellular memory modules. These modules confer permanent accessibility (potentiation) or inaccessibility (silencing) upon many different gene loci on the chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001140050655
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  • 19
    Electronic Resource
    Electronic Resource
    Untersuchungen zur Verbesserung des Designs eines alloplastischen epithelisierten Tracheaersatzes (1997)
    Springer
    HNO 45 (1997), S. 453-459 
    Details
    ISSN: 1433-0458
    Keywords: Schlüsselwörter Alloplastischer Tracheaersatz ; Polytetrafluorethylen ; Polyethylen ; Zellseeding ; Key words Alloplastic tracheal replacement ; Polytetrafluorethylene ; Polyethylene ; Cell seeding technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Replacement of the tracheal conduit remains an unresolved problem. The microporous material expanded polytetrafluorethylene (ePTFE) is suitable for tracheal reconstruction. The aim of our study was to improve the limited mechanical properties of this material by incorporating reinforcement elements and to examine the influence of these elements on host incorporation and epithelialization. In so dours ePTFE prostheses were reinforced with Ionomer cement and porous high density polyethylene (pHDPE) rings and implanted into the neck muscle of miniature pigs. One of these prostheses was epithelialized by a cell seeding technique and was thus placed into a tracheal defect. Results were examined grossly by endoscopy and than by light and scanning electron microscopy. The shapes of both types of prostheses showed a high stability. The reinforcement elements did not impair bioincorporation or the ability to epithelialize. In vivo interposition of an incorporated and epithelialized prosthesis to a host led to cell differentiation. The improved biomechanical properties of the prostheses waid and the reproducible formation of epitheliums are important advances in the solution of effectively correcting tracheal defects.
    Notes: Zusammenfassung Das Problem der Herstellung eines funktionierenden alloplastischen Tracheaersatzes ist bisher nicht gelöst. Mikroporöse Biomaterialien aus ePTFE (expanded Polytetrafluorethylen) sind für die Wandstruktur einer Tracheaprothese geeignet. Ziel unserer Untersuchungen war, die ungenügende Kompressionsstabilität dieses Materials durch zusätzliche Verstärkungselemente zu verbessern und den Einfluß dieser Elemente auf Inkorporation und Epithelisierung zu untersuchen. Hierfür wurden ePTFE-Prothesen mit Spangen aus Glasionomerzement und porösem „High-density-Polyethylen” (pHDPE) verstärkt und in den Halswendermuskel von Minischweinen implantiert. In einem Pilotversuch wurde eine solche Prothese mit der Technik des Zellseedings epithelisiert und in einen Tracheadefekt interponiert. Die Ergebnisse werden durch licht-, rasterelektronenmikroskopische und endoskopische Befunde demonstriert. Bei beiden Prothesenformen konnte eine verbesserte Kompressionsstabilität erzielt werden. Inkorporation und Epithelisierung werden durch die Verstärkungselemente nicht beeinträchtigt. Die Interposition einer bereits im Muskel inkorporierten und epithelisierten Prothese in das physiologische Milieu führt zu einer Epitheldifferenzierung. Die Verbesserung der biomechanischen Eigenschaften und die reproduzierbare Epithelisierung der Prothese sind wichtige Teilschritte auf dem Weg zur Lösung des Gesamtproblems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001060050123
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  • 20
    Electronic Resource
    Electronic Resource
    Probleme der Wachstumshormonbehandlung bei kleinwüchsigen Kindern mit normaler Wachstumshormonsekretion (1997)
    Springer
    Monatsschrift Kinderheilkunde 145 (1997), S. 1194-1196 
    Details
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Wachstumshormonmangel ; Wachstumshormontherapie ; Kleinwuchs ; Key words Growth hormone deficiency ; Growth hormone therapy ; Growth disorders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Since 1985, some studies have tested the efficiency of treatment with recombinant DNA-derived growth hormone (GH) in children without laboratory evidence of classic growth hormone deficiency. Until now, it remained uncertain whether or not GH-therapy can improve the final adult height in non-GH deficient children. Besides, some major concerns must be critically discussed in order to evaluate the indication of GH-therapy in these children with short stature for various reasons. These concerns include psychological and sociomedical aspects of unrestricted growth promoting therapy.
    Notes: Zusammenfassung In mehreren klinischen Studien und Behandlungsversuchen wurde und wird biosynthetisches Wachstumshormon (GH) auch bei Kindern eingesetzt, bei denen gemäß den aktuellen Definitionen (z.B. der Arbeitsgemeinschaft für Pädiatrische Endokrinologie) kein Wachstumshormonmangel vorliegt. Bislang ist nicht gesichert, daß die Endgröße solcher Patienten nach Abschluß des Wachstums durch die aufwendige GH-Therapie signifikant verbessert wird. Unabhängig davon sollen im folgenden Beitrag einige ernsthafte individualmedizinische (v.a. psychologische) und sozialmedizinische Probleme diskutiert werden, die zum restriktiven Umgang mit der Indikation einer Wachstumshormontherapie bei Kindern ohne GH-Mangel mahnen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001120050219
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