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  • 1
    Digitale Medien
    Digitale Medien
    Measurement of nanomolar dopamine diffusion using low-noise perfluorinated ionomer-coated carbon fiber microelectrodes and high-speed cyclic voltammetry (1989)
    s.l. : American Chemical Society
    Analytical chemistry 61 (1989), S. 1805-1810 
    Details
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac00192a004
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  • 2
    Digitale Medien
    Digitale Medien
    Theory relating in vitro and in vivo microdialysis with one or two probes (2002)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neurochemistry 81 (2002), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: In this paper, we further develop the general theory of microdialysis by extending the linear model of Bungay et al. to provide a theoretical basis for in vitro and in vivo microdialysis. Specifically, we considered the effect of active clearance processes on in vivo microdialysis, and thereby elaborated the theory of Benveniste et al. to endogenous compounds. We examined the use of steady state tissue diffusion resistance with negligible clearance processes to interpret microdialysis data. The influence of the tissue properties on the in vitro and in vivo recoveries in dual-probe microdialysis was analyzed and we simulated the effect of the operating parameters on dual probe microdialysis performance. We estimated that the minimum clearance rate constant detectable by microdialysis in a quasi-steady state is about 5.5 × 10−5 s−1. This minimum rate constant establishes a criterion, below which inhibition of the active clearance processes does not show detectable influences on the microdialysis extraction efficiency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1471-4159.2002.00793.x
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  • 3
    Digitale Medien
    Digitale Medien
    Interstitial Ascorbate in Turtle Brain Is Modulated by Release and Extracellular Volume Change (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 49 (1987), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The isolated turtle cerebellum was used as a model system to study effects of depolarizing conditions on interstitial ascorbic acid concentration. The depolarizing stimulus was Leão's spreading depression, which is characterized by transient negative extracellular potentials, high potassium levels (20–60 μM), and local depression of neuronal activity. Interstitial concentrations of ascorbate (200–400 μM) and other electroactive species were monitored voltammetrically, using graphite fiber microelectrodes. Total tissue ascorbate (1,810 nmol/g tissue wet weight) was similar to mammalian levels and was several orders of magnitude higher than catecholamine and indoleamine content. During spreading depression, a large (up to 200 μM) increase in concentration of interstitial electroactive species was monitored. Use of Nafion-and ascorbate oxidase-coated electrodes and uricase confirmed that ascorbate was the only substance detected. Simultaneous monitoring of ascorbate, extracellular potential, and extracellular volume (using tetramethylammonium and ion-selective microelectrodes) indicated that (a) the ascorbate increase began with the decrease in extracellular volume during spreading depression, and (b) much of the increase was the result of extracellular volume decrease. In sucrose-substituted medium, in which volume changes are eliminated, a 50 μM increase in interstitial ascorbate, caused by release from intracellular stores, was also seen. The ascorbate concentration increase was prolonged in sucrose medium, suggesting that an uptake process involving sodium may further regulate interstitial ascorbate concentration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1987.tb09999.x
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  • 4
    Digitale Medien
    Digitale Medien
    Quantitative dual-probe microdialysis: mathematical model
and analysis (2002)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neurochemistry 81 (2002), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Steady-state microdialysis is a widely used technique to monitor the concentration changes and distributions of substances in tissues. To obtain more information about brain tissue properties from microdialysis, a dual-probe approach was applied to infuse and sample the radiotracer, [3H]mannitol, simultaneously both in agar gel and in the rat striatum. Because the molecules released by one probe and collected by the other must diffuse through the interstitial space, the concentration profile exhibits dynamic behavior that permits the assessment of the diffusion characteristics in the brain extracellular space and the clearance characteristics. In this paper a mathematical model for dual-probe microdialysis was developed to study brain interstitial diffusion and clearance processes. Theoretical expressions for the spatial distribution of the infused tracer in the brain extracellular space and the temporal concentration at the probe outlet were derived. A fitting program was developed using the simplex algorithm, which finds local minima of the standard deviations between experiments and theory by adjusting the relevant parameters. The theoretical curves accurately fitted the experimental data and generated realistic diffusion parameters, implying that the mathematical model is capable of predicting the interstitial diffusion behavior of [3H]mannitol and that it will be a valuable quantitative tool in dual-probe microdialysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1471-4159.2002.00792.x
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  • 5
    Digitale Medien
    Digitale Medien
    Quantitative dual-probe microdialysis: evaluation of [3H]mannitol diffusion in agar and rat striatum (2002)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neurochemistry 81 (2002), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Dual-probe microdialysis was used to study interstitial diffusion in the rat brain. A radiolabelled tracer, [3H]mannitol, was continuously infused at different concentrations via a probe acutely implanted into the striatum of an anaesthetized male rat or into a dilute agar gel. Samples were collected by a second probe placed 1 mm away from the first, and the recovered [3H]mannitol was measured by liquid scintillation counting. In the striatum, the delivery of [3H]mannitol was counteracted by its removal from the extracellular space by passive uptake into cells and clearance into the microcirculation, causing the diffusion profile to approach quasi steady-state levels within 2 h. Diffusion data from brain and agar were analysed using a mathematical model. The apparent (effective) diffusion coefficient for [3H]mannitol was D* = 2.9 × 10−6 cm2/s, the effective volume fraction α* = 0.30 and the clearance rate constant κ = 2.3 × 10−5/s. A tortuosity, λ = 1.81, and penetration distance Γ = 4.2 mm, were calculated. We conclude that, using dual-probe microdialysis, parameters reflecting geometric and dynamic tissue properties may be obtained using appropriate mathematical analysis. Quantitative dual-probe microdialysis will be valuable in characterizing interstitial diffusion and the clearance processes underpinning volume transmission in the brain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1471-4159.2002.00791.x
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  • 6
    Digitale Medien
    Digitale Medien
    Cerebellum of Mormyrids (1967)
    [s.l.] : Nature Publishing Group
    Nature 215 (1967), S. 764-765 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The relationships of the fibre tracts3'4 suggest that the hypertrophy of the valvula in the Mormyrids is related to the high degree of development of the lateral line system, which to a large extent has become transformed into an electroreceptor organ5'6. Microscopically both corpus and valvula ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/215764a0
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  • 7
    Digitale Medien
    Digitale Medien
    Preface (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 481 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb27133.x
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  • 8
    Digitale Medien
    Digitale Medien
    Introductory Remarks: Dynamics of the Neuronal Microenvironment (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 481 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb27137.x
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  • 9
    Digitale Medien
    Digitale Medien
    The Migration of Substances in the Neuronal Microenvironment (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 481 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb27139.x
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  • 10
    Digitale Medien
    Digitale Medien
    Massively parallel computation of large-scale spatial price equilibrium models with discriminatory ad valorem tariffs (1996)
    Springer
    Annals of operations research 68 (1996), S. 281-300 
    Details
    ISSN: 1572-9338
    Schlagwort(e): Spatial price equilibria ; discriminatory ad valorem tariffs ; variational inequalities ; massively parallel computation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Wirtschaftswissenschaften
    Notizen: Abstract In this paper, we develop a perfectly competitive spatial equilibrium model in price and quantity variables in the presence of discriminatory ad valorem tariffs, a widely used trade policy instrument. We derive the equilibrium conditions and formulate them as a variational inequality problem. An algorithm is then proposed for the computation of the equilibrium pattern and convergence results established. The algorithm resolves the problem into very simple subproblems, each of which can be solved simultaneously and in closed form. Finally, the algorithm is implemented on the massively parallel Thinking Machines CM-2 and CM-5 architectures, known as the Connection Machines, and numerical results presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02209616
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