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  • membrane permeability transition  (3)
  • Capillary zone electrophoresis  (2)
  • time scales  (2)
  • Springer  (7)
  • American Chemical Society (ACS)
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Keywords
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  • Springer  (7)
  • American Chemical Society (ACS)
Years
  • 1
    Electronic Resource
    Electronic Resource
    Variables Aggregation in Time Varying Discrete Systems (1998)
    Springer
    Acta biotheoretica 46 (1998), S. 273-297 
    Details
    ISSN: 1572-8358
    Keywords: Approximate aggregation ; population dynamics ; time scales ; strong ergodicity ; cyclic environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this work we extend approximate aggregation methods in time discrete linear models to the case of time varying environments. Approximate aggregation consists in describing some features of the dynamics of a general system involving many coupled variables in terms of the dynamics of a reduced system with a few number of variables. We present a time discrete time varying model in which we distinguish two time scales. By using perturbation methods we transform the system to make the global variables appear and build up the aggregated system. The asymptotic relationships between the general and aggregated systems are explored in the cases of a cyclically varying environment and a changing environment in process of stabilization. We show that under quite general conditions the knowledge of the behavior of the aggregated system characterizes that of the general system. The general method is also applied to aggregate a multiregional time dependent Leslie model showing that the aggregated model has demographic rates depending on the equilibrium proportions of individuals in the different patches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1001741327984
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  • 2
    Electronic Resource
    Electronic Resource
    Linear discrete models with different time scales (1995)
    Springer
    Acta biotheoretica 43 (1995), S. 465-476 
    Details
    ISSN: 1572-8358
    Keywords: Approximate aggregation of variables ; population dynamics ; perturbations ; time scales ; eigenvalues and eigenvectors analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Aggregation of variables allows to approximate a large scale dynamical system (the micro-system) involving many variables into a reduced system (the macro-system) described by a few number of global variables. Approximate aggregation can be performed when different time scales are involved in the dynamics of the micro-system. Perturbation methods enable to approximate the large micro-system by a macro-system going on at a slow time scale. Aggregation has been performed for systems of ordinary differential equations in which time is a continuous variable. In this contribution, we extend aggregation methods to time-discrete models of population dynamics. Time discrete micro-models with two time scales are presented. We use perturbation methods to obtain a slow macro-model. The asymptotic behaviours of the micro and macro-systems are characterized by the main eigenvalues and the associated eigenvectors. We compare the asymptotic behaviours of both systems which are shown to be similar to a certain order.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713565
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  • 3
    Electronic Resource
    Electronic Resource
    On the Protection by Inorganic Phosphate of Calcium-Induced Membrane Permeability Transition (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 571-577 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondrial calcium ; inorganic phosphate ; membrane permeability transition ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of inorganic phosphate as inhibitor of mitochondrial membrane permeability transition was studied. It is shown that in mitochondria containing a high phosphate concentration, i.e., 68 nmol/mg, Ca2+ did not activate the pore opening. Conversely, at lower levels of matrix phosphate, i.e., 38 nmol/mg, Ca2+ was able to induce subsequent pore opening. The inhibitory effect of phosphate was apparent in sucrose-based media, but it was not achieved in KCl media. The matrix free Ca2+ concentration and matrix pH were lowered by phosphate, but they were always higher in K+-media. In the absence of ADP, phosphate strengthened the inhibitory effect of cyclosporin A on carboxyatractyloside-induced Ca2+ efflux. Acetate was unable to replace phosphate in the induction of the aforementioned effects. It is concluded that phosphate preserves selective membrane permeability by diminishing the matrix free Ca2+ concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022483018482
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  • 4
    Electronic Resource
    Electronic Resource
    Modulation of matrix Ca2+ content by the ADP/ATP carrier in brown adipose tissue mitochondria. Influence of membrane lipid composition (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 69-76 
    Details
    ISSN: 1573-6881
    Keywords: Matrix calcium ; BAT mitochondria ; membrane permeability transition ; adenine nucleotide translocase ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of the adenine nucleotide translocase on Ca2+ homeostasis in mitochondria from brown adipose tissue was examined. It was found that in mitochondria incubated with 50 μM Ca2+, ADP was not needed to retain the cation, but it was required for strengthening the inhibitory effect of cyclosporin on membrane permeability transition as induced by menadione. In addition, carboxyatractyloside was unable to promote matrix Ca2+ release, even though it inhibits the ADP exchange reaction. However, when the Ca2+ concentration was increased to 150 μM, carboxyatractyloside did induce Ca2+ release, and ADP favored Ca2+ retention. Determination of cardiolipin content in the inner membrane vesicles showed a greater concentration in brown adipose tissue mitochondria than that found in kidney mitochondria. It is suggested that the failure of the adenine nucleotide translocase to influence membrane permeability transition depends on the lipid composition of the inner membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109905
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  • 5
    Electronic Resource
    Electronic Resource
    Modulation of matrix Ca2+ content by the ADP/ATP carrier in brown adipose tissue mitochondria. Influence of membrane lipid composition (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 69-76 
    Details
    ISSN: 1573-6881
    Keywords: Matrix calcium ; BAT mitochondria ; membrane permeability transition ; adenine nucleotide translocase ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of the adenine nucleotide translocase on Ca2+ homeostasis in mitochondria from brown adipose tissue was examined. It was found that in mitochondria incubated with 50 μM Ca2+, ADP was not needed to retain the cation, but it was required for strengthening the inhibitory effect of cyclosporin on membrane permeability transition as induced by menadione. In addition, carboxyatractyloside was unable to promote matrix Ca2+ release, even though it inhibits the ADP exchange reaction. However, when the Ca2+ concentration was increased to 150 μM, carboxyatractyloside did induce Ca2+ release, and ADP favored Ca2+ retention. Determination of cardiolipin content in the inner membrane vesicles showed a greater concentration in brown adipose tissue mitochondria than that found in kidney mitochondria. It is suggested that the failure of the adenine nucleotide translocase to influence membrane permeability transition depends on the lipid composition of the inner membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02150680
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  • 6
    Electronic Resource
    Electronic Resource
    Separation of fluorescein dyes by capillary electrophoresis using β-cyclodextrin (1998)
    Springer
    Chromatographia 48 (1998), S. 263-267 
    Details
    ISSN: 1612-1112
    Keywords: Capillary zone electrophoresis ; Host-guest complexation ; Fluorescein dyes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A capillary electrophoresis method for the separation and determination of five synthetic dyes used in pharmaceutical preparations, cosmetics and as food additives is described. The dyes, fluorescein, dichlorofluorescein, Rose Bengal erythrosine and eosine are well separated in less than 12 min using an electrolyte of 50 mM phosphate buffer (pH 7.5), 10 mM β-cyclodextrin and 5% (v/v) methanol. A linear relationship between concentration and peak area for each dye was obtained in the concentration range 0.3–500 μg mL−1, with a correlation coefficient greater than 0.999. Intra- and inter-day precision of about 0.2–2.6% RSD (n=11) and 4.9–9.7% RSD (n=30), respectively, were obtained. The method has been used for determining the purity of fluorescein and erythrosine in practical samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467681
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  • 7
    Electronic Resource
    Electronic Resource
    Separation and simultaneous determination of quinolone antibiotics by capillary zone electrophoresis (1999)
    Springer
    Chromatographia 49 (1999), S. 419-423 
    Details
    ISSN: 1612-1112
    Keywords: Capillary zone electrophoresis ; Quinolone antibiotics ; Serum and urine samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The potential of capillary zone electrophoresis has been investigated for the separation and quantitative determination of some quinolone antibiotics. The influence of different conditions, such as the nature and concentration of the electrophoretic electrolyte, on migration time, peak symmetry, efficiency and resolution was studied. A buffer consisting of 100mm HEPES adjusted to pH 8.5 containing 10% (v/v) acetonitrile was found to furnish a very efficient and stable electrophoretic system for the separation of exoxacin, ciprofloxacin, ofloxacin, oxolinic acid, nalidixic acid and pipemedic acid. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.25–40 μg mL−1; detection limits were approximately 0.25 ng mL−1. It was demonstrated that the method can be used for the simultaneous determination of these six antibiotics in serum and urine samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467617
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