The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform

Christiane Malo - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of exogenous lipid uptake by renal and intestinal brush-border membrane vesicles
    Biochemistry and cell biology = Biochimie et biologie cellulaire, 1995
    Co-Authors: François Bellemare, Josette Noël, Christiane Malo
    Abstract:

    The transfer of radioactive phosphatidylcholine (PC*) from liposomes to rabbit jejunal and renal brush-border membrane vesicles (BBMVs) was measured with a fast-sampling, Rapid-Filtration apparatus...

  • Fast sampling, Rapid Filtration apparatus: Principal characteristics and validation from studies ofd-glucose transport in human jejunal brush-border membrane vesicles
    The Journal of Membrane Biology, 1991
    Co-Authors: Alfred Berteloot, Christiane Malo, Sylvie Breton, Michel Brunette
    Abstract:

    Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the Rapid Filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, Rapid Filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: ( i ) Rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10–40 μl) with an incubation medium (0.2–1.0 ml); ( ii ) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4/sec) sampling of the uptake mixture followed by Rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and ( iii ) fast, automated, and sampling-synchronized Filtration and washings of the quenched uptake medium (only 15–20 sec are necessary for the first Filtration followed by two washings and extra Filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na^+- d -glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the Rapid Filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the Rapid Filtration device, should help in extending its use to fields other than transport measurement.

  • Analysis of kinetic data in transport studies: New insights from kinetic studies of Na^+-d-glucose cotransport in human intestinal brush-border membrane vesicles using a fast sampling, Rapid Filtration apparatus
    The Journal of Membrane Biology, 1991
    Co-Authors: Christiane Malo, Alfred Berteloot
    Abstract:

    Using the fast sampling, Rapid Filtration apparatus (FSRFA) recently developed in our laboratory (Berteloot et al., 1991. J. Membrane Biol. 122 :111–125), we have studied the kinetic characteristics of Na^+- d -glucose cotransport in brush-border membrane vesicles isolated from normal adult human jejunum. True initial rates of transport have been determined at both 20 and 35°C using a dynamic approach which involves linearregression analysis over nine time points equally spaced over 4.5 or 2.7 sec, respectively. When the tracer rate of transport was studied as a function of unlabeled substrate concentrations added to the incubation medium, a displacement curve was generated which can be analyzed by nonlinear regression using equations which take into account the competitive inhibition of tracer flux by unlabeled substrate. This approach was made imperative since at 20°C, in the presence of high substrate concentrations or 1 mm phlorizin, no measurable diffusion was found and the resultant zero slope values cannot be expressed into a classical v versus S plot. All together, our results support the existence of a single Na^+- d -glucose cotransport system in these membranes for which Na^+ is mandatory for uptake. This conclusion is at variance with that of a recent report using the same preparation (Harig et al., 1989. Am J. Physiol. 256 :8618–8623). Since the discrepancy seems difficult to resolve on the consideration of experimental conditions alone, we have determined the kinetic parameters of d -glucose transport using one time point measurements and linear transformations of the Michaelis-Menten equation, in order to investigate the potential problems of such a widely used procedure. Comparing these approaches, we conclude that: ( i ) the dynamic uptake measurements give a better understanding of the different uptake components involved; ( ii ) it does not matter whether a dynamic or a one time point approach is chosen to generate the uptake data provided that a nonlinear-regression analysis with proper weighting of the data points is performed; ( iii ) analytical procedures which rely on linearization of Michaelian process(es) are endowed with a number of difficulties which make them unsuitable to resolve multicomponent systems in transport studies. A more general procedure which uses a nonlinear-regression analysis and a displacement curve is proposed since we demonstrate that it is far superior in terms of Rapidity, data interpretation, and visual information.

  • analysis of kinetic data in transport studies new insights from kinetic studies of na d glucose cotransport in human intestinal brush border membrane vesicles using a fast sampling Rapid Filtration apparatus
    The Journal of Membrane Biology, 1991
    Co-Authors: Christiane Malo, A Berteloot
    Abstract:

    Using the fast sampling, Rapid Filtration apparatus (FSRFA) recently developed in our laboratory (Berteloot et al., 1991.J. Membrane Biol.122:111–125), we have studied the kinetic characteristics of Na+-d-glucose cotransport in brush-border membrane vesicles isolated from normal adult human jejunum. True initial rates of transport have been determined at both 20 and 35°C using a dynamic approach which involves linearregression analysis over nine time points equally spaced over 4.5 or 2.7 sec, respectively. When the tracer rate of transport was studied as a function of unlabeled substrate concentrations added to the incubation medium, a displacement curve was generated which can be analyzed by nonlinear regression using equations which take into account the competitive inhibition of tracer flux by unlabeled substrate. This approach was made imperative since at 20°C, in the presence of high substrate concentrations or 1mm phlorizin, no measurable diffusion was found and the resultant zero slope values cannot be expressed into a classicalv versus S plot. All together, our results support the existence of a single Na+-d-glucose cotransport system in these membranes for which Na+ is mandatory for uptake. This conclusion is at variance with that of a recent report using the same preparation (Harig et al., 1989.Am J. Physiol.256:8618–8623). Since the discrepancy seems difficult to resolve on the consideration of experimental conditions alone, we have determined the kinetic parameters ofd-glucose transport using one time point measurements and linear transformations of the Michaelis-Menten equation, in order to investigate the potential problems of such a widely used procedure. Comparing these approaches, we conclude that: (i) the dynamic uptake measurements give a better understanding of the different uptake components involved; (ii) it does not matter whether a dynamic or a one time point approach is chosen to generate the uptake data provided that a nonlinear-regression analysis with proper weighting of the data points is performed; (iii) analytical procedures which rely on linearization of Michaelian process(es) are endowed with a number of difficulties which make them unsuitable to resolve multicomponent systems in transport studies. A more general procedure which uses a nonlinear-regression analysis and a displacement curve is proposed since we demonstrate that it is far superior in terms of Rapidity, data interpretation, and visual information.

  • Fast sampling, Rapid Filtration apparatus: principal characteristics and validation from studies of D-glucose transport in human jejunal brush-border membrane vesicles.
    The Journal of membrane biology, 1991
    Co-Authors: Alfred Berteloot, Christiane Malo, Sylvie Breton, Michel Brunette
    Abstract:

    Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the Rapid Filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, Rapid Filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: (i) Rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10–40 μl) with an incubation medium (0.2–1.0 ml); (ii) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4/sec) sampling of the uptake mixture followed by Rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and (iii) fast, automated, and sampling-synchronized Filtration and washings of the quenched uptake medium (only 15–20 sec are necessary for the first Filtration followed by two washings and extra Filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na+-d-glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the Rapid Filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the Rapid Filtration device, should help in extending its use to fields other than transport measurement.

Alfred Berteloot - One of the best experts on this subject based on the ideXlab platform.

  • Fast sampling, Rapid Filtration apparatus: Principal characteristics and validation from studies ofd-glucose transport in human jejunal brush-border membrane vesicles
    The Journal of Membrane Biology, 1991
    Co-Authors: Alfred Berteloot, Christiane Malo, Sylvie Breton, Michel Brunette
    Abstract:

    Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the Rapid Filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, Rapid Filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: ( i ) Rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10–40 μl) with an incubation medium (0.2–1.0 ml); ( ii ) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4/sec) sampling of the uptake mixture followed by Rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and ( iii ) fast, automated, and sampling-synchronized Filtration and washings of the quenched uptake medium (only 15–20 sec are necessary for the first Filtration followed by two washings and extra Filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na^+- d -glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the Rapid Filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the Rapid Filtration device, should help in extending its use to fields other than transport measurement.

  • Analysis of kinetic data in transport studies: New insights from kinetic studies of Na^+-d-glucose cotransport in human intestinal brush-border membrane vesicles using a fast sampling, Rapid Filtration apparatus
    The Journal of Membrane Biology, 1991
    Co-Authors: Christiane Malo, Alfred Berteloot
    Abstract:

    Using the fast sampling, Rapid Filtration apparatus (FSRFA) recently developed in our laboratory (Berteloot et al., 1991. J. Membrane Biol. 122 :111–125), we have studied the kinetic characteristics of Na^+- d -glucose cotransport in brush-border membrane vesicles isolated from normal adult human jejunum. True initial rates of transport have been determined at both 20 and 35°C using a dynamic approach which involves linearregression analysis over nine time points equally spaced over 4.5 or 2.7 sec, respectively. When the tracer rate of transport was studied as a function of unlabeled substrate concentrations added to the incubation medium, a displacement curve was generated which can be analyzed by nonlinear regression using equations which take into account the competitive inhibition of tracer flux by unlabeled substrate. This approach was made imperative since at 20°C, in the presence of high substrate concentrations or 1 mm phlorizin, no measurable diffusion was found and the resultant zero slope values cannot be expressed into a classical v versus S plot. All together, our results support the existence of a single Na^+- d -glucose cotransport system in these membranes for which Na^+ is mandatory for uptake. This conclusion is at variance with that of a recent report using the same preparation (Harig et al., 1989. Am J. Physiol. 256 :8618–8623). Since the discrepancy seems difficult to resolve on the consideration of experimental conditions alone, we have determined the kinetic parameters of d -glucose transport using one time point measurements and linear transformations of the Michaelis-Menten equation, in order to investigate the potential problems of such a widely used procedure. Comparing these approaches, we conclude that: ( i ) the dynamic uptake measurements give a better understanding of the different uptake components involved; ( ii ) it does not matter whether a dynamic or a one time point approach is chosen to generate the uptake data provided that a nonlinear-regression analysis with proper weighting of the data points is performed; ( iii ) analytical procedures which rely on linearization of Michaelian process(es) are endowed with a number of difficulties which make them unsuitable to resolve multicomponent systems in transport studies. A more general procedure which uses a nonlinear-regression analysis and a displacement curve is proposed since we demonstrate that it is far superior in terms of Rapidity, data interpretation, and visual information.

  • Fast sampling, Rapid Filtration apparatus: principal characteristics and validation from studies of D-glucose transport in human jejunal brush-border membrane vesicles.
    The Journal of membrane biology, 1991
    Co-Authors: Alfred Berteloot, Christiane Malo, Sylvie Breton, Michel Brunette
    Abstract:

    Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the Rapid Filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, Rapid Filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: (i) Rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10–40 μl) with an incubation medium (0.2–1.0 ml); (ii) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4/sec) sampling of the uptake mixture followed by Rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and (iii) fast, automated, and sampling-synchronized Filtration and washings of the quenched uptake medium (only 15–20 sec are necessary for the first Filtration followed by two washings and extra Filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na+-d-glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the Rapid Filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the Rapid Filtration device, should help in extending its use to fields other than transport measurement.

  • Analysis of kinetic data in transport studies: new insights from kinetic studies of Na(+)-D-glucose cotransport in human intestinal brush-border membrane vesicles using a fast sampling, Rapid Filtration apparatus.
    The Journal of membrane biology, 1991
    Co-Authors: Christiane Malo, Alfred Berteloot
    Abstract:

    Using the fast sampling, Rapid Filtration apparatus (FSRFA) recently developed in our laboratory (Berteloot et al., 1991.J. Membrane Biol.122:111–125), we have studied the kinetic characteristics of Na+-d-glucose cotransport in brush-border membrane vesicles isolated from normal adult human jejunum. True initial rates of transport have been determined at both 20 and 35°C using a dynamic approach which involves linearregression analysis over nine time points equally spaced over 4.5 or 2.7 sec, respectively. When the tracer rate of transport was studied as a function of unlabeled substrate concentrations added to the incubation medium, a displacement curve was generated which can be analyzed by nonlinear regression using equations which take into account the competitive inhibition of tracer flux by unlabeled substrate. This approach was made imperative since at 20°C, in the presence of high substrate concentrations or 1mm phlorizin, no measurable diffusion was found and the resultant zero slope values cannot be expressed into a classicalv versus S plot. All together, our results support the existence of a single Na+-d-glucose cotransport system in these membranes for which Na+ is mandatory for uptake. This conclusion is at variance with that of a recent report using the same preparation (Harig et al., 1989.Am J. Physiol.256:8618–8623). Since the discrepancy seems difficult to resolve on the consideration of experimental conditions alone, we have determined the kinetic parameters ofd-glucose transport using one time point measurements and linear transformations of the Michaelis-Menten equation, in order to investigate the potential problems of such a widely used procedure. Comparing these approaches, we conclude that: (i) the dynamic uptake measurements give a better understanding of the different uptake components involved; (ii) it does not matter whether a dynamic or a one time point approach is chosen to generate the uptake data provided that a nonlinear-regression analysis with proper weighting of the data points is performed; (iii) analytical procedures which rely on linearization of Michaelian process(es) are endowed with a number of difficulties which make them unsuitable to resolve multicomponent systems in transport studies. A more general procedure which uses a nonlinear-regression analysis and a displacement curve is proposed since we demonstrate that it is far superior in terms of Rapidity, data interpretation, and visual information.

Hiroshi Koga - One of the best experts on this subject based on the ideXlab platform.

  • Substrate specificity of urate transporter in rat renal brush border membranes.
    Life sciences, 1991
    Co-Authors: Takashi Dan, Hiroshi Koga
    Abstract:

    To further demonstrate the substrate specificity of urate-anion exchanger in rat renal brush border membrane vesicles, the hydroxyl ion gradient-dependent [2-14C] urate uptake was studied by a Rapid Filtration technique. The [2-14C] urate uptake was more sensitive to unlabeled urate than to unlabeled xanthine and hypoxanthine. In addition, urate derivatives which are methylated at the positions 3 and 9 hardly inhibited the urate uptake. Because of the substrate specificity, the urate-anion exchanger in brush border membranes appears to selectively use urate as the endogenous substrate.

Michel Brunette - One of the best experts on this subject based on the ideXlab platform.

  • Fast sampling, Rapid Filtration apparatus: Principal characteristics and validation from studies ofd-glucose transport in human jejunal brush-border membrane vesicles
    The Journal of Membrane Biology, 1991
    Co-Authors: Alfred Berteloot, Christiane Malo, Sylvie Breton, Michel Brunette
    Abstract:

    Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the Rapid Filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, Rapid Filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: ( i ) Rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10–40 μl) with an incubation medium (0.2–1.0 ml); ( ii ) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4/sec) sampling of the uptake mixture followed by Rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and ( iii ) fast, automated, and sampling-synchronized Filtration and washings of the quenched uptake medium (only 15–20 sec are necessary for the first Filtration followed by two washings and extra Filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na^+- d -glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the Rapid Filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the Rapid Filtration device, should help in extending its use to fields other than transport measurement.

  • Fast sampling, Rapid Filtration apparatus: principal characteristics and validation from studies of D-glucose transport in human jejunal brush-border membrane vesicles.
    The Journal of membrane biology, 1991
    Co-Authors: Alfred Berteloot, Christiane Malo, Sylvie Breton, Michel Brunette
    Abstract:

    Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the Rapid Filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, Rapid Filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: (i) Rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10–40 μl) with an incubation medium (0.2–1.0 ml); (ii) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4/sec) sampling of the uptake mixture followed by Rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and (iii) fast, automated, and sampling-synchronized Filtration and washings of the quenched uptake medium (only 15–20 sec are necessary for the first Filtration followed by two washings and extra Filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na+-d-glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the Rapid Filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the Rapid Filtration device, should help in extending its use to fields other than transport measurement.

D. Van Halem - One of the best experts on this subject based on the ideXlab platform.

  • fate of low arsenic concentrations during full scale aeration and Rapid Filtration
    Water Research, 2016
    Co-Authors: J.c.j. Gude, Luuk C. Rietveld, D. Van Halem
    Abstract:

    In the Netherlands, groundwater treatment commonly consists of aeration, with subsequent sand Filtration without using chemical oxidants like chlorine. With arsenic (As) concentrations well below the actual guidelines of 10 μg As/L, groundwater treatment plants have been exclusively designed for the removal of iron (Fe), manganese and ammonium. The aim of this study was to investigate the As removal capacity at three of these groundwater treatment plants (10-26 μg As/L) in order to identify operational parameters that can contribute to lowering the filtrate As concentration to <1 μg/L. For this purpose a sampling campaign and experiments with supernatant water and hydrous ferric oxide (HFO) flocs were executed to identify the key mechanisms controlling As removal. Results showed that after aeration, As largely remained mobile in the supernatant water; even during extended residence times only 20-48% removal was achieved (with 1.4-4.2 mg/L precipitated Fe(II)). Speciation showed that the mobile As was in the reduced As(III) form, whereas, As(V) was readily adsorbed to the formed HFO flocs. In the filter bed, the remaining As(III) completely oxidized within 2 min of residence time and As removal efficiencies increased to 48-90%. Filter grain coating analysis showed the presence of manganese at all three treatment plants. It is hypothesized that these manganese oxides are responsible for the accelerated As(III) oxidation in the filter bed, leading to an increased removal capacity. In addition, pH adjustment from 7.8 to 7.0 has been found to improve the capacity for As(V) uptake by the HFO flocs in the filter bed. The overall conclusion is, that during groundwater treatment, the filter bed is crucial for Rapid As(III) removal, indicating the importance to control the oxidation sequence of Fe and As for improved As removal efficiencies.

  • Fate of low arsenic concentrations during full-scale aeration and Rapid Filtration.
    Water research, 2015
    Co-Authors: J.c.j. Gude, Luuk C. Rietveld, D. Van Halem
    Abstract:

    In the Netherlands, groundwater treatment commonly consists of aeration, with subsequent sand Filtration without using chemical oxidants like chlorine. With arsenic (As) concentrations well below the actual guidelines of 10 μg As/L, groundwater treatment plants have been exclusively designed for the removal of iron (Fe), manganese and ammonium. The aim of this study was to investigate the As removal capacity at three of these groundwater treatment plants (10-26 μg As/L) in order to identify operational parameters that can contribute to lowering the filtrate As concentration to