Papers by Ingolf Bernhardt
Bioelectrochemistry, Aug 1, 2008
Human red blood cell Resting axolemma squid axon Quantum mechanical calculations of elastic scatt... more Human red blood cell Resting axolemma squid axon Quantum mechanical calculations of elastic scattering cross sections for some permeant ions crossing the human red blood cell and resting axolemma squid axon membranes have been carried out using the threedimensional spherically symmetric square potential well. Making the assumption that the permeability coefficient is inversely proportional to scattering cross section, we obtain the order of membrane selectivity for the ions as well as values for the permeability coefficients. Despite the relatively simple method used, good agreement between calculated permeability coefficients and data available in the literature is obtained. We suggest that elastic scattering cross section measurements for ions in various membranes would be valuable not only because they give a precise idea about the permeability ratios between ions but they also determine the form of the potential the ions are moving in.
Springer eBooks, 2003
Softcover reprint of the hardcover 1st edition 2003 http://www.springer.de The use of general des... more Softcover reprint of the hardcover 1st edition 2003 http://www.springer.de The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publisher cannot guarantee the accuracy of any information about dosage and application contained in this book. In every individual case the user must check such information by consulting the relevant literature.
Colloids and Surfaces B: Biointerfaces, 1996
PubMed, 1984
The rate constant of 86Rb efflux and total potassium release from erythrocytes under the influenc... more The rate constant of 86Rb efflux and total potassium release from erythrocytes under the influence of lysophosphatidylcholine (LPC) and osmotic pressure gradients were compared. Both osmotic pressure gradients and LPC caused a transient increase in the potassium permeability of the erythrocyte membrane. In hypotonic media without or in the presence of LPC this sudden increase is completely reversible, since the rate constant of rubidium efflux from unhaemolyzed cells, which is an indicator for the continuous potassium release, remained the same as measured in an isotonic NaCl medium without detergents. The potassium release was more pronounced in the presence of LPC and may have a protective effect against haemolysis. In an isotonic NaCl or sucrose medium, LPC caused a transient potassium release probably due to incorporation of LPC into the membrane and vesicle release, but also an increase in the rate constant of rubidium efflux due to change in the membrane structure connected with vesicle release.
Position, tasks and structure of particle size analysis. Introduction to classification. Particle... more Position, tasks and structure of particle size analysis. Introduction to classification. Particle movement in a fluid at rest. Dispersion of solids in liquids. Sedimentation. Classification methods in streaming fluids. Sieving. Evaluation, representation and use of results. Appendices. References. Index.
Biomedica biochimica acta, 1986
Active transport of sodium and potassium has been postulated for bull sperms by various authors. ... more Active transport of sodium and potassium has been postulated for bull sperms by various authors. In the present paper the sodium and rubidium efflux was determined by tracer kinetics. For uninhibited sodium and rubidium efflux a rate constant of 8.9 +/- 2.13/min and 13.9 +/- 3.89 min, respectively, was found for a bull sperm suspension (20 vol.%, 310 K). After ouabain treatment (0.1 mM), a reduction of the rate constant of sodium efflux to 5.1 +/- 1.06/min was found. After cryopreserving (pelletizing process) the majority of samples investigated did not exhibit any inhibition of sodium and rubidium efflux as compared with fresh bull sperms. The inhibition of sodium efflux observed in some cases corresponds to the reduction of the rate constant of sodium efflux caused by ouabain. At storage in seminal plasma (24 h, 278 K) the rate constant of sodium efflux is reduced to 2.7 +/- 0.25/min. Both after ouabain treatment and after cryopreserving of sperms having a reduced rate constant th...
PubMed, Sep 1, 1993
Effect of low ionic force on the passive transport of univalent cations through the erythrocyte m... more Effect of low ionic force on the passive transport of univalent cations through the erythrocyte membranes is considered. It is postulated that this effect is complex and cannot be explained on the basis of electrodiffusion. Data are presented on the already known transport pathways in the erythrocyte membranes for univalent cations. Characteristics of residual cation transport (the "leak" flux) through the erythrocyte membranes also affected by the low ionic force are presented.
PubMed, Aug 1, 1992
In the rat erythrocyte membrane five different transport pathways for K+ are present. In addition... more In the rat erythrocyte membrane five different transport pathways for K+ are present. In addition to the well characterised K+ transport via the Na+ pump, the Na,K,Cl cotransport and the Ca(2+)-activated K+ channel, there are a K,Cl cotransport and a residual (leak) K+ transport. The K,Cl cotransport is already present under physiological conditions, and can be stimulated by N-ethylmaleimide treatment but not by a cell volume increase. A low ionic strength stimulated increase of the residual K+ influx can be demonstrated in rat erythrocytes after suppressing the K,Cl cotransport pathway. Between 11 and 19 weeks of age, rats show significant differences in all transport pathways of the erythrocyte potassium influx. Using influx data from individual rats a significant correlation between the total K+ influx and the ouabain-sensitive K+ influx has been found. Maintaining the rats on a diet poor in essential fatty acids leads to a significant change of the linoleic acid content of the erythrocyte membrane phospholipids. However, no significant effect on the various K+ transport pathways has been found. An analysis of the fatty acid composition of the erythrocyte membrane phospholipids showed significant correlations between the content of oleic acid, and arachidonic acid, and the ouabain-sensitive K+ influx (as well as the total K+ influx).
PubMed, Jun 1, 1999
The (ouabain + bumetanide + EGTA)-insensitive K+ influx (defined as residual K+ influx) in the hu... more The (ouabain + bumetanide + EGTA)-insensitive K+ influx (defined as residual K+ influx) in the human erythrocyte was investigated with respect to the characterization of the recently identified K+(Na+)/H+ exchanger (Richter et al. 1997). In particular, the effects of selected ion transport inhibitors on this flux in physiological ionic strength (high ionic strength, HIS) as well as low ionic strength (LIS) solutions were qstudied. The stimulation of the K+ influx observed in LIS medium was further enhanced when DIDS, phloretin, eosin-5-maleimide, furosemide, DIOA, NPPB, or DCDPC was present at a concentration of 0.1 mmol/l. This paradoxical, inhibitor-induced increase of the K+ influx was more pronounced in LIS media where chloride (7.5 mmol/l) was replaced by nitrate. For DNDS, niflumic acid, and MK-196 (0.1 mmol/l) an enhanced K+ transport could only be observed in nitrate-containing LIS solution. Bumetanide and purine riboside, at a concentration of 0.1 mmol/l, did not cause significant changes of the K+ influx in either chloride- or nitrate-containing LIS media. Dipyridamole and ruthenium red (0.1 mmol/l), which are positively charged, significantly reduced the K+ influx in both chloride- and nitrate-containing LIS media. In nitrate-containing HIS solution only dipyridamole inhibited the K+ influx. The residual K+ influx in LIS solution was significantly increased by removing internal [Mg2+], and decreased by quinacrine (1 mmol/l). In HIS solution, no effect of altering intracellular Mg2+ occurred but a stimulation of the flux by quinacrine was observed. The results are discussed in terms of a more general surface charge effect of the used inhibitors on the K+(Na+)/H+ exchanger.
Biophysics of Membrane Transport, 1988
Biophysical Journal, Aug 1, 1997
The mechanism of the "ground permeability" of the human erythrocyte membrane for K+ and Na+ was i... more The mechanism of the "ground permeability" of the human erythrocyte membrane for K+ and Na+ was investigated with respect to a possible involvement of a previously unidentified specific transport pathway, because earlier studies showed that it cannot be explained on the basis of simple electrodiffusion. In particular, we analyzed and described the increase in the (ouabain + bumetanide + EGTA)-insensitive unidirectional K+ and Na+ influxes as well as effluxes (defined as "leak" fluxes) observed in erythrocytes suspended in low-ionic-strength media. Using a carrier-type model and taking into account the influence of the ionic strength on the outer surface potential according to the Gouy-Chapman theory (i.e., the ion concentration near the membrane surface), we are able to describe the altered "leak" fluxes as an electroneutral process. In addition, we can show indirectly that this electroneutral flux is due to an exchange of monovalent cations with protons. This pathway is different from the amiloride-sensitive Na+/H+ exchanger present in the human red blood cell membrane and can be characterized as a K+(Na+)/H+ exchanger.
The Journal of Physiology, Mar 1, 1991
1. The effect of low ionic strength media on the residual, i.e. (ouabain + bumetanide+ Ca2+)-inse... more 1. The effect of low ionic strength media on the residual, i.e. (ouabain + bumetanide+ Ca2+)-insensitive, K+ influx was characterized in human red blood cells. 2. This K+ flux was enhanced significantly in isotonic solutions of low ionic strength using sucrose to maintain constant osmolarity. This effect was found for fresh red blood cells as well as for stored (bank) red blood cells. However, the absolute magnitude of K+ influx in solutions of low ionic strength was halved for stored red blood cells. 3. Anion replacement of Cl-by CH3SO4did not affect residual K+ fluxes, showing that Cl-dependent transport pathways (e.g. the KCl co-transporter) are not involved in the low ionic strength effect. 4. The enhanced K+ influx in low ionic strength media was reversible when the cells were resuspended in a solution of physiological ionic strength. 5. K+ influx measured in light and dense fractions of erythrocytes (separated by centrifugation and corresponding to samples enriched with either 'young' or 'mature' red cells) showed that the low ionic strength effect does not change markedly with cell age. 6. Low ionic strength media elevated residual, i.e. (ouabain + bumetanide + Ca2+)insensitive, influx of both K+ and Na+ by about the same amount. In both cases the flux was linear with concentration in the range investigated (025-10 mM). No significant increase in the uptake of the cations Ca2+ and lysine in low ionic strength solutions could be found. 7. In CH3S04-containing solutions of physiological ionic strength the residual K+ influx was almost independent of cell volume, whereas this flux in CH3S04-containing solutions of low ionic strength declined as cell volume was increased. 8. K+ flux measurements in solutions of different external pH, where NaCl was replaced by sodium gluconate or sodium glucuronate, showed that the reduced ionic strength is of more importance for the enhanced residual K+ influx than the changed transmembrane potential or the changed intracellular pH. However, a small pH dependence could be found, the K+ flux passing through a minimum around pHi 7.3. 9. Hydrostatic pressure enhanced the residual K+ flux in media of low ionic MS 8628
The Journal of Membrane Biology, Aug 1, 2000
The change of intracellular pH of erythrocytes under different experimental conditions was invest... more The change of intracellular pH of erythrocytes under different experimental conditions was investigated using the pH-sensitive fluorescent dye BCECF and correlated with (ouabain + bumetanide + EGTA)-insensitive K + efflux and Cl − loss. When human erythrocytes were suspended in a physiological NaCl solution (pH o ס 7.4), the measured pH i was 7.19 ± 0.04 and remained constant for 30 min. When erythrocytes were transferred into a low ionic strength (LIS) solution, an immediate alkalinization increased the pH i to 7.70 ± 0.15, which was followed by a slower cell acidification. The alkalinization of cells in LIS media was ascribed to a band 3 mediated effect since a rapid loss of approximately 80% of intracellular Cl − content was observed, which was sensitive to known anion transport inhibitors. In the case of cellular acidification, a comparison of the calculated H + influx with the measured unidirectional K + efflux at different extracellular ionic strengths showed a correlation with a nearly 1:1 stoichiometry. Both fluxes were enhanced by decreasing the ionic strength of the solution resulting in a H + influx and a K + efflux in LIS solution of 108.2 ± 20.4 mmol (l cells hr) −1 and 98.7 ± 19.3 mmol (l cells hr) −1 , respectively. For bovine and porcine erythrocytes, in LIS media, H + influx and K + efflux were of comparable magnitude, but only about 10% of the fluxes observed in human erythrocytes under LIS conditions. Quinacrine, a known inhibitor of the mitochondrial K + (Na +)/H + exchanger, inhibited the K + efflux in LIS solution by about 80%. Our results provide evidence for the existence of a K + (Na +)/H + exchanger in the human erythrocyte membrane.
General physiology and biophysics, 1992
The Rb+(K+) efflux of erythrocytes from six mammalian species was investigated in solutions of ph... more The Rb+(K+) efflux of erythrocytes from six mammalian species was investigated in solutions of physiological and low ionic strength. A species dependent increase of the Rb+(K+) efflux in low ionic strength solution could be observed. The rate constant of Rb+(K+) efflux of erythrocytes in physiological ionic strength solution correlates with the content of arachidonic acid of the membrane phospholipids. The same relation was observed in solution of low ionic strength with the exception of human erythrocytes. In addition, an age-dependent correlation of the rate constant of Rb+(K+) efflux from calf erythrocytes in low ionic strength solution with the content of arachidonic acid of the membrane phospholipids was found. The Rb+(K+) efflux of human erythrocytes, which is enhanced in low ionic strength solution, decreases with the decreasing temperature. The temperature-dependent ESR order parameter of a fatty acid spin label for human and cow erythrocytes in solution of physiological and...
Advances in Bioscience and Biotechnology, 2010
The interactions of two types of cells (red blood cells, Caco-2 cells) with magnetic iron oxide n... more The interactions of two types of cells (red blood cells, Caco-2 cells) with magnetic iron oxide nanoparticles (non-grafted, citrate-grafted, dendrimer-grafted) of 11 nm in size have been investigated. We focused on two important physiological parameters of the cells, the intracellular pH and the intracellular Ca 2+ content. The results show that the nanoparticles do not have a significant influence on the pH and Ca 2+ content of Caco-2 cells. The Ca 2+ content of red blood cells is also not affected but the intracellular pH is slightly reduced.
Biophysics of Membrane Transport, 1990
The Journal of Physiology, 1995
1. Suspending human red blood cells in isotonic sucrose (low ionic strength, LIS) medium induces ... more 1. Suspending human red blood cells in isotonic sucrose (low ionic strength, LIS) medium induces a significant increase in membrane transport of glutamine, glutamate, lactate, histidine, taurine, glycine, serine, choline and carnitine but not sorbitol or sucrose. 2. Progressive lowering of ionic strength by sucrose or NaCl replacement gave a similar activation profile for taurine influx as found earlier for residual K+(86Rb+) flux. 3. The induced taurine transport could be measured as enhanced influx and efflux. Influx was linear with external concentration up to 10 mM, largely insensitive to alteration in cell volume, and did not vary with red blood cell age. 4. Unlike previous results for residual K+ transport, altering transmembrane potential with gluconate or glucuronate media led to an increase in taurine influx similar to that observed in LIS media. Varying medium pH confirmed the effect was not due to alteration in pH. 5. The LIS-induced flux was sensitive to a variety of 'classical' anion transport inhibitors in the order of potency DNDS, DIDS, NPPB, DIOA, niflumic acid, furosemide (frusemide), glibenclamide, nitrendipine and bumetanide. 6. The taurine flux showed a temperature dependence similar to that of the LIS-induced residual K+ flux. High hydrostatic pressure (40 MPa), however, inhibited taurine flux but stimulated residual K+ influx in LIS media. 7. A significant enhanced taurine flux could be demonstrated in red blood cells of other species, including horse, cattle, pig and high and low potassium type sheep. 8. It is concluded that lowering ionic strength activates a transport pathway for organic molecules sharing some similarities with background Cl- channels and LIS-induced residual K+ fluxes. In the latter context, however, there are certain significant differences (effect of transmembrane potential; volume; pressure sensitivity; species distribution) which may be important, and the unequivocal identity of the two transport processes remains to be confirmed.
Frontiers in Physiology, 2020
After about 120 days of circulation in the blood stream, erythrocytes are cleared by macrophages ... more After about 120 days of circulation in the blood stream, erythrocytes are cleared by macrophages in the spleen and the liver. The "eat me" signal of this event is thought to be the translocation of phosphatidylserine from the inner to the outer membrane leaflet due to activation of the scramblase, while the flippase is inactivated. Both processes are triggered by an increased intracellular Ca 2+ concentration. Although this is not the only mechanism involved in erythrocyte clearance, in this minireview, we focus on the following questions: Is the intracellular-free Ca 2+ concentration and hence phosphatidylserine exposure dependent on the erythrocyte age, i.e. is the Ca 2+ concentration, progressively raising during the erythrocyte aging in vivo? Can putative differences in intracellular Ca 2+ and exposure of phosphatidylserine to the outer membrane leaflet be measured in age separated cell populations? Literature research revealed less than dozen of such publications with vastly contradicting results for the Ca 2+ concentrations but consistency for a lack of change for the phosphatidylserine exposure. Additionally, we performed reanalysis of published data resulting in an ostensive illustration of the situation described above. Relating these results to erythrocyte physiology and biochemistry, we can conclude that the variation of the intracellular free Ca 2+ concentration is limited with 10 μM as the upper level of the concentration. Furthermore, we propose the hypothesis that variations in measured Ca 2+ concentrations may to a large extent depend on the experimental conditions applied but reflect a putatively changed Ca 2+ susceptibility of erythrocytes in dependence of in vivo cell age.
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Papers by Ingolf Bernhardt