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1

Digitale Medien

Electro-acoustic fusion of cells (1985)

Vienken, J. ; Zimmermann, U. ; Zenner, H. P. ; [weitere]

Springer

Naturwissenschaften 72 (1985), S. 441-442

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ISSN: 1432-1904

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie , Allgemeine Naturwissenschaft

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00404895

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2

Digitale Medien

Real time observations of polylysine, dextran and polyethylene glycol induced mutual adhesion of erythrocytes held in suspension in an ultrasonic standing wave field (1987)

Tilley, D. ; Coakley, W. T. ; Gould, R. K. ; [weitere]

Springer

European biophysics journal 14 (1987), S. 499-507

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ISSN: 1432-1017

Schlagwort(e): Erythrocyte ; cell adhesion, cell agglutination ; acoustic radiation force ; ultrasonic levitation ; interfacial instability ; polylysine ; dextran ; polyethylene glycol

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Physik

Notizen: Abstract A technique which enables cells to be observed in suspension for times of the order of minutes (employing acoustic radiation foreces in a 1 MHz ultrasonic standing wave field) is described. Video recordings of the mutual adhesion of human erythrocytes in suspension have been analysed. Concave-ended cell doublets and linear rouleaux developed in 0.5–1.5% w/v Dextran T500 by a gradual (2.5–17 s) increase in the area of cell contact over the cell cross-section. The concave-ended rouleaux form was not seen in polylysine or in polyethylene glycol. In 5–7% dextran and in 20μg/ml polylysine mutual adhesion was a two stage process. Cells first form a strong local contact which persists (without apparently growing in area) for a number of seconds following which the cell surfaces move suddenly to form a spherical doublet. The average initial contact time and engulfment time for cells in 7% Dextran T500 are 18 and 2.7 s, respectively. The corresponding values for cells in 20 μg/ml, 14 kDa, polylysine are 2.7 and 0.3 s. There was no initial contact delay during spherical doublet formation in mg/ml polylysine. Electron microscopy showed that the intercellular seam for spherical doublets formed with all three agglutinating molecules was bent in a wavy (λ∼4 μm) profile. The thickness of the intercellular space varied in a spatially periodic way (λ∼0.8 μm) for cells in polylysine. Examples of periodic intercellular spaces were seen by light microscopy in polyethylene glycol induced clumps. The role of interfacial instability in the adhesion processes is discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00293260

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3

Digitale Medien

Interfacial instability and the agglutination of erythrocytes by polylysine (1985)

Coakley, W. T. ; Hewison, L. A. ; Tilley, D.

Springer

European biophysics journal 13 (1985), S. 123-130

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ISSN: 1432-1017

Schlagwort(e): Erythrocyte ; interfacial instability ; surface wave ; polylysine ; cell agglutination ; cell adhesion, acrosome reaction ; membrane fusion

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Physik

Notizen: Abstract Human erythrocytes have been exposed to poylysine of molecular weight range 4 to 220 kDa and concentration range 0.5 to 2,000 μ/ml at 37°C. Threshold concentrations for cell agglutination by the polycation have been determined for the samples of different molecular weight. Light and electron micrographs show that, in the erythrocyte agglutinates, cell-cell contact is generally made only at discrete, spatially periodic, regions which are distributed over a significant part of the cell surface. The average spacing between contact regions is 0.83 μm. The cell membrane has a wavy profile between contact regions. Agglutination occurs only in cell samples whose electrophoretic mobility is significantly altered by polylysine and, in agreement with a previous report, occurs even when the electrophoretic mobility reaches high positive values. The electrophoretic mobility data implies that agglutination requires some protrusion of polylysine from the cell glycocalyx. We discuss how a resulting net attractive intercellular force could act to destabilize the aqueous layer between two cells, allowing surface wave growth which results in spatially periodic contact regions. Examples of situations where cell and membrane contact might be explained by the general concept of interfacial instability are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00256532

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4

Digitale Medien

Membrane-Membrane contact: Involvement of interfacial instability in the generation of discrete contacts (1989)

Coakley, W. T. ; Gallez, D.

Springer

Bioscience reports 9 (1989), S. 675-691

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ISSN: 1573-4935

Schlagwort(e): membrane contact ; membrane instability ; interfacial instability ; cell adhesion ; cell agglutination

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Abstract The classical approach to understanding the closeness of approach of two membranes has developed from consideration of the net effect of an attractive van der Waals force and a repulsive electrostatic force. The repulsive role of hydration forces and stereorepulsion glycocalyx forces have been recently recognized and an analysis of the effect of crosslinking molecules has been developed. Implicit in these approaches is the idea of an intercellular water layer of uniform thickness which narrows but retains a uniform thickness as the cells move towards an equilibrium separation distance. Most recently an attempt has been made to develop a physical chemical approach to contact which accommodates the widespread occurrence of localized spatially separated point contacts between interacting cells and membranes. It is based on ideas drawn from analysis of the conditions required to destabilize thin liquid films so that thickness fluctuations develop spontaneously and grow as interfacial instabilities to give spatially periodic contact. Examples of plasma membrane behaviour which are consistent with the interfacial instability approach are discussed and experiments involving polycation, polyethylene glycol, dextran and lectin adhesion and agglutination of erythrocytes are reviewed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01114806

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5

Digitale Medien

Intrinsic electric fields and membrane bending (1984)

Doulah, F. A. ; Coakley, W. T. ; Tilley, D.

Springer

Journal of biological physics 12 (1984), S. 44-51

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ISSN: 1573-0689

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Physik

Notizen: Abstract The fragmentation of human erythrocytes heated in a range of ionic environments has been examined by video microscopy, $$W$$ , the average number of surface wave crests growing on the cell rim during fragmentation by membrane externalization, andI, the percentage of cells internalizing membrane, were scored. The membrane diffusion potential was altered experimentally on decreasing the extracellular chloride concentration by substituting either membrane-impermeant sorbitol or Na gluconate for some NaCl. The external-membrane-face surface potential was altered either by surface charge depletion or by ionic strength changes. The dependence of morphological change on diffusion potential at constant cell volume and surface potentials was established over a 34-mV change in diffusion potential. The rate constants for morphological change with charge depletion at different diffusion potentials are largely independent of the diffusion potential. A l.O-mV increase in diffusion potential has an effect on morphological change of comparable magnitude to that of a 1.0-mV decrease in the modulus of the negative surface potential. When the diffusion potential increased on decreasing both the extracellular diffusible ion concentration and extracellular ionic strength, the effect on cell morphology of increasing the modulus of the surface potential was overcome by the effects of the diffusion potential change.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01858252

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6

Digitale Medien

Divalent cation effects on membrane bending in heated erythrocytes (1984)

Coakley, W. T. ; Doulah, F. A.

Springer

Journal of biological physics 12 (1984), S. 85-92

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ISSN: 1573-0689

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Physik

Notizen: Abstract The thermal fragmentation of human erythrocytes involves either surface wave growth and membrane externalization at the cell rim or membrane internalization at the cell dimple. In symmetrical monovalent electrolytes an increase in membrane internalization at the cell dimple correlates with the decrease in zeta potential arising from surface charge (sialic acid residue) depletion. The influence of divalent cations on thermal fragmentation is examined in this work. The erythrocyte zeta potential decreased when divalent cations replaced some Na+ in the cell-suspending phase. The incidence of membrane internalization increased in rank order Ca2+〉Ba2+〉Mg2+≥Sr2+. Calcium continued to influence the thermal fragmentation of cells highly depleted of sialic acid, suggesting that the ion also interacted with membrane sites other than sialic acid. The divalent cation influence on cell fragmentation was shown to be greater than that due to zeta potential decrease alone. This conclusion was supported by the observation that the divalent cation-induced changes in zeta potential showed much less cation specificity than did the changes induced in the thermal fragmentation pattern. The result implies that the specificity of the divalent cation effects was due to interactions within the erythrocyte shear layer. The possibility that the interaction is with membrane lipids is examined.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01870558

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