Browsing by Author "Webb, Dennis J."

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Open Access
Fibroblastoid and ephitelioid cells in tissue culture: differences in sensivity to ouabain and on phospholipid composition
(1974) Hülser, Dieter F.; Ristow, Hans J.; Webb, Dennis J.; Pachowsky, Heinz; Frank, Werner
Investigations on nine different mammalian cell lines revealed that permanently growing cells of one morphological class have numerous membrane properties in common which are different or even lacking in the other cell class. With electrophysiological methods it is shown that the sensitivity of the Na+-K+ pump to ouabain is three orders of magnitude higher in the ionically non-coupled epithelioid cells than in the ionically coupled fibroblastoid cells which respond like primary cultures. This is accompanied by considerably higher binding constants for ouabain of the epithelioid cells as was shown by [3 H] ouabain binding and membrane potential measurements. The epithelioid cells also revealed a 50% lower relative amount of phosphatidylethanolamine and a 60-fold less net synthesis of phospatidylinositol. Finally, although primary cultures cannot proliferate without serum, permanent fibroblastoid cells have a reduced serum requirement and permanent epithelioid cells can proliferate without any serum.
Open Access
Relation between ionic coupling and morphology of established cells in culture
(1973) Hülser, Dieter F.; Webb, Dennis J.
Ionic coupling was found in all investigated fibroblastoid cells of 7 permanent cell lines in culture, whereas in 7 epithelioid cell lines no coupling could be detected. These established lines consisted of cells of normal or malignant origin as well as cells that were able to, or failed to, produce tumors, but the only relation with ionic coupling appeared to be morphology. The ionic coupling between fibroblastoid cells was unaffected by the presence of fetal calf serum instead of calf serum; culturing in media conditioned by non-coupled cells; variation of the potential difference and phase of the cell cycle. Coupled cells could be depolarized by decreasing the bicarbonate concentration in the media; non-coupled cells were unaffected.
Open Access
The use of the tip potential of glass microelectrodes in the determination of low cell membrane potentials
(1973) Hülser, Dieter F.; Webb, Dennis J.
The tip potential of Ling-Gerard glass microelectrodes changes upon insertion into cells and thus impedes the determination of the actual membrane potential. The lower the membrane potential of a cell, the larger will be the error due to this tip potential. However, as is demonstrated, a relationship exists between the tip potential of the electrode and the measured potential difference, which allows the determination of the membrane potential of a particular cell type by linear regression. This method showed that resting lymphocytes had no membrane potential, whereas for the slime mould Dictyostelitium discoideum a membrane potential of about -9 mV could be calculated.