15 Fakultätsübergreifend / Sonstige Einrichtung

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Publication Type: search.filters.UBSTyp.ZeitschriftenartikelAuthor: search.filters.author.Hülser, Dieter F.

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    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.
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    Reduced cavitation-induced cellular damage by the antioxidative effect of vitamin E
    (1994) Suhr, Dierk; Brümmer, Franz; Irmer, Ulrich; Schlachter, Manfred; Hülser, Dieter F.
    Fragmentation of human urinary and biliary stones by shock waves in extracorporeal lithotripsy is accompanied by tissue damage. Both the fragmentation as well as the side effects are often attributed to cavitation. The hazardous potential of cavitation is not only of a physical nature but also of a chemical nature, because of the generation of free radicals, e.g. ·OH, ·H and ·O2. After the application of shock waves, we have demonstrated cavitation-generated free radicals in cell-free solutions and also in the surviving and intact suspended MGH-U1 cells by hydroethidine measurements. Under electron microscopical inspection, the same cells exhibited perinuclear cisternae, damaged mitochondria and numerous intracellular vacuoles. The contribution of free radicals to cell damage was investigated by reducing the vitamin E level in rats by a tocopherol free diet and by incubating L1210 cells in a tocopherol enriched medium. After 250 shock waves, ex vivo erythrocytes revealed a 75% increase in total cell disruption over cells from non-depleted rats. The in vitro experiments with L1210 cells exhibited a moderate protection by the addition of this scavenger of free radicals.
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    Arachidonovaja kislota obratimo blokiruet vysokopronicaemye mežkletočnye kontakty
    (1994) Hülser, Dieter F.; Zempel, Günther; Reuss, Bernhard; Suhr, Dierk; Sarovskaja, Julija J.; Murav'eva, O. V.; Dunina-Barkovskaja, Antonina; Margolis, Leonid B.
    The effect of arachidonic on intercellular coupling via gap junctions has been studied in BICR/M1R k cells - a mammary tumor cell line of the Marshall ratt. Arachidonic acid is shown to reversibly block both ionic and dye coupling in a dose-dependent manner. The cells recoupled after the washout with either serum- or albumin (essentially fatty acid-free)-containing solution. The intercellular pH decreased from 7,2 to 7,0 after arachidonic acid treatment; the same pH shift in the absence of arachidonic acid, however, had no effect on the junctional permeability. Flow cytometric measurments revealed an arachidonic acid-induced increase of the cytoplasmic free Ca 2+ concentration which was also reversible upon albumin treatment. Intracellular Ca 2+ or H+ are unlikely to be involved in the mechanism of the arachidonic acid effect on intercellular coupling: high resolution measurments using double whole-cell technique also show reversible blockage of the junctional conductance in the presence of arachidonic acid while the pipette solution was buffered with 10 mM HEPES and 10 mM EGTA to clamp intracellular calcium and proton concentrations. We suggest that arachiconic acid directly affects the gap junction channels, probably interfering with the lipid-protein interactions.
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    Characteristics of three nuclear emulsions for autoradiography at the electron microscope
    (1966) Hülser, Dieter F.; Rajewsky, Manfred F.
    Drei handelsübliche Kernspuremulsionen, Gevaert NUC 307, Ilford L4 und Kodak NTE, wurden wegen ihrer geringen Korngröße auf ihre Eignung zur elektronenmikroskopischen Autoradiographie untersucht. Korngrößenverteilungskurven wurden aufgenommen und ein geeigneter Entwickler ausgesucht. Zur Bestimmung der Empfindlichkeit dieser drei Emulsionen wurden Einkornschichten im Elektronenmikroskop mit Elektronen einer Energie von 5,7 keV, der mittleren beta-Energie des Tritiums, bestrahlt. Anschließend wurden die Emulsionen entwickelt, aber nicht fixiert. Mit dem Anteil der entwickelten AgBr-Körner kann dann über Trefferkurven die Empfindlichkeit der Emulsionen bestimmt werden. Man benötigt zur Bildung eines latenten Bildkeimes für die Ilford L4-Emulsion 1 - 1,4 Elektronen pro AgBr-Korn, für die Gevaert NUC 307-Emulsion 2 - 3 und für die Kodak NTE-Emulsion 4 - 5 Elektronen pro AgBr-Korn. Folgerungen für das Auflösevermögen bei radioaktiven Punkt- und Flächenquellen werden diskutiert. Fortschritte in der Mikroautoradiographie werden von der Entwicklung feinkörniger Emulsionen abhängen, deren Empfindlichkeit bei etwa einem Elektron pro AgBr-Korn liegen sollte.
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    Untersuchungen zur Synchronisation in vivo: temporäre Inhibition der DNA-Synthese durch Hydroxyharnstoff in normalen und malignen Säugerzellsystemen
    (1971) Rajewsky, Manfred F.; Hülser, Dieter F.; Fabricius, Erika
    Die Bearbeitung einer Reihe von Problemstellungen der experimentellen und klinischen Krebsforschung setzt die Möglichkeit einer Synchronisation proliferierender Zellsysteme in vivo voraus. Dies gilt z. B. für die Frage, ob bei Säugerzellen als Funktion ihrer Position im Zellcyclus Empfindlichkeitsunterschiede vorhanden sind, und zwar sowohl hinsichtlich der Auslösbarkeit des Prozesses der malignen Transformation durch Cancerogene, als auch in bezug auf die Inaktivierbarkeit maligner Zellen durch cytocide Agentien oder ionisierende Strahlung. In der vorliegenden Arbeit wird über Untersuchungen zur in vivo-Synchronisation verschiedener Gewebe (Embryo; Leber; Milz; transplantabler BICR/M1R-Tumor) der Ratte durch temporäre Blockade der DNA-Synthese mit Hydroxyharnstoff (HU) berichtet.
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    Elektronenmikroskopische Befunde bei einer Affenseuche (Cercopithecus aethiops)
    (1968) May, Gerhard; Knothe, Hans; Hülser, Dieter F.; Herzberg, Kurt
    Die elektronenmikroskopischen Befunde von G. Müller und D. Peters, die den Erreger einer Affenseuche (Cercopithecua aethiops) als gebogene Stäbe dargestellt haben, werden bestätigt und erweitert. Es gelang, die ätiologische Bedeutung dieser Formen durch die Kombination von Gewebekultur (menschliche Amnionzellen), Tierversuch (Meerschweinchen) und elektronenmikroskopischem Befund in dieser Reihenfolge zu sichern.
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    Bioelectric responses at fertilization : separation of the events associated with insemination from those due to the cortical reaction in sea urchin, Lytechinus variegatus
    (1982) Hülser, Dieter F.; Schatten, Gerald
    The bioelectric responses at fertilization of the sea urchin Lytechinus variegatus are a complex series of membrane potential and resistance changes that occur concomitant with gamete fusion, ionic fluxes, and the cortical granule discharge. This work attempts to separate the electrical effects of sperm-egg interactions from those of the cortical reactions. Two approaches were taken to discern the electrical events associated with insemination, distinct from cortical granule discharge: (1) fertilization of eggs treated with 3% urethane, 10 mM procaine, or 10 mM nicotine, to prevent the cortical reaction and (2) refertilization of fertilized eggs (denuded with 1 mM aminotriazole containing 1 mg/ml soybean trypsin inhibitor). Cortical granule discharge in the absence of sperm incorporation was investigated by artificial activation with 5 μM A23187 or by fertilization in the presence of 10 μM cytochalasin D, which prevents incorporation. These results are consistent with a model in which the sperm-egg interaction triggers both a rapid (50-400 msec), but minor (≅10 mV), electrical transient that leads to an action potential and then both the Na+-dependent fast block to polyspermy and the late block resulting from the secretion of the cortical granules.
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    Elektronenmikroskopische Autoradiogramme: unterschiedliche Empfindlichkeit von Photoemulsionen gegenüber Tritium
    (1971) Hülser, Dieter F.; Rajewsky, Manfred F.
    The sensitivity of the photographic emulsion is an important factor in the resolution of autoradiographs at the electron microscopic level. In a number of recent publications, single hit processes have been considered sufficient for the production of developable latent images by tritium electrons. However, since the absorbed energy required or latent image formation in AgBr crystals of commercially available emulsions is of the order of 800 eV, onIy low energy tritium electrons (up to 3 keV) will produce latent images by single hit processes in small AgBr crystals of about 400 A diameter. In emulsions with larger AgBr crystals (about 1000 A diameter), electrons with an energy of up to about 6 keV can be regisiered by single hit processes. Evidently, latent image formation may also result from multiple hits by electrons of higher energy. Since the energy absorption required for latent image formation is constant, the sensitivity of photographic emulsions must be considered proportional to the diameter of the respective AgBr crystals, unless methods become available for specific sensitization of emulsions with small AgBr crystals.
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    Ionic coupling between nonexcitable cells in culture
    (1974) Hülser, Dieter F.
    In the following sections, the electrophysiological techniques used for the demonstration of low-resistance junctions by the occurrence of ionic coupling pulses will be described. It will also be shown that for the analysis of coupling phenomena between cells, electrical parameters such as potential difference, membrane resistance, and capacitance must be taken into account. In addition, the electrical and mechanical instrumentation necessary for such measurements will be described with special emphasis on electrophysiological studies in cultured cells. Based on experiments with lymphocytes it will be shown that low-resistance junctions can be built up within minutes and that in the case of cells of established lines in culture their existence is related neither to normal nor to malignant cell properties, but appears to be associated with fibroblastoid cells.
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    Intercellular communication in phytohemagglutinin - induced lymphocyte agglutinates
    (1971) Hülser, Dieter F.; Peters, Johann H.
    Intercellular communication, as indicated by ion flow between cells, was measured with micro-glass-electrodes in lymphocytes immediately after addition of phytohemagglutinin.