15 Fakultätsübergreifend / Sonstige Einrichtung
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Item 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.Item Open Access 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.Item Open Access Cyclic-AMP reception and cell recognition in dictyostelium discoideum(1975) Gerisch, Günther; Malchow, Dieter; Huesgen, Adolfine; Nanjundiah, Vidyanand; Roos, Werner; Wick, Ursula; Hülser, Dieter F.Single cells of the slime mold, Dictyostelium discoideum, aggregate into a multicellular organism in response to cyclic AMP, which they detect by binding to cellsurface receptors. During the aggregation phase, two different responses to cyclic-AMP are observed. First, the cells orientate by chemotaxis towards the source of a concentration gradient which initially is a group of cells forming an aggregation center. Second, the cells relay pulses which are periodically generated by the centers.Item Open Access 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.Item Open Access Pulsed high-power-sonication of concrements, cancer cells and rodent-tumors in vivo(1989) Riedlinger, Rainer E.; Brümmer, Franz; Hülser, Dieter F.Extracorporeal lithotripsy has been successfully established, based on different principles of generating and focusing the shock waves. Lithotripters have also been used to investigate the influence of shocks to cancer cells and solid tumors. With two different trans-mitters (spark-gap type XL-1 and piezo-resonance type MW 2) we applied shock waves and short high power US-pulses to suspended and immobilized tumor cells and multicell spheroids. With MW 2 significant local damage on cell spheroids in gelatin was achieved, caused by locally controlled cavitation. The results are compared to each other.Item Open Access 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.Item Open Access Nervous-system-specific carcinogenesis by ethylnitrosourea in the rat: molecular and cellular aspects(1977) Rajewsky, Manfred F.; Augenlicht, Leonard H.; Biessmann, Harald; Goth, Regine; Hülser, Dieter F.; Laerum, Ole D.; Lomakina, L. Ya.A lead in the search for cellular determinants favoring neoplastic transformation may be provided by the pronounced tissue specificity of the oncogenic effect of certain carcinogens which do not require enzymatic metabolic activation, i.e., in cases where this specificity cannot be due to tissue differences in the activity of enzymes involved in the formation of the ultimate reactants. A carcinogen that fulfills this condition is the ethylating agent N-ethyl-N-nitrosourea (EtNU). Alkylation of nucleic acid constituents by N-nitroso compounds in relation to mutagenesis and carcinogenesis has received considerable attention recently.Item Open Access Molecular and cellular mechanisms in nervous system-specific carcinogenesis by N-ethyl-N-nitrosourea(1976) Rajewsky, Manfred F.; Goth, Regine; Laerum, Ole D.; Biessmann, Harald; Hülser, Dieter F.A single pulse of N-ethyl-N-nitrosourea (ENU), applied to BDIX rats during the perinatal age, specifically results in a high incidence of neuroectodermal neoplasms in the central and peripheral nervous system (NS). The pronounced sensitivity of the developing NS suggests a dependence of the carcinogenic effect on the proliferative and/or differentiative state of the target cells at the time of the ENU pulse. The specificity of ENU for the NS cannot be due to tissue variations in the degree of carcinogen-cell interactions, since the reactive, electrophilic ethyl cation is produced by rapid, nonenzymatic decomposition of ENU indiscriminately in all tissues. Correspondingly, the initial molar fractions of ethylated purine bases are similar in the DNA of "high-risk" (perinatal brain) and "low-risk" tissues (e.g., liver; adult brain). However, while the respective half lives in DNA of N7-ethylguanine and N3-ethyladenine show only minor differences for both types of tissues, the mutagenic ethylation product 06-ethylguanine is removed from brain DNA very much more slowly than from the DNA of other tissues. Together with their high rate of DNA replication during the perinatal age, the incapacity of rat brain cells for enzymatic elimination of 06-alkylguanine from their DNA could account for an increased probability of neoplastic conversion, and hence for the NS specificity of ENU in the rat.Item Open Access 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, ErikaDie 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.Item Open Access Elektronenmikroskopische Befunde bei einer Affenseuche (Cercopithecus aethiops)(1968) May, Gerhard; Knothe, Hans; Hülser, Dieter F.; Herzberg, KurtDie 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.