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 Microbial metabolism of chlorosalicylates: effect of prolonged subcultivation on constructed strains(1986) Rubio, Miguel Angel; Engesser, Karl-Heinrich; Knackmuss, Hans-JoachimThe hybrid strain Pseudomonas sp. WR4016 was subcultivated with increasing concentrations of 5-chlorosalicylate (5rarr10 mM) as sole carbon source over a period of 9 months. At intervals of approximately 3 months derivative strains WR4017, WR4018 and WR4019 were isolated which exhibited higher growth rates and increased substrate tolerance. Comparative analysis of the turnover rates of the key enzymes in chlorosalicylate degradation showed that the adaptation process did not result from structural modifications of these proteins. Instead, balanced over-production of the salicylate hydroxylase and catechol 1,2-dioxygenase prevented the accumulation of toxic chlorocatechols and accounted for the reduction of the doubling times with 4- or 5-chlorosalicylate. A comparative analysis of a genetically engineered chlorosalicylate degrader PL300-1 showed similar regulatory patterns as the most advanced isolate WR4019 from the adaptation series.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 Metabolism of 2-chloro-4-methylphenoxyacetate by Alcaligenes eutrophus JMP 134(1993) Pieper, Dietmar Helmut; Stadler-Fritzsche, Karin; Engesser, Karl-Heinrich; Knackmuss, Hans-Joachim2-Chloro-4-methylphenoxyacetate is not a growth substrate for Alcaligenes eutrophus JMP 134 and JMP 1341. It is, however, being transformed by enzymes of 2,4-dichlorophenoxyacetic acid metabolism to 2-chloro-4-methyl-cis, cis-muconate, which is converted by enzymatic 1,4-cycloisomerization to 4-carboxymethyl-2-chloro-4-methylmuconolactone as a dead end metabolite. Chemically, only 3,6-cycloisomerization occurs, giving rise to both diastereomers of 4-carboxychloromethyl-3-methylbut-2-en-4-olide. Those lactones harbonring a chlorosubstituent on the 4-carboxymethyl side chain were surprisingly stable under physiological as well as acidic conditions.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 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 Differential effects of lesions of the dorsomedial and dorsolateral caudate putamen on reaction time performance in rats(1994) Hauber, Wolfgang; Schmidt, Werner J.In order to investigate the role of the dorsomedial and dorsolateral caudate-putamen (CPu) in movement initiation of rats, we examined the effects of quinolinic acid lesions (30 nmol in 1 μl) in these striatal subregions in a simple reaction time task. Results show that lesions of the dorsomedial, but not of the dorsolateral CPu increased reaction times. These findings provide further evidence for a functional heterogenity of the CPu and demonstrate an involvement of the dorsomedial CPu in processes related to rapid initiation of responsesItem 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 Assemblage of ortho cleavage route for simultaneous degradation of chloro- and methylaromatics(1987) Rojo, Fernando; Pieper, Dietmar H.; Engesser, Karl-Heinrich; Knackmuss, Hans-Joachim; Timmis, Kenneth N.Genetic engineering is a powerful means of accelerating the evolution of new biological activities and has considerable potential for constructing microorganisms that can degrade environmental pollutants. Critical enzymes from five different catabolic pathways of three distinct soil bacteria have been combined in patchwork fashion into a functional ortho cleavage route for the degradation of methylphenols and methylbenzoates. The new bacterium thereby evolved was able to degrade and grow on mixtures of chloro- and methylaromatics that were toxic even for the bacteria that could degrade the individual components of the mixtures. Except for one enzymatic step, the pathway was fully regulated and its component enzymes were only synthesized in response to the presence of pathway substrates.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.