15 Fakultätsübergreifend / Sonstige Einrichtung
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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 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 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 Role of the medial orbitofrontal cortex and ventral tegmental area in effort-related responding(2020) Münster, Alexandra; Votteler, Angeline; Sommer, Susanne; Hauber, WolfgangDie Arbeit untersucht die Interaktion von zwei Gehirnarealen, dem medialen Orbitofrontalcortex und dem Ventralen Tegmentalen Areal, bei der Handlungssteuerung.Item Open Access 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, GeraldThe 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.Item Open Access Increased radioresistance of cells in cultured multicell spheroids. 1, Dependence on cellular interaction(1981) Dertinger, Hermann; Hülser, Dieter F.Monolayers of six different cell lines were investigated with respect to ionic coupling using micro-electrode techniques. In parallel, survival after Co-gamma-irradiation of monolayer- and spheroid cultures of these lines was compared. It was found that spheroids of coupled cell lines were more radioresistant than monolayers (contact effect). However, cell coupling did not enhance the survival of monolayers over single cells. This suggests that the contact effect is a tissue phenomenon requiring cellular interaction but is expressed only under conditions of three-dimensional growth.