Browsing by Author "Suhr, Dierk"
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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 Are biological effects of shock waves caused by free radicals?(1991) Suhr, Dierk; Brümmer, Franz; Hülser, Dieter F.Stone fragmentation in extracorporeal shock wave lithotripsy as well as accompanying tissue damage are attributed to cavitation. We attempted to demonstrate and localize the occurrence of cavitation in cell-free solutions and MGH-U1 cells using sensitive dyes for the detection of cavitation-generated free radicals.Item Open Access Biological effects and physical characterization of shock waves by an XL-1 experimental lithotripter(1989) Brümmer, Franz; Staudenraus, Joachim; Nesper, Martina; Suhr, Dierk; Eisenmenger, Wolfgang; Hülser, Dieter F.Extracorporeal shock wave lithotripsy (ESWL) has become the clinical standard method for non-invasive disintegration not only of concrements in kidney and urinary tract but also of gallstones. Despite the widespread clinical use of ESWL, the mechanism of stone destruction is not yet really understood, but several possibilities (cavitation, shock wave reflection) are discussed. The final cause of various side effects is still under discussion. Nevertheless, during the last few years much effort was put into possible extensions of ESWL applications On the other hand , physical characterizations of shock waves are rarely reported and combined measurements of biological effects in vitro and physical characterization of the applied shock waves are not available. We, therefore, examined the influence of water temperature and gas content on the shock wave efficency in biological systems and determined several physical characteristics (pressure amplitudes, rise time etc.) of the shock waves under the same experimental conditions.Item Open Access Biophysical investigations of the in vitro effects of shock waves and ultrasound(1993) Brümmer, Franz; Suhr, Dierk; Irmer, Ulrich; Bachleitner, Christoph; Hülser, Dieter F.To investigate the interactions of ultrasonic waves with biological tissues, we developed and standardized several in vitro models. Using these systems - artificial stones, human erythrocytes, L1210 mouse leukemia cells, multicellular spheroids, cavitation assay - we are able to elucidate the mechanisms of interaction as well as the cause of clinically observed side effects.Item Open Access Cavitation-generated free radicals during shock wave exposure: investigations with cell-free solutions and suspended cells(1991) Suhr, Dierk; Brümmer, Franz; Hülser, Dieter F.Extracorporeally generated shock waves as used in lithotripsy of urinary and biliary stones exhibit side effects in vivo. Furthermore, these shock waves destroy eukaryotic cells during in vitro treatment in suspension. A possible cause of these damaging effects might be cavitation, the growth and collapse of bubbles in liquids exposed to tensile stresses. During the collapse, temperature inside these cavitation bubbles rises up to several thousand K, leading to the formation of free radicals. We demonstrated the occurrence of cavitation-generated free radicals by direct reaction with fluorescent dyes in solution after shock wave treatment and investigated the resulting cell killing by variation of the cellular antioxidative defense status. We present evidence for the generation of intracellular free radicals during shock wave treatment of suspended cells.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 Sensivity of normal and malignant cells to shock waves(1992) Brümmer, Franz; Suhr, Dierk; Hülser, Dieter F.We examined the cytotoxic effect of shock waves for primary (embryonic chick kidney and thigh muscle) and permanently growing normal and malignant cells (human, rat, and mouse) in suspension. To avoid the influence of different media, the cells were suspended in phosphate buffered, saline and shock wave treated. In all cases the acute cytotoxic effect (measured by flow cytometry) was a function of the applied shock waves. The investigated cells differed in their LD 50 values which, however, do not reveal a general difference in sensitivity to shock waves for normal and malignant cells.Item Open Access Shock waves and free radicals : cell protection by vitamin E in vitro and ex vivo(1993) Suhr, Dierk; Brümmer, Franz; Irmer, Ulrich; Schlachter, Manfred; Hülser, Dieter F.The application of extracorporeal generated shock waves in medicine for the fragmentation of human kidney and gall stones proved to be a very successful technique. Shock wave lithotripsy, however, is not free of tissue damaging side effects. One major mechanism for the fragmentation of stones as well as for the side effects is cavitation, ie. the formation and movement of bubbles in liquids exposed to tensile forces. Collapse of cavitation bubbIes is accompanied by local "hot spots" of several 1,000 K, thus generating free radicals. We investigated the contribution of these free radicals to cellular injury by varying the cellular amount of a well known scavenger of free radicals, α-tocopherol.Item Open Access Standardisierte in-vitro-Modelle zur Charakterisierung von Stoßwellen(1990) Brümmer, Franz; Suhr, Dierk; Hülser, Dieter F.Zum jetzigen Zeitpunkt ist die physikalische Vermessung von Stoßwellen allerdings noch nicht problemlos möglich. Außerdem ist unbekannt, welche Stoßwellenparameter (wie Anstiegszeit und Dauer der Über- und Unterdruckamplitude) für die Steinzertrümmerung und die biologischen Nebenwirkungen bedeutsam sind. Wir haben deshalb vier in vitro-Modelle standardisiert, mit denen sich Wirkungen von Variationen der Behandlungsparameter schnell und zuverlässig aufzeigen lassen. Weiterhin kann die Stoßwellenwirkung auf Zellen, Gewebe und Steine in Lithotriptem mit unterschiedlichen Stoßwellenquellen getestet und verglichen werden.