15 Fakultätsübergreifend / Sonstige Einrichtung

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Open Access
Adolf Palm : [Nachruf]
(1994) Wurm, Friedrich; Kull, Ulrich
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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.
Open Access
Behavioural pharmacology of glutamate in the basal ganglia
(1992) Schmidt, Werner J.; Bubser, Michael; Hauber, Wolfgang
In Parkinson's disease the dopaminergic inhibition - mediated by DA2 receptors in the triatum - is reduced. Therefore glutamatergic excitation predominates in the antero-dorsal striatum. In turn the glutamatergic neurons of the subthalamic nucleus become disinhibited. Antagonists of the NMDAsubtype of glutamate receptor injected locally into the glutamatergically innervated nuclei or competitive and non-competitive NMDA-antagonista administered systemically, counteract parkinsonian symptom in animals.
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, 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.
Open Access
A contribution to the floristics and vegetation of Zanskar (Kashmir)
(1985) Seybold, Siegmund; Kull, Ulrich
Some observations on the vegetation and plant-ecology were made on a journey through Zanskar (part of Jammu and Kashmir state). Trees are growing near water-courses on about 3800m also in the dry southern part of Zanskar; the timberline on both sides of the highest ridge of the Himalayas seems to be situated at about 3800-3900m. Crop plants are grown in southern Zanskar on to about 4000m; they need irrigation. The overgrazing led to a vast extension of Artemisia and Astragalus-Acantholimon vegetation units. The 13 places of plant collection, reaching from 2600m to 4700m, are characterized, and a plant list of collected plants with precise locality data is given.
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.
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 responses
Open Access
Effects of abscisic acid on photosynthesis of protoplasts from Petunia hybrida
(1974) Hoffmann, Franz; Kull, Ulrich
Protoplasts from plants are suitable experimental objects for investigations in which substances are taken up by cells, since chemicals can reach the cell surface directly. Therefore, it is convenient to use them for experiments concerned with effects of phytohormones on metabolism. So far, some work on the application of auxins 1-3 has been described, and recently we have made some investigations on the influence of zeatin on photosynthesis and respiration of isolated mesophyll protoplasts from Petunia.
Open Access
Effects of kinetin on lipid labelling in cell organelles : [abstract]
(1982) Graf, Josef A.; Horsch, Axel; Kull, Ulrich
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Open Access
Einfluß von Zeatin auf den Kohlenhydrat- und Stickstoffhaushalt vegetativer Pflanzenteile
(1974) Kull, Ulrich; Höllwarth, Michael
Die Wirkungen von Zeatin entsprechen weitgehend denjenigen von Kinetin. Wie die hier beschriebenen Versuchsreihen sowie weitere Untersuchungen zur Fettsäurenzusammensetzung der Blattlipide und zur Atmung zeigen, können zu hohe Konzentrationen des Phytohormons den Stoffwechsel negativ beeinflussen. Diese Störungen machen sich naturgemäß im N-Haushalt deutlicher bemerkbar als bei der Kohlenhydratspeicherung.
Open Access
Einige ökophysiologische Untersuchungen auf Tenerife (Kanarische Inseln)
(1979) Höllwarth, Michael; Kull, Ulrich
Die Kanarischen Inseln sind ein klassisches Gebiet der Vegetationskunde. Während ihre Flora mittlerweile ziemlich gut bekannt ist, sind bisher nur wenige ökophysiologische Untersuchungen durchgeführt worden. Wir haben an typischen Standorten der charakteristischen Vegetationseinheiten Sukkulentenbusch, Lorbeerwald und Gebirgshalbwüste ("Gebirgssteppe") bei gleicher Großwetterlage (normale Schönwetterperiode am Ende der feuchteren Jahreszeit) die Tagesperiodik der üblichen meteorologischen Größen sowie der wichtigsten physiologischen Parameter von charakteristischen Arten gemessen und die bestehenden Korrelationen ermittelt. Es sollte dann geprüft werden, inwieweit Aussagen über die Konkurrenzfähigkeit von Arten möglich sind. Wobei dem Lorbeerwald besondere Aufmerksamkeit geschenkt wurde.
Open Access
Electrophysiological properties of ethylnitrosourea-induced, neoplastic neurogenic rat cell lines cultured in vitro and in vivo
(1976) Laerum, Ole D.; Hülser, Dieter F.; Rajewsky, Manfred F.
A comparative analysis was performed on the electrophysiological properties of 11 neoplastic neurogenic cell culture lines and five other cell lines of different origin (HV1C, rat bile duct carcinoma; BICR/M1 RK , rat mammary tumor; HeLa, human cervix carcinoma; 3T3, mouse embryo; REe, rat embryo). Neurogenic lines were derived either from N-ethyl-N-nitrosourea-induced neoplasms of the nervous system or from cultured fetal rat brain cells that had undergone neoplastic transformation in vitro after exposure to Nethyl-N-nitrosourea in vivo. Electrical membrane excitability was lacking in all neurogenic cells analyzed. Their membrane potential and input resistance values were similar to those of the nonneurogenic lines. Intercellular ionic coupling was consistently observed between cells of a fibroblastoid shape or cells bearing multiple cytoplasmic processes (i.e., all neurogenic lines HV1C, BICR/M1RK , and 3T3). Epithelioid cells (i.e., HeLa, REe, an NV1C subpopulation, and a GV1C1 variant) showed no such intercellular communication. In vivo monolayer cultures on glass coverslips were obtained by a modified i.p. diffusion chamber technique. Under these conditions, the cells (with the exception of a glioma-derived cell line) retained the morphological appearance and electrophysiological properties observed in vitro.
Open Access
Energy content, storage substances, and construction and maintenance costs of Mediterranean deciduous leaves
(1989) Diamantoglou, Stergos; Rhizopoulou, Sophia; Kull, Ulrich
At monthly intervals water content, crude fibre, total and protein nitrogen, sugars, starch, total lipids, ash content and calorific total energy were measured throughout the lifespan of the leaves of the deciduous mediterranean shrubs Pistacia terebinthus L. and Cotinus coggygria Scop. From these data the construction costs and maintenance costs, as well as the construction costs of non-storage compounds and energy expenditure values were calculated. The latter values were also calculated for the evergreen stemmed shrub Ephedra distachya for reasons of comparison with an evergreen mediterranean species. The water status in the deciduous leaves is stable for a long time during the drought period until the beginning of senescence in August/September. In Cotinus an early and considerable increase of storage compounds is found, whilst in Pistacia terebinthus the accumulation is more uniform until August. The N-content is rather low compared with other deciduous leaves, the calorific energy is in the lower range of the values reported for similar species. The construction costs of the leaves of both deciduous species are significantly lower than those calculated by Williams et al. (1987) for two drought deciduous chaparral species but are in agreement with the data reported by other authors on deciduous leaves. Contrary to the findings of Williams et al. they are lower than those of evergreen species; this is also true when the construction cost of the non-storage compounds alone is considered. The values found for Ephedra are similar to the maintenance costs do not show a significant variation in the deciduous leaves. They are higher than those known for evergreen leaves but somewhat lower than the values calculated for deciduous chaparral leaves.
Open Access
Growth inhibition of oncogene transformed rat fibroblasts by cocultured normal cells: relevance of metabolic cooperation mediated by gap junctions
(1991) Martin, Wolfgang; Zempel, Günther; Hülser, Dieter F.; Willecke, Klaus
We have studied the proliferation of rat 208F cells (a derivative of Rat-1 cells) transformed by activated c-Ha-ras, v-fgr, v-raf, v-fms, or v-src oncogenes during cocultivation with an excess of early passage rat embryonic fibroblasts or immortal 208F cells. The total number and size of foci formed by oncogene-transformed 208F cells were strongly reduced by cocultured normal fibroblasts. The extent of growth suppression of transformed foci appears to be dependent on the type of transforming oncogene and on the type of normal fibroblasts rather than on the extent of gap-junctional communication between transformed and normal cells. Total inhibition of fluorescent dye transfer between normal and transformed cells by the 3β-O-hemisuccinate of 18α-glycyrrhetinic acid (18α-carbenoxolone), an inhibitor of gap-junctional communication in human fibroblasts, did not prevent growth inhibition of transformed cells in the cocultivation assay. Since adjacent cells remained electrically coupled in the presence of this inhibitor it is possible that the strongly reduced metabolic cooperation, as indicated by the lack of fluorescent dye transfer, is sufficient for mediating the growth-inhibitory effect of normal fibroblasts. 208F cell-conditioned medium, however, also caused strong growth inhibition of transformed derivatives, suggesting that the effect is in part mediated by release of stable growth inhibitor(s) from 208F cells.
Open Access
Hydrogen ion-mediated enhancement of cytotoxicity of bis-chloroethylating drugs in rat mammary carcinoma cells in vitro
(1989) Jähde, Eckhard; Glüsenkamp, Karl-Heinz; Klünder, Irene; Hülser, Dieter F.; Tietze, Lutz-F.; Rajewsky, Manfred F.
Aerobic glycolysis, a metabolic characteristic of malignant cells, can be exploited to increase the concentration of lactic acid selectively in tumor tissues in vivo by systemic administration of glucose (E. Jähde and M. F. Rajewsky, Cancer Res., 42: 1505-1512, 1982). To investigate whether a more acidic microenvironment can enhance the effectiveness of cytocidal drugs, we have analyzed the colony-forming capacity of M1R rat mammary carcinoma cells exposed to bis-chloroethylating agents in culture as a function of extracellular pH (pHe). At pHe 6.2 the cytotoxicity of 4-hydroperoxycyclophosphamide, as measured by inhibition of colony formation, was potentiated by a factor of ∼200 as compared to pHe 7.4. Similar results were obtained with mafosfamide, nitrogen mustard, nornitrogen mustard, melphalan, and chlorambucil; not, however, with ifosfamide. As indicated by experiments using the ionophor nigericin for rapid equilibration of pHe and intracellular pH (pHi; measured with pH-sensitive microelectrodes), modulation of drug action by varying pHe primarily resulted from the concomitant decrease in pHi. The acidic microenvironment enhanced cytotoxicity most effectively during the phase of cellular drug uptake and monofunctional alkylation of DNA. DNA cross-link formation appeared to be less affected by pH, and lowering of pHe during the phase of cross-link removal was only marginally effective.
Open Access
Immunochemical and electrophysiological characterization of murine connexin40 and -43 in mouse tissues and transfected human cells
(1994) Traub, Otto; Eckert, Reiner; Lichtenberg-Fraté, Hella; Elfgang, Claudia; Bastide, Bruno; Scheidtmann, Karl Heinz; Hülser, Dieter F.; Willecke, Klaus
Human HeLa or SkHep1 cells, defective in intercellular communication through gap junctions, were transfected with coding sequences of murine connexin40 (Cx40) and -43. The transfected cells were restored in gap junctional coupling as shown by 100-fold increased electrical conductance. When studied by the double whole-cell patch-clamp technique, Cx40 HeLa transfectans exhibited single channel conductances of γ=121 ± 7 pS and γ=153 ± 5 pS. They were voltage gated with an equivalent gating charge of z=4.0 ± 0.5 for a voltage of half-maximal inactivation U 9= 44 ± 7 mV. The corresponding values or connexin43 (Cx43) HeLa transfectants are: γ=60 ± 4 pS and γ=40 ± 2 pS as well as z=3.7 ± 0.8 and U 0 = 73 ± 7 mV. Transfer of the dye Lucifer Yellow was always considerably lower in Cx4- than in Cx43-transfectants though their total junctional conductance was similar or even higher than for Cx43-transfectants.
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.
Open Access
Ist Diarthron vesiculosum (Thymelaeaceae) ein ökologisches Rätsel? : Studien an Therophyten in der Steppe Kabul/Afghanistan. 2, Die Wirkung der Dürre auf Mineralstoffverhältnisse und Kohlenhydrathaushalt
(1973) Breckle, Siegmar-Walter; Kull, Ulrich
Diarthron vesiculosum ist eine annuelle Thymelaeacee, die die trockenen und heißen Sommer in den turkmenischen Wüsten lebend überdauert. Wir haben in der Umgebung von Kabul neben Diarthron auch Ziziphora tenuior L. (Lamiaeeae) und Scabiosa olivieri COULT. (Dipsacaceae) zum Vergleich näher untersucht. Ähnlich wie schon in Teil I die phänologischen, morphologischen und osmotischen Verhältnisse keinen Hinweis ergaben, der die russische Beobachtung hätte bestätigen können, zeigte sich auch bei den Untersuchungen der Ionenverhältnisse und des Kohlenhydrathaushaltes, daß alle drei untersuchten Annuellen wenige Wochen nach Ende der Frühjahrsregenperiode absterben. Die Akkumulation an Mineralstoffen ist in den drei Arten recht unterschiedlich, die geringsten Gehalte weist Diarthron auf. Das steht in Verbindung mit dem relativ gut ausgeglichenen Wasserhaushalt. Der stenohydre Charakter zeigt sich auch im Kohlenhydrathaushalt: Diarthron vergilbt, bevor sie verwelkt, d. h. sie "verhungert", bevor sie verdurstet. Die Bedeutung des Schleims in Diarthron ist noch offen. Bei Ziziphora dagegen bricht schon wenige Tage nach Einsetzen der Dürre der Stoffwechsel völlig zusammen. Noch vorhandene Reserven an Kohlenhydraten oder Proteinen verbleiben weitgehend ungenutzt in den welkenden Pflanzen. Scabiosa hingegen nähert sich in ihrem Verhalten eher Diarthron, und vermag dieses sogar noch zu übertreffen, indem sie durch einen anpassungsfähigeren Stoffwechsel das Absterben bis Ende Juni hinauszögern kann und bis zu diesem Zeitpunkt ständig noch Blütenstände neu anlegt. Diarthron weist eine gewisse Sonderstellung auf, da bei ihm der Zuckeranteil am potentiellen osmotischen Druck im Laufe der Entwicklung abnimmt. Dies gilt entsprechend für den Zuckergehalt. Geeignete Bezugssysteme der analysierten Inhaltsstoffe werden diskutiert. Der Gehalt an anorganischen Ionen wird auch in Anteilen des potentiellen osmotischen Druck angegeben. Die Zusammensetzung der Pflanzen im Laufe ihrer raschen Entwicklung wird außerdem in absoluten Mengen ausgedrückt.
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.
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.