Universität Stuttgart
Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1
Browse
141 results
Search Results
Item Open Access Cytokinins in different cell compartments after treatment with [8-14C]-kinetin : [abstract](1985) Graf, Josef A.; Dietz, B.; Kull, Ulrich-Item Open Access Prosomes of higher plants share biochemical properties : [abstract](1988) Schliephacke, Martin; Kremp, Anette; Schmid, Hans-Peter; Kull, Ulrich-Item Open Access Introduction - Symposium on Intercellular Communication Stuttgart, 1982(1982) Hülser, Dieter F.Intercellular communication is a postulate of complex multicellular organisation. Signal transfer between cells is possible in different ways: 1.) Long distances of up to 1 m may be bridged by molecules which are produced in distinct cells and are released into the extracellular fluid where they are distributed and interact with receptors on the surface of their target cells (e.g., humoral interaction). 2.) Transmitter substances which have a limited life span or which can be inactivated by inhibitor molecules spread signals only over shorter distances (e.g., synaptic cleft, -200nm). 3.) Information can also be exchanged by direct membrane contact when two molecules interact with each other directly or via linker molecules (e.g., immune system). 4.) Intercellular communication is also possible by channels between adjacent cells, which permit the exchange of ions and molecules and the spread of electric currents; many of those pores are arranged in the membranes of the contacting cells as a quasicristalline structure forming the gap junction. A national symposium on "Intercellular Communication" in Stuttgart on 16 and 17 September 1982 serving the aim of increased "interlaboratory communication" covered most of the above aspects.Item Open Access Item Open Access Item Open Access Neuere Ergebnisse der Photosynthese-Forschung(1971) Kull, UlrichDie komplexen Vorgänge, die wir zusammenfassend als Photosynthese bezeichnen, laufen in allen grünen Pflanzen und nur in diesen (einschließlich bestimmter Bakterien) ab. Diese Vorgänge liefern die Energie für den Lebensprozeß der Pflanzen und indirekt der heterotrophen Organismen, somit insbesondere auch von Tier und Mensch. Weiterhin stammt ein erheblicher Teil der Energiereserven des Menschen aus Photosyntheseprodukten (Kohle, Erdöl). Bei der Photosynthese wird mit Hilfe von Lichtenergie organische Substanz aus anorganischer aufgebaut. Dabei ist Kohlendioxid der C-Lieferant.Item Open Access Membrane potential oscillations in homokaryons : an endogenous signal for detecting intercellular communication(1982) Hülser, Dieter F.; Lauterwasser, UrsulaFusion of cells by polyethylene glycol results in homokaryons with lower membrane input resistances than their parental cells, but otherwise unchanged membrane properties. With these large cells, long lasting intracellular recordings can be realized which are impossible with single parental cells. Homokaryons often display hyperpolarizing (up to 50 mV) oscillations of their membrane potentials. In electrically non-coupled cell lines (HeLa, L, Cl-1D) the frequencies of these endogenous signals are 3 oscillations per min. Trypsinized homokaryons of electrically coupled cell lines (BICR/M1R-K, 3T3, BT5C2) have frequencies of 0.3 oscillations per min. By recording the membrane potential oscillations of two contacting homokaryons, the formation of low resistance junctions was followed - without applying exogenous signals - by a superposition of the individual oscillations. Our electronmicroscopical investigations revealed that the intercellular coupling through the membranes of homokaryons can be attributed to gap junctions.Item Open Access Molekulare Grundlagen der Evolution(1975) Kull, UlrichDie Etablierung der Molekularbiologie in den letzten 20 Jahren führte zu der Erkenntnis, daß der Evolutionsvorgang eine molekulare Basis hat und mußte somit zwangsläufig die Frage aufwerfen, wie diese molekularen Grundlagen aussehen. Diese Ausführungen behandeln die Untersuchung der molekularen Mechanismen des Evolutionsprozesses, wobei natürlich die molekularen phylogenetischen Schemata zur Erkennung von Gesetzmäßigkeiten herangezogen werden müssen.Item Open Access Konstruktion, Leichtbau und Ökonomie bei Pflanzen(1989) Kull, Ulrich; Herbig, AstridDie Festigkeitseigenschaften von Achsen aus Pflanzenarten unterschiedlicher Stellung werden mit Hilfe der BIO-Methode (nach F. Otto) beschrieben und zu Energiegrößen in Beziehung gesetzt. Damit lassen sich Aufwandswerte K (dirnensionslos) berechnen, die dann auf die Lebensdauer der Achsen bezogen werden. Konstruktiv gute Wirtschaftlichkeit zeigen Achsen vom Bautypus der Gräser, Blattstiele von Farnen und Achsen vom Hopfen (Liane). Der K-Wert ausdauernder Achsen liegt höher, K/Lebensdauer ist aber ähnlich wie bei einjährigen. Kurzlebige Blüten- und Fruchtstiele haben einen hohen Aufwand je Zeit. Die Größe K/Lebensdauer wird in Verbindung mit der Selektion gebracht. Vergleiche mit menschlichen Konstruktionen schließen sich an.Item Open Access Der Stickstoffhaushalt immergrüner mediterraner Hartlaubblätter(1988) Diamantoglou, Stergos; Kull, UlrichThe seasonal variations of major nitrogenous components (total N, protein N) in sclerophyllous leaves of four mediterranean species - Ceratonia siliqua, Olea europaea var. sylvestris, Pistacia lentiscus and Quercus coccifera - were investigated throughout the whole lifetime of the leaves. The leaf-longevity of the first two species mentioned is about two yars, that of the latter two species is somewhat longer than one year. As reference values the raw fibre content and the total chlorophyll content of the leaves were also measured. The raw fibre content increase during leaf-growth, there-after it remains constant. In the leaves having a lifetime of two years, in the spring of the second year an additional increase, although weak, is observed. The chlorophyll content rises during the leaf growth, then remains unchanged for some time, but begins to decrease early. In the leaves of Ceratonia and Olea the shrinkage is recognized already in the spring of the second year. During the period of senescence, the decrease of chlorophyll a is more distinct than that of chlorophyll b. The total N content in all cases decreases during leaf-growth and then remains constant. In Ceratonia leaves it is reasonably high considering that it is an evergreen species. Rather early the N-content begins to decrease; which is intensified during the last months of the lifetime the leaves. This is due to the well-known export of N-compounds from senescent tissues. In Ceratonia leaves the N-content increases during the first winter; obviously they serve as N-storage organs. The content of protein-N in all species shows essentially the same variations as that of total N. Results of tests carried out in the months of January and August revealed that the proline content in the leaves of all species is higher during the drought period than during the cold period. Using the different reference-values, the variations of N-content during leaf longevity of the four species are discussed in connection with reflections on maintenance costs.