Showing papers by "University of Tübingen published in 1976"

Functional organization of the outer membrane of escherichia coli: phage and colicin receptors as components of iron uptake systems.

Abstract: The functional interaction of outer membrane proteins of E. coli can be studied using phage and colicin receptors which are essential components of penetration systems. The uptake of ferric iron in the form of the ferrichrome complex requires the ton A and ton B functions in the outer membrane of E. coli. The ton A gene product is the receptor protein for phage T5 and is required together with the ton B function by the phages T1 and o80 to infect cells and by colicin M and the antibiotic albomycin, a structural analogue of ferrichrome, to kill cells. The ton B function is necessary for the uptake of ferric iron complexed by citrate. Iron complexed by enterochelin is only transported in the presence of the ton B and feu functions. Cells which have lost the feu function are resistant to the colicins B, I or V while ton B mutants are resistant to all 3 colicins. The interaction of the ton A, ton B, and feu functions apparently permits quite different "substrates" to overcome the permeability barrier of the outer membrane. It was shown for ferrichrome dependent iron uptake that the complexing agent was not altered and could be used repeatedly. Only very low amounts of 3H-labeled ferrichrome were found in the cell. It is possible that the iron is mobilized in the membrane and that desferri-ferrichrome is released into the medium without having entered the cytoplasm. Growth on ferrichrome as the sole iron source was used to select revertants of T5 resistant ton A mutants. All revertants exhibited wild-type properties with the exception of partial revertants. In these 4 strains, as in the ton A mutants, the ton A protein was not detectable by SDS polyacrylamide gel electrophoreses of outer membranes. Albomycin resistant mutants were selected and shown to fall into 5 categories: 1) ton A; 2) ton B mutants; 3) mutants with no iron transport defects and normal ton A/ton B functions, which might be target site mutants; 4) mutants which were deficient in ferrichrome-mediated iron uptake but had normal ton A/ton B functions. We tentatively consider that the defect might be located in the active transport system of the cytoplasmic membrane; 5) a variety of mutants with the following general properties: most of them were resistant to colicin M, transported iron poorly, and, like ton B mutants, contained additional proteins in the outer membrane. The outer membrane protein patterns of wild-type and ton B mutant strains were compared by slab gel electrophoresis in an attempt to identify a ton B protein. It was observed that under most growth conditions, ton B mutants overproduced 3 proteins of molecular weights 74,000-83,000. In extracted, iron-deficient medium, both the wild-type and ton B mutant strains had similar large amounts of these proteins in their outer membranes. The appearance of these proteins was suppressed by excess iron in both wild-type and mutant. From this evidence it is apparent that the proteins appear as a response to low intracellular iron rather than being controlled by the ton B gene...

Psychoactive drug effects on a system which generates cyclic AMP in brain.

Abstract: RECENTLY a direct correlation has been reported between spontaneous motor activity, tyrosine hydroxylase activity and the responsiveness of the noradrenaline sensitive cyclic AMP-generating system in rat brain1,2. These observations may indicate that the turnover and/or level of noradrenaline in the brain is important in determining the sensitivity of the cyclic AMP-generating system to noradrenaline. Indeed, it has been shown that depletion of brain noradrenaline by the intraventricular injection of 6-hydroxydop-amine results in supersensitivity of the system to noradrenaline3,4. Furthermore treatment with reserpine, a drug known to cause depressive reactions in man, has been reported to increase the sensitivity of the adenylate cyclase of rat brain to noradrenaline5 and several antidepressant drugs have been shown to have the opposite effect in limbic forebrain6. By contrast, we now present evidence that the chronic treatment of rats with both an antidepressant, imipramine, and a depressant, chlorpromazine, reduces the sensitivity of the cyclic AMP-generating system to noradrenaline.

Uptake of Bromosulfophthalein byIsolated Liver Cells

Abstract: Uptake of the hepatodiagnostic dye bromosulfophthalein into isolated hepatocytes was studied with special regard to the kinetics of transport. The following results were obtained. 1 The uptake of bromosulfophthalein follows Michaelis-Menten kinetics only at low substrate concentrations with an apparent Km= 7 ± 2 μM and V= 2.6 ± 1.7 nmol × mg protein−1× min−1′. At higher bromosulfophthalein concentrations a second mechanism of uptake is observed as indicated by the deviation from linearity in the Lineweaver-Burk plot. 2 The activation energy of uptake was found to be 11 kcal/mol at 10 μM bromosulfophthalein. 3 Uptake is independent of metabolic energy and of the Na+ gradient across the membrane. 4 Taurocholate does not inhibit uptake while indocyanine green inhibits competitively at low bromosulfophthalein concentrations and activates uptake at high bromosulfophthalein concentrations (> 201 μM). 5 Amino acid reagents, such as dinitrofluorobenzene, mersalyl, N-ethylmaleimide, and dithionitrobenzene, which modify specific functional groups, did not affect uptake at a concentration of 100 μM. 6 No pH optimum for bromosulfophthalein uptake was observed in the physiological pH range. 7 Adsorption of bromosulfophthalein to the liver cell membrane has two distinguishable site, with affinities K1= 5.7 × 10−6 M and K2=7 × 10−5 M and binding capacities n1= 1.2 nmol/mg protein and n2= 7 nmol/mg protein. Adsorption is inhibited by indocyanine green. The results do not indicate the mediation of bromosulfophthalein uptake by a carrier protein and are consistent with the hypothesis that bromosulfophthalein is bound in an energy-consuming process to a translocating site, possibly in the undissociated form or as ion pair. The consecutive transfer across the membrane appears to require little additional energy.

Disposition of (1,2-14C) vinyl chloride in the rat.

Abstract: Rats were exposed to [1,2-14C] vinyl chloride in a closed system at initial concentrations below 100 ppm. When the system was occupied by 3 rats, a half-life of vinyl chloride in the system's atmosphere of 1.13 ± 0.12 h was observed. The volume of the system was 10.3 l. Calculation of the clearance of vinyl chloride from the system revealed that about 40% of inspired vinyl chloride is absorbed by lung. Therefore, changes in respiration did not influence uptake of vinyl chloride.

The reception of locke's two treatises of government 1690–1705

Abstract: R E M A R K A B L Y little Locke scholarship has been devoted to examining the initial reception of Two Treatises, despite the fact that the work’s fame has rested to a considerable degree on its supposed relationship to the 1688 Revolution. Only very brief surveys by J. W. Gough, E. S . de Beer, Peter Laslett and John Dunn are readily available,‘ and of more obscure sources there is only one rather poor extensive survey-Charles Bastide’s John Locke: Ses Tlie‘ories Politiqiies et Zeur Influence en AngZeterre (Paris, 1907). The value of the more recent work in this field has been its questioning that Two Treatises were very influential during the Revolution period. The character of that influence and the implications for the historian of late seventeenth-century political ideas, however, have only been considered very sketchily. Clearly TWO Treatises did eventually become a very successful work. It came to be regarded as containing the ‘Principles of 16W2 and, as David Hume indicated, it provided the Whig party of the mid-eighteenth century with its ‘philosophical or speculative system of principle^'.^ Yet the immediate reaction to the work seems rather surprising. It occasioned no critical replies until 1703,4 and it was not until 1705 that any extended attempt was made to refute Locke’s argument^.^ Of the more famous and most prolific political writers amongst the Non-jurors, George Hickes, Jeremy Collier, John Kettlewell and Henry Sacheverell took no notice whatsoever of Two Treatises in any of their political writings from 1690 to 1705. Only Charles Leslie and the anonymous author of An Essay Upon Gouernment (London, 1705) devoted any considerable effort to attacking Locke’s work but these did not appear until almost fifteen years after the first appearance of Two Treatises from the presses. Nor did Locke’s work become straightaway the principal authority of the Whigs. In fact, Locke did not introduce any startlingly new ideas into political debate. The main outline of the Treatises’ arguments was already to be found in James Tyrrell’s Putriarcha Non Monarcha (London, 1680), Algernon Sidney’s Discourses Concernitzg Government (London, 1698, but written before 1683) and Pufendorf’s De Jure Naturae et Gentium (Lund, 1672) and De Oficio Hominis

Der Ovipositor der Hydradephaga (Coleoptera) und seine phylogenetische Bedeutung unter besonderer Berücksichtigung der Dytiscidae

Abstract: Als Beitrag zur Kenntnis der Phylogenie der Hydradephaga dient die vorliegende Untersuchung der weiblichen Genitalorgane von Vertretern der Gyrinidae, Haliplidae, Noteridae, Dytiscidae und Hygrobiidae. Skelett, Muskulatur der Genitalsegmente VIII und IX sowie der Verlauf und die Anordnung der inneren Geschlechtsorgane wurden verglichen.

Convergence to the equilibrium state in the Volterra-Lotka diffusion equations.

Abstract: We introduce a diffusion term in the Volterra-Lotka model for two interacting species. For certain simple boundary conditions there exists a Lyapunov functional which allows to investigate the asymptotic behavior. Either the solution converges to equilibrium or sustained oscillations occur.

Morphogenesis, pattern formation and function of the dentition ofHeterodontus (Selachii)

Abstract: As in all skarks, the ectoderm ofHeterodontus folds in behind the jaw cartilage during embryogenesis The anterior part of this ectodermal fold becomes organized into the Inner Enamel Epithelium which cooperates with the mesenchyme Already during the infolding, both tissues begin to form teeth This process begins with a spontaneous division of the fold along its long axis into tooth-forming and non tooth-forming tissue sections In this way the tooth formula of the “first dentition” is established The Inner Enamel Epithelium and the mesenchyme only gradually attain competence for tooth formation, so that the first formed tooth germs become incomplete tooth shards (Fig 8) Shortly before the end of the embryonic phase, as soon as the infolding stops, the tooth transport mechanism begins to workHeterodontus hatches with a characteristic “first dentition”, which has a typical dental formula of 17to19/13to15

"Metabolic" action potentials in Acetabularia.

Abstract: The transient depolarizations inAcetabularia which fulfill the essential criteria of an action potential (all-or-none characteristics, triggering by depolarization, propagation, etc.) are investigated. These action potentials are analyzed by conductance measurements and voltage clamp experiments on the basis of the analog circuit of the membrane (Gradmann, D. 1975.J. Membrane Biol.25:183). It is concluded that these action potentials do not arise by permeability changes of the passive diffusion channels, but by the active pathway of the electrogenic pump, which consists of a voltage sourceEP of about −200 mV in series with two nonlinear conducting elementsP1 andP2, the latter andEP being shunted by a large quasi capacityCP of some mF cm−2. The nonlinear current-voltage relationship of the carrier system (P1) is not changed during the action potential but has an effect on its time course. However, the elementsP2 andCP, which probably reflect metabolic entities, are suggested to control the action potentials.

Vierdimensionale Stabile Ebenen

Abstract: Eine Stabile Ebene ist eine stetige Inzidenzstruktur mit eindeutig bestimmten Verbindungsgeraden zu je zwei Punkten, in der das Stabilitatsaxiom gilt: Besitzt ein Geradenpaar einen Schnittpunkt, so existiert der Durchschnitt auch fur jedes genugend nah benachbarte Paar. Stabile Ebenen wurden bislang nur unter der Voraussetzung untersucht, das der Punktraum eine Flache ist (‘ebene Ebenen’). Hier wird allgemeiner vorausgesetzt, das der Punktraum lokalkompakt und von positiver Dimension ist. Es wird bewiesen, das der Punktraum metrisierbar, lokal bogenzusammenhangend und lokal kontrahierbar ist. Das Buschel aller Geraden durch einen Punkt ist kompakt und zusammenhangend. Falls die Geraden Mannigfaltigkeiten sind, so sind die Buschel Spharen der Dimension 1, 2, 4 oder 8. Ist die Dimension der Punktmenge hochstens 4, so sind die Geraden stets Mannigfaltigkeiten. Eine stabile Ebene ist genau dann projektiv, wenn der Punktraum kompakt ist. Die Automorphismengruppe einer stabilen Ebene ist in der kompakt-offenen Topologie lokalkompakt; sie ist eine Liegruppe, falls der Punktraum R 4 ist. Unter der Voraussetzung, das alle Geraden zu R 2 homoomorph sind, werden folgende Aussagen bewiesen: Die Gruppe aller Kollineationen mit einem festen Zentrum wirkt frei und mit abgeschlossenen Bahnen auf dem Komplement des Zentrums; ist sie nicht kompakt, so gibt es durch das Zentrum genau eine Nichtschneidende zu jeder Geraden auserhalb. Involutorische Automorphismen sind entweder Punkt- oder Geradenspiegelungen, oder sie besitzen eine zweidimensionale Unterebene von Fixpunkten (‘Baer-Involutionen’). An jedem Punkt und jeder Geraden gibt es hochstens eine Spiegelung. Die Dimension der Automorphismengruppe ist hochstens 12; ist sie groser als 9, so ist die Ebene affin und desarguessch. Andererseits gibt es eine nicht-affine Ebene mit 9-dimensionaler Gruppe. Fahnenhomogene Ebenen sind genau die desarguessche affine Ebene und die komplexe hyperbolische Ebene, das heist die offene Einheitskugel der affinen Ebene mit der induzierten Struktur.

Anorganische Polyederverbindungen, III. Zintl's „Polyanionige Salze”︁: Darstellung und Eigenschaften der kristallinen Verbindungen [Na4·7 en]Sn9, [Na4·5 en]Ge9 und [Na3·4 en]Sb7 und ihrer Lösungen Die Kristallstruktur von [Na4·7 en]Sn9

Abstract: Durch Behandlung von Legierungen des Natriums mit Germanium, Zinn, Blei, Antimon oder Wismut mit athylendiamin (en) erhalt man stabile (Losungen der von Zintl als polyanionige Salze bezeichneten Verbindungen. [Na4·7 en]Sn9, [Na4·5 en]Ge9 und [Na3·4en]Sb7 werden kristallin dargestellt. Nach der Rontgenstrukturbestimmung von [Na4·7en]Sn9 liegt ein Sn -Polyeder vor, dessen Geometrie zwischen den Idealformen eines trigonalen Prismas mit seitlich aufgesetzten Pyramiden (D3h) und dem quadratischen Antiprisma mit aufgesetzter Pyramide (C4v) liegt. Die Verbindung ist stark diamagnetisch (delokalisiertes Elektronensystem). Bei vorsichtigem Entfernen von en bleibt die polyanionische Struktur Na4Sn9 bestehen. In Losungen liegen Polyeder der gleichen Zusammensetzung vor. Die Verbindungen sind sehr empfindlich gegenuber Sauerstoff und Wasser. Neben diesen Reaktionen wird das Verhalten von [Na4·7en]Sn9 gegenuber Alkalimetallen, Alkoxiden, [(C6H5)4X]Cl (X P, As), bipy, Nabipy und Na2 bipy untersucht. Inorganic Polyhedron Compounds, III Zintl's “Polyanionic Salts”: Preparation and Properties of the Crystalline Compounds [Na4·7en]Sn9, [Na4·5en]Ge9 and [Na3·4en]Sb7 and of their Solutions The Crystal Structure of [Na4·7en]Sn9 Alloys of sodium with germanium, tin, lead, antimony, or bismuth when treated with ethylenediamine (en) yield stable solutions of Zintl's so called “polyanionic salts”, from which the crystalline compounds [Na4·7en]Sn9, [Na4·5en]Ge9 and [Na3·4en]Sb7 are obtained. [Na4·7en]Sn9 contains the Sn -polyhedron (crystal structure determination) with a geometry between the ideal geometries of the tricapped trigonal prism (D3h) and the antiprism capped on one square (C4v). The compound is strongly diamagnetic (electron delocalisation). The coordinated en may be completely removed under mild conditions from [Na4·7en]Sn9 without a collapse of the polyanionic structure of Na4Sn9. In solution polyhedra of the same composition are found. The compounds are very sensitive against oxygen and water. Apart from these reactions the behaviour of [Na4·7en]Sn9 against the alkali metals, alkoxides, [(C6H5)4X]Cl (XP, As), bipy, Nabipy, and Na2 bipy is investigated.

The Global Circuit and Its Parameters

Abstract: Wilson’s hypothesis of the global air-electric circuit with the thunderstorms as generators has not been proven up to now. However, many results of measurements and considerations support the ideas of Wilson a.o. The task remains to study the significant parameters of the circuit one by one and in particular the balance of currents through this circuit. The main parameters are: the charge output of the thunderclouds to the ionosphere and to the ground, which includes the number of simultaneously acting storms and their individual output, the total air-earth current in fine-weather areas as well as in cloudy and weakly precipitating regions, the electric potential difference between ionosphere and ground and the columnar resistance. New measured values of these parameters are discussed and introduced into a new balance. It seems that a smaller value for the total current in the global circuit of about 1000–1200 A should be used in the future instead of 1800–2000 A formerly.

Radiocarbon dates of Santorini volcanics

Abstract: THE caldera walls of the ring-islands Thera and Therasia, belonging to the Santorini Group (Fig. 1) in the southern Aegean, are built up of lavas and pyroclastics, among which pumice layers are particularly striking (Fig. 2). The top layer (Bo, abbreviated from the German term “oberer Bimsstein”1) comprises air-fall pumice and ashes, overlain by thick pyroclastic flows2,3. It was produced by the catastrophic outburst of the Thera volcano in late-Minoan time, which culminated in the collapse of the Santorini caldera4. The decline of the Minoan civilisation around 1500 BC has been attributed to these volcanic events5. The Upper Pumice Series buried late-Minoan settlements on Thera and Therasia, and an important settlement near Akrotiri in the southern part of Thera is still being excavated6. The Upper Pumice Series rests on an old soil horizon (black layer in Fig. 2) in which remnants of late-Minoan houses were found in 1869 (ref. 7). Wood from such houses found at the base of the pumice quarries south of the town of Fira has provided radiocarbon dates of 3,370±100 yr b.p. (ref. 8). This age coincides exactly with archaeological data for the destruction of late-Minoan settlements on Santorini6.

On the Transport of Tripeptide Antibiotics in Bacteria

Abstract: The two tripeptide antibiotics l-2-amino-4-met hylphosphinobutyryl-alanyl-alanine (L-phosphinothricyl-alanyl-alanine) and l -(N5-phosphono)methionine-S-sulfoximinyl-alanyl-alanine, both inhibitors of the glutamine svnthetase, are transported into the cell of Esclierichia coli K 12 via the oligopeptide transport system. The uptake by this system is proved first of all by cross resistance with tri- l -ornithine using oligopeptide-transport-deficient mutants, and secondly by antagonism tests demonstrating competitive reversal of the action of the antibiotic by several peptides which have been shown to be transported via the oligopeptide transport system, e.g. tri-l-alanine, tri-l-alanine, tri-l-lysine, tri- l -serine, tri-glycine, glycyl-glycyl- l-alanine and the synthetic tripeptide l -azaadenyl-aminohexanoyl-alanyl-alanine. On the other hand, there is no effect on the action of the antibiotic in antagonism tests with compounds which use different transport systems, such as l.-alanyl-alanine, l-lysyl-lysine, glutathione and the synthetic amino acid azaadenylaminohexanoic acid, i.e. 2-amino-6-(7-amino-3H-v-triazolo-[4,5-d]-pyrimidin-3-yl)hexanoic acid. Another inhibitor of the glutamine synthetase, l-methionine-S-dioxide (methioninesulfone) could be converted into a tripeptide form by linkage to l-alanyl-alanine analogously to the tripeptide antibiotics described above. Whereas the free l-methionine-S-dioxide seems to be transported via the methionine transport system, the tripeptide form is transported via the oligopeptide transport system. Thus, this glutamine synthetase inhibitor can be taken up by the cell via two different transport mechanisms. Our results indicate that this could provide a synergistic effect. The syntheses of the new tripeptides l-azaadenylaminohexanoyl-alanyl-alanine and l -methionine-S-dioxidyl-alanyl-alanine were performed by dicyclohexylcarbodiimide couplings of the unusual N-protected l-α-amino acids azaadenylaminohexanoic acid and l-methionine-S-dioxide to l-alanylalanine-tert-butyl ester followed by common deprotection steps. Tri- l-ornithine was synthesized without carboxyl protection via two successive couplings of hydroxybenzotriazol esters of Nδ-butoxycarbotlyl-Nδ-benzyloxycarbonyl-l: ornithine to Nδ-benzyloxycarbonyl-l -ornithine

Unstirred layer thickness in perfused rat jejunum in vivo.

Abstract: The effective unstirred layer thickness in the rat jejunum perfused in vivo amounts to at least 530 μm. This value has been estimated from the absorption increase ofl-phenylalanine due to better mixing of the luminal solution by air bubbles.

On the importance of hydrogen bonding for the structural phase transitions in (CH3NH3)2MnCl4. A single‐crystal neutron diffraction study

Abstract: The crystal structure of (CH3NH3)2MnCl4 (MAMC) is determined by neutron diffraction at 188 K in the low temperature tetragonal phase (P42/ncm). The sequence of structural phase transitions of MAMC can be discussed in terms of NH … Cl bridges between NH3 and certain Cl−-ions. The order of the room temperature orthorhombic structure is determined by one dominant H-bond and that of the low temperature tetragonal structure by three equivalent H-bridges. Mit Hilfe der Neutronenbeugung wird die Kristallstruktur von (CH3NH3)2MnCl4 (MAMC) bei 188 K in der tetragonalen Tieftemperaturphase (P42/ncm) bestimmt. Die Folge der strukturellen Phasenubergange von MAMC kann entsprechend den NH … Cl Brucken zwischen NH3 und bestimmten Cl−-Ionen diskutiert werden. Die Ordnung der orthorhombischen Zimmertemperaturstruktur wird durch eine dominante H-Bindung bestimmt und diejenige der tetragonalen Tieftemperaturstruktur durch drei gleichwertige H-Brucken.

Arterio-venous anastomoses in rainbow trout gill filaments: a scanning and transmission electron microscopic study.

Abstract: The origin of arterio-venous anastomoses, connecting the efferent filament artery (EFA) with the central venous sinus (CVS) of gill filaments can be well discerned by scanning electron microscopy in the rainbow trout. Corresponding vessels between the afferent filament artery and the CVS could not be detected with the techniques applied. AVA-specific endothelial cells are characterized by their bulky shape and their microvillous surface. The general morphology of AVA's in Salmo gairdneri is very similar to that of AVA's in Tilapia mossambica (Vogel et al., 1974) but they are much longer in the trout. No filament whorls have been encountered in AVA endothelia of Salmo gairdneri.

Das Abdomenende weiblicher, terrestrisch lebender Adephaga (Coleoptera) und seine Bedeutung für die Phylogenie

Abstract: Die phylogenetischen Schlusse durfen, da sie nur auf Grund von Merkmalen des Abdomenendes gezogen werden, nur als vorlaufig betrachtet werden.

Antigenic Determinants of Murein Lipoprotein and Its Exposure at the Surface of Enterobacteriaceae

Abstract: Murein lipoprotein from the outer membrane of Escherichia coli could be fixed to erythrocytes without pretreatment of the erythrocytes. Passive hemagglutination or immune hemolysis could thus be used as sensitive assays to determine antibodies against lipoprotein. In rabbit antisera prepared against whole cells of E. coli, Salmonella, Arizona, and Shigella antibodies against lipoprotein were present. The respective titers were lowest in encapsulated smooth strains and highest in rough mutants. Antisera against deep rough mutants showed even higher anti-lipoprotein titers than anti-R-lipopolysaccharide titers. Correspondingly,absorption of lipoprotein antibodies with enterobacterial strains was most pronounced with deep rough mutants and lowest with smooth strains. Lipoprotein becomes increasingly an immunogen as well as an antigen the more sugar residues are missing in the lipolysaccharide on the cell surface. In wild-type cells lipoprotein is buried in the outer membrane; its exposure in mutant cells is related to defects at the cell surface.

Excretion of taurocholate from isolated hepatocytes.

Abstract: Efflux of taurocholate from isolated rat hepatocytes was studied to characterize the mechanism of bile acid secretion. Cells were incubated with taurocholate for 15 min. The amount of the intracellularly accumulated bile acid was directly related to the concentration in the medium. Transfer of the loaded cells from the incubation medium to a medium without taurocholate led to taurocholate efflux. Efflux was saturable, its activation energy amounted to 12 kcal/mol (50 kJ). It was strongly inhibited by the metabolic inhibitor antimycin A and to a lesser extend by the uncoupler carbonyl-cyanide-m-chlorophenylhydrazone. Dinitrofluorobenzene and mersalyl, reagents which react with amino acids, inhibited efflux by about 30% when applied at concentrations of 50 μM. Ouabain increased the rate of efflux. The observations indicate that secretory functions are maintained in isolated liver cells.