Showing papers by "University of Tübingen published in 1981"

Regulation of ferric iron transport in Escherichia coli K12: isolation of a constitutive mutant.

Abstract: The lac genes were inserted with phage Mu(Ap, lac) into the fhuA, fepA, cir and tonB genes which specify components of iron uptake systems. The expression of lac in all these operon fusions was controlled by the availability of iron to the cells, thereby facilitating a quick and simple measurement of the expression of the genes listed above. In an iron rich medium under anaerobic conditions all systems were strongly repressed. fhuA was depressed at higher iron concentration than was fepA or cir, and tonB was repressed only under anaerobic conditions and could be induced by iron limitation. Mutants constitutive for the expression of beta-galactosidase were selected in a fhuA-lac fusion strain. The outer membrane proteins Cir, FhuA, FecA, 76K and 83K were made constitutively in such mutant strains. Therefore, they were termed fur mutants. In these fur mutant strains, the synthesis of a 19K protein was reduced. Furthermore, it was found that transport of ferric enterochelin and ferrichrome was also constitutive in the fur mutant cells, and that ferric citrate uptake could be induced by only 10 microM citrate in the growth medium in contrast to wild-type cells in which at least 100 microM citrate was necessary. The fepA gene was concluded to be under an additional control, because it was not fully derepressed by the fur mutation.

Geometry of the Time-Dependent Variational Principle in Quantum Mechanics

Abstract: The time-dependent variational principle (TDVP).- Lie algebras and symplectic structures.- Symplectic structure on group representation spaces.- Geometry of the TDVP.- Simple applications.- The unitary group and examples from many-body physics.- The group SU(1,1) and rotationally invariant Hamiltonians.- Summary.

The Transition Metal‐Nitrogen Multiple Bond

Abstract: Numerous nitrido complexes of transition metals show very short metal-nitrogen bond lengths, suggesting MN-triple bonds. At present, compounds of this type are being intensively investigated. In particular the molybdenum complexes are considered as model substances for the study of at least an intermediate step of N2-assimilation. This article contains a review of the structure and bonding, as well as syntheses and reactions of these complexes.

Geometry of the Time-Dependent Variational Principle in Quantum Mechanics.

Abstract: The time-dependent variational principle (TDVP).- Lie algebras and symplectic structures.- Symplectic structure on group representation spaces.- Geometry of the TDVP.- Simple applications.- The unitary group and examples from many-body physics.- The group SU(1,1) and rotationally invariant Hamiltonians.- Summary.

Die Übergangsmetall‐Stickstoff‐Mehrfachbindung

Abstract: Zahlreiche Nitrido-Ubergangsmetall-Komplexe weisen sehr geringe Metall-Stickstoff-Bindungslangen auf, die denen von MN-Dreifachbindungen entsprechen. Verbindungen dieses Typs werden derzeit intensiv untersucht. Insbesondere die Molybdankomplexe werden als Modellsubstanzen fur das Studium zumindest eines Teilschritts der N2-Assimilation angesehen. Der vorliegende Beitrag gibt einen Uberblick uber Struktur und Bindungsverhaltnisse sowie uber Synthesewege und Reaktionen dieser Komplexe.

The obliteration of the postglomerular capillaries and its influence upon the function of both glomeruli and tubuli. Functional interpretation of morphologic findings.

Abstract: Our study in a group of patients (heterogeneous in terms of glomerular lesions), supplementing and confirming earlier findings, indicated that 1. An increase of the relative cortical interstitial volume and the serum creatinine concentration at the time ob biopsy is accompanied by a statistically significant reduction in the number of intertubular capillaries and a decrease in capillary area per area unit. 2. The length of diffusion between the intertubular capillaries and tubuli increases and the tubular epithelium becomes atrophic as relative cortical interstitial volume increases. 3. The glomerular capillaries and the Bowman's capsule are significantly larger in moderately severe mesangioproliferative or grades I to III membraneous GN with elevated serum creatinine concentrations than in equally severe renal diseases with normal serum creatinine concentrations. 4. The glomerulus in moderately severe mesangioproliferative GN progressively increases as the serum creatinine concentration rises.

Interferon-neutralizing antibodies in a patient treated with human fibroblast interferon

Abstract: During recent years clinical trials have shown that human leukocyte interferon (HuIFN-alpha) may be useful in the treatment of cancer, but very little has been done concerning the possible use of human fibroblast interferon (HuIFN-beta). Treuner et al. recently reported the successful treatment of a nasopharyngeal carcinoma with HuIFN-beta: in the course of IFN-therapy a HuIFN-beta neutralizing activity appeared in the serum of this patient. We report here that such activity is due to IgG antibodies--this study is the first to present evidence for antigenicity of IFN in a homologous system.

The adaptive changes in the isoenzyme pattern of myosin from hypertrophied rat myocardium as a result of pressure overload and physical training.

Abstract: The distribution of cardiac myosin isoenzymes is altered as a result of pressure overload and physical training. Using polyacrylamide gel electrophoresis in sodium pyrophosphate, it was found that myosin fromlleft ventricles of adult rats exists in three polymorphic form, V1, V2 and V3. Cardiac hypertrophy due to renal hypertension (Goldblatt II) led to a shift of the isoenzymes towards V3, whereas swimming training resulted in an opposite redistribution. The isoenzyme V1 predominated, only traces of V2 and V3 were detectable. The changes in the isoenzyme distribution were reflected in al altered ATPase activity of myofibrils. in a representative sample of the Goldblatt rats, the activity was reduced by 11% and the swimming training led to an increase by 10%. Changes in myofibrillar ATPase can, therefore, be traced to alterations in the isoenzyme pattern of myosin. The polymorphism of myosin has a two-faced aspect as regards cardiac performance. For example, a shift towards V3 is expected to increase the economy for tension development during isovolumetric contraction at the expense of a reduced maximum speed of ventricular contraction.

Citrate-dependent iron transport system in Escherichia coli K-12.

Abstract: Induction of the citrate-dependent iron transport system of Escherichia coli K-12 required 0.1 mM citrate and 0.1 micrometer iron in the growth medium. Five--ten-times more iron than citrate was taken up into the cells which suggests that citrate was largely excluded from the transport. Fluorocitrate and phosphocitrate induced the citrate-dependent iron transport system although they supported iron uptake only very poorly. An outer membrane protein (FecA), belonging to the transport system, was induced in fecB mutants which were devoid of citrate-dependent iron transport. The intracellular citrate and iron concentrations were 10--100-times higher than the external concentrations required for induction of the transport system. It is concluded that only exogenous ferric citrate induced the transport system, and that citrate did not have to enter the cytoplasm. The Tn10 transposon, conferring tetracycline resistance, was inserted near the fec gene region which controls the expression of the citrate-dependent iron transport system. The determination of the cotransduction frequencies of Tn10 with the fecA and fecB markers suggested the gene order fecA fecB Tn10.

Escherichia coli cells containing the plasmid ColV produce the iron ionophore aerobactin

Abstract: The first colicin to be described (colicin V) in 1925 was the product of a virulent Escherichia coli strain [1]. Since then studies have been performed with the aim of identifying the virulence factor associated with the ability to produce colicin V. ' Such a relationship has been established for humans, domestic animals and in experimental animal systems infected with pathogenic E. coli strains [2-7]. To date it is clear that several virulence enhancing factors are encoded by ColV plasmids. Synthesis of colicin V seems not to be essential for virulence enhancement [2,3] although it has been reported that colicin V inhibits macrophages [8]. E. coli strains harbouring ColV plasmids show an enhanced resistance to the bactericidal effects of serum [3,9], and their growth is supported by a new iron sequestering system [7,10,11]. It was shown that the iron ligand was of the hydroxamate type but ferrichrome, the only known ferric hydroxamate complex to be actively taken up by E. coli, was excluded [11 ]. In this paper it is reported that aerobactin is the new iron ligand produced by ColV-bearing E. coli strains. The search for the iron ligand was guided by the fact that other Enterobacteriaceae, Aerobacter aerogenes [12], Shigella flexneri [13] and Enterobacter cloacae [14] produce aerobactin. A new rapid isolation procedure was developed which is different from the one described by the discoverers of aerobactin, F. Gibson and D.I. Magrath [12], and which allows the isolation of large quantities in highly pure form.

A Content-Processing View of Hesitation Phenomena:

Abstract: Hesitation phenomena are intricately connected with prospective and retrospective speech-production tasks and mark critical points in processing. They are also causally related to types of quality control which can be expressed as conversational postulates governing wellformedness criteria. Corresponding to the concepts of forestalled versus committed errors (error-free or error-full output), two major hesitation categories suffice: stalls and repair. Supported by a corpus of English and German, the new taxonomy captures previously uncategorized information: the grammatical locus of repair operations and the structural changes they cause.

The platelet adhesion immunofluorescence test: A modification of the platelet suspension immunofluorescence test

Abstract: Platelets can adhere to surfaces by forming pseudopods. This ability is made use of here to simplify conventional platelet suspension immunofluorescence tests, since steps like serum and FITC incubations, washings and microscopic evaluation are done on platelets adhered to glass surfaces. By eliminating time-consuming manipulations like washing in individual test tubes and mounting platelets to microscopic slides, large scale studies can now be performed (up to 480 tests per day and technician). Antibodies can be detected with fresh as well as with frozen platelets from a well defined cell panel. The PAIFT is 2 to 3 times more sensitive than the NIH-standard-micro-lymphocytotoxicity-test (NIH-LCT), thus allowing earlier recognition of alloimmunization of patients.

Occurrence in soil of thermo-acidophilic bacilli possessing ω-cyclohexane fatty acids and hopanoids

Abstract: Out of different soil samples from neutral environments 50 thermo-acidophilic bacilli were isolated. All 23 strains tested contain ω-cyclohexane fatty acids in the range of 15–91% of the total fatty acids. In this group six strains possess hopane containing lipids (hopanoids). In contrast Bacillus coagulans, sometimes described as thermoacidophilic, contains no ω-cyclohexane fatty acids as was shown in seven strains. The degree to which the described strains were related to Bacillus acidocaldarius could not definitely be determined.

Functional and phylogenetic aspects of the ciliary membrane: A comparative freeze-fracture study

Abstract: This paper illustrates the structural diversity of the ciliary membrane of the somatic ciliature in 68 ciliate genera and describes the interior architecture of several presumptive sensory cilia. Freeze-fracture technique reveals a variety of intramembrane particle arrays known as ciliary necklace, ciliary plaques, and ciliary rosettes. While the function of these arrays is still largely unknown, their distribution among ciliates suggests a phylogenetic correlation. Whereas current systems of ciliate classification are primarily based on the character of the ciliature which surrounds the cytostome as well as on the morphogenesis of this oral ciliature, the data presented in this paper are well suited to emphasize the significance of the somatic ciliature for the reconstruction of ciliate phylogeny. This is particularly evident when the freeze-fracture data are mapped in parallel with a simplified phylogenetic tree based on the appearance of both the oral and the somatic ciliature. The freeze-fracture data are in agreement with hypothesis of a non-hymenostome origin of the spirotrichs and suggest a close relationship with respect to the origin of the Hymenostomatida from the Colpodida instead of from the Nassulida. The presumptive sensory cilia show a significantly greater particle density than most somatic cilia. While the particles may represent receptor proteins or ion channels, with the freeze-fracture technique it is at present impossible to specify the modalities of such "sensory" cilia.

Somatosensory evoked potentials following trigeminal nerve stimulation in trigeminal neuralgia.

Abstract: The examination of somatosensory evoked potentials following trigeminal nerve stimulation in 20 subjects with idiopathic trigeminal neuralgia revealed a pathological increase in latency of the first positive component on the involved side in 7 (41%) of the 17 patients without antecedent surgical treatment. The mean difference in latency between the two sides was 1.3 msec (2p greater than or equal to 0.005). These results are indicative of microtraumatization of the trigeminal nerve in the posterior fossa by blood vessels, for example, leading to local demyelinization. The method seems to be of diagnostic value in selecting patients for more decompression by posterior fossa operations.

Hydrothermal mounds and young ocean crust of the Galapagos: Preliminary Deep Sea Drilling results, Leg 70

Abstract: A total of 32 holes at 5 sites near 1°N, 86°W drilled on Deep Sea Drilling Project (DSDP) Leg 70 (November–December 1979) provide unique data on the origin of the hydrothermal mounds on the south flank of the Galapagos spreading center. Hydrothermal sediments, primarily Mn-oxide and nontronite, are restricted to the immediate vicinity of the mounds (⩽100 m) and are probably formed by the interaction of upward-percolating hydrothermal solutions with sea water and pelagic sediments above locally permeable zones of ocean crust. Mounds as much as 25 m in height form in less than a few × 10 5 yrs, and geothermal and geochemical gradients indicate that they are actively forming today. The lack of alteration of upper basement rocks directly below the mounds and throughout the Galapagos region indicates that the source of the hydrothermal solutions is deeper in the crust.

The second and third optic ganglia of the worker bee: Golgi studies of the neuronal elements in the medulla and lobula.

Abstract: The gross morphology and the fine-structural characteristics of neurones of the second and third optic ganglia of the honeybee Apis mellifera were investigated light microscopically on the basis of Golgi (selective silver)- and reduced silver preparations The second optic ganglion, the medulla, is ovoid in shape and has a slightly convex distal surface and a slightly concave proximal surface The medullar outer levels are characteristically composed of neuronal arrangements showing strict precision of their geometrical spacing proximally as far as a pronounced layer of tangential fibre elements comprising the serpentine layer of the medulla At the inner medullary levels retinotopic channels are again multiplied, and the arrangement of axons and dendrites contribute to a complex lattice The third optic ganglion, the lobula, is interposed between the medulla and the protocerebrum It is the site of termination of the third-order neurones The lobula in hymenopterans appears, in contrast to dipterans, odonates and lepidopterans, as a single neuropilic mass A short review of the electrophysiological data concerning these two ganglia has been tentatively correlated with some of the anatomical data

Properties of an ATP-Fueled, Cl--Dependent Proton Pump Localized in Membranes of Microsomal Vesicles from Maize Coleoptiles

Abstract: Vesicles prepared from the microsomal membrane fraction of maize coleoptiles possess an ATP-fueled H⁺-transport into the vesicles. It is highly possible that the vesicles from the microsomal membrane fraction actually are unchanged, native vesicles (originating from the ER or Golgi-apparatus) that can fuse with the plasmalemma or the vacuole. Therefore, they can reflect properties of the vacuole or the plasmalemma. The energy dependent acidification within the vesicles, which can be completely reverted through the addition of CCCP, was determined on the basis of photometric difference spectra using NR (Hager et al., Z. Naturforsch. 35 c, 794-804 1980). The proton pumps possess a very high substrate specificity; only ATP (+ Mg²⁺) can be used as substrate, while GTP, ITP, UTP and CTP or other nucleoside tri- or diphosphates cannot be used. DCCD and DES inhibit H⁺-ATPase completely, oligomycin has only a slight, orthovanadate no inhibitory effect at all. The energy dependent transport of H⁺ across the membrane takes place only in the presence of Cl⁻ or Br⁻ (not as well in the presence of I⁻). Other anions (F⁻, NO⁻₃, SO²⁻₄, SCN⁻, IDA⁻, H₂BO⁻₃ cannot cause an intravesicular acidification through ATP if chloride (or Br⁻) is not present. In the presence of chloride, however, some of these anions inibit the H⁺/Cl⁻-symport (J⁻, NO⁻₃, SO²⁻₄, SCN⁻, H₂BO⁻₃). They obviously are in competitive interaction with Cl⁻ ions for Cl⁻-binding sites on a carrier or channel without being able to be transported themselves. Pi, which renders the acidification of the vesicles at a low rate possible without Cl⁻, is the only tested anion which can augment the Cl⁻ dependent acidification. This supports the idea that either Pᵢ functions as a positive effector on the Cl⁻transport or that a Cl⁻/Pᵢ-antiporter exists which reduces Cl⁻ accumulation and therefore facilitates the Cl⁻ coupled H⁺ transport into the vesicles also. The anion transport inhibitor, DIDS, blocks the ATP-dependent H⁺-transport. This again supports the idea of a relatively tight coupling between H⁺ and Cl⁻ transport in a possibly electroneutral system. The presence of monovalent cations, such as K⁺, Na⁺, Li⁺ and choline⁺, are not important for H⁺ transport. The dependence of the ATP-fueled acidification of the vesicles on the same anion pattern which seems to regulate elongation growth and stomata aperture speaks for the eminent importance of the H⁺-pump and vesicles described in this report for growth and turgor of plant cells.

Pion Condensation and Realistic Interactions

Abstract: The static pion $p$-wave self-energy in symmetric nuclear matter is calculated, taking into account the effects of nucleon particle-hole (ph) and $\ensuremath{\Delta}$-isobar nucleon-hole ($\ensuremath{\Delta}\mathrm{h}$) states. The residual interaction between ph states is derived from a Brueckner $G$ matrix which depends on the starting energy and three momentum variables. The coupling of ph and $\ensuremath{\Delta}\mathrm{h}$ states and the $\ensuremath{\Delta}\mathrm{h}\ensuremath{-}\ensuremath{\Delta}\mathrm{h}$ interaction is described by $\ensuremath{\pi}$ and $\ensuremath{\rho}$ exchange taking into account the effects of $\mathrm{NN}$ correlations. The resulting self-energies are analyzed in the model of constant interaction strengths which is commonly used. This analysis yields effective interaction strengths weakly depending on the momentum of the pion field as well as on the nuclear density. Only in the limit of vanishing pion momentum the strength of the ph interaction is connected with the Landau parameter ${G}_{0}^{\ensuremath{'}}$. The present calculation yields pion condensation at twice the empirical nuclear matter density when isobars are included.NUCLEAR STRUCTURE Particle-hole interaction, nuclear matter. Brueckner $G$ matrix, isobar configurations, pion condensation.