Showing papers by "University of Würzburg published in 1977"

A Raman and far-infrared investigation of phonons in the rhombohedral V2–VI3 compounds Bi2Te3, Bi2Se3, Sb2Te3 and Bi2(Te1−xSex)3 (0 < x < 1), (Bi1−ySby)2Te3 (0 < y < 1)

Abstract: The Raman-active lattice vibrations of Bi2Se3, Bi2Te3, Sb2Te3, and their solid slutions, whose symmetries correspond to the R3m space group, are investigated by Raman scattering. Three of the four expected Raman modes, Eg and A1g, could be determined. The FIR optical properties of Bi2Te3 crystal surfaces of improved quality (E ∥ c and E ⟂ c) and Bi2Se3 (E ⟂ c) are re-examined near helium and room temperature with a Fourier spectrometer, allowing a determination of the infrared-active mode frequencies with higher accuracy. The results for Bi2Te3 are compared to the predicted frequencies from the lattice dynamical model, given by Jenkins et al. The frequncy shifts of the Raman-active modes in the mixed crystals show single-mode and two-mode behaviour, which is in agreement with simple models for the substitution of antimony and selenium atoms for bismuth and tellurium, respectively, in Bi2Te3.

Studies on the retinal-protein interaction in bacteriorhodopsin.

Abstract: 1 Different types of bacteriorhodopsin chromophores and their reactions are described. This includes intermediates of the reconstitution reaction of the purple complex, intermediates of the photochemical cycle and a photochemically active 500-nm chromophore. In contrast to the native chromophore (purple complex) some of these species are reducible by borohydride yielding stable retinyl proteins. 2 Hydrolysis and/or extraction of the retinyl proteins reveals that in the corresponding non reduced parent chromophores the retinal is bound either noncovalently or covalently to lysyl residues of the polypeptide chain. 3 Retinol, retinyl lysine and their retro isomers isolated from the various reduced chromophores are identified by thin-layer chromatography and mass spectrometry. 4 The absorption spectra of the retinyl proteins and binding studies with retinol and retinal indicate that the cyclohexene ring and the side chain of the retinyl moiety are forced into a coplanar conformation by interaction with the protein. The three peaked absorption band of the reduced chromophores is due to this planarized conformation and not to a retro configuration of the retinyl moiety. 5 Isomerization to retro compounds can be achieved by HCl as is known to be the case for retinyl compounds in solution. In addition photochemical isomerization is observed in the case of planarized retinyl moieties. Thus the native protein structure is responsible not only for a specific conformation of the retinyl moiety but also for its specific reactivity.

Der Einfluß des Erdmagnetfeldes auf die Schwereorientierung der Honigbiene (Apis mellifica)

Abstract: The misdirection (“Misweisung”) which indicates a definite direction in the bee's dance is correlated to daily variations of the total intensity (ΔF) of the earth's magnetic field (EMF). It depends on the orientation of the dancing place with regard to the EMF coordinates. The distance of the feeding place, however, is insignificant. There exists a positive correlation between the efficiency ofΔF and a progressive tilting of the comb toward the horizontal position. No difference is observed in the intensity and exactness of the bees' dancing whether they are dancing on the lower side of the oblique comb in a somewhat ‘hanging’ attitude or on the upper side. The efficiency ofΔF is comparable on both sides of the comb. Bees dancing on a horizontal comb orient primarily to the main first-order directions of the EMF and, to a lesser extent, to the second-order directions regardless of the direction of the feeding place.

VUV isochromat spectroscopy

Abstract: A highly sensitive isochromat spectrometer employing a frequency selective helium iodine Geiger Muller photoncounter is described. The overall resolution of ±0.36 eV at an average quantum energy of 9.6 eV compares favourably with conventional set-ups. Sample data for a polycrystalline tantal target show satisfactory agreement with earlier experiments.

Ecophysiological investigations on lichens of the Negev desert : V. A model to simulate net photosynthesis and respiration ofRamalina maciformis.

Abstract: Previous publications have reported on investigations of CO2 exchange in the desert lichenRamalina maciformis both in its natural habitat in the Negev and in the laboratory. Utilizing laboratory data, net photosynthesis and dark respiration were expressed as mathematical functions of the most important environmental factors. Based on these relationships, a model is developed that allows one to predict CO2 exchange of the plant. Input data are light intensity, temperature, and water content of the thallus, together with a measure of the rate of the seasonal change of photosynthetic and respiratory activity. The validity of the model is tested by comparing simulated daily courses of CO2 uptake and release of the lichen with independent results of CO2 exchange measurements conducted in the field during and after the condensation of dew. The sensitivity of the model is shown by simulating changes in the input data of temperature and water content of the lichen.

Carcinogenicity of trichloroethylene: fact or artifact?

Abstract: Technical trichloroethylene has been found carcinogenic in mice after high daily doses per os. A GC-MS analysis of this technical sample revealed the presence of considerable amounts of epichlorohydrin and 1.2-epoxibutane as stabilizers. These epoxides are highly mutagenic in the Ames test and are, most probably, responsible for the carcinogenic effect found in mice. The question whether trichloroethylene is carcinogenic or not remains open.

New Varieties of Sandwich Complexes

Abstract: Ubersicht uber mehrkernige Komplexe mit sandwichartigem Aufbau sowie uber Nutzen kinetischer und mechanistischer Untersuchungen fur neue Synthesewege.

Basische Metalle, III. Stabile kationische Hydrido-, Methyl- und Acylcobalt-Komplexe

Abstract: Die Komplexe C5H5CoL2 (LPMe3, PMe2Ph, PMePh2) (6–8) werden ausgehend von ClCoL3 und TlC5H5 synthetisiert. Die Chloroverbindungen ClCoL3 sind durch Reduktion von CoCl2 uber CoL4 (LPMe2Ph) oder direkt aus CoCl2 und Zn in Gegenwart von L (LPMePh2) zuganglich. Durch Reaktion von 6–8 mit HX bzw. CH3I entstehen die Kationen [C5H5CoHL2]+ bzw. [C5H5CoCH3L2]+, die sehr stabile CoH- bzw. CoCH3-Bindungen enthalten. Die Verbindungen [C5H5CoC2H5(PMe3)2]I (18) und [C5H5CoC(O)R(PMe3)2]PF6 (RCH3, C6H5) (20, 21) konnen ebenfalls dargestellt werden. [C5H5CoH(PMe3)2]BF4 (9) reagiert bei erhohter Temperatur mit einem Uberschus HBF4 in Propionsaure-anhydrid zu [C5H5Co(PMe3)3](BF4)2 (23), wobei als Zwischenverbindung [C5H5Co(PMe3)2C6H10O3](BF4)2 (C6H10O3Propionsaure-anhydrid) (22) isoliert werden kann. Der Mechanismus dieser Reaktion wird diskutiert. Basic Metals, III. Stable Cationic Hydrido-, Methyl-, and Acylcobalt Complexes The complexes C5H5CoL2 (LPMe3, PMe2Ph, PMePh2) (6–8) have been prepared starting from ClCoL3 and TlC5H5. The chloro compounds ClCoL3 can be obtained by reduction of CoCl2via CoL4 (LPMe2Ph) or, directly, from CoCl2 and Zn in the presence of L (LPMePh2). The reactions of 6–8 with HX and CH3 I give the cations [C5H5CoHL2]+ and [C5H5CoCH3L2]+, respectively, containing very stable CoH and CoCH3 bonds. The compounds [C5H5CoC2H5-(PMe3)2]I (18) and [C5H5CoC(O)R(PMe3)2]PF6 (RCH3, C6H5) (20, 21) have also been prepared. [C5H5CoH(PMe3)2]BF4 (9) reacts at higher temperatures with excess HBF4 in propionic anhydride to form [C5H5Co(PMe3)3](BF4)2 (23). An intermediate compound [C5H5Co(PMe3)2C6H10O3]-(BF4)2 (C6H10O3=propionic anhydride) (22) has been isolated. The mechanism of this reaction is discussed.

Influence of rifampicin on drug metabolism: Differences between hexobarbital and antipyrine

Abstract: Six healthy volunteers were treated with 1,200 mg of rifampicin daily for 8 days. Before and immediately afterward each received indocyanine green, hexobarbital, galactose, and antipyrine by intravenous infusion on 3 consecutive days. The plasma concentrations of the drugs were determined several times after infusion. The average elimination half-life of hexobarbital had decreased from 407 to 171 min and its metabolic clearance had increased almost threefold. In contrast, the average elimination half-life of antipyrine was virtually the same on both occasions (6.9 and 7.2 hr) and there was no change in metabolic clearance. In a tuberculous patient treated with rifampicin the antipyrine elimination rate was unaffected. Rifampicin did not influence indocyanine green clearance or galactose elimination capacity. Serum gamma glutamyl transferase was not affected but urinary D-glucaric acid excretion was increased during rifampicin treatment. The experiment with hexobarbital was repeated after 2 weeks in all subjects; half-lives and clearance values had returned to near control values. It appears that rifampicin is a selective inducer of oxidative drug metabolism in man.

Pharmacokinetic interactions with rifampicin.

Abstract: Rifampicin, a potent antituberculosis agent, is frequently combined with other antituberculosis drugs, or with drugs belonging to entirely different classes which may be required during a long period of antituberculous treatment, and therefore has a potential for drug interactions of practical clinical importance. The absorption of rifampicin is markedly decreased when it is simultaneously administered with para-aminosalicylic acid granules, due to adsorption by an excipient, bentonite. Several clinical observations and investigations have indicated that rifampicin itself accelerates the metabolism of various other compounds, including oral anticoagulants, the contraceptive pill, oral hypoglycaemic agents and digitoxin. Rifampicin seems to be a potent inducer of drug metabolism in humans and it causes a proliferation of the smooth endoplasmatic reticulum and an increase of cytochrome P450 content in the liver. It also increases its own rate of desacetylation. However, of the test compounds hexobarbitone and tolbutamide, the metabolic clearance increased 2-to 3-fold following rafampicin treatment, whereas antipyrine clearance was unaltered. This indicates that there is a certain selectivity in the enzyme induction effect of rifampicin, although it reamins unclear which compound will and which will not be affected. Rifampicin may also possibly interfere with hepatic uptake of other compounds, but the clinical significance of this type of interaction has not been clearly demonstrated; On the other hand, oral probenecid significantly increases the serum level of rifampicin, probably due to a similar depression of hepatic uptake.

Origin, destination and mapping of tritocerebral neurons of locust.

Abstract: The connectivities of the tritocerebrum of locust (Locusta migratoria L., Schistocerca gregaria (Forsk.)) were studied histologically and by means of cobalt chloride infusion. Its neuropil consists partly of fibers which traverse the tritocerebrum and areas consisting of neuropilar agglomerizations (“glomeruli”). The following direct connections between the tritocerebrum and other regions were observed: connections to 1) dorsal and lateral brain regions (mushroom body, optic lobe), 2) the ventral nerve cord, 3) the stomatogastric nervous system (here the protocerebrum and the subesophageal ganglion are also involved in these connections), 4) the retro-cerebral glands (corpora cardiaca, corpora allata), and 5) muscles of the foregut.

Clinical effectiveness of lisuride hydrogen maleate: a double-blind trial versus methysergide.

Abstract: SYNOPSIS In a controlled double-blind study of the therapeutic efficacy and clinical tolerance of lisuride hydrogen maleate (LHM), 25 mcg tid, and methysergide (MET), 2 mg tid, in 253 patients 50% or more reduction in number of attacks was noted in 53% of patients treated with LHM and in 51% of patients treated with MET. Thirty-nine percent of the MET group and 17% of the LHM group discontinued the medications because of side effects (p<0.05, Chi2 test). Complaints of muscle weakness, coldness of extremities and dizziness were less common in the LHM group than in the MET group. It is suggested that LHM is as effective as MET in the prophylaxis of migraine and is associated with fewer side effects.

Metabolic activation of chlorinated ethylenes: dependence of mutagenic effect on electrophilic reactivity of the metabolically formed epoxides.

Abstract: In chlorinated ethylenes, the chlorine substitution exerts, by its electron withdrawal effect, a stabilization of the molecule which increases with the number auf chlorine residues. All chlorinated ethylenes are metabolically transformed, in a first step reaction, to epoxides which may rearrange to aldehydes or acyl chlorides, respectively, undergo hydrolysis to diols, conjugate with glutathione, or react, by alkylation, with cellular macromolecules. The electrophilicity of the epoxides is high with those having an unsymmetric chlorine substitution, and comparatively low with the others bearing symmetric chlorine residues. According to in vitro mutagenicity testing in a modified Ames system, the following rule on structure/activity-relationship has been worked out: mutagenic potential is bound to unsymmetric substitution and high chemical reactivity (as with vinyl chloride, vinylidene chloride, and trichloroethylene), symmetric substitution results in lower chemical reactivity and non-mutagenicity. So far, the rule is substantiated by positive carcinogenic effects in animal experiments with vinyl chloride, vinylidene chloride and trichloroethylene.

Bacteriorhodopsin-mediated photophosphorylation in Halobacterium halobium

Abstract: The rate of halobacterial photophosphorylation was found to be a linear function of light intensity over a wide range (between 1 and 20 mW/cm2). At higher light intensities (above 25 mW/cm2) the ATP-synthesizing system itself limits the maximal rate of photophosphorylation. The optimal external pH range for this type of photophosphorylation is between pH 6.2 and 7.2 external. The photophosphorylation rate is directly proportional to the bacteriorhodopsin content of the cells. The quantum requirement for photophosphorylation was found to be 22 +/- 5 photons per ATP molecule synthesized. According to Mitchell's chemiosmotic hypothesis of energy coupling phosphorylation can be driven by a membrane potential or a pH gradient or a combination of both. From the results of experiments with drugs which abolish or reduce either one of the two components we conclude that the major driving force for photophosphorylation above an external pH value of 6.5 is the membrane potential, while at more acidic pH value the pH gradient becomes dominating. We did not observe a correlation between a transient alkalinization of the medium and ATP-synthesis upon illumination under certain conditions.

Mechanical stability and post-traumatic osteitis: an experimental evaluation of the relation between infection of bone and internal fixation.

Abstract: Stable and unstable internal fixation of fractures was performed in rabbits. After inoculation with Staphylococcus aureus , clinically manifest osteitis occurred only in the very unstable fractures. Abscesses, sinuses and sequestra developed in 45 per cent of the unstable fractures, whereas clinically manifest osteitis did not occur after rigid fixation. With rigid fixation there was no significant difference in the time to bony union between the infected and uninfected fractures. It seems that the development of osteitis and the healing of a fracture are both related to the degree of rigidity, but remain independent of each other. The significance of these findings in the management of post-traumatic osteitis is discussed.

Allelism studies of mitochondrial mutants resistant to antimycin A or funiculosin in Saccharomyces cerevisiae

Abstract: A rapid procedure has been employed to isolate a large number of mitochondrial mutants resistant to antimycin A or funiculosin A total of 15 antimycin A resistance mutations has been mapped by allelism tests The mutations belong to two new mitochondrial loci, designated AI and AII All funiculosin resistance mutations studied up to now map at locus AII Thus mitochondrial funiculosin resistance might allow the specific selection of mutations in AII Recombination between the two antimycin A resistance loci AI and AII occurs at frequencies from 8 to 21% Apparently the two loci are not linked to PAR1, RIB1, RIB3, OLI1, and OLI2 Mutants of the two loci AI and AII have been characterized by measurements of oxygen consumption Analysis of cytochrome spectra indicates that the mutations affect the cytochrome bc1 complex of the mitochondrial respiratory chain

Tetrakisthiobutatriene aus Perchlorbutenin und Thiolaten

Abstract: Die Reaktion von Perchlorbutenin (1) mit Thiolaten in Ether oder Dioxan bei Raumtemperatur fuhrt erwartungsgemas zu den Eninthioethern 2. In DMSO entstehen jedoch uber 2 die Tetrakisthiobutatriene 4. Auf diese Weise sind auch gemischt-substituierte Produkte wie 4h erhaltlich. Die Butatriene 4 konnen auch aus Perchlorbutatrien (6) mit Thiolaten in DMSO hergestellt werden, wie fur 4a und 4e gezeigt wurde. Die Konstitution der neuen Butatrienderivate 4 geht einwandfrei aus ihren 13C-NMR-Spektren hervor.

On the influence of age on immunity in Down's syndrome.

Abstract: In 23 subjects of different ages with Down's syndrome a number of parameters of non-specific defense of humoral and of cellular immunity were investigated. While in all age groups complement factors C3, C4 and C5 as well as phagocytosis and NBT indices were in the normal range, a dysgammaglobulinaemia increasing with age with a hyperglobulinaemia of the IgG, IgA and IgD types was found, sparing immunoglobulins IgM and IgE. In addition the transformation capacity of peripheral blood lymphocytes decreased with age. This is understood as the consequence of premature aging of the thymus-dependent immune system.

Stimulation of drug metabolism by rifampicin in patients with cirrhosis or cholestasis measured by increased hexobarbital and tolbutamide clearance

Abstract: Eleven patients with hepatic cirrhosis or cholestasis were treated with rifampicin for 7 to 132 days. Ten patients received hexobarbital (7.32 mg/kg) and five received tolbutamide (20 mg/kg) by i.v. infusion prior to and after rifampicin treatment; plasma concentrations of the two test compounds were determined during and after infusion. The average elimination half-life of hexobarbital had decreased from 624 to 262 min and that of tolbutamide from 292 to 160 min following rifampicin treatment. It was calculated that the metabolic clearance of hexobarbital had increased more than two-fold and that of tolbutamide almost two-fold. The results suggest that rifampicin is able to stimulate hepatic drug metabolism in patients with liver disease. It was apparent in general that the induction did not lead to improvement of hepatocellular function during disease as judged by laboratory findings.

Purification and properties of blood-group-specific lectins from Vicia cracca.

Abstract: The lectins from the seeds of Vicia cracca react specifically with human blood group A erythrocytes. They were purified by affinity chromatography on an adsorbent containing matrix-bound N-acyl-D-galactosamine. By a continuous pH gradient the lectins could be separated into two fractions each of which was shown to consist of several agglutinating species. The behaviour of both fractions in affinity chromatography was paralleled by the pH dependence of the interaction with the hapten sugar N-acetyl-D-galactosamine. Both lectin fractions have the same molecular (125000) and subunit (33000) weights, display the same pH dependence of their titre against A1 erythrocytes, and bind to N-acetyl-D-galactosamine at pH 8 with the same constant of about 6 X 10(3)M-1.

Untersuchungen zur Reaktivität von Metall‐π‐Komplexen, XXII. Sandwichartig gebaute (Pd–Pd)‐Zweikernkomplexe mit brückenbildenden Cyclopentadienyl‐ und Allyl‐Liganden

Abstract: Bei den Reaktionen von C5H5Pd(2-RC3H4) (2-RC3H4 2-R-Allyl) mit tertiaren Phosphinen oder Phosphiten im Molverhaltnis 1:1 entstehen in praktisch quantitativer Ausbeute die Zweikernkomplexe (C5H5)(2-RC3H4)Pd2L2 (4–20), in denen Palladium in der Oxidationszahl +1 vorliegt. Wie die Kristallstrukturanalysen von 5 (R CH3, L P(C6H5)3) und 12 (R CH3, L P(OC6H4-o-CH3)3) zeigen, sind sowohl der Cyclopentadienyl- als auch der Allyl-Ligand sandwichartig an die Pd2-Einheit gebunden. Der Pd–Pd-Abstand von 267.9 (in 5) bzw. 268.9 pm (in 12) weist auf das Vorliegen einer Metall-Metall-Bindung hin. Aufgrund der 1H- und 13C-NMR-Daten ist nicht zu entscheiden, ob in 4–20 der Cyclopentadienylring als pentahapto-oder trihapto-gebundener Ligand vorliegt. Die Reaktivitat der Zweikernkomplexe steht mit einer quadratisch-planaren Koordination der Metallatome in Einklang. Studies on the Reactivity of Metal π-Complexes, XXII. Sandwich-like Dinuclear (Pd–Pd)-Complexes with Bridging Cyclopentadienyl and Allyl Ligands The reaction of C5H5Pd(2-RC3H4) (2-RC3H4 2-R-allyl) with tertiary phosphines or phosphites in the molar ratio of 1:1 produces in practically quantitative yields the dinuclear complexes (C5H5)(2-RC3H4)Pd2L2 (4–20) in which palladium has the oxidation state +1. The crystal structure analysis of 5 (R CH3, L P(C6H5)3) and 12 (R CH3, L P(OC6H4-o-CH3)3) shows that the cyclopentadienyl as well as the allyl ligand is bonded in a sandwich manner to the Pd–Pd unit. The Pd–Pd distance of 267.9 (in 5) or 268.9 pm (in 12) is suggestive of a metal-metal bond. It is not possible to determine whether the cyclopentadienyl ring in 4–20 exists as a pentahapto- or trihapto-bonded ligand on the basis of the 1H- and 13C n. m. r. data. The reactivity of the dinuclear complexes is in agreement with square planar coordination of the metal atoms.

Expression of MuLV GP71-like antigen in normal mouse spleen cells induced by antigenic stimulation.

Abstract: ALL mouse strains investigated possess cellular DNA sequences which are homologous to the genomes of endogenous C-type particles1 Also, major envelope glycoproteins of the oncoviruses2, such as GP71, are found on the surface of normal cells and they display a considerable polymorphism An antigen serologically indistinguishable from AKR murine leukaemia virus (MuLV) GP71 is present in normal bone marrow cells of all mouse strains investigated but not in normal spleen cells3 Allogeneic4 and mitogenic stimulation5,6 of spleen cells have been reported to result in C-type particle synthesis in some but not all mouse strains We report here that both T and B lymphocytes of mice express a GP71-like antigen on their surfaces if antigenically stimulated

Spectral evidence for 2,2,3-trichloro-oxirane formation during microsomal trichloroethylene oxidation.

Abstract: During aerobic incubation of trichloroethylene with rabbit liver microsomes and NADPH a difference absorption peak appears at 451–452 nm. Trichloroethylene does not form a ligand absorption spectrum with hepatic microsomes reduced by dithionite, or in anaerobic incubates in the presence of NADPH.

Increased voltage of the muscle action potential of normal subjects after local cooling.

Abstract: The compound muscle action potential (MAP) and the isometric twitch force of the adductor pollicis of 25 normal subjects were registered after local cooling. Intramuscular temperature ranged from 36.6 to 18.0°C. The amplitude of the MAP increased while the twitch force decreased at lower temperatures. The increase of the MAP could be caused by the effect of cooling directly at the muscle cell membrane. The decreased twitch force probably is due to an effect on the contractile apparatus.