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Showing papers by "University of Marburg published in 1980"


Journal ArticleDOI
TL;DR: It is indicated that methane formation and growth are less tightly coupled at high concentrations of H2 or CO2 in the medium than at low concentrations.
Abstract: Methanobacterium thermoautotrophicum was grown on a mineral salts medium in a fermenter gassed with H2 and CO2, which were the sole carbon and energy sources. Under the conditions used the bacterium grew exponentially. The dependence of the growth rate (μ) on the concentration of H2 and CO2 in the incoming gas and the dependence of the growth yield ( $$Y_{CH_4 }$$ ) on the growth rate were determined at pH 7 (the pH optimum) and 65° C (the temperature optimum). The curves relating growth rate to the H2 and CO2 concentration were hyperbolic. From reciprocal plots apparent K s values for H2 and CO2 and μmax were obtained: app. $$K_{{\text{H}}_{\text{2}} }$$ = 20%; app. $$K_{{\text{CO}}_{\text{2}} }$$ = 11%; μ = 0.69 h-1; t δ (max)=1 h. $$Y_{CH_4 }$$ was 1.6 g mol-1 and almost independent of the growth rate, when the rate of methane formation was not limited by the supply of either H2 or CO2. The yield increased to near 3 g mol-1 when H2 or CO2 were limiting. These findings indicate that methane formation and growth are less tightly coupled at high concentrations of H2 or CO2 in the medium than at low concentrations. The physiological significance of these findings is discussed.

348 citations


Book ChapterDOI
01 Jan 1980
TL;DR: Some animals, during evolution, developed eyes which were especially adapted for good visual efficiency at low light intensities whereas others improved the remaining sensory systems.
Abstract: Animals living in the dark are faced with the problem that vision is only of limited use for orientation in the environment and for the detection and identification of relevant targets. In order to cope with this situation, some animals, during evolution, developed eyes which were especially adapted for good visual efficiency at low light intensities whereas others improved the remaining sensory systems.

209 citations


Journal ArticleDOI
TL;DR: The difference between these results and all other published data on the subunit composition of mammalian-type cytochrome c oxidase, based on gel electrophoretic analysis, is due to the insufficient resolving power of previously used gel systems and the very similar molecular weight of subunits VIa,b, c, and VIIa, b, c.
Abstract: Cytochrome c oxidase from rat liver mitochondria was separated into 12 different protein subunits by application of a highly resolving sodium dodecylsulfate/gel electrophoretic system of different compositions. The 12 protein subunits are shown to represent integral components of mammalian type cytochrome c oxidase for the following reasons. 1. All 12 subunits copurify through various purification procedures. 2. The subunit composition of the isolated enzyme is identical to that of the immunoprecipitated one. 3. All 12 subunits are present in the complex at one to one stoichiometric amounts. 4. A similar composition of 12 subunits was also found for cytochrome c oxidase from rat kidney, pig heart, rabbit liver and stone-marten liver. The difference between our results and all other published data on the subunit composition of mammalian-type cytochrome c oxidase, based on gel electrophoretic analysis, is due to the insufficient resolving power of previously used gel systems and the very similar molecular weight of subunits VIa, b, c, and VIIa, b, c.

176 citations


Journal ArticleDOI
TL;DR: Methanobacterium thermoautotrophicum, growing on medium supplemented with 2 μmol 63NiCl2/l, was found to take up 1.2 μ mol 63Ni per g cells (dry weight), and is considered to be identical with factor F430.
Abstract: Methanobacterium thermoautotrophicum, growing on medium supplemented with 2 μmol 63NiCl2/l, was found to take up 1.2 μmol 63Ni per g cells (dry weight). More than 70% of the radioisotope was incorporated into a compound, which dissociated from the protein fraction after heat treatment, was soluble in 70% acetone, and could be purified by chromatography on QAE-Sephadex A-25, Sephadex G-25, and DEAE cellulose. The purified 63Ni labelled compound had an absorption spectrum and properties identical to those of factor F430 and is therefore considered to be identical with factor F430.

133 citations


Journal ArticleDOI
TL;DR: All reactions of the proposed reductive tricarboxylic acid cycle could be demonstrated in autotrophically growing cells.
Abstract: Chlorobium limicola was grown on a mineral salts medium with CO2 as the main carbon source supplemented with specifically labeled 14C propionate and the incorporation of 14C into alanine (≙ intracellular pyruvate), aspartate (≙ oxaloacetate), and glutamate (≙ α-ketoglutarate) was studied in long term labeling experiments. During growth in presence of propionate 30% of the cell carbon were derived from propionate and 70% from CO2. Propionate was not oxidized to CO2. All three amino acids were found to be labeled. The labeling patterns indicate that propionate was assimilated via propionyl CoA, methylmalonyl CoA and succinyl CoA. When 1-14C propionate was the labeled precursor no radioactivity was found in the carboxyl group(s) of alanine, aspartate and glutamate, excluding the incorporation of propionate into the amino acids via succinate oxidation to fumarate. With 1-14C propionate preferentially aspartate (C-3) and glutamate (C-2) became labeled, with 2-14C propionate alanine (C-3) and glutamate (C-4). These findings indicate that propionate was incorporated into the amino acids via succinyl CoA, α-ketoglutarate, isocitrate, and citrate, followed by a si-type cleavage of citrate to oxaloacetate and acetyl CoA (or acetate). Similar experiments with U-14C acetate confirm these conclusions. Thus, all reactions of the proposed reductive tricarboxylic acid cycle could be demonstrated in autotrophically growing cells.

128 citations



Journal ArticleDOI
TL;DR: The location of the oxidoreductases indicate that in D. vulgaris (Marburg) H2 oxidation and sulfate reduction take place on opposite sides of the cytoplasmic membrane rather than on the same side, as has recently been proposed.
Abstract: Desulfovibrio vulgaris (Marburg) was grown on hydrogen plus sulfate as sole energy source in a medium containing excess iron. The topography of electron transport components was investigated. The bacterium contained per mg cells (dry weight) 30U hydrogenase (1U=1 μmol/min), 35 μg desulfoviridin (= bisulfite reductase), 0.6 U adenosine phosphosulfate reductase, 30 mU thiosulfate reductase, 0.3 nmol cytochrome c3 (Mr=13,000), 0.04 nmol cytochrome b, 0.85 nmol menaquinone, and 0.4 nmol ferredoxin. Hydrogenase (>95%) and cytochrome c3 (82%) were localized on the periplasmic side and desulfoviridin (≈95%), adenosine phosphosulfate reductase (87%), thiosulfate reductase (74%), and ferredoxin (71%) on the cytoplasmic side of the cytoplasmic membrane; menaquinone and cytochrome b were exlusively found in the membrane fraction. The location of the oxidoreductases indicate that in D. vulgaris (Marburg) H2 oxidation and sulfate reduction take place on opposite sides of the cytoplasmic membrane rather than on the same side, as has recently been proposed.

115 citations


Journal ArticleDOI
TL;DR: It is shown with Methanobacterium thermoautotrophicum that factor F,,, becomes labelled when the organism is grown in the presence of F-[4-14C]ALA, which is the amount predicted for a tetrapyrrole compound.

105 citations


Journal ArticleDOI
TL;DR: Results indicate that CPA induces (presumably adaptive) liver growth essentially by parenchymal hyperplasia; of the model inducers used for comparison only pregenolone-16 alpha-carbonitrile (PCN) produced a similarly strong hyperplastic response while liver enlargement elicited by a alpha-hexachlorocyclohexane (alpha-HCH), phenobarbital (PB) and 3-methylcholanthrene (3-MC

91 citations



Journal ArticleDOI
TL;DR: The finding that pyruvate was not incorporated into compounds derived from acetyl CoA, whereas acetate was incorporated into derivatives of acetylCoA and pyruVate in a 1:1 ratio demonstrates that pyrupvate is synthesized by reductive carboxylation of acety CoA.
Abstract: The pathway of autotrophic CO2 fixation in Methanobacterium thermoautotrophicum has been investigated by long term labelling of the organism with isotopic acetate and pyruvate while exponentially growing on H2 plus CO2. Maximally 2% of the cell carbon were derived from exogeneous tracer, 98% were synthesized from CO2. Since growth was obviously autotrophic the labelled compounds functioned as tracers of the cellular acetyl CoA and pyruvate pool during cell carbon synthesis from CO2.

Journal ArticleDOI
TL;DR: It is concluded that premedication with a combination of H1- and H2-receptor antagonists is indicated due to the high incidence of histamine release during anaesthesia and surgery induced by various drugs and treatments.
Abstract: Histamine release by drugs used in anaesthesia and surgery has been often demonstrated in human volunteers, but only occasionally in patients. Three questions arose from these studies. (1) Is the incidence of histamine release high in patients during routine anaesthesia and surgery? (2) Can the clinical effects of histamine release in man be prevented by H1+H2-receptor antagonists? (3) Are there any side-effects of such a premedication? These problems were investigated in patients and volunteers by randomized controlled clinical trials using only one of the histamine-liberating drugs in man, the plasma substitute Haemaccel. This drug was chosen because it causes a reproducible histamine release in man and because its mechanism of action in man is largely known. (1) Out of 600 orthopaedic patients 30 (5%) showed anaphylactoid reactions following Haemaccel infusion. 26 of these had a histamine release of more than 1 ng histamine/ml plasma. Using predictive values this gives an efficiency of the test by nearly 98%. (2) In volunteers the combination of an H1-plus H2-receptor antagonist (dimethpyrindene and cimetidine) completely prevented the clinical effects of histamine release by Haemaccel (9 allergoid and anaphylactoid reactions in the control group, none in the H1+H2-group). The incidence of histamine release, however, remained unchanged. (3) The premedication was found to release histamine itself. Cimetidine was effective when given alone but especially in combination with chlorpheniramine (4 events out of 7 applications). The clinical side-effects of these premedication were mild since apparently the free histamine was largely blocked at the receptor sites.

Journal ArticleDOI
TL;DR: Findings indicate that nickel is an essential component of factor F430, a yellow compound of unknown structure present in methanogenic bacteria.
Abstract: Factor F430 is a yellow compound of unknown structure present in methanogenic bacteria. It has recently been shown to contain nickel. In this communication the influence of the nickel concentration in the growth medium on the factor F430 content of Methanobacterium thermoautotrophicum and on the nickel content of factor F430 was studied. It was found: (1) The content of factor F430 in the cells was strongly dependent on the nickel concentration of the growth medium. Cells grown on media with 2.5 μM NiCl2 contained 28 times as much factor F430 per g as those grown on media with 0.075 μM NiCl2; (2) factor F430 was synthesized in nickel deprived cells only upon the addition of nickel Nickel uptake paralleled factor F430 synthesis; (3) independent of the nickel concentration in the growth medium, the extinction coefficient at 430 nm of factor F430 per mol nickel was always near 22,500 cm-1 (mol Ni)-1. These findings indicate that nickel is an essential component of factor F430.

Journal ArticleDOI
TL;DR: In this article, the defect concentration of a-Si : H was measured by electron bombardment and hydrogen effusion, and the results can be explained with the assumption of essentially two kinds of defect : dangling-bond and vacancy-type defects.
Abstract: Photoluminescence, photoconductivity, and dark hopping conductivity of a-Si : H have been measured as a function of defect concentration. The network defects were created by electron bombardment and by hydrogen effusion. Both methods were successively applied to samples prepared in the same run. The defect concentration was monitored by spin resonance measurements. Our results can be explained with the assumption of essentially two kinds of defect : dangling-bond and vacancy-type defects. It is necessary to assume a positive effective correlation energy for both kinds of defect.

Journal ArticleDOI
TL;DR: Observations indicated that acetate thiokinase and free acetate are not involved in autotrophic CO2 fixation in M. thermoautotrophicum.
Abstract: Methanobacterium thermoautotrophicum growing on H2 plus CO2 as sole carbon and energy source was found to contain acetate thiokinase (Acetyl CoA synthetase; EC 6.2.1.1); Acetate + ATP + CoA leads to Acetyl CoA + AMP + PPi. The apparent Km value for acetate was 40 microM. Acetate kinase (EC 2.7.2.1) and phosphotransacetylase (EC 2.3.1.8) could not be detected. The specific activity of acetate thiokinase was high in cells grown with limited H2 and CO2 supply (approximately 100 nmol/min . mg protein), it was low in exponentially grown cells (2 nmol/min . mg protein). This corresponded with the finding that cells growing linearly in the presence of acetate assimilated the monocarboxylic acid in high amounts (greater than 10% of the cell carbon was derived from acetate), whereas exponentially growing cells did not (less than 1% of cell carbon was derived from acetate). These latter observations indicated that acetate thiokinase and free acetate are not involved in autotrophic CO2 fixation in M. thermoautotrophicum. The presence and some kinetic properties of succinate thiokinase (EC 6.2.1.5), adenylate kinase (EC 2.7.4.3), and inorganic pyrophosphatase (EC 3.6.1.1) are also described.

Journal ArticleDOI
TL;DR: Chromaffin cells from adult bovine adrenal medullae kept in culture retain a large number of features typical of differentiated cells over a considerable length of time and may be profitably used to study long-term effects of drugs and interactions with other cells at morphological and biochemical levels.

Journal ArticleDOI
TL;DR: The phobic response is specifically inhibited by the protonophorous uncouplers TPMP+ and FCCP but not by the ionophores gramicidin and A23187.
Abstract: The avoidance by Stentor coeruleus of a light trap is caused by a step-up photophobic response. The phobic response invariably consists of a delay of about 200 ms, a stop response, a turn to one side, and resumption of swimming in the new direction. After this the cells enter a refractory period of 1–3 s following a phobic response, during which they will not give a second response. Phobic responses can be elicited by spatial and temporal increases in light intensity. The action spectrum for the step-up photophobic response resembles the absorption spectrum of stentorin, the proposed photoreceptor pigment, and of its chromophore, hypericin.

Journal ArticleDOI
TL;DR: Thymus tissue from myasthenia gravis patients was investigated for comparative reasons and epithelial and myoid cells displayed a strong immunoreactivity with antiactin, resembling striated muscle after denervation or various other pathologic conditions.
Abstract: Samples of normal human thymus of different ages (4–63 years old) were studied by immunofluorescence microscopy (using antibodies to smooth muscle myosin, to actin from the chicken gizzard, and antibodies to myosin from human striated muscle) as well as by routine electron microscopy Thymus tissue from myasthenia gravis patients was also investigated for comparative reasons Epithelial cells reacted with anti-smooth, but not with anti-striated muscle myosin, whereas myoid cells reacted with antibodies to striated, but not to smooth muscle myosin Both epithelial and myoid cells displayed a strong immunoreactivity with antiactin Corresponding to this immunoreactivity, both cell types contained bundles of thin, actin-like filaments Myoid cells occurred in the rounded and elongated variety, and they were a normal constituent of all thymuses investigated in this study Ultrastructurally, this non-innervated, striated muscle-like cell type possessed bundles of thin and thick filaments as well as Z lines in a rather disorganized arrangement, resembling striated muscle after denervation or various other pathologic conditions There were no overt differences in the number and structure of myoid cells between healthy and myasthenic patients

Journal ArticleDOI
TL;DR: In this paper, the capacitance of Schottky barrier diodes prepared by the deposition of Pt onto undoped and phosphorus doped a-Si:H films is studied as a function of frequency f, temperature T and applied voltage V.
Abstract: The capacitance C of Schottky barrier diodes prepared by the deposition of Pt onto undoped and phosphorus doped a-Si:H films is studied as a function of frequency f, temperature T and applied voltage V. With increasing f and decreasing T the capacitance decreases by factors as large as 10 indicating that the space charge is located in deep gap states with response times which in part are greater than 103s. The behaviour of Schottky barriers in undoped a-Si:H can well be described in terms of a model with an energy independent density of states close to 1017cm−3eV−1. Doping with PH3 results in an increase of C, accompanied by a decrease in barrier width and barrier height. Fot T > 300 K and V > 0.3 V a strong increase of C is observed which is tentatively attributed to the contribution of interface states.

Journal ArticleDOI
01 Jul 1980
TL;DR: In this article, the absorption spectra of tetracene and pentacene layers prepared by vapor deposition onto cooled substrates were measured as a function of sample formation temperature Tf, evaporation rate and recording temperature.
Abstract: Absorption spectra of tetracene and pentacene layers prepared by vapor deposition onto cooled substrates were measured as a function of sample formation temperature Tf, evaporation rate and recording temperature. Profile-analysis indicates that the main absorption peak is of gaussian shape. The width varies between 300 cm−1 and 650 cm−1, higher values referring to lower formation temperatures and/or higher evaporation rates and reflecting larger fluctuation of the site-energies. Appearance of a second electronic band equivalent to the upper Davydov component in the crystal spectrum indicates presence of short-range order. The low-energy behavior is dominated by a structural defect. No Urbacht-tail is observed. It is concluded that tetracene and pentacene layers represent examples for intermediate structural disorder.


Journal ArticleDOI
TL;DR: In this paper, a self-consistent theory of ac and dc transport in disordered hopping systems is given, which is an extension of an effective medium approximation and a Cayley tree formalism, and calculated dc and ac conductivity are compared with the results of computer simulations of R-hopping networks and data of amorphous germanium.
Abstract: A self-consistent theory is given of ac and dc transport in disordered hopping systems. The method is an extension of an effective medium approximation and a Cayley tree formalism. The calculated dc and ac conductivity are compared with the results of computer simulations of R-hopping networks and data of amorphous germanium. The agreement is very satisfactory. The exponent s of the ωs component decreases with temperature in the way observed experimentally. Es wird eine selbstkonsistente Theorie der Gleich- und Wechselstromleitfahigkeit in ungeordneten Hopping-Systemen vorgestellt. Die Methode ist eine Erweiterung einer Effektiv-Medium-Naherung im Cayley-tree-Formalismus. Die berechneten Gleich- und Wechselstromleitfahigkeiten werden mit Computer-Simulationen auf R-hopping-Netzwerken und experimentellen Daten von amorphem Germanium verglichen. Der Exponent s der ωs-Komponente fallt mit der Temperatur wie es experimentell beobachtet wird.

Journal ArticleDOI
TL;DR: A definition of the Actinobacillus-Haemophilus-Pasteurella group as a whole was established which appears to rank as a family and several misclassified species were eliminated.

Journal ArticleDOI
TL;DR: The stilbene skeleton is, therefore, synthesized from a phenylpropane moiety carrying a 4′-hydroxysubstitution, while further derivatization to the 3′-Hydroxy-4′-methoxy structure takes place at the level of stilbenes.

Journal ArticleDOI
TL;DR: Chlorobium limicola has been proposed to assimilate CO2 autotrophically via a reductive tricarboxylic acid cycle rather than via the Calvin cycle, and studies of the cell components support this interpretation.
Abstract: Chlorobium limicola has been proposed to assimilate CO2 autotrophically via a reductive tricarboxylic acid cycle rather than via the Calvin cycle. This proposal has been a matter of considerable controversy. In order to determine which pathway is operative, the bacterium was grown on a mineral salts medium with CO2 as the main carbon source supplemented with specifically labeled 14C-pyruvate, and the incorporation of 14C into alanine (≙intracellular pyruvate), aspartate (≙oxaloacetate), glutamate (≙α-ketoglutarate), and glucose (≙hexosephosphate) was measured in exponentially growing cells in long term labeling experiments. During growth in presence of pyruvate, 20% of the cell carbon were derived from pyruvate in the medium, 80% from CO2. Since pyruvate was not oxidized to CO2, only those compounds should become labeled which were synthesized from CO2 via pyruvate.

Journal ArticleDOI
TL;DR: The molecular weights of the native biliprotein aggregates C-phycocyanin and allophycOCyanin are about 139,000 and 130,000 as revealed by calibrated gel chromatography, gradient gel electrophoresis and morphological measurements on the basis of an average protein packing density.
Abstract: C-phycocyanin and allophycocyanin from the red alga Rhodella violacea were investigated by electron microscopy and biochemical methods using samples taken from the same fractions

Journal ArticleDOI
TL;DR: In order to overcome the disadvantages of erythrocytes and albumin, a totally synthetic medium for the perfusion of the isolated rat brain was developed, which contained in addition a fluorocarbon for oxygen transport and a polyol to furnish emulsifying and oncotic properties.

Journal ArticleDOI
TL;DR: Factors F430 from methanogenic bacteria have recently been shown to contain nickel and it was found that per mol nickel 8–9 mol of succinate were incorporated into the three factors F430 which is the amount predicted for a tetrapyrrole structure.
Abstract: Factors F430 from methanogenic bacteria have recently been shown to contain nickel and it has been speculated that they may have a nickel tetrapyrrole structure. This assumption was tested by determining whether succinate is incorporated by growing Methanobacterium thermoautotrophicum into three factors F430. Succinate is assimilated by Methanobacterium thermoautotrophicum into the amino acids glutamate, arginine and proline and into tetrapyrroles rather than other cell components. It was found that per mol nickel 8–9 mol of succinate were incorporated into the three factors F430 which is the amount predicted for a tetrapyrrole structure. Since the three factors F430 only contained significant amounts of glutamate rather than arginine or proline, the incorporation data suggest that factors F430 are nickel tetrapyrrole compounds. Spectral properties of the three factors F430, apparent molecular weights, and the absence of phosphor in these compounds are also described.

Journal ArticleDOI
TL;DR: Amorphous SixGe1−x:H films are prepared by decomposition of SiH4/GeH4 mixtures in a rf glow discharge as mentioned in this paper, and it is concluded that by admixture of Ge the tail state distribution becomes steeper and that the concentration of defects is considerably enhanced.
Abstract: Amorphous SixGe1−x:H films are prepared by decomposition of SiH4/GeH4 mixtures in a rf glow discharge. With increasing Ge-content the optical gap as well as the energy and the half width of the luminescence peak decrease linearly. It is concluded that by admixture of Ge the tail state distribution becomes steeper and that the concentration of defects is considerably enhanced. Already small amounts of Ge lead to a drastic decrease of the photoconductivity (ημτ-product). Amorphe SixGe1−x: H-Schichten werden durch Zersetzung von SiH4/GeH4-Mischungen in einer HFGlimmentladung hergestellt. Mit zunehmendem Ge-Gehalt nimmt sowohl das optische Gap als auch die Energie und Halbwertsbreite des Lumineszenzmaximums linear ab. Es wird angenommen, das durch die Zumischung von Ge die Verteilung der Auslauferzustlnde steiler wird und das die Konzentration von Defekten betrachtlich erhoht wird. Schon geringe Mengen von Ge fuhren zu einem drastischen Ruckgang der Photoleitfahigkeit (ημτ-Produkt).

Book ChapterDOI
TL;DR: Treatment with 2 X 10 mg memantine/day reveals an accumulation of the drug in microM concentrations in the brain, probably high enough to explain the ameliorating effect of memantine treatment in patients suffering from Parkinson's disease.
Abstract: GC-MS of tissue extracts obtained from a parkinsonian patient who died from secondary causes during memantine (l-amino-3.5-dimethyl- adamantane) treatment showed the drug to be largely unmetabolized. In the kidney and liver a second peak corresponded to less than 1% of the main peak. In the brain an accumulation of memantine could be shown in the temporal lobe, hypothalamus and pons. Thus treatment with 2×10 mg memantine/day reveals an accumulation of the drug in µM concentrations in the brain. This is probably high enough to explain the ameliorating effect of memantine treatment in patients suffering from Parkinson’s disease.