Showing papers by "University of Marburg published in 1983"

The glucocorticoid receptor binds to defined nucleotide sequences near the promoter of mouse mammary tumour virus.

Abstract: Glucocorticoids are known to induce the transcription of integrated proviral mouse mammary tumour virus (MMTV) genes in a variety of cell lines derived from mouse mammary tumours Chimaeric genes in which selectable markers are linked to the long terminal repeat (LTR) region of MMTV can be induced by the synthetic glucocorticoid dexamethasone after introduction into mouse fibroblasts This suggests that the regulatory elements required for hormonal induction are located within the cloned LTR fragments The idea is supported by the observation that glucocorticoid receptors bind to certain cloned fragments of MMTV DNA in vitro Using filter binding studies and monoclonal antibodies to the glucocorticoid receptor we have now delimited the receptor binding region to a DNA segment of 152 base pairs (bp) that has been shown to be relevant for hormonal induction In nuclease protection experiments we have identified partially homologous receptor binding sequences located in this region, all of which share the hexanucleotide 5'-TGTTCT-3'

The seasonal cycle of body weight in the Djungarian hamster: photoperiodic control and the influence of starvation and melatonin.

Abstract: Photoperiod is the primary environmental cue for seasonality in the Djungarian hamster (Phodopus sungorus). This species reduces its body weight by 30% during winter to reduce its energy requirements. The aim of this study was (1) to examine the influence of food intake on the body weight cycle and (2) to evaluate the role of photoperiod and melatonin in determining this seasonal cycle.While body weight increased slightly (7%) from August through December in long photoperiod, it dropped significantly (32%) in the natural photoperiod group and food intake gradually decreased in this group by about 20%. After two periods of 40% food restriction, the hamsters in long photoperiod rapidly returned to their initial body weight. In contrast, hamsters under natural photoperiod only gained weight until they had reached the body weight of the controls at that particular time.In a second experiment, hamsters were kept under natural photoperiod throughout the year. At 6 different intervals two groups of hamsters were implanted with melatonin capsules and transferred to either short (LD 8:16) or long photoperiod (LD 16:8). The results show that the seasonal change in body weight is caused by a combined action of photoperiod and a change in the animals' sensitivity towards photoperiod and melatonin.

The ribonucleotide reductases — A unique group of metalloenzymes essential for cell proliferation

Abstract: Reductive elimination of the 2′-hydroxyl group from ribonucleotides to yield 2′-deoxyribonucleotides, the monomeric precursors of DNA, requires an uncommon type of enzyme catalysis in which the transition metals, manganese, iron, or cobalt, and free radical intermediates cooperate In the group of deoxyadenosylcobalamin (coenzyme B 12)-dependent ribonucleotide reductases the coenzyme supplies a transient radical pair of deoxyadenosyl· and cob(II)alamin whereas in the nonheme-iron group of enzymes a protein subunit carries a stable tyrosyl radical coordinated to a binuclear iron(III) complex; the manganese-dependent enzymes are less precisely known The radicals are thought to function in hydrogen transfer from cysteine SH to the ribonucleotide substrate, and the metal complexes are apparently needed to generate and stabilize the radicals In aerobic organisms oxygen also plays a critical role in these processes and hence in DNA synthesis and cell proliferation In addition to the transition metals, Mg2+ or Ca2+ are required by several ribonucleotide reductases for structural integrity However the most potent inhibitors of deoxy-ribonucleotide biosynthesis (of potential interest in chemotherapy) are not metal chelators but radical scavengers Cell cycle arrest and cell death produced by simple chemicals like N-hydroxyurea and hydroxamates can be traced back to their reaction with ribonucleotide reductase Evidence is accumulating that independent enzymes of deoxyribonucleotide and DNA synthesis are functionally coupled in a novel type of supramolecular structure

Neue Daten zur Biostratigraphie und zur tektonischen Lagerung der Phyllit-Gruppe und der Trypali-Gruppe auf der Insel Kreta (Griechenland)

Abstract: Eine grose Zahl neuer Fossilfunde — vor allem Conodonten und Ostrakoden — in der Hochdruck/Tieftemperatur metamorphen Phyllit-Gruppe Westkretas geben Auskunft uber den stratigraphischen Umfang dieser Schichtenfolge und Hinweise auf ihre palaogeographische und tektonische Entwicklung.

Morphologic and endocrine aspects of prostatic function

Abstract: Current topics on the normal anatomy and functional organization of the human prostate are presented and related to endocrine principles studied experimentally in dogs and rats. While detailed internal organization and gross anatomical structure of the human gland are still debated by some, there is considerable unanimity on the functional interdependence and relationship between the stroma and the epithelium, as has been concluded from experimental, embryological, and pathological observations. This review also focuses on prostatic secretion, its normal postnatal development, and its functional and possible regulatory significance. Secretion is closely related to both hormonal and neurovascular regulatory mechanisms, and any changes in their balance evoke characteristic, and in some instances species-specific, morphological and functional reactions in the prostate. An hypothesis is presented on the interdependence of secretion and cell proliferation in the prostate.

Energy metabolism and biosynthesis of Vibrio succinogenes growing with nitrate or nitrite as terminal electron acceptor

Abstract: 1. Growth of Vibrio succinogenes with nitrate as terminal electron acceptor was found to be a function of the following two catabolic reactions: $$HCO _2^ - + NO _3^ - + H^ + \to CO_2 + NO _2^ - + H_2 O$$ (a) $$3HCO _2^ - + NO _2^ - + 5H^ + \to 3CO_2 + NH _4^ + + 2H_2 O.$$ (b) The latter reaction (b) was responsible for growth with nitrite. 2. Either succinate or fumarate could serve as sole carbon source during growth with nitrate or nitrite. Biosynthesis from succinate proceeded via fumarate. The ATP requirement for cell synthesis from succinate was equal to that calculated earlier for growth with fumarate as carbon source and electron acceptor (Brounder et al. 1982). 3. The cell yield at infinite dilution rate (Ymax) as obtained with chemostat cultures was 8.5g dry cells/mol formate with either nitrate or nitrite as acceptor. This value amounts to 60% of that measured earlier with fumarate as acceptor (Mell et al. 1982). 4. Membrane vesicles prepared from V. succinogenes catalyzed electron transport from H2 to nitrate. The reaction was dependent on the menaquinone present in the membrane. 5. Electron transport with H2 and nitrite was coupled to the phosphorylation of ADP. The P/H2 ratio with nitrite was 40% of that measured with fumarate as acceptor using the same preparation. The phosphorylation but not the electron transport was abolished by an uncoupling agent.

Anaerobic acetate oxidation to CO2 by Desulfobacter postgatei

Abstract: All the enzymes required for the oxidation of acetate to CO2 via the citric acid cycle were found in Desulfobacter postgatei. To obtain in vivo evidence for the operation of this cycle, the sulfate reducing bacterium was grown on [14C]acetate in the presence of a large pool of 12CO2 and the incorporation of 14C into glutamate (≙ 2-oxoglutarate), aspartate (≙ oxaloacetate), and alanine (≙ pyruvate) was studied. The labelling data were found to be consistent with (i) the oxidation of acetate to CO2 via the reactions of the citric acid cycle, (ii) the synthesis of citrate via a citrate (si)-synthase, and (iii) the anaplerotic synthesis of oxaloacetate from acetate and 2 CO2 via pyruvate as intermediate.

ATP synthesis driven by a potassium diffusion potential in Methanobacterium thermoautotrophicum is stimulated by sodium

Abstract: ATP synthesis driven by a potassium diffusion potential was studied in cell suspensions of Methanobacterium thermoautotrophicum (Marburg). This transient increase in the intracellular ATP content was stimulated five-fold by the addition of sodium ions, from about 2 nmol ATP/min × mg cells (dry weight) at 0.07 mM Na+ to about 10 nmol ATP/min × mg cells at 25 mM Na+.

Nectar production of Epilobium angustifolium L. at different air humidities; nectar sugar in individual flowers and the optimal foraging theory

Abstract: The nectar production of Epilobium angustifolium L. was investigated at 20°C and 50%, 78% and 94% ambient humidity in the climatic test chamber. By means of permanent pipettes, freshly produced nectar was sucked off immediately after secretion, and nectar samples were also taken at 10-h and 48-h intervals to investigate the postsecretory influence of ambient humidity. Volume and sugar concentration of samples from individual flowers were measured and the sugar contained was calculated. The rate of sugar production remains constant for all ambient humidities and extraction intervals investigated; the mean value for all 180 samples is 1.55 mg sucrose equivalents/24h. Sugar concentration of secretion nectar is linearly dependent on ambient humidity over the range investigated, and nectar volume and sugar concentration change according to the theoretically expected curve for solutions with a sugar content of 1.55 mg sucrose. The response of secretion nectar to steplike changes in ambient humidity was investigated and the transient function described. The nectaries respond immediately to changes in ambient humidity. The consequences of the results for nectar production and nectar reward of individual flowers in the field and for the optimal foraging of pollinators are discussed. Discussion concentrates particularly on the following questions: what influence the variability of nectar reward in individual flowers may have on flower-visiting bumble-bees; whether these animals have the sensory capabilities to measure sugar exactly; and whether the water relations of pollinators may also influence foraging behaviour.

Models and mechanism of the formation of poly(thio‐1,4‐phenylene)

Abstract: The formation of poly(thio-1,4-phenylene) does not proceed by a normal polycondensation process. The mechanism was found to be a one-electron-transfer process with radical-cations as reactive intermediates. This mechanism explains the formation of disulfides as side products. It could be shown in a model reaction that more than 20% of the disulfide can be formed in the early stage of the reaction and that the formation of disulfide is a reversible reaction, which explains the decrease of its content with the reaction time. Oligomers up to the octamer were prepared in a stepwise synthesis. The melting point and the enthalpy of melting of poly(thio-1,4-phenylene), crystallized as extended chains, were extrapolated from the melting points of the oligomers. From the UV spectra it could be deduced that the length of conjugated segments in solution is low.

Vascular participation in deep cold pain.

Abstract: As the magnitude of cold pain probably depends on blood flow and thus on internal limb temperature, the activated nociceptors should be close to or within the walls of veins. This hypothesis was tested by injecting small quantities (20 ml) of cold saline into an empty vein of the hand in 16 subjects. Saline temperatures below 26°C elicited pure cold sensations whereas temperatures below 20°C evoked both cold and pain sensations. Pain was mainly described as deep and it tended to radiate along the veins. With saline of 5°C the pain tolerance level of several subjects was reached. Pain always appeared after cold and it disappeared before or together with cold. The results can be explained on the basis of two types of vascular receptors: a sensitive specific cold receptor and a nociceptor with a threshold around 20°C

Carbon monoxide production by Methanobacterium thermoautotrophicum

Abstract: Methanobacterium thermoautotrophicum was grown in a fermenter gassed with an 80% H2/20% CO2 mixture. The effluent gas was found to contain between 30 ppm and 90 ppm carbon monoxide. Approx. 5 nmol CO were produced per min and mg cells (dry weight) by the culture. This is to our knowledge the first report on biological carbon monoxide formation under strictly anaerobic conditions.

Why do sulfate-reducing bacteria outcompete methanogenic bacteria for substrates?

Abstract: The apparent Ks values for H2 of several phylogenetically distant strains of both methanogenic bacteria and sulfate-reducing bacteria were measured. The sulfate reducers had Ks values of about 2 μM whereas the Ks values of the methanogens were 6–20 μM. This indicates that probably all sulfate-reducing bacteria have a higher substrate affinity for H2 than the methanogenic bacteria. Difference in substrate affinity can thus account for the inhibition of methanogenesis from H2 and CO2 in sulfate-rich ecosystems (mainly saltwater marshes), where the H2 concentration is well below 5 μM. Possible explanations for this general phenomenon are discussed.

Thermoregulatory set point in patients with spinal cord injuries (spinal man)

Abstract: The thermoregulatory set point in man can be estimated by the aid of quantifying thermal alliesthesial responses. Behavioural and autonomous thermoregulation in a group of nine patients with spinal cord transection was compared against a control group of six non-disabled under various room-climate conditions. Deviation of core temperature from thermoregulatory set point was estimated using a behavioural indicator (thermal alliesthesial responses) at different intervals of the exposure time. General thermal comfort sensation was rated on a subjective thermal comfort scale. The group with spinal cord transections showed, as expected, a state of partial poikilothermia. Mean skin temperature was approximately the same in both groups, but skin temperature distribution was different in the spinal cord transection when compared against the control group. The results of thermal alliesthesial responses indicated that core temperature for those with spinal cord transections were closer to their thermoregulatory set points than in the control group. It has been concluded that under conditions beyond thermal neutrality the spinal man may possess, some time after the injury, a thermoregulatory set point which varies directly with ambient thermal conditions. This phenomenon is viewed as an adaptive thermoregulatory process following spinal cord injury.

Electron spin resonance of doped glow-discharge amorphous germanium

Abstract: ESR-spectra and transport properties of a-Ge:H, prepared by decomposition of GeH4 in a glow-discharge, are investigated for different phosphorus and boron doping. Undoped and moderately doped samples show the usual resonance at g = 2.0225 due to dangling bonds. For high doping levels, however, two new lines are found: high boron doping leads to a resonance at g = 2.0535 with a linewidth of 112 G, high phosphorus doping to a line at g = 2.0120 with ΔHpp = 33 G. These lines are attributed to localized holes and electrons in the tails of valence and conduction band, respectively. The linewidth of all resonances is the combination of a g-spectrum ΔHpp(g) and a considerably smaller residual linewidth ΔHpp(r) caused by unresolved hyperfine interaction. A simple relation between the g-shift g–g0 and ΔHpp(g) is found which explains the similar doping dependence of g-value and linewidth. From the dependence of the spin density Ns on the conductivity activation energy Eσ a model for the density of states in the mobility gap is deduced. A comparison between the ESR-data of a-Ge: H and a-Si: H shows that g-shifts and linewidths of the three resonances are for a-Ge: H by a factor of about six larger than for the corresponding lines of a-Si: H. ESR-Spektren und Transporteigenschaften von a-Ge:H, hergestellt durch Zersetzung von GeH4 in einer Glimmentladung, werden fur verschiedene Phosphor- und Bor-Dotierungen untersucht. Undotierte und masig dotierte Proben zeigen die ubliche Resonanz bei g = 2,0225, die von freien Valenzen herruhrt. Bei starker Dotierung werden zwei neue Linien gefunden: hohe Bor-Dotierung fuhrt zu einer Resonanz bei g = 2,0535 mit einer Linienbreite von 112 G, hohe Phosphor-Dotierung zu einer Linie bei g = 2,0120 mit ΔHpp = 33 G. Diese Linien werden lokalisierten Lochern und Elektronen in den Auslaufern von Valenz- und Leitungsband zugeordnet. Die Linienbreite aller Resonanzen ist die Uberlagerung eines g-Spektrums ΔHpp(g) und eines betrachlich schmaleren Anteils ΔHpp(r), der durch nicht aufgeloste Hyperfein-Wechselwirkung bedingt ist. Es besteht eine einfache Beziehung zwischen g-Verschiebung g–g0 und ΔHpp(g); sie erklart die ahnliche Dotierungsabhangigkeit von g-Wert und Linienbreite. Aus der Abhangigkeit der Spindichte Ns von der Leitfahigkeits-Aktivierungsenergie Eσ wird ein Modell fur die Zustandsdichte in der verbotenen Zone abgeleitet. Der Vergleich zwischen den ESR-Daten von a-Ge:H und a-Si:H zeigt, das die g-Verschiebungen und die Linienbreiten der drei Resonanzen fur a-Ge:H um etwa den Faktor sechs groser sind als fur die entsprechenden Linien von a-Si:H.

Conversion of ecdysone and 20-Hydroxyecdysone into 26-OIC derivatives is a major pathway in larvae and pupae of species from three insect orders

Abstract: Insects convert ecdysone and 20-hydroxyecdysone into their corresponding 26-oic derivatives, named ecdysonoic acid and 20-hydroxyecdysonoic acid respectively The conversion takes piace in several tissues and can either be the only pathway for converting ecdysone into highly polar ecdysteroids, or coexist with various conjugating mechanisms 20-Hydroxyecdysonoic acid was isolated from Pieris brassicae pupae as its methyl ester derivative Its chemical structure was identified by Cl/D mass spectrometry and compared with a synthetic compound (20-hydroxy-25-deoxyecdysonoic acid) chemically prepared by oxidation of inokosterone (20,26-dihydroxy-25-deoxyecdysone) Natural ecdysonoic acids appear to exist as a mixture of 25R and 25S isomers The significance of this pathway is discussed in comparison with similar reactions occuring in the metabolism of steroid hormones in vertebrates

A 19-channel matrix drive with individually controllable fiber microelectrodes for neurophysiological applications

Abstract: An electrode matrix manipulator for independent positioning of up to 19 microelectrodes for the recording of electrical activity of a multitude of single units within a neural population is described. It is operated by the combined action of a stepping motor and a system of independently controllable solenoid-operated coupling elements for each electrode. Glass-metal fiber electrodes of 100-μm outside diameter travel in parallel capillary guide tubes, arranged in concentric array with a 220-μm interelectrode distance. Electrode movement is in steps of 2 μm. Simultaneous movement of any combination of electrodes is possible.

Theory of Hopping and Multiple-Trapping Transport in Disordered Systems

Abstract: We present a general theory to describe equilibrium as well as nonequilibrium transport properties of systems in which the carriers perform an incoherent motion that can be described by means of a set of master equations. This includes hopping as well as trapping in the localized energy region of amorphous or perturbed crystalline semiconductors. Employing the mathematical analogy between the master equations and the tight binding problem we develop approximation schemes using methods of many-particle physics to derive expressions for the averaged propagator of the carriers and the conductivity tensor. The calculated conductivity and Hall conductivity of hopping systems compare extremely well to computer simulations over the whole range of frequency, density, and temperature. We are able to derive expressions for dispersive transport in hopping as well as trapping systems that contain the results of earlier theories of Scher, Montroll and Noolandi, Schmidlin as special cases and establish criteria for the occurrence of dispersive transport in such systems. We find that in principle hopping can lead to dispersive transport if the times and densities are very low, but actual experimental data are more easily explained in terms of multiple trapping.

The uteroglobin gene region: hormonal regulation, repetitive elements and complete nucleotide sequence of the gene.

Abstract: Differential uteroglobin induction represents an appropriate model for the molecular analysis of the mechanism by which steroid hormones control gene expression in mammals. We have analyzed the structure and hormonal regulation of a 35 Kb region of genomic DNA in which the uteroglobin gene is located. The complete sequence of 3,700 nucleotides including the uteroglobin gene and its flanking regions has been determined, and the limits of the gene established by S1 nuclease mapping. Several regions containing repeated sequences were mapped by blot hybridization, one of which is located within the large intron in the uteroglobin gene. Analysis of the RNAs extracted from endometrium, lung and liver, after treatment with estrogen and/or progesterone shows that within the 35 Kb region, the uteroglobin gene is the only DNA segment whose transcription into stable RNA is induced by progesterone.