Showing papers by "University of Göttingen published in 1986"

Limitation of Photosynthesis by Carbon Metabolism: I. Evidence for Excess Electron Transport Capacity in Leaves Carrying Out Photosynthesis in Saturating Light and CO2

Abstract: It has been investigated how far electron transport or carbon metabolism limit the maximal rates of photosynthesis achieved by spinach leaves in saturating light and CO2. Leaf discs were illuminated with high light until a steady state rate of O2 evolution was attained, and then subjected to a 30 second interruption in low light, to generate an increased demand for the products of electron transport. Upon returning to high light there is a temporary enhancement of photosynthesis which lasts 15 to 30 seconds, and can be up to 50% above the steady state rate of O2 evolution. This temporary enhancement is only found when saturating light intensities are used for the steady state illumination, is increased when low light rather than darkness is used during the interruption, and is maximal following a 30 to 60 seconds interruption in low light. Decreasing the temperature over the 10 to 30°C range led to the transient enhancement becoming larger. The temporary enhancement is associated with an increased ATP/ADP ratio, a decreased level of 3-phosphoglycerate, and increased levels of triose phosphate and ribulose 1,5-bisphosphate. Since electron transport can occur at higher rates than in steady state conditions, and generate a higher energy status, it is concluded that leaves have a surplus electron transport capacity in saturating light and CO2. From the alterations of metabolites, it can be calculated that the enhanced O2 evolution must be accompanied by an increased rate of ribulose 1,5-bisphosphate regeneration and carboxylation. It is suggested that the capacity for sucrose synthesis ultimately limits the maximal rates of photosynthesis, by restricting the rate at which inorganic phosphate can be recycled to support electron transport and carbon fixation in the chloroplast.

Limitation of Photosynthesis by Carbon Metabolism: II. O2-Insensitive CO2 Uptake Results from Limitation Of Triose Phosphate Utilization

Abstract: The occurrence of O2-insensitive photosynthesis at high quantum flux and moderate temperature in Spinacia oleracea was characterized by analytical gas exchange measurements on intact leaves In addition photosynthetic metabolite pools were measured in leaves which had been rapidly frozen under defined gas conditions Upon switching to low O2 in O2-insensitive conditions the ATP/ADP ratio fell dramatically within one minute The P-glycerate pool increased over the same time Ribulose bisphosphate initially declined, then increased and exceeded the pool size measured in air The pools of hexose monophosphates and UDPglucose were higher at a partial pressure of O2 of 21 millibars than at 210 millibars These results are consistent with the hypothesis that the rate of sucrose synthesis limited the overall rate of assimilation under O2-insensitive conditions

Electronic structure of cerium and light rare-earth intermetallics

Abstract: We give an overview of the use of the impurity Anderson Hamiltonian to describe the spectroscopic and low-energy thermodynamic properties of cerium intermetallics, with emphasis on interpreting 4f photoemission spectra. We show Ce valence-band resonant photoemission, Bremsstrahlung isochromat and 3d X-ray photoemission spectra for CeRu2, CeNi2, CeIr2 and CeAl, and give a complete theoretical analysis of the spectra. We summarize the relation between the large and small energy scale properties. For each system, all the spectra, as well as the static magnetic susceptibility and Kondo temperature, can be described by the model using essentially the same parameters. We also present details of resonant photoemission spectra for five other cerium compounds, CeSi2, CeOs2, CePd3, CeCo2 and CeNi5, and discuss generally the problem of obtaining the experimental 4f spectrum. Alternative theories of 4f photoemission are examined critically and we give applications of the Anderson Hamiltonian theory to CeAl2,...

Natural and anthropogenic components of soil acidification

Abstract: The following 8 theses are theoretically founded and experimentally quantified. 1. Rocks contain only bases and no acid precursors. Therefore, with the exception of sulfide containing rocks, soils cannot acidify as a result of atmospheric rock weathering. 2. A consumption of protons in rocks and soils results in a decrease of their acid neutralizing capacity (ANC) and can result in the buildup of a base neutralizing capacity (BNC). Strong soil acidification leads to the formation of stronger acids from weaker acids in the solid phase; this may be connected with a decrease in the BNC. 3. Weak acids (carbonic acid) lead in geological times to the depletion of bases without a larger accumulation of labile cation acids. Strong acids (HNO3, organic acids, H2SO4) can lead within a few decades to soil acidification, i.e. to leaching of nutrient cations and the accumulation of labile cation acids. 4. The acid input caused by the natural emission of SO2 and NOx can be buffered by silicate weathering even in soils low in silicates. 5. The cause of soil impoverishment and soil acidification is a decoupling of the ion cycle in the ecosystem. 6. Acid deposition in forest ecosystems which persists over decades leads to soil acidification. 7. Formation and deposition of strong acids with conservative anions (SO4, NO3) shifts soil chemistry into the Al or Al/Fe buffer range up to great soil depth. In such soils eluvial conditions prevail throughout the solum and even in upper part of the C horizon: in connection with the decomposition of clay minerals, Al and eventually Fe are being eluviated. The present soil classification does not include this soil forming process. 8. In the long run, soil acidification by acid deposition results in the retraction of the root system of acid tolerant tree species from the mineral soil, and in water acidification. Naturliche und anthropogene Komponenten der Bodenversauerung Es werden folgende 8 Thesen theoretisch begrundet und experimentell quantifiziert: 1. Gesteine enthalten nur Basen- und keine Saurebildner (Ausnahme: sulfidhaltige Gesteine). Mit dieser Ausnahme konnen Boden also nicht als Ergebnis der Gesteinsverwitterung unter dem Einflus der Atmospharilien versauern. 2. Eine Konsumtion von Protonen in Gesteinen oder Boden fuhrt zur Abnahme deren Saureneutralisationskapazitat (SNK), sie kann zum Aufbau einer Basenneutralisationskapazitat (BNK) fuhren. Starke Bodenversauerung macht sich bei evtl. abnehmender BNK in einer Umbildung von schwacheren zu starkeren Sauren in der Festphase bemerkbar. 3. Schwache Sauren (Kohlensaure) fuhren in geologischen Zeitraumen zur Bodenverarmung, d.h. zur Auswaschung von Basen (Nahrstoffkationen) ohne grose Akkumulation kinetisch labiler Kationsauren. Starke Sauren (HNO3, organische Sauren, H2SO4) konnen in wenigen Jahrzehnten zur Bodenversauerung fuhren, d.h. zur Auswaschung von Nahrstoffkationen unter Akkumulation kinetisch labiler Kationsauren. 4. Der durch naturliche Emission von SO2 und NOx bedingte Saureeintrag kann selbst in silikatarmen Boden noch durch Silikatverwitterung gepuffert werden. 5. Ursache einer Basenverarmung und Bodenversauerung ist eine Entkopplung des Ionenkreislaufs im Okosystem. 6. Jahrzehnte anhaltende Saure Deposition in Waldokosysteme fuhrt zur Bodenversauerung. 7. Bildung und Eintrag starker Sauren mit konservativen Anionen (SO42-, NO3−) uberfuhren Boden bei ihrer Auswaschung bis in grose Tiefen in den Al- oder Al/Fe-Pufferbereich. In solchen Boden herrschen im Solum bis in den C-Horizont eluviale Bedingungen: unter Tonzerstorung wird Al und evtl. Fe eluviert. Die gegenwartige Bodensystematik wird diesem Bodenbildungsprozes nicht gerecht. 8. Bodenversauerung durch Saure Deposition fuhrt langfristig zum Ruckzug des Wurzelsystems sauretoleranter Baumarten aus dem Mineralboden und zur Gewasserversauerung.

Life-style and occupational risk factors in cancer of the lower urinary tract

Abstract: In a matched case-control study of cancer of the lower urinary tract in northern Germany in which 340 male and 91 female case-control pairs were interviewed between 1977 and 1982, cigarette smokers were found to have an odds ratio of 2.3 for males and 2.9 for females compared with nonsmokers. A significant dose-response relation was observed for increasing cigarette consumption, and a significant decrease in risk was shown for ex-smokers. Employment in rubber, plastics, dye, textiles, and mining industries was associated with a higher risk, and increased odds ratios were also observed for exposure to spray painting, coal pitch, chromium, and zinc. Controlling for smoking, an elevated risk of 2.3 for drinking more than four cups of coffee per day and significant odds ratios of 2.1 and 2.8 for a daily consumption of 0.5-1.0 liter and above 1.0 liter of beer, respectively, were noted among men. A highly significant odds ratio of 4.0 was found for a daily fluid intake of more than 2 liters. Dietary habits such as the frequent consumption of canned food and fatty meals were associated with a higher risk, whereas a regular consumption of fruits and vegetables was associated with a lower risk. Fourteen determinants found to be important in this case-control series were analyzed by using multiple logistic regression.

Nutritional Factors Affecting the Ratio of Solvents Produced by Clostridium acetobutylicum.

Abstract: Fermentation of whey by Clostridium acetobutylicum yielded butanol and acetone in a ratio of approximately 100:1. This ratio amounted to only 2:1 in synthetic media with glucose, lactose, or glucose plus galactose as substrates. Removal of citrate from whey and addition of minerals resulted in an increase in the amount of acetone produced. Experiments carried out in a chemostat with a low-phosphate synthetic medium revealed that the butanol/acetone ratio could be increased from 2:1 to 3.8:1 by cofermentation of l-lactate and from 2:1 to 8:1 by iron limitation. The performance of the fermentation in a low-iron glucose medium above pH 5.1 yielded l-lactate as the main product.

Effects of propofol on cardiovascular dynamics, myocardial blood flow and myocardial metabolism in patients with coronary artery disease

Abstract: The effects of propofol (emulsion formulation) on cardiovascular dynamics, myocardial blood flow and myocardial metabolism were studied in 12 patients scheduled for elective coronary artery bypass surgery. Measurements were performed with the patient awake, during steady-state maintenance anaesthesia with propofol 200 micrograms kg-1 min-1 at rest, and during sternotomy when the propofol was supplemented with fentanyl 10 micrograms kg-1. Propofol alone decreased mean arterial pressure and cardiac index; heart rate was increased. Myocardial blood flow and myocardial oxygen consumption were decreased by 26% and 31%, respectively. Myocardial lactate production was seen in one patient during this period. Surgical stimulation, under propofol-fentanyl anaesthesia, led to the return of arterial pressure and heart rate towards baseline; cardiac index decreased further. Myocardial blood flow and oxygen consumption increased such that they almost achieved their baseline values. Myocardial lactate production was seen in one patient. These results suggest that propofol may on occasions, lead to myocardial ischaemia in patients with coronary artery disease, but that it is able to block the sympathetic responses to surgical stimulation when combined with a suitable analgesic.

Density-functional treatment of an exactly solvable semiconductor model.

Abstract: The band-gap problem is studied for an exactly solvable semiconductor model. The exact exchange-correlation potential is constructed and its discontinuity is studied. Depending on the parameter range, a large or a small discontinuity is obtained. The "scissor-operator" method is compared with the local-density approximation for an impurity calculation. In general, the local-density approximation is closer to the exact solution. Some general features of the density-functional formalism are illustrated.

Rigorous statistical procedures for data from dynamical systems

Abstract: Various questions about the invariant measures of a dynamical system can be answered by computations of regular functionals or by ranking methods based on a set of observations. This includes symmetry tests and the determination of dimension coefficients. The paper contains the theoretical results and several simulations explain the methods.

Energy dependence of protein translocation into chloroplasts

Abstract: The translocation of in vitro synthesized precursor proteins into intact spinach chloroplasts was investigated with respect to its energy requirement. It was demonstrated that MgATP itself, and not a transmembrane electrochemical gradient across the envelope membrane, promotes protein import. By manipulating the external and the stromal level of MgATP, we provided evidence that MgATP energized the protein import not within the chloroplast but at the outside of the envelope membrane. It is postulated that an MgATP-dependent phosphorylation/dephosphorylation cycle at the outer membrane face was involved in the course of protein translocation into the chloroplast.

The Denseness of the Far Field Patterns for the Transmission Problem

Abstract: On considere le probleme de diffusion dans un domaine ouvert Ω de R N ou N=2 ou 3, a frontiere C 2 connexe Γ et exterieur Ω e :=R N /Ω

Verification of a mathematical model by simulating potassium uptake from soil

Abstract: This work develops the mathematical models suggested by various authors to simulate nutrient uptake of plants from soil. The simulation is based on ion transport from the soil to the roots by mass flow and diffusion and on Michaelis-Menten kinetics of nutrient uptake from soil solution by plant roots. For this purpose a differential equation is numerically integrated. Inter-root competition is allowed for by the choice of the boundary conditions. The integration procedure used makes it possible to take into account a variable buffer power which depends on soil solution concentration. The model calculates the change of nutrient concentrations in soil as a function of distance from the root surface for preestablished periods of time. Furthermore, the rate of uptake and the quantity of nutrients taken up per cm of root length is obtained. If the growth function of the root is known, nutrient uptake of a growing root system can be calculated. In order to verify the model two experiments were made: It is therefore concluded that the theoretical conception of the model is realistic and that the parameters have correctly been measured. The model thus appears to be useful to simulate such aspects of nutrient uptake of plants from soil which cannot be measured.

Metabolic products of microorganisms. 234 urdamycins, new angucycline antibiotics from streptomyces fradiae

Abstract: The colored urdamycins A to F, six new angucycline antibiotics produced by Streptomyces fradiae strain Tu 2717, were detected by chemical screening. They are biologically active against Gram-positive bacteria and stem cells of murine L1210 leukemia. The urdamycins are glycosides and differ in their aglycones, which can be liberated by acidic hydrolysis besides the sugars D-olivose and L-rhodinose. The structure of the main compound, urdamycin A, follows from the spectroscopic and chemical data in connection with an X-ray analysis. The aglycone urdamycinone A is identical with aquayamycin. The structures of urdamycin B, E, F and partial structures of urdamycin C and D, will be presented in a subsequent paper. The new term "angucycline/angucyclinone" is used for an increasing group of related antibiotics.

Comments on a phylogenetic system of the Platyhelminthes

Abstract: Using the principles and methods of phylogenetic systematics, the phylogenetic relationships among the basic closed descendent communities (monophyla) of the taxon Platyhelminthes are discussed.

Quantification and characterization of high-affinity membrane receptors for tumor necrosis factor on human leukemic cell lines.

Abstract: The expression of specific membrane receptors for TNF-alpha was determined on various human leukemic cell lines differing in their sensitivity to the growth-inhibitory activity of TNF-alpha Binding studies with 125I-labelled TNF-alpha indicated specific binding in 8/10 cell lines with approximately 10-fold differences in the quantity of TNF-alpha bound by these distinct cell lines Scatchard analyses of TNF-binding revealed the existence of high-affinity membrane receptors (Kd 15 X 10(-10) M) and approximately 3,000 binding sites/cell on both U937 and K562, representing 2 cell lines with high and low TNF sensitivity, respectively Disuccinimidyl-suberate cross-linking of receptor-bound 125I-TNF-alpha and SDS-PAGE of membrane preparations of either U937 or K562 cells suggest a single receptor protein with an apparent molecular weight of 76 kDa Comparison of the TNF-alpha binding capacity versus in vitro growth inhibition provides evidence that sensitivity to TNF-alpha is determined both at the level of receptor expression and at a post-receptor level IFN-gamma strongly enhanced the TNF-alpha-mediated growth inhibition of 3 sensitive cell lines, but had no effect on 7 other leukemic cell lines with little or no TNF sensitivity No correlation was found between this enhancement of TNF sensitivity and the IFN-gamma-mediated increase in TNF-cell membrane receptors, suggesting that IFN-gamma predominantly exerts its synergistic effect distal to TNF-binding

Availability of phosphate and potassium as the result of interactions between root and soil in the rhizosphere

Abstract: A number of findings are summarized in order to show the significance of individual plant properties and soil factors on the availability of phosphate and potassium to plants growing in soil. The flux of a nutrient into a given plant root depends directly on the concentration of the nutrient in the adjacent solution. In nutrient solution, P and K influx follows Michaelis-Menten kinetics. Almost maximum rates of influx have been observed in the range of soil solution concentrations usually found in German arable soils. Roots exhaust P and K from solutions to about 0.2 μmol P and 1 μmol K 1−1 if not replenished. At the root surface P and K concentrations in soil decrease rapidly within one day; small changes occur after this period. Initially, the extent of the depletion zone is very small but it extends radially with time. After the initial phase therefore, P and K supply to the plant depends on transport from more remote parts of the soil and also on release from undissolved sources. The degree of depletion and the extent of the depletion zone are related to the diffusion coefficient; they decrease with increasing clay content of soil. Root hairs penetrate the soil and extend the volume of soil supplying nutrients to a unit of root. P and K influx therefore increase with the length of root hairs. Proton release of roots mobilize P and K in soil. This is clearly detected by the HCl-soluble P and K fractions within 2 mm of the root surface. The activity of acid and alkaline phosphatases strongly increase in the soil in the vicinity of the root surface of several plant species. It is supposed that organic P compounds can therefore be utilized by plants. P and K influx per unit of root length and root length per unit of shoot weight differed widely between species. The product of these two parameters however was closely related to the P and K concentration of the shoots. Calculations from a mathematical model were in good agreement with measured K depletion profiles and K uptake by plants. It is therefore concluded that the main factors influencing the P and K availability of plants growing in soil have been accounted for in the mathematical model and that the parameters have been accurately measured. Pflanzenverfugbarkeit von Phosphat und Kalium als Ergebnis von Wechselwirkungen zwischen Wurzeln und Boden in der Rhizosphare Es werden eine Reihe von Ergebnissen herangezogen, um die Bedeutung einzelner Pflanzeneigenschaften und Bodenfaktoren fur die Pflanzenverfugbarkeit von Phosphat und Kalium darzustellen. Der Flux eines Nahrstoffs in die Wurzel hangt von der Konzentration der umgebenden Losung ab. In Nahrlosungen folgt die p-und K-Aufnahme der Michaelis-Menten-Kinetik. Die P- und K-Konzentration der Bodenlosung deutscher Ackerboden fuhrt haufig zu annahernd maximalen Aufnahmeraten. Die Wurzeln erschopfen die Losungen auf etwa 0,2 μmol P und 1 μmol K1-1, wenn sie nicht erganzt werden. In der Wurzelumgebung wird der Boden ebenfalls weitgehend entleert. Die raumliche Ausdehnung der Verarmungszone betragt jedoch nur wenige mm. Innerhalb eines Tages sinkt die Konzentration rasch ab; danach andert sie sich nur noch wenig, die Verarmungszone dehnt sich jedoch in radialer Richtung aus. Die Versorgung der Wurzeln hangt demnach vom Transport aus entfernteren teilen des Bodens sowie von der Freisetzung aus ungelosten Vorraten ab. Der Grad der Verarmung und die Ausdehnung der Verarmungszone nimmt mit dem Tongehalt des Bodens ab. Wurzelhaare durchdringen den wurzelnahen Boden und vergrosern den Einzugsbereich der Einzelwurzeln. Der P- und K-Influx verschiedener Pflanzenarten steigt daher pro Einheit Wurzel mit der Lange der Wurzelhaare an. Protonen-Abgabe der Wurzeln fuhrte zur Mobilisierung der P- und K-Vorrate. Dies ist an der Anderung der HCL-loslichen Fraktion des Bodens bis zu 2 mm Entfernung von der Wurzel deutlich nachzuweisen. Die Aktivitat der sauren und alkalischen Phosphatase weist im wurzelnahen Boden verschiedener Pflanzenarten eine starke Erhohung auf. Es wird angenommen, das die Pflanzen dadurch auch organische P-Verbindungen ausnutzen konnen. Pflanzenarten unterscheiden sich erheblich im P- und K-Influx je Einheit Wurzellange und in der Wurzellange je Gewichtseinheit Spros. Das Produkt dieser beiden Eigenschaften korreliert jedoch sehr eng mit dem P- und K-Gehalt des Sprosses; ihr Anteil an der P- und K-Versorgung ist demnach sehr unterschiedlich. Modellrechnungen haben gezeigt, das sowohl die K-Verarmungsprofile im wurzelnahen Boden als auch die von den Pflanzen aufgenommenen Kaliummengen mit den durch Messung erhaltenen Werten gut ubereinstimmen. Demnach sind von den Faktoren, die die Pflanzenverfugbarkeit von P und K bestimmen, die wichtigeren berucksichtigt und ihre Parameter zutreffend gemessen worden.

Lack of evidence for involvement of known human retroviruses in multiple sclerosis

Abstract: The recent report by Koprowski et al that human T-cell lymphotropic retroviruses (HTLVs) may be involved in the development of multiple sclerosis (MS) has aroused much interest The report was based largely on immunological evidence, using enzyme-linked immunosorbent assays (ELISAs) with viral antigens or disrupted virions We have accordingly sought confirmation by screening sera and cerebrospinal fluid (CSF) samples from MS patients against cell lines infected respectively with adult T-cell leukaemia (ATL) virus (ATLV/HTLV-I) of Japanese cells (MT-1 and MT-2 lines), our own isolate from British black patients with ATL, the MoT cell line which produce HTLV-II, and our own T-cell line containing a local isolate of acquired immune deficiency syndrome (AIDS) virus (C-LAV/HTLV-III) We have failed to find antibodies against these retroviruses in the sera or CSF Furthermore, neither virus could be isolated from the peripheral white blood cells of two MS patients

Localization of endogenous lectins in normal human breast, benign breast lesions and mammary carcinomas.

Abstract: Specific antisera against three mammalian β-galactoside-specific lectins of apparent molecular weights 14.5 kDa, 18 kDa and 29 kDa have been used to localize these lectins in normal breast, and in benign and malignant mammary lesions. In normal breast tissue discrete localization of two lectins (Mrs 14.5 kDa and 18 kDa) was demonstrated in fibroblasts, smooth muscle cells, myoepithelial cells and capillary endothelium. Extracellular localization of one lectin (Mr 14.5 kDa) in collagen was apparent. The third lectin (Mr 29 kDa) labelled preferentially luminal cells and their secretory product. Two benign tumours (an analyzed fibroadenoma and a papilloma) revealed strong staining with two lectins (Mrs 18 kDa and 29 kDa). Of the 24 mammary carcinomas examined, the lectin (Mr 14.5 kDa) was expressed by only occasional tumour cells, the lectin (Mr 18 kDa) occurred in many tumour cells and the lectin (Mr 29 kDa) labelled tumour cells in nearly all cases. The expression of these β-galactoside-specific endogenous lectins therefore appears to be regulated differently in normal breast compared with mammary tumours.

Cleavage of immunoglobulins by pathogenic yeasts of the genus Candida.

Abstract: The yeast-like fungi Candida albicans and Candida tropicalis are opportunistic pathogens which are distinguished from less virulent yeasts by the secretion of acid proteases. Candida proteases cleave various human immunoglobulins including IgA2 and secretory immunoglobulins. They cover a wider range of substrates than bacterial IgA-proteases, and possibly play a role in the pathogenesis of thrush and deep candidosis.

Die Rolle der Bodenversauerung beim Waldsterben: Langfristige Konsequenzen und forstliche Möglichkeiten

Abstract: Die Ursachen der Bodenversauerung werden diskutiert. Die auf allen Standorttypen mit Ausnahme kalkskeletthaltiger Kalkverwitterungsboden und Geschiebemergel in Fallstudien angetroffene starke tiefgrundige Versauerung wird auf die saure Deposition zuruckgefuhrt. Die forstlichen Moglichkeiten zur Verringerung der okosysteminternen Saureproduktion, zur Behebung akuter versauerungsbedingter Ernahrungsstorungen, zur Vertiefung des potentiellen Wurzelraums und zur Begrundung von Waldokosystemen, die ohne saure Deposition stabil mit hoher Elastizitat sein konnen, werden diskutiert.

Diagnosis of genetic disease using recombinant DNA.

Abstract: Recombinant DNA technology promises to make an important contribution to the analysis and diagnosis of inherited human disease. Direct detection and analysis of various genetic defects at the DNA level are now possible using cloned gene or oligonucleotide probes. In addition, the use of restriction fragment length polymorphisms associated with linked DNA segments should permit not only the diagnosis of hitherto undetectable disease states but also the chromosomal localization of the loci responsible. The eventual isolation of disease loci should lead to a better understanding of the molecular basis of inherited disease.