Beiträge zur Ökologie des Aphano-Matricarietum Tüxen 1937

Zusammenfassung 1. An Hand von 101 Aufnahmen wird das Aphano-Matricarietum typicum and scleranthetosum im Unteren Eichsfeld in eine typische, eineRanunculus repens-, eineGnaphalium uliginosum-und eineJuncus bufonius-Variante gegliedert.2. Durch Bestimmungen des Bodenwassergehaltes und des pflanzenverfügbaren Wassers sowie durch Berechnung des W-Wertes nachEllenberg wird die Reihe der Varianten als Reihe zunehmender Feuchtigkeit charakterisiert.3. Bei zunehmender Dichte des Getreidebestandes nehmen die dominierenden Unkräuter stark ab, die schwach deckenden Unkräuter dagegen zu.4. Aus den Deckungswerten der soziologischen Tabelle werden Konkurrenzwirkungen zwischenMatricaria chamomilla, Aphanes arvensis undStellaria media belegt.

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Summary 1. In two subassociations of a weed community (Aphano-Matricarietum typicum and scleranthetosum) 101 relevés are used for distinguish three subunits: a var. ofRanunculus repens, ofGnaphalium uliginosum and ofJuncus bufonius.By estimating the water contents and pF values of the soil and by calculating the water figure afterEllenberg this series of subunits is shown to be a series of increasing humidity.2. With increasing density of the cereal grasses, the stronger dominant weeds decrease, while the weaker ones increase.3. A method is described to calculate competition between the dominant weeds from the figures of the sociological relevés. Interactions have been found betweenMatricaria chamomilla at the one side andAphanes arvensis andStellaria media at the other side and vice versa.

     

Glutamatdehydrogenase im photosynthetischen Bakterium Rhodospirillum rubrum

Zusammenfassung Glutamatdehydrogenase wurde aus Rhodospirillum rubrum durch Fällung mit Ammoniumsulfat und Chromatographie an DEAE-Cellulose 35 fach angereichert. Das Enzym ist spezifisch auf NAD als Wasserstoffdonator/acceptor und -Ketoglutarat bzw. Glutamat. Hg-Ionen blockieren die Reaktion in beiden Richtungen; Nitrit- und Nitrationen hemmen in höheren Konzentrationen. Die Abbaurate wird durch die Anwesenheit von ATP verringert. Die Stickstoffquelle des Nährmediums wirkt sich nur wenig auf die Ausbildung des Enzyms in den Zellen aus, dagegen wird durch Produkthemmung im natürlichen Milieu bei Wachstum auf Malat und NH₄ ⁺ der Glutamatabbau praktisch unterdrückt.

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Glutamate dehydrogenase from the photosynthetic bacterium Rhodospirillum rubrum

Summary Glutamate dehydrogenase from Rhodospirillum rubrum was purified 35 fold by ammonium sulfate precipitation and chromatography on DEAE-cellulose. The enzyme is specific for NAD as hydrogen donor/acceptor and -ketoglutarate and glutamate for the synthesis, respectively the degradation of the amino acid. Hg²⁺ ions completely inhibit both synthesis and degradation; a weaker inhibition can be shown by addition of various inorganic nitrogen compounds. The rate of the glutamate degradation is reduced by ATP. The nitrogen source of the culture medium is without effect on the formation of the glutamate dehydrogenase, however, under growth conditions in a malate-NH₄ ⁺-solution the glutamate degradation is almost completely suppressed by product inhibition.

     

Carboxylierungsreaktionen in Agaricus bisporus III. Pyruvat und Phosphoenolpyruvat als CO2-Acceptoren

Zusammenfassung Zellfreie Extrakte aus Agaricus bisporus bilden Malat, Fumarat und Aspartat einerseits aus Pyruvat und CO₂ in Gegenwart von Mn²⁺ und andererseits aus Phosphoenolpyruvat und CO₂ in Gegenwart von Mg²⁺.Die Carboxylierung von Pyruvat wird durch ATP und NADPH₂ deutlich gefördert, ist aber unabhängig von der Anwesenheit von CoA-Estern. Die Reaktion erfährt durch pCMB, Oxalat und Avidin eine Hemmung.Die Carboxylierung von Phosphoenolpyruvat wird durch ADP, nicht aber durch GDP und IDP gefördert.Aus den Ergebnissen wird geschlossen, daß bei der Carboxylierung von Pyruvat sowohl Pyruvatcarboxylase als auch Malatenzym wirksam sind, während für die Oxalacetatsynthese aus Phosphoenolpyruvat PEP-Carboxykinase verantwortlich ist.Die Bedeutung der drei Enzyme im Zusammenhang mit der Ernährung des Kulturchampignons aus dem natürlichen Substrat, mit der Glucogenese und der Steuerung des Citronensäurecyclus wird diskutiert.

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Carboxylation reactions in Agaricus bisporus III. Pyruvate and phosphoenolpyruvate as CO₂-acceptors

Summary Cell-free extracts from Agaricus bisporus catalyze the synthesis of malate, fumarate and aspartate from pyruvate and CO₂ in the presence of Mn²⁺, and from phosphoenolpyruvate and CO₂ with Mg²⁺ (partially replaceable by Mn²⁺).The carboxylation of pyruvate is highly stimulated by ATP and NADPH₂, but is not affected by CoA-esters. The reaction is inhibited by pCMB, oxalate and avidin.The carboxylation of phosphoenolpyruvate is stimulated by ADP, but not by IDP and GDP.From cofactor-requirement and inhibitor studies it is concluded, that there are two enzymes, pyruvatecarboxylase and malic enzyme, which catalyze the carboxylation of pyruvate. Phosphoenolpyruvate carboxykinase is responsible for the CO₂-fixation into oxaloacetate.The significance of these three enzymes is discussed in connection with the nutrition of the fungus from its natural growth substrate and with the regulation of glycogenesis and the citric acid cycle.

     

Luciferin derivatives in bioluminescence-enhanced enzyme immunoassays

Ultrasensitive bioluminescence immunoassays for the determination of peptides and proteins (illustrated with human urinary kallikrein, bradykinin and the determination of human urinary kallikrein antibody titres) have been developed. The usable ranges of the standard curves are from 5 pg to 5000 pg per litre. The relative intra-assay coefficients of variation of the tests were between 2% and 6%, and the inter-assay coefficients of variation between 4% and 12%.     

Comparison of Transmitter Amino Acid Levels in Rat Globus Pallidus and Neostriatum During Hypoglycemia or After Treatment with Methionine Sulfoximine or γ-Vinyl γ-Aminobutyric Acid

The levels of amino acids in globus pallidus, a structure heavily innervated with gamma-aminobutyric acid (GABA)-ergic terminals but few glutamergic terminals, were compared with the levels in neostriatum, a structure richly innervated with glutamergic terminals but intermediate in GABAergic terminals. The level of glutamate in neostriatum was twice as high as in globus pallidus whereas the level of GABA in globus pallidus was three times higher than in neostriatum. The level of aspartate was similar in both regions whereas the level of glutamine was correlated with the level of glutamate. Methionine sulfoximine, a glutamine synthetase inhibitor, reduced the level of glutamine to 10-20% of control in both structures. This reduction was accompanied by the largest decrease in the level of glutamate in neostriatum, indicating that transmitter glutamate turns over more rapidly than other glutamate pools. Likewise, insulin decreased the levels of glutamate and glutamine more in neostriatum than in globus pallidus. gamma-Vinyl GABA increased the level of GABA in globus pallidus more than in neostriatum although the percent increase was largest in neostriatum. Treatment with gamma-vinyl GABA was accompanied by a large reduction in the level of GABA, indicating that a substantial proportion of the glutamine pool is linked to GABA metabolism.     

City spore concentrations in the European Economic Community (EEC). VI. Poaceae (Grasses), 1982–1986

Summary Airborne grass-pollen concentrations in six cities in the EEC are compared, based on observations from five years, 1982–1986. Results show that there are quantitative differences both between the monitoring stations and between the years. Very provisionally, the average seasonal total of the European urban airborne grass-pollen concentration can be put at 4 to 5000 per m³ of air. Also qualitatively, regarding the seasonal fluctuations, there are differences between the stations, and between the years. Generally, the results confirm that June is the most typical grass-pollen month in northwestern Europe, whereas in mediterranean Europe May is the more prominent grass-pollen period. There seems to be little coherence between the starting dates of the grass-pollen season even at relatively nearby stations in northwestern Europe, suggestive for a great influence of the actual weather situation.     

Characterization of Cellular Transport, Subcellular Distribution, and Secretion of the Neurotoxicant 1-Methyl-4-Phenylpyridinium in Bovine Adrenomedullary Cell Cultures

Cultures of bovine adrenomedullary chromaffin cells accumulated 1-[methyl-3H]methyl-4-phenylpyridinium ([3H]MPP+) in a time- and concentration-dependent manner with an apparent Km of 0.7 microM and a Vmax of 3 pmol/min/10(6) cells. The uptake was sodium dependent and sensitive to inhibitors of the cell-surface catecholamine transporter. At low concentrations of MPP+, the subcellular distribution was identical to that of endogenous catecholamines in the catecholamine-containing chromaffin vesicles. However, at a higher concentration of MPP+, a larger proportion of the toxicant was recovered in the cytosolic fraction, with less in the chromaffin vesicle fractions. When cells were prelabeled with [3H]MPP+, at 1 and 300 microM, and then permeabilized with digitonin in the absence of Ca2+, there was a proportionally greater release of MPP+ from the cells labeled at the higher concentration of the toxicant. In the presence of Ca2+, cell permeabilization induced a time-dependent secretion of catecholamines and a parallel secretion of MPP+. Under these conditions, the secretion of endogenous catecholamines was unaffected by the presence of MPP+. When the permeabilization studies were carried out in the presence of tetrabenazine, a massive release of MPP+ was observed in the absence of Ca2+ and was not further increased by Ca2+. In intact cells prelabeled with 300 microM [3H]MPP+, the secretagogues nicotine and veratridine elicited a Ca2+ -dependent secretion of catecholamines and MPP+ from the cells in similar proportions to their cellular contents. Barium-induced release of both species was independent of external Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)