Chain length-dependent association of distamycin-type oligopeptides with A·T and G·C pairs in polydeoxynucleotide duplexes

Different binding affinities of various distamycin analogs including the deformylated derivative with poly(dA-dC)·poly(dG-dT) were investigated using CD measurements. The inhibitory effect of distamycins on the DNAase I cleavage activity of DNA duplexes strongly supports the binding data. The base specificity of the ligand interaction with duplex DNA depends on the chain length of distamycin analogs. Netropsin, distamycin-2 and the deformylated distamycin-3 show no binding to dG·dC containing sequences at moderate ionic strength and are classified as highly dA·dT specific. In contrast distamycin having three, four or five methylpyrrolecarboxamide groups also forms more or less stable complexes with dG·dC-containing duplexes. These ligands possess a lower basepair specificity. The correlation between binding behavior and oligopeptide structure shows that presence of the number of hydrogen acceptor and donor sites determines the basepair and sequence specificity. The additional interaction with dG·dC pairs becomes essential when the number of hydrogen acceptor sites exceeds n = 3.     

Dynamics of the cytoskeleton in Amoeba proteus

Fluorescein-labeled muscle actin was microinjected into Amoeba proteus and followed during intracellular redistribution by means of the image-intensification technique. The fully polymerization-competent protein becomes part of the endogenous actomyosin system undergoing dynamic changes over time periods of several hours. Single-frame analysis of long-term sequences enabled the direct demonstration of both the contractile activities and morphological transformations of microfilaments in normally locomoting, immobilized and phagocytozing specimens. In normally locomoting cells the filament layer undergoes continuous changes in spatial distribution depending on the actual pattern of cytoplasmic streaming and cell shape. The highest degree of differentiation is always maintained in the intermediate region between the front and the uroid, thus indicating this segment of the cortex to be the most important site in generating motive force for pseudopodium formation and ameboid movement. In immobilized cells contracted by the application of ruthenium red or relaxed by different anesthetics, the filament layer forms a continuous thick sheath beneath the cell surface or becomes completely disintegrated. In phagocytozing cells the local polymerization of actin at the tip of pseudopodia forming the food-cup and around the nascent phagosome points to a significant participation of the actomyosin system in the process of capturing and constricting prey organisms. Although our results provide clear evidence for the overall importance of motive force generation according to the hydraulic pressure theory, some motile phenomena exist in Amoeba proteus that cannot exclusively be explained by this mechanism.     

Stimulation by 6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate and glucocorticoids of phosphoenolpyruvate carboxykinase in the isolated perfused rat liver (Short Communication)

Dibutyryl cyclic AMP stimulated the activity of phosphoenolpyruvate carboxykinase in perfused livers of rats, fed on a low-protein diet, linearly over a 6h period. The enzyme activity was also significantly elevated by dexamethasone, the effect being considerably lower than that of the cyclic nucleotide. Since the time-course of phosphoenolpyruvate carboxykinase activity in response to dibutyryl cyclic AMP resembled that observed after dibutyryl cyclic AMP injection into intact animals, it is suggested that induction of the enzyme in vivo is due to a direct action of the cyclic nucleotide on the liver. Combined administration of dibutyryl cyclic AMP and glucocorticoids did not lead to an additive increase of liver phosphoenolpyruvate carboxykinase activity, either in vivo or in the perfused organ.     

Über den Einfluß der Vorbelichtung auf die anschließende Phosphorylierung im Dunkeln bei einzelligen Grünalgen (Ankistrodesmus braunii)

Zusammenfassung Wird einzelligen Algen (Ankistrodesmus braunii) nach Vorbelichtung in anschließender Dunkelheit ³²P-markiertes Phosphat geboten, so tritt gegenüber Dauerdunkel eine erhebliche Förderung der ³²P-Einlagerung auf. Die nach Vorbelichtung bestimmte Markierung der aufgetrennten Phosphatfraktionen ähnelt sehr derjenigen im Dauerlicht. Die erhöhte Dunkelphosphorylierung nach Vorbelichtung hängt von der CO₂-Konzentration, von der Lichtintensität und der Zeit der Vorbelichtung ab. Unter den vorliegenden Bedingungen waren 7 min Vorbelichtung zur maximalen Förderung nötig. Die Halbwertzeit des Abklingens betrug etwa 4 min.Aus den Experimenten geht hervor, daß durch die Belichtung der Algen auch in vivo ein Zustand gebildet wird, der noch nach Belichtung eine Zeitlang im Dumkeln eine Erhöhung der ³²P-Einlagerung erlaubt.Es wird diskutiert, ob es sich einerseits um die Bildung einer im Licht reduzierten Substanz R handeln könnte, die für eine begrenzte Zeit in Dunkelheit noch einen cyclischen, mit Phosphorylierung gekoppelten Elektronentransport aufrechterhalten kann. Andererseits könnte durch die Vorbelichtung ein energiereiches Zwischenprodukt X _E — oder auch ein Protonenpool — gebildet werden, das bei dem Energietransfer vom Elektronentransportsystem zur ATP aufgebaut wird. Schließlich muß berücksichtigt werden, daß durch die Vorbelichtung an den Chloroplastenmembranen ein verstärkter ATP-Pi-Austausch zustande kommen könnte, der nach Belichtung nur langsam abklingt.

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Influence of preillumination on subsequent phosphorylation in the darkness of unicellular green algae (Ankistrodesmus braunii)

Summary Preilluminated unicellular green algae (Ankistrodesmus braunii) were treated in the subsequent darkness with ³²PO₄. The post-illumination dark incorporation was considerably increased compared with the control in continuous dark. The labeling of the separated phosphate-fractions was similar to that of continuous light. The light-induced dark incorporation depended from the light intensity as well as from the time of preillumination. A preillumination of 7 min was required for a maximal enhancement of this preillumination effect. On the other hand the effect diminished in darkness with a half life of approximately 4 min. Finally the enhancement was found to be greater in the absence of CO₂ than in the presence of CO₂.The experiments demonstrate the light-induced formation of a state in the algae, which permits the enhancement of ³²P-incorporation into several phosphate-fractions for a limited time during subsequent darkness.It is discussed, that this may be performed through the formation of a light-reduced substance R maintaining for a limited time a cyclic electron transport in darkness, coupled with phosphorylation. On the other hand it seems possible, that preillumination induces a high energy intermediate X _E—this could also be a pool of protons—formed in the course of energy-transfer from electron transport to ATP-formation. But we must consider also the possibility that light accellerates the ATP-Pi exchange on chloroplast-membranes for a time after preillumination.

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Abkürzungen ATP Adenosintriphosphat - ADP Adenosindiphosphat - Pi Orthophosphat - Poly-P anorganisches Polyphosphat - RNS Ribonucleinsäure - TCE Trichloressigsäure - 2,4-DNP 2,4-Dinitrophenol Stipendiat der Nishina-Gedächtnis-Stiftung (Japan) für 1963.     

Control of Mn status and infection rate by genotype of both host and pathogen in the wheat take-all interaction

Take-all is a world-wide root-rotting disease of cereals. The causal organism of take-all of wheat is the soil-borne fungus Gaeumannomyces graminis var tritici (Ggt). No resistance to take-all, worthy of inclusion in a plant breeding programme, has been discovered in wheat but the severity of take-all is increased in host plants whose tissues are deficient for manganese (Mn). Take-all of wheat will be decreased by all techniques which lift Mn concentrations in shoots and roots of Mn-deficient hosts to adequate levels. Wheat seedlings were grown in a Mn-deficient calcareous sand in small pots and inoculated with four field isolates of Ggt. Infection by three virulent isolates was increased under conditions which were Mn deficient for the wheat host but infection by a weakly virulent isolate, already low, was further decreased. Only the three virulent isolates caused visible oxidation of Mn in vitro. The sensitivity of Ggt isolates to manganous ions in vitro did not explain the extent of infection they caused on wheat hosts. In a similar experiment four Australian wheat genotypes were grown in the same Mn-deficient calcareous sand and inoculated with one virulent isolate of Ggt. Two genotypes were inefficient at taking up manganese and were very susceptible to take-all, one was very efficient at taking up manganese and was resistant to take-all, and the fourth genotype was intermediate for both characters. All genotypes were equally resistant under Mn-adequate conditions.     

Standing crop and mineral content of reed,Phragmites australis (Cav.) Trin. exSteudel,in Sweden—Management of reed stands to maximize harvestable biomass

The mean above-ground biomass of reed,Phragmites australis, in closed South Swedish stands was found to be 1 kg dry weight. m^?2 in August. Leaves, which are shed in the autumn in contrast to culms that remain standing, represent 26% of the total shoot weight. Because part of the culm will be covered by water, ice and snow 0.5 kg dry weight. m^?2 is available for winter harvest. Nutrient concentrations in shoots decrease throughout summer and winter. Although part of the maximal summer standing stock of N, P and K is lost in shed leaves, 55%, 75% and 80%, respectively, can potentially be recycled to rhizomes. Nitrogen fertilization and removal of standing litter in winter can increase above-ground biomass production in reed stands. Reed culms, cut in winter with agricultural machinery or amphibious harvesters, have been tested as a fuel for heating purposes in Sweden