First reaction of riboflavin biosynthesis —Catalysis by a guanosine triphosphate cyclohydrolase from yeast

An enzyme that uses GTP as a substrate for the formation of formate and a 2.4.5-triamino-6-hydroxypyrimidine derivative has been determined in the riboflavin overproducing yeast Pichia guilliermondii. In rib 1 mutants this enzyme is absent. This implies an involvement of the enzyme in the riboflavin biosynthesis and indicates that GTP is a purine precursor of riboflavin. Some properties of the GTP cyclohydrolase (substrate specificity, pH and temperature optima, activators and inhibitors, molecular weight, stability) were studied using a partly purified enzyme preparation. Cells grown under riboflavin overproducing conditions (iron deficiency) have 20–40-fold increased enzyme activity as compared with non-overproducing cultures (supplemented with iron).Non-Standard Abbreviations RF riboflavin - DHRiboyslAP £ 2.5-diamino-6-hydroxy-4-(1-d-ribosylamino)pyrimidine-5-phosphate - DHRibitylAP 2.5-diamino-6-hydroxy-4-(1-ribitylamino)pyrimidine - neopterin 6-(trihydroxypropyl)pterin - DMP 6.7-dimethylpterin - Fe iron deficient condition - +Fe supplemented with iron     

Peptides isolated from human liver with specific inhibitory effects on reassociation/reactivation of in vitro dissociated lactic dehydrogenase (LDH-M4 and −H4) isozymes

Two different peptides have been purified from human liver, similar to those previously reported (Schoenenberger, G.A., and Wacker, W.E.C. (1966) Biochemistry 5, 1375–1379) to be present in human urine, which may serve as metabolic regulators of lactate dehydrogenase (EC 1.1 1.27) isoenzymes (LDH-M₄ = muscle type; LDH-H₄ = heart type). By trichloroacetic acid precipitation, ultrafiltration, Sephadex G-25 and Bio-Gel P-2 columns, affinity chromatography on immobilized LDH-isozymes and HPLC two peptides which differed with respect to molecular weight, retention on the affinity columns and amino acid composition were isolated. No effect was observed when native, tetrameric lactate dehydrogenase was incubated with these peptides. However, when lactate dehydrogenase was dissociated to monomers at low pH and allowed to reassociate by adjusting the pH to 7.5 complete inhibition of the reactivation occurred when the inhibitors were incubated together with respective reassociating monomeric isozymes. The two peptides showed no cross-specificity, i.e. each peptide exhibited inhibitory activity only on one of the two isozymes LDH-M₄ or LDH-H₄. From the amino acid analyses, gel-filtration and PAGE + SDS, molecular weight of 1800 for the M₄ and ≈2700 for the H₄ inhibitor were calculated. An apparent K_i of ≈3 × 10^?5 mM for the H₄ and ≈7 × 10^?5 mM for the H₄ inhibitor was estimated. The interaction of the inhibitors with the enzyme system showed strong cooperativity with Hill coefficients of 2.9 (LDH-M₄-specific) and 2.4 (LDH-H₄-specific). Mathematical modelling of the reassociation and reactivation of lactate dehydrogenase and its specific inhibition by the peptides led to the conclusion that the peptides reacts with monomers, dimers or a transition state during the tetramerisation process. k₁ for the dimerisation step of M₄ = 2.0 × 10⁵ M^?1 · s^?1 and of H₄ = 8.2 × 10⁴ M^?1 · s^?1; k₂ for the tetramerisation step of M₄ = 2.8 × 10⁵ M^?1 · s^?1 and of H₄ = 1.2 × 10⁵ · M^?1 · s^?1, were calculated, the second step still being the faster one.     

[3H] Diazepam Displacing Activity in Human Cerebrospinal Fluid

Pooled human cerebrospinal fluid was separated by Sephadex G-50 chromatography. The presence of three peaks, A, B and C, was demonstrated by monitoring absorbance at 254 and 280 nm. All peaks showed [3H]diazepam displacing activity in the membrane receptor test. Peak B was further separated on Bio-Gel P-4. At least two major fractions free of salt and GABA in the molecular weight range of approximately 700--3600 were shown to displace [3H]diazepam in the receptor test. This activity was enhanced by a factor of 3 in the presence of 10 microM-GABA.     

Episodic secretion of opioid activity in human plasma and monkey CSF: Evidence for a diurnal rhythm

Using a radioreceptor assay, opioiod activity has been determined in human plasma and monkey CSF at two-hour intervals across a 24-hour period. In both human plasma and monkey CSF, opioid activity showed an episodic secretion and a significant variation over time, suggesting a diurnal rhythm with increased levels in the morning. This rhythm is similar to those of adrenocorticotropin and beta-lipotropin (LPH) and reciprocal to the diurnal rhythm of pain sensitivity.     

An improved method for two-dimensional gel-electrophoresis: Analysis of mutationally altered ribosomal proteins of Escherichia coli

Summary An improved method for the two-dimensional electrophoretic analysis of ribosomal proteins on acrylamide gel slabs has been developed by combining the procedures for the first dimension of Mets and Bogorad (1974) and for the second dimension of Kaltschmidt and Wittmann (1970) and by introducing several modification. Ribosomal proteins of various Escherichia coli mutants have been analyzed by the new method. Advantages are that (1) it requires only small amounts of protein (100–200 g 70S ribosomal proteins), (2) reproducibility is very high, and (3) it makes it easier to identify mutational alterations in proteins S10, L4, L10, and L21 which hardly migrate out of the sample gel with our previous electrophoresis procedure. Furthermore, the new method can be nicely adapted to analysis of the ribosomal proteins from other organisms, such as Bacilli or yeast.     

Die Spermiohistogenese des Süßwasser-Ostracoden Notodromas monacha O. F. Müller

Zusammenfassung Die Frühstadien der Spermiohistogenese des Süßwasser-Ostracoden Notodromas monacha, ovale und spindelförmige Spermatiden, werden phasen- und elektronenoptisch untersucht. Die ovalen Spermatiden sind gekennzeichnet durch das Auftreten von Caryomeren, die zu einem einheitlichen Nucleus verschmelzen, und durch die Zusammenlagerung aller Mitochondrien zu einem Nebenkern, aus dem sich zwei Derivate differenzieren. Die spindelförmigen Spermatiden gehen aus den ovalen hervor, indem Kern und Nebenkern-Derivate sowie die Zelle selbst Spindelform annehmen. Der Kern ist durch drei hinsichtlich ihrer Größe und Lage unterschiedliche granuläre Körperchen und einen von einer Doppelmembran umgebenen Bezirk ausgezeichnet. Ein Centriol konnte bisher nicht nachgewiesen werden.

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The spermiogenesis of the fresh-water ostracod Notodromas monacha O.F. Müller

Summary In Notodromas monacha the early stages of the spermiohistogenesis (oval and spindle-like spermatids) have been studied by means of phase contrast and electron microscopy. Oval spermatids are marked by the presence of caryomeres, which during development fuse to form a single nucleus. All mitochondria are accumulated in a Nebenkern which is differentiated into two derivatives. The nucleus, the Nebenkern-derivatives and the cell body become spindle-shaped and thereby the oval spermatids are transformed to spindleshaped spermatids. The nucleus of the spindle-shaped forms is characterized by three granulated particles (different in size and position) and by a double-membrane bounded region. No centriole has been found in this study.

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Für die Anregung zu diesen Untersuchungen sowie für Förderung und Diskussion danke ich meinem Lehrer, Herrn Professor Dr. Dr. h. c. W. E. Ankel.     

Zum Assimilattransport in wachsende Früchte von Phaseolus vulgaris

Zusammenfassung Nach ¹⁴CO₂-Assimilation im Blatt wurde der Eintransport markierter Assimilate in wachsende Früchte von Phaseolus vulgaris histoautoradiographisch untersucht. Die ¹⁴C-markierten Substanzen werden danach im Phloem der Fruchtstiele transportiert, in keinem Falle konnte eine Assimilatleitung in anderen Geweben des Fruchtstiels bemerkt werden. Hierzu im Widerspruch stehende Befunde von Bachofen und Wanner werden diskutiert.

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On the translocation of assimilates into ripening fruits of Phaseolus vulgaris

Summary Leaves of fruiting plants of Phaseolus vulgaris were exposed to ¹⁴CO₂ in the light. The movement of ¹⁴C-labelled assimilates from these leaves into the growing fruits was studied by histoautoradiography (dry technique). The fact that ¹⁴C-activity could be detected within the fruit stalks exclusively in the areas of the phloem may favor the hypothesis that also in this case assimilates are transported only via the phloem. The xylem was always free of ¹⁴C. The contradictory results of Bachofen and Wanner are discussed.

     

Ein flavobacterium (Flavobacterium buchneri n. sp.) als endosymbiont zweier sauginfusorien

Zusammenfassung Die beiden auf verschiedenen Hydrophiliden lebenden Sauginfusorien Discophrya speciosa Lachmann und D. guilcherae Matthes beherbergen in ihrem Endoplasma zahllose Bakterien. Die gram-negativen Keime sind häufig paarweise aneinandergelagert und an ihren freien Enden zumeist zugespitzt. Auf der Oberfläche gallertiger Nährböden wachsen sie als runde, glänzende Kolonien von intensiv gelber Farbe. Auch extreme Schleimbildung tritt auf. Während die aus den Wirten direkt freigesetzten Stäbchen unbeweglich sind, zeigen die kultivierten Keime peritriche Begeißelung und Beweglichkeit. Aus dem reichen Material wurden zwei Stämme ausgewählt (A 1=D. speciosa, A 2=D. guilcherae), die zwar Größendifferenzen zeigen, aber in ihren biochemischen Leistungen (Bunte Reihe) völlig übereinstimmen. Die identischen Keime gehören dem. Genus Flavobacterium an. Wir nennen den neuen Organismus Flavobacterium buchneri n. sp. Der obligate Charakter der Besiedlung zwingt zur Annahme eines symbiontischen Verhältnisses zwischen den Partnern. Die biochemischen Befunde geben leider keinen Hinweis für das Motiv der Symbiose. Es ist wohl im ernährungsphysiologischen Bereich zu suchen. Da D. speciosa und D. guilcherae eng miteinander verwandt sind, darf man annehmen, daß bereits ihre Stammform mit unserem Flavobacterium in Symbiose lebte. Bei deren Erstbesiedlung müssen die Keime mit dem Beuteplasma in das räuberische Sauginfusor gelangt sein. Die Weitergabe der Symbionten an die Nachkommenschaft ist durch den Knospungsmodus zwangsläufig gewährleistet.

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Summary The two infusorian Suctoria Discophrya speciosa Lachmann and D. guilcherae Matthes, which live on various Hydrophilidae, contain numerous bacteria in their endoplasm. The gram-negative bacteria frequently arrange themselves in pairs with their free ends, in the majority of cases, tapered to points. They grow on the surface of the gelatinous culture medium as round shiny colonies which have an intense yellow color. An extreme formation of slime also occurs. The rods which are liberated from the host directly are non-motile while the cultivated bacteria show peritrich flagellation and motility. Two strains were selected from an abundance of material (A 1=D. speciosa and A 2=D. guilcherae) and they showed size differences; however, they were completely identical in their biochemical behavior. The identical bacteria belong to the genus Flavobacterium. We have named the new organism Flavobacterium buchneri n. sp. The obligate character of the infection forces us to assume that a symbiotic relationship exists between the partners. Unfortunately, the biochemical findings give no indication for the motive of the symbiosis. One probably has to look for the reason in the sphere of nutrition physiology. Since D. speciosa and D. guilcherae are closely related one may assume that their primitive ancestor already had a symbiotic relationship with our Flavobacterium. By the preceding we mean that the first infection takes place or occurs when the infusorian Suctoria suck the plasma and bacteria from the prey. The continuation of the symbiosis in the progeny is inevitably guaranted through the method of budding.

     

Assimilations- und Atmungsmessungen an diploiden und polyploiden Zuckerrüben

Ohne ZusammenfassungAuszug aus der Dissertation, Darmstadt 1956. —Meinem verehrten Lehrer, Herrn Prof. Dr.O. Stocker möchte ich für die Überlassung der Arbeit ebenso herzlich danken wie Herrn Prof. Dr.E. Knapp für seine Anregungen und Unterstützungen, sowie die Bereitstellung des Saatgutes.     

Die selektive Blockierung eines an der Blühinduktion beteiligten Ribosenucleinsäure-Eiweisssystems durch 2-Thiouracil (Untersuchungen anStreptocarpus wendlandii)

Ohne ZusammenfassungMit 9 TextabbildungenMeinem verehrten Lehrer, Herrn Prof. Dr.F. Oehlkers, danke ich für sein lebhaftes Interesse am Fortgang der Arbeit, für die Überlassung von Pflanzenmaterial und Kulturraum in den Gewächshäusern. Die Untersuchungen wurden zum Teil mit Mitteln der Deutschen Forschungsgemeinschaft durchgeführt, der ich hierfür ebenfalls Dank schulde.