Die Rolle der Fimbrien bei der eigenartigen Sternbildung von Agrobacterium luteum

Zusammenfassung Die bemerkenswerte Sternbildung von Agrobacterium luteum Stamm A61 (Moll et al., 1967; Ahrens, 1968) ist auf polare Fimbrien zurückzuführen, die um die Sternaggregate ausgebreitet sind. Es wird angenommen, daß sich Schwärmzellen an den Fimbrien verfangen und durch Kontraktion rasch zum Stern gezogen werden. Nach elektronenoptischen Präparaten sind die Fimbrien bis zu 10,5 lang und können die beobachtete Sternbildung gut erklären. Agrobacterium luteum Stamm B14 besitzt ebenfalls lange polare Fimbrien. Beide Stämme tragen peritriche Geißeln, deren Struktur sich deutlich von den dünnen und unregelmäßigen Fimbrien unterscheidet.

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The function of fimbriae in the peculiar star formation of Agrobacterium luteum

Summary The remarkable way of star formation in Agrobacterium luteum strain A61 (Moll et al., 1967; Ahrens, 1968) was found to be due to polar fimbriae which are spread around the star-shaped aggregates. It is assumed that swarmers adhere to the fimbriae and, by contraction, are swiftly pulled towards the star. As seen in electron microscopic preparations, the fimbriae are up to 10,5 long and may well explain the star formation observed. Agrobacterium luteum strain B 14 also possesses long polar fimbriae. Both strains have peritrichous flagella, the structure of which being clearly distinct from the delicate and irregular fimbriae.

     

Quantum Requirement for Photosynthesis in Chlorophyll-Deficient Plants with Unusual Lamellar Structures

Neither an over-all deficiency of chlorophyll, nor an increased enzymatic capacity for maximal rates, nor an unusual lamellar structure was found to change the number of quanta required for the evolution of one molecule of oxygen in healthy aurea mutants of tobacco. The average minimal quantum number remains 10 (efficiency 0.1) as in many algae and typical higher plants. Most of the time the optimal efficiency depends on the availability of some far-red radiation, particularly in the blue region of the spectrum where blue light alone is rather inefficient. These results fit an explanation offered earlier in connection with the hydrogen or acetate photometabolism of algae in far-red light.     

HPLC separation of the enantiomers of nicotine and nicotine-like compounds

A sensitive and reproducible HPLC method utilizing a commercially available chiral α₁-acid glycoprotein (AGP) phase has been developed to separate and quantify the enantiomers of nicotine. The method is suitable for routine use as indicated by column life. The quantification of (R/S:0.05/99.95)-nicotine or (R/S:99/1)-nicotine was possible. In addition, the separation or at least partial separation of the enantiomers of nornicotine and nornicotine-derived compounds was achieved. © 1993 Wiley-Liss, Inc.     

Presynaptic Nicotinic Receptors Stimulate Increases in Intraterminal Calcium of Chick Sympathetic Neurons in Culture

Abstract: Stimulation of chick sympathetic neurons in culture by the cholinergic agonists acetylcholine, nicotine, and 1,1-dimethyl-4-phenylpiperazinium (all at 10–1,000 µmol/L) induced concentration-dependent increases of free calcium levels measured by fura 2 fluorescence in neuronal processes. The response evoked by acetylcholine had both nicotinic and muscarinic components, whereas that induced by 1,1-dimethyl-4-phenylpiperazinium was purely nicotinic. Tetrodotoxin (0.3 µmol/L) blocked completely the increase of intraterminal free calcium level evoked by electrical stimulation. On the other hand, stimulation with 1,1-dimethyl-4-phenylpiperazinium still evoked 20–25% of the control response in the presence of tetrodotoxin. The concentration-response relationship of 1,1-dimethyl-4-phenylpiperazinium stimulation did not differ in the absence and in the presence of tetrodotoxin. The nicotinic antagonists d -tubocurarine (10 µmol/L) and mecamylamine (10 µmol/L), but not α-bungarotoxin (125 nmol/L), prevented the increase of intraterminal free calcium level evoked by 1,1-dimethyl-4-phenylpiperazinium (100 µmol/L) in the presence of tetrodotoxin. These observations indicate the presence of nicotinic receptors on neuronal processes that increase the intraterminal concentration of free calcium and probably modulate transmitter release. Their pharmacological properties are similar to those of nicotinic receptors located on neuronal cell bodies.     

l-NNA inhibits the histochemical NADPH-d reaction in rat spinal cord neurons

In nerve tissue the histochemical nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reaction is considered a suitable marker for nitric oxide synthase (NOS) activity. We have previously shown that the NOS-specific inhibitorl-nitroarginine (l-NNA) can block NADPH-d staining in intermediolateral (IML) neurons of the rat spinal cord; such a reaction might serve as a control for the presence of a NOS-related catalytic activity, i.e.,l-NNA-dependent NO synthesis in these neurons. However,l-NNA inhibition of neuronal NADPH-d is inconsistent and is therefore disputed by others. This prompted us to reinvestigate the reaction conditions to provide a standardized protocol for inhibition experiments. In IML neurons of formaldehyde-fixed spinal cord tissue, inhibition of NADPH-d reaction was tested by preincubation of frozen sections with the flavin-binder diphenylene iodonium chloride (DPI, 10 M-1 mM) which blocked the NADPH-d reaction in a concentration-dependent way, suggesting an inverse relationship of inhibitor concentration and final reaction product generated. Preincubation with the NOS-specific inhibitorl-NNA in glycine-NaOH buffer (pH 8.5–9.5) but notl-nitroarginine methyl ester (l-NAME) revealed a concentration-dependent blocking effect on neuronal NADPH-d comparable to the effects seen with DPI, suggesting the existence of al-NNA sensitive NADPH-d activity. Blocking withl-NNA (100 M-10 mM) was prevented by excessl-arginine (10–100 mM), suggesting competitive binding sites. NADPH-d staining was not inhibited by 7-nitro indazole, another NOS inhibitor. Thus, in formaldehyde-fixed nervous tissue both DPI andl-NNA inhibit the NOS-associated catalytic NADPH-d activity, thereby preventing NADPH-dependent conversion of nitroblue tetrazolium to formazan.Presented in the Workshop Detection of NO-synthases at the XXXVI Symposium of the Society for Histochemistry on Oxy Radicals, 20–23 September 1994, Heidelberg, Germany     

A unique pattern of toxic synthesis in pentitol catabolism: Implications for evolution

Summary All of ourEscherichia coli C mutants blocked in the first step of D-arabitol catabolism (D-arabitol dehydrogenase) became unable to grow in the presense of D-arabitol. We have shown that this sensitivity is eliminated by a defect in the second enzyme of the pathway (D-xylulokinase), leading to a pattern of toxicity and its relief which has not been previously reported. We have found a similar pattern of toxicity and its relief in the closely related ribitol pathway. The evolutionary significance of these findings is discussed.     

Preparation in undenatured form of the main protein bound to heterogeneous nuclear RNA in liver and hepatoma cells

Particles carrying heterogeneous nuclear RNA (30 S-particles) were prepared from rat liver and Zajdela hepatoma ascites cell nuclei after ultrasonic disruption. The ribonucleoprotein structures were disintegrated in the presence of 100 mM spermidine. Using chromatography on Sepharose-polyadenylate a protein component has been obtained which possessed high affinity for heterogeneous nuclear RNA, polyuridylate and polyadenylate, and double-stranded DNA. This protein was the main species of the ribonucleoprotein studied; it showed bands with molcular weights of 37000 and 40000 respectively in SDS gel electrophoresis. The RNA-binding proteins isolated from liver and hepatoma had identical molecular weights and the same affinity for Sepharose-polyadenylate used in the isolation.Abbreviations hnRNA heterogeneous nuclear RNA - hnRNP ribonucleoprotein which contains hnRNA