Nanoplanktonic coccolithophorids (Prymnesiophyceae, Haptophyceae) from the Weddell Sea, Antarctica

The examination of whole mounts prepared for transmission electron microscopy has resulted in the finding of thirteen taxa of nanoplanktonic coccolithophorids from the Weddell Sea, Antarctica. The material was collected as part of the AMERIEZ programme, March 1986. Cold-water adapted nanoplanktonic coccolithophorids have previously been shown to constitute a recurrent plankton element at subarctic and arctic localities. Three of the Weddell Sea species, Wigwamma annulifera, W. arctica , and Papposphaera sagittifera , are conspecific with northern hemisphere material, while two species, Calciarcus alaskensis and Turrisphaera arctica , are possibly identical with previously described arctidsubarctic material. Six taxa new to science have been described from the Weddell Sea, Wigwamma antarctica, W. triradiata, Trigonaspis melvillea, Pappomonas weddellensis, Papposphaera obpyramidalis , and P. simplicissima . The cooccurrence of identical forms at the two poles, and the fact that the species described are allocated to "arctic" genera, indicate a geologically relatively recent exchange of biological material between the poles.     

H2O2 activates CD11b/CD18-dependent cell adhesion

Treatment of monoblastoid U-937 cells with low concentrations of H2O2 caused adhesion of the cells to plastic. The H2O2 induced adhesion was rapid with a t1/2 of congruent to 6 min and was optimally stimulated by 100 microM H2O2 with an ED50 of congruent to 50 microM. The response to H2O2 closely resembled the adhesive response of U-937 cells to phorbol esters in its time dependency, requirement for extracellular Mg2+ and inhibition by cytochalasin B as well as inhibition by monoclonal antibodies against the leucocyte adhesion molecules CD11b and CD18. Phorbol ester treatment of U-937 cells stimulated the phosphorylation of at least three endogenous substrates, pp28, pp34 and pp43, of which pp28 and pp43 also responded to H2O2-treatment with increased 32P-incorporation. The results suggest that H2O2 might be a physiological modulator of leucocyte adhesion, possibly operating by activating protein kinase C.     

Isolation and purification of deoxyribonucleosides from 90% 13C-enriched DNA of algal cells and their characterization by 1H and 13C NMR.

13C-enriched deoxyribonucleosides have been isolated from the DNA of Algal cells grown in an atmosphere of 90% 13C-labelled carbon dioxide. The 13C enriched DNA was quantitatively hydrolysed with DNase I, snake venom phosphodiesterase I and alkaline phosphatase of intestinal mucosa. The resulting deoxyribonucleosides were separated by preparative reversed-phase high pressure liquid chromatography in 60 minutes with detection by ultraviolet absorption at 254 nm. The final products were obtained in milligram quantities in high purity and in high yield. The 1H resonances of the base and sugar protons of these deoxyribonucleosides appear as well resolved multiplets in the 600 MHz NMR spectrum, due to the extensive 1H-13C couplings. Similarly, the 13C resonances of these deoxyribonucleosides appear as multiplets in the 75.5 MHz 13C NMR spectrum, due to 13C-13C couplings. The 1H-13C and 13C-13C coupling constants were also measured and tabulated. The isotopic enrichment of 13C these deoxyribonucleosides was obtained by integration of the 1H and/or 13C NMR spectra. It was found that the enrichment varied from carbon to carbon and species to species in the range of 70-89%, suggesting differential uptake and assimilation of 90% 13CO2 during metabolism pathways. This protocol provides experimentally useful quantities of 13C-enriched deoxyribonucleosides, which may be incorporated into site-specifically labeled oligonucleotides by chemical synthesis.     

Growth of Escherichia coli in the presence of trimethoprim-sulfamethoxazole facilitates detection of Shiga-like toxin producing strains by colony blot assay

Abstract Subinhibitory concentrations of trimethoprim-sulfamethoxazole increased the total yield of Shiga-like toxin (SLT), produced by Shigella dysenteria 1 and by enterophathogenic and enterohemorrhagic strains of Escherichia coli . Stimulation of SLT synthesis by trimethoprim-sulfamethoxazole was demonstrated by an increase in cytotoxic activity for HeLa cells and the diameter of the zone formed around bacterial colonies probed with monoclonal antibodies to SLT. Thus, supplementation of culture media with trimetroprimsulfamethoxazol will facilitate SLT purification and detection of SLT-producing bacteria.     

Zur Ultrastruktur der intrazellulären Symbionten im Embryo der KleinzikadeEuscelis plebejus Fall. (Homoptera,Cicadina)

Summary Two types of bacterial symbionts (a- and t-types) were present intracellularly in embryos of the leafhopperEuscelis plebejus. In the electron microscope, three unit membranes were seen to surround the bacteria; the two inner membranes appeared to originate from the bacteria, the outer — from the host cytoplasm. DNA-structures were not observed in the symbionts. The a-symbionts contained in their cytoplasm crystalloid bodies presumably of protein nature and, during certain stages of embryonic development, tubular membranous bodies. The t-symbionts contained in their cytoplasm chymotrypsin-resistant dense bodies, that probably invade the host cytoplasm.Zusammenfassung Das elektronenmikroskopische Bild der intrazellulären a- und t-Symbionten vonEuscelis plebejus Fall. läßt erkennen, daß die symbiontischen Bakterien von drei Elementarmembranen umgeben sind. Morphologische Gründe sprechen dafür, daß die beiden inneren den Bakterien entstammen, die äußere Hüllmembran aber vom Cytoplasma der Wirtszelle gebildet wird. Bakterien-DNS konnte noch in keinem der beiden Symbiontentypen mit Sicherheit nachgewiesen werden. Die a-Symbionten sind vor Aufnahme in die Mycetocyten reich an tubulären Membrankörpern. Sie enthalten außerdem einen mit Chymotrypsin auflösbaren kristallinen Körper. In den t-Symbionten befinden sich Chymotrypsin-resistente dense bodies, die wahrscheinlich in das Wirtscytoplasma abgegeben werden.

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Mit Unterstützung durch Mittel der Deutschen Forschungsgemeinschaft, die Herrn Prof. Dr.K. Sander zur Verfügung standen.     

Transduction of a Plasmid Carrying the Cohesive End Region from Lactococcus lactis Bacteriophage ΦLC3

Plasmids carrying the cohesive end region from temperate lactococcal bacteriophage ΦLC3 could be packaged in vivo by ΦLC3 and transduced into its host strain, Lactococcus lactis subsp. cremoris NCDO 1201. The transduction frequencies were between 10^-4 and 10^-3 transducing particles per PFU, depending on the size of the phage DNA insert. This transduction system is limited to only certain lactococcal strains. The ΦLC3 cohesive site region (cos) appears to play an important role in plasmid transduction.     

The central region of the synaptonemal complex inBlaps cribrosa studied by electron microscope tomography

The synaptonemal complex (SC) in the beetleBlaps cribrosa contains a highly organized central element (CE), two flanking lateral elements (LEs), and a number of regularly spaced transverse filaments (TFs) crossing the central region. The CE is built like a ladder with two longitudinal components running in parallel and a number of regularly spaced transverse CE components, briding the two longitudinal components. The CE is multi-layered with the ladders of the individual layers more or less in register. Essentially every TF originates in one of the LEs, crosses the CE through a transverse CE component and reaches the opposite LE; every transverse CE component in a given layer corresponds to one, and only one, TF. In a CE layer, short irregular pillars form the junctions between the transverse and longitudinal CE components. Adjacent pillars are connected to each other by fine fibrous bridges: the two pillars in the same transverse CE component are linked, and so are the pillars along each longitudinal component, and also more occasionally adjacent pillars in separate CE layers. It is proposed that a TF with the two associated short pillars represents the structural unit in the central region. The ordered structure of the CE is accomplished by linking adjacent pillars to each other into the well-defined three-dimensional organization of the CE.     

The Influence of Alarm Substance on Feeding in Zebra Danio Fish (Brachydanio rerio)

The effects of alarm substance on feeding behaviour of zebra danio fish (Brachydanio rerio) were tested by offering them high and low densities of enclosed waterfleas (Daphnia magna). Normally the fish attacked high densities of prey, but when exposed to alarm substance they preferred lower and presumably less confusing prey densities — also lowering their feeding rate.     

Increases in α-mannosidase activity in the arbuscular mycorrhizal symbiosis of Allium schoenoprasum

 Mycorrhizal and nonmycorrhizal roots of Allium schoenoprasum were tested for activities of α-mannosidase, β-glucosidase and arabinosidase. Mannosidase activity was higher by a factor of two in mycorrhizal than in nonmycorrhizal root extracts. The apparent molecular weight of the enzyme was 152 kDa and its K_M was 1.25 mM in colonized roots and 1.85 mM in uncolonized roots. α-Mannosidase activity was further characterized by an acid pH optimum and Zn²⁺ dependency. No significant differences could be found between mycorrhizal and nonmycorrhizal roots for β-glucosidase and arabinosidase activities. Accepted: 28 August 1995