Fly photoreceptors and temperature: Relative UV-sensitivity is increased by cooling

Intracellular responses from blowfly photoreceptor cells were recorded at various temperatures in order to study the behaviour of the transduction system, with particular reference to spectral sensitivity. with decreased temperature the V-log I functions showed a reduction in amplitude and the responses showed a slowed time course. For double peaked spectral sensitivity function the UV or 350 nm peak was much less dependent on temperature than the peak in the visible region. The higher UV-sensitivity is interpreted in terms of the sensitizing pigment theory to indicate changes in the effectiveness of energy transfer between the two chromophores.     

Leaf Litter Consumption by Macroarthropods and Burial of their Faeces Enhance Decomposition in a Mediterranean Ecosystem

In many terrestrial ecosystems, large amounts of leaf litter are consumed by macroarthropods. Most of it is deposited as faeces that are easily transferred into deeper soil layers. However, the decomposition of this large pool of organic matter remains poorly studied. We addressed the question of how leaf litter transformation into macroarthropod faeces, and their burial in the soil, affect organic matter decomposition in a Mediterranean dry shrubland. We compared mass loss of intact leaf litter of two dominant shrub species (Quercus coccifera, Cistus albidus) with that of leaf litter-specific faeces from the abundant millipede Ommatoiulus sabulosus. Leaf litter and faeces were exposed in the field for 1 year, either on the soil surface or buried at 5 cm soil depth. Chemical and physical quality of faeces differed strongly from that of leaf litter, but distinctively between the two shrub species. On the soil surface, faeces decomposed faster than intact leaf litter in Quercus, but at similar rates in Cistus. When buried in the soil, faeces and leaf litter decomposed at similar rates in either species, but significantly faster compared to the soil surface, most likely because of higher moisture within the soil enhancing microbial activity. The combined effects of leaf litter transformation into faeces and their subsequent burial in the topsoil led to a 1.5-fold increase in the annual mass loss. These direct and indirect macroarthropod effects on ecosystem-scale decomposition are likely more widespread than currently acknowledged, and may play a particularly important role in drought-influenced ecosystems.     

Determination of T-2 toxin,HT-2 toxin,and three other type A trichothecenes in layer feed by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS)—comparison of two sample preparation methods

A sensitive method for the simultaneous determination of T-2 toxin, HT-2 toxin, neosolaniol, T-2 triol, and T-2 tetraol in layer feed using high-performance liquid chromatography coupled to triple quadrupole mass spectrometry in the positive ionization mode (LC-ESI-MS/MS) is described. Two fast and easy clean-up methods—with BondElut Mycotoxin and MycoSep 227 columns, respectively—were tested. The separation of the toxins was conducted on a Pursuit XRs Ultra 2.8 HPLC column using 0.13 mM ammonium acetate as eluent A and methanol as eluent B. Detection of the mycotoxins was carried out in the multiple reaction monitoring (MRM) mode using ammonium adducts as precursor ions. Quantification of all analytes was performed with d₃-T-2 toxin as an internal standard. The clean-up method with MycoSep 227 columns gave slightly better results for layer feed compared to the method using BondElut Mycotoxin columns (MycoSep 227: recovery between 50 and 63 %, BondElut Mycotoxin: recovery between 32 and 67 %) and was therefore chosen as the final method. The limits of detection ranged between 0.9 and 7.5 ng/g depending on the mycotoxin. The method was developed for the analysis of layer feed used at carry-over experiments with T-2 toxin in laying hens. For carry-over experiments, it is necessary that the method includes not only T-2 toxin but also the potential metabolites in animal tissues HT-2 toxin, neosolaniol, T-2 triol, and T-2 tetraol which could naturally occur in cereals used as feed stuff as well.     

Human TLR8 senses UR/URR motifs in bacterial and mitochondrial RNA

Toll‐like receptor (TLR) 13 and TLR2 are the major sensors of Gram‐positive bacteria in mice. TLR13 recognizes Sa19, a specific 23S ribosomal (r) RNA‐derived fragment and bacterial modification of Sa19 ablates binding to TLR13, and to antibiotics such as erythromycin. Similarly, RNase A‐treated Staphylococcus aureus activate human peripheral blood mononuclear cells (PBMCs) only via TLR2, implying single‐stranded (ss) RNA as major stimulant. Here, we identify human TLR8 as functional TLR13 equivalent that promiscuously senses ssRNA. Accordingly, Sa19 and mitochondrial (mt) 16S rRNA sequence‐derived oligoribonucleotides (ORNs) stimulate PBMCs in a MyD88‐dependent manner. These ORNs, as well as S. aureus‐, Escherichia coli‐, and mt‐RNA, also activate differentiated human monocytoid THP‐1 cells, provided they express TLR8. Moreover, Unc93b1 ^−/−‐ and Tlr8 ^−/−‐THP‐1 cells are refractory, while endogenous and ectopically expressed TLR8 confers responsiveness in a UR/URR RNA ligand consensus motif‐dependent manner. If TLR8 function is inhibited by suppression of lysosomal function, antibiotic treatment efficiently blocks bacteria‐driven inflammatory responses in infected human whole blood cultures. Sepsis therapy might thus benefit from interfering with TLR8 function.     

Ein in vitro Proteinsynthesesystem aus Maiskeimlingen

Summary An amino acid incorporating system has been prepared from maize seedlings, and it has been characterized with the aid of poly-U and a mRNA enriched fraction from the same plant material.The rate of protein synthesis decreases proportionally with the incubation period. It seems to be related to the degradation of polysomes. The optimal Mg²⁺ concentration is 20 mM for the poly-U dependent protein synthesis and 10 mM for the synthesis with endogenous polysomes. The poly-U directed polyphenylalanine synthesis is increased 12-fold by addition of exogenous sRNA. Under optimal conditions poly-U causes a 40-fold increase of the phenylalanine incorporation.A mRNA enriched fraction was prepared from maize seedlings using proteinase K for deproteination of polysomes. The resulting RNA was further fractionated by successive precipitation with LiCl, NaCl and ethanol and characterized by polyacrylamide gel electrophoresis. The addition of 57 g of the mRNA-enriched sample increases the incorporation of amino acid into polypeptides by a factor of approximately 2 at a Mg²⁺ concentration of 5 mM, and by a factor of 1.5 at 15 mM Mg²⁺. The addition of 72 g rRNA does not stimulate the incorporation at low Mg²⁺ concentration, while at 15 mM Mg²⁺ a 1.3-fold increase is observed.

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Teil einer Dissertation (W. S. Sim), Bonn 1973.

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Stipendiat des Deutschen Akademischen Austauschdienstes.     

Hepatitis C virus (HCV) employs multiple strategies to subvert the host innate antiviral response

Hepatitis C virus (HCV) is a serious global health problem which accounts for approximately 40% of chronic liver diseases worldwide. HCV frequently establishes a persistent infection, although it is recognized and targeted by innate immunity as well as cellular and humoral immune mechanisms. This suggests that HCV has developed powerful strategies to escape elimination by innate and adaptive immunity. HCV-induced liver injury is thought to be mainly immune-mediated rather than due to direct cytopathic effects of the virus. Hence, therapeutic strategies should target those mechanisms favoring viral persistence since unspecific enhancement of host antiviral immunity may theoretically also promote liver injury. The present review summarizes our current understanding of how the hepatitis C virus interferes with the innate antiviral host-response to establish persistent infection.     

Human natural cell-mediated cytotoxicity against fetal fibroblasts. III. Morphological and functional characterization of the effector cells

We have isolated and characterized human natural killer cells cytotoxic to human fetal fibroblasts utilizing adsorption-elution of the effector cells from target cell-coated beads. The cell associated with enriched cytotoxicity was slightly larger than small- to medium-sized lymphocytes, the cytoplasm was pale and characteristically granular. In direct surface marker analysis the cell was Fc-receptor-positive, formed E-rosettes, and displayed strong either diffuse or granular ANAE reactivity in the cytoplasm. The ANAE reactivity could not be inhibited with sodium fluoride and in mitogen and antigen stimulation experiments the cell had T-cell characteristicis. The cell type was termed large granular lymphocyte and we suggest that it is the main direct effector cell for natural killer activity against human fetal fibroblasts.     

Initial phases of DNA synthesis in Drosophila melanogaster

Replication patterns of the X chromosomes and autosomes in D. melanogaster male and female larvae during the discontinuously labeled initial and end phases of DNA synthesis were compared. In female larvae X and autosomes behaved correspondingly during all the replication stages. In males, however, the X chromosome shows a differential replication behavior from that of the autosomes already during the discontinuously labeled initial stage.—In those nuclei of both sexes, in which the autosomes correspond in their initial replication patterns, significantly more labeled regions are to be found over the male X than over the female X. The complementary behavior during the end phases (Berendes, 1966), i.e. the reverse of that above, leads to an earlier completion of the replication cycle in most of the labeled regions of the male X chromosome. The differential replication revealed in the autoradiograms is interpreted as a consequence of the polytene structure in giant chromosomes.     

Untersuchungen über die Quantitative Bedeutung Einiger Stoffwechselwege in den Uredosporen von Puccinia Graminis var. Tritici

Zusammenfassung Der Stoffwechsel der Uredosporen von Puccinia graminis var. tritici wurde im Verlauf der Keimung untersucht. Dazu wurden die Sporen in verschiedenen Stadien der Keimung kurzzeitig (5 oder 10 min) mit ¹⁴C-Valeriansäure-1 inkubiert. Die in der Zeiteinheit von den Sporen aufgenommene Menge an radioaktiver Substanz blieb innerhalb des Versuchszeitraumes von 510 min etwa gleich. Das Eindringen der Valeriansäure wurde nicht vom endogenen Stoffwechsel beeinflußt.Der größte Anteil der inkorporierten Radioaktivität war in 40% igem Äthanol und Wasser löslich. Der Anteil der inkorporierten Aktivität, der in unlösliche Verbindungen eingebaut wurde, nahm im Laufe der Keimung ab. Die prozentuale Verteilung der Radioaktivität auf einige wichtige Stoffwechselprodukte, nämlich Glutaminsäure, Asparaginsäure, Citronensäure, Äpfelsäure, Kohlenhydrate und Alanin wurden untersucht. Ca. 70% der Radioaktivität des Rohextraktes wurden in diesen Verbindungen wiedergefunden. Den höchsten Anteil an Radioaktivität enthielt Glutaminsäure incl. Glutamin.Die endogene Zulieferung von Acetyl-CoA sank allmählich ab, dadurch sanken auch die Umsatzraten der Citronensäure und der Glutaminsäure. Der radioaktive Anteil des Acetyl-CoA (durch -Oxydation aus Valeriansäure hervorgegangen) stieg, da der Zufluß von radioaktivem Acetyl-CoA konstant war. Dadurch wurden auch die spezifischen Aktivitäten in den pools größer, solange die pool-Größen nicht anstiegen.Die pool-Größen veränderten sich während der tracer-Applikation nicht, d.h. es herrschten während dieser 10 min steady-state-Bedingungen. Im Verlauf der Keimung blieben der Citronensäure-pool und der Asparaginsäure-pool praktisch konstant, der Glutaminsäure-pool nahm ab und der Malat-pool wurde größer. Die Durchsatzraten von Glutaminsäure incl. Glutamin und Asparaginsäure incl. Asparagin waren auffallend hoch.Der TCA-Cyclus übertraf den Glyoxalat-Cyclus an Bedeutung. Im Verlauf der Keimung sank die Synthese der Glutaminsäure und stieg die Synthese von Kohlenhydraten und Asparaginsäure. Es wurde also mehr iso-Citrat durch iso-Citratlyase gespalten.Es bestanden große Unterschiede in der Syntheserate einzelner Aminosäuren. Lediglich Glutaminsäure, Asparaginsäure und Alanin wurden in größeren Mengen gebildet. Demgegenüber war die Synthese von Serin und Threonin außerordentlich gering und für eine Nettoproteinsynthese völlig unzureichend. Die Proteinsyntheserate wurde an Hand der Überführung von freier Glutaminsäure in die gebundene Glutaminsäure studiert. Nur ein verschwindend kleiner Anteil der synthetisierten freien Glutaminsäure wurde gebunden. Die Proteinsyntheserate nahm im Verlauf der Keimung ab.

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An analysis of the quantitative importance of some metabolic pathways in uredopores of Puccinia graminis var. tritici

Summary In order to investigate the metabolism of germinating uredopores of Puccinia graminis, spores were incubated at different stages of germination with ¹⁴C-valerate-1 for short times (5 or 10 min). Incorporation of the labelled substance per unit of time was nearly constant during the experiment, which lasted for 510 min. The uptake of valeric acid was not influenced by endogenous metabolism. Most of the incorporated radioactivity was soluble in 40% ethanol and water. The part of the activity taken up that was incorporated into insoluble compounds decreased during germination. Distribution of radioactivity in some important metabolites such as glutamic acid, aspartic acid, citric acid, malic acid, carbohydrates and alanine was determined in terms of the per cent of incorporated radioactivity. Radioactivity of these compounds accounted for 70% of the radioactivity of the raw extract. Most of the radioactivity of the raw extract was found in glutamic acid and glutamine.The endogenous supply of acetyl CoA decreased gradually, and thereby turnover rates of citric acid and glutamic acid decreased, too. The specific activity of acetyl CoA (formed by -oxidation of valeric acid) increased since the rate of supply of radioactive acetyl CoA was constant. Thereby the specific activities of the different pools increased, as long as pool sizes were constant.Pool sizes did not change during tracer application, indicating steady state conditions during the experiments. During germination the citric acid pool and the aspartic acid pool stayed practically constant. The glutamic acid pool decreased and the malic acid pool increased. Turnover rates of glutamic acid including glutamine and aspartic acid including asparagine were very high.Quantitatively the TCA cycle is more important than the glyoxalate cycle. During germination synthesis of glutamic acid decreased and synthesis of carbohydrates and aspartic acid increased, indicating that more iso-citrate was split by isocitratlyase.Large differences in the rates of synthesis of different amino acids were noticed. Only glutamic acid, aspartic acid and alanine were synthesized in larger amounts. On the other hand the amount of synthesis of serine and threonine was extremely low and insufficient for a net synthesis of proteins. The rate of protein synthesis was investigated by studying incorporation of free glutamic acid into bound glutamic acid. Only a very small part of the synthesized free glutamic acid was bound. The rate of protein synthesis decreased during germination.

     

Defoliation of common ragweed by Ophraella communa beetle does not affect pollen allergenicity in controlled conditions

Ragweed allergy is one of the primary causes of seasonal allergies in Europe and its prevalence is expected to rise. The leaf beetle Ophraella communa, recently and accidentally established in N-Italy and S-Switzerland, represents a promising approach to control ragweed, but negative side effects should be excluded before its use. Since biotic and abiotic stresses are known to influence the allergenicity of pollen, we set out to assess the effect of sub-lethal defoliation by O. communa on the quantity and quality of ragweed pollen. Seventeen sister pairs (including six clones) of ragweed plants were grown in controlled conditions. One of each pair was exposed to O. communa as soon as the plant started to produce reproductive structures. After 10 weeks of exposure, plant traits were measured as a proxy for pollen quantity. Pollen quality was assessed by measuring its viability and allergenicity. Generally, plants produced very few male flowers and little amount of pollen. Damage by the beetle was severe with most of the leaf tissue removed, but no treatment effect was found on any of the quantitative and qualitative traits assessed. In conclusion, O. communa did not increase the amount or allergenicity of ragweed pollen grains in our experimental conditions.