Preparative route to N-glycolylneuraminic acid phenyl 2-thioglycoside donor and synthesis of Neu5Gc-alpha-(2-->3')-lactosamine 3-aminopropyl glycoside

The spacer-armed trisaccharide, Neu5Gc-alpha-(2-->3')-lactosamine 3-aminopropyl glycoside, was synthesized by regio- and stereoselective sialylation of the suitably protected triol acceptor, 3-trifluoroacetamidopropyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-(6-O-benzyl-beta-D-galactopyranosyl)-beta-D-glucopyranoside, with the donor methyl [phenyl 5-acetoxyacetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha,beta-D-galacto-2-nonulopyranosid]onate. The donor was obtained, in turn, from methyl [phenyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha,beta-D-galacto-2-nonulopyranosid]onate by N-tert-butoxycarbonylation of the acetamido group followed by total N- and O-deacetylation, per-O-acetylation, subsequent Boc group removal, and N-acetoxyacetylation.     

The biostratigraphic and palaeoenvironmental significance of Lower Cambrian (Botomian) trilobites from the Ak-Kaya section of the Altai Mountains (southern Siberia,Russia)

The presence of one of the oldest records of polycystine Radiolaria in the Lower Cambrian sedimentary sequence of the Ak-Kaya section (Gorny Altai) requires a biostratigraphic dating. The trilobites found recently a few tens of meters below the radiolarian-bearing level belong to Calodiscus resimus Repina, Serrodiscus fossuliferus Repina and Alacephalus aff. contortus Repina; they suggest that this part of the Shashkunar Formation can be correlated with the lower part of the Botomian stage. The absence of eyes in the two former species suggests a mode of life buried in the fine pelagic sediments. Indications of the presence of a strongly developed musculature on the third species point to a palaeoenvironment characterized by a relatively high hydrodynamic regime.     

Entire hemithorax irradiation for Masaoka stage IVa thymomas

Thymomas are rare neoplasms that have an indolent growth with a preferentially intra-thoracic dissemination pattern. Surgery is currently the standard treatment of thymomas; however radiotherapy is often used in an adjuvant setting due to a high sensitivity of these tumors to such treatment. Postoperative entire hemithoracic irradiation has been used in selected Masaoka stage IVa cases after complete surgical excision of metastatic lesions.In the present article, the authors report three cases of Masaoka stage IVa thymoma that underwent entire hemithorax irradiation after surgical excision of metastatic lesions. The first two patients presented as stage IVa thymomas. The third case consisted of a pleural recurrence of a thymoma.Hemithoracic irradiation with low doses has been used by different authors; the available data shows that it is a well-tolerated treatment that could potentially lead to better loco-regional control and increased overall survival.     

Plasmodium falciparum ARFGAP: expression and crystallization of the catalytic domain

GTPase activating protein for ARF GTPAse (ARFGAP) from the malaria parasite Plasmodium falciparum was expressed, purified and crystallized. Crystals of ARFGAP belong to trigonal space group P321 (or its enantiomorph) with unit cell parameters a=b=95.89 and c=92.46 A. Diffraction data to 2.4-A resolution have been collected. Calculation of self-rotation function suggested the presence of two molecules in the asymmetric unit.     

Methionine oxidation interferes with conversion of the prion protein into the fibrillar proteinase K-resistant conformation

In recent studies, we developed a protocol for in vitro conversion of full-length mouse recombinant PrP (Mo rPrP23-230) into amyloid fibrils [Bocharova et al. (2005) J. Mol. Biol. 346, 645-659]. Because amyloid fibrils produced from recombinant Mo PrP89-230 display infectivity [Legname et al. (2004) Science 305, 673-676], polymerizatiom of rPrPs in vitro represents a valuable model for elucidating the mechanism of prion conversion. Unexpectedly, when the same conversion protocol was used for hamster (Ha) rPrP23-231, we experienced substantial difficulties in forming fibrils. While searching for potential reasons of our failure to produce fibrils, we probed the effect of methionine oxidation in rPrP. We found that oxidation of methionines interferes with the formation of rPrP fibrils and that this effect is more profound for Ha than for Mo rPrP. To minimize the level of spontaneous oxidation, we developed a new protocol for rPrP purification, in which highly amyloidogenic Ha rPrP with minimal levels of oxidized residues was produced. Furthermore, our studies revealed that oxidation of methionines in preformed fibrils inhibited subsequent maturation of fibrils into proteinase K-resistant PrP(Sc)-like conformation (PrP-res). Our data are consistent with the proposition that conformational changes within the central region of the protein (residues 90-140) are essential for adopting PrP-res conformation and demonstrate that methionine oxidation interferes with this process. These studies provide new insight into the mechanism of prion polymerization, solve a long-standing practical problem in producing PrP-res fibrils from full-length PrP, and may help in identifying new genetic and environmental factors that modulate prion disease.     

Evidence for an adaptation mechanism of mitochondrial translation via tRNA import from the cytosol

Although mitochondrial import of nuclear DNA-encoded RNAs is widely occurring, their functions in the organelles are not always understood. Mitochondrial function(s) of tRNA(Lys)(CUU), tRK1, targeted into Saccharomyces cerevisiae mitochondria was mysterious, since mitochondrial DNA-encoded tRNA(Lys)(UUU), tRK3, was hypothesized to decode both lysine codons, AAA and AAG. Mitochondrial targeting of tRK1 depends on the precursor of mitochondrial lysyl-tRNA synthetase, pre-Msk1p. Here we show that substitution of pre-Msk1p by its Ashbya gossypii ortholog results in a strain in which tRK3 is aminoacylated, while tRK1 is not imported. At elevated temperature, drop of tRK1 import inhibits mitochondrial translation of mRNAs containing AAG codons, which coincides with the impaired 2-thiolation of tRK3 anticodon wobble nucleotide. Restoration of tRK1 import cures the translational defect, suggesting the role of tRK1 in conditional adaptation of mitochondrial protein synthesis. In contrast with the known ways of organellar translation control, this mechanism exploits the RNA import pathway.     

Helicobacter pylori disrupts NADPH oxidase targeting in human neutrophils to induce extracellular superoxide release

Helicobacter pylori (Hp) infection triggers a chronic influx of polymorphonuclear leukocyte neutrophils (PMNs) into the gastric mucosa. Although Hp reside in a neutrophil-rich environment, how these organisms evade phagocytic killing is largely unexplored. We now show that live Hp (strains 11637, 60190, DT61A, and 11916) are readily ingested by PMNs and induce a rapid and strong respiratory burst that is comparable to PMA. Relative to other particulate stimuli, Hp are more potent activators of PMNs than opsonized zymosan, Staphylococcus aureus, or Salmonella. Strikingly, biochemical and microscopic analyses demonstrate that Hp disrupt NADPH oxidase targeting such that superoxide anions are released into the extracellular milieu and do not accumulate inside Hp phagosomes. Specifically, nascent Hp phagosomes acquire flavocytochrome b558 but do not efficiently recruit or retain p47phox or p67phox. Superoxide release peaks at 16 min coincident with the appearance of assembled oxidase complexes in patches at the cell surface. Oxidant release is regulated by formalin-resistant and heat-sensitive bacterial surface factors distinct from urease and Hp(2-20). Following opsonization with fresh serum, Hp triggers a modest respiratory burst that is confined to the phagosome, and ingested bacteria are eliminated. We conclude that disruption of NADPH oxidase targeting allows unopsonized Hp to escape phagocytic killing, and our findings support the hypothesis that bacteria and PMNs act in concert to damage the gastric mucosa.     

Civic integration policies from below: accounting for processes of convergence and divergence in four European cities

The introduction of integration tests on a pre-entry or post-arrival basis has drawn attention to changing national integration policies. Yet, at the local level, language and civic culture courses have often been implemented before the development of national programmes. The way these policies came into place and the extent to which they responded to similar challenges has often been overlooked. This article explores the development of these measures in four cities – Stuttgart, Vienna, Barcelona and Turin – to find out which mechanisms account for convergence in policymaking. Integration courses present traits of similarity in their contents and target groups; however, this does not imply a consistent process towards convergence. Local introduction initiatives are the product of local policy arenas, which display different policy frames of migrant integration. On the other hand, new legislation and changes in the available financial resources for integration appear to be crucial factors that trigger divergence.