bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased adult hippocampal brain‐derived neurotrophic factor and normal levels of neurogenesis in maternal separation rats
Authors: Greisen Mia H. , Altar C. Anthony , Bolwig Tom G. , Whitehead Richard , Wörtwein Gitta
Published: February 2005

Repeated maternal separation of rat pups during the early postnatal period may affect brain‐derived neurotrophic factor (BDNF) or neurons in brain areas that are compromised by chronic stress. In the present study, a highly significant increase in hippocampal BDNF protein concentration was found in adult rats that as neonates had been subjected to 180 min of daily separation compared with handled rats separated for 15 min daily. BDNF protein was unchanged in the frontal cortex and hypothalamus/paraventricular nucleus. Expression of BDNF mRNA in the CA1, CA3, or dentate gyrus of the hippocampus or in the paraventricular hypothalamic nucleus was not affected by maternal separation. All animals displayed similar behavioral patterns in a forced‐swim paradigm, which did not affect BDNF protein concentration in the hippocampus or hypothalamus. Repeated administration of bromodeoxyuridine revealed equal numbers of surviving, newly generated granule cells in the dentate gyrus of adult rats from the 15 min or 180 min groups. The age‐dependent decline in neurogenesis from 3 months to 7 months of age did not differ between the groups. Insofar as BDNF can stimulate neurogenesis and repair, we propose that the elevated hippocampal protein concentration found in maternally deprived rats might be a compensatory reaction to separation during the neonatal period, maintaining adult neurogenesis at levels equal to those of the handled rats. © 2005 Wiley‐Liss, Inc.
Cover Picture: Macromol. Chem. Phys. 3/2005
Authors: Buback Michael , Egorov Mark , Junkers Tanja , Panchenko Elena
Published: February 2005

Cover: A time‐resolved ESR trace is shown. The laser symbol at t = 0 indicates the action of the laser single pulse which induces the formation of the initial radical concentration . Data treatment is based on the formula presented in the upper right part of the figure. The termination reaction is illustrated in the lower left part of the figure.

Further details can be found in the Full Paper by M. Buback,* M. Egorov, T. Junkers and E. Panchenko on page 333.
Influence of tertiary diamines on the synthesis of high‐molecular‐weight poly(1,3‐cyclohexadiene)
Authors: Williamson David T. , Kilian Lars , Long Timothy E.
Published: February 2005

The living synthesis of poly(1,3‐cyclohexadiene) was performed with an initiator adduct that was synthesized from a 1:2 (mol/mol) mixture of N,N,N′,N′‐tetramethylethylenediamine (TMEDA) and n‐butyllithium. This initiator, which was preformed at 65 °C, facilitated the synthesis of high‐molecular‐weight poly(1,3‐cyclohexadiene) (number‐average molecular weight = 50,000 g/mol) with a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight = 1.12). A plot of the kinetic chain length versus the time indicated that termination was minimized and chain transfer to the monomer was eliminated when a preformed initiator adduct was used. Chain transfer was determined to occur when the initiator was generated in situ. The polymerization was highly sensitive to both the temperature and the choice of tertiary diamine. The use of the bulky tertiary diamines sparteine and dipiperidinoethane resulted in poor polymerization control and reduced polymerization rates (7.0 × 10−5 s−1) in comparison with TMEDA‐mediated polymerizations (1.5 × 10−4 s−1). A series of poly(1,3‐cyclohexadiene‐block‐isoprene) diblock copolymers were synthesized to determine the molar crossover efficiency of the polymerization. Polymerizations performed at 25 °C exhibited improved molar crossover efficiencies (93%) versus polymerizations performed at 40 °C (80%). The improved crossover efficiency was attributed to the reduction of termination events at reduced polymerization temperatures. The microstructure of these polymers was determined with 1H NMR spectroscopy, and the relationship between the molecular weight and glass‐transition temperature at an infinite molecular weight was determined for polymers containing 70% 1,2‐addition (150 °C) and 80% 1,4‐addition (138 °C). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1216–1227, 2005
Thiophene‐cored 2,2‐bis(methylol)propionic acid dendrimers for optical‐power‐limiting applications
Authors: Vestberg Robert , Nilsson Christina , Lopes Cesar , Lind Per , Eliasson Bertil , Malmström Eva
Published: February 2005

The synthesis and characterization of dendron‐coated 2,5‐bis(phenylethynyl)thiophene chromophores are described. The dendrimers were grown divergently on the arylthiophene core with the versatile anhydride of 2,2‐bis(methylol)propionic acid. The arylthiophene core was synthesized with Sonogashira coupling reactions. Structurally well‐defined dendrimers up to the fourth generation were grown, as confirmed by size exclusion chromatography, NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight analysis. The different dendritic substitution did not influence the absorption spectra of the compounds in or near the visible region. Solutions of arylthiophenes had good transparency at wavelengths greater than 400 nm. The dendritic thiophenes exhibited an optical‐power limit at the laser wavelength of 532 nm. However, the magnitude of the optical‐power limit of these compounds was slightly lower than that of a nondendritic arylthiophene with n‐pentyl substituents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1177–1187, 2005
Stimuli‐responsive reversible physical networks. I. Synthesis and physical network properties of amphiphilic block and random copolymers with long alkyl chains by living cationic polymerization
Authors: Yoshida Tomohide , Seno Ken‐Ichi , Kanaoka Shokyoku , Aoshima Sadahito
Published: February 2005

The living cationic polymerization of octadecyl vinyl ether (ODVE) was achieved with an 1‐(isobutoxy)ethyl acetate [CH3CH(OiBu)OCOCH3]/EtAlCl2 initiating system in hexane in the presence of an added weak Lewis base at 30 °C. In contrast to conventional polymers, poly(octadecyl vinyl ether) underwent upper‐critical‐solution‐temperature‐type phase separation in various solvents, such as hexane, toluene, CH2Cl2, and tetrahydrofuran, because of the crystallization of octadecyl chains. Amphiphilic block and random copolymers with crystallizable substituents of ODVE and 2‐methoxyethyl vinyl ether (MOVE) were synthesized via living cationic polymerization under similar conditions. Aqueous solutions of the copolymers yielded physical gels upon cooling because of strong interactions between ODVE units, regardless of the copolymer structure. The product gels, however, exhibited different viscoelastic properties: A 20 wt % solution of a block copolymer (400/20 MOVE/ODVE) became a soft physical gel that behaved like a typical gel, whereas the corresponding random copolymer gave a transparent but stiff gel with a certain relaxation time. Differential scanning calorimetry analysis confirmed that the crystalline–amorphous transition of the octadecyl chains was a key step for inducing such physical gelation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1155–1165, 2005
Structural model of human GAD65: Prediction and interpretation of biochemical and immunogenic features
Authors: Capitani Guido , De Biase Daniela , Gut Heinz , Ahmed Shaheen , Grütter Markus G.
Published: February 2005

The 65 kDa human isoform of glutamate decarboxylase, GAD65, plays a central role in neurotransmission in higher vertebrates and is a typical autoantigen in several human autoimmune diseases, such as insulin‐dependent diabetes mellitus (IDDM), Stiff‐man syndrome and autoimmune polyendocrine syndrome type I. In autoimmune diabetes, an attack of inflammatory cells to endocrine pancreatic β‐cells leads to their complete destruction, eventually resulting in the inability to produce sufficient insulin for the body's requirements. Even though the etiology of β‐cell destruction is still a matter of debate, the role and antigenic potency of GAD65 are widely recognized. Herein a model of GAD65 is presented, which is based on the recently solved crystal structures of mammalian DOPA decarboxylase and of bacterial glutamate decarboxylase. The model provides for the first time a detailed and accurate structure of the GAD65 subunit (all three domains) and of its dimeric quaternary assembly. It reveals the structural basis for specific antibody recognition to GAD65 as opposed to GAD67, the other human isoform, which shares 81% sequence similarity with GAD65 and is much less antigenic. Literature data on monoclonal antibody binding are perfectly consistent with the detailed features of the model, which allows explanation of several findings on GAD65 immunogenicity. Importantly, by analyzing the active site, we identified the residues most likely involved in catalysis and substrate recognition, paving the way for rational mutagenesis studies of the GAD65 reaction mechanism, specificity and inhibition. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Microstructural analysis of a carbon fibre reinforced AZ91D magnesium alloy composite
Authors: Russell‐Stevens M. , Todd R. , Papakyriacou M.
Published: February 2005

Interfacial regions in metal matrix composites are important in controlling the mechanical and thermal properties of these materials. An ultrahigh modulus fibre‐reinforced magnesium alloy matrix composite has been studied, with particular attention paid to the interfacial and precipitate microstructures. Fibres were surface treated but uncoated prior to composite manufacture. Observations revealed that an interface consisting of polycrystalline magnesium oxide with occasional Mg17Al12 (β) precipitate particles predominates. Discontinuous β particles formed at fibre surfaces, and continuous spherical and lamellar β precipitates nucleated at grain boundaries and fibre surfaces. High dislocation densities exist at the interface indicating matrix‐yielding subsequent to manufacture and that a high mean residual compressive stress acts on fibres. The effect that the observed microstructural features has on composite properties and on interfacial bonding is discussed and compared to examples in the literature. Copyright © 2005 John Wiley & Sons, Ltd.
Influence of Sambucus nigra bark lectin on cell DNA under different in vitro conditions
Authors: Macewicz Larysa L. , Suchorada Olena M. , Lukash Lyubov L.
Published: February 2005

The biological activity of Sambucus nigra bark lectin on Chinese hamster cells in vitro was investigated by comet‐assay and cytotoxicity testing. Mitogenic properties at the concentrations 0.063–0.25 μg/ml (but not higher) were found, and the induction of DNA breaks at concentrations 0.5 μg/ml and higher is demonstrated. S. nigra bark lectin at mitogenic concentrations decreased the level of nickel‐induced DNA damage. The character and mechanism of this lectin protective activity was probably related to the induction of DNA reparation in the cells, decreasing nickel uptake in cells, and non‐specific binding of nickel ions by protein molecules.
Dorsal Fracture–Dislocation of the Proximal Interphalangeal Joint: A Comparative Study of Percutaneous Kirschner Wire Fixation Versus Open Reduction and Internal Fixation
Authors: ALADIN A. , DAVIS T. R. C.
Published: February 2005

Nineteen patients with a dorsal fracture–dislocation of the proximal interphalangeal joint of a finger were treated with either closed reduction and transarticular Kirschner wire fixation (eight cases) or open reduction and internal fixation, using either one or two lag screws (six cases) or a cerclage wire (five cases). At a mean follow-up of 7 (range 6–9) years, most patients reported satisfactory finger function, even though some of the injuries healed with proximal interphalangeal joint incongruency (seven cases) or subluxation (four cases). Those treated by open reduction complained of more “loss of feeling” in the affected finger and those specifically treated by cerclage wire fixation reported more cold intolerance and had a significantly larger fixed flexion deformity (median, 30°: range 18–38°) and a smaller arc of motion (median, 48°: range 45–60°) at the proximal interphalangeal joint, despite having the best radiological outcomes. Closed reduction and transarticular Kirschner wire fixation produced satisfactory results, with none of the eight patients experiencing significant persistent symptoms despite a reduced arc of proximal interphalangeal joint flexion (median=75°; range 60–108°). The results of this relatively simple treatment appear at least as satisfactory as those obtained by the two techniques of open reduction and internal fixation, both of which were technically demanding.
A Cosmopolitanism from Below: Alternative Globalization and the Creation of a Solidarity without Bounds
Authors: KURASAWA FUYUKI
Published: February 2005

This paper aims to demonstrate that cosmopolitanism should be understood as a transnational mode of practice, whereby actors construct bonds of mutual commitment and reciprocity across borders through public discourse and sociopolitical struggle. This practice oriented perspective allows us to question three of the main assumptions imbedded within most frameworks theorizing global solidarity, namely cultural homogenization, political fragmentation, and social thinness. To illustrate my argument, I draw upon examples taken from the alternative globalization movement.
Aggregation ofArgulus coregoni(Crustacea: Branchiura) on rainbow trout (Oncorhynchus mykiss): a consequence of host susceptibility or exposure?
Authors: BANDILLA M. , HAKALAHTI T. , HUDSON P. J. , VALTONEN E. T.
Published: February 2005

By sampling individual rainbow trout,Oncorhynchus mykiss, at a fish farm we showed thatArgulus coregoniwere aggregated within their host population. The relative significance of susceptibility and exposure generating the observed pattern was tested using experimental infections. We examined, whether rainbow trout developed protective resistance mechanisms against the louse following a challenge infection and if there was variation between individual trout in their susceptibility toA. coregonimetanauplii. Fish were exposed to 20A. coregonifor 5, 25, 50, 85 or 120 min and the numbers attaching recorded. Three weeks later, developing argulids were removed and the experiment repeated with a standardized exposure of 20 metanauplii. Prior exposure of fish withA. coregonidid not reduce the total infection intensity compared to naïve fish, but fish gained infection more rapidly. We suggest that there is no protective acquired resistance of pre-exposed rainbow trout to subsequentArgulusexposure. The possibility that an immunosuppressive mechanism by argulids was acting enabling the higher attachment rate could be refuted since control individuals, not previously exposed to lice, gained the infection at a similar rate as the fish challenged twice. Our results do not indicate clear differences in susceptibility among individual fish but the transmission of metanauplii on fish seemed to be opportunistic and non-selective. Our results support the view that variation in exposure time, rather than differences in susceptibility of individual hosts, might be the key factor in generating the aggregated distribution ofArguluson their hosts.
Long-term investigation of the composition and richness of intestinal helminth communities in the stocked population of eel, Anguilla anguilla, in Neusiedler See, Austria
Authors: SCHABUSS M. , KENNEDY C. R. , KONECNY R. , GRILLITSCH B. , SCHIEMER F. , HERZIG A.
Published: February 2005

Data from a long-term study of the intestinal helminth parasite community of eels, Anguilla anguilla, stocked into the shallow eutrophic Neusiedler See, Austria, were collected over an 8 year period (1994–2001). In total, 720 eels from 2 sampling sites were examined. The parasite community showed characteristics similar to those in the natural eel populations in rivers of the UK and mainland Europe: it was species poor, with only 5 species (Acanthocephalus lucii, Acanthocephalus anguillae, Raphidascaris acus, Proteocephalus macrocephalus, Bothriocephalus claviceps) comprising the component community and a maximum infracommunity richness of 4 species. Over the period, the intestinal parasite community of the sampling site in Illmitz, which was originally dominated by A. lucii, changed. As levels of A. anguillae increased to a point at which it dominated the community, diversity increased whilst dominance of a single species decreased. By contrast the community in the southern sampling site remained rather constant with a continuous high infection level of A. anguillae and low abundance of A. lucii. Both acanthocephalan species exhibited higher infection levels in larger eels and in different seasons of the year and the infection parameters were significantly different between the years of study. The significant differences in the infection levels of the 2 acanthocephalan species at the 2 sampling sites were surprising as both acanthocephalan species use the same intermediate host, Asellus aquaticus, and the sampling sites were in close proximity and were similar in terms of water quality, host size and invertebrate abundance. Differences in the fish communities of the 2 sampling sites and eel movements rather than interspecific competition are discussed as possible explanations for the differences in the parasite communities of the 2 sampling sites.
T-cell depletion and immunity to malaria in HIV-infections
Authors: BUTCHER G. A.
Published: February 2005

Although early reports on HIV and malaria in co-infected subjects indicated little apparent interaction between the two infections, more recent investigations have found evidence for HIV increasing the risk from malaria. Conversely, increased viral load in susceptible cells occurs in malaria-infected people. However, the overall pattern of results is still somewhat confusing and contradictory. While morbidity from malaria may be greater in HIV-positive patients and in several reports the mortality risk is also higher, major increases in blood-stage parasitaemias that one might expect are not generally observed. The results of surveys are summarized and discussed in the context of what is known of malaria and HIV immunology in the light of recent data from humans as well as animal models.
Monocyte Chemoattractant Protein-1 Regulation of Blood–Brain Barrier Permeability
Authors: Stamatovic Svetlana M , Shakui Parvin , Keep Richard F , Moore Bethany B , Kunkel Steven L , Van Rooijen Nico , Andjelkovic Anuska V
Published: February 2005

The present study was designed to elucidate the effects of the chemokine monocyte chemoattractant protein (MCP-1) on blood–brain barrier (BBB) permeability. Experiments were conducted under in vitro conditions (coculture of brain endothelial cells and astrocytes) to study the cellular effects of MCP-1 and under in vivo conditions (intracerebral and intracerebroventricular administration of MCP-1) to study the potential contribution of MCP-1 to BBB disruption in vivo. Our results showed that MCP-1 induces a significant increase in the BBB permeability surface area product for fluorescein isothiocyanate (FITC)-albumin under in vivo conditions, particularly during prolonged (3 or 7 days) exposure (0.096±0.008 versus 0.031±0.005 μL/g min in controls at 3 days, P<0.001). Monocyte chemoattractant protein-1 also enhanced (17-fold compared with control) the permeability of the in vitro BBB (coculture) model. At the cellular level, MCP-1 causes alteration of tight junction (TJ) proteins in endothelial cells (redistribution of TJ proteins determined by Western blotting and loss of immunostaining for occludin, claudin-5, ZO-1, ZO-2). Monocyte chemoattractant protein-1-induced alterations in BBB permeability are mostly realized through the CCR2 receptor. Absence of CCR2 diminishes any effect of MCP-1 on BBB permeability in vitro and in vivo. The permeability surface area product for FITC-albumin after 3 days exposure to MCP-1 was 0.096±0.006 and 0.032±0.007 μL/g min, in CCR2+/+ and CCR2−/− mice, respectively ( P<0.001). Monocytes/macrophages also participate in MCP-1-induced alterations in BBB permeability in vivo. Monocytes/macrophages depletion (by clodronate liposomes) reduced the effect of MCP-1 on BBB permeability in vivo ∼2 fold. Our results suggest that, besides its main function of recruiting leukocytes at sites of inflammation, MCP-1 also plays a role in ‘opening’ the BBB.
In vitro Gender Differences in Neuronal Survival on Hypoxia and in 17β-Estradiol-Mediated Neuroprotection
Authors: Heyer Andrea , Hasselblatt Martin , von Ahsen Nicolas , Häfner Heinz , Sirén Anna-Leena , Ehrenreich Hannelore
Published: February 2005

Gender differences in neuropsychiatric disease are recognized but not well understood. Investigating the survival of primary rat hippocampal neurons in culture, we found significant and inverted gender differences on normoxia versus hypoxia. Male cells were more resistant under normoxia but more vulnerable under hypoxia than female cells. Male vulnerability pattern was acquired in cells from neonatally testosterone-primed females. Estrogens, acting via membrane receptors, had a higher neuroprotective power in male neurons, explained at least in part by the pronounced increase in estrogen receptor beta/alpha ratio during hypoxia in male cells only.
EPR experiments to elucidate the structure of the ready and unready states of the [NiFe] hydrogenase of Desulfovibrio vulgaris Miyazaki F
Authors: van Gastel M. , Fichtner C. , Neese F. , Lubitz W.
Published: February 2005

Isolation and purification of the [NiFe] hydrogenase of Desulfovibrio vulgaris Miyazaki F under aerobic conditions leads to a mixture of two states, Ni-A (unready) and Ni-B (ready). The two states are distinguished by different activation times and different EPR spectra. HYSCORE and ENDOR data and DFT calculations show that both states have an exchangeable proton, albeit with a different 1H hyperfine coupling. This proton is assigned to the bridging ligand between Ni and Fe. For Ni-B, a hydroxo ligand is found. For Ni-A, either a hydroxo in a different orientation or a hydroperoxo-bridging ligand is present.
Biodiversity of uptake hydrogenase systems from legume endosymbiotic bacteria
Authors: Brito B. , Baginsky C. , Palacios J.M. , Cabrera E. , Ruiz-Argüeso T. , Imperial J.
Published: February 2005

Uptake hydrogenases in legume endosymbiotic bacteria recycle hydrogen produced during the nitrogen fixation process in legume nodules. Despite the described beneficial effect on plant productivity, the hydrogen oxidation capability is not widespread in the Rhizobiaceae family. Characterization of hydrogenase gene clusters in strains belonging to Rhizobium, Bradyrhizobium and Azorhizobium reveals a similar overall genetic organization along with important differences in gene regulation. In addition, phylogenetic analysis of hup genes indicates distinct evolutionary origins for hydrogenase genes in Rhizobia.
Formate and its role in hydrogen production in Escherichia coli
Authors: Sawers R.G.
Published: February 2005

The production of dihydrogen by Escherichia coli and other members of the Enterobacteriaceae is one of the classic features of mixed-acid fermentation. Synthesis of the multicomponent, membrane-associated FHL (formate hydrogenlyase) enzyme complex, which disproportionates formate into CO2 and H2, has an absolute requirement for formate. Formate, therefore, represents a signature molecule in the fermenting E. coli cell and factors that determine formate metabolism control FHL synthesis and consequently dihydrogen evolution.
High-level transcription of large gene regions: a novel T7 RNA-polymerase-based system for expression of functional hydrogenases in the phototrophic bacterium Rhodobacter capsulatus
Authors: Drepper T. , Arvani S. , Rosenau F. , Wilhelm S. , Jaeger K.-E.
Published: February 2005

High-level synthesis of complex enzymes like bacterial [NiFe] hydrogenases, in general, requires an expression system that allows concerted expression of a large number of genes. So far, it has not been possible to overproduce a hydrogenase in a stable and active form by using a customary expression system. Therefore we started to establish a new, T7-based expression system in the phototrophic bacterium Rhodobacter capsulatus. The beneficial properties of this bacterial host in combination with the unique capacity of T7 RNA polymerase to synthesize long transcripts will allow the high-level synthesis and assembly of active hydrogenase as well as other complex enzymes in the near future.
A hydrogen-sensing multiprotein complex controls aerobic hydrogen metabolism in Ralstonia eutropha
Authors: Friedrich B. , Buhrke T. , Burgdorf T. , Lenz O.
Published: February 2005

H2 is an attractive energy source for many microorganisms and is mostly consumed before it enters oxic habitats. Thus aerobic H2-oxidizing organisms receive H2 only occasionally and in limited amounts. Metabolic adaptation requires a robust oxygen-tolerant hydrogenase enzyme system and special regulatory devices that enable the organism to respond rapidly to a changing supply of H2. The proteobacterium Ralstonia eutropha strain H16 that harbours three [NiFe] hydrogenases perfectly meets these demands. The unusual biochemical and structural properties of the hydrogenases are described, including the strategies that confer O2 tolerance to the NAD-reducing soluble hydrogenase and the H2-sensing regulatory hydrogenase. The regulatory hydrogenase that forms a complex with a histidine protein kinase recognizes H2 in the environment and transmits the signal to a response regulator, which in turn controls transcription of the hydrogenase genes.
1994–2004: 10 years of research on the anaerobic oxidation of ammonium
Authors: Jetten M.S.M. , Cirpus I. , Kartal B. , van Niftrik L. , van de Pas-Schoonen K.T. , Sliekers O. , Haaijer S. , van der Star W. , Schmid M. , van de Vossenberg J. , Schmidt I. , Harhangi H. , van Loosdrecht M. , Gijs Kuenen J. , Op den Camp H. , Strous M.
Published: February 2005

The obligately anaerobic ammonium oxidation (anammox) reaction with nitrite as primary electron acceptor is catalysed by the planctomycete-like bacteria Brocadia anammoxidans, Kuenenia stuttgartiensis and Scalindua sorokinii. The anammox bacteria use a complex reaction mechanism involving hydrazine as an intermediate. They have a unique prokaryotic organelle, the anammoxosome, surrounded by ladderane lipids, which exclusively contains the hydrazine oxidoreductase as the major protein to combine nitrite and ammonia in a one-to-one fashion. In addition to the peculiar microbiology, anammox was shown to be very important in the oceanic nitrogen cycle, and proved to be a very good alternative for treatment of high-strength nitrogenous waste streams. With the assembly of the K. stuttgartiensis genome at Genoscope, Evry, France, the anammox reaction has entered the genomic and proteomic era, enabling the elucidation of many intriguing aspects of this fascinating microbial process.
Cytochrome c nitrite reductase: from structural to physicochemical analysis
Authors: Burlat B. , Gwyer J.D. , Poock S. , Clarke T. , Cole J.A. , Hemmings A.M. , Cheesman M.R. , Butt J.N. , Richardson D.J.
Published: February 2005

The recent structural characterization of the NrfA from Escherichia coli provides a framework to rationalize the spectroscopic and functional properties of this enzyme. Analyses by EPR and magnetic CD spectroscopies have been complemented by protein-film voltammetry and these are discussed in relation to the essential structural features of the enzyme.
Alkaline cyanide biodegradation by Pseudomonas pseudoalcaligenes CECT5344
Authors: Luque-Almagro V.M. , Blasco R. , Huertas M.J. , Martínez-Luque M. , Moreno-Vivián C. , Castillo F. , Roldán M.D.
Published: February 2005

Pseudomonas pseudoalcaligenes CECT5344 uses cyanide, cyanate, β-cyanoalanine, and other cyanoderivatives as nitrogen sources under alkaline conditions, which prevents volatile HCN (pKa 9.2) formation. The cyanide consumed by this strain is stoichiometrically converted into ammonium. In addition, this bacterium grows with the heavy metal, cyanide-containing waste water generated by the jewellery industry, and is also a cyanide-resistant strain which induces an alternative oxidase and a siderophore-based mechanism for iron acquisition in the presence of cyanide. The detection of cyanase and β-cyanoalanine nitrilase activities in cyanide-induced cells suggests their implication in the cyanide degradation pathway.
Nitric oxide and nitrosative stress tolerance in bacteria
Authors: Poole R.K.
Published: February 2005

Nitric oxide is not only an obligatory intermediate in denitrification, but also a signalling and defence molecule of major importance. However, the basis of resistance to NO and RNS (reactive nitrogen species) is poorly understood in many microbes. The cellular targets of NO and RNS [e.g. metalloproteins, thiols in proteins, glutathione and Hcy (homocysteine)] may themselves serve as signal transducers, sensing NO and RNS, and resulting in altered gene expression and synthesis of protective enzymes. The properties of a number of such protective mechanisms are outlined here, including globins, flavorubredoxin, diverse enzymes with NO- or S-nitrosothiol-reducing properties and other redox proteins with poorly defined roles in protection from nitrosative stresses. However, the most fully understood mechanism for NO detoxification involves the enterobacterial flavohaemoglobin (Hmp). Aerobically, Hmp detoxifies NO by acting as an NO denitrosylase or ‘oxygenase’ and thus affords inducible protection of growth and respiration, and aids survival in macrophages. The flavohaemoglobin-encoding gene of Escherichia coli, hmp, responds to the presence of NO and RNS in an SoxRS-independent manner. Nitrosating agents, such as S-nitrosoglutathione, deplete cellular Hcy and consequently modulate activity of the MetR regulator that binds the hmp promoter. Regulation of Hmp synthesis under anoxic conditions involves nitrosylation of 4Fe-4S clusters in the global transcriptional regulator, FNR. The foodborne microaerophilic pathogen, Campylobacter jejuni, also expresses a haemoglobin, Cgb, but it does not possess the reductase domain of Hmp. A Cgb-deficient mutant of C. jejuni is hypersensitive to RNS, whereas cgb expression and holoprotein synthesis are specifically increased on exposure to RNS, resulting in NO-insensitive respiration. A ‘systems biology’ approach, integrating the methodologies of bacterial molecular genetics and physiology with post-genomic technologies, promises considerable advances in our understanding of bacterial NO tolerance mechanisms in pathogenesis.
DNA binding properties of the Escherichia coli nitric oxide sensor NorR: towards an understanding of the regulation of flavorubredoxin expression
Authors: Tucker N. , D'Autréaux B. , Spiro S. , Dixon R.
Published: February 2005

Nitric oxide is an intermediate of denitrification, and is one of the radical species deployed by macrophages against invading pathogens, therefore bacterial responses to NO are of considerable importance. The Escherichia coli flavorubredoxin and its associated oxidoreductase reduce NO to nitrous oxide under anaerobic conditions, and are encoded by the norVW transcription unit. Expression of norVW requires the NO sensing regulatory protein NorR and is dependent on RNA polymerase containing the alternative sigma factor, σ54. We have purified NorR and shown that it binds to three sites in the norVW promoter region, located 75–140 bp upstream of the experimentally verified transcription start site. We have also identified two binding sites for the integration host factor, one between the NorR sites and the σ54-RNA polymerase binding site, and a second downstream of the norVW transcription start site. Comparison of the norVW promoters of enteric bacteria along with known and putative NorR-regulated promoters from Vibrio, Ralstonia and Pseudomonas species suggests that NorR binding sites contain an invariant GT(N7)AC motif flanking an AT-rich central region. The identification of a consensus for NorR binding sites will help to elucidate additional members of the NorR regulon.
Growth factors regulate cell survival by controlling nutrient transporter expression
Authors: Edinger A.L.
Published: February 2005

Growth factors provide permission signals that allow mammalian cells to grow, proliferate and survive. One mechanism by which growth factors maintain this control is through the regulation of cell surface nutrient transporter expression. Following growth factor withdrawal, nutrient transporters are endocytosed and degraded in the lysosome, effectively terminating the cell's ability to obtain nutrients. This results in a state of pseudostarvation in which cells atrophy and initiate a catabolic metabolic programme in the midst of abundant extracellular nutrients. Oncogenic forms of Akt can support growth factor-independent nutrient transporter expression through a mechanism that depends upon mTOR (mammalian target of rapamycin). The ability of activated Akt to support nutrient transporter expression is an essential component of its prosurvival function. When the destruction of nutrient transporters is inhibited, cells are capable of long-term growth-factor-independent cell survival in the absence of receptor-dependent signal transduction. These results imply that proteins involved in nutrient transporter turnover in response to growth factor withdrawal are components of a novel tumour suppressor pathway. Preliminary data suggest that Rab7, a GTPase required for transporter degradation, functions as a tumour suppressor protein, as inhibiting Rab7 activity promotes colony formation in soft agar. These studies indicate that drugs affecting this pathway might have utility as anti-cancer chemotherapeutic agents.
Glucose as a hormone: receptor-mediated glucose sensing in the yeast Saccharomyces cerevisiae
Authors: Johnston M. , Kim J.-H.
Published: February 2005

Because glucose is the principal carbon and energy source for most cells, most organisms have evolved numerous and sophisticated mechanisms for sensing glucose and responding to it appropriately. This is especially apparent in the yeast Saccharomyces cerevisiae, where these regulatory mechanisms determine the distinctive fermentative metabolism of yeast, a lifestyle it shares with many kinds of tumour cells. Because energy generation by fermentation of glucose is inefficient, yeast cells must vigorously metabolize glucose. They do this, in part, by carefully regulating the first, rate-limiting step of glucose utilization: its transport. Yeast cells have learned how to sense the amount of glucose that is available and respond by expressing the most appropriate of its 17 glucose transporters. They do this through a signal transduction pathway that begins at the cell surface with the Snf3 and Rgt2 glucose sensors and ends in the nucleus with the Rgt1 transcription factor that regulates expression of genes encoding glucose transporters. We explain this glucose signal transduction pathway, and describe how it fits into a highly interconnected regulatory network of glucose sensing pathways that probably evolved to ensure rapid and sensitive response of the cell to changing levels of glucose.
Glucose sensing through the Hxk2-dependent signalling pathway
Authors: Moreno F. , Ahuatzi D. , Riera A. , Palomino C.A. , Herrero P.
Published: February 2005

In this work, we describe the hexokinase 2 (Hxk2) signalling pathway within the yeast cell. Hxk2 and Mig1 are the two major factors of glucose repression in Saccharomyces cerevisiae. The functions of both proteins have been extensively studied but there is no information about possible interactions among them in the repression pathway. Our results demonstrate that Hxk2 interacts directly with Mig1 in vivo and in vitro and that the ten amino acids motif between K6 and M15 is required for their interaction. This interaction has been detected at the DNA level both in vivo by chromatin immunoprecipitation experiments and in vitro using purified proteins and a DNA fragment containing the MIG1 site of the SUC2 promoter. This demonstrates that the interaction is of physiological relevance. Our findings show that the main role of Hxk2 in the glucose signalling pathway is the interaction with Mig1 to generate a repressor complex located in the nucleus of S. cerevisiae.
Trehalose metabolism and glucose sensing in plants
Authors: Avonce N. , Leyman B. , Thevelein J. , Iturriaga G.
Published: February 2005

Plants sense and respond to changes in carbon and nitrogen metabolites during development and growth according to the internal needs of their metabolism. Sugar-sensing allows plants to switch off photosynthesis when carbohydrates are abundant. These processes involve regulation of gene and protein activity to allow plants the efficient use of energy storage. Besides being a key element in carbon metabolism, glucose (Glc) has unravelled as a primary messenger in signal transduction. It has been proved that hexokinase (HXK) is a Glc sensor. An unusual disaccharide named trehalose is present in very low levels in most plants except for the desiccation-tolerant plants known as ‘resurrection’ plants where trehalose functions as an osmoprotectant. We have shown that overexpression of the Arabidopsis trehalose-6-phosphate synthase gene (AtTPS1) in Arabidopsis promotes trehalose and trehalose-6-phosphate (T6P) accumulation. Seedlings expressing AtTPS1 displayed a Glc-insensitive phenotype. Transgenic lines germinated normally on Glc, in contrast to wild-type seedlings showing growth retardation and absence of chlorophyll and root elongation. Gene-expression analysis in transgenic plants showed up-regulation of several genes involved in sugar signalling and metabolism. These data suggest that AtTPS1 and accordingly T6P and trehalose play an important role in the regulation of Glc sensing and signalling genes during plant development.
The role of trehalose-6-phosphate synthase in Arabidopsis embryo development
Authors: Gómez L.D. , Baud S. , Graham I.A.
Published: February 2005

We previously showed that trehalose-6-phosphate synthase 1 (TPS1), which catalyses the first step in trehalose synthesis, is essential for embryo maturation in Arabidopsis [Eastmond, van Dijken, Spielman, Kerr, Tissier, Dickinson, Jones, Smeekens and Graham (2002) Plant J. 29, 225–235]. The tps1 mutant embryos develop more slowly than wild type. Patterning in the tps1 embryos appears normal but they do not progress past the torpedo stage to cotyledon stage, which is when storage reserves start to accumulate in the expanding cotyledons. Our initial data led to the hypothesis that trehalose metabolism plays a key role in regulating storage reserve accumulation by allowing the embryo to respond to the dramatic increase in sucrose levels that occurs at the torpedo stage of embryo development. More recent data demonstrate that while the tps1 mutant is blocked in the developmental progression of embryos from torpedo to cotyledon stage the expression of genes involved in the accumulation of storage reserves proceeds in a similar fashion to wild type. Thus it appears that induction of metabolic processes required for accumulation of storage reserves in tps1 occurs independently of the developmental stage and instead follows a temporal programme similar to wild-type seeds in the same silique.
Acquired glucose sensitivity of k-ras transformed fibroblasts
Authors: Chiaradonna F. , Magnani C. , Sacco E. , Manzoni R. , Alberghina L. , Vanoni M.
Published: February 2005

Mutational activation of the ras gene is critical for the onset of different malignant phenotypes. We constructed a dominant negative mutant (GEF-DN) of a Ras activator protein (guanine nucleotide-exchange factor) that upon over-expression in k-ras transformed NIH 3T3 fibroblasts strongly reduces intracellular Ras•GTP, reverting these cells to wild-type phenotype for morphology, anchorage-independent growth and reduction of tumour formation in nude mice. Here we review evidence showing that the enhanced proliferation potential of NIH-ras cells requires high initial glucose concentration in the medium and sustained Ras pathway activation. The exquisite sensitivity of NIH-ras fibroblasts to a shortage in nutrient and energy supply highlights an acquired fragility of cancer cells that may be exploited for therapeutic purposes.
Glucokinase and glucose homeostasis: proven concepts and new ideas
Authors: Zelent D. , Najafi H. , Odili S. , Buettger C. , Weik-Collins H. , Li C. , Doliba N. , Grimsby J. , Matschinsky F.M.
Published: February 2005

The enzyme GK (glucokinase), which phosphorylates glucose to form glucose 6-phosphate, serves as the glucose sensor of insulin-producing β-cells. GK has thermodynamic, kinetic, regulatory and molecular genetic characteristics that are ideal for its glucose sensor function and allow it to control glycolytic flux of the β-cells as indicated by control-, elasticity- and response-coefficients close to or larger than 1.0. GK operates in tandem with the K+ and Ca2+ channels of the β-cell membrane, resulting in a threshold for glucose-stimulated insulin release of approx. 5 mM, which is the set point of glucose homoeostasis for most laboratory animals and humans. Point mutations of GK cause ‘glucokinase disease’ in humans, which includes hypo- and hyper-glycaemia syndromes resulting from activating or inactivating mutations respectively. GK is allosterically activated by pharmacological agents (called GK activators), which lower blood glucose in normal animals and animal models of T2DM. On the basis of crystallographic studies that identified a ligand-free ‘super-open’ and a liganded closed structure of GK [Grimsby, Sarabu, Corbett and others (2003) Science 301, 370–373; Kamata, Mitsuya, Nishimura, Eiki and Nagata (2004) Structure 12, 429–438], on thermostability studies using glucose or mannoheptulose as ligands and studies showing that mannoheptulose alone or combined with GK activators induces expression of GK in pancreatic islets and partially preserves insulin secretory competency, a new hypothesis was developed that GK may function as a metabolic switch per se without involvement of enhanced glucose metabolism. Current research has the goal to find molecular targets of this putative ‘GK-switch’. The case of GK research illustrates how basic science may culminate in therapeutic advances of human medicine.
High accuracy ab initio studies of Li6+, Li6−, and three isomers of Li6
Authors: Temelso Berhane , Sherrill C. David
Published: February 2005

The structures and energetics of Li6+, Li6− and three isomers of Li6 are investigated using the coupled-cluster singles, doubles and perturbative triples [CCSD(T)] method with valence and core-valence correlation consistent basis sets of double- to quadruple-ζ quality (cc-pVXZ and cc-pCVXZ, where X=D−Q). These results are compared with qualitatively different predictions by less reliable methods. Our results conclusively show that the D4h isomer is the global minimum structure for Li6. It is energetically favored over the C5v and D3h structures by about 5.1 and 7.1kcalmol−1, respectively, after the inclusion of the zero-point vibrational energy (ZPVE) correction. Our most accurate total atomization energies are 123.2, 117.6, and 115.7kcalmol−1 for the D4h, C5v, and D3h isomers, respectively. Comparison of experimental optical absorption spectra with our computed electronic spectra also indicate that the D4h isomer is indeed the most stable structure. The cation, anion, and some higher spin states are investigated using the less expensive cc-pCVDZ basis set. Adiabatic ionization energies and electron affinities are reported and compared with experimental values. Predictions of molecular properties are found to be sensitive to the basis set used and to the treatment of electron correlation.
On the correlation between surface roughness and work function in copper
Authors: Li W. , Li D. Y.
Published: February 2005

Both surface roughness (SR) and work function (WF) are important characteristics of a solid surface. Understanding the relationship between SR and WF is necessary in order to apply the Kelvin probe technique to characterize surface behavior. In this study, SR and WF of copper surfaces were measured using atomic force microscopy and scanning Kelvin probe, respectively. Experimental results showed that WF decreased with increase of SR. Using sine functions, a capacitor model was proposed and a correlation between WF and SR was established. The theoretical predictions of WF were in good agreement with experimental results. The model is also useful for analyzing the effect of tip geometry on measurements of WF.
Growth and sintering of Pd clusters on α-Al2O3(0001)
Authors: Tait Steven L. , Ngo Lien T. , Yu Qiuming , Fain Samuel C. , Campbell Charles T.
Published: February 2005

The growth and sintering of Pd nanoparticles on α-Al2O3(0001) have been studied by noncontact atomic force microscopy (NC-AFM), low-energy ion scattering spectroscopy (LEIS), temperature-programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS). This is the first study of metal nanoparticles on a well-defined oxide surface where both NC-AFM and LEIS are used for characterization. These prove to be a powerful combination in assessing particle dimensions. The clean alumina surface showed atomically flat, 200–700 nm wide terraces. The sharp step edges are straight (within our resolution) for lengths of >300nm and have heights in multiples of 0.2 nm. The Pd grows initially as two-dimensional (2D) islands at 300 K, with the transition to 3D particle growth at 0.25 ML (ML=monolayers). Upon heating at 1 K/s, the Pd starts to sinter below 400 K, and sinters at a nearly constant rate with increasing temperature, covering ∼50% less of the alumina surface by ∼1000K, with a doubling in particle diameter and an eightfold decrease in particle number density. By ∼1000K, the number density was ∼9×1011∕cm2 for 0.8 ML of Pd, with an average diameter of 5 nm and an average thickness of 1 nm.
Simulations of ponderomotive effects in inductively coupled plasmas
Authors: Sydorenko D. Y. , Smolyakov A. I. , Tyshetskiy Y. O. , Godyak V. A.
Published: February 2005

The electromagnetic quasineutral particle-in-cell code, simulating interaction of a plane electromagnetic wave with a plasma slab, is developed. The code is used to study the ponderomotive effects in a plasma with a finite temperature. Simulations in linear regime show the strong thermal reduction of the ponderomotive force, which is in a good agreement with the linear analytical theory. It is found that in the essentially nonlinear regime, when the electron trajectories are strongly modified, the amplitude of the ponderomotive force increases compared to the linear case, but remains lower than the classical cold plasma value. The transition from nonlinear to linear regime as a function of the amplitude of the driving electromagnetic field is investigated.