bluuebunny/crossref_metadata_2025 huggingface dataset:
Induced volatiles in soybean and pigeon pea plants artificially infested with the neotropical brown stink bug, Euschistus heros, and their effect on the egg parasitoid, Telenomus podisi
Authors: Carolina Blassioli Moraes Maria , Laumann Raul , Sujii Edson R. , Pires Carmen , Borges Miguel
Published: April 2005

Herbivory is known to increase the emission of volatiles, which attract natural enemies to herbivore‐damaged plants in laboratory and agricultural systems. We report on signalling through volatiles induced by Euschistus heros (F.) (Heteroptera: Pentatomidae) in two legumes that influence the attraction and retention of the egg parasitoid Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). Air‐borne extracts obtained from two host plants of E. heros, soybean, Glycine max, and pigeon pea, Cajanus cajan (Leguminosae), produce a different blend of emitted volatiles when attacked by adult males or females and nymphs of the pest species, compared with the undamaged plants. The same results were obtained when the plants were treated with extracted saliva of E. heros which had been mechanically introduced into the plants. This indicates that some substance in the saliva contributed to the release of the volatiles. Bioassays in a Y‐tube olfactometer with female T. podisi and treated plants confirmed the significant preference of the egg parasitoid for plants attacked by either males, females, or fourth instar nymphs of the pest species. On the other hand, volatile extracts obtained from soybean subjected to the velvetbean caterpillar, Anticarsia gemmatalis, a non‐host species for T. podisi, showed a different blend of volatiles compared to those obtained from plants subjected to E. heros. Additionally, the volatiles obtained from this plant–host complex were not attractive to T. podisi. These results indicate that E. heros causes an increase in the emission of specific plant volatiles, and that the induction is possibly caused by an elicitor present in the pest saliva. The possibility that these plant volatiles play an important role in the attraction and retention of the egg parasitoid T. podisi is discussed.
THE CAPITAL STRUCTURE PUZZLE: ANOTHER LOOK AT THE EVIDENCE
Authors: Barclay Michael J. , Smith Clifford W.
Published: April 2005

Since the formulation of the M & M irrelevance propositions 40 years ago, financial economists have been debating whether there is such a thing as optimal capital structure—a proportion of debt to equity that maximizes current firm value. Some finance scholars have followed M & M by arguing that both capital structure and dividend policy are largely “irrelevant” in the sense that they have no significant, predictable effects on corporate market values. Another school of thought holds that corporate financing choices reflect an attempt by corporate managers to balance the tax shields and disciplinary benefits of greater debt against the increased probability and costs of financial distress. Yet another theory says that companies do not have capital structure targets, but instead follow a financial pecking order in which retained earnings are preferred to outside financing, and debt is preferred to equity when outside funding is required.

In reviewing the evidence that has accumulated since M & M, the authors argue that taxes, bankruptcy (and other “contracting”) costs, and information costs (the main factor in the pecking order theory) all appear to play an important role in corporate financing decisions. While much if not most of the evidence is consistent with the argument that companies set target leverage ratios, there is also considerable support for the pecking order theory's contention that firms are willing to deviate widely from their targets for long periods of time.

According to the authors, the key to reconciling the different theories—and thus to solving the capital structure puzzle—lies in achieving a better understanding of the relation between corporate financing stocks (leverage ratios) and flows (specific choices between debt and equity). Even if companies have target leverage ratios, there will be an optimal deviation from those targets—one that will depend on the transactions and information costs associated with adjusting back to the target relative to the costs of deviating from the target. As the authors argue in closing, a complete theory of capital structure must take account of these adjustment costs and how they affect expected deviations from the target.
INTERNET INVESTMENT BANKING: THE IMPACT OF INFORMATION TECHNOLOGY ON RELATIONSHIP BANKING
Authors: Wilhelm William J.
Published: April 2005

The production “technology” of investment banking, particularly in the pricing and distribution of securities offerings, has long depended on the ability of bankers to build and maintain networks of relationships with institutional investors and client firms. Among other benefits, these relationships enabled banks to economize on communications with investors at a time when communicating with the investment community was quite costly. But recent advances in information technology are forcing banks to reevaluate this relationship‐based technology. For example, Goldman Sachs recently purchased a stake in Wit Capital's efforts to build a retail distribution channel via the Internet. And William Hambrecht, founder of Hambrect & Quist, has gone so far as to propose that IPOs be put up for auction over the Internet.

This article offers both historical and economic perspective on these technological innovations in investment banking. In so doing, it provides a framework for thinking about how this segment of the industry is likely to evolve in the near future. It also discusses how advances in information technology coupled with the increasing codification of investment banking practices could reduce the central role of human capital and relationships elsewhere within investment banks, and how this might influence both the organization of individual banks and the industry in general.
A SURVEY OF U.S. CORPORATE FINANCING INNOVATIONS: 1970–1997
Authors: Carow Kenneth A. , Erwin Gayle R. , McConnell John J.
Published: April 2005

In the past 30 years, major changes have occurred not only in the kinds of securities issued, but also in the way securities are issued and in the national markets where they are issued. Traditional registered offerings have been partly displaced by shelf registered offerings and Rule 144A private offerings. And once exclusively domestic U.S offerings are increasingly being supplemented by foreign market offerings by U.S. companies, and by simultaneously domestic and foreign offerings. In 1997, for example, 11% of all proceeds raised by U.S. corporations were issued in one or more foreign markets. Of the $105 billion raised in these offerings, $31 billion was denominated in currencies other than the U.S. dollar.

While traditional securities still dominate the market, the authors' research indicates that the pace of innovation in the design of securities also increased markedly during the 1980s and has continued strong throughout the 1990s. In 1997, for example, innovative securities accounted for almost 30% of total domestic offerings. Three of the most common objectives of such securities have been (1) to manage the interest rate (and other financial price) risk faced by investors and issuers; (2) to reduce information costs faced by investors when buying securities from issuers with better information about their own prospects (a condition known as “information asymmetry”); and (3) to increase the tradability of financial assets.
ESTIMATING THE EQUITY RISK PREMIUM AND EQUITY COSTS: NEW WAYS OF LOOKING AT OLD DATA
Authors: Booth Laurence
Published: April 2005

This article examines three alternative ways of estimating the expected return on the equity market in using the CAPM or some other risk premium model. The three techniques are (1) direct estimation of the average nominal equity return for use as a forecast nominal equity return; (2) estimation of the average real equity return, which can then be added to a forecast inflation rate; and (3) estimation of an average equity risk premium, which is then added to a current risk‐free rate. Ibbotson and Sinquefeld's data on annual holding period returns are used to test the validity of their assumption that the equity risk premium follows a random walk and that the third of these approaches is thus the best method.

The paper reaches three major conclusions. First, each of these three techniques involves a “bias” of some kind. The use of average equity returns as a forecast is subject to “risk‐free rate” and “inflation rate” biases, while the use of an average equity risk premium is subject to a “term premium” bias. As a result, only the data can tell us which approach is best. Second, from analyzing equity and bond return data and the trend in interest rates, the author concludes that the term premium bias when using average historic equity risk premium is by far the largest of the three sources of bias. Indeed, the popular practice of adding an historic average equity risk premium to the 30‐year Treasury bond rate significantly overstates equity costs. Third, after examining equity rates of return back to 1871, the author concludes that the real equity return seems to follow a process that is close to a random walk and is thus the “best” of the three techniques to use as a “naive” forecast.
DOLLARIZATION FOR ARGENTINA
Authors: Hanke Steve H.
Published: April 2005

In January 1999, President Carlos Menem suggested replacing the Argentine peso with the U.S. dollar. President Menem's announcement has sparked a debate throughout Latin America and Eastern Europe about what has been termed “dollarization.” That debate prompted U.S. Treasury Secretary Robert Rubin to deliver a major policy speech on alternative exchange‐rate regimes on April 21, 1999 and the U.S. Senate Banking Committee to hold dollarization hearings the following day featuring Fed Chairman Alan Greenspan and Deputy Secretary of the Treasury Lawrence Summers.

This article presents a case for officially dollarizing Argentina. Dollarization is not new. Unofficial dollarization is widespread in emerging market countries; in fact, as much as 70% of the stock of U.S. dollars now circulates abroad. Twenty‐eight countries and dependent territories are officially dollarized. Although official dollarization would result in Argentina losing seigniorage of about 0.22 percent of GDP, the author estimates that this cost would be more than offset by a reduction in interest rates that would increase Argentina's trend rate of GDP growth by about two percent.

After debunking the most common criticisms of dollarization, the article closes by offering recommendations about the specific form of dollarization and presenting a detailed dollarization statute for Argentina. The author proposes a competitive currency regime for Argentina, one in which all foreign money would be legal tender.
Improved Prediction of the Collagen Fiber Architecture in the Aortic Heart Valve
Authors: Driessen Niels J. B. , Bouten Carlijn V. C. , Baaijens Frank P. T.
Published: April 2005

Living tissues show an adaptive response to mechanical loading by changing their internal structure and morphology. Understanding this response is essential for successful tissue engineering of load-bearing structures, such as the aortic valve. In this study, mechanically induced remodeling of the collagen architecture in the aortic valve was investigated. It was hypothesized that, in uniaxially loaded regions, the fibers aligned with the tensile principal stretch direction. For biaxial loading conditions, on the other hand, it was assumed that the collagen fibers aligned with directions situated between the principal stretch directions. This hypothesis has already been applied successfully to study collagen remodeling in arteries. The predicted fiber architecture represented a branching network and resembled the macroscopically visible collagen bundles in the native leaflet. In addition, the complex biaxial mechanical behavior of the native valve could be simulated qualitatively with the predicted fiber directions. The results of the present model might be used to gain further insight into the response of tissue engineered constructs during mechanical conditioning.
PIV Measurements of Flow in a Centrifugal Blood Pump: Time-Varying Flow
Authors: Day Steven W. , McDaniel James C.
Published: April 2005

Measurements of the time-varying flow in a centrifugal blood pump operating as a left ventricular assist device (LVAD) are presented. This includes changes in both the pump flow rate as a function of the left ventricle contraction and the interaction of the rotating impeller and fixed exit volute. When operating with a pulsing ventricle, the flow rate through the LVAD varies from 0-11L∕min during each cycle of the heartbeat. Phase-averaged measurements of mean velocity and some turbulence statistics within several regions of the pump, including the inlet, blade passage, exit volute, and diffuser, are reported at 20 phases of the cardiac cycle. The transient flow fields are compared to the constant flow rate condition that was reported previously in order to investigate the transient effects within the pump. It is shown that the quasi-steady assumption is a fair treatment of the time varying flow field in all regions of this representative pump, which greatly simplifies the comprehension and modeling of this flow field. The measurements are further interpreted to identify the effects that the transient nature of the flow field will have on blood damage. Although regions of recirculation and stagnant flow exist at some phases of the cardiac cycle, there is no location where flow is stagnant during the entire heartbeat.
Cellular Cross-linking of Peptide Modified Hydrogels
Authors: Drury Jeanie L. , Boontheekul Tanyarut , Mooney David J.
Published: April 2005

Peptide modification of hydrogel-forming materials is being widely explored as a means to regulate the phenotype of cells immobilized within the gels. Alternatively, we hypothesized that the adhesive interactions between cells and peptides coupled to the gel-forming materials would also enhance the overall mechanical properties of the gels. To test this hypothesis, alginate polymers were modified with RGDSP-containing peptides and the resultant polymer was used to encapsulate C2C12 myoblasts. The mechanical properties of these gels were then assessed as a function of both peptide and cell density using compression and tensile tests. Overall, it was found that above a critical peptide and cell density, encapsulated myoblasts were able to provide additional mechanical integrity to hydrogels composed of peptide-modified alginate. This occurred presumably by means of cell-peptide cross-linking of the alginate polymers, in addition to the usual Ca++ cross-linking. These results are potentially applicable to other polymer systems and important for a range of tissue engineering applications.
Warming of the Eurasian Landmass Is Making the Arabian Sea More Productive
Authors: Goes Joaquim I. , Thoppil Prasad G. , Gomes Helga do R , Fasullo John T.
Published: April 2005

The recent trend of declining winter and spring snow cover over Eurasia is causing a land-ocean thermal gradient that is particularly favorable to stronger southwest (summer) monsoon winds. Since 1997, sea surface winds have been strengthening over the western Arabian Sea. This escalation in the intensity of summer monsoon winds, accompanied by enhanced upwelling and an increase of more than 350% in average summertime phytoplankton biomass along the coast and over 300% offshore, raises the possibility that the current warming trend of the Eurasian landmass is making the Arabian Sea more productive.
Comparative Metagenomics of Microbial Communities
Authors: Tringe Susannah Green , von Mering Christian , Kobayashi Arthur , Salamov Asaf A. , Chen Kevin , Chang Hwai W. , Podar Mircea , Short Jay M. , Mathur Eric J. , Detter John C. , Bork Peer , Hugenholtz Philip , Rubin Edward M.
Published: April 2005

The species complexity of microbial communities and challenges in culturing representative isolates make it difficult to obtain assembled genomes. Here we characterize and compare the metabolic capabilities of terrestrial and marine microbial communities using largely unassembled sequence data obtained by shotgun sequencing DNA isolated from the various environments. Quantitative gene content analysis reveals habitat-specific fingerprints that reflect known characteristics of the sampled environments. The identification of environment-specific genes through a gene-centric comparative analysis presents new opportunities for interpreting and diagnosing environments.
A Cellular MicroRNA Mediates Antiviral Defense in Human Cells
Authors: Lecellier Charles-Henri , Dunoyer Patrice , Arar Khalil , Lehmann-Che Jacqueline , Eyquem Stephanie , Himber Christophe , Saïb Ali , Voinnet Olivier
Published: April 2005

In eukaryotes, 21- to 24-nucleotide-long RNAs engage in sequence-specific interactions that inhibit gene expression by RNA silencing. This process has regulatory roles involving microRNAs and, in plants and insects, it also forms the basis of a defense mechanism directed by small interfering RNAs that derive from replicative or integrated viral genomes. We show that a cellular microRNA effectively restricts the accumulation of the retrovirus primate foamy virus type 1 (PFV-1) in human cells. PFV-1 also encodes a protein, Tas, that suppresses microRNA-directed functions in mammalian cells and displays cross-kingdom antisilencing activities. Therefore, through fortuitous recognition of foreign nucleic acids, cellular microRNAs have direct antiviral effects in addition to their regulatory functions.
Monodisperse Double Emulsions Generated from a Microcapillary Device
Authors: Utada A. S. , Lorenceau E. , Link D. R. , Kaplan P. D. , Stone H. A. , Weitz D. A.
Published: April 2005

Double emulsions are highly structured fluids consisting of emulsion drops that contain smaller droplets inside. Although double emulsions are potentially of commercial value, traditional fabrication by means of two emulsification steps leads to very ill-controlled structuring. Using a microcapillary device, we fabricated double emulsions that contained a single internal droplet in a core-shell geometry. We show that the droplet size can be quantitatively predicted from the flow profiles of the fluids. The double emulsions were used to generate encapsulation structures by manipulating the properties of the fluid that makes up the shell. The high degree of control afforded by this method and the completely separate fluid streams make this a flexible and promising technique.
Transduction of Receptor Signals by ß-Arrestins
Authors: Lefkowitz Robert J. , Shenoy Sudha K.
Published: April 2005

The transmission of extracellular signals to the interior of the cell is a function of plasma membrane receptors, of which the seven transmembrane receptor family is by far the largest and most versatile. Classically, these receptors stimulate heterotrimeric G proteins, which control rates of generation of diffusible second messengers and entry of ions at the plasma membrane. Recent evidence, however, indicates another previously unappreciated strategy used by the receptors to regulate intracellular signaling pathways. They direct the recruitment, activation, and scaffolding of cytoplasmic signaling complexes via two multifunctional adaptor and transducer molecules, β-arrestins 1 and 2. This mechanism regulates aspects of cell motility, chemotaxis, apoptosis, and likely other cellular functions through a rapidly expanding list of signaling pathways.
Acanthamoeba castellanii
Induces Host Cell Death via a Phosphatidylinositol 3-Kinase-Dependent Mechanism
Authors: Sissons James , Kim Kwang Sik , Stins Monique , Jayasekera Samantha , Alsam Selwa , Khan Naveed Ahmed
Published: April 2005

Granulomatous amoebic encephalitis due to
Acanthamoeba castellanii
is a serious human infection with fatal consequences, but it is not clear how the circulating amoebae interact with the blood-brain barrier and transmigrate into the central nervous system. We studied the effects of an
Acanthamoeba
encephalitis isolate belonging to the T1 genotype on human brain microvascular endothelial cells, which constitute the blood-brain barrier. Using an apoptosis-specific enzyme-linked immunosorbent assay, we showed that
Acanthamoeba
induces programmed cell death in brain microvascular endothelial cells. Next, we observed that
Acanthamoeba
specifically activates phosphatidylinositol 3-kinase.
Acanthamoeba
-mediated brain endothelial cell death was abolished using LY294002, a phosphatidylinositol 3-kinase inhibitor. These results were further confirmed using brain microvascular endothelial cells expressing dominant negative forms of phosphatidylinositol 3-kinase. This is the first demonstration that
Acanthamoeba
-mediated brain microvascular endothelial cell death is dependent on phosphatidylinositol 3-kinase.
Induction of Nitric Oxide Synthase inAnopheles stephensibyPlasmodium falciparum: Mechanism of Signaling and the Role of Parasite Glycosylphosphatidylinositols
Authors: Lim Junghwa , Gowda D. Channe , Krishnegowda Gowdahalli , Luckhart Shirley
Published: April 2005

Malaria parasite (Plasmodiumspp.) infection in the mosquitoAnopheles stephensiinduces significant expression ofA. stephensinitric oxide synthase (AsNOS) in the midgut epithelium as early as 6 h postinfection and intermittently thereafter. This induction results in the synthesis of inflammatory levels of nitric oxide (NO) in the blood-filled midgut that adversely impact parasite development. In mammals,P. falciparumglycosylphosphatidylinositols (PfGPIs) can induceNOSexpression in immune and endothelial cells and are sufficient to reproduce the major effects of parasite infection. These effects are mediated in part by mimicry of insulin signaling by PfGPIs. In this study, we demonstrate that PfGPIs can induceAsNOSexpression inA. stephensicells in vitro and in the midgut epithelium in vivo. Signaling byP. falciparummerozoites and PfGPIs is mediated throughA. stephensiAkt/protein kinase B and a pathway involving DSOR1, a mitogen-activated protein kinase kinase, and an extracellular signal-regulated kinase. However, despite the involvement of kinases that are also associated with insulin signaling inA. stephensicells, signaling byP. falciparumand by PfGPIs is distinctively different from signaling by insulin. Therefore, although mimicry of insulin by PfGPIs appears to be restricted to mammalian hosts ofP. falciparum, the conservation of PfGPIs as a prominent parasite-derived signal of innate immunity can now be extended to includeAnophelesmosquitoes, indicating that parasite signaling of innate immunity is conserved in mosquito and mammalian cells.
Immunological and Protective Effects of Diepitopic Subunit Dental Caries Vaccines
Authors: Smith Daniel J. , King William F. , Rivero Joy , Taubman Martin A.
Published: April 2005

As a prelude to development of broader-spectrum vaccines for dental caries, we explored the immune potential of constructs combining epitopes from mutans streptococcal glucosyltransferases (GTF) and glucan binding protein B (GbpB). Two diepitopic peptide constructs were synthesized in a multiple antigenic peptide (MAP) format. Both constructs contained SYI, a 20-mer GbpB peptide that included a sequence having major histocompatibility complex class II binding characteristics. One diepitopic construct (SYI-CAT) also contained a 22-mer sequence from the catalytic domain of GTF. Another diepitopic construct (SYI-GLU) contained a 22-mer sequence from the glucan binding domain of GTF. To assess the ability of each construct to induce antibody reactive with GbpB and GTF native proteins, rats were injected subcutaneously with SYI-CAT, SYI-GLU, or the constituent monoepitopic constructs. Only the SYI-CAT construct induced significant levels of serum immunoglobulin G (IgG) and IgA antibody to both pathogenesis-associated proteins. Also, immunization with SYI-CAT significantly (
P
< 0.001) enhanced the antibody response to the CAT peptide. Experiments then compared experimental dental caries after immunization with SYI-CAT, SYI, or CAT MAP constructs, followed by infection with
Streptococcus mutans
strain SJr. Dental caries were lower in each peptide-immunized group than in the sham-injected group. The level of protection after SYI-CAT immunization was similar to that after immunization with constituent MAP constructs. In another experiment, rats were infected with
Streptococcus sobrinus
strain 6715 under an identical protocol. Significant protection was observed on buccal surfaces in both SYI-CAT and CAT construct-immunized, but not in the SYI construct-immunized, groups. Thus, addition of the GbpB-derived SYI peptide to the GTF-derived CAT peptide construct not only enhanced the immunological response to CAT and GTF epitopes, but also extended the protective effect of the construct to include both
S. mutans
and
S. sobrinus
.
Identification and Characterization of Human Surfactant Protein A Binding Protein ofMycoplasma pneumoniae
Authors: Kannan T. R. , Provenzano D. , Wright J. R. , Baseman J. B.
Published: April 2005

Mycoplasma pneumoniaeinfections represent a major primary cause of human respiratory diseases, exacerbate other respiratory disorders, and are associated with extrapulmonary pathologies. Cytadherence is a critical step in mycoplasma colonization, aided by a network of mycoplasma adhesins and cytadherence accessory proteins which mediate binding to host cell receptors. Furthermore, the respiratory mucosa is enriched with extracellular matrix components, including surfactant proteins, fibronectin, and mucin, which provide additional in vivo targets for mycoplasma parasitism. In this study we describe interactions betweenM. pneumoniaeand human surfactant protein-A (hSP-A). Initially, we found that viableM. pneumoniaecells bound to immobilized hSP-A in a dose- and calcium (Ca2+)-dependent manner. Mild trypsin treatment of intact mycoplasmas reduced binding markedly (80 to 90%) implicating a surface-associated mycoplasma protein(s). Using hSP-A-coupled Sepharose affinity chromatography and polyacrylamide gel electrophoresis, we identified a 65-kDa hSP-A binding protein ofM. pneumoniae. The presence of Ca2+enhanced binding of the 65-kDa protein to hSP-A, which was reduced by the divalent cation-chelating agent, EDTA. The 65-kDa hSP-A binding protein ofM. pneumoniaewas identified by sequence analysis as a novel protein (MPN372) possessing a putative S1-like subunit of pertussis toxin at the amino terminus (amino acids 1 to 226), with the remaining amino acids (227 to 591) exhibiting no homology with other subunits of pertussis toxin, other known toxins, or any reported proteins. Recombinant MPN372 (MPN372) bound to hSP-A in a dose-dependent manner, which was markedly reduced by preincubation with mouse recombinant MPN372 antisera. Also, adherence of viableM. pneumoniaecells to hSP-A was inhibited by recombinant MPN372 antisera, demonstrating that MPN372, a previously designated hypothetical protein, is surface exposed and mediates mycoplasma attachment to hSP-A.
TheBrucella abortusCu,Zn Superoxide Dismutase Is Required for Optimal Resistance to Oxidative Killing by Murine Macrophages and Wild-Type Virulence in Experimentally Infected Mice
Authors: Gee Jason M. , Valderas Michelle Wright , Kovach Michael E. , Grippe Vanessa K. , Robertson Gregory T. , Ng Wai-Leung , Richardson John M. , Winkler Malcolm E. , Roop R. Martin
Published: April 2005

Two-dimensional gel electrophoretic analysis of cell lysates fromBrucella abortus2308 and the isogenichfqmutant Hfq3 revealed that the RNA binding protein Hfq (also known as host factor I or HF-I) is required for the optimal stationary phase production of the periplasmic Cu,Zn superoxide dismutase SodC. An isogenicsodCmutant, designated MEK2, was constructed fromB. abortus2308 by gene replacement, and thesodCmutant exhibited much greater susceptibility to killing by O2−generated by pyrogallol and the xanthine oxidase reaction than the parental 2308 strain supporting a role for SodC in protecting this bacterium from O2−of exogenous origin. TheB. abortus sodCmutant was also found to be much more sensitive to killing by cultured resident peritoneal macrophages from C57BL6J mice than 2308, and the attenuation displayed by MEK2 in cultured murine macrophages was enhanced when these phagocytes were treated with gamma interferon (IFN-γ). The attenuation displayed by theB. abortus sodCmutant in both resting and IFN-γ-activated macrophages was alleviated, however, when these host cells were treated with the NADPH oxidase inhibitor apocynin. Consistent with its increased susceptibility to killing by cultured murine macrophages, theB. abortus sodCmutant also displayed significant attenuation in experimentally infected C57BL6J mice compared to the parental strain. These experimental findings indicate that SodC protectsB. abortus2308 from the respiratory burst of host macrophages. They also suggest that reduced SodC levels may contribute to the attenuation displayed by theB. abortus hfqmutant Hfq3 in the mouse model.
Differential Induction of the Toll-Like Receptor 4-MyD88-Dependent and -Independent Signaling Pathways by Endotoxins
Authors: Zughaier Susu M. , Zimmer Shanta M. , Datta Anup , Carlson Russell W. , Stephens David S.
Published: April 2005

The biological response to endotoxin mediated through the Toll-like receptor 4 (TLR4)-MD-2 receptor complex is directly related to lipid A structure or configuration. Endotoxin structure may also influence activation of the MyD88-dependent and -independent signaling pathways of TLR4. To address this possibility, human macrophage-like cell lines (THP-1, U937, and MM6) or murine macrophage RAW 264.7 cells were stimulated with picomolar concentrations of highly purified endotoxins. Harvested supernatants from previously stimulated cells were also used to stimulate RAW 264.7 or 23ScCr (TLR4-deficient) macrophages (i.e., indirect induction).Neisseria meningitidislipooligosaccharide (LOS) was a potent direct inducer of the MyD88-dependent pathway molecules tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein 3α (MIP-3α), and the MyD88-independent molecules beta interferon (IFN-β), nitric oxide, and IFN-γ-inducible protein 10 (IP-10).Escherichia coli55:B5 andVibrio choleraelipopolysaccharides (LPSs) at the same pmole/ml lipid A concentrations induced comparable levels of TNF-α, IL-1β, and MIP-3α, but significantly less IFN-β, nitric oxide, and IP-10. In contrast, LPS fromSalmonella entericaserovars Minnesota and Typhimurium induced amounts of IFN-β, nitric oxide, and IP-10 similar to meningococcal LOS but much less TNF-α and MIP-3α in time course and dose-response experiments. No MyD88-dependent or -independent response to endotoxin was seen in TLR4-deficient cell lines (C3H/HeJ and 23ScCr) and response was restored in TLR4-MD-2-transfected human embryonic kidney 293 cells. Blocking the MyD88-dependent pathway by DNMyD88 resulted in significant reduction of TNF-α release but did not influence nitric oxide release. IFN-β polyclonal antibody and IFN-α/β receptor 1 antibody significantly reduced nitric oxide release.N. meningitidisendotoxin was a potent agonist of both the MyD88-dependent and -independent signaling pathways of the TLR4 receptor complex of human macrophages.E. coli55:B5 andVibrio choleraeLPS, at the same picomolar lipid A concentrations, selectively induced the MyD88-dependent pathway, whileSalmonellaLPS activated the MyD88-independent pathway.
Efficient Ex Vivo Stimulation ofMycobacterium tuberculosis-Specific T Cells by Genetically DetoxifiedBordetella pertussisAdenylate Cyclase Antigen Toxoids
Authors: Wilkinson Katalin A. , Simsova Marcela , Schölvinck Elisabeth , Sebo Peter , Leclerc Claude , Vordermeier H. Martin , Dickson Stuart J. , Brown Jillian R. , Davidson Robert N. , Pasvol Geoffrey , Levin Michael , Wilkinson Robert J.
Published: April 2005

Mycobacterium tuberculosisis a significant threat to global health.Mycobacterium bovisBCG vaccine provides only partial protection, and the skin test reagent used to aid diagnosis of both active and latent tuberculosis, purified protein derivative (PPD), lacks specificity and sensitivity. The use of genetically detoxifiedBordetella pertussisadenylate cyclase toxin (CyaA) as a delivery system for two immunodominant proteins ofM. tuberculosisthat are of greater specificity than PPD, early-secreted antigenic target 6-kDa protein (ESAT-6) and culture filtrate protein 10 (CFP-10), was therefore investigated. CyaA toxoids incorporating these antigens were able to restimulate T cells from more than 91% tuberculosis patients and healthy sensitized donors. Delivery of antigen by CyaA decreased by 10-fold the amount of ESAT-6 and CFP-10 required to restimulate T cells, and in low responders, the overall frequency of gamma interferon-producing cells detected by enzyme-linked immunospot assay was increased (P< 0.01 for both antigens). Delivery of ESAT-6 and CFP-10 by CyaA enabled the detection of both CD4+and CD8+T cells: these responses could be blocked by inhibition of major histocompatibility complex class II or class I, respectively. Covalent linkage of antigen to the CyaA vector was required for enhancement to occur, as a mixture of mock CyaA toxoid plus recombinant ESAT-6 did not lead to enhancement. In a simplified whole-blood model to detect tuberculosis infection, the frequency of positive responses to CFP-10 was increased by CyaA delivery, a potentially important attribute that could facilitate the identification of latent infection.
B-Cell and T-Cell Immune Responses to ExperimentalHelicobacter pyloriInfection in Humans
Authors: Nurgalieva Zhannat Z. , Conner Margaret E. , Opekun Antone R. , Zheng Carl Q. , Elliott Susan N. , Ernst Peter B. , Osato Michael , Estes Mary K. , Graham David Y.
Published: April 2005

The acute antibody and T-cell immune response toHelicobacter pyloriinfection in humans has not been studied systematically. Serum fromH. pylori-naive volunteers challenged withH. pyloriand cured after 4 or 12 weeks was tested by enzyme-linked immunosorbent assays for anti-H. pylori-specific immunoglobulin M (IgM) and IgA established using bacterial lysates from homologous (the infecting strain) and heterologousH. pylori. Proteins recognized by IgM antibody were identified by mass spectrometry of immunoreactive bands separated by two-dimensional gel electrophoresis. Mucosal T-cell subsets (CD4, CD8, CD3, and CD30 cells) were assessed by immunohistochemistry. All 18 infected volunteers developedH. pylori-specific IgM responses to both homologous or heterologousH. pyloriantigens.H. pyloriantigens reacted with IgM antibody at 4 weeks postinfection. IgM Western blotting showed immunoreactivity of postinfection serum samples to multipleH. pyloriproteins with molecular weights ranging between 9,000 (9K) to 150K with homologous strains but only a 70K band using heterologous antigens. Two-dimensional electrophoresis demonstrated that production ofH. pylori-specific IgM antibodies was elicited byH. pyloriflagellins A and B, urease B, ABC transporter binding protein, heat shock protein 70 (DnaK), and alkyl hydroperoxide reductase. Mucosal CD3, CD4, and CD8 T-cell numbers increased following infection. IgM antibody responses were detected to a range of homologousH. pyloriantigens 2 to 4 weeks postchallenge. The majority ofH. pyloriproteins were those involved in motility and colonization and may represent targets for vaccine development.
Relapsing Fever Spirochetes Contain Chromosomal Genes with Unique Direct Tandemly Repeated Sequences
Authors: Guyard Cyril , Chester Earl M. , Raffel Sandra J. , Schrumpf Merry E. , Policastro Paul F. , Porcella Stephen F. , Leong John M. , Schwan Tom G.
Published: April 2005

Genome sequencing of the relapsing fever spirochetes
Borrelia hermsii
and
Borrelia turicatae
identified three open reading frames (ORFs) on the chromosomes that contained internal, tandemly repeated amino acid sequences that were absent in the Lyme disease spirochete
Borrelia burgdorferi
. The predicted amino acid sequences of these genes (BH0209, BH0512, and BH0553) have hydrophobic N termini, indicating that these proteins may be secreted.
B. hermsii
transcribed the three ORFs in vitro, and the BH0512- and BH0553-encoded proteins (PBH-512 and PBH-553) were produced in vitro and in experimentally infected mice. PBH-512 and PBH-553 were on the spirochete's outer surface, and antiserum to these proteins reduced the adherence of
B. hermsii
to red blood cells. PCR analyses of 28 isolates of
B. hermsii
and 8 isolates of
B. turicatae
demonstrated polymorphism in each gene correlated with the number of repeats. Serum samples from relapsing fever patients reacted with recombinant PBH-512 and PBH-553, suggesting that these proteins are produced during human infection. These polymorphic proteins may be involved in the pathogenicity of these relapsing fever spirochetes and provide a mechanism for antigenic heterogeneity within their populations.
Mutants of
Mycobacterium tuberculosis
Lacking Three of the Five
rpf
-Like Genes Are Defective for Growth In Vivo and for Resuscitation In Vitro
Authors: Downing Katrina J. , Mischenko Vladimir V. , Shleeva Margarita O. , Young Danielle I. , Young Michael , Kaprelyants Arseny S. , Apt Alexander S. , Mizrahi Valerie
Published: April 2005

Mycobacterium tuberculosis
contains five genes,
rpfA
through
rpfE
, that bear significant homology to the resuscitation-promoting factor (
rpf
) gene of
Micrococcus luteus
, whose product is required to resuscitate the growth of dormant cultures of
M. luteus
and is essential for the growth of this organism. Previous studies have shown that deletion of any one of the five
rpf
-like genes did not affect the growth or survival of
M. tuberculosis
in vitro. In conjunction with the results of whole-genome expression profiling, this finding was indicative of their functional redundancy. In this study, we demonstrate that the single deletion mutants are phenotypically similar to wild-type
M. tuberculosis
H37Rv in vivo. The deletion of individual
rpf
-like genes had no discernible effect on the growth or long-term survival of
M. tuberculosis
in liquid culture, and the ability to resuscitate spontaneously from a nonculturable state in a most probable number assay was also unaffected for the three strains tested (the Δ
rpfB
,
ΔrpfD
, and Δ
rpfE
strains). In contrast, two multiple strains, KDT8 (Δ
rpfA
-mutation
ΔrpfC ΔrpfB
) and KDT9 (Δ
rpfA ΔrpfC ΔrpfD
), which lack three of the five
rpf
-like genes, were significantly yet differentially attenuated in a mouse infection model. These mutants were also unable to resuscitate spontaneously in vitro, demonstrating the importance of the Rpf-like proteins of
M. tuberculosis
in resuscitation from the nonculturable state. These results strongly suggest that the biological functions of the five
rpf
-like genes of
M. tuberculosis
are not wholly redundant and underscore the potential utility of these proteins as targets for therapeutic intervention.
Invasion of Epithelial Cells by Locus of Enterocyte Effacement-Negative EnterohemorrhagicEscherichia coli
Authors: Luck Shelley N. , Bennett-Wood Vicki , Poon Rachael , Robins-Browne Roy M. , Hartland Elizabeth L.
Published: April 2005

The majority of enterohemorrhagicEscherichia coli(EHEC) strains associated with severe disease carry the locus of enterocyte effacement (LEE) pathogenicity island, which encodes the ability to induce attaching and effacing lesions on the host intestinal mucosa. While LEE is essential for colonization of the host in these pathogens, strains of EHEC that do not carry LEE are regularly isolated from patients with severe disease, although little is known about the way these organisms interact with the host epithelium. In this study, we compared the adherence properties of clinical isolates of LEE-negative EHEC with those of LEE-positive EHEC O157:H7. Transmission electron microscopy revealed that LEE-negative EHEC O113:H21 was internalized by Chinese hamster ovary (CHO-K1) epithelial cells and that intracellular bacteria were located within a membrane-bound vacuole. In contrast, EHEC O157:H7 remained extracellular and intimately attached to the epithelial cell surface. Quantitative gentamicin protection assays confirmed that EHEC O113:H21 was invasive and also showed that several other serogroups of LEE-negative EHEC were internalized by CHO-K1 cells. Invasion by EHEC O113:H21 was significantly reduced in the presence of the cytoskeletal inhibitors cytochalasin D and colchicine and the pan-Rho GTPase inhibitor compactin, whereas the tyrosine kinase inhibitor genistein had no significant impact on bacterial invasion. In addition, we found that EHEC O113:H21 was invasive for the human colonic cell lines HCT-8 and Caco-2. Overall these studies suggest that isolates of LEE-negative EHEC may employ a mechanism of host cell invasion to colonize the intestinal mucosa.
Structural and Genetic Diversity of Group BStreptococcusCapsular Polysaccharides
Authors: Cieslewicz Michael J. , Chaffin Donald , Glusman Gustavo , Kasper Dennis , Madan Anup , Rodrigues Stephani , Fahey Jessica , Wessels Michael R. , Rubens Craig E.
Published: April 2005

Group BStreptococcus(GBS) is an important pathogen of neonates, pregnant women, and immunocompromised individuals. GBS isolates associated with human infection produce one of nine antigenically distinct capsular polysaccharides which are thought to play a key role in virulence. A comparison of GBS polysaccharide structures of all nine known GBS serotypes together with the predicted amino acid sequences of the proteins that direct their synthesis suggests that the evolution of serotype-specific capsular polysaccharides has proceeded through en bloc replacement of individual glycosyltransferase genes with DNA sequences that encode enzymes with new linkage specificities. We found striking heterogeneity in amino acid sequences of synthetic enzymes with very similar functions, an observation that supports horizontal gene transfer rather than stepwise mutagenesis as a mechanism for capsule variation. Eight of the nine serotypes appear to be closely related both structurally and genetically, whereas serotype VIII is more distantly related. This similarity in polysaccharide structure strongly suggests that the evolutionary pressure toward antigenic variation exerted by acquired immunity is counterbalanced by a survival advantage conferred by conserved structural motifs of the GBS polysaccharides.
Tumor Necrosis Factor Alpha Plays a Role in the Acceleration of Atherosclerosis byChlamydia pneumoniaein Mice
Authors: Campbell Lee Ann , Nosaka Tadayoshi , Rosenfeld Michael E. , Yaraei Kambiz , Kuo Cho-chou
Published: April 2005

The role of tumor necrosis factor alpha (TNF-α) inChlamydia pneumoniaeatherogenesis was evaluated in TNF-α p55 receptor-deficient C57BL/6J mice fed a high-fat/high-cholesterol diet. No acceleration of atherosclerotic lesion development was observed in infected mice compared to uninfected mice, indicating that TNF-α plays a role in the acceleration of atherosclerosis byC. pneumoniae.
Investigations on the Reduction of Molecular Oxygen on Polyphenol Oxidase-Modified Electrode
Authors: Jiang Hui , Shi Chun-Hua , Xie Yong-Shu , Liu Qing-Liang
Published: April 2005

Polyphenol oxidase (PPO, E.C.1.10.3.1) from Nicotiana tobacum, PPO II, shows a different behavior from that of PPOs from other sources. A one-electron oxygen reduction on PPO II - Nafion modified glassy carbon electrode surface has been observed by square-wave voltammetry. The cathodic peak has been found to be proportional to the concentration of dissolved oxygen. The optimum salt concentration was 0.2 mol/l. The study of its dependence on pH (4-9) indicates that the reduction of oxygen is accompanied by a one-proton-transfer process. Temperature shows little influence on the cathodic peak. The electrode storage has also been studied to evaluate its stability.
Conformational Influence on Deprotonation of Bis(methoxycarbimido)amine Ligand
Authors: Brudíková Kateřina , Breza Martin , Májek Pavel
Published: April 2005

Using MP2 treatment, the optimal geometries and corresponding electronic structures of [HN=C(OCH3)-N-C(OCH3)=NH]- (mici-), HN=C(OCH3)-NH-C(OCH3)=NH (Hmici), [Cu(mici)]2 and [Cu(Hmici)2]2+ were investigated. In agreement with experimental data, the preferred conformation of our systems depends on the ligand: mici- prefers the methoxy groups oriented to the central N atom whereas Hmici prefers the opposite orientations. The shielding by the methoxy groups is the main reason for the preferred site of deprotonation. The deprotonation of the [Cu(Hmici)2]2+ complex is more probable than that of the free Hmici ligand. Due to preferred conformation of this complex, the deprotonation proceeds by cleavage of the central N-H bond.
Some Aspects of Reaction of 6-Aminouracil and 6-Amino-2-Thiouracil with α,β-Unsaturated Ketones
Authors: Chebanov Valentin A. , Saraev Vyacheslav E. , Gura Ekaterina A. , Desenko Sergey M. , Musatov Vladimir I.
Published: April 2005

A number of 5,7-diaryl-5,8-dihydropyrido[2,3-d]pyrimidines and 5,7-diarylpyrido[2,3-d]- pyrimidines were obtained by the reaction of 6-aminouracil derivatives with α,β-unsaturated ketones. Basic catalysts decrease yields of the dihydro derivatives whereas acids increase it. In the reactions of ketones containing the dimethylamino group, elimination of the aryl substituent from position 5 of the pyridopyrimidine system was observed. Some aspects of oxidation of 5,8-dihydropyrido[2,3-d]pyrimidines and synthesis of pyrido[2,3-d]pyrimidines were also investigated.
A Method for Estimating Mass Transfer Coefficients in a Packed Column Using Reactive Absorption Data
Authors: Danilov Valery A. , Moon Il
Published: April 2005

This paper is devoted to the development of a new method for estimating mass transfer coefficients and effective area in packed columns in the case of reactive absorption. The method is based on a plug-flow model of reactive absorption of carbon dioxide with sodium hydroxide solution. The parameter estimation problem is solved using an optimization technique. Some mass transfer parameters are found to be correlated. Global sensitivity analysis by Sobol's technique showed that the unit model with the defined objective function is sensitive to the estimated parameter. Case studies of reactive absorption with different packings illustrate application of the proposed method for estimating mass transfer coefficients and effective area from column operation data. The model calculations are compared with experimental data obtained by other authors. The concentration profiles calculated by the unit model with the estimated parameters are shown to match well with experimental profiles from literature. A good agreement between estimated values and experimental data from literature confirms the applicability of this method.
The systematic position of the Late Jurassic alleged dinosaurMacelognathus(Crocodylomorpha: Sphenosuchia)
Authors: Göhlich Ursula B , Chiappe Luis M , Clark James M , Sues Hans-Dieter
Published: April 2005

Macelognathus vagans was described by O.C. Marsh in 1884, based on a mandibular symphysis from the Upper Jurassic Morrison Formation of Wyoming. Often considered a dinosaur but later tentatively referred to the Crocodylia, its phylogenetic identity has until now been enigmatic. New material of this species from the Morrison Formation of western Colorado demonstrates its affinities with basal crocodylomorphs commonly grouped together as the Sphenosuchia, which are characterized by a gracile postcranial skeleton with erect limb posture. Macelognathus shares features with Kayentasuchus from the Lower Jurassic Kayenta Formation of Arizona and Hallopus, which may be from the Morrison Formation of eastern Colorado. The new material constitutes the youngest definitive occurrence of a sphenosuchian, previously known from the Late Triassic to the Middle or Late? Jurassic.