bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconstruction of de novo pathway for synthesis of UDP‐glucuronic acid and UDP‐xylose from intrinsic UDP‐glucose in Saccharomyces cerevisiae
Authors: Oka Takuji , Jigami Yoshifumi
Published: May 2006

UDP‐d‐glucuronic acid and UDP‐d‐xylose are required for the biosynthesis of glycosaminoglycan in mammals and of cell wall polysaccharides in plants. Given the importance of these glycans to some organisms, the development of a system for production of UDP‐d‐glucuronic acid and UDP‐d‐xylose from a common precursor could prove useful for a number of applications. The budding yeast Saccharomyces cerevisiae lacks an endogenous ability to synthesize or consume UDP‐d‐glucuronic acid and UDP‐d‐xylose. However, yeast have a large cytoplasmic pool of UDP‐d‐glucose that could be used to synthesize cell wall β‐glucan, as a precursor of UDP‐d‐glucuronic acid and UDP‐d‐xylose. Thus, if a mechanism for converting the precursors into the end‐products can be identified, yeast may be harnessed as a system for production of glycans. Here we report a novel S. cerevisiae strain that coexpresses the Arabidopsis thaliana genes UGD1 and UXS3, which encode a UDP‐glucose dehydrogenase (AtUGD1) and a UDP‐glucuronic acid decarboxylase (AtUXS3), respectively, which are required for the conversion of UDP‐d‐glucose to UDP‐d‐xylose in plants. The recombinant yeast strain was capable of converting UDP‐d‐glucose to UDP‐d‐glucuronic acid, and UDP‐d‐glucuronic acid to UDP‐d‐xylose, in the cytoplasm, demonstrating the usefulness of this yeast system for the synthesis of glycans. Furthermore, we observed that overexpression of AtUGD1 caused a reduction in the UDP‐d‐glucose pool, whereas coexpression of AtUXS3 and AtUGD1 did not result in reduction of the UDP‐d‐glucose pool. Enzymatic analysis of the purified hexamer His‐AtUGD1 revealed that AtUGD1 activity is strongly inhibited by UDP‐d‐xylose, suggesting that AtUGD1 maintains intracellular levels of UDP‐d‐glucose in cooperation with AtUXS3 via the inhibition of AtUGD1 by UDP‐d‐xylose.
Investigation of the variables that impact upon the knowledge of cardiac risk factors
Authors: Liew Hui , Taylor David McD , Tjipto Alwie , Bailey Michael
Published: May 2006

Objective:  Awareness of cardiac disease risk factors is required before they can be modified. The present study aimed to investigate risk factor knowledge and the variables that impact upon this knowledge.

Methods:  We undertook an analytical, cross‐sectional survey of 226 patients attending an ED. Patients were asked to recall as many cardiac risk factors as possible and to rate the risk of nine given risk factors. Data relating to sources of risk factor information were collected. Uni‐ and multivariate (multiple linear regression) analyses determined variables that impacted upon the risk factor knowledge score.

Results:  Mean patient age was 60.2 ± 15 years, 55.3% (95% confidence interval 48.6–61.9) were male and 19.9% (95% confidence interval 15.0–25.8) had known cardiac disease. The mean risk factor knowledge score of 2.5 ± 1.5 out of a possible 12 (median 3) was indicative of poor knowledge. Smoking, poor diet and stress/worry/tension were the most common factors reported. Variables impacting significantly on the knowledge score were English as a first language (P < 0.001), age (negative correlation, P < 0.001) and the receipt of information relating to cardiac health (P < 0.001). The patients’ general practitioner and the media were the most important sources of information.

Conclusions:  Patients’ knowledge of cardiac risk factors is generally poor and education strategies are indicated. At the individual level, the general practitioner is likely to remain as an important influence on knowledge. However, complementary media education programs are indicated at the community level. Patient subgroups at ‘high risk’ through poor knowledge should be specifically targeted.
Refuge from the Lord’s Resistance Army in Uganda: A report from a Médecins Sans Frontières team leader
Authors: Caruso Ngaire
Published: May 2006

In 2005 the author worked for Médecins Sans Frontières (MSF, or Doctors without Borders) in northern Uganda. This short report shares some background information on MSF, the situation in northern Uganda as a consequence of the activities of the Lord’s Resistance Army (LRA), the work of the MSF project and the personal experience of being there.
Genetic diversity at the hinge region of the unique immunoglobulin heavy gamma (IGHG) gene in leporids (Oryctolagus, Sylvilagus and Lepus)
Authors: Esteves P. J. , Carmo C. , Godinho R. , Van Der Loo W.
Published: May 2006

Unlike other species, European rabbit (Oryctolagus cuniculus) possesses only one immunoglobulin gamma class. Allelic diversity at the Ig (immunoglobulin) gamma constant region encoded by the unique IGHG (immunoglobulin heavy gamma) gene is moreover much reduced. In the European rabbit, the genetic variation at IGGH hinge region is limited to a single nucleotide substitution, which causes a Met–Thr interchange at amino acid position 9 (IMGT hinge numbering). We have analysed the diversity at this region more in‐depth by, (1) analysing the allelic variation in 11 breeds of domestic European rabbit (Oryctolagus cuniculus cuniculus), and (2) sequencing the gamma hinge exon in wild specimens of six species of rabbit (Oryctolagus and Sylvilagus) and hares (Lepus), including the two Oryctolagus subspecies (O. cuniculus cuniculus and O. cuniculus algirus). It appeared that among leporid species, amino acid changes occur exclusively at positions 8 and 9. However, while position 8 is occupied by either Pro or Ser residues, four different residues can occur at position 9 (Met, Thr, Pro and Leu). This variation concerns sites of potential O‐glycosylation and/or proteolytic cleavage, suggesting that the underlying genetic diversity could be the outcome of selection. Preservation of the gamma hinge polymorphism in domestic stocks could therefore be important. We report here a polymerase chain reaction/restriction fragment length polymorphism protocol that has allowed the monitoring of the heterozygosity levels at the gamma hinge in 11 breeds of domestic European rabbit.
A Suction Bailer for Sampling Very Thin Saturated Zones
Authors: Hubbell Joel M. , Osiensky James L. , Nicholl Michael J. , Sisson James B.
Published: May 2006

A suction bailer is developed for the express purpose of sampling very thin perched water bodies (on the order of 1 cm thick) that may also be ephemeral. This device incorporates a semi‐permeable membrane on the bottom of the bailer that allows water entry, while simultaneously blocking air. This design allows unattended sample collection, which is monitored with a simple pressure transducer. Three prototypes were constructed and tested; one is based on a commercial suction lysimeter, while the other two are fabricated from stainless steel. All three prototypes were shown to be capable of sampling thin layers of water on the order of 1 cm thick and operating unattended for extended periods to capture intermittent events. Sample sizes of 100–1,000 mL are possible depending on fluid availability. The design does not place any constraints on the depth of emplacement.
Application of Six Sigma Methods for Improving the Analytical Data Management Process in the Environmental Industry
Authors: French Christopher M. , Duplancic Neno
Published: May 2006

Honeywell applied the rigorous and well‐documented Six Sigma quality‐improvement approach to the complex, highly heterogeneous, and mission‐critical process of remedial site environmental data management to achieve a sea change in terms of data quality, environmental risk reduction, and overall process cost reduction. The primary focus was to apply both qualitative and quantitative Six Sigma methods to improve electronic management of analytical laboratory data generated for environmental remediation and long‐term monitoring programs. The process includes electronic data delivery, data QA/QC checking, data verification, data validation, database administration, regulatory agency reporting and linkage to spatial information, and real‐time geographical information systems. Results of the analysis identified that automated, centralized web‐based software tools delivered through Software as a Service (SaaS) model are optimal to improve the process resulting in cost reductions, while simultaneously improving data quality and long‐term data usability and perseverance. A pilot project was completed that quantified cycle time and cost improvements of 50% and 65%, respectively.
Stable isotope analyses document intraguild predation in wolf spiders (Araneae: Lycosidae) and underline beneficial effects of alternative prey and microhabitat structure on intraguild prey survival
Authors: Rickers Silke , Langel Reinhard , Scheu Stefan
Published: May 2006

Intraguild predation (IGP) is common among generalist predators and an important issue in food web theory, because IGP may destabilise communities by increasing extinction of species. Also, IGP may interfere with the effectiveness of generalist predators as biological control agents. In general, occurrence of IGP in laboratory or field studies is inferred from abundance data or direct observations only. We investigated if tracing stable isotopes allows distinction between different types of predation and confirmation of IGP. Wolf spiders were chosen as model organisms for generalist predators; IGP of third instarA. cuneataon second instarP. palustriswas investigated in a laboratory experiment. The availability of alternative prey and the complexity of the microhabitat were manipulated, since both factors are thought to facilitate coexistence of predators.

Stable isotope analysis documented predation ofA. cuneataonP. palustrisand predation on alternative prey by both juveniles. Both the presence of alternative prey and the availability of shelter reduced mortality of juvenileP. palustrisduring the first week. During the second week mortality increased in complex structure without alternative prey presumably due to enhanced activity and cannibalism among starvingP. palustris. Thus, microhabitat complexity and prey abundance may foster coexistence of wolf spiders in the field.

In conclusion, stable isotope analysis was proven a powerful tool to investigate animal behaviour without direct observation. The method allowed disentangling predator feeding behaviour when more than one type of prey was present.
Role of endothelin receptor activation in secondary pulmonary hypertension in awake swine after myocardial infarction
Authors: Houweling Birgit , Merkus Daphne , Sorop Oana , Boomsma Frans , Duncker Dirk J.
Published: May 2006

We previously observed that pulmonary hypertension secondary to myocardial infarction (MI) in swine is characterized by elevated plasma endothelin (ET) levels and pulmonary vascular resistance (PVR). Consequently, we tested the hypothesis that an increased ET‐mediated vasoconstrictor influence contributes to secondary pulmonary hypertension after MI and investigated the involvement of ETAand ETBreceptor subtypes. Chronically instrumented swine with (MI swine;n= 25) or without (normal swine;n= 19) MI were studied at rest and during treadmill exercise (up to 4 km h−1), in the absence and presence of the ETAantagonist EMD 122946 or the mixed ETA/ETBantagonist tezosentan. In normal swine, exercise caused a small decrease in PVR. ETAblockade had no effect on PVR at rest or during exercise. Conversely, ETA/ETBblockade decreased PVR but only during exercise (at 4 km h−1, from 3.0 ± 0.1 to 2.3 ± 0.1 mmHg min l−1;P≤ 0.05). MI increased pulmonary arterial pressure and PVR both at rest and during exercise (bothP≤ 0.05). The increased pulmonary arterial pressure correlated with the increased plasma ET levels in resting MI swine (r= 0.71;P≤ 0.01). Furthermore, the pulmonary vasoconstrictor response to ET‐1 infusion was enhanced after MI (P≤ 0.05). ETA/ETBblockade decreased PVR in MI swine from 3.6 ± 0.3 to 3.1 ± 0.5 mmHg min l−1at rest and from 3.4 ± 0.3 to 2.4 ± 0.2 mmHg min l−1during exercise at 4 km h−1(bothP≤ 0.05). This increased response to mixed ETA/ETBblockade in MI compared to normal swine appeared to be the result of an increased ETA‐mediated vasoconstriction, as ETAblockade decreased PVR in MI swine from 3.4 ± 0.4 to 2.8 ± 0.2 mmHg min l−1at rest and from 3.1 ± 0.3 to 2.6 ± 0.2 mmHg min l−1at 4 km h−1(bothP≤ 0.05). In conclusion, increased plasma ET levels together with increased pulmonary resistance vessel responsiveness to ET result in an exaggerated pulmonary vasoconstrictor influence of ET in swine with a recent MI. This vasoconstrictor influence is the result of an emergent tonic ETA‐mediated vasoconstriction in addition to the exercise‐induced ETB‐mediated vasoconstriction that is already present in normal swine.
Residual force enhancement in skeletal muscle
Authors: Herzog W. , Lee E. J. , Rassier D. E.
Published: May 2006

Residual force enhancement has been observed consistently in skeletal muscles following active stretching. However, its underlying mechanism(s) remain elusive, and it cannot be explained readily within the framework of the cross‐bridge theory. Traditionally, residual force enhancement has been attributed to the development of sarcomere length non‐uniformities. However, recent evidence suggests that this might not be the case. Rather, it appears that residual force enhancement has an active and a passive component. The active component is tentatively associated with changes in the cross‐bridge kinetics that might be reflected in decreased detachment rates following active muscle stretching, while the passive component possibly originates from a structural protein, such as titin, whose stiffness might be regulated by calcium.
AMP‐activated protein kinase and the regulation of Ca2+ signalling in O2‐sensing cells
Authors: Evans A. Mark
Published: May 2006

All cells respond to metabolic stress. However, a variety of specialized cells, commonly referred to as O2‐sensing cells, are acutely sensitive to relatively small changes in P. Within a variety of organisms such O2‐sensing cells have evolved as vital homeostatic mechanisms that monitor O2 supply and alter respiratory and circulatory function, as well as the capacity of the blood to transport O2. Thereby, arterial P may be maintained within physiological limits. In mammals, for example, two key tissues that contribute to this process are the pulmonary arteries and the carotid bodies. Constriction of pulmonary arteries by hypoxia optimizes ventilation–perfusion matching in the lung, whilst carotid body excitation by hypoxia initiates corrective changes in breathing patterns via increased sensory afferent discharge to the brain stem. Despite extensive investigation, the precise mechanism(s) by which hypoxia mediates these responses has remained elusive. It is clear, however, that hypoxia inhibits mitochondrial function in O2‐sensing cells over a range of P that has no such effect on other cell types. This raised the possibility that AMP‐activated protein kinase might function to couple mitochondrial oxidative phosphorylation to Ca2+ signalling mechanisms in O2‐sensing cells and thereby underpin pulmonary artery constriction and carotid body excitation by hypoxia. Our recent investigations have provided significant evidence in support of this view.
Hypersensitivity of pulmonary chemosensitive neurons induced by activation of protease‐activated receptor‐2 in rats
Authors: Gu Qihai , Lee Lu‐Yuan
Published: May 2006

This study was carried out to determine the effect of protease‐activated receptor‐2 (PAR2) activation on the pulmonary chemoreflex responses and on the sensitivity of isolated rat vagal pulmonary chemosensitive neurons. In anaesthetized, spontaneously breathing rats, intratracheal instillation of trypsin (0.8 mg ml−1, 0.1 ml), an endogenous agonist of PAR2, significantly amplified the capsaicin‐induced pulmonary chemoreflex responses. The enhanced responses were completely abolished by perineural capsaicin treatment of both cervical vagi, suggesting the involvement of pulmonary C‐fibre afferents. In patch‐clamp recording experiments, pretreatment with trypsin (0.1 μm, 2 min) potentiated the capsaicin‐induced whole‐cell inward current in isolated pulmonary sensory neurons. The potentiating effect of trypsin was mimicked by PAR2‐activating peptide (PAR2‐AP) in a concentration‐dependent manner. PAR2‐AP pretreatment (100 μm, 2 min) also markedly enhanced the acid‐evoked inward currents in these sensory neurons. Furthermore, the sensitizing effect of PAR2was completely abolished by pretreatment with either U73122 (1 μm, 4 min), a phospholipase C inhibitor, or chelerythrine (10 μm, 4 min), a protein kinase C (PKC) inhibitor. In summary, our results have demonstrated that activation of PAR2upregulates the pulmonary chemoreflex sensitivityin vivoand the excitability of isolated pulmonary chemosensitive neuronsin vitro, and this effect of PAR2activation was mediated through the PKC‐dependent transduction pathway. These results further suggest that the hypersensitivity of these neurons may play a part in the development of airway hyper‐responsiveness resulting from PAR2activation.
Functions of AMP‐activated protein kinase in adipose tissue
Authors: Daval Marie , Foufelle Fabienne , Ferré Pascal
Published: May 2006

AMP‐activated protein kinase (AMPK) is involved in cellular energy homeostasis. Its functions have been extensively studied in muscles and liver. AMPK stimulates pathways which increase energy production (glucose transport, fatty acid oxidation) and switches off pathways which consume energy (lipogenesis, protein synthesis, gluconeogenesis). This has led to the concept that AMPK has an interesting pharmaceutical potential in situations of insulin resistance and it is indeed the target of existing drugs and hormones which improve insulin sensitivity. Adipose tissue is a key player in energy metabolism through the release of substrates and hormones involved in metabolism and insulin sensitivity. Activation of AMPK in adipose tissue can be achieved through situations such as fasting and exercise. Leptin and adiponectin as well as hypoglycaemic drugs are activators of adipose tissue AMPK. This activation probably involves changes in the AMP/ATP ratio and the upstream kinase LKB1. When activated, AMPK limits fatty acid efflux from adipocytes and favours local fatty acid oxidation. Since fatty acids have a key role in insulin resistance, especially in muscles, activating AMPK in adipose tissue might be found to be beneficial in insulin‐resistant states, particularly as AMPK activation also reduces cytokine secretion in adipocytes.
Temperature change does not affect force between regulated actin filaments and heavy meromyosin in single‐molecule experiments
Authors: Kawai Masataka , Kido Takanori , Vogel Martin , Fink Rainer H. A. , Ishiwata Shin'ichi
Published: May 2006

The temperature dependence of sliding velocity, force and the number of cross‐bridges was studied on regulated actin filaments (reconstituted thin filaments) when they were placed on heavy meromyosin (HMM) attached to a glass surface. The regulated actin filaments were used because our previous study on muscle fibres demonstrated that the temperature effect was much reduced in the absence of regulatory proteins. A fluorescently labelled thin filament was attached to the gelsolin‐coated surface of a polystyrene bead. The bead was trapped by optical tweezers, and HMM–thin filament interaction was performed at 20–35°C to study the temperature dependence of force at the single‐molecule level. Our experiments showed that there was a small increase in force with temperature (Q10= 1.43) and sliding velocity (Q10= 1.46). The small increase in force was correlated with the small increase in the number of cross‐bridges (Q10= 1.49), and when force was divided by the number of cross‐bridges, the result did not depend on the temperature (Q10= 1.03). These results demonstrate that the force each cross‐bridge generates is fixed and independent of temperature. Our additional experiments demonstrate that tropomyosin (Tm) in the presence of troponin (Tn) and Ca2+ enhances both force and velocity, and a truncated mutant, Δ23Tm, diminishes force and velocity. These results are consistent with the hypothesis that Tm in the presence of Tn and Ca2+ exerts a positive allosteric effect on actin to make actomyosin linkage more secure so that larger forces can be generated.
AMPK integrates nutrient and hormonal signals to regulate food intake and energy balance through effects in the hypothalamus and peripheral tissues
Authors: Xue Bingzhong , Kahn Barbara B.
Published: May 2006

The evolutionarily conserved serine/threonine kinase, AMP‐activated protein kinase (AMPK), functions as a cellular fuel gauge that regulates metabolic pathways in glucose and fatty acid metabolism and protein synthesis. Recent data strongly implicate the AMPK–acetyl CoA carboxylase (ACC)–malonyl CoA pathway in the hypothalamus in the regulation of food intake, body weight and hepatic glucose production. Furthermore, data indicate that AMPK is a mediator of the effects of adipocyte‐derived and gut‐derived hormones and peptides on fatty acid oxidation and glucose uptake in peripheral tissues. Studies are now elucidating the potential role of kinases upstream of AMPK in these metabolic effects. In addition, recently, several novel downstream effectors of AMPK have been identified. The AMPK pathway in the hypothalamus and peripheral tissues coordinately integrates inputs from multiple hormones, peptides and nutrients to maintain energy homeostasis.
Improved Concept and Model of Eddy Current Damper
Authors: Sodano Henry A. , Bae Jae-Sung , Inman Daniel J. , Belvin W. Keith
Published: May 2006

When a conductive material experiences a time-varying magnetic field, eddy currents are generated in the conductor. These eddy currents circulate such that they generate a magnetic field of their own, however the field generated is of opposite polarity, causing a repulsive force. The time-varying magnetic field needed to produce such currents can be induced either by movement of the conductor in the field or by changing the strength or position of the source of the magnetic field. In the case of a dynamic system the conductor is moving relative to the magnetic source, thus generating eddy currents that will dissipate into heat due to the resistivity of the conductor. This process of the generation and dissipation of eddy current causes the system to function as a viscous damper. In a previous study, the concept and theoretical model was developed for one eddy current damping system that was shown to be effective in the suppression of transverse beam vibrations. The mathematical model developed to predict the amount of damping induced on the structure was shown to be accurate when the magnet was far from the beam but was less accurate for the case that the gap between the magnet and beam was small. In the present study, an improved theoretical model of the previously developed system will be formulated using the image method, thus allowing the eddy current density to be more accurately computed. In addition to the development of an improved model, an improved concept of the eddy current damper configuration is developed, modeled, and tested. The new damper configuration adds significantly more damping to the structure than the previously implemented design and has the capability to critically damp the beam’s first bending mode. The eddy current damper is a noncontacting system, thus allowing it to be easily applied and able to add significant damping to the structure without changing dynamic response. Furthermore, the previous model and the improved model will be applied to the new damper design and the enhanced accuracy of this new theoretical model will be proven.
Apes Save Tools for Future Use
Authors: Mulcahy Nicholas J. , Call Josep
Published: May 2006

Planning for future needs, not just current ones, is one of the most formidable human cognitive achievements. Whether this skill is a uniquely human adaptation is a controversial issue. In a study we conducted, bonobos and orangutans selected, transported, and saved appropriate tools above baseline levels to use them 1 hour later (experiment 1). Experiment 2 extended these results to a 14-hour delay between collecting and using the tools. Experiment 3 showed that seeing the apparatus during tool selection was not necessary to succeed. These findings suggest that the precursor skills for planning for the future evolved in great apes before 14 million years ago, when all extant great ape species shared a common ancestor.
Agent-Specific Responses in the Cingulate Cortex During Economic Exchanges
Authors: Tomlin Damon , Kayali M. Amin , King-Casas Brooks , Anen Cedric , Camerer Colin F. , Quartz Steven R. , Montague P. Read
Published: May 2006

Interactions with other responsive agents lie at the core of all social exchange. During a social exchange with a partner, one fundamental variable that must be computed correctly is who gets credit for a shared outcome; this assignment is crucial for deciding on an optimal level of cooperation that avoids simple exploitation. We carried out an iterated, two-person economic exchange and made simultaneous hemodynamic measurements from each player's brain. These joint measurements revealed agent-specific responses in the social domain (“me” and “not me”) arranged in a systematic spatial pattern along the cingulate cortex. This systematic response pattern did not depend on metrical aspects of the exchange, and it disappeared completely in the absence of a responding partner.
Dispersal Limitations Matter for Microbial Morphospecies
Authors: Telford Richard J. , Vandvik Vigdis , Birks H. J. B.
Published: May 2006

In contrast with macroorganisms, whose geographical ranges are typically restricted, many microbial species appear to have cosmopolitan distributions. This observation has been explained as a consequence of ubiquitous dispersal caused by the enormous population sizes of microbial species. Recently, this “everything is everywhere, but, the environment selects” theory has been challenged by the detection of considerable regional genetic variability within microbial morphospecies. We demonstrate that, contrary to what is expected under ubiquitous dispersal, evidence of regional-scale metacommunity processes can be detected in microbial morphospecies. Our results imply that the microbial and macrobial world are structured by analogous processes.
Fast Mass Transport Through Sub-2-Nanometer Carbon Nanotubes
Authors: Holt Jason K. , Park Hyung Gyu , Wang Yinmin , Stadermann Michael , Artyukhin Alexander B. , Grigoropoulos Costas P. , Noy Aleksandr , Bakajin Olgica
Published: May 2006

We report gas and water flow measurements through microfabricated membranes in which aligned carbon nanotubes with diameters of less than 2 nanometers serve as pores. The measured gas flow exceeds predictions of the Knudsen diffusion model by more than an order of magnitude. The measured water flow exceeds values calculated from continuum hydrodynamics models by more than three orders of magnitude and is comparable to flow rates extrapolated from molecular dynamics simulations. The gas and water permeabilities of these nanotube-based membranes are several orders of magnitude higher than those of commercial polycarbonate membranes, despite having pore sizes an order of magnitude smaller. These membranes enable fundamental studies of mass transport in confined environments, as well as more energy-efficient nanoscale filtration.
Food-Caching Western Scrub-Jays Keep Track of Who Was Watching When
Authors: Dally Joanna M. , Emery Nathan J. , Clayton Nicola S.
Published: May 2006

Western scrub-jays (
Aphelocoma californica
) hide food caches for future consumption, steal others' caches, and engage in tactics to minimize the chance that their own caches will be stolen. We show that scrub-jays remember which individual watched them during particular caching events and alter their recaching behavior accordingly. We found no evidence to suggest that a storer's use of cache protection tactics is cued by the observer's behavior.
Variable Very-High-Energy Gamma-Ray Emission from the Microquasar LS I +61 303
Authors: Albert J. , Aliu E. , Anderhub H. , Antoranz P. , Armada A. , Asensio M. , Baixeras C. , Barrio J. A. , Bartelt M. , Bartko H. , Bastieri D. , Bavikadi S. R. , Bednarek W. , Berger K. , Bigongiari C. , Biland A. , Bisesi E. , Bock R. K. , Bordas P. , Bosch-Ramon V. , Bretz T. , Britvitch I. , Camara M. , Carmona E. , Chilingarian A. , Ciprini S. , Coarasa J. A. , Commichau S. , Contreras J. L. , Cortina J. , Curtef V. , Danielyan V. , Dazzi F. , De Angelis A. , de los Reyes R. , De Lotto B. , Domingo-SantamariÌa E. , Dorner D. , Doro M. , Errando M. , Fagiolini M. , Ferenc D. , FernaÌndez E. , Firpo R. , Flix J. , Fonseca M. V. , Font L. , Fuchs M. , Galante N. , Garczarczyk M. , Gaug M. , Giller M. , Goebel F. , Hakobyan D. , Hayashida M. , Hengstebeck T. , HoÌhne D. , Hose J. , Hsu C. C. , Isar P. G. , Jacon P. , Kalekin O. , Kosyra R. , Kranich D. , Laatiaoui M. , Laille A. , Lenisa T. , Liebing P. , Lindfors E. , Lombardi S. , Longo F. , LoÌpez J. , LoÌpez M. , Lorenz E. , Lucarelli F. , Majumdar P. , Maneva G. , Mannheim K. , Mansutti O. , Mariotti M. , MartiÌnez M. , Mase K. , Mazin D. , Merck C. , Meucci M. , Meyer M. , Miranda J. M. , Mirzoyan R. , Mizobuchi S. , Moralejo A. , Nilsson K. , OnÌa-Wilhelmi E. , OrdunÌa R. , Otte N. , Oya I. , Paneque D. , Paoletti R. , Paredes J. M. , Pasanen M. , Pascoli D. , Pauss F. , Pavel N. , Pegna R. , Persic M. , Peruzzo L. , Piccioli A. , Poller M. , Pooley G. , Prandini E. , Raymers A. , Rhode W. , RiboÌ M. , Rico J. , Riegel B. , Rissi M. , Robert A. , Romero G. E. , RuÌgamer S. , Saggion A. , SaÌnchez A. , Sartori P. , Scalzotto V. , Scapin V. , Schmitt R. , Schweizer T. , Shayduk M. , Shinozaki K. , Shore S. N. , Sidro N. , SillanpaÌaÌ A. , Sobczynska D. , Stamerra A. , Stark L. S. , Takalo L. , Temnikov P. , Tescaro D. , Teshima M. , Tonello N. , Torres A. , Torres D. F. , Turini N. , Vankov H. , Vitale V. , Wagner R. M. , Wibig T. , Wittek W. , Zanin R. , Zapatero J.
Published: May 2006

Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.
Analyses of Five Gallinacin Genes and the
Salmonella enterica
Serovar Enteritidis Response in Poultry
Authors: Hasenstein Jason R. , Zhang Guolong , Lamont Susan J.
Published: May 2006

Gallinacins in poultry are functional equivalents of mammalian beta-defensins, which constitute an integral component of the innate immune system.
Salmonella enterica
serovar Enteritidis is a gram-negative bacterium that negatively affects both human and animal health. To analyze the association of genetic variations of the gallinacin genes with the phenotypic response to
S. enterica
serovar Enteritidis, an F
1
population of chickens was created by crossing four outbred broiler sires to dams of two highly inbred lines. The F
1
chicks were evaluated for bacterial colonization after pathogenic
S. enterica
serovar Enteritidis inoculation and for circulating antibody levels after inoculation with
S. enterica
serovar Enteritidis bacterin vaccine. Five candidate genes were studied, including gallinacins 2, 3, 4, 5, and 7. Gene fragments were sequenced from the founder individuals of the resource population, and a mean of 13.2 single-nucleotide polymorphisms (SNP) per kilobase was identified. One allele-defining SNP per gene was utilized to test for statistical associations of sire alleles with progeny response to
S. enterica
serovar Enteritidis. Among the five gallinacin genes evaluated, the
Gal3
and
Gal7
SNPs in broiler sires were found to be associated with antibody production after
S. enterica
serovar Enteritidis vaccination. Utilization of these SNPs as molecular markers for the response to
S. enterica
serovar Enteritidis may result in the enhancement of the immune response in poultry.
Infectivity of the Highly Transformable BBE02−lp56−Mutant ofBorrelia burgdorferi, the Lyme Disease Spirochete, via Ticks
Authors: Jacobs Mary B. , Norris Steven J. , Phillippi-Falkenstein Kathrine M. , Philipp Mario T.
Published: May 2006

InfectiousBorrelia burgdorferistrains that have increased transformability with the shuttle vector pBSV2 were recently constructed by inactivating the gene encoding BBE02, a putative restriction-modification gene product expressed by the linear plasmid lp25 (Kawabata et al., Infect. Immun. 72:7147-7154, 2004). The absence of the linear plasmid lp56, which carries another putative restriction-modification gene, further enhanced transformation rates. The infectivity of these mutants was assessed previously in mice that were inoculated with needle and syringe and was found to be equivalent to that of wild-type spirochetes. Here we examined the infectivity of spirochetes to ticks after capillary inoculation ofIxodes scapularisnymphs and the subsequent spirochetal infectivity to mice via ticks by usingB. burgdorferiB31 clonal isolates lacking lp56 and/or BBE02. The absence of lp56 (but not BBE02) correlated with a lower number of spirochetes in ticks after feeding on mice; this plasmid thus may play a role, albeit not an essential one, in supporting spirochetal survival in the feeding tick. Importantly, however, the absence of lp56 and BBE02 did not detectably influence infectivity to mice via ticks.
Transcriptional Induction of the
Pseudomonas aeruginosa
Type III Secretion System by Low Ca
2+
and Host Cell Contact Proceeds through Two Distinct Signaling Pathways
Authors: Dasgupta Nandini , Ashare Alix , Hunninghake Gary W. , Yahr Timothy L.
Published: May 2006

The opportunistic pathogen
Pseudomonas aeruginosa
utilizes a type III secretion system (T3SS) to intoxicate eukaryotic host cells. Transcription of the T3SS is induced under calcium-limited growth conditions or following intimate contact of
P. aeruginosa
with host cells. In the present study, we demonstrate that expression of the T3SS is controlled by two distinct regulatory mechanisms and that these mechanisms are differentially activated in a host cell-dependent manner. The first mechanism is dependent upon ExsC, a regulatory protein that couples transcription of the T3SS to the activity of the type III secretion machinery. ExsC is essential for induction of the T3SS under low-calcium-growth conditions and for T3SS-dependent cytotoxicity towards social amoebae, insect cells, and erythrocytes. The second regulatory mechanism functions independently of ExsC and is sufficient to elicit T3SS-dependent cytotoxicity towards certain types of mammalian cells. Although this second pathway (ExsC independent) is sufficient, an
exsC
mutant demonstrates a lag in the induction of cytotoxicity towards Chinese hamster ovary cells and is attenuated for virulence in a mouse pneumonia model. We propose that the ExsC-dependent pathway is required for full cytotoxicity towards all host cell types tested whereas the ExsC-independent pathway may represent an adaptation that allows
P. aeruginosa
to increase expression of the T3SS in response to specific types of mammalian cells.
MyD88-Dependent Signaling Affects the Development of Meningococcal Sepsis by Nonlipooligosaccharide Ligands
Authors: Plant Laura , Wan Hong , Jonsson Ann-Beth
Published: May 2006

The Toll-like receptors (TLRs) and the adaptor myeloid differentiation factor 88 (MyD88) are important in the innate immune defenses of the host to microbial infections. Meningococcal ligands signaling via TLRs control inflammatory responses, and stimulation can result in fulminant meningococcal sepsis. In this study, we show that the responses to nonlipooligosaccharide (non-LOS) ligands of meningococci are MyD88 dependent. An isogenic LOS-deficient mutant of the serogroup C meningococcal strain FAM20 caused fatal disease in wild type C57BL/6 mice that was not observed in MyD88−/−mice. Fatality correlated with high proinflammatory cytokine and C5a levels in serum, high neutrophil numbers in blood, and increased bacteremia at 24 h postinfection in the wild-type mice. Infection with the parent strain FAM20 resulted in fatality in 100% of the wild-type mice and 50% of the MyD88−/−mice. We conclude that both LOS and another neisserial ligand cause meningococcal sepsis in an in vivo mouse model and confirm that meningococcal LOS can act via both the MyD88- dependent and -independent pathways, while the non-LOS meningococcal ligand(s) acts only via the MyD88-dependent pathway.
Delineating the Requirement for theBorrelia burgdorferiVirulence Factor OspC in the Mammalian Host
Authors: Stewart Philip E. , Wang Xiaohui , Bueschel Dawn M. , Clifton Dawn R. , Grimm Dorothee , Tilly Kit , Carroll James A. , Weis Janis J. , Rosa Patricia A.
Published: May 2006

We previously demonstrated that outer surface protein C (OspC) ofBorrelia burgdorferiis essential for establishing mammalian infection. However, the role of OspC in mammalian infection is unknown. Here, we report experiments designed to distinguish between two models of OspC function in the mammalian host: (i) OspC fulfills an essential physiological role for growth and host adaptation or (ii) OspC provides a protective role for evasion of components of the innate immune response. We found that aB. burgdorferi ospCmutant, previously demonstrated to be noninfectious in both immunocompetent and SCID mice, could survive in the relatively immune-privileged environment of dialysis membrane chambers implanted within the peritoneum of a rat. TheospCmutant also adapts to the mammalian environment, as determined by the protein profiles of the chamber-cultivated spirochetes. Therefore, OspC does not appear to provide a physiological function for the survival ofB. burgdorferiwithin the mammalian host. The second model, evasion of the innate immune system, was tested by assessing the infectivity of theospCmutant in mice deficient for myeloid differentiation protein 88 (MyD88). Recent studies have shown thatB. burgdorferiis prevented from reaching high cell numbers in the mammalian host by MyD88-dependent signaling pathways. TheospCmutant was incapable of infecting MyD88-deficient mice, suggesting that the role of OspC cannot be related solely to evasion of MyD88-mediated innate immunity. These results reiterate the importance of OspC in mammalian infection and eliminate simple models of function for this enigmatic protein.
Bile Acids Enhance Invasiveness of
Cryptosporidium
spp. into Cultured Cells
Authors: Feng Hanping , Nie Weijia , Sheoran Abhineet , Zhang Quanshun , Tzipori Saul
Published: May 2006

Bile salts such as sodium taurocholate (NaTC) are routinely used to induce the excystation of
Cryptosporidium
oocysts. Here we show that NaTC significantly enhanced the invasion of several cultured cell lines by freshly excysted
Cryptosporidium parvum
and
Cryptosporidium hominis
sporozoites. A variety of purified bile salts or total bile from bovine also enhanced the invasion of cultured cells by
C. parvum
. Further studies demonstrated that NaTC increased protein secretion and gliding motility of sporozoites, the key processes for successful invasion. These observations may lead to improved
Cryptosporidium
infectivity of cultured cells and help future studies on the host-parasite interaction.
Gamma Interferon, Tumor Necrosis Factor Alpha, and Nitric Oxide Synthase 2, Key Elements of Cellular Immunity, Perform Critical Protective Functions during Humoral Defense against Lethal PulmonaryYersinia pestisInfection
Authors: Parent Michelle A. , Wilhelm Lindsey B. , Kummer Lawrence W. , Szaba Frank M. , Mullarky Isis K. , Smiley Stephen T.
Published: May 2006

Pulmonary infection byYersinia pestiscauses pneumonic plague, a rapidly progressing and often fatal disease. To aid the development of safe and effective pneumonic plague vaccines, we are deciphering mechanisms used by the immune system to protect against lethal pulmonaryY. pestisinfection. In murine pneumonic plague models, passive transfer of convalescent-phase sera confers protection, as does active vaccination with liveY. pestis. Here, we demonstrate that protection by either protocol relies upon both gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) cytokines classically associated with type 1 cellular immunity. In both protocols, abrogating IFN-γ or TNF-α activity significantly decreases survival and increases the bacterial burden in pulmonary, splenic, and hepatic tissues. Neutralization of either cytokine also counteracts challenge-induced, vaccination-dependent upregulation of nitric oxide synthase 2 (NOS2). Moreover, genetic depletion of NOS2 suppresses protection conferred by serotherapy. We conclude that IFN-γ, TNF-α, and NOS2, key elements of cellular immunity, perform critical protective functions during humoral defense against lethal pulmonaryY. pestischallenge. These observations strongly suggest that plague vaccines should strive to maximally prime both cellular and humoral immunity.
Identification of
Staphylococcus aureus
Proteins Recognized by the Antibody-Mediated Immune Response to a Biofilm Infection
Authors: Brady Rebecca A. , Leid Jeff G. , Camper Anne K. , Costerton J. William , Shirtliff Mark E.
Published: May 2006

Staphylococcus aureus
causes persistent, recurrent infections (e.g., osteomyelitis) by forming biofilms. To survey the antibody-mediated immune response and identify those proteins that are immunogenic in an
S. aureus
biofilm infection, the tibias of rabbits were infected with methicillin-resistant
S. aureus
to produce chronic osteomyelitis. Sera were collected prior to infection and at 14, 28, and 42 days postinfection. The sera were used to perform Western blot assays on total protein from biofilm grown in vitro and separated by two-dimensional gel electrophoresis. Those proteins recognized by host antibodies in the harvested sera were identified via matrix-assisted laser desorption ionization-time of flight analysis. Using protein from mechanically disrupted total and fractionated biofilm protein samples, we identified 26 and 22 immunogens, respectively. These included a cell surface-associated β-lactamase, lipoprotein, lipase, autolysin, and an ABC transporter lipoprotein. Studies were also performed using microarray analyses and confirmed the biofilm-specific up-regulation of most of these genes. Therefore, although the biofilm antigens are recognized by the immune system, the biofilm infection can persist. However, these proteins, when delivered as vaccines, may be important in directing the immune system toward an early and effective antibody-mediated response to prevent chronic
S. aureus
infections. Previous works have identified
S. aureus
proteins that are immunogenic during acute infections, such as sepsis. However, this is the first work to identify these immunogens during chronic
S. aureus
biofilm infections and to simultaneously show the global relationship between the antigens expressed during an in vivo infection and the corresponding in vitro transcriptomic and proteomic gene expression levels.
Biogenesis of the
Actinobacillus actinomycetemcomitans
Cytolethal Distending Toxin Holotoxin
Authors: Ueno Yoko , Ohara Masaru , Kawamoto Toru , Fujiwara Tamaki , Komatsuzawa Hitoshi , Oswald Eric , Sugai Motoyuki
Published: May 2006

The cell cycle G
2
/M specific inhibitor cytolethal distending toxin (CDT) from
Actinobacillus actinomycetemcomitans
is composed of CdtA, CdtB, and CdtC coded on the
cdtA
,
cdtB
, and
cdtC
genes that are tandem on the chromosomal
cdt
locus.
A. actinomycetemcomitans
CdtA has the lipid binding consensus domain, the so-called “lipobox”, at the N-terminal signal sequence. Using
Escherichia coli
carrying plasmid pTK3022, we show that the 16th residue, cysteine, of CdtA bound [
3
H]palmitate or [
3
H]glycerol. Further, posttranslational processing of the signal peptide, CdtA, was inhibited using globomycin, an inhibitor of lipoprotein-specific signal peptidase II. Fractionation and immunoblotting show the lipid-modified CdtA is present in the outer membrane. Immunoprecipitation and the pull-down assay of the CDT complex from
E. coli
carrying a plasmid containing
cdtABC
demonstrated that the CDT complex in the periplasm is composed of CdtA, CdtB, and CdtC and that the CDT complex in culture supernatant is an N-terminally truncated (36 to 43 amino acids) form of CdtA (CdtA′), CdtB, and CdtC. This suggests that CDT is present as a complex both in the periplasm and the supernatant where CdtA undergoes posttranslation processing to CdtA′ in the process of biogenesis and secretion of CDT holotoxin into the culture supernatant. Site-directed mutagenesis of the 16th cysteine residue to glycine in CdtA altered localization of CdtA in the cell and reduced the amount of CDT activity in the culture supernatant. This suggests that CDT forms a complex inside the periplasm for lipid modification where posttranslational processing of CdtA plays an important role for the efficient production of CDT holotoxin into the culture supernatant.
Identification ofBurkholderia pseudomalleiGenes Required for the Intracellular Life Cycle and In Vivo Virulence
Authors: Pilatz Sabine , Breitbach Katrin , Hein Nadine , Fehlhaber Beate , Schulze Jessika , Brenneke Birgit , Eberl Leo , Steinmetz Ivo
Published: May 2006

The bacterial pathogenBurkholderia pseudomalleiinvades host cells, escapes from endocytic vesicles, multiplies intracellularly, and induces the formation of actin tails and membrane protrusions, leading to direct cell-to-cell spreading. This study was aimed at the identification ofB. pseudomalleigenes responsible for the different steps of this intracellular life cycle.B. pseudomalleitransposon mutants were screened for a reduced ability to form plaques on PtK2 cell monolayers as a result of reduced intercellular spreading. Nine plaque assay mutants with insertions in different open reading frames were selected for further studies. One mutant defective in a hypothetical protein encoded within the Bsa type III secretion system gene cluster was found to be unable to escape from endocytic vesicles after invasion but still multiplied within the vacuoles. Another mutant with a defect in a putative exported protein reached the cytoplasm but exhibited impaired actin tail formation in addition to a severe intracellular growth defect. In four mutants, the transposon had inserted into genes involved in either purine, histidine, orp-aminobenzoate biosynthesis, suggesting that these pathways are essential for intracellular growth. Three mutants with reduced plaque formation were shown to have gene defects in a putative cytidyltransferase, a putative lipoate-protein ligase B, and a hypothetical protein. All nine mutants proved to be significantly attenuated in a murine model of infection, with some mutants being essentially avirulent. In conclusion, we have identified a number of novel majorB. pseudomalleivirulence genes which are essential for the intracellular life cycle of this pathogen.