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Articles 391 - 420 of 602

Full-Text Articles in Biology

Splicing Affects Presentation Of Rna Dimerization Signals In Hiv-2 In Vitro, Jean-Marc Lanchy, Quenna N. Szafran, J. Stephen Lodmell Jan 2004

Splicing Affects Presentation Of Rna Dimerization Signals In Hiv-2 In Vitro, Jean-Marc Lanchy, Quenna N. Szafran, J. Stephen Lodmell

Biological Sciences Faculty Publications

During retroviral replication, full-length viral RNAs are encapsidated into new virus particles, while spliced RNAs are excluded. The Retroviridae are unique among viruses in that infectious viral particles contain a dimer of two identical genomic RNA strands. A variety of experimental data has suggested that dimerization and encapsidation of full-length viral RNAs are linked processes, although whether dimerization is a prerequisite for encapsidation, or conversely, dimerization follows encapsidation, has not been firmly established. If dimerization was the sole determinant for encapsidation, then spliced viral RNAs might be expected to display a reduced capacity for dimerization, resulting in their exclusion from …

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Thermodynamic Characterization Of The Binding Of Activator Of G Protein Signaling 3 (Ags3) And Peptides Derived From Ags3 With G Alpha I1, Anirban Adhikari, Stephen R. Sprang Dec 2003

Thermodynamic Characterization Of The Binding Of Activator Of G Protein Signaling 3 (Ags3) And Peptides Derived From Ags3 With G Alpha I1, Anirban Adhikari, Stephen R. Sprang

Biological Sciences Faculty Publications

Activator of G protein signaling 3 (AGS3) is a guanine nucleotide dissociation inhibitor (GDI) that contains four G protein regulatory (GPR) or GoLoco motifs in its C-terminal domain. The entire C-terminal domain (AGS3-C) as well as certain peptides corresponding to individual GPR motifs of AGS3 bound to G alpha i1 and inhibited the binding of GTP by stabilizing the GDP-bound conformation of G alpha i1. The stoichiometry, free energy, enthalpy, and dissociation constant for binding of AGS3-C to G alpha i1 were determined using isothermal titration calorimetry. AGS3-C possesses two apparent high affinity (Kd approximately 20 nm) and two apparent …

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Mitogenic Effect Of Bartonella Bacilliformis On Human Vascular Endothelial Cells And Involvement Of Groel, Michael F. Minnick, Laura S. Smitherman, D. Scott Samuels Dec 2003

Mitogenic Effect Of Bartonella Bacilliformis On Human Vascular Endothelial Cells And Involvement Of Groel, Michael F. Minnick, Laura S. Smitherman, D. Scott Samuels

Biological Sciences Faculty Publications

Bartonellae are bacterial pathogens for a wide variety of mammals. In humans, bartonellosis can result in angioproliferative lesions that are potentially life threatening to the patient, including bacillary angiomatosis, bacillary peliosis, and verruga peruana. The results of this study show that Bartonella bacilliformis, the agent of Oroya fever and verruga peruana, produces a proteinaceous mitogen for human vascular endothelial cells (HUVECs) that acts in a dose-dependent fashion in vitro with maximal activity at >72 h of exposure and results in a 6- to 20-fold increase in cell numbers relative to controls. The mitogen increases bromodeoxyuridine (BrdU) incorporation into HUVECs …

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Aada Confers Streptomycin Resistance In Borrelia Burgdorferi, Kristi L. Frank, Sharyl F. Bundle, Michele E. Kresge, Christian H. Eggers, D. Scott Samuels Nov 2003

Aada Confers Streptomycin Resistance In Borrelia Burgdorferi, Kristi L. Frank, Sharyl F. Bundle, Michele E. Kresge, Christian H. Eggers, D. Scott Samuels

Biological Sciences Faculty Publications

To enhance genetic manipulation of the Lyme disease spirochete Borrelia burgdorferi, we assayed the aadA gene for the ability to confer resistance to the antibiotics spectinomycin and streptomycin. Using the previously described pBSV2 as a backbone, a shuttle vector, termed pKFSS1, which carries the aadA open reading frame fused to the B. burgdorferi flgB promoter was constructed. The hybrid flgB promoter-aadA cassette confers resistance to spectinomycin and streptomycin in both B. burgdorferi and Escherichia coli. pKFSS1 has a replication origin derived from the 9-kb circular plasmid and can be comaintained in B. burgdorferi with extant shuttle vector pCE320, which has …

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Evolution Of Avian Locomotion: Correlates Of Flight Style, Locomotor Modules, Nesting Biology, Body Size, Development, And The Origin Of Flapping Flight, Kenneth P. Dial Oct 2003

Evolution Of Avian Locomotion: Correlates Of Flight Style, Locomotor Modules, Nesting Biology, Body Size, Development, And The Origin Of Flapping Flight, Kenneth P. Dial

Biological Sciences Faculty Publications

No abstract provided.

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Differences In Hyporheic-Zone Microbial Community Structure Along A Heavy-Metal Contamination Gradient, Kevin P. Feris, Philip W. Ramsey, Frazar Chris, Johnnie N. Moore, James E. Gannon, William E. Holben Sep 2003

Differences In Hyporheic-Zone Microbial Community Structure Along A Heavy-Metal Contamination Gradient, Kevin P. Feris, Philip W. Ramsey, Frazar Chris, Johnnie N. Moore, James E. Gannon, William E. Holben

Biological Sciences Faculty Publications

Heavy metals contaminate numerous freshwater streams and rivers worldwide. Previous work by this group demonstrated a relationship between the structure of hyporheic microbial communities and the fluvial deposition of heavy metals along a contamination gradient during the fall season. Seasonal variation has been documented in microbial communities in numerous terrestrial and aquatic environments, including the hyporheic zone. The current study was designed to assess whether relationships between hyporheic microbial community structure and heavy-metal contamination vary seasonally by monitoring community structure along a heavy-metal contamination gradient for more than a year. No relationship between total bacterial abundance and heavy metals was …

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Selective Plating Underestimates Abundance And Shows Differential Recovery Of Bifidobacterial Species From Human Feces, Juha H. A. Apajalahti, Anu Kettunen, Päivi H. Nurminen, Hanna Jatila, William E. Holben Sep 2003

Selective Plating Underestimates Abundance And Shows Differential Recovery Of Bifidobacterial Species From Human Feces, Juha H. A. Apajalahti, Anu Kettunen, Päivi H. Nurminen, Hanna Jatila, William E. Holben

Biological Sciences Faculty Publications

The aim of the present work was to compare the efficacies and levels of selectivity of different culture-dependent and -independent methods for analyzing bifidobacteria in human stool samples. The three different culture media used here significantly differed from each other, particularly with regard to the recovery of Bifidobacterium adolescentis. Bifidobacterium medium failed to recover B. adolescentis; Beerens medium recovered some B. adolescentis organisms (17% of total bifidobacteria), whereas tomato-Eugon medium recovered mainly B. adolescentis organisms (58% of total bifidobacteria). A culture-independent method that combines GC fractionation of bacterial community DNA and 16S rRNA sequencing indicated that B. adolescentis organisms accounted …

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A Structural Linkage Between The Dimerization And Encapsidation Signals In Hiv-2 Leader Rna, J. M. Lanchy, J. D. Ivanovitch, J. Stephen Lodmell Aug 2003

A Structural Linkage Between The Dimerization And Encapsidation Signals In Hiv-2 Leader Rna, J. M. Lanchy, J. D. Ivanovitch, J. Stephen Lodmell

Biological Sciences Faculty Publications

The 5' untranslated leader region of retroviral RNAs contains noncoding information that is essential for viral replication, including signals for transcriptional transactivation, splicing, primer binding for reverse transcription, dimerization of the genomic RNA, and encapsidation of the viral RNA into virions. These RNA motifs have considerable structural and functional overlap. in this study, we investigate the conformational dynamics associated with the use and silencing of a sequence in HIV-2 RNA that is involved in genomic RNA dimerization called stem-loop 1 (SL1) and its relationship with a flanking sequence that is known to be important for encapsidation of viral RNAs. We …

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Ribosomal Localization Of Translation Initiation Factor If2, Stefano Marzi, William Knight, Letizia Brandi, Enrico Caserta, Natalia Soboleva, Walter E. Hill, Claudio O. Gualerzi, J. Stephen Lodmell Aug 2003

Ribosomal Localization Of Translation Initiation Factor If2, Stefano Marzi, William Knight, Letizia Brandi, Enrico Caserta, Natalia Soboleva, Walter E. Hill, Claudio O. Gualerzi, J. Stephen Lodmell

Biological Sciences Faculty Publications

Bacterial translation initiation factor IF2 is a GTP-binding protein that catalyzes binding of initiator fMet-tRNA in the ribosomal P site. The topographical localization of IF2 on the ribosomal subunits, a prerequisite for understanding the mechanism of initiation complex formation, has remained elusive. Here, we present a model for the positioning of IF2 in the 70S initiation complex as determined by cleavage of rRNA by the chemical nucleases Cu(II):1,10-orthophenanthroline and Fe(II):EDTA tethered to cysteine residues introduced into IF2. Two specific amino acids in the GII domain of IF2 are in proximity to helices H3, H4, H17, and H18 of 16S rRNA. …

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River Flows And Water Wars: Emerging Science For Environmental Decision Making, N. Leroy Poff, J. David Allan, Margaret A. Palmer, David D. Hart, Brian D. Richter, Angela H. Arthington, Kevin H. Rogers, Judy L. Meyer, Jack Arthur Stanford Aug 2003

River Flows And Water Wars: Emerging Science For Environmental Decision Making, N. Leroy Poff, J. David Allan, Margaret A. Palmer, David D. Hart, Brian D. Richter, Angela H. Arthington, Kevin H. Rogers, Judy L. Meyer, Jack Arthur Stanford

Biological Sciences Faculty Publications

Real and apparent conflicts between ecosystem and human needs for fresh water are contributing to the emergence of an alternative model for conducting river science around the world. The core of this new paradigm emphasizes the need to forge new partnerships between scientists and other stakeholders where shared ecological goals and river visions are developed, and the need for new experimental approaches to advance scientific understanding at the scales relevant to whole-river management. We identify four key elements required to make this model succeed: existing and planned water projects represent opportunities to conduct ecosystem-scale experiments through controlled river flow manipulations; …

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Differences In Cottonwood Growth Between A Losing And A Gaining Reach Of An Alluvial Floodplain, Mary J. Harner, Jack Arthur Stanford Jun 2003

Differences In Cottonwood Growth Between A Losing And A Gaining Reach Of An Alluvial Floodplain, Mary J. Harner, Jack Arthur Stanford

Biological Sciences Faculty Publications

Interstitial flow of river (hyporheic) water influences algal productivity, benthic assemblages, and locations of fish spawning. However, little is known of the effects of hyporheic flow on the growth of riparian vegetation. By increasing water availability and nutrient delivery, regional upwelling of hyporheic water may increase the growth of terrestrial vegetation. We tested and accepted the hypothesis that cottonwood trees (Populus trichocarpa) in a gaining reach of an alluvial floodplain grow faster than trees in a losing reach by comparing basal areas and ages on an expansive floodplain in western Montana (USA). Trees in the gaining reach had …

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Phenotypic Plasticity And Interactions Among Plants, Ragan M. Callaway, Steven C. Pennings, Christina L. Richards May 2003

Phenotypic Plasticity And Interactions Among Plants, Ragan M. Callaway, Steven C. Pennings, Christina L. Richards

Biological Sciences Faculty Publications

We know a great deal about the plastic responses of plant phenotypes to the abiotic and biotic environment, but very little about the consequences of phenotypic plasticity for plant communities. In other words, we know that plant traits can vary widely for a given genotype, but we know little about the importance of trait-mediated interactions (TMI) among plants. Here, we discuss three major factors that affect the expression of phenotypic plasticity: variation in the abiotic environment, variation in the presence or identity of neighbors, and variation in herbivory. We consider how plastic responses to these factors might affect interactions among …

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Differential Expression Of The Invasion-Associated Locus B (Ialb) Gene Of Bartonella Bacilliformis In Response To Environmental Cues, Sherry A. Coleman, Michael F. Minnick Apr 2003

Differential Expression Of The Invasion-Associated Locus B (Ialb) Gene Of Bartonella Bacilliformis In Response To Environmental Cues, Sherry A. Coleman, Michael F. Minnick

Biological Sciences Faculty Publications

Bartonella bacilliformis is the causative agent of the biphasic human disease, Oroya fever. During the primary disease phase, up to 100% of the circulating erythrocytes can be parasitized and 80% lysed. During the secondary phase of this disease, bacterial invasion shifts to endothelial cells lining the vasculature. B. bacilliformis is transferred between human hosts by the sandfly, Lutzomyia verrucarum. To investigate the regulation of ialB by environmental cues signaling vector-to-host transmission; nuclease protection assays were performed to compare the amount of ialB mRNA in bacteria subjected to temperature shift, pH change, oxidative stress, or hemin limitation. The amount of ialB …

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Mapping The Galpha13 Binding Interface Of The Rgrgs Domain Of P115rhogef, Zhe Chen, William D. Singer, Clark D. Wells, Stephen R. Sprang, Paul C. Sternweis Mar 2003

Mapping The Galpha13 Binding Interface Of The Rgrgs Domain Of P115rhogef, Zhe Chen, William D. Singer, Clark D. Wells, Stephen R. Sprang, Paul C. Sternweis

Biological Sciences Faculty Publications

Structural requirements for function of the Rho GEF (guanine nucleotide exchange factor) regulator of G protein signaling (rgRGS) domains of p115RhoGEF and homologous exchange factors differ from those of the classical RGS domains. An extensive mutagenesis analysis of the p115RhoGEF rgRGS domain was undertaken to determine its functional interface with the Galpha(13) subunit. Results indicate that there is global resemblance between the interaction surface of the rgRGS domain with Galpha(13) and the interactions of RGS4 and RGS9 with their Galpha substrates. However, there are distinct differences in the distribution of functionally critical residues between these structurally similar surfaces and an …

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Five-Member Gene Family Of Bartonella Quintana, Michael F. Minnick, Kate N. Sappington, Laura S. Smitherman, Siv G. E. Andersson, Olof Karlberg, James A. Carroll Feb 2003

Five-Member Gene Family Of Bartonella Quintana, Michael F. Minnick, Kate N. Sappington, Laura S. Smitherman, Siv G. E. Andersson, Olof Karlberg, James A. Carroll

Biological Sciences Faculty Publications

Bartonella quintana, the agent of trench fever and an etiologic agent of bacillary angiomatosis, has an extraordinarily high hemin requirement for growth compared to other bacterial pathogens. We previously identified the major hemin receptor of the pathogen as a 30-kDa surface protein, termed HbpA. This report describes four additional homologues that share approximately 48% amino acid sequence identity with hbpA. Three of the genes form a paralagous cluster, termed hbpCAB, whereas the other members, hbpD and hbpE, are unlinked. Secondary structure predictions and other evidence suggest that Hbp family members are beta-barrels located in the outer membrane and contain eight …

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Wing-Assisted Incline Running And The Evolution Of Flight, Kenneth P. Dial Jan 2003

Wing-Assisted Incline Running And The Evolution Of Flight, Kenneth P. Dial

Biological Sciences Faculty Publications

Flapping wings of galliform birds are routinely used to produce aerodynamic forces oriented toward the substrate to enhance hindlimb traction. Here, I document this behavior in natural and laboratory settings. Adult birds fully capable of aerial flight preferentially employ wing-assisted incline running (WAIR), rather than flying, to reach elevated refuges (such as cliffs, trees, and boulders). From the day of hatching and before attaining sustained aerial flight, developing ground birds use WAIR to enhance their locomotor performance through improved foot traction, ultimately permitting vertical running. WAIR provides insight from behaviors observable in living birds into the possible role of incipient …

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Gyra Mutations In Ciprofloxacin-Resistant Bartonella Bacilliformis Strains Obtained In Vitro, Michael F. Minnick, Zachary R. Wilson, Laura S. Smitherman, D. Scott Samuels Jan 2003

Gyra Mutations In Ciprofloxacin-Resistant Bartonella Bacilliformis Strains Obtained In Vitro, Michael F. Minnick, Zachary R. Wilson, Laura S. Smitherman, D. Scott Samuels

Biological Sciences Faculty Publications

We isolated and characterized mutants of Bartonella bacilliformis that are resistant to the fluoroquinolone antibiotic ciprofloxacin, which targets the A subunit of DNA gyrase. Mutants had single point mutations in the gyrA gene that changed either Asp-90 to Gly or Asp-95 to Asn and had 3- or 16-fold higher resistance, respectively, to ciprofloxacin than did wild-type B. bacilliformis. Asp-95 is homologous to Asp-87 of Escherichia coli GyrA and is a common residue mutated in fluoroquinolone-resistant strains of other bacteria. This is the first report of a mutation at an Asp-90 homologue, which corresponds to Asp-82 in E. coli GyrA.

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Soil Fungi And The Effects Of An Invasive Forb On Grasses: Neighbor Identity Matters, Ragan M. Callaway, Bruce E. Mahall, Chris Wicks, Joel Pankey, Catherine Zabinski Jan 2003

Soil Fungi And The Effects Of An Invasive Forb On Grasses: Neighbor Identity Matters, Ragan M. Callaway, Bruce E. Mahall, Chris Wicks, Joel Pankey, Catherine Zabinski

Biological Sciences Faculty Publications

We studied the effects of soil fungi on interactions between Centaurea melitensis, an exotic invasive weed in central California, and two co-occurring grasses, Nassella pulchra and Avena barbata. The fungicide benomyl reduced the abundance of arbuscular mycorrhizal (AM) fungi in plant roots but did not affect non-AM fungi. Centaurea plants grown alone were >50% smaller with the resident microbial community intact than when benomyl was applied. When grown with Nassella, the effect of benomyl was reversed. Centaurea grew almost five times larger with the resident microbial community intact. Fungicide had no effect on the biomass of Centaurea …

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Characteristic Genome Rearrangements In Experimental Evolution Of Saccharomyces Cerevisiae, Maitreya J. Dunham, Hassan Badrane, Tracy Ferea, Julian Adams, Patrick O. Brown, Frank Rosenzweig, David Botstein Dec 2002

Characteristic Genome Rearrangements In Experimental Evolution Of Saccharomyces Cerevisiae, Maitreya J. Dunham, Hassan Badrane, Tracy Ferea, Julian Adams, Patrick O. Brown, Frank Rosenzweig, David Botstein

Biological Sciences Faculty Publications

Genome rearrangements, especially amplifications and deletions, have regularly been observed as responses to sustained application of the same strong selective pressure in microbial populations growing in continuous culture. We studied eight strains of budding yeast (Saccharomyces cerevisiae) isolated after 100-500 generations of growth in glucose-limited chemostats. Changes in DNA copy number were assessed at single-gene resolution by using DNA microarray-based comparative genomic hybridization. Six of these evolved strains were aneuploid as the result of gross chromosomal rearrangements. Most of the aneuploid regions were the result of translocations, including three instances of a shared breakpoint on chromosome 14 immediately adjacent to …

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Plasticity And Genetic Diversity May Allow Saltcedar To Invade Cold Climates In North America, Jason P. Sexton, J. K. Mckay, Anna Sala Dec 2002

Plasticity And Genetic Diversity May Allow Saltcedar To Invade Cold Climates In North America, Jason P. Sexton, J. K. Mckay, Anna Sala

Biological Sciences Faculty Publications

Two major mechanisms have been proposed to explain the ability of introduced populations to colonize over large habitat gradients, despite significant population bottlenecks during introduction: (1) Broad environmental tolerance-successful invaders possess life history traits that confer superior colonizing ability and/or phenotypic plasticity, allowing acclimation to a wide range of habitats. (2) Local adaptation-successful invaders rapidly adapt to local selective pressures. However, even with bottlenecks, many introduced species exhibit surprisingly high levels of genetic variation and thus the potential for evolutionary increases in invasive traits and plasticity. Here we assess the invasive potential of Tamarix ramosissima, by examining the degree of …

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Convergent Demographic Effects Of Insect Attack On Related Thistles In Coastal Vs. Continental Dunes, John L. Maron, Julie K. Combs, Svata M. Louda Dec 2002

Convergent Demographic Effects Of Insect Attack On Related Thistles In Coastal Vs. Continental Dunes, John L. Maron, Julie K. Combs, Svata M. Louda

Biological Sciences Faculty Publications

Insect herbivory is common, but the conditions under which it reduces the fitness and population size of plants remain poorly understood. We quantified population-level impacts of floral herbivory by specialized insects on cobweb thistle (Cirsium occidentale var. occidentale) in a California coastal dune ecosystem, and then compared these demographic effects to those published for Platte thistle (Cirsium canescens) in similarly designed exclusion experiments in the continental sand dune ecosystem in the Great Plains. As a separate test of the strength of the seed-to-seedling linkage, we quantified seedling establishment rates in seed addition plots and compared these …

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Groel Expression In Gyrb Mutants Of Borrelia Burgdorferi, Janet Alverson, D. Scott Samuels Nov 2002

Groel Expression In Gyrb Mutants Of Borrelia Burgdorferi, Janet Alverson, D. Scott Samuels

Biological Sciences Faculty Publications

GroEL protein and groEL mRNA transcript were up-regulated in gyrB mutants of Borrelia burgdorferi, a causative agent of Lyme disease. Furthermore, the protein and transcript levels in gyrB mutants were greater than those in experimentally heat-shocked cultures of wild-type B. burgdorferi. Circular DNA in the gyrB mutants was more relaxed than in wild-type cells, although groEL is on the linear chromosome of B. burgdorferi. To our knowledge, this is the first evidence, albeit indirect, for the effect of DNA topology on gene expression from a linear DNA molecule in a bacterium.

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Culture-Independent Microbial Community Analysis Reveals That Inulin In The Diet Primarily Affects Previously Unknown Bacteria In The Mouse Cecum, Juha H. A. Apajalahti, Hannele Kettunen, Anu Kettunen, William E. Holben, Päivi H. Nurminen, Nina Rautonen, Marja Mutanen Oct 2002

Culture-Independent Microbial Community Analysis Reveals That Inulin In The Diet Primarily Affects Previously Unknown Bacteria In The Mouse Cecum, Juha H. A. Apajalahti, Hannele Kettunen, Anu Kettunen, William E. Holben, Päivi H. Nurminen, Nina Rautonen, Marja Mutanen

Biological Sciences Faculty Publications

Inulin is a well-known fructose-based prebiotic which has been shown to stimulate the growth of bifidobacteria, a bacterial group generally considered beneficial for intestinal health. In the present study, we analyzed inulin-associated shifts in the total bacterial community of wild-type mice and mice carrying a genetically inactivated adenomatous polyposis coli tumor suppressor gene by using DNA-based approaches independent of bacterial culturability. Mice were fed a high-fat, nonfiber diet with or without inulin inclusion at a 10% (wt/wt) concentration. Cecal contents were analyzed after 0, 3, and 9 weeks on the experimental diets. Inulin inclusion significantly affected the total bacterial community …

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Distinct Interactions Of Gtp, Utp, And Ctp With G(S) Proteins, Andreas Gille, Hui-Yu Liu, Stephen R. Sprang, Roland Seifert Sep 2002

Distinct Interactions Of Gtp, Utp, And Ctp With G(S) Proteins, Andreas Gille, Hui-Yu Liu, Stephen R. Sprang, Roland Seifert

Biological Sciences Faculty Publications

Early studies showed that in addition to GTP, the pyrimidine nucleotides UTP and CTP support activation of the adenylyl cyclase (AC)-stimulating G(s) protein. The aim of this study was to elucidate the mechanism by which UTP and CTP support G(s) activation. As models, we used S49 wild-type lymphoma cells, representing a physiologically relevant system in which the beta(2)-adrenoreceptor (beta(2)AR) couples to G(s), and Sf9 insect cell membranes expressing beta(2)AR-Galpha(s) fusion proteins. Fusion proteins provide a higher sensitivity for the analysis of beta(2)AR-G(s) coupling than native systems. Nucleoside 5'-triphosphates (NTPs) supported agonist-stimulated AC activity in the two systems and basal AC …

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Review Of: Riverine Flood Plains: Present State And Future Trends, Klement Tockner, Jack Arthur Stanford Sep 2002

Review Of: Riverine Flood Plains: Present State And Future Trends, Klement Tockner, Jack Arthur Stanford

Biological Sciences Faculty Publications

Natural flood plains are among the most biologically productive and diverse ecosystems on earth. Globally, riverine flood plains cover > 2 x 10(6) km(2), however, they are among the most threatened ecosystems. Floodplain degradation is closely linked to the rapid decline in freshwater biodiversity; the main reasons for the latter being habitat alteration, flow and flood control, species invasion and pollution. In Europe and North America, up to 90% of flood plains are already 'cultivated' and therefore functionally extinct. In the developing world, the remaining natural flood plains are disappearing at an accelerating rate, primarily as a result of changing hydrology. …

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Cosolvent-Induced Transformation Of A Death Domain Tertiary Structure, Tsan Xiao, Kevin H. Gardner, Stephen R. Sprang Aug 2002

Cosolvent-Induced Transformation Of A Death Domain Tertiary Structure, Tsan Xiao, Kevin H. Gardner, Stephen R. Sprang

Biological Sciences Faculty Publications

The death domain (DD) of the protein kinase Pelle adopts a six-helix bundle fold in the crystal structure of the complex with its dimerization partner, Tube-DD. However, in crystals obtained from a solution of 45% 2-methyl-2,4-pentanediol (MPD), the C-terminal half of Pelle-DD folds into a single helix, and the N-terminal half of the molecule is disordered. The helical segment forms an antiparallel dimer with the corresponding helix of a symmetry-related molecule, and together they form extensive lattice interactions similar in number, composition, and buried surface to those in the six-helix bundle of the native fold. Secondary structure analysis by heteronuclear …

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The Neisseria Lipooligosaccharide-Specific Alpha-2,3-Sialyltransferase Is A Surface-Exposed Outer Membrane Protein, Dawn M. Shell, Lisa Chiles, Ralph C. Judd, Samar Seal, Richard F. Rest Jul 2002

The Neisseria Lipooligosaccharide-Specific Alpha-2,3-Sialyltransferase Is A Surface-Exposed Outer Membrane Protein, Dawn M. Shell, Lisa Chiles, Ralph C. Judd, Samar Seal, Richard F. Rest

Biological Sciences Faculty Publications

Neisseria gonorrhoeae and Neisseria meningitidis express an similar to43-kDa alpha-2,3-sialyltransferase (Lst) that sialylates the surface lipooligosaccharide (LOS) by using exogenous (in all N. gonorrhoeae strains and some N. meningitidis serogroups) or endogenous (in other N. meningitidis serogroups) sources of 5'-cytidinemonophospho-N-acetylneuraminic acid (CMP-NANA). Sialylation of LOS can protect N. gonorrhoeae and N. meningitidis from complement-mediated serum killing and from phagocytic killing by neutrophils. The precise subcellular location of Lst has not been determined. We confirm and extend previous studies by demonstrating that Lst is located in the outer membrane and is surface exposed in both N. gonorrhoeae and N. meningitidis. Western …

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Genetic Evidence That Interhelical Packing Interactions In The Gp41 Core Are Critical For Transition Of The Human Immunodeficiency Virus Type 1 Envelope Glycoprotein To The Fusion-Active State, Kathryn E. Follis, Scott J. Larson, Min Lu, Jack H. Nunberg Jul 2002

Genetic Evidence That Interhelical Packing Interactions In The Gp41 Core Are Critical For Transition Of The Human Immunodeficiency Virus Type 1 Envelope Glycoprotein To The Fusion-Active State, Kathryn E. Follis, Scott J. Larson, Min Lu, Jack H. Nunberg

Biological Sciences Faculty Publications

The envelope glycoprotein complex (gp120-gp41) of human immunodeficiency virus type 1 (HIV-1) promotes the fusion of viral and cellular membranes through formation of the fusion-active six-helix bundle in the gp41 ectodomain. This gp41 core structure consists of three C-terminal helices packed in an antiparallel manner into hydrophobic grooves on the surface of the N-terminal trimeric coiled coil. Alanine mutations that destabilize the N- and C-terminal interhelical packing interactions also reduce viral infectivity. Here we show that viruses bearing these mutations exhibit a marked potentiation of inhibition by peptides that make up the gp41 core. By contrast, these viruses are unchanged …

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Threshold Evolution In Exotic Populations Of A Polyphenic Beetle, Armin P. Moczek, John Hunt, Douglas J. Emlen, Leigh W. Simmons May 2002

Threshold Evolution In Exotic Populations Of A Polyphenic Beetle, Armin P. Moczek, John Hunt, Douglas J. Emlen, Leigh W. Simmons

Biological Sciences Faculty Publications

Polyphenic development is thought to play an important role in the evolution of phenotypic diversity and morphological novelties, yet the evolution of polyphenisms has rarely been documented in natural populations. Here we compare the morphologies of male dung beetles (Onthophagus taurus; Coleoptera: Scarabaeidae) from populations introduced to Australia and the eastern United States. Males in this species express two alternative morphologies in response to larval feeding conditions. Males encountering favourable conditions grow larger than a threshold body size and develop a pair of horns on their heads, whereas males that encounter poor conditions do not reach this threshold size and …

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The Fitness Consequences Of Interspecific Eavesdropping Between Plants, Richard Karban, John L. Maron May 2002

The Fitness Consequences Of Interspecific Eavesdropping Between Plants, Richard Karban, John L. Maron

Biological Sciences Faculty Publications

Although many ecologists have discounted the possibility of communication between plants, recent work demonstrates that wild tobacco plants with experimentally clipped sagebrush neighbors suffer less leaf herbivory than tobacco controls with unclipped neighbors. In this report, we examine the fitness consequences of resistance induced by eavesdropping. Annual tobacco plants with clipped sagebrush neighbors produced more flowers and seed-bearing capsules than plants with unclipped neighbors although these performance measures varied considerably over the five years of the study. Tobacco plants with clipped neighbors also suffered more frost damage than controls in one year. There was no indication that eavesdropping was more …

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