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Articles 1 - 20 of 20
Full-Text Articles in Life Sciences
An Enhancer Trap Line Associated With A D-Class Cyclin Gene In Arabidopsis, Kankshita Swaminathan, Yingzhen Yang, Natasha Grotz, Lauren Campisi, Thomas Jack
An Enhancer Trap Line Associated With A D-Class Cyclin Gene In Arabidopsis, Kankshita Swaminathan, Yingzhen Yang, Natasha Grotz, Lauren Campisi, Thomas Jack
Dartmouth Scholarship
In yeast and animals, cyclins have been demonstrated to be important regulators of cell cycle progression. In recent years, a large number of A-, B-, and D-class cyclins have been isolated from a variety of plant species. One class of cyclins, the D-class cyclins, is important for progression through G1 phase of the cell cycle. In Arabidopsis, four D-class cyclins have been isolated and characterized (CYCLIN-D1;1, CYCLIN-D2;1,CYCLIN-D3;1, and CYCLIN-D4;1). In this report we describe the characterization of a fifth D-class cyclin gene,CYCLIN-D3;2 (CYCD3;2), from Arabidopsis. An enhancer trap line, line 5580, …
Microbial Biofilms: From Ecology To Molecular Genetics, Mary Ellen Davey, George A. O'Toole
Microbial Biofilms: From Ecology To Molecular Genetics, Mary Ellen Davey, George A. O'Toole
Dartmouth Scholarship
Biofilms are complex communities of microorganisms attached to surfaces or associated with interfaces. Despite the focus of modern microbiology research on pure culture, planktonic (free-swimming) bacteria, it is now widely recognized that most bacteria found in natural, clinical, and industrial settings persist in association with surfaces. Furthermore, these microbial communities are often composed of multiple species that interact with each other and their environment. The determination of biofilm architecture, particularly the spatial arrangement of microcolonies (clusters of cells) relative to one another, has profound implications for the function of these complex communities. Numerous new experimental approaches and methodologies have been …
From Hopeful Monsters To Homeotic Effects: Richard Goldschmidt's Integration Of Development, Evolution, And Genetics, Michael Dietrich
From Hopeful Monsters To Homeotic Effects: Richard Goldschmidt's Integration Of Development, Evolution, And Genetics, Michael Dietrich
Dartmouth Scholarship
Richard Goldschmidts research on homeotic mutants from 1940 until his death in 1958 represents one of the first serious efforts to integrate genetics, development, and evolution. Using two different models, Goldschmidt tried to show how different views of genetic structure and gene action could provide a mechanism for rapid speciation. Developmental systems were emphasized in one model and a hierarchy of genetic structures in the other. While Goldschmidt tried to find a balance between development and genetics, critics, such as Sewall Wright, urged him and eventually helped him incorporate population dynamics into his models as well. As such, the history …
Fast Transport Of Neurofilament Protein Along Microtubules In Squid Axoplasm, Veena Prahlad, Brian T. Helfand, George M. Langford, Ron D. Vale, Robert D. Goldman
Fast Transport Of Neurofilament Protein Along Microtubules In Squid Axoplasm, Veena Prahlad, Brian T. Helfand, George M. Langford, Ron D. Vale, Robert D. Goldman
Dartmouth Scholarship
Using squid axoplasm as a model system, we have visualized the fast transport of non-filamentous neurofilament protein particles along axonal microtubules. This transport occurs at speeds of 0.5-1.0 microm/second and the majority of neurofilament particles stain with kinesin antibody. These observations demonstrate, for the first time, that fast (0.5-1.0 microm/second) transport of neurofilament proteins occurs along microtubules. In addition, our studies suggest that neurofilament protein can be transported as non-membrane bound, nonfilamentous subunits along axons, and that the transport is kinesin-dependent. Microtubule-based fast transport might therefore provide a mechanism for the distribution and turnover of neurofilament, and perhaps other cytoskeletal …
Consequences Of Dominance-Mediated Habitat Segregation In American Redstarts During The Nonbreeding Season, Peter P. Marra, Richard T. Holmes
Consequences Of Dominance-Mediated Habitat Segregation In American Redstarts During The Nonbreeding Season, Peter P. Marra, Richard T. Holmes
Dartmouth Scholarship
Several species of migratory songbirds exhibit a distinct form of habitat segregation while on their Neotropical wintering grounds in which males and females occupy different habitat types. In the American Redstart (Setophaga ruticilla), that sexual habitat segregation is a result of behavioral dominance of older males. In that study, we examined whether such dominance behavior and the resulting differential habitat segregation has consequences for the condition or survival of excluded individuals. We quantified the physical condition and survival of redstarts (both males and females) occupying two habitat types that differed in the proportion of males and females present …
Nitrogen Budgets Of Phloem-Feeding Bark Beetles With And Without Symbiotic Fungi, Matthew P. Ayres, Richard T. Wilkens, Jonathan J. Ruel, María J. Lombardero, Erich Vallery
Nitrogen Budgets Of Phloem-Feeding Bark Beetles With And Without Symbiotic Fungi, Matthew P. Ayres, Richard T. Wilkens, Jonathan J. Ruel, María J. Lombardero, Erich Vallery
Dartmouth Scholarship
The nitrogen content of plant tissue is low relative to that of herbivores; as a consequence, dietary N can limit the growth and reproduction of herbivores and select for attributes that increase N acquisition. Bark beetles face a particularly severe challenge because the phloem that they consume is very low in nitrogen and phosphorus relative to their requirements. We quantified variation in the phloem concentrations of N and P in the host tree, Pinus taeda, and evaluated the following hypotheses regarding the role of symbiotic fungi in nutrient budgets of the herbivore Dendroctonus frontalis: D. frontalis experience variation …
Vibrio Cholerae H-Ns Silences Virulence Gene Expression At Multiple Steps In The Toxr Regulatory Cascade, Melinda B. Nye, James D. Pfau, Karen Skorupski, Ronald K. Taylor
Vibrio Cholerae H-Ns Silences Virulence Gene Expression At Multiple Steps In The Toxr Regulatory Cascade, Melinda B. Nye, James D. Pfau, Karen Skorupski, Ronald K. Taylor
Dartmouth Scholarship
H-NS is an abundant nucleoid-associated protein involved in the maintenance of chromosomal architecture in bacteria. H-NS also has a role in silencing the expression of a variety of environmentally regulated genes during growth under nonpermissive conditions. In this study we demonstrate a role for H-NS in the negative modulation of expression of several genes within the ToxR virulence regulon ofVibrio cholerae. Deletion of hns resulted in high, nearly constitutive levels of expression of the genes encoding cholera toxin, toxin-coregulated pilus, and the ToxT virulence gene regulatory protein. For the cholera toxin- and ToxT-encoding genes, elevated expression in an …
Direct Determination Of The Kinetics Of Oxygen Diffusion To The Photocytes Of A Bioluminescent Elaterid Larva, Measurement Of Gas- And Aqueous-Phase Diffusional Barriers And Modelling Of Oxygen Supply, G. S. Timmins, E. J. Bechara, H. M. Swartz
Direct Determination Of The Kinetics Of Oxygen Diffusion To The Photocytes Of A Bioluminescent Elaterid Larva, Measurement Of Gas- And Aqueous-Phase Diffusional Barriers And Modelling Of Oxygen Supply, G. S. Timmins, E. J. Bechara, H. M. Swartz
Dartmouth Scholarship
We describe the development and use of a direct kinetic technique to determine the time taken for oxygen to diffuse from the external environment into the light-producing cells (photocytes) in the prothorax of bioluminescent larvae of Pyrearinus termitilluminans. This was achieved by measuring the time course of the pseudoflash induced through sequential anoxia followed by normoxia. We have also determined the separate times taken for this oxygen diffusion in gaseous and tissue (predominantly aqueous) phases by using helium and nitrogen as the carrier gas. Of the total time taken for diffusion, that in the gas phase required 613+/-136 ms (mean …
Integrated Temporal Regulation Of The Photorespiratory Pathway. Circadian Regulation Of Two Arabidopsis Genes Encoding Serine Hydroxymethyltransferase, C Robertson Mcclung, Meier Hsu, Janet E. Painter, Jennifer M. Gagne, Sharon D. Karlsberg, Patrice A. Salome
Integrated Temporal Regulation Of The Photorespiratory Pathway. Circadian Regulation Of Two Arabidopsis Genes Encoding Serine Hydroxymethyltransferase, C Robertson Mcclung, Meier Hsu, Janet E. Painter, Jennifer M. Gagne, Sharon D. Karlsberg, Patrice A. Salome
Dartmouth Scholarship
The photorespiratory pathway is comprised of enzymes localized within three distinct cellular compartments: chloroplasts, peroxisomes, and mitochondria. Photorespiratory enzymes are encoded by nuclear genes, translated in the cytosol, and targeted into these distinct subcellular compartments. One likely means by which to regulate the expression of the genes encoding photorespiratory enzymes is coordinated temporal control. We have previously shown in Arabidopsis that a circadian clock regulates the expression of the nuclear genes encoding both chloroplastic (Rubisco small subunit and Rubisco activase) and peroxisomal (catalase) components of the photorespiratory pathway. To determine whether a circadian clock also regulates the expression of genes …
Larval Trophodynamics, Turbulence, And Drift On Georges Bank : A Sensitivity Analysis Of Cod And Haddock, Francisco E. E. Werner, Brian R. Mackenzie, R. Ian Perry, R. Gregory Lough, Christopher E. Naimie, Brian O. Blanton, John A. Quinlan
Larval Trophodynamics, Turbulence, And Drift On Georges Bank : A Sensitivity Analysis Of Cod And Haddock, Francisco E. E. Werner, Brian R. Mackenzie, R. Ian Perry, R. Gregory Lough, Christopher E. Naimie, Brian O. Blanton, John A. Quinlan
Dartmouth Scholarship
Using an individual-based model approach we consider trophodynamic effects on the growth and survival of larval cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) on Georges Bank during late winter/early spring. These studies represent an extension of results described in Werner et al. (1996; Deep-Sea Res. II), wherein the effect of turbulence-enhanced larval-prey contact rates increased the effective prey concentration resulting in growth of cod larvae consistent with observed rates in the field. We reformulated the feeding of the larvae to include existing relationships between maximum prey-length and larval-length and we examined: (i) larval search behaviour and …
The Risks And Benefits Of Genetically Modified Crops: A Multidisciplinary Perspective, Garry D. Peterson, Saul Cunningham, Lisa Deutsch, Jon Erickson, Allyson Quinlan, Ernesto Ráez-Luna, Robert Tinch, Max Troell, Peter Woodbury, Scot Zens
The Risks And Benefits Of Genetically Modified Crops: A Multidisciplinary Perspective, Garry D. Peterson, Saul Cunningham, Lisa Deutsch, Jon Erickson, Allyson Quinlan, Ernesto Ráez-Luna, Robert Tinch, Max Troell, Peter Woodbury, Scot Zens
Dartmouth Scholarship
Worldwide, the area planted in genetically modified (GM) crops has increased dramatically in recent years. Between 1996 and 1999, it rose from 1.6 X 106 ha to more than 35 X 106 ha (James 1998, May 1999). This rapid increase has provoked an explosion of concern, particularly in Europe, over the health and environmental impacts of these crops. Despite claims of safety and warnings against popular panic, public concern over GM crops has resulted in changes in their marketing, labeling, planting, and trade. These changes have fueled an increasingly heated debate among environmental advocates, critics of industrial agriculture, …
The Docking Stage Of Yeast Vacuole Fusion Requires The Transfer Of Proteins From A Cis-Snare Complex To A Rab/Ypt Protein, Albert Price, Darren Seals, William Wickner, Christian Ungermann
The Docking Stage Of Yeast Vacuole Fusion Requires The Transfer Of Proteins From A Cis-Snare Complex To A Rab/Ypt Protein, Albert Price, Darren Seals, William Wickner, Christian Ungermann
Dartmouth Scholarship
The homotypic fusion of yeast vacuoles requires Sec18p (NSF)-driven priming to allow vacuole docking, but the mechanism that links priming and docking is unknown. We find that a large multisubunit protein called the Vam2/6p complex is bound to cis-paired SNAP receptors (SNAREs) on isolated vacuoles. This association of the Vam2/6p complex with the cis-SNARE complex is disrupted during priming. The Vam2/6p complex then binds to Ypt7p, a guanosine triphosphate binding protein of the Rab family, to initiate productive contact between vacuoles. Thus, cis-SNARE complexes can contain Rab/Ypt effectors, and these effectors can be mobilized by NSF/Sec18p-driven priming, allowing their direct …
Differential Activation Of The Tcpph Promoter By Aphb Determines Biotype Specificity Of Virulence Gene Expression In Vibrio Cholerae, Gabriela Kovacikova, Karen Skorupski
Differential Activation Of The Tcpph Promoter By Aphb Determines Biotype Specificity Of Virulence Gene Expression In Vibrio Cholerae, Gabriela Kovacikova, Karen Skorupski
Dartmouth Scholarship
Vibrio cholerae strains of the classical biotype express the genes encoding cholera toxin (CT) and toxin- coregulated pilus (TCP) under a variety of environmental conditions in vitro, whereas El Tor biotype strains express these genes only under specialized culture conditions. We show here that a single base-pair difference at positions 2 65 and 2 66 of the classical and El Tor tcpPH promoters, respectively, is responsible for the differential regulation of virulence gene expression in these two disease-causing biotypes. Analysis of tcpP-lacZ fusions in both V. cholerae and Escherichia coli indicated that transcriptional activation of the El Tor tcpPH promoter …
Richard Goldschmidt And The Crossing-Over Controversy, Michael Dietrich, Marsha Richmond
Richard Goldschmidt And The Crossing-Over Controversy, Michael Dietrich, Marsha Richmond
Dartmouth Scholarship
This book, Perspectives on Genetics, collects more than 100 of these essays, which cumulatively are a history of modern genetics research and its continuing evolution.
The Problem Of The Gene, Michael Dietrich
The Problem Of The Gene, Michael Dietrich
Dartmouth Scholarship
During the early 20th century the diverse practices of genetics were unified by the concept of the gene. This classical gene was simultaneously a unit of structure, function, mutation, and recombination. Starting in the 1940s, however, the classical gene began to fragment. Today when we speak of a gene for some malady, a regulatory gene, a structural gene, or a gene frequency, it is entirely possible that we are deploying different gene concepts even though we are using the same term. The problem of the gene addresses the fragmentation of the classical gene concept by asking to what extent a …
From Gene To Genetic Hierarchy: Richard Goldschmidt And The Problem Of The Gene, Michael Dietrich
From Gene To Genetic Hierarchy: Richard Goldschmidt And The Problem Of The Gene, Michael Dietrich
Dartmouth Scholarship
No abstract provided.
Of Moths And Men: Theo Lang And The Persistence Of Richard Goldschmidt's Theory Of Homosexuality, 1916-1960, Michael Dietrich
Of Moths And Men: Theo Lang And The Persistence Of Richard Goldschmidt's Theory Of Homosexuality, 1916-1960, Michael Dietrich
Dartmouth Scholarship
Using an analogy between moths and men, in 1916, Richard Goldschmidt proposed that homosexuality was a case of genetic intersexuality. As he strove to create a unified theory of sex determination that would encompass animals ranging from moths to men, Goldschmidt's doubts grew concerning the association of homosexuality with intersexuality until, in 1931, he dropped homosexuality from his theory of intersexuality. Despite Goldschmidt's explicit rejection of his theory of homosexuality, Thee Lang, a researcher in the Genealogical-Demographic Department of the Institute for Psychiatric Research in Munich, revived it, maintained Goldschmidt's association with it, and argued on its behalf in publications …
Unifying Biology: Evolutionary And Molecular Biology: Science Perspectives On Divine Action, Michael Dietrich
Unifying Biology: Evolutionary And Molecular Biology: Science Perspectives On Divine Action, Michael Dietrich
Dartmouth Scholarship
Book Review of Evolutionary and Molecular Biology: Science Perspectives on Divine Action by Robert J. Russell, William R. Stoeger, SJ and Francisco J. Ayla.
An American Obsession: Science, Medicine, And Homosexuality In Modern Society, Michael Dietrich
An American Obsession: Science, Medicine, And Homosexuality In Modern Society, Michael Dietrich
Dartmouth Scholarship
Book review of An American Obsession: Science, Medicine, and Homosexuality in Modern Society by Jennifer Terry, 1999.
The Global Carbon Metabolism Regulator Crc Is A Component Of A Signal Transduction Pathway Required For Biofilm Development By Pseudomonas Aeruginosa, George A. O'Toole, Karine A. Gibbs, Paul W. Hager, Paul V. Phibbs, Roberto Kolter
The Global Carbon Metabolism Regulator Crc Is A Component Of A Signal Transduction Pathway Required For Biofilm Development By Pseudomonas Aeruginosa, George A. O'Toole, Karine A. Gibbs, Paul W. Hager, Paul V. Phibbs, Roberto Kolter
Dartmouth Scholarship
The transition from a planktonic (free-swimming) existence to growth attached to a surface in a biofilm occurs in response to environmental factors, including the availability of nutrients. We show that the catabolite repression control (Crc) protein, which plays a role in the regulation of carbon metabolism, is necessary for biofilm formation in Pseudomonas aeruginosa. Using phase-contrast microscopy, we found that a crc mutant only makes a dispersed monolayer of cells on a plastic surface but does not develop the dense monolayer punctuated by microcolonies typical of the wild-type strain. This is a phenotype identical to that observed in mutants …