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Articles 1 - 11 of 11

Full-Text Articles in Life Sciences

Interactions Among Environmental Drivers: Community Responses To Changing Nutrients And Dissolved Organic Carbon, Jennifer L. Klug, Kathryn L. Cottingham Dec 2001

Interactions Among Environmental Drivers: Community Responses To Changing Nutrients And Dissolved Organic Carbon, Jennifer L. Klug, Kathryn L. Cottingham

Dartmouth Scholarship

Biological communities are frequently exposed to environmental changes that cause measurable responses in properties of the community (hereafter called environmental drivers). Predicting how communities respond to changing environmental drivers is a fundamental goal of ecology. Making predictions, however, can be very difficult, particularly when multiple environmental drivers change simultaneously and there are interactions among the drivers. We investigated the effects of the interaction between changes in nutrient loading and changes in colored dissolved organic matter (measured as dissolved organic carbon, DOC) on the dynamics of phytoplankton communities over a 7‐yr period. In 1991, Long Lake, a small seepage lake in …


Phylogenetic Relationships Within Cation Transporter Families Of Arabidopsis, Pascal Mäser, Sébastien Thomine, Julian I. Schroeder, John M. Ward, Kendal Hirschi, Heven Sze, Ina N. Talke, Anna Amtmann, Frans J.M. Maathuis, Dale Sanders, Jeff F. Harper, Jason Tchieu, Michael Gribskov, Michael W. Persans, David E. Salt, Sun A. Kim, Mary Lou Guerinot Aug 2001

Phylogenetic Relationships Within Cation Transporter Families Of Arabidopsis, Pascal Mäser, Sébastien Thomine, Julian I. Schroeder, John M. Ward, Kendal Hirschi, Heven Sze, Ina N. Talke, Anna Amtmann, Frans J.M. Maathuis, Dale Sanders, Jeff F. Harper, Jason Tchieu, Michael Gribskov, Michael W. Persans, David E. Salt, Sun A. Kim, Mary Lou Guerinot

Dartmouth Scholarship

Uptake and translocation of cationic nutrients play essential roles in physiological processes including plant growth, nutrition, signal transduction, and development. Approximately 5% of the Arabidopsis genome appears to encode membrane transport proteins. These proteins are classified in 46 unique families containing approximately 880 members. In addition, several hundred putative transporters have not yet been assigned to families. In this paper, we have analyzed the phylogenetic relationships of over 150 cation transport proteins. This analysis has focused on cation transporter gene families for which initial characterizations have been achieved for individual members, including potassium transporters and channels, sodium transporters, calcium antiporters, …


Networking Senescence-Regulating Pathways By Using Arabidopsis Enhancer Trap Lines, Yuehui He, Weining Tang, Johnnie D. Swain, Anthony L. Green, Thomas P. Jack, Susheng Gan Jun 2001

Networking Senescence-Regulating Pathways By Using Arabidopsis Enhancer Trap Lines, Yuehui He, Weining Tang, Johnnie D. Swain, Anthony L. Green, Thomas P. Jack, Susheng Gan

Dartmouth Scholarship

The last phase of leaf development, generally referred to as leaf senescence, is an integral part of plant development that involves massive programmed cell death. Due to a sharp decline of photosynthetic capacity in a leaf, senescence limits crop yield and forest plant biomass production. However, the biochemical components and regulatory mechanisms underlying leaf senescence are poorly characterized. Although several approaches such as differential cDNA screening, differential display, and cDNA subtraction have been employed to isolate senescence-associated genes (SAGs), only a limited number of SAGs have been identified, and information regarding the regulation of these genes is …


Marek's Disease Virus (Mdv) Encodes An Interleukin-8 Homolog (Vil-8): Characterization Of The Vil-8 Protein And A Vil-8 Deletion Mutant Mdv, Mark S. Parcells, Su-Fang Lin, Robert L. Dienglewicz, Vladimir Majerciak, Dan R. Robinson, Hua-Chien Chen, Zining Wu, George R. Dubyak, Peter Brunovskis, Henry D. Hunt Jun 2001

Marek's Disease Virus (Mdv) Encodes An Interleukin-8 Homolog (Vil-8): Characterization Of The Vil-8 Protein And A Vil-8 Deletion Mutant Mdv, Mark S. Parcells, Su-Fang Lin, Robert L. Dienglewicz, Vladimir Majerciak, Dan R. Robinson, Hua-Chien Chen, Zining Wu, George R. Dubyak, Peter Brunovskis, Henry D. Hunt

Dartmouth Scholarship

Chemokines induce chemotaxis, cell migration, and inflammatory responses. We report the identification of an interleukin-8 (IL-8) homolog, termed vIL-8, encoded within the genome of Marek's disease virus (MDV). The 134-amino-acid vIL-8 shares closest homology to mammalian and avian IL-8, molecules representing the prototype CXC chemokine. The gene for vIL-8 consists of three exons which map to the BamHI-L fragment within the repeats flanking the unique long region of the MDV genome. A 0.7-kb transcript encoding vIL-8 was detected in an n-butyrate-treated, MDV-transformed T-lymphoblastoid cell line, MSB-1. This induction is essentially abolished by cycloheximide and herpesvirus DNA polymerase inhibitor phosphonoacetate, indicating …


Trophic Cascades, Nutrients, And Lake Productivity: Whole-Lake Experiments, Stephen R. Carpenter, Jonathan J. Cole, James R. Hodgson, James F. Kitchell, Michael L. Pace, Darren Bade, Kathryn L. Cottingham May 2001

Trophic Cascades, Nutrients, And Lake Productivity: Whole-Lake Experiments, Stephen R. Carpenter, Jonathan J. Cole, James R. Hodgson, James F. Kitchell, Michael L. Pace, Darren Bade, Kathryn L. Cottingham

Dartmouth Scholarship

Responses of zooplankton, pelagic primary producers, planktonic bacteria, and CO2 exchange with the atmosphere were measured in four lakes with contrasting food webs under a range of nutrient enrichments during a seven-year period. Prior to enrichment, food webs were manipulated to create contrasts between piscivore dominance and planktivore dominance. Nutrient enrichments of inorganic nitrogen and phosphorus exhibited ratios of N:P > 17:1, by atoms, to maintain P limitation. An unmanipulated reference lake, Paul Lake, revealed baseline variability but showed no trends that could confound the interpretation of changes in the nearby manipulated lakes. Herbivorous zooplankton of West Long Lake (piscivorous fishes) …


The Mannose-Sensitive Hemagglutinin Of Vibrio Cholerae Promotes Adherence To Zooplankton, Deborah A. Chiavelli, Jane W. Marsh, Ronald K. Taylor Apr 2001

The Mannose-Sensitive Hemagglutinin Of Vibrio Cholerae Promotes Adherence To Zooplankton, Deborah A. Chiavelli, Jane W. Marsh, Ronald K. Taylor

Dartmouth Scholarship

The bacterium Vibrio cholerae, the etiological agent of cholera, is often found attached to plankton, a property that is thought to contribute to its environmental persistence in aquatic habitats. The V. cholerae O1 El Tor biotype and V. cholerae O139 strains produce a surface pilus termed the mannose-sensitive hemagglutinin (MSHA), whereas V. cholerae O1 classical biotype strains do not. Although V. cholerae O1 classical does not elaborate MSHA, the gene is present and expressed at a level comparable to that of the other strains. Since V. cholerae O1 El Tor and V. cholerae O139 have displaced V. cholerae O1 classical …


Nuclear Export Of 60s Ribosomal Subunits Depends On Xpo1p And Requires A Nuclear Export Sequence-Containing Factor, Nmd3p, That Associates With The Large Subunit Protein Rpl10p, Olivier Gadal, Daniela Strau, Jacques Kessl, Bernard Trumpower Feb 2001

Nuclear Export Of 60s Ribosomal Subunits Depends On Xpo1p And Requires A Nuclear Export Sequence-Containing Factor, Nmd3p, That Associates With The Large Subunit Protein Rpl10p, Olivier Gadal, Daniela Strau, Jacques Kessl, Bernard Trumpower

Dartmouth Scholarship

Nuclear export of ribosomes requires a subset of nucleoporins and the Ran system, but specific transport factors have not been identified. Using a large subunit reporter (Rpl25p-eGFP), we have isolated several temperature-sensitive ribosomal export (rix) mutants. One of these corresponds to the ribosomal protein Rpl10p, which interacts directly with Nmd3p, a conserved and essential protein associated with 60S subunits. We find that thermosensitive nmd3 mutants are impaired in large subunit export. Strikingly, Nmd3p shuttles between the nucleus and cytoplasm and is exported by the nuclear export receptor Xpo1p. Moreover, we show that export of 60S subunits is Xpo1p dependent. We …


Chromosome Movement In Mitosis Requires Microtubule Anchorage At Spindle Poles, Michael B. Gordon, Louisa Howard, Duane A. Compton Feb 2001

Chromosome Movement In Mitosis Requires Microtubule Anchorage At Spindle Poles, Michael B. Gordon, Louisa Howard, Duane A. Compton

Dartmouth Scholarship

Anchorage of microtubule minus ends at spindle poles has been proposed to bear the load of poleward forces exerted by kinetochore-associated motors so that chromosomes move toward the poles rather than the poles toward the chromosomes. To test this hypothesis, we monitored chromosome movement during mitosis after perturbation of nuclear mitotic apparatus protein (NuMA) and the human homologue of the KIN C motor family (HSET), two noncentrosomal proteins involved in spindle pole organization in animal cells. Perturbation of NuMA alone disrupts spindle pole organization and delays anaphase onset, but does not alter the velocity of oscillatory chromosome movement in prometaphase. …


Erv41p And Erv46p New Components Of Copii Vesicles Involved In Transport Between The Er And Golgi Complex, Stefan Otte, William J. Belden, Matthew Heidtman, Jay Liu, Ole N. Jensen, Charles Barlowe Jan 2001

Erv41p And Erv46p New Components Of Copii Vesicles Involved In Transport Between The Er And Golgi Complex, Stefan Otte, William J. Belden, Matthew Heidtman, Jay Liu, Ole N. Jensen, Charles Barlowe

Dartmouth Scholarship

Proteins contained on purified COPII vesicles were analyzed by matrix-assisted laser desorption ionization mass spectrometry combined with database searching. We identified four known vesicle proteins (Erv14p, Bet1p, Emp24p, and Erv25p) and an additional nine species (Yip3p, Rer1p, Erp1p, Erp2p, Erv29p, Yif1p, Erv41p, Erv46p, and Emp47p) that had not been localized to ER vesicles. Using antibodies, we demonstrate that these proteins are selectively and efficiently packaged into COPII vesicles. Three of the newly identified vesicle proteins (Erv29p, Erv41p, and Erv46p) represent uncharacterized integral membrane proteins that are conserved across species. Erv41p and Erv46p were further characterized. These proteins co- localized to …


Genes, Categories, And Species: The Evolutionary And Cognitive Causes Of The Species Problem, Michael Dietrich Jan 2001

Genes, Categories, And Species: The Evolutionary And Cognitive Causes Of The Species Problem, Michael Dietrich

Dartmouth Scholarship

Review of Genes, Categories, and Species: The Evolutionary and Cognitive Causes of the Species Problem by Jody Hey.


Firefly Flashing Is Controlled By Gating Oxygen To Light-Emitting Cells, G. S. Timmins, F. J. Robb, C. M. Wilmot, S. K. Jackson, H. M. Swartz Jan 2001

Firefly Flashing Is Controlled By Gating Oxygen To Light-Emitting Cells, G. S. Timmins, F. J. Robb, C. M. Wilmot, S. K. Jackson, H. M. Swartz

Dartmouth Scholarship

Although many aspects of firefly bioluminescence are understood, the mechanism by which adult fireflies produce light as discrete rapid flashes is not. Here we examine the most postulated theory, that flashing is controlled by gating oxygen access to the light-emitting cells (photocytes). According to this theory, the dark state represents repression of bioluminescence by limiting oxygen, which is required for bioluminescence; relief from this repression by transiently allowing oxygen access to the photocytes allows the flash. We show that normobaric hyperoxia releases the repression of light emission in the dark state of both spontaneously flashing and non-flashing fireflies, causing continual …