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Articles 31 - 54 of 54
Full-Text Articles in Physiology
Manipulating Testosterone To Assess Links Between Behavior, Morphology, And Performance In The Brown Anole Anolis Sagrei, Robert M. Cox, Derek S. Stenquist, Justin P. Henningsen, Ryan Calsbeek
Manipulating Testosterone To Assess Links Between Behavior, Morphology, And Performance In The Brown Anole Anolis Sagrei, Robert M. Cox, Derek S. Stenquist, Justin P. Henningsen, Ryan Calsbeek
Dartmouth Scholarship
Survival and reproductive success are determined by the complex interplay between behavior, physiology, morphology, and performance. When optimal trait combinations along these various phenotypic axes differ between sexes or across seasons, regulatory mechanisms such as sex steroids can often facilitate sex‐specific and/or seasonal trait expression. In this study, we used surgical castration and replacement of exogenous testosterone in adult male brown anoles (Anolis sagrei) to simultaneously examine the effects of testosterone on a suite of morphological (dewlap area, body size), physiological (immune function), behavioral (dewlap, head bob, and push‐up displays), and performance (stamina, sprint speed, bite force) traits. …
Minimum Criteria For Dna Damage-Induced Phase Advances In Circadian Rhythms, Christian I. Hong, Judit Zámborszky, Attila Csikász-Nagy
Minimum Criteria For Dna Damage-Induced Phase Advances In Circadian Rhythms, Christian I. Hong, Judit Zámborszky, Attila Csikász-Nagy
Dartmouth Scholarship
Robust oscillatory behaviors are common features of circadian and cell cycle rhythms. These cyclic processes, however, behave distinctively in terms of their periods and phases in response to external influences such as light, temperature, nutrients, etc. Nevertheless, several links have been found between these two oscillators. Cell division cycles gated by the circadian clock have been observed since the late 1950s. On the other hand, ionizing radiation (IR) treatments cause cells to undergo a DNA damage response, which leads to phase shifts (mostly advances) in circadian rhythms. Circadian gating of the cell cycle can be attributed to the cell cycle …
The Specificity Of The Search Template, Mary J. Bravo, Hany Farid
The Specificity Of The Search Template, Mary J. Bravo, Hany Farid
Dartmouth Scholarship
When searching for a target object, observers use an internal representation of the target's appearance as a search template. This study used naturalistic stimuli to examine the specificity of this template. Observers first learned several name-image pairs; they then participated in a search experiment in which the names served as cues and the images served as targets. To test whether the observers searched for the targets using an exact image template, we included targets that were transformations of the studied image and targets that belonged to the same subordinate-level category as the studied image. The same stimuli were also used …
The Leaf Ionome As A Multivariable System To Detect A Plant's Physiological Status, Ivan R. Baxter, Olga Vitek, Brett Lahner, Balasubramaniam Muthukumar, Monica Borghi, Joe Morrissey, Mary Lou Guerinot, David E. Salt
The Leaf Ionome As A Multivariable System To Detect A Plant's Physiological Status, Ivan R. Baxter, Olga Vitek, Brett Lahner, Balasubramaniam Muthukumar, Monica Borghi, Joe Morrissey, Mary Lou Guerinot, David E. Salt
Dartmouth Scholarship
The contention that quantitative profiles of biomolecules contain information about the physiological state of the organism has motivated a variety of high-throughput molecular profiling experiments. However, unbiased discovery and validation of biomolecular signatures from these experiments remains a challenge. Here we show that the Arabidopsis thaliana (Arabidopsis) leaf ionome, or elemental composition, contains such signatures, and we establish statistical models that connect these multivariable signatures to defined physiological responses, such as iron (Fe) and phosphorus (P) homeostasis. Iron is essential for plant growth and development, but potentially toxic at elevated levels. Because of this, shoot Fe concentrations are …
Systems Approach Identifies An Organic Nitrogen-Responsive Gene Network That Is Regulated By The Master Clock Control Gene Cca1, Rodrigo A. Gutierrez, Trevor L. Stokes, Karen Thum, Xiaodong Xu, Mariana Obertello, Manpreet S. Katari, Milos Tanurdzic, Alexis Dean, Damion C. Nero, C Robertson Mcclung, Gloria M. Coruzzi
Systems Approach Identifies An Organic Nitrogen-Responsive Gene Network That Is Regulated By The Master Clock Control Gene Cca1, Rodrigo A. Gutierrez, Trevor L. Stokes, Karen Thum, Xiaodong Xu, Mariana Obertello, Manpreet S. Katari, Milos Tanurdzic, Alexis Dean, Damion C. Nero, C Robertson Mcclung, Gloria M. Coruzzi
Dartmouth Scholarship
Understanding how nutrients affect gene expression will help us to understand the mechanisms controlling plant growth and development as a function of nutrient availability. Nitrate has been shown to serve as a signal for the control of gene expression in Arabidopsis. There is also evidence, on a gene-by-gene basis, that downstream products of nitrogen (N) assimilation such as glutamate (Glu) or glutamine (Gln) might serve as signals of organic N status that in turn regulate gene expression. To identify genome-wide responses to such organic N signals, Arabidopsis seedlings were transiently treated with ammonium nitrate in the presence or absence of …
A Scale Invariant Measure Of Clutter, Mary J. Bravo, Hany Farid
A Scale Invariant Measure Of Clutter, Mary J. Bravo, Hany Farid
Dartmouth Scholarship
We propose a measure of clutter for real images that can be used to predict search times. This measure uses an efficient segmentation algorithm (P. Felzenszwalb & D. Huttenlocher, 2004) to count the number of regions in an image. This number is not uniquely defined, however, because it varies with the scale of segmentation. The relationship between the number of regions and the scale of segmentation follows a power law, and the exponent of the power law is similar across images. We fit power law functions to the multiple scale segmentations of 160 images. The power law exponent was set …
Fully Codon-Optimized Luciferase Uncovers Novel Temperature Characteristics Of The Neurospora Clock, Van D. Gooch, Arun Mehra, Luis F. Larrondo, Julie Fox, Melissa Touroutoutoudis, Jennifer J. Loros, Jay C. Dunlap
Fully Codon-Optimized Luciferase Uncovers Novel Temperature Characteristics Of The Neurospora Clock, Van D. Gooch, Arun Mehra, Luis F. Larrondo, Julie Fox, Melissa Touroutoutoudis, Jennifer J. Loros, Jay C. Dunlap
Dartmouth Scholarship
We report the complete reconstruction of the firefly luciferase gene, fully codon optimized for expression in Neurospora crassa. This reporter enhances light output by approximately 4 log orders over that with previously available versions, now producing light that is visible to the naked eye and sufficient for monitoring the activities of many poorly expressed genes. Time lapse photography of strains growing in race tubes, in which the frq or eas/ccg-2 promoter is used to drive luciferase, shows the highest levels of luciferase activity near the growth front and newly formed conidial bands. Further, we have established a sorbose medium colony …
Parasites Alter Community Structure, Chelsea L. Wood, James E. Byers, Kathryn L. Cottingham, Irit Altman
Parasites Alter Community Structure, Chelsea L. Wood, James E. Byers, Kathryn L. Cottingham, Irit Altman
Dartmouth Scholarship
Parasites often play an important role in modifying the physiology and behavior of their hosts and may, consequently, mediate the influence hosts have on other components of an ecological community. Along the northern Atlantic coast of North America, the dominant herbivorous snail Littorina littorea structures rocky intertidal communities through strong grazing pressure and is frequently parasitized by the digenean trematode Cryptocotyle lingua. We hypothesized that the effects of parasitism on host physiology would induce behavioral changes in L. littorea, which in turn would modulate L. littorea's influence on intertidal community composition. Specifically, we hypothesized that C. lingua …
Following Temperature Stress, Export Of Heat Shock Mrna Occurs Efficiently In Cells With Mutations In Genes Normally Important For Mrna Export, Christiane Rollenhagen, Christine A. Hodge, Charles N. Cole
Following Temperature Stress, Export Of Heat Shock Mrna Occurs Efficiently In Cells With Mutations In Genes Normally Important For Mrna Export, Christiane Rollenhagen, Christine A. Hodge, Charles N. Cole
Dartmouth Scholarship
Heat shock leads to accumulation of polyadenylated RNA in nuclei of Saccharomyces cerevisiae cells, transcriptional induction of heat shock genes, and efficient export of polyadenylated heat shock mRNAs. These studies were conducted to examine the requirements for export of mRNA following heat shock. We used in situ hybridization to detect SSA4 mRNA (encoding Hsp70) and flow cytometry to measure the amount of Ssa4p-green fluorescent protein (GFP) produced following heat shock. Npl3p and Yra1p are mRNA-binding proteins recruited to nascent mRNAs and are essential for proper mRNA biogenesis and export. Heat shock mRNA was exported efficiently in temperature-sensitive npl3, yra1 …
A Proposal For Robust Temperature Compensation Of Circadian Rhythms, Christian I. Hong, Emery D. Conrad, John J. Tyson
A Proposal For Robust Temperature Compensation Of Circadian Rhythms, Christian I. Hong, Emery D. Conrad, John J. Tyson
Dartmouth Scholarship
The internal circadian rhythms of cells and organisms coordinate their physiological properties to the prevailing 24-h cycle of light and dark on earth. The mechanisms generating circadian rhythms have four defining characteristics: they oscillate endogenously with period close to 24 h, entrain to external signals, suffer phase shifts by aberrant pulses of light or temperature, and compensate for changes in temperature over a range of 10°C or more. Most theoretical descriptions of circadian rhythms propose that the underlying mechanism generates a stable limit cycle oscillation (in constant darkness or dim light), because limit cycles quite naturally possess the first three …
A Subset Of Arabidopsis Ap2 Transcription Factors Mediates Cytokinin Responses In Concert With A Two-Component Pathway, Aaron M. Rashotte, Michael G. Mason, Claire E. Hutchison, Fernando J. Ferreira, G. Eric Schaller, Joseph J. Kieber
A Subset Of Arabidopsis Ap2 Transcription Factors Mediates Cytokinin Responses In Concert With A Two-Component Pathway, Aaron M. Rashotte, Michael G. Mason, Claire E. Hutchison, Fernando J. Ferreira, G. Eric Schaller, Joseph J. Kieber
Dartmouth Scholarship
The plant hormone cytokinin regulates numerous growth and developmental processes. A signal transduction pathway for cytokinin has been elucidated that is similar to bacterial two-component phosphorelays. In Arabidopsis, this pathway is comprised of receptors that are similar to sensor histidine kinases, histidine-containing phosphotransfer proteins, and response regulators (ARRs). There are two classes of response regulators, the type-A ARRs, which act as negative regulators of cytokinin responses, and the type-B ARRs, which are transcription factors that play a positive role in mediating cytokinin-regulated gene expression. Here we show that several closely related members of the Arabidopsis AP2 gene family of …
Time Constraints Mediate Predator-Induced Plasticity In Immune Function, Condition, And Life History, Robby Stoks, Marjan De Block, Stefanie Slos, Wendy Van Doorslaer, Jens Rolff
Time Constraints Mediate Predator-Induced Plasticity In Immune Function, Condition, And Life History, Robby Stoks, Marjan De Block, Stefanie Slos, Wendy Van Doorslaer, Jens Rolff
Dartmouth Scholarship
The simultaneous presence of predators and a limited time for development imposes a conflict: accelerating growth under time constraints comes at the cost of higher predation risk mediated by increased foraging. The few studies that have addressed this trade-off have dealt only with life history traits such as age and size at maturity. Physiological traits have largely been ignored in studies assessing the impact of environmental stressors, and it is largely unknown whether they respond independently of life history traits. Here, we studied the simultaneous effects of time constraints, i.e., as imposed by seasonality, and predation risk on immune defense, …
The Relationship Between Frq-Protein Stability And Temperature Compensation In The Neurospora Circadian Clock, Peter Ruoff, Jennifer J. Loros, Jay C. Dunlap
The Relationship Between Frq-Protein Stability And Temperature Compensation In The Neurospora Circadian Clock, Peter Ruoff, Jennifer J. Loros, Jay C. Dunlap
Dartmouth Scholarship
Temperature compensation is an important property of all biological clocks. In Neurospora crassa, negative-feedback regulation on the frequency (frq) gene's transcription by the FRQ protein plays a central role in the organism's circadian pacemaker. Earlier model calculations predicted that the stability of FRQ should determine the period length of Neurospora's circadian rhythm as well as the rhythm's temperature compensation. Here, we report experimental FRQ protein stabilities in frq mutants at 20 degrees C and 25 degrees C, and estimates of overall activation energies for mutant FRQ protein degradation. The results are consistent with earlier model predictions, i.e., temperature compensation of …
From The Cover: Assignment Of An Essential Role For The Neurospora Frequency Gene In Circadian Entrainment To Temperature Cycles, Antonio M. Pregueiro, Nathan Price-Lloyd, Deborah Bell-Pedersen, Christian Heintzen, Jennifer J. Loros, Jay C. Dunlap
From The Cover: Assignment Of An Essential Role For The Neurospora Frequency Gene In Circadian Entrainment To Temperature Cycles, Antonio M. Pregueiro, Nathan Price-Lloyd, Deborah Bell-Pedersen, Christian Heintzen, Jennifer J. Loros, Jay C. Dunlap
Dartmouth Scholarship
Circadian systems include slave oscillators and central pacemakers, and the cores of eukaryotic circadian clocks described to date are composed of transcription and translation feedback loops (TTFLs). In the model system Neurospora, normal circadian rhythmicity requires a TTFL in which a White Collar complex (WCC) activates expression of the frequency (frq) gene, and the FRQ protein feeds back to attenuate that activation. To further test the centrality of this TTFL to the circadian mechanism in Neurospora, we used low-amplitude temperature cycles to compare WT and frq-null strains under conditions in which a banding rhythm was elicited. WT cultures were entrained …
The Caenorhabditis Elegans F-Box Protein Sel-10 Promotes Female Development And May Target Fem-1 And Fem-3 For Degradation By The Proteasome, Sibylle Jager, Hillel T. Schwartz, H. Robert Horvitz, Barbara Conradt
The Caenorhabditis Elegans F-Box Protein Sel-10 Promotes Female Development And May Target Fem-1 And Fem-3 For Degradation By The Proteasome, Sibylle Jager, Hillel T. Schwartz, H. Robert Horvitz, Barbara Conradt
Dartmouth Scholarship
The Caenorhabditis elegans F-box protein SEL-10 and its human homolog have been proposed to regulate LIN-12 Notch signaling by targeting for ubiquitin-mediated proteasomal degradation LIN-12 Notch proteins and SEL-12 PS1 presenilins, the latter of which have been implicated in Alzheimer's disease. We found that sel-10 is the same gene as egl-41, which previously had been defined by gain-of-function mutations that semidominantly cause masculinization of the hermaphrodite soma. Our results demonstrate that mutations causing loss-of-function of sel-10 also have masculinizing activity, indicating that sel-10 functions to promote female development. Genetically, sel-10 acts upstream of the genes fem-1, fem-2, and fem-3 and …
Two Arabidopsis Circadian Oscillators Can Be Distinguished By Differential Temperature Sensitivity, Todd P. Michael, Patrice A. Salome, C. Robertson Mcclung
Two Arabidopsis Circadian Oscillators Can Be Distinguished By Differential Temperature Sensitivity, Todd P. Michael, Patrice A. Salome, C. Robertson Mcclung
Dartmouth Scholarship
Circadian rhythms are widespread in nature and reflect the activity of an endogenous biological clock. In metazoans, the circadian system includes a central circadian clock in the brain as well as distinct clocks in peripheral tissues such as the retina or liver. Similarly, plants have distinct clocks in different cell layers and tissues. Here, we show that two different circadian clocks, distinguishable by their sensitivity to environmental temperature signals, regulate the transcription of genes that are expressed in the Arabidopsis thaliana cotyledon. One oscillator, which regulates CAB2 expression, responds preferentially to light–dark versus temperature cycles and fails to respond to …
Minus-End Capture Of Preformed Kinetochore Fibers Contributes To Spindle Morphogenesis, Alexey Khodjakov, Lily Copenagle, Michael B. Gordon, Duane A. Compton, Tarun M. Kapoor
Minus-End Capture Of Preformed Kinetochore Fibers Contributes To Spindle Morphogenesis, Alexey Khodjakov, Lily Copenagle, Michael B. Gordon, Duane A. Compton, Tarun M. Kapoor
Dartmouth Scholarship
Near-simultaneous three-dimensional fluorescence/differential interference contrast microscopy was used to follow the behavior of microtubules and chromosomes in living alpha-tubulin/GFP-expressing cells after inhibition of the mitotic kinesin Eg5 with monastrol. Kinetochore fibers (K-fibers) were frequently observed forming in association with chromosomes both during monastrol treatment and after monastrol removal. Surprisingly, these K-fibers were oriented away from, and not directly connected to, centrosomes and incorporated into the spindle by the sliding of their distal ends toward centrosomes via a NuMA-dependent mechanism. Similar preformed K-fibers were also observed during spindle formation in untreated cells. In addition, upon monastrol removal, centrosomes established a transient …
Asymmetry Of The Central Apparatus Defines The Location Of Active Microtubule Sliding In Chlamydomonas Flagella, Matthew J. Wargo, Elizabeth F. Smith
Asymmetry Of The Central Apparatus Defines The Location Of Active Microtubule Sliding In Chlamydomonas Flagella, Matthew J. Wargo, Elizabeth F. Smith
Dartmouth Scholarship
Regulation of ciliary and flagellar motility requires spatial control of dynein-driven microtubule sliding. However, the mechanism for regulating the location and symmetry of dynein activity is not understood. One hypothesis is that the asymmetrically organized central apparatus, through interactions with the radial spokes, transmits a signal to regulate dynein-driven microtubule sliding between subsets of doublet microtubules. Based on this model, we hypothesized that the orientation of the central apparatus defines positions of active microtubule sliding required to control bending in the axoneme. To test this, we induced microtubule sliding in axonemes isolated from wild-type and mutant Chlamydomonas cells, and then …
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 …
A Pdz-Interacting Domain In Cftr Is An Apical Membrane Polarization Signal, Bryan D. Moyer, Jerod Denton, Katherine H. Karlson, Donna Reynolds, Shusheng Wang, John E. Mickle, Michael Milewski, Garry R. Cutting, William B. Guggino, Min Li, Bruce A. Stanton
A Pdz-Interacting Domain In Cftr Is An Apical Membrane Polarization Signal, Bryan D. Moyer, Jerod Denton, Katherine H. Karlson, Donna Reynolds, Shusheng Wang, John E. Mickle, Michael Milewski, Garry R. Cutting, William B. Guggino, Min Li, Bruce A. Stanton
Dartmouth Scholarship
Polarization of the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated chloride channel, to the apical plasma membrane of epithelial cells is critical for vectorial transport of chloride in a variety of epithelia, including the airway, pancreas, intestine, and kidney. However, the motifs that localize CFTR to the apical membrane are unknown. We report that the last 3 amino acids in the COOH-terminus of CFTR (T-R-L) comprise a PDZ-interacting domain that is required for the polarization of CFTR to the apical plasma membrane in human airway and kidney epithelial cells. In addition, the CFTR mutant, S1455X, which lacks the 26 …
Measurement Of Oxygen Partial Pressure, Its Control During Hypoxia And Hyperoxia, And Its Effect Upon Light Emission In A Bioluminescent Elaterid Larva, G. S. Timmins, C. A. A. Penatti, E. J. H. Bechara, H. M. Swartz
Measurement Of Oxygen Partial Pressure, Its Control During Hypoxia And Hyperoxia, And Its Effect Upon Light Emission In A Bioluminescent Elaterid Larva, G. S. Timmins, C. A. A. Penatti, E. J. H. Bechara, H. M. Swartz
Dartmouth Scholarship
This study investigates the respiratory physiology of bioluminescent larvae of Pyrearinus termitilluminans in relation to their tolerance to hypoxia and hyperoxia and to the supply of oxygen for bioluminescence. The partial pressure of oxygen (P(O2)) was measured within the bioluminescent prothorax by in vivo electron paramagnetic resonance (EPR) oximetry following acclimation of larvae to hypoxic, normoxic and hyperoxic (normobaric) atmospheres and during periods of bioluminescence (during normoxia). The P(O2) in the prothorax during exposure to an external P(O2) of 15.2, 160 and 760 mmHg was 10.3+/-2.6, 134+/-0.9 and 725+/-73 mmHg respectively (mean +/- s.d., N=5; 1 mmHg=0.1333 kPa). Oxygen supply …
Circadian Clock-Controlled Genes Isolated From Neurospora Crassa Are Late Night- To Early Morning-Specific, Deborah Bell-Pedersen, Mari L. Shinohara, Jennifer J. Loros, Jay C. Dunlap
Circadian Clock-Controlled Genes Isolated From Neurospora Crassa Are Late Night- To Early Morning-Specific, Deborah Bell-Pedersen, Mari L. Shinohara, Jennifer J. Loros, Jay C. Dunlap
Dartmouth Scholarship
An endogenous circadian biological clock controls the temporal aspects of life in most organisms, including rhythmic control of genes involved in clock output pathways. In the fungus Neurospora crassa, one pathway known to be under control of the clock is asexual spore (conidia) development. To understand more fully the processes that are regulated by the N. crassa circadian clock, systematic screens were carried out for genes that oscillate at the transcriptional level. Time-of-day-specific cDNA libraries were generated and used in differential screens to identify six new clock-controlled genes (ccgs). Transcripts specific for each of the ccgs …
Circadian Clock Locus Frequency: Protein Encoded By A Single Open Reading Frame Defines Period Length And Temperature Compensation., Benjamin D. Aronson, Keith A. Johnson, Jay C. Dunlap
Circadian Clock Locus Frequency: Protein Encoded By A Single Open Reading Frame Defines Period Length And Temperature Compensation., Benjamin D. Aronson, Keith A. Johnson, Jay C. Dunlap
Dartmouth Scholarship
The frequency (frq) locus encodes a key component, a state variable, in a cellular oscillator generating circadian rhythmicity. Two transcripts have been mapped to this region, and data presented here are consistent with the existence of a third transcript. Analysis of cDNA clones and clock mutants from this region focuses attention on one transcript encoding a protein. FRQ, which is a central clock component: (i) mutations in all of the semidominant frq alleles are the result of single amino acid substitutions and map to the open reading frame (ORF) encoding FRQ; (ii) deletion of this ORF, or a frameshift mutation …
Recombinant Immune Interferon Increases Immunoglobulin G Fc Receptors On Cultured Human Mononuclear Phagocytes, Paul M. Guyre, Peter M. Morganelli, Renee Miller
Recombinant Immune Interferon Increases Immunoglobulin G Fc Receptors On Cultured Human Mononuclear Phagocytes, Paul M. Guyre, Peter M. Morganelli, Renee Miller
Dartmouth Scholarship
Although recent studies suggest that interferons can increase the number of IgG Fc receptor (FcR gamma) sites on mouse macrophages, direct assessment of similar effects on human mononuclear phagocytes is lacking. We therefore measured the specific binding of 125I- and fluorescein-labeled IgG1 to human monocytes and leukemic cell lines after culture in vitro with highly purified human interferons. We report that natural and recombinant human gamma-interferon causes a dramatic (nearly 10-fold) increase in the number of FcR gamma on normal human monocytes and on the human cell lines HL-60 and U-937. Alpha and beta-interferons cause a modest but significant increase …