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Search Results: 1 - 10 of 240888 matches for " James R. Bamburg "
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Rapid Changes in Phospho-MAP/Tau Epitopes during Neuronal Stress: Cofilin-Actin Rods Primarily Recruit Microtubule Binding Domain Epitopes
Ineka T. Whiteman, Laurie S. Minamide, De Lian Goh, James R. Bamburg, Claire Goldsbury
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0020878
Abstract: Abnormal mitochondrial function is a widely reported contributor to neurodegenerative disease including Alzheimer's disease (AD), however, a mechanistic link between mitochondrial dysfunction and the initiation of neuropathology remains elusive. In AD, one of the earliest hallmark pathologies is neuropil threads comprising accumulated hyperphosphorylated microtubule-associated protein (MAP) tau in neurites. Rod-like aggregates of actin and its associated protein cofilin (AC rods) also occur in AD. Using a series of antibodies - AT270, AT8, AT100, S214, AT180, 12E8, S396, S404 and S422 - raised against different phosphoepitopes on tau, we characterize the pattern of expression and re-distribution in neurites of these phosphoepitope labels during mitochondrial inhibition. Employing chick primary neuron cultures, we demonstrate that epitopes recognized by the monoclonal antibody 12E8, are the only species rapidly recruited into AC rods. These results were recapitulated with the actin depolymerizing drug Latrunculin B, which induces AC rods and a concomitant increase in the 12E8 signal measured on Western blot. This suggests that AC rods may be one way in which MAP redistribution and phosphorylation is influenced in neurons during mitochondrial stress and potentially in the early pathogenesis of AD.
Amyloid beta dimers/trimers potently induce cofilin-actin rods that are inhibited by maintaining cofilin-phosphorylation
Richard C Davis, Ian T Marsden, Michael T Maloney, Laurie S Minamide, Marcia Podlisny, Dennis J Selkoe, James R Bamburg
Molecular Neurodegeneration , 2011, DOI: 10.1186/1750-1326-6-10
Abstract: Here we demonstrate that a gel filtration fraction of 7PA2 cell-secreted SDS-stable human Aβ dimers and trimers (Aβd/t) induces maximal neuronal rod response at ~250 pM. This is 4,000-fold more active than traditionally prepared human Aβ oligomers, which contain SDS-stable trimers and tetramers, but are devoid of dimers. When incubated under tyrosine oxidizing conditions, synthetic human but not rodent Aβ1-42, the latter lacking tyrosine, acquires a marked increase (620 fold for EC50) in rod-inducing activity. Gel filtration of this preparation yielded two fractions containing SDS-stable dimers, trimers and tetramers. One, eluting at a similar volume to 7PA2 Aβd/t, had maximum activity at ~5 nM, whereas the other, eluting at the void volume (high-n state), lacked rod inducing activity at the same concentration. Fractions from 7PA2 medium containing Aβ monomers are not active, suggesting oxidized SDS-stable Aβ1-42 dimers in a low-n state are the most active rod-inducing species. Aβd/t-induced rods are predominantly localized to the dentate gyrus and mossy fiber tract, reach significance over controls within 2 h of treatment, and are reversible, disappearing by 24 h after Aβd/t washout. Overexpression of cofilin phosphatases increase rod formation when expressed alone and exacerbate rod formation when coupled with Aβd/t, whereas overexpression of a cofilin kinase inhibits Aβd/t-induced rod formation.Together these data support a mechanism by which Aβd/t alters the actin cytoskeleton via effects on cofilin in neurons critical to learning and memory.Proteolytic cleavage of amyloid precursor protein (AβPP) by β- and γ-secretases gives rise to Aβ peptides ranging in length from 36-43 amino acids [1-6]. Early onset familial AD is linked with high penetrance to mutations that lead to increased production of the most amyloidogenic species, Aβ1-42 [4,7-10]. The "amyloid hypothesis" proposes that increasing cerebral accumulation of Aβ over years to decades exacerbates cognitiv
A Genetically Encoded Reporter for Real-Time Imaging of Cofilin-Actin Rods in Living Neurons
Jianjie Mi, Alisa E. Shaw, Chi W. Pak, Keifer P. Walsh, Laurie S. Minamide, Barbara W. Bernstein, Thomas B. Kuhn, James R. Bamburg
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0083609
Abstract: Filament bundles (rods) of cofilin and actin (1:1) form in neurites of stressed neurons where they inhibit synaptic function. Live-cell imaging of rod formation is hampered by the fact that overexpression of a chimera of wild type cofilin with a fluorescent protein causes formation of spontaneous and persistent rods, which is exacerbated by the photostress of imaging. The study of rod induction in living cells calls for a rod reporter that does not cause spontaneous rods. From a study in which single cofilin surface residues were mutated, we identified a mutant, cofilinR21Q, which when fused with monomeric Red Fluorescent Protein (mRFP) and expressed several fold above endogenous cofilin, does not induce spontaneous rods even during the photostress of imaging. CofilinR21Q-mRFP only incorporates into rods when they form from endogenous proteins in stressed cells. In neurons, cofilinR21Q-mRFP reports on rods formed from endogenous cofilin and induced by all modes tested thus far. Rods have a half-life of 30–60 min upon removal of the inducer. Vesicle transport in neurites is arrested upon treatments that form rods and recovers as rods disappear. CofilinR21Q-mRFP is a genetically encoded rod reporter that is useful in live cell imaging studies of induced rod formation, including rod dynamics, and kinetics of rod elimination.
Amyloid-β and Proinflammatory Cytokines Utilize a Prion Protein-Dependent Pathway to Activate NADPH Oxidase and Induce Cofilin-Actin Rods in Hippocampal Neurons
Keifer P. Walsh, Laurie S. Minamide, Sarah J. Kane, Alisa E. Shaw, David R. Brown, Bruce Pulford, Mark D. Zabel, J. David Lambeth, Thomas B. Kuhn, James R. Bamburg
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0095995
Abstract: Neurites of neurons under acute or chronic stress form bundles of filaments (rods) containing 1:1 cofilin:actin, which impair transport and synaptic function. Rods contain disulfide cross-linked cofilin and are induced by treatments resulting in oxidative stress. Rods form rapidly (5–30 min) in >80% of cultured hippocampal or cortical neurons treated with excitotoxic levels of glutamate or energy depleted (hypoxia/ischemia or mitochondrial inhibitors). In contrast, slow rod formation (50% of maximum response in ~6 h) occurs in a subpopulation (~20%) of hippocampal neurons upon exposure to soluble human amyloid-β dimer/trimer (Aβd/t) at subnanomolar concentrations. Here we show that proinflammatory cytokines (TNFα, IL-1β, IL-6) also induce rods at the same rate and within the same neuronal population as Aβd/t. Neurons from prion (PrPC)-null mice form rods in response to glutamate or antimycin A, but not in response to proinflammatory cytokines or Aβd/t. Two pathways inducing rod formation were confirmed by demonstrating that NADPH-oxidase (NOX) activity is required for prion-dependent rod formation, but not for rods induced by glutamate or energy depletion. Surprisingly, overexpression of PrPC is by itself sufficient to induce rods in over 40% of hippocampal neurons through the NOX-dependent pathway. Persistence of PrPC-dependent rods requires the continuous activity of NOX. Removing inducers or inhibiting NOX activity in cells containing PrPC-dependent rods causes rod disappearance with a half-life of about 36 min. Cofilin-actin rods provide a mechanism for synapse loss bridging the amyloid and cytokine hypotheses for Alzheimer disease, and may explain how functionally diverse Aβ-binding membrane proteins induce synaptic dysfunction.
Calyculin A induces prematurely condensed chromosomes without histone H1 phosphorylation in mammalian G1-phase cells  [PDF]
James R. Paulson, Erica R. Vander Mause
Advances in Biological Chemistry (ABC) , 2013, DOI: 10.4236/abc.2013.33A005
Abstract:

It is shown here that one can induce prematurely condensed chromosomes (PCCs) in G1-phase human (HeLa) and mouse (FT210) cells by treating them with the protein phosphatase inhibitor calyculin A. However, histone H1 is not phosphorylated in these G1-PCCs. It has previously been proposed that histone H1 phosphorylation is responsible for mitotic chromosome condensation, but our results suggest that this is not the case. They indicate instead that phosphorylation of histone H1 is not required for chromosome condensation. It is known that the Cdk1 protein kinase, which triggers mitosis and also phosphorylates histone H1, cannot be activated in G1-phase because mitotic cyclins are not present. Since calyculin A induces PCCs in G1-phase in the absence of active Cdk1, our results suggest that inactivation of protein phosphatases may be just as important for the onset of chromosome condensation and other mitotic events as the activation of protein kinases.

External Representations in the Teaching and Learning of Introductory Chemistry  [PDF]
James R. Cox, Bethany W. Jones
Creative Education (CE) , 2011, DOI: 10.4236/ce.2011.25067
Abstract: This manuscript describes the role that external representations, such as diagrams and sketches, can play in organizing and learning concepts presented in a one-semester chemistry course (general, organic and biochemistry) designed for nursing students. Although external representations are typically found in chemistry textbooks and instructor-drawn notes, students are usually not taught or prompted to use various types of external representations to promote learning. Representations created by an instructor and a student are discussed to highlight effective ways to foster student participation in creating various diagrams. In addition, a student provides a perspective on the educational value of creating external representations and the roles of visual thinking and creativity in learning introductory chemistry. Although the model for this approach has been an introductory chemistry course, this approach can be widely applied across disciplines.
The Sociological Determination: A Reflexive Look at Conducting Local Disaster Research after Hurricane Katrina  [PDF]
Timothy J. Haney, James R. Elliott
Sociology Mind (SM) , 2013, DOI: 10.4236/sm.2013.31002
Abstract:

This paper examines the process of collecting data on New Orleanians affected by Hurricane Katrina. It does so by focusing upon the experiences of local researchers who were simultaneously conducting research on and within the disaster. It also documents one research team’s attempt to generate a random sample of residents from several New Orleans neighborhoods, stratified both by racial composition and level of damage. Further, it describes the challenges associated with navigating complex bureaucracies that are themselves affected by the disaster. Results demonstrate that our methods for drawing samples from six New Orleans neighborhoods yielded highly representative samples, even in heavily damaged neighborhoods where the long-term displacement required a multi-pronged strategy that involved contact by mail, telephone, and visits to local churches. The paper concludes by making recommendations for facilitating future research by locally affected researchers.

 

Active Management of Plant Canopy Temperature as a Tool for Modifying Plant Metabolic Activity  [PDF]
James R. Mahan, John J. Burke
American Journal of Plant Sciences (AJPS) , 2015, DOI: 10.4236/ajps.2015.61028
Abstract: The relationship between a plant and its thermal environment is a major determiner of its growth and development. Since plants grow and develop within continuously variable thermal environments, they are subjected to continuous thermal variation over their life cycle. Transpiration serves to uncouple the temperature of the plant from that of its environment in a manner that reduces the occurrence of high temperature stresses that can limit plant performance. In some agriculturally important plants, there are desirable metabolic outcomes that are associated with specific stress events (e.g. wine grapes). In these plants it is often desirable to induce temperature and water stresses of known magnitude and duration at specific points in the growing season. In this study we used a computer-controlled irrigation system that used cotton canopy temperature to control irrigation in greenhouse-grown plants over a 10-day period. The system was designed to irrigate in a manner that altered the canopy temperature relative to specific temperature thresholds (28°C, 30°C, 32°C and 34°C). The results demonstrate that automated irrigation management based on canopy temperature is capable of altering the temporal pattern of canopy temperature in a desired manner using a feed-back loop. Potential limitations on this action are related to the range of air temperatures, radiation and humidity within the environment.
Using Sports Wagering Markets to Evaluate and Compare Team Winning Streaks in Sports  [PDF]
R. Alan Bowman, Thomas Ashman, James Lambrinos
American Journal of Operations Research (AJOR) , 2015, DOI: 10.4236/ajor.2015.55029
Abstract: Point spreads and money lines from sports wagering markets are used to evaluate the impressiveness of team streaks. Sports wagering data have previously been useful in assessing competitive balance in sports. Our approach was motivated by the amount of media scrutiny that accompanied the winning streak of the NBA’s Miami Heat and the point streak of the NHL’s Chicago Blackhawks which occurred simultaneously for the most part in 2013. The topic came to the forefront again with the 2014-2015 winning streak of the Atlanta Hawks. Three streaks are highlighted in our paper. The length of the streaks, the quality of the competition, injuries, and a variety of other factors were mentioned in the media but the discussion was limited to subjective opinions as no way of properly weighing relative influence of the factors was identified. Wagering markets provide an excellent source of information for making these judgments. Several complementary measures are described and the most impressive team streaks within and across professional baseball, basketball, football, and ice hockey are identified.
Learning High School Biology in a Social Context  [PDF]
Amitabha Basu, Deborah Aglira, James R. Spotila
Creative Education (CE) , 2017, DOI: 10.4236/ce.2017.815165
Abstract: In this research, we developed a process that helped students connect cell and molecular biology concepts with problems in context of their lives. Specifically, we supplemented traditional teaching with problem, project and inquiry based laboratories, without changing the structure of the mandated biology curriculum. We ran the process twice, following the classroom based action research model. Our initial foray exhibited better student-developed projects and a modest improvement of test grades. Second time we compared changes in problem solving skills, attitude toward reading, writing and problem solving and improvement of traditional test grades from the beginning and end of the school year. This process made the biological concepts so interesting that by the end of the year nearly all students significantly (t(55) = -8.95, p ≤ 0.05) improved problem-solving skills and some students went further to develop and solve independent inquiries. They also exhibited improved attitude towards reading, writing and problem solving. However, we didn’t observe any causal relationship between improvement of problem solving skills and test grade, since its trend showed little difference between first and second trial.
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