Medicine and Health Sciences Commons^™

Spectrotemporal Modulation Provides A Unifying Framework For Auditory Cortical Asymmetries, A. Flinker, W. K. Doyle, A. D. Mehta, O. Devinsky, D. Poeppel

Journal Articles

No abstract provided.

Cellular Dynamic Simulator: An Event Driven Molecular Simulation Environment For Cellular Physiology, Michael J Byrne, M Neal Waxham, Yoshihisa Kubota

Journal Articles

In this paper, we present the Cellular Dynamic Simulator (CDS) for simulating diffusion and chemical reactions within crowded molecular environments. CDS is based on a novel event driven algorithm specifically designed for precise calculation of the timing of collisions, reactions and other events for each individual molecule in the environment. Generic mesh based compartments allow the creation / importation of very simple or detailed cellular structures that exist in a 3D environment. Multiple levels of compartments and static obstacles can be used to create a dense environment to mimic cellular boundaries and the intracellular space. The CDS algorithm takes into …

Structural Plasticity Can Produce Metaplasticity, Georgios Kalantzis, Harel Z Shouval

Journal Articles

BACKGROUND: Synaptic plasticity underlies many aspect of learning memory and development. The properties of synaptic plasticity can change as a function of previous plasticity and previous activation of synapses, a phenomenon called metaplasticity. Synaptic plasticity not only changes the functional connectivity between neurons but in some cases produces a structural change in synaptic spines; a change thought to form a basis for this observed plasticity. Here we examine to what extent structural plasticity of spines can be a cause for metaplasticity. This study is motivated by the observation that structural changes in spines are likely to affect the calcium dynamics …

Extended Kalman Filter For Estimation Of Parameters In Nonlinear State-Space Models Of Biochemical Networks., Xiaodian Sun, Li Jin, Momiao Xiong

Journal Articles

It is system dynamics that determines the function of cells, tissues and organisms. To develop mathematical models and estimate their parameters are an essential issue for studying dynamic behaviors of biological systems which include metabolic networks, genetic regulatory networks and signal transduction pathways, under perturbation of external stimuli. In general, biological dynamic systems are partially observed. Therefore, a natural way to model dynamic biological systems is to employ nonlinear state-space equations. Although statistical methods for parameter estimation of linear models in biological dynamic systems have been developed intensively in the recent years, the estimation of both states and parameters of …

Poly(A)-Binding Protein-Interacting Protein 1 Binds To Eukaryotic Translation Initiation Factor 3 To Stimulate Translation, Yvan Martineau, Mélanie C Derry, Xiaoshan Wang, Akiko Yanagiya, Juan José Berlanga, Ann-Bin Shyu, Hiroaki Imataka, Kalle Gehring, Nahum Sonenberg

Journal Articles

Poly(A)-binding protein (PABP) stimulates translation initiation by binding simultaneously to the mRNA poly(A) tail and eukaryotic translation initiation factor 4G (eIF4G). PABP activity is regulated by PABP-interacting (Paip) proteins. Paip1 binds PABP and stimulates translation by an unknown mechanism. Here, we describe the interaction between Paip1 and eIF3, which is direct, RNA independent, and mediated via the eIF3g (p44) subunit. Stimulation of translation by Paip1 in vivo was decreased upon deletion of the N-terminal sequence containing the eIF3-binding domain and upon silencing of PABP or several eIF3 subunits. We also show the formation of ternary complexes composed of Paip1-PABP-eIF4G and …

Rationale For Reading Fluconazole Mics At 24 Hours Rather Than 48 Hours When Testing Candida Spp By The Clsi M27-A2 Standard Method, Luis Ostrosky-Zeichner, John H Rex, Michael A Pfaller, Daniel J Diekema, Barbara D Alexander, David Andes, Steven D Brown, Vishnu Chaturvedi, Mahmoud A Ghannoum, Cindy C Knapp, Daniel J Sheehan, Thomas J Walsh

Journal Articles

We investigated if CLSI M27-A2 Candida species breakpoints for fluconazole MIC are valid when read at 24 h. Analysis of a data set showed good correlation between 48- and 24-h MICs, as well as similar outcomes and pharmacodynamic efficacy parameters, except for isolates in the susceptible dose-dependent category, such as Candida glabrata.

Spatial Modulation Of Primate Inferotemporal Responses By Eye Position, Sidney R. Lehky, Xinmiao Peng, Carrie J. Mcadams, Anne B. Sereno

Journal Articles

BACKGROUND: A key aspect of representations for object recognition and scene analysis in the ventral visual stream is the spatial frame of reference, be it a viewer-centered, object-centered, or scene-based coordinate system. Coordinate transforms from retinocentric space to other reference frames involve combining neural visual responses with extraretinal postural information.

METHODOLOGY/PRINCIPAL FINDINGS: We examined whether such spatial information is available to anterior inferotemporal (AIT) neurons in the macaque monkey by measuring the effect of eye position on responses to a set of simple 2D shapes. We report, for the first time, a significant eye position effect in over 40% of …

Activation Of Heat Shock And Antioxidant Responses By The Natural Product Celastrol: Transcriptional Signatures Of A Thiol-Targeted Molecule, Amy Trott, James D West, Lada Klaić, Sandy D Westerheide, Richard B Silverman, Richard I Morimoto, Kevin A Morano

Journal Articles

Stress response pathways allow cells to sense and respond to environmental changes and adverse pathophysiological states. Pharmacological modulation of cellular stress pathways has implications in the treatment of human diseases, including neurodegenerative disorders, cardiovascular disease, and cancer. The quinone methide triterpene celastrol, derived from a traditional Chinese medicinal herb, has numerous pharmacological properties, and it is a potent activator of the mammalian heat shock transcription factor HSF1. However, its mode of action and spectrum of cellular targets are poorly understood. We show here that celastrol activates Hsf1 in Saccharomyces cerevisiae at a similar effective concentration seen in mammalian cells. Transcriptional …

Repeat Length And Rna Expression Level Are Not Primary Determinants In Cug Expansion Toxicity In Drosophila Models, Gwenn Le Mée, Nader Ezzeddine, Michèle Capri, Ounissa Aït-Ahmed

Journal Articles

Evidence for an RNA gain-of-function toxicity has now been provided for an increasing number of human pathologies. Myotonic dystrophies (DM) belong to a class of RNA-dominant diseases that result from RNA repeat expansion toxicity. Specifically, DM of type 1 (DM1), is caused by an expansion of CUG repeats in the 3'UTR of the DMPK protein kinase mRNA, while DM of type 2 (DM2) is linked to an expansion of CCUG repeats in an intron of the ZNF9 transcript (ZNF9 encodes a zinc finger protein). In both pathologies the mutant RNA forms nuclear foci. The mechanisms that underlie the RNA pathogenicity …

Epstein-Barr Virus Infection Of Langerhans Cell Precursors As A Mechanism Of Oral Epithelial Entry, Persistence, And Reactivation, Dennis M. Walling, Autumn J. Ray, Joan E. Nichols, Catherine M. Flaitz, C. Mark Nichols

Journal Articles

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with many malignant and nonmalignant human diseases. Life-long latent EBV persistence occurs in blood-borne B lymphocytes, while EBV intermittently productively replicates in mucosal epithelia. Although several models have previously been proposed, the mechanism of EBV transition between these two reservoirs of infection has not been determined. In this study, we present the first evidence demonstrating that EBV latently infects a unique subset of blood-borne mononuclear cells that are direct precursors to Langerhans cells and that EBV both latently and productively infects oral epithelium-resident cells that are likely Langerhans cells. These data …

Dynamics Of A Minimal Model Of Interlocked Positive And Negative Feedback Loops Of Transcriptional Regulation By Camp-Response Element Binding Proteins, Hao Song, Paul Smolen, Evyatar Av-Ron, Douglas A Baxter, John H Byrne

Journal Articles

cAMP-response element binding (CREB) proteins are involved in transcriptional regulation in a number of cellular processes (e.g., neural plasticity and circadian rhythms). The CREB family contains activators and repressors that may interact through positive and negative feedback loops. These loops can be generated by auto- and cross-regulation of expression of CREB proteins, via CRE elements in or near their genes. Experiments suggest that such feedback loops may operate in several systems (e.g., Aplysia and rat). To understand the functional implications of such feedback loops, which are interlocked via cross-regulation of transcription, a minimal model with a positive and negative loop …

Expression Of The Neural Stem Cell Markers Ng2 And L1 In Human Angiomyolipoma: Are Angiomyolipomas Neoplasms Of Stem Cells?, So Dug Lim, William Stallcup, Benjamin Lefkove, Baskaran Govindarajan, Kit Sing Au, Hope Northrup, Deborah Lang, David E Fisher, Avani Patel, Mahul B Amin, Jack L Arbiser

Journal Articles

Angiomyolipomas are benign tumors of the kidney which express phenotypes of smooth muscle, fat, and melanocytes. These tumors appear with increased frequency in the autosomal dominant disorder tuberous sclerosis and are the leading cause of morbidity in adults with tuberous sclerosis. While benign, these tumors are capable of provoking life threatening hemorrhage and replacement of the kidney parenchyma, resulting in renal failure. The histogenesis of these tumors is currently unclear, although currently, we believe these tumors arise from "perivascular epithelioid cells" of which no normal counterpart has been convincingly demonstrated. Recently, stem cell precursors have been recognized that can give …

Bifurcation And Singularity Analysis Of A Molecular Network For The Induction Of Long-Term Memory, Hao Song, Paul Smolen, Evyatar Av-Ron, Douglas A. Baxter, John H H. Byrne

Journal Articles

Withdrawal reflexes of the mollusk Aplysia exhibit sensitization, a simple form of long-term memory (LTM). Sensitization is due, in part, to long-term facilitation (LTF) of sensorimotor neuron synapses. LTF is induced by the modulatory actions of serotonin (5-HT). Pettigrew et al. developed a computational model of the nonlinear intracellular signaling and gene network that underlies the induction of 5-HT-induced LTF. The model simulated empirical observations that repeated applications of 5-HT induce persistent activation of protein kinase A (PKA) and that this persistent activation requires a suprathreshold exposure of 5-HT. This study extends the analysis of the Pettigrew model by applying …

Cart: An Hrs/Actinin-4/Berp/Myosin V Protein Complex Required For Efficient Receptor Recycling, Qing Yan, Wei Sun, Pekka Kujala, Yasmin Lotfi, Thomas A Vida, Andrew J Bean

Journal Articles

Altering the number of surface receptors can rapidly modulate cellular responses to extracellular signals. Some receptors, like the transferrin receptor (TfR), are constitutively internalized and recycled to the plasma membrane. Other receptors, like the epidermal growth factor receptor (EGFR), are internalized after ligand binding and then ultimately degraded in the lysosome. Routing internalized receptors to different destinations suggests that distinct molecular mechanisms may direct their movement. Here, we report that the endosome-associated protein hrs is a subunit of a protein complex containing actinin-4, BERP, and myosin V that is necessary for efficient TfR recycling but not for EGFR degradation. The …

Simulation Of Drosophila Circadian Oscillations, Mutations, And Light Responses By A Model With Vri, Pdp-1, And Clk, Paul Smolen, Paul E. Hardin, Brian S. Lo, Douglas A. Baxter, John H. Byrne

Journal Articles

A model of Drosophila circadian rhythm generation was developed to represent feedback loops based on transcriptional regulation of per, Clk (dclock), Pdp-1, and vri (vrille). The model postulates that histone acetylation kinetics make transcriptional activation a nonlinear function of [CLK]. Such a nonlinearity is essential to simulate robust circadian oscillations of transcription in our model and in previous models. Simulations suggest that two positive feedback loops involving Clk are not essential for oscillations, because oscillations of [PER] were preserved when Clk, vri, or Pdp-1 expression was fixed. However, eliminating positive feedback by fixing vri expression altered the oscillation period. Eliminating …

A Reduced Model Clarifies The Role Of Feedback Loops And Time Delays In The Drosophila Circadian Oscillator, Paul Smolen, Douglas A. Baxter, John H. Byrne

Journal Articles

Although several detailed models of molecular processes essential for circadian oscillations have been developed, their complexity makes intuitive understanding of the oscillation mechanism difficult. The goal of the present study was to reduce a previously developed, detailed model to a minimal representation of the transcriptional regulation essential for circadian rhythmicity in Drosophila. The reduced model contains only two differential equations, each with time delays. A negative feedback loop is included, in which PER protein represses per transcription by binding the dCLOCK transcription factor. A positive feedback loop is also included, in which dCLOCK indirectly enhances its own formation. The model …

Influence Of Temperature Of Incubation And Type Of Growth Medium On Pigmentation In Serratia Marcescens., Robert P. Williams, Cora L. Gott, S M. Qadri, Randolph H. Scott

Journal Articles

Maximal amounts of prodigiosin were synthesized in either minimal or complete medium after incubation of cultures at 27 C for 7 days. Biosynthesis of prodigiosin began earlier and the range of temperature for formation was greater in complete medium. No prodigiosin was formed in either medium when cultures were incubated at 38 C; however, after a shift to 27 C, pigmentation ensued, provided the period of incubation at 38 C was not longer than 36 hr for minimal medium or 48 hr for complete medium. Washed, nonpigmented cells grown in either medium at 38 C for 72 hr could synthesize …