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In JoVE (1)
Other Publications (10)
- The Journal of Biological Chemistry
- Journal of Dental Education
- The Journal of Cell Biology
- Current Biology : CB
- Methods in Molecular Biology (Clifton, N.J.)
- British Journal of Psychology (London, England : 1953)
- Nature Cell Biology
- Neurologic Clinics
- Alcohol and Alcoholism (Oxford, Oxfordshire)
- Physical Medicine and Rehabilitation Clinics of North America
Articles by Stephanie Walker in JoVE
JoVE General
A Quantitative Assay for Insulin-expressing Colony-forming Progenitors
1Department of Biotechnology & Bioinformatics, California State University Channel Islands, 2Department of Diabetes, Endocrinology and Metabolism, Beckman Research Institute of City of Hope, 3The Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope
A three-dimensional clonogenic assay that allows pancreatic-like progenitors to differentiate into insulin-expressing colonies is described. This method takes advantage of semi-solid media containing methylcellulose, Matrigel and growth factors, in which single progenitors proliferate and differentiate in vitro, permitting quantification of the number of functional progenitors in a population.
Other articles by Stephanie Walker on PubMed
Specificity of Rho Insert-mediated Activation of Phospholipase D1
Members of the Rho subfamily of GTP-binding proteins regulate phospholipase D1 (PLD1) activity and signaling. In previous work, we demonstrated that binding of the Rho family member Cdc42 to PLD1 and the subsequent stimulation of its enzymatic activity are distinct events. Deletion of the insert helix from Cdc42 does not interfere with its switch I-mediated, GTP-dependent binding to PLD1 but inhibits Cdc42-stimulated PLD1 activity. To understand the mechanism of the insert-mediated activation of PLD1 by Cdc42 and to develop reagents to study Cdc42-activated PLD1 in cellular signaling events, we have undertaken a mutational analysis of the Rho insert region of Cdc42 and examined the specificity of the insert helix requirement in the other Rho family members, RhoA and Rac1. Here, we identify a critical residue, serine 124, in the Cdc42 insert helix central to its activation mechanism. Further, we examine this activation mechanism with respect to other members of the Rho family and demonstrate that each Rho protein activates PLD by distinct mechanisms, potentially allowing for unique signaling outcomes in the cell.
Interdisciplinary, Web-based, Self-study, Interactive Programs in the Dental Undergraduate Program: a Pilot
The goal of this project was to encourage interdisciplinary, integrative health teaching and research in dental education through the development of web-accessible programs, collectively called the "StudyWeb." The specific objective of the project was the construction and integration of a series of prototypes of self-study modules. Four pilot modules were developed using existing teaching materials in histology, pharmacology, prosthodontics, and oral radiology and utilizing a variety of widely available software programs, including FrontPage and Photoshop. Low-end technological choices were made in order to facilitate compatibility with a wide range of hardware, software, and types of Internet access. Modules were tested for functionality, usability, and ease of navigation. The scope of the initial project was limited to development and functionality testing of the original modules. The next phase of this project will involve testing of the effectiveness of these web-based self-instruction tools.
Akt Activation Disrupts Mammary Acinar Architecture and Enhances Proliferation in an MTOR-dependent Manner
Activation of the serine/threonine kinase Akt/PKB positively impacts on three cellular processes relevant to tumor progression: proliferation, survival, and cell size/growth. Using a three-dimensional culture model of MCF-10A mammary cells, we have examined how Akt influences the morphogenesis of polarized epithelial structures. Activation of a conditionally active variant of Akt elicits large, misshapen structures, which primarily arise from the combined effects of Akt on proliferation and cell size. Importantly, Akt activation amplifies proliferation during the early stages of morphogenesis, but cannot overcome signals suppressing proliferation in late-stage cultures. Akt also cooperates with oncoproteins such as cyclin D1 or HPV E7 to promote proliferation and morphogenesis in the absence of growth factors. Pharmacological inhibition of the Akt effector, mammalian target of rapamycin (mTOR), with rapamycin prevents the morphological disruption elicited by Akt activation, including its effect on cell size and number, and the cooperative effect of Akt on oncogene-driven proliferation, indicating that mTOR function is required for the multiple biological effects of Akt activation during morphogenesis.
PLD1 Regulates MTOR Signaling and Mediates Cdc42 Activation of S6K1
The mammalian target of rapamycin (mTOR) regulates cell growth and proliferation via the downstream targets ribosomal S6 kinase 1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1). We have identified phosphatidic acid (PA) as a mediator of mitogenic activation of mTOR signaling. In this study, we set out to test the hypotheses that phospholipase D 1 (PLD1) is an upstream regulator of mTOR and that the previously reported S6K1 activation by Cdc42 is mediated by PLD1.
Measurement of G Protein-coupled Receptor-stimulated Phospholipase D Activity in Intact Cells
Mammalian phospholipase D (PLD) activity hydrolyzes phosphatidylcholine (PC) into phosphatidic acid (PA) and free choline. This activity can be stimulated by a wide variety of extracellular agonists, including those for G protein-coupled receptors (GPCRs). This chapter outlines a protocol for the measurement of PLD activity in intact cells following stimulation by an extracellular agonist. The protocol takes advantage of a unique property of mammalian PLDs--the ability to substitute a primary alcohol for water in the hydrolytic reaction. This transphosphatidylation reaction results in the formation of a phosphatidylalcohol, which is a specific and unique marker for PLD activity. This protocol is highly sensitive for the detection of PLD activity following the stimulation of intact cells, being a valuable method for studying the regulation of PLD activity in vivo.
Face Processing and Familiarity: Evidence from Eye-movement Data
How is information extracted from familiar and unfamiliar faces? Three experiments, in which eye-movement measures were used, examined whether there was differential sampling of the internal face region according to familiarity. Experiment 1 used a face familiarity task and found that whilst the majority of fixations fell within the internal region, there were no differences in the sampling of this region according to familiarity. Experiment 2 replicated these findings, using a standard recognition memory paradigm. The third experiment employed a matching task, and once again found that the majority of fixations fell within the internal region. Additionally, this experiment found that there was more sampling of the internal region when faces were familiar compared with when they were unfamiliar. The use of eye fixation measures affirms the importance of internal facial features in the recognition of familiar faces compared with unfamiliar faces, but only when viewers compare pairs of faces.
Neurologic Injuries in Hockey
Ice hockey is a fast contact sport played on an ice surface enclosed by rigid boards. There is an intrinsic risk for injury in hockey, with many injuries potentially affecting the nervous system. This article provides an overview of neurologic injuries occurring in hockey as reported in the scientific literature. Among all injuries, a small but real risk for catastrophic cervical spinal cord injury and a high incidence of concussion emerge as the two most important neurologic issues.
Cues That Signal the Alcohol Content of a Beverage and Their Effectiveness at Altering Drinking Rates in Young Social Drinkers
The aim of this study was to assess the impact of cues that signal the alcoholic strength of a beverage on drinking rate in young social drinkers.
Neurologic Injuries in Hockey
Ice hockey is a fast contact sport played on an ice surface enclosed by rigid boards. There is an intrinsic risk for injury in hockey, with many injuries potentially affecting the nervous system. This article provides an overview of neurologic injuries occurring in hockey as reported in the scientific literature. Among all injuries, a small but real risk for catastrophic cervical spinal cord injury and a high incidence of concussion emerge as the two most important neurologic issues.
