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Pubmed Article
Relationship between human evolution and neurally mediated syncope disclosed by the polymorphic sites of the adrenergic receptor gene ?2B-AR.
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PLoS ONE
PUBLISHED: 04-11-2015
The objective of this study was to clarify the effects of disease on neurally mediated syncope (NMS) during an acute stress reaction. We analyzed the mechanism of the molecular interaction and the polymorphisms of the alpha-2 adrenoreceptor (?2B-AR) gene as the potential psychiatric cause of incentive stress. We focused on the following three genotypes of the repeat polymorphism site at Glu 301-303 in the ?2B-AR gene: Glu12/12, Glu12/9, and Glu9/9. On the basis of our clinical research, NMS is likely to occur in people with the Glu12/9 heterotype. To verify this, we assessed this relationship with the interaction of Gi protein and adenylate cyclase by in silico analysis of the Glu12/9 heterotype. By measuring the difference in the dissociation time of the Gi-? subunit twice, we found that the Glu12/9 heterotype suppressed the action of adenylate cyclase longer than the Glu homotypes. As this difference in the Glu repeat number effect is thought to be one of the causes of NMS, we investigated the evolutionary significance of the Glu repeat number. Glu8 was originally repeated in simians, while the Glu12 repeats occurred over time during the evolution of bipedalism in humans. Taken with the Glu12 numbers, NMS would likely become a defensive measure to prevent significant blood flow to the human brain.
Authors: Cristi King, Tiffany Scott-Horton.
Published: 01-08-2008
ABSTRACT
Pharmacogenetic research benefits first-hand from the abundance of information provided by the completion of the Human Genome Project. With such a tremendous amount of data available comes an explosion of genotyping methods. Pyrosequencing(R) is one of the most thorough yet simple methods to date used to analyze polymorphisms. It also has the ability to identify tri-allelic, indels, short-repeat polymorphisms, along with determining allele percentages for methylation or pooled sample assessment. In addition, there is a standardized control sequence that provides internal quality control. This method has led to rapid and efficient single-nucleotide polymorphism evaluation including many clinically relevant polymorphisms. The technique and methodology of Pyrosequencing is explained.
24 Related JoVE Articles!
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Utility of Dissociated Intrinsic Hand Muscle Atrophy in the Diagnosis of Amyotrophic Lateral Sclerosis
Authors: Parvathi Menon, Steve Vucic.
Institutions: Westmead Hospital, University of Sydney, Australia.
The split hand phenomenon refers to predominant wasting of thenar muscles and is an early and specific feature of amyotrophic lateral sclerosis (ALS). A novel split hand index (SI) was developed to quantify the split hand phenomenon, and its diagnostic utility was assessed in ALS patients. The split hand index was derived by dividing the product of the compound muscle action potential (CMAP) amplitude recorded over the abductor pollicis brevis and first dorsal interosseous muscles by the CMAP amplitude recorded over the abductor digiti minimi muscle. In order to assess the diagnostic utility of the split hand index, ALS patients were prospectively assessed and their results were compared to neuromuscular disorder patients. The split hand index was significantly reduced in ALS when compared to neuromuscular disorder patients (P<0.0001). Limb-onset ALS patients exhibited the greatest reduction in the split hand index, and a value of 5.2 or less reliably differentiated ALS from other neuromuscular disorders. Consequently, the split hand index appears to be a novel diagnostic biomarker for ALS, perhaps facilitating an earlier diagnosis.
Medicine, Issue 85, Amyotrophic Lateral Sclerosis (ALS), dissociated muscle atrophy, hypothenar muscles, motor neuron disease, split-hand index, thenar muscles
51056
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Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications
Authors: Jason M. Conley, Tarsis F. Brust, Ruqiang Xu, Kevin D. Burris, Val J. Watts.
Institutions: Purdue University, Eli Lilly and Company.
Sensitization of adenylyl cyclase (AC) signaling has been implicated in a variety of neuropsychiatric and neurologic disorders including substance abuse and Parkinson's disease. Acute activation of Gαi/o-linked receptors inhibits AC activity, whereas persistent activation of these receptors results in heterologous sensitization of AC and increased levels of intracellular cAMP. Previous studies have demonstrated that this enhancement of AC responsiveness is observed both in vitro and in vivo following the chronic activation of several types of Gαi/o-linked receptors including D2 dopamine and μ opioid receptors. Although heterologous sensitization of AC was first reported four decades ago, the mechanism(s) that underlie this phenomenon remain largely unknown. The lack of mechanistic data presumably reflects the complexity involved with this adaptive response, suggesting that nonbiased approaches could aid in identifying the molecular pathways involved in heterologous sensitization of AC. Previous studies have implicated kinase and Gbγ signaling as overlapping components that regulate the heterologous sensitization of AC. To identify unique and additional overlapping targets associated with sensitization of AC, the development and validation of a scalable cAMP sensitization assay is required for greater throughput. Previous approaches to study sensitization are generally cumbersome involving continuous cell culture maintenance as well as a complex methodology for measuring cAMP accumulation that involves multiple wash steps. Thus, the development of a robust cell-based assay that can be used for high throughput screening (HTS) in a 384 well format would facilitate future studies. Using two D2 dopamine receptor cellular models (i.e. CHO-D2L and HEK-AC6/D2L), we have converted our 48-well sensitization assay (>20 steps 4-5 days) to a five-step, single day assay in 384-well format. This new format is amenable to small molecule screening, and we demonstrate that this assay design can also be readily used for reverse transfection of siRNA in anticipation of targeted siRNA library screening.
Bioengineering, Issue 83, adenylyl cyclase, cAMP, heterologous sensitization, superactivation, D2 dopamine, μ opioid, siRNA
51218
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Inducing Plasticity of Astrocytic Receptors by Manipulation of Neuronal Firing Rates
Authors: Alison X. Xie, Kelli Lauderdale, Thomas Murphy, Timothy L. Myers, Todd A. Fiacco.
Institutions: University of California Riverside, University of California Riverside, University of California Riverside.
Close to two decades of research has established that astrocytes in situ and in vivo express numerous G protein-coupled receptors (GPCRs) that can be stimulated by neuronally-released transmitter. However, the ability of astrocytic receptors to exhibit plasticity in response to changes in neuronal activity has received little attention. Here we describe a model system that can be used to globally scale up or down astrocytic group I metabotropic glutamate receptors (mGluRs) in acute brain slices. Included are methods on how to prepare parasagittal hippocampal slices, construct chambers suitable for long-term slice incubation, bidirectionally manipulate neuronal action potential frequency, load astrocytes and astrocyte processes with fluorescent Ca2+ indicator, and measure changes in astrocytic Gq GPCR activity by recording spontaneous and evoked astrocyte Ca2+ events using confocal microscopy. In essence, a “calcium roadmap” is provided for how to measure plasticity of astrocytic Gq GPCRs. Applications of the technique for study of astrocytes are discussed. Having an understanding of how astrocytic receptor signaling is affected by changes in neuronal activity has important implications for both normal synaptic function as well as processes underlying neurological disorders and neurodegenerative disease.
Neuroscience, Issue 85, astrocyte, plasticity, mGluRs, neuronal Firing, electrophysiology, Gq GPCRs, Bolus-loading, calcium, microdomains, acute slices, Hippocampus, mouse
51458
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A Restriction Enzyme Based Cloning Method to Assess the In vitro Replication Capacity of HIV-1 Subtype C Gag-MJ4 Chimeric Viruses
Authors: Daniel T. Claiborne, Jessica L. Prince, Eric Hunter.
Institutions: Emory University, Emory University.
The protective effect of many HLA class I alleles on HIV-1 pathogenesis and disease progression is, in part, attributed to their ability to target conserved portions of the HIV-1 genome that escape with difficulty. Sequence changes attributed to cellular immune pressure arise across the genome during infection, and if found within conserved regions of the genome such as Gag, can affect the ability of the virus to replicate in vitro. Transmission of HLA-linked polymorphisms in Gag to HLA-mismatched recipients has been associated with reduced set point viral loads. We hypothesized this may be due to a reduced replication capacity of the virus. Here we present a novel method for assessing the in vitro replication of HIV-1 as influenced by the gag gene isolated from acute time points from subtype C infected Zambians. This method uses restriction enzyme based cloning to insert the gag gene into a common subtype C HIV-1 proviral backbone, MJ4. This makes it more appropriate to the study of subtype C sequences than previous recombination based methods that have assessed the in vitro replication of chronically derived gag-pro sequences. Nevertheless, the protocol could be readily modified for studies of viruses from other subtypes. Moreover, this protocol details a robust and reproducible method for assessing the replication capacity of the Gag-MJ4 chimeric viruses on a CEM-based T cell line. This method was utilized for the study of Gag-MJ4 chimeric viruses derived from 149 subtype C acutely infected Zambians, and has allowed for the identification of residues in Gag that affect replication. More importantly, the implementation of this technique has facilitated a deeper understanding of how viral replication defines parameters of early HIV-1 pathogenesis such as set point viral load and longitudinal CD4+ T cell decline.
Infectious Diseases, Issue 90, HIV-1, Gag, viral replication, replication capacity, viral fitness, MJ4, CEM, GXR25
51506
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The Use of Magnetic Resonance Spectroscopy as a Tool for the Measurement of Bi-hemispheric Transcranial Electric Stimulation Effects on Primary Motor Cortex Metabolism
Authors: Sara Tremblay, Vincent Beaulé, Sébastien Proulx, Louis-Philippe Lafleur, Julien Doyon, Małgorzata Marjańska, Hugo Théoret.
Institutions: University of Montréal, McGill University, University of Minnesota.
Transcranial direct current stimulation (tDCS) is a neuromodulation technique that has been increasingly used over the past decade in the treatment of neurological and psychiatric disorders such as stroke and depression. Yet, the mechanisms underlying its ability to modulate brain excitability to improve clinical symptoms remains poorly understood 33. To help improve this understanding, proton magnetic resonance spectroscopy (1H-MRS) can be used as it allows the in vivo quantification of brain metabolites such as γ-aminobutyric acid (GABA) and glutamate in a region-specific manner 41. In fact, a recent study demonstrated that 1H-MRS is indeed a powerful means to better understand the effects of tDCS on neurotransmitter concentration 34. This article aims to describe the complete protocol for combining tDCS (NeuroConn MR compatible stimulator) with 1H-MRS at 3 T using a MEGA-PRESS sequence. We will describe the impact of a protocol that has shown great promise for the treatment of motor dysfunctions after stroke, which consists of bilateral stimulation of primary motor cortices 27,30,31. Methodological factors to consider and possible modifications to the protocol are also discussed.
Neuroscience, Issue 93, proton magnetic resonance spectroscopy, transcranial direct current stimulation, primary motor cortex, GABA, glutamate, stroke
51631
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High-throughput Analysis of Mammalian Olfactory Receptors: Measurement of Receptor Activation via Luciferase Activity
Authors: Casey Trimmer, Lindsey L. Snyder, Joel D. Mainland.
Institutions: Monell Chemical Senses Center.
Odorants create unique and overlapping patterns of olfactory receptor activation, allowing a family of approximately 1,000 murine and 400 human receptors to recognize thousands of odorants. Odorant ligands have been published for fewer than 6% of human receptors1-11. This lack of data is due in part to difficulties functionally expressing these receptors in heterologous systems. Here, we describe a method for expressing the majority of the olfactory receptor family in Hana3A cells, followed by high-throughput assessment of olfactory receptor activation using a luciferase reporter assay. This assay can be used to (1) screen panels of odorants against panels of olfactory receptors; (2) confirm odorant/receptor interaction via dose response curves; and (3) compare receptor activation levels among receptor variants. In our sample data, 328 olfactory receptors were screened against 26 odorants. Odorant/receptor pairs with varying response scores were selected and tested in dose response. These data indicate that a screen is an effective method to enrich for odorant/receptor pairs that will pass a dose response experiment, i.e. receptors that have a bona fide response to an odorant. Therefore, this high-throughput luciferase assay is an effective method to characterize olfactory receptors—an essential step toward a model of odor coding in the mammalian olfactory system.
Neuroscience, Issue 88, Firefly luciferase, Renilla Luciferase, Dual-Glo Luciferase Assay, olfaction, Olfactory receptor, Odorant, GPCR, High-throughput
51640
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Bladder Smooth Muscle Strip Contractility as a Method to Evaluate Lower Urinary Tract Pharmacology
Authors: F. Aura Kullmann, Stephanie L. Daugherty, William C. de Groat, Lori A. Birder.
Institutions: University of Pittsburgh School of Medicine, University of Pittsburgh School of Medicine.
We describe an in vitro method to measure bladder smooth muscle contractility, and its use for investigating physiological and pharmacological properties of the smooth muscle as well as changes induced by pathology. This method provides critical information for understanding bladder function while overcoming major methodological difficulties encountered in in vivo experiments, such as surgical and pharmacological manipulations that affect stability and survival of the preparations, the use of human tissue, and/or the use of expensive chemicals. It also provides a way to investigate the properties of each bladder component (i.e. smooth muscle, mucosa, nerves) in healthy and pathological conditions. The urinary bladder is removed from an anesthetized animal, placed in Krebs solution and cut into strips. Strips are placed into a chamber filled with warm Krebs solution. One end is attached to an isometric tension transducer to measure contraction force, the other end is attached to a fixed rod. Tissue is stimulated by directly adding compounds to the bath or by electric field stimulation electrodes that activate nerves, similar to triggering bladder contractions in vivo. We demonstrate the use of this method to evaluate spontaneous smooth muscle contractility during development and after an experimental spinal cord injury, the nature of neurotransmission (transmitters and receptors involved), factors involved in modulation of smooth muscle activity, the role of individual bladder components, and species and organ differences in response to pharmacological agents. Additionally, it could be used for investigating intracellular pathways involved in contraction and/or relaxation of the smooth muscle, drug structure-activity relationships and evaluation of transmitter release. The in vitro smooth muscle contractility method has been used extensively for over 50 years, and has provided data that significantly contributed to our understanding of bladder function as well as to pharmaceutical development of compounds currently used clinically for bladder management.
Medicine, Issue 90, Krebs, species differences, in vitro, smooth muscle contractility, neural stimulation
51807
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Inhibitory Synapse Formation in a Co-culture Model Incorporating GABAergic Medium Spiny Neurons and HEK293 Cells Stably Expressing GABAA Receptors
Authors: Laura E. Brown, Celine Fuchs, Martin W. Nicholson, F. Anne Stephenson, Alex M. Thomson, Jasmina N. Jovanovic.
Institutions: University College London.
Inhibitory neurons act in the central nervous system to regulate the dynamics and spatio-temporal co-ordination of neuronal networks. GABA (γ-aminobutyric acid) is the predominant inhibitory neurotransmitter in the brain. It is released from the presynaptic terminals of inhibitory neurons within highly specialized intercellular junctions known as synapses, where it binds to GABAA receptors (GABAARs) present at the plasma membrane of the synapse-receiving, postsynaptic neurons. Activation of these GABA-gated ion channels leads to influx of chloride resulting in postsynaptic potential changes that decrease the probability that these neurons will generate action potentials. During development, diverse types of inhibitory neurons with distinct morphological, electrophysiological and neurochemical characteristics have the ability to recognize their target neurons and form synapses which incorporate specific GABAARs subtypes. This principle of selective innervation of neuronal targets raises the question as to how the appropriate synaptic partners identify each other. To elucidate the underlying molecular mechanisms, a novel in vitro co-culture model system was established, in which medium spiny GABAergic neurons, a highly homogenous population of neurons isolated from the embryonic striatum, were cultured with stably transfected HEK293 cell lines that express different GABAAR subtypes. Synapses form rapidly, efficiently and selectively in this system, and are easily accessible for quantification. Our results indicate that various GABAAR subtypes differ in their ability to promote synapse formation, suggesting that this reduced in vitro model system can be used to reproduce, at least in part, the in vivo conditions required for the recognition of the appropriate synaptic partners and formation of specific synapses. Here the protocols for culturing the medium spiny neurons and generating HEK293 cells lines expressing GABAARs are first described, followed by detailed instructions on how to combine these two cell types in co-culture and analyze the formation of synaptic contacts.
Neuroscience, Issue 93, Developmental neuroscience, synaptogenesis, synaptic inhibition, co-culture, stable cell lines, GABAergic, medium spiny neurons, HEK 293 cell line
52115
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Measurement of Smooth Muscle Function in the Isolated Tissue Bath-applications to Pharmacology Research
Authors: Brian Jespersen, Nathan R. Tykocki, Stephanie W. Watts, Peter J. Cobbett.
Institutions: Michigan State University, University of Vermont College of Medicine.
Isolated tissue bath assays are a classical pharmacological tool for evaluating concentration-response relationships in a myriad of contractile tissues. While this technique has been implemented for over 100 years, the versatility, simplicity and reproducibility of this assay helps it to remain an indispensable tool for pharmacologists and physiologists alike. Tissue bath systems are available in a wide array of shapes and sizes, allowing a scientist to evaluate samples as small as murine mesenteric arteries and as large as porcine ileum – if not larger. Central to the isolated tissue bath assay is the ability to measure concentration-dependent changes to isometric contraction, and how the efficacy and potency of contractile agonists can be manipulated by increasing concentrations of antagonists or inhibitors. Even though the general principles remain relatively similar, recent technological advances allow even more versatility to the tissue bath assay by incorporating computer-based data recording and analysis software. This video will demonstrate the function of the isolated tissue bath to measure the isometric contraction of an isolated smooth muscle (in this case rat thoracic aorta rings), and share the types of knowledge that can be created with this technique. Included are detailed descriptions of aortic tissue dissection and preparation, placement of aortic rings in the tissue bath and proper tissue equilibration prior to experimentation, tests of tissue viability, experimental design and implementation, and data quantitation. Aorta will be connected to isometric force transducers, the data from which will be captured using a commercially available analog-to-digital converter and bridge amplifier specifically designed for use in these experiments. The accompanying software to this system will be used to visualize the experiment and analyze captured data.
Biochemistry, Issue 95, smooth muscle function, receptor pharmacology, signal transduction, tissue bath, rat, aorta, aortic rings, isometric contraction, concentration response curve
52324
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Functional Reconstitution and Channel Activity Measurements of Purified Wildtype and Mutant CFTR Protein
Authors: Paul D. W. Eckford, Canhui Li, Christine E. Bear.
Institutions: Hospital for Sick Children, University of Toronto, University of Toronto.
The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a unique channel-forming member of the ATP Binding Cassette (ABC) superfamily of transporters. The phosphorylation and nucleotide dependent chloride channel activity of CFTR has been frequently studied in whole cell systems and as single channels in excised membrane patches. Many Cystic Fibrosis-causing mutations have been shown to alter this activity. While a small number of purification protocols have been published, a fast reconstitution method that retains channel activity and a suitable method for studying population channel activity in a purified system have been lacking. Here rapid methods are described for purification and functional reconstitution of the full-length CFTR protein into proteoliposomes of defined lipid composition that retains activity as a regulated halide channel. This reconstitution method together with a novel flux-based assay of channel activity is a suitable system for studying the population channel properties of wild type CFTR and the disease-causing mutants F508del- and G551D-CFTR. Specifically, the method has utility in studying the direct effects of phosphorylation, nucleotides and small molecules such as potentiators and inhibitors on CFTR channel activity. The methods are also amenable to the study of other membrane channels/transporters for anionic substrates.
Biochemistry, Issue 97, Cystic Fibrosis, CFTR, purification, reconstitution, chloride channel, channel function, iodide efflux, potentiation
52427
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A Microplate Assay to Assess Chemical Effects on RBL-2H3 Mast Cell Degranulation: Effects of Triclosan without Use of an Organic Solvent
Authors: Lisa M. Weatherly, Rachel H. Kennedy, Juyoung Shim, Julie A. Gosse.
Institutions: University of Maine, Orono, University of Maine, Orono.
Mast cells play important roles in allergic disease and immune defense against parasites. Once activated (e.g. by an allergen), they degranulate, a process that results in the exocytosis of allergic mediators. Modulation of mast cell degranulation by drugs and toxicants may have positive or adverse effects on human health. Mast cell function has been dissected in detail with the use of rat basophilic leukemia mast cells (RBL-2H3), a widely accepted model of human mucosal mast cells3-5. Mast cell granule component and the allergic mediator β-hexosaminidase, which is released linearly in tandem with histamine from mast cells6, can easily and reliably be measured through reaction with a fluorogenic substrate, yielding measurable fluorescence intensity in a microplate assay that is amenable to high-throughput studies1. Originally published by Naal et al.1, we have adapted this degranulation assay for the screening of drugs and toxicants and demonstrate its use here. Triclosan is a broad-spectrum antibacterial agent that is present in many consumer products and has been found to be a therapeutic aid in human allergic skin disease7-11, although the mechanism for this effect is unknown. Here we demonstrate an assay for the effect of triclosan on mast cell degranulation. We recently showed that triclosan strongly affects mast cell function2. In an effort to avoid use of an organic solvent, triclosan is dissolved directly into aqueous buffer with heat and stirring, and resultant concentration is confirmed using UV-Vis spectrophotometry (using ε280 = 4,200 L/M/cm)12. This protocol has the potential to be used with a variety of chemicals to determine their effects on mast cell degranulation, and more broadly, their allergic potential.
Immunology, Issue 81, mast cell, basophil, degranulation, RBL-2H3, triclosan, irgasan, antibacterial, β-hexosaminidase, allergy, Asthma, toxicants, ionophore, antigen, fluorescence, microplate, UV-Vis
50671
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Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers
Authors: Rasa Ghaffarian, Silvia Muro.
Institutions: University of Maryland, University of Maryland.
Sub-micrometer carriers (nanocarriers; NCs) enhance efficacy of drugs by improving solubility, stability, circulation time, targeting, and release. Additionally, traversing cellular barriers in the body is crucial for both oral delivery of therapeutic NCs into the circulation and transport from the blood into tissues, where intervention is needed. NC transport across cellular barriers is achieved by: (i) the paracellular route, via transient disruption of the junctions that interlock adjacent cells, or (ii) the transcellular route, where materials are internalized by endocytosis, transported across the cell body, and secreted at the opposite cell surface (transyctosis). Delivery across cellular barriers can be facilitated by coupling therapeutics or their carriers with targeting agents that bind specifically to cell-surface markers involved in transport. Here, we provide methods to measure the extent and mechanism of NC transport across a model cell barrier, which consists of a monolayer of gastrointestinal (GI) epithelial cells grown on a porous membrane located in a transwell insert. Formation of a permeability barrier is confirmed by measuring transepithelial electrical resistance (TEER), transepithelial transport of a control substance, and immunostaining of tight junctions. As an example, ~200 nm polymer NCs are used, which carry a therapeutic cargo and are coated with an antibody that targets a cell-surface determinant. The antibody or therapeutic cargo is labeled with 125I for radioisotope tracing and labeled NCs are added to the upper chamber over the cell monolayer for varying periods of time. NCs associated to the cells and/or transported to the underlying chamber can be detected. Measurement of free 125I allows subtraction of the degraded fraction. The paracellular route is assessed by determining potential changes caused by NC transport to the barrier parameters described above. Transcellular transport is determined by addressing the effect of modulating endocytosis and transcytosis pathways.
Bioengineering, Issue 80, Antigens, Enzymes, Biological Therapy, bioengineering (general), Pharmaceutical Preparations, Macromolecular Substances, Therapeutics, Digestive System and Oral Physiological Phenomena, Biological Phenomena, Cell Physiological Phenomena, drug delivery systems, targeted nanocarriers, transcellular transport, epithelial cells, tight junctions, transepithelial electrical resistance, endocytosis, transcytosis, radioisotope tracing, immunostaining
50638
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Genetically-encoded Molecular Probes to Study G Protein-coupled Receptors
Authors: Saranga Naganathan, Amy Grunbeck, He Tian, Thomas Huber, Thomas P. Sakmar.
Institutions: The Rockefeller University.
To facilitate structural and dynamic studies of G protein-coupled receptor (GPCR) signaling complexes, new approaches are required to introduce informative probes or labels into expressed receptors that do not perturb receptor function. We used amber codon suppression technology to genetically-encode the unnatural amino acid, p-azido-L-phenylalanine (azF) at various targeted positions in GPCRs heterologously expressed in mammalian cells. The versatility of the azido group is illustrated here in different applications to study GPCRs in their native cellular environment or under detergent solubilized conditions. First, we demonstrate a cell-based targeted photocrosslinking technology to identify the residues in the ligand-binding pocket of GPCR where a tritium-labeled small-molecule ligand is crosslinked to a genetically-encoded azido amino acid. We then demonstrate site-specific modification of GPCRs by the bioorthogonal Staudinger-Bertozzi ligation reaction that targets the azido group using phosphine derivatives. We discuss a general strategy for targeted peptide-epitope tagging of expressed membrane proteins in-culture and its detection using a whole-cell-based ELISA approach. Finally, we show that azF-GPCRs can be selectively tagged with fluorescent probes. The methodologies discussed are general, in that they can in principle be applied to any amino acid position in any expressed GPCR to interrogate active signaling complexes.
Genetics, Issue 79, Receptors, G-Protein-Coupled, Protein Engineering, Signal Transduction, Biochemistry, Unnatural amino acid, site-directed mutagenesis, G protein-coupled receptor, targeted photocrosslinking, bioorthogonal labeling, targeted epitope tagging
50588
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Genetic Studies of Human DNA Repair Proteins Using Yeast as a Model System
Authors: Monika Aggarwal, Robert M. Brosh Jr..
Institutions: National Institute on Aging, NIH.
Understanding the roles of human DNA repair proteins in genetic pathways is a formidable challenge to many researchers. Genetic studies in mammalian systems have been limited due to the lack of readily available tools including defined mutant genetic cell lines, regulatory expression systems, and appropriate selectable markers. To circumvent these difficulties, model genetic systems in lower eukaryotes have become an attractive choice for the study of functionally conserved DNA repair proteins and pathways. We have developed a model yeast system to study the poorly defined genetic functions of the Werner syndrome helicase-nuclease (WRN) in nucleic acid metabolism. Cellular phenotypes associated with defined genetic mutant backgrounds can be investigated to clarify the cellular and molecular functions of WRN through its catalytic activities and protein interactions. The human WRN gene and associated variants, cloned into DNA plasmids for expression in yeast, can be placed under the control of a regulatory plasmid element. The expression construct can then be transformed into the appropriate yeast mutant background, and genetic function assayed by a variety of methodologies. Using this approach, we determined that WRN, like its related RecQ family members BLM and Sgs1, operates in a Top3-dependent pathway that is likely to be important for genomic stability. This is described in our recent publication [1] at www.impactaging.com. Detailed methods of specific assays for genetic complementation studies in yeast are provided in this paper.
Microbiology, Issue 37, Werner syndrome, helicase, topoisomerase, RecQ, Bloom's syndrome, Sgs1, genomic instability, genetics, DNA repair, yeast
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Quantitative Autonomic Testing
Authors: Peter Novak.
Institutions: University of Massachusetts Medical School.
Disorders associated with dysfunction of autonomic nervous system are quite common yet frequently unrecognized. Quantitative autonomic testing can be invaluable tool for evaluation of these disorders, both in clinic and research. There are number of autonomic tests, however, only few were validated clinically or are quantitative. Here, fully quantitative and clinically validated protocol for testing of autonomic functions is presented. As a bare minimum the clinical autonomic laboratory should have a tilt table, ECG monitor, continuous noninvasive blood pressure monitor, respiratory monitor and a mean for evaluation of sudomotor domain. The software for recording and evaluation of autonomic tests is critical for correct evaluation of data. The presented protocol evaluates 3 major autonomic domains: cardiovagal, adrenergic and sudomotor. The tests include deep breathing, Valsalva maneuver, head-up tilt, and quantitative sudomotor axon test (QSART). The severity and distribution of dysautonomia is quantitated using Composite Autonomic Severity Scores (CASS). Detailed protocol is provided highlighting essential aspects of testing with emphasis on proper data acquisition, obtaining the relevant parameters and unbiased evaluation of autonomic signals. The normative data and CASS algorithm for interpretation of results are provided as well.
Medicine, Issue 53, Deep breathing, Valsalva maneuver, tilt test, sudomotor testing, Composite Autonomic Severity Score, CASS
2502
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Detection and Genogrouping of Noroviruses from Children's Stools By Taqman One-step RT-PCR
Authors: Sonia Apaza, Susan Espetia, Robert H. Gilman, Sonia Montenegro, Susana Pineda, Fanny Herhold, Romeo Pomari, Margaret Kosek, Nancy Vu, Mayuko Saito.
Institutions: Universidad Peruana Cayetano Heredia, Johns Hopkins University, University of Concepcion,Chile, University of California San Diego School of Medicine.
Noroviruses (NoVs) are the leading cause of outbreaks of sporadic acute gastroenteritis worldwide in humans of all ages. They are important cause of hospitalizations in children with a public health impact similar to that of Rotavirus. NoVs are RNA viruses of great genetic diversity and there is a continuous appearance of new strains. Five genogroups are recognized; GI and GII with their many genotypes and subtypes being the most important for human infection. However, the diagnosis of these two genotypes remains problematic, delaying diagnosis and treatment. 1, 2, 3 For RNA extraction from stool specimens the most commonly used method is the QIAmp Viral RNA commercial kit from Qiagen. This method combines the binding properties of a silica gel membrane, buffers that control RNases and provide optimum binding of the RNA to the column together with the speed of microspin. This method is simple, fast and reliable and is carried out in a few steps that are detailed in the description provided by the manufacturer. Norovirus is second only to rotavirus as the most common cause of diarrhea. Norovirus diagnosis should be available in all studies on pathogenesis of diarrhea as well as in outbreaks or individual diarrhea cases. At present however norovirus diagnosis is restricted to only a few centers due to the lack of simple methods of diagnosis. This delays diagnosis and treatment 1, 2, 3. In addition, due to costs and regulated transportation of corrosive buffers within and between countries use of these manufactured kits poses logistical problems. As a result, in this protocol we describe an alternative, economic, in-house method which is based on the original Boom et al. method4 which uses the nucleic acid binding properties of silica particles together with the anti-nuclease properties of guanidinium thiocyanate. For the detection and genogrouping (GI and GII) of NoVs isolates from stool specimens, several RT-PCR protocols utilizing different targets have been developed. The consensus is that an RT-PCR using TaqMan chemistry would be the best molecular technique for diagnosis, because it combines high sensitivity, specificity and reproducibility with high throughput and ease of use. Here we describe an assay targeting the open reading frame 1 (ORF1)-ORF2 junction region; the most conserved region of the NoV genome and hence most suitable for diagnosis. For further genetic analysis a conventional RT-PCR that targets the highly variable N-terminal-shell from the major protein of the capsid (Region C) using primers originally described by Kojima et al. 5 is detailed. Sequencing of the PCR product from the conventional PCR enables the differentiation of genotypes belonging to the GI and GII genogroups.
Virology, Issue 65, Medicine, Genetics, norovirus, gastroenteritis, RNA extraction, diarrhea, stool samples, PCR, RT-PCR, TaqMan, silica
3232
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Production and Detection of Reactive Oxygen Species (ROS) in Cancers
Authors: Danli Wu, Patricia Yotnda.
Institutions: Baylor College of Medicine.
Reactive oxygen species include a number of molecules that damage DNA and RNA and oxidize proteins and lipids (lipid peroxydation). These reactive molecules contain an oxygen and include H2O2 (hydrogen peroxide), NO (nitric oxide), O2- (oxide anion), peroxynitrite (ONOO-), hydrochlorous acid (HOCl), and hydroxyl radical (OH-). Oxidative species are produced not only under pathological situations (cancers, ischemic/reperfusion, neurologic and cardiovascular pathologies, infectious diseases, inflammatory diseases 1, autoimmune diseases 2, etc…) but also during physiological (non-pathological) situations such as cellular metabolism 3, 4. Indeed, ROS play important roles in many cellular signaling pathways (proliferation, cell activation 5, 6, migration 7 etc..). ROS can be detrimental (it is then referred to as "oxidative and nitrosative stress") when produced in high amounts in the intracellular compartments and cells generally respond to ROS by upregulating antioxidants such as superoxide dismutase (SOD) and catalase (CAT), glutathione peroxidase (GPx) and glutathione (GSH) that protects them by converting dangerous free radicals to harmless molecules (i.e. water). Vitamins C and E have also been described as ROS scavengers (antioxidants). Free radicals are beneficial in low amounts 3. Macrophage and neutrophils-mediated immune responses involve the production and release of NO, which inhibits viruses, pathogens and tumor proliferation 8. NO also reacts with other ROS and thus, also has a role as a detoxifier (ROS scavenger). Finally NO acts on vessels to regulate blood flow which is important for the adaptation of muscle to prolonged exercise 9, 10. Several publications have also demonstrated that ROS are involved in insulin sensitivity 11, 12. Numerous methods to evaluate ROS production are available. In this article we propose several simple, fast, and affordable assays; these assays have been validated by many publications and are routinely used to detect ROS or its effects in mammalian cells. While some of these assays detect multiple ROS, others detect only a single ROS.
Medicine, Issue 57, reactive oxygen species (ROS), stress, ischemia, cancer, chemotherapy, immune response
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Mapping Bacterial Functional Networks and Pathways in Escherichia Coli using Synthetic Genetic Arrays
Authors: Alla Gagarinova, Mohan Babu, Jack Greenblatt, Andrew Emili.
Institutions: University of Toronto, University of Toronto, University of Regina.
Phenotypes are determined by a complex series of physical (e.g. protein-protein) and functional (e.g. gene-gene or genetic) interactions (GI)1. While physical interactions can indicate which bacterial proteins are associated as complexes, they do not necessarily reveal pathway-level functional relationships1. GI screens, in which the growth of double mutants bearing two deleted or inactivated genes is measured and compared to the corresponding single mutants, can illuminate epistatic dependencies between loci and hence provide a means to query and discover novel functional relationships2. Large-scale GI maps have been reported for eukaryotic organisms like yeast3-7, but GI information remains sparse for prokaryotes8, which hinders the functional annotation of bacterial genomes. To this end, we and others have developed high-throughput quantitative bacterial GI screening methods9, 10. Here, we present the key steps required to perform quantitative E. coli Synthetic Genetic Array (eSGA) screening procedure on a genome-scale9, using natural bacterial conjugation and homologous recombination to systemically generate and measure the fitness of large numbers of double mutants in a colony array format. Briefly, a robot is used to transfer, through conjugation, chloramphenicol (Cm) - marked mutant alleles from engineered Hfr (High frequency of recombination) 'donor strains' into an ordered array of kanamycin (Kan) - marked F- recipient strains. Typically, we use loss-of-function single mutants bearing non-essential gene deletions (e.g. the 'Keio' collection11) and essential gene hypomorphic mutations (i.e. alleles conferring reduced protein expression, stability, or activity9, 12, 13) to query the functional associations of non-essential and essential genes, respectively. After conjugation and ensuing genetic exchange mediated by homologous recombination, the resulting double mutants are selected on solid medium containing both antibiotics. After outgrowth, the plates are digitally imaged and colony sizes are quantitatively scored using an in-house automated image processing system14. GIs are revealed when the growth rate of a double mutant is either significantly better or worse than expected9. Aggravating (or negative) GIs often result between loss-of-function mutations in pairs of genes from compensatory pathways that impinge on the same essential process2. Here, the loss of a single gene is buffered, such that either single mutant is viable. However, the loss of both pathways is deleterious and results in synthetic lethality or sickness (i.e. slow growth). Conversely, alleviating (or positive) interactions can occur between genes in the same pathway or protein complex2 as the deletion of either gene alone is often sufficient to perturb the normal function of the pathway or complex such that additional perturbations do not reduce activity, and hence growth, further. Overall, systematically identifying and analyzing GI networks can provide unbiased, global maps of the functional relationships between large numbers of genes, from which pathway-level information missed by other approaches can be inferred9.
Genetics, Issue 69, Molecular Biology, Medicine, Biochemistry, Microbiology, Aggravating, alleviating, conjugation, double mutant, Escherichia coli, genetic interaction, Gram-negative bacteria, homologous recombination, network, synthetic lethality or sickness, suppression
4056
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Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Authors: Clare L. Protheroe, Henrike (Rianne) J.C. Ravensbergen, Jessica A. Inskip, Victoria E. Claydon.
Institutions: Simon Fraser University .
Orthostatic tolerance (OT) refers to the ability to maintain cardiovascular stability when upright, against the hydrostatic effects of gravity, and hence to maintain cerebral perfusion and prevent syncope (fainting). Various techniques are available to assess OT and the effects of gravitational stress upon the circulation, typically by reproducing a presyncopal event (near-fainting episode) in a controlled laboratory environment. The time and/or degree of stress required to provoke this response provides the measure of OT. Any technique used to determine OT should: enable distinction between patients with orthostatic intolerance (of various causes) and asymptomatic control subjects; be highly reproducible, enabling evaluation of therapeutic interventions; avoid invasive procedures, which are known to impair OT1. In the late 1980s head-upright tilt testing was first utilized for diagnosing syncope2. Since then it has been used to assess OT in patients with syncope of unknown cause, as well as in healthy subjects to study postural cardiovascular reflexes2-6. Tilting protocols comprise three categories: passive tilt; passive tilt accompanied by pharmacological provocation; and passive tilt with combined lower body negative pressure (LBNP). However, the effects of tilt testing (and other orthostatic stress testing modalities) are often poorly reproducible, with low sensitivity and specificity to diagnose orthostatic intolerance7. Typically, a passive tilt includes 20-60 min of orthostatic stress continued until the onset of presyncope in patients2-6. However, the main drawback of this procedure is its inability to invoke presyncope in all individuals undergoing the test, and corresponding low sensitivity8,9. Thus, different methods were explored to increase the orthostatic stress and improve sensitivity. Pharmacological provocation has been used to increase the orthostatic challenge, for example using isoprenaline4,7,10,11 or sublingual nitrate12,13. However, the main drawback of these approaches are increases in sensitivity at the cost of unacceptable decreases in specificity10,14, with a high positive response rate immediately after administration15. Furthermore, invasive procedures associated with some pharmacological provocations greatly increase the false positive rate1. Another approach is to combine passive tilt testing with LBNP, providing a stronger orthostatic stress without invasive procedures or drug side-effects, using the technique pioneered by Professor Roger Hainsworth in the 1990s16-18. This approach provokes presyncope in almost all subjects (allowing for symptom recognition in patients with syncope), while discriminating between patients with syncope and healthy controls, with a specificity of 92%, sensitivity of 85%, and repeatability of 1.1±0.6 min16,17. This allows not only diagnosis and pathophysiological assessment19-22, but also the evaluation of treatments for orthostatic intolerance due to its high repeatability23-30. For these reasons, we argue this should be the "gold standard" for orthostatic stress testing, and accordingly this will be the method described in this paper.
Medicine, Issue 73, Anatomy, Physiology, Biomedical Engineering, Neurobiology, Kinesiology, Cardiology, tilt test, lower body negative pressure, orthostatic stress, syncope, orthostatic tolerance, fainting, gravitational stress, head upright, stroke, clinical techniques
4315
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The Resident-intruder Paradigm: A Standardized Test for Aggression, Violence and Social Stress
Authors: Jaap M. Koolhaas, Caroline M. Coppens, Sietse F. de Boer, Bauke Buwalda, Peter Meerlo, Paul J.A. Timmermans.
Institutions: University Groningen, Radboud University Nijmegen.
This video publication explains in detail the experimental protocol of the resident-intruder paradigm in rats. This test is a standardized method to measure offensive aggression and defensive behavior in a semi natural setting. The most important behavioral elements performed by the resident and the intruder are demonstrated in the video and illustrated using artistic drawings. The use of the resident intruder paradigm for acute and chronic social stress experiments is explained as well. Finally, some brief tests and criteria are presented to distinguish aggression from its more violent and pathological forms.
Behavior, Issue 77, Neuroscience, Medicine, Anatomy, Physiology, Genetics, Basic Protocols, Psychology, offensive aggression, defensive behavior, aggressive behavior, pathological, violence, social stress, rat, Wistar rat, animal model
4367
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Isolation and Kv Channel Recordings in Murine Atrial and Ventricular Cardiomyocytes
Authors: Clemens Köhncke, Ulrike Lisewski, Leonhard Schleußner, Carolin Gaertner, Saskia Reichert, Torsten K. Roepke.
Institutions: Charité Medical Faculty and Max-Delbrück Center for Molecular Medicine (MDC), Charité - Universitätsmedizin Berlin, Charité - Universitätsmedizin Berlin.
KCNE genes encode for a small family of Kv channel ancillary subunits that form heteromeric complexes with Kv channel alpha subunits to modify their functional properties. Mutations in KCNE genes have been found in patients with cardiac arrhythmias such as the long QT syndrome and/or atrial fibrillation. However, the precise molecular pathophysiology that leads to these diseases remains elusive. In previous studies the electrophysiological properties of the disease causing mutations in these genes have mostly been studied in heterologous expression systems and we cannot be sure if the reported effects can directly be translated into native cardiomyocytes. In our laboratory we therefore use a different approach. We directly study the effects of KCNE gene deletion in isolated cardiomyocytes from knockout mice by cellular electrophysiology - a unique technique that we describe in this issue of the Journal of Visualized Experiments. The hearts from genetically engineered KCNE mice are rapidly excised and mounted onto a Langendorff apparatus by aortic cannulation. Free Ca2+ in the myocardium is bound by EGTA, and dissociation of cardiac myocytes is then achieved by retrograde perfusion of the coronary arteries with a specialized low Ca2+ buffer containing collagenase. Atria, free right ventricular wall and the left ventricle can then be separated by microsurgical techniques. Calcium is then slowly added back to isolated cardiomyocytes in a multiple step comprising washing procedure. Atrial and ventricular cardiomyocytes of healthy appearance with no spontaneous contractions are then immediately subjected to electrophysiological analyses by patch clamp technique or other biochemical analyses within the first 6 hours following isolation.
Physiology, Issue 73, Medicine, Cellular Biology, Molecular Biology, Genetics, Biomedical Engineering, Anatomy, Cardiology, Cardiac Output, Low, Cardiomyopathies, Heart Failure, Arrhythmias, Cardiac, Ventricular Dysfunction, Cardiomyocytes, Kv channel, cardiac arrythmia, electrophysiology, patch clamp, mouse, animal model
50145
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A Model of Chronic Nutrient Infusion in the Rat
Authors: Grace Fergusson, Mélanie Ethier, Bader Zarrouki, Ghislaine Fontés, Vincent Poitout.
Institutions: CRCHUM, University of Montreal.
Chronic exposure to excessive levels of nutrients is postulated to affect the function of several organs and tissues and to contribute to the development of the many complications associated with obesity and the metabolic syndrome, including type 2 diabetes. To study the mechanisms by which excessive levels of glucose and fatty acids affect the pancreatic beta-cell and the secretion of insulin, we have established a chronic nutrient infusion model in the rat. The procedure consists of catheterizing the right jugular vein and left carotid artery under general anesthesia; allowing a 7-day recuperation period; connecting the catheters to the pumps using a swivel and counterweight system that enables the animal to move freely in the cage; and infusing glucose and/or Intralipid (a soybean oil emulsion which generates a mixture of approximately 80% unsaturated/20% saturated fatty acids when infused with heparin) for 72 hr. This model offers several advantages, including the possibility to finely modulate the target levels of circulating glucose and fatty acids; the option to co-infuse pharmacological compounds; and the relatively short time frame as opposed to dietary models. It can be used to examine the mechanisms of nutrient-induced dysfunction in a variety of organs and to test the effectiveness of drugs in this context.
Biomedical Engineering, Issue 78, Medicine, Anatomy, Physiology, Basic Protocols, Surgery, Metabolic Diseases, Infusions, Intravenous, Infusion Pumps, Glucolipotoxicity, Rat, Infusion, Glucose, Intralipid, Catheter, canulation, canula, diabetes, animal model
50267
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Detection of Architectural Distortion in Prior Mammograms via Analysis of Oriented Patterns
Authors: Rangaraj M. Rangayyan, Shantanu Banik, J.E. Leo Desautels.
Institutions: University of Calgary , University of Calgary .
We demonstrate methods for the detection of architectural distortion in prior mammograms of interval-cancer cases based on analysis of the orientation of breast tissue patterns in mammograms. We hypothesize that architectural distortion modifies the normal orientation of breast tissue patterns in mammographic images before the formation of masses or tumors. In the initial steps of our methods, the oriented structures in a given mammogram are analyzed using Gabor filters and phase portraits to detect node-like sites of radiating or intersecting tissue patterns. Each detected site is then characterized using the node value, fractal dimension, and a measure of angular dispersion specifically designed to represent spiculating patterns associated with architectural distortion. Our methods were tested with a database of 106 prior mammograms of 56 interval-cancer cases and 52 mammograms of 13 normal cases using the features developed for the characterization of architectural distortion, pattern classification via quadratic discriminant analysis, and validation with the leave-one-patient out procedure. According to the results of free-response receiver operating characteristic analysis, our methods have demonstrated the capability to detect architectural distortion in prior mammograms, taken 15 months (on the average) before clinical diagnosis of breast cancer, with a sensitivity of 80% at about five false positives per patient.
Medicine, Issue 78, Anatomy, Physiology, Cancer Biology, angular spread, architectural distortion, breast cancer, Computer-Assisted Diagnosis, computer-aided diagnosis (CAD), entropy, fractional Brownian motion, fractal dimension, Gabor filters, Image Processing, Medical Informatics, node map, oriented texture, Pattern Recognition, phase portraits, prior mammograms, spectral analysis
50341
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Forward Genetics Screens Using Macrophages to Identify Toxoplasma gondii Genes Important for Resistance to IFN-γ-Dependent Cell Autonomous Immunity
Authors: Odaelys Walwyn, Sini Skariah, Brian Lynch, Nathaniel Kim, Yukari Ueda, Neal Vohora, Josh Choe, Dana G. Mordue.
Institutions: New York Medical College.
Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan pathogen. The parasite invades and replicates within virtually any warm blooded vertebrate cell type. During parasite invasion of a host cell, the parasite creates a parasitophorous vacuole (PV) that originates from the host cell membrane independent of phagocytosis within which the parasite replicates. While IFN-dependent-innate and cell mediated immunity is important for eventual control of infection, innate immune cells, including neutrophils, monocytes and dendritic cells, can also serve as vehicles for systemic dissemination of the parasite early in infection. An approach is described that utilizes the host innate immune response, in this case macrophages, in a forward genetic screen to identify parasite mutants with a fitness defect in infected macrophages following activation but normal invasion and replication in naïve macrophages. Thus, the screen isolates parasite mutants that have a specific defect in their ability to resist the effects of macrophage activation. The paper describes two broad phenotypes of mutant parasites following activation of infected macrophages: parasite stasis versus parasite degradation, often in amorphous vacuoles. The parasite mutants are then analyzed to identify the responsible parasite genes specifically important for resistance to induced mediators of cell autonomous immunity. The paper presents a general approach for the forward genetics screen that, in theory, can be modified to target parasite genes important for resistance to specific antimicrobial mediators. It also describes an approach to evaluate the specific macrophage antimicrobial mediators to which the parasite mutant is susceptible. Activation of infected macrophages can also promote parasite differentiation from the tachyzoite to bradyzoite stage that maintains chronic infection. Therefore, methodology is presented to evaluate the importance of the identified parasite gene to establishment of chronic infection.
Immunology, Issue 97, Toxoplasma, macrophages, innate immunity, intracellular pathogen, immune evasion, infectious disease, forward genetics, parasite
52556
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