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https://www.readbyqxmd.com/read/28213753/electrophysiologic-studies-on-the-risks-and-potential-mechanism-underlying-the-proarrhythmic-nature-of-azithromycin
#1
Mengdan Zhang, Ming Xie, Sha Li, Ying Gao, Shuyin Xue, Huili Huang, Kesu Chen, Fuming Liu, Long Chen
The mechanisms underlying arrhythmia induced by the clinical use of azithromycin are poorly understood. We aimed to investigate the proarrhythmic effects of azithromycin using electrocardiogram (ECG) and ion channel models. In vivo and in vitro guinea pig ECG and current and voltage clamp recordings were carried out. Azithromycin at 114.6 mg/kg (three times the clinically relevant dose) reduced heart rate (HR) and prolonged the PR, QRS and rate-corrected QT (QTc) intervals of guinea pig ECG in vivo. In vitro technique revealed that azithromycin at 207...
February 17, 2017: Cardiovascular Toxicology
https://www.readbyqxmd.com/read/28210214/arginine-vasopressin-alters-both-spontaneous-and-phase-locked-synaptic-inputs-to-airway-vagal-preganglionic-neuron-via-activation-of-v1a-receptor-insights-into-stress-related-airway-vagal-excitation
#2
Xianxia Yan, Xingxin Chen, Yuhong Guo, Ding He, Yonghua Chen, Chunmei Xia, Jijiang Wang
The airway vagal preganglionic neurons (AVPNs) in the external formation of the nucleus ambiguus (eNA) play a major role in the vagal control of tracheobronchial smooth muscle tone and maintenance of airway resistance. The eNA receives vasopressinergic projection from the hypothalamic paraventricular nucleus (PVN), the key node for the genesis of psychological stress. Since airway vagal excitation is reportedly to be associated with the psychological stress-induced/exacerbated airway hyperresponsiveness in asthmatics, arginine vasopressin (AVP) might be involved in stress-related airway vagal excitation...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/28206752/columnar-self-assemblies-of-triarylamines-as-scaffolds-for-artificial-biomimetic-channels-for-ion-and-for-water-transport
#3
Susanne Schneider, Erol-Dan Licsandru, Istvan Kocsis, Arnaud Gilles, Florina Dumitru, Emilie Moulin, Junjun Tan, Jean-Marie Lehn, Nicolas Giuseppone, Mihail Barboiu
Triarylamine molecules appended with crown-ethers or carboxylic moieties form self-assembled supramolecular channels within lipid bilayers. Fluorescence assays and voltage clamp studies reveal that the self-assemblies incorporating the crown ethers work as single channels for the selective transport of K+ or Rb+. The X-ray crystallographic structures confirm the mutual columnar self-assembly of triarylamines and crown-ethers. The dimensional fit of K+ cations within the 18-crown-6, leads to a partial dehydration and to the formation of alternating K+ cation-water wires within the channel...
February 16, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28202726/two-tonoplast-mate-proteins-function-as-turgor-regulating-chloride-channels-in-arabidopsis
#4
Haiwen Zhang, Fu-Geng Zhao, Ren-Jie Tang, Yuexuan Yu, Jiali Song, Yuan Wang, Legong Li, Sheng Luan
The central vacuole in a plant cell occupies the majority of the cellular volume and plays a key role in turgor regulation. The vacuolar membrane (tonoplast) contains a large number of transporters that mediate fluxes of solutes and water, thereby adjusting cell turgor in response to developmental and environmental signals. We report that two tonoplast Detoxification efflux carrier (DTX)/Multidrug and Toxic Compound Extrusion (MATE) transporters, DTX33 and DTX35, function as chloride channels essential for turgor regulation in Arabidopsis Ectopic expression of each transporter in Nicotiana benthamiana mesophyll cells elicited a large voltage-dependent inward chloride current across the tonoplast, showing that DTX33 and DTX35 each constitute a functional channel...
February 15, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28202723/mapping-of-voltage-sensor-positions-in-resting-and-inactivated-mammalian-sodium-channels-by-lret
#5
Tomoya Kubota, Thomas Durek, Bobo Dang, Rocio K Finol-Urdaneta, David J Craik, Stephen B H Kent, Robert J French, Francisco Bezanilla, Ana M Correa
Voltage-gated sodium channels (Navs) play crucial roles in excitable cells. Although vertebrate Nav function has been extensively studied, the detailed structural basis for voltage-dependent gating mechanisms remain obscure. We have assessed the structural changes of the Nav voltage sensor domain using lanthanide-based resonance energy transfer (LRET) between the rat skeletal muscle voltage-gated sodium channel (Nav1.4) and fluorescently labeled Nav1.4-targeting toxins. We generated donor constructs with genetically encoded lanthanide-binding tags (LBTs) inserted at the extracellular end of the S4 segment of each domain (with a single LBT per construct)...
February 15, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28202576/differential-effect-of-brief-electrical-stimulation-on-voltage-gated-potassium-channels
#6
Morven Alison Cameron, Amr Al Abed, Yossi Buskila, Socrates Dokos, Nigel H Lovell, John W Morley
Electrical stimulation of neuronal tissue is a promising strategy to treat a variety of neurological disorders. The mechanism of neuronal activation by external electrical stimulation is governed by voltage-gated ion channels. This stimulus, typically brief in nature, leads to membrane potential depolarization, which increases ion flow across the membrane by increasing the open probability of these voltage-gated channels. In spiking neurons, it is activation of voltage-gated sodium channels (NaV-channels) that leads to action potential generation...
February 15, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28197715/vacuolar-ion-channels-in-the-liverwort-marchantia-polymorpha-influence-of-ion-channel-inhibitors
#7
Mateusz Koselski, Kazimierz Trebacz, Halina Dziubinska
Potassium-permeable slow activating vacuolar channels (SV) and chloride-permeable channels in the vacuole of the liverwort Marchantia polymorpha were characterized in respect to calcium dependence, selectivity, and pharmacology. The patch-clamp method was used in the study of ion channel activity in the vacuoles from the liverwort Marchantia polymorpha. The whole-vacuole recordings allowed simultaneous observation of two types of currents-predominant slow activated currents recorded at positive voltages and fast activated currents recorded at negative voltages...
February 14, 2017: Planta
https://www.readbyqxmd.com/read/28192542/functional-diversity-of-secreted-cestode-kunitz-proteins-inhibition-of-serine-peptidases-and-blockade-of-cation-channels
#8
Martín Fló, Mariana Margenat, Leonardo Pellizza, Martín Graña, Rosario Durán, Adriana Báez, Emilio Salceda, Enrique Soto, Beatriz Alvarez, Cecilia Fernández
We previously reported a multigene family of monodomain Kunitz proteins from Echinococcus granulosus (EgKU-1-EgKU-8), and provided evidence that some EgKUs are secreted by larval worms to the host interface. In addition, functional studies and homology modeling suggested that, similar to monodomain Kunitz families present in animal venoms, the E. granulosus family could include peptidase inhibitors as well as channel blockers. Using enzyme kinetics and whole-cell patch-clamp, we now demonstrate that the EgKUs are indeed functionally diverse...
February 13, 2017: PLoS Pathogens
https://www.readbyqxmd.com/read/28192441/cyclic-amp-regulates-postnatal-development-of-neural-and-behavioral-responses-to-nacl-in-rats
#9
Jie Qian, Shobha Mummalaneni, Tam-Hao T Phan, Gerard L Heck, John A DeSimone, David West, Sunila Mahavadi, Deanna Hojati, Karnam S Murthy, Mee-Ra Rhyu, Andrew I Spielman, Mehmet Hakan Özdener, Vijay Lyall
During postnatal development rats demonstrate an age-dependent increase in NaCl chorda tympani (CT) responses and the number of functional apical amiloride-sensitive epithelial Na+ channels (ENaCs) in salt sensing fungiform (FF) taste receptor cells (TRCs). Currently, the intracellular signals that regulate the postnatal development of salt taste have not been identified. We investigated the effect of cAMP, a downstream signal for arginine vasopressin (AVP) action, on the postnatal development of NaCl responses in 19-23 day old rats...
2017: PloS One
https://www.readbyqxmd.com/read/28185085/h-dependent-inorganic-phosphate-uptake-in-trypanosoma-brucei-is-influenced-by-myo-inositol-transporter
#10
Thais Russo-Abrahão, Carolina Macedo Koeller, Michael E Steinmann, Stephanie Silva-Rito, Thaissa Marins-Lucena, Michele Alves-Bezerra, Naira Ligia Lima-Giarola, Iron Francisco de-Paula, Amaia Gonzalez-Salgado, Erwin Sigel, Peter Bütikofer, Katia Calp Gondim, Norton Heise, José Roberto Meyer-Fernandes
Trypanosoma brucei is an extracellular protozoan parasite that causes human African trypanosomiasis or "sleeping sickness". During the different phases of its life cycle, T. brucei depends on exogenous inorganic phosphate (Pi), but little is known about the transport of Pi in this organism. In the present study, we showed that the transport of (32)Pi across the plasma membrane follows Michaelis-Menten kinetics and is modulated by pH variation, with higher activity at acidic pH. Bloodstream forms presented lower Pi transport in comparison to procyclic forms, that displayed an apparent K0...
February 9, 2017: Journal of Bioenergetics and Biomembranes
https://www.readbyqxmd.com/read/28183797/ca-2-binding-protein-2-inhibits-ca-2-channel-inactivation-in-mouse-inner-hair-cells
#11
Maria Magdalena Picher, Anna Gehrt, Sandra Meese, Aleksandra Ivanovic, Friederike Predoehl, SangYong Jung, Isabelle Schrauwen, Alberto Giulio Dragonetti, Roberto Colombo, Guy Van Camp, Nicola Strenzke, Tobias Moser
Ca(2+)-binding protein 2 (CaBP2) inhibits the inactivation of heterologously expressed voltage-gated Ca(2+) channels of type 1.3 (CaV1.3) and is defective in human autosomal-recessive deafness 93 (DFNB93). Here, we report a newly identified mutation in CABP2 that causes a moderate hearing impairment likely via nonsense-mediated decay of CABP2-mRNA. To study the mechanism of hearing impairment resulting from CABP2 loss of function, we disrupted Cabp2 in mice (Cabp2(LacZ/LacZ) ). CaBP2 was expressed by cochlear hair cells, preferentially in inner hair cells (IHCs), and was lacking from the postsynaptic spiral ganglion neurons (SGNs)...
February 9, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28182669/a-de-novo-loss-of-function-grin2a-mutation-associated-with-childhood-focal-epilepsy-and-acquired-epileptic-aphasia
#12
Kai Gao, Anel Tankovic, Yujia Zhang, Hirofumi Kusumoto, Jin Zhang, Wenjuan Chen, Wenshu XiangWei, Gil H Shaulsky, Chun Hu, Stephen F Traynelis, Hongjie Yuan, Yuwu Jiang
OBJECTIVE: N-methyl-D-aspartate receptors (NMDAR) subunit GRIN2A/GluN2A mutations have been identified in patients with various neurological diseases, such as epilepsy and intellectual disability / developmental delay (ID/DD). In this study, we investigated the phenotype and underlying molecular mechanism of a GRIN2A missense mutation identified by next generation sequencing on idiopathic focal epilepsy using in vitro electrophysiology. METHODS: Genomic DNA of patients with epilepsy and ID/DD were sequenced by targeted next-generation sequencing within 300 genes related to epilepsy and ID/DD...
2017: PloS One
https://www.readbyqxmd.com/read/28180184/a-gain-of-function-mutation-in-the-grik2-gene-causes-neurodevelopmental-deficits
#13
Yomayra F Guzmán, Keri Ramsey, Jacob R Stolz, David W Craig, Mathew J Huentelman, Vinodh Narayanan, Geoffrey T Swanson
OBJECTIVE: To identify inherited or de novo mutations associated with a suite of neurodevelopmental abnormalities in a 10-year-old patient displaying ataxia, motor and speech delay, and intellectual disability. METHODS: We performed whole-exome sequencing of the proband and her parents. A pathogenic gene variant was identified as damaging based on sequence conservation, gene function, and association with disorders having similar phenotypic profiles. Functional characterization of the mutated protein was performed in vitro using a heterologous expression system...
February 2017: Neurology. Genetics
https://www.readbyqxmd.com/read/28179480/transient-voltage-activated-k-currents-in-central-antennal-lobe-neurons-cell-type-specific-functional-properties
#14
Lars Paeger, Viktor Bardos, Peter Kloppenburg
Here we analyzed transient voltage-activated K(+) currents (IA) of projection neurons and local interneurons in the antennal lobe (AL) of the cockroach Periplaneta americana. The AL is the first synaptic processing station for olfactory information in insects. Local interneurons are crucial for computing olfactory information and form local synaptic connections exclusively in the AL, while a primary task of the projection neurons is the transfer of preprocessed olfactory information from the AL to the protocerebrum...
February 8, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28179135/c-terminal-residues-in-small-potassium-channel-blockers-odk1-and-osk3-from-scorpion-venom-fine-tune-the-selectivity
#15
Alexey I Kuzmenkov, Steve Peigneur, Anton O Chugunov, Valentin M Tabakmakher, Roman G Efremov, Jan Tytgat, Eugene V Grishin, Alexander A Vassilevski
We report isolation, sequencing, and electrophysiological characterization of OSK3 (α-KTx 8.8 in Kalium and Uniprot databases), a potassium channel blocker from the scorpion Orthochirus scrobiculosus venom. Using the voltage clamp technique, OSK3 was tested on a wide panel of 11 voltage-gated potassium channels expressed in Xenopus oocytes, and was found to potently inhibit Kv1.2 and Kv1.3 with IC50 values of ~331nM and ~503nM, respectively. OdK1 produced by the scorpion Odontobuthus doriae differs by just two C-terminal residues from OSK3, but shows marked preference to Kv1...
February 4, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28167075/inhibition-of-the-nmda-and-ampa-receptor-channels-by-antidepressants-and-antipsychotics
#16
Oleg I Barygin, Elina I Nagaeva, Denis B Tikhonov, Darya A Belinskaya, Nina P Vanchakova, Natalia N Shestakova
It is known that some antidepressants and antipsychotics directly inhibit NMDA-type ionotropic glutamate receptors. In this study we systematically studied action of seven drugs (Fluoxetine, Citalopram, Desipramine, Amitriptyline, Atomoxetine, Chlorpromazine, and Clozapine) on NMDA receptors and Ca(2+)-permeable and -impermeable AMPA receptors in rat brain neurons by whole-cell patch-clamp technique. Except for weak effect of fluoxetine, all drugs were virtually inactive against Ca(2+)-impermeable AMPA receptors...
February 3, 2017: Brain Research
https://www.readbyqxmd.com/read/28164251/state-dependent-block-of-voltage-gated-sodium-channels-by-the-casein-kinase-1-inhibitor-ic261
#17
Karl J Föhr, Uwe Knippschild, Anna Herkommer, Michael Fauler, Christian Peifer, Michael Georgieff, Oliver Adolph
Background and Purpose IC261 (3-[(2,4,6-trimethoxyphenyl)methylidenyl]-indolin-2-one) has previously been introduced as an isoform specific inhibitor of casein kinase 1 (CK1) causing cell cycle arrest or cell death of established tumor cell lines. However, it is reasonable to assume that not all antitumor activities of IC261 are mediated by the inhibition of CK1. Meanwhile there is growing evidence that functional voltage-gated sodium channels are also implicated in the progression of tumors as their blockage suppresses tumor migration and invasion of different tumor cell lines...
February 6, 2017: Investigational New Drugs
https://www.readbyqxmd.com/read/28161890/homology-guided-mutational-analysis-reveals-the-functional-requirements-for-antinociceptive-specificity-of-crmp2-derived-peptides
#18
Aubin Moutal, Wennan Li, Yue Wang, Weina Ju, Shizhen Luo, Song Cai, Liberty François-Moutal, Samantha Perez-Miller, Jackie Hu, Erik T Dustrude, Todd W Vanderah, Vijay Gokhale, May Khanna, Rajesh Khanna
BACKGROUND AND PURPOSE: N-type voltage-gated calcium (CaV2.2) channels are critical determinants of increased neuronal excitability and neurotransmission accompanying persistent neuropathic pain. Despite CaV2.2 antagonism being recommended as first-line treatment for neuropathic pain, calcium-current blocking gabapentinoids inadequately alleviate chronic pain symptoms and are often mired by numerous side-effects. Collapsin response mediator protein 2 (CRMP2) targets CaV2.2 to the sensory neuron membrane, and allosterically modulates Cav2...
February 5, 2017: British Journal of Pharmacology
https://www.readbyqxmd.com/read/28148856/single-cell-electroporation-of-neurons
#19
J Simon Wiegert, Christine E Gee, Thomas G Oertner
Single-cell electroporation allows the transfection of a small number of neurons in an organotypic culture with a single plasmid or a defined mixture of plasmids. Desired protein expression levels can vary depending on the experimental goals (e.g., high expression levels are needed for optogenetic experiments); however, when too much protein is expressed, cellular toxicity and cell death may arise. To a large degree, protein expression can be controlled by adjusting the concentration of plasmid DNA in the electroporation pipette...
February 1, 2017: Cold Spring Harbor Protocols
https://www.readbyqxmd.com/read/28148645/nonlinear-effects-of-hyperpolarizing-shifts-in-activation-of-mutant-nav1-7-channels-on-resting-membrane-potential
#20
Mark Estacion, Stephen G Waxman
The Nav1.7 sodium channel is preferentially expressed within dorsal root ganglion (DRG) and sympathetic ganglion neurons. Gain-of-function mutations that cause the painful disorder inherited erythromelalgia (IEM) shift channel activation in a hyperpolarizing direction. When expressed within DRG neurons, these mutations produce a depolarization of resting membrane potential (RMP). The biophysical basis for the depolarized RMP has to date not been established. To explore the effect on RMP of the shift in activation associated with a prototypical IEM mutation (L858H), we used dynamic clamp models that represent graded shifts that fractionate the effect of the mutation on activation voltage-dependence...
February 1, 2017: Journal of Neurophysiology
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