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Tetrodotoxin

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https://www.readbyqxmd.com/read/28432032/neuronal-excitation-and-permeabilization-by-200-ns-pulsed-electric-field-an-optical-membrane-potential-study-with-fluovolt-dye
#1
Andrei G Pakhomov, Iurii Semenov, M Casciola, Shu Xiao
Electric field pulses of nano- and picosecond duration are a novel modality for neurostimulation, activation of Ca(2+) signaling, and tissue ablation. However it is not known how such brief pulses activate voltage-gated ion channels. We studied excitation and electroporation of hippocampal neurons by 200-ns pulsed electric field (nsPEF), by means of time-lapse imaging of the optical membrane potential (OMP) with FluoVolt dye. Electroporation abruptly shifted OMP to a more depolarized level, which was reached within <1ms...
April 18, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28425396/development-and-single-laboratory-validation-of-a-liquid-chromatography-tandem-mass-spectrometry-method-for-quantitation-of-tetrodotoxin-in-mussels-and-oysters
#2
Andrew D Turner, Michael J Boundy, Monika Dhanji Rapkova
In recent years, evidence has grown for the presence of tetrodotoxin (TTX) in bivalve mollusks, leading to the potential for consumers of contaminated products to be affected by Tetrodotoxin Shellfish Poisoning (TSP). A single-laboratory validation was conducted for the hydrophilic interaction LC (HILIC) tandem MS (MS/MS) analysis of TTX in common mussels and Pacific oysters-the bivalve species that have been found to contain TTXs in the United Kingdom in recent years. The method consists of a single-step dispersive extraction in 1% acetic acid, followed by a carbon SPE cleanup step before dilution and instrumental analysis...
April 20, 2017: Journal of AOAC International
https://www.readbyqxmd.com/read/28423185/functional-identification-of-activity-regulated-high-affinity-glutamine-transport-in-hippocampal-neurons-inhibited-by-riluzole
#3
Jeffrey D Erickson
Glutamine (Gln) is considered the preferred precursor for the neurotransmitter pool of glutamate (Glu), the major excitatory transmitter in the mammalian CNS. Here, an activity-regulated, high-affinity Gln transport system is described in developing and mature neuron-enriched hippocampal cultures that is potently inhibited by riluzole (IC50 1.3 +/- 0.5μM), an anti-glutamatergic drug, and is blocked by low concentrations of 2-(methylamino)isobutyrate (MeAIB), a system A transport inhibitor. K(+) -stimulated MeAIB transport displays an affinity (Km ) for MeAIB of 37 +/- 1...
April 19, 2017: Journal of Neurochemistry
https://www.readbyqxmd.com/read/28418103/neurogenic-and-myogenic-patterns-of-electrical-activity-in-isolated-intact-mouse-colon
#4
T J Hibberd, M Costa, L Travis, S J H Brookes, D A Wattchow, J Feng, H Hu, N J Spencer
BACKGROUND: Relatively little is known about the electrical rhythmicity of the whole colon, where long neural pathways are preserved. METHODS: Smooth muscle electrical activity was recorded extracellularly from the serosa of isolated flat-sheet preparations consisting of the whole mouse colon (n=31). KEY RESULTS: Two distinct electrical patterns were observed. The first, long intense spike bursts, occurred every 349±256 seconds (0.2±0.2 cpm), firing action potentials for 31±11 seconds at 2...
April 18, 2017: Neurogastroenterology and Motility: the Official Journal of the European Gastrointestinal Motility Society
https://www.readbyqxmd.com/read/28408644/human-derived-gut-microbiota-modulates-colonic-secretion-in-mice-by-regulating-5-ht3-receptor-expression-via-acetate-production
#5
Yogesh Bhattarai, Bradley A Schmidt, David R Linden, Eric D Larson, Madhusudan Grover, Arthur Beyder, Gianrico Farrugia, Purna C Kashyap
Serotonin (5-hydroxytryptamine, 5-HT), an important neurotransmitter and a paracrine messenger in the gastrointestinal (GI) tract, regulates intestinal secretion by its action primarily on 5-HT3 and 5-HT4 receptors. Recent studies highlight the role of gut microbiota in 5-HT biosynthesis. In this study we determine if human-derived gut microbiota affect host secretory response to 5-HT and 5-HT receptor expression. We used proximal colonic mucosa-submucosa preparation from age matched Swiss Webster germ free (GF) and humanized (HM; ex-GF colonized with human gut microbiota) mice...
April 13, 2017: American Journal of Physiology. Gastrointestinal and Liver Physiology
https://www.readbyqxmd.com/read/28400714/deletion-of-trpc6-attenuates-nmda-receptor-mediated-ca-2-entry-and-ca-2-induced-neurotoxicity-following-cerebral-ischemia-and-oxygen-glucose-deprivation
#6
Jin Chen, Zhaozhong Li, Jeffery T Hatcher, Qing-Hui Chen, Li Chen, Robert D Wurster, Sic L Chan, Zixi Cheng
Transient receptor potential canonical 6 (TRPC6) channels are permeable to Na(+) and Ca(2+) and are widely expressed in the brain. In this study, the role of TRPC6 was investigated following ischemia/reperfusion (I/R) and oxygen-glucose deprivation (OGD). We found that TRPC6 expression was increased in wild-type (WT) mice cortical neurons following I/R and in primary neurons with OGD, and that deletion of TRPC6 reduced the I/R-induced brain infarct in mice and the OGD- /neurotoxin-induced neuronal death. Using live-cell imaging to examine intracellular Ca(2+) levels ([Ca(2+)] i ), we found that OGD induced a significant higher increase in glutamate-evoked Ca(2+) influx compared to untreated control and such an increase was reduced by TRPC6 deletion...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/28380330/to-stress-or-not-to-stress-physiological-responses-to-tetrodotoxin-in-resistant-gartersnakes-vary-by-sex
#7
Lorin A Neuman-Lee, Edmund D Brodie, Tyler Hansen, Edmund D Brodie, Susannah S French
The activation of the hypothalamic pituitary adrenal (HPA) axis is one of the most important physiological processes in coping with any deviation in an organism's homeostasis. This activation and the secretion of glucocorticoids, such as corticosterone, allow organisms to cope with perturbations and return to optimal physiological functioning as quickly as possible. In this study, we examined the HPA axis activation in Common gartersnakes (Thamnophis sirtalis) as a response to a natural toxin, tetrodotoxin (TTX)...
April 2, 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
https://www.readbyqxmd.com/read/28377845/time-dependent-decline-in-multifocal-electroretinogram-requires-faster-recording-procedures-in-anesthetized-pigs
#8
Nina Buus Sørensen, Anders Tolstrup Christiansen, Troels Wesenberg Kjær, Kristian Klemp, Morten la Cour, Jens Folke Kiilgaard
PURPOSE: The time-dependent effect of anesthetics on the retinal function is debated. We hypothesize that in anesthetized animals there is a time-dependent decline that requires optimized multifocal electroretinogram (mfERG) recording procedures. METHODS: Conventional and four-frame global-flash mfERG recordings were obtained approximately 15, 60, and 150 minutes after the induction of propofol anesthesia (20 pigs) and isoflurane anesthesia (nine pigs). In six of the propofol-anesthetized pigs, the mfERG recordings were split in 3-minute segments...
March 2017: Translational Vision Science & Technology
https://www.readbyqxmd.com/read/28370004/convergent-adaptation-to-dangerous-prey-proceeds-through-the-same-first-step-mutation-in-the-garter-snake-thamnophis-sirtalis
#9
Michael T J Hague, Chris R Feldman, Edmund D Brodie, Edmund D Brodie
Convergent phenotypes often result from similar underlying genetics, but recent work suggests convergence may also occur in the historical order of substitutions en route to an adaptive outcome. We characterized convergence in the mutational steps to two independent outcomes of tetrodotoxin (TTX) resistance in separate geographic lineages of the common garter snake (Thamnophis sirtalis) that coevolved with toxic newts. Resistance is largely conferred by amino acid changes in the skeletal muscle sodium channel (NaV 1...
March 29, 2017: Evolution; International Journal of Organic Evolution
https://www.readbyqxmd.com/read/28358321/the-influence-of-tetrodotoxin-ttx-on-the-distribution-and-chemical-coding-of-caudal-mesenteric-ganglion-camg-neurons-supplying-the-porcine-urinary-bladder
#10
Ewa Lepiarczyk, Agnieszka Bossowska, Jerzy Kaleczyc, Marta Majewska, Sławomir Gonkowski, Mariusz Majewski
The treatment of micturition disorders creates a serious problem for urologists. Recently, new therapeutic agents, such as neurotoxins, are being considered for the therapy of urological patients. The present study investigated the chemical coding of caudal mesenteric ganglion (CaMG) neurons supplying the porcine urinary bladder after intravesical instillation of tetrodotoxin (TTX). The CaMG neurons were visualized with retrograde tracer Fast blue (FB) and their chemical profile was disclosed with double-labeling immunohistochemistry using antibodies against tyrosine hydroxylase (TH), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), somatostatin (SOM), calbindin (CB), galanin (GAL) and neuronal nitric oxide synthase (nNOS)...
March 30, 2017: Marine Drugs
https://www.readbyqxmd.com/read/28352365/heart-failure-modulates-electropharmacological-characteristics-of-sinoatrial-nodes
#11
Shih-Lin Chang, Hui-Lun Chuang, Yao-Chang Chen, Yu-Hsun Kao, Yung-Kuo Lin, Yung-Hsin Yeh, Shih-Ann Chen, Yi-Jen Chen
The impact of heart failure (HF) on sinoatrial node (SAN) channel regulation and electropharmacological responses has remained elusive. The present study aimed to investigate the effects of HF on the electrical activity of SANs with and without pharmacological interventions. Action potentials (APs) were recorded in isolated SANs from normal rabbits (control) and those with HF (rapid ventricular pacing for 4 weeks) prior to and after administration of a funny current blocker (ivabradine; 0.1, 0.3, 3 or 10 µM), a calmodulin kinase II inhibitor (KN-93; 0...
February 2017: Experimental and Therapeutic Medicine
https://www.readbyqxmd.com/read/28336943/altered-glutamatergic-tone-reveals-two-distinct-resting-state-networks-at-the-cellular-level-in-hippocampal-sclerosis
#12
Jyotirmoy Banerjee, Aparna BanerjeeDixit, Arpna Srivastava, Bhargavi Ramanujam, Aanchal Kakkar, Chitra Sarkar, Manjari Tripathi, P Sarat Chandra
Hippocampal sclerosis (HS), the most common subset of drug-resistant epilepsy (DRE), is associated with large-scale network abnormalities, even under resting state. We studied the excitatory postsynaptic currents (EPSCs) recorded from pyramidal neurons in resected samples under resting conditions from the hippocampal and anterior temporal lobe (ATL) obtained from patients with HS (n = 14) undergoing resective surgery. We observed higher frequency and amplitude of spontaneous EPSCs in both the samples compared to non-seizure control samples...
March 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28332745/5-ht4-receptors-facilitate-cholinergic-neurotransmission-throughout-the-murine-gastrointestinal-tract
#13
V Pauwelyn, R A Lefebvre
BACKGROUND: In the gastrointestinal tract of several species, facilitating 5-HT4 receptors were proposed on myenteric cholinergic neurons innervating smooth muscle by in vitro study of the effect of the selective 5-HT4 receptor agonist prucalopride on submaximal cholinergic contractions. This was not yet established in the murine gastrointestinal tract. METHODS: In circular smooth muscle strips from murine fundus, jejunum and colon, contractions were induced by electrical field stimulation in the presence of guanethidine, L-NAME and for colon also MRS 2500...
March 23, 2017: Neurogastroenterology and Motility: the Official Journal of the European Gastrointestinal Motility Society
https://www.readbyqxmd.com/read/28326909/resynchronization-dynamics-reveal-that-the-ventral-entrains-the-dorsal-suprachiasmatic-nucleus
#14
Stephanie R Taylor, Thomas J Wang, Daniel Granados-Fuentes, Erik D Herzog
Although the suprachiasmatic nucleus (SCN) has long been considered the master circadian clock in mammals, the topology of the connections that synchronize daily rhythms among SCN cells is not well understood. We combined experimental and computational methods to infer the directed interactions that mediate circadian synchrony between regions of the SCN. We analyzed PERIOD2 (PER2) expression from SCN slices during and after treatment with tetrodotoxin, allowing us to map connections as cells resynchronized their daily cycling following blockade and restoration of cell-cell communication...
February 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28322255/ca-2-permeable-ampa-receptors-in-mouse-olfactory-bulb-astrocytes
#15
Damian Droste, Gerald Seifert, Laura Seddar, Oliver Jädtke, Christian Steinhäuser, Christian Lohr
Ca(2+) signaling in astrocytes is considered to be mainly mediated by metabotropic receptors linked to intracellular Ca(2+) release. However, recent studies demonstrate a significant contribution of Ca(2+) influx to spontaneous and evoked Ca(2+) signaling in astrocytes, suggesting that Ca(2+) influx might account for astrocytic Ca(2+) signaling to a greater extent than previously thought. Here, we investigated AMPA-evoked Ca(2+) influx into olfactory bulb astrocytes in mouse brain slices using Fluo-4 and GCaMP6s, respectively...
March 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28302446/electrophysiological-evidence-of-increased-glycine-receptor-mediated-phasic-and-tonic-inhibition-by-blockade-of-glycine-transporters-in-spinal-superficial-dorsal-horn-neurons-of-adult-mice
#16
Misa Oyama, Seiya Kuraoka, Shun Watanabe, Takashi Iwai, Mitsuo Tanabe
To understand the synaptic and/or extrasynaptic mechanisms underlying pain relief by blockade of glycine transporter subtypes GlyT1 and GlyT2, whole-cell recordings were made from dorsal horn neurons in spinal slices from adult mice, and the effects of NFPS and ALX-1393, selective GlyT1 and GlyT2 inhibitors, respectively, on phasic evoked or miniature glycinergic inhibitory postsynaptic currents (eIPSCs or mIPSCs) were examined. NFPS and ALX-1393 prolonged the decay phase of eIPSCs without affecting their amplitude...
February 27, 2017: Journal of Pharmacological Sciences
https://www.readbyqxmd.com/read/28298301/in-vivo-optogenetic-activation-of-nav1-8-cutaneous-nociceptors-and-their-responses-to-natural-stimuli
#17
Megan L Uhelski, Daniel J Bruce, Philippe Seguela, George L Wilcox, Donald A Simone
Optogenetic methods utilizing expression of the light-sensitive protein channelrhodopsin-2 (ChR2) in neurons have enabled selective activation of specific subtypes or groups of neurons to determine their functions. Using a transgenic mouse model in which neurons natively expressing Nav1.8, a tetrodotoxin-resistant voltage-gated sodium channel, also express the light-gated channel ChR2, we have been able to determine the functional properties of Nav1.8-expressing cutaneous nociceptors of the glabrous skin in vivo...
March 15, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28271031/enteroendocrine-derived-glucagon-like-peptide-2-controls-intestinal-amino-acid-transport
#18
Jennifer Lee, Jacqueline Koehler, Bernardo Yusta, Jasmine Bahrami, Dianne Matthews, Mahroukh Rafii, Paul B Pencharz, Daniel J Drucker
OBJECTIVE: Glucagon-like peptide-2 (GLP-2) is co-secreted with GLP-1 from gut endocrine cells, and both peptides act as growth factors to expand the surface area of the mucosal epithelium. Notably, GLP-2 also enhances glucose and lipid transport in enterocytes; however, its actions on control of amino acid (AA) transport remain unclear. Here we examined the mechanisms linking gain and loss of GLP-2 receptor (GLP-2R) signaling to control of intestinal amino acid absorption in mice. METHODS: Absorption, transport, and clearance of essential AAs, specifically lysine, were measured in vivo by Liquid Chromatography triple quadrupole Mass Spectrometry (LC-MS/MS) and ex vivo with Ussing chambers using intestinal preparations from Glp2r(+/+) and Glp2r(-/-) mice...
March 2017: Molecular Metabolism
https://www.readbyqxmd.com/read/28263757/profile-differences-in-tetrodotoxin-transfer-to-skin-and-liver-in-the-pufferfish-takifugu-rubripes
#19
Ryohei Tatsuno, Wei Gao, Kotaro Ibi, Tomoka Mine, Kogen Okita, Gregory Naoki Nishihara, Tomohiro Takatani, Osamu Arakawa
Tetrodotoxin (TTX) was intramuscularly administered to nontoxic cultured specimens of the pufferfish Takifugu rubripes to investigate differences in the toxin transfer and accumulation profiles between the skin and liver. Test fish were administered TTX at doses of 30 (Low dose; LD), 100 (Medium dose; MD), and 300 (High dose; HD) μg/individual, respectively. Liquid chromatography/mass spectrometry analysis for TTX revealed that the TTX concentration in both the skin (0.48-1.7 μg/g) and liver (0.43-6.0 μg/g) at 24 h after the toxin administration increased with an increase in the dose...
March 2, 2017: Toxicon: Official Journal of the International Society on Toxinology
https://www.readbyqxmd.com/read/28262835/high-frequency-stimulation-induces-sonic-hedgehog-release-from-hippocampal-neurons
#20
Yujuan Su, Yuan Yuan, Shengjie Feng, Shaorong Ma, Yizheng Wang
Sonic hedgehog (SHH) as a secreted protein is important for neuronal development in the central nervous system (CNS). However, the mechanism about SHH release remains largely unknown. Here, we showed that SHH was expressed mainly in the synaptic vesicles of hippocampus in both young postnatal and adult rats. High, but not low, frequency stimulation, induces SHH release from the neurons. Moreover, removal of extracellular Ca(2+), application of tetrodotoxin (TTX), an inhibitor of voltage-dependent sodium channels, or downregulation of soluble n-ethylmaleimide-sensitive fusion protein attachment protein receptors (SNAREs) proteins, all blocked SHH release from the neurons in response to HFS...
March 6, 2017: Scientific Reports
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