DOCSLIB.ORG

MECHANISM of A-LATROTOXIN ACTION at the FROG

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

MECHANISM OF a-LATROTOXIN ACTION AT THE FROG NEUROMUSCULAR JUNCTION Chris Tsang A thesis in confomiity with the requirements for the degree of Master of Science Graduate Department of Physiology University of Toronto " Copyright by Christopher Wilson Tsang 2000 Acquisitions and Acquisitions et Biblbgnphii Services aiwices bibliographiques The author has granted a non- L'auteur a accordé une licence non exclusive Licence allowing the exclusive permettant à la National Li- of Canada to Bibliothèque nationale du Canada de reproduce, loan, distriiute or seii reproduire, prêter, distniiuer ou copies of this thesis in microforni, vendre des copies de cette thèse sous paper or electronic formats. la forme de microficheffilm, de reproduction sur papier ou sur format electronique. The author retains ownership of the L'auteur conserve la proprieté du copyright in this thesis. Neither the droit d'auteur qui protege cette thèse. thesis nor substmtial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Canada MECHANISM OF a-LATROTOXIN ACTION AT THE FROG NEUROMUSCLULAR JUNCTION Chris Tsang, M. Sc. Thesis, 2000. University of Toronto, Department of Physiology. ABSTRACT a-Latrotoxin (a-LTX) is a neurotoxin purified from black widow spider venom that accelerates spontaneous transmitter release independently of extracellular ca2+.Since transmitter release is ca2+-dependent,! hypothesized that a-LTX mobilized intracellular ca2+.To address this question, standard electrophysiology and confocal imaging techniques were used to measure the rate of transmitter release and ion concentration dynarnics respectively in frog motor nerve terminais bathed in CFS. Here I report that transmitter release by a-LTX follows an increase in intracellular ca2+.The ca2+pool targeted by a-LTX is likely to be mitochondrial in origin and not endoplasmic reticulum. An increase in intracellular Na' precedes the release of ~a"suggesting that the mitochondrial ~a+/~a~+exchanger may be activated. There is also evidence to suggest that the mitochondrial peneability transition pore rnay be involved. Although the release of ca2' may accompany the increase in transmitter release produced by a-LTX, it is not necessary. .. AB STRACT ....................................................................................................II ... TABLE OF CONTENTS ..................................................................................III LIST OF TABLES ...................... ... ..................................................................vi .. LIST OF FIGURES .......................................................................................... VII LIST OF ABBREVIATIONS ...............................................................................ix ACKNOWLEDGEMENTS ................................................................................. x 1 INTRODUCTION .......................................................................................................... 1 1. 1 THE BLACK WlDOW SPIDERS .......................................................................... 1 1.1 -1 Habitat .............................................................................................*............. 1 1.1.2 Envenornation ................................................................................................ 1 1.2 a-LATROTOXIN ................... ... ............................................................................ 3 1.2.1 Purification.......................................... .. ............................... ...... 3 1.2.2 Structure ..................................................................................... .... ............... 4 1.3 ACTION OF a-LATROTOXIN.............................................................................. 6 13. Transmitter release .............................................+.......................................... 6 1.3.2 Fine Structure ................................................................................................ 7 1.4 MECHANISM OF a-LATROTOXI N ACTION ....................................................... 8 1 A.1 Pore-Forming Hypothesis .............................................................................. 8 1.4.2 Receptor Hypothesis ................................................................................... 10 7.4.2.7 Neurexins .........................................................................+............. .......... 10 . 7.4.2.2 Latrophrlrn / CIRL ............................................................. ... ................ 1 2 1.4.2.2.1Sequence .................... .. ...................................................................... 12 1.4+2.2.2Biochemica/Propetties .................... ... ................................................... 14 ~.4.2.2.3~omoîoguesand Distribution ......................... .. ..*................**........*........1 5 1.5 PURPOSEOFTHISSTUDY .....................................,.... 15 1.5.1 Hypothesis ........................................ .. ....... 15 2 MATERIALS AND METHOOS ............................................................. ,. 16 2.1 ANIMALS AND EXPERIMENTAL TREATMENT .......... .... .........*......*............16 2.2 EXPERIMENTAL SOLUTIONS ......................................................................... 16 iii 2.3 IMMUNOCYTOCHEMISTRY..................... ........... ..,, ......................................... 16 2.4 DYE LOADiiUG .......................................................................................... 19 2.5 BLOCKADE OF SPONTANEOUS ACTION POTENTIALS ......................... ,., ..,20 2.6 BLOCKADE OF POSTJU NCTIONAL RECEPTORS ...... .... ......... ..................... -20 2.7 RECORDING TRANSMITTER RELEASE......................................................... 21 2.7.1 Analyzing Spontaneous Transrnitter Release ..............................................21 2.8 FLUORESCENCE MICROSCOPY................... .. ............................................ 23 2.8.1 Perisynaptic Schwann Cell Calcium ............................................................ 23 2.8.2 Image analysis............................................................................................. 23 2.8.3 Chemicals .................................................................................................... 24 2.9 CHEMICALS.................. ... ............................... ......... ,., .....*..., -2.1 0 STATISTICAL ANALYSI S ................................................................................ -24 -2.1 1 FIGURES .................................,., ...................................................................... 24 3 RESULTS .......................,, ....., ................................................................................... 25 3.1 IS CL? LOCATED AT THE FROG NMJ? .................................... ,..,. ................-25 3.2 DOES a-LTX INCREASE INTRACELLULAR ca2+WlTH TRANSMITTER RELEASE IN CFS? .................................................................................................... 27 3.2.1 1s the Tissue Bath Norninally Free of ca2'? ............................................... 27 3.2.2 a-LTX and Presynaptic caZ+........................................................................ 27 3.2.3 a-LTX and Transmitter Release ................................................................. 29 3.2.4 Dose-dependence of a-Ln< Action ............................................................. 29 3.3 DOES a-LTX RELEASE ca2' FROM ER? ................................................... -31 3.3.1 The Effect of U-73122 ..................... ,.,, .......... ,., .......................... 31 3.3.2 The Effect of Thapsigargin ................................................................. -31 3.4 DOES a-LTX RELEASE ca2+FROM MITOCHONDRIA? ................................ 36 3.4.1 The Effect of CCCP ................................................................................... 36 3.5 DOES a-LTX INCREASE INTRACELLULAR ca2+BY INCREASING INTRACELLULAR Na'? ................... ....... ...........................................................41 3.6 CYCLOSPORIN-A ..................................................................................~..........46 3.7 1s ca2+NECESSARY FOR a-LTX-INDUCED EXOCYTOSIS? ......................... 48 3.7.1 TheEffectofBAPTA-AM ............................................................................. 48 4 DISCUSSION ............................................................................................................. 52 ................. 4.1 SUMMARY ..................... .. ................. 52 4.2 a-LTX-STIMULATED TRANSMITTER RELEASE............................................. 52 4.2.1 Vesicle Depletion ........................................................................................ 53 4.2.2 Independence of Extracellular ca2+............................................................. 53 4.2.3 Dependence on Extracellular Divalent Cations............................................ 54 4.3 a-LTX STlMULATED ca2*MOBlLlZATlON ...................................................... 55 4.3.1 Ca2+ Signais In Other Ceif Systems ............................................................. 56 2+ 4.4 NEURONAL Ca STORES ................................................... ,, ............. ...., ........ 56 4.4.1 The Endoplasmic Reticulum ........................................................................57
Recommended publications
  • Download Product Insert (PDF)

    Download Product Insert (PDF)

    PRODUCT INFORMATION α-Bungarotoxin (trifluoroacetate salt) Item No. 16385 Synonyms: α-Bgt, α-BTX Peptide Sequence: IVCHTTATSPISAVTCPPGENLCY Ile Val Cys His Thr Thr Ala Thr Ser Pro RKMWCDAFCSSRGKVVELGCAA Ile Ser Ala Val Thr Cys Pro Pro Gly Glu TCPSKKPYEEVTCCSTDKCNPHP KQRPG, trifluoroacetate salt Asn Leu Cys Tyr Arg Lys Met Trp Cys Asp (Modifications: Disulfide bridge between Ala Phe Cys Ser Ser Arg Gly Lys Val Val 3-23, 16-44, 29-33, 48-59, 60-65) Glu Leu Gly Cys Ala Ala Thr Cys Pro Ser MF: C338H529N97O105S11 • XCF3COOH FW: 7,984.2 Lys Lys Pro Tyr Glu Glu Val Thr Cys Cys Supplied as: A solid Ser Thr Asp Lys Cys Asn Pro His Pro Lys Storage: -20°C Gln Arg Pro Gly Stability: ≥2 years • XCF COOH Solubility: Soluble in aqueous buffers 3 Information represents the product specifications. Batch specific analytical results are provided on each certificate of analysis. Laboratory Procedures α-Bungarotoxin (trifluoroacetate salt) is supplied as a solid. A stock solution may be made by dissolving the α-bungarotoxin (trifluoroacetate salt) in water. The solubility of α-bungarotoxin (trifluoroacetate salt) in water is approximately 1 mg/ml. We do not recommend storing the aqueous solution for more than one day. Description α-Bungarotoxin is a snake venom-derived toxin that irreversibly binds nicotinic acetylcholine receptors (Ki = ~2.5 µM in rat) present in skeletal muscle, blocking action of acetylcholine at the postsynaptic membrane and leading to paralysis.1-3 It has been widely used to characterize activity at the neuromuscular junction, which has numerous applications in neuroscience research.4,5 References 1.
  • Recent Advances in Research on Widow Spider Venoms and Toxins

    Recent Advances in Research on Widow Spider Venoms and Toxins

    Review Recent Advances in Research on Widow Spider Venoms and Toxins Shuai Yan and Xianchun Wang * Received: 2 August 2015; Accepted: 16 November 2015; Published: 27 November 2015 Academic Editors: Richard J. Lewis and Glenn F. King Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha 410081, China; [email protected] * Correspondence: [email protected]; Tel.: +86-731-8887-2556 Abstract: Widow spiders have received much attention due to the frequently reported human and animal injures caused by them. Elucidation of the molecular composition and action mechanism of the venoms and toxins has vast implications in the treatment of latrodectism and in the neurobiology and pharmaceutical research. In recent years, the studies of the widow spider venoms and the venom toxins, particularly the α-latrotoxin, have achieved many new advances; however, the mechanism of action of the venom toxins has not been completely clear. The widow spider is different from many other venomous animals in that it has toxic components not only in the venom glands but also in other parts of the adult spider body, newborn spiderlings, and even the eggs. More recently, the molecular basis for the toxicity outside the venom glands has been systematically investigated, with four proteinaceous toxic components being purified and preliminarily characterized, which has expanded our understanding of the widow spider toxins. This review presents a glance at the recent advances in the study on the venoms and toxins from the Latrodectus species. Keywords: widow spider; venom; toxin; latrotoxin; latroeggtoxin; advance 1. Introduction Latrodectus spp.
  • Α-Neurexins Together Withα2δ-1 Auxiliary Subunits Regulate Ca

    Α-Neurexins Together Withα2δ-1 Auxiliary Subunits Regulate Ca

    The Journal of Neuroscience, September 19, 2018 • 38(38):8277–8294 • 8277 Cellular/Molecular ␣-Neurexins Together with ␣2␦-1 Auxiliary Subunits 2ϩ Regulate Ca Influx through Cav2.1 Channels X Johannes Brockhaus,1* Miriam Schreitmu¨ller,1* Daniele Repetto,1 Oliver Klatt,1,2 XCarsten Reissner,1 X Keith Elmslie,3 Martin Heine,2 and XMarkus Missler1,4 1Institute of Anatomy and Molecular Neurobiology, Westfa¨lische Wilhelms-University, 48149 Mu¨nster, Germany, 2Molecular Physiology Group, Leibniz- Institute of Neurobiology, 39118 Magdeburg, Germany, 3Department of Pharmacology, AT Still University of Health Sciences, Kirksville, Missouri 63501, and 4Cluster of Excellence EXC 1003, Cells in Motion, 48149 Mu¨nster, Germany Action potential-evoked neurotransmitter release is impaired in knock-out neurons lacking synaptic cell-adhesion molecules ␣-neurexins (␣Nrxns), the extracellularly longer variants of the three vertebrate Nrxn genes. Ca 2ϩ influx through presynaptic high- ␣ ␦ voltage gated calcium channels like the ubiquitous P/Q-type (CaV2.1) triggers release of fusion-ready vesicles at many boutons. 2 Auxiliary subunits regulate trafficking and kinetic properties of CaV2.1 pore-forming subunits but it has remained unclear if this involves ␣Nrxns. Using live cell imaging with Ca 2ϩ indicators, we report here that the total presynaptic Ca 2ϩ influx in primary hippocampal ␣ neurons of Nrxn triple knock-out mice of both sexes is reduced and involved lower CaV2.1-mediated transients. This defect is accom- ␣ ␦ panied by lower vesicle release, reduced synaptic abundance of CaV2.1 pore-forming subunits, and elevated surface mobility of 2 -1 on axons. Overexpression of Nrxn1␣ in ␣Nrxn triple knock-out neurons is sufficient to restore normal presynaptic Ca 2ϩ influx and synaptic vesicle release.
  • Lllostridium Botulinum Neurotoxinl I H

    Lllostridium Botulinum Neurotoxinl I H

    MICROBIOLOGICAL REVIEWS, Sept. 1980, p. 419-448 Vol. 44, No. 3 0146-0749/80/03-0419/30$0!)V/0 Lllostridium botulinum Neurotoxinl I H. WJGIYAMA Food Research Institute and Department ofBacteriology, University of Wisconsin, Madison, Wisconsin 53706 INTRODUCTION ........ .. 419 PATHOGENIC FORMS OF BOTULISM ........................................ 420 Food Poisoning ............................................ 420 Wound Botulism ............................................ 420 Infant Botulism ............................................ 420 CULTURES AND TOXIN TYPES ............................................ 422 Culture-Toxin Relationships ............................................ 422 Culture Groups ............................................ 422 GENETICS OF TOXIN PRODUCTION ......................................... 423 ASSAY OF TOXIN ............................................ 423 In Vivo Quantitation ............................................ 424 Infant-Potent Toxin ............................................ 424 Serological Assays ............................................ 424 TOXIC COMPLEXES ............................................ 425 Complexes 425 Structure of Complexes ...................................................... 425 Antigenicity and Reconstitution .......................... 426 Significance of Complexes .......................... 426 Nomenclature ........................ 427 NEUROTOXIN ..... 427 Molecular Weight ................... 427 Specific Toxicity ................... 428 Small Toxin ..................
  • Mitochondrial Alarmins Released by Degenerating Motor Axon Terminals

    Mitochondrial Alarmins Released by Degenerating Motor Axon Terminals

    Mitochondrial alarmins released by degenerating PNAS PLUS motor axon terminals activate perisynaptic Schwann cells Elisa Duregottia, Samuele Negroa, Michele Scorzetoa, Irene Zornettaa, Bryan C. Dickinsonb,c,1, Christopher J. Changb,c, Cesare Montecuccoa,d,2, and Michela Rigonia,2 aDepartment of Biomedical Sciences, University of Padua, Padua 35131, Italy; bDepartment of Chemistry and Molecular and Cell Biology and cHoward Hughes Medical Institute, University of California, Berkeley, CA 94720; and dItalian National Research Council Institute of Neuroscience, Padua 35131, Italy Edited by Thomas C. Südhof, Stanford University School of Medicine, Stanford, CA, and approved December 22, 2014 (received for review September 5, 2014) An acute and highly reproducible motor axon terminal degeneration of nerve terminal degeneration (21). Indeed, these neurotoxins followed by complete regeneration is induced by some animal cause activation of the calcium-activated calpains that contribute to presynaptic neurotoxins, representing an appropriate and controlled cytoskeleton fragmentation (22). system to dissect the molecular mechanisms underlying degeneration Although clearly documented (4, 5, 20), the regeneration of and regeneration of peripheral nerve terminals. We have previously the motor axon terminals after presynaptic neurotoxins injection shown that nerve terminals exposed to spider or snake presynaptic is poorly known in its cellular and molecular aspects. Available neurotoxins degenerate as a result of calcium overload and mito- evidence indicates that, in general, regeneration of mechan- chondrial failure. Here we show that toxin-treated primary neurons ically damaged motor neuron terminals relies on all three cel- release signaling molecules derived from mitochondria: hydrogen lular components of the neuromuscular junction (NMJ): the peroxide, mitochondrial DNA, and cytochrome c.
  • Rope Parasite” the Rope Parasite Parasites: Nearly Every Au�S�C Child I Ever Treated Proved to Carry a Significant Parasite Burden

    Rope Parasite” the Rope Parasite Parasites: Nearly Every AuSC Child I Ever Treated Proved to Carry a Significant Parasite Burden

    Au#sm: 2015 Dietrich Klinghardt MD, PhD Infec4ons and Infestaons Chronic Infecons, Infesta#ons and ASD Infec4ons affect us in 3 ways: 1. Immune reac,on against the microbes or their metabolic products Treatment: low dose immunotherapy (LDI, LDA, EPD) 2. Effects of their secreted endo- and exotoxins and metabolic waste Treatment: colon hydrotherapy, sauna, intes4nal binders (Enterosgel, MicroSilica, chlorella, zeolite), detoxificaon with herbs and medical drugs, ac4vaon of detox pathways by solving underlying blocKages (methylaon, etc.) 3. Compe,,on for our micronutrients Treatment: decrease microbial load, consider vitamin/mineral protocol Lyme, Toxins and Epigene#cs • In 2000 I examined 10 au4s4c children with no Known history of Lyme disease (age 3-10), with the IgeneX Western Blot test – aer successful treatment. 5 children were IgM posi4ve, 3 children IgG, 2 children were negave. That is 80% of the children had clinical Lyme disease, none the history of a 4cK bite! • Why is it taking so long for au4sm-literate prac44oners to embrace the fact, that many au4s4c children have contracted Lyme or several co-infec4ons in the womb from an oVen asymptomac mother? Why not become Lyme literate also? • Infec4ons can be treated without the use of an4bio4cs, using liposomal ozonated essen4al oils, herbs, ozone, Rife devices, PEMF, colloidal silver, regular s.c injecons of artesunate, the Klinghardt co-infec4on cocKtail and more. • Symptomac infec4ons and infestaons are almost always the result of a high body burden of glyphosate, mercury and aluminum - against the bacKdrop of epigene4c injuries (epimutaons) suffered in the womb or from our ancestors( trauma, vaccine adjuvants, worK place related lead, aluminum, herbicides etc., electromagne4c radiaon exposures etc.) • Most symptoms are caused by a confused upregulated immune system (molecular mimicry) Toxins from a toxic environment enter our system through damaged boundaries and membranes (gut barrier, blood brain barrier, damaged endothelium, etc.).
  • Α-LATROTOXIN and ITS RECEPTORS: Neurexins

    Α-LATROTOXIN and ITS RECEPTORS: Neurexins

    P1: FQP April 4, 2001 18:17 Annual Reviews AR121-30 Annu. Rev. Neurosci. 2001. 24:933–62 Copyright c 2001 by Annual Reviews. All rights reserved -LATROTOXIN AND ITS RECEPTORS: Neurexins and CIRL/Latrophilins ThomasCSudhof¨ Howard Hughes Medical Institute, Center for Basic Neuroscience, and the Department of Molecular Genetics, The University of Texas Southwestern Medical Center at Dallas, Texas 75390-9111, e-mail: [email protected] Key Words neurotransmitter release, synaptic vesicles, exocytosis, membrane fusion, synaptic cell adhesion ■ Abstract -Latrotoxin, a potent neurotoxin from black widow spider venom, triggers synaptic vesicle exocytosis from presynaptic nerve terminals. -Latrotoxin is a large protein toxin (120 kDa) that contains 22 ankyrin repeats. In stimulating exocytosis, -latrotoxin binds to two distinct families of neuronal cell-surface receptors, neurexins and CLs (Cirl/latrophilins), which probably have a physiological function in synaptic cell adhesion. Binding of -latrotoxin to these receptors does not in itself trigger exocytosis but serves to recruit the toxin to the synapse. Receptor-bound -latrotoxin then inserts into the presynaptic plasma membrane to stimulate exocytosis by two dis- tinct transmitter-specific mechanisms. Exocytosis of classical neurotransmitters (glu- tamate, GABA, acetylcholine) is induced in a calcium-independent manner by a direct intracellular action of -latrotoxin, while exocytosis of catecholamines requires extra- cellular calcium. Elucidation of precisely how -latrotoxin works is likely to provide major insight into how synaptic vesicle exocytosis is regulated, and how the release machineries of classical and catecholaminergic neurotransmitters differ. by SCELC Trial on 09/09/11. For personal use only. INTRODUCTION Annu. Rev. Neurosci. 2001.24:933-962.
  • Cortactin: Coupling Membrane Dynamics to Cortical Actin Assembly

    Cortactin: Coupling Membrane Dynamics to Cortical Actin Assembly

    Oncogene (2001) 20, 6418 ± 6434 ã 2001 Nature Publishing Group All rights reserved 0950 ± 9232/01 $15.00 www.nature.com/onc Cortactin: coupling membrane dynamics to cortical actin assembly Scott A Weed*,1 and J Thomas Parsons2 1Department of Craniofacial Biology, University of Colorado Health Sciences Center, Denver, Colorado, CO 80262, USA; 2Department of Microbiology, Health Sciences Center, University of Virginia, Charlottesville, Virginia, VA 22903, USA Exposure of cells to a variety of external signals causes consists of a highly organized meshwork of ®lamentous rapid changes in plasma membrane morphology. Plasma (F-) actin closely associated with the overlying plasma membrane dynamics, including membrane rue and membrane (Small et al., 1995). In motile cells, F-actin microspike formation, fusion or ®ssion of intracellular underlies two main types of protrusive membranes; vesicles, and the spatial organization of transmembrane lamellipodia, which contain short ®laments of F-actin proteins, is directly controlled by the dynamic reorgani- linked into orthogonal arrays and ®lopodia, comprised zation of the underlying actin cytoskeleton. Two of bundled, crosslinked actin ®laments (Rinnerthaler et members of the Rho family of small GTPases, Cdc42 al., 1988). Work within the last decade has demon- and Rac, have been well established as mediators of strated that Rac and Cdc42, two members of the Rho extracellular signaling events that impact cortical actin family of small GTPases, govern lamellipodia and organization. Actin-based signaling through Cdc42 and ®lopodia formation (Hall, 1998). Cdc42 and Rac play a Rac ultimately results in activation of the actin-related pivotal role in the transmission of extracellular signals protein (Arp) 2/3 complex, which promotes the forma- that induce cortical cytoskeletal rearrangement (Zig- tion of branched actin networks.
  • Ketabton.Com (C) Ketabton.Com: the Digital Library

    Ketabton.Com (C) Ketabton.Com: the Digital Library

    Ketabton.com (c) ketabton.com: The Digital Library ټوکسيکولوژي اثـــر: Hans Marquardt Siegfried G. Schafer Roger O. McClellan Frank Welsch ژباړن: عبدالکريم توتاخېل ۴۹۳۱ل کال (c) ketabton.com: The Digital Library د کتاب نوم: ټوکسيکولوژي ژباړن: عبدالکريم توتاخېل خـپرونـدی: د افغانستان ملي تحريک، فرهنګي څانګه وېــبپـاڼـه: www.melitahrik.com ډيـزايـنګر: ضياء ساپی پښتۍ ډيزاين: فياض حميد چــاپشمېـر: ۰۱۱۱ ټوکه چــاپـکـــال: ۰۹۳۱ ل کال/ ۵۱۰۲م د تحريک د خپرونو لړ: )۱۰( (c) ketabton.com: The Digital Library فهرست عنوان مخ مخکنۍ خبرې...................................................................................................الف د ژباړن سريزه.........................................................................................................ب لمړی فصل )کیمیاوي او بیولوژيکی عاملین(..............................................1 کیمیاوي عاملین ..............................................................................................1 بیولوژيکي عاملین ......................................................................................۲۶ دويم فصل )طبعي مرکبات(..........................................................................۵۸ پېژندنه ..............................................................................................................۵۸ د حیواناتو زهر)وينوم( او وينوم ..................................................................۵۲ د پروتوزوا او الجیانو توکسینونه...............................................................1۶۱ مايکوتوکسینونه .............................................................................................1۱۱
  • Neurotoxicity in Snakebite—The Limits of Our Knowledge

    Neurotoxicity in Snakebite—The Limits of Our Knowledge

    Review Neurotoxicity in Snakebite—The Limits of Our Knowledge Udaya K. Ranawaka1*, David G. Lalloo2, H. Janaka de Silva1 1 Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka, 2 Liverpool School of Tropical Medicine, Liverpool, United Kingdom been well described with pit vipers (family Viperidae, subfamily Abstract: Snakebite is classified by the WHO as a Crotalinae) such as rattlesnakes (Crotalus spp.) [58–67]. Although neglected tropical disease. Envenoming is a significant considered relatively less common with true vipers (family public health problem in tropical and subtropical regions. Viperidae, subfamily Viperinae), neurotoxicity is well recognized Neurotoxicity is a key feature of some envenomings, and in envenoming with Russell’s viper (Daboia russelii) in Sri Lanka and there are many unanswered questions regarding this South India [9,68–75], the asp viper (Vipera aspis) [76–82], the manifestation. Acute neuromuscular weakness with respi- adder (Vipera berus) [83–85], and the nose-horned viper (Vipera ratory involvement is the most clinically important ammodytes) [86,87]. neurotoxic effect. Data is limited on the many other acute neurotoxic manifestations, and especially delayed Acute neuromuscular paralysis is the main type of neurotoxicity neurotoxicity. Symptom evolution and recovery, patterns and is an important cause of morbidity and mortality related to of weakness, respiratory involvement, and response to snakebite. Mechanical ventilation, intensive care, antivenom antivenom and acetyl cholinesterase inhibitors are vari- treatment, other ancillary care, and prolonged hospital stays all able, and seem to depend on the snake species, type of contribute to a significant cost of provision of care. And ironically, neurotoxicity, and geographical variations. Recent data snakebite is common in resource-poor countries that can ill afford have challenged the traditional concepts of neurotoxicity such treatment costs.
  • (I) Post-Junctional Block by Alpha-Bungarotoxin

    (I) Post-Junctional Block by Alpha-Bungarotoxin

    CHARACTERISTICS OF NONDEPOLARIZING NEUROMUSCULAR BLOCK: (I) POST-JUNCTIONAL BLOCK BY ALPHA-BUNGAROTOXIN CHINGMUH LEE, DENNIS CHEN, AND RONALD L. KATZ CLASSICALLY, a neuromuscular block characterized by lack of fasciculation, fade of the train-of-four 1,2 fade of tetanus, post-tetanic facilitation, and antagonism by the de-curarizing agents, is called a "nondepolarizing" block. In view of the current understanding that d-tubocurarine (dTc) and pancuronium are pre-junctionally active, :~ one wonders whether these characteristics of "nondepolarizing" block may be partially attributable to pre-junctional effects. We therefore searched for signs of a pure post-junctional non-depolarizing block. Alpha-bungarotoxin (a-BuTX), a polypeptide with a molecular weight of ap- proximately 8,000, purified from snake venoms, has been known to produce a long- lasting nondepolarizing neuromuscular block by "irreversible" binding to the post- junctional acetylcholine receptors 4.5,~,7 or receptor sites sensitive to d-tubocurarine (dTc) and acetylcholine (Ach). s,~ Because of its high affinity and specificity of binding with the Ach receptors, it has been used in tagging, solubilization, extrac- tion, and purification of the Ach receptors from muscle and from the electric organ of eel, s,~176and in tagging of the Ach receptors in neurones, n When purified, it has no detectable pre-junctional effects, anticholinesterase activity 4,G: or ganglion- blocking property in vivo (personal observation). We therefore examined the neuromuscular blocking characteristics of this unique drug in detail. M ETHOD Twelve healthy cats, 3.2 to 3.8 kilograms in weight, were subjected to acute experiments. Anaesthesia was induced with pentobarbitone (50 mg/kg body weight) intraperitoneally.
  • Action of Black Widow Spider Venom on Quantized Release Of

    Action of Black Widow Spider Venom on Quantized Release Of

    Proc. Nat!. Acad. Sci. USA Vol. 76, No. 2, pp. 991-995, February 1979 Neurobiology Action of black widow spider venom on quantized release of acetylcholine at the frog neuromuscular junction: Dependence upon external Mg2+ (neurotoxin/membrane permeability/divalent cations/potassium/osmotic pressure) STANLEY MISLER AND WILLIAM P. HURLBUT Department of Biophysics, The Rockefeller University, New York, New York 10021 Communicated by Frank Brink, Jr., November 22, 1978 ABSTRACT Black widow spider (Latrodectus tredecim- and glucosamine at pH 6.5 as a Na+ substitute), the swelling of guttatus) venom (BWSV) increases several hundredfold the the nerve terminals that usually accompanies BWSV treatment frequency of occurrence of miniature end-plate potentials was decreased but the depletion of vesicles-and apparent ex- (Fmepp) at frog neuromuscular junctions bathed in Ringer's so- lutions containing either Ca2+ or Mg2t, but it has little effect haustion of transmitter still occurred. These authors suggested on Fmepp at junctions bathed in modified Ringer's solution that BWSV may indeed increase the Na+ and Ca2+ perme- containing 1-2 mM ethylene glycol bis(,B-aminoethyl ether) ability of the terminals but that BWSV stimulated release "by N,N'-tetraacetic acid (EGTA) but no Ca2+ or Mg2+. When Mg2+ a mechanism which may not involve its ionophore property" is added to preparations that have been treated with BWSV in (7). the modified solution, Fme increases exponentially with time. Recent results of other workers, however, suggest that di- Fmepp falls again to low values when the Mg2+ is removed. The valent cations exert a powerful effect on transmitter release rate constant of the exponential rise is proportional to [Mg2+Jo in the range 1-4 mM, and the threshold [Mg2+J0 is 0.1-0.5 mM.