Document 3J4QXZRx393bjj414mGGbZV0J

ER-8Z70-A REV. 3-64 E. I. pu Po n t d e Ne mo u r s S Co mpa n y WILMINGTON, DELAWARE 1989$ EMPLOYEE RELATIONS DEPARTMENT HASKELL LABORATORY TOXICOLOGY AND INDUSTRIAL MEDICINE Haskell Laboratory Newark, Delaware 19711 June 8, 1985 Dr. Sven a. Ellasson Department of Neurology Washington University School of Medicine St, Louis, Missouri Dear Dr. Ellassoni We certainly appreciate your interest in the problems which we are encountering in our nerve conduction experiments. If these can be solved we hope to apply your method to nerves, obtained at autopsy, from rats used for toxicological tests. Since our telephone conversation last week, we have tried nerves obtained from untreated ** rats which were stunned then given a pneumothorax. To our surprise these nerves behaved much as those obtained from the chloroformed animals; this suggests that our techniques, as well as the chloroform, are causing trouble. As a result, I am taking advantage of your kindness and describing, as briefly as possible, our techniques and equipment. Recording Equipment - Tektronix Type 561 A oscilloscope, single beam, with Type 2A65 differential amplifier and Type 2B67 time base. Voltage sensitivity 1 1 mV to 20 V per division (1 cm) oscilloscope screen; sweep speed; 1 juSeo. to 5 seconds per division oscilloscope screen. As a rule we operate at 2-5 mV and 0.2 mSeo. per division. Sweep triggered by stimulus. Stimulator - Grass SD 5 square wave stimulator with built in isolation unit. Fresh nerve* threshold stimulus 0.2 to 0.4 V when stimulus duration is 0,06 mSec. Maximal stimulus* about 2-4 V but is frequently difficult to determine when response is superimposed on shock artefact. Conduction Chamber - Harvard Apparatus Company, with platinum electrodes rearranged so as to be 5 apart. All of the equipment, with the exception of the tank containing 95 per cent oxygen and 5 per cent carbon dioxide, is in a constant temperature room maintained at 98.5 * 0.5F. The humidity, however, is low. The Ringer-Locke used to moisten the nerve during dissection. BETTER THINGS FOR BETTER LIVING . . . THROUGH CHEMISTRY N37524 Dr, Even d, Eliaasa - H 2vm S* 196$ or in which nerved are "etored**, in oxygenated with tho 9$ per sent oxygen and 3 per cent carbon dioxide mixture for >0 minutes or longer prior to use, Xneldently, the sodium chloride in tht Rlnger-Leeke io Merck preparation for biological work, and glasa-diatilled water we* used, Sew* of tho Mnger-loeke m placed in the conduction chamber almost to the height of the electrodes, and the oxygen-carbon dioxide mixture passed through it to provide a moist atmosphere of 9$ per seat oxygen end 5 per sent carbon diesSMirfO* the nerve* fhe oiueiter 'ie'. kept covered* m m alternative to the Ringer-leek* in the chamber we have tried mineral oil throng which the oayg#earben dioxide mixture .is bubbled; enough oil to never the nerve it need. to amid Jerhii^ and stretching, I do west of the dissection with a tard-farker scapel, use fled forceps to pm ligature* (him mercerised cotton) under the nerve at either end, and scissors to free the mala trunk fro* mama and underlying tissue, fe avoid slipping, I tio the ligature* rather tight. My faeteet tine, from removing rat free chloroform <r stunning it, to mounting nerve la chamber, la 4 to 5 minutes, X eaa try to shorten this time. Even thoee nervea taken from atuaaed rate and mounted jMeedlately in the ahhdtr have failed to ahow any opontaneous aotivity.* the following questions trouble ue, 1. thy do apparently '`healthy*' nervea am marked decreases la spike height and conduction velocity 10 to 15 minutes after mounting? Shi* deterioration may he accompanied by progressively increasing influence of shoek artefact as though the artefact mere prolonged on the nerve response. Can drying of nerve cause thia? 2, Would monophaalfi recording be bettor than diphasic? 1 have found it difficult to crush an area without stretching the nerve as the tissue sticks to the nemostats or to limit a km to an adequately localised area, especially when recording electrodes are close together, Is there a mere reliable method of killing the area under the distal electrode? 3* is there any way to .mark or identify on the nerve tissue the locations of the stimulus cathode and the proximal recording electrode so that conduction distance can be measured accurately? DUP050044066 . fmlJ,i 1 ms fir. Sven . filiation *3- June 196s # is it ttwml to nsaaare conduction tins tmm tbs start of tbs aboek artefact (we stalls# that tins includes excitation tiwt)t fhe conduction velecitlea which vm mm recording, serves 411st mounted* Inflection "Vbleeity ......-fteg....... 'Peak velocity ' ukm- stunned mm B~Q 30-B ebloroforiaed fists 55+ 53KMI Our "p#aieM velocity ma8ur>ennts are wore consistent tins ear IsHestles velocity seasuresenttt* 5 is it possible to reduce the duration of the shoek artefact so that aessureis^iits can be made on conduction distances shorter that 1 centimeter? it bfee* tits artefact is so prolonged as to interfere with the response when tbs om&mtXm ditben is I mttiNberj this say be associated with a deteriorating serve. d. Is epoxy cement, well -get# nourotoxie? With the idee that we mid save tie and. serve damage by leaving tbs nerve in position, wa ad* a piatimm electrode set, inelwiing both sttwslstisg and mwm&m tlfetrod**, which seals be slipped under the nerve, the sires prt held in position and insulated by epoxy swiawt. Ihr have teen disappointing bet seed itarthsp checks. X aw enclosing capita of a few of oar photographs of nerve responses in mm they nay provide Wtwmtim* I apologise for the length of this letter bet X have bees enable to reduce it and still describe ear methods. Sincerely ye*ire. Mary E. JtasfleM, Ph.D. Physiologist *i|/dyb Enclosures DUP050044067