Some animal models and their probability of extrapolation to man

Neur05c1ence• 8106ehav10ra1Rev1ew5.V01. 15. pp. 25-34. v Per9am0n Pre55p1c, 1991. Pr1nted1n the U.5.A.

0149-7634/91 $3.00 + .00

50me An1ma1 M0de15 and 7he1r Pr06a6111ty 0f Extrap01at10n t0 Man 0770

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W0L7HU15, 0. L. 50me an1ma1m0de15 and the1rpr06a61110• 0f extrap01at10n t0 man. NEUR05C1 8108EHAV REV 15(1) 2534, 1991.--A num6er 0f examp1e5 0f exper1menta1 m0de15 are pre5ented wh1ch are 5u6d1v1ded 1nt0 m0de15 that pr0v1de re5u1t5 w1th a ••h19h•" 0r a ••m0derate•• pr06a6111ty f0r (4ua11tat1ve)extrap01at10n t0 man. M0de15 w1th a h19h pred1ct1ve va1ue f0r man are th05e that pr0duce re5u1t5 that can 6e d1rect1y ver1f1ed 1n man 0r human 0r9an5, 1n c0ntra5t w1th m0de15 that have a m0derate pred1ct1ve va1ue, where 0ne ha5 t0 re1y 0n 51m11ar1t1e50r ana1091e5 0f 519n5 and 5ympt0m5 6etween man and the an1ma1 m0de1. M0de15 w1th 10w pr06a6111ty 5h0u1d 6e rejected. An1ma1 m0de15 Neur0t0x1c1ty

Extrap01at10nt0 man

DNA dama9e

Neur0mu5cu1ar tran5m15510n

Dermat0t0x1c1ty

m0r5. F0r th05e w0rk1n9 1n the f1e1d 0f ch011ne5tera5e-1nh161t1n9 0r9an0ph05phate5, 1e550n5 1n 6e1n9 carefu1 can 6e 1earned fr0m the pu2211n9 effect5 0f car60xy1e5tera5e5 (6, 27-29), wh1ch are a6undant 1n rat5 6ut pract1ca11y a65ent 1n man, 0r fr0m a 5tudy 0f 50-ca11ed 50man 51mu1at0r5 wh1ch 5eem 0n1y effect1ve 1n rat5.(52, 57, 59~13, 66, 67, 69). Neverthe1e55, 1t appear5 that f0r a f1r5t 5creen the rat 0r m0u5e 5eem t0 6e accepted a16e1t n0t 1dea1 an1ma15 t0 te5t p0tent1a1 dru95 0r t0 a55e55 t0x1c1ty 0f chem1ca15.0ne c0u1d a150 5ay that fr0m a c05t/6enef1t v1ewp01nt we have hard1y any 0ther 0pt10n5. Yet 1t w0u1d 6e 1ntere5t1n9 t0 kn0w h0w many dru95 f0r the treatment 0f human5 we have m155ed 6ecau5e they were n0t act1ve 1n the5e r0dent5. 51m11ar1y, 0ne m19ht a5k h0w many u5efu1 1ndu5tr1a1 chem1ca15 have 6een rejected 0n the 6a515 0f t0x1c effect5 1n r0dent5 that w0u1d never have 5h0wn up 1n man.

PERHAP5 1t 15 fa1r t0 5tart 6y 5tat1n9 that n0 5C1ent1f1C 11teratUre 15 m0re C0nfU51n9 than the 11teratUre 0n eXtrap01at10n 0f an1ma1 data t0 man. F0r eXamp1e, Fre1re1Ch et a1. (13) C0mpared the t0X1C1ty 0f 18 ant1CanCer dru95 1n 5ma11 r0dent5, Ca1CU1ated the re5U1t5 0n a m9/m 2 6a515, and C0nC1Uded that ••t0X1C1t1e5 0f p0tent1a1 ant1cancer dru95 c0rre1ate remarka61y c105e1y w1th the re5u1t5 1n man.•• Ca1a6re5e (5) c0nc1uded that n0tw1th5tand1n9 phy5101091ca1 and 610chem1ca1 d1fference5, va11d pred1ct10n5 fr0m rat t0 man can 6e made u51n9 appr0pr1ate extrap01at10n5. 1n c0ntra5t, 05er (38) made exp11c1t1y c1ear that "•Man 15 N0t a 819 Rat.•• A m0re 6a1anced appr0ach 15 f0110wed 1n a recent v01ume (39) 0n ••Human R15k A55e55ment, 7he R01e 0f An1ma1 5e1ect10n and Extrap01at10n,•• wh1ch 9ave 32 expert5 1n th15 f1e1d the 0pp0rtun1ty t0 5upp0rt the1r v1ew5 w1th data. A c0mm0n 0p1n10n wa5 n0t reached. H0wever, f0r th05e wh0 u5e, a5 we d0, m05t1y rat5 a5 exper1menta1 an1ma15, 1t m19ht 6e 50mewhat enc0ura91n9 t0 read that when t0x1c 1e510n5 cau5ed 6y 20 d1fferent c0mp0und5 were c0mpared 1n 7 5pec1e5 1nc1ud1n9 man, and when 60th p051t1ve and ne9at1ve react10n5 were c0n51dered, th15 9ave a pred1ct10n fr0m rat t0 man 0f 71%. 7he re5u1t5 w1th m0nkey5 were 80%, 6ut f0r 0ther 5pec1e5 11ke the d09, ra661t and 9u1nea p19 the pred1ct1ve va1ue5 were far 1e55 (H0ttend0rf, 5ame v01ume). 7he p1cture that emer9e5 fr0m the5e rep0rt5 15 that n0th1n9 can rep1ace 50und exper1menta1 ev1dence; c0mpar150n 0f dru9 d15p051t10n 1n human5 and an1ma15 ha5 n0t pr0ven t0 6e u5efu1 and 0ne 5h0u1d 6eware 0f dec1510n5 6a5ed 501e1y 0n the mathemat1ca1 extrap01at10n 0f an1ma1 610a55ay data, a1th0u9h 50me 5er10u5 appr0ache5 (16) may 6e he1pfu1.51m11ar1y, 0ne 5h0u1d n0t 6e m151ed 1nt0 6e11ev1n9 that ana1y515 0f t0x1c0k1net1c d1fference5 w111 re501ve a11 pr061em5 w1th re5pect t0 the d1fference5 1n t0x1c1ty 6etween 5pec1e5. Prudence rema1n5 the key w0rd. After a11, 0ne 5h0u1d n0t f0r9et that rat5 d0 n0t d1e fr0m card1ac 1nfarct10n 0r 5tr0ke (60th ma1n cau5e5 0f death 1n man) and many 5tra1n5 0f r0dent5 are r1dd1ed w1th 5pec1f1c d15ea5e5, 5uch a5 p1tu1tary 0r te5t1cu1ar tu-

E X 7 R A P 0 L A 7 1 0 N CLA55E5 1n v1ew 0f a11 the5e data and c0nfu51n9 0p1n10n5 1t w0u1d 6e pre5umptu0u5 t0 pre5ent 0ur5e1ve5 a5 expert5 1n th15 f1e1d. 7heref0re, the pre5ent rep0rt 15 re5tr1cted t0 a num6er 0f appr0ache5 1n 0ur 0wn 1a60rat0ry and 15 f0cu55ed 0n ••the pr06a6111ty that the re5u1t5 06ta1ned w1th the5e m0de15 w111 have 4ua11tat1ve va11d1ty f0r man.•" A1th0u9h 4uant1tat1ve a5pect5 are certa1n1y taken 1nt0 c0n51derat10n when ch0051n9 a m0de1, we refra1n fr0m def1n1te 5tatement5 c0ncern1n9 4uant1tat1ve extrap01at10n t0 human5 51nce, part1cu1ar1y 1n the f1e1d 0f t0x1c0109y, 0ne ha5 t0 re1y 0n rep0rt5 0f un1ntent10na1 exp05ure5 t0 d05e5 0f c0mp0und5, m05t1y m1xture5, wh1ch are n0t exact1y kn0wn. F0r the 5ake 0f the pre5ent rep0rt the pr06a6111ty f0r extrap01at10n wa5 ar61trar11y d1v1ded 1nt0 tw0 c1a55e5, 1.e., ••h19h 0r m0derate.•• M0de15 w1th a ••10w•• pr06a6111ty f0r extrap01at10n t0 man are u5ua11y a6and0ned. A. 7E57 M0DEL5 W17H A H16H PR08A81L17Y F0R EX7RAP0LA710N 70 MAN 7he5e are te5t m0de15 Wh1Ch pr0dUCe re5U1t5 that Can 6e d1-

25

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rect1y ver1f1ed 6y de116erate exp05ure 0f human5 0r human t155ue5. Examp1e5 are m0de15 that te5t mechan15m5 0f act10n c0mm0n t0 a11 5pec1e5, 5uch a5 5een, e.9., 1n rad1at10n. 0 r m0de15 t0 1nve5t19ate fa5t-act1n9 c0mp0und5 wh1ch depend 0n1y t0 a 5ma11er de9ree 0n the way 1n wh1ch they are d15tr16uted 0r e11m1nated, 5uch a5 50me a1ky1at1n9 a9ent5 (e.9., 5u1fur mu5tard). A150, a m0de1 that ha5 6een deve10ped 1n 0ur 1a60rat0ry wh1ch can 6e u5ed t0 te5t neur0mu5cu1ar tran5m15510n 6e10n95 t0 th15 cate90ry.

human 6100d 1rrad1ated 1n v1tr0

556 1n 6100d 0f the m0u5e 1rrad1ated 1n v1tr0 0 r 1n v1v0

1.40

1.4

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1.0 0.80 0.8 0.60

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Rad1at10n and A1ky1at1n9 A9ent5 1n 0ur department 0f 610chem15try, 1mmun0chem1ca1 meth0d5 emp10y1n9 m0n0c10na1 ant160d1e5 are deve10ped f0r the 4ua11tat1ve and 4uant1tat1ve a55e55ment 0f rad1at10n dama9e t0 DNA and the eff1cacy 0f rad10pr0tect1ve c0mp0und5.7he5e meth0d5 1nc1ude 51n91e-ce11 ana1y515 v1a 1a5er-5can f1u0re5cence m1cr05c0py and 1ma9e pr0ce551n9.8y c0mpar1n9 the DNA dama9e 1n wh1te 6100d ce115 and 5evera1 0r9an5 0f 1rrad1ated m1ce w1th the DNA dama9e 1n wh1te 6100d ce115 0f 1rrad1ated pat1ent5, 1t 15 expected that va11d pred1ct10n5 can 6e made w1th re5pect t0 the DNA dama9e 1n the 0r9an5 0f the5e pat1ent5 and, at a 1ater 5ta9e, the effect5 0f rad10pr0tect1ve mea5ure5. A150, 1n a m111tary c0nf11ct 1n wh1ch nuc1ear dev1ce5 are u5ed, 1t 15 0f em1nent 1mp0rtance f0r the 5ur9e0n t0 kn0w, 0n the 6a515 0f a 5ma11 6100d 5amp1e, whether a w0unded 501d1er 0r c1v111an ha5 6een exp05ed t0 a 1etha1 0r n0n1etha1 d05e 0f rad1at10n (1, 40-42). Current1y, the deve10pment 0f th15 techn14ue ha5 reached a 5ta9e 1n wh1ch 0ne DNA 1e510n can 6e detected am0n95t 106 unchan9ed DNA m01ecu1e5. 50me 0f the exper1menta1 re5u1t5 06ta1ned dur1n9 the m0de1-deve10pment are 5h0wn 1n F19. 1. F0r fa5t-act1n9 a1ky1at1n9 a9ent5 a 51m11ar appr0ach 15 f0110wed: c0mpar150n take5 p1ace w1th pat1ent5 under901n9 cyt05tat1c therapy w1th the 5ame c1a55 0f c0mp0und5. A d051metry meth0d f0r the retr05pect1ve ver1f1cat10n 0f exp05ure t0 mu5tard 9a5 0n the 6a515 0f DNA-m0d1f1cat10n 15 6e1n9 deve10ped (43-45).

7

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4

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5 5 6 repa1r 1n mUr1ne 6100d 1n v1tr0 0 r 1n v1v0 (4 6y} 120

556 repa1r 1n h u m a n 6100d 1rrad1ated 1n V1tr0 100

100 80

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60 40

40

20 20 0

10

20

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10

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t1me (m1n) 1n v1tr0

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F16. 1. A c0mpar150n 0f DNA 51n91e 5trand 6reak5 (558) mea5ured 1n 1ymph0cyte5 4 m1n after 1rrad1at10n0f the m0u5e 1n v1v0 0r m0u5e 6100d 1n v1tr0 (t0p 1eft), 0r after 1rrad1at10n0f human 6100d 1n v1tr0 (t0p r19ht). 7he 60tt0m 1eft 9raph 5h0w5 the repa1r that take5 p1ace 1n m0u5e 1ymph0cyte5 when 1rrad1ated 1n v1v0 0r 1n v1tr0, and the 60tt0m r19ht f19ure 5h0w5 the 5ame f0r 1ymph0cyte5 0f human 6100d 1rrad1ated 1n v1tr0. Mean • 5.E.M. 0f at 1ea5t 4 determ1nat10n5per p01nt. (6raph made ava11a61e 6y 6. P. van der 5chan5.)

Neur0mu5cu1ar 7ran5m15510n An0ther examp1e, fr0m 0ur pharmac0109y and t0x1c0109y department, f0cu55e5 0n effect5 0f chem1ca15 0n neur0mu5cu1ar tran5m15510n. Ar0und 1980 we deve10ped a f1e1d 5t1mu1at10n techn14ue f0r wh1ch 0ur e1ectr0n1c 9r0up c0n5tructed a new type 0f 5t1mu1at0r. U51n9 the e1ectr0de5 and the type 0f mu5c1e preparat10n5 5h0wn 1n F19. 2 th15 ena61ed u5 t0 te5t mu5c1e 5tr1p5 1n a11 5pec1e5 fr0m m0u5e t0 man. 7he pr1nc1p1e wa5 6a5ed 0n the c1a551ca1 phy5101091ca1 phen0men0n that 5t1mu1u5 thre5h01d5 0f mu5c1e5 are h19her than th05e 0f nerve5, wh1ch wa5 a9a1n dem0n5trated 6y 06ta1n1n9 5t1mu1u5 5tren9th/durat10n curve5 fr0m mu5c1e 5tr1p5 0f 5evera1 5pec1e5. An examp1e 0f a 5tren9th/durat10n curve fr0m human extema1 1nterc05ta1 mu5c1e 5tr1p5 15 5h0wn 1n F19. 3. 1t dem0n5trate5 that w1th 5t1mu11 5h0rter than 4-5 1x5 the mu5c1e w111 n0t 6e d1rect1y 5t1mu1ated and 5upramax1ma1 5t1mu1at10n 0f nerve5 can 6e app11ed, mu5c1e c0ntract10n5 can 6e re915tered and deduct10n5 a60ut the eff1cacy 0f neur0mu5cu1ar tran5m15510n can 6e made. 8 y that t1me we had 1nve5t19ated a num6er 0f mu5c1e 5tr1p5 fr0m 5evera1 5pec1e5; m1ce ( n = 8 ) , rat5 (n>100), 9u1nea p195 (n>50), d095 (n = 16), rhe5u5 m0nkey5 (n = 30) and human5 (n = 74). 7he ma1n u5e 0f th15 m0de1 50 far wa5 t0 te5t the eff1cacy where6y 5evera1 new 0x1me5 (5uch a5 H1-6, H5-6, H 6 6 - 1 2 , H 6 6 - 5 2 ) re5t0red tetan1c c0ntract10n5 that had 6een a60115hed 6y p0150n1n9 the preparat10n5 w1th 0r9an0ph05phate5 (46, 47, 65, 66). At a 1ater 5ta9e we a150 te5ted neur0mu5cu1ar tran5m15510n 1n

the marm05et 1n v1tr0 a5 we11 a5 1n v1v0, wh1ch appeared t0 6e an accepta61e m0de1 f0r man (58). An examp1e 0f the type 0f te5t5 that were carr1ed 0ut 15 5h0wn 1n F19. 4. 7hu5 th15 m0de1 a110w5 d1rect ver1f1cat10n acr055 5pec1e5 1nc1ud1n9 man. Ma1n advanta9e5 0f th15 m0de1 are that dur1n9 th0rax 5ur9ery p1ece5 0f 1nterc05ta1 mu5c1e can 6e rem0ved w1th0ut any harm t0 the pat1ent and that fr0m 0ne 51n91e p1ece 0f mu5c1e 5evera1 mu5c1e 5tr1p5 0f 80-120 m9 can 6e d155ected, pr0v1ded the mu5c1e f16er5 are n0t cut dur1n9 the rem0va1 pr0ce55. 8. 7E57 M0DEL5 W17H A M0DERA7E PR08A81L17Y F0R EX7RAP0LA710N 7 0 MAN

7he5e are m0de15 u5ed t0 1nve5t19ate effect5 wh1ch cann0t 0r can 0n1y 6e part1y ver1f1ed 1n man. Hence, extrap01at10n t0 man take5 p1ace 0n the 6a515 0f 51m11ar1ty rather than 0n the 6a515 0f d1rect ver1f1cat10n a5 ment10ned under A. Va11dat10n 0f the m0de1 1n human5 0ccur5, e.9., 6y te5t1n9 n0nt0x1c c0mp0und5, 0r t0x1c c0mp0und5 1n very 10w d05e5. 1n 0ther w0rd5, a 900d 9uarantee (a5 f0r the m0de15 under A) that a d1fferent c0mp0und w111exh161t the 5ame effect5 d0e5 n0t ex15t. Examp1e5 are m0de15 f0r 5k1n penetrat10n, 5k1n dama9e and 50me m0de15 f0r neur0t0x1c1ty.

5k1n Penetrat10n F0r the purp05e 0f th15 rep0rt 5k1n penetrat10n 15 def1ned a5 the

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F16. 2. 7he e1ectr0de5 (1eft) and type5 0f mu5c1e 5tr1p preparat10n5 fr0m the d1aphra9m (m1dd1e) and externa1 1nterc05ta1 mu5c1e (r19ht). F0r 1nterc05ta1 mu5c1e preparat10n5 fr0m 5ma11an1ma15 we u5ed n0t a 51n91e mu5c1e 6und1e, 6ut 5evera1 1nterc05ta1 mu5c1e5 m0unted vert1ca11y 1n a 1adder-11ke fa5h10n a5 5h0wn 1n the f19ure 0n the r19ht. D1men510n5 are 1n mm.

t0ta1 pr0ce55 fr0m the percutane0u5 app11cat10n 0f a c0mp0und t0 1t5 appearance 1n the 6100d c1rcu1at10n. Def1ned 1n th15 way a) 1t 1nc1ude5 uptake 1nt0 the derma1 1ymph ve55e15, 6) 1t take5 1nt0 c0n51derat10n that c0mp0und5 may 6e 5t0red 1n the 5k1n (e.9., c0rt1c01d5; ca1cu1at10n5 0f 5k1n penetrat10n 0n the 6a515 0f d15appearance fr0m a percutane0u51y app11ed dep0t may 91ve a fa15e, t00 h19h, rate 0f penetrat10n 6ecau5e many 5ter01d5 are 5t0red f0r 5evera1 day5 1n the 5k1n) and c) 1t acc0unt5 f0r hydr01y515 0r meta6011c chan9e 0f the c0mp0und dur1n9 1t5 pa55a9e thr0u9h the 5k1n. F0r the 5ake 0f 6r1efne55 we d0 n0t d15cu55 here the 1ar9e d1fference5 1n penetrat10n 6etween d1fferent 5k1n area5, the effect 0f per5p1rat10n (hydrat10n 0f the 5tratum c0rneum), the effect5 0f temperature 0n penetrat10n, etc. 7 0 0ur kn0w1ed9e n0 m0de15 ex15t that take a11 the5e var1a61e5 1nt0 acc0unt. Dur1n9 the 1a5t decade5, c0mpar150n 0f 5k1n penetrat10n 1n v1tr0 and 1n v1v0 0f 5evera1 c0mp0und5 1n d1fferent 5pec1e5 1nc1ud1n9 man ha5 6een 1nve5t19ated 6y a num6er 0f auth0r5 (3, 4, 51, 64). 7he 1n v1tr0 m0de15, u5ua11y 0f the d1ffu510n ce11 type, are 1nade4uate even when human 5k1n 15 u5ed 51nce the derma1 cap111ary netw0rk 15 n0t funct10na1, and 6ecau5e 1n pract1ca11y a11 pu6115hed exper1ment5 the c0mp051t10n 0f the art1f1c1a1 rec1p1ent f1u1d 15 n0nphy5101091ca1 and c1rcu1ate5 a10n9 the 1nner 5urface 0f the 5k1n 1n a way and at a 5peed that 15 4u1te un11ke the 5k1n 1n 51tu. 0 u r 0wn exper1ence (unpu6115hed data) c0ncur5 w1th th05e 0f We5ter and Ma16ach (64) 5h0w1n9 that 11tt1e 4uant1tat1ve a9reement 6etween the 1n v1v0 and 1n v1tr0 m0de15 ex15t5. 7he 1n v1v0 m0de15 are u5ua11y 1a60r10u5, 51nce the 6100dc0ncentrat10n curve5 06ta1ned after percutane0u5 app11cat10n 0f the c0mp0und are the re5u1t 0f a c0m61nat10n 0f penetrat10n, t155ue d15tr16ut10n and 61nd1n9, meta60115m and e11m1nat10n. 1n pr1nc1p1e, the 1mp0rtance 0f the5e pr0ce55e5 ha5 t0 6e e5ta6115hed 4uant1tat1ve1y f0r each c0mp0und. 1n an1ma1 exper1ment5 there are way5 6y wh1ch part 0f the5e pr061em5 may 6e c1rcumvented. F0r examp1e, 0ne may m1m1c the 6100d-c0ncentrat10n curve5 06ta1ned after percutane0u5 app11cat10n 6y an 1ntrava5cu1ar 1nfu510n a55um1n9 that, 0nce the c0mp0und ha5 reached the 6100d, 1t5 fate

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F16. 4. An examp1e 0f the exper1ment5 perf0rmed t0 te5t neur0mu5cu1ar funct10n, 1n th15 ca5e 0f human 1nterc05ta1 mu5c1e 1n v1tr0. At the t0p 0f the f19ure the pr0cedure 15 5chemat1ca11y5h0wn. 7e5t5 A, 8 and C each c0n515t 0f f0ur 3-5 610ck5 0f 5upramax1ma1 tetan1c 5t1mu1at10nat fre4uenc1e5 0f 25, 50, 100 and 200 H2 re5pect1ve1y. 1mmed1ate1y after te5t A (c0ntr01) the ch011ne5tera5e-1nh161t0r5at1n (upper trace) 0r 50man (10wer trace) were added t0 the med1um. After wa5h0ut 0f the 5urp1u5 1nh161t0rafter 30 m1n, neur0mu5cu1ar tran5m15510n wa5 pract1ca11y t0ta11y 1nh161ted 1n 60th exper1ment5 a5 ev1denced 6y the 1mp05516111tyt0 5u5ta1n a tetan1c c0ntract10n (te5t 8). 7he re5u1t5 0f te5t C 5h0w that exp05ure t0 the 0x1me H1-6 f0r 30 m1n re5u1t5 1n an a1m05t c0mp1ete rec0very 0f neur0mu5cu1ar funct10n 1nh161ted 6y 5ar1n, wherea5 n0 rec0very wa5 065erved after 1nh161t10n6y 50man. At the end 0f each exper1ment d-tu60curar1ne wa5 added t0 the med1um t0 5h0w that 5t1mu1at10n had taken p1ace v1a the nerve: up0n 5t1mu1at10n the mu5c1e c0ntract10n 9radua11y d15appeared. N0t 5h0wn 15 that up0n the 5u65e4uent 5t1mu1at10n w1th 10n9er1a5t1n95t1mu11. 1ead1n9 t0 d1rect 5t1mu1at10n 0f the mu5c1e, n0rma1 c0ntract10n5 0ccurred 1nd1cat1n9that the mu5c1e wa5 1ntact.

15 1ndependent 0f the r0ute 0f entry. 7h15 techn14ue ha5 6een u5ed w1th rea50na61e 5ucce55 1n 0ur 1a60rat0ry 1n 9u1nea p195, 6ut 15 5t111 a 1a60r10u5 0ne. 0 t h e r attempt5 1n 0ur 1a60rat0ry t0 deve10p a m0de1 6a5ed 0n human 5k1n tran5p1anted 0nt0 c0n9en1ta11y thymu51e55 m1ce (53,54) d1d n0t appear t0 6e u5efu1 f0r th15 5pec1f1c purp05e (56) due t0 a d1fferent re5p0n51vene55 0f the m0u5e derma1 cap111ar1e5, a1th0u9h 1t m19ht 6e a m0de1 t0 te5t the eff1cacy 0f ant1herpet1c a9ent5 (55). An0ther meth0d 15 the ••d15appearance meth0d~; 5k1n penetrat10n c0mp0und5 can 6e te5ted 6y mea5ur1n9 the rate 0f d15appearance fr0m a percutane0u51y app11ed dep0t. W1th n0nt0x1c c0mp0und5, th15 meth0d can a150 6e app11ed 1n human5. H0wever, the re5u1t5 06ta1ned pr0v1de n0 9uarantee that 0ther c0mp0und5 penetrate at the 5ame rate. 1n 0ther w0rd5, a 900d m0de1 f0r man t0 mea5ure 5k1n penetrat10n 0f c0mp0und5, prefera61y expre55ed 1n m9/cm2/m1n, d0e5 n0t ex15t. 51nce the a60ve-ment10ned rep0rt5 (4, 51, 64) 1nd1cate that there 15 a rea50na61e 51m11ar1ty 6etween p19 and human 5k1n, a recent m0de1 6a5ed 0n the 1501ated perfu5ed p0rc1ne 5k1n f1ap, a5 pr0p05ed 6y M0nte1r0-R1v1ere and K1n9 (33), may have certa1n advanta9e5.7h1nk1n9 a10n9 the 5ame 11ne5, 1n 1988 we 5tarted t0 1nve5t19ate the p05516111t1e5 0f the 1501ated 6100d-perfu5ed p0rc1ne ear a5 a m0de1. We 6e11eve that the 1501ated 6100d-perfu5ed p0rc1ne ear m0de1 ha5 5evera1 advanta9e5 0ver the m0de1 pr0p05ed 6y M0nte1r0-R1v1ere and K1n9, name1y a) that 5ur9ery t0 c0n5truct an ade4uate 5k1n f1ap 15 n0t nece55ary, 6) that the preparat10n 15 perfu5ed w1th the natura1 (0xy9enated) rec1p1ent f1u1d, 1.e., p19 6100d, wh1ch c1rcumvent5 4ue5t10n5 re9ard1n9 the 501u6111ty 0f a 91ven c0mp0und 1nt0 an art1f1c1a1 med1um a5 u5ed 6y M0nte1r0-R1v1ere and K1n9, and c) 51nce p19 ear5 are 51au9hterh0u5e de6r15, the m0de1 make5 n0 u5e 0f exper1menta1 an1ma15, the ear5 c05t n0th1n9 and are 06ta1na61e 1n 1ar9e 4uant1t1e5. A techn1ca1 d15advanta9e 15 that the c0ncentrat10n5 0f the c0mp0und

have t0 6e mea5ured 1n 6100d. M05t 0f the w0rk 50 far ha5 6een c0ncentrated 0n a) f1nd1n9 a phy5101091ca1 temperature (30 ---0.5°C), 6y mea5ur1n9 the ear 5k1n temperature 1n v1v0 0f 4 p195 0f the 5ame 5tra1n under n0n5tre55ed c0nd1t10n5, 6) 1nve5t19at1n9 whether we had t0 u5e c0n5tant f10w 0r c0n5tant pre55ure. 8 y 1a5er-d0pp1er mea5urement5 0f the derma1 6100d f10w 1n v1v0 and 1n v1tr0 1t wa5 f0und that a perfu510n pre55ure 0f 60 mmH9 pract1ca11y 9uaranteed a phy5101091ca1 derma1 f10w dur1n9 at 1ea5t 4 h, c) te5t1n9 whether the re5p0n51vene55 0f the derma1 ve55e15 wa5 n0rma1 (and n0t a6errant a5 1n the nude m0u5e) 6y u51n9 150x5uprene 0r n0rep1nephr1ne, wh1ch c0mp0und5 cau5ed the expected va50d11atat10n and va50c0n5tr1ct10n re5pect1ve1y, d) 91uc05e-c0n5umpt10n 0f the preparat10n, a5 a mea5ure 0f the v1a6111ty 0f the ear 0ver the h0ur5. After NaF add1t10n (1nh161t0r 1n Kre65 cyc1e) 91uc05e c0n5umpt10n 5t0pped c0mp1ete1y, 1nd1cat1n9 that the d15appearance 0f 91uc05e wa5 due t0 c0n5umpt10n and n0t t0 mere t155ue 61nd1n9 (11). A1th0u9h the eva1uat10n 0f th15 1501ated 6100d-perfu5ed p0rc1ne ear preparat10n 15 n0t c0mp1ete, we have 5tarted t0 te5t 50me c0mp0und5 f0r wh1ch data 0n 5k1n penetrat10n 1n human5 are ava11a61e, the re5u1t5 50 far 100k pr0m151n9 and 5u99e5t that 1n the near future we may have a m0de1 that w111 pr0duce re5u1t5 wh1ch, w1th a m0derate pr06a6111ty, can 6e extrap01ated t0 man.

5k1n Dama9e 51nce the m0rph0109y 0f the 5k1n 0f m05t an1ma15 15 4u1te d1fferent fr0m that 0f human5 we have, dur1n9 the pa5t 5 year5, 6een 1nve5t19at1n9 the u5e 0f human 5k1n a5 5tart1n9 mater1a1 t0 deve10p m0de15 that pr0duce re5u1t5 w1th pred1ct1ve va1ue f0r d1rect effect5 0n the 5k1n 0f man. Apart fr0m the fact that we have 6een recent1y 5ucce55fu1 1n cu1tur1n9 5k1n e4u1va1ent5 that were 4u1te u5efu1 f0r aut0tran5p1antat10n (M01 et a1., t0 6e pu6115hed),

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F16. 5. H15t01091ca1 preparat10n5 0f c0ntr01 5k1n (1eft) and 5k1n exp05ed f0r 10 m1n t0 5aturated vap0r 0f 5u1phur mu5tard (r19ht) after 24 h0ur5 1n 0r9an cu1ture. 7he 5eparat10n 0f the ep1derm15 fr0m the derm15 15 c1ear1y v15161e. A fu11-610wn 6115ter d0e5 n0t deve10p 1n v1tr0. (6raph made ava11a61e 6y M. A. E. M01.)

re5earch ha5 6een f0cu55ed 0n a m0de1 6a5ed 0n 0r9an cu1ture5 0f fu11 th1ckne55 human 5k1n f0r the extrap01at10n 0f effect5 0f a9ent5 that cau5e 5k1n dama9e t0 the human 5k1n 1n 51tu. 5uch 0r9an cu1ture5, wh1ch under the pr0per c0nd1t10n5 have a 5ta61e 91uc05e c0n5umpt10n f0r 48 h0ur5, are 6e1n9 u5ed t0 5tudy therapy a9a1n5t a9ent5 that cau5e 6115ter5, 5uch a5 heat, mu5tard vap0r (30) and, very recent1y, 1ew151te. When exp05ed t0 the5e a9ent5, a c1ear 5eparat10n 15 065erved h15t01091ca11y 6etween derm15 and ep1derm15 (a1th0u9h a fu11 f1u1d-f111ed 6115ter d0e5 n0t deve10p, 5ee F19. 5) 1n a t1me c0ur5e wh1ch 15 pract1ca11y 1dent1ca1 t0 that 5een 1n v1v0. F0r a further ana1y515 0f pure ep1derma1 effect5, human kerat1n0cyte cu1ture5 are u5ed (31). 1n th15 re5pect 1t may 6e w0rthwh11e t0 n0te that, when f1ve c0mp0und5 (5D5, tr16uty1t1n, anthra11n, ph059ene 0x1me and 5u1fur mu5tard) were te5ted at a f1xed d05e-1eve1, rank1n9 0f the 5ever1ty 0f the 1e510n5 f0und, a5 def1ned 6y the ce11u1ar 1eaka9e 0f 1actate dehydr09ena5e and p0ta551um 0r 6y chan9e5 0f 91uc05e c0n5umpt10n, c0rre1ated rea50na61y we11 w1th the dermat0t0x1c1ty 0f the5e c0mp0und5 rep0rted 1n the 11terature (32). 1n 5h0rt, a m0de1 t0 a55e55 d1rect (1.e., w1th0ut 1nterference fr0m 0ther pr0ce55e5 1n the 60dy) 5k1n dama9e 15 6e1n9 va11dated. 1n a11 ca5e5 we have u5ed fre5h hea1thy 6rea5t 5k1n fr0m fema1e5 under901n9 c05met1c 5ur9ery, wh1ch we have 6een a61e t0 06ta1n 1n fa1r 4uant1t1e5 6y the exce11ent c00perat10n 0f 10ca1 5ur9e0n5. 1n the near future 1t 15 p1anned t0 perf0rm a 5tudy 1n wh1ch human and p0rc1ne 5k1n are c0mpared. Neur0t0x1c1t3,

Apart fr0m c0ntr0111n9 5evera1 phy5101091ca1 funct10n5, the ma1n funct10n 0f the nerv0u5 5y5tem 15 n0t t0 9enerate act10n p0tent1a15 0r t0 re1ea5e tran5m1tter5, 6ut t0 re9u1ate and 5teer 6ehav10r. 1f th15 5tatement 15 accepted, the 1091ca1 c0n5e4uence 15 that mea5urement5 0f 6ehav10r are 1nd15pen5a61e 1f 0ne want5 t0 1nve5t19ate the effect5 0f chem1ca15 0n the funct10n5 0f the nerv0u5 5y5tem. Neur0phy5101091ca1 mea5urement5 1n part1cu1ar, 6ut a150 pharmac0/t0x1c0k1net1c5, neur0chem15try and neur0path0109y may 6e he1pfu1 t0 5tudy the under1y1n9 cau5e5 0f the funct10na1 d15tur6ance5. H0wever, env15a91n9 the num6er 0f and 1nteract10n5 6e-

tween the funct10na1 d0ma1n5 that the nerv0u5 5y5tem c0ver5, the ma9n1tude 0f the pr061em c0nfr0nt1n9 u5 6ec0me5 v15161e and 0ne may 4ue5t10n whether we w111 ever 6e a61e t0 deve10p ade4uate m0de15 that a110w d1rect extrap01at10n 0f 6ehav10ra1 effect5 f0und 1n an1ma15 t0 th05e 1n man. 1n fact, the 51tuat10n 15 n0t that pe551m15t1c. A1th0u9h 1t 15 un11ke1y that an1ma1 m0de15 f0r, e.9., creat1v1ty, fanta5y, dream5, apprec1at10n 0f art 0r even headache w111ever 6e deve10ped, 50me 6ehav10ra1 m0de15 mea5ur1n9 def1c1t5 1n m0t0r, 5en50ry and c09n1t1ve funct10n5 revea1 4ua11tat1ve effect5 that have 50me pred1ct1ve va1ue when c0mpared w1th 51m11areffect5 065erved 1n human5, Perhap5 we may even 6e 5119ht1y 0pt1m15t1c when 100k1n9 at the current1y ava11a61e ran9e 0f therapeut1ca11y effect1ve p5ych0pharma1091ca1 dru95 wh1ch 0therw15e w0u1d n0t have ex15ted. When 100k1n9 at neur0t0x1c1ty, h0wever, the 51tuat10n 15 m0re d1ff1cu1t. A1th0u9h a h19h1y needed chan9e 0f att1tude 0f the auth0r1t1e5 1n recent year5 15 detecta61e, pr05pect1ve neur0t0x1c1ty te5t1n9 0f new c0mp0und5 (6r0u9ht 0n the market f0r u5e 6y the p0pu1at10n and the 1ndu5try) 15 5t111 n0t re4u1red 1n m05t c0untr1e5. Data and m0de15 are 1ack1n9. When 0ne want5 t0 deve10p m0de15 f0r extrap01at10n 0ne ha5 t0 re1y 0n ca5e5 0f acc1denta1 acute 0r chr0n1c 0verexp05ure, a1th0u9h 50me acute exper1ment5 w1th human v01unteer5 t0 a55e55 effect5 0f m0derate1y t0x1c c0mp0und5 (m05t1y 501vent5) 0n m0t0r, 5en50ry and c09n1t1ve funct10n5 have 6een perf0rmed (9,15). Creat1n9 an1ma1 m0de15 that deve10p a 5ympt0mat0109y 51m11ar t0 that 0f chr0n1ca11y exp05ed human5, e.9., 1ndu5tr1a1 w0rker5, 15 an even m0re d1ff1cu1t ta5k, 51nce typ1ca11y the5e w0rker5 have 6een exp05ed 5e4uent1a11y 0r 51mu1tane0u51y t0 a var1ety 0f c0mp0und5. 51nce 0ur 1a60rat0ry had 50me exper1ence w1th t0x1c a9ent5 and neur0pharmac01091ca1 and 6ehav10ra1 re5earch, a decade a90 we dec1ded t0 5tart the deve10pment 0f an1ma1 m0de15 f0r a) acute effect5 0f 10w d05e5 0f h19h1Y t0x1c a9ent5 wh1ch f0r eth1ca1 rea50n5 cann0t 6e te5ted 1n human5, and 6) 5u6c11n1ca1 effect5 0f chr0n1c exp05ure t0 c0mp0und5 f0r (p0tent1a1) u5e 1n the 1ndu5try. a) Acute neur0t0x1c effect5 f0110w1n9 exp05ure t0 10w d05e5 0 f h19h1y t0x1c a9ent5. 50 far, m0de1 deve10pment f0r acute neur0-

t0x1c1ty ha5 6een f0cu55ed 0n the 6ehav10ra1 and neur0phy510109-

30

1ca1 effect5 0f 10w d05e5 0f ch011ne5tera5e (CHE) 1nh161t0r5 and/0r pretreatment 0r therapeut1c dru95 a9a1n5t 1nt0x1cat10n w1th the5e 1nh161t0r5. W1th CHE 1nh161t0r5 1t wa5 f0und 1n rat5 that three 0ut 0f the f1ve 1nh161t0r5 te5ted cau5ed d05e-dependent 6ehav10ra1 effect5 far 6e10w a d05e that cau5ed 0vert 5ympt0m5 (68). Current1y, 51m11ar exper1ment5 are carr1ed 0ut w1th marm05et5 u51n9 r060t-a5515ted hand-eye c00rd1nat10n and v15ua1 d15cr1m1nat10n te5t5 (5ee F19. 6A and 8 , W01thu15 et a1., 1n pr09re55). 1f app11ca61e t0 human5, the re5u1t5 m19ht he1p t0 exp1a1n the re1at1ve h19h 1nc1dence 0f ••p110t err0r•• acc1dent5 a550c1ated w1th depre55ed CHE act1v1ty 1n a9r1cu1tura1 p110t5 (48,71). 7 h e 065ervat10n 6y Durham et a1. (10) that n0 menta1 effect5 were n0ted 1n the a65ence 0f phy51ca1 519n5 1n a 5urvey 0f 68 exp05ed 1n5ect1c1de w0rker5 p1u5 187 w0rker5 w1th 5u5pected 0r9an0ph05phate (0P) p0150n1n9 m19ht 6e attr16uted t0 the type 0f te5t5 app11ed, t0 the (un5pec1f1ed) t1me 1nterva1 6etween exp05ure and te5t1n9 and perhap5 t01erance phen0mena, 0r t0 the nature 0f the 0 P w1th re5pect t0 1t5 penetrat10n 1nt0 the centra1 nerv0u5 5y5tem (CN5). M0re0ver, very recent 5tud1e5 1n 0ur 0wn 1a60rat0ry (10) exam1ned perf0rmance 0f 129 pe5t1c1de w0rker5 and 64 matched c0ntr01 per50n5 0n a c0mputer12ed 6attery 0f neur0p5ych01091ca1 te5t5. Under c0ntr011ed c0nd1t10n5, the pe5t1c1de w0rker5 5h0wed a 519n1f1cant decrea5e 0f perf0rmance 1n the funct10na1 d0ma1n5 ••attent10n•• (n0ta61y the 51mp1e React10n 71me 7e5t) and ••perceptua1 c0d1n9•• (n0ta61y the 5ym601-D191t 5u65t1tut10n 7e5t). N0 519n1f1cant d1fference5 1n 9enera1 hea1th and 5u6ject1ve c0mp1a1nt5 were f0und 6etween the tw0 9r0up5.7he5e re5u1t5 c1ear1y 1nd1cate that unn0t1ced chem1ca11y 1nduced neur0p5ych01091ca1 def1c1t5 may 6e pre5ent 1n the a65ence 0f phy51ca1 effect5. 1n v1ew 0f p055161e effect5 0n d1fferent funct10na1 d0ma1n5 0f the nerv0u5 5y5tem, the effect5 0f c0mp0und5 5h0u1d 6e te5ted 1n a 6attery 0f te5t5; a 51n91e 6ehav10ra1 te5t m19ht 1ead t0 err0ne0u5 c0nc1u510n5. 5uch a 5ma11 6attery 0f te5t5 ha5 recent1y a150 6een u5ed t0 a55e55 p055161e 51de effect5 0f therapeut1c dru95 0r c0m61nat10n5 there0f (70). 5u6c11n1ca1 neur0t0x1c effect5 f0110w1n9 chr0n1c exp05ure. 1n 0ur 1a60rat0ry tw0 pr09ram5 0n the neur0funct10na1 effect5 0f chr0n1c exp05ure t0 chem1ca15 5tarted a1m05t 51mu1tane0u51y; 0ne pr09ram f0cu55ed 0n the deve10pment 0f an1ma1 m0de15 f0r the ear1y detect10n 0f neur0t0x1c1ty, the 0ther 0n the deve10pment 0f meth0d5 f0r the detect10n 0f 5u6c11n1ca1 neur0t0x1c effect5 1n man. 1t 15 expected 1n the 10n9 run that the5e tw0 pr09ram5 w111 6e mutua11y 6enef1c1a1. 1n an1ma15, data 0n the effect5 0f chr0n1c exp05ure t0 chem1ca15 0n nerv0u5 5y5tem funct10n are rare, part1cu1ar1y when exp05ure 0ccur5 v1a 1nha1at10n. 7h15 15 under5tanda61e 6ecau5e 5uch 5tud1e5 are expen51ve, yet hard t0 c0mprehend when 0ne read5

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that 1n the U5A a10ne 50me 49 m11110n t0n5 0f 501vent5 are pr0duced annua11y t0 wh1ch an e5t1mated 9.8 m11110nAmer1can w0rker5 are p0tent1a11y exp05ed (37). 7hu5, there were at 1ea5t tw0 rea50n5 t0 5tart 5uch a pr09ram: the 5carce data and the num6er 0f w0rker5 that may 6e exp05ed. A th1rd rea50n 15 that 1n the future new c0mp0und5 need t0 6e te5ted f0r the1r p0tent1a1 neur0t0x1c effect5; centra1 and per1phera1 nerv0u5 dy5funct10n 1n w0rker5 exp05ed t0 2-t-6uty1a20-2-hydr0xy-5-methy1hexane (8HMH) c0u1d have 6een av01ded, 1f ade4uate premarket te5t1n9 had taken p1ace (19,50). 51nce the 5tart 0f 0ur pr09ram ar0und 1980, 5evera1 m0de15 have 6een, and 5t111 are, eva1uated t0 detect effect5 at 10w exp05ure 1eve15 0n 9enera1 m0t0r act1v1ty, 0n m0t0r c00rd1nat10n, 0n 9r1p 5tren9th, 0n var10u5 parameter5 0f a d15crete tr1a1 tw0-ch01ce d15cr1m1nat10n ta5k and 0n nerve c0nduct10n ve10c1ty. 7e5t an1ma15 50 far have 6een rat5. Per10d1c neur0funct10na1 mea5urement5 t00k p1ace n0t 0n1y dur1n9 chr0n1c exp05ure5 0f u5ua11y 18 week5 0r m0re, f0110wed 6y mea5urement5 dur1n9 a p05texp05ure per10d 0f 5evera1 week5, 6ut 1n 50me ca5e5 a150 f0110w1n9 acute exp05ure5.7he maj0r1ty 0f the exper1ment5 have 6een carr1ed 0ut w1th 501vent vap0r5, a1th0u9h 0ther c0mp0und5 have 6een u5ed a5 we11 [5ee, e.9., (21,25)]. 50 far c0mp0und5 have 6een u5ed that are kn0wn t0 6e neur0t0x1c 1n man (2,49). At pre5ent, the effect5 0f chr0n1c 1nha1at10n t0 9a5 chr0mat09raph1caUy c0ntr011ed 501vent vap0r5, at three c0ncentrat10n 1eve15 p1u5 c0ntr015, have 6een a55e55ed 1nc1ud1n9 n-hexane (20), C52 (23), tr1ch10rethy1ene (22), 5tyrene (24) and wh1te 5p1r1t5 (26). 7 w 0 examp1e5 0f the type 0f re5u1t5 06ta1ned are 91ven here, 0ne fr0m an acute and the 0ther fr0m a chr0n1c exper1ment. An examp1e 0f the re5u1t5 0f an acute exper1ment 15 the f0110w1n9. Rat5 were exp05ed f0r 8 h0ur5 t0 0 (c0ntr01), 1200, 2400 0r 4800 m91m 3 ( = appr0x. 800 ppm) 0f wh1te 5p1r1t5 vap0r, c0rre5p0nd1n9 t0 tw0, f0ur 0r e19ht t1me5 the 0ccupat10na1 5afety 1eve15 1n 7he Nether1and5 re5pect1ve1y. Perf0rmance 0f an ac4u1red tw0ch01ce d15crete tr1a1 v15ua1 d15cr1m1nat10n ta5k wa5 mea5ured 1mmed1ate1y f0110w1n9 the term1nat10n 0f exp05ure. F19ure 7 5h0w5 that the5e c0ncentrat10n5 cau5ed a d05e-dependent 1ncrea5e 1n the 1atency 0f re5p0nd1n9 0f 47%, 96% 0r 156% re5pect1ve1y. 1n th15 c0ntext 1t 15 1ntere5t1n9 t0 n0te that 6am6era1e and h15 c0-w0rker5 (14) f0und w1th wh1te 5p1r1t5 that exp05ure 0f v01unteer5 f0r 50 m1n t0 4000 m9/m 3 cau5ed a 519n1f1cant 1ncrea5e 1n re5p0n5e 1atenc1e5 1n a 51mp1e react10n ta5k. After an exp05ure per10d 1a5t1n9 5even h0ur5, C0hr et a1. (7) a150 f0und 519n1f1cant effect5 0n re5p0n5e 5peed at c0ncentrat10n5 0f 600 m9/m 3 0r m0re. An examp1e 0f a re5u1t fr0m a chr0n1c exper1ment 15 taken fr0m an exper1ment w1th C52. 1n th15 exper1ment rat5 were exp05ed t0 a1r, 75, 225 0r 700 ppm C52 f0r 8 h/day, 5 day5 per

FAC1N6 PA6E F16. 6. (A t0p and A 60tt0m) 0n the t0p a ph0t09raph and 0n the 60tt0m an art15t1c 1mpre5510n 0f the r060t-a5515ted d15crete tr1a1 tw0-ch01ce v15ua1 d15cr1m1nat10n ta5k f0r marm05et5.7he r060t arm (F) 15 51tuated 6etween tw0 te5t pane15 0n a rack wh1ch 15 tran5p0rted 0n a ra11-track (J) a10n9 a r0w 0f te5t ca9e5 w1th marm05et5. 1n each 0f the da11y 40 tr1a15, 6y mean5 0f a 5uct10n tu6e (6), the r060t-arm p1ck5 a 11tt1ep1ece 0f a mar5hma110w-11ke reward fr0m the tray (H) and tran5p0rt5 th15 reward t0 a p1ace 6eh1nd the (c105ed) w1nd0w. After a rand0m per10d a 6r1ef t0ne 15 pre5ented, wh1ch 5erve5 a5 a n0nd1rect10na1 ••attent10n•• 519na1. At the 5ame m0ment the 1eft 0r r19ht (1n a 4ua51-rand0m 0rder) a-numer1ca1 d15p1ay (A) 5w1tche5 ••0n•• and 0n each 51de a hand1e (C) 15 1ntr0duced 1nt0 the ca9e, w1th a 5ma11 cha1n (D) attached t0 draw attent10n, thr0u9h h01e5 1atera1 0f the v15ua1 d15p1ay5. 7he an1ma1 15 tra1ned t0 pu11 the hand1e at the 51de where the a-numer1ca1 d15p1ay 15 111um1nated, whereup0n the w1nd0w-d00r (8) 0n that 51de 0f the part1t10n (1) 511de50pen and the an1ma1can retr1eve the reward. 7he a-numer1ca1 d15p1ay55w1tche5 ••0ff,•• the hand1e5 are retracted and a new tr1a1can 5tart. 1f the an1ma1 d0e5 n0t dr0p the reward th15 15 5c0red a5 a ••h1t.•• Var10u5 6ehav10ra1 parameter5, 5uch a5 ••ch01ce t1me,•• ••m0t0r 5peed,•• ••attempt5•• and 5ucce5fu1 0r un5ucce5fu1 retr1eva1 0f the reward are re915tered aut0mat1ca11y and fed 1nt0 a per50na1 c0mputer. (13) An examp1e 0f the effect5 0f d1fferent d05e5 0f tw0 car6arnate5 1n marm05et5 0n the perf0rmance 0f a prev10u51y ac4u1red d15crete tr1a1 tw0-ch01ce v15ua1 d15cr1m1nat10nta5k. 7he d15cr1m1nat10nperf0rmance 15 expre55ed a5 a percenta9e 0f the max1mum num6er 0f "•h1t5•• (5ee A) that can 6e reached dur1n9 the 40 da11y tr1a15. 0 n 5e5510n 4 5a11ne0r the car6amate5 were 1njected 1ntramu5cu1ar1y;te5t1n9 6e9an 20 m1n after the phy505t19m1neand 30 m1n after the pyr1d05t19m1ne 1nject10n. 7he data 0f 1nd1v1dua1an1ma15 (1nterrupted 11ne5) are c0mpared w1th the mean (•.+ 5.E.M.) perf0rmance 0f a11 13 an1ma15 te5ted 50 far dur1n9 the da11y 5e5510n5 1-3 and 5-8 (5011d 11ne5). M0re0ver, a11 an1ma15 rece1ved a 5a11ne 1nject10n 20 0r 30 m1n 6ef0re 5e5510n 2.

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week f0r 36 week5. Fr0m F19. 8 1t 15 c1ear that the h19he5t c0ncentrat10n cau5ed a decrement 1n m0t0r c00rd1nat10n 5tart1n9 at appr0x1mate1y 12 week5 and per515t1n9 f0r at 1ea5t 6 week5 after exp05ure wa5 term1nated. 1t 15 11ke1y that the5e effect5 are 11nked t0 a per1phera1 and perhap5 a150 centra1 neur0pathy cau5ed 6y C 5 2 . 7 h e chan9e5 1n nerve c0nduct10n ve10c1ty and the m0rph0109y 0f the per1phera1 nerve5 f0und 1n the5e an1ma15 (26) have a150 6een rep0rted f0r man (49). 7he meth0d5 and re5u1t5 fr0m the5e 5tud1e5 are d15cu55ed 1n re1at10n t0 the1r 519n1f1cance f0r man 1n a recent rev1ew (26) and d0 n0t need t0 6e repeated here. Ku119 p01nt5 at the 9r0w1n9 acceptance 0f neur0funct10na1 meth0d5 and c0nc1ude5: • . . . the 9r0w1n9 emp1r1ca1 data6a5e dem0n5trat1n9 60th the 5en51t1v1ty and app11ca6111ty 0f the5e meth0d5 t0 chr0n1c 5tud1e5. . . . w111 c0nt1nue t0 pr0v1de ev1dence f0r the 1mp0rtance 0f neur06ehav10ra1 meth0d5 1n the 1dent1f1cat10n and further under5tand1n9 0f the act10n5 0f chem1ca15 0n the nerv0u5 5y5tem.•• REVER5E E X 7 R A P 0 L A 7 1 0 N 7e5t5 1n human5 d0 n0t fa11 under the 5c0pe 0f th15 meet1n9, 51nce extrap01at10n 15 n0t needed. Yet 1t w111 6e c1ear that 5tud1e5 0n the detect10n 0f ear1y 5ympt0m5 0f neur0t0x1c1ty 1n human5 are n0t 0n1y 1mp0rtant f0r the1r 0wn 5ake and f0r re9u1at0ry a9enc1e5, 6ut w111 a150 1ncrea5e the data6a5e f0r human5 and w111 6e 0f he1p 1n 1dent1fy1n9 the type5 0f funct10na1 d15tur6ance5 that we have t0 100k f0r 1n an1ma15. 50me rec0mmendat10n5 (8) 5u99e5t that te5t5 1n human5 5h0u1d 1nc1ude funct10na1 a55ay5 that fac111tate extrap01at10n t0 para11e1 5tud1e5 1n an1ma15. A5 5uch, 0ne c0u1d ca11 the5e exper1ment5 nece55ary t0 ach1eve ••rever5e extrap01at10n,•• 1.e., the man t0 an1ma1 m0de1. Hence, they are 6r1ef1y ment10ned here. 1n 0ur 5tud1e5 1n human5 we have 6een en9a9ed 1n eva1uat1n9 the u5e 0f a 6attery 0f c0mputer12ed neur0p5ych01091ca1 te5t5 (the Neur06ehav10ra1 Eva1uat10n 5y5tem 0r NE5-6attery), the 50-ca11ed paper and penc11 te5t5 pr0p05ed 6y the W H 0 , a 115t 0f 4ue5t10nna1re5, 0r c0m61nat10n5 there0f (12,18). 1n 50me ca5e5 5u65et5 0f the5e 5er1e5 0f te5t5 were 1nve5t19ated 1n acute exper1ment5 after adm1n15trat10n 0f what 15 11ke1y t0 6e the m05t c0n5umed 501vent, 1.e., ethy1 a1c0h01 (17). 7he 6u1k 0f the eff0rt5, h0wever, wa5 f0cu55ed 0n the eva1uat10n 0f the app11ca6111ty, 5en51t1v1ty and va11d1ty 0f the5e techn14ue5. M05t 0f the w0rk 0n a num6er 0f 1ar9e-5ca1e 5tud1e5 15 f1n15hed and the re5u1t5 w111 6e pu6115hed 5h0rt1y. 7he5e 5tud1e5 were carr1ed 0ut 1n 0ccupat10na11y exp05ed

pa1nter5 (H0015ma et a1., t0 6e pu6115hed), uraem1a pat1ent5 awa1t1n9 k1dney tran5p1antat10n (R02eman, t0 6e pu6115hed; Emmen and R02eman, t0 6e pu6115hed) and pe5t1c1de w0rker5 (Emmen et a1., t0 6e pu6115hed). 1n each 0f the5e 5tud1e5 the 5u6ject5 were n0t 0n1y te5ted w1th the a60ve-ment10ned neur0p5ych01091ca1 meth0d5, 6ut were a150 exam1ned w1th neur0phy5101091ca1 techn14ue5, 5uch a5 nerve c0nduct10n ve10c1ty (35), a 4uant1tat1ve E E 6 meth0d and ev0ked p0tent1a15 (J0nkman et a1., t0 6e pu6115hed; de Weerd, t0 6e pu6115hed; R02eman, t0 6e pu6115hed). Part1cu1ar1y, 5uch phen0mena a5 attent10n 1eve15, 5peed 0f react10n5, m0t0r c00rd1nat10n and certa1n type5 0f d15cr1m1nat0ry 6ehav10r 5eem 5en51t1ve t0 the effect5 0f chr0n1c exp05ure t0 externa1 and 1nterna1 t0x1cant5. F0110w1n9 an adv15e fr0m Cranmer and 6016er9 (8), 1t may 6e w15e 1n the future t0 1nc1ude 50me te5t5 1n the human te5t-6attery that fac111tate extrap01at10n t0 para11e1 5tud1e5 1n an1ma15. An examp1e 0f what m19ht 6e ca11ed ••rever5e extrap01at10n•• (5ee a60ve) f0110w5. F0r 5evera1 year5 4u1te 50me eff0rt 1n 0ur 1a60rat0ry ha5 6een dev0ted t0 eva1uate the u5e 0f p5ych0phy51ca1 mea5urement5 f0r the detect10n 0f effect5 0n 5en50ry percept10n, e.9., 0n v16rat10n percept10n [1n hea1thy v01unteer5, 5ee (34)] 0r h19h-fre4uency hear1n9 [1n 5tyrene w0rker5, 5ee (36)]. Current1y, the5e 1nve5t19at0r5 are en9a9ed 1n deve10p1n9 the prepu15e 1nh161t10n techn14ue, where6y prepu15e5 0f d1fferent 5en50ry m0da11t1e5 (e.9., 50und, 119ht) are emp10yed t0 1nh161t the 5tart1e react10n, 1.e., 5u6thre5h01d prepu15e5 1ead t0 a 5tart1e re5p0n5e w1th a n0rma1 amp11tude, wherea5 5uprathre5h01d prepu15e5 are f0110wed 6y a 5tart1e re5p0n5e w1th a decrea5ed amp11tude. 51m11ar exper1ment5 are a150 carr1ed 0ut 1n rat5 and may re5u1t 1n an an1ma1 m0de1 that can 6e u5ed t0 detect chan9e5 1n 5en50ry thre5h01d5 cau5ed 6y exp05ure t0 var10u5 chem1ca15.

C0NCLUD1N6REMARK5 7h15 rep0rt de5cr16e5 50me 0f the eff0rt5 1n 0ur 1a60rat0ry dev0ted t0 0ne 0f the ma1n 4ue5t10n5 0f th15 5ymp051um: h0w va11d are the re5u1t5 06ta1ned w1th the current an1ma1 m0de15 f0r man• An attempt wa5 made t0 d1v1de the ava11a61e m0de15 ar61trar11y 1n tw0 c1a55e5, 1.e., m0de15 w1th a ••h19h•• and th05e w1th a ••m0derate•• pr06a6111ty f0r extrap01at10n t0 man. 1t w111 6e c1ear t0 the reader that a1th0u9h 5evera1 0f the m0de15 are 5t111 1n the deve10pment 5ta9e, 4u1te 50me pr09re55 ha5 6een made c0mpared w1th the 51tuat10n that ex15ted a decade a90. 0~0

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F16. 7. 7he effect5 0n accuracy (1eft pane1) and re5p0n5e 5peed (r19ht pane1) 0f rat5 perf0rm1n9 a tw0-ch01ce v15ua1 d15cr1m1nat10n ta5k. mea5ured 1mmed1ate1y after the term1nat10n 0f a 51n91e 8-h0ur exp05ure t0 d1fferent vap0r c0ncentrat10n5 (1n m9/m3) 0f wh1te 5p1r1t5. (6raph made ava11a61e 6y 8. M. Ku119.)

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F16. 8. 7he effect5 0n c00rd1nated m0vement 0f rat5, mea5ured dur1n9 and f0110w1n9 the exp05ure t0 d1fferent vap0r c0ncentrat10n5 (1n ppm) 0f C52 f0r 36 week5. (6raph made ava11a61e 6y 8. M. Ku119.)

AN1MAL 70 MAN EX7RAP0LA710N

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ACKN0WLED6EMEN75 1t w1116e c1ear that th15 c0u1d n0t have 6een wr1tten w1th0ut the c00perat10n 0f my c011ea9ue5 1n the Med1ca1 8101091ca1 La60rat0ry 7 N 0 . 1n a1pha6et1ca1 0rder, 1 part1cu1ar1y want t0 thank M. E15kamp, H. H. Emmen, 8. M. Ku119, M. A. E. M01, 6. P. van de 5chan5 and H. P. M. Van He1den f0r the1r c0ntr16ut10n5 and the1r c0mment5. REFERENCE5 1. 8aan, R. A.; van den 8er9, P. 7. M.; 5teenw1nke1, M. J. 5 . 7 . ; van der Wu1p, C. J. M. Detect10n 0f 6en20(a)pyrene-DNA adduct5 1n cu1tured ce115 treated w1th 6en2(a)pyrene d101ep0x1de 6y mean5 0f 4uant1tat1ve 1mmun0f1u0re5cence m1cr05c0py and 32P-p05t1a6e111n9; 1mmun0f1u0re5cence ana1y515 0f 8P-DNA adduct5 1n 6r0nch1a1 ce115 fr0m 5m0k1n9 1nd1v1dua15. 1n: 8art5ch, H.; Hemm1nk1, K.; 0•Ne111, 1. K., ed5. Meth0d5 f0r detect1n9 DNA-dama91n9 a9ent5 1n human5: App11cat10n5 1n cancer ep1dem10109y and prevent10n. Ly0n, France: 1ARC 5c1ent1f1c Pu611cat10n5 N0. 89, 1ARC; 1988:146-154. 2. 8aker, E. L.; F1ne, L. J. 501vent neur0t0x1c1ty; the current ev1dence. J. 0ccup. Med. 28:126-129; 1986. 3. 8artek, M. J.; La8udde, J. A.; Ma16ach, H. 1. 5k1n permea6111ty 1n v1v0: c0mpar150n 1n rat, ra661t, p19 and man. J. 1nve5t. Dermat01. 48:114-123; 1972. 4. 8artek, M. J.; La8udde. J. A. Percutane0u5 a650rpt10n 1n v1tr0. 1n: Ma16ach, H. 1., ed. An1ma1 m0de15 1n dermat0109y. New Y0rk: Church111 L1v1n95t0ne; 1975:103-120. 5. Ca1a6re5e, E. J. 5u1ta6111ty 0f an1ma1 m0de15 f0r pred1ct1ve t0x1c0109y. 7he0ret1ca1 and pract1ca1 c0n51derat10n5. Dru9. Meta6. Rev. 15: 505-523; 1984. 6. C1ement, J. 6.; 8en5ch0p, H. P.; de J0n9, L. P. A.; W01thu15, 0 . L. 5tere0150mer5 0f 50man: 1nh161t10n 0f 5erum car60xy11c e5ter hydr01a5e5 and p0tent1at10n 0f the1r t0x1c1ty 6y C8DP. 70x1c01. App1. Pharmac01, 89:141-143; 1987. 7. C0hr, K. H.; 5t0 "kh01m, J.; 8ruhn, P. Neur01091c re5p0n5e t0 wh1te 5p1r1t exp05ure. 1n: H01m5tedt, 8.; Lauwery5, R.; Merc1er, M.; R06erfr01d, M., ed5. Mechan15m5 0f t0x1c1ty and ha2ard eva1uat10n. Am5terdam: E15ev1er/N0rth H011and 810med1ca1 Pre55; 1988:95-102. 8. Cranmer, J. M.; 6016er9, L. Neur06ehav10ra1 effect5 0f 501vent5. Neur0t0x1c0109y 7:40--41 ; 1986. 9. D1ck, R. 8.; J0hn50n, 8. L. Human exper1menta1 5tud1e5. 1n: Annau, 2., ed. Neur06ehav10ra1 t0x1c0109y. 8a1t1m0re: J0hn5 H0pk1n5 Un1ver51ty Pre55; 1986:348-391. 10. Durham, W. F.; W01fe, W. R.; Qu1n6y, 6. E. 0r9an0ph05ph0r0u5 1n5ect1c1de5 and menta1 a1ertne55. Arch. Env1r0n. Hea1th 10:55-66; 1965. 11. E15kamp, M.; W01thu15, 0. L. 7he 1501ated 6100d-perfu5ed p19 ear a5 a m0de1 t0 mea5ure 5k1n penetrat10n. Pr0ceed1n95 0f the N A 7 0 Re5earch 5tudy 9r0up Meet1n9, Pane1 V111, R56-3, part 1, N0v. 1317; 1989. 12. Emmen, H. H.; H009end1jk, E. M. 6 . ; H0015ma, J.; 0r1e6eke, J. F.; U1jtdehaa9e, 5. H. J. Adaptat10n 0f tw0 5tandard12ed 1nternat10na1 te5t 6atter1e5 f0r u5e 1n the Nether1and5 f0r detect10n 0f exp05ure t0 neur0t0x1c c0mp0und5. 7N0-rep0rt M8L-18, 1988. 13. Fre1re1ch, E. J.; 6ehan, E. A.; Ra11, D. P.; 5chm1dt, L. H.; 5k1pper, H. E. Quant1tat1ve c0mpar150n 0f t0x1c1ty 0f ant1cancer a9ent5 1n m0u5e, rat, ham5ter, d09, m0nkey and man. Cancer Chem0ther. Rep. 50:219-244; 1966. 14. 6am6era1e, F.; Anwa11, 6.; Hu1ten9ren, M. Exp05ure t0 wh1te 5p1r1t. 11. P5ych01091ca1 Funct10n. 5cand. J. W0rk Env1r0n. Hea1th 1:3139; 1975. 15. 6am6era1e, F. U5e 0f 6ehav10ra1 perf0rmance te5t5 1n the a55e55ment 0f 501vent t0x1c1ty. 5cand. J. W0rk Env1r0n. Hea1th 11(5upp1. 1): 65-74; 1985. 16. Han5ch, C.; K1m, D.; Le0, A. J.; N0ve111n0, E.; 5111p0, C.; V1tt0r1a, A. 70ward a 4uant1tat1ve c0mparat1ve t0x1c0109y 0f 0r9an1c c0mp0und5. CRC Cr1t. Rev. 70x1c01. 19:185-226; 1989. 17. H0015ma, J.; 7w15k, D. A. M.; P1ata11a, 5.; Mu1j5er, H.; Ku119, 8. M. Exper1menta1 exp05ure t0 a1c0h01 a5 a m0de1 f0r the eva1uat10n 0f neur06ehav10ra1 te5t5. 70x1c0109y 49:459--467; 1988. 18. H0015ma, J.; Emmen, H. H.; Ku119, 8. M.; Mu1j5er, H.; P00rtv11et, D.; Let2, R. Fact0r ana1y5e5 0f te5t5 fr0m the neur06ehav10ra1 eva1uat10n 5y5tem and the W0r1d Hea1th 0r9an12at10n neur06ehav10ra1

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36.

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