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Brit, J, industr, Med., 1970, 27, J30-140 Experimental lead poisoning in the baboon ANTHOMY HOPKINS The Institute of Neurology, Queen Square, London, Hopkins, A, (1970). Bril, J. industr, Med., 27, 130-140. Experimental lead poisoning in the baboon. Twelve large and three infant baboons were poisoned by the intratracheal injection of lead carbonate in doses ranging from 50 to 135 mg/kg for 39 to 362 days. Eight baboons had one or more epileptic fits. Weakness of the limbs, believed to be of central origin, was seen in three of them. The effect of single and multiple doses of lead on the blood lead is recorded. Anaemia and punctate basophilia were not found. Measurements of nerve conduction velocity, electromyography and histological examination showed no abnormality of the peripheral nerves. The different effects of lead upon different species are discussed. There is continuing interest in the pathological and system. The mean velocity was about 12 m/sec less physiological basis of lead intoxication in man. than the values obtained in healthy people in other The nature of lead palsy remains obscure, in spite laboratories, but the absence of reported recordings of many observations on experimental animals. on controls by these authors, and the absence of One problem is that lead produces different effects any note of measurement of limb temperature in different species. Punctate basophilia, for renders these results difficult to interpret. example, is found in the blood of lead poisoned Fullerton (1966) has recently studied the changes guinea-pigs, rabbits and man, but not in cats and in nerve conduction velocity in guinea-pigs wit!; dogs (Key, 1924). Gombault (1880) showed that lead poisoning, some of which developed mi hi some nerve fibres of chronically poisoned guinea- paralysis of the hind limbs. In 17 out of 40 animal* pigs underwent a `nevrite segmentaire periaxiie\ a examined, conduction velocity fell below the norma* process which is now* known as segmental demyelin- range of 40 to 60 m/sec, in some cases to less than ation. In the rabbit* however, segmental derayelina- 20 m/sec. These changes were associated with iion is not seen, the fibres undergoing a Wallerian segments1 -deh&'gjjna^^ type of degeneration (Shimazono, 1914), Electrophysiological studies on lead poisoned Because of the varying effects of lead on different patients have been reported by a number of workers. species, it was decided to study the effects of Hausmanowa-Petrusev/icz, Emeryk, Sobkowicz, on an experimental animal phylogeneticaiiy ciosv Wasowicz, and Tur (1962) and Delwaide and to man, This paper reports the results of measuic Chantraine (1965) both report the presence of ments of nerve conduction velocity and electro fibrillation and polyphasic potentials suggesting myography in the lead poisoned baboon, am` denervation of muscles. observations oil haemoglobin, punctate basophil'- Measurements of conduction velocity have been and blood lead, reported on a few patients with lead palsy (PreiskeJ, 1958; Simpson, Seaton, and Adams, 1964; Delwaide Methods and Chantraine, 1965) but in none was there evidence of slowing of nerve conductidhTBessa, Ferrari, and Colucci dVvrnato (1965) measured ulnar conduction velocity in 20 patients exposed to lead but without symptoms referable to the nervous Twelve large baboons (Papio anubis) were studied, the; weights ranging from 7*2 to 13-6 kg. The nine fenid. animals all showed sexual changes in the shm and may be presumed to be older than four years. The thwmale baboons weighed 7*2 to 9*5 kg, and, as adult -inal 330 N37527 Experimental lead poisoning in the baboon 131 baboons are larger than females, the male animals studied were clearly not full grown. In addition, three infant female baboons CP. anubts 2, P, hamadryas 1) were studied, their weights ranging from 2*8 to 3*3 kg. Animals were caged singly, allowed one litre of water a day and fed on a pellet diet, MJR..C. 41 B, supplemented by a thtl> fruit. All animals received LOOP /ug of Bu (Glaxo l ,i ooi atones) by injection monthly, to avoid the changes s.eti in the nerves of captive Xfacaca rhesus described by (> .nat d and Smith (1966). All animals were retained for .u least three months in the laboratory before lead intoxication was begun. During this time all animals were treated with thenium and piperazine to eliminate parasites, and had chest radiographs. Those with hemoglobin levels of less than 10 g/100 ml received >0 mg of iron a day in the drinking water. These measures vsulied in increases in haemoglobin of up to 5-6 g/100 id. and in weight of up to 2*3 kg. Sedation was induced by intramuscular injections of uencyclidine (Sernylan, Parke, Davis and Co.), 2 ng'kg, and promazine (Sparine, John Wyeth), 1 mg/kg, mravenous pentobarbitone (Nembutal, Abbott Labu atorics), 3 mg/kg, was given to produce anaesthesia for he administration of lead. After consideration of the various possible methods of 0 ministering lead, it was decided to use an intratracheal Vivction pf a suspension of lead carbonate. Minot (1924) jccessfully used this method in cats, and showed that 1 sorption was more complete from the lungs than from vt gastrointestinal tract or from a subcutaneous depot. v.!<J carbonate was prepared as a freshly agitated pension in sterile normal saline, and injected, under uesthesia, through a 21 gauge needle into the trachea, he animal was then postured at about 30 to the >rizontal for about 35 minutes, so that the suspension ick led into one or other lower lobe. A radiograph of the icst of one animal, 15 minutes after injection, is produced (Fig. 1). The usual quantity given was 1 g in 1 ml, this being equivalent to a dose of 50 to 135 mg/kg itia! weight. Smaller quantities were given to the infant boons so that the dosage per kilogram was in the me range. Blood was obtained by femoral venous puncture. The cmoglobin was estimated by a modified Haldane -hod, Blood lead was estimated on haemoiysed whole k k I using the method of Delves and Vinter (1966). :x k ! films were stained with Leishmann's stain, and high-power fields were then searched for the presence punctate basophils. induction velocity in motor andsensoiy fibres in the ianueiwe was^estimateq unoer iignt^anaesthesiaby T in the anterior tibia! nerve using the same principles. v rncvJian^andTalcral popliteal nerve trunks were .latcd through subcutaneous needles placed close be nerve trunks. Muscle action potentials were . (.led through needles with the active electrode over .belly of the abductor pollieis brovis or extensor :,`uuhi brevis muscle, the remote electrodes being ` d over the tendons. All shocks were supramaximal, `;nre was taken to avoid spread of the stimulus to Pouring nerves. The ascending nerve action poten NAP) in the median nerve was recorded at the elbow Emulation at thtTwrisf, and in the anterior tibia] Fia. 1. Chest radiograph 15 minutes after the first injection of 450 mg PbCOj. Infant baboon 15. nerve at the knee on stimulation at the ankle. A sensory nerve action potential was recorded from the median nerve at the wrist on stimulation of the index finger. Full details of the placement of the electrodes and of the stimulating and recording systems are available elsewhere (Hopkins, 1968). A number of muscles were searched for fibrillation potentials, using a coaxial needle electrode (DISA13K80). Intramuscular temperature was estimated in the forearm flexor muscles and in the anterior tibial muscles with a thermistor at a time between the measure ments of motor conduction and ascending conduction in each limb. The thermistor was also used to measure temperature in a hypothenar skin fold on the hand immediately afer an estimate of sensory nerve conduction. The animal was covered with cotton wool, the room temperature was maintained above 12 C and on occar,tons a lamp would be placed near >he animal's back, but no other external form of heating was employed. On two occasions the body temperature of control animals was anifidally lowered by funs and icepacks to study the temperature coefficient of conduction velocity (Hopkins, 1968). Results The normal blood lead Blood lead was estimated on arrival in the laboratory s 9 ftL S tfW A . 132 Anthony Hopkins si. ,^^iW'w*s.-iivt^.i;'.'Vt on all 15 baboons, and on 12 other healthy baboons used for other studies. The mean concentration was 11 *7 /xg/100 ml (range 3-27, SD 5*5), and 87% of all estimations were less than 16 jug/100 ml. The `adult* baboons Ten animals were studied until death between 39 and 265 days after the first injection of lead, the mean survival time being 120 days. In addition iwo animals were killed after 336 and 362 days respeclively. The clinical details of the illness of each animal are recorded in the Appendix (p. 139). The effect of a single injection of PbCOs on the blood lead The blood lead in one baboon (B12) was estimated at short intervals after the first injection of 1,000 mg of lead carbonate (PbC03) (105 mg/kg), Figure 2 illustrates the rise in blood lead to a peak of 310 /-ig/lQO ml by the fourth day. This level was maintained for a further seven days. The rate of decline was then approximately exponential, the blood lead remaining over 100 /xg/100 ml for at least 24 days. pronounced loss being that of baboon 7 which lost 46 %, the weight falling from 1H to 6 0 kg. Five of the remainder tost 25% or more of their initial weight. This marked loss of weight contrasted with a normal appetite, which was maintained throughout the illness. No animal showed a lead line in the gum margin. Eight out of 12 animals had one or more fits, of which 34 in all were observed. It is likely that others occurred when no observer was present. Thirteen fits and two episodes of status epilepticus were personally witnessed. AH 13 fits were grand mal, but two began with a focal seizure, which soon became generalized. These focal seizures occurred on the same day in baboon 3, 149 days after beginning poisoning. They began with focal twitching around the right eye, spreading to the rest of the right side of the face. During the next 15 seconds the right arm became involved, and then convulsions became generalized. Consciousness was recovered after about three minutes. Sometimes grand nial fits were precipitated by sudden movement of the animal as it tried to avoid transfer from one cage to another or whilst reaching up to take a banana. The grand mal fits were occasionally preceded by a cry. The tonic phase lasted about 15 seconds, during which the hind limbs and tail were extended, Generalized jactitation did not continue for more than a minute. Incontinence was not observed. Paresis of limbs was noted in three animals (baboons 1, 3 and 12), but as this was associated with fits or other evidence of encephalopathy it was thought to be of central origin. Baboon 3, which had the two Jacksonian fits affecting the right face, arm and leg, developed a postictal paresis of the right limbs which lasted about 15 minutes. Baboons 1 and 12 had a longer-lasting weakness of the limb>: associated in baboon 12 with frequent fits and papilloedema. Further details of all animals arc recorded in the Appendix (p, 139), j *? . 20. oyj qj $r mjet ion 40 50 no. 2. The changes in the blood lead after a single injection of 1,000 mg PbC03. Baboon 12. The effect of repeated Injections of PbCOa The results illustrated in Fig. 2 indicated that to maintain high levels of blood lead it was only necessary to give injections of PbC03 about every three weeks. This frequency of injections was modified according to the clinical state of the animals and the values of blood lead which had previously been obtained. Loss of weight was a striking feature in all animals, and was the most easily recognized evidence of poisoning. Five out of 12 lead poisoned animals lost 40% or more of their initial weight, the most The relationship between the clinical illness and level 0f jjj00^ jea<j figure 3 illustrates the course of the clinical illness of baboons 3 and 5. In baboon 5 poisoning was accompanied by a marked fall in weight to 62% of the initial weight, but the genera; condition remained very good even though at one time the blood lead was as high as 4.550 /l c s/I 00 ml> Ifhc haemoglobin level in this animal appears h> follow approximately the changes in weight, but this was not always the case, as is shown by the chart of baboon 3. The rate of loss of weight wa-s not related to the change in blood lead. Baboons 11 , and 12 lost weight rapidly and died, the blood lead never having exceeded 500 and 630 /xg/100 rl respectively. However, baboons 5 and 6 were ah'* to withstand levels of 4,550 and 2,200 /xg/100 m , DUP050044095 Experimental lead poisoning in the baboon 133 Percent of initial weight J OCH 30 60 40 BABOON 3 Died ,f 100 80 60 40 BABOON 5 .. Sac f Percent of initial Hb IC> 80* 60* 40 20 f .......... - 100 80 60 40 20 4000 3000 Blelaodod j2n0m00*Ji (yig/lOOml) loop* r,-ill li1,11 Jl , FITS j| lead carbonate 1 mi, ii.(9) :im ii ,m, i,i O 40 80 120 160 Day* after first injection of lead O 40 80 120 160 200 240 280 32p 360 iv, 3. Baboons 3 and 5. The changes in weight, haemoglobin and blood lead, and the occurrence of fits, after epeated injections of PbC03. dih little or no clinical deterioration, and were ventuaily killed. Inspection of the results showed that fits were urticularly frequent between 4 and 11 days after n injection of lead, a time at which the bipod lead xichcs its peak (Fig. 2). All five baboons which q*an convulsing within this period died during one f .i number of seizures which immediately followed, he three other baboons which convulsed did so -tween 23 and 29 days after the previous injection f lead, at a time when the blood lead was falling, trj all survived. nemia and punctate basophilia No consistent ;! in haemoglobin concentration was observed. : re 4 shows the relation between haemoglobin i blood lead plotted in a manner similar to that H"hiiaro.$ (1966). The results of 136 estimations food lead after the beginning of poisoning have a grouped into classes of 100 /xg/100 ml up to 0 fig/l 00 ml, with three further classes of 0,M99, 3,500-3,999 and over 2,000 /zg/100 ml f ig . 4. The relationship between haemoglobin and blood lead. The mean dz2 standard deviations of all haemo globin estimations within each blood lead class have been plotted. (5 . DUP050044096 334 Anthony Hopkins v-.^sijCA^.vA^.v'jvu All results have been included from venepunctures when haemoglobin concentration was also estimated, The mean haemoglobin concentration and two standard deviations have been calculated for the haemoglobin estimations within each blood lead class. Figure 4 shows that there is no significant decrease in haemoglobin concentration with increasing levels of blood lead. Punctate basophilia was not found on any one of 136 examinations. The peripheral nervous system As noted above, the only weakness observed was associated with encephalopathy, and in no animal was there clinical evidence of a peripheral neuropathy. Nerve conduction velocity was estimated on 16 occasions in the median and anterior tibial nerves of six baboons at times varying between 35 and 346 days after beginning injections of lead carbonate. In aHjsix animals examined repeatedly, no significarit "decrease was observed' "TrT""conduction velocity in eitFer helW examinedf, or m the size of the muscle and~nerve action potentials recorded, Estimates of conduction velocity recorded before intoxication, and final estimates before death or sacrifice, are compared in Table 1. Many of the lead poisoned baboons were extremely wasted, and intramuscular temperatures were consequently <us much as 3C lower than the initial temperatures. AH velocities have therefore been adjusted to 3.7 C using temperature coefficients calculated for the median and anterior tibial nerves of the baboon (Hopkins, 1968), The mean percentage change of final velocity compared to initial velocity for all 27 observations recorded in Table 1 was only 107%. There was no consistent decrease in the amplitude of muscle and nerve action potentials. An example of the potentials obtained is illustrated in Fig. 5, which shows the series of muscle action potentials recorded from the abductor pollicis brevis of baboon 5, which was poisoned for nearly a year. Motor units were recorded from extensor digitorum communis or brachioradialis, innervated by the radial nerve on six occasions (baboon 1, days 94, 105; baboon 4, day 123 ; baboon 6, days 123, 182; baboon 12, day 143), A temperature coefficient was not available for this nerve, but in no case was a unit found with a velocity of Jess than 58 m/sec. The mean velocity for all units was 67*9 m/sec, compared to a mean of 69*0 m/sec for five units from two control animals. Strength-duration curves were plotted for radial- TABLE 1 Co n d u c t io n Ve l o c it ie s o f Fa s t e s t Mo t o r Fib r es a n d o f Ne r v e Ac t io n Po t e n t ia l s in Me d ia n a n d An t e r io r Tib ia l Ne r v e s o f Six Ba b o o n s b e f o r e a n d a f t e r 94 t o 346 Da y s o f Po is o n in g w it h Le a d Ca r b o n a t e 13 Baboon 45 6 12 Interval between initial and final observation {days) 94 120 196 328 346 157 Mean Median nerve conduction velocity (m/sec) Motor - initial 70-5 72*8 68*8 69*8 74*8 751 -final 68-2 700 72*4 71*7 76*8 718 % change............................................, 4* 5 +3 43 -4 0 Ascending NAP -initial ... ., ........................ 77-5 88*9 83*4 86*1 90*4 86*5 -final .. ., ... ., .. .. 78*5 86*0 85*7 81*0 87*7 84*5 % change .. ., 41 -3 + 3 -- 6 --3 --2 -1-7 Sensory NAP -initial -final ... ................................. , ... .. .. . ,,, 77*3 6.8*8 59*1 66*2 64*5 72*0 67*7 70*3 66*5 61*2 % change -- -7 -1 419 0 -5 41*2 Anterior tibial nerve conduction velocity (m/sec) Motor - initial .. .. 65*3 59*4 67*1 61*2 62*0 64*9 -final ...................... . 64-7 55*0 63*4 60*5 61*7 61*5 % change ........................ ,. -1 -7 --5 -1 0 -5 Ascending NAP - initial ...................... ....................... 77*0 -- 79*5 70*3 -- 73*7 - final .............................................. . .. .. 73*4 91*8 75*4 71*4 71*6 751 % change...................... . --5 --5 T2 42 -.3*2 -1*5 1 NAP ** nerve action potential. DUP050044097 V jfs-arv Si Experimental lead poisoning in the baboon 135 ST1M. ELBOW STIM. WRIST general it appears that the infants failed to support elevation of the blood lead of a degree comparable to those produced in the `adults*. Baboon 13 died with the blood lead at its highest of 178 yu.g/100 ml. Baboon 14 lost a third of its body weight although the blood lead had never risen above 230 /ig/100 ml. As in the adults, no lead line was observed and punctate basophilia was not found. 70 -(----- 1 ___ , J Histological observations The results of histological observations on the brain and spinal cords and peripheral nerves of the affected animals will be reported in detail elsewhere. However, preliminary examination of the peripheral nerves and spinal cords has not so far revealed any abnormality. in. 5. Baboon 5. Muscle action potentials recorded oni abductor pollicis brevis at intervals during intoxiition with lead carbonate. mcrvated muscles on five occasions (baboon 1, ays 94 and 105; baboon 5, days 52, 70 and 134). ;o abnormality was found. /V search was made for fibrillation potentials in at .vst three muscles on each examination. No >ontaneous iibrillation or positive sharp waves were on, and insertion activity usually died away within to 10 seconds of moving the needle. ic three infant baboons h s of weight was observed in all three animals, hidi became progressively more wasted and timid, iboon 13 was observed to drag both hind limbs r 10 days before death, but when allowed to run " it could assume the quadripedal pasture by. The hands appeared to be used normally. > :Us were witnessed in any infant. The hacinoi'in was depressed to 66 and 79% of its initial cl in baboons 14 and 15. It was not observed to be ; W;>sed five weeks before death in baboon 13, but *his time the animal was still gaining weight. In Discussion Lead failed Jo produce any clinical, electrophysiological or, histologigare^Hence of damafe to Ihe peripheral nerves oQT ba.b5pQs^_in spite of very high levels of blood lead for periods extending up to one year. This was a surprising result in view of the isolated reports of illnesses occurring in caged primates in zoological gardens in which the illness was attributed to lead. Fisher (1954) reported a Gorilla gorilla which ate a tin of red lead paint and later developed weakness of both arms and one* leg. De Bisschop, cited by Jlucb (1959), described progressive quadriparesis occurring in a Gorilla gorilla\ with punctate basophilia in the peripheral blood and 24 mg lead/litre of urine. The cubital and median nerve trunks were inexcitable on electrical stimulation. One year before the cage had been painted with white lead paint. Hausman, $turteyant, and Wilson (1961) described an orang-utan(Pongo pygmeus) in which paresis of both legs progressed over 12 days to involve both arms. The animal was killed 14 days after the onset of both symptoms. The clinical impression was that of a Guillain-Barre syndrome. The spinal cord showed posterolateral demyel(nation, but the peripheral nerves were not examined. Equal portions of liver and kidney analysed together contained CM 89 mg lead/100 g wet tissue. On examination of the cage 12 roach hives were found, each containing about 300 mg of lead arsenate. The same authors describe the case of a young female Mandrillus sphinx which developed convulsions nine weeks after first being exhibited* Two days later a left wrist-drop was noted, and after seven days the animal became blind and remained blind until its death four months later. Punctate basophilia was noted in the peripheral blood. The liver contained 1*16 mg of lead per 100 g Wt tissue. The nervous system was not examined histologically. The paint from the cage was found to contain 5*5 % lead oxide. ? i- ? i h >. DUP050044098 136 Anthony Hopkins i There are only two previous studies on lead poisoned primates. Ferraro and Hernandez (1932) administered lead carbonate to two `monkeys' for 66 days as part of a larger study on the neuropathological changes in lead poisoned cats. In the brachial plexus and sciatic nerve of each animal there was `a certain amount of segmental degener ation of nerve fibres with swelling and fragmentation of both myelin and axis cylinders. Numerous fibres were seen surrounded by a swollen myelin covering'. However, from their illustrations it does not seem that these authors are describing segmental demyelination in the sense used by Gombault (1880). Vermande van Eck and Meigs (1960) studied abnormalities of ovarian function in M. rhesus poisoned by weekly injections of intravenous lead chloride. They noted that one animal developed a lateral popliteal palsy, but the nervous system was not examined. Table 1 shows that there was no significant fall in conduction velocity in six animals, two ofwhich were followed for almost a year, There can be no question that at least four of these animals were seriously poisoned (Bl, 3, 4 and .12) because they convulsed at some stage. Fullerton (1966) found a reduced conduction velocity in only 1 out of 6 guinea-pigs poisoned for 9 to 15 weeks, and in only 5 out of 18 guinea-pigs poisoned for 16 to 22 weeks. It might be suggested that chance alone precluded the finding of a reduced conduction velocity in the six baboons examined for between 13 and 50 weeks. Moreover, Fullerton points out that in a number of animals with normal conduction velocity many fibres were undergoing segmental demyelination or remyelination. The survival of only a few normal fibres will preserve motor conduction velocity. However, sensory nerve action potentials were recorded in the present study. The amplitude of these depends upon the arrival of a nearly synchronous volley beneath the recording electrode. In none of the lead poisoned baboons was there any significant reduction in the amplitude of the sensory action potential, indicating that in few, if any, of the fibres was velocity slowed, Wallerian-type degeneration in some fibres would not produce any slowing of conduction velocity; however, interruption of the axon and its severance from the muscle fibre would cause spontaneous fibrillation. A search of many muscles, proximal and distal, and of those innervated by the radial nerve, failed to disclose any spontaneous fibrillation. The electrophysiological findings alone suggested that the peripheral nerves were unaffected and this has been supported by a preliminary histological examination. The present study does not suggest that there is any `threshold' level of blood lead above which evidence of intoxication will occur. Some animals developed seizures and died with levels between 5 and 10 times Jess than those seen in animals which survived and maintained their weight for up to a year. This is in accord with a statement of Cantarow and Tmmper (1944) that `the concen tration of lead in the blood bears no consistent relationship to the appearance or severity of clinical manifestations of lead poisoning. The latter may he absent at high levels of blood lead, and may be present at low levels'. Anaemia and punctate basophilia were not seen in the large baboons, even in those animals which were clinically poisoned or had very high levels of blood lead. The anaemia of lead poisoning is usually attributed to defective haemoglobinization with increased mechanical fragility, although osmotic fragility is usually a little decreased. Aub, Fairhall, Minot, and Reznikoff (1925) found that the osmotic fragility of red cells in a saline solution containing 1,000 fxg of lead per 100 ml was decreased for the cells of man, rabbits, guinea-pigs and rats - species in which punctate basophilia is easily produced. There was no change in the osmotic fragility of leaded cells of horses, dogs or cats, animals which do not develop punctate basophilia or anaemia. There is clearly a difference between genera, but the occurrence of punctate basophilia in the blood of lead poisoned humans, the Gorilla cited by Ruch (1959) and the Mandrillus sphinx described by Hausman et al (1961) makes its absence in the baboon rather surprising. There are at least two possible explan ations. Stippling may not occur in the baboon because the metabolism of red cell production is different in the baboon, cat and hen from the rabbit, guinea-pig and man; or the stippled cells could be removed from the circulation as soon as they are j formed. i Although a considerable amount is now known about the effect of lead on the condensation of two molecules of ^-aminolevulinic acid to form por* phobilinogen, and on the incorporation of iron into the protoporphyrin molecule to form haem (see Waldron, 1966, for references) there is no infor* \ mation available about the varying effect of lead on porphyrin metabolism in various animals. Stippled cells are1 possibly removed from the circulation by the spleen. McFadzean and Davh (1949) showed that splenectomy performed on lea*! poisoned guinea-pigs enormously increased the numbers of circulating stippled cells, though bavin?: no quantitative effect on the stippling of the red cell precursors in the bone marrows. An alternative ; action of the spleen might be to remove the baso philic granules whilst leaving the red cell as a whole intact, or to stimulate the red cells to metabolize the granules rapidly. Although seemingly un likely, the work of Crosby (1957) suggests that this is possible. He transfused chromium-51 tagged red 'v;: DUP050044099 Experimental lead poisoning in the baboon 137 colls containing siderin granules into four recipients with spleens. The siderin granules rapidly dis appeared whilst the red cells remained. In two recipients after splenectomy siderin granules and cells remained in the same proportion. This ex planation seems unlikely to account for the results of McFadzean and Davis as the anaemia of the guinea-pigs was also ameliorated by splenectomy. The absence of punctate basophilia in the iead poisoned baboons might be due to an unusual path of red ceil formation and hacmoglobiiiization or to an ext''cmcly active retieulo-endothelial system which h able to remove the stippled ceils or granules, or to stimulate metabolism of the granules as rapidly as they are formed (Crosby, 1957). It would be interesting to search for basophilic stippling in the bone marrow of species which fail to show it in the peripheral blood when poisoned by lead. If present in the marrow, then the most likely explanation of its absence in the blood would be rapid removal of affected cells or granules by the retieulo-endothelial system. It might be suggested that the failure to produce lead palsy or histological and eleetrophysiological changes in the peripheral nerves is linked to the failure to produce anaemia and punctate basophilia. For example, the enzyme systems both of neurones and of red cells of resistant species might have features in common which allow normal function in the presence of lead. However, examination of the available data does not support this hypothesis (Table 2). In the guinea-pig, anaemia and punctate basophilia are present, and predominantly seg mental demyelination occurs, mixed with some WaJlerian-type degeneration (Gombault, 1880; Fullerton, 1966). In the rabbit, anaemia and punctate basophilia are present (Key, 1924), but segmental demyelination is not seen. Shimazono (1914) des cribed vVallerian-type degeneration in lead poisoned rabbits, and de Villaverde (1926a, b) described interruption of the axon, or at least of the argentophiiic substance, which was not always accompanied by breakdown of myelin. He also stated that the anterior horn cells were shrunken, and that the Nissl granules disappeared. De Villaverde (1930) specifically stated that segmental demyelination was very rare in lead poisoned rabbits. In the rat, anaemia andpunctate basophiliaare readily produced, but it is very difficult to produce more than the most scanty Wallerian-type degeneration (Prevost and Binct, 1889). In the cat, Goadby (1909) found it easy to produce extensor paralysis by exposure to litharge dust. Ferraro and Hernandez (1932) produced a little segmental demyelination and Wallerian-type degeneration in lead poisoned cats, and Lehmann, Spatz, and Wisbaum-Meubtlrger (1926) described extensive changes in the anterior horn cells. However, punctate basophilia and anaemia are not found in the cat. Litric work has been carried out in the dog, but again there is a Species Vlan Tfuinea-pig tabbit .. Cat laboon ... >og 'at .. .. TABLE .2 Th e Ef f e c t o f Le a d Po is o n in g in Dif f e r e n t Sp e c ie s Anaemia and punctate basophilia Encephalopathy . Palsy Changes in Wallerian-type anterior degeneration horn cell Segmental demyelination + (1) 4-4- CD .. + +(0 + 0) 0(2) 0(1) 0(1) 4-4-(3) + 4* (4) 4* (5) + (6> (infants) 4-4- (2) 4-4- (7) + 4- (8) ++ (9) 4* (4) 4 (10) 4*04) 0 (4) ; QUO) + 05) + (ID Trace (j0) ) Postictal (2) Q (2) 4- (12) *1* 06) + + (D) + +() 4*07) 4* (10) 4-(18) Rare (10) 0 (2) Rare (12) 4- (19) 0 (8) 0 4-4- (10, 20) 0(18) Very rare (21) 0 (4,10) 0 (2) 4- (19) Im: numbu's In the table relate to the references listed below: Aub, Fuiihafl, Minot, und Rc/.nikpff (i925) ' Present study OisojJc (1336) C i iillct ion (1266) Kojbcrti (1931) I'uuschcw and Garro (1966) Cmbemnle And Francois (1890) hchniann. Spat* and Wisbaum-Ncubiirger (1926) i.KHpicrcl tics Planches (1839) 1 i`:evost and Einet (1889) U. dc Villaverde (1926a) 12. Lugaro (1897) 13. Goadby (1909) 14. Herter (1895) 15. Nissl (1892) 16. Catalano (1906) 17. Gombault (1873) 18. Shimazono (1914) 19. Ferraro and Hernandez (1932) 20. Gombault (1880) 21. de Villaverde (1930) f ft- DUP0500441OO 138 Anthony Hopkins dissociation between the occurrence of encephal opathy and histological changes and the absence of changes in the blood. In the baboon it was not possible to produce any clinical or electrophysiological evidence of damage to the peripheral nervous system, and this has been supported by pre liminary histological examination;; neither was anaemia or punctate basophilia produced, yet encephalopathy was common. Punctate basophilia and anaemia occurs readily in lead poisoned man, and pathological changes have been described in the spinal cord and per ipheral nerves, Gombault (1873), in the ease report of a woman eolourer who developed wrist drop, described extensive Wallerian-type degeneration, as did Dejerinc (1879). The spinal cord in Gombault's report was normal, Herter (1895) described extensive changes in the spinal cord of a 26-year-old man with wrist drop, colic and encephalopathy. He estimated that up to one third of the anterior horn cells showed disintegration of the chromophil granules, vacuolization and pigmentation. Approximately one fibre in four of the lateral popliteal nerve was undergoing Wallerian-type degeneration. Essentially similar findings were reported by Laslett and Warrington (1898) and by other authors. Laslett and Warrington teased fibres but failed to find any evidence of segmental dcmyellnation. These findings in various species, which are summarized in Table 2, do not throw any light on the metabolic lesions produced by lead in the red cell precursors and in the neurone or Schwann cell. Moreover, even in those animals with clear histo logical lesions in the central or peripheral nervous system there is an obvious difference between those species like the guinea-pig and rabbit, which develop a mild paresis in spite of extensive lesions in the peripheral nerves, and the human situation in which a sudden severe palsy may occur, with rel atively slight changes in the peripheral nerves. The present work was carried out while the author was in receipt of a grant from the Medical Research Council, which is gratefully acknowledged. I thank Professor R. W. Gillian for his help and guidance during this work, Mr. T. Delves kindly esti mated the blood lead of the baboons. The results reported here formed a part of a lives is submitted for the degree of Doctor of Medicine of the University of London. References Aub, J. C., Fairhall, L. T., Minot, A. S., and Reznikpff, P. (1925). Lead poisoning. Medicine (Baltimore), 4,:l-250. Cantarow, H., and Trumper, M. (1944). Lead Poisoning Williams and Wilkins, Baltimore Catalano, G. (1906). Alterazioni anatomo - patologichc del sistema nervosa nelP avvelenamcnto sperimentale cronico da piembo. Policlinico sex. med., .13, 324-3.32, Combemale and Francois (1890). Rccherelies cxpcrimcntalcs sur les troubles nerveux du saturnisme chronique ct sur ies causes ddterminantes de Icur apparition. C.R. Acad. Sci. (Paris), in 27(5-278. Crosby, W. H. (1957). Siderocytes and thespleen. Blood, 12, 16S-170. Pejcrinc, J. (1879). Rccbcrches sur les lesions du systime nerwu\ dans la paralyse saturnine. C.R. Soc. Biol. (Paris), 7th scr., |, Mm.,pp. 11-17. Pelves, H, T., and Vinter, P. (1965). Scmi-automat ;c determination of lead in whole blood. J. elm. Bath., 19, 5C4-503. Dejvyaide, P. J., and Oliuntraine, J. M, (1965), Participation spin.ic dans l'intoxication Saturnine: arguments Hcctromyograpiviqut,.',, Proc. 6th International Congress of Electroencephalography and Clinical Neurophysiology, Vienna 1965. p. 643*646. Ferraro, A., and Hernandez, R, (1932). Lead poisoning. (A hh.iopathological study of the nervous system of cats and monkeys in the acute and subacute stages.) Psychiat. Quart., 6, 319-350. Fisher, L. 6. (1954). Lead poisoning in a gorilla. /. Anier, vet. and. Ass., 125,478-479. Fullerton, P. M. (1966). Chronic peripheral neuropathy produced by lead poisoning in guinea-pigs. /. Neuropath, exp. Neurol., 25, 214-236. Goadby, K. (1909). A note On experimental lead poisoning. I. Ibg, (Lond.),9, 122-133. Gombault, A. (1873). Contribution fi. l'histoirc analomiquc de Ta trophic musculaire saturnine. Arch. Physiol, norm, path., 5, 592-597. ---- (1880). Contribution a Pdtudc anatomique de la ndvrite parenchymatcuse subaiguc et chronique - n6vrite segmentaire pdri-axiic. Arch, Neurol. (Paris), 1, 11-38. Grisollc, A. (1,836). Rechorelies sur Qttelgues-uns des Accidents Cdribraux Produits par les Preparations Satamines. Paris. Hausman, R., Sturtevant, R. A., and Wilson, W. J. (1961). 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Die histologischen Vcriindcrungen des Zentralncrvensystcme bri der bleivergifteten Katze und deren Zusammcnhang mit den klinischcn Er$cheinungcn insbesondere mit KrampfanfuJlcn. Z. ges. Neurol. Psychiat., 103,323-360. Lugnro, E. (1897), Sulle alterazioni degli dementi nervosi negli avvclenamenti per arscnico e per piombo. Riv, Pat. nerv. meat., 2, 49-64. McFadzean, A. J. $., and Davis, L. J. (1949). On the nature and significance of stippling in lead poisoning, with reference to the effect of splenectomy. Quart. J. Med., 42 (n.s. 18), 57-72. McLeod, J. G., and Wray, S. ii. (1967). Conduction, velocity and fibre diameter of the median and ulnar nerves of the baboon. J. Neurol. Minot,. A. S. (1924). Lead studies. V.B. The distribution of lead imiic organism after absorption by the lungs and subcutaneous tissue. /. industr. 6, 137-148. Nml, F. (1892). Ucbcr vxpciimcnlel* etraigte VeriinJerunycn ,u den Yordcrhornzelien des R Ucke.timarks bei Kaninchcn ir>t Demonstration mikroskopischcr Prfiparatc. Allg. Z. Psyclma.. 48,675-682. Oxnard, C. E., and Smith, W. T. (1966). Neurological dcgcneruimo and reduced serum vitamin B|*-lcvels in captive monkeys. Nature (Lond.), 210,507-509. Pentschcw, A., and Garro, F. (1966). Lead cnccphaloimyelopath> oi the suckling rat and its implications on the porphyriopathic nervous diseases, with special reference to the permeability dis orders of tho neryous system's capillaries. Acta neuropath. (Perl.). 6, 266-278, Prciskcl, D. (1958). Chronic lead poisoning: myopathy or neuritis*? Ann. phys. Med., 4, 293r296. Prcvost, J. L., and Binct, P. (1889). Recherche* cxpcrimcntalcs w) Tintoxication saturnine. Rev. mid. Suisse ram., 9,606-623. DUP050044101 , .* tV'wi *..*,,*.* *s-iW, \!ttr)-Ai-s .. V vifc-** #V^JtfW0M<h . v. t &.J ix'&X- Experimental leadpoisoning in the baboon 139 K* `focrt i, C. E. (193!), Sul comportamcnio della macroglia o dcgli dementi nervosi ncilo intoswea/.ioni sperimcntali da: istammina, guanidina, acido cloridrico, acctato di piombi e acctato talloso. Rais. Studl pskldat., 20, 7. I< ucli, T. C. (1959). Diseases of Laboratory Primates. The Handbook of the Primates, Part J. Saunders, Philadelphia and London. S.rssa, T,, Ferrari, E., and Colucci P'Amato, C. (1965). Velocity di cotuiuzione nervosa nci soturnini. folia meet. (Napoli), 48,658-668. Siurrias'.ono, J, (1914). Ueber das Verbalten der zentralen und der peripheren Ncrvensubstanz bci verschiedenen Vergiftungcn und l;.rn;ihrungsstdrungen. Arch, Psyciliat. Ncrvenkr., 53, 972*1094. Simpson, J. A., Sea inn, D,. A., and Adams, J. F. (1964), Response to treatment with chelating agents of anaemia, chronic encephalo pathy, and myelopathy due to lead poisoning./. A'enrol. Ncuro- su:g. Psyc/iiat., 27, 536-541. 1 i;upic*-el dcs Planches, J.. (1839). Trait<} ties Maladies tie Plomb ou ^atvrnwes. Forra. Paris. \rr mantle-Van Eck, Cr. J.. and.Meigs, J. W. (I960). Changes in the ovary of the rhesus monkey after chronic lead intoxication. Penit.and Sterii., 11, 223-234, de ViUayerde, J. M. (1926a). Les r6sultats tardifs de 1'intoxication saturnine expdrimentale dcs nerfs. Trab. tab. Invest, biol. Univ. Math., 24, 155*179. * (J 926b). Lesions dcs nerfs dans ^intoxication saturnine experimcntale. Trab. Lab. Invest, biol. Univ. Made., 24, I**52. -- - ` (193.0). Sur l'avcnir des parties constitutiyes de la fibre nerveuse dans I'intoxicatlon exp^rimentale parle piomb. Trav. Lab. Invest, biol. Univ. Made., 26, 163-187, NS;'dron, H. A. (1966). The anaemia of lead poisoning: a review Brit. J. industr. Med., 23, 83-100'. Williams, M. K. (1966). Blood lead and haemoglobin in lead absorption. Brit. /, industr. Med.. 23, 105-111, Appendix Baboon 1 Female 13*4 kg. 5,700 mg of PbC08 given in 6 injections. -5 % loss of weight by day 63. First fit day 94,2nd fit day 9$. On day 99 noted to have definite weakness and clumsiness of the left hand when taking pellets out of the .'W'ding bin. The grip round a rod was observed to be weak, left leg normal. Weakness persisted to death, afici further observed fits on day J07. Final weight oniy 58% of initial weight. Highest blood lead 6,200 /xg/100 ml. injections. General condition remained very good. Sacrificed day 336. Final weight 88% of initial weight; highest blood lead 4,550 /xg/100 ml. Baboon 6 Anubis, female 12*0 kg. 12,700 mg of PbC03 given in 13 injections. No fits. General condition remained very good. Sacrificed day 362, Final weight 100% of initial weight; highest blood lead 2,200 /tg/lOQ ml. Baboon 7 Anufiis, female 1.1*1 kg. 3,200 mg of PbCOa given in 3 injections. Well and active, though increasingly aggressive, until sudden death day 123. Final weight 54% of initial weight; highest blood lead 1,500 /xg/100 ml. Baboon 8 Anubis, female 1.1*8 kg. 4,500 mg of PbCOa given in 5 injections. Jaundiced day 77; serum bilirubin 2*0 mg/10 ml, alkaline phosphatase 445 I.U./litre. No longer jaundiced 4 days later. Found dead day 107. Final weight 62% of initial weight; highest blood lead 725 /xg/100 ml. Autopsy showed hepatic centrilobular necrosis. Baboon 9 Anubis, female 11*8 kg. 3,000 mg of PbCOa given in 3 Injections. Well until sudden death after one fit on day 61. Final weight 70% of initial weight; highest blood lead 700 /xg/100 ml. Baboon 10 Anubis, male 7*2 kg. 1,250 mg of PbCOa given in 1 injections. Bloody diarrhoea day 39 (another control baboon also affected at this time). Died day 39. Autopsy showed haemorrhagic colitis. Fina l weight 77 % of initial weight; highest blood lead 1,100 /xg/100 ml. Baboon 2 Anubis, female 11*2 kg. 4,000 nig of PbC08 given in 4 injections. Hb dropped to 40 % of initial value by day 43, but occult blood found in stools, and Hb returned to near initial value before death in status epilepticus on day 72. Final weight 73%of initial weight; highest blood lead 3,300 /xg/100 ml. Baboon 3 Anubis, female 11*7 kg. 6,200 mg of PbCO, given in 6 ejections. First fit day 148, beginning in the right face lot lowed by a postictal paresis lasting 15 minutes. Very \a\agc between fits, pied in status epilepticus on day 156; final weight 64 % of initial weight; h ighest blood lead 1.780 /xg/100 ml. 1 taboon 4 Vnubis, female 10*7 kg. 7,800 mg of PbCOj given in 8 '.^ 'M'ons. First fit day 95, others followed. Pneumonic *iv' < began day 256; treated with sidphadimidme; seen * i ` a pneumonic death on day 265. Empyema found at n psy. Final weight 66% of initial weight; highest ''>*! lead J,150 /ig/J00 ml. Mmk h i $ Anubis, female 13*6 kg. 9,700 mg of PbCOa given in 11 Baboon 11 Anubis, male 8*6 kg. 4,800 mg of PbC03 given in 5 injections. First fit day 102, followed by others. Died in status epilepticus day 106. Final weight 58% of initial weight; highest blood lead 500 /xg/100 ml. Baboon 12 Anubis, male 9*5 kg. 4,200 mg of PbC03 given in 5 injections. Day 138, apparent weakness of hind limbs preventing the animal rising in its cage. Day 139, a series of grand mal fits observed, without recovery of con sciousness between. Phcnobarbitone, 30 mg, given intramuscularly. No further fits observed for 14 days, but flaccid quadriparesis continued, affecting left limbs more than the right. When the baboon was allowed to walk free the legs became splayed or crossed. Left fingers unable to grasp orange segments. On day 150 the animal was examined in a restraining chair. Voluntary movement present in all 4 limbs, with brisk withdrawal from pinprick. Knee jerks brisk, plantar responses flexor. Systolic B.P. 90 mm Hg. From day 139 to death on day 158 a visual disturbance was seen - the animal groped for proffered fruit and on occasions appeared not to seo it. Marked papillocdema was observed before death. Final weight 60% of initial weight; highest blood lead 630 /xg/100 ml. J? ' 1' 1, DUP050044102 140 Anthony Hopkins Baboon 13 in 4 injections. No signs save loss of weight. Sacrificed Anubls, female 2*8 kg, infant of baboon 7. 2,150 mg of day 150. Final weight 68% of initial weight; highest I J PbCOa given in 4 injections. Apparently dragging hind blood lead 230 ftg/100 ml. quarters day 107. Found dead day 117; final weight 61 % Baboon 15 of initial weight ; highest blood lead 140 ^g/100 ml. Hamadryas, female 3*3 kg. 2,150 mg of PbC03 given i 4 injections. No signs except malaise and loss of weight. 1 Found dead in cage day 75. Final weight 64% of initial : Baboon 14 weight; highest blood lead 560 pg/100 ml. I Hamadryas, female 2-5 kg. 1,950 mg of PbC03 given Received for publication August 28, 1969. i ) \ i i\ i DUP050044103