Document 65MDEKEo17ae7GqJJk76qoaEd

Inhibitory Effect of Polychlorinated Biphenyls on Liver Tumorigenesis In Rats Treated With 3'-Methyl-4-dimethylamlnoazobenzenef N-2-FIuorenylacetamide, and Diethylnltrosamine ',J Sachlo Maklura, Haruko Aoe, Seiichi Sugiliara, Kazuya Hirao, Masayuki Arai, and Nobuyuki Ito 3 SUMMARY--Sturilod were tho effects of polychlorinated biphenyls (PCB) on liver carcinogenesis In rats treated with tho hepatic carcinogens 3'-methyl-4-dImethylamlnoazobenrene (3'-Mo-DAB), N-2-fluorenylacetamlde (2FAA), and or cticthylnllrosamlne (DEN). Animals were ex amined hlstopathologlcnlly aftor they had received the experimental diet for 20 weeks and then the stock diet for 4 weeks. Liver tumors developed In 6S.2, 53.8, and 92.3% of rots In groups treated with 0.03% 3'-Me-DAB, 0.015% 2-FAA, and 0.0025% DEN, raapectively. Rats that received 0.05% PCB only did not develop liver tumors, and those Iroated with PCB end the carcinogens developed only a tow tumors. Multiple liver tumors devolopod after treat ment with 0.03% S'-Me-DAtJ plus 0.0025% DEN (92.3% Incidence) and 0.015% 2-FAA plus 0.0025% DEN (81.8%); after trontment with thoso combinations plus PCB, the Incidonco ot llvor tumors was, very low or aero. HJstologlc examination showed that PCB also inhibited development of nodular hyperplasias, oval cell Infiltration, and bile duct ^ proliferation Induced In the liver by the chemical carcino gens.--J Natl Cancer Inst 53: 1253-1257, 1974. POLYCHLORINATED BIPHENYLS (PCB) nrc used, among other ways, as a solvent in in}; and lmat-transfcr media; they also enttse environmental pollution {14). Investigators have reported chronic toxic effect* in various animals {5, 6). Ftthremann and Lichtenstein (7) reported the synergistic effects of PCB and DOT in insects. Recently, we reported that PCB alone induce hepatic tumors in mice and also promote the induction of tumors in mice by benzene hcxachloridc {8, 9). Furthermore, Kimura and Baba {JO) reported that PCB induce neopiastic hanges in the livers of female rats. This paper d'.-sorlbes the effects of PCB on llvef < arrinogenesis in .rats treated with tbc 3 hepato- carrinogrns J'-inetiiyM-dimcthylaininonzobcnzcnc i/l'-Mr-DAB), vV-jTUuorenylacctamide.^-FAA), and diiMliylnitrosamine j(t)^N). ' MATERIALS AND METHODS Male Sprnenc-Dawlcy rats (Fuji Animal Farm, Tokyo, Japan), initially weighing about 103 g, were divided into 12 groups. They were given the basal diet dcsriibcd previously (//) supplemented with 0.03',,. T-Me-DAB, 0.013% 2-FAA (both from Yoiscynma Chemical Industries I.id., Osaka, Japan) niul/or 11.05% PCB [Knnechlor 500 contains an awrage of .r>'>.0% pcntachlorobiphonyl, 2G.5% tetrachlurohiplienyl, 12.8'% hexachlorobiphcnyl, and 3.0% u iclilorol)i|)lienyl (lot 360, K&ncgnfuchi Chemical Co., Osaka, Japan)] anchor drinking water supple mented with 0.0025% DEN (Nakorai Cltcmical Ltd., Kyoto, Japan). All animals were given food and wafer ad libitum and were housed 6 per wire cage, under a natural light-dark eyrie in a room air-rondilioned at 21 C. They were weighed weekly. The carcinogens were given to 11 groups of rats as follows: group 1: :i'-Me-UAR in diet; group 2: 2-FAA in diet; group 3: DEN in water; group 4: PCI) in diet; group 3: PCB phis 3'-hlc-DAB in diet; group G: PCB plus 2-FAA in diet; group 7: PCD in diet plus DEN in water; group B: 3'-Mc-DAB in diet plus DEN in water; group 9; 2-FAA in diet plus DEN in water; group 10: PCB plus 3'-Mc-DAB in diet and DEN in water; group 11: PCB plus 2-FAA in diet and DEN in water. Rats in control group 12 were given the basal diet without carcinogens. . ... ' Animals were given experimental diets for 20 weeks and tltin stock diet (Oriental MF, Oriental Yeast Co., Tokyo, Japan) for I weeks. Animals that died within 16 weeks from the start of the experi ment were excluded. ; , At the end of the experiment* animals were denied food for IB hours, anesthetized with ether, and killed. The liver, kidneys, and ijpleeft of animals that died naturally or were killed were weighed and examined grossly. . . J For histologic examination, tissue* were fixed in . 10% buffered formalin, emixxidcd'in patafin, anti jj.. stained with <hcintqxy!in and cosin, If,' necessary, ' y, tissues were abo given Mallory'* stain and periodic nrid-Schiff, r. ,f|. vv - " N r> RESULTS , ' i. Chtngas In Body and Livar Wsight (Tabla 1) >' ^ The Ixtdy weight of all rats increased during the experiment, but animal* treated with carcinogens and/or PCB gained much less weight that) controls. lit particular, animal* in group 11 (PCB-ir2-FAA|-f- DEN) gained only about half as much weight as controls. ' The liver weight, as a percentage of the body weight, was generally at least twice as great in |)criincntnl groups as in the control. Thi* increase was due to development of tumor* and/or,1 in animals treated with PCB, to swelling of the liver. In group* 1 ^ *i ( ' ." , 1 Received Mart* 25, 1074; atreplcd July 18, 1974. > Supported in bai t by grnu for scientific research from the Ministry of Hraltr of Japan (1973), ihe Ministry of Education of Jnpou (I8015T, 19/3), and the Experimental Pathological Rcsrnrch Axsoriation (1973-74). .. * Deportment x>f Ondafoeical Palliology( Cancer Qenter Inslitute, Nara Medic*] Univmity, Kashihaiu, Nara 534, Japan. journal or Tin: naxjon/u. cancer institute, .vol. 33, no. 3, novf.moer i97* 1 1253 . DSW 027013 STLCOPCB4010975 *I . 125-1 ;*' MAICTUHA ET AL. Taiiu: 1.- -Changct in Vie boefg and lircr wcigAh of male rale treated wtlA PCB and chemical weinogent for 14 leeckt Group * 1. :r-Me-l)A0..................1................. . 2. 2-FAA..... . ................................. . 3. HEN.............................................. 8I.. PPCOBIH.U..'.-.M...l-..DAB.....................:................................... .. 0. PCB-i-2-FAA.................................... 7. 1'CIM DF.N.................................... . 1080... .2PV-CF-BMAAe|- .-|VIID-AMElMeN-1-.n.).Ai.i.NB..-..I..-..P....R....N.......................................................... . _____ 11. PGH 12-FA AH-DEN........................ 12. Conirul........................................... 2244.. 00 23. 6 2244..00 24. 0 33. 3 23. 8 20, r, 24. 0 13. 7 24. 0 Hi Initial No. of mts 24 16 10 2244 24 10 16 1100 10 12 BtflTvccoNo. of Body weight (g) rat* ' Initial Final Liver weight (final) Percent 8 wbeoidgyht a1s3 13 2139 17 9 13 U13 12 ' 10 189. 7 105. 8 182. 0 119818.. 09 190. 7 118823..39 118874..97 180.7 184.6 447253.. 85 431.5 349070.. 45 883. 2 331877.. 43 310. $ 300. 3 278. 0 SIS. a 1180.. 61 28. 7 2251.. 49 23. 1 20. 9 64. 5 2308.. 20 20. ( 11 1 48.. 95 6. 7 50.. 44 6. 0 &6 18. 7 11 2 0. 5 7.6 13 ren, 0.lii% Kann lilur 60ni'..Mc DAII, 0.03%; } FA A, 0,014%; '>**. 0.0024%. . * Animals fr 1 r\pnlin,u1nl Old For 20 vrk mid lhn mock diet lor < vk. Numbon <U Indlialt thal likU AM Mon N wk. ' Hull I hr,1 illnl a llliln H wk (rum Mod nl ript. arm rnlu<td from IdfUsI N*. 8 and 9, treated with 2 carcinogen*, livci' weigh#* increased greatly due to development of large lwer v tumor*. Qrott Findings In the Liver The livers of tats treated with PCB alone had no tumor*. The surface* were smooth and most were speckled yellowish-white (fig. I). In contrast, the liven of rat* treated with 3'-Me-DAB, "2-FAA, ami,'or DEN had irregular lurfnee* with multiple large, yellowish tumors up to 2.5 cm in diameter. Some cancerous nodule* showed central iimbilica* tions and hemorrhagic change. In many animals, malignant neoplasm* of the liver and metastase* from liver tumor* were noticed in the omentum, mesenteric lymph nodes, and diaphragm. Malignant neoplasms and metastases were most frequent in rats treated with 2 hepatocarcinogem, such as those in group 9 (fig. 2). Non-neopjastic areas of jhe liver showed cirrhotic changes, and tire surface of the liver of some rats treated with 2-FAA had many small cyst*. Administration of PCB clearly reduced neo plastic and cirrhotic changes of the liver, evtn in animals treated with 2 hepatocarcinogem (fig. 3). However, small white nodules were seen in the livers of animals treated with PCB plus 2 carcinogens. Histologic Finding* In tti llvtr (Table 2) ' I Hepatocellular carcinomas.--Treatment with l carcin ogen induced hepatocellular carcinomas. These were round in 15 of 23 rats (65.2%) treated with S'-Mc1>AR, 7 of 13 (53.8%) treated with 2-FAA, and 12 of 13 (92.3';) treated with DEN. No rats treated with l'CB alone developed hepatocellular carcinomas, rrcaimini with 2 carcinogens resulted in a higher incidence of hepatocellular carcinomas than treat ment with carcinogen plus PCB, i.e., in 12 of 13 rats (92.3',) treated with 3'-Mc-DAB plus DEN and 9 of I I (j'l-y'i') treated with 2-1'AA plus DEN. However, the incidence was very low in animals treated with 2 enmnogeni plus PCB II of 13 rats (7.7%) treated with 3'-Mc-DAB and DEN plus PCB, and none of 12 animals treated with 2-rAA and DEN plus PCB]. Nodular h)peTpljqit.--Almost Jill rtlft in groups treated with I cardnoge** developed nodular hyper plasia in the liver: 22 of'23 rafr\05.7fe) fed 3-Me- > DAB and I) of 13( rats (IDO.0%) ftd.S-FAA or DEN. * No nodular hyperplasia was found in the livers of rats treated with PCB only. Moreover, nodular hyper plasia did nbt develop in die livert of animals treated with S'-MsftDAB or DEN dlus iPCB and developed in only 1 of the 17 rats (S.9%) treated'-with 2-FAA plus PCB. All rata treated with 2 carcinogens devel-' ' oped nodular hyperplasias in the liver. However, these were found only In 4 of 13 rats (38.8%) treated with 3'-M-DAB Find DEN phis PCB pnd In 3 of 12 tats (23.0%) treated with 2dFAA and DEN plus PCB. ' Non-neoplaslic areas.--The lit&t of rats treated with PCB showed parenchymal cell hypertrophy and cerrtrolobular areas with foamy or vacuolated cytoplasm. Nuclear irregularities of parenchymal cells were oc casional (fig. 4). In rati treated-with 1 or 2 chemical , carcinogens, oval cell infiltration and bile duct proiiferation were usually noticed. Cholangiofibrosis de- ' velopcd more often in rats treated with 2 carcinogen* than in those treated with onlybne. Ih rat* treated ' with 2 carcinogen*:plus PCB, oval'cell infiltration and bile duel proliferation in the liver were alight. DISCUSSION Results of the present study show that PCB inhibit the hcpatocarcinogenic actions of 3,--Me-DAB, 2-FAA, and DEN in rats. Previously, several authors reported the tumorigenic action of PCB on rat arid mouse liver (8-10); in the present work, we observed no hepatocarcinogencsis in rats treated with PCB only. This difference may depend on the dose and period of administration of K3B, because we found that many hyperplastic nodules developed in the livers of male rats treated with 1000 ppm PCB (Kanechlor 500) for 72 weeks (Ito N, Nagasaki H, Makiuri S: Unpub- i i 1 i 1 1 i 1 I DSW 0 2 7 0 1 4 STLCOPCB4010976 P.J^r.CT OP PCD ON LIVER TUMORJOENESTS IN RAT 1255 T.\itiK 2.---liiutnpnthotugi': change* oj the lirtr in mate rate treated with PCD find chemical carcinogen* for H week* tirnup HUlopnthoIngy of liver F.lkclivo Cell No. of Kant- livper- mi* * changes \ rophy Oval cell inliiIrnlion Bile duct prolif- oration Uholnngiofibrosis * Nodular hv|KT- . pfosia* Cancer 1. 3'-.\k:-DAB............................ 2. 2-FAA.................................... :i. DI-IN i. pen. ih,b ! li'-Mv-DAB.............. ii. rni 1 2-KAA........................ 7. p<;ii ! DFN.......................... 8. DAIN DFN............ !). 2-FA A 1 DI-IN.............. ........ 10. pen 1 .'i'-Me-P AI) i- DIIN. 11. pen '-2-FAA+DllN.......... 12. Control..-- .......................... 23 13 13 10 23 17 0 13 11 13 12 10 1 :h -i- + 4i *; i (4. 3) 22 (95. 7) ir. (05. 2; 0 13 (100. 0) 7 (03. 8 1- 1 4- 0 13 (100. 0) 12 (02. 3 4 l- I- 4- d'. 4- 0 0 0 -1- 4- -k d: 0 0 0 4- 4- 4: i 1 (5. 9) 1 (5. 9) 0 I- I I- J: f 1 (11. 1) 0 0 -1- k I- 1- i : 4 (30. 8) 13 (100. 0) 12 (02. 3 -l- k 1 1 i - 0 11 (100. 0) 9 (81. 8 I- 4- i- 3 (23. 1) 4 (30. 8) 1 (7. 7 + 4- -k 2 (14.3) 3 (26. 0) 0 ----" 00 0 Srt fooinoto #, tnbto l. * Sir foulnoio c, ll)to I. - NiimiAT ..... I i*r<v>u) of i.it4 rlih chotoiiflonUrodn, nodular hypcrpluts, or umerr o( Hvi-r. Iishcd results). In the present work, the livers of rats (refill'd M'iiii l'CB alone showed fatty change* and cell hypertrophy, a* rc)>oncd by other investigators (tj, 12). Also, administration of 2 carcinogens caused movkrtt oval cell infiltration and bile duct prolifcra- lion, whereas administration of PCB with 2 corcino* gens greatly reduced these histologic changes. , Treatment for 24 weeks with 0.03% benzene hexa- t hloride (BHC) had a hcpatocarcinogenic action in mice (1.1-15), and supplementation of BHC with 0.025'V. FOB for 24 weeks promoted this effect (9). 'This suggested that a mixture of hepatocarcinogens and PCB might have a synergistic action in promoting hcpaiucnrrinogcnrsis in experimental animals. How ever, in the present work, PCB clearly inhibited the pnxltiriion in rats of liver neoplasms induced by potent hepatocarcinogens other than BHC. Incidence of cytoplasmic lesions of liver parenchy mal cells in the smooth endoplastic reticulum is im erased, and microsomal enzymes arc induced, in animals given l'CB and in man poisoned with PCB (9, //>). These effects of PCB have l>cen investigated, not only histologically and by electron microscopy Imt also by biochemical analysis (17-10), l'heno- liurbital nr mcthyichnlanlhrenc arc reported to have protective effects against the hcputocarcinocenic actions of azo dyes or 2-FAA (11, 20-24). Their effects in the test animals are apparently due to stimulation of liver enzymes which convert the car cinogens to muicarcinogenie metabolites (25). How ever, Iiorh-Ligcti cl al. (2d) and Makiuru et al. (27) reported that mctiiylchoiauthrcne did not inhibit the induction by DEN of liver cancer in rats. These results and the inhibitory effect of I'CB on the hepato- Ciii'ciiiogcnie actions of compounds such as 3-Mc- DAH :md 2-FAA suggest that a microsomal enzyme system melalrolizing drugs may be involved somehow in die inhibitory effect of PCB. However, they suggest that not only a microsomal enzyme system but also some other factors may have an important function in the inhibitory effect of PCB on the carcinogenicity of DUN. The synergistic actions of mixtures of certain hepatic carcinogens have been observed in rats (28, 20). The synet^istic actions of DEN and 3'-Me-DAB or 2-FAA were also observed in this work. Combina tions of 2 carcinogens caused marked invasive growth of hepatic carcinomas and death from lutnors early during the observation period. However, PCB in hibited the development of hopatic carcinomas even in animals treated with 2.carcinogens. This suggests that PCB must be very strong inducers of the enzymes that metabolize carcinogens. The differfence Ixitwcen the present results and re ports on the effect of PCB in promoting liver tumorigenesis induced by BHC in mice suggests that the mechanism of carcinogenesis by BHC, which contains many chloride groups, differs from that by other tiepaiocardnogcns such as 3'-Kte-DAB, 2-FAA, and DEN. REFERENCES ' (/) Kop.man JH, Tin Notvaa Dx Bxauw MC, Dt Vo RH: Chlorinated biphenyls in (kh, mussels and birds from live river Rhine and the Netherlands coastal area. Nature (bund) 221 :l 126-112fl, I960 (2) llr.vNOLDs LM: Potychlorobiphenyts (PCBs) and their interference with pesticide residue analysis. Bull Environ Contain Toxicol 4:128-143, 1969 (3) Pr.AftALL I7H, Lnteta JL: Polychlorinated biphenyls, another long life widespread chemical in the environ ment. Bicaticnce 20:958-064, 1070 (4) Tiao CH, Sullivan WN, Noanstiin I: A comparison of evaporation rates and toxicity to house (Hes of lindane and lindane-chlorinated polypheny! deposits. J Econ Entomol 4(1:882-884, 1053 , (5) Vos JC, Barns RB: Dermal toxicity studies of technical polychlorinated biphenyls and fractions thereof in rabbits. Toxicol Appl Pharmacol 10:617-633, 1971 (6) Koli.ea LP, Zinkl JC: Pathology of polychlorinated biphenyls in rabbiu. A*n J Pathol 70:363-378, 1973 (7) FuttaxiiANN TW, LtCHTtxtTXiN EP: Increase In the toxicity of organophospharus insecticides to house flies due to polychlorinated biphenyl compounds. Toxicol Appl PharmaCol 22:028-640, 1972 (t) Nagasaki H, Town S, M*ca T, et al: Hepatocarcino- genicity or peirehlorltuitcd biphenyls in mice. Gann 63:801,1471 : 'i DSW 0 2 7 0 1 -5 STLCOPCB4010977 125H MAKIURA KT AI-. (.9) Iro N, Nagasaki II, Arai M, et al: Histopathologic undid on Ihrr Itimorlgcni sis induced in mice by ttvluiiral |x>tychlinin:it< <1 hmhrnylt and ill promoting rtfrrt on liver tumors inducnl by lienzene lirxnchlorfde. J N.nl Omirrr Inst ril: 1 G'I7--11-1 cj, 11173 (to) Kim hi N, 11 ina T: Neoplastic changes In thy rut llvrr induced bv polyi'bloimated biphenyl. Gann 04:105 1011, 11173 ' (ID Mari'cami M, lro N. Kosmm Y, cl al: Influence of 3-tnethylcholaiithrcnc on liver carcinogenesis in rata ingesting IH.-cdtioninc, 3' nielliyl-'l-dimctbyinntino- n7uben/.enr, anj N-2-niiorenyJncelainide. Cancer Res'.'7:2011-2011), IW7 (/:>) ItoN, Nagasaki H, Akai M: Interactions of liver tnmorircnriis in tniee treated with technical polychlorinated biphenyls (I'CBs) and bciv/citc hesachloridc (HHG). I is I Syntp on Ecolog Chent, .Susotio, Japan, 1973, pp Ml-147 U3) Nagasaki II, Tiimii S, Meoa T, et al: Caiclnogenicity of brnrenc hrxiicliloridc (BMC). In Topics in Chemical Carcinogenesis, Proe 2d Ini Syinp of The Princess Tukainaittu Cancer Research Fund. Tokyo, Univ Tokyo Press, 1972, pp 343-353 (H) --------- : Hcpatocurcloogcnlc effect of y- and 4-isomers of benzene hexuchtorldc in mice. Gann 03:393, 1972 (IS) Ito N, Nacaiaxi H, Aai M, et nl: Histologic and ultra- itniettiral studies on hcpatocarcinogcnicity of ben- kciic hexacldorldc In mice. J Natl Cancer Inst 51:017-- B2G, 1973 (IS) Hikayama C, laiSA T, Yamamoto T: Fine structural changes of the liver In n patient with chlnrobiphenyl intoxication. Fukuoka Actn Medica 60:455-461, I9G9 (17) Tanaka K, Komatsu F: Sliatenlng of hexobarbtt&l sleeping lime after sinatl doses of PCI) In rats. Fukuoka Afta Medlru 63: 3GO-3G6, 1972 (It) I.tTittxsT CL, Faxmx TM, Hakp.h AM, et ah F.ITcct of polychlorinated biphenyls on hepatic microsomal enzymes In the rnta. Toxicol Appl Pharmacol 23: 1 12-122, 1972 (19) Ch*x TS, DuBoit KP: Studies on the aniyree Inducing cITact sf polychlorinated biphenyls Toxical AprS Pt^rn.Acol 2G:504-512, I97J 1 (HO) PxnAlwo C, Fry MR, SrAern-oT E: Reduction aad enhancement by phenobarbital of hcpatocarclnogenaii iornKod kt the rut by 2-aeerylarainoftuoreflS. n---- Rn *1:1506-1512, 1971 (J!) IsMtOATa M, Watah ask M, Ooaihdca S: Effect of barbital on carcinogenic actions and metabolism ef 4-dbnWhylatoino7.aobc.mcnc. Gann 58:267--#01, 1967 . (22) Kun* W, Schaude O, Thomas C: The effect of phtao- barbital and hnlogenitcd hydrocarbons on nitrosamlne carcinogenesis. 7, Krebsfbrsch 72:291-304. 1969 - (23) Miu.t* EC, Miuax JA, Brown RR, at al: On tfae ' protective action of certain polycyclic aromatic hydie- , carbons against carcinwcnetts by aminoaxo-dyes and - 2-acctyIaininofluorcne. Cancer Res 16:469-477, 1956 (24) Gram TE. Rooms I-A, Fours JR: Effect of pretreatmiftt ,. of fabblU with phenpbarbitfu or 3-mfethyleholanthreaa * on the distribution ofdnig-mctabelliingenzyme aetirlly In subfractlons of hepatic microaomW. T Pharmacol EaCb Tber 157:485-445, 1967 * (25) GtLKx* HV: Carcinogen!, enzyme Induction, and gessa action. Adv Oncer Ret 10:1-61, 1967 _ (26) Hoctt-Liorn C, Axoul MF, Aroos JC: Oarpbiaed ' carcinogenic effects of dlmethylnltrosamlne add Sr ' nsethyknolantltrene in the rat. J Natl Cancer but 40:535-549, 1968 (27) Makiuka S, Kawamoto Y, Suoihara S, et al: Effect* ; l-naphthyl bathlocyanate add VmethyicbolaBthnaso'i on hepatocardnogenerk in tab treated with diethyl* if nlrrosatnine. Gann 64:101-104, 1*73 ' (2t) MacDonaijj JC, Miller F.C, Miller JA, tst al: Tbs synergistic action of mixtures ef certain hepatic) carcinogens. Cancer Res 12:50-54, \9/)2 (29) Ito N, Hiaia Y, Konisiii Y, et al: Thff development of rardnotna in liver of rats treated srlOi m-td|uylene<lia-v mine and the synergistio and antagonistic effects with'1 other chemicals. Cancer'Ret 29:1137-|145, 1M6 i I' 11 .I tr 'V k' ) -'V L -'I"- i i i OSM 027016 STLCOPCB4010978 I ; 1 `1 I . . 4 . ', Vr'S,J t t *.. '/;W.-vV *.* ' ' V" . rV . ' / . v'. 1-V; <V 3/ . ' i'Jfk'y*- >' . 'V^' V v wMgmzz' V-H v^' V ...' fV'-. ^W y^V, r ,V : Fioiwr. |,--Liver ofrat given PCB. Nth ipcckled, yellowlih-white, unooth lurfuce. ^ Fiuiwr. 2.--Liver of rat treated with 3'-Mo-DAB nnd DEN. Many neoplaitlc change* agd njal/eyti a^e e&i. :, PtouaxS.--Liver of rat treated with 3'.Mc-DAB, DEN, and PCB. The unooth surfaceliaj a fcw white ipotv ' '_ Ftouae 4.--Fatty changer and nuclear irrcgularitict in liver of rat treated with PCB only. Some oval cell iridpollon fa Men. Hema> toxylin tind ocaln, X 100 ' i -Y . ' . .1 ' OSM 027017 Waxiura kt al. l$57, STLCOPCB4010979