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At 7 d, in marked contrast to ethidium, only 6 5 % o f the administered drug had been excreted ( 4 4 % in urine and 2 1 % in faeces) and in animals sacrificed at that time it was f o u n d that the majority ( 9 5 % ) o f the residual drug was present in the liver (Table II). These findings suggest that the pharmacokinetics o f berenil in bovines should be investigated as a matter o f urgency; such studies could well provide a rational explanation f o r conflicting data in the literature o n the protective action o f this drug [19, 20].


Advances in our knowledge o f the pharmacokinetics o f anti-trypanosomal drugs that have resulted in recent years f r o m the use o f radiolabeled drugs o f high specific activity justify the W H O / F A O recommendation [1 ] and stress the need f o r radiolabelling other currently used trypanocides t o probe all aspects o f 264 NEWTON and GILBERT

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their pharmacokinetics and the molecular basis o f their action. Such knowledge may suggest ways o f improving existing drugs or designing new ones and throw light on the problem o f drug resistance.

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The authors wish to record their thanks to The Boots Co. Ltd., UK and F. Bauer, Hoechst Farbwerke, A G, Federal Republic o f Germany, for generous gifts o f 14 C-ethidium and 14 C-berenil, respectively. This work was funded in part by a grant from the F o o d and Agriculture Organization o f the United Nations.


[1] WORLD HEALTH ORGANIZATION, Tech. Rep. Ser. 635 (1979).

[2] LOSOS, G.J., IKEDE, B.O., Vet. Pathol. 9 (1972) 1.

[3] BROWNING, C.H., MORGAN, G.T., ROBB, J., WALLS, L.P., J. Pathol. Bact. 46 (1938) 203.

[4] LEACH, T.M., KARIB, A.A., FORD, E.J.H., WILMSHURST, E.C., J. Сотр. Pathol.

Therap. 65 (1955) 130.

[5] WHITESIDE, E.F., 8th Meeting of the International Scientific Committee for Trypanosomiasis Research, Jos. 141, Publication 62, Commission for Technical Cooperation South of the Sahara, London (1961).

[6] JENSCH, H., Arzneim.-Forsch. 5 (1955) 634.

[7] NEWTON, B.A., J. Gen. Microbiol. 17 (1957) 718.

IAEA-SM-263/43 [8] CRAWFORD, L.V., WARING, M.J., J. Gen. Virol. 1 (1967) 387.

[9] PULLEYBANK, D.E., MORGAN, A.R., J. Mol. Biol. 91 (1975) 1.

[10] NEWTON, B.A., "Antiprotozoal drugs as biochemical probes", Biochemistry of Parasites and Host Parasite Relationships (VAN DEN BOSSCHE, H., Ed.), Elsevier, Amsterdam (1976)459.

[11] DEAN, P.M., WAKELIN, L.P.G., Philos. Trans. R. Soc. Lond. В 287 (1979) 571.

[12] WARING, M., J. Mol. Biol. 54 (1970) 247.

[13] NEWTON, B.A., "Recent studies on the mechanism of action of berenil (diminazene) and related compounds", Comparative Biochemistry of Parasites (VAN DEN BOSSCHE, H., Ed.), Academic Press, New York (1972) 127.

[14] NEWTON, B.A., "The chemotherapy of trypanosomiasis and leishmaniasis: towards a more rational approach", Ciba Foundation Symp. 20 (new series), Elsevier, Amsterdam (1974) 285.

[15] FESTY, В., STURM, J., DAUNE, M., Biochim. Biophys. Acta 407 (1975) 24.

[16] KANDASWAMY, T.S., HENDERSON, J.F., Cancer Res. 23 (1963) 250.

[17] MacGREGOR, J.T., CLARKSON, T.W., Biochem. Pharmacol. 21 (1972) 1679.

[18] LEACH, T.M., ROBERTS, C.J., Pharmacol.Therap. 13 (1981) 91.

[19] VAN HOEVE, K., CUNNINGHAM, M.P., Vet. Rec. 76 (1964) 260.

[20] CUNNINGHAM, M.P., HARLEY, J., VAN HOEVE, K., East African Trypanosomiasis Organisation Report (1966) 63.

[21] NEWTON, B.A., GILBERT, R.J., Parasitology 79 (1979) i.

[22] GILBERT, R.J., CURTIS, R.J., NEWTON, B.A., Parasitology 79 (1979) ii.

[23] GILBERT, R.J., NEWTON, B.A., in Biochemistry of Parasites and Host Parasite Relationships: The Host Invader Interplay (VAN DEN BOSSCHE, H., Ed.), Elsevier, Amsterdam (1980) 647.

[24] GILBERT, R.J., NEWTON, B.A., Parasitology (in press).

[25] CALNAN, J.S., FORD, P.M., HOLT, P.J.L., PFLUG, J.J., Br. J. Plast. Surg. 25 (1972) 164.


J. i (1973) 569.

[27] GOODWIN, L.G., TIERNEY, E.D., Parasitology 74 (1977) 33.

[28] GOODWIN, L.G., GOSS, M.D., LOCK, J.A., Br. J. Pharmacol. Chemotherap. 5 (1950) 287.

[29] TAYLOR, A.E.R., Br. J. Pharmacol. Chemotherap. 15 (1960) 235.

[30] RAETHER, W., HAJDU, P., SEIDENATH, H., DAMM, D., Z. Tropenmed. Parasitai. 23 (1972)418.

[31] RAETHER, W., HAJDU, P., SEIDENATH, H., DAMM, D., Z. Tropenmed. Parasitol. 25 (1974)42.


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Uptake of isotopically labelled mercury, cadmium and zinc from a calcareous chernozem and a podzolized brown earth by spring and winter varieties of wheat, rye and barley was investigated in pot experiments carried out until maturity of the plants. The labelled heavy metals, applied at concentrations innocuous to plant growth (0.5 ppm Hg or Cd, 50 ppm Zn), were determined radiometrically in the straw and in the grains of the harvested plants, as well as in the milling products (bran, semolina and flour) obtained by standard procedures of grain processing. Uptake of mercury was several hundred times smaller than the uptake of cadmium, if both metals were applied to the soil in equal amounts. Whereas the uptake of mercury from the acid soil was insignificant or not detectable, cadmium was taken up from this soil at a much higher rate than from the alkaline soil. Thus, not mercury, but cadmium imposes the greatest hazard on the food chain. Winter varieties of cereals took up more mercury and cadmium than did spring varieties. The heavy metal content in the plants decreased considerably when plants approached maturity. During translocation through the plants the metals were gradually retained when passing from the stalks ('straw') into the grains, and from the seed cover ('bran') into the endosperm ('flour'). The heavy metal content of the grain fractions decreased in the order: bran semolina flour. Concentrations of heavy metals in flour were 3—8 times smaller than in straw, showing that flour is least affected by heavy metal pollutions of cereals via the soil. The metal content of the various flour types was correlated with their percentage of bran and with their ash content. By adding an ion exchanger to the soil the pattern of relative distribution of heavy metals in mature plants was not changed, but the cadmium content of all cereal products was considerably lowered.

* The abstract only is published, since it is intended that the full paper will appear in the IAEA-TECDOC Series (unpriced publication).

Poster Presentations IAEA-SM-263/21

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*Instituto de Pesca, Secretaria da Agricultura, Sao Paulo Centro de Energia Nuclear na Agricultura ( C E N A ), + Universidade de Sao Paulo, Piracicaba, Brazil Fish weighing between 2 0. 6 0 and 5 3 6. 9 0 mg were exposed to 2 5. 5 0 and 100 p p b o f 203Hg(NO3)2 f o r 20 d in plastic aquaria containing 4 L o f s o f t aerated water (hardness = 36 mg C a C 0 3 ; p H = 7.2; O D = 7.0 m g / L ; T = 23°C). At each sampling interval six fish were collected and immediately sacrificed by placing them in a deep freeze [1 ]. They were then wrapped in aluminium foil, placed in a glass tube and the dose determined by gamma counting, using a single-channel spectrometer and a 3 X 3 in Nal ( T L ) well crystal [2J. 1 The average content o f mercury, in nanograms per gram fresh fish against time, is plotted in Fig 1. It was f o u n d that the highest mercury content in fish was achieved after 100 h, that is, nearly the time indicated f o r a fish toxicity bioassay test [3]. A concentration factor ( C F ) o f 168.4 o f 203Hg(NO3)2 by Guppiesafter 72 h incubation was also determined [4]. The rate at which mercury moves in and out o f fish depends on its concentration in water, as proposed by Neely [5]. Standard deviations o f experimental data decreased when the sampled fish had approximately the same weight. Whole b o d y clearance was carried out by transferring fish from the aquaria containing 35 and 70 p p b o f 203Hg(NO3)2 to mercury-free water. The doses were measured as already described. The data shown in Figs 2 and 3 give a similar rate o f clearance for both concentrations tested (X 3S = 0. 0 3 8 6 8 and

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FI G.I. Uptake and clearance of 203Hg(NO3h, in nanograms of mercury per gram fresh fish, by Lebistes reticulatus with three treatments: A = 100 ppb; В = 50 ppb and С = 25 ppb.

Points indicate average content of six fish, bars indicate one standard deviation.

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FIG.2. Elimination of mercury by Lebistes reticulatus in uncontaminated water. Fish were transferred from a water solution of 35 ppb of mercury as 203Hg (N€3)2 after a period of exposure.

270 POSTER PRESENTATIONS FIG.3. Elimination of mercury by Lebistes reticulatus in uncontaminated water. Fish were transferred from a water solution of 70 ppb of mercury as 203Hg(NO3)2 after a period of exposure.

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(r) were 0.91 and 0. 9 4 for 35 and 7 0 ppb, respectively. T h e equations differ from those obtained for w h o l e - b o d y retention o f mercury nitrate in G o l d fish [1].

The conclusions were as follows:

(1 ) Uptake rate o f mercury by Guppie is related to the mercury content in the water, which increases with the metal concentration in water (2) The highest bioconcentration o f mercury occurred at the same time in all treatments, i.e. about 100 h (3) Guppies eliminated their w h o l e - b o d y mercury content in about 5 d when transferred to a mercury-free environment (4) The rates o f mercury clearance obtained in mercury-free water were quite similar ( T b 3 5 = 17.9 h and T b 7 0 = 18.7 h ) (5) Standard deviations o f the retained dose were lower when the weight o f the sampled fish was uniform.



[1] WEISBART, M., Can. J. Zool. 51 (1973) 143.

[2] JAAKKOLA, T., et al., "Cadmium content of sea water, bottom sediment and fish, and its elimination rate in fish", Radiotracer Studies of Chemical Residues in Food and Agriculture (Proc. Panel Vienna, 1971), IAEA, Vienna (1972) 69.


[4] PRABHU, N.V., et al., Bull. Environ. Contam. Toxicol. 18 (1977) 409.

[5] NEELY, W.B., Environ. Sci. Technol. 13 (1979) 1506.


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P.H. A D A M S Pest Control Chemistry Department, Slough Laboratory, Ministry o f Agriculture, Fisheries and F o o d, Slough, United Kingdom Chlorpyrifos-methyl is an organophosphorous insecticide that has been approved in certain countries for admixture to stored cereals. It is very effective against insects that develop within the kernel o f wheat grains. T o determine why the c o m p o u n d should be so effective it was necessary t o treat individual grains with chlorpyrifos-methyl. However, a preliminary study had suggested that after treating grains in this manner there was an unexpectedly rapid loss o f insecticide.

The aims o f the current w o r k were to treat individual grains topically with 1 4 C-chlorpyrifos-methyl to measure the rate o f loss o f insecticide and t o identify the nature o f the materials lost.

The chlorpyrifos-methyl used was radiolabelled because it was necessary t o measure accurately small changes in the minute doses o f insecticide ( 3 0 0 ng or 5 p p m ) applied to single grains, with the further advantage that liquid scintillation counting (lsc) would provide information additional to that obtainable by gas liquid chromatography (glc). The treated grains were placed in glass scintillation counting vials and either left open to the atmosphere or sealed. Small filter papers were similarly treated to provide a non-biological system f o r comparison. All vials were kept at 27°C, 70% R H for up t o 7 d. Each grain or filter paper and the


inner surfaces o f each vial were analysed f o r both chlorpyrifos-methyl alone (by glc) and for the 1 4 C-insecticide, together with any radioactive degradation products (by lsc).

The results confirmed that grains stored in unsealed vials lose their 1 4 Cchlorpyrifos-methyl rapidly, possibly by volatilization directly to the atmosphere.

The loss was virtually c o m p l e t e after 7 d. By storing some o f the grains in sealed vials it was possible to prove that a portion o f the insecticide is lost as intact chlorpyrifos-methyl by volatilization to the inner vial surface where it collects together with 3,5,6-trichloro-2-pyridinol. S o m e o f the latter arises by degradation of. the chlorpyrifos-methyl on the glass; indeed this discovery was exploited as a convenient m e t h o d o f preparing the 1 4 C-pyridinol. Work is in progress to see whether any o f the pyridinol could arise f r o m degradation by the grains and subsequent volatilization to the vial surface.


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W. D E D E K Forschungsstelle fürChemische T o x i k o l o g i e, Akademie der Wissenschaften der D D R, Leipzig, German Democratic Republic The metabolic fate o f butonate, an organophosphorous insecticide o f reduced mammalian toxicity, was investigated in chemical and biological media using 32 P-labelled c o m p o u n d s synthesized in our laboratory. Analytical methods were two-phase partition, T L C scanning and autoradiography.

Butonate can be degraded by the following f o u r routes (Fig. 1):

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In aqueous non-biological media butonate is degraded at p H 5. 5 to trichlorphone, demethyl trichlorphone and demethyl butonate, at p H 5. 5 preferably to vinylbutonate, demethyl butonate and demethyl vinylbutonate with traces o f trichlorphone. Formation o f dichlorvos is possible in traces only according to the range o f pH.

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