The present situation of feed additives and drugs for animal use was reviewed from viewpoints of legal regulation and its background. The residues of chemicals in livestock products and the food safety were also discussed.

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A subacute poisoning, called Yusho, which occurred in Japan in 1968, was caused by the ingestion of specific lots of Kanemi rice bran oil which had been accidentally contaminated with large amounts of Kanechlor 400 (a commercial preparation of PCB mixture with a chlorine content of about 48%). During this decade, most of the clinical symptoms of Yusho has diminished gradually along with a decrease in PCB levels in the blood of patients. However, some of them such as subcutaneous cyst formation, pigmentation of the skin, eyelid and gingiva, eye discharge and abnormal changes of the tarsal gland were still continuing in relatively small number of the severe grade patients. Since the additional contaminants, polychlorinated dibenzofurans (PCDF) and polychlorinated quaterphenyls (PCQ), were also detected in the causal oil, their synergetic effects on the PCB poisoning have become of great concern to understand the etiology of Yusho. In this paper, studies for Yusho during these ten years were briefly reviewed dividing in the following chapters ; (1) Toxic compounds in the rice bran oil, (2) Alterations in the clinical symptoms of Yusho, (3) Relationship between the gas chromatographic patterns and levels of PCBs in the blood and the clinical symptoms, (4) Toxicological assessments of PCBs and PCDFs and (5) Treatments for Yusho.

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Biodegradability of several guanyl compounds was estimated by the use of activated sludge under aerobic conditions and soil bacteria under anaerobic conditions and soil perfusion apparatus. Soil bacteria were isolated from the sediment in a sewage drainage. Activated sludge did not biodegradate guanidine, cyanoguanidine and guanylurea which were formed from calcium cyanamide fertilizer and known to be biodegrabated to ammonia in soil. Activated sludge biodegradated some guanyl compounds such as methylguanidine, hexamethylenediguanidine, creatine and creatinine. The change of nitrogen source from polypeptone to guanidine or cyanoguanidine affected the composition and population of microorganisms in activated sludge but it did not endow activated sludge with the biodegradating activity for guanidine and cyanoguanidine. Soil bacteria anaerobically degradated guanidine, cyanoguanidine and guanylurea which were not degradated by activated sludge. Soil bacteria under anaerobic conditions, however, did not degradate any of methyl derivatives of guanyl compounds-methylguanidine, which was degradated by activated sludge, 3-methylcyanoguanidine and 5-methylguanylurea-and hexamethylenediguanidine. By soil perfusion method, biodegradability of such eight guanyl compounds as guanidine, methyl-guanidine, hexamethylenediguanidine, 3-methylcyanoguanidine, guanylurea, 5-methylguanylurea, creatine and creatinine was estimated. Methylguanidine might be degradated to nitrate via another guanyl compound in soil. Neither guanylguanidine nor 1, 1-dimethylguanylguanidine was degradated by any of estimation methods for biodegradation.

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Butyltin compounds were found to inhibit the activity of purified yeast glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in an in vitro system. The order of inhibitory effect, after tetrabutyltin, was dibutyltin, tributyltin and monobutyltin. The concentration of tetrabutyltin giving 50% inhibition of the yeast enzyme was 4.3×10^-6 M. On the other hand, the activity of the human erythrocyte enzyme was inhibited only by tributyltin, but not by monobutyltin, dibutyltin or tetrabutyltin. The inhibition of glucose-6-phosphate dehydrogenase of yeast by tributyltin and tetrabutyltin could be prevented by the addition of bovine serum albumin, whereas the inhibition of the activity of the erythrocyte enzyme by tributyltin was not affected by bovine serum albumin. However, the addition of albumin to the once-inactivated enzyme did not restore the enzyme activity. Cysteine slightly protected the yeast enzyme from the inhibition by dibutyltin but did not affect the inhibitions by tributyltin and tetrabutyltin.

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Analytical method for aromatic nitro compounds in airborne particulate matter was studied by gas chromatography (FID) and gas chromatography-mass spectrometry. Airborne particulate and diesel engine exhaust samples were collected on glass fiber filters by using high-volume air sampler and organic compounds in the samples were extracted with benzenemethanol (4 : 1) in soxhlet extractors. The compounds extracted were separated into neutral, acidic and basic fractions. Neutral fraction was chromatographed on a silica gel column and divided into four portions ; aliphatic hydrocarbons, aromatic hydrocarbons, aromatic nitro compounds and quinone compounds. The portion containing aromatic nitro compounds was analyzed by gas chromatography and gas chromatography-mass spectrometry with 3% Dexsil 400 GC and 2% PZ 179 column. 1-Nitropyrene was identified in diesel engine exhaust.

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Effect of cobalt on heme metabolism and its related enzymes were investigated and obtained the following results. 1. A single administration of cobaltous chloride dosing 40 mg/kg to rat caused an enlargement of the liver and reduction of the kidney and spleen weights. 2. Activity of heme oxygenase increased and contents of cyt. P-450 and activity of catalase decreased. 3. Activity of δ-aminolevulinic acid synthetase (ALAS) in cytoplasm increased but that of mitochondria decreased. These results suggest that cobalt inhibits the translocation of the newly synthesized ALAS from the cytosol to mitochondria. 4. Metabolic rate of aniline (Type 2) per nmol cyt. P-450 was not changed but that of aminopyrine (Type 1) increased. 5. Peroxidation rate of lipids did not change.

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Organic mercury in organic tissue (squid) was analyzed by cold vapor atomic absorption spectrometry. For a reducing procedure, a newly designed simple reducing cell was used instead of conventional reaction vessel apparatus. To assess the simple reducing cell apparatus, recovery experiment was carried out. Certain amounts of organic mercury (such as CH₃HgCl) were added to squid tissue. Then it was analyzed. The recovery was 96-98% average, and coefficient of variation 2.1-3.3%. When organic mercury in squid was analyzed, by use of both present method and gas chromatography (ECD-GC) method, it was found that in the liver organic mercury concentration was the highest (0.0292 and 0.0289 ppm wet weight) among several tissue samples of squid. No variance in result was recognized between these two methods.

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Methylmercury-forming activity in vitro and total vitamin B₁₂ content in yellowfin tuna livers were determined. A good correlation (R=0.9) was found between the total vitamin B₁₂ content and the mercury-methylating activity in vitro ; the latter was previously shown to correlate well with the amount of methylmercury accumulated in the livers, and the results thus suggest that vitamin B₁₂ may play a role in the methylmercury accumulation in tuna fish.

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