A new simplified method for microdetermination of mercury in fish is described.
In this method, the two necked oxygen-flask with two necks of 1000ml capacity was used for burning the biological material. Before the sample was burnt in the oxygen-flask, the oxygen-flask was evacuated with a vacuum pump, then the oxygen-flask was filled with oxygen. These operations were repeated three times, and at the end of these operations the internal pressure of the oxygen-flask was adjusted to about 610mm Hg for avoidance of explosion of the oxygen flask and loss of mercury.
After the sample was burnt, the oxygen-flask was cooled with a dry ice-acetone mixture to condense the vaporized mercury. Then the mercury and some vaporized components were absorbed to 0.1N sulfuric acid. The volatile components except mercury in the absorbant solution were extracted with n-hexane, the water layer being used as the prepared solution.
The mercury in the prepared solution was determined by flameless atomic absorption spectrometry. As a result of repeating this method on a few kinds of fish, it was found that the mercury in fish sample could be determined with 100-105% of recovery ratio and about 5% of variation coefficient.

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Effect of cooking, especially boiling, on the removal of organochlorine pesticide residues from polished rice, red beans and soybeans were examined.
The result shows that a little part of pesticide residues was removed from polished rice and red beans, while considerable amount of pesticide residues was removed from soybeans by boiling. 31% of α-BHC, 43% of β-BHC, 67% of γ-BHC, 20% of pp′-DDE and 80% of pp′-DDT were eliminated in the cooking process of soybeans.

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Procedures were developed for assay of staphylococcal enterotoxins in foods, using microslide gel double diffusion test.
(1) Foods were prepared for assay by addition of water (homogenization or mashing in case of cereal foods) adjustment of pH to 7.4-7.6, blending, and centrifugation. The supernatant fluids were then adjusted to pH 4.5 (in case of animal foods) or pH 6.0, and centrifuged. Supernatant fluids taken at pH 4.5 were readjusted to pH 6.0, and centrifuged. From these supernatant fluids, enterotoxins were partially purified by adsorption on CM-Sephadex C-50 equilibrated with 0.01M sodium phosphate (pH 6.0), washing with 0.01M sodium phosphate (pH 6.0), then eluted with 0.2M sodium chloride in 0.1M sodium phosphate (pH 7.6), and concentrated by dialysis against polyethylene glycol.
Adequate dosage levels of CM-Sephadex in the batch ion exchange for various foods were determined, individually.
(2) By these procedures, enterotoxins were detected in 12 out of 16 foods suspected for cause of poisoning outbreaks. Enterotoxin A (50%) and A+D (33%) were predominant types. Concentrations of enterotoxins detected in foods were ranging up to 0.3μg/g, and estimated at 0.05μg/g on the average. In 4 outbreaks, neither enterotoxins nor enterotoxin-producing staphylococci were isolated from the suspected foods.
(3) The extract from suspected cream puff containg 4.5μg of enterotoxin A induced emetic responses in a volunteer by feeding test.

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土壌に残留する農薬の野菜への移行を検討しつぎのような結果を得た.
1) 土壌中に残留する各BHC異性体は, ニンジン, カブ葉, ダイコン葉, ホウレンソウなどに多く移行し, トマト, キャベツなどへの移行は少なかった. 現在の土壌残留量から考えるとニンジン, カブ葉などで残留許容基準をこえる可能性がある.
2) アルドリンとディルドリンのキュウリ, ニンジン, ホウレンソウへの移行率は, それぞれ16.6%, 9.6%, 4.4%であった. アルドリンは野菜中でディルドリンの型で検出された. 移行率はキュウリについて文献値にほぼ一致したが, ダイコン, ニンジンについてはかなり低い値を示した.
3) エンドリンのキュウリ, キャベツ, ダイコンへの移行率は, それぞれ21.8%, 14.5%, 9.1%であった. エンドリン, アルドリン, ディルドリンの野菜への移行率と土壌残留量から考えると, 日本の残留許容基準をこえる可能性が多い.
4) DDTは土壌中にかなりの濃度で残留していたが, 野菜への移行は極めて少量であった.

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市販のスライスハム75例を材料として, CVT寒天培地 (25°, 3日培養) を用いて低温細菌による汚染状況を調査した. さらに分離株の発育至適温度, 酵素産生能などについて試験を行ない, 以下の成績を得た.
1) 低温細菌数および一般生菌数は, 両者ともほとんどが10⁶/g以下であった.
2) 5°, 7日培養とCVT培地による菌数との比較では, それほどの差は認められなかった.
3) 分離菌416株を同定分類した結果, Pseudomonas (175株, 42%), Aeromonas (53株, 12.7%), Acinetobacter (Achromobacterを含む, 38株, 9, 1%) などの順に多かった.
4) 5, 15, 25, 30°および37°の5段階で発育至適温度を検討した結果, 25°前後のものがもっとも多かった. したがって分離菌の大部分はpsychrotrophic mesophileに相当するものと考えられた.
5) 酵素産生能を25°と5°で検討した結果, 25°ではリパーゼ294株 (70.6%), プロテアーゼ93株 (22.3%), アミラーゼ19株 (4.5%) が産生した. これに対し5°ではリパーゼ298株 (71.6%), プロテアーゼ231株 (55.5%), アミラーゼ5株の成績であり, とくにプロテアーゼでは低温での産生が大であった.

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Little has been reported on 3, 4-benzopyrene in Japanese foods, but it is requested to investigate the content of this carcinogenic polycyclic hydrocarbon in our daily foods in view of the high incidence of gastric cancer in this country.
The present paper deals with the further improvement made on the previously reported analytical procedure for 3, 4-benzopyrene in Japanese teas and the application of the improved method to 18 kinds of daily foods including rice, “Miso” (bean paste), and soy sauce. The recoveries of 3, 4-benzopyrene added to each 100g of “Katsuobushi” (dried bonito) and “Nori” (purple laver) at a level of 20ppb averaged 64% and 90%, respectively. No 3, 4-benzopyrene was detected in rice, “Miso”, soy sauce and soybean which are eaten by Japanese almost everyday. On the contrary, this carcinogen was detected in all the samples of dried bonito “Katsuobushi” and sea weeds such as laver “Nori”, “Wakame” (Undaria pinnatifida), etc. in fairly large quantities; 29.8ppb in “Katsuobushi” and 31.3ppb in “Nori” at the maximum.
It was confirmed that the improved method is applicable for analyzing 3, 4-benzopyrene in many kinds of foods.

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Several methods for the determination of thiabendazole in citrus fruits were studied.
Thiabendazole was extracted with ethyl acetate and re-extracted from the organic phase with 0.1 N-HCl. The acidic extract was made alkaline, extracted with ethyl acetate, and the organic phase was re-extracted with 0.1 N-HCl. When this procedure for extraction was not carried out, the determination was interfered with unknown substance A which had an absorption maximum at 283mμ.
When its concentration was more than 1ppm, the test solution was spectrophotometrically measured at 302mμ, and when its concentration was less than 1ppm, the test solution was spectrofluorometrically measured with an excitation wavelength at 305mμ and an emission wavelength at 350mμ.
In the gas chromatographic method, it was detected with DC-200 and QF-1 at 200°C. Since its sensitivity was very weak, this method was not practical.
Thiabendazole in imported citrus fruits, grapefruits, oranges and lemons, were determined by spectrofluorometry. However, they contained unknown substance B which gave a fluorescence spectrum with an excitation maximum at 330mμ and an emission maximum at 400mμ. Fortunately, since its concentration was low, this method would be successfully applied.

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We studied on the toxicity of tetrodotoxin of Fugu which was imported to Japan, by use of mice and the following results were obtained:
1) Crystalline tetrodotoxin exhibited the strongest toxicity in mice by intracerebral injection. The degree of toxicity by administration routes was expressed by the following order: intracerebral, intravenous, intraperitoneal, subcutaneous and oral.
2) The dose of toxin corresponded to the death time.
3) The toxicity of tetrodotoxin was decreased by the addition of tissue homogenate of Fugu (tetrodon).
4) Nashi-Fugu, and Nagoya-Fugu were not so toxicic as other Fugs.

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A paper electrophoretic method for identification of nucleotides (AMP, ADP, ATP, GMP, GTP, CMT, CTP, TMP, UMP, UTP, IMP), nucleosides (adenosine, guanosine, cytidine, thymidine, uridine, inosine), and nucleic bases (adenine, guanine, hypoxanthine, cytosine, thymine, uracil) was investigated by using 5N acetic acid, 5N formic acid, 1N citric acid, M/15 disodium orthophosphate solution and 1% borax solution as the electrolyte. The relative mobilities of the compounds were expressed against flavianic acid or auramine. It was found that all compounds, investigated in this study, could be separated and identified by systematic use, in order, of the above-mentioned electrolyte.

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