Toxicity of cadmium could be exerted on the sites of its absorption and/or on the target tissues, such as bone and kidney, after being absorbed. On the other hand, toxicity of cadmium is modulated by nutritional factors, such as proteins, calcium, phosphorus and vitamin D. This review deals with our recent results concerning the role of dietary calcium and vitamin D as modulators of cadmium toxicity. The discussion was specifically focused on the interaction of calcium and cadmium at the site of intestinal absorption in the presence or absence of vitamin D. In the beginning of cadmium exposure, intestinal absorption of cadmium increased significantly in vitamin D deficient animals, but was not influenced by dietary calcium. Whereas cadmium inhibited vitamin D stimulated intestinal calcium transport in calcium deficient animals. In our experimental conditions, the metabolism of vitamin D₃ to 1, 25-(OH)₂-D₃ in kidney was not yet inhibited by cadmium. However, the binding of calcium to vitamin D dependent calcium binding protein and the activity of alkaline phosphatase in the intestine were significantly inhibited by cadmium. Moreover, the feeding of cadmium induced morphological and biochemical changes in the intestinal villi and microvilli of animals, especially raised on vitamin D deficient and/or low calcium diet. Thus, the prolonged exposure of cadmium will result in the disorders of calcium metabolism in the animals raised on a low calcium diet even in the presence of vitamin D. These results will suggest that nutritional status not to absorb cadmium and not to inhibit calcium metabolism could be vitamin D and calcium sufficient in the subjects of the normal intake of protein, carbohydrates and lipids.

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As a study of the thermal behavior of phthalic acid esters (PAE's), the thermal decomposition of di-n-butylphthalate (DBP) was carried out in a flow system at 250-500°. The major products were butene-1, butanol and phthalic anhydride (PA). Benzoic acid, butyl benzoate, phthalic acid and monobutyl phthalate (monoester), as minor products, were also isolated and identified. These minor products, especially phthalic acid and monoester, were so unstable to the heat treatment that they were not isolated in a conventional GC analysis. A simple one step analysis was achieved by the use of a GC, by pretreating the products with diazomethane to improve their heatstability. This analytical method made clear the composition of commercial polyvinyl chloride sheet (PVC) for agricultural use. It was found that the plasticizer it originally contained, di (2-ethylhexyl) phthalate (DEHP), were partially decomposed and identified the decomposition products. 2-Ethylhexanol, PA and mono 2-ethylhexyl phthalate, the thermal decomposition products of DEHP, were analyzed to be 0.1%, 0.7% and 0.1% of the products, respectively.

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In order to estimate the rate of disappearance of free available chlorine during storage in water tanks, the rate of vaporization of free available chlorine was studied and the rate of the chlorine consumption caused presumably by components in water supply, though the components were unknown, was also investigated. The rate of vaporization was proportional to the air-water interfacial area, but it was independent of the water level and the initial concentration of free available chlorine. A linear relationship exists between the logarithm of the rate of vaporization and the reciprocal of absolute water temperature. The consumption caused by the components in water supply was approximately accounted for the first order reaction. However, the rate constant for consumption varied inversely as the initial concentration of free available chlorine. The constant was not a true one. The apparent rate constant was proportional to the fourth power of water temperatnre. Our proposed model was able to give an adequate explanation of the whole course of the disappearance of free available chlorine during storage in water tanks.

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In order to obtain the tendency towards the formation of cadmium alginates, six kinds of sodium alginates were prepared and the values of metal/uronic acid residue ratio were investigated by precipitation and dialysis experiments. The guluronic acid residue alginate (G) and the mannuronic acid residue alginate (M) had the values about twice those of the insoluble fragment by partial acid hydrolysis (insoluble), the insoluble fragment at pH 2.85 (pH 2.85), the insoluble fragment at pH 1.5 (pH 1.5) and the commercial sample (CM). The correlation between the number average degree of polymerization (DP) and the affinity for divalent metals was not found. The affinity for heavy metals of sodium alginates increased markedly in both dialysis and two ions mixed experiments, and the maximum value of metal/uronic acid residue ratio came to about 2. On the other hand, the ratio for single ion by precipitation experiments was about 0.5.

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In order to develop a system for the separation of amino acids-conjugated metabolites of toxic compounds or drugs in biological samples, the ability of activated carbon to separate amino acids was investigated thin-layer chromatographically. Several kinds of thin-layer chromatoplates of activated carbon were prepared by using calcium sulfate (CaSO₄·1/2H₂O), cellulose powder or Silica Gel G as a binder. Standard amino acids were chromatographed with water and aqueous acetic acid as solvents. With water, the results were as follow : Rf value zero for Trp, Tyr and Phe : 0-0.3 for Leu, Ile, Met, His, Arg and Cys ; 0.3-0.7 for Val, Pro, Glu, Hyp, Asp, Thr and Lys ; 0.7-1.0 for Ser, Ala and Gly. The thin-layer chromatograms on activated carbon plates could be used to locate the migration positions of amino acids chromatographed on a long chromatocolumn of activated carbon. Preparative thin-layer chromatography on activated carbon was also useful for the purification of metabolites. This preparative method was utilized in a multistage chromatocolumn system in order to treat a large quantity of sample solution or sample extracts. This column system was prepared by connecting several short chromatocolumns of activated carbon. This system could be utilized for the detection of 2-(2-amino-2-carboxy-ethylthio)-3-methylbutyrylurea in the urine of a person given α-bromoisovalerylurea.

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Determination of monofluoroacetic acid was investigated according to the method of the fluorescence of thioindigo, which was formed from the ferricyanide oxidation of a reaction product of monofluoroacetic acid and thiosalicylic acid in the presence of sodium hydroxide. The recommendatory procedure is as follows : To 1 ml of a sample solution containing 20 to 100 μg of monofluoroacetic acid, add 0.5 ml of a thiosalicylic acid reagent (30 mg of thiosalicylic acid was dissolved in 0.5 ml of 1 N NaOH and made up to 10 ml with water), then heat the mixture at 105° for 60 min. To the residue, add 1 ml of 1.5 N NaOH. After heating the mixture at 130°for 80 min, add 7.5 ml of the mixed acid solution and 3 ml of a 2% potassium ferricyanide solution, then shake the mixture for 1 min vigorously. To the solution, add 10 ml of benzene, then shake the mixture for 10 min vigorously. After separation, measure the fluorescence of benzene layer at 580 nm by an excitation at 540 nm. This fluorometric method was applied to the recovery test of monofluoroacetic acid added to plant materials. After extraction with ether and subsequent silicic acid column chromatography, the monofluoroacetic acid separated from plant materials was determined by the method.

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The separation and detection of some natural dyes comprising 12 water soluble and 8 non-water soluble dyes were investigated by thin-layer chromatography by using polyamide as an adsorbent. Polyamide 11 F₂₅₄ layers and polyamide layer sheets were used as plates, two series of water and nonwater soluble dyes being developed with different solvent systems, respectively. The solvent systems for the separation of non-water soluble dyes were n-hexane, n-hexane-benzene-acetic acid (6 : 3 : 1) and acetone-acetic acid (19 : 1). Especially the development with n-hexane was most suitable for the separation of β-carotene from paprika extract. When developed with isopropanol-formic acid-water (7 : 1 : 3), all water soluble dyes were separated. In the development, dyes containing anthocyanin derivatives such as grape skin and purple corn extracts were observed as slightly overlapped spots, showing that the dyes were composed of many compounds.

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The chemical form of Zn in the low molecular weight fraction of oyster meat was examined. The acetone-insoluble fraction (fraction C) was extracted with 50% methanol and the extract was separated into high and low molecular weight fractions by Sephadex G-50 chromatography. Starting from 40 g of fraction C, 4 g of low molecular weight fraction containing 3.6 mg of Zn was obtained. Zn in this fraction was migrated to lesser extent to cathod than Zn ion in paper electrophoresis. This Zn was eluted at the similar position to that of EDTA-Zn and 1, 4, 7, 10-tetraazacyclotridecane-Zn complex and differed also from Zn ion by siliconized pore glass column chromatography. When the low molecular weight fraction was treated with diluted acid (1 N-AcOH), liberation of Zn ion was observed both in paper electrophoresis and siliconized pore glass column chromatography. These results suggest that Zn in the low molecular weight fraction of the oyster meat occurs as a chemical form of some complexes.

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The oyster was bred for a week in natural sea water containing 0.1 (control), 20 and 60 ppb Cd (CdCl₂). After the breeding, Cd content in each tissue of the oyster meat was determined by atomic absorption spectroscopy. When the exposure to 60 ppb Cd for a week, the rate of accumulation of Cd in the gill raised up to 56 times the control. Each tissue was homogenized in 0.5 M NaCl solution and an aliquot of the NaCl-soluble fraction was chromatographed on Sephadex G-50. Almost Cd was eluted at the column volume. This suggests that the chemical form of Cd in the oyster meat was characteristic of the low molecular weight materials.

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Behavior of methylmercury and selenium in rabbit blood was investigated in vitro or in vivo after separate or simultaneous administration of methylmercuric chloride and sodium selenite. When methylmercury and selenite were simultaneously added in vitro to rabbit blood, the rate of mercury uptake by the erythrocytes was very rapid in comparison with the case where methylmercury was added alone, and a considerable degree of selenium incorporation into the erythrocytes, which usually occurred at the early stage of incubation after sole addition of selenite, was not observed. These tendencies appeared to be similar to those observed in the blood of rabbit which was i.v. administered with methylmercury and selenite simultaneously. Either gel filtration (on Sephadex G-200 or G-15) or thin-layer chromatography, however, failed to detect any change in existing states of both the elements in plasma and stroma-free hemolysate after simultaneous in vivo or in vitro administration of methylmercury and selenite.

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