Selenium has two distinct faces ; one is the most toxic element regarded as one of the environmental pollutants, the other is microessential one in the nutrition of many animal species. To evaluate exactly biological roles of selenium, which are confused and controversial in the animal and human health, it is important to establish the mode of selenium metabolism and its regulation under normal and pathological conditions. This review is attempted to discuss selenium metabolism including selenium as an integral part of glutathione peroxidase molecule and its participation in the metabolisms of vitamin E, heme and other trace elements such as cadmium and mercury in mammals. Furthermore, possible biological roles of selenium in relation to the physiological status and various diseases in mammals including human being are also discussed.

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The distribution of contents of sodium n-alkylbenzenesulfonate (LAS) was investigated in the sediments of the Sagami River Estuary and its adjacent sea areas to discuss the relationship between the null points of sediment and the points where LAS was detected. Further the compositions of homologous series of LAS, sodium n-decylbenzenesulfonate (C₁₀-LAS), sodium n-undecylbenzenesulfonate (C₁₁-LAS), sodium n-dodecylbenzenesulfonate (C₁₂-LAS) and sodium n-tridecylbenzenesulfonate (C₁₈-LAS), in the sediments and in the river waters were compared. The contents of LAS were determined by combined methylene blue colorimetry and infrared spectrometry, and then homologous series of LAS were determined by high-performance liquid chromatography. LAS was contained over the range of dry weight 5.5 to 17μg/g at 3 points among 10 points in the estuary, but not detected in the sea areas. The null points of sediment which were presumed from particle size distribution and from ignition loss in the estuary nearly agreed with the points where LAS was detected. In the sediments C₁₂-LAS was the most abundant among homologous series of LAS and its average percentage was 59, and C₁₀-LAS was absent. On the other hand, in the river waters C₁₁-LAS was 50% and C₁₃-LAS was not detected. These facts were considerably different from the percentage of compositions of LAS in the commercial detergent.

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In order to clarify whether the decrease in the hydroxyproline content of cadmium-treated cultured bone is due to an inhibition of collagen synthesis or a stimulation of its degradation, femurs from 9-day chick were cultivated for six days by the roller-tube method, and CdCl₂ was added to the culture medium in the 0.2 to 30 ppm concentration range as Cd²⁺. The hydroxyproline content of the whole bone was decreased by concentrations of cadmium exceeding 1 ppm. When the whole bone was divided into the cartilage ends and bone shafts, cadmium produced a decrease in the hydroxyproline content of the former without any apparent effect on the latter. To investigate the effects of cadmium on collagen synthesis and degradation, the bones and media after culture and the uncultured bones were analyzed for hydroxyproline. The synthesis of hydroxyproline was significantly inhibited by levels of cadmium above 1 ppm. The release of hydroxyproline from the bone into the medium was inhibited by levels of cadmium above 0.2 ppm, but the percentage of the hydroxyproline released into the medium (relative to the total found in the bone and medium) was unaffected by cadmium. These results show that the decrease in hydroxyproline content of cadmium-treated bone may be due to the inhibition of collagen synthesis. On the other hand, when the bone shafts were treated with bacterial collagenase, cadmium had no effect on the hydroxyproline content but caused a decrease in the calcium content of collagenase-undigestible fraction which contained 95% of the total cadmium incorporated into the bone shafts. Cadmium seems to coexist with calcium phosphate on the basis of an elemental analysis of calcified positions of bone shafts using an energy dispersive X-ray microanalyzer.

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In an attempt to elucidate the mode of life of oyster, an important product of Hiroshima Prefecture, from biochemical viewpoints as the base of studies on the effect of pollutants on oyster, enzymological properties of hexokinase, a rate-limiting enzyme of glucose metabolism, were examined in relation to glycogenesis. It is worth noting that the amount of glycogen in oyster increased markedly from winter to spring and decreased abruptly from spring to summer. Oyster hexokinase was partially purified about 30 times by ammonium sulfate fractionation and DEAE-Sephadex A-50 column chromatography. Cellulose acetate membrane electrophoresis of this partially purified preparation of oyster hexokinase revealed a band with the mobility similar to that of mammalian hexokinase type II. The K_m values of oyster hexokinase for D-glucose and ATP were 4.9×10^-5 and 1.6×10^-4M, respectively. Oyster hexokinase activity was inhibited by 30-40% by 400 nM methylmercuric chloride competitively with respect to D-glucose and in a mixed-type manner with respect to ATP. These results indicated the similarity of enzymological properties of oyster hexokinase to those of mammalian hexokinase type II. Significance of the existence of type II-like hexokinase was discussed in reference to the regulation of glucose metabolism and sensitivity to SH-inhibitors such as mercury, etc.

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N-Nitrosodimethylamine (NDMA) in human urine was determined by chemical ionization-mass fragmentography (CI-MF), and the results were compared with those of thermal energy analyzer (TEA). Urine samples were extracted with dichloromethane and the concentrate was cleaned up on a silica gel column. CI-MF was very sensitive (detection limit was 1.2 pg at S/N=2) and the selectivity was comparable with that of TEA. NDMA levels in urine were ND-0.14 ppb. The values determined by CI-MF were similar to those by TEA, and this method was applicable to trace analysis of urinary NDMA with high sensitivity (above 0.002ppb).

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A simple and rapid gas chromatographic determination of clopidol in chicken muscle and egg was studied. After extraction with methanol from homogenized sample, the extract was cleaned up with an ion exchange resin column. Clopidol obtained was methylated with diazomethane and the resulting methyl-clopidol was determined by ECD-GC with a column (2 m×3 mm i.d.) of 10 % DC-200 on Gaschrom Q. Linear calibration curves for the gas chromatographic determination were obtained in the range of 0.01 to 0.1μg/ml for clopidol. The recoveries of clopidol added to chicken muscle and egg were 94.4 % and 93.3 % on the average, respectively. The detection limit of clopidol in this analytical procedure was 0.01μg/g in chicken muscle and egg. The analysis of actually commercial sample indicated that clopidol was detected in 44.0 % of chicken muscle and in 28.0 % of egg, and that clopidol detected was in the range of 0.30 to 3.84 μg/g for chicken muscle and 0.01 to 0.14μg/g for egg.

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Distribution and excretion of ³H-1, 1-bis (4-chlorophenyl) 2, 2, 2-trichloroethanol (³H-kelthane) after oral dosaze were studied in mice. In the distribution study of ³H-kelthane, its radioactivity was detected in various tissues, indicating extensive uptake of this compound. The radioactivity distributed in each organ in mice reached a maximum after 24-48 hr and rapidly decreased thereafter with the exception of body fat. In particular, high level of radioactivity and its prolonged retention were observed in the body fat in mice. Approximately 60 % of the administered radioactivity was excreted in the urine (20 %) and feces (40 %) of mice within 96 hr, implying that fecal excretion is the major elimination route in the oral administration of kelthane.

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Since the reactions were regarded as pseudo-first-order kinetics, the photodecompositions of anionic surfactants under various conditions were studied by use of their rate constants. The results showed that the rates of photodecompositions varied depending on the kind of anionic surfactants. No effect of environmental water was observed on the photodecomposition of sodium dodecylbenzenesulfonate. On the other hand, the rates of photodecompositions increased gradually with an increase in pH over the pH range 10 to 14.

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Most of mercuric oxide (HgO) administered p.o. to rats (5 mgHg/kg) was excreted in feces, and about 2 % of the dose was excreted in urine. The distribution of mercury in rat tissues after the oral administration of HgO was similar to that after the oral administration of the same molar dose of mercuric chloride. Mercury concentrations in the blood after the administration of HgO into the stomach or small intestine of the pyrolus-ligated rats were similar to those after the administration of the same molar dose of mercuric chloride. Taking into account the low degree of dissociation, these results suggested that HgO was able to be absorbed from the gastro-intestinal tract without transformation to mercuric chloride.

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