An existence of 5-lipoxygenase in Gracilaria asiatica, a species of red algae causing deaths of three persons who ate cooked one in Japan, was confirmed using agonists and an antagonist. The involvement of the enzyme in food poisoning was also investigated. Leukotriene (LT)B-4, a stable metabolite of arachidonic acid (AA) catalyzed by 5-lipoxygenase, increased significantly in algae with putative stimuli, such as Ca ionophore A23187, Diamide and N-ethylmaleimide, The increase of LTB4 by Diamide was inhibited significantly by AA861, a 5-lipoxygenase inhibitor. No change in concentrations of two isomers out of three, 6-trans-LTB4 and 6-trans-12-epi-LTB4, was observed when these stimuli were added. The other naturally existing isomer which possesses the same molecular weight as LTB4, but not identified stereochemically, showed a synchronized change with LTB4. The 5-lipoxygenase activity was lost by boiling raw algae for 10 min or further incubating the heated algae for 1 h at 37 degrees C with 0.03 N HCl (pH 2). However, LTB4 contents in the ethanol extracts from algae after these treatments increased significantly. These findings demonstrate that G. asiatica possesses an AA metabolic pathway via 5-lipoxygenase, but the enzyme activity would be lost by cooking, and also by ingesting in the stomach. The cortex of cooked algae would become soften in the stomach, resulting in the effective extraction of LTB4 from algae in situ.
Since early 1980s Drosophila melanogaster larvae heterozygous for recessive visible markers and those with defective DMA repair capability have been intensively used as simple in vivo testers of mutagenicity of environmental agents. In pallalel with this activity, the somatic tests have recently been deployed as tools for the detection of modifiers of the mutagenicity and understanding of basic mechanisms of the effects. Here, I characterize the somatic systems in relation to the biotransforming ability of promutagens and the outcomes from the mutagenicity tests and review some aspects of the deployment.
To study the origin of chloroform in vegetables, a simple and sensitive method was established using a gas chromatograph equipped with an electron capture detector. The method includes solvent trapping of chloroform, and gas chromatographic separation with a detection system. The average concentrations in vegetables, tea leaves and frozen vegetables were 30.9, 62.9 and 15.7 mu /kg, respectively. Tea leaves contained the highest amount, followed by vegetables. The former was 2 times the latter. There was no significant difference between chloroform levels in vegetables grown in tap water (chloroform: 19.7-25.0 mug/L) and those in boiled distilled water. On the other hand, there was a high correlation between the number of cultivation days and chloroform levels in vegetables grown in both tap water and boiled distilled water.
