Toluene and xylenes with one and two methyl groups in a benzene ring are typical methylbenzenes used widely in many industries and are not so harmful in comparison with benzene. The lower toxicity of these methylbenzenes is due to the main metabolic routes initiated by the methyl group oxidation through the reaction with active oxygen in living bodies. In these methylbenzenes, the main metabolic route is the methyl group oxidation (benzylalchols) → benzoic acids → hippuric acids (glycine conjugation), which is regarded as less toxic. By way of example, benzoic acid is easily metabolized to form hippuric acid in urine, which is permissible for the high level usage of food additives. Here, the substitution of benzene hydrogen by methyl group has been called safe replacement. On the other hand, the main metabolic route of benzene is ring oxidation (epoxide formation) → phenol, which is shown by carcinogenic and liver damage. Recently, urinary metabolites varying with hippuric acids in safe replacement routes have been detected largely following methyl groups increases in methylbenzenes. In particular, the mercapturic acids and phenols are notable in o-xylene and trimethylbenzenes with three methyl groups. Trimethylbenzenes having high boiling points are used largely as the solvents for building materials and furniture and are reported to be at high levels indoors. In this review, the metabolic routes of methylbenzenes through reactions with active oxygen (superoxide anion radical) in living bodies and indoor air pollution, such as related to sick house syndrome, are discussed on the basis of our recent studies on the urinary metabolites of rats.
A high level of ethanal (acetaldehyde) was generated from mackerel muscle homogenate by addition of potassium bromate (mild oxidizing agent) to the homogenate and heating. Lactic acid was found to be a causative substance of ethanal production (EP). However, such a high level of ethanal was not produced only by addition of potassium bromate to lactic acid in the reaction mixture and heating, suggesting the presence of unknown substances in mackerel muscle promoting the reaction of EP. In fractionation of a liquid extract of mackerel muscle on ion-exchange resin, the ampholytic substance fraction (ASF) showed a strong enhancing activity in EP from lactic acid. Sephadex G-10 gel chromatography of the ASF revealed that the amino acids-eluting fractions had an enhancing activity in EP and the substances enhancing EP were thought to be of relatively low molecular weights. In fractionation of the ASF on a SP-Sephadex C-25 cation exchange unit, the histidine-eluting fractions showed a strong enhancing activity in EP. When histidine was used instead of the ASF in reaction mixture, however, the enhancing activity of the former in EP from lactic acid was not so large as that of the latter. Iron-ion- and biological-iron-containing compounds, such as myoglobin, hemoglobin and cytochrome c, generated ethanal markedly from lactic acid. From the findings that the substances enhancing EP from lactic acid in mackerel extract had relatively low molecular weights and also from the behaviors on iron-exchange resin, it was considered that a complex of iron ions and histidine might play, at least in part, an important role in enhancing EP from lactic acid.
Groups of 20 pregnant Wistar rats were treated orally with 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TMPDIB) from day 7 through 17 of gestation at doses of 0, 160, 400 or 1,000 mg/kg, and Caesarian sections were performed on day 20. Maternal toxicity in the 400 mg/kg group was evident by decreased food consumption. Numbers of fetuses, fetal body weights and degrees of ossification were not affected by TMPDIB, and no treatment-related fetal anomalies were noted in any dose groups. These findings indicate that the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity was found to be 160 and 1,000 mg TMPDIB/kg/day, respectively.
The amount of discharged food wastes reaches 20 million metric tons/year in Japan. About 50% of food wastes from food factories are recycled, however, the recycling ratio of food wastes from households and nonmanufacturing industries is only 0.3%. In order to assess the possibility of recycling for nonmanufacturing industries we examined the conditions of food wastes discharged from hospitals and schools in Osaka city. Specific discharges of food wastes from hospitals and school-provided lunches were 0.55 kg/bed and 0.06 kg/person respectively. According to the results of analysis, contents of chlorine, fat and fiber varied to some extent, but the carbon-nitrogen ratio was stabilized. These food wastes have the potential to be recycled as compost and livestock feed through application of appropriate pretreatment.
Giardia intestinalis and Cryptosporidium parvum are well-known intestinal parasites, which cause enteric disease in humans. In Japan, there have been many cases of both parasites being found in travelers returning from endemic areas. Recent molecular studies show that both parasites are composed of multiple genotypes making molecular characterization of their isolates important for understanding the epidemiology of Giardia and Cryptosporidium infections. Here we report an imported case of mixed infection by both parasites where the Giardia isolate was genotyped as Assemblage B of G. intestinalis, which has zoonotic potential, and the Cryptosporidium isolate as C. parvum human genotype, which has been found in only humans.