Institute of Environmental Toxicology

Ibaraki, Japan

Institute of Environmental Toxicology

Ibaraki, Japan
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Fujita M.,Institute of Environmental Toxicology | Yajima T.,Institute of Environmental Toxicology | Iijima K.,Institute of Environmental Toxicology | Sato K.,Institute of Environmental Toxicology
Journal of Agricultural and Food Chemistry | Year: 2012

The uncertainty in pesticide residue levels (UPRL) associated with sampling size was estimated using individual acetamiprid and cypermethrin residue data from preharvested apple, broccoli, cabbage, grape, and sweet pepper samples. The relative standard deviation from the mean of each sampling size (n = 2 x, where x = 1-6) of randomly selected samples was defined as the UPRL for each sampling size. The estimated UPRLs, which were calculated on the basis of the regulatory sampling size recommended by the OECD Guidelines on Crop Field Trials (weights from 1 to 5 kg, and commodity unit numbers from 12 to 24), ranged from 2.1% for cypermethrin in sweet peppers to 14.6% for cypermethrin in cabbage samples. The percentages of commodity exceeding the maximum residue limits (MRLs) specified by the Japanese Food Sanitation Law may be predicted from the equation derived from this study, which was based on samples of various size ranges with mean residue levels below the MRL. The estimated UPRLs have confirmed that sufficient sampling weight and numbers are required for analysis and/or re-examination of subsamples to provide accurate values of pesticide residue levels for the enforcement of MRLs. The equation derived from the present study would aid the estimation of more accurate residue levels even from small sampling sizes. © 2012 American Chemical Society.

Tuder R.M.,Aurora University | Yoshida T.,Institute of Environmental Toxicology
Proceedings of the American Thoracic Society | Year: 2011

The maintenance of the alveolar structure is required throughout life. To accomplish this goal, alveolar cells, including endothelial, epithelial, and fibroblastic cells, provide key molecules with broad survival and antiapoptotic effects. These complex interactions are disrupted by cigarette smoke, leading to emphysema. Smoke imposes an environmental stress to the lung with the activation of "sensor-like" molecular signaling. Activation of RTP801, leading to mTOR inhibition, is paradigmatic of these responses. The accumulation of cellular damage, with the generation of endogenous mediators of inflammation, may proceed toward an aging phenotype. These alterations may impose significant challenges to cell-based regenerative or pharmacological therapies.

Gotoh H.,Institute of Environmental Toxicology | Aoyama H.,Institute of Environmental Toxicology
Congenital Anomalies | Year: 2012

Genetic disorders are usually considered to be caused by harmful gene mutations, as well as by chromosomal aberrations, including small insertions, duplications and/or deletions. However, as infertile individuals often arise among the offspring of crosses between two fertile mouse strains, we postulate that a certain combination of 'normal' genes with neither gene mutations nor chromosomal aberrations can cause such serious phenotypic alterations as reproductive dysfunction. In this study, we show evidence that a combination of multiple normal genes from two different normal mouse strains manifests a wide range of male reproductive dysfunctions, from benign changes to complete infertility. These abnormal phenotypes are thought to have occurred by epistatic interactions of alleles. © 2012 The Authors. Congenital Anomalies © 2012 Japanese Teratology Society.

Fujita M.,Institute of Environmental Toxicology | Yajima T.,Institute of Environmental Toxicology | Iijima K.,Institute of Environmental Toxicology | Sato K.,Institute of Environmental Toxicology
Journal of Agricultural and Food Chemistry | Year: 2012

To estimate variations in pesticide residue levels in crops, the variability factors (VFs, the 97.5th percentile of the residue levels in the sample divided by the average residue levels in the lot) in residue levels of acetamiprid and cypermethrin applied to cabbage and grapes were investigated, respectively. The VFs in the residue levels of both pesticides in cabbage (2.00 and 2.39, respectively) were clearly higher than those in grapes (1.82 and 1.63, respectively). Although the residue levels of both pesticides in grapes showed a normal distribution, those values in cabbage were slightly skewed at lower residue levels. Individual residue levels in grapes had a good agreement between acetamiprid and cypermethrin. In contrast, the distribution of cypermethrin residue levels in cabbage was slightly skewed at higher residue levels as compared to that of acetamiprid. These results indicate that the difference in the relative distribution of the two pesticides between cabbage and grapes might be due to the influence of various factors such as differences in crop species, plant cultivation methods, and physicochemical properties of the pesticides. © 2012 American Chemical Society.

Satsuma K.,Institute of Environmental Toxicology
Applied Microbiology and Biotechnology | Year: 2010

A novel s-triazine-mineralizing bacterium-Nocardioides sp. strain DN36-was isolated from paddy field soil treated with ring-U-14C-labeled simetryn ([14C]simetryn) in a model paddy ecosystem (microcosm). In a tenfold-diluted R2A medium, strain DN36 liberated 14CO2 from not only [14C]simetryn but also three ring-U- 14C-labeled s-triazines: atrazine, simazine, and propazine. We found that DN36 mineralized ring-U-14C-cyanuric acid added as an initial substrate, indicating that the bacterium mineralized s-triazine herbicides via a common metabolite, namely, cyanuric acid. Strain DN36 harbored a set of genes encoding previously reported s-triazine-degrading enzymes (TrzN-AtzB-AtzC), and it also transformed ametryn, prometryn, dimethametryn, atraton, simeton, and prometon. The findings suggest that strain DN36 can mineralize a diverse range of s-triazine herbicides. To our knowledge, strain DN36 is the first Nocardioides strain that can individually mineralize s-triazine herbicides via the ring cleavage of cyanuric acid. Further, DN36 could not grow on cyanuric acid, and the degradation seemed to occur cometabolically. © 2010 Springer-Verlag.

Satsuma K.,Institute of Environmental Toxicology | Masuda M.,Institute of Environmental Toxicology | Sato K.,Institute of Environmental Toxicology
Bioscience, Biotechnology and Biochemistry | Year: 2013

We have reported that a leguminous bacterial strain, Bradyrhizobium sp. strain 17-4, isolated from river sediment, phylogenetically very close to Bradyrhizobium elkanii, degraded methoxychlor through O-demethylation and oxidative dechlorination. In the present investigation, we found that B. elkanii (USDA94), a standard species deposited in the Culture Collection, degraded methoxychlor. Furthermore, Bradyrhizobium sp. strain 4-1, also very close to B. elkanii, isolated from Japanese paddy field soil, degraded methoxychlor. These B. elkanii and closely related strains degraded methoxychlor through almost identical metabolic pathways, and cleaved the phenyl ring and mineralized. In contrast, another representative Bradyrhizobium species, B. japonicum (USDA110), did not degrade methoxychlor at all. Based on these findings, B. elkanii and closely related strains are likely to play an important role not only in providing the readily biodegradable substrates but also in completely degrading (mineralizing) methoxychlor by themselves in the soil and surface water environment.

Satsuma K.,Institute of Environmental Toxicology | Masuda M.,Institute of Environmental Toxicology
Journal of Agricultural and Food Chemistry | Year: 2012

Methoxychlor [1,1,1-trichloro-2,2-bis(4-methoxyphenyl)ethane] is an organochlorine insecticide that undergoes dechlorination in natural submerged environments. We investigated the ability to dechlorinate this compound in seven environmental bacterial species (Aeromonas hydrophila, Enterobacter amnigenus, Klebsiella terrigena, Bacillus subtilis, Achromobacter xylosoxidans, Acinetobacter calcoaceticus, and Mycobacterium obuense) and the enteric bacterium Escherichia coli as a positive control. In R2A broth at 25 °C under aerobic, static culture, all species except Ach. xylosoxidans were observed to convert methoxychlor to dechlorinated methoxychlor [1,1-dichloro-2,2-bis(4-methoxyphenyl)ethane]. The medium was aerobic at first, but bacterial growth resulted in the consumption of oxygen and generated microaerobic and weakly reductive conditions. Replacement of the headspace of the culture tubes with nitrogen gas was found to decrease the dechlorination rate. Our findings suggest that extensive bacterial species ubiquitously inhabiting the subsurface water environment play an important role in the primary dechlorination of methoxychlor. © 2012 American Chemical Society.

Masuda M.,Institute of Environmental Toxicology | Satsuma K.,Institute of Environmental Toxicology | Sato K.,Institute of Environmental Toxicology
Bioscience, Biotechnology and Biochemistry | Year: 2012

Agricultural waste water containing pesticides can reach the sea via rivers and estuaries, including brackish lakes. We studied the metabolic fate of methoxychlor [MXC; 1,1,1-trichloro-2,2-bis(4-methoxyphenyl) ethane] in a model system consisting of sediment and associated water collected from two sampling sites: a brackish lake and a freshwater river. MXC degraded rapidly and was finally mineralized in both sediment systems. The first step of degradation was dechlorination to yield 1,1-dichloro-2,2-bis(4-methoxyphenyl)- ethane [de-Cl-MXC] or CN-replacement to yield 2,2- bis(4-methoxyphenyl)acetonitrile [MXC-CN], followed by O-demethylation. Although the metabolites were common to the two sediments, the dynamics of the metabolites over time were clearly distinct. In the brackish lake sediment, de-Cl-MXC accumulated transiently, whereas in the river sediment, it was rapidly converted to its demethylated metabolite. We also found that dechlorination and CN-replacement proceeded in autoclave-sterilized river sediment. In the river sediment, the abiotic reaction mediated by abundant humic acid and low oxygen level also appeared to contribute to the overall MXC metabolism.

The Developmental Neurotoxicology (DNT) Committee has been working to promote developmental neurotoxicology and related scientific areas of interest to integrate academic and regulatory sciences in this field since the Behavioral Teratology Meeting was established by the Japanese Teratology Society in 1982. The committee has led several large-scale collaborative studies to standardize existing methodologies and held symposiums and workshops periodically at the society's annual meetings. This overview provides a history of the DNT Committee, as well as a brief summary of the DNT Symposium in 2011. © 2012 Japanese Teratology Society.

Aoyama H.,Institute of Environmental Toxicology | Chapin R.E.,Pfizer
Vitamins and Hormones | Year: 2014

Methoxychlor is an organochlorine pesticide having a weak estrogenicity, which is estimated to be approximately 1000- to 14,000-fold less potent to a natural ligand, 17β-estradiol. However, its active metabolite, hydroxyphenyltrichloroethane, has much more potent estrogenic activity and probably acts in the target organs of animals exposed to methoxychlor at least 100 times stronger than the parent compound. A variety of in vivo reproductive toxicity studies have shown that treatment with methoxychlor exerts typical endocrine-disrupting effects manifest as estrogenic effects, such as formation of cystic ovaries resulting in ovulation failures, uterine hypertrophy, hormonal imbalances, atrophy of male sexual organs, and deteriorations of sperm production in rats and/or mice, through which it causes serious reproductive damages in both sexes of animals at sufficient dose levels. However, methoxychlor is not teratogenic. The no-observed-adverse-effect level of methoxychlor among reliable experimental animal studies in terms of the reproductive toxicity is 10. ppm (equivalent to 0.600. mg/kg/day) in a two-generation reproduction toxicity study. © 2014 Elsevier Inc.

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