Occurrence and ecological risk assessment of 16 plasticizers in the rivers and estuaries in Japan.

Owing to growing concerns about the adverse effects of phthalate plasticizers, non-phthalate plasticizers are being increasingly used as their replacement. However, information on the residual environmental concentrations and ecological risks posed by these plasticizers is limited. In this study, we analyzed the environmental contamination of 11 phthalates and 5 non-phthalate plasticizers in Class A and B rivers in Japan. In the considered river water samples, phthalates and non-phthalates were detected in the following order of detection frequency: phthalates (DEHP > DMP > DMEP > BBP > DNPP > DNP > DEEP > DBEP = DNOP) and non-phthalates (ATBC > DEHS > DEHA > TOTM = DIBA). Phthalate plasticizers were the most abundant and included DEHP (157-859 ng/L), DMP (

Behavioral profile alterations and predation susceptibility of Japanese medaka fish exposed to phenytoin, an antiepileptic drug.

Antiepileptic drugs, such as phenytoin, are often leaked into aquatic systems through sewage facilities due to their low metabolic rate. Fish, such as the Japanese medaka (Oryzias latipes), demonstrate abnormal swimming behavior such as equilibrium abnormalities, rotational behavior, and vertical swimming, when exposed to phenytoin. Therefore, it is hypothesized that predator avoidance may be hindered. This study aimed to investigate the effects of phenytoin exposure-induced behavioral abnormalities in predator avoidance in Japanese medaka. The results showed that individuals with behavioral abnormalities had a reduced ability to avoid danger. Furthermore, the fish demonstrated a delayed recognition reaction to approaching predators. Additionally, predatory fish, such as silver pike characin (Ctenolucius hujeta), were more likely to prey upon abnormal individuals. In conclusion, the fish exposed to phenytoin demonstrated behavioral changes that increased its predation risk. This study is the first to determine the effects of behavioral abnormalities in Japanese medaka which was induced after phenytoin exposure on predator risk avoidance.

Iopanoic acid alters thyroid hormone-related gene expression, thyroid hormone levels, swim bladder inflation, and swimming performance in Japanese medaka.

Disruption of the thyroid hormone system by synthetic chemicals is gaining attention owing to its potential negative effects on organisms. In this study, the effects of the dio-inhibitor iopanoic acid (IOP) on the levels of thyroid hormone and related gene expression, swim bladder inflation, and swimming performance were investigated in Japanese medaka. Iopanoic acid exposure suppressed thyroid-stimulating hormone ß (tshß), tshß-like, iodotyronin deiodinase 1 (dio1), and dio2 expression, and increased T4 and T3 levels. In addition, IOP exposure inhibited swim bladder inflation, reducing swimming performance. Although adverse outcome pathways of thyroid hormone disruption have been developed using zebrafish, no adverse outcome pathways have been developed using Japanese medaka. This study confirmed that IOP inhibits dio expression (a molecular initiating event), affects T3 and T4 levels (a key event), and reduces swim bladder inflation (a key event) and swimming performance (an adverse outcome) in Japanese medaka.

Evidence for Introgressive Hybridization between Native Dolly Varden (Salvelinus curilus (syn. Salvelinus malma)) and Introduced Brook Trout (Salvelinus fontinalis) in the Nishibetsu River of Hokkaido, Japan.

Hybridization is one of the negative outcomes for the introduction of non-native species, which can lead to rapid displacement and genetic extinction of native species. Salmonid fishes have been widely introduced outside of their native ranges for food supply and recreational fishing. Here, we investigate the occurrence of introgressive hybridization among native Dolly Varden (Salvelinus curilus (syn. Salvelinus malma)), white-spotted charr (Salvelinus leucomaenis), and introduced brook trout (Salvelinus fontinalis), in streams of the Nishibetsu River, Hokkaido, Japan. Microsatellite DNA analysis detected five hybrids between native Dolly Varden and introduced brook trout. This is the first evidence for hybridization between native Dolly Varden and introduced brook trout, while the latter has been known to hybridize with many other salmonids. Furthermore, incongruence between mitochondrial DNA and microsatellite DNA analyses suggested introgression among the three Salvelinus species. Further studies to estimate the hybrid fitness are necessary to understand how hybridization among the three species affects the native species.

Gram-Scale Syntheses and Conductivities of [10]Cycloparaphenylene and Its Tetraalkoxy Derivatives.

[10]Cycloparaphenylene ([10]CPP) and its tetraalkoxy derivatives were synthesized on the gram scale in 7 steps starting from 1,4-benzoquinone or 2,5-dialkoxy-1,4-benzoquinone. The key steps involve the highly cis-selective bis-addition of 4-bromo-4'-lithiobiphenyl to the quinones to produce a five-ring unit containing cyclohexa-1,4-diene-3,6-diol moiety, the platinum-mediated dimerization of the five-ring unit, and the H2SnCl4-mediated reductive aromatization of cyclohexadienediol. The tetraalkoxy substituents increased the solubility of [10]CPP in common organic solvents. The carrier-transport properties of thin films of [10]CPP and its derivatives were measured for the first time and indicated that [10]CPP derivatives could rival phenyl-C61-butyric acid methyl ester, which is used widely as an n-type active layer in bulk heterojunction photovoltaics.