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Gyrodactylus spp. are common monogenean ectoparasites that may lead to significant fish mortality. To find effective anthelmintic agents with lower toxicity, a series of natural saponins were obtained and evaluated for their anthelmintic activity against Gyrodactylus kobayashii and acute toxicity to goldfish (Carassius auratus). Among all tested compounds, six compounds (1, 2, 3, 8, 10, and 13) shown higher anthelmintic activity and safety than widely used formaldehyde-based parasiticides, especially compound 1 having 100% anthelmintic efficacy against G. kobayashii at 0.3 mg/L and a therapeutic index of 16.6. Also, the three-dimensional quantitative structure-activity relationship (3D-QSAR) studies of these saponins have been performed to explore the structural features reasonable for the anthelmintic activity against G. kobayashii. These models demonstrated that the hydroxyl group at C-17 position and the sugar moieties at C-3 position, especially the hydroxyl groups of the sugar moieties, were critical to the anthelmintic activity. The QSAR studies could provide useful information for further rational design and optimization of novel saponins for the control of gyrodactylosis. [ABSTRACT FROM AUTHOR]

Gyrodactylid monogeneans are widespread parasites of teleost fishes, and infection with these parasites results in high host morbidity and mortality in aquaculture. To comprehensively elucidate the immune mechanisms against Gyrodactylus kobayashii, the transcriptome profiles of goldfish (Carassius auratus) skin after challenge with G. kobayashii were first investigated using next-generation sequencing. Approximately 21 million clean reads per library were obtained, and the average percentage of these clean reads mapped to the reference genome was 82.25%. A total of 556 differentially expressed genes (DEGs), including 344 upregulated and 212 downregulated genes, were identified, and 380 DEGs were successfully annotated and assigned to 95 signaling pathways in Kyoto Encyclopedia of Genes and Genomes (KEGG). In addition, 14 pathways associated with immune response were identified mainly including mTOR signaling pathway, cytokine-cytokine receptor interaction, intestinal immune network for IgA production, toll-like receptor signaling pathway, and phagosome. Twelve genes were selected and validated using qRT-PCR. A similar trend of these genes between RNA-Seq and qRT-PCR was observed, indicating that RNA-Seq data was reliable. Besides, the ALP activity and NO content in serum were significantly higher in the infected goldfish compared with the non-infected goldfish. In summary, this study provides better understandings of immune defense mechanisms of goldfish against G. kobayashii, which will support future molecular research on gyrodactylids and facilitate the prevention and treatment of gyrodactylosis in aquaculture. [ABSTRACT FROM AUTHOR]

An original method for the simultaneous determination of robenidine hydrochloride (ROBH) and its main metabolites 4-chlorohippuric acid (PCHA) and 4-chlorobenzoic acid (PCBA) in fish plasma and muscle was established by high-performance liquid chromatography coupled with heat electrospray ionization tandem mass spectrometry (HPLC-HESI-MS/MS) using predefined time segments in the alternating positive/negative mode. Fish muscle samples were prepared using a modified QuEChERS procedure, and plasma samples were prepared by a liquid–liquid extraction (LLE) procedure. The entire procedure was validated according to the guidelines defined by the US Food and Drug Administration. Matrix-matched calibration curves for plasma and muscle of fish showed good linearity with correlation coefficients (R2) ≥ 0.9985. The accuracy exhibited a relative error (RE) ranging from −14.2–8.2%, and intra- and inter-day precisions of analytes expressed as relative standard deviation (RSD) were within 12.4%. Limits of detection (LODs) and limits of quantitation (LOQs) were lower than 2.5 μg L−1 and 5 μg L−1 for target compounds in plasma and not more than 2.5 μg kg−1 and 5 μg kg−1 for analytes in muscle, respectively. The present method was successfully applied to explore the kinetic profiles of ROBH and its metabolites in grass carp (Ctenopharyngodon idella), and it demonstrated that PCBA is the major metabolite of ROBH in grass carp plasma and muscle. The elimination half-lives (t1/2β) of ROBH and PCBA in grass carp muscle were calculated to be 17.31 h and 138.53 h, respectively. [ABSTRACT FROM AUTHOR]

We established a high-performance liquid chromatography-triple quadrupole mass spectrometry method for the analysis of pendimethalin residues in water, sediments, and Procambarus clarkii (Louisiana crayfish) tissues. Water samples were concentrated on a HLB solid-phase extraction column and eluted with dichloromethane and acetone (1:1). After drying under a stream of nitrogen gas, the sample volume was adjusted to 1 mL with the mobile phase solvent methanol/water/acetic acid (8:20:0.1). Pendimethalin was extracted with ethyl acetate containing 0.1% acetic acid, after rotary evaporation to dryness at 35 °C, the residue was dissolved in mobile phase solvent, purified by a neutral alumina column and graphitized carbon black powder (0.1 g). The mass characterization was conducted in positive ion mode, and the corresponding ions were detected in multi-reaction monitoring mode. The linear equations were y = 1 × 106x + 14275, at pendimethalin levels of 0.05–20 μg L−1 and y = 691029 × − 414368 for 20–200 μg L−1. The detection limits of pendimethalin in water, sediments, and P. clarkii tissues were 1.0 × 10−4μg L−1 , 5.0 × 10−3μg kg −1 and 5.0 × 10−3 μg kg −1, respectively. The spiked recoveries ranged from 81.6 to 106.3%, and the relative standard deviations ranged from 4.58 to 13.6% (n = 6). The method provided an efficient and low-cost extraction and purification procedure that enabled a sensitive determination of pendimethalin in water as well as complex matrices. [ABSTRACT FROM AUTHOR]

The m-th order detrended Brownian motion is defined as the orthogonal component of projection of the standard Brownian motion onto the subspace spanned by polynomials of degree up to m. We obtain the Karhunen-Loeve expansion for the process and establish a connection with the generalized ( m-th order) Brownian bridge developed by MacNeill (1978) in the study of distributions of polynomial regression. The resulting distribution identity is also verified by a stochastic Fubini approach. As applications, large and small deviation asymptotic behaviors for the L norm are given. [ABSTRACT FROM AUTHOR]