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Chinese sturgeons (Acipenser sinensis) are large migratory fish that are native to the Yangtze River and coastal areas of China (1). However, human activities (e.g., water-related engineering projects, fishing, pollution, [...]

Simple Summary: In commercial aquaculture, aquatic animals are generally administered medicine ad libitum (at one's pleasure) via medicated feed. However, the estimation of withdrawal times for aquatic medicine is mostly carried out through the forced administration of medicine via oral gavage, which is not consistent with commercial aquaculture. This process may influence the absorption, distribution, metabolism, and excretion of medicine in aquatic animals and further affect the calculation of withdrawal times (WTs) for medicines. Therefore, in the current study, we selected the important aquatic medicine enrofloxacin (EF) to estimate its WTs in largemouth bass (Micropterus salmoides) after the administration of medicated feed. This study will obtain practical estimations of the WT of EF in actual aquaculture to aid in the surveillance of medication residue in fish products. The present study investigated the residue depletion and WTs of EF and its main metabolite, ciprofloxacin, in largemouth bass after ad libitum administration in commercial fish farming based on statistical approaches. Samples collected at pre-determined time points were assessed using high-performance liquid chromatography. If the concentrations of medicine were less than the quantitative limit, they were set to be half of the limit of quantitative. The terminal elimination of the target compound was assumed to fit a one-compartment model. The statistical methods of Bartlett's test and Cochran's test were used to inspect the homogeneity of the log-transformed data. The lack-of-fit test and F-test were used to check the linearity of the regression line. Outliers were assessed using standardized residuals. The final WT was estimated using the 95% percentile with a 95% confidence level. The WTs of EF were calculated to be 46, 29, 33, 46, and 20 days for the muscle + skin, plasma, gill, kidney, and liver, respectively. After the risk assessment, the values of the hazard quotient were calculated to be far less than 1, indicating that the risk of residual EF was particularly low in the edible tissues of largemouth bass after medicine depletion for various WTs. [ABSTRACT FROM AUTHOR]

The purpose of this study was to measure organ blood flow (OBF) in yellow catfish (YC, Pelteobagrus fulvidraco), largemouth bass (LB, Micropterus salmoides), and grass carp (GC, Ctenopharyngodon idella) using the method of fluorescent microspheres. Yellow–green microspheres were injected into the fish via cardiac catheterization using a syringe pump at a rate of 0.8 mL/min. Reference blood samples were collected from the dorsal aorta, and fish tissues were harvested after 5 min and processed for fluorescence spectrophotometric analysis. The results showed that the OBF of the heart increased significantly with the increase in temperature from 20 to 30 °C, while there was no significant difference in the OBF of other organs/tissues in YC. The OBFs of different species of LB and GC were also determined at 25 °C. In GC, the blood flow rates of the heart, spleen, kidney, liver, others, gills, swim bladder, intestines, muscles, and skin were 9.55, 1.00, 10.3, 6.92, 6.70, 6.04, 2.06, 2.81, 1.78, and 3.72 (mL/min/g), respectively. In LB, the blood flow rates of the same organs were 8.80, 2.33, 1.01, 0.71, 4.11, 2.72, 1.22, 0.54, 9.47, and 0.40 (mL/min/g), respectively. Compared to the OBFs of YC at 25 °C, the OBFs in GC were the highest, followed by LB. These results reflect that OBF in fish has significant species differences. These studies provide fundamental physiological data on OBFs in YC, GC, and LB, which has practical implications for improving the development of disciplines associated with fish physiology. [ABSTRACT FROM AUTHOR]

Simple Summary: Tilapia is the second-most-farmed fish worldwide which plays a critical role in providing high-quality proteins to human. However, infections caused by S. agalactiae result in huge economic losses. Moreover, the spreads of antibiotic resistance restrict the use of antibiotics in treating S. agalactiae infections. Here, we tried to develop anti-S. agalactiae drugs by inhibiting SrtA to overcome infections caused by resistant bacterial strains. Sortase A (SrtA) is responsible for anchoring surface proteins to the cell wall, and has been identified as a promising target developing anti-infective drugs of Gram-positive bacteria. The aim of the study was to identify inhibitors of Streptococcus agalactiae (S. agalactiae) SrtA from natural compounds to overcome the spread of antibiotic resistance in aquaculture. Here, we found that the MIC of fraxetin against S. agalactiae was higher than 256 μg/mL, indicating that fraxetin had no anti- S. agalactiae activity. But fraxetin could dose-dependently decrease the activity of SrtA in vitro at concentrations ranging between 4–32 μg/mL by a fluorescence resonance energy transfer (FRET) assay. Moreover, the inhibition of SrtA by fraxetin decreased the anchoring of surface proteins with the LPXTG motif to the cell wall by detecting the immunofluorescence change of serine-rich repeat protein 1 (Srr1) on the bacterial cell surface. The results of fibronectin binding and cell adhesion assays indicated that fraxetin could significantly decrease the adhesion ability of S. agalactiae in a dose-dependent manner. The results were further proven by immunofluorescence staining. Animal challenge results showed that treatment with fraxetin could reduce the mortality of tilapia infected with S. agalactiae to 46.67%, indicating that fraxetin could provide a significant amount of protection to tilapia by inactivating SrtA. Taken together, these findings provided a novel inhibitor of S. agalactiae SrtA and a promising candidate for treating S. agalactiae infections in aquaculture. [ABSTRACT FROM AUTHOR]

In this paper, a stochastic Leslie-Gower model with Beddington-DeAngelis functional response driven by the Ornstein-Uhlenbeck process is studied. Some asymptotic properties of the solution of the stochastic Leslie-Gower model are introduced: the existence and uniqueness of the global solution of the model are demonstrated, the ultimate boundedness of the model is analyzed, the existence of the stationary distribution of the model is proven, and the conditions for system extinction are discussed. Finally, numerical simulations are utilized to verify our conclusions. [ABSTRACT FROM AUTHOR]

Simple Summary: Chlorpheniramine hydrochloride (ROBH) is a synthetic anticoccidial drug in global aquaculture. The abuse and inappropriate use of ROBH may result in mortality in animals and drug residues in foodborne animals. Mass balance studies not only provide insights into the drug disposal process in animals, but also provide information on the metabolite composition and elimination pathways, leading to the identification of pharmacological metabolites. However, there are no related reports of mass balance studies for ROBH in fish. In addition to prodrugs, ROBH may include PCBA and PCHA as major metabolites. Therefore, this study was conducted to monitor ROBH levels and possible metabolites in Channel catfish (Ictalurus punctatus) to provide a theoretical basis for the development of maximum residue limits (MRLs) for ROBH in aquatic animals. This study aims to determine the mass balance of chlorpheniramine hydrochloride (ROBH) in the body of Channel catfish (Ictalurus punctatus). ROBH was administered orally at a dose of 20 mg/kg; following drug administration, the water samples were collected at predetermined time points (12, 24, 48, 72, 96, 120, 144, and 168 h), the experimental fish were executed after the water samples were obtained at 168 h, and the tissue samples were collected separately from the bones. The water and tissue samples were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC–MS/MS) for concentrations of ROBH and its potential major metabolites, 4-chlorohippuric acid (PCHA) and 4-chlorobenzoic acid (PCBA). The tissue samples were prepared using a modified QuEChERS procedure; the water samples were prepared using a liquid–liquid extraction (LLE) procedure. The results show that the recovery rate of ROBH in fish is very low, less than 2% of the total amount of the drug, and the recovery in water can reach 80.7% of the total amount of the drug. The content of PCBA accounted for 42.4% of the total amount of the drug; the content of ROBH accounted for 38.3% of the total amount of the drug. The content of PCHA accounted for less than 1% of the total amount of the drug. The results show that, after a single administration, ROBH is rapidly metabolized in vivo and excreted in the form of ROBH as well as metabolite PCBA. ROBH and PCBA can be used as the main targets for the metabolism detection of ROBH in Channel catfish. [ABSTRACT FROM AUTHOR]