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In this paper, a stochastic new logistic model is proposed, and dynamic behaviors of the model have been analyzed. The existence of global positive solution of the model is proved. In the persistence analysis of the model, the weak persistence and stochastic persistence of the model are proved. Some numerical simulations are presented to illustrate the dynamic properties of the model. [ABSTRACT FROM AUTHOR]

In the paper, Karhunen-Loeve expansion and Pythagorean-type distribution identities for the additive two-sided Brownian motion are derived. As the applications of Karhunen-Loeve expansion, the corresponding Laplace transform and small ball probability for the L2 norm are presented. [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]

The bivariate Brownian bridge, a nontensor Gaussian Field, is defined by B(t1,t2)=W(t1,t2)W(1,1)=0=W(t1,t2)-t1t2W(1,1), where t1,t2∈I=[0,1] and W(t1,t2) is a Brownian sheet. We obtain a distributional identity, a consequence of the Karhunen-Loève expansion for the bivariate Brownian bridge by Fredholm integral equation and Laplace transform approach. [ABSTRACT FROM AUTHOR]

In this article, we obtain the Karhunen–Loeve expansion and Pythagorean type distribution identities for the additive detrended Brownian motion. As applications, the corresponding Laplace transform and small-deviation asymptotic behavior for theL2norm are given. [ABSTRACT FROM AUTHOR]

This paper examines an optimal stopping problem for the stochastic (Wiener-Poisson) jump diffusion logistic population model. We present an explicit solution to an optimal stopping problem of the stochastic (Wiener-Poisson) jump diffusion logistic population model by applying the smooth pasting technique (Dayanik and Karatzas, 2003; Dixit, 1993). We formulate this as an optimal stopping problem of maximizing the expected reward. We express the critical state of the optimal stopping region and the optimal value function explicitly. [ABSTRACT FROM AUTHOR]

Crayfish is a very popular aquatic food in many countries, and enrofloxacin (ENR) and ciprofloxacin (CIP) was the most frequently detected in aquatic products. However, limited information is available on the residue characterization, biotransformation rate and withdrawal period (WT) of ENR and CIP in crayfish and health risk via consumption of ENR and CIP remained crayfish. Herein, a comprehensive investigation was conducted to study residue depletion, biotransformation, ingestion risk, and WT of ENR and its predominate metabolite CIP in crayfish following different routes with repeated doses. The results showed that the elimination half-life (T 1/2) of target compounds in crayfish were all in order of hepatopancreas > muscle > gill, and the order of T 1/2 in different crayfish tissues were intramuscular (IM) route > oral (PO) treatment > immersion (IMMR) administration. The biotransformation rates from ENR to CIP varied from 0.75% to 3.45% in crayfish tissues following different exposure routes. The high dietary risk (RQ > 1) consuming muscle and hepatopancreas of ENR and CIP remained crayfish occurred at early after different administrations. WT is the key to control the drug residue risk, and the longest WT of marker residue of ENR in crayfish was calculated to be 51 d (1275 °C-day). [Display omitted] • Residue elimination characteristics of ENR and CIP in crayfish were revealed following three administration routes. • Low biotransformation ratios from ENR to CIP were found in crayfish tissues. • Dietary risk (RQ > 1) consuming crayfish occurred at early after multiple-dose administration of ENR. • WT were suggested to prevent the risk from ENR and CIP remained crayfish consumption. [ABSTRACT FROM AUTHOR]

Niclosamide is a mollusicide used for aquaculture on a large scale in China. However, it has high toxicity to aquatic animals and may cause damage to DNA. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction procedure with high-performance liquid chromatography–heated electrospray ionization-tandem mass spectrometry method was developed for its determination. Samples were extracted with ammoniated acetonitrile, and anhydrous magnesium sulfate was added to remove moisture and precipitate proteins. The extracts were further purified with octadecylsilane. The recoveries of niclosamide in fortified muscle tissue at concentrations of 0.5 to 20 µg/kg were between 76.40% and 95.60% with relative standard deviations less than 9.54%. The limits of detection and quantification were 0.2 µg/kg and 0.5 µg/kg, respectively. The developed method was used to study the adsorption of niclosamide in channel catfish after administration. [ABSTRACT FROM PUBLISHER]

In this study, a fast, concise and reliable ultra-high performance liquid chromatography-fluorescence (UHPLC/FLD) detection method for simultaneous quantification of avermectins (AVMs), including avermectin (AVM), ivermectin (IVM), emamectin (EMM), moxidectin (MOX) and doramectin (DOR) in six aquatic foods was established. Based on the QuEChERS pretreatment method, the samples were extracted with 0.2% (v/v) ammonia acetonitrile. N-methyl imidazole mixed with acetonitrile (1:1, v/v) and trifluoroacetic anhydride with acetonitrile (1:2, v/v) were used as derivatization reagents. The mobile phase consists of acetonitrile and water with a flow rate of 1.0 mL/min. An Infinity Lab Poroshell 120 EC-C18 column was used for optimum chromatographic separation of target analytes at 40 °C; the excitation and emission wavelengths were set at 365 nm and 465 nm, respectively. In six kinds of aquatic foods, the limits of detection (LODs) of AVM, IVM, EMM, MOX, and DOR were 2.7 μg/kg, 1.8 μg/kg, 2.1 μg/kg, 1.2 μg/kg, and 2.7 μg/kg, respectively, and the limits of quantification (LOQs) of AVM, IVM, EMM, MOX, and DOR were 5 μg/kg, 4.5 μg/kg, 4.5 μg/kg, 3.5 μg/kg and 5.0 μg/kg, respectively. The recoveries were all above 85.38% when the samples were spiked with the target compounds at the concentration level of 5, 10, 50, and 100 μg/kg. The intra-day and inter-day relative standard deviations (RSDs) were all less than 15%. This method considers the requirements of sensitivity, accuracy, and economics of the instrument. [ABSTRACT FROM AUTHOR]

Herein, we isolated the pathogenic strain ZZ051 from hemorrhagic channel catfish (Ictalurus punctatus). Physiological and biochemical identification, 16S rRNA gene sequence analysis, and MALDI-TOF-MS showed that the ZZ051 strain was Aeromonas veronii. After artificial infection, the diseased fish showed symptoms similar to the natural disease, and the characteristics of the bacteria reisolated from the tissues were the same as those of the original infection, indicating that the isolated strain ZZ051 was the pathogen responsible for the channel catfish disease. The ZZ051 isolate was highly sensitive to enrofloxacin but resistant to florfenicol. This study provided a theoretical basis for preventing and controlling hemorrhagic disease in channel catfish. [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]

Simple Summary: Sulfamethoxazole is a commonly used antimicrobial drug in aquaculture. In order to understand its effect on the liver transcriptome of channel catfish, we orally administered a certain proportion of sulfamethoxazole into the fish and analyzed the changes in the transcriptome to determine the effect of the drug on the fish. By studying changes in the transcriptome, we found that the drug acted on drug metabolizing functions in the liver. Stimulated fish try to ensure the normal expression of their physiological functions by accelerating the operation of various metabolisms. The detoxification process is facilitated by promoting glucuronidation in the fish liver; while lipid metabolism is increased, the antioxidant pathway is affected, and the glucose xenobiotic pathway is enhanced in order to maintain energy homeostasis and to ensure a normal energy supply for metabolism. Other cellular metabolisms are also carried out to repair damaged normal organisms. This study provides a reference for understanding drug metabolism in channel catfish and provides a warning about the use of the drug. Sulfamethoxazole is a widely used antimicrobial drug used to treat bacterial diseases in aquaculture. To understand the gene expression in channel catfish liver after treatment with sulfamethoxazole, in this study, the treatment group received sulfamethoxazole (100 mg/kg bw), which was administered orally once, and samples were taken at 5 h, 12 h, and 6 d after the administration of sulfamethoxazole, while the control group was orally administered sterile water. To further identify potentially significant genes, a transcriptome analysis using RNA-seq was carried out. More than 50 million high-quality reads were found. After filtering and quality analysis, these reads were identified as 54,169,682, 51,313,865, 51,608,845, and 49,333,491. After counting 23,707 of these transcripts for gene expression, it was discovered that 14,732 of them had genes with differential expression. Moreover, we found that the annotation with the most GO variation was "cellular process" (1616 genes), "metabolic process" (1268 genes), "binding" (1889 genes), and "catalytic activity" (1129 genes). KEGG pathways showed that the "metabolic pathway" was the pathway that was significantly enriched in both experimental groups when comparing the experimental groups: 5 h and 12 h (128 genes); 5 h and 6 d (332 genes); and 12 h and 6 d (348 genes). Also, UDP- glucuronosyltransferase (ugt), which is associated with glucuronidation, and UDP-glucuronosyltransferase 2C1-like (ugt2a1) showed significant upregulation. Carboxylesterase 5A-like (ces3), which promotes fatty acyl and cholesteryl ester metabolism, and the glutathione transferase family were upregulated in the expression of sulfamethoxazole metabolism in the liver, which significantly affected the metabolic effects of the drug. Meanwhile, dypd, uck2b, and rrm2, which are related to nucleotide synthesis and metabolism, were upregulated. Our study extends the knowledge of gene expression in drug metabolism in channel catfish and further provides insight into the molecular mechanism of sulfamethoxazole metabolism. [ABSTRACT FROM AUTHOR]

We developed a method for determination of imidacloprid and its metabolites 5-hydroxy imidacloprid, olefin imidacloprid, imidacloprid urea and 6-chloronicotinic acid in Procambarus clarkii (crayfish) tissues using quick, easy, cheap, effective, rugged, and safe (QuEChERS) and high-performance liquid chromatography-triple quadrupole mass spectrometry. Samples (plasma, cephalothorax, hepatopancrea, gill, intestine, and muscle) were extracted with acetonitrile containing 0.1% acetic acid and cleaned up using a neutral alumina column containing a primary secondary amine. The prepared samples were separated using reverse phase chromatography and scanned in the positive and negative ion multiple reaction-monitoring modes. Under the optimum experimental conditions, spiked recoveries for these compounds in P. clarkii samples ranged from 80.6 to 112.7% with relative standard deviations of 4.2 to 12.6%. The limits of detection were 0.02–0.5 μg·L−1, the limits of quantification were 0.05–2.0 μg·L−1 and the method of quantification was 0.05–2.0 μg·kg−1. The method is rapid, simple, sensitive and suitable for rapid determination and analysis of imidacloprid and its metabolites in P. clarkii tissues. [ABSTRACT FROM AUTHOR]

This correction notice addresses errors in the original publication titled "Mass Balance Studies of Robenidine Hydrochloride in the Body of Channel Catfish (Ictalurus punctatus)." The errors include miswriting the word "Chlorpheniramine" and using it instead of the correct term "Robenidine." The title, summary, abstract, keywords, reagents section, recovery section, and reference have been corrected to reflect the accurate information. The authors assure that the scientific conclusions remain unaffected. [Extracted from the article]

Pregnane X receptor (PXR) as a ligand dependent transcription factor, is capable of regulating gene expression of cytochromes P450 and transporters involved in xenobiotic/drug metabolism and elimination. Due to the species differences in the regulatory specificity of PXR, gene regulation should not be extrapolated from mammal to fish without research data. The aim of present study was to investigate the effect of 27 natural products on PXR, CYP3A30 and MDR1 genes in channel catfish (Ietalurus punetaus) kidney cells (CC-K). The results showed that bisdemethoxycurcumin, glycyrrhetnic acid, rotenone, artemisinin, dihydroartemisinin, ligustilide and matrine strongly induced the mRNA levels of PXR. Additionally, the up-regulation of CYP3A30 gene ran parallel with PXR gene after the treatment of demethoxycurcumin, glycyrrhetnic acid, artemisinin, matrine, baicalein, schisantherin A, ligustilide, and dihydroartemisinin. Moreover, we found that natural products schisandrin A, schisandrin B, schisandrol A, and schisandrol B significantly up-regulated the mRNA level of MDR1 gene. Our work with a view to provide experimental data support for further research, which will make for the rational application of natural products in channel catfish, such as to avoid adverse herb-drug interactions or accelerating the residue elimination of chemical medicine. [ABSTRACT FROM AUTHOR]

Simple Summary: Enrofloxacin (EF) is an important antibiotic in global aquaculture. Due to the abuse and the emergence of drug resistance, the excess use of EF has occurred in recent years to result in residue exceeding in the edible tissues of aquatic animals. Withdrawal time (WT) is a red line to ensure food safety for humans. However, there is no related report of WT for EF in yellow catfish (Pelteobagrus fulvidraco). In addition to yellow catfish being sensitive to temperature, it can alter the disposition and elimination of EF and its main metabolite in fish bodies, ciprofloxacin (CF), thereby changing the WT in tissues. Therefore, we will conduct a WT estimation of EF in yellow catfish at different temperatures to establish related regulations to help residue surveillance in fish products. The objective of the present study was to investigate the residue depletion of EF and CF in yellow catfish to estimate its WTs in plasma and tissues after multiple oral doses for 3 days at 20 mg/kg at 15, 20, and 25 °C. Samples were collected at pre-designed time points after oral doses. A validated method was performed to quantify EF and CF in plasma and tissues by high-performance liquid chromatography. Statistical differences were conducted using one-way ANOVA analysis. According to the maximum residue limit of China and Europe considering 95% percentile with 95% confidence, the WTs were estimated to be 44, 72, 66, 99, and 95 days at 15 °C; 32, 66, 65, 86, and 73 days at 20 °C; and 32, 61, 64, 55, and 59 days at 25 °C in the plasma, muscle and skin, gill, liver, and kidney, respectively. We found that increased temperature shortened the WTs in plasma and tissues. Therefore, this study can help the risk assessment of EF in aquatic products for human health at different temperatures to avoid residue violation. [ABSTRACT FROM AUTHOR]

The residue depletion of niclosamide (NIC) in freshwater fish including blunt snout bream (Megalobrama amblycephala), yellow catfish (Pelteobagrus fulvidraco) and channel catfish (Ietalurus Punetaus) were investigated under laboratory conditions. NIC concentrations in fish were determined by Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) with heated electrospray ionisation. The mean recoveries were in the range of 75.5-98.5%, with relative standard deviations ranging from 1.0 to 9.4%. The depletion results showed that the long half-life of NIC was 8.8-22.1 days. Risk assessment of NIC residue in edible tissues (muscle and skin) of the three species of freshwater fish was performed using the quotient (RQ), because of no maximum residue limit (MRL) has been set for NIC in fish. The results demonstrated that the RQ values were all significantly lower than 1. Therefore, the effect of NIC residues in the three species of freshwater fish at the immersion concentration was negligible to Chinese people. [ABSTRACT FROM AUTHOR]

Simple Summary: Enrofloxacin (EF) is a commonly used broad-spectrum antibiotic in aquaculture against Gram-negative and Gram-positive bacteria. Ciprofloxacin (CF) has similar antibacterial activities to EF and has been developed as an aquatic medicine. It is well known that only the free concentration of a drug is effective for killing challenging pathogens. Hence, the plasma protein binding ratio (PPBR) of drugs is an important parameter in clinical medicine. Although PPBRs of EF and CF have been reported in several livestock animals, little information is available on aquatic animals. Moreover, environmental temperatures may influence the PPBR of drugs used for aquatic animals. Therefore, this study investigates PPBRs of EF and CF in the plasma of several finfish species such as yellow catfish (Pelteobagrus fulvidraco), grass carp (Ctenopharyngodon idella), and largemouth bass (Micropterus salmoides) at different concentrations with different temperatures. The present study facilitates the design of therapeutic regimens of EF for different aquatic animals at different concentrations. The objective of this study was to investigate the PPBRs of EF and CF in the plasma of yellow catfish, grass carp, and largemouth bass at different temperatures with different concentrations. A fast and simple ultrafiltration method was used to determine the PPBRs of EF and CF. Results showed that PPBRs of EF decreased from 37.71% to 9.66%, from 46.10% to 13.52%, and from 43.90% to 4.36% in the plasma of yellow catfish with the increase of concentration from 15 to 25 °C. The same trends of PPBRs of EF were presented in the plasma of grass carp and largemouth bass. In comparison to the data at the same concentration of EF at disparate temperatures, the PPBRs of EF at a concentration of 1 µg/mL increased from 37.71% to 46.10% and then decreased to 43.90% in the plasma of yellow catfish with elevated temperature from 15 to 25 °C. There is no obvious regularity with the rise of temperature, and the same phenomenon also were found in other concentrations and species. Meanwhile, the PPBRs of CF also decreased in the three species with the rise in concentration. Under the consistent concentration, the temperature-dependent regularities were not found in the PPBRs of CF. Overall, the increased concentration reduced the PPBRs of EF and CF in the plasma of three fish species, and the alteration in temperature only has a certain effect on the PPBRs of EF and CF. [ABSTRACT FROM AUTHOR]

Antibiotics were the main fishery drugs for treating Aeromonas hydrophila (A. hydrophila) infection, which would generate selective pressure and result in the appearance of antibiotic-resistant bacteria. The bacterial quorum sensing (QS) system provides a new alternative strategy against A. hydrophila infection. QS inhibitors can reduce bacterial virulence behaviors by disrupting QS, which has no effect on bacterial growth. Therefore, we studied the effect of cinnamaldehyde from a natural plant extract on the QS of A. hydrophila aiming to reduce its pathogenicity. The efficacy of cinnamaldehyde against A. hydrophila was evaluated from various aspects, including the effects on aerolysin, lipase, protease, swarming motility, biofilm formation, acyl-homoserine lactones (AHLs), and QS-related genes. Moreover, the therapeutic effect of cinnamaldehyde in vitro and in vivo was studied. The results showed that cinnamaldehyde could decrease the virulence phenotypes of A. hydrophila regulated by QS. Moreover, the transcriptions of related genes (aerA, ahyR, and ahyI) were downregulated following the addition of cinnamaldehyde. The in vitro and in vivo therapeutic assays show that cinnamaldehyde could reduce the aerolysin-mediated A549 cell injury and increase the survival rate of crucian carp infected with A. hydrophila. These results indicate that cinnamaldehyde would be a candidate QS inhibitor against A. hydrophila infection. [ABSTRACT FROM AUTHOR]

A plasma and tissue kinetic study of sulfadiazine (SDZ) and its metabolite, N4‐acetyl sulfadiazine (ACT‐SDZ), was characterized in channel catfish (Ictalurus punctatus) following a single oral dose of 50 mg/kg at 18 and 24°C. Samples were collected at predetermined time points and determined by ultra‐performance liquid chromatography. The classical one‐compartmental method was used to estimate the pharmacokinetic parameters. Results showed that the changing of temperature was markedly influential on the kinetics of SDZ and ACT‐SDZ in plasma and tissues. When the temperature was increased from 18 to 24°C, the elimination half‐life (K10_HF) of SDZ was decreased in gill, kidney, and muscle + skin, but increased in liver and plasma. The K10_HF of ACT‐SDZ also had a decreased trend in gill, liver, and plasma but had comparable values in kidney and muscle + skin. The absorption half‐life (K01_HF), time to peak concentration (Tmax), and area under concentration–time curve (AUC0‐∞) of SDZ and ACT‐SDZ all exhibited declined tendencies in plasma and tissues. The apparent volume of distribution (V_F) of SDZ in plasma was increased from 0.53 to 1.48 L/kg, and the apparent systemic total body clearance (Cl_F) was increased from 0.028 to 0.060 L/h/kg. In a word, K01_HF, Tmax, and AUC0‐∞ of SDZ and ACT‐SDZ were decreased in plasma and tissues with the increase of temperature, whereas the V_F and Cl_F of SDZ were increased. Meanwhile, we calculated the percentage of time profile of SDZ concentration more than minimum inhibitory concentration to total time (%T > MIC) to guide clinical usage of SDZ. When the dosage interval was 24 h, the values of %T > MIC were all >90% in plasma and most tissues. Therefore, we recommend an oral dose of SDZ at 50 mg/kg once per 24 h at 18–24°C against the fish pathogens with an MIC value of ≤6.4 μg/mL. [ABSTRACT FROM AUTHOR]

Simple Summary: Aquaculture is an important source of animal protein. However, in recent years, with an intensification of farming, the risk of infectious diseases is increasing, especially the diseases caused by monogeneans, resulting in huge economic losses to aquaculture. Currently, the prevention and control of monogenean in fish mainly rely on some chemical drugs, such as formaldehyde, rotenone, and praziquantel. However, prolonged and frequent use of these chemicals leads to the occurrence of drug resistance, some adverse environmental impacts, and even contamination of fish products with drug residues. Therefore, it is urgent to develop efficient and environment-friendly drugs for the control of monogeneans in aquaculture. Natural plant-derived medicines are one of the alternative options. Therefore, in this study, anthelmintic efficacy of various essential oils was evaluated. The results indicated that palmarosa oil and curcuma oil showed potent anthelmintic activity against monogenean, and curcuma oil also had an anesthetic effect on monogenean. Moreover, these two essential oils displayed a high safety for fish. Therefore, palmarosa oil and curcuma oil could be viable alternatives for the prevention and control of monogenean infection in aquaculture. Monogeneans are a serious threat to the development of aquaculture due to the severe economic losses they cause. The prevention and treatment of this disease are increasingly difficult because of the environmental and health concerns caused by the use of chemical anthelmintics and the emergence of drug resistance. It is thus necessary to search for effective alternatives for the treatment of monogenean infections. In the current study, anthelmintic efficacy of 16 selected essential oils (EOs) was investigated using the goldfish (Carassius auratus)–Gyrodactylus kobayashii model. The screening experiment indicated that palmarosa oil and curcuma oil had satisfactory anthelmintic activity against G. kobayashii with EC100 values of 10 and 12 mg/L after 24-h exposure, respectively. The in vivo and in vitro assays indicated anthelmintic efficacy of palmarosa oil against G. kobayashii was in a time and dose-dependent manner. Interestingly, curcuma oil showed an anesthetic effect on G. kobayashii, and its anthelmintic activity was dose-dependent rather than time-dependent in the concentration range tested in this study. Additionally, the 24-h LC50 (50% lethal concentration) against goldfish of these two EOs was 8.19-fold and 5.54-fold higher than their corresponding EC50 (50% effective concentration) against G. kobayashii, respectively. Moreover, exposure to these two EOs at 100% effective concentration against G. kobayashii had no serious physiological and histopathological influence on goldfish. These results demonstrated a high safety for goldfish of these two EOs. Overall, palmarosa oil and curcuma oil could be potential candidates for the treatment of G. kobayashii infections in aquaculture. [ABSTRACT FROM AUTHOR]

Gyrodactylus spp. pose a major threat to aquaculture due to their rapid proliferation and ability to cause severe infections in farmed fish. The existing treatments currently available have notable limitations, necessitating the exploration of new anthelmintic strategies. In this trial, in vitro and in vivo anthelmintic activity of triclabendazole against Gyrodactylus kobayashii and its safety in goldfish (Carassius auratus) were evaluated. The in vitro assays demonstrated a rapid increase in the mortality of G. kobayashii with increasing concentrations of triclabendazole, with the complete death of the worms achieved within 4 and 3 h at 0.1 and 0.2 mg/L, respectively. Triclabendazole demonstrated time- and concentration-dependent anthelmintic activity in vivo , with complete elimination of worms from goldfish achieved at 0.1 mg/L after 48 h of exposure. The EC 50 values after 24 and 48 h of exposure were 0.055 and 0.047 mg/L, respectively. To further elucidate the mechanism of action of triclabendazole against G. kobayashii , scanning electron microscopy and worm movement observation after exposure to triclabendazole were conducted. Exposure to triclabendazole induced reduced mobility and noticeable tegumental damages, potentially responsible for the death of worms. The 48-h LC 50 value of triclabendazole against goldfish was 1.12 mg/L and the therapeutic index (LC 50 /EC 50) was calculated to be 23.83 after 48 h of exposure. Histopathological analysis indicated minor modifications were detected in the gill and liver tissues after triclabendazole exposure. The expressions of cyp1a , hsp70 , gst , and sod were markedly modified during the 6 or 48-h post-exposure period, but tended to return to baseline levels with longer exposure. Overall, triclabendazole demonstrated superior anthelmintic activity against gyrodactylids coupled with an adequate safety profile in goldfish. These results supported the further development of triclabendazole as an alternative treatment for gyrodactylid infections in aquaculture. • Triclabendazole showed potent anthelmintic efficacy against Gyrodactylus kobayashii with an EC 50 value of 0.047 mg/L. • The anthelmintic mechanism of triclabendazole against gyrodactylids differs from other benzimidazoles. • Triclabendazole has a favorable safety profile. • Triclabendazole is an alternative treatment for gyrodactylosis in aquaculture. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the plasma protein binding rates (PPBRs) of doxycycline (DC) in the plasma of grass carp (Ctenopharyngodon idella), yellow catfish (Pelteobagrus fulvidraco) and crayfish (Procambarus clarkii) at different temperatures (4, 18 and 25℃) with different concentrations (1, 5, 10 and 20 μg/ml). A rapid and simple method of ultrafiltration (UF) was employed to determine the PPBR of DC in the plasma. The results showed that PPBRs were increased with the rise of the concentration of DC at the same temperature. At 4 ℃, PPBRs were increased from 90.00% to 99.51%, 89.81% to 98.71% and 84.08% to 99.21% in the plasma of grass carp, yellow catfish and crayfish respectively. At 18℃ and 25℃, the same trend was also presented in the three species. Meanwhile, PPBRs of DC might have the atypical nonlinear phenomenon. Otherwise, the temperature could affect the PPBR of DC at a certain degree in the plasma of grass carp and yellow catfish at the same concentration of DC. However, no regularity was presented in the plasma of crayfish. Overall, the increased concentration of DC significantly affected the PPBR in the plasma of grass carp, yellow catfish and crayfish at the same temperature, but the temperature only had a certain influence on the PPBR of grass carp and yellow catfish. Hence, this study is beneficial to design suitable therapeutic regimens and formulations of DC in grass carp, yellow catfish and crayfish at different temperatures. [ABSTRACT FROM AUTHOR]

In this study, the plasma pharmacokinetics and tissue disposition of sulfadiazine (SDZ) and its main metabolite, N4-acetyl sulfadiazine (ACT-SDZ), were compared between 18 and 24 °C following a single oral administration of SDZ at 50 mg/kg in grass carp (Ctenopharyngodon idella). The plasma and tissues were sampled from 0.167 h up to 96 h and analyzed by ultra-performance liquid chromatography with an ultraviolet detector. The pharmacokinetic parameters were estimated using a one-compartmental approach. Results showed that pharmacokinetics of SDZ and ACT-SDZ in plasma and tissues were notably influenced by the increase of temperature. The increased temperature shortened the absorption half-life (K01_HL) of SDZ and ACT-SDZ in gill, kidney, and plasma, but increased in liver and muscle + skin. The elimination half-life (K10_HF) and the area under concentration-time curve (AUC0–∞) of SDZ and ACT-SDZ all presented a declined trend. The apparent volume of distribution (V_F) of SDZ in plasma was increased from 0.93 to 1.64 L/kg, and the apparent systemic total body clearance (Cl_F) was also increased from 0.01 to 0.05 L/h/kg. Overall, the rise of temperature decreased K10_HF, AUC0–∞ of SDZ, and ACT-SDZ in plasma and tissues, but increased V_F and Cl_F in the plasma for SDZ. [ABSTRACT FROM AUTHOR]

This study aimed to determine the bioavailability and pharmacokinetic parameters of sulfadiazine (SDZ) in channel catfish (Ictalurus punctatus) following oral gavage and intravenous injection. The healthy channel catfish were orally and intravenously administrated with SDZ solution at doses of 50 and 5 mg/kg, respectively. Plasma samples were determined by ultra‐performance liquid chromatography with an ultraviolet detector. The results demonstrated that the concentration‐time profile of SDZ after oral dosing was best described by a one‐compartmental open model with first‐order absorption. The absorption half‐life (t1/2Kα), the elimination half‐life (t1/2Ke), and the area under concentration‐time profile (AUC0‐∞) were estimated to be 0.87 h, 29.04 h, and 1311.72 mg.h/L, respectively. After intravenous administration, the concentration‐time curve of SDZ conformed to a two‐compartmental open model without absorption. The distribution half‐life (t1/2α), the elimination half‐life (t1/2β), the apparent distribution volume (Vss), the total clearance (CL), and AUC0‐∞ were calculated to be 0.19 h, 14.24 h, 0.36 L/kg, 0.018 L/h/kg, and 277.12 mg.h/L, respectively. Finally, the bioavailability was estimated to be 47.33%. This study will provide some useful information for the modification of the dosage form of SDZ in aquaculture, and is partly beneficial for appropriate use of SDZ in the future. [ABSTRACT FROM AUTHOR]

The overuse of antibiotics in aquaculture brings a range of problems. Therefore, novel approaches alternating antibiotics are urgently needed. Strategies targeting bacterial virulence have become one of the routes developing drugs against bacterial infections. Here, we found that pterostilbene (PSE) could inhibit the activity of aerolysin (AerA) and disrupt quorum sensing (QS) at sub-inhibitory concentrations. Molecular docking and dynamics simulation assays were performed to predict the binding mode and binding sites of AerA-PSE complex. Then we confirmed that PSE bound to the sites of Val189 and Ile302 and prevented AerA forming heptamer with transmembrane pores. In addition, PSE could protect to A549 cells and the channel catfish (Ictalurus punctatus) against AerA mediated cell injury and mortality infected with A. hydrophila. The findings demonstrated that targeting bacterial virulence could be a promising measure identifying agents against A. hydrophila infections. • Pterostilbene is an inhibitor of both aerolysin and quorum sensing of Aeromonas hydrophila. • Pterostilbene could reduce the pathogenicity of Aeromonas hydrophila at sub-inhibitory concentrations. • The main binding sites and mechanism of at pterostilbene against aerolysin was confirmed. [ABSTRACT FROM AUTHOR]

In this study, the characteristics of a dominant strain wx3 isolated from the tissues of several sick red swamp crayfish were studied, and the immune response of the red swamp crayfish under stress was analyzed. The whole genome analysis of wx3 identified it as Aeromonas salmonicida subsp. Masoucida , which was confirmed using the bacterial challenge test, and is the pathogen that causes red swamp crayfish head rot. The sensitivity of wx3 to a variety of antibiotics was found that wx3 was highly sensitive to 13 antibiotics, but was not sensitive to 4 antibiotics. Comparative transcriptome analysis showed that 811 differentially expressed genes (DEGs) were enriched in the hepatopancreas 48 h after wx3 infection. The KEGG pathway analysis and GO analysis detected differentially expressed immune related genes, including C-type lectin 3 and Hsp22, which were upregulated, and also enriched in immune related pathways, such as the C-type lectin receptor signaling pathway, etc. In conclusion, by analyzing transcriptome, we found that red swamp crayfish infected with wx3 can exert a strong immune response. • It was found for the first time that Aeromonas salmonicida subsp. Masoucida caused the disease of red swamp crayfish. • Aeromonas salmonicida subsp. Masoucida can induce the expression of C-type lectin 3 and Hsp22 in red swamp crayfish. • wx3 showed severe drug resistance. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila (A. hydrophila) can cause a number of diseases in both human and animals. A. hydrophila-related infections in aquaculture cause severe economic losses every year throughout the world. The emergence of antibiotic resistance that is due to the abuse of antibiotics has limited the application of antibiotics. Thus, novel approaches are needed to combat with treatment failure of antibiotics caused by resistant bacterial strains. Aerolysin plays a critical role in the pathogenesis of A. hydrophila and has been considered as a novel target for developing drugs based on anti-virulence strategies. Here, we reported that luteolin, a natural product with no anti-A. hydrophila activity, could reduce aerolysin-induced hemolysis by inhibiting aerolysin activity. The binding mode was simulated by molecular docking and dynamics simulation. Then the main binding sites were confirmed by fluorescence quenching assays. We found that luteolin could hindered the formation of functional heptamer of aerolysin according to the results of the oligomerization assay. Moreover, luteolin could protect A549 cells from aerolysin mediated cell death and increase the survival rate of A. hydrophila-infected channel catfish. These findings suggest a novel approach to developing drugs fighting against A. hydrophila, and luteolin can be a promising drug candidate for treatment of A. hydrophila-associated infections. [ABSTRACT FROM AUTHOR]

Tiamulin fumarate (TIF) is a pleuromutilin antibiotic and has high activity against animal bacterial pathogens including aquatic bacterial pathogens. However, its pharmacokinetic profiles, tissue distribution characteristics and bioavailability in aquatic animals remain unknown. The objective of this study was to investigate the pharmacokinetics and tissue distribution regularities of TIF in tilapia (Oreochromis niloticus) following a single oral (PO) dose of 20 mg/kg body weight (bw) and a single intravenous (IV) dose of 5 mg/kg bw at 22 ± 1°C, respectively. TIF concentrations in tilapia plasma and tissues were determined using the isotope dilution HPLC‐HESI‐MS/MS procedure, which was validated according to the guidelines defined by US Food and Drug Administration. TIF was well distributed throughout the body compartments of tilapia judged by the apparent volume of distribution (Vd) >1 L/kg (6.69 L/kg PO and 1.78 L/kg IV). TIF had a short mean residence time (MRT; 22.82 h PO and 14.61 h IV) and quick total body clearance (CLb) (0.62 L kg−1 h−1 PO and 0.60 L kg−1 h−1 IV). The total area under the curve (AUCtot) of plasma were 32.25 μg h−1 ml−1 (PO) and 8.30 μg h−1 ml (IV), respectively, and the oral absolute bioavailability (F%) of TIF was calculated to be approximately 97.1%. For tissue distribution, high concentrations of TIF were found in kidney, and the longest MRT was recorded in bile. The withdrawal time (WT) of TIF in muscle, skin, liver, kidney, gill, and bile was 3.75 (4) and 1.79 (2), 1.77 (2) and 2.06 (3), 6.41 (7) and 1.97 (2), 6.95 (7) and 3.98 (4), 4.92 (5) and 2.36 (3), and 7.06 (8) and 6.16 (7) days after PO and IV administration, respectively. The present investigations indicated that TIF was quickly absorbed, well distributed, rapidly eliminated in tilapia, and it could serve as reference data for establishing use regimen and provide useful information for the further development of TIF in aquaculture. [ABSTRACT FROM AUTHOR]

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]

This study aimed to examine the bioavailability (BA) and pharmacokinetic (PK) characteristics of sulfadiazine (SDZ) in grass carp (Ctenopharyngodon idellus) after oral and intravenous administrations. Blood samples were collected at predetermined time points of 0.083, 0.17, 0.5, 1, 2, 4, 8, 16, 24, 48, 72, and 96 hr (n = 6). The samples were extracted and purified by organic reagents and determined by the ultra‐performance liquid chromatography. The software named 3P97 was used to calculate relevant PK parameters. The results demonstrated that the concentration–time profile of SDZ was best described by a one‐compartmental open model with first‐order absorption after a single oral dose. The main PK parameters of the absorption rate constant (Kα), the absorption half‐life (t1/2 Kα), the elimination rate constant (Ke), the elimination half‐life (t1/2Ke), and the area under concentration–time profile (AUC0‐∞) were 0.3 1/h, 2.29 hr, 0.039 1/h, 17.64 hr, and 855.78 mg.h/L, respectively. Following intravenous administration, the concentration–time curve fitted to a two‐compartmental open model without absorption. The primary PK parameters of the distribution rate constant (α), the elimination rate constant (β), the distribution half‐life (t1/2α), the elimination half‐life (t1/2β), the apparent distribution volume (VSS), the total clearance (CL), and AUC0‐∞ were 9.62 1/hr, 0.039 1/hr, 0.072 hr, 17.71 hr, 0.33 L/kg, 0.013 L h−1 kg−1, and 386.23 mg.h/L, respectively. Finally, the BA was calculated to be 22.16%. Overall, this study will provide some fundamental information on PK properties in the development of a new formulation SDZ in the future and is partially beneficial for the appropriate usage of SDZ in aquaculture. [ABSTRACT FROM AUTHOR]

Monogenean parasites pose a significant challenge to aquaculture, leading to adverse effects on fish health and yields. Current anthelmintic treatments for monogeneans have demonstrated limited efficacy and are further complicated by potential issues, which emphasize the necessity for effective and safe therapeutic strategies to manage monogeneans in aquaculture. In this study, in vivo and in vitro anthelmintic activity of febantel against Gyrodactylus kobayashii on goldfish (Carassius auratus), as well as its toxicity to goldfish were evaluated. In vivo assays indicated that febantel exhibited potent anthelmintic activity against G. kobayashii with an EC 50 value of 0.03 mg/L and 100 % anthelmintic efficacy at 0.1 mg/L after 48 h of exposure. Moreover, in vivo trials also revealed a notable post-treatment effect of febantel, where infected goldfish transferred to drug-free water after short 6-h exposure could still result in full eradication of the worms, indicating febantel might induce persistent perturbations in parasite physiology. In vitro assays showed a negative correlation between febantel concentrations and the survival of G. kobayashii. However, increasing the febantel concentration to 2.0 mg/L did not result in the complete death of all worms. Oral administration of febantel demonstrated limited anthelmintic activity, with only 49 % efficacy at a dosage of 200 mg/kg body weight daily over five days. Acute toxicity assays revealed the 48-h LC 50 value of febantel was 5.47 mg/L, which was 182.23 times higher than the 48-h EC 50 value, indicating that febantel has a favorable safety profile. However, febantel exposure potentially interfered with hepatic metabolism and oxidative status, as indicated by variations in SOD, GST, and P450 gene expression. In conclusion, treatment with 0.1 mg/L febantel for 24 h completely eradicated G. kobayashii infection on goldfish, demonstrating febantel's potent anthelmintic activity. Coupled with its safety profile and extended post-treatment effectiveness, febantel is a promising candidate for controlling Gyrodactylus infections in aquaculture. • Febantel showed potent anthelmintic efficacy against Gyrodactylus kobayashii with an EC 50 value of 0.03 mg/L. • A notable post-treatment effect of febantel against G. kobayashii was observed. • Febantel has a favorable safety profile. • Febantel is a promising candidate for controlling Gyrodactylus infections in aquaculture. [ABSTRACT FROM AUTHOR]

Herein, the effects of Agaricus bisporus Polysaccharides (ABPs) on anti-channel catfish virus (CCV) infections to promote their application in channel catfish culture were explored. Transcriptome and metabolome analyses were conducted on the spleen of a CCV-infected channel catfish model fed with or without ABPs. CCV infections upregulated many immune and apoptosis-related genes, such as IL-6 , IFN-α3 , IFN-γ1 , IL-26 , Casp3 , Casp8 , and IL-10 , and activated specific immunity mediated by B cells. However, after adding ABPs, the expression of inflammation-related genes decreased in CCV-infected channel catfish, and the inflammatory inhibitors NLRC3 were upregulated. Meanwhile, the expression of apoptosis-related genes was reduced, indicating that ABPs can more rapidly and strongly enhance the immunity of channel catfish to resist viral infection. Moreover, the metabonomic analysis showed that channel catfish had a high energy requirement during CCV infection, and ABPs could enhance the immune function of channel catfish. In conclusion, ABPs can enhance the antiviral ability of channel catfish by enhancing immune response and regulating inflammation. Thus, these findings provided new insights into the antiviral response effects of ABPs, which might support their application in aquaculture. • ABPs enhance immune responses in ictalurus punctatus. • ABPs can inhibit the harmful inflammatory reaction in CCV infection. • ABPs improve the anti-CCV ability of channel catfish. [ABSTRACT FROM AUTHOR]

TIR domain-containing protein is an important member for some bacterial pathogens to subvert host defenses. Here we described a fish virulent Yersinia ruckeri SC09 strain that interfered directly with Toll-like receptor (TLR) function by a TIR-containing protein. Firstly, the novel TIR-containing protein was identified by bioinformatics analysis and named as TcpA. Secondly, the toxic effects of TcpA in fish was demonstrated in vivo challenge experiments through knockout mutant and complement mutant of tcpA gene. Thirdly, The study in vitro revealed that TcpA could down-regulate the expression and secretion of IL-6, IL-1β and TNF-α. Finally, we demonstrated that TcpA could inhibit the TLR signaling pathway through interaction with myeloid differentiation factor 88 (MyD88) in experiments such as NF-κB dependent luciferase reporter system, co-immunoprecipitation, GST pull-down and yeast two-hybrid. The study revealed that TcpA was essential for virulence and was able to interact with the TIR adaptor protein MyD88 and inhibit the pre-inflammatory signal of immune cells and promote the intracellular survival of pathogenic Yersinia ruckeri SC09 strain. In conclusion, our results showed that TcpA acted as a new virulence factor in Y. ruckeri could suppress innate immune response and increase virulence by inhibiting TLR and MyD88-mediated specific signaling, highlighting a novel strategy for innate immune evasion in bacteria. • TcpA is a virulence factor of the fish pathogen Yersinia ruckeri SC09 strain. • TcpA mediates inhibition of Toll-like receptor signaling during infection. • The TIR domain-containing protein TcpA enables interaction with TLR adaptor MyD88. [ABSTRACT FROM AUTHOR]

To promote the application of Agaricus bisporus polysaccharides (ABPs) in channel catfish (Ictalurus punctatus) culture, we evaluated the effects of ABPs on the growth, immunity, antioxidant, and antibacterial activity of channel catfish. When the amount of ABPs was 250 mg/kg, channel catfish's weight gain and specific growth rates increased significantly while the feed coefficient decreased. We also found that adding ABPs in the feed effectively increased the activities of ACP, MDA, T-SOD, AKP, T-AOC, GSH, and CAT enzymes and immune-related genes such as IL-1β, Hsp70, and IgM in the head kidney of channel catfish. Besides, long-term addition will not cause pathological damage to the head kidney. When the amount of ABPs was over 125 mg/kg, the protection rate of channel catfish was more than 60%. According to the intestinal transcriptome analysis, the addition of ABPs promoted the expression of intestinal immunity genes and growth metabolism-related genes and enriched multiple related KEEG pathways. When challenged by Yersinia ruckeri infection, the immune response of channel catfish fed with ABPs was intenser and quicker. Additionally, the 16S rRNA gene sequencing analysis showed that the composition of the intestinal microbial community of channel catfish treated with ABPs significantly changed, and the abundance of microorganisms beneficial to channel catfish growth, such as Firmicutes and Bacteroidota increased. In conclusion, feeding channel catfish with ABPs promoted growth, enhanced immunity and antioxidant, and improved resistance to bacterial infections. Our current results might promote the use of ABPs in channel catfish and even other aquacultured fish species. • ABPs can increase the weight gain rate and specific growth rate of channel catfish, and reduce its feed coefficient. • ABPs can enhance the ability of channel catfish to resist bacterial infection. • Long term use of ABPs will not cause pathological loss to channel catfish. [ABSTRACT FROM AUTHOR]

The aim of this investigation was to explore the effect of artemisinin (ART) on pharmacokinetic (PK) and tissue distribution characteristics of enrofloxacin (ENR) and ciprofloxacin (CIP) in channel catfish following combined and single medicine. The channel catfish in ENR group were treated with ENR, and the fish in ENR-ART group were orally co-administrated with ENR and ART. ENR and CIP concentrations in channel catfish were determined using ultra performance liquid chromatography, and PK parameters for ENR and CIP were calculated by WinNonlin software. Moreover, the multi-drug resistance 1 (MDR1) gene expression and cytochrome P-450 3A (CYP 3A) enzyme activities in channel catfish liver were measured. The results showed that lower ENR and CIP levels were observed in ENR-ART group than that in ENR group, and similar regularities in PK parameters were also found that C max , AUC and MRT values in ENR group were all greater than those in ENR-ART group. Furthermore, higher MDR1 gene expression and CYP 3A enzyme activities in channel catfish liver were observed in ENR-ART group than those in ENR group. The present investigation indicates that ART can reduce the ENR concentrations, accelerate the excretion of ENR and decrease the antibacterial efficacy of ENR in channel catfish. • ENR and CIP disposition regularities were explored after co-administration of ENR with and without ART in channel catfish. • Significant differences in levels and PK parameters of ENR and CIP were found between combined and single medicine. • Higher MDR1 gene expression and CYP 3A activity in liver were observed in ENR-ART group than that in single ENR group. • ART can reduce the ENR concentrations, accelerate the excretion of ENR and decrease the antibacterial efficacy of ENR. [ABSTRACT FROM AUTHOR]

Abstract Channel catfish is one of the most extensively cultured species worldwide, which is widely used as a classical model for comparative immunology. Interleukin-1β (IL1β) is an immunoregulatory cytokine with the potential to enhance the immune response induced by vaccines in many animals. To characterize the molecular characterization and identify the immunoadjuvant role of channel catfish IL1β, molecular cloning, phylogenetic analysis, and expression of two IL1β genes were performed, the bioactivity of their recombinant proteins (rIL1β1 and rIL1β2) were detected in vitro and their adjuvant effects on a subunit vaccine encoding C5a peptidase (pSCPI) of Streptococcus iniae were evaluated. The results indicated that two IL1βs remained highly conserved possessing five conserved motifs compared with other fish IL1βs, although there were 28 nucleotide differences and 16 amino acid differences between channel catfish IL1β1 and IL1β2. Analysis of the ratios of nonsynonymous (dN) and synonymous (dS) substitutions revealed that fish IL1β genes were subjected to negative/purifying selection with global dN/dS ratios value 0.425. The results of adjuvant effect showed that compared with injection of pSCPI alone, co-injecting pSCPI with both rIL1β1 and rIL1β2 significantly enhanced antibody levels, serum bactericidal activity, lysozyme activity, alternative complement hemolytic activity, and the expression of endogenous IL1β and TNF-α in head kidney and spleen. Although vaccination with rIL1β1 or rIL1β2 failed to offer immunoprotection against S. iniae infection, the RPS (relative percent survival) of pSCPI+rIL1β1 and pSCPI+rIL1β2 groups were both higher than pSCPI alone (RPS, 50%), with 64.26% and 60.71%, respectively. Moreover, pSCPI+rIL1β1+rIL1β2 offered significantly higher (P < 0.05) immunoprotection (RPS, 75%) against S. iniae infection than pSCPI alone. Our present results not only enrich the molecular structure study of fish IL1βs but also signify that two recombinant channel catfish IL1βs can be used as potential adjuvants in a subunit vaccine model against bacterial infection, which are of profound importance to prevent and control bacterial disease in channel catfish. Highlights • Fish IL1βs were subjected to negative/purifying selection throughout the evolution. • Channel catfish IL1βs were highly conserved with five conserved motifs. • Channel catfish IL1βs can be used as molecular adjuvants in subunit vaccine model. • rIL1β1 as adjuvant was slightly better than rIL1β2 to enhance the immune response. • Co-injection of rIL1β1+rIL1β2 induced higher immune response and immunoprotection. [ABSTRACT FROM AUTHOR]

A fast ultra-performance liquid chromatography method was developed for the separation and quantification of doxycycline, 4-epidoxycycline, and 6-epidoxycycline in the muscles of channel catfish, shrimp, eel and turtle. The analytes were separated by comprehensive optimization of the chromatographic conditions. The extraction method was performed using a modified QuEChERS methodology. 2 g of muscle sample were mixed with 5 mL Mcllvaine buffer (pH 4), and 4 g of sodium sulfate and 2 g of sodium chloride were added for liquid-liquid partitioning. The mixture was agitated for 30 s and extracted with 10 mL of acidified acetonitrile. The resulting extract was purified using 200 mg of a C18-silica adsorbent. The samples were analyzed using ultra-performance liquid chromatography with ultraviolet detection using a BEH C18 column (2.1 mm ×100 mm, 1.7 μm). The limits of detection were less than 25 μg/kg and the limits of quantitation were less than 50 μg/kg for all analytes. The recoveries of the analytes were from 62.3% to 89.0% with relative standard derivations below 10.0%. The method provided efficient extraction and purification that enabled rugged and low-cost determination of the analytes. [ABSTRACT FROM AUTHOR]

A liquid chromatography–tandem mass spectrometry quantitative method was developed for determining mebendazole and its metabolites, albendazole and its metabolites, and levamisole in muscles of bluntnose black bream, shrimp, eel and turtle based on modified QuEChERS methodology. The method included 2 g of the muscle matrix with 10 mL acetonitrile, and 0.8 g of magnesium sulphate and 0.2 g of sodium chloride for liquid-liquid partitioning. After vortex and centrifugation, the resulting liquid (5.5 mL) was purified by C 18 (50 mg) and Al-N (50 mg). The limits of detection were lower than 0.3 μg kg −1 and the limits of quantitation were no more than 1 μg kg −1 for all analytes. The recoveries of the analytes ranged from 80.0% to 113.7% with the relative standard derivation less than 10.0%. The preparation procedure provided efficient extraction and purification that enabled a sensitive and rugged determination of target compounds. [ABSTRACT FROM AUTHOR]

The use of bdellovibrios has been regarded as an alternative to control multidrug-resistant pathogens and fish bacteriosis. However, scarce information is available on the potential of bdellovibrios in the presence of copper sulfate, which is an algicide widely used to treat cyanobacterial blooms in aquaculture. In the present study, the effects of copper sulfate at sublethal and lethal levels (0.1 and 1.0 mg·L−1) on Bdellovibrio sp. strain BDF-H16 were evaluated. The growth of Bdellovibrio sp. strain BDF-H16 was significantly promoted by both concentrations of copper sulfate, but less so by the lethal concentration. The bacteriolysis of gibel carp-pathogenic Aeromonas hydrophila by Bdellovibrio sp. strain BDF-H16 was also stimulated by copper sulfate in both solid and liquid media. However, Bdellovibrio sp. strain BDF-H16 with 0.1 mg·L−1 copper sulfate clearly inhibited infection of gibel carps by A. hydrophila better than Bdellovibrio sp. strain BDF-H16 with 1.0 mg·L−1 copper sulfate did. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the pharmacokinetic (PK) properties of enrofloxacin (EF) and its metabolite, ciprofloxacin (CF), in yellow catfish (Pelteobagrus fulvidraco) after a single oral dose of EF at 20 mg/kg at 20, 25, and 30 °C. Samples were collected at pre-designed time points and determined by high-performance liquid chromatography with a fluorescent detector. Results showed that most concentrations of EF and CF in plasma and tissues at the same time point at different temperatures were statistically significant. With the increase in temperature, the terminal half-life (T 1/2λz) of EF and CF was first reduced from 20 to 25 °C but elevated from 25 to 30 °C in plasma, muscle + skin, gill, liver, and kidney, respectively. The area under the plasma concentration-time curves (AUC last) of EF were all decreased in plasma, muscle + skin, and gill except for that of EF in the liver and kidney. However, the AUC last and the apparent metabolic rate of CF were exhibited first elevated and then decreased trend. The apparent volume of distribution (Vz_F) of EF was first reduced from 20 to 25 °C but increased at 30 °C. The apparent total body clearance (CL_F) of EF was increased from 0.15 to 0.32 L/h·kg with the temperature elevation. These indicated that increased temperature markedly affected the PKs of EF and CF in yellow catfish. Through in-depth analysis, the EF dosage of 20 mg/kg is appropriate to use in yellow catfish at 20 and 25 °C but 30 °C. [Display omitted] • Enrofloxacin and ciprofloxacin's PKs were investigated in yellow catfish at 20, 25, and 30 °C. • The temperature altering markedly influenced T 1/2λz , AUC last , Vz_F, and CL_F. • T 1/2λz of enrofloxacin and ciprofloxacin were first decreased but then increased with the increase in temperature. • AUC last of enrofloxacin were all decreased in plasma, muscle + skin, and gill with temperature change. • Enrofloxacin dosage of 20 mg/kg is appropriate to use in yellow catfish at 20 and 25 °C but 30 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Residue accumulation and risk assessment of doxycycline was studied in crayfish in the natural environment. • Statistical approaches were used to evaluate the homogeneity, linearity, and normality of errors for obtained data. • The dairy assessment indicated that hazard quotients were far less than 1 after post-doses for 5 days. • Reliable withdrawal times were determined in muscle (43 d) and hepatopancreas (89 d) of crayfish. Doxycycline is an important medicine in aquaculture for treating fish diseases. However, its excess use causes residue exceeding to threaten human health. So, this study aimed to estimate a reliable withdrawal time (WT) of doxycycline (DC) in crayfish (Procambarus clarkii) based on statistical approaches and conduct a risk assessment for human health in the natural environment. Samples were collected at predetermined time points and determined by high-performance liquid chromatography. A novel statistical method was used to process the data of residue concentration. The homogeneity and linearity of the regressed line of data were evaluated by Bartlett's, Cochran's, and F tests. Outliers were excluded by establishing the standardized residual versus their cumulative frequency distribution on a normal probability scale. The calculated WT was 43 days in muscle of crayfish based on China and European stipulations. After 43 days, estimated daily intakes of DC were ranged from 0.022 to 0.052 µg/kg/d. Hazard Quotients were ranged from 0.007 to 0.014, which were far less than 1. These results indicated that established WT could avoid health risks for humans resulting from DC's residue in crayfish. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is a common zoonotic pathogen which can cause several infections both in human and animals, particular aquatic animals. Antibiotics have been widely used in the treatment of A. hydrophila infections, however, the development of resistance has limited the treatment for these infections. There is an urgent need for novel agents and strategies against these infections. Aerolysin, a pore-forming toxin secreted by most pathogenic A. hydrophila , is known to contribute to the pathogenesis of A. hydrophila infections. Therefore, aerolysin has been identified as a potential target for drug discovery. In this paper, we found that magnolol, a natural compound without anti - A. hydrophila activity, could significantly inhibit the hemolytic activity of A. hydrophila culture supernatants by inhibiting the transcription of the aerolysin encoding gene aerA at low concentrations. Furthermore, the survival assay showed that magnolol could significantly reduce the mortality induced by A. hydrophila infection in channel catfish ( Ictalurus punctatus ). Taken together, these findings provide a potent agent against A. hydrophila infections. [ABSTRACT FROM AUTHOR]

The objective of the present study was to investigate the pharmacokinetic (PK) properties of doxycycline (DC) in crayfish after three different drug administrations of oral (per os , P.O.) gavage, intramuscular (IM) injection, and intrasinus (IS) injection at a dose of 20 mg/kg at 24.0 °C. Samples of hepatopancreas, muscle, gill, and hemolymph were collected at pre-determined time points after cessation of drug treatment (n = 5 for per time point). DC concentrations were determined by high-performance liquid chromatography with an ultraviolet detector. Results demonstrated that the multiple-peak phenomenon occurred in hemolymph and tissues irrespective of using any drug administration. With the changing of drug administration, the PK parameters were correspondingly altered. The elimination rate constant (t 1/2λ) were 28.90, 32.99, and 31.70 h; 42.00, 60.21, and 25.28 h; 32.17, 26.00, and 21.15 h; 69.53, 23.25, and 31.20 h in hepatopancreas, muscle, gill, and hemolymph after P.O., IM, and IS dosing, respectively. The values of the area under the concentration-time curve (AUC last) after IM and IS treatment were comparable in hepatopancreas, muscle, gill, and hemolymph, respectively, but the value following P.O. treatment was less than the values after IM and IS treatment except for hepatopancreas that presented an opposite trend. The volume of distribution (V z _F) was estimated to be 2625.30 mL/kg, and the systemic total body (Cl_F) was 58.30 mL/h/kg. Finally, the P.O. and IM bioavailability were calculated to be 19.58% and 104.76%. This study will provide the useful PK information of DC after different administrations, and is beneficial for a specific dosage regime in line with the drug given route. • Doxycycline's PKs were investigated in crayfish after P.O., IM, and IS administrations. • The changing of drug administration considerably affected t 1/2λz , T max , C max , and AUC last. • Bioavailability values were 19.58% and 104.76% after oral and intramuscular dosing. • The results provide useful information for the effective use of doxycycline in crayfish. [ABSTRACT FROM AUTHOR]

Simple Summary: Trichloroisocyanuric acid (TCCA) has been widely used in public health and aquaculture for the prevention and treatment of diseases. As a strong oxidative disinfectant, TCCA may cause adverse influences on aquatic organisms and further poses a threat to the aquatic ecosystems. Nonetheless, the toxicological influences of TCCA on aquatic animals are still scarce and the mechanisms of the toxicity at the molecular levels in goldfish (Carassius auratus) have not been illustrated. The current study investigated the influences of sublethal concentration of TCCA on transcriptomic responses, the molecular indices of oxidative stress, and histopathological alterations in the hepatic and gill tissues of goldfish. The results indicated that TCCA exposure induced the disturbance of energy metabolism and the detoxification process. Furthermore, TCCA exposure also induced oxidative stress in the liver and caused pathological damage in gills. These findings could be useful to help understand the toxicological influences of TCCA on goldfish. In this study, goldfish (Carassius auratus) were exposed to 0 (control group) and 0.81 mg/L TCCA for four consecutive days. The liver transcriptome, the molecular indices of oxidative stress, and gills histopathology were investigated. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that energy metabolism-related pathways such as glycolysis/gluconeogenesis were significantly enriched, suggesting their perturbation in the liver of goldfish. Additionally, TCCA exposure also caused pathological damage in gills, which compromised physiological function and decreased oxygen intake capacity of gills, thus leading to the enhancement of anaerobic metabolism. This finding was confirmed by the significant upregulation of lactate dehydrogenase in the liver of goldfish. Moreover, many phase I and phase II metabolic enzymes might be activated to alleviate TCCA-induced toxicity in goldfish, and glutathione S-transferases (GSTs) and cytochrome P450s (CYPs) play a crucial role in the metabolism of TCCA in the liver of goldfish. Furthermore, the antioxidant enzyme analysis showed that TCCA exposure induced oxidative damage in the liver and partially impaired the antioxidant defense system of goldfish, evidenced by decreased superoxide dismutase (SOD) and catalase (CAT), and increased malondialdehyde (MDA) level. In summary, this study will improve our understanding of the molecular mechanisms of the TCCA-induced toxicity in goldfish. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is widely distributed in freshwater environments and aquatic products which can cause a variety of infectious diseases to aquatic, terrestrial species and human. However, the emergence of antibiotic resistant strains results in the treatment failure of antibiotics. Therefore, novel strategies need to be clarified. The pathogenesis of the bacterium is composed by the virulence factors, such as hemolytic toxins, biofilm and adhesions. Therefore, aerolysin and biofilm have been developed as targets identifying novel drugs against A. hydrophila infections. In the present study, resveratrol with little anti- A. hydrophila activity could decrease the pathogenesis of A. hydrophila by inhibiting the expression of aerolysin and biofilm formation at sub-inhibitory concentrations. Results of western-blot and qPCR assays demonstrated that RSV could decrease aerolysin and biofilm production by inhibiting aerolysin encoding gene and quorum sensing system. Furthermore, results of cell viability and experimental therapeutics assays indicated that RSV could provide a significant protection both in vitro and in vivo. Taken together, these findings provide a new approach in identifying drugs based on anti-virulence strategies. RSV is a promising candidate anti- A. hydrophila infections by decreasing the production of aerolysin and biofilm. • Resveratrol can decrease the hemolytic activity and biofilm formation by habiting the quorum sensing system. • Resveratrol can provide a significant protection to channel catfish challenged with A. hydrophila. • Findings in the present study offer a novel approach identifying drugs against Aeromonas hydrophila infections. [ABSTRACT FROM AUTHOR]

The aim of this present study was to explore the sex-related differences in disposition regularities of sulfamethoxazole (SMZ), N-acetyl-sulfamethoxazole (N-ac-SMZ) and trimethoprim (TMP) in male and female yellow catfish. Concentrations of target compounds were determined using a reliable HPLC-MS/MS approach, which was validated according to the guidelines defined by FDA. The results showed that there are significant sex-associated differences in SMZ concentrations of muscle with skin and liver, in N-ac-SMZ levels of muscle with skin and kidney, and in TMP concentrations of muscle with skin, liver and kidney. Whereas, no significant sex differences were also observed in SMZ, N-ac-SMZ and TMP levels of plasma, in SMZ concentrations of kidney and in N-ac-SMZ concentrations of liver. Longer residue time of N-ac-SMZ than SMZ was observed in male and female yellow catfish. Withdrawal time (WT) of SMZ (N-ac-SMZ as the marker residue) calculated by the WT 1.4 software, was 11 days (male) and 9 days (female), respectively. By contrast, WT of SMZ (SMZ as the marker residue) was 9 days (male) and 7 days (female), respectively. These results could serve as reference data for establishing disparate use regimen and drug withdrawal time of SMZ and TMP in male and female yellow catfish. • The sex-differences in disposition of 3 compounds were studied in yellow catfish. • Significant sex-differences in tissue concentrations of target compounds were found. • The residue time of N-ac-SMZ was longer than SMZ in tissues of yellow catfish. • Given that N-ac-SMZ as the maker residue, longer WT of SMZ would be needed. [ABSTRACT FROM AUTHOR]