Temperature-Dependent Residue Depletion Regularities of Tiamulin in Nile Tilapia (Oreochromis niloticus) Following Multiple Oral Administrations

Evaluating the persistence of malachite green residues in tilapia and pacu fish

Although banned in food-producing animals, residues of malachite green (MG) and its primary metabolite, leucomalachite green (LMG), have been found in fish due to illegal use in aquaculture and the release of industrial wastewater, which represent a serious risk to food and environmental securities. This study aimed to investigate the residue depletion profile of MG and LMG in edible tissues of Nile tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus) cultured simultaneously under the same environmental conditions to support control measures in case of abuse. An analytical method involving QuEChERS sample preparation and liquid chromatography coupled to tandem mass spectrometry was developed, validated, and applied to quantify MG and LMG residues in fish fillets from two depletion experiments after treatment by immersion bath (MG at 0.10 mg L-1 for 60 min). During the experiment, the average water temperature was 30 ºC, while the pH was 6.9. The method is selective, precise (CV = 0.4 - 22%) and accurate (recovery 92 - 114%). The limits of detection and quantification are 0.15 and 0.5 ng g-1, respectively. In both species, the sum of MG and LMG residues were quantified up to the 32nd day post-exposure, and the concentrations were significantly higher in the pacu fillets (up to 3284 ng g-1) than in Nile tilapia (up to 432 ng g-1). The sums of MG and LMG residues were below 2 ng g-1 at 44 days and 342 days for Nile tilapia and pacu, respectively - the Minimum Required Performance Limit (MRPL) for analytical methods intended to monitor forbidden substances in food according to old European Commission guidelines. The persistence of MG residues in pacu may be attributed to its higher lipid content, which favors the accumulation of the non-polar metabolite LMG. These results provide insights into the concern about human, animal, and environmental health risks resulting from unauthorized use or aquatic contamination by industrial wastewater containing MG residues.

The occurrence of typical psychotropic drugs in the aquatic environments and their potential toxicity to aquatic organisms - A review

Psychotropic drugs (PDs) and their bioactive metabolites often persist in aquatic environments due to their typical physical properties, which made them resistant to removal by traditional wastewater treatment plants (WWTPs). Consequently, such drugs and/or their metabolites are frequently detected in both aquatic environments and organisms. Even at low concentrations, these drugs can exhibit toxic effects on non-target organisms including bony fish (zebrafish (Danio rerio) and fathead minnows) and bivalves (freshwater mussels and clams). This narrative review focuses on the quintessential representatives of three different categories of PDs-antiepileptics, antidepressants, and antipsychotics. The data regarding their concentrations occurring in the environment, patterns of distribution, the degree of enrichment in various tissues of aquatic organisms, and the toxicological effects on them are summarized. The toxicological assessments of these drugs included the evaluation of their effects on the reproductive, embryonic development, oxidative stress-related, neurobehavioral, and genetic functions in various experimental models. However, the mechanisms underlying the toxicity of PDs to aquatic organisms and their potential health risks to humans remain unclear. Most studies have focused on the effects caused by acute short-term exposure due to limitations in the experimental conditions, thus making it necessary to investigate the chronic toxic effects at concentrations that are in coherence with those occurring in the environment. Additionally, this review aims to raise awareness and stimulate further research efforts by highlighting the gaps in the understanding of the mechanisms behind PD-induced toxicity and potential health risks. Ultimately, the study underscores the importance of developing advanced remediation methods for the removal of PDs in WWTPs and encourages a broader discussion on mitigating their environmental impacts.

The Use of Tricaine Methanesulfonate (MS-222) in Asian Seabass (Lates calcarifer) at Different Temperatures: Study of Optimal Doses, Minimum Effective Concentration, Blood Biochemistry, Immersion Pharmacokinetics, and Tissue Distributions

This study was conducted to determine the optimal doses and minimum effective concentrations (MECs) of tricaine methanesulfonate (MS-222) in marketable-size Asian seabass reared at two temperatures (22 and 28 °C). Serum biochemical parameters, pharmacokinetics, and tissue distributions of MS-222 following immersion at the determined optimal doses were also evaluated in order to delineate possible mechanisms dictating the temperature difference. The definition of optimal dose is set as the dose when fish attain stage III anesthesia within 5 min, sustain this stage for 3 min, and re-attain equilibrium within 5 min. The MEC is the fish serum MS-222 concentration when stage III anesthesia is reached. The results showed that water temperature exerted no or minimal impact on the designated parameters. The optimal doses at 22 and 28 °C were 140 and 150 µg/mL, while the MECs were 70.48 and 78.27 µg/mL, respectively. Fish exposed to the optimal doses of MS-222 had significantly elevated blood concentrations of lactate, glucose, calcium, magnesium, and sodium, while the blood pH was significantly decreased. The fish eliminated MS-222 faster at 28 °C than at 22 °C, with serum half-lives of 18.43 and 37.01 h, respectively. Tissue-specific distribution patterns were evident. Irrespective of water temperature, MS-222 peaked at 5 min for the brain and gill but peaked slightly later at 10-20 min for the liver and kidney. Most tissues exhibit a gradual decline of drug concentration except for the gill, which was maintained at a steady level. Muscle is the least perfused tissue with the lowest drug concentration throughout the 90 min period. This study provided physiological and pharmacokinetic evidence contributing to a better understanding of the actions of MS-222 in Asian seabass at different temperatures.

Residue Depletion Profile and Estimation of Withdrawal Period for Sulfadimethoxine and Ormetoprim in Edible Tissues of Nile Tilapia (Oreochromis sp.) on Medicated Feed

Sulfadimethoxine (SDM) and ormetoprim (OMP) are antimicrobials used in combination to treat bacterial infections in fish farming. The use of this drug combination is not yet regulated in some countries, such as Brazil. Due to the lack of regulated drugs for aquaculture in Brazil, this study investigated the residue depletion profile of SDM and OMP in Nile tilapia (Oreochromis sp.) after oral administration. Fish were treated with medicated feed containing a 5:1 ratio of SDM:OMP at the dose of 50 mg kg BW-1 for five consecutive days with an average water temperature of 28 °C. The drugs were incorporated into the feed by using a gelatin coating process which promoted homogeneity in drug concentration and prevented the drug leaching into the water during medication. The SDM and OMP determination in fish fillets (muscle plus skin in natural proportions) was performed using the QuEChERS approach followed by LC-MS/MS quantification. The analytical method was validated according to Brazilian and selected international guidelines. A withdrawal period of 9 days (or 252 °C days) was estimated for the sum of SDM and OMP residues at concentration levels below the maximum residue level of 100 µg kg-1.

Plasma and tissue kinetics of enrofloxacin and its metabolite, ciprofloxacin, in yellow catfish (Pelteobagrus fulvidraco) after a single oral administration at different temperatures

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.

Residue, biotransformation, risk assessment and withdrawal time of enrofloxacin in red swamp crayfish (Procambarus clarkii)

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).

Factors influencing degradation kinetics of mRNAs and half-lives of microRNAs, circRNAs, lncRNAs in blood in vitro using quantitative PCR

RNAs are rapidly degraded in samples and during collection, processing and testing. In this study, we used the same method to explore the half-lives of different RNAs and the influencing factors, and compared the degradation kinetics and characteristics of different RNAs in whole blood and experimental samples. Fresh anticoagulant blood samples were incubated at room temperature for different durations, RNAs were extracted, and genes, including internal references, were amplified by real-time quantitative PCR. A linear half-life model was established according to cycle threshold (Ct) values. The effects of experimental operations on RNA degradation before and after RNA extraction were explored. Quantitative analysis of mRNA degradation in samples and during experimental processes were explored using an orthogonal experimental design. The storage duration of blood samples at room temperature had the greatest influence on RNA degradation. The half-lives of messenger RNAs (mRNAs) was 16.4 h. The half-lives of circular RNAs (circRNAs), long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) were 24.56 ± 5.2 h, 17.46 ± 3.0 h and 16.42 ± 4.2 h, respectively. RNA degradation occurred mainly in blood samples. The half-life of mRNAs was the shortest among the four kinds of RNAs. Quantitative experiments related to mRNAs should be completed within 2 h. The half-lives of circRNAs and lncRNAs were longer than those of the former two.