Interpreting Bibliometric Data.

Many academic analyses of good practice in the use of bibliometric data address only technical aspects and fail to account for and appreciate user requirements, expectations, and actual practice. Bibliometric indicators are rarely the only evidence put before any user group. In the present state of knowledge, it is more important to consider how quantitative evaluation can be made simple, transparent, and readily understood than it is to focus unduly on precision, accuracy, or scholarly notions of purity. We discuss how the interpretation of 'performance' from a presentation using accurate but summary bibliometrics can change when iterative deconstruction and visualization of the same dataset is applied. From the perspective of a research manager with limited resources, investment decisions can easily go awry at governmental, funding program, and institutional levels. By exploring select real-life data samples we also show how the specific composition of each dataset can influence interpretive outcomes.

Development and Validation of a Hybrid Screening and Quantitative Method for the Analysis of Eight Classes of Therapeutants in Aquaculture Products by Liquid Chromatography-Tandem Mass Spectrometry.

A method using reverse-phase ultra-high-performance liquid chromatography coupled with tandem mass spectrometry is described for eight classes of therapeutants that are used in marine aquaculture products. Validation studies to evaluate recovery, precision, method detection limits, and measurement uncertainty were performed at three levels, using three representative matrices [salmon (fatty fish), tilapia (lean fish), and shrimp (crustaceans)] to assess the method performance for use as a screening or determinative (quantitative and confirmatory) method. A total of 16 sulfonamides (plus 2 potentiators), 2 tetracyclines, 11 (fluoro)quinolones, 7 nitroimidazoles, 3 amphenicols, 5 steroids, and 3 stilbenes met the quantitative criteria for method validation. An additional 5 triphenylmethane dyes, 2 sulfonamides, 2 tetracyclines, and 1 amphenicol met the required performance for use as a screening method. Limits of detection (LODs) for the compounds that met the quantitative criteria ranged from 0.1 to 5 µg/kg, while LODs for compounds from the screening group ranged from 0.1 to 30 µg/kg. This method provides a comprehensive approach to the determination of different classes of compounds in aquaculture products.

FIRE - Flyby of Io with Repeat Encounter: A conceptual design for a New Frontiers mission to Io.

A conceptual design is presented for a low complexity, heritage-based flyby mission to Io, Jupiter's innermost Galilean satellite and the most volcanically active body in the Solar System. The design addresses the 2011 Decadal Surveys recommendation for a New Frontiers class mission to Io and is based upon the result of the June 2012 NASA-JPL Planetary Science Summer School. A science payload is proposed to investigate the link between the structure of Io's interior, it's volcanic activity, it's surface composition, and it's tectonics. A study of Io's atmospheric processes and Io's role in the Jovian magnetosphere is also planned. The instrument suite includes a visible/near IR imager, a magnetic field and plasma suite, a dust analyzer and a gimbaled high gain antenna to perform radio science investigations. Payload activity and spacecraft operations would be powered by three Advanced Stirling Radioisotope Generators (ASRG). The primary mission includes 10 flybys with close-encounter altitudes as low as 100 km. The mission risks are mitigated by ensuring that relevant components are radiation tolerant and by using redundancy and flight-proven parts in the design. The spacecraft would be launched on an Atlas V rocket with a delta-v of 1.3 km/s. Three gravity assists (Venus, Earth, Earth) would be used to reach the Jupiter system in a 6-year cruise. The resulting concept demonstrates the rich scientific return of a flyby mission to Io.

Impact of TGF-ß inhibition during acute exercise on Achilles tendon extracellular matrix.

The purpose of this study was to evaluate the role of TGF-ß1 in regulating tendon extracellular matrix after acute exercise. Wistar rats exercised (n = 15) on a treadmill for four consecutive days (60 min/day) or maintained normal cage activity. After each exercise bout, the peritendinous space of each Achilles tendon was injected with a TGF-ß1 receptor inhibitor or sham. Independent of group, tendons injected with inhibitor exhibited ~50% lower Smad 3 (Ser423/425) (P < 0.05) and 2.5-fold greater ERK1/2 phosphorylation (P < 0.05) when compared with sham (P < 0.05). Injection of the inhibitor did not alter collagen content in either group (P > 0.05). In exercised rats, hydroxylyslpyridinoline content and collagen III expression were lower (P < 0.05) in tendons injected with inhibitor when compared with sham. In nonexercised rats, collagen I and lysyl oxidase (LOX) expression was lower (P < 0.05) in tendons injected with inhibitor when compared with sham. Decorin expression was not altered by inhibitor in either group (P > 0.05). On the basis of evaluation of hematoxylin and eosin (H&E) stained cross sections, cell numbers were not altered by inhibitor treatment in either group (P > 0.05). Evaluation of H&E-stained sections revealed no effect of inhibitor on collagen fibril morphology. In contrast, scores for regional variation in cellularity decreased in exercised rats (P < 0.05). No differences in fiber arrangement, structure, and nuclei form were noted in either group (P > 0.05). Our findings suggest that TGF-ß1 signaling is necessary for the regulation of tendon cross-link formation, as well as collagen and LOX gene transcription in an exercise-dependent manner.

Postnatal Hyperplasic Effects of ActRIIB Blockade in a Severely Dystrophic Muscle.

The efficacy of two ActRIIB ligand-trapping agents (RAP-031 and RAP-435) in treating muscular dystrophy was examined by determining their morphological effects on the severely dystrophic triangularis sterni (TS) muscle of the mdx mouse, a model for Duchenne muscular dystrophy. These agents trap all endogenous ligands to the ActRIIB receptor and thereby block myostatin signaling in a highly selective manner. Short-term (1 month) and long-term (3 months) in vivo treatment of 1-month-old mdx mice increased myonuclei and fiber cross section (FCS) density but did not alter individual fiber size. Vehicle-treated mdx mice exhibited age-dependent increases in myonuclei and FCS density, and age-dependent reductions in centronucleation that were each enhanced by treatment with RAP-435. Distributions of FCS area (FCSA) in the mdx TS were 90% identical to those from untreated age-matched nondystrophic mice and were unaltered by the substantial fiber hyperplasia observed with age and RAP-435 treatment. These results were inconsistent with injury-induced fiber regeneration which produces altered FCSA distributions characterized by a distinct class of smaller regenerated fibers. Nondystrophic mice exhibited a constant postnatal density of fiber cross sections and myonuclei, and RAP-435 treatment of nondystrophic mice increased TS mean FCSA but had no effects on myonuclei or FCS density. These results demonstrating a continual postnatal proliferation and fusion of satellite cells and a response to myostatin blockade characteristic of developing prenatal muscle suggest that the lack of dystrophin directly results in unrestrained postnatal satellite cell activation that is not necessarily dependent upon prior fiber degeneration. J. Cell. Physiol. 232: 1774-1793, 2017. © 2016 Wiley Periodicals, Inc.

Peak-ring structure and kinematics from a multi-disciplinary study of the Schrödinger impact basin.

The Schrödinger basin on the lunar farside is ∼320 km in diameter and the best-preserved peak-ring basin of its size in the Earth-Moon system. Here we present spectral and photogeologic analyses of data from the Moon Mineralogy Mapper instrument on the Chandrayaan-1 spacecraft and the Lunar Reconnaissance Orbiter Camera (LROC) on the LRO spacecraft, which indicates the peak ring is composed of anorthositic, noritic and troctolitic lithologies that were juxtaposed by several cross-cutting faults during peak-ring formation. Hydrocode simulations indicate the lithologies were uplifted from depths up to 30 km, representing the crust of the lunar farside. Through combining geological and remote-sensing observations with numerical modelling, we show that a Displaced Structural Uplift model is best for peak rings, including that in the K-T Chicxulub impact crater on Earth. These results may help guide sample selection in lunar sample return missions that are being studied for the multi-agency International Space Exploration Coordination Group.

In vivo treatment with the NF-κB inhibitor ursodeoxycholic acid (UDCA) improves tension development in the isolated mdx costal diaphragm.

INTRODUCTION: Previous experiments have indicated that in vivo administration of ursodeoxycholic acid (UDCA) inhibits nuclear NF-κB activation and has beneficial effects on the structure and function of dystrophic (mdx) muscle. We examined the effect of UDCA on tension development in dystrophic muscle. METHODS: Isometric tension development was examined in costal diaphragms that were freshly isolated from vehicle and UDCA treated mdx mice. Percent recovery scores were obtained by directly comparing these measurements to those obtained from age-matched nondystrophic mice. RESULTS: Vehicle treated mdx mice exhibited significantly reduced optimal muscle lengths (lo ) and specific twitch and tetanic tensions compared with age-matched nondystrophic mice. UDCA treated preparations exhibited significantly improved tension development with a 33% recovery score. CONCLUSIONS: Because UDCA is used in treating certain clinical disorders, these results provide a rationale for human clinical trials using this and related drugs for treatment of Duchenne and related muscular dystrophies.

Agents Which Inhibit NF-κB Signaling Block Spontaneous Contractile Activity and Negatively Influence Survival of Developing Myotubes.

Inhibiting the NF-κB signaling pathway provides morphological and functional benefits for the mdx mouse, a model for Duchenne muscular dystrophy characterized by chronic elevations in the nuclear expression of p65, the transactivating component of the NF-κB complex. The purpose of this study was to examine p65 expression in nondystrophic and mdx myotubes using confocal immunofluorescence, and determine whether inhibitors of the NF-κB pathway alter myotube development. Primary cultures of nondystrophic and mdx myotubes had identical levels of nuclear and cytosolic p65 expression and exhibited equivalent responses to TNF-α, thus excluding the hypothesis that the lack of dystrophin is sufficient to induce increases in NF-κB signaling. The NF-κB inhibitors pyrrolidine dithiocarbamate (PDTC) and sulfasalazine decreased spontaneous contractile activity and reduced myotube viability in a dose- and time-dependent manner. Similarly, a vivo-morpholino designed to block translation of murine p65 (m-p65tb-vivomorph1) rapidly abolished spontaneous contractile activity, reduced p65 expression measured by confocal immunofluorescence, and induced cell death in primary cultures of nondystrophic and mdx myotubes. Similar effects on p65 immunofluorescence and cell viability were observed following m-p65tb-vivomorph1 exposure to spontaneously inactive C2C12 myotubes, while exposure to a control scrambled vivo morpholino had no effect. These results indicate a direct role of the NF-κB pathway in myotube development and identify a potential therapeutic limitation to the use of NF-κB inhibitors in treating Duchenne and related muscular dystrophies. J. Cell. Physiol. 231: 788-797, 2016. © 2015 Wiley Periodicals, Inc.

The Development and Single-Laboratory Validation of a Method for the Determination of Steroid Residues in Fish and Fish Products.

Due to potential use in aquacultured fish products, the Canadian Food Inspection Agency has identified residue testing for steroids as a priority. These compounds are used in aquaculture primarily to direct sexual differentiation with both androgens and estrogens applied depending on the desired outcome. Published research is lacking with respect to steroid residue testing in fish; however, recent studies in other matrixes provided transferable cleanup techniques. A simple, rapid, and sensitive method was developed and validated for use in monitoring aquacultured fish products for the presence of methyltestosterone, nandrolone, epi-nandrolone, boldenone, and epi-boldenone residues. The developed method consists of solvent extraction followed by cleanup using hexane and dual cartridge SPE with analysis by ultra-HPLC-MS/MS. The method is capable of detecting and confirming steroid residue levels ranging from 0.05 to 25 ng/g in salmon and tilapia, depending on the analyte. Recoveries ranged from 88 to 130% for the analytes. Instrument repeatability was less than 13% for all compounds, while intermediate precision ranged from 5 to 25% RSD. HorRat values were within acceptable ranges.

Depletion of metronidazole in brook trout (Salvelinus fontinalis).

Metronidazole (MNZ), which is effective in the treatment of intestinal infections in fish, is also a suspected carcinogen and has been banned in numerous jurisdictions for use in any food-producing animal, including fish. Few reports have been published on the depletion of MNZ in fish. A depletion study was therefore undertaken using MNZ in feed provided to trout under controlled conditions. The water was maintained at 17.5 ± 0.9°C throughout the medication and depletion periods in the study. Following a 20-day acclimatisation period in the holding tanks, the trout (approximately 150-200 g bodyweight at the start of the study) were subjected to two separate medication and withdrawal periods: (A) 5 day medication/5 day withdrawal and (B) 5 day medication/16 day withdrawal. This simulated a potential multiple dosing in an aquaculture setting. In both medication periods, the trout were dosed with medicated feed containing 3 g MNZ kg(-1) fish. Fish were sacrificed in accordance with accepted animal care protocols and tissue samples were analysed by UPLC-MS/MS. Analyte concentrations in trout muscle ranged from a high of 27,000 ± 10,000 ng g(-1) for MNZ and 830 ± 570 ng g(-1) for MNZ-OH on day 1 of withdrawal period A to a low of 1.8 ± 2.3 ng g(-1) for MNZ and < 0.4 ng g(-1) for MNZ-OH on day 16 of withdrawal period B. The results demonstrate that when using the UPLC-MS/MS method, residues of MNZ may be detected in fish treated with MNZ after 16 days of withdrawal.

Development and method validation for the determination of nitroimidazole residues in salmon, tilapia and shrimp muscle.

The use of nitroimidazoles in aquacultured fish has been banned in many countries due to the suspected mutagenic and carcinogenic effects of these compounds. In response to the need to conduct residue testing of these compounds in fish, a simple, rapid, and sensitive method was developed and validated that is suitable for regulatory monitoring of nitroimidazole residues and their hydroxy metabolites in fish muscle tissue. Following solvent extraction of homogenized tissue and clean-up using a C18 SPE cartridge, analyses were conducted by ultra-performance UPLC-MS/MS. A precursor ion and two product ions were monitored for each of the parent compounds and metabolites included in the method. The validated method has an analytical range from 1 to 50 ng/g in the representative species (tilapia, salmon, and shrimp), with an LOD and LOQ ranging from 0.07 to 1.0 nglg and 0.21 to 3.0 nglg, respectively, depending on the analyte. Recoveries ranged from 81 to 124% and repeatability was between 4 and 17%. HorRat values were within typical limits of acceptability for a single laboratory. Working standards were stable for 12 months, extracts were stable for 5 days, and tissues for 2 months under appropriate storage conditions. This method was determined to be suitable for routine use for screening, quantification, and confirmation of nitroimidazole residues in a residue monitoring program for fish with regulatory oversight.

Accumulation of α-synuclein in the bowel of patients in the pre-clinical phase of Parkinson's disease.

Parkinson's disease primarily affects the central nervous system, but autopsy and small patient studies have revealed autonomic nervous system pathology in most cases. We looked for α-synuclein pathology in routinely acquired biopsies from patients and matched controls. Immunocytochemistry was performed and assessed blind to the clinical diagnoses. One hundred and seventeen gastrointestinal tissue samples from 62 patients, and 161 samples from 161 controls, were examined. Twelve biopsies from seven patients showed accumulation of α-synuclein within mucosal and submucosal nerve fibres, and ganglia, which was more extensive with an antibody to phosphorylated, than with an antibody to non-phosphorylated, α-synuclein. These included gastric, duodenal and colonic biopsies, and were taken up to 8 years prior to the onset of motor symptoms. All patients with positive biopsies had early autonomic symptoms and all controls were negative. This large scale study demonstrates that accumulation of α-synuclein in the gastrointestinal tract is a highly specific finding that could be used to confirm a clinical diagnosis of Parkinson's disease. We have shown that α-synuclein accumulation occurs prior to the onset of motor symptoms in the upper, as well as the lower gastrointestinal tract, remains present in serial biopsies until the onset of motor symptoms and is predominantly composed of phosphorylated α-synuclein. Accumulation of α-synuclein in the bowel therefore offers an accessible biomarker which allows further study of the early stages of the disease and could be of value in the assessment of disease modifying treatments.

Membrane cholesterol affects stimulus-activity coupling in type 1, but not type 2, CCK receptors: use of cell lines with elevated cholesterol.

The lipid microenvironment of membrane proteins can affect their structure, function, and regulation. We recently described differential effects of acute modification of membrane cholesterol on the function of type 1 and 2 cholecystokinin (CCK) receptors. We now explore the regulatory impact of chronic cholesterol modification on these receptors using novel receptor-bearing cell lines with elevated membrane cholesterol. Stable CCK1R and CCK2R expression was established in clonal lines of 25RA cells having gain-of-function in SCAP [sterol regulatory element binding protein (SREBP) cleavage-activating protein] and SRD15 cells having deficiencies in Insig-1 and Insig-2 enzymes affecting HMG CoA reductase and SREBP. Increased cholesterol in the plasma membrane of these cells was directly demonstrated, and receptor binding and signaling characteristics were shown to reflect predicted effects on receptor function. In both environments, both types of CCK receptors were internalized and recycled normally in response to agonist occupation. No differences in receptor distribution within the membrane were appreciated at the light microscopic level in these CHO-derived cell lines. Fluorescence anisotropy was studied for these receptors occupied by fluorescent agonist and antagonist, as well as when tagged with YFP. These studies demonstrated increased anisotropy of the agonist ligand occupying the active state of the CCK1R in a cholesterol-enriched environment, mimicking fluorescence of the uncoupled, inactive state of this receptor, while there was no effect of increasing cholesterol on fluorescence at the CCK2R. These cell lines should be quite useful for examining the functional characteristics of potential drugs that might be used in an abnormal lipid environment.

Vital roles of mTOR complex 2 in Notch-driven thymocyte differentiation and leukemia.

Notch plays critical roles in both cell fate decisions and tumorigenesis. Notch receptor engagement initiates signaling cascades that include a phosphatidylinositol 3-kinase/target of rapamycin (TOR) pathway. Mammalian TOR (mTOR) participates in two distinct biochemical complexes, mTORC1 and mTORC2, and the relationship between mTORC2 and physiological outcomes dependent on Notch signaling is unknown. In this study, we report contributions of mTORC2 to thymic T-cell acute lymphoblastic leukemia (T-ALL) driven by Notch. Conditional deletion of Rictor, an essential component of mTORC2, impaired Notch-driven proliferation and differentiation of pre-T cells. Furthermore, NF-κB activity depended on the integrity of mTORC2 in thymocytes. Active Akt restored NF-κB activation, a normal rate of proliferation, and differentiation of Rictor-deficient pre-T cells. Strikingly, mTORC2 depletion lowered CCR7 expression in thymocytes and leukemic cells, accompanied by decreased tissue invasion and delayed mortality in T-ALL driven by Notch. Collectively, these findings reveal roles for mTORC2 in promoting thymic T cell development and T-ALL and indicate that mTORC2 is crucial for Notch signaling to regulate Akt and NF-κB.

Differential sensitivity of types 1 and 2 cholecystokinin receptors to membrane cholesterol.

Recent studies indicate that membrane cholesterol can associate with G protein-coupled receptors (GPCRs) and affect their function. Previously, we reported that manipulation of membrane cholesterol affects ligand binding and signal transduction of the type 1 cholecystokinin receptor (CCK1R), a Class A GPCR. We now demonstrate that the closely related type 2 cholecystokinin receptor (CCK2R) does not share this cholesterol sensitivity. The sequences of both receptors reveal almost identical cholesterol interaction motifs in analogous locations in transmembrane segments two, three, four, and five. The disparity in cholesterol sensitivity between these receptors, despite their close structural relationship, provides a unique opportunity to define the possible structural basis of cholesterol sensitivity of CCK1R. To evaluate the relative contributions of different regions of CCK1R to cholesterol sensitivity, we performed ligand binding studies and biological activity assays of wild-type and CCK2R/CCK1R chimeric receptor-bearing Chinese hamster ovary cells after manipulation of membrane cholesterol. We also extended these studies to site-directed mutations within the cholesterol interaction motifs. The results contribute to a better understanding of the structural requirements for cholesterol sensitivity in CCK1R and provides insight into the function of other cholesterol-sensitive Class A GPCRs.

Simultaneous determination of 17 sulfonamides and the potentiators ormetoprim and trimethoprim in salmon muscle by liquid chromatography with tandem mass spectrometry detection.

A simple, robust method using liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the simultaneous determination of 17 sulfonamides [sulfanilamide (SNL), sulfacetamide (SAA), sulfaguanidine (SGD), sulfapyridine (SPY), sulfadiazine (SDZ), sulfathiazole (STZ), sulfamerazine (SMR), sulfamethoxazole (SOZ), sulfamoxole (SXL), sulfisoxazole (SXZ), sulfamethizole (SML), sulfamethazine (SMZ), sulfamethoxypyridazine (SMP), sulfamonomethoxine (SMM), sulfachloropyridazine (SCP), sulfaquinoxaline (SQX), and sulfadimethoxine (SDM)] and 2 potentiators [ormetoprim (OMP) and trimethoprim (TMP)] in fish tissue has been developed. The analytes were extracted from homogenized fish tissue with water-acetonitrile (50 + 50). The extract was clarified by centrifugation and a portion defatted with hexane. The analytes were partitioned into chloroform and evaporated to dryness. The redissolved residue was applied to a C18 reversed-phase column with a water-acetonitrile (0.1% acetic acid) gradient. All of the compounds were completely separated and detected in <10 min at 30 degrees C using LC/MS/MS. Standard curves were linear over the range of 0.02 to 5 ng injected. The limit of detection varied from 0.1 ng/g for SMZ and OMP to 0.9 ng/g for SXL and SOZ. Recoveries varied from 100% for SDM, SOZ, and SQX and 85% for SMR, OMP, and TMP to approximately 30% for SAA. Relative standard deviations for repeat analysis varied from 4% for SMZ and SCP to 23% for SAA.

Regulation of N-formyl peptide receptor signaling and trafficking by individual carboxyl-terminal serine and threonine residues.

Adaptation, defined as the diminution of receptor signaling in the presence of continued or repeated stimulation, is critical to cellular function. G protein-coupled receptors (GPCRs) undergo multiple adaptive processes, including desensitization and internalization, through phosphorylation of cytoplasmic serine and threonine residues. However, the relative importance of individual and combined serine and threonine residues to these processes is not well understood. We examined this mechanism in the context of the N-formyl peptide receptor (FPR), a well-characterized member of the chemoattractant/chemokine family of GPCRs critical to neutrophil function. To evaluate the contributions of individual and combinatorial serine and threonine residues to internalization, desensitization, and arrestin2 binding, 30 mutant forms of the FPR, expressed in the human promyelocytic U937 cell line, were characterized. We found that residues Ser(328), Ser(332), and Ser(338) are individually critical, and indeed sufficient, for internalization, desensitization, and arrestin2 binding, but that the presence of neighboring threonine residues can inhibit these processes. Additionally, we observed no absolute correlation between arrestin binding and either internalization or desensitization, suggesting the existence of arrestin-independent mechanisms for these processes. Our results suggest C-terminal serine and threonine residues of the FPR represent a combinatorial code, capable of both positively and negatively regulating signaling and trafficking. This study is among the first detailed analyses of a complex regulatory site in a GPCR, and provides insight into GPCR regulatory mechanisms.

Inhibition of foodborne bacteria by native and modified protamine: importance of electrostatic interactions.

Protamine is a naturally occurring cationic antimicrobial peptide (CAP) that has shown some promise for control of microorganisms in food. It was hypothesized that the antibacterial effect is partially due to protamine's electrostatic affinity to the negatively charged cell envelopes of actively growing bacteria. However, nonspecific binding of the CAPs to negatively charged food particles may reduce the effect in food systems. To test the hypothesis, the antibacterial efficacies of native and reduced charge protamines (chemically modified by randomly blocking 10 to 71% of the guanido groups of the arginine residues) were compared in model and food systems. In Tryptic Soy Broth, moderate reductions of charge (<26%) resulted in either a similar or slightly improved antimicrobial efficacy, measured as the minimum inhibitory concentration (MIC) toward 21 food-related bacteria. Further reductions in positive charge led to lower antimicrobial activity. Compared to protamine, the affinity of reduced charge protamines (10 and 20%) for binding to Listeria monocytogenes cells was higher at pH 7 and 8. As perhaps would be expected, L. monocytogenes is most sensitive to modified protamines in this pH range. Protamine with reduced charge (14 and 23%) inhibited growth of L. monocytogenes in milk as well as total bacteria and coliforms in ground beef significantly (P<0.05) better than native protamine, demonstrating that the reduced charge peptides were more inhibitory in these high protein food matrices. Electrophoretic analysis of the 21 bacteria revealed a statistically significant (P<0.01) relationship with antimicrobial activity, where the most negatively charged bacteria were also the most susceptible to protamine. In conclusion, components of food matrices interfered with the antibacterial effects of the peptides, however; these undesirable interferences were reduced by altering the electrostatic properties of protamine.

Determination of malachite green and leucomalachite green in a variety of aquacultured products by liquid chromatography with tandem mass spectrometry detection.

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for determining the residues of malachite green (MG) and leucomalachite green (LMG) in a number of aquatic species. MG and its metabolite were extracted from homogenized tissues with a perchloric acid-acetonitrile solution; the extract was centrifuged; and an aliquot was taken, concentrated, and passed through a chemically bonded octadecyl C18 solid-phase extraction column. The compounds of interest were eluted with acetonitrile, and the eluate was evaporated to dryness. The residue was dissolved in acetonitrile and diluted with water in preparation for analysis by LC/MS/MS. MG and its metabolite were determined by reversed-phase LC using a Luna C18 column with an ammonium hydroxide-formic acid buffer in acetonitrile gradient and MS/MS detection using multiple reaction monitoring. Calibration curves were linear for all analyses between 5 and 500 pg injected for both analytes, with recoveries ranging from 81% for LMG to 98% for MG in salmon spiked at the 1 ng/g level. Detection limits of 0.1 ng/g for both MG and LMG were easily obtainable using the recommended method. The operational errors, interferences, and recoveries for spiked samples compared favorably with those obtained by established methodology. The recommended method is simple, rapid, and specific for monitoring residues of MG and LMG in a number of aquatic species.

Simultaneous determination of residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in farmed aquatic species by liquid chromatography/mass spectrometry.

A liquid chromatographic (LC)/mass spectrometric (MS) method was developed for determining the residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in a number of aquatic species. The phenicols are extracted with acetone, the extracts are partitioned with dichloromethane, the aqueous layer is removed, and the organic layer is evaporated to dryness. The residue is dissolved in dilute acid and defatted with hexane, and the aqueous layer is prepared for analysis by LC. The phenicols are determined by reversed-phase LC by using a Hypersil C18-BD column with a water-acetonitrile gradient and MS detection using selected-ion recording. Calibration curves were linear for all analytes between 0.015 and 0.425 ng injected. The relative standard deviations for measurements by the proposed method were < 10% for all of the analytes studied, with recoveries ranging from 71% for florfenicol amine to 107% for florfenicol in salmon tissue spiked at the 2 ng/g level. Detection limits of 0.1 ng/g for florfenicol and chloramphenicol, 0.3 ng/g for thiamphenicol, and 1.0 ng/g for florfenicol amine are easily obtainable. The operational errors, interferences, and recoveries for spiked samples compare favorably with those obtained by established LC methodology. The proposed method is simple, rapid, and specific for monitoring residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in a number of aquatic species.