Geology topics

G. R. Stehly

Publications and source records attributed to G. R. Stehly.

18 recordsLinked to original sources

USGS2020

Optimization of a liquid chromatographic method for determination of malachite green and its metabolites in fish tissues

A liquid chromatographic (LC) method was adapted and optimized for the determination of malachite green and its metabolites in fish plasma and muscle. Residues in plasma were extracted with acetonitrile, the extract was evaporated to dryness, and residues were resolubilized for LC analysis. Residues in muscle were extracted with an acetonitrile- acetate buffer mixture, reextracted with acetonitrile, and partitioned into methylene chloride with final cleanup on alumina and propylsulfonic acid solid-phase extraction columns. Residue levels were determined by using an LC cyano column with a Pb02 postcolumn and visible detection (618 nm). Overall mean recoveries of parent malachite green (MG-C) and its major metabolite, leucomalachite green (MG-L), from plasma were 93 and 87%, respectively, at fortification levels ranging from 25 to 250 ppb. Overall mean recoveries of MG-C and MG-L from muscle were 85 and 95%, respectively, at fortification levels ranging from 5 to 100 ppb. Relative standard deviations (RSDs) of recoveries at all fortification levels ranged from 3.9 to 7.0% for plasma and from 2.1 to 5.2% for muscle. The method was applied to incurred residues in tissues sampled from catfish after waterborne exposure to [ 14 C]MG-C. Mean recoveries of total radioactive residues in plasma and muscle throughout the extraction and cleanup process were 88 and 87%, respectively, and corresponding RSDs for MG-C and MG-L were in the same range as those for fortified tissues. MG-L was confirmed as the major metabolite of MG-C in catfish.

Journal of AOAC International↗

USGS2020

Determination of benzocaine in rainbow trout plasma

A liquid chromatographic method is described for analysis of benzocaine (BZ), a proposed fish anesthetic, in rainbow trout plasma. Mean recoveries of BZ from plasma samples fortified at 44–10 100 ng/mL were 96–100%. The method detection limit is 10 ng/mL, and the limit of quantitation is 37 ng/mL. Acetylation of BZ occurs in whole blood after storage at room temperature (i.e., 21 °C) for 10 min. However, no acetylation of BZ was detected in plasma samples held at room temperature for 4 h. Mean method precision for plasma samples with incurred BZ residue is similar to that for fortified samples in the same concentration range (relative standard deviations of 0.9 and 1.2%, respectively).

Journal of AOAC International↗

USGS2020

Liquid chromatographic determination of oxytetracycline in edible fish fillets from six species of fish

The approved use of oxytetracycline (OTC) in U.S. aquaculture is limited to specific diseases in salmonids and channel catfish. OTC may also be effective in controlling diseases in other fish species important to public aquaculture, but before approved use of OTC can be augmented, an analytical method for determining OTC in fillet tissue from multiple species of fish will be required to support residue depletion studies. The objective of this study was to develop and validate a liquid chromatographic (LC) method that is accurate, precise, and sensitive for OTC in edible fillets from multiple species of fish. Homogenized fillet tissues from walleye, Atlantic salmon, striped bass, white sturgeon, rainbow trout, and channel catfish were fortified with OTC at nominal concentrations of 10, 20, 100,1000, and 5000 ng/g. In tissues fortified with OTC at 100,1000, and 5000 ng/g, mean recoveries ranged from 83 to 90%, and relative standard deviations (RSDs) ranged from 0.9 to 5.8%. In all other tissues, mean recoveries ranged from 59 to 98%, and RSDs ranged from 3.3 to 20%. Method quantitation limits ranged from 6 to 22 ng/g for the 6 species. The LC parameters produced easily in teg ratable OTC peaks without coelution of endogenous compounds. The method is accurate, precise, and sensitive for OTC in fillet tissue from 6 species of fish from 5 phylogenetically diverse groups.

Journal of AOAC International↗

USGS2020

A bridging study for oxytetracycline in the edible fillet of rainbow trout: Analysis by a liquid chromatographic method and the official microbial inhibition assay

Oxytetracycline (OTC) is a drug approved by the U.S. Food and Drug Administration (FDA) to control certain diseases in salmonids and catfish. OTC is also a likely control agent for diseases of other fish species and for other diseases of salmonids and catfish not currently on the label. One requirement for FDA to extend and expand the approval of this antibacterial agent to other fish species is residue depletion studies. The current regulatory method for OTC in fish tissue, based on microbial inhibition, lacks sensitivity and specificity. To conduct residue depletion studies for OTC in fish with a liquid chromatographic method, a bridging study was required to determine its relationship with the official microbial inhibition assay. Triplicate samples of rainbow trout fillet tissue fortified with OTC at 0.3,0.6,1.2,2.4,4.8, and 9.6 ppm and fillet tissue with incurred OTC at approximately 0.75,1.5, and 3.75 ppm were analyzed by high-performance liquid chromatography (HPLC) and the microbial inhibition assay. The results indicated that the 2 methods are essentially identical in the tested range, with mean coefficients of variation of 1.05% for the HPLC method and 3.94% for the microbial inhibition assay.

Journal of AOAC International↗

USGS2020

Liquid chromatographic determination of para-toluenesulfonamide in edible fillet tissues from three species of fish

Chloramine-T ( N -sodium- N -chloro- p -toluene-sulfonamide) is a candidate therapeutic drug for treating bacterial gill disease, a predominant disease of a variety of fish species. Research has been initiated to obtain the U.S. Food and Drug Administration’s (FDA) approval for the use of chloramine-T on a variety of fish species. An attribute of a therapeutic aquaculture drug that must be characterized before the FDA approves its use is depletion of the drug’s marker residue (the drug’s parent compound or metabolite of highest concentration in an edible tissue). para -Toluenesulfonamide (p-TSA) is the primary degradation product and marker residue for chloramine-T in rainbow trout. To conduct residue depletion studies for chloramine-T in fish, a robust analytical method sensitive and specific for p-TSA residues in edible fillet tissue from a variety of fish was required. Homogenized fillet tissues from rainbow trout ( Oncorhynchus mykiss ), walleye ( Stizostedion vitreum ), and channel cattish ( Ictalurus punctatus ) were fortified at nominal p-TSA concentrations of 17, 67, 200, 333, and 1000 ng/g. Samples were analyzed by isocratic reversed-phase liquid chromatography (LC) with absorbance detection at 226 nm. Mean recoveries of p-TSA ranged from 77 to 93.17%; relative standard deviations ranged from 1.5 to 14%; method quantitation limits ranged from 13 to 18 ng/g; and method detection limits ranged from 3.8 to 5.2 ng/g. The LC parameters produced p-TSA peaks without coelution of endogenous compounds and excluded chromatographic interference from at least 20 chemicals and drugs of potential use in aquaculture.

Journal of AOAC International↗

USGS2019

Performance of a proposed determinative method for p-TSA in rainbow trout fillet tissue and bridging the proposed method with a method for total chloramine-T residues in rainbow trout fillet tissue

Chloramine-T is an effective drug for controlling fish mortality caused by bacterial gill disease. As part of the data required for approval of chloramine-T use in aquaculture, depletion of the chloramine-T marker residue (para-toluenesulfonamide; p-TSA) from edible fillet tissue of fish must be characterized. Declaration of p-TSA as the marker residue for chloramine-T in rainbow trout was based on total residue depletion studies using a method that used time consuming and cumbersome techniques. A simple and robust method recently developed is being proposed as a determinative method for p-TSA in fish fillet tissue. The proposed determinative method was evaluated by comparing accuracy and precision data with U.S. Food and Drug Administration criteria and by bridging the method to the former method for chloramine-T residues. The method accuracy and precision fulfilled the criteria for determinative methods; accuracy was 92.6, 93.4, and 94.6% with samples fortified at 0.5X, 1X, and 2X the expected 1000 ng/g tolerance limit for p-TSA, respectively. Method precision with tissue containing incurred p-TSA at a nominal concentration of 1000 ng/g ranged from 0.80 to 8.4%. The proposed determinative method was successfully bridged with the former method. The concentrations of p-TSA developed with the proposed method were not statistically different at p < 0.05 from p-TSA concentrations developed with the former method.

Journal of AOAC International↗

USGS2009

Metabolism of pentachlorophenol by fish

Interspecies variability in the metabolism of pentachlorophenol (PCP) was investigated by exposing rainbow trout, fathead minnows, sheepshead minnow, firemouth, and goldfish to water-borne super(14)C-PCP for 64 h. The amounts of metabolites in bile and exposure water were species-dependent; all of the metabolites excreted into the water were sulphate conjugates while bile was enriched in glucuronide conjugates. Biliary excretion accounted for less than 30% of the total PCP metabolites. Biliary metabolites alone were a poor indication of the metabolites produced and of the major routes of elimination.

Xenobiotica↗

USGS2008

Effect of temperature on the pharmacokinetics of benzocaine in rainbow trout (Oncorhynchus mykiss) after bath exposures

The pharmacokinetics of benzocaine during bath exposures at 1 mg/L were determined in rainbow trout acclimated at 6 °C, 12 °C or 18 °C for at least 1 month. Individual fish were exposed to benzocaine in a recirculating system for 4 h and pharmacokinetic parameters were estimated in a unique manner from the concentration of benzocaine in the bath water vs. time curve. Elimination from plasma was also determined after the 4 h exposure. The uptake clearance and metabolic clearance increased with increased acclimatization temperatures (uptake clearance 581 ± 179 mL/min/kg at 6 °C and 1154 ± 447 mL/ min/kg at 18 °C; metabolic clearance 15.2 ± 4.1 mL/min/kg at 6 °C and 22.3 ± 4.2 mL/min/kg at 18 °C). The apparent volume of distribution had a trend for increasing with temperature that was not significant at the 5% level (2369 ± 678 mL/kg at 6 °C to 3260 ± 1182 mL/kg at 18 °C). The elimination half-life of benzocaine in plasma was variable and did not differ significantly with temperature (60.8 ± 30.3 min at 6 °C to 35.9 ± 13.0 min at 12 °C). Elimination of benzocaine from rainbow trout is relatively rapid and even more rapid at higher acclimatization temperatures based on calculated metabolic clearances and measured plasma concentrations, but was not evident by measurement of terminal plasma half-lifes.

Journal of Veterinary Pharmacology and Therapeutic↗

USGS2004

Depletion of the chloramine-T marker residue, para-toluenesulfonamide, from skin-on fillet tissue of hybrid striped bass, rainbow trout, and yellow perch

Waterborne exposure to n-sodium-n-chloro-p-toluenesulfonamide (chloramine-T) is an effective treatment for controlling fish mortalities caused by bacterial gill disease (BGD). Currently, data are being generated to gain United States Food and Drug Administration (FDA) approval for the use of chloramine-T in aquaculture. As part of the data required for an approval, depletion of the chloramine-T marker residue (para-toluenesulfonamide [p-TSA]) from the edible fillet tissue of exposed fish must be determined. Hybrid striped bass (Morone saxatilis??Morone chrysops; mean weight 357 g), rainbow trout (Oncorhynchus mykiss; mean weight 457 g), and yellow perch (Perca flavescens; mean weight 144 g) were exposed to 20 mg/l of chloramine-T for 60 min on 4 consecutive days (the most aggressive treatment expected for approved use in the United States). Groups of fish (n=15 or 19) were sampled immediately after the last treatment and periodically through 48 or 168 h after the treatment phase. Duplicate subsamples of skin-on fillet tissue from each fish were analyzed for p-TSA. Mean p-TSA concentrations in fillet tissue from fish sampled immediately after the last treatment were 142 ng/g (hybrid striped bass), 97 ng/g (rainbow trout), and 150 ng/g (yellow perch). Mean p-TSA concentrations at terminal sample times were 94 (168 h; hybrid striped bass), 74 (48 h; rainbow trout), and 35 ng/g (168 h; yellow perch). The half-lives of p-TSA in fillet tissue from fish near or at market size were 11.4 (hybrid striped bass), 4.3 (rainbow trout), and 3.2 days (yellow perch).

Aquaculture↗

USGS2002

Relatively rapid loss of lampricide residues from fillet tissue of fish after routine treatment

The selective sea lamprey ( Petromyzon marinus ) larvicide 3-trifluoromethyl-4-nitrophenol (TFM) is currently used to control parasitic sea lampreys in tributaries to the Great Lakes basin. The concentration and persistence of TFM and its major metabolite, TFM glucuronide (TFM-glu), was determined in fillet tissue of fish after a typical stream application. Rainbow trout ( Oncorhynchus mykiss ) and channel catfish ( Ictalurus punctatus ) were exposed to a nominal concentration of 12.6 nmol/mL TFM for about 12 h during a sea lamprey control treatment of the Ford River in Michigan. Concentrations of TFM and TFM-glu were greatest in the fillet tissues during the exposure period, with greater residues in channel catfish (wet wt; mean, 6.95 nmol/g TFM; mean, 2.40 nmol/g TFM-glu) than in rainbow trout (wet wt; mean, 1.45 nmol/g TFM; mean, 0.93 nmol/g TFM-glu). After the exposure period, residues in both species decreased by 90−99% within 6−12 h and were less than the quantitation limit (<0.03 nmol/g) within 36 h.

Michigan↗

USGS2001

Evaluation of AQUI-S(TM) (efficacy and minimum toxic concentration) as a fish anaesthetic/sedative for public aquaculture in the United States

A preliminary evaluation of efficacy and minimum toxic concentration of AQUI-S(TM), a fish anaesthetic/sedative, was determined in two size classes of six species of fish important to US public aquaculture (bluegill, channel catfish, lake trout, rainbow trout, walleye and yellow perch). In addition, efficacy and minimum toxic concentration were determined in juvenile-young adult (fish aged 1 year or older) rainbow trout acclimated to water at 7 ??C, 12 ??C and 17 ??C. Testing concentrations were based on determinations made with range-finding studies for both efficacy and minimum toxic concentration. Most of the tested juvenile-young adult fish species were induced in 3 min or less at a nominal AQUI-S(TM) concentration of 20 mg L-1. In juvenile-young adult fish, the minimum toxic concentration was at least 2.5 times the selected efficacious concentration. Three out of five species of fry-fingerlings (1.25-12.5 cm in length and < 1 year old) were induced in ??? 4.1 min at a nominal concentration of 20 mg L-1 AQUI-S(TM), with the other two species requiring nominal concentrations of 25 and 35 mg L-1 for similar times of induction. Recovery times were ??? 7.3 rain for all species in the two size classes. In fry-fingerlings, the minimum toxic concentration was at least 1.4 times the selected efficacious concentration. There appeared to be little relationship between size of fish and concentrations or times to induction, recovery times and minimum toxic concentration. The times required for induction and for recovery were increased in rainbow trout as the acclimation temperature was reduced.

Aquaculture Research↗

USGS2000

Effects of temperature on the elimination of benzocaine and acetylated benzocaine residues from the edible fillet of rainbow trout (Oncorhynchus mykiss)

The effect of temperature (7 degrees C and 16 degrees C) on the extent of accumulation and the elimination of benzocaine (BNZ) and its metabolite, acetylated benzocaine (AcBNZ), in the fillet tissue of rainbow trout was investigated Residues were measured after bath exposure to an anesthetizing concentration of benzocaine (30 mg/l for 5 min) followed by a maintenance concentration (15 mg/l for 30 min). Immediately after exposure, the BNZ concentration in fillet tissue was approximately 27 mu g/g at both temperatures; AcBNZ was 0.3 mu g/g at 7 degrees C and 0.6 mu g/g at 16 degrees C. The rates for elimination ( α and β ) of BNZ and AcBNZ were not significantly different between the two temperatures. Terminal half-lives of elimination for BNZ were 1.62 h at 7 degrees C and 1.63 h at 16 degrees C; half-lives for AcBNZ were 2.36 h at 7 degrees C and 2.77 h at 16 degrees C.

Food Additives and Contaminants↗

USGS1999

Liquid chromatographic determination of benzocaine and N-acetylbenzocaine in the edible fillet tissue from rainbow trout

A method was developed for determining benzocaine and N-acetylbenzocaine concentrations in fillet tissue of rainbow trout. The method involves extracting the analytes with acetonitrile, removing lipids or hydrophobic compounds from the extract with hexane, and providing additional clean-up with solid-phase extraction techniques. Analyte concentrations are determined using reversed-phase high-performance liquid chromatographic techniques with an isocratic mobile phase and UV detection. The accuracy (range, 92 to 121%), precision (R.S.D., <14%), and sensitivity (method quantitation limit, <24 ng/g) for each analyte indicate the usefulness of this method for studies characterizing the depletion of benzocaine residues from fish exposed to benzocaine. Copyright (C) 1999.

Journal of Chromatography A↗

USGS1998

Crop grouping: A proposal for public aquaculture

No abstract available.

Veterinary and Human Toxicology↗

USGS1996

Uptake, tissue distribution, and metabolism of malachite green in the channel catfish (Ictalurus punctatus)

The disposition of malachite green was determined in channel catfish ( Ictalurus punctatus ) after intravascular dosing (0.8 mg . Kg -1 ) or waterborne exposure (0.8 mg . L -1 for 1 h). After intravascular dosing, mean plasma concentrations of the parent compound exhibited a triphasic decline with a terminal elimination half-life of 6.2 h. Malachite green was rapidly absorbed and concentrated in the tissues during waterborne exposure. The rate of accumulation was directly related to pH of the exposure water. After waterborne exposure, elimination of the parent compound from plasma also was triphasic with a terminal half-life of 4.7 h. In muscle, the half-life of the parent compound was approximately 67 h. Malachite green and its metabolites were widely distributed in all tissues. In fish exposed to C-14-labeled malachite green, total drug equivalent concentrations were highest in abdominal fat and lowest in plasma. Malachite green was rapidly and extensively metabolized to its reduced form, leucomalachite green, which was slowly eliminated from the tissues. Leucomalachite green is an appropriate target analyte for monitoring exposure of channel catfish to this drug.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS1992

Disposition of 1-naphthol in the channel catfish (Ictalurus punctatus)

The pharmacokinetics, tissue distribution, and metabolism of 1-naphthol were examined in the channel catfish (Ictalurus punctatus ). After oral dosing, peak plasma concentrations of 1-naphthol occurred at 1 hr; parent compound made up less than 15% of the total radioactivity, and the bioavailability was 32%. Plasma protein binding was 92% and was independent of concentration. 1-Naphthol and metabolites were rapidly eliminated from the tissues after oral dosing.

Drug Metabolism and Disposition↗

USGS1990

Effect of pH on the accumulation kinetics of pentachlorophenol in goldfish

The kinetics of accumulation of pentachlorophenol (PCP) at various pH values were investigated to explore how pH-dependent accumulation might influence PCP toxicity. Goldfish (Carassius auratus) were exposed to 5 μg PCP/L in a static system buffered with 7.5 mM bicine or N,N -bis(2-hydroxyethyl)-2-aminoethane sulfonic acid (BES) at pH 7.0, 8.0, or 9.0. The amount of PCP in the fish, concentration of PCP in water, and the total amount of metabolites in the system were measured after exposure of fish from 1 to 96 hr. Equations for these variables based on a two compartment pharmacokinetic model were fitted simultaneously to the data using NONLIN, which uses an iterative nonlinear least squares technique. Uptake clearance, metabolic clearance, and apparent volume of distribution of PCP decreased as pH increased. The decrease in PCP accumulation with increased pH was not due solely to a pH-induced decrease in uptake. In addition, the distribution of PCP within the fish was altered by changes in the external pH. The pH-associated changes in distribution may have altered access of PCP to sites of metabolism, thereby altering the metabolic clearance. The pH-related changes in the pharmacokinetics of PCP resulted in a decrease in its bioconcentration factor with an increase in pH and account both for the decreased capacity of the fish to accumulate PCP and for its reduced LC50.

Archives of Environmental Contamination and Toxico↗

USGS1989

Disposition of pentachlorophenol in rainbow trout (Salmo gairdneri): Effect of inhibition of metabolism

The accumulation kinetics of pentachlorophenol (PCP) were investigated in rainbow trout ( Salmo gairdneri ) in the absence and presence of 25 mg/1 salicylamide, an inhibitor of PCP metabolism. After exposure to 5 μg/1 PCP over 1–96 h, the amount of PCP in the whole fish, its concentration in water and the total amount of metabolites (water, whole fish and bile) were measured. Equations for these variables, based on a two compartment pharmacokinetic model, were fitted simultaneously to the data using the computer program NONLIN, which uses an iterative nonlinear least squares technique. Salicylamide decreased the metabolic clearance of PCP, which resulted in an increase in the bioconcentration factor (BCF); this increase was partially offset by a salicylamide-induced decrease in the apparent volume of distribution of PCP. A clearance-volume compartment model permitted partitioning of the BCF in terms of the underlying physiologic and biochemical processes (uptake clearance, metabolic clearance and apparent volume of distribution). With this approach the BCF can be categorized as either dependent (e.g., PCP) or independent of uptake and metabolism (elimination) based on the relative sizes of the clearances for uptake and metabolism. Inhibition of PCP metabolism resulted in a loss of its dependence on uptake and metabolism. The BCF estimated as the apparent volume of distribution may be useful for assessment of the risk associated with exposure and bioaccumulation potential, as elimination is generally quite variable among aquatic species.

Aquatic Toxicology↗