Comparison of data acquisition modes with Orbitrap high-resolution mass spectrometry for targeted and non-targeted residue screening in aquacultured eel

RATIONALE

A current trend in monitoring chemical contaminants in animal products is to use high-resolution mass spectrometry (HRMS). In this study, several HRMS data acquistion modes using Orbitrap MS for simultaneous full-scan MS in combination with MS2 analysis were evaulated for their effectiveness in detecting and identifying both targeted and non-targeted veterinary drug residues in aquacultured eel samples.

METHODS

Sample preparation consisted of an acidic acetonitrile extraction with solid-phase extraction cleanup for analysis using LC/HRMS. Different data acquisition methods, including full-scan MS with non-targeted all ion fragmentation (AIF), multiplexed or variable data-independent analysis (mDIA or vDIA), targeted data-dependent MS2 (DDMS2), and parallel reaction monitoring (PRM) acquisition, were explored. The methods were evaluated with fortified eel tissue and imported eel samples to determine how many analytes could be detected and identified.

RESULTS

For non-targeted data acquisition, the number of analytes detected using DIA methods matched the results obtained by AIF, but the resulting product ion scans were more diagnostic because characteristic ions were predominant in the DIA MS2 spectra. In targeted analysis for a limited list of 68 compounds, full-scan MS followed by PRM was advantageous compared with DDMS2 because high-quality MS2 spectra were generated for almost all the analytes at target testing levels.

CONCLUSIONS

For residue screening, AIF has fast MS1 scan speed with adequate detection of product ions but may lead to false positive findings. DIA methods are better suited to monitor for both targeted and non-targeted compounds because they generate more characteristic MS2 spectra for retrospective library searching. For follow-up targeted analysis, PRM is prefered over DDMS2 when searching for a limited set of compounds.

Gas Chromatographic Determination of Chloramphenicol Residues in Shrimp: Interlaboratory Study

An interlaboratory study of a gas chromatographic method for determining chloramphenicol (CAP) residues in shrimp was conducted. An internal standard (Istd), the meta isomer of CAP, was added to the shrimp, and the treated shrimp were homogenized with ethyl acetate. The ethyl acetate extract was defatted with hexane, and the CAP was partitioned into ethyl acetate from an aqueous salt solution. The ethyl acetate was evaporated, and the dried residue was treated with Sylon, a trimethyl-silyl derivatizing agent, to yield the trimethylsilyl derivative of CAP. A portion of the solution containing the derivative was injected into a gas chromatograph equipped with an electron capture detector. Levels of fortified and incurred CAP were calculated from the peak area ratio of standard CAP to Istd. Recoveries of CAP from tissue directly fortified at 5 ppb were 102% (within-laboratory relative standard deviation [RSDr] = 5.6%), 104% (RSDr = 5.5%), and 108% (RSDr = 6.3%) from Laboratories 1, 2, and 3, respectively. Incurred-CAP residues at 5 and 10 ppb levels were also determined, with the following results: Laboratory 1: composite A, 4.56 ppb (RSDr = 14.0%); composite B, 8.38 ppb (RSDr = 11.6%); Laboratory 2: composite A, 4.17 ppb (RSDr = 12.5%); composite B, 8.90 ppb (RSDr = 5.60%); Laboratory 3: composite A, 4.66 ppb (RSDr = 14.9%); composite B, 11.0 ppb (RSDr = 11.8%).

Solid-Phase Extraction Cleanup and Liquid Chromatography with Ultraviolet Detection of Ephedrine Alkaloids in Herbal Products

A solid-phase extraction (SPE) cleanup and a liquid chromatographic (LC) method with UV detection is presented for analysis of up to 7 ephedrine alkaloids in herbal products. Alkaloids from herbal products are extracted with acidified buffer, isolated on a propylsulfonic acid SPE column, eluted with a high-ionic-strength buffer, and separated by LC with detection at 255 nm. LC separation is performed by isocratic elution on a YMC phenyl column with 0.1 M sodium acetate-acetic acid (pH = 4.8) containing triethyl-amine and 2% acetonitrile. Ephedrine alkaloids are completely separated in 15 min. Average recovery of 5 common alkaloids from 3 spiked matrixes is 90%, with an average relative standard deviation (RSD) of 4.4% for alkaloid spikes between 0.5 and 16 mg/g. Average quantitation of ephedrine and pseudoephedrine from 6 herbal products is 97% of declared label claims, and average quantitation of synephrine from an herbal dietary product is 85% of label claim (RSD, 3.2%). Recoveries of synephrine, norephedrine, ephedrine, pseudoephedrine, N-methylephedrine, and N-methylpseudoephedrine spiked in 4 herbal products averaged 95%. Results of ruggedness testing and of a second laboratory validation of the procedure are also presented.

Optimization and Validation of a Multiclass Screening and Confirmation Method for Drug Residues in Milk Using High-Performance Liquid Chromatography/Tandem Mass Spectrometry

The further optimization and validation of a multiresidue veterinary drug screening method for milk is described. The drug residues of regulatory interest in milk include -lactams, sulfonamides, tetracyclines, fluoroquinolones, and macrolides. A previously published procedure has been modified to incorporate new compounds and to collect both screening and confirmatory ion transitions in one acquisition method. Milk samples were extracted with an equal volume of acetonitrile. The samples were then subjected to cleanup with a bonded SPE cartridge and a MW cutoff filter. The SPE protocol was modified to effectively recover a metabolite of flunixin. Established tolerance levels are set for most of these drugs in milk; thus, the screening procedure was semiquantitative, using positive controls for comparison. The positive controls, consisting of extracts from milk fortified with the drugs at their tolerance or safe level, were used to set statistically valid minimum response criteria for unknown samples. This updated method was validated with fortified milk, as well as with milk samples from animals administered veterinary drugs.

Concurrent Determination of Four Fluoroquinolones in Catfish, Shrimp, and Salmon by Liquid Chromatography with Fluorescence Detection

A liquid chromatographic (LC) method with fluorescence detection was developed for concurrent determination of 4 fluoroquinolones: ciprofloxacin (CIPRO), enrofloxacin (ENRO), sarafloxacin (SARA), and difloxacin (DIFLX) in catfish, shrimp, and salmon. The procedure consists of extraction from fish tissue with acidified ethanol, isolation and retention on a cation exchange solid-phase extraction column, elution with basic methanol, and LC analysis with fluorescence detection. LC is performed by isocratic elution with acetonitrile–2% acetic acid (16 + 84) mobile phase, and a PLRP-S polymer column with fluorescence detection, excitation 278 nm and emission 450 nm. A target level of 20 ppb for each of the 4 fluoroquinolones has been established for this method. Fortified and incurred fish sample results are based on a 5-point standard curve calculation (10–160 ppb). Overall percent recoveries (% relative standard deviation) from fortified catfish were 78 (10), 80 (11), 70 (9.4), and 78 (10); from fortified shrimp, 69 (5.9), 85 (4.9), 79 (5.9), and 90 (4.5); and from fortified salmon, 56 (15), 93 (5.6), 61 (11), and 87 (5.0) for CIPRO, ENRO, SARA, and DIFLX, respectively. Data from the analysis of fluoroquinolone-incurred catfish, shrimp, and salmon are presented.

Liquid Chromatographic Determination of Diminazene Diaceturate (Berenil™) in Raw Bovine Milk

A simple liquid chromatographic (LC) method is presented for the determination of diminazene (DZ) in raw bovine milk. DZ is extracted from raw milk by chilled aqueous centrifugation and is isolated from milk components on a cyano solid-phase extraction column. DZ is eluted by using a methanol-ion pairing reagent. A Phenomenex LUNA CN column and an acetonitrile-buffered mobile phase with a counter ion are used for gradient LC. The LC effluent is monitored at a detection wavelength of 372 nm by using a deuterium lamp. Under the parameters described, the retention time of DZ is 8–10 min with a peak area response of 6.5 mAU/ng. The method demonstrated excellent precision over all levels tested (25–400 ppb) with an overall average recovery of 90.4 ± 14.5%. The method is applicable to the monitoring of milk for DZ residues at the 25 ppb level with a limit of quantitation of 10 ppb.

Extended liquid chromatography high resolution mass spectrometry screening method for veterinary drug, pesticide and human pharmaceutical residues in aquaculture fish

A liquid chromatography high resolution mass spectrometry (LC-HRMS) screening method was developed previously to analyze for veterinary drug residues commonly found in different types of aquaculture products. This method has been further evaluated for its feasibility to detect several other classes of compounds that might also be a concern as possible contaminants in farmed tilapia, salmon, eel and shrimp. Some chemicals could contaminate water sources used in aquaculture production through agricultural run-off. These compounds include several widely used triazine herbicides, organophosphate and carbamate pesticides, as well as various discarded human pharmaceuticals. Other possible contaminants investigated were selected disinfectants, some newer antibiotics, growth promoters, and various parasiticides. The sample preparation consisted of an acidic acetonitrile extraction followed by solid-phase extraction clean-up. Data were collected with a quadrupole-Orbitrap MS using both non-targeted and targeted acquisition. This rapid clean-up procedure and HRMS detection method described previously for veterinary drug residues also worked well for many other types of compounds. Most analytes had screening limit levels between 0.5-10 ng/g in the matrices examined using exact mass identification criteria. The strategy described in this paper for testing the performance of additional analytes will help expand the applicability of the HRMS procedure as aquaculture samples can now be analyzed for a wider range of contaminants.

Application and evaluation of a high-resolution mass spectrometry screening method for veterinary drug residues in incurred fish and imported aquaculture samples

The ability to detect chemical contaminants, including veterinary drug residues in animal products such as fish, is an important example of food safety analysis. In this paper, a liquid chromatography high-resolution mass spectrometry (LC-HRMS) screening method using a quadrupole-Orbitrap instrument was applied to the analysis of veterinary drug residues in incurred tissues from aquacultured channel catfish, rainbow trout, and Atlantic salmon and imported aquacultured products including European eel, yellow croaker, and tilapia. Compared to traditional MS methods, the use of HRMS with nontargeted data acquisition and exact mass measurement capability greatly increased the scope of compounds that could be monitored simultaneously. The fish samples were prepared for analysis using a simple efficient procedure that consisted of an acidic acetonitrile extraction followed by solid phase extraction cleanup. Two different HRMS acquisition programs were used to analyze the fish extracts. This method detected and identified veterinary drugs including quinolones, fluoroquinolones, avermectins, dyes, and aminopenicillins at residue levels in fish that had been dosed with those compounds. A metabolite of amoxicillin, amoxicillin diketone, was also found at high levels in catfish, trout, and salmon. The method was also used to characterize drug residues in imported fish. In addition to confirming findings of fluoroquinolone and sulfonamide residues that were found by traditional targeted MS methods, several new compounds including 2-amino mebendazole in eel and ofloxacin in croaker were detected and identified. Graphical Abstract Aquacultured samples are analyzed with a high-resolution mass spectrometry screening method to detect and identify unusual veterinary drug residues including ofloxacin in an imported fish.

Wide-Scope Screening Method for Multiclass Veterinary Drug Residues in Fish, Shrimp, and Eel Using Liquid Chromatography-Quadrupole High-Resolution Mass Spectrometry

A screening method for veterinary drug residues in fish, shrimp, and eel using LC with a high-resolution MS instrument has been developed and validated. The method was optimized for over 70 test compounds representing a variety of veterinary drug classes. Tissues were extracted by vortex mixing with acetonitrile acidified with 2% acetic acid and 0.2% p-toluenesulfonic acid. A centrifuged portion of the extract was passed through a novel solid phase extraction cartridge designed to remove interfering matrix components from tissue extracts. The eluent was then evaporated and reconstituted for analysis. Data were collected with a quadrupole-Orbitrap high-resolution mass spectrometer using both nontargeted and targeted acquisition methods. Residues were detected on the basis of the exact mass of the precursor and a product ion along with isotope pattern and retention time matching. Semiquantitative data analysis compared MS¹ signal to a one-point extracted matrix standard at a target testing level. The test compounds were detected and identified in salmon, tilapia, catfish, shrimp, and eel extracts fortified at the target testing levels. Fish dosed with selected analytes and aquaculture samples previously found to contain residues were also analyzed. The screening method can be expanded to monitor for an additional >260 veterinary drugs on the basis of exact mass measurements and retention times.

Determination and Confirmation of the Antiviral Drug Amantadine and Its Analogues in Chicken Jerky Pet Treats

In this study, we investigated two methods for the detection of antiviral compounds in chicken jerky pet treats. Initially, a screening method developed to detect many different chemical contaminants indicated the presence of amantadine, 1, in some pet treats analyzed. A second antiviral-specific method was then developed for amantadine and its analogues, rimantadine, 2, and memantine, 3. Both methods used an acidic water/acetonitrile extraction. The antiviral-specific method also included a dispersive sorbent cleanup. Analytes were detected and identified by LC-MS (ion trap and Orbitrap) instruments. The antiviral-specific method was validated by analyzing matrix blanks and fortified samples (2.5-50 μg/kg levels). Average recoveries for amantadine (using a deuterated internal standard) in fortified samples ranged from 76 to 123% with relative standard deviations of ≤12%. Amantadine was detected and identified in suspect chicken jerky pet treat samples at levels ranging from <2.5 μg/kg to over 600 μg/kg. Rimantadine and memantine were not detected in any samples.

A rapid liquid chromatography determination of free formaldehyde in cod

A rapid method for the determination of free formaldehyde in cod is described. It uses a simple water extraction of formaldehyde which is then derivatised with 2,4-dinitrophenylhydrazine (DNPH) to form a sensitive and specific chromophore for high-performance liquid chromatography (HPLC) detection. Although this formaldehyde derivative has been widely used in past tissue analysis, this paper describes an improved derivatisation procedure. The formation of the DNPH formaldehyde derivative has been shortened to 2 min and a stabilising buffer has been added to the derivative to increase its stability. The average recovery of free formaldehyde in spiked cod was 63% with an RSD of 15% over the range of 25-200 mg kg(-1) (n = 48). The HPLC procedure described here was also compared to a commercial qualitative procedure - a swab test for the determination of free formaldehyde in fish. Several positive samples were compared by both methods.

Challenges in implementing a screening method for veterinary drugs in milk using liquid chromatography quadrupole time-of-flight mass spectrometry

High resolution mass spectrometry (HRMS) is a valuable tool for the analysis of chemical contaminants in food. Our laboratory has successfully developed methods to screen for veterinary drug residues using liquid chromatography quadrupole time-of-flight (Q-TOF). There have been, however, significant challenges as methods are transferred from the development stage to routine regulatory analysis. Having experimental retention time and product ion information for analytes greatly facilitates the ability to determine if residues found by the HRMS searching software are false detects. These data were collected for over 200 veterinary drug residues using LC Q-TOF MS. The screening levels of detection for over 150 veterinary drug residues in milk were determined, and over half of those tested can be detected at concentrations of 10 ng/mL or less; 72% can be found in milk when present at 100 ng/mL. Tentative identification of the product ions from these analytes is also presented.

Analysis of veterinary drug residues in frog legs and other aquacultured species using liquid chromatography quadrupole time-of-flight mass spectrometry

A liquid chromatography quadrupole time-of-flight (Q-TOF) mass spectrometry method was developed to analyze veterinary drug residues in frog legs and other aquacultured species. Samples were extracted using a procedure based on a method developed for the analysis of fluoroquinolones (FQs) in fish. Briefly, the tissue was extracted with dilute acetic acid and acetonitrile with added sodium chloride. After centrifugation, the extracts were evaporated and reconstituted in mobile phase. A molecular weight cutoff filter was used to clean up the final extract. A set of target compounds, including trimethoprim, sulfamethoxazole, chloramphenicol, quinolones, and FQs, was used to validate the method. Screening of residues was accomplished by collecting TOF (MS¹) data and comparing the accurate mass and retention times of compounds to a database containing information for veterinary drugs. An evaluation of the MS data in fortified frog legs indicated that the target compounds could be consistently detected at the level of concern. The linearity and recoveries from matrix were evaluated for these analytes to estimate the amount of residue present. MS/MS data were also generated from precursor ions, and the mass accuracy of the product ions for each compound was compared to theoretical values. When the method was used to analyze imported frog legs, many of these residues were found in the samples, often in combination and at relatively high concentrations (>10 ng/g). The data from these samples were also evaluated for nontarget analytes such as residue metabolites and other chemotherapeutics.

Analysis of veterinary drugs and metabolites in milk using quadrupole time-of-flight liquid chromatography-mass spectrometry

A quadrupole time-of-flight (Q-TOF) liquid chromatography-mass spectrometry (LC-MS) method was developed to analyze veterinary drug residues in milk. Milk samples were extracted with acetonitrile. A molecular weight cutoff filter was the only cleanup step in the procedure. Initially, a set of target compounds (including representative sulfonamides, tetracyclines, β-lactams, and macrolides) was used for validation. Screening of residues was accomplished by collecting TOF (MS(1)) data and comparing the accurate mass and retention times of found compounds to a database containing information for veterinary drugs. The residues included in the study could be detected in samples fortified at the levels of concern with this procedure 97% of the time. Although the method was intended to be qualitative, an evaluation of the MS data indicated a linear response and acceptable recoveries for a majority of target compounds. In addition, MS/MS data were also generated for the [M + H](+) ions. Product ions for each compound were identified, and their mass accuracy was compared to theoretical values. Finally, incurred milk samples from cows dosed with veterinary drugs, including sulfamethazine, flunixin, cephapirin, or enrofloxacin, were analyzed with Q-TOF LC-MS. In addition to monitoring for the parent residues, several metabolites were detected in these samples by TOF. Proposed identification of these residues could be made by evaluating the MS and MS/MS data. For example, several plausible metabolites of enrofloxacin, some not previously observed in milk, are reported in this study.

Optimization and validation of a multiclass screening and confirmation method for drug residues in milk using high-performance liquid chromatography/tandem mass spectrometry

The further optimization and validation of a multiresidue veterinary drug screening method for milk is described. The drug residues of regulatory interest in milk include beta-lactams, sulfonamides, tetracyclines, fluoroquinolones, and macrolides. A previously published procedure has been modified to incorporate new compounds and to collect both screening and confirmatory ion transitions in one acquisition method. Milk samples were extracted with an equal volume of acetonitrile. The samples were then subjected to cleanup with a bonded SPE cartridge and a MW cutoff filter. The SPE protocol was modified to effectively recover a metabolite of flunixin. Established tolerance levels are set for most of these drugs in milk; thus, the screening procedure was semiquantitative, using positive controls for comparison. The positive controls, consisting of extracts from milk fortified with the drugs at their tolerance or safe level, were used to set statistically valid minimum response criteria for unknown samples. This updated method was validated with fortified milk, as well as with milk samples from animals administered veterinary drugs.

Liquid chromatographic determination of diminazene diaceturate (Berenil) in raw bovine milk

A simple liquid chromatographic (LC) method is presented for the determination of diminazene (DZ) in raw bovine milk. DZ is extracted from raw milk by chilled aqueous centrifugation and is isolated from milk components on a cyano solid-phase extraction column. DZ is eluted by using a methanol-ion pairing reagent. A Phenomenex LUNA CN column and an acetonitrile-buffered mobile phase with a counter ion are used for gradient LC. The LC effluent is monitored at a detection wavelength of 372 nm by using a deuterium lamp. Under the parameters described, the retention time of DZ is 8-10 min with a peak area response of 6.5 mAU/ng. The method demonstrated excellent precision over all levels tested (25-400 ppb) with an overall average recovery of 90.4 +/- 14.5%. The method is applicable to the monitoring of milk for DZ residues at the 25 ppb level with a limit of quantitation of 10 ppb.

Concurrent determination of four fluoroquinolones in catfish, shrimp, and salmon by liquid chromatography with fluorescence detection

A liquid chromatographic (LC) method with fluorescence detection was developed for concurrent determination of 4 fluoroquinolones: ciprofloxacin (CIPRO), enrofloxacin (ENRO), sarafloxacin (SARA), and difloxacin (DIFLX) in catfish, shrimp, and salmon. The procedure consists of extraction from fish tissue with acidified ethanol, isolation and retention on a cation exchange solid-phase extraction column, elution with basic methanol, and LC analysis with fluorescence detection. LC is performed by isocratic elution with acetonitrile-2% acetic acid (16 + 84) mobile phase, and a PLRP-S polymer column with fluorescence detection, excitation 278 nm and emission 450 nm. A target level of 20 ppb for each of the 4 fluoroquinolones has been established for this method. Fortified and incurred fish sample results are based on a 5-point standard curve calculation (10-160 ppb). Overall percent recoveries (% relative standard deviation) from fortified catfish were 78 (10), 80 (11), 70 (9.4), and 78 (10); from fortified shrimp, 69 (5.9), 85 (4.9), 79 (5.9), and 90 (4.5); and from fortified salmon, 56 (15), 93 (5.6), 61 (11), and 87 (5.0) for CIPRO, ENRO, SARA, and DIFLX, respectively. Data from the analysis of fluoroquinolone-incurred catfish, shrimp, and salmon are presented.

Freezing survival, body ice content and blood composition of the freeze-tolerant European common lizard, Lacerta vivipara

To investigate the freeze tolerance of the European common lizard, Lacerta vivipara, we froze 17 individuals to body temperatures as low as -4 degrees C under controlled laboratory conditions. The data show that this species tolerates the freezing of 50% of total body water and can survive freezing exposures of at least 24-h duration. Currently, this represents the best known development of freeze tolerance among squamate reptiles. Freezing stimulated a significant increase in blood glucose levels (16.15+/- 1.73 micromol x ml(-1) for controls versus 25.06 +/- 2.92 micromol x ml(-1) after thawing) but this increase had no significant effect on serum osmolality which was unchanged between control and freeze-exposed lizards (506.0 +/- 23.8 mosmol x l(-1) versus 501.0 +/- 25.3 mosmol x l(-1), respectively). Tests that assessed the possible presence of antifreeze proteins in lizard blood were negative. Recovery at 5 degrees C after freezing was assessed by measurements of the mean time for the return of breathing (5.9 +/- 0.5 h) and of the righting reflex (44.8 +/- 4.5 h). Because this species hibernates in wet substrates inoculative freezing may frequently occur in nature and the substantial freeze tolerance of this lizard should play a key role in its winter survival.

Influence of exercise on the activity and the distribution between free and bound forms of glycolytic and associated enzymes in tissues of horse mackerel

The effects of short-term burst (5 min at 1.8 m/s) swimming and long-term cruiser (60 min at 1.2 m/s) swimming on maximal enzyme activities and enzyme distribution between free and bound states were assessed for nine glycolytic and associated enzymes in tissues of horse mackerel, Trachurus mediterraneus ponticus. The effects of exercise were greatest in white muscle. The activities of phosphofructokinase (PFK), pyruvate kinase (PK), fructose-1,6-bisphosphatase (FBPase), and phosphoglucomutase (PGM) all decreased to 47, 37, 37 and 67%, respectively, during 60-min exercise and all enzymes except phosphoglucoisomerase (PGI) and PGM showed a change in the extent of binding to subcellular particulate fractions during exercise. In red muscle, exercise affected the activities of PGI, FBPase, PFK, and lactate dehydrogenase (LDH) and altered percent binding of only PK and LDH. In liver, exercise increased the PK activity 2.3-fold and reduced PGI 1.7-fold only after 5 min of exercise but altered the percent binding of seven enzymes. Fewer effects were seen in brain, with changes in the activities of aldolase and PGM and in percent binding of hexokinase, PFK and PK. Changes in enzyme activities and in binding interactions with subcellular particulate matter appear to support the altered demands of tissue energy metabolism during exercise.

Gene up-regulation in heart during mammalian hibernation

A cDNA library prepared from heart of hibernating golden-mantled ground squirrels, Spermophilus lateralis, was differentially screened to clone genes that were up-regulated during hibernation. Two differentially expressed clones were found after three rounds of screening and were confirmed as up-regulated by Northern blotting. Clone Ang6 encoded a polypeptide with 116 amino acids that was identified as the ventricular isoform of myosin light chain 1 (MLC1(v)). Clone Ang19 coded for 274 amino acid residues of the mitochondrially encoded protein subunit 2 of NADH-ubiquinone oxidoreductase (ND2). Both proteins showed high amino acid sequence identity with their human counterparts, 97.5% for MLC1(v) and 66% for ND2. Northern blot hybridization revealed differential expression of these genes in multiple organs during hibernation. Transcript levels of both were approximately twofold higher in heart and three- to fourfold higher in skeletal muscle of hibernating, versus euthermic, animals. ND2 was also up-regulated in hibernator liver. Hibernation-induced up-regulation of MLC1(v) suggests that a restructuring of myosin subunit composition could contribute to changes in muscle contractility needed for hypothermic function, whereas changes in ND subunit composition may affect the function of the electron transport chain during hibernation.

Gene expression during estivation in spadefoot toads, Scaphiopus couchii: upregulation of riboflavin binding protein in liver

A cDNA library constructed from liver of 2-month estivating female spadefoot toads, Scaphiopus couchii, was differentially screened to reveal genes that were induced or upregulated during estivation. After two rounds of screening a clone was isolated that showed 60% higher expression in liver of estivating, versus control, toads. The clone possessed a 1.0 kb insert which annealed to a single 0.7 kb band on Northern blots. Sequencing revealed a 1053 nucleotide full-length cDNA; the largest potential open reading frame was 708 nucleotides which encoded a protein of 235 amino acids. A homology search in Genbank indicated that the protein was a riboflavin binding protein (RfBP), a monomeric phosphoglycoprotein produced by the liver of female birds, reptiles, and mammals that functions to bind plasma riboflavin and load the vitamin into eggs or fetus. To our knowledge, this is the first demonstration that RfBP is also present in amphibians. Toad RfBP showed 50% of residues identical with the chicken or turtle liver proteins and many essential structural features were conserved in the toad protein including 18 cysteine residues, two asparagine glycosylation sites, and 6 tryptophan residues. However, a region with eight phosphoserines in the chicken or turtle proteins that functions in RfBP binding to the oocyte membrane contained only three serine residues in toad RfBP, suggesting that recognition and binding to oocyte receptors must be different in toads. Northern hybridization showed that toad RfBP was largely liver-specific; no mRNA transcripts were detected in brain, gut, heart, or kidney but low message levels occurred in hind leg skeletal muscle of estivating, but not control, toads. Upregulation of RfBP in liver of estivating toads may be linked with maturation of eggs in preparation for the explosive breeding that occurs immediately upon emergence from estivation but might also have a role for the adult in "caching" riboflavin to maintain an endogenous vitamin pool over the 9-10 months of each year that toads are dormant.

Solid-phase extraction cleanup and liquid chromatography with ultraviolet detection of ephedrine alkaloids in herbal products

A solid-phase extraction (SPE) cleanup and a liquid chromatographic (LC) method with UV detection is presented for analysis of up to 7 ephedrine alkaloids in herbal products. Alkaloids from herbal products are extracted with acidified buffer, isolated on a propylsulfonic acid SPE column, eluted with a high-ionic-strength buffer, and separated by LC with detection at 255 nm. LC separation is performed by isocratic elution on a YMC phenyl column with 0.1 M sodium acetate-acetic acid (pH = 4.8) containing triethyl-amine and 2% acetonitrile. Ephedrine alkaloids are completely separated in 15 min. Average recovery of 5 common alkaloids from 3 spiked matrixes is 90%, with an average relative standard deviation (RSD) of 4.4% for alkaloid spikes between 0.5 and 16 mg/g. Average quantitation of ephedrine and pseudoephedrine from 6 herbal products is 97% of declared label claims, and average quantitation of synephrine from an herbal dietary product is 85% of label claim (RSD, 3.2%). Recoveries of synephrine, norephedrine, ephedrine, pseudoephedrine, N-methylephedrine, and N-methylpseudoephedrine spiked in 4 herbal products averaged 95%. Results of ruggedness testing and of a second laboratory validation of the procedure are also presented.

Antioxidant defenses and metabolic depression. The hypothesis of preparation for oxidative stress in land snails

The roles of enzymatic antioxidant defenses in the natural tolerance of environmental stresses that impose changes in oxygen availability and oxygen consumption on animals is discussed with a particular focus on the biochemistry of estivation and metabolic depression in pulmonate land snails. Despite reduced oxygen consumption and PO2 during estivation, which should also mean reduced production of oxyradicals, the activities of antioxidant enzymes, such as superoxide dismutase and catalase, increased in 30 day-estivating snails. This appears to be an adaptation that allows the snails to deal with oxidative stress that takes place during arousal when PO2 and oxygen consumption rise rapidly. Indeed, oxidative stress was indicated by increased levels of lipid peroxidation damage products accumulating in hepatopancreas within minutes after arousal was initiated. The various metabolic sites responsible for free radical generation during arousal are still unknown but it seems unlikely that the enzyme xanthine oxidase plays any substantial role in this despite being implicated in oxidative stress in mammalian models of ischemia/reperfusion. We propose that the activation of antioxidant defenses in the organs of Otala lactea during estivation is a preparative mechanism against oxidative stress during arousal. Increased activities of antioxidant enzymes have also observed under other stress situations in which the actual production of oxyradicals should decrease. For example, antioxidant defenses are enhanced during anoxia exposure in garter snakes Thamnophis sirtalis parietalis (10 h at 5 degrees C) and leopard frogs Rana pipiens (30 h at 5 degrees C) and during freezing exposure (an ischemic condition due to plasma freezing) in T. sirtalis parietalis and wood frogs Rana sylvatica. It seems that enhancement of antioxidant enzymes during either anoxia or freezing is used as a preparatory mechanism to deal with a physiological oxidative stress that occurs rapidly within the early minutes of recovery during reoxygenation or thawing. Thus, a wide range of stress tolerant animals display coordinated changes in antioxidant defenses that allow them to deal with oxidative stress that occurs as part of natural cycles of stress/recovery that alter oxygen levels in tissues. The molecular mechanisms that trigger and regulate changes in antioxidant enzyme activities in these species are still unknown but could prove to have key relevance for the development of new intervention strategies in the treatment of cardiovascular ischemia/reperfusion injuries in humans.

Synthesis and confirmation of structure for a new gibberellin, 2 beta-hydroxy-GA12 (GA110), from spinach and oil palm

The identity of a new gibberellin (GA) in spinach and oil palm sap has been confirmed as 2 beta-hydroxy-GA12 (GA110) by comparisons of GC-mass spectral data obtained for the trimethylsilyl ether methyl ester derivatives with those of a synthetic sample prepared by means of a 24 step sequence from gibberellic acid; 2 beta-hydroxy-GA24 was also prepared. Experimental details for the latter part of the syntheses are described.

De novo protein biosynthesis responses to water stresses in wood frogs: freeze-thaw and dehydration-rehydration

Protein biosynthesis responses occurring during the postthaw (after 12 h freezing at -1.4 degrees C), dehydration (to 27 or 40% of total body water lost), or rehydration (after the loss of 40% of body water) were monitored in tissues of spring-collected wood frogs (Rana sylvatica) after intraperitoneal injection of 35S-labeled methionine + cysteine. All six organs tested accumulated radiolabeled amino acids and organs of both thawing and rehydrating frogs held at 3-5 degrees C showed a linear increase in amino acid incorporation into the acid-precipitable protein fraction over time. By contrast, dehydrating animals showed little or no increment in protein bound radioactivity over the course of the stress, a result that may be indicative of metabolic suppression in organs when dehydration became severe. Isoelectrofocusing (IEF) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to characterize the proteins synthesized by liver under each experimental state. IEF revealed both new peaks of 35S-labeled proteins and enhanced labeling of others in extracts from experimental animals, compared with controls. In particular, new synthesis of proteins with isoelectric points of about 6.0 was prominent and labeled proteins in this IEF peak persisted at 5, 10, or 24 h postinjection, becoming proportionally more important over time. SDS-PAGE analysis of the p(I) 6.0 peaks from thawed, dehydrated, and rehydrated frogs revealed the presence of one major low molecular weight protein in each case with molecular masses of 15, 13, and 21 kDa, respectively. These data indicate that the biochemical adaptations supporting freeze tolerance and dehydration tolerance in anurans include the stress-induced biosynthesis of a suite of proteins including the novel synthesis of selected specific proteins. These proteins may represent stress-related (or shock) proteins or may have specific roles in metabolic adaptation in each state such as in water and ionic balance or cell volume regulation.

Biochemistry below 0 degrees C: nature's frozen vertebrates

Although alien to man, the ability to endure the freezing of extracellular body fluids during the winter has developed in several species of terrestrially hibernating frogs and turtles as well as in many species of insects and other invertebrates. Wood frogs, for example, can endure freezing for at least 2 weeks with no breathing, no heart beat or blood circulation, and with up to 65% of their total body water as ice. Our studies are providing a comprehensive view of the requirements for natural freezing survival and of the physical and metabolic protection that must be offered for effective cryopreservation of vertebrate organs. Molecular mechanisms of natural freeze tolerance in lower vertebrates include: 1) control over ice crystal growth in plasma by ice nucleating proteins, 2) the accumulation of low molecular weight cryoprotectants to minimize intracellular dehydration and stabilize macromolecular components, and 3) good ischemia tolerance by all organs that may include metabolic arrest mechanisms to reduce organ energy requirements while frozen. Cryomicroscopy of tissue slices and magnetic resonance imaging (MRI) of whole animals is revealing the natural mode of ice propagation through an organism. MRI has also revealed that thawing is non-uniform; core organs (with high cryoprotectant levels) melt first, facilitating the early resumption of heart beat and blood circulation. Studies of the production and actions of the natural cryoprotectant, glucose, in frogs have shown its importance in maintaining a critical minimum cell volume in frozen organs and new work on the metabolic effects of whole body dehydration in 3 species of frogs has indicated that adaptations supporting freeze tolerance grew out of mechanisms that deal with desiccation resistance in amphibians. Studies of the regulation of cryoprotectant glucose synthesis by wood frog liver have shown the role of protein kinases and of alpha and beta adrenergic receptors in regulating the glycemic response, and of changes in membrane glucose transporter proteins to facilitate cryoprotectant distribution.

Clinical experience with patient-controlled and staff-administered intermittent bolus epidural analgesia in labour

A prospective, randomized study was performed to detail clinical experience with both patient-controlled epidural analgesia (PCEA) and midwife-administered intermittent bolus (IB) epidural analgesia during labour, under the conditions pertaining in a busy obstetric delivery unit. Both methods used 0.125% bupivacaine plus fentanyl, and similar rescue supplementation, although management decisions related to epidural analgesia were made principally by attending midwives. One hundred and ninety-eight women were recruited and data analysed from 167 (PCEA n = 82, IB n = 85). The groups were demographically similar. Median hourly pain scores, ratings of analgesia and satisfaction did not differ. Maximum pain scores were significantly higher in those receiving IB epidural analgesia (P < 0.05). The PCEA group had a significantly higher rate of supplementation and bupivacaine use (P < 0.01), and a longer duration of the second stage of labour (P < 0.03). The relative risk of instrumental delivery with PCEA versus the IB method was 1.57 (CI 1.07-2.38). Experience within our unit with PCEA is contrasted with that of IB epidural analgesia, the method most commonly used; and with that of controlled trials comparing these two methods.

Vogt-Koyanagi-Harada syndrome in a 4-year-old child

Vogt-Koyanagi-Harada syndrome is an acquired illness with ocular, cutaneous, and/or neurologic features. A 4-year-old child who acutely developed visual disturbances and headache and was found to have serous retinal detachments and aseptic meningitis is presented. Improvement was rapid with corticosteroid therapy. This is the youngest reported patient with Vogt-Koyanagi-Harada syndrome.

Gas chromatographic determination of chloramphenicol residues in shrimp: interlaboratory study

An interlaboratory study of a gas chromatographic method for determining chloramphenicol (CAP) residues in shrimp was conducted. An internal standard (Istd), the meta isomer of CAP, was added to the shrimp, and the treated shrimp were homogenized with ethyl acetate. The ethyl acetate extract was defatted with hexane, and the CAP was partitioned into ethyl acetate from an aqueous salt solution. The ethyl acetate was evaporated, and the dried residue was treated with Sylon, a trimethylsilyl derivatizing agent, to yield the trimethylsilyl derivative of CAP. A portion of the solution containing the derivative was injected into a gas chromatograph equipped with an electron capture detector. Levels of fortified and incurred CAP were calculated from the peak area ratio of standard CAP to Istd. Recoveries of CAP from tissue directly fortified at 5 ppb were 102% (within-laboratory relative standard deviation [RSDr] = 5.6%), 104% (RSDr = 5.5%), and 108% (RSDr = 6.3%) from Laboratories 1, 2, and 3, respectively. Incurred-CAP residues at 5 and 10 ppb levels were also determined, with the following results: Laboratory 1: composite A, 4.56 ppb (RSDr = 14.0%); composite B, 8.38 ppb (RSDr = 11.6%); Laboratory 2: composite A, 4.17 ppb (RSDr = 12.5%); composite B, 8.90 ppb (RSDr = 5.60%); Laboratory 3: composite A, 4.66 ppb (RSDr = 14.9%); composite B, 11.0 ppb (RSDr = 11.8%).

Frozen and alive

A variety of animals freeze solid during the winter months and thaw in the spring. This natural ability to survive freezing may yield clues to the cryopreservation of human tissue.

Metabolic rate depression and biochemical adaptation in anaerobiosis, hibernation and estivation

For many animals, the best defense against harsh environmental conditions is an escape to a hypometabolic or dormant state. Facultative metabolic rate depression is the common adaptive strategy of anaerobiosis, hibernation, and estivation, as well as a number of other arrested states. By reducing metabolic rate by a factor ranging from 5 to 100 fold or more, animals gain a comparable extension of survival time that can support months or even years of dormancy. The present review focuses on the molecular control mechanisms that regulate and coordinate cellular metabolism for the transition into dormancy. These include reversible control over the activity state of enzymes via protein phosphorylation or dephosphorylation reactions, pathway regulation via the association or dissociation of particle-bound enzyme complexes, and fructose-2,6-bisphosphate regulation of the use of carbohydrate reserves for biosynthetic purposes. These mechanisms, their interactions, and the regulatory signals (e.g., second messenger molecules, pH) that coordinate them form a common molecular basis for metabolic depression in anoxia-tolerant vertebrates (goldfish, turtles) and invertebrates (marine molluscs), hibernation in small mammals, and estivation in land snails and terrestrial toads.

Hatchling turtles survive freezing during winter hibernation

Hatchlings of the painted turtle (Chrysemys picta marginata) are unique as the only reptile and highest vertebrate life form known to tolerate the natural freezing of extracellular body fluids during winter hibernation. Turtles survived frequent exposures to temperatures as low as -6 degrees C to -8 degrees C in their shallow terrestrial nests over the 1987-1988 winter. Hatchlings collected in April 1988 had a mean supercooling point of -3.28 +/- 0.24 degrees C and survived 24 hr of freezing at -4 degrees C with 53.4% +/- 1.98% of total body water as ice. Recovery appeared complete after 20 hr of thawing at 3 degrees C. However, freezing at -10.9 degrees C, resulting in 67% ice, was lethal. A survey of possible cryoprotectants revealed a 2- to 3-fold increase in glucose content of liver and blood and a 3-fold increase in blood glycerol in response to freezing. Although quantitatively low, these responses by spring turtles strongly indicate that these may be the winter-active cryoprotectants. The total amino acid pool of blood also increased 2.25-fold in freezing-exposed turtles, and taurine accounted for 52% of the increase. Most organs accumulated high concentrations of lactate during freezing, a response to the ischemic state imposed by extracellular freezing. Changes in glycogen phosphorylase activity and levels of glucose 6-phosphate and fructose 2,6-bisphosphate were also consistent with a dependence on anaerobic glycolysis during freezing. Studies of the molecular mechanisms of natural freeze tolerance in these turtles may identify protective strategies that can be used in mammalian organ cryopreservation technology.

Freeze tolerance and intolerance as strategies of winter survival in terrestrially-hibernating amphibians

The ability to tolerate extracellular freezing as an adaptation for winter survival was tested in seven species of terrestrially-hibernating amphibians found in eastern Canada. All species had only moderate supercooling abilities, with whole animal supercooling points of -1.5 to -3 degrees C. Two salamander species, Plethodon cinereus and Ambystoma laterale, and the toad, Bufo americanus, were freezing intolerant and were killed when frozen for 24 hr at temperatures just below their supercooling points. The major winter strategy of these animals appears to behavioural avoidance of subzero temperatures. Four species of frogs Rana sylvatica, Hyla versicolor, Hyla crucifer and Pseudacris triseriata, survived extracellular freezing at moderate subzero temperatures (-2 to -4 degrees C) for periods of time ranging up to 2 weeks. All four frog species accumulated low molecular weight carbohydrates as cryoprotectants, glycerol being the major cryoprotectant in adult H. versicolor, while immature adults of this species as well as the other three species all produced high levels of glucose as the cryoprotectant.

31P nuclear magnetic resonance studies of crayfish (Orconectes virilis). The use of inversion spin transfer to monitor enzyme kinetics in vivo

31P nuclear-magnetic resonance (NMR) has been used to observed in vivo the steady-state levels of phosphorus-containing metabolites in the crayfish Orconectes virilis and the intracellular pH of the abdominal muscle was determined. Measurement of spin-lattice relaxation times and spin transfer experiments have enabled calculation of unidirectional rate constants and activation energies for the arginine kinase reaction in vivo.

Improved renal cortical tubule suspension: spectrophotometric study of O2 delivery

An improved cortical tubule suspension from the rabbit kidney is described that contains almost entirely proximal convoluted tubules with little contamination by cellular debris or glomeruli. These tubules appear to be capable of active transepithelial transport, since their tubular lumina are open and ouabain inhibits 70% of the QO2. In previous preparations with closed tubular lumina, ouabain inhibited QO2 only 40% and the base-line QO2 was one-half to one-quarter that of the present preparation. The delivery of oxygen to this tubule suspension was compared to that of slices by three different means: oxygen consumption kinetics, ATP content, and, more directly by spectrophotometric monitoring of the redox state of cytochrome oxidase. Results demonstrate that the cortical slice is evidently oxygen deficient even when the bath PO2 is in excess of 570 mmHg. In contrast, the tubule suspension is shown to be adequately oxygenated even at a bath PO2 of 10 mmHg. This tubule suspension will be highly applicable for the analysis of aerobic metabolism in a functionally intact renal preparation by optical, electrode, and biochemical assay technologies.

Role of ATP in respiratory control and active transport in tobacco hornworm midgut

The intracellular ATP, ADP, AMP, and orthophosphate (Pi) levels were measured in the midgut of Manduca sexta. The nucleotide levels were identical in tissues either "fresh" frozen or equilibrate in regular (32 mM) K or low (8 mM) K solutions. The calculated [ATP]/[ADP][Pi]ratio was approximately 300 M-1, which is low compared to other tissues. Given the ability of this ratio to control the respiratory rate, it is speculated that this low value may cause the maximal uncontrolled respiration normally observed in the midgut. The kinetics to anoxia of active transport (Isc) and the redox level of the mitochondrial cytochromes were measured simultaneously in the midgut. The cytochromes became reduced with a time constant of 0.75 +/- 0.15 min, whereas that for Isc inhibition was 2.1 +/- 0.15 min after a delay of 0.25 min. The difference between these two kinetic rates indicates that an intermediate form of energy exists in this tissue to energize active K transport. Measurements of ATP levels during the transition to anoxia indicate that its decay kinetics are sufficiently slow for ATP to be the immediate energy source for active transport in this tissue.

Coupling of active ion transport and aerobic respiratory rate in isolated renal tubules

We report the results of studies in which the cytoplasmic coupling between Na+,K+-ATPase activity (presumably a measure of active transport) and the mitochondrial respiratory rate was investigated in a tubule suspension from the rabbit kidney cortex. Simultaneous measurements of the redox state of mitochondrial nicotinamide adenine dinucleotide (NAD) (performed fluorometrically), the cellular ATP and ADP concentrations, and the oxygen consumption rate (QO2) were made under conditions known to alter the Na+,K+-ATPase turnover. Ouabain (25 microM) caused: (i) a 54% inhibition of QO2, (ii) a net reduction of NAD, and (iii) a 30% increase in the ATP/ADP ratio. The addition of K+ (5 ?M) to K+-depleted tubules caused: (i) an initial 127% stimulation of QO2 followed by a new steady-state QO2 50% above control, (ii) an initial large oxidation of NAD followed by a new steady state more oxidized than the control level, and (iii) a 47% decrease in the cellular ATP/ADP ratio. These data indicate that the cellular ATP and ADP concentrations or the ATP/ADP ratio may be part of the coupling mechanism linking Na+,K+-ATPase turnover and the aerobic metabolic rate in kidney.

Effect of streptozotocin diabetes and insulin administration on some liver enzyme activities in the post-weaning rat

Streptozotocin-induced diabetes suppressed the normal development of the nine glycolytic and lipogenic enzyme activities measured. With the exception of NADP-isocitrate dehydrogenase, insulin replacement therapy induced increased activities of the enzymes in streptozotocin-treated rats. Insulin appeared to have a specific effect on the activities of glucokinase, ATP-citrate lyase, malic enzyme, and glucose-6-P-dehydrogenase.