Ion Chemical Ionization Gas Chromatography-mass Research Articles

Plasma apolipoprotein C-III metabolism in patients with chronic kidney disease

Moderate chronic kidney disease (CKD) (defined by an estimated glomerular filtration rate of 30-60 ml/min) is associated with mild hypertriglyceridemia related to delayed catabolism of triglyceride-rich lipoprotein particles. Altered apolipoprotein C-III (apoC-III) metabolism may contribute to dyslipidemia in CKD. To further characterize the dyslipidemia of CKD, we investigated the kinetics of plasma apoC-III in 7 nonobese, nondiabetic, non-nephrotic CKD subjects and 7 age- and sex-matched healthy controls, using deuterated leucine ([5, 5, 5, ²H₃]leucine), gas chromatography-mass spectrometry, and multicompartmental modeling. Compared with controls, CKD subjects had higher concentrations of plasma and VLDL triglycerides and plasma and VLDL apoC-III (P < 0.05). The increased plasma apoC-III concentration was associated with a decreased apoC-III fractional catabolic rate (FCR) (1.21 ± 0.15 vs. 0.74 ± 0.12 pools/day, P = 0.03). There were no differences between apoC-III production rates of controls and those of CKD subjects. In CKD subjects, plasma apoC-III concentration was significantly and negatively correlated with apoC-III FCR (r = -0.749, P = 0.05) but not with apoC-III production rate. Plasma apoC-III concentration was positively correlated with plasma and VLDL triglycerides and VLDL apoB concentrations and negatively correlated with VLDL apoB FCR (P < 0.05 for all). ApoC-III FCR was negatively correlated with plasma and VLDL triglycerides and VLDL apoB concentration and positively correlated with VLDL apoB FCR (P < 0.05 for all). Altered plasma apoC-III metabolism is a feature of dyslipidemia in moderate CKD. Modification of apoC-III catabolism may be an important therapeutic target for reducing cardiovascular disease risk in moderate CKD.

Macrophage-specific expression of group IIA sPLA2 results in accelerated atherogenesis by increasing oxidative stress

Group IIA secretory phospholipase A2 (sPLA2) is an acute-phase protein mediating decreased plasma HDL cholesterol and increased atherosclerosis. This study investigated the impact of macrophage-specific sPLA2 overexpression on lipoprotein metabolism and atherogenesis. Macrophages from sPLA2 transgenic mice have 2.5 times increased rates of LDL oxidation (thiobarbituric acid-reactive substances formation) in vitro (59 +/- 5 vs. 24 +/- 4 nmol malondialdehyde/mg protein; P < 0.001) dependent on functional 12/15-lipoxygenase (12/15-LO). Low density lipoprotein receptor-deficient (LDLR-/-) mice were transplanted with bone marrow from either sPLA2 transgenic mice (sPLA2--> LDLR-/-; n = 19) or wild-type C57BL/6 littermates (C57 BL/6-->LDLR-/-; n = 19) and maintained for 8 weeks on chow and then for 9 weeks on a Western-type diet. Plasma sPLA2 activity and plasma lipoprotein profiles were not significantly different between sPLA2-->LDLR-/- and C57BL/6-->LDLR-/- mice. Aortic root atherosclerosis was increased by 57% in sPLA2-->LDLR-/- mice compared with C57BL/6-->LDLR-/- controls (P < 0.05). Foam cell formation in vitro and in vivo was increased significantly. Urinary, plasma, and aortic levels of the isoprostane 8,12-iso-iPF2alpha-VI and aortic levels of 12/15-LO reaction products were each significantly higher (P < 0.001) in sPLA2-->LDLR-/- compared with C57BL/6-->LDLR-/- mice, indicating significantly increased in vivo oxidative stress in sPLA2--> LDLR-/-. These data demonstrate that macrophage-specific overexpression of human sPLA2 increases atherogenesis by directly modulating foam cell formation and in vivo oxidative stress without any effect on systemic sPLA2 activity and lipoprotein metabolism.

Negative ion chemical ionization gas chromatography-mass spectrometry and atmospheric pressure chemical ionization liquid chromatography-mass spectrometry of low-dosed and/or polar drugs in plasma.

In clinical and forensic toxicology, doping control, and therapeutic drug monitoring, specific and sensitive detection and precise quantification of xenobiotics in biosamples are great challenges. Today, mass spectrometry techniques, coupled with gas chromatography or liquid chromatography, are the most powerful methods in analytic toxicology. The pros and cons of electron ionization (EI) and negative ion chemical ionization (NICI) gas chromatography-mass spectrometry (GC-MS) and of atmospheric pressure chemical ionization liquid chromatography-mass spectrometry (APCI-LC-MS) are described for determination of the low-dosed benzodiazepine flunitrazepam and its 7-amino and its nor-metabolite in plasma. In addition, application of NICI-GC-MS is described for sensitive chiral determination of amphetamine derivatives in plasma and application of APCI-LC-MS for screening, library-assisted identification, and validated quantification of oral antidiabetics and for validated quantification of the neuroleptic risperidone and its 9-hydroxy metabolite. These examples show that NICI-GC-MS and LC-MS are powerful tools for determination of low-dosed and/or rather polar drugs or poisons, thus becoming indispensable supplements to classic EI-GC-MS in clinical and forensic toxicology as well as in doping control.

Formation of isoprostane F 2-like compounds (phytoprostanes F 1) from α-linolenic acid in plants

Isoprostanes F 2 are biologically active prostaglandin F 2-like compounds formed by free radical–catalyzed oxidation of arachidonic acid (C20:4). Here, we show that a series of dinor isoprostanes F 1, which we term phytoprostanes F 1 (PPF 1s), are formed by nonenzymatic oxidation of linolenate (C18:3) in plants. Identification and quantification of PPF 1s were achieved by a negative ion chemical ionization gas chromatography–mass spectrometry method using oxygen 18–labeled PPF 1s as internal standards. PPF 1s were found in leaves, flowers, and roots of taxonomically distinct plant species at concentrations ranging from 43 to 1380 ng/g of dry weight. In addition, esterified PPF 1s were found at 10- to 150-fold higher concentrations. During the drying and storage of various plant organs, endogenous PPF 1 levels increased dramatically by 15- to 263-fold. Because the structurally related prostaglandin F 2α and isoprostanes F 2 exert potent biological activities (i.e., broncho- and vasoconstriction) in the nanomolar range, PPF 1s could potentially exert similar biological activities. Notably, fresh birch pollen, which can easily be inhaled, contains exceedingly high concentrations (32,440 ng/g) of free PPF 1s.

Simultaneous quantitation of cocaine, opiates, and their metabolites in human hair by positive ion chemical ionization gas chromatography-mass spectrometry.

A sensitive method is developed for the combined extraction of cocaine (COC), cocaethylene (CE), benzoylecgonine (BE), ecgonine methyl ester (EME), norcocaine (NORCOC), 6-acetylmorphine (6-MAM), codeine (COD), norcodeine (NORCOD), morphine (MOR), and normorphine (NORMOR) from human head hair using an enzyme-based digestion technique (Protease VIII/DTT/Tris-buffer pH 6.5 at 22 degrees C). After pH adjustment to 5.5, the digests are extracted with a solid-phase extraction procedure using Bond-Elut Certify columns. The extract residues are evaporated at 40 degrees C, reconstituted in 20 microL of ethyl acetate, and derivatized with the reagents N-methyl-N-trimethylsilylheptafluorobutyramide (MSHFBA), N-methyl-bis-heptafluorobutyramide (MBHFBA), and N-trimethylsilylimidazole (TMSIM). Analyses are performed by positive ion chemical ionization gas chromatography-mass spectrometry using a DB-1 capillary column. Two injections are performed on each extract to optimize sensitivity for all analytes. The assay is capable of reliably quantitating 500 pg/mg of all compounds and is linear to 50 ng/mg, except for BE, which is linear to 25.0 ng/mg. The method was used to analyze human hair samples obtained from cocaine and heroin users. COC, BE, and EME are detectable in all samples, whereas NORCOC, CE, COD, 6-MAM, and MOR are detected in only some samples. Norcodeine and normorphine are not detected. The assay is currently being used to analyze hair samples from a study investigating the mechanisms of drug disposition in hair.

Disposition of codeine in female human hair after multiple-dose administration.

Studies of the disposition of codeine into the hair of female subjects (n = 7) were performed after a multiple-dose protocol. Caucasian female subjects with dark-brown-to-black hair were administered a total dose of 450 mg codeine over 5 days (30 mg was administered three times a day for 5 days). Analyses of codeine and metabolites in plasma, urine, and hair were performed by positive ion chemical ionization gas chromatography-mass spectrometry (GC-MS) on a Finnigan Magnum" mass spectrometer. Hair was plucked from the scalp for 5 weeks and subsequently cut from the scalp for up to 10 weeks. Prior to analysis, plucked hair specimens were cut into three segments: (a) a proximal, 1-cm segment, which contained the root, (b) the next distal, 3-cm segment, which was closest to the scalp, and (c) a segment containing all remaining hair to the natural hair tip. in female subjects, the mean (plus or minus standard error of the mean) hair concentration of codeine in the proximal, 1-cm segment from plucked hair was 2.7 ng/mg (+/- 0.55) at 12 h after the last codeine dose; 0.44 ng/mg (+/- 0.20) still remained in this segment at 5 weeks. Codeine was detected in the next 3-cm hair segment (above the scalp) at 1 week; the average codeine concentration for 10 weeks in the 3-cm, distal segment was 0.54 ng/mg (+/- O.05). No codeine was detected in the remaining hair segment (to the tip) at any time. In male subjects studied previously, the mean hair concentration of codeine in the proximal, 1-cm hair segment was 2.6 ng/mg (+/- 0.34) at 12 h after the last codeine dose, and no codeine was detected at 5 weeks. Codeine was not detected in the next 3-cm hair segment (above the scalp) until 3 weeks, and the average mean codeine concentration for 10 weeks was 0.09 ng/mg (+/- 0.01). Differences noted between male and female subjects in distal codeine hair concentrations were not explained by plasma pharmacokinetics.

Characterization of cytochrome P-450-dependent arachidonic acid metabolism in rabbit intestine

We characterized cytochrome P-450-dependent arachidonate (P-450-AA) metabolism throughout the intestinal tract, since some metabolites derived via this pathway modify epithelial ion transport and regional blood flow. Microsomes (0.3 mg/ml) were prepared from each region of the intestines of anesthetized New Zealand White male rabbits and incubated with [14C]AA (7 microM) for 30 min at 37 degrees C. In the presence of NADPH (1 mM), ileal microsomes exhibited the greatest P-450-AA metabolism, whereas duodenal microsomes exhibited little or no activity. For jejunal, ileal, and cecal microsomes, AA metabolism was reduced in the absence of NADPH and by boiling microsomes, was unaffected by indomethacin (10 microM) and BW-755C (50 microM), but was significantly attenuated by the P-450 enzyme inhibitors, 7-ethoxyresorufin (1 microM) and SKF-525A (100 microM). However, colonic (ascending, transverse, and descending) microsomal activity was inhibited by both P-450 and lipoxygenase inhibitors. Analysis of ileal AA metabolites by high-pressure liquid chromatography and negative ion chemical ionization gas chromatography-mass spectrometry revealed products corresponding to monohydroxyeicosatetraenoic acids (HETEs). Semiquantitative analysis showed that 20-, 19-, 18-, 17-, and 16-HETEs were present in a ratio of 6.2:3.3:0.3:0.1:0.1, respectively. Furthermore, ileal P-450-HETEs dilated the isolated perfused mesenteric bed, as did 20-HETE, the predominant ileal AA metabolite. Because 20-HETE was also shown to affect epithelial ion transport, we suggest that P-450-AA metabolites may make important contributions to intestinal function.

On the Accurate Determination of Serotonin in Human Plasma

Serotonin (5-hydroxytryptamine, 5-HT) in blood is stored in platelets and has vascular and platelet stimulating effects when released into plasma. Accurate measurements of 5-HT in plasma are complicated by inadvertent platelet activation causing sampling artifacts and by analytical problems when determining trace levels. We developed an assay for plasma 5-HT based on solid-phase extraction (Sep-Pak C 18), aqueous acetylation, pentafluoropropionylation, and negative ion chemical ionization gas chromatography-mass spectrometry. The method was able to recover 5-HT from plasma by >90% and to quantitate with a precision of 7.5% at a level of 0.5 nmol/l. It was used to define blood sampling and sample handling procedures giving low and consistent values for 5-HT. A good blood sampling technique, adequate platelet stabilization in the test tube, and rapid high speed centrifugation of the blood resulted in low plasma levels of both 5-HT and β-thromboglobulin (a platelet release product). Using these procedures plasma 5-HT levels in healthy volunteers were found to be 0.77 ± 0.38 (mean ± S.D.; range 0.27-1.49) nmol/l (n=18), which is 4-100-fold lower than previously reported values.

Quantitative determination of hydroxy fatty acids as an indicator of in vivo lipid peroxidation: Oxidation products of arachidonic and docosapentaenoic acids in rat liver after exposure to carbon tetrachloride

An improved gas chromatography-mass spectrometry method has been applied to the quantitation of both in vitro and in vivo products of lipid peroxidation in rat liver stimulated with carbon tetrachloride. The method avoids problems of autoxidation of unsaturated fatty acids during sample preparation, and the sensitivity permits assays on as little as 1 mg of tissue. This permits small samples of tissue to be obtained by biopsy from the same organ, thus making it possible to perform in vivo time studies on a single animal. Lipids from whole tissue or cell preparations are simultaneously extracted and reduced by catalytic hydrogenation and then saponified and derivatized to their pentafluorobenzyl esters and trimethylsilyl ethers. Quantitation is accomplished by negative ion chemical ionization gas chromatography-mass spectrometry, using either deuterated compounds or naturally occurring fatty acid metabolites as internal standards. Hydroxy fatty acids which result from reduction of the hydroperoxides of arachidonic and docosapentaenoic acids are found to increase within 20 min after exposure of liver or hepatocyte suspensions to carbon tetrachloride.

A mass spectrometric method for measuring glycerol levels and enrichments in plasma using 13C and 2H stable isotopic tracers

The stable isotope tracer [1,1,2,3,3- 2H 5]glycerol has been commonly used as a tracer to measure glycerol kinetics and lipolysis in vivo. The method for measuring samples using the trimethylsilyl derivative and electron impact gas chromatograph-mass spectrometry retains only three of the five deuteriums, resulting in the possibility of incorrectly identifying the whole glycerol tracer molecule. This reports preparation of glycerol as the heptafluorobutyrl derivative and measurement by negative ion chemical ionization gas chromatography-mass spectrometry to produce a derivative with an intense molecular ion that retains all five deuterium labels. Thus the heptafluorobutyrl derivative analyzed by negative ion mass spectrometry overcomes the problems associated with fragmentation and loss of the isotopic label. Glycerol concentration using a labeled internal standard can be determined in plasma with a precision of 3%. Nanomole amounts of glycerol can be analyzed for 13C or 2H enrichments with a precision of ±0.14 mol% excess isotope. This simple, sensitive method for measuring glycerol levels and stable isotopic enrichment in plasma uses a simple extraction procedure and requires a minimal volume of plasma (<300 μl).

Quantitative determination of hydroxy fatty acids as an indicator of in vivo lipid peroxidation: Gas chromatography-mass spectrometry methods

A new method has been developed for the quantitation of lipid peroxidation products by gas chromatography-mass spectrometry. An important advantage over existing gas chromatography-mass spectrometry methods is the elimination of autoxidation during sample preparation. The sensitivity is sufficient to permit measurement of lipid peroxidation products under normal physiological conditions on as little as 1 mg of tissue. Lipids from whole tissue samples or cell preparations are reduced by catalytic hydrogenation during extraction. The hydrogenation stabilizes the compounds by saturating the double bonds and reducing the hydroperoxides to hydroxy derivatives. The saturated lipids are then saponified and the resulting fatty acids are converted to pentafluorobenzyl esters. Hydroxy fatty acids are further converted to trimethylsilyl ether derivatives. Quantitation is accomplished by negative ion chemical ionization gas chromatography-mass spectrometry, using deuterated internal standards. Specific products from polyunsaturated fatty acids can be quantitated, and the method differentiates between products produced by free-radical and photooxidation mechanisms. Increased levels of lipid peroxidation products, above normal physiological levels, that result from prooxidant conditions, such as exposure of animals to carbon tetrachloride, can be measured.

Metabolism of leukotriene E4 in isolated rat hepatocytes. Identification of beta-oxidation products of sulfidopeptide leukotrienes.

Little is known about the metabolic fate of the sulfidopeptide leukotrienes (LTC4/D4/E4). Earlier studies using radiolabeled leukotrienes have shown that these potent molecules are concentrated and metabolized in the liver when administered to mice and that isolated rat hepatocytes have a high affinity uptake system for LTE4. N-Acetyl-LTE4 has been identified as a metabolite of LTC4 in the bile of rats, but the majority of the metabolites in these studies were not characterized. Based on these earlier reports, incubation of LTE4 with isolated rat hepatocytes was chosen as a model for the study of sulfidopeptide leukotriene metabolism. [3H]LTE4 was incubated with isolated rat hepatocytes and the metabolites formed were purified extensively by ODS flash column chromatography, TLC, and reverse phase-high pressure liquid chromatography. Metabolites were identified by retention of the radiolabel and UV absorbance at 280 nm. Purified metabolites were characterized by UV spectroscopy, fast atom bombardment mass spectrometry, negative ion chemical ionization gas chromatography-mass spectrometry, and electron impact gas chromatography-mass spectrometry. Six LTE4 hepatocyte metabolites were characterized. Metabolite A was determined to be N-acetyl-LTE4. Metabolite B was determined to be the omega-oxidation product 20-carboxy-N-acetyl-LTE4. Metabolite C was characterized as the beta-oxidation product 18-carboxydinor-N-acetyl-LTE4. A further round of beta-oxidation with a concomitant double bond reduction produced Metabolite D, identified as 16-carboxytetranordihydro-N-acetyl-LTE4. The reduction of the 14-15 double bond was most likely the result of the action of 2,4-dienoyl-CoA reductase. The UV spectrum of Metabolite E indicated the presence of a conjugated tetraene, and this metabolite was determined to be 16-carboxytetranor-delta 13-N-acetyl-LTE4. Metabolite F was identified as 14-carboxyhexanor-N-acetyl-LTE4. The observed pathway of beta-oxidation of LTE4 proceeded entirely from the C-20 methyl terminus after omega-oxidation which is in contrast to the known metabolic fate of other eicosanoids. This may be due to the failure to generate the required thioester at C-1 in LTE4 through a strong interaction of the C-5 hydroxy group with the C-1 carboxyl.

Negative ion chemical ionization gas chromatography—mass spectrometry of some derivatives of tri-, tetra- and pentachlorophenols

The methane negative ion gas chromatographic (GC)—mass spectrometric and electron capture (GC) behaviour of tri-, tetra- and pentachlorophenols have been investigated as their pentafluorobenzyl ethers, pentafluorobenzoate esters, heptafluorobutyrate esters, trifluoroacetate, acetate and 2,4-dinitrophenyl ether derivatives. The derivatives of choice for optimum detection of chlorophenols are the pentafluorobenzyl ether and pentafluorobenzoate ester because of the strong negative ion signal which is derived from the chlorinated phenol, rather than reagent moieties, in each instance. Using this procedure the chlorophenols present in an industrial starch adhesive and in water collected near an industrial dumping site were determined.

Technical Pentachlorophenol: Origin and Analysis of Base-Insoluble Contaminants

Research ArticleOpen AccessTechnical pentachlorophenol: origin and analysis of base-insoluble contaminants. J R Plimmer J R Plimmer Search for more papers by this author Published:1 September 1973https://doi.org/10.1289/ehp.730541Cited by:13AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit FiguresReferencesRelatedDetailsCited by Johnson G (2017) Chlorinated Dioxin and Furan Congener Profiles from Pentachlorophenol Sources, Journal of Environmental Protection, 10.4236/jep.2017.86043, 08:06, (663-677), . Puplampu E and Dodoo D (2000) The photochemical mineralization of pentachlorophenol in a tropical marine environment, Journal of Photochemistry and Photobiology A: Chemistry, 10.1016/S1010-6030(00)00278-1, 135:1, (81-84), Online publication date: 1-Jun-2000. Gasiewicz T (1991) Nitro Compounds and Related Phenolic Pesticides Classes of Pesticides, 10.1016/B978-0-12-334163-1.50006-1, (1191-1269), . Bertrand M, Stefanidis S, Donais A and Sarrasin B (1986) Selective gas chromatographic analysis of chlorinated phenolic compounds using the nitrogen—phosphorus detector, Journal of Chromatography A, 10.1016/S0021-9673(01)87034-5, 354, (331-340), Online publication date: 1-Jan-1986. Kerkvliet N, Brauner J and Matlock J (1985) Humoral immunotoxicity of polychlorinated diphenyl ethers, phenoxyphenols, dioxins and furans present as contaminants of technical grade pentachlorophenol, Toxicology, 10.1016/0300-483X(85)90033-2, 36:4, (307-324), Online publication date: 1-Sep-1985. Shang-Zhi S and Duffield A (1984) Negative ion chemical ionization gas chromatography—mass spectrometry of some derivatives of tri-, tetra- and pentachlorophenols, Journal of Chromatography A, 10.1016/S0021-9673(01)87811-0, 284, (157-165), Online publication date: 1-Jan-1984. Slonecker P, Pyle J and Cantrell J (2002) Identification of polychlorinated dibenzo-p-dioxin isomers by powder x-ray diffraction with electron capture gas chromatography, Analytical Chemistry, 10.1021/ac00260a022, 55:9, (1543-1547), Online publication date: 1-Aug-1983. Halperin W, Honchar P and Fingerhut M (1982) Dioxin: An Overview, The American Statistician, 10.1080/00031305.1982.10482855, 36:3b, (285-289), Online publication date: 1-Aug-1982. Van Logten M, Gupta B, McConnell E and Moore J (1981) The influence of malnutrition on the toxicity of 2,3,7,8-tetrachlorodiobenzo-p-dioxin (TCDD) in rats, Toxicology, 10.1016/0300-483X(81)90018-4, 21:1, (77-88), Online publication date: 1-Jan-1981. Ervin H and McGinnis G (1980) Analysis of pentachlorophenol in waste water using high-performance liquid chromatography, Journal of Chromatography A, 10.1016/S0021-9673(00)85534-X, 190:1, (203-207), Online publication date: 1-Mar-1980. Parker C, Jones W, Matthews H, McConnell E and Hass J (1980) The chronic toxicity of technical and analytical pentachlorophenol in cattle, Toxicology and Applied Pharmacology, 10.1016/0041-008X(80)90098-8, 55:2, (359-369), Online publication date: 1-Sep-1980. Gebefügi I, Parlar H and Korte F (1979) Occurrence of pentachlorophenol in enclosed environments, Ecotoxicology and Environmental Safety, 10.1016/0147-6513(79)90017-4, 3:3, (269-300), Online publication date: 1-Sep-1979. Vermeer K, Risebrough R, Spaans A and Reynolds L (1974) Pesticide effects on fishes and birds in rice fields of Surinam, South America, Environmental Pollution (1970), 10.1016/0013-9327(74)90068-8, 7:3, (217-236), Online publication date: 1-Nov-1974. Vol. 5September 1973Metrics About Article Metrics Publication History Originally published1 September 1973Published in print1 September 1973 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.