The role of the acquisition methods in the analysis of the non-steroidal anti-inflammatory drugs in Danube River by gas chromatography-mass spectrometry.

In this paper authors describe a GC-MS acquisition study, relating to the most common, non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, ketoprofen and diclofenac. As novelties to the field, for the trimethylsilyl (TMS) oxime ester derivatives of NSAIDs, at first, a tandem mass spectrometric (MS/MS) acquisition method has been developed, and, also for the first time, the three acquisition techniques, the full scan (FS), the selective ion monitoring (SIM) and the currently optimized MS/MS ones, have been compared: all three in parallel, under strictly the same derivatization/instrumental conditions, both from model solutions and from the Danube River samples. Critical evaluation of the three acquisition protocols was collated on their analytical performances and validated with the same characteristics like the six point calibration curve, the relative standard deviation percentages (RSD%) of parallel tests, the limit of quantitation (LOQ) and the instrumental limit of quantitation (ILQ) values. Data of six point calibration (r(2)>or=0.997) and RSD% (average: 5.8 RSD%) values proved to be independent on the acquisition methods, while, LOQ and ILQ values furnished considerable differences. Decreasing LOQ data, (expressed in ng/L concentrations) were obtained in the FS, SIM, MS/MS line for ibuprofen (1.0, 0.43, 0.41), naproxen (1.1, 1.0, 0.42), ketoprofen (2.6, 1.0, 0.49) and diclofenac (1.4, 0.41, 0.21), respectively. The same trend was determined in terms of the ILQ values. The practical utility of the optimized MS/MS technique was confirmed by the quantitation of the NSAID contents of the Danube River samples, determined by all three acquisition techniques. Results obtained confirmed the primary importance of the MS/MS acquisition method, even in comparison to the SIM one: avoiding the extreme overestimation of the ibuprofen (approximately 100%) and ketoprofen (approximately 400%) concentrations in the Danube River samples.

Multiresidue analysis of pollutants as their trimethylsilyl derivatives, by gas chromatography-mass spectrometry.

This paper reports a multiresidue analysis procedure which permits the identification and quantification of sixty-three water-soluble pollutants. Subsequent to their solid-phase extraction (SPE) enrichment, analyses of species have been carried out from one solution, by a single injection, as their trimethylsilyl-oxime ether/ester derivatives, by gas chromatography-mass spectrometry, within 31min. Based on our optimized extraction, derivatization and mass fragmentation studies separation have been performed in the total ion current mode, identification and quantification of compounds have been carried out on the basis of their selective fragment ions. Including various pharmaceuticals, benzoic acid, its substituted species, different aromatic carboxylic acids, cholic acids, unsaturated and saturated fatty acids, aliphatic dicarboxylic acids, as well as synthetic pollutants of various origins (2,4-di-tert-butylphenol, different phthalates). Standard compounds were added to 500 mL effluent wastewater samples, at three concentrations (1-5 microg/L, 5-10 microg/L and 10-20 microg/L). Recoveries, using the Waters Oasis cartridges performing extractions at pH 2, pH 4 and pH 7 proved to be the optimum at pH 4 (average recoveries (94.5%), except for cholesterol (10%), paracetamol (18%) and 2,5-dihydroxybenzoic acid (25%). Carbamazepine could be recovered at pH 7, only. Responses, obtained with derivatized standards proved to be linear in the range of 4-80 microg/L levels. Limit of quantitation values varied between 0.92 ng/L (4-hydroxyphenylacetic acid) and 600 ng/L (dehydrocholic acid) concentrations. One of the most important messages of this work is the confirmation of the origin of blank values. It was shown that contaminants, mainly 2,4-di-tert-butylphenol, different phthalates and fatty acids, are sourced both from the reagents and mainly from the SPE procedure, independent on the cartridge applied. Reproducibilities, characterized with the relative standard deviations (RSDs) of measurements, varied between 0.71% and 10%, with an average of 4.38% RSD. The practical utility of the method was shown by the identification and quantification of the pollutant contents of Hungarian influent and effluent wastewaters (for six consecutive months and that of the Danube River for 2 months).

Gas chromatography-mass spectrometry of the trimethylsilyl (oxime) ether/ester derivatives of cholic acids: their presence in the aquatic environment.

This paper presents a derivatization, mass fragmentation study relating to the most common six cholic acids, such as cholic, lithocholic, chenodeoxycholic, ursodeoxycholic, 3-hydroxy,7-ketocholanic and dehydrocholic acids, identified and quantified as pollutants in the aquatic environment at the first time. Derivatizations have been performed with the two-step process (1: oximation, 2: silylation) varying the time and temperature of both reactions. Optimum responses have been obtained after 30 min oximation with hydroxylamine.HCl and 90 min silylation with hexamethyldisilazane and trifluoroacetic acid at 70 degrees C. Fragmentation patterns of the trimethylsilyl (oxime) ether/ester derivatives of all six cholic acids provided the theoretically expected, fully derivatized compounds. Reproducibility/linearity of derivatives calculated on the basis of the corresponding selective fragment ions, characterized by the relative standard deviation percentages of measurements, proved to be < or =4.9 (RSD%). The practical utility of the method was shown by the identification and quantification of cholic acids as pollutants in the aquatic environment. Subsequently to a solid phase extraction study varying the pH of extractions (pH 2, pH 4 and pH 7), applying the OASIS cartridges, it has been confirmed that the recoveries for all six cholic acids are acceptable, varying between 77% and 104%, and are independent on the pH. The total cholic acid content of a Hungarian wastewater plants' influent wastewater varied between 184 microg/L and 356 microg/L, while the Danube rivers' cholic acid content was 4.1 microg/L, only.

Identification and quantification of ibuprofen, naproxen, ketoprofen and diclofenac present in waste-waters, as their trimethylsilyl derivatives, by gas chromatography mass spectrometry.

This paper reports a derivatization, mass fragmentation study relating to the most common, non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, ketoprofen and diclofenac, identified and quantified in the aquatic environment. Derivatizations have been performed with four silylation reagents in order to select the most proper one, taking into account analytical and financial points of view, equally. The tested reagents were N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA), N-methyl-N-tert-butyldimethylsilyl-trifluoroacetamide (MTBSTFA) and for this purpose at the first time, hexamethyldisilazan (HMDS)+trifluoroacetic acid (TFAA). Varying derivatization time and temperature, taking into consideration chemical and financial advantages, HMDS+TFAA proved to be the optimum selection. Responses of derivatives have been compared, as a function of the ionization technique (external/internal ionization), as well as on the treatment of compounds' selective fragment ions (SFIs): (i) extracting the corresponding, characteristic m/z masses from TIC elutions and (ii) from SIM elutions, in parallel. Reproducibilities of measurements, expressed in relative standard deviation percentages (R.S.D.%), including the nanogram and the low picogram levels of injected derivatives, provided an average between 0.93 R.S.D.% and 4.11 R.S.D.%. NSAIDs' enrichment was performed with solid-phase extraction (SPE), applying the Oasis HLB (Waters) cartridges: recoveries in the 1-6 microg L(-1) range varied between 84% and 111%, with an average reproducibility of 6.4 R.S.D.%. The utility of the optimized derivatization method is presented, on monthly basis, by the identification and quantitation of the ibuprofen, naproxen, ketoprofen and diclofenac content of the influent and effluent waste-water samples obtained from a Hungarian waste-water treatment plant.

Different roles for RhoA during neurite initiation, elongation, and regeneration in PC12 cells.

The goal of the present study was to characterize the effects of RhoA at different stages of nerve growth factor (NGF)-induced neuronal differentiation in the PC12 model. This comparative analysis was prompted by previous studies that reported apparently opposite effects for Rho in different models of neuronal differentiation and regeneration. PC12 cells were transfected with activated V14RhoA or dominant negative N19RhoA under the control of either a constitutive or a steroid-regulated promoter. Upon exposure to NGF, V14RhoA cells continued to proliferate and did not extend neurites; however, they remained responsive to NGF, as indicated by the activation of extracellular signal-regulated kinases. This inability to differentiate was reversed by C3 toxin and activation of cyclic AMP signaling, which inactivate RhoA. N19RhoA expression led to an increase in neurite initiation and branching. In contrast, when the RhoA mutants were expressed after NGF priming, only the rate of neurite extension was altered; V14RhoA clones had neurites approximately twice as long, whereas neurites of N19RhoA cells were approximately 50% shorter than those of appropriate controls. The effects of Rho in neurite regeneration mimicked those observed during the initial stages of morphogenesis; activation inhibited, whereas inactivation promoted, neurite outgrowth. Our results indicate that RhoA function changes at different stages of NGF-induced neuronal differentiation and neurite regeneration.

Inactivation of Rho signaling pathway promotes CNS axon regeneration.

Regeneration in the CNS is blocked by many different growth inhibitory proteins. To foster regeneration, we have investigated a strategy to block the neuronal response to growth inhibitory signals. Here, we report that injured axons regrow directly on complex inhibitory substrates when Rho GTPase is inactivated. Treatment of PC12 cells with C3 enzyme to inactivate Rho and transfection with dominant negative Rho allowed neurite growth on inhibitory substrates. Primary retinal neurons treated with C3 extended neurites on myelin-associated glycoprotein and myelin substrates. To explore regeneration in vivo, we crushed optic nerves of adult rat. After C3 treatment, numerous cut axons traversed the lesion to regrow in the distal white matter of the optic nerve. These results indicate that targeting signaling mechanisms converging to Rho stimulates axon regeneration on inhibitory CNS substrates.

Lysophosphatidic acid-induced neurite retraction in PC12 cells: control by phosphoinositide-Ca2+ signaling and Rho.

The endogenous phospholipid mediator lysophosphatidic acid (LPA) caused growth cone collapse, neurite retraction, and cell flattening in differentiated PC12 cells. Neurite retraction was blocked by cytochalasin B and ADP-ribosylation of the small-molecular-weight G protein Rho by the Clostridium botulinum C-3 toxin. LPA induced a transient rise in the level of inositol 1,4,5-trisphosphate, and retraction was blocked by inhibitors of phospholipase beta. Repeated application of LPA elicited homologous desensitization of the Ca2+ mobilization response. The activation of the phosphoinositide (PIP)-Ca2+ second messenger system played a permissive role in the morphoregulatory response. Blockers of protein kinase C--chelerythrine, a myristoylated pseudosubstrate peptide, staurosporine, and depletion of protein kinase C from the cells by long-term phorbol ester treatment--all diminished neurite retraction by interfering with LPA-induced Ca2+ mobilization, which was required for the withdrawal of neurites. A brief 15-min treatment with 4 beta-phorbol 12-myristate 13-acetate also blocked retraction and Ca2+ mobilization, by inactivating the LPA receptor. Inhibition of protein tyrosine phosphorylation by herbimycin diminished retraction. Although activation of the PIP-Ca2+ second messenger system appears necessary for the Rho-mediated rearrangements of the actin cytoskeleton, bradykinin, which activates similar signaling events, failed to cause retraction, indicating that a yet unidentified novel mechanism is also involved in the LPA-induced morphoregulatory response.

Lysophosphatidic acid-induced neurite retraction in PC12 cells: neurite-protective effects of cyclic AMP signaling.

Effects of the cyclic AMP second messenger system were studied on the retraction of neurites elicited by the phospholipid mediator lysophosphatidic acid (LPA) in PC12 cells. LPA stimulation inhibited adenylyl cyclase, indicating that the LPA receptor couples to the heterotrimeric Gi proteins. However, pertussis toxin or expression of dominant negative Ras did not prevent neurite retraction. In contrast, cholera toxin, forskolin, and application of dibutyryl-cyclic AMP prevented neurite retraction. The neurite-protective effect of forskolin was blocked by Rp-adenosine 3',5'-phosphorothioate. Forskolin and dibutyryl-cyclic AMP both failed to protect neurites in A126-1B2 and 123.7 cells, which lack cyclic AMP-activated protein kinase. Data indicate that elevation of cyclic AMP levels triggers a cyclic AMP-activated protein kinase-dependent mechanism that opposes the functioning of the morphoregulatory signaling activated by LPA. ADP-ribosylation of Rho by the Clostridium botulinum C-3 toxin in 123.7 cells caused neuronal differentiation, indicated by neurite extension, and blocked LPA-induced neurite retraction. LPA activates Gq- and Gi-linked signaling in parallel; therefore, a morphoregulatory signaling network hypothesis is proposed versus the simplistic approach of a signaling pathway. The signaling network integrates the receptor-activated individual, sequential, and parallel signaling events into an interactive network whose individual components may fulfill required and permissive functions encoding the cellular response.