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At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

[Central hemodynamics, gas exchange, and gas oxygen-transporting function in combined anesthesia using xenon during operations under extracorporeal circulation].

The advantages of xenon include its good hemodynamic profile and possible cardioprotective properties. The investigation was undertaken to study central hemodynamics, lung gas exchange, and blood oxygen-transporting function in xenon anesthesia in patients operated on under extracorporeal circulation (EC). Fifteen patients aged 41-69 years operated on for coronary heart disease were examined. The severity of the patients' baseline status corresponded to NYHA functional classes I to IV. The duration of an operation was 251 +/- 10 min; that of EC was 97 +/- 5 min; aortic ligation lasted 59 +/- 3 min. After induction of anesthesia with propofol via concentration-regulated infusion (CRI) and with fentanyl, delivery of xenon was initiated at concentrations of 47 +/- 1 to 52.5 +/- 1%, which was mixed with oxygen. Propofol CRI was used during EC. After the latter, xenon was inhaled at concentrations of 47.7 +/- 1 to 53.3 +/- 1%. The mean arterial pressure (BP(mean)), heart rate (HR), and cardiac index (CI) remained unchanged during xenon anesthesia in the preperfusion period. After EC during xenon anesthesia, CI significantly rose with a moderate increase in HR without inotropic support. BP(mean) was moderately, but statistically significantly decreased. Prior to and following EC, there were no changes in the values of blood oxygen-transporting function.

Adult↗
PubMedDate not supplied

Confirmation of identity by gas chromatography/tandem mass spectrometry of sulfathiazole, sulfamethazine, sulfachloropyridazine, and sulfadimethoxine from bovine or swine liver extracts after quantitation by gas chromatography/electron-capture detection.

Four sulfonamide veterinary drug residues were quantitated by electron-capture detection (ECD) after separation by gas chromatography (GC). The identities of sulfathiazole (ST), sulfamethazine (SM), sulfachloropyridazine (SCP), and sulfadimethoxine (SDM) were confirmed in bovine or swine liver residues by tandem mass spectrometry (MS/MS). Bovine or swine liver tissues were extracted by using either the Tishler or the Manuel-Steller cleanup. The methylated residues containing ST, SM, SCP, and SDM were separated by GC prior to MS/MS daughter ion analysis. Control tissue, control tissue fortified at 0.1 ppm, and incurred tissue residues at approximately 0.1 ppm were analyzed for these 4 sulfonamides. A Finnigan Model TSQ-46 operating in the chemical ionization mode was used to perform the MS/MS daughter ion experiments. The identities of all 4 sulfonamides were confirmed in a single GC/MS/MS analysis.

Animals↗
PubMedDate not supplied

Determination of pyrantel in swine liver by flame ionization gas chromatography and confirmation by gas chromatography/mass spectrometry.

During an evaluation of the gas chromatography/mass spectrometry (GC/MS) confirmatory procedure of Lynch and Bartolucci for pyrantel residues in swine tissues, we developed a GC flame ionization method for quantitating pyrantel residues in extracts of swine liver. The method was subjected to trial principally in the laboratories of Biospherics, Inc., using control liver, fortified control liver, and incurred liver tissue samples. Although the method does not meet all of the current Food and Drug Administration criteria, it compares favorably to the official determinative method. Portions of the same extract can be used for quantitation and for GC/MS confirmation, true recoveries appear to be slightly higher, and an internal standard is not required. The precision of this method equals or exceeds that of the official determinative method.

Animals↗
PubMed1986

Chemotaxonomy of selected species of the Actinobacillus-Haemophilus-Pasteurella group by means of gas chromatography, gas chromatography-mass spectrometry and bioenzymatic methods.

Instrumental analytical and bioenzymatic methods were used to differentiate between species of the Actinobacillus-Haemophilus-Pasteurella group. Long-chain fatty acids were analysed directly with gas chromatography (GC) without derivatization. GC of trifluoroacetylated whole-cell methanolysates was a rapid method for differentiation. Cellular sugars were more suitable for differentiation than fatty acids. D-Glycero-D-mannoheptose, the major localization of which was lipopolysaccharide, distinguished H. aphrophilus from A. actinomycetemcomitans, H. paraphrophilus, H. influenzae type b, P. haemolytica, P. multocida, and P. ureae. GC of single colonies, which is a new chemotaxonomic method, was preferable to GC of liquid-grown cells. Lysozyme-and EDTA-induced bacteriolysis and reduction of methylene blue by cellular hydrogenase served as additional criteria for differentiation.

Actinobacillus↗
PubMedDate not supplied

Capillary column gas chromatographic determination of ethyl carbamate in alcoholic beverages with confirmation by gas chromatography/mass spectrometry.

A method is described for determining ethyl carbamate at low microgram/kg levels in several types of alcoholic beverages by capillary column gas chromatography with Hall electrolytic conductivity detection and confirmation by mass spectrometry. Samples are diluted to obtain a uniform concentration of ethanol (ca 10%) then saturated with NaCl and extracted with methylene chloride. Extracts are evaporated to a small volume and injected in ethyl acetate solution for chromatographic analysis. The method was evaluated by 5 laboratories, 4 employing the Hall detector and one using mass spectrometric detection. Overall between-laboratory mean percent recoveries were: wine, 85.3 +/- 21.0% coefficient of variation (CV) (spiking level 20-45 micrograms/kg); sherry, 83.8 +/- 16.1% CV (spiking level, 81-142 micrograms/kg); whiskey, 79.5 +/- 13.9% CV (spiking level 127-190 micrograms/kg); and brandy, 85.0 +/- 12.5% CV (spiking level 297-446 micrograms/kg). Mass spectrometric results agreed well with the Hall results for all commodities. Detection limits were about 5 micrograms/kg for the Hall detector and about 0.5 microgram/kg for mass spectrometric detection.

Alcoholic Beverages↗
PubMed1995

Effects of venous gas microemboli on pulmonary gas transfer function.

Dynamic lung volumes and flows, slope of phase III of the single breath oxygen test (delta-N2), closing volume (CV), and transfer factor for carbon monoxide (TICO) were measured before and 1 h after an air dive in a hyperbaric chamber to a pressure of 0.49 MPa for 40 min. Six divers had a bottom time of 20 min and a rate of decompression of 50 kPa x min-1, and six divers had a bottom time of 24 min and a rate of decompression of 100 kPa x min-1. Decompression stops were 5 min at 0.16 MPa and 10 min at 0.13 MPa for both groups. As control exposure they were breathing O2 at atmospheric pressure for 40 min. The dive and control exposure were done on different days within 1 wk, in random order. Doppler ultrasound monitoring for venous gas microemboli (VGM) was done during the first hour after the dive. VGM were detectable in all six divers with the fast decompression rate and in one subject with the slow rate (P < 0.01). In the subjects having VGM there was a significant reduction in TICO of -5.9 +/- 4.4% compared with -0.5 +/- 3.4% after the control exposure (P = 0.034). In the five subjects without detectable VGM, the changes in TICO were -2.8 +/- 3.7% and 0.2 +/- 3.8%, respectively. There were no significant changes in dynamic lung volumes and flows, CV, or delta-N2. A reduction in TICO may reflect effects of VGM after dives in which the effect of O2 exposure is negligible.

Adult↗
PubMedDate not supplied

[Gas exchange and gas transport in deeply cooled rats during slow and rapid warming using artificial pulmonary ventilation].

Artificial lung ventilation (ALV) was shown to restore the gas exchange in rats following their cooling to brain temperature 17.0-17.6 degrees C. However, the ALV proved ineffective if applied in 22.1 +/- 2.1 min after cessation of breathing. Fast warming up of the animals increased oxygen consumption and carbon dioxide production, and caused a less obvious metabolic acidosis in the rats in the course of recovering from hypothermia.

Animals↗
PubMed1976

[Bouquet qualification of wines by gas chromatography. 1. Experimental method for gas phase analysis].

In the course of our investigations we tried to find a method for the bouquet qualification of wines by gas chromatography. For this purpose, instead of aroma research studies requiring complex equipment and laboursome precise laboratory work, we developed a method for head space analysis functioning with simple experimental instruments and being sufficiently fast for serial routine work. By the method developed, the head space of a great number of samples taken from 7 different wine-types have been successfully examined. Errors of measurement were checked by standard deviation analysis and the values obtained (3,23%) were found satisfactory. According to the above, our head space analysis may provide a satisfactory basis for elaborating a method for the instrumental bouquet qualification of wines.

Acetaldehyde↗
PubMed2003

Kinetics of gas-phase hydrogen/deuterium exchange and gas-phase structure of protonated phenylalanine, proline, tyrosine and tryptophan.

Site-specific rate constants for the gas-phase hydrogen/deuterium (H/D) exchange of four, three, five and five hydrogen atoms in protonated phenylalanine (Phe), proline (Pro), tyrosine (Tyr) and tryptophan (Trp), respectively, were determined from matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICRMS) experiments with D(2)O, D(2)S, and CH(3)OD as deuterating agents. No H/D exchange was observed with D(2)S. For exchange with both CD(3)OD and D(2)O, which is about ten times slower in the latter, results indicate for all compounds protonation of the alpha-amino group in agreement with theoretical results. Also, with both reagents, all compounds exchange at the COOH site more than ten times faster than at the protonation site, with OH and NH sites of Tyr and Trp, respectively, exchanging slowest. The observation of H/D exchange despite the high differences in proton affinities between the amino acids and deuterating agent exceeding 200 kJ mol(-1) is in agreement with lowering of the barrier for proton transfer through hydrogen bonding proposed by Lebrilla and coworkers.

Amino Acids↗
PubMed1987

The vitreous after C3F8 gas instillation: long-term histologic findings after spontaneous reabsorption of the gas in rabbit eyes.

Perfluoropropane gas (C3F8) was injected intravitreally into rabbit eyes to displace the vitreous. Histologic examination by light and scanning electron microscopy revealed the vitreous material slowly expanded up to a nearly normal configuration during a follow-up of 6 months. Neither posterior vitreous detachment nor liquefaction of the vitreous could be observed.

Animals↗
PubMed1996

Gas generation and preconcentration coupled to gas phase molecular absorption spectrometry: a powerful tool for the simultaneous determination of analytes forming volatile compounds.

Different methods for a simultaneous determination of several analytes forming volatile compounds at room temperature are described. The main steps of these methods are: continuous generation, collection in a cryogenic trap, revolatilization, measurement of the volatile compounds by Gas Phase Molecular Absorption Spectrometry and resolution by multi-wavelength methods. Several mixtures containing 2, 3 or 4 components have been studied: 1) elements forming covalent hydrides; 2) arsenic organometallic compounds forming volatile gases with a similar structure to arsine; and 3) sulphur species that can evolve volatile compounds. Under the optimum conditions obtained for each mixture, detection limits range from 0.8 ng/mL (dimethylarsinic acid) to 2 microg/mL (SCN(-)).

Journal Article↗
PubMed2006

Effect of buffer gas on the fluorescence yield of trapped gas-phase ions.

We investigated the dependence of three different gases, helium, argon, and nitrogen, on the fluorescence signal intensity of rhodamine 6G cations in the gas phase. The method is based on laser-induced fluorescence of ions trapped in a Fourier transform ion cyclotron mass spectrometer. We found that the use of helium results in the highest fluorescence signal, while no fluorescence was detected when using argon under the same conditions.

Journal Article↗
PubMed2001

Gas and air embolization during hysteroscopic electrosurgical vaporization: comparison of gas generation using bipolar and monopolar electrodes in an experimental model.

STUDY OBJECTIVE: To compare the composition of gases generated by bipolar hysteroscopic vaporizing electrodes using electrolyte-rich medium (normal saline) with those of monopolar vaporizing electrodes using nonelectrolytic medium (1.5% glycine). DESIGN: In vitro study (Canadian Task Force classification II-1). SETTING: Laboratory. INTERVENTION: Fresh morbid bovine cardiac muscle was fully immersed in normal saline for the bipolar vaporizing electrode and 1.5% glycine for the monopolar vaporizing electrode. Standard hysteroscopic electrodes were activated at usual and maximum power outputs from radiofrequency electrosurgical generators appropriate for each system. The gases generated were captured and analyzed by gas chromatography and fast Fourier transform. MEASUREMENTS AND MAIN RESULTS: Gaseous by-products of electrosurgical vaporization of test tissues largely consisted of hydrogen, carbon monoxide, and carbon dioxide. The composition of gases generated by hysteroscopic monopolar and bipolar electrodes in this laboratory model appear to be similar. CONCLUSION: These gases are all highly soluble in serum. This observation suggests that emboli of gaseous by-products of electrosurgery are unlikely to have an adverse impact on patients. On the other hand, air emboli, largely composed of relatively insoluble nitrogen, are more likely to result in clinically significant cardiopulmonary events.

Animals↗
PubMed2002

Improved tert-butyldimethylsilylation gas chromatographic/mass spectrometric detection of nerve gas hydrolysis products from soils by pretreatment of aqueous alkaline extraction and strong anion-exchange solid-phase extraction.

In the analysis of tert-butyldimethylsilyl derivatives (IBDMS) of alkyl methylphosphonic acids (RMPA) and methylphosphonic acid (MPA), from soils by gas chromatography/mass spectrometry (GC/MS), the detection yields are generally low, due to the suppression of TBDMS derivatization by the soil matrix components and the adsorption of RMPA and MPA to the soils. An ion-exchange pretreatment of the aqueous soil extract can be used to overcome the former factor by removing interfering compounds. A pretreatment method is described for improving the detection yields due to the latter factor, using an alkaline extraction procedure. The recovery was estimated quantitatively using capillary electrophoresis. The soil samples tested included volcanogenous immature soils and showed a low aqueous extraction recovery and GC/MS detection yields. The inclusion of sodium hydroxide in the extraction solvent dramatically increased the recovery. Using a 0.1 M sodium hydroxide solution, the recovery was in excess of 68%. Interfering components were removed from the alkaline soil extract by solid-phase extraction of the acids on a silica-based strong anion exchanger. The alkaline soil extract was neutralized with hydrofluoric acid and applied to the cartridge in the fluoride form. After washing with water, MPA and RMPA could be eluted with methanolic ammonia nearly quantitatively. Using the established pretreatment method, MPA and RMPA were detected from all the soil samples in more than 67% yield.

Journal Article↗
PubMed2000

Effects of Gas-Phase Basicity on the Proton Transfer between Organic Bases and Trifluoroacetic Acid in the Gas Phase: Energetics of Charge Solvation and Salt Bridges.

The unimolecular dissociation pathways and kinetics of a series of protonated trimer ions consisting of two organic bases and trifluoroacetic acid were investigated using blackbody infrared radiative dissociation. Five bases with gas-phase basicities (GB) ranging from 238.4 to 246.2 kcal/mol were used. Both the dissociation pathways and the threshold dissociation energies depend on the GB of the base. Trimers consisting of the two most basic molecules dissociate to form protonated base monomers with an E(0) ~ 1.4 eV. Trimers consisting of the two least basic molecules dissociate to form protonated base dimers with an E(0) ~ 1.1-1.2 eV. These results indicate that the structures of the trimers change as a function of the GB of the basic molecule. The predominant structure of the protonated trimers consisting of the two most basic molecules is consistent with a salt bridge in which both of the basic molecules are protonated, and the trifluoroacetic acid molecule is deprotonated, whereas the predominant structure of the protonated trimers consisting of the two least basic molecules are consistent with charge-solvated complexes in which the proton is shared. The structure of the trimer consisting of the base of intermediate basicity is less clear; it dissociates to form primarily protonated base dimer, but has an E(0) ~ 1.2 eV. These results are consistent with the structure of this trimer as a salt bridge, but the resulting dissociation A(-). BH(+) product does not appear to be stable as an ion pair in the dissociative transition state.

Journal Article↗
PubMed2005

Comprehensive density functional theory study on serine and related ions in gas phase: conformations, gas phase basicities, and acidities.

Density functional theory (DFT) calculations have been performed to investigate the gas-phase conformations of serine and its three related ions (serineH(+), serine(-), and serine(2-)). The full ensemble of possible conformations, 324 conformations for serine, 108 for serineH(+), 162 for serine(-) and 54 for serine(2-), were first surveyed at B3LYP/6-31G level, and then the obtained unique conformations were further refined at B3LYP/6-311+G level. From full optimizations, 74 unique conformations for seine, 14 for serineH(+), 11 for serine(-), and 4 for serine(2-) were located, and their relative energies were also determined at B3LYP/6-311+G level. Atoms in molecules (AIM) analysis was carried out to establish rigorous definition of hydrogen bonds. Six types of intramolecular H-bonds in conformers of serine, six types in serineH(+), three types in serine(-), and two types in serine(2-) were identified within the framework of AIM theory and their relative strengths were determined based on topological properties at bond critical points (BCPs) of H-bonds. The intramolecular H-bonds were demonstrated to play an important role in deciding the relative stability of conformations of amino acids and the related ions. The enthalpies and Gibbs free energies of protonation and deprotonation reactions of serine and its related ions were calculated at B3LYP/6-311+G//B3LYP/6-31G, and B3LYP/6-311+G//B3LYP/6-311+G level. The calculated results are both in excellent agreement with the experimental data. We demonstrate in this study that B3LYP is an efficient and accurate method to predict the thermochemical and structural parameters of amino acids and the related ions.

Journal Article↗