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At least 577 records · Page 32Linked to original sources
PubMed1997

[Behavior of ventilation parameters, gas exchange and blood gases during hemodialysis (HD), in a traction during which the bicarbonate concentration in dialysis fluid is raised to a level of 60 m Eq/l].

In 9 patients with chronic renal failure treated by HD with bicarbonate-35 mEq/l containing fluid, investigations of minute ventilation, breathing patterns and blood gases were done during 5 sequential HD. During the standard HD-bicarbonate 35 mEq/l, the disturbances of minute ventilation, breathing patterns and blood gases did not appeared. During the standard HD session, between 60 to 75 minute of HD, the concentration of bicarbonate was increased to 60 mEq/l. Increased VCO2, PaCO2 and PvCO2 was observed during this 15 minutes in 45 HD sessions. Analysis of each HD in 9 patients showed that during 22 HD the values of VE, VA, VCO2 and PvCO2 were increased in 75 minute of HD compared to values obtained in 60 minute of HD. This group of HD we called responders. The different situation was during the 23 HD-non-responders. The values of PaCO2 and PvCO2 were increased in 75 minute of HD and VE and VA were decreased in this time. We conclude, that in the group of responders the increase of VE, VA, VCO2 and PvCO2 was the positive reaction of the breathing center to high values of PaCO2 and PvCO2. Decrease of VE observed in 23 HD-non-responders suggest the depressive influence of CO2 on respiratory muscles in patients with uremia.

Adult↗
PubMed1999

Sensitivity and resolution in 3D NMR microscopy of the lung with hyperpolarized noble gases.

Three-dimensional magnetic resonance images of the guinea pig lung were acquired in vivo using hyperpolarized (HP) noble gases and radial projection encoding (PE). Results obtained with 3He (voxel size 17 microl) demonstrated high image quality showing airway structure down to the 5th or 6th generations. Signal-to-noise ratios (SNRs) of 129Xe images (voxel size 40 microl) were lower by about 1 order of magnitude as a consequence of the smaller gyromagnetic ratio, a more rapid relaxation in the gas reservoir, and lower polarization and isotope abundance. Comparison between experimentally obtained SNRs and results from calculations based on a model that accounts for the three-dimensional PE acquisition scheme and the non-equilibrium situation in HP gas imaging yielded excellent agreement for small flip angles. A theoretical examination of the potential resolution in HP gas MR microscopy of the lungs suggests that in vivo visualization of alveolar clusters distal to respiratory bronchioles may be possible.

Animals↗
PubMed2006

A new approach to the remediation of heavy metal liquid wastes via off-gases produced by Klebsiella pneumoniae M426.

When the off-gas from an aerobic culture of Klebsiella pneumoniae M426 grown in the absence of added heavy metals was passed through a solution of Hg(2+), Cd(2+), Pb(2+), or Cu(2+) a yellow-white (Hg), white (Cd, Pb), or blue (Cu) precipitate was formed. Metal removal from solution was >97% within 2 h at initial concentrations of (as metal): Hg, 8.5; Cd, 12.6; Pb, 7.8; Cu, 9.5 mg/mL. Mercury was removed from solution at pH 2 and in up to 1 M NaCl. Energy dispersive X-ray microanalysis (EDX) of the precipitates showed them to comprise metal, sulfur and carbon in the case of Hg, Cd, and Pb, and, in the case of Cd and Pb, also oxygen. The pH of the solution increased by 1-2 units at an initial pH of 7 and by 4-5 units at an initial pH of 2. In the case of cadmium and lead, the presence of crystalline metal carbonates and hydroxides was confirmed by X-ray powder diffraction (XRD) analysis and additional peaks were seen which could not be assigned to known compounds in the diffraction file database. In the case of copper, hydroxides, and a form of copper sulfate, were found. In the case of mercury the XRD patterns could not be assigned to any known compound, except for HgCl in the solution at the acidic initial pH. The absence of sharp peaks in the pattern for the Hg-precipitate was indicative of poorly crystalline, nanocrystalline or amorphous material. The unknown mercury compound, since it contained non-carbonate carbon, was suggested to be derived from a volatile organothiol in the gases evolved from the culture. Analysis of the culture head gas by GC-MS showed the presence of dimethyldisulfide as a likely precipitant. No sulfur compound was found using XRD analysis in the case of cadmium and lead, although EDX analysis suggested this as a major component and the lack of XRD pattern is evidence for a non-crystalline metal-organothiol. The exact chemistry of the new materials remains to be elucidated but metal precipitation via a biogenic organothiol is a potentially effective approach to the remediation of aggressive metal wastes.

Biodegradation, Environmental↗
PubMed2002

Sensing and transfer of respiratory gases at the fish gill.

The gill is both a site of gas transfer and an important location of chemoreception or gas sensing in fish. While often considered separately, these two processes are clearly intricately related because the gases that are transferred between the ventilatory water and blood at the gill are simultaneously sensed by chemoreceptors on, and within, the gill. Modulation of chemoreceptor discharge in response to changes in O(2) and CO(2) levels, in turn, is believed to initiate a series of coordinated cardiorespiratory reflexes aimed at optimising branchial gas transfer. The past decade has yielded numerous advances in terms of our understanding of gas transfer and gas sensing at the fish gill, particularly concerning the transfer and sensing of carbon dioxide. In addition, recent research has moved from striving to construct a single model that covers all fish species, to recognition of the considerable inter-specific variation that exists with respect to the mechanics of gas transfer and the cardiorespiratory responses of fish to changes in O(2) and CO(2) levels. The following review attempts to integrate gas transfer and gas sensing at the fish gill by exploring recent advances in these areas.

Animals↗
PubMed1994

The Ferguson principle and an analysis of biological activity of gases and vapors.

The Ferguson principle, that Pnar/PO (Pnar is the partial pressure of a series of compounds giving rise to a particular effect on a given system by a physical mechanism, and PO is the saturated vapor pressure of the liquid narcotic) is constant for a series of nonreactive narcotics or toxicants in a given system, is examined and shown to have no thermodynamic basis, contrary to the position of Brink and Posternak. Conditions under which Pnar/PO might be expected to be roughly constant, as an empirical observation, are set out and it is shown that such an observation is consistent with a receptor area in which the liquid narcotic solubilities are roughly constant. An interpretation of relationships between agonist descriptors and biological effects is carried out with three simple biological models. It is shown that the biological potency of nonreactive gases and vapors can be controlled either by an equilibrium between the agonist in the gas phase and the agonist in a receptor or by an equilibrium between the agonist in the gas phase and the agonist in a receptor phase. It is further shown that with the solvation equation of Abraham, solvents can be chosen that mimic the chemical properties of the receptor or receptor phase. For the example of upper respiratory tract irritation of male Swiss OF1 mice, such solvents include N-formylmorpholine, a trialkylphosphate, and wet octanol, but not water itself.

Chemistry, Physical↗
PubMed1994

Hydrogen bonding. 30. Solubility of gases and vapors in biological liquids and tissues.

The general solvation equation log L = c + rR2 + pi H2 + a alpha H2 + b beta H2 + l log L16 has been used to analyze the solubility of solute gases and vapors, as log L values, in water, blood, and a variety of other biological fluids and tissues. The explanatory variables are R2, the solute excess molar refraction; pi H2, the solute dipolarity/polarizability; alpha H2 and beta H2, the solut hydrogen-bond acidity and basicity; and log L16, where L16 is the solute Ostwald solubility coefficient of hexadecane. The obtained coefficients then serve to characterize the biological phase as follows: r + s is the phase dipolarity/polarizability, a is the phase hydrogen-bond basicity, b is the phase hydrogen-bond acidity, ald l is the phase lipophilicity. In addition to characterization of phases, the equation can be used to determine quantitatively solute/phase interactions and predict further log L values. A similar equation in which McGowan's characteristic volume, Vx, replaces the log L16 descriptor can be used to analyze partitions between phases. For example, water/phase and blood/phase partition coefficients are analyzed, and the analysis leads again to coefficients that characterize phases and to the prediction of partition coefficients.

Blood↗
PubMed2002

MRI of the lungs using hyperpolarized noble gases.

The nuclear spin polarization of the noble gas isotopes (3)He and (129)Xe can be increased using optical pumping methods by four to five orders of magnitude. This extraordinary gain in polarization translates directly into a gain in signal strength for MRI. The new technology of hyperpolarized (HP) gas MRI holds enormous potential for enhancing sensitivity and contrast in pulmonary imaging. This review outlines the physics underlying the optical pumping process, imaging strategies coping with the nonequilibrium polarization, and effects of the alveolar microstructure on relaxation and diffusion of the noble gases. It presents recent progress in HP gas MRI and applications ranging from MR microscopy of airspaces to imaging pulmonary function in patients and suggests potential directions for future developments.

Animals↗
PubMed1993

An assay for carbonic anhydrase activity and reactions that produce radiolabeled gases or small uncharged molecules.

An assay procedure for carbonic anhydrase activity is described. Unique to this method is the use of radiolabeled bicarbonate and a reaction vessel with a gas-permeable membrane. The method detects 14CO2 production directly and can be used at room temperature and with solutions buffered over a wide pH range. Assays are rapid (5-10 s), discounting elution and scintillation counting time. The equipment required is simple and inexpensive, marking the method ideal for routine determinations of carbonic anhydrase activity. The method can also be applied to other reactions that liberate radioactive CO2, other labeled gases, or small unchanged, labeled molecules.

Animals↗
PubMed1993

Permanent gases inside healthy and microbially infected cotton fruit during development.

Permanent gases inside developing cotton fruit (Gossypium hirsutum L.) were, by weight, 46% nitrogen, 29% oxygen, 4% argon and 20% carbon dioxide, whereas plant canopy air assayed at 73% nitrogen, 25% oxygen, 2% argon and 0.3% carbon dioxide. Light exposure, fruit age, and mild infection (Erwinia) had no compositional effect but aggressive infection (Aspergillus) raised carbon dioxide content to 31% by weight and correspondingly lowered oxygen to 17%. Respiration with oxygen replenishment except during aggressive infection accounted for the fruit gas compositions.

Fruit↗
PubMed2000

Modeling protein-small molecule interactions: structure and thermodynamics of noble gases binding in a cavity in mutant phage T4 lysozyme L99A.

The complexes of phage T4 lysozyme L99A with noble gases have been studied by molecular dynamics simulation. In a long simulation of the complex with one Xe atom, the structure was found to undergo global conformation change involving a reversible opening and closing of the entrance to the substrate-binding site, during which the conformations of the N and C-terminal domains varied little. The distributions of Xe positions sampled in dynamics simulations were refined in terms of anisotropic Gaussian distributions via least-squares minimization of the difference between Fourier transforms. In addition, molecular transformation simulations have been applied in order to calculate the binding free energies of Xe, Kr and Ar relative to a standard state at a pressure of 1 bar. A single bound Xe is found to assume an equilibrium distribution over three adjacent preferred sites, while in a two-Xe complex, the two Xe atoms preferentially occupy two of these. The positions of the three sites agree closely with the positions of bound Xe determined in the refined crystal structure of a complex formed at a pressure of 8 bar Xe, and the calculated affinities agree well with the observed partial occupancies. At a pressure of 8 bar, a mixture of one-Xe and two-Xe complexes is present, and similarly for complexes with Kr and Ar, with single occupancy relatively more prevalent with Kr and Ar. (Binding of a third Xe atom is found to be quite unfavorable.) A comparison with simulation results for the binding of benzene to the same site leads to the conclusion that binding of Xe within cavities in proteins is common because of several favorable factors: (1) Xe has a large atomic polarizability; (2) Xe can be applied at a relatively high pressure, i.e. high chemical potential; (3) an unfavorable entropic term related to the need to orient the ligand in the binding site is absent. Finally, it is found that the model's binding energy of a water molecule in the cavity is insufficient to overcome the unfavorable binding entropy.

Amino Acid Substitution↗
PubMed1977

[An independent gas chromatographic procedure for measuring the composition of gases (author's transl].

The volume fraction of gas mixtures may be measured gas chromatographically by application of the 100% method, provided they can be separated. In case of gases it is not necessary to calibrate with another method. The specific character of the detector signals can be eliminated by measurements with pure components. The procedure is compared with the Scholander method. In case of O2/N2 mixtures the results agree within reproducibility, but in case of O2/CO2/N2 mixtures a systematic deviation of the CO2 fractions to smaller values is found as concerns the Scholander method. A gas mixture with 5.6 Vol% CO2 shows a difference of approximately 0.3 Vol%. The gas chromatographic method is almost 100 times as sensitive as the Scholander method. High fractions may be measured without problems and the method is not restricted to O2 and CO2.

Carbon Dioxide↗
PubMed1975

Solubility of various inert gases in rat skeletal muscle.

For the determination of solubility coefficients, isolated rat abdominal muscles were equilibrated at 37 degrees C with various inert gases saturated with water vapor. After rapid transfer into a closed chamber containing room air the amount of gas extracted from the sample by diffusion was measured by gas chromatography. Corrections for unextracted gas and for gas lost during the transfer of the sample were applied. The following mean values for the solubility coefficients, in mumol-1(-1)-torr(-1), were found: chloro-difluoro-methane (Freon 22), 56.0; acetylene, 55.5; nitrous oxide, 27.7; methane, 2.42; hydrogen, 1.13; helium, 0.608; sulfur hexafluoride, 0.559. The relationships between solubility in tissue, in water and in olive oil are discussed.

Abdominal Muscles↗
PubMed1990

Perfluorocarbon gases in the suprachoroidal space of rabbit eyes.

Four perfluorocarbon gases were injected into the suprachoroidal space of rabbit eyes. Temporary, expanding choroidal detachments were observed in all cases. Depending on the amount of gas injected (0.1 or 0.2 cc, respectively), they lasted 1 or 2 days in the case of perfluoromethane, 4 or 5 days with perfluoroethane, 6 or 8 days with perfluoropropane, and 9 or 11 days with perfluoro-N-butane. Due to its longevity, perfluoro-N-butane appeared to be the most suitable gas for temporary "buckling" of the suprachoroidal space in rabbit eyes.

Animals↗
PubMed1992

The closed chamber technique--uptake, endogenous production, excretion, steady-state kinetics and rates of metabolism of gases and vapors.

The "closed chamber technique" (CCT) is presented. It allows investigation of pharmacokinetics of volatile substances in vivo in animals and in man and in vitro using tissue fractions. During the exposure period only the atmospheric concentrations of the substance are measured. The concentration-time data obtained are pharmacokinetically analyzed by a two compartment model describing uptake, endogenous production and excretion of the unchanged substance and its metabolic elimination. Using this model, pharmacokinetics of ethylene have been determined in rats and man. For both species, the results compared well with an estimation based on an allometric species scaling. Furthermore, the applicability of CCT is demonstrated in vivo on several other gases and vapors of solvents, e.g. trichloroethylene and 1,1,1-trichloroethane, and in vitro on 1,2-epoxybutene-3.

Animals↗
PubMed2000

Influence of gases on intraperitoneal immunity during laparoscopy in tumor-bearing rats.

Laparoscopy has been associated with metastases to abdominal wall wounds. In addition, many recent experimental studies suggest that laparoscopy is associated with increased tumor dissemination. It is possible that immune or metabolic disturbances due to the use of a pneumoperitoneum could contribute to this problem. To investigate this possibility, we studied the effect of two insufflation gases and gasless laparoscopy on in vivo peritoneal macrophage function and intraperitoneal pH in an experimental model. A carcinoma was implanted into the flank of 32 experimental rats that underwent laparoscopic surgery in one of four treatment groups: anesthesia alone, gasless laparoscopy, helium insufflation, and CO2 insufflation. Intraperitoneal pH was monitored during surgery, and peritoneal macrophage function was determined 3 days after surgery by harvesting peritoneal macrophages and then examining their ability to produce tumour necrosis factor-alpha (TNF-alpha). CO2 insufflation was associated with a consistent fall in intraperitoneal pH and a significant reduction in TNFalpha production. These findings did not occur in the other study groups. The results of this study demonstrate that CO2 insufflation results in depressed intraperitoneal macrophage activity. It is possible that it is mediated by pH changes. In addition, it could be a contributing factor to the development of port-site metastases. Further studies are needed to determine whether the factors identified act during clinical surgery.

Animals↗
PubMed2001

Ventilation, gill perfusion and blood gases in dourado, Salminus maxillosus Valenciennes (teleostei, characidae), exposed to graded hypoxia.

The dourado, Salminus maxillosus, is an active and migratory teleost found in lotic waters of Southern Brazil. We have studied the relationships of gas transport in dourado to the specific ecophysiology of this-species. Measurements were performed of blood gases, O2 uptake, gill ventilation and perfusion at normoxia and various levels of hypoxia. Thus, the study aimed at a detailed assessment of the causes of O2 transport failure, using recent models for gas transport in vertebrates. Oxygen uptake was maintained down to a critical water partial O2 pressure of 42 mmHg, below which it markedly decreased. This could be explained based on ventilatory and cardiovascular responses: Ventilation increased sufficiently to match decreases of water O2 partial pressure during moderate hypoxia (partial pressure of O2 > 42 mmHg) but failed to meet O2 demands below this value. Likewise, the cardiovascular responses were insufficient to maintain an adequate transport below moderatelevels of hypoxia. Thus, combined failure of ventilation and blood gas transport account for the abrupt decreases of O2 transport. The species proved highly vulnerable to hypoxia, which is consistent with the normally well-aerated habitat and the active mode of life of the species.

Animals↗
PubMed2004

Gases and organic solvents in urine as biomarkers of occupational exposure: a review.

A brief review of urine analysis in studies of occupational exposure to volatile organic compounds and gases is provided. Analysis of exhaled breath for volatile compounds does not have a long history in occupational medicine. A number of studies has been undertaken since the 1980s, and the methods are well enough accepted to be put forward as biological equivalents of threshold limit values (TLVs) for some volatile organic compounds (VOCs) such as acetone; methanol; methyl ethyl ketone (MEK); methyl isobutyl ketone (MIBK); tetrahydrofurane; dichloromethane. In the last 20 years many scientific articles have shown that the urinary concentrations of unchanged solvents are correlated with environmental exposure and could be used for biological monitoring. The use of urine analysis of unchanged solvents in occupational applications is not yet widespread. Nonetheless, in the short time since its application, a number of important discoveries has been made, and the future appears bright for this branch of analysis. In this paper, the basic concepts and methodology of urine analysis are briefly presented with a critical revision of the literature on this matter. The excretion mechanisms of organic solvents in urine are discussed, with regard to biological variability, and the future directions of research are described.

Biomarkers↗
PubMed1989

A colorimetric method for the enzymatic analysis of gases: the determination of ethanol and formaldehyde vapors using solid alcohol oxidase.

A novel enzymatic approach to the direct determination of ethanol vapors in the gas phase is described. The system is composed of alcohol oxidase, peroxidase, and the color indicator 2,6-dichloroindophenol dispersed on microcrystalline cellulose (avicel). Simple devices are developed for the semiquantitative determination of ethanol in the breath. The devices are optimized to produce a sharp color change at a set time of 1 min for ethanol concentrations above the legal limit for driving (kinetic method) or a stable final color after 5 min (equilibrium method). Such color changes are detectable by simple visual observation. Using TLC plastic sheets and a transmittance densitometer, the system can also be used as a quantitative method for the determination of ethanol or formaldehyde vapors. Dehydrated enzymes may be useful for the analysis of hazardous gases.

2,6-Dichloroindophenol↗