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PubMed1989

Mechanisms of genetic variability in Halobacterium halobium: the purple membrane and gas vesicle mutations.

Several phenotypic variants of Halobacterium halobium arise spontaneously at extremely high frequencies (up to 1%) and are readily identified by inspection of bacterial colonies. Two mutant types, those lacking the buoyant gas vesicles or the photosynthetic purple membrane, have been studied in detail by phenotypic and molecular genetic analysis. In the wild-type NRC-1 strain, the bop gene, encoding the purple membrane protein bacterio-opsin, is found on the bacterial chromosome, while the gas vesicle protein genes, gvpA and gvpC, are present on pNRC100, a multicopy plasmid of approximately 150 kilobase pairs. The gvpA and gvpC genes are on a single transcription unit, while the major bop mRNA is monocistronic. Essentially all of the purple membrane deficient mutants contain insertion sequence (IS) elements into or upstream of the bop gene. Two elements, ISH 1 and ISH 2, account for most (80-90%) of the purple membrane mutations, but at least three other elements, ISH 23, ISH 26, and ISH S1, have also been implicated. The gas vesicle mutants are more heterogeneous, with many displaying partial phenotypes. Three major classes of gas vesicle mutants are distinguishable: class I and class III mutants are the result of large deletions in pNCR100; however, while class I mutants are partially gas vesicle deficient and contain a correspondingly reduced number of gvpAC operon copies, class III mutants contain no detectable copies of the gas vesicle genes and are essentially completely gas vesicle deficient. Class II mutants, like the purple membrane mutants, contain IS elements into or upstream of the gas vesicle genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Archaeal Proteins↗

PubMed1996

Genitourinary tract gas: imaging evaluation.

Gas-forming infections of the genitourinary tract may manifest as life-threatening conditions, often requiring aggressive medical and surgical management. Accurate interpretation of the radiologic studies is essential for early and accurate diagnosis of gas within the renal parenchyma or collecting system, bladder, uterus, and scrotum. Three distinct entities are associated with renal or perirenal gas: emphysematous pyelonephritis, emphysematous pyelitis, and gas-forming perirenal abscess. Gas in the bladder may occur secondary to emphysematous cystitis or a vesicoenteric fistula and must be differentiated from air introduced by means of instrumentation. Uterine gas usually indicates an underlying infection or a neoplasm. Gas in the scrotum is most commonly due to an infectious process or bowel herniation into the scrotal sac. Before institution of a specific therapeutic regimen, an effort should be made to establish the exact location of gas in the genitourinary tract. Plain radiography, including tomography, and ultrasonography are useful screening modalities. Although in some cases urography, barium enema studies, and other contrast material-enhanced studies enable a diagnosis to be made, in many patients computed tomography is the definitive diagnostic technique.

Adult↗

PubMed1999

Intravascular gas as an incidental finding at US after blunt abdominal trauma.

PURPOSE: To describe the occurrence and importance of intravascular gas at ultrasonography (US) during the initial examination of patients after blunt abdominal trauma. MATERIALS AND METHODS: Reports of all abdominal US examinations performed at one institution for blunt trauma from October 1995 through June 1996 were reviewed. The charts of patients with intravascular gas were examined to determine the mechanism of injury, associated findings, and clinical outcome. RESULTS: A total of 730 patients underwent abdominal US examinations during the 9 months of study; five had intravascular gas demonstrated. Two patients had portal venous gas, one had hepatic venous gas, and two had inferior vena caval gas. Four of the five patients were involved in motor vehicle accidents, and one had been assaulted. In patients in whom follow-up studies were obtained, there was no evidence of intravascular gas at US or computed tomography. No cause was found at imaging or clinical examination. CONCLUSION: Intravascular gas may occur as a transient incidental finding after blunt abdominal trauma.

Abdominal Injuries↗

PubMed1984

Measurements of gastric mucosal blood flow by hydrogen gas clearance.

The validity of the use of H2 gas clearance to measure gastric mucosal blood flow (GMBF) was investigated in the intact stomach of anesthetized dogs. With a modified, more sensitive platinum electrode, we were able to reduce the H2 gas concentration to a nonflammable gas mixture. GMBF was repeatedly measured when the dogs inhaled gas containing 100, 10, and 3-5% H2. GMBF measured using 100% H2 demonstrated close correlation with inhaled gases containing 10% H2 (r = 0.84, slope = 0.89) and 3-5% H2 (r = 0.91, slope = 0.88). At a nonflammable concentration of 3% H2, it was safe to add 20% O2 into the gas mixture. The addition of O2 into the inhaled gas eliminated the transient hypoxia noted otherwise. It was also possible to reduce the gas flow rate from 5-10 to 1-3 l/min. Regression analysis of GMBF determined by inhalation of 5% H2 at these flow rates revealed a significant linear correlation (r = 0.95, slope = 1.13). In 10 dogs GMBF determined by using these low concentrations of H2 at the low flow rates also showed a good agreement (r = 0.93, slope = 0.65) with that measured by radioactive microspheres. These two methods also demonstrated comparable changes in GMBF induced by intravenous infusion of histamine and vasopressin. It was concluded that, with the technique as modified in our laboratory, H2 gas clearance could be a safe and accurate tool for quantitating gastric mucosal blood flow.

Animals↗

PubMed2001

Mechanisms of intestinal gas retention in humans: impaired propulsion versus obstructed evacuation.

To explore the clinical role of intestinal gas dynamics, we investigated two potential mechanisms of gas retention, defective propulsion and obstructed evacuation. In healthy subjects, a gas mixture was continuously infused into the jejunum (4 ml/min) 1) during a 2-h control period of spontaneous gas evacuation and 2) during a 2-h test period either with impaired gut propulsion caused by intravenous glucagon (n = 6) or with obstructed (self-restrained) anal evacuation (n = 10) while anal gas evacuation, symptom perception (0-6 scale), and abdominal girth were measured. Impaired gut propulsion and obstructed evacuation produced similar gas retention (558 +/- 68 ml and 407 +/- 85 ml, respectively, vs. 96 +/- 58 ml control; P < 0.05 for both) and abdominal distension (8 +/- 3 mm and 6 +/- 3 mm, respectively, vs. 1 +/- 1 mm control; P < 0.05 for both). However, obstructed evacuation increased symptom perception (2.3 +/- 0.6 score change; P < 0.05), whereas gas retention in the glucagon-induced hypotonic gut was virtually unperceived (-0.4 +/- 0.7 score change; not significant). In conclusion, the perception of intestinal gas accumulation depends on the mechanism of retention.

Adult↗

PubMed1981

Exchanges of oxygen and carbon dioxide alter inert gas pattern in single-breath tests.

Concentration of inert gas in the lung is lowered when CO2 entrance exceeds O2 exit and is raised when O2 exit predominates. In air-breathing subjects who expire to residual volume, this "metabolic gas effect" often causes a rising N2 concentration when in fact there should be a terminal fall because of low N2 in apical regions. In single-breath tests, we compared the dilution of resident N2 with dilution of an inspired gas, Ne, to find the "ideal" inert gas concentration (due only to mixing of resident gas with inspired gas). The displacement from the ideal concentration vs. volume pattern depends on the timing of the breath, because early CO2 entrance gives way later to O2 exit. Sometimes observed patterns are above or below but parallel to the ideal, and sometimes the observed slope of phase III is steeper than ideal for N2 and flatter than ideal for Ne. In addition to phase III distortions, the metabolic gas effect sometimes also distorts phase IV height and the intersection between phases III and IV. The distortions depend strongly on absolute concentration of the indicator gas in the lung, so they are very small when "closing volume" maneuvers are done in the conventional manner. However, distortions can be large and misleading when single-breath maneuvers are done in unconventional ways.

Carbon Dioxide↗

PubMed1983

Gas transport during high-frequency ventilation.

During high-frequency small-volume ventilation (HFV), the transport rate of gas from the mouth to a lung region is a function of two conductances (conductance is the transfer rate of a gas divided by its partial pressure difference): regional longitudinal gas conductance along the airways (Grlongi) and gas conductance between lung regions (Ginter). Grlongi per unit regional lung (gas) volume [Grlongi/(Vr beta g)] was determined during HFV in 11 anesthetized paralyzed dogs lying supine. The distribution of Grlongi/(Vr beta g) was nearly uniform during HFV when stroke volumes were less than approximately two-thirds of the Fowler dead-space volume. By contrast, the distribution of Grlongi/(Vr beta g) was nonuniform when the stroke volume exceeded approximately two-thirds of the Fowler dead-space volume and the oscillation frequency was 5 Hz. Gas conductance along the airways per unit lung gas volume [average Glongi/(V beta g)], for the entire lung, increased with stroke volume at all frequencies, but for a given product of oscillation frequency and stroke volume, the average Glongi/(V beta g) was greater when stroke volume was large and oscillation frequency was low. The average Glongi/(V beta g) increased with frequency up to a maximal value; the frequency at which the maximum occurred depended on the kinematic viscosity of the inspired gas mixture.

Animals↗

PubMed1998

Partial liquid ventilation improves gas exchange and increases EELV in acute lung injury.

Gas exchange is improved during partial liquid ventilation with perfluorocarbon in animal models of acute lung injury. The specific mechanisms are unproved. We measured end-expiratory lung volume (EELV) by null-point body plethysmography in anesthetized sheep. Measurements of gas exchange and EELV were made before and after acute lung injury was induced with intravenous oleic acid to decrease EELV and worsen gas exchange. Measurements of gas exchange and EELV were again performed after partial liquid ventilation with 30 ml/kg of perfluorocarbon and compared with gas-ventilated controls. Oxygenation was significantly improved during partial liquid ventilation, and EELV (composite of gas and liquid) was significantly increased, compared with preliquid ventilation values and gas-ventilated controls. We conclude that partial liquid ventilation may directly recruit consolidated alveoli in the lung-injured sheep and that this may be one mechanism whereby gas exchange is improved.

Animals↗

PubMedDate not supplied

Gas absorption in the middle ear.

The middle ear (ME) pressure of alert and anesthetized rhesus monkeys was monitored by serial tympanograms in order to determine the gas absorption process in the ME cavity. During the four-hour observation period the ME pressure showed small, random fluctuations around zero pressure in the alert animals, whereas in the anesthetized animals, following an initial positive pressure phase, the ME pressure reached a plateau at an average pressure of -60 mm H2O. The ME gas composition was changed by air or oxygen gas politzerization in anesthetized animals to determine the effect of different initial gas compositions on the rate of absorption of the gas and on the magnitude of ME pressure. Politzerization with air and with oxygen gas resulted in average maximum ME pressures of -400 and -730 mm H2O, respectively. The experimental evidence suggested that the physiological composition of ME gases is nearly that of the surrounding environment and that the rate of gas absorption is low. When the gas composition of the ME is changed, the ME pressure decreases considerably. Based on these findings, a possible mechanism for the development of negative ME pressure is proposed.

Absorption↗

PubMed1999

Mastoid buffering properties: I. Gas partial pressures.

Differences in the gas partial pressures between the middle ear (ME) cavity and the blood are an important factor in ME gas economy. Differences in gas partial pressures between various regions of the ME-mastoid air cell system (ME-MACS) could play a role as well. To determine whether gas partial pressure differences do occur between various compartments in the ME, we measured the rate of gas diffusion from one compartment to another in both an artificial model and in the ME-MACS of human temporal bones. The rate of gas diffusion between various areas of the ME and the mastoid tip was found to be rapid, with a half-life on the order of 2 minutes (range 0.8 to 5.3 minutes). We suggest that this high diffusion rate prevents the buildup of significant differences in gas composition in the ME-MACS system, which can therefore be regarded as a homogeneous gas pocket.

Diffusion↗

PubMed2003

Relating landfill gas emissions to atmospheric pressure using numerical modelling and state-space analysis.

Landfill gas (CO2 and CH4) concentrations and fluxes in soil adjacent to an old, unlined Danish municipal landfill measured over a 48-hour period during the passage of a low-pressure weather system were used to identify processes governing gas fluxes and concentrations. Two different approaches were applied: (I) State-space analysis was used to identify relations between gas flux and short-term (hourly) variations in atmospheric pressure. (II) A numerical gas transport model was fitted to the data and used to quantify short-term impacts of variations in atmospheric pressure, volumetric soil-water content, soil gas permeability, soil gas diffusion coefficients, and biological CH4 degradation rate upon landfill gas concentration and fluxes in the soil. Fluxes and concentrations were found to be most sensitive to variations in volumetric soil water content, atmospheric pressure variations and gas permeability whereas variations in CH4 oxidation rate and molecular coefficients had less influence. Fluxes appeared to be most sensitive to atmospheric pressure at intermediate distances from the landfill edge. Also overall CH4 fluxes out of the soil over longer periods (years) were largest during periods with rapidly decreasing atmospheric pressures resulting in emission of large amounts of CH4 during short periods of time. This effect, however, was less significant for the CO2 fluxes.

Air Movements↗

PubMed2005

[The trial of simple gas analysis of tobacco smoke that can be used for medical education].

OBJECTIVE: The purpose of this study was to check a simple sampling and easy gas analysis of tobacco smoke for effective tobacco intervention in medical education. METHODS: The mainstream of tobacco smoke was sampled by a syringe (50 ml) at five, ten and twenty seconds. The extracted mainstream was moved to a commercial PET bottle (2000 ml), and measured with gas detector tubes. The sidestream, which rises from the tip of the cigarette, was collected into a commercial PET bottle for a duration of 30 or 60 seconds. Formaldehyde, acetaldehyde, ammonia, hydrogen cyanide, and nitrogen oxides (NO, NO2) in the tobacco smoke were measured. Then, these gasses in the tobacco smoke of four brands of cigarettes were compared. This trial was conducted in third-year medical students, and the changes in attitudes to smokers and tobacco itself were investigated. RESULTS: The method of sampling 50 ml for 5 seconds produced the highest concentration of each gas in the mainstream. The gas concentration in the sidestream increased as the sampling time increased. The gas concentration in mainstream of "Lucia" was the highest of the used four brands, and the gas concentrations in the sidestream of "Mild Seven Prime" were higher than those of the other brands. Many medical students obtained knowledge about the toxicity of smoking by this experiment study. CONCLUSION: We studied a simple sampling method of tobacco smoke, and gas analysis with gas detector tubes. This method is recommended for tobacco education and intervention in medical education.

Acetaldehyde↗

PubMed2005

The biological effects of high-pressure gas on the yeast transcriptome.

The aim of the present study was to examine the feasibility of DNA microarray technology in an attempt to construct an evaluation system for determining gas toxicity using high-pressure conditions, as it is well known that pressure increases the concentration of a gas. As a first step, we used yeast (Saccharomyces cerevisiae) as the indicator organism and analyzed the mRNA expression profiles after exposure of yeast cells to nitrogen gas. Nitrogen gas was selected as a negative control since this gas has low toxicity. Yeast DNA microarray analysis revealed induction of genes whose products were localized to the membranes, and of genes that are involved in or contribute to energy production. Furthermore, we found that nitrogen gas significantly affected the transport system in the cells. Interestingly, nitrogen gas also resulted in induction of cold-shock responsive genes. These results suggest the possibility of applying yeast DNA microarray to gas bioassays up to 40 MPa. We therefore think that "bioassays" are ideal for use in environmental control and protection studies.

Feasibility Studies↗

PubMed1988

Physiological significance of fetal blood gas changes elicited by different delivery postures.

We performed umbilical blood gas analysis for 130 pregnant women in sitting and for 50 in supine position immediately after their deliveries. To elucidate whether fetal blood gas changes were attributed to the maternal postures, we also carried out the maternal blood gas analysis during delivery (n = 145) and prior to the onset of labor (n = 100) in both positions. Blood gas values of the umbilical vein and artery in the sitting group were significantly higher in pH, PO2, base excess (BE) and oxygen saturation (SO2), and lower in PCO2 than those in the supine group. In contrast, maternal blood gas values (pH, PaCO2, PaO2 and SaO2) did not show significant differences between these two groups in both during delivery and before the onset of labor. Thus, the sitting delivery position can elicit physiologically more beneficial blood gas aspects in fetus compared with the conventional supine delivery position. Umbilical blood gas improvements induced by sitting delivery position do not appear to be a result of the maternal blood gas alteration, but appear to be mediated by other factors.

Carbon Dioxide↗

PubMed2005

Identification of gas emanated from human skin: methane, ethylene, and ethane.

We investigated whether methane, ethylene and ethane gas can be detected in gas emanating from human skin, which is called skin gas. Skin gas was collected with a homemade stainless-steel trap system, which was cooled with liquid nitrogen, and analyzed with a gas chromatograph fitted with a flame ionization detector (FID). Skin-gas samples were obtained by covering a hand for 30 min with a polyfluorovinyl bag in which pure helium gas was introduced. The bag, the trap system and GC were set up online to avoid any contamination by air. Methane, ethylene and ethane in skin gas were successfully collected at an average amount emanated for 30 min (from ten subjects) of 150 +/- 63, 20 +/- 11 and 17 +/- 8 [mean +/- SD] pg/cm2, respectively.

Adult↗

PubMed1981

Intrahepatic gas: differential diagnosis.

Twelve patients with intrahepatic gas were examined with diagnostic sonography. In nine of the patients, gas was distributed within the intrahepatic biliary ducts, and, in four, distal acoustic shadowing was identified. Three patients, including one who also had biliary tract gas, had gas within the liver parenchyma but outside the biliary tract. One of these patients had a gas-forming abscess, another a recent biopsy, and a third had a necrotic metastasis following intraarterial chemotherapy. A final patient showed an evanescent pattern of gas within the portal venous system. Sonography can identify the presence and distribution of gas within the liver. When biliary tract air is identified, the possibility of biliary tract dilatation, masked by sonographic shadowing, must also be considered. In addition, in the presence of intrahepatic gas, prominent shadowing may cause disruption of the normal hepatic parenchymal pattern and lead to misdiagnosis of parenchymal abnormalities. By coordinating sonographic findings with the clinical history, however, a useful differential diagnosis may be obtained.

Adult↗

PubMed1990

Estimating starch availability and protein degradation of steam-flaked and reconstituted sorghum grain through a gas production technique.

Five steam-flaked sorghum grain (SFSG) samples with bulk densities of 476, 412, 347, 309 and 283 g/liter made by adjusting tension between mill rollers and three reconstituted sorghum grain (RSG) samples with reconstitution times of 10, 20 and 30 d and a control sample were analyzed for gas production kinetics (rumen liquor fermentation) and enzymatic glucose release (amyloglucosidase). Protein degradation was estimated from 6-h gas production and residual ammonia in the liquid. Gas production followed first-order kinetics (r2 greater than .98; P less than .01) and was used to describe rate and extent of digestion kinetics. Rate of gas production increased as processing degree increased. The magnitude of increase in gas production, however, was much less for RSG than for SFSG. Linear relationships were observed between enzymatic glucose release and the gas production rate constant k as well as gas production at 4,6 and 8 h (r2 greater than .98; P less than .01). Protein degradation decreased with processing degree of SFSG but increased with reconstitution time. A technique based on 6-h gas production and residual ammonia in the liquid is proposed to estimate both ruminal starch availability and ruminal protein degradability for processed sorghum grain.

Animal Feed↗

PubMed1997

Neutral detergent fiber disappearance and gas and volatile fatty acid production during the in vitro fermentation of six forages.

Samples of unfractionated forage and isolated NDF from six forages were fermented in vitro, and NDF disappearance and gas and VFA production were measured over time. Rates based on each of these data sets were calculated using a one-pool logistic model. The rates of NDF disappearance and gas and VFA production did not differ within each forage. Gas and VFA production were linearly related to NDF digestion. Gas yield was .35 mL/mg (r2 = .92) of NDF digested for the isolated NDF. The amount of total VFA produced per milligram of NDF digested was more variable than gas (r2 = .72), with a slope of .01 mmol VFA/mg of NDF digested. The relationship between gas and VFA production was linear (mean slope of 1.43 mmol gas/mmol VFA, r2 = .69). The ratios of end products (gas and VFA) to NDF digestion and the ratio of acetate:propionate were variable during the first 8 h of fermentation but changed little after this time. Changes in the acetate: propionate ratio explained 23% of the variation in gas produced per millimole of total VFA detected.

Acetates↗