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PubMed1992

Function and biosynthesis of gas vesicles in halophilic Archaea.

The proteinaceous gas vesicles produced by various microorganisms including halophilic Archaea are hollow, gas-filled structures with a hydrophobic inner and a hydrophilic outer surface. The structural components of gas vesicles and their biosynthesis are still under investigation; an 8-kDa polypeptide appears to be the major constituent of the gas-vesicle envelope. Genetic analysis of the halobacterial gas-vesicle synthesis revealed an unexpected complexity: about 14 genes organized in three transcription units are involved in gas-vesicle structure, assembly, and gene regulation. Here we describe the comparison of three different genomic regions encoding gas vesicles in Halobacterium salinarium (p-vac and c-vac regions) and Haloferax mediterranei (mc-vac region) and speculate on the function of the gene products involved in gas-vesicle synthesis.

Amino Acid Sequence↗
PubMed1994

Bronchial response to breathing dry gas at 3.7 MPa ambient pressure.

In diving, pulmonary mechanical function is limited by the increased density of the gas breathed. Breathing cold and dry gas may cause an additional increase in airways resistance. We have measured forced vital capacity, forced expired volume in 1 s (FEV1) and forced midexpiratory flow rate (FEF25%-75%) before and after breathing dry or humid gas at 29-32 degrees C during a standardized exercise intensity on a cycle ergometer at an ambient pressure of 3.7 MPa. The atmosphere was a helium and oxygen mixture with a density of 6.8 kg.m-3. Six professional saturation divers aged 26-37 years participated in the study. There were no significant differences in convective respiratory heat loss between the exposures. The mean evaporative heat loss was 67 W (range 59-89) breathing dry gas and 37 W (range 32-43) breathing humid gas, corresponding to water losses of 1.7 g.min-1 (range 1.5-2.2) and 0.9 g.min-1 (range 0.8-1.1), respectively. There was a significant reduction in FEV1 of 4.6 (SD 3.6)% (P < 0.05), and in FEF25%-75% of 5.8 (SD 4.7)% (P < 0.05) after breathing dry gas. There were no changes after breathing humid gas. By warming and humidifying the gas breathed in deep saturation diving bronchoconstriction may be prevented.

Adult↗
PubMed1984

Appearance of gas-containing gallstones on sonography and computed tomography.

The diagnostic features of gas-containing gallstones on sonography and CT in 6 patients and the in vitro findings in 30 gas-containing gallstones are analyzed. On plain abdominal radiography, the stellate appearance of gas collections, though infrequent, is quite characteristic. On real-time sonography, gas-containing calculi can be observed to float within bile. Furthermore, larger gas collections within gallstones can be identified since they produce high-level echoes in the acoustic shadow of the stone, probably due to sound reverberation. These phenomena, although interesting, do not interfere with the high accuracy of sonography in the detection of gallstones. CT detects gallstones when their density differs from that of bile. Due to high-density resolution, even minute gas collections are displayed and can reveal gallstones with an isodense matrix. However, under routine abdominal scanning conditions (8 mm collimation), the gas collections often appear round or ovoid, because spatial resolution is inferior to that on plain radiography. This fact should be considered in the differential diagnosis of gas collections in the gallbladder region found on CT.

Adult↗
PubMed1995

Response to intraluminal gas in irritable bowel syndrome. Motility versus perception.

Our aim was to evaluate the response to intraluminal gas in irritable bowel syndrome and to determine whether this response was consequent upon disordered motility or altered perception. We evaluated 10 patients who satisfied the clinical criteria for the diagnosis of irritable bowel syndrome and 10 healthy controls. An eight-lumen perfused catheter assembly was positioned to monitor motor activity in the duodenum and proximal jejunum; a separate side port in the distal duodenum permitted gas infusion. Subjects recorded symptoms of abdominal pain, bloating, and nausea throughout the study, using a visual analog scale. Following an overnight fast and a 60-min basal recording period in the fasted state, subjects ate a standard meal; 60 min later, "sham" gas was administered for 20 min, followed by the actual infusion of nitrogen gas at 40 ml/min. Subjects were randomized to receive atropine (7 micrograms/kg) or placebo intravenously during the period of actual gas infusion. Patients with irritable bowel syndrome described more pain (score, mean +/- SE, control versus irritable bowel: 0.22 +/- 0.16 vs 1.65 +/- 0.5, P < 0.01) and nausea (0.25 +/- 0.21 vs 1.45 +/- 0.64, P < 0.04) during sham gas; motility indices were similar in both groups. During active gas, irritable bowel syndrome patients reported more pain (0.40 +/- 0.39 vs 2.94 +/- 1.16, P < 0.03); motility indices at all sites were similar in both groups. Symptom severity in irritable bowel syndrome subjects randomized to receive atropine was similar to control subjects during active gas infusion; motility indices were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Promotion of gas bubble formation by ingested nuclei in the ciliate, Tetrahymena pyriformis.

Cells of the ciliate Tetrahymena pyriformis were suspended with carmine or graphite particles or with Halobacterium gas vesicles, all of which promote bubble formation in aqueous suspensions when tested with 10 atm and above (0.1-0.5 X 10(7) Pa) (carmine and graphite) or 25 atm and above (gas vesicles) of nitrogen supersaturations. All three particles were ingested, but only the gas vesicles promoted intracellular gas bubble formation if the cells containing them were nitrogen or methane saturated in a slow stepwise fashion prior to rapid decompression. Cell rupture did not occur until gas saturation pressures greater than 25 atm were used; this suggests that the ciliate pellicle and cytoplasm cannot resist the mechanical forces of an expanding gas phase induced by decompression from between 25 and 50 atm and thus provides an estimate of the physical strength of these cellular components. The inability of the ingested carmine, graphite, and collapsed gas vesicles to induce intracellular gas bubble formation suggests that the phagocytic process somehow altered them. This procedure may thus provide a tool for the study of early events in the digestive processes of ciliates.

Animals↗
PubMed1998

Temporary vitreous gas tamponade by perfluoromethylcyclopentane.

Using perfluoromethylcyclopentane (FMCP; US patent no. 5,441,989, granted 1995) we have developed a new vitreous gas tamponade in a rabbit model that allows complete filling of the vitreous cavity without vitrectomy and without a significant increase in intraocular pressure. In humans this procedure would allow the blockage of inferior and posterior retinal holes without special positioning of the patient. Perfluoromethylcyclopentane (FMCP), a liquid perfluorocarbon with a boiling point slightly above body temperature, is injected in minute volumes into the vitreous cavity, where it vaporizes, thereby filling a gas volume approximately 500 times its liquid volume. FMCP was injected into the midvitreous in six rabbits (six eyes). After 2-3 days a complete gas tamponade was achieved in three eyes. Two eyes showed 75-90% filling, and one eye was filled only 50% with gas. Intraocular pressure was highest in the completely filled eyes, ranging from 26.6 to 38.8 mmHg. In all eyes the maximum expansion of the gas bubble lasted 2 weeks. One eye developed a retinal detachment. All eyes showed transient subcapsular cataracts. The results of this study showed that intravitreal injection of FMCP, a new perfluorocarbon liquid, results in a complete gas tamponade of the vitreous cavity which lasts 2 weeks without severe intraocular pressure rise and without vitrectomy. This procedure will be especially useful for eyes that have retinal detachment from inferior or posterior retinal holes. Injection of a conventional gas such as SF6 or C3F8 usually does not block retinal holes in inferior or posterior locations without tedious positioning and risk of (transient) glaucoma. Since the mechanism of transition of FMCP from liquid to gas in the vitreous is poorly understood, we are currently studying FMCP vaporization in an in vitro eye model.

Animals↗
PubMed1999

Humidified gas prevents hypothermia induced by laparoscopic insufflation: a randomized controlled study in a pig model.

BACKGROUND: This experimental study evaluated whether humidification of warmed insufflated CO2 during laparoscopic procedures would resolve the problem of laparoscopy-induced hypothermia. METHODS: Changes in core temperature were quantified over a 3-h period of high-flow CO2 insufflation in a randomized, controlled trial of five pigs. Each animal was anesthetized and studied on three occasions under standardized conditions, acting as its own control by insufflation with no gas compared with insufflation by cool dry gas and heated humidified gas. RESULTS: Core temperatures after insufflation with heated humidified gas were no different from that of controls. After insufflation with cool dry gas, core temperature dropped by 1.8 degreesC, which was significantly more than the 0.6 degreesC drop experienced by control animals and those insufflated with heated humidified gas (p < 0.01). Calculations of the heat expended in evaporation of water were also performed. The temperature drop due to water evaporation alone in pigs insufflated with cool dry gas was calculated to be 1.5 degreesC. This compares favorably with the measured 1.2 degreesC temperature difference between these animals and the control group. CONCLUSIONS: The majority of heat lost during laparoscopic insufflation is due to water evaporation, and laparoscopic hypothermia may be prevented by using heated and humidified gas insufflation.

Analysis of Variance↗
PubMed2006

Role of the jejunum versus ileum on intestinal gas dynamics during a balanced meal in healthy subjects.

Under physiological conditions, the human gut adapts intestinal gas propulsion and evacuation to prevent intestinal gaseous complaints In this study we aimed to determine influences of the jejunum versus ileum on intestinal gas dynamics during a balanced meal. Paired studies were randomly performed with seven women and three men, ages 28-42. A mixed liquid meal was infused (1 kcal/min) into the duodenum. After 30 min, gas was infused (12 ml/min) into the jejunum or ileum for 150 min. Gas expulsion was measured, and perception and girth changes were assessed. Postprandial intestinal gas propulsion was uneventful and recovery complete, with -7+/- 58 and -92+/- 44 ml final intestinal gas retention for jejunal and ileal gas infusion, respectively. Neither significant differences in abdominal perception nor changes in abdominal girth were seen. During a balanced meal, intestinal gas is effectively propulsed aborally, and this does not depend on the site of the small intestinal stimulation.

Adult↗
PubMed2004

Treatment of Excessive Intestinal Gas.

Symptoms of excessive intestinal gas may be related to eructation, excessive or odoriferous gas evacuation, and/or abdominal symptom attributed to gas retention. Patients with aerophagia and excessive eructation can be usually retrained to control air swallowing, but if present, basal dyspeptic symptoms may remain. Patients with excessive or odoriferous gas evacuation may benefit from a low-flatulogenic diet. In patients with gas retention due to impaired anal evacuation, anal incoordination can be resolved by biofeedback treatment, which also improves fecal retention, and thereby reduces the time for fermentation. Other patients complaining of abdominal symptoms that they attribute to intestinal gas, probably have irritable bowel syndrome or functional bloating, and their treatment options specifically targeting gas-related symptoms basically include prokinetics and spasmolytics. There is no consistent evidence to support the use of gas-reducing substances, such as charcoal or simethicone.

Journal Article↗
PubMed1995

Radiological decompression of bowel gas and return of mediastinal shift in congenital diaphragmatic hernia: a signal for surgical repair?

The objective of this study was to document the pattern of bowel gas decompression and mediastinal shift in infants with congenital diaphragmatic hernia (CDH) before delayed surgical correction. The setting was the Neonatal Intensive Care Unit, Royal Alexandra Hospital, Edmonton. The design was a retrospective review of radiographs and charts of all infants with CDH between January 1990 and December 1993. Bowel gas in the upper and middle one third of the hemithorax was classified as grade III and grade II, respectively. Bowel gas in the lower one third of the hemithorax or absent bowel gas was classified as grade I. All the infants showed partial return of the contralateral shift in the mediastinum toward the midline when comparing the admission chest radiographs with the immediate preoperative films. Complete return of the mediastinum to normal (using the first postoperative radiograph as the gold standard) occurred in all but 1 of the 10 infants on extracorporeal membrane oxygenation (ECMO) (90%) and 7 of 13 (54%) of conventionally treated infants (P = .12). At the time of the first radiograph, a similar proportion of non-ECMO and ECMO infants (61% versus 70%, respectively) had either grade II or III bowel gas patterns. By 72 hours none of the non-ECMO-treated infants (who were paralyzed with muscle relaxants) had bowel gas in the middle and upper one third of the hemithorax. In contrast, 66% of infants on ECMO still had a grade II bowel gas pattern at 72 hours (P < .05), with 4 infants showing an actual increase in bowel gas after discontinuation of muscle relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Case-Control Studies↗
PubMed1979

Trapped gas at maximum lung volume in intact isolated rat lungs.

Excised rat lungs were ventilated with air in a liquid filled plethysmograph that was enclosed in a large pressure chamber, C(B). The lungs were inflated then deflated by removing or adding saline to the plethysmograph while the trachea was attached to a cannula extending through the plethysmograph base. In this system, tracheal pressure, Pao, was equal to gas pressure inside C(B). The gas pressure was held constant at either ambient pressure (Pamb), Pamb + 350 Torr, or Pamb - 350 Torr. When excised lungs were ventilated slowly from their atelectatic state for 10 inflation-deflation cycles with Pao equal to any one of the three pressures, an equivalent amount of gas was trapped in the lungs. If after 10 cycles, however, lungs containing trapped gas were inflated and held at maximum lung volume, the trapped gas spaces could be made to expand in response to rarefaction or compression of the tracheal gas. The amount of expansion and contraction of the trapped gas spaces demonstrates that trapped gas is likely trapped between menisci of a foam that occlude the alveoli or small airways.

Animals↗
PubMed1986

Mechanisms of gas loss from normal and hyperinflated excised guinea pig lungs.

Increased pulmonary gas trapping was produced by in vivo inhalation exposures of guinea pigs to bronchoconstrictive aerosols. Both normal (filtered air-exposed) and hyperinflated excised lungs lost about 20% of their initial volume by 4 h; gas loss was more rapid during the first 60 min (early period) than the following 180 min (late period). During both periods, absolute rates of gas loss were positively correlated (P less than 0.001) with initial excised lung gas volumes (ELGVs). Tracheal foam movement was observed in most of the hyperinflated lungs, but only during the early period. Occlusion of the trachea reduced gas loss during the early period, but not the late. Gas volumes increased in lungs of animals exposed to SF6:O2 (tracheas tied), and decreased most rapidly in lungs of animals exposed to He:O2 (tracheas tied). Our results suggest that a major part of the early gas loss from excised guinea pig lungs occurs via the trachea and may be influenced by airway foam or menisci formation. After 60 min, airways may be closed and gas loss may occur via transpleural diffusion.

Airway Resistance↗
PubMed1989

The influence of fresh gas flow and inspiratory/expiratory ratio on tidal volume and arterial CO2 tension in mechanically ventilated surgical patients.

The relative importance of fresh gas flow and inspiratory/expiratory ratio in determining delivered tidal volume and PaCO2 was studied in anesthetized adult patients ventilated with a fixed ventilator bellows volume. The fresh gas flows studied were 2, 6, and 10 L/min, and inspiratory/expiratory ratio was either 1:2 or 1:4.5. Bellows volume and respiratory rate were held constant throughout the study. At the lowest fresh gas flow and smallest inspiratory/expiratory ratio, PaCO2 was 43 +/- 2 mm Hg. The PaCO2 decreased progressively and significantly with each increase in fresh gas flow during ventilation with either inspiratory/expiratory ratio setting. PaCO2 averaged 30 +/- 3 during ventilation with the highest fresh gas flow and largest inspiratory/expiratory ratio. As fresh gas flow increased, PaCO2 and tidal volume changed to a significantly greater degree in response to changes in inspiratory/expiratory ratio. These data demonstrate that altering either fresh gas flow or inspiratory/expiratory ratio can produce clinically significant perturbations in PaCO2 and tidal volume during anesthesia. These perturbations occur even if bellows volume is held constant. Furthermore, changes in inspiratory/expiratory ratio will affect these parameters to a greater degree as fresh gas flow is increased.

Adult↗
PubMed2003

Analysis of natural gas: the necessity of multiple standards for calibration.

The importance of natural gas as an international trading commodity and the cost to consumers has made the accuracy of determinations for the components of natural gas very important. Pricing of natural gas is based on the heating value of the gas determined from either calorimetry measurements or calculations based on individual component concentrations determined by gas chromatography (GC). Due to the expense of accurate calibration standards, many analysts and laboratories will use a single calibration standard to perform natural gas determinations. Therefore, the purpose of this study was to determine whether an analyst could accurately measure the components of natural gas, in particular methane, using a single standard, or whether a suite of standards is necessary to calibrate the analytical instrument. A suite of eight gravimetric primary standards was prepared covering a concentration range for methane of 64-94 mol%, with uncertainties of +/-0.05% relative (95% confidence interval). These natural gas primary standards also contained nitrogen, carbon dioxide, ethane, propane, iso-butane, n-butane, iso-pentane, n-pentane, and n-hexane with varying concentrations from 0.02 to 14%. A single analytical method was used in which only the amount of sample injected onto the column was altered. The results show that when injecting a 0.5 ml sample volume a second-order regression through the standards is necessary for the determination of methane. The results for nitrogen, ethane and propane also show the same trend. Only those individual standards whose methane concentration is within 1% of the test mixture predicted a concentration within 0.05% of the regression value. Those individual primary standards whose methane concentration is different by more than +/-1% of the test mixture predicted values differing by +/-0.5 to +/-2.0% from the regression value. These differences lie well outside the predicted concentration uncertainty interval of +/-0.20%. A smaller sample volume, 0.1 ml, resulted in a set of data that could be fit using linear regression. Each of the eight primary standards individually predicted the methane in the test mixture to be within +/-0.11% of the predicted value from linear regression. The data confirm that it is imperative to fully characterize the analytical system before proceeding with an analysis.

Calibration↗
PubMed2005

Suicide by carbon monoxide from car exhaust-gas in Denmark 1995-1999.

In the period 1995-1999 there were 388 car exhaust-gas suicides in Denmark. Of these 343 (88.4%) were men and 45 (11.6%) were women, the average age being 47 years. The car exhaust-gas suicides made up 9.3% of all suicides in Denmark in the period. The corresponding rate was 11.7% for men and 3.7% for women. In rural areas a larger part of all suicides were committed with car exhaust-gas compared to the more densely populated areas. Mental disease was diagnosed in 124 (32.0%) cases. A suicide note was found in 165 (42.5%) cases. A hose was fitted to the exhaust pipe in 334 (86.1%) cases. Of these the 234 (60.3%) occurred outside, typically in a forest area, while 76 (19.6%) occurred in a closed garage. All the 54 (13.9%) cases with no hose fitted to the exhaust pipe occurred in a garage. Seven (1.8%) victims were found in a burning or burnt-out car, where the following investigation revealed that it was actually a car exhaust-gas suicide. Carboxyhemoglobin was measured in 26 (6.7%) victims. In two of these victims no carboxyhemoglobin was found, as they had survived for some time after the poisoning. The average saturation of the remaining victims was 67%, the lowest saturation being 20% and the highest being 84%. In the period 1969-1987 the number of car exhaust-gas suicides in Denmark increased from 50 to approximately 190 per year and the rate of car exhaust-gas suicides compared to all suicides increased from approximately 5% to approximately 13%. In 1987-1999 these figures decreased from approximately 190 to 63 per year and from 13% to approximately 8%. During these 30 years the number of passenger cars in Denmark doubled, which explains the increase in car exhaust-gas suicides during 1969-1987. A possible explanation for the decrease in 1987-1999 is the introduction of the catalytic converter, which was made mandatory in 1990. We anticipate that car exhaust-gas suicides will continue to decrease in numbers, as more cars are equipped with catalytic converters.

Adolescent↗
PubMed2004

Gas-vapor bubble nucleation--a unified approach.

In a solution which is saturated with gas near the superheat limit, one might expect a bubble formed from both dissolved gas and vapor molecules to appear. The integration of the surface-energy concepts, that are postulated on completely different physical bases for gas and vapor bubble formation is a major issue. In this paper, we reformulate gas and vapor bubble nucleation by a scaling transformation, which turns the surface energy for the bubble formation from both dissolved gases and vapor molecules to the translational energy of a molecule, (3/2)kBT. With this unified approach, one could estimate the dissolved gas effect on the superheat limit of the liquid. The driving force and the molecular volume are important quantities for determining the number of gas and vapor molecules composed of a critical cluster. This approach, of course, can predict pure gas bubble formation, as well as pure vapor bubble formation, as limiting cases. Also, this approach makes it possible to find that the possible occurrence of gas bubble nucleation by dissolved gases prevents measuring the theoretical superheat limit of water at atmospheric pressure, 300 degrees C.

Journal Article↗
PubMed2005

The influence of additives and metal rods on the nucleation and growth of gas hydrates.

A major technical issue in industrial applications of the gas hydrate storage process is to develop a practical means for rapid hydrate formation. In this paper, the formation processes of HCFC141b (CH(3)CCl(2)F) gas hydrate in a column of water with additives and with an iron rod that was placed in the center of the column have been studied to reveal the influence of the additives and the iron rod on the nucleation and growth of the gas hydrate. The water solution column, in a cylindrical glass container, was placed in a thermostatic bath at 274.15-280.15 K and under atmospheric pressure. The experimental results show that, compared to the pure water and the HCFC141b system, the properly placed iron rod combined with proper concentrations of lauryl sodium sulfonate, lauryl sodium sulfate, and sodium dodecylbenzenesulfonate-6 considerably reduces the hydrate nucleation time and promotes formation speed. The formation rate of HCFC141b gas hydrate increases with increasing concentration of sodium dodecylbenzenesulfonate-6 in the water solution, while the addition of potassium oxalate monohydrate in water has shown no effect on the nucleation and growth of HCFC141b gas hydrate. Under the experimental conditions, both the anion surfactants and the iron rod strongly induce the first nucleation of HCFC141b gas hydrate, while the following growth of the HCFC141b gas hydrate is primarily influenced by the anion surfactant. This experiment suggests a new way of fast formation of clathrate hydrate, which may be much easier for practical application of the gas hydrate for cold storage in air conditioning systems.

Journal Article↗
PubMed2005

Geothermal ground gas emissions and indoor air pollution in Rotorua, New Zealand.

The emission of toxic gases from the soil is a hazard in geothermal regions that are also urbanized because buildings constructed on geothermal ground may be subject to the ingress of gases from the soil directly into the structure. The Rotorua geothermal field, New Zealand, is extensively urbanized but to date no studies have evaluated the extent of the ground gas hazard. The main gases emitted are hydrogen sulphide (H2S) and carbon dioxide (CO2), both of which are highly toxic and denser than air. This paper reports preliminary findings from a study of selected buildings constructed in the gas anomaly area. Properties were investigated for evidence of ingress by H2S, CO2, and 222Rn, with a view to determine the means and rates of gas entry and the nature of any consequent hazard. H2S and CO2 were investigated using infrared active gas analysers and passive detector tubes left in place for 10-48 h. 222Rn was measured over a period of 3 months by poly-allyl diglycol carbonate sensors. Eight of the nine buildings studied were found to suffer problems with soil gases entering the indoor air through the structure. The primary means of gas entry was directly from the ground through the floors, walls, and subsurface pipes. Indoor vents were located and found emitting up to approximately 200 ppm H2S and approximately 15% CO2, concentrations high enough to present an acute respiratory hazard to persons close to the vent (e.g., children playing at floor level). In some properties, gas problems occurred despite preventative measures having been made during construction or during later renovations. Typically, these measures include the under-laying of concrete floors with a gas-proof butanol seal, under-floor ventilation systems or the installation of positive-pressure air conditioning. Recently constructed buildings (<10 years) with butanol seals were nevertheless affected by ground gas emissions, and we conclude that such measures are not always effective in the long term.

Air Pollution, Indoor↗