Stabilities of Dried Suspensions of Influenza Virus Sealed in a Vacuum or Under Different Gases

Suspensions of purified influenza virus, dried to a 1.4% content of residual moisture by sublimation of ice in vacuo, were sealed in a vacuum or under different gases of high purity. The stabilities of the several preparations were determined by an accelerated storage test. Based on the times predicted for the dried preparations stored at different temperatures to lose 1 log of infectivity titer, the order of stabilities in relation to sealing in vacuum or under different gases was as follows: helium > hydrogen > vacuum > argon > nitrogen > oxygen > carbon dioxide.     

Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen

Buchheit, R. G. (Union Carbide Corp., Tonawanda, N.Y.), H. R. Schreiner, and G. F. Doebbler. Growth responses of Neurospora crassa to increased partial pressures of the noble gases and nitrogen. J. Bacteriol. 91:622-627. 1966.-Growth rate of the fungus Neurospora crassa depends in part on the nature of metabolically "inert gas" present in its environment. At high partial pressures, the noble gas elements (helium, neon, argon, krypton, and xenon) inhibit growth in the order: Xe > Kr> Ar > Ne > He. Nitrogen (N(2)) closely resembles He in inhibitory effectiveness. Partial pressures required for 50% inhibition of growth were: Xe (0.8 atm), Kr (1.6 atm), Ar (3.8 atm), Ne (35 atm), and He ( approximately 300 atm). With respect to inhibition of growth, the noble gases and N(2) differ qualitatively and quantitatively from the order of effectiveness found with other biological effects, i.e., narcosis, inhibition of insect development, depression of O(2)-dependent radiation sensitivity, and effects on tissue-slice glycolysis and respiration. Partial pressures giving 50% inhibition of N. crassa growth parallel various physical properties (i.e., solubilities, solubility ratios, etc.) of the noble gases. Linear correlation of 50% inhibition pressures to the polarizability and of the logarithm of pressure to the first and second ionization potentials suggests the involvement of weak intermolecular interactions or charge-transfer in the biological activity of the noble gases.     

Stability of Suspensions of Influenza Virus Dried to Different Contents of Residual Moisture by Sublimation In Vacuo

After freezing, suspensions of influenza virus were dried by sublimation of water in vacuo to contents of residual moisture of 3.2, 2.1, 1.7, 1, or 0.4%. The stability of the several suspensions was determined by an accelerated storage test. Based on the times predicted for the dried preparations stored at different temperatures to lose 1 log of infectivity titer, the order of stability in relation to residual moistures was as follows: 1.7% > 2.1% > 1% > 3.2% > 0.4%.     

Mixed-gas model for predicting decompression sickness in rats.

A mixed-gas model for rats was developed to further explore the role of different gases in decompression and to provide a global model for possible future evaluation of its usefulness for human prediction. A Hill-equation dose-response model was fitted to over 5,000 rat dives by using the technique of maximum likelihood. These dives used various mixtures of He, N(2), Ar, and O(2) and had times at depth up to 2 h and varied decompression profiles. Results supported past findings, including 1) differences among the gases in decompression risk (He < N(2) < Ar) and exchange rate (He > Ar approximately N(2)), 2) significant decompression risk of O(2), and 3) increased risk of decompression sickness with heavier animals. New findings included asymmetrical gas exchange with gas washout often unexpectedly faster than uptake. Model success was demonstrated by the relatively small errors (and their random scatter) between model predictions and actual incidences. This mixed-gas model for prediction of decompression sickness in rats is the first such model for any animal species that covers such a broad range of gas mixtures and dive profiles.     

Microbial growth modification by compressed gases and hydrostatic pressure

Studies of the growth-modifying actions for Escherichia coli, Saccharomyces cerevisiae, and Tetrahymena thermophila of helium, nitrogen, argon, krypton, xenon, and nitrous oxide led to the conclusion that there are two definable classes of gases. Class 1 gases, including He, N(2), and Ar, are not growth inhibitors; in fact, they can reverse the growth inhibitory action of hydrostatic pressures. Class 2 gases, including Kr, Xe, and N(2)O, are potent growth inhibitors at low pressures. For example, at 24 degrees C, 50% growth-inhibitory pressures of N(2)O were found to be ca. 1.7 MPa for E. coli, 1.0 MPa for S. cerevisiae, and 0.5 MPa for T. thermophila. Class 1 gases could act as potentiators for growth inhibition by N(2)O, O(2), Kr, or Xe. Hydrostatic pressure alone is known to reverse N(2)O inhibition of growth, but we found that it did not greatly alter oxygen toxicity. Therefore, potentiation by class 1 gases appeared to be a gas effect rather than a pressure effect. The temperature profile for growth inhibition of S. cerevisiae by N(2)O revealed an optimal temperature for cell resistance of ca. 24 degrees C, with lower resistance at higher and lower temperatures. Overall, it appeared that microbial growth modification by hyperbaric gases could not be related to their narcotic actions but reflected definably different physiological actions.     

Effect of inert gas switching at depth on decompression outcome in rats

The present investigation was performed to determine whether inert gas sequencing at depth would affect decompression outcome in rats via the phenomenon of counterdiffusion. Unanesthetized rats (Rattus norvegicus) were subjected to simulated dives in either air, 79% He-21% O2, or 79% Ar-21% O2; depths ranged from 125 to 175 feet of seawater (4.8-6.3 atmospheres absolute). After 1 h at depth, the dive chamber was vented (with depth held constant) over a 5-min period with the same gas as in the chamber (controls) or one of the other two inert gas-O2 mixtures. After the gas switch, a 5- to 35-min period was allowed for gas exchange between the animals and chamber atmosphere before rapid decompression to the surface. Substantial changes in the risk of decompression sickness (DCS) were observed after the gas switch because of differences in potencies (He less than N2 less than Ar) for causing DCS and gas exchange rates (He greater than Ar greater than N2) among the three gases. Based on the predicted gas exchange rates, transient increases or decreases in total inert gas pressure would be expected to occur during these experimental conditions. Because of differences in gas potencies, DCS risk may not directly follow the changes in total inert gas pressure. In fact, a decline in predicted DCS risk may occur even as total inert gas pressure in increasing.     

The biogeochemical controls of N2O production and emission in landfill cover soils: the role of methanotrophs in the nitrogen cycle

Emissions of N2O from cover soils of both abandoned (> 30 years) and active landfills greatly exceed the maximum fluxes previously reported for tropical soils, suggesting high microbial activities for N2O production. Low soil matrix potentials (<-0.7 MPa) indicate that nitrification was the most likely mechanism of N2O formation during most of the time of sampling. Soil moisture had a strong influence on N2O emissions. The production of N2O was stimulated by as much as 20 times during laboratory incubations, when moisture was increased from -2.0 MPa to -0.6 MPa. Additional evidence from incubation experiments and delta13C analyses of fatty acids (18:1) diagnostic of methanotrophs suggests that N2O is formed in these soils by nitrification via methanotrophic bacteria. In a NH3(g)-amended landfill soil, the rate of N2O production was significantly increased when incubated with 100 ppmv methane compared with 1.8 ppmv (atmospheric) methane. Preincubation of a landfill soil with 1% CH4 for 2 weeks resulted in higher rates of N2O production when subsequently amended with NH3(g) relative to a control soil preincubated without CH4. At one location, at the soil depth (9-16 cm) of maximum methane consumption and N2O production, we observe elevated concentrations of organic carbon and nitrogen and distinct minima in delta15N (+1.0%) and delta13C (-33.8%) values for organic nitrogen and organic carbon respectively. A delta13C value of -39.3% was measured for 18:1 carbon fatty acids in this soil, diagnostic of type II methanotrophs. The low delta15N value for organic nitrogen is consistent with N2 fixation by type II methanotrophs. These observations all point to a methanotrophic origin for the organic matter at this depth. The results of this study corroborate previous reports of methanotrophic nitrification and N2O formation in aqueous and soil environments and suggest a predominance of type II rather than type I or type X methanotrophs in this landfill soil.     

Pulmonary and bronchial blood circulation under conditions of changed gaseous environment

By means of ultrasonic method used in acute experiments on cats with closed chest under normal respiration the authors studied the blood flow in left low-lobar pulmonary artery and vein and in bronchial artery, as well as the blood pressure in pulmonary and femoral arteries in inhalation of next gaseous mixtures: 7.5% O2 in nitrogen; 30% O2; 3% CO2; 21% O2+ +79% He; 30% O2 + 67% He + 3% CO2. It was shown, that inhalation of the normoxic gaseous mixture, in which nitrogen is replaced by helium, did not call significant changes in pulmonary and systemic circulation. However, the presence of the helium in complicated gaseous mixture can change the reactivity of pulmonary and bronchial vessels to influence the components participating in these complicated gaseous mixtures.     

成都平原水稻-油菜轮作系统氧化亚氮排放

2005年6月—2006年6月利用静态箱/气相色谱法对成都平原水稻 油菜轮作系统氧化亚氮（N₂O）排放进行定位观测, 研究了该系统N₂O排放特征及土壤水热状况、氮肥施用、作物参与对N₂O排放的影响. 结果表明: 成都平原水稻-油菜轮作系统N₂O排放总量为（8.3±2.8）kg·hm^-2·a^-1, 水稻季、油菜季和休闲期对整个轮作周期N₂O排放总量的贡献分别为30%、65%和5%. 水稻季N₂O平均排放速率表现为排灌交替期最大, 持续淹水期和排水晒田期相当;氮肥施用是N₂O排放高峰出现的主要驱动力;土壤表层含水量偏低是旱季出现土壤N₂O吸收现象的主要原因. 土壤水分、土壤温度、施用氮肥和作物参与均在不同程度上影响N₂O排放, 土壤水分是影响N₂O排放的关键因子, 避免水稻季土壤频繁干湿交替或控制旱季土壤水分(表层土壤含水孔隙率介于50%～70%)可有效抑制N₂O排放.     

Membrane inlet ion trap mass spectrometry for the direct measurement of dissolved gases in ecological samples

The use of an ion trap mass spectrometer with three different membrane inlet probes is described. Two methods of removing water from the sample are compared. One is the use of a PTFE-silicone rubber double membrane, PTFE is relatively impermeable to water and so reduces the amount entering with the gas sample (Probe A). The second is the use of a silicone rubber membrane covered long probe, which condenses water out of the sample (Probe B). Response times (100%) for dissolved N2O, O2, Ar and CO2 without He in the chamber vary from between 158 and 684 s with Probe A. For the same probe with He, the response times were between 283 and 551 s. In the gas phase response times were between 99 and 153 s with He and 117 and 122 s without He. Probe B had 100% response of between 122 and 152 s for dissolved gases. Further extension of the probe by 2 m slowed response times as did increasing the ionisation time. Response times for Probe B increased to between 99 and 340 s when ionisation time increased from 1000 to 24,930 microseconds. Plots of output against concentration showed the steepest line of response for the short single membrane covered probe with 1000 microseconds ionisation time. Increasing the ionisation time, extending the probe and the use of a double membrane all reduced the gradient of output against concentration for every gas tested. In an intact sediment core, concentrations of O2, N2O and CO2 rose at the start and the concentration of N2 fell. As the disturbed sediment settled, this was reversed. The initial increase in O2 concentration stimulated respiration and inhibited the final pathway in dentrification producing higher concentrations of N2O and reducing the concentration of N2.     

Relationship of phase IV to closing volume in lateral body positions.

We studied the effect of body position in humans on the relationship between exhaled vital capacity (VC) and both helium (He) and nitrogen (N2) concentrations after delivery of an He bolus at residual volume (RV) followed by 100% oxygen to total lung capacity. Phase IV, defined as the % VC at the first sharp and permanent increase in N2 and He, occurred at a mean of 15.7% VC while seated, 60.0% VC in right lateral and 59.6% VC in left lateral positions. He bolus delivery above RV but well below 60% VC resulted in the disappearance of phase IV. Lung pressure-volume (PV) curves had inflections at the volume of phase IV in the seated position: but the inflections were well below phase IV in lateral positions. Phase IV increased to higher volumes at higher mouth pressures. The relationship between phase IV and mouth pressure fell near the respiratory system relaxation PV curves. The findings suggest the higher phase IV in lateral positions is due to sequence of emptying without airway closure and is influenced by active expiration.     

Cold atmospheric plasma jet effects on V79-4 cells

The effects of cold plasmas are due to charged particles, reactive oxygen species (ROS), reactive nitrogen species (RNS), UV photons, and intense electric field. In order to obtain a more efficient action on mammalian cells (useful for cancer therapy), we used in our studies chemically activated cold plasma (He and O2 gas mixture). V79-4 cells were exposed to plasma jet for different time periods (30, 60, 90, 120 and 150s), using different combinations of helium and oxygen inputs (He:2.5l/min + 02:12.5ml/min; He:2.51/min + O2:25ml/min; He:2.51/min + O2:37.5 ml/min). Using MTT test we demonstrated that plasma jet induced cell viability decrease in all cases. The effect of chemically activated cold plasma--apoptosis or necrosis--depends on gas mixture and treatment period. Taking into account that ROS density in cell microenvironment is related to O2 percent in the gas mixture and treatment period, we can presume that cell death is due to ROS produced in plasma jet.     

Decompression outcome following saturation dives with multiple inert gases in rats

This investigation examined the question of whether gas mixtures containing multiple inert gases provide a decompression advantage over mixtures containing a single inert gas. Unanesthetized male albino rats, Rattus norvegicus, were subjected to 2-h simulated dives at depths ranging from 145 to 220 fsw. At pressure, the rats breathed various He-N2-Ar-O2 mixtures (79.1% inert gas-20.9% O2); they were then decompressed rapidly (within 10 s) to surface pressures. The probability of decompression sickness (DCS), measured either as severe bends symptoms or death, was related to the experimental variables in a Hill equation model incorporating parameters that account for differences in the potencies of the three gases and the weight of the animal. The relative potencies of the three gases, which affect the total dose of decompression stress, were determined as significantly different in the following ascending order of potency: He less than N2 less than Ar; some of these differences were small in magnitude. With mixtures, the degree of decompression stress diminished as either N2 or Ar was replaced by He. No obvious advantage or disadvantage of mixtures over the least potent pure inert gas (He) was evident, although limits to the expectation of possible advantage or disadvantage of mixtures were defined. Also, model analysis did not support the hypothesis that the outcome of decompression with multiple inert gases in rats under these experimental conditions can be explained totally by the volume of gas accumulated in the body during a dive.     

Effect of high-pressure gas on yeast growth

Microcalorimetry is a useful tool for monitoring the growth behavior of microorganisms. In this study, microcalorimetry was used to investigate the effects of nitrogen, air, oxygen, nitrous oxide, argon, and krypton at high pressure on the growth of the yeast Saccharomyces cerevisiae. Growth thermograms (metabolic heat vs. incubation time) were generated to estimate metabolic activity under compressed gases and to determine the 50% inhibitory pressure (IP(50)) and minimum inhibitory pressure (MIP), which are regarded as indices of the toxicity of compressed gases. Based on MIP values, the most toxic to the least toxic gases were found to be: O(2) > N(2)O > air > Kr > N(2) > Ar.     

Effects of helium group gases and nitrous oxide on HeLa cells

The helium group gases and nitrous oxide at superatomospheric pressures depress multiplication of HeLa cells in monolayer cultures. The effectiveness of these gases in eliciting the pressure-dependent response follows the order N₂O, Xe > Kr > Ar > > Ne and He. The response correlates with lipid solubility of the gases. Depression of growth by 4.2 atm Xe is reversible after exposure for one and two days. Cultures exposed to 7.2 atm Xe show irreversible damage including cytoplasmic vacuolization. Cell attachment is strongly inhibited by Xe; 36% of the cell inoculum were not attached after 24 hours. Affinity for hydrophobic sites in the cell is suggested as determining the order of effectiveness of the gases in evoking the response.     

Criteria and Methodology for Identifying Respiratory Denitrifiers

Respiratory denitrification is not always adequately established when bacteria are characterized. We have tested a simple method that allows one to evaluate whether the two necessary criteria to claim denitrification have been met, namely, that N(inf2) or N(inf2)O is produced from nitrate or nitrite and that this reduction is coupled to a growth yield increase. Microorganisms were cultured in sealed tubes under a helium headspace and in the presence of 0, 2, 4, 7, and 10 mM nitrate or nitrite. After growth had ceased, N(inf2) and N(inf2)O were quantified by gas chromatography and the final protein concentration was measured. Net protein production was linearly related to nitrate concentration for all denitrifiers tested and ranged from 2 to 6 g of protein per mol of electron equivalent reduced. Nitrogen recovery as N(inf2) plus N(inf2)O from nitrate and nitrite transformed exceeded 80% for all denitrifiers. We also suggest that a rate of N gas production of >10 (mu)mol/min/g of protein can be used as an additional characteristic definitive of denitrification since this process produces gas more rapidly than other processes. These characteristics were established after evaluation of a variety of well-characterized respiratory denitrifiers and other N(inf2)O-producing nitrate reducers. Several poorly characterized denitrifiers were also tested and confirmed as respiratory denitrifiers, including Aquaspirillum itersonii, Aquaspirillum fasciculus, Bacillus azotoformans, and Corynebacterium nephridii. These criteria distinguished respiratory denitrifiers from other groups that reduce nitrate or produce N(inf2)O. Furthermore, they correctly identified respiratory denitrification in weak denitrifiers, a group in which the existence of this process may be overlooked.     

Additives to biological substances. III. The moisture content and moisture uptake of commonly used carrier agents undergoing processing conditions similar to those used in the preparation of international biological standards

Aqueous solutions of the carbohydrates alpha alpha'-trehalose, mannitol and lactose, human serum and human albumin were freeze-dried in ampoules and part of each batch was further desiccated over phosphorus pentoxide in a manner similar to that used to prepare international biological standards and related materials. The residual moisture present in the preparations and their uptake of moisture was then measured by Karl Fischer titration. In ampoules open to atmosphere [22 degrees C, 34% relative humidity (RH)] freeze-dried serum, albumin, lactose and alpha alpha'-trehalose all exhibited hygroscopic properties, their moisture contents rising over a period of 24 h, to 10%, 8%, 8% and 7%, respectively. Mannitol when dried to low moisture levels did not exhibit hygroscopic properties, but the residual moisture in different freeze-dried batches was very variable, possibly as a result of that solid's sponge-like and/or crystalline microstructure. When exposed to the same conditions, dried materials in ampoules fitted with polythene capillary leak plugs (used routinely at this Institute during the preparation of Biological Standards) exhibited a considerably reduced rate of moisture uptake. The effect of secondary vacuum drying over phosphorus pentoxide on the moisture content of these preparations is also reported.     

Effect of storage and processing of barley on its utilization by pigs and rats

Grain of 16.7% moisture content was stored in exprimental silos by four methods. These were: (1) controlled environment (a sealed container); (2) addition of 1% acid mixture (60 acetic acid: 40 propionic acid); (3) addition of 3.2% sodium hydroxide in a 32% solution to give 21.8% moisture content; and (4) air-dried (82°C) to 13.3% moisture.After 9 months storage, apparent digestibility of dry matter, nitrogen and neutral detergent fibre was measured with pigs, while true protein digestiblity, biological value and net protein utilization were measured with rats.With pigs, there was no treatment effect on dry matter digestibility, but neutral detergent fibre digestibility was reduced in the dried barley. The apparent protein digestibility was markedly depressed to 44.5% for the alkali-treated grain compared with a mean of 65.1% for the other treatments (P < 0.001). In the rat trial, true digestibility of nitrogen and biological value were severely depressed (P < 0.001) by alkali treatment, but differences between the other treatments were relatively small.     

Soil moisture effects on gross nitrification differ between adjacent grassland and forested soils in central Alberta, Canada

Background and aims

Changes in soil moisture availability seasonally and as a result of climatic variability would influence soil nitrogen (N) cycling in different land use systems. This study aimed to understand mechanisms of soil moisture availability on gross N transformation rates.

Methods

A laboratory incubation experiment was conducted to evaluate the effects of soil moisture content (65 vs. 100% water holding capacity, WHC) on gross N transformation rates using the ¹⁵N tracing technique (calculated by the numerical model FLUAZ) in adjacent grassland and forest soils in central Alberta, Canada.

Results

Gross N mineralization and gross NH ₄ ⁺ immobilization rates were not influenced by soil moisture content for both soils. Gross nitrification rates were greater at 100 than at 65% WHC only in the forest soil. Denitrification rates during the 9 days of incubation were 2.47 and 4.91 mg N kg^-1 soil d^-1 in the grassland and forest soils, respectively, at 100% WHC, but were not different from zero at 65% WHC. In the forest soil, both the ratio of gross nitrification to gross NH ₄ ⁺ immobilization rates (N/IA) and cumulative N₂O emission were lower in the 65 than in the 100% WHC treatment, while in the grassland soil, the N/IA ratio was similar between the two soil moisture content treatments but cumulative N₂O emission was lower at 65% WHC.

Conclusions

The effect of soil moisture content on gross nitrification rates differ between forest and grassland soils and decreasing soil moisture content from 100 to 65% WHC reduced N₂O emissions in both soils.     

Density-dependent reduction of nitric oxide diffusing capacity after pneumonectomy.

Airway lengthening after pneumonectomy (PNX) may increase diffusive resistance to gas mixing (1/D(G)); the effect is accentuated by increasing acinar gas density but is difficult to detect from lung CO-diffusing capacity (Dl(CO)). Because lung NO-diffusing capacity (Dl(NO)) is three- to fivefold that of Dl(CO), whereas 1/D(G) for NO and CO are similar, we hypothesized that a density-dependent fractional reduction would be greater for Dl(NO) than for Dl(CO). We measured Dl(NO) and Dl(CO) at two tidal volumes (Vt) and with three background gases [helium (He), nitrogen (N(2)), and sulfur hexafluoride (SF(6))] in immature dogs 3 and 9 mo after right PNX (5 and 11 mo of age). At maturity (11 mo), background gas density had no effect on Dl(NO), Dl(CO), or Dl(NO)-to-Dl(CO) ratio in sham controls. In PNX animals, Dl(NO) declined 25-50% in SF(6) relative to He and N(2), and Dl(NO)/Dl(CO) declined approximately 50% in SF(6) relative to He at a Vt of 15 ml/kg, consistent with a significant 1/D(G). At 5 mo of age, Dl(NO)/Dl(CO) declined 25-45% in SF(6) relative to He and N(2) in both groups, but Dl(CO) increased paradoxically in SF(6) relative to N(2) or He by 20-60%. Findings suggest that SF(6), besides increasing 1/D(G), may redistribute ventilation and/or enhance acinar penetration of the convective front.