Effects of compressed hydrocarbon gases on the growth activity of Saccharomyces cerevisiae

The inhibitory action of compressed hydrocarbon gases on the growth of the yeast Saccharomyces cerevisiae was investigated quantitatively by microcalorimetry. Both the 50% inhibitory pressure (IP(50)) and the minimum inhibitory pressure (MIP), which are regarded as indices of the toxicity of hydrocarbon gases, were determined from growth thermograms. Based on these values, the inhibitory potency of the hydrocarbon gases increased in the order methane < ethane < propane < i-butane < n-butane. The toxicity of these hydrocarbon gases correlated to their hydrophobicity, suggesting that hydrocarbon gases interact with some hydrophobic regions of the cell membrane. In support of this, we found that UV absorbing materials at 260 nm were released from yeast cells exposed to compressed hydrocarbon gases. Additionally, scanning electron microscopy indicated that morphological changes occurred in these cells.     

Some Physical and Chemical Properties of Nuclease P1

The inhibitory action of compressed hydrocarbon gases on the growth of the yeast Saccharomyces cerevisiae was investigated quantitatively by microcalorimetry. Both the 50% inhibitory pressure (IP₅₀) and the minimum inhibitory pressure (MIP), which are regarded as indices of the toxicity of hydrocarbon gases, were determined from growth thermograms. Based on these values, the inhibitory potency of the hydrocarbon gases increased in the order methane << ethane < propane < i-butane < n-butane. The toxicity of these hydrocarbon gases correlated to their hydrophobicity, suggesting that hydrocarbon gases interact with some hydrophobic regions of the cell membrane. In support of this, we found that UV absorbing materials at 260 nm were released from yeast cells exposed to compressed hydrocarbon gases. Additionally, scanning electron microscopy indicated that morphological changes occurred in these cells.     

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.     

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.     

Fermentative capacity of baker's yeast exposed to hyperbaric stress

Baker's yeast suspensions were incubated at different pressures (from 1 bar to 6 bar) and different gases [air, O(2) and a mixture of 8% (v/v) CO(2), 21% O(2) and N(2)]. Raising the air pressure from 1 bar to 6 bar stimulated cell growth but had no effect on leavening ability or viability of the cells. A 50% reduction of the CO(2) produced in dough occurred with 6 bar O(2) which also stopped growth. The fermentative capacity of the cells was stimulated by the cells exposure to increased CO(2) partial pressure up to 0.48 bar.     

Inhibition of hepatoma cell growth by analogs of adenosine and cyclic AMP and the influence of enzymes in mammalian sera

The following evidence suggests that inhibition of hepatoma cell (HTC) growth by cyclic nucleotides is an adenosine-like effect that is greatly modified by the type and treatment of serum used in the culture medium and is probably not mediated by cyclic AMP-dependent protein kinase: 1) Heating serum reduces its phosphodiesterase content, thereby slowing metabolism of cyclic AMP and reducing the inhibition of HTC cell growth by cyclic AMP; 2) Using medium that contains phosphodiesterase but lacks adenosine deaminase causes adenosine to accumulate from cyclic AMP and increases the toxicity of cyclic AMP; 3) Uridine or cytidine reverses the growth inhibition caused by adenosine, 5'-AMP or cyclic AMP; 4) adenosine, 5'-AMP and N6-(delta 2-isopentenyl) adenosine are more toxic for HTC cells than is cyclic AMP, and N6,O2-dibutyryl cyclic AMP is not toxic; and 5) N6,O2'-dibutyryl cyclic AMP inhibits growth of Reuber H35 cells, but uridine prevents this inhibition of growth. We conclude that most, if not all, of the inhibitory effects of cyclic AMP and N6,O2'-dibutyryl cyclic AMP on HTc and Reuber H35 hepatoma cell growth are due to the generation of toxic metabolites.     

Control of Penicillium martensii Development and Penicillic Acid Production by Atmospheric Gases and Temperatures

The effects of various gaseous environments and temperatures on development of Penicillium martensii NRRL 3612 and production of penicillic acid (PA) were determined. Accumulation of PA in mold-inoculated corn was measured following incubation under air; 20% CO(2), 20% O(2), 60% N(2); 40% CO(2), 20% O(2), 40% N(2); and 60% CO(2), 20% O(2), 20% N(2). Although reduced temperature initially inhibited PA production, at the end of the trial the largest quantity of PA (120 mug/g of corn) was found in air-incubated corn at the lowest test temperature (5 C). Atmospheres enriched with 60% CO(2) reduced PA accumulation below a detectable level at 5 and 10 C after a 4-week incubation period. Spore germination tests were carried out in a liquid growth medium incubated for 16 hr under several test conditions. Germ tube outgrowth at 30 C ranged from 36% in air to 2% in 60% CO(2), whereas no germination was observed in CO(2)-enriched gases at 10 C. When spore respiration rates were measured in air and O(2) in a liquid growth medium, complete removal of CO(2) from the reaction atmosphere did not reduce O(2) uptake.     

Effects of hyperbaric gases on membrane nanostructure and function in neurons

This mini-review summarizes current ideas of how hyperbaric gases (>1-10 atmospheres absolute) affect neuronal mechanisms of excitability through molecular interaction with membrane components. The dynamic nature of the lipid bilayer, its resident proteins, and the underlying cytoskeleton make each respective nanostructure a potential target for modulation by hyperbaric gases. Depending on the composition of the gas mixture, the relative concentrations of O(2) and inert gas, and total barometric pressure, the net effect of a particular gas on the cell membrane will be determined by the gas' 1) lipid solubility, 2) ability to oxidize lipids and proteins (O(2)), and 3) capacity, in the compressed state, to generate localized shear and strain forces between various nanostructures. A change in the properties of any one membrane component is anticipated to change conductance of membrane-spanning ion channels and thus neuronal function.     

压力作用下面包酵母胞内谷胱甘肽和麦角固醇的变化

以高纯空气（O2∶N2 ＝21∶79）为加压介质,研究了0.5Mpa压力下面包酵母CICC1447和CICC1339细胞生长及细胞内谷胱甘肽、麦角固醇的含量变化。结果表明：加压培养时两株酵母菌的对数生长期延迟出现,对数生长期的持续时间缩短,而且两株菌的比生长速率均明显低于对照组,同时两株菌的倍增时间也较对照组有所延长;压力刺激可显著提高面包酵母细胞内谷胱甘肽（GSH）的含量,但麦角固醇含量的变化却不明显。在0.5MPa压力下保压培养3h时CICC1447胞内谷胱甘肽含量比常压对照组提高了42.6%,而加压3h后麦角固醇含量比对照组提高了20.1％;加压培养6h时CICC1339胞内谷胱甘肽含量较对照组提高了58.7%,但其麦角固醇含量反而降低。这说明不同的酵母菌对压力刺激的反应是不同的。     

Closed-circuit metabolic system with multiple applications

A closed-circuit metabolic system has been designed and tested for multiple applications. Air pressure within a closed chamber is regulated electronically while allowing for respiratory gas exchange. Compared with a previously reported standard indirect calorimetry system, the new device had by virtue of longer duration of measurement improved precision (coefficient of variation 3% vs. 14%) during studies of O2 consumption both at room temperature and at 5 degrees C. In addition, a more physiological atmospheric environment is maintained. This system has also been utilized for simultaneously labeling groups of up to 20 weanling rats with 18O2 over a 2-day period and for exposure of rats to a hyperoxic (84% O2), normobaric environment for 4-day periods. Potential applications include maintenance of pressure (hypobaric through hyperbaric) and O2 (hypoxic through hyperoxic) controlled environments, exposure to toxic gases, study of diurnal variations in metabolic rate, measurement of metabolic expenditure with activity, and adaptation to other species including humans.     

Effect of High Oxygen Tensions on the Growth of Selected, Aerobic, Gram-negative, Pathogenic Bacteria

The in vitro effects of high O(2) tensions (P(O2)) on aerobic, enteric pathogens were examined at pressures of up to 3 atm absolute. Organisms from the genera Salmonella, Shigella, and Vibrio were usually subjected to 24-hr exposures. Tensions of 0.87, 1.87, and 2.87 atm absolute of O(2) (plus traces of CO(2) and N(2)) became progressively inhibitory for Salmonella and Shigella growth, but were bactericidal only for V. comma strains at tensions greater than 0.87 atm absolute of O(2). Growth inhibition of enteric organisms resulted from increased P(O2), rather than pressure per se, and could be mitigated nutritionally; an appropriate carbohydrate source is at least partially involved. Further studies with vibrios indicated that such mitigation was independent of medium pH. In addition, a synergistic relationship existed between O(2) and sulfisoxazole when tensions from 0.87 to 2.87 atm absolute of O(2) were maintained for 3 to 24 hr. Synergism occurred even under nutritional conditions which negated growth inhibition by O(2) alone. Bactericidal concentrations of sulfisoxazole, in the presence of increased P(O2), were reducible up to 4,000-fold. The combined procedure employed in this investigation, by use of an antimicrobial drug of known action, which also synergizes with O(2), plus nutritional studies, suggests a means for establishing a site of O(2) toxicity. These data support the concept that O(2) inhibition of growth represents a metabolic disturbance and that metabolic pathways involving p-aminobenzoic acid may be O(2)-labile. Such an approach could also guide development of antimicrobial agents as O(2) substitutes for promoting synergism.     

Antibacterial effects of a monoporphyrinato ytterbium(III) complex and its free components on Staphylococcus aureus as determined by stop-flow microcalorimetry

The antibacterial effect of Yb3+, the free porphyrin base 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin (H2TMP; 1), and the corresponding Yb3+ porphyrinato complex [Yb(III)(TMP)(H2O)3]+ Cl- (Yb(TMP); 2) towards Staphylococcus aureus was investigated by stop-flow microcalorimetry. By analyzing the obtained metabolic thermogenic curves, crucial parameters such as rate constant of bacterial growth (k), half inhibitory concentration (IC50), and generation time (t(G)) were determined. The antibacterial activities of the three compounds tested was 2>1>Yb3+, with an IC50 value of 273 mg/l for complex 2. The Yb3+ porphyrinato complex is proposed to benefit from synergetic effects of Yb3+ and the free porphyrin 1.     

Inert gas enhancement of superoxide radical production.

Two free radical generating systems, xanthine oxidase/hypoxanthine or phenazine methosulfate/NADH, were exposed to air plus He, N2, or Ar at partial pressures ranging from 0.2 to 6.0 MPa, and the rates of production of superoxide, hydroxyl, singlet O2, and H2O2 were measured. All three inert gases acted similarly to enhance the production of superoxide radicals by facilitating interactions between iron and H2O2, or O2 and organic radicals. These reactions occurred at quite low gas partial pressures, only 0.28 MPa, and hydrostatic pressures of up to 6.0 MPa had no effect on radical reactions. Enhanced radical production may be the basis for the inhibition of cellular growth mediated by inert gases, and inert gas enhancement of O2 toxicity.     

Influence of peroxides, ascorbate and glutathione on germination and growth in Lupinus albus L.

Lupinus albus L. seeds were treated with different concentrations (from 10 μM to 50 mM) of H2O2, m-chloroperoxybenzoic acid (mCPBA), ascorbate (ASC) and glutathione (GSH). The efficiency as inhibitors on germination and on the subsequent growth of the hypocotyl was mCPBA > GSH > ASC = H2O2, which suggest that inhibitory efficiency was dependent on the compound per se rather than on its redox nature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Human temperature regulation during narcosis induced by inhalation of 30% nitrous oxide.

The study investigated the effect of inhalation of 30% nitrous oxide (N2O) on temperature regulation in humans. Seven male subjects were immersed to the neck in 28 degrees C water on two separate occasions. They exercised at a rate equivalent to 50% of their maximum work rate on an underwater cycle ergometer for 20 min and remained immersed for an additional 100 min after the exercise. In one trial (AIR) the subjects inspired compressed air, and in the other trial (N2O) they inspired a gas mixture containing N2O (20.93% O2-30% N2O-49.07% N2). Sweating, measured at the forehead, and shivering thermogenesis, as reflected by O2 uptake, were monitored throughout the 100-min recovery period. The threshold core temperatures at which sweating was extinguished and shivering was initiated were established relative to resting preexercise levels. Neither the magnitude of the sweating response nor the core threshold at which it was extinguished was significantly affected by the inhalation of N2O. In contrast, shivering thermogenesis was both significantly reduced during the N2O condition and initiated at significantly lower core temperatures [change in esophageal temperature (delta T(es)) = -0.98 +/- 0.33 degrees C and change in rectal temperature (delta T(re)) = -1.26 degrees C] during the N2O than during the AIR condition (delta T(es) = -0.36 +/- 0.31 degrees C and delta T(re) = -0.44 +/- 0.22 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)     

不同耕作措施的温室气体排放日变化及最佳观测时间

在连续6 a耕作模式的基础上,利用静态箱-气相色谱法对常规耕作与免耕条件下小麦生育后期麦田CO2、CH4、N2O通量日变化进行了连续48 h观测,并确定1 d中最佳的观测时间。结果表明,常规耕作与免耕条件下小麦生育后期麦田CO2、CH4、N2O通量具有显著的日变化特征,常规耕作处理和免耕处理土壤表现为CH4的吸收汇、CO2、N2O的排放源。CH4日均吸收通量:常规耕作无秸秆还田处理(AC)>常规耕作秸秆还田处理(PC)>免耕(PZ);CO2日均排放通量:常规耕作秸秆还田处理(PC)>常规耕作无秸秆还田处理(AC)>免耕(PZ);N2O日均排放通量:常规耕作秸秆还田处理(PC)>常规耕作无秸秆还田处理(AC)>免耕(PZ)。相关性分析表明,常规耕作及免耕条件下CO2、CH4、N2O通量日变化与地表温度和5 cm地温呈极显著(P<0.01)或显著(P<0.05)的正相关关系,温度是决定温室气体日变化的主要决定因素。通过矫正系数和回归分析表明,在小麦生育后期(4—6月),CO2的最佳观测时间段在8:00—10:00,CH4为8:00—10:00,N2O为8:00—12:00。     

Effect of N2-He-O2 on decompression outcome in rats after variable time-at-depth dives

No study of decompression sickness has examined both variable gas mixtures and variable time at depth to the point of statistical significance. This investigation examined the effect of N2-He-O2 on decompression outcome in rats after variable time-at-depth dives. Unanesthetized male albino rats were subjected to one of two series of simulated dives: 1) N2-He-O2 dives (20.9% O2) at 175 feet of seawater fsw) and 2) N2-O2 dives (variable percentage of O2; depths from 141 to 207 fsw). Time at depth ranged from 10 to 120 min; rats were then decompressed within 10 s to surface pressure. The probability of decompression sickness (severe bends symptoms or death) was analyzed with a Hill equation model, with parameters for gas potency and equilibrium time for the three gases and weight of the animal. Relative potencies for the three gases were of similar magnitude for bends and statistically different for death in ascending order: O2 less than He less than N2. Estimated gas uptake rates were different. N2 took three to four times as long as He to reach full effect; the rate of O2 appeared to be considerably shorter than that of N2 or He. The large influence of O2 on decompression outcome questions the simplistic view that O2 cannot contribute to the decompression requirement.     

Effects of soil amendment on gas depth profiles in soil monoliths using direct mass spectrometric measurement

Land use and agricultural practices are known to influence the source and sink concentrations of various gases, including greenhouse gases (NOx CH4 and CO2). in soils. With everincreasing production of domestic sewage sludge and the prohibition of disposal at sea, pressure on waste disposal increases. Anaerobically digested domestic sewage sludge and/or lime were applied to an upland. Scottish soil and their effects on gas depth profiles monitored as indicators of microbial processes of the soil ecosystem. The concentrations of various gases (Ar, O2. CO2, CH4, N2, NOx) were measured simultaneously at each depth using membrane inlet mass spectrometry (MIMS). This technique enables the direct measurement of multiple gas species throughout soil cores with minimal disturbance. Intact soil monoliths were collected from the sample site, following amendment, and maintained in a constant temperature, environmental growth chambers. Statistical analyses (one-way ANOVA and LSD tests) were conducted to identify the depths at which gas concentrations in amended cores were significantly different from those in control (un-amended) cores. Significant effects were observed on the concentration of CO2, CH4, NOx and N2 at certain depths. Average CH4 concentration was consistently higher (>1 microM) in the upper horizon following application of sludge and sludge and lime together. N2 and NOx concentrations were elevated in cores treated with lime by approximately 100 and 32 microM. respectively, in much of the upper horizon. CO2 concentration increased above control mean values, at certain depths, following application of either sludge or lime. Some explanation for the changes in soil gas concentration was provided by reference to the microorganism assemblages and the gases associated with biochemistry of nitrification, denitrification, methane oxidation and methanogenesis.     

Inhibition by reactive aldehydes of superoxide anion radical production in stimulated human neutrophils

alpha,beta-Unsaturated aldehydes were investigated in vitro for their ability to inhibit superoxide anion radical (O2-.) production in stimulated human polymorphonuclear leukocytes (PMN). The aldehydes investigated were (i) trans-4-hydroxynonenal and malonaldehyde (MDA), two toxic lipid peroxidation products; (ii) acrolein and crotonaldehyde, two air pollutants derived from fossil fuel combustion; (iii) trans,trans-muconaldehyde, a putative hematotoxic benzene metabolite. Preincubation of PMN with reactive aldehydes followed by stimulation with the oxygen burst initiator phorbol myristate acetate (PMA) resulted in a dose-dependent inhibition of O2-. production. The concentration at which 50% inhibition (IC50) was observed was 21 microM for acrolein, 23 microM for trans,trans-muconaldehyde, 27 microM for trans-4-hydroxynonenal and 330 microM for crotonaldehyde. A similar inhibitory effect by these aldehydes was observed in digitonin- and concanavalin A-stimulated PMN. MDA inhibited O2-. production in PMA-stimulated PMN by 100% at 10(-2) M but gave no inhibition at 10(-3) M. The standard aldehyde propionaldehyde did not inhibit O2-. production at 10(-3)-10(-6) M. Preincubation of PMN with acrolein in the presence of cysteine completely protected against the inhibitory effect of this reactive aldehyde. The results indicate that the ability of toxic aldehydes to inhibit O2-. production in stimulated PMN correlates directly with their alkylation potential which is a function of the electrophilicity of the beta carbon.     

Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO).

Production and consumption processes in soils contribute to the global cycles of many trace gases (CH4, CO, OCS, H2, N2O, and NO) that are relevant for atmospheric chemistry and climate. Soil microbial processes contribute substantially to the budgets of atmospheric trace gases. The flux of trace gases between soil and atmosphere is usually the result of simultaneously operating production and consumption processes in soil: The relevant processes are not yet proven with absolute certainty, but the following are likely for trace gas consumption: H2 oxidation by abiontic soil enzymes; CO cooxidation by the ammonium monooxygenase of nitrifying bacteria; CH4 oxidation by unknown methanotrophic bacteria that utilize CH4 for growth; OCS hydrolysis by bacteria containing carbonic anhydrase; N2O reduction to N2 by denitrifying bacteria; NO consumption by either reduction to N2O in denitrifiers or oxidation to nitrate in heterotrophic bacteria. Wetland soils, in contrast to upland soils are generally anoxic and thus support the production of trace gases (H2, CO, CH4, N2O, and NO) by anaerobic bacteria such as fermenters, methanogens, acetogens, sulfate reducers, and denitrifiers. Methane is the dominant gaseous product of anaerobic degradation of organic matter and is released into the atmosphere, whereas the other trace gases are only intermediates, which are mostly cycled within the anoxic habitat. A significant percentage of the produced methane is oxidized by methanotrophic bacteria at anoxic-oxic interfaces such as the soil surface and the root surface of aquatic plants that serve as conduits for O2 transport into and CH4 transport out of the wetland soils. The dominant production processes in upland soils are different from those in wetland soils and include H2 production by biological N2 fixation, CO production by chemical decomposition of soil organic matter, and NO and N2O production by nitrification and denitrification. The processes responsible for CH4 production in upland soils are completely unclear, as are the OCS production processes in general. A problem for future research is the attribution of trace gas metabolic processes not only to functional groups of microorganisms but also to particular taxa. Thus, it is completely unclear how important microbial diversity is for the control of trace gas flux at the ecosystem level. However, different microbial communities may be part of the reason for differences in trace gas metabolism, e.g., effects of nitrogen fertilizers on CH4 uptake by soil; decrease of CH4 production with decreasing temperature; or different rates and modes of NO and N2O production in different soils and under different conditions.