Entry of Oxygen and Nitrogen into Intact Soybean Nodules

The apparent nitrogenase activity of soybean root nodules isreduced approximately 70% upon nodul detachment. By increasingthe partial pressure of oxygen in the assay vessel from approximate0.2 to 0.5 atm, the nitrogenase activity of detached nodulesis restored to the original attached level. Oi the other hand,maximal assayable nitrogenase activity of nodules attached tothe intact soybean plan is achieved in the presence of 0.2–0.3atm of oxygen. Exposure of attached nodules to 0.5 atm oxygeicauses a decrease in nitrogenase activity seemingly due to inactivation of nitrogenase. These and othe data suggest that,upon detachment, the entry of oxygen into the nodules is impaired.A model for th regulation of airflow into attached and detachednodules is presented. This model is also consisten with responseof nodule activity to water stress.     

The effect of non-binding molecules on the gelation of HbS

The influence of an inert globular macromolecule upon the solubility of sickle cell hemoglobin has been determined as a function of the degree of oxygenation. The thermodynamic theory required to treat this and related problems is derived partition function. The treatment includes non-ideal solution behaviour as measured by osmotic pressure of highly concentrated macromolecular. solutions. Application of the theoretical equations demonstrates how the solubility of hemoglobin is influenced by the presence of the binding ligand (oxygen) and the inert macromolecule, bovine serum albumin (BSA). Good agreement is obtained between experimentally determined and theoretically calculated solubilities using 1) oxygen binding curves to solution and gel phases, 2) activity coefficients from osmotic pressure data, 3) one solubility under the condition where oxygen and BSA are absent, and 4) the value of the water content of the gel phase. Examination of the theoretical equations suggests that inert molecules of intermediate size, that are partially excluded from crystalline or gel phases, have the potential of generally increasing the solubility when non-ideal solution effects are small.     

Oxygen solubility in evaporated seawater as a function of temperature and salinity

Most studies of oxygen solubility values for high salinity conditions have used synthetic solutions. The object of this study is therefore to propose an equation, valid for high salinity conditions, based on the analysis of oxygen saturation in evaporated seawater. In this study, the solubility of oxygen in evaporated seawater has been determined over a temperature range of 8–35°C and with salinity values of up to 133‰. Based on experimental data, an equation is proposed that introduces a S ² (salinity) term, at 1 atm pressure, giving increased importance to salinity. The equation provides a valid means of predicting the amount of dissolved oxygen in this range of temperatures and salinities. In addition, for high salinity conditions, with this equation there is no need to extrapolate other established equations, which are less accurate at salinities higher than 40‰. The use of the proposed equation offers a more precise way of calculating oxygen solubility in seawater at high salinity values (up to 133‰), and small deviations from experimental values, of the order of 2 μmol kg⁻¹, are obtained. Handling editor: J. Melack     

Lipid Peroxidation in Rat Brain Cortical Slices as Measured by the Thiobarbituric Acid Test

Abstract: Malonaldehyde formation by cortical brain slices from rat brain was determined as a function of incubation time and of oxygen pressure. This substance, a byproduct of lipid peroxidation, was detected by the thiobarbituric acid test. Significant amounts of malonaldehyde were formed by brain slices during incubation in the 0.2 (air) to 10 atm oxygen range, and a portion of it was released into the medium. The rate of malonaldehyde formation was the highest during the first 10 min. Elevation of oxygen pressure above 1 atm caused further increments in malonaldehyde production with kinetic properties similar to that seen at 1 atm pressure, but the increments per additional oxygen pressure were diminishing. The formation of a given amount of malonaldehyde can be expressed as a function of atm oxygen × min. This function has the shape of a saturation curve approaching a maximum at around 300 atm × min. The results indicate extensive lipid peroxidation in brain slices under standard incubation conditions.     

Singlet oxygen in the low-temperature plasma of an electron-beam-sustained discharge

Results are presented from experimental and theoretical studies of the production of singlet delta oxygen in a pulsed electron-beam-sustained discharge ignited in a large (～18-1) volume at a total gas mixture pressure of up to 210 Torr. The measured yield of singlet oxygen reaches 10.5%. It is found that varying the reduced electric field from ～2 to ～11 kV/(cm atm) slightly affects singlet oxygen production. It is shown experimentally that an increase in the gas mixture pressure or the specific input energy reduces the duration of singlet oxygen luminescence. The calculated time evolution of the singlet oxygen concentration is compared with experimental results.     

Undecompressed microbial populations from the deep sea.

Metabolic transformations of glutamate and Casamino Acids by natural microbial populations collected from deep waters (1,600 to 3,100 m) were studied in decompressed and undecompressed samples. Pressure-retaining sampling/incubation vessels and appropriate subsampling/incubation vessels and appropriate subsampling techniques permitted time course experiments. In all cases the metabolic activity in undecompressed samples was lower than it was when incubated at 1 atm. Surface water controls showed a reduced activity upon compression. The processes involving substrate incorporation into cell material were more pressure sensitive than was respiration. The low utilization of substrates, previously found by in situ incubations for up to 12 months, was confirmed and demonstrated to consist of an initial phase of activity, in the range of 5 to 60 times lower than the controls, followed by a stationary phase of virtually no substrate utilization. No barophilic growth response (higher rates at elevated pressure than at 1 atm) was recorded; all populations observed exhibition various degrees of barotolerance.     

Influence of high biomass concentrations on alkane solubilities

Alkane solubilities were measured experimentally for high-density biomass. The resulting Henry's law constants for propane were found to decrease significantly for both dense yeast suspensions and an actual propane-degrading biofilm consortium. At the biomass densities of a typical biofilm, propane solubility was about an order of magnitude greater than that in pure water. For example, a dense biofilm had a propane Henry's law constant of 0.09+/-0.04 atm m(3) mol(-1) compared to 0.6+/-0.1 atm m(3) mol(-1) measured in pure water. The results were modeled with mixing rules and compared with octanol-water mixtures. Hydrogels (agar) and salts decreased the alkane solubility. By considering a theoretical solubility of propane in dry biomass, estimates were made of intrinsic Henry's law constants for propane in pure yeast and biomass, which were 13+/-2 and 5+/-2 atm kg biomass mol(-1) for yeast and biofilm consortium, respectively.     

Nitrogen binding to deoxyhemoglobin at high pressures and its relation to changes in hemoglobin-oxygen affinity

The stoichiometric and thermodynamic properties of nitrogen (N2) binding to human deoxyhemoglobin (Hb) at N2 saturation pressures up to 400 atm were derived from measured N2 solubilities in protein-free buffers (pH 7.1) and in corresponding buffer + Hb (6.5% w/w) solutions at 20.0, 25.0, and 37.0 degrees C. At each temperature, approximately 3 N2 molecules bind per Hb tetramer at N2 pressures of 100 atm, while about 7 N2 molecules bind per tetramer at 400 atm N2 pressure, where available binding sites are still not fully saturated. Calculated N2-Hb binding isotherms are well described by a simple binding model with 12 independent and equivalent binding sites/Hb tetramer. N2 binding at each of the sites is hydrophobic, exhibiting the typical increase of the dissociation enthalpy with temperature. Enthalpies of dissociation are slightly more negative, while corresponding unitary entropies are somewhat less negative than those for the transfer of N2 from olive oil to water. Calculated partial molar volumes of N2 in Hb are positive but less than the corresponding partial molar volumes of N2 in buffer. Results indicate that N2 binding to Hb is accompanied by only small protein conformational changes which entail slight structural destabilization and loss of free volume in the protein that partially accommodates the volume of the N2 ligand. Results are related to previously reported effects of high pressure and high-pressure N2 on HbO2 affinity, illuminating essential features of the molecular mechanisms for these effects.     

New approach to measurement of IR absorption spectra of dissolved oxygen molecules based on photochemical activity of oxygen upon direct laser excitation

Generation of singlet oxygen upon excitation of oxygen molecules with IR diode lasers has been studied in organic media (carbon tetrachloride and acetone) saturated with air under normal pressure and temperature. A new approach to analysis of the experimental data has been developed, which takes into account the degree of overlapping of the spectral bands of oxygen absorption and laser radiation. Optical density, molar absorption coefficient, and the cross section of light absorption were determined for the main absorption maxima of O₂ at 765 and 1273 nm. The results are compared with the data of previous studies. Significance of these results for elucidation of photophysics and photochemistry of oxygen molecules and investigation of biological action of laser radiation is discussed.     

SOLUBILITY OF MUSTARD GAS [BIS (β-CHLOROETHYL) SULFIDE] IN WATER,MOLAR SODIUM CHLORIDE,AND IN SOLUTIONS OF DETERGENTS

1. The solubility of mustard (H) in water and in molar sodium chloride was found to be 5.8 x 10^–3 molar and 3.2 x 10^–3 molar respectively or 0.92 mg. per ml. and 0.5 mg. per ml. Solubility curves have been drawn and the usefulness of this method in examining the homogeneity of H preparations as well as in establishing their solubility, is discussed. 2. Certain detergents increase the solubility of H in water. The solubility was found to increase with the concentration of detergent. 3. Many detergents were found to affect the interfacial tension between H and water so that with slight agitation liquid H breaks up into minute droplets. This in turn greatly accelerates the rate of solution.     

Inhibitory effect of high oxygen pressure on potassium- induced activation of pyruvate dehydrogenase and glucose metabolism in rat brain slices

The effects of high oxygen pressure on pyruvate dehydrogenase (pyruvate: lipoate oxidoreductase (decarboxylating and acceptor-acylating), EC 1.2.4.1) activity, tissue concentration of ATP, and CO2 production from glucose were studied in rat brain cortical slices. The increase in pyruvate dehydrogenase activity and the lowering of cellular ATP, occurring during potassium-induced depolarization at 1 atm of oxygen, were reversed by increasing the oxygen pressure to 5 atm. When brain slices were incubated at 1 atm oxygen with [U-14C]glucose, a high potassium medium approximately doubled the production of 14CO2. Oxygen at 5 atm abolished this potassium-dependent increase in 14CO2 production with no significant effect on glucose oxidation in normal Krebs-Ringer phosphate medium. Adding 4 atm helium to 1 atm oxygen did not interfere with the ability of potassium ions to activate pyruvate dehydrogenase, lower ATP, or increase glucose oxidation. The results show that toxic effects of hyperbaric oxygen, not manifest in "resting" tissue, may be revealed during stress such as potassium depolarization. The site of the toxic effects of oxygen is probably the cell membrane where excess oxygen appears to interfere with the action of the sodium pump, calcium transport or other processes stimulated by increased concentrations of extracellular potassium.     

Rupture of the cell envelope by decompression of the deep-sea methanogen Methanococcus jannaschii

The effect of decompression on the structure of Methanococcus jannaschii, an extremely thermophilic deep-sea methanogen, was studied in a novel high-pressure, high-temperature bioreactor. The cell envelope of M. jannaschii appeared to rupture upon rapid decompression (ca. 1 s) from 260 atm of hyperbaric pressure. When decompression from 260 atm was performed over 5 min, the proportion of ruptured cells decreased significantly. In contrast to the effect produced by decompression from hyperbaric pressure, decompression from a hydrostatic pressure of 260 atm did not induce cell lysis.     

Interfacial preference of anesthetic action upon the phase transition of phospholipid bilayers and partition equilibrium of inhalation anesthetics between membrane and deuterium oxide

The half-height linewidth (v 1/2) of the 1H-NMR spectra of dipalmitoylphosphatidylcholine vesicles changes abruptly at the phase transition temperature. In the absence of inhalation anesthetics, proton signals from the choline head group (hydrophilic interface) and acyl-chain tails (lipid core) change at the same temperature of 39.6 degrees C. The present study compared the effect of four inhalation anesthetics, i.e., methoxyflurane, chloroform, halothane and enflurane, upon the ligand-induced phase transition of phosphatidylcholine vesicle membranes at 37 degrees C. The anesthetics showed differential action upon the phase transition of the phospholipid vesicle membranes between the lipid core and the hydrophilic interface. The concentrations of anesthetics which induced the phase transition of the lipid core were about 2-fold greater than those required for the phase transition of the interfacial choline head groups. From the area under the proton signals of inhalation anesthetics in the NMR spectra, the maximum solubilities of methoxyflurane, chloroform and halothane in 2H2O at 37 degrees C were determined to be 0.671 . 10(-4), 2.637 . 10(-4) and 1.398 . 10(-4) (expressed as mole fractions), or 3.35, 13.17 and 6.98 mmol/1000 g 2H2O, respectively. The solubilities of the anesthetic vapor in 2H2O expressed as mole fractions according to Henry's law ere 9.586 . 10(-4), 6.432 . 10(-4) and 2.311 10(-4)/atm (1.013 . 10(5) Pa) partial pressure, respectively. The presence of phospholipid vesicles in 2H2O increased the solubility of the inhalation anesthetics. From difference between solubility in 2H2O and a dipalmitoylphosphatidylcholine vesicle suspension, the partition coefficients of methoxyflurane, chloroform and halothane between the phospholipid vesicle membranes and 2H2O were estimated. These values, calculated from the mole fractions, were 3364, 1660 and 3850, respectively at 37 degrees C.     

Inhibitory effect of high oxygen pressure on potassiuminduced activation of pyruvate dehydrogenase and glucose metabolism in rat brain slices

The effects of high oxygen pressure on pyruvate dehydrogenase (pyruvate: lipoate oxidoreductase (decarboxylating and acceptor-acylating), EC 1.2.4.1) activity, tissue concentration of ATP, and CO₂ production from glucose were studied in rat brain cortical slices. The increase in pyruvate dehydrogenase activity and the lowering of cellular ATP, occurring during potassium-induced depolarization at 1 atm of oxygen, were reversed by increasing the oxygen pressure to 5 atm. When brain slices were incubated at 1 atm oxygen with [U-¹⁴C]glucose, a high potassium medium approximately doubled the production of ¹⁴CO₂. Oxygen at 5 atm abolished this potassium-dependent increase in ¹⁴CO₂ production with no significant effect on glucose oxidation in normal Krebs-Ringer phosphate medium. Adding 4 atm helium to 1 atm oxygen did not interfere with the ability of potassium ions to activate pyruvate dehydrogenase, lower ATP, or increase glucose oxidation. The results show that toxic effects of hyperbaric oxygen, not manifest in “resting” tissue, may be revealed during stress such as potassium depolarization. The site of the toxic effects of oxygen is probably the cell membrane where excess oxygen appears to interfere with the action of the sodium pump, calcium transport or other processes stimulated by increased concentrations of extracellular potassium.     

Rupture of the Cell Envelope by Decompression of the Deep-Sea Methanogen Methanococcus jannaschii

The effect of decompression on the structure of Methanococcus jannaschii, an extremely thermophilic deep-sea methanogen, was studied in a novel high-pressure, high-temperature bioreactor. The cell envelope of M. jannaschii appeared to rupture upon rapid decompression (ca. 1 s) from 260 atm of hyperbaric pressure. When decompression from 260 atm was performed over 5 min, the proportion of ruptured cells decreased significantly. In contrast to the effect produced by decompression from hyperbaric pressure, decompression from a hydrostatic pressure of 260 atm did not induce cell lysis.     

Oxygen solubility and permeability of carbohydrates

The saturated oxygen concentration in a series of aqueous solutions of sorbitol (up to 35% w/w) and maltitol (up to 50% w/w) was measured using colorimetric reagent vials based on Rhodazine D. The results indicate that the solubility of oxygen in low-water carbohydrates is considerably lower than its solubility in pure water. It was concluded that the low-oxygen solubility is a major factor contributing to the barrier properties of low-water content carbohydrates used in the encapsulation of flavours, lipids, peptides and other oxidisable species.     

The Critical Oxygen Pressures for Respiration in Intact Plants

Two methods for determining critical respiratory oxygen pressure in whole plants are described. By a polarographic method involving the use of cylindrical platinum electrodes the following critical oxygen pressures for root respiration were found: Rice (cv. Norin 36). 0.024 atm: Rice (cv. Norm 37). 0.026 atm: Eriophorum angustifolium. 0.02 atm. These values contrast markedly with those obtained in vitro, and support earlier criticisms of in vitro measurements: they call into question the use of such data in the modelling of root aeration. When the results were assessed by an electrical analogue system, it was concluded that the respiratory activity in the intact root does not follow the normally accepted hyperbolic relationship with oxygen partial pressure. The experimental data were simulated most closely by assuming the critical oxygen pressure to be a function of respiratory responses in the low porosity (high diffusional impedance) tissues of the root meristem and stele, and respiratory activity in the moderately porous root cortex to be unaffected at values greater than 0.001 atm. A critical oxygen pressure of 0.025–0.04 atm for E. angustifolium was found from analyses of the gas phase oxygen in the leaves of whole plants after submergence in the dark. It was concluded that the higher value found by this method was most likely a function of respiratory responses in root tissue remote from the leaf and should not be regarded as the critical oxygen pressure for leaf respiration. The form of the oxygen concentration vs. time plot again suggested a very much lower critical oxygen pressure for certain of the plant tissues.     

Enhanced oxygen transfer rates in fermentation using soybean oil-in-water dispersions

Summary The effect of soybean oil on the volumetric oxygen transfer coefficient during the cultivation ofAerobacter aerogenes cells is presented. For our aeration-agitation conditions (0.278 vvm and 500 rpm), it has been demonstrated that the use 19% (v/v) of soybean oil enabled a 1.85-fold increase of thek _l a coefficient (calculated on a per liter aqueous phase basis). For smaller volumetric oil fractions,k _L a increased linearly with the oil loading. Because of the oxygen-vector properties of soybean oil, this oil is able to significantly increase thek _L a of a bioreactor.Nomenclature C^*, C saturation and actual dissolved oxygen concentrations respectively (g/m³) - K_La volumetric oxygen transfer coefficient (h^–1) - K_La_initial k _La measured before the oil addition (h^–1) - M_O2 molar mass of oxygen (dalton) - N oxygen transfer rate (g/m³. h) - P_O2. P_N2 partial pressures ofO ₂ andN ₂ in the gas (atm) - P_H2OT partial pressure of water in air at the temperatureT (atm) - P_T total pressure (atm) - Q₀ volumetric flow rate of outlet air before seeding (m³/h) - Sp spreading coefficient (dynes/cm) - T absolute temperature of outlet gas (K) - V_i volume of the liquidi in the fermentor (m³) - V_M molar volume at 273 K and 1 atm (m³/mole) - _ij interfacial tension betweeni andj componants (dynes/cm) - _v volumetric fraction of the oil (v/v) - G gas - O oil - W water - i inlet - o outlet     

Rupture of the cell envelope by induced intracellular gas phase expansion in gas vacuolate bacteria.

Using a new approach, we estimated the physical strength of the cell envelopes of three species of gram-negative, gas vacuolate bacteria (Microcyclus aquaticus, Prosthecomicrobium pneumaticum, and Meniscus glaucopis). Populations of cells were slowly (0.5 to 2.9 h) saturated with argon, nitrogen, or helium to final pressures up to 100 atm (10, 132 kPa). The gas phases of the vesicles remained intact and, upon rapid (1 to 2 s) decompression to atmospheric pressure, expanded and ruptured the cells; loss of colony-forming units was used as an index of rupture. Because the cell envelope is the cellular component most likely to resist the expanding intracellular gas phase, its strength can be estimated from the minimum gas pressures that produce rupture. The viable counts indicated that these minimum pressures were between 25 and 50 atm; the majority of the cell envelopes were ruptured at pressures between 50 and 100 atm. Cells in which the gas vesicles were collapsed and the gas phases were effectively dissolved by rapid compression tolerated decompression from much higher gas saturations. Cells that do not normally possess gas vesicles (Escherichia coli) or that had been prevented from forming them by addition of L-lysine to the medium (M. aquaticus) were not harmed by decompression from gas saturation pressures up to 300 atm.     

Effects of hydrostatic pressure on the motor activity of fish from shallow water and 900 m depths; some results of Challenger cruise 6B/85

1. Two species of benthic fish from 900 m depths (90 atm pressure), Trachyscorpia cristulata echinata and Synaphobranchus kaupi, are shown to be adapted to their normal, high ambient pressure. 2. Their condition improves when they are restored to their normal pressure after experiencing decompression in a trawl and they undergo convulsions at 150 atm. 3. This contrasts with the response of shallow water species (Salmo salar, Pleuronectes platessa, Anguilla anguilla and Gadus morhua) which convulse at 93-114 atm and become immobilized and rigid at 150 atm.