Further Experiments on the Inhibition of Respiration of Peas Induced by Oxygen at High Pressures

Turner and Quartley (1956) concluded that the tricarboxylicacid cycle was a major respiratory pathway in green shelledpeas subjected to high pressures of oxygen. Additional supportfor this view has been obtained by demonstrating the depletionin content of oxaloacetic acid during treatment with oxygenand by the complete reversal of all the functions determinedfollowing a return of the samples to air after treatment forshort periods with oxygen at high pressures. Oxygen at pressures of either 5 or 3.5 atmospheres caused asimilar pattern in the behaviour of the carbon dioxide production,pH, citric and keto-acids, whilst oxygen at a pressure of 2atm. affected mainly the carbon dioxide production. This suggeststhat the respiration process can be inhibited by oxygen at highpressures in at least two different stages.     

The effects of structural parameters of zeolite on the adsorption of hydrogen: a molecular simulation study

The adsorption isotherm of hydrogen in zeolites FAU, LTA, KFI, RWY, RHO and TSC has been simulated employing grand canonical Monte Carlo procedure for a temperature range of 77 to 95 K and different pressures. The effects of structural composition, unit cell volume, framework density and specific surface area of zeolite on hydrogen adsorption in zeolites were investigated. The results clearly show that the adsorption of hydrogen in zeolites with the same silica density is a function of oxygen density at low pressures, and it is approximately the same at intermediate pressures. Nevertheless, at high pressures, the adsorption of hydrogen is a function of pore diameter for zeolites with same silica density. The effect of specific surface area on the adsorption isotherm of hydrogen on zeolites with approximately the same specific surface area is significant at low and high pressures. The results clearly indicate that the adsorption of hydrogen in RWY zeolite has maximum value at 77 K and at high pressures. The optimum condition of pressure for hydrogen adsorption isotherm in RWY zeolite is determined to be 600 bar. At a temperature of 77 K and a pressure of 600 bar, the adsorption of hydrogen in RWY zeolite is 6.93 wt %.     

Effects of controlled gas environments in solid-substrate fermentations of rice

The gas environment is solid-substrate fermentations of rice significantly affected levels of biomass and enzyme formation by a fungal species screened for high amylase production. Constant oxygen and carbon dioxide partial pressures were maintained at various levels in fermentations by Aspergillus oryzae. Control of the gas phase was maintained by a “static” aeration system admitting oxygen on demand and stripping excess carbon dioxide during fermentation. Constant water vapor pressures were also maintained by means of saturated salt solutions. High Oxygen pressures stimulated amylase productivity significantly. On the other hand, amylase production was severely inhibited at high carbon dioxide pressures. While relatively insensitive to oxygen pressure, maximum biomass productivities were obtained at an intermediate carbon dioxide pressure. High oxygen transfer rates were obtained at elevated oxygen pressures, suggesting, in view of the stimulatory effect of oxygen on amylase production, a stringent oxygen requirement for enzyme synthesis. Solid-substrate fermentations were highly advantageous as compared with submerged cultures in similar gas environments. Not only were amylase productivities significantly higher, but the enzyme was highly concentration in the aqueous phase of the semisolid substrate particles and could be extracted in a small volume of liquid. Results of this work suggest that biomass and product formation in microbial processes may be amenable to control by the gas environment. This is believed to offer an interesting potential for optimizing selected industrial fermentation processes with respect to productivity and energy consumption.     

Growth of Chlorella sorokiniana at Hyperbaric Oxygen Pressures

The growth rate of Chlorella sorokiniana decreased in a linear fashion as the partial pressure of oxygen was increased from 711 to 1,478 mm of Hg. Under two atmospheres of oxygen pressure, growth ceased after 10 to 12 hr. This cessation of growth was not due to any permanent injury, as growth resumed when oxygen partial pressure was reduced to ambient levels. The inhibition occurred under both autotrophic and heterotrophic growth conditions and was not accompanied by an increase in cell size. The results indicated that the tolerance of Chlorella cells to elevated oxygen pressures was not an absolute immunity, and that inhibition of growth at very high oxygen pressures cannot be accounted for by an inhibition of photosynthesis alone.     

EFFECTS OF INCREASED PARTIAL PRESSURES OF OXYGEN, NITROGEN AND HELIUM ON CELLS IN CULTURE

The effects of gas-phase oxygen, nitrogen and helium at superatmospheric as well as at atmospheric partial pressures have been studied, using both normal and malignant cells. The ability of certain types of cells in monolayer cultures to proliferate when exposed to high or low oxygen tensions, and to recover when cultured further under more optimal conditions, has been assessed. The presence of an inert gas at high partial pressure permits survival of various types of cells in culture at much higher oxygen tensions than would otherwise be possible. A tentative explanation for this phenomenon is provided and its significance discussed.     

Optimization of the cell envelope disruption of extremely halophilic bacteria

This paper describes an examination of the cell envelope stability opposite to disruption by chemical and physical methods of extremely halophilic bacteria. The following methods of cell treatment were studied: solvent and chelating agents; pressure shearing at several pressures; ultrasonic disintegration for various times; ballistic disintegration; grinding with cold alumina; lysozyme digestion; osmotic shock; and freezing and thawing. The procedure is based on the determination of three cytoplasmic enzymes released by the cell treatment. Menadione reductase was also used as convenient marker enzyme for damage to the permeability barrier. Of all the methods, only pressure shearing and ultrasonic disintegration yielded a crude extract with high halophilic enzyme activities. These procedures are suitable in designing a cell fractionation scheme for halophilic enzyme purifications.     

Effect of oxygen pressure on glycogen synthesis by rat-liver slices

1. Glycogen synthesized by rat-liver slices 0.5mm. thick incubated at 1atm. oxygen pressure in Hastings medium with glucose was localized in the cells of the periphery of the slice. Cells of the interior of this slice do not synthesize glycogen. 2. Inner cells of thin slices (about 0.3mm. thick) can synthesize glycogen when such slices are incubated under the same conditions, but oxygen pressures higher than 1atm. are required if inner cells of slices 0.5mm. or more thick are to be able to synthesize glycogen. 3. Localization of newly synthesized glycogen in rat-liver slices incubated in Hastings medium with glucose does not depend on glucose concentration. 4. Calculation of the minimum oxygen pressure required to synthesize glycogen gives values between 0.09 and 0.17atm. 5. The advantages of high oxygen pressures for the study of the synthesis of glycogen and other compounds that require ATP are discussed.     

Mechanism of soybean nodule adaptation to different oxygen pressures

Abstract. Soybean nodules showed the ability to adapt to oxygen pressures above and below ambient levels and this adaptation involved a decrease in cortical intercellular air-spaces with increasing oxygen pressure. Nodules were grown in oxygen pressures from 4.7 to 75 kPa and the decrease in number and size of cortical intercellular spaces with increasing oxygen pressure was the result of a change in cell structure and the deposition of an electron dense material within intercellular spaces. Exposure to a saturating pressure of acetylene caused a similar inhibition of respiration and nitrogenase activity in nodules developed in oxygen pressures from 4.7 to 47 kPa, suggesting that putative acetylene-induced changes in oxygen diffusion resistance occur by a different mechanism than that involved in long-term adaptation to oxygen. However, in nodules grown at 75 kPa oxygen, the initial specific activities were lower and did not show an acetylene induced decline. The results are discussed in terms of the current theories of regulation of nitrogenase activity by oxygen availability.     

Are there ecological implications for the proposed energetic restrictions on photosynthetic oxygen evolution at high oxygen concentrations?

It has recently been shown that, in subthylakoid particles prepared using detergent, there is inhibition of oxygen production reactions in photosynthesis by thermodynamic feedback from oxygen build-up, with 50% inhibition at 230 kPa partial pressure of oxygen. This article presents a comprehensive analysis of laboratory data on the effects of high oxygen partial pressures on photosynthesis, and on photo-lithotrophic and chemo-organotrophic growth, of oxygen-producing organisms. The article also contains an analysis of the extent to which high oxygen concentrations occur at the site of photosystem II (PSII) activity under natural conditions today and in the past. The conclusion is that the oxygen concentrations found in nature are very unlikely to reach that needed to cause 50% inhibition of the photosynthetic oxygen production reaction in subthylakoid particles, but that it is just possible that a small part of the inhibition of photosynthesis and of photo-lithotrophic growth by oxygen can be attributed to inhibition of oxygen production by PSII.     

鱼类染色体组操作的研究 Ⅰ.静水压休克诱导三倍体水晶彩鲫

采用静水压休克方法研究了促使第二极体保留诱发三倍体水晶彩鲫的最佳条件。在卵受精后4—5min采用600kg/cm~2或650kg/cm~2的静水压处理3min,不但能导致100％的三倍化,而且胚胎的存活率相当高,孵化率为对照组的90％左右。研究表明,静水压休克是进行鱼类染色体组操作的有效方法,休克的最佳条件易于掌握,处理程序易于标准化。文中讨论了静水压处理的条件与三倍体出现率和胚胎存活率的关系,以及最佳条件下和不适条件下胚胎死亡的原因。     

Tissue ammonia and amino acids in rats at various oxygen pressures

The amino acid and ammonia profiles in various tissues of the rat exposed to different pressures of pure oxygen have been studied. Well-defined changes in behavioral activity accompanied a profile of increasing pressure, culminating in convulsive activity in each group of exposed animals. After an initial depression of ammonia, in all tissues studied at 0.68 atm oxygen ammonia increased significantly at higher oxygen pressures. A rise in tissue ammonia took place in the absence of undue muscular activity on the part of the exposed animals. A significant increase in ammonia occurred first in brain and liver at 3.40 atm. Ammonia concentration was high in all tissues after convulsions occurred at 4.08 atm. Between 0.68 and 2.72 atm oxygen, tissue ammonia concentration was generally low and brain glutamate and gamma-aminobutyric acid were high. At pressures higher than 2.72 atm oxygen, tissue glutamate declined and glutamine increased. Alanine became significantly elevated in serum and muscle at high oxygen pressure, and aspartate was depressed in heart, liver, and muscle. These pressure-course experiments on ammonia accumulation in tissue confirm previous serial time course observations that ammonia accumulates in the brain and several tissues of the rat even in the absence of undue muscular activity during high-pressure oxygen exposure and is a significant factor in inducing convulsions.     

Batch and continuous cultivation of Pseudomonas fluorescens at increased pressure

The effect of increased total pressure and partial pressures of oxygen and carbon dioxide on the growth of Pseudomonas fluorescens was investigated in an airlift reactor. In batch cultivations bacterial growth was completely inhibited with air at 8 bars total pressure. The same effect was observed with aeration by pure oxygen at 1.15 bars. Carbon dioxide partial pressure did not show inhibitory effects. Continuous experiments confirm the assumption that growth inhibition at higher total pressure is caused by the increase in oxygen partial pressure. Incubation of P. fluorescens at higher oxygen partial pressure led to an increase of bacterial productivity during subsequent continuous cultivation at ambient pressure (1 bar) with air. Maximum productivity was increased by about 75% after aeration with pure oxygen. This effect is probably the result of metabolic adaption of the bacterial cells to high oxygen partial pressure.     

Potential for high hydrostatic pressure processing to control quarantine insects in fruit

Tests were conducted to determine the potential for high hydrostatic pressure (HPP) to control codling moth, Cydia pomonella (L.), and western cherry fruit fly, Rhagoletis indifferens Curran. Apples (Malus spp.) with codling moth larvae or eggs were treated at 24 and 72 h, respectively, after infestation at a series of pressures between 14,000 and 26,000 pounds per inch2 (psi). Survivorship was determined the next day for larvae and after 10 d for eggs. Codling moth eggs were more tolerant of HPP treatment than larvae. Mortality of larvae was 97% at 22,000 psi, whereas mortality of eggs at this dose was 29% and not significantly different from the untreated controls. In a second study, no codling moth eggs hatched at any high pressure treatment between 30,000 and 80,000 psi, indicating these pressures were lethal. Various stages of western cherry fruit fly were treated at pressures from 10,000 to 45,000 psi, and survivorship was determined after 24 h. Eggs and third instars were more tolerant of HPP than the first and second instars. Mortality was 100% in western cherry fruit fly eggs and larvae at pressures > or =25,000 psi. Apple and sweet cherry quality after high pressure treatment was poor, but high pressure may have applications to control quarantine pests in other fruits.     

Air pressure effects on biomass yield of two different Kluyveromyces strains

The use of air pressure as a way of improving oxygen transfer in aerobic bioreactors was investigated. To compare the air pressure effects with traditional air bubbled cultures, experiments using a pressure reactor and a stirred flask, with the same oxygen transfer rate, were made. Kluyveromyces marxianus is an important industrial yeast and some of it show a “Kluyver effect” for lactose: even under oxygen limited growth conditions, certain disaccharides that support aerobic, respiratory growth, are not fermented. This study deals with the effect of increased pressure on the physiological behavior of two Kluyveromyces strains: K. marxianus ATCC10022 is a lactose-fermenting strain, whereas K. marxianus CBS 7894 has a Kluyver-effect for lactose. For K. marxianus ATCC10022 an air pressure increase of 2 bar led to a 3-fold increase in biomass yield. When air pressure increased an enhancement of ethanol oxidation of cell yeasts was also observed. Batch cultures of K. marxianus CBS 7894 exhibited different growth behaviour. Its metabolism was always oxidative and ethanol was never produced. With the increase in air pressure, it was possible to increase the productivity in biomass of K. marxianus CBS 7894. As a response to high oxygen concentrations, due to the increase in oxygen partial pressure, oxidative stress in the cells was also studied. Antioxidant defences, such as superoxide dismutase, catalase, and glutathione reductase, were at high activity levels, suggesting that these yeast strains could tolerate the increased pressures applied.     

THE RESPIRATION OF LUMINOUS BACTERIA AND THE EFFECT OF OXYGEN TENSION UPON OXYGEN CONSUMPTION

1. The respiration of luminous bacteria has been studied by colorimetric and manometric methods. 2. Limulus oxyhaemocyanin has been used as a colorimetric indicator of oxygen consumption and indicator dyes were used for colorimetric determination of carbon dioxide production. 3. The Thunberg-Winterstein microrespirometer has been used for the measurement of the rate of oxygen consumption by luminous bacteria at different partial pressures of oxygen. 4. The effect of oxygen concentration upon oxygen consumption has been followed from equilibrium with air to low pressures of oxygen. 5. Luminous bacteria consume oxygen and produce carbon dioxide independent of oxygen pressures from equilibrium with air (152 mm.) to approximately 22.80 mm. oxygen or 0.03 atmosphere. 6. Dimming of a suspension of luminous bacteria occurs when oxygen tension is lowered to approximately 2 mm. Hg (0.0026 atmosphere) and when the rate of respiration becomes diminished one-half. 7. Pure nitrogen stops respiratory activity and pure oxygen irreversibly inhibits oxygen consumption. 8. The curve for rate of oxygen consumption with oxygen concentration is similar to curves for adsorption of gasses at catalytic surfaces, and agrees with the Langmuir equation for the expression of the amount of gas adsorbed in unimolecular layer at catalytic surfaces with gas pressure. 9. A constant and maximum rate of oxygen consumption occurs in small cells when oxygen concentration becomes sufficient to entirely saturate the surface of the oxidative catalyst of the cell.     

Influence of total and oxygen partial pressure on growth and metabolism of Methylomonas clara

The effect of total and oxygen partial pressure on metabolic activities of Methylomonas clara has been investigated in batch and continuous cultivation experiments using a pressurizable airlift loop reactor. At Oxygen partial pressures of more than 1000 mbar growth of M. Clara is retarded and completely inhibited at 1200 mbr. However, after several hours of incubation at elevated oxygen partial pressures, biomass formation is nearly doubled in subsquent continuous operation, Cells pretreated with oxygen are characterized by a change of cytochrome content; they excret carboxylic acids into the medium. The results indicate that, by sparging an aerobic culture intermittently wich pure oxygen, formation of biomass might be enbanced. (c) 1992 John Wiley & Sons, Inc.     

THE EFFECT OF LOW PRESSURES ON CELL OXIDATION

1. A method is described for measuring tissue oxidation under reduced barometric pressure. 2. The oxygen uptake of yeast is diminished by low barometric pressures to a greater extent than by a reduction of the partial pressure of oxygen, to a corresponding degree, at atmospheric pressure. 3. This effect of low pressure is not observed with certain in vitro oxidation systems. 4. The anaerobic respiration (carbon dioxide production) of yeast is not at all affected by low pressures. 5. The inhibition of tissue oxidation caused by carbon monoxide is removed by lowering the pressure.     

Effects of oxygen on responses to heating in two lizard species sampled along an elevational gradient

Thermal tolerance is an important variable in predictive models about the effects of global climate change on species distributions, yet the physiological mechanisms responsible for reduced performance at high temperatures in air-breathing vertebrates are not clear. We conducted an experiment to examine how oxygen affects three variables exhibited by ectotherms as they heat—gaping threshold, panting threshold, and loss of righting response (the latter indicating the critical thermal maximum)—in two lizard species along an elevational (and therefore environmental oxygen partial pressure) gradient. Oxygen partial pressure did not impact these variables in either species. We also exposed lizards at each elevation to severely hypoxic gas to evaluate their responses to hypoxia. Severely low oxygen partial pressure treatments significantly reduced the gaping threshold, panting threshold, and critical thermal maximum. Further, under these extreme hypoxic conditions, these variables were strongly and positively related to partial pressure of oxygen. In an elevation where both species overlapped, the thermal tolerance of the high elevation species was less affected by hypoxia than that of the low elevation species, suggesting the high elevation species may be adapted to lower oxygen partial pressures. In the high elevation species, female lizards had higher thermal tolerance than males. Our data suggest that oxygen impacts the thermal tolerance of lizards, but only under severely hypoxic conditions, possibly as a result of hypoxia-induced anapyrexia.     

Physiological behaviour of Saccharomyces cerevisiaeunder increased air and oxygen pressures

Saccharomyces cerevisiae, in a pressure batch reactor, coped with higher air (1.2-3 bar) pressures better than with pure oxygen pressures (1.2-3 bar) for an equivalent dissolved oxygen concentration. However, pure oxygen pressure enhanced ethanol production. Both pressures did not influence the type of metabolism followed by the organism which was always oxidoreductive. Growth was inhibited with the increase of air and pure oxygen pressure and almost completely inhibited with 8 bar of pure oxygen. Above 3 bar activities of mitochondrial superoxide dismutase and glutathione reductase increased with air pressure, but cytosolic superoxide dismutase and catalase increased activity only in pure oxygen pressure.