Oxygen quenching of pyrene-lipid fluorescence in phosphatidylcholine vesicles. A probe for membrane organization.

Oxygen quenching has been used as an alternative method to study the temperature dependence of the apparent excimer formation constant, kdm, of N-(10-[1-pyrene]-decanoyl)-sphingomyelin (Pyr-SPM) in 1-palmitoyl-2-oleoyl-L-alpha-phosphatidylcholine (POPC) multilamellar vesicles. In conjunction with the lifetime of Pyr-SPM monomer in the absence of excimer and oxygen, kdm can be determined from the measurements of the monomer intensity as a function of oxygen concentration. The advantage of this method is that kdm can be determined without knowledge of the excimer lifetime and intensity, and without knowledge of the true concentration of oxygen in lipid bilayers. Our results show that kdm increases monotonically with temperature from 16 to 40 degrees C, becomes insensitive to temperature from 40 to 50 degrees C and increases again at 54 degrees C. The temperature-insensitive region corresponds to the temperature range of the phase transition of Pyr-SPM determined by differential scanning calorimetry. This result suggests the existence of Pyr-SPM-enriched domains in POPC vesicles. In contrast, no abrupt change in kdm with temperature occurs in the case of 1-palmitoyl-2-[10-(1-pyrenyl) decanoyl] phosphatidylcholine (Pyr-PC).     

Oxygen distribution in the fluid/gel phases of lipid membranes

The interactions between oxygen and lipid membranes play fundamental roles in basic biological processes (e.g., cellular respiration). Obviously, membrane oxidation is expected to be critically dependent on the distribution and concentration of oxygen in the membrane. Here, we combined theoretical and experimental methods to investigate oxygen partition and distribution in lipid membranes of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in a temperature range between 298 and 323 K, specifically focusing on the changes caused by the lipid phase and phase transition. Even though oxygen is known to be more concentrated in the center of fluid phase membranes than on the headgroup regions, the distribution profile of oxygen inside gel-phase bilayers remained to be determined. Molecular dynamics simulations now show that the distribution of oxygen inside DPPC bilayers dramatically changes upon crossing the main transition temperature, with oxygen being nearly depleted halfway from the headgroups to the membrane center below the transition temperature. In a parallel approach, singlet oxygen luminescence emission measurements employing the photosensitizer Pheophorbide-a (Pheo) confirmed the differences in oxygen distribution and concentration profiles between gel- and fluid-phase membranes, revealing changes in the microenvironment of the embedded photosensitizer. Our results also reveal that excited triplet state lifetime, as it can be determined from the singlet oxygen luminescence kinetics, is a useful probe to assess oxygen distribution in lipid membranes with distinct lipid compositions.     

Thermodynamics of anti-sickling agents with hemoglobin S

The effects of oxygen and a second ligand, the anti-sickling agent butylurea, on the hemoglobin S gel-solution phase equilibrium have been studied. The results have been analyzed using thermodynamic properties of the system. In particular, the solubility of deoxy hemoglobin S as a function of butylurea concentration was determined and the thermodynamic analysis shows that there are at least two cooperatively linked butylurea binding sites. Liquid phase oxygen binding studies at various butylurea concentrations show that the linkage between oxygen and butylurea binding is small. The influence of oxygen and butylurea on hemoglobin S solubility was determined by birefringence measurements. The results were interpreted by use of the Gibbs-Duhem equation which combined ligand binding expressions with the non-ideal solution properties and properties of the gel phase. The predicted influence of oxygen and butylurea upon the solubilities of hemoglobin S agrees with experimentally determined values.     

Oxygen transport properties of blood in two different bovine breeds

1. The whole oxygen dissociation curve of oxyhemoglobin has been determined in double-muscled cattle of the Belgian White Blue breed and in Friesian cattle of different body weight. 2. In calves, P50 values are low and DPG level is high (4-20 mumol/g Hb). 3. P50 values of 25 +/- 1.4 mm Hg (mean +/- SD) and a level of DPG less than 1.5 mumol/g Hb have been found in animals weighing more than 80 kg. 4. Effects of temperature and pH on the oxygen dissociation curve have been measured at all levels of saturation. The temperature coefficient (dlog P50/dT) and the Bohr effect expressed as dlog P50/dpH were 0.017 and -0.40, respectively. 5. Hematocrit, hemoglobin concentrations and oxygen capacity of hemoglobin have been measured. 6. No difference between both breeds has been observed. 7. These data can be used to correct measured values of oxygen tension for temperature and pH and to measure oxygen content of blood in cattle.     

Temperature sensitivity of planktic foraminifera and its influence on the oxygen isotope record

We used oxygen isotope measurements from Holocene surface sediments to infer optimum temperature and temperature sensitivity of the planktic foraminiferal species Globigerinoides ruber (pink) and Globigerinoides sacculifer. The (isotopic) optimum temperature of G. ruber (pink) is close to 27°C. G. sacculifer seems to have optimum vital conditions around 22°C and is less temperature sensitive than G. ruber (pink). Our estimations of optimum temperature and temperature sensitivity are in good accordance with laboratory and field investigations. Two simple experiments show that the temperature sensitivity of planktic foraminifera, determined from oxygen isotopes, can influence phase and amplitude of oxygen isotope records, if the temperature distribution at the sea surface changes through time. To use this distortion for paleoceanography, we suggest to derive an ‘isotopic transfer function’ which allows the calculation of average temperature, temperature variability and the isotopic composition of seawater if the oxygen-isotope differences between at least three species are known.     

Effect of anaerobiosis on the adult cerambycid beetle, Rhagium inquisitor L.

Glycerol, lactate, and alanine were found accumulated in adult Rhagium inquisitor beetles which had been incubated anaerobically at +5°C for one month. However, glycerol and alanine were accumulated also in control beetles, kept aerobically at the same temperature, indicating that the accumulation of these substances is an effect of the low temperature. Lactate was rapidly destroyed when the beetles were transferred to air, and this process was accompanied by increased oxygen consumption, indicating the repaying of an oxygen debt due to lactate accumulation. This high oxygen consumption phase was followed by a second, more prolonged high oxygen consumption phase. Because this pattern of oxygen consumption was not found in the control beetles, the second phase of high oxygen consumption was also probably due to the anoxia. It is suggested that this increased oxygen consumption might be caused by a metabolic destruction of accumulated metabolites, but no substances have been identified which could account for it. For this reason the elevated oxygen consumption is more likely to be due to an extensive protein synthesis, related to the re-establishing of aerobic enzyme systems after the long-lasting anoxia.     

Growth of E. Coli W to high cell concentration by oxygen level linked control of carbon source concentration

The growth of E. coli W in a bench scale fermentor to high cell concentration is described. The method involves growth-linked introduction of ammonia to the culture, sparging the culture with oxygen, and maintenance of aerobic conditions during the final growth phase by gradually and automatically decreasing the concentration of the carbon source, sucrose, in the culture. Thus, the oxygen demand is kept within the limits of the supply capacity, and a linear growth rate during the final phase of growth is obtained. A concentration of 42 g dry cell per liter was obtained. The yield constants for nitrogen and phosphorous were determined and were compared with those obtained using the temperature variation method.     

Oxygen Ion Diffusion and Surface Exchange Properties of the α‐ and δ‐phases of Bi2O3

Fast oxide ion conduction is a highly desirable property for materials in a wide range of applications. The fastest reported ionic conductor, representing the current state of the art and an oft‐proposed effective limit of oxide ion conductivity, is the high temperature fluorite‐structured δ phase of Bi₂O₃. Here, the ionic nature of this conduction is, for the first time, directly determined through oxygen tracer diffusion measurements. This phase also presents a remarkably high oxygen surface exchange coefficient, competitive with the highest performance solid oxide fuel cell (SOFC) cathodes yet counterintuitively in a material with negligible electronic conduction. The low temperature α‐Bi₂O₃ polymorph is also investigated, revealing a remarkable drop in diffusivity of over 7 orders of magnitude with a temperature drop of just ≈150 °C. Surprisingly, the diffusion studies also reveal a secondary, significantly faster migration pathway in the α phase. This is attributed to grain boundary conduction and shown to be 3–4 orders of magnitude higher than in the bulk. This previously unobserved property could present an exciting opportunity to tailor ionic conductivity levels through manipulating microstructure down to the nanoscale.     

The Rate of Oxygen Uptake of Quiescent Cardiac Muscle

The rate of oxygen uptake of quiescent papillary muscle of the cat heart has been determined in a flow respirometer with the use of the oxygen electrode. The apparent rate of oxygen uptake as a function of the diameter of the muscle was also determined. It was found that papillary muscles from cat hearts use oxygen at a rate of 2.84 (microliters/mg. wet weight)/hour at a temperature of 35°C. Such muscles can be adequately supplied by diffusion when their surface is uniformly exposed to an atmosphere containing 95 per cent oxygen only if their diameter is 0.64 mm. or less. Papillary muscles from kitten hearts use oxygen at a rate of 4.05 (microliters/mg. wet weight)/hour at a temperature of 35°C. Such muscles can be adequately supplied by diffusion when their surface is uniformly exposed to an atmosphere containing 95 per cent oxygen only if their diameter is 0.53 mm. or less. If the muscles are small enough to be adequately supplied with oxygen by diffusion, the rate of oxygen uptake does not increase when the muscle is stretched.     

The regularities of changes in the sodium ion levels in fish erythrocytes during adaptation to a temperature

It has been shown that unlike fish blood plasma and muscles, the relation between sodium level and temperature is a specific characteristic of erythrocytes. The patterns of changes in the sodium level in fish erythrocytes under a rise in water temperature during annual cycles and under experimental conditions correspond to a certain extent to those registered when the metabolism intensity in fish is determined (the Krogh curve). These changes reflect the participation of sodium ions in the increase of the erythrocytes’ oxygen carrying capacity. This happens during adaptation of fish to oxygen deficiency due to a decrease in this gas solubility in water with increased fish metabolism in response to a rise in temperature.     

Oxygen binding to sickle cell hemoglobin.

The extent of oxygen binding and light scattering of concentrated solutions of hemoglobin S have been determined as a function of oxygen partial pressure using a thin film optical cell. Nearly reversible oxygen binding is observed as witnessed by the small hysteresis found between slow deoxygenation and reoxygenation runs. High co-operativity is noted from unusually large concentration-dependent Hill coefficients when aggregated hemoglobin S is present. The application of linkage theory with the inclusion of non-ideal solution properties permits a test of various simple models for oxygen binding to both the monomer (α₂β₂^s) and polymer (aggregated) phase. It is concluded that oxygen binding to the polymer is either negligible or small under present experimental conditions. Phase diagrams of the solution concentration in equilibrium with polymer phase as a function of oxygen partial pressure are derived using best fit values of polymer parameters.     

Respiratory response to temperature and hypoxia in the zebra mussel Dreissena polymorpha

The effects of temperature acclimation, acute temperature variation and progressive hypoxia on oxygen consumption rates (VO2) were determined for the zebra mussel Dreissena polymorpha. In the first experiment, after acclimation to 5, 15 or 25 degrees C for at least 2 weeks, VO2 was determined at 5 degrees C increments from 5 to 45 degrees C. VO2 increased in all three acclimation groups from 5 to 30 degrees C, corresponding to the normal ambient temperature range for this species. Mussels displayed imperfect temperature compensation at temperatures above 15 degrees C, but exhibited little acclimatory ability below 15 degrees C. In the hypoxia experiment, VO2 was determined over the course of progressive hypoxia, from full saturation (oxygen tension [PO2]=160 Torr [21.3 kPa]) to a PO2 at which oxygen uptake ceased (<10 Torr [1.3 kPa]). Mussels were acclimated to either 5, 15 or 25 degrees C for at least 2 weeks and their respiratory response to progressive hypoxia was measured at three test temperatures (5, 15 and 25 degrees C). The degree of oxygen regulation increased with increasing test temperature, particularly from 5 to 15 degrees C, but decreased with increasing acclimation temperature. The decreased metabolic rate observed for warm-acclimated animals, particularly in the upper portion of the temperature range of the zebra mussel, may allow for conservation of organic energy stores during warm summer months. Compared to other freshwater bivalves, D. polymorpha is a relatively poor oxygen regulator, corresponding with its preference for well-oxygenated aquatic habitats. In addition, a new quantitative method for determining the degree of oxygen regulation is presented.     

Transient Response of Continuously Cultured Heterogeneous Populations to Changes in Temperature

Completely mixed, once-through continuous culture systems of heterogeneous microbial populations of sewage origin were systematically examined for response to changes in reactor temperature. Systems were operated at two dilution rates of 0.125 and 0.25 per h. "Steady state" conditions of the systems were assessed with the reactors operating at 25 C. From this base line, temperature was decreased to as low as 8 C and increased to as high as 57.5 C. Response was assessed in the ensuing transient phase as the system approached a new "steady state." The response was measured by changes in amount and type of carbon source in the reactor effluent as determined by the chemical oxygen demand test, the anthrone test, and gas chromatography. Biological solids concentration and cell composition (protein, carbohydrate, ribonucleic acid and deoxyribonucleic acid) were also determined. These systems responded more favorably to increases than to decreases in temperature. Regardless of the direction of change, the system with the lowest dilution rate (D = 0.125 per h) responded more successfully; i.e., there was less leakage of carbon source in the effluent and less dilute-out of cells during the transient phase.     

Development of hamster one-cell embryos recovered under different conditions to the blastocyst stage

One-cell stage embryos, recovered from superovulated golden hamsters (8 to 12 weeks of age) 12 hours after egg activation, were cultured in HECM-1 medium at 37 degrees C and 5% CO(2) in air. The culture conditions investigated were the time and temperature required for embro recovery, the pH shift of the washing medium, and the oxygen concentration of the gas phase during and after embryo recovery. Each condition was assessed by the developmental efficiency of the embryo as determined by morphological criteria. As the time required for embryo recovery was reduced, the developmental rates of the embryos were improved: 2.3% (3 128 ) 26.9% (35 130 ) at 5 and 3 minutes, respectively, as determined by the number of embryos developed to the blastocyst stage. No blastocysts were obtained when more than 10 minutes were required for embryo recovery. As the oxygen concentration was reduced from 40 to 20% or to 5%, rather high developmental rates were obtained even when the time required for embryo recovery was prolonged: 6.9% (9 130 ) and 21.7% (28 129 ) of the embryos developed to the blastocyst stage when they were recovered under 5% oxygen within 10 and 5 minutes, respectively. Neither the temperature during embryo recovery (37 degrees C and 25 degrees C) nor the pH shift (pH 7.22 to 7.52) of the washing medium used in embryo recovery procedures influenced the development of the embryos. These findings suggest that the developmental block in hamster embryos may involve oxidative stress, which may result from exposure to high oxygen concentration and light during the manipulation of oocytes and embryos.     

Regulation of exoprotease production by temperature and oxygen in Vibrio alginolyticus

The production of an extracellular collagenase and an alkaline protease by Vibrio alginolyticus during stationary phase was inhibited by a temperature shift from 30 to 37°C and by a lack of oxygen. The stability of the exoproteases was unaffected by incubation at 37°C and aeration. The optimum growth temperature for the V. alginolyticus strain was 33.5°C Aeration enhanced the rate of growth of exponential phase cells. Temperature and oxygen did not affect the growth of stationary phase cells when the exoproteases were being produced. Macromolecular synthesis in stationary phase cells was not affected by temperature. There was no rapid release of the exoproteases after temperature shift down and chloramphenicol inhibited the production of the enzymes when added at time of temperature shift down from 37 to 30°C. The regulation of exoprotease production by temperature and oxygen was specific and has implications regarding the ecology of V. alginolyticus. Cerulenin, quinacrine and O-phenanthroline inhibited the production of the exoproteases.     

Transient kinetics of oxygen dissociation from ferrous subunits of iron-cobalt hybrid hemoglobins. The principal reaction controlling the co-operativity

The oxygen dissociation constants from Fe subunits in the half-ligated intermediate states of Fe-Co hybrid hemoglobins, alpha(Fe-O2)2 beta(Co)2 and alpha(Co)2 beta(Fe-O2)2, have been determined as functions of pH, temperature and inositol hexaphosphate. The oxygen dissociation rates from alpha(Fe-O2)2 beta(Co)2 are estimated to be more than 1300 s-1 for the deoxy quaternary state (T-state) and less than 3 s-1 for the oxy quaternary state (R-state) at 15 degrees C in 50 mM-Tris or Bis-Tris buffer containing 0.1 M-Cl-, while those of alpha(Co)2 beta(Fe-O2)2 are more than 180 s-1 and less than 5 s-1 for the T and R-states, respectively. The pH dependence of the oxygen dissociation rate from Fe subunits is large enough to be accounted for by the R-T transition, and implies that those half-ligated intermediate hybrids mainly exist in the R-state at pH 8.8, and in the T-state at pH 6.6, while other studies indicated that the half-ligated hybrids are essentially in the R-state at pH 7. Large activation energies of the oxygen dissociation process of 19 to 31 kcal/mol determined from the temperature dependence suggest that the process is entropy-driven.     

Oxygen binding by marine fish blood under hypothermic experimental conditions

Influence of temperature in the range of 1-15 degrees C on oxygen binding properties of blood of thermophilic--golden mullet (Liza aurata), anchovy (Engraulis encrasicolus), and cold-tolerant--sardelle (Clupeonella cultriventris) fishes has been investigated under experimental conditions. Heat dependence of oxygenation reaction in thermophilic fish blood at temperature below 10 degrees C considerably increases, which is evidenced by high deltaH values. That is accompanied by a substantial increase of blood oxygen affinity and complicates blood deoxygenation at the tissue level. This reaction is apparently determined by the change of hemoglobin interaction with intraerythrocyte medium. The concentration of NTP in erythrocytes increases, that partially compensates negative changes of blood oxygen affinity (parameter P50 is raised) under long-term maintenance of fishes at 5 degrees C. However this reaction is not observed at low temperatures (1-2 degrees C).     

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.     

Demonstration of lag phase in the sol-gel transformation of deoxygenated S hemoglobin without temperature alteration.

1). During the sol to gel transformation of deoxygenated sickle hemoglobin, a time-dependent process preceding gel formation (lag phase) was demonstrated that was inversely proportional to a function of the hemoglobin concentration and that occurred without alteration in temperature, pH, or oxygen tension. 2). As determined by the Schachman modification of the capillary viscometer, preparations of oxyhemoglobin S and A and deoxyhemoglobin A were indistinguishable when compared over a wide range of concentrations. Up to the concentration at which gelling occurred, deoxyhemoglobin S exhibited the same viscosity behavior. The viscosity of deoxygenated hemoglobin S within the lower gelling concentration range was normal during the lag phase and became abnormally high only at the time of gelation.     

Replication of ultraviolet-irradiated simian virus 40 in monkey kidney cells

This paper extends the concepts of linkage and control, previously studied in single phase allosteric and polysteric systems, to multiple phase (polyphasic) systems. In particular, a study has been made of the dependence of the solubility of sickle cell hemoglobin on oxygen partial pressure. Phase diagrams are obtained from observations of birefringence changes of hemoglobin solutions in a thin film optical cell. The effects of temperature and pH are found to be correlated largely with oxygen binding curves for non-gelling solutions. This suggests only small enthalpy and proton release changes for the gelation process. Variable time delays for the onset of birefringence were observed for partial deoxygenation of a fully oxygenated sample. The reciprocal of the time delay depends on a high power of the supersaturation ratio. The nucleation kinetics are, thereby, similar to those found in fully deoxygenated solutions in temperature-jump studies. Oxygen binding curves for non-gelling solutions of sickle cell hemoglobin were used in conjunction with the phase diagram results to evaluate oxygen binding curves for the polymer gel. Account was taken of the water content of the gel and of the large non-ideality of the solution. Analysis of the phase diagram data based on polyphasic linkage relationships suggests that some reversible oxygen-binding by the gel is present. The difference in oxygen binding between solution and gel obtained in this way is similar to that found by Hofrichter (1979) for carbon monoxide.