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PubMed2005

The effects of organic carbon, ammoniacal-nitrogen, and oxygen partial pressure on the stratification of membrane-aerated biofilms.

The purpose of this study was to examine the effects of different nutrient (carbon, nitrogen, oxygen) concentrations on the microbial activity and community structure in membrane-aerated biofilms (MABs). MABs were grown under well-defined conditions of fluid flow, substrate concentration, and membrane oxygen partial pressure. Biofilms were then removed and thin-sliced using a cryostat/microtome parallel to the membrane. Individual slices were analyzed for changes with depth in biomass density, respiratory activity, and the population densities of ammonia-oxidizing and denitrifying bacteria populations. Oxygen-sensing microelectrodes were used to determine the depth of oxygen penetration into each biofilm. Our results demonstrated that ammonia-oxidizing bacteria grow near the membrane, while denitrifying bacteria grow a substantial distance from the membrane. However, nitrifying and denitrifying bacteria did not grow simultaneously when organic concentrations became too high or ammonia concentrations became too low. In conclusion, membrane-aerated biofilms exhibit substantial stratification with respect to community structure and activity. A fundamental understanding of the factors that control this stratification will help optimize the performance of full-scale membrane-aerated biofilm reactors for wastewater treatment.

Ammonia↗
PubMed2005

Surface chemistry of nanometer-sized aerosol particles: reactions of molecular oxygen with 30 nm soot particles as a function of oxygen partial pressure.

The kinetics of the reaction between soot nanoparticles and molecular oxygen were studied by tandem differential mobility analysis (TDMA). The particles were extracted from the tip of an ethene diffusion flame. Reactions were studied at atmospheric pressure in mixtures of nitrogen and oxygen. The studies involved particles of an initial mobility diameter of 30 nm over broad ranges of temperature (500-1100 degrees C) and oxygen volume fraction (0-1). Measurements as a function of oxygen partial pressure establish that the oxidation kinetics are not first-order in oxygen volume fraction (F(O2)). Rather, the oxidation rate increases rapidly and linearly with F(O2) between 0 and 0.05 and then more slowly but still linearly between 0.05 and 1. Temperature dependent measurements are consistent with a reaction pathway involving two kinetically distinguishable oxidation sites which interconvert thermally and through oxidation. Results and conclusions are compared to those of earlier studies on the oxidation of soot.

Aerosols↗
PubMed2003

Periodic breathing induced by arterial oxygen partial pressure oscillations.

The Grodins model of respiratory control (Grodins et al., 1967) describes cardio-respiratory control for a lung with homogeneous gas concentrations. In this study we modify the Grodins model to take account of the inhomogeneities in gas concentration within the lung that are seen in many subjects with respiratory illnesses. This modification has the effect of lowering arterial oxygen partial pressure significantly. We investigate the effect on cardio-respiratory control of this low arterial oxygen signal and find that the governing equations may be reduced to a single delay-differential equation. This reduced model is found to be a good approximation to the full model and gives predictions that are similar to reported clinical data.

Humans↗
PubMed1999

Quantification of regional intrapulmonary oxygen partial pressure evolution during apnea by (3)He MRI.

We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized (3)Helium ((3)He-->). Single-breath, single-bolus visualization of (3)He--> administered to the airspaces is used to analyze nuclear spin relaxation caused by the local oxygen partial pressure p(O(2))(t). We model the dynamics of hyperpolarization in the lung by rate equations. Based hereupon, a double acquisition technique is presented to separate depolarization by RF pulses and oxygen induced relaxation. It permits the determination of p(O(2)) with a high accuracy of up to 3% with simultaneous flip angle calibration using no additional input parameters. The time course of p(O(2)) during short periods of breathholding is found to be linear in a pig as well as in a human volunteer. We also measured the wall relaxation time in the lung and deduced a lower limit of 4.3 min.

Adult↗
PubMed2000

Partial pressure of ammonia versus ammonia in hepatic encephalopathy.

Ammonia is considered the major pathogenetic factor of cerebral dysfunction in hepatic failure. The correlation between total plasma ammonia and the severity of hepatic encephalopathy (HE), however, is variable. Because ammonia that is present in gaseous form readily enters the brain, the correlation with the grade of HE of the pH-dependent partial pressure of gaseous ammonia (pNH(3)) could be better than that of total arterial ammonia levels. To test this hypothesis, 56 cirrhotic patients with acute episodes of clinical HE (median age, 54 years; range, 21-75) were studied by clinical examination and by long-latency median-nerve sensory-evoked potentials (SEPs) N70 peak, an objective and sensitive electrophysiological measure of HE. pNH(3) was calculated from arterial blood according to published methods. The clinical grade of HE correlated (P <.001) with both pNH(3) and total ammonia, but correlation was stronger with pNH(3) (r =.79 vs.69, P =.01). A similar correlation was found for N70 peak latency (r =.71 with pNH(3) vs.64 with total ammonia, respectively, P =.08). In summary, arterial pNH(3) correlates more closely than total ammonia with the degree of clinical and electrophysiological abnormalities in HE. These findings support the ammonia hypothesis of HE and suggest that pNH(3) might be superior to total ammonia in the pathophysiological evaluation of HE.

Adult↗
PubMed1995

Comparison of dose-response slopes obtained by simultaneous assessment of changes in FEV1 and transcutaneous oxygen partial pressure during methacholine challenges in asthmatic patients.

We aimed to ascertain whether monitoring changes in transcutaneous (tc) oxygen partial pressure (PO2) may be used to determine the slope of the dose-response curves to inhaled methacholine. In 10 adult asthmatic patients, FEV1 and tcPO2 were simultaneously measured during inhalation of doubling methacholine concentrations. In each patient, the slopes of the methacholine dose-response curves for FEV1 and tcPO2 were similar and strongly correlated (r = 0.72; p < 0.05). The results indicate that tcPO2 monitoring represents a useful, reliable tool for analysis of the slope of dose-response curves to inhaled methacholine in asthmatic patients. It can also be used to investigate the pathophysiological implications of bronchial hyperreactivity.

Adult↗
PubMed2001

Is the partial pressure of carbon dioxide in the blood related to the development of retinopathy of prematurity?

AIMS: To determine the role of carbon dioxide in the development of retinopathy of prematurity (ROP). METHODS: This was a retrospective cohort study of 25 consecutive infants admitted to the neonatal unit with continuously recorded physiological data. The daily mean and standard deviation (SD) of transcutaneous carbon dioxide partial pressure (tcPCO(2)) was compared between infants who had stage 1 or 2 ROP and stage 3 ROP. The time spent hypocarbic (<3 kPa) and/or hypercarbic (>10 kPa and >12 kPa) was also compared between these groups. Intermittent arterial carbon dioxide tension was also measured and compared with the simultaneous tcPCO(2) data. RESULTS: There were no significant differences in carbon dioxide variability or time spent hypocarbic and/or hypercarbic between the ROP groups on any day. 86% of transcutaneous values were within 1.5 kPa of the simultaneous arterial value. CONCLUSION: TcPCO(2) measurement can be a very useful management technique. However, in this cohort neither variable blood carbon dioxide tension nor duration of hypercarbia or hypocarbia in the first 2 weeks of life was associated with the development or severity of ROP.

Blood Gas Monitoring, Transcutaneous↗
PubMed1986

The partial pressure of isoflurane or halothane does not affect their solubility in rabbit blood or brain or human brain: inhaled anesthetics obey Henry's Law.

We tested the possibility that the solubility of halothane or isoflurane in rabbit blood or human or rabbit brain does not obey Henry's Law. We measured the blood/gas and brain/gas partition coefficients for both anesthetics at approximately 1 MAC and at 0.01 MAC at 37 degrees C. The partition coefficients determined at the high vs low partial pressures did not differ. We conclude that the solution of isoflurane and halothane in blood and brain obeys Henry's Law.

Animals↗
PubMed1990

Alveolar partial pressures of carbon dioxide and oxygen measured by a helium washout technique.

A non-invasive technique was developed for measuring alveolar carbon dioxide and oxygen tension during tidal breathing. This was achieved by solving the Bohr equations for mean alveolar carbon dioxide and oxygen tensions (PACO2, PAO2) from known values of the dead-space:tidal volume ratio measured by helium washout, and from the mixed expired partial pressure of carbon dioxide and oxygen. The derived values of wPACO2 and wPAO2 were compared with PaCO2 obtained from arterial gas analysis and PAO2 calculated from the ideal air equation. Four normal subjects and 58 patients were studied. Calculated and measured PCO2 values agreed closely with a difference in mean values (wPACO2 - PaCO2) of 0.01 kPa; the SD of the differences was 0.7 kPa. The difference in mean values between wPAO2 and PAO2 was 0.02 kPa; the SD of the differences was 0.93 kPa. The method is simple and not time consuming, and requires no special cooperation from the patients. It can be applied in the laboratory or at the bedside to any subject breathing tidally. Physiological deadspace:tidal volume ratio, PAO2 and PACO2, static lung volumes, respiratory exchange ratio, carbon dioxide production, oxygen uptake, tidal volume, and total ventilation can be measured with acceptable accuracy and reproducibility in one test. An arterial blood sample is needed initially to provide an independent measure of PaCO2 and for measurement of the alveolar-arterial PO2 difference. Subsequently, PaCO2 can be estimated from wPACO2 sufficiently well for clinical purposes and PaO2 or SaO2 can be monitored by non-invasive methods.

Adult↗
PubMed2004

Soil carbon dioxide partial pressure and dissolved inorganic carbonate chemistry under elevated carbon dioxide and ozone.

Global emissions of atmospheric CO(2) and tropospheric O(3) are rising and expected to impact large areas of the Earth's forests. While CO(2) stimulates net primary production, O(3) reduces photosynthesis, altering plant C allocation and reducing ecosystem C storage. The effects of multiple air pollutants can alter belowground C allocation, leading to changes in the partial pressure of CO(2) (pCO(2)) in the soil , chemistry of dissolved inorganic carbonate (DIC) and the rate of mineral weathering. As this system represents a linkage between the long- and short-term C cycles and sequestration of atmospheric CO(2), changes in atmospheric chemistry that affect net primary production may alter the fate of C in these ecosystems. To date, little is known about the combined effects of elevated CO(2) and O(3) on the inorganic C cycle in forest systems. Free air CO(2) and O(3) enrichment (FACE) technology was used at the Aspen FACE project in Rhinelander, Wisconsin to understand how elevated atmospheric CO(2) and O(3) interact to alter pCO(2) and DIC concentrations in the soil. Ambient and elevated CO(2) levels were 360+/-16 and 542+/-81 microl l(-1), respectively; ambient and elevated O(3) levels were 33+/-14 and 49+/-24 nl l(-1), respectively. Measured concentrations of soil CO(2) and calculated concentrations of DIC increased over the growing season by 14 and 22%, respectively, under elevated atmospheric CO(2) and were unaffected by elevated tropospheric O(3). The increased concentration of DIC altered inorganic carbonate chemistry by increasing system total alkalinity by 210%, likely due to enhanced chemical weathering. The study also demonstrated the close coupling between the seasonal delta(13)C of soil pCO(2) and DIC, as a mixing model showed that new atmospheric CO(2) accounted for approximately 90% of the C leaving the system as DIC. This study illustrates the potential of using stable isotopic techniques and FACE technology to examine long- and short-term ecosystem C sequestration.

Air Pollutants↗
PubMed1986

Temporal pattern of arterial CO2 partial pressure during exercise in humans.

The major objective of this study was to test the hypothesis that arterial CO2 partial pressure (PaCO2) does not change in transitions from rest to steady-state exercise and between two levels of exercise. Nine young adults exercised on a treadmill or a bicycle (sit or supine) for 5 min at a mild work load (heart rate = 90 beats X min-1) and then 3 min at a moderate work load (heart rate = 150 beats X min-1). In some studies the moderate work load preceded the mild work load. Arterial blood was sampled from a catheterized artery. During all exercise tasks isocapnia was not strictly maintained (F greater than 4.0, P less than 0.001). For example, a 1-to 2-Torr hypocapnia was the dominant trend during the first 15-45 s after increasing treadmill speed, and a transient hypercapnia was most prevalent when treadmill speed was decreased. During steady-state exercise PaCO2 did not deviate by more than 1-3 Torr from PaCO2 during any resting posture, and PaCO2 differences between exercise intensities and conditions did not exceed 1-2 Torr. A mouthpiece-breathing valve system was not used in most studies, but when this system was used, it did not consistently affect exercise PaCO2. Increasing inspired O2 to 40% likewise did not consistently alter exercise PaCO2. Failure to maintain isocapnia throughout exercise indicates that the matching of alveolar ventilation (VA) to lung CO2 delivery is not exquisitely precise. Accordingly it is inappropriate to base theories of the exercise hyperpnea on the heretofore contention of precise matching.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1988

Synovial oxygen partial pressure after experimental microtraumatic joint affection.

We have developed a method allowing the direct determination of the synovial oxygen partial pressure (pO2) in vivo by using puncture electrodes. The investigations were carried out on the knee joints of young adult rabbits. Immediately after a defined microtraumatization of the left knee joints, there was a decrease in the synovial pO2 down to an average of 72% of an initial value obtained from untreated control animals. But 42 and 84 days after loading, a significant rise in the synovial pO2 was detectable. The unloaded contralateral joints showed a slight consensual reaction. The dynamics of the synovial pO2 after the microtraumatization of joints is under discussion on the basis of results of micromorphological studies of the articular cartilage and the synovial membrane.

Animals↗
PubMed1994

In vitro effects of hydroquinone, benzoquinone, and doxorubicin on mouse and human bone marrow cells at physiological oxygen partial pressure.

A comparative study was undertaken in order to assess the hematotoxic effects of hydroquinone (HQ), 1,4-benzoquinone (BQ), and doxorubicin (DX) on mouse and human bone marrow (BM) cells. Initial experiments indicated that the inhibitory effects of near-ambient pO2 and HQ on granulocyte/macrophage colony-stimulating factor (GM-CSF)-induced colony formation were additive. Thus, subsequent experiments were done under conditions of continuous toxicant exposure in complete medium at physiological temperature and O2 partial pressure. Viability was measured 24 hr after exposure, and at the concentrations tested, HQ was less cytotoxic than BQ. DX did not exhibit significant cytotoxicity at the concentrations used. Both HQ and BQ were slightly more cytotoxic to mouse BM cells than to human BM cells. Dose-response analyses of HQ, BQ, or DX inhibition of GM-CSF-induced proliferative and colony-forming responses indicated that murine GM progenitors were significantly less sensitive to HQ than to the majority of myeloid BM cells that proliferated in response to GM-CSF. This preferential resistance of GM progenitors to HQ was not observed when human BM cells were used. HQ was somewhat more inhibitory to human than to mouse GM-CSF responses. Inhibition of GM-CSF-induced responses by BQ correlated closely with cytotoxicity, and DX was 1000-fold more inhibitory to GM-CSF-induced proliferative and colony-forming responses than either HQ or BQ. Again, DX appeared to be slightly more inhibitory to human BM cells than to mouse BM cells. Purified human hematopoietic progenitor cells (HPCs) were also used in the dose-response analyses of HQ, BQ, or DX inhibition of GM-CSF-induced proliferative and colony-forming responses. Inhibition of GM-CSF-induced HPC responses by HQ, BQ, and DX was very similar to that obtained when BM mononuclear cells were used, suggesting that the human HPC is a target for the direct effects of HQ, BQ, and DX.

Adolescent↗
PubMed1990

[Changes in the partial pressure of oxygen of the nasal mucosa caused by stellate ganglion block].

Stellate ganglion block (SGB) is clinically used for the treatments of various lesions diseases. SGB gives rise to nasal obstruction of transient duration. It is also suggested that derangement of the autonomic nervous system underlies nasal allergy. In order to study the hemodynamics of the nasal mucosa after SGB, two groups of the subjects, i.e. healthy volunteers and patients with nasal allergy, were included for evaluation of the partial pressure of oxygen of nasal mucosa (PtsO2) after SGB. Simultaneous evaluations were done to assess the nasal patency in the normal group and the temperature at the anterior tip of the inferior nasal turbinate in the nasal allergy group. The results thus obtained are summarized as follows: 1) In the normal group, SGB was resulted in a reduction in nasal patency on the blocked side and a significant increase in PtsO2 when compared with the non-blocked side. The PtsO2 remained higher than normal after although nasal patency was restored. 2) The PtsO2 at rest was lower in the nasal allergy group than in the normal group. 3) Changes in PtsO2 following SGB were similar in the two groups. 4) A parallelism was noted between changes in the temperature at the tip of inferior nasal turbinate and those in PtsO2 during SGB. These results suggest that SGB augments the arterial blood flow in the nasal mucosa. The compromised nasal mucosa of nasal allergy patients is in a state of hypoxia but showed virtually the similar improvement in circulation after SGB as noted in the nasal mucosa of normal subjects.

Adolescent↗
PubMed1984

Oxygen modulates growth of human cells at physiologic partial pressures.

We have examined the growth of human diploid fibroblasts (WI-38 and IMR90) as a function of initial seeding density and oxygen tension. Cells at young and mid-passage levels were subcultivated in Dulbecco's modified Eagle's medium with 10% fetal bovine serum at 0.005, 0.01, 0.03, 0.1, 0.3, 1, and 2 X 10(4) cells/cm2. Flasks were equilibrated before and after seeding with 1 of 10 gas mixtures containing the desired oxygen tension (9-591 mm Hg) and placed in incubators that measure and maintain a preset oxygen tension. The partial pressure of oxygen (PO2) in media of all flasks was determined at harvest. Cells were shielded from light of wavelength less than 500 nm. Cell growth varied inversely with oxygen tension and seeding density. At 50 cells/cm2, growth was maximal at PO2 9 and 16 mm Hg. Growth was progressively inhibited as the oxygen tension was increased. The population doubling increase at 14 d was 8.6 for PO2 9 and 16 mm Hg, 5.8 for PO2 42 mm Hg, 3.8 for PO2 78 mm Hg, 3.8 for PO2 104 mm Hg, and 3 for PO2 138 mm Hg. As the seeding density was increased, the differences in growth at PO2 less than 140 mm Hg were progressively minimized, such that at seeding densities of 10(4) cells/cm2 there was little difference in the rate of exponential growth or the final saturation density of cells cultivated between PO2 9 and 96 mm Hg. At all seeding densities tested, growth was progressively inhibited when the PO2 was increased greater than 140 mm Hg. The seeding density dependence of oxygen's influence on cellular growth is not explained by oxygen consumption of higher density cultures. Oxygen acts directly on the cells and not by destroying some essential medium component. We have found that oxygen regulates the growth of human cells under pressures of oxygen physiologic to humans, and that oxygen toxicity contributes to the seeding density dependence of cellular growth commonly seen in cell culture.

Cell Count↗
PubMed1996

Influence of oxygen partial pressure on human and mouse myeloid cell line characteristics.

Mouse and human cells have been reported to have different thiol characteristics (J. M. Messina and D. A. Lawrence, 1992, Int. J. Immunopharmacol. 14, 1221-1234). In addition, when cells are undergoing active growth, they usually have an increased thiol content. In an attempt to determine whether a mouse and a human cell line with similar characteristics can be induced to change their phenotype simply by being cultured at a lower oxygen partial pressure (pO2), the human KG-1 and mouse M1 myeloid cell lines were cultured at 5 and 20% oxygen. It is important to note that 5% O2 is close to the physiological pO2, whereas the percentage of O2 usually employed for most in vitro methods is atmospheric pO2. After long-term culturing at 5% (L cell lines) versus 20% O2 (H cell lines), the thiol content of the original (H) cell lines significantly changed. The amount of total and surface thiols was lower in both L cell lines, but only significantly different on the M1 lines, whereas the glutathione content was significantly lower in the L cell lines of KG-1 and M1. The mouse lines showed the greatest sensitivity to pO2 changes; however, the mouse cell lines were not more sensitive to hydrogen peroxide than the human cell lines even though they possess significantly less total thiols and glutathione. Interestingly, cell lines maintained at lower pO2 (physiological pO2) were more sensitive to hydrogen peroxide than their parental counterparts that were maintained at atmospheric oxygen levels.

Animals↗
PubMed1975

The relationship between mouse arterial partial pressure of oxygen (PaO2) and the effectiveness of localized tumour irradiation.

The effectiveness of localized X-irradiation on the transplantable KHT sarcoma was investigated while the host mice breathed gas mixtures ranging from 5% O2 : 95% N2 to 100% O2. Subcutaneous tumours in the flank of C3H mice anaesthetized with Nembutal (sodium pentobarbitol), Valium (diazepam), or urethane, were irradiated with doses of 1,500 or 2,500 rads and the delay in days for the tumours to grow from 4 to 10 mm in diameter was determined. Measurements of the arterial partial pressure of oxygen (PaO2) were made under conditions identical to the irradiation experiments. For PaO2 values less than 100 mm Hg (animals breathing air), growth delay decreased linearly, while for PaO2 values greater than 100 mm Hg, growth delay increased and reached a plateau at a PaO2 between 200 and 300 mm Hg, (animals breathing congruent to 50% O2). This relationship holds for the two doses and the three anaesthetics studied, and indicates the importance of investigating the Pa02 levels of patients undergoing radiotherapy treatment.

Animals↗
PubMed2003

Partial pressure dependency of 17O/16O and 18O/16O of molecular oxygen in the mass spectrometer.

A method to determine both (17)O/(16)O and (18)O/(16)O ratios for molecular oxygen with high precision by direct introduction into the mass spectrometer without gas separation is presented. Because both (17)O/(16)O and (18)O/(16)O in mixed gases have good linear correlations with their mixing ratios, these isotopic compositions can be determined without a gas-separation procedure by calibration using prepared standard gases with variable mixed ratios and by monitoring the amounts of fragment ions. Analytical precision for delta(17)O and delta(18)O of 45 and 7 per meg, respectively, were obtained. The observed partial pressure dependency of isotopic composition may be caused by isotope fractionation during admission from the ionization chamber into the flight tube of the mass spectrometer.

Mass Spectrometry↗