High PO2 Research Articles

Hematoma with High Oxygen Partial Pressure Resulting from Injection Sclerotherapy for Esophageal Varices — Report of a Case

Abstract: Endoscopic injection sclerotherapy (EIS) was performed on a 44‐year‐old Japanese male, who had been suffering from risky esophageal varices due to cirrhosis of the liver. Blood gas analysis at the beginning of therapy showed that the partial pressure of oxygen at the variceal (PO2) and arterial blood (PaO2) were 47.2 mmHg and 64.1 mmHg, respectively. Sclerosant with contrast medium was injected into the varices and the left gastric vein was embolized; this was always confirmed by endoscopic varicealography during injection scleorotherapy (EVIS). During the fifth EIS session, there was evidence of pooling of contrast medium with sclerosant and an intramural hematoma had developed, which could not be reduced by puncture. The blood gas analysis showed a drastic increase in PO2 (107.9 mmHg), whereas PaO2 remained mostly unchanged (58.8 mmHg). To our knowledge, this is the first report of blood gas analysis during hematoma and the high PO2 compared with PaO2 indicated that there was a substantial inflow of oxygen‐rich blood, possibly from the pulmonary vein into the varices. This inflow of blood into the varices may have contributed to the formation of the large hematoma in small varices following EIS. (Dig Endosc 1999; 11: 55–61)

Differential oxygen sensitivity of the K+-Cl- cotransporter in normal and sickle human red blood cells.

1. K+ influx and efflux were measured in normal (HbA) and sickle (HbS) red blood cells to investigate the interaction of swelling, H+ ions and urea with O2 (0 to 150 mmHg O2) in the presence of ouabain and bumetanide (both 100 microM). 2. In HbA cells, K+-C1- cotransport was O2 dependent. At low oxygen tensions (PO2s) the transporter was inactive and refractory to low pH, swelling or urea. 3. C1--independent K+ influxes in sickle cells were elevated at low PO2s, as previously reported. C1--dependent K+ influxes were large at both high and low PO2s, whether stimulated by swelling, H+ ions or urea. In the absence of O2, C1--dependent K+ influxes were similar in magnitude to those measured at high PO2s. The minimum for C1--dependent K+ influx was observed at PO2s of about 40-70 mmHg. 4. K+ efflux from HbS cells was stimulated by the addition of urea (500 mM). The rate constants were of similar magnitude whether measured at high PO2 or in the absence of O2, and were predominantly C1- dependent under both conditions. 5. In HbS red blood cells, reduction of extracellular Ca2+, addition of 1 mM Mg2+ or nitrendipine (10 microM) to the saline had no effect. Inhibitors of K+-C1- cotransport, [(dihydroindenyl)oxy] alkanoic acid (DIOA; 100 microM) or calyculin A (0.1 microM), inhibited influxes by a similar magnitude to C1- substitution. 6. Results are significant for the pathophysiology of sickle cell disease. Low pH and urea are able to stimulate KC1 loss from sickle cells, leading to cellular dehydration, even in regions of low PO2.

Is there a significant gas exchange through the skin of the shrew Crocidura russula monacha?

Because of its small body mass, the shrew Crocidura russula monacha has a relatively high surface area to volume ratio, thin skin, and high thermal conductance compared with larger mammals. This study was aimed at examining the possibility that such a mammal may exhibit a significant skin gas exchange. Gas composition was measured in subcutaneous gas pockets. CO2 and O2 exchange through skin were measured both in vitro and in vivo. In 7-wk-old gas pockets, the steady-state PO2 and PCO2 values were 50 Torr (where 1 Torr = 133.322 Pa) and 35 Torr, respectively, compared with PO2 and Pco2 values of 73 Torr and 33 Torr, respectively, in 1-wk-old gas pockets. These changes are attributed to an increased capillary density and a decreased skin thickness after 7 wk. There was no significant gas exchange through skin during in vitro measurements. In vivo measurements indicated that O2 uptake was 0.5% and CO2 loss was 0.9% of total body metabolism at 20 degrees C. At 35 degrees C, skin O2 uptake and CO2 loss increased to 1.3% and 2.9%, respectively. These values are only part of the expected skin metabolism; thus, the rest must come from blood. Because gas exchange through the skin of this shrew is within the range of other mammals, the relatively low PCO2 and high PO2 in the gas pockets is better explained by the relative hyperventilation state exhibited by this shrew.

Effects of temperature and chronic hypoxia on survivorship of the zebra mussel (Dreissena polymorpha) and Asian clam (Corbicula fluminea)

We examined the effects of four levels of chronic hypoxic stress at three temperatures on the survivorship of Dreissena polymorpha and Corbicula fluminea to assess the efficacy of O2 deprivation as a macrofouling control treatment and examine if critical hypoxia limits support reported distribution patterns. At 25°C, the hypoxia tolerance was examined at Po2 = 7.9, 11.9, 15.9, 23.8, and 31.8 Torr (1 Torr = 133.322 Pa) or 5, 7.5, 10, 15, and 20% of full air O2 saturation (Po2 = 159 Torr). At 15°C, the hypoxia tolerance to 7.9, 11.9, and 15.9 Torr was tested and at 7.9 Torr for 5°C treatments. For both species, Po2 and temperature influenced survivorship dramatically with increasing survivorship at higher Po2 and decreasing temperatures. At 25°C, C. fluminea experienced mortality at 7.9, 11.9, and 15.9 Torr, with LT50 values of 144, 216, and 216 h, respectively, versus 288, 384, and 480 h for the 15°C exposures. Dreissena polymorpha treatments had LT50 values of 120, 216, and 216 h at 25°C for the 7.9-, 11.9-, and 15.9-Torr treatments versus 26% mortality after 600 h and 28% mortality after 720 h at 15°C. The 7.9-Torr treatments at 5°C had LT50 values of 480 h for C. fluminea and 1056 h for D. polymorpha. This study showed that both species displayed broad seasonal variation in hypoxia tolerance and that hypoxia limits may be used to assess infestation risk.

Root Growth and Oxygen Relations at Low Water Potentials. Impact of Oxygen Availability in Polyethylene Glycol Solutions1

AbstractPolyethylene glycol (PEG), which is often used to impose low water potentials (ψw) in solution culture, decreases O2 movement by increasing solution viscosity. We investigated whether this property causes O2 deficiency that affects the elongation or metabolism of maize (Zea mays L.) primary roots. Seedlings grown in vigorously aerated PEG solutions at ambient solution O2partial pressure (pO2) had decreased steady-state root elongation rates, increased root-tip alanine concentrations, and decreased root-tip proline concentrations relative to seedlings grown in PEG solutions of above-ambientpO2 (alanine and proline accumulation are responses to hypoxia and low ψw, respectively). Measurements of root pO2 were made using an O2 microsensor to ensure that increased solutionpO2 did not increase rootpO2 above physiological levels. In oxygenated PEG solutions that gave maximal root elongation rates, rootpO2 was similar to or less than (depending on depth in the tissue) pO2 of roots growing in vermiculite at the same ψw. Even without PEG, high solution pO2 was necessary to raise rootpO2 to the levels found in vermiculite-grown roots. Vermiculite was used for comparison because it has large air spaces that allow free movement of O2 to the root surface. The results show that supplemental oxygenation is required to avoid hypoxia in PEG solutions. Also, the data suggest that the O2 demand of the root elongation zone may be greater at low relative to high ψw, compounding the effect of PEG on O2 supply. Under O2-sufficient conditions root elongation was substantially less sensitive to the low ψwimposed by PEG than that imposed by dry vermiculite.

Performance of the isolated rainbow trout heart perfused under self-controlled coronary pressure conditions: effects of high and low oxygen tension, arachidonic acid and indomethacin

The effects of arachidonic acid (AA) and indomethacin (IM) on performance, oxygen consumption and lactate release of the trout heart were studied in vitro TPa s m−3 using a perfusion system, which allowed the evaluation of the integrated function of ventricle and coronary system by continuously setting the input coronary flow and pressure proportional to the pressure and flow output of the heart. The heart was working against a fixed resistance. A reduction of input oxygen partial pressure (PO2) from 175 torr (high PO2) to 76 torr (low PO2) increased the coronary flow (from 0.51 ml min−1 kg−1 to 1.21 ml min−1 kg−1, respectively) due to a strong reduction in coronary resistance (from 0.60 TPa s m−3 to 0.19 TPa s m−3, respectively). Oxygen consumption by the heart was significantly reduced from 20.7 ml min−1 g−1 at high PO2 to 4.6 ml min−1 g−1 at low PO2, while lactate production was increased from 24 μmol h−1 g−1 to 42 μmol h−1 g−1, indicating a higher contribution of anaerobic respiration to mechanical work. Mechanical efficiency was significantly higher at low than at high PO2. Exogenous AA caused a depression of inotropism and a reduction in the aerobic metabolic rate (by 25–35%), which was not accompanied by increased lactate production. IM enhanced the depression of both inotropism and aerobic metabolism. The effect of AA and IM on the heart were amplified at low PO2.

Mechanisms of Cell Death in the Inherited Retinal Degenerations

The human retina possesses both extraordinary sensitivity and a huge adaptive range. A light flash containing only a few photons is sufficient to be consciously perceived in humans. We also can see over a range of nearly nine orders of magnitude in background illumination. The vertebrate visual system has been pushed, by evolutionary pressures, to approach its thermodynamic limitations. This exquisite tuning, however, comes at a cost. Photoreceptors are forced to carry large metabolic burdens, to renew continuously their light-sensitive outer segments and to exist under conditions of very high pO2. Modest changes in the biochemical environment or cellular structure of photoreceptors, caused by genetic lesions or environmental insults, are sufficient to induce cell death through apoptosis. For the inherited retinal degenerations, understanding the impact of each molecular defect on the biology of photoreceptors is important, in addition to studying how these effects converge upon the apoptotic pathway. Collectively, these studies should lead to the development of rational therapies that may slow or even reverse the progression of this devastating disease process.

Mixed Ionic and Electronic Conduction in Mn/Mo Doped Gadolinium Titanate

ABSTRACTRecent work has shown that Gd 2(Ti1−xMOx)2O7 (GT-Mo) exhibits high levels of mixed conduction under reducing atmospheres, making it suitable as an anode in a solid oxide fuel cell, but not as a cathode since it decomposes at high Po2. We have succeeded in extending the stability limits of GT-Mo to higher Po2 with the addition of Mn. Our earlier studies on Gd2((MoyMn1−y)xTi1−x)2O7 (GMMT) as a function of Po2,T, and composition utilizing impedance spectroscopy and x-ray diffraction are extended to include a wider range of compositions (x ≤ 0.3). In addition, a new sintering method for the GMMT material is introduced that compensates for observed materials loss and abnormal conduction behavior in previous studies. Defect models explaining the dependence of the conductivity on oxygen partial pressure, temperature, and composition are presented as well.

Defect-Property Correlations in Garnet Crystals. *VII: The Electrical Conductivity and Defect Structure of Yttrium Aluminum and Yttrium Iron Garnet Solid Solutions

The conduction mechanisms in yttrium aluminum and yttrium iron garnet solid solutions have been studied as a function of temperature, iron concentration and partial pressure of oxygen. At low concentrations of iron, ac conductivity and ionic transference measurements show the solid solution to be a mixed ionic-electronic conductor with an ionic mobility characterized by an activation energy of 2.6–2.8 eV and a p-type electronic conductivity with activation energy of 3.0–3.3 eV. High concentrations of iron cause a dramatic increase in the electrical conductivity connected with the formation of an Fe impurity band found to lie 1.9 eV below the conduction band. Transport through this band is via an activated hopping process with an activation energy of 0.7 eV for 6 fraction percent Fe. A defect model is presented which is consistent with our experimental observations including the conductivity maxima obtained at high PO2's for high Fe levels.

Development of a surface-treatment method for AIN substrates to improve adhesion with thick-film conductors

A surface-treatment method for AIN substrates to improve adhesion with thick-film conductors has been developed based on the interfacial reaction mechanism between 96% alumina and glasses. The surface-treated AIN substrates were prepared through a combination of oxidation and sol-gel processes. An oxidation atmosphere with high PO2 and low PH2O, which produced the densest Al2O3 layer on AlN, was selected as the oxidation conditions for the surface treatment. A SiO2 layer was deposited on the Al2O3 layer, using the dipping technique with a sol-gel solution. The surface-treated AlN substrates with adequate thicknesses of Al2O3 and SiO2 as the surface-treatment layers showed a good adhesion strength with conventional thick-film conductors. This is the same result as with the 96% alumina substrates, although the adhesion strength of the conductors with bare AlN substrates was poor. These results suggest that glasses in the thick-film conductors react with the surface-treated AlN substrates in the same way as they react with the 96% alumina substrates, and also that the surface-treatment layer consisting of Al2O3 and SiO2 on AlN substrates is effective because it provides good adhesion between such substrates and conventional thick-film conductors.

A novel approach for gasification of carbon using a mixed conductor

The gasification of carbon to CO without the production of nitrogen was studied using an oxide ionic and electronic mixed conductor. The oxide ionic and electronic mixed conductor CaTi0.75Fe0.25O3–α was used as a selective oxygen permeable diaphragm. The selective electrochemical permeation of oxygen across a ceramic sample was confirmed by measuring oxygen evolution rate at the low PO2 side of the oxygen gas concentration cell using sample ceramics as a diaphragm. The gasification of carbon black to CO using this diaphragm was examined. It was observed that CO and CO2 were formed without nitrogen when the opposite side of diaphragm was exposed to air at high temperature. The dependence of the CO/CO2 ratio on the partial pressure of oxygen in the high PO2 compartment and on the thickness of diaphragm was examined.

Mechanism for flux pinning in NdBa2Cu3O7−δ melt-textured in low oxygen partial pressure

When NdBa2Cu3O7−δ (Nd123) is melt-textured in low oxygen partial pressure (Po2) and subsequently annealed in oxygen to produce the superconducting phase, there is a considerable enhancement of flux pinning compared to Y123. This enhancement is accompanied by a precipitation mechanism due to a change of the solubility limits of Nd1+xBa2−xCu3O7−δ between the high temperature low Po2 conditions used in melt-textured growth and the low temperature oxygen annealing. Transmission electron microscopy reveals a coherent intermediate precipitate structure with a composition of BaCuO2 and a high density of dislocations. We believe these defects are responsible for the strong flux pinning in this material.

Intrarenal oxygen tension measured by a modified clark electrode at normal and low blood pressure and after injection of x-ray contrast media.

The oxygen tension (pO2) in the rat kidney was studied using a Clark microelectrode with a guard cathode behind the sensing cathode. The mean (+/- SEM) outer tip diameter of the electrodes used was 5.5 +/- 1.9 microm. The zero-pO2 current amounted to 12.5 +/- 0.9 pA at 37 degrees C; at air saturation it was 252 +/- 22.9 pA. Rats with a systolic blood pressure (BP) above 80 mmHg (where 1 mmHg = 133 Pa) showed an average pO2 in the cortex of 45 +/- 2 mmHg and in the outer medulla of 31 +/-1 mmHg. In rats with a BP below 80 mmHg a paradoxically high outer medullary pO2 of 40 +/- 4 mmHg was found, while the pO2 in the cortex was 27 +/- 4 mmHg. Changes in pO2 were also noted in the renal cortex and outer medulla after intravenous injections of the x-ray contrast medium diatrizoate (370 mg iodine/ml). In rats with normal BP, injection of diatrizoate caused a slight fall in pO2 in the renal cortex, from 42 +/- 4 to 38 +/-4 mmHg. In the medulla pO2 decreased significantly from 34 +/- 6 to 20 +/-4 mmHg. Ringer's solution did not induce any changes.

An isolated blood-perfused guinea-pig lung model for simultaneous registration of haemodynamic, microvascular and respiratory variables.

We have developed an optimized isolated lung perfusion system, which possesses several advantages. Firstly, studies of microvascular, respiratory, haematological and biochemical variables are combined in one model. Secondly, blood perfusion resulted in less oedema formation than buffer-perfused lungs, and high PO2 through ventilation with room air. Finally, data for the variables can be displayed, controlled and recorded in real time using a computerized system permitting subsequent processing (e.g. filtering without destroying original data). In this paper we discuss the basic behaviour of the model in terms of vascular resistance, vascular permeability, respiration and neutrophil sequestration. In addition, the effects of oleic acid, histamine and histamine receptor blockers were tested, and two methods of calculating vascular permeability are discussed. The way in which different anaesthetics affect the neutrophil content of lung tissue and blood was also investigated. In the model, oleic acid increased pulmonary vascular resistance and permeability, whereas histamine did not affect either permeability or the pre/postcapillary vascular resistance ratio. However, histamine receptor blockers increased this ratio, indicating that there was endogenous histamine release. The neutrophil content of the isolated lungs was increased, but this did not affect the variables measured. There was also accumulation of neutrophils in the lungs of blood donor animals, due to CO2 sedation. However, CO2 sedation proved to be superior to pentobarbital or ketamine anaesthesia in maintaining the levels of neutrophils circulating in the blood. In conclusion, this model seems to be sensitive and to yield reproducible results regarding the physiology or pathophysiology of the lung.

Mixed Ionic-Electronic Conduction in N1 Doped Lanthanum Gallate Perovskites

ABSTRACTLanthanum gallate is a promising material for “monolithic” fuel cells or oxygen pumps, i.e. one in which the electrolyte and electrodes are formed from a common phase. We have investigated La1−xSrxGa1–yNiyO3 (LSGNx-y) with x=0.1 and y=0.2 and 0.5 as a potential cathode material for such an electrochemical device. The σ(PO2,T) for LSGN10–20 points to a p-type electronic conductivity at high PO2 and predominantly ionic conductivity at low PO2. LSGN10–50 has an electronic conductivity suitable for SOFC applications of approximately 50 S/cm in air at high temperature. AC impedance spectroscopy on an electron blocking cell of the form M/LSG/LSGN/LSG/M was used to isolate the ionic conductivity in the LSGN10–20 material. The ionic conductivity was found to have a similar magnitude and activation energy to that of undoped LSG material with σi= 0.12 S/cm at 800°C and EA= 1.0 ± 0.1 eV. Thermal expansion measurements on the LSGN materials were characterized as a function of temperature and dopant level and were found to match that of the electrolyte under opeating conditions.

Stability and Conductivity of Gd2((Mo1/3Mn2/3)xTi1-x)2O7

ABSTRACTA composite solid state electrochemical device, with (Gd1-xCax)2Ti2O7 serving as the electrolyte and Gd2(Ti1-xMox)2O7 (GT-Mo) as the anode has recently been proposed. The latter exhibits high levels of mixed conduction under reducing atmospheres, but decomposes at high Po2. We have recently succeeded in extending the stability limits of the GT-Mo to higher Po2 with the addition of Mn. In this study, we report on the conductivity and stability of Gd2((Mo13Mn2/3)xTi1-x)207 (GMMT) as a function of Po2, T, and composition utilizing impedance spectroscopy and x-ray diffraction. The addition of Mn extends the stability region of the material to Po2 = 1 atm with little change in the magnitude of the conductivity. Defect models explaining the dependence of the conductivity on oxygen partial pressure are presented. Preliminary results from the use of an electronic blocking sandwich cell used to isolate the ionic conductivity of GMMT are also presented.

種々の酸素分圧下で作製したBi-2212/Agテープの粒界構造

Grain boundary structure of Bi-2212/Ag tapes processed in various oxgen partial pressures (PO2) was investigated by high-resolution transmission electron microscopy (HRTEM). Most frequently observed boundaries for each tape were (001) twist boundaries. Two kinds of twist boundaries were mainly observed. One has an amorphous region at the interface and the other has no amorphous region (clean boundary). The population of clean boundary increased with increasing PO2. The real part of AC susceptibility showed smaller amplitude dependence for the tapes processed in higher PO2, suggesting improved coupling of grains.

Potential for EPR oximetry to guide treatment planning for tumors.

A major contributing factor in the failure of solid tumors to be locally controlled by radiation therapy (RT) is the relative radiation resistance of hypoxic cells of tumors compared to well-oxygenated cells. Recently clinical studies have established the presence of hypoxic regions in human tumors (1,2). Further studies confirmed that relatively high tissue pO2 in human tumors correlated with positive outcomes of radiation therapy and that poor outcomes were associated with tumors with low pO2 (3–6). As a result of available studies, the conclusion has been drawn that the effective level of oxygenation in individuals could not be predicted based on tumor type, histology, staging, or even size, but had to be measured (7). With the development of methods to measure the pO2 in tumors (8), it now seems feasible to determine if this parameter, which can be of crucial importance in radiation therapy, can be used to improve treatment by permitting individualized optimization of therapy on the basis of the pO2 in the tumor.

Blood supply of the retina.

An overview of the functional anatomy of the retinal microcirculatory system and its regulation mechanisms is presented. The retinal microvasculature is characterized by thin capillaries which leave large vessel-free spaces compared to other microvascular beds. Despite high blood flow velocities, the blood flow volume within the capillaries is relatively low. This results in a high arteriovenous pO2 difference and a small capacity to tolerate periods of low perfusion. Furthermore, from the optic nerve head on there is no autonomic perivascular innervation to control the microvascular tone. A control via the bloodstream (mediators, e.g. O2, CO2, hormones), astrocytes, neurites and Müller cells (mediators, e.g. NO, prostaglandins, neuropeptides) takes over. Finally, the role of pericytes in the control of retinal hemodynamics is discussed.

Oxygen tensions in rodent tumors after irradiation with neutrons.

We started investigations on intratumoral oxygen tension after irradiations with reactor fission neutrons using the Eppendorf-pO2 Histograph. Isotransplanted AT17-mammary carcinomas on C3H-mice and osteosarcomas OTS-64 on balb C-mice received 2 or 6 Gy neutrons single dose. Before and at certain points of time after treatment the pO2 values were evaluated. Some tumors with initially low median pO2 values showed a short-lasting increase between 2 and 24 h after irradiation. In those tumors with relatively high pretherapeutic pO2 values the pO2 decreased to the range of hypoxia. A third group of tumors showed no marked changes after irradiation. No tumor stopped growth during the observation period.