Evaluation of Po2 profiles to describe the oxygen pressure field within the tissue

Baumgärtl, H.; Zimelka, W.; Lübbers, D. W.

doi:10.1016/s1095-6433(01)00532-3

Cited by 33 publications

(23 citation statements)

References 17 publications

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“…The average pO 2 values in the rat brain cortex measured by the two methods were similar, but the EPR oximetry method reported a statistically significantly higher average pO 2 . These differences in the average pO 2 measured by the two methods were consistent with other reports (3,43) and suggest that the Eppendorf electrode may report a lower than expected pO 2 , likely because of local perturbations caused by this method. We also have directly compared the absolute pO 2 and the changes in rat brain pO 2 , measured using EPR oximetry during hyperoxic treatment with the pO 2 reported by the OxyLite method at adjacent locations in the same animal (48).…”

Section: Introduction To Epr Oximetrysupporting

confidence: 89%

Repetitive Tissue pO₂ Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies

Khan

Williams²,

Hou³

et al. 2007

Antioxidants & Redox Signaling

121

133

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Tissue oxygen plays a crucial role in maintaining tissue viability and in various diseases, including responses to therapy. Useful knowledge has been gained by methods that can give limited snapshots of tissue oxygen (e.g., oxygen electrodes) or evidence of a history of tissue hypoxia (e.g., EF5) or even indirect evidence by monitoring oxygen availability in the circulatory system (e.g., NMR methods). Each of these methods has advantages and significant limitations. EPR oximetry is a technique for direct measurement of tissue pO2, which has several advantages over the other existing methods for applications in which the parameter of interest is the pO2 of tissues, and information is needed over a time course of minutes to hours, and/or for repetitive measurements over days or weeks or years. The aim of this article is to provide an overview of EPR oximetry using particulates to readers who are not familiar with this technique and its potential in vivo and clinical applications. The data presented here are from the experiments currently being carried out in our laboratory. We are confident that in vivo EPR oximetry will play a crucial role in the understanding and clinical management of various pathologies in the years to come.

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Section: Introduction To Epr Oximetrysupporting

confidence: 89%

Repetitive Tissue pO₂ Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies

Khan

Williams²,

Hou³

et al. 2007

Antioxidants & Redox Signaling

121

133

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“…Baumgartl et al (4,5) found that PO 2 varied by up to 40 Torr in regions of the kidney within a distance of only 50 m.…”

Section: Discussionmentioning

confidence: 99%

Oxygen regulation of the epithelial Na channel in the collecting duct

Husted

Sigmund

et al. 2011

American Journal of Physiology-Renal Physiology

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The PO 2 within the kidney changes dramatically from cortex to medulla. The present experiments examined the effect of changing PO 2 on epithelial Na channel (ENaC)-mediated Na transport in the collecting duct using the mpkCCD-c14 cell line. Decreasing ambient O 2 concentration from 20 to 8% decreased ENaC activity by 40%; increasing O2 content to 40% increased ENaC activity by 50%. The O 2 effect required several hours to develop and was not mimicked by the acid pH that developed in monolayers incubated in low-O2 medium. Corticosteroids increased ENaC activity at each O 2 concentration; there was no interaction. The pathways for O2 and steroid regulation of ENaC are different since O2 did not substantially affect Sgk1, ␣-ENaC, Gilz, or Usp2-45 mRNA levels, genes involved in steroid-mediated ENaC regulation. The regulation of ENaC activity by these levels of O2 appears not to be mediated by changes in hypoxia-inducible factor-1␣ or -2␣ activity or a change in AMP kinase activity. Changes in O2 concentration had minimal effect on ␣-or ␥-ENaC mRNA and protein levels; there were moderate effects on ␤-ENaC levels. However, 40% O2 induced substantially greater total ␤-and ␥-ENaC on the apical surface compared with 8% O2; both subunits demonstrated a greater increase in the mature forms. The ␣-ENaC subunit was difficult to detect on the apical surface, perhaps because our antibodies do not recognize the major mature form. These results identify a mechanism of ENaC regulation that may be important in different regions of the kidney and in responses to changes in dietary NaCl.heat shock protein-70; heme oxygenase; adenosine 5=-monophosphate kinase; hypoxia-inducible factor-1␣; corticosteroids; surface expression THE OXYGEN TENSION OF THE renal parenchyma varies from that approaching the PO 2 of arterial blood near the surface of the kidney to considerably lower values in the midcortex (35). The PO 2 of the inner medulla is substantially below that of almost all normal tissues with values of 10 -15 Torr being routinely measured (4, 35). The relatively low PO 2 in both the cortex and the medulla is the result of a functional countercurrent exchange between arterioles and venules. The lower PO 2 in the medulla is believed to predispose to tubular injury in the setting of acute hemodynamic compromise, but the physiological consequences of the widely varying PO 2 of different regions is poorly understood.The collecting duct traverses the axis of the kidney from cortex to papillary tip and, consequently, is exposed to a wide range of PO 2 . It is well known that the rate of Na absorption by the cortical collecting duct is considerably greater than that by the medullary collecting duct (19,48). The reason for this regional difference in Na transport rate is not clear. Two possibilities have been proposed: hypertonicity and the high concentration of transforming growth factor-␤ within the renal medulla (28). Another possibility is the O 2 tension: low PO 2 in lung epithelial cells reduces epithelial Na channel (ENaC) activity (...

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“…There has been an evolution of the reported oxygen pressures in tissue due in part to improved methods of anesthesia. Early reports indicated that a substantial fraction of the tissue volume had oxygen pressures of Ͻ10 torr, sometimes even Ͻ5 torr, but more recent reports (1,22,34,71) conclude that in resting muscle and in kidney the tissues have very little or no volumes with a PO 2 of Ͻ10 -15 torr. The mean oxygen pressures in the microcirculation are near the mixed venous value of 35-45 torr.…”

Section: E508 Programming and Regulation Of Metabolic Homeostasismentioning

confidence: 99%

Programming and regulation of metabolic homeostasis

Wilson

2015

American Journal of Physiology-Endocrinology and Metabolism

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Wilson DF. Programming and regulation of metabolic homeostasis. Am J Physiol Endocrinol Metab 308: E506 -E517, 2015. First published January 20, 2015 doi:10.1152 doi:10. /ajpendo.00544.2014dence is presented that the rate and equilibrium constants in mitochondrial oxidative phosphorylation set and maintain metabolic homeostasis in eukaryotic cells. These internal constants determine the energy state ([ATP]/[ADP][P i]), and the energy state maintains homeostasis through a bidirectional sensory/signaling control network that reaches every aspect of cellular metabolism. The energy state is maintained with high precision (to ϳ1 part in 10 10 ), and the control system can respond to transient changes in energy demand (ATP utilization) of more than 100 times the resting rate. Epigenetic and environmental factors are able to "fine-tune" the programmed set point over a narrow range to meet the special needs associated with cell differentiation and chronic changes in metabolic requirements. The result is robust across-platform control of metabolism, which is essential to cellular differentiation and the evolution of complex organisms. A model of oxidative phosphorylation is presented, for which the steady-state rate expression has been derived and computer programmed. The behavior of oxidative phosphorylation predicted by the model is shown to fit the experimental data available for isolated mitochondria as well as for cells and tissues. This includes measurements from several different mammalian tissues as well as from insect flight muscle and plants. The respiratory chain and oxidative phosphorylation is remarkably similar for all higher plants and animals. This is consistent with the efficient synthesis of ATP and precise control of metabolic homeostasis provided by oxidative phosphorylation being a key to cellular differentiation and the evolution of structures with specialized function. oxygen; oxidative phosphorylation; energy metabolism; oxygen pressure; metabolic control; mitochondria; respiratory control THOUSANDS OF DIFFERENT METABOLITES AND ENZYMES must work together if a cell is to survive and grow. In addition to the complex ensemble of reactions within individual cells, in organisms with extensive cellular differentiation, metabolism must support the robust cell-to-cell communication needed for different cell types to contribute to integrated function of the organism. DNA contains the blueprint needed to construct the parts of the ensemble, but in living cells metabolism has to constantly and rapidly respond to changes in the environment. These metabolic responses often occur in seconds, far faster than information encoded in the DNA can be read and implemented. Real-time control of metabolism requires a metabolic unit with intrinsic properties that drive it toward a particular metabolic condition (set point) and is connected to the rest of metabolism through a network of regulatory pathways that maintain that set point (65). To control the ensemble, this central control unit needs to have sensory input fr...

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Evaluation of Po2 profiles to describe the oxygen pressure field within the tissue

Cited by 33 publications

References 17 publications

Repetitive Tissue pO₂ Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies

Repetitive Tissue pO₂ Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies

Oxygen regulation of the epithelial Na channel in the collecting duct

Programming and regulation of metabolic homeostasis

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Evaluation of Po2 profiles to describe the oxygen pressure field within the tissue

Cited by 33 publications

References 17 publications

Repetitive Tissue pO2 Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies

Repetitive Tissue pO2 Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies

Oxygen regulation of the epithelial Na channel in the collecting duct

Programming and regulation of metabolic homeostasis

Contact Info

Product

Resources

About

Repetitive Tissue pO₂ Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies

Repetitive Tissue pO₂ Measurements by Electron Paramagnetic Resonance Oximetry: Current Status and Future Potential for Experimental and Clinical Studies