Blood oxygen tension

The partial pressure, Pq, of the oxygen in the blood (oxygen tension) is related to Sq by the oxygen dissociation curve (Fig. 2.11). The shape and position of this sigmoidal curve depend on the temperature, the hydrogen ion concentration and the concentration within the red cells of other ligands of haemoglobin... 

Because of discrepancies between experimental tests and predicted tissue oxygen response by convection-diffusion models, the influence of physiological control mechanisms was considered. It is proposed that a minimum of two autoregulatory actions (at least conceptually) are functional in helping prevent neuron damage when low blood oxygen tensions are encountered. 

In other words the permeability of the gill to sodium and H" is critically dependent upon external calcium concentrations. In addition fish are known to undergo hyper-ventilation and a lowered blood oxygen tension. In such a condition, aluminium is acutely toxic to fish. 

Implanted electrodes for the continuous monitoring of therapeutic drugs in vivo have not been yet described. Voltammetry in blood using electrochemical transducers has enabled blood oxygen tension to be determined. Several transducers have been proposed for oxygen based on the original Clark type membrane electrode [159]. The performance... 

Clark L, Wolf R, Granger D (1953) Continuous recording of blood oxygen tensions by polarography. J Appl Physiol 6 189-193... 

The relationship between the hemoglobin saturation SOj (denoting either SAOj or SVOj) and the blood oxygen tension is given by Hill s equation (West et al, 1966) ... 

L. C. Clark, R. Wolf, D. Granger and Z. Taylor, Continuous Recording of Blood Oxygen Tensions by Polarography, 1953. 

A lowered blood oxygen tension serves as a stimulus for erythropoiesis. Oianges are detected by the kidney, which responds by releasing erythnqXMetin, a hor mone that stimulates erythrocyte production. 

The presence of hemoglohin-S (Hb-S) ia red blood cells leads to the formation of Hquid crystalline aggregates iaside the ceU under conditions of low oxygen tension (43,44). The morbid aggregates ultimately arrange themselves iato a gel-like material composed of long fibers that extend the entire length of the ceU and distort its usual shape. 

Gordh, T. Linderholm, H. and Norlander, 0. Pulmonary Function in Relation to Anaesthesia and Surgery Evaluated by Analysis of Oxygen Tension of Arterial Blood. Acta Anaesth. Scand. (1958), 2 15-26. 

It is known that the endothelial cells lining the capillary bed are markedly damaged during hyperoxic exposure. However, it is not at present known whether this damage is due to free-radical-induced injury of the endothelial cells or whether endothelial cells are simply responding to the diminished blood flow produced by the severe vasoconstriction. The theoretical basis for free-radical involvement is sound and it has been proposed that low oxygen tensions (hypoxia) followed by periods of reoxygenation are the most likely explanation for the disorder (Kelly, 1993). 

Figure 7.4 Summary of some of the wide array of afferent and efferent connections of midbrain dopaminergic neurons (SN/A9, RRF/A8, and VTA/A10 in center of figure). This emphasizes their potential involvement in coordination of seemingly disparate behaviors inclusive of the sleep-wake state of the organism. Abbreviations BP, blood pressure BST, bed nucleus of the stria terminalis CEA, central nucleus of the amygdala MEA, midbrain extrapyramidal area NTS, nucleus of the solitary tract O2, oxygen tension PPN, pedunculopontine tegmental nucleus RRF, retrorubral field SN, substantia nigra VTA, ventral tegmental area.

E.M.R. Doppenberg, A. Zauner, R. Bullock, J.D. Ward, P.P. Fatouros, and H.F. Young, Correlations between brain tissue oxygen tension, carbon dioxide tension, pH, and cerebral blood flow - a better way of monitoring the severely injured brain Surg. Neurol. 49, 650-654 (1998). 

The regulation of hematopoiesis in the bone marrow is not only controlled by the cytokine composition, the cells microenvironment and the oxygen tension, but, as shown recently [55], also by the local pH. For cells of different Hneages deviating pH optima have been described. While CFU-GM proliferate best in a pH range 7.2 - 7.4 (the normal pH of blood), for erythroid cells an optimum of pH 7.6 was found. Below an acidic pH of 6.7 no differentiation or proUferation of any hematopoietic cell was observed. Cells of the erythroid lineage are even strongly inhibited at a pH below 7.1 [56]. 

T.Q. Duong, C. ladecola, S.G. Kim, Effect of hyperoxia, hypercapnia, and hypoxia on cerebral interstitial oxygen tension and cerebral blood flow, Magn. Reson. Med. 45 (2001) 61-70. 

J.E. Fishman, P.M. Joseph, M.J. Carvlin, M. Saadi-Elmandjra, B. Mukherji, H.S. Sloviter, In vivo measurements of vascular oxygen tension in tumors using MRI of a fluorinated blood substitute. Invest. Radiol. 24 (1989) 65-71. 

R.P. Mason, P.P. Antich, Tumor oxygen tension Measurement using OxygenF as a F NMR probe at 4.7 T, Artif. Cells Blood Substit. Immobil. Biotechnol. 22 (1994) 1361-1367. 

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