1,721,002 research outputs found
A new method to measure the hemoglobin oxygen saturation by the oxygen electrode
No full textWe describe a new polarographic method to measure the haemoglobin oxygen saturation in whole blood, employing up to 10 μl of sample in a standard case. The measurement is done in an anaerobic staineless-steel cuvette (1 ml) recording three oxygen tension values: (1) that of an air-equilibrated buffer before the addition of the sample; (ii) that after the addition of the sample; and (iii) that after the addition of an oxidant. The haemoglobin oxygen saturation is then calculated from the three oxygen tension values, the volume of the reagents, and solubility coefficient of oxygen. This method is simple, inexpensive and accurate, and correlates well with other standard methods
THE DISSOCIATION OF CARBON-MONOXIDE FROM THE ALPHA-SUBUNIT AND THE BETA-SUBUNIT OF HUMAN CARBONMONOXY HEMOGLOBIN
No full textWe have measured the intrinsic CO dissociation rates from the subunits of the human hemoglobin tetramers (αCO βNO)2 and (αNO βCO)2 using microperoxidase and a stopped-flow spectrophotometer. The dissociation of NO is negligible. The rate constants for the and the subunits are similar (0.014 s-1 vs. 0.011 s-1, respectively, at pH 7, 20 C; and 0.016 s-1 for both in the presence of inositol hexaphosphate), indicating that they are equivalent in the first step of the CO dissociation. Therefore, the chain unequality observed in the third and fourth steps (Samaja, M., Rovida, E., Niggeler, M., Perrella, M., and Rossi-Bernardi, L. (1987). J. Biol. Chem.: 262, 4528-4533) are not due to the intrinsic properties of the subunits, but to the conformational state of the molecule
Enhanced oxidation of bis(3,5-dibromosalicyl)fumarate a-a cross linked hemoglobin by free radicals generated by xanthine/xanthine oxidase
No full textThe xanthine/xanthine oxidase reaction produces reproducible amounts of oxygen-derived free radicals that oxidize human oxyhemoglobin (Hb). We monitored the kinetics of the oxidation of stripped Hb (sHb), purified HbA0 and α-α cross-linked Hb (HbXL99α) at [Hb] in the 5 to 150 μM (heme) range. For increasing [Hb], the oxidation halftime (t( 1/2 )) increased for all Hbs, but t( 1/2 ) was always less for HbXL99α than for HbA0 and sHb. Such feature was attributed to the lower affinity for O2 of HbXL99α and may represent a serious problem for use of this Hb as blood substitute
Computerized scheme for the reaction of hemoglobin with ligands
No full textA scheme for the reaction of hemoglobin with ligands is described, which postulates the functional heterogeneity of the chains, considers all possible combinations of the distribution of the ligand on the four chains of hemoglobin, and does not require simplifying assumptions about the hemoglobin reactivity. Ten tetrameric species are considered, together with 16 reactions between these species, each with an “on” and an “off” rate constant. The dissociation of hemoglobin tetramers into dimers is also considered, with four “on” and four “off” rate constants for the reactions between dimers, and ten equilibrium constants for the reactions between tetramers and dimers. Moreover, some side reactions, such as the “trapping” of ligands by a hemoglobin competitor, are included. A FORTRAN program, suitable for microcomputers, is described for handling this scheme, with some examples showing its advantages
Effect of temperature on the p50 value for human blood
Full text linkWe investigated the effect of temperature (19, 30, 37, and 42°C) on the p50 value for normal human blood at p(CO2) = 5.72 kPa (43 mmHg), at various pHs (range 7.0 to 7.6) and molar ratios of [2,3-diphosphoglycrate]/[Hb4] (range 0.4 to 2.4). The d(log p50)/d(pH) coefficient varied from 0.39 at 19°C to 0.35 at 43° C. The relationship between log p50 and 1/T (T = degrees Kelvin) was linear under the experimental conditions used, and the d(log p50)/d(1/T) coefficient varied between -2138 at pH 7.0 and -2162 at pH 7.6, independent of the concentration of 2,3-diphosphoglycerate. Assuming that the effect of p(CO2) on the p50 value is the same at 19, 30, and 43°C as at 37°C, one can use the reported coefficients to calculate the p50 value for normal human blood under conditions of temperature, pH, p(CO2), and 2,3-diphosphoglycerate concentrations prevailing under physiological and pathological conditions. The p50 value calculated by empirical equations, taking into account the effect of temperature, correlated well with the values for p50 determined experimentally (y = 0.9774x + 0.453; r = 0.998; n = 60), with an SD of 52 Pa (0.39 mmHg)
SEPARATION OF THE VALENCE INTERMEDIATES OF HUMAN-HEMOGLOBIN BY HIGH-PERFORMANCE CHROMATOFOCUSING
Full text linkInvestigations into the properties of haemoglobin often require the isolation of the valence intermediates (αo)2β+)2 and (α+ βo2)2. Chromatofocusing with an anion-exchange gel (Mono PTM; Pharmacia, particle size 10 μm) in an HR5/20 column at various temperatures (10-25°C) provides an excellent method for this task. A linearly decreasing pH gradient (8 to 7, generated by Polybuffer 96, Pharmacia) eluted sequentially the species methaemoglobin, (αo2β+)2, (α+ βo2)2 and oxygenated haemoglobin. Calibration graphs help in quantitative analyses. This method is simpler and less time consuming and provides a similar or even better resolution than the traditional ion-exchange or isoelectric focusing methods
IMPAIRMENT OF THE POSTANOXIC RECOVERY OF ISOLATED RAT HEARTS BY INTRAVASCULAR HYPOXANTHINE AND XANTHINE
No full textHypoxanthine is the final product of the catabolism of ATP in the stored red cell. Upon transfusion, this purine may be uptaken by the endothelial cell and oxidized in a post-ischemic or post-anoxic environment with production of oxygen-derived free radicals. We have tested this hypothesis with a isolated perfused rat heart model monitoring the recovery of the heart function from 20 min anoxia in the presence of 0.1 mM hypoxanthine or xanthine. Addition of 0.1 mM guanine minimized the fraction of hypoxanthine to be salvaged. The presence of hypoxanthine in the vascular space impaired the recovery of the end-diastolic pressure, left ventricular developed pressure, contraction rate, and coronary perfusion pressure. We conclude that intravascular hypoxanthine is oxidized by the endoghelial cell xanthine oxidase contributing to the post-anoxic reoxygenation injury. Since the injury led by equimolar xanthine was nearly half of that observed for hypoxanthine, this injury appears to be correlated to the stoichiometry of the oxygen-derived free radical generating reaction
Carboxyhemoglobin and oxygen affinity of human blood
Full text linkWe determined normal human blood p50 at various pH values (range 7.0 to 7.6) as a function of the proportion of carboxyhemoglobin (COHb) in total hemoglobin, from 0 to 23%. The d(log p50)/d[COHb] coefficient is 0.00848, independent of pH and 2,3-diphosphoglycerate. The derived equation allows the calculation of p50 as a function of COHb with an approximation of +/- 0.54 mmHg (about 72 Pa), and can be combined with other calculations (Clin Chem 27:1856-1861, 1981; Clin Chem 29:110-114, 1983) to predict p50 under any condition of pH within the range 7.0-7.6, ratio of [2,3-diphosphoglycerate] to [total hemoglobin] (range 0.3-2.5), pCO2 (range 20-90 mmHg), temperature (range 19-43 degrees C), and COHb (range 0-23%)
PURIFICATION OF HUMAN-HEMOGLOBIN VALENCE INTERMEDIATES BY PREPARATIVE IMMOBILIZED PH GRADIENTS
No full textWe compare three separation techniques for preparative purposes, i.e. ion-exchange chromatography on CM-cellulose, conventional isoelectric focusing in polyacrylamide gel slabs and immobilized pH gradients. The biological system used to test the three methods is a solution containing four hemoglobin (Hb) valence intermediates, i.e. metHb, oxyHb, (α+βO2)2 and (αO2β+)2. The ΔpI between the two valence intermediates is 0.04 pH units. Immobilized pH gradients give the best performance in terms of resolving power, total amount of protein which can be loaded and retention of biological activity by the protein (the latter assessed by determination of CO dissociation rates)
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