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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Differential binding curve measurements for oxygen in the presence of fixed carbon dioxide activities have allowed a detailed determination of the linkage between carbon dioxide and the oxygenated intermediates of human hemoglobin. Model-independent analysis of the data shows that at pH 7.4: (1) the oxygen binding curves are asymmetrical, the population of the triply oxygenated species being negligible; (2) the shape of the oxygen binding curve is invariant with carbon dioxide activity; (3) the maximum linkage is -0.32 moles carbon dioxide per mole oxygen; and (4) the overall carbon dioxide-dependent shift in the oxygen binding curve cannot be explained in terms of carbamino formation alone, the additional influence of bicarbonate being required. An allosteric model that accounts for the low population of triply oxygenated hemoglobin species is employed here as a framework from which to explore the carbon dioxide linkage mechanism at the intermediate stages of oxygenation. Carbon dioxide binding constants are found to be 780 M-1 and 580 M-1 for carbon dioxide binding to the deoxygenated alpha and beta chains, respectively, and 150 M-1 for carbon dioxide binding to the oxygenated form of both chains, as determined by simultaneous fitting of the oxygen binding curves with the model. Finally, by use of the determined binding polynomial for the carbon dioxide-oxygen linkage scheme, we have constructed a series of linkage graphs.
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PMID:Carbon dioxide and oxygen linkage in human hemoglobin tetramers. 311 59

The thermodynamic and kinetic properties of the most abundant glycated hemoglobin in human blood, HbA1c, have been studied in detail. They display significant differences as compared to normal hemoglobin, HbA0, in that (1) the shape of the oxygen binding curve of HbA1c in the Hill plot is markedly asymmetrical, with a lower asymptote extending up to approximately 40% oxygen saturation, and the oxygen affinity of the T state being tenfold higher than in HbA0; (2) oxygen pulse experiments on HbA1c show a slower rate of ligand dissociation (k = 25 s-1) even at low levels of oxygen saturation, where the T state is largely predominant; (3) kinetics of CO combination to deoxy HbA1c followed by means of stopped-flow experiments reveal the presence of a quickly reacting component, whose fraction increases upon dilution of hemoglobin. These results show that in contrast to what has been stated by other authors, HbA1c displays functional properties markedly different from HbA0. Analysis indicates that glycation of human hemoglobin affects the T quaternary structure, bringing about a more "relaxed" T state and leading to preferential binding to one type of chain (which is unaffected by chloride ions).
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PMID:Alteration of T-state binding properties of naturally glycated hemoglobin, HbA1c. 318 88

We first studied the distribution of radioactivity during continuous inhalation of C15O2 and 15O2 in traverse tomograms of the greatest diameter of legs, at rest and immediately after exercise (ankle flexions). C15O2 and 15O2 were distributed homogeneously and symmetrically in both legs of normal subjects at rest. The activity accumulated in the anterolateral region after exercise. In patients, this pattern of distribution was similar but asymmetrical, depending on the arterial pathology. No systematic distribution of either C15O2 or 15O2 was observed. In a second step, we studied quantitatively blood flow (F), oxygen uptake (R) and oxygen extraction (E) in 11 subjects: 5 normals (23 +/- 1 years) and 6 patients (60 +/- 11 years) suffering from unilateral intermittent claudication. We used the bolus inhalation technique of C15O2 and 15O2. In the normal leg at rest, ranges were 2.5 to 8.0 ml/min.hg for F, 0.9 to 21.3 mumol/min.hg for R and 3.6 to 33.4% for E. In the pathological leg at rest, ranges were 3.7 to 11.3 ml/min.hg for F, 3.8 to 10.6 mumol/min.hg for R and 7.1 to 24.5% for E. After exercise, ranges were 6.4 to 62.8 ml/min.hg for F, 66.0 to 386.3 mumol/min.hg for R and 29.2 to 89.5% for E in both legs. There was no straight difference between normal and pathological legs soon after exercise. This study allows us to expect that the demonstration of such a difference implies a longer delay of data acquisition following the slow post-ischemia recovery.
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PMID:[Regional blood flow and oxygen consumption in the leg muscles of normal subjects and in those with arterial insufficiency. Study of the distribution of C15O2 and of 15O2 using positron emission tomography]. 326 Sep 34

Lesions of one cerebral hemisphere are associated with decreased glucose metabolism, oxygen metabolism, and blood flow in the contralateral cerebellar hemisphere. We used positron emission tomography to look for a functional relationship in cerebral metabolism between the cerebral cortex and the contralateral cerebellum in normal human subjects. Twenty-four normal subjects were scanned with [18F]fluoro-2-deoxy-D-glucose while in a resting state. Asymmetry in local CMRglu (LCMRglu) in the frontal cortex was strongly correlated with asymmetry in LCMRglu in the opposite direction in the cerebellar hemispheres (r = -0.60, p less than 0.001). Widespread subregions of the frontal cortex were found to contribute to this relationship. Considering these results together with previous studies demonstrating that frontal lesions are associated with decreased metabolism in the contralateral cerebellum, we conclude that the frontal cortex exerts a strong modulating influence on metabolism in the contralateral cerebellum in normal subjects, and that this influence may be asymmetrical.
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PMID:A relationship between metabolism in frontal lobes and cerebellum in normal subjects studied with PET. 326 82

In order to evaluate regional muscle blood flow and oxygen utilization, we study with positron emission tomography (PET) the distribution of C15O2 and 15O2 in 17 subjects: 5 normals (24 +/- 3 years) and 12 patients (63 +/- 13.5 years). C15O2 and 15O2 are inhalated with a steady-state technique. Positron tomograms are recorded in supine position at the greatest diameter of the leg. Exercise consists in simultaneous ankle flexions. In all normals, C15O2 and 15O2 are distributed homogeneously and symmetrically in both legs. At rest, they concentrate in the region of vascular pedicle. After exercise, C15O2 and 15O2 are electively distributed in the anterolateral region of the leg. In patients, this pattern of distribution is similar but asymmetrical. Moreover, the regional uptake of C15O2 and 15O2 often dissociates. In conclusion, C15O2 and 15O2 allow to study repeatedly muscle blood flow and oxygen utilization in patients with peripheral ischemia, both at rest and after exercise. The broad spectrum of pathological changes observed in this study needs further metabolic investigations.
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PMID:Effect of exercise on the leg distribution of C15O2 and 15O2 in normals and in patients with peripheral ischemia: a study using positron tomography. 326 17

Blood rheology tests are traditionally used for detection of organic disease and for monitoring disease activity. More recently they have been used for prediction of blood flow in vivo, not only in overt hyperviscosity syndromes but also in the covert hyperviscosity of low-flow states. The traditional ESR test result increases with red cell aggregation induced by increases in large, asymmetrical plasma globulins. However, small increases in haematocrit and large increases in plasma viscosity each decrease the ESR, reducing both its diagnostic utility and its ability to predict blood flow in vivo. The ESR should be corrected to a standard haematocrit, or else replaced by the ZSR or plasma viscosity, which are more rapid, simple, sensitive and independent of haematocrit. For prediction of blood flow in vivo, these tests can be supplemented by measurement of whole-blood viscosity, which can be performed simply and cheaply in capillary viscometers at high shear rates. Whole-blood viscosity is determined by plasma viscosity, haematocrit and red cell deformability at high shear rates. Its measurement is useful in overt hyperviscosity syndromes, particularly in estimating the effect of red cell transfusion in anaemic patients with plasma hyperviscosity, hyperleukocytic leukaemias or sickling disorders. Blood viscosity should be related to the haematocrit or haemoglobin concentration in order to estimate oxygen delivery to tissues. Changes in blood viscosity can be compensated readily in the normal circulation but not in the compromised, low-flow circulation. In these circumstances, systemic increases in plasma viscosity, haematocrit, whole-blood viscosity, red cell aggregation and in the numbers of circulating rigid red or white blood cells can perpetuate low-flow states and ischaemia. Red cell deformability in narrow vessels is best measured by micropore filtration systems, in which the effect of white cells has been eliminated. Red cell deformability is reduced by change in shape, decrease in the ratio of surface area to volume, decreased membrane flexibility and increased internal viscosity (MCHC and inclusions). White cells have negligible effects on bulk-blood viscosity but have important effects on blood flow in narrow vessels, due to their high internal viscosity and their adhesiveness when activated. White cell filterability is lowest for monocytes and for activated granulocytes and these adhesive and rigid cells may have important effects on microcirculatory blood flow in low-flow states.
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PMID:Blood rheology in vitro and in vivo. 332 59

Scientific research in swimming over the past 10 to 15 years has been oriented toward multiple aspects that relate to applied and basic physiology, metabolism, biochemistry, and endocrinology. This review considers recent findings on: 1) specific physical characteristics of swimmers; 2) the energetics of swimming; 3) the evaluation of aerobic fitness in swimming; and 4) some metabolic and hormonal aspects related to swimmers. Firstly, the age of finalists in Olympic swimming is not much different from that of the participants from other sports. They are taller and heavier than a reference population of the same age. The height bias in swimming may be the reason for lack of success from some Asian and African countries. Experimental data point toward greater leanness, particularly in female swimmers, than was seen 10 years ago. Overall, female swimmers present a range of 14 to 19% body fat whereas males are much lower (5 to 10%). Secondly, the relationship between O2 uptake and crawl swimming velocity (at training and competitive speeds) is thought to be linear. The energy cost varies between strokes with a dichotomy between the 2 symmetrical and the 2 asymmetrical strokes. Energy expenditure in swimming is represented by the sum of the cost of translational motion (drag) and maintenance of horizontal motion (gravity). The cost of the latter decreases as speed increases. Examination of the question of size-associated effects on the cost of swimming using Huxley's allometric equation (Y = axb) shows an almost direct relationship with passive drag. Expressing energy cost in litres of O2/m/kg is proposed as a better index of technical swimming ability than the traditional expression of VO2/distance in L/km. Thirdly, maximal direct conventional techniques used to evaluate maximal oxygen consumption (VO2 max) in swimming include free swimming, tethered swimming, and flume swimming. Despite the individual peculiarities of each method, with similar experimental conditions similar results for VO2 max will be found. Free swimming (unimpeded) using the backward extrapolation method will, however, lead to reliable and valid results obtained in a condition that is closer to the competitive situation than with a direct test. A maximal indirect field-test has been recently made available. This test can predict VO2 max with an acceptable accuracy (r = 0.877), and provides a mean to evaluate the functional maximal aerobic power in swimming which corresponds to the maximal aerobic swimming velocity.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Applied physiology of swimming. 352 Jul 47

Oxygen equilibrium curves (OEC) for human red blood cells (RBC) have revealed a large asymmetry with an nmax value reached at approximately 90% saturation. This contrasts with the symmetrical shape of the OEC for diluted HbA solutions. We prepared resealed red blood cells (RRBC) through controlled hemolysis and resealing in order to obtain a low Hb concentration (approximately equal to 60 g/L) and DPG/Hb4 molar ratio ranging from 0.2 to 4. When the DPG/Hb4 was close to unity, OEC still showed a large asymmetry. On the contrary, the OEC became symmetrical when DPG/Hb4 was either negligible or 3-4 fold the normal value. The asymmetrical OEC for intact RBC can be fitted with a theoretical model taking into account the variations of free DPG concentration during oxygenation. We conclude that the asymmetrical shape of OEC observed in intact fresh RBC is not due to the high protein concentration present in the RBC but to a functional heterogeneity of Hb due to the changes of the free 2,3-diphosphoglycerate (DPG) concentration during oxygenation.
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PMID:Functional properties of hemoglobin in human red cells. I. Oxygen equilibrium curves and DPG binding. 360 19

A model is developed for hemoglobin which depends on six Bohr groups per tetramer of hemoglobin. These six groups are assumed to be located in six regions between the four subunits of hemoglobin. When the Bohr groups are assumed to be perturbed in an asymmetrical manner on binding oxygen, these groups then generate the cooperative interactions of hemoglobin. This approach makes it possible to explain oxygen binding, the Bohr effect, specific salt effects, and aggregation effects in a unified manner.
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PMID:Model for the action of hemoglobin. 527 67

We measured acute changes in monoamine metabolites in corpus striatum of immature rat pups exposed to hypoxia-ischemia, hypoxia alone, or total global ischemia. Carotid ligations and two hours of 8% oxygen environment in 7-day-old pups led to asymmetrical turning behavior, a 70% decrease in endogenous striatal dopamine levels, and a 125% increase in homovanillic acid (HVA) concentrations on the side of ligation. In contrast, hypoxia alone and total global ischemia alone were not associated with HVA level elevation. Elevation of HVA level with hypoxia-ischemia showed a threshold effect between 1 and 1.5 hours, and this time course paralleled that for production of gross morphological changes in rats raised to maturity. The data suggest that dopamine release from striatal nerve terminals is associated with events causing brain injury during perinatal hypoxia-ischemia. Tissue HVA in the animal model appears to be a quantitative marker for the effects of the insult on a population of nerve terminals.
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PMID:Effects of hypoxia-ischemia on monoamine metabolism in the immature brain. 620 78


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