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Results for “oxygen-affinity”

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10 recordsLinked to original sources
PubMed1991

Effect of pregnancy and temperature on red cell oxygen-affinity in the viviparous snake Thamnophis elegans.

The oxygen affinity of red cell suspensions from fetal garter snakes was higher than that of cell suspensions from their mothers. This difference appeared to be due to different concentrations of nucleoside triphosphate (NTP, primarily adenosine triphosphate). NTP concentrations were significantly higher, and oxygen affinities were significantly lower, in red cell suspensions from pregnant females compared with those from nonpregnant females or males; there is no precedent for such a pronounced effect of pregnancy on the oxygen affinity of maternal blood. These data indicate that pregnancy may result in an enhanced ability of adult blood to deliver oxygen to the fetus. Since the binding of organic phosphates and oxygen to hemoglobin is sensitive to temperature, and since these animals experience diurnal changes in temperature, we examined the influence of relatively low (20 degrees C) and high (34 degrees C) temperatures on red cell oxygen-affinity. The temperature increase of 14 degrees C resulted in a lowered oxygen-affinity of all red cell suspensions examined. However, this increase in temperature lowered the affinity of maternal red cells to a greater extent than it did the affinity of fetal red cells. This suggests that daytime temperatures may further enhance the ability of maternal blood to deliver oxygen to the fetus at times when fetal oxygen demand is probably greatest.

Animals↗
PubMed1978

Hemoglobin Creteil: oxygen transport by erythrocytes. In-vitro and in-vivo studies in a high oxygen-affinity mutant hemoglobin.

Hemoglobin Hb) Creteil alpha2beta(2)89 (F5) Ser leads to Asn is a high oxygen-affinity variant that has a low cooperativity, a decreased Bohr effect, and does not interact with diphosphoglycerate (DPG) (1). This hemoglobin variant was silent by routine electrophoresis. Careful analyses of the oxygen dissociation curves of erythrocytes, determined at varying pH and Pco2 in fresh and DPG-depleted cells, gave extensive information on the abnormal function of the mutant hemoglobin. From the O2 dissociation curves of the erythrocytes of the heterozygous subject it appeared that Hb Creteil is inappropriate for O2 transport to the tissues because it remained completely saturated with O2 at normal physiologic levels of Po2. In-vivo measurements showed that only one half of the total hemoglobin present actually participated in oxygen transport. Polycythemia should therefore be maintained within clinically tolerable limits because it helps to keep arterial Po2 and Pvo2 close to their normal values and thus protects the individual from a permanent increase in blood flow.

Adult↗
PubMed1977

Haemoglobin Radcliffe (alpha2beta299(Gi)Ala): a high oxygen-affinity variant causing familial polycythaemia.

Three members of an Oxfordshire family have polycythaemia. In each case their whole-blood oxygen affinity is increased. This is due to a previously undescribed haemoglobin variant which has been named haemoglobin Radcliffe (alpha2beta299(Gl)Ala). In addition to having a high oxygen affinity haemoglobin Radcliffe shows virtually no haem-haem interaction and a diminished Bohr effect. It is synthesized at the same rate and is as stable as haemoglobin A. X-ray analysis indicates that crystals of deoxyhaemoglobin Radcliffe are isomorphous with those of deoxyhaemoglobin A. Solutions of haemoglobin Radcliffe were also studied by high-resolution proton nuclear magnetic resonance spectroscopy. The structure/function relationships of haemoglobin Radcliffe are discussed in the light of these studies.

Adult↗
PubMed1992

Hemoglobin Rouen (alpha-140 (HC2) Tyr-->His): alteration of the alpha-chain C-terminal region and moderate increase in oxygen affinity.

Hb Rouen (alpha 140(HC2) Tyr-->His) is a moderately high oxygen-affinity variant that was found in coincidence with polycythemia vera in a French patient. This hemoglobin provides an example of an alteration of the C-terminus of the alpha-chain, a region involved in the mechanisms of allosteric regulation. The increase in oxygen-affinity and decrease in cooperativity of this variant is much smaller than that resulting from the same substitution in the beta-chain. This model provides additional evidence for the inequivalence between the alpha- and beta-subunits.

Aged↗
PubMed1979

Comparison of hemoglobins Wood (alpha 2 beta 2 97 leu) and Malmö (alpha 2 beta 2 97 gln). Diagnostic value of citrate agar electrophoresis.

Diagnostic value of citrate agar electrophoresis. Am J Clin Pathol 71:668-671, 1979. Of approximately three dozen hemoglobin variants that have greater than usual oxygen affinity, nearly half are inseparable from hemoglobin A by electrophoresis at pH 8.6. A comparison of hemoglobins Wood (alpha2beta297leu) and Malmö (alpha2beta297gln) is of interest from several standpoints. They represent similar substitutions at the identical locus in the beta chain. They result in identical clinical and hematologic manifestations. Oxygen affinities of these variants are identical. Both are poorly resolved from hemoglobin A by electrophoresis at pH 8.6. The position of each is identical when studied by isoelectric focusing in polyacrylamide gel. Finally, they are easily distinguished by citrate agar electrophoresis at pH 6.2. The excellent resolution of hemoglobins Malmö and Wood from each other results neither from difference in charge, nor size, nor in quaternary structure. This technic provides a simple but effective means for identifying and differentiating these hemoglobin variants. Comparison with the results of citrate agar electrophoresis of other high oxygen-affinity hemoglobins indicates that the findings for hemoglobins Malmö and Wood are unique and unambiguous.

Adolescent↗
PubMed1978

Red cell oxygen affinity in fetal sheep: role of 2,3-DPG and adult hemoglobin.

Studies were carried out during fetal life in sheep to determine the relationship of 2,3-diphosphoglycerate (DPG), the intracellular red cell and extracellular pH, and the switchover to adult hemoglobin synthesis in regulating the position of the fetal red cell oxygen-affinity curve in utero. Adult hemoglobin first appeared near 120 days of gestation. The mean oxygen tension at which hemoglobin is half saturated (P50) prior to 120 days of gestation remained constant at 13.9 +/- 0.3 (SD) Torr and then increased gradually as gestation continued, reaching 19 Torr at term. During the interval of fetal life studied, the level of DPG was 4.43 +/- 1.63 (SD) micromol/g Hb and the deltapH between plasma and red blood cells was 0.227 +/- 0.038 (SD); neither was affected by gestational age. The decrease in the red cell oxygen affinity after 120 days of gestation ocrrelated with the amount of adult hemoglobin present in the fetus (r = 0.78; P less than 0.001). This decrease can be attributed only to the amount of the adult-type hemoglobin present, and not to DPG, or to changes in the deltapH between plasma and red blood cells, because both remained stable during the last trimester.

Animals↗
PubMed2025

Global Environmental Factors Impact the Evolution of Adult Hemoglobins in Squamata Reptiles (Lizards and Snakes) and Terrestrial Turtles.

Convergent evolution of oxygen transport mechanisms arises from respiratory proteins adapting to similar environmental pressures. We examined this relationship between adult hemoglobin subunits (Hbs: HBA1, HBAD, HBB1, and HBB2) found in land reptiles (lizards, snakes, and turtles) with their global distribution variables: Altitude, latitude, ambient temperature, and biomass production. We found that biomass was positively associated with the synonymous substitution rate (dS) of HBAD, while it showed the opposite trend for HBB2 in snakes. Additionally, latitude was negatively related to the dS of HBB2 in snakes, but nonsignificant with other Hbs. Altitude was negatively associated with ω = dN/dS of HBA1 and HBAD, whereas temperature showed a similar negative trend with the ω of HBAD across reptiles and in HBB2 of snakes. At amino acid sites, we found most were conserved except for 11 (two near the heme-binding pocket) across Hbs. These fast-changing sites shifted from polar to nonpolar residues, showing a pattern seen in high-altitude mammals. Our results highlight that in reptiles (i) Hbs are diversifying at individual amino acid sites while generally some subunits exhibiting lower ω rates at higher altitudes and hotter temperatures, with the later and higher biomass ecosystems also linked to increases in dS; (ii) HBBs are the most conserved of the Hbs; (iii) latitudinal gradients only show a significant association with the dS of HBB2 in snakes; and (iv) gene conversion events occurred across HBBs in reptiles, which confound their homology assignation, except for snakes that evidenced a single major duplication in their HBBs.

Animals↗