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Biomedical subjects

R M Wells

Publications and source records attributed to R M Wells.

At least 37 records · Page 2Linked to original sources
PubMed1986

Characterization of the changes in the state of aggregation induced by ligand binding in the hemoglobin system of a primitive vertebrate, the hagfish Eptatretus cirrhatus.

Hemoglobin (Hb) from the hagfish, Eptatretus cirrhatus, is composed of subunits of approx. 20,000 mol. wt. Aggregation of the deoxy subunits occurred, particularly at low pH and at high protein concentration. Oxygen equilibrium studies indicated slight cooperativity and the presence of a small, phosphate-independent Bohr effect. Equilibrium properties were protein concentration dependent indicating an oxygen-linked dissociation in the millimolar concentration range. Kinetic studies indicated a dimer to monomer transition in the micromolar concentration range. The ligand-binding character of hagfish Hb was similar to that of lampreys, but was governed by different kinetic and equilibrium parameters.

Animals↗
PubMed1986

Physiological stress responses in big gamefish after capture: observations on plasma chemistry and blood factors.

The plasma electrolytes, Na+, K+, Ca2+, Cl- and osmolarities had high values in capture-stressed big gamefish. Blood metabolites measured after stress showed glucose and lactate elevations. The activity of the plasma enzymes alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, creatine kinase and lactate dehydrogenase suggested tissue disruptions following severe capture stress. Haematocrit values and methaemoglobin were high in capture-stressed gamefish. The plasma chemistry of resting and capture-stressed snapper (Chrysophrys auratus) was studied for comparison. Specific differences in plasma biochemistry appeared to be the result of different strategies of fish behaviour during capture.

Animals↗
PubMed1986

Blood oxygen transport in the free-swimming hagfish, Eptatretus cirrhatus.

Arterial and mixed venous blood were sampled through chronically implanted cannulae from rested and swimming hagfish. PaO2 remained high when hagfish were swum for 15 min at a velocity of 20 cm s-1. PvO2 fell from 17.2 mmHg at rest to 3.5 mmHg after swimming, and the arteriovenous pH difference increased from 0.15 to 0.25 pH units. Whole blood oxygen equilibrium curves were essentially hyperbolic (Hill's n value = 1.38) and gave a half-saturation PO2 (P50) value of 12.3 mmHg at pH 7.8 and 16 degrees C. A CO2-Bohr factor (phi = delta logP50/delta pH) of -0.43 and a limited buffering capacity of the blood, amounting to approx. 4 slykes, were observed. The role of the blood in transporting oxygen and carbon dioxide both at rest and after swimming is established by in vivo blood gas measurements and in vitro oxygen-binding data. The low internal PvO2 at rest is close to the P50 measured under similar conditions and the hyperbolic equilibrium curve permits further oxygen unloading when PvO2 falls during swimming.

Acid-Base Equilibrium↗
PubMed1985

Polycythaemia associated with a new haemoglobin variant: haemoglobin Palmerston North beta 23 (B5) val----phe.

A new haemoglobin variant, with increased oxygen affinity, has been identified in a patient with a long history of polycythaemia. This new haemoglobin, Hb Palmerston North, has an amino acid substitution of valine to phenylalanine at position beta 23 (B5). The increased oxygen affinity is accompanied by a decrease in globin stability which was responsible for the laboratory detection of the haemoglobinopathy.

Aged↗
PubMed1985

Fixed acid and carbon dioxide Bohr effects as functions of hemoglobin-oxygen saturation and erythrocyte pH in the blood of the frog, Rana temporaria.

Using a thin film, dynamic recording technique, the pH sensitivity of the oxygen equilibrium (Bohr effect) of whole blood in the frog Rana temporaria, and its dependence on CO2 and fixed acids and on plasma and erythrocyte pH values were measured. Under standard conditions (20 degrees C, PCO2 = 14.7 mm Hg, pH = 7.65) the oxygen equilibrium could be described by a P50 value of 38 mm Hg and n50 of 1.8 Hill plots of the oxygen equilibria showed increased cooperativity in oxygen binding with increasing saturation (n20 congruent to 1.2, n80 congruent to 4.0). Values of fixed acid and CO2 Bohr factors (phi AH and phi CO2, respectively) were similar at specific saturations (S20, 50, 80) but showed saturation dependence with high values occurring at high saturation. The same statements also hold for the intracellular Bohr factors (derived from the relation between blood P50 and erythrocyte pH) although the values of both phi AH and phi CO2 now were greater than those related to blood pH.

2,3-Diphosphoglycerate↗
PubMed1985

Changes in blood metabolites following stress from capture and handling of the marine teleost Girella tricuspidata.

Whole blood nucleoside triphosphate (NTP) and lactate in the parore (Girella tricuspidata, Fam: Kyphosidae) were monitored over a period of 12 hr following capture by gill net. An increase in NTP during the post-capture recovery period was mainly attributable to a significant rise (P less than 0.05) in the NTP component guanosine triphosphate (GTP). The rise in GTP levels correlated with the decline in blood lactate (r = -0.72) accumulated during the period of capture stress. It is suggested that metabolism of lactate via the Krebs cycle may be responsible for the rise in GTP.

Adenosine Triphosphate↗
PubMed1985

Oxygen binding by the blood and hematological effects of capture stress in two big game-fish: mako shark and striped marlin.

Blood from capture-stressed striped marlin cannot be fully saturated with oxygen in the presence of lactic acid because of a substantial Root effect. Titration of blood to pH 7.6 at 25 degrees C gave an O2 affinity constant, P50 = 17 mmHg. The P50 was highly sensitive to pH showing a Bohr factor phi = delta log P50/delta pH = -0.74. Blood from capture-stressed mako sharks did not show either a Root effect or a significant Bohr effect (delta log P50/delta pH = +0.16). The O2-affinity constant, P50, was 10.6 mmHg at pH 7.6 and 25 degrees C. Hematological measurements following capture gave hematocrit values of 24.2 +/- 8.1% and 32.3 +/- 10.8% for marlin and mako respectively, and high concentrations of blood lactate in both species (15-16 mmol l-1). The O2 transport properties of the blood are discussed in relation to oxygen demand and capture stress.

Animals↗
PubMed1985

Plasma catecholamines and erythrocyte swelling following capture stress in a marine teleost fish.

Plasma concentrations of adrenaline and noradrenaline were measured at rest from cannulated fish and following net capture. Adrenaline and noradrenaline concentrations in capture-stressed fish averaged 36,740 pmol l-1 and 38,860 pmol l-1 respectively, whereas resting values were less than 200 pmol l-1 for both amines. Erythrocyte swelling and raised blood lactate were evident in stressed fish. In vitro effects of 5 mmol l-1 adrenaline on erythrocyte suspensions suggested that the catecholamine had a direct effect on erythrocyte volume. The significance of these results is discussed in relation to the oxygen transport properties of the blood.

Animals↗
PubMed1984

Characterization and function of isolated hemoglobins from the marine teleost Girella tricuspidata.

Five isohemoglobins were characterized from the marine teleost fish, Girella tricuspidata, using polyacrylamide gel electrophoresis and isoelectric focusing. O2-equilibrium (OEC) studies of the five components separated by column chromatography showed functional heterogeneity with respect to Hill's coefficient n, the O2 affinity, P50, and the Bohr coefficient phi, = delta logp50/delta pH. Recombination and examination of the isolates gave an OEC similar to that of "stripped" hemolysate and similar to a curve synthesized from a model incorporating the OEC parameters of the isoHbs.

Animals↗
PubMed1983

Molecular aspects of embryonic mouse haemoglobin ontogeny.

Embryos from C57BL/6J mice between the gestational ages of 9 and 16 days possess three embryonic haemoglobins EI, EII and EIII, the proportions of which change as a function of gestational age. Component EI, originally present at approx. 65% at day 9, decreases to approx. 20% by day 16, while component EII increases in an inverse manner to that of component EI. During this period component EIII remains essentially constant at approx. 25%. Separation of these species by ion-exchange chromatography has allowed the characterization of the Hill coefficient, Bohr effect, heat of oxygenation and binding of allosterically active organic phosphates for each component. The three components show marked functional heterogeneity and also differ from maternal haemoglobin. Oxygenation curves for whole embryonic blood show distinct deviations from simple binding behaviour. The presence of a high-affinity component within the blood samples may be accounted for by the presence of haemoglobin EI. By using parameters obtained from the study of the isolated components it has been possible to synthesize mathematically the O2-binding curves, obtained experimentally, throughout the gestational period. The characteristics of the isolated haemoglobin components of embryonic mouse blood are discussed in terms of the changing demands for O2 likely to be encountered by the developing embryo.

2,3-Diphosphoglycerate↗
PubMed1983

Antagonistic effect of urea on oxygenation-linked binding of ATP in an elasmobranch hemoglobin.

The O2 affinity of "stripped" (cofactor-free) hemoglobin (Hb) of the elasmobranch, Squalus acanthias is decreased by ATP, the main erythrocytic phosphate cofactor but increased by urea at physiological concentration. When both compounds are present, as in life, urea decreases the ATP sensitivity, indicating that previous Hb oxygenation studies in the absence of urea overestimate the modulator role of phosphate cofactors in sharks. Whereas ATP decreases the O2 association equilibrium constant of the deoxygenated pigment, urea raises those of both the deoxy and the oxygenated states. Possible mechanisms for the urea-protein interactions i.e. binding at carboxy-termini or carbamylation of amino-termini of the protein chains, are discussed.

Adenosine Triphosphate↗
PubMed1983

Non-cooperative oxygen binding in the erythrocytes of pre-implanted sheep embryos.

The whole-blood oxygen equilibrium curve in sheep embryos at 17 days gestation was essentially hyperbolic, indicating non-cooperative O2 binding with Hill's coefficient, n approximately equal to 1.2. O2 affinity was higher in embryonic blood (P50 = 7.1 mmHg at pH = 7.4 and 39 degrees C) than in maternal blood (P50 = 32.6 mmHg at pH = 7.4 and 39 degrees C). The Bohr effect was apparently smaller in the embryo (delta log P50/delta pH = --0.52) than in maternal blood (--0.36).

Animals↗
PubMed1983

Allosteric interactions governing oxygen equilibria in the haemoglobin system of the spiny dogfish, Squalus acanthias.

The oxygenation-linked, allosteric interactions of erythrocytic organic phosphates and urea with the haemoglobin (Hb), and the functional significance of the Hb multiplicity, were studies in an elasmobranch, Squalus acanthias. The autochthonous red cell nucleoside triphosphates (NTP) ATP and GTP (guanosine triphosphate) strongly depress O2 affinity of the stripped (cofactor-free) Hb and increase cooperativity in O2 binding. As previously found in teleost Hbs, GTP exerts a greater effect than ATP at the same concentration. Urea, in contrast, increases O2 affinity and depresses cooperativity. It also antagonizes the modulator effectivity of NTP at physiological NTP/Hb concentration ratios. Deoxygenation of the Hb raises blood pH. This Haldane effect contrasts with earlier findings for Pacific specimens, but accords with the presence of a Bohr effect (phi = delta log P50/delta pH). S. acanthias Hb resolves into six main components (three pairs) on the basis of isoelectric point. There is no evidence for radical functional differentiation as found in teleosts with electrophoretically anodal and cathodal Hb components. The physiological implications of the findings and the possible molecular mechanisms basic to the NTP and urea effects are discussed.

Adenosine Triphosphate↗
PubMed1983

Oxygenational properties and phosphorylated metabolic intermediates in blood and erythrocytes of the dogfish, Squalus acanthias.

A typical whole blood O2-equilibrium curve from Squalus acanthias had a P50 of 13.2 mmHg and was slightly sigmoidal, having an n value of 1.6 at 15 degrees C, PCO2 = 2.2 mmHg (pH = 7.85). A small Bohr effect was present (phi = -0.28) together with a weak Haldane effect and no Root shift. The predominant trinucleotide, determined by thin layer chromatography, was ATP (0.44 +/- 0.13 S.D. mmol 1(-1) blood) with smaller amounts of GTP present (0.07 +/- 0.02) S.D. mmol 1(-1). Total nucleotide concentrations, determined enzymatically, were low by comparison with teleosts. Incubation of erythrocytes with or without oxygen, or in the presence of a metabolite-enriched 'cocktail' showed limited potential for phosphate cofactor regulation of blood oxygen affinity.

Adenosine Triphosphate↗
PubMed1982

An investigation of the allosteric functioning of the haemoglobin of the cane toad, Bufo marinus.

1. Cane toad haemoglobin shows co-operative equilibrium CO binding at pH 7.0 with n = 2.6. 2. Flash photolysis studies show that at high pH the R form of the protein is stabilised whilst low pH and the presence of IHP favours the T form. 3. The combination of stopped-flow and flash photolysis measurements allows estimation of the association and dissociation rates of CO binding for the two forms of the protein. 4. The protein functioning can be described by a modified two state model and mathematical modelling allows the estimation of the allosteric equilibrium constant for this haemoglobin.

Animals↗
PubMed1982

Oxygen binding properties of hemoglobins from antarctic fishes.

1. The half-saturation value, P50, for 'stripped' hemoglobins from Trematomus spp. (fam. Nototheniidae) at pH 8.27 and -1.8 degrees C varied from 12.1 mmHg in the pelagic species T. borchgrevinki to 1.3 mmHg in the sedentary benthic species T. centronotus. 2. The nototheniid hemoglobins showed appreciable Bohr effects (phi = delta log P50/delta pH = -0.87 to -0.48) while the hemoglobin from a bathydraconid species, Gymnodraco acuticeps, was insensitive to pH; phi = -0.02 No Root shifts were detected. 3. Cooperative oxygen binding was present in all hemoglobins with Hill's coefficient, n, ranging from 1.21 +/- 0.14 in Dissostichus mawsoni to 2.28 +/- 0.88 in T. borchgrevinki among the Nototheniidae, and n = 1.50 +/- 0.14 in G. acuticeps. 4. A small increase in P50- was promoted by ATP for hemoglobins from T. borchgrevinki, T. bernacchii and D. mawsoni but significant temperature effects on oxygen binding were manifested, with apparent heats of oxygenation, delta H, = -56.13, 62.16, and -23.98 kJ mol-1, respectively.

Animals↗
PubMed1982

An investigation of the co-operative binding of carbon monoxide to the haemoglobin of the carpet shark Cephaloscyllium.

1. Carpet Shark haemoglobin shows co-operative equilibrium CO binding at pH 7.0 (n = 1.8). 2. Flash photolysis shows that the T form of the protein is stabilised at low pH and in the presence of Inositol Hexaphosphate (I.H.P.). 3. At high pH the R form of the protein is stabilised and exhibits kinetic heterogeneity, assigned to different chain reactivities. 4. Stopped flow and flash photolysis under various conditions allows estimates to be made of the association and dissociation rates of CO binding for the two forms of the protein. 5. The functionality of the protein, with regard to CO binding, can be described by a modified two state model.

Allosteric Regulation↗