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J F Bertles

Publications and source records attributed to J F Bertles.

At least 37 records · Page 2Linked to original sources
PubMed1977

Effect of 2, 3-diphosphoglycerate on the solubility of deoxy-sickle hemoglobin.

We have examined the effect of 2, 3-diphosphoglycerate (DPG) on the solubility of deoxy-sickle hemoglobin (deoxy-Hb S) under conditions such that concentration, pH, and osmolarity of deoxy-Hb S solutions approached physiological. The range of DPG/Hb molar ratios encompassed the extremes found for this ratio in erythrocytes from individuals with sickle cell anemia. After monomer-polyer equilibrium had been established, the phases were separated by centrifugation and assayed for concentrations of Hb and DPG. DPG had no effect on the solubility of deoxy-Hb S. Furthermore, at DPG/Hb molar ratios less than one, there was no preferential incorporation of deoxy-Hb S containing bound DPG into polymers. At DPG/Hb molar ratios greater than one, concentrations of free DPG in monomer and polymer phases were virtually identical. Thus, under the specified equilibrium conditions, DPG is not a determining factor in the polymerization of deoxy-Hb S.

Anemia, Sickle Cell↗
PubMed1976

Intermolecular interactions of oxygenated sickle hemoglobin molecules in cells and cell-free solutions.

We have measured the intermolecular interactions of oxygenated sickle hemoglobin molecules in cells and in cell-free solutions, and have compared the results with similar data for liganded normal adult hemoglobin. The experiments involve the measurement of the spin-lattice relaxation time T1 of protons of solvent water molecules, as a function of an externally applied static magnetic field. From such data, one can derive a correlation time tauc, for each sample, which is a measure of the time taken for a hemoglobin molecule to randomize its orientation due to Brownian motion. Thus tauc is a measure of the freedom of rotational motion, on a molecular or microscopic level, of hemoglobin molecules. Intermolecular interactions will reduce this freedom of motion and lengthen tauc. We find that oxygenated sickle hemoglobin molecules have an additional intermolecular interaction not found for normal hemoglobin. This extra interaction is increased by the presence of either inorganic phosphate or diphosphoglycerate, and is greater for sickle hemoglobin within cells than in cell-free solutions. By comparing the present results with published data on the viscosity of oxygenated sickle and normal hemoglobin, we conclude that, at concentrations comparable to intracellular values, oxygenated sickle hemoglobin molecules form aggregates several tetramers in size. The possibility exists that these aggregates are the earliest stage of fiber formation itself, the physical basis of the sickling phenomena.

Binding Sites↗
PubMed1976

Thermodynamic studies of polymerization of deoxygenated sickle cell hemoglobin.

Solubilities of deoxygenated sickle cell hemoglobin (deoxy-Hb S), at varying pH and temperature over a range of concentrations encompassing those found in erythrocytes, were measured. The technique involved ultracentrifugation, which gave values of the supernatant concentration and the mass of the sedimented material. The data establish that the solubility of doexy-Hb S is the saturation concentration and is independent of initial concentration. The mass of the pellet phase increases linearly with initial concentration. Moreover, the saturation concentration represents the critical concentration above which monomers are in equilibrium with polymers. These polymers are the putative cause of erythrocytes deformation associated with sickle cell anemia. The solubility-pH profiles of deoxy-Hb S at various temperatures, unlike those of other proteins, show no minima at the isoelectric pH but instead show a marked decrease in solubility below pH 7.0, indicating the predominance of polymerization over the expected increase in solubility. Deoxy-Hb S, within specified ranges of temperature and pH, possesses a negative temperature coefficient of solubility, a property characteristic of hydrophobic interactions. The saturation concentration is, however, temperature independent at conditions close to physiological. The enthalpy of polymerization (3.5 kcal/mol) is temperature independent from 6 degrees to 22 degrees for all pH values between 6.45 and 7.40. In the range of 22 degrees to 38 degrees, this parameter becomes less endothermic, having a value of 2.5 kcal/mol at pH 6.45 and a value of zero at pH 7.20. Such behavior of the system suggests a phase transition near 22 degreas. Within the range of conditions examined the polymerization is entropically driven.

Hemoglobin, Sickle↗
PubMed1975

Hemoglobin S/C disease in a pregnant woman with crisis and fat embolization syndrome.

The complications of painful crisis and megaloblastic anemia are hallmarks of the pregnant patient with hemoglobin S/C disease. We describe here the clinical course in a patient with hemoglobin S/C disease in whom painful crisis and the fat embolization syndrom developed postpartum with severe neurologic abnormalities. Response to exchange blood transfusion was dramatic, and the patient recovered without neurologic impairment.

Adult↗
PubMed1975

Deformability of sickle cells as studied by microsieving.

The effect of deoxygenation on deformability of sickle cells (Hb SS RBC) was studied quantitatively by a microsieving technique with the use of polycarbonate filters having micropores of 5 mum in diameter. The rate of pressure rise and the relative resistance during filtration through polycarbonate sieves increased progressively when the P02 of Hb SS RBC suspensions was reduced below 80 mm. Hg. Control studies on Hb AA RBC did not show any significant change in either parameter when deoxygenated. The present study on the filterability of Hb SS RBC and our previous data on the viscometric behavior of Hb SS RBC serve to establish the quantitative relation between P02 and the deformability of Hb SS RBC.

Anemia, Sickle Cell↗
PubMed1973

Structure of sickled erythrocytes and of sickle-cell hemoglobin fibers.

Deoxyhemoglobin from patients homozygous for sickle-cell anemia (deoxyhb S) aggregates into long straight fibers. These may extend through most of the length of the sickled cell, forming either square or hexagonally packed bundles with lattice constants of 170-180 A. Each fiber is a tube made up of six thin filaments, which are wound around the tubular surface with a helical pitch of about 3000 A. Each filament is a string of single hemoglobin molecules linked end to end at intervals of 62 A in dry and 64 A in wet fibers. Molecules in neighboring filaments are in longitudinal register so that they form flat hexagonal rings; these rings are stacked so that successive ones are rotated about the fiber axis by 7.3 degrees . The whole structure repeats after about eight rings. In this structure each molecule makes contact with four neighbors. The likely orientation of the molecules and points of contact between them are discussed. Similar filaments are also observed in normal deoxygenated erythrocytes, but in much lower concentration and aggregated into fibers of irregular diameter. No filaments appear in oxygenated sickle, or normal, adult cells, nor in oxygenated or deoxygenated fetal cells.

Anemia, Sickle Cell↗
PubMed1973

Erythrocyte Hb-S concentration. An important factor in the low oxygen affinity of blood in sickle cell anemia.

The blood in sickle cell anemia has a very low oxygen affinity and, although 2,3-diphosphoglycerate (2,3-DPG) is increased, there is doubt as to whether this is the only factor responsible. In this study of 15 patients with sickle cell anemia (Hb SS) no correlation was found between oxygen affinity (P(50) at pH 7.13) and 2,3-DPG in fresh venous blood. Whole populations of Hb SS erythrocytes were therefore separated, by an ultracentrifuge technique, into fractions of varying density. The packed red cell column was divided into three fractions; a bottom fraction rich in deformed cells or irreversibly sickled cells (ISC), with a very high mean corpuscular hemoglobin concentration (MCHC); a middle fraction containing cells with the highest content of fetal hemoglobin; and a top fraction containing reticulocytes and discoid cells but free of deformed cells. Oxygen affinity was shifted to the right in all layers (mean P(50) (pH 7.13)+/-1SD: top 46.3+/-2.9 mm Hg: middle 49.8+/-4.9 mm Hg; bottom 61.0+/-5.8 mm Hg) compared with normal blood (top 32.1+/-0.7 mm Hg: bottom 30.1+/-0.5 mm Hg). 2.3-DPG was increased in the top fraction, but was low or normal in the bottom fraction (top 21.8+/-3.4 mumol/g Hb: middle 17.7+/-2.2 mumol/g Hb; bottom 13.8+/-3.1 mumol/g Hb; normal whole blood 14.3+/-1.2 mumol/g Hb). The level of 2,3-DPG in top fractions could not account for the degree of right shift of P(50), and in the middle and bottom fractions the even greater right shifts were associated with lower levels of 2,3-DPG. Top fraction cells depleted of 2,3-DPG had a higher, but still abnormally low, oxygen affinity. A strong relationship was found between oxygen affinity and MCHC. The fractions with the greatest right shift in P(50) had the highest MCHC (top 32.4+/-2.0; middle 36.2+/-3.1; bottom 44.6+/-3.2 g/100 ml, respectively) and the plot of P(50) vs. MCHC showed a positive correlation (r = 0.90, P < 0.001). The red cell population in sickle cell anemia is not homogeneous but contains cells of widely varying Hb F content, 2,3-DPG, and hemoglobin concentration. Paradoxically, the cells with the lowest O(2) affinity have the lowest 2,3-DPG, but they also have the highest concentration of Hb S. The dense, deformed cell called the ISC is but the end stage in a process of membrane loss and consequent increase in hemoglobin concentration. The P(50) of Hb SS blood is, to a large extent, determined by the presence of these cells (r = 0.85, P < 0.001). Increased concentration of Hb S in the cell favors deoxygenation and crystallization even at relatively high P(o2). Lowered affinity for oxygen appears to be closely associated with Hb S concentration and not with 2,3-DPG content.

Adolescent↗
PubMed1970

Abnormal rheology of oxygenated blood in sickle cell anemia.

The viscosity of oxygenated blood from patients with sickle cell anemia (Hb SS disease) was found to be abnormally increased, a property which contrasts with the well recognized viscous aberration produced by deoxygenation of Hb SS blood. Experiments designed to explain this finding led to considerations of deformation and aggregation, primary determinants of the rheologic behavior of erythrocytes as they traverse the microcirculation. Deformability of erythrocytes is in turn dependent upon internal viscosity (i.e. the state and concentration of hemoglobin in solution) and membrane flexibility. Definition of the contribution made by each of these properties to the abnormal viscosity of oxygenated Hb SS blood was made possible by analysis of viscosity measurements, made over a wide range of shear rates and cell concentrations, on Hb SS erythrocytes and normal erythrocytes suspended in Ringer's solution (where aggregation does not occur) and in plasma. Similar measurements were made on the two cell types separated by ultracentrifugation of Hb SS erythrocytes: high density erythrocytes composed of 50 to 70% irreversibly "sickled" cells (ISC) and low density erythrocytes composed of over 95% non-ISC. Under all experimental conditions (hematocrit, shear rate, and suspending medium) the viscosity of ISC exceeds that of normal erythrocytes. The viscosity of non-ISC is elevated only in the absence of aggregation and over intermediate ranges of hematocrit. Analyses of the data reveal (a) an elevated internal viscosity of ISC: (b) a reduced membrane flexibility of both ISC and non-ISC, particularly at low shear rates; and (c) a reduced tendency for aggregation displayed by both cell types. The abnormal viscosity of oxygenated Hb SS blood can be attributed to the altered rheology of ISC and, to a lesser extent, of non-ISC. These studies assign a role to the abnormal rheology of Hb SS erythrocytes in the pathogenesis of sickle cell anemia, even under conditions of complete oxygenation.

Adolescent↗