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Biomedical subjects

R B Reeves

Publications and source records attributed to R B Reeves.

At least 19 recordsLinked to original sources
PubMed1995

Regulation of cell-type-specific interleukin-2 receptor alpha-chain gene expression: potential role of physical interactions between Elf-1, HMG-I(Y), and NF-kappa B family proteins.

The interleukin 2 receptor alpha-chain (IL-2R alpha) gene is rapidly and potently induced in T cells in response to mitogenic stimuli. Previously, an inducible enhancer between nucleotides -299 and -228 that contains NF-kappa B and CArG motifs was identified. We now report the characterization of a second essential positive regulatory element located between nucleotides -137 and -64 that binds Elf-1 and HMG-I(Y). This element had maximal activity in lymphoid cells, paralleling the cell type specificity of Elf-1 expression. Transcription from the IL-2R alpha promoter was inhibited when either the Elf-1 or the HMG-I(Y) binding site was mutated. Coexpression of both proteins activated transcription of the -137 to -64 element in COS-7 cells. Elf-1 physically associated with HMG-I and with NF-kappa B p50 and c-Rel in vitro, suggesting that protein-protein interactions might functionally coordinate the actions of the upstream and downstream positive regulatory elements. This is the first report of a physical interaction between an Ets family member and NF-kappa B family proteins. These findings provide significant new insights into the protein-protein and protein-DNA interactions that regulate cell-type-specific and inducible IL-2R alpha gene expression and also have implications for other genes regulated by Elf-1 and NF-kappa B family proteins.

Animals↗
PubMed1992

Kinetics of the Root effect and of O2 exchange in whole blood of the eel.

Oxygen transfer kinetics in blood of the eel (Anguilla rostrata, A. anguilla) were measured spectrophotometrically in thin blood layers covered by Gore-Tex membranes, which allowed fast changes of the gas phase at the blood surface (Heidelberger and Reeves, 1990 J. Appl. Physiol. 68: 1854-1864). The following main results were obtained for A. rostrata (similar values were measured for A. anguilla): (1) step change in PO2 of the gas phase between 0 and 37 kPa at low PCO2 (0.19 kPa, blood pH, 8.1; 20 degrees C) yielded mean half times (t(on)) for O2 uptake of 7.1 msec, and for O2 release (t(off)), of 42.8 msec. Similar values were obtained at high PCO2 (19 kPa; blood pH, 6.9), indicating O2 kinetics to be independent of pH and PCO2; (2) decreasing the high PO2 from 37 to 14 kPa significantly prolonged oxygen uptake kinetics, but release kinetics were unaltered; (3) changing PCO2 from 0.19 to 19 kPa at constant high PO2 (37 kPa) resulted in a reduction of hemoglobin oxygen saturation (SO2) (Root-off reaction), with t(off) averaging 44.8 msec; likewise, changing PCO2 from 19 to 0.19 kPa increased SO2 with t(on) averaging 64.8 msec (Root-on reaction). As these half times comprise reactions at the hemoglobin molecule and conversion between CO2 and H(+)/HCO3-, the Root effect kinetics of the hemoglobin molecule appear to be even faster. It is concluded that the O2 exchange kinetics of eel blood are comparable with those of human blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

O2 transfer kinetics in a whole blood unicellular thin layer.

A planar monocellular layer of whole blood (WB) sandwiched between two Gore-Tex membranes is used to study O2 uptake and release kinetics at 37 degrees C. Gore-Tex, a highly gas-permeable open mesh of Teflon fibrils (78% porosity, 0.2-microns pore size, 75-microns thick), constrains WB to form a thin film without imposing an appreciable gas diffusion barrier. WB layer thickness, measured by isotope dilution, is 1.7 +/- 0.2 microns. WB films are mounted between fiber optics in a gas flow tube for dual-wavelength (536/558 nm) oxyhemoglobin saturation measurements after a step change in PO2. For isocapnic (6% CO2) step changes in PO2 between 0 and 104 Torr, WB O2 uptake half time is 10.4 +/- 0.9 ms; WB O2 release half time is 20.6 +/- 2.4 ms. Half-time values are half of those previously reported. The thin-layer method reduces erythrocyte diffusion boundary layer error and thereby offers an attractive alternative to classical rapid fluid-mixing techniques.

Adult↗
PubMed1990

Factors affecting whole blood O2 transfer kinetics: implications for theta(O2).

Half times (t0.5) of O2 uptake (on) and release (off) were measured on thin layers of whole blood (WB). Increasing film thickness (L = 1-6 microns) increased t0.5(on) from 10 to 20 ms and t0.5(off) from 20 to 45 ms. At all L, for changes in saturation (S) 0----1, t0.5(off) was about twofold greater than t0.5(on). Doubling initial onloading PO2 gradient decreased t0.5(on) 36%; t0.5(off) was unchanged. A 10-Torr change in WB O2 affinity (P50) had no significant effect on t0.5. Specific O2 conductance [theta(O2), ml O2.(min.Torr.ml WB)-1] was also computed as a function of S from these data. A bell-shaped theta(O2) vs. S relationship was always obtained; maximum values of theta(O2) reached 25. Measured values for theta(O2) at any S were highly sensitive to choice of experimental conditions, i.e., L, affinity, flux direction, initial PO2 gradient, and initial level of S. We show experimentally and theoretically that no unique relationship exists for theta(O2) as a function of S for erythrocytes in WB.

Adult↗
PubMed1989

Metallurgical evaluation of retrieved implants and correlation of failures to patient record data.

This study sought to establish an orthopedic implant retrieval program according to ASTM F561-87 (the American Society for Testing and Materials) and to describe the results of evaluation of failed implants. A total of 275 fracture fixation and prosthetic devices have been retrieved to date. Results of metallurgical evaluation showed no deviations in ASTM specifications among the failed implants evaluated. The cause of failure in most cases was fatigue following nonunion or delay in healing.

Fractures, Bone↗
PubMed1986

Oxygen equilibrium curve shape and allohemoglobin interaction in sheep whole blood.

Adult sheep (Ovis aries) exhibit hemoglobin heterogeneity controlled by two autosomal alleles with codominant expression (Hb AA, AB, BB). Isoelectric points for Hb A and Hb B were 6.94 and 7.15, respectively; for Hb AB animals, the two allohemoglobins were present in equimolar concentrations (Hb A = 52%, Hb B = 48%). Dynamic O2 equilibrium curves (O2ECs) were generated for sheep whole blood at 39 degrees C using thin-film techniques. Half-saturation PO2 values (P50) at pH 7.50 were 31.3, 35.7, and 40.7 Torr for Hb AA, AB, and BB, respectively. CO2 Bohr coefficients at saturation (S) = 0.5 (delta log P50/delta pH) were similar for all phenotypes, ranging from -0.38 to -0.40. The Bohr slopes were also saturation independent between 0.2 and 0.8 S. Standard O2ECs for each phenotype were accurately fitted to three-constant third-order polynomial expressions. Sheep equilibrium curves were not isomorphic with other mammalian O2ECs (e.g., human and dog); sheep curves exhibited greater sigmoidicity. Furthermore, allohemoglobin interaction was not detected in heterozygous sheep. The blood O2 binding characteristics (P50, curve shape, and delta log PO2/delta pH) for Hb AB sheep and an experimental blood mixture containing equal proportions of Hb AA and Hb BB erythrocytes were equivalent.

Alleles↗
PubMed1986

Pressure increases oxygen affinity of whole blood and erythrocyte suspensions.

Effect of hydrostatic pressure (HP) on whole blood (WB) or erythrocyte suspension hemoglobin (Hb) O2 affinity has been studied using newly developed techniques. O2 partial pressure at which hemoglobin is half-saturated with O2 (P50) measurements were made at 5 HP (1, 26, 51, 76, and 126 ATA) on thin films of human WB or erythrocytes at 37 degrees C. CO2 partial pressure of WB was either 28 or 57 Torr (film pH 7.51 or 7.31). HP increased affinity of erythrocytes and WB. For erythrocytes in tris(hydroxymethyl)aminomethane buffer, the ratio (r) of P50 (1 ATA)/P50 (51 ATA) was 1.089 (P less than 0.01) at pH 7.0. WB P50 decreased with HP at a rate of -3.3 X 10(-2) Torr X atm-1; change in P50 at higher HP vs. 1 ATA was highly significant (P less than 0.01). No effect of HP was seen on the CO2 Bohr coefficient. Inert gas choice, N2 vs. helium (He), had no effect. Measurement of decrease of P50 with HP at 76 ATA in hemolyzed WB gave an r of 1.15, as great or greater than that found in WB, indicates that Donnan equilibrium alteration is not involved. No effect of HP was found in WB on the ratio of P50 of erythrocytes with normal (5 mmol/l erythrocytes) 2,3-diphosphoglycerate (DPG) to P50 of erythrocytes with less than 5% of normal DPG; i.e., no effect of pressure was seen on the independent influence of DPG on P50. WB measurements of Hb O2 uptake under simulated physiological conditions are characterized by a net decrease in partial molal volume on oxygenation of 30-35 ml/mol Hb4.

2,3-Diphosphoglycerate↗
PubMed1983

Oxygen affinity and equilibrium curve shape in blood of chicken embryos.

Oxygen equilibrium curves of blood from 4- to 18-day chicken embryos were investigated at 38 degrees C. Curves were recorded at the PCO2 measured in the air cell of each egg. Since arterial PCO2 is known to closely approximate that of the air cell, these curves reflect in vivo arterial pH. Curves were also recorded at a second, higher PCO2, allowing calculation of the curve at estimated venous PCO2 and of physiological curves by interpolation. Half saturation PO2 of physiological curves increased from 38 Torr at 4 days to 52 Torr at 8 days, and then decreased to 31 Torr at 18 days. Increasing blood oxygen affinity late in development favors oxygen loading at the falling PO2 that exists at the chorioallantoic surface, while higher affinity before 8 days may be related to diffusion resistance of the inner shell membrane early in incubation. In blood from 4- to 6-day embryos, the Hill coefficient, nH, of curves at air cell PCO2 increased from 1.5 at oxygen saturation 0.1 to 6.5 at saturation 0.85. After 6 days, nH steadily increased at low saturation and decreased at high saturation. By 18 days, nH varied only from 2 to 3.4. A biphasic equilibrium curve shape (hump at the low end of the oxygen equilibrium curve) developed in 4- and 5-day embryo blood after a period of storage on ice, and was accentuated if some of the cells were intentionally lysed.

Age Factors↗
PubMed1983

Oxygen affinity of blood of adult domestic chicken and red jungle fowl.

Respiratory properties of blood from adult domestic chicken (White Leghorn) and red jungle fowl (Gallus gallus, ancestor of domestic breeds) at 41 degrees C were investigated. Oxygen affinity was the same in blood of chicken and jungle fowl (P0.5 46.7 Torr at pH 7.5, 41 degrees C, PCO2 about 30 Torr). The Hill coefficient, nH, increased from 2 at oxygen saturation 0.1 to a maximum of 4.11 at saturation 0.8. Leghorn fixed acid and CO2 Bohr coefficients were -0.51 and -0.53, with little variation over the saturation range 0.15-0.95, indicating negligible specific CO2 effect. An nH value of greater than 4 may indicate polymerization of deoxyhemoglobin, comparable to that which occurs in sickle cell hemoglobin. A biphasic equilibrium curve shape (hump at the low end of the oxygen equilibrium curve) was noted in blood having some degree of hemolysis. Factors that may have contributed to the differences between previous investigations of chicken oxygen affinity are discussed.

Acid-Base Equilibrium↗
PubMed1982

Oxygen affinity and Bohr coefficients of dog blood.

Complete dynamic oxygen equilibrium curves (O2EC) on dog whole blood were measured at 25 and 39 degrees C using a spectrophotometric micro blood film technique. O2EC were run at three CO2 levels (2, 4, and 8%) for each of three base excess levels (-10, 0, +10 meq/l). The standard curve (ph 7.4) was determined for saturations 0-0.98. At 39 degrees C the standard curve O2 pressure at half-saturation (P50) was 31.5 Torr; fixed-acid Bohr factor, -0.488; CO2 Bohr factor, -0.498; delta log P50/delta log PCO2, -0.0045. CO2 Bohr slope was linear over the pH range of 7-8. Bohr factors were not significantly saturation dependent. At 25 degrees C P50 was 15.4 Torr and CO2 Bohr factor, -0.647. The temperature coefficient (delta log P50/delta T) equaled 0.022. Dog O2EC were shown with curve-fitting techniques to be isomorphic with human blood O2EC. The absence of significant oxylabile carbamate formation in dog red blood cells (RBC) was attributed to high 2,3-diphosphoglycerate (DPG) concentrations, 6.23 mM/l RBC, equal to a DPG/Hb4 ratio of 1.12. A simple two-constant equation S = [(37,900)/(P3 + 205P) + 1]-1, where S is saturation and P is oxygen tension, was found to fit the dog 39 degrees C standard curve.

2,3-Diphosphoglycerate↗
PubMed1980

A rapid micro method for obtaining oxygen equilibrium curves on whole blood.

A method for recording complete dynamic oxygen equilibrium curves (O2EC) from microliter samples of whole blood is described. The blood sample is compressed into a thin film between two 6-micron thick Teflon membranes in order to promote rapid gas exchange with gas volume surrounding the membranes. Oxygen tension of the gas volume around the blood film is charged at a controlled rate from zero to ca. 100 Torr by a specially designated gas-exchanging cuvette. Saturation of red cell hemoglobin in the film is measured by dual-wavelength spectrophotometry using Soret wavelengths of 430-453 nm. Gas volume oxygen tension is measured with a Teflon membrane covered oxygen cathode. Full saturation is secured by introducing an oxygen mixture whose PO2 exceeds 650 Torr. A single O2EC can be run in about 4 min at 37 degrees; multiple O2EC can be recorded from the same blood film. Each curve is run isocapnically at a preselected carbon dioxide tension. Blood film pH is calculated from the CO2 partial pressure and an independently determined buffer line. Data are presented to show that normal standard curve for man as determined with this blood-film method and those determined by other methods are equivalent.

Adult↗
PubMed1980

The effect of temperature on the oxygen equilibrium curve of human blood.

The oxygen affinity of human blood was measured with the micro blood film technique over six-degree temperature intervals from 13 to 43 degrees C. Results are expressed both as standard curves at pH 7.4 and for conditions of constant carbon dioxide content. P50 (7.4) values found were 5.8, 8.3, 13.2, 19.7, 26.9 and 33.7 Torr at 13, 19, 25, 31, 37 and 43 degrees C, respectively. The shape of the blood oxygen equilibrium curve was invariant with temperature. The measured CO2-Bohr coefficient (delta log P50/delta pH) ranged from -0.46 to -0.51 and was not temperature dependent. P50 data for 7.4 followed a van't Hoff isochore with a slope, delta log P50/delta (1/T K), of -2350 degrees and an apparent enthalpy per mol of oxygen bound of -8.2 kcal/mol. Temperature dependence of blood oxygen affinity expressed for conditions of constant carbon dioxide content exceeds that of the standard curve. New data are used to calculate the temperature dependence of blood oxygen tension at constant total gas content as a function of initial PO2 and saturation.

Acid-Base Equilibrium↗
PubMed1980

Oxygen equilibria of ectotherm blood containing multiple hemoglobins.

Complete isocapnic O2 equilibrium curves (O2EC's) and related blood-gas properties are reported for whole blood of the bullfrog (Rana catesbeiana) and the aquatic turtle (Pseudemys scripta) at temperatures ranging from 5 to 35 degrees C. P50's for bullfrog and turtle blood at physiological pH and 25 degrees C were 36.6 Torr (pH 7.83) and 19.3 Torr (pH 7.55), respectively. Elevation of blood temperature significantly reduced hemoglobin oxygen affinity in both species (delta H = -8.1 and -7.8 kcal/mol O2 for Rana and Pseudemys, respectively). Bullfrog and turtle oxygen equilibrium data revealed non-standard curve shapes when compared with the Severinghaus curve for human blood (1979); ectotherm O2EC's rose more steeply below P50 (less sigmoid) and were distinctly flattened (linear) above 50% saturation. The CO2-Bohr effect for bullfrog and turtle blood varied significantly as a function of saturation. In addition, both species exhibited non-linear Hill relationships (logS/1-s vs. log PO2). These results indicate that the oxygen binding properties of the multiple hemoglobin bloods of Rana and Pseudemys (demonstrated by isoelectric focusing) are more complex than those exhibited by normal human blood. As a consequence, these ectotherm blood oxygen data are not well characterized by the limited number of simple descriptive parameters (P50, Hill's n and delta log P50/delta pH) commonly used to delineate predominantly single hemoglobin systems.

Acid-Base Equilibrium↗
PubMed1976

Intracellular pH in cold-blooded vertebrates as a function of body temperature.

Intracellular pH (pHi) was measured in vivo in tissue of frogs (Rana catesbeiana) and turtles (Pseudemys scripta) using the DMO technique. Animals were permitted 3-8 days to come to a new steady-state body temperature (Tb) which ranged 5-32 degrees C. Least squares regression equation for pHi data are: frog blood, 8.184-0.0206 Tb; frog striated muscle, 7.275-0.0152 Tb; turtle blood, 8.092-0.0207Tb; turtle muscle, 7.421-0.0186 Tb; turtle heart, 7.452-0.0122 Tb; turtle liver, 7.753-0.0233 Tb; turtle esophageal smooth muscle, 7.513-0.0141 Tb. Only turtle cardiac muscle deltapHi/deltaT was significantly different from deltapH/deltaT of blood. Results have been interpreted in terms of protein charge state alterations; in the physiological pH range, histidine residues of proteins are the principal dissociable groups (HPr+ = H+ + Pr) affected by pHi and Tb changes. Constancy of protein charge state can be assessed by monitoring alpha imidazole, alphaIM = Pr/(HPr+ + Pr). A uniform pKIM of 6.85 (20degreesC) and a deltaHO of 7 kcal/mol are assumed in calculating alphaIM. Intracellular alphaIM is preserved in the tissues studied as body temperature changes. These results indicate that ectotherm acid-base balance, alphastat control, regulates not only extracellular blood proteins, but also intracellular compartment proteins in such a way as to preserve functions dependent upon protein net charge states.

Acid-Base Equilibrium↗