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Biomedical subjects

M B Morris

Publications and source records attributed to M B Morris.

6 recordsLinked to original sources
PubMed1992

Band-3 mediated uptake of beryllofluoride complexes by human erythrocytes.

Beryllium forms several multivalent fluoride complexes in aqueous solution; the relative concentration of each is governed by the relative concentrations of the constituent ions and pH. In 9Be NMR spectra the 9Be (spin = 3/2) and 19F (spin = 1/2) spin coupling gave rise to an overlapping resonance triplet, quartet, and quintet of BeF2, BeF3-, and BeF4(2-), respectively. The low frequency shift of the quartet (0.31 ppm) and the quintet (0.62 ppm) from the triplet correlated with an increase in the number of 19F-ions in each complex. 19F NMR spectra of the complexes showed that the spin-coupled quartet of each complex was progressively shifted to higher frequency with an increase in the number of F- ions in the complex. Using 9Be and 19F NMR, the multiple equilibrium mixture of complexes was found to shift substantially to favor the BeF3- and BeF4(2-) with a relative increase of NaF concentration. The association constants for BeF2, BeF3-, and BeF4(2-) at 25 degrees C were determined directly from the peak intensities of the spectra, and by a numerical fitting procedure for multiple spectra, and were 0.51 +/- 0.17 mM-2, 0.26 +/- 0.03 mM-1, and 1.0 x 10(-2) +/- 0.1 x 10(-2) mM-1, respectively. 19F NMR spectra of human erythrocytes to which Be2+ and F- were added showed separate resonances from the intracellular populations of the complexes and these were shifted to higher frequency from their extracellular counterparts.(ABSTRACT TRUNCATED AT 250 WORDS)

Anion Exchange Protein 1, Erythrocyte↗
PubMed1992

The inhibition of ATP-dependent shape change of human erythrocyte ghosts correlates with an inhibition of Mg(2+)-ATPase activity by fluoride and aluminofluoride complexes.

The vanadate-sensitive Mg(2+)-dependent ATPase activity of the human erythrocyte ghost is believed to be involved in the shape change events that convert echinocytic ghosts to smoothed forms (biconcave discs and stomatocytes). At physiological salt concentration, pH 7.4, 2 mM ATP, 5 mM Mg2+ and 1 mM EGTA, the Mg(2+)-ATPase activity of ghosts was inhibited strongly by millimolar concentrations of sodium fluoride: I50 = 1.31 +/- 0.23 mM (mean +/- S.D.; n = 12). The addition of aluminium chloride to 15 microM reduced the concentration of NaF required for 50% inhibition to 0.76 +/- 0.21 mM (n = 10). Aluminium alone had only a small inhibitory effect on the ATPase activity (13 +/- 9%; n = 10). Desferrioxamine, a strong chelator of tervalent aluminium ion, failed to reverse the inhibition by fluoride and reversed the inhibition in the presence of aluminium and fluoride back to those values obtained with fluoride alone. Of several metal salts tested only beryllium sulfate was able to replace aluminium as an effective inhibitor in the presence of fluoride. Inhibition of the Mg(2+)-ATPase activity by fluoride and the aluminofluoride complexes correlated with an inhibition of the rate of MgATP-dependent change in red cell ghost shape from echinocytes to smoothed forms. All gross morphological changes of the smoothing process were affected, including the production of discocytes, stomatocytes and endocyctic vesicles.

Aluminum↗