Left main renal artery entrapment by diaphragmatic crura: spiral CT angiography

Entrapment of renal artery by the diaphragmatic crus is a rare cause of renal artery stenosis. Spiral computed tomography angiography provides a definitive diagnosis and shows the precise relationship of the artery to the diaphragmatic crus. The authors present a case of hypertension developing in a young 20-year-old female due to entrapment of the left renal artery by the diaphragmatic crus. This condition should be considered in young hypertensive patients with renal artery stenosis without cardiovascular risk factors

Asymmetric inhibition by phlorizin of sulfate movements across the red blood cell membrane

Measuring SO42− exchange across the red cell membrane at Donnan equilibrium, it was found that extracellular phlorizin inhibited SO42− movements while intracellular phlorizin did not. This asymmetric action of phlorizin on anion permeability is in contrast to the effect on the permeability to d-xylose. In accordance with previous findings of Beneš, I., Kolinská, J. and Kotyk, A. (1972) J. Membrane Biol. 8, 303, the penetration of the sugar was inhibited by phlorizin from either surface. It is concluded that phlorizin inhibition of anion transfer across the red cell membrane is due to interactions with binding sites which are located at the outer surface of the membrane and which do not diffuse all the way through the membrane like a sugar carrier or a lipid-soluble ionophore

The permeability of the human red blood cell to sulfate ions

Sulfate permeability was measured at Donnan equilibrium as a function of three variables, the sulfate, chloride, and hydrogen ion concentration in the medium. The data were used for a quantitative evaluation of a number of typical predictions of a fixed charge model of the ion permeable regions of the red blood cell membrane. It could be shown that more than 1,000-fold variations of sulfate flux, JSO4, could be represented as a function of a single variable SO2−4m, the sulfate concentration in the membrane. SO2−4m was calculated from the measured values of all three variables by means of a previously published equation (Passow,Progress in Biophysics and Molecular Biology, vol. 19, pt. II, pp. 425–467, 1969). In this equation, two constants can be arbitrarily chosen: Ā, the sum of the charged and uncharged forms of dissociable fixed charges, andK, the dissociation constant of the fixed charges. For the present calculations, the previously obtained values Ā=2.5 and K=1·10−9 were used

Effects of incorporated trypsin on anion exchange and membrane proteins in human red blood cell ghosts

Varying concentrations of trypsin were sealed into human red cell ghosts and the effects on membrane proteins and sulfate equilibrium exchange were studied. After incubation for 45 min at 37 °C, pH 7.2, the following observations were made: above 10 ng/ml the ghosts undergo fragmentation without lysis. Dodecyl sulfate gel electrophoresis shows that the digestion of spectrin and of the protein in band 2.1 (nomenclature of Steck (1974) J. Cell. Biol. 62, 1–19) is nearly complete at 50 ng/ml, that of the protein in band 3 at 25 μg/ml. After digestion at 25 μg/ml, about 60% of the total protein of the membrane is released and the original bands of conventional dodecyl sulfate gel electropherograms of the remaining protein are nearly completely abolished. In their place three new bands appear representing peptides with molecular weights of 58 000, 48 000 and 34 000, respectively. Sometimes a fourt peptide with a molecular weight of approx. 13 000 is also observed. Using a radioactive labeling technique it is shown that the two peptides with the highest molecular weights are derived from the protein in band 3. Labeling with diazo[3 5S]sulfanilic acid indicates that in addition to the peptides in the described four Coomassie blue-stainable bands, other peptides with molecular weights up to 100 000 are still present in the exhaustively trypsinized ghosts. External trypsin has no effect on the sulfate equilibrium exchange in ghosts while internal trypsin causes inhibition. Inhibition becomes apparent at trypsin concentrations exceeding those required to produce a complete digestion of spectrin. It remains incomplete, even at the highest intracellular concentrations which cause maximal effects on all membrane proteins, including the protein in band 3. Under these conditions strong further inhibition can be produced by agents which are known to inhibit anion transport in untreated red cells and ghosts. These agents include the penetrating 1-fluoro-2,4-dinitrobenzene and the nonpenetrating phlorizin, 4-acetamido-4′-isothiocyanato stilbene-2,2′-disulfonic acid, 4,4′-diacetamido stilbene-2,2′-disulfonic acid, and 2-(4′-aminophenyl)-6-methylbenzenethiazol-3′,7-disulfonic acid (APMB). Unlike the other nonpenetrating inhibitors APMB is not only capable of inhibiting at the outer but also at the inner membrane surface. Treatment with internal trypsin does not significantly reduce the inhibition by incorporated APMB. The described observations suggest that after exhaustive tryptic digestion of the major membrane proteins, the receptor sites for typical inhibitors of anion transport continue to exert their function

The effect of pH at hemolysis on the reconstitution of low cation permeability in human erythrocyte ghosts

Human red blood cells were hemolysed at 0°C in hypotonic media of varying pH (range 4.5–10.0). Subsequently the pH in the hemolysate was readjusted to 7.2 and the ghosts were incubated at 37°C for 45 min. The curve relating the yield of resealed ghosts to pH showed a maximum after hemolysis at pH 6 and a broad shoulder in the range between pH 7 and 9. The experiments suggest that during hemolysis buried ionizable groups become exposed to the ambient medium. The ability of these groups to return to their original locations within the hydrophobic interior of the membrane seems to depend on the charge which they assume during their exposure to the aqueous environment. However, alternative explanations cannot be excluded

The Band 3 Protein: Anion Exchanger and Anion-Proton Cotransporter

The anion transport protein of the red blood cell membrane, the so-called band 3 protein, mediates two distinct processes: anion exchange and anion-proton co-transport. The present chapter deals with the relationship between the two processes

Mediation of inorganic anion transport by the hydrophobic domain of mouse erythroid band 3 protein expressed in oocytes of Xenopus laevis

A cDNA clone of the mouse erythroid band 3 protein encoding the 556 amino acid residues of the hydrophobic domain from Thr-374 to the C-terminal Val-929 is shown by immunoprecipitation to be expressed in Xenopus oocytes. Measurements of 36Cl- efflux indicate that the translation product mediates Cl- transport, which is inhibitable reversibly by DNDS or H2DIDS, specific inhibitors of band 3-mediated transport. The apparent KI values are 3.6 microM and 0.094 microM, respectively, and hence similar to those found in the wild type band 3-mediated anion transport. The rapid reversible inhibition by H2DIDS slowly changes to irreversible inhibition. The rate of change increases with increasing pH, again similar as to the wild-type band 3. It is concluded that the hydrophobic domain of band 3 is capable of executing anion transport essentially similar to the full-length band 3, although minor differences with respect to transport and inhibition kinetics cannot be ruled out