The effect of membrane-bound calcium on the activity of adenosine triphosphatase from erythrocytes and erythrocyte permeability for monovalent cations]

The activities of Ca2+, Mg2+-ATPase and Na+, K+-ATPase and the permeability of reconstituted human erythrocytes for Na and K ions were measured, using Ca2+-EGTA, Ca2+ATP and Ca2+-sodium citrate buffers. It was found that the increase in the Ca2+/chelate ratio caused stimulation of Ca2+, Mg2+- and Na+, K+-Atpases and an increase in the rate constants of ouabain--dependent 42K+ influx and 22Na+ efflux from the erythrocytes. The use of the Ca2+-sodium citrate system as a calcium buffer did not change the parameters of the functional state of erythrocyte membranes. The data obtained are discussed in terms of a possible role of calcium ions, which are bound to the inner surface of the erythrocyte membrane, in the regulation of the systems of active and passive transport of cations.     

Elevated Na+/H+ exchange in erythrocytes of patients with hypertension

The kinetics of proton efflux from erythrocytes with acidified cytoplasm (pHi 6.4) in a medium with pH 8.0 has been studied. The participation of the anion exchanger in this process was blocked by a stilbene disulfonic acid derivative. It was shown that the rate of Na+/H+ exchange (amiloride-inhibited component of proton efflux) is increased 2 fold. The addition of protein kinase C activator (1 microM of TPA) results in the increase of the rate of Na+/H+ exchange by 4 fold.     

Isolation of lipofuscin from the bovine myocardium

The paper describes the procedure of lipofuscin isolation from bovine myocardium with the use of 15-45% (weight/volume) linear gradient of sucrose density and differential centrifugation. Two coloured populations of lipofuscin granules with different density have been distinguished. Electron microscopic studies of the isolated lipofuscin have revealed the homogeneity of fractions and good maintenance of the granules. The electron microscopic, absorptive and luminescent spectral properties of lipofuscin preparations correspond to its properties in situ. The isolation of lipofuscin preparations suggests the possibility of studying the chemical composition and intramolecular structure of the granules.     

Study of energy characteristics of 5-fluorouracil analogs by photoionization mass-spectrometry

The fragmentation pathways of N-1-alkoxyalkyl derivatives of 5-fluorouracil and various analogues of an antitumor drug ftorafur have been examined using a mass-spectrometry technique. The ionization and appearance energies for major ions of the compounds under study have been determined on the basis of the ionization efficiency curves obtained using photoionization mass-spectrometry. Different transport forms of 5-fluorouracil have been demonstrated to be similar in the stability of their pseudoglycosidic C-N bond.