A possible correlation of electro-optic changes with the deformability of erythrocytes

Erythrocyte swelling and membrane hole formation in hypotonic media as studied by conductometry

Hypoosmotic swelling of erythrocytes and the formation of membrane holes were studied by measuring the dc conductance (G). In accordance with the theoretical predictions, these processes are manifested by a decrease in G followed by its increase. Thus, unlike the conventional osmotic fragility test, the proposed methodological approach allows investigations of both the kinetics of swelling and the erythrocyte fragility. It is shown that the initial rate of swelling and the equilibrium size of the cells are affected by the tonicity of a hypotonic solution and the membrane rheological properties. Because the rupture of biological membranes is a stochastic process, a time-dependent increase in the conductance follows an integral distribution function of the membrane lifetime. The main conclusion which stems from reported results is that information about rheological properties of red blood cell (RBC) membranes and the resistivity of RBCs to a certain osmotic shock may be extracted from conductance signals.

Influence of cytoplasm electrolyte concentration on Maxwell-Wagner polarizability of bacteria E. coli

The electric polarizability of bacteria is considered in the literature to have a surface charge dependent (ChD) and a Maxwell-Wagner (MW) mechanism. We distinguish experimentally both the types of interface polarizability by the frequency of the electric field and the medium electrolyte concentration. It was shown in a previous work ( Zhivkov , A. M. ; Gyurova , A. Y. Colloids Surf., B 2008 , 66 , 201. ) that the ChD component is shown up on the outer bacteria surface even at megahertz frequencies. The MW polarizability is studied in the present work in the range from 20 kHz to 20 MHz by change in the inner (cytoplasm) electrolyte concentration. The ion transport through the cytoplasmic membrane of alive and fixed by formaldehyde E. coli K12 is accelerated by adding of ethanol in low concentration. The frequency dependence and the kinetics of the electric polarizability and the size of the bacteria are investigated by conservative electric dichroism, based on the alteration of the optical density at orientation of the cells in electric field. The conclusion is that the internal MW component has the main contribution to the change in the total bacteria polarizability, as well as the external MW and the internal ChD components are not shown up.

Direct effects of DC cardioversion on blood echogenicity: an in vitro study

Exacerbation of left atrial spontaneous echo contrast (SEC) after cardioversion of atrial fibrillation has been attributed to left atrial mechanical dysfunction induced by the procedure ("atrial stunning"). An in vitro model was devised to determine whether electrically induced changes in blood properties might contribute to SEC formation after cardioversion. Human blood echogenicity was examined quantitatively by videodensitometry before and after shocks of 1, 2, 5, and 20 J. Changes in blood cell numbers, cell morphology, and erythrocyte sedimentation rate were determined by haematological analysis. Immediately following electrical discharges, transient and dose-related, highly echogenic microbubbles were noted, but shocks of increasing intensity did not induce SEC at high blood velocity or alter the severity of SEC at low blood velocity. No quantitative or qualitative changes in haematological parameters were observed. These results suggest that direct effects of electrical shock on blood do not contribute to SEC after cardioversion. Systemic haematological responses to electric shock that might indirectly promote red cell aggregation in vivo cannot be excluded by this in vitro study.