Biomedical subjects

I D Riabova

Publications and source records attributed to I D Riabova.

11 recordsLinked to original sources

PubMed1977

[Osmotic activity and ionic permeability of membrane vesicles from Streptococcus faecalis and Micrococcus lysodeikticus cells].

Membrane fractions containing osmotically active vesicles with sufficiently low membrane permeability for K+, Na+ and Cl- ions typical for the intact cell membrane were isolated from the cells of the glycolyzing bacterium Streptococcus faecalis. In their osmotic properties and ionic permeability the membrane fractions of S. faecalis were found similar to those of the respiring bacterium Micrococcus lysodeikticus, which are capable of the energy-dependent potassium transport. It may be thus assumed that the S. faecalis fractions obtained may be used to study ionic transport. The removal of proton-dependent ATPase of the S. faecalis membrane preparations did not affect the permeability of membranes for K+ ions which is indicative of different mechanisms of proton and potassium translocation.

Adenosine Triphosphatases↗

PubMed1977

[Selective permeability of bacterial membranes for monovalent thallium ions].

Transport of monovalent thallium ions in bacterial cells was studied. An energy-dependent transport of T1+ against electrochemical gradient into the cells of S. faecalis and Micrococcus lysodeikticus, according to the Michaelis-Menten kinetics was observed. T1+, being a K+ analog, is involved into active K+ transport. Unlike K+, T1+ readily penetrates bacterial membranes, reaching the level of stationary distribution between the cells and the medium. This permits to use T1+ as a penetrating cation to study the mechanism of potassium transport in bacteria without the use of ionophores, which can destroy the integrity of cell membranes.

Biological Transport, Active↗

PubMed1976

[Energization of membrane vesicles from the cells of glycolyzing bacterium Streptococcus faecalis].

Membrane fractions were isolated from Streptococcus faecalis cells of a glycolyzing microorganism, devoid of the respiratory chain, using the methods of osmotic shock of the protoplasts, ultrasonic treatment of the cells and ultrasonic treatment of the protoplasts. All fractions possessed the ATPase activity, the highest activity being observed in the fraction isolated by ultrasonication of the protoplasts. All preparations were estimated with respect to the presence of vesicles, formed by the "inside-out" and "inside-in" membranes, using ATPase as a marker of the membrane orientation. In the membrane fractions obtained by ultrasonication of the protoplasts, the "inside-out" vesicles were prevalent. ATP-dependent energization of the membranes, sensitive to the action of dicyclohexylcarbodiimide and tetrachlorotrifluoromethyl benzimidazole, was demonstrated by measuring the transport of the lipophylic anion of phenyldicarbaundecaborane and aniline naphthalene sulfonate fluorescence.

Adenosine Triphosphatases↗

PubMed1976

[Biochemical and ultrastructural characteristics of the membranes of Streptococcus faecalis].

It is demonstrated by thin-section that S. faecalis cells (Strain BKM-B6) have no inner membranes, and their plasma membranes do not show any invagination into the cytoplasm. It is established that B and A fracture faces of the membranes in the intact bacteria, protoplasts, osmotic shock and sonicated membrane fractions contain uniformly distributed particles with a density of 200--400 and 4000--5000 particles/mu m2, respectively. Washing of the osmotic shock membrane fraction with a buffer solution of 0.25 M tris-SO4 with 2 M LiCl removes 35--40% of non-membrane proteins. Further washing (repeated 3 times) of the fraction with 0.001 M tris-SO4 removes additionally 40% of the protein, decreases the ATPase activity by 80%, and slightly decreases the cross-section of the membranes, but it does not affect of their A and B fracture faces. The membrane fracture faces A in all fractions exhibit small areas with tetragonally packed particles (with a tetragon size of 150 A X 150 A and a density of 20000--22000 particles/mu m2). These areas seem to be responsible for changing in the isolated membrane properties. Treatment of the washed membrane fractions with 0.2% triton X-100 results in a decrease of the vesicle sizes and appearance of drastic changes of their fracture faces. Changes of the membrane fracture faces under the action of triton X-100 are likely to be due to a breakdown in the hydrophobic interaction between the protein and lipid components. As it is shown by freez-fracturing technique, osmotic shock and sonicated membrane fractions contain 95% and 50% of rightside-out vesicles. It correlates with biochemical data on the membrane orientation of vesicles in different fractions.

Cell Membrane↗

PubMed1976

[Comparative study of membranes of Streptococcus faecalis and Micrococcus lysodeikticus].

A comparative study of ultrastructure and IR-spectroscopy of osmotic shock membranes from cells of glycolyzing (Streptococcus faecalis) and respiring (Micrococcus lysodeikticus) bacteria, was made. The S. faecalis and M. lysodeikticus membranes differ in their cross-section. Treatment of the preliminary washed membranes of S. faecalis and M. lysodeikticus with a low ionic strength solution removes 40% and 70% of their proteins respectively, decreases the membrane cross-section but does not change their fracture faces. Pre-cooling of the membrane suspensions within the temperature range of +5 degrees-10 degrees results in the appearance of large smooth areas on S. faecalis membrane fracture faces, but does not affect the ones of M. lysodeikticus membrane. Treatment of the washed suspensions with Triton X-100 results in the appearance of drastic changes of S. faecalis membrane fracture faces and does not change the fracture faces of M. lysodeikticus membranes; treatment by the detergent does not alter the IR-spectroscopy of membranes of both bacteria. Treatment of S. faecalis and M. lysodeikticus membranes with high temperature irreversibly changes the structure of 20% and 40% of protein components respectively,, but does not affect the distribution of the subparticles on their fracture faces. It is assumed that the differences found are determined by the composition of lipid components of the membranes studied and that the amount of proteins closely bound with lipids in the membranes of S. faecalis is likely to be greater than that of M. lysodeikticus membranes.

Bacterial Proteins↗

PubMed1973