[Dynamics of intramembrane particles during proteolysis of certain membranes]. / Dinamika vnutrimembrannykh chastits pri proteolize nekotorykh membran.

Freeze-fracture electron microscopy has been used to study the ultrastructure of proteolytic enzymes treated of the bovine photoreceptor membranes, the rat liver microsome ghosts and the rabbit sarcoplasmic reticulum membranes. The observed increase in the intramembranous particle number in the inner fracture face suggests transmembrane dipping of amphipathic integral proteins affected by the partial proteolysis.

[Temperature-dependent changes in the profile of the sarcoplasmic reticulum membrane hydrophobic zones]. / Temperaturozavisimye izmeneniia rel'efa gidrofobnoi zony membran sarkoplazmaticheskogo retikuluma.

The dependence of the state of the hydrophobic zone of rabbit sarcoplasmic reticulum (SR) membranes on temperature of the membrane fragment suspension before rapid freezing was studied by the freeze fracturing technique. It was shown that within the temperature range of--15-- +37 degrees C the amount of intramembrane particles and their distribution in the membrane plane and between their convex and concave surfaces do not practically depend on the temperature of the SR membrane suspension. This is indicative of the lack of correlation between the physical state of the phospholipid matrix (gel -- liquid crystal) before freezing and the nature of the profile of the membrane hydrophobic zone revealed after fracturing. The disturbances in the protein -- lipid interactions in the membrane under the effects of mersalyl or aqueous solutions of diethyl ester followed by complete inactivation of Ca2+-dependent ATPase lead to a decrease in the amount of intramembrane particles, which is especially well-pronounced at 37 degrees and -15 degrees C.

[Study of mechanisms of photoreceptor membrane destabilization under modifying action of oxygen]. / Issledovanie mekhanizmov destabilizatsii membran fotoretseptorov pri modifitsiruiushchem deistvii molekuliarnogo kisloroda.

Induction of lipid peroxidation in the rod outer segments (ROS) of frog retina results in fragmentation of photoreceptor disc membranes and solubilization of lipoprotein rhodopsin complexes (sedimentation coefficient 2.7S). The substrates of lipid autooxidation are mainly docosahexa- and docosapentaenoyl residues of phosphatidyl ethanolamine. Large fragments (precipitation at 5000 gX30 min) and small vesicles (precipitation at 40 000 gX60 min; average diameter 1000 A) formed from lipoperoxidized ROS differ both in their chemical composition and structural organization. In small vesicles the content of O2-modified polyenoic acyls in the phospholipids is 3,7 times higher as compared to large fragments. Correspondingly, the capacity of hydrophobic areas in the small vesicle membranes evaluated by EPR spin-probing technique is lower than in the large fragments. A mechanism of the photoreceptor membrane destabilization under modification by molecular oxygen is proposed. It is based on a decrease in the value of surface tension upon accumulation of lipid peroxidation products in ROS, the former possessing the properties of non-ionic detergents.

[Comparative study of membranes of Streptococcus faecalis and Micrococcus lysodeikticus]. / Sravnitel'noe izuchenie membran Streptococcus faecalis i 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.

[Changes in the distribution of synaptic vesicles in cone endings following electrical stimulation of the retina]. / Izmenenie respredeleniia sinapticheskikh puzyr'kov v okonchaniiakh kolbochek pri élektricheskoi stimuliatsii setchatki

The conditions were found (hypoxic state of the retina) under which exhausture of the transmitter in presynaptic endings of photoreceptors may be supposed from a decrease in responses of horizontal cells to electric stimulation of the retina. Under these conditions the electric stimulation is accompanied by a decrease in the number of small synaptic vesicles near the presynaptic membranes in cones. However, there are no reliable changes in the total number of vesicles in cone endings.