Impairment of Barrier Properties of Erythrocyte Membranes Caused by Low Temperatures is a Result of Disorganization of Hemoglobin Supramolecular Structure.

BACKGROUND: The antecedence of impairment of plasmatic membrane structure and functions forms the basis of the dominative concept about mechanisms of cell cryoinjuries. A role of alterations of hemoglobin supramolecular structure in erythrocytes remains unclear. OBJECTIVE: Comparison of continuity of membranes of native erythrocytes and resealed ghosts after freeze-thawing with a cryoprotectant at a low concentration (4%). MATERIALS AND METHODS: Cryoresistance of native erythrocytes and resealed ghosts with and without low concentrations of cryoprotectants (4% glycerol) was compared according to egress of the following markers: hemoglobin, 14С-sucrose and K+ as well as by scanning electron microscopy. RESULTS: It was found that resealed erythrocyte ghosts, where hemoglobin content was 4-5 times lower than in erythrocytes, were much more cryoresistant than native erythrocytes, which was especially noticeable when a low concentration of cryoprotectant (4% glycerol) was used. CONCLUSION: These data confirm an earlier proposed hypothesis on the role of supramolecular hemoglobin structure in cryoinjury mechanisms of erythrocytes.

Adhesion, growth, and proliferation of endothelial cells on biopolymer extracellular film matrices.

We analyzed the influence of initial properties of biopolymer fi lm extracellular matrices made of chitosan on adhesion of swine embryonic kidney epithelium-like cells, their morphology, growth, and proliferation. It was found that adhesion index of cells on the studied matrices was similar, but cell morphology had significant qualitative differences. Round non-flattened cells were described in endothelial cell cultures on chitosan-based matrices. Local variations in charge density on matrices induced by the presence of chitin nanofibers led to the appearance of flattened spindle-shaped and non-flattened sphericalal cells. Long-term culturing on biopolymer extracellular fi lm matrices was associated by the formation of spatial conglomerates of sphericalal cells.

Two-step rapid freezing method: estimation of membrane hydraulic permeability in erythrocytes at temperature exposure stage.

The processes, occurring at the stage of temperature exposure under two-step freezing of human and hibernating ground squirrel erythrocytes were studied by electron-microscopic method of freeze-fracturing. For human erythrocytes the time of intracellular crystal dissolution in human erythrocytes made 30 min and this value was shown to be slightly depending on temperature within -20 to -35 degree C range. Erythrocyte membrane permeability for water within negative temperature range has been estimated. It was noted that the value of water membrane permeability coefficient obtained theoretically, taking into account experimental values of time of dissolution for intracellular ice crystals and cell dehydration, is quite well consistent with the reported data and equals to about 0.5 x E-13 (cubic m)/N/sec for human erythrocytes and E-13 (cubic m)/N/sec for hibernating ground squirrel cells. Under two-step freezing a temperature arrest results in a qualitative change of water exchange process between cell and its environment, and the exposure duration may serve as the measure for cell dehydration. According to the data of NMR "paramagnetic doping" and freeze-fracturing the erythrocyte membrane of hibernating ground squirrels is more permeable for water than human one.

[Structural and functional characterization of cytochrome oxidase encapsulated in liposomes in sodium chloride solutions]. / Strukturno-funktsional'nye kharakteristiki tsitokhromoksidazy, vstroennoi v liposomy v rastvorakh khlorida natriia.

The effect of NaCl concentration (0-2 M) on the absorption spectrum and enzymic activity of cytochrome oxidase built in lecithin liposome has been studied at 24 and 8 degrees C. It is shown that at 0,8 M NaCl concentration a conformational transition occurs that leads to the enzyme inactivation. The relationship between protein conformation and liposome state has been established.

Quantitative biological electron probe microanalysis with a wavelength dispersive spectrometer.

This paper describes the details of quantitative electron probe microanalysis (EPMA) performed with a wavelength dispersive spectrometer (WDS). EPMA was carried out on the giant neuron of a fresh frozen ganglion from the snail Lymnaea stagnalis. The freeze-dried cryosections were compared with sections of freeze-dried, embedded tissue. It was found, that in the ganglion there are two kinds of neurons with a different chlorine concentration of 11 mmole/liter and 32 mmole/liter. Isolated neurons in culture were shown to differ in elemental composition from those in the ganglion tissue.

[The ultrastructural and dynamic characteristics of erythrocyte membranes. The effect of the physiological status and temperature]. / Ul'trastrukturnye i dinamicheskie kharakteristiki membran éritrotsitov. Vliianie fiziologicheskogo sostoianiia i temperatury.

Erythrocyte membranes of ground squirrels taken from hibernating, awakening and active animals with the body temperatures of 4, 30 and 36 degrees C, respectively, have been shown by freeze-fracture technique to differ in morphology of the PF surface, density and distribution patterns of intramembrane particles. The ultrastructural changes in membrane caused by temperature were confirmed by the data on alterations of dynamics parameters of the lipid bilayer and spectral characteristics of membrane proteins.