[Permeability of isolated rat hepatocyte plasma membranes for molecules of dimethyl sulfoxide].

We have studied permeability of isolated rat hepatocyte membranes for molecules of dimethyl sulfoxide (DMSO) at different hypertonicity of a cryoprotective medium. The permeability coefficient of hepatocyte membranes κ1 for DMSO molecules was shown to be the differential function of osmotic pressure between a cell and an extracellular medium. Ten-fold augmentation of DMSO concentration in the cryoprotective medium causes the decrease of permeability coefficients κ1 probably associated with the increased viscosity in membrane-adjacent liquid layers as well as partial limitations appeared as a result of change in cell membrane shape after hepatocyte dehydration. We have found out that in aqueous solutions of NaCl (2246 mOsm/l) and DMSO (2250 mOsm/l) the filtration coefficient L(p) in the presence of a penetrating cryoprotectant (L(pDMSO) = (4.45 ± 0.04) x 10(-14) m3/Ns) is 3 orders lower compared to the case with electrolyte (L(pNaCl) = (2.25 ± 0.25) x 10(-11) m3/Ns). This phenomenon is stipulated by the cross impact of flows of a cryoprotectant and water at the stage of cell dehydration. Pronounced lipophilicity of DMSO, geometric parameters of its molecule as well as the presence of large aqueous pores in rat hepatocyte membranes allow of suggesting the availability of two ways of penetrating this cryoprotectant into the cells by non-specific diffusion through membrane lipid areas and hydrophilic channels.

[Erythrocyte membrane permeability of Citellus undulatus during hibernation]. / Pronitsaemost' membran éritrotsitov Citellus undulatus v usloviiakh gipotermicheskogo khraneniia.

We have studied the influence of the erythrocyte hypothermic storage of long-tailed ground squirrels at various physiological states and white mongrel rats on the impairment of the barrier function of their membranes for ferricyanide. The membranes of sleeping and awakening ground squirrels demonstrate the highest stability (the structural integrity is sustained for 3-3,5 months), meanwhile rat blood erythrocytes maintain the barrier function only for 2 weeks. Beside structural and viscous changes in the erythrocyte membrane and the cytosol of hibernating ground squirrel an important role in maintaining barrier function under conditions of hypothermic storage is played by the content of animal blood plasma. Appearance of a non-typical EPR spin probe spectrum in some ground squirrel blood samples in non-equilibrium state of entering or arousing from hibernation has been observed.

[Mechanism of initiation of intracellular ice formation]. / Issledovanie mekhanizma initsiirovaniia vnutrikletochnogo l'doobrazovaniia.

Intracellular ice crystallization was studied by the method of cryomicroscopy in the systems modeling a biological suspension, such as erythrocyte concentrates. Initiation of crystallization by extracellular ice through hydrophilic channels has been shown to be the most probable mechanism of intracellular ice formation.

[Reaction of cells to hypertonic effects by cryoprotection]. / Reaktsiia kletok na gipertonicheskie vozdeistviia pri krioprotektsii.

Kinetics of volume changes in cells caused by hypertonic solutions has been investigated theoretically using an apparatus of the non-equilibrium thermodynamics. Analytical expressions for relaxation times of the two-stage process studied have been found. The reaction of mouse peritoneal exudate cells to hypertonic solutions of glycerol. PEO-400 or PEO-1500 has been studied experimentally. An agreement has been obtained between theoretical calculations and experimental results. Possible mechanism of cell injury caused by hypertony is discussed.