The most unique feature of the eye lens fiber-cell plasma membrane is its extremely high cholesterol content. Cholesterol saturates the bulk phospholipid bilayer and induces formation of immiscible cholesterol bilayer domains (CBDs) within the membrane. Our results (based on EPR spin-labeling experiments with lens-lipid membranes), along with a literature search, have allowed us to identify the significant functions of cholesterol specific to the fiber-cell plasma membrane, which are manifest through cholesterol-membrane interactions. The crucial role is played by the CBD. The presence of the CBD ensures that the surrounding phospholipid bilayer is saturated with cholesterol. The saturating cholesterol content in fiber-cell membranes keeps the bulk physical properties of lens-lipid membranes consistent and independent of changes in phospholipid composition. Thus, the CBD helps to maintain lens-membrane homeostasis when the membrane phospholipid composition changes significantly. The CBD raises the barrier for oxygen transport across the fiber-cell membrane, which should help to maintain a low oxygen concentration in the lens interior. It is hypothesized that the appearance of the CBD in the fiber-cell membrane is controlled by the phospholipid composition of the membrane. Saturation with cholesterol smoothes the phospholipid-bilayer surface, which should decrease light scattering and help to maintain lens transparency. Other functions of cholesterol include formation of hydrophobic and rigidity barriers across the bulk phospholipid-cholesterol domain and formation of hydrophobic channels in the central region of the membrane for transport of small, nonpolar molecules parallel to the membrane surface. In this review, we will provide data supporting these hypotheses.

We present the first seismic model of the crust beneath Sakhalin based on P and S‐wave arrival time data from local earthquakes. Based on the results of numerous synthetic tests, we conclude that this model has fair horizontal and vertical resolution to 20–25 km depth. At shallow depths, seismic anomalies are clearly associated with known geological structures, such as the high‐velocity Paleozoic Susunai block and the low‐velocity Cenozoic fold belts along the West Sakhalin Mountains. In vertical sections, we observe westward underthrusting of the Susunai block to a distance of at least 70 km, which may represent the regional compression and considerable crustal shortening in this area. Based on the tomography results, we hypothesize about the origin of the mud volcanism in southern Sakhalin. We propose that because of the general westward underthrusting regime in Sakhalin, hydrocarbon‐rich shelf sediments may be entrained to considerable depths under the rigid Susunai block, which serves as a nonpermeable cover. The released gases find the weakest zones around the Susunai block and along the Tym‐Poronay Fault and escape to the surface to form the South Sakhalin and Lesnovsky mud volcano fields.

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