[in Japanese]

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Myelin figures in aqueous dispersions of phospholipids and phospholipids-cholesterol mixtures were observed by light microscopy. Distearoyl, dipalmitoyl and dimyristoyl-L-a-phosphatidylcholine and dipalmitoyl-L-a-phosphatidylethanolamine in excess water spontaneously formed myelin figures at their crystalline-liquid crystalline phase transition temperatures. Above the temperature of myelin-figure formation, myelin tubes contracted and changed to liposomes. The fragments of phospholipids were converted into thin layer myelin forms or liposomes. The temperature of myelin-figure formation changed with the composition of two phosphatidylcholine mixtures in the similar way as the phase transition temperature does. When the chain lengths of the two components are different slightly, the temperature of myelin-figure formation changed lineally with the mole fraction. However in dimyristoyl-distearoylphosphatidylcholine or phosphatidylethanolamine-phosphatidylcholine mixtures, the change of the temperature of myelin-figure formation was not in proportion to the mole fraction. Especially, the variation of the temperature of myelin-figure formation for mixed dimyristoylphosphatidylcholine-dipalmitoylphosphatidylethanolamine system showed the complete phase transition.
In the presence of cholesterol, membranes of the myelin tubes of dipalmitoylphosphatidylcholine were thickened and slightly hardened. The temperature of myelin-figure formation decreased gradually with increase of the concentration of cholesterol. However the temperature of myelin-figure formation decreased sharply at concentration of about 15 mole%. In the presence of cholesterol above 25 mole%, the myelin figures were already formed at 17°C.

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