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Experiments were carried out on the 19-day old rat embryos, the 5- and 45-day old rat pups, and the 1.4-1.5-year old rats. Phospholipids and their fatty acid composition in brain cell nuclei were studied using methods of extraction, two-dimensional thin-layer chromatography, and spectrofluorimetry. In the course of ontogenesis, the percentage of different classes of nuclear phospholipids was changed; at the postembryonic period, the unsaturation index of lipids (phosphatidylcholine and phosphatidylethanolamine) and the content of unsaturated (especially polyenic) fatty acids decreased. Microviscosity of nuclear membranes increased; this changes were also shown earlier in phylogenesis of vertebrates. Thus, the facts revealed in the present work correspond to the recapitulation law. It is suggested that such change of lipid ratio and of composition of their fatty acids as well as of the membrane microviscosity serve for regulation of functions of membrane proteins and have adaptive character.

The effect of ionizing radiation (5, 20, 100, 200 and 400 Gy) on the content of phospholipids and cyclic nucleotides in the brain tissue has been studied in experiments on albino mice. During the development of evident behavioural disturbances in irradiated mice (2 h after irradiation with doses 100-400 Gy), significant changes were observed in the content of phosphatidylinositides and cyclic GMP. These changes may account for disturbances in the function of the central nervous system during cerebral forms of acute radiation injury.

In experiments with albino mice, rats and guinea pigs the effect of ionizing radiation (100 Gy) on brain phospholipids and their fatty acids has been investigated. Upon the development of manifest behavioural disturbances (2 h after irradiation) phospholipid molecules degrade insignificantly. Some changes in the relative content of phospholipids and their fatty acids are mainly found in the rat synaptosomal fraction: this may be responsible for the disturbances in the sensitivity of the receptor apparatus of cell membranes.

Proteolipid complex of Folch-Lees has been obtained and purified from the myelin and synaptosomes of the brain of the frog Rana temporaria and hen Gallus domesticus. Relative content of this proteolipid and glycolipids in the myelin is almost twice higher, whereas that of phospholipids--1 1/2 times lower than in the synaptosomal membranes of the same animal. Protein content of this complex is higher for myelin than for synaptosomal membranes; opposite relation was found with respect to phospholipid content. Within this complex, lipids are presented mainly by phospholipids, especially by acid ones which amount to 30-60%. Proteolipid complexes fro the myelin and synaptosomes differ from each other by their lipid component. Myelin proteolipid complex contains mainly phosphatidylserine and phosphatid acid, whereas synaptosomal one--phosphatidylserine and diphosphatediglycerol. No significant differences were found in fatty acid composition of phospholipids from proteolipid complex from myelin and synaptosomes as compared to this composition in the initial membranes.