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Some actual problems of higher nervous activity have been analysed on the peculiarities of brain states in the course of different types of conditioning and reactivity of the nervous structures which depend on the brain state have been considered. A concept of brain state as a specific mechanism of each temporal connection forming during the learning process has been formulated for the first time. The authors suggest that the brain represents the dynamic system with changeable structure which reveals itself in multitude nervous set constellation during various types of activity. This concept is presented to be the theoretical basis for integral evaluation of functional capacities of central nervous system.

The cholesterol, sphingomyelin and phosphatidylcholine content in different cell membranes of liver and hepatoma was studied. Significant amounts of cholesterol were found in all the subcellular fractions of hepatoma, whereas in the liver cholesterol is localized mainly in the plasma membranes. A direct relation between the content of cholesterol and sphingomyelin was demonstrated. Possible effects of the cholesterol : : sphingomyelin : phosphatidylcholine ratio on the properties of cell membranes are discussed.

Alpha-amylase was present in considerable amount in the chyme in rats both at rest and during digestion, in the latter case its level being increased. Activity of intrinsic intestinal enzymes dominated in the homogenate of the mucosa. Transition from fasting to feeding and digestion increased the level of alkaline phosphatase and dipeptidase activities in the homogenate of the mucosa. The data obtained suggest the final stages of biopolymers' hydrolysis to be localized in various enterocyte structures. The surface mucus, owing to absorbed pancreatic enzymes, binding proteins and other types of physiologically active molecules, is assumed to play the role of a specific molecular filter and take part in the initial stages of digestion.

Advances in the study of membrane digestion are described which relate to techniques for the separation of the apical glycocalyx and the study of the distribution of enzymes between the latter and the cell membrane. The regulatory properties of brush border enzymes have been demonstrated. Membrane digestion by pancreatic enzymes adsorbed on the mucosal surface and by enteric enzymes predominates in early development, whereas intraluminal digestion develops during the transition to definitive (adult) nutrition. Substrate and other, non-substrate factors are involved in the regulation of intraluminal and membrane digestion in ontogeny. The importance of lipid components of the diet for the maintenance of proximal-distal gradients of enzyme activity in the small intestine during the transition from milk to adult nutrition is discussed. At this period of development hydrocortisone affects both the synthesis of enzymes and their incorporation into the enterocyte membrane. The inducibility of different enzymes is not identical. The hypothesis has been proposed that stress is one of the factors inducing or repressing the synthesis of brush border enzymes. These effects are mediated through the hypothalamus, adrenals, hypophysis and thyroid. The experimental findings demonstrate that various stressors are responsible for the induction of sucrase, maltases, gamma-amylase, peptidases and alkaline phosphatase, and for the repression of lactase in suckling rats.