The use of phase diagrams in the crystallization of oligonucleotide duplexes. I. A model of crystallization of the (pGpT)n.(pApC)n + spermine system

A set of experimental phase diagrams revealing the region of existence of microcrystals in mixture "(pGpT)n.(pApC)n+spermine", n = 2,3,4, was obtained. All diagrams are wedge-like with the slope of the upper branch and the level of the lower one depending on the oligonucleotidd length. The presence of MPD, MgCl2 and NaCl changes the form of the diagrams in a different manner. A model explaining the peculiar features of the diagrams for mixture "oligonucleotide duplex+spermine" is proposed. The analysis of the diagrams was carried out on the basis of this model and the values of the binding constants for binding of spermine and Mg2+ to duplexes were estimated. Some conclusions about the types of complexes, which may form microcrystals in different regions of diagrams were made.     

The length of DNA determines the degree of regularity of crystals of the cro-repressor complex

The DNA-cro-repressor complex crystals have been obtained, five DNA fragments of the same nucleotide sequence and different length being used. The rotation function for crystals of complexes with hexamer (pGpT)3 . (pApC)3 and with octamer (pGpT)3 . (pApC)3 have been calculated. The order of cro-DNA complex crystals is shown to vary with DNA length, the crystal of the complex with octamer being the most perfect among all investigated complexes.     

Neuroendocrine and neurochemical mechanisms of the domestication of animals

A review of experimental data documenting that domestication of animals is associated with hereditary reorganization of neuro-endocrine mechanisms, responsible for basic processes of ontogeny, is presented. The data demonstrated changes in gonadal and pituitary-adrenal systems in domesticated animals. Analysis of evidence that selection for low aggressiveness towards man is, in fact, the selection for definite activity of brain neurotransmitters regulating aggressive behaviour and emotional stress response has been carried out. Supposed role of modifications in the mechanisms of domestication is discussed.     

The component composition of the human cortical motor potential during static muscle loading

In summation and averaging of sections of the EEG of sensorimotor cortex of both cerebral hemispheres recorded during human static effort of definite duration, a complex of negative-positive oscillations was observed. These oscillations appear before the beginning of the effort, accompany its execution and finishing and are also recorded after cessation of muscles activity. Before the beginning, the potential of readiness is formed. The execution of the effort is accompanied by a slow negative wave which in some people may be broken by a pronounced positivity. Further a "final" potential appears; its fast positive oscillation is formed before the end of the effort, and a slow negative wave in which it turns, appears only after muscles relaxation.     

Simple kinetic models explaining critical phenomena in enzymatic reactions with isomerization of the enzyme and substrate

Kinetic models for enzyme reactions are considered which take into account enzyme and substrate isomerization. Application of graph-theoretic methods allows to reveal fragments in schemes which may induce multiple stead-states or concentrational selfoscillations. The role of substrate isomers in the inhibition of enzyme isomers to produce critical phenomena is considered. The boundaries of parameter domains for critical phenomena are estimated. It is shown that the controlled change in concentrations of substrate and enzyme isomers may be important in regulation of enzyme systems, if different enzyme isomers are inhibited mainly by different substrate isomers. The models are used for interpretation of possible critical phenomena in the open reaction catalyzed by lactate dehydrogenase. It is shown that lactate dehydrogenase may act as a trigger in carbohydrate metabolism by changing "critically" its activity in relation to changes in pH and pyruvate fluxes. Slow enzyme inhibition by enolpyruvate is suggested as a possible reason for glycolytic oscillations.     

The competition of 2 types of epithelial layers in mixed cultures

The interaction of epithelial cells was studied in mixed cultures by phase contrast, time-lapse microcinematography, transmission and scanning electron microscopy. Epithelial cells, united into monolayer sheets with smooth apical surfaces, can be competing for substrate lamellae at the lower surfaces and force out each other from the substrate up to full elimination. The competition of cells for territory may be an important factor in morphogenesis in vivo.     

The stability of the alkylating derivatives of oligodeoxyribonucleotides containing a cholesterol or phenazine radical added to the 3'-termination during their interaction with Acholeplasma laidlawii PG-8]

Stability of alkylating derivatives of decathymidylates protected on the 3'-terminal by cholesterol and phenazine residues has been studied in the process of their interaction with cells of Acholeplasma laidlawii PG-8. It is shown that the studied reagents are not split by nucleases of A. laidlawii PG-8 for the time necessary for alkylation of mycoplasma biopolymers.     

"Mixed" endocrine gland cells of the duodenal epithelium in various vertebrate animals and man

Epithelium of the duodenal mucous membrane has been studied in frog, rat and man by means of electron microscopy. Together with typical endocrinocytes, incretory cells of "mixed" type are revealed in the epithelium. They are classified into two types: 1. exo-endocrinic containing in their cytoplasm simultaneously: a) mucous and EC-granules, b) mucous and S-granules, c) granules specific for Paneth's cells and S-granules, d) granules specific for Paneth's cells and L-granules; 2. endocrinocytes with incretory granules of various types: with D and I, with D and EC, with D and L granules. Various ultramicroscopic organization of the "mixed" exo-endocrinic cells is demonstrated. It can be considered as various stages of their differentiation. In cytoplasm of the "mixed" cells of the second type (endocrinic) a constant presence of D-granules is revealed, that is, evidently, characteristic, within the limits of the gastro-entero-pancreatic system, for the cells with two types of the endocrinic granules.     

Lactate dehydrogenase isoenzyme spectrum in various areas of the reticular formation of the brain in rats: the effect of emotional stress

The changes in lactate dehydrogenase (LDG) isoenzyme content in the various brain areas were studied in intact Wistar rats and upon immobilization stress. LDG fraction levels were compared to BP changes during immobilization. The proportion of "anaerobic" LDG fractions was higher and the proportion of "aerobic" fractions lower in the dorsal area of midbrain substantia reticularis than in medulla oblongata reticular formation. The changes in LDG fraction content related to BP alterations during immobilization were observed in dorsal and ventral areas of midbrain (but not medulla oblongata) substantia reticularis. The proportion of anaerobic LDG4 fraction in the dorsal area of midbrain substantia reticularis was higher in rats with hypertensive responses, than in hypotensive animals. The changes in LDG5 fraction content were opposite. In the ventral area of midbrain reticular formation BP reduction was accompanied by a significant rise in "anaerobic" and a decrease in "aerobic" LDG fraction levels. The data obtained indicate certain differences in the intensity of aerobic and anaerobic processes of carbohydrate degeneration in various areas of substantia reticularis in control rats, as well as the correlation of changes in energy metabolism in the brain with BP alterations during emotional stress.