Correlation between the stability of alpha-chymotrypsin at high temperatures and "salting in" of a strong solution]

A correlation was found between the thermal stability of alpha-chymotrypsin and the coefficient Ks of the Sechenov equation as a quantitative measure of the "salting-in" or "salting-out" capacity of solutes. At high temperatures, an increase in the concentration of "salting-in" agents (KSNC, GuHCl, urea, formamide) resulted in thermal stabilization of alpha-chymotrypsin. The maximal (about 100-fold) stabilizing effect in concentrated solutions of salting-in agents was comparable with those induced by covalent modification with hydrophilic reagents or immobilization. Conversely, an increase in the concentration of "salting-out" agents stabilized the enzyme only marginally at high temperatures. An additivity of solutes' action on the thermal stability of the protein has been demonstrated. The observed correlation was explained in terms of the solutes' action on the reversible conformational transition of the enzyme native form into a much more stable form existing at high temperatures.     

Effect of Comenic Acid on the Activation of G Proteins by Agonists of Opioid Receptors in Plasma Membranes from the Rat Brain

We studied the effect of comenic acid on transmembrane opioid signaling (in particular, on that mediated by -opioid receptors, with the use of an agonist of these receptors, [D-Ala²]-leucine enkephalin (DALE), and mediated by -opiate receptors, with the use of morphine). It was demonstrated that comenic acid modulates agonist-dependent binding of [³⁵S]GTPS in plasma membranes from the rat brain. The effect of comenic acid on the activation of G proteins via -opioid receptors possessing high affinity for DALE depended on the ion composition of the medium: in the presence of K⁺ the activation decreased, while in the presence of Na⁺ it remained invariable. Under the influence of comenic acid, the agonist-dependent activation of G proteins mediated by receptors with low affinity for DALE was intensified in the presence of both Na⁺ and K⁺. Using morphine, we observed opposite effects: in the presence of Na⁺ or K⁺ comenic acid decreased or increased, respectively, the agonist-dependent activation of G proteins. We suggest that due to the comenic acid-induced modulation the relative intensity of activation of G proteins, which control signal pathways activated by opioid receptors of different types, can be significantly changed.     

Electron microscopic and morphometric study of the effects of ENKAD preparation on photoreceptor cells of the retina in Campbell rats with hereditary retinal dystrophy

The drug , a complex of ribonucleotides, which was found to improve the vision in some patients with retinitis pigmentosa, stimulates the morphogenesis of rod outer segments (ROS) in mutant Campbell rats with inherent retinal dystrophy. Four litters of neonatal rats, which being subdivided into groups, were injected subcutaneously with either 0.1 ml of 3.5% drug (experimental group) or 0.1 ml of 0.9% NaCl (control group) daily for 6-7 days. The results were checked in posterior area of the retina at Day 7 by the method of electron microscopy and morphometry. The drug treatment resulted in the 12-20 per cent increase of ROS disc number as compared with that in control group. Therefore, photoreceptors are the first retinal cells to be stimulated by the complex of ribonucleotides in rats.     

Present-day and mid-Holocene biomes reconstructed from pollen and plant macrofossil data from the former Soviet Union and Mongolia

Fossil pollen data supplemented by tree macrofossil records were used to reconstruct the vegetation of the Former Soviet Union and Mongolia at 6000 years. Pollen spectra were assigned to biomes using the plant-functional-type method developed by Prentice et al . (1996). Surface pollen data and a modern vegetation map provided a test of the method. This is the first time such a broad-scale vegetation reconstruction for the greater part of northern Eurasia has been attempted with objective techniques. The new results confirm previous regional palaeoenvironmental studies of the mid-Holocene while providing a comprehensive synopsis and firmer conclusions. West of the Ural Mountains temperate deciduous forest extended both northward and southward from its modern range. The northern limits of cool mixed and cool conifer forests were also further north than present. Taiga was reduced in European Russia, but was extended into Yakutia where now there is cold deciduous forest. The northern limit of taiga was extended (as shown by increased Picea pollen percentages, and by tree macrofossil records north of the present-day forest limit) but tundra was still present in north-eastern Siberia. The boundary between forest and steppe in the continental interior did not shift substantially, and dry conditions similar to present existed in western Mongolia and north of the Aral Sea.     

PARALLEL EVOLUTION OF LOCAL ADAPTATION AND REPRODUCTIVE ISOLATION IN THE FACE OF GENE FLOW

Parallel evolution of similar phenotypes provides strong evidence for the operation of natural selection. Where these phenotypes contribute to reproductive isolation, they further support a role for divergent, habitat‐associated selection in speciation. However, the observation of pairs of divergent ecotypes currently occupying contrasting habitats in distinct geographical regions is not sufficient to infer parallel origins. Here we show striking parallel phenotypic divergence between populations of the rocky‐shore gastropod, Littorina saxatilis, occupying contrasting habitats exposed to either wave action or crab predation. This divergence is associated with barriers to gene exchange but, nevertheless, genetic variation is more strongly structured by geography than by ecotype. Using approximate Bayesian analysis of sequence data and amplified fragment length polymorphism markers, we show that the ecotypes are likely to have arisen in the face of continuous gene flow and that the demographic separation of ecotypes has occurred in parallel at both regional and local scales. Parameter estimates suggest a long delay between colonization of a locality and ecotype formation, perhaps because the postglacial spread of crab populations was slower than the spread of snails. Adaptive differentiation may not be fully genetically independent despite being demographically parallel. These results provide new insight into a major model of ecologically driven speciation.     

Potentialities of magnetic resonance imaging in the study of renal morphofunctional state in girls with internal genital malformations and space-occupying lesions

The diagnosis of the anatomic and functional state of urinary organs in girls with internal genital malformations and space-occupying lesions involves magnetic resonance imaging by administering the optimized dose of a magnetic resonance contrast agent (MRCA). The technology makes it possible to evaluate the anatomic features of the urinary tract (magnetic resonance urography), to perform abdominal vascular magnetic resonance angiography, and to draw a conclusion on renal functional status in the use of dynamic magnetic resonance renography. Within a study using one injected MRCA dose, both the anatomic and functional state of the kidney status can be examined, by evaluating MRCA passage singly in the cortical and medullary substances and pelvises, which increases diagnostic accuracy by 46% and promotes the optimization of management tactics in this category of patients.