Peculiarities of cytometrical methods of DNA content determination in the nucleus

This work has proposed a new theoretical approach to analysis of histograms of DNA content, which are obtained by the method of flow cytometry, in cells of Drosophila melanogaster imaginal discs. The precision of measurements of the DNA amount in G₁ and G₂(M) phases has been shown to be limited by precision of instrument tuning of zero of the flow cytometer. Use of the calculative zero of the flow cytometer and of dividing cells as standards of the DNA content is able to increase severalfold the precision of the DNA measurements in nuclei of the species. Comparative analysis of errors of various methods of measurement of the DNA content in cell nuclei is also performed. For methods of flow fluorescent cytometry, confocal scanning, and cytophotometry of the Feulgen-stained nuclei, it has been shown that, at present, the mean square errors of the DNA content measurements are within the interval of values considered acceptable for biological studies (0.02 < CV < 0.06).     

Morphological and biological specific features of two species of nine-spined sticklebacks of the genus Pungitius (Gasterosteiformes) from water bodies of Western Kamchatka

Morphological and biological specific features of populations of stickleback Pungitius pungitius and Amur (Chinese) stickleback P. sinensis from salmon rivers of the western coast of Kamchatka have been studied. With reference to the mountain-tundra Utkholok River, conditions of habitation and reproduction of nine-spined sticklebacks are described. P. pungitius is capable of reproducing at a relatively low temperature (from 4–6°C) and is represented by a large amount of spatially isolated groups with low numbers of individuals. For more warm-water P. sinensis, fluctuations in numbers at tundra sites of the lower reaches of rivers depending on temperature and water content of potential spawning grounds during the season of reproduction are typical. At the sympatry of the two species (Utkholok, Snatolvayam, Kvachina, Kol rivers), a high (up to 6%) proportion of hybrids was revealed. A geographic variability of meristic characters of Western Kamchatka and Kuril populations was traced.     

Diversification, Sympatric Speciation, and Trophic Polymorphism of Arctic Charr, Salvelinus Alpinus Complex, in Transbaikalia

In northern Transbaikalia, independently evolving landlocked populations of Arctic charr are found in mountain lakes. To assess the diversity of charr in this region, speciation modes involved in the evolution of charr forms, and the role of trophic polymorphism in their divergence, we studied the morphology and feeding of dwarf, small, and large forms of Arctic charr from a number of Transbaikalian lakes. Meristic data on charr from five lakes support the earlier conclusion that the three forms do not represent separate lineages but have independently diverged in sympatry in each of the lakes. In 10 lakes, the dwarf form showed varying degrees of differentiation from normal (small and large) charr in meristic characters (up to morphologically distinct and presumably reproductively isolated groupings), which is viewed as various levels of sympatric divergence. Indexes of gill raker length in fish from 20 lakes vary among populations of both dwarf and normal charr, with forms having short and long rakers being sympatric in some of these lakes. However, the index can be used only for comparing charr of different forms up to about 32cm fork length (FL) because it is strongly negatively correlated with size in larger fish. The study of charr diets in 21 lakes indicates that large charr are piscivorous whereas dwarf and small charr feed on a wide range of invertebrates, partitioning these resources in different ways. Planktivores, including very specialized ones, and non-planktivores (benthic feeders, insectivores) can be identified within the small and dwarf forms. The proportion of plankton in the diets of dwarf and small charr is positively correlated with the number and length of gill rakers while the proportion of benthos is negatively correlated. Allopatric planktivorous and non-planktivorous small charr differ in body proportions; parallel emergence of such morphotypes in different parts of the range is a characteristic feature of the Salvelinus alpinus complex.     

Development of skeleton elements in juvenile dwarf and small sympatric forms of <Emphasis Type="Italic">Salvelinus alpinus</Emphasis> complex from Lake Davatchan (Transbaikalia)

The development of skeleton elements was studied in prolarvae, larvae, and fry of two morphologically different forms of the Arctic char Salvelinus alpinus complex—small plankton-eating and dwarf (having a seasonal change of plankton and benthic feeding)—that sympatrically inhabit Lake Davatchan (Transbaikalia). According to genetic data, these forms diverged in this lake from a specialized lacustrine ecotype of char and reached reproductive isolation. Comparative analysis revealed similarity in the shape of anlagen and transitive states of cranial bones. In prolarvae and larvae of the dwarf form, the onset of similar morphological states of skeleton elements occurs at a smaller body length than in fish of the small form. Differences in the development of serial skeleton structures (teeth, gill rakers, fin rays, centra, and scales), heterochronies of timing of appearance and rate of differentiation of skeleton elements were found. It is suggested that these differences resulted from the ecological differentiation of the two forms according to spawning grounds that became local habitats of larvae and fry (sublittoral and hypolimnion). The initial divergence could be caused by the presence in the lake of two (autumn and spring-summer) peaks of numbers of food organisms.     

Investigation of the barrier discharge structure near the electrode with a cylindrical cross section

The approximate analytical correlations allowing for the investigation of the effect of different geometrical and physical parameters on the barrier discharge evolution near the electrode with a cylindrical cross section are obtained. The found correlations make it possible to estimate the time of the barrier discharge existence. New essential peculiarities of the barrier discharge evolution are revealed and verified.     

Permeability of human erythrocytes to asparagine

Asparagine is able to penetrate into human erythrocytes from the external medium. The dependence of the asparagine transport rate on its concentration can be described by the Michaelis-Menten equation with parameters: Km = 2.50 mM, V = 0.24 mmol/l cells per hour. Loading of erythrocytes with asparaginase does not influence their permeability to asparagine. Aspartate is accumulated inside these erythrocytes during incubation with asparagine, thus reflecting rapid transformation of penetrating asparagine by entrapped asparaginase.     

Determination of the minimum size of Gallus gallus domesticus chicken microchromosome by a pulse electrophoresis method]

The karyotype of the chicken Gallus gallus domesticus was studied by means of pulsed-field electrophoresis. An electrokaryogram was obtained for the microchromosomal (MI) portion of the chicken genome. Chicken MIs were separated into two fractions. A fraction with a higher mobility included MIs sized 3.4-4.8 Mb; the lower size limit of a less mobile fraction corresponded to MIs of approximately 5 Mb. The smallest MI in the chicken karyotype was estimated at 3.4 +/- 0.25 Mb.