Behavior of a dust grain in the double layer of an electric probe in a gas-discharge plasma

Equations for the motion of an individual dust grain in the double layer of a negatively charged cylindrical probe in a glow discharge plasma are derived and solved numerically. The distribution of the electric potential near the probe is determined, and the grain charge is calculated as a function of the distance from the probe for different probe potentials. The trajectories of grains with different initial energies are traced. An analysis of the grain trajectories shows that, at a certain distance from the probe, high-energy grains may be recharged; i.e., the grain charge may change sign. The grains are found to have no direct effect on the probe current in a dusty plasma of a glow discharge.     

Protection of the monoamine oxidase in brain synaptosomes by fat- and water-soluble antioxidants during lipid peroxidation

The protective effects of alpha-tocopherol, carnosine and their mixtures on monoamine oxidase activity, accumulation of lipid peroxidation products, lipid fatty acid composition, hydrophobicity and microviscosity of synaptic membranes during lipid peroxidation were studied. It was shown that the protective efficiency is more higher when the mixture of water and liposoluble antioxidants was used.     

Changes in synapses after gamma-irradiation of the rat head

High reactivity and, at the same time, flexibility of interneuronal contacts were observed after exposure of rat head to 2-100 Gy radiation. At high doses (200-400 Gy) radiation-induced changes played a major role in the development of the cerebral form of radiation sickness. A complete asynapsis is probably one of the causes of the animals death "under the ray" (irradiation of the head with a dose of 1000 Gy).     

Application of three-dimensional molecular hydrophobicity potential to the analysis of spatial organization of membrane domains in proteins: I. Hydrophobic properties of transmembrane segments of Na+, K+-ATPase

A new computer-aided molecular modeling approach based on the concept of three-dimensional (3D) molecular hydrophobicity potential has been developed to calculate the spatial organization of intramembrane domains in proteins. The method has been tested by calculating the arrangement of membrane-spanning segments in the photoreaction center ofRhodopseudomonas viridis and comparing the results obtained with those derived from the X-ray data. We have applied this computational procedure to the analysis of interhelical packing in membrane moiety of Na⁺, K⁺-ATPase. The work consists of three parts. In Part I, 3D distributions of electrostatic and molecular hydrophobicity potentials on the surfaces of transmembrane helical peptides were computed and visualized. The hydrophobic and electrostatic properties of helices are discussed from the point of view of their possible arrangement within the protein molecule. Interlocation of helical segments connected with short extramembrane loops found by means of optimization of their hydrophobic/hydrophilic contacts is considered in Part II. The most probable 3D model of packing of helical peptides in the membrane domain of Na⁺, K⁺-ATPase is discussed in the final part of the work.     

Swimming response of goldfish,Carassius auratus,and the tetra,Hemigrammus caudovittatus,larvae to individual food items and patches

Synopsis Swimming speed and swimming path of goldfish and tetra larvae were studied in aquaria containing food patches composed of decapsulated cysts and immobilized nauplii of Artemia salina or sparsely distributed prey. The mean swimming speed of starved larvae in the medium without food was about four times higher than the speed of larvae feeding in a patch. Satiated larvae swam about 1.5 times slower than hungry fish. Consumption of single prey items by starved larvae caused the following sequence of swimming responses: handling pause (cessation of swimming), slow swimming in a restricted area, and fast swimming (approximately twice as fast as hungry larvae before encountering food) accompanied by a widening of the area searched (area increased searching). Mean swimming speed was constant over a broad range (10¹–10³ ind·1^–1 of food density, although at extreme (high or low) values of food density it depended on swimming responses of the predator. Frequency of visits to the different parts of the aquarium strongly depended on encounters of hungry fish with food particles or patches.     

Numerical modelling of large-scale circulation in Lakes Onega and Ladoga

The results of numerical modelling of large-scale circulation in Lakes Onega and Ladoga are presented, with primary emphasis on the temporal variability of currents with time scales of days. Some typical circulation patterns have been inferred from model calculations. They reflect the existence of different dynamic regimes in the lakes, namely, forced and free circulation regimes. The forced circulation regime is the well-known wind-induced double-gyre circulation accompanied by coastal upwelling and downwelling. A case of double-gyre circulation in Lake Onega was investigated in particular detail. The second dynamic regime is a free response (or a relaxation) of the stratified lake to wind cessation, and is connected closely with the evolution of wind-induced upwelling and thermal front propagation. Diagnostic calculations demonstrate that the regime of relaxation supports the restoration of cyclonic circulation in Lake Onega. Barotropic circulation patterns in Lake Ladoga were calculated with the emphasis on prevailing winds from west to south-east. Our calculations show that the bottom relief of Lake Ladoga causes asymmetry in the double-gyre circulation patterns. In particular, approximately equal cyclonic and anticyclonic circulation cells appearing in the case of southerly wind transform to a single dominant cyclonic cell and several small anticyclonic cells in the case of westerly wind. We also found especially strong sensitivity of the sense of rotation of the largest gyre to the east-west components of the wind vector.     

Structure,molecular evolution and maintenance of copy number of extended repeated structures in the X-heterochromatin of Drosophila melanogaster

The 60 kb repeats located in the distal heterochromatin of the X chromosome of Drosophila melanogaster were cloned in overlapping cosmids. These regions, designated as SCLRs, comprised the following types of repeated elements Stellate genes, which are known to be involved in spermatogenesis; copia-like retrotransposons; LINE elements, including amplified Type rDNA insertions; and rDNA fragments. The following steps in SCLR formation were hypothesized: insertion of mobile elements into the rDNA and Stellate gene clusters: internal tandem duplication events; recombination between the rDNA cluster and Stellate tandem repeat; and amplification of the whole SCLR structure. There are about nine SCLR copies per haploid genome, but there is approximately a twofold variation in copy number between fly stocks. The SCLR copy number differences between closely related stocks are suggested to be the result of unequal sister chromatid exchange (USCE). The restricted variation in SCLR copy number between unrelated stocks and the absence of chromosomes free of SCLRs suggests that natural selection is active in copy number maintenance.