Mechanism of inactivation and mutagenesis induced by ethyleneimine in Drosophila germ cells. V. Relation of complete and mosaic mutations during the supplementary action of high temperature]

Supplementary effect of high temperature (37 degrees C) an hour after the treatment of mature sperms of Drosophila with ethylene imine resulted in an increased level of the inactivation (the frequency of dominant lethal mutation). The frequency of complete mutations (recessive sex-linked lethal mutations) increased by the supplementary effect of high temperature at low doses of E1, and it did not change under a comparatively high dose of the mutagen. The frequency of mosaic mutations decreased under the effect of high temperature at both doses of E1. No effect of high temperature was observed in 4 and 24 h after the E1 treatment. The results obtained are discussed in connection with the proportion of inactivation and mutagenesis under the effect of chemical mutagens on Drosophila germ cells.     

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.     

Characteristics of ceruloplasmin synthesis in mammalian embryogenesis. 2. The yolk sac as the site of the primary expression of the ceruloplasmin gene in rats

It was shown that the omphaloid placenta and, first of all, visceral wall of yolk sac is the site of primary synthesis of ceruloplasmin (CP), whereas the activation of CP synthesis in the liver cells is secondary and is revealed from the 12th day of embryo-genesis. The CP synthesis in the yolk sac cells proved by selective CP localization in the cells of the yolk sac visceral wall and, first of all, in the cells of visceral endoderm on sections stained by the method of indirect immunofluorescence and using the reaction of soluble peroxidase-antiperoxidase complex. A specific CP-mRNA has been revealed in the yolk sac cells which is actively translated in the polyribosomes isolated from the yolk sac and in the cell-free translation system from the rabbit reticulocytes. on the 14th day of embryogenesis CP amounts to ca. 4% of all polypeptides secreted by the yolk sac cells. As the embryogenesis proceeds, the relative rate of CP synthesis progressively decreases in the yolk sac and increases in the liver cells. CP synthesized by the yolk sac cells has a molecular mass of ca. 122 kD. Possible causes of differences between the "embryonic" and "adult" rat CPs are discussed. A suggestion has been put forward that the time of activation of CP synthesis coincides with the yolk sac formation (8-9th days of embryogenesis) and the cells of visceral endoderm are the site of primary expression of the CP gene.     

Expression of ceruloplasmin gene in mammalian organs from the data of hybridization analysis with complementary DNA probes

Expression of ceruloplasmin (Cp)-coding gene in rat and human liver and brain tissues was studied by Northern blot hybridization and by in situ hybridization with cloned species-specific cDNA probes. In rat brain structures, different levels of Cp mRNA were detected, the maximal one was found in cerebellum. The steady-state level of Cp mRNA in rat and human brain was several times lower than in parenchymatous liver cells. The size heterogeneity of Cp mRNA was found. Polyadenylated RNA prepared from human liver contains two equally abundant Cp mRNAs differing in their chain length (3.6 and 4.5 kb) while brain polyadenylated RNA contains a single Cp mRNA (4.5 kb).     

Polymorphism of nucleotide sequences of human genomic DNA linked to a mucoviscidosis locus

Polymorphism in the restriction fragments length of human DNA sequences linked to mucoviscidosis locus was studied in the healthy control group and in the families affected by mucoviscidosis. The plasmid clones metH, pJ3.11,XV-2c and pKM.19 were used as hybridization probes. The allelic frequencies of the polymorphic loci were determined for total population and for affected families. The linkage disequilibrium between the disease locus and linked polymorphic loci detectable with XV-2c (TaqI endonuclease) and pKM.19 (PstI endonuclease) was demonstrated. The high informational value of DNA-diagnosis of mucoviscidosis in the family studies with the use of four DNA probes combination has been demonstrated.     

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.