Chinese hamster cells mutant at the hypoxanthine-guanine phosphoribosyltransferase (GPRT) locus. V. Complementation analysis of ts mutants

Four temperature-sensitive HPRT clones were used for hybridological analysis, which led to increase in complementation rate about 5 times. The probability of complementation, in respect of the HPRT locus proved to be rather high: 14 of 45 hybridization-tested mutants had complementation ability (including 3 ts mutants). Analysis of the complementation rate among mutants revealed clear-cut dependence on the selection conditions: clones grown in a medium with 8-azaguanine showed most frequent complementation. The use of mutants with a new phenotype in hybridization analysis revealed four additional complementation groups, three of which are made of temperature-sensitive clones. Biochemical analysis revealed the presence of hybrid forms of the HPRT enzyme in all hybrids tested. This confirms the intragenic character of complementation. At present, the functional map of the HPRT locus is represented by 9 groups, including a group of mutants with no complementation ability.     

Effects of the season and growth stage on the contents of lipids and photosynthetic pigments in brown alga <Emphasis Type="Italic">Undaria pinnatifida</Emphasis>

Seasonal changes in the contents of lipids and photosynthetic pigments (PSP) in the brown alga Undaria pinnatifida (Harvey) Suringar (Phaeophyceae, Alariaceae) on different stages of its growth were studied. Lipids of all plant growth group comprised glyceroglycolipids (GL), phospholipids, and neutral lipids (NL). The ratio between these lipid groups and the content of particular lipids depended on the season and algal growth stage: NL predominated in seedlings; juvenile algae comprised approximately similar amounts of NL and GL; and in adult algae, GL predominated. In winter and spring, algal tissues contained relatively more free sterols than in summer. Total lipid content in seedlings and juvenile algae was higher then in adult plants. Lipid fatty acid (FA) composition was similar on all growth stages, but the content of major components differed; this is mainly related to 18:4 n-3, 20:4 n-6, and 20:5 n-3 acids. The predominant FAs in seedling lipids were saturated FAs, whereas in the lipids of juvenile and adult algae, polyunsaturated FAs predominated.     

Prediction of the three-dimensional structure of aflatoxin of Aspergillus flavus by homology modelling

Aflatoxins are polyketide-derived secondary metabolites produced by Aspergillus spp. The toxic effects of aflatoxins have adverse consequences for human health and agricultural economics. The aflR gene, a regulatory gene for aflatoxin biosynthesis, encodes a protein containing a zinc-finger DNA-binding motif. AFLR-Protein three-dimensional model was generated using Robetta server. The modeled AFLR-Protein was further optimization and validation using Rampage. In the simulations, we monitored the backbone atoms and the C-α-helix of the modeled protein. The low RMSD and the simulation time indicate that, as expected, the 3D structural model of AFLR-protein represents a stable folding conformation. This study paves the way for generating computer molecular models for proteins whose crystal structures are not available and which would aid in detailed molecular mechanism of inhibition of aflatoxin.     

Alfvén resonance heating in Uragan-2M torsatron

Uragan-2M is a medium-size torsatron with reduced helical ripples. This machine has the major plasma radius R = 1.7 m, the average minor plasma radius r _p ≤ 0.24 m and the toroidal magnetic field B ₀ ≤ 2.4 T. The Alfvén resonance heating in a high k _‖ regime is advantageous for small size machines since it can be realized at smaller plasma densities than the minority and second harmonic heating. The Alfvén resonance heating is examined numerically in the approximation of radially non-uniform plasma cylinder with identical ends. The numerical model for wave excitation and propagation accounts for the longitudinal electron thermal motion and the finite ion gyroradius which allow the model to treat correctly the propagation and damping of the kinetic Alfvén wave in hot plasma. A compact antenna consisting of four loop elements is chosen to provide operation in a high k _‖ regime. The major drawback of such an approach is the presence of plasma peripher y heating owing to unavoidable excitation of low k _‖ Alfvén resonances. Calculations show that, with the proper choice of heating regime, the periphery heating has an acceptable level and the major part of the power is deposited inside plasma column.     

Seasonal changes in the content of lipids,fatty acids,and pigments in brown alga <Emphasis Type="Italic">Costaria costata</Emphasis>

We compared the content of total lipids, particular lipid classes, fatty acids (FAs), and pigments in the brown alga Costaria costata [Turn.] Saund (Laminariaceae) in different seasons: during algal active life (April–June) and in the beginning of their degradation (the end of July). Lipids comprised only a small part of algal extractable compounds (10.9–13.4%). Their higher content was observed in May, in the period of alga preparation to sporogenesis. Polar lipids, glyceroglycolipids (GL) and phospholipids (PL), comprised a great part of total lipids in spring months and June, whereas neutral lipids, in July. GL predominated in polar lipids in spring and summer. The highest content of GL was observed in May and PL in April. Storage lipids comprised a great part of lipids in July. The content of sterols was the highest in April and May. In summer months, the content of sterols decreased and remained on unchanged level until thallus degradation. Polyunsaturated FAs (PUFAs) comprised the most part of FAs. Their highest content was observed in April. The main part of PUFAs were those of ω-3 series. In July, the level of these PUFA decreased substantially. The levels of ω-6 PUFAs were approximately similar in spring and summer months. The lowest content of monounsaturated FAs was detected in April; in May and July; the relative content of these FAs increased sharply. We also detected seasonal changes in the content of pigments and the ratios between them.     

Seasonal dynamics of the Acartia tumida Willey, 1920 (Copepoda: Calanoida) population in nearshore waters of Kievka Bay, Sea of Japan

In 2002, the neritic copepod Acartia tumida was present in the plankton of Kievka Bay from February through July at a temperature of ?1.2 to 14°C with an average population density of 6812 ind/m³ and a biomass of 532.75 mg/m³ (0.12–65.33 and 2.2–87.84% of total copepod density and biomass, respectively). The maximum population density of A. tumida (45 600 ind/m³) was recorded in the first ten-day period of April at a temperature of 2.2–3.8°C. Seasonal variations in the age and sex structure of A. tumida population were found. From February to July, A. tumida produced two generations.