Nucleotide variation in the triosephosphate isomerase (Tpi) locus of Drosophila melanogaster and Drosophila simulans

DNA sequence variation in a 1.1-kb region including the coding portion of the Tpi locus was examined in 25 homozygous third-chromosome lines of Drosophila melanogaster, nine lines of Drosophila simulans, and one line of Drosophila yakuba. Our data show that the widespread allozyme polymorphism observed in cosmopolitan D. melanogaster is due to a glutamic acid substitution occurring in a phylogenetically conserved lysine that has been identified as part of the "hinged-lid" active site of the enzyme. This observation suggests that the replacement polymorphism may have important functional consequences. One replacement polymorphism was also observed in D. simulans, although its functional relevance is more difficult to assess, since it affects a site that is not strongly conserved. This amino acid change in D. simulans is associated with a single lineage possessing seven unique silent substitutions, which may be indicative of balancing selection or population subdivision. The absence of fixed amino acid differences between D. melanogaster and D. simulans and only a single difference with D. yakuba suggests that triose phosphate isomerase is under strong functional constraint. Silent variation is slightly higher for D. melanogaster than for D. simulans. Finally, we outline the general lack of evidence for old balanced polymorphisms at allozyme loci in D. melanogaster.      

Critical periods of the mitotic cycle: influence of aminopterin and thymidine on production of chromosomal aberrations by radiation in Crepis capillaris.

The influence of aminopterin (AP), tritiated thymidine ([3H] TdR) and "cold" thymidine (TdR) on production of chromosomal aberrations in meristematic cells of Crepis capillaris irradiated in different stages of the mitotic cycle with 300 rad of 63Co gamma-rays was studied. All the chemical treatments increased most of all the frequency of aberrations induced during two "critical periods" localized before the stage of DNA synthesis (fixation 9 h after irradiation) and before that of mitosis (4 h). Treatments with TdR and [3H]TdR increased most of all the frequency of chromatid aberrations when irradiation was performed in G1, and the frequency of gaps when irradiated in G2. Treatment with AP increased the yield of different types of aberration more uniformly. The modifying effect of the chemicals tested appeared to be independent of replicative synthesis. The "critical periods" are suggested to be the stages when regular "proof reading" and correction of spontaneous errors takes place [9,13]. In addition to this regular mechanism, radiation induces an "emergency" mechanism of repair. AP inhibits the mechanism of regular repair; in addition TdR and [3H] TdR suppress the lateral spread of primary injuries across the chromosome.     

Low molecular mass phosphoproteins from the frog rod outer segments form a complex with 48 kDa protein.

Upon separation of cAMP-dependent low molecular mass phosphoproteins [Components I and II; Polans et al. (1979) J. gen. Physiol. 74, 595-613] from the frog rod outer segments by gel-chromatography, isoelectric focusing, non-denaturating electrophoresis and ion-exchange chromatography, they behave like subunits of the oligomeric complex. Apparent molecular mass of the complex determined by gel-chromatography is 52-57 kDa and by non-denaturating gradient electrophoresis is 62-66 kDa. The isoelectric point of the complex is 5.5. The elution profile of Components I and II upon gel-chromatography and ion-exchange chromatography coincides with that of major rod outer segment 48 kDa protein. The isoelectric point for them also coincides with the isoelectric point of 48 kDa protein. The amount of low molecular mass phosphoproteins is sealed rods is equal to one molecule per 60 rhodopsin molecules and coincides with that of a 48 kDa protein. It is suggested that in solution Components I and II form an oligomeric complex with 48 kDa protein.     

Absorption of infrared radiation by a thin water layer]

The unhomogeneous distribution of infrared absorption in a thin water layer and its time instability were explained. The parameters of interribbon interaction in the case of thin water layers with bound influence were evaluated.     

Comparative effectiveness of antioxidants in protecting the bacterial plasmatic membrane from the active froms of oxygen

The effect of hydroxyl radicals OH. generated by the decomposition of H2O2 by Fe2+ ions (Fenton reaction) on the barrier properties of plasma membranes of Escherichia coli cells K-12 was studied by electroorientation spectroscopy. It was found that the administration of hydrogen peroxide led to the disturbance of the barrier properties of plasma membranes only when the cells were preincubated with Fe2+ ions and their constant concentration in the system was maintained by ascorbate or dithiotreitol (150-500 microM). The extent of the toxic action on plasma membranes depended on the concentration of reacting elements and the substance used as a reducer Fe2+. The efficiency of protection of antioxidants of different classes (enzymic, SH-containing, and phenolic compounds) against the toxic action of hydroxyl radicals on plasmatic membranes was shown.     

Effect of treated with weak magnetic field aqueous salt solutions on the intrinsic fluorescence of bovine serum albumin. Isolation from solutions and partial characterization of the biologically active fluorescing fraction

It was shown that water with additions of Ca2+, Na+, K+ and Cl- ions preliminarily treated with weak combined constant (42 microT) and low-frequency alternating (0.06 microT) magnetic fields affects the intrinsic fluorescence of bovine serum albumin, the magnitude of the effect being dependent on the frequency of the alternating field and ionic composition of the aqueous salt solution. A practically complete transfer of the effect through a small portion of the solution treated with magnetic fields was revealed. It was also found that after magnetic treatment, the solution contains a rather large (molecular mass 700-900 D) and stable molecular associate, which possesses, at least partially, the properties and characteristics inherent in the whole solution that were as acquired as a result of magnetic treatment.     

Analysis of the contribution of forest pathways to the radiation exposure of different population groups in the Bryansk region of Russia

The experience gained in the aftermath of serious radiation accidents shows that forests are an important source of external and internal exposure of the affected population. This paper presents the results of an assessment of the major radiological consequences for forests of Russia, most heavily contaminated after the Chernobyl nuclear power plant (ChNPP) accident. Illustrated in the Novozybkovsky district of the Russian Federation, the significance of different forest exposure pathways is estimated and the doses resulting from forest pathways are compared with the doses from agricultural products. It has been found that the contribution of mushrooms and berries to the internal doses of the population, relative to the doses from agricultural products, varied from 10–15% in 1987 to 40–45% in 1996. The results indicate large differences in internal exposure of members of the ”critical groups” and ”normal population”, increasing with time after deposition. Data are presented that give information on the contribution of forests to the collective doses of inhabitants of the area under consideration. It has been shown that for 10 years after the accident (1987–1996), the contribution of forest products to the collective dose of the rural population living in contaminated forests of the Novozybkovsky district, amounts to about 20% (213 person Sv) of the total collective dose of internal and external exposures. However, a potential impact of these products including the dose from exported products is much higher and might reach 659 person Sv. It has been found that in the long-term after the ChNPP accident, serious attention should be given to forest countermeasures, and restoration strategies should be selected on the basis of a combined analysis of the effectiveness of forest and agricultural countermeasures. Received: 16 March 2000 / Accepted: 10 September 2000     

Analysis of factors determining the biological availability of 137Cs in forest ecosystem soils

On five forest plots varying in species composition of woody plants and soil properties, 137Cs accumulation by vegetation of the forest understorey has been studied. Differences in 137Cs availability for root uptake are shown to be dependent on a vertical distribution of 137Cs content over the soil profile, percentage of exchangeable 137Cs and distribution of plant root systems (fungous mycelium) in soil. A 137Cs-bioavailability index is suggested and its non-linear relationship with 137Cs transfer factors to different plant species in the understorey is shown.     

Effect of electromagnetic waves in the centimeter range on the production of tumor necrosis factor and interleukin-3 in immunized mice

The effect of prolonged treatment with weak microwaves on the production of tumor necrosis factor and interleukin-3 in peritoneal macrophages and T cells of male NMRI mice twice immunized by affinity-purified carboanhydrase was studied. Against the back ground of a high titer of antibody production, a significant increase in the production of tumor necrosis factor in peritoneal macrophages and splenic T lymphocytes of immunized mice was revealed, and a much stronger effect was observed for irradiated immunized animals. A tendency to increased secretion of interleukin-3 for unirradiated and irradiated immunized animals was found; in the latter group of animals, the effect being more pronounced. The stimulation of production of the cytokins, especially tumor necrosis factor, by combination of antigenic stimulation and microwaves can be used in adjuvant therapy of various immune diseases.     

Vibrational structure of absorption spectra of water in visible region

The results of the study of the temperature dependence of water absorption spectra in the visible region and in the region of vibrational overtones are discussed.