Vladimir V. Kuznetsov

Reactive oxygen species: Re-evaluation of generation, monitoring and role in stress-signaling in phototrophic organisms

This review provides an overview about recent developments and current knowledge about monitoring, generation and the functional role of reactive oxygen species (ROS) - H2O2, HO2, HO, OH(-), (1)O2 and O2(-) - in both oxidative degradation and signal transduction in photosynthetic organisms including microscopic techniques for ROS detection and controlled generation. Reaction schemes elucidating formation, decay and signaling of ROS in cyanobacteria as well as from chloroplasts to the nuclear genome in eukaryotes during exposure of oxygen-evolving photosynthetic organisms to oxidative stress are discussed that target the rapidly growing field of regulatory effects of ROS on nuclear gene expression.

Exogenous cadaverine induces oxidative burst and reduces cadaverine conjugate content in the common ice plant

The effect of free cadaverine (Cad) on its conjugates formation was analyzed in roots of the common ice plants (Mesembryanthemum crystallinum L.). It was found for the first time that Cad could induce oxidative burst in the roots of adult plants, as was evident from the sharp decrease in the content of Cad soluble or insoluble conjugates. This unusual effect was associated with the increased oxidative degradation of exogenous Cad (1mM, 1.5h) and intense H(2)O(2) production in the root cells of adult plants. Root treatment of both juvenile and adult plants with H(2)O(2) (1mM, 1.5h) reduced the content of soluble Cad conjugates and increased the content of their components, free Cad and phenols. We also found that one of the possible reasons of the negative effect of exogenous diamine on the formation of conjugated forms in adult roots was alkalization of the root apoplast at Cad addition to nutrient medium and the unusual O(2)(-) synthase function as a pH-dependent guaiacol peroxidase in the presence of a high content of H(2)O(2). This was confirmed by the data on the accumulation of O(2)(-) and enhanced superoxide dismutase activity in adult roots under treatment with Cad. It is possible that the accumulation of O(2)(-) together with H(2)O(2) was also responsible for oxidative burst, which induced a decrease in the content of Cad conjugates in adult roots of the common ice plants.

Heat transfer and film dynamic in shear-driven liquid film cooling system of microelectronic equipment

The conjugated two-dimensional model, based on long-wave theory, of a steady laminar flow of liquid film and co-current gas flow in plane channel with the height varied from 150 to 500 μm is performed. A chip with the several millimeters length is located on the bottom wall of channel. The linearised approximation of the problem is obtained analytically. Numerical calculations are executed for liquid FC-72 and Nitrogen gas flow. In contrast to a case of a large channel, there is essential an influence of liquid film deformations on pressure and velocity in a gas phase.Copyright

Downward Flow of a Nonisothermal thin Liquid Film with Variable Viscosity

Equations of a thin‐film flow with linear dependences of viscosity and surface tension of the liquid on temperature are derived. The impact of various factors on the shape of the free boundary of the film are numerically analyzed.

Experimental investigation of upward gas-liquid flow in a vertical narrow annulus

Abstract Flow structures in vertical upward two-phase flow in a concentric narrow annular channel have been studied. A map of flow patterns has been drawn. The frictional loss has been measured for the two-phase flow over a wide range of superficial liquid and gas velocities. A mathematical model predicting frictional loss has been developed.

Evaluation of nickel tolerance in Amaranthus paniculatus L. plants by measuring photosynthesis, oxidative status, antioxidative response and metal-binding molecule content

Among metals, Ni has been indicated as one of the most dangerous for the environment, and plants exposed to this metal are frequently reported to undergo a severe stress condition. In this work, the tolerance responses to different Ni concentrations at physiological and biochemical levels were evaluated in Amaranthus paniculatus L., a plant species previously characterised for their ability to phytoremove Ni from metal-spiked water. Results indicated a good metal tolerance of this plant species at environmentally relevant Ni concentrations, while clear symptoms of oxidative damages were detected at higher Ni concentrations, both in roots and leaves, by measuring lipid peroxide content. At the photosynthetic level, pigment content determination, chlorophyll fluorescence image analysis and gas-exchange parameter measurements revealed a progressive impairment of the photosynthetic machinery at increasing Ni concentrations in the solution. Regarding biochemical mechanisms involved in antioxidative defence and metal binding, antioxidative enzyme (ascorbate peroxidase, APX; catalase, CAT; guaiacol peroxidase, GPX; superoxide dismutase, SOD) activity, polyamine (PA) content, polyamine oxidase (PAO) activity and organic acid (OA) content were differently affected by Ni concentration in the growth solution. A role for GPX, SOD, PAs, and oxalic and citric acid in Ni detoxification is suggested. These results can contribute to elucidate the tolerance mechanisms carried out by plants when facing environmentally relevant Ni concentrations and to identify some traits characterising the physiological and biochemical responses of Amaranthus plants to the presence and bioaccumulation of Ni.

The synthesis of HSPs in sugar beet suspension culture cells under hyperthermia exhibits differential sensitivity to calcium

Experiments aimed at testing the effect of Ca2+ on heat shock‐induced changes in protein synthesis of cultured sugar beet cells were performed. Heat shock inhibits the synthesis of non‐heat shock proteins (non‐HSPs) and promotes the synthesis of a set of HSPs. Extracellular Ca2+ appeared to be strictly required for the synthesis of non‐HSPs. Calcium was found to differentially exert its effect on the HSP synthesis: calcium induced (96 and 76 kDa), stimulated (94, 67, 58, 52, 32, 30, 26 and 22 kDa) or did not influence (82, 17 kDa) the de novo production of various HSPs. Cell injury increased if the cells were exposed to high temperature in a Ca2+‐deficient medium. Calcium supplement to Ca2+‐depleted cells resulted in the recovery of HSP synthesis and reduced cell injury by heat shock.

Polyamines and Plant Adaptation to Saline Environments

Polyamines are universal organic polycations implicated in a wide array of fundamental processes in plants, ranging from signalling, genome expression, and plant growth and development, to plant adaptation to abiotic stresses. Stress-induced accumulation of polyamines often correlates with improvements in plant tolerance. Polyamines can protect nucleic acids and proteins and modulate the functions of macromolecules under extreme environments. Polyamines are also regulators of expression of genes encoding stress proteins. They possess antioxidant properties. Taken together, these recent findings have promoted intense efforts to characterise in detail the mechanisms of regulation of polyamine homeostasis, and to elucidate realisation of their multifaceted role in plants under stress. However, the molecular mechanisms underlying polyamine participation in plant adaptation to stress remain incompletely understood. In order to better understand the role of polyamines in plant adaptation, we focus on data concerning gene expression obtained by molecular biology methods using natural salt-tolerant species (halophytes) and also mutant and transgenic plants manifesting a high tolerance to salinity. The restriction of plant growth and productivity caused by salinity is especially acute in arid and semi-arid regions. In these regions, the influence of salt stress is aggravated by the additional action of other xerothermic factors, in particular drought and high temperature. In this chapter, particular emphasis will be paid to the possible role of polyamines in ameliorating the detrimental effects of salinity on plants during adaptation processes.

The Effect of Mutual Location of Heaters on the Falling Film Dynamics

Thin nonisothermal liquid film flowing down under action of gravity is considered. Investigation of the influence of the spanwise and streamwise arrangement of the rectangular heaters on 3-D structures, occurring at the film surface, is the main objective of the present work. Three-dimensional time-dependant mathematical model for calculation of gas-liquid interface deformations and evolution of temperature fields was developed. Our numerical investigations have shown that interaction, imposition and mutual influence of the 3D structures (bumps, lateral waves ...) takes place. In the case of streamwise arrangement of the heaters film rupture is most likely on the second heater. There is a critical backlash between the heaters, at which film deformations, including film thinning, are the largest. For the spanwise arrangement of the heaters distance between them practically do not effect on the minimum film thickness, but mutual imposition of the lateral waves and film thickening exists.

The role of pH in the synthesis of diaziridines: 2. The effect of pH on the synthesis of diaziridines from amines, carbonyl compounds and NaOCl

In the synthesis of diaziridines from amines, carbonyl compounds, and NaOCl in water, the yields of 1,2-dialkyldiaziridines and of 1,2,3-trisubstituted diaziridines prepared from amines with electron-withdrawing substituents in the side chain are less sensitive to changes in pH than the yields of 1,2,3-trialkyldiaziridines with simple alkyl substituents. The formation of 1,5-diazabicyclo[3.1.0]hexanes is insensitive to the pH in 6.5–13.0 range. This difference is explained by the occurrence of two competing pathways to the key intermediate,N-chloroaminal.