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排序方式: 共有96条查询结果,搜索用时 15 毫秒
41.
L. S. Shirokova O. S. Pokrovsky S. N. Kirpotin C. Desmukh B. G. Pokrovsky S. Audry J. Viers 《Biogeochemistry》2013,113(1-3):573-593
Active processes of permafrost thaw in Western Siberia increase the number of soil subsidencies, thermokarst lakes and thaw ponds. In continuous permafrost zones, this process promotes soil carbon mobilisation to water reservoirs, as well as organic matter (OM) biodegradation, which produces a permanent flux of carbon dioxide (CO2) to the atmosphere. At the same time, the biogeochemical evolution of aquatic ecosystems situated in the transition zone between continuous permafrost and permafrost-free terrain remains poorly known. In order to better understand the biogeochemical processes that occur in thaw ponds and lakes located in discontinuous permafrost zones, we studied ~30 small (1–100,000 m2) shallow (<1 m depth) lakes and ponds formed as a result of permafrost subsidence and thaw of the palsa bog located in the transition zone between the tundra and forest-tundra (central part of Western Siberia). There is a significant increase in dissolved CO2 and methane (CH4) concentration with decreasing water body surface area, with the largest supersaturation with respect to atmospheric CO2 and CH4 in small (<100 m2) permafrost depressions filled with thaw water. Dissolved organic carbon (DOC), conductivity, and metal concentrations also progressively increase from large lakes to thaw ponds and depressions. As such, small water bodies with surface areas of 1–100 m2 that are not accounted for in the existing lake and pond databases may significantly contribute to CO2 and CH4 fluxes to the atmosphere, as well as to the stocks of dissolved trace elements and organic carbon. In situ lake water incubation experiments yielded negligible primary productivity but significant oxygen consumption linked to the mineralisation rate of dissolved OM by heterotrophic bacterioplankton, which produce a net CO2 flux to the atmosphere of 5 ± 2.5 mol C m2 year?1. The most significant result of this study, which has long-term consequences on our prediction of aquatic ecosystem development in the course of permafrost degradation is CO2, CH4, and DOC concentrations increase with decreasing lake age and size. As a consequence, upon future permafrost thaw, the increase in the number of small water bodies, accompanied by the drainage of large thermokarst lakes to the hydrological network, will likely favour (i) the increase of DOC and colloidal metal stocks in surface aquatic systems, and (ii) the enhancement of CO2 and CH4 fluxes from the water surface to the atmosphere. According to a conservative estimation that considers that the total area occupied by water bodies in Western Siberia will not change, this increase in stocks and fluxes could be as high as a factor of ten. 相似文献
42.
Pekkoeva Svetlana N. Voronin Viktor P. Shatilina Zhanna M. Madyarova Ekaterina V. Axenov-Gribanov Denis V. Shirokova Yulia A. Timofeyev Maxim A. Nemova Nina N. Murzina Svetlana A. 《Limnology》2021,22(3):299-311
Limnology - The lipid and fatty acid content of benthopelagic scavenging amphipods Ommatogammarus flavus and O. albinus from different depths of Lake Baikal were studied. These amphipods, known to... 相似文献
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A. S. Khomich D. V. Axenov-Gribanov O. A. Bodilovskaya Y. A. Shirokova E. P. Shchapova Y. A. Lubyaga Z. M. Shatilina V. A. Emshanova A. P. Golubev 《Contemporary Problems of Ecology》2017,10(2):157-163
This study makes a multifactor analysis of the joint effect of reservoir contamination, parasitic infestation, and experimental hyperthermia on the activity of antioxidative enzymes (peroxidase, catalase, and glutathione S-transferase) in the pulmonate mollusk Lymnaea stagnalis from the clean Naroch Lake and contaminated Chizhovsky Reservoir in the Republic of Belarus. The activity of peroxidase is ascertained to be affected most strongly by the simultaneous effect of parasitic infestation and reservoir contamination and parasitic infestation coupled with experimental hyperthermia. The joint effect of parasitic infestation and reservoir pollution is found to influence the activity of catalase. Meanwhile, no correlation is found between the studied factors and the activity of glutathione S-transferase. It is shown that there is no mutual influence of the three studied factors on the activity of the investigated enzymes. 相似文献
46.
The ryanodine receptors (RyRs) are intracellular Ca2+ release channels of the sarcoplasmic reticulum (SR) involved in many cellular responses, including muscle excitation-contraction coupling. Multiple biochemical and biophysical methods are available to study RyR functions. However, most of them are somewhat limited because they can only be used to examine channels which are purified from the SR and no longer in their natural environment. In this review we discuss optical methods for studying RyR functions in situ. We describe several techniques for the investigation of local (microscopic) intracellular Ca2+ signals (a.k.a Ca2+ sparks) by means of confocal microscopy and flash photolysis of caged compounds. We discuss how these studies can and will continue to contribute to our understanding of RyR function in physiological and pathological conditions. 相似文献
47.
RyR1 S-nitrosylation underlies environmental heat stroke and sudden death in Y522S RyR1 knockin mice
Durham WJ Aracena-Parks P Long C Rossi AE Goonasekera SA Boncompagni S Galvan DL Gilman CP Baker MR Shirokova N Protasi F Dirksen R Hamilton SL 《Cell》2008,133(1):53-65
Mice with a malignant hyperthermia mutation (Y522S) in the ryanodine receptor (RyR1) display muscle contractures, rhabdomyolysis, and death in response to elevated environmental temperatures. We demonstrate that this mutation in RyR1 causes Ca(2+) leak, which drives increased generation of reactive nitrogen species (RNS). Subsequent S-nitrosylation of the mutant RyR1 increases its temperature sensitivity for activation, producing muscle contractures upon exposure to elevated temperatures. The Y522S mutation in humans is associated with central core disease. Many mitochondria in the muscle of heterozygous Y522S mice are swollen and misshapen. The mutant muscle displays decreased force production and increased mitochondrial lipid peroxidation with aging. Chronic treatment with N-acetylcysteine protects against mitochondrial oxidative damage and the decline in force generation. We propose a feed-forward cyclic mechanism that increases the temperature sensitivity of RyR1 activation and underlies heat stroke and sudden death. The cycle eventually produces a myopathy with damaged mitochondria. 相似文献
48.
Shirokova EA Khandazhinskaya AL Skoblov YS Goryunova LY Beabealashvilli RS Krayevsky AA 《Nucleosides, nucleotides & nucleic acids》2001,20(4-7):1033-1036
New gamma-substituted analogues of dNTP were synthesized and their enzymatic stability and antiviral properties were evaluated. 相似文献
49.
Kozmin LD Shirokova IE Lisitsina TA Popkova TV Reschetnyak TM Belenkiy AG Martynov AI Bliznukov OP 《Biochemistry. Biokhimii?a》2003,68(3):339-345
Blood plasma samples from patients with systemic lupus erythematosus having the anti-phospholipid antibody syndrome were found to contain anti-plasminogen antibodies of the IgG class. The titers of anti-plasminogen autoantibodies of the IgG class were elevated in these patients compared with normal controls. Part of the pool of IgG anti-plasminogen antibodies reacts with an epitope in the lysine-binding sites of plasminogen. Anti-plasminogen IgG isolated from patients' blood plasma is specific only for a native epitope of human plasminogen passively adsorbed on immunosorbent micro-titration plate. As shown by enzyme immunoassay, autoantibodies to plasminogen of the IgG class cross-react with human fibrinogen. 相似文献
50.
Shirokova EA Jasko MV Khandazhinskaya AL Yanvarev DV Skoblov YS Pronayeva TR Fedyuk NV Pokrovsky AG Kukhanova MK 《Nucleosides, nucleotides & nucleic acids》2003,22(5-8):981-985
5'-Aminocarbonylphosphonyl and aminocarbonylmethylphosphonyl diesters of AZT and d4T were synthesized as potential anti-HIV agents. 相似文献