Blockade of early and late retinal biochemical alterations associated with diabetes development by the selective bradykinin B1 receptor antagonist R-954

The chronic hyperglycemia measured alongside diabetes development is associated with significant long-term damage and failure of various organs. In the present study it was shown that hyperglycemia induced early and long term increases in nitric oxide (NO) levels, kallikrein activity and vascular capillary permeability measured as plasma extravasation, and decreases of Na/K ATPase activity in diabetic rat retina 4 and 12 weeks after streptozotocin (STZ) injection. Treatment of the animals for 5 consecutive days with a novel selective bradykinin B(1) receptor (BKB(1)-R) antagonist R-954 (2mg/kg s.c) at the end of the 4 and 12 week periods highly reduced NO, kallikrein and capillary permeability and increased Na/K ATPase activity in the retina. These results suggest that the BKB(1)-R receptor subtype is over-expressed during the streptozotocin-induced development of diabetes in rat retina as evidenced by the inhibitory effects of the BKB(1)-R antagonist R-954 on NO, kallikrein and vascular permeability increases as well as Na/K ATPase decreases. The beneficial role of the BKB(1)-R antagonist R-954 for the treatment of the diabetic retinopathy is also suggested.     

Effect of substrate nitrogen on lignin degradation by Pleurotus ostreatus

In order to determine the effect of substrate nitrogen (N) on ligninolytic activity, Pleurotus ostreatus was grown in solid media containing either growth-limiting (1mM) or excess (10mM) NH₄Cl. After 25 days, ¹⁴C–CO₂ production from ¹⁴C-cornstover lignin in low-N medium was 3 times that in nitrogen (N)-rich medium. Supplementation of low-N medium with glucose (0.3%) further enhanced ligninolytic activity. Decolorization of an aromatic, polymeric dye, Poly R-481, in solid media was also greatest under N-limiting conditions.     

Synthesis and inhibition properties of a series of pyranose derivatives towards a Zn-metalloproteinase from Saccharomonosporacanescens

The Zn-proteinase, isolated from Saccharomonosporacanescens (NPS), shares many common features with thermolysin, but considerable differences are also evident, as far as the substrate recognition site is concerned. In substrates of general structure AcylAlaAlaPhe 4NA, this neutral proteinase cleaves only the arylamide bond (non-typical activity of Zn-proteinases), while thermolysin attacks the peptide bond Ala-Phe. Phosphoramidon is a powerful tight binding inhibitor for thermolysin and significantly less specific towards NPS. The K_i-values (65 μM for NPS vs 0.034 μM for thermolysin) differ nearly 2000-folds. This implies significant differences in the specificity of the corresponding subsites. The carbohydrate moiety is supposed to accommodate in the S₁-subsite and the series of arabinopyranosides and glucopyranosides (12 compounds), which are assayed as inhibitors in a model system: NPS with SucAlaAlaPhe4NA as a substrate could be considered as mapping the S₁-subsite of NPS. Members of the series with an additional ring (3,4-epithio, 3,4-anhydro-derivatives) turned out to be reasonably good competitive inhibitors (K_i ≈ 0.1-0.2 mM are of the same order as the K_i value for phosphoramidon). The structure of these compounds (8, 9, 11 and 12) seems to fit the size of the S₁-subsite and due to an appropriately oriented OH-group in addition, to protect the active site Zn²⁺.     

Deletion of the autoregulatory insert modulates intraprotein electron transfer in rat neuronal nitric oxide synthase

Comparative CO photolysis kinetics studies on wild-type and autoregulatory (AR) insert-deletion mutant of rat nNOS holoenzyme were conducted to directly investigate the role of the unique AR insert in the catalytically significant FMN-heme intraprotein electron transfer (IET). Although the amplitude of the IET kinetic traces was decreased two- to three-fold, the AR deletion did not change the rate constant for the calmodulin-controlled IET. This suggests that the rate-limiting conversion of the electron-accepting state to a new electron-donating (output) state does not involve interactions with the AR insert, but that AR may stabilize the output state once it is formed.     

Specific sulphur metabolites stimulate β-glucosidase activity in an anaerobic sulphidogenic bioreactor

The activities of -glucosidases are stimulated by specific sulphur metabolites during the hydrolysis of complex polymeric organic carbon in an anaerobic sulphidogenic environment. While sulphate had little or no influence on enzyme activity, sulphite increased the activity of -glucosidases by 2.5 fold and sulphide increased the activity by six fold. A hypothetical model is proposed in which sulphur species (HSO₃ ^– and HS^–), liberated at different times during the sulphate reduction process, activate the -glucosidases which are associated with the organic particulate matter leading to a subsequent enhancement of hydrolysis of polymeric carbohydrate material.     

Enhanced thiosulfate-silver staining of proteins in gels using Coomassie Blue and chromium

Potassium chromium sulfate, a new sensitivity enhancer for silver staining of proteins in gels, enhanced the sensitivity of the thiosulfate-silver staining method. The sensitivity could be further improved when potassium chromium sulfate was used in association with another sensitivity enhancer, Coomassie Brilliant Blue R-250 (CBB R-250). The sensitivity of the CBB-chromium modified method to strongly basic proteins such as ribosomal proteins was about 20-fold over that of the published method. This novel method has direct applicability for 2-D gel electrophoresis used in proteomics.     

Degradation of contrasting pesticides by white rot fungi and its relationship with ligninolytic potential

The capacity of nine species of white rot fungus from a variety of basidiomycete orders to degrade contrasting mono-aromatic pesticides was investigated. There was no relationship between degradation of the dye Poly R-478, a presumptive test for ligninolytic potential, and degradation of the highly available pesticides diuron, metalaxyl, atrazine or terbuthylazine in liquid culture. However, there were significant positive correlations between the rates of degradation of the different pesticides. Greatest degradation of all the pesticides was achieved by Coriolus versicolor, Hypholoma fasciculare and Stereum hirsutum. After 42 days, maximum degradation of diuron, atrazine and terbuthylazine was above 86%, but for metalaxyl less than 44%. When grown in the organic matrix of an on-farm "biobed" pesticide remediation system, relative degradation rates of the highly available pesticides by C. versicolor, H. fasciculare and S. hirsutum showed some differences to those in liquid culture. While H. fasciculare and C. versicolor were able to degrade about a third of the poorly available compound chlorpyrifos in biobed matrix after 42 days, S. hirsutum, which was the most effective degrader of the available pesticides, showed little capacity to degrade the compound.     

农业政策环境扩展模型在我国农业面源污染研究中的应用

我国的面源污染问题逐渐受到政府和科学界的重视,然而面源污染是一个复杂的系统过程,涉及多种因素和多个过程。面源(NPS)污染模型作为解决面源污染相关问题的研究和管理工具,在进行面源污染总量估算和严重程度评价、污染物流失路径和影响因素分析、治理策略制定等方面都有重要的作用。在我国,虽然针对面源污染模型进行了大量相关研究,既包含对基于国外模型的应用与验证,也包含基于观测数据自主研发的模型,但仍然存在模型应用和验证案例不足、已有的模型应用同中国面源污染特征结合不足、模型发展同面源污染机理研究结合不足等问题,而农业政策环境扩展(APEX)模型在应对这些问题上具有一定的优势。结合我国面源污染模型相关研究存在的问题、APEX模型模块和研究进展进行了介绍,对APEX模型在我国面源污染相关问题的研究中涉及的畜禽养殖、复杂耕作系统、特定BMP和水稻田的模拟等相关问题的应用前景进行了探讨,以期能够促进我国农业面源污染模型的发展。     

Low potential manganese ions as efficient electron donors in native anoxygenic bacteria

Systematic control over molecular driving forces is essential for understanding the natural electron transfer processes as well as for improving the efficiency of the artificial mimics of energy converting enzymes. Oxygen producing photosynthesis uniquely employs manganese ions as rapid electron donors. Introducing this attribute to anoxygenic photosynthesis may identify evolutionary intermediates and provide insights to the energetics of biological water oxidation. This work presents effective environmental methods that substantially and simultaneously tune the redox potentials of manganese ions and the cofactors of a photosynthetic enzyme from native anoxygenic bacteria without the necessity of genetic modification or synthesis. A spontaneous coordination with bis-tris propane lowered the redox potential of the manganese (II) to manganese (III) transition to an unusually low value (~400?mV) at pH?9.4 and allowed its binding to the bacterial reaction center. Binding to a novel buried binding site elevated the redox potential of the primary electron donor, a dimer of bacteriochlorophylls, by up to 92?mV also at pH?9.4 and facilitated the electron transfer that is able to compete with the wasteful charge recombination. These events impaired the function of the natural electron donor and made BTP-coordinated manganese a viable model for an evolutionary alternative.