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排序方式: 共有229条查询结果,搜索用时 140 毫秒
81.
Intensive nitrogen loss over the Omani Shelf due to anammox coupled with dissimilatory nitrite reduction to ammonium 总被引:1,自引:0,他引:1
Marlene M Jensen Phyllis Lam Niels Peter Revsbech Birgit Nagel Birgit Gaye Mike SM Jetten Marcel MM Kuypers 《The ISME journal》2011,5(10):1660-1670
A combination of stable isotopes (15N) and molecular ecological approaches was used to investigate the vertical distribution and mechanisms of biological N2 production along a transect from the Omani coast to the central–northeastern (NE) Arabian Sea. The Arabian Sea harbors the thickest oxygen minimum zone (OMZ) in the world''s oceans, and is considered to be a major site of oceanic nitrogen (N) loss. Short (<48 h) anoxic incubations with 15N-labeled substrates and functional gene expression analyses showed that the anammox process was highly active, whereas denitrification was hardly detectable in the OMZ over the Omani shelf at least at the time of our sampling. Anammox was coupled with dissimilatory nitrite reduction to ammonium (DNRA), resulting in the production of double-15N-labeled N2 from 15NO2−, a signal often taken as the lone evidence for denitrification in the past. Although the central–NE Arabian Sea has conventionally been regarded as the primary N-loss region, low potential N-loss rates at sporadic depths were detected at best. N-loss activities in this region likely experience high spatiotemporal variabilities as linked to the availability of organic matter. Our finding of greater N-loss associated with the more productive Omani upwelling region is consistent with results from other major OMZs. The close reliance of anammox on DNRA also highlights the need to take into account the effects of coupling N-transformations on oceanic N-loss and subsequent N-balance estimates. 相似文献
82.
Mir AI Kumar B Tasduq SA Gupta DK Bhardwaj S Johri RK 《Indian journal of experimental biology》2007,45(7):626-629
Efficacy of a herbal product of E. officinalis (fruit) (EO) has been evaluated against carbon tetrachloride (CCl4) and thioacetamide (TAA) induced changes in rat liver. Chronic treatment of CCl4 and TAA revealed abnormal histopathology indicative of pre-fibrogenic events. EO reversed such alterations with significant regenerative changes suggestive of its preventive role in prefibrogenesis of liver. 相似文献
83.
Mohankrishna Dalvoy Vasudevarao Pushpak Mizar Sujata Kumari Somnath Mandal Soumik Siddhanta Mahadeva MM Swamy Stephanie Kaypee Ravindra C Kodihalli Amrita Banerjee Chandrabhas Naryana Dipak Dasgupta Tapas K. Kundu 《The Journal of biological chemistry》2014,289(11):7702-7717
Hydroxynaphthoquinone-based inhibitors of the lysine acetyltransferase KAT3B (p300), such as plumbagin, are relatively toxic. Here, we report that free thiol reactivity and redox cycling properties greatly contribute to the toxicity of plumbagin. A reactive 3rd position in the naphthoquinone derivatives is essential for thiol reactivity and enhances redox cycling. Using this clue, we synthesized PTK1, harboring a methyl substitution at the 3rd position of plumbagin. This molecule loses its thiol reactivity completely and its redox cycling ability to a lesser extent. Mechanistically, non-competitive, reversible binding of the inhibitor to the lysine acetyltransferase (KAT) domain of p300 is largely responsible for the acetyltransferase inhibition. Remarkably, the modified inhibitor PTK1 was a nearly non-toxic inhibitor of p300. The present report elucidates the mechanism of acetyltransferase activity inhibition by 1,4-naphthoquinones, which involves redox cycling and nucleophilic adduct formation, and it suggests possible routes of synthesis of the non-toxic inhibitor. 相似文献
84.
85.
Maize seeds were bacterized with siderophore-producing pseudomonads with the goal to develop a system suitable for better iron uptake under iron-stressed conditions. Siderophore production was compared in fluorescent Pseudomonas spp. GRP3A, PRS9 and P. chlororaphis ATCC 9446 in standard succinate (SSM) and citrate (SCM) media. Succinate was better suited for siderophore production, however, deferration of media resulted in increased siderophore production in all the strains. Maximum siderophore level (216.23 microg/ml) was observed in strain PRS9 in deferrated SSM after 72 h of incubation. Strains GRP3A and PRS9 were used for plant growth promotion experiments. Strains GRP3A and PRS9 were also antagonistic against the phytopathogens, Colletotrichum dematium, Rhizoctonia solani and Sclerotium rolfsii. Bacterization of maize seeds with strains GRP3A and PRS9 showed significant increase in germination percentage and plant growth. Maximum shoot and root length and dry weight were observed with 10 microM Fe3+ along with bacterial inoculants suggesting application of siderophore producing plant growth promoting rhizobacterial strains in crop productivity in calcareous soil system. 相似文献
86.
Afforestation is a recommended practice to mitigate global warming. However, their implementation may generate undesirable impacts, mostly if exotic species are used. Plantations of Pinus radiata D Don in Ventania (Bs. As., Argentina) soils showed notorious increments of extractable P (Pe), which could affect the dynamic of this element as well as the degree of phosphorus saturation (GSPBray). The objectives of this study were: i) to quantify the GSPBray in Mollisols afforested with P. radiata comparing the results with those coming from adjacent, natural grassland areas (base line); ii) to evaluate the potential environmental risk induced by afforestation through the identification of a change point (PC) in the GSPBray indicative of a phosphate leaching increment. Treatments included mature stands of P. radiata (TB) and adjacent areas with natural grassland vegetation (TP). Samples were taken at 0-15; 15-30 and 30-45 cm soil depth, and texture, pH, total organic carbon (COT), Pe, soluble reactive phosphorus (PSR), phosphorus sorption index (ISP) and GSPBray were determined. The results showed a significant acidification in TB and an increase in the COT stock, indicating an additional atmospheric CO2 sequestration by the trees. The Pe and PSR values were notoriously higher in TB, and they were reflected in a significant increment in the GSPBray with respect to TP. The detection of a significant PC in the GSPBray-PSR regression indicates higher chances of phosphate leaching in the forest stands, which could reach water courses, lakes and artificial reservoirs promoting their eutrophication. Because of the potential environmental pollution risk of biologic origin derived from the afforestation with P. radiata in Mollisols areas, their inclusion in clean development practices must be reconsidered. 相似文献
87.
88.
C S Gupta G N Johri 《Journal of hygiene, epidemiology, microbiology, and immunology》1983,27(3):289-293
The present study concerns with the effects of larval inoculation with either a single dose or two or more spaced doses of 200 larvae on the serum protein profiles. No significant difference occurred in the various fractions among the three groups indicating that the total quantity of antigenic stimulation in the most important factor in eliciting such changes, no matter whether the dose is given once or spaced in two or three small doses. Serum protein fractions of Swiss albino mice undergoing experimental infection of Nematospiroides dubius do not tend to rise further due to repeated exposures in comparison to those that received a challenge dose only (1). Hence, experiments were designed to ascertain whether there is any difference in serum protein patterns due to breaking up of the infective dose into two or three spaced doses of N. dubius larvae. 相似文献
89.
C S Gupta G N Johri 《Journal of hygiene, epidemiology, microbiology, and immunology》1983,27(2):197-202
The paper deals with the alterations in serum protein profiles and its possible correlation with the worm burden in Swiss white mice infected with single and repeated doses of N. dubius infective larvae. Marked changes observed in serum protein fractions in all the groups were found to be further raised with increase in dose levels. However, maximum (optimal) changes of different fractions depend on the total number of larvae inoculated irrespective of the number of inoculations given. Percentage of worm retention was found to be inversely proportional to the number of larvae inoculated. Worm expulsion during repeated infections was attributed to the therefore, participation of increased amount of immunoglobulins and, humoral immunity (immediate type) has been suggested to play a major role in the immune mechanism of this model. 相似文献
90.
Thein vitro embryoids ofEschscholzia californica do not form normal plantlets in cultures. However, 6-benzylaminopurine and gibberellic acid, when added to the medium, partially alleviate this inhibition. Experiments involving decotylization, and culture of embryoids at different stages, indicated the cardinal role of cotyledons in plumular growth. 相似文献