Browsing by Author "Ashok Kumar Pandey"

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Estimation of gas hydrate saturation using isotropic and anisotropic modelling in the Mahanadi basin
(Springer, 2019) Uma Shankar; Ashok Kumar Pandey
A base of gas hydrate stability zone was established after coring and drilling under the National Gas Hydrate Program (NGHP) Expedition-01 in the Mahanadi basin. At two sites, logging-while-drilling log data, and, at one site, wireline log data, were acquired during the NGHP Expedition-01. Gas hydrate reservoirs modelling can be performed in two different ways. One way is isotropic (load bearing) and, on the other hand, anisotropic media (fracture filling with gas hydrate). Here, we have performed anisotropic modelling and estimated gas hydrate saturation using P-wave velocity, assuming an incidence angle of 75∘ represents the vertical fracture. The estimated gas hydrate saturation at sites NGHP-01-08 and NGHP-01-09, assuming anisotropic media, reduces the estimate by half compared to the saturation estimation by assuming isotropic media. The saturation at site NGHP-01-19 estimated from the isotropic and anisotropic P-wave velocity models are more or less similar except in the zone (175–210 m) just above the bottom simulating reflector depth, and this zone shows similar reduction in saturation as estimated at sites NGHP-01-08 and NGHP-01-09. Observations show that average gas hydrate saturations are relatively low (up to 5% of the pore space). The saturation of a gas hydrate estimated from an isotropic P-wave model varies from 5% to 20%. However, the saturation estimated from the anisotropic P-wave model shows a variation up to 10% of the pore spaces at three sites. © 2019, Indian Academy of Sciences.
In vitro activation of murine peritoneal macrophages by recombinant YopJ: Production of nitric oxide, proinflammatory cytokines and chemokines
(2011) Ajit Sodhi; Ashok Kumar Pandey
Recently it was reported that 3 μg/ml of recombinant YopJ induced apoptosis in murine peritoneal macrophages in vitro. However, in this study, we report the activation of murine peritoneal macrophages in vitro on treatment with sub-apoptotic dose of recombinant YopJ protein (1 μg/ml). The activation involves enhanced production of nitric oxide (NO), tumor necrosis factor-α (TNF-α), IL-12, and IL-6. Production of NO and IL-6 was found to peak at 24. h of rYopJ treatment, whereas IL-12 and IFN-γ production peaked at 18. h of rYopJ treatment. Increased mRNAs expression of nitric oxide, IL-12, IL-6 and IFN-γ molecules, was also observed in rYopJ-treated macrophages by RT-PCR. rYopJ induced the enhanced activity of protein tyrosine kinases which was inhibited by pharmacological inhibitor genestein, wortmanin and H-7 suggesting the role of tyrosine kinases, PI3K and PKC in the above process. rYopJ also induced increased enhanced production chemokines MIP-1α, MCP-1, and RANTES in macrophages. Significantly, increased expression of TLR-2, TLR-6, MyD 88 and IRAK-1 was also observed by immunoblotting in rYopJ-treated macrophages. rYopJ induced production of NO, TNF-α and IL-6 was significantly inhibited in macrophages pretreated with pharmacological inhibitor wortmanin, genestein and H-7 demonstrating the probable involvement of protein tyrosine kinases in the above process. © 2010 Elsevier GmbH.
Metal free TBHP-promoted intramolecular carbonylation of arenes: Via radical cross-dehydrogenative coupling: Synthesis of indenoquinolinones, 4-azafluorenones and fluorenones
(Royal Society of Chemistry, 2016) Kalpana Mishra; Ashok Kumar Pandey; Jay Bahadur Singh; Radhey M. Singh
A metal-free, TBHP-promoted economical route is developed via the sp2 C-H bond functionalization strategy for the synthesis of indenoquinolinones, 4-azafluorenones and fluorenones. Reactions provided excellent yield of the products under mild conditions. We have successfully synthesized 11H-indeno[1,2-b]quinolin-11-one, an antibacterial agent, in excellent yields. © The Royal Society of Chemistry.
Recombinant YopJ induces apoptosis in murine peritoneal macrophages in vitro : Involvement of mitochondrial death pathway
(2009) Ashok Kumar Pandey; Ajit Sodhi
Yersinia species during infection adhere to host immune cells primarily to macrophages and employ its secretary proteins known as Yersinia outer proteins to trigger death in infected cells. In the present study, it is shown that recombinant Yersinia outer protein J (rYopJ) could induce apoptosis in murine peritoneal macrophages in vitro as assessed by morphological features, internucleosomal DNA fragmentation, change in mitochondrial membrane potential (MMP) (Δψm), activation of caspases and Annexin V binding. rYopJ-induced cell death was dose and time dependent. Pre-treatment with broad-spectrum caspase inhibitor Z-VAD-FMK, caspase-3 inhibitor Ac-DEVD-CHO and caspase-8 inhibitor Z-IETD-FMK prevented the change in MMP and DNA fragmentation, suggesting caspase-dependent apoptosis of rYopJ-treated macrophages. Blocking the endocytosis by pre-treatment of cells with cytochalasin B did not prevent the rYopJ-induced macrophages apoptosis. The data further suggest that rYopJ-induced apoptosis is mediated by molecules upstream of caspase-8 and relay through mitochondrial pathway involving Bax, Bcl-2, activation of caspase-8 and caspase-3, Bid and polyadenosine diphosphate-ribose polymerase cleavage, cytochrome c release and DNA fragmentation. The Japanese Society for Immunology. © 2009. All rights reserved.
Recombinant YopJ induces apoptotic cell death in macrophages through TLR2
(2011) Ashok Kumar Pandey; Ajit Sodhi
Bacterial species evolved evasive maneuvers to bypass their recognition by the receptors primarily TLRs of the innate immune cells. We have reported that 3 μg/ml of recombinant YopJ when provided extracellularly induced apoptosis in murine peritoneal macrophages in vitro. The present investigations demonstrate the role of TLR2 in apoptotic signals induced by rYopJ protein in murine peritoneal macrophages. The role of TLR2 in rYopJ induced macrophage apoptosis was shown by neutralization experiments and its co-immunoprecipitation with downstream molecule MyD88. The observed functional consequence of TLR2 neutralization were the inhibition of caspase-8 and caspase-3 activation, change in mitochondrial membrane potential (Δψm) and DNA fragmentation induced by rYopJ in macrophages. Further, rYopJ induced enhanced expression of IRAK-4, FADD, phosphorylation of IκB and p38 MAP kinase in macrophages. Pharmacological inhibitor of p38 MAP kinase and neutralization of TLR2 with neutralizing antibodies significantly inhibited the rYopJ induced caspases activation and DNA fragmentation, suggesting the possible involvement of TLR2 and p38 MAP kinase in rYopJ induced macrophages apoptosis. © 2010 Elsevier Ltd.
Spectroscopic, electrochemical and antifungal studies of transition metal complexes with macrocycles containing nitrogen and sulphur donor atoms
(1992) Lallan Mishra; Ashok Kumar Pandey
Biologically relevant and electrochemically important macrocyclic thioureas viz. 1,8,10,17-tetra-azacyclo-octadecane-9,18-dithione (L), 1,10,12,21-tetra-azacyclodoeico-sane-11,22-dithione (L′) and their smallest analogue imidazolidine-2-thione (L″) have been synthesized and complexed with cobalt(II), nickel(II), copper(II), zinc(II) and platinum (IV) chlorides. The polymeric complexes [except copper(II) with L″] thus synthesized were characterized by their elemental analyses, conductance, magnetic moments, IR, UV-Vis, NMR, ESR and mass spectra along with powder X-ray diffraction studies. © 1992.