Showing papers by "Amit Singh published in 2009"

Mycobacterium tuberculosis WhiB3 Maintains Redox Homeostasis by Regulating Virulence Lipid Anabolism to Modulate Macrophage Response

Abstract: The metabolic events associated with maintaining redox homeostasis in Mycobacterium tuberculosis (Mtb) during infection are poorly understood. Here, we discovered a novel redox switching mechanism by which Mtb WhiB3 under defined oxidizing and reducing conditions differentially modulates the assimilation of propionate into the complex virulence polyketides polyacyltrehaloses (PAT), sulfolipids (SL-1), phthiocerol dimycocerosates (PDIM), and the storage lipid triacylglycerol (TAG) that is under control of the DosR/S/T dormancy system. We developed an in vivo radio-labeling technique and demonstrated for the first time the lipid profile changes of Mtb residing in macrophages, and identified WhiB3 as a physiological regulator of virulence lipid anabolism. Importantly, MtbΔwhiB3 shows enhanced growth on medium containing toxic levels of propionate, thereby implicating WhiB3 in detoxifying excess propionate. Strikingly, the accumulation of reducing equivalents in MtbΔwhiB3 isolated from macrophages suggests that WhiB3 maintains intracellular redox homeostasis upon infection, and that intrabacterial lipid anabolism functions as a reductant sink. MtbΔwhiB3 infected macrophages produce higher levels of pro- and anti-inflammatory cytokines, indicating that WhiB3-mediated regulation of lipids is required for controlling the innate immune response. Lastly, WhiB3 binds to pks2 and pks3 promoter DNA independent of the presence or redox state of its [4Fe-4S] cluster. Interestingly, reduction of the apo-WhiB3 Cys thiols abolished DNA binding, whereas oxidation stimulated DNA binding. These results confirmed that WhiB3 DNA binding is reversibly regulated by a thiol-disulfide redox switch. These results introduce a new paradigmatic mechanism that describes how WhiB3 facilitates metabolic switching to fatty acids by regulating Mtb lipid anabolism in response to oxido-reductive stress associated with infection, for maintaining redox balance. The link between the WhiB3 virulence pathway and DosR/S/T signaling pathway conceptually advances our understanding of the metabolic adaptation and redox-based signaling events exploited by Mtb to maintain long-term persistence.

Proposal of biostimulation for hexachlorocyclohexane (HCH)-decontamination and characterization of culturable bacterial community from high-dose point HCH-contaminated soils.

Abstract: To locate a high-dose point hexachlorocyclohexane (HCH)-contaminated site, to identify HCH-degrading bacteria in it and assay HCH-decontamination by biostimulation. Methods and Results: Bacteria were isolated by serial dilution method from HCH-contaminated soil samples collected from areas near an HCH-manufacturing unit and its dumpsite in North India. After confirming the presence of indigenous HCH-degraders (seven of 24 strains), an ex situ biostimulation experiment was conducted. For this, residue levels in soil were diluted by mixing with pristine garden soil and aeration, moisture and nutrients were provided intermittently. This soil was monitored for reduction in Σ-HCH (sum of α-, β-, γ- and δ-HCH) levels and stimulation of HCH-degraders. Experiments were conducted twice, in March-April (c. 75 μg Σ-HCH g−1 soil) and October-November 2006 (c. 280 μg Σ-HCH g−1 soil) at 26-30°C. Σ-HCH levels were reduced to <30% of the original in 24 days and <3% in 240 days in the experimental pits. Terminal restriction fragment length polymorphism analysis reflected changes in microbial community structure during the course of experiment. Conclusions: Our results show presence of HCH-degrading sphingomonads at a high-dose point HCH-contaminated site and presents biostimulation as an effective approach for its decontamination via aeration, addition of nutrients and moisture, of the indigenous population. Significance and Impact of the Study: The study demonstrates that biostimulation of indigenous HCH-degrading microbial population can be used for decontamination of chronically HCH-contaminated sites.

Inhalable microparticles containing isoniazid and rifabutin target macrophages and ‘stimulate the phagocyte’ to achieve high efficacy

Abstract: Macrophage responses to infection with Mycobacterium tuberculosis (MTB) and treatment with soluble isoniazid (INH) plus rifabutin (RFB) versus microparticles containing equivalent amounts of drugs were compared. It was investigated whether macrophages driven to alternative activation upon infection with MTB could be rescued to display the classical activation phenotype. It was established that microparticles sustain high levels of drugs in the cytosol of macrophages for longer periods as compared to soluble drugs. Microparticles co-localized with intracellular bacteria, and induced a variety of innate bactericidal responses, including induction of free radicals, alteration of mitochondrial membrane potential and apoptosis. The data strongly suggest that additional benefit may be derived from the nature of the drug delivery system, which fulfils Koch’s dictum for curing tuberculosis: “stimulate the phagocyte”.

Catastrophic drop breakup in electric field.

Abstract: We report novel observations revealing the catastrophic breakup of water drops containing surfactant molecules, which are suspended in oil and subjected to an electric field of strength ∼105 V/m The observed breakup was distinctly different from the gradual end pinch-off or tip-streaming modes reported earlier in the literature There was no observable characteristic deformation of the drop prior to breakup The time scales involved in the breakup and the resultant droplet sizes were much smaller in the phenomenon observed by us We hypothesize that this mode of drop breakup is obtained by the combined effect of an external electric field that imposes tensile stresses on the surface of the drop, and characteristic stress−strain behavior for tensile deformation exhibited by the liquid drop in the presence of a suitable surfactant, which not only lowers the interfacial tension (and hence the cohesive strength) of the drop but also simultaneously renders the interface nonductile or brittle at high enough co

Shape and size selective separation of gold nanoclusters by competitive complexation with octadecylamine monolayers at the air-water interface.

Abstract: The paper presents a time-dependent study of shape-dependent preferential complexation of gold nanoparticles to the octadecyl amine (ODA) monolayers at the air–water interface. Room temperature reduction of chloroaurate ions using lemon grass leaf extract yields a mixture of spherical and triangular nanoparticles, which were used for this study. These nanoparticles have a net negative charge on their surface due to the presence of biomolecules from plant extract and thus a strong attractive electrostatic interaction with the positively charged ODA monolayers drives the complexation process. The extent of preferential complexation of the gold nanoparticles to the ODA monolayers is a function of the charge on the particles and the relative mobility of the nanoclusters in the medium. The complexation process has been followed in real time by a host of techniques such as surface pressure–area (π–A) isotherms, UV–vis–NIR spectroscopy and Brewster angle microscopy. The charge and mobility of the gold nanoparticles was confirmed by measurement of their electrophoretic mobility. Langmuir–Blodgett films of the nanogold–ODA composites have been characterized by UV–vis–NIR spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. These measurements clearly indicate that the cluster mobility and complexation increase with decreasing cluster size. In the competitive complexation process of large and small gold particles, it was observed that some bigger gold particles were also incorporated into the amine matrix even though the cluster mobility is higher for smaller gold particles.

Hand geometry verification system: A review

Abstract: Biometric system is becoming increasingly important, since they provide more reliable and efficient means of identity verification. The physical dimensions of a human hand contain information that is capable of authenticating the identity of an individual. This information has been popularly known as hand or palm geometry; the hand geometry based identity verification system is being widely used in various applications like access control, time and attendance, point-of-scale, anti-pass back and interactive kiosks etc. This paper presents biometric user recognition system based on hand geometry. The goal of a biometric verification system consists in deciding whether two characteristics belong to the same person or not.

Bacteriophage immobilization for biosensors

Abstract: A method is disclosed for anchoring a bacteriophage on a substrate, the bacteriophage having a phage amine moiety, the method comprising: producing a free amine terminal moiety on the substrate by chemical modification of the substrate; activating the free amine terminal moiety with a cross-linking agent to produce an active functional group to couple to the phage amine moiety; and anchoring the bacteriophage to the substrate using the active functional group. A sensor is also disclosed comprising: a substrate; an anchor group attached by chemical modification to the substrate and having an active functional group produced by the activation of a free amine terminal moiety; and a bacteriophage having a phage amine moiety coupled to the active functional group to anchor the bacteriophage to the substrate.

Efficacy and tolerability of cefditoren pivoxil in uncomplicated skin and skin structure infections in Indian patients.

Abstract: Background: Uncomplicated skin and skin structure infections (uSSSI) are commonly encountered community-acquired infections and are typically confined to the superficial layers of the skin. Hence, they seldom lead to the destruction of skin structures. Aims: To evaluate the efficacy and tolerability of cefditoren pivoxil in uSSSI in Indian patients. Methods: One hundred and seventy-eight patients diagnosed with uncomplicated SSSI were enrolled in this randomized, comparative, multicentric study. Patients received either cefditoren pivoxil or cefdinir for ten days. Efficacy was assessed both clinically and microbiologically. Safety evaluation consisted of reporting of type, frequency, severity, and causal relationship of adverse events. Results: One hundred and fifty-one patients completed the study. Clinical and bacteriological efficacy of cefditoren pivoxil was comparable to that of cefdinir in the treatment of uSSSI. One hundred and five patients were eligible for per protocol (PP) analysis of bacteriological outcome and clinical efficacy. Clinical cure or improvement was achieved in 98.00% patients treated with cefditoren pivoxil and 98.18% patients treated with cefdinir. In the modified Intent to Treat (mITT) patient population, clinical cure or improvement was recorded in 97.33% patients treated with cefditoren pivoxil and 96.20% patients treated with cefdinir. Microbiological eradication (or presumed eradication) was recorded in 88.00% patients treated with cefditoren pivoxil and 94.55% patients treated with cefdinir. The above differences in the outcome rates between the two drugs were not statistically significant. Six adverse events (AEs) (two in cefditoren group and four in cefdinir group) were reported in this study. Conclusion: Cefditoren pivoxil 200 mg b.i.d. was effective and well tolerated in the treatment of uSSSI.

Fodder productivity and economics of pearlmillet (Pennisetum typhoides) with legumes intercropping under various row proportions.

Abstract: A field experiment was conducted during the summer seasons of 2007 and 2008 at Sabour to assess the productivity and economics of intercropping of forage pearlmillet [Pennisetum typhoides (L) R Br Emend & Stuntz] with cowpea [Vigna unguiculata (L) Walp], clusterbean [Cyamposis tetragonaloba (L) Taub] and rice bean [Vigna umbellata (Thumb) ohwi and ohashi] under 4 row proportions, viz, 1: 1, 1: 2, 2: 1 and 2: 2 Fodder yields of both the component crops were substantially reduced under intercropping system compared with their sole stands Pooled analysis of 2 years showed that pearlmillet + cowpea (2: 2) recorded significantly higher total green (528 t/ha), dry fodder (1324 t/ha), crude protein yield (136 t/ha), as well as net returns (Rs 24,060/ha) compared with the other treatments The highest land-equivalent ratio (142), relative crowding coefficient (654) and lowest value of competitive ratio (129) also indicated superiority of pearlmillet + cowpea system Among the component crops, pearlmillet was more competitive and aggressive to legume intercrops However, maximum aggressivity index (055) and competitive ratio (342) were obtained with pearlmillet + clusterbean (1: 2) Thus, intercropping of pearlmillet and cowpea in 2: 2 row ratio may be adopted for higher fodder productivity, quality and profitability during summer

Rock Mechanics challenges of depillaring at deep cover

Abstract: Underground coal mining at deeper cover encounters difficult underground environment due to increase in gas content and rise in temperature transition of a mining practice from shallow to high depth cover encounters a big change in the rock mass characteristics and the stress condition becomes more complex. At higher depth of cover, the excavation starts encountering stress control regime rather than structural control behavior of the rock mass. Mechanisation and automation of underground mining activities is a solution to improve the performance of deeper mines but the approach should match with the rock mass and stress conditions of the site. Since inception, CIMFR (formerly, CMRI) is continuously working to understand behavior of the rock mass through laboratory testing, field investigations and study on simulated models. Obtained experiences during these investigations are observed to be of strategic importance during application of a modern technology to improve practical mining conditions. This paper reviews rock mechanics aspects of different mechanized pillar extraction approaches during mining of a deep seated coal seam and, also attempts to present an appraisal of some of the recent technical developments to overcome the challenges of a deep underground coal mining.