Showing papers by "Amit Singh published in 2010"

Reductive stress in microbes: implications for understanding Mycobacterium tuberculosis disease and persistence.

Abstract: Mycobacterium tuberculosis ( Mtb ) is a remarkably successful pathogen that is capable of persisting in host tissues for decades without causing disease. Years after initial infection, the bacilli may resume growth, the outcome of which is active tuberculosis (TB). In order to establish infection, resist host defences and re-emerge, Mtb must coordinate its metabolism with the in vivo environmental conditions and nutrient availability within the primary site of infection, the lung. Maintaining metabolic homeostasis for an intracellular pathogen such as Mtb requires a carefully orchestrated series of oxidation–reduction reactions, which, if unbalanced, generate oxidative or reductive stress. The importance of oxidative stress in microbial pathogenesis has been appreciated and well studied over the past several decades. However, the role of its counterpart, reductive stress, has been largely ignored. Reductive stress is defined as an aberrant increase in reducing equivalents, the magnitude and identity of which is determined by host carbon source utilisation and influenced by the presence of host-generated gases (e.g. NO, CO, O 2 and CO 2 ). This increased reductive power must be dissipated for bacterial survival. To recycle reducing equivalents, microbes have evolved unique electron ‘sinks’ that are distinct for their particular environmental niche. In this review, we describe the specific mechanisms that some microbes have evolved to dispel reductive stress. The intention of this review is to introduce the concept of reductive stress, in tuberculosis research in particular, in the hope of stimulating new avenues of investigation.

Multivitamin and micronutrient treatment improves semen parameters of azoospermic patients with maturation arrest.

Abstract: The study was undertaken to evaluate the efficacy of multivitamin and micronutrient supplementation in azoospermic patients with maturation arrest. A total of 35 azoospermic patients showing maturation arrest on testicular biopsy were recruited in this study. The patients were divided into two groups. Untreated group (n=11) without any treatment and treated group (n=24) who received multivitamins, micronutrients and co-enzyme Q10. The sperm concentration, motility and morphology were evaluated at monthly interval. The results showed reduction in liquefaction time and relative viscosity of the semen in the treated group. Further, in treated group there was appearance of spermatozoa (4.0 million/ml) exhibiting progressive motility (7%) and normal morphology (6%), even in the first follow up visit. The sperm count, motility and normal morphology increased significantly on subsequent visits. Within 3 months (3 visits) 2 pregnancies were reported. These observations indicate that multivitamin and micronutrient supplementation improve the qualitative and quantitative parameters of seminogram in patients with azoospermia of maturation arrest.

SiCN nanomechanical resonators for array-based biosensor applications

Abstract: We report the high-yield fabrication of SiCN doublyclamped nanomechanical resonator arrays for the specific detection of proteins. As a proof of concept, specific detection of Protein A has been demonstrated. The resonant frequencies of the individual resonators were determined using optical interferometry. The bare resonators displayed resonance frequencies of ~ 17 MHz. Immobilization of single domain antibody fragments resulted in frequency downshifts of ~ 341 kHz due to the added mass. Attachment of protein A yielded a further reduction of frequency by ~ 216 kHz. A much smaller frequency reduction of ~ 54 kHz was observed when the resonators are exposed to an identical solution containing no protein A.

Bioluminescent model for the quantification of photothermal ablative breast cancer therapy mediated by near-infrared nanoparticles

Abstract: Multifunctional theranostic nanoparticles hold promise for enabling non-invasive image guided cancer therapy such as photothermal therapy. Human breast tumor models in which response to image guided therapy can quickly and non-invasively be determined are needed to facilitate translation and application of these technologies. We hypothesize that a system utilizing a murine light-reporter mammary tumor cell line and near-infrared nanoparticles (NIR-NP) can be used to quantify response to therapy and determine fate of nanoparticles following photothermal ablation.

Chromatographic Purification of Bacteriophages for Improved Surface Capture of Bacteria – Towards a General Approach

Abstract: We report in this study the largest surface capture density of E Coli using the wild-type T4 bacteriophage; whereby higher surface capture density can enable higher sensitivities for surface-based biosensors. This was possible due to our purification of the phage lysate, which significantly improved phage surface density, achieving maximum (jamming) surface coverage. Our methods could be generalized to be applicable to a large set of phage biodiversity. We can develop a new screening method to select for the best bacteriophage, for bacterial biosensor application, out a set of candidate phages.