Ultrastructural analysis of cell wall of drug resistant and sensitive Mycobacterium tuberculosis isolated from cerebrospinal fluid by transmission electron microscope

Drug‐resistant tuberculosis is being increasingly recognized and is one among the leading cause of death worldwide. Remarkable impermeability of cell wall to antituberculous drugs protects the mycobacteria from drug action. The present study analyzed the cell wall thickness among first‐line drug resistant and sensitive Mycobacterium tuberculosis (Mtb) isolated from cerebrospinal fluid by transmission electron microscopy (TEM). The average thickness of the cell wall of sensitive isolates was 13.60 ± 0.98 nm. The maximum difference (26.48%) in the cell wall thickness was seen among multi‐drug resistant (18.50 ± 1.71 nm) isolates and the least difference (4.14%) was shown by streptomycin‐resistant (14.18 ± 1.38 nm) isolates. The ultrastructural study showed evident differences in the cell wall thickness among sensitive and resistant isolates. Preliminary TEM examination of cells indicates that morphological changes occur in the cell wall which might be attributed to the drug resistance. The thickened wall of Mtb appears to help the bacilli to overcome the action of antituberculous drugs.     

Antimicrobial and Amyloidogenic Activity of Peptides. Can Antimicrobial Peptides Be Used against SARS-CoV-2?

At present, much attention is paid to the use of antimicrobial peptides (AMPs) of natural and artificial origin to combat pathogens. AMPs have several points that determine their biological activity. We analyzed the structural properties of AMPs, as well as described their mechanism of action and impact on pathogenic bacteria and viruses. Recently published data on the development of new AMP drugs based on a combination of molecular design and genetic engineering approaches are presented. In this article, we have focused on information on the amyloidogenic properties of AMP. This review examines AMP development strategies from the perspective of the current high prevalence of antibiotic-resistant bacteria, and the potential prospects and challenges of using AMPs against infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).     

Structural,microstructural, and thermal characterizations of a chalcopyrite concentrate from the Singhbhum shear zone,India

The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron mi...     

Numerical Preservation of Velocity Induced Invariant Regions for Reaction–Diffusion Systems on Evolving Surfaces

We propose and analyse a finite element method with mass lumping (LESFEM) for the numerical approximation of reaction–diffusion systems (RDSs) on surfaces in \({\mathbb {R}}^3\) that evolve under a given velocity field. A fully-discrete method based on the implicit–explicit (IMEX) Euler time-discretisation is formulated and dilation rates which act as indicators of the surface evolution are introduced. Under the assumption that the mesh preserves the Delaunay regularity under evolution, we prove a sufficient condition, that depends on the dilation rates, for the existence of invariant regions (i) at the spatially discrete level with no restriction on the mesh size and (ii) at the fully-discrete level under a timestep restriction that depends on the kinetics, only. In the specific case of the linear heat equation, we prove a semi- and a fully-discrete maximum principle. For the well-known activator-depleted and Thomas reaction–diffusion models we prove the existence of a family of rectangles in the phase space that are invariant only under specific growth laws. Two numerical examples are provided to computationally demonstrate (i) the discrete maximum principle and optimal convergence for the heat equation on a linearly growing sphere and (ii) the existence of an invariant region for the LESFEM–IMEX Euler discretisation of a RDS on a logistically growing surface.     

Single-Component CMOS-Like Logic using Diketopyrrolopyrrole-Based Ambipolar Organic Electrochemical Transistors

Complementary circuits based on organic electrochemical transistors (OECTs) are attractive for the development of inexpensive and disposable point-of-care bioelectronic devices. Ambipolar OECTs, which employ a single channel material, could decrease the fabrication complexity and manufacturing costs of such circuits. An ideal channel material for ambipolar OECTs should be electrochemically stable in aqueous environments, afford facile ion insertion for both cations and anions, and also facilitate high and balanced electron and hole transport. In this study, triethylene glycol functionalized diketopyrrolopyrrole (DPP)-based polymer is proposed for the development of ambipolar OECTs. It is shown that DPP-based OECTs have a high and comparable figure of merit for both n- and p-type operations. Logic NOT, NAND, and NOR operations with corresponding complementary circuits constructed from identical DPP-based OECT devices are demonstrated. This study is an important step toward the development of sophisticated complementary metal–oxide–semiconductor-like logic circuits using single-component OECTs.     

Hedgehog Antagonist Pyrimidine–Indole Hybrid Molecule Inhibits Ciliogenesis through Microtubule Destabilisation

One of the crucial regulators of embryonic patterning and tissue development is the Hedgehog‐glioma (Hh‐Gli) signalling pathway; its uncontrolled activation has been implicated in different types of cancer in adult tissues. Primary cilium is one of the important factors required for the activation of Hh signalling, as it brings the critical components together for key protein–protein interactions required for Hh pathway regulation. Most of the synthetic and natural small molecule modulators of the pathway primarily antagonise Smoothened (Smo) or other effectors like Hh ligand or Gli. Here, we report a previously described Hh antagonist, with a pyrimidine–indole hybrid (PIH) core structure, as an inhibitor of ciliogenesis. The compound is unique in its mode of action, as it shows perturbation of microtubule dynamics in both cell‐based assays and in vivo systems (zebrafish embryos). Further studies revealed that the probable targets are α‐tubulin and its acetylated form, found in the cytoplasm and primary cilia. PIH also showed axonal defasiculation in developing zebrafish embryos. We thus propose that PIH antagonises Hh signalling by repressing cilia biogenesis and disassembling α‐tubulin from its stabilised form.     

Facile route to the synthesis of porous α-Fe2O3 nanorods

The requirements of simple and reliable protocols for the synthesis of anisotropic structures with controlled morphology continue to be a major challenge in nanoscience. In this paper we describe the facile synthesis of porous hematite (α-Fe₂O₃) nanorods using anionic surfactant as a rod-like template. α-FeOOH nanorods with diameters of 170–210 nm and lengths up to 3–5 μm were synthesized in high yield via hydrothermal method using sodium dodecyl sulphate as a template. The porous α-Fe₂O₃ was obtained after solvent extraction and calcining the as-obtained α-FeOOH nanorods at 500 °C for 6 h. Even after removal of template by solvent extraction and calcination the shape of the nanorods was intact except the generation of pores on the nanorods. The porous nanorods were analysed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission and high-resolution transmission electron microscopy (TEM & HRTEM), scanning electron microscopy (SEM) and superconducting quantum interference device (SQUID) measurements. SEM and TEM images showed that the morphology of hematite nanostructure is homogeneous in the shape of rods and full of porosity and magnetization measurements of the porous α-Fe₂O₃ nanorods showed weak ferromagnetic behavior. The surfactant SDS (sodium dodecyl sulphate) plays a key role in controlling the nucleation and growth of the nanorods and their use as a new class of inorganic scaffolds for the synthesis of nanomaterials are salient features of the work with implications in crystal engineering and nanocomposites design for various applications.     

Gum arabic as a phytochemical construct for the stabilization of gold nanoparticles: in vivo pharmacokinetics and X-ray-contrast-imaging studies

Gold nanoparticles (AuNPs) have exceptional stability against oxidation and therefore will play a significant role in the advancement of clinically useful diagnostic and therapeutic nanomedicines. Despite the huge potential for a new generation of AuNP-based nanomedicinal products, nontoxic AuNP constructs and formulations that can be readily administered site-specifically through the intravenous mode, for diagnostic imaging by computed tomography (CT) or for therapy via various modalities, are still rare. Herein, we report results encompassing: 1) the synthesis and stabilization of AuNPs within the nontoxic phytochemical gum-arabic matrix (GA-AuNPs); 2) detailed in vitro analysis and in vivo pharmacokinetics studies of GA-AuNPs in pigs to gain insight into the organ-specific localization of this new generation of AuNP vector, and 3) X-ray CT contrast measurements of GA-AuNP vectors for potential utility in molecular imaging. Our results demonstrate that naturally occurring GA can be used as a nontoxic phytochemical construct in the production of readily administrable biocompatible AuNPs for diagnostic and therapeutic applications in nanomedicine.     

A study of an n-unit system operating in a random environment

An n-unit system operating in a random environment is considered. The environment determines the number of units required for the satisfactory performance of the system. Assuming that the environment is described by a Markov process, we obtain expressions for: (1) the distribution and the moments of the time to the first disappointment; and (2) the mean number of disappointments over an arbitrary interval.