Operational Principles for the Dynamics of the In Vitro ParA-ParB System

In many bacteria the ParA-ParB protein system is responsible for actively segregating DNA during replication. ParB proteins move by interacting with DNA bound ParA-ATP, stimulating their unbinding by catalyzing hydrolysis, that leads to rectified motion due to the creation of a wake of depleted ParA. Recent in vitro experiments have shown that a ParB covered magnetic bead can move with constant speed over a DNA covered substrate that is bound by ParA. It has been suggested that the formation of a gradient in ParA leads to diffusion-ratchet like motion of the ParB bead but how it forms and generates a force is still a matter of exploration. Here we develop a deterministic model for the in vitro ParA-ParB system and show that a ParA gradient can spontaneously form due to any amount of initial spatial noise in bound ParA. The speed of the bead is independent of this noise but depends on the ratio of the range of ParA-ParB force on the bead to that of removal of surface bound ParA by ParB. We find that at a particular ratio the speed attains a maximal value. We also consider ParA rebinding (including cooperativity) and ParA surface diffusion independently as mechanisms for ParA recovery on the surface. Depending on whether the DNA covered surface is undersaturated or saturated with ParA, we find that the bead can accelerate persistently or potentially stall. Our model highlights key requirements of the ParA-ParB driving force that are necessary for directed motion in the in vitro system that may provide insight into the in vivo dynamics of the ParA-ParB system.     

Tyloxapol Niosomes as Prospective Drug Delivery Module for Antiretroviral Drug Nevirapine

With the aim of assuring more patient compliant pharmacotherapy for acquired immuno deficiency syndrome, a formulation of the first line anti-retroviral drug, nevirapine (NVP), has been developed by encapsulating it within niosomes. Biocompatible niosomes were fabricated using a biological surfactant, tyloxapol, with variable cholesterol concentrations. Formulation with surfactant/cholesterol molar ratio 1:0.1 exhibits maximum stability and optimum hydrophobicity. Thus, it is most suitable for the entrapment of NVP and has high entrapment efficiency of 94.3%. FTIR and DSC results indicate that NVP has sufficient compatibility with the excipients of the formulation. Photoluminescence quenching measurements were employed to elucidate the position of drug molecules in niosome bilayer along with the partition coefficient. Dissolution results indicate that the efflux of drug is sustained which creates a depot effect and decreases the fluctuations in drug release. Such a versatile and improved formulation of NVP is expected to increase its therapeutic index and alleviate toxic systemic side effects while improving the quality of life and duration of survival of the patients.KEY WORDS: cholesterol, encapsulation, nevirapine, sustained release, tyloxapol niosomes     

CuO thin film based uric acid biosensor with enhanced response characteristics

An electrochemical approach for detection of individual single nucleotide polymorphisms (SNPs) based on nucleobase-conjugated apoferritin probe loaded with metal phosphate nanoparticles is reported. Coupling of the nucleotide-modified nanoparticle probe to the mutant sites of duplex DNA was induced by DNA polymerase I (Klenow fragment) to preserve Watson-Crick base-pairing rules. After sequential liquid hybridization of biotinylated DNA probes with mutant DNA and complementary DNA, the resulting duplex DNA helixes were captured to the surface of magnetic beads through a well known and specific biotin-streptavidin affinity binding. For signaling each of eight possible Single-nucleotide polymorphisms (SNPs), Pb, Cu, Cd and Zn phosphate-loaded apoferritin nanoparticle probes were linked to adenosine (A), cytidine (C), guanosine (G), and thymidine (T) mononucleotides, respectively. Monobase-conjugated apoferritin probes were coupled to the mutant sites of the formed duplex DNA in the presence of DNA polymerase. Electrochemical stripping analyses of the metals loaded in apoferritin nanoparticle probes provide a means for detection and quantification of mutant DNA. Each mutation captures different nucleotide-conjugated apoferritin probe and provide a distinct four-potential voltammogram, whose peak potentials reflect the identity of the mismatch. The method is sensitive enough to accurately determine AG mutation, as the most thermodynamically stable mismatch to detect, in the range of 50-600 pM. The proposed protocol provides a simple, fast, cost-effective, accurate and sensitive method for detection of SNPs.     

Antimicrobial Use and Resistance in Swine Waste Treatment Systems

Chlortetracycline and the macrolide tylosin were identified as commonly used antimicrobials for growth promotion and prophylaxis in swine production. Resistance to these antimicrobials was measured throughout the waste treatment processes at five swine farms by culture-based and molecular methods. Conventional farm samples had the highest levels of resistance with both culture-based and molecular methods and had similar levels of resistance despite differences in antimicrobial usage. The levels of resistance in organic farm samples, where no antimicrobials were used, were very low by a culture-based method targeting fecal streptococci. However, when the same samples were analyzed with a molecular method detecting methylation of a specific nucleotide in the 23S rRNA that results in resistance to macrolides, lincosamides, and streptogramin B (MLS_B), an unexpectedly high level of resistant rRNA (approximately 50%) was observed, suggesting that the fecal streptococci were not an appropriate target group to evaluate resistance in the overall microbial community and that background levels of MLS_B resistance may be substantial. All of the feed samples tested, including those from the organic farm, contained tetracycline resistance genes. Generally, the same tetracycline resistance genes and frequency of detection were found in the manure and lagoon samples for each commercial farm. The levels of tetracycline and MLS_B resistance remained high throughout the waste treatment systems, suggesting that the potential impact of land application of treated wastes and waste treatment by-products on environmental levels of resistance should be investigated further.     

Corticosteroids: the mainstay in asthma therapy

Inflammation is now marked as a central feature of asthma pathophysiology and aims of current asthma management are not only to treat acute symptoms of wheezing, breathlessness, chest tightness, cough but also to suppress the underlying inflammatory component. Despite the availability of a number of drugs, corticosteroids remain the mainstay in the management of all types of asthma as these are the most potent and effective antiinflammatory agents available so far. Corticosteroids suppress virtually every step in inflammation. However therapeutic doses of oral glucocorticoids are associated with a range of adverse reactions. To overcome these side effects, inhalations have been developed to deliver glucocorticoids directly to the lungs and in the process a number of aerosol preparations have become available, which have advantage of significantly lower toxicity due to low systemic absorption from the respiratory tract and rapid inactivation. Despite considerable efforts by pharmaceutical industry, it has been difficult to develop novel therapeutic agents for asthma management, which could surpass inhaled corticosteroids. Currently the data favours using inhaled corticosteroids as monotherapy in the majority of patients in all kinds of asthma. If combination therapy is recommended to achieve additional control in severe asthma cases, other drugs such as beta-agonists, antileukotrienes, theophylline, etc. are considered as adjunct therapies to corticosteroids. This review discusses the importance of corticosteroids as first line therapy for asthma treatment with the availability of inhaled corticosteroids for chronic treatment and oral formulations for treating acute exacerbations of moderate to severe asthma.     

Synthesis and in vitro antineoplastic evaluation of certain 16-(4-substituted benzylidene) derivatives of androst-5-ene

In a systematic effort aimed at identifying new steroidal cytotoxic agents with potent antiproliferative activity against cancer cells, we synthesized certain 16-[4-(NO2, CN, and i-Pr)substituted]benzylidene derivatives of androst-5-ene, 7-25, with pyrrolidino functionality in the 3beta-position of the steroid nucleus, i.e., 13-18 and 25. The selected compounds were examined for their cytotoxicity against a panel of three human cancer cell lines at the National Cancer Institute (NCI), Bethesda, USA. The results presented herein provide experimental evidence that compounds 7, 9, 10, 12, 16, and 19-21 induced apoptosis in human cancer cells.     

Molecular Mechanisms of Meditation

Meditation is a complex process involving change in cognition, memory, and social and emotional control, and causes improvement in various cardiovascular, neurological, autoimmune, and renal pathologies. Meditation also become widely used in medical and psychological treatment therapies for stress-related physical and mental disorders. But still, biological mechanisms in terms of effect on brain and body are poorly understood. This paper explains the basic changes due to meditation in cerebral cortex, prefrontal area, cingulate gyrus, neurotransmitters, white matter, autonomic nervous system, limbic system, cytokines, endorphins, hormones, etc. The following is a review of the current literature regarding the various neurophysiological mechanisms, neuro-endocrine mechanisms, neurochemical substrates, etc. that underlies the complex processes of meditation.     

Salmonella–Macrophage Interactions upon Manganese Supplementation

Various studies indicate the role of manganese (Mn) in the virulence of pathogens. Salmonella is an intracellular pathogen which is able to multiply within the macrophages. The present study was therefore, designed to assess the effect of Mn supplementation on Salmonella–macrophage interactions particularly in reference to Salmonella virulence and macrophage functions. A 50-fold decrease in the lethal dose 50 (LD₅₀) of Salmonella typhimurium was observed when mice were infected with Salmonella grown in the presence of Mn as compared to the LD₅₀ in the absence of Mn indicating an increase in the virulence of the organism. A significant increase was observed in the levels of superoxide dismutase (SOD) of S. typhimurium grown in presence of manganese. Upon Mn supplementation, macrophage functions were also found to be altered. Decreased phagocytic activity of macrophages interacted with Salmonella was observed in presence of Mn as compared to the activity in the absence of Mn. A significant increase was observed in the extent of lipid peroxidation along with significant decreases in the activities of SOD and catalase as well as nitrite levels of macrophages interacted with S. typhimurium upon supplementation with Mn. These observations indicate that Mn supplementation might have increased the expression of Mn transporters in Salmonella resulting in increased levels of its superoxide dismutase. The altered Salmonella function in turn might have been responsible for inhibiting phagocytosis and impairing the balance between the oxidant and antioxidant profile of macrophages, thus protecting itself by exhibiting exalted virulence.